Chapter Outline
Genu Varum (Bowlegs) 713
Genu Valgum (Knock-Knees) 733
Tibial Torsion 739
Bowing of the Tibia 741
Congenital Pseudarthrosis of the Fibula 757
Deformities of the tibia and fibula are probably the most common and obvious abnormalities that affect a child’s lower extremity. They can be congenital or acquired, physiologic or pathologic, but all draw immediate attention to themselves because of the real or apparent detrimental effect they have on gait and upright activity. Most lower leg “deformities” are in fact physiologic and resolve spontaneously, so early recognition of the benign nature of such deformities is as important as the correct diagnosis of true pathologic conditions. This can reassure parents, avoid unnecessary treatment, and minimize excessive attention to a nonpathologic problem. The various conditions affecting the lower part of the leg are discussed in this chapter in relation to their anatomic occurrence, proceeding from proximal to distal.
Genu Varum (Bowlegs)
Genu varum (bowlegs) is an extremely common pediatric deformity, and parents uniformly seek evaluation even though it is rarely symptomatic in the age group (younger than 2 years) in which it is most common. Determining whether the condition represents physiologic genu varum or a pathologic process, such as infantile tibia vara, is critical because the prognosis and treatment differ profoundly.
Physiologic Genu Varum
Physiologic genu varum is a deformity with a tibiofemoral angle of at least 10 degrees of varus, a radiographically normal physis, and apex lateral bowing of the proximal end of the tibia and often the distal end of the femur. The legs of most newborns are typically bowed, with 10 to 15 degrees of varus angulation. When the infant begins to stand and walk, the bowing may appear more prominent and often seems to involve both the tibia and the distal part of the femur. Concomitant internal tibial torsion may exacerbate the deformity ( Fig. 22-1, A ). Children with physiologic genu varum and internal tibial torsion typically come to medical attention after standing age (between 12 and 24 months), usually because of parents’ concern about the appearance of the legs. These children have no other significant findings on clinical examination. In the typical manifestation, radiographs generally are not needed to determine the physiologic nature of the deformity. Although radiographs at this time may show an apparent delay in ossification of the medial side of the distal femoral and proximal tibial epiphyses (see Fig. 22-1, B ) or flaring of the medial distal femoral metaphysis, the physes have a normal appearance.
Clinical measurements of the tibiofemoral angle and intercondylar distance in normal children show maximal varus at 6 to 12 months old, neutral alignment by 18 to 24 months, maximal genu valgum at 4 years (8 degrees of tibiofemoral valgus), and a gradual decrease in genu valgum to a mean of 6 degrees by the age of 11 years. The presence of genu varum in children older than 2 years can be considered abnormal, but this “expected” pattern of change over time from genu varum to genu valgum is a generalized standard, and variations may be observed ( Fig. 22-2 ). A distinct subset of patients with more severe varus angulation at initial evaluation, slower resolution to neutral alignment by 3 to 4 years old, and radiographic femora vara have been described.
Spontaneous resolution of the varus to neutral tibiofemoral alignment by 24 months old and to an adult valgus alignment after 3 years old is well documented ( Fig. 22-3 ), as is the variation just noted. Patients can be formally observed to ensure that the varus resolves. Parents are reassured that the condition is usually self-correcting but also advised that reevaluation with radiographs may be warranted if the varus deformity persists or progresses beyond 24 months old. Nonresolving, asymmetric deformity is the main indication for radiographs.
The differential diagnosis of persistent genu varum still includes physiologic genu varum, which remains the most common etiology, even in a deformity that is slow to resolve and appears to be pathologic (see Fig. 22-2 ). One must also consider infantile tibia vara, physeal disturbance secondary to trauma or infection, metabolic bone disease, generalized skeletal dysplasia, and focal fibrocartilaginous dysplasia. * All these conditions are diagnosed radiographically.
Tibia Vara
* References .
Tibia vara is defined as growth retardation at the medial aspect of the proximal tibial epiphysis and physis usually resulting in persistent or progressive bowleg. Two forms of the deformity are recognized based on age at onset of the condition: infantile tibia vara, if younger than 3 years, and adolescent tibia vara, if 10 years or older. The two forms have distinctively different radiographic characteristics and treatment results, with infantile tibia vara being more common.Tibia vara has alternatively been classified as infantile, juvenile, and adolescent, with the juvenile form occurring between 4 and 10 years old and the adolescent form occurring after 10 years. The term late-onset tibia vara includes both the juvenile and the adolescent forms. Some authors have used “late onset” to define tibia vara in older children, but there are differences of opinion regarding whether late-onset tibia vara describes classic adolescent tibia vara or is a distinct entity. We have not found these distinctions useful and continue to classify tibia vara as either infantile or adolescent, with the “juvenile” form being a late or undiagnosed manifestation of infantile tibia vara and “late-onset” tibia vara being synonymous with adolescent tibia vara.
Infantile Tibia Vara (Blount Disease)
Infantile tibia vara, first described by Erlacher in 1922, is best known as Blount disease after the classic description by Blount in 1937. Blount characterized the deformity as an abrupt angulation just below the proximal physis, an irregular physeal line, and a wedge-shaped epiphysis with a “beak” at the medial metaphysis ( Fig. 22-4 ). Apparent lateral subluxation of the proximal end of the tibia is often present.
Etiology
Several authors have reported a familial occurrence of the condition, and one report of infantile tibia vara in a family suggested that the disease may be inherited as an autosomal dominant condition with variable penetrance. However, as noted by Langenskiöld and Riska, because the radiographic features of infantile tibia vara have never been seen in patients younger than 1 year and rarely in patients younger than 2 years, the condition is considered a developmental disorder and not a congenital one. Other studies have found no evidence of an inherited condition and have concluded that the etiology is multifactorial.
Physiology
Histologic evaluations of affected physis and the corresponding part of the metaphysis in infantile tibia vara have been conducted by a number of authors. The general findings have included (1) islands of densely packed cartilage cells displaying greater hypertrophy than expected from their position in the physis, (2) islands of nearly acellular fibrocartilage, and (3) exceptionally large clusters of capillary vessels. The physeal cell columns become irregular and disordered in arrangement and normal endochondral ossification is disrupted, both in the medial aspect of the metaphysis and in the corresponding part of the physis. The varus deformity progresses as long as ossification is defective and growth continues laterally. In later stages of the deformity, an actual bony bridge may tether medial growth, and the medial tibial plateau may appear to be deficient posteromedially. However, actual depression of the posteromedial tibial articular surface is probably not present, at least at the outset of the deformity. The “deficiency” is probably unossified abnormal fibrocartilage whose delay in ossification produces the appearance of a defect and is directly related to the underlying histopathology. Ligamentous laxity on the lateral side of the knee frequently develops in a neglected or recurrent deformity.
Clinical Features
The typical child with infantile tibia vara appears similar to a child with physiologic genu varum, with two major differences. First, patients with tibia vara are often obese, exceeding the 95th percentile for weight. Significant differences in body mass index (BMI) percentile have also been observed for toddlers presenting at similar ages and timing of walking who developed infantile tibia vara. Finite element analysis of the knee has shown that a compressive force sufficient to retard physeal growth by the Hueter-Volkmann principle is produced on the medial tibial plateau of a 2-year-old in the 90th percentile for body weight and with a 20-degree varus deformity during single-limb stance. Greater radiographic varus malalignment and procurvatum deformity has been correlated with higher BMI in infantile tibia vara. This relationship between obesity and risk for Blount disease may warrant early intervention and nutrition counseling in young patients.
Second, patients with infantile tibia vara often have a clinically apparent lateral thrust of the knee during the stance phase of gait that resembles a limp (see Fig. 22-4 ). This sudden lateral knee movement with weight bearing is caused by varus instability at the joint line in concert with the angulation. In our practice, the presence of this thrust, though not pathognomonic for infantile tibia vara, raises our level of suspicion and is an indication for radiography, regardless of the age of the patient.
Radiographic Findings
Radiography is central to establishing the diagnosis of infantile tibia vara ( Box 22-1 ). A standing anteroposterior view of the lower extremities from hip to ankle should be obtained. The diagnosis is based on familiar radiographic changes in the proximal end of the tibia: (1) a sharp varus angulation in the metaphysis, (2) a widened and irregular physeal line medially, (3) a medially sloped and irregularly ossified epiphysis, and (4) prominent beaking of the medial metaphysis with lucent cartilage islands within the beak (see Fig. 22-4 ).
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Varus angulation at the epiphyseal-metaphyseal junction
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Widened and irregular physeal line medially
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Medially sloped and irregularly ossified epiphysis, sometimes triangular
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Prominent beaking of the medial metaphysis with lucent cartilage islands within the beak
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Lateral subluxation of the proximal end of the tibia
Unequivocal radiographic changes diagnostic of infantile tibia vara are rarely observed before 18 months old (the youngest published case was radiographically diagnosed at 17 months old). However, a normal knee radiograph in a toddler does not rule out infantile tibia vara. As an aid to early identification of toddlers who are at risk for the development of infantile tibia vara but who have no physeal or metaphyseal changes, Levine and Drennan measured the tibial metaphyseal–diaphyseal angle (MDA), the angle created by the intersection of a line connecting the most prominent medial portion of the proximal tibial metaphysis (the “beak”) and the most prominent lateral point of the metaphysis with a line drawn perpendicular to the long axis of the tibial diaphysis ( Fig. 22-5 ). Blount lesions visible on radiographs subsequently developed in 29 of 30 patients whose MDA was greater than 11 degrees, whereas such changes developed in only 3 of 58 patients with an angulation of 11 degrees or less. However, subsequent studies measuring the MDA, the tibiofemoral angle, or the mechanical axis have not improved early detection of infantile tibia vara, nor have radiographic measurements been helpful in establishing the severity of disease once the condition is present. Any limb malrotation during radiographic examination can affect the measured MDA and the tibiofemoral angle. Thus, although measurement of the MDA may have some prognostic accuracy, it has not by itself been reliable to diagnose impending infantile tibia vara.
The tibial epiphyseal–metaphyseal angle has been proposed as an adjunctive measurement to aid early diagnosis of infantile tibia vara. An angle greater than 20 degrees in combination with an MDA greater than 10 degrees indicates a toddler at risk. However, true infantile tibia vara cannot be diagnosed without the unequivocal presence of the characteristic lesion in the proximal medial tibial metaphysis. If this radiographic finding is not present, the patient by definition has physiologic genu varum. Although patients with large MDAs may be at risk for the development of infantile tibia vara and must be monitored, we currently recommend no treatment before the appearance of an unequivocal Blount lesion, which is often manifested between 18 and 24 months old.
Attempts to use magnetic resonance imaging (MRI) to assess the growth disturbance in infantile tibia vara are ongoing. MRI characterizes the extent of the ossified and cartilaginous epiphysis, along with any physeal anatomic disruption ( Fig. 22-6 ). While not necessary to confirm the diagnosis, such imaging studies are useful preoperative tools to evaluate location and size of the physeal bridge (see Fig. 22-6, D and E ), as well as the presence or absence of “true” intraarticular deformity (see Fig. 22-6, A to C ). MRI assessment of physeal function to determine whether the physis is bridged or sufficiently disrupted, in order to predict cessation of medial growth, is not yet proven to be accurate.
In later evaluated or “relapsed” cases of infantile tibia vara, a more severe bony deformity, including depression and sloping of the posteromedial epiphyseal surface, has been identified by computed tomography (CT) ( Fig. 22-7 ). However, CT lacks the added benefit of visualizing the cartilaginous articular surface, which may occupy most of the medial plateau. The occurrence of “true” intraarticular deformity in young patients is debatable. Patients younger than 6 years old have not demonstrated such plateau depression as demonstrated by intraoperative arthrography showing preservation of a normal-appearing joint line despite the osseous defect ( Fig. 22-8 ). However, the clinical finding of lateral thrust and the radiographic appearance of lateral tibial subluxation on the femur could be explained by the presence of such a defect from the outset.
Differential Diagnosis
The most common entity in the differential diagnosis is physiologic genu varum, in which no Blount lesion is seen on a radiograph; indeed, the physis and epiphysis are normal. Although the deformity may be dramatic, especially in patients with femora vara (see Fig. 22-2 ), the bowing is often symmetric or nearly so, and the child is otherwise normal.
Nonphysiologic causes of genu varum, all demonstrated on radiographs, include skeletal dysplasias (e.g., metaphyseal chondrodysplasia, spondyloepiphyseal dysplasia, multiple epiphyseal dysplasia, achondroplasia), metabolic diseases (e.g., renal osteodystrophy, vitamin D–resistant rickets), posttraumatic deformity, postinfectious sequelae, and proximal focal fibrocartilaginous dysplasia.
Classification
In 1952, Langenskiöld classified infantile tibia vara according to the degree of metaphyseal-epiphyseal changes seen on radiographs, with six stages varying with advancing age ( Fig. 22-9 ). General prognostic guidelines were also provided. Restoration to normal was common in disease stages I and II and possible in stages III and IV, whereas disease stages V and VI were associated with recurrence and permanent sequelae after treatment by mechanical realignment (osteotomy).
Although Langenskiöld’s classification was primarily intended to be a radiographic description of infantile tibia vara, prognostic implications have gradually been derived from later studies. In 1964, Langenskiöld and Riska reported that a simple osteotomy could cure the deformity in patients 8 years old or younger. In the few cases in which simple osteotomy failed, inadequate surgical correction was implicated. Radiographic stage progression of the deformity was thought to be a consequence of skeletal maturation rather than an indication of progressive inhibition of medial physeal growth and worsening of the condition.
The premise that 8 years is the critical age up to which the condition is surgically curable has undoubtedly resulted in a certain complacency in treating young children, particularly those with demonstrable stage progression. A number of investigators have reported difficulty applying the Langenskiöld classification to predict outcome in their own patients.
The Langenskiöld classification is inaccurate for prognosis when applied to a predominantly nonwhite population in North America and the Caribbean. Major inconsistencies are that (1) all stages can occur earlier than Langenskiöld described (as young as 17 months old); (2) disease stages II and III can progress to stage VI despite treatment ( Fig. 22-10 ), whereas previously it was thought that surgery cured the disease in these patients ; (3) there is a marked tendency for progression of deformity in black girls and thus an even worse prognosis for these patients; and (4) predictably good results from a single tibial osteotomy are achieved only if the surgery is performed by 4 years of age, a notable departure from the previous guideline of 8 years.
The unanticipated difficulty in curing stages III and IV lesions by osteotomy alone has been confirmed by other investigators. In the non-Scandinavian patient population, infantile tibia vara proved to have a more malignant course, and the results of treatment were poorer than Langenskiöld’s 1964 or 1981 guidelines suggested. The poorer outcomes seemed to be, at least in part, due to the delay in surgical treatment of younger patients. However, the poorer outcomes may also be attributable simply to a different type and severity of disease that is encountered in the nonwhite population. Reports from Scandinavian and Japanese centers continue to attest to a relatively benign course in more than 50% of their patients and to a condition that will spontaneously resolve, with the varus deformity correcting without treatment in up to three fourths of patients—an experience diametrically opposite to the ones in the United States and the Caribbean.
From our experience, it appears that only stages I and II lesions can predictably have full restoration (i.e., cure) with a single osteotomy or bracing. Definitive correction must be achieved by 4 years old. Stage III lesions may be restored, whereas stages IV to VI lesions cannot be restored with a simple osteotomy and require complex reconstruction and physeal procedures, with a guarded outcome at best.
Treatment
Untreated infantile tibia vara generally results in a nonresolving and sometimes progressive varus deformity that produces joint deformity and growth retardation, which can then be corrected only with complex surgical procedures. Even when such surgery is performed, substantial articular disruption of both compartments of the knee may have already occurred. Thus, once the radiographic diagnosis of infantile tibia vara is certain, the orthopaedist should recommend treatment immediately because patients treated in the early stages of the disease have a better prognosis. There is no justification for simply observing a patient with an unequivocal diagnosis. Treatment choices and prognosis depend greatly on the age of the patient at the time of diagnosis, which should be the same age at which treatment is recommended.
Orthoses
If the child is younger than 3 years old and the lesion is no greater than Langenskiöld stage II, orthotic treatment is recommended because 50% or more of these patients can be successfully treated with braces, especially if they have only unilateral involvement. There may be an inclination to brace patients before a true Blount lesion is visible on radiographs, particularly when the MDA is suggestive of varus progression. Thus when evaluating the reported good outcomes from brace treatment, one must realize that some patients probably had physiologic genu varum rather than true infantile tibia vara. Nevertheless, orthotic treatment appears to affect the natural history favorably.
The type of orthosis prescribed and the length of time that the orthosis is worn during a 24-hour period vary. Raney and associates used a knee-ankle-foot orthosis (KAFO) that produced a valgus force by three-point pressure in 60 tibiae (38 patients), with lesions in 54 tibiae (90%) resolving without surgery. Significant risks for failure included ligamentous instability, patient weight greater than the 90th percentile, and late initiation of bracing. Of the 54 tibial lesions that resolved, 27 were treated by full-time orthotic use, 23 by nighttime use only, and 4 by daytime use. Three of the six tibiae requiring surgery had been treated with full-time orthotic use and three with nighttime use only. Based on these findings, the authors conjectured that nighttime-only bracing might be as efficacious as full-time bracing, although they acknowledged that one inherently would expect daytime use (i.e., during weight bearing) to be the most important factor in successful orthotic treatment. On the other hand, Zionts and Shean reported daytime ambulatory bracing to be successful in altering the natural history of tibia vara in patients younger than 3 years with Langenskiöld stage I or II disease.
We have used conventional KAFOs, conventional hip-knee-ankle-foot orthoses (HKAFOs), and elastic KAFOs in the treatment of infantile Blount disease. Since 1987, the elastic Blount brace, a medial upright design that uses a wide elastic band just distal to the knee joint ( Fig. 22-11 ), has been used almost exclusively because of its ease of fabrication and smaller profile. With this orthosis, 65% of tibiae had successful outcomes at an average follow-up of 5.9 years. However, corrective osteotomies for one or both extremities were eventually required in 70% of patients with bilateral involvement, as opposed to only 6% of patients with unilateral involvement. All patients were instructed to use the brace during the day (i.e., during weight bearing). Depending on the patient’s physician, some patients were encouraged to use the brace for 20 to 24 hours per day.
Early brace treatment therefore appears to be effective in stage I or II disease up through 36 months old, especially in those with unilateral involvement. Patients with bilateral involvement may also benefit from orthotic management, but surgical correction is more likely to be needed for one or both extremities. Full-time orthotic treatment (i.e., 23 hours per day) is traditional so that the knee is fully protected during the day when it is maximally exposed to varus forces during weight bearing and so that appropriate valgus force continues to be applied at nighttime during non–weight bearing, although we recognize that part-time wear has been successful as well.
Valgus correction should be increased by bending the medial upright every 2 months until standing radiographs show that at least a neutral mechanical axis has been achieved. Brace wear can then be gradually tapered over a period of several months. To ensure permanent correction, the metaphyseal lesion should start resolving radiographically while the mechanical axis is being corrected, and the lesion should have nearly resolved by the time that the patient is no longer using the orthosis.
Brace therapy is not generally appropriate for children older than 3 years. A maximum trial of 1 year of orthotic treatment to correct the varus deformity is recommended; thus, if correction is not achieved within this time frame in a child younger than 3 years, the orthopaedist can still perform definitive osteotomy before the patient is 4 years old. Good results from this single surgical intervention by this age are seen in almost 90% of cases. To begin orthotic treatment after age 3 means that the outcome of treatment will not be known until the patient is older than 4 years if brace therapy is given an adequate trial of 1 year. Such delay risks postponing corrective osteotomy past the critical age of 4 years, if 1 year of orthotic treatment is not successful. As melodramatic as it may seem, even a few months’ delay in performing surgery by 4 years old can result in failure to achieve permanent reversal of inhibition of the proximal medial physis. For stage III lesions and especially for stage IV lesions, it is debatable whether mechanical realignment with a single osteotomy can ever reverse the physeal inhibition (see Fig. 22-10 ). The association between those older than 5 years and biologic physeal arrest (stages IV and greater) cannot be overemphasized.
Treatment of Langenskiöld Stage II Lesions.
Surgical treatment in the early stages of the disease (stage II) is crucial to achieve permanent and lasting correction and to avoid the sequelae of joint incongruity, limb shortening, and persistent angulation. Patients with stage I or II disease have a significantly lower incidence of repeat osteotomy than do those with stage III disease. Surgical overcorrection of the mechanical axis to at least 5 degrees of valgus by 4 years of age, along with lateral translation of the distal osteotomy fragment, is believed to be optimal. Such overcorrection ensures that the supine correction attained at surgery will be sufficient to translate the mechanical axis into the lateral compartment of the knee once the patient begins bearing weight. Overcorrection of the mechanical axis offsets the tendency of the knee to go back into varus as a result of any sloping of the medial epiphyseal surface and relaxation of the lateral ligaments.
Although correction to within 5 degrees of neutral alignment may prove to be adequate, most authors recommend physiologic valgus or overcorrection. Based on the physeal inhibition phenomenon, overcorrection to absolute valgus alignment is required to reverse the excessive compressive forces medially and allow a Langenskiöld II or III physis not already irreversibly damaged to respond to such mechanical unloading.
The specific type of proximal tibial osteotomy (e.g., dome, closing wedge, or opening wedge) in young children is not important as long as the appropriate valgus and lateral translation are obtained. The level of osteotomy should be just distal to the patellar tendon insertion to avoid the proximal physis and its most distal extent. Internal tibial torsion should be addressed by external rotation of the distal fragment. Fibular osteotomy in the proximal third of the diaphysis should be performed routinely through a separate incision. Because long-leg casts must often be split during the postoperative period, some form of internal fixation (e.g., with Kirschner wires) is helpful in maintaining correction. Prophylactic fasciotomy of the anterior, lateral, and posterior compartments is recommended because of the not insignificant incidence of compartment syndrome. After proximal tibial osteotomy there may be subtle weakness of the extensor hallucis longus despite fasciotomy. This weakness, which is frequently overlooked, is probably due to partial peroneal nerve palsy.
The concept of “guided growth” using extraperiosteal nonlocking plates may prove to be an attractive alternative to conventional acute corrective osteotomy in young patients (younger than age 4) with Stage I and II disease. The technique relies upon the tension band principle as opposed to physeal compression, and observed rates of correction are equivalent and possibly more rapid than stapling with comparable effectiveness in desired normalization of mechanical axis. While our institution lacks experience applying this technique to treat infantile tibia vara, an 89% success rate of mechanical alignment attainment in this population (average age 4.8) has been reported. Currently no long-term outcome data exist to answer whether or not rebound deformity occurs following this minimally invasive technique and warrants further investigation before definitive recommendation.
Treatment of Langenskiöld Stage III Lesions.
Stage III lesions can respond to corrective osteotomy alone in patients older than 4 years. However, the longer the delay in surgery after 4 years old, the greater the risk for recurrence, which is not uncommon with stage III lesions (see Fig. 22-10 ). Thus, because of the worsening prognosis, neither observation nor orthotic treatment is recommended beyond this age, especially if the deformity exceeds 10 degrees of femorotibial varus.
Treatment of Langenskiöld Stages IV/V Lesions.
Lesions greater than stage III cannot be definitively corrected by simple mechanical realignment because physiologic physeal arrest has already occurred by stage IV ( Fig. 22-12 ). Even though no bony bridge can be visualized by tomographic methods in stage IV or V lesions, physeal damage has progressed to the point where stages IV and V lesions effectively act as medial physeal arrests.
Because stage IV lesions can be seen in children as young as 6 years, their treatment presents a significant problem in management. Repeated osteotomies, required because of the predictable and certain recurrence of deformity, may help prevent intraarticular deformity but do not address limb shortening and, because of the repeated neurovascular risk, are clearly an unattractive approach.
Alternatively, some form of lateral epiphysiodesis—permanent or transient—will prevent recurrence by eliminating growth from the lateral side of the proximal tibial physis but will obviously result in significant limb length discrepancy when performed in such a young patient. Total physeal closure at the time of osteotomy prevents recurrence but, by producing unacceptable shortening in young patients, predictably commits them to subsequent limb-lengthening procedures.
Thus, treatment must be carefully individualized for stage IV or greater lesions in patients younger than 10 years with at least 2 years of growth remaining. Realignment combined with medial epiphysiolysis and the use of interposition material to prevent rebridging is the treatment of choice for these patients. The medial physis at this stage is so damaged that it will inevitably progress to a fully ossified physeal bridge (stage VI) (see Fig. 22-12 ). Epiphysiolysis can restore symmetric growth of the proximal end of the tibia and prevent retethering medially, thereby reducing the likelihood of recurrent deformity or disruption of the articular surface. A review of 24 patients undergoing this treatment for stage IV or greater infantile tibia vara at our institution demonstrated that the procedure was valuable in gaining meaningful growth. Eighty percent of children operated on at younger than 7 years gained enough growth that they required only angular correction (by osteotomy or hemiepiphysiodesis), if indeed they needed any further treatment at all ( Fig. 22-13 ). Adequate valgus alignment beyond a 0-degree femorotibial angle after epiphysiolysis and osteotomy was also important in the success of the procedure. In patients older than 7 years, epiphysiolysis was effective in fewer than 50% of cases, thus suggesting that alternative methods of treatment should be considered.
Technique.
Preoperative assessment by MRI is essential to determine the amount of abnormal physis in three dimensions ( Fig. 22-14 ; see Fig. 22-6 , A to C ). A curved skin incision allowing access proximal to the mid-medial joint line and metaphysis distal to the level of the tibial tubercle anteriorly is made so that the epiphysiolysis and a corrective high tibial osteotomy can be performed through the same incision. A separate longitudinal incision is made over the proximal end of the fibula for performance of a fibular osteotomy.
The pes anserine tendons are sharply elevated in an anterior-to-posterior direction to expose the drooping epiphyseal-metaphyseal junction. A curved osteotome is placed in the cleft between the “beak” of the epimetaphysis and the normal metaphysis. Under fluoroscopic control, the osteotome is advanced in a semicircular path proximally and posteriorly to resect the fibrocartilaginous “beak,” with exit just distal to the medial tibial plateau surface (see Fig. 22-14, C ). This mass of abnormal fibrocartilage lies just under the weight-bearing surface of the medial aspect of the tibia; once it is removed, the true physis can be identified by direct vision and fluoroscopy. A dental burr or small curets are used to further undercut and visualize the normal physis from the metaphyseal side so that any remaining abnormal metaphysis can be completely removed (see Fig. 22-14, D and E ). The defects in the metaphysis and epiphysis supporting the articular surface are then filled with an interposition material, which also covers the medial physis. We prefer Cranioplast because it can be molded in the putty state to a precise fit within the metaphyseal beak, thereby covering all raw bone surfaces securely. It can be anchored to the epiphysis via small Steinmann pins so that the cement will not migrate distally with growth (see Fig. 22-14, G ). The Cranioplast/pin construct also supports the medial tibial joint surface. Technical inadequacy of the metaphyseal and physeal resection—that is, the resection does not proceed far enough laterally to remove all abnormal metaphyseal bone and the presumed abnormal physis immediately adjacent to it—probably plays an important role in eventual failure of the untethering of subsequent growth (see Fig. 22-14, H ).
After hardening of the polymethyl methacrylate, a closing wedge/lateral displacement osteotomy of the proximal end of the tibia just distal to the tibial tubercle is performed (see Fig. 22-14, F ). The osteotomy should be internally fixed, usually with one or more pins, in case proximal control by cast immobilization is compromised by the not infrequent need for cast splitting or partial removal because of neurovascular concerns. Slight overcorrection into valgus alignment is mandatory, primarily to ensure transfer of the mechanical axis into the lateral compartment of the knee. This technique is especially important in knees where long-standing lateral joint laxity may not be apparent until the patient resumes the weight-bearing position or where a small component of joint obliquity encourages recurrent varus. Inadequate valgus alignment after epiphysiolysis is implicated in failure of the procedure.
The extremity is usually placed in a cast for 8 weeks to ensure healing of the osteotomy before any weight bearing. Full weight bearing is then gradually allowed after the patient regains active knee range of motion while non–weight bearing.
Treatment of Langenskiöld Stage VI Lesions.
Treatment of stage VI lesions with established bony bridges must also be individualized. Factors to be considered are patient age, the amount of skeletal growth remaining, and the degree of deformity of the joint surface. If the patient has less than 2 years of growth remaining and a relatively normal joint surface, corrective osteotomy with complete physeal closure is a practical means of obtaining and maintaining correction. The osteotomy can be made through the physis so that the mechanical correction is placed as close to the joint as possible and permanent physeal closure occurs.
As previously mentioned, resection of the bony bridge with placement of interposition material is appropriate in patients younger than 7 years. Unfortunately, a patient with a stage VI lesion will probably be older than this age limit, when epiphysiolysis is less predictable. Treatment options in patients with more than 2 years’ growth remaining include completion of the lateral tibial epiphysiodesis, angular correction, and lengthening, if indicated, usually during the same treatment session. In patients requiring limb length equalization with or without correction of deformity, correction by external fixation and distraction osteogenesis is an effective and invaluable method for salvaging a potentially unsatisfactory extremity. Breaking of a physeal bridge by asymmetric physeal distraction has been described as an alternative approach to resection of the bony bridge in children near skeletal maturity.
In children older than 10 years, the deformity in recurrent or neglected advanced-stage lesions may be so significant that medial plateau elevation by intraarticular osteotomy, along with mechanical axis correction, may be indicated We recommend careful preoperative evaluation of potential joint incongruity as suggested by plain radiographs and confirmation with an MRI because the “true” articular surface may be maintained by cartilage (see Fig. 22-6, A to C ). Intraoperative assessment of the joint line with arthrography (see Fig. 22-8 ) may also assist in identifying which patients may benefit from intraarticular osteotomy to improve joint congruity. Fluoroscopic varus and valgus stress views can demonstrate significant joint instability as a result of “true” joint surface depression. By elevating the medial plateau with the knee in maximal valgus alignment, the instability of the medial compartment during weight bearing is theoretically relieved ( Fig. 22-15 ). Therefore, restoration of joint congruity and removal of varus instability provide rationale for this treatment. Remember that the intraarticular osteotomy represents one component of the procedure and that a separate proximal tibia osteotomy is required to correct the mechanical axis, the so-called double level osteotomy. ( Fig. 22-16 ). The realignment component can be achieved acutely or gradually, which has the advantage of concurrent deformity correction and lengthening because completion of the lateral proximal tibia and fibula epiphysiodesis is also performed.
Although the plateau elevation procedure has been performed for more than 20 years, long-term outcome studies are not available. Short-term results are generally encouraging with a reported decrease in pain and instability, satisfactory healing, and reconstitution of the tibial plateau. The ability of the proposed procedure to maintain joint congruity and mechanical alignment over time and prevent early medial compartment degenerative disease, characteristic of stage VI deformity, remains to be proven. Furthermore, no comparative studies of single proximal and double level tibia osteotomies exist. The intraarticular osteotomy must be considered a final salvage procedure in older patients with severe joint deformity secondary to inadequate early treatment of infantile tibia vara.
Technique.
Fluoroscopic visualization of the proximal end of the tibia is essential to perform the osteotomy without intraarticular displacement of the medial plateau. A straight anterior incision is made to expose the medial plateau proximal to the tibial tubercle. The osteotomy begins distal to the insertion of the medial collateral ligaments. A series of holes (see Fig. 22-16 , A ) tracing the curve of the osteotomy and stopping just short of the subchondral bone, just lateral to the tibial spine, are drilled in an anterior-to-posterior direction (with the popliteal structures protected). The drill holes are then connected with a curved osteotome (see Fig. 22-16 , B and C ), and the medial plateau fragment is gradually hinged proximally while maintaining the articular surface intact. With the knee in maximal passive valgus stress, the medial fragment is hinged upward to close the “gap” under the medial femoral condyle. Once the maximal elevation desired is achieved, provisional fixation with interfragmentary pins or screws is then followed by a buttress plate to maintain the opening wedge, and the defect under the medial plateau is filled with iliac crest bone graft, a structural strut graft (autograft or allograft), or both (see Fig. 22-16 , D to F ). Completion of the lateral tibial and fibular epiphysiodesis is important to prevent further asymmetric growth, and corrective high tibial osteotomy is necessary to restore the mechanical axis. These components of the procedure can be performed simultaneously or in a staged fashion after ensuring consolidation of the plateau elevation .
Complications of Surgery.
Complications of proximal tibial osteotomy in a growing child can be numerous. The osteotomy must be performed distal to the tibial tubercle to avoid growth arrest. Injury to the proximal tibial physis at the level of the tibial tubercle produces proximal tibial recurvatum, with resulting hyperextension instability of the knee. The optimal site of the osteotomy, distal to the tubercle, is near the level of the trifurcation of the popliteal artery. The anterior tibial artery, which passes through the interosseous membrane and enters the anterior compartment, can be injured in as many as 29% of osteotomy procedures. Prophylactic fasciotomy of all the compartments should be performed during all osteotomy procedures, with appropriate postoperative neurovascular surveillance for the first 48 hours. Other reported complications include peroneal nerve palsy, deep and superficial infections, iatrogenic fractures, and loss of correction. †
† References .
Unexpected recurrence of varus deformity in early-stage Langenskiöld lesions may be due to inadequate correction or loss of correction, with subsequent progression of the Langenskiöld stage and early asymmetric physeal closure. If such recurrence happens within 1 or 2 years of the osteotomy, repeat osteotomy and medial epiphysiolysis with placement of interposition material may correct the problem, particularly in a skeletally immature patient. Failure of physeal bridge resection to at least maintain alignment is usually an indication for epiphysiodesis of the lateral half of the proximal tibial physis, with later limb-lengthening equalization procedures used as necessary.Summary.
As can be readily discerned from the complex treatment options and numerous complications discussed under the treatment of Langenskiöld stages IV to VI lesions and the risks involved in general for any osteotomy or repeat procedure, early treatment aimed at curing infantile tibia vara is far more attractive and more likely to produce a good outcome than later treatment of the more advanced condition. Early diagnosis plus corrective treatment (orthotic or osteotomy) by 4 years old is the most reliable way to avoid a poor outcome in both joint and leg function and cannot be overemphasized.
Adolescent Tibia Vara
The adolescent form of tibia vara, less common than the infantile form, is a distinctly different entity because of the later age at onset and, consequently, the more mature physis and more ossified chondroepiphysis, which are more resistant to mechanical compression and disruption.
In the original description by Blount, the adolescent form was defined as occurring after 6 years of age, and Langenskiöld used the term adolescent to describe partial premature closure as a result of trauma or infection in patients between 6 and 13 years old. A more widely accepted definition used at our institution describes increasing tibia vara after 8 years of age in a patient who is usually male, morbidly obese, and without a history of trauma, infection, or other physeal insult to explain the proximal medial tibial physeal inhibition.
Although some authors have subdivided patients with onset after 3 years of age into a juvenile group (4 to 10 years old) and an adolescent group (11 years or older), it can arguably be determined that in most cases the “juvenile” onset merely represents the lack of definitive radiographic diagnosis before age 4, perhaps in the setting of a milder clinical deformity. Furthermore, the adolescent form has little in common with the so-called juvenile tibia vara, with the response to osteotomy generally being more favorable in the adolescent form and recurrence more common in the juvenile form, as would be predicted for a child with infantile tibia vara treated after 4 years old.
Finally, some authors have used the term late-onset tibia vara to include both the juvenile and the adolescent types, whereas others use late-onset tibia vara interchangeably with what is normally understood to be adolescent tibia vara. For this discussion the term adolescent is used exclusively to refer to those with onset after age 8.
Etiology
Adolescent tibia vara is frequently observed in patients who had a mild degree of physiologic genu varum as younger children that never completely resolved to neutral alignment or physiologic valgus. Concurrent with the adolescent growth spurt in children who are significantly obese, a gradual varus of the proximal end of the tibia develops because of growth suppression from mechanical causes. Although such occult varus can be confirmed by the history in many cases (family photographs are often available), not all investigators have been able to determine either that a mild varus preexisted or that it was required for adolescent tibia vara to develop. Trauma and infection, sometimes described as etiologic factors and known to produce physeal arrest, are not considered factors in the development of adolescent tibia vara (which technically is idiopathic) unless one wishes to define chronic growth suppression secondary to obesity as trauma.
Histopathologically, biopsy specimens of the medial physis show evidence of injury, with fissuring and clefts in the physis, fibrovascular and cartilaginous repair tissue at the physeal-metaphyseal junction, and disorganization and sequestered islands of hypertrophic chondrocytes. Although these findings cannot be considered pathognomonic of repetitive trauma, in the absence of a history of significant trauma or infection they are consistent with microscopic damage secondary to mechanical compression according to the Hueter-Volkmann principle.
True bony bridges have rarely been demonstrated in specimens from adolescent tibia vara, suggesting that the onset of the repetitive “trauma” occurs once the physis and epiphysis are much more developed than in the infantile form. Furthermore, mechanical realignment to unload the compressed medial physis is usually successful in curing adolescent tibia vara, as is gradual mechanical realignment produced by a lateral epiphysiodesis. Consequently, even though there may be marked clinical deformity and significant radiographic physeal widening (evidence of disruption), the actual histologic insult to the physis must be relatively moderate, as evidenced by its acute or gradual response to mechanical unloading
The additive effect of vitamin D deficiency on a growth plate susceptible to high mechanical loads is under investigation. A retrospective analysis of obese children identified a relationship between vitamin D deficiency and likelihood of adolescent tibia vara. However, confirmation of low vitamin D levels as an independent risk factor for developing Blount disease is not yet determined.
Clinical Features
The typical patient with adolescent tibia vara is a male teenager, often black, whose body weight greatly exceeds 2 standard deviations (SD) greater than the mean ( Fig. 22-17 ). At our institution, patients weighing up to 200 kg in the early teenage years have been treated. The average weight of patients with adolescent tibia vara has been reported to exceed the 95th percentile for age by a mean of 43 kg. Involvement is frequently unilateral, but bilateral cases are also seen. The preponderance of male patients has not been explained.
Patients may seek medical care either because of the deformity itself or because of the deformity with symptoms. Many patients are essentially asymptomatic but, on close questioning, may describe an aching in the medial or anteromedial portion of the knee associated with activity or occurring toward the end of the day. An area of tenderness along the medial joint line is almost universal, and occasionally there are patellofemoral complaints. Internal tibial torsion is frequently present but variable in severity. In unilateral cases, limb length discrepancy is generally present, and the choice of treatment may be influenced by a discrepancy greater than 2.5 cm.
Investigation of other conditions associated with obesity completes the evaluation of an adolescent with tibia vara. Because of the concomitant external rotation of the thigh in obese patients, slipped capital femoral epiphysis might be expected. Simultaneous occurrence of these conditions has been reported but rarely. Of greater concern, a high incidence (61%) of obstructive sleep apnea among adolescents with tibia vara has been recognized at one institution, warranting thorough preoperative evaluation to avoid potential perioperative airway complications in these patients.
Radiographic Findings
Radiographically, the shape of the tibial physis is relatively normal, without the depression and beaking in the metaphysis that are typical of infantile tibia vara ( Box 22-2 ). The sine qua non of diagnosis is widening of the proximal medial physis. This widening may be restricted to the medial fourth of the physis, or it may extend completely across the proximal tibial physis, suggestive of epiphysiolysis, as might occur with slipped capital femoral epiphysis (see Fig. 22-17 ). The widening of the medial tibial physis is significantly more than that on the lateral side of the physis or the physeal width in the normal, contralateral knee. The lack of sloping or inferior beaking of the medial proximal aspect of the tibia (with absence of medial articular depression) suggests that the proximal tibial physis and chondroepiphysis formed and ossified normally for a number of years before being compressed later in childhood, coincident with the weight gain and adolescent growth spurt in a susceptible individual.
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Shape of the epiphysis relatively normal
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Lack of beaking of the medial tibial metaphysis
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Widening of the proximal medial physeal plate, sometimes extending across to the lateral side of the physis
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Widening of the lateral distal femoral physis in comparison to either the medial femoral physis of the same knee or the distal femoral physis of the normal knee
In addition, there may be widening of the lateral distal femoral physis when compared with either the medial femoral physis of the same knee or the distal femoral physis of the normal knee. This traction widening on the lateral side of the varus deformity of the femur would appear to be consistent with Wolff’s law (that bone remodels according to the stress placed on it), although interestingly, there is usually no localized widening of the lateral proximal tibial physis. Distal femoral varus, described in several studies, probably results from the tension overgrowth suggested by localized widening of the lateral proximal tibial physis and can be detected by measuring the lateral distal femoral angle (normal, 88 degrees; range, 86 to 90 degrees). As opposed to the situation in infantile tibia vara, where femoral varus is not routinely present, the femoral varus in an adolescent exceeds 10 degrees beyond normal in nearly 20% of patients. In one report, correction of femoral varus was necessary in nearly two thirds of patients undergoing simultaneous proximal tibial correction.
Distal tibial valgus—presumably a physiologic adaptation to the proximal tibial varus in the same bone—may also develop in a significant number of patients, although this finding has not been consistently present in other series.
Treatment
Treatment is predominantly surgical. Orthotic management in patients with this degree of obesity is impossible and ineffective. Weight loss is undoubtedly desirable and should be recommended. However, it is probably not curative once the deformity is established and, because of the morbid obesity of most patients, is unrealistic to expect. The goal of surgical treatment is to correct the mechanical axis so that physeal growth, if any remains, is restored and degenerative arthritis of the medial compartment of the knee can be avoided. Long-term studies correlating various radiographic parameters with clinical outcome scores and pain scales are currently lacking.
Osteotomy.
High tibial osteotomy is the standard and most direct method to correct adolescent tibia vara. Correction to a neutral mechanical axis is sufficient to restore growth from the medial physis and thus prevent recurrence, although premature closure of the entire physis has been observed after high tibial osteotomy (see Fig. 22-17 ). Overcorrection in adolescent tibia vara is contraindicated, as opposed to the recommended intentional overcorrection into valgus for infantile tibia vara.
There is an interesting dilemma when contemplating correction of the mechanical axis in these patients, in that correction to a neutral mechanical axis in patients with morbidly obese thighs actually produces an unsightly cosmetic result that appears to be excessive valgus. In addition, when these patients undergo correction to neutral alignment, they may have difficulty ambulating because their thighs impinge during normal gait after mechanical realignment (see Fig. 22-17, G and H ). Although undercorrection may invite recurrence of the deformity, it has been our observation that a final femorotibial angle of 0 to 5 degrees varus is probably the best compromise between the mechanical correction desired and the problem posed by the massive proximal thigh girth.
Valgus-producing high tibial osteotomy with rigid internal fixation for acute correction of the mechanical malalignment is probably the most commonly used approach. Again, because of the massive thigh girth, external immobilization with casts is not effective in maintaining alignment of the osteotomy, and rigid internal fixation is far superior. The obvious challenge with this approach is that correct alignment must be achieved at surgery because it cannot be changed postoperatively without reoperation. Loss of fixation and inappropriate intraoperative alignment are causes of postoperative undercorrection or overcorrection. In addition, the well-known complications of high tibial osteotomy (e.g., nerve palsy, compartment syndrome, infection, delayed union or malunion, and in this patient population, the possibility of deep vein thrombosis) make acute correction a formidable surgical task. Special large-circumference tourniquets are required for intraoperative hemostasis, and the logistics of performing high tibial osteotomy in a very obese patient must be taken into account before bringing such a patient into a pediatric operating room.
Emphasis on recognition and treatment of distal femoral varus has added a further dimension of complexity to treatment of adolescent tibia vara. Femoral varus of more than 5 degrees beyond the normal femoral mechanical axis (lateral distal femoral angle >93 degrees) has been reported in more than 50% of patients, with 19% having deformities of more than 10 degrees of varus. Distal femoral varus was corrected acutely in two thirds of limbs undergoing simultaneous proximal tibial osteotomy with correction by external fixation, the indication being mechanical femoral varus greater than 5 degrees beyond normal. The rationale for correction by external fixation (see “Realignment by External Fixation”) is the adjustability of the postoperative limb position to avoid malcorrection in these obese patients, in whom intraoperative control of alignment is challenging. Pain-free and clinically stable knees were reflective of the short-term results studying this comprehensive approach, but avoidance of early degenerative joint disease remains unproven. Because there are no reports comparing these results with proximal tibia osteotomy alone, the value of the additional levels of correction remains uncertain.
Realignment by External Fixation.
The problem of achieving the desired alignment intraoperatively in this patient population is more challenging than is often acknowledged, and the inability to postoperatively adjust internal fixation is a significant disadvantage. In addition, limb length inequality may exist in unilateral cases, and the ability to achieve equalization by lengthening after angular realignment makes external fixation all the more attractive. A direct retrospective comparison of acute versus gradual correction in a small series of patients using external fixation suggested a higher frequency of accurate angulation and mechanical axis correction with the gradual approach, but the clinical relevance of such small differences in radiographic measurements is unclear. The major disadvantages of external fixation are pin or wire complications, which can produce loosening, sepsis, or nerve palsy; and joint stiffness and muscle weakness, which can complicate prolonged treatments. Because the total treatment time with external fixation is definitely longer than the 6 to 8 weeks until union by conventional osteotomy, these disadvantages may have a significant effect on the ultimate outcome.
Three methods of external fixation have been reported. (1) External fixation can be used to align an extremity acutely after complete tibial and fibular osteotomy. (2) Alternatively, a corticotomy technique with gradual correction (distraction osteogenesis) can be performed with either circular or monolateral external fixators ( Fig. 22-18 ). ‡ (3) Hemichondrodiastasis, or asymmetric physeal distraction, has also been used, with mixed results, depending on the rapidity and strength of bony consolidation in the physeal distraction gap. Because of the almost certain physeal closure after physeal distraction methods, use of asymmetric physeal distraction is limited to patients nearing skeletal maturity. The time to consolidation with physeal distraction can be prolonged, and thus this approach appears to offer little advantage over conventional metaphyseal corticotomy.
‡ References .
The trade-off for the postoperative adjustability of external fixators is a prolonged treatment time that averages 12 weeks to union or frame removal and not infrequently takes up to 6 months in the frame. Obese patients may have difficulty engaging in postoperative rehabilitation activities with a circular frame and walker or crutches, thus leading to increased reliance on non–weight-bearing mobility. This, in turn, can slow bony consolidation. Knee discomfort as a result of fixation wires near the joint may compound the immobility; consequently, half-pin techniques that involve more anterior pin placement are better tolerated.Although correction by external fixation has the advantage of postoperative adjustability, the technique is just as formidable as traditional osteotomy. Gradual deformity correction carries a different set of problems related to maintaining function and tolerating longer treatment periods with potential fixation and pin complications.
Lateral Epiphysiodesis.
Because of the potential complications associated with proximal tibial osteotomy and either acute or gradual correction, correction by lateral proximal tibial epiphysiodesis is an attractive alternative procedure. The technique is significantly simpler and associated with minimal morbidity, the only real complication being that angular correction is at times not realized. Assuming that the epiphysiodesis is technically adequate, incomplete or inadequate correction may be due to a medial physis that is simply too suppressed to respond to the tethering effect of the lateral epiphysiodesis. The main disadvantage of lateral epiphysiodesis is that rotational deformity cannot be addressed.
Patients treated with this technique have a 50% to 87% response rate in which correction of the varus malalignment is judged to be satisfactory at maturity and no further treatment is necessary ( Fig. 22-19 ). Our institution reported a failure rate, defined by need for osteotomy or mechanical axis deviation exceeding 40 mm, of 66% following lateral hemiepiphysiodesis. Factors associated with a higher risk of failure included an age older than 14, BMI greater than 45 kg/m 2 , and more severe varus deformity. While variable amounts of correction can be expected, performing a lateral epiphysiodesis in no way complicates subsequent correction by high tibial osteotomy and remains a viable option for initial treatment, particularly in younger patients with mild-moderate deformity. Surgical decision making should weigh the benefits of a less morbid procedure against a more extensive but predictable realignment achieved with an osteotomy.
A lateral epiphysiodesis can be performed either as an open procedure or percutaneously ( Fig. 22-20 ). The percutaneous technique probably has a higher rate of failure because of technical inadequacy of the actual curettage of the physis. In addition, the main advantage of the percutaneous technique, cosmesis, may not be a critical factor in treatment of this patient population. We have found that an open epiphysiodesis performed through a miniincision under fluoroscopic control is reliable in terms of ensuring that the lateral physis is obliterated by curettage under direct vision. A local bone graft from the metaphysis and epiphysis immediately adjacent to the physis is packed into the physeal excavation. In selected patients, a distal lateral femoral epiphysiodesis can also be performed if there is radiographic evidence of distal femoral varus. We have not performed proximal fibular epiphysiodesis as part of the treatment of adolescent tibia vara in the 13- to 15-year-old patient population. A significant difference in fibular overgrowth was reported when proximal tibia epiphysiodesis was performed alone compared with combined fibular epiphysiodesis and controls, with an estimated rate of 3 mm/yr reported from one institution. Unless expected overgrowth exceeds 2 cm, benefits of this added procedure are unlikely because symptomatic fibular overgrowth is not anticipated.
Hemiepiphyseal Stapling.
Lateral hemiepiphysiodesis of the proximal end of the tibia (and distal end of the femur) can also be produced by insertion of Vitallium staples spanning the physis. This procedure, introduced by Blount and Clarke in 1949, theoretically creates the possibility of a transient hemiepiphysiodesis and should be used in younger patients in whom eventual removal is planned when the deformity has corrected, or slightly overcorrected, and growth remains. Stapling can be effective in patients with late-onset tibia vara with mild to moderate deformity and a chronologic age of 12 years or younger. In this setting, 27 of 29 patients obtained a successful or partially successful outcome from stapling, with minimal morbidity from the procedure itself or from a second procedure to remove or revise staples, required in approximately a third of patients. Severe preoperative varus (zone 4 medial mechanical axis deviation in the Mielke-Stevens classification ) and older adolescents with less growth remaining will not benefit from stapling, just as a permanent hemiepiphysiodesis by curettage might also be ineffective.
The timing of the stapling procedure is not as crucial in avoiding overcorrection as it may be in permanent hemiepiphysiodesis, although patient compliance with follow-up is mandatory with either procedure. We have observed that most patients with adolescent tibia vara have advanced bone age, and thus there is a lessened risk for valgus overcorrection with permanent hemiepiphysiodesis in patients older than 11 years. Stapling has its greatest indication in patients younger than 11, in whom valgus overcorrection is a distinct possibility with any form of hemiepiphysiodesis, including stapling, and thus the transient method with appropriate follow-up is more useful.
Hemiepiphyseal Plating.
The advent of extraperiosteal plate and screw systems introduced an alternative method to nonpermanent deformity correction in patients with open physes ( Fig. 22-21 ). The technique employs a tension-band concept as opposed to the physeal-compressive effect exerted by stapling and has proven to be equally effective in restoring mechanical alignment. However, awareness of potential technical pitfalls when using these devices is essential as more mechanical failures have been reported in obese patients characteristic of adolescent tibia vara (see Fig. 22-21 ). The intersection of the screw shank at the lateral cortex in the metaphyseal region accounted for the failures in nearly all cases. Biomechanical testing of different guided growth constructs suggests fatigue strength is superior for solid compared with cannulated screws with stainless steel screws yielding the highest number of cycles to failure. When using extraperiosteal plating in this high-risk population, consider adding a second parallel plate or a single four-hole plate, noncannulated screws, and possibly stainless steel implants to avoid potential screw breakage and the need for revision surgery.
Tibia Vara Secondary to Focal Fibrocartilaginous Dysplasia
Occasionally, an infant or toddler is seen with unilateral varus of the tibia, the deformity appearing slightly more distal than the knee joint itself. If the child has reached standing age, hyperextension of the knee may also be noted ( Fig. 22-22 ). This latter finding is not usually present in a toddler with infantile tibia vara, although the lateral thrust seen in stance phase can mimic this deformity. The radiographic finding of focal fibrocartilaginous dysplasia separates this entity from infantile tibia vara, as do the pathologic findings discovered during surgical treatment.
Radiographic Findings
Radiographs of focal fibrocartilaginous dysplasia ( Box 22-3 ) show a characteristic abrupt varus at the metaphyseal-diaphyseal junction of the tibia, clearly not involving the physis (see Fig. 22-22, C ). There is cortical sclerosis in and around the area of the abrupt varus on the medial cortex. A radiolucency may appear just proximal to this area of cortical sclerosis, which probably corresponds to the fibrocartilaginous tissue found at surgery in the area of insertion of the pes anserine tendons. The etiology of this defect and the pathogenesis of the deformity are unknown.
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Abrupt varus at the metaphyseal-diaphyseal junction of the tibia not involving the physis
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Cortical sclerosis in and around an area of abrupt varus on the medial cortex
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Radiolucency possibly appearing just proximal to the area of cortical sclerosis
Treatment
The importance of recognizing this variation of infantile tibia vara is that the deformity can resolve without surgery. Some 60 cases of tibia vara secondary to focal fibrocartilaginous dysplasia have now been reported, with slightly more than half spontaneously correcting because of the normal proximal tibial physeal growth. Surgical treatment may be necessary if the deformity progresses or fails to resolve during a period of observation or orthotic management (see Fig. 22-22 ). In most reported cases, the deformity resolves without osteotomy, particularly if the varus is less than 30 degrees. Some authors advocate long-term follow-up despite spontaneous resolution because progressive limb length discrepancy may result.
In two of three patients treated at our institution, the deformity resolved without surgery. Another patient, treated several years before the first report of this condition in 1985, had radiographic findings characteristic of both infantile tibia vara and, in retrospect, focal fibrocartilaginous dysplasia ( Fig. 22-23 ). The condition responded nicely to orthotic management. The consensus treatment of nonoperative management (observation, orthosis) appears to be sound, with a corrective high tibial osteotomy becoming necessary only when the deformity fails to resolve or progresses.
Genu Valgum (Knock-Knees)
Valgus alignment of the lower extremities is normal in a child between 2 and 8 years old ( Fig. 22-24 ). The maximal amount of physiologic valgus occurs between the ages of 2 and 4 years, after which the alignment of the lower extremity assumes a mild valgus femoral–tibial angle, the normal alignment in an adult. Therefore, by 8 years old there should be little or no change in alignment of the lower extremity ( Fig. 22-25 ), and preparation for treatment of what is deemed excessive physiologic valgus may be made at this age.