Rotational Osteotomy of The Tibia

Ronald J. Van Heerwaarden

Robert A. Teitge

INTRODUCTION

Pathogenesis

Congenital torsion deformities of the lower extremity may be a consequence of growth disorders of the acetabulum, femur, tibia, or foot and may be the cause of substantial functional limitations and symptoms at the hip, knee, and ankle joints in adolescents and adults.¹,²
The antetorsion of the acetabular fossa at birth remains to a large extent unchanged during growth. Minimal changes may be seen depending on the development of the femoral head. In contrast, the femur and tibia, which are aligned in internal rotation at birth, rotate externally during childhood. No further changes in acetabular antetorsion or femoral and tibial rotation are to be expected after the age of 8 years.³,⁴,⁵,⁶
Excess femoral anteversion may or may not be associated with increased external tibial torsion.⁵,⁷,⁸ This is often called compensatory with no evidence that it is a compensation.
Congenital torsion deformities can lead to serious symptoms and cause functional limitations of all joints of the lower extremity in adolescence and adulthood.
The joint most frequently affected is the knee because it has very little ability for rotatory compensation compared with the hip or upper ankle joint.⁵,⁷,⁹,¹⁰
Torsional malalignment of the lower extremity can result in increased patellar contact pressure with secondary retropatellar cartilage damage or retropatellar joint degeneration or patellofemoral malalignment with subluxation/dislocation of the patella.²,⁵,⁷,⁹,¹¹,¹²
The contribution of abnormal femoral or tibial torsion to osteoarthritis of the knee is not yet clear. Yagi¹⁰ reported increased internal tibial torsion in association with varus medial compartment osteoarthritis. Goutallier et al¹³ reported that increased femoral anteversion was associated with decreasing joint space in the lateral knee compartment after valgus HTO for medial compartment arthritis.
Torsion deformity of the leg affects gait pattern and heel-to-toe weight bearing and can lead to arthrotic alterations because of unphysiologic load distribution at the upper ankle joint and foot.⁹

Nomenclature

The term “torsion” describes the physiologic rotation of a bone segment in the longitudinal axis, for example, of long bones such as the femur and tibia. In contrast, the term “rotation” defines rotation between two bone segments and, therefore, describes relationships at a joint, for example, internal or external rotation of the hip joint.
Torsion angle is defined as the angle of alignment of the distal joint axis of a long bone in relation to the alignment of the proximal joint in the transverse plane.
Different authors have used different lines to define the proximal and distal transverse plane tibial axis; therefore, the literature is widely divergent on what is normal. A recent review indicates that the published range of normal values for tibial torsion is 14° to 41.7°. Rosskopf stated 30° was average normal, Jend stated 41° was average normal, Turner used clinical observation with caliper on the malleoli of the ankle and a marker on tibial tuberosity (he does not define a tibial axis) and stated an average of 19° is normal with a range of 15° to 25°. Strecker reported 34° average as normal. Most of these publications fail to define the exact method of torsional measurement and this can be challenged. It is also challenging to decide what values are truly normal. Most studies do not start with a measure of tibial specimens-only radiographic images.
Yagi¹⁰ reported tibial torsion as 23.5° ± 5.1°. Yagi based the study on 13 normal control subjects using CT scan, without specifying cut levels or providing examples of measurements.
Standard values differ across different ethnic groups.¹⁴

Pathological torsion has been defined as two standard deviations outside of the normal values, but the evidence for pain or functional limitation is incomplete.⁸

TABLE 36.1 Indications and Contraindications for Rotational Osteotomy

Indications	Contraindications
Since the etiology of pain and functional impairment is usually multifactorial, there is no evidence for suggesting specific torsion angles as indications for surgery. Correction should be performed at the level of the deformity because compensatory rotational osteotomy at an unaffected site will only make the deformity more complex.	Isolated torsion deformities of the leg without clinical symptoms do not require correction. If there are clinical signs but pathologic torsion is only slight (up to two standard deviations from the norm on the computed tomography scans), conservative treatment is recommended.

Table 36.1 lists indications and contraindications for rotational osteotomy. Since the etiology of pain and functional impairment is usually multifactorial, there is no evidence for suggesting specific torsion angles as indications for surgery.

EVALUATION

Physical Examination and Findings

Clinical examination must evaluate the alignment of the lower extremity in both the frontal and the sagittal planes. Particular attention must be paid to the alignment of the patellae and the position of the feet. In the absence of patello-femoral pathology the patella usually rests near the center of the distal femur. The tibia normally has an external tibial torsion, so with the patella pointing forward the foot posts slightly outward.
A medial pointing patella, valgus weight-bearing axis or inward pointing of the foot may indicate increased internal torsion of the femur. Outward pointing of the knee, patella, or foot may indicate femoral retrotorsion.
Similarly, a lateralized patella, varus weight-bearing axis, or external rotation deformity of the feet may indicate femoral retrotorsion.
Miserable malalignment was defined as a combination of deformities by Stanley James in 1979. He stated the clinical picture with miserable malalignment as characterized by femoral anteversion, squinting patellae, genu varum, patella alta, increased Q angle, external tibial rotation, tibia varum, and compensatory pronation of the feet. The increased Q angle is a manifestation of the inward-pointing knee as is the squinting patellae, and the external tibia rotation is probably due to external tibial torsion.
Staheli⁸ stated that an indication for tibial osteotomy would be foot-thigh axis 3 standard deviations beyond normal. He recommended supramalleolar osteotomy.
The assessment protocol by Staheli is well suited to determine the exact location and extent of a deformity.⁴,⁸
First, the gait pattern is analyzed and the rotational alignment of the foot is assessed. The forefoot is normally positioned in 10° to 35° external rotation at the moment of touchdown.
Next, the internal and external rotation capabilities at the hip are analyzed with the patient in the prone position. There is a wide range of normal internal and external rotation of the hip, whereby attention must be paid to side-to-side differences.
The angle between the foot axis and a straight line through the thigh is measured with the patient in the prone position, the knee in 90° flexion, and the upper ankle joint in the neutral position (norm: 10°-30°). Here, the focus is on the lower leg torsion although possible foot deformities (eg, crescent-like feet, clubfoot) must be taken into account.

Imaging

Mathematical formulae can be applied to diagnose femoral and tibial torsion from conventional x-rays.⁷,¹²
Axial computed tomography (CT) will, however, simplify precise measurement of these angles. Imaging is performed with the patient in the supine position with the legs parallel.
Scans are obtained at the level of the femoral head, at the base of the femoral neck, at the femoral condyles, at the tibial condyles, and at the level of the ankle joint. The method for obtaining the torsion angles is illustrated in Figure 36.1.
The tibial tubercle-trochlear groove (TT-TG) distance is measured. It is normally 10 to 15 mm. It is not a measure of torsion. The TT-TG measurement must be corrected for any rotation of the tibia on the femur, which is common with patellar instability.¹,¹⁵

SURGICAL MANAGEMENT

Preoperative Planning

Osteotomy Technique

The osteotomy techniques presented here aim to correct the deformity by a one-stage correction osteotomy. Multidimensional and gradual corrections with application of external fixation systems (unilateral fixator, ring fixator) are not the subject of this chapter.³,¹²,¹⁶
Osteotomy techniques depend on the planned fixation method.
Percutaneous drill osteotomy or the use of a Gigli saw through a mini skin incision is appropriate for an intramedullary nail or external fixator.
Application of an intramedullary saw followed by intramedullary nail fixation can be used for osteotomy of the diaphysis of the long bones.¹⁷
Osteotomy with the oscillating saw permits better visualization of the osteotomy plane but requires a more invasive approach and may lead to heat-induced bone necrosis.

Figure 36.1 Computed tomography measurements of torsion angle of the femur and the tibia by superimposition of axial cuts at the hip, knee, and ankle. A, Femoral torsion angle is the angle between the line that connects the center of the femoral head and the center of the base of the femoral neck (from two superimposed sections at these levels) and the tangent at the posterior femoral condyles measured in the transverse plane. B, Tibial torsion angle is the angle between the posterior tangent of the proximal tibial condyles and the central distal transmalleolar axis after cessation of growth.

Osteotomy Level

Growth and healing potential in the metaphyseal zone of the long bones is excellent, whereas the diaphyseal region has a longer bone consolidation time.

The proximal tibia can be osteotomized inferior or superior to the tibial tuberosity.

Figure 36.2 Level of rotational osteotomy at the proximal tibia. A, Transverse osteotomy proximal to the tuberosity. B, Transverse osteotomy distal to the tuberosity. C, Transverse osteotomy at the level of the tuberosity with anterior saw cut ascending obliquely in a cranial direction. D, Transverse osteotomy at the level of the tuberosity with anterior saw cut descending obliquely in a caudal direction. E, Transverse osteotomy at the level of the tuberosity with separate osteotomy of the tuberosity.

Good bone healing can be assumed for a saw cut in the metaphyseal zone above the tuberosity, but it leaves little room for stable fixation in the proximal segment (Figure 36.2A).
The disadvantage of osteotomy below the tuberosity (Figure 36.2B) is poorer bone consolidation, but it does permit secure fixation of the proximal segment.
A transverse saw cut at the level of the tibial tuberosity will provide better healing potential than a diaphyseal osteotomy.
The tuberosity can be left intact by making an anterior saw cut ascending cranially behind the tuberosity (Figure 36.2C) or a descending oblique cut (Figure 36.2D). In the latter technique, a lag screw is used to prevent avulsion fracture caused by the forces exerted by the patellar tendon.
If a transverse osteotomy at the level of the tuberosity is combined with a separate tuberosity osteotomy (Figure 36.2E), two or three lag screws are recommended for tuberosity fixation.
Osteotomies above the tuberosity must take into account the fact that rotation of the distal segment leads to medial or lateral translation of the tuberosity. The extent of translation can be determined by tracing it from the CT images or by mathematical calculation using the formula given in Figure 36.3.
Rotational osteotomy below the tuberosity is not a problem because the tuberosity remains on the proximal segment and the distance to the femoral trochlea (TT-TG distance) thus remains unchanged after rotational correction of the distal segment.
If it becomes apparent during preoperative planning that the rotational osteotomy will lead to a pathologically increased or decreased TT-TG distance, an alternative osteotomy level or a separate tuberosity osteotomy with appropriate lateral or medial translation of the tuberosity should be considered.

The obvious mechanical effect of external tibial torsion depends on the gait pattern with balanced motion of knee joint and ankle joint. External tibial torsion results in the lower tibia turning outward relative to the upper tibia. In the presence of excess external tibial torsion, if the foot is placed in a forward direction during gait, the knee joint is necessarily pointed inward, which increases the lateral displacement vector of the quadriceps. Osteotomy below the tuberosity corrects this abnormally elevated lateral quadriceps vector. MacWilliams et al performed gait analysis in 10 patients with external tibial torsion before and after supramalleolar internal rotational osteotomy and noted significant differences between normal controls in gait kinematics before surgery with return toward normal after surgery. Restoration of normal foot progression angle was one such variable. Stott and Stevens’ large series of rotational osteotomy below the tibial tuberosity would give credence to the belief that tibial torsion correction below the tuberosity is appropriate. Because tibial torsion is a deformity that misaligns the axis of the knee flexion with the axis of ankle flexion, it is not a deformity of a malpositioned tibial tuberosity. According to senior author (RT), in most cases, the rotational osteotomy should be placed below the level of the patellar tendon insertion. An osteotomy at any location between the patellar tendon insertion and the ankle joint will allow restoration of the proper angle between the knee joint axis and the ankle joint axis without altering a normal trochlear tubercle relationship.

Figure 36.3 Preoperative calculation of tuberosity translation during proximal tibial rotational correction when osteotomy is performed above the level of tuberosity. As per the formula, for the intended rotational correction of 20° and r = 2 cm (based on average normal proximal tibia diameter), the tibial tuberosity will translate 7.2 mm medially after internal rotational correction.

If it is true that the goal of correction is to establish the normal angular relation between the ankle joint axis and the knee joint axis, then an osteotomy anywhere between the tibial tuberosity and the ankle joint should gives equivalent results. The choices are thus a proximal tibial osteotomy below tibial tuberosity, a diaphyseal osteotomy, or a supramalleolar osteotomy. Owing to the good bone healing potential, distal tibial rotational osteotomies should be positioned in the metaphyseal region above the tibiofibular syndesmosis.
Rotation in the diaphyseal region may cause incongruence and clinical symptoms because of the triangular cross section of the tibial shaft.

Soft-Tissue and Neurovascular Structures

Although diaphyseal and distal torsional changes of the tibia may cause twisting and elongation of the muscle compartments or a change in direction of pull of the tendons, functional limitations have not been reported as long as the correction angle is less than 45°.¹²
Because the peroneal nerve runs around the fibula, increased internal torsion of the proximal tibia during internal rotation osteotomy may result in overextension of the nerve or entrapment in the intercompartmental septum between the anterior and the lateral muscle compartments.
The peroneal nerve may be damaged during external rotation osteotomy because of compression within the septum or because of tension in the anterior compartmental fasciae.¹²
This problem can be avoided by careful decompression of the nerve or by performing diaphyseal or distal derotation where the correction angle is greater than 20°.
Distal external rotation osteotomy of the tibia may cause overextension of the posterior tibial nerve
within the posterior compartmental fasciae of the lower leg and tension in the fasciae of the abductor hallucis in the tarsal tunnel.¹² These complications can be prevented by release of both fasciae in the tarsal tunnel.
If more than 20° rotational correction of the tibia is planned, careful decompression of the peroneal nerve is essential in proximal tibial rotational osteotomies or, alternatively, a diaphyseal or distal derotation site should be chosen.
In any case, intracompartmental decompression by fasciotomy is recommended.