Miscellaneous Complex Pathological Conditions of the Knee





Introduction


In addition to common knee pathologies which present to a sports medicine practice, there are other relatively uncommon pathologies which rely on one’s physical examination skills and knowledge of anatomy to correctly diagnose and treat. This chapter reviews some of these less common and treatable knee pathologies.


Lateral Patellar Facetectomy


Isolated patellofemoral arthritis (PFA) is a common musculoskeletal condition affecting up to 24% of women and 11% of men older than age 55 years. The lateral patella facet is more often involved, with up to 90% of patients with isolated PFA experiencing involvement of the lateral portion of the patella. Isolated PFA and subsequent anterior knee pain can lead to significant limitations in both activities of daily living and recreational activities and athletics. Nonoperative treatment modalities such as patellofemoral taping or bracing, physical therapy with an emphasis on patellofemoral mobility and injection therapy with either corticosteroids or viscosupplementation exist with varying success rates reported. Surgical intervention is considered when pain and dysfunction persist after nonoperative management in patients with a captured patellofemoral joint who have a large overhanging lateral facet.


Arthroscopic partial lateral facetectomy is a viable surgical treatment option for patients with isolated PFA with an overhanging lateral patellar osteophyte who have persistent anterior knee pain after nonoperative management. The primary goals of this joint-preserving procedure are to improve patella mobility and reduce patellofemoral contact pressures on the arthritic lateral facet. Although more invasive procedures such as patellofemoral arthroplasty or total joint arthroplasty with patellofemoral resurfacing exist, arthroscopic partial lateral facetectomy is a viable, minimally invasive alternative with less immediate postoperative recovery and morbidity in appropriate individuals. , Patients with advanced tricompartmental osteoarthritis, pain in other areas of the knee or lateral patellar instability should not be considered for this procedure.


Preoperative Evaluation


A thorough physical examination of the knee preoperatively and during an examination under anaesthesia is performed with particular attention paid towards patellar mobility, instability, position and potential crepitus. Standard knee radiographs, including a Merchant or sunrise view, should be obtained. The presence and size of the lateral patellar osteophyte and the amount of resection required can be calculated from the preoperative sunrise radiograph .




Fig. 37.1


Excision of the fabella performed in a right knee under direct visualisation. After the arthroscopic identification of the fabella and evaluation of the surrounding tissues, the excision is performed. Care must be taken to avoid damage to the lateral gastrocnemius tendon, which is in proximity.

Reproduced with permission from Provencher MT, Sanchez G, Ferrari MB, et al. Arthroscopy-assisted fabella excision: surgical technique. Arthrosc Tech. 2017;6(2):e369–e374.


Surgical Technique


The patient is placed supine on an operating table with the operative leg placed into a leg holder (Mizuho OSI, Union City, CA) and the nonoperative leg placed into a well-padded abduction leg holder. The operative extremity is prepped and draped in a sterile fashion, and a well-padded thigh-high tourniquet is inflated to achieve exsanguination for a bloodless operative field. Standard anterolateral and anteromedial arthroscopic portals are made, and a 30-degree arthroscope is introduced into the knee. A diagnostic arthroscopy is performed in all compartments of the knee, and any associated pathological condition, such as meniscal injury, loose bodies or loose chondral flaps, is addressed.


Direct visualisation and confirmation of impingement of the lateral patellar osteophyte with the trochlea is made by taking the knee through a full range of motion with the arthroscope in the anterolateral portal. A radiofrequency device is then used to delineate the amount of lateral facet to be removed based on intraoperative findings and preoperative planning. A 5.5-mm burr is then used to remove the lateral patellar facet with a burr under direct visualisation with the knee held at 20 degrees of flexion. The typical width for resection is, at a minimum, 5.5 mm, which equals one width of the burr. Resection is typically started at the inferior aspect of the patella, which helps prevent both under- and overresection of the lateral patellar facet resection. Once the appropriate amount of the lateral facet has been removed, patella tracking is reexamined. There should be no residual impingement, patellar mobility should be improved and there should be no residual catching of the patella as the knee is brought into flexion. The superolateral aspect of the patella can at times be difficult to reach, and a third accessory portal can be made if residual impingement or any sharp bony edges remain in this area. Great care should be taken during resection to preserve the overlying lateral patellar retinaculum. Resection from the joint side and careful respect of the lateral soft tissues can help avoid injury to the lateral retinaculum and resultant iatrogenic medial patellar instability. Once dynamic visualisation confirms adequate lateral facet resection, haemostasis with a radiofrequency device is achieved, the portal sites are closed and a sterile dressing is applied. Table 37.1 lists pearls and pitfalls for this procedure.



TABLE 37.1

Pearls and Pitfalls for Lateral Patellar Facetectomy
















Pearls Pitfalls
Appropriate candidate selection Generalised patellofemoral and advanced tricompartmental osteoarthritis are contraindications.
Proper preoperative planning of resection Underresection of bone can lead to persistent pain and inferior outcomes; overresection can compromise the lateral soft tissue attachments.
Protection of the lateral retinaculum and vastus lateralis attachment Soft tissue disruption can lead to iatrogenic medial patellar instability.


Postoperative Rehabilitation


Patients are allowed range of motion as tolerated, and flexion/extension exercises are encouraged immediately after lateral facetectomy. Although weightbearing is allowed as tolerated, crutches are encouraged during the first week until patients are able to walk with no visible limp. Patella mobilisation, quadriceps and hamstring exercises and stationary biking with no resistance are encouraged immediately as well. At postoperative week 3, balance exercises and toe and heel raises are initiated, followed by swimming and 7% incline treadmill walking at week 7. Return to sport as tolerated by the patient typically occurs around postoperative week 20.


Outcomes


Arthroscopic partial lateral facetectomy has been shown to be a safe, minimally invasive surgical treatment option for patients with isolated PFA of the lateral facet. In a prospective case series of 20 patients, Marten and De Rycke reported 90% good to moderate results at a mean follow-up of 2 years. Yercan et al. reported a sustained improvement in functional scores in 11 patients at an average follow-up of 8 years. An additional study involving 39 knees demonstrated Knee Society Score improvement in 84% of patients, with only 30% of subjects progressing to an arthroplasty procedure at an average follow-up of 10 years. A similar retrospective review by Wetzels et al. of 62 knees showed progression to arthroplasty in 39% of patients at an average of 8 years after partial lateral facetectomy. Furthermore, studies have demonstrated equivalent complication rates and successful outcomes of patellar arthroplasty in patients with a history of prior lateral facetectomy. ,


Several investigators have questioned the utility of adding an open lateral release or a tibial tubercle osteotomy to a partial lateral facetectomy. The addition of these procedures has failed to demonstrate a statistically significant improvement in outcomes compared with a partial lateral facetectomy alone, and therefore they have not been recommended. ,


In conclusion, arthroscopic partial lateral facetectomy is a viable surgical treatment option for patients with isolated patellar arthritis with anterior knee pain, a captured patellofemoral joint and an overhanging lateral patellar facet osteophyte. Although results in the literature appear promising, additional long-term studies are necessary to compare partial lateral facetectomy with more invasive arthroplasty procedures for management of isolated PFA.


Fabella Excision for Fabella Syndrome


Preoperative Evaluation


The fabella is a sesamoid bone located in the tendon of the lateral head of the gastrocnemius muscle. Its presence in the general population is variable, ranging anywhere from 20% up to 87%. Although the vast majority are asymptomatic, individuals with a fabella can sometimes present with posterolateral knee pain that is particularly worse in full extension when the fabella is compressed against the posterior lateral femoral condyle. , Occasionally numbness or radicular pain can develop if the common peroneal nerve is also involved. , Focal posterolateral knee pain can result from cartilage softening and degeneration and periosteal inflammation from mechanical compression on either the lateral femoral condoyle or the fabella itself. , A complete and thorough knee examination is essential to rule out any potential ligament or meniscal injury because the findings associated with fabella syndrome are often nonspecific. Reproducible tenderness to palpation at the lateral gastrocnemius insertion on the femoral condyle is often the only finding present.


Plain radiographs are routinely performed to confirm the presence of a fabella. Magnetic resonance imaging (MRI) can help exclude any other associated pathological conditions in the differential diagnosis for posterolateral knee pain. In cases of isolated fabella syndrome, MRI can also at times reveal thickening of the lateral gastrocnemius tendon, inflammation and oedema around the fabella itself, as well as evidence of grooving or compression of the articular cartilage of the lateral femoral condyle. ,


After fabella syndrome has been appropriately diagnosed, a trial of nonoperative management should be entertained for a minimum of 6 months before surgery should be considered. Steroid injections into the area of maximal tenderness and activity modification have been shown to be beneficial in some cases.


Surgical Technique


Preoperative setup


The patient is placed supine on an operating table with the operative leg placed into a leg holder (Mizuho OSI) and the nonoperative leg placed into a well-padded abduction leg holder. The operative extremity is prepped and draped in a sterile fashion, and a well-padded thigh-high tourniquet is inflated to achieve exsanguination for a bloodless operative field.


Incision and exposure


After the operative knee has been prepped and draped, surface anatomy landmarks including the Gerdy tubercle, the fibular head, the lateral joint line and the iliotibial (IT) band should be marked. A roughly 8 cm long incision from the Gerdy tubercle extending proximally along the course of the posterior border of the IT band centred over the lateral joint should be made with sharp dissection. The IT band should be incised along the same course as the previously made skin incision with great care taken to avoid deep dissection and resultant injury to the popliteus tendon, anterolateral ligament or fibular collateral ligament (FCL). Additionally, dissection should never proceed posterior to the long head of the biceps tendon to avoid injury to the common peroneal nerve. Blunt dissection anterior to the biceps femoris is carried out through the interval between the lateral gastrocnemius and the FCL, aiming distally and medially to the fibular head. Adhesions between the lateral gastrocnemius and the posterolateral capsule can be released with blunt digital dissection or with the use of a Cobb elevator.


After the adhesions have been released, digital palpation is used to identify the fabella, which is then secured with an Allis clamp ( Fig. 37.1 ). Arthroscopy is performed before fabella excision to limit fluid extravasation before intraarticular pathological conditions are addressed. After diagnostic arthroscopy, a 70-degree arthroscope is used to create a posterolateral portal and to verify friction of the fabella with the posterior lateral femoral condyle under direct visualisation ( Fig. 37.2 ). Once all intraarticular work is completed, either a 30-degree or 70-degree arthroscope is used to aid in fabella excision under direct visualisation to minimise capsular tissue removal during excision. After the fabella has been excised, the arthroscope is used to confirm complete removal and elimination of the friction and compression through a full range of motion.




Fig. 37.2


Arthroscopic visualisation of the fabella and the surrounding structures performed in a right knee. The arthroscopic portion of the procedure is performed after the open identification of the fabella. A diagnostic arthroscopy is performed in all the compartments to evaluate associated injuries. After this, a needle is used to delimit the margins of the fabella. This allows for proper identification of the fabella and avoids overresection of the surrounding tissues. F, Fabella; LFC, lateral femoral condyle.

Reproduced with permission from Provencher MT, Sanchez G, Ferrari MB, et al. Arthroscopy-assisted fabella excision: surgical Technique. Arthrosc Tech. 2017;6(2):e369–e374.


Postoperative Rehabilitation


Full range-of-motion exercises as well as quad sets, ankle pumps, and straight leg raises are initiated immediately after surgery to help minimise quadriceps atrophy and stiffness. Weightbearing to tolerance is also initiated immediately after surgery. Crutch use is encouraged until ambulation can be done without a limp. Braces are not routinely used, and full return to competitive sport typically occurs in approximately 3 months.


Outcomes


Because of the rarity of this condition, few studies have been published on the results of both operative and nonoperative management of symptomatic fabella. Weiner et al. reported on the largest case series of patients ( n = 16) with a symptomatic fabella; 11 were treated with surgery and 5 were treated nonoperatively. A total 4 of the 5 patients treated nonoperatively reported continued periodic pain, whereas all 11 patients treated with surgery reported significant relief of symptoms at an average follow-up of 22 months. Several other case reports in the literature have demonstrated significant reduction in symptoms with minimal to no complications after fabella excision. , ,


Arthroscopic Notchplasty


Congruency of the anterior cruciate ligament (ACL) and the intercondylar notch of the femur is an important relationship that must be maintained for the knee to achieve full extension and for patients to have a normal gait pattern. These two structures come into close proximity with the knee in full extension, and in some pathological conditions, such as intercondylar osteophyte formation associated with osteoarthritis, there may be a disruption of this normal relationship, with associated decreased knee extension and function. A notchplasty procedure describes the arthroscopic technique of removal of bone from the intercondylar notch of the femur to reestablish full knee extension. Although this technique is well described in the context of ACL reconstruction in patients with ligamentous instability, its role in the treatment of limited knee extension in patients with degenerative disease is less well documented. The goal of this portion of the chapter is to describe this facet of the notchplasty procedure, including pathoanatomy, mechanics, indications and surgical technique.


Presentation


Patients with intercondylar osteophyte formation leading to decreased extension and ACL impingement may complain of generalised knee pain and stiffness associated with osteoarthritis. They typically describe a gradual onset of symptoms, although many may identify a specific injury or a specific time point of symptom exacerbation. Their physical examinations are remarkable for an extension deficit both with active and passive range of motion. Significant effusions, joint line pain, mechanical symptoms, limping with normal gait and ligament instability should be noted and may indicate additional intraarticular pathological conditions. Standard imaging consists of radiographs, which may indicate degenerative change, particularly intercondylar and anterior tibial anvil osteophyte formation. MRI may demonstrate damage to the ACL from impingement or mucoid degeneration.


Treatment


Nonoperative modalities are the initial preferred treatments for patients with symptomatic osteoarthritis and intercondylar impingement leading to decreased extension. For some patients who fail nonoperative management, arthroscopic notchplasty may be a helpful procedure to regain more normal extension. Patients with advanced degenerative change and significant associated pain may not benefit as much from the procedure, and appropriate preoperative counselling and decision making are imperative in these cases.


For patients who are good candidates for this procedure, an examination under anaesthesia is the first critical step. Range of motion of the affected knee should be objectively assessed and quantified with a goniometer and compared with the contralateral knee. A complete standard examination should also be performed, including a full assessment of effusion, patellar mobility and ligamentous stability.


Once the examination under anaesthesia is complete, the procedure is begun with the creation of a standard anterolateral portal followed by an anteromedial portal under direct visualisation. A diagnostic arthroscopy is subsequently performed to document and address any associated pathological conditions. At this point, attention should be turned to the intercondylar notch, taking care to assess for intercondylar notch and anterior tibial anvil osteophytes. Often there is a visible interface between the osteophyte, which is whiter, and the normal adjacent cartilage of the femoral condyle. Identification of this interface can be helpful to guide resection of the osteophyte. Resection of the osteophyte may then be performed with the use of an osteotome, burr or bone-cutting shaver. For this resection, the camera is typically placed in the anteromedial portal and the working instruments are delivered through the anterolateral portal, although both portals should be used to facilitate a comprehensive and systematic intercondylar osteophyte resection to restore the normal contour of the roof and edges of the intercondylar notch. Care additionally should be taken to remove any resected osteophyte particles to prevent the creation of any loose bodies in the joint. After resection of the intercondylar notch osteophytes, a shaver is used to remove any abnormal or scar tissue in the notch, taking care not to damage the ACL or the posterior cruciate ligament (PCL). Finally, the anterior tibia should similarly be assessed and any associated anvil osteophyte in this region should be resected. Care must be taken to protect the anterior horns of the medial and lateral menisci and the anterior intermeniscal ligament during this portion of the procedure.


After complete resection of abnormal tissue and osteophytes from the intercondylar notch, the knee is again taken through range of motion and improvement in knee extension is assessed and documented with the use of a sterile goniometer. If any additional impingement is visualised, more bone and tissue can be resected to facilitate range-of-motion recovery.


After surgery, patients are weightbearing as tolerated immediately with the aid of crutches for approximately 1 week. They have no restriction on range of motion, and emphasis is placed on full extension recovery and maintenance from the outset. Functional strengthening is typically initiated at 8 weeks postoperatively, and a running progression is started at 3 months. Most patients are able to return to their full level of activity by 4 months postoperatively.


Outcomes


Although the clinical implications of intercondylar impingement are likely still not fully understood, intercondylar notch geometry and volume have been the subject of several studies that have noted differences with respect to age and gender that may be clinically important. , Adjusting the shape and size of the intercondylar notch with a notchplasty procedure is relatively well described in the context of ACL reconstruction for patients with ligamentous instability; however, its role in the recovery of terminal extension in degenerative conditions such as osteoarthritis is less well documented, despite the fact that intercondylar osteophyte formation in osteoarthritis is well understood. León et al. described four different types of intercondylar osteophyte formation depending on lesion of location and type of impingement created.


Although the literature is quite limited regarding the role of notchplasty in the context of osteoarthritis and extension deficit, there are some reports that show good clinical outcomes. Puddu et al. described improvement in knee range of motion after resection of anterior tibial anvil and intercondylar notch osteophyte in their series. Furthermore, León et al. in their description of different types of notch osteophyte formation reported good clinical outcomes after the notchplasty procedure. A survey of experienced knee arthroscopists reported that most considered notchplasty a reasonable procedure to address extension deficit in osteoarthritis, although only 20% of them described good or excellent results with the procedure.


Conclusions


Arthroscopic notchplasty may be a good adjunct technique for some patients to help restore knee extension, which may in turn allow patients to return to their desired activities and prolong the life of their native knee in cases of degenerative disease. Careful patient selection and diligent surgical technique are critical to successful outcomes with this procedure.


Snapping Hamstring Syndrome


Snapping medial hamstring syndrome is the condition of knee pain caused by snapping of the hamstring tendons along the posteromedial knee. The diagnosis can be difficult to make, and the condition is scarcely described in the literature. , Patients may have audible or visible snapping of the hamstring tendons with knee range of motion and loading. Because the condition is rarely described, the symptoms are not easily recognised, a situation that often leads to delayed diagnoses, unsuccessful arthroscopic treatment and prolonged morbidity. Although success after directed surgical treatment of snapping medial hamstring syndrome has been described, there is no consensus on optimal surgical strategy. The goal of this section is to illuminate this clinical entity and describe the known literature on the condition.


Presentation


Although the literature regarding snapping medial hamstring syndrome is made up of case reports and case series, those described in these reports are young, active individuals who describe pain localised to the posteromedial knee associated with audible and palpable snapping with active knee range of motion. Although patients may describe a remote history of injury, most do not recall a specific moment in which their symptoms began and instead report a chronic history of gradual worsening over months to years. Patients characteristically do not endorse swelling or instability but do complain chiefly of mechanical symptoms that are often reproducible in the clinical setting. Symptoms are often exacerbated by loading the flexed knee in a squatting position or with the ascension of stairs. Passive range of motion of the knee may cause fewer symptoms or may not cause snapping at all in these individuals. Patients are often tender to palpation along the pes anserine bursa and proximally extending up the proximal hamstring tendons. They may have generalised medial sided joint pain but typically do not have specific joint line pain or other signs of intraarticular pathological conditions. Diagnosis is typically clinical, although the use of ultrasound has been described.


Treatment


Although successful surgical treatment of this condition is described, there is no standard treatment for snapping medial hamstring syndrome. Nonoperative adjuncts such as physical therapy and localised injections are often prescribed; however, their utility is unclear. Given the rarity of this clinical entity and the lack of a standardised surgical approach, a trial of nonoperative treatment is likely warranted in most patients.


If nonoperative treatment is unsuccessful, several surgical strategies have been used with good results, although the literature is limited to a small number of patients. All strategies have in common a release of the medial hamstring tendons from their insertion on the anteromedial tibia. Geeslin and LaPrade described sectioning of the semitendinosus and gracilis tendons from the anteromedial tibia. Others have harvested the semitendinosus and/or gracilis hamstring tendons completely, , , and one report describes sectioning the semitendinosus with subsequent suture fixation to the semimembranosus. The surgical approach used in these reports has more commonly been described in the context of hamstring harvest for ligament reconstruction.


Discussion


Snapping medial hamstring syndrome is a rare clinical entity only scarcely described in the literature. In a 2010 review, Geeslin and LaPrade described three patients, all successfully treated with surgical intervention. In this series one patient had complete harvest of the semitendinosus hamstring tendon and two had sectioning of the tendons from the anteromedial tibia. All did well clinically, with normal knee function and no recurrent snapping at 2-year follow-up. Before this report, the largest series of patients was a series of four documented by Bollen and Arvinte in 2008. These authors reported clinical success after complete harvesting of both the semitendinosus and gracilis in their patients.


A fundamental knowledge of the anatomy of the medial knee is important for recognition and successful management of this pathological condition. The medial hamstring tendons, known as the pes anserine or ‘goose foot’, insert along the anteromedial tibia in a common insertion. These tendons, the sartorius, semitendinosus and gracilis, originate from the anterosuperior iliac spine, the ischial tuberosity and the ischiopubic ramus, respectively. The semitendinosus has a more posterior course than the gracilis, lying superficial to the semimembranosus, before fusing with the gracilis tendon 1.8 cm proximal to the tendons’ common insertion with the sartorius on the anteromedial tibia. The exact location of the pathological lesion in snapping medial hamstring syndrome is unknown, although patients most commonly report symptoms proximal to the pes anserine insertion in the region of the posteromedial knee. Although surgical treatment for snapping medial hamstring syndrome has been described as hamstring sectioning or harvest, the long-term ramifications of tendon harvest on strength and function are still controversial.


Conclusions


Although reports of this condition are limited, snapping medial hamstring syndrome may represent a significant source of disability and morbidity for some patients. A working knowledge of this clinical entity is invaluable for physicians and providers who treat active individuals with knee pain because recognition and precise treatment may be effective for restoring function and quality of life.


Proximal Tibiofibular Joint Instability


Ogden first described the anatomy of the proximal tibiofibular joint (PTFJ) in 1974 and reported that there were only about 108 cases in the preceding century, making it an exceedingly rare injury. , The rationale for the uncommon nature of this injury is that it is in a protected anatomical location with extensive attachments around the joint that provide it stability. Patients often present with very vague symptoms and sometimes no history of memorable trauma. Therefore the clinical presentation of PTFJ instability is easily confused with other pathological conditions. Patients may even have had previous surgery for some of the other confounding pathological conditions without relief. Such confounding pathological conditions include lateral meniscus tears, FCL injuries, biceps femoris pathological conditions and even IT band syndrome. Data suggest that PTFJ instability may be more common than initially described by Ogden. Volunteers were screened at the San Diego marathon in 1995, and 9 out of 22 volunteers were found to have PTFJ hypermobility. Although hypermobility does not equal symptomatic instability, this study suggests that there might be more laxity and mobility around the joint than was initially thought, and it may not be quite as protected from instability as initially believed.


Anatomy


The PTFJ is a synovial joint with variable shape and orientation, and it communicates with the knee joint in about 12% of cases. The fibula has a triangular cartilage surface, and the tibia has an ovoid or circular articular surface. The most common shape is a saddle or tricoid. More important than the shape is the orientation of the joint. Looking from the lateral radiographic projection, if there is less than 20 degrees off the horizontal axis, it is considered a horizontal orientation. It is an oblique joint if there is more than 20 degrees’ deviation off the horizontal axis. This oblique orientation provides less rotatory stability to the joint, and it is more vulnerable to rotational forces. The oblique orientation is the most common variant, present in up to 85% of individuals. Ogden reported that up to 70% of cases of instability were seen in this more common oblique orientation. ,


The PTFJ has abundant soft tissues attachments. It is reinforced by the PTFJ ligaments, FCL, biceps femoris and popliteofibular ligament (PFL), as well as other muscular attachments. These structures tend to relax in flexion, so there is some normal laxity to anterior translation at 90 degrees of knee flexion. The anatomy around the PTFJ has been further elucidated by Anavian et al. and Marchetti et al. The authors investigated the biomechanical properties and anatomical location of these PTFJ ligaments. The anterosuperior ligaments are the strongest ligaments, with 517 N ultimate load to failure versus the 322 N ultimate load to failure for the posterior ligaments. These numbers are consistent with previous investigations demonstrating the increased relative strength of the anterior ligaments. The anterior ligaments are thicker, and there are one to four thickened bands anteriorly, whereas the thinner posterior ligaments are typically the ones that are injured with instability. Initially one posterior broad band was described. The 2018 study by Anavian et al. demonstrated that two additional posterior ligaments are present in many specimens, although there still remains one predominant band. The middle posterior ligament is the predominant ligament.


Classification


In addition to describing the anatomy of the PTFJ, Ogden also classified the patterns of injury to this joint. Sixty-seven percent of instability cases in his study were anterolateral dislocations. These disrupt the posterior ligaments because they are weaker, and the fibula is able to rotate around the stronger anterior ligaments, often without disrupting them.


The other types of dislocations are less common. Atraumatic subluxations occur in up to 23% of cases. Superior dislocations and posteromedial dislocations are much less common, and the posteromedial dislocations are almost always associated with a peroneal nerve injury.


Treatment


Acute dislocation of the PTFJ is treated with urgent reduction. The reduction can be facilitated by placing the knee at 90 degrees of flexion, dorsiflexing the foot and everting the foot. This relaxes all of the supporting structures around the PTFJ and allows a manual reduction force to reduce the PTFJ. Some experts advocate putting the knee in a long leg cast for about 3 weeks, but others argue that this can be detrimental to knee range of motion (ROM). Either way, weightbearing progresses over 4 to 6 weeks.


The treatment of chronic atraumatic instability is initially conservative. An initial trial of immobilisation for 2 to 3 weeks is employed if pain is a limiting factor. A stabilising strap placed 1 cm down from the fibular head can both aid in the treatment of symptoms and also act as a diagnostic tool to help confirm the diagnosis. Activity modification should include avoidance of deep squats. Despite conservative measures, up to 57% of people will continue to experience pain and chronic instability that ultimately requires surgical intervention. There are many described surgical techniques for this pathological condition, ranging from arthrodesis with midfibular osteotomy to proximal fibular head resection to some nonanatomical reconstructions. , Using local autograft such as biceps and IT band can compromise some of those structures that provide accessory stability to the PTFJ, and nonanatomic reconstructions can overconstrain the knee or stretch out over time. Therefore the authors of this publication advocate for an anatomically based reconstruction using semitendinosus autograft. This anatomically based reconstruction, described by Horst and LaPrade in 2010, reconstructs the central band of posterior ligaments.


Surgical Technique


Horst and LaPrade described an anatomical reconstruction of the posterior proximal tibiofibular ligaments using a semitendinosus autograft through fibular and tibial tunnels. , The procedure starts out with an examination under anaesthesia, which will often demonstrate laxity, even in full knee extension. A lateral hockey stick incision is made with a posteriorly based skin flap. The common peroneal nerve is identified, and 6-cm peroneal nerve neurolysis is carried out. Great care must be taken, however, because any subluxation of the fibular head during the approach can distort the anatomy, putting the nerve at slightly increased risk for iatrogenic injury. The fibular head is then exposed, and dissection is carried out posterior to the fibular head between the peroneal nerve and the biceps femoris tendon. The interval between the lateral head of the gastrocnemius tendon and the soleus muscle is entered, and the soleus is elevated off of the posterior fibula and tibia to expose the entirety of the posterior PTFJ. A retractor is placed anterior to the lateral head of the gastrocnemius to protect the neurovascular structures. A 2.4-mm guide pin is placed from anterior to posterior in the fibula exiting in the anatomical location of the posterior proximal tibiofibular ligaments on the fibula using an aiming guide. A 6-mm tunnel is then reamed through the fibula. This is an anteroposterior tunnel centred in the fibular head. Great care is taken not to be too proximal and to be in the centre of the bone so as not to break out the cortex of the proximal fibula. The anteroposterior nature of this tunnel serves two purposes. It more accurately reconstructs the posterior ligaments, and it avoids damaging the insertion of the FCL, which inserts laterally onto the proximal fibula near the same level.


Dissection is then carried anterior on the tibia; the tibial tunnel starts on the flat spot on the anterior tibia that lies between the Gerdy tubercle and the tibial tubercle and exits posteriorly on the tibia, approximately 1 cm medial and 1 cm proximal to the exit point of the fibular tunnel. A 2.4-mm guide pin is drilled into the appropriate position and checked with fluoroscopy if needed. A 6-mm tunnel is similarly reamed for the tibial tunnel. Of note, a Chandler-type retractor should be placed in front of the lateral head of the gastrocnemius during all drilling and reaming to protect the posterior neurovascular structures ( Fig. 37.3 ). Once the tunnels have been drilled, a semitendinosus autograft is harvested in standard fashion and prepared with a whipstitch on each end. The graft is passed through the fibular tunnel and fixed in place with a 7- by 23-mm interference screw in the fibula. The remaining graft is brought from posterior to anterior through the tibial tunnel ( Fig. 37.4 ). The PTFJ is then reduced, and the graft is tensioned with the knee in 60 degrees of flexion and neutral rotation. It is fixed with a 6 mm interference screw in the tibial tunnel. This completes the reconstruction. The excess of the graft is then excised, and the wounds are closed in standard fashion.


May 3, 2021 | Posted by in ORTHOPEDIC | Comments Off on Miscellaneous Complex Pathological Conditions of the Knee
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