The knee consists of 2 primary articulations—the tibiofemoral joint and the patellofemoral (PF) joint. The PF joint is composed of the patella and the femoral trochlea. Throughout normal range of motion, the shape of the trochlea, as well as the surrounding soft tissues, including the medial patellofemoral ligament, medial retinaculum, and vastus medialis muscle, holds the patella within its groove. Occasionally, the PF joint becomes unstable, leading to the sensation of the patella slipping out of place. When a patient develops subluxation or dislocation, the condition is referred to as PF instability.
Treatment of the young (age 15 to 40 years) athletic patient with PF instability poses a significant challenge to orthopedic surgeons. Athletes place high demands on their PF joints, as demonstrated by studies showing peak PF joint compressive forces between 5 and 6 times the body weight during running activities.1,2 Treatment options for PF instability include both operative and nonoperative management. The majority of patients experiencing PF dislocation can be treated nonoperatively, with a 73% satisfaction rate following nonsurgical management, as reported by Garth et al.3 However, a minority of patients can develop persistent symptoms of instability following a 1-time dislocation event, resulting in inability to return to prior activity levels. Following dislocation, recurrent symptoms are typically due to laxity of medial restraints within the medial PF ligament (MPFL) and its deep capsular layer.4,5
The natural history of patellar dislocation following nonoperative management yields a recurrence rate between 15% and 44%.5–7 In the athletic population, the recurrence rate may be higher due to the demands placed on the PF joint during athletic competition. Athletes with valgus alignment of their knee are especially at high risk for PF instability. This type of alignment causes these athletes to have a wider Q angle than normal (usually 14° in men and 17° in women). With a Q angle >20°, the patella becomes malaligned laterally within the trochlear groove (PF maltracking), leading to subluxation and/or dislocation. The need for an effective and durable surgical intervention is essential in this population of athletes who are at higher risk of failing conservative treatment.
Physical examination of athletes presenting with suspected PF instability begins with a gait assessment and visual inspection of both knees. The examiner then performs palpation of the medial and lateral facets of the patella for tenderness. The apprehension test (manual subluxation of the patella laterally) is then performed with the knee in both full extension and 30° of flexion. Medial, lateral, superior, and inferior translation of the patella are likewise assessed. The examiner can then attempt to displace the patella in a distal lateral direction (by approximately 2 cm) with the knee flexed to 30° in an effort to detect for disruption of the MPFL.
Positive PF instability test criteria include ease of patellar translation and a softer end point compared with a normal knee.8 Following inspection, palpation, and stability testing, the knee should be brought through a range of motion while the physician assesses for crepitation. Crepitus of the PF joint can be of synovial or arthritic origin; the former is deemed present by a snapping sensation, whereas the latter is marked by a fine, grinding sensation. The PF compression test (performed with the patient flexing and extending the knee while the examiner manually compresses the patella) should be performed, and it is considered positive if the patient complains of pain or discomfort throughout the movement. The presence or absence of a J sign (proximal and lateral deviation of the patella with terminal knee extension) is also noted.
Athletes who have sustained a patellar dislocation or who experience recurrent instability without dislocation should initially undergo a prolonged course of nonoperative management. If aggressive functional rehabilitation, patellar bracing, or patellar taping are unsuccessful in improving joint stability, patients may require surgical intervention to facilitate return to their sport. A variety of studies have described surgical techniques for recurrent PF instability and associated patellar pathology.9–20
To determine candidacy for surgical realignment, all patients should undergo the following bilateral radiographs to assess patellar tilt and position: standing anteroposterior view, merchant (45°) view, standing anteroposterior 45° flexion view (Rosenberg view), and 30° flexed lateral view (Figures 1 and 2). Patella alta (high-riding patella) versus patella baja (low-riding patella), patellar tilt (lateral tilt associated with instability), and the presence of osteochondral fragments or arthritic changes are noted. Preoperative magnetic resonance imaging should be obtained on all patients to assess for associated meniscal and chondral injuries and to evaluate the status of the MPFL. For cases in which the MPFL is attenuated and persistent laxity is demonstrated, a medial reefing procedure (tightening of the soft tissue capsule and ligament medial to the patella) is performed to further enhance patellar stability.
Figure 1. Preoperative flexion lateral radiograph demonstrates patella alta, with the inferior pole of the patella significantly higher than Blumensatt’s line.
Figure 2. Preoperative sunrise view of the knee demonstrating lateral patellar subluxation and lateral tilt.
If a patient is deemed appropriate for surgical repair of PF instability, several surgical options are available. The cornerstones of the surgical approach include: (1) correction of malalignment; (2) correction of patella alta; and (3) unloading of the PF joint. The authors’ procedure of choice involves a modified Fulkerson osteotomy with arthroscopic lateral release (Figures 3 and 4). The Fulkerson osteotomy involves cutting and moving the tibial tubercle from its native location to a more medial (inner) and anterior (forward) position. The tubercle is fixed to its new position with screws. Arthroscopic lateral release allows for a minimally invasive release of the tight tissues along the lateral (outer) aspect of the patella. Overall, this procedure allows for correction of patella alta and malalignment via distalization and medialization of the tubercle, respectively, while unloading the damaged or at-risk distal medial facet of the patella via anteriorization of the tubercle.
Figure 3. The osteotomy is directed postero-laterally while beginning along the medial border of the patellar tendon.
Figure 4. Postoperative radiograph demonstrates a healed osteotomy and correction of patella alta.
Following this procedure, patients are evaluated at regular intervals: 1 and 6 weeks, 3 and 6 months, and 1 year postoperatively. All patients are placed on a continuous passive motion machine for 7 to 10 days postoperatively, which is continued until 110° of flexion and full extension are achieved. For the first 6 weeks, patients are allowed to bear weight as tolerated, with a functional knee brace locked in extension. Goals during this first rehabilitation phase include quadriceps activation and acquiring range of motion from 0° to 90° of flexion. After 6 weeks, the brace is unlocked and closed-chain exercises and strengthening are initiated. The brace is discontinued after full range of motion and quadriceps control are achieved, typically approximately 8 weeks postoperatively. Return to full, unrestricted activity is usually allowed 4 to 5 months after surgery, given adequate quadriceps strength and restoration of full range of motion.
Recently, we reviewed a series of 34 athletes21 who presented with patellar instability and failed nonoperative management and ultimately underwent surgical correction via modified Fulkerson osteotomy and arthroscopic lateral release. As mentioned above, the osteotomy addresses the underlying malalignment predisposing the patient to PF instability. In this study, 97% of the athletes were successfully returned to their previous level of athletic competition.
An alternative procedure that has proven useful in the surgical management of PF instability is MPFL repair or reconstruction because this ligament is commonly disrupted in acute lateral PF dislocation events. The majority of MPFL injuries occur at the femoral site. In this procedure, following diagnostic arthroscopy, an incision is made between the patella and the medial epicondyle, and the MPFL is identified by its location deep to the vastus medialis (the most medial quadriceps muscle). The MPFL can then be repaired directly to the bone with suture anchors or can be reconstructed with autograft or allograft tissue augmentation.22–27
Patellofemoral instability is a complicated pathology that can be extremely frustrating for athletes, coaches, and physicians. The goals of treatment involve strengthening the muscles around the knee joint, particularly the quadriceps muscles. If nonoperative treatment fails, surgical approaches revolve around reestablishing the patient’s knee anatomy in such a way that allows adequate tracking of the patella within the trochlear grove. With proper surgical technique and strict compliance with postoperative rehabilitation, most athletes can expect a complete return to full activity.
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