Patellar Instability: Osteochondral Fixation & MPFL Repair in Adolescent Case

A 16-year-old female high school junior with a history of recurrent patellar instability experienced left knee pain following a patellar dislocation. The incident occurred when she stepped onto a slippery surface, causing her knee to twist and her patella to dislocate laterally. While the patella spontaneously reduced, she was unable to walk due to pain, swelling, and a sensation of instability. Prior to this, she had been managed with anti-inflammatory medications, crutches, bracing, rest, activity modification, and physical therapy, but had not undergone surgery.

Examination revealed a significant effusion and tenderness along the medial and lateral retinacula. Her range of motion was limited to 0° to 20° of flexion due to pain. The patellar apprehension test was positive, indicating instability. Ligamentous stability was confirmed through varus and valgus stress testing. Initial radiographs showed an osteochondral injury at the median ridge of the patella, without significant degenerative changes in the knee compartments. Further investigation with MRI without contrast revealed a large effusion, a substantial chondral defect in the medial facet, a large loose body within the lateral recess, attenuation of the medial patellofemoral ligament (MPFL), and a normal tibial tubercle to trochlear groove (TT-TG) distance of 12.3 mm.

Understanding Osteochondral Fractures and Patellar Instability

Osteochondral fractures, injuries involving both the cartilage and underlying bone, are not uncommon in the knee, particularly following a traumatic event like a patellar dislocation. The patella, or kneecap, relies on a complex interplay of ligaments and cartilage for stable movement. Recurrent instability, as seen in this patient’s history, can predispose individuals to these types of injuries. The presence of a loose body – a fragment of cartilage and bone – within the knee joint can further contribute to mechanical symptoms like locking, catching, or pain. The MPFL plays a crucial role in preventing lateral patellar dislocation, and its attenuation suggests a contributing factor to the instability.

The TT-TG distance, a measurement used to assess patellar tracking, was normal in this case, suggesting that bony anatomy wasn’t the primary driver of the instability. But, a normal TT-TG distance doesn’t rule out other contributing factors, such as ligamentous laxity or muscle imbalances. As highlighted in recent orthopedic discussions, a comprehensive approach is necessary to address both bony and soft-tissue contributors to patellar instability.

Surgical Intervention: A Combined Approach

Given the patient’s persistent symptoms and the presence of a large loose body, surgical intervention was elected. The procedure involved arthroscopy – a minimally invasive technique using a camera and tiny instruments – to address the loose body and assess the osteochondral defect. The surgical team also considered the possibility of fixing the osteochondral fragment and repairing the attenuated MPFL, with a contingency plan for cartilage restoration if the fragment proved unsuitable for fixation. This staged approach allows for tailored treatment based on intraoperative findings.

The surgery began with a standard arthroscopic examination, confirming a large osteochondral defect on the medial patellar facet. The trochlea, menisci, and cruciate ligaments were found to be intact. The loose body was carefully mobilized and removed. A longitudinal incision was then made to allow for direct visualization of the patella and MPFL. The MPFL was found to be redundant and was subsequently imbricated and repaired using Vicryl suture. The osteochondral fragment was debrided and secured with resorbable compression screws and fibrin glue to promote healing.

Postoperative Recovery and Outcomes

The patient’s postoperative course was favorable. At six months, she had regained full, painless range of motion and demonstrated stable patellar tracking. Radiographs confirmed the stable reduction of the osteochondral fragment and evidence of reintegration into the patella. She was able to return to unrestricted activity. This case demonstrates the potential for successful outcomes with a combined approach of osteochondral fragment fixation and MPFL repair in adolescents with patellar instability.

Successful osteochondral fixation relies on careful assessment of fragment viability and appropriate fixation techniques. Research indicates that early intervention and precise fixation can improve the chances of successful cartilage healing and long-term joint preservation.

The Importance of Comprehensive Evaluation

This case underscores the importance of a thorough evaluation in patients presenting with patellar instability. MRI is a critical tool for identifying osteochondral injuries, loose bodies, and MPFL tears. Understanding the underlying anatomy and biomechanics of the patellofemoral joint is essential for developing an individualized treatment plan. In adolescents, addressing both bony and soft-tissue contributors to instability is crucial for preventing recurrent dislocations and preserving long-term knee function.

The increasing prevalence of patellar instability in young athletes and active individuals highlights the need for continued research and advancements in treatment strategies. Recent scam alerts emphasize the importance of verifying information and seeking guidance from qualified healthcare professionals.

Looking Ahead: Cartilage Restoration and Long-Term Monitoring

While this patient achieved a successful outcome with fragment fixation and MPFL repair, it’s important to recognize that cartilage restoration procedures, such as matrix-induced autologous chondrocyte implantation (MACI), may be necessary in cases where the osteochondral defect is too large or the fragment is not viable. Long-term follow-up is essential to monitor for any signs of recurrent instability or cartilage degeneration. Continued research is needed to optimize cartilage restoration techniques and improve the long-term outcomes for patients with osteochondral injuries.

Kevin Credille, MD; Sanjiv Gopalkrishnan, MD, MBA; Robert Jack, MD; and Jennifer Liu, MD, can be reached at Houston Methodist Hospital in Houston, Texas. Credille’s email: [email protected]. Gopalkrishnan’s email: [email protected]. Liu’s email: [email protected]. Jack’s email: [email protected].