The current standard of care treatment of first-time patellofemoral dislocations is nonoperative care. Often, patients are not seen by an orthopedic surgeon after their first instability episode. In the literature, the incidence of recurrent instability following the first episode is controversial; but skeletally immature patients are emerging as a high-risk group.
A retrospective study from the Mayo Clinic identified open or closing distal femoral physis as a major risk factor for recurrent instability after a first dislocation. When skeletally immature patients also exhibited trochlear dysplasia as identified on lateral knee radiographs, the risk of recurrence was found to be nearly 70%. With a high rate of chondral and osteochondral injury in first-time patellofemoral dislocations, recurrent instability raises concern for early post-traumatic arthritis, particularly in this young population.
Study to prove efficacy of surgical intervention
For pediatric and adolescent patients with open tibial tubercle apophyses, distal realignment in the form of tibial tubercle osteotomy involves the risk of premature closure and resulting knee recurvatum. Thus, the focus in skeletally immature patients is on proximal soft tissue stabilization. The medial patellofemoral ligament (MPFL) is the primary restraint to lateral translation of the patella, and reconstruction of this ligament has therefore gained popularity and evidence basis for its use in patients of all ages with recurrent instability. In presentations at the Arthroscopy Association of North America and International Patellofemoral Study Group meetings in 2015, Green and colleagues demonstrated the safety of MPFL reconstruction around an open physis using fluoroscopic guidance and an angled femoral socket (Figures 1 and 2).
Figure 1. AP and lateral fluoroscopic images of a femoral socket for an MPFL in a patient with an open physis are shown. The tunnel is angled inferiorly to avoid injury to the growth plate.
Source:Shubin Stein B/Munch J
In an effort to carefully and properly study the efficacy of surgical intervention for first-time patellofemoral dislocations, a multicenter consortium has undertaken the 5-year, prospective, randomized, controlled Pediatric and Adolescent Patellofemoral Instability study. The centers, which include both pediatric sports and general sports-trained surgeons with a focus on patellar instability, will recruit patients for randomization to either a physical therapy or surgical intervention (MPFL reconstruction) arm. First-time patellofemoral dislocators with open or closing distal femoral physes will be included. Careful attention will be paid to risk factors, such as trochlear dysplasia, coronal malalignment in the form of tibial tubercle-to-trochlear groove (TT-TG) distance, patella alta, ligamentous laxity as measured by the Beighton criteria, mechanism of injury, etc.
Several studies to date have attempted examination of patellofemoral instability in a randomized fashion, however, none has studied children and adolescents as a separate group. In addition, none of the existing studies included utilization of the commonly accepted surgical intervention for MPFL reconstruction.
Beth E. Shubin Stein
We hope to demonstrate in a prospective fashion an ability to dramatically reduce the risk of recurrence for skeletally immature, first-time patellofemoral dislocators when MPFL reconstruction is undertaken early. If our hypothesis is proven, the treatment algorithm for patellofemoral instability will be adjusted to resemble glenohumeral instability in terms of its stratification by the patient’s age. An ability to reduce the recurrence rate in young patients would also allow us to mitigate the potential risk of early posttraumatic arthritis as a result of recurrent chondral injury.
Beth E. Shubin Stein, MD is an associate professor at Weill Cornell Medical College and an orthopedic surgeon in the Department of Orthopaedic Surgery & Sports Medicine
at Hospital for Special Surgery in New York, 535 E. 70th St., New York, NY 10021.
Jacqueline Munch, MD is an assistant professor in the Department of Orthopaedics and Rehabilitation at Oregon Health and Science University, 3181 S.W. Sam Jackson Park Rd., Portland, OR 97239.
Disclosures: Shubin Stein and Munch report no relevant financial disclosures.
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