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First Time Patellofemoral Dislocation In Pediatric and Adolescent Patients

Sunday, October 21, 2012: 10:06 AM
Melrose (Hilton Riverside)
Laura Lewallen, MD, Amy McIntosh, MD and Diane Dahm, MD, Orthopedic Surgery, Mayo Clinic, Rochester, MN

Purpose

The goal of this study was to describe the demographics of pediatric and adolescent patients with a first time patellofemoral dislocation, and to determine predictors of recurrent instability.

Methods

This single institution IRB approved (#11-003720) retrospective study from January 1998 to December 2010 generated 2039 patients after searching the Mayo Medical Index database. Inclusion criteria were: (1) age 18 years or younger (2) no prior history of patellofemoral subluxation or dislocation of affected knee (3) x-rays within four weeks of the initial instability episode (4) a dislocated patella requiring reduction, or convincing history/findings suggestive of acute patellar dislocation (a subluxation or dislocation event associated with full giving away, effusion/hemarthrosis, tenderness along the medial parapatellar structures and apprehension with lateral patellar translation).

Exclusion criteria were associated ACL, PCL, or LCL injury. Patients with chronic or recurrent instability were excluded. Those who did not have radiographs within the appropriate time frame were also excluded. X-rays were evaluated for trochlear dysplasia (Dejour classification) and patella alta (Caton-Deschamps index and Insall-Salvati index); and were graded for skeletal maturity of the distal femoral and proximal tibial physes (open vs. closing vs. closed).

Results

222 patients, 120 males (54.1%) and 102 females (45.9%) with an average age of 14.9 years (range 9-18), met the above criteria. 84 patients (37.8%) had trochlear dysplasia and 100 (45.0%) had patella alta. 115 patients had open (28) or closing (87) physes, and 107 patients had completely closed physes. 24 patients (10.8%) underwent early surgery for the treatment of osteochondral fractures. All others were initially treated nonoperatively. Of the 198 patients in this group, 76 (38.4%) had recurrent patellofemoral instability, and 39 (51.3%) of these required subsequent surgical treatment. Recurrent instability events were associated with an open/closing physis (p=0.0583), a sports-related mechanism of injury (p=0.0585), and trochlear dysplasia (p<0.0001). Age, gender, BMI and patella alta were not statistically associated with recurrent instability.

Conclusion

First time patellofemoral dislocation in patients aged 18 years or younger had a nearly equal distribution between males and females. Conservative treatment for first time patellofemoral dislocation yields a 62% success rate. However, half of patients with recurrent instability require surgical intervention to gain stability. Immature physes, sports-related injuries, and trochlear dysplasia were associated with recurrent instability events.