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Osteochondral Injury After Acute Patellar Dislocation In a Pediatric Population

Sunday, October 21, 2012: 9:59 AM
Melrose (Hilton Riverside)
Mark A. Seeley, M.D., Michael Knesek, M.D. and Kelly L. Vanderhave, MD, Department of Orthopaedic Surgery, University of Michigan, Ann Arbor, MI

Purpose: To describe the incidence of osteochondral injury and associated injury patterns in a pediatric population following acute first time patellar dislocation (APD) and to assess functional outcomes after treatment. 

Methods: Following approval by the IRB, a query was performed to identify all patients between the ages of 11 and 18 years evaluated following APD over a 10-year period.  120 patients were identified.  46 patients had confirmed osteochondral fracture (OCF) on MRI.  Demographic data, including age, gender, knee affected, mechanism of injury, recurrence, operations performed, and condition at last follow up were retrieved from the medical record.  The operative reports were used to characterize the location of OCF and treatment method (chondroplasty, internal fixation, loose body removal).  Associated injury to the VMO and MPFL were determined from MRI.   The functional outcome of each patient with an OCF was assessed using the Pedi-IKDC questionnaire. 

Results: 46 patients, including 32 males and 14 females with a mean age of 14.6 years (range 11-18 years), were included.  OCF occurred at the patella in 35 patients (76%) and the femoral condyle in 11 patients (24%).  3 of those patients had OCF at both locations (6.5%).   In 21 patients (44%), MRI confirmed OCF despite the plain radiograph interpretation as negative for fracture.  26 patients (68%) subsequently underwent surgery following injury.   6 patients required arthrotomy, 6 patients underwent arthroscopy, and 14 had a combination of procedures.  Loose body removal was required in 20 patients, and 6 patients underwent ORIF. On preoperative MRI, MPFL injury was present at the patellar insertion in 18 patients (39%), femoral insertion in 4 patients (9%), and more than one location in 23 patients (50%).   15 patients (32.6%) underwent a concomitant medial repair (MPFL repair, medial advancement) at the time of surgery.  No statistical correlation was found between location of OCF and recurrence of patellar dislocation.  Patients that sustained OCF to the distal femur on average had a lower IKDC score than those with patella OCF (72.3±18  vs.  91.1 ± 10.2,  p<0.003).  Of those patients that sustained femoral OCF, weightbearing surface lesions (75.27±18.19) scored significantly lower than lesions that that occurred on nonweightbearing surface (93.22±7.47) in both their IKDC score and how they rated their current level of function (p<0.001 and p<0.004, respectively). 

Conclusion: There is a high incidence of OCF following APD in children. Osteochondral fractures may initially go unrecognized on plain radiographs, supporting the role for MR imaging in these patients.  Our results suggest that short term functional outcomes are dependent on the location of injury, with functional scores higher in patients with patellar osteochondral injuries.