title: Osteochondral injury after acute patellar dislocation in children and adolescents.
abstract: BACKGROUND
  Acute patellar dislocation (APD) is a common injury in the pediatric patient population and may be associated with a spectrum of soft tissue and osteochondral injuries. This study describes the incidence of osteochondral fracture and associated injury patterns in a pediatric population after first-time APD and assesses functional outcomes after treatment.
  
  
  METHODS
  One hundred twenty-two patients, aged 11 to 18 years, who were evaluated after first-time APD over a 10-year period were identified, 46 of whom had confirmed osteochondral injury on magnetic resonance imaging (MRI). Demographic data, including knee affected, mechanism of injury, recurrent dislocation, operations performed, and condition at last follow-up, were retrieved from the medical record. Operative reports and MRI were used to characterize the location of osteochondral injury. The functional outcome of each patient with an osteochondral fracture was assessed using the Pedi-IKDC questionnaire.
  
  
  RESULTS
  Forty-six patients, mean age 14.6 years (range, 11 to 18 y), were included. Osteochondral fracture occurred at the patella in 35 patients (76%), the lateral femoral condyle in 11 patients (24%), and at both locations in 3 patients (6.5%). In 21 patients (44%), MRI confirmed osteochondral injury despite the plain radiograph interpretation as negative for fracture. Twenty-six patients (68%) subsequently underwent surgery after injury. Injury to the medial patellofemoral ligament was identified on MRI in 97.8% of patients (45/46). Fifteen patients (32.6%) underwent a concomitant medial repair at the time of surgery. Osteochondral injury to the distal femur on average had a lower International Knee Documentation Committee score than patellar injuries (72.3±18 vs. 91.1±10.2, P<0.003). Femoral osteochondral injury involving the weight-bearing surface (75.27±18.19) scored lower than non-weight-bearing surface injuries (93.22±7.47; P<0.001).
  
  
  CONCLUSIONS
  The incidence of osteochondral injury associated with APD is high. Osteochondral fractures may initially go unrecognized on plain radiographs. Patients with weight-bearing lateral femoral condyle injuries had lower short-term functional scores, suggesting that outcomes depend on location of injury.
  
  
  METHODS
  Level IV, diagnostic and therapeutic study.
authors.affiliation: Department of Orthopaedic Surgery, University of Michigan, Ann Arbor, MI 48109, USA.
authors.forename: Mark A
authors.initials: MA
authors.lastname: Seeley
authors.forename: Michael
authors.initials: M
authors.lastname: Knesek
authors.forename: Kelly L
authors.initials: KL
authors.lastname: Vanderhave
mesh_terms: D000293:Adolescent; D002648:Child; D005260:Female; D005264:Femoral Fractures / Q000209:etiology / Q000601:surgery; D005269:Femur / Q000293:injuries / Q000601:surgery; D005500:Follow-Up Studies; D050723:Fractures, Bone / Q000209:etiology* / Q000601:surgery; D006801:Humans; D015994:Incidence; D008279:Magnetic Resonance Imaging; D008297:Male; D010329:Patella / Q000293:injuries*; D031222:Patellar Dislocation / Q000150:complications*; D017847:Patellar Ligament / Q000293:injuries; D012008:Recurrence; D012189:Retrospective Studies; D011795:Surveys and Questionnaires; D013997:Time Factors; D016896:Treatment Outcome