Initial conservative treatment of osteochondral fracture of the patella following first-time patellar dislocation

There has been no gold standard of the initial treatment strategy for acute patellar dislocation (APD) with osteochondral fracture (OCF). Hence the study aim is firstly, to review and compare clinical outcomes of patients who underwent conservative treatment for APD with or without OCF. Secondly, to characterize the location and size of fracture fragment. Sixty-nine consecutive patients who were retrospectively evaluated after first-time APD over a 2- year period were divided into two groups (group 1 (n = 24): APD with OCF and group 2 (n = 45): APD only). Magnetic resonance imaging (MRI) was used to assess patients with APD and OCF from the medial patella. All patients were treated with a supervised course of immobilization followed by progressive range of motion and strength exercise protocol. History of a recurrent dislocation, radiologic and functional scores were analyzed. Redislocation rate was 31.2% in group 1 and 26.6% in group 2, showing no significant difference between the two groups (p = 0.690). Intergroup differences in terms of final Kujala and IKDC scores were not significant (p = 0.117 and p = 0.283, respectively). Fracture sites of the patella in group 1 were classified as follows: patellar medial margin (12), inferomedial facet (7), and inferomedial facet involving central ridge (5). In the subgroup of patient with OCF of the inferomedial facet of the patella, the fragments were found in the lateral gutter and did not cause pain or mechanical symptoms. Thus, loose body removal was not performed. However, all five patients with large OCF involving the central ridge of the patella failed non-operative treatment with recurrent dislocations, ultimately requiring fragment refixation and medial retinacular imbrication. First, APD patients with OCFs of medial margin or inferomedial facet showed similar redislocation rates and functional knee scores with those without OCFs after conservative treatment. Second, initial conservative treatment failed in some APD patients with large OCF, especially when OCFs were fractured from inferomedial facet involving central ridge. Surgery should be considered with this type.