Acute patellar dislocation may result in OCF. In the past, OCFs following patellar dislocation were thought to be a rarity. In 1976 Rorabeck and Bobechko reported an incidence of 5% after acute patellar dislocation [10
]. However, several recent studies report a higher incidence of OCF after patellar dislocation, ranging from 39% to 71% [1
]. As the aforementioned studies show, the incidence of such injuries had previously been underestimated. Nevertheless, despite the higher incidence of chondral injuries, not all injuries were displaced, requiring surgical treatment.
In the majority of cases of OCF with only one small bony fragment diagnosis is frequently missed. Plain radiographs often underestimate the size of the displaced fragments and therefore clinical signs such as hemarthrosis and the knowledge that such injuries are quite common is the key to proper diagnosis of OCF. Knee MRI scan or knee arthroscopy will confirm the diagnosis and may reveal the true extent of the cartilage damage.
The presence of OCF is a primary indication for surgical intervention after acute patellar dislocation. In the past, excision of the OCF was a predisposing factor for early degenerative arthritis [5
]. Since then several materials have been developed for reliable fixation of the OCF fragments including metal pins and headless screws. The main disadvantage of these metal fixation devices is that they require removal after fragment consolidation. Microfracturing at the area of the lesion, osteochondral grafting, allogeneic, or autogenous osteochondral implantation, and autologous chondrocyte implantation have all been applied to repair such lesions [6
]. Although good short-term results are reported, more studies with longer followup are needed to properly evaluate these techniques [6
The introduction of biodegradable fixation devices was a revolution in the field of OCF fixation. Their main advantage is that they do not require removal. However, they are associated with a few complications, such as synovitis or foreign body reaction, as reported in the literature [14
]. Poly L-lactic acid pins were applied for fixation of OCF fragments in the present study since they do not induce signs of inflammation or synovitis or other adverse reactions [9
The postoperative follow-up period varied from 22 months to 5 years (mean time 34 months). The initial apparent consolidation of 17 of the 18 treated OCF lesions, seen postoperatively on plain radiographs, was confirmed by postoperative MRI findings (). The reintegration rate using poly-L-lactic acid pins was very encouraging (94%) in the short- and middle-term followup. Follow-up MRI findings confirmed joint surface congruity and the vitality of the reintegrated OCF for up to 36 months after surgery. In all patients in whom reintegration was obtained, full ROM was restored and the knee joint was pain free. Another patellar dislocation was not reported in any patient. Radiological analysis demonstrated no major degenerative changes in the articular surface of the lateral condyle or the patella during postoperative followup.