Between 2006 and 2011, six patients were referred to our specialist knee unit with undiagnosed anterior knee pain. Two of these patients were keen football players, and four were keen runners. All were male patients, with an age range of 19-26 years old at presentation. All patients gave a history of a direct blow to the anterior aspect of the knee while playing sport or following a fall whilst running. They reported no prior history of knee pain and were all otherwise fit and well.
Physical examination was unremarkable apart from localised tenderness over the patellar synchondrosis. Plain radiography in all cases confirmed a bipartite patella with no evidence of obvious other bony pathology (Fig. 1). All cases were of unilateral bipartite patella. The patients were investigated with MRI scans which revealed a rupture of the synchondrosis and adjacent bone marrow oedema with retropatellar chondral separation (Figs. 2a, b, c).
In all 6 patients, the pain remained refractory to non-surgical management including rest, physiotherapy, ultrasound-guided local anaesthetic and steroid injections by an experienced musculoskeletal radiologist (40mmol Depomedrol, used in 2 cases, as previously recommended by Weaver, 1977 and Ogata, 1994) and non-steroidal anti-inflammatory drugs. Non-surgical options were trialled for a mean period of four months (range 3-12 months).
The patients were therefore counselled and consented for operative fixation, and all were treated with open reduction and internal fixation using 3.5 mm cortical screws. The procedures were performed via a midline longitudinal incision. Multiple green needles were used to identify the plane of the synchondrosis (Fig. 3). The retinaculum overlying the synchondrosis was divided, allowing it to be opened like a book (Fig. 4) and exposing the synchondrosis. This was debrided back to cancellous bone on both sides of the synchondrosis. The bipartite fragment was then reduced to the patella using a fracture reduction clamp. Fixation was achieved with fully threaded cortical lag screws (Fig. 5); no bone graft was required. There were no intra-operative complications.
Post-operatively, mobilisation was allowed using a range-of-movement brace from 0-30 degrees of flexion for 2 weeks, increasing to 90 degrees of flexion by 6 weeks. The brace was then removed and patients were encouraged to continue lower limb strengthening exercises. Regular manual patellar glides were encouraged throughout this period.
Clinical and radiological union was achieved at 6 weeks follow-up (Fig. 6). All patients had complete symptomatic relief at 3 months. Clinically, full knee function was restored in all cases, with return to previous level of activity by 6 months, and patients were discharged. One patient required proximal screw removal due to hardware irritation at 12 months post-operatively.