The Knee 11 (2004) 129–131
Short communication
An unusual double patella: a case report Eric Yeung, John Ireland* Holly House Hospital, Buckhurst Hill, Essex, UK Received 30 November 2002; accepted 3 January 2003
Abstract Double patella following a ‘sleeve fracture’ in the lower pole of the patellar is rare and even more so after surgical treatment to the original injury. We report such a case in a boy injured at the age of 10, and presenting 3 years later with weakness and effusion. The management is described, including the technique of excision of the accessory patella and the lowering of the larger patella to a normal level. We believe that this is the first such case to be reported after surgical treatment of the primary fracture. 䊚 2003 Elsevier B.V. All rights reserved. Keywords: Patella; Sleeve fracture; Duplication
1. Introduction A symptomatic congenital bipartite patella is not uncommon, but true duplication of the patella is rare and only isolated cases have been described w1–3x. Double patella as a result of trauma is usually caused by extensive ossification following tendo-periosteal avulsion of the lower pole, the so-called ‘sleeve’ fracture. In this report, an unusual double patella following surgical treatment of such a fracture is described. 2. Case report A 10-year-old boy injured his left knee playing soccer and was found to have a displaced ‘sleeve’ fracture of the patella (Fig. 1). Primary operative treatment was undertaken with suture of the displaced fragments and plaster immobilisation for 6 weeks (Fig. 2). Early functional recovery was satisfactory with return to soccer. Three years later the knee produced discomfort after sports and had a constant small effusion. It lacked the hyperextension seen in the opposite right knee. Both knees were in marked valgus alignment, of which there was a strong family history. *Corresponding author. 17 Kings Avenue, Woodford Green, Essex IG8 0JD, UK. Tel.: q44-20-85053211; fax: q44-20-85591161. E-mail address:
[email protected] (J. Ireland).
By the age of 16 the left knee was the cause of increasing discomfort with crepitus, constant effusion and two distinct patellar elements were evident clinically and radiologically (Fig. 3). At arthroscopy extensive chondral debris was evident and grossly abnormal patellar articular appearances were noted with areas of exposed subchondral bone. Closed drilling of the exposed bone was carried out and a 1.5-cm loose body was removed. In spite of symptomatic improvement the knee continued to have a moderate effusion and prevented satisfactory return to running sports. Because of these continuing symptoms it was decided to excise the smaller ‘accessory’ patella, and lower the larger upper patella to a normal level. At the age of 17 this was undertaken. A mid-line exposure was used mobilising the extensor mechanism through a lateral para-patellar exposure. The upper major patella had reasonable articular cartilage over its upper half and a thin skin of fibro-cartilage over the lower half but no frank bone exposure. A small supra-patella ossicle was mobile and was removed. The lower ‘accessory’ patella was rounded and irregular without articular cartilage on its deep aspect. It was excised by sharp dissection. The femoral trochlea was abnormally flattened with patchy deep chondral loss but no sub-chondral bone exposure.
0968-0160/04/$ - see front matter 䊚 2003 Elsevier B.V. All rights reserved. doi:10.1016/S0968-0160Ž03.00040-1
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E. Yeung, J. Ireland / The Knee 11 (2004) 129–131
Fig. 2. Post-operative view of the sleeve fracture. Fig. 1. Radiograph (lateral view) showing the sleeve fracture of patella.
The tibial tubercle was elevated on a 6=2 cm2 bone block. It was transposed 2 cm distally and lateral check X-rays undertaken to confirm correct patellar height. The bone block was securely fixed with three corticocancellous screws (Fig. 4) and the knee was immobilised in 15 degrees of flexion in a plaster cylinder. Full early weight bearing was encouraged and the plaster converted to a removable splint at 3 weeks postoperatively. Early union of the tibial bone block was evident at 2 months and the fixation screws were removed at 6 months. At clinical review 2 years post-operatively the patient was able to run without difficulty and mentioned only occasional ache in the knee after strenuous activity. He preferred not to kneel on the left. The left knee had no effusion and lacked only 1 or 2 degrees of hyperextension, flexion being full and there was no extensor lag. 3. Discussion A ‘sleeve’ avulsion fracture of the lower patella provides a focus for extensive ossification and can lead to the formation of an accessory patella. Only isolated cases of traumatic double patella have been reported in
Fig. 3. Lateral view of the double patella.
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Ref. w4x. Almost all occurred in adolescence, the teenage growth spurt possibly contributing to the ossific process. In the cases reported, the original avulsion fractures were often not diagnosed initially. They presented with an acute knee injury, often with an unremarkable radiological appearance. The avulsion, occurring at the tendo-periosteal junction, is often not visible in the acute phase. Clinical examination may be difficult because of swelling and pain and it may not be possible to assess the extensor mechanism adequately. The diagnosis can thus be difficult and is often not made. Early recognition of such avulsions and prompt surgical treatment aim to eliminate the ectopic focus of ossification and thus prevent the formation of an accessory patella w4x. In this case we report the formation of such an accessory patella, despite surgical treatment of a ‘sleeve’ fracture. Duplication of the patella after surgical treatment has not been reported. References
Fig. 4. Post-operative view of tibial tubercle transplantation.
w1x Visconti D, Della Sala SW, Bianchini G, Manera V. Double congenital patella: case report and review of literature. Eur Radiol 1996;6(4):566 –569. w2x Gasco J, Del Pino JM, Gomar-Sancho F. Double patella. A case report of duplication in the coronal plane. J Bone Joint Surg wBrx 1987;69(4):602 –603. w3x Yochum TR, Sprowl CG, Barry MS. Double patella syndrome with a form of multiple epiphyseal dysplasia. J Manip Physiol Ther 1995;18(6):407 –410. w4x Cipolla M, Cerullo G, Franco V, Gianni E, Puddu G. The double patella syndrome. Knee Surg Sports Traumatol Arthrosc 1995;3(1):21 –25.
