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An unusual case of intra-articular dislocation of the patella
Injury, 9, 321-322
321
Printed in Great Britain
An unusual case of intra-articular dislocation of the patella James Colville Orthopaedic Department, Mater Misericordiae Hospital, Dublin Summary
An unusual case of intra-articular dislocation of the patella is described and the mechanism of injury suggested.
intra-articular dislocation of the patella, where rotation through 90 ~ occurred about the vertical axis.
INTRODUCTION
CASE REPORT
INTRA-ARTICULAR dislocation of the patella is an extremely rare injury, there being only 28 reported cases in the world literature. The first case was reported by Middelfart in 1887. Subsequent reports have described a dislocation characterized by rotation of the patella through 90 ~ about its horizontal axis. This report describes a case of
A 16-year-old schoolboy was brought to the casualty department approximately 30 rain after injuring his left knee while playing football. There was no previous history of injury to or trouble with the knee. He said he had been tackled and that he had borne the full weight of his opponent against the 'outside' of his knee, the knee being 'straight' at the time. He felt something 'snap' and fell to the ground. He was in
Fig. 1. The left knee on admission, Showing the
Fig.2.Lateralradiographoftheleftkneejointshowing
prominent bony ridge,
the patella to be rotated on its vertical axis.
322 considerable pain on admission and held the knee in extension. Examination revealed a bony ridge palpable anteriorly (Fig. 1) and any attempted movement was resisted, the quadriceps muscles being in spasm. Palpation of the bony ridge revealed one side (medial) to be smooth and the other side (lateral) to be rough. A lateral radiograph of the left knee (Fig. 2) showed the patella to be rotated through 90~ about its vertical axis. Under general anaesthesia the patella was rotated medially through 90~ with little difficulty. After reduction, and while still under the general anaesthetic, the collateral and cruciate ligaments were examined and found to be normal. A Robert Jones bandage was applied and weight bearing was forbidden for 2 weeks during which time quadriceps exercises were practised. After 2 weeks a light supportive bandage was applied. The patient regained a full range of movement and was asymptomatic within 4 months of the accident.
Injury: the British Journal of Accident Surgery Vol. 9/No. 4
rotation of the patella. Reichel (1904) suggested that in children and young people under the age of 20, laxity of the patellar attachments allows for greater mobility of the patella and therefore an increased risk of disIocation. The suggested mechanism of injury in this case is as follows. A severe valgus strain on the knee joint when in extension could cause the patella to be rotated on its vertical axis with the articular surface facing medially, provided that there was a tearing or giving way of the medial part of the quadriceps mechanism. The continued pull of the quadriceps muscle would then hold the patella on its edge.
Acknowledgements I wish to thank Mr Martin Walsh, MCh, FRCSI, for permission to publish this report, and Mr George Scully for the photographs.
DISCUSSION Previously described dislocations of this nature have been given a variety of names--downward, horizontal, interarticular and intercondylar. They all had one feature in common in that the rotation occurred around the horizontal plane with or without rupture of the quadriceps. In every case except one (Allen, 1944) the knee was held in flexion. The mechanism was in most cases described as a direct force which pushed the upper pole of the patella down into the joint (Brady and Russell, 1965), and Frangakis (1974) described a sequence of events whereby continued contraction of the quadriceps muscle produced
REFERENCES
Allen F. J. (1944) Intercondylar dislocation of the patella. South Afr. Med. J. 18, 66. Brady T. A. and Russell D. (1965) Interarticular horizontal dislocation of the patella. A case report. J. Bone Joint Surg. 47A, 1393. Frangakis E. K. (1974) Intra-articular dislocation of the patella. J. Bone Joint Surg. 56A, 423. Middelfart V. (1887) Ensjelden luxation of patella. Norsk Mag. Laegevidensk. 4, Rii, 588. Reichel P. (1904) Injuries and diseases of the knee and leg. In: von Bergmann E., yon Bruns P. and von Mikulicz J. (ed.) Surgery o f the Extremities. London, Williams & Norgate, p. 565.
Requestsfor reprintsshouldbe addressedto: James Colville,FRCS, Cappagh OrthopaedicHospital, Cappagh, Dublin.
321
Printed in Great Britain
An unusual case of intra-articular dislocation of the patella James Colville Orthopaedic Department, Mater Misericordiae Hospital, Dublin Summary
An unusual case of intra-articular dislocation of the patella is described and the mechanism of injury suggested.
intra-articular dislocation of the patella, where rotation through 90 ~ occurred about the vertical axis.
INTRODUCTION
CASE REPORT
INTRA-ARTICULAR dislocation of the patella is an extremely rare injury, there being only 28 reported cases in the world literature. The first case was reported by Middelfart in 1887. Subsequent reports have described a dislocation characterized by rotation of the patella through 90 ~ about its horizontal axis. This report describes a case of
A 16-year-old schoolboy was brought to the casualty department approximately 30 rain after injuring his left knee while playing football. There was no previous history of injury to or trouble with the knee. He said he had been tackled and that he had borne the full weight of his opponent against the 'outside' of his knee, the knee being 'straight' at the time. He felt something 'snap' and fell to the ground. He was in
Fig. 1. The left knee on admission, Showing the
Fig.2.Lateralradiographoftheleftkneejointshowing
prominent bony ridge,
the patella to be rotated on its vertical axis.
322 considerable pain on admission and held the knee in extension. Examination revealed a bony ridge palpable anteriorly (Fig. 1) and any attempted movement was resisted, the quadriceps muscles being in spasm. Palpation of the bony ridge revealed one side (medial) to be smooth and the other side (lateral) to be rough. A lateral radiograph of the left knee (Fig. 2) showed the patella to be rotated through 90~ about its vertical axis. Under general anaesthesia the patella was rotated medially through 90~ with little difficulty. After reduction, and while still under the general anaesthetic, the collateral and cruciate ligaments were examined and found to be normal. A Robert Jones bandage was applied and weight bearing was forbidden for 2 weeks during which time quadriceps exercises were practised. After 2 weeks a light supportive bandage was applied. The patient regained a full range of movement and was asymptomatic within 4 months of the accident.
Injury: the British Journal of Accident Surgery Vol. 9/No. 4
rotation of the patella. Reichel (1904) suggested that in children and young people under the age of 20, laxity of the patellar attachments allows for greater mobility of the patella and therefore an increased risk of disIocation. The suggested mechanism of injury in this case is as follows. A severe valgus strain on the knee joint when in extension could cause the patella to be rotated on its vertical axis with the articular surface facing medially, provided that there was a tearing or giving way of the medial part of the quadriceps mechanism. The continued pull of the quadriceps muscle would then hold the patella on its edge.
Acknowledgements I wish to thank Mr Martin Walsh, MCh, FRCSI, for permission to publish this report, and Mr George Scully for the photographs.
DISCUSSION Previously described dislocations of this nature have been given a variety of names--downward, horizontal, interarticular and intercondylar. They all had one feature in common in that the rotation occurred around the horizontal plane with or without rupture of the quadriceps. In every case except one (Allen, 1944) the knee was held in flexion. The mechanism was in most cases described as a direct force which pushed the upper pole of the patella down into the joint (Brady and Russell, 1965), and Frangakis (1974) described a sequence of events whereby continued contraction of the quadriceps muscle produced
REFERENCES
Allen F. J. (1944) Intercondylar dislocation of the patella. South Afr. Med. J. 18, 66. Brady T. A. and Russell D. (1965) Interarticular horizontal dislocation of the patella. A case report. J. Bone Joint Surg. 47A, 1393. Frangakis E. K. (1974) Intra-articular dislocation of the patella. J. Bone Joint Surg. 56A, 423. Middelfart V. (1887) Ensjelden luxation of patella. Norsk Mag. Laegevidensk. 4, Rii, 588. Reichel P. (1904) Injuries and diseases of the knee and leg. In: von Bergmann E., yon Bruns P. and von Mikulicz J. (ed.) Surgery o f the Extremities. London, Williams & Norgate, p. 565.
Requestsfor reprintsshouldbe addressedto: James Colville,FRCS, Cappagh OrthopaedicHospital, Cappagh, Dublin.