Secondary collapse of lateral femoral condyle following bone bruise ...

696 N. VANNET, P. KEMPSHALL, J. DAVIESFig. 1 (A+B). — MR Imaging of the knee. T 1 and T 2 weightedimages showing the area of bone bruising in the lateral femoralcondyle.Fig. 2. — CT scan showing collapse of the lateral femoralcondyle.CASE REPORTThe following case presentation is that of an18-year-old male motorcyclist who sustained aninjury to his left knee when he fell off his bikewhilst negotiating a corner at approx 15 mph andslid into a car.Initially no fracture was identified on plain radiographs.Subsequent review in fracture clinicrevealed an effusion, marked tenderness over themedial collateral ligament and difficulty reachingfull extension. He was advised to mobilise pain permitting,and an MRI scan was arranged to assess theintra and extra articular ligaments around the knee.Following the MRI scan (fig 1), prior to subsequentoutpatient appointment, the swelling of theknee improved, and the boy returned to normalactivity, although he was experiencing some pain.He presented again to the accident and emergencydepartment 12 days after the MR scan with apainful swollen left knee following a subsequentminor trauma when riding a pedal cycle. Plain filmsshowed a possible depression fracture of the lateralfemoral condyle, this was confirmed by a CT scanwhich showed a marked depression in the lateralfemoral condyle (fig 2).The previous MR image, when reviewed, showeda tear of the posterior horn of the lateral meniscus,a rupture of the medial collateral ligament (MCL),a probable rupture of the anterior crruciate ligament(ACL), and a large bone bruise in the lateralfemoral and tibial condyles with no cortical depression.The patient was treated surgically, with arthroscopicassisted elevation of the lateral femoralcondyle under image intensifier control (fig 3).A depression in the articular surface of the lateralfemoral condyle was visualised at arthroscopyand measured to a depth of five millimetres. Theimpaction extended from the notch increasing progressivelylaterally. The ACL was indeed ruptured ;anterior draw, Lachman’s test and pivot shift wereall positive on examination under anaesthesia. Abucket handle tear of the lateral meniscus was alsoconfirmed. Punches were used under image intensifiercontrol through a window in the lateral femur.The aim of this presentation is to emphasise thatthe bone bruise is not necessarily an innocuous incidentallesion that can be forgotten about.ClassificationThe first classification of bone bruises was constructedby Mink and Deutsch, who used the termoccult to mean hidden. Fractures of the marrow orarticular surface that are undetectable by conventionalradiographs become visible on MRI (8).Subsequently modified by Vellet et al, bone bruiseswere divided into three categories depending ontheir position in the subcortical bone and theirActa Orthopædica Belgica, Vol. 75 - 5 - 2009