Upsala Journal of Medical Sciences. 2011; 116: 285–288 CASE REPORT Recurrent dislocation of the patella accompanying hypotrochlea of the femur and malalignment of the patella AKIRA HORIKAWA1, HIROYUKI KODAMA1, NAOHISA MIYAKOSHI2, SHIN YAMADA2 & SEIYA MIYAMOTO3 1South Akita Orthopedic Clinic, Seiwakai, 96-2 Kaidousita, Syowa-Ookubo, Katagami 018-1401, Japan, 2Department of Orthopedic Surgery, Akita University Graduate School of Medicine, 1-1-1 Hondo, Akita 010-8543, Japan, and 3Department of Orthopedic Surgery, Nakadori General Hospital, 3-15 Minamidoori-Misono, Akita 010-8577, Japan Abstract This case report describes a rare case of recurrent dislocation of the patella which was accompanied with trochlear dysplasia and malalignment of the patella in a 15-year-old girl. She complained of hemoarthrosis and recurrent patellar dislocation in the early knee ﬂexion phase. Plain radiography and computed tomography (CT) showed patellar malalignment (quadriceps angle 20 ) and severe dysplasia of the trochlea of the femur (sulcus angle 170 ). Surgery was performed, consisting of trochleoplasty in addition to proximal and distal realignment. Trochleoplasty was undertaken using a modiﬁed Dejour technique. After surgery, the patient complained of joint contracture. Arthroscopic release of ﬁbrous tissue relieved symptoms and obtained normal range of motion without patellar dislocation. Postoperative radiography and CT demonstrated improvement of the quadriceps angle (10 ) and sulcus angle (140 ). Key words: Dislocations, knee, patella Introduction Although biomechanics and surgical treatments have been examined for recurrent dislocation of the patella, few studies have reported on the combination of troch- lear dysplasia and recurrent patellar instability. In addi- tion, treatment methods have only been reported in a few cases. We present herein a case with successful surgical outcomes for the treatment of recurrent dislocation of the patella with trochlear dysplasia and malalignment of the patella. Case report A 15-year-old girl who had complained of recurrent patellar dislocation for more than 5 years presented with left knee hemoarthrosis. Physical examination revealed patellar dislocation at slight knee ﬂexion of approximately 30 that was easily reduced without pain. No signs of apprehension, joint laxities, or sys- tematic disease were observed. Plain radiography showed a lateralized tibial tubercle with increased quad- riceps angle (Q angle) of 20 and dysplasia of the trochlea as deﬁned by the ‘crossing sign’ (1) without patella alta. Computed tomography (CT) also demon- strated marked trochleodysplasia of the femur, with a sulcus angle of 170 (Figure 1). Arthroscopic examination showed a ﬂat, hypoplastic trochlea of the femur and frequent patellar dislocation with knee motion. Surgery consisted of trochleoplasty, followed by proximal and distal realignment. Tro- chleoplasty was performed as a modiﬁed Dejour tech- nique (2). This technique involved: 1) shaving of the subchondral bone; 2) making an incision from the aspect of the groove to the anterior femoral cortex; 3) cutting a subchondral trench; 4) undermining the ﬂap to allow collapse of the osteochondral ﬂap; 5) impaction using ﬁnger pressure; and 6) ﬁxation of Correspondence: Akira Horikawa, MD, South Akita Orthopedic Clinic, Seiwakai, 96-2 Kaidousita, Syowa-Ookubo, Katagami 018-1401, Japan. E-mail: horikawa@virgo.interq.or.jp (Received 19 February 2011; accepted 8 June 2011) ISSN 0300-9734 print/ISSN 2000-1967 online 2011 Informa Healthcare DOI: 10.3109/03009734.2011.596291