ABSTRACT
BACKGROUND: During transtrochanteric rotational osteotomy (RO), it is important to preserve the posterior column artery (PCA), which is generally located in the adipose tissue underneath the quadratus femoris muscle (QF). If there is a defect in the QF, the risk of injuring the PCA, subsequently resulting in total necrosis of the femoral head, may increase. Therefore, we investigated: (1) the frequency of defects of the QF at the time of RO, and (2) clinical outcome of RO based upon a defect of the QF. HYPOTHESIS: The presence of defects of the QF at the time of RO could be detected pre-operatively by magnetic resonance imaging. METHODS: RO was performed in 124 hips between 2001 and 2010. In all, 95 of the hips were in male patients and 29 in female patients. The mean age was 45.4 years (range: 11-61 years) at the time of surgery and MRI was performed before RO in all cases. We retrospectively evaluated the progression of a collapse through 3 years after RO. RESULTS: MRI showed a defect in the QF in four hips (3.2%) (2 males, 2 females), all of which were confirmed intra-operatively. Among the four patients, one (25%) underwent total hip arthroplasty because of varus deformity of the osteotomy site due to total necrosis of the femoral head 1 year after RO. The 120 hips with a normal QF showed no evidence of total necrosis or progression of necrosis of the femoral head, indicating that the presence of defects of the QF may increase the risk of poor survivorship of this procedure. CONCLUSIONS: Defects of the QF have been reported to occur in 1-2% of all patients, whereas in our study the incidence in ON was approximately 3%. In ON patients with QF defects, pre-operative MRI evaluation of the QF appears to be important when planning RO, followed by a carefully performed surgical procedure. LEVEL OF EVIDENCE: IV; retrospective case series without control group.
