MRI‐based surgical simulation of transtrochanteric rotational osteotomy for femoral head osteonecrosis

Abstract

Transtrochanteric rotational osteotomy (TRO) is one of the joint-preserving surgical treatments for osteonecrosis of the femoral head (ONFH). It can prevent collapse of the femoral head as necrotic lesions in the weight-bearing portion can be moved sufficiently to a less weight-bearing portion by anterior rotation, posterior rotation, or varus angulation. Patient selection and preoperative planning are important to determine indications for TRO. It has been reported that successful TRO requires at least 34% of the weight-bearing area supported by the intact part of the femoral head. However, this ratio is difficult to preoperatively quantify according to the rotation angle using conventional two-dimensional MR images or X-rays. Therefore, we developed a method of simulating TRO using three-dimensional (3D) models reconstructed from 3D MR images and applied it to serial patients with types C1 and C2 osteonecrosis at stage 1 or 2. The simulation visualized positional changes of the necrotic lesion in the weight-bearing area and enabled quantitation of the postoperative intact ratio. Our surgical simulation is useful for evaluating the postoperative intact ratio and for determining indications for TRO as well as the optimal angle of femoral head rotation and varus angulation. Osteonecrosis of the femoral head (ONFH) predominantly occurs in young and middle-aged adults. 1 If a necrotic lesion in the weight-bearing portion is large, the femoral head will progressively collapse in the natural course, resulting in osteoarthrosis of the hip that requires total hip arthroplasty even in young patients. The ratio to which the necrotic lesion of the ONFH occupies the weight-bearing portion of the acetabulum on anteroposterior (AP) radiographs or magnetic resonance (MR) images has been reported to be closely associated with the prognosis of idiopathic ONFH. 2 The type classification of idiopathic ONFH by the working group of the Japanese Ministry of Health, Labor and Welfare 3 is based on this ratio and consists of types A, B, C1, and C2 (Fig. 1). Patients with type C1 and C2 lesions that exceed the medial two-thirds of the weight-bearing portion have a poor prognosis of progressive collapse in the absence of surgical intervention, 2 so joint-preserving strategies such as osteotomy are important for such patients.Transtrochanteric rotational osteotomy (TRO) 4-6 is one of the joint-preserving surgical treatments for ONFH (Fig. 2), that can prevent collapse of the femoral head and consequent osteoarthrosis of the hip. To achieve this, the necrotic lesion of the femoral head in the weight-bearing portion must be moved sufficiently to less weight-bearing portion after transtrochanteric osteotomy by rotating the femoral head and neck anteriorly or posteriorly along the femoral neck axis with or without varus angulation. To accurately determine indications for TRO, and for TRO to be successful, patient selection and preoperative planning are critical. It has been reported that the ratio of the transposed intact articular...

Nontraumatic Osteonecrosis of the Femoral Head: Where Do We Stand Today?

“…Evidence has shown that small, medially located, asymptomatic lesions may be treated with observation alone, whereas the recommended options for symptomatic precollapse stage lesions are decompression 7,86-90 , osteotomy [91][92][93][94][95][96][97][98][99][100][101][102][103][104][105][106][107][108] , and non-vascularized or vascularized bone-grafting 90,[109][110][111] . Once the early postcollapse stage is reached, total hip arthroplasty provides consistent results; however, satisfactory results have also been demonstrated with bone-grafting [112][113][114][115][116][117][118][119][120][121][122][123][124][125] .…”

Femoral neck rotational osteotomy: a modified method for treating necrotic femoral heads with large and laterally located lesions

“…Osteotomies were suggested for treating AVN with Ficat stage of Type 2b or 3 [ 11 , 12 ]. By releasing the retinaculum, FNRO through a surgical hip dislocation approach transposed enough viable bone to the weight-bearing zone of femoral head.…”