1 Introduction

Osteonecrosis of the femoral head (ONFH) is a condition that commonly affects young people and can cause collapse of the femoral head, leading to hip pain and reduced quality of life.^1,2 It is commonly treated with total hip arthroplasty (THA),^3,4 but can lead to the need for multiple revision surgeries in the future in young-onset ONFH.⁵ Therefore, joint-preserving surgery should be performed whenever possible for young-onset ONFH. The main joint-preserving surgeries for ONFH have been reported to be core decompression,⁶ vascularized graft,⁷ and osteotomy.^8,9 Among these joint-preserving surgeries, trochanteric rotational osteotomy (TRO) is generally the procedure of choice in cases with extensive necrotic areas of the femoral head.⁶ Favorable long-term results have been reported with TRO for ONFH.¹⁰

Multifocal osteonecrosis occurred in the humerus, knee, and acetabulum, and rarely in the trochanteric region, concurrent with ONFH.¹¹ It has been reported that biological activity, including osteoblast action, is reduced in necrotic areas.¹² There is concern that in osteonecrosis of the trochanteric (ONT) occurring simultaneously with ONFH, loss of biological activity in the same area may affect subsequent THA and joint-sparing surgery. In this report, we describe a case of ONT concomitant with ONFH, in which single-photon emission computed tomography (SPECT) and bone scintigrams were performed to evaluate the biological activity of the osteonecrosis and TRO was performed with good results.

2 Case report

A 28-year-old woman was diagnosed with acute lymphoblastic leukemia (ALL). The patient was treated with vincristine, daunorubicin, cyclophosphamide, l-asparaginase, methotrexate, and prednisolone (96 mg/day) for four weeks, according to the protocol of the Japan Adult Leukemia Study Group.¹³ Steroids (>2500 mg) were administered before ONFH was diagnosed. The patient went into remission, but one year after starting treatment, she developed pain in her left hip. When she presented to our clinic, she had claudication due to left hip pain and had a Harris hip score (HHS) of 49 (Fig. 5A).

Plain radiographs taken at the initial examination showed subchondral lucency (crescent sign) and cortical collapse in the left femoral head (Fig. 1A and B). The coronal T1-weighted magnetic resonance imaging (MRI) scan showed a linear area of low signal intensity, suggestive of avascular necrosis in the left femoral head extending beyond the lateral rim of the acetabulum (Fig. 2A). Axial MRI showed areas of necrosis, mainly anterior to the femoral head (Fig. 2B), and was classified as type C2, stage 3A, by the Japanese Investigation Committee of the Ministry of Health, Labour, and Welfare.¹⁴ We also found that the central slice of the femoral diaphysis also showed an area of mixed high and low signal at 36 mm in the AP direction and 28 mm in the ML direction at the trochanteric region on the coronal T1-weighted MRI image (Fig. 3A). The coronal computed tomography (CT) slice showed an area of low signal intensity on T1-weighted MRI in the trochanteric region showed an osteosclerotic image on CT (Fig. 3B). Bone scintigraphy and SPECT showed no uptake in the necrotic area of the left femoral head and high uptake in the surrounding area, with both cold and hot patterns (Fig. 3C and D). Focusing on the area of the ONT, the high-signal region on T1-weighted MRI showed no uptake in bone scintigraphy and SPECT, while the low-signal region on T1-weighted MRI showed mild uptake (Fig. 3C and D). Based on these imaging findings, we assumed that the trochanteric osteotomy line was biological activity and planned to perform an anterior rotational osteotomy (ARO) of the left ONFH.

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Fig. 1 The case of a 28-year-old woman. The Harris Hip Score at the first visit was 49. 1-A: Plain radiograph of the hip joint, 1- B: Lauenstein radiograph of the left hip joint.

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Fig. 2 T-1 weighted magnetic resonance imaging. 2-A: coronal slice of the head center. 2-B: axial slice of the head center.

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Fig. 3 Coronal slice of the head center. 3-A: T1-weighted magnetic resonance images 3-B: Computed-tomography 3-C: Bone scintigraphy 3-D: Single-photon emission computed tomography.

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Our plan was to achieve a healthy area of more than 34% in the loading zone after 90° anteriorly rotation of the femoral head. ARO was performed in the lateral position. ARO was performed following the technique of Sugioka trans-trochanteric anterior rotational osteotomy in the lateral position. The greater trochanter was osteotomized after separating the short external rotator muscle group from the femur. The bone fragments were inverted while attached to the gluteus medius and minimus muscles. The quadratus femoris was partially dissected, with attention paid to the medial femoral circumflex artery, and the obturator externus muscle was identified and dissected. The joint capsule then attached to the hip joint was circumferentially dissected. The first osteotomy was performed 160° to the bone axis, and the second osteotomy was performed perpendicular to the bone axis in the middle of the lesser trochanter. In addition, the femoral head was rotated anteriorly by 70° and fixed in place. Implants included 115° tube plates with a brim 3 holes (Meira, Nagoya, Japan) and 1.8-mm titanium cables (AI wiring system, Aimedic MMT, Tokyo, Japan). We implanted hydroxyapatite (NEOBONE®, Aimedic MMT, Tokyo, Japan) just above the lesser trochanter to compensate for the leg length discrepancy (Figs. 4 and 5A). We allowed up to 10 kg of weight-bearing immediately after surgery, 20 kg of weight bearing three weeks after surgery, and full body weight-bearing 10 weeks after surgery. Six months after the surgery, bone union was observed in the osteotomized area (Fig. 5B). The implants were removed one year after surgery (Fig. 5C). Two years after the surgery, complete bone union was observed (Fig. 5D). At the time of the final follow-up, the leg length discrepancy was 5 mm; however, the gait was normal and there were no subjective symptoms. The patient was able to walk independently without hip pain, and the HHS improved to 100.

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Fig. 4 An intraoperative image showing the completion of a transtrochanteric rotational osteotomy and fixation of the femoral head.

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Fig. 5 Chronological change of the plain radiographs of the left hip joint. The Harris Hip Score at the final. follow-up was 100. 5-A: Immediately after surgery 5-B: Six months after surgery 5-C: one year after surgery 5-D: two years after surgery.

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3 Discussion

The exact pathogenesis of ONFH is still not fully understood,¹⁵ and necrosis is known to occur in other joints such as the humerus, knee, and acetabulum.¹¹ Cases with necrosis at three or more sites are termed multifocal osteonecrosis (MFON),¹⁶ and steroid-related ONFH is considered more likely to lead to MFON.¹¹ MFON can also cause extra-articular necrosis, with a reported probability of necrosis occurring in the diaphysis of long bones in approximately 4% of patients.¹⁶ Kim et al. reported that approximately 5% of patients with ONFH had extensive necrosis extending to the medial femoral trochanter.¹¹ Gao et al. reported that 21 of 192 patients (10.9%) had concomitant necrosis of the femoral trochanter.¹⁷ However, the clinical significance of necrosis in the femoral trochanter is unclear. There are few reports on the surgical management of cases with femoral metaphyseal necrosis, and there is concern about the impact on subsequent surgical management due to reduced biological activity, such as osteoblast action, in the necrotic area.^14,18 Therefore, it is important to evaluate the biological activity of the ONT. In this case, bone scintigraphy and SPECT were used to evaluate the ONT on MRI to confirm biological activity and to evaluate the possibility of bone fusion after osteotomy, with good results.

In this case, as with ONFH, the region of osteonecrosis-like changes in the trochanter exhibited hypointensity on bone scintigraphy and non-intensity on SPECT within areas of high signal intensity on T1-weighted MRI. Furthermore, the region of low T1 signal demonstrated hyperintensity on both bone scintigraphy and SPECT. MRI is the gold standard for diagnosing osteonecrosis of the femoral head.¹⁸ Both bone scintigraphy and SPECT, similar to MRI, are effective diagnostic tools for osteonecrosis.¹⁹ Moreover, SPECT uptake has been documented to occur in regions of elevated bone metabolism.²⁰ In comparison to ONFH on bone scintigraphy and SPECT, ONT revealed distinct imaging findings. Based on the bone scintigraphy and SPECT imaging observations, we inferred that the femoral trochanter, where the osteotomy was planned, was biologically active and optimal bone fusion could be anticipated, resulting in a successful ARO with favorable outcomes.

This study has two limitations. First, it remains uncertains whether bone union can be achieved without bone scintigraphy or SPECT uptake. Even if the biological activity of cancellous bone at the osteotomy site is reduced, bone union can still be achieved by membranous ossification of the cortical bone. The present study is the first report of osteotomy in a case of ONT. Comparing MRI imaging with bone scintigraphy and SPECT imaging in ONFH and ONT of the trochanter may aid in comprehending the pathogenesis of ONFH. Second, other treatment options could be considered for this case. In particular, core decompression is a relatively simple surgical procedure, and more stable results have been reported in combination with other materials. However, these methods may not always yield good results for ONFH of Type C2. In contrast, ARO has been reported to produce good treatment outcomes for Type C2 ONFH and can be preferred when there is adequate blood flow to the osteotomy site. Still, ARO is a technically challenging surgical procedure, and rotating the femoral head bone fragment sufficiently to match the preoperative plan is a difficult surgical procedure. In this case, although the plan was to rotate the femoral head fragment anteriorly by 90°, the actual rotation achieved was about 70°.

In conclusion, we reported a case of ARO of the femoral head in a patient with ONFH and concomitant osteonecrosis-like region of the proximal femur. Bone scintigraphy and SPECT were effective in distinguishing biological activity in necrotic areas.

Institutional review board

All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards. The study was approved by the Bioethics Committee of our University (No. 2020–0272).

Consent

Consent for the case report was obtained from the patients in this report.

Funding statement

This case study did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Ethical statement

This case study was conducted in accordance with ethical standards and approved by the ethics committee of Nagoya University.

CRediT authorship contribution statement

Hiroto Funahashi: attended conferences where cases were discussed to determine policy, prepared the manuscript and revision. Yusuke Osawa: attended conferences where cases were discussed to determine policy and performed surgeries, contributed to the manuscript drafting and revision. Yasuhiko Takegami: attended conferences where cases were discussed to determine policy, contributed to the manuscript drafting and revision. Shiro Imagama: attended conferences where cases were discussed to determine policy and approved the submitted version of the manuscript and agreed to be accountable for any part of the work.