Femoral head subchondral fragility fracture is a pathological fracture of the femoral head bearing part based on bone fragility such as osteoporosis. It was first reported by Bangili et al. in 1996 11). In the early stages of the disease, plain radiographs do not show obvious abnormalities, often delaying diagnosis.

1. epidemiology

It tends to occur more often in osteoporotic patients (elderly/female). Occurrence after renal transplantation and, although rare, in young individuals have also been reported. It is also considered as one of the etiologies of rapidly destructive hip arthritis 12) 13) 14).

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2. Diagnosis (Table)

In patients with osteoporosis, it often develops as a result of minor trauma such as a near fall or overload such as walking more than usual, but sometimes there is no trigger at all. However, in recent years, there have been reports of intractable SIFFH being treated using hip arthroscopy, and it has been clarified that it is frequently associated with hip labrum injury 15). Therefore, due to the microinstability caused by the hip joint labrum injury, stress fractures gradually occur, so even middle-aged and elderly sports enthusiasts develop the disease.

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• Plain X-ray

In the early stages, there are few abnormal findings. In cases where the crush did not progress, sclerosis is seen after several months. In the case of advanced crushing, an irregular image of the load-bearing part and a subchondral fracture line are observed. The zonal sclerosis characteristic of idiopathic femoral head necrolysis is rarely seen.

• MRI examination

This fracture is a pathological fracture and is an essential examination. Characteristic findings are a strong low-intensity band immediately below the femoral head-loaded part and a surrounding bone marrow edema pattern on T1-weighted images (Fig. 2). This band image is often irregular, meandering, and centrally convex, and is important for differentiation from femoral head necrosis (distal convex band) 13) 14). If MRI cannot be performed due to a pacemaker, etc., bone scintigraphy should be considered.

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3) Arthroscopic classification

Uchida et al classified the arthroscopic findings of SIFFH as follows: Microinstability is considered to be the cause of the pathology because all cases were accompanied by hip labrum injury.

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Grade 0: normal

Grade I: Before crushing

Grade IA: Cartilage intact and stable upon probing

Grade IB: fissured or fibrillated cartilage

Grade IC: Partial discontinuity in cartilage, unstable on probing

Grade II:  subchondral bone crush

Grade IIA: No arthritic change Partial discontinuity in cartilage, unstable on probing

Grade IIB: Moderate arthropathic changes Cartilage degeneration

Grade III: Cartilage completely collapsed Severe arthropathy

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3. treatment

In cases where the collapse has not progressed, rest and weight-bearing conservative therapy are performed. If conservative therapy does not improve the condition and the condition is pre-collapse, arthroscopic surgery is effective. Grade I to Grade IIA are indications for arthroscopic surgery. Repair the labrum and correct FAI if there is impingement due to FAI. The SIFFH lesion is internally fixed using hydroxyapatite poly-L lactate pins under arthroscopy, and finally the joint capsule is sutured (Fig. 3).

Treatment for osteoporosis is also started at the same time. In cases with advanced crushing, head and hip arthroplasty is often performed. There is also a report of femoral head rotation osteotomy for juvenile onset 16).

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4. Points to avoid misdiagnosis

SIFFH can occur as a complication of osteoporosis or labrum injury, even if there is no particular history. A definitive diagnosis should be made with MRI before crushing occurs. When interpreting MRI images, pay attention to the direction and shape of the band image.

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11) Bangil M, Soubrier M, Dubost JJ, et al. Subchondral insufficiency fracture of the femoral head. Rev Rhum Engl Ed. 1996;63(11):859–861.

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12) Yamamoto T, Bullough PG. Subchondral insufficiency fracture of the femoral head: a differential diagnosis in acute onset of coxarthrosis in the elderly. Arthritis Rheum. 1999;42(12):2719–2723.

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13) Yamamoto T, Schneider R, Bullough PG. Insufficiency subchondral fracture of the femoral head. Am J Surg Pathol. 2000;24(3):464–468.

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14) Ikemura S, Yamamoto T, Motomura G, Nakashima Y, et al. MRI evaluation of collapsed femoral heads in patients 60 years old or older: Differentiation of subchondral insufficiency fracture from osteonecrosis of the femoral head. AJR Am J Roentgenol. 2010; 195(1): W63–W68.

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15)Uchida S, Noguchi M, Utsunomiya H, et al. Hip arthroscopy enables classification and treatment of precollapse subchondral insufficiency fracture of the femoral head associated intra-articular pathology. Knee Surg Sports Traumatol Arthrosc. 2018;26(8):2527‐ 2535.

​This is a new surgical method published by Wakamatsu Hospital.

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16)Sonoda K, Motomura G, Ikemura S, et al. Favorable Clinical and Radiographic Results of Transtrochanteric Anterior Rotational Osteotomy for Collapsed Subchondral Insufficiency Fracture of the Femoral Head in Young Adults. JB JS Open Access. 2017;2(1):e0013 .

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