Ischiofemoral impingement (IFI) is a relatively rare condition affecting the hip and pelvis, characterized by pain and sometimes snapping or clunking in the groin and/or buttock. IFI is caused by entrapment of soft tissue, the quadratus femoris muscle (QFM) in the ischiofemoral space (IFS) or quadratus femoris space (QFS). As reported, conservative treatment for IFI may consist of correction of leg length using insoles, physiotherapy with stretching and strengthening of the QFM, other exorotator muscles and abductors or radiological guided infiltration. Surgical intervention is indicated in cases of persistent symptomatic IFI after conservative therapy for at least three months. The aim of a potential surgical strategy is to correct underlying pathologies; for example, femoral osteotomy, offset correction after total hip arthroplasty, gluteal tendon repair or surgical revision of hamstring pathology, ischioplasty or an open or endoscopic resection of the lesser trochanter may provide an appropriate option^1-6). A treatment algorithm was provided by Gollwitzer et al.¹⁾.

A 52-year-old female presented in our office with persistent bilateral, deep-gluteal pain. On physical examination, she exhibited a normal range of motion with negative FADIR (flexion, adduction, internal rotation) and FABER (flexion-abduction-external rotation) signs, painful hyperextension of both hips and bilateral palpatory pain just lateral of the ischial tuberosity. The long stride walking test was positive. She had previously undergone a cervical spinal fusion and wrist arthroplasty. Otherwise she was in good health. The spinal clinical examination showed normal findings with no signs of (pseudo-) radiculopathies and intact strength and sensitivity in the lower extremities. A magnetic resonance imaging (MRI) of the spine showed mild degenerative changes of the lower spine without discoradicular conflicts or stenosis. The MRI of the pelvis showed oedema in both QFMs, suggestive of bilateral IFI. IFS measured 5.17 mm on the left side, and 5.2 mm on the right side (Fig. 1, 2).

Figure 1. Magnetic resonance imaging of the pelvis showing a reduced ischiofemoral space on the left (5.17 mm) and right side (5.2 mm).

Figure 2. Magnetic resonance imaging of the left hip showing oedema in the quadratus femoris muscle, between the ischial bone and lesser trochanter.

The diagnosis was IFI. Conservative therapy was continued, consisting of oral non-steroidal anti-inflammatory drugs, optimisation of physiotherapy for more than three months with stretching and muscle training and computed tomography (CT)-guided infiltrations.

No improvement of the symptoms was observed over a period of three months. Therefore an endoscopic resection of the lesser trochanter on the left side was performed. A biopsy was not performed, given the precise clinical, anamnestic and radiologic diagnosis and intraoperatively, no aberrant tissue was found. The original classic technique described by Ilizaliturri and Camacho-Galindo⁷⁾ via two anterolateral portals was used. The hip was then flexed at 30° and externally rotated. The iliopsoas tendon was released and the lesser trochanter properly exposed. A complete resection of the lesser trochanter was then performed using intraoperative fluoroscopic controls in neutral position, endorotation and exorotation to ensure complete resection (Fig. 3, 4). The patient was discharged the next day.

Figure 3. Intraoperative image of the resected lesser trochanter of the left hip.

Figure 4. Intraoperative fluoroscopy showing an anteroposterior view of the left hip with a resected lesser trochanter.

The patient’s initial recovery was good, with no pain, a full range of motion and proper wound healing. After surgery, weight bearing was allowed as tolerated with the support of two crutches for the first two weeks. Physiotherapy, which was started immediately after surgery, included passive and active mobilization, muscle strengthening and gait training. Two weeks postoperatively, she developed pain in the left groin and was no longer able to bear weight.

No signs of infection and good wound healing were observed upon physical examination. Although mobilisation of the hip was still possible and relatively pain free, a straight leg raise was not possible. The laboratory results were negative. No signs of synovitis, no collections and no calcifications or callus formation were detected by X-ray (Fig. 5) and ultrasound. The initial working diagnosis was pain resulting from excessive physical exertion after the operation and starting physiotherapy or a stress fracture.

Figure 5. Postoperative anteroposterior (A) and lateral (B) X-ray of the left hip.

No improvement was observed four weeks later, despite modification of activity and non–weight-bearing. Bone scintigraphy was performed. According to our nuclear radiologist, the tracer uptake was indicative of a stress fracture and was too elevated to be described as normal or as a physiological or postoperative change (Fig. 6).

Figure 6. (A, B) Bone scintigraphy with increased tracer uptake at the level of the lesser trochanter of the left hip.

In addition, a scintigraphy performed two years prior to the endoscopic resection of the lesser trochanter for a different problem, showed no altered uptake in the trochanteric region.

Instead of an operative stabilisation, we decided to continue the conservative therapy with protected weight bearing and administration of a one-time intravenous (IV)-dose of alendronic acid. During the next clinical control, three weeks after undergoing bone scintigraphy, the patient reported an obvious improvement of her complaints. Thus we were dissuaded from performing additional operations. Six weeks after the diagnosis of a stress fracture and starting the protected weight bearing, the patient had recovered sufficiently to allow full weight bearing again. At the last clinical control, six months after the endoscopic resection of the lesser trochanter, the findings from a normal clinical investigation demonstrated a normal gait, full range of motion, a negative result on the posterior impingement test, and a negative result on the long stride walking test. The patient was able to walk 15 km and ride a bike for over 70 km without any problems.

IFI was first described in 1977 by Johnson⁸⁾ in three patients, two patients following total hip arthroplasty and one patient following proximal femoral osteotomy. IFI was eventually recognised as a potential source of hip and buttock pain in native hips and even in paediatric cases^9,10). However, it remains a relatively underdiagnosed condition. The problem of IFI is now better understood as a result of improved diagnostic tools and understanding of the hip and pelvis. A wide variety of predisposing factors, including coxa valga, developmental dysplasia of the hip, hereditary exostoses, fracture or avulsion of the lesser trochanter, previous surgery leading to loss of offset such as valgus osteotomy or total hip arthroplasty, acquired deformities resulting in superomedial migration of the femur such as Legg–Calvé–Perthes disease, loss of abductor strength, or hamstrings enthesopathy are regarded as possible reasons for IFI^1,11-13). The sexual dimorphism might explain a predominantly female distribution¹⁴⁾.

As described, IFI is caused by entrapment of the QFM in the IFS or QFS. The IFS is defined as the shortest distance between the lesser trochanter laterally and the lateral border of the ischium medially. The QFS is determined by the superolateral part of the hamstring tendons and the posteromedial side of the psoas tendon or lesser trochanter^1,15). Tenderness upon palpation in the IFS, load-dependent deep gluteal pain and/or a positive result on the long-stride walking test or IFI test (extension, external rotation, and adduction)¹⁶⁾ are clinical signs of IFI. MRI, which is regarded as the diagnostic study of choice, shows a narrow IFS or QFS with oedema, partial tear and/or fatty infiltration of the QFM^12,15,17-19).

The patient was referred to our practice by her general practitioner. She had already undergone physiotherapy and had received an anti-inflammatory treatment. Optimizing the physiotherapy and performance of an additional CT-guided infiltration were not helpful. Based on the refractory nature of the condition, the obvious narrowing of the IFS (left 5.17 mm and right 5.2 mm, reported reference values between 18 mm and 26 mm)¹⁾ and the fraying^1,20,21) of the QFM, we decided to proceed with performing an operation. No flowchart or treatment algorithm that might be helpful in the decision-making process was available at that time¹⁾.

A stress fracture is described as a fatigue-related fracture resulting from repeated submaximal stress²²⁾. A bone scan or scintigraphy, which offers the advantage of high sensitivity (74%-100%) and moderate specificity (68%)²³⁾, was chosen over MRI given the potential for false positives during the acute phase after surgery.

This case report highlights the importance of avoiding an overzealous resection of the lesser trochanter, which can potentially cause a stress fracture. To the best of our knowledge, this complication has never been reported after an open or endoscopic resection of the lesser trochanter. Few complications have been reported due to the relative scarcity of literature on the diagnosis and treatment as well as small patient cohorts. Aguilera-Bohórquez et al.²⁴⁾ reported a case series of 97 hips with subgluteal space pathologies. IFI was diagnosed in 17 of these hips (5 isolated and 12 combined IFI and sciatic nerve entrapment). Of the 97 hips, 19 hips eventually developed a postoperative complication. After isolated endoscopic resection of the lesser trochanter, no postoperative problems were observed in any of the five patients. Among the 12 cases of IFS decompression combined with sciatic nerve decompression, two complications were reported. One patient showed signs of symptomatic intra-abdominal fluid extravasation, and the other patient showed permanent nerve damage. A stress fracture was not diagnosed in any of the 97 hips.

The therapy that we initiated consisted of protected weight bearing and a one-time IV dose of alendronic acid. The position of bisphosphonates in acute or stress fractures remains unclear. According to a recent meta-analysis by Gao et al.²⁵⁾, fracture healing showed no improvement; however, an increase in changes in bone mineral density and a reduction in bone synthesis and resorption markers was observed. Thus it can be regarded as an appropriate choice for fracture healing. With the inhibition of bone resorption, an important step in the process of fracture healing, as well as an increase in callus size and the potential for greater callus strength, it can be regarded as a viable option in the acute treatment of fractures, when administered in a timely manner^25-29). According to Robertson and Wood³⁰⁾, a short period of protected weight bearing is recommended in cases involving stress fractures of the femoral shaft.

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