Extract
Hip pain with mechanical snapping is a common symptom with a wide-ranging differential diagnosis, including both extra and intra-articular etiologies. Femoroischial impingement should also be considered since many cases of recalcitrant hip pain may be misdiagnosed cases of this form of impingement.
Hip pain with mechanical snapping is a common symptom with a wide-ranging differential diagnosis, including both extra and intra-articular etiologies. Femoroischial impingement should also be considered since many cases of recalcitrant hip pain may be misdiagnosed cases of this form of impingement.
To the best of our knowledge, femoroischial impingement was first described by Johnson in 19771. He hypothesized that superior and medial migration of the lesser trochanter as a result of degenerative changes, posttraumatic changes, or surgery causes a decrease in the distance from the lesser trochanter to the ischium, thus leading to painful impingement. His report included three cases that were limited to older patients: there were two cases with a malpositioned total hip prosthesis and one case with degenerative changes prior to arthroplasty. Subsequent reports have involved only adult patients2-5.
Quadratus femoris muscle tears have also been described as an unusual cause of hip pain6-8, and they have been reported in cases of femoroischial impingement3,5. They affect women much more frequently than men3,5, and they may or may not include a history of trauma or surgery9. The pain may radiate to the legs, which may be related to the proximity of the sciatic nerve4,10. Anti-inflammatory medications have been used with variable results as a first-line treatment3-5. Lesser trochanteric resection has been advocated in recalcitrant cases1,2,5.
To our knowledge, we present the first documented case of primary femoroischial impingement as a cause of snapping hip syndrome in a fourteen-year-old girl. This diagnosis should be considered in the investigation of snapping hip syndrome as a readily identifiable and treatable cause of hip pain. We offer guidance in the diagnosis and definitive management of femoroischial impingement, and we advocate a novel surgical technique with minimal morbidity for treatment of this pathology. The patient and her parents were informed that data concerning the case would be submitted for publication, and they provided consent.
A fourteen-year-old girl presented after three years of worsening severe right hip pain. She had seen a number of health care professionals and was treated nonoperatively for presumed causes of snapping hip syndrome (including snapping iliotibial band, snapping iliopsoas, athletic pubalgia, and labral tear) with activity modification, anti-inflammatory medications, and physical therapy. The patient was only able to walk with crutches and bear partial weight on the affected side; she had completely withdrawn from normal activities. She had a markedly antalgic gait, walking on the lateral border of the foot and with an internal foot progression angle of about 30°. The rotational profile was within normal limits, although the range of right hip rotation was limited by pain. She was able to demonstrate a dramatic, painful “clunking” phenomenon by standing with the affected hip slightly adducted and then sequentially rotating the hip internally and externally. No specific areas of tenderness were identified around the hip. Other provocative tests for hip pathology, including the FABER test11 and the impingement test12, were negative. The remainder of the musculoskeletal and neurovascular examinations was normal.
Radiographs of the pelvis demonstrated no evidence of dysplasia or femoroacetabular impingement (Fig. 1). A magnetic resonance (MR) arthrogram ruled out intra-articular pathology and showed a normal labrum. Magnetic resonance imaging (MRI) verified no pathology involving the psoas tendon, but did clearly demonstrate intense signal change consistent with edema in the quadratus femoris muscle (Fig. 2-A). The MRI also showed reduced space between the ischium and the lesser trochanter on the right side compared with the contralateral side (Fig. 2-B). A computed tomography (CT) scan of the lower limb confirmed a normal rotational profile.
A dynamic examination under anesthesia (EUA) confirmed femoroischial impingement by reproducing the clunking phenomenon and by documenting the proximity of the lesser trochanter to the ischium. With use of fluoroscopy, the impingement was visualized most clearly on a cross-table lateral view (Figs. 3-A and 3-B). In the position of hip extension and mild adduction, as well as with progressive external rotation, the lesser trochanter could be visualized to approach the lateral tuberosity of the ischium, impinge on it, and, with a palpable clunk, force its way anteriorly. The patient was subsequently offered an ischioplasty procedure.
After general anesthesia was administered, the patient was positioned in the lateral decubitus position on a radiolucent table and draped with two split sheets. With the hip flexed and adducted, a 5-cm longitudinal incision was made directly over the ischial tuberosity. The gluteus maximus muscle was split along the fibers overlying the ischial tuberosity. The sciatic nerve was not specifically dissected out for protection since it courses well lateral to this plane of dissection. The origins of the biceps femoris and medial hamstring muscles were split longitudinally, and they were gently peeled from their attachment. Subperiosteal dissection exposed the ischial tuberosity (Fig. 4-A), and a finger was placed to confirm the impingement as the hip was extended, adducted, and rotated. A half-inch osteotome was used to resect the lateral 50% of the ischial tuberosity (approximately 1 cm in thickness) (Fig. 4-B). The depth of the ischial tuberosity was retained so as not to affect sitting balance or height. A finger was again used to confirm that the impingement was gone. The origins of the hamstrings were repaired over the ischium, and the wound was closed. The postoperative radiographic appearance can be seen in Figure 5.
Postoperatively, the patient was allowed to bear weight as tolerated with crutches, and she was discharged home two days later. No neurologic complications were identified, and the ability to perform the clunking phenomenon immediately ceased. At the twelve-week follow-up, the patient showed dramatic improvement, was completely pain free, was able to walk without crutches, and had regained a normal gait for the first time in three years.
Although described by Johnson in 19771, femoroischial impingement is rarely considered in the differential diagnosis for a painful snapping hip. Johnson stated that the lesser trochanter and ischium are usually positioned approximately 2 cm from each other when the hip is in slight adduction, external rotation, and extension.
Diagnostically, radiographs of femoroischial impingement may show the decreased distance between the osseous prominences of the lesser trochanter and ischium, as well as degenerative changes on the ischial side4, but radiographs are more likely to show normal findings. Ultrasound can be used to rule out a snapping psoas tendon, and an MR arthrogram is useful to rule out intra-articular pathology. MRI may show the hallmark quadratus femoris muscle edema, with or without a tear, as well as the narrowed distance between the lesser trochanter and ischium. Torriani et al. defined the ischiofemoral space as the smallest distance between the lateral cortex of the ischial tuberosity and the medial cortex of the lesser trochanter; the quadratus femoris space was defined as the smallest space for passage of the quadratus femoris muscle, delimited by the superolateral surface of the hamstring tendons and the posteromedial surface of the iliopsoas tendon or lesser trochanter5. They defined narrowing as an ischiofemoral space of less than 17 mm and a quadratus femoris space of less than 8 mm. A CT scan and rotational profile are useful if torsional or acetabular version issues are suspected.
Rest and nonsteroidal anti-inflammatory medications are the first-line treatments3-5. The role of physical therapy has not been defined. Image-guided injection of the quadratus femoris muscle can give symptomatic relief4,5 and can be used as a confirmatory test. With our patient, we utilized an EUA with fluoroscopy to reproduce the clunking and to radiographically document the dynamic phenomenon of abutment of the lesser trochanter against the ischium as the hip was extended, adducted, and alternately rotated both internally and externally. This was clearly visualized with the fluoroscopic cross-table lateral view.
In the few documented cases of surgical treatment of femoroischial impingement, lesser trochanter resection has been described with successful outcomes1,2,5. However, these were all cases with improper positioning of the lesser trochanter because of degenerative changes, previous trauma, or surgery. Also, to reach the lesser trochanter from the posterolateral approach to the femur requires substantial soft-tissue stripping. This could conceivably be addressed by using a medial approach, but both approaches will theoretically jeopardize the vascular supply to the femoral head in the skeletally immature patient because of the proximity of the medial circumflex femoral artery. Furthermore, excising the lesser trochanter will risk long-term hip flexor weakness. We offer a novel alternative in the ischioplasty procedure, which specifically confronts the primary pathology. This approach is commonly used in biopsy of musculoskeletal tumors or more extensively for resection of the ischium, and the vascular supply to the femoral head is not at risk. It allows direct visualization and palpation of the pathological impingement to assist with adequate ischial recession. Because the origins of the hamstrings are split longitudinally and lifted subperiosteally, they can be repaired without functional deficit. We recommend weight-bearing as tolerated with crutches for six weeks, primarily for pain relief. We saw complete resolution of symptoms by twelve weeks and a full return to activities in our patient.
In summary, femoroischial impingement should always be considered in the differential diagnosis for hip pain and a painful snapping hip. The combination of clinical examination, MRI, and fluoroscopy is diagnostic. For cases that are recalcitrant to conservative therapy, ischioplasty offers an elegant, safe, and effective definitive surgical treatment.
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Disclosure: None of the authors received payments or services, either directly or indirectly (i.e., via his or her institution), from a third party in support of any aspect of this work. One or more of the authors, or his or her institution, has had a financial relationship, in the thirty-six months prior to submission of this work, with an entity in the biomedical arena that could be perceived to influence or have the potential to influence what is written in this work. No author has had any other relationships, or has engaged in any other activities, that could be perceived to influence or have the potential to influence what is written in this work. The complete Disclosures of Potential Conflicts of Interest submitted by authors are always provided with the online version of the article.