Image Quiz

Flexion Contracture and Cyclic Hip Pain in a Twenty-Three-Year-Old Woman (continued)

Answer: Endometriosis involving the obturator nerve and obturator internus and obturator externus muscles.


Fig. 1		 Fig. 1 Anteroposterior pelvic radiograph showing demineralization and external rotation of the right hip.

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Fig. 2		 Fig. 2 Axial proton-density T2-weighted magnetic resonance image without fat saturation (repetition time, 2000 msec; echo time, 30 msec), showing an extensive mass at the pelvic sidewall on the right, consistent with endometriosis. The short external rotators are thickened and contain bright foci consistent with endometriosis.

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A computerized tomographic scan demonstrated a 5 to 7-cm-diameter mass in the right obturator fossa. A computerized tomography-guided needle biopsy of the mass was performed, and a pathologic diagnosis of endometriosis was made. In addition, pelvic ultrasonography showed some evidence of an endometrioma inside the right ovary. A repeat pelvic magnetic resonance imaging scan with and without gadolinium was performed to better delineate the extent of the disease process. This scan showed multiple punctate foci of increased signal about both pelvic sidewalls, particularly on the right, which were thought to represent small endometrial implants or endometriomas (Fig. 2). The right obturator internus and externus muscles were seen to be thickened and contained multiple focal lesions consistent with the diagnosis of endometriosis. Tiny areas of endometriosis involving the right adnexa were also seen. These lesions were best seen on axial proton-density T2-weighted images without fat saturation.

The patient underwent an exploratory laparotomy and right pelvic dissection by a gynecologic surgical team, followed by a right hip exploration by our orthopaedic team. The right ovary was noted to have a surface lesion that was consistent in appearance with a cystadenofibroma. This ovary and the right fallopian tube were resected. The left ovary appeared normal. There was thickening along the right pelvic sidewall, and the posterior part of the uterus and cul-de-sac contained obvious foci of endometriosis. These foci were biopsied, and the diagnosis was confirmed histologically intraoperatively.

Nodal tissue surrounding the external iliac artery and vein was removed. The obturator nerve was noted to be compressed but was dissected free of the pelvic sidewall. The sidewall mass was resected as completely as possible, and later histologic examination confirmed the diagnosis of endometriosis. The inferior part of the abdomen was further explored. No classic "pocket sign," or retraction of the soft tissue into the sciatic notch resulting from contracture caused by the endometriosis, was seen during the exploration. The abdomen was closed, and the patient was placed in the left lateral decubitus position. The hip was exposed through a curved lateral incision centered on the greater trochanter. The fixed external rotation contracture made exposure of the posterior part of the capsule difficult. The short external rotators were identified and released, which resulted in approximately 10° of additional internal rotation. In spite of the findings seen on magnetic resonance images, there was no histologic evidence of endometriosis in the short rotators or the capsule, but both were thickened. The sciatic notch was palpated, and no masses were detected. A longitudinal posterior capsular release at the margin of the acetabulum was then performed, allowing for approximately 50° of internal rotation of the hip. The short external rotators were left unattached, and the fascia and wound were closed.

Pathological examination of the resected specimen revealed a 3.3 × 2 × 1.8-cm fibroma of the right ovary and a normal fallopian tube. The findings of the cul-de-sac biopsies were consistent with endometriosis. Examination of seven lymph nodes obtained from the right obturator fossa revealed endometriosis in a single node. Lymph nodes obtained from the right pelvis and the area surrounding the obturator nerve were normal. Histologic examination of the hip capsule revealed dense fibrovascular connective tissue.

Postoperatively, the patient maintained a full range of motion of the hip but had some recurrence of the pelvic pain. Lupron Depot (leuprolide acetate) injections were begun, and an exercise program was prescribed. Three years postoperatively, the patient reported a continued full range of motion of the right hip but had some persistent pain, which was controlled with hormone therapy.

Discussion

Our patient had a fixed flexion and external rotation contracture of the hip and cyclic pelvic and groin pain secondary to endometriomas that were lying adjacent to the obturator nerve and were causing edema and contracture of the obturator externus and internus muscles. The hip contracture was primarily capsular in origin as it was mostly relieved by surgical release of this structure. However, a component of the contracture was also muscular in origin as release of the short external rotators also helped to restore some hip motion. The groin pain probably was due to cyclic compression of the obturator nerve by the periodic hypertrophy of the endometrial tissue stimulated by estrogen and progesterone during the menstrual cycle. It is interesting that the symptom of stiffness preceded the pain in this patient. This finding may indicate that there was involvement of the short external rotators before symptomatic obturator nerve compression developed.

The location of the endometrial tissue and the presence of a fixed hip-joint contracture in our patient are unique findings that apparently have not been described in previous reports in the literature. Cyclic pain in the hip region often has been attributed to involvement of the sciatic nerve, and there have been reports of hip, thigh, or groin pain due to endometriomas involving other structures, including the lateral pelvic sidewall and retroperitoneum, the deep hamstrings fascia, the external oblique aponeurosis, the pubic tubercle, the obturator foramen, the ureter, the ilioinguinal nerve, and the extraperitoneal portion of the round ligament. However, we have not encountered any other published reports in which the short external rotators were involved. In addition, fixed hip contracture followed by cyclic groin pain has not been previously reported as a presenting symptom complex in association with endometriosis. Bjornsson described the case of a patient who had cyclic sciatica with a coexisting hip abduction contracture due to an endometrioma extending into the obturator foramen. However, the contracture occurred late (after surgical excision of the endometriosis lesion), developed after hormone suppression therapy had ceased, and remitted after hormone therapy had been resumed.

The mechanism by which the endometriomatous tissue infiltrated the short external rotators is unknown. Other investigators have suggested hematogenous or lymphatic seeding in cases of ectopic foci. Smith and Ward proposed that the mesocolon provides a direct anatomical pathway for extension of intra-abdominal access to the hip region. The mesocolon may allow for spread along the iliopsoas muscle, which inferiorly is in intimate contact with the hip capsule. It is possible that a similar pathway of direct extension via the retroperitoneum and obturator foramen led to ectopic foci of endometriosis in this case. Regardless of the mechanism, the case of our patient is consistent with the observation by Pellegrini et al. that 88% of documented extraperitoneal lesions have been unilateral and have involved the right side.

Other cases of cyclic pain about the hip due to endometriosis have been treated successfully with surgical excision, hormone suppression, or both. Our patient had both of these treatments in addition to a release of the structures that were contributing to the extreme rotation contracture of the hip. It is doubtful that joint motion would have been regained with hormone-suppression therapy alone because of the fibrotic, contracted nature of the hip-joint capsule and the involvement of the short external rotator muscles.

In conclusion, endometriosis should be considered in the differential diagnosis for women of childbearing age who have hip contracture along with pelvic and/or groin pain related to the menstrual cycle.

Reference

1. Spirt AA, Morrey BF, Pritchard DJ, Stanhope CR. Fixed hip contracture and cyclic hip pain secondary to endometriosis. A case report. J Bone Joint Surg Am. 2005;87:177-80.