1039 - A case of osteoporosis of the hip in pregnancy presenting with severe hip pain

38-year-old female, G1P0 at 36w6d with no medical/surgical history, presented to the rehabilitation clinic with severe left hip pain. Pain began two months prior in the left low back and buttock, following a long walk 10 days prior progressed to severe lateral hip pain. Pain was exacerbated by turning in bed, bending forward, and walking/weight-bearing. She purchased crutches to offload while ambulating, and managed pain with lidocaine patches, heat/ice, and Tylenol. 

Exam significant for antalgic gait, full lower extremity strength, positive Scour, Stinchfield, FABER, FADIR, and Log Roll of the left hip. MRI of the left hip without contrast showed pronounced bone marrow edema of the femoral head extending into the femoral neck and intertrochanteric region consistent with pregnancy related transient osteoporosis of the hip (PR-TOH), and subchondral fracture line in the femoral head without articular collapse.  


Discussions: PR-TOH is a rare self-limiting condition typically presenting during the 3rd trimester or while breastfeeding. Incidence of PR-TOH is unknown, as it's under-diagnosed and requires MRI for diagnosis. Risk factors include advanced maternal age, low BMI, family history of osteoporosis, smoking, and IVF. Presentation is vague with severe pain in the groin, buttocks, and anterior thigh with intolerance to weight-bearing. Management is conservative protected weight-bearing and analgesia. Symptoms and radiographic findings spontaneously resolve within months; however, can progress to avascular necrosis. Etiology is unknown, however may be related with pregnancy hormonal and bone metabolism changes, and fetal calcium demand.

Conclusions: PR-TOH is rare and often misdiagnosed as other musculoskeletal conditions which occur in pregnancy. It's important to take a detailed history, conduct thorough musculoskeletal and neurologic exams, and pregnancy safe imaging when indicated. In cases of PR-TOH, discussions about weight-bearing, pain management, delivery method, breastfeeding, nutrition, and return to activity should be conducted in a multi-disciplinary team.