A painful right hip

A 59-year-old man presented to the acute care clinic complaining of right hip, groin, and pelvic pain that started 4 days ago when he stood up and stretched getting out of bed. He states that he felt and heard a “clunk” from his right total hip replacement just before the pain started. The patient said he has not been able to flex his right hip normally for the past few days and has returned to using a cane while walking. He says the pain is getting worse and making it more difficult for him to walk. The pain is worse with weight bearing and reduced with sitting.

The patient denies any trauma such as falling. He says he had an uncomplicated right hip replacement in 2004 but that 2 weeks postoperatively, the hip “blew out” when he was walking, requiring an immediate revision surgery. He has had no hip problems since the revision.

The patient has a history of atrial fibrillation, heart failure, aortic stenosis, cardiomyopathy, hyperlipidemia, hypertension, and hypothyroidism. He has had an aortic valve replacement and has an implanted cardioverter-defibrillator (ICD). He takes warfarin, carvedilol, digoxin, furosemide, isosorbide mononitrate, potassium chloride, lisinopril, metolazone, zolpidem, and levothyroxine.

The patient's vital signs were: BP, 142/64 mm Hg; pulse, 77 and regular; respirations, 20 and unlabored; SpO₂, 94% on room air; and temperature, 98.4° F (36.9° C). He was in good spirits, alert and oriented, and in no distress. The patient exhibited an antalgic gait with the use of a cane and was able to get on and off the examining and radiograph tables with some assistance. His pelvis was stable on examination. Vascular examination of the lower extremities revealed normal temperature to touch with bilateral peripheral vascular disease with 2+ pitting edema. Pulses were 2/4, with good capillary refill in the feet and toes.

Examination of the left hip revealed full range of motion (ROM) with flexion, extension, and adduction with minimal crepitus and no pain. Examination of the right hip showed a well-healed lateral hip replacement scar with the skin intact. The patient had no pain with palpation to the hip or groin area. Passive ROM of the right hip revealed severe crepitus with reproduction of the patient's pain with flexion, extension, and adduction. Which imaging study is the best choice to evaluate this patient's chief complaint?

The correct answer is plain AP and lateral radiographs of the right hip—an MRI cannot be used because the patient has an ICD. Ultrasound would evaluate the patient's vascular status but not hip stability. CT is not recommended as a first-line imaging study over in-office radiographs.

A total hip replacement includes the femoral stem, femoral head that attaches to the end of the stem, and acetabular liner that fits into the acetabular component. The major causes of failure in hip replacements are dislocation, loosening of the stem and cup, and stem failure.1 Pain may be a sign of infection.2 Stem loosening is a late complication that most often occurs 5 to 10 years after hip replacements.1 Total hip dislocation occurs in 1% to 4% of patients after primary replacement and up to 16% of patients who have had hip replacement revision surgery.3

Given the patient's history and the acuteness of his pain, hip infection was less likely. Plain radiographs of the hip in both the AP and lateral view are normally sufficient to evaluate for hip replacement loosening, dislocation, or bone fracture. Additional radiographs, including oblique/frog lateral views, can be obtained if needed.

The patient's radiograph (Figure 1) showed that the femoral head had detached from the femoral stem and was lodged in the thick membranous capsule surrounding the hip joint. As a result, the femoral stem was in direct contact with the acetabular liner and acetabular component, causing the patient's pain and severe lack of ROM.

The patient's orthopedic surgeon practiced locally and was reached by phone. The patient was transferred to a local ED for admission and hip replacement revision after he was medically stabilized and cleared for surgery by the intensivist and anesthesia. During the surgery, a small femur fracture was found and repaired with a femoral fracture hook and cerclage wires (Figure 2). The patient was discharged home several days after surgery and is now able to walk with assistance.

1. Orthopaedic Research Institute, St. George Hospital Campus, University of New South Wales, Australia. The hip joint: how to recognize a failing hip replacement. www.ori.org.au/hipjoint/failing.html. Accessed March 15, 2016. [Context Link]

2. Spinarelli A, Patella V, Conserva V, et al. Hip painful prosthesis: surgical view. Clin Cases Miner Bone Metab. 2011;8(2):14–18. Bibliographic Links [Context Link]