1433 - Post-Operative ‘Pop’ Following Total Hip Arthroplasty

Case Diagnosis: Rectus femoris direct head avulsion with retraction

Case Description: A 56 year old female with history of right anterior approach total hip arthroplasty five weeks prior presents for right anterolateral thigh pain. Post-operatively, she had minimal pain and was feeling well. Ten days prior to presentation, she was standing up from kneeling, heard a pop and had sharp pain and ecchymosis in her right anterolateral hip with difficulty bearing weight. Since then, she notes a throbbing pain with activity.
On physical examination, the right hip was slightly warmer to touch with minimal tenderness around her incision. Neuromuscular exam of the lower extremities was unremarkable other than 3/5 right hip flexor strength.
A diagnostic musculoskeletal ultrasound demonstrated a complete tear of the right direct head of the rectus femoris tendon off the anterior inferior iliac spine (AIIS) with a four centimeter retraction. She was managed conservatively following sports orthopedics consultation.

Discussions: Rectus femoris avulsions are rare and typically occur with high eccentric loading during rapid contraction leading to asynchronous activation, as seen in young soccer or football players when kicking and sprinting. Avulsions are even rarer in skeletally mature adults. For the direct anterior approach hip arthroplasty, the joint is accessed via reflection of the rectus femoris indirect head. This patient was an avid yogi and dancer, and the combination of increased flexibility, with the recent hip arthroplasty, may have predisposed her to the avulsion. This case highlights a complete tear of the rectus femoris direct head tendon off the AIIS after an anterior approach total hip arthroplasty, a previously unreported complication.

Conclusions: This is the first case to our knowledge in the literature of a rectus femoris direct head avulsion with retraction following a direct anterior approach total hip arthroplasty. Although rare, this diagnosis should be considered in the event of post-surgical injury.