Complete Extra-articular Ankylosis of Hip and Stiff Elbow in a Case of Extensive Myositis Ossificans: A Rare Presentation

Introduction: Myositis ossificans (MO) is a benign ossifying lesion. It is also known as heterotopic ossification of muscle, in which lamellar bone is formed in the muscle most commonly due to trauma or neurological injury. Complete extra-articular ankylosis due to extensive MO is rare.

Case Report: We report a case of 22-year-old female with post-traumatic MO following head injury. The patient developed extensive MO in iliopsoas and brachialis muscle leading to complete extra-articular ankylosis of hip and stiffness of elbow which lead to severe functional disability to the patient. Hematological parameters were normal. Surgical excision of the bony mass was done in two stages- hip followed by an elbow. The patient had marked functional improvement in hip and elbow.

Conclusion: Complete extra-articular ankylosis of hip is rare in the case of MO. The massive size of bony mass connecting the femur to pubis is not common and computed tomography angiography is beneficial if bony mass is in the vicinity of neurovascular bundle. Good functional results can be obtained with excision of bony mass after ruling out bony malignancy.