Heterotopic ossification after local steroid injection

Background

Pachydermodactyly (PDD) is a rare, benign disease that causes soft tissue swelling resulting in thickening of the skin over the proximal interphalangeal (PIP) joints of fingers II–IV.1 PDD classically occurs in adolescent men, typically as a consequence of repetitive mechanical trauma from tic-like behaviour.2 This disease rarely extends to the metacarpophalangeal joints and does not affect the bone or synovium.3 Diagnosis is based on clinical presentation, laboratory testing and imaging studies. It is typically treated with rehabilitation, which involves cessation of the repetitive movements that caused the lesions and intralesional steroid injections.3

There are several recognised complications after steroid injections such as pain at injection site, soft tissue atrophy, tendon and cartilage attrition, and while subcapsular calcification has been recognised as a complication after steroid injection, heterotopic ossification has never been reported. To the best of our knowledge, we describe here the first case of heterotopic ossification following local steroid injection. In addition, we aim to review the management of PDD, a rare but important differential diagnosis for plastic surgeons to consider in a hand patient presenting with joint swelling.

Case presentation

We present the case of a 37-year-old right-hand dominant male engineer and concert pianist with no significant medical history who presented with enlargement surrounding the PIP joints of his right middle and ring fingers. The enlargement around his middle finger PIP joint was painless, but its size sometimes interfered with his piano playing. His ring finger PIP joint was less significantly affected and asymptomatic. The patient endorsed a history of cracking his knuckles and gnawing on the sides of his right middle and ring fingers since he was a teenager up until 2 years prior to presentation. The enlargement began in his teenage years and stabilised in his early 20s. He denied any morning stiffness of his joints or reduced joint function and had no medical, surgical or substance use history.

Physical examination of the right hand was significant for localised swelling of the soft tissues surrounding the middle finger PIP joint and to a lesser degree the ring finger PIP joint (figures 1 and 2). The joints and soft tissues were soft, non-erythematous, non-tender and stable to stress. There was no pain on axial loading. The patient had full active range of motion with global hyperextensibility and was neurovascularly intact.

Investigations

Plain films of the right hand (figure 3) were obtained and showed localised soft tissue swelling surrounding the aforementioned joints but no bony abnormalities. Routine laboratory values that the patient had previously obtained including complete blood count (CBC), comprehensive metabolic panel (CMP) and thyroid stimulating hormone (TSH) were unremarkable.

Differential diagnosis

A diagnosis of PDD was made given the characteristic findings of painless soft tissue swelling and lack of signs consistent with inflammatory or bony disorders. Plain films of the right hand (figure 3) were obtained and showed localised soft tissue swelling surrounding the aforementioned joints but no bony abnormalities which is consistent with PDD. In addition, routine laboratory values that the patient had previously obtained including CBC, CMP, and TSH were unremarkable which is consistent with PDD.

Treatment

While the patient had stopped engaging in repetitive finger gnawing and knuckle cracking for 2 years, he was cautioned on the importance of continued abstinence from these repetitive movements to prevent worsening of his disease. After discussing surgical and non-surgical options, including the risks and benefits of local steroid injection, the patient elected to proceed with local steroid injection. 0.5 cc of Kenalog-40 (triamcinolone acetonide injectable suspension 40 mg/mL) was injected using a 25-gauge needle into the dermal and capsular layers of each side surrounding the right middle finger PIP joints. The patient reported satisfaction and improved mobility after local steroid injection, which was performed three times over a period of 6 months. Follow-up appointments revealed thinning of the injected region and improved range of motion. The patient denied any pain or concerns.

Outcome and follow-up

However, 2 years after his last injection, the patient returned to clinic complaining of decreased range of motion and pain of the right middle finger PIP joint. He reported feeling a hard lump proximal to his ulnar middle finger PIP joint 6 months after his last steroid injection, which gradually enlarged and led to pain that limited his ability to flex his finger. He denied any trauma to his right hand that preceded these symptoms. Examination revealed increased soft tissue enlargement around his right middle finger PIP joint and stable soft tissue enlargement around the right ring finger PIP joint. He was tender to palpation around the middle finger PIP joint and flexion was limited by pain.

X-ray reviewed new para-articular calcifications and heterotopic ossification of the ulnar proximal phalanx soft tissues with persistent soft tissue swelling and skin thickening of the middle finger (figure 4). The diagnosis of heterotopic ossification was made radiographically as the bone in this patient’s soft tissue is not amorphous calcification as seen in calcium pyrophosphate dihydrate crystal deposition disease or tumorous calcinosis. Rather, radiographically, the calcific density in the soft tissue appears like mature bone and is corticated with central cancellous appearance. Management of heterotopic ossification was discussed with the patient and treatment with indomethacin was begun.

The patient returned after 8 weeks of treatment with indomethacin and noted decreased pain and stiffness though he was still unable to make a fist. He also noted interval increase in size of the ulnar proximal phalanx mass. Notable changes in the examination were a decrease in range of motion of the middle finger PIP joint 0–90 degrees (0–135 degrees other digits). X-ray revealed increased size of heterotopic ossification and persistent soft tissue swelling (figure 5). Excision of the heterotopic ossification was offered to the patient; however, the patient declined surgery and opted for continued indomethacin treatment.