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Case discussion #18: osteochondral defect and loose body stuck in the posterior ankle

Mrs S is a delightful 67 year old lady who presented to Dr Touzell with a four month history of spontaneous right ankle pain. She described a sense of her ankle 'catching' during certain movements and struggled to walk downhill or wear heels due to pain in her ankle (this limitation of movement in plantarflexion is suspicious for posterior impingement).


There was no history of trauma, and Mrs S is otherwise very fit and well. She lives on a large property and also runs a small business, and was frustrated that her ankle pain limited her normal active lifestyle.


She had seen a Podiatrist who very appropriately trialled a simple heel lift which had helped reduce, but not eliminate, her pain. Her podiatrist was worried about the mechanical symptoms and posterior ankle pain, and was very correctly concerned about early arthritis or possibly a loose body in the ankle joint so referred Mrs S back to her General Practitioner for evaluation, investigations and orthopaedic opinion.


On examination, Mrs S was limping with her ankle in plantarflexion to avoid impinging the back of her ankle. She was very tender to palpation posteriorly and initially it was thought this may be insertional Achilles tendinopathy with retrocalcaneal bursitis. However she was very sore to deep palpation in the posterior ankle, but the actual Achilles was non tender. She had absolutely no tenderness to palpation over the medial or lateral talar domes or the talonavicular joint, and had decreased range of motion of her right ankle due to pain. Her ankle was stable to anterior drawer on her peroneal tendons and tibialis posterior tendonn were non-tender.


Plain x-rays were normal An MRI demonstrated a moderate sized posterior osteochondral defect with a displaced loose body caught in the posterior ankle joint (see below). She also had some evidence of arthritic change in the talonavicular joint, but (as is quite common) this was asymptomatic clinically.

Given Mrs S had mechanical symptoms and impingement from a loose body, we were concerned that non-operative management such as a steroid injection or strengthening would not be effective long-term. Surgery was therefore discussed. This was a posterior ankle arthroscopy, removal of the loose body and debridement of the osteochondral defect.

This was a relatively simple day-stay procedure. A posterior arthroscopy was performed, the loose body identified and removed and the osteochondral defect was debrided and microfractured. Mrs S was permitted to weight bear as tolerated in a post-operative shoe immediately post-operatively. She was completely pain free at her two-week post-operative appointment and was elated with her pain-free range of motion. She commenced strengthening exercises without restriction with her referring podiatrist two weeks after surgery, and five months later remains pain free. She is aware that she has some early arthritic change in her ankle and radiological evidence of arthritis in her talonavicular joint and may develop further arthritic symptoms in the future.


DISCUSSION

Osteochondral defects and loose bodies are common causes of mechanical symptoms in the ankle. Non-operative measures such as mobilisation, a heel lift and steroid injections are reasonable non-operative techniques to try before surgical referral, but pain from mechanical symptoms is often resistant to non-operative measures. In the elderly population, osteochondral defects can be due to arthritis rather than trauma which is more prevalent in a younger, active population. Plain x-rays and CT scans can be reported as normal, and an MRI scan is the investigation of choice when concerned about an osteochondral defect. This is because the majority of the lesion is often cartilagenous rather than bony, and therefore not visible on x-ray or CT.

As described in this article, debridement and microfracture is a reliable surgical procedure for osteochondral defects less than 15mm in diameter. Larger defects have less reliable results with microfracture alone, and the discussion of grafting and reconstructive procedures should be had with patients with larger defects.



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