Medial joint line bone bruising at MRI complicating acute ankle inversion injury: What is its clinical significance?

Aim

To assess the incidence and clinical significance of medial joint line bone bruising following acute ankle inversion injury.

Materials and methods

Forty-five patients who underwent ankle magnetic resonance imaging (MRI) within 2 weeks of acute ankle inversion injury were included in this prospective study. Integrity of the lateral collateral ligament complex, presence of medial joint line bone bruising, tibio-talar joint effusion, and soft-tissue swelling were documented. Clinical follow-up at 6 months was carried out to determine the impact of injury on length of time out of work, delay in return to normal walking, delay in return to sports activity, and persistence of medial joint line pain.

Results

Thirty-seven patients had tears of the anterior talofibular ligament (ATFL). Twenty-six patients had medial joint line bone bruising with altered marrow signal at the medial aspect of the talus and congruent surface of the medial malleolus. A complete ATFL tear was seen in 92% of the patients with medial joint line bone bruising (p = 0.05). Patients with an ATFL tear and medial joint line bone bruising had a longer delay in return to normal walking (p = 0.0002), longer delay in return to sports activity (p = 0.0001), and persistent medial joint line pain (p = 0.0003). There was no statistically significant difference in outcome for the eight patients without ATFL tears.

Conclusion

Medial joint line bone bruising following an acute ankle inversion injury was significantly associated with a complete ATFL tear, longer delay in the return to normal walking and sports activity, as well as persistent medial joint line pain. Its presence should prompt detailed assessment of the lateral collateral ligament complex, particularly the ATFL.

Introduction

Acute inversion injury of the ankle is a very common injury.1, 2, 3 The lateral collateral ligament complex, comprising of the anterior talofibular, calcaneofibular, and posterior talofibular ligaments, is the most commonly affected group of ligaments in acute ankle inversion injury.4, 5 As it is the weakest of the three ligaments, the anterior talofibular ligament (ATFL) is the most frequently torn.4, 6 ATFL tears can result in anterolateral impingement⁷ and chronic lateral ankle instability.

Most patients are treated conservatively.2, 8 However, in some cases, chronic pain and instability may develop.9, 10, 11 The reasons for such an outcome are not clearly understood but may relate to associated injury to the bones of the ankle.12, 13

Medial joint line bone bruising may be seen together with lateral ligamentous injuries in the ankle usually due to “contrecoup” impaction and rotational forces during an inversion injury¹⁴ (Fig 1). It is related to microfractures of the trabecular bone and oedema or haemorrhage within the bone marrow.6, 15, 16, 17 The clinical significance of bone contusions detected at magnetic resonance imaging (MRI) is unknown but it is generally accepted that continued stress placed on the contused bone can lead to more severe osteochondral injury or fracture with progressive disability.18, 19

Although bone bruises have been well-described in the knee joint,19, 20 little is known about the presence of medial joint line bone bruising in the ankle joint. Therefore, the aim of the present study was to assess the incidence and clinical significance of medial joint line bone bruising identified at MRI in patients following acute ankle inversion injury.