Acute Achilles tendon rupture: Do cast boots produce adequate equinus when used for functional rehabilitation?

Acute Achilles tendon rupture is frequently treated conservatively using functional rehabilitation protocols in which the ankle is held in equinus. Equinus is achieved using a variety of means including equinus casts and rigid boots with heel wedges. Concerns have been raised that rigid boots with heel wedges do not achieve adequate equinus. Patients presenting to our institutions with an acute Achilles tendon rupture were randomised to treatment with an equinus cast or rigid boot with heel wedges. After application of these lateral radiographs of the hindfoot and ankle were taken, and these used to measure tibiotalar angle (TTA), tibio-1st metatarsal angle (TMA) and posterior malleolar to calcaneal tip height (PCH). 15 patients were randomised to a rigid boot and 14 to an equinus cast. The mean TTA was 124° in the rigid boot group and 136° in the equinus cast group (p<0.001). The mean TMA was 134° in the rigid boot group and 147° in the equinus cast group (p<0.001). The mean PCH was 25mm in the rigid boot group and 15mm in the equinus cast group (p<0.05). Our results demonstrate that the rigid boots with heel wedges used in our institutions produce significantly less equinus than an equinus cast. Whilst the clinical relevance of this remains uncertain, clinicians should be aware that rigid boots with wedges and equinus casts may not achieve the same degree of Achilles tendon shortening.