Peak Contact Pressures of the Posterior Heel in a Commonly Used Controlled Ankle Motion (CAM) Orthosis

Submission Type: Other Research Type: Level 4 – Case series Introduction/Purpose: Controlled ankle motion (CAM) boots are commonly and increasingly used after orthopaedic injury or in the post-operative setting. However, the use of a CAM boot is not benign, and pressure injury is a concern. The incidence of complications related to prefabricated pneumatic braces is on the rise. “Floating” the heel (no direct contact) has been studied and is important for pressure injury prevention in lower extremity plaster splints. Dermal arteriolar capillaries collapse with a pressure of 32mmHg, but no biomechanical studies have measured posterior heel contact pressures nor described the significance of floating the heel in a rigid CAM boot. This study aims to quantify baseline contact pressures of the posterior heel and assess the efficacy of floating the heel in a CAM boot. Methods: Twenty legs from ten healthy subjects were analyzed. A pressure transducer was positioned over the posterior heel to measure peak contact pressure in a CAM boot with the heel both resting flat and when elevated with a pillow under the calf and ankle. Both absolute pressures and relative pressure improvements were recorded. Results: With the posterior heel in the CAM boot resting flat, no leg reached a pressure below the critical 32mmHg threshold. However, when the heel was floating freely, 55% (11/20) of legs achieved contact pressures below 32mmHg. The average contact pressure with the heel floating was 40mmHg, indicating a 53% improvement in pressure reduction compared to the heel resting down. Conclusion: Prolonged used of a CAM boot should be undertaken with some degree of caution due to the risk of pressure-related complication. Patients must be counseled to float the heel when at rest. Frequent skin assessment and position changes are recommended to detect signs of impending pressure injury in the posterior heel. In cases where rigid immobilization is not essential, alternative orthoses that offload the heel should be considered, especially in those with neurogenic compromise, specifically the neuropathic patient and those with prolonged regional peripheral nerve blocks.