The Beagle Böhler Walker - reduction of load transmission in a below knee cast

J. Berwin, T. Burton, J. Taylor, A. McGregor, A. Roche

Background: The current 'gold standard' method for enabling weightbearing during non-invasive lower limb immobilisation is to use a Patella Tendon-Bearing (PTB) or Sarmiento cast. The Beagle Böhler Walker™ is a non-invasive frame that fits onto a standard below knee plaster cast. It is designed to achieve a reduction in force across the foot and ankle. Our objective was to measure loading forces through the foot to examine how different types of casts affect load distribution. We aimed to determine whether the Beagle Böhler Walker™ is as effective or better, at reducing load distribution during full weightbearing.

Methods: We applied force sensors to the 1st and 5th metatarsal heads and the plantar surface of the calcaneum of 14 healthy volunteers. Force measurements were taken without a cast applied and then with a Sarmiento Cast, a below knee cast, and a below knee cast with Böhler Walker™ fitted.

Results: Compared to a standard below knee cast, the Böhler Walker™ reduced the mean peak force through the first metatarsal head by 58.9% (p < .0001); 73.1% through the fifth metatarsal head (p < .0001); and by 32.2% (p < .0001) through the calcaneum. The Sarmiento cast demonstrated a mean percentage reduction in peak force of 8.6% (P = .39) and 4.4% (P = .87) through the 1st and 5th metatarsal heads respectively, but increased the mean peak force by 5.9% (P = .54) through the calcaneum.

Conclusions: Using a Böhler Walker™ frame applied to a below knee cast significantly reduces loadbearing through the foot compared to a Sarmiento cast or a standard below knee cast. This could mean early weightbearing is safer and better tolerated in patients with a wide variety of foot and ankle pathologies, which can in turn improve quality of life and reduce the incidence of immobility dependent morbidity.