In vivo tendon tension and bone strain measurement and correlation

Abstract Recent advances in strain gauges and bonding techniques permit the recording of bone strain in the living animal. Such strain is caused by tendon tension and by weight bearing. Both lateral and medial bone strain are recorded from the third metacarpal bone of the walking horse. These strains are typically 430 μ strain and 150 μ strain respectively, peak to peak. The tension in the common extensor tendon, recorded during walking, is found to be up to 170 N on occasions. The two sets of readings are cross-correlated and a theory is presented to account for the major features of the bone strain recordings in terms of tendon action, weight bearing, and locomotion. Comparison of results from large and small foil resistance strain gauges indicates that gauges covering 1 mm 2 of bone surface give valid results.