COMBINED ULTRASOUND, ELECTRICAL-STIMULATION, AND LASER PROMOTE COLLAGEN-SYNTHESIS WITH MODERATE CHANGES IN TENDON BIOMECHANICS

The biomechanical, biochemical, and ultrastructural effects of a multi therapeutic protocol were studied using regenerating rabbit Achilles t endons. The multitherapeutic protocol was composed of low-intensity Ga :As laser photostimulation, low intensity ultrasound, and electrical s timulation. Achilles tendons of 63 male New Zealand rabbits were tenot omized, sutured, immobilized, and subjected to the multitherapeutic pr otocol for five days, after which casts were removed and the therapy w as continued for nine more days without electrical stimulation. The te ndons were excised and compared with control tendons. Multitherapy tre atment produced a 14% increase in maximal strength, a 42% increase in load-at-break, a 20% increase in maximal stress, a 45% increase in str ess-at-break, a 21% increase in maximal strain, and a 14% increase in strain-at-break, Similarly, multitherapy treatment was associated with an increase in Young's modulus of elasticity of 31 %, an increase in energy absorption at maximum load of 9%, and an increase in energy abs orption at load-at-break of 11%. Biochemical analysis of the tendons s howed an increase of 23% in the total amount of collagen in the multit herapy-treated tendons, with fewer mature crosslinks (decrease of 6%). Electron micrographs revealed no ultrastructural or morphologic chang es in the tendon fibroblasts or in the extracellular matrix. The impro vements measured in tendons receiving multitherapy were consistent but less remarkable compared with our earlier works with single modality protocols. The results warrant the hypothesis that the beneficial effe cts of ultrasound and laser photostimulation on tendon healing may cou nteract one another when applied simultaneously.