Purpose: Several techniques have been described for tenotomy of the Achilles tendon. The first method uses an open approach and consisted in classication stairstep tenotomy followed by suture. The second is a percutaneous method using two opposite transverse incisions along the width of the tendon followed by tension to glide the tendon fibres over each other. The biomechanical and histological properties of operated tendons was analysed in an experimental study in the rabbit.
Material and methods: Eighteen New Zealand rabbits were operated on. The operated and control tendons were harvested at the fifteenth and thirtieth day. Their biomechanical properties (resistance, elasticity, deformation) were measured with an Instrom device. Histological examination focused on the tendon junction using standard staining techniques.
Results: The two methods provide excellent technical reproducibility. We did not have any cases with skin problems or infection. Twelve tendons harvested at different times were tested in correct histological and technical conditions. The Instrom fixation system was the only factor limiting this method. Results for the first tendons tested did not demonstrate any difference for maximal force (TC15=118N, TP15=127 N) or for force at rupture (TC15=104N, TC15=114N). Conversely maximal lengthening before rupture (TC15=27mm, TP15=43mm), tendon section (TC15= 35mm2, TP15=27mm2), maximal strength (TC15=3.5mPa, TP15=4.6mPa), percentage of deformation at maximal force (TC15=39%, TP15=28%), fibre strength (TC15=6041 Cm/Denier, TP15=6451 Gm/Denier) and elasticity (TC15=27.7 mPa, TP15=43.7 mPa) were different.
Discussion: Section of the tendons is different with the two techniques. Macroscopically, TP tendons have a regular fusiform aspect which is not found for TC tendons. Maximal resistance and maximal force before rupture were identical for the two cohorts. We consider that if the two tendons have identical cross section, TP tendons would be significantly more resistant. Gliding the tendon fibres over each other is the explanation. Furthermore, gliding is achieved by applying force on the fibres, lengthening occurring at the cost of tearing the least resistant and least elastic fibres. Histologically, the healing process is also different between the two techniques, which has an effect on the final outcome.
Conclusion: The resistant and elastic properties are different between the two techniques of tenotomy. The biomechanical properties are excellent, tendon fibre healing and recruitment being adapted to physiological solicitations. Under these conditions, percutaneous lengthening is an excellent technique due to its reliability, easy execution, and the quality of the fibre healing.
