RECONSTRUCTION OF THE FLEXOR PULLEY - THE EFFECT OF THE TENSION AND SOURCE OF THE GRAFT IN AN IN-VITRO DOG-MODEL

Flexor pulleys in the hindpaw digits of twenty-eight adult mixed-breed dogs were reconstructed in order to investigate the influence, on the reconstruction, of the source of the autogenous tissue (intrasynovial compared with extrasynovial tendon) and the tension applied during th e repair. The ipsilateral peroneus longus tendon was used to reconstru ct the A2 pulley,vith an around-the-bone technique in twenty-one digit s; the graft was sutured at a tension of 0.49, 0.98, and 1.96 newtons in seven digits each. The flexor digitorum profundus tendon of an adja cent digit was used to reconstruct the A2 pulley, at a tension of 0.98 newton, in seven additional digits. The contralateral digits were use d as controls for all twenty-eight treated digits. The digits were tes ted in a custom apparatus designed to measure the frictional force gen erated between the reconstructed pulley and the tendon beneath it. The frictional force did not differ significantly (p > 0.5) among the thr ee groups repaired with peroneus longus tendon; however, the average v alue was more than five times that produced in the contralateral, cont rol digits. The average frictional forces created by the flexor digito rum profundus grafts were similar to those in the contralateral, contr ol digits. Reconstruction with the flexor digitorum profundus at a ten sion of 0.98 newton produced significantly less frictional force (p < 0.05) than that produced by the peroneus longus graft at the same tens ion. This in vitro model of reconstruction of the A2 pulley demonstrat ed that tendon from an intrasynovial source (the flexor digitorum prof undus) produced less frictional resistance to gliding of the tendon th an did tendon from an extrasynovial source (the peroneus longus), This result is consistent with previously published findings that intrasyn ovial tendons may make better grafts than extrasynovial tendons for th e reconstruction of gliding flexor tendons because of decreased fricti on and better healing qualities. Intrasynovial tendons may also make b etter grafts for the reconstruction of flexor pulleys.