An evaluation of two autologous tendon grafting techniques in ponies

OBJECTIVE: To compare the healing and mechanical strength of a multiple split autologous tendon graft (MG) to a whole autologous tendon graft (WG) in the deep digital flexor tendon of ponies. STUDY DESIGN: In vitro evaluation of two different tendon-grafting techniques. ANIMALS OR SAMPLE POPULATION: Six ponies of mixed gender and age. METHODS: Tenotomies performed in forelimb deep digital flexor tendons (DDFT) distal to the insertion of the accessory ligament (AL-DDFT) were repaired with free autologous grafts from the hindlimb lateral digital extensor tendon (LDET). Grafts were either whole (WG) or split into three longitudinal strips (multiple graft, MG). Tendons and graft sites were collected and loaded (2.54 cm/s) to failure at either 4 or 8 weeks after surgery. Cross-sectional area was determined by both impression cast (IC) and an inkblot (IB) method. Tissue maturity and inflammation were evaluated by microscopy. RESULTS: Gap formation was a consistent finding in all repair sites. No statistical differences were found in healing or mechanical variables between MG and WG techniques. The failure stress for the 8-week repairs (15.51 +/- 3.1 MPa IB and 11.73 +/- .77 MPa IC, 16.13 +/- 2.2 MPa IB and 10.22 +/- .76 MPa IC for MG and WG, respectively) were significantly greater (P <.0005) than for 4-week repairs (3.71 +/- 1.7 MPa IB and 2.68 +/- 1.44 MPa IC, 2.81 +/- 1.46 MPa IB and 2.3 +/- 1.7 MPa IC for MG and WG, respectively). The repair tissue was more mature (P <.05) at 8 weeks than at 4 weeks, but there was no significant difference in inflammatory responses at 4 and 8 weeks. CONCLUSIONS: There was a sixfold increase in strength between 4 and 8 weeks of healing, but no significant difference in healing or strength between the MG and WG techniques. CLINICAL RELEVANCE: In ponies, autologous tendon grafting contributes to a strong repair during the early convalescent period, but splitting a tendon graft seemingly offers no appreciable advantage over use of a whole graft.