Comparison of zone II flexor tendon repairs using an in vitro linear cyclic testing protocol

Background. This study used in vitro cyclic testing protocol to examine the dynamic properties from a survivorship point of view for a modified Kessler core suture with a running epitenon suture, a modified Kessler core suture with a cross-stitched epitenon suture and a 4-strand Savage core suture with a running epitenon suture. Methods. A survivorship analysis using in vitro dynamic mechanical testing was performed using 20 N and 33 N with 500 cycles to simulate early rehabilitation. The gap formation was recorded by direct measurement with an electronic calliper every 100 cycles at the point of lowest force during the cycle at the site of greatest gap formation. Results were analysed using a log rank test for survival analysis and the relative risk of deterioration calculated. Findings. No significant increased risk of gap formation was noted for the Kessler with a cross-stitched epitenon over the standard Kessler repair. A significant decrease in the risk of significant gap formation in the Savage repair over the two Kessler repairs (>10-fold difference in the standard (P < 0.01) and >7-fold in the cross-stitched (P < 0.05) was found. Interpretation. The survivorship testing protocol found the Savage repair to be superior to the other methods under dynamic loading. Survival curves and relative risks provide a unique way to assess the properties of different repair techniques.