Gap Formation in Transpatellar Patellar Tendon Repair

Abstract

Background Postfixation loosening within the Krackow stitch–tendon construct may be associated with gap formation in patellar tendon repair. Hypothesis Pretensioning the Krackow stitch–tendon construct decreases postfixation gap formation in transpatellar patellar tendon repair. Study Design Controlled laboratory study. Methods Patellar tendon rupture was simulated in 8 pairs of cadaveric knees. Standard manual traction was used in all specimens to remove Krackow stitch slack. In the experimental group, specimens were pretensioned with a simulated active concentric quadriceps contraction with cycling of the knee 10 times from 90° to 5° of flexion. All specimens were then cycled at 0.25 Hz from 90° to 5° for 1000 cycles until failure, which was defined as 3 or 5 mm of gap formation. Results A 3-mm gap occurred at 1 cycle (mean, 3.5 mm) and 35 cycles (4.0 mm) in the control and experimental groups, respectively. Gapping of 5 mm occurred at 35 (5.9 mm) and 100 cycles (5.0 mm) in the control and experimental specimens, respectively. Gap formation was smaller in the experimental group through 100 cycles (P < .05). Conclusion Gapping was lower with pretensioning in the early cycling stages. However, significant gapping occurred in both groups with repetitive concentric active loading ranging from 90° to 5° of flexion. Clinical Relevance Tightening of the Krackow stitch as done in this study does not result in a clinically important decrease in gapping. This observation may be generalizable to other applications of the Krackow stitch.