Arthroscopic knot tying: the role of instrumentation in achieving knot security.

PURPOSE: To determine the role of arthroscopic knot-tying instrumentation in achieving knot security. TYPE OF STUDY: Biomechanical study. METHODS: The security achieved by 3 different commercially available knot-tying instruments using No. 2 braided suture and a standardized knot configuration was compared. Instrumentation included (1) a single-hole knot pusher, (2) a cannulated double-diameter knot pusher, and (3) a mechanical end-splitting knot tightener. Hand-tied knots served as controls. Testing included both cyclic loading and load to failure parameters using the Bionix 858 (MTS Inc, Eden Prairie, MN) and Instron Mini 44 (Instron, Canton, MA) materials testing systems, respectively. An experienced arthroscopic shoulder surgeon and a less experienced junior-level orthopaedic resident surgeon performed tying. RESULTS: Knot displacement after cyclic loading was smallest for the mechanical end-splitting knot tightener (average, 0.054 mm) and did not differ statistically from hand-tied knots (average, 0.058 mm). Knots tied with this device also withstood the greatest load to failure (average, 126.0 N) and were statistically similar to hand-tied knots (average, 134.1 N). The single-hole pusher had an average cyclic loading displacement of 0.095 mm and failed at 108.6 N. The cannulated double-diameter pushers had an average cyclic loading displacement of 0.106 mm and failed at 93.1 N. Both were statistically less secure than hand-tied knots or those tied with the end-splitting tightener. Investigator experience did not affect knot security with those tied by the mechanical end-splitting tightener or hand-tied knots. CONCLUSIONS: The end-splitting tightener provided the most secure arthroscopic knots that were statistically as secure as those tied by hand for both investigators. The knot-tying instrument used in arthroscopic shoulder surgery may be an important consideration with potential clinical implications based on knot security. CLINICAL RELEVANCE: The specific knot tying instrument that is selected for use in arthroscopic shoulder surgery may play an important role in the degree of ultimate knot security achieved in suture repair.

Strength and knot security of braided polyester and caprolactone/glycolide suture.

BACKGROUND: Appropriate suture selection is necessary in providing mechanical stability to soft tissue reconstructions. Caprolactone/glycolide (Panacryltrade mark) became a popular suture, possessing excellent handling properties; however, clinical observations questioned the knot security of caprolactone/glycolide. Caprolactone/glycolide is still available on many commercial suture anchor systems. This study compared the security of the knots and ultimate tensile strength of braided caprolactone/glycolide suture to that of a commonly used suture material, braided polyester (Ethibondtrade mark). MATERIALS: Suture knots of No. 2 braided polyester suture and No. 2 braided caprolactone/glycolide suture were submersed in a physiologic saline solution and stressed using a continuous (non-cyclic) load, simulating a single maximal loading event in a clinical setting. Continuous loading was done to achieve clinical suture knot failure (3-mm knot slippage), then continued until catastrophic suture failure (suture breakage) occurred. Ten trials of each suture were tested. RESULTS: Force required to cause knot slippage of 3 mm was greater for braided polyester than for braided caprolactone/glycolide (p <. 0001, unpaired Students' t-test). Forces resulting in catastrophic failure were greater for braided polyester than braided caprolactone/glycolide (p = .0284, unpaired Students' t-test). CONCLUSIONS: These data have important implications in the selection of suture materials for repair of soft tissue injuries. In the clinical setting, a single maximal loading event may result in suture failure. These data indicate that braided polyester possesses superior in-vitro mechanical properties and suggest that braided polyester may provide greater security in-vivo than braided caprolactone/glycolide suture.

Retrograde removal of an incarcerated solid titanium femoral nail after subtrochanteric fracture.

Intramedullary nailing with a solid titanium nail can result in significant bone ingrowth. Failure of an implant requires removal for replacement with another device. Previous methods have included use of extractors for cannulated nails. When extractors are not available or are inadequate, a simple retrograde push-out method can be used as described here.