The arthroscopic square knot: a biomechanical comparison with open and arthroscopic knots.

PURPOSE: To compare the loop and knot security of arthroscopic square knots with other arthroscopic and open knots with the use of 2 commonly used suture types.

METHODS: Five knot configurations were tested 12 times each. The arthroscopic square knot was compared with the open square knot, arthroscopic and open half hitches with alternating posts, and the Duncan loop. Load-to-failure testing was performed at a rate of 1.25 mm/sec, and cyclic testing was performed between 7 N and 30 N at a rate of 1 N/sec for 50 cycles. Two suture types were tested: No. 2 Ethibond suture and No. 2 FiberWire.

RESULTS: Among the No. 2 Ethibond sutures, the arthroscopic Duncan loop had the highest load-to-failure at 165 N. The remaining knot types failed at between 142 N and 148 N. The load at 3 mm of lengthening was between 100 N and 120 N for all knots. The No. 2 FiberWire failed at higher loads than the No. 2 Ethibond suture for all knot types except the Duncan loop. The arthroscopic half hitches, arthroscopic square knots, and open half hitches all failed at between 220 N and 264 N. The open square knot failed at 188 N, and the Duncan loop failed at 147 N. The load at 3 mm of lengthening was between 130 N and 165 N for all knots except the Duncan loop, which failed at 95 N. With cyclic testing, arthroscopic square knots performed better than all knot types, but the differences were clinically insignificant.

CONCLUSIONS: Arthroscopic square knots have the same or greater strength when compared with other arthroscopic or open knots tied with the same suture type, and they perform as well or better in the face of cyclic loads. Good knot security can be attained with all of the knots tested, regardless of suture type. Equivalent knots tied with No. 2 FiberWire fail at higher loads, except for those tied with the Duncan loop.

CLINICAL RELEVANCE: Arthroscopic square knots can be used in the clinical setting with no compromise in function when compared with open square knots.