Arthroscopic sliding knot: how many additional half-hitches are really needed?
OBJECTIVE
To evaluate the optimal number of additional half-hitches needed to achieve optimal knot-holding capacity (KHC) of lockable sliding knots.


METHODS
Mechanical testing study.


METHODS
Four configurations of arthroscopic knots (Duncan loop, Field knot, Giant knot, and SMC knot) were tested for their knot-holding capacity. For each knot configuration, 6 sequential knots were made including the initial sliding knot and an additional 5 knots by increasing the half-hitches 1 at a time. Each additional half-hitch was made as a reverse half-hitch with alternate posts. For each sequential knot configuration, 12 knots were made using No. 2 braided sutures. On the Servo-hydraulic materials testing system (Instron 8511; MTS, Minneapolis, MN), cyclic loading, load to clinical failure (3-mm displacement), load to ultimate failure, and mode of failure were measured.


RESULTS
Most of the initial loops without additional half-hitches showed dynamic failure with cyclic loading. However, after 1 additional half-hitch, all 3 (SMC, Field, and Giant) knots showed resistance to dynamic cyclic load. After 2 additional half-hitches, the Duncan loop was secured without slippage from the cyclic loading test. The mean displacement after the end of cyclic loading decreased with each additional half-hitch. In particular, the SMC and Giant knot reached plateau at 0.1-mm or less displacement after 1 additional half-hitch. The Field knot and Duncan loop needed 3 additional half-hitches. The SMC knot and Duncan loop needed 1 additional half-hitch to reach greater than 80 N at clinical failure, whereas the other 2 knots needed 2 additional half-hitches. For the load exceeding 100 N for clinical failure, the SMC knot required 3 additional half-hitches and the other 3 knots needed 4 additional half-hitches. Addition of more than 3 half-hitches did not increase the load to clinical failure in the SMC knot. However, load to clinical failure increased up to 4 additional half-hitches in the other 3 knots (P < .05). The load to ultimate failure reached plateau when 3 or more additional half-hitches were made for all knot configurations. As the number of additional half-hitches increased, the mode of failure switched from pure loop failure (slippage) to material failure (breakage). The Duncan loop showed poor loop security--even with 5 additional half-hitches, some failed by slippage (17%). On the other hand, after 3 additional half-hitches, the 3 other knots showed greater than 75% of failure by material breakage mode (SMC and Field 92%, Giant 75%).


CONCLUSIONS
Even with its own locking mechanism, a lockable sliding knot alone does not withstand the initial dynamic cyclic load. For all tested variables, the SMC knot required a minimum of 2 additional half-hitches. All knots showed a near plateau in knot security with 3 or more additional half-hitches. The Duncan loop may need more than 3 additional half-hitches for optimal security.


CONCLUSIONS
The study shows that the knots tested needed at least 2 additional half-hitches, so this should become standard clinical practice.
Kim
Seung-Ho
SH
Departments of Orthopaedic Surgery, Sungkyunkwan University School of Medicine, Samsung Medical Center, Seoul, Korea.
Yoo
Jae Chul
JC
Wang
Joon Ho
JH
Choi
Kui Won
KW
Bae
Tae Soo
TS
Lee
Chang Yang
CY
D000704:Analysis of Variance; D001182:Arthroscopy / Q000379:methods*; D001696:Biomechanical Phenomena; D006801:Humans; D013536:Suture Techniques; D016896:Treatment Outcome