Limb occlusion pressure for blood flow restricted exercise: Variability and relations with participant characteristics.

OBJECTIVE: Assess lower-extremity blood flow restricted exercise (BFR) limb occlusion pressure (LOP) variability and identify related intrinsic characteristics using a portable Delphi BFR system. DESIGN: Repeated measures. SETTING: Laboratory. PARTICIPANTS: Forty-two healthy males (n = 25) and females (n = 17) (25.8 ± 5.2 y, 1.76 ±0 .09 m, 78.9 ± 14.9 kg) completed two visits. Brachial artery blood pressure, thigh circumferences (TC), and LOP were measured supine. MAIN OUTCOME MEASURES: Linear mixed-effects models (LMM) and generalizability theory were used to evaluate LOP between legs and days, determine intrinsic characteristic relations, and assess random variance components. RESULTS: LOP was not different between legs (p = .730) or days (p = .916; grand mean = 183.7 mmHg [178.4, 189.1]). LOP varied significantly between participants (p = .011, standard error = 47.3 mmHg). 47% of LOP variance was between participants, 18% and 6% was within participants between days and legs, respectively, and 28% was associated with random error. The relative error variance was 14.4 mmHg. Pulse pressure (PP) (p = .005) and TC (p = .040) were positively associated with LOP. A LMM including PP and TC predicted LOP with a mean absolute difference of 11.1 mmHg [9.7, 12.6] compared to measured LOP. CONCLUSIONS: The relative error variance suggests that clinicians should measure LOP consistently for each patient to ensure BFR safety and effectiveness.

Comparing the Influence of Different Overhand/Underhand Stacking Combinations of Reversing Half-Hitches on Alternating Posts on Arthroscopic Knot Security.

INTRODUCTION: Previous literature demonstrated the importance of stacking at least three reversing half-hitches on alternating posts (RHAPs) following arthroscopic knot placement. However, RHAPs construction involves looping the suture in either an "overhand" or an "underhand" manner as it relates to the post, which may affect knot security. This study investigated the presently unidentified influence of different stacking combinations of three RHAPs and suture material on arthroscopic knot security. METHODS: Four different RHAPs stacking combinations were tied with three different suture materials. Ten knots of each configuration were tied using each suture material, resulting in 120 evaluated knots. A single load-to-failure test was performed. The mode of failure and mean ultimate clinical failure load were recorded. RESULTS: Different overhand/underhand stacking combinations of three RHAPs had a statistically significant effect on arthroscopic knot strength and security; however, all combinations surpassed the minimum ultimate clinical failure threshold. Knots constructed with either Force Fiber® or braided fishing line had mean ultimate clinical failure loads of greater than 200 N and most commonly failed due to suture material breakage (100%, 60 - 80% respectively). Conversely, FiberWire® demonstrated lower mean ultimate clinical failure loads and had a higher incidence of elongated but intact failure (60 - 90%). CONCLUSION: Different overhand/underhand stacking combinations of three RHAPs yielded an arthroscopic knot capable of secure tissue fixation. A significant effect was observed for suture materials on the knot strength. This study increases our understanding of suitable RHAPs construction following arthroscopic knot placement that can lead to improving the ultimate clinical failure loads of constructed arthroscopic knots observed between orthopedic surgeons.

A Biomechanical Comparison of Varying Base Knot Configurations with Different Overhand/Underhand Combinations of Reversing Half-Hitches on Alternating Posts After Basic Instructional Training.

Background: Constructing a durable arthroscopic knot is critical for secure tissue fixation. The effect of various arthroscopic base knot configurations paired with various overhand/underhand stacking combinations of three reversing half-hitches on alternating posts (RHAPs) on knot strength and integrity remains unanswered. Methods: Three common base knots (Surgeon's, Weston and, Tennessee Slider) followed by different overhand/underhand stacking combinations of three RHAPs were evaluated. Ten knots of each combination were tied by four subjects with varying levels of experience, resulting in the analysis of 480 total knots. A single load-to-failure test was performed to evaluate knot strength and integrity. The ultimate clinical failure load and mode of failure were recorded. Results: All knots created surpassed the estimated minimum required load per suture. There was, however, statistically large inter-subject variability for each base knot configuration. The Surgeon's base knot was found to vary the least in knot strength, while the Tennessee base knot was found to vary the most. Knot security was mostly influenced by the base knot configuration than the different overhand/underhand RHAP stacking combinations. Knot slippage failure mode was higher with knots tied with the Weston base knot compared to the other two configurations. Conclusions: Arthroscopic base knot configurations paired with different overhand/underhand stacking combinations of RHAPs yielded knot capable of secure tissue fixation. A short instructional training period appears to be sufficient for inexperienced individuals to learn easier base knot configurations, more challenging and complicated knots, however, may require training in a more gradual fashion. Clinical Relevance: The findings of this study provide information that the importance of hands-on experience for inexperienced individuals, such as residents, in performing arthroscopic knot tying, and that can lead to improving the securely constructed arthroscopic knots, which increase positive outcomes related to strengthened soft tissue to bone fixation of post-operative patients.Level of Evidence: V.