The dynamic control ratio masks bilateral asymmetries - A gender-specific analysis of 264 healthy and ACL-injured athletes.

Isokinetic strength tests are frequently applied to assess anterior cruciate ligament (ACL) rehabilitation processes. However, diverging methodologies cause misleading conclusions. This cross-sectional study evaluated the effects of gender (male vs. female), group (healthy vs. ACL-injured) and limb (dominant/healthy vs. non-dominant/ACL-injured) on thigh muscle balance of 138 female and 126 male athletes (50% ACL-injured, averagely 12.8 months after surgery). Balance was analysed between legs (bilateral asymmetry) and between concentric knee extensor (Qcon) and eccentric knee flexor strength (Hecc) (DCR = dynamic control ratio, DCRe = DCR at the equilibrium point). Females were generally 17-27% weaker than males. Independent of gender and time after surgery, ACL-injured athletes demonstrated bilateral asymmetries (7-20%) in peak (PMQcon, PMHecc) and DCRe moments (p ≤0.030; 0.018≤ηp2≤0.215). ACL-injured athletes' affected (24-28%) and unaffected (12-24%) hamstrings and quadriceps peak moments were significantly weaker compared to healthy athletes (p<0.001; 0.061≤ηp2≤0.362). The bilateral asymmetries of PMQcon significantly decreased from early to late self-reported rehabilitation phases (p<0.001; ηp2=0.158). Peak and DCRe moments detected bilateral asymmetries, whereas DCR revealed ~50% false negative attributions. This knowledge provides guidance for future design and interpretation of isokinetic tests.

Osteoconductive resorption characteristics of a novel biocomposite suture anchor material in rotator cuff repair.

BACKGROUND: Bioabsorbable suture anchors have been associated with bone-derived complications, such as osteolysis and cyst formation, after rotator cuff repair. The purpose of this study was to assess the osseous degradation process of the novel biocomposite suture anchor material polylactic-co-glycolic acid (PLGA)/beta-tricalcium phosphate (ß-TCP)/calcium sulfate (CS) after arthroscopic single-row rotator cuff repair. The focus of interest was the appearance of osteolysis and the rate of total resorption of the implants after 21 months. METHODS: Forty-eight patients with 82 implanted suture anchors who had undergone arthroscopic rotator cuff repair between January 2015 and March 2016 at our institution were retrospectively evaluated by postoperative magnetic resonance imaging. The appearance of osteolysis was classified by measurement of the peri-implant fluid. The degree of resorption was measured by grading the persistent visibility of the anchor structures. The integrity of the rotator cuff tendon was analyzed to discover possible retear or anchor pull-out complications. RESULTS: After a follow-up of 21.2 (± 5.4) months, osteolysis was detected in only two anchors (2.4%), and none of these defects exceeded the diameter of the former suture anchor (5.5 mm). Fifty percent of the anchors were fully degraded and no longer visible. Furthermore, only two retears of the rotator cuff occurred, and no anchor pull-out complications were detected. CONCLUSION: PGLA/ß-TCP/CS is a fully resorbable and osteoconductive suture anchor material that seems to have superior resorption characteristics compared to those of other bioabsorbable suture anchor materials commonly used in arthroscopic rotator cuff repair. TRIAL REGISTRATION: The presented study was retrospectively registered by the commission for ethics at the Ärztekammer Nordrhein with the registration number 2016433 on January 17, 2017. All participating patients gave written consent for participation and the publication of their data. LEVEL OF EVIDENCE: IV.

In vitro comparison of the pullout strength of 3 anterior double-screw fixation techniques with different screw angulations.

OBJECT: The pullout resistance of double-screw fixation systems in anterior spine surgery has been shown to be dependent on screw length as well as on screw angulation. The objective of the study was to evaluate the pullout strength of anterior double-screw systems with different angulations. METHODS: The authors conducted a comparative pullout test of converging, parallel, and diverging angulations of double-screw systems in human cadavers. Twenty-four human vertebral bodies from T-11 to L-1 were harvested from 8 donors, dissected from surrounding tissue, and matched to 3 different fixation groups. Three systems were tested: VentroFix, with near parallel screw direction; the Hopf Anterior Fixation System (HAFS), with converging screw angulation; and the ART anterior system, with diverging screw angulation. RESULTS: The mean (± SD) pullout strength of the VentroFix system was 699 ± 214 N, whereas the HAFS resisted to 591 ± 372 N. The ART anterior system with diverging screws demonstrated a pullout resistance of 810 ± 273 N. There was no significant difference amongst the pullout forces of the 3 groups (p > 0.05). In the HAFS and the ART anterior group, a weak correlation of pullout strength and bone mineral density measured by quantitative CT was found (r = 0.59 and r = 0.62, respectively), whereas the pullout force of the VentroFix system was not correlated with bone mineral density (r = 0.33). CONCLUSIONS: The in vitro pullout resistance of anterior double-screw systems does not appear to depend on screw angulation.