Diminished cartilage-lubricating ability of human osteoarthritic synovial fluid deficient in proteoglycan 4: Restoration through proteoglycan 4 supplementation.

OBJECTIVE: The purposes of this study were 1) to quantify the proteoglycan 4 (PRG4) and hyaluronan (HA) content in synovial fluid (SF) from normal donors and from patients with chronic osteoarthritis (OA) and 2) to assess the cartilage boundary-lubricating ability of PRG4-deficient OA SF as compared to that of normal SF, with and without supplementation with PRG4 and/or HA. METHODS: OA SF was aspirated from the knee joints of patients with symptomatic chronic knee OA prior to therapeutic injection. PRG4 concentrations were measured using a custom sandwich enzyme-linked immunosorbent assay (ELISA), and HA concentrations were measured using a commercially available ELISA. The molecular weight distribution of HA was measured by agarose gel electrophoresis. The cartilage boundary-lubricating ability of PRG4-deficient OA SF, PRG4-deficient OA SF supplemented with PRG4 and/or HA, and normal SF was assessed using a cartilage-on-cartilage friction test. Two friction coefficients (µ) were calculated: static (µ(static, Neq) ) and kinetic (<µ(kinetic, Neq) >) (where N(eq) represents equilibrium axial load and angle brackets indicate that the value is an average). RESULTS: The mean ± SEM PRG4 concentration in normal SF was 287.1 ± 31.8 µg/ml. OA SF samples deficient in PRG4 (146.5 ± 28.2 µg/ml) as compared to normal were identified and selected for lubrication testing. The HA concentration in PRG4-deficient OA SF (mean ± SEM 0.73 ± 0.08 mg/ml) was not significantly different from that in normal SF (0.54 ± 0.09 mg/ml). In PRG4-deficient OA SF, the molecular weight distribution of HA was shifted toward the lower range. The cartilage boundary-lubricating ability of PRG4-deficient OA SF was significantly diminished as compared to normal (mean ± SEM <µ(kinetic, Neq) > = 0.043 ± 0.008 versus 0.025 ± 0.002; P < 0.05) and was restored when supplemented with PRG4 (<µ(kinetic, Neq) > = 0.023 ± 0.003; P < 0.05). CONCLUSION: These results indicate that some OA SF may have decreased PRG4 levels and diminished cartilage boundary-lubricating ability as compared to normal SF and that PRG4 supplementation can restore normal cartilage boundary lubrication function to these OA SF.

Risk of injury associated with body checking among youth ice hockey players.

CONTEXT: Ice hockey has one of the highest sport participation and injury rates in youth in Canada. Body checking is the predominant mechanism of injury in leagues in which it is permitted. OBJECTIVE: To determine if risk of injury and concussion differ for Pee Wee (ages 11-12 years) ice hockey players in a league in which body checking is permitted (Alberta, Canada) vs a league in which body checking is not permitted (Quebec, Canada). DESIGN, SETTING, AND PARTICIPANTS: Prospective cohort study conducted in Alberta and Quebec during the 2007-2008 Pee Wee ice hockey season. Participants (N = 2154) were players from teams in the top 60% of divisions of play. MAIN OUTCOME MEASURES: Incidence rate ratios adjusted for cluster based on Poisson regression for game- and practice-related injury and concussion. RESULTS: Seventy-four Pee Wee teams from Alberta (n = 1108 players) and 76 Pee Wee teams from Quebec (n = 1046 players) completed the study. In total, there were 241 injuries (78 concussions) reported in Alberta (85 077 exposure-hours) and 91 injuries (23 concussions) reported in Quebec (82 099 exposure-hours). For game-related injuries, the Alberta vs Quebec incidence rate ratio was 3.26 (95% confidence interval [CI], 2.31-4.60 [n = 209 and n = 70 for Alberta and Quebec, respectively]) for all injuries, 3.88 (95% CI, 1.91-7.89 [n = 73 and n = 20]) for concussion, 3.30 (95% CI, 1.77-6.17 [n = 51 and n = 16]) for severe injury (time loss, >7 days), and 3.61 (95% CI, 1.16-11.23 [n=14 and n=4]) for severe concussion (time loss, >10 days). The estimated absolute risk reduction (injuries per 1000 player-hours) that would be achieved if body checking were not permitted in Alberta was 2.84 (95% CI, 2.18-3.49) for all game-related injuries, 0.72 (95% CI, 0.40-1.04) for severe injuries, 1.08 (95% CI, 0.70-1.46) for concussion, and 0.20 (95% CI, 0.04-0.37) for severe concussion. There was no difference between provinces for practice-related injuries. CONCLUSION: Among 11- to 12-year-old ice hockey players, playing in a league in which body checking is permitted compared with playing in a league in which body checking is not permitted was associated with a 3-fold increased risk of all game-related injuries and the categories of concussion, severe injury, and severe concussion.

A prevention strategy to reduce the incidence of injury in high school basketball: a cluster randomized controlled trial.

OBJECTIVE: To examine the effectiveness of a sport-specific balance training program in reducing injury in adolescent basketball. DESIGN: Cluster randomized controlled trial. SETTING: Twenty-five high schools in Calgary and surrounding area. SUBJECTS: Nine hundred and twenty high school basketball players (ages 12-18). INTERVENTION: Subjects were randomly allocated by school to the control (n = 426) and training group (n = 494). Both groups were taught a standardized warm-up program. The training group was also taught an additional warm-up component and a home-based balance training program using a wobble board. MAIN OUTCOME MEASURES: All injuries occurring during basketball that required medical attention and/or caused a player to be removed from that current session and/or miss a subsequent session were then recorded and assessed by a team therapist who was blinded to training group allocation. RESULTS: A basketball-specific balance training program was protective of acute-onset injuries in high school basketball [RR = 0.71 (95% CI; 0.5-0.99)]. The protective effect found with respect to all injury [RR = 0.8 (95% CI; 0.57-1.11)], lower-extremity injury [RR = 0.83 (95% CI; 0.57-1.19)], and ankle sprain injury [RR = 0.71 (95% CI; 0.45-1.13)] were not statistically significant. Self-reported compliance to the intended home-based training program was poor (298/494 or 60.3%). CONCLUSIONS: A basketball-specific balance training program was effective in reducing acute-onset injuries in high school basketball. There was also a clinically relevant trend found with respect to the reduction of all, lower-extremity, and ankle sprain injury. Future research should include further development of neuromuscular prevention strategies in addition to further evaluation of methods to increase compliance to an injury-prevention training program in adolescents.

Survey of sport participation and sport injury in Calgary and area high schools.

OBJECTIVE: To examine (1) sport participation and (2) sport injury in adolescents. DESIGN, SETTING, AND PARTICIPANTS: This was a retrospective survey design. In total, 2873 adolescents were recruited from a random sample of classes from 24 Calgary and area high schools. Each subject completed an in-class questionnaire in March 2004. MAIN OUTCOME MEASUREMENTS: Overall and sport-specific participation rates (number of sport participants/number of students completing survey). Overall and sport-specific injury rates (number of injuries/number of participants). RESULTS: In the previous 1 year, 94% of students participated in sport. The top 5 sports by participation for males were basketball, hockey, football, snowboarding, and soccer, and for females, basketball, dance, volleyball, snowboarding, and soccer. The injury rate including only injuries requiring medical attention was 40.2 injuries/100 adolescents/y (95% CI, 38.4-42.1), presenting to a hospital emergency department was 8.1 injuries/100 adolescents/y (95% CI, 7.1-9.2), resulting in time loss from sport was 49.9 injuries/100 adolescents/y (95% CI, 48-51.8), and resulting in loss of consciousness was 9.3 injuries/100 adolescents/y (95% CI, 8.3-10.5). The greatest proportion of injuries occurred in basketball, hockey, soccer, and snowboarding. The top 5 body parts injured were the ankle, knee, head, back, and wrist. The top 5 injury types were sprain, contusion, concussion, fracture, and muscle strain. A previous injury was associated with 49% of the injuries and direct contact with 45% of injuries. CONCLUSIONS: Rates of participation in sport and sport injury are high in adolescents. Future research should focus on prevention strategies in sports with high participation and injury rates to maximize population health impact.