R.J. Johnson

Strain within the anterior cruciate ligament during hamstring and quadriceps activity

The objectives of this study were to measure strain in the ACL during simulated: (1) hamstring activity alone, (2) quadriceps activity alone, and (3) simultaneous quadriceps and hamstring activity. Seven knee speci mens removed from cadavers were studied. Heavy sutures applied to load cells were attached to the hamstring and quadriceps tendons. Loads were then applied manually (hamstrings) and/or with an Instron testing machine (quadriceps) to simulate isometric con tractions of the various muscle groups. Strain was measured using a Hall effect transducer. Acting alone, the isometric hamstring activity decreased ACL strain relative to the passive normal strain at all positions tested. Thus, hamstring exercises are not detrimental to ACL repairs or reconstruction and can be included early in the rehabilitation program after ACL surgery. Acting alone, at flexion angles of 0° to 45°, the quad riceps significantly increased the strain within the ACL relative to the passive normal strain. Strain in the ACL during simultaneous hamstring and quadriceps activity was significantly higher than that during passive normal motion from full extension to 30° of flexion. The ham strings are not capable of masking the potentially harm ful effects of simultaneous quadriceps contraction on freshly repaired or reconstructed ACLs unless the knee flexion angle exceeds 30°.

The treatment of injuries of the anterior cruciate ligament.

The treatment of injuries of the anterior cruciate ligament. R Johnson;B Beynnon;C Nichols;P Renstrom; The Journal of Bone & Joint Surgery

The role of the musculature in injuries to the medial collateral ligament.

With a knee-testing device we measured the valgus stiffness of the medial musculoligamentous complex of the knee in five volunteers. Tests were done with the muscles quiescent and with contraction of the sartorius and vastus medialis. Contraction of those muscles substantially increased the valgus stiffness. In eight subjects the voluntary reaction times were measured. With either a visual or a tactile impulse for prophylactic muscle contraction, the muscles acted too slowly to augment the stiffness of the knee so as to prevent injury. In fifty-one volunteers we applied the maximum torque to the leg, just short of eliciting pain, and showed that even then the muscle contraction would occur too late to protect the knee in typical sports situations.

Skiing Injuries in Children, Adolescents, and Adults*

We prospectively gathered data on skiing injuries that had been sustained at the Sugarbush North ski area since 1972 and at the Sugarbush South ski area since 1981. The purpose of the current study was to document the overall rates of injury in children, adolescents, and adults participating in alpine skiing. We also sought to determine the ten most common injuries in each age-group. Finally, we analyzed short-term and long-term trends to determine if changes in equipment had had an effect on the frequency or pattern of injury. From the 1981–1982 to the 1993–1994 season, there were 2.79 injuries per 1000 skier days: 4.27 injuries in children, 2.93 in adolescents, and 2.69 in adults. During the last eight years of the study, the most common injuries were a contusion of the knee in children, a sprain of the ulnar collateral ligament of the thumb in adolescents, and a grade-III sprain of the anterior cruciate ligament in adults. The short-term trends revealed that, in children, the frequency of tibial fractures decreased 10 per cent while that of fractures of the upper extremity increased 8 per cent. The long-term trends showed that, in adults, the rate of tibial fractures decreased 89 per cent while that of injuries of the anterior cruciate ligament increased 280 per cent. The overall rate of injury decreased 43 per cent from the beginning of the study in 1972 to the end of the study in 1994; the decrease was 58 per cent in children, 45 per cent in adolescents, and 42 per cent in adults. Data on the types of equipment and the binding-release values were collected prospectively from injured skiers and from 2083 non-injured skiers. Of the fifty-nine skiers who sustained a spiral fracture of the tibia, forty-two (71 per cent) had binding-release values that were higher than the average for the uninjured group. We believe that the use of properly functioning modern equipment will decrease the rate of injury, particularly in children.

Snowboarding Injuries Trends Over Time and Comparisons With Alpine Skiing Injuries

Background: Participation in snowboarding as a winter sport is comparable to alpine skiing concerning the demographics of the participants, risk of injury, and variation in types of injuries sustained. Purpose: To examine the types of snowboarding injuries and changes in injury patterns over time. We also sought to highlight important differences in injury patterns between snowboarders and alpine skiers as affected by age, experience, and sex. Study Design: Case control; Level of evidence, 3. Methods: Data were collected on injured snowboarders and skiers in a base-lodge clinic of a ski resort in Vermont over 18 seasons (1988-2006) and included extensive information about injury patterns, demographics, and experience. Control data were also obtained during this time period to provide information about the population at risk. Results: The injury rates were assessed as mean days between injuries (MDBI). The average MDBI for all injuries among snowboarders was 345 as compared with 400 for skiers (the lower the number, the higher the injury rate). The most common type of injury for snowboarders was a wrist injury (MDBI, 1258), while for skiers, it was an anterior cruciate ligament (ACL) sprain (MDBI, 2332). Wrist injuries accounted for 27.6% of all snowboard injuries and 2.8% of skiing injuries, and ACL injuries composed 1.7% of all snowboard injuries and 17.2% of skiing injuries. Among snowboarders, more wrist injuries, shoulder soft tissue injuries, ankle injuries, concussions, and clavicle fractures were seen, while skiers had more ACL sprains, medial collateral ligament (MCL) sprains of the knee, lateral collateral ligament (LCL) sprains of the knee, lower extremity contusions, and tibia fractures. The trend analysis revealed an increased incidence of clavicle fractures (P < .01) and a decrease in MCL injuries (P < .01) and ankle injuries (P < .025) among snowboarders over time. Skiers had a decrease in thumb metacarpophalangeal-ulnar collateral ligament (MCP-UCL) injuries (P < .001) and MCL injuries of the knee (P < .001) over time. We found the highest rate of injury among young, inexperienced, female snowboarders. When examining the location of injury, 21.8% of snowboard injuries occurred in the terrain park compared with 6.5% of ski injuries. Conclusion: Injury rates in snowboarders have fluctuated over time but currently remain higher than in skiers. Wrist, shoulder, and ankle injuries are more common among snowboarders, while knee ligament injuries are more common in skiers. Injured snowboarders were significantly younger, less experienced, and more likely to be female than injured skiers or snowboard control participants. We did not find any evidence that those who spend time in terrain parks are overrepresented in the injury population.

Increased Slope of the Lateral Tibial Plateau Subchondral Bone Is Associated With Greater Risk of Noncontact ACL Injury in Females but Not in Males A Prospective Cohort Study With a Nested, Matched Case-Control Analysis

Background: There is an emerging consensus that increased posterior-inferior directed slope of the subchondral bone portion of the tibial plateau is associated with increased risk of suffering an anterior cruciate ligament (ACL) injury; however, most of what is known about this relationship has come from unmatched case-control studies. These observations need to be confirmed in more rigorously designed investigations. Hypothesis: Increased posterior-inferior directed slope of the medial and lateral tibial plateaus are associated with increased risk of suffering a noncontact ACL injury. Study Design: Case-control study; Level of evidence, 3. Methods: In sum, 176 athletes competing in organized sports at the college and high school levels participated in the study: 88 suffering their first noncontact ACL injury and 88 matched controls. Magnetic resonance images were acquired, and geometry of the subchondral bone portion of the tibial plateau was characterized on each athlete bilaterally by measuring the medial and lateral tibial plateau slopes, coronal tibial slope, and the depth of the medial tibial plateau. Comparisons between knees of the same person were made with paired t tests, and associations with injury risk were assessed by conditional logistic regression analysis of ACL-injured and control participants. Results: Controls exhibited side-to-side symmetry of subchondral bone geometry, while the ACL-injured athletes did not, suggesting that the ACL injury may have changed the subchondral bone geometry. Therefore, the uninjured knees of the ACL-injured athletes and the corresponding limbs of their matched controls were used to assess associations with injury risk. Analyses of males and females as a combined group and females as a separate group showed a significant association between ACL injury risk and increased posterior-inferior directed slope of the lateral tibial plateau slope. This relationship was not apparent when males were analyzed as a group. Multivariate analyses indicated that these results were independent of the medial tibial plateau slope, coronal tibial slope, and depth of the medial tibial plateau, which were not associated with ACL injury. Conclusion: There is a 21.7% increased risk of noncontact ACL injury with each degree increase of the lateral tibial plateau slope among females but not among males. The medial tibial plateau slope, coronal tibial slope, and depth of the medial tibial plateau were not associated with risk of injury for females or males.

The Effects of Level of Competition, Sport, and Sex on the Incidence of First-Time Noncontact Anterior Cruciate Ligament Injury

Background: Anterior cruciate ligament (ACL) injuries are disabling and are associated with the early onset of posttraumatic osteoarthritis. Little is known regarding the incidence rate of first-time noncontact ACL injuries sustained during athletic events and how they are independently influenced by level of competition, type of sport, and the participant’s sex. Hypothesis: Level of competition (college or high school), type of sport (soccer, basketball, lacrosse, field hockey, football, rugby, volleyball), and the athlete’s sex independently influence the incidence rate of first-time noncontact ACL injuries. Study Design: Cohort study; Level of evidence, 2. Methods: Between fall 2008 and spring 2012, first-time noncontact ACL injury data were collected from 8 colleges and 18 high schools across 7 sports. Athlete exposure was computed retrospectively using team rosters and numbers of scheduled practices and games. Injury incidence rates (IRs) were computed per 1000 athlete exposures. The independent effects of level of competition, sport, and sex on ACL injury risk were estimated by Poisson regression. Results: Colleges reported 48 ACL injuries with 320,719 athlete exposures across all sports studied (IR = 0.150 per 1000 person-days), while high schools reported 53 injuries with 873,057 athlete exposures (IR = 0.061). After adjustment for differences in sport and sex, college athletes had a significantly higher injury risk than did high school athletes (adjusted relative risk [RR], 2.38; 95% CI, 1.55-3.54). The overall IR for female athletes was 0.112 compared with 0.063 for males. After adjustment for sport and level of play, females were more than twice as likely to have a first-time ACL injury compared with males (RR, 2.10; 95% CI, 1.34-3.27). With lacrosse as the reference group, risk of first-time noncontact ACL injury was significantly higher for soccer players (RR, 1.77) and for rugby players (RR, 2.23), independent of level of play and sex. Conclusion: An athlete’s risk of having a first-time noncontact ACL injury is independently influenced by level of competition, the participant’s sex, and type of sport, and there are no interactions between their effects. Female college athletes have the highest risk of having a first-time noncontact ACL injury among the groups studied.

An Analysis of Specific Lower Extremity Injury Rates on Grass and FieldTurf Playing Surfaces in National Football League Games 2000-2009 Seasons

Background: Players in the National Football League (NFL) sustain injuries every season as the result of their participation. One factor associated with the rate of injury is the type of playing surface on which the players participate. Hypothesis: There is no difference in the rate of knee sprains and ankle sprains during NFL games when comparing rates of those injuries during games played on natural grass surfaces with rates of those injuries during games played on the artificial surface FieldTurf. Study Design: Descriptive epidemiology study. Methods: The NFL records injury and exposure (ie, game) data as part of its injury surveillance system. During the 2000-2009 NFL seasons, there were 2680 games (5360 team games) played on grass or artificial surfaces. Specifically, 1356 team games were played on FieldTurf and 4004 team games were played on grass. We examined the 2000-2009 game-related injury data from those games as recorded by the injury surveillance system. The data included the injury diagnosis, the date of injury, and the surface at the time of injury. The injury data showed that 1528 knee sprains and 1503 ankle sprains occurred during those games. We calculated injury rates for knee sprains and ankle sprains—specifically, medial collateral ligament (MCL) sprains, anterior cruciate ligament (ACL) sprains, eversion ankle sprains, and inversion ankle sprains—using incidence density ratios (IDRs). We used a Poisson model and logistic regression odds ratios to validate the IDR analysis. A multivariate logistic regression model was used to adjust the odds ratio for weather conditions. Results: The observed injury rate of knee sprains on FieldTurf was 22% (IDR = 1.22, 95% confidence interval [CI], 1.09-1.36) higher than on grass, and the injury rate of ankle sprains on FieldTurf was 22% (IDR = 1.22, 95% CI, 1.09-1.36) higher than on grass. These differences are statistically significant. Specifically, the observed injury rates of ACL sprains and eversion ankle sprains on FieldTurf surfaces were 67% (P < .001) and 31% (P < .001) higher than on grass surfaces and were statistically significant. The observed injury rates of MCL sprains and inversion ankle sprains were also not significantly higher on FieldTurf surfaces (P = .689 and .390, respectively). Conclusion: Injury rates for ACL sprains and eversion ankle sprains for NFL games played on FieldTurf were higher than rates for those injuries in games played on grass, and the differences were statistically significant.

Relationship Between the Risk of Suffering a First-Time Noncontact ACL Injury and Geometry of the Femoral Notch and ACL A Prospective Cohort Study With a Nested Case-Control Analysis

Background: The morphometric characteristics of the anterior cruciate ligament (ACL) and the femoral intercondylar notch within which it resides have been implicated as risk factors for injuries to this important stabilizer of the knee. Prior research has produced equivocal results with differing methodologies, and consequently, it is unclear how these characteristics affect the injury risk in male and female patients. Hypothesis: The morphometric characteristics of the ACL and femoral intercondylar notch are individually and independently associated with the risk of suffering a noncontact ACL injury, and these relationships are different in male and female patients. Study Design: Case-control study; Level of evidence, 3. Methods: Magnetic resonance imaging scans of the bilateral knees were obtained on 88 case-control pairs (27 male, 61 female) matched for age, sex, and participation on the same sports team. Patients had suffered a grade III, first-time, noncontact ACL tear. The femoral notch width at 4 locations, the thickness of the bony ridge at the anteromedial outlet of the femoral notch, the femoral notch volume, ACL volume, and ACL cross-sectional area were measured. Results: Multivariate analysis of combined data from male and female patients revealed that decreased ACL volume (odds ratio [OR], 0.829), decreased femoral notch width (OR, 0.700), and increased bony ridge thickness at the anteromedial outlet of the femoral notch (OR, 1.614) were significant independent predictors of an ACL injury. Separate analyses of male and female patients indicated that the femoral notch ridge may be more strongly associated with a risk in female patients, while ACL volume is more strongly associated with a risk in male patients. However, statistical analysis performed with an adjustment for body weight strengthened the association between ACL volume and the risk of injuries in female patients. Conclusion: Morphometric features of both the ACL and femoral notch combine to influence the risk of suffering a noncontact ACL injury. When included together in a multivariate model that adjusts for body weight, the effects of the morphometric measurements are similar in male and female patients. If body weight is not taken into consideration, ACL volume is not associated with a risk in female patients.

An in vivo comparison between intraoperative isometric measurement and local elongation of the graft after reconstruction of the anterior cruciate ligament

This study was designed to determine if isometric measurement can be used to predict the pattern of elongation (the change in length) of a bone-patellar ligament-bone graft during passive flexion-extension of the knee at the time of reconstruction of the anterior cruciate ligament in vivo. A standard operative reconstruction technique was performed on nine patients. The tunnel sites for the grafts were selected, and the change in the distance between these sites was measured, with use of a CA-5000 drill-guide isometer as the knee was subjected to passive flexion-extension. After the reconstruction was completed, a Hall-effect transducer was implanted in the graft to measure the local displacement in the mid-substance of the graft that was produced by passive flexion-extension of the knee. For comparison, the isometric measurements and the values for local displacement of the graft were normalized by calculation of the percentage change in the length. With the knee in 10 to 30 degrees of flexion, the average isometric measurements and the measurements of local displacement demonstrated a decrease in length; however, the two techniques of measurement deviated at angles of flexion of 40 degrees and more. On the average, the isometric measurement of elongation between the trial insertion sites predicted that the graft would increase in length in flexion relative to extension, in contrast to the response of the graft after fixation. There was no significant correlation between the isometric measurements and the local elongation of the graft (r2 = 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)