Kam-Ming Mok

Understanding acute ankle ligamentous sprain injury in sports

This paper summarizes the current understanding on acute ankle sprain injury, which is the most common acute sport trauma, accounting for about 14% of all sport-related injuries. Among, 80% are ligamentous sprains caused by explosive inversion or supination. The injury motion often happens at the subtalar joint and tears the anterior talofibular ligament (ATFL) which possesses the lowest ultimate load among the lateral ligaments at the ankle. For extrinsic risk factors to ankle sprain injury, prescribing orthosis decreases the risk while increased exercise intensity in soccer raises the risk. For intrinsic factors, a foot size with increased width, an increased ankle eversion to inversion strength, plantarflexion strength and ratio between dorsiflexion and plantarflexion strength, and limb dominance could increase the ankle sprain injury risk. Players with a previous sprain history, players wearing shoes with air cells, players who do not stretch before exercising, players with inferior single leg balance, and overweight players are 4.9, 4.3, 2.6, 2.4 and 3.9 times more likely to sustain an ankle sprain injury. The aetiology of most ankle sprain injuries is incorrect foot positioning at landing – a medially-deviated vertical ground reaction force causes an explosive supination or inversion moment at the subtalar joint in a short time (about 50 ms). Another aetiology is the delayed reaction time of the peroneal muscles at the lateral aspect of the ankle (60–90 ms). The failure supination or inversion torque is about 41–45 Nm to cause ligamentous rupture in simulated spraining tests on cadaver. A previous case report revealed that the ankle joint reached 48 degrees inversion and 10 degrees internal rotation during an accidental grade I ankle ligamentous sprain injury during a dynamic cutting trial in laboratory. Diagnosis techniques and grading systems vary, but the management of ankle ligamentous sprain injury is mainly conservative. Immobilization should not be used as it results in joint stiffness, muscle atrophy and loss of proprioception. Traditional Chinese medicine such as herbs, massage and acupuncture were well applied in China in managing sports injuries, and was reported to be effective in relieving pain, reducing swelling and edema, and restoring normal ankle function. Finally, the best practice of sports medicine would be to prevent the injury. Different previous approaches, including designing prophylactice devices, introducing functional interventions, as well as change of games rules were highlighted. This paper allows the readers to catch up with the previous researches on ankle sprain injury, and facilitate the future research idea on sport-related ankle sprain injury.

Kinematics Analysis of Ankle Inversion Ligamentous Sprain Injuries in Sports 2 Cases During the 2008 Beijing Olympics

Background:Ankle ligamentous sprain is common in sports. The most direct way to study the mechanism quantitatively is to study real injury cases; however, it is unethical and impractical to produce an injury in the laboratory. A recently developed, model-based image-matching motion analysis technique allows quantitative analysis of real injury incidents captured in televised events and gives important knowledge for the development of injury prevention protocols and equipment. To date, there have been only 4 reported cases, and there is a need to conduct more studies for a better understanding of the mechanism of ankle ligamentous sprain injury.Purpose:This study presents 5 cases in tennis and a comparison with 4 previous cases for a better understanding of the mechanism of ankle ligamentous sprain injury.Study Design:Case series; level of evidence, 4.Methods:Five sets of videos showing ankle sprain injuries in televised tennis competition with 2 camera views were collected. The videos were transformed, sy...

Kinematics Analysis of Ankle Inversion Ligamentous Sprain Injuries in Sports Five Cases From Televised Tennis Competitions

Background: Ankle ligamentous sprain is common in sports. The most direct way to study the mechanism quantitatively is to study real injury cases; however, it is unethical and impractical to produce an injury in the laboratory. A recently developed, model-based image-matching motion analysis technique allows quantitative analysis of real injury incidents captured in televised events and gives important knowledge for the development of injury prevention protocols and equipment. To date, there have been only 4 reported cases, and there is a need to conduct more studies for a better understanding of the mechanism of ankle ligamentous sprain injury. Purpose: This study presents 5 cases in tennis and a comparison with 4 previous cases for a better understanding of the mechanism of ankle ligamentous sprain injury. Study Design: Case series; level of evidence, 4. Methods: Five sets of videos showing ankle sprain injuries in televised tennis competition with 2 camera views were collected. The videos were transformed, synchronized, and rendered to a 3-dimensional animation software. The dimensions of the tennis court in each case were obtained to build a virtual environment, and a skeleton model scaled to the injured athlete’s height was used for the skeleton matching. Foot strike was determined visually, and the profiles of the ankle joint kinematics were individually presented. Results: There was a pattern of sudden inversion and internal rotation at the ankle joint, with the peak values ranging from 48°-126° and 35°-99°, respectively. In the sagittal plane, the ankle joint fluctuated between plantar flexion and dorsiflexion within the first 0.50 seconds after foot strike. The peak inversion velocity ranged from 509 to 1488 deg/sec. Conclusion: Internal rotation at the ankle joint could be one of the causes of ankle inversion sprain injury, with a slightly inverted ankle joint orientation at landing as the inciting event. To prevent the foot from rolling over the edge to cause a sprain injury, tennis players who do lots of sideward cutting motions should try to land with a neutral ankle orientation and keep the center of pressure from shifting laterally.

An ankle joint model-based image-matching motion analysis technique

This study presented a model-based image-matching (MBIM) motion analysis technique for ankle joint kinematic measurement. Five cadaveric below-hip specimens were manipulated through a full range of ankle joint motions in bare-foot and shoed conditions. The ankle motions were analyzed by bone-pin marker-based motion analysis and MBIM motion analysis techniques respectively. The root mean square errors of all angles of motion were less than 3°. The average Intraclass Correlation Coefficients (ICCs) for the intra-rater reliability were greater than 0.928 and the average ICCs for the inter-rater reliability were greater than 0.948 for all angles of motion. Excellent validity, intra-rater reliability and inter-rater reliability were achieved for the MBIM technique in both bare-foot and shoed conditions. The MBIM technique can therefore provide good estimates of ankle joint kinematics.

The Effect of Thigh Marker Placement on Knee Valgus Angles in Vertical Drop Jumps and Sidestep Cutting

Knee valgus angles measured in sidestep cutting and vertical drop jumps are key variables in research on anterior cruciate ligament (ACL) injury causation. These variables are also used to quantify knee neuromuscular control and ACL injury risk. The aims of the current study were to (1) quantify the differences in the calculated knee valgus angles between 6 different thigh marker clusters, (2) investigate the trial ranking based on their knee valgus angles, and (3) investigate the influence of marker clusters on the cross-talk effect. Elite female handball and football players (n = 41) performed sidestep cutting and vertical drop jumping motions. We found systematic differences up to almost 15° of peak valgus between the marker sets in the drop jump test. The Spearmans rank correlation coefficient varied from .505 to .974 among the 6 marker sets. In addition, the cross-talk effect varied considerably between the marker clusters. The results of the current study indicate that the choice of thigh marker cluster can have a substantial impact on the magnitude of knee valgus angle, as well as the trial ranking. A standardized thigh marker cluster, including nonanatomical landmark, is needed to minimize the variation of the measurement.

Head impact velocities in FIS World Cup snowboarders and freestyle skiers: Do real-life impacts exceed helmet testing standards?

Introduction Prior to the 2013–2014 season, the International Ski Federation (FIS) increased the helmet testing speed from a minimum requirement of 5.4 to 6.8 m/s for alpine downhill, super-G and giant slalom and for freestyle ski cross, but not for the other freestyle disciplines or snowboarding. Whether this increased testing speed reflects impact velocities in real head injury situations on snow is unclear. We therefore investigated the injury mechanisms and gross head impact biomechanics in four real head injury situations among World Cup (WC) snowboard and freestyle athletes and compared these with helmet homologation laboratory test requirements. The helmets in the four cases complied with at least European Standards (EN) 1077 (Class B) or American Society for Testing and Materials (ASTM) F2040. Methods We analysed four head injury videos from the FIS Injury Surveillance System throughout eight WC seasons (2006–2014) in detail. We used motion analysis software to digitize the helmet’s trajectory and estimated the head’s kinematics in two dimensions, including directly preimpact and postimpact. Results All four impacts were to the occiput. In the four cases, the normal-to-slope preimpact velocity ranged from 7.0(±SD 0.2) m/s to 10.5±0.5 m/s and the normal-to-slope velocity change ranged from 8.4±0.6 m/s to 11.7±0.7 m/s. The sagittal plane helmet angular velocity estimates indicated a large change in angular velocity (25.0±2.9 rad/s to 49.1±0.3 rad/s). Conclusion The estimated normal-to-slope preimpact velocity was higher than the current strictest helmet testing rule of 6.8 m/s in all four cases.

Association Between Anatomical Characteristics, Knee Laxity, Muscle Strength, and Peak Knee Valgus During Vertical Drop-Jump Landings

STUDY DESIGN Controlled laboratory study; cross-sectional. OBJECTIVES To investigate the relationship among anatomical variables, knee laxity, muscle strength, and peak knee valgus angles during a vertical drop-jump landing task. BACKGROUND Excessive knee valgus has been associated with anterior cruciate ligament injury in females; however, the influence of anatomical characteristics, knee laxity, and muscle strength on frontal plane knee motion is not completely understood. METHODS Norwegian elite female soccer players (n = 279; mean ± SD age, 21 ± 4 years; height, 167 ± 6 cm; body mass, 63 ± 7 kg) were evaluated from 2009 through 2012. The evaluation included 3-D motion analysis of a vertical drop jump, anatomical measures (height, static knee valgus, leg length, and static foot posture), knee laxity, and muscle strength (quadriceps, hamstrings, and hip abductors). Multiple linear regression analyses were used to investigate the relationships among anatomical characteristics, knee laxity, muscle strength, and peak knee valgus angles. RESULTS Anatomical characteristics explained 11% of the variance in peak knee valgus angles (P<.001), with height and static knee valgus being significant predictors. CONCLUSION Greater body height and static knee valgus were associated with greater peak knee valgus angles during a vertical drop-jump landing task. However, these variables only explained 11% of the variance in peak knee valgus.

Reliability of lower limb biomechanics in two sport-specific sidestep cutting tasks

Abstract The purpose of this study was to assess the within- and between-session reliability of lower limb biomechanics in two sport-specific sidestep cutting tasks performed by elite female handball and football (soccer) athletes. Moreover, we aimed at determining the minimum number of trials necessary to obtain a reliable measure. Nineteen elite female handball and 22 elite female football (soccer) athletes (M ± SD: 22 ± 4 yrs old, 168 ± 5 cm, 66 ± 8 kg) were tested. The reliability was quantified by intra-class correlations (ICCs), typical error and Spearman’s rank correlation. Only minor improvements in ICC values were seen when increasing the number of trials from 3 to 5. Based on trials 1–3, all variables showed good to excellent within-session reliability (M ICC: 0.91, 95% CI: 0.89–0.93), fair to good between-session reliability (M ICC: 0.73, 95% CI: 0.70–0.76), moderately positive between-session rank correlation coefficients (M: 0.72, 95% CI: 0.69–0.76). A few frontal plane biomechanical variables displayed lower between-session reliability in the football task compared with the handball task. The moderately positive between-session ranking and practically small typical error implies that the measurements could reliably reproduce the ranking of individuals in multiple-session studies. Adequate reliability could be attained from 3 trials, with only minor improvements when adding more trials.

Reconstruction of head impacts in FIS World Cup alpine skiing

Introduction Prior to the 2013/2014 season, the International Ski Federation (FIS) increased the helmet testing speed from 5.4 to 6.8 m/s for alpine downhill, super-G and giant slalom. Whether this increased testing speed reflects head impact velocities in real head injury situations on snow is unclear. We therefore investigated the injury mechanisms and gross head impact biomechanics in seven real head injury situations among World Cup (WC) alpine skiers. Methods We analysed nine head impacts from seven head injury videos from the FIS Injury Surveillance System, throughout nine WC seasons (2006–2015) in detail. We used commercial video-based motion analysis software to estimate head impact kinematics in two dimensions, including directly preimpact and postimpact, from broadcast video. The sagittal plane angular movement of the head was also measured using angle measurement software. Results In seven of nine head impacts, the estimated normal to slope preimpact velocity was higher than the current FIS helmet rule of 6.8 m/s (mean 8.1 (±SD 0.6) m/s, range 1.9±0.8 to 12.1±0.4 m/s). The nine head impacts had a mean normal to slope velocity change of 9.3±1.0 m/s, range 5.2±1.1 to 13.5±1.3 m/s. There was a large change in sagittal plane angular velocity (mean 43.3±2.9 rad/s (range 21.2±1.5 to 64.2±3.0 rad/s)) during impact. Conclusion The estimated normal to slope preimpact velocity was higher than the current FIS helmet rule of 6.8 m/s in seven of nine head impacts.

Eccentric hamstring strength deficit and poor hamstring-to-quadriceps ratio are risk factors for hamstring strain injury in football: A prospective study of 146 professional players

OBJECTIVES The purpose of this study was to investigate whether preseason isokinetic strength measures were predictive of future HSI among professional football players. DESIGN Prospective cohort study, Level of evidence 2. METHODS A total of 169 professional players participated in a preseason isokinetic strength screening, followed by a 10-month competitive season. Testing protocol included the concentric performance of both knee flexion and extension at 60degs-1 and 240degs-1 and the eccentric performance of the knee flexor at 30degs-1. Strength deficits, bilateral differences, and hamstring to quadriceps strength ratios were computed. Univariate and multivariate logistic regressions were used to identify potential risk factors of HSI. Receiver operating characteristic (ROC) curves were used to investigate the sensitivity and specificity of the strength measures. RESULTS Forty-one acute HSIs were sustained, and 12% (n=5) reoccurred within the study period. In the multivariate analysis, we have shown an association between the injury risk and eccentric hamstring peak torque below 2.4Nmkg-1 (OR=5.59; 95% CI, 2.20-12.92); concentric H/Q ratio below 50.5% (OR=3.14; 95% CI, 1.37-2.22); players with previous injury of HSI (OR=3.57; 95% CI, 3.13-8.62). ROC analysis displayed an area under curve (AUC) of 0.77, indicating fair combined sensitivity and specificity of the overall predicting model. CONCLUSIONS Professional football players with significant lower isokinetic hamstring strength, lower hamstring-to-quadriceps strength ratio, and a previous injury of HSI were linked to an increased risk of acute HSI.