Epidemiology of cervical spine abnormalities in asymptomatic adult professional rugby union players using static and dynamic MRI protocols: 2002 to 2006.

OBJECTIVE: In this study, the prevalence of abnormalities in the cervical spine of asymptomatic professional rugby players using both static and dynamic magnetic resonance imaging (MRI) in order to improve the detection of abnormalities and prevention of related injuries was investigated. DESIGN: Prospective observational study. SETTING: French professional rugby union clubs, between 2002 and 2006. PARTICIPANTS: 206 elite male adult players. INTERVENTION: Static sagittal T2 and axial T2* fast spin echo (FSE), and dynamic sagittal single-shot FSE weighted MRI scans of the C2-C7 region were examined for the presence of abnormalities. Participants' spines were in supine neutral position for the static protocol but were allowed complete flexibility in a sagittal plane for the dynamic protocol. MAIN OUTCOME MEASUREMENTS: The medulla-to-canal ratio (MCR) was measured at every vertebral disc level for both MRI methods. When observed, anatomical abnormalities were categorised. RESULTS: Anatomical abnormalities mainly consisted of degenerative discopathy and were most frequently observed in players aged>21 years, as well as in players whose MCR was abnormally high based on medical expertise. Most MCRs that were initially assessed as intermediate with static MRI were subsequently assessed as abnormal with dynamic MRI assessment. CONCLUSIONS: Since dynamic MRI is more accurate than static techniques in examining the cervical spine, it contributes substantially to identifying the risk of spinal injuries in professional rugby players, and when used in association with clinical assessment, it can assist in preventing spinal injury.

Training habits and injuries of masters' level football players: a preliminary report.

OBJECTIVE: To profile training habits and injuries in football players participating in a national Masters tournament. METHODS: A cross-sectional retrospective study design was used to survey male football players attending the 2008 New Zealand Masters Games. Information regarding player demographics, football injuries, football related training, and risk factors for injury were collected. RESULTS: 199 Players were recruited, with a median age of 44 yrs (range 35-73) and a median football playing history of 15 yrs (range 0-66). Irrespective of age, 112 (84%) players included a warm-up and 104 (78%) included a stretching regime in their regular training programme. In the 12 months prior to the tournament, 128 football related injuries were reported by 93 players (64 injuries/100 players or 46 injured players/100 players). The most frequently injured region was the lower limb; specifically the lower leg (n=23), ankle (n=18), hamstring (n=17), knee (n=15), and Achilles tendon (n=15). CONCLUSION: This study provides a preliminary insight into the training habits and injury profiles of Masters football players. Despite all players including some form of injury prevention strategy in their training, a significant number of players experienced an injury in the 12 months prior to the tournament.

Determining rigid body transformation parameters from ill-conditioned spatial marker co-ordinates.

The three-dimensional location of a body-fixed axis system is described by position and orientation parameters that can be calculated knowing local and global coordinates of three or more body-fixed markers. However, marker distribution can become ill-conditioned when marker placement is symmetrical with respect to the mean of the markers. As symmetry and ill-conditioning increases, random errors in marker locations can affect the stability of orientation parameters as a result of the mathematical approach adopted. The present study investigates the methods of Veldpaus et al. [1988; Journal of Biomechanics 21, 45], Challis [1995; Biomechanics 28, 733] and Andriacchi et al. [1998; Journal of Biomedical Engineering 120, 743] for obtaining segment orientation parameters when segment markers ranged from well-defined to highly ill-conditioned depending on the symmetry of segment markers. A novel fourth approach is also presented that enabled comparisons of the root mean square error of reconstructed marker coordinates to verify that an optimal solution was obtained. No single method produced optimal results for all axis orientation parameters when reconstructing movement trials. The best performed was the method of Veldpaus et al. [1988; Journal of Biomechanics 21, 45] based on consistent results and ease of implementation. The fourth approach presented provided a reliable method in all but the highly ill-conditioned markers, however implementation was computationally difficult. The method of Challis [1995; Biomechanics 28, 733] was only suited to well-conditioned marker sets which avoided markers lying in a single plane with symmetries in marker distribution relative to the mean. The method of Andriacchi et al. [1998; Journal of Biomedical Engineering 120, 743] produced, at best, orientation parameters that approximated the results obtained by least squares methods.

Dynamic coordinate data for describing muscle-tendon paths: a mathematical approach.

When modelling the musculoskeletal system over a range of joint angles the use of fixed points to describe muscle-tendon paths has inherent limitations. These result in fewer deflection points and the use of effective insertions to accommodate both relative marker movement and avoid muscle paths contacting bony structures. Model performance is dependent on the joint angle relative to the anatomical position where the muscle-tendon paths were defined. The present study proposes a scheme for the implementation of dynamic coordinates for describing muscle-tendon paths. For each muscle-tendon element a plane is defined in which the muscle-tendon complex acts when crossing a given joint. The muscle-tendon plane is dependent on 3D segment orientations and describes one degree of freedom, while the remaining two degrees of freedom are described by polar coordinates and locate the dynamic point in the muscle-tendon plane. The dynamic approach is implemented on four muscles of the lower limb in modelled and simulated joint movements and offers a significant improvement on previous approaches based on fixed deflection points. The scheme accommodates compound 3D rotations about joint axes, is not computationally difficult or require large data sets, and does not impose limitations on the number of points that may be defined along a muscle-tendon path.

Effect of premanipulative tests on vertebral artery and internal carotid artery blood flow: a pilot study.

BACKGROUND: Neck manipulation occasionally causes stroke after trauma to the vertebral or internal carotid artery. Premanipulativ e tests involving cervical spine rotation or extension have been recommended to detect patients at risk of neurovascular ischemia. However, the effect of these procedures on extracranial blood flow is not well established, and their validity is thus controversial. OBJECTIVE: To determine the effect of premanipulative tests involving cervical spine rotation or extension on vertebral artery and internal carotid artery blood flow parameters. DESIGN: Two-group experimental study. SUBJECTS: Twenty subjects consisting of 16 patients treated with physiotherapy and four volunteers. METHODS: Subjects were tested with a recommended premanipulative protocol by both an independent physiotherapist and an investigator. One group consisted of 10 subjects with signs or symptoms indicative of neurovascular ischemia on premanipulative testing, with 10 subjects with no signs or symptoms indicative of neurovascular ischemia on premanipulative testing comprising the second group. Hemodynamic measurements for both vertebral and both internal carotid arteries were taken by use of duplex Doppler ultrasonography with color-flow imaging with the subjects in the following positions: neutral, end-range extension, 45 degrees contralateral rotation, end-range contralateral rotation, and combined end-range contralateral rotation/extension. RESULTS: The reliability of premanipulative testing was supported. Significant changes in flow velocity of the vertebral artery (and to a lesser extent of the internal carotid artery) were shown in end-range positions involving rotation and extension. No meaningful significant differences were found between the two groups. CONCLUSIONS: Screening procedures that use rotation and extension may be useful tests of the adequacy of collateral circulation. A larger study is needed to determine whether subjects testing positive significantly differ from those testing negative.

The nature and circumstances of tackle injuries in rugby union.

This study describes the nature and circumstances of injury occurring in rugby union tackles (33% of 569 injury events) using data from the Rugby Injury and Performance Project (RIPP) and provides supplementary information on the nature of tackles involving injury from analysis of videotape of tackle injury events. The most common tackle injuries in the RIPP data were sprains/strains (41%) followed by haematomas/bruising (26%). The most frequently injured body sites were the head/neck/face (22%) and the knee (17%). The ball carrier and tackler were injured in tackles in similar proportions in both RIPP and New Zealand Rugby Football Union (NZRFU) video tackle incidents. Both players were most often in motion in the tackle at the time of injury with approximately 70% of injuries occurring when the injured player was running or diving/falling to the ground. Tackle injury was most often caused by impact with another player rather than impact with the ground. The use of protective padding may reduce the risk of impact injury. The majority of tackle injuries were associated with stopping tackles to the trunk which were from the front (63%), rather than from the side or behind. Thus consideration should be given to coaching strategies or to rule changes which reduce the likelihood or prohibit front-on tackles.

Warm-up effect on active and passive arthrometric assessment of knee laxity.

OBJECTIVE: To determine the influence of a warm-up protocol suitable for use in clinical settings on tibial displacement and muscle activity during arthrometric knee laxity assessment. DESIGN: Intervention study in which the subjects served as their own controls. SETTING: The Biomechanics Research Laboratory, University of Wollongong, Wollongong, New South Wales, Australia. SUBJECTS: Ten volunteers who reported no history of knee trauma or disease. INTERVENTION: A warm-up consisting of 10 minutes of ergometer cycling (60rpm) followed by two sets of three hamstring muscle stretches. MAIN OUTCOME MEASURES: Outcome measures were: (1) anterior tibial translation and knee extension force assessed using a Dynamic Cruciate Tester for each subject's right knee during active and passive testing, and (2) intensity of quadriceps and hamstring muscle activity during knee laxity testing. RESULTS: There was significantly less quadriceps activity after warm-up (t = 2.419, p = .039). However, there was no significant difference between anterior tibial translation, knee extension force, or hamstring muscle activity results before and after warm-up in either active or passive tests. CONCLUSION: A warm-up suitable for use in a clinical setting is not required before arthrometric assessment of knee laxity.

Lumbosacral loads in bedmaking.

The purpose of this study was to determine whether the introduction of larger and heavier beds which were lower to the floor increased the physical stress on employees responsible for room cleaning and bedmaking in the hospitality industry. More specifically, this study assessed the effect of bed size (single, double and king) and bed height (460 and 560 mm) on dynamic and static estimates of L5/S1 compression force and static L5/S1 shear force for six simulated components of the overall bedmaking task. Results confirmed the view that static models severely underestimate the loads on the lumbar spine under inertial lifting conditions, and also indicated that: (i) tasks with the greatest hand loads were not necessarily associated with the greatest spinal loads due to differences in the way each task was performed; (ii) L5/S1 loads produced during bedmaking may exceed recommended safe lifting limits for certain task-size height combinations; and (iii) the use of larger and heavier beds in the hospitality industry imposes increased loads on the lumbar spine. The investigation of alternative work practices designed to minimise loads on the lumbar spine is recommended.

Shoe-surface interaction and the reduction of injury in rugby union.

While it is quite clear that footwear can provide protection against lower limb injury in running and some court sports, the literature related to footwear design and injury prevention in most sports played on natural turf is limited. Nowhere is this more apparent than in the design of footwear for rugby union and rugby league. Therefore, in this article, information from other sporting codes will be applied to the design and performance characteristics of footwear and surfaces in an attempt to understand the causes of equipment-related injuries in rugby. A complete understanding of the complex interactions between the leg, foot, footwear and the surface has not yet been achieved and as a consequence, precise footwear design criteria to minimise injury, while not compromising the performance aspects of shoe design, have yet to be established. The variable surface conditions experienced by players makes it difficult to provide recommendations as to the ideal footwear for all (or any) conditions. Equally, the ground reaction loads experienced by each player (and playing position) vary sufficiently to make generalisations difficult. Also the foot-fall pattern during weight-bearing is highly individualised and further prohibits making general recommendations about selecting footwear for rugby.

Reproducibility of knee laxity assessment results using the dynamic cruciate tester.

The purpose of the study was to examine reproducibility of knee laxity measurements obtained using the Dynamic Cruciate Tester (DCT) from day-to-day, set-to-set, and trial-to-trial. In Part I, peak anterior tibial translation (ATT) was assessed for 1 anterior cruciate ligament (ACL) deficient and 16 control subjects during two sets of three active trials (maximal isometric quadriceps contractions) and three passive trials (240 N load) conducted over four consecutive days. In Part II, peak ATT was recorded for 12 chronic ACL deficient subjects during one set of five active and five passive trials within one day. Results were analysed using mixed repeated measures ANOVA designs with intraclass reliability coefficients (ICC) calculated from the ANOVA results. There were no significant differences in the mean peak ATT results among the four tests days or between the two test sets conducted within a day, with ICC ranging from R1 = 0.939 to 0.980. It was concluded peak ATT measurements obtained using the DCT were reproducible from day-to-day and set-to-set. A significant main effect of trial was found on both active (F(2,32) = 13.93; p < 0.001) and passive (F(2,32) = 57.21; p < 0.001) peak ATT results. It was therefore recommended a full pretrial should be conducted before knee laxity assessment using the DCT to ensure reproducible results.

Conjugate imagery in the automated reproduction of three dimensional coordinates from two dimensional coordinate data.

The three-dimensional video analysis of human motion commonly utilises automated image processing and digitisation processes to produce real-time unidentified two-dimensional coordinate data of segmental markers. In what can be a time-consuming process the two-dimensional data are then identified and tracked to produce three-dimensional coordinates. This paper presents an approach to the automated reproduction of three-dimensional coordinates from two-dimensional coordinates data. Conjugate imaging techniques were utilised in the development of four criterion measures for determining the validity of conjugate (corresponding) image points. An algorithm based on the criterion measures was then developed for the automated reproduction of three dimensional coordinates from camera image coordinate data. The algorithm was tested with a 55 point marker system viewed in four video cameras (digitisation error approx. 0.2%, lab point separation > or = 6 cm). The success of the algorithm was dependent on the closeness of markers, the accuracy of the photogrammetric system, and the number of markers visible in two camera images. The present research has developed techniques based on conjugate imagery for the automated reproduction of three-dimensional coordinates from two-dimensional data, and provided a bases for further development of automated three-dimensional tracking.

Effect of torso position on arthrometric assessment of anterior knee laxity.

The purpose of the study was to examine the effect of changes in torso position on arthrometric assessment of knee laxity. Anterior tibial translation (ATT) of 12 control and 12 ACL deficient subjects was assessed using a Dynamic Cruciate Tester during five maximal isometric knee extensions and five passive tests (240 N load) on the right and left knee in each of three torso positions: vertical, reclined, and supine. Electromyographic activity of rectus femoris, vastus lateralis, biceps femoris, and semimembranosus were sampled during arthrometric assessment. Results indicated there was no significant difference in mean ATT as a function of torso position. However, subjects demonstrated significantly greater hamstring activity when seated vertically compared to reclined or supine and significantly greater hamstring activity when reclined compared to supine.

Biomechanics of rugby union scrummaging. Technical and safety issues.

In the game of ruby union, the scrum epitomises the physical nature of the game. It is both a powerful offensive skill, affording a base for attacking play, and a defensive skill in denying the opposition clean possession. However, the scrum has also been implicated in a large proportion of serious spinal injuries in rugby union. The majority of injuries are found to occur at engagement where the forces experienced by front-row players (more than two-thirds of a tonne shared across the front-row) can exceed the structural limits of the cervical spine. These large forces are a consequence of the speed of engagement and the weight (and number) of players involved in the scrum. This highlights not only the need for physical preparation of all forwards but particularly player restraint at engagement, and justifies the 'crouch-pause-engage' sequence recently introduced to 'depower' the scrum. As the hooker is the player exposed to the greatest loads throughout the scrum and subsequently most at risk, he should determine the timing of engagement of the 2 front-rows. Stability of the scrum is an indication of front-row players' ability to utilise their strength to transmit the force to their opponents as well as the push of second-row and back-row players behind them in the scrum. This appears to be independent of the size of players. Equally, it reflects the risk of chronic degeneration of the musculoskeletal system through repeated exposure to these large stresses. However, not only are older and more experienced players better able to generate and transmit these forces, they are also able to maintain the integrity of the scrum. A large proportion of individual players' efforts to generate force is lost in their coordinated effort in a normal scrum. It is assumed these forces are dissipated through players re-orientating their bodies in the scrum situation as well as to less efficient shear forces and to the elastic and compressive tissues in the body. It again reinforces the importance of physical preparation for all forwards to better withstand the large forces involved in scrummaging. Despite negative publicity surrounding the risk of serious spinal injury in rugby union, limited research has been conducted to examine either the mechanisms of injury or techniques implicated in causing injury. Biomechanical information can provide systematic bases for modifying existing techniques and assessing the physical capacities necessary to efficiently and safely play in the serum. This will both improve performance of game skills and minimise the potential for injury.

The kinetics of rugby union scrummaging.

Two rugby union forward packs of differing ability levels were examined during scrummaging against an instrumented scrum machine. By systematically moving the front-row of the scrum along the scrum machine, kinetic data on each front-row forward could be obtained under all test conditions. Each forward pack was tested under the following scrummaging combinations: front-row only; front-row plus second-row; full scrum minus side-row, and full scrum. Data obtained from each scrum included the three orthogonal components of force at engagement and the sustained force applied by each front-row player. An estimate of sub-unit contributions was made by subtracting the total forward force on all three front-row players from the total for the complete scrum. Results indicated the primary role of the second-row appeared to be application of forward force. The back-row ('number eight') forward did not substantially contribute any additional forward force, and added only slightly to the lateral and vertical shear force experienced by the front-row. The side-row contributed an additional 20-27% to the forward force, but at the expense of increased vertical forces on all front-row forwards. Results of this investigation are discussed in relation to rule modification, rule interpretation and coaching.

Summation of segmental velocities in the golf swing.

The downswing phase in golf was represented as a double pendulum pivoted at the shoulder joint and hinged at the wrist. The motion of such a pendulum was used to derive a series of equations which were used to describe the instantaneous values of several of the component features of the downswing. Results of this analysis showed that an initial delay in the uncocking of the wrist would allow (a) acceleration of the arm to reach a greater value and (b) the acceleration of the club to be summed with the existing maximum angular acceleration of the proximal segment.