Spectrum of injuries associated with paediatric ACL tears: an MRI pictorial review

OBJECTIVE: Magnetic resonance imaging (MRI) findings in anterior cruciate ligament (ACL) injury are well known, but most published reviews show obvious examples of associated injuries and give little focus to paediatric patients. Here, we demonstrate the spectrum of MRI appearances at common sites of associated injury in adolescents with ACL tears, emphasising age-specific issues. METHODS: Pictorial review using images from children with surgically confirmed ACL tears after athletic injury. RESULTS: ACL injury usually occurs with axial rotation in the valgus near full extension. The MRI findings can be obvious and important to management (ACL rupture), subtle but clinically important (lateral meniscus posterior attachment avulsion), obvious and unimportant to management (femoral condyle impaction injury), or subtle and possibly important (medial meniscocapsular junction tear). Paediatric-specific issues of note include tibial spine avulsion, normal difficulty visualising a thin ACL and posterolateral corner structures, and differentiation between incompletely closed physis and impaction fracture. CONCLUSION: ACL tear is only the most obvious sign of a complex injury involving multiple structures. Awareness of the spectrum of secondary findings illustrated here and the features distinguishing them from normal variation can aid in accurate assessment of ACL tears and related injuries, enabling effective treatment planning and assessment of prognosis. TEACHING POINTS: • The ACL in children normally appears thin or attenuated, while thickening and oedema suggest tear. • Displaced medial meniscal tears are significantly more common later post-injury than immediately. • The meniscofemoral ligaments merge with the posterior lateral meniscus, complicating tear assessment. • Tibial plateau impaction fractures can be difficult to distinguish from a partially closed physis. • Axial MR sequences are more sensitive/specific than coronal for diagnosis of medial collateral ligament (MCL) injury

COACHING ADVICE THAT REDUCES LOADS ASSOCIATED WITH BIOMECHANICAL PREDICTORS OF ILIOTIBIAL BAND SYNDROME

It has been previously described that the normalized hip adduction moment correlates significantly with the risk of developing iliotibial band syndrome. To advance this research we developed coaching advice that would result in reducing the peak hip adduction moment. Five marathon runners were assessed to determine their normal kinematic and kinetics while running. Runners were then coached to run their normal speed but while lowering their upper bodies by ~1 inch (2.54cm). The runners reduced their peak adduction moments by 21.8% (

FOOT-TO-BALL INTERACTION IN PREFERRED AND NON-PREFERRED LEG AUSTRALIAN RULES KICKING

Kicking is an integral skill within Australian Rules Football (ARF) and the ability to kick with either foot is essential at the elite level. A principal technical factor in the kicking skill is the nature of impact between the kicking foot and ball (Ball, 2008a). This study compared characteristics of foot-to-ball interaction between preferred and non-preferred kicking legs in Australian Rules football (ARF). Eighteen elite ARF players performed a maximum distance kick on their preferred and non-preferred legs. From high-speed video (6000Hz), two-dimensional digitised data of seven points (five on the kick leg, two on the ball) were used to quantify parameters near and during impact. The preferred foot produced significantly larger foot speed, ball speed, work done on the ball, ball displacement while in contact with the foot and change in shank angle during the ball contact phase

KICK IMPACT CHARACTERISTICS OF JUNIOR KICKERS

Impact is important to kicking performance and while differences have been found between kick distances and between preferred and non-preferred leg kicks, no work has examined junior kickers. This study examined impact characteristics of the Australian football (AF) drop punt kick for juniors and compared these data with seniors from Smith et al. (2009). Twenty one junior AF players performed a maximum distance kick. The foot, ball and shank were digitised from 6000 Hz video to calculate seven foot/ball parameters. Junior players produced significantly smaller foot and ball speeds but not foot to ball speed ratios compared to senior players. Work was also significantly different due to lesser force being applied to the ball. Junior players should focus on increasing foot speed and force on the ball to increase kick distance

BENEFICIAL KINETIC ADAPTATIONS AFTER ENDURANCE TRAINING

Endurance training produces adaptations in running kinetics, although it does not produce changes in kinematics. We performed a prospective study of 23 runners who joined established marathon training teams. Each was tested in their first month of training and again two weeks prior to their marathon. The approximate time between tests was three months. Four peak ground reaction forces were reduced significantly after the training: lateral (15.4%), acceleration (7.10%), vertical (2.1%) and the normalized resultant (2.1%). Kinetic variables associated with iliotibial band injuries and anterior knee pain also had significant reductions. Peak hip adduction moments were reduced by 6.0%, peak patellofemoral contact force was reduced by 7.6%

INJURY INCIDENCE, DISTRIBUTION, AND SEVERITY DURING A MARATHON TRAINING SEASON AND THE IMPLICATIONS

Marathon runners and their coaches are concerned about the potential for injury during an individual season. No published studies of running injuries address this training season as a meaningful entity. This study reports the incidence of injury and the distribution of injuries for runners (n=75) on two established marathon training teams during an individual season. An injury was defined as affecting seven consecutive days or three consecutive workouts. The incidence/risks of overuse injuries, for marathon runners in a single season were found to be: anterior knee pain (20%), iliotibial band syndrome (29%), plantar fasciitis (1%), Achilles tendonitis (9%) shin splints (16%) and stress fractures (4%). This risk, overall injury distribution, severity and length of longest run prior to presentation of injury are of interest to runners, coaches and biomechanists