Injuries in cricket: epidemiology and factors associated with lumbar spine injury in cricket fast bowlers

The purpose of this thesis was to examine the nature and extent of cricket fast bowling injuries. In particular, the thesis investigated the risk factors for the lumbar bone stress injuries with particular emphasis on exploring whether paraspinal muscle asymmetry is a genuine risk factor and previously identified. A secondary aim was to determine if the previously published injury surveillance data that highlighted a high injury incidence, prevalence and severity of fast bowling injuries, such as lumbar bone stress injuries also existed in elite Sri Lankan fast bowlers. The results from this thesis confirm that elite level Sri Lankan fast bowlers have higher injury incidence and prevalence compared to other player positions. In particular, lumbar bone stress injuries were the most severe injury and resulted in the most game-days missed. A review of published literature demonstrated that lumbar bone stress injuries occur near the biomechanically vulnerable region of the pars interarticularis, at the posterior element of the vertebra. There were numerous risk factors identified, including bowling technique, workload and more recently quadratus lumborum (QL) muscle asymmetries. The latter part of the thesis explored the methods used to measure the magnetic resonance imaging (MRI) derived QL cross-sectional areas that have been used to determine asymmetry. A method for measuring QL from MRI was proposed and tested in subsequent chapters, demonstrating reliable measurements. Finally, MRI scans performed in asymptomatic adolescent and adult fast bowlers were reviewed and QL asymmetries reported. As expected large QL asymmetries were found in both groups but the pattern of asymmetry differed, with adolescents having an even distribution of larger sized QL muscles on both sides, whereas adult fast bowlers had larger muscle size (asymmetry) favouring the QL on bowling-arm side. The differences between the groups were explained by potential age related factors such as chronic bowling workloads and possibly bowling technique differences. In the participants studied, QL asymmetries were not associated with increased risk of lumbar spine injury in either adult or adolescent bowlers. These results question the previously published links between QL asymmetry and lumbar spine injury in fast bowlers. More research is required to determine the relationship between bowling technique, bowling workloads, muscle asymmetry and lumbar spine injury. This may determine if there is an algorithm of factors that are related to lumbar spine injury in cricket fast bowlers.