The Breakdown: Investigating hamstring muscle injuries in men’s professional rugby union

The aim of the thesis was to establish the mechanisms of hamstring muscle injury (HMI) in rugby union (rugby), and to better understand factors associated with subsequent HMI. All original research included was carried out at a professional men’s rugby team in Ireland. The aim of Chapter 2 was to analyse and describe the mechanism of acute HMI in professional rugby using systematic video analysis. Video footage of the instances during which HMIs occurred were collected from the Leinster Rugby match and training video database. Five injury mechanisms were identified – ‘running’, ‘decelerating’, ‘kicking’, ‘tackle’, ‘rucking’ and ‘direct trauma’. Hamstring muscle lengthening, characterised by trunk flexion and relative knee extension, appears to be a fundamental characteristic of the mechanisms of acute HMI in rugby. Ipsilateral trunk rotation was also deemed to be a characteristic feature. Knowledge of the specific patterns of HMI identified may be useful in injury prevention and rehabilitation. Chapter 3 is comprised of a narrative review, the purpose of which was to determine whether intramuscular tendon (IMT) injuries of the hamstring warrant being classified as a distinct clinical entity with expected different outcomes to other HMIs. While some studies have reported longer time to return to play and higher subsequent HMI rates following IMT disruption, other double-blinded studies have reported small or no differences in these respective outcome metrics. A bespoke “intramuscular tendon-oriented” approach to rehabilitation has been advocated, though this requires replication. Substantial homogeneity of sport and level, study design, and approaches to rehabilitation make cross-comparison of these outcome metrics difficult. Chapter 4 is a retrospective cohort study. The aim of this study was to analyse the influence of injury location (specifically, injury to the IMT and distal T-Junction) on time to return to full training and subsequent injury rates in men’s professional rugby. Players took 3 times longer to return to full training following injuries with IMT involvement versus injuries without IMT involvement. This difference was statistically significant. Fischer exact test determined that there was no statistically significant difference in the rate of re-injury/subsequent injury for HMIs with or without IMT involvement. The median time to return to full training was 18 days for biceps femoris injuries with no T-junction involvement and 24 days for biceps femoris injuries with T-junction involvement. This difference was not statistically significant.In Chapter 5, by analysing the MRIs of index and subsequent HMIs, and extracting data relating to the time taken to return to full training from the club’s electronic medical records system, we compared the location and severity of index and subsequent hamstring muscle injuries in professional men’s rugby union. Twenty-two index HMIs with related subsequent injury within twelve months were included. Almost two-thirds of subsequent HMIs did not occur at the same location as the index injury. Most subsequent HMIs occurred in the same area (proximal/central/distal) of the muscle as the related index injury. Fifty-five per cent of subsequent injuries required a longer TTRFT than their associated index injury, albeit the differences were small (average difference = 2 days). Chapter 6 presents a retrospective case series of eight male professional rugby athletes following surgical repair of the IMT of the hamstring repair. Surgical repair required prolonged TTRFT compared to what may be expected from non-surgical management. However, we found that it is possible to return to previous levels of hamstring strength and maximal speed following surgery. It is anticipated that our findings can advance the management of HMI in rugby, influencing practice and future research.