Pars interarticularis stress lesions in the lumbar spine of cricket fast bowlers

Purpose: This prospective magnetic resonance (MR) imaging study investigated the development of symptomatic pars lesions in the lumbar spine of adolescent cricket fast bowlers. Methods: Annual MR examinations of the lumbar spine in male fast bowlers (N = 51) and swimmers (N = 20) without a prestudy history of symptomatic back injury were conducted to identify stress-induced pars injuries over 4 and 2 yr periods, respectively. Results: Symptomatic L4 and L5 pars lesions developed in 11 of 51 and 1 of 51 of the bowlers, respectively. Preexisting L5 lesions were observed in both bowlers (10 of 51) and swimmers (4 of 20). No significant difference existed between the proportion of bowlers and swimmers with preexisting L5 lesions (P = 1.00, Fisher's exact test). In contrast, bowlers had a significantly greater proportion of L4 pars lesions compared with swimmers, with 22% of the bowlers developing L4 injuries during the study, whereas there were no L4 lesions in the swimmers (P = 0.027, Fisher's exact test). The symptomatic L4 lesions in the bowlers developed between 15 and 17 yr of age, and all were unilateral lesions lateralized to the nonbowling-arm side. The MR characteristics of the L4 pars lesions were consistent with a stress fracture through the cortical bone. Of the acquired L4 lesions in the bowlers, 4 of 11 and 7 of 11 developed in individuals with and without preexisting L5 defects, respectively. No significant association existed between the acquired L4 pars lesions and preexisting L5 defects in the bowlers (P = 0.216, Fisher's exact test). Conclusion: Fast bowling was directly associated with the development of symptomatic pars lesions of the lumbar spine, particularly unilateral L4 stress lesions, in a significant proportion of the adolescent bowlers examined in this prospective MR study.