Clinical outcome of symptomatic unilateral stress injuries of the lumbar pars interarticularis.

STUDY DESIGN: A prospective case-series study.

OBJECTIVE: To evaluate the results of nonoperative and operative treatment of symptomatic unilateral lumbar pars stress injuries or spondylolysis.

SUMMARY OF BACKGROUND DATA: Most patients become asymptomatic following nonoperative treatment for unilateral lumbar pars stress injuries or spondylolysis. Surgery, however, is indicated when symptoms persist beyond a reasonable time affecting the quality of life in young patients, particularly the athletic population.

METHODS: We treated 42 patients (31 male, 11 female) with unilateral lumbar pars stress injuries or spondylolysis. Thirty-two patients were actively involved in sports at various levels. Patients with a positive stress reaction on single photon emission computerized tomography imaging underwent a strict protocol of activity restriction, bracing, and physical therapy for 6 months. At the end of 6 months, patients who remained symptomatic underwent a computed tomography (CT) scan to confirm the persistence of a spondylolysis. Eight patients subsequently underwent a direct repair of the defect using the modified Buck's Technique. Baseline Oswestry Disability Index (ODI) and Short-Form-36 (SF-36) scores were compared with 2-year ODI and SF-36 scores for all patients.

RESULTS: Eight of nine fast bowlers in cricket were right-handed. The spondylolytic defect appeared on the left side of their lumbar spine. In the nonoperated group, the mean pretreatment ODI was 36 (SD = 10.5), improving to 6.2 (SD = 8.2) at 2 years. In SF-36 scores, the mean score for physical component of health (PCS) improved from 30.7 (SD = 3.2) to 53.5 (SD = 6.5) (P < 0.001), and the mean score for the mental component of health (MCS) improved from 39 (SD = 4.1) and 56.5 (SD = 3.9) (P < 0.001) at 2 years. Twenty of 32 patients resumed their sporting career within 6 months of onset of treatment, and a further 4 of 32 patients returned to sports within 1 year. The 8 patients who remained symptomatic at 6 months underwent a unilateral modified Buck's repair. The most common level of repair was L5 (n = 5). One patient with spina bifida and a right-sided L5 pars defect remained symptomatic following direct repair. The mean preoperative ODI was 39.4 (SD = 3.6), improving to 6.4 (SD = 5.2) at the latest follow-up. The mean score of PCS (SF-36) improved from 29.6 (SD = 4.4) to 49.2 (SD = 6.2) (P < 0.001), and the mean score of MCS (SF-36) improved from 38.7 (SD = 1.9) to 54.5 (SD = 6.4) (P < 0.001).

CONCLUSIONS: The increased incidence of the unilateral lumbar pars stress injuries or frank defect on the contralateral side in a throwing sports, e.g., cricket (fast bowling), may be related to the hand dominance of the individual. Nonoperative treatment for patients with a unilateral lumbar pars stress injuries or spondylolysis resulted in a high rate of success, with 81% (34/42) of patients avoiding surgery. If symptoms persist beyond a reasonable period, i.e., 6 months, and reverse gantry CT scan confirms a nonhealing defect of the pars interarticularis, one may consider a unilateral direct repair of the defect with good functional outcome. Direct repair in patients with spina bifida at the same lumbar level as the unilateral defect may be complicated by nonunion.