Direct repair for treatment of symptomatic spondylolysis and low-grade isthmic spondylolisthesis in young patients: no benefit in comparison to segmental fusion after a mean follow-up of 14.8 years

The aim of the present study was to assess the long-term clinical, functional, and radiographic outcome of direct repair of spondylolysis using cerclage wire fixation according to Scott in young patients with symptomatic spondylolysis or low-grade isthmic spondylolisthesis as compared to the outcome after uninstrumented posterolateral in situ fusion. Twenty-five out of 28 patients of the direct repair group (89%) and 23 out of 28 of the fusion group (82%) were available for follow-up examination. The assessment by independent observers included a structured interview (Oswestry questionnaire [ODI], visual analogue scale, SRS questionnaire), a clinical examination, functional testing, plain radiography, and MRI. The groups were comparable as to the mean age at operation (18.2 vs. 16.2 years.), the follow-up time (14.8 vs. 15.0 years), and the amount of preoperative slip (7.2 vs. 13.1%). The mean ODI and SRS total scores were significantly better in the fusion group (4.3 [0–16] and 96 [57–117]) as compared to the direct repair group (11.4[0–52] and 87[53–107]; P=0.02 and P=0.011, respectively). In functional testing, both groups reached normal values for abdominal and back muscle strength. The lumbar spine flexion and extension ROM was decreased in both groups showing no statistical difference between the groups. Significant progressive narrowing of the olisthetic disc was detected on the plain radiographs after direct repair. On the flexion-extension radiographs, in the direct repair group, the mobility in the lytic/olisthetic segment was decreased in comparison to normal values from the literature. The mobility at the level above the operated segment was decreased in the direct repair group as compared to the fusion group (P=0.057). On T2-weighted MR images in the direct repair group, the signal intensity of the disc below the affected vertebra was decreased in 17/23 (74%) patients. There was no difference between the groups in the nucleus signal intensity of the adjacent disc above the operated segment. No association between the disc degeneration on MRI and the outcome of the patients could be established. In the direct repair group the following complications were seen: transient nerve root irritation (2), superficial infection (1), UTI (1); in the fusion group the complications were: subcutaneous seroma (2) and UTI (1). There were six re-operations, cerclage removal(4), conversion into segmental fusion(2) in the direct repair group, and one re-operation, instrumented respondylodesis, in the fusion group. In conclusion, the results of direct repair of the spondylolysis using cerclage wire fixation according to Scott were very satisfactory in 76% of the patients after a mean follow-up of 14.8 years. After direct repair, the ODI deteriorated with time leading to a clinically moderate but statistically significant difference in favour of segmental fusion. Lumbar spine mobility was decreased after direct repair. Secondary segmental instability above the spinal fusion was not detected. The procedure does not seem to be capable of preventing the olisthetic disc from degeneration. The theoretical benefits of direct repair could not be proven.