Abstract
We describe the clinical results of a technique of direct pars repair stabilised with a construct that consists of a pair of pedicle screws connected with a modular link that passes beneath the spinous process. Tightening the link to the screws compresses the bone grafted pars defect providing rigid intrasegmental fixation.
20 patients aged between 9 and 21 years were included in this prospective study. Each of the patients had high activity levels and suffered from significant back pain without radicular symptoms or signs. Patients had either no or grade I spondylolisthesis. Definitive pseudoarthrosis and fracture were confirmed via computerize tomography (CT). Magnetic resonance imaging was performed in every patient to assess the adjacent disc spaces which demonstrated normal signal intensity.
A midline incision was used for surgery. The pars interarticularis defect was exposed and filled with autologous iliac crest bone graft prior to screw insertion. After screw insertion, a link was contoured to fit, and placed just caudal to the spinous process, deep to the interspinous ligament of the affected level, and attached to each pedicle screw. There was early mobilization post-operatively without a brace. The average inpatient stay was 3 days. Post-operative complications included 1 superficial wound haematoma and two superficial wound infections which responded to antibiotic treatment. Follow-up was at 6 weeks, 6 months and at 18 months, and 24 months. Clinical assessments for all patients was via the Oswestry disability index (ODI) and visual analogue scores (VAS). At the latest follow-up, 18 out of the 20 patients showed a significant (p<0.05) improvement in their ODI and VAS scores. The mean post-operative ODI score was 8%. All patients had radiographs and CT scans which showed fusion rates of 80% in those patients followed up for a minimum of 24 months. This new technique for direct pars repair demonstrates high fusion rates in addition provides the possible benefits of maintaining adjacent level motion. Clinically this group had good-to excellent functional outcomes as indicated by visual analogue scales and the Oswestry Disability Index in 18 out of 20 patients studied with a minimum follow-up of 2 years.
