Success and Failure of Percutaneous Minimally Invasive Direct Pars Repair: Analysis of Fracture Morphology.

BACKGROUND

Spondylolysis is a defect in the pars interarticularis that typically presents with axial back pain. Recently, minimally invasive spine techniques have increased in popularity and have been applied to the Buck technique of direct pars repair.

CASE DESCRIPTION: In our series, 2 patients underwent minimally invasive direct pars repair by the percutaneous insertion of a cannulated lag screw across the pars defect with compression against the lamina. The defect was then decorticated and packed with bone grafting material through a tubular retractor. The clinical records, including preoperative imaging characteristics and intraoperative variables, were collected. The first patient was a 22-year-old woman with bilateral pars defects, and the second was a 21-year-old woman with a left-sided pars defect. They underwent minimally invasive direct pars repair without complications and were discharged home within 24-48 hours. In the first patient, the fusion was successful; however, the second experienced screw back out and required subsequent revision. The follow-up period was 25 months for patient 1 and 21 months for patient 2. The fracture morphology differed. The successfully repaired fractures were linear with smooth cortical edges and oriented perpendicular to the screw trajectory. The failed repair involved a unilateral, curved defect with comminuted cortical edges.

CONCLUSION

Minimally invasive direct pars repair can be performed safely and effectively with shortened hospital stays and reduced morbidity. Fracture morphology and orientation could be important predictors of the success of surgery.