Minimally invasive direct pars repair with cannulated screws and recombinant human bone morphogenetic protein: case series and review of the literature.

OBJECTIVE The objective of this study was to describe the use of a minimally invasive surgical treatment of lumbar spondylolysis in athletes by a fluoroscopically guided direct pars screw placement with recombinant human bone morphogenetic protein-2 (rhBMP-2) and to report on clinical and radiographic outcomes. METHODS A retrospective review was conducted of all patients treated surgically for lumbar spondylolysis via a minimally invasive direct pars repair with cannulated screws. Demographic information, clinical features of presentation, perioperative and intraoperative radiographic imaging, and postoperative data were collected. A 1-cm midline incision was performed for the placement of bilateral pars screws utilizing biplanar fluoroscopy, followed by placement of a fully threaded 4.0-mm-diameter titanium cannulated screw. A tubular table-mounted retractor was utilized for direct pars fracture visualization and debridement through a separate incision. The now-visualized pars fracture could then be decorticated, with care taken not to damage the titanium screw when using a high-speed drill. Local bone obtained from the curettage was then placed in the defect with 1.05 mg rhBMP-2 divided equally between the bilateral pars defects. RESULTS Nine patients were identified (mean age 17.7 ± 3.42 years, range 14-25 years; 6 male and 3 female). All patients had bilateral pars fractures of L-4 (n = 4) or L-5 (n = 5). The mean duration of preoperative symptoms was 17.22 ± 13.2 months (range 9-48 months). The mean operative duration was 189 ± 29 minutes (range 151-228 minutes). The mean intraoperative blood loss was 17.5 ± 10 ml (range 10-30 ml). Radiographic follow-up was available in all cases; the mean length of time from surgery to the most recent imaging study was 30.8 ± 23.3 months (range 3-59 months). The mean hospital length of stay was 1.13 ± 0.35 days (range 1-2 days). There were no intraoperative complications. CONCLUSIONS Lumbar spondylolysis treatment with a minimally invasive direct pars repair is a safe and technically feasible option that minimizes muscle and soft-tissue dissection, which may particularly benefit adolescent patients with a desire to return to a high level of physical activity.