[MINIMALLY INVASIVE SURGERY FOR DIRECT REPAIR OF LUMBAR SPONDYLOLYSIS BY UTILIZING INTRAOPERATIVE NAVIGATION AND MICROENDOSCOPIC TECHNIQUES].

OBJECTIVE: To analyze the effectiveness of direct screw repair for lumbar spondylolysis by using intraoperative O-arm based navigation and microendoscopic techniques.

METHODS: Between February 2012 and May 2014, 11 consecutive patients with lumbar spondylolysis were treated with Buck's procedure by the aid of intraoperative O-arm based navigation and minimally invasive approach. The debridement and autograft of pars interarticularis defects was performed under microendoscopy. There were 7 males and 4 females, with an average age of 28.4 years (range, 19 - 47 years) and an average disease duration of 10.5 months (range, 8-23 months); no nerve symptoms or signs of lower limb was observed. The radiological examinations showed single level bilateral lumbar spondylolysis without obvious disc degeneration, lumbar instability, or spondylolisthesis. Isthmic injury located at L4 in 2 cases and at L5 in 9 cases. Of 11 patients, 7 were rated as grade 2 disc degeneration, and 4 as grade 3 disc degeneration according to the modified Pfirrmann classification system. The operation time, intraoperative blood loss, and complications were recorded. The fluoroscopic examinations were performed to assess defect repair and screw position. Visual analogue scale (VAS) score was used to evaluate the improvement of low back pain.

RESULTS: The average operation time was 147.6 minutes (range, 126-183 minutes). The average blood loss was 54.9 mL (range, 40-85 mL). Primary healing of incision was obtained. There was no complication of nerve root injury, dural tear, or infection. Three patients had pain at donor site postoperatively, and pain disappeared within 3 weeks. The average follow-up duration was 15.7 months (range, 10-23 months). VAS score of low back pain was significantly decreased from preoperative 7.1 ± 2.3 to 1.8 ± 0.4 at last follow-up (t = 13.42, P = 0.01). Of 22 isthmic bone grafting, bilateral isthmic bony fusion was achieved in 7 patients and unilateral isthmic bony fusion in 3 patients at 6-10 months (mean, 7.9 months). One patient failed bilateral isthmic bony fusion, and had bony resorption.

CONCLUSION: Debridement, autograft, and percutaneous intralaminar screw fixation by microendoscopy and O-arm based navigation may provide safe and effective treatment for spondylolysis. Minimally invasive direct repair can obtain satisfactory effectiveness.