Low profile pelvic fixation with the sacral alar iliac technique in the pediatric population improves results at two-year minimum follow-up

Abstract

Study design: Retrospective review.

Objective: Anchor stability and prominence are problems with pelvic fixation in pediatric spinal deformity surgery. We compared the new sacral alar iliac (SAI) fixation technique (with a starting point in the sacral ala and in-line anchors deep under the midline muscle flap) with other methods of screw fixation.

Summary of background data: Iliac anchors have been shown to provide the best form of pelvic fixation. A trajectory from the posterior sacral surface to the iliac wings has recently been described. To our knowledge, no clinical series has compared this method of pelvic fixation in children to others.

Methods: Of 32 consecutive pediatric patients who underwent SAI fixation, 2 died and 26 returned for follow-up (>2 years). Mean age at surgery was 14 years. Average screw size was 67 mm long and 7 to 9 mm in diameter. Clinical examinations, radiographs, and computed tomography scans were analyzed. Outcomes included pain over the implants, screw placement, implant prominence, radiographic lucency, need for revision, and infection. SAI patients were compared with 27 previous patients who had pelvic fixation via other screw techniques.

Results: For SAI fixation, correction of pelvic obliquity and Cobb angles were 20° ± 11° (70%) and 42° ± 25° (67%), respectively. For other pelvic fixation methods, those values were 10° ± 9° (50%), and 46° ± 16° (60%), respectively. Compared with other screws, SAI screws provided significantly better pelvic obliquity correction (P = 0.002) but no difference in Cobb correction. There were 2 lucencies adjacent to screws in both groups. Computed tomography scans of 18 SAI patients showed no intrapelvic protrusion, but 1 screw extended laterally (<5 mm). One early SAI patient required revision with larger screws, which relieved pain; there was 1 revision in the comparison group. SAI patients had no deep infections, implant prominence, late skin breakdown, or anchor migration; traditional patients had 3 deep infections (P = 0.09) and 3 instances of implant prominence, skin breakdown, or anchor migration.

Conclusion: SAI pelvic fixation produces better correction of pelvic obliquity than do previous techniques. Radiographic and clinical anchor stability is satisfactory at 2-year follow-up.