Introduction: Anchor stability and prominence are problems with pelvic fixation in pediatric spinal deformity surgery. A new method of iliac fixation with a starting point in the S2 ala offers in‐line anchors that are deep under the midline muscle flap. We report the clinical results of this technique.
Methods: 32 consecutive patients with the S2AI technique and >2y follow‐up were studied. Diagnoses were 23 cerebral palsy, 2 myelomeningocele, and 7 syndromic. Fusion was 15.8 levels (SD 2.7, R 12–18). Clinical examinations, radiographs and CT scans were analyzed. Outcomes included sacropelvic pain, screw placement, implant prominence, radiographic lucency, need for revision and infection. S2AI patients were compared with 17 prior patients who had pelvic fixation using traditional sacral and iliac screws.
Results: Mean age at surgery was 14.3 y (SD 2.3, R 9.8–19.3). S2AI screws were 67 mm (R 45–85) in length and 7–9 mm in width (Fig 1). Pelvic obliquity was corrected 21.1 ±2.3° (74%) using the S2AI technique and 11.4±2.5° (52.9%) using traditional iliac screws. Cobb angle correction was 48.7±4.5° (73%) using the S2AI technique and 51.1±3.1° (63%) using traditional iliac screws. S2AI fixation had better pelvic obliquity correction (p=0.01) but there was no difference in Cobb correction. Three of 64 screws showed adjacent lucencies of 1.3 mm (R 1.0–2.0). CT scans of 23 patients showed no intrapelvic protrusion, but three screws protruded laterally (all <5mm). One early patient required revision to bilaterally longer iliac screws to relieve pain. There were 2 superficial infections in the S2AI group and 1 deep infection in the traditional group. No S2AI patient had implant prominence, skin breakdown or anchor migration versus 3 in the traditional group.
Conclusion: S2AI pelvic fixation produces satisfactory results with improved correction of pelvic obliquity and fewer clinical complications than prior techniques. Radiographic and clinical anchor stability is satisfactory at two year follow‐up.