Outcomes of Lumbopelvic Fixation for the Treatment of Adult Deformity with Modified Iliac Screw Starting Point: Single Institution Experience

Presented at SMISS Annual Forum 2016
By Kunwar Khalsa MD
With Ehsan Jazani MD, Kelley Banagan MD, Tristan Weir BS, Eugene Koh MD, PhD, Daniel Gelb MD, Steven Ludwig MD,

Disclosures: Kunwar Khalsa MD None Ehsan Jazani MD None, Kelley Banagan MD None, Tristan Weir BS None, Eugene Koh MD, PhD B; Biomet: Paid Consultant., Daniel Gelb MD A; AOSpine North America: faculty at courses. D; Advanced Spinal Intellectual Property(ASIP). F; Depuy-Synthes Spine: IP royalties, paid presenter or speak, Globus Medical: IP Royalties., Steven Ludwig MD A; AO Spine North America Spine Fellowship Support: Research Support, PCORI Grant: Submitted, Cervical Spine Research Society: Board or committee member, Journal of Spinal Disorders and Techniques, Th,

Introduction

Lumbopelvic fixation has been an important advancement in adult deformity correction. However, Iliac screws are not without complications. Previous authors have found a high rate of late pain, screw prominence, infection and instrumentation failure. Our institution utilizes modified iliac screw starting point, placing the iliac screw head in line with S1 pedicle screw but avoiding sacroiliac joint penetration. 

Aims/Objectives

We hypothesize this technique is associated with a decreased rate of elective screw removal secondary to prominence, a reduced rate of infection and instrumentation failure. 

Methods

IRB approved retrospective review of patients treated between 2006-2015 revealed 57 patients undergoing lumbopelvic fixation with a modified iliac screw starting site, for treatment of adult deformity secondary to degenerative scoliosis, posttraumatic kyphoscoliosis, and flat back syndrome. Patients were contacted via telephone to ensure there is no loss to follow-up with respect to elective removal of hardware or revision surgery at outside institutions. Primary outcome measure: rate of elective removal of Iliac screws. Secondary outcomes: 1) infection rate, 2) instrumentation failure rate (breakage of rods/pelvic screws/pedicle screws), 3) rate of revision surgery for Pseudoarthrosis/instrumentation failure. 

Results

The average follow-up was 22 months. The rate of elective removal of Iliac screws was 3.5%(n-2). Overall the rate of infection was 15.7% (early 3.5%, late 12.2%). The rate of radiographic instrumentation failure was 35%(n-20), but rate of revision surgery for pseudoarthrosis/instrumentation failure was only 5.2% (3 out of 57 patients). 15 out of 20 patients had instrumentation failure below L5 pedicle screw, 3 had both above and below, and 2 had failure above the L5 pedicle screw. Average time of diagnosis of broken instrumentation was 16 months. Rate of revision surgery for proximal junctional failure/kyphosis was 3.5%(2 out of 57 patients). The rate of revision surgery for proximal junctional failure/kyphosis was 3.5% (2 out of 57 patients) but was unrelated to sagittal balance obtained at surgery. 

Conclusions

A modified iliac screw starting point demonstrated a low rate of elective screw removal, possibly due to decreased prominence. Radiographic instrumentation failure was high but did not necessarily require surgical revision as many patients were minimally symptomatic. Additionally, the average time to instrumentation failure was 16 months, indicating patients with adult deformity reconstruction should be followed past the 1-year benchmark.