Risk factors for and assessment of symptomatic pseudarthrosis after lumbar pedicle subtraction osteotomy in adult spinal deformity.

STUDY DESIGN: Retrospective review of prospectively collected data. OBJECTIVE: To assess the prevalence, risk factors, and clinical outcomes for pseudarthrosis after a lumbar pedicle subtraction osteotomy (PSO). SUMMARY OF BACKGROUND DATA: There exists no large series that examines pseudarthrosis rates of PSOs. METHODS: Data of 171 consecutive patients with adult deformity who underwent a lumbar PSO by 2 surgeons at a single institution with a minimum 2-year follow-up were analyzed. Pseudarthrosis diagnosed through sagittal malalignment and instrumentation failure noted on radiograph was confirmed intraoperatively. RESULTS: Eighteen (10.5%) of 171 patients developed pseudarthrosis after a PSO. Eleven of the 18 patients (6.4% of all patients, 61.1% of the 18 patients with pseudarthrosis) had pseudarthrosis at the PSO site, L3 being the most common; other locations included the lumbosacral junction (4/18), thoracolumbar junction (2/18), and upper thoracic spine (1/18). Preoperative pseudarthrosis level was a predictor of the postoperative level of pseudarthrosis (93%). Fifteen of the 18 patients (83%) had no interbody fusion directly above or below the PSO site, 16 (88%) had a history of pseudarthrosis at the time of PSO surgery and 2 of 3 patients who had prior radiation to the lumbar region developed pseudarthrosis. Most pseudarthroses occurred within the first 2 years (n = 13/18), between 2 and 5 years (n = 3/18), and more than 5 years (n = 2/18) postoperatively. Prior pseudarthrosis (P < 0.0001), pseudarthrosis at the PSO site (P < 0.0001), prior decompression in the lumbar region (P = 0.0037), prior radiation to the lumbar region (P < 0.0001), and presence of inflammatory/neurological disorders (P < 0.0036) were identified as risk factors. All 18 patients with pseudarthroses required revision surgery (posterior-only surgery, n = 12; anteroposterior surgery, n = 6) due to loss of sagittal alignment and pain. The mean pre-revision Scoliosis Research Society score was 85, post-revision score was 95 (P = 0.0166), and the mean pre-revision Oswestry Disability Index score was 42.5, post-revision score was 34.5 (P = 0.0203). CONCLUSION: The overall prevalence of pseudarthrosis was 10.5% of which 61% occurred at the actual PSO site and Scoliosis Research Society and Oswestry Disability Index scores improved significantly after pseudarthrosis repair. LEVEL OF EVIDENCE: 4.

RhBMP-2 is superior to iliac crest bone graft for long fusions to the sacrum in adult spinal deformity: 4- to 14-year follow-up.

STUDY DESIGN: Matched cohort comparison. OBJECTIVE: To compare the use of bone morphogenetic protein (BMP) or iliac crest bone graft (ICBG) on the long-term outcomes in patients undergoing long fusions to the sacrum for adult spinal deformity. SUMMARY OF BACKGROUND DATA: No long-term studies beyond a 2-year follow-up have been performed comparing the use of BMP versus ICBG for fusion rates in long fusions to the sacrum in adult spinal deformity. METHODS: A total of 63 consecutive patients, from 1997-2006, comprised of 31 patients in the BMP group and 32 patients in the ICBG group, operated on at a single institution with a minimum 4-year follow-up (4-14 yr) were analyzed. Inclusion criteria were ambulators who were candidates for long fusions (thoracic as the upper level) to the sacrum. Exclusion criteria were revisions, neuromuscular scoliosis, ankylosing spondylitis, and patients who had both BMP and ICBG used for fusion. Oswestry Disability Index and 3 domains of the Scoliosis Research Society score were used to assess outcomes. RESULTS: The 2 groups were similar with respect to age, sex, smoking history, comorbidities, BMI, number of fusion levels and Cobb angles. Eight patients in the BMP group underwent a posterior only, whereas 23 underwent combined anterior and posterior (A/P) surgery. All 32 patients in the ICBG had A/P fusion. The average BMP level was 11.1 mg (3-36 mg). The rate pseudarthrosis was 6.4% (2/31) in the BMP and 28.1% (9/32) in the ICBG group (P = 0.04) using Fisher exact test and odds ratio = 5.67. The fusion rates for BMP group were 93.5% and 71.9% for the ICBG group. Oswestry Disability Indexes were similar between groups. However, the BMP group demonstrated superior sum composite Scoliosis Research Society scores in pain, self-image and function domains (P = 0.02). CONCLUSION: BMP is superior to ICBG in achieving fusion in long constructs in adult deformity surgery. The rate of pseudarthrosis was significantly higher in the ICBG group than BMP group. The concentration and dosage of recombinant human bone morphogenetic protein 2 (rhBMP-2) used seems to have an effect on the rate of fusion and pseudarthrosis rate because no patient receiving more than 5 mg per level had apparent or detected pseudarthroses (n = 20/20). LEVEL OF EVIDENCE: 3.