Pseudarthrosis in Long Adult Spinal Deformity Instrumentation and Fusions: Risk factor and Clinical Outcome Analysis of 228 cases

Information provided by

Keith Bridwell, MD

Orthopaedic Surgeon

Washington University School of Medicine

Lawrence G. Lenke, MD

The Jerome J. Gilden Professor of Orthopedic Surgery

Co-Chief Pediatric & Adult Spinal, Scoliosis & Reconstructive Surgery

Purpose: To analyze the incidence of and risk factors for pseudarthrosis in adult long spinal deformity instrumentation and fusions.

Methods: A clinical and radiographic assessment of 228 adult spinal deformity patients (average age 40.8 years, range 18.1- 77.3 years, 142 primary/86 revision cases, 39 male/189 female) who were surgically treated at a single institution between 1985 and 2002 was performed. All patients underwent long (greater than or equal to 4 vertebrae) spinal instrumentation and fusion with a minimum 2-year follow up (average 5.0 years; 2-16.8 years) were analyzed.

Results: 35 patients had pseudarthroses (15%, average age 47.4 years). 22 patients (63%) demonstrated nonunion (NU) between T10 and L2 and 9 patients (26%) between L4 and S1.

19 patients (54%) presented with multiple levels involved (2-6). Pseudarthrosis was most commonly detected at three years postop (27 patients; 70%) but was detected after 5 years in three patients (9%). Patient age at surgery significantly correlated with the nonunion (NU) rate (16NU/48 patients greater than or equal to 55 years, 19NU/180 patients between 18 and 55 years) (P<0 .0001). The number of fused vertebrae was also significantly related with pseudarthrosis (23NU/107 patients more than 12 vs 12NU/121 or less fused) (P="0.020)." Smoking history did not increase the nonunion rate (7NU/27 smokers 28NU/201 nonsmokers) Pseudarthrosis preoperative comorbidity (16NU/ 81 19NU/ 146 patients) Revision surgery (15NU/82 revisions 20/146 primaries, p="1.000)." Performance osteotomies (12/78 23/150 no osteotomy, Any posterior decompression (previous present) demonstrated a higher (10NU/27 decompression, P="0.003)." Nonunion (NU) incidence according to lowest instrumented vertebra significant in those S1 (18NU/78 patients, 23%) and L5 above (17NU/150 11%) Coronal deformity large major Cobb angle (greater equal 70º; 5NU/28 thoracic kyphosis (T5T12>40°; 4NU/ 56 patients) did not demonstrate a higher nonunion rate (P=0.779 and 0.73 respectively). Thoracolumbar kyphosis (T10-L2 greater than or equal to 20º; 13NU/26 patients) demonstrated a significantly higher nonunion rates (P<0 .0001). Preoperative global positive sagittal (greater than or equal to 5cm) and coronal imbalance (>2cm) did not increase the nonunion rate (P=0.345 and 0.450 respectively). Patients with pseudarthrosis had lower total SRS 24 outcome score (average 81) than those without (average 91) (p=0.028).

Conclusion: The overall incidence of pseudarthrosis following adult long spinal followed by deformity fusions was 15%. The thoracolumbar spine was the most common area, followed by the L4-sacrum region. The higher number of fused vertebrae, fusion to the sacrum, older age, thoracolumbar kyphosis, and posterior decompression procedures significantly increased the risks of pseudarthrosis to a statistically significant extent. SRS-24 outcomes scores were significantly lowered with pseudarthrosis.