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

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.