Pseudarthrosis in adult spinal deformity following multisegmental instrumentation and arthrodesis.

BACKGROUND: There have been few detailed reports concerning pseudarthrosis following spinal instrumentation and arthrodesis in adults with spinal deformity since the introduction of modern segmental fixation techniques. The purposes of this study were to analyze the prevalence, risk factors, and outcome scores on the Scoliosis Research Society Instrument-24 associated with pseudarthrosis following instrumentation and arthrodesis for the treatment of spinal deformity in adults. METHODS: A clinical and radiographic assessment of 232 adults with spinal deformity who were treated surgically at a single institution was conducted. The average age of the patients was 40.8 years, and the operation was a primary procedure in 150 patients and a revision procedure in eighty-two patients. All patients who underwent a long (four vertebrae or more) spinal instrumentation and arthrodesis with a minimum follow-up of two years were included in the analysis. Clinical outcomes were assessed with the Scoliosis Research Society questionnaire. RESULTS: Forty patients had a pseudarthrosis. Factors that were found to be significantly associated with pseudarthrosis were preoperative thoracolumbar kyphosis of >20 degrees (p < 0.0001), an age of more than fifty-five years (p = 0.001), arthrodesis to S1 compared with arthrodesis to L5 or a cephalad level (p = 0.002), and arthrodesis of more than twelve vertebrae (p = 0.037). Patients with a pseudarthrosis had lower total outcome scores on the Scoliosis Research Society questionnaire, on the average, than those without a pseudarthrosis (p = 0.001). CONCLUSIONS: The prevalence of pseudarthrosis following long arthrodesis with use of modern segmental spinal instrumentation for the treatment of spinal deformity in adults was 17%, and the clinical outcome in these patients can be negatively affected by the pseudarthrosis.

Biomechanical evaluation of segmental occipitoatlantoaxial stabilization techniques.

STUDY DESIGN: Biomechanical study using human cadaveric cervical spines. OBJECTIVE: To evaluate the construct stability of 3 different segmental occipitoatlantoaxial (C0-C1-C2) stabilization techniques. SUMMARY OF BACKGROUND DATA: Different C0-C1-C2 stabilization techniques are used for unstable conditions in the upper cervical spine, all with different degrees of risk to the vertebral artery. Techniques with similar stability but less risk to the vertebral artery may be advantageous. METHODS: Six human cadaveric cervical spines (C0-C5) (age: 74 +/- 5.0 years) were used. After testing the intact spines, instability was created by transecting the transverse and alar ligaments. The spines were instrumented from the occiput to C2 using 3 different techniques which varied in their attachment to C2. All spines had 6 screws placed into the occiput along with lateral mass screws at C1. The 3 variations used in attachment to C2 were (1) C2 crossing laminar screws, (2) C2 pedicle screws, and (3) C1-C2 transarticular screws. The C1 lateral mass screws were removed before placement of the C1-C2 transarticular screws. Range of motion across C0-C2 was measured for each construct. The data were analyzed using repeated measures ANOVA. The following post hoc comparisons were made: (1) intact spine versus each of the 3 techniques, (2) laminar screw technique versus the pedicle screw technique, and (3) laminar screw technique versus the transarticular screw technique. The level of significance was alpha = 0.01 (after Bonferroni correction for 5 comparisons). RESULTS: All 3 stabilization techniques significantly decreased range of motion across C0-C2 compared to the intact spine (P < 0.01). There was no statistical difference among the 3 stabilization methods in flexion/extension and axial rotation. In lateral bending, the technique using C2 crossing laminar screws demonstrated a trend toward increased range of motion compared to the other 2 techniques. CT scans in both axial and sagittal views demonstrated greater proximity to the vertebral artery in the pedicle and transarticular screw techniques compared to the crossing laminar screw technique. CONCLUSION: Occipitoatlantoaxial stabilization techniques using C2 crossing laminar screws, C2 pedicles screws, and C1-C2 transarticular screws offer similar biomechanical stability. Using the C2 crossing laminar screw technique may offer an advantage over the other techniques due to the reduction of the risk to the vertebral artery during C2 screw placement.

Orthopaedic complications of myotubular myopathy.

Myotubular myopathy is a rare genetic disease that was uniformly fatal until recent developments in long-term ventilation. Today, however, it is not unusual for a patient to live into the second decade. The orthopaedic manifestations of the disease have not been reported in the literature. We present our experience with complications related to the spine and extremities in a series of 4 patients with this disease who have survived beyond early childhood.

Pseudarthrosis in primary fusions for adult idiopathic scoliosis: incidence, risk factors, and outcome analysis.

STUDY DESIGN: A retrospective study. OBJECTIVE: To analyze the incidence, characteristics, risk factors, and Scoliosis Research Society Instrument-24 (SRS-24) outcome scores of pseudarthrosis in adult idiopathic scoliosis primary fusions. SUMMARY OF BACKGROUND DATA: The healing of spinal fusion is complex and difficult to study in a clinical setting. There are no detailed reports on pseudarthrosis in primary fusion for adult idiopathic scoliosis since the introduction of "modern" segmental fixation techniques. METHODS: A retrospective chart and radiographic review of 96 patients (average age 42.2 years; range 18.2-62.9 years) with adult idiopathic scoliosis undergoing first time (primary) spinal instrumentation and fusion with a minimum 2-year follow-up (average 5.9 years; range 2-16.8 years) treated at a single institution between 1985 and 2001 were analyzed. RESULTS: Sixteen patients had pseudarthroses (17%). Fifty-nine percent of the pseudarthroses occurred between T9 and L1, and 81% presented with multiple levels involved (2-6 levels). The site of crosslinks or dominoes correlated with pseudarthrosis site in 69%. Pseudarthroses were detected radiologically at 32.4 months (range 12-67 months) postoperatively. Patient age at surgery more than 55 years significantly correlated with pseudarthrosis (P = 0.007). The number of fused levels more than 12 vertebrae is also significantly correlated with pseudarthrosis (P = 0.03). Smoking history and comorbidity did not increase the pseudarthrosis rate (P = 0.71 and 0.19, respectively). A larger preoperative Cobb angle (> or =70 degrees) and a greater thoracic kyphosis (T5-T12 >40 degrees) did not correlate with a higher pseudarthrosis rate (P = 0.76 and 0.73, respectively). Thoracolumbar kyphosis (T10-L2 > or =20 degrees) correlated with a significantly higher pseudarthrosis rate (P < 0.0001). Preoperative global sagittal and coronal imbalance did not increase the pseudarthrosis rate (P = 0.45 and 0.62, respectively). Patients with pseudarthrosis had lower SRS-24 scores than those without (P = 0.01). CONCLUSION.: The incidence of pseudarthrosis following adult idiopathic scoliosis primary fusion was 17%. The pseudarthrosis was most likely to occur at the thoracolumbar junction. Older patients (>55 years), longer fusion (>12 vertebrae), and those with thoracolumbar kyphosis (> or =20 degrees) demonstrated increased risk for pseudarthrosis. Patients' outcomes as measured by the SRS-24 were "negatively" affected by the pseudarthrosis.

Long adult deformity fusions to L5 and the sacrum. A matched cohort analysis.

STUDY DESIGN: A matched cohort analysis of long adult deformity fusions according to distal fusion level (L5 vs. S1). OBJECTIVE.: To compare the results of long adult deformity fusions to either L5 or the sacrum in the presence of a "healthy" 5-1 disc using a matched cohort analysis. SUMMARY OF BACKGROUND DATA: For adult spinal deformity, the decision often arises whether to terminate a long fusion at L5 or the sacrum. The decision is especially challenging in the presence of a "healthy" (Grade 0 to 1 degeneration) 5-1 disc. MATERIALS AND METHODS: A total of 95 adult deformity patients that underwent fusion from the thoracic spine to either L5 or the sacrum were sorted according to five preoperative criteria: 5-1 disc status, patient age, smoking status, number of levels fused, and sagittal balance. Two cohorts (L5, 27 patients; sacrum, 12 patients) were precisely matched according to the five criteria. Patients were evaluated at 2-year minimum follow-up according to radiographic data, complications, and SRS-24 outcomes. RESULTS: Correction of sagittal imbalance was superior for sacrum patients (C7 plumb line: L5, 0.9 cm; sacrum, 3.2 cm; P = 0.03). At latest follow-up (L5, 5.2 years; sacrum, 3.7 years), 67% of L5 patients had radiographic evidence of advanced 5-1 disc degeneration and the L5 cohort tended to have inferior sagittal balance (C7 plumb line: L5, +4.0 cm; sacrum, +1.2 cm; P = 0.06). The sacrum cohort, however, required more surgical procedures (L5, 1.7; sacrum, 2.8; P = 0.03) and experienced a greater frequency of major complications (L5, 22%; sacrum, 75%; P = 0.02), including nonunion (L5, 4%; sacrum, 42%; P = 0.006) and medical morbidity (L5, 0%; sacrum, 33%; P = 0.001). SRS-24 scores reflected a similar patient assessment of outcome and function for the two cohorts (L5, 89; sacrum, 87). DISCUSSION AND CONCLUSION: At 3 to 5 years' mean follow-up, long adult fusions to the sacrum required more procedures and had a higher frequency of complications than similar fusions to L5. For fusions to L5, subsequent subjacent disc degeneration is common and may be associated with a forward shift in sagittal balance. The ultimate influence of these factors on long-term outcomes remains to be seen.

Thoracolumbar deformity arthrodesis to L5 in adults: the fate of the L5-S1 disc.

STUDY DESIGN: A retrospective clinical and radiographic analysis of long adult deformity fusions terminating at L5. OBJECTIVES: To define the results of thoracolumbar fusions to L5 in adult deformity patients with critical evaluation for potential subsequent L5-S1 disc degeneration and L5 implant loosening. SUMMARY OF BACKGROUND DATA: Few studies have reported the results of long adult fusions to L5 and the potential for subsequent advanced L5-S1 disc degeneration is unknown. MATERIALS AND METHODS: Thirty-four consecutive patients fused from the thoracic spine to L5 at a single institution were evaluated at a mean follow-up of 5.6 years (2.1-14.3 years). SRS-24 functional outcome questionnaire results were obtained for all patients at most recent follow-up. RESULTS: By latest follow-up, subsequent advanced L5-S1 disc degeneration (SAD) developed in 19 of 31 patients (61%) assessed as having "healthy" discs before surgery. SAD was associated with a forward shift in sagittal balance (P = 0.02) and need for revision surgery (P = 0.02). Risk factors for the development of SAD were preoperative positive sagittal balance (P = 0.01), younger age (P = 0.03), and the presence of even mild radiographic degeneration before surgery (P = 0.004). Loss of L5 implant fixation occurred in six patients (18%) and was associated with deep seating of L5 within the pelvis (P = 0.0001). Inferior SRS-24 outcome measures were associated with preoperative advanced L5-S1 disc degeneration and the development of postoperative sagittal imbalance. CONCLUSIONS: Subsequent L5-S1 DDD developed in 61% of patients after long adult fusions to L5 and was associated with a significant loss of sagittal alignment and an increased likelihood for or definite need for another operation. Loss of L5 implant fixation is not uncommon, especially in patients with a deep-seated L5 vertebra.