Unilateral and bilateral pedicle screw fixation in transforaminal lumbar interbody fusion: radiographic and clinical analysis.

BACKGROUND: Transforaminal lumbar interbody fusion with bilateral segmental pedicle screw (PS) fixation is a widely used and well-recognized technique that provides fixation and load-bearing capacity, while restoring morphometric spine parameters and relieving symptoms in patients with degenerative disc disease. A supplemental interspinous process fixation plate (ISFP) as an adjunct to unilateral PS fixation allows for reduced invasiveness of this technique compared with bilateral PS placement. The biomechanical comparison results have been previously reported, but the significance of these findings has not been studied in clinical settings. METHODS: A prospective cohort study with a supplemental retrospective chart review and radiographic analysis was performed. Patients were divided into 2 groups: bilateral PS fixation (n = 75) or unilateral PS fixation + ISFP (n = 96). Lateral lumbar standing radiographs were obtained for preoperative and postoperative foraminal height (FH), disc height, segmental sagittal alignment, and lumbar sagittal alignment measurements. Standardized questionnaires were used to compare postoperative clinical outcomes. RESULTS: The estimated blood loss, duration of procedure, and length of hospital stay were significantly lower for 1-level and 2-level procedures in the unilateral PS + ISFP group. A statistically significant mean disc height increase was observed in both groups. Regardless of the disc height increase, a statistically significant FH loss was detected in the bilateral PS group (from 17.1 mm to 16.3 mm; 4.7% loss; P = 0.04) compared with FH height loss in the unilateral PS + ISFP group that was not statistically significant (from 19.0 mm to 18.4 mm; 3.2% loss; P = 0.1). The analysis of segmental sagittal alignment, lumbar sagittal alignment, clinical outcomes, and fusion rates did not demonstrate any statistically significant differences. CONCLUSIONS: Significantly reduced surgical invasiveness was associated with unilateral PS + ISFP fixation, which represents the major advantage of this technique. Unilateral fixation was also associated with a slightly lower reduction in FH and was equally effective as bilateral PS fixation in regard to fusion rates, clinical outcomes, and other radiographic outcomes studied.

Complications in patients undergoing combined transforaminal lumbar interbody fusion and posterior instrumentation with deformity correction for degenerative scoliosis and spinal stenosis.

BACKGROUND: Utilization of the transforaminal lumbar interbody fusion (TLIF) approach for scoliosis offers the patients deformity correction and interbody fusion without the additional morbidity associated with more invasive reconstructive techniques. Published reports on complications associated with these surgical procedures are limited. The purpose of this study was to quantify the intra- and postoperative complications associated with the TLIF surgical approach in patients undergoing surgery for spinal stenosis and degenerative scoliosis correction. METHODS: This study included patients undergoing TLIF for degenerative scoliosis with neurogenic claudication and painful lumbar degenerative disc disease. The TLIF technique was performed along with posterior pedicle screw instrumentation. The average follow-up time was 30 months (range, 15-47). RESULTS: A total of 29 patients with an average age of 65.9 years (range, 49-83) were evaluated. TLIFs were performed at 2.2 levels on average (range, 1-4) in addition to 6.0 (range, 4-9) levels of posterolateral instrumented fusion. The preoperative mean lumbar lordosis was 37.6° (range, 16°-55°) compared to 40.5° (range, 26°-59.2°) postoperatively. The preoperative mean coronal Cobb angle was 32.3° (range, 15°-55°) compared to 15.4° (range, 1°-49°) postoperatively. The mean operative time was 528 min (range, 276-906), estimated blood loss was 1091.7 mL (range, 150-2500), and hospitalization time was 8.0 days (range, 3-28). A baseline mean Visual Analog Scale (VAS) score of 7.6 (range, 4-10) decreased to 3.6 (range, 0-8) postoperatively. There were a total of 14 (49%) hardware and/or surgical technique related complications, and 8 (28%) patients required additional surgeries. Five (17%) patients developed pseudoarthrosis. The systemic complications (31%) included death (1), cardiopulmonary arrest with resuscitation (1), myocardial infarction (1), pneumonia (5), and pulmonary embolism (1). CONCLUSION: This study suggests that although the TLIF approach is a feasible and effective method to treat degenerative adult scoliosis, it is associated with a high rate of intra- and postoperative complications and a long recovery process.

Interhemispheric propagation time and temporal lobe epileptogenicity.

Long-term subdural electroencephalographic (EEG) recording was performed in a series of patients with medically intractable complex partial seizures to test the hypothesis that ictal interhemispheric propagation time (IHPT) is correlated with temporal lobe epileptogenicity. In 41 patients, the duration from initial subdural EEG seizure onset to the first appearance of subdural EEG epileptic activity in the contralateral hemisphere (IHPT) was measured in seconds and analyzed for a quantitative relationship to temporal lobe seizure interval (frequency⁻¹), in hours. A statistically significant, nonlinear correlation between IHPT and seizure interval was found (Arctan y=-0.009x²+0.598x+75.187, y=IHPT, in seconds, x=seizure interval, in hours, r=0.326, d.f.=39, t=2.15, p<0.05). The results suggest that, for seizure intervals less than 33h, increasing IHPT is associated with increasing seizure interval (i.e. decreasing epileptogenicity). Conversely, for seizure intervals greater than 33h, decreasing IHPT is associated with increasing seizure interval. Because the relationship between IHPT and seizure interval is a trigonometric (i.e. arctangent) function of a second degree polynomial, small changes in IHPT are associated with substantial changes in seizure interval. These findings suggest that temporal lobe epileptogenicity is a complex, nonlinear function of the electrocorticographic EEG time factor (i.e. IHPT) involved in the transmission of ictal epileptic activity from the seizure focus to the contralateral hemisphere. The results suggest that, on an electrophysiologic basis, patients with temporal lobe epilepsy represent two distinct populations based on seizure interval. The results should improve the understanding of the electrocorticographic pathophysiology of temporal lobe epilepsy. The development of cortical neuromodulation strategies designed to suppress temporal lobe seizures should consider this complex relationship between temporal lobe interhemispheric propagation time and epileptogenicity.