Posterior Segmental Instrumented Fusion Research Articles

Importance of intraoperative dynamic spinal cord mapping (DSCM) during complex spinal deformity surgery

Case report and review of literature. To illustrate the importance of "dynamic spinal cord mapping" (DSCM) in locating the site of neurophysiologic data loss during severe spinal deformity correction. During marked correction of severe spinal deformities, intra-operative neuromonitoring remains of paramount importance. This case illustrates the importance of a unique type of monitoring, particularly useful when obtaining correction at multiple sites. A patient with symptomatic, progressive, severe kyphoscoliosis underwent multiple periapical posterior column osteotomies, partial T8 and complete T9 vertebral column resections and T2 to L3 posterior segmental instrumented fusion. During correction maneuvers, complete loss of spinous process descending neurogenic evoked potentials occurred. A flexible epidural catheter was placed at different spinal levels to dynamically stimulate the spinal cord and map out the site of data loss corresponding to the area of neural compromise. Using DSCM, the site of data loss was identified to the apex of the proximal thoracic region cephalad to the VCR site. This was rectified by releasing correction at the proximal end of the construct, and neurophysiologic data promptly returned to baseline. Postoperatively the patient was neurologically intact. Dynamic spinal cord mapping helps map areas of neurophysiologic data loss permitting focused attention to the site of compromise to reverse the offending agent. This improves the chance for return of baseline data, avoiding the potential for permanent neurologic catastrophe for the patient. LOE: IV.

Predictors of Extended Length of Hospital Stay in Adolescent Idiopathic Scoliosis Patients Undergoing Posterior Segmental Instrumented Fusion: An Analysis of 407 Surgeries Performed at a Large Academic Center.

Retrospective cohort study. The aims of this study were to (1) compare patient and procedure-specific characteristics among those who had short versus long hospital stays and (2) identify independent risk factors that may correlate with extended length of hospital stay (LOS) in patients with adolescent idiopathic scoliosis (AIS) who underwent posterior segmental instrumented fusion (PSIF). Reducing the LOS and identifying risk factors associated with extended admission have become increasingly relevant to healthcare policy makers. There is currently limited research identifying risk factors that correlate with extended stay in patients undergoing PSIF for AIS. A single-institution, longitudinally maintained database was queried to identify 407 patients who met specific inclusion and exclusion criteria. Based on the distribution and median LOS in the cohort (4 days), patients were divided into those who had long versus short LOS. In both groups, patient demographics, comorbidities, preoperative scoliosis curve measurements, surgery-related characteristics, and complications were analyzed. A univariate and multivariate regression analysis was then conducted to identify independent risk factors associated with extended LOS. Patients who had extended LOS tended to be women (84.6% vs. 75%, P = 0.01), had more levels fused (9 ± 2 vs. 7 ± 2 levels, P < 0.001), had more major postoperative complications (0.8% vs. 7.4%, P = 0.002), had more blood loss during surgery (723 ± 548 vs. 488 ± 341 cm, P < 0.001), and received less epidural analgesia for pain control (69% vs. 89%, P < 0.001). Except for higher thoracic kyphosis, long LOS patients did not have worse preoperative radiographic curve parameters. Multivariate logistic analysis identified female sex, having ≥9 ± 2 levels of fusion, operative blood loss, major postoperative complications, lack of epidural analgesia, and higher thoracic kyphosis as independent risk factors correlating for extended LOS. Independent risk factors identified by this study may be used to recognize patients with AIS at risk of prolonged hospital stay. 3.

Radiographic and clinical outcomes following combined lateral lumbar interbody fusion and posterior segmental stabilization in patients with adult degenerative scoliosis.

A hybrid approach of minimally invasive lateral lumbar interbody fusion (LLIF) followed by supplementary open posterior segmental instrumented fusion (PSIF) has shown promising early results in the treatment of adult degenerative scoliosis. Studies assessing the impact of this combined approach on correction of segmental and regional coronal angulation, sagittal realignment, maximum Cobb angle, restoration of lumbar lordosis, and clinical outcomes are needed. The authors report their results of this approach for correction of adult degenerative scoliosis. Twenty-six patients underwent combined LLIF and PSIF in a staged fashion. The patient population consisted of 21 women and 5 men. Ages ranged from 40 to 77 years old. Radiographic measurements including coronal angulation, pelvic incidence, lumbar lordosis, and sagittal vertical axis were taken preoperatively and 1 year postoperatively in all patients. Concurrently, the visual analog score (VAS) for back and leg pain, the Oswestry Disability Index (ODI), and Short Form-36 (SF-36) Physical Component Summary (PCS) and Mental Component Summary (MCS) scores were used to assess clinical outcomes in 19 patients. At 1-year follow-up, all patients who underwent combined LLIF and PSIF achieved statistically significant mean improvement in regional coronal angles (from 14.9° to 5.8°, p < 0.01) and segmental coronal angulation at all operative levels (p < 0.01). The maximum Cobb angle was significantly reduced postoperatively (from 41.1° to 15.1°, p < 0.05) and was maintained at follow-up (12.0°, p < 0.05). The mean lumbar lordosis-pelvic incidence mismatch was significantly improved postoperatively (from 15.0° to 6.92°, p < 0.05). Although regional lumbar lordosis improved (from 43.0° to 48.8°), it failed to reach statistical significance (p = 0.06). The mean sagittal vertical axis was significantly improved postoperatively (from 59.5 mm to 34.2 mm, p < 0.01). The following scores improved significantly after surgery: VAS for back pain (from 7.5 to 4.3, p < 0.01) and leg pain (from 5.8 to 3.1, p < 0.01), ODI (from 48 to 38, p < 0.01), and PCS (from 27.5 to 35.0, p = 0.01); the MCS score did not improve significantly (from 43.2 to 45.5, p = 0.37). There were 3 major and 10 minor complications. A hybrid approach of minimally invasive LLIF and open PSIF is an effective means of achieving correction of both coronal and sagittal deformity, resulting in improvement of quality of life in patients with adult degenerative scoliosis.

Biomechanical Analysis of Sacral Screw Strain and Range of Motion in Long Posterior Spinal Fixation Constructs

A cadaveric biomechanical experiment was conducted to assess the range of motion (ROM) and screw strain at S1 in a long instrumented spinal fusion construct to compare the effects of various surgical strategies for L5-S1 stabilization. To directly quantify and compare S1 screw strains and lumbosacral ROM for 4 different L2-S1 posterior segmental instrumented fusion constructs: an L2-S1 pedicle screw (PS) construct alone and PS with each of 3 different augmentations, anterior lumbar intebody fusion (ALIF), anterior axial interbody threaded rod (AxiaLITR), or iliac screws. Iliac screws and anterior interbody devices are commonly used as augmentation to reduce the incidence of S1 screw loosening in long fusion constructs. Alternatives, such as AxiaLITR, may provide similar biomechanical advantages without many of the same long-term limitations and morbidities. Pure moment flexibility testing was performed in 6 cadaveric lumbosacral spines. Specimens were tested with 4 instrumentation constructs: (1) PS L2-S1, (2) PS with ALIF, (3) PS with AxiaLITR, and (4) PS with iliac screws. Bilateral S1 PS were instrumented with strain gauges, directly measuring screw loading while simultaneously measuring L5-S1 ROM with a noncontact camera system. Average S1 screw strains were the greatest with the PS group and were reduced by 38% with the ALIF group, 75% with the AxiaLITR group, and 78% with the iliac screw group in flexion-extension (P < 0.05). Similar trends were observed in torsion (P < 0.05). Strains in lateral bending were smaller in magnitude and were similar among all 4 constructs. The AxiaLITR and iliac screw groups demonstrated a similar ROM and significant reduction in ROM at L5-S1 compared with both the PS and ALIF groups (P ≤ 0.02 and P < 0.03). The results of this study indicated that iliac screws and AxiaLITR provide similar stability at L5-S1, while significantly reducing the strain on the S1 screws.

Posterior Transpedicular Decompression for Thoracolumbar Burst Fractures

To demonstrate the feasibility of spinal canal decompression through the posterior transpedicular approach in patients with thoracolumbar burst fractures. We present 25 consecutive patients (19 men and 6 women; mean age 36 years; age range, 24-48 years) with incomplete neurological deficits (ASIA B and C) resulting from thoracolumbar burst fractures treated by posterior transpedicular spinal canal decompression and posterior segmental instrumented fusion. Canal compromise at presentation was 51.7 +/- 11.2%. The mean surgical time was 122 minutes (range, 108-122 minutes), and the mean blood loss was 528 +/- 123 ml. Canal compromise improved to 15.3 +/- 7.8%. At a mean followup of 14 months (range, 6-18 months), fourteen patients improved to ASIA D and were able to walk with an orthosis; seven improved to ASIA C, and four had no improvement (ASIA B). Seven ASIA B and all ASIA C patients had immediate postoperative neurological improvement to ASIA C and ASIA D; two ASIA B patients improved to ASIA C within six weeks after the operation. Anterior decompression was necessary in two (8%) ASIA B patients who did not improve after the initial operation; these patients, subsequently improved to ASIA C. There were no intraoperative complications. Superficial wound infections occurred in two patients and were treated with wound care and antibiotics; deep infection occurred in one patient and was treated with debridement and antibiotics. Posterior transpedicular spinal canal decompression and instrumentation is a reasonable alternative technique to anterior decompression procedures and circumferential fusion, providing for satisfactory canal decompression and neurological improvement.