Posterior column reconstruction improves fusion rates at the level of osteotomy in three-column posterior-based osteotomies.

PURPOSE: To determine the incidence of pseudarthrosis at the osteotomy site after three-column spinal osteotomies (3-COs) with posterior column reconstruction. METHODS: 82 consecutive adult 3-COs (66 patients) with a minimum of 2-year follow-up were retrospectively reviewed. All cases underwent posterior 3-COs with two-rod constructs. The inferior facets of the proximal level were reduced to the superior facets of the distal level. If that was not possible, a structural piece of bone graft either from the local resection or a local rib was slotted in the posterior column defect to re-establish continual structural posterior bone across the lateral margins of the resection. No interbody cages were used at the level of the osteotomy. RESULTS: There were 34 thoracic osteotomies, 47 lumbar osteotomies and one sacral osteotomy with a mean follow-up of 52 (24-126) months. All cases underwent posterior column reconstructions described above and the addition of interbody support or additional posterior rods was not performed for fusion at the osteotomy level. Among them, 29 patients underwent one or more revision surgeries. There were three definite cases of pseudarthrosis at the osteotomy site (4%). Six revisions were also performed for pseudarthrosis at other levels. CONCLUSION: Restoration of the structural integrity of the posterior column in three-column posterior-based osteotomies was associated with > 95% fusion rate at the level of the osteotomy. Pseudarthrosis at other levels was the second most common reason for revision following adjacent segment disease in the long-term follow-up.

The use of fusion mass screws in revision spinal deformity surgery.

STUDY DESIGN: To report the use of a posterior based 'fusion mass screw' (FMS) as a primary or salvage fixation point in a revision spinal deformity following a previous posterior spinal fusion (PSF). Our experience of this technique in a case report and the clinical and radiological results are reported. OBJECTIVES: To describe the technique and uses of the FMS as a primary/salvage fixation point in osteotomies in previously arthrodesed spinal deformity surgery. Obtaining fixation points to correct and stabilize a spinal deformity with coronal and sagittal imbalance in a previously arthrodesed spine during revision surgery can be challenging. Several alternate pedicle fixation techniques and laminar screw techniques have been described in the literature. However, there is no description of these techniques in the presence of a spinal fusion with distorted anatomy. A pedicle screw placed coronally across a thick posterior fusion mass can provide an alternate method of fixation in these cases with complex anatomy. METHODS: Two cases of complex spinal deformity and corrective spinal osteotomies using fusion mass screws (FMSs) placed coronally across the posterior fusion mass are described. The first case is an 8-year-old patient with Marfan's syndrome who developed a crank shaft phenomenon and severe thoracolumbar kyphoscoliosis following a previous PSF. The second case is a 53-year-old patient with coronal imbalance following PSF as a child using Harrington instrumentation who developed distal degeneration with stenosis in her remaining mobile segments. Both patients underwent vertebral column resection and osteotomy closure plus stabilisation using FMS. The clinical and radiological results and technique for insertion of the FMS are described. CONCLUSION: In this report, we present a novel method of using posterior FMSs to achieve fixation and correction in cases of revision deformity surgery with difficult anatomy. While we feel pedicle screws are the gold standard in deformity correction, knowledge of alternatives such as the FMS can allow surgeons to achieve stable constructs when faced with challenging situations.

Postoperative Distal Coronal Decompensation After Fusion to L3 for Adolescent Idiopathic Scoliosis Is Affected by Sagittal Pelvic Parameters.

STUDY DESIGN: Retrospective study. OBJECTIVE: To identify on early postoperative radiographs the risk factors for late distal decompensation in adolescent idiopathic scoliosis (AIS) patients undergoing posterior fusion surgery to L3. SUMMARY OF BACKGROUND DATA: Sparing distal fusion levels in AIS surgery is considered beneficial for postoperative mobility and outcomes; nonetheless, late distal decompensation is of concern. L3 is often advocated as lower instrumented vertebra in posterior fusion, but progressive angulation of the L3/4 disc is commonly observed. METHODS: A retrospective analysis was conducted on 78 AIS patients who underwent posterior fusion to L3 from 2007 to 2014. Patients' demographic data, early and 2-year postoperative standing radiographs by biplanar imaging system were investigated. Late decompensation was defined as progressive increase of L3-4 disc wedging angle at 2-year follow-up. Coronal, sagittal, and rotational radiographic parameters were compared between those with and without decompensation. SRS-30 scores were reviewed. RESULTS: Mean age was 14.5-year, and fusion levels averaged 12.0 (range: 6-15); 43 out of 78 patients (55%) experienced progressive L3-4 disc wedging, with 6 showing wedging >5°. L3 translation from the central sacral vertical line (13.9 vs. 11.1 mm, P = 0.13) and increased pelvic tilt (13.3° vs. 8.6°, P = 0.06) on the early postoperative radiograph were associated with increased L3-4 disc wedging. Multivariate analysis revealed that larger pelvic tilt was a significant risk factor for decompensation (odds ratio = 1.1 per 1°, 95% confidence interval: 1.0-1.1, P = 0.04). SRS-30 scores did not differ significantly between the two groups (4.0 vs. 4.1, P = 0.44). CONCLUSIONS: Pelvic retroversion and increased translation of L3 from the central sacral line on the early postoperative radiograph were associated with late L3-4 disc wedging in AIS fusions to L3. Careful surgical planning and correction of sagittal alignment are imperative to ensure the long-term outcomes. LEVEL OF EVIDENCE: 4.

Impact of Various Weights in the Intraoperative Skull-Skeletal Traction on Correction of Adolescent Idiopathic Scoliosis.

STUDY DESIGN: A retrospective study. OBJECTIVES: Intraoperative skull-skeletal traction (ISST) facilitates the surgical scoliosis correction, but it is also associated with neurological risk. The objective of the present study was to investigate the impact of various traction weights on neurophysiological change and curve correction in surgery for adolescent idiopathic scoliosis (AIS). METHODS: A retrospective review of a consecutive series of posterior spinal fusions for AIS patients undergoing corrections with the use of ISST by 2 surgeons in one institution was performed. Intraoperative prone, post-traction radiographs were performed on all cases. The cases were divided into 2 groups, high and low traction weights, based on whether the weight used was ≥35% or <35% of body weight. The frequency of neurophysiological changes and the curve correction were compared between the 2 groups. RESULTS: The intraoperative correction magnitudes by ISST were significantly larger in the high ISST group than in the low ISST group (35° vs 26°, P < .001). Changes in motor-evoked potential (MEP) were more frequently observed in the high ISST group (47% vs 26%, P = .049). A multivariate analysis showed that high ISST was associated with 3 times higher risk of MEP change (95% confidence interval = 1.1-8.0, P = .03) and higher final postoperative correction rates (68% vs 60%, P = .001). CONCLUSIONS: The high ISST for AIS was associated with increased intraoperative and ultimate curve corrections, and potentially facilitated better final correction. However, the high weight group was associated with an increased frequency of intraoperative MEP changes.

T12 Sagittal Tilt Predicts Thoracic Kyphosis.

STUDY DESIGN: Retrospective review and analysis of lateral long cassette radiographs. OBJECTIVE: The purpose of this paper is to assess whether certain radiographic features routinely seen on lumbar radiographs can predict a structural thoracic deformity. SUMMARY OF BACKGROUND DATA: Obtaining proper sagittal alignment is an essential factor contributing to favorable clinical outcomes following spinal deformity surgery. The majority of patients treated with lumbar fusions do not undergo long cassette radiographs, and therefore physicians must rely upon clinical examination to determine the presence of a structural thoracic kyphotic deformity. METHODS: A total of 193 consecutive lateral long cassette radiographs of outpatients without prior spine surgery presenting to a spine surgeon were independently reviewed. Statistical analysis was performed on sagittal parameters that included the T12 slope, pelvic incidence, sacral slope, T2-T12 and T5-T12 kyphosis, and T12-S1 lordosis, and correlated with patient demographics. RESULTS: The age of the patient combined with the sagittal slope of T12 can be used to assess a patient's risk of having a structural thoracic deformity defined in this series as >35 degrees from T5 to T12 and >40 degrees from T2 to T12. Based on our findings, for a given 20-year-old patient, the threshold T12 sagittal angle was about 17-18 degrees. This angle decreased 2-3 degrees per decade so that the threshold value was 12-13 degrees by age 40, 7-9 degrees by age 60, and 3-4 degrees by age 80. CONCLUSION: Age and the sagittal slope of the 12th thoracic vertebra are effective predictors of kyphosis between T2-T12 and T5-T12. This information may be used to determine the need for long cassette radiographs to further examine the possible presence of kyphotic deformity in the thoracic spine. LEVEL OF EVIDENCE: Level IV.

Comparison of pedicle subtraction and Smith-Petersen osteotomies in correcting thoracic kyphosis when closed with a central hook-rod construct.

STUDY DESIGN: Retrospective analysis. OBJECTIVE: To demonstrate the effectiveness of hook-rod constructs in closing thoracic osteotomies safely and effectively. SUMMARY OF BACKGROUND DATA: The outcomes of hook-rod instrumentation in osteotomies for the correction of kyphosis at the lumbar region of the spine have been described. Little literature exists on the outcomes at the thoracic level. METHODS: The radiographs and clinical scores of 38 patients who underwent pedicle subtraction osteotomy or Smith-Petersen osteotomy in the thoracic spine with the osteotomies closed using a central rod were retrospectively reviewed. Measurements included osteotomy angle, thoracic kyphosis (T2-T12), and maximum kyphosis. Perioperative and long-term complications were reviewed. RESULTS: Thirty-eight patients underwent thoracic level osteotomies. There were 8 males and 30 females with a mean age of 51.9 years (range, 18-76 yr) at the time of surgery. The mean construct length was 13.2 levels (4-25). Kyphosis correction was equal in the 2 groups. In the pedicle subtraction osteotomy group, a mean of 24.7° (4°-47°) correction was obtained through the osteotomies compared with 24.0° (9°-65°) in the Smith-Petersen osteotomy group. Correction per osteotomy was 23.7° (4°-47°) in the pedicle subtraction osteotomy group compared with 11.8° (2.8°-46.0°) in the Smith-Petersen osteotomy group. No difference in the amount of correction achieved at the different regions of the thoracic spine was observed with either type of osteotomy with central rod closure. CONCLUSION: Central hook-rod constructs provide a safe and effective means of closing thoracic osteotomies and result in good correction of rigid sagittal plane deformities. LEVEL OF EVIDENCE: 4.

Responding to neuromonitoring changes in 3-column posterior spinal osteotomies for rigid pediatric spinal deformities.

STUDY DESIGN: Retrospective review of prospectively collected data on the neuromonitoring changes recorded during a consecutive series of cord level 3-column posterior spinal osteotomies for the correction of rigid pediatric spinal deformities in children between 2005 and 2012. OBJECTIVE: To review the neuromonitoring changes observed during the performance of these procedures, to highlight the high-risk steps, and to describe actions taken to avert major neurological injury. SUMMARY OF BACKGROUND DATA: Significant motor evoked potentials (MEP) changes are common during the performance of spinal osteotomies in children. The real-time intraoperative information provided by MEPs can provide the necessary information to direct key surgical decisions. METHODS: The neuromonitoring changes occurring during the performance of 37 3-column, cord level, posterior spinal osteotomies in 28 patients were recorded. The procedures were divided, for comparative purposes, into 2 groups based on the presence or absence of alerts. A decrease in somatosensory evoked potentials and transcranial MEPs greater than 50% of baseline was considered an alert. Alerts were classified chronologically as type I: prior to decompression, type II: occurring during decompression and bone resection, type III: occurring after osteotomy closure. RESULTS: Somatosensory evoked potential alerts occurred in 3 patients, all of whom had significant MEP alerts. There were 2 type I, 15 type II, and 6 type III MEP alerts. Increasing blood pressure improved MEPs in all with the exception of 8 type II and 4 type III. The unresponsive 8 type II alerts were treated with osteotomy closure with the expectation that spinal shortening would decompress the spinal cord and improve spinal cord perfusion. The unresponsive 4 type III alerts all responded to reopening, manipulation, and subsequent reclosure of the osteotomy either with a cage or less correction. There were 5 immediate postoperative motor deficits. No patient had a permanent deficit. CONCLUSION: Changes unresponsive to increasing blood pressure occurring during decompression and bone resection (type II) responded well to osteotomy closure. Unresponsive changes during osteotomy closure (type III) were treated successfully with opening the osteotomy, cage adjustment, and less correction.

Posterior column reconstruction with autologous rib graft after en bloc tumor excision.

STUDY DESIGN: Retrospective review of consecutive case series. OBJECTIVE: To evaluate the efficacy of using autologous rib graft for fusion across long posterior column defects. SUMMARY OF BACKGROUND DATA: Achieving fusion across large posterior column defects after en bloc tumor resection can be difficult. Rib graft can be harvested from the local wound, and its shape and structural properties are well suited for reconstruction of thoracic posterior column deficits. METHODS: After Research Ethics Board approval, a retrospective review of the charts of 17 consecutive patients undergoing posterior column reconstruction after en bloc tumor resections was carried out. Autologous vascularized and nonvascularized rib grafts were utilized in 8 and 9 cases, respectively; 14 patients with malignant tumors and 3 with benign etiology. After surgery, patients underwent routine clinical and radiographic follow-up, with a computed tomographic scan performed at a minimum of 6 months in all surviving patients. Clinical and radiographic films were analyzed. RESULTS: Computed tomographic scans at a minimum of 6 months demonstrated graft incorporation in all surviving cases. There was no obvious difference at 6-month imaging to differentiate vascularized from nonvascularized grafts. There were no cases of graft dislodgement or fracture. Graft site morbidity was difficult to isolate from the morbidity of these large procedures. No complications related to the graft were identified. CONCLUSION: The use of autologous rib graft with a proximal step-cut and distal saddle-cut supplemented with posterior instrumentation allowed immediate stabilization of the posterior column defect created by the en bloc tumor resection. This technique of fashioning the graft and taking advantage of its natural curved structure for immediate press-fit was associated with graft incorporation in our cases.

Upper instrumented vertebral fractures in long lumbar fusions: what are the associated risk factors?

STUDY DESIGN: A retrospective comparative study. OBJECTIVE: To investigate the risk factors associated with upper instrumented vertebral (UIV) fractures in adult lumbar deformity. SUMMARY OF BACKGROUND DATA: Long segment lumbar fusions may lead to junctional failures. The purpose of this study was to determine factors associated with junctional failures. METHODS: Twenty-seven consecutive patients from 2001 to 2008 with minimum 4 levels fused, lower instrumented vertebra (LIV) of L5 or S1, upper instrumented vertebra of T10 or distal, and no previous surgery proximal to the instrumentation were retrospectively reviewed. We describe the UIV angle, the sagittal angle of the upper instrumented vertebra with the horizontal. Patients were divided into 3 groups: group 1, 7 patients with UIV fractures; group 2, 6 patients with other proximal failures; and group 3, 14 patients with no proximal complications. RESULTS: The mean number of levels fused was 5.7 (4-7), 5.2 (4-8), and 6.2 (4-8); mean age was 64.1, 61.8, and 64.1, and mean body mass index was 33.5, 30.0, and 31.6 for groups 1, 2, and 3, respectively (P > 0.05). Osteotomies were performed in 5 of 7 in group 1, 1 of 6 in group 2, and 5 of 14 in group 3. Mean follow-up was 26.3 months. The average intraoperative UIV angle (UIV0) and immediate postoperative UIV angle (UIV1) were 18.6°/15.4° for group 1, 5.7°/5.3° for group 2, and 10.3°/7.1° for group 3 (P < 0.05). Surgical revision rates were higher in group 1 (71%) compared with groups 2 (50%) and 3 (43%). Eight of 11 (73%) patients with upper instrumented vertebra of L1 or L2 had either UIV fracture or other proximal failure compared with 5 of 16 (31%) in patients with upper instrumented vertebra of T10, T11, or T12. CONCLUSION: Our series of long lumbar fusions had a high long-term complication and revision rate. A high UIV angle on intraoperative lateral radiograph was strongly associated with UIV fractures. UIVs of L1 or L2 had a higher rate of adjacent segment or UIV failure.

Neurophysiological changes in deformity correction of adolescent idiopathic scoliosis with intraoperative skull-femoral traction.

STUDY DESIGN: Retrospective review of 36 consecutive patients undergoing coronal plane deformity correction with intraoperative skull-femoral traction between 2005 and 2008 with motor evoked potential (MEP)/somatosensory evoked potential monitoring. OBJECTIVE: To determine the prevalence and significance of neurophysiological changes with intraoperative skull-femoral traction in adolescent idiopathic scoliosis. SUMMARY OF BACKGROUND DATA: Intraoperative skeletal traction can be associated with spinal cord stretching and ischemia with resultant electrophysiological changes. The prevalence and risks of such changes and their clinical significance is unknown. METHODS: Thirty-seven procedures involving 36 patients (27 females and 9 males) with a mean age of 14.8 (12-18) years were divided into two groups on the basis of the presence (group 1, n = 18 procedures) or absence (group 2, n = 19) of significant MEP changes with surgery. They were compared with patients undergoing correction without traction (group 3). RESULTS: Significant differences among the groups were observed in mean preoperative Cobb angle (86° vs. 70° vs. 59°), mean intraoperative posttraction Cobb angle (50.0° vs. 34.6°), traction index (0.41 vs. 0.50), flexibility index (0.14 vs. 0.27 vs. 0.25), and presence of primary lumbar curves (0% vs. 32% vs. 14%). Initial onset of MEP amplitude loss (group 1) occurred at a mean of 94 (1-257) minutes from the onset of surgery, was bilateral in 13 procedures, and improved at a mean of 5.5 (1-29) minutes after decreasing or removing the traction. At closure, complete bilateral recovery to baseline was observed in 10 procedures, recovery to >50% baseline in five, and recovery to <50% baseline in three procedures. There were no neurologic deficits in this series. CONCLUSION: Intraoperative traction is associated with frequent changes in MEP monitoring. The thoracic location of the major curve, increasing Cobb angle, and rigidity of major curve are significant risk factors for changes in MEP with traction. The presence of any MEP recordings irrespective of its amplitude at closure was associated with normal neurological function. Somatosensory evoked potential monitoring did not correlate with the traction induced MEP amplitude changes.

Technique of Reverse Smith Petersen Osteotomy (RSPO) in a patient with fixed lumbar hyperlordosis and negative sagittal imbalance.

STUDY DESIGN: Case report. OBJECTIVE: To determine the viability and safety of Reverse Smith Petersen Osteotomy (RSPO) to re-established sagittal balance in patients with fixed lumbar hyperlordosis. SUMMARY AND BACKGROUND DATA: Lumbar hyperlordosis is seen as a compensatory mechanism in thoracic Scheuermann disease and in sagittal decompensation in severe neuromuscular scoliosis. Hyperlordosis may also be seen after overcorrection with spinal osteotomies, but rarely causes clinically significant negative sagittal imbalance because of the thoracic compensation. We describe a case using a kyphosing osteotomy to treat hyperlordosis in a patient that was treated with a pedicle subtraction osteotomy for post-Harrington kyphosis. METHODS: The radiographs and clinical chart were reviewed of a patient treated with a RSPO at L2-L3 to correct the negative sagittal imbalance created by a previous extension of her fusion to the sacrum with a pedicle subtraction osteotomy. RESULTS: A reduction in the lumbar lordosis by 20 degrees at L2-L3 and restoration of the global sagittal balance was achieved with the RSPO. CONCLUSION: RSPO is a viable surgical technique that can be used to re-establish sagittal balance in patients with fixed lumbar hyperlordosis. Appreciation of a patient's balanced sagittal alignment and available compensatory mechanisms can help ensure appropriate osteotomies are performed.

A technique of anterior screw removal through a posterior costotransversectomy approach for posterior-based osteotomies.

STUDY DESIGN: Case report. OBJECTIVE: To describe a novel technique to remove anterior instrumentation from a posterior approach while performing posterior-based osteotomies for spinal deformities. SUMMARY OF BACKGROUND DATA: Posterior-based osteotomies such as pedicle subtraction osteotomies (PSOs) and vertebral column resections are performed to restore sagittal alignment. The removal of previously placed anterior implants at the desired osteotomy level can often be challenging. We propose a technique for the removal of anterior instrumentation through a posterior approach to facilitate osteotomy closure and deformity correction, while avoiding the need for an anterior incision. METHODS: A 34-year-old woman presented with a residual deformity after several anterior and posterior procedures. The residual coronal Cobb angle measured 60 degrees between T7 and L2, with a 46 degrees thoracolumbar kyphosis between T10 and L2. The screw head at the desired osteotomy level was in close proximity to the liver after the previous right-sided thoracoabdominal approach. Therefore, the T11 anterior screw was accessed through a posterior costotransversectomy approach and disconnected from the rod proximally and distally with a high-speed side-cutting burr. A portion of the right lateral vertebral body of T11 was removed to expose the neck of the screw, which was separated from the shaft with the same burr. A PSO was performed at T11 and the remaining screw shank was removed with the posterior-based osteotomy. RESULTS: No major complications were encountered during the procedure. The anterior screw at T11 was removed from posteriorly, and the PSO was completed successfully. Postoperative recovery was without incident, and the patient was very satisfied with her results. CONCLUSION: This technique describes a novel, safe, and effective method to deal with anterior instrumentation from the posterior approach while performing posterior-based osteotomies for rigid spinal deformities.