A distal start point facilitates safer insertion of S2-alar-iliac screws fixation.

This study aimed to show that a more distal insertion of S2-alar-iliac screws (S2AI) towards the S2 foramen facilitates a more natural trajectory and results in fewer breaches of the iliac wing due to the anteroposterior relationship of the sacrum and pelvis. Thirty-six consecutive patients who had received S2AI and postoperative computed tomography (CT) imaging were retrospectively reviewed. A freehand technique was used to insert all screws. Screws were stratified into two groups (Zone A and Zone B) based on the insertion point within the sacrum. Zone A was defined as screw insertion proximal to the second sacral foramen. Zone B was defined as screw insertion at or distal to the level of the second sacral foramen. CT imaging was reviewed to identify passage of the screw through either the fibrous or bony sacroiliac joint, and to check for instrumentation breach of the iliac wing. Sixty-two S2AI in 36 patients were identified. Twenty-six screws (42%) were inserted into Zone A and 36 (58%) into Zone B. There were 11 instrumentation breaches of the iliac wing in Zone A (42%) and 0 in Zone B (p < 0.0001). In Zone A, 24 screws (92%) passed through the upper, fibrous portion of the sacroiliac joint. In Zone B, no screws passed through this region (p < 0.0001). In conclusion, insertion of S2AI at or distal to the second sacral foramen facilitates improved screw placement due to the anteroposterior relationship of the sacrum and pelvis at this level.

Accuracy Analysis of Iliac Screw Using Freehand Technique in Spinal Surgery : Relation between Screw Breach and Revision Surgery.

OBJECTIVE: To analyze the accuracy of iliac screws using freehand technique performed by the same surgeon. We also analyzed how the breach of iliac screws was related to the clinical symptoms resulting in revision surgery. METHODS: From January 2009 to November 2015, 100 patients (193 iliac screws) were analyzed using postoperative computed tomography scans. The breaches were classified based on the superior, inferior, lateral, and medial iliac wall violation by the screw. According to the length of screw extrusion, the classification grades were as follows : grade 1, screw extrusion <1 cm; grade II, 1 cm ≤ screw extrusion <2 cm; grade III, 2 cm ≤ screw extrusion <3 cm; and grade IV, 3 cm ≤ screw extrusion. We also reviewed the revision surgery associated with iliac screw misplacement. RESULTS: Of the 193 inserted screws, 169 were correctly located and 24 were misplaced screws. There were eight grade I, six grade II, six grade III, and four grade IV screw breaches, and 11, 8, 2, and 3 screws violated the medial, lateral, superior, and inferior walls, respectively. Four revision surgeries were performed for the grade III or IV iliac screw breaches in the lateral or inferior direction with respect to its related symptoms. CONCLUSION: In iliac screw placement, 12.4% breaches developed. Although most breaches were not problematic, symptomatic violations (2.1%) could result in revision surgery. Notably, the surgeon should keep in mind that lateral or inferior wall breaches longer than 2 cm can be risky and should be avoided.

Risk Factors for Postoperative Coronal Balance in Adult Spinal Deformity Surgery.

STUDY DESIGN: A retrospective case-control study. OBJECTIVES: To determine factors influencing the ability to achieve coronal balance following spinal deformity surgery. METHODS: Following institutional ethics approval, the radiographs of 47 patients treated for spinal deformity surgery with long fusions to the pelvis, were retrospectively reviewed. The postoperative measurements included coronal balance, L4 tilt, and L5 tilt, levels fused, apical vertebral translation and maximum Cobb angle. L4 and L5 tilt angles were measured between the superior endplate and the horizontal. Sagittal parameters including thoracic kyphosis, lumbar lordosis, pelvic incidence, and sagittal vertical axis were recorded. Coronal balance was defined as the distance between the central sacral line and the mid body of C7 being ≤40 mm. Surgical factors, including levels fused, use of iliac fixation with and without connectors, use of S2A1 screws, interbody devices, and osteotomies. Statistical tests were performed to determine factors that contribute to postoperative coronal imbalance. RESULTS: Of the 47 patients reviewed, 32 were balanced after surgery and 14 were imbalanced. Coronal balance was 1.30 cm from center in the balanced group compared to 4.83 cm in the imbalanced group (P < .01). Both L4 and L5 tilt were statistically different between the groups. Gender and the use of transverse connectors differed between the groups but not statistically. CONCLUSIONS: In adult spinal deformity patients undergoing primary fusions to the pelvis, the ability to level the coronal tilt of L4 and L5 had the greatest impact on the ability to achieve coronal balance in this small series. A larger prospective series can help validate this important finding.

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.

Posterior Versus Three-Column Osteotomy for Late Correction of Residual Coronal Deformity in Patients With Previous Fusions for Idiopathic Scoliosis.

STUDY DESIGN: Retrospective case series. OBJECTIVE: To compare the early results of posterior column (PCO) and three-column (3CO) osteotomies performed in patients with previously fused idiopathic scoliosis and review their abilities to achieve coronal correction of residual deformities. SUMMARY OF BACKGROUND DATA: Residual deformity of previously fused AIS can accelerate adjacent segment degeneration secondary to lowest instrumented vertebra (LIV) tilt and rotation. Many of these patients are not satisfied with their cosmetic appearance and would choose revising the deformity when future surgery is indicated. METHODS: The data from 29 consecutive patients who underwent PCOs or 3COs for late revisions of idiopathic scoliosis were reviewed. Measurements included Cobb angle, focal osteotomy angle, and coronal balance. Perioperative data, complications, and patient-reported outcomes were also reviewed. RESULTS: Fourteen patients were treated with PCOs and 15 with 3COs. Global coronal correction was equal between the two groups. In the PCO group, where patients underwent a mean of 2.4 osteotomies, 20.2° of correction was obtained compared to 19.5° in the 3CO group (p = .33), which all underwent single osteotomies. The average coronal correction was 9.2°/osteotomy for the PCO group and 14.1°/osteotomy for the 3CO group (p < .01). Estimated blood loss was 1,417.5 mL in the PCO group compared to 3,199.3 in the 3CO group (p < .01). Five patients (36%) had intraoperative complications in the PCO group compared to 12 (80%) in the 3CO group (p < .05). There were no differences in operative times, length of stay, or patient-reported outcomes between groups. CONCLUSION: PCOs and 3COs performed in patients with previously fused spines for idiopathic scoliosis are effective in achieving residual deformity correction. In cases of posterior fusions, where the patient has a mobile anterior column, PCOs should be considered over 3COs because of their decreased risk of blood loss and complications.

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.

The Deformity Angular Ratio: Does It Correlate With High-Risk Cases for Potential Spinal Cord Monitoring Alerts in Pediatric 3-Column Thoracic Spinal Deformity Corrective Surgery?

STUDY DESIGN: A retrospective analysis. OBJECTIVE: The purpose of this study was to determine whether the deformity angular ratio (DAR) can reliably assess the neurological risks of patients undergoing deformity correction. SUMMARY OF BACKGROUND DATA: Identifying high-risk patients and procedures can help ensure that appropriate measures are taken to minimize neurological complications during spinal deformity corrections. Subjectively, surgeons look at radiographs and evaluate the riskiness of the procedure. However, 2 curves of similar magnitude and location can have significantly different risks of neurological deficit during surgery. Whether the curve spans many levels or just a few can significantly influence surgical strategies. Lenke et al have proposed the DAR, which is a measure of curve magnitude per level of deformity. METHODS: The data from 35 pediatric spinal deformity correction procedures with thoracic 3-column osteotomies were reviewed. Measurements from preoperative radiographs were used to calculate the DAR. Binary logistic regression was used to model the relationship between DARs (independent variables) and presence or absence of an intraoperative alert (dependent variable). RESULTS: In patients undergoing 3-column osteotomies, sagittal curve magnitude and total curve magnitude were associated with increased incidence of transcranial motor evoked potential changes. Total DAR greater than 45° per level and sagittal DAR greater than 22° per level were associated with a 75% incidence of a motor evoked potential alert, with the incidence increasing to 90% with sagittal DAR of 28° per level. CONCLUSION: In patients undergoing 3-column osteotomies for severe spinal deformities, the DAR was predictive of patients developing intraoperative motor evoked potential alerts. Identifying accurate radiographical, patient, and procedural risk factors in the correction of severe deformities can help prepare the surgical team to improve safety and outcomes when carrying out complex spinal corrections. LEVEL OF EVIDENCE: 3.

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.

Modified T4 hemivertebrectomy for persistent high left shoulder after surgery for double thoracic scoliosis.

STUDY DESIGN: Case report. OBJECTIVE: To surgically regain shoulder balance in patients with adolescent idiopathic scoliosis after loss of alignment after posterior fusion for Lenke II deformity correction. SUMMARY OF BACKGROUND DATA: Shoulder balance is known to have a large effect on patient satisfaction after deformity correction. Previous studies have outlined guidelines for determining levels of instrumentation to prevent postoperative high left shoulder. However, to our knowledge, no study has provided instructions on how to correct coronal imbalance in patients with previously fused scoliosis. We describe a case using a T4 unilateral pedicle subtraction osteotomy and contralateral Smith-Petersen osteotomy to treat high left shoulder in a patient who had previously undergone posterior instrumented fusion for adolescent idiopathic scoliosis. METHODS: The radiographs and clinical charts were reviewed for a 17-year-old female patient treated with a revision fusion and modified T4 hemivertebrectomy for a persistently high left shoulder after previous correction of a Lenke II idiopathic scoliosis. RESULTS: A reduction in the T1 tilt angle from 19.2° to 10.1° and an improvement in the coronal Cobb angle of the proximal thoracic curve from 37° to 17° were obtained. Shoulder balance was greatly improved. CONCLUSION: A proximal thoracic partial vertebrectomy with unilateral pedicle subtraction osteotomy and contralateral Smith-Petersen osteotomy is a technique that can be used to successfully correct fixed shoulder imbalance after posterior instrumented fusion of a double thoracic adolescent idiopathic scoliosis. LEVEL OF EVIDENCE: N/A.

Tension Pneumothorax as a Complication of Inadvertent Pleural Tears During Posterior Spinal Surgery.

OBJECTIVE: To review and expose the occurrences of tension pneumothorax as a result of pleural tear during posterior spinal surgery. METHODS: Intraoperative reports were retrospectively reviewed for 2 patients who underwent posterior spinal fusion and experienced pleural tear and subsequent tension pneumothorax. Surgical decisions for recognition and treatment were also reviewed. RESULTS: Unrecognized pleural tearing led to the formation of tension pneumothorax in both patients studied. Onset of respiratory signs and symptoms were delayed, occurring in the recovery room for the first patient and intraoperatively for the second. Both patients were successfully treated with conversion to open pneumothorax and placement of chest tubes. CONCLUSIONS: Tension pneumothorax is a complication that can arise during posterior thoracic spinal surgery as a result of an inadvertent pleural tear. Awareness of this potentially fatal complication will greatly help in the timely recognition and treatment of this condition if this situation occurs. The authors recommend a low threshold for chest tube placement in patients with known or suspected pleural tears or in patients with undiagnosed respiratory failure undergoing posterior thoracic spine surgery.