Pedicle Subtraction Osteotomy Procedure Research Articles

Load-sharing biomechanics of lumbar fixation and fusion with pedicle subtraction osteotomy

Pedicle subtraction osteotomy (PSO) is an invasive surgical technique allowing the restoration of a well-balanced sagittal profile, however, the risks of pseudarthrosis and instrumentation breakage are still high. Literature studied primary stability and posterior instrumentation loads, neglecting the load shared by the anterior column, which is fundamental to promote fusion early after surgery. The study aimed at quantifying the load-sharing occurring after PSO procedure across the ventral spinal structures and the posterior instrumentation, as affected by simple bilateral fixation alone, with interbody cages adjacent to PSO level and supplementary accessory rods. Lumbar spine segments were loaded in vitro under flexion–extension, lateral bending, and torsion using an established spine tester. Digital image correlation (DIC) and strain-gauge (SG) analyses measured, respectively, the full-field strain distribution on the ventral surface of the spine and the local strain on posterior primary rods. Ventral strains considerably decreased following PSO and instrumentation, confirming the effectiveness of posterior load-sharing. Supplemental accessory rods considerably reduced the posterior rod strains only with interbody cages, but the ventral strains were unaffected: this indicates that the load transfer across the osteotomy could be promoted, thus explaining the higher fusion rate with decreased rod fracture risk reported in clinical literature.

Preoperative, Intraoperative, and Postoperative Standing Lordosis After Pedicle Subtraction Osteotomy: An Analysis of Radiographic Parameters and Surgical Strategy

Study DesignRetrospective consecutive case series. ObjectivesThe objective of this study was to investigate the relationship between intraoperative and postoperative lumbar spine measurements after pedicle subtraction osteotomy (PSO). We analyzed the amount of lordosis lost between the prone intraoperative image and the final upright standing film. The outcome of this analysis should be used in preoperative planning for osteotomy procedures. MethodsSixteen patients had pre-, intra- and postoperative measurements of lumbar lordosis. Pre- and postoperative measures of pelvic parameters were also determined. Comparisons were made between pre-, intra- and postoperative measures of pelvic parameters, with specific attention to lumbar lordosis correction and the loss of correction with transition to a standing position. ResultsThe average pelvic mismatch between preoperative lumbar lordosis and pelvic incidence was 37 degrees whereas the postoperative mismatch measured 3.2 degrees. All patients had a significant correction of their lumbar lordosis. The lumbar lordosis showed a highly significant loss of 12.5 degrees from the intraoperative prone position to the postoperative standing position, with the average lumbar lordosis intraoperatively (67 degrees) decreasing to a standing lumbar lordosis of 54 degrees (p < .000001). ConclusionsThis analysis should aid in preoperative planning for sagittal global alignment correction and can reduce the chance of over- or under-correction in patients having a PSO procedure. Given the narrow postoperative target that is associated with better outcomes for patients, the loss of lumbar lordosis from prone to standing position may be a crucial variable in this planning process.

Comparison of Clinical and Radiological Improvement Between the Modified Trephine and High-speed Drill as Main Osteotomy Instrument in Pedicle Subtraction Osteotomy.

High-speed drill is the main osteotomy instrument in pedicle subtraction osteotomy (PSO) currently. Considering the long duration of surgery, the large amount of blood loss, and the high incidence of neurovascular injury, the osteotomy procedure is challenging. Use of trephine for the osteotomy displays high efficiency by shortening surgery time and reducing blood loss in anterior cervical corpectomy and fusion. However, the potential risk of neurological injury is high. We modified the trephine by adding locking instrument, when the serrated top of the trephine reaches the tip of the probe; the locking instrument on the probe restricts the trephine and improves security during the osteotomy procedure.The aim of this study was to compare the clinical and radiological improvement between the modified trephine and high-speed drill as main osteotomy instrument in PSO.From February 2009 to 2013, 50 patients with severe thoracolumbar kyphotic deformity caused by old compressive vertebrae were prospectively reviewed. All patients were randomly assigned to the experimental group (27 patients received PSO with modified trephine) and the control group (23 patients received PSO with high-speed drill). The clinical records were reviewed and compared for surgical time, operative blood loss, functional improvement (Oswestry Disability Index), and pain relief (visual analog scale). The radiological records were reviewed and compared for correction of kyphotic deformity postoperatively and correction loss at 2-year follow-up.All patients successfully finished the PSO procedure, and got satisfactory kyphotic deformity correction and overall function improvement. The surgery time was shorter in the experimental group than that in the control group (132.7 ± 12.6 vs 141.7 ± 16.7 min; P = 0.03). No significant difference was found in blood loss (882.9 ± 98.9 mL vs 902.2 ± 84.9 mL; P = 0.47) or correction of the kyphotic angle (33.4 ± 3.4° vs 32.1 ± 2.5°, P = 0.13) postoperatively between the 2 groups. At 24-month follow-up, no difference was discovered in loss of the correction (4.9 ± 1.6° vs 4.5 ± 1.6°; P = 0.42), change of Oswestry Disability Index (49.4 ± 6.2% vs 48.2 ± 4.2%; P = 0.44), or in back pain relief (6.2 ± 1.4 vs 6.4 ± 1.2 min; P = 0.51) between the 2 groups. No internal fixation related complication occurred and bony fusion was detected in lateral X-ray in all patients. In the control group, 2 patients had transient nerve root deficit, 14 patients at 3-month follow-up and 3 patients at 2-year follow-up experienced graft donor site morbidity, and pain killer medicine was always required.In conclusion, the modified trephine obviously shortens surgery time, and prevents graft donor site morbidity when compared to a high-speed drill. The learning curve for using the modified trephine in PSO procedure is short.

Will Immediate Postoperative Imbalance Improve in Patients with Thoracolumbar/Lumbar Degenerative Kyphoscoliosis? A Comparison between Smith–Petersen Osteotomy and Pedicle Subtraction Osteotomy with an Average 4 Years' Follow-Up

Introduction There was a paucity of literature paying attention to the postoperative imbalance after pedicle subtraction osteotomy (PSO) or Smith–Petersen osteotomy (SPO) and natural evolution of the imbalance. This study aims to compare compensatory behavior of coronal and sagittal alignment following PSO and SPO for degenerative kyphoscoliosis. Patients and Methods A retrospective study was performed on 68 consecutive patients with degenerative kyphoscoliosis treated by lumbar PSO (25 patients) or SPO (43 patients) procedures at a single institution. Long-cassette standing radiographs were taken preoperatively, postoperatively, and at last, follow-up and radiographic parameters were measured. The LIV and level of osteotomy were compared between the patients with and without improvement. Results Negative SVA was observed in PSO group postoperatively, implying an overcorrection of SVA. This negative SVA improved spontaneously during follow-up ( p &lt; 0.05). Coronal balance was found to worsen immediately post-op in the SPO group ( p &lt; 0.05). At the last follow-up, spontaneous improvement was observed in 15 patients and the average CB decreased to 16.35 mm. For the 15 patients with improved CB, fusion at L5 or above was more common compared with the 11 patients with persisted postoperative imbalance ( p = 0.027), whereas no difference in term of levels of osteotomy was found ( p &gt; 0.05). Conclusion The overcorrection of SVA is more often seen in PSO group. The coronal imbalance is more likely to occur in SPO group. The postoperative sagittal imbalance often spontaneously improves with time. LIV at S1 or with pelvic fixation should be regarded as potential risk factors for persistent coronal imbalance in patients with SPO.

Lung volume change after pedicle subtraction osteotomy in patients with ankylosing spondylitis with thoracolumbar kyphosis.

A retrospective clinical study. To investigate the lung volume (LV) change in patients with ankylosing spondylitis (AS) with thoracolumbar kyphosis after the pedicle subtraction osteotomy procedure. Thoracolumbar kyphosis with respiratory impairment is the consequence of most untreated AS patients. Restrictive pulmonary function is prevalent in these patients. The ideal evidence for restrictive pulmonary function impairment is to investigate the LV. A computed tomography (CT)-based method can help to obtain accurate LV change during the osteotomy. Twenty-eight patients with AS with thoracolumbar kyphosis were included. All of these patients underwent pedicle subtraction osteotomy to correct their sagittal deformity. Pre- and postoperative full-length radiographs and CT scans were reviewed. The sagittal correction of the spine was measured. CT scans were used to estimate the pre- and postoperative LV with software. The relationship between the sagittal correction and the LV change was investigated. All the patients were followed up for 2 years at least. The pedicle subtraction osteotomy procedure was performed safely on each patient without serious complications. The average preoperative T1-S1 Cobb was 67.7° (42°∼88°) and the postoperative was 7.6° (-11°∼21°). T1-S1 Cobb change was 60.0° in average (P < 0.05). The LV increased by 396 mL in average. Significant correlation was found between the percentage of LV change and T1-S1 Cobb change (r = 0.7219, P < 0.05). The location we selected for pedicle subtraction osteotomy varied from T12 to L3. No relationship was found between the osteotomy location and the LV change. The pedicle subtraction osteotomy effectively corrected the sagittal deformity of patients with AS. LV increased significantly after the osteotomy. 4.

Novel application of pre-operative vertebral body embolization to reduce intraoperative blood loss during a three-column spinal osteotomy for non-oncologic spinal deformity

Three column osteotomies (3CO) of the lumbar spine are powerful corrective procedures used in the treatment of kyphoscoliosis. Their efficacy comes at the cost of high reported complication rates, notably significant estimated blood loss (EBL). Previously reported techniques to reduce EBL have had modest efficacy. Here we describe a potential technique to decrease EBL during pedicle subtraction osteotomy (PSO) of the lumbar spine by means of pre-operative vertebral body embolization – a technique traditionally used to reduce blood loss prior to spinal column tumor resection. We present a 62-year-old man with iatrogenic kyphoscoliosis who underwent staged deformity correction. Stage 1 involved thoracolumbar instrumentation followed by transarterial embolization of the L4 vertebral body through bilateral segmental arteries. A combination of polyvinyl alcohol particles and Gelfoam (Pfizer, New York, NY, USA) were used. Following embolization there was decreased angiographic blood flow to the small vessels of the L4 vertebral body, while the segmental arteries remained patent. Stage 2 consisted of an L4 PSO and fusion. The EBL during the PSO procedure was 1L, which compared favorably to that during previous PSO at this institution as well as to quantities reported in previous literature. There have been no short term (5month follow-up) complications attributable to the vertebral body embolization or surgical procedure. Although further investigation into this technique is required to better characterize its safety and efficacy in reducing EBL during 3CO, we believe this patient illustrates the potential utility of pre-operative vertebral embolization in the setting of non-oncologic deformity correction surgery.

The posterior surgical correction of congenital kyphosis and kyphoscoliosis: 23 cases with minimum 2 years follow-up

The purpose of this study is to review our operative experience of congenital kyphosis or kyphoscoliosis undergoing either pedicle subtraction osteotomy (PSO) or posterior vertebral column resection (pVCR) according to certain criteria we have established. From December 2003 to 2009, 23 consecutive patients of congenital kyphosis or kyphoscoliosis were treated by means of PSO or pVCR procedure in a single institution. The average preoperative kyphosis angle was 74.3º. The C7 plumb line was 12.6 mm posterior to the posterior-superior corner of S1 on average, showing negative imbalance. In the 11 cases who had accompanied scoliosis, the average preoperative scoliosis angle was 42.6º. The average Oswestry Deficiency Index (ODI) for back pain was 14.6 before surgery. Eleven patients had compromise of neurological functions. After PSO or pVCR procedure, the average kyphosis angle decreased to 20.0º, and the accompanied scoliosis also decreased to 15.8º. The average follow-up time after surgery was 34.3 months. At the last follow-up, the average kyphosis corrective rate was 73.7 %, and the average scoliosis corrective rate was 61.7 %. The negative imbalance improved, with the C7 plumb line being 1.5 mm posterior to the posterior-superior corner of S1 on average. After surgery, the average ODI for back pain had 40.6 % improvement, and most patients who had neurological symptoms before surgery had varying degrees of relief. The total satisfactory rate to corrective surgery was 91.3 %. No permanent neurological damage was observed. If selected appropriately, both PSO and pVCR procedures can achieve compatible and satisfactory correction results in the surgical treatment of congenital kyphosis or kyphoscoliosis.

Major Complications and Comparison Between 3-Column Osteotomy Techniques in 105 Consecutive Spinal Deformity Procedures

A retrospective review. To characterize the risk factors for the development of major complications in 3-column osteotomies and determine whether the presence of a major complication affects ultimate clinical outcomes. Three-column spinal osteotomies, including pedicle subtraction osteotomy (PSO) and vertebral column resection (VCR), are common techniques to correct severe and/or rigid spinal deformities. Two hundred forty consecutive PSO (n = 156) and VCR (n = 84) procedures in 237 patients were performed at a single institution between 1995 and 2008. Of these, 105 patients (87 PSOs, 18 VCRs) had complete preoperative and minimum 2-year postoperative clinical outcomes data available for analysis. Using established criteria, we reported complications as major or minor and further stratified complications as surgical versus medical and permanent versus transient. Risk factors for complications and their effect on Scoliosis Research Society (SRS) clinical outcomes at baseline and at 2 years or more were assessed. Major medical and surgical complications occurred at similar rates in both PSOs and VCRs (38%, 33 of 87 vs. 22%, 4 of 18; P = 0.28). Overall, 24.8% (26 of 105) experienced major surgical complications (3 permanent) and 15.2% (16 of 105) experienced major medical complications (4 permanent). Patients with PSO were older (53 vs. 29 yr; P < 0.001), had greater estimated blood loss (1867 vs. 1278 mL; P = 0.02), and showed a trend toward fewer fused levels (10.1 vs. 12.2; P = 0.06). Risk factors for major complications included preoperative sagittal imbalance of 40 mm or more (P = 0.01), age 60 years and older (P = 0.01), and the presence of 3 or more medical comorbidities (P = 0.04). Both groups improved significantly from baseline in SRS subscores; however, patients with PSO started off worse but improved more than VCRs in both the pain (+1.0 vs. +0.1; P < 0.001) and function (+0.6 vs. +0.2; P = 0.01) domains, with no differences in final satisfaction (4.1 vs. 4.3; P = 0.54). PSO and VCR patients with no complications had slightly higher satisfaction scores than patients with minor-only complications, major transient complications, and major permanent complications. There were no significant differences among the groups with respect to change in SRS subscores from baseline, and all complication groups improved significantly from baseline (P = 0.04). Major complications occurred in 35% of 3-column osteotomies and at similar rates for both PSO (38%) and VCR (22%) procedures. The presence of a major complication did not affect the ultimate clinical outcomes at 2 years or more.

Thoracic pedicle subtraction osteotomy in a pediatric patient: a case report

Study design: Case report.Objective: To describe a case of thoracic pedicle subtraction osteotomy (PSO) for congenital kyphosis in a child.Background information: Although congenital kyphosis is rare, it is a challenging cause of pediatric myelopathy and frank paralysis. Even less common is the use of PSO for the surgical management of focal congenital kyphosis. We present the case of a child with congenital kyphosis that was managed with a pedicle subtraction osteotomy.Methods: A detailed history and physical examination were performed with careful review of the patient’s medical records and x-ray studies. A PSO at T11 was performed along with T9 through L1 instrumented posterolateral fusion.Case description: A 10-year-old girl was evaluated for walking difficulty and a lump on her back. Physical examination revealed a sharp gibbus kyphosis in the lower thoracic spine with tenderness and bilateral back muscle spasms. The patient displayed difficulty with balance lacking a smooth, regular gait rhythm. Clonus and radiculopathy were not present. Plain x-ray of the thoracolumbar spine revealed hyperkyphosis and failure of anterior wall segmentation between T10 and T11 vertebral bodies. Cobb’s angle measured 65 degrees. Due to her symptoms and degree of correction required, we elected to perform a PSO at T11 along with T9 to L1 posterolateral instrumentation fusion. No intraoperative complications occurred. There was a significant improvement in her posture and gait.Discussion: A thoracic PSO for congenital kyphosis was safely performed with an excellent outcome. To our knowledge, this is the first PSO procedure performed in Uganda.

Can We Safely Reduce Blood Loss During Lumbar Pedicle Subtraction Osteotomy Procedures Using Tranexamic Acid or Aprotinin?

Retrospective, observational study. To compare the safety and efficacy of 2 pharmaceutical antifibrinolytic agents, aprotinin and tranexamic acid, in controlling blood loss during lumbar pedicle subtraction osteotomy (PSO) in adults. Reconstructive spinal surgeries, in particular lumbar PSOs, have been associated with large blood losses despite interventions (intraoperative blood salvaging, controlled hypotensive anesthesia). Since the 1990s, intraoperative administration of antifibrinolytics (aprotinin, tranexamic acid, e-aminocaproic acid) has gained popularity. This study assesses the safety and efficacy of 2 antifibrinolytics, aprotinin and tranexamic acid, during adult lumbar PSO procedures at one institution. A retrospective comparative analysis of 44 consecutive adults undergoing posterior spinal fusion procedures with lumbar PSO at one institution was performed. Patients were analyzed according to treatment group: controls (10), aprotinin (14), and tranexamic acid (20). There were no significant differences in demographic (gender, age, comorbidities) or surgical traits (length of surgery, levels fused/exposed, preoperative hematocrit, bone graft source, primary/revision) between the 3 groups. The aprotinin group had significantly less intraoperative blood loss (1114 +/- 992 mL; P < 0.01) than the tranexamic acid and control group (2102 +/- 1076 mL and 2260 +/- 1580 mL, respectively). The aprotinin group received significantly less blood (577 +/- 806 mL; P < 0.002) during the surgical procedure than the tranexamic acid (1838 +/- 1096 mL) and the control group (1502 +/- 1241 mL). There were no major intraoperative complications for any of the treatment groups. There were no postoperative cases of seizures, MI, CVA, DVT, or PE with any of the treatment groups. There was one acute tubular necrosis event in the aprotinin group, which resolved before discharge but did required several days of dialysis. The aprotinin treatment group lost significantly less blood and received significantly fewer blood transfusions than both the tranexamic acid and control groups without significant differences in intra- and postoperative complications. These results may justify further study of aprotinin and other antifibrinolytics for this specific indication (3-column lumbar osteotomies in the adult spinal deformity population). A multicenter randomized comparative analysis would be ideal.