Transpedicular closed wedge osteotomy in ankylosing spondylitis: results of surgical treatment and prospective outcome analysis

Changes of the abdomen in patients with ankylosing spondylitis kyphosis

STUDY DESIGN

A retrospective clinical study.

OBJECTIVE

To investigate changes of the abdomen in patients with ankylosing spondylitis kyphosis.

SUMMARY OF BACKGROUND DATA

Since 1945, many authors had reported the good clinical and radiographical outcomes and higher patient satisfaction rates of spinal osteotomy techniques. However, to our knowledge, whether the visceral and diaphragmatic compression that results from the inferior edge of the thoracic cage is relieved by the surgery has not yet been reported.

MATERIALS AND METHODS

From July 2010 to July 2013, 26 patients (24 males, and 2 females) with severe ankylosing spondylitis kyphosis, who underwent pedicle subtraction osteotomy in the Department of Orthopaedics at Chinese People's Liberation Army General Hospital were studied. Preoperative and postoperative computed tomographic scan, 3-dimensional reconstruction, and preoperative pulmonary function test were performed. Via those tests, the minimum distance on the median sagittal plane of the abdomen (MD), the acreage of the abdominal median sagittal plane (AMSPA), the diaphragm angle on median sagittal plane can be gained. A paired sample t test was performed to determine the differences between the preoperative and postoperative AMSPA and MD and diaphragm angle on median sagittal plane, respectively. Postoperative MD/preoperative MD and postoperative AMSPA/preoperative AMSPA and global kyphosis were also analyzed by performing independent sample t test for the 2 groups.

RESULTS

The diaphragm angle on median sagittal plane has changed significantly in all the patients. There was significant change of both MD and AMSPA in patients whose abdominal wall was folded into abdomen, whereas neither MD nor AMSPA in patients without the factor.

CONCLUSION

To a certain degree, the diaphragmatic compression and the visceral compression could be compensated for by turning to flattening or even developing into kyphosis of the lumbar lordosis before surgery, which could be corrected by a spinal osteotomy. Sagittal rotation of diaphragm in ankylosing spondylitis kyphosis could also be improved by a spinal osteotomy.

Can pelvic tilt be predicated by the sacrofemoral-pubic angel in patients with thoracolumbar kyphosis secondary to ankylosing spondylitis?

STUDY DESIGN

A retrospective radiographical study.

OBJECTIVE

To construct a predictive model for pelvic tilt (PT) based on the sacrofemoral-pubic (SFP) angle in patients with thoracolumbar kyphosis secondary to ankylosing spondylitis (or AS).

SUMMARY OF BACKGROUND DATA

PT is a key pelvic parameter in the regulation of spine sagittal alignment that can be used to plan the appropriate osteotomy angle in patients with AS with thoracolumbar kyphosis. However, it could be difficult to measure PT in patients with femoral heads poorly visualized on lateral radiographs. Previous studies showed that the SFP angle could be used to evaluate PT in adult patients with scoliosis. However, this method has not been validated in patients with AS.

METHODS

A total of 115 patients with AS with thoracolumbar kyphosis were included. Full-length anteroposterior and lateral spine radiographs were all available, with spinal and pelvic anatomical landmarks clearly identified. PT, SFP angle, and global kyphosis were measured. The patients were randomly divided into group A (n=65) and group B (n=50). In group A, the predictive model for PT was constructed by the results of the linear regression analysis. In group B, the predictive ability and accuracy of the predictive model were investigated.

RESULTS

In group A, the Pearson correlation analysis revealed a strong correlation between the SFP angle and PT (r=0.852; P<0.001). The predictive model for PT was constructed as PT=72.3-0.82×(SFP angle). In group B, PT was predicted by the model with a mean error of 4.6° (SD=4.5°) with a predictive value of 78%.

CONCLUSION

PT can be accurately predicted by the SFP angle using the current model: PT=72.3-0.82×(SFP angle), when the femur heads are poorly visualized on lateral radiographs in patients with AS with thoracolumbar kyphosis.

LEVEL OF EVIDENCE

4.

Clinical Outcome and Complications of Transpedicular Closing-wedge Osteotomy for Correction of Deformity in Ankylosing Spondylitis in a Regional Hospital

Study design

Prospective study of surgical correction of thoracolumbar kyphotic deformity caused by ankylosing spondylitis.

Objectives

To assess surgical outcomes and complications of thoracolumbar kyphotic deformity corrected with transpedicular closing-wedge osteotomy performed in a regional hospital.

Summary of background data

There have been several studies reporting on the results of surgical correction of deformity in ankylosing spondylitis all over the world. However, there has not been any local data published.

Methods

From 2003 to 2011, we had performed 12 transpedicular closing-wedge osteotomies in 9 patients with ankylosing spondylitis for correction of kyphotic and scoliotic deformity in thoracolumbar spine. Operative outcomes were assessed clinically by recording the Japanese Orthopaedic Association (JOA) scores, visual analogue scale (VAS) pain scores, Oswestry Disability Index (ODI) preoperatively and postoperatively and patient satisfaction postoperatively. Radiological outcome was assessed by measuring thoracic kyphosis, lumbar lordosis and sagittal plumb line preoperatively and postoperatively as well as the degree of surgical correction. Occurrence of complications was recorded by our standard audit protocol.

Results

All patients had a single level of osteotomy done at a time. Most of the osteotomies were done at L2 or L3. The mean amount of correction was 21.6°. Complications included dural tear, pseudoarthrosis and transient radiculopathy. The extent of correction and incidence of complications improved with experience.

Conclusion

Despite transpedicular closing-wedge osteotomy being a major operation that is not without complications, most of our patients had good clinical results and subjective satisfaction.

Two-level spinal osteotomy for severe thoracolumbar kyphosis in ankylosing spondylitis. Experience with 48 patients

STUDY DESIGN

A retrospective study.

OBJECTIVE

To report surgical results for severe thoracolumbar kyphosis secondary to ankylosing spondylitis (AS) corrected with 2-level spinal osteotomy.

SUMMARY OF BACKGROUND DATA

Transpedicular osteotomy in the lumbar spine is the major approach to correct kyphosis in AS. Most surgical procedures were performed at 1 level and only few literature report 2-level osteotomy in 1 patient.

METHODS

From January 2003 to June 2011, we reviewed 48 patients experiencing AS with severe thoracolumbar kyphosis who underwent stage 2-level spinal osteotomy in our hospital. The osteotomies were performed at T12 and L2 or L1 and L3, according to the apex of kyphosis. Preoperative and postoperative height, chin-brow vertical angle, sagittal balance, and the sagittal Cobb angle of the vertebral osteotomy segment were documented. Intraoperative, postoperative, and general complications were recorded.

RESULTS

The chin-brow vertical angle improved from 65.0° ± 28.0° to 5.0°± 10.0° (P = 0.000) and the sagittal imbalance distance improved from 26.9 ± 10.4 cm to 10.6 ± 5.6 cm (P = 0.000). The mean amount of correction was 24.9° at the superior site of the osteotomy and 38.1° at the inferior site of the osteotomy. Postoperatively, all patients could walk with horizontal vision and lie on their backs. No major acute complications such as death or complete paralysis occurred. Five patients experienced complications such as infections (n = 1) and cerebrospinal fluid leaks (n = 4). Both Oswestry Disability Index and Scoliosis Research Society scores improved largely. Fusion at the osteotomy site was achieved in each patient, and no implant failures were noted.

CONCLUSION

Single-stage 2-level osteotomy can effectively and safely correct kyphotic deformities of the thoracolumbar spine caused by AS.

LEVEL OF EVIDENCE

3.

Neurological risks in scheduled spinal surgery

Spinal surgery is a high-risk specialty with an ever-increasing patient volume. Results are very largely favorable, but neurologic damage, the most severe complication, may leave major sequelae, some of which can be life-threatening. Neurologic complications may be classified according to onset (per- vs. postoperative) and surgical site (cervical vs. thoracolumbar). The present paper provides quantitative data for the risks involved. Knowledge of these complications and their risk of onset is the best means of guiding prevention strategies. The spine surgeon is part of a multidisciplinary team, with the radiologist and electrophysiologist, which is able to identify risk factors preoperatively and diagnose neurologic complications per- or postoperatively.

Change of aortic length after closing-opening wedge osteotomy for patients with ankylosing spondylitis with thoracolumbar kyphosis: a computed tomographic study

STUDY DESIGN

A computed tomographic study.

OBJECTIVE

To investigate the change in aortic length in patients with ankylosing spondylitis (AS) with thoracolumbar kyphosis after closing-opening wedge osteotomy (COWO).

SUMMARY OF BACKGROUND DATA

Several previous studies reported that COWO can effectively correct severe thoracolumbar kyphosis caused by AS. However, one disadvantage of COWO is elongation of the aorta, which increases the risk of aortic injury. To date, no studies have analyzed the alteration in aortic length in patients with AS undergoing COWO for thoracolumbar kyphosis.

METHODS

A total of 21 consecutive patients with AS with a mean age of 38.9 years undergoing COWO for the correction of thoracolumbar kyphosis were retrospectively studied. Radiographical measurements included global kyphosis, thoracic kyphosis, lumbar lordosis, angle of fusion levels, local kyphosis, and anterior height of the osteotomized vertebra. The computed tomographic scans of the spine were used to measure the aortic diameter (at the site of the osteotomy) and length (the length between the superior endplate of the upper instrumented vertebra and the inferior endplate of L4).

RESULTS

The aortic length increased by an average of 2.2 cm postoperatively. Significant changes in global kyphosis, local kyphosis, angle of fusion levels, lumbar lordosis, anterior height of the osteotomized vertebra, and aortic diameter at the site of the osteotomy were observed (P < 0.01). Significant correlation was noted between aortic length and changes in global kyphosis (r = 0.525, P = 0.015), local kyphosis (r = 0.654, P = 0.001), angle of fusion levels (r = 0.634, P = 0.002), and lumbar lordosis (r = 0.538, P = 0.012).

CONCLUSION

Aortic lengthening after COWO for correction of kyphosis was quantitatively confirmed by this study. Spine surgeons should be aware of the potential risk for the development of aortic injury in patients with AS undergoing COWO for the correction of thoracolumbar kyphosis.

LEVEL OF EVIDENCE

4.

JARID1A, JMY, and PTGER4 polymorphisms are related to ankylosing spondylitis in Chinese Han patients: a case-control study

Susceptibility to ankylosing spondylitis (AS) is largely genetically determined. JARID1A, JMY and PTGER4 have recently been found to be associated with AS in patients of western European descent. We aim to examine the influence of JARID1A, JMY, and PTGER4 polymorphisms on the susceptibility to and the severity of ankylosing spondylitis in Chinese ethnic majority Han population. This work can lead the clinical doctors to intervene earlier. Blood samples were drawn from 396 AS patients and 404 unrelated healthy controls. Both the AS patients and the controls are Han Chinese. The AS patients are classified based on the severity of the disease. Thirteen tag single nucleotide polymorphisms (tagSNPs) in JARID1A, JMY and PTGER4 are selected and genotyped. Frequencies of different genotypes and alleles are analyzed among the different severity AS patients and the controls. The rs2284336 SNP in JARID1A, the rs16876619 and rs16876657 SNPs in JMY are associated with susceptibility of AS. The rs11062357 SNP in JARID1A, the rs2607142 SNP in JMY and rs10440635 in PTGER4 are related to severity of AS. Haplotype analyses indicate PTGER4 is related to susceptibility to AS; JARID1A and JMY are related to severity of AS.

Two-level pedicle subtraction osteotomy for severe thoracolumbar kyphotic deformity in ankylosing spondylitis

STUDY DESIGN

A retrospective clinical study.

OBJECTIVE

To evaluate the outcomes of two-level (T12 and L3) pedicle subtraction osteotomy (PSO) for severe thoracolumbar kyphosis in ankylosing spondylitis (AS), and to discuss the surgical strategies of this surgery.

BACKGROUND

Cases were limited on the results of two-level PSO for correction of severe kyphosis caused by AS, nor on surgical strategies of this type of surgery.

METHODS

From March 2006 to December 2010, nine consecutive AS patients with severe kyphotic deformity, underwent T12 and L3 PSOs. Chin-brow vertical angle (CBVA) and radiographic assessments which contain thoracic kyphosis (TK), lumbar lordosis (LL), global kyphosis (GK), and sagittal vertical axis were carefully recorded pre and postoperatively to evaluate the sagittal balance. Intra and postoperative complications were also registered. All patients were asked to fill out Oswestry Disability Index before surgery and at the last follow-up visit.

RESULTS

All nine patients (8M/1F), averaged 41.4 years old (range 35-51 years), were received two-level (T12 and L3) PSO, and were followed up after surgery for a mean of 39.9 months (range 24-68 months). Good cosmetic results were achieved in all patients. Mean correction at two-level PSO was 67.9 ± 5.5°. All CBVA, TK, LL, and GK were changed significantly after surgery (P < 0.05), the mean amount of correction of which were 59.5 ± 13.8, 34.7 ± 3.8, 33.2 ± 2.4, and 54.0 ± 14.8 degrees, respectively, and with a small loss of correction at the last follow-up visit. Sagittal imbalance was significantly improved from 27.3 ± 4.4 to 3.4 ± 0.7 cm postoperatively. Neither mortalities nor any major neurological complications were found. The mean ODI score was significantly improved from 53.4 ± 15.5 before surgery to 8.2 ± 4.7 at the last visit.

CONCLUSION

The outcomes of follow-up showed that two-level (T12 and L3) PSO can effectively and safely correct severe thoracolumbar kyphosis in AS.

Analysis of PPARGC1B, RUNX3 and TBKBP1 polymorphisms in Chinese Han patients with ankylosing spondylitis: a case-control study

Background

Susceptibility to and severity of ankylosing spondylitis (AS) are largely genetically determined. PPARGC1B, RUNX3 and TBKBP1 have recently been found to be associated with AS in patients of western European descent. Our purpose is to examine the influence of PPARGC1B, RUNX3 and TBKBP1 polymorphisms on the susceptibility to and the severity of ankylosing spondylitis in Chinese ethnic majority Han population.

Methods

Blood samples are drawn from 396 AS patients and 404 unrelated healthy controls. All the patients and the controls are Han Chinese and the patients are HLA-B27 positive. The AS patients are classified based on the severity of the disease. Twelve tag single nucleotide polymorphisms (tagSNPs) in PPARGC1B, RUNX3 and TBKBP1 are selected and genotyped. Frequencies of different genotypes and alleles are analyzed among the different severity AS patients and the controls.

Results

After Bonferroni correction, the rs7379457 SNP in PPARGC1B shows significant difference when comparing all AS patients to controls (p = 0.005). This SNP also shows significant difference when comparing normal AS patients to controls (p = 0.002). The rs1395621 SNP in RUNX3 shows significant difference when comparing severe AS patients to controls (p = 0.007). The rs9438876 SNP in RUNX3 shows significant difference when comparing normal AS patients to controls (p = 0.007). The rs8070463 SNP in TBKBP1 shows significant difference in genotype distribution when comparing severe AS patients to controls (p = 0.003).

Conclusions

The rs7379457 SNP in PPARGC1B is related to susceptibility to AS in Chinese Han population. The rs7379457 SNP in PPARGC1B, the rs1395621 and rs9438876 SNPs in RUNX3, and the rs8070463 SNP in TBKBP1 are related to the severity of AS in Chinese Han population.

Pseudo-hypotension in patients with ankylosing spondylitis during posterior osteotomy for correction of kyphosis

STUDY OBJECTIVE

To report the occurrence of pseudo-hypotension during posterior osteotomy for correction of kyphosis in patients with ankylosing spondylitis.

DESIGN

Retrospective case series.

SETTING

University-affiliated hospital.

MEASUREMENTS

The records of 36 patients with ankylosing spondylitis, who had severe thoracolumbar kyphosis and who underwent one-level transpedicular wedge osteotomy for correction from 2008 to 2010, were reviewed. Details of the patients' condition, anesthetic induction and maintenance, hemodynamic responses during correction and the corresponding treatment, intraoperative course, and immediate postoperative neurological complications were analyzed.

MAIN RESULTS

The posterior osteotomy corrected all patients' kyphosis. There were no deaths. In 8 cases, a significant decrease in radial arterial blood pressure (BP) occurred during the correction, but BP recovered to normal levels immediately after the ipsilateral clavicle was drawn downward. Three of the 8 patients suffered numbness and muscle weakness of the upper extremities postoperatively.

CONCLUSIONS

This decrease in BP may be associated with stenosis of the thoracic outlet with compression of neurovascular bundle due to correction, similar to the thoracic outlet syndrome.

Perioperative Outcomes and Complications of Pedicle Subtraction Osteotomy in Cases With Single Versus Two Attending Surgeons

STUDY DESIGN

Retrospective case series.

OBJECTIVE

To assess the perioperative morbidity of pedicle subtraction osteotomy (PSO) based on the presence of 1 versus 2 attending surgeons.

BACKGROUND SUMMARY

Pedicle subtraction osteotomies are challenging cases with high complication rates and substantial physiological burden on patients. The literature supports the benefits of 2-surgeon strategies in complex cases in other specialties.

METHODS

We reviewed a single institution database of all pedicle subtraction osteotomies (78 cases) from 2005-2010 and divided the cohort into single versus 2-surgeon groups (42 vs. 36 cases, respectively). We performed subset analysis after excluding cases before 2007 and excluding patients with staged anterior and posterior procedures. We analyzed cases for estimated blood loss, length of surgery, length of stay, radiographic analysis, rate of return to the operating room within 30 days, and medical and neurological complications.

RESULTS

The groups were similar when comparing mean number of posterior levels fused, levels decompressed and revision rates, however, the average age of the single surgeon and 2 surgeon groups was 57.6 and 64.3 years, respectively (p = .02). The 2 groups had comparable correction of radiographic parameters. Mean percent estimated blood loss for single versus 2 surgeons was 109% versus 35% (p < .001) and estimated blood loss was 5,278 versus 2,003 mL (p < .001). Average surgical time for single versus 2 surgeons was 7.6 versus 5.0 hours (p < .001). A total of 45% of single-surgeon patients compared with 25% of 2-surgeon patients experienced at least 1 major complication within 30 days. In the single-surgeon group, 19% had unplanned surgery within 30 days, versus 8% in the 2-surgeon group.

CONCLUSIONS

The use of 2 surgeons at an experienced spine deformity center decreases the operative time and estimated blood loss, and may be a key factor in witnessed decreased major complication prevalence. This approach also may decrease the rate of premature case termination and return to operating room in 30 days.

Pedicle subtraction osteotomy through pseudarthrosis to correct thoracolumbar kyphotic deformity in advanced ankylosing spondylitis

INTRODUCTION

Surgical treatment is mandatory for spinal pseudarthrosis in advanced ankylosing spondylitis (AS) patients with painful sagittal deformity and/or neurological deficits. However, the most effective and safe surgical procedure for AS-related symptomatic thoracolumbar pseudarthrosis is still controversial. The purpose of this study is to explore the outcomes of pedicle subtraction osteotomy (PSO) at the level of pseudarthrotic lesion combined with supplemental anterior fusion for patients suffering from kyphotic pseudarthrosis in AS.

MATERIALS AND METHODS

Seven AS patients with thoracolumbar pseudarthrosis and kyphotic deformity were reviewed. There were 6 males and 1 female with a mean age of 41.7 years. All patients had back pain. Imaging findings demonstrated 3-column extensive discovertebral destruction in all patients. The preoperative global kyphosis averaged 75° (range, 37°-114°) with the apex at the level of pseudarthrosis. Three patients had incomplete neurological deficits (Frankel D) preoperatively. All patients underwent PSO at the level of pseudarthrosis in the first stage followed by supplemental anterior fusion in the second stage. Radiographic and clinical outcomes were assessed with an average follow-up of 38 months (range, 24-59 months). The visual analogue scale (VAS) was compared before surgery and at the final follow-up.

RESULTS

All patients showed significant pain relief postoperatively and were satisfied with the kyphosis correction as well. Solid bony fusion was shown at the final follow-up. Three patients with neurological deficits had complete recovery of neurological function. The global kyphosis was corrected from 75º to 30º, with a mean correction of 45º. The VAS showed significant improvement. No surgical complication was observed.

CONCLUSION

PSO can be safely performed through the site of pseudarthrotic lesion in AS patients with pseudarthrosis and kyphotic deformity. After PSO, supplemental anterior fusion is sometimes necessary to support the anterior and middle column in a second stage if there is a bone defect in the osteotomy site.

Thoracolumbar imbalance analysis for osteotomy planification using a new method: FBI technique

INTRODUCTION

Treatment of spine imbalance by posterior osteotomy is a valuable technique. Several surgical techniques have been developed and proposed to redress the vertebral column in harmonious kyphosis in order to recreate correct sagittal alignment. Although surgical techniques proved to be adequate, preoperative planning still is mediocre. Multiple suggestions have been proposed, from cutting tracing paper to ingenious mathematical formulas and computerised models. The analysis of the pelvic parameters to try to recover the initial shape of the spine before the spine imbalance occurred is very important to avoid mistakes during the osteotomy planification.

MATERIAL AND METHOD

The authors proposed their method for the osteotomy planning paying attention to the pelvic, and spine parameters and in accordance with Roussouly's classification. The pre operative planning is based on a full-body X-ray including the spine from C1 to the femoral head and the first 10 cm of the femur shaft. Using all the balance parameters provided, a formula name FBI is proposed. Calculation of the osteotomy is basic goniometry, the midpoint of the C7 inferior plateau (point a) is transposed horizontally on the projected future C7 plumb line (point b) crossing posterior S1 plateau on a sagittal X-ray. These are the first two reference points. A third reference point is made on the anterior wall of the selected vertebra for osteotomy at mid height of the pedicle (point c) mainly L4 vertebra. These three points form a triangle with the tip being the third reference point. The angle represented by this triangle is the theoretical angle of the osteotomy. Two more angles should be measured and eventually added. The femur angulation measured as the inclination of the femoral axis to the vertical. And a third angle named the compensatory pelvic tilt to integrate the type of pelvis. If the pelvic tilt is between 15 and 25° or is higher than 25° you must add 5 or 10°, respectively. This compensatory tilt is based on a clinical analysis of operated patients.

RESULTS

This planification was applied in a retrospective study of 18 patients and showed why in some cases improper correction was performed and prospectively in 8 cases with good clinical outcomes and correct spinal alignment. Sometimes it is necessary to find an acceptable compromise when rebalancing the spine paying attention to the general parameters of the patients like: age, osteoporosis, systemic disease etc.

CONCLUSION

This FBI technique can be used even for small lordosis restoration: it gave a good evaluation of the amount of correction needed and then the surgeon had the choice to use the appropriate technique to obtain a good balance.

2010 update of the ASAS/EULAR recommendations for the management of ankylosing spondylitis

This first update of the ASAS/EULAR recommendations on the management of ankylosing spondylitis (AS) is based on the original paper, a systematic review of existing recommendations and the literature since 2005 and the discussion and agreement among 21 international experts, 2 patients and 2 physiotherapists in a meeting in February 2010. Each original bullet point was discussed in detail and reworded if necessary. Decisions on new recommendations were made — if necessary after voting. The strength of the recommendations (SOR) was scored on an 11-point numerical rating scale after the meeting by email. These recommendations apply to patients of all ages that fulfill the modified NY criteria for AS, independent of extra-articular manifestations, and they take into account all drug and non-drug interventions related to AS. Four overarching principles were introduced, implying that one bullet has been moved to this section. There are now 11 bullet points including 2 new ones, one related to extra-articular manifestations and one to changes in the disease course. With a mean score of 9.1 (range 8-10) the SOR was generally very good.

Biomechanical analysis of cervicothoracic junction osteotomy in cadaveric model of ankylosing spondylitis: effect of rod material and diameter

Object

Ankylosing spondylitis (AS) is a genetic condition that frequently results in spinal sagittal plane deformity of thoracolumbar or cervicothoracic junctions. Generally, a combination of osteotomy and spinal fixation is used to treat severe cases. Although surgical techniques for traumatic injury across the cervicothoracic junction have been well characterized in clinical and biomechanical literature, the specific model of instrumented opening wedge osteotomy in autofused AS has not been studied biomechanically. This study characterizes the structural stability of various posterior fixation techniques across the cervicothoracic junction in spines with AS, specifically considering the effects of posterior rod diameter and material type.

Methods

For each of 10 fresh-frozen human spines (3 male, 7 female; mean age 60 ± 10 years; C3–T6), an opening wedge osteotomy was performed at C7–T1. Lateral mass screws were inserted bilaterally from C-4 to C-6 and pedicle screws from T-1 to T-3. For each specimen, 3.2-mm titanium (Ti), 3.5-mm Ti, and 3.5-mm cobalt chromium (CoCr) posterior spinal fusion rods were tested. To simulate the anterior autofusion and long lever arms characteristic of AS, anterior cervical plates were placed from C-4 to C-7 and T-1 to T-3 using fixed angle screws. Nondestructive flexion-extension, lateral bending, and axial rotation tests were conducted to 3.0 Nm in each anatomical direction; 3D motion tracking was used to monitor primary range of motion across the osteotomy (C7–T1). Biomechanical tests used a repeat-measures test design. The order of testing for each rod type was randomized across specimens.

Results

Constructs instrumented with 3.5-mm Ti and 3.5-mm CoCr rods were significantly stiffer in flexion-extension than those with the 3.2-mm Ti rod (25.2% ± 16.4% and 48.1% ± 15.3% greater than 3.2-mm Ti, respectively, p < 0.05). For axial rotation, the 3.5-mm Ti and 3.5-mm CoCr constructs also exhibited a significant increase in rigidity compared with the 3.2-mm Ti construct (36.1% ± 12.2% and 52.0% ± 20.0%, respectively, p < 0.05). There were no significant differences in rigidity seen between the 3 types of rods in lateral bending (p > 0.05). The 3.5-mm CoCr rod constructs showed significantly higher rigidity in flexion-extension than the 3.5-mm Ti rod constructs (33.1% ± 15.5%, p < 0.05). There was a trend for 3.5-mm CoCr to have greater rigidity in axial rotation (36.2% ± 18.6%), but this difference was not statistically significant (p > 0.05).

Conclusions

The results of this study suggest that 3.5-mm CoCr rods are optimal for achieving the most rigid construct in opening wedge osteotomy in the cervicothoracic region of an AS model. Rod diameter and material properties should be considered in construct strategy. Some surgeons have advocated anterior plating in patients with AS after osteotomy for additional stability and bone graft surface. Although this effect was not examined in this study, additional posterior stability achieved with CoCr may decrease the need for additional anterior procedures.

Personalised modified osteotomy using computer-aided design-rapid prototyping to correct thoracic deformities

The correction of severe thoracic deformities is challenging. However, the usual imaging modalities are not sufficient for performing the surgery. Our objective was to describe the procedure and results of posterior modified wedge osteotomy aided by the techniques of computer-aided design-rapid prototyping (CAD-RP) to correct thoracic deformities. Twenty-one patients with thoracic deformities (eight males; 13 females) formed the study group. All patients underwent computed tomography (CT) scanning and CAD-RP, and a model of thoracic deformities and navigation templates of pedicles were created for each patient and used to analyse the spinal deformities and serve as anatomical reference. Aided by these models, personalised modified wedge osteotomy combining the eggshell technique and posterior vertebral column resection was performed. Using CAD-RP improved the safety and accuracy of surgery and screw placement in the 21 patients in whom 41 vertebrae were removed and 216 pedicle screws were placed. The average operation time was 260 (200-420) min, with an average blood loss of 1,900 ml (range 800-3560 ml). The percentage of deformity correction was 56.3% (from 72.1° to 31.5°) in the coronal plane and 60.4% (from 81.6° to 32.3°) in the sagittal plane. No patient had serious complications or implant failure. Personalised single-stage posterior modified wedge osteotomy is an effective procedure for treating thoracic deformities. Using CAD-RP and the RP models have significant benefits for personalised surgical treatment of complex thoracic deformities.

Osteotomy of the spine to correct the spinal deformity

There are a number of reports on Smith-Petersen osteotomy (SPO), pedicle subtraction osteotomy (PSO) and vertebral column resection (VCR). However, there are few systematic reviews of all three kinds of osteotomies. Literature review and author's experience of SPO, PSO and VCR osteotomy will be described. Various surgical techniques can be applied according to the disease entity and magnitude of the deformity. The most appropriate methods for deformity correction should be chosen and the potential complications should be considered. Before attempting an osteotomy of the spine for a spinal deformity, sufficient surgical experience and a thorough understanding of the anatomy of the spine and adjacent structures are needed. In addition, a well-organized team with the other departments is essential.