Analysis of serum levels of titanium and aluminium ions in patients with early onset scoliosis operated upon using the magnetic growing rod—a single centre study of 14 patients

Study design A cross-sectional retrospective Level 3 study. Objective To study the serum levels of Titanium and Aluminium ions in patients operated using the magnetically controlled growing rod (MCGR) system. Summary of background data 14 consecutive patients of early onset scoliosis with varying etiology managed with MCGR system with a minimum follow-up of 24 months were selected for the study. The group consisted of two boys (14.3%) and 12 girls (85.7%). The average age of the patients at the time of surgery was 10.4 years (5–15 years). The average period of follow-up was 43.7 months (28–79 months). After informed consent of the subjects and their caretakers, serum levels of titanium and aluminium were measured. These levels were then assessed with regards to the number of screws used, number of distractions and complications. Methods The concentration of titanium and aluminium ions in the serum was measured using high resolution inductively coupled plasma mass spectrometry. Results For the sake of ease of assessment, patients were divided into three etiology-based groups—idiopathic (n = 6), neuromuscular (n = 2) and syndromic (n = 6). The mean serum titanium level was 15.9 μg/L (5.1–28.2 μg/L) while that of aluminium was 0.1 μmol/L (0.1–0.2 μmol/L). Of the 14 patients, 2 (14.2%) patients had mechanical failure (actuator pin dysfunction), 3 (21.4%) had rod breakage requiring revision surgery and one patient (7.1%) had surgical site infection managed with appropriate antibiotics. Patients undergoing revision for rod breakage did not show any metallosis of the tissues during surgery. Conclusion Analysis of patients with scoliosis operated using the magnetic growing rod system concludes that it is accompanied by presence of titanium in the blood but whether clinically significant or not needs to be ascertained by comparison of preoperative and postoperative blood concentrations of the titanium ions in individual subjects. The aluminium ion concentration remains within normal limits. Though implant malfunction may raise the titanium levels in the blood, its clinical significance needs to be determined. The aluminium levels are not affected irrespective to the presence or absence of complications. The long-term effects of raised titanium levels in the blood also warrant further prospective studies designed for precise and deeper analyses.

Determination of limiting and legitimate values of drawing coeffi cient and delta-criterion for deformation zone shape during wire drawing

The limiting and legitimate values of the drawing coefficient and delta-criterion Δ for the deformation zone shape depending on the friction coefficient for different models of hardening and the values of the drawing angle and the back-pull stress are determined by numerically solving the corresponding equations. The limiting and legitimate values of the drawing coefficient decrease with increase in the friction coefficient, while the analogous values of the criterion increase. Increase in the safety factor causes decrease in the allowable drawing and increase in the delta-criterion. The limiting and legitimate values of the drawing coefficient decrease from the application of back tension in the absence of strain hardening. The nature of the effect of back tension on the limiting and legitimate values of the drawing coefficient and the delta-criterion depends on the deformation parameters with intensive hardening and significant value of the friction coefficient. The possibility of the absence of limiting values of the drawing coefficient and criterion Δ under hypothetical drawing conditions is shown: intensive hardening of the wire material at low friction coefficient and the calculation of the limiting values of these indicators based on the value of the I.L. Perlin safety factor, equal to 1. The estimation of the reliability of the approximate equality is carried out to determine the nature of the relationship between the criterion Δ and the index of the deformed state. It is shown that with small value of the delta-criterion (Δ < 2) wire breakage at the die exit is not guaranteed, since the limiting value of the drawing coefficient is slightly greater than 1. The drawing production technologist needs assessment of the limiting and legitimate values of the drawing coefficient and delta-criterion for predicting of wire (rod) breakage at given deformation parameters.

Scoliosis Research Society-Schwab Grade 6 Osteotomy for Severe Congenital Angular Kyphoscoliosis: An Analysis of 17 Cases With a Minimum 2-Year Follow-up

BACKGROUND For some patients with severe congenital angular kyphoscoliosis (SCAK), 1-level vertebral column resection is insufficient and the Scoliosis Research Society (SRS)-Schwab Grade 6 osteotomy may be necessary. However, the indications and clinical outcomes of SRS-Schwab Grade 6 osteotomy in patients with SCAK have not been investigated in depth. OBJECTIVE To investigate the middle-term radiographic and clinical outcomes, and to evaluate the safety of this high technique-demanding procedure. METHODS Patients with SCAK undergoing SRS-Schwab Grade 6 osteotomy from 2005 to 2016 followed up at least 2 yr were retrospectively reviewed. The potential indications of SRS-Schwab Grade 6 osteotomy were analyzed. The coronal Cobb angle, segmental kyphosis (SK), deformity angular ratio (DAR), coronal balance, and sagittal vertical axis (SVA) were measured in the preoperative, postoperative, and final follow-up. The intraoperative and postoperative complications were recorded. RESULTS A total of 17 patients with SCAK (10 M and 7F) were included, and the mean follow-up was 30.8 ± 16.4 mo. The indications of SRS-Schwab Grade 6 osteotomy were as follows: multiple “pushed-out” hemivertebrae (13, 76.5%) and multilevel anterior block (4, 23.5%). Compared with preoperation, the coronal Cobb angle, SK and SVA at postoperation were significantly improved (P &lt; .05 for all). The mean total DAR was 33.4 ± 9.9 at preoperation. Three patients were found to have postoperative neurological deficit. Rod breakage occurred in 3 patients at 15- to 48-mo follow-up, and revision surgeries were performed. At the last follow-up, firm bony fusion was observed in all patients. CONCLUSION The technique-demanding SRS-Schwab Grade 6 osteotomy, if well indicated, could provide satisfying correction of the SCAK deformity.

Instrumented surgical treatment for metastatic spinal tumors: is fusion necessary?

OBJECTIVEThe goal of this study was to evaluate the radiographic and clinical results of instrumentation surgery without fusion for metastases to the spine.METHODSBetween 2010 and 2017, patients with spinal tumors who underwent instrumentation without fusion surgery were consecutively evaluated. Preoperative and postoperative clinical data were evaluated. Data were inclusive for last follow-up and just prior to death if the patient died. Instrumentation-related complications included screw migration, screw or rod breakage, cage migration, and screw loosening.RESULTSExcluding patients who died within 6 months, a total of 136 patients (140 operations) were recruited. The average follow-up duration was 16.5 months (median 12.4 months). The pain visual analog scale score decreased from 6.4 to 2.5 (p < 0.001) and the Eastern Cooperative Oncology Group scale score improved (p < 0.001). There were only 3 cases (2.1%) of symptomatic instrumentation-related complications that resulted in revisions. There were 6 cases of nonsymptomatic complications. The most common complication was screw migration or pull-out (5 cases). There were 3 cases of screw or rod breakage and 1 case of cage migration. Two-thirds of the cases of instrumentation-related complications occurred after 6 months, with a mean postoperative period of 1 year.CONCLUSIONSThe current study reported successful outcomes with very low complication rates after nonfusion surgery for patients with spinal metastases, even among those who survived for more than 6 months. More than half of the instrumentation-related complications were asymptomatic and did not require revision. The results suggest that nonfusion surgery might be sufficient for a majority of patients with spinal metastases.

EVALUATION OF ROD BREAKAGE AFTER THREE-COLUMN OSTEOTOMY

ABSTRACT Objective To identify the incidence and possible risk factors associated with rod breakage in patients who underwent vertebral column resection (VCR) or pedicle subtraction osteotomy (PSO) to treat complex deformities of the spine. Methods Retrospective analysis of a series of 32 patients operated from 2014 to 2018 in a single center. The patients were analyzed for demographic (sex, age), biometric (BMI), radiographical (pre- and postoperative angular variations), and surgical (arthrodesed and osteotomized levels) characteristics. Descriptive analyses were performed for the numerical variables (mean, standard deviation, maximum, median, and minimum) and frequency analysis was performed for the categorical variables. Logistic regression analysis was performed for the dependent variable “rod breakage”, using a stepwise technique to select the variables for the best model, assuming statistical significance of 0.05. Results Of the 32 patients selected, rod breakage occurred in 34.4%. Mean age was 36.6 years (± 19.8), ranging from 10 to 74 years, and the mean BMI was 25.1 (±6.0). Most patients were subjected to VCR (75.0%), were males (56.2%) and did not smoke (90.6%). Logistic regression analysis showed that “arthrodesed levels” were was positively associated with rod breakage (OR 1.72; CI95%: 1.13-3.10; p<0.05). The other factors were not associated with breakage. Conclusion Rod breakage is a frequent complication after three-column osteotomy, especially in long constructions. Level of evidence III; Retrospective Study.

Complication rates associated with 3-column osteotomy in 82 adult spinal deformity patients: retrospective review of a prospectively collected multicenter consecutive series with 2-year follow-up

OBJECTIVEAlthough 3-column osteotomy (3CO) can provide powerful alignment correction in adult spinal deformity (ASD), these procedures are complex and associated with high complication rates. The authors' objective was to assess complications associated with ASD surgery that included 3CO based on a prospectively collected multicenter database.METHODSThis study is a retrospective review of a prospectively collected multicenter consecutive case registry. ASD patients treated with 3CO and eligible for 2-year follow-up were identified from a prospectively collected multicenter ASD database. Early (≤ 6 weeks after surgery) and delayed (> 6 weeks after surgery) complications were collected using standardized forms and on-site coordinators.RESULTSOf 106 ASD patients treated with 3CO, 82 (77%; 68 treated with pedicle subtraction osteotomy [PSO] and 14 treated with vertebral column resection [VCR]) had 2-year follow-up (76% women, mean age 60.7 years, previous spine fusion in 80%). The mean number of posterior fusion levels was 12.9, and 17% also had an anterior fusion. A total of 76 early (44 minor, 32 major) and 66 delayed (13 minor, 53 major) complications were reported, with 41 patients (50.0%) and 45 patients (54.9%) affected, respectively. Overall, 64 patients (78.0%) had at least 1 complication, and 50 (61.0%) had at least 1 major complication. The most common complications were rod breakage (31.7%), dural tear (20.7%), radiculopathy (9.8%), motor deficit (9.8%), proximal junctional kyphosis (PJK, 9.8%), pleural effusion (8.5%), and deep wound infection (7.3%). Compared with patients who did not experience early or delayed complications, those who had these complications did not differ significantly with regard to age, sex, body mass index, Charlson Comorbidity Index, American Society of Anesthesiologists score, smoking status, history of previous spine surgery or spine fusion, or whether the 3CO performed was a PSO or VCR (p ≥ 0.06). Twenty-seven (33%) patients had 1–11 reoperations (total of 44 reoperations). The most common indications for reoperation were rod breakage (n = 14), deep wound infection (n = 15), and PJK (n = 6). The 24 patients who did not achieve 2-year follow-up had a mean of 0.85 years of follow-up, and the types of early and delayed complications encountered in these 24 patients were comparable to those encountered in the patients that achieved 2-year follow-up.CONCLUSIONSAmong 82 ASD patients treated with 3CO, 64 (78.0%) had at least 1 early or delayed complication (57 minor, 85 major). The most common complications were instrumentation failure, dural tear, new neurological deficit, PJK, pleural effusion, and deep wound infection. None of the assessed demographic or surgical parameters were significantly associated with the occurrence of complications. These data may prove useful for surgical planning, patient counseling, and efforts to improve the safety and cost-effectiveness of these procedures.

A Novel 4-Rod Technique Offers Potential to Reduce Rod Breakage and Pseudarthrosis in Pedicle Subtraction Osteotomies for Adult Spinal Deformity Correction

BACKGROUND Pedicle subtraction osteotomy (PSO) can be used to treat rigid sagittal plane deformities. Nonunions and rod breakages are known complications of PSO. OBJECTIVE To assess outcomes of 2 methods of posterior instrumentation for PSO, traditional 2 rods vs a novel 4-rod technique in which 2 additional rods span only the osteotomy level. METHODS This study was a retrospective, radiographic review of consecutive PSOs performed at 2 centers. The primary difference in technique between the centers was the use of 4 rods including 2 independent rods attached only to the vertebral levels immediately adjacent to the PSO (group 1, n = 29 patients) vs the traditional 2-rod technique (group 2, n = 20 patients). RESULTS Demographics and preoperative to postoperative radiographic measurements were similar between the study groups, including the PSO wedge resection angle (P = .56). The rod breakage rate was 25% with 2 rods and 0% with 4 rods (P = .008), and the pseudarthrosis rate with 2 rods was 25% and with 4 rods was 3.4% (P = .035). The patient with pseudarthrosis from group 1 had an infection and developed pseudarthrosis only after instrumentation removal. Rates of other complications did not differ significantly between the study groups. CONCLUSION This study provides a comparison between 2 techniques for rod placement across a PSO and suggests that the described novel 4-rod technique may help to reduce the rates of pseudarthrosis and rod failure. It will be important to confirm these findings in a prospectively designed study with multiple institutions in order to better control for potentially confounding factors.