Number Of Instrumented Levels Research Articles

Prevention of Proximal Junctional Kyphosis: Are Polyaxial Pedicle Screws Superior to Monoaxial Pedicle Screws at the Upper Instrumented Vertebrae?

Evidence regarding whether the polyaxial pedicle screws at the upper instrumented vertebrae (UIV) are superior to monoaxial pedicle screws in prevention of proximal junctional kyphosis (PJK) is not clear. The aim of this study was therefore to explore the influence of different types of pedicle screws at UIV on the incidence of PJK. We reviewed retrospectively 242 patients surgically treated with instrumented segmental posterior spinal fusion at a minimum of 4 motion segments. Polyaxial pedicle screws were used at UIV in 125 patients (polyaxial group), and monoaxial pedicle screws were used at UIV in 117 patients (monoaxial group). According to the occurrence of PJK at final follow-up, patients in both the polyaxial and monoaxial groups were then divided into 2 subgroups: PJK and no proximal junctional kyphosis (NPJK). To investigate the risk factors of PJK, 2 categorized variables were analyzed statistically: 1) patient characteristics: age, sex, body mass index (BMI), bone mineral density (BMD), sagittal vertical axis (SVA), thoracic kyphosis, thoracolumbar junctional angle, lumbar lordosis (LL), pelvic incidence, pelvic tilt, and sacral slope. 2) Surgical variables: Changes of radiographic parameters include the SVA, thoracic kyphosis, thoracolumbar junctional, LL, pelvic incidence, pelvic tilt, sacral slope, pedicle-upper end plate angle, the number of instrumented levels, and the most proximal and distal levels of the instrumentation. PJK was developed in 26 of 117 patients (22.2%) in the monoaxial group and 30 of 125 patients (24.0%) in the polyaxial group. Until the final follow-up, there was no significant difference in the incidence of PJK (χ2= 0.107, P= 0.734) between the monoaxial and polyaxial groups. There was no significant difference in patient characteristics and surgical variables between the 2 groups, except the proximal junctional angle change (P= 0.031). In the monoaxial group, there were no significant differences in patient characteristics between the PJK and NPJK subgroups, except BMI (P= 0.042) and BMD (P= 0.037). There were no significant differences in change of radiographic parameters, except SVA change (P= 0.036), proximal junctional angle change (P= 0.029), LL change (P= 0.025), and lower instrumented vertebrae location (P= 0.036). Multivariate logistic regression analysis revealed that obesity, osteoporosis, lower instrumented vertebra at sacrum, and LL change >10 degrees were independently associated with PJK. In the polyaxial group, there were no significant differences in patient characteristics between the PJK and NPJK subgroups, except BMI (P= 0.032) and BMD (P= 0.040). There were no significant differences in change of radiographic parameters between the PJK and NPJK subgroups, except P-UP angle (P= 0.037) and lower instrumented vertebrae location (P= 0.017). Multivariate logistic regression analysis revealed that obesity, osteoporosis, and lower instrumented vertebra at sacrum were independently associated with PJK. Polyaxial pedicle screws at UIV is not superior to monoaxial pedicle screws in prevention of PJK. Obesity, osteoporosis, and lower instrumented vertebra at sacrum are risk factors for PJK in all the patients. Excessive LL reconstruction is the unique risk factor of PJK when monoaxial pedicle screws were used at UIV.

Incidence and risk factors for the progression of proximal junctional kyphosis in degenerative lumbar scoliosis following long instrumented posterior spinal fusion.

The aim of this study was to identify the prevalence of proximal junctional kyphosis (PJK) in degenerative lumbar scoliosis (DLS) following long instrumented posterior spinal fusion, and to search for predictable risk factors for the progression of junctional kyphosis.In total 98 DLS patients with a minimum 2-year follow-up were reviewed prospectively. According to the occurrence of PJK at the last follow-up, patients were divided into 2 groups: PJK group and non-PJK group. To investigate risk values for the progression of PJK, 3 categorized factors were analyzed statistically: patient characteristics—preoperative data of age, sex, body mass index (BMI), bone mineral density (BMD) were investigated; surgical variables—the most proximal and distal levels of the instrumentation, the number of instrumented levels; pre- and postoperative radiographic parameters include the scoliotic angle, sagittal vertical axis, thoracic kyphosis, thoracolumbar junctional angle, lumbar lordosis, pelvic incidence, pelvic tilt, and sacral slope.PJK was developed in 17 of 98 patients (17.3%) until to the final follow-up and were enrolled as the PJK group, and 81 patients without PJK at final follow-up were enrolled as the non-PJK group. There was no statistically significant difference between the 2 groups in age at operation (P = 0.900). The patient's sex was excluded in statistical analysis because of the predominance of female patients. There were statistically significant difference between the 2 groups in BMI ([25.5 ± 1.7] kg/m2 in the PJK group and [23.6 ± 1.9] kg/m2 in the non-PJK group, P < 0.001) and BMD ([–1.4 ± 0.8] g/cm2 in the PJK group and [−0.7 ± 0.3] g/cm2 in the non-PJK group, P < 0.001). No specific surgery-related variables were found to be associated with an increased risk of developing PJK, except when the most proximal instrumented vertebrae stopped at thoracolumbar junction (T11-L1). The upper instrumentation vertebrae (UIV) at thoracolumbar junction was more common in the PJK group than that in the non-PJK group (P = 0.007). No preoperative and early postoperative variable did reveal a statistically significant difference between the 2 groups. When included in a multivariate logistic regression model, BMI>25 kg/m2, osteoporosis, and UIV at thoracolumbar junction were independently associated with PJK.In conclusion, osteoporosis, obesity, and UIV at thoracolumbar junction are risk factors for the development and progression of PJK in DLS patients following long instrumented posterior spinal fusion. Antiosteoporosis treatment extends the fusion level above the thoracolumbar region and controlling body weight before and after surgery could provide opportunities to reduce the rate of PJK and to improve therapeutic outcomes.

Special article: Update on the magnetically controlled growing rod: tips and pitfalls.

Magnetically controlled growing rods (MCGR) have become an important treatment option in young patients with spinal deformities. This device allows for gradual lengthening on an outpatient setting with continuous neurological monitoring in an awake patient. With its growing popularity and interest, this study reports the tips, pitfalls, and complications of the MCGR for management of scoliosis. On 3 June 2015 at the University of Hong Kong, 32 participants from 16 regions shared their experience with MCGR. Current indications for surgery include early-onset scoliosis patients. Adolescent idiopathic scoliosis and congenital scoliosis patients have less favourable outcomes. The number of instrumented levels should be minimised, as all instrumented levels must be included in the definitive fusion surgery. Rod contouring is important and owing to the straight portion of the rod housing the magnet, there is limited proximal rod portion for proper contouring, which may predispose to proximal junctional kyphosis. There is currently no consensus on the rod configuration, timing, frequency, technique, and amount of distraction. Risk factors for distraction failure include larger patients, internal magnets too close to each other, and magnets too close to the apex of the major curve. Future studies should resolve the issues regarding the technique of distraction, optimal frequency and amount of distraction per session. More comprehensive cost analyses should be performed.

Are Rib Versus Spine Anchors Protective Against Breakage of Growing Rods?

Study DesignRetrospective multicenter, case-control study. ObjectiveTo compare the risks of rod breakage and anchor complications between distraction-based growing rods with proximal spine versus rib anchors. Summary of Background DataRod breakage is a known complication of distraction-based growing rod instrumentation. MethodsA total of 176 patients met inclusion criteria: minimum 2-year follow-up, younger than age 9 years at index surgery, non–Vertical Expandable Prosthetic Titanium Rib distraction-based growing rods, and known anchor locations. Mean follow-up was 56 months (range, 24–152 months). Survival analyses using Cox proportional hazards model (accounting for varying lengths of follow-up) of rod breakage, anchor complications, preoperative Cobb angle, number of growing rods, age, and number of levels instrumented were performed using a significance level of p < .05. ResultsThirty-four patients had rib-anchored growing rods and 142 had spine-anchored growing rods. This analysis found that proximal rib-anchored growing rods have a 23% risk of lifetime rod breakage compared with spine-anchored growing rods (6% vs. 29%) (p = .041) without a significant increase in risk of anchor complications (38% vs. 33%) (p = .117). The number of implanted rods (p = .839), age (p = .649), and number of instrumented levels (p = .447) were not statistically significant regarding rod breakage risk, although higher preoperative Cobb angles were significant (p = .014). ConclusionsPreoperative Cobb angle appears to be the most influential factor in determining whether growing rods break (p = .014). Univariate analysis found that rib anchors were associated with less than one-fourth the risk of rod breakage than spine anchors (p = .04) but multivariate analysis found no significant association between anchors and rod breakage (p = .07). This trend suggests that rib-anchored growing rod systems may be associated with less rod breakage because the system is less rigid as a result of some “slop” at the hook–rib interface, as well as the normal motion of the costovertebral joint.

Morbidity and mortality in adult spinal deformity surgery: Norwich Spinal Unit experience

This study analyses the complications of spinal deformity surgery in adults to highlight pre-disposing factors. The clinical records and imaging were reviewed for 48 consecutive patients, 12 males and 36 females, with a mean age of 64 (31-86), who had surgery for spinal deformity. Mean follow-up time was 36 months (24-60). Patient data recorded were age, diagnosis and co-morbidities; deformity assessment: curve type, sagittal and coronal balance, Cobb angle. Operation details: number of instrumented levels, duration and intra-operative complications. complications, re-operations, balance and Cobb angle. 28 patients (58 %) had at least 1, 15 patients (27 %) had 2 and 5 patients (9.5 %) had more than 2 co-morbidities. Average time between 1st presentation and operation was 13 months (1-41). The mean number of levels fused was 10.8 (4-23). In addition to posterior pedicle screw instrumentation, 40 patients had chevron osteotomies and 8 had pedicle substraction osteotomies. Posterior interbody fusions were performed at one level in 17 of which 7 had 2 level fusion. Two patients had combined anterior and posterior approaches. Fusion to the pelvis was performed in 19 patients. There were a total of 27 major and minor complications in 19/48 (39.5 %) patients. Late complications included 5 patients who had revisions for proximal junctional kyphosis, 1 patient had revision for pseudoarthrosis and 4 patients had removal of mal-positioned screws. Factors associated with high complication rate in adult spinal deformity surgery are age, co-morbidities and severe sagittal imbalance at the time of presentation.

Does Wide Posterior Multiple Level Release Improve the Correction of Adolescent Idiopathic Scoliosis Curves?

Retrospective matched cohort study. To compare results of posterior correction and fusion with a hybrid construct using a standard posterior release (SPR) versus adding a wide posterior release (WPR), in adolescent idiopathic scoliosis (AIS) treated at a single institution, with a minimum 2-year follow-up. Although the importance of posterior release has been enhanced for the correction of AIS, there have been no reports comparing correction results when posterior wide release (excision of all posterior ligaments and bilateral extended facetectomy at multiple levels) is used. A retrospective study of 46 patients with AIS was performed. Posterior-only hybrid instrumentation with sublaminar wires was included. SPR group consisted of 25 patients and WPR group consisted of 21 patients. There was no difference in sex, age, type of curve, number of instrumented levels, length of surgery, and preoperative main curve Cobb (SPR: 60±10 degrees WPR: 59±8 degrees). In the WPR group, the amount of main curve correction obtained was significantly greater (SPR: 57% vs. WPR: 68.6%) P<0.001, and maintained at final follow-up (SPR: 51.6% vs. WPR: 61.8%) P<0.05. Preoperative and postoperative proximal thoracic and lumbar secondary curves were similar in both the groups. T5-T12 preoperative kyphosis were (SPR: 22.2±11 degrees vs. WPR: 19±11 degrees) the degrees corrected in postoperation (SPR: +1.2±6 degrees vs. WPR: -0.9±9 degrees) and at final follow-up (SPR: +1.6±8 degrees vs. WPR: -0.8±11 degrees), and were not statistically different P>0.05. Minor complications were similar in both groups and no major complications were found. Posterior wide release at multiple levels improves coronal main curve correction in patients with AIS, without an increase in the incidence of complications. Furthermore, it improves fusion surface and makes insertion of sublaminar wires easier.

Selection of short- or long-segment posterior fixation for treatment of unstable thoracolumbar fractures

Objective To discuss the selection of short- or long-segment posterior fixation for treatment of unstable thoracolumbar fractures. Methods A total 134 patients with thoracolumbar fractures treated with pedicle instrument fixation from January 2005 to December 2008 were studied retrospectively. According to AO fracture classification, there were 70 patients with type A fractures, 37 with type B and 27 with type C. The patients were divided into two groups according to the number of instrumented levels; short-segment posterior fixation (SSPF) group (four screws; one vertebral body above or below the fractured vertebrae) and long-segment posterior fixation (LSPF) group (eight screws; two vertebral bodies above or below the fractured vertebrae). Clinical outcomes and radiological parameters (superior-inferior endplate angle, vertebral body angle, displacement of vertebral body) were compared according to AO fracture classification. Results All type A fractures were treated with SSPF, mean superior-inferior endplate angle changed from preoperative 21.3° to postoperative 8.5° and 11.1° at final follow up. There was no statistical difference in the correction of Cobb angle for type B fractures in SSPF group (26 patients) and LSPF group (11 patients), while the correction loss of vertebral body angle was 3. 64° in SSPF group and 1.09° in LSPF group, with statistical difference (P < 0. 05). There was no statistical difference in the correction of Cobb angle for type C fractures in SSPF group (7 patients) and in LSPF group (20 patients), but the correction loss of vertebral body angle was 3.6° in SSPF group and 0. 8° in LSPF group, with statistical difference (P < 0. 05). There was no statistical difference in vertebral displacement correction. Conclusions Most types A and Bl fractures should be treated with SSPF; most types B2, B3 and C fractures should be treated with LSPF. Key words: Spinal fractures; Thoracic vertebrae; Lumbar vertebrae; Fracture fixation, internal; Fracture classification

Does Superior-Segment Facet Violation or Laminectomy Destabilize the Adjacent Level in Lumbar Transpedicular Fixation?

This is an in vitro biomechanical study. The current investigation was performed to evaluate adjacent level kinematic change following unilateral and bilateral facet violation and laminectomy following 1-, 2-, and 3-level reconstruction. The incidence of superior-segment facet violation with lumbar transpedicular fixation has been reported as high as 35%; however, its contribution to biomechanical instability at the supradjacent level is unknown. In addition, superior-segment laminectomy has been implicated as a risk factor for the development of adjacent level disease. The authors assess the acute biomechanical effects of proximal facet violation and subsequent laminectomy in an instrumented posterior fusion model in 10 cadaveric specimens. Biomechanical testing was performed on 10 human cadaveric spines under axial rotation (AR), flexion-extension (FE), and lateral bending (LB) loading. After intact analysis, pedicle screws were inserted from L5-S1 and testing repeated with: (1) preserved L4-L5 facets, (2) unilateral facet breach, (3) bilateral breach, and (4) L5 laminectomy. Following biomechanical analysis, instrumentation was extended to L4, then L3 and biomechanical testing repeated. Full range of motion (ROM) at the proximal adjacent levels were recorded and normalized to intact (100%). Supradjacent level ROM was increased for all groups under all loading methods relative to intact (P < 0.05). However, AR testing revealed progressive instability at the adjacent level in groups 3 and 4, relative to group 1, following 1-, 2- and 3-level fixation (P < 0.05). During FE, supradjacent level ROM was significantly increased for group 4 specimens compared with group 1 after L5-S1 fixation (P < 0.05), and was greater than all other groups for L3-S1 constructs (P < 0.05). Interestingly, under lateral bending, facet joint destabilization did not change adjacent segment ROM. There were significant changes in proximal level ROM immediately after posterior stabilization. However, an additional increase in supradjacent segment ROM was recorded during AR after bilateral facet breach.Subsequent complete laminectomy at the uppermostfixation level further destabilized the supradjacent segment in FE and AR. Therefore, meticulous preservation of the cephalad-most segment facet joints-is paramount to ensure stability.

Anterior Thoracoscopic Instrumentation in Adolescent Idiopathic Scoliosis

A Systematic Review of published series of patients with adolescent idiopathic scoliosis treated with anterior thoracoscopic instrumentation. To conduct a systematic review of the results of thoracoscopic surgery and to compare them with those of open anterior and posterior spine instrumentation to enable surgeons judge the applicability of the method. Instrumentation through video-assisted thoracoscopic surgery is an attractive alternative for the treatment of thoracic adolescent idiopathic scoliosis. The advantages claimed by its proponent over conventional instrumentations are better cosmesis and reduced morbidity due its minimal invasive nature. However, superiority of thoracoscopic instrumentation over conventional methods has not been proven so far. Via Medline, Pubmed, and other literature searches, 8 articles met the inclusion criteria for our systematic review. The evaluations were made according to the parameters employed for evaluating spinal deformities. Instrumentation through video-assisted thoracoscopic surgery results were compared to those of open anterior or posterior surgeries. Mean number of instrumented levels was 7. The extent of disc excision was not indicated in any of the studies. The mean operative time was found to be approximately 5.2 hours. Average blood loss was 391.7 mL (100-1300 mL). The average Cobb curve correction was 64.6%. The mean preoperative kyphosis angle was 21.3 degrees ; the postoperative kyphosis angle was 25.2 degrees . These angular corrections were found to be comparable to posterior procedures using hooks, but less than with pedicle screws. Two studies reported on patient satisfaction favoring thoracoscopic instrumentation. Instrumentation-related complications were the most predominant. Anterior thoracoscopic instrumentation is comparable in terms of curve correction to anterior or posterior procedures. Theoretical advantages of better cosmesis and less aggressiveness seem to be offset by the increased operative and intensive care unit time, and complication rate. More prospective studies need to be conducted to determine the benefit and general applicability of this procedure.

Perioperative Aspects of Endoscopic Anterior Scoliosis Surgery: The Learning Curve for a Consecutive Series of 100 Patients

The reported benefits of endoscopic versus open scoliosis surgery include improved visualization, a muscle sparing approach, reduced pulmonary morbidity, reduced pain, and improved cosmesis. Some aspects of the surgical learning curve for this technically demanding method have been previously reported; however, improvements in other factors with increasing experience have not been quantified. This paper presents a series of 100 consecutive endoscopic anterior scoliosis corrections performed between April 2000 and February 2006. We report changes in the following perioperative factors with increasing experience; operative set-up time, operative time, x-ray irradiation time, number of instrumented levels, blood loss, intercostal catheter drainage, chest drain removal time, days in intensive care, days to mobilize, days in hospital, and early complications. Statistical comparisons were made between the first 20 (1 to 20), middle 20 (41 to 60), and last 20 (81 to 100) cases. Results showed statistically significant improvements and increased consistency in operative time, operative set-up time, x-ray irradiation time, blood loss, hospital stay, and mobilization time with experience. The complication rate was comparable to other recently published endoscopic studies. In the last 20 cases of the series, operative times had reduced to 35 minutes per level, x-ray irradiation times to 15 seconds per level, and blood loss to 38 mL per level. Most perioperative surgical factors therefore improve significantly with increasing experience in endoscopic anterior scoliosis correction.