Purpose of the study. To investigate the efficacy of pedicle screw instrumentation in correcting spinal deformity in patients with quadriplegic cerebral palsy. Also to assess quality of life and functional improvement after deformity correction as perceived by the parents of our patients. Summary of Background Data. All pedicle screw constructs have been commonly used to correct adolescent idiopathic scoliosis. There is limited information on their effectiveness in treating patients with cerebral palsy and neuromuscular scoliosis. Methods. We reviewed the medical records and serial radiographs of 45 consecutive patients with quadriplegia who underwent spinal arthrodesis using pedicle screw/rod instrumentation and a standardised surgical technique (prospectively collected single surgeon's series). All patients were wheelchair bound with collapsing thoracolumbar scoliosis and pelvic obliquity. Twenty-eight patients had associated sagittal deformities. A telephone survey was performed by an independent investigator to assess parents' perception on surgical outcome. Results. Thirty-eight patients underwent posterior-only and 7 staged anteroposterior spinal arthrodesis. Mean age at surgery was 13.4 years (range 9-18.3) and mean postoperative follow-up 3.5 years (range 2.8-5). Pedicle screw instrumentation extended from T2/T3 to L5 with bilateral pelvic fixation using iliac bolts. Scoliosis was corrected from mean 82.5° to 21.4° (74.1%). Pelvic obliquity was corrected from mean 24° to 4° (83.3%). In posterior-only procedures, average blood loss was 0.8 blood volumes, ICU stay 3.5 days, and hospital stay 17.6 days. In anteroposterior procedures, average blood loss was 0.9 blood volumes, ICU stay 8.9 days, and hospital stay 27.4 days. Major complications included one deep infection and one re-operation to remove prominent implants but no deaths, no neurological deficit and no detected pseudarthrosis. Parents' survey demonstrated 100% satisfaction rate. Conclusion. Pedicle screw instrumentation can achieve excellent correction of spinopelvic deformity in quadriplegic cerebral palsy with low complication and re-operation rates and high parent satisfaction. Our study has demonstrated that spinal correction using segmental pedicle screw/rod constructs can be performed safely and with lesser major complications and reoperations compared to the traditionally used Unit rod or hybrid instrumentation. The greater degree of deformity correction and lesser rate of complications and reoperations due to non-union, prominent instrumentation or failed pelvic fixation using a pedicle screw compared to the Unit rod technique should be balanced against the increased implant cost

Anterior instrumentation is an established method of correcting King I adolescent idiopathic scoliosis. Posterior segmental pedicle screw instrumentation, with its more powerful corrective force over hooks, could offer significant advantages. The purpose of our study is to compare the results of anterior instrumentation versus segmental pedicle screw instrumentation in adolescent idiopathic thoracolumbar scoliosis. A retrospective analysis was conducted on 36 consecutive female patients with adolescent idiopathic thoracolumbar scoliosis who had surgery from December 1997. All had a minimum of two year follow-up. Eleven patients had posterior surgery performed on them. Mean age at surgery was similar between both groups. Length of surgery was significantly shorter in the posterior group (189 minutes versus 272 minutes). Length of hospital stay was shorter in the posterior group (6.2 days versus eight days). Estimated blood loss, duration of analgesia, and ICU stay did not differ significantly between the two groups. No complications were encountered in both groups at latest follow-up. The magnitudes and flexibility of the thoracolumbar curves did not differ significantly between the two groups. The number of levels in the major curve was also similar between the groups. Fusion levels were shorter in the anterior group (mean 4.1 versus 5.0). The percentage correction of scoliosis was similar between the two groups at all stages of follow-up, being 74% at one week post-surgery, 70% at six months post-surgery, 68% at one year post-surgery and latest follow-up in the anterior group; and 71% at one week post-surgery, 67% at six months post-surgery, 68% at one year post-surgery, and 67% at latest follow-up in the posterior group. Thoracolumbar sagittal alignment at T11 to L2 was maintained for both groups throughout the follow-up period. The incidence of proximal junctional kyphosis was higher in the posterior group (p < 0.01). In conclusion, surgical correction of both the frontal and sagittal plane deformity are comparable to anterior instrumentation. Shorter length of surgery and hospital stay are the potential benefits of posterior surgery. Posterior segmental pedicle screw instrumentation offers significant advantage, and is a viable alternative to standard anterior instrumentation in idiopathic thoracolumbar scoliosis

Introduction: Rotation is becoming an increasingly important consideration in the management of scoliosis yet it is difficult to measure reliably. The Perdriolle technique is a widely used and validated technique for estimating the rotation of the apical vertebra. The landmarks required to measure vertebral rotation using this technique are frequently obscured following instrumentation and the application of bone graft. We propose that the Perdriolle technique cannot be applied reliably in the presence of pedicle screw constructs. Method: This was a manual radiographic measurement analysis comparing intraobserver and interobserver reliability of the Perdriolle “Torsiometre” and the Cobb angle measurement in scoliosis prior to and after pedicle screw instrumentation. Results: Mean difference and 95% limits of agreement between pre-operative intra-observer readings was 2.5° (−15° and 20°). This suggests on average there was little systematic disagreement between the two readings (2.5° on average). There were large discrepancies between individual pairs of readings. 29.6% of post-operative films (17%–39%) were judged to have sufficient landmarks visible to enable measurement of vertebral rotation compared to 10% of pre-operative films. Marked increase in systematic bias between consultants with post-operative radiographs to pre-operative films was observed. Conclusion: We question the validity in measuring the rotation of the curve using the Perdriolle technique on post-operative films following pedicle screw instrumentation. The predominant factors for the obscuration of landmarks include the presence of bone graft, pedicle screws and rods

The aim of this study was to compare the treatment ouctomes of severe idiopathic scoliosis (IS) (>90 degrees) using the staged surgery with initial limited internal distraction and typical IS treated using segmental pedicle screw instrumentation. We hypothesized that staged surgical treatment of severe scoliosis would improve more HRQoL and pulmonary function (PF) as compared with posterior spinal fusion (PSF) for typical IS curves. It was a retrospective review of a consecutive series of 60 IS, severe group (SG) vs. moderate group (MG) with min. 2 years of follow up (FU). The mean preoperative major curve (MC) was 120° and thoracic kyphosis (TK) was 80° for the SG and 54° and 17° for the MG, respectively (p<0.001). The MC was corrected to 58° and TK to 32° for the SG; the MC to 26° and TK to 14°, for the MG, respectively (p<0.001). The mean preoperative AVT was 8.9 cm and improved to 2.8 cm at the final FU for the SG and from 6.5 cm to 2.2 cm at the final FU for the MG (p<0.001). At baseline, the FVC% & FEV1% values were significant different between the two groups (41.5% vs. 83%, p <0.001) & (41.6% vs. 77%, p <0.001). Compared the baseline for SG vs. the values at 2-year FU the FVC % values were (41.5% vs. 66.5%, p <0.001), and the baseline for MG vs. the values at 2-year FU, the FEV1 values were (77% vs. 81%, NS). At last FU, no complications were reported. Gradual traction with complicity of multilevel Ponte's osteotomies and neuromonitoring followed by staged pedicle screws instrumentation in severe IS proved to be a safe and effective method improving spinal deformity (52% correction), PF (improved percentage of predicted forced vital capacity by 49%), and health-related quality and allows to achieve progressive curve correction with no neurologic complications associated to more aggressive one-stage surgeries

Objective. To evaluate the outcomes of the treatment of acute thoracolumbar burst fractures by transpedicular balloon kyphoplasty with Calcium phosphate cement and posterior instrumented fusion. Methods: Twenty-three consecutive patients (average age 48 years) who sustained thoracolumbar A3-type burst fracture with or without neurologic deficit were included in this prospective study. Twenty-one out 23 patients had single fractures and the left 2 had each one additional A1 compression contiguous fracture. On admission 5(26%) out 23 patients had neurologic lesion (5 incomplete, one complete). Bilateral transpedicular balloon kyphoplasty was performed with quick hardening calcium phosphate cement to reduce segmental kyphosis and restore vertebral body height and supplementary pedicle screw instrumentation (long including 4 vertebrae for T9-L1 fractures and short (3 vertebrae) for L2 to L4 fractures. Gardner kyphosis angle, anterior and posterior vertebral body height ratio and spinal canal encroachment were calculated pre–to postoperatively. Results: All 23 patients were operated within two days after admission and were followed for at least 24 months after index surgery. Operating time and blood loss averaged 70 minutes and 250 cc respectively. The 5 patients with incomplete neurologic lesions improved by at least one ASIA grade, while no neurological deterioration was observed in any case. Overall sagittal alignment was improved from an average preoperative 16o to one degree kyphosis at final follow up observation. The anterior vertebral body height ratio improved from 0.6 preoperatively to 0.9 (P< 0.001) postoperatively, while posterior vertebral body height was improved from 0.95 to 1 (P< 0.01). Spinal canal encroachment was reduced from an average 32% preoperatively to 20% postoperatively. No differences in preoperative values and postoperative changes in radiographic parameters between short and long group were shown. Cement leakage was observed in 4 cases: three anterior to vertebral body and one into the disc without sequalae. In the last CT evaluation, continuity was shown between calcium phosphate and cancellous vertebral body bone. Posterolateral radiological fusion was achieved within 6–8 months after index operation. There was no instrumentation failure or measurable loss of sagittal curve and vertebral height correction in any group of patients. Conclusions: Balloon kyphoplasty with calcium phosphate cement secured with posterior long and short fixation in the thoracolumbar and lumbar spine respectively provided excellent immediate reduction of posttraumatic segmental kyphosis and significant spinal canal clearance and restored vertebral body height in the fracture level in an equal amount both in short and long instrumentation

Lowest instrumented vertebra (LIV) selection is critical to preventing complications following posterior spinal arthrodesis (PSA) for thoracolumbar/lumbar adolescent idiopathic scoliosis (TL/L AIS), but evidence guiding LIV selection is limited. This study aimed to investigate the efficacy of PSA using novel unilateral convex segmental pedicle screw instrumentation (UCS) in correcting TL/L AIS, to identify radiographic parameters correlating with distal extension of PSA, and to develop a predictive equation for distal fusion extension using these parameters. We reviewed data (demographic, clinical, radiographic, and SRS-22 questionnaires) preoperatively to 2-years' follow-up for TL/L AIS patients treated by PSA using UCS between 2006 to 2011. 53 patients were included and divided into 2 groups: Group-1 (n=36) patients had PSA between Cobb-to-Cobb levels; Group-2 (n=17) patients required distal fusion extension. A mean curve correction of 80% was achieved. Mean postoperative LIV angle, TL/L apical vertebra translation (AVT), and trunk shift were lower than previous studies. Six preoperative radiographic parameters significantly differed between groups and correlated with distal fusion extension: thoracic curve size, thoracolumbar curve size, LIVA, AVT, lumbar flexibility index, and Cobb angle on lumbar convex bending. Regression analysis optimised an equation (incorporating the first five parameters) which is 81% accurate in predicting Cobb-to-Cobb fusion or distal extension. SRS-22 scores were similar between groups. We conclude that TL/L AIS is effectively treated by PSA using UCS, six radiographic parameters correlate with distal fusion extension, and a predictive equation incorporating these parameters reliably informs LIV selection and the need for fusion extension beyond the caudal Cobb level

A retrospective descriptive preliminary study on early experience using all pedicle screw correction

Pedicle screw fixation enables enhanced correction of spinal deformities. However, the technique is still in early development in our clinic. Tends of the scoliosis patient to come in late ages make maximum correction failed.

A total 16 patients are subjected to pedicle screw fixation for spinal deformities were analyzed descriptively as an early follow-up in the last two-year. 14 patients are girl and 2 are boys. The age range between 12 to 18 year. 8 are Kings type II and 8 are Kings type III, 212 screws were inserted between Th3 – L2 (14-18 screws per-patient), all concave pedicles were inserted with screws but in convex side every two or three pedicles were inserted. The position of screws was analyzed using the post-operative plain X ray film.

Before surgery the mean deformity measurement are 52.56° (range, 42-72°, correction achieved was 18° (range 10-34%, it was correlated to 68% achievement (range, 53-80%). All patients are happy with their image improvement.

In total 212 screws inserted, 28 screws are malpositions (13.2%), but no clinical complication recorded.

In this early experience using all pedicle screw scoliosis surgery, all patients are happy with the results although the correction only 53-80(. More patients are needed to improve this achievement.

Introduction: Historically segmental sublaminar wiring (SLW) fixation has been used for the correction of spinal deformity in neuromuscular scoliosis, however pedicle screw (PS) fixation is gaining popularity. We compared the results of both techniques in patients with Duchenne Muscular Dystrophy (DMD).

Methods: Two groups of patients with DMD were matched according to the age at surgery, magnitude of deformity and vital capacity. Indications for surgery included loss of sitting balance, rapid decline of vital capacity and curve progression. In Group 1 (22 patients) SLW fixation was used from T2 to S1 with the Galveston technique. In Group 2 (18 patients) PS fixation was used from T2 to L5. Minimum follow-up was 2 years (range 2–13 years). Radiographs, SRS-22 and lung function tests were performed at standardised intervals.

Results: Mean Cobb angle in Group 1 improved from 47° (range 26°–75°) to 23.5° (range10°–36°) and mean pelvic obliquity improved from 15° (range8°–25°) to 2.4° (range0°–8°). Mean Cobb angle in Group 2 improved from 46° (range28°–82°) to 8.5° (range 0°–18°) and mean pelvic obliquity improved from 15° (range7°–30°) to 1.1° (range 0°–6°) [p< 0.05]. Mean operating time and blood loss were less in Group 2 [p< 0.05]. In Group 1, the infection rate and instrumentation failure was higher, and SRS-22 outcomes showed no significant difference between the groups. Interestingly the mean Body Mass Index (BMI) in Group 2 was much higher than group 1.

Conclusions: PS fixation resulted in superior correction and controlled pelvic obliquity to a large extent without the need for pelvic fixation. Lower rates of infection and failure of instrumentation were noted with PS fixation, despite high BMI of patients presumably due to steroid therapy. We recommend the use of PS instrumentation for the correction of spinal deformity in DMD.

Purpose

Bone morphogenic protein (BMP-2) is used in spinal arthrodesis to induce bone growth. Studies have demonstrated that it achieves similar fusion rates compared to iliac crest bone graft when used in instrumented fusions. Our study aims at evaluating the requirement for instrumentation in one and two-level spinal arthrodeses when BMP-2 is used in conjunction with local bone to achieve fusion.

Objectives: To determine if high quality, thin slice (1–3)mm CT scan images would allow proper evaluation of interbody fusion through titanium cages in view of the fact that there are no universally accepted radiological criteria. ¹

Design: Patients undergoing interbody lumbar fusion were prospectively evaluated with a CT scan and plain radiographs six months following surgery. These were blindly and independently evaluated by a consultant radiologist and a research fellow. They were assessed for bridging bony trabeculation both through and surrounding the cages as well as for changes at the cage endplate interface.

Subjects: Fifty-three patients (156 cages) undergoing posterior lumbar interbody fusion using titanium inter-body cages were evaluated. Posterior elements were used to pack the cages and no graft was packed outside the cages.

Outcome Measures: Kappa co-efficient and chi-squared analysis.

Results: On the CT scan both observers noted bridging trabeculation in 95%of the cages-Kappa 0.85, while on radiographs they were present in only 4%-Kappa 0.74. Both observers also identified bridging trabeculation surrounding the cages on the CT scans in 90%-Kappa 0.82, while on the radiographs this was 8%-Kappa 0.86. Radiographs also did not identify all the loose cages.

Conclusions: High quality CT scan images can demonstrate bridging bony trabeculation following the use of titanium interbody cages. It also demonstrated consistent bone growth outside the cages inspite of not using any bone graft.

Aim:

To determine radiographic variables that predict the need for distal extension of the fusion beyond Cobb-to-Cobb levels in treating thoracolumbar/lumbar (TL/L) scoliosis (Lenke 5) in adolescent patients.

We considered three different device systems for the treatment of lumbar and lumbosacral instability. From a prospective database in use in our Institution, we obtained a 45-patient cohort of individuals who received a one-level lumbar or lumbosacral fusion procedure between 1995 and 1998. All patients had presented with disabling back and/or radicular pain and severe degenerative changes at one disc level or low-grade spondylolisthesis. First group: 15 patients, six male and nine female, with an average age of 41 years, were treated by an interbody fusion using cylindrical threaded cages; the levels fused were L5-S1 in 10 patients and at L4-L5 in five. Second group: 15 patients, eight male and seven female, with an average age of 39 years were treated by nine cylindrical, threaded cages and seven square cages, combined with posterior pedicle screws; the levels fused were L5-S1 in 11 and L4-L5 in four. Third group: 15 patients, eight male and seven female, with an average age of 40 years, underwent posterolateral fusion with posterior pedicle screws instrumentation alone; the levels fused were L5-S1 in 10 and L4-L5 in the remaining five. At a mean follow-up of 8 years in the first group, eight patients (53%) required a second operation (five posterior instrumentation, two root decompression and one repair of dural tear). The clinical results were fair in six patients (40%) and poor in three (20%); five patients (33%) presented uncertain fusion signs. In the second group, two patients (13%) required a second operation (one root decompression and one dural repair). All patients (100%) presented definite fusion signs. The clinical results 6.5 years after primary surgery were fair in two (13%) patients and poor in two (13%). In the third group, two patients (13%) required a second operation (one dural repairand one implant removal). The clinical results were fair in two cases (13%) and no poor results were seen. At a mean follow-up of 6.5 years, 14 patients (93%) showed definite fusion signs. According to the present data, we can conclude that in terms of fusion success, clinical outcome and complication rates, the use of posterior interbody cages alone is not as safe and effective for the management of one level degenerative disc disease or low-grade spondylolisthesis as the posterior pedicle screw instrumentation combined with two posterior cages or the stand-alone pedicle screw instrumentation

We described a technique of measuring the flexibility of the rib prominence clinically before surgery, and aimed to analyse the results in patients with adolescent idiopathic scoliosis who underwent posterior correction with pedicle screw instrumentation. This prospective study investigated the magnitude of rib humps before and after the operation when the patient was in Adam's forward bending posture. Also preoperatively, a flexion and derotation manoeuvre was performed and the corrected rib prominence was measured. This is compared to the magnitude of the rib hump present postoperatively at three months' follow up. Seven consecutive patients with adolescent idiopathic scoliosis that underwent posterior surgical correction. Clinical measurement of rib prominence using scoliometer. The magnitude of the curve improved from a mean preoperative Cobb angle of 53.6+/−11.2° (range 45.3–72.5°) to a mean postoperative Cobb angle of 7.8+/−9.3° (range 0.4–17.6°). The mean preoperative magnitude of the rib hump was 12.3+/−6.9° (range 5-20°) which was then corrected to a mean magnitude of 1.3+/−2.2° (range 0-5°) by performing the above described flexion derotation manoeuvre. The mean postoperative magnitude of the rib hump was 3.0+/−3.1° (range 0-8°) with the patient in Adam's forward bend position. There was positive correlation between the postoperative residual rib hump and the reduced rib hump measured preoperatively using our described technique (r=0.8,p=0.05). This flexion derotation test is a useful in assessing the amount of postoperative persistent rib hump after posterior correction of adolescent idiopathic scoliosis using pedicle screw instrumentation with derotation technique

Background. Partial facetectomies with pedicle screw instrumentation is widespread and a well described technique for achieving posterior correction of scoliosis. Newton et al. first described the use of the UBS in the posterior correction of AIS in 2014. The aim of this study was to compare the effectiveness of the UBSPO in achieving posterior correction in Type1 AIS as compared to the traditional partial facetectomies. Aim of this study was to assess the effectiveness of USBPO in achieving posterior correction in Type 1 AIS as compared to partial facetectomies. Methods. A retrospective review of 40 patients with type 1 AIS who had undergone a posterior correction of scoliosis between 2010 and 2016 was performed. Group A (n=20) consisted of consecutive patients that had partial facetectomies while Group B (n=20) consisted of consecutive patients having UBSPO. Both groups were matched for demographic parameters. Pre and post-operative radiographic parameters and operative data in both groups were compared. The Mann-Whitney U test was used for statistical analysis. Results. There was no significant difference between the two groups in terms of age, sex, magnitude of curves, apical rotation and flexibility on the preop imaging. There was a significant difference between the mean postop Cobb angle (21.9° vs 9.8°, p<0.0005), correction (63.04% vs 84.3%, p<0.0005) and postop apical rotation (p = 0.008) in favour of the UBSPO group. At 2-year follow-up there was a statistically significant increase in the cobb angle in the facetectomy group (21.89° (immediate post op) Vs 24.64° P=0.033) and no such difference in the UBSPO group. There was no significant difference between surgical time (p = 0.536) and blood loss (p = 0.380). Conclusion. The use of the UBSPO for posterior release provides more effective correction in the coronal and axial planes than traditional partial facetectomies in type 1 AIS

Introduction. We aimed to determine the midterm effect of pedicle screw instrumentation on sagittal plane alignment, compared with a hybrid alignment, in the treatment of thoracic adolescent idiopathic scoliosis (AIS). Methods. 88 consecutive patients with AIS with a Lenke type 1 curve treated between 1998 and 2003 were analysed. Thoracic hooks were used in 45 patients (group Hy) and thoracic screws alone in 43 patients (group TPS). Preoperative average age (Hy 15·3 years vs TPS 16 years), sex (38 female and seven male vs 37 female and six male), Risser sign (2·9 vs 2·9), main thoracic curve (64° vs 65·5°), and thoracic kyphosis (22·6° vs 21·4°) were similar in both groups. Pearson correlation coefficient and univariate ANOVA were used. Results. At a mean follow-up of 7·3 years (range 5–10), the TPS group had a greater final main thoracic curve correction (Hy 46·4% vs TPS 58·4%; p<0·001), with inferior loss of initial correction (–11·1° vs TPS –1·3°; p<0·0005). Absolute final thoracic kyphosis was similar in both groups (31·4° vs 25·4°; r=0·002; p>0·05), with both groups showing an equally statistically significant amelioration of the sagittal contour (Hy 49·2%; p<0·001 vs TPS 43·4%; p<0·001) (difference between groups p>0·05). We recorded a significant correlation between absolute kyphosis correction (final preoperative) and percentage main thoracic curve initial correction loss in the Hy group (r=0·35, p<0·001). The SRS–30 assessment showed an improvement in self-image and satisfaction, with no significant differences between groups. Conclusions. The previously reported loss of kyphosis after a pedicle screw instrumentation in AIS, when compared with hybrid or hook only implants, should be questioned. At a minimum 5 years of follow-up, sagittal contour in the thoracic spine was not less kyphotic when pedicle screws were compared with hybrid constructs. The higher the loss of initial correction of main thoracic curve, the greater the postoperative absolute kyphosis at T5–T12 level. The clinical relevance of such radiographic differences is still undetectable with present self-assessment methods

Background Data: Postoperative spondylothesis had been noted for many years, first reported by White in 1977. Biomechanic effect of the facetectomy was reported by Abumi in 1992. There were few reports about the results of surgical treatment for postoperative spondylolisthesis. Purpose: To assess the outcome of surgical treatment for postoperastive spondylolisthesis and examine the factors that might correlate with postoperative spondylolisthesis. Materials and Methods: This study retrospectively reviewed twenty seven patients (eleven male and sixteen female), from 1979 to 1996, who received pedicle screws instrumentation and posterolateral fusion for postoperative spondylolisthesis. Average age was 57.3 years old (from 36.6 to 79.5 years old). Average follow-up time was 40.0 months (from 24 months to 72 months). The grade of fcetectomy, percentage of vertebral slipping, and disc narrowing was checked by plain X-ray. End results were assessed using the modified Stauffer-Coventry’s evaluation criteria. Results: The mean period of postoperative instability was 49.3 months (from 6 months to 141 months) in whole group, 43.7 months (from 6 months to 129 months) in laminectomy group, 43.4 months (from 17months to 82 months) in laminectomy and disectomy groups, and 74.6 months (13 months to 141 months) in disectomy group. After an average follow-up period of 40 months, 29.6 % of patients had excellent results, 44.5% had good results, and 25.9 % had fair result. No complication was found in this study. Conclusions: Pedicle screw instrumentation with posterolateral fusion can get satisfactory result for postoperative spondylolisthesis

Introduction. Posterior spinal arthrodesis with thoracoplasty and an open anterior approach, with respect to a posterior only fusion, have a deleterious effect on pulmonary function for up to 5 years after surgical treatment of adolescent idiopathic scoliosis. We aimed to compare two groups of adolescents surgically treated for their spinal deformity either by posterior segmental fusion alone (PSF) or by posterior spinal fusion and thoracoplasty (PSF+T). We focused on the long-term effects of thoracoplasty on pulmonary function in the surgical treatment of adolescent idiopathic scoliosis. Methods. We compared 40 consecutive adolescent patients surgically treated between 1998 and 2001 by PSF+T with a similar cohort of 40 adolescents treated in the same period by PSF. Inclusion criteria were pedicle screw instrumentation alone and a minimum 5 years of follow-up. A radiographic analysis and a chart review were done, evaluating the pulmonary function tests (PFTs), the SRS-30 score questionnaire, and the Lenke classification system. A radiographic rib-hump (RH) assessment was also undertaken. Results. The entire series was reviewed at an average clinical follow-up of 8·3 years. The two groups did not differ significantly in terms of sex, age (PSF+T 16·3 years vs PSF 15·2 years), Lenke curve type classification, and preoperative Cobb main thoracic (MT) curve magnitude (66° vs 63°); however, final MT percentage correction (53·03% vs 51·35%; p<0·03), RH absolute correction (–2·1 cm vs –1·05; p<0·01), and RH overall percentage correction (55·4% vs 35·4%; p<0·0001) were greater in the PSF+T group than in the PSF group. We recorded no statistical differences between the two groups in PFTs both preoperatively and at last follow-up. Nevertheless, comparing preoperative with final PFTs within each group, only in the PSF group was both forced vital capacity and forced expiratory volume in 1 s significantly improved at final evaluation. At last follow-up visit, the SRS-30 scores did not differ significantly between the two groups (total score 4·1 vs 4·3). Conclusions. Our findings suggest that thoracoplasty did not adversely affect long-term PFTs in patients with adolescent idiopathic scoliosis treated by posterior spinal fusion alone with pedicle screws instrumentation, as already shown in previous reports. A trend towards better coronal plane correction and rib-hump improvement was recorded, although this improvement was not clearly reported in a self-assessment disease-specific questionnaire

Many pedicle screw instrumentation systems are currently available to the spine surgeon. Each system has its unique characteristics. It is important for the surgeon to understand the differences in these pedicle screw systems. 1. Following the introduction of a new spinal instrumentation set to our clinical practice we encountered two cases of pedicle screw breakage. We thus decided to investigate the mechanism of this screw failure (screw A) in these particular cases and to compare the biomechanical properties, through independent analysis, of a variety of pedicle screws from different manufacturers. Samples of the broken pedicle screws were retrieved at surgery. Surface analysis of the fracture area using the electron microscope, demonstrated features consistent with fatigue fracture. Pedicle screws of comparable size from a variety of manufacturers were gathered for independent analysis. Shadowgraph analysis was performed of each screw allowing multiple measurements to be taken of the screw’s geometry. Using this data stress concentration factors were determined demonstrating screw A to have larger values than all the other screws ranging from 2 – 3.6 times the nominal stress. The smaller teeth of screw A, spaced further apart than in the other screws, means that the large proportion of the load which would be carried by the threads is distributed over a smaller area resulting in higher stresses in the threads. The sharp corner at the root of the thread, acting as a stress concentrator, would become the focal point of these high stresses, and magnify them by 2 to 3.6 times. These increased stresses most likely account for an increased susceptibility to fatigue fracture seen in screw A. In conclusion it is important to be careful with the introduction and use of new pedicle screw materials and designs, that all the standard biomechanical testing has been performed to a satisfactory standard. Knowing the physical characteristics of the available pedicle screw instrumentation systems may allow the choice of pedicle screw best suited for a given clinical situation

Aims. Anchorage of pedicle screw rod instrumentation in the elderly spine with poor bone quality remains challenging. Our study aims to evaluate how the screw bone anchorage is affected by screw design, bone quality, loading conditions, and cementing techniques. Methods. Micro-finite element (µFE) models were created from micro-CT (μCT) scans of vertebrae implanted with two types of pedicle screws (L: Ennovate and R: S. 4. ). Simulations were conducted for a 10 mm radius region of interest (ROI) around each screw and for a full vertebra (FV) where different cementing scenarios were simulated around the screw tips. Stiffness was calculated in pull-out and anterior bending loads. Results. Experimental pull-out strengths were excellently correlated to the µFE pull-out stiffness of the ROI (R. 2. > 0.87) and FV (R. 2. > 0.84) models. No significant difference due to screw design was observed. Cement augmentation increased pull-out stiffness by up to 94% and 48% for L and R screws, respectively, but only increased bending stiffness by up to 6.9% and 1.5%, respectively. Cementing involving only one screw tip resulted in lower stiffness increases in all tested screw designs and loading cases. The stiffening effect of cement augmentation on pull-out and bending stiffness was strongly and negatively correlated to local bone density around the screw (correlation coefficient (R) = -0.95). Conclusion. This combined experimental, µCT and µFE study showed that regional analyses may be sufficient to predict fixation strength in pull-out and that full analyses could show that cement augmentation around pedicle screws increased fixation stiffness in both pull-out and bending, especially for low-density bone. Cite this article: Bone Joint Res 2021;10(12):797–806

Purpose of the study. To investigate the efficacy of pedicle screw instrumentation in correcting thoracolumbar/lumbar idiopathic scoliosis in adolescent patients. Summary of Background Data. Thoracolumbar/lumbar scoliosis has been traditionally treated through an anterior approach and instrumented arthrodesis with the aim to include in the fusion the Cobb-to-Cobb levels and preserve distal mobile spinal segments. Posterior instrumentation has been extensively used for thoracic or thoracic and lumbar scoliosis. In the advent of all-pedicle screw constructs there is debate on whether thoracolumbar/lumbar scoliosis is best treated through an anterior or a posterior instrumented arthrodesis. Methods. We reviewed the medical notes and radiographs of 19 consecutive adolescent patients with Lenke 5C idiopathic scoliosis (17 female-2 male, prospectively collected single surgeon's series). We measured the scoliosis, thoracic kyphosis and lumbar lordosis angles, apical vertebral rotation (AVR) and translation (AVT), trunk shift (TS), as well as the lower instrumented vertebra angle (LIVA) both pre-and post-operatively and at minimum 2-year follow-up. SRS 22 data was available for all patients. Results. All patients underwent posterior spinal arthrodesis of the primary thoracolumbar/lumbar curve using all-pedicle screw constructs. Mean age at surgery was 15.1 years. We identified 3 separate groups: Group 1 (9 patients) had a fusion to include the preoperative Cobb-to-Cobb levels of the curve; in Group 2 (8 patients) the fusion extended 1-2 levels distal (all patients) +/− proximal (4 patients) to the end Cobb vertebrae; in Group 3 (2 patients) the fusion extended to one level proximal to the lower end Cobb vertebra. Eight patients had compensatory thoracic curves. Mean Cobb angle before surgery was 60.3° (range: 43-91°). This was corrected by 79% to mean 13° (p<0.001) with no patient losing >2° correction at follow-up. Mean preoperative Cobb levels of the thoracolumbar/lumbar curve were 6.3; mean levels of instrumented fusion were 7 (mean extent of fusion: preoperative Cobb angle + 0.7 levels). Mean preoperative thoracic kyphosis was 34.7° and lumbar lordosis 45.3°. Mean postoperative thoracic kyphosis was 36.6° and lumbar lordosis 43°. Mean theatre time was 3.8 hours, hospital stay 7.5 days and intraoperative blood loss 0.26 blood volumes. There were no neurological complications other than one temporary brachial plexus neuropraxia (recovered before patient discharge from hospital), no wound infections or detected non-union at follow-up. Mean preoperative SRS 22 score was 3.7; this was improved to 4.5 at 2-year follow-up (p=0.01). Pain and self-image demonstrated significant improvement (p=0.02, p=0.001 respectively) with mean satisfaction rate 4.8. Comparison between Groups 1 and 2 showed similar age at surgery but higher preoperative scoliosis in Group 2 (Group 1: 54°/Group 2: 65°, p=0.05). Preoperative AVR, TS and LIVA were similar between the 2 groups (p>0.05). Preoperative AVT was significantly higher in Group 2 (Group 1: 3.3 cm/Group 2: 5 cm, p=0.01). Conclusion. Pedicle screw instrumentation can achieve excellent correction of Lenke 5C idiopathic scoliosis which is maintained at follow-up. This is associated with high patient satisfaction and low complication rates. Greater preoperative AVT and scoliosis angle predicted the need for longer fusion both distally and proximally beyond the end vertebra of the preoperative Cobb angle