Anterior vertebral body tethering (AVBT) is a growth modulating procedure used to manage idiopathic scoliosis by applying a flexible tether to the convex surface of the spine in skeletally immature patients. The purpose of this study is to determine the preliminary clinical outcomes for an adolescent patient cohort.

18 patients with scoliosis were selected using a narrow selection criteria to undergo AVBT. Of this cohort, 11 had reached a minimum follow up of 2 years, 4 had reached 18 months, and 3 had reached 6 months. These patients all demonstrated a primary thoracic deformity that was too severe for bracing, were skeletally immature, and were analysed in this preliminary study of coronal plane deformity correction.

Using open-source image analysis software (ImageJ, NIH) PA radiographs taken pre-operatively and at regular follow-up visits post-operatively were used to measure the coronal plane deformity of the major and compensatory curves.

Pre-operatively, the mean age was 12.0 years (S.D. 10.7 – 13.3), mean Sanders score 2.6 (S.D. 1.8-3.4), all Risser 0 and pre-menarchal, with mean main thoracic Cobb angle of 52° (S.D. 44.2-59.8°). Post-operatively the mean angle decreased to 26.4° (S.D. 18.4-32°) at 1 week, 30.4° (S.D. 21.3-39.6°) at 2 months, 25.7° (S.D. 18.7-32.8°) at 6 months, 27.9° (S.D. 16.2-39.6°) at 12 months, and 36.8° (S.D. 22.6– 51.0°) at 18 months and 38.2° (S.D. 27.6-48.7°) at 2 years. The change in curve at 2 years post-operative was statistically significant (P=0.004).

There were 4 tether breakages identified that did not require return to theatre as yet, one patient underwent a posterior spinal instrumented fusion due to curve progression.

AVBT is a promising new growth modulation technique for skeletally immature patients with progressive idiopathic scoliosis. This study has demonstrated a reduction in scoliosis severity.

The relationship between radiologic union and clinical outcome in thoracoscopic scoliosis surgery is not clear, as apparent non-union does not always correspond to a poor clinical result. Our aim was to evaluate CT fusion rates 2yrs after thoracoscopic surgery, and explore the relationship between fusion scores and; (i) rod diameter, (ii) graft type, (iii) fusion level, (iv) implant failure, and (v) lateral position in disc space.

Between 2000 and 2006 a cohort of 44 patients had thoracoscopic scoliosis correction. Discectomies were performed and defect was packed with either autograft (n=14) or allograft (n=30). Instrumentation consisted of either 4.5mm (n=24) or 5.5mm (n=20) single titanium anterior rod and vertebral body screws. Fusion quality and implant integrity were evaluated 2yr following surgery using low-dose CT. At each disc space, left, right and mid-sagittal CT reconstructions were generated and graded using the Sucato 4-point scale (Sucato, 2004) which is based on calculated percentage of fusion across disc space.

Fusion scores were measured for 259 disc spaces in 44 patients. Rod diameter had a strong effect on fusion score, with a mean score of 2.12±0.74 for 4.5mm Ti rod, decreasing to 1.41+0.55 for 5.5mm Ti rod, and to 1.09+0.36 for 5.5mm Ti-alloy rod. Mean fusion scores for autograft and allograft subgroups were 2.13±0.72 and 2.14±0.74 respectively. Fusion scores were highest in the middle of implant construct, dropping off by 20–30% toward the ends. Fusion scores adjacent to the rod (2.19±0.72) were significantly higher than on the contralateral side of the disc (1.24±0.85). Levels where rod fracture occurred (n=11) had lower fusion scores than those without fracture (1.09±0.67 vs 1.76±0.80). Levels where top screw pullout occurred (n=6) had lower CT fusion scores than those without (1.25±0.60 vs 1.83±0.76).

Rod diameter (larger), intervertebral level (proximal or distal), lateral position in disc (further from rod) and rod fracture or screw pullout all reduce fusion scores, while graft type does not affect scores. The assumed link between higher fusion score and better clinical outcome must be treated with caution, because rod fractures did not necessarily occur in patients with lower fusion scores. It is possible that with a stiffer rod, less bony fusion mass is required for a stable construct. We propose that moderate fusion scores secure successful clinical outcomes in thoracoscopic scoliosis surgery.

Introduction

Luk (Luk et al. Spine vol 23(21) 2303-2307 1998) has shown that in posterior surgery, the correction achieved can be predicted by fulcrum bending films. The relevance to anterior correction has been disputed, as this commonly involves shortening the spine by the removal of intervertebral discs. The aim of the study was to see whether the pre-operative bending angle reflected the degree of correction achieved.

Purpose

1. To evaluate how radiological parameters change during the first 3 years following anterior endoscopic surgery. 2. To report complications encountered in this period.

Introduction

Radiographic parameters have been shown to have a poor correlation with clinical outcome after open scoliosis procedures. However this has not been previously addressed after endoscopic surgery. The purpose of our study was to examine prospectively the relationship between curve correction and clinical outcome for endoscopic scoliosis surgery.

Introduction: Compared with open instrumented anterior spinal fusion for adolescent idiopathic scoliosis (AIS), endoscopic surgery offers clinical benefits that include reduced pulmonary morbidity and improved cosmesis. However, quantitative data on the radiological improvement of vertebral rotation using this method is limited. The aim of this study was to measure pre-operative and postoperative axial vertebral rotational deformity at the curve apex in endoscopic anterior instrumented scoliosis surgery patients using computed tomography (CT), and assess the relevance of these findings to clinically measured chest wall rib hump deformity correction.

Methods: Between November 2002 and August 2005, twenty patients with right-sided thoracic curves underwent endoscopic single-rod anterior instrumented fusion. Pre and post surgical axial vertebral rotation was measured at the curve apex on preoperative and two-year postoperative CT using Aaro and Dahlborn’s method. Rib hump deformity correction was retrieved from a surgical database and correlated to the CT findings. Linear regression was used to investigate the correlation between apical vertebral rotation measured on CT and rib hump measured using a scoliometer.

Results: The mean angle of correction achieved in axial vertebral body derotation at the apical vertebra as measured by CT was 7.9°. This equated to a 43% improvement (range 20–90%). The preoperative and postoperative clinical measurements i.e. rib hump deformity correction, correlated significantly with CT measurements using regression analysis (p=0.03) and the mean improvement in rib hump deformity was 55%.

Conclusion: To our knowledge, this is the first quantitative CT study to confirm that endoscopic anterior instrumented fusion for AIS substantially improves the axial vertebral body rotational deformity at the apex of the curve. The margin of correction of 43% compares favourably historically published figures for all-hook-rod constructs in posterior spinal fusion. In addition, the CT measurements obtained significantly correlated to the clinical outcome of rib hump deformity correction.

Study Aims: This study’s objectives were to measure pre-operative and postoperative axial vertebral rotational deformity at the curve apex in endoscopically-treated anterior-instrumented scoliosis patients using CT, and assess the relevance of these findings to clinically measured chest wall rib hump deformity correction.

Introduction: Thoracoscopic instrumented anterior spinal fusion for adolescent idiopathic scoliosis (AIS) has clinical benefits that include reduced pulmonary morbidity, postoperative pain, and improved cosmesis. However, quantitative data on radiological improvement of vertebral rotation using this method is lacking.

Methods: Between November 2002 and August 2005, 20 AIS patients with right-sided thoracic major curves underwent endoscopic single-rod anterior fusion. Preoperative and two-year postoperative CT was performed to assess axial vertebral rotation at the curve apex. Correlation between apical vertebral rotation measured on CT and rib hump measured using a scoliometer was assessed.

Results: The mean angle of correction achieved in axial vertebral body derotation at the apical vertebra measured by CT was 7.9° and equated to 43% improvement. Preoperative and postoperative rib hump deformity correction correlated significantly with CT measurements using regression analysis (p=0.03). The mean improvement in rib hump deformity was 55%. Conclusion: We believe this is the first quantitative CT study to confirm that endoscopic anterior instrumented fusion for AIS substantially improves axial vertebral body rotational deformity at the apex of the curve. The margin of correction of 43% compares favourably with historically published figures of 24% for patients with posterior all-hook-rod constructs. CT measurements correlated significantly to the clinical outcome of rib hump deformity correction.

Ethics: local committee approval

Statement of Interest: none

Introduction: The occurrence of non-union following instrumented scoliosis correction may predispose to pseudarthrosis and subsequent implant failure. Although non-union is often multifactorial, it is widely accepted that bone graft of adequate quality and quantity is fundamental to achieve solid fusion. Conventionally, autologous rib graft or iliac crest harvest has been utilised for endoscopic anterior instrumented scoliosis surgery. However, these techniques increase the operative duration and cause donor site morbidity, both of which may lengthen hospital stay. Alternatives such as allograft bone and bone morphogenetic proteins have gained more widespread use and may improve fusion rates although this remains controversial. The aim of this study was to compare two-year postoperative fusion rates for a series of patients who underwent endoscopic anterior instrumentation for thoracic scoliosis utilising various bone graft types.

Methods: 19 patients who had undergone endoscopic anterior instrumented scoliosis correction using identical instrumentation (4.5mm diameter titanium anterior rod and vertebral body screws, Eclipse, Medtronic) between May 2000 and August 2005 were identified from a surgical database of 132 consecutively treated individuals. All patients received bone graft to supplement thoracic fusion. Discectomy was performed at the levels to be instrumented and intervertebral spaces were packed with autologous rib heads (8 patients), iliac crest (1 patient), or mulched femoral head allograft (10 patients). The quality of thoracic fusion and implant integrity were evaluated two years following scoliosis correction using low-dose CT performed in accordance with local ethical approval. The intervertebral fusion was assessed using a modified Sucato method (1). Each level was graded using a 4-point scale based on calculated percentage of fusion across the disc space. 0 points indicated no fusion; 1 point, fusion < 25%; 2 points, fusion between 25 and 50%; 3 points, fusion between 50 and 75%; 4 points > 75% or complete fusion. The fusion was considered solid with a score of 3 points or more. Data was analysed with non-parametric tests using a significance level of 0.05.

Results: Of the cohort, nine had evidence of implant failure with rod fracture. All implant failures occurred in the group who received either rib head or iliac crest graft. No rod fractures were identified in the femoral allograft group. The mean fusion grade in the autologous bone graft group was 1.91 whereas in the allograft group this was 3.30 (95% confidence intervals 1.38–2.44 and 2.99–3.61 respectively) with a statistically significant difference in fusion rates between these two groups (p=0.001).

Discussion: This study demonstrated significantly better rates of thoracic fusion in endoscopic anterior instrumented scoliosis correction using mulched femoral allograft compared with autologous rib heads and iliac crest graft. This could be partly explained by the difficulty obtaining sufficient quantities of autologous graft. The lower fusion rate seen in the autologous graft group appears to predispose to rod fracture although the longer-term clinical consequence of implant failure in this group is not clear and warrants further study.

Introduction: Open instrumented anterior spinal fusion for adolescent idiopathic scoliosis (AIS) is a proven technique for vertebral derotation that, compared with posterior spinal fusion procedures, invariably requires fewer distal fusion levels to be performed. With the advent and evolution of endoscopic anterior instrumentation, further clinical benefits are possible such as reduced pulmonary morbidity, improved cosmesis and less postoperative pain. However, quantitative data on the radiological improvement of vertebral rotation using this method is limited. The aim of this study was to measure preoperative and postoperative axial vertebral rotational deformity at the apex of the curve in endoscopic anterior instrumented scoliosis surgery patients using computed tomography (CT), and assess the relevance of these findings to clinically measured chest wall rib hump deformity correction.

Methods: Between November 2002 and August 2005, adolescent idiopathic scoliosis patients with right-sided thoracic major curves were selected for endoscopic single-rod anterior fusion by the senior authors. Low-dose pre-operative CT was performed as described previously (1) and two-year postoperative CT was also performed on consenting patients in accordance with local ethical committee approval. The pre and post surgical axial vertebral rotation was measured at the curve apex using Aaro and Dahlborn’s method (2). Intraobserver and interobserver variability was assessed. Additional clinical information such as rib hump deformity correction and change in the Cobb angle was retrieved from a surgical database and correlated to the CT findings. Least squares linear regression was used to investigate the correlation between apical vertebral rotation measured on CT and rib hump measured using a scoliometer.

Results: Twenty patients were included in the study. The mean angle of correction achieved in axial vertebral body derotation at the apical vertebra measured by CT was 7.9° (median preoperative angle 17.3° [range 12.5° to 27.3°] and median postoperative angle 10.3° [range 1.8° to 18.1°]. This equated to a 43% improvement (range 20–90%). The preoperative and postoperative clinical measurements i.e. rib hump deformity correction, correlated significantly with CT measurements using regression analysis (p=0.03) and the mean improvement in rib hump deformity was 55% (median preoperative 15.0° [range 10° to 30°] and median postoperative 7.0° [range 4° to 10°]). 95% confidence intervals for intraobserver and interobserver validity were within the ranges ±4.5° to ±6.4°.

Discussion: We believe this is the first quantitative CT study to confirm that endoscopic anterior instrumented fusion for AIS substantially improves the axial vertebral body rotational deformity at the apex of the curve. The margin of correction of 43% compares more favourably than the historically published figure of 24% in a cohort of patients with all-hook-rod constructs used for posterior spinal fusion (3). Patient age and gender demographics, curve magnitude and curve types in the historical study were similar to our group, and an identical CT protocol for measuring vertebral derotation was utilised. In addition, the CT measurements obtained significantly correlated to the clinical outcome of rib hump deformity correction.

Introduction Endoscopic scoliosis surgery can be complicated by rod breakage. The aim of this study was to examine the effect of rod breakage on clinical outcome and to determine any predisposing factors.

Methods We studied 83 consecutive patients that had undergone endoscopic correction for scoliosis. Patients were assessed pre-operatively and at regular intervals for up to three years post-operatively. Those patients sustaining rod breakages were compared with those that did not. Clinical outcome was assessed using the Scoliosis Research Society outcome instrument (SRS-24). Radiological assessment included coronal Cobb angles and the angle between adjacent screws.

Results There were 13 (15.7%) patients sustaining 16 rod breaks at a mean time from operation of 21.5 months. No significant change in Cobb angle occurred after rod breakage (mean 18.3 vs 19.7 degrees), p> 0.05. Comparing patients with and without rod breaks we found no difference in SRS-24 scores for pain (4.30 vs 4.39), self image (3.50 vs 3.70), function (3.56 vs 3.35) or patient satisfaction (4.22 vs 4.58). There was no significant difference in screw angle for those patients that developed rod breakages (mean 3.2 vs 2.7 degrees). Significantly more breakages occurred with rib (11/40) and iliac crest (2/7) autograft compared with femoral allograft (0/36), p< 0.01.

Discussion Rod breakage can occur following endoscopic scoliosis surgery. Our study shows that this is not associated with any significant loss of curve correction and has no effect on clinical outcome. Since changing to femoral allograft and by increasing the rod diameter no further rod breakages have occurred.

Introduction Radiographic parameters have been shown to have a poor correlation with clinical outcome after open scoliosis procedures. However this has not been previously addressed after endoscopic surgery. The purpose of our study was to prospectively examine the relationship between curve correction and clinical outcome for endoscopic scoliosis surgery.

Methods We studied 50 consecutive patients that underwent endoscopic instrumentation, with a minimum follow-up of two years. All patients were assessed pre-operatively and at 24 months post-operatively. Radiological parameters were measured from plain standing radiographs including the coronal Cobb angle, sagittal alignment, coronal alignment and shoulder elevation. Clinical outcome was assessed using the Scoliosis Research Society Outcomes Instrument (SRS-24). Correlation between radiological parameters and SRS-24 scores were determined using the Pearson correlation coefficient.

Results There were 45 females and 5 males with a mean age of 16.4 years (range, 10 to 46). The pre-operative coronal Cobb angle was mean 51.7 ± 8.5 and the postoperative instrumented Cobb angle was mean 20.4 ± 7.8 corresponding to a mean curve correction of 60.7%.

There was a positive correlation between instrumented Cobb angle and total SRS-24 score (p=0.03, r2=0.085) and between curve correction and total SRS-24 score (p=0.04, r2=0.081). No correlation was found between coronal alignment, sagittal alignment, shoulder elevation or size of rib hump and the SRS-24 scores (p> 0.05).

Discussion Overall endoscopic scoliosis surgery was associated with a good clinical outcome for our series of patients. Using a validated assessment instrument, clinical outcome correlated well with the amount of curve correction achieved.

Autograft – Since before modern surgical techniques were described, ancient Greeks new of the possibilities for bone to grow after fracture. Studying open fractures, often post mortem, they new of the importance of both the “amount and integrity of bone architecture” that was necessary for two ends of a bone to heal. More recently, modern spinal surgical techniques, many pioneered by surgeons such as John Moe MD, use the same knowledge that for the intentional arthrodesis of two or more bony spinal levels there requires a certain amount and quality of bone – both capturing osteoinductive and osteoconductive properties.

Autograft can be harvested in many ways for spinal arthrodesis and can be taken from iliac crest, tibia or fibula, and from local vertebral sources. Often requiring a separate skin and/or fascial incision, morbidities such as pain, neurovascular injury, infection, blood loss, haematoma, seroma, and fracture can plague the technique. Limited quantities, especially in children, can also be an issue with autograft. Cancellous or cortico-cancellous structural grafts can be milled and used for posterolateral fusion, interbody fusion, and can be mixed with other graft substitutes/expanders. Morbidity profile aside, autograft still remains the gold standard for spinal arthrodesis with regards “ideal properties” of bone grafts.

Allograft – Currently, allograft is the most common substitute for autograft bone in spinal fusion. Allograft is primarily osteoconductive, with minimal osteoinductive potential. Avoidance of donor site morbidity, quantity issues, and surgical time saving are all features of allograft. Increased costs and potential for infection are negative issues. Preparation can vary and fresh unprocessed grafts are no longer used. Freeze drying (lyophilization) involves drying of the grafts before freezing at sub zero temperatures, and the technique reduces immunogenicity, though upon rehydration, structural strength is lost by around 50%. Low dose radiation (< 20kGy) can also be used to process the grafts, as can ethylene oxide, yet both techniques also reduce mechanical strength of the trabecular architecture. With adequate donor screening and tissue processing, the risk of developing HIV from an allograft is estimated to be less than 1 in a million.

Incorporation of allograft is similar to that of autograft, though the process takes more time. Allograft cancellous particles provide a larger surface area and therefore incorporate faster. Studies suggest that mulched allograft femoral heads provides as good a fusion rate in posterior spinal surgeries for children with scoliosis as does the use of autograft. Combination of osteoinductive agents (BMP etc) with allograft is now possible and will likely enhance its further use. Structural fibular allografts in cervical interbody fusion and femoral ring allografts in lumbar interbody fusion have been well described and have very high rates of fusion.

Introduction Endoscopic instrumentation for scoliosis has several advantages compared with open procedures. The purpose of our study was to prospectively assess the clinical outcome of patients after endoscopic anterior instrumentation and to evaluate their responses over time.

Methods A total of 83 consecutive patients underwent endoscopic instrumentation performed at a single unit. Patients completed the SRS-24 Outcomes Instrument pre-operatively and at 3, 6, 12 and 24 months postoperatively. The seven domains of the SRS-24 score were compared between each of the follow-up intervals. The dataset contained 24 responses at 3 months, 65 responses at 6 months, 63 responses at 12 months and 49 responses at 24 months.

Results There were 74 females and nine males with a mean age of 16.4 years (range, 10 to 46 years). The mean Cobb angle improved from 52.8 degrees pre-operatively to 21.9 degrees post-operatively. Over the follow-up period there were significant improvements in the activity level (p< 0.05), function from back condition (p< 0.05) and post-operative function (p< 0.01) domains. Most of this improvement occurred during the first post-operative year and none of the domains improved further after this time interval. There was no significant change in the pain, self image and patient satisfaction domains.

Discussion Our results for endoscopic scoliosis correction are comparable with those reported for open procedures. The greatest improvement in SRS scores occurred between six and twelve months post-operatively. The SRS-24 scores at one year from surgery may provide a good indicator of patient outcome in the long-term.

Introduction The use of anterior techniques to address scoliosis is well established. The method employed is dependent on the curve type, degree and the institution. There are apparent immediate perioperative advantages of an endoscopic technique over an open thoracotomy. In addition, endoscopic instrumentation and fusion has become accepted as a reliable method to address thoracic scoliosis.

Methods 101 patients have undergone anterior endoscopic instrumented correction for scoliosis at the Mater Children’s Hospital, Brisbane between 2000 and 2005. In 2002, a case series study was established to assess perioperative aspects. The majority of patients were entered into a database prospectively. A total of 83 patients were included in the study at the point of data analysis for this paper. The perioperative factors considered were: Theatre times; Blood management; Mobility; and Complications.

Results The mean age was 16 years. 75 curves were adolescent idiopathic. Eight curves were in neuromuscular patients. The majority, 59 (79%) were Lenke Type 1 curves. Operating times were divided into anaesthetic, surgical and X-ray. There was a mean reduction in anaesthetic time between the first and last 20 cases of 22 minutes (p=0.20). For X-ray this was 73 seconds (p< 0.001). The mean surgical time was 288 minutes. The mean reduction in surgical time was 76 minutes (p< 0.001). A scatter plot was also performed of surgical time versus case number. The surgical time has an apparent plateau after approximately 30 cases. This may suggest a learning curve of this number. The mean intra-operative blood loss was 380mls with no allogenic transfusions. The mean length of stay was 5.8 days. There was an overall perioperative complication rate of 12%. There were six reinsertions of ICC, one conversion to an open thoracotomy, two postoperative chest infections and one patient requiring re-intubation in intensive care due to narcosis. There were no subsequent problems for these patients with perioperative complications.

Discussion The use of endoscopic techniques to address scoliosis is employed in centres specializing in spinal deformity. The results above are comparable to those previously reported for both open and endoscopic anterior techniques. The results outlined demonstrate this to be a safe method regarding the perioperative morbidity and complications associated with the procedure.

Introduction The goals of this study were to investigate the association between paediatric flexion-distraction fractures of the lumbar spine and abdominal injuries and to analyse the variety of the abdominal injuries seen with this type of fracture.

Methods A retrospective chart review was performed at three hospitals (British Columbia Children’s Hospital, Vancouver, Canada, Mater Children’s Hospital and Royal Children’s Hospital, Brisbane). All patients under the age of fifteen who had suffered a flexion-distraction fracture were included. Data collected from the chart related to seating position, the use of seat belts and the spinal and abdominal injuries. The time elapsed from presentation to the time of diagnosis of abdominal injury was also recorded.

Results Forty one patients were included. There were 16 male and 25 female patients. All injuries were due to motor vehicle accidents. The average age at the time of accident was 9 years and 8 months. Twenty-two of the forty-one patients (53%) suffered an intra-abdominal injury. Twenty-one of these patients required operative intervention for their abdominal trauma. The spectrum of injuries included small bowel, large bowel, mesenteric and solid organ injuries. Eighteen of the twenty-two patients sustained a small bowel injury.

Discussion Abdominal trauma after flexion-distraction fractures of the lumbar spine is common. Often the abdominal trauma is significant and may require a laparotomy. A high index of suspicion should be maintained for all patients who present to the orthopaedic department with this type of injury.