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Biomedical subjects

John K Webb

Publications and source records attributed to John K Webb.

15 recordsLinked to original sources
PubMed2006

A segmental radiological study of the spine and rib--cage in children with progressive infantile idiopathic scoliosis.

BACKGROUND: The role of rib cage in the development of progressive infantile idiopathic scoliosis (IIS) has not been studied previously. No report was found for rib growth in children with IIS. These findings caused us to undertake a segmental radiological study of the spine and rib-cage in children with progressive IIS. The aim of the present study is to present a new method for assessing the thoracic shape in scoliotics and in control subjects and to compare the findings between the two groups. MATERIALS AND METHODS: In the posteroanterior (PA) spinal radiographs of 24 patients with progressive IIS, with a mean age of 4.1 years old, the Thoracic Ratios (TRs) (segmental convex and concave TRs), the Cobb angle, the segmental vertebral rotation and vertebral tilt were measured. In 233 subjects, with a mean age of 5.1 years old, who were used as a control group, the segmental left and right TRs and the total width of the chest (left plus right TRs) were measured in PA chest radiographs. Statistical analysis included Mann-Whitney, Spearman correlation coefficient, multiple linear regression analysis and ANOVA. RESULTS: The comparison shows that the scoliotic thorax is significantly narrower than that of the controls at all spinal levels. The upper chest in IIS is funnel-shaped and the vertebral rotation at T4 early in management correlates significantly with the apical vertebral rotation at follow up. CONCLUSION: The IIS thorax is narrower than that of the controls, the upper chest is funnel-shaped and there is a predictive value of vertebral rotation at the upper limit of the thoracic curve of IIS, which reflects, impaired rib control of spinal rotation possibly due to neuromuscular factors, which contribute also to the funnel-shaped chest.

Journal Article↗
PubMed2006

Anterior instrumentation for thoracolumbar adolescent idiopathic scoliosis: do structural interbody grafts preserve sagittal alignment better than morselized rib autografts?

STUDY DESIGN: This is a retrospective, sequential cohort study of 34 patients treated by anterior instrumented fusion with single solid rod, single screw constructs with at least 2-year follow-up. Sixteen of the patients received structural grafts as interbody spacers in disc levels below T12, while the other 18 patients received only morselized rib autograft. OBJECTIVE: To determine if structural interbody grafts preserve sagittal alignment better than morselized rib autograft. SUMMARY OF BACKGROUND DATA: Some studies have shown that structural grafts are more effective in preserving sagittal alignment, while others have found them to be no more effective than morselized rib graft. METHODS: Anterior-posterior radiographs were measured for primary, secondary, and fractional Cobb curves, and C7-sacrum plumb lines. Lateral radiographs were measured for: T5-HIV (highest instrumented vertebrae), instrumented levels, LIV (lowest instrumented vertebrae)-S1, T12-LIV, and T12-S1 angles, C7-sacrum plumb lines, and LID-A (lowest instrumented disc-angle). RESULTS: The increase in kyphosis from preoperative to follow-up radiographs of the angle between T12-LIV was significantly more for the patients with morselized rib graft compared with those with structural grafts, 9 degrees and 1 degree, respectively (P < 0.05). CONCLUSIONS: The structural grafts placed in disc spaces below T12 were able to maintain sagittal alignment over this region, while the spines that received only morselized rib graft collapsed into kyphosis.

Adolescent↗
PubMed2006

Intraoperative pulmonary embolism of Harrington rod during spinal surgery: the potential dangers of rod cutting.

This is a case report and laboratory-based biomechanics study. The objective is to report the first case of Titanium rod embolisation during scoliosis surgery into the Pulmonary artery. To investigate the potential of an unconstrained cut Titanium rod fragment to cause wounding with reference to recognised weapons. Embolisation of a foreign body to the heart is rare. Bullet embolisation to the heart and lungs is infrequently reported in the last 80 years. Iatrogenic cases of foreign body embolisation are very rare. Fifty 1-2 cm segments of Titanium rod were cut in an unconstrained manner and a novel method was used to calculate velocity. A high-speed camera (6,000 frames/s) was used to further measure velocity and study projectile motion. The wounding potential was investigated using lambs liver, high-speed photography and local dissection. Rod velocities were measured in excess of 23 m s(-1). Rods were seen to tumble end-over-end with a maximum speed of 560 revolutions/s. The maximum kinetic energy was 0.61 J which is approximately 2% that of a crossbow. This is sufficient to cause significant liver damage. The degree of surface damage and internal disruption was influenced by the orientation of the rod fragment at impact. An unconstrained cut segment of a Titanium rod has a significant potential to wound. Precautions should be taken to avoid this potentially disastrous but preventable complication.

Adult↗
PubMed2006

Is there a role for selective anterior instrumentation in neuromuscular scoliosis?

Our objective was to report on the clinical and radiological outcome from a cohort of patients with neuromuscular scoliosis who underwent selective anterior single rod instrumentation for correction of thoraco-lumbar and lumbar scoliosis. Traditionally combined anterior release with long posterior instrumentation has been advocated for the treatment of neuromuscular scoliosis. Neuromuscular curves tend to be long and may have significant pelvic obliquity. However, certain neuromuscular curves with minimal pelvic obliquity may lend themselves to selective anterior correction thereby saving motion segments and allow continued ambulation for those patients. Nine patients with neuromuscular scoliosis underwent selective anterior instrumentation between 1994 and 2000. The mean follow up was 2 years and 9 months (range 24-55 months). The clinical outcome (including parent and caregiver satisfaction), radiological outcome (Cobb angle, apical vertebral translation, pelvic obliquity, truncal shift, thoracic kyphosis, lumbar lordosis, sagittal vertical axis) and complications are reported. Subjective outcome was excellent in six patients and good in three. All nine patients retained their ability to walk. There were no neurological or vascular complications. Supplementary posterior surgery was required in two patients. The mean pre-operative Cobb angle of 52 degrees (range 44-60) improved to 20 degrees (range 10-28) at 3 months, achieving Cobb angle correction of 61% and was 19 degrees (range 7-28) at final follow-up. The mean pre-operative compensatory curve of 31 degrees (range 20-42) spontaneously corrected to 18 degrees (range 14-24) at 3 months and was maintained at 18 degrees (range 10-26) at final follow up. The mean pre-operative pelvic obliquity of 7 degrees (range 0-14) corrected to 4 degrees (range 0-8) at 3 months and was 3 degrees (range 0-8) at final follow up. Selective anterior instrumentation and fusion in carefully selected patients with neuromuscular scoliosis (short flexible curves, minimal pelvic obliquity, pre-operative walkers, slow or non-progressive pathology) appears to have satisfactory clinical and radiological outcome at least in the short-term.

Adolescent↗
PubMed2005

A prospective, randomised controlled trial of femoral ring allograft versus a titanium cage in circumferential lumbar spinal fusion with minimum 2-year clinical results.

The literature reports on the safety and efficacy of titanium cages (TCs) with additional posterior fixation for anterior lumbar interbody fusion. However, these papers are limited to prospective cohort studies. The introduction of TCs for spinal fusion has resulted in increased costs, without evidence of superiority over the established practice. There are currently no prospective controlled trials comparing TCs to femoral ring allografts (FRAs) for circumferential fusion in the literature. In this prospective, randomised controlled trial, our objective was to compare the clinical outcome following the use of FRA (current practice) to the use of TC in circumferential lumbar spinal fusion. Full ethical committee approval and institutional research and development departmental approval were obtained. Power calculations estimated a total of 80 patients (40 in each arm) would be required to detect clinically relevant differences in functional outcome. Eighty-three patients were recruited for the study fulfilling strict entry requirements (>6 months chronic discogenic low back pain, failure of conservative treatment, one- or two-level discographically proven discogenic low back pain). The patients completed the Oswestry Disability Index (ODI), Visual Analogue Score (VAS) for back and leg pain and the Short-Form 36 (SF-36) preoperatively and also postoperatively at 6, 12 and 24 months, respectively. The results were available for all the 83 patients with a mean follow-up of 28 months (range 24-75 months). Five patients were excluded on the basis of technical infringements (unable to insert TC in four patients and FRA in one patient due to the narrowing of the disc space). From the remaining 78 patients randomised, 37 received the FRA and 41 received the TC. Posterior stabilisation was achieved with translaminar or pedicle screws. Baseline demographic data (age, sex, smoking history, number of operated levels and preoperative outcome measures) showed no statistical difference between groups (p<0.05) other than for the vitality domain of the SF-36. For patients who received the FRA, mean VAS (back pain) improved by 2.0 points (p<0.01), mean ODI improved by 15 points (p=<0.01) and mean SF-36 scores improved by >11 points in all domains (p<0.03) except that of general health and emotional role. For patients who received the TC, mean VAS improved by 1.1 points (p=0.004), mean ODI improved by 6 points (p=0.01) and SF-36 improved significantly in only two of the eight domains (bodily pain and physical function). Revision procedures and complications were similar in both groups. In conclusion, this prospective, randomised controlled clinical trial shows the use of FRA in circumferential lumbar fusion to be associated with superior clinical outcomes when compared to those observed following the use of TCs. The use of TCs for circumferential lumbar spinal fusion is not justified on the basis of inferior clinical outcome and the tenfold increase in cost.

Adult↗
PubMed2005

Single photon emission computerized tomography and reverse gantry computerized tomography findings in patients with back pain investigated for spondylolysis.

BACKGROUND: Athletes with low back pain may have sustained a bone stress injury in the lumbar neural arch, including spondylolysis. Single photon emission computerized tomography (SPECT) and reverse gantry computerized tomography (rg-CT) help localize bone stress response and spondylolyses. OBJECTIVES: To describe the SPECT and rg-CT findings in those patients suspected of suffering from a spondylolysis. STUDY DESIGN: Large retrospective case series. SETTING: Secondary and tertiary care center in England. PATIENTS: A total of 213 patients presenting to the Spinal Unit and Sports Medicine Clinics between 1995 and 2000 with low back pain and subsequently investigated for spondylolysis by SPECT and rg-CT. METHODS: An experienced consultant musculoskeletal radiologist reported the SPECT and rg-CT, and these results along with data from the patient's medical records were analyzed. MAIN OUTCOME MEASURES: Sites and sides of increased scintigraphic activity in the lumbar neural arch seen on SPECT and complete and incomplete spondylolyses were recorded. RESULTS: Single photon emission computerized tomography scan showed increased scintigraphic uptake in 145 patients, mostly (42.3%) at L5. Marked increase in scintigraphic uptake was noted on the left side of the neural arch in 31 patients and on the right in 17 (chi; P < 0.05). Spondylolysis was identified on rg-CT in 81 patients. Spondylolyses were bilateral on 44 occasions, but unilateral lesions occurred in the left pars 36 times and on the right 16 times (chi; P < 0.01) CONCLUSIONS: Spondylolyses were a frequent finding on rg-CT in young athletes with low back pain. The sports most commonly associated with this stress response in the pars interarticularis were cricket and soccer. The lower lumbar levels are more likely to show abnormalities on SPECT and computerized tomography. Among those investigated for spondylolysis, left-sided lower lumbar pain was more common than right, and a marked increase in scintigraphic uptake was noted on the left more often than the right. Although bilateral spondylolyses were common, left-sided spondylolyses were more common than right. The asymmetric repetitive movements of certain sports may be responsible. In particular, fast bowlers developed spondylolysis on the opposite side of the body to their bowling arm.

Adolescent↗
PubMed2004

Discitis.

Discitis is not an uncommon condition and can be potentially life threatening if diagnosed late. This article reviews recent publications and discusses the clinical presentation, pathoaetiology, diagnosis, treatment and pitfalls.

Age Distribution↗
PubMed2003

A prospective randomized comparison of coralline hydroxyapatite with autograft in cervical interbody fusion.

STUDY DESIGN: A prospective randomized trial with independent clinical and radiographic outcome review of patients receiving either hydroxyapatite or tricortical iliac crest graft for cervical interbody fusion was conducted. OBJECTIVE: To determine whether coralline-derived hydroxyapatite is a suitable bone graft substitute in cervical interbody fusion. SUMMARY OF BACKGROUND DATA: Tricortical iliac crest bone is the "gold standard" graft material for cervical interbody fusion. Various bone substitutes have been used for this procedure to avoid potential donor site morbidity. ProOsteon 200 is a coralline-derived hydroxyapatite product, the use of which remains unclear for cervical interbody fusion. METHODS: In this study, 29 patients undergoing anterior cervical fusion and plating were randomized to receive either ProOsteon 200 or iliac crest grafts. The SF-36 and Oswestry Disability Index were used to measure clinical outcome. Postoperative radiographs were analyzed for graft fragmentation, loss of height, angular alignment, and hardware failure to assess structural integrity of the graft material. Plain radiographs and computed tomography scans were used to evaluate fusion. RESULTS: Both the ProOsteon 200 and iliac crest groups demonstrated significant improvement in clinical outcome scores. There was no significant difference in clinical outcome or fusion rates between the two groups. Graft fragmentation occurred in 89% of the hydroxyapatite grafts and 11% of the autografts (P = 0.001). Significant graft settling occurred in 50% of the hydroxyapatite grafts, as compared with 11% of the autografts (P = 0. 009). One patient in the ProOsteon 200 group required revision surgery for graft failure. CONCLUSIONS: ProOsteon 200 does not possess adequate structural integrity to resist axial loading and maintain disc height or segmental lordosis during cervical interbody fusion.

Bone Transplantation↗
PubMed2002

Biomechanical evaluation of immediate stability with rectangular versus cylindrical interbody cages in stabilization of the lumbar spine.

BACKGROUND: Recent cadaver studies show stability against axial rotation with a cylindrical cage is marginally superior to a rectangular cage. The purpose of this biomechanical study in cadaver spine was to evaluate the stability of a new rectangular titanium cage design, which has teeth similar to the threads of cylindrical cages to engage the endplates. METHODS: Ten motion segments (five L2-3, five L4-5) were tested. From each cadaver spine, one motion segment was fixed with a pair of cylindrical cages (BAK, Sulzer Medica) and the other with paired rectangular cages (Rotafix, Corin Spinal). Each specimen was tested in an unconstrained state, after cage introduction and after additional posterior translaminar screw fixation. The range of motion (ROM) in flexion-extension, lateral bending, and rotation was tested in a materials testing machine, with +/- 5 Nm cyclical load over 10 sec per cycle; data from the third cycle was captured for analysis. RESULTS: ROM in all directions was significantly reduced (p < 0.05) with both types of cages. There was no significant difference in reduction of ROM in flexion-extension (p = 0.6) and rotation (p = 0.92) between the two cage groups, but stability in lateral bending was marginally superior with the rectangular cages (p = 0.11). Additional posterior fixation further reduced the ROM significantly (p < 0.05) in most directions in both cage groups, but did not show any difference between the cage groups. CONCLUSIONS: There was no significant difference in immediate stability in any direction between the threaded cylindrical cage and the new design of the rectangular cage with endplate teeth.

Journal Article↗
PubMed2002

Pelvic or lumbar fixation for the surgical management of scoliosis in duchenne muscular dystrophy.

STUDY DESIGN: This retrospective study evaluates two groups of patients with scoliosis and Duchenne muscular dystrophy, treated with two different surgical stabilization methods. OBJECTIVE: To determine whether fixation to the sacropelvis is always necessary for adequate stabilization of scoliosis in Duchenne muscular dystrophy. SUMMARY OF BACKGROUND DATA: Pelvic fixation is generally recommended for scoliosis in Duchenne muscular dystrophy. Recent studies describe a more selective approach toward lumbar or pelvic fixation. Pelvic fixation is reserved for larger curves and established pelvic tilt. METHODS: Fifty cases of Duchenne muscular dystrophy, operated in two different centers and followed up for a minimum of 3 years, were reviewed. In the first group (Oswestry), 31 patients had fixation to the pelvis, using standard Luque instrumentation and pelvic fixation. The Galveston technique was used in 9 cases and L-rod configuration in 22 cases. In the second group (Nottingham), 19 cases had fixation to L5 using pedicle screws in the lumbar spine and sublaminar wires in the thoracic spine. These cases were operated on early, usually shortly after becoming wheelchair dependent. RESULTS: In the pelvic fixation group, the mean age at the time of surgery was 14 years, and forced vital capacity was 44%. The mean Cobb angle and pelvic obliquity were 48 degrees and 19.8 degrees at the time of surgery, 16.7 degrees and 7.2 degrees immediately after surgery, and 22 degrees and 11.6 degrees at the final follow-up (mean 4.6 years), respectively. The mean blood loss was 4.1 L, and the average hospital stay was 17 days. There were five major complications, including a deep wound infection in one case, revision of instrumentation prominence at the proximal end in two cases, and loosening of pelvic fixation in two cases. In the lumbar fixation group, the mean age at the time of surgery was 11.7 years, and forced vital capacity was 58%. The mean Cobb angle and pelvic obliquity were 19.8 degrees and 9 degrees at the time of surgery, 3.2 degrees and 2.2 degrees immediately after surgery, and 5.2 degrees and 2.9 degrees at the final follow-up (mean 3.5 years), respectively. The mean estimated blood loss (3.3 L) and mean hospital stay (7.7 days) were much less compared with the pelvic fixation group. Pelvic obliquity was corrected and maintained below 10 degrees in all but two cases, who had an initial pelvic obliquity exceeding 20 degrees. One patient had instrumentation failure at the proximal end, and one had a deep wound infection. CONCLUSION: Lumbar fixation to L5 is adequate if the surgery is performed early, soon after becoming wheelchair bound, and with smaller curves and minimal pelvic obliquity. Use of pedicle screws in lumbar spine provides a solid foundation to maintain the correction over the period of relatively short life expectancy of these children. Pelvic fixation may be necessary in older children, who have larger curves and established pelvic obliquity. In the presence of deteriorating lung function, this is associated with a greater morbidity and higher complication rate.

Adolescent↗
PubMed2002

Patient and parental perception of adolescent idiopathic scoliosis before and after surgery in comparison with surface and radiographic measurements.

STUDY DESIGN: This prospective 2-year follow-up study evaluated patients treated surgically for adolescent idiopathic scoliosis (AIS). OBJECTIVE: To report parents' perception, patients' perception, and pain and disability before and after surgery and to examine their relationship to anthropometric, back surface, and radiographic measurements. SUMMARY OF BACKGROUND DATA: No longitudinal studies have examined these factors and their interrelationships. METHODS: Between 1995 and 1999, 39 AIS patients treated by anterior or posterior USS (Universal Spine System, Stratec, Oberdorf, Switzerland) instrumentation had complete prospective questionnaire, back surface, and radiographic appraisal. RESULTS: The preoperative Visual Analogue Score (VAS) for pain-predominantly mild backache-was 24 mm (range, 0-78 mm), and the Oswestry Disability Index (ODI) score was 9.2% (0-44.4%). Patients and parents wanted surgery to correct spinal curvature, stop curve progression, and correct the rib-hump (thoracic) and hip and waist asymmetry (thoracolumbar curves). The maximum angle of trunk inclination correlated with VAS and with short-form McGill Pain Questionnaire scores for thoracic curves (P = 0.005, Spearman rank correlation coefficient). Apical vertebral translation correlated with short-form McGill scores and ODI for thoracolumbar curves (P < 0.006, Spearman rank correlation coefficient). Parents rated scoliosis problems more severely than did their children (P < 0.0001, repeated measures of multivariate analysis of variants). There was no change in body image, VAS, ODI, or short-form McGill scores by 2 years' follow-up. Parents and patients perceived scoliosis problems to be less by 2 years' follow-up (P < 0.0005, Wilcoxon matched-pairs signed ranks test). The preoperative surface asymmetry score correlated with the patients' grading of their rib-hump (P = 0.007). CONCLUSIONS: Back pain incidence was higher than reported for healthy adolescents. Oswestry Disability Index was within normal adult limits. Pain varied by curve type, related to the maximum angle of trunk inclination and the maximum apical vertebral translation. After surgery, back pain and ODI were unchanged, but concerns regarding scoliosis were reduced.

Adolescent↗
PubMed2002

Treatment of congenital scoliosis in an 8-month-old child.

Congenital scoliosis due to fully segmented hemivertebrae is most often progressive and requires treatment. Currently, the operative treatment recommended includes (a) posterior spinal fusion with or without instrumentation and (b) anterior and posterior exposure with fusion, epiphysiodesis or hemivertebral excision. We report the case of a patient who was operated on at the age of 8 months by a single-stage posterior approach with a transpedicular hemivertebral resection and convex hemepiphysiodesis combined with a low-profile posterior unilateral instrumentation. The goals were the prevention of progression, potential correction by growth on the concave side, short hospital stay, reduction in the morbidity associated with a separate anterior approach, and no need for postoperative bracing. Preliminary results after a follow-up period of 2 years support the impression that this approach bears significant advantages compared to previously preferred anteroposterior procedures.

Disease Progression↗