Biomedical subjects
John K Webb
Publications and source records attributed to John K Webb.
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.
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.
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.
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.
Re: Koch et al. Adolescents undergoing surgery for idiopathic scoliosis: how physical and psychological characteristics relate to patient satisfaction with cosmetic result. (Spine 2001;26:2119-24).
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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.
Comment to "Clinical outcome and radiographic results after operative treatment of Scheuermann's disease", by R. W. Poolman et al.
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