 |
||
|
BRITSPINE 2010 2011Britspine 2010 homepage PRIZES Best Scientific Content
OSTEOPOROTIC VERTEBRAL DEFORMITIES ARE DUE TO "CREEP" AS WELL AS INJURY J Luo PhD, P Pollintine PhD*, P Dolan PhD, M A Department of Anatomy, *Department of Mechanical Engineering, Objective Osteoporotic vertebral deformities are conventionally attributed to fracture, although deformity is often insidious, and bone is known to "creep" under constant load. We hypothesise that deformity can arise from creep that is accelerated by minor injury. Study Design Thirty-nine thoracolumbar "motion segments" were tested from cadavers aged 42-92 yrs. Vertebral body BMD was measured using DXA. A 1.0 kN compressive force was applied for 30 mins, while the height of each vertebral body was measured using a MacReflex optical tracking system. After 30 mins recovery, one vertebral body from each specimen was subjected to controlled micro-damage (<5mm height loss) by compressive overload, and the creep test was repeated. Load-sharing between the vertebral body and neural arch was evaluated from stress measurements made by pulling a pressure transducer through the intervertebral disc. Results Creep was inversely proportional to BMD below a threshold BMD of 0.5 g/cm2 (R2=0.30, P<0.01) and did not recover substantially after unloading. Creep was greater in the anterior cortex compared to the posterior (p=0.01) so that anterior wedge deformity occurred. Vertebral micro-damage usually affected a single endplate, causing creep of that vertebra to increase in proportion to the severity of damage. Anterior wedging of vertebral bodies during creep increased by 0.10o (STD 0.20o) for intact vertebrae, and by 0.68o (STD 1.34o) for damaged vertebrae. Conclusion Creep is substantial in elderly vertebrae with low BMD, and is accelerated by micro-damage. Preferential loss of trabeculae from the anterior vertebral body could explain greater anterior creep and vertebral wedging. Best Impact for change in clinical practice: J Luo PhD, P Pollintine PhD*, P Dolan PhD, M A Department of Anatomy, *Department of Mechanical Engineering, Objective Osteoporotic vertebral deformities are conventionally attributed to fracture, although deformity is often insidious, and bone is known to "creep" under constant load. We hypothesise that deformity can arise from creep that is accelerated by minor injury. Study Design Thirty-nine thoracolumbar "motion segments" were tested from cadavers aged 42-92 yrs. Vertebral body BMD was measured using DXA. A 1.0 kN compressive force was applied for 30 mins, while the height of each vertebral body was measured using a MacReflex optical tracking system. After 30 mins recovery, one vertebral body from each specimen was subjected to controlled micro-damage (<5mm height loss) by compressive overload, and the creep test was repeated. Load-sharing between the vertebral body and neural arch was evaluated from stress measurements made by pulling a pressure transducer through the intervertebral disc. Results Creep was inversely proportional to BMD below a threshold BMD of 0.5 g/cm2 (R2=0.30, P<0.01) and did not recover substantially after unloading. Creep was greater in the anterior cortex compared to the posterior (p=0.01) so that anterior wedge deformity occurred. Vertebral micro-damage usually affected a single endplate, causing creep of that vertebra to increase in proportion to the severity of damage. Anterior wedging of vertebral bodies during creep increased by 0.10o (STD 0.20o) for intact vertebrae, and by 0.68o (STD 1.34o) for damaged vertebrae. Conclusion Creep is substantial in elderly vertebrae with low BMD, and is accelerated by micro-damage. Preferential loss of trabeculae from the anterior vertebral body could explain greater anterior creep and vertebral wedging.
Best Impact for change in clinical practice:
'DOCTOR, WILL MY BACK SET OFF ANY ALARMS?' DETECTION OF SPINAL IMPLANTS BY AIRPORT METAL DETECTORS* Yee Leung, F Chinwalla, M Grevitt. Centre for Spinal Studies & Surgery, Objective: Determine the detection rate of modern spinal implants using the curennt technology. Background: There is a paucity of data regarding detection rates of modern spinal implants using modern walk-through pulsed archway metal detectors (AMDs). No published reports compare detection capability with hand-held metal detectors (HHMDs). Study Design: ex-vivo & in-vivo comparison of detection rates using AMD & HHMD (set to maximum DoT sensitivities), in patients of varying Body Mass Index (BMI), implants, implant mass / density and alloys. Subjects: 40 patients with: lumbar disc replacement (CoCr) (n=8), cervical disc replacement (CoCr) (1), posterior deformity instrumentation (17), anterior deformity instrumentation (2), anterior reconstruction (2), PLIF (6), interspinous distraction device (1), anterior cervical plate (2) ALIF (1), All implants were titanium unless indicated. Mean metal mass was 98g (range 6g-222g).
Results: The AMD did not detect any instrumentation individually or in combination up to a titanium mass totalling 215g. The HHMD detected all instrumentation at a distance of 5cm; with the minimum mass being 2g
No implants were detected in patients by the AMD. The HHMD did not detect any anterior lumbar or thoracic surgical implants. It detected anterior cervical implants. The HHMD detected all posterior surgical implants. There was no significant relationship between detection, BMI, total metal mass, and metal density/segment.
Conclusions: AMD detectors do not detect modern spinal implants. HHMD detect all modern posterior spinal implants; this has implications for patient documentation.
'DOCTOR, WILL MY BACK SET OFF ANY ALARMS?' DETECTION OF SPINAL IMPLANTS BY AIRPORT METAL DETECTORS* Yee Leung, F Chinwalla, M Grevitt. Centre for Spinal Studies & Surgery, Objective: Determine the detection rate of modern spinal implants using the curennt technology. Background: There is a paucity of data regarding detection rates of modern spinal implants using modern walk-through pulsed archway metal detectors (AMDs). No published reports compare detection capability with hand-held metal detectors (HHMDs). Study Design: ex-vivo & in-vivo comparison of detection rates using AMD & HHMD (set to maximum DoT sensitivities), in patients of varying Body Mass Index (BMI), implants, implant mass / density and alloys. Subjects: 40 patients with: lumbar disc replacement (CoCr) (n=8), cervical disc replacement (CoCr) (1), posterior deformity instrumentation (17), anterior deformity instrumentation (2), anterior reconstruction (2), PLIF (6), interspinous distraction device (1), anterior cervical plate (2) ALIF (1), All implants were titanium unless indicated. Mean metal mass was 98g (range 6g-222g).
Results: The AMD did not detect any instrumentation individually or in combination up to a titanium mass totalling 215g. The HHMD detected all instrumentation at a distance of 5cm; with the minimum mass being 2g
No implants were detected in patients by the AMD. The HHMD did not detect any anterior lumbar or thoracic surgical implants. It detected anterior cervical implants. The HHMD detected all posterior surgical implants. There was no significant relationship between detection, BMI, total metal mass, and metal density/segment.
Conclusions: AMD detectors do not detect modern spinal implants. HHMD detect all modern posterior spinal implants; this has implications for patient documentation.
D. Wardlaw1, J. Van Meirhaeghe 2, L. Bastian 3 and S. Boonen 4 for the Fracture Reduction Evaluation (FREE) Study Investigators
Background & Methods Balloon kyphoplasty (BKP) is a minimally invasive treatment for vertebral fractures (VCF) aiming to correct deformity using balloon tamps and bone cement to stabilize the body. Patients with 1 - 3 non-traumatic acute VCF were enrolled within three months of diagnosis and randomly assigned to receive either BKP (N=149) or nonsurgical care (N=151). Follow-up was 2 years. The mean SF-36 physical component summary (PCS) score improved 5.1 points (95%CI, 2.8-7.4; p<0.0001) more in the kyphoplasty than the nonsurgical group at one month, the primary endpoint of the study. Kyphoplasty improved the PCS score by an average of 3.0 points (95%CI, 1.6-5.4; p=0.002) during the two-year follow-up. There was a significant interaction between treatment and follow-up time (p=0.003), indicating that the treatment effect over the year is not uniform across follow-up; a result from early improvement that persists in the kyphoplasty group whereas the nonsurgical group shows more incremental improvement over time. Overall, patients assigned to kyphoplasty also had statistically significant improvements over the two years compared to the control group in global quality of life (EQ-5D), pain relief (VAS), back disability (RMDQ) and days of limited activity (within a two-week period). There was no statistical significant difference between groups in the number of patients with adverse events or new VCF's over 24 months. Conclusion Compared to the control, BKP improved quality of life and reduced back pain and disability and did not increase adverse events including the risk of new vertebral fractures over 2 years.
Special Posters:
SIGNIFICANCE OF THE INVERTED RADIAL REFLEX IN ASYMPTOMATIC SUBJECTS Alexander J Gibson, Satyen S Mehta, Ben Goss and Richard P Williams AO Spine Reference Centre, Tapping the radial side of the wrist normally elicits a reflex contraction producing elbow flexion, wrist extension and wrist radial deviation. An abnormal response, consisting of finger flexion when performing this manoeuvre is known as the inverted radial (supinator) reflex (IRR). The significance of this reflex in asymptomatic subjects is unknown. To document the frequency of the IRR in an asymptomatic population and to identify any presymptomatic pathology in those subjects. The study group consisted of patients and staff at the senior author's institution. Patients were taken from clinics where the complaints were of lower limb symptoms. Subjects were excluded if they had any history of neck pain or stiffness or if they had any subjectively abnormal sensation. The radial reflex was elicited with a tendon hammer. Those subjects with an IRR were asked to attend for a MRI scan of the cervical spine to investigate for any abnormality. 47 subjects were studied. There were 8 subjects who displayed an IRR. In 4 subjects the IRR was unilateral and in 4 bilateral. Seven subjects consented to further investigation by MRI. The average age of these patients was 36 years. The MRI scans revealed normal appearances in 6 cases. There was no cord signal abnormality in any case. The IRR occurred with a frequency of 17% in the study group. There was no significant cervical pathology identified in these subjects. In young asymptomatic patients, the presence of an inverted radial reflex is of no diagnostic relevance. Ethics approval None Interest Statement None Alexander J Gibson, Satyen S Mehta, Ben Goss and Richard P Williams AO Spine Reference Centre, IntroductionTapping the radial side of the wrist normally elicits a reflex contraction producing elbow flexion, wrist extension and wrist radial deviation. An abnormal response, consisting of finger flexion when performing this manoeuvre is known as the inverted radial (supinator) reflex (IRR). The significance of this reflex in asymptomatic subjects is unknown. AimsTo document the frequency of the IRR in an asymptomatic population and to identify any presymptomatic pathology in those subjects. MethodsThe study group consisted of patients and staff at the senior author's institution. Patients were taken from clinics where the complaints were of lower limb symptoms. Subjects were excluded if they had any history of neck pain or stiffness or if they had any subjectively abnormal sensation. The radial reflex was elicited with a tendon hammer. Those subjects with an IRR were asked to attend for a MRI scan of the cervical spine to investigate for any abnormality. Results47 subjects were studied. There were 8 subjects who displayed an IRR. In 4 subjects the IRR was unilateral and in 4 bilateral. Seven subjects consented to further investigation by MRI. The average age of these patients was 36 years. The MRI scans revealed normal appearances in 6 cases. There was no cord signal abnormality in any case. ConclusionThe IRR occurred with a frequency of 17% in the study group. There was no significant cervical pathology identified in these subjects. In young asymptomatic patients, the presence of an inverted radial reflex is of no diagnostic relevance. Ethics approval None Interest Statement None
|
| © British Association of Spinal Surgeons 2007 | Sitemap | Website by Regency Medical Marketing |