Current therapies for osteoporosis are limited to generalised antiresorptive or anabolic interventions, which do not target specific regions to improve skeletal health. Moreover, the adaptive changes of separate and combined pharmacological and biomechanical treatments in the ovariectomised (OVX) mouse tibia has not been studied yet. Therefore, this study combines micro- computed tomography (micro-CT) imaging and computational modelling to evaluate the efficacies of treatments in reducing bone loss. In vivo micro-CT (10.4µm/voxel) images of the right tibiae of N=18 female OVX C57BL/6 mice were acquired at weeks 14, 16, 18, 20 and 22 of age for 3 groups: mechanical loading (ML), parathyroid hormone (PTH) or combined therapies (PTHML). All mice received either injection of PTH (100μg/kg/day, 5days/week) or vehicle from week 18. The right tibiae were mechanically loaded in vivo at week 19 and 21 with a 12N peak load, 40 cycles/day and 3 days/week. Bone adaptation was quantified through spatial changes in bone mineral density (BMD) and strain distribution was obtained from micro-CT-based finite element models.Abstract
Objectives
Methodology
Prediction of bone adaptation in response to mechanical loading is useful in the clinical management of osteoporosis. However, few studies have investigated the effect of repeated mechanical loading in the mouse tibia. Therefore, this study uses a combined experimental and computational approach to evaluate the effect of mechanical loading on bone adaptation in a mouse model of osteoporosis. Six female C57BL/6 mice were ovariectomised (OVX) at week 14 and scanned using in vivo micro computed tomography (10.4µm/voxel) at week 14, 16, 18, 20 and 22. The right tibiae were mechanically loaded in vivo at week 19 and 21 with a 12N peak load, 40 cycles/day, 3 days/week. Linear isotropic homogeneous finite element (microFE) models were created from the tissue mineral density calibrated microCT images. Changes in bone adaptation, densitometric and spatial analyses were measured by comparing the longitudinal images after image registration.Abstract
Objectives
Methods
Both navigation and instrumented bone referencing use unreliable intraoperative landmark identification or fixed referencing rules which don't reflect patient specific variability. PSI, however, lacks the flexibility to adapt to soft tissue factors not known during preoperative planning, in addition to suffering error from guide fit. A novel method of recreating surgical cut planes that combines preoperative image based identification of landmarks and planning with intraoperative adjustability is under development. This method uses an intraoperative 3D scan of the bone in conjunction with a preoperative CT scan to achieve the desired cuts and so avoids issues of intraoperative identification of landmarks. During TKA surgery, a reference device is placed on the exposed femur. The device is used to position a target block which is pinned to the bone (see Figure 1). The condyles and target block are then scanned, the process taking a second to complete. This 3D scan is filtered to remove extraneous bodies and noise leaving only the bony geometry and target block (see Figure 2). The scan is then reconciled to the known bone geometry taken from preoperative CT scans. A cutting block is then fixed to the target block with a reference array visible to the camera attached. Pre-planned cut planes on a computer model of the bone are compared to the position and configuration of the distal cutting guide. Software guides the surgeon in real-time on the necessary configuration changes required to align the cutting block. The cut is performed on the distal femur, the cutting guide removed from the target-block, and a second scan performed. The software repeats the filtering and alignment processes and provides the surgeon with data on how closely the performed cut matches the alignment planned.Introduction
Method
the mid-sagittal plane of 10 male and 10 female discs aged 13–79 years; 7 parasagittal slices through a single disc; discs showing various types of tears.
Most chondrocytes were unicellular but bicellular and multicellular chondrons were common in the margins of large tears and the nucleus in degenerate discs. Cellularity was highest in the right posterior quadrant, lowest in the left anterior quadrant, about equal in the left posterior and right anterior quadrants, and substantially higher in the right half of the nucleus. The correlation of increasing age with declining cell density was much stronger for the nucleus than for the annulus. Nucleus cellularity continued to decline throughout life whereas the annulus ceased its decline after the age of 50. Cell density was low in the vicinity of tears but elsewhere the disc was unaffected. Extensive inferior and superior end-plate separations reduced cellularity throughout the disc. Increased thickness of the cartilage end-plate was associated with higher cellularity in the nucleus.
INTRODUCTION: Intradiscal electrothermal therapy (IDET) is being used increasingly as a minimally-invasive treatment for chronic discogenic low back pain, with success reported in up to 70% of cases. The mechanism of action however is poorly understood. Proposed mechanisms include the contraction of collagen and the coagulation of annular nociceptors. An ovine model was used to assess the innervation of peripheral posterolateral annular lesions and the potential for IDET to denervate this region. METHODS: Posterolateral annular incisions were made in 36 lumbar discs of 18 sheep. After twelve weeks the sheep underwent IDET at one level and a sham treatment at the other level. IDET was performed using a modified intradiscal catheter (SpineCATHTM, Oratec Interventions Inc., Menlo Park, CA). Temperatures were recorded in the nucleus and the posterior annulus. The spines were harvested at intervals of up to eighteen months. Histological sections of the discs were stained with haematoxylin and eosin and an antibody to the general neuronal marker PGP 9.5. RESULTS: The target temperature of 90°C at the catheter tip was reached in all cases. The mean maximum TPa was 63.6°C and the mean maximum TN was 67.8°C. Vascular granulation tissue consistent with a healing response was observed in the region of the posterior annulus tear of all incised discs from 12 weeks. PGP 9.5 positive nerve fibres were clearly identified in the adjacent periannular tissue, but were scarce within the outer few lamellae of the annulus. There were no fewer nerve fibres identified in those specimens that had undergone IDET. From six weeks after IDET there was evidence of thermal necrosis in the inner annulus, sparing the periphery of the disc. DISCUSSION: IDET delivered at 90°C in the sheep consistently heats the posterior annulus and the nucleus to a temperature associated with coagulation of nociceptors and collagen contraction. Thermal necrosis was observed within the inner annulus from six weeks after IDET. In this model IDET did not appear to produce denervation of the posterior annular lesion.
To assess the potential for IDET to ablate nerve fibres in an experimentally induced peripheral annular lesion. Intradiscal electrothermal therapy (IDET) is being increasingly used as a minimally-invasive treatment for discogenic low back pain, with success reported in up to 70% of cases. One proposed mechanism of IDET is ablation reported in up to 70% of cases. One proposed mechanism of IDET is ablation of nerve fibres in the peripheral annulus. An ovine model was used to assess the innervation of peripheral annular lesions and the potential for IDET to denervate this region of the disc. Postero-lateral annular incisions were made in 32 lumbar discs of 16 sheep. At twelve weeks the sheep underwent IDET at one level and a sham treatment at the other level. IDET was performed using a modified Intradiscal Catheter (SpineCath, Oratec Interventions Inc., Menlo Park, CA). The spines were harvested at intervals up to six months. Histological sections of the discs were stained with H&
E and an antibody to the general neuronal marker PGP 9.5. Vascular granulation tissue consistent with a healing posterior annular tear was observed in all incised discs from 12 weeks, extending to an average depth of 850 μm at 0 weeks to 690 μm at 6 months. PGP 9.5 positive nerve fibres were clearly identified outside the discs but were scarce within the discs. Nerves were identified up to 300 μm inside the annulus, from the earliest time point, and there was a trend towards less innervation with time. There were no fewer nerve fibres identified in those specimens that had undergone IDET. Specimens obtained six weeks after IDET showed evidence of thermal necrosis in the inner annulus, sparing the periphery of the disc. The reported benefit from IDET appears to be related to factors other than denervation. Thermal necrosis within the annulus six weeks after IDET.
Are peak posterior annular and nuclear temperatures obtained during IDET within the temperature range normally associated with nociceptor destruction and contraction of collagen? Pain relief following intradiscal electrothermal therapy (IDET) has been reported to result from coagulation of annular nociceptors and contraction of collagen. This requires temperatures respectfully of 45°C and 60°C. A cadaveric study using an intradiscal catheter (Spinecath, Oratec Interventions Inc., CA) reported sufficient temperatures for these events to occur. However a human study reported temperatures sufficient only to coagulate nociceptors. This study reports peak posterior annular and nuclear temperatures attained in-vivo with an intradiscal catheter in sheep. Twenty sheep were anaesthetised and the lumbar spine exposed. In two non-adjacent discs a stab incision was made in the left postero-lateral annulus and the wound closed. Twelve weeks later the animals returned for a second operation. The spine was approached from the right. Under fluoroscopic control the intradiscal catheter was placed into a previously operated disc. One thermocouple sensor needle was placed 2mm posterior to the catheter to record the posterior annular temperature and a second was inserted 2mm anterior to record the nuclear temperature. The process was repeated for a non-operated control disc. Electrothermal energy was delivered according to the recommended heating protocol. The target temperature of 90°C at the catheter tip was reached in all cases. Data were tabulated with the mean and standard deviation calculated for each site. There was no significant difference between temperatures reached in the ‘degenerate’ discs and those in the control discs. The mean maximum posterior annular temperature was 63.6°C (range 46.8 to 77.7) and the mean maximum nuclear temperature was 67.8°C (Range 51.1 to 81.2). Intradiscal electrothermal therapy delivered at 90°C in the sheep consistently heats the posterior annulus and the nucleus to a temperature associated both with coagulation of nociceptors and collagen contraction. These findings may contribute to understanding the mechanism of pain relief following IDET.
Primary disc space infections are thought to occur in children because of the abundant vascularity of the disc prior to skeletal maturity, and while they generally resolve with treatment, little is known about the long-term consequences on the spine. An ovine model of discitis was used to investigate the effects of discitis on spinal development in the growing sheep. Six-week-old lambs underwent lumbar discography at multiple spinal levels using either radiographic contrast inoculated with Staphylococcus epidermidis (inoculated group) or radiographic contrast only (control group). Plain x-rays of the spines were taken at intervals up to 18 months before the animals were killed and the spines removed for histologic and morphometric analysis. Discs from animals in the control group were radiologically and histologically normal at all time points, and as expected there was a steady increase in vertebral body and disc dimensions. Although not all inoculated animals showed histologic evidence of discitis, disc abnormalities were evident from an early stage. In particular disc height was significantly reduced from 2 weeks after inoculation and vertebral body dimensions were significantly reduced from one year. Infection of discs at a young age, whether or not it progresses to discitis, has a significant effect on spinal development.
The ‘Pi’ plate is an anatomical titanium plate recently introduced for the internal fixation of comminuted intra-articular distal radius fractures. We report our experience with this implant in a prospective series of twelve patients with an average age of thirty six years (range, 26–52 years). A dorsal approach with release of the EPL tendon and extra-compartmental exposure of the radius between the second and fourth extensor compartments was employed in all cases. Iliac bone graft and a styloid K-wire were used to augment the plate fixation. Post-operatively, active mobilisation was started after wound healing. Wrist motion and grip strength measurements were made at six weeks, three months and six months by the therapist. At six months, patients recovered an average of 85% of range of movement compared with the opposite wrist, except for palmar flexion (65%). No loss of reduction was observed on follow-up radiographs. Complications were compartment syndrome, intraoperative EPL rupture and two cases of extensor tendonitis requiring implant removal. The ‘Pi’ plate affords rigid fixation of distal radius fractures permitting early rehabilitation. It is however a demanding technique that is not without complications.