Bone cutting produces heat which macroscopically leads to charring and the formation of bone dust. As part of a project to design a novel bone cutting device, we studied the extent of histological thermal damage from bone cutting with different cutting blades.

Three blades were used: a bone hacksaw made in the nineteenth century which was used for amputation, a sagittal saw blade made by Ortho Solutions, and a sagittal saw blade made by Stryker. Sheep femurs were harvested from recently euthanised animals and cuts were made with these three devices, producing ring-shaped bone specimens. Specimens were immediately stored in formaldehyde, decalcified, and stained with hematoxylin and eosin. The edge of the specimens was then photographed microscopically, and the images examined with the computer programme Axiovision (Carl Zeiss AG, Oberkochen, Germany). Visual examination allowed identification of live and dead osteocytes, and also to measure their depth from the surface.

A minimal of 7 images was obtained per blade. The hacksaw specimens had the highest percentage of live osteocytes (n=214, 59.8%), and with the shortest average depth where live osteocytes were located (169μm, SD 78.15). In comparison, the percentage of live osteocytes for the Ortho Solutions (n=156, 17.4%) and Stryker (n=168, 29.5%) blades were much lower. The difference in average depths where live osteocytes were located was statistically significant between the three groups (p < 0.001). The average depths of dead osteocytes were shallowest for the Stryker (115μm, SD 67.56) and hacksaw (118.28 μm, SD 75.16) groups with no statistical difference between them.

In conclusion the hacksaw appeared to produce the least thermal damage histologically during cutting. The results reflect a relationship between certain features in cutting blade designs and the extent of thermal damage. Future experiments to directly measure heat produced during cutting are planned.

Bone cutting produces heat which macroscopically leads to charring and the formation of bone dust. As part of a project to design a novel bone-cutting device, we studied the extent of histological thermal damage from different cutting blades. Three blades were used: a nineteenth century bone hacksaw, and modern sagittal saw blades manufactured by Ortho Solutions and Stryker. Sheep femurs were harvested from recently euthanised animals and cuts were made with these blades. Specimens were immediately stored in formaldehyde, decalcified, and stained with hematoxylin and eosin. The edge of the specimens was then photographed microscopically, and the images examined with Axiovision software (Carl Zeiss AG, Oberkochen, Germany). Visual examination allowed identification of live and dead osteocytes, and also to measure their depth from the surface. A minimal of 7 images was obtained per blade. The hacksaw specimens had the highest percentage of live osteocytes (n=214, 59.8%), and the shortest average depth where live osteocytes were located (169 μm, SD 78.15). In comparison, the percentage of live osteocytes for the Ortho Solutions (n=156, 17.4%) and Stryker (n=168, 29.5%) blades were much lower. The difference in average depths where live osteocytes were located was statistically significant between the three groups (p<0.001). In conclusion the hacksaw appeared to produce the least thermal damage histologically during cutting. The results reflect a relationship between certain features in cutting blade designs and the extent of thermal damage. Future experiments to monitor heat produced during cutting are planned.

Background

Hyperlaxity is associated with a high incidence of shoulder dislocations. Collagen V regulates the diameter of fibrils of the abundant collagen type I. Decorin and biglycan are members of the small leucine rich proteoglycans(SLRP's)family and play important roles in the regulation of collagen fibrillogenesis. The aim of this study was to identify if there was a link in hyperlaxity, capsule strength, collagen V and SLRP's expression.

Background

Hyperlaxity is associated with a high incidence of sporting injuries. Collagen V regulates the diameter of fibrils of the abundant collagen type I. Decorin and biglycan are members of the small leucine rich proteoglycans(SLRP's)family and play important roles in the regulation of collagen fibrillogenesis. The aim of this study was to identify if there was a link in hyperlaxity, tissue strength, collagen V and SLRP's expression.

Background: Muscle tears and injuries are a huge problem throughout the world. Ways of reducing these injuries are welcome, with warm-up and stretching of muscles prior to use established methodologies. Forces associated with muscles can be thought of as active (stimulated muscle: actin-myosin) and passive (relaxed muscle: elastic proteins and connective tissue). In muscle tears, the connective tissue component is damaged, but there is very little information in the literature on this component of the muscle.

Objective: To examine passive (elastic) components in muscle during impact loading at differing temperatures. In particular to test the hypothesis that the connective tissue component fails at different loads according to the temperature.

Methods: Gastrocnemius and Soleus were isolated from 36 male rat limbs, clamped and exposed to increasing impact loads, by dropping a known weight from increasing heights. Muscle was given one minute to recover before an increased force was applied. Temperature was varied from 17 C to 42 C (to encompass the physiological range) in 5 C increments. The height of drop causing non-recoverable deformation, and the maximum deceleration of the weight (measured using an accelerometer attached to a picoscope) at a constant height was recorded for each temperature.

Results: The energy to failure, i.e. the point at which non-recoverable deformation occurred was found to increase above 32 C (p < 0.01) and the maximum deceleration at impact found to have a downward trend with increasing temperatures. At 17 C, the energy to failure was 317.7 ± 20 mJ, At 22 C, the energy to failure was 301.8 ± 29 mJ, At 27 C, the energy to failure was 317.7 ± 40 mJ, At 32 C, the energy to failure was 333.5 ± 21.2 mJ, At 37 C, the energy to failure was 460.2 ± 15.8 mJ, At 42 C, the energy to failure was 619.5 ± 21.2 mJ,

Conclusions: Muscle was shown to act in an increasingly elastic nature with temperature. At higher temperatures a larger energy is required to deform the muscle permanently, and the muscle decelerates more slowly, both in keeping with elastic properties. The same energy at a lower temperature causes significant deformation within the muscle. This has numerous clinical implications, as the temperature at which this change occurs is encountered during surgery and also by sportsmen on outdoor pitches. More research is required to look at the passive components within muscles in humans.

X-ray is the standard method for monitoring fracture healing however it is not ideal; signs of healing are not normally visible on X-ray until around 6–8 weeks post fracture. Ultrasonography allows the detection of both the initial haematoma, usually formed immediately after fracture, and the small calcium deposits laid down between broken bone ends in the first stages of fracture healing. It has been reported that these early indicators of the healing process are visible as early as 1–2 weeks after fracture. We use Freehand 3D Ultrasound to monitor the early stages of fracture healing as both the bone surface and surrounding soft tissues can be imaged simultaneously.

The Freehand 3D Ultrasound system consists of a standard Ultrasound machine, a PC running STRAD-WIN (Medical Imaging Group, Cambridge University) 3D software, and an optical tracking devise (NDI Polaris) to record the position and orientation of the Ultrasound probe during scanning. Images are transferred from the Ultrasound machine to the PC using RF capture through out a scan. Calibrating the system matches up the correct image with the correct probe position to produce a 3D dataset.

We segment features of interest on the sequence of 2D images to construct a 3D model. These models are rotatable and provide views of the scanned anatomy that are not otherwise achievable using conventional Ultrasound or X-ray. The 3D data set can also be resliced through any plane to provide further views.

To conduct a 3D Ultrasound scan takes the same amount of time as a conventional 2D scan. The production of the 3D model takes between 15–60 minutes depending on the level of detail required. Distances are measurable to within ±0.4mm meaning fracture gaps of sub-millimeter width can be resolved. The system has already been evaluated on healthy volunteers and a clinical study currently underway.

An uncomplicated, quantitative method of determining density from X-rays would be of extreme value to clinicians. In this study we perform a thorough assessment of applying a step wedge to grey level calibration method to X-rays obtained using Computed Radiography (CR).

An Aluminium step wedge of ten, 5mm-thick steps was X-rayed with a Fuji CR system together with a knee phantom (3M) at various energy and Fuji processing settings. Automatic detection of the steps by means of the Hough transform was used to assess optimum CR settings. Background variation due to the anode Heel effect was evaluated by acquiring an “empty field” X-ray at different energy settings and with copper filtering. The effects of beam hardening were considered with a custom-made phantom which was also used to assess correcting for soft tissue and bone thickness.

X-rays taken at higher energy settings and with wider windowing imaged the widest number of steps (nine) and gave the best accuracy in modelling the step thickness to grey level relationship. Fitting a straight line to the log of the net grey levels gives an excellent model of the data (R2 = 0.99). X-rays of copper sheeting show that automatic histogram analysis is performed by the Fuji CR system, which can have unpredictable effects on aluminium thickness to grey level relationship. Background variation in the anode-cathode direction due to the Heel effect was corrected with a 1D exponential model (R2 = 0.99), allowing position-independent measurements to be obtained. Correcting for bone thickness, soft tissue and beam hardening further improves measurement quality.

Use of step wedge calibration to provide quantitative information on plain X-rays without altering their clinical quality is possible using digital radiography. However, a thorough assessment of the entire X-ray process is necessary to achieve accurate and comparable information.

Thermonecrosis either results in bone loss which may weaken the purchase of surgically-inserted screws leading to loosening or the dead bone may remain in situ and become infected resulting in a ring sequestrum. The aim of this project was to measure the heat generated during drilling of bone. By using a novel realtime thermal camera the thermal events could be visualised topographically.

An experimental setup comprising a force table, an infrared camera, a power drill and a new surgical 2.5mm drill bit was constructed. This enabled measurements of the force applied and temperature changes in sheep cortical bone during a drilling operation. The temperature was observed throughout the drilling period and for further 15s after the drill bit was withdrawn. Images were grabbed using a LAND FTI Mv thermal camera which was driven by LIPS Mini software. Calibration was made in the range 20-200 degrees C, the upper value being provided by a high wattage resistor. Data was processed using routines written in MATLAB.

It was found that 12s were required to drill through a single cortex. Within one second of drilling, the maximum recorded temperature in the vicinity of the drill increased from the baseline of 20 to 170 degrees C. It remained above this temperature for 25s. Immediately after the drill bit was withdrawn, a region of approximately 15mm of diameter of cortical surface had a sustained temperature above 50 degrees C. After 15s of cooling, this diameter had only reduced to 10mm. By modelling the cooling curve, the maximum temperature at the drill tip was extrapolated to be between 500-600 degrees C.

Thermography has proven to be useful in the study of the thermal characteristics of bone during drilling. The process of drilling generates significant increase in temperature in the vicinity of the drill. This temperature elevation has been found to be sustained for a significant period of time.

Distal radial fractures account for 17% of all fractures treated, with peaks in the bimodal distribution corresponding to young and senior patients. External fixation is one of the best techniques to allow quick patient recovery and is necessary for complex fractures, such as that of the distal radius. However, the safe removal time for these frames remains unclear. A conservative approach commonly leaves the external fixator in place for six weeks, which may be unnecessarily prolonged and lead to increased complications. The aim of this work is to develop a technique to quantify, objectively, a safe removal time for these frames. Studies have been conducted on external fixation of tibial fractures, however there are differences that do not allow transfer of these studies to the external fixation of distal radial fractures. These differences include configuration of the fixation frame, bone and fracture geometries, and the application and transfer of the load to the bone. In this work, the dynamic transfer of the load between the fractured bone and the fixator is investigated. An instrumented grip and a measuring device have been developed to monitor the axial force and displacement when the patient applies a load. Using measurements collected by the instrument and data specifying the frame geometry, a finite element model is used to calculate the load carried by the fixator and by the bone, and the rigidity of the new callus is determined. Plotting the rigidity on semi-logarithmic scale the healing rate can be established. This technique has been successfully verified in a laboratory simplified structure representative of bone fracture. The rigidity of several intra-gap materials has been estimated experimentally using the technique, and the results compared to the real value of the material. These measurements do not interfere in any way with the patient treatment and they can be collected from the first day after the operation. The technique has been tested on 14 volunteer patients and the increase in callus rigidity can be detected by measurements during treatment using the technique described. A randomised prospective study has been initiated to validate this technique and investigate the healing process. A positive outcome would enable the rigidity of the new callus bone and the healing rate to be monitored during clinical assessment. Any healing delay or non-union could be promptly detected, improving the quality of the treatment.