Slavko Davila

Cortical bone drilling and thermal osteonecrosis

BACKGROUND Bone drilling is a common step in operative fracture treatment and reconstructive surgery. During drilling elevated bone temperature is generated. Temperatures above 47°C cause thermal osteonecrosis which contributes to screw loosening and subsequently implant failures and refractures. METHODS The current literature on bone drilling and thermal osteonecrosis is reviewed. The methodologies involved in the experimental and clinical studies are described and compared. FINDINGS Areas which require further investigation are highlighted and the potential use of more precise experimental setup and future technologies are addressed. INTERPRETATION Important drill and drilling parameters that could cause increase in bone temperature and hence thermal osteonecrosis are reviewed and discussed: drilling speed, drill feed rate, cooling, drill diameter, drill point angle, drill material and wearing, drilling depth, pre-drilling, drill geometry and bone cortical thickness. Experimental methods of temperature measurement during bone drilling are defined and thermal osteonecrosis is discussed with its pathophysiology, significance in bone surgery and methods for its minimization.

Intraoperative measurement of bone electrical potential: a piece in the puzzle of understanding fracture healing

INTRODUCTION Bone electrical potentials change with the force applied. Also, fracture alters the bone electrical potential, so it becomes more electronegative. These potentials have an important role in fracture healing, bone growth and remodelling. Literature data on the influence of fracture operative treatment on bone electrical potentials, and possible consequences of this influence, are sparse. The objective of this study was to establish a method of intraoperative bone potential measurement, and to try to find a correlation between electrical potential and fracture type, osteosynthesis method and prognosis. PATIENTS AND METHODS 52 patients with a pertrochanteric fracture were included in the study. Bone electrical potentials were measured intraoperatively using a thin Kirschner wire introduced through bone cortex at the selected point and pointed to opposite cortex, not penetrating it. Kirschner wires were connected using clamps to multimeter (YF-78 Multimeter) device. Neutral electrode (inductive rubber) was placed behind ipsilateral gluteus. RESULTS Near the fracture site potentials of -199 up to -267 mV were recorded. Mean measured potential of bone plate after fixation was -240 mV. Bone potentials correlated with the subtype of fracture and early mobilisation of patients. CONCLUSIONS Bone potentials, caused by fracture, can be measured intraoperatively; the operative procedure appears to influence their generation. Measured potentials depend on the fracture type, and could be correlated with prognosis.

Thermal changes during healing of distal radius fractures : Preliminary findings

INTRODUCTION The bone healing process is very complex. In simple terms, bone healing comprises three basic steps, the inflammation phase, the repair phase and the remodelling phase. The increase in blood flow around the fracture during the healing process increases the temperature of the surrounding tissue. Infrared thermography is a method of measuring body temperature that can detect temperature changes during bone healing. Studies on the application of thermography in traumatology are scarce, and there are no studies of thermal changes during normal bone healing. The authors have tried to determine the dynamics of thermal changes during bone healing. MATERIAL AND METHODS The Flir ThermaCam B2 (FLIR Systems, Inc., Oregon, USA) was used for all measurements. Thermographic recordings were made one, three, five, 11 and 23 weeks after fracture. The contralateral, healthy, forearm was used for comparison. RESULTS A total of 25 patients of mean age 65.9±10.4 years (range 50-80 years) with fracture of the distal radius were examined in this study. The mean temperature difference between healthy and fractured distal forearm one week after fracture was 1.20±0.48°C, three weeks after fracture was 1.42±0.54°C, five weeks after fracture was 1.04±0.53°C, 11 weeks after fracture was 0.50±0.30°C, and 23 weeks after fracture was 0.22±0.25°C. CONCLUSION Preliminary findings during this research showed significant temperature changes during healing of distal radius fractures. Infrared thermography is a simple and reliable method in clinical practice that could be used as a good follow-up method in traumatology, but further investigations on more patients are needed.

Reducing damage to the periosteal capillary network caused by internal fixation plating: An experimental study

BACKGROUND The importance of the periosteum in fracture healing is well-known. Preserving periosteal vascularisation is essential during internal plate fixation of fractures. METHODS This was an experimental randomised, controlled animal study on nine sheep. Standard dynamic compression plate (DCP) and four different newly designed reefed plates, with different plate-bone contact surface areas and different reef directions, were fixated on to the tibia or radius. After two weeks the plates were removed and the underlying periosteum was analysed. Blood vessels were marked by immunohistochemical staining (CD31 and CD34), microphotographs were taken and blood vessels counted to calculate blood vessel density. RESULTS Median blood vessel density beneath the standard plate was significantly lower than in the intact periosteum (18.0 vs 27.7mm(3)/cm(3)). Blood vessel density in the periosteum beneath plates with reefs was significantly increased compared with the intact periosteum, and was highest beneath the plate with the lowest bone-plate contact area and crosswise reefs (51.5mm(3)/cm(3)), followed by plates with transverse, oblique and longitudinal reefs, respectively. The direction of the reefs did not have much influence on the periosteal capillary network. Lower contact surface area seems to be the main factor that increases blood vessel density beneath the plates. CONCLUSIONS The results show that plates with lower contact surface area stimulate angiogenesis in the underlying periosteum, which results in much higher blood vessel density compared with standard DCP. A randomised clinical trial is needed to prove the clinical relevance of these findings.

Mathematical approximation of fibular malleolus curvature

While there are several manuscripts describing the articular surfaces of the ankle joint and the fibula itself, there is no study describing the outer surface and the degree of curvature of the fibular malleolus. This paper aims to approximate the sagital curvature of the outer surface of the lateral malleolus mathematically. Such data would facilitate the design of the anatomic plate that can be used for the ostheosynthesis of the fibular malleolus fracture. 30 males who were examined in the emergency department due to ankle sprains, where they underwent a standard anteroposterior x-ray of the ankle in the neutral position were recruited. The radiographs which revealed no bony injury were digitized and statistically processed. A mathematical function for each separate fibula was obtained through the processing of the digitized x-rays. When all the functions were applied to one graph, common traits of all fibulas were noted. The mean value of all functions was obtained and it corresponds to the polynomial function of degree 6. Mathematical approximation of the curvature is a simple and reliable method that can be applied to other ellipsoid human bone structures besides the ankle, thus being a valuable method in anthropometric, radiological and virtual geometric calculations.