Comparison of Results Based on the Number of Kirschner Wires of Different Diameters in Antegrade Intramedullary Fixation of Fifth Metacarpal Neck Fractures

Purpose: The purpose of this study was to compare the clinical and radiological results of patients with fifth metacarpal neck fractures using different sizes and numbers of Kirschner wires (K-wire).Methods: A single institutional retrospective review identified 67 patients with a fifth metacarpal neck fracture between January 2015 and July 2020. The minimum follow-up time was 6 months and they were all treated within 6.4 days of the initial injury. Either one K-wire (1.6 mm), two K-wires (1.1 mm), or three K-wires (0.9 mm) was used. We analyzed the bone union period, and K-wire removal period, duration of surgery, total active motion, intramedullary diameter, pre/postoperative shortening, and pre/postoperative angulation clinically. We used a Method of Shortening Stipulated to measure shortening and the Medullary Canal-lateral view method for angulation. The intramedullary diameter was measured in the mid-shaft of the fifth metacarpal bone in the coronal view. Total active motion was measured at the time of follow-up in our outpatient department.Results: Clinical and radiological parameters showed no statistically significant differences. Even though it did not present a statistical significance, the absolute mean duration of surgery was the shortest in a single K-wire group. Conclusion: The clinical and radiological outcomes of surgery were comparable regardless of the number of K-wires inserted. However, we could look forward to gaining potential benefit from shortened operation time in a single K-wire group. Since stable fixation can be obtained even if one K-wire is used, inserting one thick K-wire into the intramedullary canal can be an alternative according to the surgeon’s preference.

Bone Tissue Response to Different Grown Crystal Batches of Octacalcium Phosphate in Rat Long Bone Intramedullary Canal Area

The microstructure of biomaterials influences the cellular and biological responses in the bone. Octacalcium phosphate (OCP) exhibits higher biodegradability and osteoconductivity than hydroxyapatite (HA) during the conversion process from OCP to HA. However, the effect of the microstructure of OCP crystals on long tubular bones has not been clarified. In this study, two types of OCPs with different microstructures, fine-OCP (F-OCP) and coarse-OCP (C-OCP), were implanted in rat tibia for 4 weeks. F-OCP promoted cortical bone regeneration compared with C-OCP. The osteoclasts appearance was significantly higher in the C-OCP group than in the control group (defect only) at 1-week post-implantation. To investigate whether the solubility equilibrium depends on the different particle sizes of OCPs, Nano-OCP, which consisted of nanometer-sized OCPs, was prepared. The degree of supersaturation (DS) tended to decrease modestly in the order of C-OCP, F-OCP, and Nano-OCP with respect to HA and OCP in Tris-HCl buffer. F-OCP showed a higher phosphate ion concentration and lower calcium ion concentration after immersion in the buffer than C-OCP. The crystal structures of both OCPs tended to be converted to HA by rat abdominal implantation. These results suggest that differences in the microstructure of OCPs may affect osteoclastogenesis and result in osteoconductivity of this material in long tubular bone by altering dissolution behavior.

Single-cell RNA sequencing of intramedullary canal tissue to improve methods for studying fracture repair biology

The ability to study the bone microenvironment of failed fracture healing may lead to biomarkers for fracture nonunion. Herein the authors describe a technique for isolating individual cells suitable for single-cell RNA sequencing analyses from intramedullary canal tissue collected by reaming during surgery. The purpose was to detail challenges and solutions inherent to the collection and processing of intramedullary canal tissue samples. The authors then examined single-cell RNA sequencing data from fresh and reanimated samples to demonstrate the feasibility of this approach for prospective studies.

Numerical Modeling of Fat Embolism Syndrome for a Knee Replacement Operation

Knee replacement operations usually involve reaming the intramedullary canal of the femur bone and the insertion of an intramedullary device (e.g., nail or stem). The effect of reaming velocity on the pressure distribution within the bone was investigated numerically by solving the full three-dimensional momentum, equations together with the continuity equation, using the finite element technique. Viscosity was also varied to obtain a pressure envelope. It was found that all the experimental data follow the same trends as the envelopes predicted by the finite element model. It was clear that an increase in either the insertion reaming rate or the viscosity resulted in an increase in pressure in the intramedullary canal. Furthermore, the effect of hammering an intramedullary nail/stem was also studied. The permeability was varied in order to establish a pressure envelope. It was found that all experimental data follow the same trend obtained by the numerical model.

Experimental Parametric Study of the Factors Leading to Elevated Femoral Intramedullary Pressure and Fat Embolus Syndrome in Orthopaedic Procedures

During orthopaedic procedures such as total knee arthroplasty (TKA), total hip arthroplasty (THA), and intramedullary nailing, it is necessary to hammer implants into the intramedullary canal of long bones. This hammering action can generate a high intramedullary pressure, leading to the release of bone marrow fat globules into the cardiovascular system, and ultimately, the possible development of fat embolism syndrome. In the present study, the effect of parameters such as implant tip geometry, peak impact force, hammer tip material, bone to implant radial gap, and marrow viscosity, on the resulting intramedullary pressure generated when hammering implants into a simulated femur analogue was examined. The bone analogue consisted of a porous plastic cylinder, having similar porosity and pore size to human femoral bone, with bone marrow being represented by a paraffin wax/petroleum jelly mixture. It was found that intramedullary pressure is only slightly lowered by a change in implant tip geometry, and that the use of a steel tipped (as opposed to rubber) hammer resulted in an increase in average pressure in the proximal portion of the bone, but a decrease distally. A lower implant insertion speed, lower hammering force, and a larger bone to implant radial gap were found to significantly reduce the intramedullary pressure. The number of hammer strikes required to insert an implant was found to increase significantly with marrow viscosity, but the average intramedullary pressure was found to decrease with increasing viscosity. Numerical modelling was also found to offer great promise for analysing hammering procedures for orthopaedic research into fat embolism syndrome. Numerical and experimental results were matched with approximately a 20% deviation.

Experimental characterization of the pressure buildup in the intramedullary canal during orthopaedic reaming using a synthetic bone analogue

During certain orthopaedic procedures such as total hip or total knee arthroplasty, it is necessary to ream the intramedullary canal of long bones prior to the insertion of the implant. This reaming procedure can generate significant intramedullary pressure elevations, potentially leading to the release of embolic fat into the blood stream, and thus increasing the risk of a potentially fatal complication, i.e., fat embolism syndrome. In this thesis, a two layer synthetic bone analogue with open cell porosity and mechanical properties similar to that of real bone was developed and used to evaluate the effect of reaming parameters such as RPM, advancement speed, reamer size, bone marrow viscosity and clogged reamer on resulting intramedullary pressure elevations. All the aforementioned parameters, except the reamer size, were found to significantly influence the medullary pressure. It was found that increases in the reamer advancement speed increased the pressure, whereas increases in the reamer RPM decreased the pressure. The correlation between the simulated intramedullary pressure, imposed forces to the bone and applied torque to the reamer was also assessed. No significant correlations between these variables could be established.

Experimental characterization of the pressure buildup in the intramedullary canal during orthopaedic reaming using a synthetic bone analogue

During certain orthopaedic procedures such as total hip or total knee arthroplasty, it is necessary to ream the intramedullary canal of long bones prior to the insertion of the implant. This reaming procedure can generate significant intramedullary pressure elevations, potentially leading to the release of embolic fat into the blood stream, and thus increasing the risk of a potentially fatal complication, i.e., fat embolism syndrome. In this thesis, a two layer synthetic bone analogue with open cell porosity and mechanical properties similar to that of real bone was developed and used to evaluate the effect of reaming parameters such as RPM, advancement speed, reamer size, bone marrow viscosity and clogged reamer on resulting intramedullary pressure elevations. All the aforementioned parameters, except the reamer size, were found to significantly influence the medullary pressure. It was found that increases in the reamer advancement speed increased the pressure, whereas increases in the reamer RPM decreased the pressure. The correlation between the simulated intramedullary pressure, imposed forces to the bone and applied torque to the reamer was also assessed. No significant correlations between these variables could be established.

Experimental Parametric Study of the Factors Leading to Elevated Femoral Intramedullary Pressure and Fat Embolus Syndrome in Orthopaedic Procedures

During orthopaedic procedures such as total knee arthroplasty (TKA), total hip arthroplasty (THA), and intramedullary nailing, it is necessary to hammer implants into the intramedullary canal of long bones. This hammering action can generate a high intramedullary pressure, leading to the release of bone marrow fat globules into the cardiovascular system, and ultimately, the possible development of fat embolism syndrome. In the present study, the effect of parameters such as implant tip geometry, peak impact force, hammer tip material, bone to implant radial gap, and marrow viscosity, on the resulting intramedullary pressure generated when hammering implants into a simulated femur analogue was examined. The bone analogue consisted of a porous plastic cylinder, having similar porosity and pore size to human femoral bone, with bone marrow being represented by a paraffin wax/petroleum jelly mixture. It was found that intramedullary pressure is only slightly lowered by a change in implant tip geometry, and that the use of a steel tipped (as opposed to rubber) hammer resulted in an increase in average pressure in the proximal portion of the bone, but a decrease distally. A lower implant insertion speed, lower hammering force, and a larger bone to implant radial gap were found to significantly reduce the intramedullary pressure. The number of hammer strikes required to insert an implant was found to increase significantly with marrow viscosity, but the average intramedullary pressure was found to decrease with increasing viscosity. Numerical modelling was also found to offer great promise for analysing hammering procedures for orthopaedic research into fat embolism syndrome. Numerical and experimental results were matched with approximately a 20% deviation.

Differences in soft tissue damage using a percutaneous versus open approach for antegrade straight humeral nailing: a quantitative and qualitative anatomical study

Background: Percutaneous insertion of third-generation straight humeral nails is a recent alternative to the conventional open method. Rather than splitting, retracting and subsequently repairing the supraspinatus fibers to visualize the humeral head entry site, the percutaneous approach utilizes a cannulated awl to enter the intramedullary canal through the supraspinatus fibers without visualizing internal shoulder structures. Despite recent evidence demonstrating satisfactory outcomes in the percutaneous method, the potential for iatrogenic injury to the rotator cuff and other shoulder structures is not fully understood. Materials and Methods: We performed an anatomical study of 46 shoulders in 23 cadavers to compare damage caused to internal shoulder structures between the open and percutaneous techniques. Dimensions and morphologies of supraspinatus and humeral head perforations were recorded. Results: The percutaneous technique produced greater latitudinal tearing ( p = 0.002) and less longitudinal tearing ( p < 0.001) of muscle fibers, however there was no difference in supraspinatus hole area ( p = 0.748). The long head biceps tendon was within 3 mm of the bone entry hole in 13 (28%) shoulders, with one shoulder in the open group exhibiting full tendon transection. Conclusions: Percutaneous insertion of intramedullary nails using a cannulated awl appears to produce similar soft tissue and bone entry site morphology as compared to the conventional open technique. The percutaneous method was associated with slightly greater latitudinal tearing, however the effects of this remain to be clarified through clinical studies. External rotation should be avoided during instrumentation to reduce the risk of biceps tendon transection.

Vancomycin bone and tissue concentrations following tibial intraosseous administration – evaluated in a porcine model

Introduction. Systemic perioperative vancomycin may not provide sufficient prophylactic target-site concentrations in the prevention of prosthetic joint infections. Intraosseous vancomycin potentially provides high target-site concentrations. The objective of the present study was to evaluate the local bone and tissue concentrations following tibial intraosseous vancomycin administration in a porcine model. Methods. Eight pigs received 500 mg diluted vancomycin (50 mg/mL) through an intraosseous cannula into the proximal tibial cancellous bone. No tourniquet was applied. Microdialysis was applied for sampling of vancomycin concentrations in adjacent tibial cancellous bone, in cortical bone, in the intramedullary canal of the diaphysis, in the synovial fluid of the knee joint, and in the subcutaneous tissue. Plasma samples were obtained as a systemic reference. Samples were collected for 12 h. Results. High vancomycin concentrations were found in the tibial cancellous bone with a mean peak drug concentration of 1236 (range 28–5295) µg/mL, which remained high throughout the sampling period. The mean (standard deviation) peak drug concentration in plasma was 19 (2) µg/mL, which was obtained immediately after administration. Peak drug concentration, time to peak drug concentration, and area under the concentration–time curve were within the same range in the intramedullary canal, the synovial fluid of the knee, and the subcutaneous tissue. Conclusion. Tibial intraosseous administration of vancomycin provided high concentrations in tibial cancellous bone throughout a 12 h period but with an unpredictable and wide range of peak concentration. The systemic absorption was high and immediate, thus mirroring an intravenous administration. Low mean concentrations were found in all the remaining compartments.