Novel Vacuum-Assisted Method for Harvesting Autologous Cancellous Bone Graft and Bone Marrow From the Proximal Tibial Metaphysis

Background: Autogenous cancellous bone graft and bone marrow aspirate are commonly used in lower extremity fusion procedures to enhance fusion potential, and frequently in revision situations where bone loss and osteolysis may be a feature. The tibial metaphysis is a common donor site for bone graft, with the procedure typically performed using a curette or trephine to harvest the cancellous bone. Some limitations of this technique include suboptimal harvest of the marrow portion in particular, incomplete graft harvest, and loss of graft material during the harvest process. We describe a novel vacuum-assisted bone harvesting device to acquire cancellous bone and marrow from the proximal tibia. Methods: This is a retrospective study of a single surgeon’s consecutive patients who underwent foot and ankle arthrodesis procedures using proximal tibia autograft obtained using a vacuum-assisted bone harvesting device. Descriptive statistics were used to summarize patient and operative characteristics and outcomes. We identified 9 patients with a mean age of 51 years, 4 of whom were female. Results: On average, the skin incision was slightly more than 2 cm, and 27 mL of solid graft and 16 mL of liquid phase aspirate were collected. At 6 weeks after the procedure, there was minimal to no pain at the donor site, and we did not observe any fractures or other complications. Conclusions: We report the use of a novel vacuum-assisted curette device to harvest bone graft from the proximal tibial metaphysis for use in foot and ankle fusions. This device has been reliable and efficient in clinical practice. Level of Evidence: Level IV, retrospective case series.

Negligible Effect of Estrogen Deficiency on Development of Skeletal Changes Induced by Type 1 Diabetes in Experimental Rat Models

Although postmenopausal osteoporosis often occurs concurrently with diabetes, little is known about interactions between estrogen deficiency and hyperglycemia in the skeletal system. In the present study, the effects of estrogen deficiency on the development of biochemical, microstructural, and mechanical changes induced by streptozotocin-induced diabetes mellitus (DM) in the rat skeletal system were investigated. The experiments were carried out on nonovariectomized (NOVX) and ovariectomized (OVX) control and diabetic mature female Wistar rats. Serum levels of bone turnover markers (CTX-I and osteocalcin) and 23 cytokines, bone mass and mineralization, histomorphometric parameters, and mechanical properties of cancellous and compact bone were determined. The results were subjected to two-way ANOVA and principal component analysis (PCA). Estrogen deficiency induced osteoporotic changes, with increased bone resorption and formation, and worsening of microstructure (femoral metaphyseal BV/TV decreased by 13.0%) and mechanical properties of cancellous bone (the maximum load in the proximal tibial metaphysis decreased by 34.2%). DM in both the NOVX and OVX rats decreased bone mass, increased bone resorption and decreased bone formation, and worsened cancellous bone microarchitecture (for example, the femoral metaphyseal BV/TV decreased by 17.3% and 18.1%, respectively, in relation to the NOVX controls) and strength (the maximum load in the proximal tibial metaphysis decreased by 35.4% and 48.1%, respectively, in relation to the NOVX controls). Only in the diabetic rats, profound increases in some cytokine levels were noted. In conclusion, the changes induced by DM in female rats were only slightly intensified by estrogen deficiency. Despite similar effects on bone microstructure and strength, the influence of DM on the skeletal system was based on more profound systemic homeostasis changes than those induced by estrogen deficiency.

Evaluation of Implants with Different Macrostructures in Type I Bone—Pre-Clinical Study in Rabbits

The objective of this study was to assess the primary stability and the osseointegration process in implants with different macrostructures (Cylindrical vs. Hybrid Conical) in rabbit tibiae. Twenty-four (24) rabbits were used, divided into 3 experimental periods (2, 4 and 8 weeks) with 8 animals each. Each animal bilaterally received 2 implants from each group in the tibial metaphysis: Cylindrical Implant (CI) and Hybrid Conical Implant (HCI). All implants were assessed for insertion torque. After the experimental periods, one of the implants in each group was submitted to the removal counter-torque test and descriptive histological analysis while the other implant was used for microtomographic and histometric analysis (%Bone-Implant Contact). HCI implants showed higher insertion torque (32.93 ± 10.61 Ncm vs. 27.99 ± 7.80 Ncm) and higher % of bone-implant contact in the 8-week period (79.08 ± 11.31% vs. 59.72 ± 11.29%) than CI implants. However, CI implants showed higher values of removal counter-torque than HCI implants in the 8-week period (91.05 ± 9.32 Ncm vs. 68.62 ± 13.70 Ncm). There were no differences between groups regarding microtomographic data. It can be concluded that HCI implants showed greater insertion torque and bone-implant contact in relation to CI implants in the period of 8 weeks when installed in cortical bone of rabbits.

Ischemic Stroke Reduces Bone Perfusion and Alters Osteovascular Structure

RationaleStroke patients lose bone mass and experience fracture at an elevated rate. Although functional intraosseous vasculature is necessary for skeletal maintenance, the effect of stroke on osteovasculature is unknown.ObjectiveTo characterize changes to osteovascular function, structure, and composition following mild-to-moderate-severity ischemic stroke in mice, both with and without exercise therapy.Methods and ResultsTwelve-week-old male mice (n=27) received either a stroke (middle cerebral artery occlusion) or sham procedure, followed by four weeks of daily treadmill or sedentary activity. Intraosseous perfusion, measured weekly in the proximal tibial metaphysis, was reduced by stroke for two weeks. In the second week of recovery, exercise nearly restored perfusion to sham levels, and perfusion tended to be lower in the stroke-affected limb. At the conclusion of the study, osteovascular structure was assessed with contrast-enhanced computed tomography in the distal femoral metaphysis. Stroke significantly increased osteovascular volume and branching but reduced the relative number of blood vessels close to bone surfaces (6-22 µm away) and increased the relative number more than 52 µm away. These differences in vessel proximity to bone were driven by changes in the stroke-exercise group, indicating compounded effects of stroke and exercise. Exercise, but not stroke, nearly reduced the amount of osteogenic Type H blood vessels in the proximal tibial metaphysis, quantified with immunofluorescence microscopy.ConclusionsThis study is the first to examine the effects of stroke on osteovasculature. Stroke increased the amount of osteovasculature, but since blood vessels close to bone are associated with bone remodeling, the shift in osteovascular structure could play a role in bone loss following stroke. The exercise-induced reduction in the amount of Type H vessels and the stroke-exercise effect on osteovascular structure suggest moderate aerobic activity may have detrimental effects on bone remodeling during early stroke recovery.

Novel Technique for Fixation of Medial Malleolus Fractures

Category: Ankle, Trauma Introduction/Purpose: The traditional method for fixation of medial malleolar fractures has been with partially threaded (PT) lag screws extending beyond the physeal scar. Recent studies have shown fully threaded (FT) bicortical fixation in the tibial metaphysis provides superior biomechanical, radiographic and clinical outcomes. Risks with the bicortical technique include drill bit breakage, as well as injury to structures lateral to the tibial metaphysis if the far cortex is overdrilled. We hypothesized that far endosteal fixation, without penetration of the far cortex, would provide increased biomechanical strength compared to traditional PT lag screw fixation, while minimizing the risks associated with bicortical fixation. Methods: Twelve matched pairs of cadaver ankles were harvested and an oscillating saw was used to make an osteotomy at a 45- degree angle to the axilla. The medial malleolus was then re-approximated and held in the correct orientation using two kirschner wires. A 2.7 mm drill bit was used to drill a unicortical pilot hole perpendicular to the osteotomy. The left ankle was used for all PT 3.5 mm cancellous screws and all screw lengths were 45 mm. For the contralateral ankle, the 2.7 mm drill bit was used to drill to the lateral tibial cortex. The depth gauge was then used and five millimeters was added to the measured number to achieve endosteal purchase with the appropriate FT screw. Screw lengths varied in size from 55-70 mm. Screws were then placed using a torque measuring screw driver and final torque was recorded. Finally, radiographs were taken to confirm appropriate placement. Results: Average torque for unicortical PT cancellous screws was 5.02 inch-pounds with a standard deviation of 2.34. Average torque for all FT cortical screws was 7.63 inch-pounds with a standard deviation of 3.86 (Fig. 1A). A paired student’s t-test was performed comparing both fixation methods and the measured P-value was <0.01. Visual and radiographic inspection revealed no displacement of the fracture site using the FT endosteal screw (Fig. 1C). Conclusion: Our results indicate superior biomechanical torque with far endosteal fixation as compared to a traditional PT lag screw, while minimizing risks associated with bicortical fixation. This novel technique may provide added strength with minimal risk in vivo. Further clinical studies comparing radiographic results and outcomes of far endosteal fixation versus bicortical fixation are needed to ascertain the value of this fixation technique for medial malleolus fractures.