Femoral bone blood flow after reaming and intramedullary canal preparation: a canine study using laser Doppler flowmetry.

This study was conducted to determine the effect of intramedullary reaming and canal preparation on bone blood flow in the proximal femur. Thirty-five adult dogs were randomly assigned to have their intramedullary canals prepared after reaming in the following manner: group 1, ream only; group 2, lavage; group 3, methylmethacrylate cement introduction; group 4, cement pressurization after placing a cement restrictor; group 5, lavage then cement introduction; and group 6, lavage then cement pressurization. Bone blood flow was measured at both metaphyseal and diaphyseal sites by using laser Doppler flowmetry before reaming, after reaming, after lavage, after cementing, and at 6 weeks after the procedure just before euthanasia. Reaming significantly decreased bone blood flow in the diaphysis (P = .046) but not in the metaphysis. Cement introduction and cement pressurization both significantly decreased bone blood flow in the metaphysis (P = .035, P = .004) and diaphysis (P = .007, P = .029). Pressurization of cement had a significantly greater relative effect than cement introduction alone in the diaphysis (P = .006) but not in the metaphysis. Lavage had no effect on bone perfusion. Bone blood flow was significantly increased at 6 weeks after the initial procedure in both the metaphysis (P = .049) and the diaphysis (P = .004). The results suggest that reaming decreases diaphyseal cortical but not metaphyseal bone blood flow significantly, whereas lavage has no effect. Cement introduction with or without pressurization has a significant detrimental effect on metaphyseal and diaphyseal blood flow. These findings have implications for intramedullary nailing and for canal preparation when performing arthroplasty.

The role of methylmethacrylate monomer in the formation and haemodynamic outcome of pulmonary fat emboli.

We examined the roles of methylmethacrylate (MMA) monomer and cementing technique in the formation, and haemodynamic outcome, of pulmonary fat emboli. The preparation of the femoral canal and the cementing technique were studied in four groups of adult dogs as follows: control (no preparation); lavage; cement pressurisation; and cement pressurisation after lavage. We measured the intramedullary pressure, pulmonary artery pressure (PAP), pulmonary capillary wedge pressure and bilateral femoral vein levels of triglyceride, cholesterol and MMA monomer at rest and after reaming, lavage, and cementing. Femoral vein triglyceride and cholesterol levels did not vary significantly from resting levels despite significant elevations in intramedullary pressure with reaming, lavage and cementing (p = 0.001). PAP was seen to rise significantly with reaming (p = 0.0038), lavage (p = 0.0031), cementing (p = 0.0024) and cementing after lavage (p = 0.0028) while the pulmonary capillary wedge pressure remained unchanged. MMA monomer was detected in femoral vein samples when cement pressurisation was used. Intramedullary lavage before cementing had no significant effect on the MMA level. Haemodynamic evidence of pulmonary embolism was noted with reaming and intramedullary canal preparation, irrespective of the presence of MMA monomer. We found no relationship between MMA monomer level and intramedullary pressure, PAP or pulmonary capillary wedge pressure. Our findings suggest that the presence of MMA monomer in femoral venous blood has no effect on the formation of fat emboli or their pulmonary haemodynamic outcome during cemented hip arthroplasty.

A Madreporic-surfaced femoral component in a canine total hip arthroplasty model: bone remodelling response at 6 and 24 months.

OBJECTIVE: To evaluate the bone-remodelling response at 6 and 24 months after total hip arthroplasty around a two-thirds Madreporic-surfaced femoral component in a canine model. DESIGN: A research study in dogs. Statistical analysis was by multivariate analysis of variance. SETTING: A musculoskeletal research laboratory in a university teaching hospital. MATERIAL: Ten mature mixed-breed dogs. INTERVENTION: Unilateral implantation of total hip arthroplasty in the right femur with a Madreporic-surfaced prosthesis. Studies were conducted at 6 months in five dogs and at 24 months in five dogs. In each case, the nonoperated femur was the study control. MAIN OUTCOME MEASURES: Fluorescence microscopy analysis on comparable sections at four levels of the femora, percent porosity computed by image analysis, cortical atrophy. RESULTS: Cancellous hypertrophy was most prominent at the junction of the beaded and smooth portions of the femoral stem. At 6 months the cortex demonstrated atrophy predominant in the anteromedial quadrant. Active bone turnover was present within the interstices of the prosthesis at 6 and 24 months. No significant cortical bone loss occurred between 6 and 24 months. Stress transfer to the bone-prosthesis interface and endosteal cortical "cancellization" appear to be linked phenomena.