Martin A. McNally

Total hip replacement, lower limb blood flow and venous thrombogenesis

The effect of Charnley cemented total hip replacement on venous blood flow in the legs and its relationship to deep-vein thrombosis were investigated in 413 patients. Blood flow was measured using strain-gauge plethysmography before operation, after surgery, and after discharge from hospital. There was a significant reduction in both venous capacitance and venous outflow, affecting both legs but greater in the operated leg. Venous flow remained significantly below preoperative levels in the operated leg six weeks after surgery. There was a highly significant correlation between the degree of reduction in blood flow and the development of postoperative deep-vein thrombosis. Venous stasis was shown to be a major factor in venous thrombogenesis.

Numerical model of deep venous thrombosis detection using venous occlusion strain gauge plethysmography

Strain gauge plethysmography (SGP) is a non-invasive method used in the detection of deep venous thrombosis (DVT). The technique is based on the measurement of calf volume changes in response to venous occlusion by a thigh cuff, the volume changes reflecting the rates of arterial inflow and venous outflow. A numerical model of the blood circulation within the limb and the response of this to a SGP test has been derived, based on treating the different parts of the circulatory system in the leg as resistance and capacitance elements. The simulation results were compared with clinical studies and support the ability of SGP to detect non-occlusive clots of more than 50–60% of the lumen, as well detecting calf vein pressure appears to be a particularly important factor within the model. In addition, increases in venous tone due to post-operative venospasm were shown to be a potential source of false positive results.

ILIZAROV TECHNIQUE FOR SALVAGE ANKLE ARTHRODESIS

Introduction Ankle fusion presents a difficult problem in the presence of infection and poor bone stock. The Ilizarov method provides stability with remote fixation and allows weight bearing. Patients and method Fourteen consecutive patients were studied (10 males, 4 females). The mean age at onset of disease was 50 years (range 4–70). Thirteen of the patients had either clinical or radiological evidence of infection prior to ankle fusion surgery. Mean duration of problem was 52 months (range 8–372). Aetiology included traumatic arthritis in five, failed fusion in six, septic arthritis in one, infected ankle fracture non-union in one and avascular necrosis of talus in one. Local excision was followed by Ilizarov frame compression. Diagnosis of infection was based on microbiology and histology. Antibiotic treatment was continued until union. On radiological evidence of union the frame was dynamized and removed. A below-knee cast was applied for 4 weeks. Results At a mean period of 5 months, complete ankle fusion was found in 13/14 patients. One patient who had partial fusion of the ankle had recurrence of infection requiring amputation. Complications included pin site infection, lateral impingement, deep infection, hind-foot pain and neuroma at amputation site. Conclusion The Ilizarov ankle fusion is a reliable salvage procedure in difficult ankle problems.