Clinical field testing of polyurethane feet for trans-tibial amputees in tropical low-income countries.

In a prospective controlled study, 172 polyurethane feet of different designs were fitted to 155 amputees with trans-tibial prostheses. These were followed in respect of their durability. The amputee compliance was in general good, and 87% were satisfied with their device. After 18 months the failure rate of 20% with the CIREC spring-blade foot was significantly better than the others, but poorer craftsmanship, higher complaint rate and lower compliance rate cast some doubt on the results. The results with the conventional SACH foot constructions with polyurethane as filling and covering materials were so poor after 18 months that their use cannot be recommended in tropical areas of the developing world.

Clinical field testing of vulcanized rubber feet for trans-tibial amputees in tropical low-income countries.

In a prospective, controlled study, 186 prosthetic rubber feet of different designs were fitted to amputees with trans-tibial prostheses. There were 158 amputees available for follow-up. The amputee compliance was good and 89% were satisfied with their device. After 18 months of use one VI-Solid rubber foot from VVAF in Cambodia had failed, as compared to 11% failures with the same foot with a heel cavity, 3% with the EB-1 sandwich construction from POF in Vietnam, all performing significantly better than the 62% encountered with the vulcanized rubber foot from ICRC in Cambodia; the latter representing half of the feet failing in amputees walking bare-footed. Nearly all failures were located at the foot-sole or the keel. The failure rate was 20% for the HI-Cambodia foot after 12 months. After 24 months of use, still only one VI-Solid rubber foot had failed and this foot design was found superior to the others in regard of durability.

Life expectancy and social consequences of through-knee amputations.

Amputation surgery for gangrene of the lower limb has two primary goals, to save life and to bring the patients back to their previous living conditions. If this can be achieved with restored walking ability the result of the treatment is considered a full success. The purpose of this paper is to describe the risk of death and possibility of returning through-knee amputees to their own home, relating the results to other major levels of amputation of the lower limb.

Success rate of prosthetic fitting after major amputations of the lower limb.

Rehabilitation after amputation at through-knee level is described and analysed in relation to amputations at above-knee and below-knee levels.

Operative technique in knee disarticulation.

The operative technique is described in detail. Pitfalls are emphasized and comparisons made with other techniques.

The healing of through-knee amputations in relation to skin perfusion pressure.

The healing in 20 through-knee amputations was compared with preoperatively measured skin perfusion pressure, determined as the minimal external pressure required to stop the washout of isotopes injected intradermally 10 cm distal to the knee joint. Out of 18 amputations with a skin perfusion pressure of above 20 mmHg only 2 failed to heal, whereas 2 out of 4 cases with skin perfusion pressure below 20 mmHg failed to heal. It is concluded that the through-knee amputation must be considered in cases where the circulation is borderline for healing in below-knee amputation.

Additional mechanical tests of bone cements.

A revision of the ISO-standard for bone cement testing has been proposed to include compressive strength after 24 hours in air and 4-point bending testing after 50 hours in a 37 degrees water bath. Nine commercially available bone cements were tested in accordance with the new program. Compressive strength varied from 78 to 100 MPa, bending strength from 48 to 74 MPa and bending modulus from 2.2 to 2.8 GPa. The highest strengths, but also the highest stiffness, were encountered with Simplex brands and low-viscosity cements.

Mechanical failure of hydroxyapatite-coated titanium and cobalt-chromium-molybdenum alloy implants. An animal study.

Defects in the hydroxyapatite (HA) ceramic coatings applied to metallic implant systems may occur at the time of insertion or at the time of in vivo loading. However, defects may also occur with time because of interaction with physiological fluids. A canine study was performed to make a histological and biomechanical evaluation of HA-coated titanium and cobalt-chromium-molybdenum alloy implants in a non-weight-bearing model. Twelve cylindrical plugs were inserted into the medial femoral condyle on 6 mongrel dogs. HA-coatings of 80-120 microns thickness were applied to 6 Cr-Co-Mo implants and 6 Ti-6AI-4V implants. The implants were removed together with adjacent bone tissue after 4 weeks. There were no statistically significant differences between the two groups for interface shear strength. No differences were encountered with HA-coating on Cr-Co-Mo or on Ti-6AI-4V, failure consistently being caused by disruption between the metal surface and the HA-coating, which remained fixed to the bone. At histologic evaluation the HA-coated implants exhibited a great amount of direct bone-to-implant contact. In spite of that, this study indicates that HA-coating on smooth metal surfaces might not be suitable for clinical use, because of low bonding strength between metal and coating.

Hemi-arthroplasty of the hip followed by ipsilateral fracture of the femoral shaft.

In a series of 74 ipsilateral fractures of the femoral shaft in relation to hemi-arthroplasties, treatment by a cemented long-stem total hip replacement was found to be superior to conservative treatment or internal fixation without removal of the prosthesis. Acceptable clinical results were obtained in 89 per cent of these cases.