Björn Albrektsson

Heat caused by drilling cortical bone. Temperature measured in vivo in patients and animals.

In vivo temperature measurements were performed at drilling in the femoral cortex of the rabbit, dog and man. In the clinical study the bone temperature was measured at fixation of a Richards plate to stabilize a pertrochanteric fracture. With a drill speed of around 20 000 rpm and saline cooling, temperatures of 40 degrees C in rabbits, 56 degrees C in dogs and 89 degrees C in patients were recorded at a distance of 0.5 mm from the periphery of the drill hole. The difference in temperature between the animal and clinical studies was mainly attributed to the difference in cortical thickness between the species. When drilling straight through the canine femur from the lateral to the medial side, a 9 degrees C higher temperature was measured in the remote, medial cortex compared to that recorded in the lateral cortex. This difference arose because it is difficult for the cooling agent to reach the medial cortex. The results of the present study indicate that temperatures measured in animal experiments are not applicable to the clinical situation where very high temperatures may arise on drilling in cortical bone, even if saline cooling is used.

Osseointegration of titanium implants.

Forty-eight screws, six double cylindrical implants and six T-plates were inserted into the tibia or femur of 6 dogs. Two titanium screws were inserted into the proximal tibia of 5 patients to anchor a titanium mould. The implants were removed en bloc with adjacent bone tissue after 3 to 14 months. They were sectioned using a technique that allowed analysis of the intact tissue-to-metal specimens. Osseointegration, defined as a direct bone-to-implant contact without interposed soft tissue, was confirmed in all screw-shaped implants while the cylindres had only partial bone contact as did the T-plates. We conclude that osseointegrated implants may be applicable in joint reconstruction for arthrosis or rheumatoid arthritis.

Implant fixation improved by close fit Cylindrical implant – bone interface studied in rabbits

Cylindric titanium implants of three different diameters were inserted and stabilized in a 3.7-mm burr hole in the rabbit tibia. The purpose of the study was to investigate the interfacial reaction to screw- and cylinder-shaped implants, and to determine if there is a critical gap at the insertion between bone and implant that prevents direct cortical bone apposition on the implant. The study indicated that this critical gap approached zero.

Microcirculation in Grafted Bone:A Chamber Technique for Vital Microscopy of Rabbit Bone Transplants

A method enabling in vivo observations of the microcirculation in orthotopically transplated bone in the rabbit is presented. The technique permits repeated study of a well-defined bone tissue compartment both before and after grafting to an autogenous or allogenous recipient site, respectively. It yields information about the reorganization of the microvascular system and the resorptive and formative processes of bone remodelling during incorporation of grafted bone. In the autologous experimental series, new capillaries were seen in the bone grafts 4 to 5 days after transplantation. No re-utilization of pre-existing graft vessels was observed.

Wear of ion-implanted pure titanium against UHMWPE

Six specimens were manufactured from commercially pure titanium (grade IV) to resemble femoral head prostheses, and five of them ion implanted to increase the wear properties. Together with three cobalt-chrome controls they were run for one million cycles on a 10-station joint simulator. For the first time both the polymer and metallic wear were quantified in the same study. The purpose of the investigation was to estimate the potential for using commercially pure titanium as a bearing surface against ultrahigh-molecular-weight polyethylene for total joint application. It was concluded that the wear properties of titanium were improved by ion implantation, and that these positive effects could probably be enhanced with development of a better polishing technique, and by finding methods of extending the penetration depth of the nitrogen ions.

Morphometrical studies of human femoral condyles.

Thirty-six cadaver knees were examined by various morphometrical methods in order to obtain mathematical and graphical data concerning the geometry of the lower end of the femora. It was found that the paramedian sagittal curves represented magnifications of a certain curvature pattern specific to the medial and the lateral femoral condyle. These curves could be expressed mathematically for each condyle. Furthermore, we found dimensional as well as geometrical intervariations between the different size groups in the knee sample. This could serve as an argument for preferring a different design for medial and lateral condyle components in knee prostheses.

Stepwise introduction of a bone-conserving osseointegrated hip arthroplasty using RSA and a randomized study: I. Preliminary investigations—52 patients followed for 3 years

Background We developed a total hip system using osseointegration guidelines, a metaphyseal-loading proximal femoral replacement in the retained neck and a dual-geometry titanium shell in the acetabulum. Patients and methods A randomized controlled clinical trial was undertaken in 52 patients (53 hips), using the cemented Spectron stem and cementless Harris-Galante II cup as control implants (24 patients in experimental group, 29 control patients). Clinical measures of Harris Hip Score (HHS), pain score and radiostereometric analysis (RSA) at regular intervals for up to three years were used to monitor progress. Results No statistically significant differences were found in HHS and pain score; the stability of the cementless experimental implant was also comparable to that of the cemented controls by RSA. 3 revisions were required for migration in the experimental group and 1 was required for component dislocation in the control group. Interpretation Our findings indicate the practicality of osseointegration of titanium implants, but suggest that current performance is inadequate for clinical introduction. However, the stable fixation achieved in the retained neck in the majority of patients is indicative of osseointegration. This finding will encourage technical and design improvements for enhancement of clinical osseointegration and should also encourage further study. Periprosthetic osteolysis might be avoided by the establishment and maintenance of direct implant-bone connection: “osseointegration”.

Femoral neck retention in hip arthroplasty A cadaver study of mechanical effects

The compression forces on the medial cortex of the femoral neck were measured in 6 cadaver specimens using pressure-sensitive film. A hip prosthesis was loaded in an Instron machine comparing the situation with retained versus resected neck. The results indicate that retaining the neck can be mechanically valuable.

SACRAL RHIZOTOMY IN CASES OF ANO-COCCYGEAL PAIN A Follow-up of 24 Cases

The long-term effect of sacral rhizotomy in 24 patients with coccygodynia was evaluated. Prior to section of both the S-4 and S-5 roots all patients had coccygeal pain and tenderness which had not responded to severe conservative and surgical therapeutic measures. In 8 patients the coccalgia (S-4 S-5 pain) was associated with unilateral pain in the S-3 area, in another 8 patients it was associated with disabling lumbago and in the remaining group of 8 patients coccalgia occurred without pain in neighbouring areas. Only 6 patients responded well to sacral rhizotomy. All these patients belonged to the final group of 8 patients with pain distribution limited to the S-4 S-5 area. Serious complications occurred after 6 of the 24 rhizotomies. Five of these patients belonged to the two groups who besides coccalgia also had disabling lumbago or signs of rhizopathy about the S-4 level. A restrictive attitude to sacral rhizotomy in coccalgia is recommended especially when it is associated with pain in neighbouring areas and also if there is any reason to believe that there are factors present predisposing to the development of arachnoiditis.