Roentgen stereophotogrammetric analysis as a predictor of mechanical loosening of knee prostheses.

The tibial components in 143 patients with total knee replacements performed before 1988 were assessed for micromotion using roentgen stereophotogrammetric analysis (RSA) over a period of 13 years. The fixation of the prostheses remained clinically sound in all cases, although revision had been required for other reasons in seven. In a second group taken from all cases with RSA available on our full database to 1990, 15 tibial components had been followed by RSA from the insertion until, 1 to 11 years after the initial arthroplasty, they were revised for mechanical loosening of the tibial component; 12 of these comprised all the loosenings in the base group, thus making a total of 155 consecutive cases, while an additional three were inserted after the base material had been compiled. The mean migration in the first group was about 1 mm at one year, but subsequent migration was slower, reaching a mean of about 1.5 mm after ten years. About one-third migrated continuously throughout follow-up, while two-thirds ceased to migrate after one to two years. In the revision group, 14 components had migrated continuously and at one year significantly more than those in the first group. One revision case lacked the crucial one-year follow-up and could not be classified. These findings suggest that mechanical loosening begins early in the postoperative period. Clinical symptoms which necessitate revision, seen at this stage in 20% of abnormally migrating tibial components, may not appear until up to ten years after the operation.(ABSTRACT TRUNCATED AT 250 WORDS)

A new radiographic method for detection of tibial component migration in total knee arthroplasty.

In a prospective study the accuracy of a new radiographic method, Matched Indicators for Radiographic Assessment (MIRA), used to assess tibial component migration in total knee arthroplasty was evaluated. Radiopaque markers were placed in the tibial component and the tibial metaphysis in a standardized way so that four vertical distances could be measured on standard radiographs. Subsidence during the first postoperative year was measured both with this new method and with roentgen stereophotogrammetric analysis in 27 Freeman-Samuelson total knee arthroplasties. The error of measurement of MIRA was determined using the known error of roentgen stereophotogrammetric analysis. The new method was found to be promising with an accuracy of 1 mm, and the correlation between MIRA and roentgen stereophotogrammetric analysis was high when subsidence exceeded this value. Therefore, subsidence of clinical importance should be detected with MIRA. The method is simple and well suited for routine follow-up examination of large patient materials.

Proximally cemented versus uncemented Freeman-Samuelson knee arthroplasty. A prospective randomised study.

We studied the effect of a layer of cement placed under the tibial component of Freeman-Samuelson total knee prostheses with a metal back and an 80 mm intramedullary stem, using roentgen stereophotogrammetry to measure the migration of the tibial component during one year in 13 uncemented and 16 cemented knees. The addition of cement produced a significant reduction in migration at one year, from a mean of 1.5 mm to one of 0.5 mm (p less than 0.01), including a significant reduction in pure subsidence. One year postoperatively the clinical results were similar between the groups, but, at three years, one uncemented knee had required revision.

The effect of a stem on the tibial component of knee arthroplasty. A roentgen stereophotogrammetric study of uncemented tibial components in the Freeman-Samuelson knee arthroplasty.

We studied the effect of a metal tray with an intramedullary stem on the micromotion of the tibial component in total knee arthroplasty. Of 32 uncemented Freeman-Samuelson knee arthroplasties performed in London and Gothenburg, nine had a metal backing and stem added to the tibial component. Micromotion of the tibial components, expressed as migration and inducible displacement, was analysed using roentgen stereophotogrammetric analysis up to two years follow-up. The addition of a metal back and a 110 mm stem to the standard polyethylene component significantly reduced both migration over two years and inducible displacement.

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.

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.

Osseointegrated knee prostheses. An experimental study in rabbits.

Osseointegration, defined as direct bone-to-implant contact, has been suggested as an approach for improving the results of arthroplasties of the major joints. An experimental investigation in femoral-patellar joint of the rabbit was performed to evaluate whether osseointegration could be achieved in a one-stage surgical procedure. After three months, it was found that the screws used for anchorage of the prosthesis showed an average direct bone-to-implant contact of 60% in three selected consecutive threads on each side. The range was 40-90%. These figures correspond well with previously reported ones from bone anchored titanium fixtures. It was therefore concluded that osseointegration of dynamically loaded screws used for anchorage of a femoral-patellar joint prosthesis may be achieved in spite of the fact that no controlled healing period for the screws was observed.

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.

Micromotion of noncemented Freeman-Samuelson knee prostheses in gonarthrosis. A roentgen-stereophotogrammetric analysis of eight successful cases.

Micromotion of the tibial component of eight Freeman-Samuelson arthroplasties without cement for gonarthrosis were followed for two years and studied by roentgen-stereophotogrammetric analysis (RSA). In five cases, displacement over time was studied, and in all cases migration was found to range from 0.7 to 4.8 mm after two years. One tibial component migrated continuously during the period studied, while the remaining prostheses migrated mostly during the first six months. The direction of the migration was erratic. Inducible displacement ranging from 0.8 to 5.0 mm was found in all cases. Clinically, all of the patients were scored as successful although one with continuous migration had the lowest score. This degree of micromotion is compatible with good results after two years, and appears to be a characteristic of the immediate interlocking fixation used in the Freeman-Samuelson prosthesis.

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.

ICLH knee arthroplasty. A consecutive study of 108 knees with uncemented tibial component fixation.

One hundred eight ICLH knee arthroplasties with cementless tibial component fixation were performed from 1978 through 1982 in Gothenburg, Sweden. The patients were followed for 2-8 years (mean, 4 years) with clinical and radiographic examinations at regular intervals, and the data were computer-analyzed. Patellar subluxation-dislocation, often accompanied by pain, occurred in 50% of the knees. Eleven arthroplasties failed due to aseptic loosening. Survival rate analysis performed using three different definitions of failure resulted in cumulative success rates after 8 years of 86%, 78%, and 72%. Most failures occurred between 2 and 5 years after surgery. Patients with bilateral arthritis were overrepresented among the failures. There was a significant correlation between failure and poor bone sclerosis around the polyethylene pegs. Most patients can be treated with cementless fixation, but other types of fixation should be considered for elderly patients and patients with severe bilateral disease.

The mechanical properties of cement and loosening of the femoral component of hip replacements.

Mechanical and biomechanical testing of a new bone cement suggests that improved load transfer to the proximal femur could be achieved with the combination of a cement having a lower modulus, a greater ductility and a lower creep resistance than polymethylmethacrylate and a suitably shaped femoral component.

Acute tissue reactions to potassium alginate with and without colour/flavour additives.

The acute tissue reactions to potassium alginate, locally applied to a microvascular bed, were studied with the use of the vital microscopic hamster cheek pouch model combined with correlative histology. This experimental model permitted us to study microvascular permeability, blood flow, vessel diameters and leucocyte adhesion to vessel walls intravitally, and leucocyte migration and mastcell degranulation histologically. Deionized water alone and potassium alginate with flavour and colour mixed in saline was found to cause severe microvascular alterations, while potassium alginate, without flavour and colour, but mixed in saline and applied to the microvasculature resulted in a minor inflammatory reaction.

Total prosthetic replacement of ankylosed knees.

Total knee arthroplasty is reliable for achieving pain relief, increasing range of motion, maintaining stability, and improving walking ability. In this study, the results in knees with a preoperative range of motion of 0 were reviewed to determine whether an ankylosed knee can be replaced successfully. In eight of nine knees, the results with regard to pain, stability, and walking ability were good at follow-up evaluations greater than 2 years after operation. Range of motion was also improved in all knees but was still limited. Motion achieved was in a physiologic arc with all knees having full, or nearly full, extension.

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.

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.

Bristow-Latarjet procedure for recurrent anterior dislocation of the shoulder. A 2-5 year follow-up study on the results of 112 cases.

A follow-up study of 111 out of 112 patients operated on for shoulder joint dislocation according to the Bristow-Latarjet procedure during the years 1975 through 1979 in four Swedish hospitals is presented. The average follow-up time was 30 months (range 24-60 months). There were seven cases of significant recurrences (6 per cent). During follow-up, further surgery had been performed on four of these. Another eight patients (7 per cent) had experienced occasional insignificant subluxations. In one case neurolysis of the musculocutaneous nerve was undertaken because of postoperative paresis of elbow flexors. The average limitation of outward rotation as compared with the nonoperated side was 19 degrees in adduction and 21 degrees in abduction. There was a measurable difference in strength between the operated and nonoperated shoulders. The results were considered excellent or good by 101 of the patients (90 per cent), fair by eight and bad by three. Of 12 cases with failed surgery before the Bristow-Latarjet procedure 10 regarded the result as good or excellent.