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Biomedical subjects

M A Freeman

Publications and source records attributed to M A Freeman.

At least 91 records · Page 5Linked to original sources
PubMed1990

The effect of a metal-back without a stem upon the fixation of a tibial prosthesis.

Three methods of tibial component fixation without cement (as part of TKA) have been used at the London Hospital. All three methods have used the same polyethylene component fixed with two HDP (Day) pegs. A metal-back without a stem was added to the HDP in group 1. Group 2 consisted of an HDP-only component. In group 3 a stem was added to the metal-back used in group 1. Radiological comparison showed the fixation of the polyethylene component with metal back but no stem to be inadequate; the component tilted into varus more frequently than the other configurations. It is suggested that failure was due to the increased rigidity of the metal-backed component (as compared with the HDP only) and that the rigidity (and the resultant tendency to rock) can be offset by a stem. It is concluded that rigid (ie, metallic) tibial components should have a stem.

Aged↗
PubMed1990

Unconstrained knee arthroplasty after patellectomy.

The authors report seven cases of unconstrained knee arthroplasty with excision of both cruciate ligaments, after previous patellectomy. Six of these seven cases were completely painfree and function was satisfactory in all cases. The reasons for previously reported pain and instability after total unconstrained knee arthroplasty with excision of the cruciate ligaments and a previous patellectomy are discussed.

Aged↗
PubMed1990

ICLH double-cup arthroplasty, 1980-1987.

The results are presented of 92 double-cup arthroplasties modified in light of previously published experience. The review period lasted up to 7 years after operation. Eighty-six had a metal femoral component and six had a ceramic femoral component. Forty metal femoral cups were matched with a cemented acetabulum, while with 46 the acetabular implant was cementless. The overall revision rate for the metal femoral cups was 23.3%, and a further 31.8% demonstrated radiological signs suggestive of loosening. There was no difference between the cemented and uncemented cups in terms of revision rates or clinical results. The clinical results of those hips that have not yet loosened were excellent. A histological study showed that femoral lossening was associated with an erosive cellular response. Surface arthroplasty of the hip with current materials should be abandoned.

Adult↗
PubMed1990

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.

Adult↗
PubMed1990

A correlative study of the geometry and anatomy of the distal femur.

Sixteen knees were examined roentgenographically in the lateral plane. Ten knees were examined from autopsy subjects. The distal articular femur may be represented by three circular surfaces: (1) the floor of the patellar groove (articulating with the patella from 10 degrees to 100 degrees), (2) the posterior femoral condyles (articulating with the tibia from 10 degrees to 150 degrees), and (3) the distal condyles (articulating with the tibia from 0 degrees to 10 degrees). The radii of these surfaces, their angular arcs, and the distances between their centers varied with the size of the femur but fell within a narrow range. The radii of the patellar groove and the posterior femoral condyles averaged 24 mm and 21 mm, and the average angle subtended by these arcs was 90 degrees and 140 degrees, respectively. The average distance between the centers of these two circles was 20 mm. The femoral attachment of the synovial and patellar retinacular reflections was found in the area of the center of the patellar groove circle. The femoral attachments of the medial collateral and posterior cruciate ligaments and of the lateral collateral and anterior cruciate ligaments were found to be in the area of the center of the circle of the medial and lateral posterior femoral condylar circles, respectively.

Femur↗
PubMed1989

The patellofemoral joint in total knee prostheses. Design considerations.

Some desirable design features of the patellofemoral joint in a total knee arthroplasty condylar prosthesis are proposed. These are that the femoral element should be grooved, have a high anterior flange, and be circular as viewed from the side. The groove should be about 5 mm deep and have relatively vertical walls. The patellar component should have a saddle-shaped articular surface matching the femur and should be countersunk into the patella. The components should be placed so as to position the joint automatically. Results with such a design are reported; loosening, wear, dislocation, and fracture have been rare. Osteolysis of the patella has not been seen after 9 years, so that the cementless press-fit fixation of an H.D.P. patellar prosthesis to date seems safe and efficacious.

Aged↗
PubMed1989

Torsional stability of the femoral component of hip arthroplasty. Response to an anteriorly applied load.

Torsional instability of femoral components has not received much attention, and is difficult to detect in conventional radiographs. To test this we designed a system to apply a load in an anteroposterior direction to the head of a femoral component, implanted into a cadaveric femur. Rotation within the bone was measured, using a purpose built transducer, with and without preservation of the neck, with and without cement, and with longitudinal ridges but no cement. The results show that torsional instability may be a problem in uncemented replacement. Preservation of the femoral neck and the use of a ridged prosthesis increases resistance to rotation. Rotational movements occurring in vivo during such activities as climbing stairs and rising from the seated position may contribute to mechanical loosening.

Biomechanical Phenomena↗
PubMed1989

The measurement of migration of the acetabular component of hip prostheses.

Individual components of a total hip replacement are difficult to evaluate and quantify. We have studied the assessment of the acetabular component, and conclude that the measurement of migration allows the comparison of implants, although there is no established link between migration and significant loosening. A method of measurement based on clinical radiographs has been developed, and its limitations estimated. The accuracy of the technique was calculated to be +/- 3 mm.

Acetabulum↗
PubMed1988

Homograft bone in revision acetabular arthroplasty. A clinical and radiographic study.

Thirty-seven patients with extensive acetabular defects due to loose implants had revisions with uncemented components, the acetabulum being augmented with homograft bone. In six of these, a histological study of graft incorporation was made. At a mean follow-up of 1.5 years 34 patients were free of pain and 35 could walk for 30 minutes or longer. No graft had obviously sequestrated. Two components had radiological evidence of migration but remain asymptomatic. We conclude that cementless revision surgery with homograft supplementation of the acetabulum is clinically successful in the short-term. The long-term outcome is unknown.

Acetabulum↗
PubMed1988

Range of movement poor index of hip function.

Conventional systems of assessing the hip before and after surgery use the range of movement as an indicator of functional results. We found that the range of movement, defined as the flexion arc or the total range, is a poor indicator of function as measured by ability to reach the feet. A different and more direct basis for assessing function is proposed.

Adult↗
PubMed1987

The relationship of neck orientation to the shape of the proximal femur.

Neck angles and various dimensions measured from 70 normal cadaver femora and from clinical radiographs of 120 normal hips were analyzed. The neck-shaft angle and the inclination of the medial trabecular system varied over a range of approximately 35 degrees. The location of the femoral head center in relation to the femoral shaft and to the trochanters was related to neck orientation. As the neck became vertical, horizontal offset of the head center from the shaft decreased and its vertical level relative to that of the trochanter increased. The abductor muscle lever arm was measured with two methods. Values obtained when assuming that the joint resultant force follows the medial trabeculae demonstrated the closest relationship to the distance from head center to body midline. The normal shape of the proximal femur is variable, and variations in the absence of intrinsic bone disease appear to reflect adaptation to physiologic variations in the line of action of muscle forces.

Adult↗
PubMed1987

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.

Ankylosis↗