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Biomedical subjects

M A Freeman

Publications and source records attributed to M A Freeman.

At least 127 records · Page 7Linked to original sources
PubMed1983

Alignment in total knee arthroplasty. Correlated biomechanical and clinical observations.

The initial experience with the Freeman-Swanson (ICLH) total knee arthroplasty (1971-1975) led to changes of tibial component size, alignment, instruments, and surgical technique in 1975. Certain patients in this initial series, however, have shown excellent long-term (5 1/2-9 years) results. In patients with overall alignment between 1 degrees and 13 degrees valgus, the success rate was 89%. In patients with knees aligned between neutral and 8 degrees varus, the success rate was only 14%. This startling difference in long-term results was investigated by using eccentric loading tests to simulate varus and valgus malalignment. Knee arthroplasties failed in eccentric loading at very low loads. Failure by lift-off of the unloaded side occurred at 9%-18% and failure of bone due to compression on the loaded side occurred at 34%-51% of the load at failure under ideal uniform loading conditions. Thus, both the long-term clinical study and the laboratory analysis demonstrate the importance of proper overall alignment in total knee arthroplasty.

Biomechanical Phenomena↗
PubMed1983

Cementless fixation of prosthetic components in total arthroplasty of the knee and hip.

An appropriately designed implant can be fixed without cement to accurately prepared bone surfaces so as to give results comparable with those of cemented fixation in the short term. The unchanging appearance of the roentgenograms suggests that these results may be maintained in the long term. If these conclusions are valid, polymethylmethacrylate (PMMA) may be thought of as an optional alternative in joint arthroplasty. Thus, theoretically, inert materials, e.g., carbon, can be directly interfaced with the skeleton. Since the authors have achieved interlock with viable bone without relying on bony ingrowth, these materials need not be porous. It is strongly suspected (but as yet unsupported by data) that adequate fixation can be obtained without relying even on the authors' relatively unsophisticated finned peg, provided that (1) the overall shape of the implant achieves interlock on the gross scale, with acceptably low shear stresses at the interface; and (2) the surgical technique achieves a correctly positioned implant applied to accurately cut bone surfaces. However, if for any reason accurate bone cuts can not be achieved, the authors advocate use of PMMA as a valuable fixation agent.

Acetabulum↗
PubMed1983

Revision of failed hip resurfacing.

Resurfacing arthroplasty of the hip is a relatively recent innovation that has theoretic advantages in certain instances. One alleged advantage is "revisability." At the London Hospital 28 resurfaced hips that were converted to stemmed hip arthroplasties have been reviewed. Follow-up periods averaged 2.8 years (range, 1-9 years). Almost 90% of these hips were functioning satisfactorily at the time of review. The data suggest that the result of revising a resurfaced hip may be predictably better than that of revising a stemmed hip arthroplasty.

Aged↗
PubMed1982

Cementless fixation of the tibial component for the ICLH knee.

The use of polymethylmethacrylate bone cement in joint replacement surgery is not without drawbacks. Certain hazards have been appreciated and the bone cement interface may not be as stable in the long run as was once felt. This paper reports the results in 52 knees which were replaced using the uncemented ICLH (Imperial College/London Hospital) tibial component; the average follow up was two years (range six months to four years). The results were compiled with regard to pain as well as clinical examination and X-ray evaluation. The results were comparable to those achieved in knees replaced using bone cement. Roentgenographic evaluation revealed no evidence of loosening nor sinkage of any of these prostheses. Considerations in the development of a knee prosthesis to be utilized without bone cement and the operative technique employed to implant such a prosthesis are presented. The merits of such a system are discussed.

Adult↗
PubMed1982

Observations upon the interface between bone and polymethylmethacrylate cement.

The occurrence of a radiolucent line at the interface of bone and cement in total joint prostheses is a frequently observed, although little understood, phenomenon. Because of an operative technique utilised in instances of bone loss, we have, within a single implant mass used in each of a series of 18 total knee replacements, been able to observe two separate interfaces, one between bone and cement and the other between bone and cobalt chrome. The average period of observation was 32 months. All of the knees except one demonstrated a lucency at the bone-cement interface; only one of the knees had a similar lucency at the bone-CoCr interface. One of the knees was studied histologically. In the light of the universal observation of macrophages at bone-cement interfaces and the recent finding that osteoclasts are derived from macrophages, these observations are significant in relation to the aetiology of bone-cement lucencies.

Adult↗
PubMed1981

A roentgenographic technique to evaluate and document hindfoot position.

The position of the posterior portion of the foot is difficult to evaluate and document on the basis of clinical examination. Conventional roentgenographic techniques also do not allow objective determination of hindfoot position. A new roentgenographic technique utilizing a double-exposure has been developed to allow accurate documentation of the position of the calcaneus relative to the ankle. Normal adult values for this technique have been determined from 60 normal feet.

Ankle↗
PubMed1980

Sequelae of arthrodesis of the hip.

Twenty-two patients with unilateral arthrodesis of the hip were reviewed clinically and radiologically ten years or more after operation. There was evidence of degenerative disease in 63.6% of the contralateral hips, 68.2% of the ipsilateral knees and in 59.1% of the contralateral knees. Both knees were affected in 50% of cases. All the patients had some degree of backache. The incidence of these problems in contrast with previously reported series is discussed.

Arthrodesis↗
PubMed1978

ICLH cemented douple cup hip replacement.

The ICLH (Imperial College-London Hospital) double cup hip replacement as it exists today consists of a metal femoral component which caps the femur and a polyethylene acetabular component which resurfaces the acetabulum. Both components are cemented in place. The first prosthesis was inserted in 1972 and during the following two years complications emerged which necessitated changes in the prosthesis and the operative technique. Since November 1974 there have been no changes in the prosthetic design or operative procedure and complications have been infrequent. An approach has been developed whereby trochanteric osteotomy is not necessary. Up to December 1977 159 hips were replaced in 154 patients. Clinically, the results of a successful double cup arthroplasty are similar to those obtained by conventional hip replacement. No deterioration in the quality of the results is suggested when early results are compared with those of patients who are now two years and longer since surgery. Technical errors to be avoided are varus placement of the femoral component and excessive vertical placement of the acetabular component. Conclusions drawn are tentative due to the fact that to date the follow-up period is inadequate.

Biomechanical Phenomena↗
PubMed1978

Loosening of the femoral component in surface replacement of the knee.

The incidence of loosening of the femoral component of the ICLH knee has been found to be lower than that of the tibial component. This is thought to be due to the fact that the compressive strength of the distal femur has been found to be greater than that of the proximal tibia. It has further been shown that the strength of even the femur can be so reduced by the osteoporosis accompanying Rheumatoid Arthritis that it becomes insufficient for adequate prosthetic fixation.

Bone Cements↗
PubMed1978

Patellar fracture after replacement of the tibio-femoral joint with the ICLH prosthesis.

Four cases are reported of spontaneous fracture of the patella after ICLH replacement of the knee for Rheumatoid Arthritis. Three of these occur-red in patellae that had not themselves been replaced; one in a resurfaced patella. The former required no specific treatment but the latter required revision surgery. It is argued that the existence of this complication may represent a contra-indication to patellar replacement in the osteoporotic rheumatoid knee.

Arthritis, Rheumatoid↗
PubMed1978

The production and biology of polyethylene wear debris.

Polyethylene in the form of a concave bearing surface at the hip wears very slowly, and clinical and histological evidence suggests that the volume of debris so released is well tolerated. However, significantly greater volumetric wear rates are produced when (1) polyethylene is used as the convex component of a joint and (2) abrasives such as PMMA or bone enter the joint. Further, large quantities of polyethylene debris lead to the replacement of bone at the bone-cement interface by soft tissue. Evidence is presented which strongly suggests that this mechanism can produce joint component loosening.

Acrylic Resins↗