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Biomedical subjects

M A Freeman

Publications and source records attributed to M A Freeman.

At least 145 records · Page 8Linked to original sources
PubMed1978

Mechanical tests on the tibial components of non-hinged knee prostheses.

Cadaveric knees replaced with the Geomedic, ICLH, Marmor and Total Condylar prostheses were tested in axial compression, in rotation and in hyperextension in order to observe the strength of fixation of the tibial components. In axial compression the strengths at failure varied widely, both with any one prosthesis and between prostheses. This is attributed largely to the strength of the cancellous bone of the tibia, which was measured in each case and also varied widely. Three natural knees failed at loads of 7300, 7600 and 8300 newtons respectively, whereas the strengths of replaced knees ranged from 3000 to 15750 newtons. At least one example of each design failed at less than 7300 newtons, suggesting little or no reserve of strength. The strength of fixation was greater when the tibial prosthesis was large enough to rest on the whole cross-section of the tibia. In rotation the three prostheses embodying rollers in troughs were stiffer than the Marmor which had a nearly flat tibial-bearing surface. The presence or absence of the cruciate ligaments had a negligible effect on torsional stiffness. In hyperextension, knees replaced with the ICLH, Marmor and Total Condylar prostheses failed by rupture of the posterior capsule at moments of about 60 newton-metres, compared with about 100 for natural knees. With the Marmor prosthesis the anterior cruciate ligament was avulsed at about 20 newton-metres compared with about 75 in natural knees, suggesting that in this respect the retention of the cruciate ligaments contributes little. None of the four knees tested after inserting a Geomedic prosthesis showed strengths as high as those replaced with the other three designs.

Humans↗
PubMed1978

ICLH arthroplasty of the knee: 1968--1977.

The essentially satisfactory results from the ICLH implant as used until 1975 were marred by examples of loosening and sinking of the tibial implant, by patellar pain of varying severity, by wear of the tibial implant caused by fragments of cement and by failure consistently to control the alignment of the leg. This report describes the methods now being used to overcome these complications and gives an account of the success so far achieved.

Arthroplasty↗
PubMed1977

Sepsis rates in hip replacement surgery with special reference to the use of ultra clean air.

A study is reported of sepsis rates in 836 total hip replacements carried out in various physical environments including ultra-clean air. In a further sutdy the bacteriology of the air around the wound and of the wound itself was investigated during the course of 32 joint replacement operations with and without ultra-clean air. Bacteriological contamination of the air was markedly reduced by the use of ultra-clean air but the wounds themselves were no cleaner than with conventional air conditioning provided that unsterile personel were kept at least Imetri away from the sterile area. The sepsis rate was high at the outset of the study (when a physically apalling theatre was in use, the operative technique was novel and prophylactic antibiotics were not employed). Thereafter it fell and remained unchanged in spite of the introduction of ultra-clean air. We conclude that the efficacy of techniques amiced at sterilizing the air around the wound may now be unprovable in view of the low sepsis rates which can be obtained in a conventional environment. Our results do however show that unsterile personel should not be allowed to approach within Imetri of the sterile area, whatever venitlation is employed.

Air Microbiology↗
PubMed1977

A comparison of osteotomy and joint replacement in the surgical treatment of the arthritic knee.

The relatively small numbers of knees compared in this study make it impossible to draw conclusions with great confidence. On the other hand we believe that the quality of our comparison has been improved by our effort to match the groups of knees under study. Our results lead to the controversial conclusion that, at least in RA and in elderly patients with OA, ICLH arthroplasty is preferable to osteotomy regardless of the pathology and preoperative deformity and that osteotomy should not be used as a temporizing procedure before ICLH arthroplasty. We are unable to say whether or not similar conclusions would apply to other forms of arthroplasty but we suspect that they would. Certainly joint replacement is now widely preferred to osteotomy at the hip and it is difficult to see why the knee should be different. It should not be concluded from these results that replacemnt is to be preferred to osteotomy for the mildly damaged knee. It does however appear that if osteotomy fails (for technical or other reasons), it may then be difficult to obtain a satisfactory result even by replacement. Thus if a patient with a mildly damaged knee is not to be disabled irreparably, it may be better to avoid osteotomy until the day comes when the causes of failure after this operation can be predicted preoperatively and prevented. The data presented here suggest (as do those in many other studies) that one step in this direction is to confine osteotomy to the varus OA knee. Even in this group the surgeon should, we believe, do his utmost to avoid surgery altogether until the parents' disability is unacceptable. In summary therefore, we now advance the view that if the arthritic knee is sufficiently disabling to require major surgery, it should be replaced. If the disability is less severe, the joint should be treated conservatively.

Adult↗
PubMed1977

Replacement of the severely damaged arthritic knee by the ICLH (Freeman-Swanson) arthroplasty.

A multi-centre clinical trial of ICLH (Freeman-Swanson) arthroplasty has been in progress since 1971. In this paper the results up to two years after operation are reported in seventy-one knees displaying at least 30 degrees of fixed flexion, 25 degrees of valgus or 20 degrees of varus, before operation. It has been found that knees displaying 70 degrees of fixed flexion, 70 degrees of valgus, 30 degrees of varus or 50 degrees of valgus/varus instability can be satisfactorily aligned and stabilised with acceptable function. Three knees required revision. The other complications are listed and were unremarkable in nature. These results depend upon the prosthesis and upon the operative technique. The latter avoids damage to healthy bone but does involve the replacement of the tissues in the midline of the knee.

Adult↗
PubMed1977

A techinque for recording the results of knee surgery.

A research form for recording clinical data relating to the arthritic knee is described. Data are recorded using a numerical code which facilitates transfer to a computer and provides an easily read record. Any form must be a compromise but the one described has been proven clinically by providing the data for a multi-center evaluation of hundreds of knees observed over a period of 5 years. A shorter form is described for routine follow-up purposes.

Arthritis↗
PubMed1977

The presentation of the results of knee surgery.

A method is described by which the detailed results of knee surgery may be presented in a compact, readily understood and easily analyzable fashion. The data can be analyzed and presented either manually or by a computer and if the latter is used no special print-out equipment is required. The success of the method has been proved over a 5-year period in the monitoring of the results of a multi-institutional investigation of total knee arthroplasty.

Arthroplasty↗
PubMed1976

The relation between stimulus frequency and the relative size of the components of the biphasic response of the vas deferens to electrical stimulation at different temperatures.

1. Electrical stimulation of the guinea-pig or rat vas deferens (pre- or post-ganglionically) at frequencies from 2-5 to 40 Hz with trains of stimuli of 30 sec duration induced a biphasic response. A rapid contraction (component A) was followed after a brief relaxation by a slower contraction (component B); the two phases were seen most clearly with stimulation frequencies of less than 10 Hz. 2. The responses to post-ganglionic stimulation were always larger than those to preganglionic stimulation. In general, at low frequencies component A exceeded component B whilst at high frequencies component B was the larger. Separation of the two components on the basis of their frequency response characteristics was better for rat than for guinea-pig vasa. 3. Log. frequency-response curves to transmural (post-ganglionic) electrical stimulation and log dose-response curves to noradrenaline were recorded for guinea-pig and rat vasa deferentia at 32 degrees, 22 degrees and 12 degrees C. For the guinea-pig reduction of bath temperature to 12 degrees C increased the amplitude of component A at 2-5 and 5 Hz; component B could not confidently be distinguished at this temperature. At 22 degrees C there was potentiation of B at lower frequencies and depression of B at higher frequencies. There was no response to noradrenaline at 12 degrees C. At 22 degrees C the response to noradrenaline was increased except to doses at or near the maximum to which the response was reduced. 4. For the rat was deferens component A was little changed by reduction of temperature. Component B at 12 degrees C was greatly depressed at higher frequencies. The response to noradreanaline was increased to lower doses and decreased to higher doses as the temperature was lowered. 5. The B component of the response of guinea-pig vasa at 22 degrees C and rat vasa at 32 degrees C was more sensitive than the A component to inhibition by thymoxamine. 6. Further analysis of the mechanisms underlying the A and B components of the biphasic response may be facilitated by relative isolation of each component by the appropriate selection of parameters of electrical stimulation and of temperature for the species being investigated. The contractions of the B component are similar to, if not identical with, those produced by exogenously applied noradrenaline.

Animals↗
PubMed1976

The pathogenesis of Perthes' disease.

It has been shown that in the puppy, two infarcts separated by an interval of four weeks produce a disorder of long duration which results in flattening and broadening of the femoral head and which reproduces the radiological changes seen in Perthes' disease in man. The histological appearances produced by two infarcts are characteristic. In this study the histological appearance of fifty-seven femoral head biopsy specimens in Perthes' disease in man have been studied. In 51 per cent of hips histopathological changes characteristic of double infarction were present, and there were grounds for postulating that double infarction might eventually occur in all cases. The findings support the concept that the deformation of the femoral head and the chronicity of Perthes' disease in man may be due at least as much or even more to repeated episodes of infarction and the ensuing abnormalities of growth as to mechanical factors related to weight-bearing.

Adolescent↗
PubMed1976

ICLH (Freeman/Swanson) arthroplasty in the treatment of arthritic knee: a 2 to 4-year review.

A prospective follow-up using a standardized data recording form was carried out by independent, experienced orthopedic surgeons on a small number (116) of knees operated upon at The London Hospital in the period January 1, 1971 to October 31, 1973. An additional 93 knees have been operated upon at other hospitals and followed prospectively using the same data recording system. A total of 159 knees have been reviewed 2 to 4 years after operation. The complications specific to ICLH arthroplasty have been unremarkable and generally correctable. Two tibial components have sunk and have been revised at The London Hospital. The results show that ICLH arthroplasty has been used to correct satisfactorily flexion deformities up to 70 degrees, valgus deformities up to 45 degrees, and varus deformities up to 35 degrees. (Deformities of greater magnitude can be corrected but were not present among the knees in this study.) The operation may be said to be "worthwhile" with reference to pain in 94 per cent of the knees, with reference to the ability to walk in 80 per cent of the knees, and with reference to the range of movement in 71 per cent. Overall, 47 per cent of the knees had no complaint postoperatively, while a further 47 per cent were improved; thus for 94 per cent the procedure was "worthwhile."

Adult↗
PubMed1975

Engineering considerations in the design of an ankle joint.

A prothesis has been designed to replace the articulating surfaces of the human ankle joint. The prothesis is in two parts, each forming a segment of a right circular cylinder with a single axis of rotation. The concave tibial component is manufactured from ultra-high molecular weight polyethylene and the talar component is manufactured from medical grade stainless steel. It is likely, however, that the talar component will be commercially manufactured from cobalt chrome alloy (Vitallium or Vinertia). The two components are secured to the cancellous bone by polymethylmethacrylate bone cement and laboratory tests have indicated that the bond should be strong enough to withstand the loads encountered at the ankle joint in vivo. The tests have also shown that the stability and strength of the ankle are not seriously reduced by implantation of the prosthesis. Laboratory wear tests and clinical experience over the last two years encourage optimism over the long term performance of the prothesis.

Adult↗
PubMed1975

Contact pressures in the loaded human cadaver hip.

The purpose of the work described was to find the average pressure on each of several areas of the acetabular cartilage of the cadaver hip under physiological loads. By obtaining load-deflection curves for one chosen area of cartilage, firstly with all the cartilage present and then after the successive removal of other areas, the fractions of the original load carried by the several areas were found, and hence the average pressures on those areas. Seventeen hips (age range twenty-two to eighty-seven years) were examined. Local pressures varied from zero to 3.4 times the average pressure in each hip. The highest pressures in the series (about 4 to 5 megaNewtons per square metre) were on the areas of thin fibrocartilage which were identified at the zenith of certain acetabula. The results are too few to establish whether or not the pressure distribution was age-related. The higher pressures found are within the range which in other experiments has led to fatigue failure of femoral head cartilage, and it is suggested that hips in which such pressures exist under loads of three times body weight may be predisposed to osteoarthritis.

Acetabulum↗