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Biomedical subjects

M A Freeman

Publications and source records attributed to M A Freeman.

214 records · Page 12Linked to original sources
PubMedDate not supplied

A hyperparasitic microsporidian infecting the salmon louse, Lepeophtheirus salmonis: an rDNA-based molecular phylogenetic study.

The sea louse, Lepeophtheirus salmonis, is an obligate ectoparasitic copepod that lives on the external surface of salmonid fish. It is the most common ectoparasite of marine cage-reared salmonids, causing major economic loss to the aquaculture industry. During a sea louse monitoring programme, samples of L. salmonis were found to harbour an unreported microsporidian parasite. The microsporidian was observed in pre-adult and adult stages of both male and female copepods, with a prevalence of up to 5%. Unfixed spores were slightly pyriform in shape measuring 2.34 microm by 1.83 microm (+/- 0.01 microm) and were not observed to be enclosed by a sporophorous vesicle. The microsporidian infection was observed in all areas of the copepods' body, xenoma-like cysts forming directly under the cuticle in the epidermal tissue layer. In the present study, rDNA (530f-580r) sequence data gathered from the unidentified microsporidian parasite isolated from infected sea lice were compared with equivalents available in the databases in an attempt to identify its systematic position. The microsporidian was found to group within the phylogenetic clade containing the family Enterocytozoonidae, being most similar to members of the intranuclear genus Nucleospora. This is the first report of a hyperparasitic microsporidian infecting a caligid copepod.

Animals↗
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Development and evolution of the ICLH ankle replacement.

In 1972 the original ICLH ankle was first used clinically, and since then the authors have implanted 75 ICLH ankles. The overall percentage of acceptable results in this series is about 70%. The most frequent complication seen was delayed wound healing. Talomalleolar contact with resultant pain was a significant problem early in the series. Partial collapse of the talus has occurred in five ankles. Our experience has shown that it is possible to replace the ankle and initially achieve a functioning, pain-free arthroplasty. There are many factors that may adversely influence the ultimate outcome; and thus, the procedure should be approached with caution.

Ankle Joint↗
PubMedDate not supplied

Freeman-Samuelson total arthroplasty of the knee.

Experience with cementless fixation over the last six years indicates that the technique offers greater opportunities for bone conservation. Thus, when cement is used, and especially if it is forced into the skeleton under pressure, the amount of bone incorporated into the implant is considerable. Conversely, if no cement is used, grafting techniques to fill defects are becoming increasingly routine, so that today no bone may be removed from the replaced knee or hip--all fragments that are excised are repositioned as grafts in defects. Thus, cementless fixation meets the fundamental orthopedic maxim of the conservation of bone stock. Given that an implant can be fixed with satisfactory clinical results without cement and without bone ingrowth, it becomes difficult to demonstrate a clinical advantage for the latter. Nevertheless, bone ingrowth is possible both experimentally and (with less confidence) in man. Thus, it is clearly a technique that should be evaluated. However, it is not, in the senior author's view, a technique that should as yet be generally used. Hopefully, investigations of this problem will take place in a restrained scientific way rather than by the current method, which is in response to the dictates of fashion and commerce.

Adult↗
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ICLH replacement of the knee: 1977 and 1978.

Investigations which began in 1968 have culminated in a knee arthroplasty which can now be confidently used to treat most patients with arthritic knee deformities. Our earlier studies showed that a prosthetic knee arthroplasty must be reliably aligned and stabilized in extension, that patellar pain and polyethelene wear were significant potential problems and that loosening and sinkage of the tibial component must be avoided. Our present knee prosthesis and instrumentation if properly used should avoid these pitfalls. Beginning in January 1977 we performed 84 knee arthroplasties utilizing the present design. A series of 79 knees has been available for our computer-assisted review; 46 patients had a diagnosis of inflammatory arthritis and 29 had primary osteoarthrosis: 22 knees had been previously operated upon. Although all femoral components were fixed with polymethylmethacrylate, the tibial components were completely cemented in 21 knees, partially cemented in 20, and no cement was used in 38 cases. In these latter knees special pegs provided a mechanical interlock with the tibia for fixation. Thirty-six patellae were replaced, of which 11 were fixed with a similar interlocking peg. The arthroplasties failed in 8 patients. Of the remainder, 90% of knees had acceptable pain relief and all but 4 patients were able to walk outdoors. Flexion to 90 degrees or more was achieved in 85% of the knees. Only 2 patients had unacceptable alignment. To date we feel that with the use of this improved prosthesis, in conjunction with the instruments which allow proper placement of the prosthesis, the majority of arthritic knees can be successfully corrected. However, further careful long-term follow-up studies must continue.

Arthritis↗
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Excision of the cruciate ligaments in total knee replacement.

The cruciate ligaments (and the intercondylar eminence of the tibia) should be removed when the knee is replaced. A mechanically unlinked prosthesis can be designed which will then be capable of restoring "cruciate" stability, i.e., anteroposterior stability of the tibia in the flexed knee. A knee replaced with such a prosthesis will only be stable if the prosthesis is inserted using the correct instruments and technique. Stability depends as much on precise surgical technique as it does on prosthetic design.

Arthritis, Rheumatoid↗
PubMedDate not supplied

Implant arthroplasty in the adult hindfoot.

In patients with mild to moderate valgus deformity and localized pain due to lateral impingement, the subtalar implant has been effective in controlling position and relieving localized pain. When used in conjunction with a talonavicular resurfacing prosthesis in the absence of talonavicular subluxation, the implant has been effective in relieving pain and maintaining the foot in a normal or nearly normal position. In feet with valgus deformity and talonavicular subluxation, both the subtalar implant and the talonavicular prosthesis with a built-in stop must be used. Use of these implants requires that the foot be supple and correctable to at least neutral position at surgery. The valgus hindfoot with a subluxated but otherwise normal talonavicular joint presents a greater problem. In this condition correction can be maintained only if the subtalar implant is used in conjunction with the modified talonavicular joint with a built-in stop. External supports in the shoe have not been routinely used in all patients after operation for a variety of reasons (mostly nonmedical). It may be advisable in patients who have had correction of a deformity to continue to use some sort of support in the shoe for most ambulation. Arthroplasty early in the disease course, before severe deformities develop, may prevent progression of the disorder, but more experience is necessary to validate clinical impressions.

Arthroplasty↗
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Some anatomical and mechanical considerations relevant to the surface replacement of the femoral head.

The internal structure of the arthrosic and normal femoral heads are grossly different although both are roughly circular. In particular bone is destroyed or defective superolaterally in the former. The compressive strength of the femoral head depends upon the medial trabecular system which runs through the head at approximately 20 degrees to the vertical i.e. the plane of the resultant of the major loads borne by the hip. Ideally a femoral resurfacing prosthesis should be placed in this axis. The bone of the arthrosic femoral head can be sustained by blood reaching it within the neck. Thus vessels on the intracapsular surface of the neck need not be preserved.

Biomechanical Phenomena↗
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Cemented double cup arthroplasty of the hip: a 5 year experience with the ICLH prosthesis.

The ICLH (Imperial College-London Hospital) total hip arthroplasty is a procedure in which a metal femoral component caps the proximal femur and a polyethylene acetabular component resurfaces the acetabulum with both components cemented in place. Between June, 1972, and November, 1974, changes were made in prosthetic design and in operative technique in response to 2 specific problems encountered. The loosening rate was high until the original polyethylene femoral component was redesigned so that it was metal. The incidence of femoral neck fractures was unacceptable until trochanteric osteotomy was discontinued. Since November, 1974, 116 hips have been replaced and neither the prosthesis nor the operative technique has changed. Pain relief has been comparable to that obtained with conventional Charnley-type hip replacement. All patients walk out of doors and no patient's walking capacity is limited by pain in the operated hip. No hip has lost motion and 36% have an effectively full range. No deterioration in the quality of these results is suggested when the first postoperative assessment is compared to those at 2 years and longer postoperative. Technical errors to be recognized and avoided are varus placement of the femoral component and excessive vertical placement of the acetabular component.

Aged↗