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Biomedical subjects

R J Minns

Publications and source records attributed to R J Minns.

At least 19 recordsLinked to original sources
PubMed2005

The role of gait analysis in the management of the knee.

Gait analysis has been used as an investigative tool for locomotion disorders since the early 20th century when it was done using time-lapsed photography. Since the advent of video and advances in strain gauge technology and fast data-handling devices coupled with computers, many of the movements and forces acting on and around the knee can now be measured with a high degree of accuracy. The magnitude and position of the force in 3-dimensional space can be accurately determined relative to the anatomy of the knee, consequently the clinician can assess and evaluate the forces and movements of the structures around and within the knee. This information can help the clinician predict and monitor post-surgery changes to the anatomy of the knee, and the forces and movements on these structures.

Biomechanical Phenomena↗
PubMed2003

The use of a reconstructed three-dimensional solid model from CT to aid the surgical management of a total knee arthroplasty: a case study.

The use of a rapid prototyping method was utilised to produce a pre-operative solid model of the proximal tibia in a patient with a massive defect of the medial tibial plateau. The solid model was reconstructed from aligned sequential CT images of the knee. This was then used to determine the level of bone resection of the proximal tibia for the optimum placement of the tibial component of a total knee replacement. This technique gives the surgeon both the three-dimensional anatomical information needed to ascertain whether there is adequate bony support after cutting for the prosthesis, as well as a solid model on which to carry out the proposed surgery, before undertaking the procedure on the patient.

Arthroplasty, Replacement, Knee↗
PubMed1997

Preliminary design and experimental studies of a novel soft implant for correcting sagittal plane instability in the lumbar spine.

STUDY DESIGN: A novel soft implant design for resisting the instability of the lumbar spine in the sagittal plane was mechanically tested. OBJECTIVES: To ascertain whether a soft preformed implant made of differing grades of silicone would contribute to stabilizing the lumbar spine in the sagittal plane. SUMMARY OF BACKGROUND DATA: Methods of stabilizing the lumbar spine in patients who present with chronic low back pain have usually concentrated on rigidly fixing the associated segment. This has many inherent problems with both the surgical methods and the long-term rigidity at and away from the stabilized site. To the authors knowledge, no "soft" interspinous spacer that would allow a certain amount of flexion but still stabilize the movements associated with instability at the level of the lesion has been investigated mechanically as an alternative to rigid fixation or prosthetic replacement. METHODS: The apparatus was designed to allow a cadaveric lumbar motion segment to be tested in compression at four angles of flexion with loads up to 700 N. The intradiscal pressure and sagittal plane stiffness were recorded during loading, with and without various sizes of the soft silicone implants placed between the spinous processes. RESULTS: Insertion of the silicone implants between the spinous processes reduced the intradiscal pressure under load at the angles of flexion tested. The size of the interspinous space determines the optimal diameter of the implant that afforded sagittal stability, the load-bearing contribution of the implant, and the prevention of disc space narrowing at the level investigated. CONCLUSIONS: A circular silicone spacer placed between the spinous processes appears to contribute to the stability of the cadaveric lumbar spine. There are many attractions to using a simple, soft implant that can be placed with minimal surgery between the spinous processes.

Adult↗
PubMed1997

Wear in retrieved condylar knee arthroplasties. A comparison of wear in different designs of 280 retrieved condylar knee prostheses.

The plastic components of 280 retrieved unicondylar and total knee arthroplasties were studied. Wear was visually scored using a relative ranked data method. Although wear on the components was highly variable, several conclusions could be drawn regarding the nature and causes. Wear was associated more with the medial than the lateral condyle. Delamination was the most severe type of wear and occurred in short (< 5 year)-, medium (5-10 years)-, and long (> 10 years)-term retrievals. In the short term, delamination wear was associated with hot pressing of the tibial plastic or with fracture of the tibial baseplate. For a single design, a significant difference in the amount of delamination on hot-pressed and non-hot-pressed tibial components was observed. In medium- and long-term retrieved specimens of the designs with moderately high conformity, delamination wear was associated with restriction of rotational movement of the femoral component or with abrupt changes in the radius of the tibial component. In flatter, less conforming designs, wear was associated with laxity, such that the polyethylene delaminated toward the edges of the tibial component. Wear attributed to cement abrasion or entrapment occurred on the more conforming designs. Delamination was associated with the presence of fusion defects in the polyethylene but could also occur in the absence of such defects. That delamination was the principal were type and that this is caused by a fatigue mechanism mean that the incidence of failure could accelerate considerably over follow-up periods beyond 10 years. Designs of moderate conformity without abrupt changes in radii may prolong the duration of plastic tibial components before serious delamination occurs.

Cementation↗
PubMed1993

The repair of inguinal hernias using carbon fibre patches--a five-year follow-up.

One hundred and eight inguinal hernias were treated following a standard surgical technique, using 3-mm thick loosely woven carbon-fibre patches. The average follow-up was five and a half years. There was one recurrence. Otherwise, excellent clinical results without pain were found in all but one patient and only a further three experienced a slight discomfort in the area of the implant, without any restriction on function. The technique is simple and permeation of the carbon-fibre patch by fibrous tissue showed a lasting repair.

Adult↗
PubMed1993

Muscle strength following total hip arthroplasty. A comparison of trochanteric osteotomy and the direct lateral approach.

Twenty-seven patients who had hip arthroplasty operated on with trochanteric osteotomy were compared with 54 patients when the direct lateral approach was used. The strength of the hip abductors, adductors, extensors, and flexors were measured at least 2 years following surgery. The strength of these muscle groups recovered to the same level as those on the nonoperated side, and there was no significant difference between the two groups of patients. Functionally, the direct lateral approach is a safe alternative to trochanteric osteotomy.

Aged↗
PubMed1992

Surgical instrument design for the accurate cutting of bone for implant fixation.

Oscillating saws and rotary drills are the most common instruments used in orthopaedic surgery for the cutting of bone and the drilling of holes through the cortex in preparing surfaces for implants to be placed on the bone ends. To obtain precision of placement of the surfaces and holes, various techniques have been developed to guide the instruments, such as holes, slots and flat surfaces. For sawing surfaces in total knee replacement a survey was conducted to assess the accuracy of cutting the distal end of the femur and the proximal end of the tibia with both slotted and surface guides used in some of the currently available prostheses instrument sets.

Clinical Competence↗
PubMed1992

Measuring outcome of total knee replacement using quality of life indices.

A series of 26 patients was studied before and after total knee replacement to determine the change in their quality of life, expressed as a gain in Quality Adjusted Life Years (QALYs). Global health status was assessed using the Nottingham Health Profile, disability by the Harris scale, pain by the McGill Pain Questionnaire, and anxiety and depression by the Hospital Anxiety and Depression Scale. Substantial reductions were found in pain, anxiety and depression, and a significant improvement was found in mobility. These data were used to generate a 'QALY' (Quality Adjusted Life Year) comparable to the measure used by Williams (1) in his comparative evaluation of medical and surgical treatments. A gain of only 0.42 QALY was found for knee replacement, which is about one-tenth the figure given by Williams for hip replacement. The difference appears to be attributable not to differences in the success of the operations, but rather to the scope that QALY calculations give for allocating comparable patients to different quality of life states. Tighter criteria are needed if QALYs are to be used to guide resource allocation.

Aged↗
PubMed1991

A simple guide for rotational alignment of the tibial component in knee arthroplasty.

A guide system was designed for use in conjunction with knee arthroplasty instruments. A pin is guided into the upper tibial cortex parallel to the sagittal axis of the femoral component with the patella in its normal position and the knee at 20 degrees of flexion. The holes and/or slots for the tibial component using the appropriate drill guide can now be made, with the patella displaced totally for exposure of the cut tibial surface, to allow correct rotational alignment of the prosthesis in the tibia.

Humans↗
PubMed1990

Biological response to woven carbon fibre pads in the knee. A clinical and experimental study.

We assessed the use of woven carbon fibre pads to resurface osteochondral defects in animals and in patients. The pads became filled with structurally strong and compliant fibrous tissue and did not provoke a synovial reaction, though pigmentation was induced in some animals. Of the patients, 77% had a satisfactory response to resurfacing, with no synovitis. Our initial experiments indicate that carbon pads may provide a satisfactory treatment for localised articular defects.

Adolescent↗
PubMed1990

Replacement of the rabbit medial meniscus with a polyester-carbon fibre bioprosthesis.

Eighteen New Zealand white rabbits underwent prosthetic replacement of the meniscus which was attached to the intercondylar area of the tibia through a predrilled hole and around the internal surface of the capsule by sutures, in one knee, and meniscectomy alone in the contralateral knee. The animals were killed 3 and 6 month after implantation. Fragmentation of carbon fibres was noted in six knee joints. Histological sections demonstrated more progressive articular cartilage degeneration of the tibial surface which had the meniscus removed alone (P = 0.05). The implant was incorporated into the capsule with minimal invasion of fibrous tissue into the interstices of the prosthesis. Scanning electron microscopy revealed the extent of articular cartilage fibrillation which was more evident in the area where the meniscus covered the tibia.

Animals↗
PubMed1989

Torsional characteristics of the Minns meniscal knee prosthesis.

A quasi-static analysis of axial rotation of the femoral component and the torsional forces at different angles of knee flexion was performed on knee preparations. The meniscal knee design had very much lower axial torque against axial rotation characteristics through the whole range of knee flexion than the total condylar design and could be rotated up to 59 degrees in both internal and external rotation before dislocating (i.e., a total axial rotation of 118 degrees). The sliding plateau design had torque-rotation characteristics comparable to those of the total condylar design. Torsional strain was measured on cemented and uncemented preparations, and little difference between the two was observed.

Biomechanical Phenomena↗
PubMed1989

The Minns meniscal knee prosthesis: biomechanical aspects of the surgical procedure and a review of the first 165 cases.

The Minns knee prosthesis has been designed so that the ligaments, soft tissues and musculature about the knee can return to their full functioning during the movement and loading that occur in usage. By utilising a third component made of polyethylene that slides back and forth in a straight line between the metallic femoral and tibial components, the knee is able to roll and slide at the plastic/metal junctions without creating high forces and loosening moments on the tibial component. The tibial tray has a central cut-out to allow the functioning of both cruciate ligaments, and the femoral component is of the total condylar design. Experimental and theoretical studies on the functioning and clinical performance of this design and the biomechanical implications of the technique of surgical implantation are described. The results of the first 165 cases, followed up for a maximum of 5 years, were ranked according to pain, mobility, and restoration of function; 75% were rated as excellent, both subjectively and objectively, 13% as good, and 9% as fair. The average range of motion measured at least 6 months postoperatively was 103 degrees. Eight knees dislocated laterally because of instability and were successfully revised using the sliding plateau without being necessary to remove the metallic components. Minimal wear has been seen on the removed menisci up to 4.5 years' use.

Biomechanical Phenomena↗
PubMed1989

Techniques for measuring the static and dynamic properties of the patella.

An electrogoniometric method was used together with a new standardized radiographic technique to accurately determine the rotation of the patella during knee flexion of both normal subjects and patients referred for retropatellar pain. A preliminary study using these techniques shows that retropatellar pain is very much a multi-factoral clinical problem and that combinations of patello-femoral articulation abnormalities, patellar shape and mechanical influences are present in all forms of the painful patella.

Adolescent↗
PubMed1989

Mechanical and histological response of carbon fibre pads implanted in the rabbit patella.

Small carbon fibre pads (3 mm in diameter) were implanted into rabbit patellae to ascertain the relationship between their mechanical and histological responses. After 3 months a highly vascularized collagenous matrix is formed within and around the implant securely anchored to the bone and providing a continuous layer to the articular surface. Mechanically, the resulting repair is much more compliant than the original articular cartilage/bone structure since the subchondral bone plate is not present within the implant; it also provides a functioning congruent surface with no evidence of fragmentation. This may be attractive in the long term by decreasing friction and the subsequent degeneration and wear commonly seen in fibrillated, disrupted articular cartilage.

Animals↗
PubMed1989

Woven carbon-fibre patch versus Dacron mesh in the repair of experimental defects in the lumbar fascia of rabbits.

Defects were created in the lumbar fascia of adult New Zealand white rabbits and repaired with either woven carbon-fibre or Dacron mesh. The histological and mechanical properties of the two materials were compared at intervals up to 12 wk post-operatively. Microscopy showed an abundant orderly deposition of collagen highly vascularized with a minimal inflammatory response on the carbon fibre, whereas the Dacron mesh induced the formation of a flimsy collagenous capsule, with a marked inflammatory response. Mechanical testing showed a significant increase in the strength of the carbon-fibre patch after 2 wk (P = .001), the patch becoming much stronger than the Dacron mesh (P = .002) 5 to 12 wk after implantation.

Animals↗