Biomedical subjects

D J Beevers

Publications and source records attributed to D J Beevers.

5 recordsLinked to original sources

PubMed2003

Metal vs bioabsorbable interference screws: initial fixation.

Interference screws are used for graft fixation in anterior cruciate ligament reconstruction. There is current debate as to whether metal or bioabsorbable varieties provide the optimal results. This paper provides a critique of the single load-to-failure uniaxial tensile test data available in the literature, which provide the initial postoperative characteristics. Both metal and bioabsorbable screws were found to give similar levels of pull-out force and stiffness when used on similar types of graft material. Screws with bone-patellar tendon-bone grafts provided the greatest values, exceeding the forces transmitted through the native anterior cruciate ligament during normal daily activities. Hamstring grafts provided lower values, only being comparable with the forces of daily living. Consequently, this raises the question as to whether the rehabilitation regime of the hamstring patient must not be aggressive in the early postoperative stages when using either metal or bioabsorbable screws. This would ensure that the graft will not fail in the initial postoperative period before biological fixation occurs, which will then boost the strength to an acceptable level.

Absorbable Implants↗

PubMed1999

A new concept for a metacarpophalangeal prosthesis: consequence on joint biomechanics.

OBJECTIVE: The purpose of this work was to establish whether surface replacement non-constrained prostheses can duplicate the normal biomechanics of the metacarpophalangeal joint. DESIGN: A series of mathematical models. BACKGROUND: A non-constrained prostheses has been designed for the replacement of the metacarpophalangeal joint. It uses the concept of surface replacement in that it attempts to replicate the anatomy of the original cartilage surfaces. The centre of rotation of the prosthesis is also sited at the same position as in the natural joint to maintain the balance between the flexor and extensor tendon forces, such that the prosthesis duplicates the biomechanics of the normal joint. Due to the unique dimensions of each joint that may present for surgery, the four sizes of prosthesis that are available for implantation may not always produce an exact replication of the joint kinematics. These situations were examined to establish whether the biomechanics of the joint can indeed be restored. METHODS: Mathematical models for each size of prosthesis implanted into a range of different sized metacarpophalangeal joints were developed. The prosthetic and cartilage surface profiles were compared and the balance between the tendon forces was examined. RESULTS: Differences in size that may occur between the surface profiles of the normal joint and prosthesis, together with any relocation of the centre of rotation, would have negligible effects on the normal joint biomechanics. CONCLUSIONS: All four sizes of the non-constrained prosthesis can duplicate the normal biomechanics of the joint and hence provide normal function.

Biomechanical Phenomena↗

PubMed1995

Metacarpophalangeal joint prostheses. A review of the clinical results of past and current designs.

The clinical results of past and current hinge, flexible and third generation designs of MP prosthetic joints are reviewed. The hinged prostheses did not achieve acceptable short term clinical results while the silastic and third generation prostheses provided good results with with correction of deformity and adequate range of motion (ROM). These good short term results did, however, get progressively worse with the recurrence of deformities and loss of ROM. It is evident that while most of the existing prostheses can relieve pain and restore appearance, none provide the degree of stability and ROM that is required to restore normal function to the MP joint. The moderate results could be partly due to the stage of the disease at which the surgery is carried out. At present, surgery on patients with rheumatoid arthritis is undertaken at a stage in the disease where the muscles and the ligaments surrounding the joint, and the bone, are generally in a poor condition. Surgery at this stage is really only a salvage procedure.

Arthritis, Rheumatoid↗

PubMed1995

Design of a non-constrained, non-cemented, modular, metacarpophalangeal prosthesis.

A non-constrained, non-cemented, modular prosthesis for replacement of the metacarpophalangeal joints of the fingers has been developed. The prosthesis is of a surface design which is modular in construction and is implanted into the bones with a press fit. The prosthesis is designed to be implanted into patients with traumatic injuries, post-traumatic osteoarthritis and into patients with rheumatoid arthritis at an early stage in the disease where the muscles and ligaments that surround the joint are still functional and can provide joint stability.

Arthritis, Rheumatoid↗

PubMed1993

Metacarpophalangeal joint prostheses: a review of past and current designs.

The anatomy and biomechanics of the metacarpophalangeal (MCP) joint are briefly described. Hinge, flexible and surface designs of past and current MCP prosthetic joints are reviewed, outlining their respective advantages and disadvantages. Although existing prostheses can restore cosmetic appearance and relieve pain, none can equal the stability and versatility of the natural joint. Delayed reconstructive surgery may be partly responsible for the mediocre results experienced, since the later the surgery the worse will be the condition of the muscles and ligaments surrounding the joint. These are the structures responsible for strength, movement and stability of the joint. From a mechanical viewpoint it may be desirable to operate at an earlier stage of the disease than is currently indicated, but this is a clinical decision. Some design aspects, namely fixation and wear, require a different approach when designing an MCP prosthesis from that adopted in the case of prosthetic hips and knees.

Biomechanical Phenomena↗