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Biomedical subjects

R G Volz

Publications and source records attributed to R G Volz.

At least 37 records · Page 2Linked to original sources
PubMed1980

Biomechanics of the wrist.

The wrist joint is a complex linkage between forearm and hand which is capable of an impressive arc of motion yet retaining a remarkable degree of stability. Carpal stability is derived from numerous intra-and intercarpal ligaments in addition to closely approximated wrist flexors and extensors. Motion occurring at the carpus is predominantly biplane--radial ulnar deviation and palmar flexion and extension. The center of motion for these planes of movement is located within the proximal and palmar pole of the capitate. When painful conditions arise at the wrist, a loss of wrist motion usually follows. Occasionally a loss of volitional control over wrist extensors is noted with the abnormal recruitment of wrist flexors with finger flexor activity. When instability and pain co-exist at the wrist, deformity can arise as a result of the inherent motor imbalance noted between the 6 wrist motors. Vector force analyses disclose that the flexor carpi ulnaris is the dominant wrist motor with the least significant force being supplied by the extensor carpi radialis longus. Although wrist motion is not essential for most activities of daily living, the preservation of wrist motion is for some individuals essential for the performance of specific occupational or recreational activities.

Biomechanical Phenomena↗
PubMed1979

Bilateral total knee replacement under one anesthetic.

The postoperative results and complications among 41 patients undergoing bilateral total knee arthroplasty were compared with 40 patients who underwent unilateral total knee replacement. Among the bilateral group, the most common diagnosis was rheumatoid arthritis (68%), while degenerative arthritis prevailed in the unilateral group (50%). Preoperatively, patients in the bilateral group exhibited generally a greater degree of physical disability and limitation of activity due to multiple joint involvement. Postoperatively, no change in the arc of motion was noted in either group, although flexion contractures were significantly diminished in both. The degree of postoperative pain relief was identical in both groups as was the decreased need for walking devices. The most commonly observed complication among the unilateral group was prosthetic loosening (12.%). This was felt explainable on the basis of the increased postoperative activity level of patients with degenerative arthritis and single joint disease. Patients in the bilateral group showed a higher incidence of wound problems, presumably secondary to the long-term use of steroids. The infection rate was identical in each group, but the bilateral group displayed a higher incidence of pulmonary emboli (9.7 vs. 2.5%). The postoperative need for rehabilitation services and the duration of time before dependent walking was achieved was not prolonged in the bilateral group. Hospitalization of the bilateral group was increased only 20%. No deaths were reported in either group. When the need for total knee replacement exists bilaterally, bilateral replacement with a single anesthetic would appear reasonable, provided careful patient selection and technical guidelines are followed.

Anesthesia↗
PubMed1979

Enhancement of healing in osteochondral defects by collagen sponge implants.

Implants of porous, highly cross-linked collagen sponge (CS) were tested for their capacity to enhance the healing of osteochondral defects in rabbits. Comparison was made to the healing of similar defects with polyvinyl alcohol sponge (PVAS) implants and with no implants (CONT). Evaluation was carried out up to 44 weeks following implantation and included observation of host cellular response, biodegradability of implant, gross appearance of restored joint surface, collagenous architecture of repair tissue, and properties of the junctions of implants and host articular cartilage, subchondral bone, and medullary bone. Collagen sponge proved most effective in promoting healing of osteochondral defects with fibrous and fibrocartilaginous tissue over restored subchondral bone. Collagen sponge showed many desirable properties as a potential material for biologic resurfacing of damaged joints. These properties included porosity, biodegradability, biocompatability, ability to mechanically protect cells and matrix while directing cell ingrowth, and an available chemical technology for modifying its biomechanical and biological properties. Comparative analysis of results of healing of CS, PVAS, and CONT osteochondral defects suggest rational design criteria for implant materials to improve their effectiveness in restoration of articular surfaces.

Animals↗
PubMed1978

Upper extremity total joint replacement.

Current techniques of total joint replacement surgically correct badly destroyed joints by the insertion of plastic and metal components, which are secured to the skeleton by methylmethacrylate cement. This approach began in England in 1962 and in the United States in 1967. Recent development in the field of upper extremity joint replacement allow implementation of refined total shoulder, elbow, and wrist prostheses. Although less experience has been gained with these prostheses than with total hip and knee replacements, preliminary results are encouraging.

Arm↗
PubMed1977

Illusory biplane radiographic images.

The commonly held belief that radiographs taken at right angles to one another will accurately portray the precise location of a metallic implant within a skeletal structure is erroneous. To the contrary, such biplane radiographs often provide misinformation about the exact location of metallic implants. The explanation for this phenomenon is discussed along with several methods to determine the accurate location of metallic implants when only biplane radiographs are available. Orthopedic surgeons should be particularly aware of this potential problem when biplane radiographs are taken at the time of insertion of multiple pins about the proximal femur.

Adolescent↗
PubMed1977

The painful migrated ununited greater trochanter in total hip replacement.

The migrated painful ununited trochanter following total hip replacement can provoke a significant degree of functional disability. Although this condition is infrequently observed after total hip replacement, its occurrence causes definite problems for its operative management. A technique employing the trochanteric bolt for reattachment of the migrated painful trochanteric fragment is described. The results of this approach in five patients to date are relief from pain and decreased disability in all five. The factors promoting migration of the osteotomized fragment include the quality of the trochanteric bone, the stresses placed on the osteotomy site by the patient during the postoperative period, and the precise method of reattachment of the trochanter at the time of total hip replacement.

Arthroplasty↗
PubMed1977

Factors affecting the mechanical stability of the cemented acetabular component in total hip replacement.

In thirty-six dissected hips from cadavera, six types of fixation of the prosthetic acetabular component to the acetabular tissue were devised, utilizing combinations of a variety of technical procedures: decorticating the cartilage, intruding the cup, reaming the bone, and perforating the residual bone tissue with anchoring holes (for cement). Mechanical tests showed that the greatest stability was achieved when the prosthetic cup was completely intruded, when all articular cartilage was removed and the socket was reamed, and when anchoring holes for cement were devised.

Acetabulum↗
PubMed1976

[Clinical experiences with a new total wrist prosthesis (author's transl)].

For many individuals the preservation of wrist motion is essential for augmentation of fine motor control of the hand and fingers. When significant functional disability exists at the wrist, currently available surgical treatment includes soft tissue arthroplasty, carpectomy, or arthrodesis. A total wrist joint has recently been developed which offers the patient the potential of a pain-free, stable, and mobile wrist. Based upon the principles of total joint replacement as applied to the hip and knee, the prosthesis is secured to the carpus and radius with methylmethacrylate cement following removal of the navicular, lunate, and head of the capitate. The configuration of the prosthesis interface provides for the two planes of motion normally seen at the wrist; 90 degrees of flexion and extension and 50 degrees of radial ulnar deviation are permitted by the design. Candidates for total wrist replacement are patients who exhibit far advanced disease at the wrist and who might be considered for arthrodesis, but in whom the permanent loss of motion would represent a significant handicap. To date, 20 prostheses have been inserted in 17 patients. The longest follow-up is 14 months. All but 2 patients have gained a useful range of motion. All patients have noted dramatic relief of pain and deformity, permitting them to perform tasks which were preoperatively impossible.

Humans↗
PubMed1976

The development of a total wrist arthroplasty.

For many individuals the preservation of wrist motion is essential for augmentation of fine motor control of the hand and fingers. When significant functional disability exists at the wrist, currently available surgical treatment includes soft tissue arthroplasty, carpectomy, or arthrodesis. A total wrist joint arthroplasty offers the patient the potential of a pain-free, stable, and mobile wrist. Based upon the principles of total joint replacement as applied to the hip and knee, the prosthesis is secured to the carpus and radius with methylmethacrylate cement, following removal of the navicular, lunate, and head of the capitate. The design of the prosthesis provides for the two planes of motion normally seen at the wrist; 90 degrees of flexion and extension and 50 degrees of radial ulnar deviation are permitted by the design. Candidates for total wrist arthroplasty are patients who exhibit far-advanced disease at the wrist and who might be considered as candidates for arthrodesis, but in whom the permanent loss of motion would represent a significant handicap. To date 17 arthroplasties have been performed in 14 patients. The longest follow-up is 14 months. All but 2 patients have gained a useful range of motion. All patients have noted dramatic relief of pain and deformity, permitting them to perform tasks which were preoperatively impossible.

Arthroplasty↗