Biomedical subjects
Publications and source records attributed to L S Matthews.
Use of a simple method for injection of cooled methylmethacrylate into the distal part of the femur through the canal of a Küntscher rod to stabilize distal femoral-shaft fractures proved experimentally to greatly increase the torsional stability at the fracture site. This method may allow rapid ambulation of debilitated patients and prevent the complications of extended bed rest.
An experimental evaluation of the stability of rotational fixation of unstable, subcapital femoral-neck fractures as provided by either the multiple pin and side-plated Deyerle device or the heavy duty Jewett triflanged nail showed no significant difference between the two devices. The determination of moment versus deformation behavior included study of two torsional axis orientations and superposition of simulated body-weight and muscular-force impaction loadings.
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Small-diameter interference screws are a widely used method of securing bone-tendon grafts during anterior cruciate ligament reconstructive procedures. Recent reports document tunnel widening and subsequent loss of fixation, leading to a need for alternative fixation methods. In cadaver tissue, the fixation strength of large-diameter (11-, 13-, and 15-mm) interference screws was tested and compared with that of clinically used 9-mm diameter screws. Patellar-tendon sections were fashioned into three grafts, each with bone plugs measuring 10 x 20 x 7.5 mm. Tunnels were created in the epiphyseal bone of the femurs and tibias, resulting in gap sizes of 4.5-, 6.5-, 8.5-, and 10.5-mm for the 9-, 11-, 13-, and 15-mm diameter screws, respectively. Grafts were pulled from the tunnel at a rate of 51 cm/min. Average fixation strengths were 276, 302, 328, and 328 N for the 9-, 11-, 13-, and 15-mm screws, respectively. No significant difference existed between the fixation strengths (ANOVA, P < or = .05).
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Experience with three different designs of total knee systems indicates that generally excellent knee function can be afforded the majority of patients for many years. The identification of patients who presently cannot expect satisfactory long-term function (the young, muscular, or obese, yet otherwise normal, individual, for instance) and their exclusion as candidates is important for long-term success. The importance of postoperative limb alignment and component position is emphasized. Gross instability and great metaphyseal bone loss are identified as the indications for linked, primary, or revision total knee arthroplasty. The role of the dynamic behavior of trabecular bone is hypothesized to be of major importance in long-term prosthetic knee joint function.
The spherocentric knee, designed to allow triaxial rotation and provide intrinsic stability, includes desirable design features of metal on high density polyethelene bearing surfaces, metal support for all plastic components, metal-cement-bone interfacing for all fixation surfaces, sufficient strength to eliminate fatigue fracture of metallic components as a potential source of failure, cam deceleration for hyperextension control, and an inverted central plastic socket which minimizes wear. The system assures a low coefficient of friction and thereby minimizes loosening. This prosthesis has been used for surgical arthroplasty in 134 knees with gross instability or severe fixed deformity or both, in which optimal results would not have been anticipated with non-articulated resurfacing prostheses. The patients have been followed for an average of nearly 3 years (range one to 5 years). Results in terms of correction of deformity, improvement of stability, range of motion, pain relief and improved function, have been outstanding. Problems of infection, loosening and fracture of adjacent bone have been less than with other intrinsically stable prostheses (hinge prostheses) and are less than most reports of non-articulated resurfacing prostheses followed for a comparable time. There have been no failures within the prosthesis. Our loose prostheses represent failures that occurred between the prostheses and the bone. The spherocentric prosthesis is the prosthesis of choice for arthroplasty of a knee with severe preoperative deformity or severe instability or both in which optimal results would not be anticipated following insertion of a resurfacing type of prosthesis.
Standardized plaster replicas of bony specimens were made to determine the mechanical and architectural requirements for arthrodesis subsequent to failed arthroplasty. Surprisingly small differences were noted in the total volume of bone removed from control compared with arthroplasty patients. There were correspondingly small differences in the bone and/or limb lengths. Limb length is not a consideration in selecting a prosthesis type. Varying with the type of prosthesis, there were wide differences in the contact area of trabecular bone remaining for fusion. Bulky femoral and tibial stems or protrusions are undesirable and greatly diminish the interface areas.