Search PubMed⌕ Search

Biomedical subjects

L S Matthews

Publications and source records attributed to L S Matthews.

At least 55 records · Page 3Linked to original sources
PubMed1989

Pitfalls in the use of interference screws for anterior cruciate ligament reconstruction: brief report.

Arthroscopically assisted bone patellar tendon bone reconstruction of the anterior cruciate ligament (ACL) is becoming an increasingly popular surgical technique. Use of interference screw fixation of the bone plugs within bony tunnels has been shown to improve fixation and pull-out strength. Several potential pitfalls exist which can jeopardize results of the surgical procedure when this form of fixation is used. This article describes the potential pitfalls and suggests methods to avoid them.

Arthroscopy↗
PubMed1989

Arthroscopic stabilization procedures for recurrent anterior shoulder instability.

Anterior shoulder instability is a common and functionally disabling problem in young athletes. The goal in treatment of this condition is a stable, yet mobile, joint. Current methods now being utilized in the arthroscopic stabilization of the anterior shoulder include staple capsulorrhaphy, removable rivet capsulorrhaphy, cannulated screw fixation, and the transglenoid suture technique. These techniques and the clinical experience with each are reviewed, with an emphasis on providing stability, improving function, and allowing earlier rehabilitation in the unstable shoulder of the athlete.

Arthroscopes↗
PubMed1988

Arthroscopic staple capsulorrhaphy for recurrent anterior shoulder instability.

Beginning in 1983, the principles of staple capsulorrhaphy of the shoulder utilizing arthroscopic techniques were applied to the treatment of patients with recurrent anterior shoulder instability. This paper describes the results of arthroscopic staple capsulorrhaphy of the shoulder in the first 25 consecutive cases in which these techniques were utilized. The patient population includes 4 females and 19 males, 2 of whom underwent bilateral staged procedures. Eleven of the patients had documented recurrent anterior dislocations while the remaining 12 patients were determined to have subluxation of the shoulder. The average age of the patient population was 23 years. Follow-up averaged 36 months. Results were determined by utilizing a strict 100 point rating scale as described by Rowe. Utilizing this scale, 67% of patients achieved good or excellent results. Five patients came to undergo additional surgical procedures. There were no complications of infection or neurovascular injury, but one patient suffered staple impingement upon the humeral head leading to excoriation thereof and secondary pain. An average loss of external rotation of 9 degrees, as compared to the contralateral shoulder, was noted postoperatively.

Adult↗
PubMed1988

Proximal tibial osteotomy. Factors that influence the duration of satisfactory function.

Survival analysis studies of 40 patients treated with high tibial osteotomy for arthritis with angular deformity were performed to determine the dominant factors that adversely affected long-term knee function. Obesity, advanced age, and postoperative overcorrection or undercorrection resulted in short durations of successful function. On the average, the probabilities for continued useful function of the knee at tested intervals were: one year, 86%; three years, 64%; five years, 50%; and nine years, 28%.

Adult↗
PubMed1987

Analysis of cumulative strain in tendons and tendon sheaths.

Twenty-five fresh frozen flexor digitorum profundus tendons stratified by sex were subjected to uniaxial step stress and cyclic loads in twelve intact human cadaver hands. By attaching specially designed clip strain gage transducers on tendons just proximal and distal to an undisrupted carpal tunnel, the interactions of the tendons, tendon sheath and retinacula were measured. The elastic and viscous response of the tendon composites to step stresses were found to fit fractional power functions of stress and time respectively. A significant and quantifiable decrease in strain from the proximal to the distal tendon segment was found to be a function of wrist deviation. The results indicate that an accumulation of strain does occur in tendinous tissues during physiologic loading.

Aged↗
PubMed1987

Bacteria isolated from late prosthetic joint infections: dental treatment and chemoprophylaxis.

The recommended administration of prophylactic antibiotics, before and during dental procedures, to persons with total joint prostheses is not without controversy. Hospital and dental charts of 2,693 patients in whom total prosthetic joints were placed at the Veterans Administration Hospitals of Ann Arbor and Allen Park, Michigan, as well as the University of Michigan Hospital, were analyzed. The identity of the micro-organism associated with the late (6 months after placement) infected prosthetic joint and the sensitivity of the organisms to specific antibiotics were recorded. Of the 30 (1.1%) late prosthetic joint infections, only one (0.04%) could be temporally associated with dental treatment. Fifty-three percent of the isolates were gram-positive staphylococci, the most common isolate being Staphylococcus epidermidis (36%). Pseudomonas aeruginosa was the most frequent gram-negative isolate cultured. Twenty-five of 34 isolates tested were resistant to penicillin, while only 3 of 36 isolates tested were resistant to a cephalosporin and 5 of 21 isolates tested were resistant to methicillin.

Anti-Bacterial Agents↗
PubMed1987

A biomechanical evaluation of the Lenox Hill knee brace.

This study was conducted to determine the effectiveness of the Lenox Hill knee brace in limiting anterior translation and external rotation of the tibia in reference to the femur in normal and ligament-deficient knees. Four fresh cadaver knees were fitted with Lenox Hill knee braces according to the manufacturer's guidelines. A computer-assisted testing apparatus was constructed that allowed each knee to be tested as a function of knee flexion angle, joint load, and soft tissue integrity. Each knee served as its own control. While 45 kg of anterior force was applied to the tibia of the anterior cruciate ligament deficient knees, the Lenox Hill knee brace was able to decrease anterior translation from an average of 10 mm, to 5.7 mm, at 30 degrees of flexion when no vertical load was present. This limiting effect was lost when the medial collateral ligament was sectioned in addition to the anterior cruciate ligament or when both the medial and the lateral collateral ligaments were sectioned along with the anterior cruciate ligament. When 20 Newton-meters (Nm) of torque was applied to the femurs at 30 degrees of flexion without vertical load, the Lenox Hill knee brace limited external rotation of the tibia in all tested categories. For intact knees at 30 degrees of flexion and no vertical load, the Lenox Hill knee brace decreased external rotation from 18 degrees to 10 degrees. In the anterior cruciate ligament-sectioned knees, external rotation was decreased from an average of 20.2 degrees to 16.1 degrees. In the knees with sectioned anterior cruciate and medial collateral ligaments, the average reduction was from 21.2 degrees to 15.4 degrees.(ABSTRACT TRUNCATED AT 250 WORDS)

Biomechanical Phenomena↗
PubMed1987

Resection arthroplasty as a salvage procedure for a knee with infection after a total arthroplasty.

Between 1970 and 1983, resection arthroplasty was done as a salvage procedure for twenty-eight knees (twenty-six patients) with infection after total arthroplasty. Eleven patients had multiarticular rheumatoid arthritis; fourteen, osteoarthritis; and one, multiarticular neuropathic arthropathy. Systemic signs of infection were eliminated in all patients and local signs, in 89 per cent of the patients. After resection arthroplasty alone, fifteen patients were able to walk independently. Six patients with monoarticular osteoarthritis who found the resection arthroplasty to be unacceptable had a successful secondary arthrodesis. In three patients a spontaneous bone fusion developed after the resection, with the knee in a good position. Two patients who were unable to walk before the resection arthroplasty were still unable to do so postoperatively. Neither the patient's disease nor the type of prosthesis that had been used was a reliable predictor of success of the resection arthroplasty. The patients who had had the most severe disability before the total knee arthroplasty were most likely to be satisfied. Patients who had had less disability were more likely to find the results of resection arthroplasty to be unsatisfactory.

Adult↗
PubMed1986

Patellar surface strain.

We measured longitudinal surface strains on the anterior patella at controlled simulated quadriceps loads, quadriceps angles, and knee flexion angles. We studied both the natural patella and patellas resurfaced with domed, bifaceted, and metal backed polyethylene components. Twelve matched pairs of fresh human cadaver knee specimens were tested. Midanterior longitudinal patellar strains were greatest at knee flexion angles at 45 to 60 degrees of knee flexion. Alterations in quadriceps angle medially and laterally did not decrease recorded strain values significantly. Polyethylene patellar prostheses increased patellar strains but a bifaceted component or "total contact" design minimized this effect. Metal support for the prosthetic patella decreased the recorded surface strains. This study of patellar surface strain at the three midline locations provides experimental results that may prove useful for design and validation of analytic models of the patella. The study also suggests that patellar surface strain measures may provide a method for evaluating the effects of patellar prosthesis design and resurfacing procedures.

Aged↗
PubMed1986

Computed tomography and plain radiography in experimental fracture healing.

We evaluated the relative contribution of plain radiographs and computed tomography to the assessment of fracture healing under experimental circumstances. In 15 sheep, we performed midshaft femoral osteotomies and internal fixation of the resultant segmental fractures. Radiographs were obtained preoperatively and immediately postoperatively. Animals were sacrificed at 3 weeks, 6 weeks, 12 weeks, 24 weeks, and 36 weeks after surgery, and the femoral specimens radiographed. After removal of the internal fixation devices, computed tomographic scans of the specimens were performed. By 3 weeks, callus was visible, but at 6 weeks, a trabecular pattern in the callus was seen on plain films but not on computed tomography. There was progressive organization of the callus on both studies. At 24 weeks, computed tomography demonstrated fracture lines not seen due to overlying callus on plain films and also more accurately showed incomplete union. By 36 weeks, healing was essentially complete according to both modalities, although there still were small gaps in the callus detectable on computed tomography but not on plain films. Computed tomography may be of value in the evaluation of fractures of long bones in those cases in which clinical examination and plain radiographs fail to give adequate information as to the status of healing.

Animals↗
PubMed1986

Spherocentric arthroplasty of the knee. A long-term and final follow-up evaluation.

The spherocentric knee was designed as an intrinsically stable prosthesis to manage the problems of deformity, instability, and metaphyseal bone loss in joints too severely involved to use resurfacing arthroplasty. Follow-up information has been obtained on 58 of the first 82 knees requiring spherocentric arthroplasty. After an average eight-year followup period, the results are gratifying with respect to pain, ambulatory ability, deformity, and instability. The infection and reoperation rates of 5% and 15% seem satisfactory when one considers the severely disabled patient and pathologic conditions of the knee joint.

Evaluation Studies as Topic↗
PubMed1986

Resection arthroplasty: an alternative to arthrodesis for salvage of the infected total knee arthroplasty.

Arthrodesis remains the procedure of choice for salvage of an infected total knee arthroplasty in patients with relatively minor preprosthetic arthroplasty disability. Patients with very severe preprosthetic disability resulting from multiarticular disease or other systemic disease may be treated best by a resection arthroplasty. Systemic sepsis can be eliminated in almost all patients, and drainage can be eliminated in most. Those patients who find the stability of a resection arthroplasty inadequate for their needs can have a secondary arthrodesis performed with an intramedullary rod, which yields a high probability of success. External immobilization is not necessary. The advantages of a two-stage arthrodesis are that it is an elective procedure, performed in a limb free of sepsis. The patient has been psychologically prepared for the arthrodesis, and the two-stage procedure has a high probability of success. Neither the underlying diagnosis, nor the infecting organism, nor the type of infected prosthesis is a reliable predictor of success or failure of either a resection arthroplasty or a second-stage arthrodesis.

Aged↗
PubMed1985

A biomechanical model of the lumbosacral joint during lifting activities.

A biomechanical model of the lumbosacral region was constructed for the purpose of systematically studying the combined stresses and strains on the local ligaments, muscles and disc tissue during sagittal plane two-handed lifting. The model was validated in two ways. The first validation was a comparison of experimental study results with model predictions. In general predictions compared very reasonably with observed values of several authors with the exception of strain predictions on the articular ligaments. Second, a sensitivity analysis was performed over a wide range of lifting tasks. The predicted stress/strain values followed anticipated patterns and were of reasonable magnitudes. On the basis of the results of the sensitivity analysis it was concluded that typical lifting tasks can lead to excessive disc compressive forces, muscle moment generation requirements, and possibly lumbodorsal fascia strains. Conversely, annulus rupture of a healthy disc due to overstrain appears very unlikely.

Biomechanical Phenomena↗
PubMed1985

Anterior portal selection for shoulder arthroscopy.

A posterior portal site has become the accepted standard for introduction of the arthroscope for routine diagnostic procedures of the shoulder. Few published guidelines exist, however, on the optimum and safe positions of accessory portals for introduction of a probe or surgical instruments during shoulder arthroscopy. The relatively thick surrounding muscle layers and the close proximity of vital neurovascular structures would make guidelines for safer and more reproducible accessory portal selection helpful to minimize the risk of injury to these structures. The "intraarticular triangle" bounded by the humeral head, the glenoid rim, and the biceps tendon has been found to be an excellent intraarticular landmark for placement of an accessory anterior portal for shoulder arthroscopy. Anatomical dissections on 20 cadaver shoulders have confirmed that instruments passed through this location are at little risk to injure adjacent neurovascular structures about the shoulder. Clinical data in 30 shoulder arthroscopies performed utilizing this landmark for placement of an anterior portal have confirmed this position to be a safe and useful location for portal placement if proper precautions are followed.

Arthroscopy↗