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Biomedical subjects

L S Matthews

Publications and source records attributed to L S Matthews.

At least 19 recordsLinked to original sources
PubMed2000

Human osteoblast-like cells and osteosarcoma cell lines synthesize macrophage inhibitory protein 1alpha in response to interleukin 1beta and tumour necrosis factor alpha stimulation in vitro.

Recent investigations have demonstrated that macrophage inhibitory protein 1alpha (MIP-1alpha) plays a critical role in haematopoiesis. In part, MIP-1alpha limits the differentiation of early haematopoietic cells, thereby ensuring that sufficient quantities of blood precursors are available to meet haematopoietic demands. MIP-1alpha is produced by cells of the marrow microenvironment (marrow stromal cells) in response to a variety of stimuli, including interleukin 1beta (IL-1beta) and tumour necrosis factor alpha (TNF-alpha). Our recent investigations demonstrated that normal human osteoblast-like cells (HOBs) maintain the early phenotype of haematopoietic precursors, like other members of the bone marrow stroma. Although the precise molecular mechanisms for these observations have not been determined, the production of MIP-1alpha remains one such possibility. In the present study, we investigated whether cells of the osteoblast lineage under basal, IL-1beta and/or TNF-alpha stimulation produce MIP-1alpha. We observed that IL-1beta and TNF-alpha stimulated HOBs and human osteosarcoma cells to rapidly express MIP-1alpha mRNA and to secrete large quantities of the protein. MIP-1alpha mRNA and protein was not, however, detected under basal conditions. Perhaps more importantly, enriched human CD34+ bone marrow cells in co-culture may be capable of stimulating the expression of MIP-1alpha mRNA by HOBs in vitro. These findings suggest that human osteoblast-like cells may produce MIP-1alpha in vivo to support haematopoiesis at sites where osteoblasts and haematopoietic cells are closely associated.

Bone Neoplasms↗
PubMed1999

Arthroscopic versus open distal clavicle resection: a biomechanical analysis on a cadaveric model.

A fresh cadaver shoulder model was used to evaluate the difference in joint laxity between arthroscopic and open distal clavicle resection procedures. Twelve shoulders were mounted in a load frame that allowed compressive loading of the distal clavicle into the acromion. Specimens were loaded to 100 N (20 N/sec) while load and deformation data were recorded for three conditions: (1) intact, (2) 5-mm closed resection, and (3) 10-mm open resection. The displacement at the 100-N load and the stiffness of the load/displacement curves were compared for the intact, arthroscopic, and open procedures. Significant differences (ANOVA, P< or =.05) in displacement and stiffness were observed between the intact joint and both surgically resected joints. No significant differences were observed between the two surgically resected joints. The amount of bone removed arthroscopically was sufficient to prevent further bony contact in the axially loaded acromioclavicular joint.

Acromioclavicular Joint↗
PubMed1999

Pathways of economic influence on adolescent adjustment.

An important part of a science aimed at the prevention of human dysfunction involves the development of empirically based models that identify processes of risk for or protection from emotional distress or behavioral problems over time. The present study developed and evaluated such a model that proposed two pathways through which family economic pressure was expected to influence change in adolescent internalizing symptoms (depression and anxiety) during the period from the eighth to the tenth grades. A total of 377 rural families in a midwestern state provided data for the analyses. The results were generally consistent with the conceptual model in that family economic pressure increased adolescent perceptions of family economic hardship, which, in turn, reduced the adolescent's sense of control or mastery over time. Lowered mastery was associated with increases in emotional distress. Also consistent with the model, prior levels of mastery appeared to reduce the magnitude of economic stress experienced by the adolescent, whereas prior emotional distress intensified the economic stress process. Although gender differences were found in these processes, the overall pattern of results suggests that girls and boys are both at risk for internalizing problems when families experience economic pressure. Implications of the findings for the development of effective preventive interventions with financially stressed families in rural areas are discussed.

Adaptation, Psychological↗
PubMed1997

Leg injuries.

Injuries in the leg span a broad spectrum of patient age and athletic level. Overuse injuries, such as medial tibial stress syndromes and stress fractures, tend to occur in the young athlete, whereas tennis leg usually occurs in the older population. With a few exceptions, most of these injuries can be successfully treated nonoperatively. Particularly with the young athlete, it is important to stress the necessity to rest and avoid activities that would compound the injury.

Athletic Injuries↗
PubMed1997

Optimal side plate fixation for unstable intertrochanteric hip fractures.

OBJECTIVES: To quantitatively determine the minimal screw number needed for stable side plate fixation to the femoral shaft in treating unstable intertrochanteric hip fractures. DESIGN: Laboratory/biomedics study. SETTING: Orthopaedic biomechanics laboratory. PATIENTS OR OTHER PARTICIPANTS: The convenience sample was made up of one saw bone, one steel pipe, and ten human cadaveric femur specimens. Human specimens were selected by ruling out pathology and excess osteopenia. Ten specimens were tested to completion. INTERVENTION: Telescoping hip screw and hip screw side plate secured with various numbered combinations of side plate screws. MAIN OUTCOME MEASURES: Decreases in tension experienced by all previously inserted screws when an additional screw was applied were recorded and labeled as "protection." RESULTS: Protection offered by a third screw on all previous screws was 787.3 newtons in the steel pipemodel, 71.2 newtons in the sawbone model, and 158.3 newtons in the human model (p < 0.005). A fourth bone screw did not decrease tension in previous screws by more than 11 newtons. The protective effect of the fourth screw on screw #3 increased with decreasing screw application torque by a maximum of 21.8 newtons (p < 0.005). CONCLUSION: This study suggests that three bone screws provide an optimal distribution of tensile forces. The insertional torque used to place screws, once screw-plate contact has been established, does not play a significant role in screw protection. Additional studies are needed to assess the role of cortical bone density, and cyclical loading and bending forces experienced by the side plate screws, before definite clinical recommendations can be made.

Biomechanical Phenomena↗
PubMed1997

Infection around joint replacements in patients who have a renal or liver transplantation.

The results of thirty-five joint (hip or knee) replacements in nineteen patients who had an organ transplantation were retrospectively reviewed. The patients received a standard immunosuppressive induction regimen at the time of the transplantation and were maintained on a combination of prednisone, azathioprine, and cyclosporine A. All patients received antibiotics perioperatively, but antibiotic-impregnated bone cement was not used for any procedure. Six joint replacements, in three patients who were an average of 48.2 years old at the time of the arthroplasty, were performed before a renal transplantation. Twenty-four joint replacements, in fourteen patients who were an average of 40.9 years old at the time of the arthroplasty, were performed after an organ transplantation. Two patients, who were an average of 53.8 years old at the time of the arthroplasty, each had a joint replacement both before and after a liver transplantation (a total of five joint replacements). The average duration of follow-up from the first joint replacement was 8.8 years (range, one to twenty-three years). The Harris hip score or The Hospital for Special Surgery knee score was determined at the time of the latest follow-up examination. An infection developed around the implant in five patients who had had the joint replacement after a transplantation. The average interval from implantation of the prosthesis until detection of the infection was 3.4 years (range, one to six years). One patient who had a liver transplant was infected with Pseudomonas aeruginosa and another one was infected with Escherichia coli. One patient who had a renal transplant was infected with Staphylococcus epidermidis; one, with Enterococcus; and one, with Serratia marcescens. We found that patients who had a joint replacement after an organ transplantation had a very high risk of devastating infection. The rate of such infection was 19 per cent (five of twenty-seven joint replacements in sixteen patients).

Adult↗
PubMed1996

Prescribing exercise for your patient.

The lack of exercise by most Americans is a major contributing factor to many chronic diseases. Physicians are now prescribing exercise for patients just as they would drugs. Compliance with any exercise program depends on realizing the needs and goals of the individual. The fundamental principles of an exercise prescription apply to all persons regardless of age, sex, or level of fitness. A systematic manipulation of the components of frequency, duration, intensity, and progression with periodic reevaluation allows the program to be individualized. The guidelines for the program should include all of the components of health-related physical fitness. These include cardiorespiratory endurance, body composition, muscular strength and endurance, and flexibility. A program for exercise should fit the lifestyle of the patient and be a life-long prescription.

Chronic Disease↗
PubMed1996

An ultrasound method to evaluate polyethylene component wear in total knee replacement arthroplasty.

Evaluation of a painful total knee replacement has been limited to physical examination, aspiration, plain radiographs, and radionuclide studies. Visualization of the polyethylene tibial-bearing component without surgery has not been possible. Polyethylene wear is a well-recognized cause of total knee replacement failure. We have developed an ultrasound method to evaluate polyethylene insert shape and thickness with the ability to clearly demonstrate structural loss of plastic. Before clinical trials, a total knee replacement was cemented into a fresh cadaver knee. Ultrasound imaging of the polyethylene insert was performed in the longitudinal plane using a 10 MHz linear transducer. A characteristic bone/metal/polyethylene interface enabled recognition of the insert material from which its dimension was estimated. The entire perimeter of the liner, the metal tray, and the bone-metal interface was visualized. Five consecutive measurements at each location were performed on each of the 8-, 10-, and 12-mm polyethylene liners with the ultrasonographer blind to the insert thickness. Once removed, measurements were made directly on the liners adjacent to the marked points with an electronic caliper. Coefficient of variation (r2) ranged from 1.6% to 8.3% for the ultrasound measurements, and 0.26% to 1.5% for the caliper measurements. A plot of ultrasound versus caliper measurements allowed calculation of a linear equation, with r2 = 0.98, demonstrating high correlation between the two measurements. Our ultrasound measurements are accurate to 0.5 mm with a 95% confidence interval. Ultrasound is an accurate way to measure the dimensions of the polyethylene liner in total knee replacement arthroplasty. Early experiences with ultrasound evaluation prior to revision have been very encouraging for the evaluation of polyethylene wear, defects, and of prosthetic loosening.

Anthropometry↗
PubMed1995

Scapulothoracic anatomy for the arthroscopist.

Because endoscopic management has recently been introduced as treatment for painful subscapular snapping, we designed a cadaveric study to identify the boundaries of the scapulothoracic spaces and the relationship of important neurovascular structures to safe portal sites for arthroscopic surgery. We studied eight fresh, unembalmed cadaveric shoulders by anatomic dissection alone and eight fresh, unembalmed cadaveric shoulders by dissection after arthroscopy. We noted the following findings: (1) the scapulothoracic articulation has two triangular spaces, the serratus anterior space and the subscapularis space, that are divided obliquely by the serratus anterior muscle; (2) the boundaries of the larger serratus anterior space include the chest wall anteriorly, the serratus anterior muscle posteriorly, and the rhomboids medially; (3) the boundaries of the subscapularis space are the serratus anterior muscle anteriorly, the subscapularis muscle posteriorly, and the axilla laterally; and (4) a well-defined bursa occupies the serratus anterior space. Based on these findings, we recommend that portals for arthroscopic surgery should be inferior to the spine of the scapula and three to four finger-breadths from the vertebral border of the scapula (1) to avoid the neurovascular structures at the superomedial angle of the scapula, (2) to avoid the dorsosacpular nerve and artery, and (3) to prevent perpendicular orientation of the arthroscope to the lateral chest wall.

Arthroscopy↗
PubMed1995

Use of patellar allograft to reconstruct a patellar tendon-deficient knee after total joint arthroplasty.

A catastrophic complication after total knee arthroplasty (TKA) is rupture of the patellar tendon. Several techniques for treatment have been described, including cast immobilization with or without operative repair, the use of a semitendinosus, fascia lata, or hamstring tendon autogenous graft, the use of a Dacron 4-mm vascular graft (U.S. Catheter and Instrument, Glen Falls, NY), the use of bovine xenograft and even transplantation of an entire allograft extensor mechanism. Treatment results of patellar tendon rupture after TKA can be discouraging. Altered tissue quality secondary to connective tissue diseases, diabetes, rheumatoid arthritis, lupus erythematosus, secondary hyperparathyroidism, or concurrent steroid medications contributes to poor results. Additionally, no one treatment has provided consistent clinical success. Successful treatment of a patient with a ruptured patellar tendon after TKA using the bone-patellar tendon-bone allograft commonly used for anterior cruciate ligament reconstruction is reported.

Aged↗
PubMed1994

Displacements of the menisci under joint load: an in vitro study in human knees.

The purpose of this study was to test whether the menisci displace under joint compression combined with internal-external torques and anterior-posterior forces at fixed flexion angles. We further determined differences in displacements between the medial and lateral menisci. Loads were applied to the joint, and joint load and displacements were measured. Meniscal displacements were measured radiographically. With a joint compressive load of 1 kN, internal and external joint rotations caused the lateral meniscus to displace, on average, 0.37 mm deg-1 in the anterior-posterior direction, while the medial meniscus displaced 0.19 mm deg-1. Anterior and posterior joint translation, performed under 1 kN joint compression, caused the lateral meniscus to displace, on average, 0.66 mm mm-1 in the anterior-posterior direction, while the medial meniscus displaced 0.43 mm mm-1. Greater meniscal displacements were found at 15 and 30 degrees flexion than at 0 degrees for the lateral meniscus in internal rotation. Lateral meniscal displacements were larger than those of the medial with posterior tibial translation at full extension and with internal rotation.

Femur↗
PubMed1994

Localized pigmented villonodular synovitis of the patellar fat pad: a report of two cases.

Pigmented villonodular synovitis (PVNS) of the knee is a well-recognized entity. We report on two cases of localized PVNS that involved the patellar fat pad, an area of involvement not previously reported. Diagnostic and therapeutic arthroscopies were performed, and typical findings of localized PVNS were found. Complete resection of the lesions were performed arthroscopically. At short-term follow-up, all symptoms had resolved. Arthroscopy can be used as an effective diagnostic tool for identification of intraarticular PVNS of the knee. In the case of localized involvement, it also can be considered as definitive treatment.

Adipose Tissue↗
PubMed1994

Fractures of the patella.

Patellar fractures usually occur from distraction and three-point bending of the patella as well as from direct blows. Surgical treatment is necessary for fractures that are displaced more than 2 mm and may include open reduction and internal fixation, partial patellectomy, or rarely, total patellectomy. We have presented a new technique for the stabilization of a simple transverse fracture that has provided superior results in laboratory tests. Postoperative complications can be minimized by good attention to wound care, accurate fracture reduction, secure fracture fixation and an early range of motion. Despite the surgeon's best efforts, however, post-traumatic osteoarthrosis can develop and may require additional treatment.

Fracture Fixation↗
PubMed1993

Fixation strengths of patellar tendon-bone grafts.

Secure fixation of bone-patellar tendon-bone grafts is essential to allow early joint mobilization after anterior cruciate ligament (ACL) reconstruction surgery. This study was designed to evaluate four fixation methods of patellar tendon-bone grafts in cadaveric knees. Fifty-one fresh cadaveric patellar tendon-bone specimens were anchored in tibial or femoral metaphyseal bone tunnels. Group I grafts were fixed with Kurosaka interference screws. In Group II the grafts were initially fixed as in Group I, but the screws were then removed, the bone plugs repositioned, and the grafts resecured with screws. In Group III the grafts were anchored with three no. 2 nonabsorbable sutures tied over a screw and washer, whereas in Group IV no. 5 nonabsorbable sutures were used. Each bone specimen was mounted in the biomechanical testing machine, and a vertical tensile load was applied at a strain rate of 51 cm/min until failure of fixation, bone plug fracture, or tendon disruption occurred. The mean force to failure in Groups I, II, III, and IV were 435.0 N, 458.2 N, 454.2 N, and 415.8 N, respectively. There was no significant difference in the force to failure among the four methods of fixation. However, the modes of failure were diverse. In three specimens the Kurosaka screws diverged from the plugs and failed to achieve fixation. These specimens were excluded and will be discussed separately. Although technique-related difficulties may arise, interference screw fixation of patellar tendon-bone grafts affords strong graft fixation--often stronger than the graft itself. Secondary screw fixation appears to be equal in strength to primary screw fixation.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Arthroscopic treatment of synovial diseases of the shoulder.

A wide spectrum of synovial disorders may affect the shoulder joint. This article provides a detailed description of the clinical features of synovial disorders of the shoulder. The role of arthroscopic surgery in the diagnosis and treatment of this spectrum of disease is discussed also.

Arthritis↗