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Biomedical subjects

L S Matthews

Publications and source records attributed to L S Matthews.

At least 37 records · Page 2Linked to original sources
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↗
PubMed1992

Diverse effects of insulin-like growth factor I on glucose, lipid, and amino acid metabolism.

The metabolic effects of recombinant human insulin-like growth factor I (rhIGF-I) on glucose, amino acid, and free fatty acid (FFA) metabolism were examined in nine healthy nonobese subjects. Each received a 3-h primed continuous infusion of rhIGF-I (20 micrograms/kg bolus, 0.4 microgram.kg-1.min-1) while maintaining euglycemia using an exogenous glucose infusion. Total IGF-I levels increased from 125 +/- 11 to 444 +/- 22 ng/ml, and free IGF-I levels rose from undetectable to 73 +/- 5 ng/ml. Insulin levels fell from 95 +/- 9 to 64 +/- 8 pM, and C-peptide fell from 453 +/- 48 to 206 +/- 29 pM; circulating glucagon levels also declined from 72 +/- 9 to 42 +/- 4 pg/ml, rhIGF-I produced a two- to threefold increase in glucose uptake as measured by [3H] glucose (from 10.3 +/- 0.6 to 27.4 +/- 3 mumol.kg-1.m-1), and, despite the fall in insulin secretion, there was a marked 60-70% inhibition of hepatic glucose production. Furthermore, FFA and branched-chain amino acids declined by 40-60% (411 +/- 58 to 165 +/- 36 and 406 +/- 23 to 219 +/- 14 microM, respectively). Our data demonstrate that rhIGF-I has potent effects on glucose (hepatic and peripheral), lipid, and amino acid metabolism in normal humans. The scope of the actions of rhIGF-I closely resemble those of insulin, despite a concomitant inhibitory effect on insulin secretion.

Adult↗
PubMed1992

Proximal femoral bone density and its correlation to fracture load and hip-screw penetration load.

The bone mineral density of 22 random, fresh proximal human femora was estimated by roentgenography using the Singh index (SI) and measured using a regional bone mineral density computed tomographic protocol. Uniaxial compression was used to produce an impacted subcapital fracture. The femoral heads then were isolated and mounted on a sliding screw plate compression device and loaded to failure in a push-out or hip-screw penetration mode. Wide intraobserver variation, poor reproducibility, and poor prediction of the experimental fracture properties of the proximal femur were noted for SI values. Regional bone mineral density provided a reliable estimate of both the gross fracture loads and hip-screw penetration loads. In addition, there was a high correlation between trabecular density and the experimental fracture properties of the proximal femur. Therefore, The validity of the SI as an indicator of the mechanical properties of the proximal femur should be reconsidered.

Biomechanical Phenomena↗
PubMed1992

Interlocking intramedullary nails. An improved method of screw placement combining image intensification and laser light.

Insertion of distal interlocking screws in femoral nails can be technically demanding and may entail substantial exposure. A method of insertion of femoral interlocking screws that uses a laser guiding system in addition to the standard image intensifier was used in an attempt to improve the accuracy of distal screw placement and to limit radiation exposure. Using this technique, 97% of the distal femoral drill holes attempted were successfully made with the first pass of a drill. Little or no resistance to the drill was met from contacting the femoral nail. Average fluoroscopy time was 0.4 minute. Laser-assisted screw placement requires relatively inexpensive modifications of existing equipment and is easy to master. Compared with the more commonly used freehand method, laser-assisted screw placement appears to offer a reduction in the amount of time and radiation exposure required to insert distal interlocking femoral screws.

Bone Nails↗
PubMed1992

The prosthesis-bone interface in total knee arthroplasty.

Classic methods of implant component fixation, including the use of screw and impact-tapered, interference-fit stabilization, have provided longevity of function for total knee arthroplasties (TKAs). Optimal cement stabilization may be limited by the degradation characteristics of methyl-methacrylate. Modern application of porous coating for bony ingrowth fixation has not been as successful as expected, particularly as applied to the tibial component in TKA. Based on their in vivo research, the authors have developed a tibial component with an array of porous-coated cones that ensure immediate fixation and a graduated stress field to the host trabecular bone. This may improve the reliability and durability of tibial component fixation.

Animals↗
PubMed1992

Airport detection of modern orthopedic implant metals.

The sensitivity of airport metal detectors to a variety of orthopedic implants shows that total hip and total knee replacements, intramedullary nails, hip compression screws, and bone plates can escape detection. The metallurgic composition of the undetected implants were titanium, titanium-aluminum-vanadium alloy, cobalt-chrome-molybdenum alloy, and some stainless steel. The implants were tested individually, in combination, and as a whole in each of three different metal detectors. Only one of the screened implants activated a metal detector: an old Austin Moore straight fenestrated endoprosthesis that individually activated one of the three metal detectors. All of the other screened implants were not detected by any of the three tested metal detectors. Furthermore, the Moore endoprosthesis failed to activate two of the three tested metal detectors. Metal objects are identified by metal detectors based on their ferrous content. Contemporary orthopedic implants use little, if any, ferrous metal and therefore escape detection by airport metal detectors.

Aviation↗
PubMed1991

Trabecular bone remodeling: an experimental model.

An experimental model, capable of inducing controlled stress fields to the distal femoral metaphyses of large dogs, is presented. This model utilized an implantable hydraulic device incorporating five loading cylinders and platens in direct contact with an exposed plane of trabecular bone. A microprocessor controls the loading characteristics, and finite element models were created to calculate the induced stress and strain fields. The trabecular remodeling response is measured using serial in vivo computed tomography, in vitro microcomputed tomography, and histologic analysis. The results of the experiment indicate that significant remodeling can be induced by the activated implant. An increase in trabecular orientation toward the loaded platens was observed, and a statistically significant decrease in connectivity was documented. The greatest effect was associated with a change in the loading rate. A fast rise time (70 ms) loading waveform induced significant bone ingrowth at the implant interface when compared to a slow rise time waveform (700 ms), and demonstrated high correlations with the calculated stress fields as remodeling approached an equilibrium state.

Animals↗
PubMed1991

The joint-contact area of the ankle. The contribution of the posterior malleolus.

Eight ankles from fresh cadavera were tested under simulated clinical conditions to determine the effect of increasing the size of the posterior malleolar fracture on the contact area of the ankle joint and on the distribution of joint pressure. The surface area of contact decreased with increased size of the posterior malleolar fragment. However, the documented changes were smaller than expected on the basis of the findings of Ramsey and Hamilton; they reported a 42 per cent reduction in contact area with only a one-millimeter lateral shift of the talus, which clinically would be associated with a similar one-millimeter shift of the distal tibial fragment. In addition, clinical experience has shown a high rate of post-traumatic degenerative arthritis associated with an inadequately reduced one-half-size posterior fragment. There were considerable changes in the load-distribution patterns, with increased confluence and concentration of loads as the size of the fragment was increased. In plantar flexion, many specimens had three separate areas of contact between the tibia and the talus. With increased size of the posterior fragment, the three areas of contact always joined to become one. Similarly, for all positions of the ankle, increased size of the posterior fragment caused decreases in the contact area. The maximum loss of contact area was 35 per cent for specimens with one-half-size fractures that were tested in the neutral position.

Ankle Joint↗
PubMed1991

Arthrodesis of the knee with an intramedullary nail.

The cases of twenty patients who had an arthrodesis in which an intramedullary nail was used for stabilization were reviewed at an average follow-up of six years. The predominant indications were infection after total knee arthroplasty and post-traumatic pain and instability. Other indications included aseptic loosening of the components of a total knee arthroplasty, reconstruction after resection of a giant-cell tumor, non-union of a fracture of the distal part of the femur or the proximal part of the tibia, and failed external-compression arthrodesis. Success was achieved in seventeen patients (85 per cent), and functional stability immediately postoperatively was gained in all twenty. Of the three patients in whom the arthrodesis failed, all had sustained an intraoperative fracture, and infection eventually developed. Of the twelve nails that were secured to the greater trochanter with a loop of stainless-steel wire, none showed evidence of proximal migration. Of the eight nails that were not thus secured, two migrated proximally, necessitating removal of the nail. Two drawbacks to this operation are the long duration and the large amount of blood that is lost. The major advantage is that a high percentage of patients have progression to a stable fusion despite serious problems. Furthermore, all but seven patients (including the six who had a tumor or who had sustained an intraoperative fracture) were able to bear full weight by the second postoperative week. Only a few patients needed an external support for walking.

Adult↗
PubMed1990

Traction force profiles associated with the use of a fracture table: a preliminary report.

A load cell was developed that can reliably monitor longitudinal traction forces applied to limbs during several different orthopaedic procedures. This permitted determination of tensile loads and the effects of patient limb positions on tension magnitudes. The relationships between the magnitude and duration of applied tension to functional nerve changes were also studied. This preliminary report reviews traction force data on seven patients for eight operations. Mean peak loads for femoral, tibial, and hip procedures were 686, 356, and 306 N, respectively. Adduction of the limb around a fixed peroneal post caused great increases in traction forces.

Adult↗
PubMed1990

Treatment of juxtaarticular nonunion fractures at the knee with long-stem total knee arthroplasty.

A retrospective study of ten patients with juxtaarticular nonunions at the knee treated with long stem total knee arthroplasty was performed. The average age of the patients was 76 years old, with an average follow-up of 36 months. The nonunions were present for an average of 36 months. There were six patients in the series with prior total knee arthroplasty. Clinical union was achieved in all ten patients. All patients improved their ambulatory status. Range of motion improved from an average preoperative range of 40 degrees to an average postoperative range of 85 degrees. Complications occurred in three of ten patients, with one being a postoperative infection. Surgical techniques are described to aid in treatment of difficult juxtaarticular nonunion fragments.

Aged↗
PubMed1990

Results of treatment of displaced patellar fractures by partial patellectomy.

The results of partial patellectomy as a treatment for displaced patellar fractures were assessed retrospectively with use of clinical, radiographic, and isokinetic strength-testing criteria. Forty patients who had been followed for an average of 8.4 years were studied. In the extremity that had been operated on, the mean active range of motion was 94 per cent, the circumference of the thigh was 100 per cent, and the strength of the quadriceps was 85 per cent of these measurements in the contralateral extremity. The over-all result was rated as excellent in twenty patients, good in eleven, fair in six, and poor in three. There was a significant statistical correlation between the type of fracture and the outcome. The results of this study indicate that partial patellectomy can be an effective treatment for selected patellar fractures.

Adult↗
PubMed1990

Tips of the trade #28. Accurate tunnel placement using drill guides in knee ligament reconstruction.

Knee ligament reconstruction is optimized when intra-articular grafts are placed isometrically. Several drill guides have been designed to facilitate accurate tunnel placement. The use of an intra-articular keying hole, made with a burr, enhances proper and secure drill guide placement. Sterile mineral oil lubrication of the drill guide components will help prevent their distortion and will eliminate improper tunnel placement.

Anterior Cruciate Ligament↗
PubMed1989

Comparison of the trabecular and cortical tissue moduli from human iliac crests.

The purpose of this study was to design a method to produce and test mechanically microspecimens of trabecular and cortical tissue from human iliac crests, and compare their measured moduli. Rectangular beam specimens were prepared on a low-speed diamond blade saw and a miniature milling machine. The final specimen dimensions ranged from approximately 50-200 microns for base and height. The modulus of each specimen was measured using three-point bending tests across a span length of 1.04 mm and performed at a constant rate of displacement. A subset of specimens was recovered for a radiographic estimation of degree of mineralization. The results showed the mean trabecular tissue modulus of all iliac crest specimens to be 3.81 GPa, whereas cortical tissue specimens averaged 4.89 GPa. This was a significant difference according to a two-way analysis of variance that controlled for differences between donors. No strong correlations were found between modulus and mineral density. Future investigations that consider other microstructural characteristics and their contributions to modulus, and specimen size effects, are indicated.

Bone and Bones↗
PubMed1989

The limitations of canine trabecular bone as a model for human: a biomechanical study.

Distal canine femurs were sectioned into 8 mm cubic specimens. Orthogonal compression tests were performed to preyield in two or three directions and to failure in a third. Apparent density and ash weight density were measured for a subset of specimens. The results were compared to the human distal femur results of Ciarelli et al. (Transactions of the 32nd Annual Meeting of the Orthopaedic Research Society, Vol. 11, p. 42, 1986). Quantitative similarities existed in the fraction of components comprising the trabecular tissue of the two species. Qualitative similarities were seen in the positional and anisotropic variation of the mechanical properties, and also in the form and strength of the relationships between the mean modulus and bone density, ultimate stress and density, and ultimate stress and modulus. However, significantly different regression equations resulted for the mean modulus-density, and ultimate stress modulus relationships, indicating that for the same density, canine trabecular bone displays a lower modulus than human, and may achieve greater compressive strains before failure.

Animals↗
PubMed1989

Subacromial anatomy for the arthroscopist.

One of the most significant recent advances in arthroscopic surgery of the shoulder has been in the evaluation of the subacromial space and the anatomical structures within. Arthroscopic visualization of this area provides an unusual perspective of the anatomy that was not heretofore appreciated through open surgical techniques. This study was undertaken to attempt to define better the anatomy of the subacromial space as it pertains to arthroscopic surgery. Clinical arthroscopic evaluation of the subacromial space was correlated with gross anatomical dissections of 12 fresh cadaver shoulders and a review of the pertinent anatomical and surgical literature. By doing so, we have attempted to define better the boundaries of the subacromial space, the portions of the rotator cuff that are readily visualized arthroscopically, as well as those areas that are "blind" to arthroscopic evaluation. In addition, the anatomy of the coracoacromial ligament, the inferior surface of the acromion, and the acromioclavicular (AC) joint as viewed arthroscopically is presented with gross anatomical correlation. We feel that this information will help arthroscopists better understand the advantages as well as the limitation of arthroscopy of the subacromial space.

Acromioclavicular Joint↗