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D C Mears

Publications and source records attributed to D C Mears.

At least 55 records · Page 3Linked to original sources

External fixation of the pelvis.

During the past decade the useful classification and principles of management of the fractured pelvis have progressed rapidly. For the acute management the principal consideration is the control of severe intrapelvic hemorrhage. A protocol has been developed that combines the early application of external fixation with a closed reduction of the pelvic fracture. A marked decrease in the anticipated amount of intrapelvic hemorrhage has been documented. The coupled double anterior frame and its biomechanical equivalent, the newly developed triangular system, are easily applied to the pelvic ring and provide adequate stability for the treatment of the patient with a stable or unstable pelvic ring fracture. Thus the complex earlier design has been replaced by a simpler system. The triangular frame provides adequate stability so that the patient can undertake independent bed-to-chair transfers and early resumption of a weight-bearing gait. Late pulmonary, gastrointestinal, and urologic complications with prolonged bed rest and cast immobilization therefore have greatly diminished. In the present series in which external fixation has been applied to unstable pelvic ring fractures with a single posterior disruption, late loss of reduction, nonunion, and malunion almost have been entirely avoided. In addition, a simple triangular frame provides access to the abdominal wall and offers minimal postoperative interference with nursing care of the patient. Once the general condition of the patient has stabilized, supplementary techniques of open reduction and internal fixation may be applied to appropriate complex fracture patterns. These methods are fully reviewed elsewhere. Thus early rigid stabilization of the patient who sustains a pelvic ring fracture facilitates diminution of fracture pain, early mobilization of the patient, discharge, improved morale, and ultimately, decreased fracture morbidity and mortality.

Adult↗

Comparison of unrepaired, primarily repaired, and polyglactin mesh-reinforced Achilles tendon lacerations in rabbits.

The tensile and histologic characteristics of sharply transected Achilles tendons treated by cast immobilization, surgical repair, and surgical repair reinforced with polyglactin mesh were evaluated in 31 rabbits. All modes of tendon treatment resulted in tensile failure at significantly lower loads than in the contralateral control tendons. However, when the cross-sectional area and rupture stress of each pair of tendons were considered, the surgically repaired tendons more closely approximated the load tolerance of the control side than did the unrepaired, casted tendons. The mesh-reinforced tendons exhibited no mechanical superiority to the suture-repaired tendons. No microscopic difference in the quality of collagen deposition for the three types of repairs was apparent. Subcutaneous mesh did not evoke a significant cellular or fibrous reaction and was totally absorbed by the time of necropsy. A significant difference was found between the tolerated stress of the unrepaired and repaired tendons, but no functional benefit of repairing acutely transected Achilles tendons with synthetic mesh was observed.

Achilles Tendon↗

Ferrographic analysis of wear in human joints. Evaluation by comparison with arthroscopic examination of symptomatic knees.

Ferrography is a technique for analysing wear by means of the magnetic separation of wear particles. To evaluate its application in human joints, the results of the ferrographic analysis of saline washings of symptomatic human knees were compared with the results of the arthroscopic examination of the same knees. Ferrography was found to be an extremely sensitive monitor of articular erosion, with a resolution far greater than that of arthroscopy. This was particularly apparent with knees suffering from a torn anterior cruciate ligament: arthroscopy detected no damage to the cartilaginous surfaces whereas ferrography detected a substantial level of "microdamage". The spectrum of wear particles showed qualitative and quantitative alterations depending upon the condition of the knee. Ferrography thus holds much promise as a potential differential diagnostic technique of great sensitivity, with particular relevance to the very early changes which precede clinical symptoms. Study of wear particles is also justified by evidence indicating an active role in the pathophysiological progression of arthritis.

Adolescent↗

Release of neutral proteinases from mononuclear phagocytes and synovial cells in response to cartilaginous wear particles in vitro.

Cartilaginous wear particles were retrieved from synovial fluid aspirates of human diarthrodial joints and added to cultures of human or murine mononuclear phagocytes or human synovial cells. In each case, addition of the wear particles elevated the production of proteinases active at neutral pH against collage, gelatin, azocasein and the synthetic pentapeptide phenylazobenzyloxycarbonyl-L-Pro-L-Leu-Gly-L-Pro-D-Arg. Synovial cells secreted more than five times as much collagenase as the same number of the other cells. All types of cell secreted significant quantities of enzymes active against the noncollagenous substrates. Mild treatment of the spent media with trypsin stimulated all of these eurmymic activities. The spent culture media of synovial cells which had been exposed to cartilaginous wear particles released hydroxyproline and glycosaminoglycan from powdered cartilage, indicating the production of enzymes which degrade both the collagen and proteoglycan of th cartilaginous matrix. Cultures of mononuclear phagocytes, in contrast, while solubilizing chondroitin sulphate from cartilage, released very little hydroxyproline. The ability of wear particles to elicit these effects suggests a role for them in the pathogenesis of osteoarthritis and other types of joint deterioration.

Animals↗

A preliminary ferrographic survey of the wear particles in human synovial fluid.

The technique of ferrography has been applied to the analysis of wear particles in human synovial fluid aspirates. A number of discrete, identifiable classes of wear particles were found, including particles indicative of cutting wear and rubbing wear. The spectrum of particles varied among different groups of patients, suggesting an eventual diagnostic use for this method.

Arthritis, Rheumatoid↗

The wear particles of synovial fluid: their ferrographic analysis and pathophysiological significance.

This article reviews recent progress in our investigations into the wear particles which accumulate in prosthetic and natural diarthrodial joints. Ferrographic analysis of these particles is providing new insight into the manner in which joints undergo wear in situ. It also has the potential to serve as a diagnostic and prognostic technique, with special application to monitoring very early changes in the wear status of joints and distinguishing the various arthritides. Wear particles interact with periarticular cells and tissues, provoking the release of lytic enzymes and eliciting other biochemical changes, which exacerbate the destruction of the joint.

Adolescent↗

Binding of the bone-seeking agent 99mTc-1-hydroxyethylidene-1,1-diphosphonic acid to cartilage and collagen in vitro and its stimulation by Er3+ and low pH.

The bone-seeking agent 99mTc-labeled 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP) unexpectedly binds to particles of human articular cartilage as well as cortical bone in vitro. Collagen also sequesters this compound, suggesting that collagen contributes to the uptake of 99mTc-HEDP by cartilage and bone. Particles of the bone mineral calcium hydroxyapatite also bind 99mTc-HEDP in vitro. Pretreatment of particles with Er3+ stimulates binding in each case. Lowering the pH of incubation to pH 2 has this effect for bone, cartilage, and collagen, but not for calcium hydroxyapatite. Mechanisms additional to the simple ionic attraction between the phosphonate groups of HEDP and metal cations such as Ca2+ are responsible for the uptake of 99mTc-HEDP by body tissues.

Adult↗

Knee fusion with external skeletal fixation after an infected hinge prosthesis: a case report.

Deep sepsis is a serious postoperative complication of total knee hinge arthroplasty. Measures to eradicate the infection are time-consuming, expensive and often a threat to the limb and occasionally the life of the patient. At best, a successful result is a short leg with an arthrodesed knee. More often the patient is left with a painful fibrous ankylosis, or an above-knee amputation. The Hoffman external skeletal fixation device provides rigid fixation and allows early ambulation. Its use in combination with debridement and bone grafting can result in a successful arthrodesis with a minimum amount of shortening.

Arthrodesis↗

External fixation in pelvic fractures.

The treatment of unstable pelvic ring fractures, markedly comminuted and displaced acetabular fractures, and combinations of these insults to the pelvis has been an unsolved problem in orthopedics up to the present time. Of the previous methods of treatment, external fixation has appeared to hold the most promise for certain major pelvic insults, especially those accompanied by instability of the pelvic ring. Many of the previously used external fixation devices, however, have not provided adequate stability. Recently we have modified the Hoffmann external frame to provide a simple method of treatment for unstable pelvic ring fractures that permits the patient to undergo immediate mobilization from bed to chair. Certain other complex central acetabular fractures and combined insults involving the pelvic ring, central acetabulum, and proximal femur have been treated by extensive external frames. The results of these methods are described. Although such external devices appear to be superior to previously available methods, nevertheless, in view of their inherent limitations, we have begun to explore possible methods of internal fixation of the posterior portion of the disrupted pelvic ring combined with internal or external fixation of the anterior segment of the pelvis.

Adolescent↗

Modern concepts of external skeletal fixation of the pelvis.

The treatment of unstable pelvic ring fractures, markedly comminuted and displaced acetabular fractures and combinations of these insults to the pelvis is an unsolved problem. Of all the previously described methods, external fixation has appeared to hold the most promise for certain pelvic bone injuries of major proportions which are accompanied by instability of the pelvic ring. Many of the external fixation devices of the past have not provided adequate stability. A modification of the Hoffmann external frame provides a simple method of treatment for unstable pelvic ring fractures that immediately permits the patient to move from bed to chair. Complex pelvic and central acetabular fractures also are responsive to treatment by extensive external frames. While this external skeletal fixation is superior to previously available devices, internal fixation is under consideration for stabilization of the posterior portion of the pelvic ring. A combination of internal and external fixation may also be advantageous for severely disrupted pelvic bones.

Acetabulum↗

Ferrographic analysis of wear particles in arthroplastic joints.

Analysis of aspirated synovial fluid appears to be a useful method for the study of the rates, mechanisms, and biological responses to wear in surgical joint replacements. Ferrography, an industrial technique of magnetic separation of particulate matter from samples of lubricating solutions, allows separation of wear debris from synovial fluid. Bichromatic microscopy and SEM X-ray analysis permit identification of metallic particles from arthroplastic joints. Polarized light microscopy characterizes and differentiates polyethylene and polymethacrylate debris. The number and morphology of the wear particles in synovial specimens from arthroplastic joints correlate with the rate and the mechanisms of wear, as confirmed by examination of the implant and the adjacent synovial tissue.

Color↗

Preparation and testing of goat anti--thymocyte globulin.

This study details methods of production, purification and testing of large volumes of uniformly potent, non-toxic, anti-human thymocyte globulin (ATG). Plasma from 70 goats immunised with human thymic lymphocytes was fractionated by ammonium sulphate precipitation to its IgG component. Contaminating antibodies were removed by absorption methods. After fractionation and absorption, ATG retained its ability to inhibit the formation of rosettes by human lymphocytes with sheep red blood cells. Antibodies to human glomerular basement membrane were not detected in any tested preparation. Tests performed on monkeys, mice and rabbits revealed low toxicity.

Absorption↗

The use of dissimilar metals in surgery.

Previously, the use of dissimilar metals for the construction of surgical implants has been strongly discouraged because the combination of metals was likely to provoke more rapid corrosion of one metal. With the passive alloys that are in present and future application, however, a reconsideration of the use of dissimilar metals is required. Presently available electrochemical tests allow accurate prediction of safe and unsafe combinations of metals. The use of dissimilar metals would permit selection of the alloy of appropriate mechanical properties for each part of an implant and would allow improved corrosion resistance that certain alloys can convey to other alloys with which they are in contact.

Alloys↗