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Biomedical subjects

H D Clarke

Publications and source records attributed to H D Clarke.

14 recordsLinked to original sources
PubMed2001

Knee: axial instability.

The long term results of total knee replacement are among the most successful of any orthopedic procedure; however, certain patterns of failure have been identified including varus-valgus instability and anterior-posterior instability in flexion. While trauma may cause acute ligamentous injury that results in instability, the majority of cases likely result from intraoperative decisions that result in malalignment and inadequate soft tissue balancing. Failure to restore medial-lateral soft tissue balance with symmetric flexion and extension spaces may result in postoperative instability. Techniques to achieve correct soft tissue balancing and symmetric flexion and extension gaps, as well as the management of postoperative instability, are reviewed.

Arthroplasty, Replacement, Knee↗
PubMed2001

Revision total knee arthroplasty: planning, management, controversies, and surgical approaches.

Revision total knee arthroplasty can be a technically challenging procedure fraught with potential complications. In many cases, obtaining adequate exposure is difficult, and failure to do so can directly cause technical errors and complications. Patient-specific systemic comorbidities and anatomic details can further complicate the procedure. Careful preoperative evaluation can help to facilitate optimal results. Furthermore, specific surgical techniques help to improve the surgical exposure and can minimize complications such as wound healing problems, component malposition, and extensor mechanism disruption. All surgeons undertaking these procedures require a thorough understanding of these principles.

Adult↗
PubMed2000

Acromioclavicular joint injuries.

Injuries to the acromioclavicular joint are common, and most can be treated nonoperatively. Appropriate treatment depends on accurate diagnosis and appreciation of the classification of these various injuries. Descriptions of the commoner acromioclavicular joint injuries, details of the nonoperative treatment, and indications for surgical treatment are reviewed.

Acromioclavicular Joint↗
PubMed1999

Head and neck replacement prostheses in revision hip arthroplasty: experience with a single modern design.

This study reviewed 52 revision hip arthroplasties in which calcar cortical deficiencies were addressed by implantation of a cemented, modern-design head and neck replacement femoral prosthesis. Mean clinical follow-up was 38 months. Radiographic follow-up beyond 22 months was available for 34 patients (mean: 35.8 months). Mean Mayo clinical hip score (maximum: 80) improved from 28.2 preoperatively to 55.2 at last follow-up. No femoral component was revised for aseptic loosening. However, radiographic analysis demonstrated one prosthesis was probably loose and two were possibly loose. A 92.7% Kaplan-Meier 5-year implant survival rate free from radiographic loosening was projected. This type of prosthesis has yielded good clinical results and excellent early survival.

Adult↗
PubMed1998

Head and neck replacement endoprosthesis for pathologic proximal femoral lesions.

Records of 28 patients with pathologic lesions in the proximal femur treated by implantation of a femoral head and neck replacement prosthesis between 1984 and 1995 were reviewed. Mean clinical followup was 47.8 months in the eight living patients and 15.8 months in the 20 patients who had died. The underlying diagnosis was metastatic disease or myeloma in 22 patients. The most frequently occurring indication for implantation of this device was a pathologic fracture in 26 patients (18 displaced, eight impending), followed by resection and reconstruction in two patients. All femoral components were cemented: 23 were bipolar hemiarthroplasties and five were total hip arthroplasties. Implant survivorship was good (93%), with only two prostheses removed during the followup period, both for infection. However, radiographic analysis revealed increasing lucencies with time, particularly in the most proximal zones, resulting in radiographic failure in an additional case. Deep infection occurred in three cases, leading to resection arthroplasty in two patients. Periprosthetic fractures occurred in three cases, but only one occurred intraoperatively. Despite a high complication rate, the good implant survival during the shortened life span of these patients supports the continued use of femoral head and neck replacement prostheses in this population.

Adult↗
PubMed1998

Salvage of failed femoral megaprostheses with allograft prosthesis composites.

The records of 11 consecutive adult patients who underwent revision of a failed femoral megaprosthesis (aseptic loosening, nine; periprosthetic fracture, one; and prosthesis fracture, one) to an allograft prosthesis composite were reviewed retrospectively. Complications included radiographic component subsidence in two patients (18%), hip instability in three patients (27%), deep infection in two patients (18%), and allograft fractures in two patients (18%). Five patients (45%) required subsequent reoperations; four patients underwent removal of the allograft prosthesis composite at a mean of 16 months (range, 5-41 months) and one patient (9%) with hip instability underwent revision of the failed megaprosthesis to a constrained acetabulum. Reconstruction of a failed femoral megaprosthesis is a complex problem caused by extensive bone loss and violation of soft tissue attachments. Despite a high complication rate, six patients (55%) remained ambulatory and had mild or no pain at a mean followup exceeding 5.5 years.

Adult↗
PubMed1998

Peroneal tendon injuries.

Injury to the peroneal tendons is a frequently overlooked cause of persistent lateral ankle pain after trauma. Peroneal tendon anatomy, biomechanics, diagnostic studies, and traumatic disorders were reviewed.

Adult↗
PubMed1997

Acute pseudo-obstruction of the colon as a postoperative complication of hip arthroplasty.

Acute pseudo-obstruction of the colon (Ogilvie syndrome) results in massive colonic dilatation that may lead to a life-threatening perforation. This complication is known to occur after arthroplasty of the hip, yet the prevalence of the complication and its effects on the outcome of the procedure are unknown. We reviewed the records of thirty patients (mean age, 74.3 years; range, fifty-six to ninety years) in whom acute colonic pseudo-obstruction developed after hip arthroplasty between 1984 and 1993. During this ten-year period, 10,468 hip arthroplasties were performed at our institution; therefore, the prevalence of acute colonic pseudo-obstruction was 0.29 per cent. The most common presenting symptom was abdominal distention, which occurred a mean of 3.5 days (range, one to eleven days) postoperatively and was noted in twenty-seven of thirty patients. Nausea (fourteen patients), vomiting (eight patients), and abdominal pain (two patients) were observed less frequently. Twenty-one associated medical complications, including pulmonary embolism (four patients), upper gastrointestinal bleeding (three patients), and deep infection (not evident intraoperatively) at the site of the arthroplasty (two patients), developed in fifteen patients. Eighteen of the twenty-one complications occurred after the onset of colonic pseudo-obstruction. The associated medical problems resulted in four deaths (13 per cent). Recognition by the orthopaedic surgeon of the presenting features of acute colonic pseudo-obstruction is important in order to facilitate prompt initiation of treatment, which may hasten recovery and reduce the morbidity and the mortality associated with this complication.

Abdomen↗
PubMed1992

Myofilament lengths of cat skeletal muscle: theoretical considerations and functional implications.

The cat is the primary model for neuromuscular research. However, sarcomere geometry, in particular thin-myofilament lengths of cat skeletal muscles, is not known, thus preventing adequate muscle modeling on the sarcomere level. The purpose of this study was to determine thin-myofilament lengths in cat skeletal muscle. It was found that average thin-myofilament lengths of cat tibialis anterior muscles (1.12 microns) were larger than the average values reported for frog (approximately 0.95 microns), rat (1.09 microns), and rabbit muscles (1.09 microns) and were smaller than the values reported for monkey (1.16 microns) and human skeletal muscles (1.27 microns). According to the cross-bridge theory of muscular contraction, this result implies that the range of sarcomere length on the ascending limb of the force-length relation for cat muscle is between those of frog, rat, and rabbit on the one side and monkey and human on the other side. It is speculated that the differences in thin-myofilament lengths of different animals are related to the functional demands of these muscles in everyday movement tasks. Isolated experimental observations appear to support this speculation.

Actin Cytoskeleton↗
PubMedDate not supplied

The effect of daunomycin on platelets in vitro.

Daunomycin (rubidomycin, daunorubicin), an anthracycline antimetabolite used in the therapy of acute leukemia, is highly toxic to both normal and malignant cells. Treatment with daunomycin may produce thrombocytopenia and bleeding which have been attributed to bone marrow toxicity. We have examined daunomycin to determine if a direct drug effect on platelet structure and function could contribute to a hemorrhagic diathesis in some patients on therapy. Normal citrated platelet-rich plasma was reacted in vitro with daunomycin and/or collagen with structural assessment by phase and electron microscopy and functional studies by platelet aggregation, [2-14C]5-hydroxytryptamine release studies and assays for released cytoplasmic marker enzyme, lactic dehydrogenase, in the supernatant fluid. High [greater than 0.04 mg/ml (greater than 0.07 mM)] concentrations of daunomycin were associated with structural changes, specifically by platelet swelling, vacuole formation and mitochondrial swelling with interruption of the trilaminar membrane. Platelets, exposed to low doses of daunomycin, 0.001 to 0.01 mg/ml (0.00177-0.0177 mM) of platelet-rich plasma, were dysfunctional with decreased aggregation with collagen and decreased [2-14C]5-hydroxytryptamine release. These studies indicate that daunomycin has a direct effect on platelets in vitro which may explain certain instances of bleeding observed in some patients undergoing therapy.

5-Hydroxytryptophan↗