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Biomedical subjects

H K Dunn

Publications and source records attributed to H K Dunn.

33 records · Page 2Linked to original sources
PubMed1980

Hemodilution and induced hypotension for insertion of a Harrington rod in a Jehovah's Witness patient.

The case of a 28-year-old Jehovah's Witness illustrates the feasibility of using a combined technique of induced hypotension and hemodilution to minimize the surgical loss of red blood cells during the insertion of a Harrington rod. A Swan-Ganz catheter with thermister tip was inserted to measure pulmonary arterial pressure, pulmonary arterial wedge pressure and cardiac output. Other intraoperative monitoring included continuous arterial pressure, electrocardiography, oropharyngeal temperature, esophageal stethoscope, arm-cuff blood pressure and urinary output from an indwelling Foley catheter. A total of 10 L of crystalloid was infused over a 2 1/2-hour period while hypotension was induced by intravenous nitroprusside and enflurane anesthesia. Hematocrit was diluted from 46% to 26% intraoperatively with an estimated surgical blood loss of 2,740 ml. The 24-hour postoperative hematocrit was 30% and recovery was uneventful. This method may be useful in any orthopedic procedure in which heavy blood loss is anticipated and the patient refuses transfusion of blood or blood products. However, the patient must be in good health and have an uncompromised cardiopulmonary system.

Adult↗
PubMed1979

Degradation resistance of some candidate composite biomaterials.

The degradation resistance of matrix, fiber and composite systems which we have been studying as candidate orthopedic materials has been examined in two appropriate environments. Both resistance to steam sterilization in an autoclave environment and resistance to a simulated physiologic solution have been studied. In the autoclave study, samples were placed in a pressure cooker at 123 degrees C for differing amounts of time and tested for retention of mechanical properties. Results indicate that most of the materials tested could be autoclaved several times, as long as autoclave times did not exceed 1 hr. Longer autoclave times result in an accelerated degradation and loss of strength of all materials except the polypropylene. Polysulfone degrades after even the shortest autoclave duration. Resistance to the simulated physiologic environment was tested by measured retention of mechanical properties after immersion times in pseudo-extracellular fluid (PECF) at 37 degrees C for as long as three years. None of the materials showed any significant changes in properties after immersion in the PECF.

Amides↗
PubMed1977

Fixation of Dwyer screws for the treatment of scoliosis. A postmortem study.

The strength of fixation of Dwyer screws in seven or eight vertebral bodies in each of six fresh osteoporotic cadavera was measured under the following conditions: with fixation with only the screw; with the staple-screw combination; with each of these modes of fixation combined with polymethylmethacrylate placed in the hole prior to insertion of the screw; and with the screw reinserted after failure and filling the hole with methacrylate. The strength of fixation of the screw-staple combination was increased almost twofold by the methacrylate, and after failure followed by reinsertion of the screw embedding it in methacrylate, strong fixation was restored.

Bone Cements↗
PubMed1976

Radiology of knee joint replacement.

As total knee replacement becomes more successful due to advances in surgery and bioengineering, a greater number of patients will be offered this procedure as a viable alternative to arthrodesis. Radiologic consultation will be sought for evaluation of proper alignment as well as postoperative complications such as loosening, instability, dislocation, limitation of range of motion, fracture, and infection. This evaluation may be accomplished by plain films and arthrography. Radiographic aspects of these features are discussed and illustrated.

Biomechanical Phenomena↗
PubMed1976

Ski pole thumb injury.

Disabling injuries can occur in the area of the MP joint of the thumb when a skier falls against the planted ski pole while holding the ski strap in the usual fashion. This is presently the most common ski injury of the upper extremity. It is important to determine if instability has resulted, because there may be disruption of the ulnar aspect of joint capsule as well as of the extensoradductor hood mechanism. If this has occurred, it is immediately to prevent the development of the chronic "gamekeeper's thumb."

Athletic Injuries↗
PubMed1976

Total hip reconstruction in chronically dislocated hips.

The pathological anatomy of chronically dislocated hips makes reconstruction for more difficult in them than in most cases. The acetabular component must be seated at the site of the original triradiate cartilage and the femur must be shortened four or more centimeters to prevent excessive limb lengthening. This means that the femoral component must be seated in the smallest, strightest portion of the intramedullary canal. A specially designed prosthesis is often needed. Twenty-two hips were operated on in this series, and all patients had relief of pain and improvement of gait. One major complication occured: a sciatic-nerve palsy due to overlengthening of the femur and improper postoperative positioning.

Acetabulum↗
PubMed1975

A single unit digital flexor tendon prosthesis.

Historically, the surgical repair of serious injuries to the flexor tendons of the hand have met with less than satisfactory clinical results. In an attempt to solve this problem, studies have been made on the design and testing of a Dacron polyester tendon prosthesis for complete replacement of the digital flexor tendon. The prosthesis attaches proximally at the anatomical musculotendon junction via collagen ingrowth into a fabric structure and in similar manner distally via bone ingrowth at the anatomical insertion site. These fabrics are continuous with the tendon body of the prosthesis consisting of an inextensible braided cord which is silicone rubber coated to prevent tissue adherence in the glide zone of the tendon bed. An added benefit of the prosthesis is a simple means of length adjustment which can easily be carried out on the operating table. Studies have been performed in both dogs and chickens which indicate that sufficient tissue ingrowth occurs at both the distal and proximal anastomoses for retention of full load bearing capability in these animals and that postoperative adhesions are negligible, if present at all. Full prostheses have been implanted in dogs for periods of over 1 year and chickens for 2 months. The chicken is the preferred animal model as a tendency for extensive scar tissue generation was shown in the dog. Both in vivo mechanical testing and histological characterization have been made on sacrificed animals which have received the full prostheses.

Animals↗
PubMedDate not supplied

Intraoperative force measurements during correction of scoliosis.

Intraoperative forces applied to the spine were measured during the routine application of Harrington instrumentation for correction of scoliosis. This was accomplished by instrumenting the outrigger and distractor with strain gauges. Measurements were obtained in 16 patients undergoing their first operative procedure for scoliosis. Outrigger forces employed by two surgeons unapprised of the force data were not significantly different. Outrigger forces were significantly different for adolescent and adult groups of idiopathic scoliotics. Unusually low initial outrigger forces appeared to correlate with lower final correction obtained. In addition, in several cases transient distractor forces were observed that exceeded average levels at which bone failure is postulated to occur.

Adolescent↗
PubMedDate not supplied

A prospective evaluation of untreated acute grade III acromioclavicular separations.

We prospectively studied the natural history of untreated acute grade III acromioclavicular separations. Twenty-five patients were treated nonoperatively with a sling for comfort through progressive early range of motion as tolerated. Ten additional uninjured subjects underwent strength testing to evaluate the difference between the dominant and nondominant sides so that patient data could be standardized. The patients were examined at intervals of 6, 12, 24, 36, and 52 weeks after injury, at which time they completed a subjective questionnaire and underwent isometric dynamometer testing as well as military press and bench press strength testing. One patient underwent a surgical procedure at 2 weeks after injury because of cosmetic concerns. Twenty of the 25 patients completed the 1-year evaluation and strength-testing protocol. Subjectively, 4 of the 20 patients (20%) thought that their long-term outcome was suboptimal, although for 3 of them it was not enough to warrant surgery. Objective examination and strength testing of the 20 patients revealed no limitation of shoulder motion in the injured extremity and no difference between sides in rotational shoulder muscle strength. The bench press was the only strength test that showed a significant short-term difference, with the injured extremity being an average of 17% weaker. This study documents the natural history of patients with an untreated acute grade III acromioclavicular separation and provides a reference with which to judge all other proposed methods of treatment.

Acromioclavicular Joint↗