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Biomedical subjects

D D Lewis

Publications and source records attributed to D D Lewis.

At least 19 recordsLinked to original sources
PubMed2002

Intramedullary interlocking nail stabilisation of 21 humeral fractures in 19 dogs and one cat.

OBJECTIVE: To assess the suitability of the intramedullary interlocking nail to stabilise humeral diaphyseal fractures in dogs and cats. METHOD: This multi-centre study retrospectively examined medical records, between June 1994 and May 2001, of 19 dogs and one cat, in which a total of 21 humeral fractures were stabilised with intramedullary interlocking nails. RESULTS: Animals ranged in body-weight from 4 to 97 kg. Eighteen (86%) of the fractures were comminuted. Adjunctive stabilisation was used in twelve (57%) fractures and bone grafts in nine (43%) fractures. A rapid return of function was noted in the majority of animals, with 14 (67%) having good or excellent function within four days of surgery. In two fractures the repair collapsed when a single proximal transcortical screw was placed cranial to the tricipital line of the humerus. This suggests that if a single transcortical screw is placed proximally the screw should be distal or caudal to the tricipital line in order to engage sufficient cortical bone. Eighteen (86%) of the fractures healed when stabilised with intramedullary interlocking nails. Three fractures did not heal. One was in a dog where a pathological fracture was temporarily stabilised with an intramedullary interlocking nail, one in a dog that died of an abdominal crisis three weeks after surgery and one in a dog in which fracture stabilisation collapsed due to incorrect implant selection. CONCLUSION: Intramedullary interlocking nails are well suited to the stabilisation of humeral diaphyseal fractures in dogs and cats.

Animals↗
PubMed2001

Recent advances in external skeletal fixation.

While the use of external skeletal fixation was once associated with substantial postoperative morbidity, clinical and experimental studies have led to technological advances and modifications in application techniques that have greatly improved the results obtained with this treatment modality. The past decade saw numerous advances in external skeletal fixator implants, components and instrumentation, including improvements in fixation pin design, and the development of new linear external skeletal fixation systems and economical circular external skeletal fixation systems specifically engineered for use in dogs and cats. In addition, a greater understanding of fixator biomechanics and the pathobiology of the bone-fixation pin interface have improved fixator application practices. This article reviews many of the more significant recent advances in external skeletal fixation.

Animals↗
PubMed2001

Effects of ring diameter and wire tension on the axial biomechanics of four-ring circular external skeletal fixator constructs.

OBJECTIVE: To determine relative effects of ring diameter and wire tension on axial biomechanical properties of 4-ring circular external skeletal fixator constructs. SAMPLE POPULATION: 4-ring circular external skeletal fixator constructs and artificial bone models. PROCEDURE: 4-ring constructs were assembled, using 50-, 66-, 84-, or 118-mm-diameter rings. Two 1.6-mm-diameter fixation wires were attached to opposing surfaces of each ring at intersection angles of 90 degrees and placed through a gap-fracture bone model. Three examples of each construct were loaded in axial compression at 7 N/s to a maximum load of 400 N at each of 4 wire tensions (0, 30, 60, and 90 kg). Response variables were determined from resulting load-displacement curves (construct stiffness, load at 1 mm of displacement, displacement at 400 N). RESULTS: Ring diameter and wire tension had a significant effect on all response variables and had a significant interaction for construct stiffness and displacement at 400 N. Significant differences within all response variables were seen among all 4 ring diameters and all 4 wire tensions. As ring diameter increased, effect of increasing wire tension on gap stiffness and gap displacement at 400 N decreased. Ring diameter had a greater effect than wire tension on all response variables. CONCLUSIONS AND CLINICAL RELEVANCE: Although effects of wire tension decrease as ring diameter increases, placing tension on wires in larger ring constructs is important because these constructs are inherently less stiff. The differential contribution of ring diameter, wire tension, and their interactions must be considered when using circular external skeletal fixators.

Animals↗
PubMed2001

Effect of alpha-tocopheryl acetate supplementation on vitamin E concentrations in Greyhounds before and after a race.

OBJECTIVES: To determine effect of alpha-tocopherol supplementation on serum vitamin E concentrations in Greyhounds before and after a race. ANIMALS: 8 adult racing Greyhounds. PROCEDURE: Dogs were given 2 capsules of alpha-tocopheryl acetate (total, 680 units [0.5 g]) with food that contained < or = 15 mg of vitamin E/kg each morning for 7 days. Dogs were exercised in a 30 X 30-m grass paddock for 15 minutes twice a day and raced for 500 m twice a week. Blood samples were collected before and 5 minutes after a race, before supplementation was begun, and after 7 days of supplementation. Blood and diet samples were analyzed for tocopherols and alpha-tocopheryl acetate. RESULTS: Before supplementation, serum alpha-tocopherol concentration after racing (mean +/- SD, 6.7 +/- 2.4 mg/L ) was significantly lower than before racing (12.2 +/- 3.1 mg/L). After supplementation, alpha-tocopherol concentrations were significantly higher overall, although values obtained before (26.6 +/- 5.2 mg/L) and after (29.8 +/- 3.6 mg/L) racing were not significantly different. CONCLUSIONS AND CLINICAL RELEVANCE: Supplementation with alpha-tocopheryl acetate increased serum alpha-tocopherol concentrations and eliminated the decrease in alpha-tocopherol concentration that was detected after a race, which may decrease oxidation during exercise and improve performance or recovery.

Animals↗
PubMed2001

Effects of racing and training on serum thyroid hormone concentrations in racing Greyhounds.

OBJECTIVES: To determine the effects of racing and training on serum thyroxine (T4), triiodothyronine (T3), and thyroid stimulating hormone (TSH) concentrations in Greyhounds. ANIMALS: 9 adult racing Greyhounds. PROCEDURE: Serum thyroid hormone concentrations were measured before and 5 minutes after a race in dogs trained to race 500 m twice weekly for 6 months. Resting concentrations were measured again when these dogs had been neutered and had not raced for 3 months. Postrace concentrations were adjusted relative to albumin concentration to allow for effects of hemoconcentration. Thyroid hormone concentrations were then compared with those of clinically normal dogs of non-Greyhound breeds. RESULTS: When adjusted for hemoconcentration, total T4 concentrations increased significantly after racing and TSH concentrations decreased; however, there was no evidence of a change in free T4 or total or free T3 concentrations. Resting total T4 concentrations increased significantly when dogs had been neutered and were not in training. There was no evidence that training and neutering affected resting TSH, total or free T3, or free T4 concentrations. Resting concentrations of T3, TSH, and autoantibodies against T4, T3, and thyroglobulin were similar to those found in other breeds; however, resting free and total T4 concentrations were lower than those found in other breeds. CONCLUSIONS AND CLINICAL RELEVANCE: Except for total T4, thyroid hormone concentrations in Greyhounds are affected little by sprint racing and training. Greyhounds with low resting total and free T4 concentrations may not be hypothyroid.

Animals↗
PubMed2001

Effect of increased dietary protein and decreased dietary carbohydrate on performance and body composition in racing Greyhounds.

OBJECTIVE: To determine effects of increased dietary protein and decreased dietary carbohydrate on hematologic variables, body composition, and racing performance in Greyhounds. ANIMALS: 8 adult Greyhounds. PROCEDURE: Dogs were fed a high-protein (HP; 37% metabolizable-energy [ME] protein, 33% ME fat, 30% ME carbohydrate) or moderate-protein (MP; 24% ME protein, 33% ME fat, 43% ME carbohydrate) extruded diet for 11 weeks. Dogs subsequently were fed the other diet for 11 weeks (crossover design). Dogs raced a distance of 500 m twice weekly. Rectal temperature, hematologic variables before and after racing, plasma volume, total body water, body weight, average weekly food intake, and race times were measured at the end of each diet period. RESULTS: When dogs were fed the MP diet, compared with the HP diet, values (mean +/- SD) differed significantly for race time (32.43 +/- 0.48 vs 32.61 +/- 0.50 seconds), body weight (32.8 +/- 2.5 vs 32.2 +/- 2.9 kg), Hct before (56 +/- 4 vs 54 +/- 6%) and after (67 +/- 3 vs 64 +/- 8%) racing, and glucose (131 +/- 16 vs 151 +/- 27 mg/dl) and triglyceride (128 +/- 17 vs 104 +/- 28 mg/dl) concentrations after racing. CONCLUSIONS AND CLINICAL RELEVANCE: Greyhounds were 0.18 seconds slower (equivalent to 0.08 m/s or 2.6 m) over a distance of 500 m when fed a diet with increased protein and decreased carbohydrate. Improved performance attributed to feeding meat to racing Greyhounds apparently is not attributable to increased dietary protein and decreased dietary carbohydrate.

Animal Feed↗
PubMed2001

Comparison of the radius of curvature of the ulnar trochlear notch of Rottweilers and Greyhounds.

OBJECTIVE: To compare radius of curvature along the ulnar trochlear notch of Rottweilers and Greyhounds to determine whether morphologic differences exist that may contribute to the cause and pathogenesis of fragmented coronoid process in Rottweilers. SAMPLE POPULATION: Paired elbow joints from 13 Rottweilers and 14 Greyhounds. PROCEDURE: Elbow joints were radiographically scored on the basis of severity of osteoarthritic lesions. The articular contour of each ulnar trochlear notch was digitized. The radius of curvature at defined points along the ulnar trochlear notch was compared between breeds. RESULTS: Radius of curvature of the ulnar trochlear notch was not a constant function of arc length in either breed but had a consistent characteristic appearance in both breeds. Radius of curvature was greatest at each end of the ulnar trochlear notch and had 2 peaks in the midportion of the notch in both breeds. These peaks occurred farther distally in the notch and were larger in Rottweiler ulnae than Greyhound ulnae. A significant difference in mean radius of curvature was detected between breeds at these peaks. Greyhounds had significantly greater mean radius of curvature at the end of the medial coronoid process, compared with Rottweilers. CONCLUSIONS AND CLINICAL RELEVANCE: Radius of curvature of the ulnar trochlear notch is a complex function of arc length in Rottweilers and Greyhounds. The waveform has a consistent characteristic appearance in both breeds. Although significant differences were identified between breeds, associations between these differences and cause or pathogenesis of fragmented coronoid process in Rottweilers were not apparent.

Animals↗
PubMed2000

Risk factors affecting the outcome of surgery for atlantoaxial subluxation in dogs: 46 cases (1978-1998).

OBJECTIVE: To identify risk factors for successful surgical management of dogs with atlantoaxial subluxation (AAS). DESIGN: Retrospective study. ANIMALS: 46 dogs managed surgically for AAS. PROCEDURE: Age at onset of clinical abnormalities, duration of clinical abnormalities prior to surgery, radiographic appearance of the dens, type (dorsal or ventral procedure) and number (1 or 2) of surgeries performed, grade of postoperative atlantoaxial joint reduction, and neurologic status prior to surgery (preoperative), when dogs were discharged from the hospital (postoperative), and during a follow-up evaluation (final) were obtained from the dogs' medical records. Risk factors for surgical success and degree of neurologic improvement were identified and analyzed for predictive potential. RESULTS: Age at onset of clinical abnormalities < or = 24 months was significantly associated with greater odds of a successful first surgery and final outcome and a lower postoperative neurologic grade. Duration of clinical abnormalities < or = 10 months was significantly associated with greater odds of a successful final outcome and a lower final neurologic grade. A preoperative neurologic grade of 1 or 2 was significantly associated with a lower final neurologic grade. Potential risk factors that did not affect odds of a successful outcome included type of surgery performed, grade of atlantoaxial joint reduction, radiographic appearance of the dens, or need for a second surgery. CONCLUSIONS AND CLINICAL RELEVANCE: Age at onset of clinical abnormalities, duration of clinical abnormalities prior to surgery, and preoperative neurologic status are risk factors for success of surgical management of AAS in dogs.

Animals↗
PubMed2000

Use of a circular external skeletal fixator for stifle arthrodesis in a dog.

Arthrodesis of the right stifle was performed in a 21 kg German shepherd dog that had sustained a comminuted fracture of the lateral femoral condyle as a result of a gunshot wound. The arthrodesis was stabilised with a circular external skeletal fixator. A simplified technique to facilitate creation of the osteotomies of the femur and tibia, and positioning of the stifle at the desired angle, is described. Compression of the subchondral bone surfaces of the distal femur and proximal tibia was achieved using tensioned coiled transarticular Kirschner wires. Arthrodesis of the stifle was confirmed radiographically 21 weeks following surgery, and the fixator was removed. After union of the arthrodesis and removal of the fixator, the dog was fully weightbearing when standing or walking, and intermittently weightbearing or non-weightbearing at faster gaits.

Animals↗
PubMed2000

Effect of hyperbaric oxygen treatment on incorporation of an autogenous cancellous bone graft in a nonunion diaphyseal ulnar defect in cats.

OBJECTIVE: To determine whether hyperbaric oxygen treatment (HBOT) would affect incorporation of an autogenous cancellous bone graft in diaphyseal ulnar defects in cats. ANIMALS: 12 mature cats. PROCEDURE: Bilateral nonunion diaphyseal ulnar defects were created in each cat. An autogenous cancellous bone graft was implanted in 1 ulnar defect in each cat, with the contralateral ulnar defect serving as a nongrafted specimen. Six cats were treated by use of hyperbaric oxygen at 2 atmospheres absolute for 90 minutes once daily for 14 days, and 6 cats were not treated (control group). Bone labeling was performed, using fluorochrome markers. Cats were euthanatized 5 weeks after implanting, and barium sulfate was infused to evaluate vascularization of grafts. Ulnas were evaluated by use of radiography, microangiography, histologic examination, and histomorphometric examination. RESULTS: Radiographic scores did not differ between treatment groups. Microangiographic appearance of grafted defects was similar between groups, with all having adequate vascularization. Differences were not observed between treated and nontreated groups in the overall histologic appearance of decalcified samples of tissue in grafted defects. Mean distance between fluorescent labels was significantly greater in cats given HBOT than in nontreated cats. Median percentage of bone formation in grafted defects was significantly greater in cats given HBOT. CONCLUSIONS: Hyperbaric oxygen treatment increased the distance between fluorescent labels and percentage of bone formation when incorporating autogenous cancellous bone grafts in induced nonunion diaphyseal ulnar defects in cats, but HBOT did not affect revascularization, radiographic appearance, or qualitative histologic appearance of the grafts.

Animals↗
PubMed1999

Radiographic evaluation of elbow joints before and after surgery in dogs with possible fragmented medial coronoid process.

OBJECTIVE: To determine the usefulness of 5 radiographic projections of the elbow joint for identification of fragmented coronoid process (FCP) and associated secondary degenerative changes in dogs. DESIGN: Longitudinal clinical study. ANIMALS: 19 dogs suspected of having FCP (7 dogs, 1 elbow joint; 12 dogs, both elbow joints). PROCEDURE: 5 radiographic projections were obtained before and after surgery for all elbow joints on which exploratory arthrotomy was performed because of suspected FCP. Radiographs obtained before surgery were compared with radiographs obtained after surgery and radiographs taken of the excised fragments. Each projection was evalated for its utility in definitively identifying FCP and 7 specific degenerative changes. Interevaluator agreement, use of each radiographic projection for definitively identifying a feature, and ability of the 4 evaluators to definitively identify a feature were analyzed. RESULTS: The craniolateral-caudomedial oblique (Cr15L-CdMO) projection had a significantly higher sensitivity for definitively identifying FCP, compared with the other 4 projections. Interevaluator and kappa agreement for the 5 projections did not differ significantly among the 7 degenerative changes evaluated. The radiographic projection with the highest sensitivity and specificity for detection of a particular degenerative change varied by feature. CLINICAL IMPLICATIONS: Of the 5 radiographic projections evaluated, the Cr15L-CdMO projection provided the highest sensitivity and was the best projection to use for definitively identifying FCP. The craniocaudal, Cr15L-CdMO, and mediolateral projections most reliably allowed for identification of secondary degenerative changes.

Animals↗
PubMed1999

Distraction osteogenesis.

Distraction osteogenesis and the use of circular external skeletal fixation has increased the capacity of veterinary surgeons to manage difficult orthopedic conditions including limb-length discrepancies, angular deformity, distal and severely comminuted fractures, and bone defects. This article discusses the historical developments of the Ilizarov method of distraction osteogenesis in veterinary surgery, circular external skeletal instrumentation, and the biological principles. There is also discussion of use of this method for correction of angular deformity and bone transport and complications associated with this technique.

Animals↗
PubMed1999

Estimating the non-heart-beating donor potential at a trauma center.

The number of people awaiting a life-saving transplant far outweighs the number of organs available for transplantation. Our organ procurement organization sought to identify the non-heart-beating donor potential at a large urban level 1 trauma center. We modified the death-record reviews for a 2-year period and determined that a total of 23 patients who expired were suitable for non-heart-beating donation. Therefore, it can be hypothesized that if all large urban level 1 trauma centers participated in non-heart-beating donation, more organs would be available for transplantation.

Brain Death↗
PubMed1998

Comminuted supracondylar humeral fractures repaired with a modified type I external skeletal fixator construct.

Highly comminuted supracondylar humeral fractures were stabilised in six large-breed dogs with a modified type I external fixator using a craniomedial acrylic connecting column and an intramedullary pin which was incorporated into the connecting frame. This construct provided sufficient stability to allow satisfactory bone healing in five of the six dogs, while premature removal of the intramedullary pin and external fixator resulted in subsequent refracture of the humerus in the remaining dog. Limb function at the time of final assessment was considered excellent in two dogs, good in three dogs and poor in one dog. The craniomedial acrylic connecting column simplified application of this modified type I(a) configuration to the humerus by reducing the number of clamps required; the acrylic column also facilitated contouring of the craniomedial connecting column to the brachium and was readily extended proximally to engage the intramedullary pin. In addition, the acrylic connecting column allowed placement of intramedullary pins of varying diameter.

Animals↗
PubMed1998

Non-heart-beating donors: a case study in procurement.

To help meet the increasing need for transplantable organs, especially kidneys, organ procurement organizations are recovering organs from non-heart-beating patients. This article outlines the successful recovery and transplantation of kidneys from such a donor. Consent issues and historical background are also discussed.

Accidents, Traffic↗