Biomedical subjects

M D Markel

Publications and source records attributed to M D Markel.

At least 91 records · Page 5Linked to original sources

PubMed1991

Mechanical and morphometric analysis of the third carpal bone of Thoroughbreds.

The third carpal bone (C3) was collected from both forelimbs of 27 Thoroughbreds. On the basis of age, training, and history, specimens were assigned to 1 of 5 groups: yearling, untrained horses (group 1, n = 4); 2- to 3-year-old, untrained horses (group 2, n = 7); trained 2-year-old horses (group 3, n = 6); trained 3-year-old horses (group 4, n = 6); and 3-year-old, trained horses with carpal pathologic features (group 5, n = 4). A transverse section of subchondral bone 5-mm thick was cut in a precise fashion 10 mm below the proximal articular surface of all specimens. After high-detail radiography was done, indentation testing was performed on the proximal surface of the section at points 5 mm apart. The stiffness of the subchondral cancellous bone was determined from the slope of the load vs displacement curve. Topographic plots of stiffness measurements were compared with radiographs of each specimen. Point determinations were averaged to derive measures for the radial and intermediate facets, and for regions 5, 10, 15, and 20 mm from the dorsal margin of C3. Area fraction (1-p; p = porosity) was measured for the radial and intermediate facets, using an automated image analysis system. Significant (P less than 0.05) increases in stiffness and area fraction were found in the C3 from trained horses (groups 3 to 5), compared with untrained horses (groups 1 to 2). Stiffness and area fraction of the radial facet of pathologic C3 were significantly higher than the same variables measured in C3 from any other group.(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗

PubMed1991

Formation of bone in tibial defects in a canine model. Histomorphometric and biomechanical studies.

The histomorphometric, material, and structural properties of the reparative tissue and bone that formed in a two-millimeter tibial defect in dogs were determined at two, four, eight, and twelve weeks after the operation. At two weeks, the tibial defect was filled mainly with undifferentiated connective tissue. After two weeks, the relative proportion of undifferentiated connective tissue decreased and the amount of bone progressively increased throughout the twelve weeks. New bone formed primarily by intramembranous ossification, with a small degree of endochondral ossification. At twelve weeks, bone occupied 62 per cent of the defect. The calcium content of the reparative tissue increased between four and eight weeks and then, at twelve weeks, reached a plateau of 77 per cent that of normal cortical bone. Anisotropy of the new bone that formed in the defect increased from 13.8 per cent to 26 per cent, and the mean width of the trabecular bone increased 27 per cent between the eighth and twelfth weeks. Maximum torque and torsional stiffness increased between two and eight weeks and then, by twelve weeks, the values leveled off at 44 and 29 per cent of the values for intact bone. Indentation stiffness increased between the fourth and twelfth weeks; at twelve weeks, it was 22 per cent of the stiffness of normal cortical bone. Indentation stiffness increased 283 per cent between eight and twelve weeks, despite insignificant changes in calcium content, amount of new bone, non-osseous space, water content, or volume of trabecular bone during this time. This change in indentation stiffness did correlate with increases in anisotropy of the new bone between eight and twelve weeks.

Animals↗

PubMed1990

A study of fracture callus material properties: relationship to the torsional strength of bone.

This study was designed to quantitate the local material properties of fracture callus during gap healing and to relate these local properties to the torsional strength of bone in a canine model under external fixation. Bilateral tibial transverse osteotomies were performed in 32 dogs and stabilized using unilateral external skeletal fixators with a 2-mm gap. Dogs were divided into four equal groups and euthanized at either 2, 4, 8, or 12 weeks. The torsional properties of one bone of each pair were determined. In both bones of each pair, the indentation stiffness, calcium content, and histomorphometric properties of six sites of periosteal callus, six sites of endosteal callus, four sites of cortical bone, and two sites of gap tissue were determined. Each of the four types of tissue had a specific structural or material property change during the study period. The indentation stiffness of periosteal callus increased up to 8 weeks and then plateaued. Endosteal callus stiffness peaked at 8 weeks and then decreased by 12 weeks. Gap tissue stiffness increased linearly over time. Cortical bone stiffness decreased over time. Indentation stiffness was significantly associated with the calcium content of periosteal callus (R2 = 0.50, p less than 0.0001) and gap tissue (R2 = 0.66, p less than 0.0001). The local stiffnesses of gap tissue and periosteal callus were significantly associated with the maximum torque (gap, R2 = 0.50, p less than 0.0001; periosteal, R2 = 0.34, p less than 0.05) and the torsional stiffness (gap, R2 = 0.44, p less than 0.0001; periosteal, R2 = 0.65, p less than 0.0001) of the bone.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1990

Quantification of bone healing. Comparison of QCT, SPA, MRI, and DEXA in dog osteotomies.

Four noninvasive imaging modalities were used to quantitatively evaluate and compare tibial osteotomy healing in dogs. Quantitative computed tomography (QCT), magnetic resonance imaging (MRI), single-photon absorptiometry (SPA), and dual-energy x-ray absorptiometry (DEXA) were the four techniques examined. Bilateral tibial osteotomies were performed in 32 dogs divided into four groups. The osteotomies were stabilized with a 2-mm gap using unilateral external skeletal fixation. Dogs were anesthetized, imaged with the four noninvasive techniques, and killed at 2-12 weeks. Invasive techniques were used to determine: 1) the torsional properties of the bone; and 2) the local stiffness properties and calcium content within the bone. The techniques which had the strongest associations with the torsional properties of the osteotomies were QCT, SPA and DEXA. Generally, QCT and SPA had marginally stronger correlations than DEXA; but, overall, there were no differences between the techniques. MRI had the poorest associations with the torsional properties of the osteotomies. Generally, QCT had the strongest correlations with local material properties, such as indentation stiffness and calcium content. SPA had the second strongest correlations with calcium content and had the third strongest correlations with indentation stiffness behind DEXA. DEXA had the third strongest correlations for calcium content. With the exception of some of the correlations with indentation stiffness, MRI had the poorest associations with the local parameters studied.

Absorptiometry, Photon↗

PubMed1989

Prevention of large colon displacements and volvulus.

Results of these studies have demonstrated that colopexy of the left large colon to the abdominal wall is a relatively simple and quick procedure that is permanent 1 year after surgery. The technique does not appear to be associated with long-term weight loss or abdominal pain after surgery. It has been used in pregnant mares, both experimentally and clinically, without apparent complications. In addition, horses used for pleasure-riding and show hunting have returned to performance and have not had complications. Large colon resection is a useful technique, especially for animals with strangulating large intestinal lesions. The surgeon must decide whether a technique to prevent recurrence should be performed at the first surgery or whether it should be performed only in horses with recurrence of these lesions. Until a large number of large colon resections or colopexies are performed on horses either at the initial surgery or after recurrence, it is impossible to predict the true efficacy of these techniques.

Animals↗

PubMed1989

The effect of low dose heparin therapy on complication and survival rates in horses following exploratory celiotomy.

A randomised, blind prospective study was performed to evaluate effects of low dose heparin therapy on complication and survival rates in 33 horses following exploratory celiotomy. Four horses had non-strangulating lesions and seven had strangulating lesions of the small intestine, 19 had non-strangulating lesions of the large intestine, and three had duodenitis-proximal jejunitis. Eighteen required an enterotomy or intestinal resection and anastomosis. Sixteen received heparin subcutaneously (66 iu/kg every 12 h) post operatively and 17 received a saline placebo for a mean of 3.7 days. There was a significant (P < 0.01) mean decrease in PCV (29.1 per cent) in the heparin group. No significant differences in complication or survival rates were seen between groups. Long term follow-up was obtained for 10 horses in each group. There were no significant differences between groups.

Abdomen↗

PubMed1988

Colopexy of the equine large colon: comparison of two techniques.

A study was designed to evaluate 2 colopexy techniques (A and B) in 8 clinically normal horses to determine which technique would prevent recurrence of large-colon displacement and/or volvulus. For technique A, 35 cm of the lateral free band of the left ventral colon was sutured to the abdominal wall, 6 cm to the left of ventral midline. For technique B, the medial free band of the left ventral colon was sutured to the medial free band of the right ventral colon, and 8 cm of the lateral free band of the left ventral colon was sutured to the abdominal wall, 6 cm to the left of ventral midline. One horse from each group was euthanatized at 6 months, and another at 12 months after surgery. The position of the large colon, the integrity of the colopexy, and other adhesions within the abdominal cavity were evaluated. At necropsy, attempts were made to manually create displacement and volvulus of the large colon. The remaining horses in each group were anesthetized 6 months or 12 months after surgery, and the integrity of the colopexy was evaluated. After a 60-day recovery period, these horses were exercised for 2 months. Although each horse initially lost weight, the weight of all but 2 was acceptable at the conclusion of the study. Two horses that had technique-B colopexies had progressive weight loss serious enough to warrant euthanasia. Both colopexy techniques prevented manual creation of large-colon displacement and large-colon volvulus centered at the sternal and diaphragmatic flexures. Technique-A colopexy also prevented manual creation of volvulus of the large colon centered at its base.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1988

Colopexy of the large colon in four horses.

Colopexy of the left ventral colon to the abdominal wall was performed in 4 horses with recurrence of large-colon displacement or volvulus. Horses were discharged between 5 and 27 days after surgery. At follow-up evaluation (mean, 10.5 months; range, 7 to 13 months) of the horses, none had recurrence of signs of abdominal pain, and all had normal body weight. Three horses were exercised regularly; signs of abdominal pain were not observed.

Animals↗

PubMed1988

Genital neoplasms treated by en bloc resection and penile retroversion in horses: 10 cases (1977-1986).

The medical records of 10 horses with invasive neoplasms of the penis, prepuce, and/or superficial inguinal lymph nodes in which treatment involved en bloc resection and penile retroversion were reviewed. All were geldings and ranged in age from 12 to 25 years (mean, 19 years). Evaluation of biopsy specimens obtained before surgery confirmed lymphosarcoma in 1 horse and squamous cell carcinoma in 9 horses. Typical history included swelling, ulceration, and abscessation of the penis and prepuce and large superficial inguinal lymph nodes. Complications after surgery included dehiscence of the urethrostomy site (4 horses), dehiscence of the ventral skin incision (1 horse), urine scalding of 1 hind limb (1 horse), cystitis (1 horse), severe hemorrhage (1 horse), and diarrhea (1 horse). One horse was euthanatized during hospitalization, because of severe dehydration secondary to diarrhea. At necropsy, firm nodules were scattered in the pulmonary parenchyma, myocardium, thyroid gland, parathyroid glands, cranial mediastinum, kidneys, and hilar lymph nodes. Microscopic examination of the nodules revealed undifferentiated carcinoma. Nine horses were discharged from the hospital between 1 and 5 weeks after surgery. The mean follow-up interval was 27 months (range, 6 to 96 months). Eight horses had no evidence of recurrence. One horse had recurrence of neoplasm at 6 months and was euthanatized 12 months later.

Animals↗

PubMed1988

Prevention and management of peritonitis in horses.

Peritonitis and adhesions in the horse are best managed through prevention. Perioperative antimicrobial therapy, nonsteroidal anti-inflammatory therapy, experienced personnel, and good surgical techniques should minimize complications after surgery. Despite preventative measures, some horses still develop peritonitis after surgery. Immediate, intensive treatment is necessary to enhance their chances for survival.

Animals↗

PubMed1988

In vitro comparison of three fixation methods for humeral fracture repair in adult horses.

The stiffness, load to failure, and bending moments of adult intact equine humeri and humeri repaired with 3 fixation techniques were determined in vitro. Bones were tested in axial compression (30 pairs), mediolateral 3-point bending (15 pairs), and caudocranial 3-point bending (15 pairs). An oblique osteotomy of 1 humerus of each pair was performed to simulate the long spiral oblique fractures that occur clinically in horses. Bones were repaired in 3 ways: group 1--nylon band cerclage fixation (20 bones); group 2--multiple intramedullary pinning (20 bones); and group 3--nylon band cerclage fixation and multiple intramedullary pinning (20 bones). Intact bones were significantly (P less than 0.05) stronger than repaired bones in each testing mode. Bones repaired with bands only were significantly less stiff in bending than were bones repaired with pins only or with pins and bands. In compression, only specimens repaired with pins and bands were significantly stiffer than were bones repaired with bands only. Bones repaired with bands only required significantly less load to failure in compression and in caudocranial bending than did bones repaired with pins only or with pins and bands. Bones repaired with pins only deformed through the full displacement of the actuator (5 cm), and pins deformed plastically. Bones repaired with pins and bands were stiffer and had higher bending moments than did bones repaired with pins only, but the differences were not significant.

Animals↗

PubMed1987

Nuclear scintigraphic evaluation of third metacarpal and metatarsal bone fractures in three horses.

Nuclear scintigraphy was used to evaluate healing of third metacarpal bone (MC III) fractures in 2 horses (horses 1 and 2) and a third metatarsal bone fracture in 1 horse (horse 3) after stabilization of each fracture with 2 broad dynamic compression plates. In horse 1, the fracture had uniform uptake of 99mTc methylene diphosphonate on days 1, 15, and 30 after surgery. The fracture healed, and the horse was discharged from the clinic on day 52. In horse 2, a 6-cm photopenic region (ie, area of low radioactivity) was seen over the diaphysis of MC III on day 3. The region persisted and became more distinct by day 32. The diaphysis of MC III sequestered, and horse 2 was euthanatized on day 44. In horse 3, vascularity was seen bridging the fracture on day 5, with a 3-cm photopenic region over the dorsal diaphysis of the third metatarsal bone. By days 18 and 32, uptake of 99mTc methylene diphosphonate in the region had increased, indicating vascularization of the site. the fracture healed, and horse 3 was discharged from the clinic on day 47. Our findings indicated that serial nuclear scintigraphy can be used to evaluate fracture vascularization after surgery in horses.

Animals↗

PubMed1987

Surgical reconstruction of chronic coronary band avulsions in three horses.

Three adult horses were admitted with chronic coronary band avulsions of 2-, 3-, and 46-month durations, respectively. The hoof had a typical appearance in all 3 horses, with a spur of coronary band and associated horn growing at right angles to the hoof wall. Each horse was anesthetized, and the coronary band was reconstructed. Follow-up evaluation of the 3 horses (12, 15, and 23 months after surgery, respectively), revealed healing of all 3 avulsed coronary bands. Mild roughening of the hoof wall distal to the previous avulsion site was observed.

Animals↗

PubMed1987

Strangulated umbilical hernias in horses: 13 cases (1974-1985).

The medical records of 13 horses with strangulated umbilical hernias were reviewed. Typical history included increased swelling, warmth, and firmness of the hernial sac. Enterocutaneous fistulas had developed in 2 horses. Four horses had signs of abdominal pain. Surgery was performed on all horses, and the hernia was reduced by an open reduction technique. Incarcerated tissue included omentum (1 horse), jejunum (5), ileum (4), cecum (1), and ventral colon (2). All horses survived and were discharged from the hospital. Follow-up information on 9 horses (5 to 52 months after discharge) revealed no complications in 6 horses. Of the remaining 3 horses, one horse was euthanatized 5 months after discharge because of laminitis. One horse had persistent drainage from the skin incision requiring removal of nonabsorbable suture material 8 months after discharge. One foal required a second surgery because of signs of abdominal pain 17 days after the initial surgery. The foal was euthanatized during surgery because of severe peritonitis secondary to anastomotic leakage.

Animals↗

PubMed1986

Cellulitis associated with coagulase-positive staphylococci in racehorses: nine cases (1975-1984).

Nine Thoroughbred racehorses were admitted with cellulitis (of one or more limbs) associated with coagulase-positive staphylococci. The right hindlimb was affected in 4 horses, the right forelimb in 2, the left hindlimb in 1, and both hindlimbs in 2. Typical abnormalities included high values for rectal temperature (9 horses) and heart rate (5 horses), hyperfibrinogenemia (7 horses), leukocytosis (7 horses), and neutrophilia (6 horses). The staphylococcal isolants were speciated in 3 horses and classified as Staphylococcus aureus. Complications included skin loss (5 horses), laminitis of the affected limb (2 horses), laminitis of the contralateral limb (4 horses), osteomyelitis and sequestrum formation (2 horses), and bacteremia (1 horse). Five horses were euthanatized because of the severity of the complications, ie, laminitis in 4 horses and severe skin loss in 1 horse. The remaining 4 horses were discharged from the clinic. At follow-up evaluation (mean, 16.7 months), the swelling in 3 of the horses had completely resolved. One horse returned to racing; of 2 used for pleasure riding, one was mildly lame. The remaining horse was not lame, but was used for breeding because of persistent swelling of the affected limb.

Animals↗

PubMed1986

Multiple myeloma in a horse.

Multiple myeloma was diagnosed in a 22-year-old Arabian mare with a history of chronic weight loss. Quantitative immunoglobulin analysis revealed monoclonal gammopathy (IgG(T), 9,800 mg/dl). Due to progressive weight loss, the horse was euthanatized. Microscopy of tissues revealed plasma cell infiltrates in bone marrow, spleen, pituitary gland, adrenal cortex, muscle of the tongue, and bronchial, renal, and mesenteric lymph nodes.

Animals↗

PubMed1986

Vertebral body osteomyelitis in the horse.

Over a 4-year period, vertebral body abscess was diagnosed in 5 young cattle. The laboratory findings in most of these cases did not suggest a diagnosis of vertebral body abscess. The most important basis for diagnosis of this condition was a thorough neurologic examination. In 4 cases, necropsy revealed abscesses in the lungs or thoracic cavity as well, suggesting that a history of pneumonia preceding paresis may favor the diagnosis of vertebral body abscess.

Animals↗

PubMed1985

Complications associated with left dorsal displacement of the large colon in the horse.

Four horses operated on for left dorsal displacement of the large colon (LDDLC) had major intraoperative or postoperative complications. One horse was euthanatized during surgery because of extensive necrosis of the large colon. Three horses that were discharged after surgical correction of LDDLC were readmitted with signs of abdominal pain between 5 weeks and 13 months after surgery. Two horses had recurrence of LDDLC, and the third horse had an omental adhesion attached to and obstructing the pelvic flexure. The displacements were corrected, the adhesion was broken down, and the horses were discharged. One horse was readmitted a third time 16 months after the second surgery and required a third surgical correction of LDDLC.

Animals↗