Biomedical subjects

M D Markel

Publications and source records attributed to M D Markel.

At least 37 records · Page 2Linked to original sources

PubMed2000

Colic surgery in 206 juvenile thoroughbreds: survival and racing results.

The purpose of our study was to determine the types of lesions that cause colic in juvenile Thoroughbreds, factors associated with these lesions and the subsequent survival and athletic performance of the juveniles. The age of juvenile Thoroughbreds requiring surgical exploration for abdominal pain has an influence on the type of lesion causing colic. The short-term survival rate (discharge from the hospital) after colic surgery for foals was 85% and was strongly influenced by the lesion causing colic. Thirteen percent of juveniles recovered from the first surgery experienced another severe colic episode requiring additional surgery or euthanasia. Eight percent of foals recovered from the first celiotomy developed adhesions. Adhesion formation was related to the initial lesion causing colic and the foals' age at the first surgery. Foals being suckled (15 days to 6 months) were at greatest risk for adhesions and more frequently required multiple surgeries. Juvenile Thoroughbreds that had a celiotomy were significantly less able to race (63%) than their unaffected siblings (82%), and age at the initial surgery was associated with the percentage of horses that raced. However, affected foals able to race won as much money, raced as often, and made as many starts as their siblings. Colic and surgical treatment have a negative impact on athletic performance, but the majority of foals discharged from the hospital after colic surgery will perform athletically as adults.

Animals↗

PubMed2000

Histomorphometric analysis of the proximal portion of the femur in dogs with osteoarthritis.

OBJECTIVE: To describe cancellous architecture of the proximal portion of the femur in dogs with osteoarthritis. ANIMALS: 30 dogs with coxofemoral osteoarthritis. PROCEDURE: All dogs had femoral head and neck excision or total hip arthroplasty. Histomorphometry software was used to analyze computer images of 100-microm-thick coronal and transverse plane sections of the head and neck of the femur. Histologic preparations of coronal and transverse sections of articular cartilage were graded. RESULTS: Bone volume/total volume, trabecular thickness, trabecular number, and bone surface/total volume were significantly higher in the femoral head than femoral neck. Trabecular alignment (anisotropy) and separation were significantly higher in the femoral neck than femoral head. Anisotropy was significantly increased in the medial portion of the femoral head in the coronal plane and in the cranial portion of the femoral neck in the transverse plane, compared with healthy dogs. The medial half of femoral head cartilage that overlies the proximomedial cancellous bone region had significantly more degraded cartilage than the lateral half. Histologic grades for cranial and caudal halves of femoral head articular cartilage were similar. CONCLUSIONS AND CLINICAL RELEVANCE: Most findings were similar to those in healthy dogs. Greater trabecular alignment in the proximomedial region of the femoral head and craniolateral region of the femoral neck in dogs with osteoarthritis suggests an altered transfer of load through the coxofemoral joint. Greater cartilage degradation on the medial half of the femoral head supports an association between increased trabecular alignment and cartilage degradation.

Animals↗

PubMed2000

Histomorphometric analysis of the proximal portion of the femur in healthy dogs.

OBJECTIVE: To describe the cancellous bone architecture of the head and neck of the femur in healthy dogs by use of automated histomorphometry techniques in conjunction with histologic grading of articular cartilage. ANIMALS: 30 mature male dogs with healthy coxo-femoral joints PROCEDURE: Dogs were 1.5 to 4 years old and weighed 27 to 37 kg. Computer images of fine-detail radiographs of 100-microm-thick coronal and transverse plane sections of the head and neck of the femur (14 dogs) were analyzed by use of histomorphometry software. Statistical comparisons among histomorphometric indices of 4 regions were performed. Histologic preparations of coronal and transverse plane sections of femoral head articular cartilage (16 dogs) were graded. Median grades for lateral, medial, cranial, and caudal halves of the femoral head articular cartilage were determined. RESULTS: Bone volume/total volume, trabecular thickness and number, and bone surface/total volume were significantly higher in the femoral head than in the femoral neck. Anisotropy (trabecular alignment) and trabecular separation were significantly higher in the femoral neck than in the femoral head. Anisotropy was significantly higher in the caudal half of the femoral neck than in the cranial half. Cartilage had histologic grades indicating health without significant differences among lateral, medial, cranial, and caudal halves of femoral head cartilage. CONCLUSIONS AND CLINICAL RELEVANCE: A predictable cancellous architecture in the head and neck of the femur is associated with healthy cartilage.

Animals↗

PubMed1999

Alterations in bone remodeling in the femur after medullary reaming and cemented hip arthroplasty in dogs.

OBJECTIVE: To determine whether medullary reaming alone, or followed by cemented hemiarthroplasty, influenced porosity, vascularity, and new bone formation in the proximal portion of the femur in dogs. ANIMALS: 12 adult mixed-breed dogs. PROCEDURE: Unilateral femoral head and neck excisions were performed, followed by femoral medullary reaming in 6 dogs and femoral medullary reaming and cemented hemiarthroplasty in 6 dogs; the contralateral femur was used as a control. All dogs were euthanatized 28 days after surgery, and femurs were harvested. Vascularity, porosity, and new bone formation were quantified for all femurs of dogs from both groups at 3 proximal-to-distal levels, 3 regions (periosteal, midcortical, and endosteal), and 4 quadrants (cranial, caudal, medial, and lateral) of the femur. RESULTS: Medullary reamed and cemented hemiarthroplasty femurs had significant increases in vascularity and porosity at all levels and in new bone formation at levels 2 and 3. Porosity was increased significantly in the periosteal region of the cemented hemiarthroplasty (9.7+/-0.7%), compared with control (2.3+/-0.2%) and medullary reamed (8.4+/-0.7%) femurs. Porosity was increased in the caudal and medial quadrants in the medullary reamed and cemented hemiarthroplasty femurs; vascularity results were similar. CONCLUSION: Increased porosity, vascularity, and new bone formation in reamed and cemented hemiarthroplasty-treated femurs supports the theory that surgical trauma associated with medullary reaming is an important factor in early cortical bone loss after hip arthroplasty. CLINICAL RELEVANCE: Femoral remodeling associated with reaming and broaching is appreciable but may be only a temporary response, whereas other factors may be responsible for chronic cortical bone loss.

Analgesics, Opioid↗

PubMed1998

Urinary obstruction in a hermaphroditic llama.

A 24-hour-old cria was admitted for evaluation of stranguria evident shortly after birth. On physical examination, the prepuce appeared to be normally formed and small drops of fluid dripped from it as the cria strained to urinate. Testes could not be palpated. Ultrasonographic examination revealed that the bladder was distended. The only abnormality detected on serum biochemical analysis was high creatinine concentration. Tube cystostomy was performed, and the cria was treated with saline (0.9% NaCl) solution administered intravenously and antibiotics. Four days after admission, the cria could not urinate normally when the cystostomy tube was occluded. Five days after admission, normograde cystography and retrograde urethrography were performed. Radiographic findings indicated the cria was an intersex llama with urethral duplication. The llama was euthanatized at the owner's request. Necropsy revealed bilateral ovotestes with a phenotypically female reproductive tract and urethral duplication. Urethral duplication should be considered as a cause of stranguria in male neonatal crias, and hermaphroditism should be included as a cause of urethropathies in llamas.

Animals↗

PubMed1998

In vitro and in vivo study on the effect of autogenous cancellous bone and intramedullary polymethylmethacrylate on allograft construct strength.

An in vitro study was performed to compare the effects of augmenting interlocking nails of one of two diameters (5 or 6 mm) with intramedullary polymethylmethacrylate. Subsequently, an in vivo study was performed to compare the effects of augmenting the interlocking nail with five combinations of intramedullary polymethylmethacrylate and autogenous cancellous bone applied to the periosteal surface or within the medullary canal. Dogs were killed 6 months after the procedure for biomechanical evaluation of the femora in axial compression, mediolateral and craniocaudal bending, and torsion. Results from the in vitro study at the proximal osteotomy indicated the 6-mm interlocking nail with intramedullary polymethylmethacrylate had greater stiffness than the 5-mm interlocking nail without it (p < 0.05). At the distal osteotomy, regardless of the diameter of the interlocking nail, the addition of intramedullary polymethylmethacrylate increased stiffness (p < 0.05). Results from the in vivo study indicated greater global construct stiffness with an interlocking nail alone, an interlocking nail augmented with intramedullary polymethylmethacrylate and cancellous bone at the periosteal surface, and an interlocking nail augmented with cancellous bone within the medullary canal and at the periosteal surface (p < 0.05). At the osteotomy level, the interlocking nail augmented with intramedullary polymethylmethacrylate and cancellous bone at the periosteal surface had greater stiffness than did an interlocking nail alone or an interlocking nail augmented with either intramedullary polymethylmethacrylate, cancellous bone within the medullary canal, or cancellous bone at the periosteal surface (p < 0.05) but produced the same results as an interlocking nail augmented with cancellous bone within the medullary canal and at the periosteal surface. The results suggest that augmenting interlocking nail fixation with intramedullary polymethylmethacrylate by itself offers no advantage but that a combination of intramedullary polymethylmethacrylate and cancellous bone at the periosteal surface improves structural properties at 6 months.

Animals↗

PubMed1998

Effect of intramedullary polymethylmethacrylate and autogenous cancellous bone on healing of frozen segmental allografts.

This study was designed to compare bone mineral density, periosteal callus production, new bone formation, bone porosity, histologic appearance, and union of mid-diaphyseal segmental allografts of the femur stabilized with an interlocking nail technique in a canine model 6 months after the procedure. An in vivo study was performed to compare the effects of augmenting interlocking nail fixation with an interlocking nail alone, intramedullary polymethylmethacrylate, intramedullary polymethylmethacrylate and autogenous cancellous bone applied to the periosteal surface of the host-allograft junction, autogenous cancellous bone applied to the endosteal surface of the allograft, autogenous cancellous bone applied to the periosteal surface of the host-allograft junction, and autogenous cancellous bone applied to the periosteal surface of the host-allograft junction and to the endosteal surface of the allograft. There were no differences among treatments for bone mineral density at any time interval. Callus area 4 weeks after the procedure was greater along the lateral and cranial surfaces for treatments with periosteal cancellous bone (p < 0.05). New bone within the allograft segment did not differ among treatments and was reduced compared with the host-allograft junctions (p < 0.05). The amount and quality of bone tissue at the host-allograft junctions were greatest with treatments of intramedullary polymethylmethacrylate and autogenous cancellous bone applied to the periosteal surface of the host-allograft junction and of autogenous cancellous bone applied to the periosteal surface of the host-allograft junction and to the endosteal surface of the allograft (p < 0.05). The rate of bone union was lower, and there was a greater gap (non-bone tissue) remaining between host and allograft bone with treatment involving just intramedullary polymethylmethacrylate than with other treatments (p < 0.05). The results suggest that augmenting interlocking nail fixation with intramedullary polymethylmethacrylate by itself offers no advantage but that a combination of intramedullary polymethylmethacrylate and cancellous bone at the periosteal surface or of cancellous bone within the medullary canal and at the periosteal surface improves the quality of healing at 6 months.

Animals↗

PubMed1998

In vitro effects of holmium. YAG laser on caprine stifle retinacular restraints.

This study was designed to evaluate the efficacy of the Holmium:YAG laser for performing lateral release and medial joint capsular tightening intracapsularly and to compare the efficacy of the laser versus a scalpel blade for performing a lateral release by performing arthroscopic surgery on 29 caprine patellofemoral joints. Specimens were divided into six treatment groups and treatments consisted of lateral release alone, medial capsular tightening alone, or both treatments, and the effect of each treatment on patellar tracking was evaluated using video analysis of optical markers. Each treatment caused significantly different magnitudes of medial patellar displacement throughout a 75 degrees range of motion: medial tightening followed by lateral release (1.5 +/- 0.10 mm, mean +/- standard error of the mean); lateral release followed by medial tightening (1.1 +/- 0.11 mm); medial tightening alone (0.73 +/- 0.10 mm); lateral release alone (0.36 +/- 0.09 mm); and sham (-0.15 +/- 0.05 mm). There were no significant differences between performing the lateral release using the laser (1.5 +/- 0.10 mm) versus a scalpel (1.4 +/- 0.11 mm). This study shows that lateral release can be performed as effectively with the laser as with a scalpel and that the laser is an effective tool for performing lateral release and medial joint capsular tightening procedures intracapsularly in this caprine model.

Analysis of Variance↗

PubMed1997

Clinical and radiographic findings, treatment, and outcome in cattle with osteochondrosis: 29 cases (1986-1996).

OBJECTIVE: To summarize the radiographic and clinical findings, treatment, and outcome in cattle with osteochondrosis diagnosed radiographically. DESIGN: Retrospective case series. SAMPLE POPULATION: 29 cattle with radiographic evidence of osteochondrosis. PROCEDURES: Medical records were reviewed, and owners or referring veterinarians were contacted for outcome assessment. Data were analyzed for potential interactions between osteochondrosis classification (osteochondritis dessicans vs subchondral cyst-like lesions), clinical and radiographic findings, treatment, and outcome, using Fisher's exact test and descriptive statistics. RESULTS: Osteochondrosis was associated with young, male, purebred cattle, clinical evidence of lameness, and radiographic evidence of concurrent degenerative joint disease. Osteochondritis dissecans and subchondral cyst-like lesions had similar clinical findings and outcomes but varied significantly in their radiographic distribution among joints. Osteochondrosis often manifests clinically as a unilateral condition, but bilateral lesions were often found (88%) when limbs were radiographically examined. Cattle managed conservatively tended to be culled (within 6 months of diagnosis because of lameness) more often than those managed surgically, despite the lack of treatment bias. CLINICAL IMPLICATIONS: Osteochondrosis in cattle is often associated with lameness or degenerative joint disease. Conservative management does not result in a favorable clinical prognosis for long-term, lameness-free survival, and more studies need to be completed to evaluate the efficacy of surgical treatment of osteochondrosis in cattle.

Animals↗

PubMed1997

Prepubic urethrostomy for relief of urethral obstruction in a sheep and a goat.

Urethral obstruction is common in castrated male small ruminants. Perineal urethrostomy is the recommended treatment in animals not intended for breeding; however, stricture formation is a common complication, and few surgical options are available once a stricture has formed. Prepubic urethrostomy has been used successfully in dogs and cats to treat urethral trauma or stricture formation, and in this report, use of prepubic urethrostomy in 2 small ruminants to treat urethral strictures that developed alter perineal urethrostomy is described. Both animals maintained urinary continence and were able to void urine normally. Complications after prepubic urethrostomy included recurrent cystitis in sheep and urethral stricture in goats. Prepubic urethrostomy may be considered in as an alternative for treatment of urethral disorders in small ruminants.

Animals↗

PubMed1997

Effect of nonablative laser energy on the joint capsule: an in vivo rabbit study using a holmium:YAG laser.

BACKGROUND AND OBJECTIVE: The nonablative application of holmium:yttrium-aluminum-garnet (Ho:YAG) laser energy to the joint capsule of patients with glenohumeral instability has been found to shrink capsular tissue and to help stabilize the joint. The purpose of this study was to evaluate the effect of nonablative laser energy on the short-term histological properties of joint capsular tissue in an in vivo rabbit model. STUDY DESIGN/MATERIALS AND METHODS: Eighteen mature New Zealand white rabbits were used in this study. One randomly selected stifle was treated with laser energy, and the contralateral stifle was sham-operated. Animals were euthanized immediately after surgery (day 0), at 7 days postsurgery and 30 days postsurgery. Specimens were processed for histology and transmission electron microscopy. RESULTS: Laser-treated samples at day 0 showed diffuse hyalinization of collagen with nuclear karyorrhexis of fibroblasts. Laser-treated tissue at 7 days postsurgery revealed fibroblast proliferation around and into acellular hyalinized regions of collagen. At 30 days postlaser treatment, areas of fused collagen were greatly reduced as large reactive fibroblasts migrated and secreted matrix. CONCLUSION: This study illustrates the short-term in vivo tissue response to nonablative laser treatment, where acellular hyalinized regions of collagen are infiltrated by fibroblasts that have used the treated collagen as the framework for migration and secretion of new collagen matrix in order for tissue repair to proceed.

Animals↗

PubMed1997

Stability of proximal femoral grafts in canine hip arthroplasty.

In a canine model, the fixation stability of a prosthesis and proximal bone graft composite were measured relative to the distal femur. One group had the prosthesis graft composite cemented into the distal femur. The second group had the prosthesis graft composite press fit into the distal femur for biologic ingrowth. Displacements of the proximal femoral grafts relative to the host bone in each group were measured after ex vivo (acute with graft) implantation and 4 months after implantation. A third group with no osteotomy (acute intact) simulated perfect graft to host bone union. Relative displacements representing 6 degrees freedom (translation and rotation) were calculated from the displacement values measured by 9 eddy current transducers. Measurements of displacement were used to test the hypothesis that distal press fit fixation equals distal cement fixation at 4 months after implantation. In all cases the measured translations and rotations of the graft to implant construct were small and of a magnitude that should encourage bone ingrowth (< 0.05 mm and < 0.1 degree, respectively). The stability of the press fit group at 4 months was not significantly different from the cemented group in axial and transverse displacement during axial and transverse loading, respectively. There was no difference in stabilities at 4 months between distal press fit and cemented fixation in hip replacements requiring a proximal femoral graft.

Animals↗

PubMed1996

Treatment of inflammatory arthritis by synovial ablation: a comparison of the holmium: YAG laser, electrocautery, and mechanical ablation in a rabbit model.

BACKGROUND AND OBJECTIVE: Although the majority of patients with immune-mediated inflammatory arthritis are managed conservatively, some patients may require synovectomy if they have persistent pain secondary to chronic unresponsive swelling of a joint. In this study, three methods of synovial ablation using laser energy, electrocautery, and mechanical debridement were compared in an in vivo chronic synovitis rabbit model. STUDY DESIGN/MATERIALS, AND METHODS: In the first phase of this study, the optimal laser energy/pulse frequency combination for synovial ablation in this model was determined. In the study's second phase, 48 mature rabbits were then divided into four equal groups: laser synovectomy, electrocautery synovectomy, mechanical synovectomy, and control. Chronic synovitis was induced in both stifles of all treatment groups and in the right stifle of the control rabbits. Synovectomy was performed on one stifle of each rabbit; the contralateral stifle served as a sham-operated control. Six rabbits per group were euthanized 2 weeks and 3 months after surgery, respectively. RESULTS: There were no differences among groups in synovial fluid parameters, except at 2 weeks, when the electrocautery group had significantly more white blood cells than the laser and mechanical debridement groups. Histologic examination revealed that mechanical debridement resulted in significantly more synovial hemorrhage, capillary dilatation, plasma cell infiltration, lymphocyte infiltration, joint capsular defects, and poorer synovial ablation than ablation achieved with either laser energy or electrocautery. CONCLUSION: Laser energy and electrocautery achieved similar results when used for ablative purposes, although electrocautery did not achieve the same degree of synovial ablation as laser energy.

Analysis of Variance↗

PubMed1996

Fixation of femoral allograft/prosthesis composites after 25%, 50% and 75% resection.

The relative linear and angular displacements of proximal femoral reconstructions were compared within six different replacement techniques during ex vivo axial compression, mediolateral bending, and axial torsion in dogs. Each femur was osteotomized at 25%, 50%, or 75% of its length and the proximal portion subsequently replaced using one of six techniques. The reconstruction techniques included various combinations of proximal and distal fixation methods (graft fixation/distal fixation): (1) an allograft/prosthesis composite (APC) press-fit proximally and cemented distally (press-fit/cement); (2) APC cemented proximally and distally (cement/cement); (3) APC cemented proximally and the host bone/graft interface double plated (cement/plates); (4) APC cemented proximally and secured distally with bicortical screws (cement/screws); (5) APC secured proximally and distally with bicortical screws (screws/screws); (6) Segmental proximal femoral replacement cemented into the distal femur without an allograft (no graft/cement). For axial compression and mediolateral bending, the combined resection lengths revealed no differences in linear and angular displacements, respectively, between reconstruction methods. During axial torsion, the cement/cement technique allowed larger angular displacements than all but the press-fit/cement technique which had larger displacements than the cement/screws, screws/screws, and no graft/cement groups (p < 0.0001). Overall, the measured implant stability was solid and consistent as evidenced by small amounts of relative displacement and small error values.

Animals↗

PubMed1996

Fracture biology, biomechanics, and internal fixation.

The success of orthopedic surgery in ruminants is directly related to the surgeon's knowledge and understanding of bone physiology and mechanics. The relationship of the macro and micro structure and function of bone as it relates to fracture physiology and repair is discussed. A basic review of the biomechanical principles of bone, bone fracture, and fracture repair are presented. The clinical and biomechanical principles of internal fixation are described for fracture repair in ruminants.

Animals↗

PubMed1996

Fractures of the femur.

Fractures of the femur in cattle are second in frequency only to fractures to the metacarpal and metatarsal bones. Common clinical presentations and the diagnosis of femur fractures are described. Treatment options, prognosis, postoperative complications are discussed for conservative therapy and for various forms of external and internal fixation.

Animals↗

PubMed1996

The effect of nonablative laser energy on the ultrastructure of joint capsular collagen.

This study was designed to evaluate the effect of laser energy at nonablative levels on the ultrastructure of joint capsular collagen. The femoropatellar joint capsules of six mature New Zealand white rabbits were harvested immediately after death. Specimens were divided into three treatment groups (5, 10, and 15 watts) and one control group. Laser energy was applied using a holmium: YAG laser. Transmission electron microscopy showed significant ultrastructural alterations in collagenous architecture for all laser treatment groups, with increased fibril cross-sectional diameter for each of the treated groups. The fibrils began to lose their distinct edges and their periodical cross-striations at subsequently higher energy densities. A morphometric analysis showed that each subsequently higher laser energy caused a significant increase in collagen fibril diameter. Ultrastructural alteration of collagen fibril architecture caused by the thermal effect of laser energy is probably the dominant mechanism of laser-induced tissue shrinkage.

Animals↗

PubMed1996

[Changes in articular capsular tissue using holmium:YAG laser at non-ablative energy densities. Potential application in non-ablative stabilization procedures].

Multidirectional and unidirectional glenohumeral instability constitute an important clinical problem, particularly in the athlete. Numerous methods have been described for treatment of glenohumeral instability, including closed management, open and arthroscopic procedures, but none have achieved universal success. The purpose of this study was to evaluate the effect of laser energy at non-ablative energy densities on the mechanical properties of joint capsular tissues in a rabbit model. Femoropatellar joint capsular tissues from 12 mature New Zealand white rabbits were harvested and divided using a randomized block design into three treatment groups with laser at 5 W, 10 W and 15 W, and one control group. Mechanical testing was performed before and after application of laser energy. The application of laser energy resulted in 9%, 26% and 38% reduction in capsular tissue length for the 5-W, 10-W and 15-W group, respectively. Laser energy caused a significant decrease in tensile stiffness in the 10-W and 15-W groups only (P < 0.05). Laser energy did not change the relaxation properties of capsular tissue at any energy density. The loads required to return specimens to their original length were significantly lower for the 5-W group than for the 10-W and 15-W groups. This study demonstrates that significant capsular shrinkage can be achieved with the application of non-ablative Ho:YAG laser energy without detriment to the relaxation properties of the tissue, although at higher energy densities, laser energy did lessen capsular stiffness properties.

Animals↗