Michael A. Collier

Effects of holmium: YAG laser on equine articular cartilage and subchondral bone adjacent to traumatic lesions: A histopathological assessment

This study was performed to investigate the effects of holmium:yttrium-aluminum-garnet (Ho:YAG) laser energy on articular cartilage and subchondral bone adjacent to traumatically created cartilage lesions in a continuous weight-bearing model. The 2.1-microns wavelength was delivered efficiently and precisely in hand-controlled contact and near-contact hard tissue arthroscopic surgery in a saline medium. Bilateral arthroscopy was performed on normal antebrachiocarpal and intercarpal joints of four adult horses. One hundred twenty traumatic lesions were created on three weight-bearing articular surfaces with a knife, curet, or motorized burr. Depths of the lesions were partial and full thickness. Configurations of the lesions were lacerations, scrapes, and craters. Left limbs were used as controls. Right limb lesions were treated with various intensities of laser energy: 0.1. 0.16, and 0.2 J. Animals were killed at intervals of 1, 3, and 8 weeks. Gross microscopic anatomy was documented, and tissue sections were subjected to blind review by a pathologist. Mankin grading for cellularity and proteoglycan content was used to qualitatively evaluate cartilage response. Cartilage adjacent to all lesions exposed to laser energy had better cellularity and proteoglycan content (p < 0.05) than did corresponding controls by Mankin grading. Mankin grades for levels of 0.16 and 0.2 J were lower (p < 0.05) than were those of controls or lesions exposed to 0.1 J. There was loss of cellularity and necrosis in subchondral bone at higher energy levels (0.16 and 0.2 J). This study examined the effects of Ho:YAG laser on articular cartilage and subchondral bone in terms of depth of damage and healing response over time in a weight-bearing model. Additional research to define dose-response curves for Ho:YAG laser treatment of cartilage and subchondral bone are indicated.

Bioabsorbable Suture Anchor (Co-polymer 85/15 D,L lactide/glycolide) Implanted in Bone: Correlation of Physical/Mechanical Properties, Magnetic Resonance Imaging, and Histological Response

A novel bioabsorbable suture anchor has been introduced for shoulder rotator cuff surgical repair made of the co-polymer 85/15 D,L lactide/glycolide. Previous clinical reports on the use of this material in anterior cruciate ligament reconstruction have described intraosseous edema at various time intervals following implantation. The purpose of this study was to analyze the implants loss of physical properties and to correlate magnetic resonance imaging (MRI) finding with gross and histological observations at various time intervals after intraosseous implantation in the experimental animal. Six drill holes were made in the tibias of 11 dogs. The spherical implant was placed in 5 of the drill holes and the sixth was preserved as a sham control. The dogs were killed at 3, 4, 6, 9, 12, and 26 weeks for gross and microscopic inspection. Correlative MRIs were taken from the 4-, 12-, and 26-week specimens. Gross inspection showed that the overlying soft tissue healed to bone in 3 weeks. The implants were surrounded by new bone by 6 weeks. The implants maintained gross physical integrity for 6 to 12 weeks. Histologically, there was minimal inflammatory response to the degrading implant. The implant site had been completely replaced by bone at 12 weeks. Correlative MRI showed edema adjacent to the implant sites, but there was no correlative inflammation or cyst formation through the time necessary for complete absorption of the implant. Correlative MRI identified and differentiated the image of the intact and degrading implant.

Use of force sensing array technology in the development of a new equine saddle pad: Static and dynamic evaluations and technical considerations

Summary Scientific approaches to the classical art of saddle-pad fitting with the horse have become available during the past few years. Force Sensing Array (FSA) technology has offered clinicians in the medical profession innovative systems for rehabilitation applications. With proven usefulness in the medical sector, the application of Force Sensing Array (FSA) technology in pressure mapping of the equine back and saddle has potential clinical and research applications in veterinary medicine. The objective in this study was to apply FSA technology in evaluation of an equine athletic saddle pad and pad liners and to document any observed/potential areas of error within the system that would affect objectivity of data collection/interpretation. All dynamic scans demonstrated a repeatable pattern of pressure distribution that is associated with gait, load distribution and horse limb placement. The in motion scans gave the best overall evaluation of effectiveness of the pad liners studied. This study did not define “normal” static or dynamic saddle-pad-horse pressure gradients or patterns. The pressure distribution pattern is the most valuable data to be gained from Force Sensing Arrays and should be the primary use of the device. Precise scientific methodology must be used in these type of studies. Potential exists for animal and operator induced error when using this technology.

Treatment of Acute Laminitis: Supportive Therapy

Over the last decade, both the farriery and veterinary professions have greatly increased their collective experience and understanding of the treatment of acute laminitis. Many horses that would have not been considered candidates for treatment 10 to 15 years ago are now saved, and some progress to successful careers as athletes. Unfortunately, the difficulties over prediction of the course of the disease persist, which continues to complicate treatment decisions. By its nature, supportive therapy is designed to make the horse more comfortable and limit further laminar injury by countering adverse biomechanical forces. Therefore, the success of treatment depends on the degree of instability between the distal phalanx and the hoof when treatment is started as well as the effectiveness of medical and supportive therapy.

An arthroscopic biopsy procedure for obtaining osteochondral samples from the equine midcarpal joint.

An in vivo biopsy technique was developed to harvest cylindrical osteochondral core samples (2 mm diameter x 2 mm depth) from the articular surfaces of radial carpal bones in adult horses for use in osteoarthritis drug kinetic studies. A 25 degree arthroscope was introduced into the midcarpal joint through the dorsolateral surface, and a custom-built motorized core drill was introduced through the dorsomedial surface to create the osteochondral core samples. A total of 24 core samples were sequentially harvested in vivo, and 16 at postmortem, from eight horses on four different occasions within a 96-h period. Cores ranged in weight, from 5.0 to 19.0 mg with a median of 13.25 mg, mostly due to the amount of subchondral bone present. No evidence of carpal bone fractures was observed associated with core sample sites at postmortem. No tissue distortion or thermal damage occurred to the osteochondral core samples. No detrimental effects on the tissue surrounding the biopsy sites was detected on microscopic examination. This technique offers a simple and effective procedure for obtaining multiple in vivo osteochondral core samples at various time intervals for cartilage or osteoarthritis research or analysis of clinical joint disease in the horse.

Effects of holmium:YAG laser on equine articular cartilage and subchondral bone adjacent to traumatic lesions

The effects of Ho:YAG laser energy on articular cartilage and subchondral bone adjacent to traumatically created cartilage lesions in a continuous weight-bearing model were investigated. The 2.1 micrometers wavelength was delivered in hand-controlled contact and near-contact hard tissue arthroscopic surgery in a saline medium. Bilateral arthroscopy was performed on normal antebrachiocarpal and intercarpal joints of four adult horses. One-hundred twenty traumatic lesions were created on three weight-bearing articular surfaces with a knife, curette, or a motorized burr. Depths of the lesions were partial and full thickness. Configurations of the lesions were lacerations, scrapes, and craters. Left limbs were used as controls. Right limb lesions were treated with various intensities of laser energy. Animals were sacrificed at intervals of 1, 3, and 8 weeks. Gross microscopic anatomy was documented, and tissue sections were subjected to blind review by a pathologist. Mankin grading for cellularity and proteoglycan content was used to qualitatively evaluate cartilage response. Cartilage adjacent to all lesions exposed to laser energy had better cellularity and proteoglycan content than corresponding controls by Mankin grading.

3H-PSGAG concentration in the synovial fluid of the equine antebrachiocarpal, metacarpophalangeal, coronopedal and tibiotarsal joints following a 500 MG i

Summary Eight mature horses were administered a single intramuscular injection of 500 mg polysulfated glycosaminoglycan (PSGAG) labeled with 2.044 mCi tritium. Synovial fluid samples were collected from the antebrachiocarpal (carpal), metacarpophalangeal (fetlock), tibiotarsal (hock) and coronopedal (coffin) joints prior to injection and at 2, 4, 8, 12, and 24 hours after injection. The samples were subjected to scintillation counting in decays per minute and were converted to μg PSGAG per ml. The levels achieved in the synovial fluid of the various joints were compared to levels of PSGAG described as adequate to inhibit enzymes which degrade articular cartilage matrix components and hyaluronic acid and adequate to stimulate production of new matrix components and hyaluronic acid in diseased joints. Mean synovial fluid 3 H-PSGAG levels indicated that peak concentrations of 3 H-PSGAG were achieved 2 hours post injection in all joints and that these concentrations were within the therapeutic range for PSGAG. The peak concentrations were not significantly different among the joints except between the antebrachiocarpal and the metacarpophalangeal joints. The areas under the concentration-time curves (AUC) for each joint were computed by the trapezoidal method from hour 0 through hour 24 and by empirical exponential decay beyond hour 24. These values were subjected to an analysis of variance (ANOVA). The overall multivariate test of AUC among all joints was not significant. The data from this study indicate that a single intramuscular 500 mg injection of PSGAG provided therapeutic levels of the drug in the equine antebrachiocarpal, metacarpophalangeal, tibiotarsal, and coronopedal joints within 2 hours of injection. While there were differences in levels between joints at certain time points, the AUC values suggest similar distribution of the drug in all joints tested.

Reparative and degenerative changes in surgically induced articular cartilage defects in the horse during the early post-operative period

Summary This study evaluated early changes in full-thickness (FT) and partial-thickness (PT) articular cartilage defects created by arthroscopic surgery. The defects were of various configurations in a model (horse) that was weight-bearing immediately after surgery. The objectives were to evaluate recellularization and to examine the effect defect configuration had on adjacent cartilage cellularity and proteoglycan content. Thirty-six PT lacerations, FT lacerations, PT scrapes, PT craters, and FT craters were created in the antebrachiocarpal and intercarpal joints of eight adult horses. The configurations were lacerations by knife blade, scrapes by a curette, and craters created by motorized burr. Horses were euthanized one, three, and eight weeks after surgery. Histologic examination was performed using hematoxylin and eosin and safranin-O staining. All FT craters showed evidence of early repair. None of the lacerations showed evidence of early repair. One PT scrape and four PT craters bad fibrous tissue within the defect. All defects had degenerative changes in adjacent cartilage. Craters and scrapes had significantly worse degenerative changes than lacerations. Patients undergoing arthroscopic surgery who will be weight-bearing immediately after surgery should have full thickness crateriform debridement if a healing response is desired. Partial thickness debridement does not show evidence of repair. Degenerative changes in adjacent cartilage occurred in all defects and they are directly proportional to the amount of trauma and instrumentation used at surgery. Full thickness (FT) cartilage defects that penetrate the zone of calcified cartilage rely on hemorrhage from subchondral bone and the resultant fibrin clot to initiate repair. The fibrin clot acts as a matrix for cellular repair that results in formation of fibrous tissue. The quality of repair (i.e. fibrous tissue, fibrocartilage, or hyaline cartilage) relies on metaplasia of fibrous tissue. This mechanism of articular cartilage healing, referred to as extrinsic repair 1,2 occurs after subchondral abrasion with motorized instrumentation; 3,4,5 however, the quality and durability of repair tissue has been questioned. 5,6,7 Partial thickness (PT) cartilage defects do not penetrate the zone of calcified cartilage and do not bleed. Healing of PT defects relies on mitotic activity of chondrocytes and increased metabolic activity adjacent to the defect to create intrinsic repair. 2 Many investigators have shown the inability of PT defects to heal. 3,8,9,10,18 It has recently been shown that PT defects may undergo further degeneration. 3 The fibrin clot and other extrinsic factors released during hemorrhage in FT defects are reported to be important in initiating repair of articular cartilage. 5 Mesenchymal cells from the subchondral bone initiate the recellularization process in FT defects. 11,12,13 If PT defects are to heal with any degree of consistency then a “modified” extrinsic repair must occur or blood clot must attach to the defect and recellularization from synovial cells within the joint must take place. Early reparative changes in articular cartilage of other species have been documented. Most studies investigating articular cartilage healing in the horse are long-term studies evaluating the quality and durability of repair tissue. The purpose of this study was to investigate early recellularization of FT and PT defects created by arthroscopic surgery in articular cartilage located within the same joint surface in a model in which the operated horse was weight-bearing immediately after surgery. The objectives were to evaluate early recellularization and to examine the effect various types of defects had on adjacent cartilage cellularity and proteoglycan content at one, three, and eight weeks after surgery.

Repairable fractures in horses

Summary If the leg is adequately immobilized one should notice an immediate improvement in the patients condition. The pulse will decrease, the heart rate will decrease, one should evidence a decrease in pain. If this sort of immobilization is carried out the animal can then be safely referred to a veterinary clinic that is capable of doing orthopedic surgery. The splint can be left on until the horse is anesthetized and positioned on the operating table and then be removed and further x-rays can be taken and a more accurate prognosis can be given to the owner.