Direct current stimulation of bone production in the pony: observations with a diaphyseal osteotomy model

Electrically induced osteogenesis exhibits a dose response curve and can induce bone formation in the absence of trauma and in nonunions. Electrically induced osteogenesis, using direct electric current (DC) in a third metacarpal diaphyseal osteotomy model, in conjunction with internal fixation and postoperative loading, was investigated. Twelve young adult ponies of mixed sex were divided into 2 treatment groups (A and B) of 3 stimulated and 3 controls each and evaluated, using a specifically designed procedure. Stimulated ponies in both groups were given 20 microA of DC via an implanted bone growth stimulator (BGS); group A ponies were stimulated for 60 days and group B ponies for 120 days. Biocompatibility of the BGS was excellent in all ponies. Radiographically, there was more advanced healing with better vascular development in the ponies stimulated for 60 days compared with controls, but no discernible difference was seen at 120 days. Nuclear medical bone imaging revealed a peak uptake at 4 weeks in stimulated groups and the uptake decreased after 8 weeks. Radiopharmaceutical uptake in stimulated ponies was consistently below control uptake throughout the study. Mean specific gravity (SG) of specimens prepared for testing materials properties for group A and B controls were 2.044 +/- 0.119 and 1.939 +/- 0.065, respectively. The SG for group A and group B stimulated were 1.992 +/- 0.049 and 1.876 +/- 0.031, respectively. The SG of specimens obtained from metacarpi of age-matched control ponies was 2.194 +/- 0.166. The ultimate bending strengths and the flexural moduli of elasticity in 60-day control ponies and stimulated ponies were 57 +/- 8.4, 59 +/- 23.9 MN/m2 and 89 +/- 3.5, 106 +/- 6.5 MN/m2 and in 120-day control ponies and stimulated ponies were 13 +/- 1.0, 13 +/- 3.2 GN/m2 and 13 +/- 2.89, 15 +/- 0.577 GN/m2, respectively. Sixty-day samples and 120-day samples had pending strengths (SU) of 25% and 50% that of unfractured cortex, respectively. These findings indicate that 20 microA of DC stimulation on a diaphyseal osteotomy model may not stimulate sufficient bone production to affect the mechanical properties of the bone. Therefore, based on our research, clinical use of BGS in fresh fracture management cannot be recommended.     

Cervical vertebral interbody fusion in the horse: a comparative study of bovine xenografts and autografts supported by stainless steel baskets

A modified form of the Cloward technique for anterior cervical fusion in human beings was used in the application of different grafts for evaluation of their effectiveness in stabilizing equine cervical vertebrae. Results of bovine xenograft implants in 8 horses were compared with results of stainless steel baskets (SSB) packed with cancellous autogenous bone in 8 horses. Graft material was incorporated in all cases. Evidence of graft rejection was not present. Both forms of implants decreased the mobility of the intervertebral space in which they were implanted. A fibrous connective tissue union was prevalent after xenograft implantation. Osseous union was prevalent after implantation of the SSB. Reduction in range of motion was greatest at those sites with the SSB.     

Fracture healing after stabilization with intramedullary xenograft cortical bone pins: a study in pigeons

OBJECTIVE: To investigate the effectiveness of intramedullary xenograft cortical bone pins compared with stainless steel Kirschner wire for the repair of a standardized avian humeral fracture. STUDY DESIGN: Prospective randomized study. SAMPLE POPULATION: Thirty mature pigeons (Columba livia). METHODS: Birds were randomly assigned to 3 groups. Transverse mid-diaphyseal humeral fractures were created in 1 humerus in each bird. Fractures were stabilized with intramedullary ostrich or canine xenograft cortical bone pins or Kirschner wire. Radiographic, histological, and biomechanical assessments were used to compare fracture healing 6 weeks after fracture stabilization. The contralateral humerus of each bird was used as a control. RESULTS: All fractures healed regardless of intramedullary pin type. There were no statistically significant biomechanical differences among groups or within groups. Xenograft cortical bone pins induced a mononuclear inflammatory reaction that did not impair bone healing. Bones stabilized with intramedullary cortical bone pins had more periosteal callus and inflammation at the fracture site than bones stabilized with stainless steel Kirschner wires. CONCLUSIONS: Intramedullary xenograft cortical bone pins, derived from mammalian or avian sources, appear to represent an alternative for the repair of avian humeral fractures. CLINICAL RELEVANCE: Intramedullary xenograft cortical bone pins are biodegradable and may reduce the need for additional surgery to remove implants after fracture healing.     

Preliminary study on the use of a silver oxide watch battery (1.5 V) for electrical enhancement of bone healing

A totally implantable watch battery (1.5 V) having 2 cathodes connected with 2 cortical screws of an osteosynthesis plate and one anode in the adjacent tissues gave positive results when used for enhancement of healing in experimentally fractured model.     

Preliminary study on the use of a silver oxide watch battery (1.5 V) for electrical enhancement of bone healing

A totally implantable watch battery (1.5 V) having 2 cathodes connected with 2 cortical screws of an osteosynthesis plate and one anode in the adjacent tissues gave positive results when used for enhancement of healing in experimentally fractured model.     

Keratoconjunctivitis sicca associated with fracture of the stylohyoid bone in a horse

Keratoconjunctivitis sicca developed in a mare with fracture of the stylohyoid bone. Treatment was directed at preserving the health of the globe while local inflammation at the fracture site was resolved.     

Feline model for the study of frozen osteoarticular hemijoint transplantation: qualitative and quantitative assessment of bone healing

Twenty-four outbred cats underwent massive osteoarticular allograft and control autograft transplantation, using the right distal femur with its articular cartilage, capsule, and medial collateral ligament intact. The cats were monitored clinically and radiographically for 1 year. Groups of cats (4 allografts and 2 control autografts) were euthanatized at 3-, 6-, 9-, and 12-month intervals. At necropsy, the grafts were photographed and assessed for bone healing and replacement by standard radiography, quantitative 99mTc bone scans, microradiography, and histologic examination of decalcified and nondecalcified specimens. The osteosynthesis site of the allografts usually healed by 5 months, compared with the autografts that healed by 3 months. As illustrated by quantitative bone scans, creeping appositional new bone slowly invaded and replaced the allograft bone. Seemingly, the cat can be used as an acceptable and clinically comparable model for the massive osteoarticular allografts currently being used for the reconstruction of joints damaged or destroyed by neoplasm surgery in limb-sparing procedures in human beings. This model may also be used to assess the rate and method of bone healing.     

Subchondral bone cysts with fractures of the extensor processes in a horse.

Probable cause of fracture in a Paint gelding was a congenital bone defect involving the extensor process area of the right and left forelimb distal phalanges. Radiographically and histologically, subchondral bone cysts at the fracture lines were suspected. These cysts were thought to have developed in association with abnormal ossification centers at the extensor process areas of the third phalanx. Partial avulsion of weak extensor processes would then occur from natural forces exerted on these weakened bony prominences via the common digital extensor tendon. Support for osteochondrosis as a cause of this bone cyst formation was seen in histologic examination of fragments removed. Within the bony trabeculae, a dysplastic focus of cartilage with mineralized plaques and osseous tissues was observed. Findings supported a diagnosis of osteochondrosis, to the extent that the disease is presently understood in horses. Surgical correction by fragment removal was performed to circumvent progression of degenerative joint disease, which was evident as partial cartilage erosion of the distal dorsal articular surface of the second phalanx and fracture fragments. Recovery from surgery was rapid, and several months after surgery, the horse was sound for pleasure riding.     

A study on the effect of electrical stimulation on living tissue: potential before, during and after galvanization with constant current of 20 microA through platinum electrodes

Two platinum needles (therapeutic electrode) were inserted into the rabbit's auricle, and with the medial angle of the eye as the datum point of measurement, the electric potential was measured before, during, and after the galvanization with micro-current (20 microA). With the insertion of the needles alone, the potential between the needles and the datum point showed -0.10 to +0.28 V, which gradually decreased thereafter to reach stable levels ranging from -0.02 to +0.17 V in 3 or 4 days. When galvanized, the potential stood +0.75 to +1.30 V between the anode and the datum point, and -0.37 to -0.50 V between the cathode and the datum point. Then, 3 days later, the voltage rose +1.40 to +1.65V between the anode and the datum point, and went down -0.60 to -0.85 V between the cathode and the datum point. When the micro-current was switched off, the potential immediately decreased, and slight potential endured after 24 hrs. These findings revealed that the insertion of needles generated electric potentials, that galvanization charged the tissue, and that cessation of stimulation led to storage and discharge of electricity.     

Internal abdominal abscesses in the horse: a study of 25 cases

internal abdominal abscesses in 25 horses, including 8 horses that died or were euthanatized, were found to be caused by Streptococcus equi, Streptococcus zooepidemicus, or Corynebacterium pseudotuberculosis. Breed or sex predilection was not found. Although horses of all ages were affected, those under 5 years of age were more commonly affected. Nearly all of the horses had a history of respiratory catarrh or lymphadenitis. Horses with internal abdominal abscesses also had intermittent, prolonged colic or chronic weight loss. Most horses had increased rectal temperature, increased heart and respiratory rates, and varying degrees of anorexia. Chronic depression anemia, increased plasma fibrinogen concentration, increased total plasma protein with hypergammaglobulinemia, and hypoalbuminemia were prominent clinicopathologic findings. Results of rectal examination or surgical exploration often revealed an abdominal mass. Peritoneal fluid from 14 horses was examined, and the protein content was greater than 2.5 g/dl, with increased numbers of neutrophils. Culture results were negative in all 14 cases, although bacteria were seen intracellularly in 5 cases. Long-term (2- to 6-month) antimicrobial therapy with procaine penicillin G resulted in clinical resolution in most of these animals.     

Radius fractures in the horse: a retrospective study of 47 cases

The case records, radiographs and treatment results of 47 consecutive equine radius fractures presented to The Ohio State University Veterinary Hospital from 1975 to 1985 were examined retrospectively. Chip fractures and incomplete fractures were not considered. Both diaphyseal fractures and fractures involving the physes were included. Diaphyseal fractures were placed into three major categories: comminuted, oblique and transverse; and subclassified as proximal, mid-diaphyseal, or distal. Fractures involving a physis were classified using the Salter-Harris classification system. The horses ranged in age from one day to 19 years old. Nineteen of the patients were destroyed humanely on presentation, and 28 were treated. Twenty-four of the 28 fractures treated were repaired by open reduction and internal fixation. Success rate was related to the age of the horse and the type of fracture. Adult radius fractures have a poor prognosis. Most fractures in foals are either physeal fractures or transverse or oblique diaphyseal fractures and have an excellent to good prognosis when repaired adequately.     

Colic surgery in the horse: a retrospective study of 272 patients

In the period from January 1995 until December 2000, 272 horses underwent a laparotomy for gastrointestinal disorders. The results of these surgeries were evaluated. From these 272 patients 176 (= 65%) were discharged in good health from the hospital. When the patients that were euthanized immediately after the start of the surgery, because of a fatal deterioration, were not taken into account, the short time survival rate was 77%. Strangulated small and large intestinal obstructions (48%) had a lower short time survival rate than non-strangulated obstructions (87%). Fatal postoperative complications occurred in 18% of the patients in which the surgery was completed. Postoperative shock was the most common cause. Non-fatal complications were found in 16% of the patients which survived surgery. The major non-fatal complications were incisional hernia and thrombophlebitis of the jugular vein. From the patients that survived the surgery 81% returned to their former level of performance. Early referral may decrease the percentage of fatal complications and improve the prognoses of surgery.     

Evaluation of Key's hypothesis in the feline tibia: an experimental model for augmented bone healing studies

Key's hypothesis states that a segmental long bone defect 1.5 times the diaphyseal diameter exceeds the regenerative capacity of bone in skeletally mature dogs and results in nonunion. This hypothesis was evaluated in 5 adult cats with rigidly fixated segmental tibial ostectomies ranging from 1.25 to 1.52 times the diaphyseal diameter. Clinical, radiographic, and histologic data were obtained over a 12-week period. Healing was classified as mature bony union, clinical union, delayed union, or nonunion. Absence of a consolidating callus and instability after removal of fixation devices was found for all cats at 12 weeks. Scant formation of new bone within the gap was histologically evident for only 1 cat. In the remaining 4 cats, fibrous tissue and striated muscle predominated within the gap, and independent healing of the proximal and distal cut ends of the bone were observed. The occurrence of 4 nonunions and 1 equivocally delayed union indicated that Key's hypothesis overestimates the regenerative capacity of bone in the cat. Failure of this experimental model to produce clinical union within 12 weeks demonstrated that this model is a valid method of investigating augmented bone healing techniques that promote union within this period in the cat.     

In vitro comparison of proximal ulnar osteotomy and distal ulnar osteotomy with release of the interosseous ligament in a canine model

Objective: To determine the effect of proximal ulnar osteotomy (PUO), distal ulnar osteotomy (DUO), and DUO with release of the interosseous ligament (DOLR) on displacement of the proximal ulna at the radioulnar joint. Study Design: Experimental mechanical study. Sample Population: Cadaveric, skeletally mature canine thoracic limb pairs (n=11). Methods: Thoracic limbs disarticulated at the elbow were randomly assigned to 1 of 2 groups: (A) limbs were tested with no treatment (NOTX), then with PUO; (B) limbs were tested with DUO followed by DOLR. A distraction force was applied to the proximal ulna with the distal limb secured in a frame, and displacement of the proximal ulnar segment at the radioulnar joint was recorded. Results: Mean displacement was 0.36 mm (95% confidence interval [CI]: 0?1.12 mm) in the NOTX group, 4.68 mm (95% CI: 3.82–5.55 mm) for PUO limbs, 0.95 mm (95% CI: 0.52–1.39 mm) for the DUO group, and 4.36 mm (95% CI: 3.71–5.02 mm) for the DOLR group. Mean ulnar displacement of the DOLR group was significantly different compared with the DUO group, but there was no significant difference between the PUO and DOLR groups. Conclusions: No significant difference was observed in displacement of the proximal ulnar segment after DOLR compared with PUO.     

Disseminated alimentary mycobacteriosis in the horse: a retrospective study of nine cases

This paper summarises the clinical findings of 9 cases of disseminated alimentary mycobacteriosis in horses presented at a Finnish referral equine hospital 2009–2014. Four of 9 horses were Standardbreds and 8/9 horses were male. The median age was 2 years, ranging from 6 months to 15 years. The duration of clinical signs before admission ranged from 2 weeks to 6 months. All horses demonstrated deterioration of the clinical signs after a protracted period of the disease and were finally subjected to euthanasia after poor response to multiple medical therapies. The most common complaints on admission were weight loss and diarrhoea (9/9), pyrexia (7/9), ventral oedema (7/9), lethargy (7/9) and inappetance (6/9). The most common clinicopathological abnormalities were hypoalbuminaemia and hyperfibrinogenaemia, which were present in all horses. Rectal biopsy specimens were examined from 5/9 horses and specimens were stained with Ziehl‐Nielsen (ZN). At rectal biopsy, mild multifocal neutrophilic or mild granulomatous proctitis was recognised in all 5 horses, but the ZN stain for mycobacteria was positive in only one biopsy. A liver biopsy was taken from one horse in which hepatomegaly was observed clinically and revealed marked granulomatous hepatitis with the presence of mycobacteria. The rectal biopsy from this horse was ZN negative. At post mortem examination, chronic, multifocal to coalescing granulomatous typhlocolitis and lymphadenitis were found in all horses with the small intestine less frequently involved. At histopathological examination of post mortem samples, a ZN stain was performed and intracellular acid‐fast bacilli were identified in macrophages and multinucleated giant cells in the large intestine, liver and lymph nodes in 9/9 horses and in the small intestine in 5/9 horses. Mycobacterium avium ssp. hominissuis was isolated in 5/9 horses from post mortem samples.     

Oral administration of tepoxalin in the horse: a PK/PD study

Tepoxalin is a non-steroidal anti-inflammatory drug with analgesic, anti-inflammatory, and antipyretic properties and has been recently introduced into veterinary medicine. The aim of this study was to evaluate the pharmacokinetic/pharmacodynamic (PK/PD) profile of tepoxalin to assess whether it would be suitable for clinical use in horses. Six female fasting/fed horses were given 10mg/kg tepoxalin orally in a cross-over study. After administration, tepoxalin underwent rapid and extensive hydrolytic conversion to its carboxylic acid metabolite RWJ-20142. In animals that had been fed, the plasma concentrations of tepoxalin were undetectable, whereas in fasting animals they were close to the limit of quantification of the method. No differences between the fasting/fed groups in RWJ-20142 plasma concentrations were shown. Tepoxalin showed a strong and long-lasting ex vivo inhibitory activity against cyclooxygenase (COX)-1, mainly due to its main metabolite RWJ-20142. Tepoxalin and RWJ-20142 do not seem to possess either COX-2 or 5-lipoxygenase inhibitory activity in the horse. These features suggest that the drug is a selective COX-1 inhibitor in horses, with no significant anti-inflammatory activity. Thus, its long term use in equine practice could be of concern.     

Core decompression of the equine navicular bone: an in vivo study in healthy horses

Objective: To determine the physiologic response of the equine navicular bone to core decompression surgery in healthy horses. Study Design: Experimental in vivo study. Materials: Healthy adult horses (n=6). Methods: Core decompression was completed by creating three 2.5‐mm‐diameter drill channels into the navicular bone under arthroscopic control. The venous (P_V), arterial (P_A), articular (P_DIPJ), and intraosseous pressures (IOP) were recorded before and after decompression drilling. Each IOP measurement consisted of a baseline (IOP_B) and a stress test (intramedullary injection of saline solution, IOP_S) recording. Lameness was assessed subjectively and using force plate gait analysis. Fluorochrome bone labeling was performed. Horses were euthanatized at 12 weeks. Navicular bone mineral density (BMD) was measured, and bone histology evaluated. Results: Peak IOP (IOP_max) after stress testing was significantly (P<.05) reduced immediately after core decompression; however, the magnitude of these effects was decreased at 3 and 6 weeks after decompression. A significant (P<.05) correlation existed between IOP_max and BMD. No lameness was observed beyond the first week after surgery. Substantial remodeling and neovascularization was evident adjacent the surgery sites. Conclusion: Navicular bone core decompression surgery reduced IOP_max, and, with the exception of a mild short‐lived lameness, caused no other adverse effects in healthy horses during the 12‐week study period.     

Endoscopic anatomy of the cervical vertebral canal in the horse: a cadaver study

Reason for performing study: Localisation of spinal cord compression in horses with cervical vertebral stenotic myelopathy is inexact. Vertebral canal endoscopy has been used in man to localise spinal cord lesions and has the potential to become a useful diagnostic technique in horses. Objective: To establish a surgical approach via the atlanto‐occipital space to the cervical vertebral canal in equine cadavers and describe the endoscopic anatomy of the cervical epidural and subarachnoid spaces. Methods: The cadavers of 25 mature horses were used to assess 3 surgical methods to approach the cervical vertebral canal, including 2 minimally invasive and one open technique. Once the approach had been made, a flexible videoendoscope was inserted into the epidural space (epiduroscopy) or the subarachnoid space (myeloscopy) and advanced caudally until the intervertebral space between C7 and T1 was reached. Results: The epidural and subarachnoid spaces could not be accessed reliably using the minimally invasive techniques. Furthermore, damage to the nervous tissues was a frequent complication with these procedures. The open approach allowed successful insertion of the videoendoscope into the epidural and subarachnoid spaces in all horses and no inadvertent damage was observed. Anatomical structures that could be seen in the epidural space included the dura mater, nerve roots, fat and the ventral internal vertebral venous plexus. In the subarachnoid space, the spinal cord, nerve roots, blood vessels, denticulate ligaments and external branch of the accessory nerve were seen. Conclusions: Using the open approach, epiduroscopy and myeloscopy over the entire length of the cervical vertebral canal are possible in the mature horse. Potential relevance: Cervical vertebral canal endoscopy may become a valuable tool to localise the site of spinal cord injury in horses with cervical vertebral stenotic myelopathy and could aid in the diagnosis of other diseases of the cervical spinal cord.     

Idiopathic muscular hypertrophy of the oesophagus in the horse: a retrospective study of 31 cases

REASONS FOR PERFORMING STUDY: To present the first report of a case series concerning equine idiopathic muscular hypertrophy of the oesophagus (IMHO). OBJECTIVES: To investigate the clinical and pathological features of the disorder. METHODS: The medical records of 31 horses suffering from the disorder were reviewed retrospectively. In all these animals the diagnosis was confirmed at post mortem examination. RESULTS: The median age of the affected horses was 12.5 +/- 5.6 years (range 1-26) without sex or breed predilection. Only 2 out of 31 horses showed clinical signs associated with oesophageal dysfunction, indicating that the muscular hypertrophy was rather a coincidental post mortem finding. Histology revealed thickening of the distal portion of the oesophagus mainly involving the circular layer of the tunica muscularis without fibrosis or inflammation. In 8 cases, the disorder was seen in concurrence with idiopathic hypertrophy of the tunica muscularis of various other parts of the gastrointestinal tract. CONCLUSIONS: In the majority of patients, IMHO was a coincidental finding at post mortem examination usually confined to the smooth, circular muscle layer of the tunica muscularis externa. POTENTIAL RELEVANCE: Further research is necessary to study the precise effect of IMHO on oesophageal function.     

Incarcerated umbilical hernia in the horse: a case with a review of the literature

Umbilical hernias are common in foals. This article provides a review of the literature and presents a case of an 1.5-year-old Friesian mare with an incarcerated umbilical hernia. After reposition of the incarcerated intestine (with a lot of effort), the practising veterinarian referred the mare to the Department of Equine Sciences. Preperforative peritonitis was diagnosed, presumed to be caused by necrotic bowel. After laparotomy, this tentative diagnosis was confirmed. The necrotic part of the small intestine was resected and intensive medical treatment was started. Initially, the mare recovered well, but seven days after surgery her general condition deteriorated and she had to be euthanized. At necropsy, impaction of the stomach and rupture of the stomach wall were found. The impaction was probably a result of the generalized peritonitis.