Locking compression plate osteosynthesis of complicated mandibular fractures in six horses.

Complicated mandibular fractures were recognised in one foal, one pony and four horses. The foal was two months old while the adult animals ranged in age from 12 to 24 years. Three horses had a unilateral horizontal ramus fracture. Two fractures were open and one was closed. Comminution was present in one of these patients while the other two horses had marked displacement of the fragments. Two suffered from comminuted fractures of the horizontal and vertical ramus of the mandible. One of these patients had open and infected fractures. One foal had a bilateral horizontal ramus fracture with marked periosteal 'new bone' formation and malalignement which required corrective osteotomy. Each horse underwent locking compression plate (LCP) osteosynthesis consisting of open fracture reduction and application of one to three 4.5/5.0 mm LCP at the ventral, lateral or caudal aspect of the mandible under fluoroscopic control. Two 3.5 mm LCP were used in the foal. Plate fixation was supported by application of a cerclage wire construct between the incisor and premolar teeth in most patients. Complete fracture healing, with an excellent functional and cosmetic outcome, was achieved in all of the patients. Complications encountered included seroma formation, screw and wire breakage, as well as implant and apical tooth root infections. The LCP was removed after fracture healing had occurred in four patients.

Fracture configurations of the equine radius and tibia after a simulated kick.

The objective of this postmortem study was to determine the fracture configurations of the equine radius and tibia after a simulated kick. Fracture configurations of 35 radii and 36 tibiae from 19 adult horses were evaluated after a simulated kick in an experimental ex-vivo study. The bones were dissected, the proximal and distal ends were embedded in resin, fixed horizontally and preloaded in compression, and a steel impactor, designed to simulate a shod equine hoof, was dropped from a height of three to six metres onto the diaphysis. The experiments were filmed with a high-speed camera (30,000 pictures/second). The bones were then photographed and radiographed using a C-arm based 3D imaging device. A software programme (Osirix) was used to reconstruct the fissured and fractured bones three-dimensionally on a computer screen for assessment of the fracture configuration and fissure lines. Incomplete fractures occurred in 26 bones and complete fractures in 42. The complete fractures included 22 butterfly and 20 simple fractures; the latter included 17 oblique, two transverse and one longitudinal fracture. Additional longitudinal fissures occurred in 98% of the fractures. The butterfly fragment was always located on the side opposite the impact. There was a significant correlation between the type of bone and the fracture configuration: butterfly and oblique fractures occurred more frequently in the tibia, and incomplete fractures occurred more frequently in the radius. The data collected can be used to optimize evaluation of fractures and fissures caused by a kick and thereby improve surgical stabilization.

Does surface anodisation of titanium implants change osseointegration and make their extraction from bone any easier?

OBJECTIVES: Titanium implants have a tendency for high bone-implant bonding, and, in comparison to stainless steel implants are more difficult to remove. The current study was carried out to evaluate, i) the release strength of three selected anodized titanium surfaces with increased nanohardness and low roughness, and ii) bone-implant bonding in vivo. These modified surfaces were intended to give improved anchorage while facilitating easier removal of temporary implants. MATERIAL AND METHODS: The new surfaces were referenced to a stainless steel implant and a standard titanium implant surface (TiMAX). In a sheep limb model, healing period was 3 months. Bone-implant bonding was evaluated either biomechanically or histologically. RESULTS: The new surface anodized screws demonstrated similar or slightly higher bone-implant-contact (BIC) and torque release forces than the titanium reference. The BIC of the stainless steel implants was significant lower than two of the anodized surfaces (p = 0.04), but differences between stainless steel and all titanium implants in torque release forces were not significant (p = 0.06). CONCLUSION: The new anodized titanium surfaces showed good bone-implant bonding despite a smooth surface and increased nanohardness. However, they failed to facilitate implant removal at 3 months.

[The art of horseshoeing--between empiricism and science]. / Die Kunst des Hufbeschlags--zwischen Empirie und Wissenschaft.

To correctly shoe a horse requires the farriers to have a good working knowledge of postural anomalies and movement patterns, as well as of the different concepts of horseshoeing and to be able to apply the appropriate technique to every individual horse they shoe. The correct technique for specific problem cases is frequently a subject of debate amongst specialists and many theories would benefit from objective gait analyses. The case study presented examines the influence of different shoeing conditions on selected gait analysis parameters. The measurements were conducted on a Warmblood mare: (A) shod with long toes, (B) properly trimmed without shoes, (C) conventionally shod with rolled toes and finally (D) shod using the 4-point technique. Data on force-, time- and distance parameters were recorded using an instrumented treadmill. First contact and breakover of the hooves were documented using high-speed videography. A long toe resulted in a prolongation of the breakover time and, therefore, in a prolongation of the second half of the stance phase. Additionally, the prolonged stance duration associated with an unaltered force impulse, led to decreased force peaks. It was possible to objectively record differences between the trimmed, unshod foot, the shod long-toe and the shod rolled toe configurations. The differences between the rolled toe and the 4 point shoe however, were minimal. Gait analysis is a technique well suited for objective evaluation of different shoeing techniques under standardised conditions.

Mosaicplasty with photooxidized, mushroom shaped, bovine, osteochondral xenografts in experimental sheep.

The goal was to study the performance of mushroom shaped, photooxidized, osteochondral grafts in mosaicplasty focusing on graft stability and survival. Mushroom shaped, photooxidized grafts (6 mm for the cartilaginous head of the mushroom, 3 mm for the stem) were implanted in the medial femoral condyle of 10 sheep. Four transplants were inserted per condyle in an overlapping fashion using the pressfit technique (n=40 grafts in 10 condyles). The grafts were followed for 6 and 12 months. Semi-quantitative evaluation of graft performance was performed using a validated score system. All grafts were mechanically stable at 6 and 12 months with one exception, where the mushroom head broke off. The formation of cystic lesions in the subchondral bone area was minimal. Repopulation of the old photooxidized cartilage was noticed with cells invading the matrix from the subchondral bone area and also from the pannus on the surface. Fusion between host and graft cartilage was observed in some of the grafts at 12 months, while remodeling of the calcified cartilage zone and tidemark was noticed in all grafts. Results scored significantly better for the 6 months compared to the 12 months group if cartilage surface integrity was compared (p<0.05). In all other variables no significant differences were found between groups. Despite moderate graft recession in the 12 months group partial fusion of grafts and functional results were satisfactory. The photooxidized mushroom shaped osteochondral transplants may be a suitable type of graft for functional results in cartilage resurfacing if stable anchorage of the grafts can be achieved.

[Investigation about the clinical use of brushite- and hydroxylapatite-cement in sheep]. / Untersuchungen uber den klinischen Einsatz von Brushite- und Hydroxylapatit-Zement beim Schaf.

For future clinical use as synthetic bone replacement, an injectable brushite-(chronOS-Inject) and hydroxylapatite-(Biobon) cement were compared in a drill hole model in 10 sheep over time at 2, 4, 6, 8, 16 and 24 weeks. Results were compared regarding their practical use, biocompatibiliy, resorption mechanism and subsequent new bone formation. The cements were filled into drill holes (psi 8 x 13mm) of the proximal and distal humerus, and femur and the samples evaluated macroscopically, radiologically and microscopically including histomorphometrical quantification of percentages of new bone, fibrous tissue and remnants of cements. The cement area decreased continuously from 2 to 24 weeks with chronOS-Inject, as well as the area of granules. Inversely, the subsequent new bone formation increased from 2-24 weeks accordingly. With Biobon the cement area decreased slower between 2 and 24 weeks, and the new bone formation was less. Both cements were well integrated into the bone in long bones. chronOS-Inject demonstrated good biocompatibility and was almost completely replaced through bone within 24 weeks. Biobon was resorbed considerably slower and initially a slight inflammatory reaction including bone resorption was observed within the adjacent host bone.

Compositional changes of a dicalcium phosphate dihydrate cement after implantation in sheep.

A hydraulic calcium phosphate cement having dicalcium phosphate dihydrate (DCPD) as end-product of the setting reaction was implanted in a cylindrical defect in the diaphysis of sheep for up to 6 months. The composition of the cement was investigated as a function of time. After setting, the cement composition consisted essentially of a mixture of DCPD and beta-tricalcium phosphate (beta-TCP). In the first few weeks of implantation, the edges of the cement samples became depleted in DCPD, suggesting a selective dissolution of DCPD, possibly due to low pH conditions. The cement resorption at this stage was high. After 8 weeks, the resorption rate slowed down. Simultaneously, a change of the color and density of the cement center was observed. These changes were due to the conversion of DCPD into a poorly crystalline apatite. Precipitation started after 6-8 weeks and progressed rapidly. At 9 weeks, the colored central zone reached its maximal size. The fraction of beta-TCP in the cement was constant at all time. Therefore, this study demonstrates that the resorption rate of DCPD cement is more pronounced as long as DCPD is not transformed in vivo.

In vivo behavior of three different injectable hydraulic calcium phosphate cements.

Two dicalcium phosphate dihydrate (DCPD) hydraulic cements and one apatite hydraulic cement were implanted in epiphyseal and metaphyseal, cylindrical bone defects of sheep. The in vivo study was performed to assess the biocompatibility of the DCPD cements, using the apatite cement as control. After time periods of 2, 4 and 6 months the cement samples were clinically and histologically evaluated. Histomorphometrically the amount of new bone formation, fibrous tissue and the area of remaining cement were measured over time. In all specimens, no signs of inflammation were detectable either macroscopically or microscopically. All cements were replaced by different amounts of new bone. The two DCPD-cements showed the highest new bone formation and least cement remnants at 6 months, whereas the apatite was almost unchanged over all time periods.

Long term in-vivo studies of a photo-oxidized bovine osteochondral transplant in sheep.

BACKGROUND: Articular cartilage has limited capacity to repair. Defects greater than 3 mm heal with formation of inferior fibrous cartilage. Therefore, many attempts have been made to find the ideal graft for larger cartilage lesions. Different grafts, such as untreated or cryopreserved osteochondral transplants, have been used with variable success. METHODS: Photo-oxidized osteochondral grafts were implanted in both femoral condyles of one ovine knee. Untreated xenogeneic and autogeneic grafts served as controls. Three groups of 8 sheep each were formed and they were sacrificed 6, 12 or 18 months after surgery. RESULTS: The macroscopic evaluation of the condyle and graft showed a well-maintained cartilage surface in most grafts at all time points. However, the host cartilage matrix deteriorated considerably in all xenogeneic, most autogeneic and fewer of the photo-oxidized grafts at 12 and 18 months, respectively. The blue colour of the photo-oxidized grafts resulting from the process of photo-oxidation was visible in all grafts at 6 months, had diminished at 12 months and had completely disappeared at 18 months after surgery. Histologically a loss of matrix staining was almost never noticed in untreated xenografts, transiently at 6 months in photo-oxidized grafts and increased at 12 and 18 months. Fusion between graft and host cartilage could be seen in photo-oxidized grafts at 12 and 18 months, but was never seen in autografts and xenografts. CONCLUSIONS: The photo-oxidation of osteochondral grafts and its use as transplant appears to have a beneficial effect on cartilage and bone remodelling. Osteochondral grafts pre-treated with photo-oxidation may be considered for articular cartilage replacement and therefore may delay artificial joint replacements in human patients.

Effect of exogenous hyaluronic acid on joint function in experimentally induced equine osteoarthritis: dosage titration studies.

A single intra-articular injection of 20 or 40 mg of purified hyaluronic acid of rooster comb origin resulted in restoration of normal joint function in horses with experimentally induced osteoarthritis. The functional improvement, measured by pressure sensitive force plate techniques, was detectable within one week after treatment and persisted throughout a four week experimental period despite continued use of the joints. The response was dose dependent in that injection of 0 (saline), 5 or 10 mg hyaluronic acid per joint space resulted in no significant change in joint function while dosages of 20 or 40 mg produced maximum improvement.

Comparison of the performance of linear resistance and ultrasonic pneumotachometers at rest and during lobeline-induced hyperpnoea.

The performance of a Fleisch No. 5 pneumotachometer (F), and two commercial ultrasonic pneumotachometers, the BRDL (B) and the Spiroson (S) systems were compared in respect to their use for determination of ventilatory parameters at rest and during lobeline-induced hyperpnoea. Five clinically healthy Thoroughbred horses were tested with the three pneumotachometers in random order. Respiratory airflow, respired gas concentrations, oesophageal pressures, pressures within the mask systems and arterial blood gases were determined before and during lobeline-induced hyperpnoea. Because measured peak expiratory airflow rates exceeded the stated linear range of the Fleisch pneumotachometer ( approximately +/- 25 l s(-1)) differential pressure-flow curves were determined in vitro over the range of flows recorded in vivo. Expired flows greater than the linear range were corrected according to the derived regression equation. No differences in any of the measured variables among the three systems were present at rest. At peak ventilation of lobeline-induced hyperpnoea mask pressures [Delta P(mask)(mean (SEM)): F: 9.6 (2.8) cm H(2)O, B: 0.8 (0.4) cm H(2)O, S: 1.4 (0.8) cm H(2)O] and end tidal carbon dioxide [ ET CO(2)(mean (SEM)): F: 2. 6 (0.1)%, B: 2.1 (0.2)%, S: 2.1 (0.1)%] were significantly higher in system F. Despite a tendency for respiratory frequency and peak inspired and expired flows, to be lower with system F, no significant differences in the measurements of ventilatory mechanics were detected. In conclusion, the ultrasonic flowmeters pose significantly lower resistive loads onto the respiratory system during ventilation above resting levels than Fleisch No 5 pneumotachometers. However, at the flowrates achieved during lobeline-induced hyperpnoea an in vitro calibration of the differential pressure-flow relationship allows correction for expiratory alinearity in system F. In addition, the performance of the Spiroson flowmeter is accurate in determining ventilatory mechanics at rest and during lobeline-induced hyperpnoea.

Treatment of radial fractures in adult horses: an analysis of 15 clinical cases.

Fifteen cases of radial fractures in adult horses weighing more than 300 kg are discussed. Four of the horses were destroyed on humane grounds immediately because of a poor prognosis and expense of internal fixation; and two horses at five days and five weeks, respectively after treatment by cast application was initiated. Internal fixation was used in nine horses but of these only two horses recovered completely and resumed their former activities. In eight cases, two plates were applied, one lateral or medial and the other cranial. The internal fixation techniques of all nine horses were scrutinised and suggestions made for the future treatment of radial fractures. These suggestions are (1) the use of ASIF 5.5 mm cortical bone screws using the total width or thickness of the bone in each case. (2) Application of the dynamic condylar screw with its plate in distal or proximal fractures to allow more support. (3) Incorporation of a cancellous bone graft to the fracture. (4) Possible table recovery to prevent breakdown of the fixation during recovery. It is important that bone plates are applied over the total length of the bone. The fact that only two out of 15 horses survived and recovered completely underlines the problems associated with treatment of radial fractures in the adult horse.

Review of pulsing electromagnetic field therapy and its possible application to horses.

The relevant literature on electrostimulation in general, and pulsing electromagnetic fields in particular, is reviewed. DC current influences cell behaviour by affecting transmembrane ion transport, which is often under enzymatic control. Pulsing electromagnetic fields influence cell functions through adsorption of ions or dipole formation at the cell membrane. Invasive and non-invasive DC current stimulation is compared to pulsing electromagnetic fields. The mode of application of pulsing electromagnetic fields to the equine limb and suggested treatment times are briefly discussed. Two case reports are used to illustrate the effect of pulsing electromagnetic fields in equine fracture treatment.

Compensatory load redistribution of horses with induced weightbearing hindlimb lameness trotting on a treadmill.

REASONS FOR PERFORMING STUDY: The compensatory mechanisms of horses with weightbearing hindlimb lameness are still not fully understood. HYPOTHESIS: That weightbearing, unilateral hindlimb lameness would not only alter stride characteristics to diminish structural stress in the affected limb but also induce compensatory load adjustments in the other supporting limbs. OBJECTIVE: To document the load and time shifting mechanisms of horses with unilateral weightbearing hindlimb lameness. METHODS: Reversible lameness was induced in 8 clinically sound horses by applying a solar pressure model. Three degrees of lameness (subtle, mild and moderate) were induced and compared with the nonlame (sound) control measurement. Vertical ground reaction forces were recorded for all 4 limbs simultaneously on an instrumented treadmill. RESULTS: Compared to the sound situation, moderate hindlimb hoof lameness induced a decrease in stride duration (-3.3%) and stride impulse (-3.1%). Diagonal impulse decreased selectively in the lame diagonal stance (-7.7%). Within the diagonal limb pair, vertical impulse was shifted to the forelimb during the lame diagonal stance (+6.5%) and to the hindlimb during the sound diagonal stance (+3.2%). Peak vertical force and vertical impulse decreased in the lame limb (-15%), but only vertical impulse increased in the contralateral hindlimb (+5.7%). Stance duration was prolonged in both hindlimbs (+2.5%). Suspension duration was reduced to a greater extent after push-off of the lame diagonal limb pair (-21%) than after the sound diagonal limb pair (-9.2%). CONCLUSIONS: Four compensatory mechanisms could be identified that served to reduce structural stress, i.e. peak vertical force on the affected limb: 1) reduction of the total vertical impulse per stride; 2) diagonal impulse decreased selectively in the lame diagonal; 3) impulse was shifted within the lame diagonal to the forelimb and in the sound diagonal to the hindlimb; and 4) the rate of loading and peak forces were reduced by prolonging the stance duration. POTENTIAL RELEVANCE: Load shifting mechanisms are not only effective in diminishing peak forces in the affected limb, but also suppress compensatory overload in other limbs. Selected force and time parameters allow the unequivocal identification of the lame limb. Future studies have to examine how far these compensatory mechanisms may be generalised for other defined orthopaedic problems in the hindlimb.

Recovery from anaesthesia in ponies: a comparative study of the effects of isoflurane, enflurane, methoxyflurane and halothane.

The duration and quality of recovery after separate 2 hour anaesthetic periods with equipotent alveolar concentrations of isoflurane, enflurane, halothane and methoxyflurane were evaluated in experimental ponies. Recovery was shortest after isoflurane anaesthesia, followed by enflurane, halothane and finally methoxyflurane, although standing was achieved more rapidly after enflurane than after isoflurane. This sequence of recovery times was compatible with the respective solubilities of the 4 agents. The smoothest recovery was obtained after isoflurane anaesthesia, followed by methoxyflurane, halothane and then enflurane. The isoflurane recovery was characterized by very quiet and prolonged sternal recumbency with excellent coordination upon standing. The chief difficulties with halothane recovery were shivering and delayed coordination upon standing. Enflurane anaesthesia was followed by a very brief period of sternal recumbency but there was considerable shivering and incoordination upon standing. This may have been due to central nervous stimulation during anaesthesia producing a residual excitatory effect. On the basis of this investigation, isoflurane was considered to be the most satisfactory volatile anaesthetic for the horse.

Upregulation of mRNA of interleukin-1 and -6 in subchondral cystic lesions of four horses.

This study investigated the potential association of interleukin-1beta (IL-1beta) and interleukin-6 (IL-6) in subchondral cystic lesions (SCL) in horses. With the technique of in situ hybridisation in paraffin sections of fibrous tissue of SCL and quantitative real-time PCR in fresh frozen fibrous tissue and undecalcified bone sections of SCL embedded in acrylic resin, upregulation of mRNA of both cytokines could be demonstrated. mRNA of IL-1beta was upregulated at the periphery of the cystic lesion adjacent to normal bone, whereas IL-6 mRNA was upregulated within the fibrous tissue found within the centre of the SCL. It was concluded that both cytokines are associated in pathological bone resorption observed in SCL and, in combination with increased production of prostaglandin E2, may be responsible for the slow healing, maintenance or further expansion of the cystic lesions.

Spontaneous production of nitric oxide (NO), prostaglandin (PGE2) and neutral metalloproteinases (NMPs) in media of explant cultures of equine synovial membrane and articular cartilage from normal and osteoarthritic joints.

Nitric oxide (NO), prostaglandin E2 (PGE2), and the activity of neutral metalloproteinases (NMPs) were measured in conditioned media of equine synovial membrane and articular cartilage explant cultures from horses with normal joints (n = 7) and from horses affected with moderate (n = 7) or severe osteoarthritis (n = 14) as judged by macroscopic appearance. Normal articular cartilage appeared glossy and bluish-white, was of normal thickness and showed no evidence of discolouration, fibrillation or other cartilage discontinuity. Slight discolouration and fibrillation or minor clefts of the cartilage were considered as moderate OA, whereas erosions of articular cartilage down to the subchondral bone were considered as cases of severe OA. Explant cultures of equine synovial membrane and articular cartilage released the local mediators, NO and PGE2, as well as detectable levels of NMP activity into culture media. Concentrations of NO were higher in articular cartilage explants compared to synovial membrane explants, whereas concentrations of PGE2 were higher in synovial membrane explants. The NMPs with collagenolytic activities were similar in both explant cultures, whereas gelatinolytic activities were higher in synovial membrane explant cultures and caseinolytic activities were generally higher in articular cartilage explant cultures. Furthermore it was shown that concentrations or enzyme activities increased according to the severity of disease of the joints. Concentrations for NO, collagenolytic and gelatinolytic NMPs were relatively stable, whereas PGE2 and caseinolytic NMP concentrations increased over time in culture.

Periosteal transection and periosteal stripping for correction of angular limb deformities in foals.

Valgus deformities were created in 6 pony foals by hemicircumferential transection of the periosteum and periosteal stripping (HCTP and PS) just proximally to the distal physis on the medial side of 1 radius (principal thoracic limb). The opposite thoracic limb served as a control. One month after this surgical procedure was done, the limbs were radiographed and the angle of deviation was determined. All horses developed a valgus deformity of the principal limb. In an effort to correct the acquired valgus deformity, the 2nd surgical procedure was performed--HCTP and PS on the lateral aspect of the principal radius. The carpal valgus deformities corrected within 3 months. To determine the differences in growth, stainless steel wires were introduced into both legs of each foal at certain points on the distal part of the radius. Growth changes in response to the HCTP and PS were not significantly different in the 2 groups of thoracic limbs. Increased bone growth did occur at the medial aspect of the bone in response to the 1st surgical procedure and an increase was found on the lateral aspect of the bone in response to the 2nd. The reasons for the statistically insignificant changes are discussed. A significant increase in bone width at the level of growth plate developed in response to the 1st and 2nd HCTP and PS procedures.

Healing of surgically created defects in the equine superficial digital flexor tendon: collagen-type transformation and tissue morphologic reorganization.

Full-thickness defects were surgically created in the superficial digital flexor tendons of the front limbs of 20 horses. Tissues formed within the defect were evaluated histologically, and the collagen composition of the tissue was determined by immunofluorescence. Transformation occurred from loose fibrillar areas of types I and III collagen and pericellular types IV and V collagen to dense bundles of type I collagen fibers. Loose fibrillar areas of types I and III collagen were present after 24 weeks. Histologically, in horses killed after 2 weeks, the tissue within the defect was a randomly oriented mass of fibrovascular tissue. In horses killed after 24 weeks the tissue within the defect resembled normal tendon tissue.

Healing of surgically created defects in the equine superficial digital flexor tendon: effects of pulsing electromagnetic field therapy on collagen-type transformation and tissue morphologic reorganization.

The effect of pulsing electromagnetic field (PEMF) therapy on the healing of surgically created defects in equine superficial digital flexor tendons was evaluated. Defects were created in both front superficial digital flexor tendons of 20 horses. The defect in 1 limb was exposed to a PEMF for 2 hours daily. The other limb served as a control. Histologic and immunofluorescent evaluations were done in horse killed at postsurgical weeks 2, 4, 8, 12, and 24. Therapy with the PEMF significantly (P less than 0.05) delayed the maturation of the tissue formed within the defect at postsurgical weeks 8 and 12, as determined by histologic examination. The collagen-type transformation was also delayed by the PEMF therapy, but to a degree that was not significant.