Radiation exposure during simulated equine head and limb fan beam standing computed tomography appears safe for personnel using lead shielding.

OBJECTIVE: To evaluate the radiation dose to personnel locations during simulated head and limb scans with a novel equine standing CT (sCT) system. METHODS: Measurements were made with the use of a helical fan beam sCT system (Equina; Asto CT Inc). Scatter radiation was measured in different positions in the sCT room to mimic the location of the control operator, horse handler, and lead rope handler during simulated equine head and limb imaging. Operator/handler dose was quantified at each location using entrance air kerma measured with a spherical ionization chamber and electrometer. RESULTS: Radiation dose to the control operator, horse handler, and lead rope handler locations wearing a lead apron during simulated head imaging was 13.3, 3.5, and 6.8 µGy, respectively. Radiation dose to the control operator location wearing a lead apron was 1.3 µGy, and dose to the lead rope handler location wearing a lead apron was 0.2 and 5.4 µGy during simulated pelvic limb and thoracic limb imaging, respectively. CONCLUSIONS: With the more widespread clinical use of equine sCT units in clinical practice, there is concern for increased risk of radiation exposure to personnel who stay in the sCT room during scanning. The control operator location had the highest dose during simulated head imaging, and the lead rope handler location in thoracic limb sCT had the highest dose during simulated limb imaging. Limiting the number of personnel in the sCT room, rotating personnel between handler positions, increasing operator distance from the scanner, and using lead shields and eyeglasses are recommended. CLINICAL RELEVANCE: Our findings suggest that scanning large numbers of horses per year with the Asto CT Equina would not lead to occupational radiation exposure above the recommended safe threshold for handlers using lead shields and eyeglasses.

Comparison of radiography and computed tomography for identification of third metacarpal structural change and associated assessment of condylar stress fracture risk in Thoroughbred racehorses.

BACKGROUND: Catastrophic injury has a low incidence but leads to the death of many Thoroughbred racehorses. OBJECTIVES: To determine sensitivity, specificity, and reliability for third metacarpal condylar stress fracture risk assessment from digital radiographs (DR) and standing computed tomography (sCT). STUDY DESIGN: Controlled ex vivo experiment. METHODS: A blinded set of metacarpophalangeal joint DR and sCT images were prepared from 31 Thoroughbreds. Four observers evaluated the condyles and parasagittal grooves (PSG) of the third metacarpal bone for the extent of dense bone and lucency/fissure and assigned a risk assessment grade for condylar stress fracture based on imaging features. Sensitivity and specificity for detection of subchondral structural changes in the condyles and PSG, and for risk assessment for condylar stress fracture were determined by comparison with a reference assessment based on sCT and joint surface examination. Agreement between observers and the reference assessment and reliability between observers were determined. Intra-observer repeatability was also assessed. RESULTS: Sensitivity for detection of structural change was lower than specificity for both imaging methods and all observers. For agreement with the reference assessment of structural change, correlation coefficients were generally below 0.5 for DR and 0.49-0.82 for sCT. For horses categorised as normal risk on reference assessment, observer assessment often agreed with the reference. Sensitivity for risk assessment was lower than specificity for all observers. For horses with a reference assessment of high risk of injury, observers generally underestimated risk. Diagnostic sensitivity of risk assessment was improved with sCT imaging, particularly for horses categorised as having elevated risk of injury from the reference assessment. Assessment repeatability and reliability was better with sCT than DR. MAIN LIMITATIONS: The ex vivo study design influenced DR image sets. CONCLUSIONS: Risk assessment through screening with diagnostic imaging is a promising approach to improve injury prevention in racing Thoroughbreds. Knowledge of sensitivity and specificity of fetlock lesion detection provides the critical guidance needed to improve racehorse screening programs. We found improved detection of MC3 subchondral structural change and risk assessment for condylar stress fracture with sCT ex vivo.

Ex vivo study shows novel, rapid, suture-free tenotomy technique for the equine deep digital flexor tendon.

OBJECTIVE: To describe the feasibility of a novel thread-transecting technique for the tenotomy of the equine deep digital flexor tendon (DDFT). ANIMALS: 39 equine distal limb specimens. METHODS: Under ultrasonographic guidance, a surgical thread was percutaneously placed around the DDFT through 2 needle punctures (lateral and medial) using a Tuohy needle in equine limbs (22 forelimbs, 17 hindlimbs). The DDFT was transected by a back-and-forth motion of the thread until the loop emerged from the entry puncture site. Each specimen was dissected and assessed for completeness of transection and iatrogenic damage under direct visualization. Descriptive statistics were reported. RESULTS: Complete DDFT transection was achieved in all 39 limbs, taking an average of 8.6 minutes per procedure. Iatrogenic damage to surrounding structures occurred in 17 (44%) limbs, with 6 (15%) limbs having more than 1 structure damaged. Damage to the communicating branch of the palmar or plantar nerves was the most commonly seen. CLINICAL RELEVANCE: DDFT tenotomy in equine limb specimens was effectively performed using a novel thread-transecting technique. The procedure is quick, and no suturing is needed, but damage to surrounding structures is possible. Further assessment of the procedure and clinical significance of its potential iatrogenic damage in clinical cases is needed.

Genetic architecture and polygenic risk score prediction of degenerative suspensory ligament desmitis (DSLD) in the Peruvian Horse.

Introduction: Spontaneous rupture of tendons and ligaments is common in several species including humans. In horses, degenerative suspensory ligament desmitis (DSLD) is an important acquired idiopathic disease of a major energy-storing tendon-like structure. DSLD risk is increased in several breeds, including the Peruvian Horse. Affected horses have often been used for breeding before the disease is apparent. Breed predisposition suggests a substantial genetic contribution, but heritability and genetic architecture of DSLD have not been determined. Methods: To identify genomic regions associated with DSLD, we recruited a reference population of 183 Peruvian Horses, phenotyped as DSLD cases or controls, and undertook a genome-wide association study (GWAS), a regional window variance analysis using local genomic partitioning, a signatures of selection (SOS) analysis, and polygenic risk score (PRS) prediction of DSLD risk. We also estimated trait heritability from pedigrees. Results: Heritability was estimated in a population of 1,927 Peruvian horses at 0.22 ± 0.08. After establishing a permutation-based threshold for genome-wide significance, 151 DSLD risk single nucleotide polymorphisms (SNPs) were identified by GWAS. Multiple regions of enriched local heritability were identified across the genome, with strong enrichment signals on chromosomes 1, 2, 6, 10, 13, 16, 18, 22, and the X chromosome. With SOS analysis, there were 66 genes with a selection signature in DSLD cases that was not present in the control group that included the TGFB3 gene. Pathways enriched in DSLD cases included proteoglycan metabolism, extracellular matrix homeostasis, and signal transduction pathways that included the hedgehog signaling pathway. The best PRS predictive performance was obtained when we fitted 1% of top SNPs using a Bayesian Ridge Regression model which achieved the highest mean of R2 on both the probit and logit liability scales, indicating a strong predictive performance. Discussion: We conclude that within-breed GWAS of DSLD in the Peruvian Horse has further confirmed that moderate heritability and a polygenic architecture underlies the trait and identified multiple DSLD SNP associations in novel tendinopathy candidate genes influencing disease risk. Pathways enriched with DSLD risk variants include ones that influence glycosaminoglycan metabolism, extracellular matrix homeostasis, signal transduction pathways.

Ex vivo evaluation of a percutaneous thread-transecting technique for desmotomy of normal palmar/plantar annular ligaments in horses.

OBJECTIVE: To develop and describe a minimally invasive, ultrasound-guided, percutaneous technique for the desmotomy of equine palmar/plantar annular ligaments (PALs) using a transecting thread. STUDY DESIGN: Ex vivo study. SAMPLE POPULATION: Twenty-one normal equine distal limb specimens. METHODS: Under ultrasonographic guidance, a surgical thread was percutaneously placed around the PAL through 2 skin punctures (proximal and distal) using a 18 gauge spinal needle in equine limbs (11 forelimbs, 10 hindlimbs) with normal PALs. The ligament was transected by a back-and-forth motion of the thread until the loop emerged from the proximal skin puncture site. Each specimen was dissected and assessed for completeness of transection and iatrogenic damage under direct visualization. Descriptive statistics were reported. RESULTS: The PAL was completely transected in 17/21 limbs. The mean duration of the procedure was 16 minutes. Superficial needle puncture or subtle abrasion of the superficial digital flexor tendon was noticed in 4 limbs. No iatrogenic injury to other intrathecal structures was identified. After PAL division, the needle entry and exit points had a mean diameter of 1.2 and 1 mm, respectively. CONCLUSION: Desmotomy of normal PALs in equine limb specimens was performed effectively using the percutaneous thread-transecting technique with minimal iatrogenic damage to adjacent structures. CLINICAL SIGNIFICANCE: Information from this study will allow refinement of the technique for use in equine clinical cases either in standing or anesthetized horses.

Use of a novel helical fan beam imaging system for computed tomography of the distal limb in sedated standing horses: 167 cases (2019-2020).

OBJECTIVE: To evaluate the diagnostic capabilities of a novel helical fan beam CT system used for imaging of horses with a range of clinical distal limb problems. ANIMALS: 167 horses. PROCEDURES: Medical records were reviewed of horses presented for CT of the distal limb at 2 university-based veterinary hospitals. The following data were recorded: age, sex, breed, presenting complaint, sedation used for imaging, scanning time, procedure time, other diagnostic imaging methods performed, imaging diagnosis, clinical diagnosis, and complications during imaging. RESULTS: Most horses were Thoroughbreds and Quarter Horses. Procedure times ranged from 15 to 40 minutes, with scanning completed in 15 to 45 seconds for each region of interest. The foot or pastern region was commonly scanned (88/167 [53%] horses), with navicular bone disease diagnosed in 42 of 88 (48%) horses. The fetlock region was also commonly scanned (42/167 [40%] horses), with palmar or plantar osteochondral disease diagnosed in 17 of 42 (40%) horses. Horses were compliant during scanning, and no complications with sedation or damage to the scanner occurred. A specific imaging diagnosis for the lameness was achieved more frequently with CT imaging (166/167 [99%]) than with planar digital radiography (26/58 [45%]). CLINICAL RELEVANCE: The helical fan beam CT system could be used safely to scan sedated standing horses from the carpal or tarsal region distally. Subjectively, the machine was easy to operate, allowing CT to be incorporated into lameness investigations. CT imaging was very likely to result in a clinical diagnosis in horses with distal limb lameness.

Use of a novel helical fan beam imaging system for computed tomography of the head and neck in sedated standing horses: 120 cases (2019-2020).

OBJECTIVE: To evaluate the diagnostic capabilities of a novel helical fan beam CT system used for imaging of horses with clinical problems of the head and neck. ANIMALS: 120 horses. PROCEDURES: Medical records were reviewed of horses presented for CT of the head or neck at 2 university hospitals. The following data were recorded: age, sex, breed, presenting complaint, sedation used for imaging, scanning time, procedure time, other diagnostic imaging methods performed, imaging diagnosis, clinical diagnosis, and complications during imaging. RESULTS: Quarter Horses and Warmbloods were the most common breeds, and the most common complaint was nasal discharge. The head (101/120 [84%] horses) was scanned most frequently, and the most common diagnoses were primary dental disease and a space-occupying lesion of the paranasal sinuses. Nuchal bursitis was the most common imaging diagnosis in the neck region. Procedure time ranged from 20 to 45 minutes with a scanning time of 30 to 40 seconds. No complications with horse sedation occurred, and horses tolerated scanning well. An imaging diagnosis was more frequently achieved with CT (109/120 [91%] horses) than with planar digital radiography (23/61 [38%] horses). CLINICAL RELEVANCE: The helical fan beam CT system had fast scanning times and could be used safely for routine imaging of the teeth and sinuses in horses. The caudal extent of scanning in the neck region was limited by the shape of the horse's neck and thorax.

Selection signature analyses and genome-wide association reveal genomic hotspot regions that reflect differences between breeds of horse with contrasting risk of degenerative suspensory ligament desmitis.

Degenerative suspensory ligament desmitis is a progressive idiopathic condition that leads to scarring and rupture of suspensory ligament fibers in multiple limbs in horses. The prevalence of degenerative suspensory ligament desmitis is breed related. Risk is high in the Peruvian Horse, whereas pony and draft breeds have low breed risk. Degenerative suspensory ligament desmitis occurs in families of Peruvian Horses, but its genetic architecture has not been definitively determined. We investigated contrasts between breeds with differing risk of degenerative suspensory ligament desmitis and identified associated risk variants and candidate genes. We analyzed 670k single nucleotide polymorphisms from 10 breeds, each of which was assigned one of the four breed degenerative suspensory ligament desmitis risk categories: control (Belgian, Icelandic Horse, Shetland Pony, and Welsh Pony), low risk (Lusitano, Arabian), medium risk (Standardbred, Thoroughbred, Quarter Horse), and high risk (Peruvian Horse). Single nucleotide polymorphisms were used for genome-wide association and selection signature analysis using breed-assigned risk levels. We found that the Peruvian Horse is a population with low effective population size and our breed contrasts suggest that degenerative suspensory ligament desmitis is a polygenic disease. Variant frequency exhibited signatures of positive selection across degenerative suspensory ligament desmitis breed risk groups on chromosomes 7, 18, and 23. Our results suggest degenerative suspensory ligament desmitis breed risk is associated with disturbances to suspensory ligament homeostasis where matrix responses to mechanical loading are perturbed through disturbances to aging in tendon (PIN1), mechanotransduction (KANK1, KANK2, JUNB, SEMA7A), collagen synthesis (COL4A1, COL5A2, COL5A3, COL6A5), matrix responses to hypoxia (PRDX2), lipid metabolism (LDLR, VLDLR), and BMP signaling (GREM2). Our results do not suggest that suspensory ligament proteoglycan turnover is a primary factor in disease pathogenesis.

Long-Term Outcome of Horses Undergoing Unilateral Mandibular Condylectomy and Meniscectomy for Temporomandibular Joint Disease.

Background: There are no reports describing the long-term outcome of sport horses undergoing unilateral mandibular condylectomy with meniscectomy (UMC) for treatment for severe temporomandibular joint (TMJ) disease (TMD). Whether horses undergoing UMC require a specialized diet, can return to riding with a bit, or return to intended function after surgery is unknown. Objective: To determine the long-term outcome of horses undergoing UMC for treatment of severe TMD. Study Design: A multi-institutional, retrospective study. Methods: Medical records obtained from seven equine referral hospitals of horses with severe TMD that underwent UMC were reviewed. Details regarding the presenting complaints, results of clinical examination, findings of diagnostic imaging, surgical technique, and outcome (including long-term follow-up with an owner questionnaire) were recorded. Results: Eleven horses fit the inclusion criteria. Three had severe idiopathic osteoarthritis, and eight had confirmed septic osteoarthritis of the TMJ. The most common post-operative complications were drainage and peri-incisional swelling (n = 5). One horse developed a hematoma at the surgical site because the facial artery was inadvertently transected during the approach, causing the condylectomy to be postponed. All horses were discharged alive from the hospital, and 10 returned to their previous or intended use. All had complete resolution of clinical signs of TMD. One mare was retired from athletic use due to her genetic value as a broodmare. One horse was euthanized 2 years after UMC due to progressively worsening of clinical signs of temporohyoid osteoarthropathy (THO), which were not present before surgery. When available, owner satisfaction of the results of the procedure was excellent. Main Limitations: Sample size; multiple institutions; owner bias. Conclusions: Unilateral mandibular condylectomy should not be considered a salvage procedure. Horses treated for severe TMD by UMC can return to their previous or intended level of athletic performance and do not require a specialized diet.

Standing Intraoral Extraction of the Right Mandibular Third Molar Tooth in a Cow Utilizing Tooth Sectioning.

A 2-year-old Holstein heifer presented to a university teaching hospital with an apical tooth infection of the right mandibular third molar. A standing oral extraction technique was attempted for tooth removal; however, the molar could not be delivered intact. A tooth sectioning technique was performed, and the affected molar was successfully delivered. Three months postextraction, the heifer had fully recovered, and the extraction site had healed. To the authors' knowledge, this is the first description of a tooth extraction in a cow using a tooth sectioning technique. This case describes an alternative technique for tooth removal in cattle with an apical tooth infection. The clinical, diagnostic, and therapeutic features of this case may be helpful to clinicians when they approach similar cases in the future.

Computed tomographic assessment of brain tissue disruption and skull damage in equine cadaveric heads caused by various firearm-ammunition combinations applied as potential gunshot methods for euthanasia of horses.

OBJECTIVE: To evaluate with CT the characteristics of brain tissue disruption and skull damage in cadaveric heads of adult horses caused by each of 6 firearm-ammunition combinations applied at a novel anatomic aiming point. SAMPLE: 53 equine cadaveric heads. PROCEDURES: Heads placed to simulate that of a standing horse were shot with 1 of 6 firearm-ammunition combinations applied at an aiming point along the external sagittal crest of the head where the 2 temporalis muscles form an inverted V. Firearm-ammunition combinations investigated included a .22-caliber long rifle pistol firing a 40-grain, plated lead, solid-core or hollow-point bullet (HPB); a semiautomatic 9-mm pistol firing a 115-grain, jacketed HPB; a semiautomatic .223-caliber carbine firing a 55-grain, jacketed HPB; a semiautomatic .45-caliber automatic Colt pistol firing a 230-grain, jacketed HPB; and a 12-gauge shotgun firing a 1-oz rifled slug. Additional heads placed in a simulated laterally recumbent position were shot with the semiautomatic 9-mm pistol-HPB combination. All heads underwent CT before and after being shot, and images were evaluated for projectile fragmentation, skull fracture, and cerebrum, cerebellum, and brainstem disruption. RESULTS: Computed tomography revealed that all firearm-ammunition combinations caused disruption of the cerebrum, cerebellum, and brainstem that appeared sufficient to result in instantaneous death of a live horse. Hollow-point ammunition was as effective as solid-core ammunition with regard to brain tissue disruption. Brain tissue disruption was not affected by head positioning. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicated that the examined firearm-ammunition combinations, when applied at a novel aiming point, appear to be reasonable options for euthanasia of horses.

Multicenter retrospective study of complications and risk factors associated with castration in 106 pet pigs.

Castration of pet pigs is becoming a commonly performed procedure. However, little information is available regarding surgical techniques and complications. Medical records of 106 pet pigs admitted to 3 teaching hospitals for castration were reviewed. All descended testicles were approached via pre-scrotal skin incisions, which were either closed (59.4%) or left open (22.6%). The inguinal rings were closed in 42% of cases. Of the 106 pet pigs, 4.7% developed a complication after surgery, which consisted of peri-incisional swelling. Pigs which underwent inguinal ring closure were 6.6 times more likely to develop a post-operative complication (confidence interval: 1.16 to infinity, P = 0.035). Age and weight at time of castration were not significantly associated with complications (P = 0.698 and P = 0.685, respectively). The results from this retrospective study suggest that castration in pet pigs is a safe procedure with a minimal rate of complications.

Étude rétrospective multicentre des complications et facteurs de risque associés avec la castration de 106 porcs miniatures. La castration de porcs miniatures est en voie de devenir une procédure effectuée couramment. Toutefois, peu d'informations sont disponibles concernant les techniques chirurgicales et les complications. Les dossiers médicaux de 106 porcs miniatures admis à trois hôpitaux vétérinaires d'enseignement pour castration ont été revus. Tous les testicules descendus furent approchés via des incisions cutanées préscrotales, qui furent soient fermées (59,4 %) ou laissées ouvertes (22,6 %). Les anneaux inguinaux étaient fermés dans 42 % des cas. Parmi les 106 porcs miniatures, 4,7 % ont développé des complications après la chirurgie, consistant en oedème péri-incisionnel. Les porcs qui ont dû subir une fermeture de l'anneau inguinal étaient 6,6, fois plus à risque de développer des complications post-opératoires (intervalle de confiance : 1,16 à l'infini, P = 0,035). L'âge et le poids au moment de la castration n'étaient pas associés de manière significative avec des complications (P = 0,698 et P = 0,685, respectivement). Les résultats de la présente étude rétrospective suggèrent que la castration de porcs miniatures est une procédure sécuritaire avec un taux minime de complications.(Traduit par Dr Serge Messier).

Complications and survival in horses with surgically confirmed right dorsal displacement of the large colon.

This study compared post-operative complications and survival in horses with right dorsal displacement of the large colon (RDD) and horses with other non-strangulating large colon (NSLC) lesions. Data were obtained from medical records of horses undergoing exploratory laparotomy from 2000 to 2016 and from owner questionnaire. Of 137 horses that fitted the inclusion criteria, 67 (49%) had RDD and 70 (51%) had NSLC lesions. Twenty-eight horses with RDD (42%) and 27 horses with NSLC (39%) experienced ≥ 1 complication after surgery. The RDD group showed more severe complications than the NSLC group (P = 0.0145). Horses with RDD were more likely to develop colic in the short term (P = 0.0111), but not in the long-term (P = 0.453), and were more likely to have a 2nd laparotomy (P = 0.0003). There was no significant difference in short- or long-term survival between groups. Major post-operative complications in the RDD group did not influence short- or long-term survival.

Complications et survie des chevaux atteints d'un déplacement dorsal droit du gros côlon confirmé par chirurgie. Cette étude a comparé les complications et la survie postopératoires chez les chevaux atteints d'un déplacement dorsal droit du gros côlon (DDD) et les chevaux atteints d'autres lésions non étranglantes du gros côlon (LNEGC). Des données ont été obtenues dans les dossiers médicaux de chevaux qui avaient subi une laparatomie exploratoire entre 2000 et 2016 et dans un questionnaire auprès des propriétaires. Parmi les 137 chevaux qui satisfaisaient aux critères d'inclusion, 67 (49 %) avaient eu un DDD et 70 (51 %) avaient eu des lésions LNEGC. Vingt-huit chevaux atteints d'un DDD (42 %) et 27 chevaux qui avaient une LNEGC (39 %) ont éprouvé ≥ 1 complication après la chirurgie. Le groupe DDD a manifesté des complications plus graves que le groupe LNEGC (P = 0,0145). Il était plus probable que les chevaux atteints de DDD développent des coliques à court terme (P = 0,0111), mais pas à long terme (P = 0,453) et il était plus probable qu'ils aient à subir une deuxième laparotomie (P = 0,0003). Il n'y avait aucune différence significative au niveau de la survie à court ou à long terme entre les groupes. Les complications postopératoires majeures du groupe DDD n'ont pas influencé la survie à court ou à long terme.(Traduit par Isabelle Vallières).

Use of tube cystostomy in the surgical management of obstructive urolithiasis in a Bactrian camel.

CASE DESCRIPTION: A 6-year-old castrated male Bactrian camel was evaluated because of a 14hour history of oliguria and stranguria that progressed to anuria. CLINICAL FINDINGS: Perineal urethral pulsations and intermittent tail flagging with no accompanying urination were observed. Ultrasonography of the urethra revealed multiple hyperechoic foci with shadowing artifact indicative of calculi present in the penile urethra distal to the sigmoid flexure. Rectal palpation revealed a pulsating hard urethra and intact distended urinary bladder. Further clinical examination was not possible because of challenges associated with handling the camel. TREATMENT AND OUTCOME: Urethral catheterization through a perineal urethral incision failed to achieve urinary bladder decompression. Tube cystostomy was performed to prevent bladder rupture. Urethrocystography performed 3 days after surgery revealed a urethral rupture at the level of the prepuce. Five weeks after surgery, the camel could urinate a steady stream via the urethrotomy site. Seven weeks after surgery, the cystostomy tube was removed, and the urethrotomy site was modified to provide a permanent urethral opening via perineal urethrostomy. During 6 years of subsequent periodic follow-up by telephone, the owner reported that the camel continued to do well and urinate through the revised opening. CLINICAL RELEVANCE: To the authors' knowledge, this is the first detailed description of a tube cystostomy in an adult camel with obstructive urolithiasis that includes information on the patient's long-term outcome. This technique was a viable option in the surgical management of obstructive urolithiasis in this camel and may be useful for other large camelids as well.

In vivo evaluation of effects of sedation on results of acoustoelastography of the superficial digital flexor tendons in clinically normal horses.

OBJECTIVE To assess the effects of sedation on results of acoustoelastography of the superficial digital flexor tendons (SDFTs) in clinically normal horses. ANIMALS 27 clinically normal horses. PROCEDURES For each horse, the pathology index (PI) for the SDFT of each thoracic limb was determined by use of acoustoelastography at 4 locations (5, 10, 15, and 20 cm distal to the accessory carpal bone). Horses were evaluated before and after they were sedated with a combination of detomidine hydrochloride (0.01 mg/kg, IV) and butorphanol tartrate (0.01 mg/kg, IV). A repeated-measures ANOVA was used for statistical analysis. RESULTS Overall, the PI was lower after sedation than before sedation. In addition, the PI was lower at more distal locations than at more proximal locations. There was not a significant effect of limb (left or right). Differences among individual horses accounted for the largest variance effect. CONCLUSIONS AND CLINICAL RELEVANCE Sedation with detomidine and butorphanol facilitated acoustoelastography; however, it decreased the SDFT PI in clinically normal horses and should be used consistently in prospective studies. Variance associated with each individual horse in the sample population had the greatest effect on the PI.

3D FSE Cube and VIPR-aTR 3.0 Tesla magnetic resonance imaging predicts canine cranial cruciate ligament structural properties.

Estimation of cranial cruciate ligament (CrCL) structural properties in client-owned dogs with incipient cruciate rupture would be advantageous. The objective of this study was to determine whether magnetic resonance imaging (MRI) measurement of normal CrCL volume in an ex-vivo canine model predicts structural properties. Stifles from eight dogs underwent 3.0 Tesla 3D MRI. CrCL volume and normalized median grayscale values were determined using 3D Fast Spin Echo (FSE) Cube and Vastly under-sampled Isotropic PRojection (VIPR)-alternative repetition time (aTR) sequences. Stifles were then mechanically tested. After joint laxity testing, CrCL structural properties were determined, including displacement at yield, yield load, load to failure, and stiffness. Yield load and load to failure (R(2)=0.56, P <0.01) were correlated with CrCL volume determined by VIPR-aTR. Yield load was also correlated with CrCL volume determined by 3D FSE Cube (R(2)=0.32, P <0.05). Structural properties were not related to median grayscale values. Joint laxity and CrCL stiffness were not related to MRI parameters, but displacement at yield load was related to CrCL volume for both sequences during testing (R(2)>0.57, P <0.005). In conclusion, 3D MRI offers a predictive method for estimating canine CrCL structural properties. 3D MRI may be useful for monitoring CrCL properties in clinical trials.

In Vivo Measures of Shear Wave Speed as a Predictor of Tendon Elasticity and Strength.

The purpose of this study was to assess the potential for ultrasound shear wave elastography (SWE) to measure tissue elasticity and ultimate stress in both intact and healing tendons. The lateral gastrocnemius (Achilles) tendons of 41 New Zealand white rabbits were surgically severed and repaired with growth factor coated sutures. SWE imaging was used to measure shear wave speed (SWS) in both the medial and lateral tendons pre-surgery, and at 2 and 4 wk post-surgery. Rabbits were euthanized at 4 wk, and both medial and lateral tendons underwent mechanical testing to failure. SWS significantly (p < 0.001) decreased an average of 17% between the intact and post-surgical state across all tendons. SWS was significantly (p < 0.001) correlated with both the tendon elastic modulus (r = 0.52) and ultimate stress (r = 0.58). Thus, ultrasound SWE is a potentially promising non-invasive technology for quantitatively assessing the mechanical integrity of pre-operative and post-operative tendons.

Biomechanical evaluation of a novel subcuticular skin stapling device for use in equine abdominal surgeries.

OBJECTIVE: To compare the in vitro biomechanical properties of a novel subcuticular stapling device to current methods of abdominal skin closure for equine abdominal surgery. STUDY DESIGN: In vitro randomized, matched design. SAMPLE POPULATION: Equine ventral median abdominal skin specimens (n = 24 horses). METHODS: Subcuticular absorbable staples (SAS), metallic staples (MS), polyglyconate suture (PG), and nylon monofilament (NYL) were applied to longitudinally transected portions of equine ventral midline skin. Loads that resulted in an initial failure point and the ultimate failure load and mechanism were recorded. RESULTS: Mean ± SD loads at initial failure for PG (86 N ± 64 N), NYL (81 N ± 142 N), and SAS (70 N ± 20 N) were not significantly different from each other. PG and SAS were significantly higher than MS (43 N ± 17 N; P < .05). Ultimate failure load for PG (563 N ± 157 N) and NYL (558 N ± 162 N) were significantly higher than either MS (175 N ± 44 N) or SAS (96 N ± 20N; P < .001). For the suture groups, nearly all failures occurred because of skin pull through whereas all SAS staples failed because of staple fracture. Failure patterns were mixed for MS. CONCLUSIONS: SAS had the lowest ultimate failure load; however, other measured variables identified characteristics of SAS that may be clinically beneficial.

Reproducibility and feasibility of acoustoelastography in the superficial digital flexor tendons of clinically normal horses.

OBJECTIVE: To evaluate the feasibility and repeatability of in vivo measurement of stiffness gradients by means of acoustoelastography in the superficial digital flexor tendons (SDFTs) of clinically normal horses. ANIMALS: 15 clinically normal horses. PROCEDURES: For each horse, stiffness gradient index and dispersion values for SDFTs in both forelimbs were evaluated in longitudinal orientation by use of acoustoelastography at 3 sites (5, 10, and 15 cm distal to the accessory carpal bone) by 2 observers; for each observer, data were acquired twice per site. The left forelimb was always scanned before the right forelimb. Lifting of the contralateral forelimb with the carpus flexed during image acquisition resulted in the required SDFT deformation in the evaluated limb. Interobserver repeatability, intraobserver repeatability, and right-to-left limb symmetry for stiffness gradient index and dispersion values were evaluated. RESULTS: Stiffness gradient index and dispersion values for SDFTs at different locations as well as effects of age or sex did not differ significantly among the 15 horses. Interclass correlation coefficients for interobserver repeatability, intraobserver repeatability, and limb symmetry revealed good to excellent agreement (intraclass correlation coefficients, > 0.74). CONCLUSIONS AND CLINICAL RELEVANCE: Results indicated that acoustoelastography is a feasible and repeatable technique for measuring stiffness gradients in SDFTs in clinically normal horses, and could potentially be used to compare healthy and diseased tendon states.