Sabrina H. Brounts

Detection of Articular Pathology of the Distal Aspect of the Third Metacarpal Bone in Thoroughbred Racehorses: Comparison of Radiography, Computed Tomography and Magnetic Resonance Imaging

OBJECTIVE To compare digital radiography (DR), computed tomography (CT), and magnetic resonance imaging (MRI) for detection of pathology of the distal aspect of the third metacarpal bone (MC3) and to assess whether arthrography would improve detection of articular cartilage or subchondral bone cracking. STUDY DESIGN Cross-sectional study. SAMPLE POPULATION Limb specimens from 17 Thoroughbred horses after catastrophic injury and 4 age-matched control horses. METHODS Standard DR, CT, and MRI images of the metacarpophalangeal joint were acquired before and after iohexol injection. Pathologic features detected with imaging and on visual inspection of cartilage and subchondral bone of the distal aspect of MC3 were graded. Imaging observations were compared with pathologic abnormalities. RESULTS Inspection revealed obvious changes in the cartilage and subchondral bone surfaces in Thoroughbreds. Both CT and MRI were superior to DR for detection of subchondral bone pathology. Cracking of cartilage was not detected by any imaging modality. Signal changes associated with cartilage loss and development of repair tissue were evident on MRI in 9/19 cases. There was significant correlation (P < .05) between subchondral bone pathology detected on both CT and MRI, and cartilage pathology on gross examination. Contrast arthrography did not improve the detection of articular cartilage or subchondral plate cracking. CONCLUSION Both CT and MRI are superior to DR for detection of subchondral bone pathology, but underestimate the extent of joint adaptation and pathologic damage. MRI was able to detect cartilage degeneration.

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.

High affinity binding of an engineered, modular peptide to bone tissue.

Bone grafting procedures have become common due in part to a global trend of population aging. Native bone graft is a popular choice when compared to various synthetic bone graft substitutes, owing to superior biological activity. Nonetheless, the insufficient ability of bone allograft to induce new bone formation and the insufficient remodeling of native bone grafts call for osteoinductive factors during bone repair, exemplified by recombinant human bone morphogenetic protein 2 (rhBMP2). We previously developed a modular bone morphogenetic peptide (mBMP) to address complications associated with the clinical use of rhBMP2 as a bone graft substitute. The mBMP is designed to strongly bind to hydroxyapatite, the main inorganic component of bone and teeth, and to provide pro-osteogenic properties analogous to rhBMP2. Our previous in vivo animal studies showed that mBMP bound to hydroxyapatite-coated orthopedic implants with high affinity and stimulated new bone formation. In this study, we demonstrate specific binding of mBMP to native bone grafts. The results show that mBMP binds with high affinity to both cortical and trabecular bones, and that the binding is dependent on the mBMP concentration and incubation time. Importantly, efficient mBMP binding is also achieved in an ex vivo bone bioreactor where bone tissue is maintained viable for several weeks. In addition, mBMP binding can be localized with spatial control on native bone tissue via simple methods, such as dip-coating, spotting, and direct writing. Taken together with the pro-osteogenic activity of mBMP established in previous bone repair models, these results suggest that mBMP may promote bone healing when coated on native bone grafts in a clinically compatible manner.

Gene profiling of the rat medial collateral ligament during early healing using microarray analysis

Ligament heals in a synchronized and complex series of events. The remodeling process may last months or years. Experimental evidence suggests the damaged ligament does not recover its normal functional properties. Specific mechanisms to prevent scar formation and to regenerate the original mechanical function remain elusive but likely involve regulation of creeping substitution. Creeping substitution creates a larger hypercellular, hypervascular, and disorganized granulation tissue mass that results in an inefficient and nonregenerative wound healing process for the ligament. Control of creeping substitution may limit the extent of this tissue compromise and reduce the time necessary for healing. The objective of this study is to better understand the mechanism behind scar formation by identifying the extracellular matrix factors and other unique genes of interest differentially expressed during rat ligament healing via microarray. For this study, rat medial collateral ligaments were either surgically transected or left intact. Ligaments were collected at day 3 or 7 postinjury and used for microarray, quantitative PCR, and/or immunohistochemistry. Results were compared with the normal intact ligament. We demonstrate that early ligament healing is characterized by the modulation of several inflammatory and extracellular matrix factors during the first week of injury. Specifically, a number of matrix metalloproteinases and collagens are differentially and significantly expressed during early ligament healing. Additionally, we demonstrate the modulation of three novel genes, periostin, collagen-triple helix repeat containing-1, and serine protease 35 in our ligament healing model. Together, control of granulation tissue creeping substitution and subsequent downstream scar formation is likely to involve these factors.

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.

Comparison of fixation methods for treatment of long bone fractures in llamas and alpacas.

OBJECTIVE To determine outcome after repair of long bone fractures in llamas and alpacas. STUDY DESIGN Case series. ANIMALS Llamas (n=11) and alpacas (8). METHODS Medical records (1998-2008) of camelids with long bone fractures were reviewed for history, repair method, and complications. Outcome was also assessed by owner telephone questionnaire. RESULTS Mean age at repair was 39 months. There were 8 males and 11 females. Fracture distribution was tibia (n=6), metatarsus (5), metacarpus (4), radius and ulna (2), humerus (1), and femur (1), with 13 closed and 6 open fractures. Fracture repair was by internal fixation (n=11), external fixation with a transfixation pin cast (5), external coaptation (2), and cross-pinning (1). In 1 llama, the limb was amputated to revise a failed external fixation repair. Seventeen animals (89%) were discharged, and 2 were euthanatized. Outcome was available for 13 animals: 9 were used for breeding and 4 as pets. Fewer major complications occurred with internal fixation than with external fixation with a transfixation pin cast (P<.005); however, there were no significant differences in minor complications between groups. CONCLUSIONS Internal fixation with bone plates was associated with fewer major complications than external fixation with a transfixation pin cast.

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.

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.

A less invasive technique for spaying pet pigs.

OBJECTIVES To determine if ovariectomy (OVE) by electrothermal bipolar vessel sealing (EBVS) is a safe alternative to ovariohysterectomy (OVH) by hand-tied ligatures as a method of spaying in pigs. STUDY DESIGN Retrospective case series. ANIMALS Intact female pigs (n = 14). METHODS Medical records (2001-2010) of pigs admitted for sterilization were reviewed for signalment, surgical technique, intra- and postoperative complications, length of hospitalization, and outcome. Long-term follow-up was obtained by owner questionnaire. RESULTS Mean ± SD age and mean weight was 131 ± 86 days and 13.0 ± 6.2 kg, respectively. There were 5 OVH pigs and 9 OVE pigs; age and weight were not significantly different between groups. When comparing OVE to OVH, mean incisional length was less (12 ± 6 cm OVE; 22 ± 6 cm OVH; P < .01) and surgical time was short (50 ± 9 min OVE; 103 ± 15 min OVH; P < .01). Intraoperative hemorrhage occurred in 1 OVH pig. Postoperative complications included hemorrhage (n = 1), fever (3), hypothermia (2), surgical site infection (1), and inappetence (3). Return to normal behavior and appetite was significantly shorter for OVE pigs (1.10 ± 0.93 days; 4.30 ± 0.94 days OVH; P < .01). After a mean follow-up of 36 months, no difference between groups could be observed. CONCLUSION OVE using EBVS is a faster surgical technique with less perioperative complications when compared to OVH with ligatures. OVE can potentially replace OVH as a spaying method in pigs.Objectives To determine if ovariectomy (OVE) by electrothermal bipolar vessel sealing (EBVS) is a safe alternative to ovariohysterectomy (OVH) by hand-tied ligatures as a method of spaying in pigs. Study Design Retrospective case series. Animals Intact female pigs (n = 14). Methods Medical records (2001–2010) of pigs admitted for sterilization were reviewed for signalment, surgical technique, intra- and postoperative complications, length of hospitalization, and outcome. Long-term follow-up was obtained by owner questionnaire. Results Mean ± SD age and mean weight was 131 ± 86 days and 13.0 ± 6.2 kg, respectively. There were 5 OVH pigs and 9 OVE pigs; age and weight were not significantly different between groups. When comparing OVE to OVH, mean incisional length was less (12 ± 6 cm OVE; 22 ± 6 cm OVH; P < .01) and surgical time was short (50 ± 9 min OVE; 103 ± 15 min OVH; P < .01). Intraoperative hemorrhage occurred in 1 OVH pig. Postoperative complications included hemorrhage (n = 1), fever (3), hypothermia (2), surgical site infection (1), and inappetence (3). Return to normal behavior and appetite was significantly shorter for OVE pigs (1.10 ± 0.93 days; 4.30 ± 0.94 days OVH; P < .01). After a mean follow-up of 36 months, no difference between groups could be observed. Conclusion OVE using EBVS is a faster surgical technique with less perioperative complications when compared to OVH with ligatures. OVE can potentially replace OVH as a spaying method in pigs.

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.