Clinically relevant doses of tiludronate do not affect bone remodelling in pasture-exercised horses.

BACKGROUND: Bisphosphonates are widely used in equine athletes to reduce lameness associated with skeletal disorders. Widespread off-label use has led to concern regarding potential negative effects on bone healing, but little evidence exists to support or refute this. OBJECTIVES: To investigate the influence of clinically relevant doses of tiludronate on bone remodelling and bone healing. STUDY DESIGN: Randomised, controlled in vivo experiments. METHODS: Each horse had a single tuber coxae biopsied (Day 0), then were divided into a treatment (IV tiludronate) or control (IV saline) group. Treatments were administered 30 and 90 days following initial biopsy. Biopsy of the tuber coxae was repeated on Day 60 to evaluate bone healing following a single treatment. Oxytetracycline was administered on Days 137 and 147 to label bone formation. The contralateral tuber coxae was biopsied on Day 150 to evaluate effects of repeated treatment. Bone biopsies were evaluated with micro-computed tomography and/or dynamic histomorphometry using standard techniques. RESULTS: Nineteen horses completed the study, with no complications following the biopsies and treatments. No significant differences in the trabecular bone parameters or bone formation rate were observed between treatment groups. MAIN LIMITATIONS: The use of a first-generation bisphosphonate may mean some effects of these drugs are underrepresented using this model. The results pertain to the tuber coxae and may not reflect injury or the healing response that occurs in long bones in training or racing. CONCLUSIONS: In this model, tiludronate did not affect normal bone remodelling in the horse, despite repeat dosages.

Pharmacokinetics and pharmacodynamics of clodronate disodium evaluated in plasma, synovial fluid and urine.

BACKGROUND: Clodronate is a non-nitrogenated bisphosphonate approved for use in horses. There are no peer-reviewed published reports describing the pharmacokinetics or evaluating renal health indices and urinary excretion patterns in conjunction with plasma and synovial fluid concentration following the systemic administration of clodronate to horses. OBJECTIVES: Describe clodronate concentrations in plasma, urine and synovial fluid and evaluate the effects on renal indices after intramuscular administration to healthy horses. STUDY DESIGN: Experimental study with repeated measures. METHODS: Six healthy adult horses received a single intramuscular dose of clodronate (1.8 mg/kg). Blood, synovial fluid and urine were collected prior to and after administration of clodronate up to 72, 48 and 168 hours respectively. Drug concentrations were measured using LC-MS/MS and noncompartmental pharmacokinetic analysis was performed. Renal function indices were also evaluated. RESULTS: Clodronate was quantifiable for up to 24 hours in plasma and 48 hours in synovial fluid and detected at all time points in urine. Maximum plasma concentration of clodronate 210 ± 68.2 ng/mL occurred at approximately 34.8 ± 0.2 minutes after administration, while peak synovial concentration (57.7 ± 32.8 ng/mL) occurred at 2.67 ± 2.32 hours after administration and peak urine concentration (88 358.2 ± 79 521.4 ng/mL) occurred at 2.67 ± 2.58 hours post administration. Terminal half-life in plasma was 3.32 ± 1.25 and was 4.8 ± 3.05 hours in synovial fluid. Creatinine concentrations rose significantly after treatment but remained within normal adult reference ranges at all times. MAIN LIMITATIONS: Limited number of animals and sampling times and the absence of urine collection for determination of concentration beyond 7 days. CONCLUSIONS: Clodronate is rapidly cleared from the blood and synovial fluid. It has variable and biphasic urinary excretion. While significant increase in blood creatinine concentrations was present after a single intramuscular dose of clodronate, values were never above the normal reference range. Further studies are warranted in horses undergoing exercise and those undergoing multiple dosing schemes.

Evaluation of peer teaching and deliberate practice to teach veterinary surgery.

OBJECTIVE: To assess the impact of peer teaching and deliberate practice on surgical skills acquisition and retention in first- and second-year veterinary students. STUDY DESIGN: Randomized, prospective, comparative study. SAMPLE POPULATION: Eighteen first-year and 25 second-year students from 1 college of veterinary medicine who had previously demonstrated proficiency in basic surgical skills. METHODS: Forty-three participants were divided into 3 groups: the test group (group A, n = 15), who participated in a structured peer-assisted learning program using deliberate practice; the time-practice control group (group B, n = 15), who participated in an unstructured peer-supported environment; and the assessment-only control group (group C, n = 13), who participated in the assessments. Participants performed a subcutaneous mass removal on a cadaver model and were assessed via a global rating system. Three assessment points were evaluated: pretraining, immediate posttraining, and retention. RESULTS: The number of participants who achieved acceptable or excellent grand total scores in group A increased after training. Among all participants, 22% in group A, 35% in group B, and 38% in group C did not achieve an acceptable total score at the retention assessment. CONCLUSION: The study population improved in skill level and retention through the use of standardized video and peer instruction with attention to effective learning strategies, particularly deliberate practice. CLINICAL SIGNIFICANCE: Use and enhancement of the format introduced in this study could augment veterinary surgical education.

Tiludronate and clodronate do not affect bone structure or remodeling kinetics over a 60 day randomized trial.

BACKGROUND: Tiludronate and clodronate are FDA-approved bisphosphonate drug therapies for navicular disease in horses. Although clinical studies have determined their ability to reduce lameness associated with skeletal disorders in horses, data regarding the effect on bone structure and remodeling is lacking. Additionally, due to off-label use of these drugs in young performance horses, effects on bone in young horses need to be investigated. Therefore, the purpose of this randomized, experimental pilot study was to determine the effect of tiludronate and clodronate on normal bone cells, structure and remodeling after 60 days in clinically normal, young horses. Additionally, the effect of clodronate on bone healing 60 days after an induced defect was investigated. RESULTS: All horses tolerated surgery well, with no post-surgery lameness and all acquired biopsies being adequate for analyses. Overall, tiludronate and clodronate did not significantly alter any bone structure or remodeling parameters, as evaluated by microCT and dynamic histomorphometry. Tiludronate did not extensively impact bone formation or resorption parameters as evaluated by static histomorphometry. Similarly, clodronate did not affect bone formation or resorption after 60 days. Sixty days post-defect, healing was minimally affected by clodronate. CONCLUSIONS: Tiludronate and clodronate do not appear to significantly impact bone tissue on a structural or cellular level using standard dose and administration schedules.

Assessment of tuber coxae bone biopsy in the standing horse.

OBJECTIVE: To describe a biopsy technique in standing horses with minimal morbidity that consistently provides a substantial bone biopsy with intact, undamaged architecture. STUDY DESIGN: Experimental, prospective study. ANIMALS: Ten Thoroughbred horses. METHODS: Biopsies were obtained from the tuber coxae of 10 sedated, standing horses using an oscillating saw. Bilateral biopsies, separated by 60 days, were evaluated with micro-computed tomography (microCT). The first biopsy was prepared for decalcified histology; the second for undecalcified histology. Both biopsies were evaluated qualitatively for histologic quality. RESULTS: The biopsy technique did not result in any significant complications, was well tolerated and all biopsies were of good histologic quality. CONCLUSION: Cortical and trabecular bone biopsies can be successfully collected from the tuber coxa using a simple technique that creates minimal morbidity and allows sequential samples to be collected. The biopsies were larger than those described previously, provided adequate bone for multiple histologic sections, and had intact, undamaged architecture on examination with microCT and light microscopy.

The management of equine acute laminitis.

Laminitis is an extremely painful condition resulting in damage to the soft tissues anchoring the third phalanx to the hoof, which can result in life-threatening debilitation. Specific therapy is not available. The most important principles of therapy include aggressive nutritional and medical management of primary disease processes, cryotherapy, anti-inflammatory therapy, pain management, and biomechanical support. This review focuses on the principles of evidenced-based therapies.

An in vitro biomechanical comparison of hydroxyapatite coated and uncoated ao cortical bone screws for a limited contact: dynamic compression plate fixation of osteotomized equine 3rd metacarpal bones.

OBJECTIVES: To compare the monotonic biomechanical properties of a broad 4.5 mm limited contact-dynamic compression plate (LC-DCP) fixation secured with hydroxyapatite (HA) coated cortical bone screws (HA-LC-DCP) versus uncoated cortical bone screws (AO-LC-DCP) to repair osteotomized equine 3rd metacarpal (MC3) bones. STUDY DESIGN: Experimental. SAMPLE POPULATION: Adult equine cadaveric MC3 bones (n = 12 pair). METHODS: Twelve pairs of equine MC3 were divided into 3 test groups (4 pairs each) for: (1) 4 point bending single cycle to failure testing; (2) 4 point bending cyclic fatigue testing; and (3) torsional single cycle to failure testing. For the HA-LC-DCP-MC3 construct, an 8-hole broad LC-DCP (Synthes Ltd, Paoli, PA) was secured on the dorsal surface of each randomly selected MC3 bone with a combination of four 5.5 mm and four 4.5 mm HA-coated cortical screws. For the AO-LC-DCP-MC3 construct, an 8-hole 4.5 mm broad LC-DCP was secured on the dorsal surface of the contralateral MC3 bone with a combination of four 5.5 mm and four 4.5 mm uncoated cortical screws. All MC3 bones had mid-diaphyseal osteotomies. Mean test variable values for each method were compared using a paired t-test within each group. Significance was set at P < .05. RESULTS: Mean yield load, yield bending moment, composite rigidity, failure load, and failure bending moment, under 4 point bending, single cycle to failure, of the HA-LC-DCP fixation were significantly greater than those of the AO-LC-DCP fixation. Mean ± SD values for the HA-LC-DCP and the AO-LC-DCP fixation techniques, respectively, in single cycle to failure under 4 point bending were: yield load, 26.7 ± 2.15 and 16.3 ± 1.38 kN; yield bending moment, 527.4 ± 42.4 and 322.9 ± 27.2 N-m; composite rigidity, 5306 ± 399 and 3003 ± 300 N-m/rad; failure load, 40.6 ± 3.94 and 26.5 ± 2.52 kN; and failure bending moment, 801.9 ± 77.9 and 522.9 ± 52.2 N-m. Mean cycles to failure in 4 point bending of the HA-LC-DCP fixation (116,274 ± 13,211) was significantly greater than that of the AO-LC-DCP fixation 47,619 ± 6580. Mean yield load, mean composite rigidity, and mean failure load under torsional testing, single cycle to failure was significantly greater for the broad HA-LC-DCP fixation compared with the AO-LC-DCP fixation. In single cycle to failure under torsion, mean ± SD values for the HA-LC-DCP and the AO-LC-DCP fixation techniques, respectively, were: yield load, 101.3 ± 14.68 and 70.54 ± 10.20 N-m; composite rigidity, 437.9 ± 32.9 and 220.7 ± 17.6 N-m/rad; and failure load: 105.7 ± 15.5 and 75.28 ± 10.1 N-m. CONCLUSION: HA-LC-DCP was superior to AO-LC-DCP in resisting the static overload forces (palmarodorsal 4 point bending and torsional) and in resisting cyclic fatigue under palmarodorsal 4 point bending.

In vitro biomechanical comparison of dynamic compression plates with a rough contact surface and a polished contact surface for fixation of osteotomized equine third metacarpal bones.

OBJECTIVES: To compare the number of cycles to failure of 4.5 mm broad dynamic compression plates (DCP), 4.5 mm broad limited-contact dynamic compression plates (4.5-LC-DCP), and 5.5 mm broad limited-contact dynamic compression plates (5.5-LC-DCP) having a rough (denoted by a prefix R-) versus a standard smooth contact surface for the fixation of osteotomized equine 3rd metacarpal (MC3) bones. STUDY DESIGN: Experimental. ANIMAL POPULATION: Fifteen pairs of adult equine cadaveric MC3 bones. METHODS: Fifteen pairs of equine MC3 were divided into 3 test groups (5 pairs each) for comparison of (1) R-DCP fixation with DCP fixation, (2) R-4.5-LC-DCP fixation with 4.5-LC-DCP fixation, and (3) R-5.5-LC-DCP fixation with 5.5-LC-DCP fixation to repair osteotomized equine MC3 bones under palmarodorsal 4-point bending cyclic fatigue testing. For each group an 8-hole plate with rough contact surface was applied to the dorsal surface of one randomly selected bone from each pair and a corresponding 8-hole plate with smooth contact surface was applied dorsally to the contralateral bone from each pair. All plates and screws were applied using standard ASIF techniques. All MC3 bones had mid-diaphyseal osteotomies. Mean number of cycles to failure for each method were compared using a paired t-test within each group. Significance was set at P < .05. RESULTS: Mean cycles to failure ± standard deviation was significantly greater for the R-DCP fixation (230,025 ± 23,129) compared with the DCP fixation (103,451 ± 14,556), for the R-4.5-LC-DCP fixation (99,237 ± 14,390) compared with the 4.5-LC-DCP fixation (46,464 ± 6325) and for the R-5.5-LC-DCP fixation (65,113 ± 7796) compared with the 5.5-LC-DCP fixation (34,224 ± 3835). CONCLUSION: For the fixation of osteotomized MC3 bones, the constructs with plates having rough contact surface were superior to the corresponding constructs with plates having standard smooth contact surfaces in resisting cyclic fatigue under palmarodorsal 4-point bending.

A mechanical comparison of equine proximal interphalangeal joint arthrodesis techniques: an axial locking compression plate and two abaxial transarticular cortical screws versus an axial dynamic compression plate and two abaxial transarticular cortical screws.

OBJECTIVES: To compare in vitro monotonic biomechanical properties of an axial 3-hole, 4.5 mm narrow locking compression plate (ELCP) using 5.0 mm locking screws and 5.5 mm cortical screws in conjunction with 2 abaxial transarticular 5.5 mm cortical screws inserted in lag fashion (ELCP-TLS) with an axial 3-hole, 4.5 mm narrow dynamic compression plate (DCP) using 5.5 mm cortical screws in conjunction with 2 abaxial transarticular 5.5 mm cortical screws inserted in lag fashion (DCP-TLS) for equine proximal interphalangeal (PIP) joint arthrodesis. DESIGN: Experimental. ANIMAL POPULATION: Cadaveric adult equine forelimbs (n = 18 pairs). METHODS: For each forelimb pair, 1 PIP joint was stabilized with an axial ELCP using 5.0 mm locking screws and 5.5 mm cortical screws in conjunction with 2 abaxial transarticular 5.5 mm cortical screws inserted in lag fashion and 1 PIP joint with an axial 3-hole narrow DCP (4.5 mm) using 5.5 mm cortical screws in conjunction with 2 abaxial transarticular 5.5 mm cortical screws inserted in lag fashion. Six matching pairs of constructs were tested in single cycle to failure under axial compression, 6 construct pairs were tested for cyclic fatigue under axial compression, and 6 construct pairs were tested in single cycle to failure under torsional loading. Mean values for each fixation method were compared using a paired t-test within each group with statistical significance set at P < .05. RESULTS: Mean yield load, yield stiffness, and failure load under axial compression, single cycle to failure, of the DCP-TLS fixation were significantly greater than those of the LCP-TLS fixation. There was no significant difference between the mean number of cycles to failure in axial compression of the LCP-TLS and the DCP-TLS fixations. Mean yield load, yield stiffness, and failure load under torsion, single cycle to failure, of the LCP-TLS fixation were significantly greater than those of the DCP-TLS fixation. CONCLUSION: The DCP-TLS construct provided significantly greater stability under axial compression in single cycle to failure than the ELCP-TLS construct, the ELCP-TLS construct provided significantly greater stability under torsional loading in single cycle to failure than the DCP-TLS construct, and there was no significant difference in stability between the 2 constructs for cyclic loading under axial compression.

An in vitro biomechanical comparison of equine proximal interphalangeal joint arthrodesis techniques: two parallel transarticular headless tapered variable pitch screws versus two parallel transarticular AO cortical bone screws inserted in lag fashion.

OBJECTIVES: To compare the mean number of cycles to failure under axial compression of equine proximal interphalangeal (PIP) joint arthrodesis constructs created by 2 parallel transarticular Acutrak Plus screws (AP-TS) or 2 parallel transarticular 5.5 mm cortical screws inserted in lag fashion (AO-TLS). STUDY DESIGN: Paired in vitro biomechanical testing of 2 methods of stabilizing cadaveric adult equine forelimb PIP joints. SAMPLE POPULATION: Cadaveric adult equine forelimbs (n=5 pairs). METHODS: For each forelimb pair, 1 PIP joint was stabilized with AP-TS and 1 with AP-TLS. The 5 construct pairs were tested for cyclic fatigue under axial compression. Mean number of cycles to failure for each fixation method were compared by a paired t-test within each group with statistical significance set at P<.05. RESULTS: The mean number of cycles to failure under axial compression for AO-TLS fixation and AP-TS fixation were 57,723±8488 and 35,322±4698, respectively. CONCLUSION: The AO-TLS was superior to the AP-TS in resisting cyclic fatigue under axial compression.

In vitro biomechanical comparison of a modified 5.5 mm locking compression plate fixation with a 5.5 mm locking compression plate fixation of osteotomized equine third metacarpal bones.

OBJECTIVES: To compare number of cycles to failure for palmarodorsal 4-point bending of a modified 5.5 mm broad locking compression plate (M5.5-LCP) fixation with a 5.5 mm broad LCP (5.5-LCP) fixation used to repair osteotomized equine third metacarpal (MC3) bones. STUDY DESIGN: In vitro biomechanical testing. ANIMAL POPULATION: Adult equine cadaveric MC3 bones (n=6 pairs). METHODS: An 8-hole, M5.5-LCP, obtained by having a 1.0 mm thickness removed from the bone contact portion of the 5.5-LCP, was applied to the dorsal surface of 1 randomly selected MC3 from each pair, and an 8-hole, 5.5-LCP was applied dorsally to the contralateral bone from each pair using a combination of cortical and locking screws. Plates and screws were applied using standard ASIF techniques to MC3 bones with a mid-diaphyseal osteotomy. MC3 constructs had palmarodorsal 4-point bending cyclic fatigue testing. Mean cycles to failure for each method were compared using a paired t-test within each group. Significance was set at P<.05. RESULTS: Mean±SD cycles to failure of the M5.5-LCP fixation (188,641±17,971) was significantly greater than that of the 5.5-LCP fixation (166,497±15,539). CONCLUSION: M5.5-LCP fixation was superior to 5.5-LCP fixation of osteotomized equine MC3 bones in resisting cyclic fatigue under palmarodorsal 4-point bending. CLINICAL RELEVANCE: This suggests that biological plate fixation is not the ideal choice for osteotomized equine MC3 bones.

An in vitro biomechanical comparison of a 5.5 mm locking compression plate fixation with a 4.5 mm locking compression plate fixation of osteotomized equine third metacarpal bones.

OBJECTIVES: To compare the monotonic biomechanical properties and fatigue life of a 5.5-mm-broad locking compression plate (5.5 LCP) fixation with a 4.5-mm-broad locking compression plate (4.5 LCP) fixation to repair osteotomized equine 3rd metacarpal (MC3) bones. STUDY DESIGN: In vitro biomechanical testing of paired cadaveric equine MC3 with a middiaphyseal osteotomy, stabilized by 1 of 2 methods for fracture fixation. ANIMAL POPULATION: Fifteen pairs of adult equine cadaveric MC3 bones. METHODS: Fifteen pairs of equine MC3 were divided into 3 test groups (5 pairs each) for (1) 4-point bending single cycle to failure testing, (2) 4-point bending cyclic fatigue testing, and (3) torsional single cycle to failure testing. An 8-hole, 5.5 LCP was applied to the dorsal surface of 1 randomly selected bone from each pair and an 8-hole, 4.5 LCP was applied dorsally to the contralateral bone from each pair using a combination of cortical and locking screws. All plates and screws were applied using standard ASIF techniques. All MC3 bones had middiaphyseal osteotomies. Mean test variable values for each method were compared using a paired t-test within each group with significance set at P<.05. RESULTS: Mean yield load, yield bending moment, composite rigidity, failure load, and failure bending moment, under 4-point bending, single cycle to failure, of the 5.5 LCP fixation were significantly greater than those of the 4.5 LCP fixation. Mean cycles to failure in 4-point bending of the 5.5 LCP fixation (170,535+/-19,166) was significantly greater than that of the 4.5 LCP fixation (129,629+/-14,054). Mean yield load, mean composite rigidity, and mean failure load under torsional testing, single cycle to failure was significantly greater for the broad 5.5 LCP fixation compared with the 4.5 LCP fixation. In single cycle to failure under torsion, the mean+/-SD values for the 5.5 LCP and the 4.5 LCP fixation techniques, respectively, were: yield load, 151.4+/-19.6 and 97.6+/-12.1 N m; composite rigidity, 790.3+/-58.1 and 412.3+/-28.1 N m/rad; and failure load: 162.1+/-20.2 and 117.9+/-14.6 N m. CONCLUSION: The 5.5 LCP was superior to the 4.5 LCP in resisting static overload forces (palmarodorsal 4-point bending and torsional) and in resisting cyclic fatigue under palmarodorsal 4-point bending. CLINICAL RELEVANCE: These in vitro study results may provide information to aid in selection of an LCP for repair of equine long bone fractures.

Compressive forces achieved in simulated equine third metacarpal bone lateral condylar fractures of varying fragment thickness with Acutrak Plus screw and 4.5 mm AO cortical screws.

OBJECTIVES: To compare compression pressure (CP) of 6.5 mm Acutrak Plus (AP) and 4.5 mm AO cortical screws (AO) when inserted in simulated lateral condylar fractures of equine 3rd metacarpal (MC3) bones. STUDY DESIGN: Paired in vitro biomechanical testing. SAMPLE POPULATION: Cadaveric equine MC3 bones (n=12 pair). METHODS: Complete lateral condylar osteotomies were created parallel to the midsagittal ridge at 20, 12, and 8 mm axial to the epicondylar fossa on different specimens grouped accordingly. Interfragmentary compression was measured using a pressure sensor placed in the fracture plane before screw placement for fracture fixation. CP was acquired and mean values of CP for each fixation method were compared between the 6.5 mm (AP) and 4.5 mm (AO) for each group using a paired t-test within each fracture fragment thickness group with statistical significance set at P<.05. RESULTS: AO screw configurations generated significantly greater compressive pressure compared with AP configurations. The ratio of mean CP for AP screws to AO screws at 20, 12, and 8 mm, were 21.6%, 26.2%, and 34.2%, respectively. CONCLUSION: Mean CP for AP screw fixations are weaker than those for AO screw fixations, most notably with the 20 mm fragments. The 12 and 8 mm groups have comparatively better compression characteristics than the 20 mm group; however, they are still significantly weaker than AO fixations. CLINICAL RELEVANCE: Given that the primary goals of surgical repair are to achieve rigid fixation, primary bone healing, and good articular alignment, based on these results, it is recommended that caution should be used when choosing the AP screw for repair of lateral condylar fractures, especially complete fractures. Because interfragmentary compression plays a factor in the overall stability of a repair, it is recommended for use only in patients with thin lateral condyle fracture fragments, as the compression tends to decrease with an increase in thickness.

An in vitro biomechanical comparison of equine proximal interphalangeal joint arthrodesis techniques: an axial positioned dynamic compression plate and two abaxial transarticular cortical screws inserted in lag fashion versus three parallel transarticular cortical screws inserted in lag fashion.

OBJECTIVES: To compare in vitro monotonic biomechanical properties of an axial 3-hole, 4.5 mm narrow dynamic compression plate (DCP) using 5.5 mm cortical screws in conjunction with 2 abaxial transarticular 5.5 mm cortical screws inserted in lag fashion (DCP-TLS) with 3 parallel transarticular 5.5 mm cortical screws inserted in lag fashion (3-TLS) for the equine proximal interphalangeal (PIP) joint arthrodesis. STUDY DESIGN: Paired in vitro biomechanical testing of 2 methods of stabilizing cadaveric adult equine forelimb PIP joints. SAMPLE POPULATION: Cadaveric adult equine forelimbs (n=15 pairs). METHODS: For each forelimb pair, 1 PIP joint was stabilized with an axial 3-hole narrow DCP (4.5 mm) using 5.5 mm cortical screws in conjunction with 2 abaxial transarticular 5.5 mm cortical screws inserted in lag fashion and 1 with 3 parallel transarticular 5.5 mm cortical screws inserted in lag fashion. Five matching pairs of constructs were tested in single cycle to failure under axial compression, 5 construct pairs were tested for cyclic fatigue under axial compression, and 5 construct pairs were tested in single cycle to failure under torsional loading. Mean values for each fixation method were compared using a paired t-test within each group with statistical significance set at P<.05. RESULTS: Mean yield load, yield stiffness, and failure load under axial compression and torsion, single cycle to failure, of the DCP-TLS fixation were significantly greater than those of the 3-TLS fixation. Mean cycles to failure in axial compression of the DCP-TLS fixation was significantly greater than that of the 3-TLS fixation. CONCLUSION: The DCP-TLS was superior to the 3-TLS in resisting the static overload forces and in resisting cyclic fatigue. CLINICAL RELEVANCE: The results of this in vitro study may provide information to aid in the selection of a treatment modality for arthrodesis of the equine PIP joint.

Distal interphalangeal joint arthrodesis in seven cattle using the Acutrak Plus screw.

OBJECTIVES: To report a technique for arthrodesis of the distal interphalangeal joint (DIPJ) with two 6.5 mm Acutrak Plus (AP) compression screws from a solar approach and outcome in 7 cattle. STUDY DESIGN: Case series. ANIMALS: Cattle (n=7) with DIPJ arthritis. METHODS: Retrieved data from medical records of cattle that had undergone DIPJ arthrodesis using 2 AP screws via a solar approach were signalment, history, clinical signs, preoperative blood work, preoperative radiographs, complications, postoperative radiographs, and postoperative lameness evaluation. Outcomes, assessed by owner interview 6-26 months after surgery, were classified as excellent, good, or poor. RESULTS: Fusion of the DIPJ was evident by 6 months. All cattle returned to full function with minimal lameness and normal appearance to the distal aspect of the limb. Four thoracic limbs and 3 pelvic limbs were affected; 3 medial and 4 lateral claws. Complications included moderate lameness associated with implants (n=2) that resolved after screw removal. CLINICAL RELEVANCE: Use of the AP screw system in cattle is an excellent option for DIPJ arthrodesis with minimal postoperative morbidity and excellent return to function.

In vitro biomechanical comparison of locking compression plate fixation and limited-contact dynamic compression plate fixation of osteotomized equine third metacarpal bones.

OBJECTIVE: To compare monotonic biomechanical properties and fatigue life of a broad locking compression plate (LCP) fixation with a broad limited contact dynamic compression plate (LC-DCP) fixation to repair osteotomized equine third metacarpal (MC3) bones. STUDY DESIGN: In vitro biomechanical testing of paired cadaveric equine MC3 with a mid-diaphyseal osteotomy, stabilized by 1 of 2 methods for fracture fixation. ANIMAL POPULATION: Cadaveric adult equine MC3 bones (n=12 pairs). METHODS: MC3 were divided into 3 groups (4 pairs each) for: (1) 4-point bending single cycle to failure testing; (2) 4-point bending cyclic fatigue testing; and (3) torsional single cycle to failure testing. The 8-hole, 4.5 mm LCP was applied to the dorsal surface of 1 randomly selected bone from each pair. One 8-hole, 4.5 mm LC-DCP) was applied dorsally to the contralateral bone from each pair. All plates and screws were applied using standard ASIF techniques. All MC3 bones had mid-diaphyseal osteotomies. Mean test variable values for each method were compared using a paired t-test within each group. Significance was set at P<.05. RESULTS: Mean yield load, yield bending moment, composite rigidity, failure load and failure bending moment, under 4-point bending, single cycle to failure, of the LCP fixation were significantly greater than those of the LC-DCP fixation. Mean cycles to failure for 4-point bending was significantly greater for the LCP fixation compared with LC-DCP fixation. Mean yield load, mean composite rigidity, and mean failure load under torsional testing, single cycle to failure was significantly greater for the broad LCP fixation compared with the LC-DCP fixation. CONCLUSION: The 4.5 mm LCP was superior to the 4.5 mm LC-DCP in resisting the static overload forces (palmarodorsal 4-point bending and torsional) and in resisting cyclic fatigue under palmarodorsal 4-point bending. CLINICAL RELEVANCE: The results of this in vitro study may provide information to aid in the selection of a biological plate for the repair of equine long bone fractures.

An in vitro biomechanical comparison of a 5.5 mm limited-contact dynamic compression plate fixation with a 4.5 mm limited-contact dynamic compression plate fixation of osteotomized equine third metacarpal bones.

OBJECTIVES: To compare monotonic biomechanical properties and fatigue life of a 5.5 mm broad limited-contact dynamic compression plate (5.5-LC-DCP) fixation with a 4.5 mm broad LC-DCP (4.5-LC-DCP) fixation to repair osteotomized equine third metacarpal (MC3) bones. STUDY DESIGN: In vitro biomechanical testing of paired cadaveric equine MC3 with a mid-diaphyseal osteotomy, stabilized by 1 of 2 methods for fracture fixation. SAMPLE POPULATION: Adult equine cadaveric MC3 bones (n=18 pair). METHODS: MC3 were divided into 3 test groups (6 pairs each) for: (1) 4-point bending single cycle to failure testing; (2) 4-point bending cyclic fatigue testing; and (3) torsional single cycle to failure testing. The 8-hole, 5.5 mm broad LC-DCP (5.5-LC-DCP) was applied to the dorsal surface of 1 randomly selected bone from each pair. One 8-hole, 4.5 mm broad LC-DCP (4.5-LC-DCP) was applied dorsally to the contralateral bone from each pair. Plates and screws were applied using standard ASIF techniques. All MC3 bones had mid-diaphyseal osteotomies. Mean test variable values for each method were compared using a paired t-test within each group. Significance was set at P<.05. RESULTS: Mean yield load, yield bending moment, composite rigidity, failure load and failure bending moment under 4-point bending, single cycle to failure, of the 5.5-LC-DCP fixation were significantly greater (P<.024) than those of the 4.5-LC-DCP fixation. Mean cycles to failure for 4-point bending was significantly (P<.05) greater for the 4.5-LC-DCP fixation compared with the 5.5-LC-DCP fixation. Mean yield load, mean composite rigidity, and mean failure load in torsion for the 5.5-LC-DCP fixation was not significantly different (P>.05) than those with the 4.5-LC-DCP fixation. CONCLUSION: 5.5-LC-DCP fixation was superior to 4.5-LC-DCP fixation in resisting the static overload forces under palmarodorsal 4-point bending. There was no significant difference between 5.5-LC-DCP fixation and 4.5-LC-DCP fixation in resisting static overload forces under torsion; however, the 5.5-LC-DCP offers significantly less stability (80% of that of the 4.5-LC-DCP) in cyclic fatigue testing. CLINICAL RELEVANCE: The results of this in vitro study may provide information to aid in the selection of a biological plate for long bone fracture repair in horses.

In vitro biomechanical comparison of equine proximal interphalangeal joint arthrodesis techniques: prototype equine spoon plate versus axially positioned dynamic compression plate and two abaxial transarticular cortical screws inserted in lag fashion.

OBJECTIVES: To compare in vitro monotonic biomechanical properties of an equine spoon plate (ESP) with an axial 3-hole, 4.5 mm narrow dynamic compression plate (DCP) using 5.5 mm cortical screws in conjunction with 2 abaxial transarticular 5.5 mm cortical screws (DCP-TLS) inserted in lag fashion for equine proximal interphalangeal (PIP) joint arthrodesis. STUDY DESIGN: Paired in vitro biomechanical testing of 2 methods of stabilizing cadaveric adult equine forelimb PIP joints. ANIMAL POPULATION: Cadaveric adult equine forelimbs (n=18 pairs). METHODS: For each forelimb pair, 1 PIP joint was stabilized with an ESP (8 hole, 4.5 mm) and 1 with an axial 3-hole narrow DCP (4.5 mm) using 5.5 mm cortical screws in conjunction with 2 abaxial transarticular 5.5 mm cortical screws inserted in lag fashion. Six matching pairs of constructs were tested in single cycle to failure under axial compression with load applied under displacement control at a constant rate of 5 cm/s. Six construct pairs were tested for cyclic fatigue under axial compression with cyclic load (0-7.5 kN) applied at 6 Hz; cycles to failure were recorded. Six construct pairs were tested in single cycle to failure under torsional loading applied at a constant displacement rate (0.17 radians/s) until rotation of 0.87 radians occurred. Mean values for each fixation method were compared using a paired t-test within each group with statistical significance set at P<.05. RESULTS: Mean yield load, yield stiffness, and failure load for ESP fixation were significantly greater (for axial compression and torsion) than for DCP-TLS fixation. Mean (+/- SD) values for the ESP and DCP-TLS fixation techniques, respectively, in single cycle to failure under axial compression were: yield load 123.9 +/- 8.96 and 28.5 +/- 3.32 kN; stiffness, 13.11 +/- 0.242 and 2.60 +/- 0.17 kN/cm; and failure load, 144.4 +/- 13.6 and 31.4 +/- 3.8 kN. In single cycle to failure under torsion, mean (+/- SD) values for ESP and DCP-TLS, respectively, were: stiffness 2,022 +/- 26.2 and 107.9 +/- 11.1 N m/rad; and failure load: 256.4 +/- 39.2 and 87.1 +/- 11.5 N m. Mean cycles to failure in axial compression of ESP fixation (622,529 +/- 65,468) was significantly greater than DCP-TLS (95,418 +/- 11,037). CONCLUSION: ESP was superior to an axial 3-hole narrow DCP with 2 abaxial transarticular screws inserted in lag fashion in resisting static overload forces and cyclic fatigue. CLINICAL RELEVANCE: In vitro results support further evaluation of ESP for PIP joint arthrodesis in horses. Its specific design may provide increased stability without need for external coaptation support.

Evaluation of gastrointestinal activity patterns in healthy horses using B mode and Doppler ultrasonography.

Healthy adult horses were examined by using transabdominal ultrasonography to quantitatively and qualitatively evaluate activity of the jejunum, cecum, and colon with B mode and Doppler techniques. Doppler ultrasound was used to assess jejunal peristaltic activity. Examinations were performed on multiple occasions under imposed colic evaluation conditions, including fasting, nasogastric intubation, and xylazine sedation. In fasted horses, jejunal visibility was increased and jejunal, cecal, and colonic activity was decreased. The stomach was displaced ventrally and was visualized ventral to the costochondral junction. Xylazine sedation in fed horses had minimal effects; however, in fasted horses, xylazine significantly decreased jejunal and cecal activity. Nasogastric intubation in fasted horses had no observable effects on activity, but moved the stomach dorsally. B mode and Doppler jejunal activity were strongly correlated. Prior feeding and sedation status need to be considered when interpreting the results of equine abdominal ultrasound examinations. Doppler techniques may be useful for assessing jejunal activity.