Timothy B. Lescun

Applications of a New Handheld Reference Point Indentation Instrument Measuring Bone Material Strength

A novel, hand-held Reference Point Indentation (RPI) instrument, measures how well the bone of living patients and large animals resists indentation. The results presented here are reported in terms of Bone Material Strength, which is a normalized measure of how well the bone resists indentation, and is inversely related to the indentation distance into the bone. We present examples of the instruments use in: (1) laboratory experiments on bone, including experiments through a layer of soft tissue, (2) three human clinical trials, two ongoing in Barcelona and at the Mayo Clinic, and one completed in Portland, OR, and (3) two ongoing horse clinical trials, one at Purdue University and another at Alamo Pintado Stables in California. The instrument is capable of measuring consistent values when testing through soft tissue such as skin and periosteum, and does so handheld, an improvement over previous Reference Point Indentation instruments. Measurements conducted on horses showed reproducible results when testing the horse through tissue or on bare bone. In the human clinical trials, reasonable and consistent values were obtained, suggesting the Osteoprobe® is capable of measuring Bone Material Strength in vivo, but larger studies are needed to determine the efficacy of the instruments use in medical diagnosis.

Comparison of transvaginal natural orifice transluminal endoscopic surgery (NOTES®) and laparoscopy for elective bilateral ovariectomy in standing mares.

OBJECTIVE To compare surgical trauma, perioperative pain, surgical time, and complication rate in mares undergoing standing bilateral ovariectomy by natural orifice transluminal endoscopic surgery (NOTES) or laparoscopy. STUDY DESIGN Experimental study. ANIMALS Healthy mares (n = 12). METHODS Ovariectomy was performed with a vessel-sealing device by transvaginal NOTES (n = 6) using a flexible endoscope and specialized instruments or by bilateral flank laparoscopy (n = 6). Preoperative and postoperative complete blood count (CBC), plasma fibrinogen concentration, serum amyloid A concentration, peritoneal nucleated cell count, and total protein concentration were compared using repeated measures ANOVA. Surgical times were compared using an unpaired t-test. Mares were monitored for 2 weeks postoperatively and necropsy was performed at 3 weeks (n = 6) or 3 months (n = 6) to assess short- and medium-term effects of each procedure. Complication rate, necropsy, and bacteriology findings were compared using a Fishers exact test. Significance was set at P < .05. RESULTS All surgical procedures were performed successfully and all but one laparoscopy mare were bright, alert, and maintained a good appetite until euthanasia. Mean ± SD surgical time was similar between groups (NOTES: 100 ± 40 minutes; laparoscopy: 107 ± 47 minutes). There were no significant temporal differences in vital parameters, CBC, plasma fibrinogen concentration, serum amyloid A concentration, peritoneal nucleated cell count, and total protein concentration between groups. CONCLUSIONS Bilateral ovariectomy by transvaginal NOTES or laparoscopy resulted in minimal inflammation and surgical trauma.

Standing ovariectomy in mares using a transvaginal natural orifice transluminal endoscopic surgery (NOTES®) approach.

OBJECTIVE To develop and assess the feasibility of standing transvaginal Natural Orifice Transluminal Endoscopic Surgery (NOTES®) ovariectomy in the mare. STUDY DESIGN Descriptive study. ANIMALS Mares (n=10). METHODS The technique was developed in 6 mares and then evaluated in a short-term study in 4 mares. Abdominal access was developed using controlled access vaginal cannula placement under endoscopic guidance. With viewing provided by a flexible endoscope, hemostasis, and transection of ovarian pedicles was performed using a customized bipolar vessel-sealing device. The ovaries were retrieved and the colpotomy was sutured. Surgical time, intra-, and postoperative complications were recorded. Necropsy was performed immediately after surgery in 6 mares and 15 days after surgery in 4 mares to assess short-term complications. RESULTS After the instruments and techniques were developed, transvaginal NOTES® ovariectomy was successfully performed. Analgesia during the procedure was adequate in all cases. The visual field provided by the endoscope was acceptable. The customized 60 cm vessel-sealing device provided good hemostasis and a comfortable working length. Intraoperative complications included difficult viewing that prolonged operative time and inability to remove the second ovary in 1 mare. Postoperative recovery was excellent. Postmortem findings of 1 true positive microbial culture, elevated cell counts in abdominal fluid, and adhesion formation raise questions that must be addressed in future studies. CONCLUSION Using specialized instruments, transvaginal NOTES® ovariectomy is technically feasible in mares.

Risk factors associated with cast complications in horses: 398 cases (1997–2006)

OBJECTIVE To determine the frequency of and risk factors for complications associated with casts in horses. DESIGN Multicenter retrospective case series. ANIMALS 398 horses with a half-limb or full-limb cast treated at 1 of 4 hospitals. PROCEDURES Data collected from medical records included age, breed, sex, injury, limb affected, time from injury to hospital admission, surgical procedure performed, type of cast (bandage cast [BC; fiberglass tape applied over a bandage] or traditional cast [TC; fiberglass tape applied over polyurethane resin-impregnated foam]), limb position in cast (flexed, neutral, or extended), and complications. Risk factors for cast complications were identified via multiple logistic regression. RESULTS Cast complications were detected in 197 of 398 (49%) horses (18/53 [34%] horses with a BC and 179/345 [52%] horses with a TC). Of the 197 horses with complications, 152 (77%) had clinical signs of complications prior to cast removal; the most common clinical signs were increased lameness severity and visibly detectable soft tissue damage Cast sores were the most common complication (179/398 [45%] horses). Casts broke for 20 (5%) horses. Three (0.8%) horses developed a bone fracture attributable to casting Median time to detection of complications was 12 days and 8 days for horses with TCs and BCs, respectively. Complications developed in 71%, 48%, and 47% of horses with the casted limb in a flexed, neutral, and extended position, respectively. For horses with TCs, hospital, limb position in the cast, and sex were significant risk factors for development of cast complications. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that 49% of horses with a cast developed cast complications.

Evaluation of the effects of transendoscopic diode laser palatoplasty on clinical, histologic, magnetic resonance imaging, and biomechanical findings in horses

OBJECTIVE To determine the effects of diode laser palatoplasty on the soft palate in horses. ANIMALS 6 clinically normal horses and 6 euthanized horses from another study. PROCEDURES 6 horses underwent diode laser palatoplasty (treated horses); 3 received low-dose laser treatment (1,209 to 1,224 J), and 3 received high-dose treatment (2,302 to 2,420 J). Six other horses received no treatment (control horses). The upper respiratory tracts of all treated horses were evaluated immediately following surgery (day 0) and on days 2, 7, 14, 21, 30, and 45. Horses were euthanized on day 45, and magnetic resonance imaging (MRI) of the head was performed. The soft palate was removed from treated and control horses, evaluated grossly, and scored for edema, inflammation, and scarring. Soft palates from all horses were sectioned for histologic and biomechanical evaluations. RESULTS Endoscopic examination revealed a significant increase in soft palate scarring and decrease in edema and inflammation in treated horses by day 7. Gross postmortem findings corresponded with MRI findings. Gross and histologic examination revealed a significant increase in scarring, edema, and inflammation at day 45. Histologic evaluation of palatal tissue from high-dose-treated horses revealed full-thickness injury of skeletal muscle, with atrophy of muscle fibers; findings in low-dose-treated horses indicated superficial injury to skeletal muscle. After surgery, treated horses had a significant decrease in soft palate elastic modulus, compared with control horses. CONCLUSIONS AND CLINICAL RELEVANCE Laser palatoplasty resulted in soft palate fibrosis and skeletal muscle loss; however, the fibrosis did not result in an increase in soft palate elastic modulus.

In vitro evaluation of three intravenous fluid line warmers

OBJECTIVE To determine in vitro output temperature differences of 3 IV fluid warmers. DESIGN Prospective, randomized study. SAMPLE 3 IV fluid warmers. PROCEDURES Warming capabilities of a distance-dependent blood and fluid warmer marketed for human and veterinary use (product A) and a veterinary-specific distance-dependent fluid warmer (product B) were compared at 0, 4, 8, and 12 cm from the device to the test vein and at flow rates of 20, 60, 100, 140, 180, 220, 260, and 300 mL/h with room temperature (approx 22°C) fluids (phase 1). The superior warming device was compared against a distance-independent IV fluid warmer (product C) with room temperature fluids at the same flow rates (phase 2). The effect of prewarmed fluids (38°C) versus room temperature fluids was evaluated with the superior warming device from phase 2 (phase 3). RESULTS In phase 1, product B produced significantly warmer fluids than product A for all flow rates and distances. Both distance-dependent devices produced warmer fluid at 0 cm, compared with 4, 8, and 12 cm. In phase 2, product B produced warmer fluid than product C at 60, 100, 140, and 180 mL/h. In phase 3, there was no significant benefit to use of prewarmed fluids versus room temperature fluids. Output temperatures ≥ 36.4°C were achieved for all rates ≥ 60 mL/h. CONCLUSIONS AND CLINICAL RELEVANCE Product B had superior warming capabilities. Placing the fluid warmer close to the patient is recommended. Use of prewarmed fluids had no benefit. Lower IV fluid flow rates resulted in lower output fluid temperatures.

Effect of heparin administration on urine protein excretion during the developmental stage of experimentally induced laminitis in horses.

OBJECTIVE To investigate the effects of heparin administration on urine protein excretion during the developmental stages of experimentally induced laminitis in horses. ANIMALS 13 horses. Procedures-Horses received unfractionated heparin (80 U/kg, SC, q 8 h; n=7) or no treatment (control group; 6) beginning 3 days prior to induction of laminitis. All horses were given 3 oligofructose loading doses (1 g/kg each) at 24-hour intervals and a laminitis induction dose (10 g of oligofructose/kg) 24 hours following the final loading dose (designated as 0 hours) via nasogastric tube. Serum glucose and insulin concentrations were measured before administration of the first loading dose (baseline) and at 0 and 24 hours; urine protein-to-creatinine (UP:C) ratio was determined at 0 hours and every 4 hours thereafter. Lameness was evaluated every 6 hours, and horses were euthanized when Obel grade 2 lameness was observed. RESULTS Mean±SD time until euthanasia did not differ significantly between the heparin-treated (28.9±6.5 hours) and control (29.0±6.9 hours) horses. The UP:C ratio was significantly increased from baseline at 20 to 28 hours after induction of laminitis (ie, 4±4 hours before lameness was evident) in control horses but did not change significantly from baseline in heparin-treated horses. Serum glucose or insulin concentration did not change significantly from baseline in either group. CONCLUSIONS AND CLINICAL RELEVANCE Urine protein excretion increased during the developmental stages of carbohydrate-induced laminitis in horses; administration of heparin prevented that increase, but did not delay onset or decrease severity of lameness.

Short-term effect of ovariectomy on measures of insulin sensitivity and response to dexamethasone administration in horses

OBJECTIVE To evaluate the effect of ovariectomy on insulin sensitivity in horses and determine whether the effects of suppression of the hypothalamo-pituitary-adrenal axis differ before and after ovariectomy. ANIMALS 6 healthy mares. PROCEDURES The horses underwent an IV glucose tolerance test (IVGTT), an insulin sensitivity test, and a dexamethasone suppression test before and 5 weeks after ovariectomy. Body weight, serum cortisol and plasma ACTH concentrations, serum insulin-to-blood glucose concentration ratios, and changes in blood glucose concentration with time after injection of glucose or insulin were compared before and after ovariectomy. RESULTS The dexamethasone injection resulted in a decrease in serum cortisol concentration before and after ovariectomy. In all horses, baseline plasma ACTH concentrations were within the reference range before and after ovariectomy. For each mare, results of an IVGTT before and after ovariectomy were considered normal. No significant differences in basal blood glucose concentration or time to reach baseline glucose concentration after an IVGTT were observed. Basal serum insulin concentration and serum insulin-to-blood glucose concentration ratios were not significantly different before or after ovariectomy, nor was the mean time to attain a 50% decrease in blood glucose concentration after insulin injection. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that ovariectomy does not appear to modify dexamethasone response in horses and that it does not modify short-term measures of insulin sensitivity. Findings suggested that horses undergoing ovariectomy are not at higher risk of developing equine metabolic syndrome or hypothalamo-pituitary-adrenal axis dysfunction and associated morbidity.

Effect of sequential hole enlargement on cortical bone temperature during drilling of 6.2-mm-diameter transcortical holes in the third metacarpal bones of horse cadavers

OBJECTIVE To compare the bone temperature and final hole dimensions associated with sequential overdrilling (SO) and single 6.2-mm drill bit (S6.2DB) methods used to create transcortical holes in the third metacarpal bones (MCIIIs) of horse cadavers. SAMPLE 60 MCIIIs from 30 horse cadavers. PROCEDURES In phase 1, hole diameter, tap insertion torque, peak bone temperature, and postdrilling bit temperature for 6.2-mm-diameter holes drilled in the lateral or medial cortical region of 12 MCIIIs via each of three 2-bit SO methods with a single pilot hole (diameter, 3.2, 4.5, or 5.5 mm) and the S6.2DB method were compared. In phase 2, 6.2-mm-diameter transcortical holes were drilled via a 2-bit SO method (selected from phase 1), a 4-bit SO method, or a S6.2DB method at 1 of 3 locations in 48 MCIIIs; peak bone temperature during drilling, drill bit temperature immediately following drilling, and total drilling time were recorded for comparison. RESULTS Hole diameter or tap insertion torque did not differ among phase 1 groups. Mean ± SD maximum bone temperature increases at the cis and trans cortices were significantly less for the 4-bit SO method (3.64 ± 2.01°C and 8.58 ± 3.82°C, respectively), compared with the S6.2DB method (12.00 ± 7.07°C and 13.19 ± 7.41°C, respectively). Mean drilling time was significantly longer (142.9 ± 37.8 seconds) for the 4-bit SO method, compared with the S6.2DB method (49.7 ± 24.3 seconds). CONCLUSIONS AND CLINICAL RELEVANCE Compared with a S6.2DB method, use of a 4-bit SO method to drill transcortical holes in cadaveric equine MCIIIs resulted in smaller bone temperature increases without affecting hole accuracy.

Comparison of hydroxyapatite-coated and uncoated pins for transfixation casting in horses

OBJECTIVE To determine the extent to which a hydroxyapatite coating promotes pin stability in the third metacarpal bone during transfixation casting in horses. ANIMALS 14 adult horses. PROCEDURES 7 horses each were assigned to either an uncoated or hydroxyapatite-coated pin group. Three transcortical pins were placed in the third metacarpal bone of each horse and incorporated into a cast for 8 weeks. Insertion and extraction torque were measured, and torque reduction was calculated. Radiography was performed at 0, 4, and 8 weeks. Lameness evaluation was performed at 2, 4, 6, and 8 weeks. Bacteriologic culture of pins and pin holes was performed at pin removal. RESULTS All horses used casts without major complication throughout the study. Insertion torque was higher in uncoated pins. There was no effect of group on extraction torque. Hydroxyapatite-coated pins had lower torque reduction. Five of 15 hydroxyapatite-coated pins maintained or increased stability, whereas all uncoated pins loosened. Pin hole radiolucency, lameness grades, and positive bacteriologic culture rates were not different between groups. CONCLUSIONS AND CLINICAL RELEVANCE Hydroxyapatite coating increased pin stability within the third metacarpal bone of horses during 8 weeks of transfixation casting but did not improve pin performance on clinical assessments. Clinical use of hydroxyapatite-coated transfixation pins may result in greater pin stability; however, further research is necessary to improve the consistency of pin osteointegration and elucidate whether clinical benefits will ultimately result from this approach in horses.