Extreme seasonal water-level changes and hydraulic modeling of deep, high-altitude, glacial-carved, Himalayan lakes.

Himalayan lakes represent critical water resources, culturally important waterbodies, and potential hazards. Some of these lakes experience dramatic water-level changes, responding to seasonal monsoon rains and post-monsoonal draining. To address the paucity of direct observations of hydrology in retreating mountain glacial systems, we describe a field program in a series of high altitude lakes in Sagarmatha National Park, adjacent to Ngozumba, the largest glacier in Nepal. In situ observations find extreme (>12 m) seasonal water-level changes in a 60-m deep lateral-moraine-dammed lake (lacking surface outflow), during a 16-month period, equivalent to a 5 [Formula: see text] m[Formula: see text] volume change annually. The water column thermal structure was also monitored over the same period. A hydraulic model is constructed, validated against observed water levels, and used to estimate hydraulic conductivities of the moraine soils damming the lake and improves our understanding of this complex hydrological system. Our findings indicate that lake level compared to the damming glacier surface height is the key criterion for large lake fluctuations, while lakes lying below the glacier surface, regulated by surface outflow, possess only minor seasonal water-level fluctuations. Thus, lakes adjacent to glaciers may exhibit very different filling/draining dynamics based on presence/absence of surface outflows and elevation relative to retreating glaciers, and consequently may have very different fates in the next few decades as the climate warms.

The effects of a novel lateral extracapsular suture system on the kinematics of the cranial cruciate deficient canine stifle.

OBJECTIVE: To evaluate the relative position of the femur and tibia in cranial cruciate ligament-intact stifles, cranial cruciate ligament-deficient stifles, and cruciate-deficient stifles following lateral extracapsular suture system (LESS) stabilization under load at specific joint angles. STUDY DESIGN: In vitro biomechanical study. METHODS: Twenty pelvic limbs from 11 dogs were used to evaluate the relative position of the femur and tibia between three stifle conditions (cranial cruciate ligament-intact, cranial cruciate ligament-deficient, and LESS-stabilized) at a load of 30% of body weight and stifle angles of 125°, 135°, and 145° using electromagnetic tracking sensors. RESULTS: Cranial cruciate ligament-deficient stifles had significantly greater (p <0.0001) cranial displacement and internal rotation of the tibia relative to the femur than cranial cruciate ligament-intact or LESS stifles at all stifle angles. Cranial displacement of the tibia relative to the femur for cranial cruciate ligament-intact and LESS stifles were not significantly different from one another at a stifle angle of 125°, but were significantly different at stifle angles of 135° (p = 0.0182) and 145° (p = 0.0012). There was no significant difference in internal rotation of the tibia relative to the femur between the cranial cruciate ligament-intact and LESS stifles at any of the stifle angles. CLINICAL SIGNIFICANCE: The LESS procedure effectively decreased cranial tibial displacement and eliminated internal rotation of the tibia relative to the femur in the cranial cruciate ligament-deficient stifles at stifle angles of 125°, 135°, and 145° in vitro.

Effect of tibial insertion site for lateral suture stabilization on the kinematics of the cranial cruciate ligament deficient-stifle during early, middle and late stance: an in vitro study.

OBJECTIVE: To evaluate the effect of two tibial attachment sites for lateral suture stabilization (LSS) on the three-dimensional femorotibial translational and rotational movements of the cranial cruciate ligament- deficient canine stifle during the early, middle and late stance phases. STUDY DESIGN: In vitro biomechanical study: 32 hindlimbs from 16 canine cadavers. METHODS: Limbs were mounted in a testing jig and an electromagnetic tracking system was used to determine the three-dimensional femorotibial translational and rotational movements under 33% of body weight load during early, middle and late stance in the following sequence: cranial cruciate ligament-intact, cranial cruciate ligament-deficient and LSS with the distal anchor through the tibial tuberosity (LSSTT) or through the cranial eminence of the extensor groove (LSSEG). The proximal anchor point was the lateral femorofabellar ligament. RESULTS: Post-LSS stifle three-dimensional femorotibial translational and rotational movements were more comparable to normal than post-transection movements for both techniques. Both LSS techniques restored femorotibial movements in cranial cruciate ligament-deficient stifles to varying amounts but neither technique successfully restored normal three-dimensional femorotibial movements. The LSSEG improved femorotibial movements of the cranial cruciate ligament-deficient stifle in the medial-lateral direction and axial rotation but performed poorly in restoring femorotibial movements in the cranial-caudal direction as compared to the LSSTT. CLINICAL SIGNIFICANCE: Both the LSSTT and LSSEG techniques failed to completely restore normal three-dimensional femorotibial translational and rotational movements in cranial cruciate ligament-deficient stifles in vitro.

In vitro biomechanical comparison of three methods for internal fixation of femoral neck fractures in dogs.

The in vitro biomechanical properties of three methods for internal fixation of femoral neck fractures were evaluated. Fifty cadaveric femura from Beagle dogs were used. Ten intact femora served as controls. In 40 femura, an osteotomy of the femoral neck was performed to simulate a transverse fracture. With the remaining 30 femura, three repair methods (two medium Orthofix pins, a 2.7 mm cortical bone screw placed in lag fashion and an anti- rotational Kirschner wire, or three divergent 1.1 mm Kirschner wires) were used to stabilize the osteotomies, and 10 osteotomies were stabilised per repair method. These 30 femura where then subject to monotonic loading to failure. Construct stiffness and load to failure were measured. In the remaining 10 femura, pressure sensitive film was placed at the osteotomy site prior to stabilization with either two Orthofix pins (n = 5) or a screw placed in lag fashion (n = 5) to determine the compressive pressure (MPa), compressive force (KN) and area of compression (cm²). There was no significant difference in the stiffness or load to failure for the three repair methods evaluated. There was no significant difference in the compressive pressure, compressive force or area of compression in osteotomies stabilized with Orthofix pins and 2.7 mm bone screws.

The effect of tibial tuberosity advancement and meniscal release on kinematics of the cranial cruciate ligament-deficient stifle during early, middle, and late stance.

OBJECTIVES: To evaluate the effect of tibial tuberosity advancement (TTA) and meniscal release on cranial-caudal and axial rotational displacement during early, middle and late stance phases in the canine cranial cruciate ligament- (CCL) deficient stifle. STUDY DESIGN: In vitro biomechanical study. METHODS: Eighteen pelvic limbs were evaluated for the effects of TTA on cranial-caudal displacement and axial rotation under a load equivalent to 30% bodyweight, and under the following treatment conditions: normal (intact CCL), CCL deficient, TTA-treated (CCL deficient + TTA), and meniscal release (TTA treated + meniscal release). The limbs were evaluated in the early, middle, and late stance phases using electromagnetic tracking sensors to determine cranial tibial displacement and tibial rotation relative to the femur. RESULTS: Transection of the CCL resulted in significant cranial tibial displacement during early, middle, and late stance (p < 0.0001) and significant internal rotation during early (p = 0.049) and middle stance (p = 0.0006). Performance of TTA successfully eliminated cranial tibial displacement in early, middle, and late stance (p <0.0001); however, the TTA was unsuccessful in normalizing axial rotation in middle stance (p = 0.030). Meniscal release had no effect on cranial-caudal or rotational displacement when performed in conjunction with the TTA. CLINICAL SIGNIFICANCE: Tibial tuberosity advancement effectively eliminates cranial tibial displacement during early, middle and late stance; however, TTA failed to provide rotational stability in mid-stance.

Changes to articular cartilage following remote application of radiofrequency energy and with or without Cosequin therapy.

OBJECTIVE: To determine the short- and long-term changes in the biomechanical properties and metabolic activity of articular cartilage following the remote application of bipolar radiofrequency (bRF) and monopolar radiofrequency (mRF) energy within the rabbit stifle joint. METHODS: The rabbits were randomly assigned to either Group-1 (normal rabbit food), or they were assigned to Group-2 (2% Cosequin in the diet). Each rabbit underwent bilateral stifle arthroscopy with either bRF or mRF applied to the infrapatellar fat pad for 45 seconds. Cartilage samples were collected at zero, four, and 14 weeks after surgery. Data were analyzed with a mixed model analysis of variance (ANOVA) for chondrocyte death, amount of GAG synthesis, and the equilibrium compressive modulus. RESULTS: A significant increase in histological damage was noted at weeks four and 14 compared to week zero. Most of the chondrocyte death noted with confocal laser microscopy (49 of 56 samples) was noted in the superficial region (outer 25%) of the articular cartilage. GAG synthesis was not significantly different between groups or devices at any time point. A significant difference was not noted in equilibrium compressive modulus throughout the study. CONCLUSIONS: Remote application of bRF and mRF energy lead to immediate chondrocyte death. Most of the damage was superficial hence the metabolic activity and biomechanical properties of the extracellular matrix were maintained throughout this study. Treatment with Cosequin did not prevent superficial chondrocyte death caused by the application of radiofrequency (RF) energy with in the joint.

Evaluation of compression generated by self compressing Orthofix bone pins and lag screws in simulated lateral humeral condylar fractures.

A simulated lateral humeral condylar fracture was created in each of the 52 humeri collected from 26 dogs. One humerus from each pair was stabilized with a 2.0 mm cortical bone screw which was inserted in lag fashion. The other humerus from each pair was stabilized with a 2.2 mm threaded diameter Orthofix pin inserted across the condyle. Prior to each repair, an antirotational K-wire was placed and then the Pressurex Sensitive film was inserted in the osteotomy site in order to determine the compressive pressure (MPa), compressive force (KN), and area of compression (cm(2)) achieved during fixation. The maximum insertional torque achieved before stripping was measured for each implant. The mean compression generated by insertion of a 2.0 mm lag screw was 20.36 +/- 1.51 MPa compared to 18.88 +/- 1.76 MPa generated by a 2.2 mm Orthofix pin (p < 0.003). The mean area of compression generated by insertion of a 2.0 mm lag screw was 2.39 +/- 1.29 cm(2), compared to 1.16 +/- 0.84 cm(2) generated by insertion of a 2.2 mm Orthofix pin (p < 0.0001). The mean compressive force (compression x area compressed) generated by insertion of a 2.0 mm lag screw was 4.96 +/- 2.90 Kn, compared to 2.20 +/- 1.65 Kn generated by insertion of a 2.2 mm Orthofix pin (p < 0.0001). The mean insertion torque to failure for the lag screws was 0.49 +/- 0.07 NM, compared to 0.91 NM +/- 0.18 NM generated by the Orthofix pins (P < 0.0001). Both repair methods are likely to be acceptable for the repair of similar fractures in small breed dogs.

The role of negative intra-articular pressure in the maintenance of shoulder joint stability in dogs.

The objective of this study was to evaluate the effect of negative intra-articular pressure on shoulder joint stability in canine cadavers. Cadaver forelimbs from 12 mature dogs were used. The forelimbs were placed in a testing frame and axially preloaded with 4 kg of weight. Shoulder joint stability was tested in flexion, extension, and neutral position before and after venting of the joint capsule. Humeral translation relative to the glenoid was induced by applying a 3 kg load in three different directions (cranial, lateral, and medial) and quantitatively measured by use of an electromagnetic motion tracking system. Peak translational data were compared in each joint position before and after venting of the joint capsule. After venting the shoulder joint capsule, a significant increase in translation was observed in the cranial direction with the joint in neutral position and in the medial direction with the joint in extension. The horizontal translations measured after venting of the joint capsule were likely not clinically relevant. Negative intra-articular pressure is not a major contributor to shoulder stability in dogs during weight-bearing.

The use of radiofrequency energy during arthroscopic surgery and its effects on intraarticular tissues.

The use of radiofrequency (RF) energy has become very popular in human and veterinary arthroscopic surgery since the late 1990s. Both monopolar and bipolar RF units are available. Application of RF energy to joint capsular tissue leads to immediate tissue shrinkage that is both power and temperature dependent. Changes in joint capsular tissue have been noted at temperatures greater than 65 degrees C. Treatment of articular cartilage with RF energy leads to immediate chondrocyte damage. This damage is also power and temperature dependent and is observed at temperatures as low as 45 degrees C. Caution should be used when applying RF energy within a joint to prevent or minimize articular cartilage injury.

Evaluation of healing in feline femoral defects filled with cancellous autograft, cancellous allograft or Bioglass.

Cancellous bone grafting is a widely accepted technique in human and veterinary orthopaedic surgery. However, the use of autogenous bone graft is limited by the additional surgical time required to harvest the graft, the morbidity associated with the donor site, and the limited availability of cancellous bone, especially in feline patients. Various allografts and bone graft substitutes are available commercially but have not been fully evaluated for efficacy in the cat. The purpose of this study was to compare the incorporation of autogenous and allogenous cancellous bone graft and Bioglass, a synthetic bone graft substitute, in femoral defects in cats. Four (4.0 mm diameter) defects were created in the lateral diaphyseal cortex of the left femur with an orthopaedic drill. In each femur, one of the cortical defects was filled with autogenous cancellous graft (harvested from the tibia), one was filled with allogenic cancellous graft, and one was filled with Bioglass. The fourth defect remained unfilled. Graft incorporation within the femoral defects was evaluated by radiographic evaluation every two weeks. Six weeks after the grafting procedure, the cats were euthanatized and high detailed radiography, dual energy X-ray absorptiometry (DEXA), histopathology and histomorphometry of the defects were performed. Satisfactory bone healing was observed within all of the defects.

Hind limb lameness in the young patient.

Hind limb lameness is seen frequently in young dogs and may result from congenital abnormalities, traumatic injuries, or developmental diseases. An understanding of the patient's history, a good physical and radiographic evaluation, and sound knowledge of the common diseases affecting immature dogs permit early diagnosis and successful treatment in most cases.

Kinetic and kinematic gait analysis in dogs.

Kinetic and kinematic gait analysis provides objective, quantifiable, and repeatable information on normal and abnormal gait in dogs. Data collection requires specialized equipment, and techniques must be carefully controlled to ensure that accurate measurements are obtained. Force-plate and kinematic analysis is currently used primarily as a research tool to study various gait abnormalities and objectively assess treatment efficacy. As future research identifies characteristic changes associated with specific types of lameness, the use of gait analysis to evaluate individual clinical patients with lameness should become more valuable. Specialized gait analysis techniques may eventually enable veterinarians to accurately diagnose subtle lameness, better evaluate dogs with resolving lameness, and accurately select the appropriate time to return an athletic dog to exercise after recovery from an injury.

The effect of chronic food and water restriction on open-field behaviour and serum corticosterone levels in rats.

In operant conditioning experiments, two methods are commonly used to motivate laboratory rats to perform designated tasks. The first is restricting food so that rats are forced to lose 20% of body weight within one week, followed by maintenance at 80% of the baseline weight for the remainder of the experiment. The second is restricting access to water to 15 min in each 24 h period. These methods are effective in motivating the animals. There is, however, little information available on the effects on performance in tests of behaviour that are not related to operant conditioning. In addition, it is not clear if these commonly used methods of food and water restriction will lead to physiological stress as indicated by an elevation of serum corticosterone. Male rats were either food-restricted to reduce and maintain their weight at 80% of baseline weight, or were restricted to 15 min access to water every 24 h. Activity in the open field was significantly greater in food-restricted rats than in water-restricted or control rats, but freezing behaviour was similar in all experimental groups. Food-restricted rats had a higher mean serum corticosterone level than water-restricted and control rats 37 days after the start of the experimental period. These data suggested that chronically restricting food and maintenance of body weight at 80% of baseline body weight led to significant behavioural changes and physiological stress. In contrast, water restriction did not lead to changes in behaviour or corticosterone levels. A second experiment was conducted to compare the effects of food restriction to 80% of baseline body weight, as described above, with a less stringent protocol in which test rats were initially reduced to 80% of baseline weight, but were then maintained at 80% of an ad libitum fed control rat's weight. Serum corticosterone levels and adrenal gland weights were measured after the initial week of forced weight loss and after maintenance for 21 days. Forced loss of 20% of body weight in the first week led to significantly increased serum corticosterone levels and adrenal gland weights compared to ad libitum fed controls. Serum corticosterone levels and adrenal gland weights in rats maintained at 80% of their initial body weight for 21 days remained higher than ad libitum fed control rats. However, rats maintained at 80% of an ad libitum fed control rat's weight did not differ from control rats in serum corticosterone levels or adrenal gland weights at the end of the 21-day study period. Adjustment of the feeding regimen in this manner eliminated physiological evidence of chronic stress.

Bone plate fixation of distal radius and ulna fractures in small- and miniature-breed dogs.

Bone plate fixation was reviewed in 29 distal radial fractures of small- and miniature-breed dogs. Twenty-two fractures in 18 dogs were available for follow-up. Number of complications and return to function were evaluated. Complications occurred in 54% of the fractures. Catastrophic complications occurred in 18% of fracture repairs with follow-up, while minor complications occurred in 36%. Sixteen (89%) of 18 dogs had a successful return to function. Bone plate fixation is a successful repair method for distal radius and ulna fractures in small-breed dogs, compared to previously reported methods.

Scintigraphic evaluation of dogs with acute synovitis after treatment with glucosamine hydrochloride and chondroitin sulfate.

OBJECTIVE: To evaluate the effects of orally administered glucosamine hydrochloride (GlAm)-chondroitin sulfate (CS) and GlAm-CS-S-adenosyl-L-methionine (SAMe) on chemically induced synovitis in the radiocarpal joint of dogs. ANIMALS: 32 adult mixed-breed dogs. PROCEDURE: For 21 days, all dogs received a sham capsule (3 groups) or GlAm-CS (prior treatment group) in a double-blinded study. Unilateral carpal synovitis was induced by injecting the right radiocarpal joint with chymopapain and the left radiocarpal joint (control joint) with saline (0.9% NaCl) solution. Joints were injected on alternate days for 3 injections. After induction of synovitis, 2 groups receiving sham treatment were given GlAm-CS or GlAm-CS-SAMe. Another group continued to receive sham capsules (control group). Joint inflammation was quantified, using nuclear scintigraphy, before injection of joints and days 13, 20, 27, 34, 41, and 48 after injection. Lameness evaluations were performed daily. RESULTS: Dogs given GlAm-CS before induction of synovitis had significantly less scintigraphic activity in the soft-tissue phase 48 days after joint injection, significantly less uptake in the bone phase 41 and 48 days after joint injection, and significantly lower lameness scores on days 12 to 19, 23, and 24 after injection, compared with other groups. CONCLUSIONS AND CLINICAL RELEVANCE: Analysis of results of this study suggest that prior treatment with GlAm-CS for 21 days had a protective effect against chemically induced synovitis and associated bone remodeling. Prior treatment with GlAm-CS also reduced lameness in dogs with induced synovitis.

Water content and glycosaminoglycan disaccharide concentration of the canine meniscus.

OBJECTIVE: To determine the regional composition of water and glycosaminoglycan (GAG) disaccharides of the canine meniscus. SAMPLE POPULATION: 52 menisci from the stifle of dogs. PROCEDURE: Regional sections of each meniscus were weighed, dried, and reweighed to determine water content. Dried tissue specimens were subjected to enzymatic digestion. Analysis and quantification of disaccharide degradation products were performed, using high-performance liquid chromatography. RESULTS: Water content was approximately 65% in polar and central regions of the canine meniscus. Water content of the central region of the lateral meniscus was significantly higher than that of the medial meniscus (P = 0.0090). Chondroitinase digestion of canine meniscal tissue yielded detectable delta Di-HA, delta Di-4S, and delta Di-6S GAG disaccharides. Disaccharides specific to dermatan sulfate and chondroitin D or E sulfate were not detected. Concentrations of delta Di-4S and delta Di-6S were significantly greater in the lateral central region, compared with the medial central region (P = 0.0005 and 0.0002, respectively). CONCLUSION: Water content and delta Di-4S and delta Di-6S concentrations were significantly lower in the central region of the medial meniscus, compared with the central region of the lateral meniscus. Reduced tissue hydration of the medial central region may have been a direct result of its overall decrease in total GAG content. CLINICAL RELEVANCE: The ability to evaluate subtle differences in tissue GAG composition by analytical measurement of their constituent disaccharides may aid in the understanding of the complex material properties of the normal and diseased meniscus, which may be applied to the study of meniscal healing and biomechanics.

Scintigraphic assessment of distal extremity perfusion in 17 patients.

To assess the role of scintigraphic evaluation of distal limb perfusion, the medical records and scintigraphic perfusion images of 17 animals (8 dogs, 2 cats, 2 calves, 4 birds and 1 ferret) with clinical signs of distal limb ischemia were examined retrospectively. Images were obtained at 5 and 10 minutes following injection of 99mTc-MDP, or 99mTc-DTPA. The initial scintigraphic diagnoses of 17 animals included complete ischemia (8/17), partially reduced perfusion (5/17), and normal to increased perfusion (4/17). In 4 of the animals with partially reduced perfusion, follow-up scans indicated progression to complete ischemia (1/4) or normal to increased perfusion (3/4). Nine of 17 animals had a final scintigraphic diagnosis of complete distal limb ischemia, and these animals were either euthanized (5/9) or had limb amputation (4/9). A final diagnosis of complete ischemia was supported with either repeat scanning (3/10), continued clinical observation (6/10) and/or pathological examination (10/10). Clinical signs of ischemia resolved in all (7/17) animals with increased or normal perfusion on their final scan. Scintigraphy provided a safe and noninvasive assessment of distal limb perfusion, which corresponded with clinical outcome.

Fascia lata autograft for treatment of congenital cranial cruciate ligament deficiency in a llama.

An 11.4-kg female llama that had been born without assistance while its dam was under observation at the veterinary teaching hospital was observed to ambulate abnormally on its right hind limb. A cranial drawer sign could be elicited in the right stifle. Cranial displacement of the tibia relative to the femur and dysplasia of the proximal end of the tibia were seen on radiographs. When the cria was 10 days old, the joint was stabilized with a fascia lata autograft. At the time of surgery, a segment of thin, loose tissue was found where the cranial cruciate ligament would have been. Three years after surgery, the llama gave birth to a normal cria and was 60 days pregnant with a second cria. To our knowledge, congenital cranial cruciate ligament deficiency with tibial dysplasia has not been reported in llamas. The heritability of these defects is unknown.

Effects of subject velocity on ground reaction force measurements and stance times in clinically normal horses at the walk and trot.

OBJECTIVE: The objective of the study reported here was to evaluate the effects of changing velocity on stance time and ground reaction force (GRF) measurements in horses at the walk and trot. DESIGN: Force plate gait analysis was used to evaluate clinically normal horses at variable velocities. Ground reaction force measurements and stance times were recorded and compared. ANIMALS: 12 adult horses. PROCEDURE: Data were obtained from 192 valid trials at the walk and 162 valid trials at the trot. Vertical, braking, and propulsive peak forces and impulses were measured. Pearson's correlation coefficients were determined for velocity and stance time and all measured forces and impulses in the forelimbs and hind limbs. Trials were divided into distinct velocity ranges. Trials obtained at velocities within the established ranges were analyzed to evaluate changes in vertical, braking, and propulsive peak forces and impulses at differing speeds within the walk and trot gaits. RESULTS: At the walk and trot, a significant negative correlation was found between velocity and forelimb and hind limb stance times. Velocity and stance time were significantly correlated with many of the GRF and impulse measurements. Velocity was significantly correlated with vertical and braking forces in the hind limbs at the walk, with vertical force in the forelimbs at the trot, and with braking force in the forelimbs and hind limbs at the trot. Velocity and stance time correlated significantly with forelimb and hind limb vertical impulses. Forelimb and hind limb stance times decreased significantly as velocity increased. Hind limb braking force increased and forelimb and hind limb vertical impulses decreased significantly as walk velocity increased. Forelimb braking force increased significantly between velocity ranges at the trot. CONCLUSIONS: Results of this study confirm that a significant negative linear correlation exists between subject velocity and stance times in clinically normal horses at the walk and trot. Significant correlations were also identified between velocity and many GRF measurements, indicating that subject velocity does influence the generation of GRF measurements in horses. Variation in subject velocity should be minimized when performing force-plate analysis in horses.