Forelimb and hindlimb ground reaction forces of walking cats: Assessment and comparison with walking dogs

Microcomputed tomographic analysis of the trabecular and cortical architecture of the proximal femur and hip bone of cats and small breed dogs

This study aims to provide an initial database to gain more detailed knowledge of the trabecular and cortical bone structure of pelvic and femur bones in cats and smaller dogs. Additionally, the bony microarchitecture between cats and smaller dogs was compared to identify possible differences between those species. These findings could potentially improve the development of non-cemented total hip replacement (THR). To determine the bony microarchitecture, a total of 48 pelvises and thus 96 acetabuli and femora of smaller dogs (n = 21) and cats (n = 27) were analysed using microcomputed tomography. The parameters bone volume (BV/TV), bone surface (BS/BV), trabecular thickness (Tb.Th), number of trabeculae (Tb.N), trabecular spacing (Tb.Sp), degree of anisotropy (DA), connectivity density (Conn. D) and mean bone density were measured and compared between the species. In addition, the femoral angle of antetorsion was determined on both sides of the body. Overall, cats had fewer but thicker trabeculae than the small dogs in the analysed areas of the pelvis and femur. This resulted in a greater trabecular distance in cats than in small dogs. Together with a higher cortical bone density at the femoral shaft in cats, it could be determined that cats have a more stable bone architecture in the measured areas than smaller dogs. The angle of antetorsion did not differ significantly between the cats and the dogs examined.

Role of forelimb morphology in muscle sensorimotor functions during locomotion in the cat

Previous studies established strong links between morphological characteristics of mammalian hindlimb muscles and their sensorimotor functions during locomotion. Less is known about the role of forelimb morphology in motor outputs and generation of sensory signals. Here, we measured morphological characteristics of 46 forelimb muscles from six cats. These characteristics included muscle attachments, physiological cross-sectional area (PCSA) and fascicle length. We also recorded full-body mechanics and EMG activity of forelimb muscles during level overground and treadmill locomotion in seven and 16 adult cats of either sex, respectively. We computed forelimb muscle forces along with force- and length-dependent sensory signals mapped onto corresponding cervical spinal segments. We found that patterns of computed muscle forces and afferent activities were strongly affected by the muscle's moment arm, PCSA and fascicle length. Morphology of the shoulder muscles suggests distinct roles of the forelimbs in lateral force production and movements. Patterns of length-dependent sensory activity of muscles with long fibres (brachioradialis, extensor carpi radialis) closely matched patterns of overall forelimb length, whereas the activity pattern of biceps brachii length afferents matched forelimb orientation. We conclude that cat forelimb muscle morphology contributes substantially to locomotor function, particularly to control lateral stability and turning, rather than propulsion. KEY POINTS: Little is known about the role of forelimb muscle morphology in producing motor outputs and generating somatosensory signals. This information is needed to understand the contributions of forelimbs in locomotor control. We measured morphological characteristics of 46 muscles from cat forelimbs, recorded cat walking mechanics and electromyographic activity, and computed patterns of moment arms, length, velocity, activation, and force of forelimb muscles, as well as length- and force-dependent afferent activity during walking. We demonstrated that moment arms, physiological cross-sectional area and fascicle length of forelimb muscles contribute substantially to muscle force production and proprioceptive activity, to the regulation of locomotor cycle phase transitions and to control of lateral stability. The obtained information can guide the development of biologically accurate neuromechanical models of quadrupedal locomotion for exploring and testing novel methods of treatments of central nervous system pathologies by modulating activities in neural pathways controlling forelimbs/arms.

ROLE OF FORELIMB MORPHOLOGY IN MUSCLE SENSORIMOTOR FUNCTIONS DURING LOCOMOTION IN THE CAT

Previous studies established strong links between morphological characteristics of mammalian hindlimb muscles and their sensorimotor functions during locomotion. Less is known about the role of forelimb morphology in motor outputs and generation of sensory signals. Here, we measured morphological characteristics of 46 forelimb muscles from 6 cats. These characteristics included muscle attachments, physiological cross-sectional area (PCSA), fascicle length, etc. We also recorded full-body mechanics and EMG activity of forelimb muscles during level overground and treadmill locomotion in 7 and 16 adult cats of either sex, respectively. We computed forelimb muscle forces along with force- and length-dependent sensory signals mapped onto corresponding cervical spinal segments. We found that patterns of computed muscle forces and afferent activities were strongly affected by the muscle's moment arm, PCSA, and fascicle length. Morphology of the shoulder muscles suggests distinct roles of the forelimbs in lateral force production and movements. Patterns of length-dependent sensory activity of muscles with long fibers (brachioradialis, extensor carpi radialis) closely matched patterns of overall forelimb length, whereas the activity pattern of biceps brachii matched forelimb orientation. We conclude that cat forelimb muscle morphology contributes substantially to locomotor function, particularly to control lateral stability and turning, rather than propulsion.

A NEW POSTURAL MOTOR RESPONSE TO SPINAL CORD STIMULATION: POST-STIMULATION REBOUND EXTENSION

Spinal cord stimulation (SCS) has emerged as a therapeutic tool for improving motor function following spinal cord injury. While many studies focus on restoring locomotion, little attention is paid to enabling standing which is a prerequisite of walking. In this study, we fully characterize a new type of response to SCS, a long extension activated post-stimulation (LEAP). LEAP is primarily directed to ankle extensors and hence has great clinical potential to assist postural movements. To characterize this new response, we used the decerebrate cat model to avoid the suppressive effects of anesthesia, and combined EMG and force measurement in the hindlimb with intracellular recordings in the lumbar spinal cord. Stimulation was delivered as five-second trains via bipolar electrodes placed on the cord surface, and multiple combinations of stimulation locations (L4 to S2), amplitudes (50-600 uA), and frequencies (10-40 Hz) were tested. While the optimum stimulation location and frequency differed slightly among animals, the stimulation amplitude was key for controlling LEAP duration and amplitude. To study the mechanism of LEAP, we performed in vivo intracellular recordings of motoneurons. In 70% of motoneurons, LEAP increased at hyperpolarized membrane potentials indicating a synaptic origin. Furthermore, spinal interneurons exhibited changes in firing during LEAP, confirming the circuit origin of this behavior. Finally, to identify the type of afferents involved in generating LEAP, we used shorter stimulation pulses (more selective for proprioceptive afferents), as well as peripheral stimulation of the sural nerve (cutaneous afferents). The data indicates that LEAP primarily relies on proprioceptive afferents and has major differences from pain or withdrawal reflexes mediated by cutaneous afferents. Our study has thus identified and characterized a novel postural motor response to SCS which has the potential to expand the applications of SCS for patients with motor disorders.

Modulation of limb mechanics in alligators moving across varying grades

Graded substrates require legged animals to modulate their limb mechanics to meet locomotor demands. Previous work has elucidated strategies used by cursorial animals with upright limb posture, but it remains unclear how sprawling species such as alligators transition between grades. We measured individual limb forces and 3D kinematics as alligators walked steadily across level, 15 deg incline and 15 deg decline conditions. We compared our results with the literature to determine how limb posture alters strategies for managing the energetic variation that accompanies shifts in grade. We found that juvenile alligators maintain spatiotemporal characteristics of gait and locomotor speed while selectively modulating craniocaudal impulses (relative to level) when transitioning between grades. Alligators seem to accomplish this using a variety of kinematic strategies, but consistently sprawl both limb pairs outside of the parasagittal plane during decline walking. This latter result suggests alligators and other sprawling species may use movements outside of the parasagittal plane as an axis of variation to modulate limb mechanics when transitioning between graded substrates. We conclude that limb mechanics during graded locomotion are fairly predictable across quadrupedal species, regardless of body plan and limb posture, with hindlimbs playing a more propulsive role and forelimbs functioning to dissipate energy. Future work will elucidate how shifts in muscle properties or function underlie such shifts in limb kinematics.

Biomechanical Comparison between Inverted Triangle and Vertical Configurations of Three Kirschner Wires for Femoral Neck Fracture Fixation in Dogs: A Cadaveric Study

The purpose of this study was to compare single-cycle axial load and stiffness between inverted triangle and vertical configurations of three Kirschner wires (K-wires) for femoral neck fracture fixation in small dog cadaveric models. In each of the eight cadavers, the basilar femoral neck fracture model was prepared on both sides of the femur. One side of the femur was stabilized with three 1.0 mm K-wires of an inverted triangle configuration (group T), and the other femur was stabilized with a vertical configuration (group V). Postoperatively, the placement of the K-wires was evaluated with radiographic and computed tomography (CT) images, and static vertical compressive loading tests were performed. The mean yield load and the lateral spread were significantly higher in group T compared to group V (p = 0.023 and <0.001). On the cross-section of femoral neck at the level of the fracture line, the surface area between K-wires was significantly larger (p < 0.001) and the mean number of cortical supports was significantly higher in group T (p = 0.007). In this experimental comparison, the inverted triangle configuration of three K-wires was more resistant to failure under axial loading than the vertical configuration for canine femoral neck fracture fixation.

The Limb Kinetics of Goat Walking on the Slope with Different Angles

The study aimed to assess the gait adjustment techniques of limbs on different slopes and investigate the relationship between forelimb and hindlimb kinetics and the center of mass (COM) during the uphill movement of a specific Boer goat using a pressure-sensitive walkway (PSW). During the uphill and downhill movements at a comfortable walking speed, we measured the ground reaction force (GRF) of the forelimbs and hindlimbs on the slope, the change in the included angle of the propulsive force direction of the forelimbs and hindlimbs, and the impulse relationship between GRF and propulsive force. According to the study, since the forelimbs of the goat were nearer the COM, they were primarily adjusted during the movement on the slope. By lowering the initial included angle of the propulsive force and the angle variation range, the forelimbs and hindlimbs could walk steadily. The forelimbs and hindlimbs exhibited completely different adjustment strategies during uphill and downhill movements. In particular, the forelimbs performed braking and the hindlimbs performed driving. In addition, we discovered that the goat altered its adjustment strategy when climbing the steep slope. All findings of this study indicate the need to understand the gait adjustment mode of the Boer goat during movement on the slope to thoroughly comprehend the driving strategy of quadrupeds with the ability to walk on specialized terrains.

Biomechanical Tests on Long-Bone Elliptical Medullary-Canal Endoprostheses for Limb Salvage in Dogs

Simple Summary

Currently, more owners look for offering a better quality of life to their pets. In fact, the complete limb amputation seems to be the last option considered by pet owners in surgeries to save their pets’ lives. Although this field is under development in veterinary medicine, we believe that 3D-printed implants for this market sector will improve the advancement in its research by reducing production costs. This would allow the pet owners to select this solution without large expenses, allowing at the same time, advances in this field. For this purpose, mechanical tests have been carried out on implants printed in a high-performance plastic that resembles the resistance of metals—that are traditionally used in veterinary surgery—and the properties of dogs’ bones as well. The results obtained have confirmed that the implants could withstand the dog weight in its different gaits, although further comparative studies on the effect of rotation forces applied during the animal’s change of direction (evaluated at different paces) are required to confirm their suitability.

Abstract

Exo-endoprosthesis is a limb salvage procedure poorly described for animals, as only expensive metal devices have been used so far. Currently, additive manufacturing (AM) can make this type of implant affordable by exploring a wide new range of materials. However, safety factors should be considered and could be related to kinetic and kinematic studies of canine natural gaits. The suitability of a novel inner part of an exo-endoprosthesis manufactured by fuse deposition modeling (FDM) was assessed for long canine bones with an elliptical medullary canal. Polyether ether ketone (PEEK) was the material used as an alternative to metal for veterinary traumatology. Poisson’s ratio of 3D-printed PEEK material and ex vivo mechanical tests of the customized endoprosthesis were performed for the evaluation. The customized endoprostheses had promising outcomes for the radii of 20 kg dogs. Quasistatic mechanical tests of bone-inserted endoprostheses—pure compression tests—reached a maximum force of 1045.0 ± 78.0 N. In fatigue tests, the samples reached 500,000 cycles without failure or detriment to their quasistatic results. These outcomes surpass the natural weight-bearing of dogs, even during a galloping pace. Furthermore, torque tests with different adhesives were performed to obtain reference data for future assessments comparing with natural dog movements.

Biomechanical Test of a New Endoprosthesis for Cylindrical Medullary Canals in Dogs

Exo-endoprosthesis is a limb salvage procedure for animals, although only expensive metal devices have been described. Now-a-days, new materials for this type of implant could be considered due to novel and affordable manufacturing techniques. However, a factor of safety (FoS) should be considered. There are kinetic and kinematic studies of canine natural gaits, which can be used to establish an FoS for mechanical tests for new non-metallic devices. Polyetheretherketone (PEEK) is used in different specialties in human medicine. Its mechanical properties (and its close mechanical stiffness to that of bone) make this polymer an alternative to metals in veterinary traumatology. PEEK could also be used in 3D printing. The suitability of a novel inner part of an exo-endoprosthesis manufactured by fuse deposition modeling (FDM) was presented in this study for long canine bones. Mechanical characterization of 3D-printed PEEK material and ex vivo mechanical tests of a customized endoprosthesis were performed to address it. Young's modulus of 3D-printed PEEK suffered a reduction of 30% in relation to bulk PEEK. Customized 3D-printed PEEK endoprostheses had promising outcomes for the tibiae of 20 kg dogs. Pure compression tests of the non-inserted endoprostheses showed a maximum force of 936 ± 199 N. In the bending tests of non-inserted endoprostheses, the PEEK part remained intact. Quasistatic mechanical tests of bone-inserted endoprostheses (compression-bending and pure compression tests) reached a maximum force of 785 ± 101 N and 1,642 ± 447 N, respectively. In fatigue tests, the samples reached 500,000 cycles without failure or detriment to their quasistatic results. These outcomes surpass the natural weight-bearing of dogs, even during a galloping pace. In conclusion, the 3D-printed PEEK part of the endoprosthesis for an exo-endoprosthesis can withstand loading, even during a galloping pace.

Long-term follow up of 44 cats undergoing total hip replacement: Cases from a feline hip registry (2010-2020)

OBJECTIVE

To report indications, complications, and long-term outcomes following feline total hip replacement (THR) using a client-based clinical metrology questionnaire, the Feline Musculoskeletal Pain Index (FMPI), and owner satisfaction.

STUDY DESIGN

Multi-institutional retrospective cohort study.

ANIMALS

Cats (n = 44) that underwent THR (n = 56).

METHODS

Feline THRs submitted to a registry over a 10-year period were reviewed. The FMPI and owner satisfaction surveys were used to assess outcome.

RESULTS

Forty-four cats met the inclusion criteria. Median age was 2 years (range: 0.9-11), and median bodyweight 5 kg (range: 3.3-7.6). British Shorthair and Domestic Shorthair were the most frequent breeds. Most cats were neutered males (33/44) and slipped capital femoral epiphysis (SCFE) was the most common surgical indication (34/56). All implants were cemented micro and nano hip implants. Overall complications (11/56) included 9 major complications. The median duration of follow up was 752 days (range: 102-3089). No association was found between clinical variables and complications. The FMPI score improved from 0.111 (range: 0-1.222) to 2.111 (range: 0.888-3.666) postoperatively (P < .001). Owner satisfaction was reported as "very good" in 30/33 cases (90.9%).

CONCLUSION

A validated client metrology questionnaire showed clinical improvement in cats following THR. The most common indication for THR in cats was SCFE occurring in young male neutered cats. Complication rates were comparable to previous reports.

CLINICAL SIGNIFICANCE

Total hip replacement appears to be a successful surgical treatment for feline hip disease with very good owner satisfaction and acceptable complication rates.

A portable non-invasive microwave based head imaging system using compact metamaterial loaded 3D unidirectional antenna for stroke detection

A metamaterial (MTM) loaded compact three-dimensional antenna is presented for the portable, low-cost, non-invasive microwave head imaging system. The antenna has two slotted dipole elements with finite arrays of MTM unit cell and a folded parasitic patch that attains directional radiation patterns with 80% of fractional bandwidth. The operating frequency of the antenna is 1.95–4.5 GHz. The optimization of MTM unit cell is performed to increase the operational bandwidth, realized gain, and efficiency of the antenna within the frequency regime. It is also explored to improve radiation efficiency and gain when placed to head proximity. One-dimensional mathematical modelling is analyzed to precisely estimate the power distribution that validates the performance of the proposed antenna. To verify the imaging capability of the proposed system, an array of 9 antennas and a realistic three-dimensional tissue-emulating experimental semi-solid head phantom are fabricated and measured. The backscattered signal is collected from different antenna positions and processed by the updated Iterative Correction of Coherence Factor Delay-Multiply-and-Sum beamforming algorithm to reconstruct the hemorrhage images. The reconstructed images in simulation and experimental environment demonstrate the feasibility of the proposed system as a portable platform to successfully detect and locate the hemorrhages inside the brain.

The efficacy of a nutritional supplement containing green-lipped mussel, curcumin and blackcurrant leaf extract in dogs and cats with osteoarthritis

Background

Osteoarthritis is a common disease in dogs and cats, and the search for novel treatment options is needed. The combination of green‐lipped mussel, curcumin and blackcurrant leaf extract has to date not been studied in dogs and cats.

Objectives

The aim of this study was to test the effect of a supplement containing green‐lipped mussel (Perna canaliculus), curcumin (Curcuma longa) and blackcurrant (Ribes nigrum) leaf extract on locomotion and behaviour in client‐owned dogs and cats suffering from mild to moderate osteoarthritis.

Methods

To this end, 32 dogs and 16 cats were enrolled in a double‐blinded, randomised, crossover, placebo‐controlled trial for 10 weeks in cats and 16 weeks in dogs. Outcome parameters were the Helsinki Chronic Pain Index (HCPI) by pet owners in dogs and cats, Canine OsteoArthritis Staging Tool (COAST) by a veterinarian in dogs and Force Plate Analysis (FPA) in 18 dogs.

Results

In dogs, the COAST improved significantly in the supplement group compared to baseline but was not different than the placebo group. In cats, the ability to groom, activity level, playfulness and walking up the stairs improved in the supplement group. No differences were found on HCPI scores and FPA in dogs. Several non‐responders were noted in both species, which were irrespective of the stage of osteoarthritis.

Conclusions

Overall, the supplement had only partial positive effects in client‐owned dogs and cats with mild to moderate osteoarthritis. Further research with a larger sample size and longer duration is needed to expand these findings.

Refinement of the Feline Musculoskeletal Pain Index (FMPI) and development of the short-form FMPI

OBJECTIVES

The aim of this study was to investigate the reliability and responsiveness of the Feline Musculoskeletal Pain Index (FMPI) using the collective results of multiple clinical studies and iteratively refine the FMPI for future use.

METHODS

Data were compiled from previously conducted studies involving client-owned cats with degenerative joint disease (DJD) and which used the FMPI. The reliability of the FMPI was assessed using the data from the initial visits of those studies. For the assessment of responsiveness of the FMPI, only placebo-controlled studies that used analgesic treatments were included. Treatment groups from each study were combined and categorized as 'placebo' group and 'analgesic' group. Then, the mean change from baseline in score of each FMPI item and across all items within and between these groups were assessed. Based on the results of the reliability and responsiveness of the FMPI, stepwise elimination was used to remove the items that were least able to distinguish between the placebo and analgesic groups. Finally, after the stepwise elimination, a proposed new FMPI-short form (FMPI-sf) was constructed and its reliability was reassessed using the data sets described above. Individual and combined data sets of the studies were also used to compare the responsiveness of the original FMPI and the FMPI-sf.

RESULTS

The data from 180 cats from four studies were included. The original FMPI had a reasonable reliability, but low/no responsiveness. The elimination process of FMPI items refined the responsiveness of the instrument while maintaining its reliability. When the responsiveness was compared between the original FMPI (17 items) and the FMPI-sf (nine items), the treatment effect between groups was always greater when the FMPI-sf was used.

CONCLUSIONS AND RELEVANCE

The proposed FMPI-sf may be able to better distinguish between placebo and analgesic effects in cats with DJD.

The menisci are not shock absorbers: A biomechanical and comparative perspective

The lateral and medial menisci are fibrocartilaginous structures in the knee that play a crucial role in normal knee biomechanics. However, one commonly cited role of the menisci is that they function as "shock absorbers." Here we provide a critique of this notion, drawing upon a review of comparative anatomical and biomechanical data from humans and other tetrapods. We first review those commonly, and often exclusively, cited studies in support of a shock absorption function and show that evidence for a shock absorptive function is dubious. We then review the evolutionary and comparative evidence to show that (1) the human menisci are unremarkable in morphology compared with most other tetrapods, and (2) "shock" during locomotion is uncommon, with humans standing out as one of the only tetrapods that regularly experiences high levels of shock during locomotion. A shock-absorption function does not explain the origin of menisci, nor are human menisci specialized in any way that would explain a unique shock-absorbing function during human gait. Finally, we show that (3) the material properties of menisci are distinctly poorly suited for energy dissipation and that (4) estimations of meniscal energy absorption based on published data are negligible, both in their absolute amount and in comparison to other well-accepted structures which mitigate shock during locomotion. The menisci are evolutionarily ancient structures crucial for joint congruity, load distribution, and stress reduction, among a number of other functions. However, the menisci are not meaningful shock absorbers, neither in tetrapods broadly, nor in humans.

Relation of Computed Tomography-Based Static Axial Radioulnar Incongruence Measurements under General Anaesthesia and Dynamic, In Vivo RUI during the Walk in Canine Elbow Joints with and without Medial Coronoid Process Disease

OBJECTIVE

 This study aimed to evaluate the correlation of static axial radioulnar incongruence (sRUI) measured under general anaesthesia with the real in vivo dynamic RUI (dRUI) during walking.

STUDY DESIGN

 This was a prospective clinical study that included 6 sound elbows (5 dogs) and 7 medial coronoid process disease (MCPD) affected elbows (6 dogs).

MATERIALS AND METHODS

 Static axial radioulnar incongruence was measured using the sphere fitting technique on computed tomography-based three-dimensional (3D) models of radius and ulna. The in vivo pose of radius and ulna was derived from radiostereometric analysis during the walk and transferred onto previously calculated 3D models. Dynamic RUI was measured on those adjusted models using the sphere fitting technique, providing a measurement of RUI over time during walk.

RESULTS

 Mean sRUI was 0.2 mm (standard deviation [SD]: 0.30) in control and 1.4 mm (SD: 0.73) in elbow joints with MCPD; being significantly different (p = 0.0035; confidence interval [CI]: 0.4772-1.8824). Mean dRUI in controls (-0.4 mm; SD: 0.47) was significantly different (p = 0.0004; CI: 0.9918-2.5225) from dRUI in the affected elbows (1.4 mm; SD: 0.73). Comparison of sRUI and dRUI within each group showed difference in the control group (0.2 vs. -0.4 mm; p = 0.0138; CI: 0.1820-1.0014). In affected elbows, no difference between sRUI and dRUI was found (1.4 vs. 1.4 mm; p = 0.8963).

CONCLUSION

 In normal elbow joints, sRUI does not represent the in vivo condition during weight bearing. Dynamic and slightly negative RUI occurs during loading (0.2 mm positive to -0.4 mm negative RUI). In MCPD affected elbows with sRUI, no dynamic change of RUI occurs during the walk.

Comparison of Extracapsular Stabilization Techniques Using an Ultrasonically Implanted Absorbable Bone Anchor (Weldix) after Cranial Cruciate Ligament Rupture in Cats-An In Vitro Study

Simple Summary

One reason for lameness in cats is the rupture of the cranial cruciate ligament. This ligament is located in the stifle joint and contributes to its stabilization during excessive forward movement and internal rotation of the tibia. One method for the surgical treatment of cranial ligament rupture is the placement of an extracapsular suture. Different materials and methods of suture fixation have been used in dogs and cats. This study investigated the use of a novel polylactide absorbable bone anchor that was implanted with ultrasound technology for suture fixation and compared this with suture fixation alone and fixation with a nonabsorbable bone anchor using an ex vivo modified limb-press model. For evaluation, distance measurements on radiographs were performed and the angles between defined bony structures were calculated. The acquired measurements accounted for both craniocaudal and mediolateral movements, and the results showed that the absorbable anchor could neutralize excessive movement within the stifle joint in two of three measurements and seems to be a good alternative to well-known surgical methods.

Abstract

Background: This study evaluated joint stability after surgical repair of cranial cruciate ligament (CrCL)-deficient stifle joints in cats using a novel absorbable polylactide bone anchor in an ex vivo model. Methods: Thirty-six hindlimbs from cats with intact (G_i group) and transected CrCLs were treated with fabellotibial suture alone (G_FW group), suture combined with an absorbable polylactide bone anchor (G_WD group), or suture combined with a nonabsorbable bone anchor (G_FT group), positioned in a limb press with predefined joint angles (stifle joint: 120 ± 5°; hock joint: 120 ± 5°) and loaded with 10%, 20%, and 30% of body mass (BM). Predefined points were measured on lateral radiographs and with a coordinate measurement machine. Distances on radiographs (mm) were measured and angles (°) were calculated to represent the craniocaudal movement and the internal rotation of the tibia. Results: There were no differences for craniocaudal movement between G_i and G_FW or G_FT, but for G_WD regarding angle measurement at 30% BM. For internal rotation, there was no significant difference between G_i and G_FW or G_WD, but for G_FT. Conclusion: The used absorbable polylactide bone-anchor was able to stabilize the stifle joint regarding internal rotation and craniocaudal movement as calculated from distance measurements.

Hoof Pressure Distribution Pattern of Blue Sheep During Walking on Different Slopes: A Subject-Specific Analysis

The purpose of this study was to quantitatively assess the vertical force distribution (VFD) of subject-specific healthy blue sheep while walking on different slopes using a pressure-sensing walkway. The blue sheep was trained to walk over the pressure-sensing walkway by choosing a comfortable walking speed, and the slope angle increased from 0° to 25°. The sheep's hooves were divided into four quadrants, namely, the cranio-lateral, cranio-medial, caudo-lateral, and caudo-medial quadrants, to investigate the VFD of the peak vertical force (PVF), vertical impulse (VI) and occurrence time of the PVF during the stance phase (TPVF). This study demonstrates that the main stressed quadrant of the front hoof changes from the caudo-medial quadrant to the cranio-medial quadrant with increasing slope. The main stressed quadrant of the rear hoof is the cranio-medial quadrant and does not change with the increasing slope. For all the slopes, the vertical force shifted from the lateral quadrant to the medial quadrant and from the caudal quadrant to the cranial quadrant. All the results obtained in the study suggest the feasibility of detecting gait changes in blue sheep, which has potential for the diagnosis of lower limb musculoskeletal diseases in quadrupeds.

Development of a three-dimensional computer model of the canine pelvic limb including cruciate ligaments to simulate movement

Gait analysis as subjective visual assessment forms the foundation of the veterinarian's lameness examination. Pelvic limb lameness is frequently seen in dogs and the stifle joint with its cruciate ligaments, is a main cause of lameness due to cruciate ligament deficiency. In this study, we developed an open-source three-dimensional musculoskeletal pelvic limb model of a 30 kg Labrador Retriever including cruciate ligaments, simulating the gait cycle of the walking movement with the open-source programs NMSBuilder (Institutio Ortopedico Rizzoli, Bologna, Italy) and OpenSim (National Center for Simulation in Rehabilitation Research (NCSRR), Stanford, CA, USA). The computer model generated muscle activations based on motion data. The computed activations were similar to experimental electromyogram data. Highest joint torque was in extension/flexion in the stifle joint at 54 Nm at 14% of the gait cycle with cruciate ligaments. Highest stifle joint reaction force was 408 N at 16% of the gait cycle and was reduced after adding cruciate ligaments. Especially the cranial cruciate ligament loads up to 102 N (34% body weight). Cranial cruciate ligament forces increase with stifle extension and decrease with stifle flexion. On the contrary, the caudal cruciate ligament loads up to 27 N (9% body weight) during the swing phase with a flexed stifle joint. The model was validated with electromyogram data. The model's predictions are plausible because joint torques and forces match the applied ground reaction forces in curve progression and in timing. This model forms a basis for further investigations into stifle surgery after cruciate ligament deficiency.

Design of Two-Wheeled Motorcycle Tire Crown Contour Bioinspired by Cat Paw Pads

The grip force of tires is crucial for vehicle security and drivability under different driving conditions. A small contact area and stress concentration in the contact patch of two-wheeled motorcycle (TWM) tires result in a reduction in grip performance and wear resistance. Even worse, improving the grip and wear resistance together is difficult to achieve. The purpose of the current study is to analyze the dynamic grounding characteristics and geometry of a cat paw pad and then apply its structure to the TWM tire to improve the contact area and wear resistance under different operating conditions. A nonlinear finite element tire model that could accurately reconstruct the tire structure and realistically reflect the mechanical response to different loads was employed. Then, the accuracy of the tire model was validated by a static test with a control tire. For cats, the dynamic grounding characteristics and topology of paw pads were determined using a pressure-sensitive walkway and a three-dimensional (3D) laser scanner. The results indicated that the cat forepaw third pad (CFTP) exhibited excellent grip capacity. According to similarity transformation, a bionic tire crown was designed according to the lateral fitting curve of the CFTP. Comparative results showed the enlargement of the contact area and decreases in peak pressure and frictional energy rate for the bionic tire under different conditions. With these improvements, the grip performance was improved, and the service life was extended synchronously. These research results can be applied for the design of TWM tires, especially cross-country motorcycle tires.

Feline musculoskeletal ageing: How are we diagnosing and treating musculoskeletal impairment?

PRACTICAL RELEVANCE

An understanding of the process of musculoskeletal ageing - which all senior and geriatric cats will experience - is vital to maintaining the health and welfare of our ageing cat population.

CLINICAL CHALLENGES

Assessment of the feline musculoskeletal system is not always straightforward. Diagnosis of impairment relies on input from owners and veterinarians in terms of visual observation, and clinical and orthopaedic examination, in addition to diagnostic imaging.

AUDIENCE

This review is written for the primary care veterinary team.

AIMS

The goals are to raise awareness and improve clinical diagnosis of musculoskeletal impairment as a result of ageing. The article also reviews therapeutic options and considers the evidence available for the prevention/deceleration of musculoskeletal ageing and impairment.

EVIDENCE BASE

There is good evidence of a high prevalence of osteoarthritis (OA) and degenerative joint disease (DJD) in older cats. There is also good evidence to indicate that functional impairment and chronic pain are sequelae of musculoskeletal disease. However, there is a paucity of information for what is best practice for the management and treatment of musculoskeletal impairment in a clinical situation. There is also a lack of evidence on how prevention of central stimulation of the nervous system caused by musculoskeletal impairment and, in turn the development of chronic pain, can be avoided.

Clinical Outcomes and Stifle Osteoarthritis Assessment of Nine Cats Before and After Tibial Plateau Levelling Osteotomy

This study aimed to evaluate the clinical and radio graphical outcome of cats following TPLO surgery for cranial cruciate ligament deficiency. Each cat underwent orthopedic assessment, pre-operative radio graphical evaluation, surgical procedure, postoperative management and clinical re-examination 1, 2, and 12 months following surgery. Age, body weights, TPAs, meniscal tears, implants and osteoarthritis progression were recorded. Postoperative OA score was compared with that obtained 1 year after surgery using a paired t-test with commercially available software. Radio graphical evaluation performed 1 year after surgery showed no significant OA progression (P-value > 0.1). Minor complications occurred in one case (#7) in which a mild to moderate seroma was observed ten days after surgery. No major complications were recorded. Although TPLO surgery in cats remains controversial, this study suggests that it was a suitable option for surgical treatment of feline cranial cruciate ligament rupture, but considering the ex vivo outcomes recently published, further in vivo evaluation is strongly recommended.

Evaluation of a pressure plate for detection of hind limb lameness in cats

Detection of lameness in cats can be very time-consuming and frustrating. Feline studies have shown that the success of treatment can be evaluated by measurement of the ground reaction force (GRF). However, the possibility of multiple limb involvement or the presence of a compensatory mechanism has not been investigated. Furthermore, there has been no research in cats on possible differences in GRFs between those with stifle problems and those with hip problems, as reported in dogs. In this study, we compared temporospatial parameters and GRFs in 20 lame cats after femoral head and neck ostectomy (FHO) or stifle disease to those in 15 healthy cats. An orthopedic examination was performed in all cats and radiographs were obtained to confirm the disease. GRFs, including peak vertical force (PFz), vertical impulse (IFz), time to PFz, and temporospatial parameters, including step length, paw contact area, and stance phase duration, were calculated. We also calculated the symmetry index (SI) in the forelimbs and hind limbs. The GRFs were normalized to total force (% TF). We found that the IFz (% TF) and PFz (% TF) were lower in the affected limb than in the other limbs in the lame cats. When the lame cats were compared with the sound cats, this difference was only significant for IFz (% TF). The SI values for the PFz and IFz were significantly higher in the hind limbs than in the forelimbs in the lame cats group but there was no difference in the SI according to whether the problem was in the hip or stifle. There were also differences in stance phase duration and paw contact area in both the forelimbs and hind limbs between the sound group and the lame group. There was no difference in PF_Z (% TF) or IF_Z (% TF) in the affected limb between the lame cats with stifle and those after FHO; however, there were changes in time to PFz and step length. In conclusion, mild to moderate lameness can be detected and measured in cats using pressure plates. The compensatory mechanisms in cats at a walk appear to involve shifting the weight to the other three legs without favoring either the contralateral or the diagonal limb.

Biomechanical Comparison of Two Conical Coupling Plate Constructs for Cat Tibial Fracture Stabilization

OBJECTIVE

 This study aimed to compare the biomechanical characteristics of two conical coupling plate (CCP) constructs in an ex vivo feline tibial fracture gap model.

STUDY DESIGN

 Paired tibiae harvested from eight recently euthanatized cats were alternately assigned to one of two stabilization groups. One tibia was stabilized with a standard, 6-hole, 2.5-mm CCP and the contralateral tibia was stabilized with a 6-hole, 2.5-mm prototype CCP (pCCP). Non-destructive cyclic four-point craniocaudal bending, mediolateral bending and axial compression testing were performed, and stiffness was recorded. The specimens were then loaded to failure in axial compression, and yield and failure loads were recorded.

RESULTS

 During non-destructive testing, the pCCP constructs were significantly stiffer than the CCP constructs in both modes of bending and axial loading. Both constructs demonstrated significantly greater craniocaudal bending stiffness compared with mediolateral bending. Yield load and failure load were significantly greater for the pCCP constructs.

CONCLUSION

 The augmented design of the pCCP yielded superior mechanical characteristics during both non-destructive and destructive testings compared with constructs employing standard CCP. The more rigid design of the pCCP suggests that this implant may be better at withstanding greater loads, particularly when applied in a bridging fashion, during the postoperative convalescence. Further investigations are warranted to prospectively evaluate the clinical performance of the pCCP.

Biomechanical comparison of knotted and knotless stabilization techniques of the tarsal medial collateral ligament in cats: A cadaveric study

OBJECTIVE

To compare mechanical properties of intact feline medial collateral ligaments and three techniques for treatment of feline medial tarsal instability.

STUDY DESIGN

Controlled laboratory study.

SAMPLE POPULATION

Forty-eight normal, adult feline tarsi.

METHODS

Three repairs were tested: a bone tunnel with polypropylene (PP) suture, a bone tunnel with polyethylene (PE) cord, and a knotless anchor technique with PE cord. A cyclic (6-N preload; 5-N amplitude; 2-Hz frequency) tensile test (600 cycles) was performed on feline tarsi with either the long or the short medial tarsal ligament intact, with each reconstruction technique followed by a single-cycle load-to-failure test (0.5 mm/s) with a failure point at 2 mm of displacement. Total elongation, peak-to-peak elongation, stiffness, and maximum load to failure point were compared with the intact condition.

RESULTS

No differences in stiffness, total elongation, or peak-to-peak elongation were found between specimens repaired with the knotless technique and intact controls (P > .04), whereas tarsi repaired with the tunnel technique and PP were weaker (P < .008). Total and conditioning elongation were greater after tunnel reconstruction with PP than after knotless reconstruction (P = .005). Mean load to 2 mm of displacement tended (P = .03) to be higher after knotless than after knotted PP repairs and did not differ (P = .47) between tarsi repaired with the tunnel or anchor repairs with PE.

CONCLUSION

The mechanical properties of intact tarsi were superior to those of tarsi repaired with tunnel techniques and PP but were similar to those of tarsi repaired with knotless techniques with PE.

CLINICAL SIGNIFICANCE

Feline tarsal stabilization with the knotless technique for tarsal medial collateral ligament insufficiency may reduce the requirement for or duration of postoperative coaptation.

Kinetic analysis of felines landing from different heights

Background

Kinetic motion analysis has been used in canines and equines as a fundamental objective evaluation measurement. Cats are very capable jumpers, and this ability has biomimetic applications. It is essential to understand movement patterns and physical adaptations of this species, as cats are popular pets for humans. Further to this, motion analysis of a cat's movement patterns may provide potentially valuable information in relation to limb disease and injury. Therefore, the aim of this study was to investigate kinetic differences in cats when landing from varying preselected controlled heights.

Methods

The peak vertical force (PVF) and paw contact area (CA) of both the forelimbs and hindlimbs were collected from seven healthy Chinese domesticated cats while landing from heights of 30 cm, 50 cm, 70 cm and 90 cm respectively. The falling motivation for the cats was facilitated with the use of a flip board. This device provided the basis for the cats to land passively.

Results

The results indicated that the PVF of all examined limbs (fore right, fore left, hind right, hind left) significantly increased as the height increased. When the PVF from the hindlimbs and forelimbs were compared, the forelimbs recorded significantly greater values for all heights examined (P < 0.001). The PVF of the hindlimbs was symmetrical at all heights, but forelimb symmetry only occurred at the lower heights. The hindlimbs demonstrated larger CA than the forelimbs measured from all heights on landing (P < 0.001). Moreover, the paw CA on the left and right limbs were symmetrical.

Discussion

The paw CA of cats may be an effective parameter to evaluate abnormalities or diseases in the limbs of cats. Additionally, these findings highlight how cats land from varying heights, which may also provide reference values for the bionic design of artificial limbs for felines and treatment for limb diseases in this species.

Unique Differences of Minimally Invasive Fracture Repair in the Feline

As the saying goes, "cats are not small dogs." Throughout veterinary medicine history, most of the literature focus has been on the canine. Feline patients, however, now constitute a larger proportion of the pet population and are unique in many aspects. They differ anatomically and biomechanically from canines and have specific recovery needs and different pain-related behaviors. It is important that veterinary surgeons understand these differences and improve their knowledge base in the treatment of cats. This article highlights the differences in cats relevant to minimally invasive fracture repair and how they affect a surgeon's approach to fractures in cats.

Comparison of ground reaction force measurements in a population of Domestic Shorthair and Maine Coon cats

Current research on gait analysis mostly involves horses and dogs. Feline kinetics and kinematics are being investigated and receiving more clinical interest at present. Ground reaction forces measured on pressure-sensitive mattresses have been established in healthy Domestic Shorthair cats (DSH). Currently, no further information exists on either breed-specific measured gait reaction forces or comparisons among breeds. Because Maine Coon (MC) cats appear to be over-represented with orthopaedic diseases of the hind limb (hip dysplasia, patellar luxation), we evaluated ground reaction force GRF measurements in MC cats and compared them with those of DSH cats. Pre-evaluation radiological and clinical exams determined that the cats were not lame. The parameters evaluated were peak vertical force (PFz), vertical impulse (IFz), time to PFz (TPFz), step length (SL), paw contact area (PCA), stance phase duration (SPD) and symmetry index (SI) for the fore- and hind limbs. In both breeds, PFz and IFz were greater in forelimbs than in hind limbs. The PFz and IFz in Newtons were higher in the MC cats compared to the DSH cats, but not after normalisation for total force (%TF) and body mass (%BM). Furthermore, due to their body conformation, MC cats have a longer SL, larger PCA, and higher body weight than DSH cats. No other parameters differed significantly, except that the TPFz displayed an earlier value in the MC hind limbs. Measured symmetry indices were similar to those reported in dogs and did not differ between breeds. This is the first study to report GRF values and temporospatial parameters in a healthy MC cat population. However, our results could not confirm differences between normalized PFz and IFz and temporospatial parameters between the breeds. The authors therefore conclude that genetic or other causes may be involved in orthopaedic hind limb pathogenesis seen in MC cats more often than in other breeds.

Pressure Mat Analysis of Walk and Trot Gait Characteristics in 66 Normal Small, Medium, Large, and Giant Breed Dogs

Objectives: To document temporospatial variables and gait symmetry measured by the GAITRite® system for normal, healthy dogs at the walk and trot with the leash side recorded.

Study Design: Observational, prospective, cohort study.

Sample Population: 66 healthy dogs of various common breeds with no evidence of lameness that were small (< 10 kg), medium (10- < 25 kg), large (25- < 40 kg), or giant (≥40 kg).

Methods: Dogs walked and trotted at their preferred velocity on a pressure sensing walkway system. Video observation confirmed inclusion criteria were met for three valid trials at each gait for each dog. Coefficients of variance were used to summarize the data for analysis. Fore and hindlimb ratios were compared. Gait symmetry was assessed with the leash on the left and right side.

Results: Coefficients of variation for gait parameters ranged from 20 to 28% for all except velocity and hind reach. There was no statistically significant difference in differences in fore and hindlimb ratios for stance %, GLS, TPI, or step:stride ratio, across weight categories or between walk and trot. Less than 8% of normal dogs had a GLS score < 90 (indicating lameness). Leash side did influence gait symmetry, since GLS, TPI, and step:stride all had statistically significant differences in means between leash side, irrelevant of the weight category or gait.

Conclusions and Clinical Relevance: This system allowed simple, reliable gait assessment and values reported may be considered normal reference ranges for temporospatial variables collected with this system within the weight ranges and gaits reported. Controlling leash side and patient size is recommended for therapeutic intervention studies.

Effective Mechanical Advantage Allometry of Felid Elbow and Knee Extensors

Larger terrestrial mammals have generally been found to use more extended limb postures, a mechanism which maintains muscular requirements at larger sizes by improving the effective mechanical advantage (EMA) of limb musculature. Felids, however, have been documented to maintain joint angles across body sizes. If felid morphology scales isometrically, it would mean larger felids have relatively weaker muscles, compromising locomotor activities. Here, we examine the allometric relationships between the EMA of the elbow and knee extensors and body mass, finding that the EMA of the triceps brachii and quadriceps muscles scale with positive allometry. When species-specific joint angles were used rather than felid-average joint angles, EMA scales to body mass with more positive allometry. When the scaling of the muscle and ground reaction force (GRF) lever arms were investigated individually the allometric signal was lost; however, the muscle lever arms generally have allometric slope coefficients that are consistent with positive allometry, while the GRF lever arms demonstrate negative allometric slope coefficients. This suggests there are subtle alterations to limb morphology allowing different felid species to achieve an increased EMA via distinctive mechanisms. The quadriceps EMA was found to scale with sufficient positive allometry to compensate for increases in size without alteration in muscular anatomy; however, this is not the case for the triceps brachii EMA. Anat Rec, 2018. © 2018 Wiley Periodicals, Inc. Anat Rec, 302:775-784, 2019. © 2018 Wiley Periodicals, Inc.

The Site of Bone Marrow Acquisition Affects the Myeloid to Erythroid Ratio in Apparently Healthy Dogs

Bone marrow (BM) cytology and histopathology are complementary tools used to investigate hematological diseases. The purpose of this study was to determine if there are site-dependent differences in the diagnostic quality, myeloid to erythroid ratio (MER), and discordant findings in samples from different sites in the same dog. Eighteen apparently healthy dogs were used in the study. The sequence of sample acquisition was randomized according to a Latin square, and samples for BM cytology and histology were collected from both humeri and both ilial crests immediately after death. Board-certified clinical and anatomical pathologists read the cytology and histology, respectively. The data were analyzed using a mixed-effect model. The site of BM acquisition did not affect BM sample quality. The rate of discordant clinical findings between sites was 0.05 (95% confidence interval, 0.01-0.13). In general, by cytology, the MERs were slightly but significantly greater in samples from the ilial crests than from the humeri ( P = .01). The measured MER for histology was nearly twice that for cytology for all sites ( P < .001). In conclusion, there was a low-rate, site-dependent discordance in diagnostic findings in BM samples and differences in MER between the ilial crest and the humerus. A similar study is justified in sick dogs with hematological disease to determine the effect of sampling site on discordant findings between sites.

Spontaneous painful disease in companion animals can facilitate the development of chronic pain therapies for humans

OBJECTIVE

To outline the role that spontaneous osteoarthritis (OA) in companion animals can play in translational research and therapeutic pharmacological development.

OUTLINE

Narrative review summarizing the opportunities and limitations of naturally occurring, spontaneous OA as models of human OA pain, with a focus on companion animal pets. The background leading to considering inserting spontaneous disease models in the translational paradigm is provided. The utility of this model is discussed in terms of outcome measures that have been validated as being related to pain, and in terms of the potential for target discovery is outlined. The limitations to using companion animal pets as models of human disease are discussed.

CONCLUSIONS

Although many steps along the translational drug development pathway have been identified as needing improvement, spontaneous painful OA in companion animals offers translational potential. Such 'models' may better reflect the complex genetic, environmental, temporal and physiological influences present in humans and current data suggests the predictive validity of the models are good. The opportunity for target discovery exists but is, as yet, unproven.

In vivo fluoroscopic kinematography of dynamic radio-ulnar incongruence in dogs

Aim of the study was to investigate dynamic radio-ulnar incongruence (dRUI) in the canine elbow joint comparing orthopedic healthy and dysplastic dogs in a prospective in vivo study design. In 6 orthopedic sound elbow joints (5 dogs, median age 17 months & mean body weight 27.9 kg) and 7 elbow joints with medial coronoid disease (6 dogs, median age 17.5 months & mean body weight 27.6 kg) 0.8 mm Ø tantalum beads were surgically implanted into radius, ulna and humerus for dynamic radiosteriometric analysis (RSA) using high-speed biplanar fluoroscopy with the dogs walking on a treadmill. dRUI, in the form of proximo-distal translation of the radius relative to the ulna, was measured for the first third of stance phase and compared between groups using unpaired t-testing. Healthy elbow joints exhibited a relative radio-ulnar translation of 0.7 mm (SD 0.31 mm), while dysplastic joints showed a translation of 0.5 mm (SD 0.30 mm). No significant difference between groups was detected (p = 0.2092, confidence interval -0.6 – 0.2). Based on these findings dRUI is present in every canine elbow joint, as part of the physiological kinematic pattern. However, dysplastic elbow joints do not show an increased radio-ulnar translation, and therfore dRUI cannot be considered causative for medial coronoid disease.

Transplants of Neurotrophin-Producing Autologous Fibroblasts Promote Recovery of Treadmill Stepping in the Acute, Sub-Chronic, and Chronic Spinal Cat

Adult cats show limited spontaneous locomotor capabilities following spinal transection, but recover treadmill stepping with body-weight-supported training. Delivery of neurotrophic factors such as brain-derived neurotrophic factor (BDNF) and neurotrophic factor 3 (NT-3) can substitute for body-weight-supported training, and promotes a similar recovery in a shorter period of time. Autologous cell grafts would negate the need for the immunosuppressive agents currently used with most grafts, but have not shown functional benefits in incomplete spinal cord injury models and have never been tested in complete transection or chronic injury models. In this study, we explored the effects of autologous fibroblasts, prepared from the individual cats and modified to produce BDNF and NT-3, on the recovery of locomotion in acute, sub-chronic and chronic full-transection models of spinal injury. Fourteen female cats underwent complete spinal transection at T11/T12. Cats were separated into four groups: sham graft at the time of injury, and BDNF and NT-3 producing autologous fibroblasts grafted at the time of injury, 2 weeks after injury, or 6 weeks after injury. Kinematics were recorded 3 and 5 weeks after cell graft. Additional kinematic recordings were taken for some cats until 12 weeks post-graft. Eleven of 12 cats with neurotrophin-producing grafts recovered plantar weight-bearing stepping at treadmill speeds from 0.3 to 0.8 m/sec within 5 weeks of grafting, whereas control cats recovered poor quality stepping at low speeds only (≤ 0.4 m/sec). Further, kinematic measures in cats with grafts were closer to pre-transection values than those for controls, and recovery was maintained up to 12 weeks post-grafting. Our results show that not only are autologous neurotrophin-producing grafts effective at promoting recovery of locomotion, but that delayed delivery of neurotrophins does not diminish the therapeutic effect, and may improve outcome.

Coefficients of variation of ground reaction force measurement in cats

Gait analysis has been extensively performed in dogs and horses; however, very little is known about feline biomechanics. It was, therefore, the aim of this study to determine the coefficient of variation (CV) among three ground reaction force (GRF) measurements taken for 15 client-owned European shorthaired cats without a training period and a short acclimatisation time. Gait was measured as each cat walked across a pressure-sensitive walkway, and measurements were made three times over a multi-week period (range: 2 to 17 weeks). The parameters evaluated were peak vertical force (PFz), vertical impulse (IFz), stance phase duration (SPD), step length (SL), paw contact area (PCA) and symmetry index (SI%) of the front and hind limbs. After averaging each of the values from the three measurements, the CV and 95% confidence interval (CI) were calculated for all parameters. PFz showed the lowest CV (~ 3%), while IFz showed the highest CV (~11%) when normalised to body mass. When the GRFs were normalised to total force, the CV of PFz dropped to ~2% and that of IFz dropped to ~3%. The CV of SL and PCA were lower (~6% respectively ~5%) compared to the CV for SPD (~10%). The SI% for both PFz and IFz were comparable to the values reported in the gait analysis literature for dogs. Results of the current study indicate that gait analysis of cats using pressure-sensitive walkways produces reliable data and is a promising approach for evaluation of lameness. The results also suggest that PFz may be a more reliable parameter than IFz and that normalisation to percent of total force may aid in interpretation of the evaluated data.

Characterization and validation of a split belt treadmill for measuring hindlimb ground-reaction forces in able-bodied and spinalized felines

BACKGROUND

The measurement of ground reaction forces (GRFs) in animals trained to locomote on a treadmill after spinal cord injury (SCI) could prove valuable for evaluating training outcomes; however, quantitative measures of the GRFs in spinal felines are limited.

NEW METHOD

A split belt treadmill was designed and constructed to measure the GRFs of feline hindlimbs during stepping. The treadmill consists of two independent treadmill assemblies, each mounted on a force plate. The design allows measurements of the vertical (Fz), fore-aft (Fy) and mediolateral (Fx) ground-reaction forces for both hindlimbs while the forelimbs are resting on a platform.

RESULTS

Static and dynamic noise tests revealed little to no noise at frequencies below 6Hz. Validation of the force plate measurements with a hand-held force sensor force showed good agreement between the two force readings. Peak normalized (to body mass) vertical GRFs for intact cats were 4.89±0.85N/kg for the left hindlimb and 4.79±0.97N/kg for the right. In comparison, trained spinalized cats peak normalized vertical GRFs were 2.20±0.94N/kg for the left hindlimb and 2.85±0.99N/kg for the right.

COMPARISON WITH OTHER EXISTING METHODS

Previous methods of measuring GRFs used stationary single force plates or treadmill mounted to single force plate. Using independent treadmills for each hindlimb allows measurement of the individual hindlimb's GRFs in spinalized cats following body-weight supported treadmill training.

CONCLUSIONS

The split belt force treadmill enables the simultaneous recording of ground-reaction forces for both hindlimbs in cats prior to spinalization, and following spinalization and body-weight-supported treadmill training (BWST).

Grizzly bear (Ursus arctos horribilis) locomotion: forelimb joint mechanics across speed in the sagittal and frontal planes

The majority of terrestrial locomotion studies have focused on parasagittal motion and paid less attention to forces or movement in the frontal plane. Our previous research has shown that grizzly bears produce higher medial ground reaction forces (lateral pushing from the animal) than would be expected for an upright mammal, suggesting frontal plane movement may be an important aspect of their locomotion. To examine this, we conducted an inverse dynamics analysis in the sagittal and frontal planes, using ground reaction forces and position data from three high-speed cameras of four adult female grizzly bears. Over the speed range collected, the bears used walks, running walks and canters. The scapulohumeral joint, wrist and the limb overall absorb energy (average total net work of the forelimb joints, -0.97 W kg^-1). The scapulohumeral joint, elbow and total net work of the forelimb joints have negative relationships with speed, resulting in more energy absorbed by the forelimb at higher speeds (running walks and canters). The net joint moment and power curves maintain similar patterns across speed as in previously studied species, suggesting grizzly bears maintain similar joint dynamics to other mammalian quadrupeds. There is no significant relationship with net work and speed at any joint in the frontal plane. The total net work of the forelimb joints in the frontal plane was not significantly different from zero, suggesting that, despite the high medial ground reaction forces, the forelimb acts as a strut in that plane.

Repeatability of quantitative sensory testing in healthy cats in a clinical setting with comparison to cats with osteoarthritis

Objectives

The aim of this study was to evaluate the repeatability of quantitative sensory tests (QSTs) in a group of healthy untrained cats (n = 14) and to compare the results with those from cats with osteoarthritis (n = 7).

Methods

Peak vertical force (PVF) and vertical impulse were measured on a pressure plate system. Thermal sensitivity was assessed using a temperature-controlled plate at 7°C and 40°C. Individual paw lifts and overall duration of paw lifts were counted and measured for each limb. Paw withdrawal thresholds were measured using manual and electronic von Frey monofilaments (MVF and EVF, respectively) applied to the metacarpal or metatarsal pads. All measurements were repeated twice to assess repeatability of the tests.

Results

In healthy cats all tests were moderately repeatable. When compared with cats with osteoarthritis the PVF was significantly higher in healthy hindlimbs in repeat 1 but not in repeat 2. Cats with osteoarthritis of the forelimbs showed a decrease in the frequency of paw lifts on the 7°C plate compared with cats with healthy forelimbs, and the duration of paw lifts was significantly less than healthy forelimbs in the first repeat but not in the second repeat. Osteoarthritic limbs had significantly lower paw withdrawal thresholds with both MVF and EVF than healthy limbs.

Conclusions and relevance

QSTs are moderately repeatable in untrained cats. Kinetic gait analysis did not permit differentiation between healthy limbs and those with osteoarthritis, but thermal sensitivity testing (cold) does. Sensory threshold testing can differentiate osteoarthritic and healthy limbs, and may be useful in the diagnosis and monitoring of this condition in cats in the clinical setting.

Vertical force distribution in the paws of sound Labrador retrievers during walking

In contrast to gait analysis in humans, where pedobarography is an integral part of biomechanical studies, veterinary researchers have rarely investigated vertical force distribution (VFD) in the paws of dogs. The aim of this study was to investigate the VFD of peak of vertical force (PFz), vertical impulse (IFz) and time of occurrence of PFz during stance phase (TPFz) in 20 sound, adult Labrador retrievers walking normally on a pressure plate. A technique was used that divided the canine paw prints into quadrants. A general linear model was introduced to investigate the effects of forelimbs/hindlimbs, body side, and medial/lateral and cranial/caudal quadrants on VFD as they related to the total force (sum of all PFz/IFz values). For PFz and IFz, there were significantly greater effects on VFD in the lateral quadrants compared to the medial quadrants, respectively (6.49 ± 2.56% vs. 6.01 ± 2.60% and 6.62 ± 3.06% vs. 5.88 ± 3.21%; P < 0.001), in the forelimbs compared to the hindlimbs (8.02 ± 2.13% vs. 4.48 ± 1.61% and 8.02 ± 2.83% vs. 4.48 ± 2.36%; P < 0.001), and in the cranial quadrants compared to the caudal quadrants (7.87 ± 2.09% vs. 4.63 ± 1.93% and 8.57 ± 2.17% vs. 3.88 ± 1.98%; P < 0.001). The cranial/caudal ratio was higher in the hindlimbs than in the forelimbs (PFz: 2.10 ± 0.45 vs. 1.65 ± 0.32; P = 0.001; and IFz: 3.35 ± 0.80 vs. 2.04 ± 0.46; P < 0.001). The TPFz was reached earlier in the hindlimbs than in the forelimbs (46.86 ± 19.16% vs. 54.08 ± 19.62%; P < 0.001) and in the caudal quadrant than in the cranial quadrant (32.57 ± 5.77% vs. 68.37 ± 10.01%; P < 0.001). These data from sound Labrador retrievers could be used as a basis for future research investigating orthopedically- and/or neurologically-impaired animals.

Pilot evaluation of a novel unilateral onychectomy model and efficacy of an extended release buprenorphine product

Background

Non-steroidal anti-inflammatory drugs (NSAIDs), transdermal fentanyl patches, and transmucosal buprenorphine are probably the most commonly used options for providing post-operative analgesia in the early at-home period. However, these require daily administration or are associated with abuse concerns. One of the significant unmet needs in veterinary surgery and pain management is for longer acting opioids for cats to effectively bridge the gap between the in-hospital and at-home recovery periods.

A proof of concept study of an extended release formulation of buprenorphine HCL (ER-Bup) was conducted using objective kinetic measures and a unilateral onychectomy model. Using a blinded, randomized, two period crossover design, four cats were allocated to control (saline) or ER-Bup (0.6 mg/kg, subcutaneously [SC]) treatment groups. All animals underwent a unilateral forelimb onychectomy per period with a washout/recovery period in between. Observational pain scores and kinetic data (using a pressure sensitive walkway [PSW]) were collected prior to (baseline) and at intervals for 72 h following surgery. Symmetry indices were derived for kinetic variables (peak vertical force [PVF]; vertical impulse [VI]) of each forelimb for landing following a jump and for walking. A rescue analgesic protocol was in place. Effect of surgery and treatment were evaluated using a mixed model statistical approach.

Results

No cats required rescue analgesics based on subjective pain score. ER-Bup had a positive influence on subjective pain scores during the 72 h postsurgery (p = 0.0473). PVF and VI of the operated limb were significantly decreased for both landing (p < 0.0001 and p < 0.0001) and walking (p < 0.0001 and p < 0.0001 respectively) compared to control. ER-Bup resulted in significantly decreased asymmetry in limb use during landing (PVF, p < 0.0001; VI, p < 0.0001) and walking (PVF, p = 0.0002, VI, p < 0.0001). The novel use of data collected following a jump from an elevated platform appeared to provide all desired information and was easier to collect than walking data.

Conclusion

This study demonstrates that SC administration of ER-Bup may be an effective analgesic for a 72 h period postoperatively. Furthermore, landing onto a PSW from an elevated perch may be a useful and efficient way to assess analgesics in cats using a unilateral model of limb pain.

Electronic supplementary material

The online version of this article (doi:10.1186/s12917-017-0943-5) contains supplementary material, which is available to authorized users.

Effect of tibial tuberosity advancement on cranial tibial subluxation in the feline cranial cruciate deficient stifle joint: An ex vivo experimental study

The effects of Tibial Tuberosity Advancement (TTA) on Cranial Tibial Subluxation (CTS) and Tibial Rotation Angle (TRA) were evaluated in a model of feline Cranial Cruciate Ligament (CrCL)-deficient stifle joint. Ten hindlimbs of adult cats were used. Quadriceps and gastrocnemius muscles were simulated using cables, turnbuckles and a spring. An axial load of 30% body weight was applied. The stifle and talocrural joint angles were adjusted to 120°. Patellar tendon angle (PTA), CTS and TRA were measured radiographically before and after CrCL section, after TTA and after additional advancement by 1 and 2mm. CrCL section resulted in a CTS of 8.1±1.5mm and a TRA of 18.4±5.7 °. After TTA, PTA was significantly decreased from 99.1±1.7° to 89.1±0.7°; CTS and TRA did not change significantly (7.8±1.0mm and 15.9±5.7° respectively). Additional advancement of the tibial tuberosity by 1mm did not significantly affect CTS and TRA. Additional advancement of the tibial tuberosity by 2mm significantly reduced the PTA to 82.9±0.9°. A significant decrease of CTS (6.9±1.3mm) and TRA (14.7±3.6°) was also observed. A lack of stabilization of the CrCL deficient stifle was observed after TTA in this model of the feline stifle. Even though the validity of the model can be questioned, simple transposition of the technique of TTA from the cat to the dog appeared hazardous.

Grizzly bear (Ursus arctos horribilis) locomotion: gaits and ground reaction forces

Locomotion of plantigrade generalists has been relatively little studied compared with more specialised postures even though plantigrady is ancestral among quadrupeds. Bears (Ursidae) are a representative family for plantigrade carnivorans, they have the majority of the morphological characteristics identified for plantigrade species, and they have the full range of generalist behaviours. This study compared the locomotion of adult grizzly bears (Ursus arctos horribilis Linnaeus 1758), including stride parameters, gaits and analysis of three-dimensional ground reaction forces, with that of previously studied quadrupeds. At slow to moderate speeds, grizzly bears use walks, running walks and canters. Vertical ground reaction forces demonstrated the typical M-shaped curve for walks; however, this was significantly more pronounced in the hindlimb. The rate of force development was also significantly higher for the hindlimbs than for the forelimbs at all speeds. Mediolateral forces were significantly higher than would be expected for a large erect mammal, almost to the extent of a sprawling crocodilian. There may be morphological or energetic explanations for the use of the running walk rather than the trot. The high medial forces (produced from a lateral push by the animal) could be caused by frontal plane movement of the carpus and elbow by bears. Overall, while grizzly bears share some similarities with large cursorial species, their locomotor kinetics have unique characteristics. Additional studies are needed to determine whether these characters are a feature of all bears or plantigrade species.