Deep digital flexor tendon force and digital mechanics in normal ponies and ponies with rotation of the distal phalanx as a sequel to laminitis.

REASONS FOR PERFORMING STUDY: Previous studies have implicated tension in the deep digital flexor tendon (DDFT) in the rotation of the distal phalanx (DP) after the breakdown of the dorsal laminae caused by laminitis. Howeveer, once the DP has rotated, the DDFT should become shorter, reducing the force it exerts on the DP. OBJECTIVE: To compare DDFT force and ground reaction forces (GRFs) in normal ponies and ponies with rotation of the DP as a sequel to laminitis. METHODS: Six normal ponies (Group 1) and 6 sound ponies with 6-13 degrees of rotation of the DP in relation to the dorsal hoof wall (Group 2) were assessed at trot using forceplate and motion analysis. The force in the DDFT was calculated by assuming that the extending moment at the distal interphalangeal (DIP) joint resulting from the GRF was equal to the flexing moment created by the force in the DDFT during the stance phase (inverse dynamics). RESULTS: In early stance, the peak DDFT force (mean+/-s.d.) in the normal ponies was 1.92+/-1.63 N/kg. However, in Group 2, the point of zero moment was palmar to the centre of rotation of the DIP joint for the first 40% of stance and hence DDFT force was zero. Force in the DDFT reached a peak of 10.00+/-3.56 N/kg at 60.7+/-5.6% of stance in Group 1 and 6.41+/-1.37 N/kg at 79.2+/-9.6% of stance in Group 2. CONCLUSIONS: DDFT force in Group 2 laminitic ponies was much reduced until late stance, when it neared normal values. POTENTIAL RELEVANCE: Further studies of ponies with rotation of the DP as a sequel to laminitis should assist farriery aimed at reducing the force in the DDFT through the breakover phase of stance to protect damaged dorsal laminae.

In vitro mechanical properties of different equine hoof wall crack fixation techniques.

Hoof wall cracks need mechanical stabilisation to allow healing. Common techniques are fixation with screws, wires and plates or bonding of a patch across the crack. An in vitro system to determine the shear properties of equine hoof crack repairs is described. The force and displacement at yield, stiffness and ultimate force were determined for 4 repair techniques based on an acrylic material, polyurethane patch attached with cyanoacrylate adhesive, steel plate attached with screws and a transverse metal bar cut into the hoof wall. The cyanoacrylate bonded patch repair had lower values for all parameters measured (n = 8, P<0.05) and the other 3 repairs had similar mechanical properties. This study demonstrates that acrylic adhesive repairs can resist similar shear forces to traditional screw plate repairs without risk of penetrating into the sensitive structures of the foot. The transverse bar mounted across the crack had similar resistance to shear as the much larger screw plate and plain bonding repair techniques. This novel technique may be a useful adjunct to other repair methods.

In vitro evaluation of a novel prosthesis for laryngoplasty of horses with recurrent laryngeal neuropathy.

A prosthesis, composed of a steel cable and stress-reducing washers, was developed to prevent failure of laryngoplasty, a common treatment for horses affected by recurrent laryngeal neuropathy. Laryngoplasties were performed on 15 cadaveric larynges using a polyester suture on one side and the cable prosthesis on the other. Each prosthesis was distracted at a displacement rate of 20 mm/s using a servohydraulic materials testing machine until laryngoplasty failed. Distraction force and actuator displacement were recorded and analysed. All 15 laryngoplasties performed with a suture failed at the muscular process at a mean +/- s.d. force of 55.8 +/- 13.1 N. Six laryngoplasties performed with the cable prosthesis failed at the muscular process at mean force 219.6 +/- 125.0 N. In the other 9, the arytenoid cartilage was avulsed from the larynx at mean force 206.4 +/- 75.3 N, and the cable then tore through the muscular process at mean force 357.0 +/- 32.0 N. The difference in force required to cause failure of laryngoplasty was significant (P<0.0001). Although the prosthesis resisted substantially higher forces than did the suture, the effects of the prosthesis in vivo must be evaluated.

In vitro evaluation of nonrigid support systems for the equine metacarpophalangeal joint.

Metacarpophalangeal (MCP) joint extension is primarily resisted by the digital flexor tendons and suspensory ligament. A variety of external support techniques are used to protect these supporting structures from or after injury by resisting MCP joint extension, although not all are effective and/or practical for use in an exercising horse. In this study, 7 forelimbs were loaded in vitro to determine the effect of a simple gamgee bandage, a 3-layered bandage with and without a contoured palmar splint, a neoprene exercise boot, and an innovative carbon fibre composite exercise boot (Dalmar tendon support boot). There was no significant resistance to MCP joint extension by the gamgee or neoprene exercise boot. The 3-layered bandage had a significant (P<0.01) supporting effect at MCP angles of > or = 245 degrees, and when combined with the contoured splint at angles of > or = 230 degrees. The Dalmar tendon support boot resisted MCP extension at angles of > or = 245 degrees (settings 1 and 2) and > or = 225 degrees (setting 3). These data demonstrate that the contoured splint and the Dalmar tendon support boot (which is also easily fitted for use during exercise) are useful for the management of tendon/ligament injury and during rehabilitation.

Are there associations among physical activity, fatigue, sleep quality and pain in people with mental illness? A pilot study.

Good mental health is imperative to well-being. Symptoms of fatigue, chronic pain and poor sleep are common in people with mental illness and contribute to substantial loss of functioning. Physical exercise interventions have shown to decrease these symptoms in a range of populations; however, their possible association with physical activity related to day-to-day functioning have not been explored in people hospitalized with severe mental illness. Inpatients (n = 4) of a metropolitan mental health facility were fitted with an Actiwatch, which collected physical activity and sleep measures for an anticipated 14-day data collection period. During this time, morning and evening pain and fatigue scores were collected on an 11-point numerical rating scale. Significant associations were found between morning pain and morning fatigue scores (ß = -0.44, P = 0.023), morning pain and physical activity (ß = 12.34, P = 0.042), and physical activity and evening pain scores (ß = 0.20, P = 0.017). Fatigue tended towards interfering more with quality of life than did pain, but this was not significant (P = 0.07). This study provided preliminary data suggesting associations between pain and fatigue, and intensity of pain and physical activity levels. This information can be used to generate hypotheses for future clinical trials.

Forces applied with a hoof tester to cadaver feet vary widely between users.

Hoof testers are commonly used in equine practice. In this study, we determined the intraoperator and interoperator reliability of force application with hoof testers for different groups: experienced veterinarians, novices and farriers. For this purpose, we have developed and validated an instrumented hoof tester. Forces varied significantly between the different regions of the foot for experienced operators applying the highest forces to the heels, then the frog, then the toe, and the lowest forces to the quarters. Novices applied significantly more force to the toe versus the frog. Intraoperator reliability varied significantly between regions and operators. Novices had the narrowest width of limits of agreement for the frog and heel, but the widest for the toe and the quarters, whereas farriers had the narrowest width of agreement for the toe and quarter. Force application differed significantly between groups for the frog and heel regions, but not the toe and quarters. Veterinarians applied higher forces to the frog compared with farriers and novices, and higher forces to the heel compared with novices. This study showed that hoof tester forces vary widely within and between operators, and standardisation of hoof tester use is needed to make this diagnostic test more reliable.

Modification of a force plate system for equine gait analysis on hard road surfaces: a technical note.

Studies on horseshoe materials have been limited to the analysis of kinematic data to determine slip times and distances, since equine force plate analysis is traditionally undertaken on a rubber-surfaced force plate. The purpose of this study was to modify a force plate for measuring ground reaction forces on a road surface and report preliminary data from the system. A steel-reinforced concrete top plate of 18 mm thickness and mass 23 kg, and a 12 mm thick top plate of 6 mm bituminous macadam wear coat (road surface) contained in a tray constructed of 2 mm thick steel, mass 21 kg, were constructed. The top plates were bolted to a forceplate and resonance frequency of the force plate top plate combinations were 278 Hz (concrete) and 218 Hz (roadway), respectively. Simultaneous kinetic and kinematic data were collected while a horse, shod in steel horseshoes, was trotted over the concrete-topped force plate until 8 foot placements were recorded. The foot slipped for mean +/- s.d. 35 +/- 7 mm in 29 +/- 8 ms after impact and both Fy and Fz increased during foot slip. The ratio of Fy/Fz during slip was relatively constant at 0.56 +/- 0.05. The top plates have proved resilient in use and have withstood a variety of horseshoe designs and tungsten-capped stud nails with minimal damage. They enable measurement of ground reaction forces on hard surfaces and the calculation of the energy dissipated via foot slippage by integration of the craniocaudal force-foot position data after impact.

The effect of shoe material on the kinetics and kinematics of foot slip at impact on concrete.

Previous studies on shoeing have demonstrated that shoe material alters the time taken from foot impact to the foot stopping sliding (slip time) and the distance slid. These are assumed to reflect differences in the craniocaudal ground reaction force (GRF) between the shoe and the ground during foot slip. This study tested the hypothesis that the slip time and distance are reflected in the resistance to slippage of the foot after impact. The forefeet of 8 horses were shod in horseshoes constructed of steel, plastic and rubber. Each horse was trotted for 8 placements per forefoot in each shoe type over a concrete topped forceplate and simultaneous kinematic data recorded at 240 Hz. Slip distance and slip time were calculated from the kinematic data and craniocaudal (Fy), and vertical (Fz) GRFs determined during slip the averaged for each shoe type. The slip time and distance were variable between runs in all 3 shoe types, and there was no significant difference between the mean values for the 3 shoe types. Fy reached a value of 0.98 +/- 0.17 N/kg during slip in the plastic shoes which was significantly lower than the rubber shoes, at 1.13 +/- 0.17 N/kg, P = 0.02. The Fy/Fz ratio (a measure of dynamic friction) was significantly lower in the plastic shoes, 0.34 +/- 0.08, compared to the steel shoes, 0.46 +/- 0.04, P = 0.003. This study is being extended to investigate effects of shoe slippage at the end of the stance phase and the energy dissipation during foot slip in the different shoe types. Future investigations should aim to identify the optimum slip characteristics to modulate loading (magnitude and rate) during impact, with the aim of reducing the risk of injury.