The College of Animal Physiotherapy. Diploma in Animal Physiotherapy. Module 8 Gait analysis and exercise prescription

Transcription

1 The College of Animal Physiotherapy Diploma in Animal Physiotherapy Module 8 Gait analysis and exercise prescription Copyright: The College of Animal Physiotherapy Ltd

2 AIMS This module aims to provide students with a good understanding of locomotion and with the ability to design treatment plans for rehabilitation. OBJECTIVES At the end of this module you should be able to; Recognise good and bad conformation and understand how conformation effects movement. Discuss basic biomechanics and understand how forces are involved in locomotion. Recognise and describe the different gaits and stages of movement. Recognise gait abnormalities and identify the possible causes of an abnormal gait. Create treatment plans and prescribe exercises. Understand the importance of fitness. INTRODUCTION It is essential to understand the parameters of a normal gait in order to recognise gait abnormalities. The veterinary diagnosis you have been given will inform you of the gait abnormality and its source but is essential that the physiotherapist can firstly, understand the link between the lameness and the injury and secondly, recognise any changes to this lameness, good or bad, so that the vet can be kept informed of the animal s progress. The physiotherapist s treatment is the core treatment in the rehabilitation of an animal. However if after that treatment the owner does not follow a careful follow up plan then re-injury will often occur. The second section of this module will cover exercise plans. The application of specifically tailored exercises and a graduated fitness program will enhance the benefits of your work. 1

3 CONTENTS Introduction 1 Section 1 Conformation 4-8 o Test questions 8 Section 2 The study of movement 9-18 o Biomechanics 9 o Kinematics, Kinetics, Kinesiology 10 o Stride 11 o The gaits 11 o The step cycle swing and stance 12 o Centre of gravity 13 o Gait analysis 14 o Observation 17 o Locating muscle injuries 18 o Test questions 18 Section 3 Exercise prescription o Time spans 20 o The team and facilities 21 o Patient compliance 21 o Tailor your plan 21 o Exercises 22 o Designing exercise plans 22 Appendix - Sample exercise plan 24 2

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5 SECTION 1 CONFORMATION Conformation is determined by the skeletal outline of an animal and can influence its action. Conformation is inherited and fixed. It is true to say that gait abnormalities can be imposed by poor hoof balance in the horse, and with good farriery, this can be corrected. However, it is not true to say that an animals conformation can be changed by farriery or schooling. There are many tricks that can change the appearance of a conformation fault such as clever trimming and more or less muscle or fat development. It is essential that the physiotherapist can see through these superficial changes to the animal s true conformation. Poor conformation can lead to unusual stresses and strains on joints and other structures of the body. Poor conformation can also cause gait abnormalities. These conformational problems are also true in dogs. Conformation defect Effects Base wide More stress on the inside of the limb and hoof/foot Base narrow Plaiting, brushing, stumbling. More stresses on the outside of leg. Toe in Dishing. More stress on the outside of hoof/foot Toe out Winging in, interference, brushing. More stress on the inside of limb and hoof/foot Over at the knee If severe can cause stumbling Back at the knee Extra stress on the front of the knee joint and flexor tendons. Can cause carpitis, tendinitis and chip fractures. Sickle hocks Hock is less able to extend fully. More stress on plantar ligaments and tendons. Curbs. Straight hocks Hock is less flexible and able to absorb shock. Extra stresses on hock. Bone spavin, bog spavin, thoroughpin. 4

6 Camped out behind More difficult to engage hind limbs (hocks) Cow hocks Crooked movement (rotation of hocks). More stress on the inside of limb and hoof/foot. Bone spavin, bog spavin, thoroughpin. Straight stifle Extra stress on stifle joint. Cruciate rupture, locking patella, gonitis (inflammation of the stifle) Straight shoulder Stilted movement. Increased concussion in the shoulder and foreleg. Lack of jumping scope. 5

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8 **Using your texts and other sources of information, study the anatomy of the limbs and complete the following table: Conformation Defect Effects Contracted heels Flat soles Long, sloping pasterns From left to right Straight movement, winging in due to toe out conformation, dishing due to toe in conformation. 7

9 Dogs, horses and all quadrupeds are potentially susceptible to the same conformation faults. Consider how much the extra stresses and strains, we put on the working animal, contribute to disease of the locomotor system. Test questions When is it possible for skeletal conformation to be altered? What trend in showing animals can predispose them to limb injuries? If a plumb line were dropped from the point of buttock, in an animal with ideal hindlimb conformation, how would it dissect the remaining structures of the limb? What is the hoof/pastern axis? Define topline Compare and contrast a long back and a short back 8

10 SECTION 2 THE STUDY OF MOVEMENT Biomechanics Biomechanics is the study of the structure and function of biological systems using methods of mechanics. This study encompasses a wide spectrum of biological activities as diverse as the mechanics of the circulatory system, the physical properties of the skin and the response of bone to loading during locomotion. Terms used in Biomechanics; Force A measure of the action of one body against another that can change that body s state of rest or direction. Gravity and friction are two important forces involved in locomotion. Force can be calculated using the following formula: Force= Mass x Acceleration o Centrifugal force outward force o Centripetal force - inwardly directed force o Eccentric force Force exerted on a body that does not pass through its centre. This tends to cause rotation of the body o External force between a body and the environment o Internal force between body parts All animals and objects are subject to the same physical laws. Due to gravity the weight of the animal is a downward force. The ground exerts an upward force, supporting the body and when the animal is moving the friction with the ground provides braking and propulsive forces. Levers The skeleton is a complex system of levers. A lever is a rigid body (e.g. a long bone) rotating around a fulcrum (e.g. a joint) increasing the effect 9

11 produced when a force is exerted on a body and reducing the effort required. Torque Also known as a moment of force, this term refers to rotational forces. An example of torque is propulsion. In the horse, as the leg leaves the ground the deep flexor muscles pull the pedal bone back. The rotation of the coffin joint and the upward movement of the fetlock provide forward propulsive force. This is aided further by the elastic properties of the suspensory ligament. Displacement This is the movement of an animal from one place to another. Velocity The rate of movement. This can be calculated using the following formula; Velocity = Displacement Time taken Vector The direction or orientation of displacement e.g. 50m south Kinematics This is a branch of biomechanics describing the motion of bodies. Temporal kinematics describe the timing and co-ordination of limb movements Linear kinematics (linear distance and displacement) describe how far a body moves over a period of time Angular kinematics (angular distance and displacement) describe how far the body rotates over a period of time Kinetics This is a branch of biomechanics describing the forces involved in creating and changing motion. Linear kinetics describes the forces associated with linear motion 10

12 Angular kinetics describes the forces associated with angular motion Kinesiology This is the science of movement. Stride A stride is defined as a cycle of body movements, which begins with the contact of one foot with the ground and ends when that foot makes contact with the ground again. Stride characteristics and timings are controlled by the CNS and occur in a cyclic pattern. A stride has four parameters. These are: Stride length the linear distance between two successive footfalls of an individual limb Stride duration the time taken to complete a stride cycle (the time between one footfall and the next) Stride frequency - the number of strides per unit of time Stride pattern The variable sequence of repetitive limb movements A particular stride pattern (i.e. the trot) is described as a gait. Gaits can be symmetric or asymmetric and should be light and easy and appear smooth and fluid. The Gaits The walk Symmetric Four beat (the only natural four beat, symmetrical gait) No moment of suspension Sequence of footfalls is; Left hind, Left fore, Right hind, Right fore 11

13 The trot Symmetric Two beat Moment of suspension Sequence of footfalls is; Left hind and Right fore together, moment of suspension, Right hind and Left fore together, moment of suspension. The Canter/Gallop Asymmetric The three beat-gallop is known as the CANTER The asymmetric gaits are characterised by a leading leg (left or right) The three-beat gallop (canter) is slower than the gallop CANTER Sequence of footfalls for left canter is: Right hind, Left hind and Right fore together, Left fore, moment of suspension GALLOP Sequence of footfalls with a left lead is; Right hind, Left hind, Right fore, Left fore, moment of suspension Note that in the dog, a rotary canter is a normal gait. In the horse, this would be considered a disunited canter and considered abnormal. Dogs will spend more time in a rotary canter because it aids their rapid turning. The sequence of footfalls for a left lead rotary canter is left hind, right hind and right fore together, left fore, moment of suspension. The step cycle swing and stance phase A step cycle is the most basic unit of a gait and includes a stance and a swing phase. The stance phase is when the limb is weight bearing and can be subdivided into; Impact initial deceleration on landing Support continues braking forces until the centre of gravity transfers over the limb Propulsion final acceleration The limb then moves into the swing phase. The swing phase can be sub- divided into; 12

14 Caudal swing immediately the foot leaves the ground Cranial swing covering ground Caudal swing which ends in the foot touching the ground. Centre of gravity The Centre of gravity is at the mid chest level behind the scapula. Therefore 60% of the body mass is carried over the forelimbs while standing at ease. As the animal moves forward, with propulsion from the hindquarters, the centre of gravity moves downwards due to the force of gravity moves forwards due to the propulsive forces This results in the forelimbs undergoing more breaking forces than the hindlimbs and the hindlimbs undergoing more propulsive forces than the forelimbs. The centre of gravity 13

15 As the centre of gravity moves forwards and downwards the animal becomes on the forehand. This is a term commonly used in training the equine. It is essential that the centre of gravity is moved backwards, in order to achieve, lightness, balance and therefore self-carriage to free the forelimbs so that they are able to move freely and fold up to jump fences. In the ridden animal this can be achieved by correct riding. In the dog or cat the centre of gravity moves back during movement uphill. In the smaller un-ridden animal the fact that it is on the forehand is not always an area of concern but in the ridden animal with the added weight of the rider - if this is not addressed - the extra weight and impact on the forelegs can lead to injuries both short and long term. However, many dogs become front wheel drive and put their forelimbs under excessive strain, never really using their hindlimbs. This predisposes them to forelimb lameness. As they age, a lifetime of underutilised hindlimbs means that they become weaker and weaker in the hind end and eventually go off their back legs. If the hind legs had been appropriately strengthened earlier on in life, this scenario could possibly be avoided. Gait Analysis This is the study of gaits and movements. The veterinarian will have analysed the animal and you will have a diagnosis to work from. However, it is important that the physiotherapist can recognise deviations from normal movement and understand how this is relative to the diagnosis so that any developments, good or bad, can be reported to the Vet. Gait abnormalities may arise from a number of factors; Pain related This could be diverse. Due to a direct insult such as a pricked pad or an indirect insult such as a poorly fitting saddle. Mechanical often arising from problems with associated reduction in range of movement but can be due to other factors such as shoeing and conformation. Resistance Horses will often change their gait in order to compensate for rider imbalance. Also there are many evasions that horses will exhibit in order to avoid discomfort from man made issues such as a poorly fitting saddle or bit. This is seen less often in dogs 14

16 but they will sometimes show resistance e.g. when being asked to be lead from the opposite side to which they are accustomed. Lack of co-ordination particularly in young animals Anticipation due to the memory of previous discomfort Neurological Lameness score Lameness can be scored in a number of ways. individual vet. An example is a five-point scale: This will depend on the Level 1 very mild Near-Normal gait Very mild head nod or hip drop Weight is almost evenly distributed Abduction and adduction are minimal This subtle lameness is only visible to the experienced observer Level 2 mild Minor abnormalities which may be exaggerated with manipulation of the limb Level 3 moderate Gait is affected with a shortened stride in at least one limb Level 4 moderate to severe Obvious limping Favouring one limb Difficulty turning Level 5 severe Reluctant or unable to weight bear If moving, may stop frequently Reluctant to rise from lying down It is important to use the same lameness scoring as the treating to vet, for 15

17 each particular case, to limit inconsistency. 16

18 There are many other techniques that the veterinarian will use to determine the source of a gait abnormality. Some examples of these are; Flexion tests manipulation of a joint or joints in order to exacerbate a suspected injury Nerve blocks a process of elimination by the isolating and numbing certain areas Diagnostic imaging Blood sampling Motion analysis An example of this is Equinalysis. Eqinalysis is the procedure where after an initial analysis of a horse s movement, video provides more information about its locomotion. The video records have enabled a process of baseline measurement of the following to be developed while the horse is moving; o Joint flexion and extension o Stride length o Limb medial and lateral displacement This means that the needs of the limb can be taken into account, if required, instead of just shoeing the foot. This is important, because as well as a fitting a shoe to accommodate the horses movement there is growing awareness that shoeing should take into account the amount of loading on a limb. Loading is directly related to the effectiveness of the joints and can affect tendon and ligament health. The motion analysis software, tailored for the experienced equine veterinarian, allows reliable biomechanical data to be collected so contributes towards a more evidence-based approach to equine gait analysis. It also provides slow motion and frame-by frame viewing of video clips. We believe the benefits of Equinalysis for lameness and pre-purchase examinations to be far reaching. 17

19 (Nixon and Marshall - Assessment and management of the sport horse - supplement) Observation It is important to observe the animal while standing at ease. The animal should be happy to stand squarely and weight bear evenly on all four feet. Signs of being unable to do this are; Pointing a toe Holding a foot in an unusual position Favouring a limb (the opposite limb to one causing pain) 18

20 It should be noted that it is normal to see a horse resting a hindlimb. However, it is not normal to see a horse rest a forelimb or to see a dog or a cat resting any limb whilst standing. Locating muscle injuries Observing an animals movement can indicate areas of muscle soreness or injury. This observation, if carried out alongside palpation, can help to isolate an injured muscle or muscle group. Using your knowledge of the function of each muscle you will be able to critically observe an animals movement. Through this observation you will be able to identify which muscles or muscle groups seem to be causing the animal discomfort or which he is reluctant to use. Test questions Define Biodynamics A fault that causes the outside of the foot to make contact with the ground first will cause what stresses on the limb? What is the anterior phase? What is the posterior phase? What % of the propulsive forces required for locomotion are provided by the hindlimbs? 19

21 At the gallop, what is the difference between the vertebral column of the dog and the horse? Forward propulsion requires the foot to have what force with the ground? Compare the movement of the head and neck, at the walk and trot List the characteristics of forelimb lameness. List the characteristics of bilateral hindlimb lameness. 20

22 SECTION 3 EXERCISE PRESCRIPTION A treatment plan should be developed to reflect the rehabilitation needs of the patient. The veterinary surgeon and the physiotherapist should put together a flexible plan to rehabilitate the animal to as near complete return to pre-injury condition as is possible. The factors that will affect the outcome are; The nature and extent of the injury Time span since initial injury The veterinary treatment or surgical repair The age and condition of the animal The access to facilities and a good team Patient/owner compliance Any complications in the healing process You will work with many different vets both within the same practice and from different practices. Depending on their era and training different vets will work in different ways. It is vital that your treatment always complements that of the vets and you always consult the vet and keep him/her informed of; The progress Your observations Your treatment Any changes to the plan you wish to make Any concerns you have Time spans The time span of the healing process depends on many factors. You can formulate your plan to comply with the usual time spans but you must be flexible and readily change any part of your plan if necessary. Reduce the intensity of your plan if at any point the animal shows signs of; Discomfort Stress Fatigue 21

23 The team and facilities The recovery of the animal will, to a large degree, depend on the team of people working on the animal. Utilise vet nurses for the initial stages of recovery, if you are not able to do this yourself. With the permission of the vet, show the vet nurses what they can do to help the animal when you are not there and how to use any equipment which the vet already has or which you have hired to them. The owner will have a large part to play. If the owner works all day then exercises will be limited to the time they are at home, so this could possibly slow down recovery. Conversely, a dedicated owner who is at home all the time may tend to over work the animal in attempt to help it recover more quickly and this could lead to overstress on the injured part. The yard owner/manager will usually be involved with the rehabilitation of the horse. If this is the case it is important to have regular conversations with him/her in order to avoid any confusion in the forwarding of information from the owner. Patient compliance An aggressive or uncooperative patient will have an effect on the rate of recovery, e.g. a dog that pulls away and tenses up every time you try to carry out PROM or a horse that is on box rest but who box walks all day. In these circumstances you need to use your initiative to find a way around these problems, but sadly, in some cases they will lead to a poorer outcome than intended. Tailor your plan It is important to tailor your plan to each patient. Take into account all the contributing factors e.g. considering where the dog sleeps; Is it in a draft? Is its bed too high? 22

24 Is its bed to difficult to get to? Take in which the environment which the animal is kept Does the horse have to turn immediately every time it comes out of its stable? Is its bed too deep at the back and too shallow at the front resulting in the horse standing down hill to eat its hay? When hacking out are there only hills and no flat surfaces? It is important to notice the little things which could make all the difference to the recovery of the animal e.g. The owner walks the dog/horse in the camber of the road. This could lead to torque stresses on the limbs Exercise prescription There are many different exercises that owners can carry out and that you can use as part of your treatment. These will be covered during your practical training. Designing exercise plans Stage 1 - Evaluate the patient and the treatment he/she has received The age of the animal The breed of the animal The condition of the animal The muscle tone, any particular areas of concern Gait The type of surgery The type of medication The amount of restriction since the injury Stage 2 - Evaluate the team and facilities The treating Vet The team of Vet nurses 23

25 The dedication of the owner The home environment The yard owner/manager The rider/handler Access to facilities such as a pool Stage 3 Determine the outcome goal The expectations of the Vet The expectations of the owner What activities the animal will be required to do once he is rehabilitated 24

26 APPENDIX 1 SAMPLE EXERCISE PLAN Details Patient: 8-year-old cob used for hacking. Horse can be difficult to lead (very strong). General manner Bored and bolshy. Horse has been on box rest for 3 months. Owner has been strapping the horse daily, maintaining his condition as much as possible. However he has lost general muscle tone and has gained a little weight. Injury and treatment: Tendinitis of the superficial flexor tendon right fore. No medication other than original oral NSAIDs. Prescribed three months box rest and physiotherapy. Physiotherapy treatment Ultrasound every other day during the first week. Owner hired a PEMF machine and treated the horse twice a day for the initial 6 weeks then once a day until the present day. No recorded puffiness since 3 weeks post-injury. Tendon is now cold and hard. Pre-injury condition: Correct weight and fit. Hacking out 1 hr a day. Owner: Dedicated. Visits the horse twice a day. Has more time in the morning and works in the afternoons. Facilities and team: The horse is kept at livery. The yard owner is a slight lady but one of the staff (a strong male) handles the horse. Small village roads, not consistently level. Local ground is clay. It is summertime. Week 1 Before commencing any exercise, prepare tissues by: PEMF rug for 10 minutes OR a vigorous groom OR Equissage for 20 minutes 25

27 Walk in hand (advise strong groom takes him out). Build up to 15 minutes a day split into two sessions if possible. Towards the end of the week introduce tack. (have saddle checked). Graze in hand. Continue with PEMF. Week 2 Introduce some gentle proprioceptive exercises i.e. weight shifting. Start ridden exercise. Build up to 20 minutes of ridden work a day. Graze in hand. On day 12 the horse shied at a bird in the hedge and trotted off. On the morning of day 16 the right fore was slightly puffy. The horse was sound. Day 16 Cold hose for 10 minutes every four hours. Graze in hand. No exercise Day 17 Tendon cold and hard. PEMF twice a day. Walk for 15 minutes. Graze in hand. Day 18 Same as above, walk for 30 minutes. Day 19 Same as above, walk for 45 minutes. Day 20 Same as above, walk for an hour. Thereafter: Gradually increase work as normal fittening program. Gradually increase proprioceptive exercises: o Work on different surfaces (deep or hard going should be avoided until the horse is fully fit and the tendon is strengthened) 26

28 o Introduce poles o Bandage legs o Weight shifting Re-introduce the horse to the field as soon as possible, taking all necessary precautions to avoid re-injury. 27