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APE 4: Muscles and their Actions – Tutor - 2016-17 Lesson Plan Tutors Last week students covered the peripheral nervous system and learnt the anatomy of the main limb nerves. They should now understand the difference between a spinal nerve root and a peripheral nerve and should have learnt the dermatomes. This session should build on this to learn the myotomes and the motor distribution of the nerves as well as learning to locate and test muscle groups. They have been looking at muscles and tendons today in the DR and will have covered origins and insertions For All APE sessions The aim of APE is to teach clinical skills with surface anatomy. This is not a re-teach of dissection room anatomy. Students must do this as SDL and direct appropriate anatomical questions to the anatomists. These sessions have been lovingly crafted by clinicians. If you have a problem with the content or the way something is taught, please discuss with me directly – we welcome your feedback – but do not change the session It is ok to say ‘I don’t know’ – you are not expected to know everything! Ask me – I am always around Please do not say ‘you need to do it this way for the OSCEs’. Exams are important and motivate people, but this is not the point of these sessions. Good clinical skills are for life, not just for OSCEs! 1 APE 4: Muscles and their Actions – Tutor - 2016-17 Suggested Timing 1 13.3013.35 (5 mins) Activity Introduction Introductions, register Run through objectives Suggested Timing 2 15.3015.35pm (5mins) 13.3513.45 (10 mins) Activity 1 – Muscles and tendon Help the students find the structures and help answer the questions 15.3515.45 (10 mins) 13.4513.50 (5 mins) 13.5014.00 (10 mins) Activity 2 – Muscle actions and compartments Work through the actions and questions with the students Activity 3 – Revision of the PNS Using the ‘nerve roots’, conceptualise the PNS again (done last week) 15.4515.50 (5 mins) 15.5016.00 (10 mins) 14.0014.15 (15 mins) Activity 4 – Myotomes and PN - LL Introduce concepts Run through movements, naming nerves and myotomes 16.0016.15 (15 mins) 14.1514.30 (15 mins) Activity 5 – Myotomes and PN - UL Introduce concepts Run through movements, naming nerves and myotomes 16.1516.30 (15 mins) 14.3014.45 (15 mins) Activity 6 – Power testing Stage 2 demonstration of elbow flexion and extension Stage 4 in pairs; get them to do knee flexion and extension Ensure good technical practice 16.3016.45 (15 mins) 14.4515.00 (15 mins) Activity 7 – Clinical context Work through the questions Keep concepts and terminology simple 16.4517.00 (10 mins) Close and summarise Reiterate learning objectives, signpost SDL, answer any questions 2 APE 4: Muscles and their Actions – Tutor - 2016-17 Learning Objectives At the end of this session, and with SDL, students should be able to: Identify certain landmark muscles and tendons Identify key muscle groups and describe their actions Define a muscle compartment Understand the concept of a myotome Identify the myotomes in the limbs Know how to test muscle power Dress Code Shorts (or loose jogging bottoms) and t-shirts, so that legs can be accessed from mid-thigh and arms from the shoulder. PE Overview This session will explore the positions and actions of key muscles and tendons. You will learn how muscles are arranged in groups and the principles of their nerve supply. You will learn how to test a muscle. Activity 1: Muscles and tendons (10 minutes) You will have spent this morning naming and identifying muscles on the cadavers. You also will have noted their attachment to the bones by tendons. We have found and palpated some of these before… With the help of your tutors, find the following on yourself and answer the questions together: Tutors – Help them identify the following structures, get them to make the movements, and see and feel the muscle contracting Patella tendon o The patella is a sesamoid bone formed within the tendon substance. o Other than the patella, what is the other bony landmark here? o What muscle does this attach to? What is its action? Tibial tuberosity = insertion of quadriceps – extension of the knee 3 APE 4: Muscles and their Actions – Tutor - 2016-17 Achilles tendon o Which muscle does it attach to which bone? o What is the action of this muscle? Combined gastrocnemius and soleus tendons, attached to the calcaneus – plantarflexion of ankle. Extensor hallucis longus tendon o What is the action here? (the clue’s in the name!) o Where is the muscle located? Extension of the hallux/big toe; anterior lower leg – we will be using this landmark next week. Sterno-cleido-mastoid o What are the attachments here? o This has a number of actions. Look over one of your shoulders. Which muscle is working (left or right)? How would we describe this movement using our technical nomenclature? Help by breaking down name and deduction, Sterno= sternum, Cleido=clavicle and the mastoid –get them to palpate all of these and ensure they have understood the 2 heads. ‘Contralateral’/opposite side SCM – get them to feel the muscle contacting. ‘Lateral rotation of the head’ (other actions are lateral flexion and involved in flexion) Gluteus medius o Get your tutor to help you find this by palpating the origin and insertion on the right o If the origin is fixed, what happens to the leg if the muscle contracts and shortens? o What now if the insertion is fixed? Ask your tutor why this is so important for walking. Tutors – Get them all standing for this one Origin = iliac crest, insertion = greater trochanter – get them to palpate these on the right. If origin (ie pelvis) is fixed, a shortened, contracted muscle will abduct the leg – this one of its main actions. Get them to do this whilst feeling the muscle. Now get them to put their weight on their RIGHT leg – the insertion is now fixed. What happens to the pelvis if the muscle contracts? – it tilts, lifting up on the LEFT. Get them to feel the muscle in action by raising and lowering the LEFT knee whilst feeling the right Glut Med. Please explain – with respect to walking, it is not so much that Glut Medius tilts the pelvis up, but stops it from dropping on the left – this stabilizes the pelvis to allow us to … Get them to walk feeling both Glut Med at once 4 APE 4: Muscles and their Actions – Tutor - 2016-17 Activity 2: Muscle actions and compartments (5 minutes) Muscles are often grouped in pairs that perform opposite actions, such as flexion and extension, adduction and abduction. These are known as agonist and antagonist muscles. As one contracts, the other relaxes. 1. Identify the flexors and extensors of the elbow. What compartments are these located in? Biceps brachii (brachialis, brachioradialis) – Anterior; Triceps brachii (Anconeus) Posterior 2. Do the same for the flexors and extensors of the knee – what are the muscles called? What compartments are they in? Flexors – hamstrings (biceps femoris; semi-membranosis; semi-tendinosis) – posterior Extensors – Quadriceps – anterior What other compartment is there in the thigh? What does it contain? Lateral - Hip adductors-adductor magnus, longus, brevis and gracilis. They can feel these muscles contract using resisted hip adduction (push medial knee against hand) It is important to note that most ‘compartments’ are supplied by the same nerves and blood vessels. 3. Think back to the anatomy of the lower limb peripheral nerves from last week. Which nerves do you think supply the flexor and extensor compartments of the thigh? Extensors (anterior) – femoral; flexors (posterior) – sciatic (Lateral – obturaror) We will come back to this idea later Activity 3: Revision – Conceptualising the Peripheral Nervous System (10 minutes) Last week we used a model to help us visualize the peripheral nervous system – Let’s do this again to remind us of the three main areas – nerve roots, plexus and peripheral nerves. 5 S3 S2 S1 L5 L4 L3 L2 Nerve Root Lumbosacral Plexus Sciatic Femoral Peripheral Nerve APE 4: Muscles and their Actions – Tutor - 2016-17 6 APE 4: Muscles and their Actions – Tutor - 2016-17 Tutors – The aim of this exercise is to conceptualise the PNS more simplistically in 3 parts in order to help understand the significance peripheral nerve testing in the neurology exam (i.e. why we test certain areas and how this helps us localize pathology – reiterated in clinical context activity Last week we conceptualized the upper limb neurology; we will now consider the lower limb (the principles remain the same): Get them to draw the main peripheral nerves (in different colours)- give them the ‘root values’/write on whiteboard (they do not need to know this by heart) Femoral L2, L3, L4 Sciatic L4, L5, S1, S2, S3 There are many more peripheral nerves, but these are the main 2 we will be considering in this session. Once this has been done, please emphasise the 3 parts – Root/Plexus/Peripheral Nerve. The pattern of loss for each area will be different on examination e.g. the sciatic nerve contains fibres from a number of different roots, so if damaged will give different examination findings compared with one nerve root being damaged. As last week, please also remind them that these structures all contain both sensory (afferent) fibres and motor (efferent) fibres, but today will be considering the motor part only. Activity 4: Myotomes and peripheral nerves – Lower Limb (15 minutes) Tutors- please introduce the concepts below before moving on to the activity Muscles have a segmental origin, like skin. The muscle tissue supplied by a single spinal nerve root is a “myotome”. This is the motor equivalent of a dermatome. Instead of testing areas of skin to assess integrity of a nerve root, we assess movements and the power of the muscles performing those movements. Look back to the answers you gave for the last question of Activity 2. Testing the integrity of peripheral nerves is in the main straightforward, as one movement is mostly supplied by one peripheral nerve. Nerve roots however, as seen in the previous exercise, innervate a number of different muscle groups and therefore will be involved in a number of movements. Look at the picture below and run through all the movement with your tutor, reciting the nerve roots (root value) and the peripheral nerve as you go. Tutors- Run through below – get the students to do the movements, naming the main peripheral nerve and root value of each 7 APE 4: Muscles and their Actions – Tutor - 2016-17 Myotome groups of lower limb movements and respective nerve roots Hip Hip flexors L2, L3 Knee Hip extensors L4, L5 Knee extensors L3, L4 Femoral Hallux (Big Toe) Ankle Dorsiflexion of big toe L5 Common peroneal Dorsiflexion of foot L4, L5 Common peroneal Plantarflexion of foot S1, S2 Tibial Ankle inversion L4 Knee flexors L5, S1 Sciatic Plantarflexion of big toe S1, S2 Tibial Ankle eversion L5, S1 Common peroneal Reference: adapted from Last’s Anatomy - Regional & Applied, 11th Edition, pp16-17 8 APE 4: Muscles and their Actions – Tutor - 2016-17 Activity 4: Myotomes and peripheral nerves – Upper Limb (15 minutes) Now run through all the movements of the upper limb with your tutor, reciting the nerve roots (root value) and the peripheral nerve as you go. Myotomes of upper limb movements and respective nerve roots Shoulder Elbow Flexors C5, C6 Musculocutaneous Abductors C5 Axillary Supinators C6 Radial Extensors C7, C8 Radial Adductors C6, C7 Pronators C7, C8 Median Extensors C6, C7 Radial Wrist Flexors C6, C7 Median/Ulnar Fingers Extensors C7, C8 Radial Abductors/ Adductors T1 Ulnar Flexors C7, C8 Median/Ulnar 9 APE 4: Muscles and their Actions – Tutor - 2016-17 You may have noted the median and ulnar nerves have some overlap. Specific testing for the median nerve often includes thumb abduction (abductor pollicis brevis). Tutors – Demonstrate this movement for them Similar to dermatomes, there is some variation between different resources. This is a lot to remember! Watch the YouTube video of the myotome dance to help you recall the major movements innervated by each nerve root. Tutors – signpost to ‘myotome dance’ SDL Activity 6 – Muscle power testing (15 minutes) To test the integrity of the nerves, making the movement is not enough, we also need to test strength for detecting more subtle weaknesses. We are going to test the movements we did in Activity 2. Watch you tutor demonstrate elbow flexion and extension testing. 1. Now practice this in pairs. Please start with consent. Ensure you are giving your ‘patient’ instructions that they understand. 2. Use the same approach for testing knee flexion and extension. Tutors – Stage 2 demo of elbow flexion/extension only Specific key points to address: Intro and consent – jargon free language Isolating the movement – with the student’s arm in a flexed position, see if they can ‘pull you towards them’ without using biceps (i.e. get them to use shoulder muscles) – this highlights to importance of this Use equivalent force Compare side to side Get the students to do in pairs (stage 4) – watch and give feedback for above points Remember the important points: - Use lay language and give clear instructions - Isolate the movement - Use an equivalent amount of force 10 APE 4: Muscles and their Actions – Tutor - 2016-17 Clinical context Work through the following questions with your tutor: Tutors – get them to refer back to diagrams in handbook if struggling 1. A patient has radial nerve damage (‘mononeuropathy’ or ‘palsy’). What movements will be weak? Elbow, wrist and finger extension, supination – depending on where the lesion occurs – see if they can recall where it may become damaged (fractured humerus – mentioned last week) Please emphasise that lack of wrist extension (wrist drop is often a prominent feature of radial nerve palsy) 2. A patient has a compression of C5 nerve root. a. What movements will be weak? Shoulder abduction, (elbow flexion) b. Where will they experience sensory loss? C5 dermatome (covered last week) – lateral upper arm 3. A patient is unable to dorsiflex their foot. a. Which peripheral nerve may be affected? Common peroneal b. Which nerve root may be affected? L4/L5 – mostly ‘foot drop’ is associated with L5 c. How could we tell the difference between these on examination? Very difficult! Some other movements will be weak with nerve root – hip extension, knee flexion (i.e. other actions in L5 myotome) Sensory loss may help (but common peroneal/L5 distributions very similar) d. How would the patient walk? (i.e. What would their gait look like?) High-stepping gait, also ‘slapping’ gait – demonstrate! 4. A patient is unable to move or feel his whole left leg. Where (in the peripheral nervous system) could the problem be? Left lumbosacral plexus 5. Weakness is described medically as a paresis (Greek parienai – to let fall). The patient in Q4 has a monoparesis. a. What is a hemiparesis? Half the body is weak one side of sagittal plane – e.g. in stroke. Most likely location for pathology will be opposite (contralateral) side of the brain (will be covered later with central nervous system) 11 APE 4: Muscles and their Actions – Tutor - 2016-17 b. What is a quadraparesis? Weakness in all 4 limbs c. What is a paraparesis? Weakness in both lower limbs (below the transverse plane) – though this could be a problem in both plexuses, most likely location for para- and quadraparesis is the spinal cord 6. A large weight has fallen on your patient’s thigh? It has badly crushed the anterior compartment. Discuss the consequences of this with your tutor. Compartment syndrome – swelling/bleeding from tissue damage increases pressure within fixed enclosed compartment. This compresses nerves and blood supply which can lead to tissue death and irreversible nerve damage. The fascia of the compartment needs to be cut open as an emergency. 7. Your patient has a painful right hip due to arthritis and walks with a limp (antalgic gait). This means they are using their right leg less to weight-bear. a. What muscle do you think will become wasted (atrophy)? Gluteus medius (right) b. What will happen if they stand on their left leg? Ask your tutor for the name of this sign Right hip and leg will drop down – Trendelenberg sign (NOT test) c. What if both muscles are weak – how will they walk? ‘Waddling gait’ – trunk swings from side to side to compensate for the hip drop (Trendelenberg) – demonstrate! This is common in muscle diseases (myopathies) especially those that affect proximal muscles e.g. muscular dystrophies Self- directed learning Practice naming the muscles, nerve root and nerves performing the movements of the upper and lower limb Watch the ‘myotome dance’ Find out: o What is claw hand? o What is Erb’s palsy? Additional resources O’Brien M. Aids to the Examination of the Peripheral Nervous System (5th Edition) 12