Abstract
Drawing has always been an integral part of the FRCS examination, be it as a method to understand a complex process during revision or as a tool for explanation in the viva itself. In order to use drawings in the viva exam the candidate must be able to draw, explain and answer questions simultaneously. Thus, practice and understanding are essential.
In this chapter, we have selected the drawings that we think are most useful, having recently been through the examination or taught on this subject for many years.
Drawing has always been an integral part of the FRCS examination, be it as a method to understand a complex process during revision or as a tool for explanation in the viva itself. In order to use drawings in the viva exam the candidate must be able to draw, explain and answer questions simultaneously. Thus, practice and understanding are essential.
In this chapter, we have selected the drawings that we think are most useful, having recently been through the examination or taught on this subject for many years.
By no means are you expected to turn out a quality piece of art, and these drawings are not intended as such. Some of the drawings are deliberately schematic in order to simplify the subject matter and reinforce key points.
We hope, though, that by using these drawings to either act as an aide memoir during revision, or indeed to explain difficult concepts in the viva, the time saved and level of understanding shown will allow you to showcase your knowledge in pursuit of the higher marks.
Good luck.
Tips on drawing
An exam is not just about knowledge but the presentation of that knowledge. Playing the game is important. There is a lot of paper at every station, and sometimes it’s useful to draw even if not asked to do so. Remember the old adage ‘a picture is worth a 1000 words’. If you are not the first at the viva table, there are often ‘paper scars’, tales of the last viva! Do not let these distract you.
If using a drawing in the viva, whether as an aid to explain an answer or as the result of being asked to do so, then here are some tips.
1. Draw big. Fill the page. Drawing small does not show confidence.
2. Work from the outside in. Simplify to the bare image. For example, if drawing a cross-section of a limb, first draw a circle to illustrate the skin then add in the bones, then compartments, then muscles, then NV structures.
3. Draw schematic. The examiners will not be assessing you on your artistic skill.
4. Speak while you draw. You have limited time to earn marks, so do not lose this time by drawing in silence.
Anatomy
Anatomy is assumed knowledge for surgeons; it is, after all, a subject matter we deal with every day. Thus, an anatomy question in the exam should be dealt with confidently and efficiently, otherwise the examiner may prod more deeply to assess the true level of knowledge. Anatomy will also be the subject that most examiners will revert to if you are struggling with a question.
NB: some of the illustrations below are of cross-sectional anatomy in the limbs. Not only do these convey a knowledge of surrounding structures and relative anatomy of vessels and nerves, but they can be used very succinctly to demonstrate approaches, as seen by the numbered arrows where appropriate. We have given you both anatomically correct and schematic diagrams for these, and it is best to familiarize yourself with one or the other.
Upper limb
Brachial plexus (Figure 31.1)
Figure 31.1 R, roots; T, trunks; D, divisions; C, cords; B, branches. P, phrenic nerve (contribution); DS, dorsal scapular; S, suprascapular; LP, lateral pectoral; MC, musculocutaneous; US, upper subscapular; T, thoracodorsal; LS, lower subscapular; AX, axillary; R, radial; MP, medial pectoral; MBC, medial brachial cutaneous (of arm); MAC, medial antebrachial cutaneous (of forearm); U, ulnar; 1st IC: first intercostal; LT, long thoracic nerve (of Bell).
The candidate not only needs to know the anatomy of the brachial plexus but also how to apply it to a clinical picture/examination. Once familiar with the above illustration, the candidate can then picture where the lesion is in accordance to which muscle groups have been affected. There are a number of Youtube videos that teach you how to draw this very quickly.
The candidate can also demonstrate whether the lesion has occurred before (pre-ganglionic) or after (post-ganglionic) the dorsal root ganglion (see Figure 31.2).
Dorsal root ganglion (Figure 31.2)
Figure 31.2 DRG, dorsal root ganglion.
Figure 31.2 clearly shows where the division between pre- and post-ganglionic injuries exists. Pre-ganglionic injuries may present with Horner’s syndrome, periscapular wasting (rhomboids affected from dorsal scapula nerve) or medial scapula winging (long thoracic nerve). Pre-ganglion injuries carry a poorer prognosis.
Erb’s point (Figure 31.3)
Figure 31.3 Erb’s point.
Not to be confused with the cardiology Erb’s point (third intercostal space on the left sternal border where S2 heart sound is best auscultated) or the head and neck Erb’s point (posterior border of the sternocleidomastoid muscle where four superficial branches of the cervical plexus emerge from). The Erb’s point that concerns us is a site at the upper trunk of the brachial plexus located 2–3 cm above the clavicle. It is named for Wilhelm Heinrich Erb, a nineteenth-century German neurologist. Erb’s point is formed by the union of the C5 and C6 nerve roots. At the nerve trunk, branches of suprascapular nerve and the nerve to the subclavius also merge. The merged nerve divides into the anterior and posterior division of C5 and C6. Due to this convergence, it is an area that can be torn relatively easily, as its mobility is limited.
Humeral spaces (Figure 31.4)
Figure 31.4 Humeral spaces.
A useful aide memoir for this is to place the index and middle fingers of your right hand at right angles to your left hand index and middle fingers to create the same shape. Thus, your left middle finger is teres minor, left index finger teres major. Your right index is long head of triceps and your right middle the humerus.
Clinically, these spaces are important when performing the posterior approach to the shoulder, knowing that finding the interval between infraspinatus and teres minor prevents you from straying too low and thus endangering the axillary nerve and posterior circumflex humeral artery.
Humerus cross-section (Figure 31.5)
Figure 31.5 CV, cephalic vein; MC, musculocutaneous nerve; BA, brachial artery; BV, basilica vein; UN, ulnar nerve; MN, median nerve; RN, radial nerve; PB, profunda brachii.
LHB, long head biceps; SHB, short head biceps; B, brachialis.
Lateral T, lateral head of triceps; MT, medial head of triceps; Long T, long head of triceps.
The above illustration can be used to succinctly demonstrate the approaches to the humerus.
1. Anterior – retract biceps laterally, identify radial nerve distally, split dually innervated brachialis.
2. Posterior – develop interval between long and lateral heads of triceps, split medial head, protect radial nerve as it sits in the spiral groove.
Schematic drawing (Figure 31.6)
1. First draw a large circle and label the anterior and posterior.
2. Add the humerus centrally and divide the cross-section into anterior and posterior compartments. It initially looks like a Pokemon ball. By drawing the mid-humeral cross-section you avoid complications of coracobrachialis and deltoid insertions proximally and the forearm musculature distally.
3. In the anterior compartment, divide between the biceps superficially and the brachialis deep. The musculocutaneous nerve lies in the plane between these muscles and supplies the medial half of the muscle.
4. In the posterior compartment the three heads of triceps are drawn easily: medial, long and lateral heads.
5. The radial nerve runs in the spiral groove and supplies the muscles of the posterior compartment. The ulnar nerve, median nerve and medial cutaneous nerve of the forearm run medially with the brachial artery within their own neurovascular compartment.
Figure 31.6 Schematic drawing of humerus cross-section.
Mid-forearm cross-section (Figure 31.7)
Figure 31.7 RN, radial nerve; LCNF, lateral cutaneous nerve of the forearm; RA, radial artery; MN, median nerve; UA, ulnar artery; UN, ulnar nerve; PIA, posterior interosseous artery; PIN, posterior interosseous nerve.
BR, brachioradialis; FCR, flexor carpi radialis; FDS, flexor digitorum superficialis; PL, palmaris longus; FPL, flexor pollicis longus; FDP, flexor digitorum profundus; FCU, flexor carpi ulnaris.
ECRL, extensor carpi radialis longus; ECRB, extensor carpi radialis brevis; EDC, extensor digitorum communis; EPB, extensor pollicis brevis; EPL, extensor pollicis longus; EDM, extensor digiti minimi; ECU, extensor carpi ulnaris.
Schematic drawing (Figure 31.8)
Figure 31.8 Schematic drawing of mid-forearm cross-section.
Drawing the forearm cross-section (Figure 31.8) is a daunting task but can be approached in a similar way to the upper arm.
1. Again, draw a large circle.
2. Draw the radius and ulna and divide the forearm into three compartments – anterior, posterior and the mobile wad.
3. Divide the compartments into superficial and deep and then divide the anterior superficial into four, deep into three; and both in the posterior compartment into three; the mobile wad into three.
4. Fill the mobile wad first – all muscles supplied by the radial nerve. BR lies anterior-most, followed by ECRL and ECRB.
5. Thinking of Henry’s approach, FCR can then be added. FCU lies next to FCR on the opposite side. The other superficial muscles are the palmaris longus and FDS.
6. We know the SRN and radial artery lie between FCR and BR.
7. The deep anterior compartment is next, with FDP below FDS. As half of the FDP is supplied by the ulnar nerve, this is where the ulnar nerve and artery lie.
8. The remainder of the deep compartment depends on the level, so considering the scotty dog picture in the next section, PT and FPL are drawn here.
9. The median nerve lies deep to palmaris longus and the AIN on the anterior aspect of the interosseous membrane.
10. Posteriorly, start with the superficial compartment. ECU lies adjacent to FCU. On the other side of the superficial compartment lies EDC, which forms the interval for Thompson’s posterior approach to the radius.
11. The remaining extensors depend on the level being sectioned. EDM lies centrally.
12. In the deep layer, the supinator lies around the radius; it is likely to only be partially present at this level, but worth drawing for its importance for approaches; EPL and APL fill the other two spaces.
13. The PIN lies within the supinator.
14. Finally, the common approaches to the forearm can be added – Henry’s between FCR and BR; Thompson’s between ECRB and EDC.
Approaches to the midshaft radius (Figure 31.9)
Figure 31.9 Approaches to the midshaft radius.
1. Henry’s approach – the true Henry’s approach develops the plane between the brachioradialis and the radial artery. The modified Henry’s approach (which we use for distal radius fractures) differs by going through the bed of the FCR, creating a plane between the FCR and radial artery.
2. Thompson’s approach – develop the interval between ECRB and EDC.
Radius muscle insertions
Radius muscle insertions are often combined with the cross-section of the forearm. This is especially true if Henry’s approach is being discussed. The muscles’ insertion on the anterior aspect of the radius are simple to understand. There is one supinator (excluding the biceps attachment), two pronators, and two interspersing long flexors to the digits. If you turn the radius on its side the insertions look like a scotty dog. The supinator for the ears, the flexors (FPL and FDS) for the body and the pronators (PQ and PT) for the legs (Figure 31.10).
Figure 31.10 Radius muscle insertions.
The deep dissection of Henry’s approach to the radius requires the supinator to be incised at its insertion on the radius, when the forearm is in full supination to displace the PIN laterally, away from the operative field. The FDS insertion begins just distal to the bicipital tuberosity and is ulnar to the supinator. Pronator teres in the middle third of the radius is dissected by pronating the arm to better expose its insertion.
Hand and wrist
Carpal tunnel
Figure 31.11 UN, ulnar nerve; UA, ulnar artery; MN, median nerve; FDS, flexor digitorum superficialis; FDP, flexor digitorum profundus; FPL, flexor pollicis longus.
H, hamate; Tq, triquetrum; L, lunate; S, scaphoid.
The contents of the carpal tunnel are easily tested. This diagram (Figure 31.11) can be a quick way to detail the necessary knowledge. The ulnar nerve and artery are clearly shown not to be in the carpal tunnel, instead lying separately in Guyon’s canal.
The carpal tunnel spans from the scaphoid tubercle and trapezium ridge to the hook of hamate and pisiform. The roof is the transverse carpal ligament with the floor being the proximal carpal row. The contents are the median nerve, FPL tendon, four FDS tendons and four FDP tendons.
As well as the cross-sectional anatomy the candidate should be familiar with the branches of the median nerve, e.g. palmar cutaneous branch and recurrent motor branch and their anatomical variations (recurrent motor branch – extraligamentous 75% of time, subligamentous 13%, transligamentous 12%).
Extensor compartments (Figure 31.12)
Figure 31.12 Compartment 1: APL, abductor pollicis longus; EPB, extensor pollicis brevis.
Compartment 2: ECRL, extensor carpi radialis longus; ECRB, extensor carpi radialis brevis.
Compartment 3: EPL, extensor pollicis longus.
Compartment 4: EDC, extensor digitorum communis; EIP, extensor indicis propius.
Compartment 5: EDM, extensor digiti minimi.
Compartment 6: ECU, extensor carpi ulnaris.
Clinically, this illustration can be used to demonstrate approaches to the wrist. It also details the proximity of EPL to Lister’s tubercle, which can contribute to attritional rupture of the tendon.
Ulnar canal (Figure 31.13)
The ulnar canal or ulnar tunnel (also known as Guyon’s canal or tunnel) is a semi-rigid longitudinal canal in the wrist that allows passage of the ulnar artery and ulnar nerve into the hand. The roof of the canal is made up of the superficial palmar carpal ligament (PCL) and floor by the transverse carpal ligament (TCL).
Anatomy is a possible question especially due to zones of injury.
Zone 1: proximal to bifurcation of nerve (mixed motor and sensory, usually hamate pathology or compression in canal).
Zone 2: Surrounds deep motor branch (motor only, usually hamate pathology).
Zone 3: Surrounds superficial sensory branch (sensory only, usually ulnar artery pathology).
Figure 31.13 Ulnar canal.
Sites of ulnar nerve compression (Figure 31.14)
Management of ulnar nerve compression depends on an accurate diagnosis, yet localizing the site of nerve compression can be challenging. The accepted sites of potential ulnar nerve compression are depicted here: arcade of Struthers, the medial intermuscular septum, the bony retrocondylar groove and the overlying cubital tunnel retinaculum, Osborne’s band, the volar antebrachial fascia just proximal to the wrist crease (proximal Guyon’s canal), and the leading edge of the hypothenar musculature overlying the deep motor branch of the ulnar nerve (distal Guyon’s canal).
Figure 31.14 Sites of ulnar nerve compression.
Finger cross-sectional anatomy
Figure 31.15 TRL, transverse retinacular ligament.
This axial section (Figure 31.15) shows the relationship of the neurovascular bundles to that of the fascial sheets in the finger. This is particularly important in Dupuytren’s disease where a diseased Grayson’s ligament (remember Cleland’s ligament is not involved in Dupuytren’s disease) can cause an aberrant path of the neurovascular bundle which the surgeon must be aware of.
Nail anatomy (Figure 31.16)
Figure 31.16 Nail anatomy.
Nail tip injuries are commonly seen in orthopaedic practice hence the need for accurate knowledge of the relevant anatomy. With relative ease this viva topic could quickly proceed to high levels talking about potential incisions to extend wounds, nail bed repair or flap coverage.
Lower limb
Blood supply to neck of femur (Figure 31.17)
