Surface Marking of Limbs
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Direct answer
Palpation converts skeletal landmarks into living anatomy: the brachial artery is drawn from the lower border of teres major to the midpoint of the cubital crease, medial to the biceps tendon, and the femoral artery from the midinguinal point — halfway between the anterior superior iliac spine and the pubic symphysis — to the adductor tubercle, the artery occupying the upper two-thirds of that line. Nerves are marked against the bones that injure them: the radial nerve across the spiral groove, the common peroneal against the fibular neck. Viva examiners insist every line run from one named bony point to another, never eyeballed.
What you must remember
- Upper limb arterial lines: subclavian artery from the sternoclavicular joint to the clavicle's midpoint, arching about 2 cm above it; axillary artery from the same midpoint to behind the coracoid process with the arm abducted; brachial artery continuing down the medial arm to the cubital crease.
- Lower limb arterial lines: femoral artery along the upper two-thirds of the midinguinal point to adductor tubercle line; posterior tibial artery at the midpoint between the medial malleolus and the calcanean tendon; dorsalis pedis just lateral to the extensor hallucis longus tendon.
- Nerves at risk against bone: radial nerve in the spiral groove; ulnar nerve behind the medial epicondyle; axillary nerve at the surgical neck of the humerus; common peroneal nerve at the fibular neck, the most frequently injured nerve of the lower limb.
- Pulse points: radial lateral to the flexor carpi radialis tendon; brachial medial to the biceps tendon, where the blood pressure cuff listens; femoral below the midinguinal point; popliteal, deepest in the fossa.
- Veins worth marking: the great saphenous vein crosses in front of the medial malleolus — the infant cutdown site — runs a hand's breadth behind the patella, and pierces the saphenous opening about 3-4 cm below and lateral to the pubic tubercle; the cephalic vein ascends the deltopectoral groove.
- Landmark traps: the midinguinal point is not the midpoint of the inguinal ligament, which marks the deep inguinal ring; at the groin, NAVEL from lateral to medial reads nerve, artery, vein, empty space, lymphatics — the femoral vein cannulation rule.
Working through a marking viva
Start with the femoral artery. Flex and laterally rotate the hip, identify the anterior superior iliac spine and pubic symphysis, and take their midpoint — the midinguinal point. Draw a line to the adductor tubercle on the medial femoral condyle; the artery corresponds to the upper two-thirds, after which it leaves through the adductor hiatus in Hunter's canal. Then the relations: femoral nerve a finger's breadth lateral to the pulse, femoral vein a finger's breadth medial — why a central line enters medial to the artery, and why the artery landmarks a femoral nerve block.
For the upper limb, follow the same discipline with the brachial artery, from teres major's lower border to the medial side of the cubital crease. That line marks the pulse, the compression point, and the nerve block target. Finish with the radial nerve's crossing of the spiral groove and the common peroneal nerve at the fibular neck — lines that predict wrist drop and foot drop.
Where candidates lose marks
Two errors dominate. The first is drawing the femoral artery from the midpoint of the inguinal ligament; that point marks the deep inguinal ring, and conflating the two turns an easy question into a failure. The second is answering in vague corridors — "along the medial arm" — instead of named point-to-point lines, which score nothing in a marking viva. A quieter slip is the anatomical snuffbox: its boundaries are recited (abductor pollicis longus and extensor pollicis brevis in front, extensor pollicis longus behind), but the payload is forgotten — scaphoid in the floor, tender when fractured, with the radial artery crossing into the palm.
Frequently asked questions
Which surface point marks the start of the femoral artery?
The midinguinal point, halfway between the anterior superior iliac spine and the pubic symphysis — not the midpoint of the inguinal ligament, which marks the deep inguinal ring's surface position.
Where is the common peroneal nerve marked and why does it matter?
It is rolled against the neck of the fibula before dividing into superficial and deep branches; pressure here from a plaster or cross-legged posture produces foot drop.
How is the brachial artery marked?
By a line from the lower border of teres major to the midpoint of the cubital crease, medial to the biceps tendon, where the pulse is felt and blood pressure is auscultated.
Which vein is used for cutdown in infants, and at what landmark?
The great saphenous vein, at its constant position immediately in front of the medial malleolus — reliable even in a shocked neonate with collapsed veins.
What is the full surface course of the great saphenous vein?
It ascends in front of the medial malleolus, crosses the medial tibia, passes a hand's breadth behind the patella, and ends at the saphenous opening just below the inguinal ligament.