MCQs – Anatomy 2

MCQs-Anatomy 2
(deltoid); then technically internervous between infraspinatus (suprascapular) and teres minor (axillary).

– the posterior approach to the humerus – dissection is between lateral and medial heads of triceps (radial nerve and profundus running between). Remember: the posterior approach is good for more distal humeral fractures, because the distal 1/3 of the humerus at the front is covered by the brachialis which at this level is hard to move out of the way. The posterior approach is limited superiorly by radial nerve – you can always slip the plate underneath it.

– the radial nerve is found between medial and lateral heads of triceps, and at the elbow, between brachialis and brachioradialis

– Musculocutaneous nerve: (C4), C5,6,7
– Axillary nerve: C5,6
– Radial nerve: C5, 6, 7, 8, T1
– Median nerve: (C5), C6,7,8, T1
– Ulnar nerve: (C7), C8, T1

– the ulnar nerve pierces the IM septum about 8-10 cm above the medial epicondyle to run in the posterior compartment, just on the ANTERIOR surface of the medial head of triceps. It then pierces the two heads of FCU to run deep to flexor digitorum superficialis and flexor carpi ulnaris, but superficial to FDP.

– like the ulnar nerve, the median nerve also passes under the fibrous arch of FDS and runs between FDS and FDP

– the last muscle to recover from radial nerve injury is extensor indicis proprius. It is actually distal to EPL.

– for high radial nerve injury: order of re-innervation. Complicated question. The brachioradialis and ECRL obvious return first. The PIN goes through supinator and emerges (often giving off ECRB before going through supinator, or ECRB gets it from the superficial branch). As it emerges from the distal end of supinator, there are two main distributions of the PIN – one superficial to the EDC, EDMinimi, and ECU; and one that travels more deep to innervate APL, EPL, EPB, and finally most distally, Ext Indices Proprius. Notice that it looks like EPL might get innervated before EPB. Arguable. In any event, index finger extension will return before thumb retropulsion because EDC is reinnervated before EPL.

– so the order: EDC, EDMinimi, ECU (all the superficial ones); then APL, EPL, EPB, Eindicis (the deep ones)
– note that EDMinimi is innervated quite high

– posterior branch of obturator artery – this is what comes through the ligamentum teres

– the medial Ludloff approach to the hip: superficial exposure goes under adductor longus (between adductor longus and gracilis). Pectineus is more medial, and lies about at the same level as adductor (though it inserts just anterior to longus on the femur). This interval then gets you onto adductor brevis. The deep dissection then goes UNDER brevis between adductor brevis and adductor magnus which is an internervous plane between the anterior branch of obturator nerve (supplying brevis) and the posterior branch (supplying magnus). By lifting up on brevis and pulling down on magnus, you will see the lesser trochanter with the iliopsoas tendon attachment.. Note that the brevis is sorta “sandwhiched” between the anterior and posterior divisions of the obturator nerve (but is supplied by the anterior)

– the profunda femoris lies on pectineus then curves posteriorly – it gives off the medial circumflex artery, which passes posterior to pectineus and then curls behind the iliopsoas tendon (in close proximity to the tendon!) – YOU HAVE TO WATCH OUT FOR THIS ARTERY WHEN YOU DO THE DEEP DISSECTION. After the superficial dissection, you get between longus and brevis – the artery is in this plane as it heads under iliopsoas. You avoid it here by going deep to brevis (between brevis and magnus), but then you end up exposing iliopsoas tendon in the deep dissection – and the artery is RIGHT THERE!

– therefore, during the medial Ludloff approach, the most endangered structure is the medial circumflex femoral artery. Also exposed are both the anterior branch of the obturator nerve (during superficial exposure) and the posterior branch