Which muscles would you recruit to manually express how you're feeling these days?
hmmm...perhaps...
extensor digitorum of the 3rd digit and
flexor digitorum profundus of digits 2, 4 and 5
flexor digitorum superficialis of digits 2, 4 and 5
flexor pollicis longus, flexor pollicis brevis, adductor pollicis, and the 1st palmar interosseous
What makes up (hard and soft tissue elements) the wrist joint proper (radiocarpal joint)?
The distal radius
the scaphoid
the lunate
the triquetrum
the articular disc of the distal ulna
What type(s) of bone is the pisiform?
seasmoid & short bone
Which ligament(s) is/are most likely implicated in wrist instability during palmarflexion?
Dorsal radiocarpal
For the following question select one of the following pick:
i. The palmar ligament is the strongest ligament of the carpometacarpal joint
ii. The 5th carpometacarpal joint is the least mobile of the carpometacarpal joints in the hand
iii. Neither medial nor lateral rotation at the MCP joints can occur in isolation
iv. The finger digits (2-5) laterally rotate at the IP joints during flexion
v. the thumb medially rotates during flexion
D)
For the following question select one of the following pick:
i. the tendon of flexor carpi radialis runs directly through the flexor retinaculum
ii. only one nerve passes through the carpal tunnel
iii. all of the extrinsic digital flexor tendons run through the carpal tunnel.
iv. the radial and ulnar arteries do not run through the carpal tunnel
v. the tubercles of the scaphoid and the trapezium form the lateral border of the carpal arch.
E)
True or false (if false, provide the correct information): the manual flexor digiti minimi muscle inserts into the lateral margin of the extensor hood of the 5th digit.
FALSE. The abductor digiti minimi muscle inserts into the medial margin of the extensor hood of the 5th digit.
True or false (if false, provide the correct information): the superficial palmar arch is fed by a branch of the radial artery.
TRUE
True or false (if false, provide the correct information): the digital branches of the median nerve supplies one thenar muscle and sends back sensory information from the dorsal tips of digits 1-3.
FALSE. They supply the two most lateral lumbricals, but they do actually send back sensory information from the dorsal tips of digits 1-3.
A patient presents with compromised sensation on the dorsal medial hand. Which nerve is implicated?
The dorsal branch of ulnar nerve
Describe the innervation of the manual lumbricals, providing the nerve and spinal levels.
1st and 2nd lumbircals are innervated by the 1st and 2nd digital branches of the median nerve. The 3rd and 4th lumbircals are innervated by the deep branch of the ulnar nerve. Both carry fibers from C8, T1.
List all of the muscles inserting into or arising from anywhere along the 3rd digit (extensor hoods, metacarpals and/or phalanges). BE SPECIFIC with muscle heads if necessary.
Extensor carpi radialis brevis
flexor carpi radialis
2nd lumbircal
2nd and 3rd dorsal interossei
flexor digitorum superficialis
flexor digitorum profundus
extensor digitorum
both heads of adductor pollicis
If your C8 and T1 were completely non-functional, would you still be able to extend your thumb? Explain why or why not.
Yes, through the abductor pollicis longus, extensor pollicis longus and extensor pollicis brevis muscles, which all receive spinal fibers from C7 as well as C8.
If the lateral root of your median nerve was cut (YIKES!), would you still be able to oppose your thumb? Explain your answer, either way.
Mostly...the lateral root of the median nerve carries fibers from C5, C6 & C7. The muscles that oppose the thumb carry fibers from radial C7 and C8 (abductor pollicis longus, and those levels are just fine), median C8 and T1 (really recurrent median for flexor pollicis brevis, abductor pollicis brevis and opponens pollicis), and ulnar C8 and T1 (adductor pollicis and 1st palmar interosseous). But you would have compromised ability to flex the pollical distal phalanx b/c median C7 is out, which will impact anterior interosseous and consequently FPL. So you'd be relatively fine...in this respect.
If the fibers from the medial cord going to ulnar were non-functional, would you still be able to oppose your thumb to the distal phalanges of digits 2-5? Explain your answer in detail.
Hmmmm...yes for digits 2 and 3 but you'd look a bit odd and no for digits 4 and 5. You'd lose C8 and T1 from ulnar (though not from median), meaning you've lost adductor pollicis and the 1st palmar interosseous, so your ability to adduct at the thumb at the MCP joint would be gone. But depending on the ratio between your thumb and other fingers, maybe opposition would remain possible...
. You could still:
-flex and medially rotate the thumb MCP and IP joints through FPL and flexor pollicis brevis (anterior interosseous and recurrent branch of median, respectively, so no ulnar branches)
-abduct the thumb at the CMC joint through abductor pollicis longus (posterior interosseous, no ulnar)
-flex digits 2&3 at the MCP and IP joints through flexor digitorum profundus and superficialis (anterior interosseous and median, respectively)
So for digits 2 and 3, opposition remains possible but it would look odd b/c you can't adduct the thumb (meaning that you'd have to really flex your digits).
However, since the DIP joints of digits 4 and 5 are flexed by FDP (innervated by C8 and T1 from ulnar), it is unlikely that the thumb would be able to reach the distal phalanges of digits 4 and 5, particularly given that it cannot adduct. Maybe slight flexion at the DIPs of 4th and 5th occur b/c of contraction of their shared muscle belly w/ the 3rd digit (which is innervated by anterior interosseous), but that is not a given.
Also, this is a bananas question and I wouldn't ask something like this on the exam. But it is useful to test yourself!
If your ulnar artery was completely blocked as it passed through the carpal tunnel would you lose your primary blood supply to opponens digiti minimi? Explain your answer.
No because the ulnar artery does not pass through the carpal tunnel.
If your ulnar artery was completely blocked as it passed into the wrist, would you lose your blood supply to opponens digiti minimi? Explain your answer.
No for various reasons. First, primary is from branches of the deep palmar arch, which is the continuation of the radial artery. Also, the arches create continuous blood flow between radial and ulnar in the deep and superficial palm, so blockage in any one artery will not result in full blood loss.
Which structures function to decrease joint pressure acting at the MCP joints and how do they do so?
The medial and collateral ligaments at the IP joints, the palmar ligaments and the extensor hoods. They increase the articular surface area along the MC and phalangeal joint surfaces. Since pressure is inversely related to surface area, the additional surface area provided by these will decrease pressures acting at these joints.
What is the common function of the flexor sheaths and the extensor retinaculum?
They both prevent bowing of tendons and hold them in place (flexor sheaths of the long flexor tendons, extensor retinaculum of the extensor tendons of the posterior forearm)
What function is enabled through the manual extensor hoods?
The simultaneous flexion at the MCP joint and extension at the IP joints.
