MCQs – Hand 6

MCQs-Hand 6
if it is more responsible for the PIP flexion contracture. In truth, the triangular ligament contracture occurs secondary to the PIP hyperextension of a swan-neck deformity – it then helps to keep the lateral bands subluxed DORSALLY, thus, maintaining the PIP hyperextension. It really doesn’t cause the PIP deformity, but rather is secondary to the changes at this joint.

– In the thenar eminence, most are innervated by the recurrent motor branch of the median nerve. The flexor pollicis brevis may be innervated in whole or in part by the ulnar nerve. This is significant in the low median nerve palsy – there may be enough innervation of the FPB to not require opponensplasty. 30-40% with complete median nerve palsy will not require opponensplaty because of this.

– Opposition is a composite of 2 motions: 1. rotation of the thumb into pronation so that the pulp surfaces of the thumb and index finger face one another, and 2. abduction or lifting away the thumb from the palm of hand
– the combination of these two motions is true opposition. In order to render the thumb maximally functional, not only must the thumb be positioned in true opposition, it must also have short flexor action (FPB) so that it can be brought against the fingers with reasonable power through the MP and CMC joints of the thumb.

– the median nerve supplies APB, opponens pollicis, and part of FPB, and the two radial lumbricals. The ulnar nerve supplies the hypothenar eminence (abductor digiti minimi, flexor digiti minimi brevis, and opponens digiti minimi), the volar and dorsal interossei, the ulnar two lumbricals, and often part of FPB. It does not typically innervate opponens pollicis

– innervation of the ring and small finger lumbrical (3rd and 4th) is the ulnar nerve.

– the borders of the midpalmar space (the more medial of the two spaces) – the thenar space is the more lateral – include the fascia from 3rd metacarpal (oblique septum), the hypothenar fascia, the metacarpal fascia, and the flexor tendon fascia. The space is deep to the flexor tendons, so it is unlikely that the superficial palmar fascia is a boundary.

– the collateral ligaments insert to the volar plate

– most mallet fractures can be treated just like pure ligamentous mallet fingers – with extension splinting. The only really good indication for doing something about them is if the fracture is associated with significant displacement (unusual) or if the distal phalanx is markedly subluxed volarly (a mallet fracture/dislocation).

– in complex MCP dislocations, the metacarpal head ruptures between the lumbricals radially, and the flexor tendons ulnarly

– for complex MCP dislocations – the volar plate is ruptured and goes WITH the proximal phalanx, ultimately laying on the dorsal surface of the metacarpal head and thus preventing reduction. If approaching this injury DORSALLY, you can try to push the volar plate back under the MCP, or you can incise it longitudinally. At the same time, the metacarpal head ruptures volarly between the lumbrical (radially) and flexor tendons (ulnarly) – the flexor tendons remain in their fibrous sheath attached to the volar plate and are kept tight by the displacement, maintainng the tight tendo-lumbrical encirclement about the metacarpal neck. (the Chinese finger trap). Traction applied to attempt reduction further tightens this entrapment, making closed reduction impossible.

– indications for ORIF of a distal radius fracture (according to R&G):
– joint displacement of 2 mm
– radial shortening of 5 mm
– dorsal angulation exceeding 20o
– “Every effort should be made to restore LENGTH, ALIGNMENT, and ARTICULAR SURFACE CONGRUENCY. Open reduction is preferred when joint incongruity is evident by articular surface displacement of more than 2mm.”

– indications for doing carpal tunnel release after distal radius fracture – if symptoms are severe and increasing, decompression is warranted. For mild, chronic median neuropathy, observation may be employed for 3-4 months. Ie. the patient