MCQs – Hand 6

Modern Study Review (AI-Generated)

High-Yield Summary

This topic is a staple of the Royal College exam, focusing heavily on hand ligament anatomy, nerve innervation, and fracture management thresholds. The single most important clinical trade-off is deciding surgical intervention for distal radius fractures based on displacement (>2 mm), radial shortening (>5 mm), and dorsal angulation (>20°). While classic teaching emphasizes ligament contractures in deformities like swan-neck and mallet finger, modern practice integrates nuanced understanding of dynamic anatomy and nerve variations, especially in median nerve palsy management. Mastery of complex MCP dislocation anatomy is critical for surgical planning and avoiding failed closed reductions.

High-Yield Decision Matrix

Active Recall Q&A

Ligament Contractures & Deformities

Q: What deformity does a contracture of the oblique retinacular ligament cause?
A: It causes a DIP extension contracture.
Related Pearl: The oblique retinacular ligament coordinates PIP and DIP joint motion; contracture disrupts this balance, leading to DIP hyperextension.

Q: Does a triangular ligament contracture cause PIP flexion contracture?
A: No, it occurs secondary to PIP hyperextension in swan-neck deformity and helps maintain PIP hyperextension by keeping lateral bands dorsally subluxed.
Related Pearl: Triangular ligament contracture is a secondary stabilizer, not the primary cause of swan-neck deformity.

Nerve Innervation & Function

Q: Which nerve innervates most muscles in the thenar eminence?
A: The recurrent motor branch of the median nerve.
Related Pearl: Variability in FPB innervation by the ulnar nerve can preserve thumb function in median nerve palsy.

Q: What percentage of patients with complete median nerve palsy do not require opponensplasty due to FPB innervation?
A: 30-40%.
Related Pearl: This anatomical variation influences surgical decision-making in median nerve palsy.

Q: What two motions compose true thumb opposition?
A: 1) Rotation of the thumb into pronation so pulp surfaces face each other, and 2) abduction (lifting away from the palm).
Related Pearl: Both motions are essential for functional opposition; loss of either reduces thumb utility.

Q: Which muscles does the median nerve supply in the hand?
A: Abductor pollicis brevis (APB), opponens pollicis, part of flexor pollicis brevis (FPB), and the two radial lumbricals.
Related Pearl: Median nerve injury impairs precision pinch and fine motor control.

Q: Which muscles does the ulnar nerve supply in the hand?
A: Hypothenar muscles, volar and dorsal interossei, ulnar two lumbricals, and often part of FPB.
Related Pearl: Ulnar nerve injury causes clawing and intrinsic muscle weakness.

Q: Which nerve innervates the ring and small finger lumbricals (3rd and 4th)?
A: The ulnar nerve.
Related Pearl: This explains the ulnar nerve’s role in fine finger flexion at the MCP joints.

Anatomical Spaces & Ligaments

Q: What are the anatomical borders of the midpalmar space?
A: Fascia from the 3rd metacarpal (oblique septum), hypothenar fascia, metacarpal fascia, and flexor tendon fascia; lies deep to flexor tendons.
Related Pearl: Precise knowledge of these boundaries is critical for surgical drainage of deep palmar infections.

Q: Where do the collateral ligaments insert in the finger?
A: To the volar plate.
Related Pearl: This insertion stabilizes PIP and DIP joints against lateral stresses.

Fractures & Dislocations

Q: How are most mallet fractures treated?
A: With extension splinting, similar to pure ligamentous mallet fingers.
Related Pearl: Surgery is reserved for significant fracture displacement or volar subluxation of the distal phalanx.

Q: In complex MCP dislocations, where does the metacarpal head rupture?
A: Between the lumbricals radially and the flexor tendons ulnarly.
Related Pearl: This rupture pattern creates a “Chinese finger trap” mechanism preventing closed reduction.

Q: What happens to the volar plate in complex MCP dislocations?
A: It ruptures, remains attached to the proximal phalanx, and lies dorsally over the metacarpal head, blocking reduction.
Related Pearl: Surgical approaches may require volar plate incision or repositioning for successful reduction.

Q: What are the indications for ORIF in distal radius fractures?
A: Joint displacement >2 mm, radial shortening >5 mm, and dorsal angulation >20°.
Related Pearl: Restoring length, alignment, and articular congruency prevents long-term dysfunction.

Classic Clinical Notes

• A contracture of the oblique retinacular ligament is bound to cause a DIP extension contracture; not sure if a triangular ligament contracture will do the same, or 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, maintaining 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 20°
• “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.”

Last Updated on January 25, 2026 by Christian Veillette