17 The Interosseous Membrane

David J. Slutsky

17 The Interosseous Membrane

17.1 Interosseous Membrane Anatomy

In an anatomical study of 30 forearm specimens, Noda et al identified that the interosseous membrane (IOM) included five ligaments: the central band (CB), the accessory band (AB), the distal oblique bundle (DOB), the proximal oblique cord, and the dorsal oblique accessory cord (▶Fig. 17.1a–c). ¹ They further subdivided the IOM into proximal, middle, and distal portions. The middle ligamentous complex consists of the CB and the AB. The CB is the broadest and thickest of these ligaments. The CB originates from the interosseous crest of the radius, then courses distally and ulnarly to insert into the interosseous border of the ulna. The mean width was 9.7 ± 3 mm (range, 4.4–16 mm) and the mean thickness 1.3 ± 0.2 mm (range, 1–1.6 mm). The AB consists of several ligaments either proximal or distal to the CB that were often less than 1 mm in thickness and varied in location and number (▶Fig. 17.2).

**Fig. 17.1** (a) Volar aspect of a right forearm dissection demonstrating the components of the interosseous membrane. (b) Backlight specimen highlighting the distal oblique bundle (DOB), the thin accessory band (AB), and the thick central band (CB). (c) Schematic diagram. (Reproduced with permission from Noda et al. ¹ )

**Fig. 17.2** Dorsal aspect of a left forearm dissection with labeling of the IOM components. The interosseous artery penetrates through a hole in the distal membrane (*arrow*). AB, accessory band; CB, central band; DOA, dorsal oblique accessory cord; DOB, distal oblique bundle.

The DOB is an inconstant ligament that is present within the distal membranous portion. It originates from the distal sixth of the ulnar shaft, at the proximal border of the pronator quadratus muscle, blending into the capsule of the distal radioulnar joint (DRUJ) and inserting into the inferior rim of the sigmoid notch and dorsal and palmar radioulnar ligaments (▶Fig. 17.3a,b). The mean width was 4.4 ± 1.1 mm (range, 2–6 mm) and the mean thickness 1.5± 0.5 mm (range, 0.5–2.6 mm). The DOB appeared to form an isometric collateral ligament with the triangular fibrocartilage complex (TFCC) to stabilize the forearm during rotation, because the ulnar insertions of these ligaments coincide with the axis of rotation. ²

**Fig. 17.3** (a) Dorsal aspect of a left forearm dissection showing the intimate relationship between the distal oblique bundle (DOB) blending with the dorsal radioulnar ligament and triangular fibrocartilage (*). CB, central band; DIC, dorsal intercarpal ligament; DRCL, dorsal radiocarpal ligament. (b) Schematic diagram demonstrating the axis of rotation which passes through the ulnar head. (Reproduced with permission from Moritomo et al. ² )

The proximal oblique cord (ligament of Weitbrecht) was seen in the proximal membranous portion. It originates from the anterolateral aspect of the coronoid process of the ulna and inserts just distal to the radial tuberosity (▶Fig. 17.4a,b). The mean width was 3.7 ± 1.6 mm (range, 1.5–8 mm) and the mean thickness 1.1 ± 0.5 mm (range, 0.4–2 mm). A less constant dorsal oblique accessory cord was seen on the posterior aspect of the forearm, originating from the distal two-thirds of the ulnar shaft and inserting into the interosseous crest of the radius (▶Fig. 17.5a,b). The mean width was 3.2 ±1 mm (range, 1.9–5 mm) and the mean thickness 0.9 ± 0.2 mm (range, 0.5–1 mm).