Interosseous Membrane

The interosseous membrane is a fibrous sheet of connective tissue that spans the space between two long bones. In the forearm, it connects the radius and ulna, while in the leg, it joins the tibia and fibula. This structure plays a crucial role in stabilizing the bones, transmitting forces, and providing attachment sites for muscles.

Location

There are two primary interosseous membranes in the human body:

• Forearm Interosseous Membrane: Found between the radius and ulna, stretching from just below the radial tuberosity to the distal radioulnar joint.
• Leg Interosseous Membrane: Located between the tibia and fibula, extending along the length of the interosseous borders of both bones.

Structure

The interosseous membrane is composed of dense fibrous connective tissue, primarily collagen fibers aligned obliquely. Its fibers are not uniformly oriented but follow specific patterns based on the functional needs of the limb.

Forearm

• Mostly downward and medially directed fibers.
• Contains apertures for passage of vessels (e.g., the posterior interosseous artery).
• Thicker proximally and thinner distally.

Leg

• Fibers run downward and laterally from the tibia to the fibula.
• Upper and lower openings allow for neurovascular structures (e.g., anterior tibial vessels).
• Thicker and more rigid than its forearm counterpart.

Attachments

The interosseous membrane serves as an important site of muscle origin and structural attachment.

Function

The interosseous membrane has several biomechanical and anatomical functions:

• Stabilization: Maintains proper spacing between paired long bones and prevents excessive separation during movement.
• Force Transmission: Distributes mechanical loads between bones — for instance, transferring compressive forces from the radius to the ulna or from the tibia to the fibula.
• Muscle Attachment: Provides surface area for origin of deep muscles in both the forearm and leg.
• Compartment Separation: Helps separate the anterior and posterior muscular compartments.
• Vascular Channeling: Has strategically placed openings to allow passage of vessels and nerves.

Development

The interosseous membrane forms during embryonic limb development, derived from mesenchymal connective tissue that differentiates alongside the long bones. As the radius-ulna and tibia-fibula segments elongate and ossify, fibrous tissue persists between them, differentiating into the membrane and associated ligaments.

Clinical Significance

• Essex-Lopresti Injury: A high-energy injury involving radial head fracture, disruption of the interosseous membrane, and distal radioulnar joint dislocation. Loss of membrane integrity can lead to longitudinal instability of the forearm.
• Compartment Syndrome: Though rare, trauma to the interosseous membrane may contribute to increased pressure in the anterior or posterior compartments.
• Interosseous Membrane Calcification: Seen in some metabolic conditions or post-trauma, may reduce mobility or indicate underlying pathology.
• Chronic Overuse: Repetitive stress in athletes (e.g., weightlifters, throwers, or runners) may cause strain or inflammation of the membrane.

Blood Supply and Innervation

• Forearm: Supplied by the anterior and posterior interosseous arteries (branches of the ulnar artery). Innervated by nearby branches of the radial and median nerves.
• Leg: Supplied by the anterior tibial artery, which passes through the proximal opening. Nerve supply is minimal, mostly from surrounding deep fibular and tibial nerves.

Imaging and Visualization

The interosseous membrane can be visualized using:

• MRI: Best modality for detecting tears, degeneration, or inflammation.
• Ultrasound: Useful in assessing superficial pathology and guiding injections or aspirations.
• CT scans: May detect ossification or mineralization in chronic conditions.

Variations

• The thickness and elasticity of the membrane can vary among individuals, often correlating with athletic activity or chronic loading.
• Accessory slips or fibrous bands may occur between the bones, especially in the forearm.