Deformity of Upper Limb/The forearm is the portion of the upper extremity extending from the elbow to the wrist. The skeletal framework for this region arises from two primary osseous structures, the radius laterally and the ulna medially. These long bones serve as origins and insertions for many muscle groups allowing for normal physiologic dynamic movements. They also provide the supportive structure needed for the passage of neurovascular bundles between the proximal and distal aspects of the upper extremity. The extent of clinical pathology involving the anatomic osseous structures of the forearm include
Biceps brachii – inserts on the radial tuberosity, a bony prominence on the medial aspect of the proximal end of the radius; allows for flexion and supination of the forearm.
Brachialis – inserts on the coronoid process of the ulna and the ulnar tuberosity; allows for flexion of the forearm.
Triceps and anconeus – insert on the olecranon process of the ulna allowing for the extension of the forearm.
The Compartment and Deformity of Upper Limb
Flexor carpi radialis, palmaris longus, and the humeral heads of the pronator teres and flexor carpi ulnaris – originate from the common flexor origin. The ulnar head of the pronator teres originates from the coronoid process. The ulnar head of the flexor carpi ulnaris arises from the olecranon. The pronator teres inserts to the lateral surface of the radius and is responsible for pronation and flexion of the forearm. Each of the other muscles inserts in the wrist or hand and is responsible for more distal movements.
Flexor digitorum superficialis – arises from the anterior border of the radius, the medial epicondyle of the humerus, and the coronoid process and inserts on the middle phalanges of the medial four digits.
Flexor digitorum profundus – arises from the ulna and interosseous membrane and inserts on the distal phalanges.
Flexor pollicis longus – originates from the radius and the interosseous membrane and inserts on the distal phalanx of the thumb.
Pronator quadratus – originates from the distal end of the ulna and inserts on the distal end of the radius. Responsible for forearm pronation.
Brachioradialis, extensor carpi radialis longus, extensor carpi radialis brevis, extensor digitorum, extensor digiti minimi, and extensor carpi ulnaris– originate from the distal lateral edge of the humerus. The brachioradialis inserts just proximal to the styloid process of the radius and is responsible for flexion of the forearm, especially in pronation. The remainder of the muscles originating from this area insert distally and are responsible for movements within the wrist and hand.
Supinator – originates from the lateral epicondyle, radial collateral and annular ligaments, supinator fossa and the crest of the ulna with insertion on the lateral side of the radius. It is responsible for forearm supination.
Abductor pollicis longus and extensor pollicis longus – originates from the posterior surface of the ulna and interosseous membrane with attachments in the hand.
Extensor indicis – originates from the posterior surface of the distal third of the ulna and the interosseous membrane with attachment in the hand.
Extensor pollicis brevis – originates from the posterior surface of the distal third of the radius and the interosseous membrane with attachment in the hand.
- Both the radius and ulna are fundamental to the structure of the upper extremity; the literature describes no significant physiologic variants. However, pathological variants such as radial aplasia as part of the VACTERL association or thrombocytopenia with absent radii have been established and are covered above.[rx]
Surgical Considerations for Deformity of Upper Limb
The surgeon can usually reach the ulna without endangering other structures because of its proximity to the skin surface. In contrast, the radius, particularly the proximal portion, is encircled by muscles. Additionally, the posterior interosseous nerve abuts the proximal radius. As such, an approach to the radius is typically more complicated. There are three primary surgical approaches to the forearm bones[rx][rx][rx]:
The approach to expose the shaft of the ulna – is typically considered the simplest of the approaches because of the proximity of the bone to the skin. The patient is usually supine with the arm placed across the chest to best identify the ulna. Identification and preservation of the ulnar artery and nerve are key.
The volar (Henry) approach – to the radius can safely expose the entire length of the bone. The patient is typically supine with an arm board securing the arm in supination. Care must be taken to identify and avoid damaging the posterior interosseous nerve, the superficial radial nerve, and the radial artery.
The dorsal (Thompson) approach – to the radius provides access to the extensor side of the bone where the placement of the plates should be if possible. The patient is again supine with the forearm either pronated on an arm board or supinated and placed across the chest. The critical aspect is protecting the posterior interosseous nerve.
The primary pathology involving the radius and ulna arises from fractures, which can be classified based on specific patterns and sites of involvement. Fractures usually occur in the middle third of the bones and can involve dislocation of the nearest joint due to the transmission of force via the interosseous membrane. Regardless of the site of the fracture, management should begin with a history and physical followed by plain films of the affected site, and if possible the joint above and below, orthogonal radiographic views of each site are mandatory to appropriately manage each fracture within the guidelines of the standard of care management. Common fractures include[rx]:
Dorsally displaced distal radius fractures (commonly referred to as “Colle fractures”) – One of the most common forearm fractures. It involves a complete transverse fracture of the distal 2 cm of the radius. The distal fragment is displaced posteriorly resulting in the classic “dinner fork” deformity. The etiology is usually a fall on an outstretched hand with concomitant hyperextension. The fracture site can often be comminuted, and avulsion of the ulnar styloid process is also a feature.
Reverse Colles fracture (Smith fracture) – A complete transverse fracture of the distal 2 cm of the radius with anterior displacement of the distal fragment. Usually secondary to a fall on a flexed hand.
Monteggia fracture – A fracture within the proximal third of the ulna with concomitant dislocation of the radial head.[rx]
Galeazzi’s fracture – A fracture of the distal third of the radius with accompanying dislocation of the distal radioulnar joint.
Barton’s fracture – An intraarticular fracture of the distal radius with concomitant dislocation of the radiocarpal joint.[rx]
Essex-Lopresti fracture-dislocation – Fracture of the radial head with dislocation of the distal radioulnar joint and rupture of the interosseous membrane.[rx]
Chauffeur fracture – An intraarticular fracture of the radial styloid process.[rx]
Both Bone forearm fractures – descriptive term to describe many different types of patterns involving fractures of the radius and ulnar shaft long bone
Incomplete fracture patterns of the forearm
Isolated ulnar shaft fracture -(greenstick fracture of the ulna)
Isolated “buckle” or “torus” fracture pattern of the radius. Seen in pediatric patients as a manifestation of a pathologic force compromising one cortex of the bone (resulting in compression on one side depending on the direction of the force)
Rotator Cuff Disease
- Involves impingement, tendonitis, as well as tearing of the tendons of the muscles of the rotator cuff. The majority of the cases involve the tendon of the supraspinatus muscle. This is thought to be due to its poor blood supply. The patient complains of pain, especially while lying down on the affected arm or when doing overarm activities. In the clinic, it can be tested by the Hawking’s test and Neer test. The drop test is confirmatory. An MRI is also advised to rule out or confirm a tendon tear. Treatment depends on severity. Management involves NSAIDs, physiotherapy, and arthroscopic repair.
- This is the congenital ipsilateral absence or hypoplasia of pectoralis major and pectoralis minor muscles with hypoplasia of the corresponding ribs. It is hypothesized to be caused by an in-utero defect of blood supply to the developing chest. Poland syndrome is commonly associated with defects in breast and/or upper limb development.
Winging of the Scapula
- Denervation of the serratus anterior muscle causes palsy of the long thoracic nerve. This causes lateral and posterior movement of the scapula, away from the underlying ribs, giving it a wing-like appearance.
- Lateral epicondylitis (tennis elbow) is caused by a combination of repetitive or sustained contraction of the extensor muscles of the forearm leading to inflammation of the common extensor origin. Medial epicondylitis (golfers elbow) is due to the repetitive or sustained contraction of the flexor muscles of the forearm leading to inflammation of the common flexor origin. Patients present with pain and tenderness over the affected epicondyle that worsens with the extension (in the case of lateral epicondylitis) or flexion (when suspecting medial epicondylitis)
[bg_collapse view=”button-orange” color=”#4a4949″ expand_text=”Show More” collapse_text=”Show Less” ]