Radial clubhand.

Radial clubhand is a deficiency along the preaxial or radial side of the extremity. Although considerable forearm and hand anomalies are the classic findings, proximal deficiencies also can occur throughout the arm and shoulder girdle

Radial clubhand is classified into the following 4 types, based on the amount of radius present:

  • Type I deficiency - The mildest type, this is characterized by mild radial shortening of the radius without considerable bowing. Minor radial deviation of the hand is apparent, although considerable thumb hypoplasia may be evident.
  • Type II deficiency - This is characterized by a miniature radius with distal and proximal physeal abnormalities and moderate deviation of the wrist.
  • Type III deficiency - This is characterized by a partial absence of the radius (most commonly the distal portion) and severe wrist radial deviation.
  • Type IV deficiency - The most common variant (see image below), this is characterized by a complete absence of the radius. The hand tends to develop a perpendicular relationship to the forearm.

 

History of the procedure

In 1733, Petit first described radial clubhand in an autopsy of a neonate with bilateral clubhands and absent radii. Subsequent autopsy observations detailed the anomalous anatomy associated with radial clubhand and the associated malformations of other body systems.

Initial surgical treatment of radial clubhand involved an ulnar osteotomy to correct the bow, along with splitting of the distal ulna for insertion of the carpus. Reconstruction of the radius with a bone graft to support the carpus was reported in the 1920s, and nonvascularized epiphyseal transfer was reported in 1945. Results of these procedures were disappointing. They had multiple causes of failure, including disruption of the ulnar growth plate and subsequent increase in limb-length discrepancy, inadvertent ankylosis or arthrodesis of the wrist and loss of motion, and failure of the transplanted bone to grow, with eventual loss of radial support.

Centralization of the carpus on the distal ulna has emerged as the preferred surgical technique to correct radial clubhand. Pioneers in congenital hand surgery developed the basis for this procedure. Numerous modifications have been described to obtain or maintain correction of the wrist on the ulna.

Radialization is a technique that involves overcorrection of the carpus on the ulna combined with tendon transfer to further rebalance the wrist.

Frequency

The reported incidence of radial clubhand varies between 1 per 55,000 and 1 per 100,000 live births. Most cases are sporadic without any definable cause. However, exposure to teratogens, such as thalidomide and radiation, can yield radial deficiencies.

Radial deficiency is bilateral in 50% of cases and is slightly more common in males than in females (3:2). The incidence of radial deficiency within the same family is small, ranging from approximately 5 to 10% of reported cases; it is most common in radial aplasia associated with cardiac abnormalitie

Etiology

In the 19th century, the etiology of radial clubhand was theorized to be either a congenital absence or an acquired defect secondary to syphilis. In 1895, Kummel proposed the cause to be abnormal pressure upon the embryo along the radial bud between the third and seventh week of gestation.

Current theory relates the etiology of radial clubhand to the apical ectodermal ridge (AER). This structure is a thickened layer of ectoderm that directs differentiation of the underlying mesenchymal tissue and limb formation. Removal of a portion of the AER in chick embryos has produced anomalies similar to radial clubhand. Therefore, a defect of the AER is the most probable cause of radial clubhand, with the extent of deformity related to the degree and extent of the AER absence.

Pathophysiology


The forearm is foreshortened, and the wrist is positioned in radial deviation. This malalignment assumes a perpendicular relationship over time

The right-angled position further shortens the limb and limits the ability to reach into space. The awkward angulation between the wrist and forearm places the extrinsic flexors and extensors at a mechanical disadvantage. The tendons must traverse this angle to elicit finger motion, which limits the ability to move the digits.

Indications

The objectives of treatment in radial clubhand are to reduce the functional deficit incurred by a short or absent radius, a short ulna, an abnormal muscular anatomy, and a radial deviation of the wrist. Type I radial clubhands have minor radial deviation of the wrist, which creates less of a functional problem than types II, III, and IV. In those children with considerable absence of the radius, the wrist assumes severe radial deviation that increases to 90° over time. This further compromises the flexor and extensor tendons, creating functional difficulty.

Thumb hypoplasia also requires consideration when formulating a treatment plan for radial clubhand. An absent or deficient thumb inhibits use of the hand. Reconstruction or pollicization is necessary to optimize hand function. Thumb reconstruction is usually delayed until after forearm treatment.

The basic goals of treatment are as follows

  • Correct radial deviation of the wrist
  • Balance the wrist on the forearm
  • Maintain wrist and finger motion
  • Promote growth of the forearm
  • Improve function of the extremity
  • Enhance limb appearance for social and emotional benefit

Centralization is indicated in radial clubhand types II, III, and IV, in which there is severe radial wrist deviation and insufficient support of the carpus.

Anatomy

Bone and joint abnormalities

Clinical features of radial deficiency (types II, III, and IV) are dramatic, with abnormalities of the entire extremity. The scapula is often small, and the clavicle is often shorter, with an increased curvature. The humerus may or may not be short, and deficiencies of the capitellum and trochlea are common. Elbow motion is usually diminished more in flexion than in extension. The forearm is always decreased in length, and the ulna is approximately 60% of the normal length at the time of birth. This discrepancy persists throughout the growth period and into adulthood. True forearm rotation is absent in patients with partial or complete aplasia of the radius.

The wrist is radially deviated and develops a perpendicular relationship to the forearm over time. The articulation between the carpus and ulna is usually fibrous and abnormal, although some hyaline cartilage can be found. Wrist motion is primarily in the radial/ulnar plane, with some flexion/extension. Ossification of the carpal bones is delayed, with the scaphoid and trapezium often absent or hypoplastic. The capitate, hamate, and triquetrum are usually present but ossify late.

The fingers are often stiff, with limited motion at the metacarpophalangeal and interphalangeal joints. The preaxial index and long fingers are more affected than the postaxial ring and small digits.

Muscle and tendon abnormalities

Numerous muscular abnormalities are found throughout the upper extremity. The deltoid or pectoralis major muscle can be hypoplastic, can be partially absent, or can have an abnormal insertion. The biceps may be absent or fused to the underlying brachialis muscle.

The forearm demonstrates the most severe abnormalities, involving any muscle that originates or attaches to the radius. This includes the extensor carpi radialis longus, extensor carpi radialis brevis, pronator teres, flexor carpi radialis, palmaris longus, flexor pollicis longus, pronator quadratus, and supinator muscles. The extrinsic flexors and extensors of the fingers are usually adherent, with abnormal origins and insertions. The flexor and extensor carpi ulnaris, as well as the interossei, lumbricals, and hypothenar muscles, are often normal, while abnormalities of the thumb muscles are more related to the degree of thumb hypoplasia.

Nerve and artery abnormalities

The radial nerve usually terminates at the elbow, and the ulnar nerve is normal. An enlarged median nerve substitutes for the absence of the radial nerve and supplies a dorsal branch for dorsoradial sensibility. This subcutaneous branch is positioned in the fold between the wrist and forearm and must be protected during surgery. The vascular anatomy demonstrates a normal brachial and ulnar artery. The radial artery is often absent, and the interosseous arteries usually remain patent.

Associated abnormalities

Radial deficiency is associated with numerous systemic conditions, including Holt-Oram syndrome (cardiac septal defects); TAR syndrome; Fanconi anemia (aplastic anemia); and VACTERL syndrome.In addition to these conditions, a variety of associated musculoskeletal deformities appear sporadically. These include cleft palate, clubfoot, kyphosis, scoliosis, torticollis, and rib deformities.