Ulnar clubhand is much less common than radial clubhand and is more appropriately referred to as ulnar deficiencies of the forearm. Most cases are sporadic in occurrence, although genetic syndromes are associated with ulnar dysplasia. [1, 2] Focal dermal hyperplasia, or Goltz syndrome (also known as Goltz-Gorlin syndrome), is an X-linked dominant condition that consists of ulnar dysplasia, long-bone defects, and split-hand or split-foot, with skin atrophy; anal, vulval, or lip papillomata; microphthalmia; iris coloboma; and mental retardation. [3, 4, 5, 6, 7] Split-hand and split-foot with ulnar dysplasia have an autosomal dominant inheritance.  An ulnar defect with mammary gland aplasia syndrome is associated with polydactyly or camptodactyly.
Close to 70% of cases of ulnar clubhand are unilateral. A partial rather than complete absence of the ulna is common. Ulnar shortening with radial bowing and abnormal digits is the classic presentation of this condition, and digital anomalies can be found in close to 90% of cases with postaxial absence of ulnar rays.  The fourth and fifth metacarpals, as well as the capitate, lunate, triquetrum, hamate, and pisiform, are absent or deformed.
Synostosis with the humerus is possible when the ulna is present; radiohumeral synostosis can also be present. The radial head is dislocated in close to 50% of cases.
Radial bowing is produced by the tethering effect of the fibrocartilaginous ulnar anlage, which can also tether the carpus, producing limitation of wrist movement. The radiocarpal joint has a fixed ulnar deviation in these cases. In most cases, however, function is very good, and the carpus can be actively centralized. The presence of a thumb makes for a functional hand, unlike the case for radial clubhands.
Elliott et al studied 28 patients with posterior congenital dislocation of the radial head and proximal radioulnar fusion to help identify whether they are different clinical manifestations of the same primary developmental abnormality. Of 28 patients studied, 16 had bilateral involvement (8 had posterior dislocation of the radial head only; 5 had posterior radial head dislocation with radioulnar fusion; and 2 had radioulnar fusion without dislocation). Nine patients had only left-sided involvement, and 3 had only right-sided involvement. According to the authors, the suggestion of a developmental relationship between posterior dislocation of the radial head and proximal radioulnar fusion is supported by the fact that the 2 anomalies can occur in the same patient. In addition, they noted that both anomalies can be seen in different patients with the same genetic diagnosis, further supporting the notion that these defects are developmentally related. 
Nygaard et al evaluated the pressure distribution in the wrist joints with ulnar shortening and lengthening. They found that compressive forces in loaded wrists were distributed with 67% across the radiocarpal joint and 33% across the ulnocarpal joint; that shortening the ulna by 3 mm increased load in the radius to 80%; and that lengthening the ulna by 1 mm increased its load to 55%. In addition, they noted that load share of the distal radioulnar joint was constant even when the ulna was shortened 3-4 mm. They therefore suggested shortening the ulna by 3 mm, since the increased load in the related joints are constant within a range of -2 to -4 mm. 
Oberg et al described the rare combination of right radial and left ulnar deficiencies in 2 cases. In one case, there was a history of 2 separate, distinct episodes of bleeding during early gestation. In the other case, there was associated hematoma formation early in development. According to the authors, variation in longitudinal deficiencies is likely related to the timing and duration of an insult during early limb development, and in experimental models, teratogenic insults have been shown to induce ulnar deficiencies earlier in gestation than radial deficiencies. 
Ulnar deficiency of the forearm is much less common than the occurrence of radial clubhand.
Most cases of ulnar deficiency of the forearm are sporadic in occurrence, although genetic syndromes are associated with ulnar dysplasia (see Introduction).
The patient's affected upper limb is examined in supination, pronation, extension, and flexion. Clinical considerations of this condition include the following:
Ulnar deviation of the hand
Absent ulnar digits 
Limited pronation, supination, or both
Radial head subluxation or dislocation
Deficient carpal bones
Upper limb-length discrepancy
According to the traditional classification, there are 4 types of ulnar deficiencies of the forearm, which can have varying degrees of radial bow, with or without radial head dislocation. The classification is as follows:
Type 1 – Ulnar shortening (distally) with minor radial bow
- Hypoplasia of the ulna
- Proximal and distal epiphyses present
- Hypoplastic or absent ulnar digits
- Minimal radial bowing
Type 2 – Significant ulnar shortening with a fibrocartilaginous anlage attached to the ulnar carpus, with significant radial bowing
- Partial aplasia of the ulna, distal third
- Distal ulnar anlage
- Bowed radius with anlage acting as a tether
- Presence/absence of progressive radial head dislocation
Type 3 – Complete absence of the ulna
- Unstable elbow
- Straight radius
Type 4 – Complete absence of the ulna, with a fibrocartilaginous anlage attached to the ulnar carpus
- Radiohumeral synostosis at the elbow
- Bowed radius
See Treatment, Surgical therapy.
Nonspecific contraindications to ulnar clubhand surgery are as follows:
The presence of no or minimal functional deficit. In such cases, the surgeon is wary of making the condition functionally worse. (In most cases, the hand is reasonably functional, and correction of the forearm deformity is required to position the hand in a more favorable position in space.)
Any surgical risk factor due to associated syndromes
A severely affected limb and poor neurologic function