The hamate facet of the lunate: a radiographic study in an Arab population from Bahrain

Abstract

Based on the presence of a facet for the hamate two types of lunate bone have been described in the wrist; type I is without a facet for the hamate while type II bears a facet on the medial surface for articulation with the proximal pole of the hamate. Compared to type I lunates, type II lunates have been shown to have different kinematics, are more prone to clinically relevant degenerative changes in the hamato-lunate joint and may cause ulnar-sided wrist pain. The incidence of type II lunates seems to vary in different populations. Postero-anterior (PA) view of plain radiographs of the hand was studied in Arab subjects from Bahrain (n=381; 307 males and 74 females) to determine the incidence of type I and type II lunates. The mean age of the subjects was 31.1 years, the range being 18-80 years. In the population studied, only 148 (38.8%) of the 381 wrists showed type II lunate; 121 (31.7%) were found in males and 27 (7.1%) in females. There was no significant difference in the mean age of subjects with type I or type II lunates (P=0.16). There was no correlation between side and gender with the presence or absence of a hamate facet on the lunate. The incidence of type II lunate was much lower than reports in the literature of populations from the Western world, which could be attributed to a genetic variation in the Arab population in Bahrain. These data indicate that osteoarthritis of the hamate or lunate is less likely to be a cause of ulnar-sided wrist pain in Bahraini Arabs.

The Effect of Lunate Morphology in Kienböck Disease

“…9 Subsequent reports have noted the prevalence of a type II lunate to range from 27% to 73%. 20,23,24 In cohort studies of patients with scaphoid nonunions and scapholunate dissociations, a type II lunate was present in 53% (24 of 45) and 57% (33 of 58) of wrists, respectively. 12, 13 Kato et al noted a type II lunate in 26% (6 of 23) of the unaffected (contralateral) wrist in patients with radiographic findings consistent with Kienböck disease.…”

Association Between Lunate Morphology and Carpal Collapse in Cases of Scapholunate Dissociation

“…24 For example, Dharap et al found that the incidence of type II lunates was 39% in Arab subjects from Bahrain, whereas type II lunates existed in 66% of Bulgarian subjects in another study. 9,26 Lunate type has been classified by one of two methods in the literature. One method is to determine the absence or presence of the medial (hamate) facet of the lunate on neutral PA wrist radiographs (Fig.…”

Imaging Recognition of Morphological Variants at the Midcarpal Joint

“…37 The authors found no clear definition of a type II lunate in the literature. The absence of a clear definition of a type II lunate has led to inconsistencies in the reporting of lunate type, with some studies including lunates with a small ulnar cartilaginous facet in a type I group, 33,37,40 and others including them in a type II group. 3,12,13,17,23,24,30,36 The authors believe that lunate type is better described as a spectrum, with type I lunate at 1 end and type II at the other.…”