LATERAL LUNATE MORPHOLOGY - AN X-RAY STUDY

The lunate has been described by Kauer as being thinner dorsally than volarly when measured proximal to distal. We used an x-ray method to m easure the shape of the lunate in order to compare dorsal and volar th icknesses after recognizing clinically a group of patients with scapho lunate dissociation in whom volar flexed lunates were present. Using t his method, 292 standard lateral views of the lunate were collected ra ndomly and measured. The shape of the lunate could be classified into 3 types: type D lunates have a thinner dorsal segment and correspond t o Kauer's description; type V lunates have a thinner volar segment; ty pe N lunates have equal dorsal and volar segments. There were 196 type D lunates (67%), 67 type V lunates (23%), and 29 type N lunates (10%) . The radiolunate angles were measured in a random selection from type D and type V lunates to determine any relationship between the volar segment to dorsal segment thickness (wedge) ratio. No relationship wit hin these groups was identified. However, there was a significant diff erence in the radiolunate angles between these two groups. Recognition of the prevalence of the type V lunate alters concepts proposed by Ka uer and warrants further investigation of factors influencing lunate p osition.