Questioning the axiom: Is hyperflexed scaphoid a common occurrence in South Indian population? - An observational study

Background Scapholunate angle SLA greater than 80° is one of the indicators of surgery for carpal instability. The normal SLA is between 30-60°. This is based on studies which were conducted several decades ago in the western part of the world. The SLA of Indian population has never been measured before. The knowledge of normal SLA in each population becomes imperative because it lays down the guidelines for surgical and non-surgical management of wrist fractures and instability in that population. In this study, we aim to measure the SLAs in asymptomatic volunteers of South Indian origin and compare the results with existing data. Methods An observational study was done in a tertiary care hospital in South India. Lateral radiographs of the wrist of asymptomatic volunteers were taken. The SLA was measured using a software in the PACS system. The relation of SLA to gender, age, left and right sides and handedness was compared. These were compared to pre-existing global data available on SLAs. Results The SLA of the 202 radiographs with 47 males and 54 females were studied. The average SLA was 51.33° and the range was between 29° and 74°. The average SLA of males was 51.8° and females 50.8°. There was no significant difference between the two. Similarly, there was no significant difference between the SLA of right and left sides in right handed and left handed subgroups. However, there was an increasing trend in SLA among females with age. But no similar pattern was seen among males. Interestingly, 39 out of the 202 radiographs (19.3%) had a SLA above 60°. Conclusion This study suggests the normal SLA in South Indians may be higher than the previously established reference values and serves as a pilot project and a reference for further studies on SLA.