Landmark positioning on maxilla of cleft lip and palate infant--a reality?

In this study, we tested the precision of landmark positioning for a set of landmarks that can be used for the edentulous cleft lip and palate maxilla of the infant, by analyzing intraobserver and interobserver repositioning and measuring on a series of 121 (unilateral and bilateral) study casts. To date, no data on interobserver and only minimal data on intraobserver reproducibility are available. We found intraobserver reproducibility acceptable with total measurement errors ranging from 0.51 to 1.54 mm. Interobserver reproducibility was only slightly less with total measurement errors ranging from 0.63 to 1.57 mm. Total measurement errors were found to be relatively high for some variables. Both the intra- and interobserver analyses show insight into expected precision of landmark positioning during placement of these points on casts. A learning effect for precise positioning has been demonstrated in both analyses. The points with the highest precision overall are Q and Q', followed by the linear measurements PL and P'L'. Quality of regular study casts (impressions) is an important factor, with room for improvement. Reproducible landmark positioning on the cleft lip and palate infant's maxilla, can only be a reality if the quality of the cast is optimal and the investigator is experienced. Intraobserver and interobserver reproducibility are in the same range, which justifies the comparison of results from different studies and relieves future investigators of the need to have all measurements within a study conducted by the same investigator. Aspects of the biologic meaning of landmarks are also discussed.