A five-grade categorization of age-related change in the acromio-clavicular joint derived from the skeletal remains of early 19th century Londoners of known sex and age

Abstract

Parts of the articular surfaces of the 152 joints available in the study were often protected by dried articular tissue. The 18–25 year group were categorized as normal. Using hand-lens and dissecting microscope, probable nutritional canals were found in normal articular surfaces, together with hemispherical configurations that may relate to attachment of the fibres of fibro-cartilage. At about 35 years, changes were detected: areas of increase of canals, confluence of canals, disorder in arrangement of hemispherical configurations and, probably at a more advanced stage of change, irregularities in their shapes: jaggedness, flattening and finally absence so leaving a smooth surface. A new type of perforation appeared; some pouting with sloping sides like volcanoes were regarded as perforations of the subchondral plate by the destructive vascular tissue of osteoarthrosis which, together with changes in surface configurations, probably begin during the stages of initial change in cartilage that morbid anatomists categorize as Grades 1 and 2 in their Collins 4-Grade system. Hence a parallel five-grade system suitable for use on skeletal material was constructed with the addition of an intermediate Grade 3A to provide for detailed characterization of the bony changes the palaeopathologist depends on. Probably the facets, even when eroded, were covered with an articular tissue. Measurement, expressed as a size index, and the development of overlapping margins to acromial facets, often overhanging the subacromial surface, suggested that the facets increased in size before any osteoarthrosis occurred. Copyright © 1999 John Wiley & Sons, Ltd.