Abstract
Loosening of the glenoid component after Total Shoulder Arthroplasty is an established phenomenon with long-term follow-up studies showing radiolucency in 65% of glenoid components at 10 years (Stewart and Gray, 1997). Glenoid component designs are based on anthropometric measurements of normal shoulder joints. The purpose of this study was to study the surface anatomy of both bony and cartilaginous layers of the normal glenoid fossa in more detail.
We have developed a reproducible and inexpensive technique of surface shape assessment using laser morphometric analysis and applied this to thirty normal glenoid fossae mounted in the scapular plane. Surface analysis was carried out before and after removal of the glenoid labrum and after papain digestion of the articular cartilage allowing assessment of the skeleton alone allowing comparison with other studies using bony or cartilaginous landmarks in assessment of glenoid version. Using a specially designed program, five equi-distant lines were placed across the glenoid from which analysis of the orientation of the fossa was determined.
None of the scapulae presented a single surface that could be judged anteverted or retroverted by an amount representable by a single figure. All scapulae demonstrated a twist about the vertical axis. Two main types were identified.
Type 1 – Superior retroversion (mean 16.0 degrees) becoming progressively less to the lower pole (mean 3.0 degrees)
Type 2 – Retroverted superiorly, twisting to reach the position of maximal anteversion in the lower half of the glenoid, twisting back into more retroversion towards the lower pole. None of the specimens were morphologically equivalent to currently available glenoid prostheses. The surface shape of the glenoid is so variable that we should explore the relationship between this and the kinematics of the shoulder joint. There may be implications for the design of shoulder replacements and possibly custom prostheses.
The abstracts were prepared by Nico Verdonschot. Correspondence should be addressed to him at Orthopaedic Research Laboratory, University Medical Centre, PO Box 9101, 6500 HB Nijmegen, The Netherlands.
