Placing the GPG (Glenoid Positioning Guide) clamp on the shoulder blade neck is simple and reproducible.
The GPG clamp allows the installation of a guide wire simultaneously at the centre of the surface of the glenoid bone and in the orientation of the shoulder blade neck.
The jaws of the clamp are positioned on the anterior and posterior sides of the scapular neck at the GvOC level – approximately 15 to 20mm medial to the glenoid rim.
2 guiding tunnels allow to position the pin guide either centered in the middle of the clamp, or shifted vertically by 7mm.
Incorrect placement of a glenoidal implant directly influences the clinical and radiographic results of total shoulder arthroplasty (1).
The placement of a glenoidal implant for total shoulder prosthesis is made difficult (a) by a superficial aspect of the glenoid bone which is not always reliable to determine the deep geometry of the scapular neck, and (b) by the erosion of the arthritic glenoid which alters the interpretation of its native anatomical orientation.
Several anatomical studies have shown that the plane of the scapular blade is not a reliable landmark for determining the retroversion, tilt, rotation and offset planes of the pre-pathological native glenoid. Especially since this reference plan evolves with the age of the patient (2). The authors show that the plane of the Glenoid vault Outer Cortex (Gvoc) is comparatively more reliable, and especially does not seem to evolve with the aging of the patient.
(1) Accuracy of Glenoid Component Placement in Total Shoulder Arthroplasty and its Effect on Clinical and Radiological Outcome in a Retrospective, Longitudinal, Monocentric Open Study. T.Gregory, A.Sankey, B.Augereau, E.Vandenbussche, A.Amis,R.Emery, U.Hanssen. Plos one-Oct 2013 – Volume 8 – Issue 10 – e75791.
(2) Does the Orientation of the Glenoid Rim respect the Scapula Blade evloving wiyh Age compared to the Glenoid Vault Outer Cortex Plane? T.Gregory, M.Artuso. SECEC 2019 Abstract Proceedings – JSES Open Access 3 (2019) 233-260.
(3) Is the Glenoid Vault Outer Cortex a more Accurate Reference Plane than Conventional Methods in Shoulder Arthroplasty? T.Gregory, S.Hurst, L.Merlini, U.Hansen, J.Gregory, R.Emery. DOI: https://doi.org/10.21203/rs.3.rs-93174/v1