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. 2022 May 18;9(1):46.
doi: 10.1186/s40634-022-00481-z.

The Y plane is a reliable CT-based reference for glenoid component positioning in shoulder arthroplasty

Jean-Marc Glasson  1   2 , Floris van Rooij  3 , Luca Nover  4 , Mo Saffarini  4 , Jean Kany  5
Affiliations

The Y plane is a reliable CT-based reference for glenoid component positioning in shoulder arthroplasty

Jean-Marc Glasson et al. J Exp Orthop. .

Abstract

Purpose: To determine the reliability of anatomic references for mediolateral component positioning in shoulder arthroplasty.

Materials and methods: The computed tomography scans of 86 shoulders free of arthritic or anatomic deformities were studied. Two surgeons independently digitized a series of points, including the intersection of the 3 bone branches of the scapular spine (Y), the center of the glenoid surface (G), the most medial point of the scapula (MS), the cortical convergence (CC) of the anterior and posterior margins of the glenoid, the base of the coracoid (BC), the anterior (HA) and posterior (HP) margins of the subchondral bone.

Results: The mean mediolateral distances between G and Y, BC, CC were respectively - 19.6 mm, - 1.5 mm, and - 36.8 mm. The consistency of anatomic landmarks was greatest for Y (standard deviation (SD) =2.3 mm; interquartile range (IQR) =3 mm), compared to BC (SD = 4.6 mm; IQR = 7 mm), and CC (SD = 6.6 mm; IQR = 8 mm). The repeatability of anatomic landmarks was excellent for all measurements. The mean ratios (relative to humeral head size) of distances between G and Y, BC, CC were respectively - 0.45, - 0.04, and - 0.85. The consistency of ratios was greatest for Y (SD = 0.05; IQR = 0.06), compared to BC (SD = 0.11; IQR = 0.14), and CC (SD = 0.13; IQR = 0.17). The repeatability of ratios was excellent for Y and BC, while it was good for CC.

Conclusions: The Y-plane is a reliable reference for glenoid component positioning in shoulder arthroplasty, with a consistent distance from the center of the glenoid surface, and could therefore be suitable for preoperative planning.

Study design: Level III, comparative anatomic study.

Keywords: Computed tomography; Lateralization; RSA; TSA; Y-point.

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Conflict of interest statement

JMG declares receiving royalties and consultancy fees from Smith & Nephew. JK declares receiving royalties and consultancy fees from FH Orthopedics and consultancy from DePuy-Mitek (Johnson & Johnson), as well as consultancy fees from VIMS. FVR, MS and LN declare that they have no competing interests.

Figures

Fig. 1
Fig. 1
The reference planes were defined using the 3D multi-planar reformat (MPR) mode to enable direct measurement of dimensions and angles in all three planes: a An axial slice passing close to the glenoid equator was used to locate the scapular axis, passing through the medial border of the scapula and the centre of the glenoid; b The coronal view was used to locate the glenoid equator more accurately, and the corresponding axial slice was used to finetune the scapular axis; c The para-sagittal view (parallel to glenohumeral joint space) was used to locate the ‘Y-plane’, by scrolling from lateral to medial until both superior and inferior cortices of the scapular spine were in continuity with the body of the scapula
Fig. 2
Fig. 2
The 7 following points were digitized and named on each CT scan: a The Y point was digitized in the parasagittal view, at the intersection of the 3 bone branches (Y) on the aforementioned ‘Y-plane’; b The centre of the glenoid (G), the most medial point of the scapula (MS), and the cortical convergence (CC) of the anterior and posterior margins of the glenoid were all digitized in the same axial plane; c The base of the coracoid (BC) was digitized where the lateral cortex of the coracoid process merges with the cortex of the scapula in the axial view; d The anterior (HA) and posterior (HP) margins of the humeral head were digitized in the axial plane where the humeral head appeared to have the greatest size
See this image and copyright information in PMC

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