Glenoid Positioning Guide (GPG)
What is it?
It is a surgical instrument for positioning a K-wire into the glenoid vault, providing the maximum bone axis of the vault together with the non- eroded version, inclination, rotation and offset of the pre-eroded glenoid.
How does it work?
This GPG is a re-sterilised surgical device that can be adjusted to fit any company's shoulder prosthesis box set. It is a pair of arms forming a clamp, fixing on both anterior and posterior aspect of the glenoid vault with grips adjusting to the complex geometry of the outer vault.
As Compared With PSI, the GPG has the Following Advantages
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Laboratory results are equivalent if not improved
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Positioning of the clamp is peri-operatively much easier with better usability
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Instrument can be re-sterilised and placed in any company simple box set
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Positioning of the glenoid prosthesis is performed during the procedure; no compulsory need for pre-operative planning, i.e. no extra time for the surgeon
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Avoids downside of PSI: time consuming & steep learning curve, complicated setup, difficult usability, requires qualified support
What is the Benefit for Anatomical Shoulder Arthroplasty, Reverse Shoulder Arthroplasty and Revision Reverse Shoulder Arthroplasty (Bio-RSA)
For Anatomical Total Shoulder Arthroplasty
The glenoid positioning guide assists the surgeon to recover the anatomical glenoid position with respect to it’s version, inclination, off-set and supero-inferior position. The fixation in the vault is optimal and it prevents break-through of the cortex. Therefore, the clinical results for shoulder motion and both short and long term fixation of implant are improved. This is the same for both for cemented and non cemented implants-- GPG favours bone ingrowth.
For Reverse Shoulder Arthroplasty
The fixation quality and bone ingrowth are optimal because the central peg is in the maximal bone axis. The GPG guides the surgeon with greater precision, thereby enabling them to use maximal length screws (superior and inferior).
For Reverse Shoulder Arthroplasty
In addition to the above mentioned advantages, the GPG allows surgeons to fix the metaglenoid in the maximum remaining bone axis. When drilling the k-wire in this maximal bone axis, the surgeon feels a resistance when the k-wire is in contact with the tip inner-cortex of the vault triangle. As a result, the surgeon is able to measure the remaining bone axis dimension and subsequently choose the optimal length of the central peg(s); all while taking into consideration the dimension of a potential bone graft (Bio-RSA).
Why do we Believe the Glenoid Positioning Guide Works
Our data from both in vitro and in vivo experiments convincingly demonstrates that our Glenoid Positioning Guide:
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Provides accurate placement of the glenoid prosthesis-- the version and inclination of the glenoid vault and of the glenoid surface do correspond with an accuracy of 2°.
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In addition, the centre of the glenoid surface corresponds to the centre of the glenoid vault with an accuracy of within 0.3mm.
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Has a high reproducibility-- The maximal deviation between measurements was 1.8° in the antero-posterior direction and 3° in the supero-inferior direction
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Easy to place intra-operatively
Proof of Concept
As a proof of concept, the clamp has been tested on a series of 15 cadaver scapulas with a large range of varying glenoid surface orientation.
After placing the K-wire according to the clamp, the scapulas were CT-scanned. We observed that in each case, the K-wire was accurately centred within the glenoid vault, in the direction of the maximal bone stock.
