Patient-specific instrumentation for total shoulder arthroplasty

Abstract

Shoulder arthroplasty is a demanding procedure with a known complication rate. Most complications are associated with the glenoid component, a fact that has stimulated investigation into that specific component of the implant. Avoiding glenoid component malposition is very important and is a key reason for recent developments in pre-operative planning and instrumentation to minimise risk.Patient-specific instrumentation (PSI) was developed as an alternative to navigation systems, originally for total knee arthroplasty, and is a valid option for shoulder replacements today. It offers increased accuracy in the placement of the glenoid component, which improves the likelihood of an optimal outcome.A description of the method of pre-operative planning and surgical technique is presented, based on the author's experience and a review of the current literature. Cite this article: Gomes N. Patient-specific instrumentation for total shoulder arthroplasty. EFORT Open Rev 2016;1:177-182. DOI: 10.1302/2058-5241.1.000033.

Keywords: PSI; arthritis; arthroplasty; glenoid; patient-specific instrumentation; prosthesis; shoulder.

Fig. 1

Three anatomical points (red dots) used as landmarks for the definition of the scapular plane and the neutral inclination axis (red line): the inferior scapular angle point, the glenoid centre point and the trigonum spinae point.

Fig. 2

a) Radiograph and b) MRI of a shoulder with extensive glenoid destruction for a reverse prosthesis; c) coronal, and d) transverse view of the pre-operative planning. (From Zimmer-Biomet software; with permission).

Fig. 3

a) Sterilised bone model and glenoid guide, with b) one inferior-tilted pin hole for a reverse procedure and a second superior one for an anatomical procedure.

Fig. 4

a) Glenoid central pin placement for an anatomical prosthesis in a right shoulder; b) good exposure of the anterosuperior glenoid rim is required for the proper seating of the guide.

Fig. 5

a) Reverse prosthesis in a left shoulder and guided central pin drilling; b) native glenoid and patient-specific bone models are compared to check accurate placement of the guide on a very deformed scapula; c) central screw drilling completed over a guide pin that keeps its stability due to the integrity of the far cortex with no glenoid vault perforation, made possible with an accurate drilling direction.

Fig. 6

Good baseplate alignment on the same patient as shown in Figs 2 and 5, with severe glenoid deformation requiring bone grafting.

Fig. 7

Digitised image from pre-operative plan of an anatomical glenoid component, displaying peg penetration from the vault posteriorly. (From Zimmer-Biomet software; with permission).