Glenoid baseplate screw fixation in reverse shoulder arthroplasty: does locking screw position and orientation matter?

Sejla Abdic¹, Jason Lockhart², Naser Alnusif³, James A Johnson⁴, George S Athwal⁵

Affiliations

¹ The Roth|McFarlane Hand and Upper Limb Centre, St. Joseph's Hospital, London, ON, Canada; Department of Surgery, Western University, London, ON, Canada.
² The Roth|McFarlane Hand and Upper Limb Centre, St. Joseph's Hospital, London, ON, Canada; Mechanical and Materials Engineering, Western University, London, ON, Canada.
³ The Roth|McFarlane Hand and Upper Limb Centre, St. Joseph's Hospital, London, ON, Canada; Division of Orthopaedic Surgery, London Health Sciences Center, London, ON, Canada.
⁴ The Roth|McFarlane Hand and Upper Limb Centre, St. Joseph's Hospital, London, ON, Canada; Department of Surgery, Western University, London, ON, Canada; Mechanical and Materials Engineering, Western University, London, ON, Canada.
⁵ The Roth|McFarlane Hand and Upper Limb Centre, St. Joseph's Hospital, London, ON, Canada; Department of Surgery, Western University, London, ON, Canada; Division of Orthopaedic Surgery, London Health Sciences Center, London, ON, Canada. Electronic address: gathwal@uwo.ca.

PMID: 32858196
DOI: 10.1016/j.jse.2020.08.009

Glenoid baseplate screw fixation in reverse shoulder arthroplasty: does locking screw position and orientation matter?

Sejla Abdic et al. J Shoulder Elbow Surg. 2021 May.

. 2021 May;30(5):1207-1213.

doi: 10.1016/j.jse.2020.08.009. Epub 2020 Aug 25.

Authors

Sejla Abdic¹, Jason Lockhart², Naser Alnusif³, James A Johnson⁴, George S Athwal⁵

Affiliations

¹ The Roth|McFarlane Hand and Upper Limb Centre, St. Joseph's Hospital, London, ON, Canada; Department of Surgery, Western University, London, ON, Canada.
² The Roth|McFarlane Hand and Upper Limb Centre, St. Joseph's Hospital, London, ON, Canada; Mechanical and Materials Engineering, Western University, London, ON, Canada.
³ The Roth|McFarlane Hand and Upper Limb Centre, St. Joseph's Hospital, London, ON, Canada; Division of Orthopaedic Surgery, London Health Sciences Center, London, ON, Canada.
⁴ The Roth|McFarlane Hand and Upper Limb Centre, St. Joseph's Hospital, London, ON, Canada; Department of Surgery, Western University, London, ON, Canada; Mechanical and Materials Engineering, Western University, London, ON, Canada.
⁵ The Roth|McFarlane Hand and Upper Limb Centre, St. Joseph's Hospital, London, ON, Canada; Department of Surgery, Western University, London, ON, Canada; Division of Orthopaedic Surgery, London Health Sciences Center, London, ON, Canada. Electronic address: gathwal@uwo.ca.

PMID: 32858196
DOI: 10.1016/j.jse.2020.08.009

Abstract

Background: The longevity of a reverse total shoulder arthroplasty prosthesis can be compromised by glenoid baseplate loosening. Circular baseplate designs can be secured with superoinferior (SI) locking screws and anteroposterior (AP) compression screws or vice versa (AP-locking and SI-compression screws). This biomechanical cadaveric study investigated screw position (locking screws SI vs. AP and compression screws AP and SI) and screw orientation (parallel vs. divergent) to determine quantitative differences in baseplate micromotion.

Methods: Ten paired fresh-frozen cadaveric scapulae (n = 20) were implanted with a standard circular baseplate (∅ = 29 mm). The specimens were randomized into SI-locking or AP-locking screw configurations with the screw orientation directed either parallel or angled divergently at 15°. This yielded a total of 4 groups for statistical comparison: SI-locking_parallel, SI-locking_divergent, AP-locking_parallel, and AP-locking_divergent, which were subjected to axial eccentric loading on the implanted baseplates, similar to the American Standard of Testing of Materials standard for shoulder joint arthroplasty.

Results: In both static and cyclic testing, there were no statistically significant differences (P = .6) in micromotion between SI-locking (2.9 ± 0.8 μm) and AP-locking (3.5 ± 1.5 μm) configurations. In addition, there were no statistically significant differences (P = .2) in the divergent screw orientation group (2.0 ± 0.7 μm) vs. the parallel group (4.0 ± 1.5 μm).

Conclusion: All configurations of screw position and screw orientation tested in a circular reverse baseplate have similar time-zero fixation in an intact glenoid bone model. In addition, the resultant micromotions for all configurations tested fell far below the 150 μm threshold for bone ongrowth.

Keywords: Reverse shoulder arthroplasty; baseplate fixation; compression screw; cuff tear arthropathy; locking screw; micromotion; screw orientation.

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Glenoid baseplate screw fixation in reverse shoulder arthroplasty: does locking screw position and orientation matter?

Affiliations

Glenoid baseplate screw fixation in reverse shoulder arthroplasty: does locking screw position and orientation matter?

Authors

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Abstract

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LinkOut - more resources

Full Text Sources