Optimal baseplate rotational alignment for locking-screw fixation in reverse total shoulder arthroplasty: A three-dimensional computer-aided design study

Byron F. Stephens, Casey T. Hebert, Frederick M. Azar, William Mihalko, Thomas W. Throckmorton

Research output: Contribution to journalArticle

6 Citations (Scopus)

Abstract

Background: Baseplate loosening in reverse total shoulder arthroplasty (RTSA) remains a concern. Placing peripheral screws into the 3 pillars of the densest scapular bone is believed to optimize baseplate fixation. Using a 3-dimensional computer-aided design (3D CAD) program, we investigated the optimal rotational baseplate alignment to maximize peripheral locking-screw purchase. Methods: Seventy-three arthritic scapulae were reconstructed from computed tomography images and imported into a 3D CAD software program along with representations of an RTSA baseplate that uses 4 fixed-angle peripheral locking screws. The baseplate position was standardized, and the baseplate was rotated to maximize individual and combined peripheral locking-screw purchase in each of the 3 scapular pillars. Results: The mean ± standard error of the mean positions for optimal individual peripheral locking-screw placement (referenced in internal rotation) were 6° ± 2° for the coracoid pillar, 198° ± 2° for the inferior pillar, and 295° ± 3° for the scapular spine pillar. Of note, 78% (57 of 73) of the screws attempting to obtain purchase in the scapular spine pillar could not be placed without an in-out-in configuration. In contrast, 100% of coracoid and 99% of inferior pillar screws achieved full purchase. The position of combined maximal fixation was 11° ± 1°. Conclusions: These results suggest that approximately 11° of internal rotation is the ideal baseplate position for maximal peripheral locking-screw fixation in RTSA. In addition, these results highlight the difficulty in obtaining optimal purchase in the scapular spine.

Original languageEnglish (US)
Pages (from-to)1367-1371
Number of pages5
JournalJournal of Shoulder and Elbow Surgery
Volume24
Issue number9
DOIs
StatePublished - Sep 1 2015

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Computer-Aided Design
Arthroplasty
Spine
Scapula
Arthritis
Software
Tomography
Bone and Bones

All Science Journal Classification (ASJC) codes

  • Surgery
  • Orthopedics and Sports Medicine

Cite this

Optimal baseplate rotational alignment for locking-screw fixation in reverse total shoulder arthroplasty : A three-dimensional computer-aided design study. / Stephens, Byron F.; Hebert, Casey T.; Azar, Frederick M.; Mihalko, William; Throckmorton, Thomas W.

In: Journal of Shoulder and Elbow Surgery, Vol. 24, No. 9, 01.09.2015, p. 1367-1371.

Research output: Contribution to journalArticle

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abstract = "Background: Baseplate loosening in reverse total shoulder arthroplasty (RTSA) remains a concern. Placing peripheral screws into the 3 pillars of the densest scapular bone is believed to optimize baseplate fixation. Using a 3-dimensional computer-aided design (3D CAD) program, we investigated the optimal rotational baseplate alignment to maximize peripheral locking-screw purchase. Methods: Seventy-three arthritic scapulae were reconstructed from computed tomography images and imported into a 3D CAD software program along with representations of an RTSA baseplate that uses 4 fixed-angle peripheral locking screws. The baseplate position was standardized, and the baseplate was rotated to maximize individual and combined peripheral locking-screw purchase in each of the 3 scapular pillars. Results: The mean ± standard error of the mean positions for optimal individual peripheral locking-screw placement (referenced in internal rotation) were 6° ± 2° for the coracoid pillar, 198° ± 2° for the inferior pillar, and 295° ± 3° for the scapular spine pillar. Of note, 78{\%} (57 of 73) of the screws attempting to obtain purchase in the scapular spine pillar could not be placed without an in-out-in configuration. In contrast, 100{\%} of coracoid and 99{\%} of inferior pillar screws achieved full purchase. The position of combined maximal fixation was 11° ± 1°. Conclusions: These results suggest that approximately 11° of internal rotation is the ideal baseplate position for maximal peripheral locking-screw fixation in RTSA. In addition, these results highlight the difficulty in obtaining optimal purchase in the scapular spine.",
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