Varus-valgus alignment of humeral short stem in reverse total shoulder arthroplasty: does it really matter?

Autor: Cho SH; Department of Orthopedic Surgery, Seoul St. Mary's Hospital, The Catholic University of Korea, Seoul, Republic of Korea., Park CJ; Department of Orthopedic Surgery, Seoul St. Mary's Hospital, The Catholic University of Korea, Seoul, Republic of Korea., Kim SJ; Department of Orthopedic Surgery, Seoul St. Mary's Hospital, The Catholic University of Korea, Seoul, Republic of Korea., Lee KG; Department of Orthopedic Surgery, Seoul St. Mary's Hospital, The Catholic University of Korea, Seoul, Republic of Korea., Baek GR; Orthopaedic Biomechanics Laboratory, Congress Medical Foundation, Pasadena, CA, USA., Chung MS; Orthopaedic Biomechanics Laboratory, Congress Medical Foundation, Pasadena, CA, USA., Hui AT; Orthopaedic Biomechanics Laboratory, Congress Medical Foundation, Pasadena, CA, USA., McGarry MH; Orthopaedic Biomechanics Laboratory, Congress Medical Foundation, Pasadena, CA, USA., Lee TQ; Orthopaedic Biomechanics Laboratory, Congress Medical Foundation, Pasadena, CA, USA., Jung S; Central R&D Center, Corentec Co., Ltd., Seoul, Republic of Korea., Kim J; Central R&D Center, Corentec Co., Ltd., Seoul, Republic of Korea., Kim YS; Department of Orthopedic Surgery, Seoul St. Mary's Hospital, The Catholic University of Korea, Seoul, Republic of Korea. Electronic address: kysoos@catholic.ac.kr.
Jazyk: angličtina
Zdroj: Journal of shoulder and elbow surgery [J Shoulder Elbow Surg] 2024 Aug; Vol. 33 (8), pp. 1762-1770. Date of Electronic Publication: 2024 Jan 17.
DOI: 10.1016/j.jse.2023.11.024
Abstrakt: Background: The utilization of short humeral stems in reverse total shoulder arthroplasty has gained attention in recent times. However, concerns regarding the risk of misalignment during implant insertion are associated with their use.
Methods: Eight fresh-frozen cadaveric shoulders were prepared for dissection and biomechanical testing. A bespoke humeral implant was fabricated to facilitate assessment of neutral, varus, and valgus alignments using a single stem, and 10° was established as the maximum permissible angle for misalignments. Shift in humerus position and changes in deltoid length attributable to misalignments relative to the neutral position were evaluated using a Microscribe 3DLx system. The impingement-free range of motion, encompassing abduction, adduction, internal rotation, and external rotation (ER), was gauged using a digital goniometer. The capacity for abduction was evaluated at maximal abduction angles under successive loading on the middle deltoid. A specialized traction system coupled with a force transducer was employed to measure anterior dislocation forces.
Results: Relative to the neutral alignment, valgus alignment resulted in a more distal (10.5 ± 2.4 mm) and medial (8.3 ± 2.2 mm) translation of the humeral component, whereas the varus alignment resulted in the humerus shifting more superiorly (11.2 ± 1.3 mm) and laterally (9.9 ± 0.9 mm) at 0° abduction. The valgus alignment exhibited the highest abduction angle than neutral alignment (86.2°, P < .001). Conversely, the varus alignment demonstrated significantly higher adduction (18.4 ± 7.4°, P < .001), internal rotation (68.9 ± 15.0°, P = .014), and ER (45.2 ± 10.5°, P = .002) at 0° abduction compared to the neutral alignments. Anterior dislocation forces were considerably lower (23.8 N) in the varus group compared to the neutral group at 0°ER (P = .047). Additionally, abduction capability was markedly higher in varus alignment at low deltoid loads than the neutral alignment (5N, P = .009; 7.5 N, P = .007).
Conclusions: The varus position enhances rotational range of motion (ROM) but increases instability, while the valgus position does not significantly impact ROM or instability compared to the neutral position.
(Copyright © 2024. Published by Elsevier Inc.)
Databáze: MEDLINE
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