Clinical Orthopaedics and Related Research®

, Volume 471, Issue 3, pp 940–946

Lateralized Reverse Shoulder Arthroplasty Maintains Rotational Function of the Remaining Rotator Cuff

  • Stefan Greiner
  • Christan Schmidt
  • Christian König
  • Carsten Perka
  • Sebastian Herrmann
Basic Research

DOI: 10.1007/s11999-012-2692-x

Cite this article as:
Greiner, S., Schmidt, C., König, C. et al. Clin Orthop Relat Res (2013) 471: 940. doi:10.1007/s11999-012-2692-x

Abstract

Background

Humeral rotation often remains compromised after nonlateralized reverse shoulder arthroplasty (RSA). Reduced rotational moment arms and muscle slackening have been identified as possible reasons for this impairment. Although several clinical studies suggest lateralized RSA may increase rotation, it is unclear whether this is attributable to preservation of rotational moment arms and muscle pretension of the remaining rotator cuff.

Questions/purposes

The lateralized RSA was analyzed to determine whether (1) the rotational moment arms and (2) the origin-to-insertion distances of the teres minor and subscapularis can be preserved, and (3) their flexion and abduction moment arms are decreased.

Methods

Lateralized RSA using an 8-mm resin block under the glenosphere was performed on seven cadaveric shoulder specimens. Preimplantation and postimplantation CT scans were obtained to create three-dimensional shoulder surface models. Using these models, function-specific moment arms and origin-to-insertion distances of three segments of the subscapularis and teres minor muscles were calculated.

Results

The rotational moment arms remained unchanged for the middle and caudal subscapularis and teres minor segments in all tested positions (subscapularis, −16.1 mm versus −15.8 mm; teres minor, 15.9 mm versus 15.3 mm). The origin-to-insertion distances increased or remained unchanged in any muscle segment apart from the distal subscapularis segment at 0° abduction (139 mm versus 145 mm). The subscapularis and teres minor had increased flexion moment arms in abduction angles smaller than 60° (subscapularis, 2.7 mm versus 8.3 mm; teres minor, −6.6 mm versus 0.8 mm). Abduction moment arms decreased for all segments (subscapularis, 4 mm versus −11 mm; teres minor, −3.6 mm versus −19 mm).

Conclusions

After lateralized RSA, the subscapularis and teres minor maintained their length and rotational moment arms, their flexion forces were increased, and abduction capability decreased.

Clinical Relevance

Our findings could explain clinically improved rotation in lateralized RSA in comparison to nonlateralized RSA.

Supplementary material

11999_2012_2692_MOESM1_ESM.docx (24 kb)
Supplementary material 1 (DOCX 25 kb)

Copyright information

© The Association of Bone and Joint Surgeons® 2012

Authors and Affiliations

  • Stefan Greiner
    • 1
  • Christan Schmidt
    • 1
  • Christian König
    • 2
  • Carsten Perka
    • 1
  • Sebastian Herrmann
    • 1
  1. 1.Center for Musculoskeletal SurgeryCharité-University Medicine BerlinBerlinGermany
  2. 2.Julius Wolff InstituteCharité University Medicine BerlinBerlinGermany