Cow-hitch-suture cerclage for fixation of the greater tuberosity in fracture RTSA

Florian Grubhofer; Elias Bachmann; Christian Gerber; Karl Wieser; Lukas Ernstbrunner; Jon Jp Warner; Samy Bouaicha

doi:10.1016/j.jseint.2020.10.016

Cow-hitch-suture cerclage for fixation of the greater tuberosity in fracture RTSA

JSES Int. 2020 Dec 14;5(2):270-276. doi: 10.1016/j.jseint.2020.10.016. eCollection 2021 Mar.

Authors

Florian Grubhofer¹, Elias Bachmann¹, Christian Gerber¹, Karl Wieser¹, Lukas Ernstbrunner¹, Jon Jp Warner², Samy Bouaicha¹

Affiliations

¹ Balgrist University Hospital, Department of Orthopedics, University of Zürich, Zürich, Switzerland.
² Massachusetts General Hospital, Department of Orthopedics, Harvard Medical School, Boston, MA, USA.

Abstract

Background: The treatment of complex proximal humerus fractures in the elderly with reverse total shoulder arthroplasty is an established treatment option. Healing of the greater tuberosity (GT) is associated with better outcomes. It was the aim of this cadaver study to compare the stability of GT refixation obtained with the so-called "cow hitch" cerclage fixation with that of the recommended standard suture cerclage technique.

Methods: A 4-part proximal humerus fracture was created in 10 fresh-frozen, human cadaveric shoulders. A CT was performed preoperatively to ensure the comparability of bone density and fracture patterns. In the experimental group the GT was reattached to the stem of the reverse total shoulder arthroplasty with the "cow hitch" suture cerclage (CH) technique, the conventional (CON) technique recommended for the tested implant was used in the control group. Humeri were tested with a uniaxial material testing machine. In total, 5000 loading cycles with forces from 250 to 350N were applied while motion (in mm) of the tuberosities was recorded with a telecentric camera.

Results: After 5000 loading cycles, the CH group showed a significantly smaller displacement of the bone fragment (0.74 ± 0.31 mm) than the CON group [2.29 ± 1.08 mm (P < .05)]. After the first three cycles the mean displacement was 0.14 mm (±0.12) in the CH and 1.42 mm (±0.21) in the CON (P < .0001) groups.

Conclusions: GT reattachment with the "cow hitch" suture cerclage showed a significantly more stable fixation compared with the currently for the used prosthetic system recommended suture cerclage technique in an in vitro 4-part proximal humeral fracture model.

Keywords: Cadaver study; Proximal humerus fracture; cow hitch cerclage; greater tuberosity fixation technique; in vitro stability testing of the greater tuberosity; reverse total shoulder arthroplasty.