Elsevier

JSES International

Volume 5, Issue 6, November 2021, Pages 1027-1033
JSES International

Shoulder
Shoulder arthroplasty
Cow-hitch fixation in fracture hemiarthroplasty

https://doi.org/10.1016/j.jseint.2021.07.011Get rights and content
Under a Creative Commons license
open access

Background

The treatment of complex proximal humerus fractures with hemiarthroplasty is associated with a high failure rate due to secondary displacement of the tuberosities. It was the aim of this in-vitro study to compare the mechanical stability of tuberosity reattachment obtained with the so-called “Cow-Hitch” (CH) cerclage compared with conventional tuberosity reattachment.

Methods

A 4-part proximal humerus fracture was created in 10 fresh-frozen, human cadaveric shoulders. The greater and lesser tuberosity were reattached to the hemiarthroplasty stem with in total 4 CH Cerclages in the Cow-Hitch group. The conventional technique—recommended for the tested implant—was used in the control group using 6 sutures. A total of 5000 loading cycles with forces of 350N were applied, while motion (in mm) of the tuberosities was recorded in 3 directions (anteroposterior = AP, mediolateral = ML, inferosuperior = IS) with a telecentric camera.

Results

After 5000 loading cycles, the CH group showed less fragment displacement (AP: 2.3 ± 2.3 mm, ML: 1.8 ± 0.9 mm, IS: 1.3 ± 0.5 mm) than the conventional group (AP: 9.8 ± 12.3 mm, ML: 5.5 ± 5.6 mm, IS: 4.5 ± 4.7 mm). The differences were not statistically significant (AP: P = .241; ML: P = .159; IS: P = .216). The lesser tuberosity fragment displacement in the CH group after 5000 cycles was less in the AP (2.3 ± 3.3 vs. 4.0 ± 2.8, P = .359) and IS (1.9 ± 1.2 vs. 3.1 ± 1.8; P = .189) directions but higher in the ML direction (7.2 ± 5.7 vs 6.3 ± 3.6, P = .963).

Conclusions

In-vitro, “Cow-Hitch” cerclage results in mean greater tuberosity displacements of 2 mm and reliably prevents displacements greater than 5 mm. In contrast, the conventional fixation technique yields unreliable, variable stability with low to complete displacement upon cyclical loading.

Level of evidence

Basic Science Study
Biomechanics

Keywords

Proximal humerus fracture
Hemiarthroplasty
Greater tuberosity reattachment
Lesser tuberosity reattachment
Cow Hitch Cerclage
Cadaver study

Cited by (0)

This study was approved by the Ethical Committee Zürich (Cantonal Ethical Committee number: ZH-Nr.2018-00588).