Effect of rotator cuff dysfunction on the initial mechanical stability of cementless glenoid components

Daniel R. Sua´rez, Edward R. Valstar, Jacqueline C. van der Linden, Fred van Keulen, Piet M. Rozing

Received: 5 July 2008 / Accepted: 3 March 2009 / Published online: 21 March 2009
The Author(s) 2009. This article is published with open access at Springerlink.com

Abstract:
The functional outcome of shoulder replacement
is related to the condition of the rotator cuff. Rotator
cuff disease is a common problem in candidates for total
shoulder arthroplasty; this study relates the functional status
of the rotator cuff to the initial stability of a cementless
glenoid implant. A 3D finite element model of a complete
scapula was used to quantify the effect of a dysfunctional
rotator cuff in terms of bone-implant interface micromotions
when the implant is physiologically loaded shortly
after surgery. Four rotator cuff conditions (from fully intact
to progressively ruptured rotator cuff tendons) as well as
two bone qualities were simulated in a model. Micromotions
were significantly larger in the worst modeled
cuff dysfunction (i.e. the supraspinatus and infraspinatus
tendons were fully dysfunctional). Micromotions were also
significantly different between conditions with healthy
and poor bone quality. The implant’s initial stability was
hardly influenced by a dysfunctional supraspinatus alone.
However, when the infraspinatus was also affected, the
glenohumeral joint force was displaced to the component’s
rim resulting in larger micromotions and instability of the
implant.