Stress shielding in radial head arthroplasty: a comparative analysis of partially vs. fully grit-blasted press-fit stems.

BACKGROUND

Stress shielding is a known cause of periprosthetic bone loss in joint arthroplasty, but its clinical implications in radial head arthroplasty (RHA) remain unclear. Design modifications, such as partially grit-blasted stems, aim to mitigate proximal radial bone resorption while maintaining stability. We hypothesized that partially grit-blasted stems will have less stress shielding than fully grit-blasted stems.

METHODS

A retrospective review of 28 patients who underwent press-fit RHA with either partially grit-blasted (n = 21) or fully grit-blasted (n = 7) short-stem implants between 2011 and 2016 was performed. Radiographic evaluation of osteolysis was conducted using the Chanlalit staging system across 5 zones. Two blinded observers measured stem radiolucency twice to assess inter- and intraobserver reliability. Clinical outcomes included Disabilities of the Arm, Shoulder, and Hand scores, elbow range of motion, heterotopic ossification, and reoperation rates.

RESULTS

At a minimum of 6 months of follow-up, radiographic osteolysis was observed in 90% of partially grit-blasted and 100% of fully grit-blasted implants (P = .397), with the majority classified as Stage I. Two cases of Stage III osteolysis with mechanical failure occurred in the partially grit-blasted group; no failures occurred in the fully grit-blasted group. Heterotopic ossification was noted in 52% of partially grit-blasted and 86% of fully grit-blasted cases. Disabilities of the Arm, Shoulder, and Hand scores improved from 69.8 to 35.3, and range of motion improved in all planes. Four patients required reoperation, only one due to stem loosening.

CONCLUSION

Radiographic evidence of stress shielding is common following press-fit RHA, regardless of stem surface design. Although early osteolysis was observed in both groups, mechanical failure occurred only in the partially grit-blasted cohort. These findings suggest that while radiographic bone loss is frequent, it rarely results in clinical failure.