Table III.
Rates of instability according to diagnosis and prosthesis design
| Studies included | Shoulders | Instability present | Rate, % | P value | |
|---|---|---|---|---|---|
| Diagnosis | |||||
| Cuff tear arthropathy | 15 | 905 | 21 | 2.3 | .02 vs. PHF; <.001 vs. failed arthroplasty |
| PHF | 36 | 1654 | 67 | 4.1 | .03 vs. failed arthroplasty |
| Failed arthroplasty | 29 | 1243 | 72 | 5.8 | .62∗ vs. instability arthropathy |
| Instability arthropathy | 4 | 80 | 3 | 3.8 | >.99∗ vs. PHF; .44∗ vs. CTA |
| Prothesis design | |||||
| LG/MH | 22 | 1021 | 20 | 2.0 | .02 vs. MG/LH |
| MG/LH | 16 | 1888 | 17 | 0.9 | .02 vs. LG/MH |
| LG/LH | 1 | 45 | 2 | 4.4 | — |
| Subtotal | 39 | 2954 | 39 | 1.3 | <.001 vs. MG/MH |
| MG/MH | 73 | 2932 | 116 | 4.0 | — |
| Author | P value vs. Zumstein et al | ||||
| Zumstein et al | 21 | 782 | 37 | 4.7 | — |
| Current study | 137 | 9303 | 308 | 3.3 | .04 |
| Current study: subtotal of non-Grammont designs | 39 | 2954 | 39 | 1.3 | <.001 |
PHF, proximal humerus fracture; LG, lateralized glenoid; MH, medialized humerus; MG, medialized glenoid; LH, lateralized humerus; CTA, cuff tear arthropathy; JSES, Journal of Shoulder and Elbow Surgery.
The Grammont design (MG/MH) had a significantly higher instability rate vs. all other designs combined (4.0%, 1.3%; P < .001), instability rates, especially modern non-Grammont designs, have significantly decreased compared to Zumstein et al (JSES, 2011).
Bold indicates statistical significance (P < .05).
∗
Fisher exact test.