PRIMA Stem Surgical technique
It is possible to reposition the metaphyseal sizer ring on the resected humeral surface after removing the Ø 6mm intramedullary rod (Figures 16-17). In this case, PRIMA Stem won’t be any more aligned with the intramedullary canal of the humerus. Warning: Modifying the position alters the alignment of the stem within the humeral canal, and in extreme cases diaphyseal impingement may occur. Secure the metaphyseal sizer ring to the humeral resection plane in the desired position on the resection plane by sliding the spike bushing over it until the second click is heard (Figure 18). Once the metaphyseal sizer ring is secured to the humerus, remove the Ø 6 mm intramedullary rod and insert the checking rod all the way down in the metaphyseal sizer ring. Make sure there is no cortical contact in this phase. If the checking rod is not flush on the metaphyseal sizer ring, impingement is occurring (Figure 19). Optional: mark the AP and ML reference lines along the sizer’s ring slots which can help verify the humeral trial and final implant version. Remove the checking rod and insert the metaphyseal K-Wire through the central hole in the metaphyseal sizer ring until engaged in the lateral cortex (Figure 20). Note. During this phase, to prevent soft tissue damage especially the axillary nerve, use of a Homann or other retractor as protection during drilling phase is recommended.
Figure 16
Figure 18
Figure 17
x Impingement
ü Ok
Finally remove the sizer ring and the spike bushing.
Figure 19
Figure 20
18
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