Purpose: When aiming to enhance the strength of a suture anchor construct, typically in osteoporotic bone, it is often suggested to employ a method referred to as "under-tapping" (UT). A comprehensive assessment of tapping protocols for anchor placement was conducted to ascertain if this contributes to the prevention of anchor failure. Further, supplementary fixation techniques were examined to offer methods for secure fixation in the event of unanticipated failure.
Hypothesis: Under-tapping can increase load to failure compared to standard tapping (ST). If the initial fixation fails, using larger diameter anchors or bioabsorbable Trim-IT pins (TIP) via cross-pinning can provide stable fixation.
Methods: Two paired proximal humeri cadaver models underwent Computed Tomography (CT) scanning protocol to identify osteoporotic sites using Hounsfield Units (HU) for suture anchor placement. We employed the standard tapped (ST) and UT fixation methods to establish baseline data on anchor failure. Subsequently, additional strategies for managing suture anchor failure were explored. This included upsizing and a novel cross pinning technique utilizing TIP.
Results: No significant increase in load to failure (LTF) was observed between the standard and under tapped techniques in both the 4.75 mm BioComposite (BC) and 5.5 mm BC groups, with p-values of .498 and .763, respectively. Significant differences were found between the 5.5mm BC anchors with 1.5 Trim-It Pin (TIP) and 5.5 mm BC following 4.75mm UT LTF, 148.75 N vs 93.12 N (p=.004). No significant difference was observed in anchor LTF between 5.5 mm BC placement after either 4.75 mm BC(UT) or 4.75 BC(ST) failure. Nor was there a significant difference in LTF following 5.5mm ST or UT failures managed with 6.25mm anchors. Though, there was a significant difference in LTF between 6.25mm BC with 2.0 TIP vs 6.25 mm BC for failed 5.5mm BC(ST) and 5.5mm (BC)UT, 154.99N, 98.57N and 67.12N respectfully, both with a p <.001. However, the LTF for the 5.5mm BC 1.5 TIP vs. 6.25mm BC 2.0 TIP did not show any significant statistical findings.
Conclusion: Modern suture anchors provide surgeons with the resources to successfully treat rotator cuff injuries. As patients age, surgeons face the challenge of effectively managing osteoporosis, a condition that elevates the probability of suture anchor failure. Preoperative planning with standard tapping protocol and selection of large diameter anchors allows for increased LTF without the need to UT. Additionally, the implementation of a cross-pinning technique utilizing Bioabsorbable TIP produces a more robust anchor and improved LTF in osteoporotic bone after initial failure with smaller diameter anchors compared to upsized anchors alone.
