Editorial Commentary: All-Suture Anchors, Foam Blocks, and Biomechanical Testing

Clinical and radiological outcome of all-suture anchors in shoulder and elbow surgery

Background

All-suture anchors (ASAs) are noted to cause various bone reactions when used in upper limb surgery but clinical implications are unknown.

Methods

88 shoulders and 151 elbows with a mean follow-up of 47.1 ± 17.7 months were invited for follow-up including clinical examination, questionnaires and radiographs. The anchor drill holes were radiographically assessed.

Results

At final follow up, mean DASH was 12.9 ± 13.8 and mean VAS 2.2 ± 2.4 in the shoulder population. In the elbow group mean MEPS was 91.8 ± 12.7 and mean VAS 1.5 ± 1.9. Implant-specific complications were seen in 10 elbow cases but none in the shoulder group. The mean diameter of the 1.4 mm all-suture anchor drill hole was enlarged to 2.5 ± 1.4 mm in the shoulder group and to 2.9 ± 1.0 mm in the elbow group. 50% of the 1.4 mm anchor drill holes showed abnormal morphology but these morphologic changes did not correlate with clinical outcome, complications or reoperation rate.

Discussion

Satisfying clinical outcomes are found in upper limb surgery using ASAs. Various bone changes are seen after implantation of an ASA, but these are not clinically relevant. Long-term consecutive follow-up data is required.

Conventional rotator cuff versus all-suture anchors-A biomechanical study focusing on the insertion angle in an unlimited cyclic model

PURPOSE

The purpose of this study was to compare the biomechanical properties of an all-suture anchor to a conventional anchor used commonly in rotator cuff repairs. Furthermore, the biomechanical influence of various implantation angles was evaluated in both anchor types in a human cadaveric model.

METHODS

30 humeri were allocated into three groups with a similar bone density. The two different anchor types were inserted at a predefined angle of 45°, 90° or 110°. Biomechanical testing included an initial preload of 20N followed by a cyclic protocol with a stepwise increasing force of 0,05N for each cycle at a rate of 1Hz until system failure. Number of cycles, maximum load to failure, stiffness, displacement and failure mode were determined.

RESULTS

27 anchors failed by pullout. There was no significant difference between the conventional and the all-suture anchor regarding mean pullout strength. No considerable discrepancy in stiffness or displacement could be perceived. Comparing the three implantation angles no significant difference could be observed for the all-suture or the conventional anchor.

CONCLUSION

All-suture anchors show similar biomechanical properties to conventional screw shaped anchors in an unlimited cyclic model. The exact insertion angle is not a significant predictor of failure.

Editorial Commentary: All-Suture Shoulder Glenoid Anchors: Can We Adequately Tension Them or Knot?

All-suture anchors require smaller drill holes (often under 2.0 mm) than comparable solid glenoid anchors (e.g., Gryphon: 2.5-mm drill). A smaller drill allows closer anchor approximation, but there is no indication that this improves repair biomechanics. In fact closely associated multiple fixation points are associated with glenoid fractures, and the same multiple fixation points can be achieved with double- or triple-loaded conventional anchors. All-suture anchors require deployment immediately adjacent to intact cortical bone. Without this, slack and pistoning of the suture ball anchor occur during cyclic loading and have been associated with bone cavitation, repair loosening, and gap formation. A mechanical tensioning mechanism more effectively removes the slack than hand tensioning by the surgeon. Drill length is another concern. All-suture anchor drills measure between 20 and 24 mm long. This length is commonly associated with far cortex penetration and places the suprascapular nerve and axillary nerve at increased risk of contact damage. Maximizing all-suture anchor performance is associated with mechanical deployment systems rather than hand traction applied by the surgeon. Finally, no current all-suture anchor is biodegradable, osteoconductive, or replaced by bone.

Editorial Commentary: Anchors Away! Reflections on Anchor Placement and Number in Rotator Cuff Repair

The ideal construct for a rotator cuff repair continues to be a hot topic for debate and biomechanical investigation. A recent study shows that anchors could be placed as close as 1 mm apart without impact on pullout strength. However, further overlap (the buddy anchor construct) led to earlier failure. This conclusion differs from other studies that have recommended the "buddy anchor" construct as a bail-out option in osteoporotic bone. Biomechanical studies are an important source of information for surgical decision making, but often do not directly predict the in vivo environment. The final determination of anchor number and placement in a rotator cuff repair should be based on 4 factors: minimizing cost, avoiding complications, using appropriate technique, and proper restoration of anatomy.