Biomechanical Analysis of All-Suture Suture Anchor Fixation Compared With Conventional Suture Anchors and Interference Screws for Biceps Tenodesis.

PURPOSE: To compare the biomechanical properties of all-suture suture anchors (ASSAs) with conventional interference screws (CISs) and conventional suture anchors (CSAs) for long head of the biceps tendon fixation during proximal biceps tenodesis (BT). METHODS: We randomized 21 fresh-frozen human cadaveric shoulders into 3 subpectoral BT treatment groups: ASSA, CSA, and CIS. Each construct was cyclically loaded from 5 to 70 N for 500 cycles (1 Hz). All specimens that survived cyclic loading were then pulled to failure (1 mm/s). Elongation, maximum load, energy, and failure mode were recorded. The humerus was stripped of tissue and then subjected to torsional displacement at a rate of 1°/s until fracture occurred. Maximum load, displacement, stiffness, and energy were recorded. RESULTS: During tendon testing, 3 specimens (43%) in the CIS group failed early during cyclic testing by the tendon tearing at the screw-tendon interface. All other specimens in the CIS group, as well as all specimens in the ASSA and CSA groups, survived cyclic testing and failed during pull-to-failure testing. Failure occurred at the tendon-anchor or -screw interface in all specimens (100%), with no anchor or screw pullout. The CIS group had significantly decreased elongation (8.9 ± 2.23 mm) at maximum load compared with the ASSA (19.2 ± 5.2 mm) and CSA (18.9 ± 2.23 mm) groups (P = .001). During torsional testing, the ASSA group was able to withstand significantly greater torsional displacement (9.22° ± 0.86°) before failure and had greater energy to failure (497.3 ± 45 Nmm-degrees) than the CIS group (6.13° ± 1.24° and 256.6 ± 70.3 Nmm-degrees, respectively; P = .005). CONCLUSIONS: This study shows that the biomechanical properties of ASSA, CSA, and CIS constructs are similar. The interference screw group had lower tendon elongation at maximum load but had several early failures compared with the suture anchor groups. The use of suture anchors results in maximum tendon and torsional bone loads similar to interference screws for the long head of the biceps tendon. Torsional testing of the CIS resulted in spiral fractures traversing the screw tunnel in 100% of the specimens, which was not found in the suture anchor groups. CLINICAL RELEVANCE: The ASSA is a viable fixation method for BT in comparison with the CSA and CIS.

Surgical Repair of Distal Triceps Tendon Injuries: Short-term to Midterm Clinical Outcomes and Risk Factors for Perioperative Complications.

BACKGROUND: Few large-scale series have described functional outcomes after distal triceps tendon repair. Predictors for operative success and a comparative analysis of surgical techniques are limited in the reported literature. PURPOSE: To evaluate short-term to midterm functional outcomes after distal triceps tendon repair in a broad patient population and to comparatively evaluate patient-reported outcomes in patients with and without pre-existing olecranon enthesopathy while also assessing for modifiable risk factors associated with adverse patient outcomes and/or revision surgery. STUDY DESIGN: Case series; Level of evidence, 4. METHODS: This study was a retrospective analysis of 69 consecutive patients who underwent surgical repair of distal triceps tendon injuries at a single institution. Demographic information, time from injury to surgery, mechanism of injury, extent of the tear, pre-existing enthesopathy, perioperative complications, and validated patient-reported outcome scores were included in the analysis. Patients with a minimum of 1-year follow-up were included. RESULTS: The most common mechanisms of injury were direct elbow trauma (44.9%), extension/lifting exercises (20.3%), overuse (17.4%), and hyperflexion or hyperextension (17.4%). Eighteen patients were identified with pre-existing symptomatic enthesopathy, and 51 tears were caused by an acute injury. A total of 36 complete and 33 partial tendon tears were identified. Bone tunnels were most commonly used (n = 30; 43.5%), while direct sutures (n = 23; 33.3%) and suture anchors (n = 13; 18.8%) were also used. Perioperative complications occurred in 21.7% of patients, but no patients experienced a rerupture at the time of final follow-up. No statistically significant relationship was found between patient age (P = .750), degree of the tear (P = .613), or surgical technique employed (P = .608) and the presence of perioperative complications. CONCLUSION: Despite the heightened risk of perioperative complications after primary repair of distal triceps tendon injuries, the current series found favorable functional outcomes and no cases of reruptures at short-term to midterm follow-up. Furthermore, age, surgical technique, extent of the tear, and mechanism of injury were not associated with adverse patient outcomes in this investigation. Pre-existing triceps enthesopathy was shown to be associated with increased complication rates.

Biomechanical Analysis of Medial-Row All-Suture Suture Anchor Fixation for Rotator Cuff Repair in a Pair-Matched Cadaveric Model.

PURPOSE: To compare the biomechanical properties of all-suture suture anchors (ASSAs) with conventional suture anchors (CSAs) for double-row rotator cuff repair (RCR). METHODS: Fourteen fresh-frozen human cadaveric shoulders were randomized into 2 RCR treatment groups: ASSA and CSA. All constructs received a double-row repair, with the lateral-row implants consisting of two 5.5-mm PEEK (polyether ether ketone) Footprint anchors. Each construct was loaded to a 10-N preload for 2 minutes, followed by cyclic loading from 10 to 160 N at a rate of 100 N/s for 100 cycles. Load-to-failure testing was performed immediately after cyclic loading testing at 1 mm/s from the zero position until failure. Cyclic creep, elongation amplitude, maximum load, stiffness, energy, and failure mode were recorded. RESULTS: No significant difference in cyclic creep (P = .117) or elongation amplitude (P = .428) was found between the ASSA and CSA groups during cyclic testing. Three specimens in each group (43% in each) failed by the suture tearing through the tendon. The remaining specimens in each group failed by the anchor pulling out of the humeral head. The mean maximum load was 617.73 ± 177.77 N and 545.13 ± 212.98 N for the ASSA and CSA groups, respectively (P = .339). Maximum elongation before failure was not different between groups (P = .122). Mean energy and stiffness were not statistically different between the ASSA and CSA groups (P = .629 and P = .973, respectively). CONCLUSIONS: In this cadaveric analysis with a simplified unidirectional experimental setup, failure mechanics and maximum load between the ASSA and CSA constructs were similar, with no difference in energy and stiffness. Although the ASSA group showed slightly larger elongation than the CSA group, these differences may not be clinically relevant. CLINICAL RELEVANCE: This study provides a biomechanical head-to-head comparison of ASSAs and CSAs, indicating that ASSAs may be clinically equivalent to CSAs for use in an RCR.

Sclerostin inhibition reverses skeletal fragility in an Lrp5-deficient mouse model of OPPG syndrome.

Osteoporosis pseudoglioma syndrome (OPPG) is a rare genetic disease that produces debilitating effects in the skeleton. OPPG is caused by mutations in LRP5, a WNT co-receptor that mediates osteoblast activity. WNT signaling through LRP5, and also through the closely related receptor LRP6, is inhibited by the protein sclerostin (SOST). It is unclear whether OPPG patients might benefit from the anabolic action of sclerostin neutralization therapy (an approach currently being pursued in clinical trials for postmenopausal osteoporosis) in light of their LRP5 deficiency and consequent osteoblast impairment. To assess whether loss of sclerostin is anabolic in OPPG, we measured bone properties in a mouse model of OPPG (Lrp5(-/-)), a mouse model of sclerosteosis (Sost(-/-)), and in mice with both genes knocked out (Lrp5(-/-);Sost(-/-)). Lrp5(-/-);Sost(-/-) mice have larger, denser, and stronger bones than do Lrp5(-/-) mice, indicating that SOST deficiency can improve bone properties via pathways that do not require LRP5. Next, we determined whether the anabolic effects of sclerostin depletion in Lrp5(-/-) mice are retained in adult mice by treating 17-week-old Lrp5(-/-) mice with a sclerostin antibody for 3 weeks. Lrp5(+/+) and Lrp5(-/-) mice each exhibited osteoanabolic responses to antibody therapy, as indicated by increased bone mineral density, content, and formation rates. Collectively, our data show that inhibiting sclerostin can improve bone mass whether LRP5 is present or not. In the absence of LRP5, the anabolic effects of SOST depletion can occur via other receptors (such as LRP4/6). Regardless of the mechanism, our results suggest that humans with OPPG might benefit from sclerostin neutralization therapies.