Minimum Distance of Suture Anchors Used for Rotator Cuff Repair Without Decreasing the Pullout Strength: A Biomechanical Study

Risk Factors and Corresponding Management for Suture Anchor Pullout during Arthroscopic Rotator Cuff Repair

INTRODUCTION

Due to the aging of the population, the incidence of rotator cuff tears is growing. For rotator cuff repair, arthroscopic suture-anchor repair has gradually replaced open transosseous repair, so suture anchors are now considered increasingly important in rotator cuff tear reconstruction. There are some but limited studies of suture anchor pullout after arthroscopic rotator cuff repair. However, there is no body of knowledge in this area, which makes it difficult for clinicians to predict the risk of anchor pullout comprehensively and manage it accordingly.

METHODS

The literature search included rotator cuff repair as well as anchor pullout strength. A review of the literature was performed including all articles published in PubMed until September 2021. Articles of all in vitro biomechanical and clinical trial levels in English were included. After assessing all abstracts (n = 275), the full text and the bibliographies of the relevant articles were analyzed for the questions posed (n = 80). Articles including outcomes without the area of interest were excluded (n = 22). The final literature research revealed 58 relevant articles. Narrative synthesis was undertaken to bring together the findings from studies included in this review.

RESULT

Based on the presented studies, the overall incidence of anchor pullout is not low, and the incidence of intraoperative anchor pullout is slightly higher than in the early postoperative period. The risk factors for anchor pullout are mainly related to bone quality, insertion depth, insertion angle, size of rotator cuff tear, preoperative corticosteroid injections, anchor design, the materials used to produce anchors, etc. In response to the above issues, we have introduced and evaluated management techniques. They include changing the implant site of anchors, cement augmentation for suture anchors, increasing the number of suture limbs, using all-suture anchors, using an arthroscopic transosseous knotless anchor, the Buddy anchor technique, Steinmann pin anchoring, and transosseous suture repair technology.

DISCUSSION

However, not many of the management techniques have been widely used in clinical practice. Most of them come from in vitro biomechanical studies, so in vivo randomized controlled trials with larger sample sizes are needed to see if they can help patients in the long run.

Pull-out Strength of Suture Anchor and Torque of Buddy Anchor for an Osteoporotic Humeral Head in Rotator Cuff Repair: Parallel Versus Divergent Insertion

BACKGROUND

The buddy anchor technique is useful to reinforce loose anchors in the osteoporotic humeral head during arthroscopic rotator cuff repair. However, theoretical parallel insertion of the buddy anchor to index a loose anchor is challenging in arthroscopy and can widen the entry site and decrease structural integrity.

PURPOSE

To investigate and compare the biomechanical stability between 2 buddy anchor insertion techniques (parallel insertion vs divergent insertion) in the osteoporotic humeral head.

STUDY DESIGN

Controlled laboratory study.

METHODS

A total of 24 paired fresh-frozen cadaveric shoulders were used, and each pair was randomly assigned to either the parallel insertion group or the divergent insertion group. In the parallel insertion group, the buddy anchor was inserted parallel to the index loose anchor. In the divergent insertion group, the buddy anchor was inserted at a 20° angle in the medial direction to the index loose anchor. The insertion torque of the buddy anchor and ultimate pull-out strength of the index anchor were measured and compared between the 2 groups.

RESULTS

The mean maximum insertion torque was significantly higher in the parallel insertion group (16.1 ± 1.8 cN·m) compared with the divergent insertion group (12.0 ± 1.5 cN·m) (P < .001). The mean ultimate pull-out strength was significantly higher with divergent insertion (192.2 ± 28.6 N) than with parallel insertion (147.7 ± 23.6 N) (P < .001).

CONCLUSION

For application of the buddy anchor system in the cadaveric osteoporotic humeral bone model, divergent insertion showed better ultimate pull-out strength than conventional parallel insertion, despite inferior maximum insertion torque.

CLINICAL RELEVANCE

The results of this study widen the applicability and accessibility for the buddy anchor system.

3D-Printed Double-Helical Biodegradable Iron Suture Anchor: A Rabbit Rotator Cuff Tear Model

Suture anchors are extensively used in rotator cuff tear surgery. With the advancement of three-dimensional printing technology, biodegradable metal has been developed for orthopedic applications. This study adopted three-dimensional-printed biodegradable Fe suture anchors with double-helical threads and commercialized non-vented screw-type Ti suture anchors with a tapered tip in the experimental and control groups, respectively. The in vitro study showed that the Fe and Ti suture anchors exhibited a similar ultimate failure load in 20-pound-per-cubic-foot polyurethane foam blocks and rabbit bone. In static immersion tests, the corrosion rate of Fe suture anchors was 0.049 ± 0.002 mm/year. The in vivo study was performed on New Zealand white rabbits and SAs were employed to reattach the ruptured supraspinatus tendon. The in vivo ultimate failure load of the Fe suture anchors was superior to that of the Ti suture anchors at 6 weeks. Micro-computed tomography showed that the bone volume fraction and bone surface density in the Fe suture anchors group 2 and 6 weeks after surgery were superior, and the histology confirmed that the increased bone volume around the anchor was attributable to mineralized osteocytes. The three-dimensional-printed Fe suture anchors outperformed the currently used Ti suture anchors.

Cost of Arthroscopic Rotator Cuff Repairs Is Primarily Driven by Procedure-Level Factors: A Single-Institution Analysis of an Ambulatory Surgery Center

PURPOSE

To identify intraoperative drivers of cost associated with arthroscopic rotator cuff repairs (RCRs) through analysis of an institutional database.

METHODS

This was a single-institution retrospective review of arthroscopic RCRs performed at an ambulatory surgical center between November 2016 and July 2019. Patient-level factors analyzed included age, sex, insurance type (private, Medicare, Medicaid, self-pay, and other government), American Society of Anesthesiologists grade (I, II, III, and missing), and Charlson comorbidity index (0, 1, 2, and ≥3). Procedure-level factors included use of biologics (decellularized dermal allograft or bioinductive healing implant), anesthesia type (regional block, monitored anesthesia care, or general), number of anchors and sutures, additional procedures (biceps tenodesis, distal clavicle resection, subacromial decompression), and operative time. Multivariate linear regression analysis was used to identify factors significantly associated with higher or lower charges.

RESULTS

A total of 712 arthroscopic RCRs were included. The risk-adjusted operative charges were $19,728 (95% confidence interval $16,543 to $22,913). The above factors predicted nearly 65% of the variability in operative charges. The only patient-level factor significantly associated with lower charges was female sex (- $1,339; P = .002). Procedure-level factors significantly associated with higher charges were use of biologics (+ $17,791; P < .001), concurrent open biceps tenodesis (+ $4,027; P < .001), distal clavicle resection (+ $2,266; P = .039), use of regional block (+ $1,256; P = .004), number of anchors (+ $2,245/anchor; P < .001), and increasing operative time ($26/min). Other factors had no significant association.

CONCLUSIONS

Procedural factors are the most significant drivers of operative cost in arthroscopic RCRs, such as quantity and type of implants; additional procedures such as biceps tenodesis and distal clavicle resection; and perioperative conditions such as type of anesthesia and total operating room time. Overall, patient-level factors were not shown to correlate well with operative costs, other than lower charges with female sex.

LEVEL OF EVIDENCE

IV, economic study.

Novel and reproducible technique coping with intraoperative anchor pullout during arthroscopic rotator cuff repair

PURPOSE

To evaluate the incidence of intraoperative anchor pullout during arthroscopic rotator cuff repair, to compare the outcomes of different methods of managing anchor pullout, and to introduce a new technique for anchor pullout.

METHODS

1076 patients who underwent arthroscopic rotator cuff repair using a single-row repair technique were included. In 483 patients, rotator cuff repair was performed using a screw-in type anchor, and in 593 patients, soft anchors were used. When intraoperative anchor pullout occurred, it was managed by buddy screwing, anchor insertion in a different location, cement augmentation, or by bar anchoring using a threaded Steinmann pin. Plain radiography and sonography were used to check anchor locations and healing.

RESULTS

Fifty-two patients experienced anchor pullout intra- or postoperatively (48 and four patients, respectively). Anchor pullouts were more frequently observed for larger tears, women, older patients, and in patients with preoperative stiffness (limitations of both active and passive movements of the affected shoulder joint). For screw-in type anchors, pullout during surgery occurred in 16 patients (3.3%, 16/483), and all were managed using the buddy screwing technique. For soft anchor cases, pullout occurred in 32 patients (5.4%, 32/593) and was managed by anchor insertion in a different location (17 patients), cement augmentation (two patients), or bar anchoring using a threaded Steinmann pin (13 patients). Three patients managed by buddy screwing and two patients managed by anchor insertion in a different location had anchor failure after repair. Tendon healing at 6 months was observed in 12/16 patients treated by buddy screwing, 11/17 treated by anchor insertion in a different location, 2/2 treated by cement augmentation, and 12/13 treated by bar anchoring with a threaded Steinmann pin.

CONCLUSION

Intraoperative anchor pullout during arthroscopic rotator cuff repair is an uncommon but cumbersome complication. There are some techniques already introduced to deal with this complication. In comparison, not one technique is overwhelmingly superior to others; however, our new technique which is bar anchoring with a threaded Steinmann pin could be another solution, since it could utilize primary anchor sites and results appear to be acceptable. Level of evidence III.

Mobility Assessment of the Supraspinatus in a Porcine Cadaver Model Using a Sensor-Enhanced, Arthroscopic Grasper

Tendon mobility is highly relevant in rotator cuff surgery. Objective data about rotator cuff mobility is rare. Tendon mobility still needs to be evaluated subjectively by the surgeon. This study aims to establish a porcine animal model for mobility analysis of the supraspinatus. In this context, we introduce a sensor-enhanced, arthroscopic grasper (SEAG) suitable for objective intraoperative measurements of tendon mobility in clinical praxis. Tendon mobility of 15 fresh porcine cadaver shoulders with artificial rotator cuff tears was evaluated using the SEAG. Mobility characteristics (load–displacement curves, maximum load, stiffness) were studied and inter- and intraobserver agreement (intraclass correlation coefficient (ICC)) were tested. Factors with a potential adverse effect (plastic deformation and rigor mortis) were also evaluated. All shoulders showed characteristic reproducible load–displacement curves with a nonlinear part at the start, followed by a linear part. Mean maximum load was 28.6 N ± 12.5. Mean stiffness was 6.0 N/mm ± 2.6. We found substantial interobserver agreement (ICC 0.672) and nearly perfect intraobserver agreement (0.944) for maximum load measurement. Inter- (0.021) and intraobserver (0.774) agreement for stiffness was lower. Plastic deformation and rigor mortis were excluded. The animal model demonstrates reliable and in vivo-like measurements of tendon mobility. The SEAG is a reliable tool for tendon mobility assessment.

Enhancing percutaneous pedicle screw fixation with hydroxyapatite granules: A biomechanical study using an osteoporotic bone model

Introduction

Percutaneous pedicle screw (PPS) can provide internal fixation of the thoracolumbar spine through a minimally invasive surgical procedure. PPS fixation has been widely used to treat various spinal diseases. Rigid fixation of PPS is essential for managing osteoporotic spine in order to prevent the risks of screw loosening and implant failure. We recently developed a novel augmentation method using hydroxyapatite (HA) granules for PPS fixation. The aim of this study was to evaluate the strength and stiffness of PPS fixation augmented with HA granules using an osteoporotic bone model.

Methods

Screws were inserted into uniform synthetic bone (sawbones) with and without augmentation. The uniaxial pullout strength and insertion torque of the screws were evaluated. In addition, each screw underwent cyclic toggling under incrementally increasing physiological loads until 2 mm of screwhead displacement occurred. The maximal pullout strength (N), maximal insertion torque (N·cm), number of toggle cycles and maximal load (N) required to achieve 2-mm screwhead displacement were compared between the screws with and without augmentation.

Results

The maximal pullout strength was significantly stronger for screws with augmentation than for those without augmentation (302 ± 19 N vs. 254 ± 17 N, p < 0.05). In addition, the maximal insertion torque was significantly increased in screws with augmentation compared to those without augmentation (48 ± 4 N·cm vs. 26 ± 5 N·cm, p < 0.05). Furthermore, the number of toggle cycles and the maximal load required to reach 2 mm of displacement were significantly greater in screws with augmentation than in those without augmentation (106 ± 9 vs. 52 ± 10 cycles; 152 ± 4 N vs. 124 ± 5 N, p < 0.05).

Conclusions

Augmentation using HA granules significantly enhanced the rigidity of PPS fixation in the osteoporotic bone model. The present study suggested that novel augmentation with HA granules may be a useful technique for PPS fixation in patients with osteoporotic spine.

When deadman theory meets footprint decortication: a suture anchor biomechanical study

Background

The optimal insertion angle for suture anchor insertion has long been of great interest. Although greater tuberosity decortication is commonly performed during rotator cuff repair, the effect of decortication on the suture anchor insertion angle remains unclear. The purpose of this study was to compare the pullout strength of threaded suture anchors inserted at 45° and 90° in decorticated and non-decorticated synthetic bone models.

Methods

Two kinds of synthetic bones were used to simulate the decorticated and non-decorticated conditions, for which 40 metallic suture anchors were used. Anchors were inserted at 45° and 90° in both decorticated and non-decorticated models and tested under cyclic loading followed by load-to-failure testing. The number of completed cycles, ultimate failure load, and failure modes was recorded.

Results

In the decorticated model, the ultimate failure load of anchors inserted at 45° (67.5 ± 5.3 N) was significantly lower than that of anchors inserted at 90° (114.1 ± 9.8 N) (p <  0.001). In the non-decorticated model, the ultimate failure load of anchors inserted at 45° (591.8 ± 58 N) was also significantly lower than that of anchors inserted at 90° (724.9 ± 94 N) (p = 0.003). Due to the diverse failure modes in the non-decorticated model, specimens with a failure mode of suture anchor pullout were analyzed in greater detail, with results showing a significantly larger pullout strength for anchors inserted at 90° (781.6 ± 53 N) than anchors inserted at 45° (648.0 ± 43 N) (p = 0.025).

Conclusion

Regardless of decortication, the pullout strength of anchors inserted at 90° was greater than those inserted at 45°. The clinical relevance is that inserting suture anchors at 90° is recommended due to the significantly larger ultimate failure load in both decorticated and non-decorticated bones.

Surgical Considerations in Managing Osteoporosis, Osteopenia, and Vitamin D Deficiency During Arthroscopic Rotator Cuff Repair

Osteopenia and osteoporosis are common in older adults and are associated with increased risk of fragility fractures. Vitamin D deficiency caused by chronic disease, poor nutrition, and inadequate sun exposure affects bone quality. Chronic rotator cuff tears can deteriorate the bone mineral density of the greater tuberosity and have been linked to reduced anchor pullout strength and high re-tear rate after repair especially in older patients with larger tear size. This article summarizes the current evidence on rotator cuff tear and bone quality and provides treatment strategies for rotator cuff repair in patients with poor bone quality.

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.