Biomechanical characteristics of the horizontal mattress stitch: implication for double-row and suture-bridge rotator cuff repair

Biomechanical Characterization of a New Locking Loop Stitch for Graft Fixation versus Krackow Stitch

Background

The purpose of this study was to quantify and compare the biomechanical characteristics of a new locking loop stitch (LLS), developed utilizing the concepts of both running locking stitch and needleless stitch, to the traditional Krackow stitch.

Methods

The Krackow stitch with No.2 braided suture and the LLS with 1.3-mm augmented polyblend suture tape were compared biomechanically. The LLS was performed with single strand locking loops and wrapping suture around the tendon, resulting in half the needle penetrations through the graft compared to the Krackow stitch. Twenty bovine extensor tendons were divided randomly into two groups. The tendons were prepared to match equal thickness and cross-sectional area. Each suture-tendon was stitched and preloaded to 5 N for 60 seconds, cyclically loaded to 20 N, 40 N, and 60 N for 10 cycles each, and then loaded to failure. The deformation of the suture-tendon construct, stiffness, yield load, and ultimate load were measured.

Results

The LLS had significantly less deformation of the suture-tendon construct at 100 N, 200 N, 300 N, and at ultimate load compared to the Krackow stitch (Krackow stitch and LLS at 100 N: 1.3 ± 0.1 mm and 1.0 ± 0.2 mm, p < 0.001; 200 N: 3.0 ± 0.3 mm and 1.9 ± 0.2 mm, p < 0.001; 300 N: 5.1 ± 0.6 mm and 2.9 ± 0.4 mm, p < 0.001; ultimate load: 12.8 ± 2.8 mm and 5.0 ± 1.2 mm, p < 0.001). The LLS had significantly greater stiffness (Krackow stitch and LLS: 97.5 ± 6.9 N/mm and 117.2 ± 13.9 N/mm, p < 0.001) and yield load (Krackow stitch and LLS: 66.2 ± 15.9 N and 237.9 ± 93.6 N, p < 0.001) compared to the Krackow stitch. There was no significant difference in ultimate load (Krackow stitch: 450.2 ± 49.4 N; LLS: 472.6 ± 59.8 N; p = 0.290).

Conclusions

The LLS had significantly smaller deformation of the suture-tendon construct compared to the Krackow stitch. The LLS may be a viable surgical alternative to the Krackow stitch for graft fixation when secure fixation is necessary.

Modified double-pulley suture-bridge techniques with or without medial knot tying show comparable clinical and radiological outcomes in arthroscopic rotator cuff repair

PURPOSE

The optimal technique for arthroscopic rotator cuff repair is still controversial. The aim of this study was to compare modified arthroscopic double-pulley suture-bridge (DPSB) technique with medial knot tying to those without tying, considering clinical and radiological outcomes.

METHODS

This study included 292 patients with large full-thickness rotator cuff tears treated with modified DPSB technique. The patients were divided into 158 cases with medial knot tying (knot-tying group) and 134 without tying (knotless group). At follow-up, clinical outcome was assessed by the Constant score, American Shoulder and Elbow Surgeons (ASES) score, and Shoulder Rating Scale of the University of California at Los Angeles (UCLA) score. The assessment of tendon healing was performed with magnetic resonance imaging (MRI) at a minimum of 12 months postoperatively.

RESULTS

The Constant score, ASES score and UCLA score in the knot-tying and knotless groups all improved significantly from before surgery to 12 months postoperatively (P < 0.05, respectively). No significant differences were observed between groups for each phase evaluated (n.s.). Tendon healing was categorised according to Sugaya's classification. The retearing rate was 27/158 (17.0%) in the knot-tying group and 20/134 (14.9%) in the knotless group, with no statistically significant difference between groups (n.s.). Additionally, the retear was classified using the Cho's classification. When comparing the retear rates of different types independently, no statistically significant differences were found between groups (n.s.).

CONCLUSIONS

The knotless modified DPSB technique showed comparable short-term functional outcomes to those of the knot tying method in large full-thickness rotator cuff tears. Additionally, no significant differences in repair integrity were observed between the two methods. Both techniques can be considered effective treatments for patients with large-sized full-thickness rotator cuff tears.

LEVEL OF EVIDENCE

III.

Supraspinatus tendon transosseous vs anchor repair surgery: a comparative study of mechanical recovery in the rabbit

BACKGROUND

Supraspinatus (SSP) tendon ruptures requiring surgical repair are common. Arthroscopic suture anchor fixation has gradually replaced transosseous repair in supraspinatus tendon tear. Our objective was to compare mechanical properties between transosseous and anchor supraspinatus repair in the first 6 postoperative weeks in a rabbit model.

METHODS

One hundred and fifty-two rabbits had one supraspinatus tendon repaired either with an anchor suture 1 week after detachment or with transosseous sutures. Rabbits were euthanized at 0, 1, 2, 4 or 6 postoperative weeks. Experimental and contralateral tendons (304 tendons) were mechanically tested to failure. Data are expressed as percent of contralateral.

RESULTS

Anchor repair had higher loads to failure compared to transosseous repair, at immediate repair (week 0, 52 ± 21% vs 25 ± 17%, respectively; p = 0.004) and at 1 postoperative week (64 ± 32% vs 28 ± 10%; p = 0.003) with no difference after 2 weeks. There was no difference in stiffness. Transosseous repairs showed higher rates of midsubstance failures compared to anchor repairs at 1 (p = 0.004) and 2 postoperative weeks (p < 0.001). Both transosseous and anchor repairs restored supraspinatus mechanical properties after 4 postoperative weeks.

CONCLUSION

Anchor repair provided better initial tensile strength while transosseous repair led to a faster normalization (namely, midsubstance) of the mode of failure. Research to optimize supraspinatus repair may need to consider the advantages from both surgical approaches.

Optimizing the Double-Row Construct: An Untied Medial Row Demonstrates Equivalent Mean Contact Pressures in a Rotator Cuff Model

Background:

The merits of a double-row rotator cuff repair (RCR) construct are well-established for restoration of the footprint and lateral-row security. The theoretical benefit of leaving the medial row untied is to prevent damage to the rotator cuff by tissue strangulation, and the benefit of suture tape is a more even distribution of force across the repair site. These benefits, to our knowledge, have not been evaluated in the laboratory.

Hypothesis:

Leaving the medial row untied and using a suture bridge technique with suture tape will offer more even pressure distribution across the repair site without compromising total contact force.

Study Design:

Controlled laboratory study.

Methods:

A laboratory model of RCR was created using biomechanical research-grade composite humeri and human dermal allografts. The pressure distribution in a double-row suture bridge repair construct was analyzed using the following testing matrix: double-loaded suture anchors with the medial row tied (n = 15) versus untied (n = 15) compared with double-loaded suture tape and anchors with the medial row tied (n = 15) versus untied (n = 15). A digital pressure sensor was used to measure pressure over time after tensioning of the repair site. A multivariate analysis of variance was used for statistical analysis with post hoc testing.

Results:

The total contact force did not significantly differ between constructs. The contact force between double-loaded suture anchors and double-loaded suture tape and anchors was similar when tied (P = .15) and untied (P = .44). An untied medial row resulted in similar contact forces in both the double-loaded suture anchor (P = .16) and double-loaded suture tape and anchor (P = .25) constructs. Qualitative increases in focal contact pressure were seen when the medial row was tied.

Conclusion:

An untied medial row did not significantly affect the total contact force with double-loaded suture anchors and with double-loaded suture tape and anchors. Tying the medial row qualitatively increased crimping at the construct’s periphery, which may contribute to tissue strangulation and hinder clinical healing. Qualitative improvements in force distribution were seen with double-loaded suture tape and anchors.

Clinical Relevance:

Both tied and untied medial rows demonstrated similar pressures across the repair construct.

The effect of loop size on loop security and elongation of a knot

INTRODUCTION

While repairing a teared rotator cuff tendon with suture anchors and horizontal mattress suture configurations, knots should be secure at time zero while approximating the tendon to the bone, otherwise any failure in loop security may cause undesired clinical results. Optimum distance between suture limbs passed through the tendon, in other words the bite size, is still not clear in the literature. The aim of this study was to test the effect of loop size, which is directly related to the bite size, on loop security and elongation of a knot.

HYPOTHESIS

We hypothesized that a knot with a smaller loop size would be more secure. We asked if a knot with shorter circumference (1) would offer a better knot security; (2) would produce less elongation following repeated traction cycles.

MATERIAL AND METHODS

Two parallel metal rods in 3.0mm diameter were fixed to load cells of dynamic testing machine. Four groups, from A to D, had the initial rod to rod distances of 2-4-6-8mm respectively (n=10). Surgeon's knots were prepared with 2/0 Ultrabraid® sutures around the rods. A tension meter was used for tying each half hitch under equal tension. Crosshead distances were recorded after 7N pre-load and subsequent 1000 repetitive cyclic loads between 7-30N.

RESULTS

Elongations after a 7N preload for groups A to D were 0.107mm (±0.006), 0.143mm (±0.018), 0,16mm (±0.025), 0.185mm (±0.018) respectively. This increase was significant (p<0.05, power>0.95) between each group except between groups B and C. Maximum elongations after 1000^th cycle for groups A to D were 0.32mm (±0.124), 1.12mm (±0.333), 1.162mm (±0.211), 1.292mm (±0.241) respectively. Only samples in group A (0.732mm±0.124) elongated significantly less than others (p<0.05, power >0.95). No knots unravelled or ruptured.

DISCUSSION

This study basically reports that a knot with a shorter loop circumference has superior properties regarding loop security and resistance to elongation. From the perspective of clinical importance, shorter distance between suture limbs of mattress configuration may provide a more secure fixation of the rotator cuff tendon to the bone.

LEVEL OF EVIDENCE

II.

Biomechanics of an interlinked suture anchor rotator cuff repair in a human cadaveric model

Background

The purpose of this study was to evaluate the initial fixation of a transosseous-equivalent rotator cuff repair and an interlinked medial repair, quantifying the cyclic and failure loading properties of each construct.

Methods

Twenty-four human cadaveric shoulders from 12 matched pairs were dissected, and full-thickness supraspinatus tears were created. In each pair, 1 side was repaired with a transosseous-equivalent repair (control) and the other, with an interlinked repair. All specimens were cycled to 1 MPa of effective stress at 1 Hz for 500 cycles, and gap formation was recorded with a digital video system. All samples were then loaded to failure, and the ultimate load and displacement and modes of failure were recorded.

Results

The interlinked repair showed a decrease in the amount of construct gapping after cycle 50 and in peak construct gapping compared with the control group (control, 3.4 ± 0.9 mm; interlinked, 2.5 ± 0.8 mm; P = .048). The interlinked repair also showed a higher ultimate load to failure (control, 318.7 ± 77.9 N; interlinked, 420.6 ± 93.7 N; P = .007). No other significant differences were detected between constructs for preparation or testing metrics.

Conclusions

The interlinked repair, in which 1 continuous suture linked the medial anchors, showed decreased construct gapping and increased ultimate load to failure compared with the control construct. This study establishes the biomechanical validity of the new interlinked repair construct compared with a previously validated construct.

Subacromial bone erosion due to suture-knots in arthroscopic rotator cuff repair: A report of two cases

Knot impingement can cause shoulder-joint motion pain after rotator-cuff repair. Previous studies have revealed only subacromial effusion in magnetic resonance imaging (MRI) evaluations of knot impingement. We report two cases of patients with symptomatic knot impingement. In both patients, bursal-side partial-thickness tear of the supraspinatus tendon had been repaired by a single-row technique using one suture anchor and two polyester sutures with a long-chain polyethylene core. Three-dimensional computed tomography and arthroscopy revealed bony erosion at the lateral side of the anterior half of the acromial undersurface in both patients. The size of the erosion was 1.7 cm (anteroposterior direction) × 0.7 cm (mediolateral direction) in one patient and 1.2 cm × 0.5 cm in the other. Arthroscopy showed that suture knots that had been placed at the muscle-tendon junction of the supraspinatus tendon were impinging on the area of bone erosion during shoulder abduction. Although the sutures themselves were of soft material, knot-tying made them stiff and thus led to bone erosion. Surgeons need to be aware of the possibility of subacromial bone erosion caused by suture knots in arthroscopic rotator cuff repair.

Biomechanical Comparison of 3 Novel Repair Techniques for Radial Tears of the Medial Meniscus: The 2-Tunnel Transtibial Technique, a "Hybrid" Horizontal and Vertical Mattress Suture Configuration, and a Combined "Hybrid Tunnel" Technique

BACKGROUND

Historically, radial meniscal tears were treated with partial or near-total meniscectomy, which usually resulted in poor outcomes. Radial meniscal tears function similar to a total meniscectomy and are challenging to treat. Repair of radial meniscal tears should be performed to prevent joint deterioration and the need for salvage procedures in the future.

PURPOSE/HYPOTHESIS

The purpose was to compare 3 repair techniques for radial tears of the medial meniscus: the 2-tunnel, hybrid, and hybrid tunnel techniques. It was hypothesized that there would be no differences among the 3 groups in regard to gapping and ultimate failure strength.

STUDY DESIGN

Controlled laboratory study.

METHODS

Thirty human male cadaver knees (10 matched pairs, n = 20; 10 unpaired, n = 10) were used to compare the 2-tunnel, hybrid, and hybrid tunnel repairs. A complete radial tear was made at the midbody of the medial meniscus. Repairs were performed according to the described techniques. Specimens were potted and mounted on a universal material testing machine where each specimen was cyclically loaded for 1000 cycles before experiencing a pull to failure. Gap distances at the tear site, ultimate failure load, and failure location were measured and recorded.

RESULTS

After 1000 cycles of cyclic loading, there were no significant differences in displacement among the 2-tunnel repair (3.0 ± 1.7 mm), hybrid repair (3.0 ± 0.9 mm), and hybrid tunnel repair (2.3 ± 1.0 mm; P = .4042). On pull-to-failure testing, there were also no significant differences in ultimate failure strength among the 2-tunnel repair (259 ± 103 N), hybrid repair (349 ± 149 N), and hybrid tunnel repair (365 ± 146 N; P = .26). However, the addition of vertical mattress sutures to act as a "rip stop" significantly reduced the likelihood of the sutures pulling through the meniscus during pull-to-failure testing for the hybrid and hybrid tunnel repairs (4 of 16, 25%) as compared with the 2-tunnel repair (7 of 9, 78%; P = .017).

CONCLUSION

The results showed equivalent biomechanical testing with regard to gap distance and pull-to-failure strength among the 3 repairs. The addition of the vertical mattress sutures to act as a rip stop was effective in preventing meniscal cutout through the meniscus.

CLINICAL RELEVANCE

Effective healing of radial meniscal tears after repair is paramount to prevent joint deterioration and symptom development. Each tested repair showed a biomechanically equivalent and stable construct to use to repair radial meniscal tears. The authors recommend that rip stop vertical mattress sutures be used, especially in poor-quality meniscal tissue, to prevent suture cutout.

Clinical and structural outcomes after arthroscopic rotator cuff repair: a comparison between suture bridge techniques with or without medial knot tying

Purpose

To compare arthroscopic suture bridge (SB) techniques with medial tying to those without tying, considering clinical and structural outcomes.

Methods

We included 124 patients with rotator cuff tears after arthroscopic rotator cuff repair (ARCR). Fifty-three patients with clinical and structural evaluations 3, 12, and 24 months postoperatively were included and divided into 29 patients with medial tying (WMT group) and 24 without tying (WOMT group). Clinical outcomes comprised the University of California Los Angeles (UCLA) and Japanese Orthopaedic Association (JOA) scores. Structural outcomes were evaluated with magnetic resonance images (MRI) using Sugaya classifications.

Results

JOA and UCLA scores in the WMT and WOMT groups improved significantly from before surgery to 24 months after surgery (P < 0.01, respectively). No significant difference was noted between groups. No significant postoperative retears (Sugaya types 4 and 5) between WMT and WOMT groups were noted at 3 months (5 vs 3 cases), 12 months (6 vs 5 cases), and 24 months (7 vs 6 cases) postoperatively. Complete healing (Sugaya type 1) was noted at 3 months (8 vs 11 cases), 12 months (10 vs 10 cases), and 24 months (8 vs 13 cases, P = 0.024) postoperatively. Incomplete healing (Sugaya types 2 and 3) were noted at 3 months (16 vs 10 cases), 12 months (13 vs 9 cases), and 24 months (14 vs 5 cases, P = 0.024) postoperatively.

Conclusion

Clinical outcomes for both techniques were comparable, but the number of incompletely healed tendons in SB with medial tying was significantly larger at 24 months after surgery.

Level of evidence

This study is a level III, case-control study.

Clinical relevance

This study revealed the influence of medial tying in rotator cuff repair.

Pullout Strength of All-Suture Anchors: Effect of the Insertion and Traction Angle-A Biomechanical Study

PURPOSE

To evaluate the pullout strength of the all-suture anchor (ASA), based on the angles of anchor insertion and traction.

METHODS

Synthetic saw bones of 2 densities (0.16 and 0.32 g/cm³) with 3 mm thick cortical bone models were used. ASAs were inserted at 45°, 60°, 75°, or 90° and pulled at 2 angles from the surface: 45° (simulating the physiological pull of the supraspinatus) and 90° (simulating pulling out during knot tying). Five consecutive pullout tests for each insertion and traction angle combination per saw bone were conducted to evaluate the ultimate load to failure and mode of failure (80 tests total). Thereafter, 9 matched pairs of human cadaveric humeri with 2 ASA types were used (insertion angles, 45°, 75°, 90°; traction angle, 90°). Nine consecutive tests were conducted for each insertion angle and anchor type (54 tests total).

RESULTS

The pullout strength was significantly higher for high density- than for low-density saw bones (all P < .05). The pullout strength was higher at the 45°than at the 90° traction angle (all P < .05) and was significantly higher at the 90° and 75° than at the 45° insertion angle in both high-density saw bones and cadaveric humeri (all P < .05). However, the pullout strength was not significantly different by ASA type (all P > .05).

CONCLUSIONS

ASA showed stronger pullout strength in higher density bones. Furthermore, it presented stronger pullout strength in the physiological traction direction of supraspinatus rather than in the knot-tying direction, consistent with the deadman theory. However, stronger pullout strength was observed in the vertically directed insertion angle, not 45°. Therefore, implanting the ASA vertically may be clinically more beneficial not only when performing knot tying during surgery, but also when the supraspinatus tendon loads the ASA postoperatively.

CLINICAL RELEVANCE

The study provides biomechanical evidence that the optimal insertion angle for an ASA is more vertical than the 45°.

Tight medial knot tying may increase retearing risk after transosseous equivalent repair of rotator cuff tendon

BACKGROUND

Retearing mechanism after transosseous equivalent (TOE) rotator cuff repair has not been fully clarified yet.

OBJECTIVE

The purposes of this study were to compare the stress distribution pattern in the tendon stump between knotted and knotless TOE repair and to investigate the role of suture tension applied during medial knot tying using a 3-dimensional finite element (3D-FE) method.

METHODS

Both knotted and knotless TOE repairs were simulated on the 3D-FE human rotator cuff tear model. Elastic analysis was performed to compare the stress distribution pattern inside the tendon between the two models. The amount of compressive load applied to the medial-row sutures was then changed as 0, 20, 40, 60, 80, and 100 N in the knotted model.

RESULTS

Knotted model demonstrated more distinct stress concentration inside the tendon around medial-row sutures than the knotless model. Mean von Mises equivalent stress in this area in the 0, 20, 40, 60, 80, and 100 N models was 0.26, 0.35, 0.50, 0.70, 1.11, and 1.14 MPa, respectively.

CONCLUSIONS

In the knotted TOE repair, tight medial knot tying might cause a high stress concentration around medial knots, which may constitute one of the pathogenetic factors of postoperative retearing at this site.

Editorial Commentary: Musculotendinous Junction Mattress Sutures Are Inefficient

Medial row sutures placed at the musculotendinous junction are more likely to cut through the tendon than those sutures placed 10 mm lateral to the junction. Even if there is little tendon left, putting the stitches at the junction is a bad idea. In this instance, a single-row repair is better.

The primary factor for suture configuration at rotator cuff repair: Width of mattress or distance from tear edge

OBJECTIVES

The aims of this study was first to investigate whether the bite size or the bite distance from the tear edge is of primary importance in mattress suture configuration for rotator cuff repair. Secondly, whether the use of a 450 left side bent Arthro-Pierce™ (Smith & Nephew, Andover, USA) during suture passage can be more effective on the strength of the configuration compared to a straight Arthro-Pierce™.

MATERIALS AND METHODS

Twenty-eight bovine infraspinatus muscle tendons were randomized into four groups. Group 1; 5 mm wide 'bite size' × 15 mm length 'distance from the tear edge's mattress'; Group 2: 7.5 mm × 10 mm; Group 3: 15 mm × 5 mm 'using straight Arthro-Pierce™' and Group 4: 5 mm × 15 mm using left sided 450 bent Arthro-Pierce™. The repair specimens underwent cyclic loading prior to loading the failure testing. Cyclic elongation (mm), peak-to-peak displacement (mm), ultimate load (N), stiffness (N/mm) and failure mode were recorded for each specimen.

RESULTS

The mean ultimate load in Group 1 was higher compared to group 3. The peak to peak displacement was higher in Group 4 compared to Group 1 (p < 0.05). The predominant failure mode in Groups 1, 2 and 4 was suture rupture. The Group 3 most specimens failed due to suture cut through the tendon.

CONCLUSION

Bite size from the edge of the tendon seems to be more important than the width of the mattress. The curve of the suture passing device may also have an effect on the strength of the suture tendon interface.

A Novel Repair Method for Radial Tears of the Medial Meniscus: Biomechanical Comparison of Transtibial 2-Tunnel and Double Horizontal Mattress Suture Techniques Under Cyclic Loading

BACKGROUND

Complete radial tears of the medial meniscus have been reported to be functionally similar to a total meniscectomy. At present, there is no consensus on an ideal technique for repair of radial midbody tears of the medial meniscus. Prior attempts at repair with double horizontal mattress suture techniques have led to a reportedly high rate of incomplete healing or healing in a nonanatomic (gapped) position, which compromises the ability of the meniscus to withstand hoop stresses.

HYPOTHESIS

A newly proposed 2-tunnel radial meniscal repair method will result in decreased gapping and increased ultimate failure loads compared with the double horizontal mattress suture repair technique under cyclic loading.

STUDY DESIGN

Controlled laboratory study.

METHODS

Ten matched pairs of male human cadaveric knees (average age, 58.6 years; range, 48-66 years) were used. A complete radial medial meniscal tear was made at the junction of the posterior one-third and middle third of the meniscus. One knee underwent a horizontal mattress inside-out repair, while the contralateral knee underwent a radial meniscal repair entailing the same technique with a concurrent novel 2-tunnel repair. Specimens were potted and mounted on a universal testing machine. Each specimen was cyclically loaded 1000 times with loads between 5 and 20 N before experiencing a load to failure. Gap distances at the tear site and failure load were measured.

RESULTS

The 2-tunnel repairs exhibited a significantly stronger ultimate failure load (median, 196 N; range, 163-212 N) than did the double horizontal mattress suture repairs (median, 106 N; range, 63-229 N) (P = .004). In addition, the 2-tunnel repairs demonstrated decreased gapping at all testing states (P < .05) with a final measured gapping of 1.7 mm and 4.1 mm after 1000 cycles for the 2-tunnel and double horizontal mattress suture repairs, respectively.

CONCLUSION

The 2-tunnel repairs displayed significantly less gapping distance after cyclic loading and had significantly stronger ultimate failure loads compared with the double horizontal mattress suture repairs.

CLINICAL RELEVANCE

Complete radial tears of the medial meniscus significantly decrease the ability of the meniscus to dissipate tibiofemoral loads, predisposing patients to early osteoarthritis. Improving the ability to repair medial meniscal radial tears in a way that withstands cyclic loads and heals in an anatomic position could significantly improve patient healing rates and result in improved preservation of the articular cartilage of the medial compartment of the knee. The 2-tunnel repair may be a more reliable and stronger repair option for midbody radial tears of the medial meniscus. Clinical studies are warranted to further evaluate these repairs.

A Modified Suture Bridge Technique for Application With Bone Anchors in Foot and Ankle Surgery

We present a suture bridge technique for reattachment of tendon or ligament to bone for use in foot and ankle surgery. The method is a simple, strong, and reproducible technique that could decrease the risk of irritation of the overlying cutaneous barrier and minimizes the likelihood of tendon strangulation when combined with soft tissue bone anchors. The present report serves as a guide to the use of this suture technique for reattachment of the Achilles tendon.

A review of biomechanics of the shoulder and biomechanical concepts of rotator cuff repair

In this article, we describe the basic knowledge about shoulder biomechanics, which is thought to be useful for surgeons. Some clinical reports have described that the excellent outcome after cuff repair without acromioplasty and a limited acromioplasty might be enough for subacromial decompression. It was biomechanically demonstrated that a 10-mm medial shift of the tendon repair site has a minimum effect on biomechanics. Many biomechanical studies reported that the transosseous equivalent repair was superior to other techniques, although the tendon may lose its inherent elasticity. We herein introduce our recent experiment data and latest information on biomechanics.