Footprint Contact Pressure Research Articles

Biomechanical comparison of knotless wide suture double-row SutureBridge rotator cuff repair to double-row standard suture repair

A comparison of self-reinforcement and footprint compression between standard- and wide-diameter suture material in double-row SutureBridge repair techniques has not been performed. The aim of this study was to compare the self-reinforcement and footprint contact pressure generated under progressive tensile loads between 2 double-row SutureBridge rotator cuff repair techniques: 1 performed with FiberWire and 1 performed with FiberTape in a knotless technique. Rotator cuff repairs were performed in 10 pairs of ovine shoulders. One group underwent a double-row SutureBridge repair using FiberWire. The other group underwent an identical repair with FiberTape. Footprint contact pressure was measured from 0° to 60° of abduction under loads of 0-60 N. Pull-to-failure tests were then performed. In both repair constructs at 0° of abduction, each 10-N increase in rotator cuff tensile load led to a significant increase in footprint contact pressure (P < .05). The rate of increase in footprint contact pressure was greater in the FiberTape construct (ratio, 1.68; P = .00035). In both repair constructs, the highest values for footprint contact pressure were seen at 0° of abduction. No difference in pull to failure, peak load, or total energy was found between the groups. Self-reinforcement was seen in both double-row SutureBridge repairs with standard- and wide-diameter suture material but was greater in the repair with the wide-diameter suture material construct. Footprint compression is greater in a knotless double-row SutureBridge repair with wide-diameter suture material than in a knotted double-row SutureBridge repair with standard-diameter suture material at 20° of abduction.

Arthroscopic Rotator Cuff Repair (Double Row Repair): Current Evidence

BACKGROUND: Surgical techniques for rotator cuff tears have improved from single row repair (SR) to double row repair (DR) including transosseous equivalent repair as new surgical devices or suture anchors were developed. Many biomechanical evidence favors DR with respect to footprint contact area and pressure and compression for cuff tendons. Some surgeons reported better clinical outcomes of DR compared to SR, whereas some described no difference of clinical outcomes between SR and DR. The purpose of this article was to review the current evidence regarding outcomes of DR comparing to SR and clarify whether better clinical or radiological outcomes can be obtained by performing DR. METHODS: We conducted a systematic review of clinical studies published for last 5 years which compared SR to DR. A systematic review of the literature was performed to identify all publications in the English literature. The databases MEDLINE and Google Scholar were searched. Also, we reviewed the latest systematic review and meta-analysis published between 2012 and 2018. RESULTS: Four clinical articles with evidence Levels I or II published in last 5 years were identified. Two of them documented superiority of DR over SR. Four systematic review and meta-analysis published between 2012 and 2018 were identified. Among them, two showed that DR provides better clinical outcomes and a lower re-tear rate compared with SR but its superiority is seen in the limited situation (only large tears or UCLA score). CONCLUSION: Although some reports with higher evidence Levels showed DR provides better clinical outcomes, it may be too early to conclude which repair technique is better because of lack of enough evidence.

Arthroscopic Rotator Cuff Repair (Double Row Repair): Current Evidence

BACKGROUND: Surgical techniques for rotator cuff tears have improved from single row repair (SR) to double row repair (DR) including transosseous equivalent repair as new surgical devices or suture anchors were developed. Many biomechanical evidence favors DR with respect to footprint contact area and pressure and compression for cuff tendons. Some surgeons reported better clinical outcomes of DR compared to SR, whereas some described no difference of clinical outcomes between SR and DR. The purpose of this article was to review the current evidence regarding outcomes of DR comparing to SR and clarify whether better clinical or radiological outcomes can be obtained by performing DR. METHODS: We conducted a systematic review of clinical studies published for last 5 years which compared SR to DR. A systematic review of the literature was performed to identify all publications in the English literature. The databases MEDLINE and Google Scholar were searched. Also, we reviewed the latest systematic review and meta-analysis published between 2012 and 2018. RESULTS: Four clinical articles with evidence Levels I or II published in last 5 years were identified. Two of them documented superiority of DR over SR. Four systematic review and meta-analysis published between 2012 and 2018 were identified. Among them, two showed that DR provides better clinical outcomes and a lower re-tear rate compared with SR but its superiority is seen in the limited situation (only large tears or UCLA score). CONCLUSION: Although some reports with higher evidence Levels showed DR provides better clinical outcomes, it may be too early to conclude which repair technique is better because of lack of enough evidence.

Computer simulation of tire rolling resistance using finite element method: Effect of linear and nonlinear viscoelastic models

This research work is devoted to the study of the effect of model parameters and material properties on tire rolling resistance. The main goal of this research is to investigate and clarify the effect of the adopted hyper-viscoelastic material model on tire rolling resistance simulation results. For this purpose, some new approaches were used and current shortcomings were introduced. Computer simulations were carried out using Abaqus standard command line. Linear and parallel rheological framework viscoelastic models were implemented and rolling resistance of a passenger car tire was determined. Different parametric simulations were carried out and the results were compared with rolling resistance data obtained from experimental tests. The results revealed that the calculated rolling resistance force depends on the implemented viscoelastic model. The linear viscoelastic model could not accurately predict the trend of rolling resistance with variation of tire inflation pressure and applied load. On the contrary, parallel rheological framework could cope with this trend. The parallel rheological framework model is more sensitive to inflation pressure. However, the sensitivity of both models to applied vertical load is nearly the same. Although cornering simulation is independent of the adopted viscoelastic model, the type of viscoelastic model could affect the footprint contact pressure contour.

Shoulder abduction diminishes self-reinforcement in transosseous-equivalent rotator cuff repair in both knotted and knotless techniques.

The self-reinforcement mechanism after double row suturebridge rotator cuff repair generates increasing compressive forces at the tendon footprint with increasing tendon load. Passive range of motion is usually allowed after rotator cuff repair. The mechanism of self-reinforcement could be adversely affected by shoulder abduction. Rotator cuff tears were created ex vivo in nine pairs of ovine shoulders. Two different repair techniques were used. One group was repaired using a double row 'suturebridge' construct with tied horizontal medial row mattress sutures (Knotted repair group). The other group was repaired identically except that medial row knots were not tied (Knotless repair group). Footprint compression was measured at varying amounts of abduction and under tendon loads of 0, 10, 20, 30, 40, 50 and 60N. The rate of increase of contact pressure (degree of self-reinforcement) was calculated for each abduction angle. Abduction diminishes footprint contact pressure in both knotted and knotless double row suturebridge constructs. Progressive abduction from 0 to 40 abduction in the knotless group and 0-30 in the knotted group results in a decrease in self-reinforcement. Abduction beyond this does not cause a further decrease in self-reinforcement. There was no difference in the rate of increase of footprint contact pressure at each angle of abduction when comparing the knotted and knotless groups. In the post-operative period, high tendon load combined with minimal abduction would be expected to generate the greatest amount of footprint compression which may improve tendon healing. Therefore, to maximize footprint compression the use of abduction pillows should be avoided while early isometric strengthening should be used.

Knotless double-row SutureBridge rotator cuff repairs have improved self-reinforcement compared with double-row SutureBridge repairs with tied medial knots: a biomechanical study using an ovine model

In double-row SutureBridge (Arthrex, Naples, FL, USA) rotator cuff repairs, increasing tendon load may generate progressively greater compression forces at the repair footprint (self-reinforcement). SutureBridge rotator cuff repairs using tied horizontal mattress sutures medially may limit this effect compared with a knotless construct. Rotator cuff repairs were performed in 9 pairs of ovine shoulders. One group underwent repair with a double-row SutureBridge construct with tied horizontal medial-row mattress sutures. The other group underwent repair in an identical fashion except that medial-row knots were not tied. Footprint contact pressure was measured at 0° and 20° of abduction under loads of 0 to 60 N. Pull-to-failure tests were then performed. In both repair constructs, each 10-N increase in rotator cuff tensile load led to a significant increase in footprint contact pressure (P < .0001). The rate of increase in footprint contact pressure was greater in the knotless construct (P < .00022; ratio, 1.69). The yield point approached the ultimate load to failure more closely in the knotless model than in the knotted construct (P = .00094). There was no difference in stiffness, ultimate failure load, or total energy to failure between the knotless and knotted techniques. In rotator cuff repair with a double-row SutureBridge configuration, self-reinforcement is seen in repairs with and without medial-row knots. Self-reinforcement is greater with the knotless technique.

Knotless Transosseous-Equivalent Rotator Cuff Repair Improves Biomechanical Self-reinforcement Without Diminishing Footprint Contact Compared With Medial Knotted Repair

To assess the effect of medial-row knots on self-reinforcement and footprint contact characteristics for transosseous-equivalent repair compared with the same construct without knots. In 8 fresh-frozen human shoulders, transosseous-equivalent repairs with and without medial-row mattress knots were performed in each specimen. A pressure sensor was fixed at the tendon-footprint interface for all repairs. Parameters measured included footprint contact area, force, and pressure. The supraspinatus tendon was loaded sequentially from 0 to 60N at 0° and 30° of abduction. Both repairs provided a linear progression (slope) of footprint force and pressure as increasing tendon loads were applied. However, the knotless repair had a significantly higher progression ("self-reinforcement" effect) than the knotted repair at both abduction angles (P= .006 at 0° and P= .021 at 30°). The addition of medial-row knots did not significantly change the footprint contact area (in square millimeters), contact force (in newtons), contact pressure (in kilopascals), or peak pressure (in kilopascals) at each load tested, as well as at both abduction angles. For a given repair, only the knotless repair had significant decreases in contact area, contact force, contact pressure, and peak pressure with increasing abduction angles from 0° to 30° (P= .004 and P= .048). Knotless transosseous-equivalent repair shows an improved self-reinforcement effect, without diminishing footprint contact, compared with the same repair with medial knots. Although knotless repair itself can show diminished footprint contact with abduction, medial knots show an adverse biomechanical effect by inhibiting self-reinforcement, without improving contact characteristics compared with knotless repair at each abduction angle tested. Clinical outcomes with specific indications, on the basis of these findings, require further investigation. This study biomechanically helps to validate studies that have shown clinical success with knotless transosseous-equivalent repair. The inhibition of self-reinforcement may provide a quantified biomechanical rationale for medial tear patterns seen with knotted repairs.

Tape Versus Suture in Arthroscopic Rotator Cuff Repair: Biomechanical Analysis and Assessment of Failure Rates at 6 Months.

Background:Rotator cuff retears after surgical repair are associated with poorer subjective and objectives clinical outcomes than intact repairs.Purpose:The aims of this study were to (1) examine the biomechanical differences between rotator cuff repair using No. 2 suture and tape in an ovine model and (2) compare early clinical outcomes between patients who had rotator cuff repair with tape and patients who had repair with No. 2 suture.Study Design:Controlled laboratory study and cohort study; Level of evidence, 3.Methods:Biomechanical testing of footprint contact pressure and load to failure were conducted with 16 ovine shoulders using a tension band repair technique with 2 different types of sutures (No. 2 suture [FiberWire; Arthrex] and tape [FiberTape; Arthrex]) with the same knotless anchor system. A retrospective study of 150 consecutive patients (tape, n = 50; suture, n = 100) who underwent arthroscopic rotator cuff repair by a single surgeon with tear size larger than 1.5 × 1 cm was conducted. Ultrasound was used to evaluate the repair integrity at 6 months postsurgery.Results:Rotator cuff repair using tape had greater footprint contact pressure (mean ± standard error of the mean, 0.33 ± 0.03 vs 0.11 ± 0.3 MPa; P < .0001) compared with repair using No. 2 sutures at 0° abduction with a 30-N load applied across the repaired tendon. The ultimate failure load of the tape repair was greater than that for suture repair (217 ± 28 vs 144 ± 14 N; P < .05). The retear rate was similar between the tape (16%; 8/50) and suture groups (17%; 17/100).Conclusion:Rotator cuff repair with the wider tape compared with No. 2 suture did not affect the retear rate at 6 months postsurgery, despite having superior biomechanical properties.

Finite Element Modeling with Embed Rebar Elements and Steady State Rolling Analysis for Rolling Resistance Test of Pneumatic Tire

Finite element model of tire rolling resistance test on the drum was developed using 3D steady state rolling analysis coupling with pre-inflation of 2D axisymmetric tire analysis. The complex components of the radial tires composing tread, sidewall, ply layers, steel belts, and lead wires were modeled using rebar elements which were embed into the rubber element using the tying equation. The Mooney-Rivlin hyperelastic constitutive model was employed to describe the large deformation behavior of tread and sidewall, while other components such as plies, steel belts and bead wires were assigned the linear isotropic material. The tire rolling resistance system was modeled by inflation of slick tire and compression on the drum for the footprint analysis regarding the rolling resistance test. The tire’s steady state characteristics such as footprint contact pressure, rolling resistance force, and time response characteristic of tires were predicted instead the experiment of the prototype.

The Effect of Medial Knots on Footprint Contact and Self-Reinforcement in TOE Rotator Cuff Repair

Transosseous-equivalent (TOE) rotator cuff repair has been shown to demonstrate a self-reinforcing effect, providing a protective mechanism in the face of potentially destructive forces. A variant, which uses tape-type sutures, has been performed clinically with and without medial row mattress knots. This study assessed the effect of medial row knots at the tendon-footprint interface. In 8 fresh frozen human shoulders, TOE supraspinatus repairs using tape-type sutures with (knotted) and without (knotless) two medial row mattress knots were performed in each specimen. A Tekscan pressure sensor was fixed at the tendon-footprint interface prior to all repairs. Parameters included footprint contact force, area, pressure and peak pressure. The supraspinatus tendon was loaded with 0, 15, 30, 45, and 60 N at 0° and 30° abduction, with 0° humeral rotation. Medial row knots did not significantly change footprint contact force, area, pressure, or peak pressure under all conditions. The knotted repair had increases in footprint contact pressure with increasing load at both abduction angles. The knotless repair demonstrated the same relationships for footprint contact pressure with increasing load. This relationship was also seen for footprint contact force for both repairs. With increasing load, the knotless repair had a significantly higher progression (slope) of footprint force and pressure (P < 0.05). There is no measurable change in tendon-footprint contact force, area, pressure, or peak pressure with the addition of medial row knots at both abduction angles. In addition, the lower progression (slope) of footprint force and pressure seen with the addition of medial row knots demonstrates that they can inhibit the self-reinforcing effect of the TOE repair. Knotless TOE repair using tape-type sutures may provide superior tendon-footprint interface characteristics and improve healing potential under post-operative conditions, while avoiding the risk of medial over-tensioning, strangulation, and catastrophic failure at the medial tendon.

Modified Suture-Bridge Technique to Prevent a Marginal Dog-Ear Deformity Improves Structural Integrity After Rotator Cuff Repair

Background: The arthroscopic suture-bridge technique has proved to provide biomechanically firm fixation of the torn rotator cuff to the tuberosity by increasing the footprint contact area and pressure. However, a marginal dog-ear deformity is encountered not infrequently when this technique is used, impeding full restoration of the torn cuff. Purpose: To evaluate the structural and functional outcomes of the use of a modified suture-bridge technique to prevent a marginal dog-ear deformity compared with a conventional suture-bridge method in rotator cuff repair. Study Design: Cohort study; Level of evidence 2. Methods: A consecutive series of 71 patients aged 50 to 65 years who underwent arthroscopic rotator cuff repair for full-thickness medium-sized to massive tears was evaluated. Patients were divided into 2 groups according to repair technique: a conventional suture-bridge technique (34 patients; group A) versus a modified suture-bridge technique to prevent a marginal dog-ear deformity (37 patients; group B). Radiographic evaluations included postoperative cuff integrity using MRI. Functional evaluations included pre- and postoperative range of motion (ROM), pain visual analog scale (VAS), the University of California, Los Angeles (UCLA) shoulder rating scale, the Constant score, and the American Shoulder and Elbow Surgeons (ASES) score. All patients were followed up clinically at a minimum of 1 year. Result: When the 2 surgical techniques were compared, postoperative structural integrity by Sugaya classification showed the distribution of types I:II:III:IV:V to be 4:20:2:4:4 in group A and 20:12:4:0:1 in group B. More subjects in group B had a favorable Sugaya type compared with group A (P < .001). The postoperative healed:retear rate was 26:8 in group A and 36:1 in group B, with a significantly lower retear rate in group B (P = .011). However, there were no significant differences in ROM and all functional outcome scores between the 2 groups postoperatively. When surgical techniques were compared across healed (n = 62) and retear (n = 9) groups, significantly fewer modified suture-bridge technique repairs were found in the retear group (P = .03). There were significant differences between healed and retear groups in functional outcome scores, with worse results in the retear group. Conclusion: A modified suture-bridge technique to prevent a marginal dog-ear deformity provided better structural outcomes than a conventional suture-bridge technique for medium-sized to massive rotator cuff tears. This technique may ultimately provide better functional outcomes by decreasing the retear rate.

Does transosseous-equivalent rotator cuff repair biomechanically provide a “self-reinforcement” effect compared with single-row repair?

Transosseous-equivalent (TOE) rotator cuff repair has been theorized to be "self-reinforcing" against potentially destructive and increasing tendon loads. The goal of this study was to biomechanically verify and characterize the effect of increasing tendon load on frictional resistance over a repaired footprint for single-row (SR) and TOE repair techniques. In 10 fresh frozen human shoulders, TOE and SR supraspinatus tendon repairs were performed in each specimen. For all repairs, a pressure sensor was secured at the tendon-footprint interface. The supraspinatus tendon was loaded with 0, 20, 40, 60, and 80N at 0° and 30° abduction. Paired t tests and multivariate regression analyses were used for comparisons. The SR repair had significant increases in footprint contact force, area, and pressure between each and all tendon-loading conditions (P<.05). The TOE repair similarly demonstrated increases in footprint contact force with increasing tendon load (P<.05). Comparing between repairs, TOE repair had more footprint contact force, area, pressure, and peak pressure at each load for both abduction angles (P<.05). With increasing load, the TOE repair had a significantly higher progression (slope) of footprint force and pressure compared with the SR repair. Self-reinforcing capacity in rotator cuff repair has been biomechanically characterized and verified. The TOE repair, with tendon-bridging sutures fixed medially and spanning the footprint, provides disproportionately more progressive footprint frictional resistance with increasing tendon loads compared with the SR repair secured over isolated fixation points. This self-reinforcing effect could help sustain structural integrity and potentially improve healing biology.

Is Transosseous-Equivalent Rotator Cuff Repair “Self-Reinforcing” Compared to Single-Row Repair?

Transosseous-equivalent (TOE) rotator cuff repair has been theorized to be “self-reinforcing” with increasing tendon load. The purpose of this study was to biomechanically verify and characterize the effect of increasing tendon load on frictional resistance over a repaired footprint with both single row (SR) and TOE repair techniques. In ten fresh-frozen human shoulders, TOE and SR supraspinatus tendon repairs were performed. For all repairs, a Tekscan pressure sensor was secured on the greater tuberosity at the tendon-footprint interface. The supraspinatus tendon was loaded with 0, 20, 40, 60, and 80 N. The shoulders were tested at 0° and 30° abduction with 0° of humeral rotation. The area of interest was defined at 160 mm2. For comparisons, paired t-tests and multivariate regression analyses were employed. The SR repair had significant (p<0.05) increases in footprint contact force (N) between each and all tendon loading conditions (1.36 ± 0.54 N, 2.94 ± 0.81 N, 4.57 ± 1.27 N, 6.00 ± 1.64 N, 7.59 ± 2.05 N for tendon loads of 0, 20, 40, 60, and 80 N, respectively). The TOE repair demonstrated the same relationships for footprint contact force with increasing tendon load (p<0.05) (5.93 ± 1.21 N, 10.60 ± 1.65 N, 14.07 ± 2.15 N, 16.60 ± 2.62 N, 18.41 ± 3.06 N, for each progressive tendon load, respectively). This relationship was also seen for contact area and pressure for both repairs. Comparing between repairs, TOE repair had more footprint contact force, area, pressure, and peak pressure at each load, for both 0 and 30 degrees of abduction (p<0.05). Abduction did not significantly affect contact variables. With increasing load, the TOE repair had a significantly higher progression (slope) of footprint force and pressure compared to the SR repair. Self-reinforcing capacity in rotator cuff repair has been biomechanically verified and characterized. While the SR repair demonstrated increasing footprint force and pressure with progressive tendon loading, this effect was significantly greater with the TOE repair. Tendon-bridging sutures spanning the footprint can provide a compression vector and increasing frictional resistance over the footprint with tendon loading; this may protect structural integrity and improve healing biology. In contrast, without footprint bridging sutures, SR repair cannot provide a self-protective effect. Footprint contact force increases with increasing tendon load. The contact force progression (slope of the measurements) was significantly higher with the TOE repair, demonstrating a “self-reinforcing” effect with tendon loading. (Vertical axis, footprint contact force; N, Newtons; Horizontal axis, supraspinatus tendon load [N]).

The biomechanical effects of polytetrafluoroethylene suture augmentations in lateral-row rotator cuff repairs in an ovine model

This study investigated the biomechanical effects of expanded polytetrafluoroethylene (ePTFE) suture augmentation patches in rotator cuff repair constructs. The infraspinatus tendon in 24 cadaveric ovine shoulders was repaired using an inverted horizontal mattress suture with 2 knotless bone anchors (ArthroCare, Austin, TX, USA) in a lateral-row configuration. Four different repair groups (6 per group) were created: (1) standard repair using inverted horizontal mattress sutures, (2) repair with ePTFE suture augmentations on the bursal side of the tendon, (3) repair with ePTFE suture augmentations on the articular side, and, (4) repair with ePTFE suture augmentations on both sides of the tendon. Footprint contact pressure, stiffness, and the load to failure of the repair constructs were measured. Repairs with ePTFE suture augmentations on the bursal side exerted significantly more footprint contact pressure (0.40 ± 0.01 MPa) than those on the articular side (0.34 ± 0.02 MPa, P = .04) and those on both sides (0.33 ± 0.02 MPa, P = .01). At 15 degrees of abduction, ePTFE-augmented repairs on the bursal side had higher footprint contact pressure (0.26 ± 0.03 MPa) compared with standard repairs (0.15 ± 0.02 MPa, P = .01) and with ePTFE-augmented repairs on the articular side (0.18 ± 0.02 MPa, P = .03). The ePTFE-augmented repairs on the bursal side demonstrated significantly higher failure loads (178 ± 18 N) than standard repairs (120 ± 17 N, P = .04). Inverted horizontal mattress sutures augmented with ePTFE patches on the bursal side of the tendon enhanced footprint contact pressures and the ultimate load to failure of lateral-row rotator cuff repairs in an ovine model.

What’s New in Shoulder and Elbow Surgery

This annual update on shoulder and elbow surgery is based on a review of presentations at meetings of the Arthroscopy Association of North America (Specialty Day, March 25, 2006, Chicago, Illinois; Twenty-fifth Annual Meeting, May 18 to 21, 2006, Hollywood, Florida), the American Shoulder and Elbow Surgeons (Twenty-second Open Meeting, Specialty Day, March 25, 2006, Chicago, Illinois; Twenty-third Closed Meeting, September 13 to 15, 2006, Chicago, Illinois), The American Orthopaedic Society for Sports Medicine (Specialty Day, March 25, 2006, Chicago, Illinois), the American Academy of Orthopaedic Surgeons (Seventy-third Annual Meeting, March 22 to 25, 2006, Chicago, Illinois), and the Orthopaedic Research Society (Fifty-second Annual Meeting, March 19 to 22, 2006, Chicago, Illinois). ### Rotator Cuff #### Basic Science Park proposed a transosseous equivalent rotator cuff repair technique and performed a biomechanical study to evaluate footprint contact pressure in a variety of repair configurations. A “suture-bridging” technique utilizing medial anchors with suture limbs traversing over the cuff to a lateral interference screw attachment was compared with a double-row anchor repair. A four-limb suture bridge (two medial anchors with four limbs over the cuff laterally) established a significantly higher mean contact pressure area (72.3%) compared with a two-limb suture bridge (57.3%) and a double-row repair (35.1%) (p < 0.05). The authors concluded that increasing footprint contact pressure may aid in rotator cuff healing. #### Impingement Milano investigated the influence of acromioplasty on outcome following arthroscopic rotator cuff repair. Eighty patients were prospectively randomized into two groups, with half undergoing rotator cuff repair with acromioplasty and half undergoing rotator cuff repair without acromioplasty. The outcome measures that were evaluated were the Constant score and the Quick-DASH and Work-DASH self-administered questionnaires. Comparison between the two groups failed to demonstrate a significant difference at two years of follow-up. The authors concluded that acromioplasty does not affect the outcome of arthroscopic rotator cuff repair. …

Footprint Contact Restoration Between the Biceps-Labrum Complex and the Glenoid Rim in SLAP Repair: A Comparative Cadaveric Study Using Pressure-Sensitive Film

To compare pressurized footprint contact and interface pressure between the biceps-labrum complex and the superior glenoid rim after SLAP repair using 3 different techniques. Twenty-four fresh-frozen human cadaveric shoulders were divided into 3 groups. SLAP lesions were repaired by (1) 2 single-loaded anchors in a simple suture configuration (group T), (2) a double-loaded anchor in a simple suture configuration in a V shape (group V), or (3) a double-loaded anchor by use of a hybrid simple and mattress suture configuration (group H). Pressure-sensitive film quantified pressurized contact areas and interface pressures between the biceps-labrum complex and the glenoid rim after SLAP repair. Groups T and V showed significantly larger contact areas than group H (P < .0001). However, there was no significant difference between groups T and V. Despite a substantial contact area around the biceps-labrum complex in group T, there was a lack of sufficient contact area just below the biceps anchor. Group V showed a uniform contact area around the entire biceps-labrum complex, but in group H the contact area was concentrated only around the posterior superior labrum, where the simple suture was used. The methods using 2 single-loaded suture anchors and using 1 double-loaded suture anchor with a simple suture configuration showed significantly larger pressurized contact areas than the method using 1 double-loaded suture anchor with both a simple and mattress suture configuration. The interface pressure was not significantly different among groups. Although there have been several kinds of repair techniques and biomechanical studies for the type II SLAP lesion, there has been no study about footprint restoration on the superior glenoid rim. This study analyzed and compared the footprint contact restoration after type II SLAP repair among 3 different techniques.

Evaluation of footprint contact area and pressure using a triple-row modification of the suture-bridge technique for rotator cuff repair

Studies suggest that arthroscopic repair techniques may have high recurrence rates for larger rotator cuff tears. A more anatomic repair may improve the success rate when performing arthroscopic rotator cuff repair. We hypothesized that a triple-row modification of the suture-bridge technique for rotator cuff repair would result in significantly more footprint contact area and pressure between the rotator cuff and the humeral tuberosity. Eighteen ovine infraspinatus tendons were repaired using 1 of 3 simulated arthroscopic techniques: a double-row repair, the suture-bridge technique, and a triple-row repair. The triple-row repair technique is a modification of the suture-bridge technique that uses an additional reducing anchor between the medial and lateral rows. Six samples were tested per group. Pressure-indicating film was used to measure the footprint contact area and pressure after each repair. The triple-row repair resulted in significantly more rotator cuff footprint contact area and contact pressure compared with the double-row technique and the standard suture-bridge technique. No statistical difference in contact area or contact pressure was found between the double-row technique and the suture-bridge technique. The triple-row technique for rotator cuff repair results in significantly more footprint contact area and contact pressure compared with the double-row and standard suture-bridge techniques. This more anatomic repair may improve the healing rate when performing arthroscopic rotator cuff repair.

Biomechanics of Synthetic Patch Rotator Cuff Repairs

Introduction: Massive irreparable rotator cuff tears are difficult to manage. Synthetic materials have been proposed as one solution to bridge tendon defects in these tears. This study aimed to analyze the biomechanical properties of synthetic patch-bone repairs using 2 different repair configurations. Methods: An irreparable rotator cuff defect was created ex vivo in 12 ovine shoulders and then secured to a synthetic patch (2 mm Gore-Tex ePTFE, Gore, Flagstaff, AZ). The patch was then repaired to the humeral footprint with 2 suture anchors using either vertical mattress sutures (n=6) or the inverted mattress tension-band repair (n=6) technique. Footprint contact pressure was measured at 10-N, 20-N, and 30-N tension and −10, 0, and +10 degrees of abduction. Repair strength was determined using a pull-to-failure test. Results: Tension-band repairs provided significantly higher footprint contact pressure than mattress repairs in 7 out of 9 tension/abduction combinations (P<0.05). Footprint contact was maximized with decreasing abduction angle and increasing tension. Tension-band repairs had higher pullout strength (220 N ±7) than mattress repairs (188 N ±10) (P<0.03). Discussion: The tension-band repair technique of synthetic patch to bone provided better footprint contact and was stronger than mattress repairs of synthetic patch to bone. Interestingly, tendon-synthetic patch-bone repairs had higher contact pressure and pullout strength than similar tendon-bone repairs.

Biomechanical Considerations for Rotator Cuff Repairs

The ideal rotator cuff repair should have strong initial fixation strength to resist early structural failure and high footprint contact pressure to assist biological healing. Fixation strength can be enhanced by using more suture anchors in the repair construct and by placing anchors in area of high bone density such as the proximal part of the tuberosities. High footprint contact pressure can be achieved by using tension band repair constructs such as inverted mattress and suture bridge technique. These techniques pass sutures over the bursal surface of the tendon with lateral fixation. These bursal sutures push the tendon down to the footprint insertion creating a larger pressurized contact area beneficial for healing. Postoperative external rotation should be avoided to minimize strain on the anterolateral region of the repaired tendon. Abduction of 30 degrees should minimize loading stress on the repair construct and also facilitates blood flow to the footprint insertion.

Repair of Partial-Thickness Rotator Cuff Tears: A Biomechanical Analysis of Footprint Contact Pressure and Strength in an Ovine Model

The purpose of this study was to determine whether transtendon repair by use of a novel small-diameter knotless anchor showed enhanced mechanical properties compared with tear completion and repair. Articular-sided partial-thickness tears were created ex vivo in the infraspinatus of 24 ovine shoulders. The specimens were randomized into 4 groups of 6 each: (1) no repair, (2) transtendon repair, (3) completion of tear with tension-band single-row repair, and (4) completion of tear with double-row repair. Footprint contact pressure and ultimate load to failure were measured in each specimen. Technical failure of the transtendon anchors occurred in 3 of 15 shoulders. Transtendon repair (mean +/- SEM, 0.8 +/- 0.1 MPa) and double-row repair (1 +/- 0.09 MPa) showed 3-fold (P < .001) greater footprint contact pressures than tension-band single-row repair (0.3 +/- 0.03 MPa) and no repair (0.3 +/- 0.02 MPa). The ultimate load to failure for transtendon repair (544 +/- 22 N) was more than 3 times greater than that for the double-row repair (157 +/- 23 N) (P < .001) and the single-row repair (116 +/- 11 N) (P < .001). Transtendon repair of partial-thickness tears by use of specifically designed anchors biomechanically outperformed tear completion and repair in an ovine model. Transtendon repair showed the best combination of high footprint contact pressure and high ultimate failure load. However, the high insertion failure rate of these transtendon anchors is of concern. On the basis of the biomechanical data, transtendon repair of partial-thickness rotator cuff tears may be used as an alternative to tear completion and repair, but the specific transtendon anchors used in this study need further evaluation before their clinical use can be recommended.