Pullout Strength Of Suture Anchors Research Articles

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.

Augmentation of suture anchors with magnesium phosphate cement – Simple technique with striking effect

BackgroundSuture anchors have a large field of application in orthopedic trauma surgery like the refixation of patellar, quadriceps and Achilles tendon or the treatment of rotator cuff tears. The fixation of suture anchors in osteoporotic bone is difficult, a problem that becomes increasingly relevant in the elderly. MethodsTwo types of suture anchors: 1.) Titanium CorkScrew Fast Track II with a knotted eyelet and 2.) polyether ether ketone (PEEK) SwiveLock C with a knotless eyelet were chosen for evaluation in open cell bone blocks with densities of 5–20 pcf supplied by Sawbones AB. A pilot hole of 7 mm diameter and 20 mm depth was drilled in the bone blocks and filled with an experimental drillable magnesium phosphate cement (powder: 92.5 wt% Mg3(PO4)2, 7.5 wt% MgO, liquid: 25 wt% phytic acid (C6H18O24P6)). Anchors were then inserted into the cement and allowed to cure for 24 h (37 °C, 100% humidity) before pullout testing was conducted with a material testing machine. Suture anchors inserted in the blocks after predrilling and tapping served as control. ResultsThrough augmentation with magnesium phosphate cement pullout strength and stiffness of the suture anchors could be significantly increased in all bone blocks up to 22-fold. CorkScrew anchors failed by rupture of the eyelet with higher pullout strengths, whereas no failure of SwiveLock C anchors could be observed when reinforced with additional FibreWire at the tip. ConclusionsWe present a simple technique, whereby pullout strength of suture anchors can be significantly increased in bone with compromised density. The experimental resorbable and drillable magnesium phosphate cement proved to be effective in resisting tensile load, dispersing in the adjacent bone, and thus increasing the bone-anchor contact surface. Therefore, the experimental magnesium phosphate cement is a promising candidate for clinical application in the numerous scenarios mentioned.

Calcium Phosphate Bone Void Filler Increases Threaded Suture Anchor Pullout Strength: A Biomechanical Study

To compare the response to cyclical loading and ultimate pull-out strength of threaded suture anchor with and without calcium phosphate bone void filler augmentation in a polyurethane foam block model and invitro proximal humerus cadaveric model. This controlled biomechanical study consisted of 2 parts: (1) preliminary polyurethane foam block model, and (2) invitro cadaveric humeri model. The preliminary foam block model intended to mimic osteoporotic bone using a 0.12 g/mL foam material. Half of the foam block models were first filled with injectable calcium phosphate bone substitute material (CP-BSM), whereas the other half were not augmented with CP-BSM. Each specimen was then instrumented with a threaded suture anchor. The same technique and process was performed in a matched cadaveric humeri model. Testing then consisted of a stepwise, increasing axial load protocol for a total of 40 cycles. If the anchor remained intact after cyclic loading, the repair was loaded to failure. The number of completed cycles, failure load, and failure modes were compared between groups. Average pull-out strength for suture anchor with CP-BSM in the osteoporotic foam block model was significantly higher at 332.68 N ± 47.61 compared with the average pull-out strength of suture anchor without CP-BSM at 144.38 N ± 14.58 (P= .005). In the matched cadaveric humeri model, average pull-out strength for suture anchor with CP-BSM was significantly higher at 274.07 N ± 102.07 compared with the average pull-out strength of suture anchor without CP-BSM at 138.53 N ± 109.87 (P= .029). In this time zero, biomechanical study, augmentation of osteoporotic foam block and cadaveric bone with calcium phosphate bone substitute material significantly increases pull-out strength of threaded suture anchors. Considering concerns about suture anchor pull-out from osteoporotic bone, augmentation with calcium phosphate bone substitute material increases load to failure resistance.

Effect of structural design on the pullout strength of suture anchors for rotator cuff repair.

Various types of suture anchor designs are currently available for rotator cuff repair. The purpose of our study was to investigate the pullout strength of such anchors based on their structural design and the predominant geometric design factors affecting the pullout strength using finite element analysis. Finite element models were constructed using five cadaveric humeri and ten suture anchors with different designs. The pullout strength and distribution of bone stress around the anchor at three different directions of the applied force (0°, 45°, and 75°) were analyzed. The following geometric factors of suture anchor design were computed and their correlations with pullout strength assessed: Overall length, minor, and major diameters; number of threads; height of thread; distance between threads; helix angle; contact surface area between the anchor threads and surrounding bone; contact surface area between the cylindrical portion of the anchor; and surrounding bone and total contact surface area between the anchor and surrounding bone. The pullout strength and distribution of bone stress around the anchor varied according to the suture anchor designs and the direction of the applied force, respectively. The pullout strength had a strong positive correlation with the contact surface area between the anchor threads and surrounding bone, overall length, and the number and height of threads. This study demonstrated that suture anchor designs with increased contact surface area between the anchor threads and surrounding bone, overall length, and the number and height of threads can enhance the pullout strength during rotator cuff repair. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:3318-3327, 2018.

Does Greater Trochanter Decortication Affect Suture Anchor Pullout Strength in Abductor Tendon Repairs? A Biomechanical Study

Background: Greater trochanter decortication is frequently performed at the time of abductor tendon repair to theoretically increase healing potential. No previous studies have determined the effect that greater trochanter decortication has on the pullout strength of suture anchors. Hypothesis/Purpose: The purpose of this study is to determine whether greater trochanter decortication and bone mineral density affect suture anchor pullout strength in abductor tendon repair. The authors hypothesize that both will have a significant detrimental effect on suture anchor pullout strength. Study Design: Controlled laboratory study. Methods: Nineteen cadaveric proximal femurs with accompanying demographic data and computed tomography scans were skeletonized to expose the greater trochanter. Bone density measurements were acquired by converting Hounsfield units to T-score, based on a standardized volumetric sample in the intertrochanteric region of the femur. The gluteus medius insertion site on the lateral facet of the greater trochanter was evenly divided into 2 regions, anterior-distal and posterior-proximal, and each region was randomly assigned to receive either no decortication or 2 mm of bone decortication. A single biocomposite anchor was implanted in each region and initially tested with cyclic loading for 10 cycles at 0-50 N, 0-100 N, 0-150 N, and 0-200 N, followed by load to failure (LTF) tested at 1 mm/s. For each trial, the number of cycles endured, LTF, mechanism of failure, and stiffness were recorded. Results: Greater trochanters with no decortication and 2 mm of decortication survived a mean ± SD 35.1 ± 6.4 and 28.5 ± 10.6 cycles, respectively (P < .01). Load to failure for nondecorticated specimens was 206.7 ± 75.0 N versus 152.3 ± 60.2 N for decorticated specimens (P < .001). In a multivariate analysis, decortication and bone density were determinants in LTF (P < .05). Conclusion: Decortication and decreased bone mineral density significantly decreased the pullout strength of suture anchors in the lateral facet of the greater trochanter. Clinical Relevance: Bone density should be considered when determining whether to perform greater trochanter decortication in abductor tendon repairs.

Subacromial corticosteroid injections transiently decrease suture anchor pullout strength: biomechanical studies in rats

Arthroscopic rotator cuff (RC) repair incorporates suture anchors to secure torn RC tendons to the greater tuberosity (GT) bone. RC repair strength depends on the anchor-bone interface and on the quality of the GT. We evaluated the effect of single and multiple corticosteroid injections on the pullout strength of suture anchors. Fifty rats were divided into those receiving saline solution injection (control group), a single methylprednisolone acetate (MTA) injection (MTA1 group), or 3 once-weekly MTA injections (MTA3 group). Rats were killed humanely at 1 or 4 weeks after the last injection. A mini-suture anchor was inserted into the humeral head through the GT. Specimens were tested biomechanically. At 1 week after the last injection, the mean maximal pullout strength was significantly reduced in the MTA1 group (63.5%) and MTA3 group (56%) compared with the control group (P < .05 for both). Mean stiffness decreased significantly in both treatment groups compared with controls (P < .05). At 4 weeks after the last injection, there was a significant increase in the mean maximal pullout strength after single and triple MTA injections compared with values recorded at the 1-week time point (P < .05). At 4 weeks, the mean maximal pullout strength after a single MTA injection was 92.8% of the pullout strength measured in the control group. We showed a significant detrimental effect of corticosteroid exposure on the pullout strength of a suture anchor at 1 week. However, this effect was transient and resolved within a relatively short period. These findings indicate that a waiting period is required between subacromial corticosteroid injection and RC repair surgery that involves the use of suture anchors.

Increasing pullout strength of suture anchors in osteoporotic bone using augmentation—A cadaver study

BackgroundRotator cuff tears are of increasing clinical impact in the physically active elderly patients. Recent research revealed, that a high percentage of these patients present with significant loss of bone mineral density at the insertion site of the rotator cuff, thereby compromising suture anchorage for operative repair. We therefore hypothesized that augmentation of suture anchors improves biomechanical properties in low bone quality. Methods28 osteoporotic humeral heads were included in this biomechanical study. Bone quality at the anchor insertion sites (group 1: posterior–medial; group 2: anterior–lateral) within the greater tuberosity was analyzed using HR-pQCT (voxel size: 82μm). Anchor positions of identical quality were then randomized to either conventional screw anchorage or polymethylmethacrylat augmented screw anchorage. All anchors were cyclically ramp-loaded until pullout. FindingsPullout strength accounted for 226N in group I for conventional anchorage and for 332N in augmented technique. In group 2 (anterior–lateral) the pullout strength was 209N (conventional) and 304N (augmented). Pull-out strength of augmented screw anchors was significantly higher in both groups (p<0.05). InterpretationCompared to conventional insertion techniques, the cement augmentation technique increases the pullout strength of suture anchors in low bone quality significantly. Cement augmentation could therefore be a helpful tool for improved suture anchor stability, especially in locations of low bone quality.

In vivo microstructural analysis of the humeral greater tuberosity in patients with rotator cuff tears using multidetector row computed tomography.

BackgroundIn arthroscopic surgery, the suture anchor technique has become popular for rotator cuff repair. Preoperative evaluation of the bone microstructure is of utmost importance because, especially in elderly patients, osteoporotic changes may cause anchor pullout, which results in failure of rotator cuff repair. Many groups have reported humeral microstructural analysis; however, most studies were experiments using porcine specimens or human cadavers. In this study, we used multidetector row computed tomography to successfully perform in vivo evaluation of the bone microstructure of the humeral greater tuberosity in patients with rotator cuff tears.MethodsTen patients were examined. Regions of interest were defined in six quadrants of the greater tuberosity (medial, lateral, and far lateral rows of the anterior and posterior areas). The local bone mineral density and the trabecular microstructural parameters, including the mean bone volume to total volume (BV/TV), trabecular thickness, trabecular separation, and structure model index (SMI), were measured using bone analysis software.ResultsThe BV/TV of the posteromedial region was highest and the SMI of the posteromedial region was lowest. These findings suggest that the bone quality of the posteromedial portion is the highest within the greater tuberosity.ConclusionBecause the bone quality may be correlated with the pullout strength of suture anchors, our method can help to understand the individual and regional variance in bone quality and may lead to the creation of personalized surgical protocols.Electronic supplementary materialThe online version of this article (doi:10.1186/1471-2474-15-351) contains supplementary material, which is available to authorized users.

Bioabsorbable Tricalcium Phosphate Bone Cement Strengthens Fixation of Suture Anchors

Failure of suture anchor fixation in rotator cuff repair can occur at different interfaces. Prior studies show fixation at the bone-anchor interface can be augmented using polymethylmethacrylate (PMMA) cement, and screw fixation into bone can be strengthened using bioabsorbable tricalcium phosphate cement. We wished to determine whether augmentation of suture anchor fixation using bioabsorbable tricalcium phosphate cement would increase pullout strength of suture anchors from bone and the number of cycles to failure, to determine the mode of failure after cement augmentation, and to compare strength and mode of failure with those after augmentation with PMMA. We used 10 matched pairs of cadaveric proximal humeri and implanted a metal screw-type suture anchor in one side and on the other side injected tricalcium phosphate cement into the anchor holes before anchor placement. We tested all specimens to failure using a ramped cyclic loading protocol. Tricalcium phosphate cement augmentation increased the final load to failure by 29% and the number of cycles to failure by 20%. Visual inspection confirmed that failure occurred at the cement-bone interface. Tricalcium phosphate cement appears to augment suture anchor fixation into bone, reducing the risk of anchor pullout and failure. When relying on suture anchor fixation in bone of questionable quality, we suggest considering augmentation of suture anchor fixation with bioabsorbable cement. This method also provides potential for bioabsorbability and may be more amenable to arthroscopic application.

The effect of the trabecular microstructure on the pullout strength of suture anchors

This study investigates how the microstructural properties of trabecular bone affect suture anchor performance. Seven fresh-frozen humeri were tested for pullout strength with a 5 mm Arthrex Corkscrew in the greater tuberosity, lesser tuberosity, and humeral head. Micro-computed tomography analysis was performed in the three regions of interest directly adjacent to individual pullout experiments. The morphometric properties of bone mineral density (BMD), structural model index (SMI), trabecular thickness (TbTh), trabecular spacing (TbS), trabecular number (TbN), and connectivity density were compared against suture anchor pullout strength. BMD ( r=0.64), SMI ( r=−0.81), and TbTh ( r=0.71) showed linear correlations to the pullout strength of the suture anchor with p-values<0.0001. A predictive model was developed to explain the variances in the individual BMD, SMI, and TbTh correlations. The multi-variant model of pullout strength showed a stronger relationship ( r=0.86) compared to the individual experimental results. This study helps confirm BMD is a major influence on the pullout strength of suture anchors, but also illustrates the importance of local microstructure in pullout resistance of suture anchors.

Pullout strength of suture anchors: Effect of mechanical properties of trabecular bone

This study investigated the relationships between trabecular microstructure and elastic modulus, compressive strength, and suture anchor pullout strength. Twelve fresh-frozen humeri underwent mechanical testing followed by micro-computed tomography (μCT). Either compression testing of cylindrical bone samples or pullout testing using an Arthrex 5 mm Corkscrew was performed in synthetic sawbone or at specific locations in the humerus such as the greater tuberosity, lesser tuberosity, and humeral head. Synthetic sawbone underwent identical mechanical testing and μCT analysis. Bone volume fraction (BVF), structural model index (SMI), trabecular thickness (TbTh), trabecular spacing (TbSp), trabecular number (TbN), and connectivity density were compared against modulus, compressive strength, and pullout strength in both materials. In cadaveric bone, modulus showed correlations to all of the microstructural properties, while compressive and pullout strength were only correlated to BVF, SMI, and TbSp. The microstructure of synthetic bone differed from cadaveric bone as SMI and TbTh showed little variation across the densities tested. Therefore, SMI and TbTh were the only microstructural properties that did not show correlations to the mechanical properties tested in synthetic bone. This study helps identify key microstructure–property relationships in cadaveric and synthetic bone as well as illustrate the similarities and differences between cadaveric and synthetic bone as biomechanical test materials.

Bearing area: A new indication for suture anchor pullout strength?

Studies performed to quantify the pullout strength of suture anchors have not adequately defined the basic device parameters that control monotonic pullout. The bearing area of a suture anchor can be used to understand and predict anchor pullout strength in a soft-bone model. First, conical-shaped test samples were varied in size and shape and tested for pullout in 5, 8, and 10 pcf sawbone models. Next, bearing area and pullout strength relationships developed from the test samples were validated against nine commercially available suture anchors, including the Mitek QuickAnchor and SpiraLok, Opus Magnum(2), ArthroCare ParaSorb, and Arthrex BioCorkscrew. The samples showed a direct correlation between bearing area and pullout strength. Increased insertion depth was a secondary condition that also increased pullout strength. The pullout strength for the suture anchors followed the predicted trends of conical devices based on their individual bearing areas. For the 5 and 8 pcf models, only two and three devices, respectively, fell outside the predicted pullout strength range by more than a standard deviation. The use of a synthetic sawbone model was validated against the pullout strength of an Arthrex Corkscrew in five fresh-frozen cadaver humeral heads. The bearing area of a suture anchor can be used to predict the pullout strength independent of design in a soft-bone model. This work helps provide a foundation to understand the principles that affect the pullout strength of suture anchors.

The Relationship between Glenoid Bone Density and the Pullout Strength of Suture Anchors

Background The use of suture anchors in glenoid labral reattachment is now routine in many shoulder procedures. However, debate still surrounds the biomechanical characteristics of suture anchors and the interplay with bone quality. Methods Eight embalmed cadaveric glenoids were investigated using a microCT and a tensile testing machine to study the correlation between the bone mineral density of four different regions on the glenoid rim and the pullout strength of the suture anchor. Six constructs failed by suture breakage whilst the remaining 25 positions suffered suture pullout. This study differed from previous investigations by using Orthocord, a much stronger suture material permitting better evaluation of bone properties. Results The mean failure load at pullout and suture compromise was 125 ± 40 N and 189 ± 25 N, respectively. The largest value of bone mineral density (BMD) was found at the posterior suture site, whilst the lowest occurred at the inferior edge of the anterior margin. For those constructs that failed by anchor pullout a significant correlation was observed between failure load and local bone mineral density (rPearson = 0.56, p = 0.004). Conclusion This relationship between local bone quality and pullout strength maybe a clinical indicator of the relative risk of failure following the suture repairs and warrants further exploration.

Patellar Tendon Repair With Suture Anchors Using a Combined Suture Technique of a Krackow-Bunnell Weave

Suture repair of the ruptured patellar tendon is the treatment of choice for patients requiring operative management. This standard technique includes fixation through transosseous tunnels in the patella. The use of suture anchor fixation has several advantages over the standard approach, including less dissection, decreased surgical time, more accurate suture placement, and a low-profile construct. Additionally, the pullout strength of suture anchors warrants consideration of this technique in these repairs. This article describes using suture anchors for repair of the acute ruptured patellar tendon with a combination of Krackow and Bunnell sutures.

Suture anchor fixation strength in osteopenic versus non-osteopenic bone for rotator cuff repair

Rotator cuff tears are increasing with age. Does osteopenic bone have an influence on the pullout strength of suture anchors? SPIRALOK 5.0 mm (DePuy Mitek), Super Revo 5 mm and UltraSorb (both ConMed Linvatec) suture anchors were tested in six osteopenic and six healthy human cadaveric humeri. Incremental cyclic loading was performed. The ultimate failure load, anchor displacement, and the mode of failure were recorded. In the non-osteopenic bone group, the absorbable SPIRALOK 5.0 mm achieved a significantly better pullout strength (274 N +/- 29 N, mean +/- SD) than the titanium anchor Super Revo 5 mm (188 N +/- 34 N, mean +/- SD), and the tilting anchor UltraSorb (192 N +/- 34 N, mean +/- SD). In the osteopenic bone group no significant difference in the pullout strength was found. The failure mechanisms, such as anchor pullout, rupture at eyelet, suture breakage and breakage of eyelet, varied between the anchors. The present study demonstrates that, in osteopenic bone, absorbable suture anchors do not have lower pullout strengths than metal anchors. In normal bone, the bioabsorbable anchor in this study even outperformed the non-absorbable anchor.

Pullout strength of suture anchors in comparison with transosseous sutures for rotator cuff repair

Suture anchors are increasingly gaining importance in rotator cuff surgery. This means they will be gradually replacing transosseous sutures. The purpose of this study was to compare the stability of transosseous sutures with different suture anchors with regard to their pullout strength depending on bone density. By means of bone densitometry (CT scans), two groups of human humeral head specimens were determined: a healthy and a osteopenic bone group. Following anchor systems were being tested: SPIRALOK 5.0 mm (resorbable, DePuy Mitek), Super Revo 5 mm (titanium, Linvatec), UltraSorb (resorbable, Linvatec) and the double U-sutures with Orthocord USP 2 (partly resorbable, DePuy Mitek) and Ethibond Excel 2 (non-resorbable, Ethicon). The suture anchors/double U-sutures were inserted in the greater tuberosity 12 times. An electromechanical testing machine was used for cyclic loading with power increasing in stages. We recorded the ultimate failure loads, the system displacements and the modes of failure. The suture anchors tended to bring about higher ultimate failure loads than the transosseous double U-sutures. This difference was significant in the comparison of the Ethibond suture and the SPIRALOK 5.0 mm-both in healthy and osteopenic bone. Both the suture materials and the SPIRALOK 5.0 mm showed a significant difference in pullout strength on either healthy or osteopenic bone; the titanium anchor SuperRevo 5 mm and the tilting anchor UltraSorb did not show any significant difference in healthy or osteopenic bone. There was no significant difference concerning system displacement (healthy and osteopenic bone) between the five anchor systems tested. The pullout strength of transosseous sutures is neither on healthy nor on osteopenic bone higher than that of suture anchors. Therefore, even osteopenic bone does not constitute a valid reason for the surgeon to perform open surgery by means of transosseous sutures. The choice of sutures in osteopenic bone is of little consequence anyway since it is mostly the bone itself which is the limiting factor.

Pullout Strength of Suture Anchors for the Rotator Cuff Repair: A Biomechanical Study

Pullout Strength of Suture Anchors for the Rotator Cuff Repair: A Biomechanical Study

Biomechanical Comparison of Suture Anchor Pullout Strength with Different Numbers of Sutures

Biomechanical Comparison of Suture Anchor Pullout Strength with Different Numbers of Sutures

Anchor Design and Bone Mineral Density Affect the Pull-Out Strength of Suture Anchors in Rotator Cuff Repair

Background Different metal and biodegradable suture anchors are available for rotator cuff repair. Poor bone quality may result in anchor loosening and tendon rerupture. Hypotheses Higher bone mineral density is associated with higher pull-out strength of suture anchors. Depending on anchor placement, pull-out strengths of anchors are different within the greater tuberosity. Study Design Cadaveric biomechanical study. Methods Trabecular and cortical bone mineral densities were determined for different regions within the greater tuberosity. Metal screw-type and biodegradable hook-type anchors were cyclically loaded. Results Mean failure load of metal and biodegradable anchors was 273 N and 162 N, respectively, for the proximal part (P < .01) and 184 N and 112 N, respectively, for the distal part (P < .01). Both types of anchors showed higher failure loads in the proximal-anterior and -middle parts of the greater tuberosity than in the distal part (P < .01). A significant positive correlation was found between cortical bone mineral density and failure load of metal anchors (P < .01). Conclusion Bone quality, anchor type, and anchor placement have a significant impact on anchor failure loads. Clinical Relevance Suture anchors should be placed in the proximal-anterior and -middle parts of the greater tuberosity. In the distal parts, biodegradable hook-like anchors should be used with caution.

The relationship of suture anchor failure and bone density to proximal humerus location: a cadaveric study.

The purpose of this study was to evaluate spatial variations in the pullout strength of a suture anchor in the proximal humerus, and to correlate any differences with the local mineral density (BMD). Screw-type suture anchors threaded with wire sutures were inserted at six different anchor insertion sites in 11 human cadaveric humeri (average age, 80 years). Load to failure tests with forces applied in line with the axis of insertion were performed, and bone mineral density measurements were then made at these sites. The greater tuberosity showed anterior and posterior differences in anchor pullout force (P = .03), with the posterior portion showing higher strength (154 N) than the anterior area (96 N). Neither the lesser tuberosity (185 N anterior area and 177 N posterior area) nor the humeral neck (170 N anterior and 174 N posterior area) showed significant differences, and they were statistically equivalent to the greater tuberosity. There was no demonstrable difference in BMD at any of the six sites tested. There is no support for the hypothesis that significant differences in load to failure exist among the lesser tuberosity, humeral neck, and greater tuberosity. Also, there is no support for the hypothesis that the load to failure variations for the proximal humerus are dependent on BMD. Bone mineral density appears to have no correlation with the pullout strength of a screw-type suture anchor.