Suture anchors are widely used to secure tendons and ligaments to bone during both arthroscopic and open surgery. However, single stage insertion suture anchors, i.e. anchors that could be inserted without predrilling of the bone, are not currently available. We aimed to record the impact needed for insertion of the new design single stage suture anchors, and to compare their pull out strength with another range of commercially available suture anchors. The force required to insert the new design of suture anchors was investigated using an impact hammer capable of recording the number and force of each of the hits. The anchors were inserted in a consistent manner into animal (porcine) bone at sites analogous to common anchor sites used in clinical practice. Pull out strength was assessed using a digital force gauge after tying the suture to create a secure loop. Thereafter, force was applied steadily until either the anchor or the suture failed and compared with a popular range of commercially available suture anchors (Mitek). Our initial investigations using prototype designs for small, medium and large anchors compared favourably with the Mini-mitek, GII, and Superanchor range of Mitek anchors. Essentially the most common point of failure for each of the suture anchor families was the suture itself with both suture anchor systems performing similarly. In addition, similar pull out strengths were demonstrated for both the Mitek and new design of suture anchors when loaded parallel, or at 90°, to the line of anchor insertion. The new design single stage suture anchors have an equivalent pull out strength compared with a popular commercially available family of suture anchors, but in addition have the significant advantage of being suitable for single stage insertion in many clinical settings

Aims. This study aimed to establish the optimal fixation methods for calcaneal tuberosity avulsion fractures with different fragment thicknesses in a porcine model. Methods. A total of 36 porcine calcanea were sawed to create simple avulsion fractures with three different fragment thicknesses (5, 10, and 15 mm). They were randomly fixed with either two suture anchors or one headless screw. Load-to-failure and cyclic loading tension tests were performed for the biomechanical analysis. Results. This biomechanical study predicts that headless screw fixation is a better option if fragment thickness is over 15 mm in terms of the comparable peak failure load to suture anchor fixation (headless screw: 432.55 N (SD 62.25); suture anchor: 446.58 N (SD 84.97)), and less fracture fragment displacement after cyclic loading (headless screw: 3.94 N (SD 1.76); suture anchor: 8.68 N (SD 1.84)). Given that the fragment thickness is less than 10 mm, suture anchor fixation is a safer option. Conclusion. Fracture fragment thickness helps in making the decision of either using headless screw or suture anchor fixation in treating calcaneal tuberosity avulsion fracture, based on the regression models of our study. Cite this article: Bone Joint Res 2023;12(8):504–511

To assess the current literature on suture anchor placement for the purpose of identifying factors that lead to suture anchor perforation and techniques that reduce the likelihood of complications. Three databases (PubMed, Ovid MEDLINE, EMBASE) were searched, and two reviewers independently screened the resulting literature. Methodological quality of all included papers was assessed using Methodological Index for Non-Randomized Studies criteria and the Cochrane Risk of Bias Assessment tool. Results are presented in a narrative summary fashion using descriptive statistics. Fourteen studies were included in this review. Four case series (491 patients, 56.6% female, mean age 33.9 years), nine controlled cadaveric/laboratory studies (111 cadaveric hips and 12 sawbones, 42.2% female, mean age 60.0 years), and one randomized controlled trial (37 hips, 55.6% female, mean age 34.2 years) were included. Anterior cortical perforation by suture anchors led to pain and impingement of pelvic neurovascular structures. The anterior acetabular positions (three to four o'clock) had the thinnest bone, smallest rim angles, and highest incidence of articular perforation. Drilling angles from 10° to 20° measured off the coronal plane were acceptable. The mid-anterior (MA) and distal anterolateral (DALA) portals were used successfully, with some studies reporting difficulty placing anchors at anterior locations via the DALA portal. Small-diameter (< 1 .8-mm) suture anchors had a lower in vivo incidence of articular perforation with similar stability and pull-out strength in biomechanical studies. Suture anchors at anterior acetabular rim positions (3–4 o'clock) should be inserted with caution. Large-diameter (>2.3-mm) suture anchors increase the likelihood of articular perforation without increasing labral stability. Inserting small-diameter (< 1 .8-mm) all-suture suture anchors (ASAs) from 10° to 20° using curved suture anchor drill guides, may increase safe insertion angles from all cutaneous portals. Direct arthroscopic visualization, use of fluoroscopy, distal-proximal insertion, and the use of nitinol wire can help prevent articular violation

Introduction. This study was performed prospectively and randomly to compare clinical outcomes of modified-Brostrom procedure using single and double suture anchor for chronic lateral ankle instability. Material & Methods. Forty patients were followed up for more than 2 years after modified-Brostrom procedure for chronic lateral ankle instability. Twenty modified-Brostrom procedures with single suture anchor and 20 procedures with double suture anchor randomly assigned were performed by one surgeon. The mean age was 30.6 years, and the mean follow-up period was 2.6 years. The clinical evaluation was performed according to the Karlsson scale and Sefton grading system. The measurement of talar tilt angle and anterior talar translation was performed through anterior and varus stress radiographs. Results. At the last follow-up, the Karlsson scale had improved significantly from preoperative average 45.4 points to 90.5 points in single suture anchor group, from 46.2 points to 91.3 points in double suture anchor group. There were 8 excellent, 10 good, and 2 fair results according to the Sefton grading system in single anchor group, and 9 excellent, 8 good, 3 fair results in double anchor group. Therefore, 18 cases (90%) in single anchor group and 17 cases (85%) in double anchor group achieved satisfactory results. Talar tilt angle had improved significantly from preoperative average 15.7° to 6.1° in single anchor group, from 16.8° to 4.2° in double anchor group. There was significant difference in postoperative talar tilt angle between single and double anchor group. Conclusion. Significant differences in clinical and functional outcomes were not found between single and double suture anchor technique. On stress radiographs for evaluation of mechanical stability, modified-Brostrom procedure using double anchor showed less talar tilt angle than single anchor technique

Restoring of anatomic footprint may improve the healing and mechanical strength of repaired tendons. A double row of suture anchors increases the tendon-bone contact area, reconstituting a more anatomic configuration of the rotator cuff footprint. We aimed to investigate if there were differences in clinical and imaging outcome between single row and double row suture anchor technique repairs of rotator cuff tears. We recruited 60 patients affected by a rotator cuff tear diagnosed on clinical grounds, magnetic resonance imaging evidence of cuff tear and inadequate response to nonoperative management, an unretracted and sufficiently mobile full-thickness rotator cuff lesion to allow a double row repair found at the time of surgery. In 30 patients, rotator cuff repair was performed with single row suture anchor technique (Group 1). In the other 30 patients, rotator cuff repair was performed with double row suture anchor technique (Group 2). 8 patients (4 in the single row anchor repair group and 4 in the double row anchor repair group) were lost at follow up. A modified UCLA shoulder rating scale was used to evaluate preoperative and postoperative shoulder pain, function and range of motion, strength and patient satisfaction. All patients received a post-operative MR arthrography at the final follow up appointment. At the 2 year follow-up, no statistically significant differences were seen with respect to the UCLA score and ROM values. Post-operative MR arthrography at 2 years of follow up in group 1 showed intact tendons in 14 patients, partial thickness defects in 10 patients and full thickness defects in 2 patients. In group 2, MR arthrography showed an intact rotator cuff in 18 patients, partial thickness defects in 7 patients, and full thickness defects in 1 patient. Biomechanical studies comparing single versus double row suture anchor technique for rotator cuff repair show that a double row of suture anchors increases the tendonbone contact area and restores the anatomic rotator cuff footprint, providing a better environment for tendon healing. Our study shows that there are no advantages in using a double row suture anchor technique to restore the anatomical footprint. The mechanical advantages evidenced in cadaveric studies do not translate into superior clinical performance when compared with the more traditionally, technically less demanding, and economically more advantageous technique of single row suture anchor repair

Introduction and Aims: To evaluate the technique of the knotless suture anchor for the treatment of anterior shoulder instability. Method: 109 patients were reviewed. Each patient underwent a standardised procedure by the same surgeon under a regional interscalene block and/or general anaesthesia. An average of three anchors were placed in the 3, 4 and 5 o’clock positions. 40 patients had additional thermal shrinkage to reduce excess capsular volume. Each patient was assessed using the Constant, Rowe and Walch-Duplay scores. Results: Follow-up period was 18 months, with an average of two years. The average operating time was one hour. Four patients (3.6%) redislocated following surgery. Two of these patients had a glenoid bone deficiency of > 20% and associated full thickness rotator cuff tears, one had an associated humeral avulsion of the glenohumeral ligament (HAGL) lesion, which was not repaired arthroscopically, and one had returned to contact sports as early as 12 weeks after surgery. Three patients had single episodes of subluxations that have not required revision. The average Rowe score was 90.8, average Constant score was 89.9 and the average Walch-Duplay score was 81.4. Conclusion: Early results indicate that capsulolabral reconstruction using the knotless suture anchor is an effective procedure in the treatment of post-traumatic anterior shoulder instability. The incorporation of a south to north capsular shift technique during labral reattachment reduces the necessity of additional thermal to reduce redundant capsular volume. Relative contraindications of this technique include; presence of a HAGL lesion, and anterior glenoid bone deficiency. The procedure may be performed as a day case under regional anaesthesia, has a high index of patient satisfaction and is an acceptable alternative to open surgery

Purpose: The use of a bioabsorbable suture anchor across a joint as a means of internal stabilization has not previously been described. This study assesses the iatrogenic damage caused by such a procedure in the normal immature porcine hip. Materials and Methods: Six twelve week old pigs underwent unilateral transarticular suture anchorage of the hip using a Panalok® RC Quick Anchor® Plus with Panacryl® suture. (Mitek® Products Johnson and Johnson). Anteroposterior pelvic radiographs were taken pre-operatively and six weeks post-operatively. Acetabular index, diameter of the femoral head ossific nucleus of both hips on both occasions were measured and compared. Pigs were sacrificed six weeks post-operatively. Specimens were analysed macroscopically for femoral head diameter, acetabular dimensions, and presence of gross chondrolysis. Histological analysis was performed to assess the presence of articular chondrolysis, and proximal femoral physeal arrest. Results: In four out of six hips the rate of change of the acetabular index slowed as compared to the unoperated side though none worsened. The diameter of the femoral ossific nucleus on the operated side continued to increase in size at a similar rate as the unoperated side, despite the surgical procedure according to radiographic comparison. Similar findings were made in the macroscopic analysis of the hip geometry. Gross and histological analysis of the articular cartilage show only local areas of chondrolysis related to the drill holes, and in one hip where a second hole was drilled, cartilage regeneration was noted. Metaphyseal growth at the proximal femoral physis was unaffected by the procedure. Conclusions: The use of a trans-articular suture anchor across the hip appears to cause marginal retardation of acetabular development in the normal hip. The procedure does not appear to affect proximal femoral physeal or epiphyseal growth and the presence of a bioabsorbable suture within the joint did not result in chondrolysis

Background: Arthroscopic stabilisation surgery for the shoulder remains a controversial choice of treatment for post traumatic anterior instability. We present the results of a consecutive initial series of 50 patients who were stabilised using a knotless labral repair technique. Methods: The study group included 41 men and 9 women with an average age of 26 years. 58% were affected on the dominant side. The average duration of preoperative syptoms was 3.8 years. 72% of patients had dislocations, whilst the remainder experienced subluxations. Each patient underwent a standardised procedure by the same surgeon with a regional interscalene block and/or general anaesthesia. Anchors were placed in the 3, 4 and 5 o’clock positions. Each patient was assessed using the Constant, Rowe and Walch-Duplay scores at an average of 18 months follow up (range 12–36 months). Results: At review 95% of shoulders remained stable. One patient had a true dislocation 6 months post surgery. One patient experienced a subluxation following a direct whilst skiing. 6 patients remained apprehensive. 3 patients had minor restriction of external rotation. The average Rowe score was 90.8, average Constant score was 89.9 and the average Walch-Duplay score was 81.4Conclusions: Early results indicate that capsulolabral reconstruction using the knotless suture anchor combined with a south to north capsular shift is an effective procedure in the treatment of post-traumatic anterior shoulder instability. This procedure may be performed as a day case under regional anaesthesia and is associated with a high index of patient satisfaction with a return to sporting activities

The behaviour of two different methods of reattachment of the flexor digitorum profundus tendon insertion was assessed. Cyclical testing simulating the first 5 days of a passive mobilisation protocol was used to compare the micro Mitek anchor to the modified-Bunnell pull-out suture. Twelve fresh-frozen cadaveric fingers were dissected to the insertion of the FDP tendon. The FDP insertion was then sharply dissected from the distal phalanx and repaired using one of two methods: group 1 -modified Bunnell pullout suture using 3/0 Prolene; group 2 micro Mitek anchor loaded with 3/0 Ethibond inserted into the distal phalanx. Each repaired finger was mounted on to a material testing machine using pneumatic clamps. We cyclically tested the repair between 2N and 15N using a load control of 5N/s for a total of 500 cycles. Gap formation at the tendon bone interface was measured every 100 cycles. No specimens failed during cyclical testing. After 500 cycles, gap formation of the tendon-bone interface was 6.6mm (SD = 1.2mm), and 2.1 mm (SD = 0.3mm) for the pullout technique and the micro Mitek anchor repair respectively. Concerns related to suture anchors, such as anchor failure or protrusion, joint penetration, and anchor-suture junction failure, were not encountered in this study. Cyclical loading results suggest that the repair achieved with both methods of fixation is sufficient to avoid failure. However, significant gap formation at the tendon-bone interface in the modified Bunnell group is of concern, suggesting it may not be the ideal fixation method

Arthroscopic stabilisation of the shoulder is a technically-demanding and developing technique, and the reported results have yet to match those for open surgery. We present a consecutive initial series of 55 patients with post-traumatic recurrent anteroinferior instability managed since September 1999 using a titanium knotless suture anchor. Patients were reviewed from 12–33 months postoperatively and assessed using the Rowe, Walch-Duplay and Constant scores. Following mobilisation of the capsulolabral complex, labral reconstruction was achieved using a two-portal technique and an average of three anchors placed on the glenoid articular rim. In 13 cases, additional electrothermal shrinkage was required to reduce capsular redundancy in the anterior and inferior recesses following labral repair, although 11 of these were in the first 18 months. Incorporation of a south-to-north capsular shift has reduced the need for supplementary shrinkage. Complications have included one instance of anchor migration requiring open retrieval and two documented episodes of recurrent instability, although these occurred in patients having surgery within the first six months after the introduction of this technique. Based on our initial experience, we believe that arthroscopic labral repair is a viable alternative to open Bankart repair and have now expanded the indications to include patients with primary dislocation, those participating in gymnastic and contact/collision sports, and revision cases with failed open repairs

One of the recently introduced anchors is the absorbable suture anchor BIOKNOTLESS-RC, a press-fit anchor whose special feature is the knotless reconstruction of the ruptured rotator cuff. We compared the new knotless anchor BIOKNOTLESS-RC with established anchors. The absorbable pressfit anchor BIOKNOTLESS-RC (DePuyMitek, Raynham, MA, USA), the titanium screw anchor SUPER-REVO 5mm and the tilting anchor ULTRASORB (both ConmedLinvatec, Largo, FL, USA) were tested 12 times in the greater tuberosity of human cadaveric humeri (mean age: 74 years). They were inserted according to the manufacturers instructions with the supplied suture material. An incremental cyclic loading was performed, starting with 75N. Until failure the tensile load was increased by 25N after every 50 cycles. The ultimate failure loads, the anchor displacements and the modes of failure were recorded. The anchor displacement of the BIOKNOTLESS-RC (15.3mm) after the first cycle with 75N was significantly higher than with the two others (SUPER-REVO 2.1mm, ULTRASORB: 2.7mm). The ultimate failure loads of the tested anchors were comparable: BIOKNOTLESS-RC 150N, SUPER-REVO 150N, ULTRASORB 151N (p> 0,05). Rupture of the suture material at the eyelet occurred more frequently with the SUPER-REVO. BIOKNOTLESS-RC and ULTRASORB showed a tendency towards anchor pullout. Our results do not confirm the higher pullout strength of metal anchors, which was found in other studies. Knotless anchors facilitate surgery by eliminating the technically challenging step of arthroscopic knot tying. The disadvantage of the BIOKNOTLESS-RC is its unsatisfactory primary stability. Its initial displacement of a mean of 15.3 mm is clinically significant and jeopardizes the rotator cuff repair. Because of the high initial displacement and the possible gap formation between tendon and bone, the use of the BIOKNOTLESS-RC in a zone of minor tension, for instance as a second-row anchor in double row technique only is recommend

Research in to tendon-bone healing techniques focus on increasing bone growth at the interface such as cell or growth factor (e.g. BMP-2) augmentation. Demineralised bone matrix (DBM) is osseoinductive and is in use clinically. Hypothesis: DBM augmentation of a healing tendon-bone interface will result in improved function at 3, 6, 9 and 12 weeks, and a morphology that more closely resembles that of a normal enthesis at 12 weeks. Materials and methods: An ovine patellar tendon model was used. 19 skeletally mature ewes were allocated to the control group or DBM group. In both groups the patellar tendon was detached, and following tibial tubercle osteotomy, was re-attached using 3 suture anchors. In the DBM group a piece of DBM was placed between the tendon and bone. 2 animals were sacrificed at 6 weeks and 6 animals at 12 weeks. Animals underwent force plate analysis at 3, 6, 9 and 12 weeks. The tendon-bone interface length which was fibrous or fibrocartilaginous, and the area of fibrocartilage, mineralised fibrocartilage and new bone was quantified. Results: 3 control group animals (33%) failed within 6 weeks. None failed in the DBM group. The DBM group was significantly better than the control at all time points (p< 0.05). DBM produced a significantly more fibrocartilaginous enthesis than the control group (p< 0.05). Controls were significantly more fibrous than the DBM group (p< 0.05). DBM produced significantly more fibrocartilage (p< 0.05), and mineralised fibrocartilage (p< 0.05). Discussion: 33% of the control group failed within 6 weeks, whilst no failures were observed in the DBM group. DBM animals mobilised earlier and had significantly better function at all time points. Histologically, the DBM group showed a more mature direct type enthesis at earlier time points. Conclusion: DBM augmentation of a healing tendon-bone interface enhances functional and morphological recovery at earlier time points

Suture anchor have been used in surgical procedure of tendon or ligament repair. Recently, there has been developed an all suture anchor (soft anchor) which can be used even when the insertion area is narrow. But, the stability of soft anchors due to narrow zone has not been elucidated. This purpose of this study was to investigate stability of soft anchors with respect to their fixation intervals. Polyurethane foams with two different bone densities (10 pcf; 0.16g / cm³, 20 pcf; 0.32g / cm³) were used. All suture anchors and conventional suture anchors were fixed at 10mm, 5mm, and 2.5mm intervals. The failure load was measured using a mechanical testing machine. The average load to failure of conventional suture anchor were 200.4N, 200.2N, 184.7N in the 10mm, 5mm and 2.5mm interval with 10pcf foam bones and 200.4 N, 200.2 N and 184.7 N with the 20 pcf foam bone respectively. Average load to failure load of soft anchor was 97.3N, 93.9N and 76.9N with 10pcf foam bones and 200.4 N, 200.2 N and 184.7 N with 20 pcf foam bone. Suture screw spacing and bone density are important factors in anchor pullout strength. In osteoporotic bone density, insertion of the suture screw interval of 5 mm might be necessary

Introduction. Suture anchor have been used in surgical procedure of tendon or ligament repair. Recently, there has been developed an all suture anchor (soft anchor) which can be used even when the insertion area is narrow. But, the stability of soft anchors due to narrow zone has not been elucidated. This purpose of this study was to investigate stability of soft anchors with respect to their fixation intervals. Methods. Polyurethane foams with two different bone densities (10 pcf; 0.16g / cm³, 20 pcf; 0.32g / cm) were used. All suture anchors and conventional suture anchors were fixed at 10mm, 5mm, and 2.5mm intervals. The failure load was measured using a mechanical testing machine. Results. The average load to failure of conventional suture anchor were 97.3N, 93.9N, and 76.9N in the 10mm, 5mm and 2.5mm interval with 10pcf foam bones and 200.4 N, 200.2 N and 184.7 N with the 20 pcf foam bone respectively. Average load to failure load of soft anchor was 97.3N, 93.9N and 76.9N with 10pcf foam bones and 200.4 N, 200.2 N and 184.7 N with 20 pcf foam bone. Conclusion. Suture screw spacing and bone density are important factors in anchor pullout strength. In osteoporotic bone density, insertion of the suture screw interval of 5 mm might be necessary

Rotator cuff tendons are typically reattached to the proximal humerus using either transosseous sutures or suture anchors. Their primary mode of failure is at the tendon bone interface 1. Surgical adhesives are used to bond cartilage, tendons and bone, and to close wounds. In an attempt to increase the tendon-bone interface we investigated the addition of a novel adhesive secreted from a species of Australian frog (Notaden bennetti) 2 to different methods of rotator cuff repair. Forty two fresh frozen sheep infraspinatus tendons were repaired using 3 different techniques: transosseous sutures; two Mitek RC Quickanchors with 1 suture per anchor and two Opus Magnum anchors with 1 suture per anchor all using a mattress stitch configuration. In each group 7 shoulders were repaired with the addition of a small amount of frog glue to the infraspinatus footprint while 7 were used as control with no adhesive. Mechanical testing was performed using a mechanical tensile testing machine. The strongest construct in the control groups was the Mitek suture anchors (mean 86±5 N) followed by the Opus suture anchor (69±6N) and transosseous repair (50±6N). This proved significant (p< 0.05) between both metallic anchors and the transosseous repair.{BR}The addition of frog glue resulted in a significant increase in load to failure and total energy required until failure in all repair techniques (p< 0.01). There was a 2 fold increase in load to failure of both the Opus Magnum (143±8N) and Mitek RC Fastin (165N±20 N) anchors while the transosseous repair (86± 8 N) had a 1.7 fold increase in its load to failure. This data suggests that:. suture anchor fixation is a stronger construct requiring a larger amount of total force to fail than transosseous repair using a one suture repair technique, that. the addition of an adhesive to the tendon-bone interface significantly enhances both ultimate load and total energy required to failure in all repair types. The unique properties of this frog glue (strong, flexible, sets in water and biocompatibility) may ultimately lead to the production of a useful adjunct for rotator cuff repair in humans

The purpose of this study was to assess the clinical outcomes of three different rotator cuff repair techniques and to correlate these results with the integrity of the cuff as determined by ultrasonographic evaluation. Three cohorts of patients had repair of a symptomatic rotator cuff tear using:. an open technique with Mitek RC Quickanchor double row, one mattress suture per anchor (n = 49);. arthroscopic knotted Mitek RC Fastin single row, two simple sutures per anchor (n = 53);. arthroscopic knotless with Opus Magnum single row, one inverted mattress suture per anchor (n = 57) by one surgeon. Standardised patient and examiner determined outcomes were obtained prospectively pre-operatively and at 6 weeks, 3 months and 6 months post-operatively. Ultrasound studies were performed with a validated protocol at 6 months post surgery. Arthroscopic knotless repair was, on average,14 minutes faster than both open cuff repair (p< 0.001) and arthroscopic knotted repair (p< 0.01).Clinical outcomes were similar with the exception that the arthroscopic groups had, on average, 20% better ASES scores than the open group at 6 months (p< 0.001). The only complication was re-tear, which correlated with tear size (r=0.5, p< 0.001) and operation time (r=0.3, p< 0.001) and occurred more frequently following open repair (39%) compared with arthroscopic knotted (25%) and arthroscopic knotless (16%) repair (p< 0.01). The retear rates of tears > 8cm2 were significantly greater (p< 0.01) when using an open (88%) or arthroscopic knotted (67%) technique compared to the arthroscopic knotless (25%) cohort. Rotator cuff repair, whether performed via an open or arthroscopic technique resulted in improvements in pain, motion, strength and function. An intact cuff on ultrasound corresponded to better results with regard to supraspinatus strength, patient outcomes and rotator cuff functional ability. Tears > 8cm2 fixed with an arthroscopic knotless technique had better structural outcomes at 6 months

The study objective was to assess if the mechanical properties of Polylactic Acid (PLA) bio-absorbable suture anchors vary with temperature? Bio-absorbable suture anchors may offer advantages over metal anchors. However, their performance at body temperature has been questioned in recent literature (Meyer et al). In particular, constant tension at body temperature caused early failure at the anchor eyelet. Using a previously validated mechanical jig, 15 standard locked sliding arthroscopic knots (Duncan Loop + three alternate hitches) were tied by the senior author using PAN-ALOK anchors (DEPUY MITEK, Edinburgh, UK) and ETHIBOND sutures (ETHICON) and placed under a standard constant tensile load reproducing the action of the surgically repaired rotator cuff. All anchors were loaded for at least five days to match previous studies. Eight were incubated at a constant 37°C and six were kept at room temperature. The elongation of the suture knot/anchor construct was assessed by a rheostat within the mechanical jig. Sample unused, room temperature and body temperature anchors were blindly analysed using plane polarized light microscopy with a graticule to assess deformation, concentrating on the eyelet region. Mean elongation of body temperature anchors = 0.461mm (0.159 – 0.952) Mean elongation of room temperature anchors = 0.278mm (0.159 – 0.793) Unpaired t-test: p=0.24 Microscopic analysis of the anchor material showed no difference in structural deformation in the three anchors. Our model suggests no significant increase in elongation at body temperature for this commonly used arthroscopic suture anchor / knot construct. This counters previous work. It gives us confidence to continue to use such devices

The incidence of rotator cuff tears increases with age, thus the rotator cuff tear is often associated with osteoporotic or osteopenic bone in the proximal humerus, especially with female patients. For testing of fixation devices such as suture anchors used in rotator cuff repair often animal bones are used. They are easily to obtain, inexpensive and some have been found to be similar to human bone. But can we rely on the results drawn from these studies in our daily surgical practice?. The purpose of this study was to compare the trabecular bone mineral density, the trabecular bone volume fraction and the cortical layer thicknes in the greater tubercle in different species to evaluate their infiuence on primary stability of suture anchors under a cyclic loading protocol representing the physiologic forces placed on rotator cuff repairs in vivo. We hypothezised that maximum pullout forces as well as the modes of failure are different for a suture anchors in different humeri. The available three different types of anchor fixation design (screw: Spiralok 5mm, Super Revo 5mm, press-fit: Bioknotless RC, wedging: Ultrasorb) were tested. The bone mineral density (BMD) of the humeri was measured by a 64-slice-computed tomography system. Each anchor was tested individually until failure. The sutures were pulled at 135° to the axis of the humeral shaft, simulating the physiological pull of the supraspinatus tendon. Starting with 75 N the tensile load was gradually increased by 25 N after everey 50 cycles until failure of the anchor fixation system occurred. The ultimate failure load, the system displacement after the first pull with 75 N and the mode of failure were recorded. The ultimate failure loads of each anchor were different in the human osteopenic, human healthy, ovine and bovine humeri. The statistical significancies for pull out forces between the anchors varied from species to species. The biomechanical testing of suture anchors for arthroscopic rotator cuff repair in ovine and bovine humeri does not give reliable data that can be transferred to the human situation. The significances between the suture anchors found in ovine and bovine humeri are different from the results in human humeri. When taking the impaired bone quality of older patients into account the results from ovine and bovine humeri are even less predictable. We found a positive correlation between maximum failure load and cortical layer thickness for the Super Revo and the Ultrasorb anchor. The ultimate failure load seems to depend mainly on the cortical thickness and on the subcortical trabecular bone quality

Suture anchors have gained popularity in recent years, particularly owing to their ease of use for attaching soft tissues to bone and improved biomechanical properties. Three methods to reattach avulsed finger flexor tendons to the distal phalanx were biomechanically compared: a 1.8mm metal Mitek barbed suture anchor, twin 1.3mm PLA suture anchors (Microfix), or a pull-out suture over a button. The suture-anchor interface was tested by pulling the suture at 0, 45, 90° to the anchor's axis. The anchors were tested similarly in plastic foam bone substitute. Repairs of transected tendons in cadaveric fingers were loaded cyclically, then to failure. The results were subject to statistical analysis using Student t test (p< 0.001) and 1-way ANOVA (p<0.0001). The suture failed prematurely if pulled across the axis of the anchor. Conversely, fixation in bone substitute was stronger when pulling at an angle from the axis. Cyclic loads caused significantly more gap formation in-vitro with twin 1.3mm anchors than the other methods; this method was significantly weaker. The 1.8mm anchor gave similar performance to the pull-out suture and button, while the twin 1.3mm anchors were weaker and vulnerable to gap formation even with passive motion alone. A suture anchor embedded at between 45 and 90o to the direction of pull gave greater strength than if the pull was in-line. The absorbable 1.3 mm Microfix PLA anchors appeared to be a weak construct, even when twin 1.3 mm anchors were compared to a single metallic 1.8 mm Mitek anchor or the pull-out suture over button technique. All three methods are likely to be satisfactory for reattachment of finger flexor tendons if a low load or non-loading rehabilitation of the hand is planned; however the gap formation on cyclic loading with the Microfix is a concern even if patients are restricted to passive motion

Rotator cuff tears are a common cause of shoulder pain and dysfunction. Therefore, the purpose of this in-vitro biomechanical study was conducted to determine the effects of simulated tears and subsequent repairs of the rotator cuff tendons on joint kinematics. Eight paired fresh-frozen cadaveric shoulder specimens (mean age: 66.0 ± 8.7 years) were tested using a custom loading apparatus designed to simulate unconstrained motion of the humerus. Cables were sutured to the rotator cuff tendons and the deltoid. Loads were applied to the cables based on variable ratios of electromyographic (EMG) data and average physiological cross-sectional area (pCSA) of the muscles. An electromagnetic tracking device (Flock of Birds, Ascension Technologies, VT) was used to provide real-time feedback of abduction angle, to which the loading ratio was varied correspondingly. 2 and 4cm tears were made starting at the rotator cuff interval and extending posteriorly. Specimens were randomised to receive either single or double suture anchor repair. In order to quantify repeatability, five successive tests on each of the intact, torn, and repaired cases were performed. Statistical significance was established using One- and Two-way Repeated Measured ANOVAs (p< 0.05). Rotator cuff tears caused alteration in glenohumeral kinematics. A 2cm tear caused the humerus to consistently move posterior through the arc of abduction; however, as the tear increased to 4cm the humerus moved anteriorly, returning towards the intact state. Double row suture anchor repairs more accurately reproduced the kinematics of the intact specimen compared to single row suture anchor repair. The initial posterior displacement in the plane of elevation with the sectioning of the supraspinatus is related to the diminished anterior moment on the glenohumeral joint. As the tear proceeds into the infraspinatus, the anterior and posterior forces become more balanced and a return to near normal intact kinematics was observed. This study demonstrates that double row suture anchor repair more accurately reproduces active shoulder kinematics of the intact shoulder specimens