The diagnosis of infection following shoulder arthroplasty is notoriously difficult. The prevalence of prosthetic shoulder infection after arthroplasty ranges from 3.9 – 15.4% and the most common infective organism is Cutibacterium acnes. Current preoperative diagnostic tests fail to provide a reliable means of diagnosis including WBC, ESR, CRP and joint aspiration. Fluoroscopic-guided percutaneous synovial biopsy (PSB) has previously been reported in the context of a pilot study and demonstrated promising results. The purpose of this study was to determine the diagnostic accuracy of percutaneous synovial biopsy compared with open culture results (gold standard).

This was a multicenter prospective cohort study involving four sites and 98 patients who underwent revision shoulder arthroplasty. The cohort was 60% female with a mean age was 65 years (range 36-83 years). Enrollment occurred between June 2014 and November 2021. Pre-operative fluoroscopy-guided synovial biopsies were carried out by musculoskeletal radiologists prior to revision surgery. A minimum of five synovial capsular tissue biopsies were obtained from five separate regions in the shoulder. Revision shoulder arthroplasty was performed by fellowship-trained shoulder surgeons. Intraoperative tissue samples were taken from five regions of the joint capsule during revision surgery.

Of 98 patients who underwent revision surgery, 71 patients underwent both the synovial biopsy and open biopsy at time of revision surgery. Nineteen percent had positive infection based on PSB, and 22% had confirmed culture positive infections based on intra-operative tissue sampling. The diagnostic accuracy of PSB compared with open biopsy results were as follows: sensitivity 0.37 (95%CI 0.13-0.61), specificity 0.81 (95%CI 0.7-0.91), positive predictive value 0.37 (95%CI 0.13 – 0.61), negative predictive value 0.81 (95%CI 0.70-0.91), positive likelihood ratio 1.98 and negative likelihood ratio 0.77.

A patient with a positive pre-operative PSB undergoing revision surgery had an 37% probability of having true positive infection. A patient with a negative pre-operative PSB has an 81% chance of being infection-free. PSB appears to be of value mainly in ruling out the presence of peri-prosthetic infection. However, poor likelihood ratios suggest that other ancillary tests are required in the pre-operative workup of the potentially infected patient.

This study evaluated the impact of smoking on the surgical outcome of rotator cuff repair controlling for age, gender, and size of tear.

Two hundred and fifty patients were evaluated by a blind evaluator and by self report (SST and WORC questionnaires) at baseline and one year post-op. Types of cuff repair included arthroscopic, mini-open and open procedures. Smoking status was evaluated as a current smoker, quit, or never smoked. Smoking history was subsequently dichotomised into smoker and non-smoker. Generalised linear modeling was used to determine the impact of smoking on surgical outcome using age, gender, and tear size as covariates.

The mean age of the population used was 56+/−11 years in which 70% were males and 30% females. Tear size was distributed amongst this population as small (0–1 cm {44.9%}), moderate (1–3cm {22.7%}), large (3–5cm {15.2%}) and massive (5+cm {17.2%}). All preliminary analyses indicated gender affected tear size and surgical outcomes, and was also associated with smoking status. Due to this confounding effect, males and females were separated for subsequent analysis. The SST questionnaire found smoking to have a significant negative effect on the 1-year l outcomes of males (8.5 vs. 6.1 p=0.025). A similar trend was seen with the WORC (p=0.07). No significant effects were seen for females, but the sample size was underpowered.

Analysis of this population of rotator cuff repairs showed complex interrelationships may exist between gender, age, physical demands and smoking status. The existence of these confounding interrelationships may explain the mixed results seen in the literature concerning smoking and orthopedic procedures. This relatively large cohort established a negative impact of smoking on outcome, after controlling for covariates and confounders. Future research on mediators of cuff outcome should consider potential confounders. Conclusion: Smoking negatively effected surgical outcomes for males but was inconclusive for females. Sex behaved as a confounding variable that masked the smoking effects.

Hemiarthroplasty has been accepted as a viable alternative in the treatment of painful arthritis due to massive rotator cuff failure in patients with well-preserved functional active forward elevation of the shoulder. Unfortunatley, the early clinical results and long-term durability of hemiarthroplasty for rotator cuff tear arthropathy (RCTA) have been inferior to those seen in other disorders, most notably concentric osteoarthritis. Concern regarding the potential need for revision to a reverse shoulder arthroplasty has given rise to the notion of a resurfacing prosthesis as a primary procedure rather than a traditional stemmed-hemiarthroplasty in the hopes of reducing procedural and postoperative complications.

Eleven resurfacing humeral arthroplasties (Global CAP, Depuy) were performed for RCTA as a primary arthroplasty. There were six males and five females, average age of 74.7 years. 36% had undergone previous surgery on the affected side. All had failed a minimum of one year of non-operative treatment prior to surgery. Follow-up averaged eight months (range 4–12).

Prospective mean data analysis showed an improvement in all scales from preoperative baseline levels inclusive of the SST (3.5–6), ASES assessment form (8–17.5), Constant score (49–79) and the DASH (50–27). Mean active forward elevation remained relatively unchanged (one hundred and nine to one hundred degrees), while mean active external rotation improved (thirty-three to fifty-four degrees). Mean computerised muscle testing showed improvement in both elevation (5.1–7.7 N/m) and external rotation strength (2.6–5 N/m). Radiographic analysis has not shown any evidence of implant loosening to date.

Resurfacing humeral arthroplasty seems to demonstrate early favorable clinical results in this group of patients with RCTA. This may serve as an alternative to a stemmed-hemiarthroplasty in these patients and possibly result in a less complicated revision to a reverse prosthesis in the future should this be deemed necessary. Given these results are early, ongoing clincal followup will be necessary to define the longer-term durability of this procedure.

This study evaluated the impact of surgical wait-list times on the functional status and productivity of patients with rotator cuff tear

Two hundred and five patients were evaluated by a blind evaluator and by self report when referred for surgical management of cuff tear (confirmed by ultrasound or MRI). Patients were assessed on a monthly basis prior to surgery (two year limit). ROM and strength were assessed by an independent evaluator; patient’s self-reported comorbidity, functional status (WORC, SST), work limitations (WLQ-26) and work lost-time. Changes in health status were assessed using repeated measures ANOVA and GLM.

The mean age of the population used was 56+/−11 years in which 74% were males and 26% females. Tear size was distributed amongst this population as small (0–1 cm {45%), moderate (1–3cm 27%), large (3–5cm 23.2%) and massive (5+cm 15%). Patients had symptoms or an average of fourteen months prior to referral. Despite this, decline in strength (p mental demands) (output demands > time management demands). Loss in productivity exceeded 15%.

Rotator cuff tear causes substantial at work-limitation and work lost time. Patients lost strength and declined in functional status while waiting for surgical repair of a torn rotator cuff. The burden of illness, while waiting for cuff repair its substantial.

We compared the initial strength of two techniques for repair of rotator cuff tears. Eight paired cadaveric shoulders with a standardized supraspinatus defect were studied. A transosseous suture and anchor repair was conducted on each side. Specimens were tested under cyclic loading, while fixation was monitored with an optical tracking technique. Mode of failure, number of cycles and load to failure were measured for 50% (5 mm) and 100% (10 mm) loss of repair. Anchors provide improved repair strength at 50% repair loss, in comparison to sutures (p< 0.05). Strength was unaffected by bone mineral density, age and gender.

The purpose of this study was to compare the initial strength of two rotator cuff repair techniques.

Repair strength with anchors was superior to sutures. Strength was unaffected by bone quality.

Anchors, enabling a quicker, less invasive arthroscopic repair, offer improved fixation over sutures, which are more time consuming and invasive.

Eight paired shoulders with a standardized supra-spinatus defect were randomized to anchor or suture repair, and subjected to cyclic loading. Repair migration was measured using a digital camera. Failure mode, cycles and load were measured for 50% and 100% loss of repair. Results were correlated with bone mineral density, age and gender.

The anchors failed at the anchor-tendon interface, whereas the sutures failed through the sutures. Mean values for 50% loss of repair were 205.6 ± 87.5 cycles and 43.8 ± 14.8 N for the sutures, and 1192.5 ± 251.7 cycles and 156.3 ± 19.9 N for the anchors (p< 0.05). The corresponding values for 100% loss of repair were 2457.5 ± 378.6 cycles and 293.8 ± 27.4 N for the sutures, and 2291.9 ± 332.9 cycles and 262.5 ± 28.0 N for the anchors (p> 0.05). These results did not correlate with bone quality.

This study has demonstrated that anchors provide improved repair strength, in comparison to sutures. This may be due to the relative less deformability of the anchors. Repair strength did not correlate with bone quality. This may be attributed to each repair failing primarily through the repair construct or at the anchor-tendon interface, and not through bone.

This cohort study reports outcomes of patients with comminuted radial head fractures treated with a modular radial head arthroplasty. Twenty-six patients (mean age = fifty-four) were prospectively followed at three, six, twelve, and twenty-four months following surgery. Patient satisfaction with this procedure was high. This data indicates favorable results using a modular radial head arthroplasty with rapid improvement in disability and physical impairment occurring in all measures in the first six months and further improvement in most patients up to two years. The Mayo Elbow Performance Index was at one year and eighty-four at two years.

To investigate the objective and subjective outcomes of unreconstructable radial head fractures treated with a modular radial head arthroplasty.

This data indicates favorable results using a modular radial head arthroplasty with improvement in satisfaction, disability and physical impairment occurring in all measures in the first six-months and continued improvement for up to two-years.

Comminuted radial head fractures are challenging to treat with ORIF. Radial head arthroplasty is an alternative treatment that compares favorably to reported results for ORIF of similar fractures.

Significant improvements were noted over time in self-reported and measured impairments as follows: ASES pain: baseline = 30/50, two years = 15/50; ASES function: baseline = 5/36, two years 27/36; MEPI one year = eighty-two, two years = eight-four. At two years, little impairment was observed compared to the unaffected side in grip 22/26 kg, flexion 141°/145°, or pronation 74°/79°. Moderate differences were noted in extension 28°/2°, supination 57°/72° and strength measures: extension = 29/38, flexion = 31/40, supination = 43/65, pronation = 37/53 (Nm). Patient satisfaction was high at three months (9/10) and remained high at two years (9.1/10).

A cohort of twenty-six patients (seventeen female, mean age fifty-four) with non-reconstructable radial head fractures was treated using a modular metallic radial head arthroplasty (Evolve TM, Wright Medical Technology, Arlington, TN). All patients were prospectively followed at three, six, twelve and twenty-four months. Self-report of limb function, general health, measured ROM and isometric strength were assessed by an independent observer.

Funding Institution research foundation support was provided by Wright Medical Technology. None of the authors received direct compensation for commercial products related to the content of this study.

Purpose: This in-vitro study was conducted to assess the effect of a computer-assisted method of performing shoulder hemiarthroplasty, in comparison to traditional techniques, on passive glenohumeral joint kinematics during abduction.

Methods: Seven pairs of fresh-frozen cadaveric shoulders were tested. One specimen from each pair was randomized to the computer-assisted technique, while the contralateral shoulder underwent a traditional hemiar-throplasty using standard surgical guides by an experienced shoulder surgeon. A simulated four-part proximal humerus fracture was created in each shoulder and was reconstructed using a modular shoulder hemiarthroplasty system (Anatomical Shoulder Hemiarthroplasty System, Centrepulse Orthopaedics Inc, Austin, TX). CT data and computerized simulations of anatomical characteristics were used in the computer-assisted technique. An electromagnetic tracking device (Flock of Birds, Ascension Technologies, Burlington, VT) in conjunction with custom-written software (LabVIEW, National Instruments, Austin, TX) enabled real-time intra-operative feedback.||Passive abduction of the glenohumeral joint was conducted and the resulting motion was quantified using the aforementioned tracking device. Coordinate systems, created on both the humerus and scapula from digitized anatomical landmarks, were used to transform the kinematic data into clinically relevant parameters. Statistical analyses were performed using one-way Analyses of Variance (ANOVAs) followed by post-hoc Student-Newman-Keuls multiple comparisons (p< 0.05).

Results: In the superior-inferior direction, a significant difference in joint kinematics (p=0.011) was found between the computer-assisted and the traditional technique, with the traditional technique resulting in a more inferiorly positioned humeral head at all angles of elevation. There was no difference in translation between the native shoulders and the computer-assisted hemiarthroplasty (p> 0.05). In the anterior-posterior direction there was no difference measured in the position of the humeral head between the two surgical techniques, which were both similar to the native shoulder (p> 0.05).

Conclusions: This is the first known study to examine the effects of a computer-assisted method for performing shoulder hemiarthroplasty. Our results show that the computer-assisted approach should allow improved restoration of glenohumeral joint kinematics relative to conventional techniques, potentially resulting in improved patient outcomes and implant durability.

Purpose: Glenoid replacement remains challenging due to the difficult visualization of anatomical reference landmarks and highly variable version angles. Improper positioning of the glenoid component leads to loosening, early wear, and instability. The objective of this study was to develop and evaluate a tracking system for glenoid implantation. We hypothesized that Computer Assisted Glenoid Implantation (CAGI) would achieve a more accurate and reliable placement of the glenoid component compared to traditional methods.

Methods: 3D CT models of sixteen paired cadaveric shoulder specimens were reconstructed and angles were measured using 3D modeling softwares. Jigs were developed to track instruments and to correct for scapular motion. A standardized protocol for determining in real-time via electromagnetic tracking the glenoid centre, version, inclination and ultimate component placement was previously developed and validated in our laboratory. Specimens were randomized to either traditional or CAGI performed by one of two blinded fellowship trained shoulder surgeons. The mean age was 67 years (range 61–88). Native version and inclination were similar in both groups. All phases of glenoid implantation were navigated.

Results: CAGI was more accurate in achieving the correct version during all phases of glenoid implantation (p < 0.05; paired t-test). CAGI CONTROL Initial pin * 6.3 ± 2.9° Reaming *7.0 ± 3.9° Post drilling * 0.6 ± 0.4° 8.3 ± 4.6°|Post cement * 2.3 ± 2.0° 7.9 ± 3.6°|Post implant CT * 1.8 ± 0.9° 7.7 ± 4.0°. Table 1. Absolute values of the mean error ± SD of version angles obtained with either CAGI or the traditional method (goal = 0° version; * p < 0.05). The largest errors with traditional were observed during drilling and reaming where visualization was especially obscured by the reamer heads. The trend was to retrovert the glenoid. There was no difference with respect to inclination angles (p > 0.05).

Conclusions: Preoperative planning using CT imaging with 3D modeling and intra-operative tracking were combined to produce improved accuracy and reliability of glenoid implantation.

Funding : Other Education Grant

Funding Parties : National Sciences & Engineering Research Council research grant

Twenty fresh-frozen clavicles were fractured and randomized to one of four fixation techniques. Three plates were used: the LCP (locking compression plate), LCDCP (low contact dynamic compression plate) and Recon (pelvic reconstruction plate). One intramedullary device was used (the Rockwood Clavicle Pin). The constructs were tested for stiffness in bending and torque modes and ultimate strength in bending. The three plates were significantly stiffer then the Pin. Of the three plates, the Recon was significantly less stiff and weaker in ultimate strength then the LCP and LCDCP plates.

This study was conducted to compare and evaluate different fixation techniques for clavicle fractures.

Plate fixation with LCP (locking compression plate), LCDCP (low contact dynamic compression plate) and Recon (reconstruction plate) is stiffer then Pin fixation. The Recon plate was weaker and less stiff then the other two plates.

Fractures of the clavicle are common and account for approximately 5–10% of all fractures and represent 35–45% of shoulder girdle fractures. Open reduction, internal fixation is becoming a standard for more clavicle fractures with the recognition of the limitations of non-operative management. There is a great disparity in biomechanical literature on clavicle fixation.

The average bending stiffness compared to the intact clavicles for each construct was: Recon=104%, LCDCP=124%, LCP=122%, and Pin=69%. The average torque stiffness for each construct was: Recon=83%, LCDCP=91%, LCP=99%, and Pin=46%. The three plate constructs provided significantly more rigid fixation in both bending and torque testing then the clavicle pin (p< 0.05). Ultimate bending strength for each construct was: Recon=8.5 Nm, LCDCP=21.3 Nm, LCP=21.8 Nm, and Pin=15.8 Nm. The Recon plate was significantly weaker the three other constructs (p< 0.05).

Twenty fresh frozen cadaver clavicles were randomized to one of the four fixation groups. An Instron materials testing machine was used to compare the fixation constructs. Each clavicle was tested for its bending and torque stiffness. Following construct stiffness testing, all samples were brought to their ultimate failure strength with a superior bending load.

This study has shown that plate fixation of clavicle fractures yields stiffer constructs then pin fixation. However, plate fixation requires extensive dissection and stripping of the periclavicular soft tissue and may result in prominent hardware. In fracture situations with significant comminution, the LCP and LCDCP offer significantly greater fracture fixation then the reconstruction plate.

Funding: No external funding was received from a commercial party. Implants were donated by Synthes Canada and Depuy Canada.

This study prospectively evaluated the functional outcome and strength of patients after rotator cuff surgery. Thirty-three patients were evaluated pre-operatively and post-operatively for one year. Each patient underwent clinical evaluation of shoulder range of motion and machine strength testing. Additionally they completed the SF-36, DASH, Western Ontario Rotator Cuff, and Washington Simple Shoulder Test questionnaires. The study showed that patients with small and large tears showed improvement after surgery. Smaller tears had better outcomes. Workplace Safety and Insurance Board (WSIB) patients had lower functional outcomes despite strength and range of motion showing no difference with non- WSIB patients.

This study prospectively evaluated strength and functional outcome after rotator cuff surgery.

Thirty-three patients, mean age 55.6, were evaluated pre-operatively and post-operatively for one year. Twenty-eight patients were male and five were female. Seventeen patients involved the Workplace Safety and Insurance Board and sixteen patients had non-WSIB related tears. The patients were also divided based on tear size into two groups (< 3cm and > 3.1cm). Allpatients underwent an acromioplasty. Twenty-two also had an open or mini-open repair. Two underwent arthroscopic repair. Five patients had a debridement and four patients had Latissimus Dorsi Transfer. All had an evaluation of range of motion(ROM), machine isometric strength testing, and completion of the SF-36, DASH, Western Ontario Rotator Cuff (WORC) and Washington Simple Shoulder Test (WST) at each visit.

Based on tear size, there was a significant difference in functional outcome on the SF-36 (p< 0.05), DASH (p< 0. 005), WORC (p< 0.001) and WST (p< 0.01). Within each group there was significant improvement in strength (p< 0.01) over time. The smaller tear group showed significantly greater strength. The ROM was improved within each group over time (p< 0.01), though no statistical difference was determined between groups. In comparing the sample based on WSIB status, functional outcomes were better in Non-WSIB patients (p< 0.01). Although no statistical difference in strength and ROM was noted.

Patients with both small and large tears showed improved functional outcome, strength and ROM over time, with the smaller tear group having better outcomes. WSIB patients had lower functional outcomes despite strength and ROM showing no difference between the two groups.

This in-vitro study was conducted to determine the effect of rotator cuff tears on joint kinematics. A shoulder simulator produced unconstrained active abduction of the humerus. Three sequential 1cm lesions were created, the first two in the supraspinatus tendon and the third in the subscapularis tendon. The plane of abduction moved posteriorly and became more abnormal throughout abduction as the size of the tear increased. It is concluded that in order to generate the same motions achieved by the intact joint other muscle groups must be employed, inevitably resulting in altered joint loading.

This in-vitro study was conducted to determine the effect of simulated progressive tears of the rotator cuff on active glenohumeral joint kinematics.

Five cadaveric shoulders were tested using a shoulder simulator designed to produce unconstrained active motion of the humerus. Forces were applied to simulate loading of the supraspinatus, subscapularis, infraspinatus/teres minor, anterior, middle, and posterior deltoid muscles based upon variable ratios of electromyographic data and average physiological cross-sectional area of the muscles. Three sequential 1cm lesions were created, the first two in the supraspinatus tendon and the third in the subscapularis tendon. Simulated active glenohumeral abduction was performed following the creation of each lesion. Five successive tests were performed to quantify repeatability.

The plane of abduction moved posteriorly and became more abnormal throughout abduction as the size of the lesion increased (p=0.01) (Figure 1).

In order to generate the same motions achieved with an intact rotator cuff other muscle groups must be employed, inevitably resulting in altered joint loading.

A better understanding of the effects that rotator cuff tears have on the kinematics of the glenohumeral joint may result in the development of innovative rehabilitation strategies to compensate for this change in muscle balance and improve the clinical outcomes.

Please contact author for diagram and/or graph.

This study was conducted to determine the effect of passive and active muscle loading on humeral head translation during glenohumeral abduction. A shoulder simulator produced unconstrained active glenohumeral abduction using several sets of loading ratios. Significantly greater translations occurred in passive motion as compared to active motion between 30 and 70 degrees of elevation in three dimensions and in the anterosuperior plane. No difference was found between the active motions. Also, translations of the humeral head decreased with active simulation of abduction emphasizing the importance of the rotator cuff muscles in creating and maintaining the ball-and-socket kinematics of the shoulder.

This in-vitro study was conducted to determine the effect of passive and active loading on humeral head translation during glenohumeral abduction.

Five cadaveric shoulders were tested using a shoulder simulator designed to produce unconstrained abduction of the humerus. Forces were applied to simulate loading of the supraspinatus, subscapularis, infraspinatus/teres minor, anterior, middle, and posterior deltoid muscles using four different sets of loading ratios. These were based on:

equal loads to all cables (Constant-Constant);

In three dimensions, significantly greater translations occurred in passive motion as compared to active motion between 30 and 70 degrees of elevation (p< 0.001). No difference was found between the active motions. Similar results were observed in the two-dimensional resultant translations in the anterosuperior plane of the scapula, with more translation occurring during passive motion (3.6 ± 1.1mm) than active (2.1 ± 1.0mm) (p=0.002), and no significant differences between the active loading methods (Figure 1). The majority of translation tended to occur in the superior-inferior direction for all loading ratios employed.

It was clearly shown that the translations of the humeral head decreased with active simulation of abduction. These findings are in agreement with other in-vivo and in-vitro investigations.

This emphasizes the importance of the rotator cuff muscles in creating and maintaining the ball-and-socket kinematics of the shoulder.

Forty-nine patients with a repair of their rotator cuff were evaluated at baseline and at six-months after surgery using four self-reports scales (DASH, Western Ontario Rotator Cuff (WORC,) SF-36 and Washington Simple Shoulder (SST) scales. Standardized response means were used to determine responsiveness. The DASH was most responsive (SRM=1.27), the WORC (SRM=1.0) and SST (0.91) were intermediary and the least response was the SF-36 (0.73). These results suggest that the DASH may be preferable to either a disease specific scale or a shoulder scale for detecting clinical progress following cuff repair.

A number of self-report scales exist for shoulder problems, including regional, joint-specific and disease specific scales. Determining the most responsive scale is essential for outcome evaluation and clinical trials.

Forty-nine patients with a repair of their rotator cuff were evaluated at baseline and at six-months after surgery using four self-reports scales (DASH, Western Ontario Rotator Cuff (WORC,) SF-36 and Washington Simple Shoulder (SST) scales. An independent research assistant administered scales. Standardized response means were used to determine responsiveness.

The DASH was most responsive (SRM=1.27), the WORC (SRM=1.0) and SST (0.91) were intermediary and the least response was the SF-36 (0.73). The subscale of the WORC that showed the most change was lifestyle. Physical subscales of the SF-36 showed improvement; whereas, minimal impact on mental health was observed.

The DASH can be used for a variety of upper extremity conditions, whereas the WORC was designed specifically for rotator cuff disease. Unless a disease specific scale is more responsive, there is little reason to adopt a scale than can only be used for one condition. This data supports the ability of the DASH to indicate upper extremity function and the important role of the rotator cuff in function.

The implications of these findings are that the DASH may be preferable to either a disease specific scale for rotator cuff disease or a shoulder scale for detecting clinical progress.

Introduction and Aims: Suture anchors allow consistent reattachment of tendons and ligaments to bone. Many options are available. The purpose of this study was to compare the initial strength of two rotator cuff repair techniques. The hypothesis was that rotator cuff repair strength with anchors would be inferior to transosseous sutures.

Method: Eight paired shoulders with a standardised supraspinatus defect were randomised to bioabsorbable nonsuture-based anchor or transosseous suture repair. Each specimen was then subjected to a stepwise cyclic loading protocol, utilising a custom-designed loading apparatus. Repair site migration was measured using an optical measurement system, consisting of a digital camera and custom software. Mode of failure, number of cycles and load to failure were measured for 50% (5 mm) and 100% (10 mm) loss of repair. These results were correlated with bone mineral density, age and gender. Statistical analysis utilised paired t-tests and Pearson correlations.

Results: The anchors failed at the anchor-tendon interface, whereas the sutures failed through the sutures. Mean values for 50 percent loss of repair were 206 ± 88 cycles and 44 ± 15 N for the sutures, and 1193 ± 252 cycles and 156 ± 20 N for the anchors (p< 0.05). The corresponding values for 100 percent loss of repair were 2458 ± 379 cycles and 294 ± 27 N for the sutures, and 2292 ± 333 cycles and 263 ± 28 N for the anchors (p> 0.05). These results may be due to the relative less deformability of the anchors. This may be relevant clinically, as in the early post-operative period, while tendon healing to bone is occurring, anchors may offer improved strength, allowing improved initial healing. Strength was unaffected by bone quality. This may be attributed to each repair failing primarily through the repair construct or at the anchor-tendon interface, and not through bone. Strengths of this study include the use of paired specimens, the stepwise cyclic loading protocol, as well as increased accuracy of our measurement system. Limitations include the use of an in vitro model, as well as a simulated, standardised rotator cuff tear.

Conclusion: Repair strength with anchors was superior to sutures. Strength was unaffected by bone quality. Anchors facilitate an arthroscopic procedure, decrease operative time, and may allow a faster post-operative recovery. This study has described a new high-resolution method of measuring tendon repair failure and may be useful in future studies.