Total shoulder arthroplasty (TSA) is an effective treatment for end-stage glenohumeral arthritis. The use of high modulus uncemented stems causes stress shielding and induces bone resorption of up to 63% of patients following TSA. Shorter length stems with smaller overall dimensions have been studied to reduce stress shielding, however the effect of humeral short stem varus-valgus positioning on bone stress is not known. The purpose of this study was to quantify the effect of humeral short stem varus-valgus angulation on bone stresses after TSA.

Three dimensional models of eight male cadaveric humeri (mean±SD age:68±6 years) were created from computed tomography data using MIMICS (Materialise, Belgium). Separate cortical and trabecular bone sections were created, and the resulting bone models were virtually reconstructed three times by an orthopaedic surgeon using an optimally sized short stem humeral implant (Exactech Preserve) that was placed directly in the center of the humeral canal (STD), as well as rotated varus (VAR) or valgus (VAL) until it was contacting the cortex. Bone was meshed using a custom technique which produced identical bone meshes permitting the direct element-to-element comparison of bone stress. Cortical bone was assigned an elastic modulus of 20 GPa and a Poisson's ratio of 0.3. Trabecular bone was assigned varying stiffness based on CT attenuation. A joint reaction force was then applied to the intact and reconstructed humeri representing 45˚ and 75˚ of abduction. Changes in bone stress, as well as the expected bone response based on change in strain energy density was then compared between the intact and reconstructed states for all implant positions.

Both varus and valgus positioning of the humeral stem altered both the cortical and trabecular bone stresses from the intact states. Valgus positioning had the greatest negative effect in the lateral quadrant for both cortical and trabecular bone, producing greater stress shielding than both the standard and varus positioned implant. Overall, the varus and standard positions produced values that most closely mimicked the intact state.

Surprisingly, valgus positioning produced large amounts of stress shielding in the lateral cortex at both 45˚ and 75˚ of abduction but resulted in a slight decrease in stress shielding in the medial quadrant directly beneath the humeral resection plane. This might have been a result of direct contact between the distal end of the implant and the medial cortex under loading which permitted load transfer, and therefore load-reduction of the lateral cortex during abduction. Conversely, when the implant was placed in the varus angulation, noticeable departures in stress shielding and changes in bones stress were not observed when compared to the optimal STD position. Interestingly, for the varus positioned implant, the deflection of the humerus under load eliminated the distal stem-cortex contact, hence preventing distal load transfer thus precluding the transfer of load.

Introduction

Total shoulder arthroplasty (TSA) is an effective treatment to restore shoulder function and alleviate pain in the case of glenohumeral arthritis [1]. Stress shielding, which occurs when bone stress is reduced due to the replacement of bone with a stiffer metallic implant, causes bone resorption of up to 9% of the humeral cortical thickness following TSA [2]. Shorter length stems and smaller overall geometries may reduce stress shielding [3], however the effect of humeral head backside contact with the resection plane has not yet been fully investigated on bone stress. Therefore, the purpose of this study was to quantify the effect of humeral head contact conditions on bone stresses following TSA.

Propionibacterium acnes infection of the shoulder after arthroplasty is a common complication. Current detection methodologies for P. acnes involve prolonged anaerobic cultures that can take up to three weeks before findings can be reported. Our aim was to develop a polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) approach that is both sensitive and specific to P. acnes that would enable a 24-hour turnaround between biopsy and results.

Comparisons between the 16S ribosomal sequences of P. acnes and closely related bacteria identified two unique regions in P.acnes to which PCR primers were designed. Additionally, two unique restriction enzyme cut sites for HaeIII were identified within this amplicon. To test the PCR method, arthroscopic surgical biopsies were mechanically homogenised and boiled for 20 minutes to lyse the cellular membranes. PCR was performed using standard conditions followed by a one hour HaeIII enzymatic digest of the PCR product. Resultant fragments were visualised on polyacrylamide gels stained with ethidium bromide. All experiments included no-template controls to rule out reagent contamination and independently confirmed P. acnes DNA as a positive control. Serial dilutions of P. acnes cultures in Robertson's cooked-meat broth and spectrophotometric analysis of cellular concentration were used to assess the sensitivity of the PCR reaction.

A unique 564 base-pair PCR amplicon was derived from different strains of P. acnes. This amplicon was confirmed as P. acnes DNA by gel excision and DNA sequencing. HaeIII digests of the amplicon yielded 3 restriction fragments at the sizes predicted by in silico analyses. Sensitivity testing confirmed that as few as 10 P. acnes cells in a 50µl reaction volume could be detected using this assay. P. acnes was also detected in surgical biopsy samples.

P. acnes infections following shoulder arthroplasty are a serious complication placing a burden on the healthcare system and the patient due to the lengthy surgical revision process that follows. The infections are also difficult to diagnose. This unique assay combines the sensitivity of PCR with the specificity of RFLP mapping to specifically identify P. acnes in surgical isolates. We anticipate that this assay will allow us to determine if a biopsy is P. acnes positive within 24-hours of sampling, allowing for more aggressive antibiotic therapy and monitoring to avoid implant failure and revision surgery. Additionally, this PCR-RFLP method may decrease the false positive rate of extended length cultures due to P. acnes contamination.

Rotator cuff repair is performed to treat shoulder pain and disability. Failure of the tendon repair site is common; one strategy to improve healing is to enforce a period of post-operative immobilisation. Immobilisation may have unintended effects on tendon healing. Tenocytes under uniaxial strain form more organised collagen and up regulate expression of proliferative genes. Vitamin C (ascorbic acid), an anti-oxidant that is a co-factor for collagen synthesis, has also been reported to enhance collagen deposition and organisation. The purpose of this study was to compare human tenocyte cultures exposed to uniaxial cyclical strain with or without slow-release ascorbic acid (ascorbyl-2 phosphate) to determine their individual and combined effects on tissue remodelling and expression of tissue repair genes.

Rotator cuff tissues were collected from degenerative supraspinatus tears from eight patients. Tenocytes were incorporated into 3D type I collagen culture matrices. Cultures were divided into four groups: 1) ascorbic acid (0.6mMol/L) + strain (1%–20% uniaxial cyclic strain at 0.1 Hz), 2) ascorbic acid unstrained, 3) strain + vehicle 4) unstrained + vehicle. Samples were fixed in paraffin, stained with picrosirius red and analysed with circular polarising light. A second set of cultures were divided into three groups: 1) 0.5mM ascorbic acid, 2) 1mM ascorbic acid, 3) vehicle cultured for 24, 72, 120 and 168 hours. Cell-free collagen matrix was used as a control. Tenocyte proliferation was assessed using the water soluble tetrazolium-1 (WST1) assay and f tissue repair gene expression (TGFB1, COL1A1, FN1, COLIII, IGF2, MMP1, and MMP13), were analysed by qPCR. The data were analysed using a Split model ANOVA with contrast and bonferroni correction and a one-way ANOVAs and Tukey's test (p<0.05 was significant).

Our results indicated that unstrained cultures with or without exposure to slow release ascorbic acid exhibited greater picrosirius red birifringency and an increase in collagen fiber deposition in a longitudinal orientation compared to strained tenocytes. We found that slow release ascorbic acid promoted significant dose and culture-time dependent increases in tenocyte proliferation (p<0.05) but no obvious enhancement in collagen deposition was evident over cultures without ascorbic acid supplementation.

Based on these data, applying strain to tenocytes may result in less organised formation of collagen fibers, suggestive of fibrotic tissue, rather than tendon remodelling. This may indicate that a short period of immobilisation post-rotator cuff repair is beneficial for the healing of tendons. Exposure to slow release ascorbic acid enhanced tenocyte proliferation, suggesting that supplementation with Vitamin C may improve tendon repair post-injury or repair. Future studies will assess levels of tissue repair-associated proteins as well as comparing traumatic and degenerative rotator cuff tears to healthy uninjured rotator cuff tissue.

Purpose: Glenoid component loosening is a common reason for failed total shoulder arthroplasty. Multiple factors have been suggested as causes for component loosening including asymmetric loading of the glenoid prosthesis by the humeral head (rocking horse phenomenon). A novel technique was employed to measure in-vitro strain in the subchondral bone adjacent to a cemented all polyethylene pegged glenoid prosthesis. The purpose of the study was to develop and validate a testing protocol to investigate load transfer in the polyethylene glenoid implant and bone construct.

Method: Eight polyethylene components were implanted using standard cementing techniques in eight cadaveric specimens. Loading was performed with a pneumatic actuator capable of applying loads at various angles. A dynamic 10 N/s force was applied for a total of 15 seconds producing a maximum force of 150N at angles of 0, 10, 20, 30, 40 and 50o. Strain gauges were placed around the implant 1mm proximal to the bone-cement interface at the four quadrants. The humeral head was simulated with a custom steel ball with a non-conforming diameter in relation to the prosthesis that is typical in total shoulder arthroplasty.

Results: During pure compressive loading, tension was observed in the superior and inferior quadrants of the glenoid. Superior and inferior loading caused increasing same side (ipsilateral) tension, occurring from 0 to 30o and 0 to 20o, respectively. Compression was recorded superiorly when loading was applied at 40o and 50o in the superior direction while contralateral tension was recorded in the inferior gauges. Strain measurements were less consistent in the anterior and posterior glenoid quadrants and varied between tension and compression.

Conclusion: Tension measurements in the ipsilateral direction at lower angles were unexpected. This observation differs from the previous assumption that applied loads at relatively perpendicular angles to the implant should dissipate as compression. Tension at the bone cement interface is unfavorable. The identification of tension in some quadrants of the implant in this study, therefore, may have revealed a mechanism of implant loosening. Our data support the previously described rocking horse phenomena and also illustrate a new umbrella type effect of polyethylene flexure, which causes the periphery of the glenoid implant to flex upwards superiorly and inferiorly. These findings have the potential to influence future designs of total shoulder arthroplasty perhaps leading to increased implant survival.

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.

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.

Purpose: Frozen Shoulder Syndrome (FSS) frequently occurs in association with Dupuytren’s Disease (DD). Beta-catenin is a signaling pathway implicated in the pathogenesis of DD. The purpose of this study is to determine if beta-catenin is also associated with FSS.

Methods: Tissue obtained during shoulder arthroscopy for capsule release in patients with FSS was subjected to immunohistochemical staining (IHC) and Western Blot analysis. Control tissue was obtained from the rotator cuff interval from patients undergoing arthroscopy for rotator cuff syndrome.

Results: IHC analysis showed that the vast majority of cells within lesions expressed b-catenin while cells within marginal tissue stained weakly for b-catenin. Western blotting analysis of FSS specimens showed that lesional tissues expressed increasing amounts of b-catenin compared to RCS tissue.

Conclusions: Beta-catenin expression is upregulated in FSS. The current lack of knowledge about the biochemical mechanisms of FSS coupled with the limited therapeutic intervention available emphasizes the need for a better understanding of the basic biology of this fibrosing disorder.

Funding : Educational Grant from the Canadian Orthopaedic Foundation.

The functional outcomes of twenty-eight patients with capitellum and trochlea fractures treated with open reduction and internal fixation were evaluated at a mean follow-up of fifty-five ± thirty-three months. Patients were independently evaluated by a series of questionnaires, radiographs, physical examination and strength testing. Patients with simple fractures did better than those with complicated fractures. The average DASH score was 19/100 and the average ROM was 20 – 130°. Two fractures did not unite and required conversion to total elbow arthroplasty.

A classification system is proposed based on fracture patterns, surgical technique and clinical outcomes.

Capitellum and trochlea fractures are uncommon fractures of the distal humerus. There is limited information about the functional outcome of patients managed with open reduction and internal fixation.

The functional outcome of twenty-eight patients (average age: forty-three ± thirteen years [range, twenty – seventy-one]) who were treated with open reduction and internal fixation for capitellum and trochlea fractures was evaluated at a mean follow-up of fifty-five ± thirty-three months (range, fourteen – one hundred and twenty-one). Patient outcomes were assessed by physical examination, radiographs, range of motion measurements, strength testing and self reported questionnaires (DASH, SF-36 ASES and PREE elbow scales).

There were eleven fractures involving the capitellum, four involving the capitellum and trochlea as one piece and thirteen in which the capitellum and trochlea were separate fragments. These fractures were further defined by the presence or absence of posterior comminution. Fourteen had isolated fractures and fourteen were associated with other elbow, forearm or wrist injuries. Patients with complicated fractures required more extensive surgery, had more complications resulting in secondary procedures and had poorer outcomes compared to those with simple fractures. The average DASH score (19/100), quality of life scores (SF-36: Physical=46, Mental=49) and the average ROM (20 – 130°) suggest favorable patient outcomes overall.

Patients with simple fractures had better results than those with more complicated fractures. A fracture classification system based on fracture patterns, surgical technique and clinical outcomes is proposed.

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.

The strength of the intact and four reconstruction techniques (figure-eight, docking, single strand utilizing interference screws, and a single strand) of the medial collateral ligament (MCL) of the elbow were compared. Twenty cadaveric specimens were tested with a cyclic valgus loading protocol. The peak loads to failure of the MCL reconstructions were inferior compared to the intact ligament (p< 0.05). The docking and single strand reconstruction utilizing an endobutton for ulnar fixation were equivalent and had greater initial strength than the interference screws or figure-eight technique. It is suggested that improved interference screws are required for this repair.

The purpose of this study was to compare the initial strength of the intact medial collateral ligament (MCL) of the elbow and four reconstruction techniques.

The docking and endobutton reconstructions showed equivalent peak load to failure.

Improved interference screws are required before they are employed clinically.

The average peak load to failure or 5mm of joint gapping was 142.5±39.4N for the intact, 53.0±9.5N for the docking, 52.5±10.4N for the endobutton, 41.0±16.0N for the interference screw, and 33.3±7.1N for the figure-eight reconstructions. The peak load to failure was higher for the intact specimens compared to any of the reconstructions (p< 0.001). The docking reconstruction showed higher peak loads than the figure-eight or interference screw reconstruction, and the endobutton reconstruction showed higher peak loads than the figure-eight reconstruction (p< 0.004). There was no difference in peak loads between the docking and endobutton reconstructions (p> 0.05).

Twenty (ten pairs) unpreserved cadaveric upper extremities were mounted in a custom jig with the elbow at 90°, and a valgus force was applied 12cm from the elbow joint. The specimens were loaded starting at 20N with the load increased in increments of 10N (200 cycles at each load), until either complete ligament failure or a 5mm increase in the distance between the attachment sites of the MCL. The results support that a single strand or multistrand ligament reconstruction can be equivalent with respect to maximal peak loads and cyclic loading. There are concerns with regard to the use of interference screw fixation in the clinical situation.

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.

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.

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

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.

Purpose: Metal radial head arthroplasty is a proven technique for the treatment of complex radial head fractures. Little previous research is available on the utility and longevity of metal radial head arthroplasty for elbow reconstruction. The purpose of this study was to evaluate the functional outcome of patients with metal radial head arthroplasty (RHA) for elbow reconstruction.

Methods: This was a retrospective review from one institution with three senior orthopaedic surgeons. 23 consecutive patients with 23 RHA were included in the study, 4 patients were lost to follow up. RHA was performed for conditions of rheumatoid arthritis, post traumatic radial head nonunion, post traumatic radial head malunion, elbow instability following previous radial head excision and failed silicone radial head implants. Patients were excluded from the study if they were treated for an acute injury with RHA (under 2 months from injury). There were 8 males and 15 females with a minimum of 2 year follow up. Analysis included chart review, personal interview, physical examination, radiographs and strength testing. Region specific questionnaires were used including: DASH, ASES, MEPI, PRWE, WOS and SF-36. Mean follow up was 9 yrs.

Results: Mayo elbow performance scores were excellent in 11 patients, good in 4 patients, fair in 4 patients and poor in 4 patients. Subjective patient satisfaction was averaged at 8.4 out of 10. Patients demonstrated significantly less isometric strength and grip strength in the affected versed unaffected elbow. There was no statistically significant difference seen in ulnar variance or ulnohumeral joint space between the affected and unaffected limbs.

Conclusions: In conclusion, RHA for elbow reconstruction is a safe procedure that provides patients with long term functional ROM and pain relief.

The purpose of this study was to determine if arthroscopic release is safe and effective in the management of elbow contracture. Twenty patients (mean age of forty-two), undergoing arthroscopic contracture release were retrospectively reviewed at a minimum follow-up of one year (mean twenty-five months). Most patients had combined extrinsic & intrinsic causes for contractures. Mean flexion improved from 122 to 137°. Mean extension improved from 38° to 18°. The mean arc improvement was 35° (p < 0.001). None of the patients had instability and there were no major neuro-vascular complications. All patients had decreased pain and improved elbow function.

To determine if arthroscopic release is safe and effective in the management of elbow contracture.

Twenty patients (mean age of forty-two), undergoing arthroscopic contracture release were retrospectively reviewed at a minimum follow-up of one year (mean twenty-five months). Most patients had combined extrinsic & intrinsic causes for contractures. Motion and strength were measured with standard goniometry and the LIDO isokinetic system by independent evaluators.

Mean flexion improved from 122 ± 16° to 137 ± 12°. Mean extension improved from 38 ± 18° to 18 ± 14°. The mean arc improvement was 35 ± 21° (p < 0.001). Arthroscopic release did not affect forearm rotation or strength. One patient developed a permanent medial antebrachial cutaneous neuroma. One patient required a repeat surgery to remove a loose body. There were no instability and no major neurovascular complications. All patients had improved elbow function with a mean ASES score of thirty-one out of thirty-six. Most patients were satisfied with their surgery, had minimal pain, considered themselves in good physical health on the SF-36, and had minimal impairment on the DASH.

Arthroscopic release is safe and effective in experienced hands.

Results are comparable to traditional open techniques. The theoretical advantages of arthroscopy include improved joint visualization, decreased morbidity and earlier rehabilitation.

Disadvantages include the potential for serious neurovascular complications, and the inability to deal with ulnar nerve pathology or heterotopic ossification. Indications for conversion to open release include excessive swelling, and failure to maintain adequate view.

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.

The reliability and accuracy of plain radiographs, MRI and CT Arthrography to detect the presence of loose bodies was evaluated in twenty-six patients with mechanical elbow symptoms. The location of loose bodies found by the imaging studies was compared to arthroscopic findings. Overall sensitivity for the detection of loose bodies was 88 – 100% and specificity was 20 – 70%. Plain radiographs had a similar sensitivity and specificity of 84% and 71% respectively. MRI and CT Arthrography were similar to plain radiography, suggesting that routine use of these modalities is not indicated.

The purpose of this study was to determine the clinical utility of MRI and CT Arthrography (CTA) to reliably and accurately predict the presence of loose bodies in the elbow.

Twenty-six patients with mechanical elbow symptoms underwent plain radiography, MRI and CTA, followed by standard elbow arthroscopy. Three musculoskeletal radiologists reviewed the ‘blinded’ plain radiographs with both the MRI and CTA at separate sittings. The location and number of loose bodies on the MRI and CTA were recorded. The preoperative plain radiographs, MRI and CTA were compared to the arthroscopic findings.

Agreement between radiologists was higher for the number of loose bodies identified in the posterior compartment (ICC=0.72 for both MRI and CTA) than in the anterior compartment (ICC=0.41 and 0.52 for MRI and CTA respectively). The correlation between the number of lose bodies observed on MRI and CTA compared to those found arthroscopically was also higher in the posterior compartment (r=0.54–0.85) than in the anterior compartment (r=0.01–0.45). Both MRI and CTA had excellent sensitivity (92–100%) but moderate to low specificity (15–77%) in identifying posteriorly located loose bodies. Neither MRI nor CTA were consistently sensitive (46–91%) or specific (13–73%) in predicting anterior loose bodies. Overall sensitivity for the detection of loose bodies in either compartment was 88–100% and specificity was 20–70%. The preoperative radiographs had a similar sensitivity and specificity of 84% and 71% respectively.

MRI and CTA were similar to plain radiography in the prediction of elbow loose bodies.

Single-strand medial collateral elbow ligament (MCL) reconstruction strength was evaluated using double docking (DD) and interference screw (IS) methods with either palmaris longus (PL) or Graft Jacket_ (GJ) as the reconstruction material. Thirteen upper-extremities were mounted in 90° valgus orientations, and subjected to increasing cyclic valgus loading until failure. DD reconstructions outperformed IS reconstructions (P< 0.05), while PL and GJ performed comparably (P> 0.05). The initial Graft Jacket strength makes it a potential alternative to palmaris longus tendons; Laboratory evaluation of graft strength during healing is required. For its simplicity and strength, the DD technique should be considered, clinically.

Single-strand medial collateral elbow ligament (MCL) reconstruction strength was evaluated using double docking (DD) and interference screw (IS) methods with either palmaris longus (PL) or Graft Jacket_ (GJ) as the reconstruction material.

Thirteen, fresh-frozen upper-extremities (66 ±5 years) were cleaned of all soft tissues except the medial and lateral collateral ligaments, flexed to 90° and mounted in a rigid, valgus testing system. DD or IS reconstructions were performed using either PL or GJ. A cyclic (0.5Hz) load was applied 12cm distal to the medial epicondyle. After 500 cycles, the load was increased by 10N until catastrophic failure or a length increase of 10mm.

The mean maximum load for the DD with GJ was 65 ±12N; for the IS with GJ: 45 ±5N; for the DD with PL: 59 ±11N; and for the IS with PL: 56 ±14N. The mean maximum number of cycles endured by the DD with GJ was 1292 ±562; for the IS with GJ: 356 ±292; for the DD with PL: 1104 ±479; and for the IS with PL: 924 ±690. For both the maximum load and number of cycles, the DD outperformed the IS (P< 0.05) and the GJ and PL performed comparably (P> 0.05).

Single-strand reconstructions using the double dock method outperform the interference screw technique. For its simplicity and strength, the DD technique should be considered, clinically. The initial Graft Jacket strength makes it a potential alternative to palmaris longus tendons; laboratory evaluation of graft strength during healing is required.

Funding: This study was partially funded by Wright Medical Technology (Arlington, TN) and the Canadian Institute for Health Research.

Please contact author for graphs and/or diagrams.

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.

Introduction and Aims: Ganglia are commonly seen during investigation of patients with wrist pain. Our aim was to determine the prevalence of ganglia in an asymptomatic population.

Method: Following Institutional Ethical approval, Magnetic Resonance Imaging (MRI) was performed on the wrists of 103 asymptomatic volunteers. There were 67 males and 37 females, with an average age of 36, range 19–67 years. There were 52 right wrists and 51 left wrists.

Using a 1.89 Tesla surface coil Magnetic Resonance Imager the following sequences were obtained: Coronal T 1, Proton Density, T 2 and Inversion Recovery sequences; Sagittal Inversion Recovery sequences; Axial T 1 and Inversion Recovery Sequences. The images were then evaluated independently by two Muskuloskeletal Radiologists and one Orthopaedic Surgeon.

Results: Wrist Ganglia were identified in 53 out of 103 wrists. Wrist Ganglia were more prevalent in females than males, 58% compared to 48% respectively. The average long axis measurement was 7.5 mm (range 2.7–22.2), the average short axis measurement was 3.2 mm (range 1.6–10.1). Seventy percent of the Ganglia were found to originate from the volar capsule in the region of the interval between the Radio-Scapho-Capitate Ligament and the Long Radio-Lunate Ligament. Fourteen percent of the ganglia were dorsal and originated from the dorsal, distal fibres of the Scapho-Lunate Ligament. Two ganglia had surrounding soft tissue oedema and one had an associated intra-osseous component.

Conclusion: The prevalence of asymptomatic wrist ganglia is high – 51%. Unlike previous surgical and pathological series, our study showed volar wrist ganglia are more common than dorsal wrist ganglia in the asymptomatic population. The vast majority of these asymptomatic ganglia do not show associated ligamentous disruption, soft tissue oedema or intra-osseous communication.