Figure 3 GH translations for forward elevation following therestoration of the scapular winging. (A to C) X, Y, and Zglenohumeral translations obtained from the cadaveric shouldermodel undergoing humeral elevation in the coronal plane atbaseline, scapular winging, and restored scapular position.

Figure 4 GH translation in the 0° to 60° range of forwardelevation. (A to C) X, Y, Z glenohumeral translations obtained fromthe cadaveric shoulder model undergoing humeral elevation in thescapular plane at baseline and after supraspinatus tear and repair.

Rosso et al. Journal of Orthopaedic Surgery and Research 2013, 8:24 Page 5 of 7http://www.josr-online.com/content/8/1/24

motion due to pain, and translational/rotational instabil-ity of the actual pin [18]. Recent in vivo investigationshave moved from tracking of markers to the use of CTand fluoroscopy for 3D tracking to 2D motion tracking,

with the main limitations being radiation-exposed[22,23].Previous ex vivo shoulder kinematic analyses including

finite element analysis [24] and cadaveric modeling[8,11,25-29] have shown similar constraints as the pro-posed system with the elimination of the muscles as

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dynamic stabilizers of the GH joint. In some studies,loading the tendons of the selected muscles or musclegroups was simulated, but this adaptation is technicallydemanding for dynamic motions and is applied beston a small scale with a limited number of joints inquestion. Previous ex vivo studies have also shownhigh intersubject variability as observed in this study.The major improvement of this testing system overthe current ex vivo methods is its ability to study theentire shoulder girdle (including the scapulothoracic,acromioclavicular, and sternoclavicular joints) and toreproduce a wide variety of basic and complex shouldermotions with high accuracy and precision, whileallowing for real-time data acquisition. Moreover, theproposed system is capable of following an exact motiontrajectory throughout all steps of the test. Nonetheless,the interaction of the apparatus, the marker clusters,and the cameras can affect the visibility of the markersand requires careful planning and operation.There are a number of limitations associated with this

preliminary study. First of all, the speed of the simulatedshoulder motion was much lower than that usually ob-served in human subjects. This was done to avoid anyunintended damage to the cadaver. While humeral ele-vation speed was shown to alter GH biomechanics [26]in active shoulder models, it remains unclear whetherthese findings can be transferred to passive cadavericmodels. However, it was beyond the scope of this studyto explore the association between motion speed andGH kinematics in our model. Nevertheless, this could beclarified in future studies. We included one cadavericshoulder and demonstrated the effects of the implemen-tation and restoration of only two shoulder pathologieswith respect to the intact condition. The scapularwinging condition may stand for all pathologies that aredistant to the GH joint but are capable of affecting GHtranslations, while the rotator cuff tear may represent allpathologies that are intrinsic to the joint and can directlyaffect its translations. Had we not restricted this study tothe analysis of these two characteristic pathologies, thenthe number of lesions up for debate would have easilyexceeded the boundaries of an evaluation study.Given the limited feedback on leverage forces effectively

applied by the actuator to the GH joint with no dynamicstabilization of the joint by muscle forces, the extent ofjoint translations may vary among anthropometrically dif-ferent specimens. Cadaver-specific tissue elasticity accen-tuated after the thawing process may further contribute tothe observed interspecimen variability. There is also an in-herent variability associated with the calibration of theanatomical landmarks in each specimen using a pointingwand, since these landmarks are areas rather than discretepoints [29]. Nevertheless, our data indicate that changesin translation from one condition to the other may be

quite consistent among different shoulders, particularly ifspecific segments of a motion are analyzed. Therefore, fu-ture studies may primarily compile between-conditionchanges observed in different specimens and subject theseto paired comparative statistical tests.

ConclusionIn conclusion, we have shown that the presented cadav-eric, stereophotogrammetric testing system is capable ofdifferentiating GH translations in sequential clinical con-ditions over a series of repetitions with a high degree ofreproducibility in cadaveric tissue. These results confirmthat this dynamic testing apparatus could be used tostudy cadaveric shoulder kinematics and simulate rele-vant clinical scenarios.

Competing interestsThe authors declare that they have no competing interests.

Authors’ contributionsCR, AM, VE, WD, BM, SS, and DL contributed towards data acquisition, dataanalysis, manuscript preparation, and final approval. UD and AC contributedtowards data analysis, manuscript preparation, and final approval. AR, JD, andAN contributed towards study design, data acquisition, surgical procedures,manuscript preparation, and final approval. All authors read and approvedthe final manuscript.

AcknowledgementsThe authors would like to acknowledge the Medical Advisory Committee forMajor League Baseball (AJR and AN) and the Department of OrthopaedicSurgery at Beth Israel Deaconess Medical Center, Boston, MA (AN and AJR)for funding this project. They would like to gratefully acknowledge theNational Institute of Health (L30 AR056606) for providing funding to AN, theSwiss National Science Foundation for providing funding to CR and AMM,and the Swiss Orthopaedic Society for providing support to CR to work onthis project. They would also like to acknowledge the efforts of Mr. Dan Indiaand the technical staff at Qualisys, AB and Dr. Glenn Fleisig and his teamfrom the American Sports Medicine Institute for their help with the motionanalysis component of the project.

Author details1Center for Advanced Orthopaedic Studies, Beth Israel Deaconess MedicalCenter and Harvard Medical School, 330 Brookline Avenue, RN115, Boston,MA 02215, USA. 2Orthopaedic Department, University Hospital Basel,University of Basel, Basel, Switzerland. 3Department of Orthopaedic Surgery,Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA02115, USA. 4Department of Information Engineering, Political Sciences andCommunication Sciences, University of Sassari, Sassari 07100, Italy.

Received: 25 March 2013 Accepted: 15 July 2013Published: 24 July 2013

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doi:10.1186/1749-799X-8-24Cite this article as: Rosso et al.: Preliminary evaluation of a roboticapparatus for the analysis of passive glenohumeral joint kinematics.Journal of Orthopaedic Surgery and Research 2013 8:24.

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