In Vivo Analysis Length Changes Of Collateral Ligaments Of The Elbow During Flexion Using Three-dimensional Computed Tomography

Background: Collateral ligaments of the elbow play an important role in maintainingthe elbow stability. Ligamentous injuries commonly occur in the elbow. Although thefunctional anatomy of the collateral ligament has been investigated, current informationwas most based on the cadaveric studies and undefined collateral ligament’s footprint. Thepurpose of this study was to investigate in vivo length changes of collateral ligamentsduring elbow flexion with3dimensional computed (CT) tomography, and to clarify the3Dfunctional anatomy of the ligaments as well as to identify the isometric point for thereconstructed collateral ligaments of the elbow where the grafted tendon should beanchored.Methods: We obtained computed tomography scans of the right elbows of6volunteers with a mean age of27years (4males, and2females) in four positions between0°and120°of flexion. We selected three ligament paths consisting of the anterior bundleof the medial collateral ligament (AMCL), the posterior bundle of the medial collateralligament (PMCL) and the lateral ulnar collateral ligament (LUCL). We reconstructed the3D elbow joint structures with customized software (Mimics10.01), and measured thelength of the ligaments using Geomagic Studio12.0and Geometer’s Sketchpad V5.0. TheAMCL, PMCL and LUCL were subdivided into3ligaments, respectively. We calculatedchanges in lengths of these9ligaments during elbow flexion.All measurements of thelengths of the9ligaments were performed twice by two persons and the average of the twovalues was used for data analyses. We analyzed the length changes using repeated-measuretwo-way analysis of variance followed by post hoc paired t-tests. All p values are2-tailed,with p<0.05indicating significance. Statistical analyses were performed with SPSS17.0software.Results:From0°to full flexion of elbow, the lengths of the3subgroups of AMCLincreased with different extents. The middle group elongated by10%,13%and21%, and the lengths increased significantly between the4positions of the elbow (p<0.05). From0°to50°flexion of elbow, the lengths of the3subgroups of PMCL increased gradually(p>0.05), but increased significantly from50°to90°, and then to120°of elbow flexion(p<0.01). At the position of120°flexion, the lengths of3subgroups all elongated by about90%. From0°to50°flexion and from90°to120°flexion of elbow, the lengths of the3subgroups of LUCL increased gradually (p>0.05), and from50°to90°flexion, the lengthsof these3ligaments increased significantly (p<0.05).Conclusions: Three-dimensional reconstruction of CT scans in vivo can be used toinvestigate the biomechanics of elbow jointeffectively. During the elbow flexion, thetension of collateral ligaments increased to some extents, compared with the position ofelbow full extension. Changes of the tension of the collateral ligaments showed certainregularity. In ligament reconstruction of AMCL, the medial and lateral bundles can be usedapproximately to double isometric reconstructions. The original anatomic attachments ofthe PMCL and LUCL are not suitable to serve as the isometric point for the reconstructedligaments.