The Three Dimensinal Visualization Of The Precise Anatomy Of The Rotator Interval And Its Value For Diagnosis Of The Frozen Shoulder

BackgroundRotator interval(RI)is the triangular crack between the supraspinatus(SSP)and subscapularis(SSC).It is a very important and clinically relevant complex.There are two functional anatomy complexes in the RI: CHL complex and the stabilization structures of the LHBT.The precise anatomy of these complexes remains vague.And the distinction between the superior subscapularis recess(SSR)which is the protrusion of the RIC and the subscapular bursa(SSB)is not clear till now.The detailed anatomy of the RI is the important base for the surgeon to understand the pathology,identify the RI lesions,make an accurate diagnosis and initiate the appropriate treatment.Thus,it’s very important to further verify the precise anatomy of the RI.Frozen shoulder is an idiopathic pathologic condition involving the RI that present with pain and progressive limitation of active and passive shoulder motion.Imaging studies such as MR imaging or MR arthrography are playing an increasingly important role for the diagnosis of the frozen shoulder.But,the studies especially regarding on the sectional and three dimensional(3D)anatomy of the RI are few,so the RI lesions were not easily to be identified on the MR image.Furthermore,there exist many differences in the diagnostic criteria for the frozen shoulder.Besides,the diagnostic value of the SSR sign on the MR image for the frozen shoulder is a debatable point.These unclear things could easily result in the misdiagnosis or missed diagnosis of frozen shoulder.So,it’s of great clinical significance to figure out these vague issues about the diagnostic criteria of the frozen shoulder.The serial sections of the Chinese Visible Human(CVH)data sets are the images with high res-olution,thin slice thickness and natural color.Such that,the contour profile and texture of different structures can be easily recognized and differentiated on these sections.It’s possible to 3D visualize the RI based on the CVH.ObjectiveTo create the 3D model of the RI based on the CVH and analyze the sectional anatomy of the RI.To verify the precise anatomy of the CHL complex and stabilization structures of the LHBT using 3D visualization technique histologically and anatomically.To identify the relationship of the SSR and SSB,and present the MR appearance of the SSB.Materials and Methods1 Three dimentional visualization of the RI and its adjacent structures1.1 To design the image segmentation technique based on the analysis of the CVH images comprising the hind foot and ankle.With the technique,we tempted to reconstruct the 3D model of the RI based on the axial CVH images.1.2 To retrieve the sagittal oblique and coronal oblique sections from the primitive CVH dataset using the specially designed resampling technique.The sectional anatomy of the RI and the adjacent structures were observed and noted on these sections on three standard planes respectively.Then,the 3D model of the RI was visualized based on the sagittal oblique CVH sections,and registered with 3D model reconstructed based on the axial CVH sections.2 The precise anatomy and functional orientation of the important functional structures of the RI2.1 Three embalmed cadaver shoulders were applied for histological study.After embedded in sodium carboxyl methyl cellulose,serial sections(25um thickness)which is orthogonal to the central axis of the SSP were made using fully computerized cryomacrotome,after dehydrated,they were stained with Masson trichrome stain and HE stain.The histological sectional images were registered with the images of the section of the cadaver shoulders.Then,the RI was segmented and 3D reconstructed based on the histological sections.2.2 The histological characteristics of the stabilization structures of the LHBT were observed and noted.With the characteristics,the 3D model of the stabilization structures was obtained based on the CVH sections.The dimensions of the biceps pulley were calculated with the number of sections multiplied by the thickness of the section.2.3 The SSB and adjacent structures were 3D visualized based on the images of 8 shoulders from CVH data sets,the dimensions and volume of the SSB were achieved directly using Amira software.After the SSB was exposed eosin stain was instilled into the SSB(7 cadaveric shoulders)or the joint(1 cadaveric shoulder)to identify the communication between the bursa and joint cavity.3 The significance of precise anatomy of the RI for the diagnosis of the frozen shoulder.3.1 The sections of the 8 shoulders from the CVH data sets were studied.The anatomy parameters were measured using the previously reported methods on the CVH images to evaluate the quantitative diagnostic criteria.3.2 MR imaging were performed in 7 embalmed cadaveric shoulders prior to dissection,after the SSB was exposed and instilled with contrast agent,MR imaging were completed in the cadaveric shoulders with SSB.4 Statistical analysisThe differences were statistically evaluated using t test or one-way ANOVA with SPSS 15.0 software(SPSS,Chicago,IL),significance being set at the P < 0.05 level.Results1 The image segmentation technique which is applied to the RI was found successfully.2 The SSP、CHL、SGHL and RIC were difficult to be identified and segmented on the axial CVH sections.So did on the 3D model obtained based on the axial sections.3 The standard coronal oblique and sagittal oblique CVH sections were achieved successfully with specially designed resampling technique.The sagittal oblique CVH images were more preferable for displaying the RI structures than axial and coronal sections.The registering result showed that the 3D model of the RI reconstructed based on the sagittal oblique CVH sections was a correct model without deform.Meanwhile,the extension range of the CHL and the intimate spatial relationship of the stabilization structures of the LHBT were not confirmed on the sagittal oblique CVH sections.4 The histological sections showed that the characteristic of the position relationship between the ISP and SSP.The distance anterior margin of the ISP and the posterior margin of the SSP became smaller from medial to lateral side.The ISP covered posterior portion of the SSP near the insertion sites.The CHL originated from the horizontal limb and base of the coracoid process and enveloped the cranial part of the SSC and anterior part of the SSP.The superficial layer of the ligament covered a broad area of the anterior surface of the SSC muscle and superior surface of the SSP,the fibers filling the space between the ISP and SSP connected that of the CHL.The region of the SGHL was consisted of the dense fibers on the joint cavity side of the RI capsule.The 3D model reconstructed from the histological sections was similar with that from the CVH sections,but it can show the range of the extension more accurately.5 The fibers were not uniformly distributed in the region of the LHBT,and the characteristics of the distribution of the fibers were diversity in different segmentation of the LHBT.The biceps pulley was mainly consisted with the fibers from the SGHL,CHL.There were two different tissues below the pulley: the posterior tendinous tissue of SSC and anterior fibrous tissue of CHL.According to the histological study,the stabilization structures of the LHBT was 3D visualized reconstructed based on the CVH sections.The width of the biceps pulley was 13.46±1.22 mm.The pulley could be divided into two portions using the site where the SGHL wound on the SSC,the width of the medial and lateral portion were 5.19±0.60 mm and 8.28±1.34 mm respectively.6 The SSB and its adjacent structures were 3D visualized using Amira software in all of the 8 CVH shoulders.The SSB lied between SSC and scapula as a flat and irregular shaped entity.The largest longitudinal length was 13.80±5.05 mm,the largest transverse width was 7.22±3.43 mm,and the volume of the bursa was 130.56±140.51mm3.A thin spectrum between the SSB and joint cavity could be identified on the CVH sections.The SSB was identified in all the cadaveric shoulders,the MR appearance of the S SB was in the shape of saddlebag or narrow strip as the sectional anatomy of the SSB on the CVH sections,the contrast agent didn’t escape into the joint cavity.7 Coracoacromial ligment could contribute the thickness of the CHL.The thickness of the RI capsule measured using 2 different methods varied greatly(p<0.05).There were no significant difference between the height and the width of the RI(p>0.05).Conclusions1 The image segmentation technique could apply to the segmentation of the RI and the adjacent structures on the CVH images.The characteristics of the RI on the axial,coronal oblique,and sagittal oblique were diversity.The sagittal oblique CVH sections are the best to present the detail of the RI.2 According to the histological sections,the anatomical relationship of the CHL and the rotator cuff could be identified.And an accurate and detail 3D model of the CHL complex could be reconstructed based on these sections.The intimate relationship fo the CHL and ISP、SSP、SSC seggest that the stress on any strucutre of the CHL complex could be dispersed to the other porpotions of the same complex,and together they form a functional unity.3 The stabilization structure of the LHBT is composed of the biceps pulley as a capsuloligamentous structures and superior portion of the SSC tendon.In the early stage of the lesion,the pulley would like to be detached from the interface between these two different tissues.The procedure of reducing and fixing the pulley could be an effective repair technique.4 The quantitative criteria could be measured using a modified method on MR image.The previously reported RI area might be insufficient for demonstrated the RI pathology.5 The SSB is a separate entity which is liable to be confused with SSR on the MR image.Understanding the anatomy and MR appearance of the SSB will help to deal with the confusion and inappropriate diagnoses.Further study will be needed to figure out the correlation between the isolated SSB effusion on the MR image and the shoulder disorders.