Thin Sectional Anatomy Of The Rotator Interval And Its Preliminary Application In Routine MRI Findings Of Frozen Shoulder

BackgroundFrozen shoulder, also known as adhesive capsulitis, is an inflammatory condition ofglenohumeral joint capsule and synovium leading to restricted range of motion. The currentconsensus definition of the American Shoulder and Elbow Surgeons is "a condition ofuncertain etiology characterized by significant restriction of both active and passiveshoulder motion that occurs in the absence of a known intrinsic shoulder disorder". Frozenshoulder most commonly affects women aged between40and60years. In China, frozenshoulder is called the "50s shoulder''. Frozen shoulder, as well as adhesive capsulitis, iscommonly accepted in the oversea literature.Frozen shoulder is primarily a clinical diagnosis, and it is usually diagnosed on thebasis of clinical findings including history and physical examination. But we poorly graspof the etiology and pathophysiology of frozen shoulder, and initial diagnosis andsubsequent treatment of frozen shoulder is a poorly correct entity today. Invasivearthroscopic findings as the reference "gold standard" for the diagnosis of frozen shoulderis not generally used in routine work. Hence, noninvasive imaging is more and moreimportant in the diagnosis of frozen shoulder.Recently, a number of publications have described the imaging assessment of thediagnosis of frozen shoulder, Some reports have associated osteopenia of the proximalhumerus with frozen shoulder. The glenohumeral joint capacity is less than10ml, whichcan be an indicator of frozen shoulder, using arthrography of the shoulder. Thickenedcoracohumeral ligament can be suggestive of frozen shoulder, using ultrasound. Thepresence of a hypoechoic region with increased vascularity in the rotator interval correlateswith the fibrovascular inflammatory tissue that is usually present and can provide early andaccurate diagnosis of frozen shoulder.Currently, plain magnetic resonance imaging (MRI) and MR arthrography can provide reliable imaging indicators of frozen shoulder, and these findings on MRI have been shownto correlate well with surgical findings, although some studies in the radiologic literature donot support this. Joint capsule and synovium thickness greater than4mm is a useful MRcriterion for the diagnosis of frozen shoulder. Some reports showed that thickness ofcapsule and synovium of the axillary recess greater than3mm is a practical MR criterionfor the diagnosis of frozen shoulder when measured on oblique coronal T2-weighted MRarthrography images without fat suppression. Some reports indicated that blood flow to thesynovium involving the glenohumeral joint increased in the frozen shoulder. The presenceof enhancing fibrovascular scar tissue in the rotator interval(RI), soft tissue thickeningaround the biceps anchor and thickening of the axillary pouch on MR imaging are signssuggestive of frozen shoulder. Some reports showed that thickening of the joint capsule andsynovium and diminished filling ratio of the axillary recess to posterior joint cavityappeared to be useful criterion for the diagnosis of frozen shoulder. Some reports showedthat thickening of the CHL and the joint capsule in the rotator interval, as well as thesubcoracoid triangle sign,were characteristic MR arthrographic findings in frozen shoulder.Some reports showed that there were statistically significant differences in RI dimensionsincluding height, base, RI index, and RI ratio between patients with and without frozenshoulder. Estimating the dimensions of the RI in frozen shoulder using MR arthrographymay prove to be valuable for assessing patients with frozen shoulder preoperatively. Somereports showed that coracohumeral ligament (CHL) thickness on MR arthrographycorrelates with the range limitation of external rotation and internal rotation IR in patientswith frozen shoulder.In the publications, the glenohumeral joint capsule, the rotator interval and thecoracohumeral ligament became the key region of interest of the studies on the frozenshoulder with magnetic resonance imaging (MRI). The thicken CHL was useful for thediagnosis of frozen shoulder, but the measurement of the CHL thickness depended on theCHL visualization rate, and that rate depended on the fat in the rotator interval displayingheperintensity with MRI. Hence, MRI evaluation of the fat distribution type in the rotatorinterval was very important to diagnose the frozen shoulder. However, few studies haveattempted to investigate the fat distribution in the rotator interval, the CHL visualizationrate and the CHL thickness in normal shoulders, using routine magnetic resonance imaging (MRI). There were no reports on the fat distribution in the rotator interval correlated withfrozen shoulder. Some studies showed that the presence of enhancing fibrovascular scartissue in the rotator interval and thickened joint capsule and synovium was useful for thediagnosis of frozen shoulder.However, routine magnetic resonance imaging (MRI) ismainly used in the patients with shoulder pain, there were no reports on the signal intensityof the rotator interval and the axillary recess correlated with frozen shoulder, using routinemagnetic resonance imaging (MRI).Furthermore, frozen shoulder, also known as type Ⅰof RI lesions, was confused withthe other types of the RI lesions because of the poorly understood anatomy of the RI.Though the structures that define the borders of the RI were well agreed upon in theliterature, there remained some controversy as to the exact components comprising thecapsule that bridges this space and their degree of contribution. There were few correlativestudies between thin-sectional anatomy and magnetic resonance imaging (MRI). It wasimportant to explore the morphological features of sectional anatomy of the the RI for thediagnosis and therapy of frozen shoulder.ObjectiveThe current study started from correlative study between thin-sectional anatomy andmagnetic resonance imaging (MRI) based on the subdataset of shoulder from ChineseVisible Human(CVH), to explore the morphological features of continual thin-sectionalanatomy of the important components in the RI. Then, the current study explored therelationship between the fat distribution in the rotator interval, the CHL visualization rateand CHL thickness, using routine magnetic resonance imaging (MRI) to determine the scanplane for measuring the CHL thickness. Finally, The present study investigated thecorrelation between the fat distribution in the rotator interval, the CHL visualization rateand CHL thickness and frozen shoulder, and investigated the correlation between the signalintensity of the rotator interval and the axillary recess and frozen shoulder, using routinemagnetic resonance imaging (MRI). The objective of the present study was provide thedetailed thin-sectional anatomy of the RI for the diagnosis and treatment of the RI lesions,and to investigate whether the patients with frozen shoulder had some useful signs withroutine MRI. The objective of the present study was also to supply the magnetic resonanceimaging features for diagnosing frozen shoulder, evaluating the stages and therapy of frozen shoulder.Materials1.The subdataset of the shoulder from Chinese Visible Human(CVH)Number1toNumber5,20shoulder joints of the normal volunteer individuals,5shoulders withoutabnormalities from5patients underwent MR arthrography, a1.5-T system, and an imageworkstation with the visualizational software were included to use in the first part of thepresent study.2. One hundred and twenty shoulder joints in60normal volunteer individuals (a meanage of50.5years),72shoulder joints in72patients(a mean age of53.5years)with frozenshoulder, and a1.5-T system were included to use in the second part of the present srudy.3. One hundred and twenty shoulder joints in60normal volunteer individuals (a meanage of50.5years),120shoulder joints in120patients (a mean age of53.3years) withfrozen shoulder, and a1.5-T system were included to use in the third part of the presentsrudy.Methods1.The subdataset of shoulder from CVH was observed to compare the detailedsectional anatomy structure of the RI with routine MRI and MR arthrography. The anatomystructure of the RI and its components was marked from CVH, routine MRI and MRarthrography one by one with Photoshop CS2software.2.A MRI evaluation index included the fat distribution type, the rate of CHLvisualization, and the CHL thickness. The fat distribution types included type A, type B,type C, type D and type E. A chi-square test was used to analyze the data for the fatdistribution type and the rate of CHL visualization. A two-way ANOVA was used to analyzethe maximum thickness of CHL for different lateral shoulders and different gendershoulders.Two-tailed hypothesis tests were used, and local statistical significance wasassumed to be P <0.05for all parameters.3.Evaluation index included the signal intensity (SI)of the RI(the SItra, the SIsag,andthe SIcor of the RI), the SI of the cortical bone of coracoid process(CP)(the SItra, theSIsag,and the SIcor of the cortical bone of CP), the SI of the axillary recess(AR)(theSItra and the SIcor of the AR), and the SI of the cortical bone of humerus (the SItra and theSIcor of the cortical bone of humerus). Evaluation Indicator also included the relative SItra (RSItra) of the RI, the RSIsag of the RI, the RSIcor of the RI, the RSItra of the axillaryrecess(AR), and the RSIcor of the AR. A two-way ANOVA was used to analyze theevaluation index for different lateral shoulders and different gender shoulders. A one-wayANOVA was used to analyze the the RSItra of the RI, the RSIsag of the RI and the RSIcorof the RI. An independent-samples t test was used to analyze the RSItra of the AR and theRSIcor of the AR. Two-tailed hypothesis tests were used, and local statistical significancewas assumed to be P <0.05for all parameters.Results1.The inferior border(the superior margin of SSC)of the RI and the medial border(CP))of RI were markedly displayed on transverse, sagittal oblique and coronal obliqueplane. The CHL was markedly displayed on the sagittal oblique and coronal oblique plane,using plain MRI, and the rate of the CHL was low on the transverse plane.The SGHL wasmarkedly displayed on the CVH, especially in the transverse plane. The LBT was markedlydisplayed on the CVH, and the intraarticular full segment of the LBT was also markedlydisplayed on the CVH. The LBT was markedly displayed on the sagittal oblique plane ofMR arthrography. The RIC was markedly displayed on the CVH, and was not displayedwith plain MRI and MR arthrography. The biceps reflection pulley was markedly displayedon the sagittal oblique plane with CVH and MR arthrography. The SGHL and the LBT wereparallel to the coracoid process on the transverse plane from CVH. The CHL wasperpendicular to the LBT in the transverse plane from CVH. The CHL was perpendicular tothe SGHL, with T-shaped link anterior to the LBT on the sagittal oblique plane.The axillaryrecess (AR) was markedly displayed on transverse plane from the subdataset of theshoulder of CVH, but the AR was difficult to differentiate between the anterior band andthe posterior band of the inferior GHL complex. The thickness of the glenohumeral jointcapsule in the AR was too thinner to be measured in fat-suppressed T1WI from MRarthrography.The glenohumeral joint capsule in the AR displayed low signal intensity in thefat-suppressed PDWI, and was markedly displayed in the transverse and coronal obliqueplanes.2.(1)A comparison of the fat distribution types in the RI in the patients with frozenshoulder versus the control group showed that the number of the type A decreased, thenumber of the type B and type E increased, and there was significant difference, using the x2test (P＜0.05).(2)A comparison of the CHL visualization rate in the patients with frozenshoulder versus the control group showed that the CHL visualization rate (91.7%) in thecontrol group was significantly greater than that rate in the frozen shoulder group (79.2%),and the CHL visualization rate(95%) in the female shoulder from the control group wassignificantly greater than that rate(80%) in the female shoulder with frozen shoulder (P＜0.05). The CHL visualization rate in the coronal oblique images was86.7%in the controlgroup, and87.5%in the frozen shoulder group, and there was no significant difference (P＞0.05). The CHL visualization rate in the transverse images was24.2%in the controlgroup, and19.4%in the frozen shoulder group, there was no significant difference (P＞0.05).(3)A comparison of the CHL thickness in the patients with frozen shoulder versus thecontrol group showed that the CHL thickness (3.99±1.68mm)on sagittal oblique plane inthe patients with frozen shoulder was significantly greater than that thickness (3.08±1.32mm) for the control group, using a two-way ANOVA (P＜0.05). The CHL thickness(4.37±1.71mm)on coronal oblique plane in the patients with frozen shoulder wassignificantly greater than that thickness (2.84±0.79mm) for the control group(P＜0.05),and the CHL thickness on the coronal oblique plane in the female shoulders wassignificantly greater than that thickness in the male shoulders (P＜0.05). The CHLthickness (3.93±1.49mm)on transverse plane in the patients with frozen shoulder wassignificantly greater than that thickness (2.29±0.65mm) for the control group (P＜0.05).3.A comparison of the SItra and the RSItra of the RI in the patients with frozenshoulder versus the control group was significant, using a two-way ANOVA(P＜0.001),andthe SItra and the RSItra of the RI in the female shoulders was significantly greater than thatSItra and RSItra in the male shoulders (P＜0.05). The SIsag and the RSIsag of the RI wasthe same result as that SItra and the RSItra of the RI between the patients and the controlgroup (P＜0.001), and the RSIsag of the RI in the right shoulders was significantly greaterthan that RSIsag of the RI in the left shoulders (P＜0.05). A comparison of the SIcor andthe RSIcor of the RI in the patients with frozen shoulder versus the control group wassignificant(P＜0.001). A comparison of the SItra,the RSItra the AR in the patients withfrozen shoulder versus the control group was significant (P＜0.001), and the SIcor andthe RSIcor of the AR was the the same result as that SItra and the RSItra of the AR betweenthe patients and the control group (P＜0.001). The SItra and the RSItra of the AR in the female shoulders was significantly greater than that SItra and that RSItra of the AR in themale shoulders (P＜0.05). The SItra and the RSItra of the AR in the right shoulders wassignificantly greater than that SItra and of that RSItra the AR in the left shoulders (P＜0.05).A comparison of the SItra, the SIsag and the SIcorof the cortical bone of CP in the patientswith frozen shoulder versus the control groupwas significant(P＜0.001),and the SIsag ofthe cortical bone of CP in the left shoulderswas significantly greater than that SIsag in theright shoulders (P＜0.05). A comparison of the SItra and the SIcor of the cortical bone ofhumerus in the patients with frozen shoulder versus the control group was significant.Conclusions1.The SSC and the CP is important positioning mark for evaluating of the anatomy andlesions of the RI,using MRI. It is complementary for MRI and CVH displaying thecomponents of the RI. The sagittal oblique is the best position for displaying the borders ofthe RI, the components of the RI and the biceps reflection pulley, and that plane was usefulfor the scanning-position mark and reading the film of MRI. The SGHL and the LBT wereparallel to the coracoid process in the transverse plane from CVH.The CHL wasperpendicular to the LBT in the transverse plane from CVH. The CHL was perpendicular tothe SGHL, with T-shaped link anterior to the LBT on the sagittal oblique plane from CVHand MR arthrography. That spatial relationship among those components of the RI wasuseful for the scanning-position mark and reading the film of MRI. The glenohumeral jointcapsule in the AR displayed low signal intensity in the fat-suppressed PDWI, and wasmarkedly displayed in the transverse and coronal oblique planes for the anatomy andlesions of the glenohumeral joint capsule.2. The change of the fat distribution type in the RI, the rate of CHL visualization andthe thickened CHL correlates with frozen shoulder. There is a few of imaging signs of thefrozen shoulder with routine MRI.The number of the type A for the fat distribution in theRI decreases, and the number of the type B and type E increases in the patients with frozenshoulder. The rate of CHL visualization decreases in the patients with frozen shoulder.Thecoronal oblique plane is the best to the CHL depiction and measuring the CHL thickness inthe patients with frozen shoulder. A thickened CHL in the coronal oblique plane(4.37mm)and in the sagittal oblique plane (3.99mm) is highly suggestive of frozen shoulder, perhapstaken as one of the most characteristic MR findings for frozen shoulder. 3.The hyperintensity of the rotator interval and the axillary recess in fat-suppressedproton-density weighted spin-echo images(PDWI) correlates with frozen shoulder, usingroutine magnetic resonance imaging (MRI). Routine MRI is useful for the diagnosis offrozen shoulder, and the key regions of interest of lesions with frozen shoulder in thefat-suppressed PDWI should be orbserved from the order: at first, the AR in the transverseplane should be orbserved. then, the AR in the coronal oblique plane,the RI in the sagittaloblique plane and the RI in the transverse plane. at last, the RI in the coronal oblique planeshould be orbserved. Of course, the affected area of frozen shoulder may include theproximal humerus and the CP.