Width of high signal and extension posterior to biceps tendon as signs of superior labrum anterior to posterior tears on MRI and MR arthrography

OBJECTIVE: The purpose of our study was to determine the accuracy of two signs for superior labrum anterior to posterior (SLAP) tears: increased width of high signal between the superior labrum and glenoid, and high signal posterior to the biceps tendon. MATERIALS AND METHODS: Forty-one patients with SLAP tears and 40 patients without a tear at surgery who had undergone MRI or MR arthrography were retrospectively evaluated. The MR studies were combined and interpreted in a blinded manner. The reviewers measured the width of high signal that extended to the articular surface on oblique coronal images and determined whether the high signal extended posterior to the biceps. A Student's t test was used to determine statistical significance between the means of the signal width. RESULTS: High-signal width was greater in patients with a SLAP tear than in the control group on both MRI and MR arthrography (both p = 0.003). The sensitivity and specificity of at least 2.0 mm on MRI are 39% (11/28) and 89% (24/27) and at least 2.5 mm on MR arthrography are 46% (6/13) and 85% (11/13). The sensitivity and specificity of high signal posterior to the biceps are 54% (15/28) and 74% (20/27) on MRI and 69% (9/13) and 54% (7/13) on MR arthrography. CONCLUSION: Increased width of high signal has a moderate specificity but a poor positive predictive value for distinguishing a SLAP tear from a normal recess. In addition, labral signal posterior to the biceps tendon is not rare in patients with no SLAP tear.     

Increased risk of posterior glenoid labrum tears in football players

OBJECTIVE: This study was designed to test our hypothesis that football players with shoulder pain, shoulder instability, or both requiring MR arthrography for evaluation are at an increased likelihood relative to non-football players for having a tear of the posterior glenoid labrum. CONCLUSION: We conclude that posterior glenoid labrum tears are more prevalent in football players than in non-football players.     

Capsulo-labro-ligamentous lesions of the shoulder: evaluation with MR arthrography

PURPOSE: The aim of the study was to analyse the accuracy of MR arthrography in the evaluation of capsulo-labro-ligamentous lesions of the shoulder in patients with glenohumeral joint instability. MATERIALS AND METHODS: From 1999 to 2001 fifty-eight patients with glenohumeral joint instability were studied by MR arthrography. Twenty-seven patients underwent surgical repair: 11 by arthroscopic and 16 by arthrotomic approach. All shoulder evaluations were performed with T1 and T2 weighted axial, coronal and sagittal oblique images, before and after intra-articular injection of gadolinium contrast. RESULTS: Forty capsulo-ligamentous lesions (including 14 capsular ruptures with extravasation of the contrast medium) were detected by MR arthrography. Fifty-two labral tears (36 of the anterior, 13 of the superior and 3 of the posterior glenoid labrum) were identified: 11 out of 52 were not recognized before gadolinium contrast injection. Five rotator cuff tears were identified, one of which was not shown in the pre-injection examination. Surgical results confirmed the MR arthrographic findings in 25/27 patients. In one case MR arthrography did not recognize a SLAP lesion; in another case it identified a tear of the capsule but not of the glenoid labrum. CONCLUSIONS: In many cases of subacute glenohumeral joint lesions with intracapsular fluid, MR may accurately evaluate capsulo-labral-ligamentous lesions. Indeed, the examination of lesions is limited by the absence of the natural contrast determined by fluid; in such cases, intra-articular injection of gadolinium contrast is necessary. MR arthrography evaluates the degree of capsulo-labro-ligamentous tears and may guide the surgical approach.     

The POLPSA lesion: MR imaging findings with arthroscopic correlation in patients with posterior instability

OBJECTIVE: To evaluate the features of the posterior labrocapsular periosteal sleeve avulsion (POLPSA) lesion on MR imaging in athletes with posterior shoulder instability. DESIGN AND PATIENTS: Six male athletes (age range 19-43 years) with avulsion of the posterior glenoid periosteum were identified on MR imaging. There were four football players, one wrestler, and one competitive weightlifter. The weightlifter had a bilateral condition so that seven shoulders were evaluated. MR imaging was performed with a 1.5 T magnet utilizing conventional and fat-saturated fast spin-echo coronal oblique and sagittal oblique sequences and a 3D-GRE transaxial sequence. Surgical correlation was available in all shoulders. RESULTS: All patients presented with pain and a joint effusion. The size of the periosteal sleeve and redundant joint recess was variable. Fibrous proliferation was noted arthroscopically in four shoulders beneath the sleeve. Although the posterior labrum was detached in all studies, only one labrum had a tear while two showed marked degeneration. CONCLUSION: The POLPSA lesion is an abnormality that can be associated with posterior instability. It differs from a reverse Bankart lesion because the periosteum, although detached, remains intact with the posterior capsule and detached posterior labrum. This lesion may represent an acute form of a Bennett lesion.     

Role of us in the preoperative evaluation of patients with anterior shoulder instability

PURPOSE: To assess the value of ultrasonography (US) in the preoperative evaluation of patients with anterior shoulder instability. MATERIALS AND METHODS: Twenty-two patients with one-sided anterior shoulder instability were examined with US by using three dynamic scanning approaches: two frontal and one axillary. The anterior labrum, the anterior ligamental-capsular complex, and the presence of humeral head and glenoid rim fractures were evaluated. Arthroscopy or arthrotomy was subsequently performed in all patients and was considered the standard. RESULTS: US correctly depicted the presence (n = 20) or absence (n = 1) of humeral head fractures and the presence (n = 10) or absence (n = 9) of glenoid rim fractures. All 22 patients had anterior labral tears; 21 tears were correctly depicted with US. The labral tear was seen as a hypoechoic zone larger than 2 mm (n = 15), labral movement (n = 10), a degenerated labrum (n = 6), or a vacuum phenomenon (n = 3). The anterior ligamental-capsular complex was correctly evaluated in 14 patients. The use of multiple approaches helped to prevent misinterpretation, but there were no substantial differences among the approaches in the depiction of the anterior shoulder structures. CONCLUSION: The high accuracy in the depiction of labral tears and associated fractures indicates that US can provide useful preoperative information in patients with anterior shoulder instability.     

Shoulder MR arthrography: which patient group benefits most?

OBJECTIVE: We sought to compare the diagnostic accuracy of conventional MRI versus MR arthrography of the shoulder in the assessment of high-performance athletes (professional baseball players) and to compare our findings in these patients with the conventional MRI and MR arthrographic findings in an age-matched control group of nonprofessional athletes. MATERIALS AND METHODS: Conventional MRI and MR arthrographic examinations of the shoulder in 20 consecutive professional baseball players with shoulder pain were reviewed retrospectively by two musculoskeletal radiologists in consensus. These interpretations were compared with retrospective consensus interpretations of conventional MRI and MR arthrographic examinations of the shoulder obtained in a control group of 50 consecutive nonprofessional athletes with shoulder pain. MR images were assessed for full- or partial-thickness supraspinatus tendon tears, superior labral anteroposterior (SLAP) tears, and anterior or posterior labral tears. RESULTS: In the 20 consecutive professional athlete patients, two full-thickness and six partial-thickness undersurface supraspinatus tendon tears were seen on MR arthrography but not seen on conventional MRI as well as six SLAP tears, two anterior labral tears, and one posterior labral tear. Three patients had both SLAP tears and full- or partial-thickness supraspinatus tendon tears. Of 14 patients with findings on MR arthrography that were not seen on MRI, 11 had arthroscopic correlation. In all 11, arthroscopic findings confirmed findings on MR arthrography. In the group of 50 nonprofessional athlete patients, five had additional findings on MR arthrography not seen on conventional MRI: two anterior labral tears, two partial-thickness supraspinatus tendon tears, and two SLAP tears. One patient had both a partial-thickness supraspinatus tendon tear and a SLAP tear seen on MR arthrography. The five patients with additional findings on MR arthrography had arthroscopy. In all five, arthroscopic findings confirmed the findings on MR arthrography. CONCLUSION: MR arthrography is considerably more sensitive for detection of partial-thickness supraspinatus tears and labral tears than conventional MRI. MR arthrography showed injuries in addition to those seen on conventional MRI in 14 of 20 patients in the high-performance athlete group. These results suggest high-performance athletes may be a subgroup of patients for whom MR arthrography yields considerably more diagnostic information than conventional MRI.     

3.0T常规MRI与MR髋关节造影诊断髋臼唇撕裂的对比研究

目的 在3.0 T场强中,比较常规髋关节MRI及MR髋关节造影对髋臼唇撕裂的诊断价值.方法 回顾分析44例髋关节病变患者的患侧髋关节常规MRI及MR髋关节造影资料,将每例患者的臼唇划分为前、上、后3处区域(共计132处),确定有无撕裂,并进行分型.其中5例患者经髋关节镜检查.对于常规MRI及MR髋关节造影获得的臼唇撕裂及分型数据差异比较采用Wilcoxon秩和检验,一致性比较采用Kappa检验.结果 常规MRI与MR髋关节造影诊断完全相同者计116处臼唇,只有16处存在诊断差异.其中,前者诊断无撕裂而后者诊断撕裂者9处,前者诊断撕裂但后者诊断无撕裂者6处,其余1处两者均诊断为撕裂但分型不同.常规MRI与MR髋关节造影的评价差异没有统计学意义(Z=0.347,P＞0.05),且具有极好的一致性(K=0.781,P＜0.01).在接受关节镜的5例患者中,常规MRI、MR髋关节造影及关节镜结果均完全吻合.结论 对髋臼唇撕裂,3.0 T常规髋关节MRI可获得与MR髋关节造影基本相同的诊断效果.     

肩盂肱关节不稳的CT关节造影表现

目的　总结分析盂肱关节不稳在CT关节造影上的表现。方法　 16例经关节镜手术检查证实病例 ,对盂唇撕裂 ,关节囊撕脱 ,关节盂骨折等在CT关节造影上表现特点进行总结分析。结果　关节内损伤包括盂唇撕裂 ,见盂唇内有造影剂充盈 ;关节盂唇软骨剥脱 ,正常关节软骨三角形结构消失 ,骨性关节盂裸露于关节囊内 ;关节囊撕脱 ,表现有关节囊腔扩大 ,关节囊附着点位置改变等 ;以及骨性关节盂缘骨折 ,肱骨外上方压缩骨折等。结论　肩盂肱关节CT造影对比性好 ,断层图像无重叠 ,可清晰显示出关节内损伤 ,是肩盂肱关节不稳的一种有效准确的检查方法     

Shoulder instability: accuracy of MR imaging performed after surgery in depicting recurrent injury--initial findings.

PURPOSE: To analyze a series of postoperative magnetic resonance (MR) images obtained in patients with recurrent signs or symptoms of instability in whom subsequent surgical correlation was performed to determine the accuracy in diagnosing recurrent injury. MATERIALS AND METHODS: The authors identified 24 patients who underwent MR imaging after shoulder instability surgery and had recurrent instability requiring repeat surgery. Twelve nonenhanced MR images and six indirect and six direct MR arthrograms were retrospectively reviewed with consensus to determine the presence or absence of recurrent labral or rotator cuff tear. Operative reports were reviewed to confirm the presence or absence of labral or rotator cuff tear. The mean interval between initial surgery and MR imaging was 10 months. The mean interval until repeat surgery was 2 months. RESULTS: Overall, the accuracy of postoperative MR imaging was 79% in depicting recurrent labral tear and 88% in depicting recurrent rotator cuff tear. Indirect MR arthrography had 100% accuracy for recurrent labral tear detection, whereas direct MR arthrography and nonenhanced MR imaging had accuracies of 67% and 75%, respectively. Direct MR arthrography was more sensitive, 100% versus 71%, but less specific, 60% versus 80%, than nonenhanced MR imaging in depicting recurrent labral tears. Direct MR arthrography had 100% accuracy in depicting rotator cuff tear, whereas both indirect MR arthrography and nonenhanced MR imaging had 83% accuracy. CONCLUSION: MR imaging, indirect MR arthrography in particular, appears to be an accurate means of evaluating the shoulder following instability surgery.     

MR imaging and MR arthrography of paraglenoid labral cysts

OBJECTIVE: We investigated the pathophysiology of paraglenoid labral cysts on the basis of MR imaging, MR arthrography, and cyst aspiration. MATERIALS AND METHODS: From 2211 MR imaging examinations, 51 (2.3%) cysts in 46 patients were identified. MR arthrography (n = 5), cystography (n = 1), arthroscopy (n = 17), percutaneous needle aspiration (n = 4), and medical records were also reviewed (n = 46). RESULTS: On MR imaging and arthrography, cysts were best viewed on T2-weighted images. Mean cyst diameter and volume were 2.2 cm and 2.8 cm3, respectively. Fifty-seven percent of cysts were located adjacent to the posterior labrum. On MR imaging and arthroscopy, a labral tear was identified in 27 (53%) and 15 (88%) patients, respectively. Eight cysts that caused compression neuropathy were large (mean size, 3.1 cm; p = 0.04) and located next to the posterior or inferior labrum. In four of five patients, MR arthrograms showed no intraarticular contrast material in the cyst. Cystograms showed no communication with the glenohumeral joint space, and cyst aspiration resulted in temporary symptom relief; however, cysts recurred in three of four patients. CONCLUSION: Most paralabral cysts are associated with labral tears. Paralabral cysts may be difficult to identify on MR arthrography unless a T2-weighted sequence is performed. Direct communication between a cyst and joint space rarely occurs. A posterior or inferior cyst may cause compression neuropathy of the suprascapular or axillary nerve, respectively. Cyst aspiration may result in temporary relief of symptoms, but an untreated labral tear should be suspected if cysts recur.     

MR arthrography of the shoulder: comparison with conventional MR imaging

Twenty-three patients underwent both conventional MR imaging of the shoulder and MR shoulder arthrography for clinically suspected labral or rotator cuff abnormalities. Images obtained before and after contrast administration were studied independently, and without knowledge of clinical findings, by two radiologists for the presence of abnormalities of the glenoid labrum or rotator cuff. Results were correlated with surgical findings in all patients. Nine patients had surgically proved labral tears. MR arthrography detected all nine labral abnormalities, while six of the nine were missed on conventional MR imaging. Fourteen patients had surgically proved rotator cuff tears. MR arthrography detected 11 of the 14 tears and missed three partial tears on the bursal surface. Conventional MR imaging detected nine cuff tears and missed five tears; two of these were complete rotator cuff tears and three were partial tears of the undersurface of the rotator cuff. Our results suggest that MR arthrography enhances the accuracy of MR in the evaluation of the glenoid labrum and rotator cuff tendon.     

合并肩袖损伤的肩关节盂唇损伤的临床特征

目的 分析合并肩袖损伤的肩关节盂唇损伤患者的临床特征,提出其发病规律与病变特点,为临床微创手术治疗提供参考. 方法 本组50例,其中男28例,女22例;年龄30～58岁,平均45岁.记录患者的损伤机制、损伤时间、临床症状、体征,摄X线片和MRI.根据临床诊断,采用肩关节镜微创手术修复盂唇和肩袖损伤,记录损伤部位、范围及程度并进行分析.本组表现前盂唇损伤37例,上盂唇撕裂8例,后盂唇损伤5例;肩袖损伤轻度36例,中度10例,重度3例,特大裂口1例.其中肩袖前侧(冈上肌前侧)损伤21例,中部损伤(冈上肌与冈下肌部)16例,后部损伤(冈下肌部、小圆肌)13例.盂唇损伤的MRI表现为:三角外形消失,前关节囊扩大.肩袖损伤表现为:损伤部位高信号,连续性丧失. 结果 本组患者平均随访36个月(6～72个月),临床效果满意.美国加州洛杉矶大学关节功能评分标准(UCLA)评分:术前(15±3)分,术后(32±3)分(P＜0.01). 结论 创伤性肩关节盂唇损伤患者常同时合并肩袖损伤,临床上应予重视,避免遗漏诊断或耽误治疗.盂唇损伤范围与肩袖损伤部位存在对应关系,盂唇损伤范围越大,肩袖损伤越接近后侧.     

Direct MR arthrography of the shoulder: is exercise prior to imaging beneficial or detrimental?

PURPOSE: To define the beneficial and detrimental effects of adding exercise to direct magnetic resonance (MR) shoulder arthrography. MATERIALS AND METHODS: Direct, intraarticular, gadolinium arthrography of the shoulder was performed in 41 patients, who underwent 1.5-T MR imaging before and after 1 minute of arm swinging. Fourteen milliliters of dilute gadolinium solution was injected. Two readers blinded to exercise independently graded the randomly distributed images with a five-point scale for capsular contrast material resorption; extraarticular contrast material leakage; rotator cuff, glenoid labrum, and anterior capsule conspicuity; and partial-thickness or full-thickness rotator cuff tear and labral tear detectability. The sign test was performed to evaluate the significance of differences between preexercise and postexercise grading for each reader. A second review was performed, with direct side-by-side comparison of preexercise and postexercise images. RESULTS: There was evidence of increased capsular resorption after exercise but no alteration in the depiction of the rotator cuff tendons or glenoid labrum. There was no significant extraarticular contrast material leakage after exercise and no alteration in depiction of the anterior capsule. There was no difference in the detectability of rotator cuff or labral tears. CONCLUSION: Exercise with direct shoulder MR arthrography has no beneficial or detrimental effect on image quality or on the depiction of rotator cuff or labral tears.     

Posterior shoulder labrocapsular structures in all aspects; 3D volumetric MR arthrography study

Pathologies of the posterior labrocapsular structures of the shoulder joint are far less common than anterior labrocapsuloligamentous lesions. Most of these pathologies have been associated with traumatic posterior dislocation. A smaller portion of the lesions include posterior extension of superior labral anteroposterior lesions, posterior superior internal impingement, and damage to the posterior band of the inferior glenohumeral ligament. Labrocapsular anatomic variations of the posterior shoulder joint can mimic labral pathology on conventional MR and occasionally on MR arthrographic images. Knowledge of this variant anatomy is key to interpreting MR images and studying MR arthrography of the posterior labrocapsular structure to avoid misdiagnosis and unnecessary surgical procedures. In this article, we review normal and variant anatomy of the posterior labrocapsular structure of the shoulder joint based on MR arthrography and discuss how to discriminate normal anatomic variants from labrocapsular damage.     

Synovial fold of the posterior shoulder joint capsule

Purpose  The purpose of the study is to describe, based on shoulder MRI and MR arthrography with arthroscopic correlation, a posterior joint capsule fold. Materials and methods  A retrospective review of 410 shoulder MRIs and direct MR arthrograms with arthroscopic correlation in positive cases (when available) was obtained with IRB approval and HIPPA compliance. The study was performed by three musculoskeletal radiologists. The criteria utilized to establish the diagnosis of posterior synovial fold included: (1) axial T1-weighted (T1W) on MR arthrography or axial T2* GRE-weighted on MRI demonstrating rounded thickening of the posterior shoulder joint capsule with a thickness at least 2 mm in diameter. (2) The posterior synovial fold extends in an oblique craniocaudal direction from the posterior–inferior joint capsule adjacent to the posterior–inferior glenoid labrum (7 o'clock) and continues superiorly away from the glenoid labrum to the posterior–superior joint capsule (11 o'clock). Results  Although uncommon, the posterior synovial fold was present in 2% (8/410) of studies reviewed and found predominantly in women (75%, 6/8). Four patients had arthroscopic confirmation of the posterior synovial fold. A higher percentage of posterior synovial folds were observed on shoulder MR arthrography (2.7%, 4/150) than on shoulder MRI (1.5%, 4/260). Conclusion  Although rare, the posterior synovial fold can be recognized and should not be confused with a posterior labral tear. Further investigation is needed to assess its histologic properties and its clinical significance.     

Hypoplasia of the glenoid neck of the scapula: imaging findings and report of 16 patients

OBJECTIVE: Our purpose was to describe the primary and associated imaging findings in patients with glenoid hypoplasia required for an accurate diagnostic appraisal of this uncommon abnormality. METHODS: The medical records and imaging studies of 16 patients with glenoid hypoplasia were retrospectively reviewed. Plain films were available in all patients, arthrography in 2, computed tomography (CT) in 5, CT arthrotomography in 3, magnetic resonance (MR) imaging in 9, and MR arthrography in 3 patients. The imaging studies were reviewed with special attention to the primary and secondary findings associated with glenoid hypoplasia. RESULTS: On radiographs, the 21 abnormal shoulders documented in the 16 patients with glenoid hypoplasia had an irregular (n=15) or shallow and smooth (n=6) articular surface of the glenoid. Computed tomography findings showed subluxation of the humeral head in 5 cases. On MR images, the hypoplastic bony glenoid and scapular neck were replaced by abnormal tissue of inhomogeneous signal intensity, showing the signal intensity characteristics of fibrocartilage (n=6) or fat (n=5). Widening of the inferior glenohumeral joint space was seen in all cases. Magnetic resonance imaging or MR arthrography revealed variable abnormalities of the labrum, including enlargement (10 shoulders), detachment of labrum from the bony glenoid (6 shoulders), intrasubstance tear (4 shoulders), and perilabral cyst (2 shoulders). The posterior labrum was absent (n=1) or torn (n=1) in one patient with bilateral deformity. Other findings included partial tear of the subscapularis tendon (n=1) and rotator cuff atrophy (n=1) and tear (n=2). CONCLUSION: Glenoid hypoplasia is a developmental skeletal anomaly comprising a spectrum of associated osseous and cartilaginous changes of the articular cartilage and glenoid labrum. Cross-sectional imaging studies, with or without arthrography, may help further characterize associated derangements of the shoulder, some of which are indicative of shoulder instability.     

Arthroscopic treatment of posterior and multidirectional instability

The author can answer the three fundamental questions which were posed in the beginning of this chapter as follows: Atraumatic posterior and multidirectional laxity is attributable to capsular ligamentous laxity and can be asymptomatic initially. Over the time, repetitive subluxation of the humeral head exerts excessive rim-loading on the posteroinferior glenoid labrum which can develop into retroversion of the glenoid labrum and eventually leading to labral tears. In this stage, a patient develops shoulder pain during daily and sports activities. Besides increased translation, the diagnosis should be based on the symptoms reproduced by the jerk and Kim tests. The jerk test is a hallmark for predicting the prognosis of nonoperative treatment in posteroinferior instability. Shoulders with a painful jerk test have posteroinferior labral lesion and are unresponsive to nonoperative treatment. In these patients, early surgery may be indicated. Any successful surgical procedure should correct both the capsular laxity and the retroversion of the posteroinferior glenoid labrum. Simple capsular plication or an inferior capsular shift is insufficient for correcting the two major pathologies. Arthroscopic capsulolabroplasty restores capsular tension as well as labral height.     

Humeral avulsion of the posterior band of the inferior glenohumeral ligament: MR arthrography and clinical correlation in 17 patients

OBJECTIVE: The purpose of this article is to describe the MR arthrography findings of humeral avulsion of the posterior band of the inferior glenohumeral ligament in 17 patients. To elucidate the clinical importance of this abnormality, we also correlate our imaging findings with the presence of coexisting structural abnormalities; clinical presentation; and, when available, arthroscopic evaluation (n = 8). CONCLUSION: Humeral avulsion or insufficiency of the posterior band of the inferior glenohumeral ligament can be easily detected using MR arthrography. This ligamentous abnormality may be seen in isolation, or it may occur in conjunction with posterior or, less often, anteroinferior capsulolabral abnormalities. The presence of this lesion in a subgroup of patients with the clinical diagnosis of multidirectional instability may offer insight into the causes and pathogenesis of this complex entity.     

Computed tomography (CT) arthrography of shoulder instabilities in athletes

Sixty professional and recreational athletes underwent CT arthrography of the shoulder for evaluation of suspected shoulder joint derangement. These athletes, 46 males and 14 females ranging in age from 15 to 60 years (mean, 32 years), all had persistent pain that interfered with their sports activity and was resistant to conservative treatment. Seventeen patients had shoulder instability based on clinical manifestations and CT arthrographic findings. An additional five patients, also based on clinical manifestations and CT arthrographic findings, were considered to have an unobtrusive degree of anterior joint laxity. Patients with anterior instability (20 cases) all had an anteroinferior tear or detachment of the glenoid labrum, as well as some violation of the insertion of the joint capsule onto the scapula. Those with posterior instability (two cases) had a combination of labral and capsular tears. Two other major patterns of labral tears, both unaffiliated with shoulder instability, were identified. These included total or partial detachment of superior segments of the labrum, and anterior labral tears at the midglenoid level. Moreover, various degrees of labral attenuation (or, less often, enlargement), osteophyte formation, and alterations in articular cartilage were observed. Surgical correlation was obtained in 25 patients, with 95% accuracy of CT arthrographic findings. CT arthrography is a minimally invasive and highly accurate technique for investigation of glenohumeral derangement. Specifically, the extent of pathologic changes associated with instability can be determined and differentiated from other intraarticular causes of incapacity, such as labral tears caused by throwing, or degenerative changes.     

Sublabral sulcus at the posteroinferior acetabulum: a potential pitfall in MR arthrography diagnosis of acetabular labral tears

OBJECTIVE: Our study correlated findings on hip MRI and MR arthrography with hip arthroscopy to assess the location, prevalence, and potential pitfall of a normal acetabular sublabral sulcus. MATERIALS AND METHODS: We retrospectively collected 58 hip MRI studies along with surgical reports in 58 patients who underwent hip arthroscopy over a 5-year period. Intraoperative photography (n = 23), radiography (n = 56), unenhanced MRI (n = 13), and MR arthrography (n = 54) studies were available for review. Two radiologists described hip anatomy on radiology studies with agreement by consensus. RESULTS: A normal posteroinferior sublabral groove was confirmed on available arthroscopy photographs in four (17.4%) of 23 hips. In each of these four patients, the anatomic sublabral groove correlated with apparent partial labral detachment on MR arthrography. On review of all studies, 13 hips (22.4%) without a posterior labral tear at surgery had imaging findings of a sublabral sulcus. The sulcus was not associated with acetabular dysplasia, which was radiographically noted in 12 cases (21.4%). Preoperatively, the sulcus was misdiagnosed as a tear in two cases. Labral tears were anterior or anterosuperior in 51 patients. CONCLUSION: A posteroinferior sublabral groove is a relatively common normal anatomic hip variation. If not recognized as normal, the sulcus may serve as a diagnostic pitfall on MR arthrography. Its location is distinct from most labral tears. We did not discover a sublabral sulcus at the anterior or anterosuperior acetabulum, the most common sites of labral injury.