[CME Rheumatology 26: Bone Marrow Edema of the Sacro-Iliac Joint = Spondyloarthritis? What the General Practicioner Should Know]. / CME Rheumatologie 26: Knochenmarködem im Iliosakralgelenk = Spondyloarthritis? Was die Hausärztin/der Hausarzt wissen sollte CME-Fragen.

CME Rheumatology 26: Bone Marrow Edema of the Sacro-Iliac Joint = Spondyloarthritis? What the General Practicioner Should Know Abstract. Axial spondyloarthritis is a chronic inflammatory joint disease mainly involving the sacroiliac joints (ISG) and the spine. The diagnosis can be made early due to acute inflammatory changes in the ISG on magnetic resonance imaging (MRI). Radiographs of the ISG do not help in early diagnosis because structural damage is not apparent on radiographs until an advanced stage. In recent years, however, several studies have shown that bone marrow edema - hyperintense signals (= bright spots) as a possible MRI correlate for inflammation - does not specifically occur in axial spondyloarthritis, but can also be seen in healthy people, athletes, people with high mechanical stress (e.g. military recruits) and postpartum women. The diagnosis of axial spondyloarthritis should therefore never be based solely on an MRI finding, but must always include the overall clinical context.

[CME Rheumatology 24/Answers: DISH of the Hand and Undifferentiated Polyarthritis]. / CME-Rheumatologie 24/Antworten: DISH der Hand und undifferenzierte Polyarthritis.

CME Rheumatology 24/Answers: DISH of the Hand and Undifferentiated Polyarthritis Abstract. We present a case with undifferentiated, unclassified polyarthritis and with peripheral diffuse idiopathic skeletal hyperostosis (DISH). We discuss the differential diagnoses of "seronegative" polyarthritis and explain the radiographic findings of the little-known peripheral aspects of DISH.

[CME Rheumatology 24: DISH of the Hand and Undifferentiated Polyarthritis]. / CME-Rheumatologie 24: DISH der Hand und undifferenzierte Polyarthritis CME-Fragen.

CME Rheumatology 24: DISH of the Hand and Undifferentiated Polyarthritis Abstract. We present a case with undifferentiated, unclassified polyarthritis and with peripheral diffuse idiopathic skeletal hyperostosis (DISH). We discuss the differential diagnoses of "seronegative" polyarthritis and explain the radiographic findings of the little-known peripheral aspects of DISH.

Dose-optimized computed tomography of the cervical spine in patients with shoulder pull-down: Is image quality comparable with a standard dose protocol in an emergency setting?

PURPOSE: Superimposing soft tissue and bony structures in computed tomography (CT) of the cervical spine (C-spine) is a limiting factor in optimizing radiation exposure maintaining an acceptable image quality. Therefore, we assessed image quality of dose-optimized (DO) C-spine CT in patients capable of shoulder pull-down in an emergency setting. METHODS AND MATERIALS: DO-CT (105mAs/120 kVp) of the C-spine in trauma settings was performed in patients with shoulder pull-down if C5 was not superimposed by soft tissue on the lateral topogram, otherwise standard-dose (SD)-CT (195 mAs/120 kVp) was performed. 34 DO (mean age, 68y ±â€¯21; BMI, 24.2 kg/m2 ±â€¯3.2) and 34 SD (mean age 70y ±â€¯19; BMI 25.7 kg/m2 ±â€¯4.4) iterative reconstructed CTs were evaluated at C2/3 and C6/7 by two musculoskeletal radiologists. Qualitative image noise and morphological characteristics of bony structures (cortex, trabeculae) were assessed on a Likert scale. Quantitative image noise was measured and effective dose (ED) was recorded. Parameters were compared using Mann-Whitney-U-test (p < 0.05). RESULTS: At C2/3, DO-CT vs. SD-CT yielded comparable qualitative noise (mean, 1.3 vs. 1.0; p = 0.18) and morphological characteristics, but higher quantitative noise (27.2 ±â€¯8.8HU vs. 19.6 ±â€¯4.5HU; p < 0.001). At C6/7, DO-CT yielded lower subjective noise (1.9; SD-CT 2.2; p = 0.017) and better morphological characteristics with higher visibility scores for cortex (p = 0.001) and trabeculae (p = 0.03). Quantitative noise did not differ (p = 0.24). Radiation dose was 51% lower using DO-CT (EDDO-CT 0.80 ±â€¯0.1 mSv; EDSD-CT 1.63 ±â€¯0.2 mSv; p < 0.001). CONCLUSION: C-spine CT with dose reduction of 51% showed no image quality impairment. Additional pull-down of both shoulders allowed better image quality at lower C-spine segments as compared to a standard protocol.

Do Patients With Skin Psoriasis Show Subclinical Axial Inflammation on Magnetic Resonance Imaging of the Sacroiliac Joints and Entire Spine?

OBJECTIVE: To explore potential subclinical involvement of the axial skeleton by magnetic resonance imaging (MRI) of the sacroiliac (SI) joints and the entire spine in patients with skin psoriasis without clinical evidence of peripheral or axial inflammation. METHODS: Twenty patients with skin psoriasis but no clinical evidence of peripheral or axial inflammation and 22 healthy controls underwent standardized dermatologic and rheumatologic clinical examination and unenhanced 1.5T MRI of the SI joint and the entire spine. Two blinded readers globally assessed the presence or absence of SI joint inflammation simultaneously on T1-weighted and short tau inversion recovery MRI sequences with a confidence estimate. Bone marrow edema, fat metaplasia, erosion, and ankylosis of the SI joint, and vertebral corner inflammatory lesions and fat lesions were recorded using standardized modules. The prevalence of each lesion type was calculated in both groups, averaged across 2 readers. The number of subjects with lesions in the SI joint and spine (≥1, 2, 3, 4, or 5 lesions) as concordantly assessed by both readers was recorded. RESULTS: The median duration of skin psoriasis was 23.0 years, the median age of patients was 48.5 years, and 25.0% of patients and 9.1% of healthy controls were concordantly classified by both readers as having SI joint inflammation (P = 0.23). The prevalence of bone marrow edema and structural lesions was comparable across patients and controls, both on SI joint and spine MRI. CONCLUSION: In this controlled study, patients with skin psoriasis but no clinical arthritis or spondylitis showed limited evidence of concomitant subclinical axial involvement by SI joint and spine MRI. These findings do not support routine screening for subclinical axial inflammation in patients with longstanding skin psoriasis.

The medial border of the tibial tuberosity as an auxiliary tool for tibial component rotational alignment during total knee arthroplasty (TKA).

PURPOSE: The objective of this study was to quantify the amount of ensuing internal rotation of the tibial component when positioned along the medial border of the tibial tubercle, thus establishing a reproducible intraoperative reference for tibial component rotational alignment during total knee arthroplasty (TKA). METHODS: The angle formed from the tibial geometric centre to the intersection of both lines from the middle of the tibial tuberosity and its medial border was measured in 50 patients. The geometric centre was determined on an axial CT slice at 10 mm below the lateral tibial plateau and transposed to a slice at the level of the most prominent part of the tibial tuberosity. Similar measurements were taken in 25 patients after TKA, in order to simulate the intraoperative appearance of the tibia after making its proximal resection. RESULTS: This angle was found to be similar (n.s.) in normal and post-TKA tibiae [median 20.4° (range 15°-24°) vs. 20.7° (range 16°-25°), respectively]. In 89.3 % of the patients, the angle ranged from 17° to 24°. No statistical difference (p n.s.) was found between women and men in both normal [median -20.7° (range 16°-25°) vs. 19.9° (range 15°-24°)] and post-TKA tibiae [median 21.4° (range 19°-24°) vs. 20° (range 16°-25°)]. CONCLUSION: This study found that in 90 % of the patients, the medial border of the tibial tuberosity is internally rotated 17°-24° in relation to the line connecting the middle of the tuberosity to the tibial geometric centre. Since this anatomical landmark may be more easily identifiable intraoperatively than the commonly used "medial 1/3", it can provide a better quantitative reference point and help surgeons achieve a more accurate tibial implant rotational position. LEVEL OF EVIDENCE: Cohort and case control studies, Level III.

[Imaging findings of cristal deposit disorders]. / Radiologische Diagnostik der Kristallarthropathien.

Cristal deposit disorders are characterised by cristal deposits in hyaline and fibrocartilage, in synovium, capsule, ligaments and tendons and periarticular soft tissue. Calciumpyrophosphatedihydrate (CPPD), hydroxyapatite (calcific tendinitis) and uric acid arthropathies are the most common cristal deposit diseases. Radiography is still the number one image modality for initial imaging and the identification of cristal-induced inflammatory arthropathies. Differentiation between the entities of cristal deposit arthropathies can be challenging. Clincial and radiological findings may overlap in different cristal deposit arthropathies, owing a certain diagnosis difficult.

Increased Osseous (99m)Tc-DPD Uptake in End-Stage Ankle Osteoarthritis: Correlation Between SPECT-CT Imaging and Histologic Findings.

BACKGROUND: We analyzed the histopathologic findings in end-stage osteoarthritic ankle joint tissue that display increased uptake of bone-seeking radiotracer in single-photon emission computed tomography-computed tomography (SPECT-CT) imaging. METHODS: Six consecutive patients with end-stage osteoarthritis undergoing total ankle replacement received preoperative SPECT-CT imaging using (99m)Technetium dicarboxypropane diphosphonate ((99m)Tc-DPD). Using imaging data for stratification, osteochondral tissue sections were prepared from SPECT-positive (+) and -negative (-) areas of tibial and talar resection specimens. Histomorphometric analyses of osteoblast numbers, collagen deposition, and cartilage degeneration were performed on hematoxylin and eosin, van Gieson's and Safranin-O stained tissue sections. Osteoclast activity was visualized using tartrate-resistant acid phosphatase (TRAP) staining. RESULTS: Increased (99m)Tc-DPD uptake was observed exclusively subjacent to the subchondral bone plate of tibial and talar joint compartments. SPECT(-) tissues displayed typical fatty marrow morphology containing mainly collagen-positive blood vessels and few marrow and bone-lining cells. SPECT(+) tissues were characterized by increased numbers of active bone-lining osteoblasts depositing collagen fibers. Collagen area fraction of subchondral bone marrow was significantly increased in SPECT(+) (0.52 ± 0.21) compared with SPECT(-) (0.29 ± 0.13) tissues (P = .30). Multinucleated TRAP(+) osteoclasts were absent from bone formation sites, but associated with vascular structures invading articular cartilage through the subchondral bone plate. Increased (99m)Tc-DPD uptake was specifically and strongly correlated with increased osteoblast numbers (P = .011), and with collagen area fraction (P = .030) but not with Mankin score (P = .202), or with osteoclast number (P = .576). CONCLUSION: Subchondral bone tissues in SPECT(+) areas of end-stage ankle osteoarthritis were histologically characterized by increased osteoblast-mediated bone formation in the absence of functional osteoclasts, and increased cellularity and collagen deposition in marrow tissues. CLINICAL SIGNIFICANCE: Our findings suggest a pathologic bone-remodeling process in end-stage ankle OA areas with increased (99m)Tc-DPD uptake.

Generation and characterization of osteochondral grafts with human nasal chondrocytes.

We investigated whether nasal chondrocytes (NC) can be used to generate composite constructs with properties necessary for the repair of osteochondral (OC) lesions, namely maturation, integration and capacity to recover from inflammatory burst. OC grafts were fabricated by combining engineered cartilage tissues (generated by culturing NC or articular chondrocytes - AC - onto Chondro-Gide® matrices) with devitalized spongiosa cylinders (Tutobone®). OC tissues were then exposed to IL-1ß for three days and cultured for additional 2 weeks in the absence of IL-1ß. Cartilage maturation extent was assessed (immune) histologically, biochemically and by delayed gadolinium-enhanced magnetic resonance imaging of cartilage (dGEMRIC) while cartilage/bone integration was assessed using a peel-off mechanical test. The use of NC as compared to AC allowed for more efficient cartilage matrix accumulation and superior integration of the cartilage/bone layers. dGEMRIC and biochemical analyzes of the OC constructs showed a reduced glycosaminoglycan (GAG) contents upon IL-1ß administration. Cartilaginous matrix contents and integration forces returned to baseline up on withdrawal of IL-1ß. By having a cartilage layer well developed and strongly integrated to the subchondral layer, OC tissues generated with NC may successfully engraft in an inflammatory post-surgery joint environment.

Long-term outcomes of muscle volume and Achilles tendon length after Achilles tendon ruptures.

PURPOSE: The best treatment for Achilles tendon (AT) ruptures remains controversial. Long-term follow-up with radiological and clinical measurements is needed. METHODS: In this retrospective multicentre cohort study, patients (n = 52) were assessed at a mean of 91 months follow-up after unilateral AT rupture treated by open, percutaneous or conservative (non-surgical) treatment. Demographic parameters, time off work, maximum calf circumference and clinical scores (ATRS, Hannover, AOFAS) were evaluated. Muscle volume and cross-sectional area of the calf and AT length were measured on MR images and were compared between groups and to each patient's healthy contralateral leg. RESULTS: Reduced muscle volume was found across all groups with a higher muscle volume in the conservative (729.9 ± 130.3 cm(3)) compared to the percutaneous group (675.9 ± 207.4 cm(3), p = 0.04). AT length was longer in the affected leg (198.4 ± 24.1 vs. 180.6 ± 25.0 mm, p < 0.0001) without difference in subgroup analysis. Clinically measured ankle dorsiflexion showed poor correlation with AT length (R (2) = 0.07, p = 0.008). Muscle volume strongly correlated with the cross-sectional area (R (2) = 0.6, p < 0.0001) but showed a weak correlation with the Hannover score (R (2) = 0.08, p = 0.048). Maximum calf circumference correlated with muscle volume (R (2) = 0.42, p < 0.0001). CONCLUSIONS: No significant difference between the treatment groups was found in muscle volume, AT length, clinical measures or days off work. Cross-sectional area and maximum calf circumference are cost-effective measurements and a good approximation of muscle volume and can thus be used in a clinical setting while clinical dorsiflexion should not be used.

Radiographic diagnosis and differentiation of an aggressive angiomyxoma in a male patient.

Aggressive angiomyxoma is a rare soft-tissue tumor which usually occurs in female patients of reproductive age. Its occurrence in men is even more unusual and as illustrated in this case the difference between pathology suggested by a physical examination and its actual extent can be quite striking. We present a case report of an 81-year-old man with the typical MRI appearances of a pelvic aggressive angiomyxoma, describe imaging and histopathologic features of this rarely seen locally infiltrative neoplasm and also discuss therapeutic options for patients with an aggressive angiomyxoma.

Quantitative MRI can detect subclinical disease progression in muscular dystrophy.

Oculopharyngeal muscular dystrophy (OPMD) is a rare autosomal dominant muscular dystrophy with late onset and slow progression. The aim of this study was to compare different methods of quantitative MRI in the follow-up of OPMD to semiquantitative evaluation of MRI images and to functional parameters. We examined 8 patients with genetically confirmed OPMD and 5 healthy volunteers twice at an interval of 13 months. Motor function measurements (MFM) were assessed. Imaging at 1.5 T (Siemens Magnetom Avanto) comprised two axial slice groups at the largest diameter of thigh and calf and included T1w TSE, 2-point Dixon for muscular fat fraction (MFF) and a multi-contrast TSE sequence to calculate quantitative T2 values. T1 images were analyzed using Fischer's semiquantitative 5-point (0­4) scale. MFM and visual scores showed no significant difference over the study period. Overall T2 values increased in patients over the study period from 49.4 to 51.6 ms, MFF increased from 19.2 to 20.7%. Neither T2 values nor MFF increased in controls. Changes in T2 correlated with the time interval between examinations (r 2 = 0.42). In this small pilot trial, it was shown that quantitative muscle MRI can detect subclinical changes in patients with OPMD. Quantitative MRI might, therefore, be a useful tool for monitoring disease progression in future therapeutic trials.

Long-term treatment with infliximab in patients with sarcoidosis.

BACKGROUND: Long-term benefit and safety of infliximab treatment in patients with chronic sarcoidosis remain unclear. OBJECTIVES: It was the aim of this study to assess the clinical benefit and safety of long-term infliximab treatment in patients with chronic steroid-resistant sarcoidosis. METHODS: We conducted a retrospective chart review of all patients with chronic steroid-resistant sarcoidosis who received infliximab between January 2003 and November 2010. Pulmonary function tests and index lesions before and after infliximab therapy were assessed. RESULTS: Between January 2003 and November 2010, 28 patients received in-fliximab, 16 of them for more than 12 months. Five (31%) of these 16 patients with long-term infliximab treatment had a predominantly pulmonary disease, whereas 11 (69%) had a predominantly extrapulmonary involvement. Mean duration of treatment for the 16 patients was 29 months (range 12-62). Six of 11 (55%) patients with mainly extrapulmonary sarcoidosis showed a complete remission of their index lesion, 4/11 (36%) had a partial remission and 1/11 (9%) showed no response. One out of 5 patients with predominantly pulmonary sarcoidosis showed a >10% improvement in percentage predicted forced vital capacity, 3/5 showed a 0-10% improvement, and in 1/5 patients, percentage predicted forced vital capacity declined during infliximab treatment. Thus, overall, 14/16 (88%) patients profited from long-term infliximab treatment. Suspected adverse effects which lead to a temporary withdrawal of infliximab therapy were noticed in 1/16 (6%) patients. CONCLUSIONS: This retrospective study indicates that long-term infliximab is very efficient and safe in patients with chronic steroid-resistant sarcoidosis when assessed with individualized treatment targets. Patients with predominantly extrapulmonary sarcoidosis seem to profit more than patients with a predominantly pulmonary disease.

A novel imaging method for osteochondral lesions of the talus--comparison of SPECT-CT with MRI.

BACKGROUND: Magnetic resonance imaging (MRI) is the current standard in noninvasive diagnostics of osteochondral lesions (OCLs) of the talus. Single-photon emission computed tomography-computed tomography (SPECT-CT) is a new technique that displays different imaging qualities. The influence of the aforementioned diagnostic information on treatment decision making in talar OCLs is not known. PURPOSE: The aim of the study was to evaluate SPECT-CT in comparison with MRI for image interpretation and decision making in OCLs of the talus. STUDY DESIGN: Case series; Level of evidence, 4. METHODS: Magnetic resonance imaging and SPECT-CT of 25 patients (average age, 32 years; range, 18-69 years) were analyzed by 3 independent orthopaedic surgeons blinded to the study. Raters had to analyze images for predefined criteria of cartilage, subchondral bone plate, and subchondral bone, including bone marrow edema on MRI and scintigraphic activity on SPECT-CT. For MRI alone, SPECT-CT alone, and their combination, the treatment decision had to be defined. RESULTS: In comparison with MRI alone, treatment decision making changed in 48% of the cases with SPECT-CT alone and 52% with SPECT-CT and MRI combined. While cartilage showed good correlation for interpretation between MRI and SPECT-CT, the subchondral bone plate and subchondral bone showed substantial differences. Poor intrarater correlation highlighted the different information provided by the 2 imaging techniques. Poor interrater correlation showed a high heterogeneity in the treatment decision making of OCLs. CONCLUSION: Compared with MRI, SPECT-CT provides additional information and influences the decision making of OCL treatment. For thorough diagnostic evaluation in OCLs, performing both MRI and SPECT-CT is recommended. Further clinical investigation is needed to see if SPECT-CT in addition to MRI results in improved treatment outcomes.

Feasibility study of simultaneous physical examination and dynamic MR imaging of medial collateral ligament knee injuries in a 1.5-T large-bore magnet.

OBJECTIVE: To determine the feasibility of evaluating medial knee joint laxity with dynamic magnetic resonance (MR) imaging and simultaneous physical joint examination in a large-bore 1.5-T system. MATERIALS AND METHODS: The study included 10 patients (5 women, 5 men; mean age 35 years) with clinically diagnosed and categorized acute injuries of the medial collateral ligament (MCL). Intermittent valgus stress was applied separately to both the affected and the contralateral knee joint during dynamic MR imaging with a two-dimensional fast low-angle shot sequence. The width of the medial joint space and the opening angle between the femoral condyles and the tibial plateau were measured. Results obtained from dynamic MR imaging of the affected knee were compared with morphological MCL changes on static MRI, to kinematics of the contralateral side and to the clinical grading of MCL injuries. RESULTS: On clinical examination, all patients had grade 2 MCL injuries except one, who had a grade 1 lesion. Using morphological MRI criteria, 9 grade II and 1 grade III injuries were seen. Mean medial joint space width and opening angles of all affected knees were 2.8 mm and 2.7° respectively, compared with 1.7 mm and 2.1° on the contralateral side. The Wilcoxon signed rank test indicated that the differences in width (P = 0.005) and opening angle (P = 0.037) between the affected and contralateral knees were significant. CONCLUSION: Dynamic MR imaging and simultaneous physical joint examination is feasible. Our results suggest that this technique might enable the imaging documentation of medial ligamentous knee instability.

Impact of motion on T1 mapping acquired with inversion recovery fast spin echo and rapid spoiled gradient recalled-echo pulse sequences for delayed gadolinium-enhanced MRI of cartilage (dGEMRIC) in volunteers.

PURPOSE: To evaluate the impact of motion on T1 values acquired by using either inversion-recovery fast spin echo (IR-FSE) or three-dimensional (3D) spoiled gradient recalled-echo (SPGR) sequences for delayed gadolinium-enhanced magnetic resonance imaging of cartilage (dGEMRIC) in volunteers. MATERIALS AND METHODS: Single-slice IR-FSE and 3D SPGR sequences were applied to perform dGEMRIC in five healthy volunteers. A mutual information-based approach was used to correct for image misregistration. Displacements were expressed as averaged Euclidean distances and angles. Averages of differences in goodness of fit (Deltachi(2)) tests and averages of relative differences in T1 values (DeltaT1) before and after motion correction were computed. RESULTS: Maximum Euclidean distance was 3.5 mm and 1.2 mm for IR-FSE and SPGR respectively. Mean +/- SD of Deltachi(2) were 10.18 +/- 8.4 for IR-FSE and -1.37 +/- 5.5 for SPGR. Mean +/- SD of DeltaT1 were 0.008 +/- 0.0048 for IR-FSE and -0.002 +/- 0.019 for FSPGR. Pairwise comparison of Deltachi(2) values showed a significant difference for IR-FSE, but not for 3D-SPGR. Significantly greater variability in T1 values was also noted for IR-FSE than for 3D-SPGR. CONCLUSION: Involuntary motion has a significant influence on T1 values acquired with IR-FSE, but not with 3D-SPGR in healthy volunteers.

Anterior cruciate ligament reconstruction by using bioabsorbable femoral cross pins: MR imaging findings at follow-up and comparison with clinical findings.

PURPOSE: To determine the frequency of imaging findings and complications related to bioabsorbable femoral cross pins at follow-up magnetic resonance (MR) imaging studies after anterior cruciate ligament (ACL) reconstruction and compare these MR imaging findings with clinical evaluation findings. MATERIALS AND METHODS: The institutional review board approved this retrospective study, and informed consent was waived. Follow-up MR imaging studies (average, 26 months after surgery) in 218 patients with prior ACL reconstruction were retrospectively reviewed. Cross-pin fracture, posterior transcortical breach, migration, resorption, and lateral prominence of cross pins, as well as the cross-pin angle relative to the transepicondylar line, were investigated on MR images. The clinical evaluation included Lachman, anterior drawer, and pivot shift tests, as well as assessment for joint tenderness. RESULTS: Fracture, posterior transcortical breach, migration, and lateral prominence of cross pins were excluded from analysis when at least one cross pin was completely resorbed (n = 16 patients). Forty-five fractured cross pins were seen in 35 (17%) of 202 patients. The posterior femoral cortex was breached in 57 (28%) of 202 patients. Migration of fractured pin fragments occurred in 12 (6%) of 202 patients. There was a significant relationship between fractures and posterior breach of cross pins (P = .001), as well as between cross-pin angles and fractures (P = .002). Both cross pins were completely resorbed in 12 (6%) of 218 patients (average time since surgery, 53 months; range, 8-92 months). No significant association was found between any MR imaging finding related to cross pins and clinical test findings. CONCLUSION: Fracture and posterior transcortical breach of bioabsorbable femoral cross pins, commonly seen at follow-up MR imaging studies, do not correlate with clinical findings of joint instability or pain. Posteriorly angulated cross pins and posterior transcortical breach are significantly associated with cross-pin fractures.

MR arthrography of the hip: differentiation between an anterior sublabral recess as a normal variant and a labral tear.

PURPOSE: To retrospectively evaluate imaging characteristics of surgically proved sublabral recesses and labral tears in the anterior portion of the acetabulum at magnetic resonance (MR) arthrography. MATERIALS AND METHODS: Institutional review board approval was obtained; informed consent was waived. The study included 57 patients (36 women [mean age, 37 years], 21 men [mean age, 32 years]) who underwent MR arthrography and either surgery or arthroscopy as reference standard. On MR images, location of sublabral contrast material interposition and depth, shape, and extension into the labral substance of contrast material interpositions were described. Abnormal labral signal intensity (areas of high signal intensity), acetabular cartilage lesions, osseous abnormalities, and perilabral cysts were noted. Mann-Whitney U and Fisher exact tests were performed; interobserver agreement was calculated (kappa statistic and intraclass correlation coefficient). RESULTS: Surgical procedures revealed that 10 (18%) of 57 patients had recesses and 44 (77%) of 57 had tears. Locations of recesses and tears, respectively, were as follows: seven and none, in the 8-o'clock position; two of each, in the 9-o'clock position; one and 22, in the 10-o'clock position; and none and 20, in the 11-o'clock position. None of the recesses extended into the substance of the labrum or through the full thickness of the labral base; 51% (22 of 43) of tears extended into the substance and 49% (21 of 43) of tears extended along the entire labral base. Shape of sublabral contrast material interposition was linear in five (83%) of six recesses and 21 (49%) of 43 tears. Recesses were not associated with abnormal signal intensity of the labrum, cartilage lesions, osseous abnormalities, or perilabral cysts. Of 43 tears, 32 (74%) were associated with abnormal signal of the labrum; 23 (53%), with cartilage damage; 11 (26%), with osseous abnormalities; and eight (19%), with perilabral cysts. CONCLUSION: Recesses occur as normal variants in the anteroinferior part of the acetabulum. Location in the 8-o'clock position, linear shape of contrast material interposition, partial separation of the labrum, and absence of perilabral abnormalities are characteristics of a recess.