Cervical facet oedema: prevalence, correlation to symptoms, and follow-up imaging.

AIM: To evaluate the prevalence of cervical facet oedema in patients referred for magnetic resonance imaging (MRI) to investigate neck pain and/or radiculopathy, and to investigate whether there is a correlation between the presence of oedema and patients' symptoms. MATERIALS AND METHODS: A retrospective report review of 1885 patients undergoing cervical spine MRI between July 2008 and June 2015 was performed. Exclusion criteria included acute trauma, surgery, neoplastic disease, or infection in the cervical spine. One hundred and seventy-three MRI studies with cervical facet oedema were evaluated by each of the two radiologists. In these patients, the grade of bone marrow oedema (BMO) and corresponding neuroforaminal narrowing at the cervical facets was assessed. Correlation with symptoms was performed based on pre-MRI questionnaire. RESULTS: The prevalence of cervical facet oedema was 9%; the most commonly affected levels were C3-4, C4-5, and C2-3. A total of 202 cervical facets were evaluated: mild BMO was seen in 35%, moderate in 41%, and severe in 24% of cases. Surrounding soft-tissue oedema was observed in 36%, 69%, and 92% of the BMO grades, respectively. The correlations between unilateral radiculopathy and ipsilateral facet BMO grades were 79%, 83%, and 73% (chi-square, p<0.001), respectively. Furthermore, neuroforaminal narrowing on the corresponding level was found in 35%, 38%, and 11% of cases, respectively. At follow-up imaging, facet oedema was most likely to remain unchanged or to decrease. CONCLUSION: The prevalence of cervical facet oedema is 9%. Cervical facet oedema is associated with ipsilateral radiculopathy. Neuroforaminal narrowing, however, is not associated with facet oedema.

Glenoid notch MRI findings do not predict normal variants of the anterior and superior labrum.

AIM: To determine (1) the relationship of a glenoid notch to the presence of a normal labral variant in the anterior-superior glenoid labrum; (2) the inter- and intra-observer reliability of recognising a glenoid notch; and (3) whether magnetic resonance arthrography (MRA) is more reliable than non-contrast magnetic resonance imaging (MRI) in visualising a glenoid notch. MATERIALS AND METHODS: From 1995 through 2010, 104 patients underwent MRI or MRA before diagnostic shoulder arthroscopy by the senior author. Five blinded musculoskeletal radiologists independently read the images twice to evaluate for the presence or absence of a glenoid notch. Fifty-nine (57%) patients had normal anterior-superior labral variants. The authors calculated the relationship of the readings to the arthroscopically determined presence or absence of a normal labral variant and the reading's diagnostic performance and rater reliability. RESULTS: On average, 38% (range 9-65%) of the glenoid scans were read as notched. The sensitivity, specificity, positive predictive value, and negative predictive value of the notch relative to the presence of a normal variant were 43.1%, 71.2%, 70.2%, and 48% versus 44.3%, 77.5%, 79.4%, and 56.1% for MRI and MRA, respectively. The overall average intra-observer κ-values were 0.438 (range 0.203-0.555) and 0.346 (range -0.102 to 0.570) for MRI and MRA, respectively. The average interobserver intra-class correlation coefficient reliability values were 0.730 (range 0.693-0.760) and 0.614 (range 0.566-0.662) for MRI and MRA, respectively. CONCLUSIONS: A notched glenoid on MRI lacks sufficient diagnostic performance and rater reliability for the clinical detection and prediction of normal anterior-superior labral variants.

Three-dimensional magnetic resonance imaging analysis of hip morphology in the assessment of femoral acetabular impingement.

AIM: To determine a possible association between femoral-acetabular impingement (FAI) volume and the development of labral tear using a three-dimensional (3D) model reconstruction of the acetabulum and the femoral head. MATERIALS AND METHODS: Magnetic resonance arthrography images of the hip in 42 patients with pain and suspected labral tear were acquired using a 1.5T MRI machine. Using 3D analysis software, outlines of the acetabular cup and femoral head were drawn and 3D reconstruction obtained. To control for differences in patient size, ratios of acetabulum : femoral head volume (AFV) and acetabulum : femoral head surface area (AFA) were used for analysis. The association between volume of acetabulum : femoral head and FAI was investigated using ANOVA analysis. RESULTS: There were 19 men and 23 women with a mean age of 39 years (range 18-78 years). The average AFV was 0.64 (range 0.37-1.05, SD 0.16) and AFA was 0.73 (range 0.36-1.26, SD 0.23). Herniation pit was significantly associated with a small AFV. CONCLUSION: Femoral neck herniation pits are associated with a low AFV. Gross volume and surface area ratios do not appear to correlate with labral tears or cartilage loss. This technique will enable more advanced analysis of morphological variations associated with FAI.

Cancer chemotherapy: an annotated history.

Treating cancer with drugs is an ancient art, but it is from discoveries made during and after the Second World War that real clinical success with cancer chemotherapy has occurred. Human and veterinary cancer chemotherapy have coevolved in the context of fascinating historical, political, and scientific events created by equally fascinating individuals.

MRI of injuries to the first interosseous cuneometatarsal (Lisfranc) ligament.

OBJECTIVE: The objective of this study was to assess the utility of MRI in diagnosing injury to the first interosseous cuneometatarsal (Lisfranc) ligament and to additionally determine the associated patterns of traumatic soft tissue and osseous injury. MATERIALS AND METHODS: Fifteen patients (16 feet) who were referred for MRI evaluation of the Lisfranc ligament, and had operative exploration or examination under anesthesia, were included for analysis. Standard non-contrast MRI foot imaging was performed in all cases. Evaluation of the following components was performed: the dorsal and plantar bundles of the Lisfranc ligament, the plantar tarsal metatarsal ligaments, soft tissue edema and fluid, and bone marrow edema and fractures. Surgical reports were regarded as the reference standard in all cases. RESULTS: Seven of 10 cases of grade 3 Lisfranc ligament injuries at surgery were correctly graded at MRI. No cases of surgically proven complete Lisfranc ligament tears (grade 3) were interpreted as normal at MRI. All Lisfranc ligament sprains (grade 2 or 3) at surgery were detected at MRI. Two of six cases reported as grade 1 injuries at MRI were normal at surgery. No cases of surgically proven normal or sprained Lisfranc ligaments were interpreted as grade 3 tears on MRI. Four of six of our cases of normal or sprained Lisfranc ligaments demonstrated fractures; while the minority of complete Lisfranc ligament tears (3/10) contained fractures. CONCLUSION: MRI is reasonably accurate at detecting traumatic injury to the Lisfranc ligament. However, in clinically suspected cases of traumatic Lisfranc ligament injury, true positive rate for sprain is low.

MRI of rupture of the spring ligament complex with talo-cuboid impaction.

The spring ligament complex is essential for the stability of the longitudinal arch of the foot and includes the ligaments between the calcaneus and the talus at the superomedial to inferoplantar aspect of the foot. Tears of the spring ligament complex are most commonly degenerative in etiology and secondary to concomitant abnormality of the posterior tibial tendon. We report MRI findings in a 30-year-old man who presented with traumatic rupture of the spring ligament complex, seen following dislocation of the talonavicular joint. We also describe the previously unreported MRI features of talo-cuboid impaction secondary to disruption of the spring ligament complex.

Use of a novel percutaneous biopsy localization device: initial musculoskeletal experience.

OBJECTIVE: To preliminarily evaluate a new CT-biopsy guidance device, the SeeStar (Radi, Uppsala, Sweden), for use in musculoskeletal applications. DESIGN: The device was evaluated using an imaging phantom and in various simulated clinical biopsy situations. The phantom study was undertaken to optimize the linear metallic artifacts produced by the guidance device. The phantom and guidance device were imaged with CT after altering different imaging parameters, including field of view, filter, focal spot size, kV, mAs, slice thickness and pitch. Clinical biopsy situations were simulated for a superficial biopsy, a deep biopsy and a horizontal biopsy approach. RESULTS: Altering CT parameters had little effect on the subjective appearance of the linear metal artifact, which is used to plan the biopsy approach. Placement of an 18-G needle inside of the biopsy device was subjectively helpful in exaggerating the artifact. Use of this artifact could be helpful in planning biopsy approach for deep lesions or lesions near critical structures. The metal guide on the device adequately supports a standard biopsy needle, making it potentially advantageous for biopsy of superficial lesions and lesions approached from a horizontal orientation. CONCLUSION: Use of this CT-biopsy guidance device is potentially useful for musculoskeletal applications. The linear metal artifact produced by the device can help plan the biopsy approach. The device can also be useful in biopsy situations where the biopsy needle requires external support during imaging.

MRI of bone marrow edema-like signal in the pathogenesis of subchondral cysts.

OBJECTIVE: To determine if a relationship exists between bone marrow edema-like signal and subchondral cysts on magnetic resonance imaging (MRI). DESIGN: Retrospective cohort of 32 patients with two sequential knee MRI. Patients with acute trauma, infection, neoplasm, or osteonecrosis were excluded. The degree of osteoarthritis was assessed using an adaptation of the Baltimore Longitudinal Study of Aging (BLSA) scale. Initial and follow-up exams were reviewed for presence, location, size and changes of marrow edema-like signal, subarticular cysts and cartilage abnormality. All locations in the knee were aggregated for analysis with descriptive statistics. RESULTS: The mean time interval between exams was 17.52 months (range 2.1-40.1 months). There were 23 cysts: 11 (47.8%) new, 6 (26.1%) increased size, 1 (4.4%) decreased size, and 5 (21.7%) no change in pre-existing lesions. Cysts always arose from regions of marrow edema-like signal. There were 68 subarticular areas of marrow edema-like signal: 16 (23.5%) new, 23 (33.8%) increased size, 17 (25%) decreased size, 11 (16.2%) resolved and 1 (1.5%) no change in pre-existing lesion. Marrow edema-like signal size always changed with cyst development: increased in 6/11 (54.5%), decreased in 2/11 (18.1%) and resolved in 3/11 (27.2%). Change in cyst size was always accompanied by a change in edema-like signal size. An MRI visible cartilage abnormality was adjacent to 87% (20/23) of cysts. The mean BLSA score changed from 2.6 to 3.6 indicating an overall progression of osteoarthritis. CONCLUSION: Subchondral cysts develop in pre-existing regions of subchondral bone marrow edema-like signal.

Cartilage anlagen adapt in response to static deformation.

Connective tissue adaptation, including the development of cartilaginous anlagen into bones, is widely believed to be related to dynamic, intermittent load and stress histories. Static stresses, on the other hand, are generally believed deleterious in tissue adaptation. Using serial MRI in a natural human experiment (manipulation and corrective casting of infant clubfoot), we have observed casting produces two effects: (1) the well recognized change in relative positions of the hindfoot anlagen; (2) a newly recognized immediate shape change in the anlagen. These changes seemingly enhance the rate of growth of the anlagen and of the ossific nucleus. The shape change or deformation in the anlagen would occur as a result of alterations in the magnitudes and directions of loading from soft tissue attachments and muscle activity and would necessarily be associated with changes in the stress states within the anlagen and, when present, the ossific nuclei. Given the known role of load and stress history in tissue adaptation, we presume the reduced stress histories influence the enhanced growth rates. These observations contradict some current theories of tissue adaptation since static, rather than dynamic stresses play a crucial role in accelerating the growth and development of anlagen in the infant clubfoot.

Assessment of bone biopsy needles for sample size, specimen quality and ease of use.

OBJECTIVE: To assess whether there are significant differences in ease of use and quality of samples among several bone biopsy needles currently available. DESIGN: Eight commonly used, commercially available bone biopsy needles of different gauges were evaluated. Each needle was used to obtain five consecutive samples from a lamb lumbar pedicle. Subjective assessment of ease of needle use, ease of sample removal from the needle and sample quality, before and after fixation, was graded on a 5-point scale. The number of attempts necessary to reach a 1 cm depth was recorded. Each biopsy specimen was measured in the gross state and after fixation. RESULTS: The RADI Bonopty 15 g and Kendall Monoject J-type 11 g needles were rated the easiest to use, while the Parallax Core-Assure 11 g and the Bard Ostycut 16 g were rated the most difficult. Parallax Core-Assure and Kendall Monoject needles had the highest quality specimen in the gross state; Cook Elson/Ackerman 14 g and Bard Ostycut 16 g needles yielded the lowest. The MD Tech without Trap-Lok 11 g needle had the highest quality core after fixation, while the Bard Ostycut 16 g had the lowest. There was a significant difference in pre-fixation sample length between needles (P<0.0001), despite acquiring all cores to a standard 1 cm depth. Core length and width decrease in size by an average of 28% and 42% after fixation. CONCLUSION: Bone biopsy needles vary significantly in performance. Detailed knowledge of the strengths and weaknesses of different needles is important to make an appropriate selection for each individual's practice.

MR imaging of the diabetic foot.

Diabetes is a common disease with potentially devastating complications affecting the foot and ankle. A combination of vascular disease, peripheral neuropathy, and immunopathy result in a cascade of conditions including ischemia/infarction, tendinopathy, atrophy, edema, deformity, neuropathic osteoarthopathy, callus, ulceration, and infection. The MR imaging appearance of these complications will be discussed. Recognition of these MR imaging patterns facilitates formulation of medical or surgical treatment plans.

MR imaging of inflammatory conditions of the ankle and foot.

Infection and noninfection inflammatory diseases commonly affect the foot and ankle; they have a significant impact on the cost of medical care and are a major source of referral for MR imaging evaluation. Recognition of the MR imaging appearance of the various manifestations of these disorders is important so that prompt and appropriate medical or surgical management can be instituted. This article emphasizes MR imaging of the most important diseases in this category, diabetic foot infection and the rheumatoid foot, but will also discuss manifestations in the foot and ankle of various other inflammatory diseases, such as gout and seronegative spondyloarthropathies.

Medial patellofemoral ligament injury following acute transient dislocation of the patella: MR findings with surgical correlation in 14 patients.

PURPOSE: The purpose of this study was to determine the accuracy of MRI in determining both the extent and the location of injury to the medial patellofemoral ligament (MPFL). METHOD: MR findings were compared to the surgical results of 14 consecutive patients who experienced transient patellar dislocation. Two musculoskeletal radiologists, blinded to the surgical results, retrospectively reviewed the MR studies, and a consensus reading was obtained. RESULTS: Surgery demonstrated complete disruption of the MPFL in 7 of 14 patients (50%), with stretching or partial tearing of the MPFL in the remaining 7 (50%) patients. MRI was 85% sensitive and 70% accurate in detecting MPFL disruption. Vastus medialis obliquus muscle elevation was present in 12 of 14 (85%). CONCLUSION: MRI accurately depicts both the extent and the location of MPFL injury following transient patellar dislocation and can therefore play a significant role in directing surgical management of these patients.

MRI of the foot and ankle: prevalence and distribution of occult and palpable ganglia.

The purpose of this study was to evaluate the prevalence and anatomic distribution of occult and palpable ganglia of the foot and ankle as seen by MRI. Within a 7-year period MRI of the ankle was performed on 2813 patients, and MRI of the foot on 2277 patients using a 1.5T magnet. In all, 167 ganglia in 155 patients were detected. MR images of these patients were reviewed retrospectively by two observers with regard to prevalence, imaging characteristics, and exact anatomic location of ganglia. Clinical findings and (when available) surgical reports were also reviewed. One hundred fifty-seven ganglia in 145 patients were present on MR images of the ankle, and 10 ganglia in 10 patients on MR images of the foot, resulting in a prevalence of 5.6% (157/2813) in the ankle, and a prevalence of 0.4% (10/2277) in the foot. The most common location was the tarsal sinus or tarsal canal (57/167 ganglia [34.1%]). However, only four of these (7%) were palpable as a soft-tissue mass. The second most common location was around the Lisfranc joint (23/167 [13.8%]), of which 11/23 [47.8%] were clinically palpable. Palpable ganglia were statistically larger in size than occult ganglia measured in any of three diameters (P = 0.01-0.002). In addition, ganglia of the foot and ankle represented 42% of all clinically suspected soft-tissue masses. Ganglia in the foot and ankle are an infrequent finding on routine MRI of the foot and ankle. When they occur, these ganglia are most frequently located in the tarsal sinus and tarsal canal, where they are occult to clinical palpation. If ganglia are clinically palpable, they are most commonly located around the Lisfranc joint. In addition, palpable ganglia are larger than occult ganglia.

Injuries to the distal gastrocnemius muscle: MR findings.

PURPOSE: The purpose of this work was to demonstrate the MR findings of injuries to the distal gastrocnemius muscle. METHOD: Twenty patients with clinically confirmed injuries to the distal gastrocnemius muscle underwent MRI. The injuries were evaluated with regard to abnormal morphology or signal abnormality, site, and degree of tearing. RESULTS: Twenty-three injuries to the distal gastrocnemius occurred in 20 patients, with involvement of the myotendinous junction in 22 of 23 (96%) injuries. An interstitial tear of the proximal Achilles tendon was present in one instance. Myotendinous strains were the most common injuries (10/23; 43%); partial tears (7/23; 30%) and complete tears (5/23; 22%) of the myotendinous junction or proximal Achilles tendon were less frequent. When an injury to the gastrocnemius myotendinous junction was present, involvement of the medial head (19/22; 86%) was more frequent than involvement of the lateral head (3/22; 14%). CONCLUSION: MRI allows accurate imaging of distal gastrocnemius muscle injuries. When occurring, distal gastrocnemius muscle injuries most frequently involve the myotendinous junction of the medial gastrocnemius head and occasionally the lateral gastrocnemius head or the proximal Achilles tendon.

Partial interosseous ligament tears of the wrist: difficulty in utilizing either primary or secondary MRI signs.

PURPOSE: Prior reports on scapholunate ligament (SLL) and lunotriquetral ligament (LTL) tears have evaluated complete tears. As these complete tears have markedly different biomechanical manifestations and surgical considerations than do partial tears, we evaluated the accuracy of MR and the usefulness of secondary MR signs to diagnose partial interosseous ligament tears. METHOD: Fifty wrists in 50 patients underwent arthroscopy following 1.5 T MR. Images were evaluated by two independent blinded observers for normal or partially torn SLL and LTL and for three secondary signs potentially seen as mechanical sequelae of tears: osseous offset, arc disruption, or focal osteoarthritis. RESULTS: Arthroscopically, there were 16 SLL and 14 LTL partial tears. Accuracy of primary MR signs of partial tears was lower than that described in the literature for complete tears [sensitivity/specificity (kappa) = 0.56/0.56 (0.12)-SLL, 0.31/0.76 (0.13)-LTL]. Secondary signs showed low sensitivity but high specificity, particularly for LTL tears: arc disruption [0.17/0.83 (0.43)-SLL, 0.0/1.00 (1.0)- LTL], focal osteoarthritis [0.32/0.78 (0.18)-SLL, 0.11/0.91 (0.12)-LTL], and focal osseous offset [0.39/0.75 (0.10)-SLL, 0.26/0.93 (0.39)-LTL]. Additionally, there was poor interobserver consistency for both primary and secondary signs. CONCLUSION: The sensitivity of morphologic evaluation for diagnosing partial intercarpal ligament tears, particularly those of the LTL, is limited. Secondary signs increase specificity but have low sensitivity, and with the exception of arc disruption, all signs had poor interobserver agreement.

Autogenous osteochondral "plug" transfer for the treatment of focal chondral defects: postoperative MR appearance with clinical correlation.

OBJECTIVE: To describe the MR appearance following autogenous osteochondral "plug" transfer for the treatment of focal chondral defects of the knee. DESIGN AND PATIENTS: Twenty-nine 1.5-T MR knee studies including dynamic gadolinium enhancement were performed on 21 patients following autogenous osteochondral "plug" transfer. Three musculoskeletal radiologists retrospectively reviewed images to evaluate graft and donor site appearance and MR findings were correlated with clinical outcomes. RESULTS: MR images demonstrated graft protuberance (n=12/21; range 1-2 mm), depression (n=2/21; range 1 mm), and surface incongruity: mild (n=17/21), moderate (n=2/21), marked (n=1/21). The T2 signal of graft cartilage was similar to that of adjacent cartilage in 25 of 29 examinations, and increased in four. Graft cartilage thickness relative to adjacent cartilage was <50% in six patients, 50-100% in 15. Graft enhancement in bone was absent at 2 weeks, but present at between 4 and 6 weeks following surgery. All patients had clinical follow-up examinations and knee outcome survey scores were obtained in 15 patients with follow-up greater than 3 months after surgery. All patients demonstrated the expected short-term progressive clinical improvement. CONCLUSION: MR images reveal a wide range of appearances following osteochondral "plug" transfer. Minor variations in graft orientation and surface congruity do not result in adverse clinical outcome in the short term.

MR imaging of the posterior cruciate ligament graft: initial experience in 15 patients with clinical correlation.

PURPOSE: To describe the magnetic resonance (MR) appearance of the posterior cruciate ligament (PCL) graft in the 1st postoperative year and to correlate the MR findings with clinical examination findings. MATERIALS AND METHODS: Nineteen MR examinations were performed in 15 patients (with 15 grafts) 1-33 months after PCL reconstruction. Results of clinical follow-up were available in 14 patients. Graft shape and thickness were recorded, and intrasubstance signal intensity at T2-weighted imaging was graded. The MR findings were correlated with the time between surgery and clinical examination. RESULTS: At MR imaging, 13 grafts appeared intact, one could not be assessed owing to hardware artifact, and one initially appeared disrupted. Graft thickness was 7-19 mm. There was no significant difference between graft thickness versus time since surgery and signal intensity versus time since surgery (P =.14). In two of three patients who underwent sequential MR examinations, graft thickness and intrasubstance signal intensity decreased as the time between reconstruction and MR imaging increased. Two of 14 patients who underwent physical examination had a posterior drawer, and one also had an anterior cruciate ligament graft tear. Both patients with knee instability demonstrated intact PCL graft fibers at MR imaging. There was no correlation between knee stability and graft thickness, signal intensity, or shape. CONCLUSION: After PCL reconstruction, MR imaging in the 1st year depicts a thickened graft with increased signal intensity. There does not appear to be a relationship between clinical stability and findings at MR imaging.

Indirect MR arthrography of the knee: effects of low-intensity ultrasound on the diffusion rate of intravenously administered Gd-DTPA in healthy volunteers.

RATIONALE AND OBJECTIVES: To evaluate whether application of low-intensity ultrasound may increase the diffusion rate of intravenously administered gadopentetate dimeglumine (Gd-DTPA) and increase the amount of joint fluid on indirect magnetic resonance (MR) arthrography. METHODS: Conventional MR imaging, indirect MR arthrography, and power Doppler ultrasonography were performed before and after application of therapeutic, pulsed low-intensity ultrasound in 12 asymptomatic knees of 12 volunteers. Intra-articular diffusion of intravenously administered Gd-DTPA as measured by signal intensity differences of the intra-articular joint fluid before and after ultrasound treatment was assessed. In addition, the amount of joint fluid was rated, and differences in synovial blood flow as evidenced by power Doppler ultrasonography were noted. RESULTS: All volunteers tolerated well the application of therapeutic low-intensity ultrasound. A significant increase in intra-articular diffusion of intravenously administered Gd-DTPA was noted in all knees, and an increase in joint fluid was noted in 8 of 12 knees (66.6%). Detection of power Doppler flow signal in the synovium of the suprapatellar recess was possible in one instance at posttreatment exam. CONCLUSIONS: Use of pulsed, therapeutic low-intensity ultrasound may increase the diffusion rate of intravenously administered Gd-DTPA and may induce joint effusion.

MR imaging of meniscal cysts: incidence, location, and clinical significance.

OBJECTIVE: The purpose of this study was to determine the incidence of medial versus lateral meniscal cysts as seen on MR imaging. MATERIALS AND METHODS: A total of 2572 knee MR imaging reports were retrospectively reviewed for the presence of meniscal tears and cysts. Two musculoskeletal radiologists reviewed all images with reported cysts. The type and location of meniscal tear and the presence and location of meniscal cysts were recorded. RESULTS: A total of 1402 meniscal tears were reported in 2572 MR examinations (922 [66%] of 1402 in the medial compartment; 480 [34%] of 1402 in the lateral compartment). Meniscal cysts were present in 109 (4%) of 2572 knees. Of the 109 cysts, 72 (66%) were in the medial compartment, and 37 (34%) were in the lateral compartment. Meniscal cysts were found in association with 72 (7.8%) of the 922 medial meniscal tears and 37 (7.7%) of the 480 lateral meniscal tears. Meniscal cysts showed direct contact with an adjacent meniscal tear in 107 (98%) of 109 cases, with the tear showing a horizontal component in 96 (90%) of 107 cases. CONCLUSION: Meniscal cysts occur almost twice as often in the medial compartment as in the lateral compartment. Medial and lateral tears occur with the same frequency. These findings, when viewed in the context of the historical literature on meniscal cysts, suggest that MR imaging detects a greater number of medial meniscal cysts than physical examination or arthroscopy, and that MR imaging can have an important impact on surgical treatment of patients.