Hugue Ouellette

Ischiofemoral impingement syndrome: an entity with hip pain and abnormalities of the quadratus femoris muscle.

OBJECTIVE The purpose of this study was to describe the MRI findings of an entity in which patients present with hip pain, abnormal MR signal intensity of the quadratus femoris muscle, and narrowing of the ischiofemoral space. MATERIALS AND METHODS We reviewed MR images of 12 hips in nine patients with hip pain and abnormal MR signal intensity of the quadratus femoris muscle. Using axial MR images, two musculoskeletal radiologists measured the ischiofemoral and quadratus femoris spaces. We also examined changes to muscles and tendons for the presence of edema and tears. Data were compared with 11 hips in 10 control subjects. Statistical analyses determined interobserver variability and differences between groups. RESULTS Subjects with an abnormal quadratus femoris muscle were all women 30-71 years old (mean age, 53 years) and had significantly narrower ischiofemoral spaces when compared with control subjects (13 +/- 5 vs 23 +/- 8 mm, respectively; p = 0.002). The quadratus femoris space was significantly narrower in affected subjects (7 +/- 3 vs 12 +/- 4 mm; p = 0.002). Abnormalities of the quadratus femoris muscle included edema (100%), partial tear (33%), and fatty infiltration (8%). The hamstring tendons of affected subjects showed evidence of edema (50%) and partial tears (25%). CONCLUSION Ischiofemoral impingement may represent a cause of hip pain and should be considered in cases with MR signal abnormality of quadratus femoris muscle.

Dual energy CT in gout: a prospective validation study

Objective The authors prospectively determined: (1) the specificity and sensitivity of dual energy CT (DECT) for gout; and (2) the interobserver and intraobserver reproducibility for DECT urate volume measurements. Methods Forty crystal-proven gout patients (17 tophaceous) and 40 controls with other arthritic conditions prospectively underwent DECT scans of all peripheral joints using a gout protocol that color-codes the composition of tissues. A blinded radiologist identified urate deposition to calculate specificity and sensitivity of DECT for gout. Inter-rater volumetric reproducibility was determined by two independent radiologists on 40 index tophi from the 17 tophaceous gout patients using automated software. Results The mean age of the 40 gout patients was 62 years, the mean gout duration was 13 years and 87% had a history of urate-lowering therapy (ULT). The specificity and sensitivity of DECT for gout were 0.93 (95% CI, 0.80 to 0.98) and 0.78 (0.62 to 0.89), respectively. When the authors excluded three gout cases with unreadable or incomplete scans, the sensitivity was 0.84 (95% CI, 0.68 to 0.94). The urate volumes of 40 index tophi ranged from 0.06 cm3 to 18.74 cm3 with a mean of 2.45 cm3. Interobserver and intraobserver intraclass correlation coefficients for DECT volume measurements were 1.00 (95% CI, 1.00 to 1.00) and 1.00 (95% CI, 1.00 to 1.00) with corresponding bias estimates (SD) of 0.01 (0.00) cm3 and 0.01 (0.03) cm3. Conclusions These prospective data indicate high reproducibility of DECT urate volume measures. The specificity was high, but sensitivity was more moderate, potentially due to frequent ULT use in our patients.

Impingement of lesser trochanter on ischium as a potential cause for hip pain.

The bony anatomy of the hip leads to a limited array of impingement syndromes, more frequently resulting from abnormal contact between the femoral neck and acetabulum. We report an unusual case of osseous impingement between the lesser trochanter and ischium, with involvement of the intervening quadratus femoris muscle. While the prevalence and etiology of this finding is unclear, it may represent a cause for hip pain.

Dual-Energy CT: A Promising New Technique for Assessment of the Musculoskeletal System

OBJECTIVE Dual-energy CT (DECT) characterizes the chemical composition of material according to its differential x-ray attenuation at two different energy levels. Applications of DECT in musculoskeletal imaging include imaging of bone marrow edema, tendons, and ligaments and the use of monoenergetic techniques to minimize metal prosthesis beam-attenuating artifacts. CONCLUSION The most validated application of DECT is undoubtedly its noninvasive and highly specific ability for confirming the presence of monosodium urate deposits in the assessment of gout.

Value of PET in the Assessment of Patients with Neurofibromatosis Type 1

OBJECTIVE The objective of our study was to investigate the use of PET in the detection of malignant peripheral nerve sheath tumors (MPNSTs) in patients with neurofibromatosis type 1 (NF1). MATERIALS AND METHODS Forty-five patients with NF1 who underwent whole-body PET for suspected MPNST based on clinical symptoms or radiologic examinations were retrospectively evaluated. Ten patients underwent additional carbon-11 (11C) methionine PET because of equivocal 18F-FDG PET findings or because of a discrepancy between the FDG PET and clinical findings. PET images were evaluated for the distribution and uptake pattern, and the standardized uptake values (SUVs) were obtained. Twenty-seven patients underwent biopsy or surgery of the detected lesions and 18 patients were followed up clinically and with repeat imaging studies. RESULTS Fifty lesions were identified on FDG PET. There were eight false-positive results and one false-negative on FDG PET. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of FDG PET in detecting MPNSTs in patients with NF1 were 95%, 72%, 71%, 95%, and 82%, respectively. Using 11C methionine PET in combination with FDG PET reduced the number of false-positive results from eight to two, which increased the specificity from 72% to 91%. In five patients, 11C methionine FDG PET contributed additional information about nontarget lesions that influenced treatment planning. CONCLUSION FDG PET is a sensitive technique in the detection of MPNSTs in patients with NF1. The addition of 11C methionine PET increases specificity in equivocal cases. PET may improve preoperative tumor staging by detecting metastases or second primary tumors, which often are present in patients with NF1.

MR imaging of rectus femoris origin injuries

ObjectiveTo describe the MR imaging findings of acute and chronic rectus femoris origin (RFO) injuries.Materials and methodsA retrospective review of pelvic and hip MR imaging procedures was performed over a 4-year period for detection of cases with injuries to the RFO. Subjects were classified as having either acute or chronic symptoms. MR imaging studies, radiographs, CT scans, radiology reports, medical records, and operative notes were reviewed. Imaging analysis was directed to assess injuries affecting the direct and indirect heads of the RFO. Concurrent osseous, cartilaginous and musculotendinous injuries were tabulated.ResultsThe incidence of RFO injuries on MR imaging was 0.5% (17/3160). With the exception of one case of anterior inferior iliac spine apophysis avulsion and partial tear of the direct head of RFO, all subjects had indirect head of RFO injuries (acute injury 8/9, chronic injury 8/8). Partial tear of the direct head of RFO was less frequently seen (acute injury 3/9, chronic injury 2/8). Partial tears of the conjoint tendon were least frequent (acute 1/9, chronic 2/8). No full-thickness tears of the RFO were noted. Associated labral tears were seen in only one case, with no other concomitant abnormality of the articular cartilage or surrounding soft tissues. All RFO injuries were treated non-operatively.ConclusionInjuries of the RFO are uncommon on MR examinations of pelvis/hips and may occur in a sequence progressing from indirect head injury to involvement of direct head and conjoint tendon in more severe cases.

MR imaging of the elbow in baseball pitchers

Baseball pitcher throwing biomechanics are important to understanding the pathophysiology and magnetic resonance (MR) imaging appearances of injuries in baseball pitchers. Baseball pitchers experience repetitive excessive valgus forces at the elbow. Typical injuries are secondary to medial joint distraction, lateral joint compression, and rotatory forces at the olecranon. MR imaging is useful for evaluation of the elbow in baseball pitchers.

Artifacts in Dual-Energy CT Gout Protocol: A Review of 50 Suspected Cases With an Artifact Identification Guide

OBJECTIVE The objective of our study was to discover the types and incidence of artifacts in dual-energy CT (DECT) using datasets of 50 consecutive patients who underwent a four-limb DECT protocol for the evaluation of suspected gout. Identification of artifacts and techniques for artifact reduction are discussed. CONCLUSION Artifacts commonly occur in DECT performed for gout assessment but are usually readily recognizable. For 90% of the patients in our study who underwent imaging for suspected gout, DECT showed some type of artifact, with nail bed and skin artifacts being the most common.

Incidence and MR imaging features of fractures of the anterior process of calcaneus in a consecutive patient population with ankle and foot symptoms

ObjectiveTo determine the incidence, appearances and associated injuries of fractures affecting the anterior process of calcaneus from a general population with foot and ankle symptoms.Design and patientsA retrospective review of foot and ankle MR imaging procedures was performed for detection of cases with a fracture affecting the anterior process of calcaneus over a four year period. Radiographs, MR imaging studies, radiology reports, medical records, and operative notes were reviewed. Imaging analysis included fracture pattern, displacement, associated fractures, and presence of tendon and ligamentous injuries.ResultsThe incidence of anterior process of calcaneus fracture on MR imaging was 0.5% (14/2577). Fractures were more common in female subjects (71%, 10/14). Fracture orientation was predominantly vertical (93%, 13/14). No comminuted fractures were seen and only three fractures were displaced. Three of the eight MR imaging evident fractures of anterior process of calcaneus were seen on radiographs. Associated fractures of the talus (n=5), navicular bone (n=3), cuboid (n=2), and calcaneal body (n=1) were noted. Associated injuries to the anterior talofibular ligament (n=3) and tears of the peroneus brevis (n=3) and peroneus longus (n=1) tendons were present. All fractures were treated non-operatively. Two patients had subtalar joint steroid injection for symptomatic relief.ConclusionsFractures of the anterior process of the calcaneus are uncommon in MR examinations of a general population of patients with foot and ankle symptoms. Although anterior process of calcaneus fractures are rare, there was a moderately high incidence of associated bone and soft-tissue injuries.

MRI of Metatarsal Head Subchondral Fractures in Patients with Forefoot Pain

OBJECTIVE The purpose of our study was to determine the MRI features of metatarsal head subchondral fractures in symptomatic adults. MATERIALS AND METHODS A retrospective review of foot MRI procedures was performed to detect cases of metatarsal head subchondral fractures over a 6-year period. MR images of selected cases were analyzed by two reviewers for the presence of subchondral fracture, marrow edema-like pattern, metatarsal head flattening, and subchondral sclerosis. Patients with a history of foot surgery, infection, or inflammatory arthritis were excluded. Assessment for coexisting osseous and soft-tissue abnormalities was also performed. RESULTS Subchondral fractures of the metatarsal heads were seen in 14 patients. All patients were women. The metatarsal head most commonly affected was the second (71%, 10/14) and the dorsal third of the metatarsal articular surface was involved in 79% (11/14). MRI findings of subchondral fracture of the metatarsal head with severe marrow edema-like pattern were seen in 71% (10/14), suggesting early stage changes. Metatarsal head collapse with subchondral sclerosis and mild or absent marrow edema-like pattern were seen in 29% (4/14) indicating late-stage changes. Concurrent abnormalities included three patients (21%) with metatarsal shaft fractures and one patient (7%) with an interdigital neuroma. One subject was treated surgically. CONCLUSION Subchondral fractures of the metatarsal heads can be detected on MR examinations of adults with forefoot pain. A subchondral fracture with associated marrow edema-like pattern is the most common presentation and likely reflects early stages of metatarsal head infraction.