Nicolas Theumann

Wrist ligament injuries: value of post-arthrography computed tomography

Abstractu2008u2008Objective: To evaluate the use of post-arthrography high-resolution computed tomography in wrist ligament injuries.nDesign and patients: Thirty-six consecutive patients who had a history and clinical findings suggestive of ligamentous injuries of the wrist were prospectively studied. The findings of three-compartment arthrography and post-arthrography computed tomography (arthro-CT) were compared with those of arthroscopy. The evaluation concentrates on the detection and precise localization of ligament lesions in the triangular fibrocartilage (TFC), the scapholunate ligament (SLL) and the lunotriquetral ligament (LTL).nResults: For TFC, SLL and LTL lesions, standard arthrography responded with a sensitivity and specificity of 85% and 100%, 85% and 100%, 80% and 100% respectively, while arthro-CT showed a sensitivity and specificity of 85% and 100%, 100% and 100%, 80% and 100% respectively. The precise localization of the lesions was possible only with arthro-CT.nConclusion: The sensitivity and specificity of standard arthrography and arthro-CT are similar, although the latter shows the site of tears or perforation with greater precision, while conventional arthrography demonstrates them indirectly. This precision is essential and may have clinical implications for the success of treatment procedures.

Soft Tissue Artifact Assessment During Treadmill Walking in Subjects With Total Knee Arthroplasty

Accurate measurement of knee kinematics during functional activities suffers mainly from soft tissue artifact (STA): the combination of local surface deformations and rigid movement of markers relative to the underlying bone (also called rigid STA movement: RSTAM). This study proposes to assess RSTAM on the thigh, shank, and knee joint and to observe possible features between subjects. Nineteen subjects with knee arthroplasty were asked to walk on a treadmill while a biplane fluoroscopic system (X-rays) and a stereophotogrammetric system (skin markers) recorded their knee movement. The RSTAM was defined as the rigid movement of the cluster of skin markers relative to the prosthesis. The results showed that RSTAM amplitude represents approximately 80-100% of the STA. The vertical axis of the anatomical frame of the femur was influenced the most by RSTAM. Combined with tibial error, internal/external rotation angle and distraction-compression were the knee kinematics parameters most affected by RSTAM during the gait cycle, with average rms values of 3.8° and 11.1 mm. This study highlighted higher RSTAM during the swing phase particularly in the thigh segment and suggests new features for RSTAM such as the particular shape of some RSTAM waveforms and the absence of RSTAM in certain kinematics during the gait phases. The comparison of coefficient of multiple correlations showed some similarities of RSTAM between subjects, while some correlations were found with gait speed and BMI. These new insights could potentially allow the development of new methods of compensation to avoid STA.

Direct magnetic resonance arthrography of the wrist with axial traction: A feasibility study to assess joint cartilage†

To assess the impact of axial traction during acquisition of direct magnetic resonance (MR) arthrography of the wrist with regard to joint space width and amount of contrast material between the opposing cartilage surfaces.

Soft tissue artifact distribution on lower limbs during treadmill gait: Influence of skin markers' location on cluster design

Segment poses and joint kinematics estimated from skin markers are highly affected by soft tissue artifact (STA) and its rigid motion component (STARM). While four marker-clusters could decrease the STA non-rigid motion during gait activity, other data, such as marker location or STARM patterns, would be crucial to compensate for STA in clinical gait analysis. The present study proposed 1) to devise a comprehensive average map illustrating the spatial distribution of STA for the lower limb during treadmill gait and 2) to analyze STARM from four marker-clusters assigned to areas extracted from spatial distribution. All experiments were realized using a stereophotogrammetric system to track the skin markers and a bi-plane fluoroscopic system to track the knee prosthesis. Computation of the spatial distribution of STA was realized on 19 subjects using 80 markers apposed on the lower limb. Three different areas were extracted from the distribution map of the thigh. The marker displacement reached a maximum of 24.9 mm and 15.3 mm in the proximal areas of thigh and shank, respectively. STARM was larger on thigh than the shank with RMS error in cluster orientations between 1.2° and 8.1°. The translation RMS errors were also large (3.0 mm to 16.2 mm). No marker-cluster correctly compensated for STARM. However, the coefficient of multiple correlations exhibited excellent scores between skin and bone kinematics, as well as for STARM between subjects. These correlations highlight dependencies between STARM and the kinematic components. This study provides new insights for modeling STARM for gait activity.

Is spinal stenosis assessment dependent on slice orientation? A magnetic resonance imaging study

IntroductionLumbar spinal stenosis (LSS) treatment is based primarily on the clinical criteria providing that imaging confirms radiological stenosis. The radiological measurement more commonly used is the dural sac cross-sectional area (DSCA). It has been recently shown that grading stenosis based on the morphology of the dural sac as seen on axial T2 MRI images, better reflects severity of stenosis than DSCA and is of prognostic value. This radiological prospective study investigates the variability of surface measurements and morphological grading of stenosis for varying degrees of angulation of the T2 axial images relative to the disc space as observed in clinical practice.Materials and methodsLumbar spine TSE T2 three-dimensional (3D) MRI sequences were obtained from 32 consecutive patients presenting with either suspected spinal stenosis or low back pain. Axial reconstructions using the OsiriX software at 0°, 10°, 20° and 30° relative to the disc space orientation were obtained for a total of 97 levels. For each level, DSCA was digitally measured and stenosis was graded according to the 4-point (A–D) morphological grading by two observers.ResultsA good interobserver agreement was found in grade evaluation of stenosis (kxa0=xa00.71). DSCA varied significantly as the slice orientation increased from 0° to +10°, +20° and +30° at each level examined (Pxa0<xa00.0001) (−15 to +32% at 10°, −24 to +143% at 20° and −29 to +231% at 30° of slice orientation). Stenosis definition based on the surface measurements changed in 39 out of the 97 levels studied, whereas the morphology grade was modified only in two levels (Pxa0<xa00.01).DiscussionThe need to obtain continuous slices using the classical 2D MRI acquisition technique entails often at least a 10° slice inclination relative to one of the studied discs. Even at this low angulation, we found a significantly statistical difference between surface changes and morphological grading change. In clinical practice, given the above findings, it might therefore not be necessary to align the axial cuts to each individual disc level which could be more time-consuming than obtaining a single series of axial cuts perpendicular to the middle of the lumbar spine or to the most stenotic level. In conclusion, morphological grading seems to offer an alternative means of assessing severity of spinal stenosis that is little affected by image acquisition technique.

Direct magnetic resonance arthrography of the knee: utility of axial traction

The purpose of this study was to determine the impact of axial traction during acquisition of direct magnetic resonance (MR) arthrography examination of the knee in terms of joint space width and amount of contrast material between the cartilage surfaces. Direct knee MR arthrography was performed in 11 patients on a 3-T MR imaging unit using a T1-weighted isotropic gradient echo sequence in a coronal plane with and without axial traction of 15xa0kg. Joint space widths were measured at the level of the medial and the lateral femorotibial joint with and without traction. The amount of contrast material in the medial and lateral femorotibial joint was assessed independently by two musculoskeletal radiologists in a semiquantitative manner using three grades (‘absence of surface visualization, ‘partial surface visualization or ‘complete surface visualization’). With traction, joint space width increased significantly at the lateral femorotibial compartment (meanu2009=u20090.55xa0mm, pu2009=u20090.0105) and at the medial femorotibial compartment (meanu2009=u20090.4xa0mm, pu2009=u20090.0124). There was a trend towards an increased amount of contrast material in the femorotibial compartment with axial traction. Direct MR arthrography of the knee with axial traction showed a slight and significant increase of the width of the femorotibial compartment with a trend towards more contrast material between the articular cartilage surfaces.

Magnetic resonance imaging of peripheral nerves: Differences in magnetization transfer

Introduction: Magnetic resonance imaging (MRI) is an excellent imaging modality for soft tissues. Magnetization transfer (MT) imaging is an MRI technique that is sensitive to the bound protons of macromolecules and therefore can aid in the assessment of nerve damage.

Optimal 3-T MRI for depiction of the finger A2 pulley: comparison between T1-weighted, fat-saturated T2-weighted and gadolinium-enhanced fat-saturated T1-weighted sequences

ObjectiveTo compare three spin-echo sequences, transverse T1-weighted (T1WI), transverse fat-saturated (FS) T2-weighted (T2WI), and transverse gadolinium-enhanced (Gd) FS T1WI, for the visualisation of normal and abnormal finger A2 pulley with magnetic resonance (MR) imaging at 3xa0 tesla (T).Materials and methodsSixty-three fingers from 21 patients were consecutively investigated. Two musculoskeletal radiologists retrospectively compared all sequences to assess the visibility of normal and abnormal A2 pulleys and the presence of motion or ghost artefacts.ResultsNormal and abnormal A2 pulleys were visible in 94% (59/63) and 95% (60/63) on T1WI sequences, in 63% (40/63) and 60% (38/63) on FS T2WI sequences, and in 87% (55/63) and 73% (46/63) on Gd FS T1WI sequences when read by the first and second observer, respectively. Motion and ghost artefacts were higher on FS T2WI sequences. Seven among eight abnormal A2 pulleys were detected, and were best depicted with Gd FS T1WI sequences in 71% (5/7) and 86% (6/7) by the first and the second observer, respectively.ConclusionIn 3-T MRI, the comparison between transverse T1WI, FS T2WI, and Gd FS T1WI sequences shows that transverse T1WI allows excellent depiction of the A2 pulley, that FS T2WI suffers from a higher rate of motion and ghost artefacts, and transverse Gd FS T1WI is the best sequence for the depiction of abnormal A2 pulley.

Painful fingertip swelling of the middle finger

Osteoid osteoma (OO) is a benign bone-forming tumour that accounts for about 12% of benign and 3% of all bone neoplasms [1]. It mainly affects patients during childhood or early adulthood, with a male preponderance. Despite its predilection for the long bones of the lower limbs, this tumour can occur in any bone of the skeleton and may be found in the hand and wrist in up to 10% of cases [2]. However, OOs of the distal phalanx are relatively uncommon, with only a few case series reported in the English literature so far [3–5]. The diagnosis of distal phalangeal OO is challenging for several reasons. First, the typical clinical features may not be present [2, 3, 5]. Pain may not be worse at night, or be relieved by aspirin. Moreover, soft-tissue swelling and erythema, as well as nail deformities, may mislead the physician. Second, its imaging characteristics (i.e. a small radiolucent lesion with central calcification, peripheral sclerosis and periosteal reaction [1]) may also be atypical [3–6]. Because of the presence of thickened Sharpey’s fibres, a periosteal reaction is rarely found in the distal phalanx [6]. Besides, endosteal sclerosis may be counterbalanced by local osteopaenia. Furthermore, other bony lesions of the fingertips, such as chronic osteomyelitis, epidermoid cyst, enchondroma or glomus tumour, may mimic an OO [3, 5, 6]. Zampa et al. recently reported the added value of dynamic contrast-enhanced MR imaging for OO in atypical locations, in terms of nidus conspicuity and diagnostic confidence [7]. Third, the histological features may even be unusual [5]. All those reasons could explain the delay, sometimes of several months to years, in the diagnosis and the treatment of phalangeal OOs. The main clinical differential diagnosis of painful fingertip swelling includes whitlow or paronychia, osteomyelitis, glomus tumour, subungual exostosis, arthritis and OO [3, 5, 6]. In our case, conventional radiographs (see Fig. 1 in the Question), ultrasound and previous CT and MR imaging studies (all not shown) barely displayed a focal lesion at the base of the distal phalanx. Follow-up MRI, performed at our institution several months after the onset of symptoms and after failure of initial surgery, demonstrated persisting diffuse inflammatory changes of the distal and middle phalanges as well as in the The case presentation can be found at doi:10.1007/s00256-011-1218-z

Percutaneous radiofrequency ablation of primary intraosseous spinal glomus tumor

The glomus tumor is a rare, benign, but painful vascular neoplasm arising from the neuromyoarterial glomus. Primary intraosseous glomus tumor is even rarer, with only about 20 cases reported in the literature so far, 5 of which involved the spine. Surgical resection is currently considered the treatment of choice. We herewith present an uncommon case of primary intraosseous spinal glomus tumor involving the right pedicle of the eleventh thoracic vertebra (T11). To our knowledge, this is the first case of primary intraosseous spinal glomus tumor successfully treated by percutaneous CT-guided radiofrequency ablation (RFA).