Bone Tissue in Magnetic Resonance Imaging: Contribution of New Zero Echo Time Sequences

The introduction of new ultrashort and zero echo time (ZTE) sequences is revolutionizing magnetic resonance imaging (MRI) and optimizing patient management. These sequences acquire signals in tissues with very short T2: mineralized bone, cortical bone, and calcium deposits. They can be added to a classic MRI protocol. ZTE MRI provides computed tomography-like contrast for bone.

[Is medical imaging iatrogenic?]

Imaging is an indispensable element of modern medicine but is not without risk. Low-dose irradiation due to spinal, abdominal, pelvic or cardiac radiography, and the increasing use of CT carries an additional, albeit moderate risk of cancer. Iodinated and gadolinium-containing contrast media, besides their direct toxicity, can trigger hypersensitivity and allergic-like reactions. Spinal and articular diagnostic injections can also lead to complications. This article reviews the direct iatrogenicity of diagnostic imaging and current efforts to limit it through the use of new radiological systems, lower-dose CT non ionic contrast media, and alternative imaging techniques. The authors also examine the less known but more frequent problem of indirect iatrogenesis, which is highly dependent on the quality of the imaging personnel and technique. Finally, we propose some legislative solutions to this problem.

Interventional musculoskeletal ultrasonography of the lower limb

In this case series, out of 823 ultrasound-guided injections carried out over a period of one and a half years, 60% were of the lower limb (LL). In the hip (61% of LL injections), the main indications were pathologies of the gluteal tendons and bursae (80%) and pathologies of periprosthetic soft tissue; in the knee (15% of LL punctures), these procedures were for cysts (51%), tendinopathies and bursopathies (18%), and joint aspirations (7%); in the calf, haematoma drainage; in the foot and the ankle (24% of LL punctures), Morton's neuroma (47%), tenosynovitis (22%), pathologies of the plantar fascia (13%), cysts (7%), joint aspirations (5%), and bursopathies. For each of these indications, we will detail the specific technique and equipment used, useful tips, and post-procedure care.

Musculoskeletal interventional ultrasonography: the upper limb

Forty percent of the 823 ultrasound-guided injections performed in our centre over a year and a half concerned the upper limb, injections involving the shoulder, for subacromial bursitis and the treatment of calcific tendinitis, being the prime indications (24%). The wrist represented 8% of the prescriptions, for treatment of tendinopathy, ganglion cysts, carpal tunnel syndrome and rhizarthrosis. Trigger finger, tenosynovitis and pulley ganglia made up 6% of the indications and the elbow 2.5%. Ultrasound improves the accuracy of the procedure by helping guide the path of the needle and allowing the distribution of the substance injected to be visualised. We shall give details of the technique used for each indication, with advice and hints and post-procedure recommendations.

Stenosing tenosynovitis

Tenosynovitis refers to an inflammatory condition involving the synovial sheath of a tendon. Stenosing tenosynovitis is a peculiar entity caused by multiple factors, including local anatomy, mechanical factors, and hormonal factors. The main forms include de Quervain tendinopathy; trigger finger (stenosing tenosynovitis involving the flexor digitorum tendons); stenosing tenosynovitis of the extensor carpi ulnaris, extensor carpi radialis, or extensor comunis tendons; stenosing tenosynovitis of the flexor hallucis tendon; and stenosing tenosynovitis of the peroneal tendons. The cardinal finding on ultrasonography is the presence of a thickened retinaculum or pulley that constricts the osseofibrous tunnel through which the tendon runs.

US appearance of partial-thickness supraspinatus tendon tears: Application of the string theory. Pictorial essay

The supraspinatus tendon is composed of 5 different layers consisting of intertwining bundles. On a front portion of the tendon, the layers become coated bundles which insert on the trochanter. At the insertion, the superficial or bursal surface of the tendon corresponding to the tendon fibers in contact with the subacromial bursa can be distinguished from the deep surface corresponding to the fibers in contact with the glenohumeral joint. A tendon tear may involve partial or total disruption of the tendon fibers and is called full-thickness tear if it affects the entire tendon, and partial-thickness tear if it involves only part of the tendon. Partial-thickness tears of the supraspinatus tendon include lesions of the superficial, deep and central surface or tendon delamination.A contrast enhanced examination requires injection of contrast agent into the joint (arthrography followed by computed tomography (CT) or magnetic resonance imaging (MRI)) to study the deep surface, and injection into the subacromial bursa (bursography followed by CT) to study the superficial surface. MRI and ultrasound (US) examination allow the study of these different tendon layers without the use of contrast agent (which is not possible at CT).

Standardized way for imaging of the sagittal spinal balance

Nowadays, conventional or digitalized teleradiography remains the most commonly used tool for the study of the sagittal balance, sometimes with secondary digitalization. The irradiation given by this technique is important and the photographic results are often poor. Some radiographic tables allow the realization of digitalized spinal radiographs by simultaneous translation of X-ray tube and receptor. EOS system is a new, very low dose system which gives good quality images, permits a simultaneous acquisition of upright frontal and sagittal views, is able to cover in the same time the spine and the lower limbs and study the axial plane on 3D envelope reconstructions. In the future, this low dose system should take a great place in the study of the pelvispinal balance. On the lateral view, several pelvic (incidence, pelvic tilt, sacral slope) and spinal (lumbar lordosis, thoracic kyphosis, Th9 sagittal offset, C7 plumb line) parameters are drawn to define the pelvispinal balance. All are interdependent. Pelvic incidence is an individual anatomic characteristic that corresponds to the "thickness" of the pelvis and governs the spinal balance. Pelvis and spine, in a harmonious whole, can be compared to an accordion, more or less compressed or stretched.

[Recent advances in imaging of hip and knee prostheses]

More than 222 000 hip and knee prostheses are implanted each year in France and this number is growing. Simple radiography is generally used to examine these prostheses in situ but this method has several limitations, including superimposition, the inability to visualize some parts of the prosthesis and to study them in the axial plane, and poor visualization of intra- and peri-articular soft tissues. This article describes the advantages offered by computed tomography and ultrasonography in this setting

[Foot imaging]

Foot and ankle problems are frequent, daily pathologies. Nowadays, imaging is able to put in evidence the most part of these affections, in a simple, non traumatic way. A good clinical examination is of highest importance to guide the imaging technique. Well done simple X-rays in a standing position is the first mandatory step. Ultrasonography has revolutionized the study of the smooth parts of the foot: tendons, sprains, pathologies of plantar aponeurosis, hind-foot problems....It is therefore the first exam to ask for. Ultrasonography is enough to resolve a very important part of the superficial soft tissues pathologies. When this technique fails, whatever the reason, RMI is the best way to study soft tissues and bone marrow (stress fractures, small intraosseous lesions, osteonecrosis...). CTscan remains the best tool to study the hard part of the skeleton. Neither CTscan nor RMI can directly put in evidence the joint's cartilage with a high degree of precision. So, an arthrography remains mandatory to have a good study of the cartilage of the ankle.

[Muculoskeletal radiology: ankle and foot in adults]

The main views and indications in adult foot and ankle radiography are detailed. Among foot and ankle diseases, mechanical ones are most frequent, including usual podologic changes (commonly followed by peculiar involvement of certain bones, ligaments, joints, tendons and other soft tissues), synostoses, occult and stress fractures, sprains, and tendon changes. Although they are less frequently encountered in common clinical practice, the radiographic appearance of inflammatory, infectious, and tumoral diseases of foot and ankle are disclosed as well. The correlation existing between some subtle radiographic changes and their counterpart on US, CT, or MR examinations are also emphasized.

[Plain X-rays of the spine: dynamics and elements of semiology]

Man is standing up and he moves himself in a world subject to the gravity's laws. His spine reflects these constraints. Each bivertebral unit that composes the long supple stem of the spine has an anatomic cohesion with some mobility. The mobility of the spine is the sum of the motilities of its elementary units. Despite the criticisms, all deserved, the dynamic radiographies in flexion (seating position) and in extension (standing position, lower limbs straight and buttocks wedged) give major informations with important clinical consequences. Some semiologic points of the radiographic study of the vertebra are perfectly explained by its specific architecture: a radiolucent lesion is difficult to see whereas a sclerotic one is much more easy to individualize; the sclerotic line of the vertebral endplate must be continuous and any interruption is pathologic; the corners of the vertebra must be sharp; the foramen's shape reflects the size of the spinal canal.

Le « de Sèze » magnétique

The authors propose that a coronal STIR sequence with large FOV, similar to the de Sèze projection, including lumbar spine, sacrum, pelvis and hips should be obtained in all patients as part of the lumbar spine MRI protocol. For an additional few minutes of scanning time, this additional sequence could demonstrate the presence of lesions (hips, pelvis, sacrum, SI joints, retroperitoneum...) that would otherwise go undetected on standard sagittal and axial MRI images of the lumbar spine.

Imagerie normale et pathologique du système suro-achilléo-plantaire propulseur du pied

The extensor system of the foot is mainly composed by a powerful engine, the triceps surae muscle, equiped with a very sophisticated driving belt, the unit Achilles tendon-posterior part of calcaneus bone-plantar aponeurosis, in continuity with the fibrous skeleton of the triceps surae. The exact knowledge of the anatomy of this fibrous skeleton allows us to understand the occurence of the main anatomical lesions of the extensor system and its imaging. On these solid bases, it's possible to divide the lesions of the foot's extensor system in different subtypes with, for each one, a typical clinical feature, a characteristic imaging and an codified treatment. The pair radiography-ultrasonography is enough for diagnosis and follow-up of the majority of lesions. The others need MRI.

[Superficial US of superficial bones]

Although bones are not well imaged by US this imaging modality can be helpful in the assessment of bone surface and can be complementary to standard radiographs. A focal irregularity of the hyperechoic cortical line indicates a fracture, a cortical avulsion, a local bulging of the cortex or a foreign body related or not to previous surgery. Subperiosteal collections either purulent or hemorrhagic are easily detected and can be aspirated under US guidance if an infection is suspected. US also allows diagnosis of epiphyseal fractures when involving the distal epiphysis of the metatarsals, radial head, humeral head (Hill-Sachs fracture) growing cartilages... US examination of joints can detect osteophytes and marginal erosions (allowing early diagnosis of rheumatoid arthritis together with visualization of hyperaemic pannus and joint effusion) Cortical continuity in a location where in normal conditions a joint space is found indicates a synostosis. In children US, by directly visualizing the cartilaginous component of the non ossified bones, allows detection and serial follow-up of many congenital malformation (pes equinus...). US may be obtained in all patients where standard radiographs are not diagnostic because of it is efficient, non-invasive and relatively inexpensive.

Échographie dynamique

The ability to perform dynamic evaluation is a great advantage of ultrasound especially for musculoskeletal evaluation. Different manoeuvres are routinely used. The importance of the mobility of a structure or an articulation, but also the grade of compression of the lesion, can provide useful diagnostic information. For ligaments, the tension of each band is important and mobilisation is often able to depict some conflicts between the tendons and others structures. Muscle contraction is also an important element for making the diagnosis and, similar to a Valsalva manoeuvre for the diagnosis of a hernia. Interventional procedures are also facilitated by this dynamic evaluation. On the other hand, this great advantage requires the presence of a physician during the examination.

[Evolution of musculoskeletal ultrasonography]

Sonography is a safe, inexpensive and readily accessible technique which has acquired a major place in musculoskeletal imaging over the past two decades. Thanks to recent technical innovations such as high-definition multifrequency probes, compound effect, use of harmonic frequencies, power Doppler, and extended field of view, today's sonographic images are extremely precise. At the same time, based on magnetic resonance imaging (MRI) and computed tomography (CT) acquisitions, the sonographic anatomy has become broader and more detailed, and the sonographic semiology is more precise and reliable. In this article the authors evaluate current uses of diagnostic and interventional sonography in musculoskeletal disorders.

Traitement percutané d’un pseudo-kyste gazeux épidural : cause rare de sciatique

Gas containing epidural pseudocyst is a rare cause of lumbar radicular compression. We present the case of a 42 year old woman presenting with right L5 radicular pain. CT showed vacuum phenomenon and a gas containing epidural pseudocyst compressing the right L5 root. Resolution of radicular pain occurred following CT guided aspiration and steroid injection. The patient remained asymptomatic at one year follow-up.

[Anomalous insertion of the pectoralis minor muscle: ultrasound findings]

PURPOSE

With anomalous insertion of the pectoralis minor muscle, its distal fibers pass over the coracoid process instead of inserting on it, following sometimes a trajectory very similar to that of the coracohumeral ligament. The aim of this prospective study was to evaluate the frequency of detection of this anomalous insertion by ultrasonography.

MATERIALS AND METHODS

Ultrasound demonstrated the abnormal insertion of the pectoralis minor muscle by directly visualizing its fibers slipping over the coracoid process during external and internal rotation of the humerus. Three hundred and three individuals underwent ultrasound of the shoulders (64,7% female, mean age of 45 years), for a total of six hundred and six shoulders; 30% (183/606) were symptomatic.

RESULTS

An abnormal insertion was demonstrated in 9,57% of the examined shoulders (58/606), with a statistically significant predominance on the left side (12,2%) compared to the right side (6,9%), and of women (12,2%) compared to men (4,7%).

CONCLUSION

Ultrasound demonstrated an abnormal insertion of the pectoralis minor muscle in 9,57% of 606 examined shoulders. There was a female and left side predominance and no significant correlation with symptoms.

Pain immediately upon sitting down and relieved by standing up is often associated with radiologic lumbar instability or marked anterior loss of disc space

STUDY DESIGN

Comparison of functional radiographs in consecutive patients with low back pain with or without pain on sitting down and relieved by standing up.

OBJECTIVES

To detect radiologic signs possibly associated with a clinical symptom.

SUMMARY OF BACKGROUND DATA

No link has been established between increased vertebral mobility and a specific pain pattern or a clinical symptom.

METHODS

Forty-two patients seen consecutively with low back pain occurring immediately on sitting down and relieved on standing up were compared with 32 controls whose low back pain did not show this pattern. Dynamic radiographs were taken in extension, erect, flexion, and sitting in the painful position. The segments thought to be responsible for the pain were identified by comparing clinical, radiographic, and magnetic resonance data. Endplate angles, rotation, and translation were measured. The radiographs were read twice each by two independent observers.

RESULTS

Eighty-six percent (95% confidence interval, 72-99%) of the patients with the symptom were female. The segments identified as the source of pain were as follows: L4-L5 in 20 cases and L1-L2 to L3-L4 in 22 cases. Mean rotation of these segments was 13.9 +/- 4.5 degrees in the patient group versus 7.5 +/- 4.3 degrees in the control group (P < 0.001). In 14% of the patients (vs. 3% of controls), it exceeded 20 degrees (P = 0.13). Anterior or posterior translation >10% was seen in 31% of the patients (vs. 0% of controls; P < 0.001). In flexion, the endplate angle was -5.2 +/- 3.6 degrees (patients) versus 1.2 +/- 5.7 degrees (controls) (P < 0.01) and <-5 degrees in 55% of patients versus 12.5% of controls (P < 0.001). This value of <-5 degrees was associated with marked anterior loss of disc space.

CONCLUSION

Low back pain occurring immediately on sitting down and relieved on standing up was statistically associated with instability (specificity 100%, sensitivity 31%) or marked anterior loss of disc space in flexion (specificity 87%, sensitivity 55%).

[Imaging of lumbar stenosis]

The spinal canal is a type of articulated pipe, with rigid rings articulated by joints. It can be divided into a central part, which contains the dural sac, and lateral parts, which contain the nerve roots. The role of imaging is to detect the presence and characterize the nature, level, and severity of stenotic lesions and their impact on neural elements. Stenoses can be constitutional or acquired and involve the central and/or lateral canal. Constitutional stenoses affect both rigid and soft segments whereas acquired stenoses affect mainly the mobile segments. Signs of constitutional stenoses at conventional radiography, CT and MRI will be described. Acquired stenoses are multi-factorial in etiology and more difficult to evaluate. Intra-spinal soft tissues and dynamic factors, poorly assessed at CT and MRI (static imaging), play a major role in this type of stenoses. Currently, only myelography with dynamic evaluation is able to demonstrate the importance of these factors or degree of dynamic stenosis. The lateral canal is divided in three parts: two mobile segments (disco-articular interval, and intervertebral foramen) on each side of a fixed bony segment (lateral recess). The different types of stenoses involving these segments and best imaging technique to demonstrate their presence are described.

[Evaluation of spinal alignment disorders in adults]

Evaluation of the alignment of the spine in the frontal and sagittal planes is an important part in the work up of many disorders of the spine. This type of study requires only frontal and lateral 30 x 90cm radiographs performed in the standing position and including spine, pelvis and proximal femurs. The relationship between spine, pelvis and lower limbs is stressed.

Description of the potential of an arthrometer for standard and reduced radiographs suitable to measurement of angles and segments of hip, knee, foot and joint space widths

BACKGROUND

Primary osteoarthritis is usually selected in either epidemiological or therapeutic studies. This implies exclusions. Among cases of secondary osteoarthritis considered for either stratification or exclusion--or for prognosis and treatment in daily practice--are those due to architectural defects. Parameters of the latter should be measured to ascertain diagnosis. At present, measurements have to be performed either on digitized reduced films or standard radiographs.

OBJECTIVE

To finalize an instrument capable of measuring the main angles and segments characteristic of the main dysmorphisms of the hip, knee and foot on different sizes of films.

METHODS

An arthrometer drawn on transparent material to be placed on radiographs was designed, involving several appropriate protractors and millimetric scales; it was tested on 60 hip, 35 knee and 17 foot radiographs with various architectural defects. Angles and segments most often used according to literature were measured. Reduction rates of films were various, reflecting the range of radiograph sizes currently used in everyday practice.

RESULTS

Measurements were easily performed on radiographs from standard (100%) up to 50% of reduction rate. So the arthrometer allows the recognition, especially in moderate, not obvious forms, of the following developmental or acquired dysmorphisms: hip congenital dysplasia and subluxation, including coxa valga and neck excess of anteversion; acetabular protrusion and coxa vara; tilt deformity; knee: patellar height abnormalities, patellar maltracking, trochlear depth insufficiency; foot: pes cavus, flatfoot. Angle and segment ratios do not change in reduced film, whereas segments (absolute lengths) obviously should be converted according to the reduction rate for retrieving the classical values established for decades.

CONCLUSION

The arthrometer allows us to measure the relevant parameters of various dysmorphisms without drawing lines over the films themselves. It is suitable to reduced as well to standard radiographs. However, only the instrument and its ability to be used in various films sizes are here presented. Study of reproducibility of measurements--especially concerning the joint space width--remain to be performed.

Ultrasound of the ankle

Because of their size and superficial location the ankle tendons can be well evaluated with ultrasound (US). The excellent definition of the modern high frequency probes allows us to consider US the technique of first choice in their assessment. Basic US appearances correlate well with the MRI findings. Since US can diagnose most tendon disorders including tendinopathies, tears, dislocations and enthesopathies MRI is less often utilized. US can easily depict the main ankle ligaments. The basic US appearance of ligament tears is well known. US can be considered an inexpensive and accurate technique in the evaluation of ankle sprains.

[Foot and ankle imaging: what is the best modality]

There are numerous foot and ankle's pathologies and also numerous imaging technics. In fact, it often appears an inadequacy between the suspected pathology and the diagnostic tool used for its study. Aims. Know the qualities and the faults of each foot and ankle imaging technic. Know the best way of using these technics, according to the clinical problem, of a medical and economic point of view, in main skeletal pathologies, mechanical arthropathies of the hindfoot, tendonopathies, infections, and forefoot diseases.

[Ultrasonography of tendons and ligaments of foot and ankle]

The main ligaments and tendons of the ankle and the hind-foot can now be studied by US. This simple and safe technic constitutes a more and more reliable alternative to MRI and CT scan.

AIMS

Know the normal US appearance of the tendons and ligaments of the ankle and the hind-foot, and how to study them with US. Know their main usual pathological appearance.

[Radio-anatomy markers and applications of current imaging of the ankle and back of the foot]

The only aim of this work is to emphasize some anatomic and pathologic particularities of the constitutional elements of the ankle and the hind-foot, and their application in the actual imaging of this region. The characteristics of talus, calcaneus, navicular bone, talo-crural, sub-talar, medio-tarsal and tarso-metatarsal joints, calcaneus tendon, plantar aponevrosis, medial and lateral tendon of the ankle are successively detailed.

Time dependence of iopamidol and iodixanol in arthrography of the knee

PURPOSE

The safety and diagnostic efficacy of iodixanol (Visipaque) 270 mg I/ml was compared to that of iopamidol (Iopamiron) 300 mg I/ml in knee arthrography.

MATERIAL AND METHODS

This trial was a bi-center double-blind trial including 128 patients (iodixanol/iopamidol 64/64 patients). Efficacy was evaluated by blinded grading of the diagnostic quality of the p.a. images taken 0, 12 and 25 min after contrast administration by the examining radiologist and later at a consensus evaluation by two experienced skeletal radiologists. Adverse events were recorded.

RESULTS

No patient experienced any adverse event. The proportion of better images at both 12 and 25 min after injection was higher in the iodixanol group compared to the iopamidol group both by the examining radiologist and at the consensus evaluation.

CONCLUSION

In the knee joint iodixanol is a safe contrast medium. The contrast effect of iodixanol lasted longer than that of iopamidol, which can be important when performing arthrography, especially CT arthrography, where the time between puncture and examination can be prolonged.

[The medial collateral ligament of the knee]

Injuries of the medial collateral ligament (MCL) of the knee are easily diagnosed on clinical grounds. These lesions are generally treated conservatively. Radiological examinations are generally unhelpful. However, injuries of the MCL may be associated with those of many other ligaments of the knee in the case of complex strain of the knee so that the clinical diagnosis may be challenging; in some cases, surgical repair of associated lesions is indicated. In these cases of multiple ligamentous injuries, a radiological study of ligamentous abnormalities may be of interest. The anatomical background and the different radiological findings including those of X-rays, US, arthrography and MRI, obtained in patients with injuries of the MCL, are described; radiological differentiation of ruptures of the MCL with or without knee instability is emphasized.

[Fractures of the ischium after laminoarthrectomy. Retrospective study of a series of 31 patients]

PURPOSE OF THE STUDY

Pars interarticularis fracture is one possible source of pain after laminoarthrectomy. The purposes of this study were: to describe the pars defect, to determine its causes and to analyse its consequences on the functional final result.

MATERIAL AND METHOD

31 patients operated for disc herniation or degenerative lumbar stenosis were retrospectively studied. Clinical symptoms were evaluated before and 3 months after initial surgery, at the time of postlaminectomy radiological examination and at last follow-up according to Beaujon rating scale. Radiological evaluation included: description of the pars defect on plain radiographs and CT imaging, calculation of the amount of bone just above the inferior articular process that was resected, analysis of the postoperative stability of the spine both on static and dynamic radiographs. Any remaining disc herniation or stenosis were also noted.

RESULTS

39 pars interarticularis fractures were disclosed. These fractures were identified as a linear luency on plain radiographs or on reformed CT imaging view. Asymmetric widening of the facet joint space just below the pars defect was easier to observe and was present in 66 per cent of the cases on plain radiographs and in 79 per cent on CT imaging. After initial surgery 12 slipping appeared. In all of these cases pars fracture was bilateral at the same level or associated to a complete unilateral facetectomy at the same level. The amount of bone resected just above the inferior facet process was 66 per cent in average, range from 45 to 84 per cent. All the patients complained for low back pain and/or leg pain. In 62 per cent of cases symptoms occurred within one year after surgery, at an average onset of 7.6 months postlaminectomy. 27 patients were reported Revision surgery was in all cases a posterolateral fusion with or without instrumentation; new decompression was performed in 15 cases. At last follow-up, according to our classification, results were very good in 9 cases, good in 15 cases and fair in the remaining 3 cases. Improvement rate obtained after the initial surgery was 75 per cent in average, it was 59 per cent after revision surgery, difference was statistically significant.

CONCLUSION

Pars interarticularis fractures may be a source of postlaminectomy pain. They appear to be caused primarily by an excessive resection (more than one half) of the bone immediately superior to the inferior articular process at the level of the laminectomy. These results suggest that caution in resection of this bone or additional posterolateral fusion in case of large resection of pars interarticularis, can avoid the problem. Asymmetric widening of the joint space just below the defect seems to be the key to this diagnosis in the postoperative lumbar laminectomy patient with persistent or recurrent pain.

[L5-S1 herniated disk migrated to the anterior part of the right sacral wing with compression of the right lumbosacral roots]

PURPOSE OF THE STUDY

The goal of this study was to report an exceptional case of far lateral and anterior disc herniation at L5-S1 level.

CASE REPORT

A 47 year-old man presented a right L5 radicular pain with motor deficit of tibialis anterior and extensor hallucis longus resisting to medical management. Standard X-rays showed a degenerative process of L5-S1 disc. The CT scan was at first considered as normal. The myelogram was normal. A second study of the CT scan showed an opacity next to the L5 right root in front of the sacral wing. A discography combined with CT scan was then performed showing the migrated herniated disc from L5-S1 to the anterior part of the right sacral wing in contact with L5 root.

RESULTS

Surgery was performed by transperitoneal approach and needed a difficult dissection of hypogastric vessels. The herniated disc was found behind the L5 root. A L5-S1 disc excision and arthrodesis with iliac grafts were performed. The result has been very good with relief of the pain and recovery of the palsy within a month.

CONCLUSION

The lecture of a CT scan should include the far extraforaminal zone if there is no compression in the spinal canal. Such an anterior migration of an herniated disc has not been already described as far as we know.

Traumatic atlantooccipital dislocation with survival: case report and review of the literature

We present the case of a patient with traumatic atlantooccipital dislocation. The initial neurological examination showed no abnormalities. Dislocation was the result of rapid deceleration in a motor vehicle accident. The mechanism of injury was hyperextension/rotation, probably combined with a distraction force. Only a few cases of atlantooccipital dislocation without neurological involvement have been reported. Every report pointed out difficulties of initial diagnosis. Special attention should be directed toward the atlanto-odontoid-basion relationships as seen on lateral radiographs. Prompt recognition and surgical stabilization are essential to avoid further neurological injury.

Chemonucleolysis: correlation of results with the size of the herniation and the dimensions of the spinal canal

The aim of this study was to determine whether the results of chemonucleolysis are related to the size of the disc herniation and to the dimensions of the spinal canal. Short and long-term results (average follow-up 4 and a half years) of 148 patients were evaluated. Measurements made with a divider included the size of the disc herniation related to the sagittal diameter of the spinal canal at the discal level and the transverse interligamentous diameter at the level of the facet joints. The morphology of the lateral recess was also assessed. Measurements were initially made by five observers and were repeated eight times and on eight computed tomography (CT) scans in order to assess intra- and interobserver variability. Measurements of the entire series were then made by the two observers demonstrating a good intra- and interobserver reproducibility. Of the 148 patients 74% had an overall successful result. No significant difference was disclosed when comparing the various parameters of the clinical results with the size of the herniation. Similarly, a lack of correlation was also found between the clinical results and the dimensions of the spinal canal and of the lateral recess. In this series, the results were not significantly influenced by the size of the herniation or the morphology of the spinal canal.

[What remains of arthrography?]

At the time of RMI, arthrography appears sometimes old-fashioned. However this exam, which knows a second youth in relation with the supply of CT-scan (arthro-CT) remains the gold-standard in the exploration of many pathologic situations: intra-articular foreign bodies, tears of glenoid or acetabular labrum, precise assessment of chondral or ligamentous lesions (especially of the ankle), sub-scapularis tendon tears, adhesive capsulitis, complications of prosthesis, appreciation of intra-articular position of the needle's tip before injection of a therapeutic drug. Arthrography, completed or not by CT-slices gives, in this indications, excellent spatial resolution images, easy to perform, to read, to understand and to transmit at the clinicians, with a reasonable cost and a minor risk. RMI is a more and more used alternative, especially for the study of meniscus and ligaments of the knee, and rotator's cuff of the shoulder. It's sure that, with the increase of the RMI image's quality, other common indications will slip towards this technique, but nevertheless at this time (and it seams to me, for a long time) arthrography and arthro-CT will remain an excellent diagnostic tool with a very competitive advantages/inconvenience ratio.

[Lesions of the acetabular rim. Clinical manifestations, therapeutic strategies and perspectives]

Partial rupture of the acetabular rim have usually been described as accompanying traumatic or dysplasic dislocations of the hip. The five cases reported here are in favor of a specific pathology of this fibrocartilage as it is in the knee or the shoulder. Besides, the functional symptoms are not without reminding that of these two joints with sudden onset of cracks, jerks, blockings and even a real joint instability. The pain is never isolated, but may accompany other disorders. The cases were selected in order to evaluate the clinical manifestations and the therapeutic consequences of such a lesion according to the articular history. The diagnosis can only be confirmed with arthrography, which, in addition, permits to evaluate the size of the rim and the condition of the cartilage. The three patients who underwent surgery presented the lesions shown on arthrography. The problem lies in the possible arthrogenic potential of a tear, left in place because minimally disabling for the patient.

[Echography of the musculoskeletal system]

The recent, highly efficient and simple systems have enabled ultrasound to find a specific place in the imaging of the musculoskeletal system within a few years. The daily "on-site" examination currently completes plain radiographs with a particularly effective, non-traumatic and cheap exploration of a number of pathological cases, including traumatic musculotendinous lesions and periarticular soft tissue. After describing the normal images and the semiology of the major diseases for which this technique can be used, the author reviews the appearance of the main regional osteoarticular lesions (shoulder, hip, knee, extremities, etc.), with ultrasound.

[Unusual indications for scanning in osteoarticular pathology]

The authors take stock of current applications of the scanner in osteoarticular pathology. At first (1978-1983 approximately), only the vertebral column could be studied by this technique. Now, almost all the osteoarticular system is susceptible to study. Established examples are: study of the sacrum, of the traumatized acetabulum, of the femoropatellar apparatus, and measurement of torsion in the lower limbs. New applications are: study of the back of the foot, of the patellar cartilage, of the glenoid cavity, of the bones and soft parts of the hand, three-dimensional reconstructions, scanning radiology. The authors index and analyse these new techniques.

[X-ray computed tomographic exploration of cervico-brachial neuralgia. Value of the intravenous injection of contrast media]

Cervicobrachial neuralgias can now be easily evaluated by computerized tomography of the cervical spine due to recent technical progress (improved resolution, ultra-thin cuts, precise localization by computed radiography), and especially the use of intravenous contrast material, thus avoiding intrathecal metrizamide. The authors describe normal findings obtained by this method as well as disk herniations and disco-uncarthrosis. On the basis of this initial study of 35 patients (7 disk herniations and 16 disco-uncarthrosis), this method could be employed following routine studies as the first preoperative examination for cervicobrachial neuralgia. Thus, the indications for cervical myelography would decrease, limiting the use of a more invasive procedure and patient discomfort.

Anatomy and radiological anatomy of the lumbar radicular canals

The radicular canal is the lateral portion of the spinal canal when it is trefoil. It is a bony and ligamentary, monovertebral and indeformable space, the measurements of which are reproducible. The anatomy of this radicular canal has been studied in the whole of the lumbar vertebrae of 50 anatomical subjects. Its radiological anatomy has been defined by sagittal and computerised tomographies of these anatomical specimens, while sagittal tomographies were done for 25 control individuals devoid of symptoms. This canal, exceptional in the upper part of the lumbar canal, has been found in 72% of the cases in L4 and always in L5 and S1. Its sagittal diameter, which when measured must take into account the upper margin of the pedicle, has a theoretical minimal diameter of 3 mm to 3.8 mm, according to the vertebral level. 13% of the vertebrae were asymmetrical and no significant relationship exists between the median sagittal diameter of the spinal canal and the diameters of the radicular canals. Conventional sagittal tomography provides two types of images, according to the shape of the mouth of this canal and furnishes the best measurements (92% of the measurements were concordant), as long as the technique is followed closely. Transverse computerised tomography is less reliable, for the positioning of the section plane still remains the principal cause for error in measuring, but it provides a definition of the relations of the nerve elements with this canal. This radiological study will be suitable for sagittal reconstruction by computerised tomography, once this kind of examination can produce pictures of bones as detailed as those of conventional tomography.

[Cervical spondylolysis. 7 cases. Review of the literature]

Seven cases of cervical spondylolysis are reported one of them with cervical myelopathy, and the literature is reviewed. The particular anatomical features of the articular processes observed in 4 cases, as well as the many characteristics common to cervical and lumbar spondylolysis, suggest that both diseases might be caused by acquired fatigue fractures of the isthmus due to abnormal stress in patients predisposed by neural rich malformations.