Complex distal insertions of the tibialis posterior tendon: detailed anatomic and MR imaging investigation in cadavers

PURPOSE: The purpose of this report was to demonstrate the normal complex insertional anatomy of the tibialis posterior tendon (TPT) in cadavers using magnetic resonance (MR) imaging with anatomic and histologic correlation. MATERIAL AND METHODS: Ten cadaveric ankles were used according to institutional guidelines. MR T1-weighted spin echo imaging was performed to demonstrate aspects of the complex anatomic distal insertions of the TPT in cadaveric specimens. Findings on MR imaging were correlated with those derived from anatomic and histologic study. RESULTS: Generally, the TPT revealed a low signal in all MR images, except near the level of the medial malleolus, where the TPT suddenly changed direction and "magic angle" artifact could be observed. In five out of ten specimens (50%), a type I accessory navicular bone was found in the TPT. In all cases with a type I accessory navicular bone, the TPT had an altered signal in this area. Axial and coronal planes on MR imaging were the best in identifying the distal insertions of the TPT. A normal division of the TPT was observed just proximal to the insertion into the navicular bone in five specimens (100%) occurring at a maximum proximal distance from its attachment to the navicular bone of approximately 1.5 to 2 cm. In the other five specimens, in which a type I accessory navicular bone was present, the TPT directly inserted into the accessory bone and a slip less than 1.5 mm in thickness could be observed attaching to the medial aspect of the navicular bone (100%). Anatomic inspection confirmed the sites of the distal insertions of the components of the TPT. CONCLUSION: MR imaging enabled detailed analysis of the complex distal insertions of the TPT as well as a better understanding of those features of its insertion that can simulate a lesion.     

Trigeminal nerve: anatomic correlation with MR imaging

Through correlation with cryomicrotic sections, the appearance of the trigeminal nerve and its branches on magnetic resonance images is described in healthy individuals and in patients with tumors involving this nerve. Coronal images are best for defining the different parts of the nerve and for making a side-to-side comparison. Sagittal images are useful to demonstrate tumors involving the gasserian ganglion.     

Thoracic outlet: anatomic correlation with MR imaging

OBJECTIVE: The purpose of this report is to describe the normal MR anatomy of the thoracic outlet and its modification after postural maneuvers using an anatomic-MR imaging correlation. CONCLUSION: MR imaging appears to be a useful technique to study the thoracic outlet and its contents because of its excellent soft-tissue depiction and its multiplanar capabilities. T1-weighted images obtained in the sagittal plane clearly depicted the different compartments of the cervicothoracic-brachial junction. Hyperabduction maneuvers may have potential applications in the assessment of the thoracic outlet syndrome by showing the location of compression.     

Avulsion of the posteromedial tibial plateau by the semimembranosus tendon: diagnosis with MR imaging

Two sports-related knee injuries resulted in small fractures at the posteromedial corner of the tibial plateau. Magnetic resonance imaging demonstrated findings consistent with an avulsion injury at the semimembranosus insertion, as well as a similar pattern of internal derangement in both cases.     

MR imaging of the normal shoulder: anatomic correlation

The complex anatomy and the requirement to image in the peripheral magnetic field have made the shoulder difficult to examine with MR. However, the use of high-resolution scanning techniques and specialized surface coils has improved the quality of MR images obtained. Seventy-five scans of the shoulders of normal volunteers were correlated with multiplanar cryomicrosections of six cadaver shoulders to study the MR appearance of normal structures. MR was shown to provide excellent depiction of shoulder anatomy.     

Acute spinal ligament disruption: MR imaging with anatomic correlation

Disruption of spinal ligaments can lead to instability that jeopardizes the spinal cord and nerve roots. Magnetic resonance (MR) imaging can directly image spinal ligaments; however, the sensitivity with which this modality demonstrates ligament injury has, to the authors' knowledge, not been reported. On a biomechanical testing machine, 28 cadaveric spines were subjected to controlled injury that resulted in ligament tears. The spines were then imaged with plain radiography, computed tomography, and MR imaging (1.5 T). The images were analyzed for evidence of ligament injury before dissection of the specimen. Forty-one of 52 (79%) ligament tears of various types were correctly identified at MR imaging. Disruptions of the anterior and posterior longitudinal ligaments were most conspicuous and were detected in all seven cases in which they were present (no false-positive or false-negative results); disruptions of the ligamentum flavum, capsular ligaments, and interspinous ligaments could also be identified but less reliably (three false-positive and 11 false-negative results). That MR imaging can reliably and directly allow assessment of spinal ligament disruption in this in vitro model suggests its potential utility for this assessment in patients.     

Posteromedial corner of the knee: MR imaging with gross anatomic correlation

Objective. The objective of this study was to illustrate the magnetic resonance (MR) image appearance of the structures of the posteromedial ”corner” of the knee with particular emphasis on the anatomy and differentiation between the medial collateral ligament and the posterior oblique ligament. Design. Six cadaveric knee specimens underwent MR imaging, before and following instillation of intra-articular contrast material. The knees were sectioned in the axial, coronal, and coronal oblique planes and the gross morphology of the posteromedial corner and surrounding structures was studied and correlated with the MR images. Patients. The human cadaveric specimens were from two female and four male patients (age at death, 72–86 years; average, 78 years). Results and conclusions. The contrast-enhanced sequences and the coronal oblique images allowed for improved visualization of the structures. Received: 26 October 1998 Revision requested: 11 December 1998 Revision received: 21 January 1999 Accepted: 26 January 1999     

Normal MR imaging findings of the midhand and fingers with anatomic correlation

In the present article, we correlate MR imaging studies of cadavers, volunteers and patients with cadaveric dissection and sectioning. First anatomy at wrist level is discussed. In a next section, we address the midhand with the flexor and extensor tendons, and interosseous and lumbricalis muscles. The dorsal hood at the level of the metacarpophalangeal joint is also addressed. An overview of the anatomy of the thenar is provided. Finally, the flexor system of the fingers with pulleys and volar plates, as well as the central and distal insertion of the finger extensor tendons is discussed.     

Alterations in the supraspinatus tendon at MR imaging: correlation with histopathologic findings in cadavers

To determine the histopathologic correlates of alterations in the rotator cuff at magnetic resonance (MR) imaging, 13 cadaveric shoulders (in subjects aged 26-83 years at the time of death) underwent MR imaging in the coronal oblique plane at 1.5 T with proton-density- and T2-weighted spin-echo sequences. Areas corresponding to sites of MR imaging alterations were then examined histologically. Increased signal intensity on proton-density-weighted images (without further increased signal intensity on T2-weighted images) and an indistinct margin at the articular side of the supraspinatus tendon corresponded to eosinophilic, fibrillar, and mucoid degeneration and scarring. Areas of increased signal intensity on T2-weighted images were associated with severe degeneration and disruption of the supraspinatus tendon. Although other authors have suggested that certain MR findings are indicative of tendinitis, the histologic data in this study were not those of active inflammation but rather tendon degeneration.     

Sonography and MR imaging of bifid median nerve with anatomic and histologic correlation

OBJECTIVE: Imaging of a bifid median nerve has not been previously described in the radiology literature. We present three cases of bifid median nerve. The first is a patient with carpal tunnel syndrome seen on sonography and confirmed at surgery. The other two were found among 10 cadaveric specimens and were imaged with sonography and MR imaging. Confirmation of bifid median nerve in these two specimens was obtained using anatomic and histologic correlation. CONCLUSION: Sonography and MR imaging can allow effective diagnosis and delineation of a bifid median nerve in the wrist. This diagnosis is important to make before carpal tunnel release or other wrist surgeries are performed to avoid nerve injury. Furthermore, the sonographic size criteria for diagnosing carpal tunnel syndrome in nonbifid median nerves may not be accurate in evaluating bifid median nerves.     

Cavernous sinus: correlation between anatomic and dynamic gadolinium- enhanced MR imaging findings

Dynamic magnetic resonance (MR) images were evaluated and compared with conventional T1-weighted spin-echo (SE) images obtained before and after administration of gadopentetate dimeglumine in 20 patients with normal cavernous sinuses. Starting 10 seconds after rapid injection of gadopentetate dimeglumine (0.1 mmol/kg), six to eight serial images were obtained every 30 seconds for 3-5 minutes. The venous spaces of the cavernous sinus were markedly enhanced 30 seconds after injection. Cranial nerves III and IV, V1 and VI, and V2 were seen on 75% of dynamic images each; they were seen, respectively, on 62%, 30%, and 28% of conventional postcontrast images. The medial wall was demarcated on 90% of dynamic, 15% of precontrast, and 55% of postcontrast images. A small area of connective tissue was identified within the cavernous sinus on dynamic images showing gradual enhancement. It is concluded that dynamic MR images proved useful in delineating and distinguishing abnormal tissue from normal structures.     

MR imaging of the tarsal tunnel and related spaces: normal and abnormal findings with anatomic correlation

The tarsal tunnel syndrome may be caused by extrinsic or intrinsic pressure on the posterior tibial nerve or its terminal branches. The specific symptoms depend on the extent of nerve involvement, and compression distal or proximal to the tarsal tunnel may result in variants of the syndrome. To define better the capability of MR imaging for evaluating this entity, we performed MR imaging on three normal subjects and correlated the images with cryomicrotome sections. Six patients with symptoms suggestive of tarsal tunnel syndrome also were studied with MR. In all normal subjects, MR images showed the flexor retinaculum and the structures passing deep to the retinaculum: the tibialis posterior tendon, flexor digitorum longus tendon, flexor hallucis longus tendon, and the posterior tibial neurovascular bundle. The medial calcaneal sensory branch(es) and the medial and lateral plantar nerves also were delineated. Mechanical causes of compression were shown in all six symptomatic patients. The pathologic entities included two neurilemomas, tenosynovitis involving all three tendons, a ganglion cyst arising from the flexor hallucis longus tendon sheath, posttraumatic fibrosis, and post-traumatic fibrosis with associated posttraumatic neuroma. The MR findings were confirmed surgically in five cases. MR imaging can accurately depict the contents of the tarsal tunnel and the courses of the terminal branches of the posterior tibial nerve. In our small series, MR imaging accurately showed the lesions responsible for tarsal tunnel syndrome.     

Biceps tendon dislocation: evaluation with MR imaging

The magnetic resonance (MR) images from six patients with biceps tendon dislocation--two in whom it was surgically proved and four in whom it was suspected--were retrospectively evaluated. The dislocated tendon can be identified medial to the bicipital groove, best seen on the axial and oblique coronal and sagittal images. Associated abnormalities of the biceps tendon include thickening (n = 3), high signal intensity (n = 3), and surrounding fluid (n = 4). The factors thought to contribute to dislocation can also be well seen on MR images. These include abnormal shape of the bicipital groove (n = 2), disruption of the coracohumeral ligament (n = 6), disruption (n = 4) and thinning (n = 1) of the subscapularis tendon, and supraspinatus tendon tear (n = 4). Since MR imaging is becoming the modality of choice for the evaluation of shoulder derangements, familiarity with the appearance of biceps tendon dislocation on MR images is important.     

Complete rupture of the distal semimembranosus tendon with secondary hamstring muscles atrophy: MR findings in two cases

Complete rupture of the hamstring muscles is a rare injury. The proximal musculo-tendinous junction is the most frequent site of rupture. We present two cases of complete rupture of the distal semimenbranosus tendon, which clinically presented as soft-tissue masses. MR imaging permitted the correct diagnosis. There has been only one other such case reported. Received: 15 October 1999 Revision requested: 6 February 2000 Revision received: 8 March 2000 Accepted: 13 March 2000