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FUNCTIONAL EVALUATION OF THE JOINTS USING KINEMATIC MRI:
PART II. SHOULDER AND WRIST

Contributed by: Frank Shellock, Ph.D.
December 7, 2000

KINEMATIC MRI OF THE SHOULDER

Kinematic MRI of the shoulder has been used primarily during internal and external rotation movements. At least one study has reported good visualization of the anterior glenoid labrum (AGL) and demonstrated the role of the AGL in stabilizing the glenohumeral joint anteriorly, in conjunction with the capsular ligaments (Bonutti et al. 1993).

Kinematic MRI may be used to demonstrate the AGL limiting the range of motion of the shoulder by becoming entrapped at the extremes of motion. Avulsions of the AGL may also be better characterized using kinematic MRI of the shoulder. The distance between the lesser tuberosity and coracoid process can be measured to quantify the degree of subcoracoid impingement on the kinematic MR images of the shoulder (Bonnutti et al. 1993, Allman et al. 1997).

More recently, kinematic MRI of the shoulder has been performed using a highly-specialized MR system that has both vertically and horizontally opened spaces (Signa SP, 0.5 Tesla MR System, General Electric Medical Systems, Milwaukee, WI). Use of this MR system permits greater patient access and the ability to perform an MR-guided physical examination of the shoulder. As a result, kinematic MRI of the shoulder has been effectively utilized to identify and characterize mechanical impingement syndromes (Allman et al. 1997).

THE WRIST

Kinematic MRI has been applied to various aspects of wrist function. To date, this technique has been reported to reveal subtle abnormalities of carpal motion, instability patterns, transitory subluxation, and other conditions that are not easily evaluated by routine, static-view MRI (Shellock 1996, 1997; Shellock and Powers, in press). Kinematic MRI of the wrist offers several advantages over standard wrist fluoroscopy. For example, kinematic MRI can provide tomographic information and a direct means of viewing the interosseous ligaments. Idiopathic pain syndromes related to motion are often not sufficiently characterized by static-view MR techniques, especially if transitory subluxations are present. The kinematic MRI examination provides enhanced imaging of the muscles, tendons, ligaments, hyaline, and fibrocartilaginous structures during controlled motion.

A report by Ton and colleagues (1995). indicated that a kinematic MRI examination using a device to hold the wrist in "radial stress" and "ulnar stress" positions, while obtaining coronal plane images, was useful to detect interosseous ligament defects, especially those involving the scapholunate and lunotriquetral ligaments. This simple kinematic MRI method improves the diagnostic accuracy for abnormalities that are considered to be particularly challenging to assess using conventional techniques.

The small size of the wrist makes it necessary to use a surface coil to obtain high-resolution images for kinematic imaging. A positioning device is used to incrementally position the wrist through radial and ulnar deviated positions as well as through flexion and extension. The patient is typically placed in a prone position with the elbow extended, and foam padding is placed at various sites under the axilla, arm, and elbow for support and comfort. As with other types of kinematic MR studies, either multiple static images or a cine loop format may be used to view the acquired images. However, the cine loop display is best for demonstrating subtle instability patterns of the carpal bones.

On coronal plane images, kinematic MRI of normal motion of the wrist in radial, neutral, and ulnar positions shows the carpal bones, bordered by the radius and ulna, moving in a symmetrical manner. Any deviation from this symmetrical movement of the carpal bones is indicative of instability. These abnormalities may be caused by a torn ligament, laxity of a ligament, or a carpal bone fracture.

Assessment of intercarpal spacing on the kinematic MRI may also provide evidence of a wrist abnormality. Spacing should be evenly distributed between the carpal bones, without any significant or uneven intercarpal widening, proximal or distal movement, or anterior or posterior displacement of the carpal bones. The normal intercarpal space is approximately 1 to 2 mm wide. Increased joint space is suggestive of an abnormal ligament, increased joint fluid, synovial hypertrophy, or other forms of pathokinematics. Decreased joint space may be caused by an abnormal ligament, loss of cartilage, carpal coalition, or dislocated or subluxated carpal bones.

The presence of ulnar variance, whether positive or negative, should also be noted on kinematic MR coronal plane images because it may provide an indication of the mechanism responsible for the abnormality. For example, positive ulnar variance has been associated with tears of the triangular fibrocartilage complex and articular erosions of the lunate and triquetrum. Alternatively, negative ulnar variance is often seen with Kienbock's disease or avascular necrosis of the lunate.

Carpal bone instability is typically caused by a hyperextension impact injury. The specific carpal site of the instability is dependent on the position of the hand (i.e., whether it is flexed or extended, or in ulnar or radial deviation) at the time of contact. Early detection and treatment of carpal bone dissociations are crucial for a satisfactory clinical outcome. Conventional plain film x-rays, computed tomography, or static-view MR imaging may be inconclusive in identifying carpal bone instability because the abnormality may be so subtle that it escapes detection unless the wrist is manipulated so that asynchronous motion of the carpals, widening of the joint space, or both may be appreciated. Kinematic MRI of the wrist provides an adequate depiction of the pathokinematic aspects of carpal instability.

SUMMARY AND CONCLUSIONS

Kinematic MRI procedures enhance the ability to evaluate joints because they provide functional information that is not provided using standard, static-view MRI examinations. The diagnostic advantages of kinematic MRI are summarized in Table 1.

Kinematic MRI studies should be used on a routine basis whenever the pertinent indications are present. To effectively accomplish this, specialized-training is required for MRI technologists and radiologists so that the kinematic MRI procedures are performed in a technically acceptable manner and interpreted properly. In addition, the appropriate staff member of the MRI center needs to be proactive, informing and educating referring physicians (i.e., orthopedic surgeons, physiatrists, neurologists) about the availability of kinematic MRI at the imaging facility.

Table 1:
Indications for Kinematic MRI Examinations

KINEMATIC MRI OF THE ANKLE

  • Tendon dysfunction
  • Impingement syndromes
  • Identifies position-dependent pathologic findings
  • Determines subluxation of the peroneal tendons
  • Useful in the assessment of subtalar instability syndrome
  • Helps to differentiate partial from full-thickness tears of the ligaments and tendons

KINEMATIC MRI OF THE CERVICAL SPINE

  • Instabilities
  • Cervical spondylotic disease
  • Rheumatoid arthritis
  • Identifies position-dependent pathologic findings

KINEMATIC MRI OF THE PATELLOFEMORAL JOINT

  • Identifies and characterizes patellar alignment and tracking abnormalities
  • Useful for evaluation of treatment methods

KINEMATIC MRI OF THE SHOULDER

  • Glenohumeral instability
  • Mechanical impingement

KINEMATIC MRI OF THE WRIST

  • Distal radioulnar joint instability
  • Carpal instability
  • Scapholunate and lunotriquetral ligament tears
  • Ulnolunate impaction syndrome
  • Identifies position-dependent pathologic finding
  • Helps to differentiate partial from full-thickness tears of the intercarpal ligaments

Suggested References:

SHOULDER

WRIST

 

 
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