Midcarpal instability: a diagnostic role for dynamic ultrasound?

EURO-MUSCULUS/USPRM Dynamic Ultrasound Protocols for Wrist and Hand

ABSTRACT

In this dynamic protocol, ultrasound evaluation of the wrist and hand is described using various maneuvers for relevant conditions. Scanning videos are coupled with real-time patient examination videos. The authors believe that this practical guide - prepared by the international consensus of several experts - will help musculoskeletal physicians perform a better and uniform/standard examination approach.

Dorsal Wrist Plication for Midcarpal Instability

PURPOSE

Midcarpal instability (MCI) is a cause of chronic wrist pain for which treatment remains controversial. This study's purpose was to determine the outcome of a treatment algorithm for MCI that included immobilization and surgical interventions.

METHODS

We prospectively enrolled 23 consecutive patients (12 males, average age 27 years) with 27 symptomatic wrists. All had generalized wrist pain with an average duration of 22 months. All had MCI and a catch-up clunk that reproduced the symptoms. Initial treatment was full immobilization for 6 weeks. When necessary, recurrence after immobilization was treated with an anatomically based surgical procedure to plicate the dorsal capsule and extrinsic ligaments to stabilize the midcarpal joint. Failure of surgical plication was followed by 4-corner intercarpal arthrodesis when necessary. Patients were observed for instability, grip strength, wrist motion, and Patient-Rated Wrist Evaluation.

RESULTS

For 22 wrists there was partial relief of symptoms with full-time cast or orthosis immobilization; however, symptoms quickly returned with mobilization. The other wrists had previously been immobilized and patients refused further nonsurgical care. All patients underwent surgical plication of the dorsum of the wrists. Postoperative follow-up (35 months) showed statistically significant improvements in grip strength and Patient-Rated Wrist Evaluation scores. All patients had improved pain at final follow-up. Most improvement was in female patients aged under 25 years, with hypermobility and without major traumatic or work-related injuries. This contrasted with poorer outcomes in men aged over 25years who had moderate or severe trauma that was mostly work-related. Instability recurred in 2 patients who then had a 4-corner arthrodesis.

CONCLUSIONS

Immobilization was not successful in controlling pain and recurrence of instability in patients with MCI. Surgical midcarpal capsular plication was less effective in men with posttraumatic instability. The capsular plication procedure was successful in young female patients with ligament laxity and a history of only minor or repetitive trauma and no history of major trauma.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic IV.

Imaging in carpal instability

Carpal instability is a complex and heterogeneous clinical condition. Management requires accurate identification of structural injury with an understanding of the resultant movement (kinematic) and load transfer (kinetic) failure. Static imaging techniques, such as plain film radiography, stress views, ultrasound, magnetic resonance, MR arthrography and computerized tomography arthrography, may accurately depict major wrist ligamentous injury. Dynamic ultrasound and videofluoroscopy may demonstrate dynamic instability and kinematic dysfunction. There is a growing evidence base for the diagnostic accuracy of these techniques in detecting intrinsic ligament tears, but there are limitations. Evidence of their efficacy and relevance in detection of non-dissociative carpal instability and extrinsic ligament tears is weak. Further research into the accuracy of existing imaging modalities is still required. Novel techniques, including four-dimensional computerized tomography and magnetic resonance, can evaluate both cross-sectional and functional carpal anatomy. This is a narrative review of level-III studies evaluating the role of imaging in carpal instability.

Wide field of view computed tomography and mid-carpal instability: the value of the sagittal radius-lunate-capitate axis--preliminary experience

PURPOSE

Dynamic four dimensional (4D) computed tomography (CT) has recently emerged as a practical method for evaluating complex functional abnormality of joints. We retrospectively analysed 4D CT studies undertaken as part of the clinical management of hand and wrist symptoms. We present our initial experience of 4D CT in the assessment of functional abnormalities of the wrist in a group of patients with mid carpal instability (MCI), specifically carpal instability non-dissociative. We aim to highlight unique features in assessment of the radius-lunate-capitate (RLC) axis which allows insight and understanding of abnormalities in function, not just morphology, which may be contributing to symptoms.

MATERIALS AND METHODS

Wide field of view multi-detector CT scanner (320 slices, 0.5 mm detector thickness) was used to acquire bilateral continuous motion assessment in hand flexion and extension. A maximum z-axis coverage of 16 cm was available for each acquisition, and a large field of view (FOV) was used. Due to the volume acquisition during motion, reconstructions at multiple time points were undertaken. Dynamic and anatomically targeted multi-planar-reconstructions (MPRs) were then used to establish the kinematic functionality of the joint.

RESULTS

Our initial cohort of 20 patients was reviewed. Three findings were identified which were present either in isolation or in combination. These are vacuum phenomenon, triggering of the lunate and capitate subluxation. We provide 4D CT representations of each and highlight features considered of clinical importance and their significance. We also briefly discuss how the current classifications of dynamic wrist abnormalities may alter with the supplementary information provided by dynamic 4D CT MSK acquisitions.

CONCLUSION

4D CT has provided a unique insight into motion disorders. We highlight our early experience with the ability of 4D CT to investigate the RLC axis and three signs which have provided a unique assessment of MCI. This improved assessment of wrist motion disorders has highlighted sufficient differences in the dynamic CT classifications we have described and suggests that further research may result in refinement of the MCI classification system.

Imaging of snapping phenomena

Snapping phenomena result from the sudden impingement between anatomical and/or heterotopical structures with subsequent abrupt movement and noise. Snaps are variously perceived by patients, from mild discomfort to significant pain requiring surgical management. Identifying the precise cause of snaps may be challenging when no abnormality is encountered on routinely performed static examinations. In this regard, dynamic imaging techniques have been developed over time, with various degrees of success. This review encompasses the main features of each imaging technique and proposes an overview of the main snapping phenomena in the musculoskeletal system.

Midcarpal instability: a radiological perspective

Midcarpal instability (MCI) is the result of complex abnormal carpal motion at the midcarpal joint of the wrist. It is a form of non-dissociative carpal instability (CIND) and can be caused by various combinations of extrinsic ligament injuries that then result in one of several subtypes of MCI. The complex patterns of injury and the kinematics are further complicated by competing theories, terminology and classifications of MCI. Palmar, dorsal, ulna midcarpal instability, and capitolunate or chronic capitolunate instability are all descriptions of types of MCI with often overlapping features. Palmar midcarpal instability (PMCI) is the most commonly reported type of MCI. It has been described as resulting from deficiencies in the ulna limb of the palmar arcuate ligament (triquetrohamate-capitate) or the dorsal radiotriquetral ligaments, or both. Unstable carpal articulations can be treated with limited carpal arthrodesis or the ligamentous defects can be treated with capsulorrhaphy or ligament reconstruction. Conventional radiographic abnormalities are usually limited to volar intercalated segment instability (VISI) patterns of carpal alignment and are not specific. For many years stress view radiographs and videofluoroscopy have been the methods of choice for demonstrating carpal instability and abnormal carpal kinematics respectively. Dynamic US can be also used to demonstrate midcarpal dyskinesia including the characteristic triquetral "catch-up" clunk. Tears of the extrinsic ligaments can be demonstrated with MR arthrography, and probably with CT arthrography, but intact yet redundant ligaments are more difficult to identify. The exact role of these investigations in the diagnosis, categorisation and management of midcarpal instability has yet to be determined.