Diagnosing extensor carpi ulnaris tendon dislocation with dynamic rotation MRI of the wrist
Introduction
Subluxation and dislocation of the extensor carpi ulnaris (ECU) tendon can be one cause for ulnar-sided wrist pain. The reason for dislocation or subluxation is an injury to the ECU tendon sub-sheath caused by trauma or rheumatic genesis [1, 2]. The ECU tendon sub-sheath is an independent layer of connective tissue underneath the extensor retinaculum stabilizing the ECU tendon [3]. Three different types of injury patterns of the sub-sheath leading to a dislocation or subluxation have been described: (1) a disruption from the ulnar wall of the ulnar groove, (2) a disruption from the radial wall of the ulnar groove and (3) a detachment of the periosteum of the ulnar wall of the ulnar groove [4, 5].
Although the assessment of ECU tendon subluxation or dislocation is made by clinical examination, imaging is necessary to confirm and visualize the diagnosis and to exclude other concomitant injuries or pathologies causing ulnar-sided wrist pain. Ultrasound as well as MRI can be used to visualize any ECU tendon pathology, like tendinopathy, tenosynovitis, tendon rupture or subluxation [[6], [7], [8]].
Previously ultrasound was described as the modality of choice to visualize ECU tendon subluxation or dislocation as it is a dynamic examination method [1, 5, 9, 10]. Some authors stated that MRI was useful in excluding other pathologies like lesions of the triangular fibrocartilage complex (TFCC) but not suitable to make a diagnosis of ECU tendon subluxation or dislocation because of its static examination character [5, 9].
Dynamic interactions of osseous and soft tissue structures, however, can be assessed by the use of kinematic MRI. Therefore, the purpose of this study was to evaluate the kinematic dynamic rotation MRI (DR-MRI) of the wrist for assessment of ECU tendon subluxation and dislocation. It was hypothesized that MRI could visualize ECU tendon subluxation and dislocation and distinguish in-between both.
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Material and methods
A retrospective analysis was performed on the data of all patients who received a DR-MRI of the wrist because of symptomatic ulnar sided wrist pain with clinical signs and suspicion of an ECU tendon subluxation or dislocation between 1999 and 2013 at the department for radiology and the department for trauma surgery of the XXXXX. Institutional review board approval was granted by means of a general waiver for studies with retrospective data analysis (Local research ethics committee, XXXXX; 20th
Results
The right wrist was affected from ECU tendon dislocation or subluxation 15 times and the left wrist 10 times. One patient showed bilateral wrist involvement.
MRI findings showed an ECU subluxation in 12 cases and an ECU dislocation in 13 cases. Surgery showed an ECU subluxation in 13 cases and an ECU dislocation in 12 cases (ĸ = 0.92). Fig. 2 shows a DR-MRI image series visualizing an ECU tendon dislocation. The subluxation group showed an amount ranging from 50% to 90% of the tendon's width
Discussion
The most important finding of the present study was that DR-MRI can adequately visualize the ECU tendon's position in relation to the ulnar groove at the wrist in a rotational pronation-supination movement. Thus, ECU tendon subluxation or dislocation can be diagnosed correctly by the use of DR-MRI. There was one case, which showed a dislocation on the MRI images but only a subluxation during surgery. This finding might be due to the sometimes difficult differentiation in the nomenclature in
Conclusion
In conclusion, DR-MRI is a feasible method to visualize and grade ECU tendon subluxation and dislocation and is important in excluding concomitant pathologies.
Declaration of interest
None.
Conflict of interest
The authors Kaiser Peter, Kellermann Florian, Arora Rohit, Henninger Benjamin and Rudisch Ansgar declare that they have no conflict of interest.
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