Ulnar sided wrist pain after falling on the extended wrist or torque loading in work
injuries is common and often related to lesion of the triangular fibrocartilage complex
(TFCC). Traumatic lesions of the radioulnar ligaments of the TFCC can lead to distal
radioulnar joint (DRUJ) instability as these structures are the main contributors to
DRUJ stability. In clinical examination of DRUJ instability the observer manually feels
and subjectively quantify the anterior posterior translation of the DRUJ, and the
method has limited reproducibility. Likewise, imaging methods such as computer
tomography scans and magnetic resonance scans have inadequate specificity and
sensitivity for TFCC injuries. Therefore, the gold standard diagnostic method of TFCC
injuries is arthroscopic evaluation. However, it is not feasible to operate patients to get
a diagnosis. Thus, a valid objective tool to diagnose TFCC injuries and grade DRUJ
instability before and after surgical treatment is warranted. Radiostereometry (RSA) is
a very precise and accurate method, which has been used for decades to evaluate hip
and knee implant migration with repeated imaging over time in a static setting.
Dynamic RSA has been used for experimental as well as clinical evaluation of joint
kinematics with high precision, but never before for evaluation of the DRUJ.
The focus of this PhD thesis was TFCC injuries and application of static and dynamic
RSA as an objective measure of DRUJ stability.
In Study I, the feasibility and precision of AutoRSA for analysis of RSA imaging of
DRUJ translation was demonstrated experimentally. Lesion of the distal and proximal
insertion of the TFCC to the ulna styloid and ulna fovea, led to increasing DRUJ
translation during Static RSA examination during a Piano key test.
In Study II, a surgical treatment with foveal reinsertion of the TFCC or Adams TFCC
reconstruction was compared in a randomizes experimental study. The Piano key test
was used to apply DRUJ translation, which was recorded by static RSA at end-points.
A stabilizing effect was demonstrated by foveal TFCC reinsertion, whereas the
variation in the stabilizing effect of Adams TFCC reconstruction was large and did not
prove a statistically significant reduction of DRUJ translation.
In Study III, the feasibility and precision of a AutoRSA for analysis of dynamic RSA
imaging during a Press test was demonstrated in a clinical study. DRUJ kinematics
during an active Press test was recorded in participants with asymptomatic clinical
stable non-injured DRUJs and classified as “normal DRUJ kinematics”. Using a DRUJ
position ratio was recommended to take individual sigmoid notch size into account.
In Study IV, DRUJ kinematics during a patient active Press test was recorded with
dynamic RSA and a paired comparison was done between the patients asymptomatic
non-injured DRUJ and the symptomatic DRUJ with an arthroscopically verified foveal
TFCC lesion. A statistically significant difference of the DRUJ position ratio in foveal
TFCC injured DRUJs compared to the asymptomatic side was demonstrated as the
ulnar head center translated 10 percent points more volar in the sigmoid notch with
foveal TFCC injury. Surgical treatment with open foveal TFCC reinsertion was
performed and postoperative clinical and dynamic RSA imaging showed a stabilizing
effect on the DRUJ stability towards normal values at 6-month and 1-year follow-up.
Surgery did not normalize grip strength and AROM to the level of the non-injured
contralateral side, but PROMs (QDASH, PRWE, and pain during activity) were
improved to the level of the minimal clinically important difference (MCID).
In conclusion, this thesis documented static and dynamic RSA imaging and AutoRSA
analysis to be a feasible and precise method for evaluation of DRUJ kinematics and
stability. The studies contributed with precise estimates of DRUJ kinematics and
improved the understanding of normative DRUJ kinematics, and the kinematic impact
of TFCC injuries. This inspires to further explore the DRUJ kinematic patterns using
clinically relevant and more complex DRUJ exercises that mimic the situations in
which patient’s report symptoms and DRUJ instability. Furthermore, dynamic RSA
imaging and AutoRSA analysis of the DRUJ now makes it possible to evaluate the
stabilizing effect of existing and new surgical treatments for DRUJ instability.