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de Quervain's disease (dQD) is a stenosing tenosynovitis of the first extensor compartment of the wrist which is formed by the tendons of the abductor pollicis longus (APL) and extensor pollicis brevis (EPB).1,–,3 Thirty-three consecutive patients with a clinical diagnosis of dQD underwent ultrasound (US). The inclusion criteria were (1) a history of pain over the radial aspect of the wrist aggravated by excessive use of the thumb; (2) an orthopaedic diagnosis of dQD; and (3) a positive Finkelstein test. The control group consisted of 24 healthy subjects and was matched for age and sex. All studies were performed using a Vivid 7 machine (General Electric, Milwaukee, Wisconsin, USA) with a 12 MHz matrix linear array transducer. The sonographer was not blinded to the identity of the control subjects. Statistical analysis was performed using the Student t test to assess differences between group means; χ2 and Fisher exact tests were used for testing the association between qualitative variables.
In the control group the mean±SD thickness of the retinaculum was 0.43±0.11 mm (range 0.3–0.8). Septation of the first compartment was found in seven subjects (29.2%). In the group with dQD the following findings were observed (table 1):
The mean ± SD thickness of the first compartment retinaculum was 2.01 ± 0.53 mm (range 1.2–3.0), which was significantly higher than the control group (p < 0.0001).
The thickening was found to involve either both the EPB and APL (72.7%, type I dQD) or the EPB alone (27.3%, type II dQD).
Tendon sheath effusion and hypervascularisation were found to be highly associated with type I dQD (p < 0.001 and p < 0.002, respectively).
Patients with type I dQD were older than patients with type II dQD (p=0.009).
The first relevant finding of our work is that the main US characteristic of dQd is the thickening of the retinaculum at the level of the first compartment. In fact, a hypoechoic thickness of the retinaculum was found in all the patients but in none of the control subjects. Inflammatory involvement of tendons was an inconstant feature with effusion and hypervascularisation found in 72.7% and 57.6% of patients, respectively. The second interesting finding is that US evaluation allowed us to distinguish two forms of dQD. Type I dQD is characterised by a tight constriction of both tendons by a clear loop-shaped retinaculum with no evidence of septation between the two tendons. On the other hand, type II dQD is characterised by an evident septation and the retinaculum compresses only the EPB (figure 1). We believe that the two subsets are caused by an anatomical difference consisting of a septation of the compartment. In our study the frequency of septation in control subjects was very similar to that of patients with type II dQD.
The recognition of the two distinct forms may have therapeutic implications. In fact, although the intrasheath steroid injection is a very effective treatment for dQD, there is a failure rate varying from 15% to 20%.2,–,4 Several authors have already proved in different ways that this failure is probably due to the presence of septation.5,–,7 These findings are consistent with ours; moreover, we can hypothesise that, in case of injection failure due to septation, a US-guided injection targeting the EPB may be effective and allow us to avoid recourse to surgical intervention. It is therefore of clinical relevance to distinguish the two types of dQD by US before steroid injection as well as before surgery.
Competing interests None.
Patient consent Obtained.
Ethics approval Local ethics committee of the Sacro Cuore Hospital of Negrar approved the study protocol and all participants gave their written informed consent.
Provenance and peer review Not commissioned; externally peer reviewed.