This is a case study of a patient with a wrist effusion and 'out of plane' guided radiocarpal joint injection. The patient was a jeweller in their 30's with a six month history of left wrist pain. The pain was felt more towards the radial side of the wrist and there was pain predominantly during gripping activities. Her work entailed gripping objects for extended periods of time and was therefore problematic. If she ignored the pain and continued working she then could experience some pins and needles in the fingers in the median nerve distribution reminiscent of Carpal Tunnel Syndrome (CTS).
Other activities that could bring on pain were push ups on the floor and certain Yoga poses. She did not however have classic CTS symptoms and never had pain at night nor did she experience sensory changes in the hand when resting.
On examination, there was no visible effusion. There was no significant limitation of range of movement , although her pain could be reproduced with resisting palmar flexion.
On ultrasound, there was a distinct hypo-echogenic layer between the carpal tunnel contents (Figure 1) and the bony floor of the carpal tunnel. Careful ultrasound evaluation on dynamic flexion showed some fluid fluctuation ( see video clip at the start of this article) indicating that this was a small effusion and was not representative of teno-synovitis of the flexor tendons. Please also see comparison with the non- symptomatic side (Figure 2)
This condition had been persistent for many months and had not responded to good quality physiotherapy consisting of exercises and advice. I therefore suggested a local steroid injection of the radiocarpal joint. In order to directly target the area affected a deep injection was required, with the steroid deposited directly in the radiocarpal joint beyond the contents of the carpal tunnel.
Avoiding penetration of the flexor tendons will reduce discomfort of this procedure. Due to the fairly close proximity of various neurovascular structures such as median nerve, ulnar nerve and radial and ulnar artery, I opted for an out of plane technique. (Figure 3) This technique is very useful in areas where the location of the structures to be observed is known in relation to the ultrasound image. In order to orientate the key structures please see ( Figure 4). The longitudinal in plane approach would make it difficult to navigate around tendons and also if accidentally the needle moves oblique to the ultrasound probe (i.e you lose the needle tip) there is a risk of penetrating an adjacent neurovascular structure.
As Ultrasound is real time, additional assurance of correct positioning of the needle is obtained by pressing the needle cap in the target area (in this case between (FPL and FCR). Clear tissue movement can be seen very focally between the two above structures indicating accurate positioning. This is followed by a distinct hyper-echogenic focus in the target area which is where the needle crosses the ultrasound beam (Figure 5). This is evidence of accurate needle placement and Figure 6 shows the steroid being discharged in this area.
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