Introduction

“Trigger wrist” is a general term previously referred to any triggering or clicking phenomenon around the wrist joint, which can be produced by finger motion, wrist motion, or rotation of the forearm [1]. However, many authors suggest that “trigger wrist” should be accurately used only when the triggering occurs particularly in relation to movements of the wrist joint [2–5]. To clearly differentiate from the other conditions, current literature recommends the term “true trigger wrist” for this clinical entity [2–6].

True trigger wrist caused by the extensor tendon pathology is rare. There are three cases formerly reported in literature, but none were associated with the acute partial tendon rupture [2–4].

We report a case of acute true trigger wrist following the partial rupture of the extensor carpi radialis brevis (ECRB). The clinical presentation, intraoperative findings, and the triggering mechanism of the patient are described.

Case report

A 27-year-old, right-handed, male army private sustained a right wrist injury due to a slip while climbing up the rope ladder during military training. The dorsal wrist pain occurred suddenly when he used his right hand to hang on a ladder rung. He denied previous symptoms of wrist pain and his past medical history of any illnesses or other injuries. Because of the constant pain, he saw the general practitioner a couple of days later. X-ray films of the hand and wrist demonstrated normal findings. He was prescribed oral nonsteriodal anti-inflammatory pills. After having taken the medication for 3 days, the pain was still persistent and he started to notice the triggering whenever he flexed and extended the wrist. Therefore, the patient was referred to our department.

At our examination 1 week after the injury, he had tenderness and mild swelling on the dorsal radial aspect of the distal radius. The patient had full passive and active range of the wrist motion. However, there was a painful, visible, and localized triggering over the area just distal to the Lister’s tubercle on every attempted active extension and flexion while the wrist passed neutral position. The triggering was more obvious when the patient maintained his thumb in full abduction and extension actively. Repeated radiographs were normal. The patient was treated conservatively with the oral nonsteriodal anti-inflammatory medication and immobilization in a short arm cast for 4 weeks. The triggering returned immediately and became more pertinent after the cast removal. As the patient had the difficulty using his right hand for any activities due to the painful triggering, he decided to have the operative treatment to be done. The preoperative ultrasound examination detected the presence of extensor pollicis longus (EPL) tendon snapping originating from the area just distal to the Lister’s tubercle. However, we could not demonstrate the accurate mechanism and pathology because the triggering occurred rapidly and the ultrasound image was easily out of focus when performed in dynamic fashion.

Surgery was performed 6 weeks after the original injury under a local anesthesia with a tourniquet on the upper arm. The dorsal curved incision was done over the course of the EPL tendon, and an extensor retinaculum was exposed. When the patient flexed and extended the wrist, we observed the triggering in the third extensor compartment. The EPL tendon was exposed and pulled away to visualize the adjacent structures. There was some inflamed synovium around the tendons in the second and third compartments. Following the removal of the synovium, the extensor carpi radialis longus, extensor digitorum communis, and EPL tendons appeared normal, but a partial rupture in the dorsal portion of the ECRB with 30% involvement of tendon substance was apparent. The torn tendon fibers were peeled away distally, bunching and forming a 6-mm nodule adjacent to the EPL tendon (Fig. 1). The nodule slipped under the EPL radialward and proximalward with wrist dorsi flexion (Fig. 2) and ulnarward and distalward with wrist volar flexion (Fig. 3). We also noticed a significantly thickened distal edge of the second compartment retinaculum. With active wrist dorsi flexion, a direct impingement of the torn tendon against this thickened edge was evident. We released the impinged retinaculum, removed the ECRB nodule, and trimmed down the fraying tendon edge. The torn part of ECRB tendon was repaired with epitendinous suture using 5-0 nylon to create the smooth tendon surface. Normal gliding of the EPL and ECRB tendons was consequently obtained. The retinaculum of the third extensor compartment was repaired over the EPL tendon. The intraoperative active wrist motion was reassessed showing no triggering or catching. The skin was closed, and dressing was applied. Three months after the operation, he was able to return to full duty and had full active range of wrist motion with no triggering.

Fig. 1
figure 1

The partial tear of the ECRB tendon was revealed just distal to the thickened distal edge of extensor retinaculum (black arrowhead). The torn tendon fibers were peeled away distally, bunching, and forming a nodule (white arrowhead). The EPL was slung with the white vessel loop and pulled distally and ulnarly

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Fig. 2
figure 2

The nodule was slipped under the EPL radialward and proximalward with wrist dorsi flexion

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Fig. 3
figure 3

The nodule was slipped ulnarward and distalward with wrist volar flexion. The black arrowhead indicates the ECRB nodule. The EPL was slung with the white vessel loop

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Discussion

True trigger wrist was firstly described by Lemon and Engber in 1985 referring to the triggering induced by wrist motion [2]. The previous reported true trigger wrists were produced by the abnormality in either tendon [2–5], ligament [7–9] or carpal bone [10–12]. True trigger wrist originated from the injury of extensor tendon is rare with only two prior case reports [2, 3]. In both patients, the nodules of the extensor tendons were apparently located just distal to the extensor retinaculum. One patient had the history of repetitive trauma from playing tennis, whereas the other sustained an injury from landing on the outstretched hand. For the former, the multiple nodules of EPL and wrist extensor tendons were assumed to be a result of repetitive microtrauma [3]. For the latter, a nodule with mucoid and hemorrhagic degeneration of ECRB was revealed; however, the etiology was not mentioned [2]. In our report, the patient also had only single episode of acute injury. Triggering was presented within a week after the injury, which is relatively shorter than other reports. As the surgical exploration was performed early, the partial rupture of ECRB tendon which was forming a nodule was clearly noticeable. Triggering following the partial tendon injury is well recognized in flexor tendon [13, 14]. The established hypotheses in this occurrence were a bulky bulbous scar at the area of laceration [15], or the folding of the cut fibers on themselves contributed to the nodule formation [16]. Al-Qattan et al. [17] proposed that triggering was likely caused by torn tendon fiber bunching rather than the scar formation if occurring shortly in three to 5 days after the injury.

A diagnosis of extensor retinaculum impingement owing to the extensor tendons impinging on a distal retinacular border was recently described by VanHeest et al. [18]. This condition was seen in athletes who bore full body weight on the wrist frequently in a position of hyperextension including gymnastics, platform diving, and shot put. The distinct and thickened appearance of distal retinacular border was believed to be the predisposing factor. The tendon tear in our patient seems to happen with the same mechanism, but in an acute fashion because the patient has no history of the overuse or other trauma. Intraoperatively, we noticed that the torn area of tendon was bumped up against the thickened distal edge of retinaculum, while the patient actively extended the wrist. Surgical release or resection of the distal retinacular border should be considered when there is evident extensor retinaculum impingement [18]. Based on a biomechanical study, there will be no increase in bowstringing of the extensor tendons if less than one centimeter of retinaculum is released [19].

Preoperative evaluation with MRI may be useful to detect the lesion of the tendon and rule out other pathology but cannot demonstrate the mechanism of triggering in real time. The ultrasound was reportedly useful in establishing the presurgical diagnosis of trigger finger following the partial tendon laceration [14]. However, for the trigger wrist assessment, as the study was performed in dynamic fashion, we had some technical problems while trying to focus on the extensor tendons, which are located in the uneven area.

The conservative treatment with cortisone injection, medication, or splint appeared to be ineffective in curing true trigger wrist with extensor tendon nodule [2, 3]. Regarding two previous reports of true trigger wrist, the authors explained that triggering occurred because the nodule of wrist extensor tendon was rubbing against the extensor retinaculum. Differently, we found that the triggering was produced by the snapping of nodule with the EPL, which courses obliquely over the ECRB. In our opinion, the surgical exploration should be done under local anesthesia, while the patient is awake in order to find the source of triggering accurately and assess the effectiveness of procedure intraoperatively.