A complicated course of extensor carpi ulnaris tendon luxation

Background: Psychological disorders may have influence on functional outcome after wrist and hand surgery, and this condition should not be underestimated. Aims: The aim of this article is to describe one exemplary case in which an interim poor functional outcome was not based on surgical failure. Methods: A 40-year-old woman presented with left non-traumatic extensor carpi ulnaris tendon luxation primarily treated by surgical repair of the fibro-osseous tunnel utilizing the extensor retinaculum. The early functional outcome regarding supination of her forearm was poor that required revision surgery, however, a surgical failure could be excluded. Therefore, a psychological disorder had to be suggested. Results and conclusion: In order to manage this critical situation, a meeting was held involving the surgeon, the patient, and the physical and occupational therapists. The specific Feldenkrais method for rehabilitation was applied that resulted at the end in an excellent functional outcome. However, before suggesting a psychological disorder as possible cause for poor functional outcome, a surgical failure should be excluded in every instance with revision surgery (i.e. „second look“). *Correspondence to: Ingo Schmidt, Medical Centre Wutha-Farnroda (Department of Orthopaedics and Hand Surgery), Ringstr. 20, 99848 WuthaFarnroda; Hospital Bad Salzungen GmbH (Department of Traumatology and Orthopaedics, Teaching Hospital of the Friedrich-Schiller-University Jena, Germany), Lindigallee 3, 36433 Bad Salzungen, Germany, E-mail: schmidtingo62@googlemail.com


Introduction
The extensor carpi ulnaris tendon originates from the lateral epicondyle of the humerus and the dorsal surface of the ulna, passes through the groove dorsally at the ulnar head within a fibro-osseous tunnel of extensor retinaculum (6th compartment) ( Figure 1A), having an own tendon subsheath for its stabilization there, and inserts on the base of the 5th metacarpal medially angled to its position in the groove of ulnar head.
ECU tendon luxation out off its groove is uncommon and can be caused either by an injury or by chronic tendinopathy / tenosynovitis subsequently leading to insufficiency or disruption of its tendon subsheath accompanied by elongation of the extensor retinaculum. Surgical treatment is detected when conservative treatment (splinting) has been failed, however, all surgical procedures are not free of any complications. We present one complicated course after surgical treatment that was not based on surgical failure but on a specific condition of chronic regional pain syndrome (CRPS) type I.

Case presentation
A 40-year-old skinny woman (height: 1,75 m, body weight: 64 kg) reported painful snapping at her left ulnar head when turning the forearm for many years. A real injury was not remembered in the past, but generally she has hypermobile joints. At clinical examination, a luxation of the ECU tendon ulnar-and palmarwards out over the ulnar rim of its groove could be provoked when turning her forearm from pronation to supination ( Figure 1B, Preoperative video of the patientsupplementary material). Surgical revision was detected by us.
Dorsal surgical incision was done typically at the left ulnar head and distal ulna. After incision of the marked elongated extensor retinaculum (6th dorsal compartment) we could no longer see a sufficient ECU tendon subsheath, and the luxation of the ECU tendon in ulnar and palmar direction could be confirmed when turning the forearm from pronation to supination (Figure 2A). The 6th compartment was reconstructed with gathering of the extensor retinaculum which was fixated both at the ulnar and radial rim of the groove utilizing two titanium microanchors. After that, the ECU tendon was sufficiently stabilized again in its groove ( Figure 2B). Primary wound closure was done, and the overall left arm was immobilized in a plaster splint (suggesting for five weeks). Wound healing was uneventful.
Three weeks after surgery, supination of the left forearm was completely painful restricted. Hence, the plaster splint was completely removed and physical therapy was started. However, three months after surgery there was unchanged a marked painful restriction of supination, and the patient tried to compensate her loss of supination by adduction and external rotation of the arm in her shoulder joint ( Figure 2C). Hence, revision surgery was detected by us. Noted that The ECU tendon (blue pointed line) luxates ulnar-and palmarwards out over the ulnar rim of its groove (yellow stars) when turning the patient's forearm from pronation to supination (provide also the patient's video in supplementary material). Note that the ECU tendon course is medially angled to its insertion on the base of the 5th metacarpal when the forearm is held in pronation (i.e. relaxed course), whereas in supination the ECU tendon is maximally tensioned as predisposing factor for its luxation

Figure 2. (A)
Intraoperatively, the ECU tendon luxation out over the ulnar rim of its groove could be confirmed when turning the forearm from pronation to supination. (B) Intra-and postoperatively, the ECU tendon could be sufficiently stabilized in its groove utilizing the extensor retinaculum. Note the correctly intraosseous placed two microanchors at the ulnar head. (C) Three months postoperatively, there was a marked restriction of supination, and the patient tried to compensate the loss of function with adduction and external rotation in her shoulder joint (yellow arrow) there was no local swelling and hyperthermia, and the patient reported "anxiety that she might lose her day time job".
Revision surgery was performed in subaxillar plexus anaesthesia. Before surgical incision a closed mobilization was done, after that, a nearly complete restoration of forearm supination could be achieved ( Figure 3A). Surgical incision was performed via the pre-existing approach. We saw a sufficient formerly reconstructed 6th compartment in the absence of any (sub)luxation tendencies of the ECU tendon, and the ECU tendon showed an excellent gliding through its fibro-osseous tunnel with a complete restoration of pronation and supination (Figure 3 B-C).
However, three weeks after revision surgery, supination was completely restricted again associated with pronounced muscle tightness at the forearm ( Figure 4A), and the patient subjectively reported: "my left arm is no longer a piece of me". Therefore, a meeting was held involving the surgeon, the patient, and the physical and occupational therapists indicating the specific Feldenkrais method. Six months after initial surgery (i.e. three months after revision surgery) the patient was very satisfied with her outcome associated with complete restoration of pronation and supination ( Figure 4B). The patient could be completely re-employed in her original occupation as a manual worker in manufacturing orthotic devices.

Discussion
ECU tendon luxation, mainly observed out over the ulnar rim of its groove in ulnar and palmar direction, is a rare condition and can often be overlooked or misdiagnosed. The rationale behind this condition is that ECU tendon angles medially at the wrist before inserting on the base of the 5th metacarpal. The angle formed becomes more acute with the forearm in supination and the wrist in ulnar deviation. In this position, the ECU tendon is maximally tensioned and is inclined to (sub)luxate if the subsheath that contains it is incompetent, whereas in Trauma Emerg Care, 2020 doi: 10.15761/TEC.1000191 pronation the ECU tendon adopts a relaxed course to its insertion and causes minimal force on the subsheath ( Figure 1B) [1][2][3][4][5]. Therefore, clinical examination should be done in every instance under dynamic conditions ( Figure 1B, Preoperative video of the patient -supplementary material). ECU tendon luxation can be diagnosed as well utilizing the so-called "ice cream scoop test" in which the patient moves the wrist from pronation-ulnar deviation to flexion-ulnar deviation and finally to flexion-supination against resistance and direct palpation of the tendon by the examiner [6]. ECU tendon (sub)luxation are classified into three subtypes: (A) the fibro-osseous sheath is disrupted at its ulnar side and the tendon may lie beneath the fibro-osseous sheath, (B) the sheath is disrupted from its radial wall and the tendon may overlie it and prevent healing, and (C) the tendon dislocates into a false pouch formed by stripping of the periosteum from the ulna [7,8].
Traumatic ECU tendon luxation, either by direct trauma or by acute / repetitive rotational wrist injuries, is mainly observed in professional athletes such as in water-polo players, tennis players, and golfers at the dominant side [2,[8][9][10][11]. Predisposing factors for non-traumatic ECU (sub)luxation could be congenital flattening of the groove at the ulnar head and/or congenital or required impaired mechanical properties of the tendon subsheath due to chronic overload for example in pre-existing hypermobile joints (i.e. hyperlaxity) which is similar in peroneal tendon luxation (Figures 5 A-B) [2,12]. Surgical reconstruction includes various options: a direct repair is possible in acute lesions when the tendon subsheath is disrupted at the radial rim whereas the use of the extensor retinaculum (slings, strips, pedicled or free flaps) is recommended in cases of an ulnar disruption [7,9,[13][14][15], and deepening of the groove which is similar as well for surgical treatment of peroneal tendon (sub)luxation (Figures 6 A-D) [2,12,14,16,17]. However, deepening of the groove at the ulnar head remains controversial, it can be followed by recurrent subluxation or rim fractures [18,19]. Another approach for surgical treatment of chronic tendinopathy with or without subluxation is lengthening of the ECU tendon in order to reduce the forces on the subsheath while supination [1]. Postoperative care should include generally physical and/or occupational therapy in order to achieve satisfactory functional outcomes [20,21].    However, surgical reconstruction of the fibro-osseous tunnel utilizing the extensor retinaculum is not free of any problems. Longterm outcomes revealed that approximately one third of patients developed complications such as injuries of the sensory branches of the dorsal ulnar nerve, and stiffness or stenosing ECU tendinitis when the repair of the fibro-osseus tunnel was too tight [13]. With our patient, the latter could be ruled out as part of our revision surgery. Therefore, the pronounced muscle tightness resulting in complete restriction of forearm's supination had to be suggested as a specific condition of CRPS type I.
Poor outcome or development of CRPS type I based on psychological factors (anxiety, depression, or catastrophic thinking) with female predominance after wrist and hand surgery in the absence of surgical failures is a concern and unpredictable [22][23][24][25][26][27][28][29][30][31][32]. With our patient, psychological factors were probably the main causes of the interim poor functional outcome ("anxiety that she might lose her day time job", "my left arm is no longer a piece of me"). Therefore, the initiated meeting involving the surgeon, the patient, and the physical and occupational therapists was absolutely mandatory to manage this critical situation.
The Feldenkrais method, detected by us, is named after its founder the Israeli physicist, engineer, and self defense technique teacher (judo, jiu jitsu, krav maga) with interest in alternative medicine and neuropsychology Dr. Moshe Feldenkrais , and is described as a method of motion-related somatic learning ("learning how to learn") [33,34]. This method is widely applied in medical, athletic, pedagogic, and artistic fields [35]. It is based on the fact that we interact with the brain through movement and stimulate it to form new patterns. We use movement in the Feldenkrais method, but unlike many other methods, we do not use it with the intention of stretching or training muscles, but to bring about changes in the brain. There is a natural urge for the brain to develop and to interact with the environment more precisely, effectively and appropriately. This natural process is increasingly known today under the term neuroplasticity: the ability of the brain to make new connections at any time -its real task for a lifetime. Some case reports revealed clinical improvements in muscle stiffness, recovery of hand function, and playing instruments [36].

Conclusion
We present one complicated course after surgical repair of an ECU tendon luxation that was not based on a surgical failure. For those conditions, psychological disorders should be born in mind which can be managed with an interdisciplinary approach.

Funding
None.

Conflicts of interest
The authors declare no conflict of interest, financial or otherwise.