Endoscopic Treatment of Intrasheath Peroneal Tendon Subluxation

Intrasheath subluxation of the peroneal tendons within the peroneal groove is an uncommon problem. Open exploration combined with a peroneal groove-deepening procedure and retinacular reefing is the recommended treatment. This extensive lateral approach needs incision of the intact superior peroneal retinaculum and repair afterwards. We treated three patients with a painful intrasheath subluxation using an endoscopic approach. During this tendoscopy both tendons were inspected. The distal muscle fibers of the peroneus brevis tendon were resected in two patients. A partial tear was debrided in the third patient. All patients had a good result. No wound-healing problems or other complications occurred. Early return to work and sports was possible. An endoscopic approach was successful in treatment of an intrasheath subluxation of the peroneal tendons.


Introduction
Peroneal tendon dislocation is a well-known entity in literature [1]. e peroneal tendons dislocate over the lateral malleolus and cause posterolateral ankle pain and a snapping sensation. On the other hand, only a few publications exist about intrasheath peroneal subluxation, as pathology is uncommon [2,3]. Patients with an intrasheath subluxation present with the common subjective feelings of popping, snapping, or clicking associated with pain. ey do not demonstrate objective clinical evidence of subluxation over the lateral malleolus. Static and dynamic ultrasound has been shown valuable in diagnosis of this pathology [4]. It demonstrates the both peroneal tendons switching their relative positions. In the few publications intrasheath subluxation is associated with a low-lying peroneal muscle belly, a peroneus quartus muscle and tendon, a tear of 1 or both of the peroneal tendons. In all described cases the superior peroneal retinaculum was intact [2,3].
Most patients with peroneal tendon lesions can be treated conservatively with activity modi�cation, NSAIDs, physical therapy, footwear changes, temporary immobilization, and corticosteroid injections [5]. Operative treatment is usually reserved for patients who have failed 3 to 6 months of conservative management [6].
Surgical treatment usually uses an extensive lateral exposure to facilitate adequate visualisation, diagnosis, and treatment [7,8]. is approach needs incision of the superior peroneal retinaculum and repair aerwards. e problems associated with long open exposures are scar formation, adhesions, and entrapment of the sural nerve [8]. Oen prolonged immobilisation is needed.
In this paper, we describe an endoscopic approach in patients with intrasheath subluxation of the peroneal tendons. e hypertrophied muscle belly was resected in two patients. A partial tear of the peroneus brevis tendon was debrided in the third patient. In all patients the outcome was successful.

Case 1.
A 23-year-old man had 2 years persisting pain in the right ankle despite conservative treatment consisting of activity modi�cation, insoles, nonsteroidal anti-in�ammatory medication, physical therapy, and cortisone injections. e patient was not aware of an important ankle injury. But he played soccer at regional level and had some minor ankle sprains in the years before.
Clinical examination showed localized tenderness behind the lateral malleolus. Contraction of the peroneal tendons cause a snapping movement. is snapping movement causes a reproducible painful audible click (Movie 1; see Supplementary Material available online at http://dx.doi.org/10.1155/2013/274685). e tendons were found to switch their relative positions at the level just posterior to the tip of the lateral malleolus. is was visual during clinical examination.
Dynamic ultrasonography demonstrated a switching of the both peroneal tendons. No tendon lesions were found. No dislocation out of the retromalleolar groove occurred. MRI revealed no lesions. We decided to treat this patient surgically and a tendoscopy was planned.

Case 2.
e second patient is a 26-year-old man with complaints of retromalleolar pain during more than 6 months. He also plays soccer and has a very similar history. e diagnosis was con�rmed by ultrasonography. No tendon lesions were found.

Case 3.
e third patient is a 38-year-old man with complaints of retromalleolar pain since one year started aer an ankle sprain. He is a long-distance runner, but unable to sport owing to his complaints. �ltrasonography con�rmed the diagnosis of an intrasheath subluxation. MRI revealed a partial rupture of the peroneus brevis tendon.

Surgical
Technique. e operation was performed under regional anaesthesia. e patient was placed in lateral decubitus. A tourniquet was applied.
Two portals were performed ( Figure 1). e proximal portal is made �rst. An incision is made 2.5 cm above the tip of the lateral malleolus. e tendon sheath is incised and a blunt trocar is introduced. e cannula is aimed distally along the course of the tendons. We use a 4 mm arthroscope with an inclination of 30 ∘ . Aer �lling the tendon sheath with a saline solution, the second portal is performed by use of transillumination. e distal portal is situated 2.0 cm distal to the �bula tip. A blunt probe was introduced. e full length of both tendons was probed. In the �rst two patients no tendon ruptures were found. e retinaculum was intact. No abnormalities of the peroneal groove were found. e most remarkable �nding was the very distal location of muscle �bers around the peroneus brevis tendon (Figure 2). With a shaver the distal muscle �bers were resected over a length of 2 cm (Figure 3). We used the two portals interchangeably for both the arthroscope and the resector. In the third patient a partial tear of the peroneus brevis tendon was found. e tear was debrided with the shaver.

Postoperative Management.
Postoperative course was uneventful. Immediate mobilisation and total weight bearing was allowed. Physiotherapy was started with active and passive full range of motion exercises aer 5 days. e �rst patient returned to sports (cycling and soccer) 2 months  following surgery. e second patient returned to work aer two weeks, running aer 6 weeks and soccer aer 10 weeks. e third patient started running aer 8 weeks. Two months postoperatively all patients were pain free and no snapping sensation reoccurred. Aer 2 years of follow-up the patients still had a normal function and no complaints.
3. Discussion e present study demonstrates the possible endoscopic treatment for intrasheath subluxation of the peroneal tendons.
e initial treatment of peroneal tendon disorders is conservatively. is nonsurgical treatment includes activity modi�cation, physiotherapy, footwear changes, temporary immobilisation, and corticosteroid injections.
e open surgical treatment uses extensive exposure to facilitate visualisation. is is associated with scar formation and sural nerve entrapment [8]. Recently, several authors reported good to better results with an endoscopic technique. Van Dijk and Kort reported in 1998 an endoscopic approach for the diagnosis and treatment of peroneal tendon pathology [9]. Peroneal tendoscopy has been used for several indications. As a diagnosing tool it allows an extended evaluation of the tendons in a rather minimally invasive approach. It also allows to treat several disorders: adhesiolysis, synovectomy, resection of a �bular or calcaneal exostosis, debridement or suturing of partial tendon rupture, groove deepening. Lui described an endoscopic reconstruction of the peroneal retinaculum [10]. Tendoscopy has demonstrated several advantages, such as less pain, outpatient treatment, functional aer-treatment, and rapid resumption of work and sport activities.
Dislocation of the peroneal tendons out of the peroneal groove is well known in literature. Only a few publications exist about intrasheath subluxations. Raikin et al. described intrasheath subluxation of the peroneal tendons in 14 patients [2]. In thirteen patients a convex peroneal groove was found. Four patients involved a longitudinal split within the peroneus brevis tendon. Patients were treated with an open peroneal groove-deepening procedure with retinacular ree�ng and a surgical repair if needed. ey reported good to excellent results. In our patients no groove deepening procedure was performed. According to the suggestions of Ferran and Maffulli, we do not see a convex peroneal groove as a pathologic �nding [11]. e retro�bular cartilage is not formed by the concavity of the �bula, but by a relatively pronounced ridge of �brocartilage [12]. Anatomical studies demonstrate an the incidence of a �at or convex sulcus ranging from 18 to 30% in normal cadaveric specimens [11].
omas et al. report 7 patients with intrasheath subluxation [3]. Six of the seven patients had either a low-lying peroneal muscle belly or a peroneus quartus muscle and tendon, 6 experienced a tear of either 1 or both peroneal tendons, and 1 of the 7 had only a peroneus brevis tendon tear without any other muscle anomaly.
In our �rst two cases no rupture was found. Neither was there any history of an important ankle injury. e tendon snapping was probably caused by the very distal located muscle �bers. A good result aer resection of these �bers con�rms this hypothesis. According to omas et al., the low lying peroneus muscle belly causes an increased internal cubic content of the �bro-osseous tunnel [3]. ese increasing compressive forces contribute to the intrasheath subluxation. e same is true in case of an accessory peroneus muscle, a tendon tear or a convex �bular groove.
Although the number of patients in our study is low, the results are very promising. If surgery is indicated, we recommend an endoscopic approach in all patients without major tear or obvious dislocation. Dislocation of the peroneal tendons over the lateral malleolus is considered as a relative contraindication. Possible complications are prolonged in�ammation, damage to the sural nerve, and thickening and scarring. ese complications are more likely in an open procedure. Experience in endoscopic surgery is mandatory. Endoscopy of the peroneal tendons is a technically demanding procedure and requires the skill of an experienced arthroscopist. Concomitant lesions of the lateral ligaments should be excluded or treated.
e endoscopic procedure allows an extended investigation of the tendon in a minimally invasive approach. is approach avoids opening and suturing of the intact superior retinaculum. If no tear is found, we recommend a debridement of the distal muscle �bers. A small tear can be debrided endoscopically. In case of an unexpected major tendon tear, conversion to an open procedure is easy and always possible. As the tear is endoscopically located, the length of the incision for the open approach can be minimized.
In conclusion, tendoscopy of the peroneal tendons is a useful tool to investigate and treat peroneal tendon disorders. Endoscopic resection of the distal muscle �bers or debridement of a partial tear was successful in treatment of a persisting snapping of the peroneal tendons.