Introduction

Recurrent peroneal tendon dislocation is an uncommon pathology [3, 15].

Traumatic causes have been implicated, mostly in sports which require cutting movements. Skiing accidents have been reported to cause peroneal tendon dislocation [15]. Detachment of the superior peroneal retinaculum usually occurs during the traumatic event and can produce a recurrent instability if not managed properly [14]. Acute operative management by either endoscopic [12] or open [13] repair are recommended. Non-traumatic causes due to a shallow retro-malleolar groove have been reported [10, 17]. Operative treatments in recurrent cases are divided into two major groups, depending on the aetiology and the anatomical predisposing factors. Soft tissue techniques consist of an open [1, 3, 11] superior retinaculum re-insertion, superior retinaculum retention [18] and superior retinaculum reattachment and reinforcement [8]. Endoscopic peroneal retinaculum reconstruction has also been described [6, 12]. Bony techniques consist of tendon rerouting techniques utilising the bony attachment [5], retro-malleolar groove impaction and fibular grooving [9].

Retromalleolar groove deepening has been considered a good option for treating recurrent peroneal tendon dislocation in adults due to a flat retromalleolar groove [20]. To our knowledge, this treatment has not been previously reported in children.

This report is the first report concerning the endoscopic treatment of a patient with an open distal fibular growth plate and recurrent peroneal tendon dislocation.

Case report

A 13-year-old male patient presented to the outpatient department complaining of right recurrent painful peroneal tendon instability. He had previously suffered a severe right ankle sprain while playing football (competition level) 18 months prior to the beginning of his symptoms. He was initially immobilised with a removable splint (duration of one month) with weight bearing followed by ankle mobilisation and rehabilitation. This specific rehabilitation was correctly done for 6 months.

The patient clearly described an audible, painful and recurrent tendon subluxation with eversion and dorsiflexion of the right ankle. Since his injury, the patient had stopped all sporting activities.

Detailed clinical examination showed normal mobility of the ankle with no medial or anterolateral pain. No signs of ankle instability were detected. Palpation of the retro-malleolar area elicited tenderness. The patient was able to voluntarily reproduce the tendon subluxation on demand.

Radiological analysis showed the absence of fractures and an open distal fibular growth plate (Fig. 1). The preoperative MRI showed normally situated tendons with no signs of a superior retinaculum injury.

Fig. 1
figure 1

AP and lateral radiographs of the patient confirming absence of fractures and persistence of growth plates

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The patient was operated upon after acquiring the signed consent of both parents.

A fibular tendon endoscopy was first performed through classic portals (Video 1). No tendon pathology was found. An intramuscular needle was introduced under direct visualisation and implanted into the inferior part of the growth plate while reclining the tendons posteriorly. The needle’s position was verified using intraoperative fluoroscopy. This allowed perfect visualisation of the fibular groove and detection of the growth plate simultaneously. With the aid of a motorised shaver and burr, the groove was deepened, making sure not to overshoot the needle superiorly.

Intra-operative testing after groove deepening revealed stable tendons with an intact superior retinaculum. The patient was immobilised in a below knee cast with no weight bearing for a period of 30 days.

At 3 months, the patient had normal ankle mobility with no recurrence of tendon instability. The 12-month radiographs showed persistence of the growth plate with no signs of epiphysiodesis. Post-operative MRI showed normally placed tendons in the created groove and a persistent inferior fibular growth plate at 12 months (Fig. 2). The patient was satisfied with the results and was able to return to the same level of activity prior to the injury. The AOFAS score improved from 72 points preoperatively to 100 points post-operatively (last clinical follow-up 24 months after surgery).

Fig. 2
figure 2

Twelve months post-operative MRI images showing the position of the fibular tendons in the neo groove and the intact distal fibular growth plate

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Discussion

The most important finding of this report was that an endoscopic stabilisation of peroneal tendons in a child with open physes gives good functional outcomes without growth plate disturbance.

Operative treatment of recurrent peroneal tendons instability is well-established, and a lot of techniques have been described [1, 3, 5, 7–9, 11, 12, 18]. Results of different techniques seem to be equivalent with a very high rate of success and return to sports after surgery [21]. Selmani et al. [16] and Kumai [9] reported excellent results after open fibular grooving in adults.

Recent publications concerning endoscopic groove deepening techniques have also proven their efficacy with an extremely favourable outcome [22]. No patient in their study had an active distal fibular growth plate.

There are a few studies available on the treatment of peroneal tendon dislocation in the paediatric population. All authors reported cases operated on by an open approach and a calcaneofibular transfer [2, 4]. Stenquist et al. thus concluded that there was a high risk of post-operative stiffness that could be a limitation of the above-mentioned procedure in children [19].

The particularity of this case is the presence of the active distal fibular growth plate and a flat groove. The endoscopic groove deepening procedure can be an option in treating paediatric patients.