The effect of surgical decompression on symptoms in peroneal nerve entrapment neuropathy

Objective CPN entrapment neuropathy is a form of lower extremity entrapment, most commonly seen at the level of the bula head, often presenting with foot drop ndings. We aimed to investigate whether decompressive surgical intervention contributes to neuropathy clinic. Materials and methods Patients who were admitted to our clinic with a preliminary diagnosis of peroneal entrapment neuropathy and underwent surgical intervention were included in the study. Preoperative and postoperative motor functions and pain were evaluated. Results Postoperative signicant changes in pain and muscle strength scores were observed. A signicant decrease was observed in the postoperative VAS score. Conclusion Surgical decompression is the right option for the recovery of motor function in the treatment of peroneal nerve entrapment neuropathy.


Introduction
Common Peroneal Nerve (CPN) neuropathy is the most common entrapment neuropathy in the lower extremity and accounts for 15% of all peripheral entrapment neuropathies [1,2]. CPN trapping is most often at the level of the bula head. The nerve at the level of the bular head is super cial under the skin and is surrounded by facial bands. Because of this anatomic location, it is more susceptible to compression and injury [2]. It can be seen in all age groups but tends to be higher in adults and men [3] The most common etiologic factor is compression of CPN. Traumatic factors that causes entrapment are dislocation of the knee, serious ankle inversion injuries, lacerations and traumas directly on the nerve. The consequences of these traumas are poor [4,5]. Apart from mechanical compression, many other factors contribute to the formation of CPN neuropathy. The link between diabetes mellitus and lower extremity neuropathies is well known [6]. Iatrogenic injury is also a common cause. Acute foot drop, which is frequently seen during hip, knee and ankle surgery, develops due to neuropathy of CPN. Other causes of iatrogenic injury include position during anesthesia, prolonged bed rest, orthoses, tight wrapping per knee and bula, and the use of pneumatic compression devices [7][8][9]. Recently, studies have shown that CPN at the level of the bular head becomes more susceptible with the reduction of subcutaneous fat tissue due to excessive weight loss [10]. Lesions such as ganglion cysts and schwannomas cause compression of the CPN with a mass-occupying effect on the head of the bula. In addition, the habit of crossing legs and prolonged kneeling leads to an increased risk of peroneal palsy and acute miscarriage [11].
The most common symptoms of CPN neuropathy are weak ankle and toe dorsi exion, di culty in ambulation, loss of sensation in the dorsum of the forefoot and foot. The resulting low foot and gait problems can signi cantly affect an individual's quality of life. In 90% of cases, ndings are seen in only one extremity [1,2] The rst choice of treatment is the use of anti-in ammatory drugs. Patients are advised to avoid compression and activities that may aggravate the problem, such as crossing their legs. Physical therapy practices contribute to the healing process of symptoms. Surgical neuroplasty or decompression is needed if symptoms do not regress within 3 or 6 months and persistent or worsening motor de cits occur [3].
The aim of this study was to present the results of surgical intervention performed in patients with CPN entrapment neuropathy in the last 5 years.

Materials And Methods
Patients who were admitted to our clinic with a preliminary diagnosis of peroneal entrapment neuropathy and underwent surgical intervention were included in the study. Patients whose symptoms improved with medical treatment and patients with incisor-penetrating injuries did not undergo surgery and were excluded from the study. Electrophysiological study and lumbar MRI imaging were performed in all patients. All patients were given anti-in ammatory treatment and followed up for 3 months.
Motor functions before and after treatment were graded on a scale of 0-5 according to the British Medical Research Council (MRC) classi cation system. Pain was evaluated according to the visual analogue score (VAS). Surgical intervention was performed in patients who did not improve according to MRC and VAS scores or whose symptoms were increased.

Surgical procedure
Surgical intervention was performed under general or spinal anesthesia. A curved skin incision was made distally from the bular neck, starting proximal to the biceps femoris tendon. With the help of automatic retractors, subcutaneous fat and fascia were passed through vertically and CPN was found just below. The nerve was freed as much as possible from tight facial bands and perineural adhesions that wrapped around it with ne-tipped scissors. The procedure was continued distally up to the level of bifurcation of the super cial and deep peroneal nerve branches. This decompression was completed along the medial direction of the upper biceps femoris tendon of the popliteal fossa of CPN and down to the point where the peroneus longus muscle of the CPN and the peroneal tunnel entered. The patients were followed-up at the outpatient clinic for an average of 3 years.

Statistical evaluation
Postoperative MRC and VAS scores were evaluated. The paired t-test was used to evaluate changes in VAS and MRC scores. All statistical analyses were performed using the SPSS statistical software, version 17.0 (SPSS Inc., Chicago, IL, USA).

Results
The age range of 20 patients who were diagnosed as peroneal nerve for the last ve years and admitted for decompression surgery was 17-76 (mean 50) and consisted of 8 female and 12 male patients. All patients underwent conservative medical treatment and FTR treatment prior to surgery. 14 patients had symptomatic complaints on the right and 6 patients on the left. In EMG, CPN was trapped at bula level in all patients. Blunt trauma was detected in 9 patients and no trauma was observed in 11 patients. CPN entrapment neuropathy was associated with diabetic neuropathy in 5 patients ( Table 1). The mean preoperative VAS score was 9.4, while a signi cant decrease was observed in the postoperative period (VAS = 4.3, p < 0.05). The same results were similar in muscle strength scoring. The mean preoperative MRC was 3.4 and postoperative 4.6 (p < 0.05, Fig. 2).

Discussion
CPN entrapment neuropathy is a form of lower extremity entrapment, most commonly seen at the level of the bula head, often presenting with low foot clinical ndings. CPN is a terminal branch of L4-S2 spinal nerves separated from the sciatic nerve [12]. After separating from the popliteal fossa, it enters the brotendinous bular tunnel at the level of the peroneus longus muscle and bular head. Because the site of nerve is super cial and surrounded by facial brous bands, this region is more sensitive to compression and trauma and is vulnerable to trauma. These facial bands extending from the gastrocnemius and soleus muscles surround the CPN in the lateral region of the bula head and neck. Especially when the knee is bent, it can compress the nerve [2,3,13].
Apart from iatrogenic causes in the etiology, pressure effects of mass, penetrating or compressive injuries, positional pressure causes, excessive weight loss can be recognized. The presence of diabetic neuropathy contributes to the formation of the clinic.
The most important method in diagnosis is electromyography (EMG). EMG can detect whether there is a signi cant decrease in conduction block, amplitude or a signi cant slowdown in conduction velocity throughout the bular head. The presence of active or chronic denervation in the muscles innervated by CPN makes the diagnosis [3]. Therefore, EMG is the guiding factor in surgical decision making. Some researchers argue that surgical intervention is unnecessary and that treatment with steroid injection and conservative approach is su cient. It is recommended to wait at least 6 months after the onset of clinical symptoms [2]. However, according Dallari et al., they recommended early surgery immediately after the diagnosis, regardless of the cause [14]. In a similar study, Ismael et al. Changed and reported that functional recovery increased when the decision was made early [15].
In our study, CPN was decompressed by surgical intervention in patients whose foot muscle strength did not improve or worsened after conservative treatment. Postoperative increase in motor strength and decrease pain were observed.

Conclusion
In conclusion, surgical decompression is the right option for the recovery of motor power in the treatment of peroneal nerve entrapment neuropathy.

Declarations
Ethical Publication Statement: We con rm that we have read the Journal's position on issues involved in ethical publication and a rm that this report is consistent with those guidelines. The study was approved by Institutional Review Board, Eskişehir Osmangazi University Ethical Committee (25403353-050.99-E.76044) Consent for publication: The patients were given detailed information on the procedure and informed written consent was obtained from all of them.
Availability of data and materials: Data sharing not applicable to this article as no datasets were generated or analysed during the current study. Figure 1 The nerve was freed as much as possible from tight facial bands and perineural adhesions that wrapped around it with ne-tipped scissors.