Exploration of the clinical effect of modified peroneal nerve block in foot operation under the plane 2 of the ankle joint ： a non-randomized clinical feasibility observational study.

【 Abstract 】 Background This study was aimed at exploring the clinical effect of a modified dorsal peroneal nerve block in foot operation under the ankle plane. Methods The study was observational 35 study , thirty patients ( n =30) were observed with single-center and non-randomized. The patients were 36 treated with an ankle nerve block (including the posterior tibial nerve, superficial peroneal nerve, 37 saphenous nerve, and sural nerve block in the plane of the ankle) and a deep peroneal nerve block (7.5 38 mg/ml). The primary outcomes were intraoperative visual analogue scale score (0-10 points), numeric 39 rating scale score (0-10 points), and Neuropen score (0-2 points). The secondary outcomes were 40 postoperative pain VAS (visual analogue scale) and NRS(numeric rating scale scores) (0-10). Histograms 41 and normal probability QQ plots were used to test the distribution of normality. Results We analyzed 42 the data of 30 patients. It was found that after 20 min of ankle block and deep peroneal nerve block, 23 43 patients achieved a perfect block effect (VAS and Neuropen scores = 0), and the operation was 44 performed smoothly. Six patients experienced slight pain (VAS: ≤ 3, Neuropen score = 1). An 45 intravenous sedative drip (dexmedetomidine 4 µg/ml, 1 µg/kg dexmedetomidine hydrochloride 46 injection 2 ml:0.2 g; Jiangsu Nhwa Pharmaceutical Co., Ltd., China) was used. The block failed in one 47 patient, and the operation was performed under general anesthesia with a laryngeal mask in this 48 patient. Conclusions The modified deep peroneal nerve block combined with an ankle nerve block can 49 meet the anesthesia needs for foot surgery under the ankle plane. However, due to the limited number 50 of patients evaluated, it is difficult to accurately predict the effect and a large degree of uncertainty 51 exists regarding these findings. Trial registration This study had been registered


Introduction 57
The most common types of foot surgery under the plane are hallux valgus osteotomy, high arch 58 osteotomy, fixation for foot fracture, as well as surgery for common foot trauma. Foot and ankle nerve 59 blocks are effective ways of ensuring anesthesia and analgesia [1] . The distribution of the foot nerves is 60 not complicated. However, the nerves in the foot are often accompanied by blood vessels and the 61 sheath of each nerve and vessel, which could easily be damaged due to vascular compression injury. 62 The innervation of the foot under the plane of the foot and ankle includes the tibial, superficial 63 peroneal, saphenous, sural, and deep peroneal nerves. The block point of the tibial meridian in the foot 64 and ankle is located in the middle of the line between the Achilles tendon and the medial malleolus, 65 which is in the ankle canal, and the superficial peroneal nerve. The deep peroneal nerve and dorsalis 66 pedis artery coexist in a narrow space in the anterior part of the ankle [2] . 67 Foot operations can be performed by blocking the foot nerves through the ankle. The analgesic effect 68 after foot operation is similar to that achieved with the femoral nerve and sciatic nerve block, while 69 patient comfort is increased because a nerve block at the far end of the limb can make the movement 70 of the affected limb more convenient. Foot and ankle nerve blocks are not rare; however, they are often 71 associated with serious complications. An important clinical consideration is the narrow gap at the 72 block site, because of which it is easy to cause local nerve injury or even ischemic limb necrosis after 73 drug injection. This complication is more likely to occur when the deep peroneal nerve is blocked. Some 74 studies have shown that blocking the deep peroneal nerve in the front of the foot and ankle can cause 75 foot limb necrosis due to compression of the dorsal foot artery [3][4] . Therefore, the application of a foot 76 A cadaver study found that the deep peroneal nerve divides into internal and external terminal 78 branches at the foot and ankle, from the medial terminal to the far dorsum of the foot, and the internal 79 terminal branch is distributed on the dorsum skin opposite to the first and second toes [5][6] . Only this 80 branch is the sensory branch in foot operations under the plane of the foot and ankle. Therefore, we 81 attempted to block the medial terminal branch of the deep peroneal nerve at the dorsum of the foot, 82 which could also block the innervation of the deep peroneal nerve in the sensory area of the foot. 83 There are two reasons for choosing such a block method: (1) The requirement of muscle relaxation in 84 foot operation is low, and the block can meet the requirements of the operation, and (2) improved 85 deep peroneal nerve block could reduce the overall risk associated with an ankle nerve block. Ankle 86 nerve block for patients undergoing foot surgery afforded greater postoperative comfort. 87

Patients and design 89
This was a single-center, non-randomized clinical feasibility observational study in  Human Well Pharmaceutical Co., Ltd., China) and dezocine 5 mg (dezocine injection 1 ml:5 mg; Yangtze 127 River Jiangsu Nhwa Pharmaceutical Co., Ltd., China) through a vein 30 min before the operation. The 128 same type of operation was performed by the same group of orthopedic doctors. All operations were 129 routine; no modified procedures or complex procedures were used. During the operation, a tourniquet 130 was tied to the patient's ankle or not used. 131

Regional block and success assessment 132
We defined the end time of the drug injection as the beginning of the observation period. Before the 133 operation, we measured the pain score every 5 minutes to achieve the ideal analgesic effect (VAS = 0, success rate of 77%. Among the seven cases in which a complete block could not be achieved with 169 intravenous drugs, the operation was completed in six, while the procedure failed in the seventh case. 170 As for the onset time of anesthetic drugs, an NRS score of 0 appeared slightly later than VAS and 171 Neuropen scores of 0. We believe that this may be due to the discomfort caused by some deep 172 sensation, the small number of cases, and because the scores cannot distinguish between pain and 173 discomfort. Of course, the overall findings of this clinical observational study suggest that the improved 174 deep peroneal nerve block causes no major change in the whole foot and ankle block and shows 175 positive effects in reducing complications and promoting foot and ankle block. The average time of recovery was 22 hours after the operation. With postoperative oral medication, 177 patient discomfort was greatly relieved. More importantly, patients' leg movement after the operation 178 was normal, and they reported substantial relief from discomfort. 179

Discussion 180
To our knowledge, this is the first clinical observational study to evaluate the effect of deep peroneal 181 nerve block via the dorsalis pedis in foot surgery. We found that this block shows no significant 182 difference from the traditional anterior tibial block. Before designing this prospective clinical 183 observational study, we assessed a large amount of anatomical and clinical anesthesiologic data to 184 determine if this improved block could achieve the ideal anesthesia effect. However, due to the small 185 sample size, although this report presents positive results, there are many uncertain and negative 186 aspects to be considered, which should be the main topics for future research on this block. Some of 187 the debatable issues related to the results are outlined below. 188 First, some experts suggest that the anesthesia effect of deep peroneal nerve innervation can be solved 189 by skin infiltration anesthesia, which can not only reduce the risk of acupuncture but also make 190 anesthesia simpler. However, our literature review suggested that this is not feasible for the following 191 reasons: (1) skin infiltration anesthesia cannot guarantee an ideal anesthesia effect and anesthesia time, 192 while injection of the drug solution into the peripheral nerve can ensure an ideal anesthesia effect [7] . 193 Although an improved block is still a traumatic operation, it is essential to ensure the appropriate 194 anesthesia effect in patients. ② In the three types of regional evaluations, the dynamic pain score 195 reached the ideal value slightly later than the static score. The anatomical literature suggests that the 196 probability of variations in nerve branches is very high [5.6] , and the sensory nerves that may dominate 197 the region will also be distributed in the deep facial block, so the effect of a block at the nerve branches 198 is higher than that of skin infiltration. 199 The ankle regional block has minimal effects on lower limb movement and the patients' systemic 212 circulation and cardiovascular system [8]. It is suitable for daytime operations and short procedures for 213 both feet. The postoperative complications are fewer; safety is greatly improved; the duration of 214 hospitalization is reduced; and a lot of medical resources are saved [9] . This is especially applicable to 215 underdeveloped countries and regions with underdeveloped economies and limited medical resources, 216 since this technique can reduce the burden of patients and hospitals in such cases [10] . Improvements in 217 the deep peroneal nerve block, which has the highest risk of complications among ankle blocks, can 218 promote the application of ankle blocks in such operations. 219 The sensory branch of the deep peroneal nerve is located at the intersection of the proximal phalanx of 220 the second toe and the proximal phalanx of the third toe, where the deep peroneal nerve block does 221 not show an anesthetic effect, thereby reducing the risk of injury of the deep peroneal nerve-muscle 222 branch and the risk of vascular compression due to the passage of the artery to the sole. 223 In the current clinical observational study, we assessed only a small number of samples without a 224 control group or randomization, which limited the generalizability of the findings. We expect to improve 225 on these aspects in subsequent study designs. The main purpose of our clinical observational study was 226 to provide some information for the optimal design of a randomized controlled double-blind 227 experiment that could meet ethical and clinical requirements with the improved technique. Thus, the 228 application of this technique has great clinical significance. 229 For the six patients who required sedative drugs and the one patient for whom the technique was a 230 failure, we concluded that the 20-min period was insufficient. Thus, the starting time of the operation 231 should be adjusted to achieve the purpose of completing the operation only through the block. In the 232 follow-up clinical observational studies, we hope to assess the psychological and physiological factors of 233 the patients and adjust the type and measurement of preoperative medication to ensure the safety of 234

patients. 235
In summary, this improved technique can provide the same blocking effect as the original technique, 236 providing much supports for a follow-up study. However, there is no clinical data to support whether 237 the novel block can completely replace the original block. This report presents a mostly positive trend, 238 which is significant for our hypothesis of providing patients with an effective and safe new block point. 239

Conclusion 240
The modified deep peroneal nerve block combined with the ankle nerve block can meet the anesthesia 241 needs of foot surgery under the ankle plane. However, considering the limited number of observation 242 samples, its effect is not completely predictable, and the uncertainty ratio in the existing observation 243 patients is still large, necessitating further data to support these findings.