The calcaneus, as one of tarsal bones, is a part of the hind foot. Though calcaneus fracture is rare, it occupies most of the tarsal fractures. Successful surgical treatment and reduction of postoperative pain and complications are undoubtedly important factors for ERAS. Proximal thigh tourniquets are currently used during most of the alcaneal fracture surgery to ensure a clear vision surgery and increase surgical comfort. Simultaneously, the incidence of small vessel and nerve damage such as the small saphenous vein and the sural nerve are dramatically decreased. However, related complications impede postoperative rehabilitation such as aggravated postoperative pain, incidence of DVT, and the soft tissue injury.
4.1 Unique characters of Low position tourniquet
The placement of low tourniquets is generally 10cm above the ankle, where tourniquet inflation pressure is significantly reduced due to little soft-tissue and the blood superficial vessels. The ischemic area induced by low position tourniquets is significantly reduced, which effectively aviods ischemia reperfusion injury. The low position tourniquet is personally put on the thigh, thus decreasing the interval time between tourniquet running and operation taking place.
In this study, no significant difference in surgical fields, operation time, bleeding volume, and fracture healing time was found between two groups. Even though there is no difference in AOFAS scores on the whole, the scores of low position tourniquet group were higher than those of high position tourniquet group within 4 weeks after surgery, indicating that the former has more advantages. In addition, VAS scores of low position tourniquet group was significantly lower than those of high position tourniquet group within two weeks after surgery, which also indicates that the application of low position tourniquet group is conductive to ERAS. Similar study was researched that the use of tourniquets in knee joint replacement was beneficial to the early rehabilitation of knee joint function. In terms of complications, although, any tourniquet has complications theoretically, the related complications of the traditional high position tourniquet group were significantly higher than those of the low position tourniquet group in this study.
4.2 Analysis of superiority of the low position tourniquet group
This study focused on minimizing the impact of the tourniquet on normal tissues instead of traditional thinking mode.
Results of VAS scores were comprehensively analyzed as followed. Firstly pression of tourniquets and Ischemic tissues were significantly decreased so that the compression of skin, quadriceps, sciatic nerve and muscle necrosis was greatly reduced. secondly, the hypoxic harmful substances and myoglobin in the blood were effectively reduced, which can attenuate the ischemia-reperfusion injury. 
The motion of ankle and AOFAS scores of low position tourniquet group were higher than the high position tourniquet group four weeks after surgery. Postoperative pain in the affected limb was reduced, and patients passively or actively accepted early functional exercises, which created conditions for patients to perform early functional recovery or ERAS, improving their early ankle range of motion and functional scores.
As for soft tissue complication, the patients in the low position tourniquet group did not have skin caking and congestion. There were fewer muscles at the binding site of the low position tourniquet. The anterior tibial artery and vein were superficial, which significantly reduced the inflation pressure of the tourniquet, and thus effectively reduced the tissue damage. In addition, DVT mostly occurred in the long tubular veins of the lower limbs instead of the short veins far from ankle, thus the low position tourniquet not directly invading the proximal part. The lower tourniquet pressure reduced the damage of the blood vessels, which was also an important reason for the reduction of DVT.
4.3 Precautions and prospects
In summary, the use of tourniquets, whatever low position or high position, can meet the the requirements of surgical field in ankle fracture surgery so that the clinician can smoothly complete the operation under safe conditions, even though the lower position tourniquet may perform better, nevertheless. The primary reasons why most clinicians still choose high position tourniquets in the current clinical practice are that the high position tourniquets are not required to operate by clinicians and that low complications are not paid attention to by clinicians. It is conceivable that with the gradual deepening of the concept of ERAS and the increasing requirements of society, the use of low position tourniquets may become more and more widespread. However, we experientially choose the pressure setting of 1.5 times systolic pressure and the holding time of no more than 1.5 hours in view of little literature in this field before. Moreover, small sampling and short-term following up limit the research. Further studies are required to explore tourniquets more accurately in future.