Study On The Influencing Factors Of Pain After Total Knee Arthroplasty

Objective: To study the influencing factors of postoperative pain in patients undergoing total knee arthroplasty(TKA).Methods: A total of 235 patients who underwent TKA in the Department of Arthritis Surgery,Affiliated Hospital of Qingdao University from February 2019 to May 2019 were enrolled.Record patients’ age,gender,height and weight,angle of knee varus deformity,pain sensitivity,perioperative use of opioids,tourniquet using time,total degree of intraoperative soft tissue release,local infiltration anesthesia drug kinds and dosage,patients’ serum c-reactive protein(CRP)of preoperation and 2,4 days after the operation,patients’ limb pain degree before and 2,4,7,28 days after the operation.According to age,the patients were divided into elderly group(≥65 years old)and middle-aged group(< 65 years old).The patients were divided into male group and female group according to gender.According to body mass index(BMI),the patients were divided into low body weight group(< 30kg/m2)and high body weight group(≥30kg/m2).According to the degree of varus deformity before surgery,the patients were divided into two groups: mild varus deformity(0°～10°)and moderate and severe varus deformity(≥10°).According to the visual analogue score of preoperative pain,the patients were divided into two groups:mild pain(≤ 3 points)and moderate and severe pain(> 3 points).According to the preoperative acupuncture pain score,the patients were divided into insensitive(0 point),sensitive(1 point)and extremely sensitive(≥2 points)3 groups in total.The patients were divided into betamethasone group(ropivacaine + betamethasone)and non-betamethasone group(ropivacaine + epinephrine)according to the composition of local infiltration narcotic drugs.According to the degree of intraoperative soft tissue release,the patients were divided into small amount of release group(<3 points),medium amount release group(3 points)and large amount release group(>3points).According to the use time of tourniquet,the patients were divided into two groups: short time group(< 70 min)and long time group(≥70 min).After eliminating the interference factors,the patients in the group were compared to see if there was any difference in postoperative pain between the groups,and the differences in serum CRP and opioid dosage were analyzed.Result: There was no difference in postoperative pain score and analgesic dosage between the elderly group and the middle-aged group(P>0.05).There was no difference in postoperative pain score and analgesic dosage between male and female groups(P>0.05).There were no differences in postoperative pain scores and opioid dosage between the low and high weight groups(P>0.05).There were no differences in postoperative pain scores and opioid dosage between mild varus deformity group and moderate and severe varus deformity group(P>0.05).Compared with the mild pain group,the moderate and severe pain group had more varus deformity(P=0.002)and more degree of intraoperative soft tissue release(P<0.001)and higher pain sensitivity(P<0.001)and had higher pain scores at 2,4,7,and 28 days postoperatively(P<0.05),after eliminating the effects of intraoperative soft tissue release degree and pain sensitivity,the postoperative pain difference between the groups disappeared(P>0.05).Compared with the sensitive group and the insensitive group,the extremely sensitive group had higher pain scores 2 and 4 days after surgery(P<0.05),and the use of opioids was greater(P<0.05),there was no difference in postoperative CRP(P>0.05).The pain scores of the betamethasone group were lower than those of the non-betamethasone group at 2,7 and 28 days postoperatively(P<0.05),less opioid use(P<0.001),lower postoperative CRP(P<0.001).Large amount release group had higher pain scores at 2,4,7,28 days after surgery than medium amount release group and small amount release group(P<0.05).The pain scores of the long time group were higher than those of the short time group at 4 and 7 days postoperatively(P<0.05).Conclusion: Age,gender,BMI,preoperative varus deformity degree of the knee and preoperative pain degree were not the direct influencing factors of postoperative pain in TKA patients.Sensitivity to needling pain can reflect pain sensitivity and affect postoperative pain,and patients with high sensitivity should increase the dosage of opioids.Betamethasone can significantly reduce the inflammatory response of patients after TKA,reduce the postoperative pain experience and reduce the amount of opioids.It is recommended to add betamethasone to local infiltration anesthesia drugs.The increased degree of intraoperative soft tissue release may aggravate the postoperative pain of patients through both inflammatory response and non-inflammatory response.For patients with higher degree of intraoperative release,it may be necessary to increase the use of opioids.Prolonged use of tourniquet will aggravate postoperative pain,so it is necessary to reduce the use time of tourniquet as much as possible.