To explore the difference of pain and muscle strength between continuous femoral nerve block (CFNB)and single femoral nerve block combined (SFNB) with periarticular injection (PAI) in the early stage after total knee arthroplasty (TKA) and to evaluate their analgesic effect and performance in functional rehabilitation.

The data of the patients using continuous femoral nerve block and single femoral nerve block combined with periarticular injection after TKA in Peking University Third Hospital from January 2020 to December 2020 were retrospectively collected. The patients who underwent unilateral primary TKA with intraspinal anesthesia and perioperative management by the same surgical group were included. The patients who had knee surgery history, severe varus deformity, valgus deformity or extra-articular deformity, and abnormal muscle strength and muscle tension were excluded. The patients who met the inclusion criteria were divided into two groups according to analgesia plan: the CFNB group and the combined group. The differences of demographic data, surgical time and additional analgesic were studied between the two groups. Deep vein thrombosis (DVT) of lower extremity, accidental pullout of nerve block catheter, infection in the area of nerve block catheter and other complications during hospitalization were analyzed. The degrees of pain and muscle strength of quadriceps were recorded at 12, 24, 48 and 72h after surgery. Independent sample t test, chi-square test, Kruskal-Wallis test, Wilcoxon signed rank test or ANOVA test were used for statistical analysis.

A total of 144 patients were enrolled, including 65 patients in the CFNB group and 79 patients in the combined group. There was no statistically significant difference in demographic data, surgical time, additional analgesics and the incidence of DVT between the two groups (all P>0.05). No complication such as accidental pullout of nerve block catheter, infection in the area of nerve block catheter occurred. There was also no statistically significant difference in self-assessed visual analogue scale (VAS) scores between the two groups at 12 and 72h postoperatively (both P>0.05). The VAS scores of CFNB group[(1.8±1.3), (2.6±0.8)] were lower than those of combined group [(3.2±0.7), (4.0±0.8)]at 24 and 48 h postoperatively [t =-7.670, 10.250, both P<0.001]. There was no statistically significant difference in muscle strength of quadriceps between the two groups at 12h postoperatively (P>0.05). The muscle strength of quadriceps of CFNB group were lower than those of combined group at 24, 48 and 72h postoperatively (H=62.944, 88.486, 120.694, all P<0.01).

SFNB combined with PAI can achieve the same clinical analgesic effect as CFNB in the early postoperative stage after TKA, but the combined group patients have faster recovery of muscle strength of quadriceps and a lower risk of DVT, which is one of the desirable analgesic methods after TKA.