The analgesic effect of a popliteal plexus blockade after total knee arthroplasty: A feasibility study

Abstract

INTRODUCTION: An obturator nerve block (ONB) and a femoral triangle block (FTB) provide effective analgesia after total knee arthroplasty (TKA) without impeding the ambulation, although the ONB produces motor blockade of the hip adductor muscles. The popliteal plexus (PP) in the popliteal fossa is formed by contribution from the tibial nerve and the posterior obturator nerve, innervating intraarticular genicular structures and the posterior capsule of the knee. We hypothesised that a popliteal plexus block (PPB) as a supplement to an FTB would reduce pain after TKA without anaesthetising motor branches from the sciatic nerve in the popliteal fossa. AIM: To assess the analgesic effect of adding a PPB to an FTB in 10 subjects with significant pain after TKA. METHODS: All subjects underwent unilateral TKA with spinal anaesthesia and received an FTB. The cutaneous sensation and the postoperative pain were assessed. The primary outcome was the proportion of subjects with pain above numeric rating scale (NRS) 3 followed by a reduction to NRS 3 or below after conducting a PPB. RESULTS: Ten subjects with a median pain of NRS 5.5 (interquartile range [IQR] 4-8) after unilateral TKA received a PPB. All 10 subjects experienced a reduction in pain to NRS 3 or below (NRS 1.5 [IQR 0-3]) within a mean time of 8.5 (95% CI 6.8-10.2) minutes. Three subjects were completely pain free after the PPB. The ankle muscle strength was not affected. CONCLUSIONS: The PPB provided effective pain relief without affecting the ankle muscle strength in all 10 subjects with significant pain after TKA and an FTB.