Anatomical Study Of Cutaneous Nerve Around The Knee To Assess Electrode Placement For TENS In Knee Osteoarthritis

ObjectiveThrough the dissection of the medial femoral cutaneous nerve,the intermediate femoral cutaneous nerve and the infrapatellar branch of saphenous nerve(IPBSN)around the knee of the adult specimens and identify the location of the relatively high density nerve branches area.The goal of this study is to assess the optimal location of the electrode for transcutaneous electrical nerve stimulation(TENS)in knee osteoarthritis(OA)based on the anatomical basis of the high density nerve branches area in the pain zones for knee osteoarthritis.MethodsThis study was divided into two parts.First,20 adult formalin-fixed cadavers were involved.Through the dissection,we exposed the distribution of nerve branches in the anterior and medial pain zones around the knee which are the most frequently identified as painful zones for knee OA.Then identify the location of high density nerve branches area.The 4×4 cm2 electrodes were placed on the high density nerve branches area.With the patella,the medial knee joint line and the medial border of patellar ligament as the anatomical landmarks,the horizontal and the vertical distances from the electrodes to the designated anatomical landmarks were measured by two researchers,respectively.The ratio of the horizontal and vertical distances to patella width was calculated to compensate for individual differences in patients.The measurements above allowed us to propose the optimal TENS electrode placements for the clinical application.Secondly,to assess the reliability of the proposed placements,the electrode placements were performed on 2 specimens,then through the dissection of these 2 cadavers was performed to verify whether these electrodes were on the high density nerve branches.ResultsThe anterior and medial pain zones around the knee were the most frequently identified as painful zones for knee OA.The anterior pain zone around the knee was mainly innervated by the intermediate femoral cutaneous nerve and the infrapatellar branch of saphenous nerve.The medial pain zones around the knee was mainly innervated by the medial femoral cutaneous nerve and the infrapatellar branch of saphenous nerve(IPBSN).These pain zones contained four high density nerve branches areas.The intermediate femoral cutaneous nerve:the ratio of distance between the base of patella and the inferior margin of the electrode(A)to patella width(P)was 26.31%and equal to approximately 1/4(95%CI 24.24-28.38%),the ratio of distance between the medial margin of the patella and the medial margin of the electrode(B)to patella width(P)was 17.96%and equal to approximately 16(95%CI 16.28-19.64%);The anterior aspect of the infrapatellar branch of saphenous nerve:the ratio of distance between the inferior pole of the patella and the superior border of the electrode(C)to patella width(P)was 24.73%and equal to approximately 1/4(95%CI 22.37-27.09%),the ratio of distance between the medial border of the patellar ligament and the medial margin of the electrode(D)to patella width(P)was 16.06%and equal to approximately 1/6(95%CI 14.32-17.79%).The medial femoral cutaneous nerve:the ratio of distance between the medial joint line and the inferior margin of the electrode(E)to patella width(P)was 36.19%and equal to approximately 1/3(95%CI 31.93-40.45%),the ratio of distance between the medial margin of patella and the lateral border of the electrode(F)to patella width(P)was 21.76%and equal to approximately 2/9(95%CI 19.12-24.41%);The medial aspect of the infrapatellar branch of saphenous nerve:the ratio of distance between the medial joint line and the superior border of the electrode(G)to patella width(P)was 18.91%and equal to approximately 1/5(95%CI 16.18-21.64%),the ratio of distance between the medial margin of patella and the lateral border of the electrode(H)to patella width(P)was 21.25%and equal to approximately 1/5(95%CI 19.13-23.36%).The method of electrode placements was proposed based on the above data,and the method was verified by dissection of the two specimens.ConclusionsIn this study,we explored the high density nerve branches area in the pain zones for knee OA and proposed the method of TENS electrode placements.It could guide the therapist or patients using portable TENS device in clinical practice or at home.