Objective To investigate the safe zone and the soft tissue damage of two-incision minimally in-vasive total hip replacement,and to retrospectively analyze the clinical result.Method 20 adult cadavers(40 hips) were used for anatomic research.The Course of the later femoral cutaneous nerve was recorded.The angle between the intermission of the piriformis muscle and gluteus medius muscle with horizontal plane was also recorded.Analogue operation was taken on 3 fresh cadavers to assess the injury extent of soft tissues around incisions.27 cases under-went two-incision minimally invasive total hip replacement.Results LFCN was found potentially at risk as far as 6～71 mm medial to anterior superior iliac spine(ASIS)along the inguinal ligament,as much as 21～112 mm distal on the lateral border sartorius muscle from the ASIS.With the operative leg fully adducted,flexed over the nonopera～tire leg and the patella placed horizontal,the angle between the intermission of the piriformis muscle and gluteus medius muscle with horizontal plane is(60±5)°(range 55°-68°).Imitating modified two-incision THA on 3 freshhips revealed muscle contused on gluteus medius-piriformis muscle and gluteus minimus muscle.The average length of the anterior incision was 5.0 cm(4.6～6.5 cm)and of the posterior incision 3.7 em(3.0～4.2 cm).All of the patients were ambulant the day after surgery.Blood transfusion was carried out in 4 cases including one case of femo-ral neck fracture.The patients were followed up for 18 months(13～25 months).No other complications occurred.The mean Harris score was 94.5(92～96).Conclusion Front incision from the point inferior ASIS 3 cm and 1cmlater from ASIS vertically 6 cm should be chosen and the real incision should be 60°with horizontal plane.GIuteus medius,piriformis muscle and ghteus minimus muscle will be contused in two-incision minimally invasive surgeryto-tal hip replacement.Two-incision total hip replacement has the advantage of being muscle sparing and minimally in-vasive with less blood loss and rapid recovery.However,this technique is time consuming,technically demanding,and requires fluoroscopy.