| Objective:Lateral direct anterior approach(LDAA)total hip arthroplasty(THA)pelvis will rotate back and forth due to the use of Hohmann hooks.The reason for this is that when the Hohmann puller is used to file and place the acetabulum,the puller placed behind the acetabulum is often applied to the hip when it is used to fully retract the strong flexor fasciae and gluteus musculus.The hook on the front edge of the mortar is much stronger.Even if there is a blockage of the THA front and back posture,it still causes the entire pelvis lying on the side to rotate to the rear to varying degrees.The rotation of the pelvis to the rear will cause the acetabular anteversion angle to change visually,resulting in a misjudgment of the acetabular cup anteversion placement angle during surgery.This misplacement of the acetabular cup anteversion angle is the main cause of anterior or posterior dislocation of the hip joint after THA.We have consulted a large number of DAA-related literatures and found no articles on the determination of pelvic rotation angle during LDAA surgery.Therefore,the purpose of this study is to use mobile phone spirit level software to measure the pelvic rotation value of LDAA patients during the acetabular rasping stage.The research results have important clinical application value for the accurate placement of the acetabular cup forward angle.Method:From September 2018 to August 2019,a total of 60 patients with LDAA THA participated in this study(a total of 55 patients).The above patients are all cases of avascular necrosis of the femoral head(Ficat stage Ⅳ)undergoing THA,and the exclusion criteria are patients with pelvic deformity or spinal deformity.Among them,30 cases in the control group(18 males and 12 females),the average age was 63.4±8.1years(41-83years),and the body mass index(BMI)was 23.9±1.2kg /m2(21.5-26.3kg/m2).The control group did not use intraoperative pelvic rotation measurement and "compensation",but directly placed the acetabular cup with the floor reference method in the operating room.30 cases in the experimental group(17 males and 13 females),with an average age of 61.7±8.6 years(45-77years),and a body mass index(BMI)of 23.8± 2.1kg/m2(20.3-30.5kg/m2).The experimental group used a mobile phone spirit level to measure the pelvic rotation angle during the operation,and the acetabular cup was placed with the corresponding “compensation” value.The mobile phone for measurement is i Phone 6 plus,and the measurement software Spirit Level APP(version 1.1,R & D software co.,LTD).The mobile phone is placed on an aluminum alloy holder through a sterile film seal and connected with a 2.5 mm Kirschner wire.This Kirschner wire is fixed on the anterior superior iliac spine bone.During the operation,there was no hook before the acetabular file and when the acetabular file was fully exposed,the values displayed on the APP were recorded separately,and the difference between the values was the pelvic rotation angle.The pelvic DR was performed 4 weeks after the operation,and the anteversion angle of the acetabular cup was measured and calculated by Widmer’s method.This study mainly analyzes(1),the value of intraoperative pelvic rotation angle;(2),comparison of postoperative pelvic plain acetabular anteversion angle of control group and experimental group;(3)whether pelvic rotation is related to the patient’s BMI.SPSS20.0 software was used for statistical analysis.The data results were expressed in the form of mean ± standard deviation(`x±s).The difference between groups was compared by t test method.P <0.05 indicated that the difference was statistically significant.Result:The use of Hofmann hooks in LDAA THA will cause the pelvis to rotate backwards,with a rotation angle of 9.1°±1.0°(range:7.4°to10.9°).The pelvis also tilts up or down at the same time,but the tilt angle is relatively small and has no statistical significance.There was no statistically significant correlation between pelvic rotation and patient height(r =0.138,P =0.467),body weight(r =0.255,P =0.174)or BMI(r =0.090,P =0.637).The average anteversion angle of the experimental group was significantly lower than that of the control group(15.9°±4.4°vs 23.8°± 4.9°,P <0.001).There was no statistically significant difference between the average abduction angle of the experimental group and the control group(44.9°±1.3°vs 45.1°±1.2°,P =0.49).The Lewinnek safety zone in the experimental group had more cup positions than the traditional group(96.7% vs 60.0%,P <0.001).Conclusion:In THA operation using LDAA,the pelvis rotates backwards when the Hofmann hook fully reveals the acetabulum,which causes the acetabular anteversion to change visually by about 9°when the pelvis is placed with the floor of the operating room as the reference mark.If the acetabular cup is placed at a standard 20 degrees without “compensation”,when the Hofmann hook is released,the actual acetabular anteversion is about 29°,which is a huge potential factor for the DAA anterior hip dislocation.The backward rotation of the pelvis caused by Hofmann’s hook pull is independent of the patient’s height,weight,and BMI.When the pelvic plain films of the experimental group and the control group were analyzed after operation,it was found that the anteversion angle of the control group was significantly larger than that of the experimental group.This experiment provides an accurate theoretical basis for LDAA to better place the acetabular cup anteversion angle,and has potential clinical guidance significance for reducing the postoperative hip dislocation rate. |
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