Data source
A total of 120 patients were randomly assigned to the control and ultrasound groups, and underwent DAA THA from September 2019 to June 2020. All patients provided informed consent, and the protocol was approved by the Ethics Committee of our institute. Inclusion criteria: patients suffered from a fracture of neck of femur, femoral head necrosis, or osteoarthritis of the hip joint and need primary hip arthroplasty. Exclusion criteria: patients had a poor cardiopulmonary function, and hence, could not be burdened with the crisis of anesthesia and surgery and experienced other operations in the same hip joint with scar or anatomical disorder. Moreover, general characteristics, including age, sex, and body measurement index (BMI), were evaluated.
Ultrasound Mapping
In the ultrasound group, two skilled physiatrists with neuromuscular ultrasound experience examined the 3D distribution using an ultrasound machine (SonoSite M-turbo, USA) with a 10 MHz linear array transducer to detect the LFCN. The ASIS and sartorius muscle was used as a reference to describe the continuous course of LFCN. Three cross-sectional areas were selected to trace the position of LFCN relative to skin and tensor fasciae latae (TFL). The first point was that LFCN left the pelvis near ASIS and inguinal ligament (IL), and the second and third recording points were 5 cm and 10 cm distal to the ASIS, respectively. The depths of LFCN to the skin at the three points were recorded as D1, D 2, and D3, respectively. The lengths of LFCN to the medial edge of TFL at the three points were recorded as L1, L 2, and L3, respectively. If LFCN was located on the medial side of TFL, it was recorded as –L, and if lateral, it was + L (Fig. 1. a, b). Finally, the course of the LFCN was mapped on the skin using a marker pen. These data will be taken as reference for surgeons to avoid damaging LFCN during operation (Fig. 1. c, d). In the control group, nothing tracked the course of LFCN.
All hip arthroplasties were performed by one experienced and skilled surgeon. One and three months after surgery, all participants underwent follow-up in the Out-patient Department. The LFCN injury was evaluated based on the aspect of sensation to the anterolateral aspect of the thigh (including hypesthesia, pain or dysesthesia, and their area pained by the patients themselves), and Harris score of the hip joint were evaluated.
Surgical Technique
All surgeries were performed by one experienced DAA surgeon and three assistant surgeons. After intravenous anesthesia, the participant lied on a standard surgical bed in the supine position, and the hip joint that required arthroplasty was 10 cm higher than the other side. The skin incision was 2 cm lateral from ASIS and proceeded distally for about 8–10 cm that was parallel to the line of ASIS and lateral of the patella. Briefly, after subcutaneous and fascia dissection, the sartorius, temoriss, and tensor fascia were isolated, the muscle interval was uncovered, and the branches of lateral femoral circumflex artery ligated. The anterior capsulotomy and femoral neck osteotomy were performed, and then the acetabulum was exposed. The acetabulum was prepared using different sizes of offset reamers at 40–45° abduction and 15° anteversion until the surface oozed blood. After the installation of an artificial prosthesis of the acetabulum, the femoral preparation continued in a modified figure-four position of the leg with 45° hyperextension and elevation of the femur by a double-tipped retractor behind the greater trochanter. The distance from the horizontal line of the great trochanter to the center of the rotation of the femoral head based on the result of pelvic radiograph was used to evaluate the length of the leg, and the range of movement was effectuated to assess the stability of leg. After introducing the artificial femoral component and head, the deep fascia, subcutaneous tissue, and intracutaneous were sutured step by step.
To identify the consistent results between preoperative ultrasound data and anatomical positions, five patients were informed and consented to expose the LFCN in surgery. Based on the preoperative ultrasound 3D distribution data, including the depth to skin, the mapping path and the length to TFL, we accomplished to show the anatomy of the LFCN intraoperation. It demonstrated the nerve located medical side of our incision and provided practical parameters for surgeons to keep the suture at an appropriate distance from border of incision while avoiding the LFCN. (Fig. 2)
Evaluation Of Lfcn Injury In Patients
At 1month and 3 months after surgery, all patients underwent follow-up in the Outpatient Department. Also, the abnormal sensation in the anterolateral thigh, including hypesthesia, dysesthesia, numbness, and pain was assessed. If a patient experiences abnormal sensation, he/she would be asked to mark the region area using a black marking pen (Fig. 3). This area was estimated by multiplying the longest diameter with the shortest diameter. An experienced doctor assessed the function of hip joint after DAA THA surgery.
Statistics
As the continuous variables are presented as mean ± SD, Student’s t-test was used to analyze data for normal distribution and Mann-Whitney U-test for abnormal distribution. On categorical variables, Fisher’s exact test was used. P < 0.05 indicated the statistical significance. Statistical Package for the Social Science version 23.0 (INM Corporation, Armonk, NY, USA) was utilized to analyze these data.