Currently, the most popular surgical approaches for total hip arthroplasty (THA) are the direct anterolateral approach (DAA) and the posterolateral approach (PLA). The PLA approach, as the earliest and most widely used clinical approach, is also known as the traditional approach and is still widely used in hospitals in China. The DAA approach was proposed by Huter in 1881 and gradually became popularized by Smith et al. The DAA approach can use the gap between the vastus tensor fasciae latae muscle and the rectus femoris muscle and protect the surrounding muscles, blood vessels, nerves and other tissues as much as possible, thus avoiding the need to cut or loosen the muscles, as in the PLA approach. The DAA approach can utilize the gap between the tensor fascia lata muscle and rectus femoris muscle to protect the surrounding muscles, blood vessels, nerves and other tissues as much as possible, thus avoiding the need to cut or loosen the muscles as in the PLA approach and accelerating patient recovery. Due to the popularity of minimally invasive surgery and rapid recovery, the DAA approach is gradually becoming mainstream in clinical practice. At present, the DAA approach has not yet been able to replace the traditional PLA approach in clinical practice because of the long learning curve, the possible increase in operating time, and the imperfections in the study of medium- and long-term therapeutic efficacy.
There are many clinical articles on comparative studies of the efficacy of the two approaches for THA, but there are no valid data to support which approach can definitively affect the placement of the prosthesis [1]. Many studies have shown [2, 3] that the DAA approach is significantly better than the PLA approach in promoting early functional recovery in patients. A domestic study on the efficacy of bilateral hip joint arthroplasty in 106 patients who underwent anterior or posterior approach arthroplasty revealed [4] that THA via the DAA was superior to THA via the PLA in terms of blood transfusion, hospitalization time, one-week postoperative improvement in pain, and early recovery of hip function and that there was no significant difference between the two approaches in terms of operation time or postoperative complications. The authors concluded that the data of the two patients in this report conformed to the above research pattern. A recent foreign study comparing the mid- and long-term efficacy of the two approaches revealed [5] that the anterior approach had a greater rate of lateral femoral revision (periprosthetic fracture and aseptic loosening) and a lower rate of early infection and dislocation, suggesting that the DAA approach is still questionable in terms of mid- and long-term efficacy.
Clinically, we should consider the surgical approach that is most appropriate for THA, and we should strive to minimize the higher revision rates and associated complications that are specific to the use of a particular approach based on the orthopedic surgeon's own level of experience with each approach and patient selection. We have summarized our experience in both prosthesis placement and joint capsule management.
The placement of the prosthesis at the appropriate abduction and anterior tilt angles is a major factor in preventing dislocation of the prosthesis after THA. The current clinical placement angles of the acetabular prosthesis recognized by most clinicians are as follows: abduction, 45° (± 5°), and anterior tilt, 20° (± 5°). Most clinicians position the acetabulum at 40–45° abduction and 15–20° anterior tilt based on bony landmarks. Although the safety zone for acetabular anterior tilt (15 ± 10°) is the gold standard, this safety zone is not applicable in cases of abnormal femoral anterior tilt or severe pelvic tilt when combined anterior tilt is considered. The generally accepted intraoperative combined anterior tilt angle should be between 25° and 50°, with 20° to 30° for men and 30° to 45° for women. If the joint anterior tilt angle is too small, posterior dislocation is likely to occur after surgery; if the joint anterior tilt angle is too large, anterior dislocation is likely to occur. Wang Yuan et al. [6] reported that for patients with ankylosing spondylitis affecting the hip joint, the use of the joint anterior tilt technique during surgery can improve the accuracy of prosthesis implantation, promote kinetic recovery of the hip joint, and reduce the occurrence of postoperative complications. In the author's opinion, the anterior approach mainly involves exposing the anterior joint capsule, taking the anterolateral view of the hip joint for prosthesis replacement, and the operator's visual judgment to adjust the position of the prosthesis is prone to cause the anterior tilt angle of the socket cup to be too small. We can slightly adjust the anterior socket cup placement angle according to the bony landmarks; similarly, we can adjust the posterior socket cup anterior tilt angle to achieve the optimal fitting position. In addition, to more accurately adopt the combined anterior inclination technique for prosthesis replacement, a protractor or three-dimensional goniometer [7] can be used intraoperatively to measure and adjust the femoral anterior inclination and acetabular anterior inclination, respectively, to achieve the maximum fit between the prosthesis and the affected limb.
Dislocation of the hip joint prosthesis is a serious complication of THA surgery, which not only causes secondary trauma to the patient but also may lead to revision surgery, which can increase the economic burden on the patient. Clinically, many doctors tend to rely on the mobility and stability of the joint prosthesis itself and habitually resect the ligaments around the hip joint and the peripheral joint capsule, seriously ignoring the protective and restrictive effect of the joint capsule on the hip joint. The joint capsule has a role in limiting hip hyperextension, external rotation, abduction, flexion, internal rotation and resistance to longitudinal traction, which can maintain the stability of the joint at the limit of activity and limit the separation of the head and socket. Previous studies have shown [8] that the dislocation rate in THA patients who did not have the joint capsule preserved was as high as 4.8% with the posterior-lateral approach, while the dislocation rate in THA patients who had the repaired joint capsule preserved was only 0.7%. In addition, after THA, due to the reduction in acetabular head volume and other reasons and intraoperative preservation of the joint capsule alone, the postoperative joint capsule binding force is still decreased, and the failure of the joint capsule limiting function has a greater impact on the posterior joint capsule, while the intraoperative repair of the joint capsule is able to partially restore the limiting effect. In the author's opinion, for the treatment of the joint capsule, we can adopt THA under the posterior approach, preserving the anterior joint capsule and repairing the tight posterior joint capsule; THA under the anterior approach, repairing the anterior joint capsule and preserving the posterior joint capsule; and THA under the direct lateral approach, which is preserved at the time of visualization and repairs the joint capsule at the time of suture, to maximize protection and recovery of postoperative hip joint function.