In any surgical decision, the safety of patients is always important. Considering the uncertainty and controversy in relation to the influence of posterior capsule repair on the incidence of hip dislocation following primary THA, we sought to evaluate the body of evidence linking posterior capsule repair with the risk of hip dislocation following primary THA carrying out a comprehensive systematic review of observational studies and RCTs. This meta-analysis included 8 studies (2 RCTs and 6 nRCTs) that analyzed 4523 patients (4624 hips) and directly compared the clinical effectiveness of the posterior capsule repair group and the control group without posterior capsule repair. The pooled data indicated significant differences between the 2 groups in terms of dislocation rates, HSS, and so on. The approach of posterior capsule repair in total hip arthroplasty is superior to the control group without posterior capsule repair on the basis of the present evidence base. The risk of hip dislocation was higher in the control group without capsule repair, while the complication rate was lower in the posterior capsule repair group. However, those differences might be caused by the significant between-article heterogeneity which was able to affect accuracy of the outcomes in meta-analysis. The influence of heterogeneity might be reduced by using Random effects model, subgroup analysis, or sensitivity analysis to pool data. However, it does not eliminate it. The current evidence base—with a good number of methodological inadequacies such as the limited usage of power calculations and poor or absent blinding of both patients and assessors—can cause assessor bias. The evidence base was also guilty of documenting methods of recruitment, thus permitting allocation or recruitment bias. In relation to these factors, the presented evidence base, being substantial in size, may be questioned regarding to its quality.
At present, the primary THA has become a routine treatment for hip diseases such as osteonecrosis of the femoral head (ONFH), developmental dysplasia of hips (DDH), femoral neck fractures, osteoarthritis of the hip, ankylosed hip, and so on. Hip replacement operations restore patients' function earlier, and reduce bedridden complications and mortality . However, with the large-scale popularization of THA surgery, there are more and more complications after THA. The complications of hip replacement can’t be ignored, in which postoperative dislocation is catastrophic . The complication of postoperative hip dislocation is second only to aseptic loosening. Currently, the posterior approach is commonly used in total hip arthroplasty, which has the advantages of a short operative time, less bleeding and a shorter hospital stay. However, its disadvantage is also the higher rate of postoperative dislocation .
The reasons for postoperative hip dislocation include patient-related factors, such as sex, hip dysplasia, previous hip surgery, patient compliance, and neurologic compromise [32-35]. Currently, it is believed that there are three major reasons for the high incidence of posterior dislocation of the posterolateral incision. Firstly, the Short external rotation muscle and the joint capsule are cut off in the posterior approach without careful repair when the incision is closed, resulting in the imbalance of the structural stability of the posterior soft tissue. Secondly, due to insufficient exposure of the surrounding soft tissue in the posterior approach, the prosthesis is easily pushed back when placing the acetabular cup, which changes the forward angle of the acetabular cup. That is to say, the incorrect position of the prosthesis affects the postoperative stability of the hip joint to a great extent. Thirdly, the unskilled surgical technique of the operator will also increase the rate of postoperative dislocation.
Some scholars investigated the reasons for dislocation considering prosthesis. McCollum, D.E. and W.J. Gray thought that the misplacement of acetabular components is considered to be an important cause of postoperative dislocation of the hip joint as well as Coventry, M.B., et al did [9, 36]. Etienne, A., Z. Cupic, and J. Charnley indicated that the dislocation rate after hip arthroplasty is related to the design of prosthesis . Cobb, T.K., B.F. Morrey, and D.M. Ilstrup suggested that an elevated liner can improve the stability of the hip joint after THA, particularly in hips which are at greater risk for the prosthesis dislocation . Sierra, R.J., et al suggested using a 32-mm head in association with posterior joint capsular repair should reduce the rate of dislocation . Hummel, M.T., et al recommended that larger femoral head size and joint capsule tissue repair can increase the stability of the hip joint . McCollum, D.E. and W.J. Gray provided a safe angle for acetabular cup placement to prevent dislocation . Larger femoral head sizes can reduce the incidence of dislocation [40-42]. Other scholars linked the stability of the posterior capsule to the posterior dislocation after THA. Clayton, M.L. and R.G. Thirupathi thought that the brace treatment after total hip arthroplasty can improve the stability and reduce the rate of recurrent dislocations . Wu, H.M. and A.Y. He reached a decision that posterior capsule repair can reduce the rate of early dislocation after primary THA (within the first six months after surgery) . Two senior authors used the method of posterior soft tissue enhancement to prove that posterior capsule repair can prevent postoperative posterior dislocation of the total hip arthroplasty through a posterior approach . Dixon, M.C., et al reported a simple capsulorrhaphy following a posterior approach which minimized the incidence of postoperative dislocation . Hedley et al. described a method of preserving the posterior capsule for primary hip replacement, with only 2 out of 259 cases of dislocation . Pierchon, F., et al demonstrated that soft tissue imbalance was the major cause of dislocation by CT scan . Stahelin, t. et al. confirmed through experiments that the posterior capsule of the hip joint needs higher torque to repair dislocation . However, some scholars thought that the technique of posterior capsule suture often failed. Stahelin, T., et al, American scholars, placed markers which could not pass through X-rays during the operation, and observed the distance between the two markers through postoperative X-ray plain films. As a result, even though the posterior capsule was repaired in total hip arthroplasty, and most of them were not strong enough to resist the tension of the repair during the healing position, eventually the repair failed. Therefore, in terms of posterior structure suture techniques, it is necessary for us to further explore better techniques to improve the curative effect .
Limitations and Strengths
The limitations of this study are as follows. Firstly, most of the included studies are observational studies (case-controlled studies), in which the reliability of the conclusion needs to be confirmed, because they are more likely to be biased and the number of included literatures is relatively small. Secondly, there is diversity in the design of the prosthesis such as the size of the femoral head and so on, or it has not been reported in detail, so the heterogeneity is increasing among included studies. 28 mm ceramic heads were used in 3 studies, but it is not clear in other articles. We tried to contact the authors, but failed. So we cannot perform a subgroup analysis to see if the dislocations rates were different with studies reporting larger head sizes (36 mm and more) versus smaller head sizes. Thirdly, gender, age and specific diseases in the included studies are significantly different. Thus, it also becomes a possible source of heterogeneity. Fourthly, some studies have been omitted because of the search strategy we performed. To overcome this limitation, we have consulted researched synonyms, optimized the search strategy, and conducted an extensive search. Fifthly, it was not clear whether or not TXA was used in the eight studies included. We also tried to contact the authors, but failed. So this may be a big confounding effect. Sixthly, performing a true RCT is difficult. Only 2 of 8 studies were RCTs, in which it was very difficult to realize the blind method. In most of the studies, the method of operation depended on the patient and the doctor; thus, it was difficult to ensure the baseline balance between the 2 groups. Kwon, M.S., et al performed a meta-analysis to compare dislocation rates with and without soft tissue repair after THA. However, the posterior capsule repair had not been specifically described in this systematic literature review . Compared with the above-mentioned meta-analysis, we included some new clinical researches, and our outcomes are more up to date. We performed this study in line with the PRISMA statement, while some authors studied in accordance with the Chinese Cochrane Center. To strengthen our meta-analysis, we need further prospective randomized trials investigating dislocation incidence and other clinical parameters.