Use of Surgical Approach Is Not Associated With Instability After Primary Total Hip Arthroplasty

A Meta-Analysis Comparing Direct Anterior and Posterolateral Approaches

Elina Huerfano, MD; Maria Bautista, MD, MSc; Manuel Huerfano, MD, MSc; Juan M. Nossa, MD


J Am Acad Orthop Surg. 2021;29(22):e1126-e1140. 

In This Article

Abstract and Introduction


Introduction: Posterolateral approach (PA) has been historically associated with an increased risk of dislocation after primary total hip arthroplasty (THA), especially when compared with the direct anterior approach (DAA). However, current evidence is inconsistent regarding the risk of dislocation with either approach. The purpose of this study is to determine whether surgical approach influences joint stability.

Methods: A systematic search in PubMed, MEDLINE, and Embase databases was performed. Randomized controlled trials (RCTs) and non-RCTs comparing DAA with PA in primary THA were included. Pooled effect measure of risk differences, relative risk and mean differences for postoperative dislocation, acetabular implant positioning, and leg length discrepancy were calculated.

Results: Twenty-five studies (5 RCTs and 20 non-RCTs) of 7,172 THAs were assessed. There were no significant differences in dislocation rates between approaches (risk difference = −0.00, 95% confidence interval: −0.01 to 0.00; P = 0.92; I2 = 0%). Results were similar in the subgroup analysis of RCTs (P = 0.98), posterior soft-tissue repair (P = 0.50), and learning curve (P = 0.77). The acetabular implant was better positioned within the safe zone in the DAA group (relative risk = 1.17; 95% confidence interval: 1.03 to 1.33; P = 0.01), but no significant differences were found in cup inclination (P = 0.8), anteversion (P = 0.10), and leg length discrepancy (P = 0.54).

Conclusion: Dislocation rates after THA are not different between DAA and PA. Furthermore, no differences in the rate of dislocation were associated with cup positioning or surgical factors related with hip instability. Therefore, the surgical approach has little influence in prosthesis instability after primary THA.

Level of Evidence: Level III


Prosthetic instability is the main indication of hip revision surgery in the United States[1] and is associated with poor patient-reported outcomes; therefore, prevention of this complication is one of the main hip arthroplasty goals. Both patient and surgical factors associated with hip instability must be considered to reduce the frequency of prosthetic hip dislocations.[2]

Although instability is multifactorial, the surgical approach has been historically associated with an increased risk of postoperative dislocation.[2] The posterolateral approach (PA) is one of the most widely used approaches for total hip arthroplasty (THA);[3] however, the disruption of posterior soft-tissue structures with this approach and its role in hip stability after THA remains a major concern. On the other hand, the direct anterior approach (DAA) has become popular in recent years,[4] as it minimizes muscle damage and weakness by using an intermuscular plane.[5]

Different authors have described that DAA is associated with lower dislocation rates compared with the PA;[6,7] however, after introducing extended offset femoral stems and larger femoral head diameters, a substantial decrease in the rate of dislocation was observed in the PA.[8] There is conflicting evidence regarding a straight association between the surgical approach and the risk of postoperative instability; moreover, current knowledge is mostly derived from arthroplasty registers and administrative data claims. The purpose of this study was to determine whether the surgical approach used in primary THA is associated with postoperative hip instability through the analysis of dislocation rates and other surgical outcomes such as learning curve, implant positioning, posterior soft-tissue repair, and leg length discrepancy.