DIRECT ANTERIOR APPROACH
Muscle Sparing. The Direct Anterior (DA) approach to the hip is minimally invasive because its muscle-sparing. When defining the term “minimally invasive” its important to recognize that skin incision size is important, but its not the whole story. The amount of muscle stripping and reflection is probably more important to postoperative pain and speed of recovery. The DA utilizes native inter-nervous muscle planes to approach the hip leading to less muscle injury (in contrast to both anterior-lateral and posterior-lateral, which require greater degrees of muscle reflection)  .
Early Recovery. Multiple studies suggest that DA reduces immediate postop pain, systemic inflammation, and allows earlier functional recovery [1, 3, 4]     . In comparison to the posterior or antero-lateral approach, the DA shows:
Improved postop pain scores
Reduced pain medication
Decreased length of stay
Greater discharge home
It is unclear how many weeks postop the DA offers improved outcomes compared to other approaches. Some studies suggest the improvements last only 2 weeks , while others suggest 6 weeks [5, 6] , or 6 months to 1 year .
Functional outcomes after 6 weeks diminish.
Increased Stability. Lower dislocation rates have been shown because the posterior capsule and soft tissue is preserved, protecting the hip during sitting (where it most susceptible to dislocation)  
Learning Curve. Femoral Exposure can be a challenge in this approach and a sequential series of capsular releases are essential to obtain the necessary exposure, leading to higher complication rates in surgeons changing approaches  .
Femur Fracture. The acetabulum is very accessible during the DA, however, the femur is less accessible. Broaching is a challenge, and the femur can be torqued or over tensioned to obtain exposure. The combination of these challenges have lead to an increased rate of femur fracture via this approach   .
Technique. Patient Positioning and Sequential Capsular Releases are the keys to the procedure. The patient can be placed supine on a standard radiolucent table or placed on a specialized table, such as the Hana Table. C-arm fluoroscopy is typically available in the room. On a standard table the pubic symphysis is placed over the break in the table, and a small bump is placed under the coccyx slightly off-center (closer to the operative side). During femoral exposure, a femoral elevator (hook that goes posterior behind the the femur) is fixed to the table and pulls the proximal femur out of the wound, while the table is “opened” – foot of table dropped to 45° and the bed is 15° of Trendelenburg.
The posterior approach remains the gold standard for THA.
Extensile. Gives excellent exposure distally to access the entire femur. Gives excellent exposure proximally to access the posterior wall and acetabulum. When broaching the femur, the surgeon is in-line with the femoral shaft, giving excellent access and low risk for femoral cortex injury.
Dislocation risk. While initial studies suggested increased risk of THA dislocation with the posterior approach, a meticulous soft-tissue repair  and larger femoral head significantly reduces dislocation risk, and rates are similar to other approaches (anterolateral and direct anterior)  . Other studies suggest a persistent slightly higher risk for posterior  . However, hip precautions are recommended for posterior approach regardless of the quality of soft tissue repair. Precautions are not required for DA . Because hip instability is related to both patient factors (ie compliance) and surgical factors, patients are faced with additional risk factors for dislocation with the posterior approach (as compared with DA).
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