A Prospective Randomized Trial of the Direct Anterior Approach versus the Posterior Approach in Primary Total Hip Arthroplasty

Participants will be randomized into two groups to undergo hip replacement surgery via the anterior or posterior approach. Surgery will be performed by 2 senior orthopaedic surgeons at a single institution. Participants will be assessed pre and post-operatively up to 3 months post operatively using a series of questionnaires. The anterior approach used utilizes a modified varient of the Hueter anterior approach. This surgery is expected to take between 1-2 hours to peform depending on complexity. The incision is made 2cm posterior and 1cm distal to the anterior superior iliac spine (ASIS) and extended in a straight line distally and slightly posterior ending approximately 2cm anterior to the greater trochanter (GT) The interval between Sartorius and tensor fascia lata (TFL) is palpated and then incised. The lateral femoral cutaneous nerve is identified and protected. TFL is then retracted laterally while Sartorius is retracted medially. The interval is then further developed through the interval between rectus femoris and gluteus medius until the lateral hip capsule can be palpated. Iliopsoas and rectus femoris are gently elevated and retracted medially to complete the exposure of the hip capsule. The lateral circumflex vessels are then identified and ligated. Capsulotomy is then performed and the edges tagged, reflected and protected to allow for subsequent reconstruction. The femoral neck is then cut and femoral head delivered. The femur is now externally rotated approximately 45 degrees to facilitate acetabular exposure Precautions are taken during external rotation to prevent fractures. Preparation of the acetabulum can now occur. The anterior musculature is retracted carefully to minimize soft tissue damage. Labral excision is completed and the inferior capsule band incised to facilitate liner placement. Reaming is done under direct vision and acetabular component trialling is done under radiographic guidance. On completion of acetabular preparation, the femur is externally rotated to 90 degrees and the hip adducted and hyperextended. If there is inadequate exposure of the femur, release of obturator internus with piriformis can be performed. Once exposure is adequate, the femur is then breached with a box cut and broached. Broaching is undertaken carefully to prevent proximal femur fractures, cortical perforation and excessive anteversion. Broaching is completed when the size matches that of the preoperative template. This is guided by feel and depth. The femoral components are then trialled guided by the pre-operative template and final broach size. The hip reduced with internal rotation. Leg length, offset and stability are checked clinically and with the aid of the image intensifier. On meeting the parameters, the hip is then dislocated, trial components removed, prosthesis inserted and hip reduced. The capsular incision is now repaired. Haemostasis with diathermy or ligation is achieved prior to closure of the soft tissue and skin.