Robotic-Assisted Total Hip Arthroplasty Through the Posterior Approach

Abstract

Background: Robotic-assisted total hip arthroplasty (THA) through the posterior approach is indicated in cases of symptomatic hip arthritis. The goal of the procedure is to relieve pain and restore function while minimizing postoperative complications such as dislocation. Dislocation often occurs despite traditionally well placed components 1,2 . The hip-spine relationship can be a causative factor in postoperative instability, particularly in patients with altered spinopelvic kinematics as a result of spinal fusions or degenerative spine disease, in whom component placement based on anatomic landmarks may lead to functional malpositioning 3,4 . Therefore, we present our technique for robotic-assisted THA through the posterior approach, which incorporates patient-specific spinopelvic kinematic data to maximize impingement-free range of motion and minimize the risk of dislocation. Description: Preoperative computed tomography (CT) scans are obtained in order to generate a 3D model of the patient’s unique hip anatomy. Lateral lumbar radiographs with the patient in the sitting and standing positions are also obtained preoperatively. The sacral slope is measured in each position, imported into the robotic software, and utilized to aid in positioning the components for optimal leg length, offset, and stability of the hip replacement based on the patient’s unique spino-kinematic profile. The procedure begins with 3 partially threaded pins being driven into the ipsilateral iliac crest about 2 cm posterior to the anterior superior iliac spine. The robotic pelvic array is fastened to the pins. A standard posterior approach to the hip is utilized. Skin and subcutaneous tissues are dissected down to the iliotibial band and gluteus maximus fascia. The fascia is longitudinally incised, and a small metallic pin is malleted into the distal aspect of the greater trochanter. Initial leg length and offset values are captured. The short external rotators and posterior hip capsule are elevated. The hip is dislocated, and a neck resection is made at a level determined preoperatively with use of the robotic software. The acetabulum is exposed, and osseous registration is carried out to establish a relationship between the 3D model built with use of the robotic software and the patient’s anatomy in vivo. The acetabulum is single-reamed, and the final cup is impacted in the desired position. The proximal femur is broached with increasingly sized broaches until rotational and axial stability has been achieved. A trial femoral neck and head are attached to the final broach, and the hip is reduced. Posterior and anterior hip stability are assessed, and leg length and offset are rechecked via the robotic system. Once the surgeon is satisfied, the hip is dislocated, the broach is removed, and the final femoral stem and head are manually implanted. The hip is then reduced for the final time. Closure is performed according to surgeon preference. Alternatives: Surgical alternatives include THA with use of manual instrumentation or navigation through other approaches to the hip, including the direct anterior, anterolateral, and direct lateral approaches 5–7 . Nonoperative alternatives include physical therapy, the use of nonsteroidal anti-inflammatory pain medication, and intra-articular corticosteroid injections 8 . Rationale: Robotic-assisted THA is particularly advantageous in patients with abnormal spinopelvic kinematics who require precise and specific component positioning to optimize hip stability 9–11 . In these patients, manually placing components relative to anatomic landmarks may lead to functional malpositioning and ultimately dislocation. Additionally, cases in which there is an anticipated difficulty in acetabular exposure or preparation because of a large body habitus or large pannus, retained acetabular hardware, or severe acetabular wear or dysplasia may benefit from the use of this technique 9 . Expected Outcomes: Patients who undergo robot