Robotic-Assisted and Computer Navigation in the Direct Anterior Approach

David R. Maldonado

Matthew S. Hepinstall

Benjamin G. Domb

Key Learning Points

Robotic-assisted and computer navigation technologies allow total hip arthroplasty (THA) customization based on the patient’s unique anatomy.
Pelvic tilt has been recognized as a critical factor to be considered for acetabular component placement; as such, the current robotic-assisted and computer navigation technologies allow the surgeon to take this into consideration during THA preplanning and execution.
Robotic-assisted and computer navigation technologies can be used in conjunction with the direct anterior approach (DAA), combining the previously mentioned benefits with a less invasive approach.

Introduction

Primary THA is an effective treatment for end-stage hip osteoarthritis. Multiple advances have been made regarding bearing surfaces and design to prolong the longevity of implants. These improvements in survivorship have allowed focus on other aspects of surgical care. Rapid recovery and outpatient primary THA surgery have become commonplace, which accounts for some of the increase in popularity of the DAA. Additionally, robotic-assisted and computer navigation technologies were introduced to yield more accurate and reproducible acetabular cup placement while also allowing length, offset, and femoral version to be measured intraoperatively. These technologies also allow this procedure to be performed with the patient’s unique anatomy and pelvic incidence in mind. This chapter discusses these concepts through the lens of one specific platform (Figure 16.1)—the Mako Robotic Arm System (Stryker, Mahwah, NJ, USA) and the Hana table (Mizuho OSI, Union City, CA, USA).

FIGURE 16.1 A, The patient is positioned in the supine position on the Hana table in preparation for a right hip robotic-assisted THA through the direct anterior approach. B, Drapes extend to cover the feet.

Robotic-Assisted and Computer Navigation in Total Hip Arthroplasty: A Literature Review

The goal of robotic assistance is to improve component placement during THA, leading to the restoration of kinematics, decreased instability and impingement, and improved patient-reported outcomes. At the moment, several robotic-assisted options exist¹ and have evolved following the development of predicate systems over time. A landmark example was the Robodoc Surgical System (THINK Surgical, Fremont, CA, USA), which was one of the first robotic- assisted technologies available. The system used a preoperative computed tomographic image of the patient’s pelvis and hip, which generated a 3-dimensional (3D) virtual model of the joint. Based on these results, a surgical plan was generated that is customized to the patient’s anatomy. An active robotic arm was used to mill into the femoral neck, preparing a canal for the stem implantation. Bargar et al² demonstrated no failures due to stem loosening at a mean follow-up of 14 years using this technology.

Unlike Robodoc, the Mako robotic arm system is not fully automated and is instead based on haptic feedback technology. Nodzo et al³ prospectively evaluated the accuracy of THA implant placement using the Mako robotic arm in 20 patients. Using a tridimensional computed tomographic scan, an independent engineering team postoperatively assessed the acetabular version, inclination, and femoral version values that were obtained intraoperatively. The correlation between intraoperative and postoperative values for acetabular anteversion, acetabular inclination, and femoral component version was 0.87, 0.79, and 0.80, respectively. Moreover, intraoperative values obtained using robotic arm-assisted THA for the hip center, hip offset, and leg length significantly correlate with postoperative computed tomographic measurements. The authors concluded that the robotic arm technology was accurate for the measurement of acetabular and femoral version. These findings demonstrated that the robotic arm accurately places THA components.

Two of us published our results comparing the Mako robotic-assisted THA with manual THA at a midterm follow-up.⁴ Sixty-six robotic-assisted THAs were matched in a 1:1 ratio to manual THA based on age at surgery, sex, laterality, approach, and body mass index. In addition to the 89% reduced risk of acetabular implant placement beyond the Lewinnek safe zone and the 79% reduced risk of placement beyond the Callanan safe zone for the robotic-assisted THA, patients in this cohort reported higher patient-reported outcome measurements at a minimum 5-year follow-up. Another of us has shown that robotic arm assistance has a marked and immediate impact on the accuracy and precision of acetabular component position, even during the learning curve, whereas fluoroscopic guidance for the DAA requires substantial experience to improve component positioning.⁵

Instability after THA is a multifactorial problem⁶; however, component placement is one of the key elements impacting stability.⁷^,⁸ With conventional THA, the annual rate of dislocations after primary THA ranges between 0.2% and 10%.⁹^,¹⁰ Almost 50% of dislocations occur within the first 3 months after the index surgery¹¹ and over 75% within the first year.¹² Illgen et al¹³ performed a minimum 2-year follow-up study with Mako robotic arm-assisted THA in 100 consecutive patients and reported a 0% dislocation rate; the same result has been obtained by others.¹⁴

Computer navigation in primary THA has demonstrated increased precision in acetabular cup component placement relative to freehand.¹⁵ Notwithstanding, more research is needed to determine whether improvement in patient-reported outcomes, psychometric tools, and a reduction of complications and revisions is associated with this technology.¹⁶^,¹⁷

Authors’ Preferred Robotic-Assisted Surgical Technique

Preplanning

Patients received preoperative 3D computed tomographic scans to generate a 3D image of their hip and pelvis for the Mako robotic arm system.⁴ The software allows the surgeon to preoperatively assess and plan the acetabular version and inclination (Figure 16.2). Although we use the Lewinnek and Callanan safe zones as reference for the vast majority of our cases,⁴^,¹⁸ we recognized that these traditional safe zones for cup position may not apply for every patient, particularly in the presence of pathologic spinopelvic motion.¹⁹ Recently, the most current software version of this technology accounts for pelvic incidence during preplanning and enables simulation of standing and sitting positions to verify motion without component impingement (Figure 16.3).²⁰

FIGURE 16.2 Preoperative robotic-assisted left THA planning.

A, The difference measured in millimeters can be noticed on the screen between the operative (left) hip and the nonoperative side. B, The plan has been made. In this particular case, the following was selected: an acetabular cup size of 48 mm with 20° of anteversion and 40° of inclination, a cementless femoral stem size of 3/132°, and a femoral head of 36 mm + 2.5 mm. Changes in leg length and femoral offset can be seen in respect to both the nonoperative and operative sides.

FIGURE 16.3 Assessment for motion without impingement from the (left) standing to the (right) sitting position was also performed preoperatively.

For our current preoperative radiography protocol, every patient gets a lateral lumbosacral projection in the standing and sitting positions. We calculated the variation in sacral slope and pelvic tilt in both positions; these data are then used by the software to perform the previously mentioned simulations to determine if there will be any anticipated implant/bone impingement. We seek to match the patient’s native acetabular anteversion, keeping the anterior margin of the acetabular component at or just within the anterior wall of the acetabulum, while also targeting 10° to 25° standing and 20° to 35° sitting anteversion. In keeping with the concept of combined anteversion, we can partially compensate for abnormal femoral anteversion with changes in acetabular position. When these various targets conflict rather than overlap, we err in the direction of matching anatomy and choosing a large-diameter or dual-mobility bearing to optimize stability.

In planning the acetabular component size and position, we seek to optimize acetabular coverage and femoral head diameter while minimizing acetabular bone removal from the anterior and posterior walls of the acetabulum to preserve bone stock. Three-dimensional planning may be particularly helpful in cases of acetabular deformities such as those secondary to developmental hip dysplasia in which the robot helps plan and achieve the desired prosthetic hip center of rotation.

An additional goal is to use the smallest acetabular cup size appropriate for the bone resection. Previously, we have demonstrated that the use of this technology leads to acetabular bone stock preservation with smaller components needed compared with manual THA.²¹ With that goal in mind, the software allows the surgeon to visualize the cup position in the sagittal, transversal, and coronal planes because the amount of acetabular bone resection can be assessed and quantified by millimeter superiorly, posteriorly, and medially (Figure 16.4).

FIGURE 16.4 Acetabular cup preplanning in a left hip.

The sagittal, transversal, and coronal planes as the amount of acetabular bone resection can be assessed and quantified by millimeter superiorly, posteriorly, and medially.

Only gold members can continue reading. Log In or Register to continue