2015- Domb et al. Does Robotic-Assisted Computer Navigation Affect Acetabular Cup Positioning in Total Hip Arthroplasty in the Obese Patient?

Asheesh Gupta, MD, MPH, JohnM. Redmond,MD, Jon E. Hammarstedt, BS, Alexandra E. Petrakos, BA, S. Pavan Vemula, MA, Benjamin G. Domb, MD

Obese populations present challenges for acetabular cup placement during total hip arthroplasty (THA). This study examines the accuracy of acetabular cup inclination and version in the obese patient with roboticassisted computer navigation. A total of 105 patients underwent robotic-assisted computer navigation THA with a posterior approach. Groups were divided on body mass index (BMI, kg/m2) of b30, 30-35, and N35. There was no statistical difference between the BMI b30 (n = 59), BMI 30-35 (n = 34) and BMI N35 (n = 12) groups for acetabular inclination (P = 0.43) or version (P = 0.95). Robotic-assisted computer navigation provided accurate and reproducible placement of the acetabular cup within safe zones for inclination and version in the obese patient.

Obesity remains a significant challenge to medical practitioners as theworldwide obesity rate has nearly doubled since 1980 [1]. According to the World Health Organization (WHO) over 500 million people worldwide are considered obese. TheWHO's definition of obesity is calculated by the body mass index (BMI) defined as a person's weight in kilograms divided by the square of his height in meters (kg/m2). A BMI ≥25 kg/m2 is overweight, and a BMI ≥30 kg/m2 is obese. Obesity is subdivided into class I (30-34.9 kg/m2), class II (35-39.9 kg/m2), and class III (≥40 kg/m2) which is defined as "morbid obesity."

Obesity is a major risk factor for noncommunicable diseases such as cardiovascular disease (heart disease and stroke), diabetes, musculoskeletal disorders (including osteoarthritis), and some cancers (endometrial, breast, and colon). Total hip arthroplasty (THA) in the obese patient presents a unique set of challenges to the surgeon. Morbid obesity has been shown to increase mean operative time for total hip arthroplasty. The risk for dislocation in THA has also been shown to be increased in obese patients

Component positioning in the obese patient can present a challenge to surgeons. Malpositioning of the acetabular cup can result in increased risk for dislocation, higher bearing surface wear, and component instability