Total Hip Arthroplasty with Robotic Arm Assistance for Precise Cup Positioning: A Case-Control Study

Abstract

Objective: To determine whether more precise cup positioning can be achieved with robot-assisted total hip arthroplasty (THA) as compared to conventional THA.

Methods: In this study, between July 2019 and May 2021, 93 patients aged 23-75 years with osteonecrosis of the femoral head (ONFH) and adult developmental dysplasia of hip who underwent first hip surgery were included in the study. They were randomly assigned to either the robotic-assisted THA group (n = 45) or the conventional THA group (n = 48). After the operation, all patients were given routine rapid rehabilitation guidance. The duration of operation was recorded to estimate the learning curve through cumulative summation analysis. We compared the demographics, duration of operation, cup positioning, leg length discrepancy, hip offset, and Harris Hip Score between robot-assisted THA and manual THA. Precision in the positioning of the acetabular prosthesis using the MAKO system was also compared between the two groups.

Results: The mean duration of operation for the robot-assisted THA group was 91.37 ± 17.34 min (range: 63 to 135 min), which was significantly higher than that for the conventional THA group. When the number of procedures was increased to 13, the duration of operation in the robot-assisted group decreased significantly and gradually became stable. In terms of duration of operation, robot-assisted THA was associated with a learning curve of 13 cases. The mean amount of bleeding in the robot-assisted THA group was not significantly different from that in conventional THA group (328 ± 210 ml vs 315 ± 205 ml) (p = 0.741). There was no significant difference in the proportion of prostheses located within Lewinnek's safe zone between robot-assisted THA group and conventional THA group (69.81% vs 64.41%). The leg length discrepancy (LLD) was significantly smaller in the robot-assisted THA group than in the conventional THA group (p < 0.001), but both were within acceptable limits (10 mm). The inclination and anteversion angles of the acetabular prosthesis planned before operations were correlated with the actual measurement (r = 0.857 p < 0.001, r = 0.830, p < 0.001). After surgery, none of the patients experienced hip dislocation, aseptic loosening, or periprosthetic infection during the 3 months of follow-up.

Conclusion: The proportion of acetabular prostheses in the Lewinnek's safety zone was higher and the extent of LLD was significantly lower in the robot-assisted THA group, as compared to the same metrics in the conventional THA group. The MAKO robot improved the accuracy of implant placement in THA.

Keywords: cup positioning; learning curve; robot-assisted surgery; total hip arthroplasty.

Fig. 1

Scatter plot between the duration of operation in robot‐assisted THA. (The solid red line represents the mean duration of operation of robot‐assisted THA; the solid green line represents the mean duration of operation of conventional THA)

Fig. 2

The LC‐CUSUM analysis of the duration of operation in robot‐assisted THA group

Fig. 3

The scatter plot of cup positioning in robot‐assisted THA and conventional THA

Fig. 4

A robot‐assisted THA process for a patient with necrosis of the femoral head. A 67‐year‐old man complained that he had pain in his right hip joint when he was walking, which bothered him for 2 years. The X‐ray plain film of the hip joint showed necrosis of the right femoral head. In 2019 the patient underwent Mako robot‐assisted THA on the right side. The patient reported good recovery, no pain, and good mobility. (A) preoperative X‐ray of the hip; (B) MAKO Robotic Arm Interactive Orthopaedic System; (C) preoperative planning; (D) acetabular registration; (E) acetabulum reaming; (F) prosthesis impaction; (G) postoperative X‐ray of the hip