Clinical Outcomes Are Comparable With Robotic and Manual Total Hip Arthroplasty
Key findings
- This study is the first to compare patient-reported outcomes after robotic and manual total hip arthroplasty (THA) using thresholds for clinical relevance: the minimal clinically important difference for improvement (MCID-I) and worsening (MCID-W)
- Data were analyzed retrospectively on 341 patients who underwent robotic THA and 1,023 patients who underwent manual THA, matched on age, sex, body mass index, and Charlson Comorbidity Index
- The MCID-I and MCID-W were similar for the two groups on the PROMIS Global Health Physical, PROMIS Global Health Mental, PROMIS Physical Function Short Form 10a, and Hip Injury and Osteoarthritis Outcome Score–Physical Function Short Form
- The two groups were also similar in implant survival rates, 2-year revision rates, and 90-day rates of pulmonary embolism, deep vein thrombosis, dislocations, emergency department visits, and hospital readmissions
- The choice between robotic and manual THA should center on rigorous patient selection, shared decision-making with the patient, and an institution-by-institution consideration of the potential added costs or cost savings of robotic THA
The introduction of robotic technology in total hip arthroplasty (THA) has been associated with more accurate and more precise component positioning, reduced leg-length discrepancy, and shorter length of stay. Patient outcomes are unclear, though. Primary studies have compared postoperative scores for robotic and manual THA, but numerical changes may not always be clinically meaningful.
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Christopher M. Melnic, MD, Perry L. Lim, BS, and colleagues, of the Department of Orthopaedic Surgery at Massachusetts General Hospital, are the first researchers to use established thresholds for clinically relevant changes to examine patient outcomes after robotic versus manual THA. In The Journal of Arthroplasty they show robotic assistance does not reduce the likelihood of achieving the minimal clinically important difference for improvement.
Study Methods
The team identified 5,431 patients who underwent primary elective THA between January 1, 2016 (the inception of a prospectively collected multihospital registry) and December 30, 2022. The patients completed at least one outcomes questionnaire preoperatively (0–6 months before index surgery) and postoperatively (6 months to 2 years afterward).
Because the patients were not randomly assigned to robotic versus manual surgery, the team matched them 1:3 according to age, sex, body mass index, and Charlson Comorbidity Index. That left 1,364 patients: 341 who underwent robotic THA and 1,023 who had manual procedures. All robotic THA was performed using the Mako Total Hip Robot (Stryker Corp., Kalamazoo, Michigan).
Small Differences in Scores
As in previous research, postoperative scores were significantly different between the groups, favoring manual THA:
PROMIS Global Health Physical
- Postoperative—49.1 for manual THA vs. 47.3 for robotic THA (P=0.002)
- Delta (difference between mean pre- and postoperative scores)—7.9 vs. 6.5 (P=0.001)
PROMIS Global Health Mental
- Postoperative—52.8 vs. 51.4 (P=0.02)
- Delta—Similar for the 2 groups
PROMIS Physical Function Short Form 10a
- Postoperative—45.8 vs. 43.9 (P=0.002)
- Delta—9.9 vs. 8.4 (P=0.007)
Hip Injury and Osteoarthritis Outcome Score–Physical Function Short Form
- Postoperative—83.3 vs. 80.3 (P=0.012)
- Delta—Similar for the 2 groups
No Differences in Clinically Important Change
On all four questionnaires, there were no significant differences between the manual and robotic THA groups with respect to achieving the minimal clinically important difference for improvement, having no significant change, or meeting the minimal clinically important difference for worsening.
During the first 90 days there were no significant differences between groups in the incidence of pulmonary embolism, incidence of deep vein thrombosis (none), and number of dislocations, emergency department visits, and hospital readmissions.
Neither was there any significant difference in the number of revision surgeries required in the first 2 years. The revision-free 1-year survival rate was 99% in both groups, as was the 2-year rate.
Guidance for Decision-Making
Some evidence suggests robotic assistance can be particularly helpful to lower-volume surgeons and for patients who have developmental hip dysplasia. In all cases, determinations about whether to use robotic surgery should center on rigorous patient selection, shared decision-making, and an institution-by-institution consideration of the potential added costs or cost savings.
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