1 Introduction

Total Knee Arthroplasty (TKA) is one of the most common surgical procedures for the management of knee osteoarthritis, with significant improvements in patient activity and reduction in pain. However, despite advances in implant design, understanding of native knee kinematics, peri-operative pain management and early-rehabilitation protocols, 15–20% of patients report dissatisfaction after TKA.¹

Clinical outcomes after TKA are dependent on surgical factors, patient factors and implant factors. Studies have established the role of robotics in improving component positioning and limb alignment,^2–4 and more recent studies have reported reduced pain and improved clinical outcomes with the use of robotic-assisted techniques.^5,6

Song et al. previously published their report on differences in clinical outcomes between robotic and conventional jig-based TKA in patients undergoing bilateral simultaneous TKA, with one technique used in either knee.⁷ This was with the older ROBODOC system. Newer semi-autonomous robotic systems such as the MAKO (Stryker, Mahwah) feature haptic-boundary based systems, which reduced saw blade excursion within soft tissues, with minimal soft-tissue damage. Studies have shown that the use of the MAKO robotic-arm haptic boundaries reduced soft tissue trauma, reduced inflammatory markers in the post-operative period which translated into reduced pain and early recovery, and shorter length of stay.^5,8–11

No study till date has assessed differences in pain after surgery with the MAKO Robotic system in patients undergoing bilateral staged TKA (Two staged hospital admissions with two separate anaesthetic inductions). This unique population of patients who have undergone manual TKA in the past, provide insight regarding recovery after robotic TKA and its comparison to Manual TKA.

The aim of this study was to assess patient reported outcome measures and patient satisfaction, to manual and robotic TKA performed in the same patient, undergoing staged bilateral total knee arthroplasty.

2 Material and methods

This was a retro-prospective non-randomized study conducted at a high-volume arthroplasty centre of patients undergoing bilateral staged TKA, between January 2020 to January 2021. The study was approved by the Institutional Ethics Committee (SIEC/2020/437) and was conducted in accordance with the principles of the Declaration of Helsinki.¹²

Eligibility criteria include patients undergoing staged bilateral primary TKA, who underwent TKA for the first knee by manual jig-based techniques (MTKA). The eligible patients are those who opted for robotic-assisted TKA (RATKA) for the second knee. Interval between the two procedures is variable, based on patient preference. Inclusion criteria consisted of those patients undergoing bilateral staged TKA, who underwent MTKA and RATKA for primary OA of the knee, with a minimum follow-up of 1-year after the robotic TKA surgery. Exclusion criteria were-patients with previous history of knee surgeries on either side, post-traumatic arthritis, inflammatory arthropathy, requirement of higher degree of constraint in either manual or robotic TKA procedures, those who required revision or re-operation due to any cause and those lost to follow-up.

The patients included in this study underwent TKA surgery for both knees in the same institute, with surgery performed by a single surgeon. All knees (MTKA and RATKA) were operated with standard institutional pre-operative analgesic and anaesthetic protocols. All patients received only spinal anaesthesia, with single-shot post-operative adductor canal block, which was administered under ultrasound guidance in the operating room after sterile wound dressings were completed. All cases were operated via midline anterior incision and through a medial para-patellar approach, with initial soft-tissue releases done till the level of the deep medial collateral ligament. All cases received multi-site peri-articular analgesic cocktail infiltration based on uniform preparation, without variations in site of injection or constitution of the cocktail. Post-operative pain management and physical therapy protocols were identical in all cases. All patients are planned for discharge on the second post-operative day if rehabilitation goals are met and the patient has adequate analgesia.

Primary outcome assessed was the patient reported Oxford Knee Score (OKS). Secondary outcomes included patient satisfaction, comparison of patient perspectives on pain during physical therapy, time taken to walk without aid after surgery (mean duration in days), joint perception evaluated with the Forgotten Joint Score (FJS-12), and whether the patient would undergo manual or robotic-assisted TKA if they had to take the decision again. The questions framed for assessment of patient perspectives on recovery after TKA are summarized in Table 2. Patient satisfaction was assessed using a validated 4-point Likert scale with responses as follows- 1-Very satisfied, 2-Satisfied, 3- Dissatisfied and 4- Very dissatisfied. All patients were contacted either telephonically or were surveyed during follow-up in the out-patient department (OPD), after completion of a minimum of 1-year follow-up after the robotic-assisted surgery for the second knee.

3 Results

There was a total of 60 patients who underwent bilateral staged TKA, of which 5 patients (8.3%) were lost to follow-up. 55 patients were included in the final analysis. The demographic characteristics of the study population is summarized in Table 1. The minimum follow-up after robotic-assisted TKA (the second knee operated) was 1-year post-operative. The mean age of the study group was 66.6 years (SD = 7.45), with a female preponderance (n = 35, 63.6%) and 20 males (36.4%). Of the 55 patients included in final analysis, 18 (32.7%) patients were interviewed telephonically and 37 (67.3%) were interviewed in the Out-patient department.

The mean follow-up after the first-knee surgery with the manual jig-based technique was 5.3 years (SD = 3.5 years). The mean follow-up after robotic assisted TKA was 1.8 years (SD = 1.46 years). There was a significant difference in the follow-up duration after conventional and robotic procedures, however this is a single group of patients who serve as internal controls.

The frequency distribution of implants used during the manual jig-based TKA done for the first knee are summarized in Table 3. All implants used were done with PCL sacrifice and Posterior-stabilized design.

4 Discussion

This study demonstrated significantly higher patient satisfaction, reduced time taken for independent ambulation, and improved joint perception during daily activities (FJS) after robotic-assisted TKA. The primary outcome (Oxford knee score) was comparable between RATKA and MTKA at final follow-up. Though FJS showed statistical significance, the difference was not clinically relevant. The MCID of FJS score has been reported in literature to be a difference of 13.7 points.¹³ Majority of patients in this study would prefer to undergo RATKA if they had to undergo surgery again and would also recommend robotic-assisted TKA surgery to others.

Though sometimes methodologically challenging, comparisons between two interventions in the same patient undergoing bilateral total knee arthroplasty have certain advantages. The patients serve as internal controls which theoretically reduces confounding factors related to risk stratification, comorbidities, subjectivity of pain perception amongst others. Studies have been published in the past comparing two techniques (Robotic versus conventional TKA), comparing two philosophies (Gap balancing versus measured resection), different design philosophies (Ultra-congruent versus posterior-stabilized inserts) all in the same patient undergoing simultaneous bilateral total knee arthroplasty.^7,14–16

There is only one published report comparing robotic versus manual total knee arthroplasty in the same patient undergoing simultaneous bilateral knee arthroplasty by Song et al.⁷ They reported comparable outcomes with both techniques based on the HSS, WOMAC scores. Interestingly this paper also reported patient preference regarding robotic versus conventional techniques for TKA. Majority of the patients preferred robotic assisted TKA in the post-operative follow-up, during multiple assessments over a period. The findings in our study were similar.

Several studies have been published reporting patient reported outcomes after robotic total knee arthroplasty, comparing the technique with manual surgery done in a different set of patients. Some studies demonstrated clear reduction in pain and improved rehabilitation after robotic-assisted surgery in the early -postoperative period.^5,10,17 However, the results were comparable at completion a minimum of 12-months follow-up. Li et al. reported no benefit with RATKA at a very early follow-up of 30-days after surgery.¹⁸

The clinical benefits of robot-assisted TKA are often debated. The advantages of robotics over manual techniques in accuracy of implant positioning and limb alignment have been established. Recent studies have shown improved soft-tissue protection, reduced inflammatory markers, reduced opiate requirement in the immediate post-operative period.^9,19,20 These seem to contribute to faster rehabilitation and improved knee range of motion and patient comfort in the early assessment after TKA. However, some reports show that these advantages are short-lived, with long term outcomes showing no difference in functional outcomes or complication rates between robotic or manual techniques.²¹

We observed a similar trend with a greater proportion of patients more comfortable with the knee operated with robotic-assisted technique at 6-months follow-up. This marginally reduced at 12-months but was still significant. Patients reported ease with daily activities at around 1-year post-operative, with either technique.

Some studies have reported improved patient satisfaction after robotic TKA compared to manual TKA, with reports of increased satisfaction in the short-term follow-up.^6,22,23 These reports were similar to the findings of this study, which demonstrated a significantly higher number of patients were more likely to be very satisfied or satisfied after knee replacement with robotic-arm assistance. Zhang et al. performed an extensive systematic review and meta-analysis of the radiological and clinical benefits and concluded that RATKA was associated with improved patient reported outcomes in the short-term, however, the differences may not be clinically relevant based on MCID (Minimum Clinically Important Difference) values of assessment tools.²⁴

Assessment in patients undergoing simultaneous bilateral TKA (as reported by Song et al.) is often difficult as rehabilitation cannot be differentiated easily, as both knees are operated on the same day. It makes assessment of independent ambulation, functional status, satisfaction more difficult. Patients undergoing bilateral staged total knee arthroplasty provide us with a unique opportunity to assess patient perspectives and PROMS after each procedure, with a period of recovery between both knees. Patients can easily compare their recovery after both procedures and in our opinion, better placed to report outcomes reliably to differentiate between both procedures.

The main limitation of this study is the retrospective recall of post-operative recovery after the first knee, operated using manual jig-based techniques. However, outcome scores were calculated based on functional status at the latest follow-up, without recall bias. The patients and assessors were not blinded to the intervention. The overall sample of patients is relatively small, and the findings of the study cannot be generalized to all populations.

The strengths of this study are that all surgeries (manual and robotic) were performed at a single institute by a single senior arthroplasty surgeon. There were no variations in the institutional peri-operative pain and anaesthetic protocols in either group. There was limited attrition of the study sample at final follow-up with complete response rate on the generic questions used to evaluate patient perspectives on recovery.

5 Conclusion

Robotic-assisted surgery was associated with significantly improved patient satisfaction, faster independent ambulation compared to manual techniques in the same patients undergoing staged bilateral TKA. PROMs however, were comparable without a clinically significant difference. Majority of patients would prefer to opt for robotic surgery if they would undergo surgery again and majority of patients would recommend robotic-surgery to others seeking treatment.

Funding/sponsorship

This research did not receive any specific grant from funding agencies in the public, commercial or not-for-profit sectors.

Institutional ethical committee approval

This research was approved by the Institute Ethics Committee (SIEC/2020/437).

CRediT authorship contribution statement

Praharsha Mulpur: Methodology, Writing – original draft, Writing – review & editing. A.B.Suhas Masilamani: Conceptualization, Writing – review & editing. Mrinal Prakash: Formal analysis, Investigation. Adarsh Annapareddy: Investigation, Formal analysis. Kushal Hippalgaonkar: Supervision, Investigation. A.V.Gurava Reddy: Methodology, Resources, Writing – review & editing, Supervision.