PROMs in Total Hip Arthroplasty: A Comparison between Robotic Mako Assisted Versus Manual Technique

Introduction

Total hip arthroplasty is one of the most successful orthopedic interventions and, because of this, it has been called the surgery of the century [1]. The number of arthroplasty surgeries has significantly grown in recent decades, and the trend is that it will progressively increase. Population growth, progressive aging of the population, and the increased functional demand due to young patients with osteoarthritis and early necrosis will lead to an exponential increase in the demand for hip arthroplasty. The popularity of this procedure has increased, with a projected growth of 170% by 2030 and with more than 193,000 procedures performed annually in the United States [2].

Among the British population, the projection of historical rates predicts an exorbitant number of TKA and THA procedures in 2035: about 96,000 THAs and about 119,000 TKAs, although some forecasting models indicate even higher figures. The study was conducted to provide information to policy makers on what the future surgical demand on arthroplasty might be [3].

By 2030 in the US the demand for THA is estimated to grow by 174% and by 673% for TKA. The estimated number is necessary for a proper policy plan on the use of adequate resources that meet this need [4].

Patients undergoing arthroplasty surgery due to osteoarthritis have a high level of expectations before both THA and TKA surgeries. It is well known that generally both interventions significantly improve activities, even though the rate of satisfaction is considerably higher after THA. Preoperative expectations are a major contributor to the final degree of satisfaction one year after surgery. Therefore, preoperative interaction between health care providers and patients is essential to achieve a reasonable outcome [5].

There is increasing interest in robotic-assisted surgery which theoretically aims at achieving short-term and long- term outcomes, as well as a higher survival of the prostheses. Firstly, it is shown that it has a higher surgical precision in reducing misplacements which has been associated, especially for the hip, with higher rates of dislocation, impingement, wear, discrepancy in limb lengths and thus an increase in revisions. In the study by Hadley et al., it has been highlighted that the robotic-assisted THA performed better than the standard technique [6].

In the 2021 review by Ahmed Emara et al., it is shown that robotic-arm assisted hip replacement had higher rates of cup orientation within the Lewinnek and Callanan safe zones, improved femoral stem alignment and offset [7]. In the study by Marcovigi et al., robotic technology was used to assess the influence of native femoral version on final SV and combined anteversion using a straight, uncemented stem and excellent results were delivered [8].

Patient Reported Outcome Measures (PROMs) are questionnaires that are completed by patients in order to collect information about their health status. The term PROMs appeared in the early ’60 of the latest century and their use increased along with the growth of publications since 1980. Today’s challenge is to find reliable and valid instruments for scientific purposes, which are able to determine also the clinical decision-making process [9]. The use of instruments that measure the outcome from the patient’s point of view is well known also in orthopedics and thus in arthroplasty. PROMs instruments with methodological requirements must measure the patients’ general health and well-being, as well as be reliable, valid, determine responsiveness to changes and be acceptable to the intended population. Knowing the results is crucial to interpret whether a patient has had real improvement, for example after surgery [10]. Unfortunately, today there are major obstacles that prevent its full implementation, its proper use and especially the benefits that might result from the use of Patient Reported Outcome Measures [11].

Our study focuses on the use of PROMS because we strongly believe – as Eric C. Makhni explains in his recent 2021 study – that these comprise valuable data, when combined with traditional clinical information and are invaluable tools for improving care and in shared decision-making with patients. PROMs should be introduced in preoperative and postoperative care for clinical monitoring and should be used for predictive analytics and for value-based healthcare delivery pathways [12].

Materials and Methods

The study was approved by Ethics Committee for Clinical Trials of Tuscany Region with Prot. n°13111- 2018 (June 18, 2018) and Det.n°1594 (June 20, 2018).

The observational study was carried out at a hospital in the Asl Toscana Sudest from November 2017 to March 2019. The study considers a sample of patients operated on hip arthroplasty, both by robotic-arm assisted technique and by standard manual technique.

Results

A total of 94 robotic-asssited THA surgeries were performed between Nov 2017 and March 2019. Among all, 70 patients participated in the study and in follow-up visits that lasted for 12 months (Table 1). There were 36 males and 34 women, with a mean age of 63,76 years. Laterality was 30 left-THA and 40 right-THA. All patients were admitted to the orthopedic department with an average hospital stay of 3.07 days (LOS). Among these, 40 patients were then hospitalized in the low/medium-intensity rehabilitation department, with an average of additional 2.98 days.

The other 30 patients were discharged home directly from the orthopedic surgery department. 37 out of 70 patients were ambulatory on day 0, i.e., the same day of surgery, about 3-4 hours after surgery was completed. The other 33 were ambulatory on day 1, that is the morning after surgery. Walking aids could be either the walker with arm support or forearm crutches, depending on whether the patient felt safe or not.

Hemoglobin before surgery averaged 15.12 (11.6 min - 17.1 max), at discharge it was 11.47 (8.1 min- 14.6 max). ASA-score data were collected. There were 12 patients with ASA 1, 42 patients with ASA 2, 6 patients with ASA 3, 10 patients with unspecified ASA in medical records.

The patients’ height was also measured, with an average of 167, 95 cm. Among these, 159 cm was noted in females and 176, 5 cm in males. The average weight was 82, 24 kg. Among these, 73 kg were registered in females and 92 kg in males. The average BMI was also monitored. The average score was 29, 01; 28, 54 of which were females and 29, 48 were males.

Discussion

Robotic surgery in literature appears to have higher outcomes both in THA and TKA, as compared with standard surgery. Specifically, the preeminence of robotic prosthesis has been demonstrated by accuracy in placement of prosthetic components. Through the use of robotics, the so-called outliers in anatomic-radiographic outcomes are reduced.

Robotic hip replacement appears to be associated with greater accuracy of both the acetabular and femoral components. This facilitates restoration of the center of rotation with the corresponding acetabular, femoral and global offsets. In addition, the MAKO technique offers a customized dynamic 3D-planning by matching preoperative CT data with intra-operatively detected data. This enables to quantify and to correct pathological-anatomical data, as well as the components’ sizing, such as length, offset, cup and femoral neck version, and especially the so-called combined version (cup + acetabulum). The mutual anteversion of the acetabular cup and stem neck is the key element for the functional kinematics of hip prosthesis and for reducing the probability of negative phenomena in hip replacement i.e. impingement, edge loading and instability, which could consequently lead to dislocation and increased wear. Robotic planning and execution reduce the likelihood of these negative phenomena occurring, as they can highlight and reduce anatomical orientation defects through anteversion modification of prosthetic components. (Images 1-2-3-4-5 by Dr P.Caldora) (Figures 2-6).

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Robotic hip replacement thus appears to be associated with greater accuracy of the center of rotation, optimization of offset and precise positioning of the acetabular component, as compared with manual prosthesis. This was confirmed by the study of Kayani et al. that emphasized the Mako system, since this gave more favorable outcomes with similar complications to standard surgery [22].

In addition to the level of accuracy of the prosthetic components, other comparative factors related to the manual technique were studied. The study by Caldora et al. (2020) demonstrates that there is statistical significance in the reduction in the number of transfusions (p<0.001) and hospital stay (p<0.01) in favor of robotic-assisted THA versus standard surgery [23]. The 2021 study by Clement et al. reported that patients who underwent robotic-assisted THA had a greater functional outcome than standard THA, related to improved positioning of components, although there was no difference between the two groups in postoperative general health and satisfaction [24].

In our previous study by Banchetti, et al. [25] we observed that - when comparing PROMs between 120 standard procedures and 100 robotic THA - there was statistical significance in favor of robotics concerning the length of hospital stay, which was lower in robotic prostheses. There were no significant differences between the robotic and standard groups with regard to the outcomes obtained from the PROMs used but rather a significant improvement with regard to postoperative outcomes 2 years after surgery in both surgical techniques (P<0.001).

Although the advantage of implant accuracy is evident when using robotics, other authors amplify some of its limitations, such as the robot’s cost, the presence of additional professionals, such as the biomedical engineer during operation or the consideration that not all hospitals are able to acquire this technology, which is considered expensive and not yet beneficial if compared to cost [26].

Domb’s [27] study reports that 5 years after surgery outcomes are more favorable for robotic prostheses with higher scores than standard prostheses, with 89% reduced risk on acetabular implant placement.

Despite all, scientific studies highlight how hip or knee replacements – operated on with manual and robotic techniques – result in significant improvement from a functional, quality-of-life, and pain point of view. Some studies specify that the outcomes in THA are superior to those concerning TKA, with higher quality-of-life satisfaction in THA. Satisfaction seems to derive from a high level of expectation in the preoperative phase: where it is higher, the outcome seems greater from a quality perspective [28, 29].

Other studies affirm that expectations with regard to pain and walking ability are moderately or not at all correlated with satisfaction [30, 31].

The findings of our study reveal how robotic-assisted THA have an inevitable progressive improvement in both pain and quality of life over time, before surgery and up to the first year, with statistical significance. Furthermore, the satisfaction scale has become increasingly crucial over time for the outcome of arthroplasty. It does not clarify what the patient is satisfied with, and for that reason it is definitely a multidimensional construct. It can be related to the process of care delivery, empathy with the surgeon and nursing staff, or negatively linked to problems in the postoperative process (delay in starting physical therapy or difficulty in motor recovery, persistent pain). Satisfaction could be correlated with improvement in the ability to perform work or recreational activities and with the extent of pain relief [32, 33, 34]. In our study, robotic patients reported an excellent outcome 1 year after surgery (4, 77±0, 54), very close to the maximum score, which is 5. Also patients operated on by standard method have a very high value 1 year after surgery (4,47±0,83) but what is definitely interesting is the outcome obtained in our study in favor of robotics, with statistical significance (P<0,05). More studies are necessary in order to define the factors that influence patient satisfaction after THA surgery – especially in robotic-assisted THAs – such as young age, good preoperative physical condition and good mental health, including the optimistic expectation of results by the surgeon [35].

Overall, it is evident that, one year later, meeting the expectations [36] is highly correlated with improvement in mobility and pain. This confirms that satisfaction is not associated with age, gender, race or social status [37] but with the expectation in the preoperative phase of an optimal quality of life with absence of pain.

We can deduce, then, that the perception of forgetting the artificial joint during everyday life and in recreational activities is an added value that thus determines the patient’s satisfaction and the patient’s preference of one surgical technique over another [38].

The FJS scale provides us with important information with regard to the process of adaptation to prosthesis and it is in line with the outcomes of the Oxford scale. For this reason, many studies are moving toward the combined use of the Oxford and FJS scales to have more and more specific data on functional outcomes in arthroplasty [39]. In the study by U. G. Longo, et al. [40], a range of FJS values (69.8 to 91.7) was found, which is considered as cut-offs within which there is a minimal clinical difference (MCDI) and an acceptable state of symptoms (PASS) that can correspond to a satisfactory quality of life.

On the other hand, in the study by Puliero, et al. [41] it is ascertained that only with scores higher than 93 in the FJS, patients perceive the replaced hip as if it is natural, that is, they forget that it is artificial. However, in 20-30% of cases, the Womac scale combined to FJS failed to identify the forgotten joint because patients did not perceive adaptation, although the outcomes reached the maximum score.

In our study, the 1-year values of FJS in robotic-assisted (86.27± 21.10) and standard (87.02 ±16.57) arthroplasty are similar. There is no statistical significance and they are within the range of scores considered as cut offs in Longo’s study, and in any case not far from Puliero’s 93 score. In the two types of interventions, the outcomes cancel each other out in the long term. Therefore, more studies are needed in order to strengthen the evidence for comprehensive answers.

Conclusions

Patients who undergo hip arthroplasty surgery all have a high level of expectation and clinical outcomes are very satisfactory regardless of the robotic technique. The index of functional improvement, well-being, satisfaction and quality of life increases with time after surgery. Some studies report more favorable short/medium-term outcomes, fewer transfusions, and fewer days of hospital stay in the robotic- assisted surgery compared to the standard one, while differences in function and quality of life in the first year after the two different types of surgery tend to cancel each other out. Our study showed no statistically significant differences between the robotic and manual samples with regard to the FJS scale but instead it gave statistical significance for the satisfaction scale. The latter parameter could also depend on the psychological conditioning of the patient for being operated on with advanced technology but still represents a positive aspect for the patient and a coefficient of attraction for the hospital and the surgical team.

This study makes some points that need to be evaluated more carefully and with more targeted studies of higher level. One question is, why the greater accuracy of prosthetic component placement with the robotic technique does not result in better functional outcomes (FJS scale) one year later, when compared to the sample of manually operated hip replacements? The other question is, how come that at the same time robotic patient shows greater satisfaction?

Our study has some limitations. It was a retrospective analysis and the sample had a small number, especially of patients operated on with standard method. In addition, the lack of long-term follow-ups does not highlight any differences in complications in both robotic and standard groups of patients. Further research is needed in order to report functional outcomes, data on survival of the prosthesis, complications, cost-effectiveness but also research with regard to long-term PROMs i.e. beyond 10 years.