Keywords
orthopedic - TKA - RATKA - score - outcome
Advances in operative technology have led to the use of robotic-assisted devices in
several medical fields.[1]
[2]
[3] Recently, robotics have been adopted in adult reconstructive surgery.[4]
[5]
[6]
[7] The development of robotic arm-assisted total knee arthroplasty (RATKA) potentially
provides orthopedic surgeons an additional tool to achieve successful outcomes. Specifically,
RATKA has been found to be able to accurately and consistently achieve implant placement
along the hip–knee axis within the desired 3 degrees of alignment.[8]
[9]
[10]
Although mechanical axis alignment is important for long-term functionality and implant
survivorship,[11]
[12]
[13]
[14] it is unknown whether the improved positioning achieved using robotic technology
is superior to manual techniques in terms of patient outcomes. In fact, patient satisfaction
is so important that surveys, such as the Press Ganey survey, can impact a hospital's
reputation are shared with the public and can even affect surgeon reimbursement.[15]
[16]
[17]
[18]
[19]
[20]
[21]
As new technologies and surgical techniques such as the RATKA are introduced, it is
essential to verify their positive impact on patients. Limited data are available
assessing patient outcomes. Therefore, the purpose of this study was to assess short-term
patient outcomes in TKA patients, by specifically, using the Western Ontario and McMaster
Universities Arthritis Index (WOMAC) to compare (1) pain scores, (2) physical function
scores, and (3) total patient satisfaction outcomes at 6 months postoperatively.
Methods
Patient Selection
RATKAs performed by a single orthopedic surgeon at a high-volume institution between
July 1, 2016 and August 15, 2016 were included in this study. A total of 28 cemented
RATKAs were performed. The first 7 days of robotic-assisted device use (eight cases)
were considered as an adjustment period for both the surgeon and the operating room
team. This assessment was based on several factors: (1) the surgical technique for
using the robot, in terms of performance of bone cuts and soft tissue balancing, was
modified until a uniform method was established, (2) the learning curve time for the
surgeon performing the cases began normalizing closer to the mean operative time and
mean in-room time after an initial increase. This left 20 consecutive cemented RATKAs
that were analyzed in this study and matched to 20 consecutive manual TKAs performed
directly prior to implementation of the robotic technology. The mean age and standard
deviation (SD) for the RATKA cohort were 69 years (range: 50–88 years, SD: 10 years),
while for the manual TKA cohort was 67 years (range: 54–83 years, SD: 8 years). The
mean operative time and SD for the RATKA cohort was 79 minutes (range: 66–104 minutes,
SD: 10 minutes), while for the manual TKA cohort was 74 minutes (range: 50–106 minutes,
SD: 20 minutes). There were 14 (70%) women and 6 (30%) men in the RATKA cohort and
10 (50%) women and 10 (50%) men in the manual TKA cohort.
Robotic Total Knee Arthroplasty System Operative Details
A standard medial parapatellar approach with minimal medial release was performed.
A preoperative plan was made from a computed tomography scan. The robot used in this
study was Mako system (Stryker, Mahwah, NJ). A robotic-assisted checkpoint was placed
in the tibia, followed by a checkpoint in the femur. Navigation data points were then
collected from the tibia and femur. Using the robotic-assisted software, the prosthesis
was then manipulated allowing for optimal balancing and realignment. The robotic arm
was then brought to make sequential cuts first on the distal femur, the posterior
chamfer, anterior condyle cuts, anterior chamfer, and finally the proximal tibia.
Implant trials were then placed, the knee was brought into extension, and alignment
was checked with the robotic-assisted device both in extension and at 90 degrees of
flexion. Patellar tracking was also checked. After any soft tissue balancing was performed,
the appropriate implants (Triathlon Cruciate Retaining System; Stryker) were cemented
in place and alignment and tracking were once again checked before the knee closure.
Manual Total Knee Arthroplasty Operative Details
A standard medial parapatellar approach with minimal medial release was performed.
Measured resection techniques were utilized with intramedullary alignment for femoral
measurements and external alignment for tibial measurements. Sequential bone cuts
were made on the distal femur, posterior chamfer, anterior condyle cuts, anterior
chamfer, and finally the proximal tibia. Implant trials were then placed and trialed
by bringing the knee into flexion and extension, confirming appropriate alignment.
Patellar tracking was also checked. After any soft tissue balancing was performed,
the case was performed with cemented implants (Triathlon Cruciate Retaining System;
Stryker) similarly to how the robotic cases were done.
Postoperative Rehabilitation
Postoperatively, both the manual and RATKA patients followed the same rehabilitation
protocols. While the exact protocol followed by an individual patient might have been
unique to that patient, in general, patients started their rehabilitation within 1
day after their procedure. Initial stages of rehabilitation included weight bearing
as tolerated, stretching exercises, and the full weight bearing as the patient was
encouraged to walk on the implant. Once patients felt more comfortable, they were
then encouraged to start a light strength training program to help build surrounding
muscle tone. Almost all patients completed the above protocol at outpatient physical
therapy facilities and supplemented those visits with self-driven in-home exercises.
Western Ontario and McMaster Universities Arthritis Index Survey
The WOMAC is a commonly used survey to assess hip and knee arthritis.[22]
[23]
[24]
[25] The self-administered survey consists of 24 questions in three subcategories: pain
(5 questions), stiffness (2 questions), and physical function (17 questions). Higher
WOMAC scores correlate to worse total mobility and function. Both the manual and robotic
cohort patients completed these surveys during their 6 months postoperative visits.
Pain Scores
The pain score was assessed by having patients rank five items on level of difficulty.
Specifically, the patients ranked their pain levels during: (1) walking, (2) using
stairs, (3) in bed, (4) sitting or lying, and (5) standing upright. Higher pain scores
correlate to worse total mobility and function. Both the manual and robotic cohort
patients completed the pain survey during their 6 months postoperative visits.
Physical Function Scores
The physical function score was calculated based on 17 patient-reported items. Specifically,
patients were asked to assess their ability to: (1) descend stairs, (2) ascend stairs,
(3) rise from sitting, (4) stand, (5) bend, (6) walk, (7) get in and out of a car,
(8) shop, (9) put on and (10) take off socks, (11) rise from bed, (12) lie in bed,
(13) get in and out of the bath, (14) sit, (15) get on and off of the toilet, (16)
perform heavy domestic duties as well as perform, and (17) light domestic duties.
Higher physical function scores correlate to worse total mobility and function. Both
the manual and robotic cohort patients completed the physical function survey during
their 6 months postoperative visits.
Total Patient Satisfaction Score
The total patient satisfaction score was calculated by taking the sum of the patient
pain and patient physical function score.
Data Analysis
For each patient, the pain component, physical function component, and combined total
WOMAC score were calculated. Analysis was performed comparing the means, ranges, and
SDs of each component of each score, for both the manual and robotic TKA cohorts at
their 6 months postoperative clinic visit. Scores were recorded in a Microsoft Excel
Spreadsheet (2013 Microsoft Office Professional Plus; Redmond, WA). A cutoff p-value of < 0.05 was set to determine statistical significance of results. All statistical
analyses were performed using SPSS version 24 (International Business Machine Corporation,
Armonk, NY).
Results
Pain Scores
The mean postoperative pain scores for the manual cohort were found to be 5 ± 3 (range:
0–10, [Table 1]). The 6 months postoperative mean pain score for the robotic cohort was found to
be 3 ± 3 (range: 0–8). The robotic-assisted cohort had a significantly lower mean
pain score (p < 0.05).
Table 1
Six-month manual versus robotic TKA WOMAC scores
|
Surgical technique
|
Manual TKA
|
Robotic arm-assisted TKA
|
p-Value
|
|
Mean 6-mo postoperative WOMAC—pain
|
5 ± 3 (range: 0–10)
|
3 ± 3 (range, 0–8)
|
<0.05
|
|
Mean 6-mo postoperative WOMAC—physical function
|
9 ± 5 (range: 0–17)
|
4 ± 5 (range, 0–14)
|
0.055
|
|
Mean 6-mo postoperative WOMAC—total score
|
14 (range: 0–27, SD: ±8)
|
7 (0–22; SD: ±8)
|
<0.05
|
Abbreviations: SD, standard deviation; TKA, total knee arthroplasty; WOMAC, Western
Ontario and McMaster Universities Arthritis Index.
Physical Function Scores
The mean physical function score for the manual cohort was found to be 9 ± 5 (range:
0–17, [Table 1]). The mean physical function score for the robotic cohort was 4 ± 5 (range: 0–14).
Although the physical function score for the robotic-assisted cohort was nearly half
of that for the manual cohort, no statistical significance was found between the two
scores (p = 0.055).
Total Patient Satisfaction Score
The mean total patient satisfaction score for the manual cohort was 14 ± 8 (range:
0–27, [Table 1]). The mean total patient satisfaction score for the robotic cohort was 7 ± 8 (range:
0–22). The robotic-assisted cohort had a significantly lower mean total patient satisfaction
score (p < 0.05), indicating greater patient satisfaction and clinical outcome for the robotic
cohort.
Discussion
Robotic TKA is a new surgical technology that has shown potential in achieving mechanical
axis alignment—a crucial factor for the success of any TKA.[11]
[12]
[13]
[14] However, along with these clinical outcomes, patient satisfaction contributes an
equal amount to the overall patient and surgical outcome. In fact, patient satisfaction
can play such an important role that it can markedly guide the direction of a clinical
practice. For this reason, it is necessary to continuously evaluate satisfaction surveys,
particularly for new technologies. Therefore, the purpose of this study was to assess
short-term patient satisfaction outcomes in RATKA versus manual TKA patients. Specifically,
we used the WOMAC patient satisfaction outcome survey to compare 6 months postoperative
mean pain, physical function, and total patient satisfaction scores. Patients who
underwent robotic-assisted surgery reported significantly better 6-month mean pain
and overall satisfaction scores (p < 0.05).
There were several limitations to this study. This study was small and conducted at
a single institution and each surgery was performed by a single orthopedic surgeon.
However, to this point, this particular study design helped limit potential confounding
factors, as both the manual and robotic-assisted cohorts were managed by the same
or similar house staff, clinical, and surgical teams. Furthermore, this study only
looked at short-term satisfaction (up to 6 months); therefore, future studies should
evaluate RATKA at longer time points.
Similar to this study, other studies have also found RATKA to be associated with better
patient satisfaction outcomes as compared with manual techniques. Although these are
older studies that used a different robotic-assisted device, their results are still
potentially relevant. Liow et al[26] performed a randomized controlled trial of 60 knees (31 robotic assisted and 29
manual), and found the robotic-assisted cohort to have higher Short Form (SF)-36 quality
of life measures. Specifically, the group noted a significant difference in SF-36
vitality (p = 0.03), emotional role (p = 0.02), and a larger number of patients reaching SF-36 vitality minimum clinically
important difference (48 vs. 14%, p = 0.009), all in favor of the robotic group. In addition, Kim et al[27] performed a study on 32 patients who underwent RATKA and found Knee Society scores
significantly improved postoperatively (27–82.8, p < 0.001).
In contrast, other studies have not found significantly greater patient satisfaction
after RATKA. Song et al[28] performed a prospective randomized controlled trial of 100 patients (50 robotic
assisted and 50 manual) who underwent unilateral TKA and found no statistical differences
between the cohorts with respect to postoperative Hospital of Special Surgery (HSS)
scores (robotic: 96, manual: 95) and WOMAC scores (robotic: 29, manual: 30). Song
et al[29] also performed another study with 30 patients who underwent bilateral sequential
total knee replacement with one knee operated on using the robotic device and the
other using the manual technique. The group found the robotic cohort to have nonsignificantly
better last follow-up HSS scores (95.2 vs. 94.7) and WOMAC scores (11 vs. 13) than
the manual cohort. Although these studies report nonsignificant differences in patient
satisfaction, both studies still report greater overall clinical satisfaction in patients
who underwent RATKA.
Although a paucity of literature exists comparing RATKA and patient outcomes, there
have been some studies performed on unicompartmental knee arthroplasty (UKA). Pearle
et al[30] performed a multicenter prospective study on 797 patients (909 knees) who underwent
robotic-assisted UKA utilizing Mako system (Stryker). They had a mean 30-month (range,
22–52 months) follow-up period and found excellent results both with the survivorship
of the implant and with patient satisfaction. At the 2.5-year follow-up point, only
11 knees required revision, resulting in a 99% survivorship. Also, the group found
that for the 898 knees (99%) that were not revised, 92% of patients were very satisfied
or satisfied with their surgery. Cobb et al[31] conducted a prospective, randomized controlled trial using the Acrobot Surgical
System (The Acrobot Co. Ltd., London, United Kingdom) to perform UKA on 27 patients
(28 knees) and found that patients who underwent robotic-assisted UKA had significantly
better American Knee scores at 6 and 18 weeks postoperatively (p = 0.004). In addition, Conditt et al[32] performed a multicenter study with six surgeons who performed robotic-assisted UKA
on 788 patients (890 knees) using Mako system (Stryker). The group found a 2-year
revision rate of 1.1%, and at a mean of 2-year follow-up, 93% of patients reported
very satisfied or satisfied outcomes.
Conclusion
As new technology continues to be introduced in the operative room, continued evaluation
of this technology is essential to ensure physicians are providing the best care possible
to their patients. To the best of our knowledge, this is the first study evaluating
short-term patient satisfaction outcomes in this new RATKA. This technology has been
shown to significantly improve mechanical axis alignment and reduce alignment outliers—factors
which can influence the survivorship and functionality of an implant.[11]
[12]
[13]
[14] However, since this technology is relatively new, additional studies correlating
clinical outcomes and patient satisfaction are necessary. The results from this study
show a distinct advantage in the patients who underwent RATKA with better overall
patient satisfaction scores.
