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Robotic Knee Replacement

What is robotic assisted knee replacement?

Traditionally, knee replacements are performed with manual instruments which involves an element of eyeballing by the surgeon. Robot-assisted joint replacement is a new advance in the field of total knee arthroplasty. This has been shown to improve the precision of knee replacement surgery. ROSA stands for Robotic Surgical Assistant.

No. It is important to understand that the robot does not perform the operation. Your surgeon still remains in control. The robotic system helps your surgeon perform the operation more precisely. Very fine corrections can be done intra-operatively which is difficult to perform by manual techniques (up to 0.5 mm and 0.5 degrees).

During conventional surgery, mechanical instruments are used to plan the bone cuts which involves some amount of eyeballing. In Robotic assisted knee replacement, a 3 D bone model is already created based on your 2 D x-rays. During surgery, the surgeon places tracker pins into the thigh bone and leg bone. The knee joint is mapped carefully by your surgeon and the optical camera in the robotic system captures the reference points (it is like a high-tech GPS system). Once the mapping is done, the surgeon then can fine tune the cuts based on the individual 3-D anatomy. Once the plan is approved by the surgeon, the ROSA will position the cutting guided precisely in the planned position for the surgeon to do the cuts. ROSA also has imageless option where the 3D mapping is directly done during surgery.

Total knee replacements are one of the commonly done orthopaedic procedures. Studies have shown that the have excellent long-term survivorship. However, multiple studies have shown that about 20% of the patients still are not happy with their knee replacements (i.e., 1 in 5 patients). The functional outcome and patient satisfaction following knee replacements are not as good as hip replacements. This has not changed significantly despite various improvements in implant designs and techniques like computer assisted surgery. While there are multiple reasons for less satisfactory outcome, it is being increasingly recognised that one of the problems may be that the gold standard neutral mechanical alignment technique (even if done accurately) may not be the correct target for several patients.

While aiming for the same alignment target for every patient may make the surgical procedures reproducible within the margin of human error, it probably means that even if the correct universal target of mechanical alignment is achieved perfectly during surgery, it may not be the correct target for that patient resulting in poor outcome despite good looking x-rays. If the alignment target is personalised, the knee replacement may feel more natural and potentially may result in better functional outcome. Essentially, the aim of personalised alignment knee replacement is to recreate the knee joint to pre-arthritic anatomy is the hope that we could reduce the proportion of dissatisfied patients. There are recent reports indication that functional outcome following personalised alignment technique may be better than conventional technique.

It is important to understand that the personalization of alignment is not just in a single plane. Knee joint is a complex 3-dimensional structure. It is quite difficult for the human eye and conventional mechanical instruments to do this personalization. In addition, while personalization is desirable, knee replacements are still mechanical devices and hence personalization still probably should be within certain limits to minimise mechanical failure. This required a precise tool to execute the plan. This is where the Robotic Assistant like the ROSA come into play. ROSA was initially used for brain surgery and now has been adapted to help with knee replacement, bringing in the precision which is difficult to be matched by human eye. Multiple studies have shown that robotic assisted knee replacement is more precise compared to conventional mechanical instruments. There are also recent studies suggesting less soft tissue damage and faster recovery following Robotic assisted knee replacement.

Mr. Ganapathi has been performing 3-D planned knee replacements using MRI based patient specific 3-D moulds since 2012. In his vast experience of almost 1000 knee replacements using 3D mould technique, Mr. Ganapathi has gained significant experience in 3D planning including Personalised Alignment. However, the 3 D mould technique requires MRI scan and also creation of 3D moulds. The advantage of using ROSA is that there is no requirement for MRI scans and 3D moulds. Finer adjustments could also be done easily during surgery with ROSA.

Mr. Ganapathi has been using ROSA in his NHS practice already since October 2021. With personalised alignment technique, the requirement for soft tissue releases have become very less and patients seem to be recovering quicker in general. This is also shown in the scientific literature.

Recent studies are indicating better functional outcome with Personalised Alignment technique as it makes the knee replacement feel closer to your natural knee joint. The aim of Personalised knee replacement using Robotic assistance is to reduce the proportion of knee replacement patients with less-than-optimal outcome. However, the knee joint is quite complex structure and there are still many unknown factors which may result in less than satisfactory outcome. Other complications of any major surgery like infection can still occur resulting in less-than-optimal function.

Any patient who needs a knee replacement could be considered for Robotic knee replacement.

Mr. Ganapathi offers Robotic knee replacement at Spire Murrayfield Hospital, Wirral. For enquires about Robotic Assisted Knee replacement and costs, please contact the customer service team at Spire Murrayfield Hospital at Tel: 0151 929 5408

Scientific Literature:

  1. Patient-reported outcomes after total hip and knee arthroplasty: comparison of midterm results

J Arthroplasty. 2009 Feb;24(2):210-6.

Vikki Wylde 1Ashley W BlomSarah L WhitehouseAdrian H TaylorGiles T PattisonGordon C Bannister

Abstract: The aim of this study was to compare the midterm functional outcomes of total knee arthroplasty (TKA) and total hip arthroplasty (THA). A cross-sectional postal audit survey of all consecutive patients who had a primary joint replacement at one orthopedic center 5 to 8 years ago was conducted. Participants completed an Oxford hip score or Oxford knee score, which are self-report measures of functional ability. Completed questionnaires were returned from 1112 THA patients and 613 TKA patients, giving a response rate of 72%. The median Oxford knee score of 26 was significantly worse than the median Oxford hip score of 19 (P < .001). In conclusion, TKA patients experience a significantly poorer functional outcome than THA patients 5 to 8 years postoperatively.

  1. Comparison of hip and knee arthroplasty outcomes at early and intermediate follow-up

Orthopedics. 2009 Mar;32(3):168.

Seamus O’Brien 1Damien BennettEmer DoranDavid E Beverland

Abstract: A common perception among clinicians and patients is that recovery is similar following total hip arthroplasty (THA) and total knee arthroplasty (TKA). Improvement in the outcomes of 337 THAs and 256 TKAs implanted by the same surgeon between April 2003 and November 2005 were compared. Improvement was measured using changes in Oxford hip and knee scores measured preoperatively, at first follow-up, and 1 year postoperatively for each patient. Improvements between preoperative review and first follow-up and between preoperative review and 1-year postoperative follow-up were significantly greater for THA compared to TKA patients. Improvements between first postoperative follow-up and 1-year postoperative follow-up were not significantly different between THA and TKA patients. Although THA patients displayed a significantly worse score preoperatively, they displayed a significantly better score at both first follow-up and 1-year postoperative follow-up. While both procedures improve postoperative pain and physical function, as measured by the Oxford score, improvements measured relative to preoperative levels were significantly smaller for TKA compared to THA patients. Despite recent advances in knee arthroplasty surgery, a significant proportion of TKA patients achieve relatively poor outcome scores postoperatively. This study shows that pain and function improve less and more slowly in the early and intermediate postoperative periods for knee compared to hip arthroplasty patients.

  1. Robotic-Arm Assisted Total Knee Arthroplasty Demonstrated Greater Accuracy and Precision to Plan Compared with Manual Techniques

J Knee Surg. 2019 Mar;32(3):239-250.

Emily L Hampp 1Morad Chughtai 2Laura Y Scholl 1Nipun Sodhi 3Manoshi Bhowmik-Stoker 1David J Jacofsky 4Michael A Mont 3

Abstract: This study determined if robotic-arm assisted total knee arthroplasty (RATKA) allows for more accurate and precise bone cuts and component position to plan compared with manual total knee arthroplasty (MTKA). Specifically, we assessed the following: (1) final bone cuts, (2) final component position, and (3) a potential learning curve for RATKA. On six cadaver specimens (12 knees), a MTKA and RATKA were performed on the left and right knees, respectively. Bone-cut and final-component positioning errors relative to preoperative plans were compared. Median errors and standard deviations (SDs) in the sagittal, coronal, and axial planes were compared. Median values of the absolute deviation from plan defined the accuracy to plan. SDs described the precision to plan. RATKA bone cuts were as or more accurate to plan based on nominal median values in 11 out of 12 measurements. RATKA bone cuts were more precise to plan in 8 out of 12 measurements (p ≤ 0.05). RATKA final component positions were as or more accurate to plan based on median values in five out of five measurements. RATKA final component positions were more precise to plan in four out of five measurements (p ≤ 0.05). Stacked error results from all cuts and implant positions for each specimen in procedural order showed that RATKA error was less than MTKA error. Although this study analyzed a small number of cadaver specimens, there were clear differences that separated these two groups. When compared with MTKA, RATKA demonstrated more accurate and precise bone cuts and implant positioning to plan.

  1. Early recovery following Personalised alignment’

Bone Joint J. 2018 Jul;100-B(7):930-937.

B Kayani 1S Konan 1J Tahmassebi 2J R T Pietrzak 1F S Haddad 3


Aims: The objective of this study was to compare early postoperative functional outcomes and time to hospital discharge between conventional jig-based total knee arthroplasty (TKA) and robotic-arm assisted TKA.

Patients and methods: This prospective cohort study included 40 consecutive patients undergoing conventional jig-based TKA followed by 40 consecutive patients receiving robotic-arm assisted TKA. All surgical procedures were performed by a single surgeon using the medial parapatellar approach with identical implant designs and standardized postoperative inpatient rehabilitation. Inpatient functional outcomes and time to hospital discharge were collected in all study patients.

Results: There were no systematic differences in baseline characteristics between the conventional jig-based TKA and robotic-arm assisted TKA treatment groups with respect to age (p = 0.32), gender (p = 0.50), body mass index (p = 0.17), American Society of Anesthesiologists score (p = 0.88), and preoperative haemoglobin level (p = 0.82). Robotic-arm assisted TKA was associated with reduced postoperative pain (p < 0.001), decreased analgesia requirements (p < 0.001), decreased reduction in postoperative haemoglobin levels (p < 0.001), shorter time to straight leg raise (p < 0.001), decreased number of physiotherapy sessions (p < 0.001) and improved maximum knee flexion at discharge (p < 0.001) compared with conventional jig-based TKA. Median time to hospital discharge in robotic-arm assisted TKA was 77 hours (interquartile range (IQR) 74 to 81) compared with 105 hours (IQR 98 to 126) in conventional jig-based TKA (p < 0.001).

Conclusion: Robotic-arm assisted TKA was associated with decreased pain, improved early functional recovery and reduced time to hospital discharge compared with conventional jig-based TKA.

  1. Patient satisfaction following total knee arthroplasty using restricted kinematic alignment

Bone Joint J. 2021 Jun;103-B (6 Supple A):59-66.

Sarag Abhari 1Thomas M Hsing 1 2Max M Malkani 3Austin F Smith 1Langan S Smith 4Michael A Mont 5Arthur L Malkani 1


Aims: Alternative alignment concepts, including kinematic and restricted kinematic, have been introduced to help improve clinical outcomes following total knee arthroplasty (TKA). The purpose of this study was to evaluate the clinical results, along with patient satisfaction, following TKA using the concept of restricted kinematic alignment.

Methods: A total of 121 consecutive TKAs performed between 11 February 2018 to 11 June 2019 with preoperative varus deformity were reviewed at minimum one-year follow-up. Three knees were excluded due to severe preoperative varus deformity greater than 15°, and a further three due to requiring revision surgery, leaving 109 patients and 115 knees to undergo primary TKA using the concept of restricted kinematic alignment with advanced technology. Patients were stratified into three groups based on the preoperative limb varus deformity: Group A with 1° to 5° varus (43 knees); Group B between 6° and 10° varus (56 knees); and Group C with varus greater than 10° (16 knees). This study group was compared with a matched cohort of 115 TKAs and 115 patients using a neutral mechanical alignment target with manual instruments performed from 24 October 2016 to 14 January 2019.

Results: Mean overall patient satisfaction for the entire cohort was 4.7 (SE 0.1) on a 5-point Likert scale, with 93% being either very satisfied or satisfied compared with a Likert of 4.3 and patient satisfaction of 81% in the mechanical alignment group (p < 0.001 and p < 0.006 respectively). At mean follow-up of 17 months (11 to 27), the mean overall Likert, Knee Injury and Osteoarthritis Outcome Score for Joint Replacement, Western Ontario and McMaster Universities Osteoarthritis Index, Forgotten Joint Score, and Knee Society Knee and Function Scores were significantly better in the kinematic group than in the neutral mechanical alignment group. The most common complication in both groups was contracture requiring manipulation under anaesthesia, involving seven knees (6.1%) in the kinematic group and nine knees (7.8%) in the mechanical alignment group.

Conclusion: With the advent of advanced technology, and the ability to obtain accurate bone cuts, the target limb alignment, and soft-tissue balance within millimetres, using a restricted kinematic alignment concept demonstrated excellent patient satisfaction following primary TKA. Longer-term analysis is required as to the durability of this method.


  1. Kinematic alignment versus mechanical alignment in primary total knee arthroplasty: an updated meta-analysis of randomized controlled trials

J Orthop Surg Res. 2022 Apr 4;17(1):201.

Binfeng Liu 1 2 3Chengyao Feng 1 3Chao Tu 4 5


Background: The purpose of this study was to perform an updated meta-analysis to compare the outcomes of kinematic alignment (KA) and mechanical alignment (MA) in patients undergoing total knee arthroplasty.

Methods: PubMed, EMBASE, Web of Science, Google Scholar, and the Cochrane Library were systematically searched. Eligible randomized controlled trials regarding the clinical outcomes of patients undergoing total knee arthroplasty with KA and MA were included for the analysis.

Results: A total of 1112 participants were included in this study, including 559 participants with KA and 553 patients with MA. This study revealed that the Western Ontario and McMaster Universities Osteoarthritis Index, Knee Society Score (knee and combined), and knee flexion range were better in the patients with kinematic alignment than in the mechanical alignment. In terms of radiological results, the femoral knee angle, mechanical medial proximal tibial angle, and joint line orientation angle were significantly different between the two techniques. Perioperatively, the walk distance before discharge was longer in the KA group than in the MA group. In contrast, other functional outcomes, radiological results, perioperative outcomes, and postoperative complication rates were similar in both the kinematic and mechanical alignment groups.

Conclusions: The KA technique achieved better functional outcomes than the mechanical technique in terms of KSS (knee and combined), WOMAC scores, and knee flexion range.