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67 (); 7-13
doi:
10.1016/j.jor.2024.12.016

Comparison of outcomes between resurfaced and unresurfaced patella in total knee arthroplasty using medial congruent liners: A retrospective study

, , , ,
Department of Orthopaedic Surgery, College of Medicine, University of Saskatchewan, Saskatoon, SK, Canada

⁎Corresponding author: Johannes M. van der Merwe. jov777@mail.usask.ca

Received: , Accepted: ,
Professor P K Surendran Memorial Education Foundation
Disclaimer:
This article was originally published by Reed Elsevier India Pvt. Ltd. and was migrated to Scientific Scholar after the change of Publisher.

Abstract

Abstract

Total knee replacements are becoming more prevalent. There is still a lot of controversy regarding patellar resurfacing. Surgeons advocating for resurfacing state reduced risk for anterior knee pain and need for future revision surgery. Our goal was to determine if patients would have similar outcomes if the patella is left unresurfaced or resurfaced with a medial congruent liner design.

A multi-surgeon retrospective chart review was conducted in a tertiary academic center, to identify all patients who received a total knee arthroplasty utilizing a medial congruent (MC) polyethylene liner between January 1, 2020 to December 31, 2020. All included patients were subsequently sent a survey package via mail to complete. Patients who did not return mail packages were contacted via phone.

We included 188 patients in the final analysis. There was no statistical difference between the groups in regards to age (p = 0.77), sex (p = 0.075), BMI (p = 0.22), hospital stay (p = 0.86), laterality (p = 0.51), ASA score (p = 0.52), Kellgren Lawrence medial compartment OA score (p = 0.33) and Kellgren Lawrence lateral compartment OA score (p = 0.49). There was a statistically significant difference in favour of the control group (patella not resurfaced) with the KOOS JR score (p = 0.045). This difference was not observed with the Kujala score (p = 0.98) and the Oxford knee score (0.89).

There might be a role in performing a patella resurfacing, even in newer total knee designs. We did not observe a clinically meaningful difference in PROMS between PR and non-PR TKA at medium-term follow-up. In addition, we did not observe any demographic factors that influenced the surgeon's decision to perform patella resurfacing. Further high-quality research is warranted.

Keywords

Medial congruent
Total knee arthroplasty
Patella resurfacing
Patient satisfaction
1

1 Introduction

1.1

1.1 Background

Total knee Arthroplasty (TKA) is a commonly performed successful procedure that mainly aims to improve pain and function after end-stage knee osteoarthritis.1–3 Addressing the patella is left at the surgeon's discretion. Traditional indications to resurface the patella include older age, inflammatory arthritis, patellar mal-tracking, and obese patients.4 Some surgeons always resurface the patella while others never resurface or selectively resurface. Patella resurfacing (PR) remains a controversial issue with no definitive evidence supporting its use.5 Proposed advantages of PR include reduced rates of anterior knee pain, lower rates of revision and costs, and higher patient satisfaction.1 Disadvantages include the potential for patellar fractures, extensor mechanism disruption, patellar clunk syndrome, and mal-tracking.1 With the surgical volume of TKA expected to increase over the next decade due to an aging population, it is crucial to re-address the need for patella resurfacing in order to deliver the best results.6,7 Newer TKA designs claim improved patella femoral dynamics due to lateralized proximal trochlear design, single radius knee design, deepened trochlear grooves, increased distal extent of the trochlea groove, and conformity of the anterior flange groove.4 Contrary to older TKA designs, newer designs have shown promise in outcomes by not resurfacing the patella.8–10 Medial congruent TKA designs state asymmetric femoral condyles (lateral femoral condyle larger than medial, which promotes femoral roll-back), anterior constraint of the liner, and potential retention of the PCL. These changes theoretically should eliminate the potential for paradoxical anterior translation of the lateral femoral condyle, which in turn could decrease anterior knee pain 11,12.

Unfortunately, even though multiple studies have been performed to assess the need for PR, they are limited by reduced numbers which can lead to low statistical power; in addition, there are a wide variety of components which influence the outcomes due to confounding variables, as well as a wide variety of patient-reported outcome measures are being used with only short-to-medium term follow-up.4

1.2

1.2 Objective

We aimed to determine if there is a difference in patient satisfaction between PR or non-PR in a modern TKA design using a medial congruent concept only (Persona Medial Congruent TKA, Zimmer-Biomet, Warsaw, IN). Secondly, we assessed if there are specific demographic factors that influence surgeons’ decision to resurface the patella or not. To assess the satisfaction, we used 3 patient-reported outcome measures (PROMS): Oxford Knee Score (OKS), Knee Injury and Osteoarthritis Outcome Score, Joint Replacement (KOOS JR), and the Kujala Score. PROMS have become increasingly important for assessing outcomes after TKA, not solely for research purposes but also in clinical practice. OKS is a 12-question PROMs designed to evaluate pain and function before and after a TKA. It was developed and validated in 1996 and 1998, respectively. Scoring ranges between 12 (fully functional) and 60 (maximum difficulty).13 KOOS JR is a short-form PROM that was developed in 2016 and consists of 7 questions derived from the original 42-question KOOS score.14 It is graded out of 28 by summing the raw responses. The result is then converted on a scale from 0 to 100, where 100 reflects perfect knee health.15 The Kujala Score is a 13-question survey that assesses symptoms that correlate with anterior knee pain. It is graded out of 100 with 100 being the highest score and equates to perfect knee health.16 The minimal clinically important difference (MCID) reflects the minimum change in PROMs that a patient perceives as a change in their health.17 The MCID for KOOS JR is 16 points, Oxford Knee Score is 6.1 and the Kujala Score is 10 points.13,18,19

1.3

1.3 Significance

To our knowledge, there are no studies at present determining the satisfaction in patients undergoing PR in a medial congruent TKA design.

2

2 Patients and methods

After obtaining ethics approval (Bio-REB 3384) we did a multi-surgeon retrospective chart review utilizing the Discharge Abstract Database (DAD) from the University of Saskatchewan. The DAD was developed in 1963 and captures administrative, clinical, and demographic data on hospital discharges. We identified and included all patients who received a total knee arthroplasty utilizing a medial congruent (MC) polyethylene liner between January 1, 2020 to December 31, 2020. These patients then underwent a detailed radiographic review of their preoperative and postoperative imaging. Inclusion criteria were patients who had an MC polyethylene liner, data on patella resurfacing or non-resurfacing, Kellgren-Lawrence (KG) Grade 3 or 4 osteoarthritis (OA) of their medial and/or lateral tibiofemoral joints, and only mild-moderate (KG grade 1 or 2) patellofemoral degenerative changes. Exclusion criteria included those with incomplete data, inflammatory arthropathy, those in whom arthroplasty was performed despite low-grade pre-operative arthritis changes in the tibiofemoral compartments on radiographs (KG Grades 1 or 2), those with preoperative radiographically severe patellofemoral OA (KG grade 3 or 4), previous ipsilateral knee surgeries, or those who had ipsilateral hip arthritis with Kellgren-Lawrence Grade 3 or 4 radiographic changes. The included patient's charts were reviewed for relevant demographic data, and details pertaining to their total knee arthroplasty (brand of components, surgeon, laterality), ASA score, contralateral knee or hip surgeries, and patella resurfacing. We identified two groups: a control group (non-PR) and a treatment group (PR). All the included total knee arthroplasties (TKA) were performed in a tertiary center utilizing a Persona Medial Congruent bearing (Zimmer Biomet Inc, Warsaw, IN). All the surgeries were performed utilizing a medial parapatellar approach. All included patients were subsequently sent a blinded survey package via mail to complete. These mail packages consisted of educational material surrounding their operation (detailing the controversy surrounding patella resurfacings), the purpose of our study, and three separate knee patient-reported outcome surveys (KOOS JR Knee Survey, Oxford Knee Score Survey, and the KUJALA Questionnaire). The anonymous returned surveys (patient identifiers were used) were then entered into a database for statistical analysis. Patients in whom no mail package was returned were then contacted via phone, with a maximum of 2 attempts (once per day). All phone calls to collect data were performed by one investigator (WT) and each question with all answer choices was presented to every patient.

3

3 Statistical analysis

3.1

3.1 Group comparison

Both groups' demographic data was analyzed to ensure that cases and controls were comparable. Questionnaire scores were compared to determine the difference between groups. Either Fisher's exact test, Student's t-test, or the Mann-Whitney U test was employed, depending on the variable.

Fisher's exact test is a statistical test used to determine if there are non-random associations between two categorical variables in a relatively small sample size. It calculates the probability of observing a particular arrangement of data assuming that the null hypothesis (no association) is true.

Student's t-test is a statistical test used to determine if there is a significant difference between the means of two groups, taking into account the variability within each group. It assesses whether the means are significantly different from each other, considering the sample size and variance.

The Mann-Whitney U test is a non-parametric statistical test used to compare two independent groups to determine if their distributions differ significantly. It assesses whether the medians of the groups are statistically different, making minimal assumptions about the data distribution.

3.2

3.2 Correlation

Correlation is used to measure the strength and direction of the relationship between two variables, helping to understand how changes in one variable relate to changes in another. Correlation was assessed both between the group designation and the dataset, as well as between the certain variables within the dataset. Cramer's V, Point-biserial correlation, or Pearson Correlation coefficient were used, depending on the variables.

Cramer's V is a statistical measure used to assess the strength of association between categorical variables. It ranges from 0 to 1, with 0 indicating no association and 1 indicating a perfect association.

Point-biserial correlation measures the relationship between a continuous variable and a dichotomous variable. It ranges from −1 to 1, where positive values indicate a positive relationship and negative values indicate a negative relationship.

The Pearson correlation coefficient measures the strength and direction of the linear relationship between two continuous variables. It ranges from −1 to 1, where 1 indicates a perfect positive linear relationship, −1 indicates a perfect negative linear relationship, and 0 indicates no linear relationship.

4

4 Results

We identified 883 patients. After applying the inclusion and exclusion criteria we included 246 patients to receive the mail packages. We received completed questionnaires from 124 patients (50.4 %). After phoning the remaining 122 patients (49.6 %) we obtained data on a further 64 patients (26 %). We included 188 patients in the final analysis (76.42.%) (Fig. 1). The control group (non-PR) consisted of 79 patients (42 %) while the treatment group (PR) contained 109 patients (58 %). The mean follow-up was 45 months (39–51 months). The mean age between the groups was 68.18 (control group) and 67.87 (treatment group) (P = 0.77). The mean BMI between the control and treatment groups was 34.05 kg/m2 and 35.95 kg/m2, respectively (P = 0.22). There was no statistical difference between the groups in regards to sex (p = 0.075), laterality (p = 0.51), ASA score (p = 0.52), Kellgren and Lawrence medial compartment OA score (p = 0.33), Kellgren and Lawrence lateral compartment OA score (p = 0.49), and previous surgery on the contralateral knee (P = 0.88) (See Table 1). The mean hospital stay was 3.45 days in the control group and 3.41 in the treatment group (P = 0.86). There was no correlation found regarding the surgeon's decision to resurface the patella (PR) and the patient's age, BMI, sex, and ASA score (see Table 2).

Glow diagram of the methods of patient collection.
Fig. 1 Glow diagram of the methods of patient collection.
Table 1 Significance between the control group (no resurfacings) and treatment group (patella resurfacings).
Comparison between control and treatment group
Column Significance
t-test
Age 0,776133
BMI 0,223591
Hospital Stay days 0,864957
Fisher's exact test
Sex 0,075156
Side 0,514175
ASA 0,520364
Other knee already done before? 0,886925
Kellgren-Lawrence Medial Compartment OA 0,330642
Kellgren-Lawrence Lateral Compartment OA 0,496021
Table 2 Correlation between age,BMI,sex and ASA score on decision to resurface the patella during a Total Knee Arthroplast
Decision if Patella should be Resurfaced
Point-Biserial Statistic's value Significance
Correlations
Age −0,01826 0,776133
BMI 0,107469 0,223591
Cramer's V
Sex 0,13165 0,119656
ASA 0,210378 0,487293

There was a statistically significant difference in favour of the control group (patella not resurfaced) with the KOOS JR score (p = 0.048) (See Fig. 2). Using a minimally clinically important difference (MCID) of 1620 for the KOOS JR score it was not considered clinically relevant. There was also no statistically significant or clinically important difference observed between the Kujala score (p = 0.98) and the Oxford knee score (0.89) (SeeTables 3 and 4). When evaluating the individual sub-divisions that form part of the KOOS Jr score (stiffness, pain, and function/daily living) the main difference was observed with pain and function/daily living between the control and treatment groups (SeeTable 5). Pain was significantly better in the control group but function/daily living favoured the treatment group. Sub-analysis between adult reconstruction surgeons (high volume or fellowship-trained surgeons (ARS)) and non-adult reconstruction surgeons (low volume or not fellowship trained (non-ARS)) using the mean score for both the control and treatment group, demonstrated a KOOS JR (ARS 9.4; non ARS 5.24), Oxford Knee Score (ARS 18.84, non-ARS 21.42) and Kujala Score (ARS 71.06, non-ARS 74.02) which was not statistically different between the ARS and non-ARS groups, possibly due to the small sample size. There was a statistical difference between the ARS and the non-ARS groups in regards to performing patella resurfacing, with the non-ARS group doing significantly less patella resurfacings compared to the ARS group (P=<0.001) (See Fig. 3). There were no revisions in either group by the conclusion of the study period.

Mean KOOS JR score 0 = No resurfacings; 1 = Patella resurfaced.
Fig. 2 Mean KOOS JR score 0 = No resurfacings; 1 = Patella resurfaced.
Table 3 Assessment of significance between PROMS between control (no patella resurfacings) and treatment groups (patella resurfacing).
Comparison between control and treatment group
Column Significance
Mann-Whitney Test
KUJALA total 0,981284
OXFORD total 0,895094
KOOS JR ∗0,045552
Table 4 Mean values of PROMS between the control group and the Treatment group.
N Mean
KUJALA total Control group 79 67.35
Treatment group 107 71.06
OXFORD total Control group 80 19,91
Treatment group 108 18,41
KOOS Jr Control group 82 7.02
Treatment group 111 9,29
Table 5 Comparing the 3 subdivisions comprising the KOOS Jr score between the control and treatment group. ∗Mann-Whitney U test utilized.
N Mean
KOOS Question: S6 (Stiffness) (P = 0.617) Control group 67 1,58
Treatment group 88 1,59
KOOS Questions: P2,P3,P6,P9 (Pain) (P=<0.001)∗ Control group 79 3,76
Treatment group 108 5,3
KOOS Questions: A3,A5 (Function, daily living)(P=<0.001)∗ Control group 79 6,05
Treatment group 108 3,13
Bar chart comparing ARS and non ARS practises regarding patella resurfacing with TKA. 0 = no patella resurfacing; 1 = patella resurfacings.
Fig. 3 Bar chart comparing ARS and non ARS practises regarding patella resurfacing with TKA. 0 = no patella resurfacing; 1 = patella resurfacings.
5

5 Discussion

The key findings of this study include no minimal clinically important differences (MCID) between PROMs in PR and non-PR in medial congruent TKA's with a 3 year and 9-month follow-up. We did not observe any demographic factors that influenced the surgeon's decision to resurface the patella. There was no statistically significant difference in PROMS between ARS and non-ARS surgeons, but PR was statistically significantly more performed in the ARS group.

Patient satisfaction is crucial for the success of a TKA. While PROMs provide valuable insights into patient's perceptions of their outcomes, they are considered to be subjective with no clear standardization across studies and cultures. In addition, they might not capture all the aspects of patient satisfaction. PROMs however are commonly used to assess patient satisfaction. Multiple studies did not observe minimal clinically important differences (MCID) between PROMs in PR and non-PR TKA's.21–26,27,28,29 Two studies did observe a benefit in PR with TKA.27,28 They found a decrease in anterior knee pain and improved PROMs, although not clinically meaningful. We also did not observe a clinically meaningful difference between PR and non-PR in medial congruent knee designs.

We are unable to categorically explain why patients with a resurfaced patella experience poorer pain control but better function. Possible explanations could be better function due to improved mechanical alignment and stability provided by the PR, which can enhance mobility despite ongoing knee pain. Another explanation could be that patients experience less pain during specific activities or movements, leading to a perception of better function even if overall pain control is not optimal. Dong et al.28 commented that twenty-seven percent of patients preferred their PR and 21 % preferred non-PR, while around 50 % did not have any preference. In addition, Naeder et al.30 demonstrated with their expected-value decision analysis that the probability of having AKP following a non-PR TKA is 26 %, with only 74 % of patients achieving maximum health utility compared to 88 % in PR. This was similar in our study with 84 % patients satisfied in the patella resurfaced group compared to 79 % in the un-resurfaced group.

Even though secondary resurfacing can improve patients' clinical outcomes, it is usually still inferior to the outcomes of primary TKA.31 Among the patients who are unhappy with their non-PR TKA, the success of undergoing an isolated PR provides inferior results for the majority of the patients.30,31–34 This doesn't necessarily mean that patients do not improve after their secondary resurfacing. Studies did show improvement in PROMS after secondary resurfacings, but not to the same extent as PROMS following a primary TKA.

Patella resurfacings are geographically influenced. In the American Joint Registry (AJRR, 2020), 90.4 % of TKA undergoes PR compared to 38.44 % and 54.6 % of PRs in the United Kingdom and Canada, respectively.32 Multiple studies have shown an increased revision rate in patients with an unresurfaced patella.21,31–34 The rates for revisions in PR knees vary between 2.92 and 7.1 % (7–20-year follow-up) compared to 3.87–9.2 % (7–20-year follow-up) in non-PR TKA.32 Sub-analysis demonstrated a decreased revision rate with PR in patients older than 65 years of age. This finding was statistically significant only in the female population.32 We did not find any correlation between age and sex in the surgeon's decision to resurface or not. Sandiford et al.35 also did not see a correlation between age, sex, laterality, BMI, or ASA score in decision-making regarding resurfacing. They questioned 619 practicing surgeons in the United Kingdom about the indications to resurface the patella and found the three most common indications include Rheumatoid arthritis (35 %), severe PFJ OA (35 %), and severe tibio-femoral osteoarthritis (16 %). Furthermore, we did not observe any revisions in either group. One reason for this can be due to the relatively short follow-up period of 45 months.

We found a significant difference between ARS and non-ARS in regards to PR, with ARS being more prone to PR. Interestingly, Eiel et al.21 found in their retrospective study a decrease in rates (95.9 %–90.4 %) in PR between 2012 and 2021 in ambulatory surgery centers among high-volume surgeons. This trend can be explained by using newer “patella-friendly” TKA designs, and faster operating times associated with not resurfacing the patella.21 Sandiford et al.35 found that the majority of surgeons in the UK resurface 50 % of the time while the always-resurface group (28 %) is slightly higher than the never-resurface group (24 %). Contrary they did not find a difference in resurfacing rates between ARS and non-ARS. However, they did find that high-volume surgeons (>50 TKA/year) and higher experienced surgeons (>15 years in practice) had an elevated tendency to resurface the patella35

This study is to our knowledge the only study examining patient satisfaction following PR or non-PR in medial congruent TKA's with a mean follow-up of 45 months. Since the patella's function and biomechanics differ in medial congruent TKA compared to other designs, understanding the effectiveness of resurfacing in this specific context helps surgeons make informed decisions, improving postoperative function and reducing complications.

5.1

5.1 Limitations

There are some limitations. Firstly, the study's retrospective nature may introduce selection bias and limit the ability to establish causal relationships between variables. Second, using the Discharge Abstract Database (DAD) for data collection may result in incomplete or inaccurate data, potentially affecting the study's validity.

Third, despite efforts to control for confounding variables, other factors not accounted for in the study design may influence the outcomes. Fourth, relying on patient-reported outcome surveys may introduce response bias or inaccuracies. Lastly, there is a chance for information bias, due to the reliance on patient-reported outcomes which may introduce information bias if data are inaccurately recorded or reported.

5.2

5.2 Future directions

Our aim is to longitudinally follow this cohort of patients to obtain PROMs at medium and long-term intervals. This longitudinal approach will enable us to assess the durability and sustainability of outcomes associated with total knee arthroplasty utilizing a medial congruent polyethylene liner, particularly in relation to patella resurfacing. By tracking PROMs over time, we seek to provide valuable insights into the long-term efficacy and patient satisfaction of this surgical approach, ultimately informing clinical decision-making and enhancing patient care in the field of orthopedics. We plan to employ patient experience surveys to augment PROMs in determining patient satisfaction.

6

6 Conclusion

PR is a highly contentious topic in TKA. Our study demonstrated that there are no clinically meaningful differences in PROMS with PR or non-PR in medial congruent TKA. With the lack of large randomized controlled trials and long-term follow-up, surgeons should persist in leveraging their expertise and clinical-acumen to inform decision-making processes.

CRediT authorship contribution statement

Nebojsa Kuljic: Conceptualization, Methodology, Software, Formal analysis, Investigation, Writing – original draft. Wyatt Tyndall: Formal analysis, Investigation, Writing – original draft. Michael Thatcher: Formal analysis, Investigation, Writing – original draft. Michaela Nickol: Formal analysis, Writing – original draft. Johannes M. van der Merwe: Conceptualization, Methodology, Validation, Formal analysis, Investigation, Writing – original draft.

Data available statement

Description: With data statement, an author can provide information about the data presented in an article and provide a reason if data is not available to access. You could choose the most suitable one for your research from the following statement templates.Availability of dataTemplate for data availability statementData openly available in a public repository that issues datasets with DOIsThe data that support the findings of this study are openly available in [repository name e.g “figshare”] at http://doi.org/10.1016/j.jor.2024.12.016, reference number [reference number].Data openly available in a public repository that does not issue DOIsThe data that support the findings of this study are openly available in [repository name] at [URL], reference number [reference number].Data derived from public domain resourcesThe data that support the findings of this study are available in [repository name] at [URL/DOI], reference number [reference number]. These data were derived from the following resources available in the public domain: [list resources and URLs]Embargo on data due to commercial restrictionsThe data that support the findings will be available in [repository name] at [URL/DOI link] following an embargo from the date of publication to allow for commercialization of research findings.Data available on request due to privacy/ethical restrictionsThe data that support the findings of this study are available on request from the corresponding author. The data are not publicly available due to privacy or ethical restrictions.Data subject to third party restrictionsThe data that support the findings of this study are available from [third party]. Restrictions apply to the availability of these data, which were used under license for this study. Data are available [from the authors/at URL] with the permission of [third party].Data available on request from the authorsThe data that support the findings of this study are available from the corresponding author upon reasonable request.Data sharing not applicable – no new data generatedData sharing is not applicable to this article as no new data were created or analyzed in this study.Author elects to not share dataResearch data are not shared.Data available in article supplementary materialThe data that supports the findings of this study are available in the supplementary material of this articleData sharing not applicable – no new data generated, or the article describes entirely theoretical researchData sharing not applicable to this article as no datasets were generated or analyzed during the current study

1. The data that support the findings of this study are openly available in Database: xxxx (e.g., TAIR: AT1G01020; CCDC: 734053; PDB: 1XFN).

2. The authors confirm that the data supporting the findings of this study are available within the article [and/or] its supplementary materials.

3. The data that support the findings of this study are available from the corresponding author upon reasonable request.

4. Due to the nature of this research, participants of this study did not agree for their data to be shared publicly, so supporting data is not available.

5. No new data, model were used in this research.

Ethics statement

Description: Studies on patients or volunteers require ethics committee approval, which should be documented in the paper.

If no patients or volunteers have been involved in the research, it is recommended to include the following sentence: Ethics approval were waived for this study because no patients’ data were reported.

Patient and guardian consent

This is not applicable to this study – No identifiable names, images, videos are in the manuscript.

Funding

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

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