1 Introduction

There is an increasing requirement for primary total knee arthroplasty (TKA) in the UK,¹ mirrored by an ageing population with patients outliving their TKA.² However, the focus is shifting towards the growing demand for revision total knee arthroplasty (RTKA)³ with a predicted 6-fold increase in demand from 2005 to 2030.^4,5 RTKA surgery is expensive and resource-demanding,^2,5 and with the volume of RTKA increasing at a greater rate, there will be a subsequent increased strain on healthcare systems.^6,7

We observe those under 65 years of age as the fastest growing cohort requiring RTKAs,^2,8 this group are currently under the UK government state pension age⁹ and so failure to return to work can potentially have significant socio-economic implications.¹⁰ Not only is there a reduction in productivity within society, but importantly active work participation is an associated important factor for improving quality of life, feeling useful to society and structuring day to day life.^10,11 There are also associated psychological and mental well-being benefits of working.

Primary TKAs have high success rates with excellent quality adjusted life years (QALY),¹² survivorship figures are high.¹³ RTKA have less consistent outcomes with lower rates of implant survival, patient satisfaction and increased risk of complications.^3,14 Lower functional outcomes are observed in patients with RTKA compared to TKA,^15–17 a measure closely associated with the ability to engage in everyday activities and return to work. There are large financial implications including the cost of RTKA,² alongside the substantial cost of sick leave.¹⁸

Literature exploring return to work in patients <65 years of age following RTKA is lacking conclusive evidence. Return to work following TKA shows largely positive results,^18,19 with a multicentre study²⁰ finding that 98% of patients aged 18–60 returned to work after TKA surgery. There is ongoing research in this field with a multicentre study evaluating occupational health interventions after TKA.²¹

Literature is less reassuring when assessing RTKA, with a study¹⁵ concluding only 7% of patients <65 years returned to work after one year, in a cohort where 93% were employed prior to surgery. It is widely accepted that outcomes following RTKA are inferior to TKA and consequently, the numbers of those who return to work are less.²² However, with the increasingly younger population receiving RTKA patients need to be informed before electing for surgery.²³

Indication for surgery and preoperative clinical status of the patient has been shown to correlate and predict patient satisfaction following RTKA³ and may account for poorer results observed in RTKA especially as many are in smaller cohorts than TKA studies.

2 Material and methods

Our NHS institution in the United Kingdom conducted 132 RTKA procedures on 113 consecutive patients aged 65 years or younger between 2009 and 2020. These procedures were included in our study. All procedures were discussed pre-operatively in a multi-disciplinary meeting to confirm the management plan. Surgery was performed or supervised by 4 consultants specialising in knee arthroplasty surgery in a unit undertaking >100 revision knee procedures per year. Rehabilitation was standardised.

We performed a retrospective observational study using a contemporaneously updated local database. All patients aged ≤65 who underwent revision knee arthroplasty at our NHS institution between 2009 and 2020 were included. Revisions were defined as the removal and re-implantation of at least one tibial/femoral TKR component; poly exchange was excluded from the study. In patients undergoing staged procedures for infection, or who underwent a re-revision TKA, only the most recent and definitive surgery was included. Procedures include primary TKR-revision (n = 99), re-revisions (n = 33 procedures in n = 14 patients), patella resurfacing (n = 1) and debridement and implant retention (DAIR) procedures (n = 2).

Primary implants included cruciate retaining and posterior stabilised prostheses from the Triathlon Knee System (Stryker Orthopaedics, Michigan). Revision implants included the Triathlon TS, Modular Rotating Hinge (Stryker Orthopaedics, Michigan), Endo-Link Hinge (Link, UK) and RT-Plus Rotating Hinged Knee (Smith and Nephew). Cones and augments were also used when required.

Eligible patients were identified from our local revision knee database. Demographic and surgical information was collected from MyCare, an electronic notes system. Data included sex, age at surgery, length of hospital stay, and American Society for Anaesthesiology (ASA) grade.

The Oxford Knee Score (OKS) was completed pre-operatively. Post-operatively the OKS, the Work, Osteoarthritis and joint-Replacement Questionnaire (WORQ) score, the EuroQol-5 dimensions 5L (EQ-5D-5L) score and the departmental return to work questionnaire were completed. The external scores are validated and have been widely used in the literature.^1–4 The departmental questionnaire asked patients about employment status pre- and post-operatively, the nature of their work and their ability to return to work post-operatively.

Pre-operative patient reported outcome measures (PROMs) were retrospectively obtained from patient notes, in the form of the OKS. Follow-up data collection was independent of routine clinical care. Patients were invited to participate in follow-up via postal questionnaire, which included a pre-paid stamp for return postage, between 10/2021–03/2022 median follow up from the date of surgery: 5.74 years (2.36–8.96). Patients were also contacted via telephone.

Local Institutional Review Board approval was gained for this study (PEOCIRB21 004).

3 Results

3.6

3.6 WORQ

Work, Osteoarthritis and Joint Replacement Questionnaire (WORQ) scores collected post-operatively following RTKA are displayed in Fig. I. Similar patterns were observed in both groups, with ‘driving a vehicle’, ‘using peddles’ and ‘sitting’ impacting day-to-day activities the least. ‘Kneeling’, ‘clambering’ and ‘crouching’ impacted day-to-day activities the most; however, using the Chi squared test the only statistically significant result was comparing the category of ‘lifting and carrying’, p = 0.011.

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Fig. 1 Work, Osteoarthritis and joint Replacement Questionnaire (WORQ) score following RTKA in all patients (n = 62).

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4 Discussion

Overall, this cohort study demonstrated the benefits of RTKA with 61% of patients returning to work following surgery, this is an 8% increase in preoperative employment status. RTKA also facilitated the return to work of participants with an increase of n = 5 employed following revision. It is widely acknowledged the results following RTKA are not as satisfactory as TKA.^3,15,17,26 However, there are limited studies examining the return to work following RTKA. If we compare with the return to work following TKA, expecting to observe worse outcomes, we are surprised that this is not always the case. A study¹⁰ observing patients undergoing TKA aged <65 found only 40% of patients employed before surgery returned to work, and at a median time of 13.5 weeks, compared to our study with a median of 12 weeks. Research³ comparing TKA and RTKA was aligned with our expectation that TKA produces greater postoperative PROMs than RTKA, however, still confirming our findings with the conclusion that RTKA does still provide improved PROMs. Functional assessment of RTKA using PROMs was significant for post-operative OKS and EQ-5D-5L index score suggesting those patients with less pain and improved functional outcomes return to work.

Despite observed differences in pre- and post-operative OKS between the RTW and NRTW groups, only the post-operative score showed significant differences. As there is no statistical difference in preoperative OKS, those patients presenting with poor pre-operative OKS can be reassured this is not always an indication of the surgical outcome. We can conclude that the outcome of this study is concerning the performance of participants' RTKA as there was no statistical significance associated with EQ-5D-5L health score. The EQ-5D-5L health score is a holistic look at the patient's health state, this is a self-reported assessment but is corroborated by using ASA grade as an objective measure of participants' general health. We do acknowledge that EQ-5D-5L is a holistic broad look at patients' overall health, but we did not assess statistical significance for individual comorbidities. Previous research¹⁰ suggests depression is associated with not returning to work. We found the EQ-5D-5L index score which includes assessing anxiety/depression as 1 of the 5 sections, was statistically significant, but the pain/discomfort had the biggest impact on patients. Although all PROMs were scoring higher in the RTW group compared to the NRTW group not all were statistically significant. This may suggest that PROMs are multifactorial, and the focus of each scoring system is unique hence multiple are required as is difficult to assess objectively.

Of those who RTW, more were employed in light or heavy manual jobs before their RTKA. This suggests that this cohort was more physically able and engaging in more demanding everyday activities before RTKA. This is in conjunction with a statistically significant difference in the WORQ score criteria for ‘lifting or carrying’ which was higher at the point of follow-up in the RTW group. We cannot conclude from these results alone if this trend is observed in the wider population due to the small sample size, but this is initially reassuring that patients who are more physically able before RTKA have good outcomes. Similar results have been observed in TKA where heavy/moderate manual work positively predicted return to work,^10,23 it should be noted that this study and ours involved a significantly smaller cohort size compared to other research²⁰ conversely suggesting the physical nature of the job is not associated with return to work in TKA. This can guide pre-operative advice and guidance for patients to improve outcomes. We have not explored whether motivation is associated with RTW or if it shows a correlation with the ability to return to work and importantly the type of work.

This study is specifically investigating the return to work of participants aged ≤65 years, the age was selected as it is currently the state pension age in the UK. A meta-analysis recently conducted by van der Wilk et al.,²³ showed a pooled mean RTW of 86%, although only in two studies. We acknowledge that one study concluded a 96% RTW²⁷ and the other a 7%¹⁵ RTW following RTKA at 1 year. A key difference in Dahm et al.,²⁷ research compared to both this study and Scott et al.,¹⁵ work, which comparatively showed a large reduction in the RTW of participants, was age. Dahm et al.,²⁷ had a mean age of 69 years (31–87), both this study and the one by Scott et al.,¹⁵ had cohorts ≤65 years. Dahm et al.,²⁷ study included results from 1995 to 2000, we recognise that the type of implants have changed slightly over the years. In the years since this research was conducted, those ≤65 years are the fastest growing cohort requiring RTKAs,^2,8 additionally, research demonstrates younger patients are less happy with outcomes and exhibit reduced levels of activity.⁸ Whilst our results are not as positive as Dahm et al.,²⁷ considering this research focuses on a cohort identified as potentially having reduced satisfaction with their outcome, the results are optimistic that RTKA in younger patients is successful. We hypothesise that the difference in our results could be due to co-morbidities and those patients requiring RTKA younger often are complex with multiple co-morbidities. We do not have direct comparators between both studies.

For the NRTW group, n = 17 (71%) did not intend to return to work. As pre-operative OKS did not significantly correlate with each group, patients could be advised not to make this decision prior to surgery as retiring early can have significant socioeconomic implications as the current state pension age in the UK is > 65 depending on the year of birth.⁹ This study suggests that NRTW was associated with poorer functional outcomes which impacted return to work. However, as the majority of the NRTW group did not intend to return to work we must question whether their RTKA was an influencing factor, as previous studies for TKA show high functional improvement with many patients aged <65 not returning to work.¹⁰ Further research is needed exploring socioeconomic status to determine if relative affluence impacts decisions to return to work. This study did not consider the reasons behind patients not returning to work, it has previously been proposed that affluence may be a contributing factor in decisions to return decided before surgery and not based on surgical outcomes.¹⁰

Although not significantly different between groups, those who returned to work were more satisfied with their surgical outcome on average. We do not know if this correlates with their expectations, post-operative function, employment or another cause.

5 Conclusion

In summary, these results are important in providing some reassurance when counselling patients. It is encouraging that the majority of patients who wished to return to work following RTKA did so, and that pre-operative PROMs can be improved with surgical intervention allowing patients increased quality of life to return to work, which historically wasn't often possible.

Author contribution

All authors contributed equally to this manuscript.

Ethical committee approval

Not applicable.

Patient Consent

Not applicable.

Funding

None.