Obesity does not adversely impact the outcome of unicompartmental knee arthroplasty for osteoarthritis: a meta-analysis of 80,798 subjects

Effect of body mass index on 30-day complication rate and implant survival rate after simultaneous bilateral unicompartmental knee arthroplasty: a multicentre retrospective study

OBJECTIVE

The practice of simultaneous bilateral unicompartmental knee arthroplasty (SBUKA) remains a topic of debate, particularly in patients with obesity. Thus, the purpose of this study was to assess the impact of body mass index (BMI) on the 30-day complication rate and the survival rate of the implant following SBUKA.

METHODS

We retrospectively examined the clinical records of 245 patients (490 knees) who underwent SBUKA at the Affiliated Hospital of Qingdao University and the Third Hospital of Hebei Medical University between January 2010 and December 2020. Patients were categorised based on their BMI at the time of surgery into four groups: normal weight (BMI 18.5 to 22.9 kg/m2), overweight (BMI 23.0 to 24.9 kg/m2), obese (BMI 25.0 to 29.9 kg/m2), and severely obese (BMI ≥30 kg/m2). Variables such as length of hospital stay, duration of surgery, and costs of hospitalisation were compared across all groups. Additionally, we recorded the 30-day postoperative complication rate and the time from surgery to any required revision. The Kaplan-Meier survival analysis was employed to evaluate and compare the implant survival rates.

RESULTS

The follow-up period for the 245 patients ranged from 39 to 114 months, with an average of 77.05±18.71 months. The incidence of complications within 30 days post-surgery did not significantly differ across the groups (χ2 = 1.102, p = 0.777). The implant survival rates from the lowest to the highest BMI groups were 97.14%, 93.9%, 94.44%, and 96.43%, respectively. Both the rate of implant revision (χ2 =1.612, p = 0.657) and the survival curves of the implants (p = 0.639) showed no statistically significant differences among the groups.

CONCLUSIONS

BMI did not influence the 30-day complication rate nor the survival rate of implants following SBUKA, suggesting that SBUKA should not be contraindicated based on BMI alone.

Unicompartmental knee replacement: controversies and technical considerations

BACKGROUND

Unicompartmental knee replacement (UKR) is one of the effective interventions for the treatment of symptomatic knee osteoarthritis. Moreover, it has multiple advantages over total knee arthroplasty (TKA), including reduced intraoperative blood loss, decreased risk of transfusion, and faster recovery. This study aimed to discuss critical technical considerations regarding UKR and some of the controversies and updates.

METHODS

We conducted a review to provide an overview of the controversies and technical considerations about UKR in several aspects. Only peer-reviewed articles were included, up to December 2023 using PubMed, Google Scholar, ERIC, and Cochrane database for systematic reviews databases.

RESULT

UKR is associated with superior patient-reported clinical and functional outcomes, as well as shorter hospital stays, fewer postoperative complications, and revealed favorable outcomes in patients' return to sport. The choice between mobile- and fixed-bearing prostheses depends, in part, on the surgeon's preference. The mobile-bearing UKR is a less constrained prosthesis and can potentially result in less wear, but it is more technically demanding. While no significant difference between mobile-bearing versus fixed-bearing prostheses, cementless is superior to cemented design. Furthermore, UKR can be a good alternative for high tibial osteotomy (HTO) and still can be considered after a failed HTO. Lastly, recent reviews have shown a revision rate comparable to that of TKA. This is probably influenced by Improved comprehension of the best indications, patient selection criteria, as well as of the design, materials, and technological advances.

CONCLUSION

UKR treatment for unicompartmental knee osteoarthritis is secure and effective. Based on clinical and functional outcomes, decreased morbidity and mortality, and cost-effectiveness, long-term studies suggest that UKR is superior to TKA. Further investigation in this area is warranted.

Morbidly Obese Patients Undergoing Unicompartmental Knee Arthroplasty Compared to Total Knee Arthroplasty: A Retrospective Case-Controlled Analysis

BACKGROUND

In this study, we assess the effects that morbid obesity (body mass index (BMI) ≥ 40) has on: (1) Ninety-day medical complications and readmission rates; (2) costs of care and lengths of stay (LOS); and (3) 2-year implant complications in patients undergoing unicompartmental knee arthroplasty (UKA) versus total knee arthroplasty (TKA).

METHODS

A retrospective query of TKA and UKA patients were identified using a national database. Morbidly obese UKA patients were matched 1:5 to morbidly obese TKA patients by demographic and comorbidity profiles. Subgroup analyses were conducted using the same process between morbidly obese UKA patients and BMI <40 TKA patients, as well as to BMI <40 UKA patients.

RESULTS

Morbidly obese patients who underwent UKA had significantly fewer medical complications, readmissions, and periprosthetic joint infections than TKA patients; however, UKA patients had greater odds of mechanical loosening (ML). The TKA patients had significantly longer LOS (3.0 versus 2.4 days, P < .001), as well as significantly greater costs of care than UKA patients ($12,869 versus $7,105). Morbidly obese UKA patients had similar rates of medical complications, and significantly lower readmissions, decreased LOS, and decreased costs when compared to TKA patients who had a BMI <40.

CONCLUSION

In patients who have morbid obesity, complications were decreased in UKA compared to TKA. Moreover, morbidly obese UKA patients had lower medical utilizations and similar complication rates when compared to TKA patients with the recommended cutoff of BMI <40. However, UKA patients had greater rates of ML than TKA patients. A UKA may be an acceptable treatment option for unicompartmental osteoarthritis in morbidly obese patients.

Obese Patients Achieve Good Improvements in Patient-Reported Outcome Measures After Medial Unicompartmental Knee Arthroplasty Despite a Lower Preoperative Score

BACKGROUND

In this study, we examined the association between obesity and patient-reported outcome measures after medial unicompartmental knee arthroplasty (MUKA), assessed through score changes, Patient Acceptable Symptom State (PASS), and minimal important change (MIC). Second, the association between obesity and early readmissions was examined.

METHODS

A total of 450 MUKAs (mean body mass index [BMI] 30.3, range, 19.6-53.1), performed from February 2016 to December 2020, were grouped using BMI: <30, 30-34.9, and >34.9. Oxford Knee Score (OKS), Forgotten Joint Score (FJS), and Activity and Participation Questionnaire (APQ) were assessed preoperatively and at 3, 12, and 24 months, postoperatively. The 12-month PASS and MIC were also assessed, defining PASS as OKS = 30, MIC-OKS as change in OKS = 8, and MIC-FJS as change in FJS = 14.

RESULTS

No significant differences in OKS change were found between BMI groups. After 12 months, patients who had a BMI of 30-34.9 had lower change in FJS (estimate -8.1, 95% CI -14.9 to -1.4) and were less likely to reach PASS (odds ratio 0.4, 95% CI 0.2-0.7) as well as MIC-FJS (odds ratio 0.5, 95% CI 0.2-0.9). Both obese groups had lower change in APQ after 12 months. Differences in 90-day readmission rates were nonsignificant between groups.

CONCLUSION

Our findings of no differences in OKS improvement between BMI groups and achieving MIC for BMI > 34.9 suggest good improvements in obese patients despite lower preoperative scores, supporting contemporary indications for MUKA. Lower APQ development and achievement of 12-month PASS may be used when addressing expectations of recovery.

Obesity increases the risk of conversion to total knee arthroplasty after unicompartimental knee arthroplasty: a meta-analysis

PURPOSE

The aim of this meta-analysis was to to determine the influence of obesity on patient outcome and implant survivorship after primary unicompartmental knee arthroplasty (UKA).

METHODS

A PRISMA systematic review was conducted by searching the Medline (PubMed), EMBASE, and Cochrane electronic databases to identify clinical studies investigating the effect of obesity on outcomes after UKA. Data were collected on aspecifically designed extraction form. Methodological quality was assessed using the Methodological Index for Nonrandomized Studies score. Quantitative meta-analysis was carried out using RevMan 5.4 software.

RESULTS

A total of 17 studies were included; 43,845 primary UKA patients were classified by their BMI: on-obese (BMI 25 to < 30 kg/m²); obese (BMI 30 to < 35 kg/m²); severely obese (BMI > 35 kg/m²). Pooled analysis showed no statistically significant difference in Knee Society Score (KSS) pain in the obese (n.s.) and the severely obese (n.s.) group compared to the non-obese group, while the KSS function score was lower in the severely obese (P = 0.0002) compared to the obese (P = 0.06) and the non-obese group. Postoperative Oxford Knee Score (OKS) was lower in the obese group (P = 0.01) but not in the severely obese group (P = 0.16). Postoperative Range of Motion (ROM) was comparable in the obese and non-obese group (P = 0.16). Implant survival at 10 years follow-up was significantly lower in the obese (82.5-95.3%; P < 0.0001) and the severely obese group (87.5-93.8%; P < 0.0001) thanthe non-obese group (83.6-98.6%).

CONCLUSION

Obesity and severe obesity were associated with significantly higher revision and lower implant survival rates. Obesity did not influence clinical and most functional outcomes after UKA, whereas KSS function score was significantly lower only for the severely obese patient group.

LEVEL OF EVIDENCE

III, meta-analysis.

Medial/central PF arthritis and functionally stable ACL deficiency do not compromise outcomes of fixed-bearing medial UKA

BACKGROUND

There is limited published data assessing functional scores and patient satisfaction following unicompartmental knee arthroplasty (UKA) in patients with patellofemoral (PF) arthritis or anterior cruciate ligament (ACL) deficiency. The purpose of this study was to determine whether medial/central PF arthritis or functionally stable ACL deficiency compromise outcomes of fixed-bearing medial UKA at a minimum follow-up of 2 years. The hypothesis was that equivalent outcomes can be achieved in patients with substantial medial/central PF arthritis or with functionally stable ACL deficiency.

METHODS

The authors studied a consecutive series of 229 patients (240 knees) at 36.9 ± 6.3 months after receiving fixed-bearing medial UKA. Patients completed pre- and post-operative (2 years) clinical outcome questionnaires for Oxford Knee Score (OKS), EQ-5D, Knee injury and Osteoarthritis Outcome Score Physical Function Short Form (KOOS-PS), University of California, Los Angeles (UCLA) activity score, and Forgotten Joint Score (FJS). Multivariable analyses were performed to determine associations between clinical scores, patient demographics, PF arthritis and functionally stable ACL deficiency.

RESULTS

Of the 240 knees, 125 (54%) had substantial medial/central PF arthritis and 21 (9%) functionally stable ACL deficiency. Multivariable analyses revealed no association between outcomes and medial/central PF arthritis, but knees with functionally stable ACL deficiency were associated with better KOOS-PS (β = 8.99, p = 0.012).

CONCLUSION

Fixed-bearing medial UKA grants satisfactory outcomes at 2 years even in knees with substantial medial/central PF arthritis or functionally stable ACL deficiency. Longer-term prospective studies with larger cohorts are needed to confirm these promising findings regarding outcomes in patients traditionally contraindicated for medial UKA.

Unicompartmental Knee Replacement in Obese Patients: A Systematic Review and Meta-Analysis

Thanks to modern surgical techniques and implants, traditional exclusion criteria for unicompartmental knee arthroplasty (UKA) are no longer considered contraindications. The aim of this study is to clarify the impact of obesity on functional outcomes and revision rates of UKA. We performed a comprehensive systematic review using PubMed–Medline, Google Scholar and Cochrane Central. Then, we extracted data related to body mass index (BMI), age and follow-up, functional outcome scores and rate of revisions (all-cause, aseptic and septic). Patients were stratified according to BMI into two groups: non-obese (BMI < 30) and obese (BMI ≥ 30). We identified 22 eligible studies, of which 13 were included in the meta-analysis. Patients with a BMI > 30 had a significantly higher likelihood for revision (p = 0.02), while the risk of septic revision was similar (p = 0.79). The clinical outcome measures showed a significant difference in favor of patients with a BMI < 30 (p < 0.0001). The improvements in Oxford Knee Score and Knee Society Score were significant in both obese and non-obese patients, although the latter showed inferior results. The results of this systematic review and meta-analysis show that BMI is not a contraindication to UKA. However, obese patients have a higher risk for aseptic failure and lower improvement in clinical scores compared to non-obese patients.