Comparable Early Outcomes Between Cemented and Cementless MAKO Functional Alignment Total Knee Arthroplasty: A Propensity-Matched Analysis

1. INTRODUCTION

Cemented fixation has long been regarded as the gold standard in total knee arthroplasty (TKA), supported by decades of excellent survivorship data.^1-3 However, recent advances in implant design, biomaterials (highly porous titanium, hydroxyapatite coatings), and surgical technique have led to a resurgence of cementless TKA, particularly in younger, more active patients with good bone quality.^4-8 Cementless fixation may offer advantages such as preservation of bone stock, avoidance of cement-related third-body wear, reduced risk of osteolysis and loosening, shorter operative time, and shorter length of stay in some cohorts.^9-11 Cemented fixation is associated with a higher risk of aseptic loosening over time, and this is thought to result from alterations at the bone-cement interface and increased third-body wear from cement debris, which can cause osteolysis and subsequent loosening.^8,9 Currently, five and ten-year survivorship rates for both fixation methods are mostly comparable.^1,12 However, cementless fixation has been associated with higher rates of aseptic loosening and revision for pain in obese and morbidly obese patients.^13,14

To the authors’ knowledge, two studies have compared cementless vs cemented fixation robotic-assisted mechanically aligned (MA) MAKO TKA. Molho et al. found that there was a higher rate of return to the operating room in the cemented group compared to the cementless group.¹⁵ McCormick et al. reported no significant differences in patient-reported outcomes, complication rates, and revision surgery rates between the two cohorts at six months, one year, and two years.¹⁶ These studies have been conducted in Western populations and have predominantly applied a mechanically aligned philosophy. Ethnic and anatomical differences in Asian patients may influence knee morphology and bone density, which in turn can affect fixation behavior and functional recovery.¹⁷

Functional alignment (FA) is an individualized approach to gap balancing, which can influence component loading, kinematics, and soft-tissue tension in ways that differ from mechanical alignment (MA), potentially altering bone and implant interface interactions, including the outcomes of cementless fixation.^18,19 Existing literature on cementless versus cemented robotic-assisted TKA has largely been based on MA principles, which may not fully capture the performance of implants under FA conditions.

To our knowledge, the present study is the first propensity-matched pair study to evaluate cemented versus cementless functional alignment MAKO TKA in an Asian cohort. We hypothesized that cementless fixation would demonstrate non-inferior early functional outcomes and patient-reported outcome measures compared with cemented fixation at six months postoperatively.

2. MATERIAL AND METHODS

3. RESULTS

4. DISCUSSION

The most important finding of the present study was that cementless MAKO-assisted functional alignment TKA achieved comparable rates of MCID achievement across all patient-reported outcome measures, functional scores, and complication rates when compared with cemented fixation in a propensity score-matched Asian cohort. The only statistically significant difference observed was a marginally higher SF-36 Mental Component Score in the cemented group at six months (57.7 ± 8.2 vs. 52.4 ± 11.3; p = 0.043); however, both groups exceeded the predefined MCID threshold of 10 points, and this difference is unlikely to reflect a true clinical advantage of cemented fixation. These results reinforce the growing body of evidence suggesting that modern cementless designs perform equivalently to cemented fixation in the short term, particularly in the Asian population.

Both groups demonstrated robust functional improvement by 6 months, with near-identical performance in validated PROMs. The isolated difference in SF-36 MCS did not translate into lower satisfaction or diminished expectation fulfilment. Our study’s findings are consistent with those reported by McCormick et al. and Molho et al., the only other studies comparing cementless versus cemented MAKO TKA.^15,16 Additionally, Graham et al. demonstrated that even in obese patients, cementless and cemented TKA had similar outcomes²⁸, while Puri et al. reported a 24% reduction in operative time with cementless TKA and comparable short-term survivorship.²⁹ This study complements the existing results as the first matched-pair evaluation of functional alignment MAKO TKA in an Asian cohort. Considering known anatomical and alignment differences across ethnic groups, our findings provide important evidence supporting the applicability of cementless fixation in a multi-racial Asian population.³⁰ Our results indicate that cementless fixation is a safe, effective and reliable option for Asian patients undergoing individualized, functional-alignment MAKO total knee arthroplasty, with no adverse impact on early recovery or short-term clinical outcomes.

An important contribution of this study is the inclusion of an Asian cohort, which addresses a gap in the existing literature predominantly based on Western populations. Asian patients often present with smaller bone morphology, narrower femoral and tibial dimensions, a higher incidence of severe tibia vara (MPTA < 84), and different coronal and sagittal alignment patterns, which may influence both implant fit and fixation biomechanics.^30,31 Furthermore, Asians have a higher prevalence of osteoporosis and lower bone mineral density than their Caucasian counterparts, which may compromise implant fixation and increase the risk of periprosthetic fracture.^32,33 By evaluating cementless MAKO-assisted functional alignment TKA in this population, our findings provide clinically relevant evidence that these implants perform safely and effectively across this unique population.

Large registry data and meta-analysis have revealed the survivorship advantage of cementless fixation over cemented fixation in primary TKA.^34,35 Furthermore, avoiding cement also offers procedural simplicity, shorter surgical time, yields cost benefits, and eliminates cement-related risks.^11,36 Taken together, our early postoperative results indicate that cementless implants represent a safe, efficient, and clinically reliable alternative to cemented fixation for MAKO functional alignment TKA, particularly in Asian patients.

A key limitation of this study is the 6-month follow-up, which captures only early postoperative outcomes and short-term functional recovery. Although our follow-up was limited to 6 months, prior studies have shown that PROs after TKA generally plateau by this time with minimal changes between 6 months and 2 years.^26,37

At six months, no periprosthetic fractures or major complications were observed. Nonetheless, the short-term follow-up limits conclusions regarding long-term fixation performance. Longer-term follow-up, together with more advanced imaging modalities such as radiostereometric analysis, is required to more comprehensively evaluate radiographic migration, implant survivorship, aseptic loosening, and revision rates. Additionally, the relatively small number of patients undergoing functional TKA, particularly after propensity score matching, reflects both the novelty of the procedure and the single-surgeon setting, highlighting the need for larger cohorts to enhance generalizability. The choice between cemented and cementless fixation was guided by surgeon preference, age, gender, presence of valgus deformity, and intra-operative bone quality assessed by the indentation test, which introduces the potential for selection bias and confounding by indication. Large comparative cohorts and PSM analyses of cemented vs cementless TKA usually adjust for age, sex, BMI, and baseline function, but not DEXA-based BMD because it is rarely measured in routine practice.^38,39 Therefore, to reduce baseline differences, propensity score matching was applied for age, gender, BMI, and baseline function, which are established determinants of bone quality and implant selection. Nevertheless, residual confounding may persist due to the absence of objective measures of bone quality such as DEXA-derived BMD. This is a notable limitation in an Asian arthroplasty population, in which the prevalence of osteoporosis and osteopenia among patients awaiting TKA is high.³² Finally, the retrospective design carries inherent risks of selection bias and unmeasured confounding; however, PSM was employed to mitigate these risks and achieve balanced covariates between groups.

5. LIMITATIONS

Several limitations should be acknowledged. First, the 6-month follow-up captures early postoperative recovery but limits assessment of long-term implant fixation and survivorship. Although prior studies suggest that patient-reported outcomes (PROs) generally plateau by 6 months with minimal subsequent change, longer-term follow-up and advanced imaging modalities such as radiostereometric analysis are needed to evaluate implant migration, aseptic loosening, and revision rates. Second, the relatively small cohort, particularly after propensity score matching, reflects the novelty of functional TKA and single-surgeon setting and may limit generalizability. Third, the choice of cemented versus cementless fixation was based on surgeon preference, age, gender, valgus deformity, and intraoperative bone quality assessed by indentation testing, introducing potential selection bias and confounding by indication. Although comparative studies and PSM analyses typically adjust for demographic and clinical factors, DEXA-based bone mineral density is rarely available in routine practice and could not be incorporated. Larger, multicentre cohorts with longer follow-up are therefore warranted to validate these findings.

6. CONCLUSION

In this propensity score-matched Asian cohort, cementless MAKO-assisted functional alignment TKA demonstrated comparable early functional outcomes, patient satisfaction, and complication rates to cemented fixation at six months. While the six-month follow-up limits assessment of long-term implant durability, prior studies suggest that patient-reported outcomes generally plateau by this time. These findings support the short-term safety and feasibility of cementless fixation within a functional alignment framework; however, longer follow-up and larger cohorts are needed to evaluate osseointegration and implant survivorship.In this propensity score-matched Asian cohort, cementless MAKO-assisted functional alignment TKA demonstrated comparable early functional outcomes, patient satisfaction, and complication rates to cemented fixation at six months. While the six-month follow-up limits assessment of long-term implant durability, prior studies suggest that patient-reported outcomes generally plateau by this time. These findings support the short-term safety and feasibility of cementless fixation within a functional alignment framework; however, longer follow-up and larger cohorts are needed to evaluate osseointegration and implant survivorship.In this propensity score-matched Asian cohort, cementless MAKO-assisted functional alignment TKA demonstrated comparable early functional outcomes, patient satisfaction, and complication rates to cemented fixation at six months. While the six-month follow-up limits assessment of long-term implant durability, prior studies suggest that patient-reported outcomes generally plateau by this time. These findings support the short-term safety and feasibility of cementless fixation within a functional alignment framework; however, longer follow-up and larger cohorts are needed to evaluate osseointegration and implant survivorship.In this propensity score-matched Asian cohort, cementless MAKO-assisted functional alignment TKA demonstrated comparable early functional outcomes, patient satisfaction, and complication rates to cemented fixation at six months. While the six-month follow-up limits assessment of long-term implant durability, prior studies suggest that patient-reported outcomes generally plateau by this time. These findings support the short-term safety and feasibility of cementless fixation within a functional alignment framework; however, longer follow-up and larger cohorts are needed to evaluate osseointegration and implant survivorship.In this propensity score-matched Asian cohort, cementless MAKO-assisted functional alignment TKA demonstrated comparable early functional outcomes, patient satisfaction, and complication rates to cemented fixation at six months. While the six-month follow-up limits assessment of long-term implant durability, prior studies suggest that patient-reported outcomes generally plateau by this time. These findings support the short-term safety and feasibility of cementless fixation within a functional alignment framework; however, longer follow-up and larger cohorts are needed to evaluate osseointegration and implant survivorship.In this propensity score-matched Asian cohort, cementless MAKO-assisted functional alignment TKA demonstrated comparable early functional outcomes, patient satisfaction, and complication rates to cemented fixation at six months. While the six-month follow-up limits assessment of long-term implant durability, prior studies suggest that patient-reported outcomes generally plateau by this time. These findings support the short-term safety and feasibility of cementless fixation within a functional alignment framework; however, longer follow-up and larger cohorts are needed to evaluate osseointegration and implant survivorship.In this propensity score-matched Asian cohort, cementless MAKO-assisted functional alignment TKA demonstrated comparable early functional outcomes, patient satisfaction, and complication rates to cemented fixation at six months. While the six-month follow-up limits assessment of long-term implant durability, prior studies suggest that patient-reported outcomes generally plateau by this time. These findings support the short-term safety and feasibility of cementless fixation within a functional alignment framework; however, longer follow-up and larger cohorts are needed to evaluate osseointegration and implant survivorship.In this propensity score-matched Asian cohort, cementless MAKO-assisted functional alignment TKA demonstrated comparable early functional outcomes, patient satisfaction, and complication rates to cemented fixation at six months. While the six-month follow-up limits assessment of long-term implant durability, prior studies suggest that patient-reported outcomes generally plateau by this time. These findings support the short-term safety and feasibility of cementless fixation within a functional alignment framework; however, longer follow-up and larger cohorts are needed to evaluate osseointegration and implant survivorship.