The Effect of Tibial and Femoral Component Coronal Alignment on Survivorship After Total Knee Arthroplasty

Abstract

Background:

Component alignment in contemporary total knee arthroplasty (TKA) is frequently achieved through personalized alignment philosophies that aim to restore prearthritic knee anatomy. The long-term clinical efficacy and safety of these approaches remain uncertain. This comprehensive review assessed the relationship between coronal component alignment and TKA implant survivorship.

Methods:

A scoping review was performed of published primary TKA studies that (1) reported postoperative tibial or femoral component coronal alignment on long-leg radiography, (2) reported survivorship with a minimum 12-month follow-up, and (3) were written in English. The review adhered to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines and its scoping review extension (PRISMA-ScR). The primary a priori outcome was all-cause aseptic revision. Included studies underwent qualitative synthesis.

Results:

Of 3,786 screened studies, 332 underwent full-text review and 51 met inclusion criteria, encompassing 7,944 patients (9,687 TKAs) (mean [SD] age 68.1 [3.2] years; mean [SD] follow-up 4.6 [3.3] years). Most studies (76.5%, n = 39/51) investigated a single alignment philosophy (most commonly mechanical alignment [MA], n = 23, 56.1% of single-philosophy studies), while 10/51 (19.6%) compared 2 philosophies. Only 5 studies (9.8%) included >500 TKAs. Long-term follow-up (>10 years) was reported in 9 MA studies (28.1% of MA reports), 5 of which noted decreased survivorship with component varus or valgus. Survivorship ranged from 74.2% to 79.3% with increased tibial varus, 90% with increased femoral varus, and 83.3% with femoral valgus. Two kinematic alignment (KA) studies with >10-year follow-up reported no survivorship concerns. Decreased short-term to mid-term survivorship was reported in 2 KA studies (10.5%). No long-term data existed for other alignment philosophies, and the largest personalized alignment series included only 338 TKAs.

Conclusion:

Most studies demonstrated excellent short-to-midterm (5-year) survivorship regardless of coronal component alignment. However, limited evidence suggests increased early revision risk with some personalized alignment philosophies and reduced long-term (>10 years) survivorship with nonmechanical component alignment. Until higher-quality, long-term evidence with aseptic survivorship as the primary outcome is available, mechanically aligned TKA remains the most extensively validated approach.

Level of Evidence:

Level II. See Instructions for Authors for a complete description of levels of evidence.

Background

Alignment in total knee arthroplasty (TKA) has long been regarded as a critical determinant of implant survivorship^1-4. Traditionally, TKA has been performed according to biomechanical principles aiming to restore a neutral mechanical axis, with tibial and femoral cuts perpendicular to the mechanical axis⁵. Known as “mechanical alignment” (MA) or “classic alignment”, this seeks to minimize forces that accelerate polyethylene wear, component loosening, tibial subsidence, and aseptic mechanical failure^6,7. Multiple studies have demonstrated consistently favorable long-term outcomes with MA TKA, irrespective of native knee anatomy, alignment, or arthritis severity⁸.

Despite its established efficacy and safety, the precise relationship between overall limb alignment (typically assessed via hip-knee-ankle [HKA] angle) and aseptic survivorship has been questioned in large, long-term series^9,10. This uncertainty, together with advances in surgical precision offered by new technologies^11,12, improved understanding of native knee kinematics, and concern that altering prearthritic anatomy may compromise TKA performance¹³, has driven the development of alternative, personalized alignment philosophies^14-16. These approaches broadly aim to restore prearthritic knee anatomy^15,16, producing coronal component positions that frequently deviate from MA targets¹⁷. Examples include unrestricted Kinematic Alignment ([uKA]; alignment following native anatomy without boundaries), restricted KA ([rKA; alignment following native anatomy with boundaries), inverse KA (iKA), and functional alignment (FA), among others. Proposed benefits include reduced soft-tissue releases^18,19 and improved knee balance and function²⁰. However, whether these techniques yield clinically meaningful improvements in patient-reported outcomes compared with MA remains controversial^21-23, and concern persists that restoring anatomy that led to arthritis may accelerate implant failure^24,25. It is also unclear whether personalized techniques can be safely applied to all knee morphologies²⁶.

Multiple studies indicate that personalized philosophies achieve the same overall limb alignment as MA^27-31. Although differences may exist in sagittal and axial planes, personalized approaches are primarily distinguished from MA by coronal component alignment, with varying degrees of tibial and femoral varus or valgus²⁷. The specific impact of coronal component alignment on TKA survivorship has received less attention than the effect of limb alignment³² and has not been adequately addressed in prior large-scale analyses^9,10. Deviations in coronal component position may alter loading biomechanics^33-35, polyethylene wear patterns³⁶, trochlear orientation³⁷, and patellofemoral tracking³⁸; effects potentially exacerbated when using implants designed for MA positioning³⁹. Furthermore, the safe threshold for coronal varus or valgus remains undefined⁴⁰.

As annual TKA volumes continue to rise, the burden of revision procedures will place increasing demands on healthcare systems^41-43. Given the growing adoption of personalized alignment philosophies, it is essential to determine whether intentional deviations in coronal component alignment influence long-term survivorship⁴⁴. The present scoping review therefore synthesizes studies that (1) reported postoperative tibial or femoral component coronal alignment on long-leg radiography, (2) documented TKA survivorship with at least 12 months of follow-up, and (3) were published in English.

Materials and Methods

Search Strategy

This scoping review was conducted and reported in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA-2020) guidelines and the PRISMA extension for Scoping Reviews (PRISMA-ScR)^45,46. The protocol was prospectively registered (PROSPERO: CRD420251035914). A literature search was performed in February 2025 across MEDLINE, Embase, PubMed, Web of Science, EBM Reviews, and the Cochrane Central Register of Controlled Trials using a combination of controlled vocabulary and free-text keywords (Appendix 1).

Only English-language studies published between January 1, 1946, and February 11, 2025, were considered (no eligible studies were identified before 2006). ClinicalTrials.gov was searched for unpublished data, and reference lists of relevant systematic reviews and meta-analyses were hand-searched for additional eligible studies. Two independent investigators (W.H. and C.G.) conducted the search and screening using Covidence Systematic Review Software (Veritas Health Innovation, 2021).

Study Eligibility

Eligible studies were prospective or retrospective reports of primary TKA that (1) measured postoperative tibial or femoral component coronal alignment on long-leg standing radiographs or supine CT scanograms^47,48, (2) reported survivorship with a minimum 12-month follow-up, and (3) were published in English. Studies were excluded if full text was inaccessible, only titles/abstracts were available, or if they concerned bi-cruciate-retaining implants or unicompartmental knee arthroplasty. Alignment measurements derived from short-leg radiographs^49,50 or solely from intraoperative navigation/robotic data⁵¹ were also excluded.

Data Extraction

Titles and abstracts were screened independently by 2 reviewers (W.H. and C.G.). Disagreements were resolved by discussion. Full texts of potentially eligible studies were then reviewed (Fig. 1). Data extracted into Excel (Microsoft included study characteristics, patient demographics, surgical details, preoperative and postoperative alignment, and all reported outcomes at final follow-up. The primary outcome, defined a priori, was all-cause aseptic revision. Owing to heterogeneity in study design, alignment reporting, measurement methods, and outcome association, meta-analysis was planned but not performed. Descriptive statistics and qualitative synthesis were used, with subgroup analysis by alignment philosophy, failure mode, and preoperative deformity.

Fig. 1.

Preferred Reporting Items for Systematic Reviews and Meta-Analyses chart.

Risk of Bias

Risk-of-bias in randomized studies was assessed independently by 2 reviewers (W.H. and C.G.) using the Cochrane Risk-of-Bias 2 tool⁵². Methodological quality of nonrandomized studies was evaluated with the Newcastle-Ottawa Scale⁵³.

Results

Study Characteristics and Demographics

Of 3,786 screened records, 332 full texts were reviewed, and 51 studies (12 prospective, 39 retrospective) from 17 countries (2006-2025) met inclusion criteria (Fig. 1; Appendix Table 1). These studies included 7,944 patients (9,687 TKAs) with a mean [SD] age of 68.1 [3.2 years, 73.6% female predominance, mean [SD] BMI of 29.4 [3.0] kg/m², and mean [SD follow-up of 4.6 [3.3] years. Most studies were single-center (94.1%, n = 48) and single-surgeon (64.7%, n = 33). Eleven studies reported mean follow-up of 5 to 10 years^54-64, and 7 reported ≥10 years^65-71. Only 5 studies included >500 TKAs^{55,56,58,66,72}, with 2 sharing the same data set^55,56.

Surgical Characteristics

Alignment philosophy, technology utilization, robotic assistance, prosthesis type, bearing design, fixation method, and patellar resurfacing are summarized in Appendix Table 2. Most studies investigated a single alignment philosophy (76.5%, n = 39/51), predominantly MA (n = 23, 56.1% of single-philosophy studies)^{54-56,58,60,62,64,66,67,69-82}, followed by KA (n = 14, 36.6%)^{57,63,65,68,83-92}, adjusted MA (aMA; n = 1)⁵⁹, and functional alignment (FA; n = 1)⁹³. Among KA studies, 7 used uKA^{57,63,65,83,84,89,91}, 5 rKA^{68,85,86,88,92}, 1 was unspecified⁹⁰, and 1 was described as “modified” KA⁸⁷. Alignment philosophies were categorized based on the authors' self-reported descriptions to reflect the variability in definitions across the literature. Ten studies (19.6%, n = 10/51) compared 2 philosophies^61,94-102; the remaining 2 (3.9%, n = 2/51) comprised a retrieval analysis⁶² and a risk-factor study¹⁰³.

Appendix Table 3 presents the methodological quality of 45 nonrandomized studies, with most limited by lack of comparators. Appendix Table 4 presents risk-of-bias for 6 randomized studies^{66,79,94,96,99,102}, with concerns primarily in deviations from intended interventions.

Overall Outcomes: Aseptic Revision

Among 48 studies reporting outcomes for a defined alignment philosophy, 33 (68.8%) reported 100% aseptic survivorship at final follow-up^{54,58-60,64,69,70,73-80,82,83,85,87-99,101,102,104}, 19 (39.6%) reported 95 to 100% survivorship^{57,58,61,63-68,72,81,83,84,86,93,94,96,99,100}, and 4 (8.3%) reported <95% survivorship^55,56,58,100 (Appendix Tables 5 and 6).

Mechanical Alignment TKA

Of 32 studies reporting MA outcomes (single-series or comparative), 21 (65.6%) described short-term follow-up with 96.5 to 100% survivorship^{54,64,73-82,94-102}, irrespective of preoperative alignment in several reports⁷⁵. Similar results were observed in 2 mid-term studies^60,64. Nine studies provided long-term follow-up (>10 years)^{55,56,58,66,67,69-72}, and 5 of these reported decreased aseptic survivorship with non-neutral component alignment, with further decline after the 15-year follow-up in multiple series^{55,56,58,67,71}. Four long-term studies reported 97.2 to 100% survivorship even with varus tibial components^66,69,70,72. However, varus or valgus malalignment was associated with reduced survivorship in 5 reports^{55,56,58,67,71}.

Personalized Alignment TKA

Twenty-six studies examined personalized alignment techniques, most frequently KA (73.1%, n = 19)^{57,61,63,65,68,83-92,94-96,100}. Twelve KA studies reported 95.9% to 100% survivorship in the short-term across unrestricted, restricted, and modified techniques^{83-85,87-92,94-96,100}, with similar findings in 4 mid-term reports^57,61,63,86. Two single-surgeon studies with >10-year follow-up reported 98.4% to 99% survivorship with uKA⁶⁵ and rKA⁶⁸. Decreased survivorship was observed in 2 (10.5%) KA studies: 16% aseptic failure at 3 years with rKA¹⁰⁰ and a 2.2-fold increased revision hazard (p = 0.037) compared with a national registry at up to 8 years⁶¹. The degree of coronal alignment and whether revisions occurred in outliers was not reported in these 2 studies. Seven studies reported other personalized techniques (aMA^59,98,101, FA^93,97,102, anatomical alignment [AA]⁹⁹; all described excellent short-term to mid-term survivorship (97%-100%). No long-term data exist for these approaches.

Comparative Studies

Ten studies compared alignment philosophies, all using MA as the reference. Five compared MA with KA^61,94-96,100, 2 with aMA^98,101, 2 with FA^97,102, and 1 with AA⁹⁹. One rKA study reported markedly higher revision at 3 years (16% vs. 2%)¹⁰⁰, and 1 image-derived KA study showed increased revision versus registry controls using the same implant⁶¹. No other comparative study identified differences in short-term revision rates. Follow-up in comparative studies was predominantly short term (≤5 years).

Preoperative Alignment

Eleven studies restricted inclusion to varus (n = 8)^{54,59,69,72,75,87,98,99} or valgus (n = 3) knees^73,74,93. Survivorship in varus cohorts ranged from 97.2% to 100% across alignment philosophies and follow-up durations. MA was reported in 6 (75%) studies^{54,69,72,75,98,99} (mean 29-month–10-year follow-up), aMA in 2 studies (25%)^58,98 (mean 3.2-7.3-year follow-up), AA in 1 (12.5%)⁹⁹ with (mean 4.9-year follow-up), and modified KA in 1 study (12.5%)⁸⁷ (mean follow-up of 36 months).

Valgus cohorts achieved 100% survivorship with MA at short-term follow-up (27-36 months)^73,74. One FA study restricted to valgus knees reported 97.7% survivorship at 18 months, with failures limited to alignment outliers exceeding target boundaries⁹³.

Discussion

This scoping review synthesizes 51 studies encompassing 7,944 patients (9,687 TKAs) to examine the association between postoperative tibial and femoral coronal component alignment, measured on long-leg radiography, and aseptic primary TKA survivorship. Most included studies were small, single-surgeon, retrospective series with short-term to mid-term follow-up (mean 4.6-years) and focused primarily on MA. Overall, excellent aseptic survivorship was observed across alignment philosophies and component positions in the short-term to mid-term. Reduced survivorship emerged predominantly in 2 contexts: (1) isolated reports of early-to-mid-term failure with KA techniques and (2) long-term follow-up (>10 years) of MA TKA, where non-neutral (varus or valgus) coronal component alignment was associated with increased aseptic revision risk. The long-term revision outcomes of personalized alignment philosophies are underreported and require further assessment.

In MA TKA, short-term and mid-term series consistently demonstrated 96.5% to 100% aseptic survivorship, even when some components fell outside neutral targets. However, among the 9 studies with long-term follow-up, 5 reported declining survivorship when tibial or femoral components were positioned in varus or valgus. Notable examples include 74.2% to 79.3% survivorship with increased tibial varus, 90% with femoral varus, and 83.3% with femoral valgus at 15+ years^{55,56,58,67,71}. Compared with neutral components, increasing varus was associated with a 5.8× increased aseptic revision rate in 1 study⁵⁸. Supporting evidence from radiostereometric analysis (RSA) and retrieval studies suggests that varus positioning may accelerate tibial component migration and polyethylene damage, predisposing to late aseptic loosening^{34,69,71,89,103}. Nevertheless, findings are not uniform: several long-term MA series reported durable survivorship despite varus tibial components^66,69,70,72, RSA suggests no overall difference in tibial component migration between KA and MA⁹⁶ and that the amount of migration is minimal⁸⁹, and some retrieval data implicate overall limb varus more strongly than isolated component varus³⁵. These inconsistencies highlight that the strength and mechanisms of the association between coronal malalignment and long-term failure remain incompletely understood.

The association of component alignment and revision may only be seen in large, long-term studies¹⁰⁵. Personalized alignment philosophies, particularly KA, were evaluated in 26 studies, but long-term data (>10 years) were limited to only 2 single-surgeon series showing 98.4% to 99% survivorship^65,68. The largest series of any personalized technique contained just 338 TKAs⁸³. While most short-term to mid-term KA reports described 95.9% to 100% survivorship across unrestricted, restricted, and modified variants, 2 studies raised concerns: 1 reported a 16% aseptic failure rate at 3 years with restricted KA¹⁰⁰, and another identified a 2.2-fold increased revision hazard compared with national registry controls at up to 8 years⁶¹. Early failures in personalized techniques have occasionally been linked to outliers exceeding predefined boundaries^84,93, suggesting that tolerances for coronal deviation may exist. However, the precise thresholds for safe varus or valgus remain undefined, and inconsistent reporting of alignment in revised cases precludes firm conclusions.

Valgus component malalignment also warrants attention. Several KA and registry studies associated femoral and/or tibial valgus with elevated rates of patellofemoral complications, including maltracking, erosion, and stiffness^{38,61,84,88,106}. These findings align with long-term MA data showing increased revision risk with valgus components^56,67. Patellofemoral issues after TKA are multifactorial (trochlear geometry, component rotation, soft-tissue balance, implant design), yet coronal and axial plane changes inherent to many personalized philosophies may contribute. Only 1 study restricted to valgus knees evaluated a personalized approach (FA), achieving 97.7% survivorship at 18 months with failures confined to outliers⁹³.

Multiple confounders likely influence the relationship between coronal alignment and revision risk. Preoperative factors (deformity severity, bone loss, obesity, activity level), implant design, bearing type, fixation method (cemented vs. cementless), and surgical technique all interact^24,107-110. Most included studies used cemented fixation and a limited number of implant designs, limiting generalizability to contemporary cementless and more conforming prostheses. Improved standardization of alignment reporting, comprehensive adjustment for confounders, and longer-term follow-up of personalized techniques are essential to clarify these relationships.

Several limitations of this review are acknowledged. Inclusion of all study designs without formal exclusion based on quality or risk-of-bias introduces heterogeneity and potential publication bias, particularly given the predominance of retrospective, single-surgeon series¹¹¹. We have not accounted for this in results and risk-of-bias was not formally integrated into the synthesis due to the scoping focus. Loss to follow-up in many nonrandomized studies may underestimate revision rates. Planned meta-analysis was precluded by substantial variability in design, alignment measurement methods, and outcome reporting and without this, our findings lack objectivity. Generalizing the results of published studies is difficult, as it may only be that certain outlier cases create a difference in outcomes and assessing mean component alignment may not assess this. All studies reported actual postoperative alignment rather than targets alone, allowing assessment of the association between achieved alignment and survivorship; however, comparisons between philosophies account for self-reported surgical approaches, which may influence how deviations from targets affect outcomes. Reporting in many studies made it difficult to ascertain why a TKA failed, and the cause may be multifactorial. The review focused exclusively on static coronal alignment assessed on long-leg radiographs; dynamic, three-dimensional, and axial/sagittal plane factors are infrequently reported and thus not evaluated^112-115. Finally, survivorship was prioritized as the primary outcome per the a priori protocol. Potential advantages of personalized alignment philosophies in patient-reported function, satisfaction, or kinematics were not assessed, although existing comparative evidence remains inconclusive²² and there are inherent limitations of these outcomes^116,117.

Conclusions

This scoping review synthesizes the available literature on coronal tibial and femoral component alignment in TKA, assessed through long-leg radiography. Although most, primarily small studies reported excellent short-term to mid-term aseptic survivorship irrespective of alignment philosophy or component position, long-term data (>10-15-years) suggest superior survivorship with mechanically aligned components. It remains uncertain whether the poorer long-term outcomes observed with unintended varus/valgus in MA TKA also apply to the deliberate non-neutral alignment typically targeted in personalized philosophies. Personalized techniques have been evaluated in comparatively small series with limited long-term follow-up, and their applicability across all degrees and patterns of arthritis is unclear. Whether boundary restrictions are required to prevent early or late failure remains unresolved. MA remains the only philosophy supported by large-scale, long-term data across diverse patient populations. Until robust, long-term evidence with aseptic revision as the primary endpoint becomes available, MA TKA should continue to be regarded as the most thoroughly validated approach.

Appendix

Supporting material provided by the authors is posted with the online version of this article as a data supplement at jbjs.org (http://links.lww.com/JBJSOA/B182). This content was not copyedited or verified by JBJS.