Anatomic Versus Mechanically Aligned Total Knee Arthroplasty for Unicompartmental Knee Arthroplasty Revision

Patellar alignment compared between kinematic and mechanical unicompartmental knee arthroplasties

Background

Surgical treatment of unicompartmental knee arthritis is typically treated by unicompartmental knee arthroplasty (UKA). UKA may be performed by more traditional mechanical alignment, or alternatively, kinematic alignment. The purpose of this study is to compare pre- and post-operative patellar tendon alignment between mechanical and kinematic UKA.

Methods

A retrospective study at Medstar Washington Hospital Center from 2015 to 2022 identified 156 cases of partial knee arthroplasties. Of these, 95 had mechanical alignments and 61 had kinematic alignments. Patients were evaluated pre and post-surgically for Insall-Salvati and Blackburne-Peel ratios. Analysis of joint imaging x-ray imaging was performed by a blinded MSK-trained radiologist.

Results

Pre-and-post-operative Insall-Salvati and Blackburne-Peel ratios were calculated for kinematic and mechanical knee replacement patients. The ratio differences for the kinematically aligned cohort demonstrated an average for Blackburne-Peele operative ratio difference of 0.089 ( ± 0.30) and an average Insall-Salvati ratio difference of 0.18 ( ± 0.34), whereas for mechanically aligned patients, the Blackburne-Peele ratio difference was 0.054 ( ± 0.47) and the Insall-Salvati ratio difference was 0.41 ( ± 0.31). There was a statistically significant difference in operative Insall-Salvati ratios between kinematic and mechanical patients. Additionally, a two-sample t-test found a significant difference between the postoperative Blackburne-Peel and Insall-Salvati ratios for the kinematically aligned knees with a p-value of 2.33 × 10-16 below the significance level of 0.05. A two-sample f-test found a significant difference in the standard deviation of the difference between mechanical and kinematically aligned knees with respect to the Blackburne-Peel ratio, with a p-value of 0.00183.

Conclusion

This study demonstrates that sagittal patella-femoral knee alignment when comparing Blackburne-Peel and Insall-Salvati ratios are more accurately reproduced with kinematically aligned knees, and a greater variability among the kinematically aligned knees.

Sparse and inconsistent reporting of pre- and post-operative radiographic angles of total knee arthroplasty using true unrestricted kinematic alignment: An umbrella review and secondary meta-analysis

PURPOSE

To identify, synthesise and critically appraise findings of systematic reviews and meta-analyses on pre- and post-operative radiographic angles (lateral distal femoral angle [LDFA], medial proximal tibial angle [MPTA] and hip-knee-ankle [HKA] angle) of unrestricted kinematic alignment versus mechanical alignment in total knee arthroplasty (TKA).

METHODS

Two authors searched MEDLINE, EMBASE and Epistemonikos for systematic reviews, with or without meta-analyses, that reported on TKA outcomes using unrestricted kinematic alignment. The methodological quality of the included systematic reviews and meta-analyses was independently assessed using A MeaSurement Tool to Assess systematic Reviews (AMSTAR-2). The effect size with its 95% confidence interval (CI) for radiographic angles was extracted from the systematic reviews and meta-analyses. The characteristics of clinical studies included in systematic reviews were listed and tabulated. Pre- and post-operative MPTA, LDFA and HKA angles were summarised using meta-analytic random-effects models.

RESULTS

Nineteen records were eligible for data extraction. Systematic reviews and meta-analyses included 44 clinical studies, of which 31 were on unrestricted kinematic alignment and 13 were on restricted versions of kinematic alignment. None of the included systematic reviews or meta-analyses fulfiled all seven critical AMSTAR-2 domains. Few comparative studies reported both pre- and post-operative angles (LDFA, n = 3; MPTA, n = 4; and HKA angle, n = 10). Mean pre- and post-operative LDFAs were 88.0° (range, 83-94°) and 88.0° (range, 80-96°) for the kinematic alignment group, and 88.2° (range, 83-95°) and 90.2° (range, 84-97°) for the mechanical alignment group. Mean pre- and post-operative MPTAs were 86.0° (range, 78-93°) and 87.1° (range, 78-94°) for the kinematic alignment group and 86.4° (range, 77-94°) and 89.6° (range, 84-95°) for the mechanical alignment group. Mean pre- and post-operative HKA angles were -3.3° (range, -24° to 24°) and -0.3° (range, -10° to 8°) for the kinematic alignment group and -6.9° (range, -25° to 7°) and -0.9° (range, -8° to 7°) for the mechanical alignment group.

CONCLUSION

Most systematic reviews and meta-analyses that report outcomes of TKA using kinematic alignment do not distinguish between the different versions of kinematic alignment. The clinical studies included in systematic reviews are limited and inconsistent in their reporting of radiographic angles. Different alignment strategies are often grouped under the umbrella term of kinematic alignment, which contributes to conflicting reports, confusion and unresolved questions regarding the efficacy of true unrestricted kinematic alignment.

LEVEL OF EVIDENCE

Level IV.

Robotic-assisted medial unicompartmental knee arthroplasty restored prearthritic alignment and led to superior functional outcomes compared with conventional techniques

PURPOSE

Robotic-assisted medial unicompartmental knee arthroplasty (UKA) can ensure precise preoperative planning, minimise soft tissue damage and restore native coronal alignment. However, few studies have investigated how these advantages translate into differences in early postoperative outcomes. This study aimed to compare differences in early outcomes between conventional UKA (C-UKA) and robotic-assisted UKA (R-UKA).

METHODS

This retrospective study investigated two groups of patients who underwent medial UKA: C-UKA group (n = 35) and R-UKA group (n = 35). We assessed (1) serum indicators (hemoglobin, creatine kinase and C-reactive protein) and pain visual analogue scale (VAS) at postoperative days (PODs) 1, 2, 4 and 6; (2) radiologic parameters including joint line height change and arithmetic and mechanical hip-knee-ankle angle (aHKA and mHKA); (3) patient-reported outcomes including Knee Society Scores, Western Ontario and Mcmaster Universities Arthritis Index (WOMAC) and Forgotten Joint Score-12 (FJS-12) at 1-year follow-up.

RESULTS

Despite similar serum indicator results, pain VAS was lower in the R-UKA group than in the C-UKA group at PODs 2 (2.5 ± 1.3 vs. 3.6 ± 1.2, p = 0.02), 4 (2.4 ± 0.9 vs. 3.3 ± 1.0, p = 0.03) and 6 (1.9 ± 1.1 vs. 3.1 ± 1.1, p < 0.01). The joint line height change was significantly lower in the R-UKA group than in the C-UKA group (0.9 mm ± 0.6 mm vs. 2.0 mm ± 1.3 mm, p = 0.02). The equivalence test for preoperative aHKA and postoperative mHKA revealed equivalence in only the R-UKA group (p < 0.01). The R-UKA group showed better WOMAC and FJS-12 compared to C-UKA group at 1-year follow-up.

CONCLUSION

R-UKA led to lower pain VAS in the early postoperative period compared with C-UKA. Additionally, R-UKA effectively restored the joint line and prearthritic lower limb alignment, resulting in superior functional outcomes at 1-year follow-up compared with C-UKA.

LEVEL OF EVIDENCE

Level III.

Restoration of preoperative tibial alignment improves functional results after medial unicompartmental knee arthroplasty

PURPOSE

The alignment obtained after unicompartmental knee arthroplasty (UKA) influences the risk of failure. Kinematic alignment after UKA based on Cartier angle restauration is likely to improve clinical outcomes compared with mechanical alignment. The purpose of this study is to analyze the influence of implant alignment and native knee restoration after UKA using the conventional techniques on clinical outcomes.

METHODS

This retrospective study included 144 medial UKA patients from 2015 to 2020. Radiographic measurements were performed pre- and postoperatively. Outliers were defined as follows: Δ Cartier > 3° (difference between the preoperative and postoperative Cartier angle); Δ MPTA (Medial Proximal Tibial angle) and postoperative TCA (Tibial Coronal component Angle) > 3° (difference between the positioning of the tibial implant and the preoperative proximal tibial deformity). The Knee injury and Osteoarthritis Outcome Score (KOOS), the International Knee Society (IKS) Function and Knee score, the Forgotten Joint Score (FJS), and the Subjective Knee Value (SKV) were evaluated. A Student t test or a non-parametric Wilcoxon test was used for non-normal data to compare pre- and postoperative values for functional scores and angular measurements. The correlation of postoperative angles with functional outcomes was assessed by the Spearman's rank correlation coefficient.

RESULTS

During the inclusion period, 214 patients underwent medial UKA, 71 patients were excluded, and 19 were lost to follow-up leaving 124 patients with 144 knees (20 bilateral UKA) included for analysis with a mean follow-up of 54.7 months ± 22.1 (24-95). The Δ Cartier was significantly correlated with IKS function (R2 = 0.06, p < 0.001) and FJS (R2 = 0.05, p < 0.01) scores. The Δ preoperative MPTA-TCA was significantly correlated (p < 0.001) with KOOS (R2 = 0.38), IKS Knee (R2 = 0.17), IKS function (R2 = 0.34), SKV (R2 = 0.08), and FJS (R2 = 0.37) scores. In subgroup analysis, non-outliers (< 3°) for Δ preoperative MPTA-TCA had better KOOS score (Δ = 23.5, p < 0.001) and IKS Function (Δ = 17.7, p < 0.001) compared to outliers (> 3°) patients.

CONCLUSION

Functional results after medial UKA can be influenced by implant alignment in the coronal plane with slight clinical improvement when positioning the tibial implant close to the preoperative tibial deformity, rather than by restoring the Cartier angle. This series suggests the interest of a more personalized alignment strategy, but these results will have to be confirmed by other controlled studies.

LEVEL OF EVIDENCE

IV, retrospective case series.

Restricted Kinematically Aligned Total Knee Arthroplasty Following Failed Oxford Unicompartmental Knee Arthroplasty

In this report, we describe how to revise a failed Oxford unicompartmental knee arthroplasty to kinematically aligned total knee arthroplasty (TKA). Its benefits are the maintenance of the native joint line along with the avoidance of supplemental parts, such as metal augments and stems. This can be applied to patients whose medial tibial cortex is well preserved. The distal cutting plane and rotation alignment are decided before the removal of the femoral component. The tibial cutting plane is up to 12 mm below the lateral joint surface and the varus is up to 5° below the extramedullary rod. Eventually, the native joint line and alignment along with the soft tissue envelope can be well maintained, similar to the restricted kinematically aligned TKA.

Kinematic alignment of medial UKA is safe: a systematic review

PURPOSE

Owing to the improved understanding of knee kinematics and the successful introduction of the kinematic alignment (KA) technique for implanting total knee arthroplasty (TKA), it was recently understood that the "Cartier angle technique" corresponds to a kinematic implantation of the uni-compartmental knee arthroplasty (UKA) components. When compared to the universally spread mechanical alignment (MA) technique for implanting UKA, the KA method generates a more anatomic prosthetic knee that may be clinically advantageous. The aims of this study are to determine if KA UKAs are associated with acceptable functional performance and patient satisfaction (question 1), rates of residual pain and tibia plateau fracture (question 2), and rates of reoperation and revision (question 3), and to define the component orientation and limb alignment as measured on radiograph (question 4), and the stress shielding related bone loss in the proximal tibia (question 5) with KA UKA, and where possible to compare with MA UKA.

STUDY HYPOTHESIS

KA UKA generates good clinical outcomes, similar or superior to the ones of MA UKA.

METHOD

Systematic review of literature databases were primarily searched using Healthcare Databases Advanced Search (HDAS). Two primary searches were conducted using the electronic databases MEDLINE, EMBASE, and PubMed, and a secondary search was conducted using review articles and bibliography of obtained papers in order to ascertain more material.

RESULTS

Nine eligible non-comparative prospective (3) or retrospective (6) cohort studies, which cumulated 593 KA UKAs with follow-up between 3.2 and 12 years, fulfilled the inclusion criteria for this systematic review. The findings demonstrated high Knee Society Score (KSS) (from 87 to 95) and function scores (from 81 to above 91) in addition to patient satisfaction scores of 88%. There was no revision for tibia plateau fracture, 0.8% (5 cases) for unexplained pain tibia, 2.0% (12 cases) for component loosening, and 5.6% (33 cases) for any causes of aseptic failures reported for KA UKA. The prosthetic lower limb and tibia implant alignments were both found to be in slight varus (means between 3 and 5°), and the postoperative joint line and tibia component was shown to be parallel to the floor when standing. The KA UKA components migration, as measured on radiostereometry, was acceptable.

DISCUSSION/CONCLUSION

The KA technique is an alternative, personalised, more physiological method for implanting UKA, which could be clinically advantageous when compared to the MA technique. The literature supports the good mid- to long-term clinical safety and good efficacy of KA UKA; however, comparison between KA and MA techniques for UKA was not performed due to limited literature. Further investigations are needed to better define the clinical impact of KA UKA, and the acceptable limits for KA of the UKA tibial component.

LEVEL OF EVIDENCE

Level 4; systematic review of level 4 studies.

Revision of a Medial UKA to a Kinematic Aligned TKA: Comparison of Operative Complexity, Postoperative Alignment, and Outcome Scores to a Primary TKA

Revision of a medial unicompartmental knee arthroplasty (UKA) to a mechanically aligned total knee arthroplasty (MA TKA) is inferior to a primary TKA; however, revision with kinematic alignment (KA) has not been well studied. The present study determined whether patients revised with KA had a higher use of revision components, different postoperative alignment, and different clinical outcome scores from patients with a primary KA TKA. From 2006 to 2017, all patients suitable for a revision of a failed medial UKA to a TKA and a primary TKA were treated with KA. Reasons for the revision performed in ten females and six males at a mean age 67 ± 8 years included progression of osteoarthritis in the lateral hemi-joint (n = 6), aseptic loosening (n = 4), unremitting medial pain without loosening (n = 4), and insert wear (n = 2). Patients with a revision were matched 1:3 with a control cohort treated with a primary KA TKA. Revisions were performed with primary components without augments, stem extensions, or bone grafts. Seven postoperative alignment parameters of the limb and components were comparable to the control cohort (p > 0.05). At a mean follow-up of 5 years (1-10), implant survival was 100%, and the revision/primary group clinical outcome scores were 39/43 points for the Oxford Knee Score (OKS), 2.2/1.0 cm for the Visual Analog Pain Score, and 12/7 points for the Western Ontario and McMaster Universities Osteoarthritis Index score. When compared with primary KA TKA, surgeons that revise a failed medial UKA to a TKA with use of KA can expect similar operative complexity, comparable postoperative alignments, and a mean OKS of 39 points, which is higher than the mean 27 to 30 point range reported for revision of a failed UKA to a TKA with the use of MA.

Planning a total knee arthroplasty through an application for mobile devices: case report

For decades, the main cause of failure in total knee arthroplasty (TKA) is still the malalignment of prosthetic components. The authors present a case of advanced knee arthrosis, treated by TKA. Preoperative planning was performed with a mobile application and the patient was submitted to primary TKA using an implant developed with inspiration from the theory of "modified GAP" with a rotated tibial tray. Neutral mechanical alignment of the lower limbs was obtained and the application proved to be viable regarding its proposed plan for this case.

Outcome of kinematic alignment using patient-specific instrumentation versus mechanical alignment in TKA: a meta-analysis and subgroup analysis of randomised trials

INTRODUCTION

Kinematic alignment (KA) in total knee arthroplasty (TKA) matches component position to the pre-arthritic anatomy of an individual patient, with the aim of improving functional outcomes. Recent randomised controlled trials (RCTs) comparing KA to traditional neutral mechanical alignment (MA) have been mixed. This collaborative study combined raw data from RCTs, aiming to compare functional outcomes between KA using patient-specific instrumentation (PSI) and MA, and whether any patient subgroups may benefit more from KA technique.

MATERIALS AND METHODS

A literature search in PubMed, EMBASE and Cochrane databases identified four randomised controlled trials comparing patients undergoing TKA using PSI-KA and MA. Unpublished data including Western Ontario McMaster Universities Arthritis Index (WOMAC) and Knee Society Score (KSS) were obtained from study authors. Meta-analysis compared MA to KA change (post-op minus pre-op) scores. Subgroup-analysis on KA patients looked for subgroups more likely to benefit from KA and the impact of PSI accuracy.

RESULTS

Meta-analyses of change scores in 229 KA patients versus 229 MA patients were no different from WOMAC (mean difference 3.4; 95% confidence interval - 0.5 to 7.3), KSS function (1.3, - 3.9 to 6.4) or KSS combined (7.2, - 0.8 to 15.2). A small advantage was seen for KSS pain in the KA group (3.6, 95% CI 0.2-7.1). Subgroup-analysis showed no difference between varus, valgus and neutral pre-operative alignment groups, and those who did and did not achieve KA plans. Pain-free patients at 1-year were more likely to achieve KA plans.

CONCLUSION

Patient-reported outcome scores following TKA using PSI-KA are similar to MA. No identifiable subgroups benefited more from KA, and long-term results remain unknown. Inaccuracy of the PSI system used in KA patients could potentially affect outcome.