Short-term follow-up of kinematically vs. mechanically aligned total knee arthroplasty with medial pivot components: A case-control study

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.

Kinematic alignment adequately restores trochlear anatomy, patellar kinematics and kinetics in total knee arthroplasty: A systematic review

PURPOSE

Patellofemoral pain, maltracking and instability remain common and challenging complications after total knee arthroplasty. Controversy exists regarding the effect of kinematic alignment on the patellofemoral joint, as it generally leads to more femoral component valgus and internal rotation compared to mechanical alignment. The aim of this systematic review is to thoroughly examine the influence of kinematic alignment on the third space.

METHODS

A systematic search of the Pubmed, Cochrane and Web of Science databases was performed to screen for relevant articles published before 7 April 2024. This led to the final inclusion of 42 articles: 2 cadaveric, 9 radiographic, 12 computer simulation and 19 clinical studies. The risk of bias was evaluated with the risk of bias in non-randomised studies - of interventions tool as the lowest level of evidence of the included clinical studies was IV. The effects of kinematic alignment on patellar kinematics and kinetics, trochlear anatomy reconstruction and patellofemoral complication rate were investigated.

RESULTS

Kinematic alignment closely restores native patellar kinematics and kinetics, better reproduces native trochlear anatomy than mechanical alignment and leads to a 0%-11.4% incidence of patellofemoral complications. A more valgus joint line of the distal femur can cause lateral trochlear undercoverage and a trochlear angle orientation medial to the quadriceps vector when applying kinematic alignment, both of which can be solved by using an adjusted design with a 20.5° valgus trochlea.

CONCLUSION

Kinematic alignment appears to be a safe strategy for the patellofemoral joint in most knees, provided that certain precautions are taken to minimize the risk of complications.

LEVEL OF EVIDENCE

Level IV clinical studies, in vitro research.

Does the posterior tibial slope in caliper-verified unrestricted kinematically aligned TKA using manual instruments match the slope in the contralateral healthy knee and improve function?

PURPOSE

Unrestricted kinematically aligned total knee arthroplasty (unKA TKA) strives to restore the pre-arthritic posterior tibial slope (PTS), however consistency of achieving this alignment target is unknown. The present study determined the proportion of subjects with differences in PTS less than 2° from the target and the improvement in patient-reported function after unKA TKA.

METHODS

A review of 562 postoperative scanograms identified 99 patients (51 female) with a unKA TKA in one limb, a contralateral healthy limb, and a postoperative axial CT scan. All patients were treated with a primary unKA TKA performed with mechanical instruments where the alignment target was setting the PTS to match that of the medial compartment of the contralateral healthy knee. The PTS of the TKA and the healthy medial tibial plateau were measured and the difference determined. The patient-reported Oxford Knee Score (OKS) measured pre- and post-operative function.

RESULTS

The proportion of subjects within a tolerance interval of ±2° of the contralateral healthy knee at 95% confidence was 85%. The median OKS improved from 20 points preoperatively to 47 points (range 18-48) at 15 months postoperatively. Greater differences of the PTS from healthy were unrelated to poorer Oxford Knee Scores.

CONCLUSION

Unrestricted KA TKA using manual instruments with caliper verification of resection thickness restored a high percentage of patients within a clinically acceptable tolerance of the posterior tibial slope of the contralateral healthy knee. The median postoperative OKS indicated clinically important improvement in patient-reported function.

Mechanically Aligned Second-Generation Medial Pivot Primary Total Knee Arthroplasty Does Not Reproduce Normal Knee Biomechanics: A Gait Analysis Study

Background: This study aimed to evaluate post-operative lower limb function following second-generation mechanically aligned medial pivot (MP) TKA implantation. Standard gait analysis was performed to collect kinematic and kinetic data, which were then compared with physiological data from the literature obtained using the same evaluation methodology as the present study. The hypothesis was that this TKA would not fully restore normal knee and adjacent joint motion during walking. Methods: Our cohort comprised 15 patients consecutively enrolled from September 2019 to December 2022 who underwent primary TKA with the second-generation MP Evolution Knee System (MicroPort Orthopaedics Inc., Arlington, TN, USA). Pre-operatively and 6 months post-surgery, gait analysis during level walking was performed on all patients, as well as clinical evaluations using the Knee Society Score (KSS), the Knee Injury and Osteoarthritis Outcome Score (KOOS), and the Visual Analogue Scale (VAS). Results: The clinical scores improved significantly (p < 0.001) after surgery (pre-/post-operative KSS functional, KSS clinical, VAS, and KOOS: 51.7 ± 17.3/84 ± 18.4, 45.3 ± 16.2/74.1 ± 12.6, 6.9 ± 1.8/2.0 ± 1.9, and 33.9 ± 11.8/69.1 ± 16.5, respectively). The statistical parametric mapping (SPM) analysis between the post-operative and reference control data revealed significant differences in the initial and final 20% of the gait cycle for the rotation of the knee in the frontal and transverse planes and for the rotation of the ankle in the sagittal plane. Conclusions: This study shows that new-generation MP TKA with mechanical alignment does not fully restore normal gait biomechanics, particularly in knee rotational movements, indicating a need for improved surgical techniques and prosthetic designs.

Limitations of the knee society score in kinematically aligned total knee arthroplasty

Purpose

The Knee Society Scoring System (KSS) is a frequently used outcome score which quantifies functional patients' outcomes before and after total knee arthroplasty (TKA). Several problems arise when trying to implement KSS for obtaining postoperative outcomes after more personalised aligned TKAs. Scoring for valgus femorotibial angle (FTA) intervals outside moderate ranges is often poorly explained, the specific version of KSS used for outcome collection is frequently unclear and the exact measuring methods are typically not described in the literature. The aims of this systematic review were to investigate the latest user practice, the application of KSS and its limitations after kinematically aligned (KA) TKA.

Methods

A systematic literature search following PRISMA guidelines was conducted on PubMed, Embase, Medline and Scopus to identify potentially relevant articles for this review, published from the beginning of January 2013 until the end of January 2023. Broad Mesh terms such as 'kinematic alignment', 'total knee arthroplasty' and 'knee society score' were used for building search strategy in each database accordingly. Articles reporting postoperative values of the objective surgeon-assessed KSS after KA TKA or KA and mechanically aligned TKA were included. For assessing included randomised control trials (RCTs), an Agency for Healthcare Research and Quality's design-specific scale for assessing RCTs was used. The non-RCTs were assessed by using the Joanna Briggs Institute Critical Appraisal Tool. The Ottawa-Newcastle Score system was also used. Studies were additionally evaluated for their radiological methodology by using a five-question checklist (Radiological Assessment Qualit criteria).

Results

The initial search identified 167 studies, of which 129 were considered for screening. Ten studies reporting outcomes after KA TKA did not use the objective surgeon-assessed part of KSS for clinical outcome measurement, and 30 studies reporting outcomes after KA TKA did not use KSS at all for clinical and/or functional outcomes. From the 10 included studies, only six have used the latest KSS score (2011), the rest using its 1989 variant; and out of these six studies, only two presented values of the FTA, which is needed for calculating the KSS's 'alignment' subcomponent, the rest presenting hip-knee-ankle angle (HKA) values. Additionally, when converting these HKA values to FTA intervals, the authors of this systematic review found that KA TKA FTA intervals display limits, which tend to be outside the 'well-scored' KSS anatomical alignment interval.

Conclusion

The inconsistent and nonstandardised use of the surgeon-assessed KSS across studies reviewed compromises assessment reliability and patient outcome scores. To enhance precision and comparability, it is crucial to standardise the KSS application, incorporating personalised alignment strategies for more accurate patient evaluations.

Level of Evidence

Level III.

Methods of alignment in total knee arthroplasty, systematic review

Introduction

Although total knee arthroplasty (TKA) is a very frequent surgery, one in five patients is not completely satisfied. Mechanical alignment (MA) is the most popular technique for implanting TKA. However, to improve clinical outcomes, new techniques that aim to rebuild the native alignment of the knee have been developed.

Objective

The aim of this study is to perform a systematic review of the available clinical trials and observational studies comparing clinical and radiological outcomes of different methods of alignment (kinematic, anatomic, functional) to MA.

Methods

A systematic review is performed comparing results of patient reported outcome measures (PROMs) questionnaires (WOMAC, OKS, KSS, KOOS, FJS), radiological angles (HKA, mLDFA, MPTA, JLOA, femoral rotation and tibial slope) and range of motion (ROM).

Results

Kinematic and functional alignment show a slight tendency to obtain better PROMs compared to mechanical alignment. Complication rates were not significantly different between groups. Nevertheless, these results are not consistent in every study. Anatomic alignment showed no significant differences compared to mechanical alignment.

Conclusion

Kinematic alignment is an equal or slightly better alternative than mechanical alignment for patients included in this study. However, the difference between methods does not seem to be enough to explain the high percentage of dissatisfied patients. Studies implementing lax inclusion and exclusion criteria would be needed to resemble conditions of patients assisted in daily surgical practice. It would be interesting to study patient's knee phenotypes, to notice if any method of alignment is significantly better for any constitutional deviation.

Higher satisfaction and function scores in restricted kinematic alignment versus mechanical alignment with medial pivot design total knee arthroplasty: A prospective randomised controlled trial

PURPOSE

Restricted kinematic alignment (rKA) in total knee arthroplasty (TKA) and medial pivot (MP) knee designs already showed superior outcomes in independent comparative studies. The objective of this study was to assess whether rKA with MP TKA provides better clinical and functional outcomes compared to mechanical alignment (MA) with MP TKA.

METHODS

This is a randomised, parallel two group study involving a total of 98 patients with end-stage knee osteoarthritis. Patients were randomly allocated to either rKA or MA TKA procedures conducted with a MP prothesis using patient-specific instruments between 2017 and 2020. Final follow-up was at 2 years postoperatively. Demographic data and clinical and functional scores (Oxford knee score, knee society score [KSS], Western Ontario and McMaster Universities Osteoarthritis Index [WOMAC], forgotten joint score [FJS]) were collected and compared preoperative, 1 year postoperative and 2 years postoperative. Coronal plane alignment of the knee and functional knee phenotype classification were recorded.

RESULTS

A total of 47 patients (rKA) and 51 patients (MA) were included in final analysis. Superior joint awareness scores (FJS) were found at 1 year postoperative for rKA (62.2 vs. 52.4, p = 0.04). KSS subscores (expectation score, satisfaction score) improved with rKA with significant differences at both 1 and 2 years postoperatively. Major differences between rKA and MA were found in subgroup analysis of varus and neutral CPAK phenotypes. Both 1 year and 2 years postoperatively, FJS was significantly better in KA compared with MA in varus CPAK phenotypes (63.1 vs. 44.9, p = 0.03; 71.1 vs. 46.0, p = 0.005). Further clinical and functional scores showed improvement in the varus CPAK phenotypes with predominantly significant improvement in the expectation and satisfaction KSS subscores. No significant differences were found in the comparison of rKA and MA in neutral CPAK phenotypes.

CONCLUSION

The rKA of MP TKA design shows superior patient satisfaction and self-reported function when compared to MA MP TKA. Furthermore, rKA MP TKA shows superior joint awareness at early postoperative stage. The most important clinical relevance of this study is the clear superiority of rKA in varus phenotypes.

LEVEL OF EVIDENCE

Level II.

Correcting for asymmetry of the proximal tibial epiphysis is warranted to determine postoperative alignment deviations in kinematic alignment from planned alignment of the tibial component on the native tibia

BACKGROUND

In total knee arthroplasty, unrestricted kinematic alignment aims to restore pre-arthritic lower limb alignment and joint lines. Joint line orientations of the contralateral healthy proximal tibia might be used to evaluate accuracy of tibial component alignment post-operatively if asymmetry is minimal. Our objective was to evaluate left-to-right asymmetry of the proximal tibial epiphysis in posterior tibial slope and varus-valgus orientation as related to unrestricted kinematic alignment principles.

METHODS

High resolution CT images (0.5 mm slice thickness) were acquired from bilateral lower limbs of 11 skeletally mature subjects with no skeletal abnormalities. Images were segmented to generate 3D tibia models. Asymmetry was quantified by differences in orientations required to shape-match the proximal epiphysis of the mirror 3D tibia model to the proximal epiphysis of the contralateral 3D tibia model.

FINDINGS

Systematic and random differences (i.e. mean ± standard deviation) in tibial slope and varus-valgus orientation were - 0.8° ± 1.2° and - 0.2° ± 0.8°, respectively. Ninety five percent confidence intervals on the means included 0° indicating that systematic differences were minimal.

INTERPRETATION

Since random differences due to asymmetry are substantial in relation to random surgical deviations from pre-arthritic joint lines previously reported, post-operative computer tomograms of the contralateral healthy tibia should not be used to directly assess accuracy of tibial component alignment on a group level without correcting for differences in tibial slope and varus-valgus orientation due to asymmetry.

Analysis of Short-Term Clinical and Functional Outcomes in Patients Undergoing Total Knee Arthroplasty with Kinematic Alignment Technique

BACKGROUND

Surgery remains the best option for more advanced stages of knee osteoarthritis (OA). Kinematic alignment (KA) is an innovative surgical technique that aims to co-align the rotational axes of the femoral, tibial, and patella components with the three kinematic axes of the knee. This study aims to evaluate and analyze short-term clinical, psychological, and functional outcomes in patients undergoing total knee replacement with the KA technique.

METHODS

Twelve patients who underwent total knee replacement surgery with kinematic alignment from May 2022 until July 2022 were prospectively followed and interviewed. Before surgery, the day after surgery, and postoperative day 14, the following tests were evaluated: VAS, SF-12 PS, SF-12 MS, KSS, KSS-F, PHQ-9, and KOOS-PS.

RESULTS

The mean BMI value of 30.4 (±3.4) Kg/m², mean age of 71.8 (±7.2) years. All the scores on the various tests administered consistently showed statistically significant improvement, not only immediately after surgery but also comparing the first to the fourteenth postoperative day.

CONCLUSION

Kinematic alignment technique as a surgical treatment for KO allows the patient a fast postoperative recovery and good clinical, psychological, and functional results in a short time. Further studies are needed with a larger sample size, and prospective randomized studies are essential to compare these results with mechanical alignment.

Comparison of weight-bearing full-length radiography and three-dimensional computed tomography scan-based models to assess knee joint coronal alignment following total knee arthroplasty

BACKGROUND

The validity of standing long-leg radiography (LLR) - the standard method for evaluating coronal alignment after total knee arthroplasty (TKA) - remains controversial. We evaluated the measurement reliability and validity of LLR following TKA by comparing postoperative radiographs with three-dimensional computed tomography (3DCT) scans of the lower extremities.

METHODS

We retrospectively collected the data of 55 knees from 44 patients who underwent postoperative 3DCT and 5-day and 6-month LLR for coronal alignment evaluation following TKA. The coronal femoral component angle (CFA) and coronal tibial component angle (CTA) were measured using 3DCT and LLR images. Correlations between the hip-knee-ankle angle (HKAA), CFA and CTA were analysed using Pearson's correlation coefficient (PCC); Bland-Altman plots were constructed to assess agreement between 5-day and 6-month radiographic and 3DCT scan measurements.

RESULTS

The mean difference in HKAA between 3DCT, and 5-day and 6-month LLR was 1.3 ± 1° and 1.1 ± 0.7°, respectively. Differences of >1° in HKAA between 3DCT, and 5-day and 6-month LLR were observed in 31 (56.4%) and 28 (50.9%) knees, respectively; differences of >2° in these parameters were observed in 15 (27.3%) and nine (16.4%) knees, respectively. The 3DCT scan and radiograph measurements of HKAA, CFA and CTA were strongly correlated (PCC, 0.81-0.92; P < 0.001). Bland-Altman plot validity was within acceptable limits.

CONCLUSION

LLR shows good reliability and validity for measuring coronal alignment. When comparing 3DCT scans and radiographs, a high number of HKAA values differed by more than 1° and 2°; this indicates that rigorous alignment evaluation requires 3DCT measurements.

Kinematic alignment results in clinically similar outcomes to mechanical alignment: Systematic review and meta-analysis

PURPOSE

It is unclear whether a difference in functional outcome exists between kinematically aligned (KA) and mechanically aligned (MA) knee replacements. The aim of this study is to perform a comprehensive systematic review and meta-analysis of the available level I-IV evidence.

METHODS

A meta-analysis of randomised controlled trials and observational studies comparing patient reported outcome measures (PROMs), range of motion (ROM), gait analysis and complications in TKA with KA and MA was performed. Quality assessment was performed for each study using the Joanna Briggs Institute (JBI) critical appraisal tools.

RESULTS

Twelve randomised controlled trials and fourteen observational studies published between 2014 and 2022 were included in the final analysis. Meta-analysis revealed KA to have significantly better Oxford Knee Score (OKS) (p = 0.02), Forgotten Joint Score (FJS) (p = 0.006), Knee Society Score (KSS) Objective Knee (p = 0.03) and KSS Functional Activity (p = 0.008) scores. However, these improvements did not exceed the minimum clinically important difference (MCID) values reported in the literature. Subgroup analysis showed robotic assisted KA-TKA to have a clinically superior FJS (p = 0.0002) and trend towards KSS Objective Knee score (p = 0.10), compared to PSI. Gait and plantar pressure distribution of KA cohorts more closely represented healthy cohorts, and KA showed a weak association of a decreased knee adduction moment (KAM) compared to MA. Differences in Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), Knee Injury and Osteoarthritis Outcome Score (KOOS), range of motion and complications were not significant between groups.

CONCLUSION

Although KA results in several improved functional outcomes, these do not reach clinical significance. Further standardised large-scale randomised studies are required to improve the quality of evidence. As it stands, it is difficult to recommend one philosophy over the other.

Coronal knee alignment measurements differ on long-standing radiographs vs. by navigation

BACKGROUND

The long-standing radiograph (LSR) is the reference tool for assessing knee alignment after total knee arthroplasty (TKA). However, its value is debatable, as many factors can influence measurement accuracy. Computer-assisted surgery (CAS) provides accurate measurements. Few studies have compared LSR and computer-assisted measurements of knee alignment. The objective of this study was to compare hip-knee-ankle (HKA) angle values obtained before and after TKA on LSRs to those obtained during CAS.

HYPOTHESIS

The HKA angle values measured on LSRs before and after surgery are identical to those measured during CAS.

MATERIAL AND METHODS

The HKA angles of 126 knees were measured on bipedal full-weight-bearing LSRs obtained before and 3 months after TKA. The results were compared to the values obtained during CAS.

RESULTS

Before surgery, the standard deviation was 2.672, with limits of agreement of {-5.391; + 5.082}. The intra-class coefficients were good for the overall measurements (0.9), good for detecting>10° varus (0.89), fair for<10° varus and valgus (0.66 and 0.71, respectively), poor for>10° valgus (0.43) and poor for normal alignment (0). Post-operatively, the standard deviation was 3.113, with limits of agreement of {-6.426; +5.776}. The intra-class coefficient was poor for the overall measurements (0.20), negative for normal alignment (-0.05) and<10° valgus (-0.05), and positive for<10° varus (0.017) and for>10° varus and valgus (0.33).

CONCLUSION

Before TKA, the LSR overestimates the deformity compared to CAS. After surgery, the two methods are not comparable. These findings underline the relevance of routinely obtaining LSRs and for using LSR results to estimate costs for healthcare insurance reimbursement purposes.

LEVEL OF EVIDENCE

IV, retrospective observational cohort study.

No kinematical difference between ultra-congruent and medial-congruent total knee arthroplasty when implanted with mechanical alignment: an in vivo dynamic RSA study

PURPOSE

To explore in vivo kinematical behavior of the same total knee arthroplasty (TKA) cruciate-retaining (CR) femoral design with either medial-congruent (MC) or ultra-congruent (UC) inlay using model-based dynamic radiostereometric analysis (RSA). The hypothesis was that there would be comparable kinematics between the two groups.

METHODS

A cohort of 16 randomly selected patients (8 MC Persona Zimmer, 8 UC Persona Zimmer) was evaluated through dynamic radiostereometric analysis (RSA) at a minimum of 9 months after TKA, during the execution of a sit-to-stand. The antero-posterior (AP) translation of the femoral component and the AP translation of the low point of medial and lateral femoral compartments were compared through Student's t test (p < 0.05).

RESULTS

Both groups showed a medial pivot behavior, with a significantly greater anterior translation of the Low Point of the lateral compartment with respect to the medial compartment (MC medial range: 2.4 ± 2.4 mm; MC lateral range: 7.7 ± 3.0 mm; p < 0.001 - UC medial range: 3.3 ± 3.3 mm; UC lateral range: 8.0 ± 3.2 mm; p < 0.001). A statistically significant greater degree of flexion was clinically recorded at follow-up visit in the MC group respect to the UC group (126° vs 101°-p = 0.003).

CONCLUSION

The present study did not show difference in the medial pivot behavior between ultra-congruent and medial-congruent total knee arthroplasty when implanted with mechanical alignment; however, the MC group demonstrated a greater degree of flexion. The MC design examined is a valid alternative to the UC design, allowing to achieve a screw-home movement restoration combined with a high flexion.

LEVEL OF EVIDENCE

IV.

Clinical radiographic outcomes and survivorship of medial pivot design total knee arthroplasty: a systematic review of the literature

BACKGROUND

Total knee arthroplasty is a reliable procedure able to reduce pain and disability in patients suffering from osteoarthritis. However, a considerable percentage of patients still experiences unsatisfactory results. Medial pivot total knee arthroplasty has been introduced in the clinical practice to overcome problems related with classic design implants and better mimic native knee kinematics. The aim of this study was to analyze survivorship and clinical and radiographic outcomes of medial pivot implants.

METHODS

A systematic research was conducted in eight different databases. Thirty-four studies met the inclusion criteria and were included in the analysis. Data on objective and patients-reported outcomes, radiographic alignment, and survivorship were collected and analyzed. Revision rate was expressed as revision per 100 components years.

RESULT

A total of 3377 procedures were included. Mean follow-up was 85.7 months (range, 12-182). The revision per 100 components years was 0.19, which corresponds to a revision rate of 1.9% after 10 years. Mean post-operative range of motion was 117.3 ± 0.4°. Mean clinical and functional Knee Society Score were, respectively, 85.9 ± 1.1 and 84.7 ± 3.5 at final follow-up. Post-operative femorotibial alignment was 177.1 ± 0.5°. Alfa and beta angles were 95.7 ± 0.1° and 89.2 ± 0.1°, respectively. Gamma and delta angles were 2.3 ± 0.6° and 86.7 ± 0.4°.

CONCLUSION

Medial pivoting implants provided excellent survivorship and low revision rate, as well as good-to-excellent results in term of objective and patient-reported clinical outcomes, and reliable correction of radiographic parameters. More high-quality studies with long-term follow-up are needed to clarify the role of medial pivoting implants.

Current concepts in total knee arthroplasty : mechanical, kinematic, anatomical, and functional alignment

Limb alignment in total knee arthroplasty (TKA) influences periarticular soft-tissue tension, biomechanics through knee flexion, and implant survival. Despite this, there is no uniform consensus on the optimal alignment technique for TKA. Neutral mechanical alignment facilitates knee flexion and symmetrical component wear but forces the limb into an unnatural position that alters native knee kinematics through the arc of knee flexion. Kinematic alignment aims to restore native limb alignment, but the safe ranges with this technique remain uncertain and the effects of this alignment technique on component survivorship remain unknown. Anatomical alignment aims to restore predisease limb alignment and knee geometry, but existing studies using this technique are based on cadaveric specimens or clinical trials with limited follow-up times. Functional alignment aims to restore the native plane and obliquity of the joint by manipulating implant positioning while limiting soft tissue releases, but the results of high-quality studies with long-term outcomes are still awaited. The drawbacks of existing studies on alignment include the use of surgical techniques with limited accuracy and reproducibility of achieving the planned alignment, poor correlation of intraoperative data to long-term functional outcomes and implant survivorship, and a paucity of studies on the safe ranges of limb alignment. Further studies on alignment in TKA should use surgical adjuncts (e.g. robotic technology) to help execute the planned alignment with improved accuracy, include intraoperative assessments of knee biomechanics and periarticular soft-tissue tension, and correlate alignment to long-term functional outcomes and survivorship.

Oxford Knee Score and EQ-5d poorly predict patient's satisfaction following mechanically aligned total knee replacement: A cross-sectional study

BACKGROUND

Patient satisfaction is increasingly used to measure the success of arthroplasty. Satisfaction with the outcome of a total knee replacement (TKR) is traditionally thought to be associated with improvements in functional status and quality of life measures. This study aims to answer the following questions: 1. What is the level of patient satisfaction, improvement in knee function and patient quality of life associated with mechanically aligned TKR? 2. What is the relationship between OKS, EQ-5d scores and 'outcome satisfaction'?

HYPOTHESIS

TKR is associated with a significant improvement in function, satisfaction and quality of life and that there is a strong correlation between OKS, EQ-5d and 'outcome satisfaction'.

METHOD

Five thousand eight hundred and ninety six patients underwent primary TKR between January 2010 and December 2017 and had complete preoperative and 2-year follow-up data for OKS, EQ-5d and satisfaction scores. Outcomes data were collected prospectively and recorded on our institutional database. Minimal clinically important difference (MCID) and the Patient acceptable symptomatic state (PASS) were calculated for OKS and EQ-5d, the association between OKS, EQ-5d and 'outcome satisfaction' was measured using regression analysis.

RESULTS

The median 2-year 'outcome satisfaction' score was 90/100 with 79% of patients reporting excellent satisfaction (≥80/100) and 93.4% of patients satisfied (≥50/100). Postoperatively, median scores were 39 for OKS and 0.8 for EQ-5d. The mean increase in scores was 15.85 for OKS and 0.32 for EQ-5d. Satisfaction showed moderate positive correlation with postoperative OKS (r=0.69) and EQ-5D (0.58) scores, but weaker correlation with the change in OKS (r=0.57) and EQ-5d (r=0.32) scores from preoperative levels.

DISCUSSION/CONCLUSION

Mechanically aligned TKR is overall a successful operation responsible of fair rate of patient satisfaction. OKS and EQ-5d are imperfect predictors for satisfaction as they are significantly influenced by patients' comorbidities. This should be taken into account when evaluating the success of an operation.

LEVEL OF EVIDENCE

IIc; observational study (based on prospectively collected data from an institutional registry).