Reoperation, Implant Survival, and Clinical Outcome After Kinematically Aligned Total Knee Arthroplasty: A Concise Clinical Follow-Up at 16 Years

Causative factors for varus tibial baseplate subsidence in primary total knee arthroplasty: A retrospective analysis

Background

In this retrospective study, the focus was on identifying potential causative factors associated with varus subsidence of the tibial component in primary total knee arthroplasty (TKA). The research aimed to investigate the risk factors contributing to aseptic varus tibial baseplate subsidence (VTBS) leading to revision TKA procedures.

Patients and methods

A total of 120 patients with documented VTBS complications post-TKA were compared with a control group of 52 patients. Factors such as patient demographics, surgical data and comorbidities were included. The study also explored the Coronal Plane Alignment of the Knee (CPAK) classification pre- and post-operatively to understand its implications on varus subsidence.

Results

Significant differences noted in the VTBS group in variables including younger patient age (P=<0.001), increased BMI (P = 0.003), larger proportion of patients with tibial component oversize or undersizing (P=<0.001), less tibial stem extensions used (P < 0.001), higher CCI (P < 0.001) and a higher proportion of patients in CPAK group 2 (P = 0.044).

Conclusion

This investigation provides valuable insights into potential risk factors for VTBS, aiming to optimize patient outcomes and assist in preventing complications associated with TKA procedures.

Lateral Instability 13 Years After Kinematically Aligned Total Knee Arthroplasty

To reduce unsatisfied patients following total knee arthroplasty (TKA), kinematic alignment has been introduced as an alternative to mechanical alignment. Studies have shown no significant differences in functional outcomes and early revision rates between alignment strategies. This case report presents a 64-year-old patient who developed progressive varus alignment and lateral instability 13 years after a kinematically aligned TKA. The case highlights the impact of varus alignment on the risk of medial plastic wear and lateral soft tissue attenuation. Both can contribute to lateral instability, a lateral thrust, and progressive varus deformity in unrestricted kinematic alignment TKA. This article suggests that excessive varus alignment should be avoided and restricted alignment targets should be considered when using kinematic, or functional alignment in TKA for varus osteoarthritis.

Increased prevalence and severity of femoral bone wear in Japanese patients with varus knee osteoarthritis

PURPOSE

The calliper technique in kinematic alignment total knee arthroplasty assumes nearly identical medial and lateral femoral condylar radii and negligible subchondral bone wear. However, racial differences were not considered. This study aimed to assess the degree and severity of bone wear in Japanese patients with varus knee osteoarthritis.

METHODS

This cross-sectional study included 155 knees from 130 patients who underwent total or unicompartmental knee arthroplasty for primary varus-type knee osteoarthritis between April 2020 and March 2024. Preoperative computed tomography scans were used to measure the femoral condylar radii via a circle-fitting technique. Bone wear was assessed at 0° and 90° by measuring the distance between the best-fit circle and the subchondral bone periphery, with additional measurements at the peak wear angle, if present.

RESULTS

Among 155 knees, 16 (10.3%) exhibited bone wear. Bone wear >1 mm at 0° was observed in 3.2% of the cases. The peak wear angle was 43.1 ± 5.0°, with a mean depth of 2.0 ± 0.7 mm. The medial and lateral condylar radii were nearly identical (18.3 ± 1.2 mm vs. 18.2 ± 1.2 mm, p = 0.002), with a strong correlation (R2 = 0.94, p < 0.001).

CONCLUSION

Bone wear exceeding 1 mm at 0° was observed in 3.2% of cases, while overall bone wear was present in 10.3% of knees. Although the difference in radii between the medial and lateral femoral condyles was statistically significant, it was clinically negligible. This finding supports the reliability of the cylindrical axis as a reference for surgical techniques. These results highlight the importance of recognizing potential racial differences in bone wear and underscore the need for accurate assessment to achieve anatomic restoration in kinematic alignment total knee arthroplasty.

LEVEL OF EVIDENCE

Level III.

In functionally aligned total knee arthroplasty, femoral component rotation follows the transepicondylar axis to achieve flexion balance

PURPOSE

In functionally aligned (FA) total knee arthroplasty (TKA), femoral component rotation (FCR) is personalised to optimise flexion gap balance. As axial malalignment has been attributed to patellofemoral complications, this study assessed FA FCR in relation to the surgical transepicondylar axis (TEA) and early implant survivorship.

METHODS

We analysed 446 robotic-assisted primary TKAs in 393 patients using FA with preresection gap balancing. Femoral and tibial coronal resection boundaries were 6° valgus to 3° varus and 6° varus to 3° valgus, respectively. The TEA and posterior condylar axis (PCA) were identified on preoperative computed tomographic scans. Intraoperatively, FCR was initially set parallel to the PCA, then rotated to achieve flexion balance within 6° boundaries to the TEA. The primary outcome was the mean angular difference between the TEA and final FCR and the proportion of patients with FCR within 2°, 4° and 6° from the TEA. Secondary outcomes included all-cause revisions for the robotic-assisted TKAs in this series from our in-house database and a national joint replacement registry at a mean of 3.3 years postoperatively (range 2.2-5.5).

RESULTS

Mean FCR was 0.0° (SD 2.1°) relative to the TEA and 1.8° (SD 1.4°) externally rotated to the PCA. Final FCR was within 2° in 74.9%, within 4° in 97.3% and within 6° in 99.6% of patients relative to the TEA. There were seven postoperative procedures (1.6%) within the study period: two reoperations (0.5%) for early arthrotomy failure requiring repair (both exhibiting FCR within 1° to the TEA) and three revisions (0.7%) for deep surgical site infection (one after early traumatic arthrotomy failure, one revision for instability and one manipulation for stiffness).

CONCLUSION

In FA TKA, femoral components more closely align to the TEA than the PCA to achieve a balanced flexion gap. In conjunction with a low incidence of revision surgeries, this suggests the FA technique does not result in significant patellofemoral complications.

LEVEL OF EVIDENCE

Level III.

Comparative outcomes of kinematically aligned TKA with medial stabilized design vs. mechanically aligned TKA with bi-cruciate stabilized design: A propensity score-matched analysis

Purpose

Patient dissatisfaction after total knee arthroplasty (TKA) is often linked to altered knee kinematics and stability. This study compared the short-term clinical outcomes of kinematically aligned TKA (KA-TKA) and mechanically aligned TKA (MA-TKA) using bi-cruciate stabilized (BCS) implants.

Methods

In this propensity score-matched study, 60 patients who underwent either KA-TKA or MA-TKA (30 per group) with BCS implants were analyzed. Baseline characteristics, including age, sex, preoperative range of motion (ROM), and hip-knee-ankle alignment, were matched. ROM and clinical outcomes were evaluated preoperatively and at 1 year postoperatively using the 2011 Knee Society Score (KSS) subscales and Forgotten Joint Score-12 (FJS).

Results

At 1 year, the KA group achieved higher scores in KSS subscales for symptoms (23.2 vs. 20.0, p < 0.001), satisfaction (28.1 vs. 22.5, p < 0.001), functional activities (82.1 vs. 74.2, p = 0.011), and FJS (83.8 vs. 62.5, p < 0.001). No significant differences were observed in maximum extension, flexion, or KSS expectations.

Conclusions

KA-TKA demonstrated superior satisfaction and functional recovery than MA-TKA with BCS implants in the short term. These results suggested that KA-TKA, which reconstructs patient-specific alignment, may provide a more natural knee feel, leading to higher patient satisfaction compared to implant-driven BCS-TKA.

Enhanced recovery pathways improve early outcomes and reduce length of stay in primary hip and knee arthroplasty: A systematic review of randomized controlled trials

BACKGROUND

Enhanced Recovery After Surgery (ERAS) protocols represent an evidence-based approach to perioperative care, though evidence from randomized controlled trials in primary hip and knee arthroplasty remains limited.

OBJECTIVE

This systematic review aims to synthesize evidence from randomized controlled trials (RCTs) comparing ERAS protocols with standard care for primary hip and knee arthroplasty.

METHODS

Four databases were searched following PRISMA guidelines. RCTs comparing ERAS protocols with standard care for primary hip or knee arthroplasty were included. Primary outcome was length of stay (LOS), with secondary outcomes including patient-reported outcomes, functional measures, and complications.

RESULTS

Five RCTs (710 patients) met inclusion criteria. ERAS pathways reduced LOS by an average of 4.7 days compared to standard care. Patients in ERAS protocols demonstrated superior early functional recovery, particularly in the first postoperative week, with improved performance in mobility tests and daily activities. Patient-reported outcomes generally favoured ERAS protocols, though measurement heterogeneity limited synthesis. No studies reported increased complications with ERAS implementation. The role of multidisciplinary teams, particularly nurse coordinators, was identified as an important for protocol success.

CONCLUSION

This systematic review of RCTs provides strong evidence that ERAS pathways reduce length of stay following primary hip and knee arthroplasty without compromising patient outcomes or safety. While ERAS protocols were associated with improved early functional recovery, heterogeneity in assessment methods limits definitive conclusions.

The Benefit of Combining Kinematic Alignment and a Medial Pivot Implant in Total Knee Arthroplasty, The KA-MP Knee: Why and How

Kinematic alignment (KA) has emerged as an alternative alignment technique for total knee arthroplasty with the goal of duplicating the pre-arthritic joint surface. Medial pivot (MP) total knee implants duplicate the medial stability of the natural knee and recreate the medial rotational axis of the knee. Each has had favorable results. Combining the two, the KA-MP knee, creates a synergy and achieves better results than KA or MP alone.

A bone graft from the tibial resection or patella that rectified a tibial over-resection reliably healed and improved clinical outcome scores: A retrospective study of kinematically aligned TKA

PURPOSE

During kinematically aligned (KA) total knee arthroplasty (TKA), the surgeon may need to rectify an over-resection of the medial, lateral or posterior tibia. This study tested the hypothesis that a bone graft taken from the tibial resection or patella and impacted beneath a tibial baseplate would heal, regardless of whether the tibial component and knee were in outlier ranges according to mechanical alignment (MA) criteria. The study also tested the hypothesis that the Oxford Knee Score (OKS) and Knee Injury and Osteoarthritis Outcome Score for Joint Replacement (KOOS JR) would improve beyond the substantial clinical benefit and that the source and thickness of the bone graft would not influence their improvement.

METHODS

This retrospective study radiographically assessed the healing of a bone graft from the tibial resection (n = 19) or patella (n = 10) in 29 KA TKAs (18 females, mean age 65 years). The tibial component and knee alignment were categorized as in-range or outliers based on reported MA criteria for bone graft healing and implant survival. The one-sample t test identified differences in the improvement of the OKS and KOOS JR from their reported substantial clinical benefit of 16 and 20 points, respectively.

RESULTS

At an average follow-up of 37 months, all bone grafts healed even though ≥55% of tibial components and 34% of knees were varus outliers according to MA criteria for bone healing and implant survival. Amongst the 29 patients, the mean OKS and KOOS JR improvements of 25 ± 11 and 47 ± 21 points, respectively, surpassed the threshold of their respective substantial clinical benefit (p < 0.01) and were not influenced by the bone graft's source and thickness (p ≥ 0.51).

CONCLUSIONS

During cemented KA TKA, the surgeon can use a bone graft from the tibial resection or patella to rectify a tibial over-resection. This technique led to consistent bone healing and improved outcome scores.

LEVEL OF EVIDENCE

Level IV.

The John N. Insall Award: Functional Versus Mechanical Alignment in Total Knee Arthroplasty: A Randomized Controlled Trial

BACKGROUND

Mechanical alignment (MA) in total knee arthroplasty is regarded as a gold standard; however, some patients report dissatisfaction postsurgery. Functional alignment (FA) is a potential alternative, integrating kinematic alignment (KA) principles with preresection bone balancing within defined boundaries. The use of FA aims to improve outcomes by restoring native joint lines and optimizing soft-tissue balance. However, comparative evidence is limited.

METHODS

This prospective, randomized controlled trial compared MA (n = 121) and FA (n = 123) in robotic-assisted total knee arthroplasty. For MA, components were positioned perpendicular to the limb mechanical axis, with soft-tissue releases to achieve balance. For FA, initial virtual component positioning was used to match native knee anatomy, with adjustments for soft-tissue balance before bone cuts. The primary outcome was the forgotten joint score (FJS). Outcomes were compared with a mixed-model analysis of variance.

RESULTS

At the 2-year follow-up, the mean FJS was comparable (MA: 64.4 ± 30.1 versus FA: 70.1 ± 25.6, P = 0.10). The MA cases had more soft-tissue releases than FA (65 versus 16%, P < 0.001). Compared to MA patients, FA patients had higher Knee Injury and Osteoarthritis Outcome (KOOS) Symptoms (86.6 ± 12.9 versus 82.5 ± 14.0, P = 0.01) and KOOS-Quality of Life scores (76.1 ± 20.3 versus 70.7 ± 22.7, P = 0.03). More FA patients "would recommend" the procedure (94 versus 82%, P < 0.01). For patients who had preoperative Coronal Plane Alignment of the Knee Type I, FA had higher FJS (71.3 ± 24.8 versus 56.8 ± 31.6, P = 0.02) and KOOS-Quality of Life (76.4 ± 21.7 versus 64.2 ± 19.2, P = 0.02) than MA. No other differences were seen in patient-reported outcomes (Oxford Knee Score, KOOS, EuroQol-5 Dimensions, Pain Visual Analog Scale), clinical outcomes (length of stay, functional physio tests), reoperations, or implant survivorship (FA: 1 versus MA: 0 revisions).

CONCLUSIONS

While FA required fewer soft-tissue releases compared to mechanical alignment, at 2 years patient-reported and clinical outcomes were similar. The use of FA may provide improved outcomes for a specific subgroup of patients based on their preoperative alignment.

Femoral cartilage thickness measured on MRI varies among individuals: Time to deepen one of the principles of kinematic alignment in total knee arthroplasty. A systematic review

PURPOSE

Kinematically aligned total knee arthroplasty (KA TKA), as a pure resurfacing procedure, is based on matching implant thickness with bone cut and kerf thickness, plus cartilage wear. However, the assumption of a consistent 2 mm femoral cartilage thickness remains unproven. This study aimed to systematically review the available literature concerning magnetic resonance imaging (MRI) assessment of femoral cartilage thickness in non-arthritic patients. Our hypothesis was that cartilage thickness values would vary significantly among individuals, thereby challenging the established KA paradigm of 'one-cartilage-fits-all'.

METHODS

Systematic literature searches (Pubmed, Scopus and Cochrane Library) followed PRISMA guidelines. English-language studies assessing distal and posterior femoral cartilage thickness using MRI in non-arthritic adults were included. Studies lacking numerical cartilage thickness data, involving post-operative MRI, considering total femoro-tibial cartilage thickness, or failing to specify the compartment of the knee being studied were excluded.

RESULTS

Overall, 27 studies comprising 8170 MRIs were analysed. Weighted mean femoral cartilage thicknesses were: 2.05 ± 0.62 mm (mean range 1.06-2.6) for the distal medial condyle, 1.95 ± 0.4 mm (mean range 1.15-2.5) for the distal lateral condyle, 2.44 ± 0.5 mm (mean range 1.37-2.6) for the posterior medial condyle and 2.27 ± 0.38 mm (mean range 1.48-2.5) for the posterior lateral condyle.

DISCUSSION

Femoral cartilage thickness varies significantly across patients. In KA TKA, relying on a fixed thickness of 2 mm may jeopardize the accurate restoration of individual anatomy, leading to errors in implant coronal and rotational alignment. An intraoperative assessment of cartilage thickness may be advisable to express the KA philosophy at its full potential.

LEVEL OF EVIDENCE

Level IV.

Excellent results of restricted kinematic alignment total knee arthroplasty at a minimum of 10 years of follow-up

PURPOSE

While restricted kinematic alignment (rKA) total knee arthroplasty (TKA) with cemented implants has been shown to provide a similar survivorship rate to mechanical alignment (MA) in the short term, no studies have reported on the long-term survivorship and function.

METHODS

One hundred four consecutive cemented cruciate retaining TKAs implanted using computer navigation and following the rKA principles proposed by Vendittoli were reviewed at a minimum of 10 years after surgery. Implant revisions, reoperations and clinical outcomes were assessed using knee injury and osteoarthritis outcome score (KOOS), forgotten joint score (FJS), patients' satisfaction and joint perception questionnaires. Radiographs were analyzed to identify signs of osteolysis and implant loosening.

RESULTS

Implant survivorship was 99.0% at a mean follow-up of 11.3 years (range: 10.3-12.9) with one early revision for instability. Patients perceived their TKA as natural or artificial without limitation in 50.0% of cases, and 95.3% were satisfied or very satisfied with their TKA. The mean FJS was 67.6 (range: 0-100). The mean KOOS were as follows: pain 84.7 (range: 38-100), symptoms 85.5 (range: 46-100), function in daily activities 82.6 (range: 40-100), function in sport and recreation 35.2 (range: 0-100) and quality of life 79.1 (range: 0-100). No radiological evidence of implant aseptic loosening or osteolysis was identified.

CONCLUSION

Cemented TKA implanted with the rKA alignment protocol demonstrated excellent long-term implant survivorship and is a safe alternative to MA to improve patient function and satisfaction.

LEVEL OF EVIDENCE

Level IV, continuous case series with no comparison group.

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.

Kinematical alignment better restores native patellar tracking pattern than mechanical alignment

PURPOSE

The purpose of this study was to assess whether kinematic alignment (KA) outperforms mechanical alignment (MA) in restoring patellar tracking to native patterns by using a clustering algorithm.

METHODS

Twenty cadavers (40 knees) were evaluated. For each cadaver, one knee was randomly assigned to KA and the other to MA. KA total knee arthroplasty (TKA) procedures were performed using a caliper-verified technique, while MA TKA procedures utilized a measured resection technique. Subsequently, all specimens were mounted on a customized knee-testing system, and patellar tracking was measured using a motion analysis system. All patellar tracking data were clustered using the density-based spatial clustering of applications with noise algorithm. Differences in patellar tracking patterns and the restoration of native patellar tracking were compared between the two alignment strategies.

RESULTS

Patellar tracking patterns following KA were considerably different from MA. Pre- and post-TKA patellar tracking patterns following MA were grouped into separate clusters, whereas a substantial proportion of patellar tracking patterns following KA were grouped into the pre-TKA dominant cluster. Compared to MA, a greater proportion of patellar tracking patterns following KA showed similar patterns to native knees (p < 0.05) and more patellar tracking patterns following KA paired with preoperative patterns (p < 0.01).

CONCLUSION

KA restored native patellar tracking patterns more closely compared to MA.

LEVEL OF EVIDENCE

Level I, therapeutic study.

The Influence of Kinematic Alignment on Patellofemoral Joint Biomechanics in Total Knee Arthroplasty

Background: Anterior knee pain is a prevalent issue post total knee arthroplasty, often necessitating revision surgery. Various factors contribute to this complication, including patellar maltracking and excessive patellofemoral load. Kinematic alignment has emerged as an alternative, showing promising outcomes in clinical studies. However, its impact on patellofemoral biomechanics needs to be more adequately understood. This study compared the effects of kinematically versus mechanically aligned total knee arthroplasty on patellofemoral joint biomechanics. Methods: Eight fresh-frozen human knee specimens underwent biomechanical testing in a knee rig setup, performing an active weight-loaded knee joint flexion of 30-130°. After the testing of native kinematics, kinematically and mechanically aligned total knee arthroplasty was performed using a medial pivot implant design without patellar resurfacing. Quadriceps force, retropatellar peak pressure and the retropatellar contact area were measured during knee flexion using a patellar pressure-sensitive film. Patella kinematics (shift and tilt) was tracked using an optoelectrical measurement system. Functional regressions were used to determine the influence of the alignment on the kinematics and loading of the knee joint. Results: Kinematically aligned total knee arthroplasty resulted in reduced quadriceps force during knee flexion compared to mechanically aligned total knee arthroplasty. Retropatellar peak pressure, retropatellar contact area and patella kinematics did not vary between the alignments. Conclusions: Kinematic alignment offers potential benefits in reducing quadriceps force during knee flexion, which may mitigate anterior knee pain risk. Further research is needed to elucidate its effects in varying anatomical conditions and alignment strategies.

Calipered Kinematically Aligned Medial Unicompartmental Knee Arthroplasty: A Surgical Technique

This study presents a surgical technique for kinematically aligned medial unicompartmental knee arthroplasty with the MOTO (Medacta Corporate, Switzerland) partial knee implant. This technique aims to replicate the native medial femoral and tibial morphology by providing caliper-verified bone resections and kinematic alignment principles. The paper provides a comprehensive overview of the surgical steps and discusses the implications for implant longevity.

Anteroposterior axis of the tibia for kinematic aligned total knee arthroplasty

Purpose

It is not known where the anatomical axis of rotation on the tibial side will be in kinematic alignment (KA), a rapidly expanding area of total knee arthroplasty (TKA) alignment technique today. The purpose of this study was to define the tibial axis for KA-TKA.

Methods

Fifty patients who underwent computed tomography (CT) examination of the lower extremities at a single institution were included. The posterior condylar axis (PCA) and surgical epicondylar axis (SEA) were identified in the CT axial view and projected onto the tibial slice. The respective perpendicular lines that pass through was attachment of the posterior cruciate ligament (PCL) were identified as the anatomic axis of rotation of the tibia relative to the PCA and SEA, and the position of each axis of rotation. Furthermore, the relationship of these perpendicular lines with the Akagi line was evaluated.

Results

The axis of tibial rotation to the SEA was similar to that of the Akagi line; the axis of tibial rotation to the PCA was located approximately 2.9° medial to the Akagi line, and when the origin of the tibial axis was set at the PCL attachment site, the intersection point of the tibial axis was approximately 2.5 mm medial to the medial border of the tibial tuberosity. The distribution of tibial axis had a wide range.

Conclusion

Although there is a large individual variation, the average tibial axis for KA-TKA is 2.9° more internally rotated than the Akagi line.

Level of Evidence

Level IV.

Specific tibial landmarks to improve to accuracy of the tibial cut during total knee arthroplasty. A case control study

INTRODUCTION

More personalized alignment techniques in total knee arthroplasty (TKA) have recently been described particularly for the young and active patients. Performing the ideal tibial cut might be challenging with a conventional ancillary. Therefore the aims of this study were: (1) to describe specific tibial landmarks to optimize the tibial cut in TKA; (2) to compare the accuracy of the tibial cut with these landmarks compared to a conventional technique.

METHODS

This retrospective case-control study compared primary TKAs performed using a conventional technique with extramedullary guide associated with specific tibial landmarks. For each case, one control patient was matched based on body mass index (BMI), age, preoperative Hip Knee Ankle (HKA) angle, and Medial Proximal Tibial Angle (MPTA). All control patients were operated by the same surgeon and similar conventional technique but without landmarks. The MPTA target was to reproduce preoperative deformity with a 3° of varus limit. 34 TKA were included in each group. There was no preoperative difference between both groups. Mean age was 63 years old ± 8. Mean BMI was 32 kg/m2 ± 5. Mean HKA was 170.6° ± 2.5. Mean MPTA was 85.1° ± 2.3. The radiographic assessment was performed preoperatively and at 2 months: HKA, mechanical Medial Distal Femoral Angle (mMDFA), MPTA, tibial slope, restoration of the joint line-height.

RESULTS

The tibial landmarks corresponded to the line of insertion of the deep medial collateral ligament fibers extended to the capsular insertion above the Gerdy tubercle. The postoperative MPTA was significantly more varus (87.2° ± 1.6 in landmark group versus 88.3° ± 2.2; p = 0.027) and closer to preoperative bone deformity in landmark group (p = 0.002) with significantly less outliers than in the conventional group. There was no significant difference between both groups postoperatively for HKA (175.4° ± 2.3 versus 175.9° ± 2.5; p = 0.42); mMDFA (88.9° ± 2.3 versus 88.2° ± 2.1; p = 0.18); tibial slope (82.6° ± 1.9 versus 82.4° ± 2.6; p = 0.67), the restoration of the joint line-height (1.5 mm ± 2 versus 1.8 mm ± 2; p = 0.56).

CONCLUSION

Specific tibial landmarks during TKA can be used to increase the accuracy of the tibial cut when using personalized alignment techniques in TKA.

LEVEL OF EVIDENCE

IV.

The Viability and Success of Noncemented Kinematic Total Knee Arthroplasty

BACKGROUND

The prevalence of noncemented total knee arthroplasty (TKA) is increasing as personalized knee alignment strategies deviate from implanting components on a strict mechanical axis. This retrospective study evaluated the outcomes of 74 consecutive noncemented unrestricted kinematic TKA procedures.

METHODS

This study included 74 consecutive noncemented kinematic TKAs performed by one surgeon at a tertiary academic medical center from 2021 to 2023. The technique used was unrestricted femur-first caliper kinematic TKA. The outcomes included revision, pain scores, and radiographic measurements.

RESULTS

Of the 74 procedures performed, there were no revisions or readmissions for problems related to TKA. The mean follow-up was 17.6 months, with 74% of patients being followed up for more than 1 year postoperatively. On the day of surgery, postoperative measurements showed that the average tibial mechanical, distal femoral, and anatomic tibiofemoral angles were 3.3°, 7.7°, and 5.8°, respectively. 5 knees were observed initially with signs of radiolucency, which all resolved by the most recent appointment. None of the knees was radiographically loose. Of the patients, 65%, 19%, and 16% reported no pain, minimal pain, and some pain, respectively, at the 6-week follow-up visit. This improved to 78%, 19%, and 3% at the most recent follow-up.

CONCLUSION

Combining kinematic alignment with noncemented fixation showed excellent clinical and radiographic outcomes with short-term survivorship. Although the use of both kinematic alignment and noncemented TKAs has been controversial, these early data suggest that noncemented kinematic TKA is safe and effective.

Calipered kinematic alignment restored the arithmetic hip-knee-ankle angle, achieved high satisfaction and improved clinical outcomes

PURPOSE

The purpose of this study was to determine whether unrestricted calipered kinematic alignment (KA), coupled with a medial-stabilised (MS) implant system, can reproduce the patient's constitutional alignment as per the arithmetic hip-knee-ankle (aHKA) and improve clinical outcomes.

METHODS

One-hundred and ninety-three patients received total knee arthroplasty by the senior author. To determine whether the constitutional alignment was achieved, the postoperative hip-knee-ankle (HKA) alignment was compared against the aHKA. Range of motion (ROM) was determined preoperative and postoperatively at 6 months and 2 years by measuring the active flexion and extension. Patient-Reported Outcomes Measures (PROMs) including Oxford Knee Score (OKS), Knee Injury and Osteoarthritis Outcome Score (KOOS), Forgotten Joint Score (FJS) and Visual Analogue Scale for Satisfaction were also completed. The Sports and Recreation component of KOOS was used to assess the patient's ability to return to sports and daily activities.

RESULTS

There was a strong correlation between postoperative HKA and aHKA (r = 0.7, p < 0.05). There was a significant improvement in both extension and flexion seen from as early as 6 months postoperatively, with a mean flexion of 123° ± 11° and extension of 1° ± 3° at 2 years. PROMs had significant improvements with a mean score of 42.8 ± 6.0 for the OKS and all KOOS subscales consisting of Symptoms (88.0 ± 11.7), Pain (91.4 ± 11.6), Activities of Daily Living (91.1 ± 12.4), Sports (76.8 ± 22.1) and Quality of Life (83.0 ± 19.1). The FJS had significant improvements from 6 months to 2 years of 19.9 (p < 0.05), with a mean score of 69.2 ± 26.6 at 2 years. Ninety-three percent (180 patients) were classified as 'satisfied' at the 2-year timepoint. The KOOS Sports component was completed by 64% (124 patients), whereby the mean age was younger than the noncompliant patients (67.7 ± 9.4 vs. 71.7 ± 8.2 years).

CONCLUSION

Unrestricted calipered KA can result in an alignment that closely resembles the patient's constitutional alignment, as per the aHKA. This resulted in improved knee ROM and patient satisfaction, as well as assisting younger patients to return to sports and daily activities.

LEVEL OF EVIDENCE

Level IV.

Superiority of kinematic alignment over mechanical alignment in total knee arthroplasty during medium- to long-term follow-up: A meta-analysis and trial sequential analysis

PURPOSE

To compare and determine the reliability and conclusiveness of the medium- and long-term efficacy in terms of patient-reported outcome measures and the risk of revisions or reoperations (RRRs) of kinematic alignment (KA) and mechanical alignment (MA) in total knee arthroplasty.

METHODS

A comprehensive search was conducted in Medline, EMBASE, Web of Science and Cochrane Database Library to identify relevant literature. Only randomised clinical trials (RCTs) published before July 2023 were included. The Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), Oxford Knee Score (OKS), Forgotten Joint Score (FJS) and RRR were compared. Additionally, OKS and RRR were subjected to a trial sequential analysis.

RESULTS

Seven RCTs involving 572 knees were identified. The pooled analysis of the included studies demonstrated that KA showed better medium-term WOMAC and OKS (mean difference [MD] = -6.3, 95% confidence interval [CI]: -9.52 to -2.99, p < 0.05 and MD = 1.1, 95% CI: 0.05-2.15, p < 0.05), respectively), but no significant differences were observed in the long-term follow-up (MD = 2.1, 95% CI: -3.21 to 7.31, not significant [n.s.] and MD = 0.01, 95% CI: -2.43 to 2.46, n.s., respectively). FJS (standardised MD = -0.03, 95% CI: -0.25 to 0.19, n.s.) and RRR (risk ratio = 1.0, 95% CI: 0.57 to 1.74, n.s.) showed no significant intergroup differences (n.s.). The evidence quality ranged from moderate to high, and the trial sequential analysis indicated the need for additional high-quality RCTs to draw more conclusive results.

CONCLUSIONS

KA showed better medium-term WOMAC and OKS, while KA and MA had similar FJS without increasing the RRR in medium- and long-term follow-up. Further research is needed for more conclusive results.

LEVEL OF EVIDENCE

Level II (meta-analyses).

Caliper-verified unrestricted kinematically aligned total knee arthroplasty in Asian patients showed efficacious mid- to long-term results regardless of postoperative alignment categories

PURPOSE

There have been insufficient data regarding the long-term results of unrestricted kinematically aligned total knee arthroplasty (unKATKA) in Asian patients. We investigated mid- to long-term clinical and radiological follow-up data of Korean patients after caliper-verified unKATKA of minimum 7.4-10 years including categorised data of postoperative tibial component, limb and knee alignment. Additionally, we analysed the preoperative distribution and postoperative restoration of coronal plane alignment of knee (CPAK) phenotypes.

METHODS

This study is a retrospective analysis of 63 patients: 96 osteoarthritic underwent consecutive caliper-verified unKATKA between October 2013 and May 2016 by a single surgeon. Implant survivorship was investigated for revision for any reason. Each knee was categorised into an in-range or outlier group by three postoperative alignment parameters: tibial component, knee and limb alignment. Statistical analyses were done for any significant differences in clinical scores and implant survival rates between groups. Finally, all knees were classified into CPAK classification postoperatively and postoperatively. The CPAK restoration rate was calculated.

RESULTS

Among 85 knees in the clinically confirmed group, implant survival was 98.8%. There was one case of revision due to periprosthetic fracture. The percentage postoperatively aligned in the varus (valgus) outlier range was 100% (0%) for tibial component, 16.7% (24.8%) for the knee alignment and 51% (0%) for the limb alignment. All three categories did not affect implant survival or clinical scores. Eighty one out of 96 knees (84.4%) were restored to their CPAK phenotype postoperatively.

CONCLUSION

With the limitation of a case series having a small number of patients and gender deviation, our study suggests that caliper-verified unKATKA could be a good option regardless of geographical variation of constitutional alignment in patients with osteoarthritis (OA).

LEVEL OF EVIDENCE

Level IV, therapeutic study.

Risk of tibial baseplate loosening is low in patients following unrestricted kinematic alignment total knee arthroplasty using a cruciate-retaining medial conforming insert: A study using radiostereometric analysis at 2 years

PURPOSE

Assessing the risk of tibial baseplate loosening in patients after unrestricted kinematically aligned (unKA) total knee arthroplasty (TKA) using a medially conforming insert is important because baseplates generally are aligned in varus which has been linked to an increased incidence of aseptic loosening following mechanically aligned TKA. Two limits that indicate long-term stability in patients are a change in maximum total point motion between 1 and 2 years (ΔMTPM) < 0.2 mm and anterior tilt at 2 years < 0.8°. The purposes were to determine: (1) the number of patients with ΔMTPM > 0.2 mm, (2) the number of patients with anterior tilt > 0.8° and (3) whether increased varus baseplate and limb alignment were associated with increased migration.

METHODS

Thirty-five patients underwent cemented, caliper-verified, unKA TKA using a medially conforming tibial insert with posterior cruciate ligament (PCL) retention. Biplanar radiographs acquired on the day of surgery and at 1.5, 3, 6, 12 and 24 months were processed with model-based radiostereometric analysis (RSA) software to determine migration and the number of patients with migration above the two stability limits. Medial proximal tibial angle (MPTA), hip-knee-ankle angle (HKAA) and posterior slope angle (PSA) were analyzed for an association with migration in six degrees of freedom and in MTPM.

RESULTS

Thirty-two of 35 patients were available for analysis at 2 years. One patient exhibited ΔMTPM > 0.2 mm. The same patient exhibited anterior tilt > 0.8°. Varus rotation (p = 0.048, r ≤ 0.34) and medial translation (p = 0.0273, r ≤ 0.29) increased with increased varus baseplate alignment.

CONCLUSION

The results indicate low risk of long-term baseplate loosening in patients. Although varus rotation and medial translation increased with increased varus baseplate alignment, the magnitudes of the migrations were minimal and did not increase ΔMTPM and anterior tilt.

LEVEL OF EVIDENCE

Level II, therapeutic prospective cohort study.

Clinical and Functional Outcomes of Kinematic Aligned Total Knee Arthroplasty with a Medial Pivot Design: Two-Year Follow-Up

BACKGROUND

Kinematic alignment (KA) restores native limb alignment following total knee arthroplasty (TKA). The association of this technique with a medial pivot implant design attempts to re-establish the physiological kinematics of the knee. This study aims to analyze the clinical and radiological outcomes of patients undergoing MP-TKA with kinematic alignment and to assess the effect of limb alignment on the clinical outcomes.

METHODS

We retrospectively analyzed 55 patients who underwent kinematic aligned medial pivot TKA from September 2018 to January 2020. Patient-related outcomes (PROMs) were collected at baseline, 3, 12, and 24 months after surgery. Long-standing weight-bearing radiographs were performed three months after surgery.

RESULTS

We demonstrated a significant improvement in clinical outcomes from 3 months after surgery up to 24 months of follow-up. This clinical improvement was independent of limb alignment. The radiological analysis showed that the patient's native limb alignment was restored and that their joint line orientation was parallel to the floor.

CONCLUSION

The association of kinematic alignment and a medial pivot TKA implant allows for a fast recovery, with good clinical and functional outcomes up to a minimum of 2 years of follow-up, independent of the final limb alignment.