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Different techniques for aligning total knee arthroplasty implants on a patient with 6° constitutional varus limb alignment. From left to right, kinematic alignment (KA), restricted KA (rKA), adjusted mechanical alignment (aMA), anatomical alignment (AA), mechanical alignment (MA). Except for the KA technique, all other techniques necessitate varying amounts of soft-tissue release (more so for systematic techniques than hybrid techniques).
Source publication
- Mechanical or anatomical alignment techniques create a
supposedly ‘biomechanically friendly’ but often functionally
limited prosthetic knee.
- Alternative techniques for alignment in total knee arthroplasty
(TKA) aim at being more anatomical and patientspecific,
aiming to improve functional outcomes after TKA.
- The kinematic alignment (KA)...
Context in source publication
Context 1
... recently developed and tested more anatomy-friendly techniques for TKA. 9 Because the optimal knee soft-tissue tension 10 and com- ponent alignment in TKA remain a matter of debate, 9 this instructional review aims to classify the multiple tech- niques (systematic, patient-specific and hybrid alignment techniques) for knee implant positioning ( Fig. 1 and to summarize the evidence behind each ...
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Aims
Once knee arthritis and deformity have occurred, it is currently not known how to determine a patient’s constitutional (pre-arthritic) limb alignment. The purpose of this study was to describe and validate the arithmetic hip-knee-ankle (aHKA) algorithm as a straightforward method for preoperative planning and intraoperative restoration of the...
Citations
... The idea of implementing a uniform alignment approach in all cases of TKA has been challenged recently [41,42]. While mechanical alignment is the most utilized surgical alignment goal for TKA, a more personalized goal accounting for the constitutional alignment of each patient may be the key to addressing patient dissatisfaction [43]. ...
Total knee arthroplasty (TKA) is a common orthopedic surgery, yet postoperative dissatisfaction persists in around 20% of cases. Robotic total knee arthroplasty (rTKA) promises enhanced precision, but its impact on patient satisfaction compared to conventional TKA remains controversial (cTKA). This systematic review aims to evaluate patient satisfaction post-rTKA and compare outcomes with cTKA.
Papers from the following databases were identified and reviewed: PubMed, Scopus, Web of Science, and the Cochrane Online Library, using keywords like "Knee replacement," "Total knee arthroplasty," "Robotic," and "Patient satisfaction." Extracted data included patient satisfaction measures, Knee Society Score, Oxford Knee Score, Forgotten Joint Score, SF-36, HSS, and KOOS. Statistical analysis, including odds ratio and 95% CI was performed using R software. Heterogeneity was assessed using Cochrane's Q test.
The systematic review included 17 articles, involving 1148 patients (571 in the rTKA group and 577 in the cTKA group) assessing patient satisfaction following rTKA. An analysis of proportions reveals rTKA satisfaction rate was 95%, while for cTKA, it was 91%. A meta-analysis comparing rTKA and cTKA found no statistically significant difference in patient satisfaction. Additionally, various patient-reported outcome measures (PROMs) were examined, showing mixed results across different studies and follow-up periods.
The results of this study found no difference in patient satisfaction outcomes in the short to mid-term for rTKA compared to conventional methods. This study does not assert superiority for the robotic approach, highlighting the need for careful consideration of various factors influencing outcomes in knee arthroplasty.
... Kinematic alignment (KA) is an alternative alignment technique for total knee arthroplasty (TKA), aiming to create a more physiologically prosthetic knee by restoring the native knee anatomy and maintaining physiological soft-tissue balance [1][2][3]. In contrast to the mechanical alignment (MA) technique, conventionally performed to achieve neutral leg alignment by cutting the distal femoral and proximal tibial bones perpendicular to the mechanical axes, KA involves aligning the femoral component on the cylindrical axis and performing anatomical bone cuts; no soft tissue release is required [4]. The advantage of this technique lies in the expected restoration of similarity to the native joint line and kinematics [5]. ...
Purpose
Restricted kinematic alignment (rKA) is a modified technique of kinematically aligned total knee arthroplasty (TKA) within a safe alignment range for long‐term implant survivorship. The purpose of this study was to clarify (1) the distribution of functional knee phenotypes in patients who underwent TKA in Japan and (2) whether the application of this classification results in anatomically neutral alignment after rKA TKA.
Methods
Overall, 114 TKA surgeries (mechanical alignment [MA]: 49; rKA: 65) were performed. The joint line orientation angle (JLOA), hip–knee–ankle angle (HKA), femoral mechanical angle (FMA) and tibial mechanical angle (TMA) were obtained. The knees were categorized using a functional knee phenotype classification. Clinical evaluations, including the Knee Injury and Osteoarthritis Outcome, 12‐question Forgotten Joint and Oxford Knee Scores, were performed 3 years postoperatively. Between‐group comparisons were made.
Results
The most common preoperative functional knee phenotype was VAR HKA 3° + NEU FMA 0° + VAR TMA 3° (11.4%). In the preoperative population, 51 knees (44.7%) had VAR FMA ≥ 3°. Postoperatively, the most common functional knee phenotype was NEU HKA 0° + VAR FMA 3° + VAL TMA 3° (14 knees, 28.6%) in the MA and NEU HKA 0° + NEU FMA 0° + NEU TMA 0° in the rKA group. The percentage of postoperative JLOA within ±3° from the floor was 27% and 72% in the MA and rKA groups, respectively ( p < 0.001). The functional knee phenotype after rKA TKA was neutrally reproduced, and the joint line was more parallel to the ground in the standing position than that of MA. Between‐group differences in clinical outcomes were not significant.
Conclusion
The application of functional knee phenotyping to knee osteoarthritis in Japan suggested the presence of racial morphological characteristics. This classification could help better visualize potential femoral varus, contributing to protocol deviation in applying restricted KA TKA.
Level of Evidence
Level IV.
... 2.2° in varus). UKAs were reported to restore the constitutional knee anatomy-like kinematic alignment by the ligamentand bone-sparing methods of UKAs [31]. Therefore, our PA-BCR TKA technique might reproduce constitutionallike limb alignment. ...
Background
Bicruciate-retaining (BCR) prosthesis has been introduced to recreate normal knee movement by preserving both the anterior and posterior cruciate ligaments. However, the use of BCR total knee arthroplasty (TKA) is still debatable because of several disappointing reports. We have been performing BCR TKAs with personalized alignment (PA). This study aimed to reveal the limb alignment and soft tissue balance of FA-BCR TKAs and compare the clinical outcomes of FA-BCR TKAs with those of unicompartmental knee arthroplasty (UKA).
Methods
Fifty BCR TKAs and 58 UKAs were included in this study. The joint component gaps of BCR TKA were evaluated intraoperatively and the postoperative hip–knee–ankle (HKA) angle, medial proximal tibial angle (MPTA), and lateral distal femoral angle (LDFA) were measured using full-length standing radiography. The short-term clinical outcomes of BCR TKAs were compared with those of UKA using the scoring system of 2011 Knee Society Scoring (KSS) and the knee injury and osteoarthritis outcome score (KOOS) at an average of 2 years postoperatively (1-4yeras).
Results
The coronal alignment values of PA-BCR TKA were as follows: HKA angle, 177.9° ± 2.3°; MPTA, 85.4° ± 1.9°; and LDFA, 87.5° ± 1.9°. The joint component gaps at flexion angles of 10°, 30°, 60°, and 90° were 11.1 ± 1.2, 10.9 ± 1.4, 10.7 ± 1.3, and 11.2 ± 1.4 mm for the medial compartment and 12.9 ± 1.5, 12.6 ± 1.8, 12.5 ± 1.8 and 12.5 ± 1.7 mm for the lateral compartment, respectively. The patient expectation score and maximum extension angle of PA-BCR TKA were significantly better than those of UKAs.
Conclusions
The short-term clinical outcomes of PA-BCR TKA were comparable or a slightly superior to those of UKAs.
... To achieve this, surgeons have traditionally employed systematic approaches for more simplicity and reliability. However, this systematic implant positioning disregards patient-specific knee joint anatomy, as implants are consistently placed in the same manner for every patient, without accounting for the constitutional alignment of each patient, which is the alignment they have had since they reached skeletal maturity [7,17]. ...
Dissatisfaction following total knee arthroplasty (TKA) has been extensively documented and it was attributed to numerous factors. In recent years, significant focus has been directed towards implant alignment and stability as potential causes and solutions to this issue. Surgeons are now exploring a more personalized approach to TKA, recognizing the importance of thoroughly understanding each individual patient’s anatomy and functional morphology. A more comprehensive preoperative analysis of alignment and knee morphology is essential to address the unresolved questions in knee arthroplasty effectively. The crucial task of determining the most appropriate alignment strategy for each patient arises, given the substantial variability in bone resection resulting from the interplay of phenotype and the alignment strategy chosen. This review aims to comprehensively present the definitions of different alignment techniques in all planes and discuss the consequences dependent on knee phenotypes.
Level of evidence V.
... 78 Alternative alignment strategies proposed try to be more anatomical and patient-specific, better-respecting ligament tension and geometry of the articulating partner's. 79 To improve at least flexion gap balancing, axial femoral rotation was adjusted to the ligament tension in flexion. 80 As the usual tibiofemoral joint line is usually oriented 3° ascending from medial to lateral (called valgus orientation), 81 a technique was proposed respecting this orientation thus called anatomical alignment. ...
Osteoarthritis of the knee is common. Early sports trauma or cartilage defects are risk factors for osteoarthritis. If conservative treatment fails, partial or total joint replacement is often performed. A joint replacement aims to restore physiological biomechanics and the quality of life of affected patients. Total knee arthroplasty is one of the most performed surgeries in musculoskeletal medicine. Several developments have taken place over the last decades that have truly altered the way we look at knee arthroplasty today. Some of the fascinating aspects will be presented and discussed in the present narrative review.
... Over the past decade, personalized realignment strategies have gained attention to improve patient outcomes [18,29,41,42]. One of these alternative methods is unrestricted, caliper-verified kinematic alignment (KA) [21,22]. ...
Purpose
Mechanically Aligned Total Knee Arthroplasty (MA TKA) typically addresses fixed flexion contractures (FFC) by raising the joint line during extension. However, in unrestricted Kinematically Aligned TKA (KA TKA) utilizing a caliper-based resection technique, the joint line is not raised. This study aims to determine the efficacy of KA TKA in restoring full extension in patients with FFC without increasing distal femoral resection, considering tibial bone resection and sagittal component positioning.
Methods
A retrospective study was conducted by a single surgeon, involving patients who underwent primary robotically assisted cruciate retaining unrestricted KA TKA between June 1, 2021, and December 1, 2022. Complete intraoperative resection and alignment data were recorded, including the thickness of distal femoral and proximal tibial bone cuts. Patients with a preoperative FFC ≥ 5° (study group) were compared to those with FFC < 5° (control group). The impact of variations in tibial resection and sagittal component positioning was assessed by comparing the heights of medial and lateral resections, sagittal femoral component flexion, and tibial slope. Group comparisons were analyzed using the Wilcoxon Signed Rank Test, with a significance level set at p < 0.05.
Results
A total of 48 KA TKA procedures met the inclusion criteria, with 24 performed on women. The mean preoperative FFC in the study group was 11.2° (range: 5–25°), while the control group exhibited 1° (range: 0–4°) ( p < 0.001). There were no statistically significant differences observed between the study and control groups in terms of distal femoral resections, both medially ( p = 0.14) and laterally ( p = 0.23), as well as tibial resection heights, both medially ( p = 0.66) and laterally ( p = 0.74). The alignment of the femoral component flexion and tibial slope was comparable between the two groups ( p = 0.31 and p = 0.54, respectively). All patients achieved within 5 degrees of full extension at closure.
Conclusion
Robotic arm-assisted unrestricted KA TKA effectively restores full extension without raising the joint line during extension for patients with a preoperative fixed flexion contracture.
Level of evidence
III.
... In flexion, prior studies have found that a loose lateral flexion gap does not adversely affect outcome so long as the medial flexion gap is not loose [22,41,42]. A trapezoidal flexion space with the lateral side looser may be physiologic and is targeted in traditional KA techniques [19,43], with one study showing that a looser lateral flexion gap is associated with improved patient-reported outcomes [44]. Other data has shown that a balanced flexion gap is favorable [21]. ...
Background
Kinematic alignment (KA) and related personalized alignment strategies in total knee arthroplasty (TKA) target restoration of native joint line obliquity and alignment. In practice, deviations from exact restoration of the prearthritic joint surface are tolerated for either the femur or tibia to achieve ligamentous balance. It remains unknown what laxity, balance, and alignment would result if a pure resurfacing of both femur and tibia were performed in a KA TKA technique.
Methods
We used data from 382 robot-assisted TKA performed with a digital joint tensioner to simulate TKA with a pure resurfacing KA technique for both femur and tibia. All knees had the posterior cruciate ligament retained. Knees were subdivided into 4 groups based on preoperative coronal alignment: valgus, neutral, varus, and high varus. Medial and lateral laxity in extension and flexion, balance in extension and flexion, and coronal plane alignment were compared between groups using analysis of variance testing.
Results
In simulated pure resurfacing KA TKA across a range of preoperative coronal plane deformities, only 11%-31% of knees would have mediolateral extension ligament balance within ±1 mm, and 20%-41% would have a medial flexion gap that is looser than the lateral flexion gap. Over 45% of knees would have coronal hip-knee-ankle angle >3 degrees from mechanical neutral.
Conclusions
In simulations of pure resurfacing KA TKA, there was wide variability in the resulting laxity and alignment outcomes. Most knees had alignment and balance outcomes outside of normally accepted ranges. Techniques that deviate from pure resurfacing in order to achieve balance appear favorable.
... The MA technique pursues neutral alignment, the prosthesis is vertical to the mechanical axis of the lower limbs, and the pressure of the lower limbs is evenly distributed in the inner and outer compartments of the tibia, thereby slowing the wearing down of bone cement and reducing the loosening of the prosthesis. MA has been termed a biomechanical friendly approach, a mature and systematically applied technique [5][6][7][8]. Nevertheless, the MA technique changes the intrinsic joint line of the patient, the lower limb force line, the soft tissue balance, and the Q angle, and the postoperative satisfaction of patients is still below par [9][10][11][12][13][14]. ...
Background The differences in prosthetic positioning resulting from total knee arthroplasty (TKA) employing different alignment strategies (kinematic alignment [KA] versus mechanical alignment [MA]) lead to differences in patellar tracking. This study aimed to analyze the effect of imaging-related attributes and clinical efficacy of patellar tracking after TKA with KA via the mini-subvastus approach. Methods This prospective randomized controlled study involved 100 patients who were randomly and equally divided into the KA and MA groups prior to undergoing the TKA surgical procedure. The preoperative and postoperative patellar tilt angle, lateral patellar shift, Knee Society Score (KSS), and Oxford Knee Score (OKS) were compared between patients of the KA and MA groups. In addition, the intraoperative lateral patellar retinaculum release rate was also compared between these two patient groups. Results All patients were followed up for 6 months post-TKA. There was no significant difference in the demographics and preoperative and postoperative imaging-related attributes of the patellar tracking between the two groups (p > 0.05). The postoperative KSS and OKS of the KA group were significantly higher than those of the MA group (p < 0.05). The release rate of the lateral retinaculum of the patella was 6.00% (3/50) in the KA group and 28.00% (14/50) in the MA group, and the difference was statistically significant ( x ² = 8.575, p < 0.05). Conclusion Good patellar tracking was achieved in both groups after TKA via the mini-subvastus approach. Nevertheless, the KA strategy was associated with a lower rate of intraoperative lateral patellar retinaculum release and higher knee function scores and therefore, may be considered the superior strategy for TKA.
... Consequently, when aiming for neutral alignment by using mechanical alignment approaches in TKA, the native joint orientation is inevitably modified in many patients [2]. The results indicate the need in individualized alignment paradigms that adjust for variations in individual knee morphology, such as kinematic alignment or personalized alignment approaches [13,22,33,36,37]. HKA (°) −9.3 ± 3.7 −3.6 ± 3.0 5.6 ± 5.8 −9.2 ± 3.5 −3.7 ± 3.2 6.8 ± 6.5 −9.8 ± 6.1 −0.9 ± 5.5 7.6 ± 7.7 MAD (mm) 31.0 ± 11.9 11.9 ± 10.0 −19. ...
Purpose:
Osteoarthritis of the knee is commonly associated with malalignment of the lower limb. Recent classifications, as the Coronal Plane Alignment of the Knee (CPAK) and Functional Phenotype classification, describe the bony knee morphology in addition to the overall limb alignment. Data on distribution of these classifications is not sufficient in large populations. The aim of this study was to analyse the preoperative knee morphology with regard to the aforementioned classifications in long leg radiographs prior to total knee arthroplasty surgery using Artificial Intelligence.
Methods:
The cohort comprised 8739 preoperative long leg radiographs of 7456 patients of all total knee arthroplasty surgeries between 2009 and 2021 from our institutional database. The automated measurements were performed with the validated Artificial Intelligence software LAMA (ImageBiopsy Lab, Vienna) and included standardized axes and angles [hip-knee-ankle angle (HKA), mechanical lateral distal femur angle (mLDFA), mechanical medial proximal tibia angle (mMPTA), mechanical axis deviation (MAD), anatomic mechanic axis deviation (AMA) and joint line convergence angle (JLCA)]. CPAK and functional phenotype classifications were performed and all measurements were analysed for gender, age, and body mass index (BMI) within these subgroups.
Results:
Varus alignment was more common in men (m: 2008, 68.5%; f: 2953, 50.8%) while neutral (m: 578, 19.7%; f: 1357, 23.4%) and valgus (m: 345, 11.8%; f: 1498, 25.8%) alignment was more common in women. The most common morphotypes according to CPAK classification were CPAK Type I (2454; 28.1%), Type II (2383; 27.3%), and Type III (1830; 20.9%). An apex proximal joint line (CPAK Type VII, VIII and IX) was only found in 1.3% of all cases (n = 121). In men, CPAK Type I (1136; 38.8%) and CPAK Type II (799; 27.3%) were the most common types and women were spread more equally between CPAK Type I (1318; 22.7%), Type II (1584; 27.3%) and Type III (1494; 25.7%) (p < 0.001). The most common combination of femur and tibia types was NEUmLDFA0°,NEUmMPTA0° (m: 514, 17.5%; f: 1004, 17.3%), but men showed femoral varus more often. Patients with a higher BMI showed a significantly lower age at surgery (R2 = 0.09, p < 0.001). There were significant differences between men and women for all radiographic parameters (p < 0.001).
Conclusion:
Distribution in knee morphology with gender-specific differences highlights the wide range in osteoarthritic knees, characterized by CPAK and phenotype classification and may influence future surgical planning.
Level of evidence:
Level III.
... This ensures reproducible goals and reduces the risk of missed targets and catastrophic outliers (9). The robotic platform should allow for real-time 3D feedback on flexion and extension gaps and implant positioning and alignment suited to the patient's individual native ligament balance and bony anatomy as well as joint line restoration (2,36). FA differs from other personalized TKA techniques in that it has defined targets for joint height, obliquity and balanced gaps throughout the range of motion with objective soft tissue laxity endpoints (35). ...
Current limitations in total knee arthroplasty (TKA) function and patient satisfaction stimulated us to question our practice. Our understanding of knee anatomy and biomechanics has evolved over recent years as we now consider that a more personalized joint reconstruction may be a better-targeted goal for TKA. Implant design and surgical techniques must be advanced to better reproduce the anatomy and kinematics of native knees and ultimately provide a forgotten joint. The availability of precision tools as robotic assistance surgery can help us recreate patient anatomy and ensure components are not implanted in a position that may compromise long-term outcomes. Robotic-assisted surgery is gaining in popularity and may be the future of orthopedic surgery. However, moving away from the concept of neutrally aligning every TKA dogma opens the door to new techniques emergence based on opinion and experience and leads to a certain amount of uncertainty among knee surgeons. Hence, it is important to clearly describe each technique and analyze their potential impacts and benefits. Personalized TKA techniques may be classified into 2 main families: unrestricted or restricted component orientation. In the restricted group, some will aim to reproduce native ligament laxity versus aiming for ligament isometry. When outside of their boundaries, all restricted techniques will induce anatomical changes. Similarly, most native knee having asymmetric ligaments laxity between compartments and within the same compartment during the arc of flexion; aiming for ligament isometry induces bony anatomy changes. In the current paper, we will summarize and discuss the impacts of the different robotic personalized alignment techniques, including kinematic alignment (KA), restricted kinematic alignment (rKA), inverse kinematic alignment (iKA), and functional alignment (FA). With every surgical technique, there are limitations and shortcomings. As our implants are still far from the native knee, it is primordial to understand the impacts and benefits of each technique. Mid to long data will help us in defining the new standards.
