Neutral Mechanical Alignment Research Articles

Fixed-bearing medial unicompartmental knee arthroplasty restores pre-arthritic coronal alignment and achieves satisfactory functional outcomes: a retrospective study

PurposeThis study aimed to (1) analyze the Coronal Plane Alignment of the Knee (CPAK) classification in patients undergoing unicompartmental knee arthroplasty (UKA), (2) assess whether UKA can restore pre-arthritic coronal alignment by utilizing the arithmetic hip-knee-ankle angle (aHKA), and (3) evaluate the relationship between patient-reported outcome measures (PROMs) and postoperative alignment following UKA.MethodsWe retrospectively analyzed 152 consecutive patients who underwent fixed-bearing medial UKA. A radiological analysis was conducted using an EOS imaging system. Postoperative alignment was classified as neutral (varus ≤ 3°), mild varus (3° < varus ≤ 7°), or marked varus (varus > 7°) based on the mechanical hip-knee-ankle angle (mHKA). The aHKA was calculated and the CPAK classification was used to categorize knee phenotypes. The PROMs were obtained both before and after the surgery.ResultsA total of 152 knees from 113 patients were included with a mean two-year follow-up. The mean difference between the postoperative mHKA and the estimated aHKA was 0.80° (90% CI 0.35 to 1.24; P = 0.003). Postoperatively, 63 (41.45%) of the 152 knees were in neutral group, 54 (35.53%) mild varus, and 35 (23.03%) marked varus. The neutrally aligned cohort did not exhibit significantly higher scores in range of motion, VAS, HSS, WOMAC, or FJS-12 scores compared to the mild or marked varus cohort (P = 0.205, 0.118, 0.076, 0.140, and 0.788, respectively) during the short-term follow-up.ConclusionNon-robotically assisted, fixed-bearing medial UKA can restore pre-arthritic coronal alignment and achieve satisfactory PROMs. Fixed-bearing medial UKA aims to restore the pre-arthritic alignment rather than achieving neutral mechanical alignment.

No single safe zone exists for the valgus cut angle to reproduce neutral mechanical alignment in the presence of femoral bowing in total knee arthroplasty.

The aim of this study is to report the prevalence of femoral bowing in the Egyptian arthritic knees as a representative of the middle eastern population and to study the correlation between the femoral bowing and the degree of arthritis, varus deformity and the distal femoral valgus cut angle (VCA). This is a single-center observational cross-sectional study. Out of 562 knees Scheduled for TKA, 124 knees were excluded leaving 438 knees eligible for the study. The following angles were measured by two independent orthopedic surgeons: Femoral bowing angle (FBA), HKA angle, LDFA, MPTA and VCA. Out of 438 knees, 21knees (4.8%) had medial bowing (< - 3°), 111 (25.3%) had normal bowing (+ 3° to - 3°) and 306 (69.9%) had LFB of which 111 (25.34%) had mild LFB (+ 3 to + 5°) and 195 (44.52%) had severe LFB (> + 5°) bowing. LFB was more in older age group (p = 0.005), in females (p < 0.001), and in grade 4 OA, (p < 0.001). Also, there was a significant positive correlation between FBA and age and increasing varus HKA, and with varus orientation of the distal femur and the tibial plateau. The mean and the 95% confidence interval of the VCA for the medial bowing group was 3.43 (3.01-3.85°), for the normal bowing group was 5.42 (5.15-5.68°), for the mild lateral bowing was 6.74 (6.47-7°), and for the severe bowing group was 9.23 (8.89-9.55°). There is no single safe zone for the VCA to reproduce postoperative neutral coronal alignment especially in cases of severe lateral femoral bowing in TKA. However, the VCA should be analyzed in term of how much femoral bowing exists. In other words, for each subset of femoral bowing there is a safe zone for the VCA.

Restoring the Preoperative Phenotype According to the Coronal Plane Alignment of the Knee Classification After Total Knee Arthroplasty Leads to Better Functional Results

BackgroundMechanical alignment after total knee arthroplasty (TKA) is still widely used in the surgical community, but the alignment finally obtained by conventional techniques remains uncertain. The recent Coronal Plane Alignment of the Knee (CPAK) classification distinguishes 9 knee phenotypes according to constitutional alignment and joint line obliquity (JLO). The aim of this study was to assess the phenotypes of osteoarthritic patients before and after TKA using mechanical alignment and to analyze the influence of CPAK restoration on functional outcomes. MethodsThis retrospective multicenter study included 178 TKAs with a minimum follow-up of 2 years. Patients were operated on using a conventional technique with the goal of neutral mechanical alignment. The CPAK grade (1 to 9), considering the arithmetic Hip-Knee-Ankle angle (aHKA) and the JLO, was determined before and after TKA. Functional results were assessed using the following patient-reported outcome measures: Knee Injury and Osteoarthritis Outcome Score, the Simple Knee Value, and the Forgotten Joint Score. ResultsA true neutral mechanical alignment was obtained in only 37.1%. Isolated restoration of JLO was found in 31.4%, and isolated restoration of the aHKA in 44.9%. Exact restoration of the CPAK phenotype was found in 14.6%. Restoration of the CPAK grade was associated with an improvement in the “daily living”: 79.2 ± 5.3 versus 62.5 ± 2.3 (R2 = 0.05, P < .05) and “Quality of life” Knee Injury and Osteoarthritis Outcome Score subscales: 73.8 ± 5.0 versus 62.9 ± 2.2 (R2 = 0.02, P < .05). ConclusionsThis study shows that few neutral mechanical alignments are finally obtained after TKA by conventional technique. A major number of patients present a postoperative modification of their constitutional phenotype. Functional results at 2 years of follow-up appear to be improved by the restoration of the CPAK phenotype, JLO, and aHKA. Level of clinical art evidenceIII, Retrospective Cohort Study.

True Confessions of Neutral Mechanical Disciple-How I Learned to Love a Patient-Specific Target.

Classical neutral mechanical alignment in total knee arthroplasty (TKA) has been a standard paradigm, while more recently, other alignment schemas, such as kinematic, individualized, and functional, have been explored. This study aimed to investigate the effect of three-dimensional (3D) computed tomography (CT)-based surgical robotics inputs on a classically trained surgeon's TKA component positions and alignment targets over time. Data from 1,394 consecutive robotically-assisted TKAs by a single surgeon from 2016 to 2020 were analyzed. Metrics collected included pre-balance planned implant component positions, final planned implant component positions after soft tissue balancing, and constitutional alignment from CT scans. Joint line obliquity was plotted against the arithmetic hip-knee angle (aHKA) using coronal plane alignment of the knee (CPAK). Three categories of alignment strategy were defined: true mechanical alignment (tMA), adjusted mechanical alignment (aMA), and no mechanical alignment (noMA). A shift to overall varus component positioning was observed over the years. Joint line obliquity according to CPAK showed a wider spread in later years, and the distribution of tibial and femoral coronal alignment angles expanded over time. The study revealed a change in alignment targets and final positioning of components away from neutral biomechanical axes in a large volume of TKAs by a single, classically trained surgeon over five years of using a robotic arm-assisted TKA system with CT-based planning. The most dominant factor for this change was the use of 3D CT planning, allowing the surgeon to assess patient-specific anatomy and plan accordingly. Outcome data is needed to determine if this change in behavior and surgical technique was beneficial. In summary, using a CT scan-based robotically assisted technique led to a gradual and complete shift from tMA to predominantly a non-mechanically aligned philosophy in TKA.

Is 80% satisfaction still the expectation in modern TKA mechanically aligned with robot assist? We think not

Several studies reported that20% of patients were unhappy with the outcome of their total knee arthroplasty (TKA). Having commenced robot assist TKA whilst maintaining the goal of implanting the prosthesis to a neutral mechanical axis, we reviewed our patients to find out if we also have a 20% rate of patients being unhappy with the outcome of their knee replacement surgery. We hypothesized that rate of patient satisfaction would be higher than 90% with robot-surgical assistant (ROSA) technique. The first 175 patients who underwent ROSA TKA were reviewed at a minimum of 1 year postoperatively. All TKAs were performed using ROSA technique with Persona cementless prosthesis aiming to restore neutral mechanical coronal alignment with flexion gap balancing. We investigated whether or not the patients were happy they had their knee replacement surgery and whether they were happy with the outcome. 165 (94%) of 175 patients, were contactable with 1 deceased and 9 uncontactable. From the 165 patients who participated in the study, 95% of patients were happy they had the surgery done and 93% were happy with the outcome of their knee replacement. A sub analysis showed that patients who had simultaneous bilateral TKA were significantly less likely to be happy than staged procedures (p < 0.05). Total knee replacement utilising robot technique with modern implants and aiming for mechanical coronal alignment of the implants to restore the mechanical axis with flexion gap balancing may result in > 90% of patients being happy with the outcome of their surgery.

Functional Outcome of Mechanical Alignment in Total Knee Arthroplasty Surgery: A Short-Term Cohort Study at an Indian Tertiary Care Hospital.

In severe arthritis cases, goal of total knee arthroplasty (TKA) management is to attain pain-free joint and restore the overall limb alignment. There are limitedshort-term studies publishedfrom Indian hospitals that investigated the importance of neutral mechanical component alignment in TKA patients. Retrospective and prospective study was conducted at the Department of orthopaedics, Sancheti Institute for Orthopaedics and Rehabilitation, Pune from June 2020 to September 2022. Enrolled patients were assessed preoperatively and postoperatively using clinical examination, radiological assessment and functional outcomes through the Oxford knee score, Knee society score and VAS score. 204 patients enrolled, and 267 knees were evaluated for the study. Osteoarthritis was the commonest diagnosis (254 knees, 95.13%). Pre-operatively, 92.13% knees were varus, 4.87% valgus and 3% neutral while post-operatively, 51.69% were varus, 16.1% were valgus, and 32.32% were with neutral axis. Majority of patients with a pre-operative neutral axis converted to varus axis (62.5%), while most valgus axis cases preoperatively converted to a neutral axis (53.84%). For pre-operative varus subgroup, the majority patients with < 10° pre-operative axis converted to neutral (41.28%). Majority patients with 10°-20° pre-operative axis remained varus (60.53%) and with > 20° pre-operative axis remained varus (78.26%). Functional outcome parameters were significantly improved at follow-up (P < 0.05). Short-term postoperative functional scores were significantly improved in postoperative cases, with the postoperative alignment of 0° ± 3° relative to the mechanical axis was achieved. Thus, postoperative neutral mechanical alignment of 0° ± 3° can be the standard of care for patients undergoing TKA.

Accuracy and outcome of a handheld accelerometer-based navigation device compared to conventional alignment method in total knee arthroplasty in a Chinese population

Background Total knee arthroplasty (TKA) is a successful procedure in treatment of degenerative disease of the knee, and optimal component placement is essential for long-term implant survival. The purpose of this study was to compare the accuracy of the accelerometer-based KneeAlign 2 (KA2) navigation system against conventional methods for accurate positioning of the femoral and tibial components in TKA in a Chinese population. Methods A total of 123 (37 conventional and 86 KA2) cases of elective primary TKA were reviewed. Hip-knee-ankle (HKA) angle, mechanical lateral distal femoral angle (mLDFA), and anatomical lateral distal femoral angle (aLDFA) were measured from hip-to-ankle EOS radiographs. Accuracy of conventional alignment and KA2 navigation system was assessed by measuring the difference between intraoperative goal and postoperative radiographic measurements of the components for each respective case. Results There was no significant difference between conventional alignment methods and KA2 navigation in achieving a neutral mechanical alignment of the lower limb. KA2 navigation was significantly more accurate than conventional alignment methods for optimal positioning of the tibial component in both the coronal and sagittal plane, while no significant difference between the two groups was appreciated in the positioning of the femoral component in the coronal plane. Conclusions TKA using the accelerometer-based KA2 system was found to offer a high degree of accuracy in component alignment, and in particular, significantly improved tibial component alignment in comparison with conventional alignment methods in a Chinese population. However, no significant improvements were observed in neutral mechanical axis of the lower limb alignment and femoral component placement in the coronal plane.

Neutral Mechanical Alignment and Prevalence of Constitutional Varus Knees Among the Saudi Population at King Saud University Medical City.

Background Various studies have described the restoration of the neutral mechanical alignment of the lower limb in total knee replacement (TKR) as a key factor of knee implant durability. Mechanical alignment of the knee requires that the tibial and femoral cuts are perpendicular to the mechanical axis of each bone in the coronal plane. Objectives The aim of this study is to investigate mechanical knee alignment and the prevalence of constitutional varus knee among the Saudi population at a single tertiary center with no history of musculoskeletal abnormalities. Methodology This is a retrospective cross-sectional study involving patients with no musculoskeletal abnormality who had their lower limb X-ray Centigram using the universal viewer zero footprint system made between 2015 and 2021. The study took place at King Saud University Medical City. The X-rays were obtained from patients' electronic medical records retrospectively. A total of 728 knees of 370 males and 358 females were included in this study. Results The results showed that 165 male knees (44.4%) and 218 female knees (60%) had constitutional varus alignment with the hip-knee-ankle (HKA) angle of ≤3° or less. The average HKA angle was smaller in males than in females: -3.69° versus -1.98°, respectively. Conclusion We have identified variables and factors that can help surgeons detect the constitutional varus on a full leg radiograph preoperativelyat the time of TKA, regardless of the osteoarthritic changes of the knee. We encourage the scientific community to look for causes and risk factors for developing constitutional varus.

Predicting Rates of Angular Correction After Hemiepiphysiodesis in Patients With X-Linked Hypophosphatemic Rickets.

Patients with X-linked hypophosphatemic rickets (XLH) often develop coronal plane knee deformities despite medical treatment. Hemiepiphysiodesis is an effective way to correct coronal plane knee deformities in skeletally immature patients, but a full understanding of the rate of angular correction after hemiepiphysiodesis in XLH patients, compared with idiopathic cases is lacking. We retrospectively reviewed charts of 24 XLH patients and 37 control patients without metabolic bone disease who underwent hemiepiphysiodesis. All patients were treated with standard-of-care medical therapy (SOC=active vitamin D and phosphate salt supplementation) in our clinical research center and had a minimum of 2-year follow-up after hemiepiphysiodesis. Demographic data as well as complications, repeat procedures, or recurrence/overcorrection were recorded. Standing lower extremity radiographs were evaluated before the surgical intervention and at subsequent hardware removal or skeletal maturity, whichever came first. Mean axis deviation, knee zone, mechanical lateral distal femoral angle (mLDFA), and medial proximal tibial angle were measured on each radiograph. The rate of angular correction was calculated as the change in mLDFA and medial proximal tibial angle over the duration of treatment. The magnitude of the initial deformity of the distal femur was greater in XLH patients as compared with control for varus (XLH mLDFA 97.7 +/- 4.9 vs. Control mLDFA 92.0 +/- 2.0 degrees) and valgus (XLH mLDFA 78.7 +/- 6.2 vs. Controls mLDFA 83.6 +/- 3.2 degrees). The rate of correction was dependent on age. When correcting for age, XLH patients corrected femoral deformity at a 15% to 36% slower rate than control patients for the mLDFA (>3y growth remaining XLH 0.71 +/- 0.46 vs. control 0.84 +/- 0.27 degrees/month, <3y growth remaining XLH 0.37 +/- 0.33 vs. control 0.58 +/- 0.41 degrees/month). No significant differences were seen in the rate of proximal tibia correction. XLH patients were less likely to end treatment in zone 1 (55.0% XLH vs. 77.8% control). XLH patients had longer treatment times than controls (19.5 +/- 10.7 vs. 12.6 +/- 7.0mu, P value <0.001), a higher average number of secondary procedures than controls (1.33 +/- 1.44 vs. 0.62 +/- 0.92 number of procedures), a higher rate of overcorrection than controls (29.2% vs. 5.4%), and a higher rate of subsequent corrective osteotomy than controls (37.5% vs. 8.1%). There was no significant difference in the rate of complications between groups (8.3% vs. 5.4%). Patients with XLH undergoing hemiepiphysiodesis have a 15% to 36% slower rate of femoral deformity correction that results in longer treatment times, a higher likelihood to undergo more secondary procedures, and a lower likelihood to reach neutral mechanical alignment. This study provides important information to guide the timing and treatment of patients with XLH and coronal plane knee deformities. In addition, results from this study can be educational for families and patients with respect to anticipated treatment times, success rates of the procedure, complication rate, and likelihood of needing repeat procedures.

Mid-Term Clinical and Radiological Results at a Tertiary Care Hospital in Türkiye: Is Residual Varus Really Important After Mechanically-Aligned Total Knee Arthroplasty?

Traditionally, in total knee arthroplasty (TKA), it is aimed to keep the mechanical axis of the lower extremity neutral (mechanical alignment:3° varus-valgus in thecoronalplane) to improve long-term outcomes. This study aimed to assess the mid-term radiological and clinical results of patients with postoperative residual varus (more than 3° of varus) aftermechanically-aligned TKA. A total of 616 individuals who had undergoneTKAforprimaryknee osteoarthritisbetween 2008 and 2013 in our tertiary care hospital were retrospectively examined.All TKAs were performed with the mechanical alignment strategy.For radiological evaluation, hip-knee-ankle (HKA) angle, knee alignment angle (KAA), mechanical medial proximal tibial angle (mMPTA), knee inclination (KI), joint line orientation angle relative to ground (JLOA-G), posterior tibial slope (PS), joint line convergence angle (JLCA) were measured. Besides, patients' latest radiographs were screened for any clue of aseptic loosening or mechanical failure. Knee Society Score (KSS) (knee and functional subgroups), and Lysholm, Oxford, and Tegner scores were used for clinical evaluation. In addition, knee flexion and extension limitations were assessed. After applying the exclusion criteria, a minimum of five-year follow-up result of 110 patients was demonstrated.There were 101 females (92%) and nine males (8%). The mean follow-up time was 65.8 ± 6.3 months (range: 60.8-75.8 years). The mean age was 65.9 ± 7.7 years (range: 39 to 89 years). Thepreoperative mean mechanical axis angle of the lower extremity was17.3° ± 7.8° (range: 13.4-43.9°), whereas it was 8.3° ± 3.6° (range: 3.2-19.8°) postoperatively.The preoperative mean flexion angle was 90.7° ±23.8° (range: 40-130°), andthe extension limitation was -2.5° ± 7.4° (range: -40-0°), whereas, postoperatively, they were102.8° ± 15.4° (range from 40° to 150°) and -3.7° ± 7.5°(range from -40° to0°), respectively.The latest follow-up's mean KSS knee subgroup was 67 ± 18.4 (range: 12-93), the mean KSS functional subgroup was 74 ± 23.6 (range: 20-100), the mean Lysholm score was 81.7 ± 15.7 (range:25-100), the mean Tegner score was 3.65 ± 0.99 (range: 1-5), the mean Oxford score was 37.4 ± 6.5 (range: 9-48). There was no patient with aseptic loosening or mechanical failure. In the mid-term follow-up of patients with residual varus aftermechanically-alignedTKA, satisfactoryclinicaland radiological results were obtained without aseptic loosening or implant failure.

Current Concepts in Alignment in Total Knee Arthroplasty

BackgroundIn an effort to increase satisfaction among total knee arthroplasty (TKA) patients, emphasis has been placed on implant positioning and limb alignment. Traditionally, the aim for TKA has been to achieve a neutral mechanical alignment (MA) to maximize implant longevity. However, with the recent spike in interest in individualized alignment techniques and with the advent of new technologies, surgeons are slowly evolving away from classical MA. MethodsThis review elucidates the differences in alignment techniques for TKA, describes the concept of knee phenotypes, summarizes comparative studies between MA and individualized alignment, and provides a simple way to incorporate the latter into surgeons’ practice. ResultsIn order to manage patients by applying these strategies in day-to-day practice, a basic understanding of the aforementioned concepts is essential. Transition to an individualized alignment technique should be done gradually with caution in a stepwise approach. ConclusionAlignment and implant positioning are now at the heart of the debate and surgeons are investigating a more personalized approach to TKA.

Alignment options and robotics in total knee arthroplasty.

Total knee arthroplasty is one of the most widely performed surgical procedures today. Its widespread popularity has helped drive innovation and improvement in the field. Different schools of thought have developed regarding the best way to perform this operation. Specifically, there are controversaries regarding the best alignment philosophy for the femoral and tibial components to optimize implant stability and longevity. Traditionally, neutral mechanical alignment has been the preferred alignment target. More recently, some surgeons advocate for alignment matching the patient's pre-arthritic anatomic alignment ("physiologic" varus or valgus), which has been described as kinematic alignment. Functional alignment is a hybrid technique that focuses on the coronal plane minimizing soft tissue releases. To date, there is no evidence demonstrating superiority of one method over another. There is growing popularity of robotic surgical techniques to improve accuracy of implant position and alignment. The choice of alignment philosophy is an important aspect of robotic assisted TKA surgery and has the potential to clarify the optimal alignment technique.

A retrospective study of articular surface mounting computer-assisted total knee arthroplasty in alignment, knee function, and survival

Background Hong Kong Chinese exhibits a greater varus lower limb mechanical axis and coronal bowing when compared to Caucasians. This anatomical difference may affect the accuracy of bone cuts in total knee arthroplasty (TKA) using western anatomy-based intramedullary TKA cutting jigs. Use of computer navigation may avoid suboptimal cuts due to altered anatomy. This is the first study evaluating clinical function, radiological alignment and long-term survival of computer-assisted TKA amongst Hong Kong Chinese patients. Methods Retrospective study comparing articular surface mounting computer-assisted TKA (ASM-CATKA) and conventional TKA performed in a single centre from 2008 to 2010. Patients were followed up for ​assessment of clinical parameters including range of motion, Knee Society Knee score, and radiological parameters such as limb alignment, component alignment, and survival. Results Seventy-five patients were included in this study. Baseline clinical and radiological data were similar between groups. The computer-navigated group had superior radiological mechanical alignment ( p &lt; 0.001), tibial component alignment ( p = 0.016) and femoral component alignment ( p &lt; 0.01) when compared to conventional TKA. There were no differences in knee scores ( p = 0.488), range of motion ( p = 0.432) and survival at 117 months ( p = 0.986) between the two groups. Conclusion This retrospective study showed that ASM-CATKA was more accurate in achieving neutral mechanical axis and component alignment amongst Hong Kong Chinese. Clinical outcomes and implant survival were comparable.

Influence of Kinematic Alignment on Soft Tissue Releasing and Manipulation Under Anesthesia Rates in Primary Total Knee Arthroplasty.

Total knee arthroplasty (TKA) is typically performed to restore a neutral mechanical alignment. Recently, there has been increased interest in kinematic alignment to restore the patient's individual alignment. The purpose of this study is to determine if kinematic balancing reduces the need for intraoperative soft tissue releases and rates of manipulation under anesthesia compared to mechanical alignment. A query was performed between January 2021 and July 2022 to identify all patients who underwent a primary TKA that was performed with kinematic alignment (KA), which revealed 97 patients (107 TKAs). A cohort of consecutive patients from the preceding six months was gathered of patients who underwent primary TKA with mechanical alignment (MA). This cohort consisted of 199 patients (223 TKAs), yielding a total study cohort of 296 patients (330 knees). Mean age was 64.7 years, mean body mass index (BMI) was 33.1 kg/m2, and 57.1% of patients were female. Rates of manipulation under anesthesia and intraoperative release status were analyzed. Average range of motion preoperatively improved from 108.9° to 114.4° in the KA group but decreased from 112.3° to 109.9° in the MA group at six weeks (p<0.0001). Three of 107 knees (2.8%) required an additional pie-crusting of the superficial MCL in the KA group, whereas 58 of 223 knees (26.0%) did in the MA group (p<0.0001). Three of 107 knees (2.8%) in the KA group and 24 of 223 knees (10.8%) in the MA group required MUA (p<0.0001). Kinematic alignment significantly reduced the need for intraoperative soft tissue releases and postoperative manipulation under anesthesia. Further studies of the influence of kinematic alignment on these outcomes across multiple surgeons should be performed and/or compared to mechanical alignment.

No advantage with navigated versus conventional mechanically aligned total knee arthroplasty—10 year results of a randomised controlled trial

PurposeComputer-assisted surgery (CAS) total knee arthroplasty (TKA) remains a controversial area of surgical practice. The aim of this study is to report the ten-year revision rates and patient-reported outcome measures (PROMS) of a single-blinded, prospective, randomised controlled trial comparing electromagnetically (EM) navigated and conventional TKA.Methods199 patients were randomised to receive either EM navigated or conventional TKA where the aim of implantation was neutral mechanical alignment in all cases. Ten-year revision rates were collated and compared between the two intervention groups. Longitudinal PROMS data was collected prospectively at various time points up to 10 years post-operatively.ResultsOver the ten-year period, there were 23 deaths (22.8%) in the EM navigation cohort and 30 deaths (30.6%) in the conventional cohort. At 10 years post-operatively, there was no statistically significant difference in all cause revision between the EM navigation and conventional cohort (4.0 vs 6.1%, p = 0.429). When analysing causes of revision that might be influenced by utilising EM navigation, there was no statistically significant difference in revisions (3.0% EM navigated vs 4.1% conventional group, p = 0.591). Patients that received navigated TKAs had improved Oxford Knee Society, American Knee Society Score and range of motion at 3 months following surgery compared to conventional TKA (p = 0.002, p = 0.032, and p = 0.05, respectively). However, from 1 to 10 years post-operatively, both interventions had equivalent outcomes.ConclusionThere is no difference in revision rates or clinical outcomes comparing EM navigated versus conventional TKA at ten-year follow-up. The expected mortality rate makes it unlikely that a difference in revision rates will reach statistical significance in the future. In the setting of an experienced knee arthroplasty surgeon, it is difficult to justify the additional costs of CAS in TKA surgery.Level of evidenceI

Neutral Mechanical Alignment Alters the Native Distal Femoral Joint Line: A Virtual Three-Dimensional Planning Total Knee Arthroplasty Study

BackgroundAlternative alignment concepts have garnered great interest in an effort to improve patient satisfaction following primary total knee arthroplasty (TKA). The purpose of this study is to determine variation or deviation from an individual’s native joint line in primary TKA using neutral mechanical versus a restricted kinematic technique. MethodsAn institutional review board–approved prospective cohort study was performed evaluating the effect of neutral mechanical alignment (nMA) versus a restricted kinematic alignment (rKA) on the native joint line in 100 consecutive patients undergoing primary TKA. Using preoperative computed tomography and intraoperative 3-dimensional software, 2 virtual preoperative plans were created: nMA and rKA. Templated bone resections were recorded. Change in joint line was calculated using known implant planar thickness and planned bone resection. ResultsnMA yielded significantly greater deviation from the patient’s native joint line along the lateral compartment of the knee (lateral distal femoral condyle, lateral posterior femoral condyle, lateral tibial resection). With nMA, the lateral distal femoral joint line was distalized by a mean 4.3 versus 2.6 mm using rKA technique (P < .001). In rKA, >60% of knees had <3 mm of deviation from the native lateral posterior femoral offset, whereas in nMA, >95% of knees had ≥3 mm change in the lateral posterior femoral condylar offset. ConclusionnMA-TKA resulted in statistically larger joint line deviations compared to rKA-TKA, most notably along the lateral distal femoral condyle joint line. Further analysis is needed to determine the clinical consequences of joint line deviation from the native anatomy using nMA as the target for primary TKA.

Current concept of kinematic alignment total knee arthroplasty and its derivatives.

The kinematic alignment (KA) approach to total knee arthroplasty (TKA) has recently increased in popularity. Accordingly, a number of derivatives have arisen and have caused confusion. Clarification is therefore needed for a better understanding of KA-TKA. Calipered (or true, pure) KA is performed by cutting the bone parallel to the articular surface, compensating for cartilage wear. In soft-tissue respecting KA, the tibial cutting surface is decided parallel to the femoral cutting surface (or trial component) with in-line traction. These approaches are categorized as unrestricted KA because there is no consideration of leg alignment or component orientation. Restricted KA is an approach where the periarthritic joint surface is replicated within a safe range, due to concerns about extreme alignments that have been considered ‘alignment outliers’ in the neutral mechanical alignment approach. More recently, functional alignment and inverse kinematic alignment have been advocated, where bone cuts are made following intraoperative planning, using intraoperative measurements acquired with computer assistance to fulfill good coordination of soft-tissue balance and alignment. The KA-TKA approach aims to restore the patients’ own harmony of three knee elements (morphology, soft-tissue balance, and alignment) and eventually the patients’ own kinematics. The respective approaches start from different points corresponding to one of the elements, yet each aim for the same goal, although the existing implants and techniques have not yet perfectly fulfilled that goal.

Functional Outcome Based on Mechanical Axis Alignment Following Total Knee Arthroplasty.

BackgroundTotal knee arthroplasty (TKA) is the most commonly performed and highly successful surgical intervention for end-stage osteoarthritis of the knee, and it offers patients pain relief, functional recovery, and improved quality of life. The success of knee arthroplasty depends on various factors such as precise surgical technique, alignment of the limb and components, patient selection, and compliance with rehabilitation. Mechanical alignment of the lower limb has been considered an important factor in planning and assessing the success of TKA. Optimal alignment remains a matter of controversy; hence, it is paramount to assess the alignment and functional outcomes.Aim and objectiveThis study aimed to evaluate the reliability of conventional instrumentation in imparting the intended femoral and tibial coronal alignment, as well as study the functional outcome among the neutrally aligned outliers with respect to the mechanical axis of the lower limb using standing long-leg radiographs.MethodologyThis is a prospective, hospital-based, observational study that was conducted on 60 knees in 42 patients with primary osteoarthritis of the knee joint in the department of orthopedics, Satguru Partap Singh (SPS) Hospitals, Ludhiana. Patients undergoing total knee arthroplasty who fulfilled the inclusion criteria were included in our study and evaluated using Knee Society Score and knee flexion range at periodic follow-up till six months. Preoperative and postoperative standing long-leg radiographs were done for all the patients, and their functional outcome was compared among inliers and outliers.ResultsOut of these 60 total knee arthroplasties, 18 patients were operated on both knees, and 24 patients were operated on a single knee. There were 25 female patients and 17 male patients. The mean for pre-operative mechanical axis alignment angle was 11.88° ± 5.63° with a range from -3° to 27°, which changed to 2.90° ± 1.59° with a range from 0° to 8° at six months follow-up. It was observed that 42 of the knees were in the inliers, and the remaining 18 knees were in the outliers group. On comparison among inliers and outliers, we found that the mean range of motion was 108.29° ± 4.82° for the inliers group and 106.11° ± 4.04° for the outliers group (p = 0.091), depicting non-significant statistical comparison. Mean Knee Society Score values in inliers and outliers group were 152.45 ± 5.33 and 151.61 ± 3.55, respectively (p = 0.740), showing no statistical significance.ConclusionAt six months follow-up, there is no difference in the knee range of motion and Knee Society Scores between mechanical axis inliers and outliers. Thus, we conclude that although every knee arthroplasty is intended to have neutral mechanical alignment, there is no effect of mild mechanical axis malalignment on functional outcome following total knee arthroplasty in the short term.

Less soft tissue release in total knee arthroplasty for anteromedial compared to posteromedial knee osteoarthritis

In total knee arthroplasty (TKA), the aim of achieving a mechanically straight leg axis as well as symmetrical and equally wide gaps has become established as the gold standard in terms of surgical technique. In contrast to TKA unicompartmental knee arthroplasty (UKA) is performed in anteromedial osteoarthritis (AMOA) and does not normally require releases. This raises the hypothesis whether the type of osteoarthritis (AMOA vs. posteromedial osteoarthritis (PMOA)) determines the requirement for soft tissue releases in TKA.In this retrospective study, 114 patients with medial osteoarthritis of the knee who had been treated with a navigated total knee replacement were consecutively included. On the basis of the preoperative lateral radiographs, the patients were divided into two groups: AMOA and PMOA. The incidence and the extent of releases performed were recorded using the navigation records.Patient-specific data (gender, age) did not differ between the groups (NS). Knees with AMOA presented an overall varus alignment of 5.3 ± 3.5°, knees with PMOA 8.0 ± 4.0° (p < 0.001). 30 cases (44%) had to be released in the AMOA group, compared with 33 cases (72%) in the PMOA group (p = 0.004). In the case of medial release, the extension gap increased 3.3 ± 2.4 mm in the AMOA compared to 5.3 ± 3.7 mm in the PMOA group (p = 0.006). The medial flexion gap was released 2.2 ± 2.6 mm in the AMOA and 2.9 ± 3.0 mm in the PMOA group (p = 0.008).To achieve a neutral mechanical alignment, a release has to be performed due to asymmetry of the extension gap more often if PMOA is present than in AMOA. Surgeons should be prepared to perform more frequent and extensive medial releases in PMOA. Higher constrained implants should be available in case of unintended over release in PMOA.

Complex Patellofemoral Reconstruction for Recurrent Instability

Background: Patellofemoral instability is due to a combination of bony and soft tissue factors. While recurrent patellar dislocations are rare, evaluation and treatment of these conditions require addressing patellar height and lateralization of the tibial tubercle (TT), restraint to lateral patellar subluxation, and trochlear dysplasia. Other factors to consider are coronal limb-length alignment outside of the physiologic 5 to 8° of valgus, which may significantly alter the Q angle and contribute to lateral instability. Other ligaments around the patella contribute to soft-tissue restraint, including the medial and lateral patellotibial ligaments, patellomeniscal ligaments, and the medial quadriceps tendon femoral ligament. Patellar tilt is assessed with and without quadriceps contraction to further evaluate the patella’s relationship to the trochlear groove. The Caton-Deschamps Index, as well as patellar trochlear index (PTI), are used to measure patellar height for patella alta or baja. Technique Description: The technique is to surgically manage a patient in neutral mechanical alignment on standing limb radiographs, with moderate-to-severe DeJour type B trochlear dysplasia and a trochlear sulcus angle of around 145°, patella alta with a Caton-Deschamps Index of 1.6 and PTI of 0.22, a TT to trochlear groove (TT-TG) distance of 8 mm, and a deficient medial patellofemoral ligament (MPFL). The MPFL reconstruction is done first, with harvesting of the ipsilateral quadriceps tendon and maintenance of its distal attachment on the superior patellar pole. The quadriceps tendon graft is folded medially upon its distal attachment and fixed in this position with suture anchors. Tibial tubercle osteotomy is accomplished by spacing drill holes 2 mm apart, medially and laterally, on the TT and connecting the drill holes with an osteotome and reciprocating saw. A distalized location to secure the TT is selected and superficial bone is excised. A medial parapatellar arthrotomy is performed, and bur attachments are used to drill into the subchondral bone beneath the femoral articular surface to create a V-shaped flap of trochlear cartilage. An arthroscope is inserted under the trochlear flap during this process to visualize the appropriate depth. The trochlear flap is then secured with screws passed over guide pins to secure the flap to the desired location. Cannulated screws and washers are then used to secure the TT to its distalized and/or medialized position, with fluoroscopic verification of screw depth and location. The arthrotomy is then closed with the knee at 45°. The quadriceps graft is passed through a subretinacular channel and secured with suture anchors, adjacent to the adductor tubercle, to complete the MPFL reconstruction. Before closure, appropriate tracking and translation of the patella is verified. Results: Sulcus-deepening trochleoplasty, with or without MPFL reconstruction, has been reported to obtain satisfactory outcomes at 2 years, with close to 85% return to sport and 100% return to work, with improvements in International Knee Documentation Committee (IKDC) scores from 50.8 to 79.1 in some studies. MPFL reconstruction with tibial tubercle osteotomy (TTO) has yielded a 94.5% patient satisfaction rate in the literature. Discussion/Conclusion: In patients with recurrent patellar instability and DeJour types B-D trochlear dysplasia, MPFL reconstruction with TTO and sulcus-deepening trochleoplasty provides excellent subjective outcomes and restores patellar tracking with elimination of recurrent subluxation.