Goal Of Total Knee Arthroplasty Research Articles

Kinematic Patterns of Different Loading Profiles Before and After Total Knee Arthroplasty: A Cadaveric Study

One of the major goals of total knee arthroplasty (TKA) is to restore the physiological function of the knee. In order to select the appropriate TKA design for a specific patient, it would be helpful to understand whether there is an association between passive knee kinematics intraoperatively and during complex activities, such as ascending stairs. Therefore, the primary objective of this study was to compare the anterior–posterior (AP) range of motion during simulated passive flexion and stair ascent at different conditions in the same knees using a six-degrees-of-freedom joint motion simulator, and secondary, to identify whether differences between TKA designs with and without a post-cam mechanism can be detected during both activities, and if one design is superior in recreating the AP translation of the native knee. It was shown that neither TKA design was superior in restoring the mean native AP translation, but that both CR/CS and PS TKA designs may be suitable to restore the individual native kinematic pattern. Moreover, it was shown that passive and complex loading scenarios do not result in exactly the same kinematic pattern, but lead to the same choice of implant design to restore the general kinematic behavior of the native individual knee.

Real-world gait and turning in individuals scheduled for total knee arthroplasty

BackgroundImproving mobility – specifically walking – is an important treatment goal of total knee arthroplasty. Objective indicators for mobility, however, are lacking in clinical evaluations. This study aimed to compare real-world gait and turning between individuals scheduled for total knee arthroplasty and healthy controls, using continuous monitoring with inertial measurement units. MethodsReal-world gait and turning data were collected for 5–7 days in individuals scheduled for total knee arthroplasty (n = 34) and healthy controls (n = 32) using inertial measurement units on the feet and lower back. Gait and turning parameters were compared between groups using a linear regression model. Data was further analyzed by stratification of gait bouts based on bout length, and turns based on turning angle and turning direction. FindingsDominant real-world gait speed was 0.21 m/s lower in individuals scheduled for total knee arthroplasty compared to healthy controls. Stride time was 0.05 s higher in individuals scheduled for total knee arthroplasty. Step time asymmetry was not different between the groups. Regarding walking activity, individuals scheduled for total knee arthroplasty walked 72 strides/h less than healthy controls, and maximum bout length was 316 strides shorter. Irrespective of the size of the turn, turning velocity was lower in individuals scheduled for total knee arthroplasty. InterpretationIndividuals scheduled for total knee arthroplasty showed specific walking and turning limitations in the real-world. Parameters derived from inertial measurement units reflected a rich profile of real-world mobility measures indicative of walking limitation of individuals scheduled for total knee arthroplasty, which may provide a relevant outcome dimension for future studies.

Soft tissue laxity is highly variable in patients undergoing total knee arthroplasty

BackgroundOne major goal of total knee arthroplasty (TKA) is to achieve balanced medial and lateral gaps in flexion and extension. While bone resections are planned by the surgeon, soft tissue laxity is largely intrinsic and patient-specific in the absence of additional soft tissue releases. We sought to determine the variability in soft tissue laxity in patients undergoing TKA.MethodsWe retrospectively reviewed 113 patients undergoing TKA. Data on preoperative knee deformity were collected. Data from a dynamic intraoperative stress examination were collected by a robotic tracking system to quantify maximal medial and lateral opening in flexion (85–95 degrees) and extension (-5–20 degrees). T-tests were used to assess the differences between continuous variables.ResultsA valgus stress opened the medial compartment a mean of 4.3 ± 2.3 mm (0.0–12.4 mm) in extension and 4.6 ± 2.3 mm (0.0–12.9 mm) in flexion. A varus stress opened the lateral compartment a mean of 5.4 ± 2.4 mm (0.3–12.6 mm) in extension and 6.2 ± 2.5 mm (0.0–13.4 mm) in flexion.The medial compartment of varus knees opened significantly more in response to valgus stress than valgus knees in both extension (5.2 mm vs. 2.6 mm; P < 0.0001) and flexion (5.4 mm vs 3.3 mm; P < 0.0001). The lateral compartment of valgus knees opened significantly more in response to varus stress than varus knees in both extension (6.7 mm vs. 4.8 mm; P < 0.0001) and flexion (7.4 mm vs. 5.8 mm; P = 0.0003).ConclusionsSoft tissue laxity is highly variable in patients undergoing TKA, contributing anywhere from 0–13 mm to the post-resection gap. Only a small part of this variability is predictable by preoperative deformity. These findings have implications for either measured-resection or gap-balancing techniques.Level of EvidenceLevel III.

Evaluating the accuracy of a new robotically assisted system in cadaveric total knee arthroplasty procedures

BackgroundRobot-assisted total knee arthroplasty (TKA) has been shown to facilitate high-precision bone resection, which is an important goal in TKA. The aim of this cadaveric study was to analyze the accuracy of the target angle and bone resection thickness of a recently introduced robotic TKA system.MethodsThis study used 4 frozen cadaveric specimens (8 knees), 2 different implant designs, navigation, and a robotic system. The 4 surgeons who participated in this study were trained and familiar with the basic principles and operating procedures of this system. The angle of the bone cuts performed using the robotic system was compared with the target angles from the intraoperative plan. For each bone cut, the resection thickness was recorded and compared with the planned resection thickness.ResultsThe mean angular difference for all specimens was less than 1°, and the standard deviation was less than 2°. The mean difference between the planned and measured angles was close to 0 and not significantly different from 0 except for the difference in the frontal tibial component angle, which was 0.88°. The mean difference in the hip-knee-ankle axis angle was − 0.21°± 1.06°. The mean bone resection difference for all specimens was less than 1 mm, and the standard deviation was less than 0.5 mm.ConclusionsThe results of the cadaveric experimental study showed that the new TKA system can realize highly accurate bone cuts and achieve planned angles and resection thicknesses. Despite the limitations of small sample sizes and large differences between cadaveric and clinical patients, the accuracy of cadaveric experiments provides strong support for subsequent clinical trials.

Total knee replacement with an accelerometer-based, hand-held navigation system improves knee alignment: reliable in all patients.

Achieving adequate alignment has traditionally been an important goal in total knee arthroplasty to achieve long-term implant survival. While accelerometer-based hand-held navigation systems (ABN) has been introduced as a way to achieve alignment, there is a limited body of evidence on its accuracy, especially in patients under 65 years with differing etiologies for knee arthritis. This study aimed to assess the precision of a specific ABN system in restoring the mechanical axis and report surgical variables and complications, with particular attention to younger patients. We conducted a retrospective review of 310 primary TKA performed with ABN from May 2016 to February 2021. The mean patient age was 67.4 (SD 8.9) years, with 43% under 65 years and mean body mass index of 33.2 (SD 6.8). The average surgical time was 96.8min (57-171) and the average follow-up was 3.3 years (1.9-6.7). Data regarding length of stay, pain, range of motion (ROM), complications, and reinterventions were collected from the institutional joint arthroplasty registry and the medical records. Preoperative mechanical axis measurements and postoperative radiological data, including mechanical axis, component alignment and mechanical alignment outliers were analyzed. The mean preoperative mechanical axis was 175.4° (SD 7.6), with 248 knees (80%) in preoperative varus. The mean postoperative mechanical axis was 179.5° (SD 1.96) with 98% of knees falling within ± 3° of the neutral mechanical axis. Only 6 knees (2 varus, 4 valgus) fell outside the ± 3° range. And 3 knees (1 varus, 2 valgus) fell outside the ± 5° range. In the sagittal plane, 296 knees (95.5%) knees were within ± 3° of goal of 3 degrees of femoral flexion and 302 (97.4%) knees were within ± 2° of goal 1° of slope for tibial component. Far outliers (alignment outside ± 5° of targeted position) were found in 3 knees. Factors such as posttraumatic arthrosis, previous surgery, presence of retained hardware, and age below 65 years were not associated with increase in alignment outliers and far outliers. No complications related to the navigation system were observed. There were 22 complications and 20 reoperations, including 2 revisions for periprosthetic joint infection and 1 revision for flexion instability. Patients that required knee manipulation achieved an ultimate flexion of 110° (SD 14.1). The ABN system proved to be user-friendly and accurate in reducing alignment outliers in both coronal and sagittal planes in all patient populations. It offers a straightforward navigation solution while preserving surgeon autonomy and the use of traditional surgical tools. These findings advocate for the integration of this navigation system as a valuable tool to enhance the precision of TKA surgery in all patient groups.

Measuring Parallelism to the Ground in Bipedal Stance Phase: Mechanical Versus Kinematic Alignment in Total Knee Arthroplasty.

Introduction The goal of total knee arthroplasty is to replace diseased cartilage and bone with an artificial implant to improve the patient's quality of life. The knee has historically been reconstructed to the patient's mechanical axis (MA). However, kinematically aligned techniques have been increasingly used. Kinematic alignment requires less soft-tissue resection and aligns the knee with what is anatomically natural to the patient, while there is concern that kinematically aligned knees will lead to earlier failure due to potential unequal weight distribution on the implant. The purpose of this study is to compare the parallelism from the floor of the joint-line cuts using kinematic and mechanical alignment and understand if the MA is a proper estimation of the tibial-ankle axis (TA). Methods A retrospective study was conducted by recruiting all high tibial osteotomy and distal femoral osteotomy recipients operated on by two surgeons in two MedStar Health hospitals from 01/2013 to 07/2020 with full-length films in preparation for restorative procedures. Baseline osteoarthritis was graded using the Kellgren-Lawrence classification system with all patients presenting as Grade 0. The TAand the joint-line orientations of the MAand kinematic axis (KA) were measured on 66 legs. The average distance from parallelism to the ground was compared between the MA and the KA and between the MA and the TA using a paired t-test. Results KA joint-line orientation (1.705° deviation) was more parallel to the floor in the bipedal stance phase than the MA (2.316° deviation, p=0.0156). The MA (2.316° deviation) was not a proper estimation of the TA (4.278° deviation, p=0.0001). Conclusion By utilizing the KA technique, the restoration of the natural joint line, as well as a joint that is more parallel to the floor in the stance phase compared to the MA, is achieved.The parallelism to the ground of the KAduring the bipedal stance phase suggests an even load distribution across the knee.In addition, due to its similarity to the KA and anatomical significance in weight-bearing distribution, further investigation into the hip-to-calcaneal axis as an approximation of the joint line is warranted.

Total knee arthroplasty and rehabilitation

Arthroplasty is the reconstruction of the joint to relieve pain, increase range of motion and provide stabilization in any joint. The main goals of total knee arthroplasty are to relieve pain, improve function, improve quality of life, create a long-lasting artificial joint, and prevent or reduce surgical complications. Joint infection, sepsis or systemic infections, neuropathic arthropathy, painful stiff knee fusion due to complex regional pain syndrome (CRPS), genu recurvatum due to neuromuscular weakness, painless and well-functioning knee arthrodesis are absolute contraindications to total knee arthroplasty. In addition, the patient should be monitored for circulation, sensation and infections during the acute period (1-5 days). An appropriate DVT prophylaxis should be given. There is evidence that long-term physical deficiencies persist after arthroplasty. Since decreased muscle strength, decreased flexibility, abnormalities in walking, and deficits in postural stability can be detected, it is recommended to continue exercise programs for at least 1 year.

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.

Optimizing Asymmetric Native Knee Flexion Gap Balance Promotes Superior Outcomes in Primary Total Knee Arthroplasty.

Replicating native knee kinematics remains the ultimate goal of total knee arthroplasty (TKA). Technology, such as robotics, provides robust intraoperative data; however, no evidence-based targets currently exist for improved clinical outcomes. Furthermore, some surgeons target a rectangular flexion space in TKA unlike the native knee. This study evaluated the effect of in vivo flexion gap asymmetry on patient-reported outcome measures (PROMs) in contemporary TKA. In vivo tibiofemoral joint space dimensions were measured during 129 TKAs using a calibrated tension device before and after complete posterior cruciate ligament resection. PROMs were compared based on the final dimensions and the change in flexion gap dimensions at 90° of flexion: (1) equal laxity, (2) lateral laxity, and (3) medial laxity. Groups did not differ by demographics ( P ≥ 0.347), clinical follow-up ( P = 0.134), tibiofemoral alignment ( P = 0.498), or preoperative PROMs ( P ≥ 0.093). Mean follow-up for the cohort was 1.5 years (range, 1-3). Pain with climbing stairs, pain while standing upright, and knees "always feeling normal" scores were superior for patients with equal or lateral laxity compared with medial laxity ( P ≤ 0.064). Pain with level walking, University of California Los Angeles activity level, KOOS JR, and satisfaction scores also tended to be superior for patients with equal or lateral laxity, although it lacked statistical significance ( P ≥ 0.111). Results of this study suggest that patients with either an equally tensioned rectangular flexion space or with later-flexion lateral laxity after posterior cruciate ligament resection may achieve superior PROMs. Findings support the clinical benefit of facilitating posterolateral femoral roll back in flexion, which mimics native knee kinematics and further helps define targets for advanced technology.

Kinematic alignment matches functional alignment for the extension gap: a consecutive analysis of 749 primary varus osteoarthritic knees with stress radiographs.

The alignment goal in total knee arthroplasty (TKA) remains debated. Two major strategies have emerged based on recreating the native knee: kinematic and functional alignment (KA and FA). Recently a new Coronal Plane Alignment of the Knee (CPAK) classification for KA, based on bony landmarks, was described considering joint line obliquity and the arithmetic HipKneeAnkle angle (aHKA). Valgus corrected HKA medial angle (vcHKA) was measured on distractive valgus preoperative radiographs compensating for cartilage wear and ligament balance in varus osteoarthritis. The purpose of this study was to determine if aHKA accounts for differences in medial laxity for the extension gap by comparing vcHKA to aHKA. The hypothesis was that no significant difference would be observed between the two measurements. This is a retrospective analysis of 749 knees in consecutive patients presenting to a single-centre with primary medial osteoarthritis. Patients underwent standardized weight bearing long-leg and valgus stress radiographs. Tibial mechanical angle (TMA), femoral mechanical angle (FMA) and vcHKA were measured using digital software. aHKA and vcHKA were compared to determine differences due to soft tissue balancing. The mean FMA was 91.3 ± 2.2° (range 82°-97°), the mean TMA was 85.7 ± 2.5° (range 75°-98°), the mean aHKA was 177.0 ± 3.0° (range 164°-185°) and the mean vcHKA was 176.6 ± 3.1° (range 165°-192°). No significant difference was observed between aHKA and vcHKA (p = 0.06). A significant correlation was found between vcHKA and TMA (ρ = 0.3; p < 0.001) and between vcHKA and FMA (ρ = 0.41; p < 0.001). This study showed that vcHKA was similar to aHKA confirming that aHKA accounts for ligamentous medial laxity. Therefore, kinematic alignment based on the CPAK classification matches the pre-arthritic coronal alignment of the knee for the extension gap. IV.

Evaluation of the result of total knee replacement in various arthritic condition of knee

Introduction: Osteoarthritis is the most common form of the arthritis and is a leading cause of disability in older adults. The management of knee arthritis depends upon severity of arthritis. It starts from conservative management in earlier stage and goes upto the total knee replacement (TKR) in severely advance stage. TKR is an operation to restore pain-free motion to a joint, muscle, ligament, and other soft tissue structures that control joint. The goal of total knee arthroplasty is as simple as to relieve pain, provide motion, maintain stability, and simultaneously correcting deformity. The purpose of this study is to evaluate pain, mobility, stability after TKR in arthritis and to evaluate functional outcome. Materials and Methods: The case material for present study was selected from the out patient Department of Orthopaedics, S.N. Medical College and Hospital, Agra. Each patient would be subjected to detailed clinical history and examination and necessary radiological and pathological investigation. Data was collected by interviews, observation of clinical and radiological findings and assessment of function done using knee society knee score (having 100 points). Results: In this study, evaluation of 10 total knee arthroplasty was performed in S.N. Medical College and Hospital, Agra. In our study most of cases (70%) have age ≥60 years and most of (70%) cases are female in whom TKR was performed. The pre-operative ROM at knee were between 51⁰ and 80⁰ in all the cases (100%). But post-operative after 6 months all the cases have their range of motion between 91⁰ and 110⁰. Maximum number of the cases (80%) have moderate continuous pain at knee before the operation and rest 20% have moderate occasional pain at their knee preoperatively. After the operation, maximum number of cases (90%) have no pain or mild occasional pain after the operation. Maximum number of cases (90%) have ≥30⁰ increase in their range of motion, after operation. Similarly after TKR, there is an increase in post-operative functional knee scores at 6 months (86.5%) as compared preoperative scores (21%). Though there is an initial fall (16.5%) in the functional score in initial 15 days after operation, it then starts increasing at 1 month and ultimately at 6 month. Conclusions: Total knee arthroplasty should definitely be performed over 60 years of age having pain at knee not responding to analgesics with or without any significant deformity at knee. As we found that is no or occasional pain with good range of movement after 6 month of operation so that patient satisfaction level is very high. But large number of patient and ling follow-up is required for long-term result.

Improved total knee arthroplasty pain outcome when joint gap targets are achieved throughout flexion.

Achieving a balanced knee is accepted as an important goal in total knee arthroplasty; however, the definition of ideal balance remains controversial. This study therefore endeavoured to determine: (1) whether medio-lateral gap balance in extension, midflexion, and flexion are associated with improved outcome scores at one-year post-operatively and (2) whether these relationships can be used to identify windows of optimal gap balance throughout flexion. 135 patients were enrolled in a multicenter, multi-surgeon, prospective investigation using a robot-assisted surgical platform and posterior cruciate ligament sacrificing gap balancing technique. Joint gaps were measured under a controlled tension of 70-90N from 10°-90° flexion. Linear correlations between joint gaps and one-year KOOS outcomes were investigated. KOOS Pain and Activities of Daily Living sub-scores were used to define clinically relevant joint gap target thresholds in extension, midflexion, and flexion. Gap thresholds were then combined to investigate the synergistic effects of satisfying multiple targets. Significant linear correlations were found throughout extension, midflexion, and flexion. Joint gap thresholds of an equally balanced or tighter medial compartment in extension, medial laxity ± 1mm compared to the final insert thickness in midflexion, and a medio-lateral imbalance of less than 1.5mm in flexion generated subgroups that reported significantly improved KOOS pain scores at one year (median ∆ = 8.3, 5.6 and 2.8 points, respectively). Combining any two targets resulted in further improved outcomes, with the greatest improvement observed when all three targets were satisfied (median ∆ = 11.2, p = 0.002). Gap thresholds identified in this study provide clinically relevant and achievable targets for optimising soft tissue balance in posterior cruciate ligament sacrificing gap balancing total knee arthroplasty. When all three balance windows were achieved, clinically meaningful pain improvement was observed. Level II.

Neutral boundary alignment in total knee arthroplasty: a novel concept

The goal of total knee arthroplasty (TKA) surgery is to provide a stable and functional knee joint using current implant designs. Several alignment philosophies and surgical techniques have been introduced to provide a stable and functional knee joint, such as mechanical alignment (MA), kinematic alignment (KA), and anatomical alignment (AA). Recently, functional alignment (FA) is proposed. In this concept article, we propose a TKA approach, which we termed “Neutral Boundary Alignment (NBA).” The proposed approach seeks to establish the overall limb alignment in the direction of gravity at the midstance of gait cycle; consequently, a potential native knee can be restored from an arthritic state by establishing the joint line parallel to the ground. Herein, the NBA approach is described, and an iterative algorithm of structural layout patterns of truss is developed. The following three hypotheses are proposed: 1) The joint line should be parallel to the ground during the midstance of gait as an important initial condition for stability when transitioning toward gait propulsion in the gait cycle; 2) The NBA stability criteria purports that the leg is stable when the direction of gravity is simultaneously situated within the hip, knee and ankle during the midstance of gait, which generally agrees with the Varus/Valgus 3 degree envelope of MA; 3) Femoral and tibial resections that are made parallel to the ground remain within 1.5 degrees of traditional mechanical alignment resections.

Influence of posterior tibial slope on knee flexion in posterior stabilized fixed bearing primary total knee arthroplasty

&lt;p class="abstract"&gt;&lt;strong&gt;Background:&lt;/strong&gt; The goal of total knee arthroplasty (TKA) is to relieve pain and maintain stable range of motion (ROM) for day to day activities. Among the various factors, posterior tibial slope slope (PTS) may play an important role in achieving good postoperative knee flexion. Our study aims to know the effectiveness of PTS on the ROM of the knee in a posterior cruciate ligament (PCL)-substituting TKA.&lt;/p&gt;&lt;p class="abstract"&gt;&lt;strong&gt;Methods:&lt;/strong&gt; A total of 125 unilateral PCL-substituting TKA’s were included in the study. Based on postoperative PTA which was measured on lateral radiograph, patients were divided into 3 groups, Group A (PTS of ≤2) comprise of 24 patients. Group B consists of 91 patients (PTS of 3 to 7). Group C includes 10 patients (PTS of 8 or more). Functional outcome was measured by using knee society score (KSS) and Western Ontario and McMaster Universities osteoarthritis index (WOMAC) which were evaluated preoperatively and at 18months post operatively.&lt;strong&gt;&lt;/strong&gt;&lt;/p&gt;&lt;p class="abstract"&gt;&lt;strong&gt;Results:&lt;/strong&gt; Mean postop ROM was 92.91 ± 10.632; 107.24±10.905; 107.49±13.944 in group A, B, C respectively which was significantly related to mean postop PTS (0.74; 5.62; 9.87 in group A, B, C respectively) (P&amp;lt;0.05). Functional outcome was measured by KSS and WOMAC which showed no significant difference pre and postoperatively.&lt;/p&gt;&lt;p class="abstract"&gt;&lt;strong&gt;Conclusions:&lt;/strong&gt; The results of our study validate the hypothesis that a positive correlation exists between the postoperative flexion and PTS in the PCL-substituting TKA, an increase in PTS can lead to a greater degree of the knee flexion for every extra degree of PTS.&lt;/p&gt;&lt;p&gt; &lt;/p&gt;

Imageless, robotic-assisted total knee arthroplasty combined with a robotic tensioning system can help predict and achieve accurate postoperative ligament balance.

BackgroundAchieving balanced gaps is a key surgical goal in total knee arthroplasty, yet most methods rely on subjective surgeon feel and experience to assess and achieve knee balance intraoperatively. Our objective was to evaluate the ability to quantitatively plan and achieve a balanced knee throughout the range of motion using robotic-assisted instrumentation in a tibia-first, gap-balancing technique.MethodsA robotic-assisted, gap-balancing technique was used in 121 consecutive knees. After resection of the proximal tibia, a computer-controlled tensioning device was inserted into the knee joint and the pre-femoral-resection knee gaps were acquired dynamically throughout flexion under controlled load. Predicted gap profiles were used to plan the femoral implant by adjusting the implant alignment and position within certain boundaries to achieve a balanced knee throughout the range of flexion. Femoral cuts were then made according to this plan using a miniature robotic-assisted cutting guide. The tensioning device used to measure the pre-femoral-resection gaps was then reinserted into the joint to quantify the final gap balance under known tension. The final gap profiles were then compared with the predictive gap plans.ResultsThe overall root mean square error between the predicted and achieved gaps was 1.3 mm and 1.5 mm for the medial and lateral sides, respectively. Use of robotic assistance resulted in over 90% of knees having mediolateral balance within 2 mm across the flexion range. Gaps at 0° flexion were 2 mm smaller than the gaps at 90°. This difference decreased to less than 1 mm when comparing the tibiofemoral gaps at 10°, 45°, and 90°.ConclusionsImageless, robotic-assisted total knee arthroplasty accurately predicts postoperative gaps before femoral resections. This allows surgeons to virtually plan femoral implant alignment and optimize gap balance throughout the range of motion. The accurate prediction of gaps throughout the arc of motion combined with precise, robotically assisted femoral resection produces accurate postoperative ligament balance consistently.

SHORT-TERM RESULTS OF CRUCIATESUBSTITUTING CEMENTED TOTAL KNEE ARTHROPLASTY

Background: Total Knee Arthroplasty(TKA) is indicated in individuals with painful, disabling arthritis, having radiographic evidence of joint damage and not responding to conservative treatment, thus resulting in diminished quality of life. The goal of TKA is to relieve pain, provide motion, maintain stability and correct deformity. Aim: To evaluate short-term clinico-radiological results and complications of TKA. Material and methods: A prospective randomized controlled study was conducted between December 2006 and June 2009 on 41 patients(61 knees) who underwent TKA and were followed for one year or more. Mean follow-up was 19.69±5.69 months (minimum-12, maximum-30). Posterior Cruciate Ligament (PCL)- substituting cemented Press Fit Condylar(PFC) Sigma prosthesis(Depuy Orthopaedics) was used in all cases. Fixed-bearing design was used in 39 patients(57 knees) while mobile-bearing rotating-platform design(PFC-sigma-RP) was used in 2 patients(4 knees). Patella was resurfaced in 2 patients(2 knees). Pain(using Visual analogue scale-VAS), fixed flexion deformity(FFD), maximum flexion and Knee Society Score(KSS) were evaluated preoperatively and postoperatively. Radiological analysis included assessment of femoral-tibial alignment, radiolucencies and patellar tracking. Changes at 3, 6, 12 and 24 months were statistically analyzed. Observations and results: Mean age was 61.17 ± 9.51 years(range 40- 77 years). Male to female ratio was 1:2.4. Osteoarthritis(OA) with varus deformity was present in majority. By the end of 1 year, most patients had either no pain or only mild occasional pain. Preoperatively 93% patients had poor functional score(FS) and 98% knees had poor knee score(KS). After TKA, about 85% patients had excellent or good FS while nearly 97% knees had excellent or good KS. Near maximum improvement in KSS is achieved by the end of 1 year with no further significant improvement thereafter. The mean maximum flexion was 114.750 preoperativly and 113.770 at 1 year which was not statistically significant. There were very few complications. Infection was present in 3 cases while peroneal nerve palsy in one. There were no progressive radiolucencies, polyethylene wear, implant failure, patello-femoral complications or clinical deep venous thrombosis(DVT). One knee with mobilebearing prosthesis had insert spin-off after 2 weeks. Conclusion: TKA is a very successful, safe and costeffective treatment for patients with knee arthritis who do not respond to nonsurgical therapies. Cemented TKA is still the gold standard and fixedbearing, cruciate-substituting prosthesis continues to function well after 2-years of follow-up. Keywords: Knee arthritis, cemented cruciate-substituting Total knee arthroplasty, short- term results.

The Use of Precision Alignment Technology to Circumvent Patient- Specific Roadblocks in Performing Total Knee Arthroplasty

The goal of total knee arthroplasty (TKA) is to provide the patient with a well-functioning, pain-free knee that will last for many years. To improve implant survival, the goal is to position the prosthesis in a way that restores proper biomechanical alignment, and advances in technology have enabled arthroplasty surgeons to produce accurate results on a more consistent basis. One of these advances is the use of computer-assisted orthopaedic surgery (CAOS) to assist in proper component alignment and produce accurate restoration of the biomechanical axis consistently.1–17 Functional scores and revision-free survival are at least equivalent to conventional arthroplasty.17–26 Traditional cutting guides for TKA rely on intramedullary femoral instruments, and either intramedullary or extramedullary tibial instruments, to obtain proper axial alignment. In cases where retained hardware is present, or in patients with knee osteoarthritis associated with pre-existing femoral or tibial extra-articular deformity, CAOS has proved to be an exceptionally useful, effective, and appealing option.27–37 A portable, accelerometer-based navigation device (OrthAlign, OrthAlign Inc., Aliso Viejo, CA) for TKA has demonstrated promising results with regard to the alignment accuracy of large-console CAOS systems.10–14 We present three patients who underwent TKA with retained femoral hardware. Two patients had intramedullary femoral fixation and one patient had an interference screw from a previous anterior cruciate ligament (ACL) reconstruction that would interfere with the use of a conventional intramedullary alignment guide. A novel, portable, accelerometer-based navigation (OrthAlign® precision alignment system, OrthAlign Inc., Aliso Viejo, CA) guide enabled performance of TKA without the need for surgical removal of hardware.

Suboptimal patellofemoral alignment is associated with poor clinical outcome scores after primary total knee arthroplasty.

Proper patellofemoral alignment is an important goal in total knee arthroplasty (TKA). Acceptable patellar alignment is defined as patellar tilt less than or equal to 5° and patellar displacement less than or equal to 5mm. Previous studies reported an incidence of post-operative patellar malalignment in TKA from 7 to 35%. However, correlation between patellar malalignment and clinical outcome after TKA remains unclear. The purpose of the present study was to evaluate the effect of patellar tilt and displacement on the clinical outcome of TKA. A retrospective review of 138 primary TKAs with a minimum of 2 year follow-up is reported. Pre-operative and post-operative mechanical axis, patellar tilting angle and patellar displacement were measured. Clinical outcomes were evaluated by the knee functional scores including the Knee Society Score (KSS), Knee injury and Osteoarthritis Outcome Score (KOOS), and Western Ontario McMaster University Osteoarthritis Index (WOMAC) at final follow-up. Forty-two (30%) primary TKAs had suboptimal patellofemoral alignment with a patellar tilt angle greater than 5° or lateral patellar displacement of more than 5mm. There was no statistical difference in pre-operative mechanical axis, pre-operative patellar tilt angle, or pre-operative lateral patellar displacement between the primary TKAs with proper patellofemoral alignment and those with suboptimal alignment. Patients with post-operative patellar tilt or displacement had clinically significant reductions in KSS, KOOS, and WOMAC when compared with patients without post-operative patellar tilt or displacement. The odds of having a fair or poor post-operative result, an odds ratio of 3.4 (95% CI 1.6-7.2) for KSS, 6.4 (95% CI 2.9-14.2) for KOOS, and 5.9 (95% CI 2.6-13.5) for WOMAC, were associated with suboptimal patellofemoral alignment. Establishing proper patellofemoral alignment remains an essential goal of primary TKA. There is a strong association between suboptimal post-operative patellofemoral alignment and poor clinical outcome scores after primary TKA.

Slight under-correction following total knee arthroplasty for a valgus knee results in similar clinical outcomes.

Restoration of correct coronal alignment is one of the main goals of total knee arthroplasty (TKA). Traditionally, TKA has been considered successful when a neutral mechanical hip-knee-ankle (HKA) axis within 3° is achieved. Recent studies have reported no differences or improved clinical outcomes following a slight under-correction of the HKA axis for a varus knee. However, the influence of under-correction of a valgus knee has not been reported. This study investigated the influence of post-operative HKA alignment in TKA patients with valgus deformity on clinical outcomes. Ninety-three knees (93 patients) with pre-operative valgus alignment were evaluated with a mean follow-up period of 60months. All patients were classified into three groups based on post-operative HKA alignment: neutral (0 ± 3°), mild valgus (3°-6°), and severe valgus (> 6°). These groups were compared using the Western Ontario and McMaster Universities osteoarthritis (WOMAC) index, the Knee Society (KS) knee score, KS function score, α-angle, β-angle, patella tilt angle, and the congruence angle. Sixty-nine knees were included in the neutral group, seventeen knees in the mild valgus group, and seven knees in the severe valgus group. In all cases, post-operative clinical and functional scores significantly improved compared to pre-operative scores. There were no differences between the three groups in post-operative clinical and functional scores. More post-operative patellar tilt angle outliers (> 10°) and congruence angle outliers (> 16°) were apparent in the severe valgus group (patellar tilt angle, 13 vs. 17 vs. 57.1%, p = 0.022; congruence angle, 32 vs. 47 vs. 71%, p = 0.035). Slight under-correction following TKA for a valgus knee resulted in similar clinical outcomes. A residual valgus angle of more than 6° can induce patellar maltracking. III, Retrospective comparative study.

Optimization of sagittal and coronal planes with robotic-assisted unicompartmental knee arthroplasty

BackgroundOne of the anatomic goals of total knee arthroplasty (TKA) is optimizing in the coronal and sagittal plane. Accurate alignments of both planes have been correlated to functional outcome and range of motion. There is a paucity of evidence on the accuracy of unicompartmental knee arthroplasty (UKA) in balancing biplanar knee alignment – specifically sagittal plane alignment. Because robotic assisted UKA has an advantage of more accurately manipulating sagittal plane for optimal alignment and kinematics based on pre-operative and intraoperative CT planning we assessed the accuracy. MethodsWe reviewed the clinical and radiographic information of 94 robotic assisted UKA surgeries for balancing of sagittal and coronal knee anatomy using radiographic parameters, such as posterior condylar offset ratio (PCOR), posterior tibial slope (PTS), femoral-tibial angle, and joint line. ResultsIn the sagittal plane, we found no significant difference between pre and postoperative PCOR values. As planned, PTS was significantly lower after UKA compared to the native knee (4.91° vs 2.28°; p<0.0001). In the coronal plane, there was no significant difference in the joint line however pre and post-operative mechanical axis were significantly different (5.43°±2.58 of varus vs. 2.76°±2.14 of varus; p<0.0001). ConclusionThis study attempts to quantify sagittal and coronal plane alignment after robotic assisted UKA. More attention should be paid to the role of sagittal plane alignment after UKA. We believe modifying posterior tibial slope, while maintaining PCOR is fundamental in achieving native kinematics and optimizing range of motion in the sagittal plane. This may be best-accomplished using robotic techniques for UKA.