Introduction. In total knee arthroplasty (TKA), component realignment with bone-based surgical correction (BBSC) can provide soft tissue balance and avoid the unpredictability of soft tissue releases (STR) and potential for more post-operative pain. Robotic-assisted TKA enhances the ability to accurately control bone resection and implant position. The purpose of this study was to identify preoperative and intraoperative predictors for soft tissue release where maximum use of component realignment was desired. Methods. This was a retrospective, single center study comparing 125 robotic-assisted TKAs quantitatively balanced using load-sensing tibial trial components with BBSC and/or STR. A surgical algorithm favoring BBSC with a desired final mechanical alignment of between 3° varus and 2° valgus was utilized. Component realignment adjustments were made during preoperative planning, after varus/valgus stress gaps were assessed after removal of medial and lateral osteophytes (pose capture), and after trialing. STR was performed when a BBSC would not result in
The Coronal Plane Alignment of the Knee (CPAK) is a recent method for classifying knees using the hip-knee-ankle angle and joint line obliquity to assist surgeons in selection of an optimal alignment philosophy in total knee arthroplasty (TKA)1. It is unclear, however, how CPAK classification impacts pre-operative joint balance. Our objective was to characterise joint balance differences between CPAK categories. A retrospective review of TKA's using the OMNIBotics platform and BalanceBot (Corin, UK) using a tibia first workflow was performed. Lateral distal femoral angle (LDFA) and medial proximal tibial angle (MPTA) were landmarked intra-operatively and corrected for wear. Joint gaps were measured under a load of 70–90N after the tibial resection. Resection thicknesses were validated to recreate the pre-tibial resection joint balance. Knees were subdivided into 9 categories as described by MacDessi et al.1 Differences in balance at 10°, 40° and 90° were determined using a one-way 2-tailed ANOVA test with a critical p-value of 0.05. 1124 knees satisfied inclusion criteria. The highest proportion of knees (60.7%) are CPAK I with a varus aHKA and Distal Apex JLO, 79.8% report a Distal Apex JLO and 69.3% report a varus aHKA. Greater medial gaps are observed in varus (I, IV, VII) compared to neutral (II, V, VIII) and valgus knees (III, VI, IX) (p<0.05 in all cases) as well as in the Distal Apex (I, II, III) compared to Neutral groups (IV, V, VI) (p<0.05 in all cases). Comparisons could not be made with the Proximal Apex groups due to low frequency (≤2.5%). Significant differences in joint balance were observed between and within CPAK groups. Although both hip-knee-ankle angle and joint line orientation are associated with joint balance, boney anatomy alone is not sufficient to fully characterize the knee.
In total knee arthroplasty (TKA), tibial insert thickness is determined intraoperatively by applying forces that generate varus-valgus moments at the knee and estimating the resulting gaps. However, how the magnitude of applied moments and the surgeon's perception of gaps affect the thickness selection is unclear. We determined this relationship using an in vitro human cadaveric model. Six pelvis-to-toe specimens (72±6 years old, four females) were implanted by an expert surgeon with a PS TKA using measured resection. Pliable sensors were wrapped around medial and lateral aspects of the foot and ankle to measure the applied forces. The forces were scaled by limb length to obtain the moments generated at the knee. Six surgeons with different experience levels independently assessed balance by applying moments in extension and 90° of flexion and choosing the insert they believed fit each knee. Peak moments and the accompanying extension and flexion gap openings as perceived by surgeons were recorded. The two measures were then related to insert choice using a generalized estimating equation.Introduction
Methods
The aim of mechanical alignment in total knee arthroplasty is to align all knees into a fixed neutral position, even though not all knees are the same. As a result, mechanical alignment often alters a patient’s constitutional alignment and joint line obliquity, resulting in soft-tissue imbalance. This annotation provides an overview of how the Coronal Plane Alignment of the Knee (CPAK) classification can be used to predict imbalance with mechanical alignment, and then offers practical guidance for bone balancing, minimizing the need for soft-tissue releases. Cite this article:
Background. Despite the success of total knee arthroplasty (TKA) restoration of normal function is often not achieved. Soft tissue balance is a major factor for poor outcomes including malalignment, instability, excessive wear, and subluxation. Computer navigation and robotic-assisted systems have increased the accuracy of prosthetic component placement. On the other hand, soft tissue balancing remains an art, relying on a qualitative feel for the balance of the knee, and is developed over years of practice. Several instruments are available to assist surgeons in estimating soft tissue balance. However, mechanical devices only measure the joint space in full extension and at 90° flexion. Further, because of lack of comprehensive characterization of the ligament balance of healthy knees, surgeons do not have quantitative guidelines relating the stability of an implanted to that of the normal knee. This study measures the ligament balance of normal knees and tests the accuracy of two mechanical distraction instruments and an electronic distraction instrument. Methods. Cadaver specimens were mounted on a custom knee rig and on the AMTI VIVO which replicated passive kinematics. A six-axis load cell and an infrared tracking system was used to document the kinematics and the forces acting on the knee. Dynamic knee laxity was measured under 10Nm of varus/valgus moment, 10Nm of axial rotational moment, and 200N of AP shear. Measurements were repeated after transecting the anterior cruciate ligament, after TKA, and after transecting the posterior cruciate ligament. The accuracy and reproducibility of two mechanical and one electronic distraction device was measured. Results. The maximum passive varus laxity measured over the range of flexion was 6.4°(±2.0) and maximum passive valgus laxity was 2.6°(±0.7), (p < 0.05). The maximum passive rotational laxity measured was 9.0°(±0.57) for internal and 14.1°(±1.6) for external rotation (p < 0.05). Average stiffness of the knee (Nm/deg) was 1.7 (varus), 2.4 (valgus), 0.8 (internal rotation), and 0.5 (external rotation). The difference in tibiofemoral gap between flexion and extension was 2.9mm (±1.6). The stiffness of the mechanical and electronic distractors was very linear over a distraction range of 0 to 6mm. At forces ranging from 40N to 120N, the accuracy and repeatability of the mechanical distractors was within 1mm, and that of the dynamic electronic distractor was 0.2mm. The electronic distractor measured the varus of the tibial cut and the distal femoral cut within 0.5°, and the rotation of the posterior femoral cut within 0.7° of surgical navigation measurements. Conclusions. The dynamic electronic distraction device was significantly more accurate than mechanical instruments and measured
Aims. It is unknown whether kinematic alignment (KA) objectively improves
Aims. A comprehensive classification for coronal lower limb alignment with predictive capabilities for
Aims. It is unknown whether gap laxities measured in robotic arm-assisted total knee arthroplasty (TKA) correlate to load sensor measurements. The aim of this study was to determine whether symmetry of the maximum medial and lateral gaps in extension and flexion was predictive of
Introduction. Studies have shown that dissatisfaction following TKA may stem from poor component placement and iatrogenic factors related to variability in surgical execution. A CT-based robotic assisted system (RA) allows surgeons to dynamically balance the joint prior to bone resection. This study aimed to determine if this system could improve TKA planning, reduce soft tissue releases, minimize bone resection, and accurately predict component size in varus knee. Method. Four hundred and seventy four cases with varus deformity undergoing primary RATKA were enrolled in this prospective, single center and surgeon study. Patient demographics and intraoperative surgical details were collected. Initial and final 3-dimensional alignment, component position, bone resection depths, use of soft tissue releases,
Introduction. A careful evaluation of new technologies such as robotic-arm assisted total knee arthroplasty (RATKA) is important to understand the reduction in variability among users. While there is data reviewing the use of RATKA, the data is typically presented for experienced TKA surgeons. Therefore, the purpose of this cadaveric study was to compare the variability for several surgical factors between RATKA and manual TKA (MTKA) for surgeons undergoing orthopaedic fellowship training. Methods. Two operating surgeons undergoing orthopaedic fellowship training, each prepared six cadaveric legs for cruciate retaining TKA, with MTKA on one side (3 knees) and RATKA on the other (3 knees). These surgeons were instructed to execute a full RATKA or MTKA procedure through trialing and achieve a balanced knee. The number of recuts and final poly thickness was intra-operatively recorded. After completion of bone cuts, the operating surgeons were asked if they would perform a cementless knee based on their perception of final bone cut quality as well as rank the amount of mental effort exerted for required surgical tasks. Two additional fellowship trained orthopaedic assessment surgeons, blinded to the method of preparation, each post-operatively graded the resultant bone cuts of the tibia and femur according to the perceived percentage of cut planarity (grade 1, <25%; grade 2, 25–50%; grade 3, 51–75%; and grade 4, >76%). The grade for medial and lateral tibial bone cuts was averaged and a Wilcoxon signed rank test was used for statistical comparisons. Assessment surgeons also determined whether the knee was balanced in flexion and extension. A balanced knee was defined as relatively equal medial and lateral gaps under relatively equal applied load. Results. Operating surgeons used 9mm polys in all 6 RATKA specimens, and 3/6 MTKA specimens. Operating surgeons said they would do cementless in 4/6 RATKA specimens, and 1/6 MTKA specimen. In MTKA specimens, 5/6 cases had a recut on the tibia or femur to obtain
First generation condylar knee replacements suffered from 2 prominent observations: Difficulty in stair climbing and Limited range of motion. Improved understanding of knee kinematics, the importance of femoral rollback, and enhanced stability in flexion led to 2 differing schools of thought: posterior cruciate ligament retention or posterior cruciate substitution. The advantages of posterior cruciate substitution include predictable CAM-post engagement leading to rollback, predictable ROM, stability during stair climbing, ease of
Introduction and Aims: Computer-assisted bone and soft tissue balancing in total knee arthroplasty (TKA) may aid in achieving perfect knee alignment leading to better function and prosthesis survival. The ‘Measured Resection’ technique was compared to a ‘Computer Assisted Gap Equalisation’ (CAGE) technique of
Introduction. Soft tissue releases are often required to correct deformity and achieve gap balance in total knee arthroplasty (TKA). However, the process of releasing soft tissues can be subjective and highly variable and is often perceived as an ‘art’ in TKA surgery. Releasing soft tissues also increases the risk of iatrogenic injury and may be detrimental to the mechanically sensitive afferent nerve fibers which participate in the regulation of knee joint stability. Measured resection TKA approaches typically rely on making bone cuts based off of generic alignment strategies and then releasing soft tissue afterwards to balance gaps. Conversely, gap-balancing techniques allow for pre-emptive adjustment of bone resections to achieve
Introduction. Valgus deformity in an end stage osteoarthritic knee can be difficult to correct with no clear consensus on case management. Dependent on if the joint can be reduced and the degree of medial laxity or distension, a surgeon must use their discretion on the correct method for adequate lateral releases. Robotic assisted (RA) technology has been shown to have three dimensional (3D) cut accuracy which could assist with addressing these complex cases. The purpose of this work was to determine the number of soft tissue releases and component orientation of valgus cases performed with RA total knee arthroplasty (TKA). Methods. This study was a retrospective chart review of 72 RATKA cases with valgus deformity pre-operatively performed by a single surgeon from July 2016 to December 2017. Initial and final 3D component alignment,
Backgrounds. It is well accepted that gap balancing is one of the important step for total knee arthroplasty (TKA). In order to evaluate gap balancing during operation, many tension devises have been used and developed. However, during operation, proper load to be applied, ideal gap amount, appropriate angle formed between femoral component and tibial cut surface are not clearly defined. Understanding the relationship between applied load and gap pattern will provide important information. The purpose of this study is to precisely analyze gap amount and inclination in extension and flexion using digital analyzer during TKA and characterize gap pattern. Methods. We analyzed 39 knees in 39 cases that underwent TKA with Scorpio NRG PS knee prosthesis operated by modified gap balancing technique. A customized digital
Computer navigated Total Knee Arthroplasty is routinely performed with gratifying results. New navigation software is now designed to help surgeons balance soft tissues in Total Knee Arthroplasty (TKA). The aim of our study was to compare functional scores at two years between two different techniques of
The February 2015 Knee Roundup. 360 . looks at: Intra-operative sensors for
First generation condylar knee replacements suffered from two prominent observations: 1) Difficulty in stair climbing, 2) Limited range of motion (ROM). Improved understanding of knee kinematics, the importance of femoral rollback, and enhanced stability in flexion led to 2 differing schools of thought: Posterior Cruciate ligament retention vs. Posterior Cruciate substitution. The advantages of posterior cruciate substitution include predictable cam-post engagement leading to rollback, predictable ROM, stability during stair climbing, ease of
Introduction. Close to 30% of the surgical causes of readmission within 90 days post-total knee arthroplasty (TKA) and nearly half of those occurring in the first 2 years are caused by instability, arthrofibrosis, and malalignment, all of which may be addressed by improving
Introduction. Partial knee arthroplasty (PKA) has demonstrated the potential to improve patient satisfaction over total knee arthroplasty. It is however perceived as a more challenging procedure that requires precise adaptation to the complex mechanics of the knee. A recently developed PKA system aims to address these challenges by anatomical, compartment specific shapes and fine-tuned mechanical instrumentation. We investigated how closely this PKA system replicates the balance and kinematics of the intact knee. Materials and Methods. Eight post-mortem human knee specimens (age: 55±11 years, BMI: 23±5, 4 male, 4 female) underwent full leg CT scanning and comprehensive robotic (KUKA KR140 comp) assessments of tibiofemoral and patellofemoral kinematics. Specimens were tested in the intact state and after fixed bearing medial PKA. Implantations were performed by two experienced surgeons. Assessments included laxity testing (anterior-posterior: ±100 N, medial-lateral: ±100 N, internal-external: ±3 Nm, varus- valgus: ±12 Nm) under 2 compressive loads (44 N, 500 N) at 7 flexion angles and simulations of level walking, lunge and stair descent based on in-vivo loading profiles. Kinematics were tracked robotically and optically (OptiTrack) and represented by the femoral flexion facet center (FFC) motions. Similarity between intact and operated curves was expressed by the root mean square of deviations (RMSD) along the curves. Group data were summarized by average and standard deviation and compared using the paired Student's T-test (α = 0.05). Results. During the varus-valgus balancing assessment the medial and lateral opening of the PKAs closely resembled the intact openings across the full arch of flexion, with RMSD values of 1.0±0.5 mm and 0.4±0.2 mm respectively. The medial opening was nearly constant across flexion, its average was not statistically different between intact (3.8±1.0 mm) and PKA (4.0±1.1 mm) (p=0.49). Antero-posterior envelope of motion assessments revealed a close match between the intact and PKA group for both compression levels. Net rollback was not statistically different, either under low compression (intact: 10.9±1.5 mm, PKA: 10.7±1.2, p=0.64) or under high compression (intact: 13.2±2.3 mm, PKA: 13.0±1.6 mm, p=0.77). Similarly, average laxity was not statistically different, either under low (intact: 7.7±3.2 mm, PKA: 8.6±2.5 mm, p=0.09) or under high (intact: 7.2±2.6 mm, PKA: 7.8±2.2 mm, p=0.08) compression. Activities of daily living exhibited a close match in the anterior-posterior motion profile of the medial condyle (RMSD: lunge: 2.2±1.0 mm, level walking: 2.4±0.9 mm, stair descent: 2.2±0.6 mm) and lateral condyle (RMSD: lunge: 2.4±1.4 mm, level walking: 2.2±1.4 mm, stair descent: 2.7±2.0 mm). Patellar medial-lateral tilt (RMSD: 3.4±3.8°) and medial-lateral shift (RMDS: 1.5±0.6 mm) during knee flexion matched closely between groups. Conclusion. Throughout the comprehensive functional assessments the investigated PKA system behaved nearly identical to the intact knee. The small residuals are unlikely to have a clinical effect; further studies are necessary as cadaveric studies are not necessarily indicative of clinical results. We conclude that PKA with anatomical, compartment specific shapes and fine-tuned mechanical instrumentation can be adapted precisely to the complex mechanics of the knee and replicates intact
Background. Despite the success of total knee arthroplasty (TKA) restoration of normal function is often not achieved. Soft-tissue balance is a major factor leading to poor outcomes including malalignment, instability, excessive wear, and subluxation. Mechanical ligament balancers only measure the joint space in full extension and at 90° flexion. This study uses a novel electronic ligament balancer to measure the ligament balance in normal knees and in knees after TKA to determine the impact on passive and active kinematics. Methods. Fresh-frozen cadaver legs (N = 6) were obtained. A standard cruciate-retaining TKA was performed using measured resection approach and computer navigation (Stryker Navigation, Kalamazoo, MI). Ligament balance was measured using a novel electronic balancer (Fig 1, XO1, XpandOrtho, Inc, La Jolla, CA, USA). The XO1 balancer generates controlled femorotibial distraction of up to 120N. The balancer only requires a tibial cut and can be used before or after femoral cuts, or after trial implants have been mounted. The balancer monitors the distraction gap and the medial and lateral gaps in real time, and graphically displays gap measurements over the entire range of knee flexion. Gap measurements can be monitored during soft-tissue releases without removing the
Background. Flexion-extension gap balancing is recognized as an essential part of total knee arthroplasty (TKA). The gap is often evaluated using spacer blocks, laminar spreader, or tensor device. The evaluation of gap balancing with the patella in the reduced position is more physiological and reproducible than with patellofemoral (PF) joint everted. However, in the knee with a reduced PF joint, it is difficult to comprehend the anteroposterior position of the tibia to the femur. So, we developed a new tensor to lift up the tibia ahead and fix the anteroposterior position of the tibia to the femur with the PF joint reduced [Fig.1]. Purpose. To investigate how accurate the extension and flexion gaps would be measured by comparing our new tensor with the conventional tensor which could not fix the position of the tibia to the femur. Methods. This study includes 60 knees in 48 patients underwent TKA using the Posterior Stabilized (PS) Prosthesis (Striker), for varus osteoarthritis. The mean age of patients was 78.2 (62 to 88) at the time of surgery. All knees were exposed using a standard medial parapatellar approach. The posterior cruciate ligament was sacrificed at the beginning of the procedure. A balanced gap technique was used for the femoral and tibial bone cuts. After the completion of bony resection, osteophyte removal, and soft-tissue balancing by the release of the medial collateral ligament (MCL), the offset
Adequate soft tissue balance at the time of total knee arthroplasty (TKA) prevents early failure. In cases of varus deformity, once the medial osteophytes have been resected, a progressive release of the medial soft tissue sleeve (MSS) from the proximal medial tibia is needed to achieve balance. The “classic” medial soft tissue release technique, popularised by John Insall et al., consists of a sharp subperiosteal dissection from the proximal medial tibia that includes superficial and deep medial collateral ligament (MCL), semimembranosus tendon, posteromedial capsule, along with the pes anserinus tendons, if needed. However, this technique allows for little control over releases that selectively affect the flexion and extension gaps. When severe deformity is present, an extensive MSS release can cause iatrogenic medial instability and the need to use a constrained implant. It has been suggested that the MSS can be elongated by performing selective releases. This algorithmic approach includes the resection of the posterior osteophytes as the initial balancing gesture. If additional MSS release is necessary in extension, a subperiosteal release of the posterior aspect of the MSS is performed with electrocautery, detaching the posterior aspect of the deep MCL, posteromedial capsule and semimembranosus tendon for the proximal and medial tibia. Dissection is rarely extended more than 1.5 cm distal to the joint line. If additional release is necessary in extension, the medial compartment is tensioned with a laminar spreader and multiple needle punctures (generally less than 8) are performed in the taut portion of the MSS using an 18G or 16G needle. If additional release is necessary to balance the flexion gap, multiple needle punctures in the anterior aspect of the MSS are performed. This stepwise approach to releasing the MSS in a patient with a varus deformity allows the surgeon to target areas that selectively affect the flexion and extension gaps. Its use has resulted in diminished use of constrained TKA constructs and subsequent cost savings. We have not seen an increase in post-operative instability developing within the first post-operative year. We recommend caution when implementing this technique. Unlike the traditional release method, pie-crusting is likely technique-dependent and failure can occur within the MCL itself. Due to the critical importance of the MCL in knee stability, further research and continuous follow up of patients undergoing TKA with this technique are warranted. Intra-operative sensing technology may be useful to quantitate the effect of pie-crusting on the compartmental loads and overall
The June 2023 Knee Roundup360 looks at: Cementless total knee arthroplasty is associated with early aseptic loosening in a large national database; Is cementless total knee arthroplasty safe in females aged over 75 years?; Could novel radiological findings help identify aseptic tibial loosening?; The Attune cementless versus LCS arthroplasty at introduction; Return to work following total knee arthroplasty and unicompartmental knee arthroplasty; Complications and downsides of the robotic total knee arthroplasty; Mid-flexion instability in kinematic alignment better with posterior-stabilized and medial-stabilized implants?; Patellar resurfacing does not improve outcomes in modern knees.
The aim of this study was to investigate the distribution of phenotypes in Asian patients with end-stage osteoarthritis (OA) and assess whether the phenotype affected the clinical outcome and survival of mechanically aligned total knee arthroplasty (TKA). We also compared the survival of the group in which the phenotype unintentionally remained unchanged with those in which it was corrected to neutral. The study involved 945 TKAs, which were performed in 641 patients with primary OA, between January 2000 and January 2009. These were classified into 12 phenotypes based on the combined assessment of four categories of the arithmetic hip-knee-ankle angle and three categories of actual joint line obliquity. The rates of survival were analyzed using Kaplan-Meier methods and the log-rank test. The Hospital for Special Surgery score and survival of each phenotype were compared with those of the reference phenotype with neutral alignment and a parallel joint line. We also compared long-term survival between the unchanged phenotype group and the corrected to neutral alignment-parallel joint line group in patients with Type IV-b (mild to moderate varus alignment-parallel joint line) phenotype.Aims
Methods
Orthopaedic surgeons are currently faced with an overwhelming number of choices surrounding total knee arthroplasty (TKA), not only with the latest technologies and prostheses, but also fundamental decisions on alignment philosophies. From ‘mechanical’ to ‘adjusted mechanical’ to ‘restricted kinematic’ to ‘unrestricted kinematic’ — and how constitutional alignment relates to these — there is potential for ambiguity when thinking about and discussing such concepts. This annotation summarizes the various alignment strategies currently employed in TKA. It provides a clear framework and consistent language that will assist surgeons to compare confidently and contrast the concepts, while also discussing the latest opinions about alignment in TKA. Finally, it provides suggestions for applying consistent nomenclature to future research, especially as we explore the implications of 3D alignment patterns on patient outcomes. Cite this article:
The anatomic resection approach is based on the patient's unique anatomy adjusting for worn cartilage or bone loss. The femoral component is aligned around the primary transverse distal femoral axis around which the tibia follows a multi-radius of curvature. The tibia cut is made according to the patient's native anatomy adjusting for worn cartilage and bone loss, and applying an anatomic amount of tibial slope. This technique minimises the need for ligamentous releases to a large degree preserving the competence of the patient's soft tissue. Ligament and capsular releases can be used in difficult cases. Adjustments for the natural varus up to 3 degrees and slope of the tibial bone cut (3 – 10 degrees) further aids in
Background. Mechanical alignment (MA) techniques for total knee arthroplasty (TKA) introduce significant anatomic modifications and secondary ligament imbalances. A restricted kinematic alignment (rKA) protocol was proposed to minimize these issues and improve TKA clinical results. Method. rKA tibial and femoral bone resections were simulated on 1000 knee CT-Scans from a database of patients undergoing TKA. rKA is defined by the following criteria: Independent tibial and femoral cuts within ± 5° of the bone neutral mechanical axis and; a resulting HKA within ±3° of neutral. Medial-lateral (ΔML) and flexion-extension (ΔFE) gap differences were calculated and compared with measured resection MA results. Results. Extension space ML imbalances ≥3mm occurred in 33% of TKA with MA technique versus 8% with rKA, and ≥5mm were present in up to 11% of MA knees versus 1% rKA (p<0.001). Using the MA technique, for the flexion space, higher ML imbalance rates were created by both MA techniques (using TEA or 3°PC) versus rKA (p<0.001). When all the differences between ΔML and ΔFE are considered together: using MA with TEA there were 41% of the knees with <3mm imbalances throughout; using PC this was 55% and using rKA it was 92% (p<0.001). Conclusion. Significantly less ML or FE gap imbalances are created using rKA versus MA for TKA. Using rKA may help the surgeon to preserve native
This study compared patient-reported outcomes of three total knee arthroplasty (TKA) designs from one manufacturer: one cruciate-retaining (CR) design, and two cruciate-sacrificing designs, anterior-stabilized (AS) and posterior-stabilized (PS). Patients scheduled for primary TKA were included in a single-centre, prospective, three-armed, blinded randomized trial (n = 216; 72 per group). After intraoperative confirmation of posterior cruciate ligament (PCL) integrity, patients were randomly allocated to receive a CR, AS, or PS design from the same TKA system. Insertion of an AS or PS design required PCL resection. The primary outcome was the mean score of all five subscales of the Knee injury and Osteoarthritis Outcome Score (KOOS) at two-year follow-up. Secondary outcomes included all KOOS subscales, Oxford Knee Score, EuroQol five-dimension health questionnaire, EuroQol visual analogue scale, range of motion (ROM), and willingness to undergo the operation again. Patient satisfaction was also assessed.Aims
Methods
Measured resection approach (anatomic) is based on the patients' unique anatomy adjusting for worn cartilage or bone loss. The femoral component is aligned around the primary transverse distal femoral axis around which the tibia follows a multi-radius of curvature. The tibia cut is made according to the patient's native anatomy adjusting for worn cartilage and bone loss, and applying an anatomic amount of tibial slope. This technique minimises the need for partial ligamentous releases to a large degree preserving the competence of the patient's soft tissue, though ligament and capsular releases can be used in difficult cases. Adjustments for the varus/valgus (up to 3 degrees) or slope of the tibial bone cut (3–10 degrees) further aids in
This systematic review aims to compare the precision of component positioning, patient-reported outcome measures (PROMs), complications, survivorship, cost-effectiveness, and learning curves of MAKO robotic arm-assisted unicompartmental knee arthroplasty (RAUKA) with manual medial unicompartmental knee arthroplasty (mUKA). Searches of PubMed, MEDLINE, and Google Scholar were performed in November 2021 according to the Preferred Reporting Items for Systematic Review and Meta-Analysis statement. Search terms included “robotic”, “unicompartmental”, “knee”, and “arthroplasty”. Published clinical research articles reporting the learning curves and cost-effectiveness of MAKO RAUKA, and those comparing the component precision, functional outcomes, survivorship, or complications with mUKA, were included for analysis.Aims
Methods
Introduction. A femoral rotational alignment is one of the essential factors, affecting the postoperative
Background. Total knee arthroplasty (TKA) surgical techniques attempt to achieve equal flexion and extension gaps to produce a well-balanced knee, but unexplainable unhappy patients persist. Mid-flexion instability is one proposed cause of unhappy patients. There are multiple techniques to achieve equal flexion and extension gaps, but their effects in mid-flexion are largely unknown. Purpose of study. The purpose of the study is to determine the effects that changing femur implant size and/or adjusting the femur and tibia proximal -distal and femur anterior-posterior implant positions have on cruciate retaining (CR) TKA mid-flexion ligament balance when equal flexion and extension gaps are maintained. Methods. A computational analysis was performed simulating knee flexion of two CR TKA designs (JOURNEY II CR and LEGION HFCR; Smith & Nephew) using previously validated software (LifeMOD/KneeSim; LifeModeler). Deviations from the ideal implant position were simulated by adjusting tibiofemoral proximal-distal position and femur anterior-posterior position and size (Table 1). Positioning the femur more proximal was accompanied by equal anterior femur and proximal tibia shifts to maintain equal flexion and extension gaps. The forces in ligaments connecting the femur and tibia, which included superficial and posterior MCL, LCL, popliteal-fibular ligament complex, iliotibial band, and anterior-lateral and posterior-medial PCL, were collected. Total tibiofemoral ligament load and PCL load for 15–75° knee flexion were analyzed versus proximal-distal implant position, implant size, implant design, and knee flexion using a MANOVA in Minitab 16 (Minitab). Results. Total tibiofemoral ligament load was significantly reduced by a more proximal implant position (p<.001) (Figure 1) but was not affected by implant size (p>0.6). PCL load was not affected by implant proximal-distal position or size (p>0.9) (Figure 2). Therefore, the PCL did not contribute to changes in mid-flexion balance caused by proximal-distal implant position. Implant design and knee flexion significantly influenced total tibiofemoral ligament and PCL loads (p<.05), but the interactions with implant proximal-distal position and size were not significant (p>0.7) indicating that the effects of implant proximal-distal position applies across the studied implant designs and 15°–75° knee flexion range. Conclusions. Our results suggest that a CR TKA can be well balanced at 0° and 90° knee flexion and be too tight or loose in mid-flexion. Since placement of implant was the variable studied, when the knee is too tight in mid-flexion, our recommendation to loosen the knee is to resect more distal and posterior femur, downsizing if necessary, and increase the tibial insert thickness. The opposite could be done to guard against the knee being too loose in mid-flexion. Finally, it is recommended to gauge balance in more than simply 0° and 90° to determine overall
INTRODUCTION. The extension and flexion gaps are affected by different factors in total knee arthroplasty (TKA). Flexion but not extension gap measurements are influenced by posterior cruciate ligament (PCL) preservation or resection and patella reduction or eversion and thigh weight. If the flexion gap is measured with the thigh placed on the tibia, the measurement results must include the thigh weight; nevertheless, there is no detailed report regarding the thigh weight influence on the flexion gap. In this study, we investigated how thigh weight affected flexion gap measurement. METHODS. Four knees of whole-body fresh-frozen cadavers (Mongolian race) were investigated. The femur and tibia were dissected with a standard measured resection technique. After the femoral component was set, the flexion gap was measured with a
Introduction. 11%–19% of patients are unsatisfied with outcomes from Total Knee Arthroplasty (TKA). This may be due to problems of alignment or soft-tissue balancing. In TKA, often a neutral mechanical axis is established followed by soft tissue releases to balance and match the flexion/extension gaps with the distal femoral and proximal tibial resections at right angles to the mechanical axis. Potential issues with establishment of soft tissue balance are due to associated structures such as bone tissue of the knee, the static (or passive) stabilizers of the joint (medial and lateral collateral ligaments, capsule, and anterior and posterior cruciate ligaments), and the dynamic (or active) stabilizers around the knee. An optimized balance among these systems is crucial to the successful outcome of a TKA. Additionally, the importance of correct femoral rotation has been well documented due to its effect on patella alignment and flexion instability, range of motion, and polyethylene wear. There are several methods used in TKA procedures to establish femoral component rotation. The more prominent ones are a conventional method of referencing to the posterior condylar axis with a standard external rotation of 3° (PCR), anterior-posterior line or “Whiteside's line” (AP axis), transepicondylar axis (TEA) (Figure 1), and the gap balancing technique, however, it is not yet clear, which method is superior for femoral rotational component alignment. In the current study, we sought to investigate an alternative method based on soft-tissue, dynamic
Introduction. Evaluation of post-operative soft tissue balancing outcomes after Total Knee Arthroplasty (TKA) and other procedures can be measured by stability tests, with Anterior-Posterior (AP) drawer tests and Varus-Valgus (VV) ligamentous laxity tests being particularly important. AP stability can be quantified using a KT1000 device; however there is no standard way of measuring VV stability. The VV test relies on subjective force application and perception of laxity. Therefore we sought to develop and validate a device and method for quantifying
Introduction. Patient specific surgical guide (PSSG) is a relatively new technique for accurate total knee arthroplasty (TKA), and there are many reports supporting PSSG can reduce the rate of outlier in the coronal plane. We began to use PSSG provided by Biomet (Signature®) and have reported the same results. Before using Signature, we performed TKA by modified gap technique (parallel cut technique) to get the well balanced flexion gap. Signature is the one of the measured resection technique using the anatomical landmarks as reference points on the images of CT or MR taken before surgery. We usually measure the center gap width and gap balance during operation with the special device “knee balancer”(Fig. 1) that can be used on patella reposition. After cutting all of the bone with Signature, gap balance in the extension position was very good but the gap balance was shown slight lateral opening in the 90 degrees flexion position. So we have changed the surgical procedure. We use Signature for cutting only distal femur and proximal tibia to get extension gap and apply the modified gap technique to decide the rotation of the femoral component (Signature with modified gap technique). The purpose of this study is to compare the gap balance between the two techniques. Materials & Methods. From November, 2012 through March, 2014, 50 CR type TKA (Vanguard Knee®, Biomet) in osteoarthritis patients were performed using Signature. 25 TKA were performed using only Signature (group S) and other 25 TKA were done using Signature with modified gap technique (group SG). After all osteotomies of femur and tibia were completed, applying femoral trial, center gap width and gap balance (plus means lateral opening angle) were measured using
Surgeons commonly resect additional distal femur during primary total knee arthroplasty (TKA) to correct a flexion contracture, which leads to femoral joint line elevation. There is a paucity of data describing the effect of joint line elevation on mid-flexion stability and knee kinematics. Thus, the goal of this study was to quantify the effect of joint line elevation on mid-flexion laxity. Six computational knee models with cadaver-specific capsular and collateral ligament properties were implanted with a posterior-stabilized (PS) TKA. A 10° flexion contracture was created in each model to simulate a capsular contracture. Distal femoral resections of + 2 mm and + 4 mm were then simulated for each knee. The knee models were then extended under a standard moment. Subsequently, varus and valgus moments of 10 Nm were applied as the knee was flexed from 0° to 90° at baseline and repeated after each of the two distal resections. Coronal laxity (the sum of varus and valgus angulation with respective maximum moments) was measured throughout flexion.Aims
Methods
Total knee arthroplasty (TKA) using functional alignment aims to implant the components with minimal compromise of the soft-tissue envelope by restoring the plane and obliquity of the non-arthritic joint. The objective of this study was to determine the effect of TKA with functional alignment on mediolateral soft-tissue balance as assessed using intraoperative sensor-guided technology. This prospective study included 30 consecutive patients undergoing robotic-assisted TKA using the Stryker PS Triathlon implant with functional alignment. Intraoperative soft-tissue balance was assessed using sensor-guided technology after definitive component implantation; soft-tissue balance was defined as intercompartmental pressure difference (ICPD) of < 15 psi. Medial and lateral compartment pressures were recorded at 10°, 45°, and 90° of knee flexion. This study included 18 females (60%) and 12 males (40%) with a mean age of 65.2 years (SD 9.3). Mean preoperative hip-knee-ankle deformity was 6.3° varus (SD 2.7°).Aims
Methods
Introduction. Accurate soft tissue balancing in knee arthroplasty is essential in order to attain good postoperative clinical results. In mobile-bearing UKA (Oxford Partial Knee unicompartmental knee arthroplasty, Biomet), since determination of the thickness of the spacer block depends on the individual surgeon, it will vary and it will be difficult to attain appropriate
Deformity correction is a fundamental goal in total knee arthroplasty. Severe valgus deformities often present the surgeon with a complex challenge. These deformities are associated with abnormal bone anatomy, ligament laxity and soft tissue contractures. Distorted bone anatomy is due to bone loss on the lateral femoral condyle, especially posteriorly. To a lesser extent bone loss occurs from the lateral tibia plateau. The AP axis (Whiteside's Line) or epicondylar axis must be used as a rotational landmark in the severely valgus
Deformity correction is a fundamental goal in total knee arthroplasty. Severe valgus deformities often present the surgeon with a complex challenge. These deformities are associated with abnormal bone anatomy, ligament laxity and soft tissue contractures. Distorted bone anatomy is due to bone loss on the lateral femoral condyle, especially posteriorly. To a lesser extent bone loss occurs from the lateral tibia plateau. The AP Axis (Whiteside's Line) or Epicondylar axis must be used as a rotational landmark in the severely valgus
This study was conducted to investigate the correlation between intra-operative Flexion Balance (IFB) and post-operative Flexion instability in Posterior-Stabilized Total Knee Arthroplasty (TKA). Eighty-three knees (4 males and 79 females, average 74 y/o) with primary TKA (Zimmer NexGen LPS flex fixed-bearing) for varus osteoarthritis in our hospital between January 2006 and December 2007, were included in this study. After bone-cutting independently and balancing manually, Extension Balance (EB) and IFB were measured with seesaw type tensor. Post-operative Flexion Balance (PFB) was evaluated as post-operative instability with Kanekasu’s Epicondylar view at the least more than 6 months postoperatively. Varus inclination (lateral joint opening) was indicated as plus. In addition, pre-operative standing FTA (femorotibial angle), the change of FB (CFB=PFB-IFB) and True Correction Angle (TCA=FTA-174-EB), we had defined, were calculated. The TCA was hypothesized to mean the extent of medial soft tissue release. With these data, the correlation between IFB and PFB, CFB and TCA were analyzed. Of these, furthermore, in the well-balanced knees (IFB ≥ ±2°), same analyses were done. Statistical analysis was performed with StatView software. Each data (n=83) in all subjects was as follows (Mean ± SD, degrees.); EB: 2.74 ±2.74, IFB: 1.61 ±3.67, PFB: 1.73 ±2.66, CFB: 0.01 ±4.25, FTA: 185.3 ±6.7, TCA: 8.65 ±6.52, respectively. Though there was no correlation between IFB and PFB (r=−0.09, p=0.57), CFB was correlated with TCA (r=0.40, p<
0.01). Each data in the well-balanced knees (n=43) was as follows, EB: 3.09 ±2.71, IFB: 0.70 ±1.30, PFB: 1.22 ±2.52, CFB: 0.57 ±2.3, FTA: 185.5 ±6.5, TCA: 8.42 ±6.09, respectively. There was a correlation between IFB and PFB (r=0.41, p<
0.01), however, FBC was not correlated with TCA (r=−0.26, p=0.10). Same rectangular balance has been thought to be one the most important factors to obtain the good postoperative stability in TKA. For correcting alignment of lower extremity, medial or posteromedial release are generally needed to perform mainly in extended knee. Even if well-balanced EB was achieved, IFB does not necessarily prove to be well, rather than sparse. This might be because intra-operative balance was not measured under physiological condition, especially after wide posteromedial release. Soft tissues released for balancing would be repaired and shortened over time, so it seems to be natural that intra-operative balance would change. We have reported that EB was correlated with post-operative instability in the previous congress (ISTA 2006). However, it remains unknown as for FB. Our study demonstrated that CFB increased in accordance with the extent of soft tissue release (TCA), and that IFB was correlated with PFB only in the well balanced knees. This means that the measurement of IFB was not useful for predicting PFB in the imbalanced knees. That’s why we should achieve adequate balance &
gap during operation and should recognize that FB was influenced by various factors, not only soft tissues but also rotation and inclination of components. In the future, how to measure IFB, including tensor and measurement condition, should be considered and established to predict
Aims. There is little literature about total knee arthroplasty (TKA) after distal femoral osteotomy (DFO). Consequently, the purpose of this study was to analyze the outcomes of TKA after DFO, with particular emphasis on: survivorship free from aseptic loosening, revision, or any re-operation; complications; radiological results; and clinical outcome. Patients and Methods. We retrospectively reviewed 29 patients (17 women, 12 men) from our total joint registry who had undergone 31 cemented TKAs after a DFO between 2000 and 2012. Their mean age at TKA was 51 years (22 to 76) and their mean body mass index 32 kg/m. 2. (20 to 45). The mean time between DFO and TKA was ten years (2 to 20). The mean follow-up from TKA was ten years (2 to 16). The prostheses were posterior-stabilized in 77%, varus-valgus constraint (VVC) in 13%, and cruciate-retaining in 10%. While no patient had metaphyseal fixation (e.g. cones or sleeves), 16% needed a femoral stem. Results. The ten-year survivorship was 95% with aseptic loosening as the endpoint, 88% with revision for any reason as the endpoint, and 81% with re-operation for any reason as the endpoint. Three TKAs were revised for instability (n = 2) and aseptic tibial loosening (n = 1). No femoral component was revised for aseptic loosening. Patients under the age of 50 years were at greater risk of revision for any reason (hazard ratio 7; p = 0.03). There were two additional re-operations (6%) and four complications (13%), including three manipulations under anaesthetic (MUA; 10%). The Knee Society scores improved from a mean of 50 preoperatively (32 to 68) to a mean of 93 postoperatively (76 to 100; p < 0.001). Conclusion. A cemented posterior-stabilized TKA has an 88% ten-year survivorship with revision for any reason as the endpoint. No femoral component was revised for aseptic loosening. Patients under the age of 50 years have a greater risk of revision. The clinical outcome was significantly improved but
Deformity correction is a fundamental goal in Total Knee Arthroplasty. Severe valgus deformities often present the surgeon with a complex challenge. These deformities are associated with abnormal bone anatomy, ligament laxity and soft tissue contractures. Distorted bone anatomy is due to bone loss on the lateral femoral condyle, especially posteriorly. To a lesser extent bone loss occurs from the lateral tibia plateau. The AP Axis (Whiteside's Line) or Epicondylar axis must be used as a rotational landmark in the severely valgus
Introduction. In valgus
Introduction. The success of total knee arthroplasty depends on many factors, including the preoperative condition of the patient, the design and materials of the components and surgical techniques. It is important to position the femoral and tibial components accurately and to balance the soft tissues. Malpositioning of the component can lead to failures due to aseptic loosening, instability, polyethylene wear and dislocation of the patella. In order to improve post-operative alignment, computer-aid systems have been developed for total knee arthroplasty. Many clinical and experimental studies of these systems have shown that the accuracy of implanted components can be improved in spite of the increase in costs and operating time. This may not, however, improve the outcome in the short-term. Restoration of the normal mechanical axis of the
The objective of this study was to compare early postoperative
functional outcomes and time to hospital discharge between conventional
jig-based total knee arthroplasty (TKA) and robotic-arm assisted
TKA. This prospective cohort study included 40 consecutive patients
undergoing conventional jig-based TKA followed by 40 consecutive
patients receiving robotic-arm assisted TKA. All surgical procedures
were performed by a single surgeon using the medial parapatellar
approach with identical implant designs and standardized postoperative inpatient
rehabilitation. Inpatient functional outcomes and time to hospital
discharge were collected in all study patients.Aims
Patients and Methods
The role of high tibial osteotomy (HTO) is being questioned by
the use of unicompartmental knee arthroplasty (UKA) in the treatment
of medial compartment femorotibial osteoarthritis. Our aim was to
compare the outcomes of revision HTO or UKA to a total knee arthroplasty
(TKA) using computer-assisted surgery in matched groups of patients. We conducted a retrospective study to compare the clinical and
radiological outcome of patients who underwent revision of a HTO
to a TKA (group 1) with those who underwent revision of a medial
UKA to a TKA (group 2). All revision procedures were performed using
computer-assisted surgery. We extracted these groups of patients
from our database. They were matched by age, gender, body mass index,
follow-up and pre-operative functional score. The outcomes included
the Knee Society Scores (KSS), radiological outcomes and the rate
of further revision.Aims
Patients and Methods
Total knee replacement (TKR) smart tibial trials
have load-bearing sensors which will show quantitative compartment
pressure values and femoral-tibial tracking patterns. Without smart
trials, surgeons rely on feel and visual estimation of imbalance
to determine if the knee is optimally balanced. Corrective soft-tissue
releases are performed with minimal feedback as to what and how
much should be released. The smart tibial trials demonstrate graphically
where and how much imbalance is present, so that incremental releases
can be performed. The smart tibial trials now also incorporate accelerometers
which demonstrate the axial alignment. This now allows the surgeon
the option to perform a slight recut of the tibia or femur to provide
soft-tissue balance without performing soft-tissue releases. Using
a smart tibial trial to assist with soft-tissue releases or bone
re-cuts, improved patient outcomes have been demonstrated at one
year in a multicentre study of 135 patients (135 knees). Cite this article:
Because posterior cruciate ligament (PCL) resection makes flexion
gaps wider in total knee replacement (TKR), preserving or sacrificing
a PCL affects the gap equivalence; however, there are no criteria
for the PCL resection that consider gap situations of each knee.
This study aims to investigate gap characteristics of knees and
to consider the criteria for PCL resection. The extension and flexion gaps were measured, first with the
PCL preserved and subsequently with the PCL removed (in cases in
which posterior substitute components were selected). The PCL preservation
or sacrifice was solely determined by the gap measurement results,
without considering other functions of the PCL such as ‘roll back.’Objectives
Methods
At least four ways have been described to determine
femoral component rotation, and three ways to determine tibial component
rotation in total knee replacement (TKR). Each method has its advocates
and each has an influence on knee kinematics and the ultimate short
and long term success of TKR. Of the four femoral component methods,
the author prefers rotating the femoral component in flexion to
that amount that establishes a stable symmetrical flexion gap. This
judgement is made after the soft tissues of the knee have been balanced
in extension. Of the three tibial component methods, the author prefers rotating
the tibial component into congruency with the established femoral
component rotation with the knee is in extension. This yields a
rotationally congruent articulation during weight-bearing and should
minimise the torsional forces being transferred through a conforming tibial
insert, which could lead to wear to the underside of the tibial
polyethylene. Rotating platform components will compensate for any
mal-rotation, but can still lead to pain if excessive tibial insert
rotation causes soft-tissue impingement. Cite this article:
Patients with skeletal dysplasia are prone to
developing advanced osteoarthritis of the knee requiring total knee replacement
(TKR) at a younger age than the general population. TKR in this
unique group of patients is a technically demanding procedure owing
to the deformity, flexion contracture, generalised hypotonia and ligamentous
laxity. We retrospectively reviewed the outcome of 11 TKRs performed
in eight patients with skeletal dysplasia at our institution using
the Stanmore Modular Individualised Lower Extremity System (SMILES)
custom-made rotating-hinge TKR. There were three men and five women
with mean age of 57 years (41 to 79). Patients were followed clinically
and radiologically for a mean of seven years (3 to 11.5). The mean
Knee Society clinical and function scores improved from 24 (14 to
36) and 20 (5 to 40) pre-operatively, respectively, to 68 (28 to
80) and 50 (22 to 74), respectively, at final follow-up. Four complications
were recorded, including a patellar fracture following a fall, a
tibial peri-prosthetic fracture, persistent anterior knee pain,
and aseptic loosening of a femoral component requiring revision.
Our results demonstrate that custom primary rotating-hinge TKR in
patients with skeletal dysplasia is effective at relieving pain,
with a satisfactory range of movement and improved function. It compensates
for bony deformity and ligament deficiency and reduces the likelihood
of corrective osteotomy. Patellofemoral joint complications are
frequent and functional outcome is worse than with primary TKR in
the general population.
We studied the influence of soft-tissue releases and soft-tissue balance on the outcome of 526 total knee replacements one year after operation. The surgery had been performed by seven surgeons in five centres in the United Kingdom between October 1999 and December 2002. Balancing was carried out by five surgeons using spacers and trials and by two surgeons using a ‘balancer’ instrument. All the surgeons assessed the adequacy of their releases by taking measurements with the balancer after soft-tissue release before implanting the components. Independent observers collected the Oxford knee scores and applied the American Knee Society functional and knee scores as well as recording the range of movement of the replaced knee. These were compared with the pre-operative scores and the extent of the releases. We found differences in outcomes between minimal and extensive releases and between balanced and imbalanced knees. Knees requiring extensive soft-tissue releases showed greater change in the short-term clinical outcome without increased complications and achieved similar results at one year compared with those with less deformity pre-operatively which had required less soft-tissue release. Balancing an imbalanced knee improved the short-term knee outcome.
We compared the results of 146 patients who received an anatomic modular knee fixed-bearing total knee replacement (TKR) in one knee and a low contact stress rotating platform mobile-bearing TKR in the other. There were 138 women and eight men with a mean age of 69.8 years (42 to 80). The mean follow-up was 13.2 years (11.0 to 14.5). The patients were assessed clinically and radiologically using the rating systems of the Hospital for Special Surgery and the Knee Society at three months, six months, one year, and annually thereafter. The assessment scores of both rating systems pre-operatively and at the final review did not show any statistically significant differences between the two designs of implant. In the anatomic modular knee group, one knee was revised because of aseptic loosening of the tibial component and one because of infection. In addition, three knees were revised because of wear of the polyethylene tibial bearing. In the low contact stress group, two knees were revised because of instability requiring exchange of the polyethylene insert and one because of infection. The radiological analysis found no statistical difference in the incidence of radiolucent lines at the final review (Student’s We found no evidence of the superiority of one design over the other at long-term follow-up.