The traditional method of soft-tissue balancing during TKA is subjective in nature, and stiffness and instability are common indications for revision, suggesting that TKA balancing by subjective assessment is suboptimal. This study examines the intraoperative mediolateral loads measured with a nanosensor-enabled tibial insert trial and the sequential balancing steps used to achieve quantitative balance. Data obtained from a prospective multicenter study was assessed to determine the effect of targeted ligament release on intra-articular loading, and to understand which types of releases are necessary to achieve quantified ligament balance. A group of 129 patients received sensor-assisted TKA, as part of a prospective multicenter study. Medial and lateral loading data were collected pre-release, during any sequential releases, and post-release. All data were collected at 10, 45, and 90 degrees during range of motion testing. Ligament release type, release technique type, and resultant loading were collected.Introduction & Aims
Methods
Total knee arthroplasty (TKA) is currently one of the most common elective surgical procedures in the United States. The increase in the proportion of younger patients in receipt of surgery, in concert with a dramatic rise in the incidence of obesity, has contributed to the on-going, exponential increase in the number of arthroplasties performed annually. Despite materials advances for implants, the U.S. revision burden has remained static for the last decade. According to the 2013 CMS MEDPAR file the typical CMS reimbursement falls far short of costs incurred by the hospital, resulting in an average net loss of revenue of $9,539; and over 90% of hospitals lose money for every revision case performed. Today, approximately 5% of all primaries performed will result in an early revision (< 3 years). In order to understand ways with which to mitigate the incidence of early revision due to mechanical complications, a multicentric group of sensor-assisted patients was follow-up out to 3 years. In this study, 278 sensor-assisted patients were followed out to 3 years. The intraoperative devices used in this study contain microsensors and a processing unit. Kinetic and center of load location data are projected, in real-time, to a screen. Because of the wireless nature of the intraoperative sensors, the patella can be reduced, and kinematic data can be evaluated through the range of motion. For each patient, the soft-tissue envelope was balanced to within a mediolateral differential of 15 lbf., through the ROM, as per the suggestion of previously reported literature. The average patient profile indicates: age = 69.7 years, BMI = 30.4, gender distribution = 36% male/64% female. Any adverse event within the 3-year follow-up interval was captured. By 3 years, 1 patient in this population has required revision surgeon due to mechanical complicatons. Overall adverse events included: pain in hip (3), pain in contralateral knee (2), wound drainage (3), DVT (1), death (1), stiffness in operative knee (2), infection (3), global pain (2), back pain (2). Based on the average reported number of early revisions that occur in the U.S. (5% of primaries), it was anticipated for this patient group to require approximately 13 revisions by the 3-year follow-up interval. Using 2013 CMS MEDPAR data, these 13 revisions would have resulted in $124,007 cost-to-hospital. However, only 1 revision (0.4%) was observered, therefore $114,468 in additional costs were spared for the aggregate of participating hospitals. This data suggests that the incorporation of kinetic sensors in TKA may assist the surgeon in achieving soft-tissue balance and thereby avoiding adverse mechanical complications that require surgical intervention.
Total knee arthroplasty (TKA) patients are consistently reported to be less satisfied than total hip arthroplasty (THA) patients. A patient's perception of success of his/her own total knee is dictated by their levels of post-operative pain and function, and many return to follow-up visits with inexplicable pain and stiffness that contradict favorable radiographic results. Several of these chief complaints that contribute to dissatisfaction are associated with soft-tissue imbalance. Therefore, in an effort to thoroughly understand the post-operative impact of soft-tissue balance on satisfaction, a multicenter study was conducted to evaluate the satisfaction outcomes of quantifiably balanced patients. In this study, 102 sensor-assisted patients were followed out to 3 years. The intraoperative devices used in this study project kinetic loading (lbf.) and center of load location data, in real-time, to a screen. Because of the wireless nature of the intraoperative sensors, the patella can be reduced, and kinematic data can be evaluated through the range of motion. The target balance window that was used in this study has been previously reported in literature and includes: 1) a mediolateral differential of 15 lbf., through the ROM, and 2) Sagittal plane stability as determined by a posterior drawer analysis. A robust, face-validated satisfaction survey was administered at 3-year follow-up and included 7 questions with answers on a 5-point Likert scale. At 3 years, post-operatively, 97.2% of this patient group reported being “satisfied” to “very satisfied” with their procedure, in comparison to the 81% average TKA satisfaction reported in literature (df = 11). The comparative literature included annual satisfaction intervals from 1 to 5 years (n = 33,775) which is comparable to the interval reported in this patient group. The sensor-assisted patient group exhibited a 16% increase in the proportion of satisfaction over what is currently reported in the comparative literature (p = 0.001). Despite the success rate of TKA, unfavorable patient-reported satisfaction continues to present a problem for operative recipients and surgeons. Because satisfaction is dependent upon several variables – including pain, function, and activity levels – the satisfaction survey used in this study represents a more accurate account of patient perception than many traditional surveys. It was shown that sensor-balanced TKA patients exhibited a 16% increase in the proportion of those reporting being “satisfied” to “very satisfied”, over the average satisfaction reported in literature. Allowing the surgeon to quantitatively balance the soft-tissue envelope, dynamically, has continued to a significant decrease in the proportion of dissatisfaction.
The rate of technological innovation in procedural total knee arthroplasty has left little time for critical evaluation of a new technology before the adoption of even newer modalities. With more drastic financial restrictions being placed on operating room spending, orthopaedic surgeons are now required to provide excellent results on a budget. It is integral that both clinical efficacy and cost-effectiveness of these intraoperative technologies be fully understood in order to provide patients with effectual, economically conscious care. The purpose of this qualitative analysis of literature was to evaluate clinical and economic efficacy of the three most prominent technologies currently used in TKA: computer navigation, patient-specific instrumentation, and kinetic sensors. Three hundred and ninety one publications were collected; 100 were included in final qualitative analysis. Criteria for inclusion in the analysis was defined only insofar as that each piece assessed one of the above listed aspects of the three technologies Literature included in the final evaluation contained background information on each respective technology, clinical outcomes, revision rates, and/or cost analyses. All comparisons were conducted in a strictly qualitative manner, and no attempts were made to conduct interstudy statistical analyses due to the high level of variability in methodology and data collected.Introduction
Methods
Instability after total knee arthroplasty (TKA) represents, in excess of, 7% of reasons for implant failure. This mode of failure is correlated with soft-tissue imbalance, and has continued to be problematic despite advances in implant technology. Thus, understanding the options available to execute safe and effective soft-tissue release is critical to mitigating future complications due to instability. This study aimed to use intraoperative sensors to evaluate a multiple needle puncturing technique (MNPT), in comparison with traditional transection-based release, to determine its biomechanical and clinical efficacy. Seventy-five consecutive, cruciate-retaining TKAs were performed, as part of an 8-site multicenter study. All procedures were performed with the use of an intraoperative sensor to ensure quantitative balance, as per previously reported literature. Of the 75-patient cohort, 50 patients were balanced with the MNPT; 20 patients were balanced with traditional transection. All patients were followed out to 1-year, and administered KSS, WOMAC, and satisfaction. Alignment and ROM was captured for all patients, pre-operatively and at the 1-year follow-up interval.Introduction
Methods
Improper soft-tissue balancing can result in postoperative complications after total knee arthroplasty (TKA) and may lead to early revision. A single-use tibial insert trial with embedded sensor technology (VERASENSE from OrthoSensor Inc., Dania Beach, FL) was designed to provide feedback to the surgeon intraoperatively, with the goal to achieve a “well-balanced” knee throughout the range of motion (Roche et al. 2014). The purpose of this study was to quantify the effects of common soft-tissue releases as they related to sensor measured joint reactions and kinematics. Robotic testing was performed using four fresh-frozen cadaveric knee specimens implanted with appropriately sized instrumented trial implants (geometry based on a currently available TKA system). Sensor outputs included the locations and magnitudes of medial and lateral reaction forces. As a measure of tibiofemoral joint kinematics, medial and lateral reaction locations were resolved to femoral anterior-posterior displacement and internal-external tibial rotation (Fig 1.). Laxity style joint loading included discrete applications of ± 100 N A-P, ± 3 N/m I-E and ± 5 N/m varus-valgus (V-V) loads, each applied at 10, 45, and 90° of flexion. All tests included 20 N of compressive force. Laxity tests were performed before and after a specified series of soft-tissue releases, which included complete transection of the posterior cruciate ligament (PCL), superficial medial collateral ligament (sMCL), and the popliteus ligament (Table 1). Sensor outputs were recorded for each quasi-static test. Statistical results were quantified using regression formulas that related sensor outputs (reaction loads and kinematics) as a function of tissue release across all loading conditions. Significance was set for p-values ≤ 0.05.Introduction
Methods
Aseptic loosening has been reported to be the most common, contemporary mode of total knee arthroplasty failure. It has been suggested that the etiology of revision due to loosening can be attributed, in part, to joint imbalance and the variability inherent in standard surgical techniques. Due to the high prevalence of revision, the purpose of this study was to quantify the change in kinetic loading of the knee joint before versus after the application of the final cement-component complex. Ninety-two consecutive, cruciate-retaining TKAs were performed, between March 2014 and June 2014, by two collaborating surgeons. Two different knee systems were used, each with a different viscosity cement type (either medium viscosity or high viscosity). All knees were initially balanced using a microelectronic tibial insert, which provides real-time feedback of femoral contact points and joint kinetics. After the post-balance loads were captured, and the surgeon was satisfied with joint balance, the final components were cemented into place, and the sensor was re-inserted to capture any change in loading due to cementing technique.Introduction
Methods
Understanding the relationship between knee specific tissue behavior and joint contact mechanics remains an area of focus. Seminal work from 1990's established the possibility to optimize tissue properties for recreation of laxity driven kinematics (Mommersteeg et al., 1996). Yet, the uniqueness and validity of such predictions could be strengthened, especially as they relate to joint contact conditions. Understanding this interplay has implications for the long term performance of joint replacements. Development of instrumented knee implants, highlighted by a single use tibial insert trial with embedded sensor technology (VERASENSE, Orthosensor Inc.), may offer an avenue to establish the relationship between tissue state and joint mechanics. Utilization of related data also has the potential to confirm computational predictions, where both rigid body motions and associated reactions are explicitly accounted for. Hence, the goal of this work was to evaluate an approach for optimization of ligament properties using joint mechanics data from an instrumented implant during laxity style testing. Such a framework could be used to inform joint balancing techniques, improve long term implant performance, and alternatively, qualify factors that may lead to poor outcomes
The INTRODUCTION
METHODS
Achieving balance in TKA is critical in assuring favorable outcomes. But, in order to achieve quantifiably balanced loading values, is it more advantageous to make bony corrections or release soft-tissue? The answer to this question will be paramount in evaluating the most appropriate surgical techniques for use with new dynamic technology, thereby maximizing favorable clinical outcomes. Therefore, the purpose of this investigation was to evaluate a possible quantitative loading threshold, using intraoperative sensors, which may dictate surgical correction of bone versus soft-tissue release. A retrospective analysis of 122 multicenter patients, in receipt of sensor-assisted primary TKA, was conducted. 40 lbs. was used as a threshold, above which bone was corrected; below which soft-tissue was corrected. All patients were categorized in to the following groups: Group A – candidates for bony correction, but received soft-tissue correction; Group B – candidates for soft-tissue/receiving soft-tissue; Group C – candidates for bony correction/receiving bony correction.INTRODUCTION
METHODS
Patient-reported satisfaction is a critical measure in understanding the clinical success of total knee arthroplasty. Yet, satisfaction levels in TKA patients are generally lower than THA patients; and surgeon-patient agreeability regarding clinical success is typically in discordance. Thus, the purpose of this evaluation was to report on the one-year satisfaction data of a group of sensor-assisted TKA patients, and compare that data to the average satisfaction reported in literature, as measured by a meta-analysis. One hundred and thirty five patients received TKA utilizing intra-operative sensing technology to evaluate soft-tissue balance as part of a prospective multicenter study. Patients were classified by two groups: “balanced” and “unbalanced”. Quantitative “balance” was defined as a mediolateral intercompartmental loading difference of ≤ 15 pounds; all loading exceeding 15 pounds was classified as “unbalanced”. At the one-year follow-up visit, a 7-question patient satisfaction survey was administered. The answering schema of this survey was modeled using a modified five-point Likert scale, ranging from “True” to “False” (or “Very Satisfied” to “Very Dissatisfied,” where appropriate). A meta-analysis of literature was performed and studies selected for inclusion in this analysis were required to meet the following criteria: all patients were in receipt of a primary TKA; satisfaction data was collected post-operatively; and the proportion of patients who were “satisfied” to “very satisfied” was statistically described.INTRODUCTION
METHODS
The cost associated with the TKA revision burden is projected to reach 13 billion dollars, annually. Complications reported by post-TKA patients include: pain (44%, multilocational), sensation of instability (21% reason for revision), and joint stiffness (17% reason for revision); problems that may be attributed to soft-tissue imbalance. One of the possible reasons for the substantial prevalence of such complications is the subjectivity associated with defining soft-tissue balance. A priority must be placed on developing new objective methods with which to avoid costly post-operative complications, including the integration of intraoperative sensing technology. The purpose of this evaluation was to report on the disparity between the patient-reported outcomes scores of quantitatively balanced versus unbalanced patients, at 1-year, using a group of 135 multicenter patients. 135 prospective patients, from 8 U.S. sites, have had primary TKA performed with the use of intraoperative sensors. Patients were classified by two groups: “balanced” and “unbalanced”. Quantitative “balance” was defined as a mediolateral intercompartmental loading difference of ≤ 15 pounds; all loading exceeding 15 pounds was classified as “unbalanced”. For all patients, the following kinematic data was captured: varus/valgus stability, anteroposterior stability, flexion contracture (if any), extension lag (if any), anatomic alignment, and ROM. Also at each clinical follow-up visit, activity levels and two patient-reported outcomes measures were administered, including: the American Knee Society Score (KSS), and the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC).INTRODUCTION
METHODS
During primary total knee arthroplasty, the surgeon may encounter excessive medial collateral ligament tension while addressing a varus knee. This may be due to medial ligament/capsular complex contractures, and/or, due to the creation of a 0 degree mechanical axis in a varus knee. This tension leads to increased loading in the medial compartment, which contributes to an unbalanced extension and flexion gap. If uncorrected, this imbalance can lead to unfavorable clinical outcomes, including: pain, accelerated polyethylene degradation, joint instability, and limited ROM. Currently, intercompartmental soft-tissue balance is obtained by a subjective surgeon's “feel”. However, this method of judging soft-tissue tension is both variable and unreliable. Most surgeons can detect gross instability, but judging ligament tension is difficult. The following technique describes the integration of intraoperative microelectronic tibial inserts to assess and modify ligament tension, utilizing real-time dynamic sensor feedback 500 TKAs were performed between September 2012 and April 2013, by three collaborating surgeons. All surgeons used the same implant system, compatible with an embedded microelectronic tibial insert with which to receive real-time feedback of femoral contact points and joint kinetics. Intraoperative kinematic data, displayed loading patterns consistent with identifiable intercompartmental imbalance through a full ROM. All mediolateral imbalance, secondary to an excessively tight medial compartment, was addressed with the technique described herein.Introduction
Methods
Post-operative clinical outcomes of TKA are dependent on a multitude of surgical and patient-specific factors. Malrotation of the femoral and/or tibial component is associated with pain, accelerated wear of the tibial insert, joint instability, and unfavorable patellar tracking and dislocation. Using the transepicondylar axis to guide implantation of the femoral component is considered to be an accurate anatomical reference and is widely used. However, no gold standard currently exists with respect to ensuring optimal rotation of the tibial tray. Literature has suggested that implantation methods, which reference the tibial tubercle, reduce positioning outliers with more consistency than other anatomical landmarks. Therefore, the purpose of this evaluation is to use data collected from intraoperative sensors to assess the true rotational accuracy of using the mid-medial third of the tibial tubercle in 98 TKAs. The data for this evaluation was retrieved from 98 consecutive patients who underwent primary TKA from the same highly experienced surgeon. Femoral component rotation was verified in every case via the use of the Whiteside line, referencing the transepicondylar axis, and confirming appropriate patellar tracking. Tibial tray rotation was initially established by location of the mid-medial third of the tibial tubercle. Rotational adjustments of the tibial tray were evaluated in real-time, as the surgeon corrected any tibiofemoral incongruency and tray malpositioning. The initial and final angles of tibial tray rotation were captured with intraoperative video feed, and recorded. A z-test of differences between pre- and post-rotational correction was performed to assess the statistical significance of malrotation present in this cohort.Introduction
Methods
Flexion instability of the knee accounts for, up to, 22% of reported revisions following TKA. It can present in the early post-operative phase or present— secondary to a rupture of the PCL— in the late post-operative phase. While most reports of instability occur in conjunction with cruciate retaining implants, instability in a posterior-stabilized knee is not uncommon. Due to the prevalence of revision due to instability, the purpose of constructing the following techniques is to utilize intraoperative sensors to quantify flexion gap stability. 500 posterior cruciate-retaining TKAs were performed between September 2012 and April 2013, by four collaborating surgeons. All surgeons used the same implant system, compatible with a microelectronic tibial insert with which to receive real-time feedback of femoral contact points and joint kinetics. Intraoperative kinematic data, as reported on-screen by the VERASENSE™ knee application, displayed similar loading patterns consistent with identifiable sagittal plane abnormalities. These abnormalities were classified as: “Balanced Flexion Gap,” “Flexion Instability” and “Tight Flexion Gap.” All abnormalities were addressed with the techniques described herein.Introduction
Methods
Acetabular component positioning is highly correlated with total hip arthroplasty (THA) outcomes. Multiple reports however indicate that less than 50% of acetabular cups are placed within surgeon-desired ranges for abduction and anteversion angles when using conventional cup positioning techniques. Issues with improper placement include instability-dislocation, impingement and impact on range of motion, polyethylene wear, leg length discrepancy, and gait mechanics. Accuracy in placement of the acetabular component is complicated by the need to estimate cup impactor angles to create desired cup position. A low cost approach to THA using Image-based Ultrasonic Guidance (IUG) (Orthosensor, Sunrise, FL) coupled to existing surgical tools is presented. IUG utilises acoustic measurement techniques for achieving optimal component positioning and leg length. A precisely machined Hip Test Fixture (HTF) has been built to simulate the anatomical pelvis, acetabular cup, and femur to validate system accuracy. The IUG was affixed to the HTF to demonstrate placement of the cup during THA. The HTF was loaded onto a 27-inch Graphic User Interface (GUI) providing three-dimensional CAD data of the HTF. Registration points included the Iliac Crest and 10 points around the acetabular cup. These points were mapped to the CAD data by the GUI. The HTF was set to 45° of abduction and 0° of version to begin testing. Abduction and version were measured over a +15° range in 1-degree increments while leg length and offset were measured over a +5mm range in 2mm increments. A high-resolution coordinate measurement machine (FaroArm EDGE) verified the accuracy and margin of error for inclination, version, leg length and offset at each increment. The HTF provided a precise means for evaluating IUG system accuracy of simulated THA in a controlled environment. Acceptable margins of error were reported on the HTF: mean error for version was 0.36° (SD 0.02°; 0.25° to 0.38°); mean error for inclination was 1.04° (SD 0.52°; 0.48° to 1.66°); mean error for leg length and offset were respectively 0.36mm (SD 0.86mm; −0.65 to 1.55mm) and 0.41mm (SD 0.28; 0.05 to 0.80mm). IUG provides a means for achieving acceptable precision and accuracy in component placement during THA as evaluated with the HTF. Further study is however necessary to correlate accuracy of IUG with clinical utility and short-term clinical outcomes.
Optimized tibial tray rotation during a total knee replacement (TKR) is critical for tibiofemoral congruency through full range of motion, as it affects soft tissue tension, stability and patellar tracking. Surgeons commonly reference the tibial tubercle, or the “floating tibial tray,” while testing the knee in flexion and extension. Utilization of embedded sensors may enable the surgeon to more accurately assess tibiofemoral contact points during surgery. The malrotation of the tibiofemoral congruency when utilizing the mid to medial 1/3 of the tibial tubercle for tibial rotation was evaluated in 50 posterior cruciate ligament-retaining TKRs performed by an experienced, high-volume surgeon. Sensors were embedded in the tibial trials; the rotation of the tibial tray was defined, and the femoral contact points in each compartment were captured. The surgical procedure was performed to size and then appropriately rotate the tibial tray. The anterior medial tray was pinned to control anterior-posterior and medio-lateral displacement, and allow internal and external rotation of the tray. With the capsule closed and patella reduced, the knee was reduced with trial implants. The femoral contact points and medial-lateral soft tissue tension were documented. Patellar tracking and changes in soft tissue tension were also documented.Introduction
Methods
