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
Successful clinical outcomes following unicompartmental knee arthroplasty (UKA) depend on component positioning, soft tissue balance and overall limb alignment which can be difficult to achieve using manual instrumentation. Recently, robotically guided technology has been used to improve post-operative implant positioning, and limb alignment in UKA with the expectation that this will result in greater implant longevity. This multi-center study examines the survivorship of this robotically guided procedure coupled with a novel, anatomically designed UKA implant at two years follow up. This study examines the two year survivorship and patient satisfaction of an anatomically designed UKA implant using a new robotically guided technology that has been shown to improve implant positioning and alignment.INTRODUCTION
OBJECTIVES
Proper tibial rotation has been cited as an important prerequisite to optimal total knee replacement. The most commonly recognized rotational landmark is the medial 1/3rd of the tibial tubercle. The purpose of this study was to quantify the amount of variability this structure has from a common reference as well as to understand the effects of component design when referencing this structure. Subjects were prospectively scanned into a Virtual Bone Database (Stryker Orthopaedics, Mahwah, NJ), which is a collection of body CT scans from subjects collected globally. All CT scans displayed cropped bones were excluded. SOMA™ (Stryker) is a unique tool with the ability to take automated measurements of quantities such as distances and angles on a large number of pre-segmented bone samples which was then to perform calculations represented in this study. Demographic information for each subject was recorded were known. For the analysis, the mechanical axis of the tibia (MAT) was established by connecting the center of the proximal tibia to the center of the ankle. From the MAT, a perpendicular resection plane was made at a distance of 9 mm from the most proximal portion of the lateral condyle. This plane was then used as a virtual resection plane to establish the points for the remaining structures which was the medial 1/3rd of the tibial tubercle and the posterior notch of the PCL insertion. The following axes were identified: 3TT (line between the medial 1/3rd of the tibial tubercle and the posterior notch of the tibia); 3CTT (line between the medial 1/3rd of the tibial tubercle and the center of the tibia); and the posterior axis of the tibia (line connecting the two most posterior points of the tibia at the virtual resection plane). Measurements made were the angle of the 3TT Line to the posterior axis and the angle of the 3CTT Line to the posterior axis.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
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
Unicompartmental knee arthroplasty (UKA) can achieve excellent clinical and functional results for patients suffering from single compartment osteoarthritis. However, UKA is considered to be more technically challenging to perform, and malalignment of the implant components has been shown to significantly contribute to UKA failures. The purpose of this investigation was to determine the clinically realized accuracy of UKA component placement using surgical navigation and dynamically referenced tactile-robotics. Pre-op CT, post-op CT, and surgical plan were available for 22 knees out of the first 45 procedures performed using a new tactile-guided robotic system. 3D component placement accuracy was assessed by comparing the pre-operative plan with the post-operative implant placement (desired versus actual). Bone and implant models were obtained from postoperative CT scans taken immediately following the surgery. A 3D to 3D iterative closest point registration procedure was performed and the measured implant position was directly compared to the preoperative plan. Errors were assessed as single axis root-mean-square (RMS) entities.INTRODUCTION
METHODS
Clinical outcomes of UKA procedures are sensitive to malalignment of the components, and thus show significant variability in the literature. A new robotic procedure addresses isolated medial compartment osteoarthritis with the classic indications of UKA. Using precision planning through patient specific 3D modeling and reconstruction, a robotic arm gives the surgeon control of resurfacing the knee joint, allowing for consistent precision according to the previously chosen plan. Through the precise preparation of bone surfaces and inter-component alignment, this procedure is designed to significantly increase accuracy and decrease mal-alignment, thus increasing post-operative physical and function outcomes. This paper evaluates four year clinical outcomes of this novel surgical procedure. The first seventy-three (42 male, 31 female) patients (average age: 71 ±10yrs) to receive a robotically assisted UKA enrolled in an IRB approved outcomes registry. Eleven patients were four years post operative and sixty-two patients were three years post operative at the time of the study. The average follow ups were 45 months and 35 months, respectively (range: 30 to 47 months). The tibial component for all patients was an all-poly inlay design.Introduction
Methods
Bicompartmental osteoarthritis involving the medial tibiofemoral and the patellofemoral compartments is often treated with total knee replacement. Improved implants and surgical techniques have led to renewed interest in bicompartmental arthroplasty. This study evaluates the radiographic and early clinical results of bicompartmental arthroplasty with separate unlinked components implanted with the assistance of a robotic surgical arm. In addition, we examine the amount of bone resected using unlinked bicompartmental components compared to total knee replacement. Finally, a retrospective review of total knee cases examines the applicability of this early intervention procedure. 97 patients received simultaneous but geometrically separate medial tibiofemoral and patellofemoral arthroplasties with implants specifically designed to take advantage of a new bone and tissue sparing implantation technique using haptic robotics. These patients came from four surgeons at four different hospitals. The average follow-up was 9 months. Pre- and post-operative radiographs were taken. ROM, KSS and WOMAC scores were recorded. The patients had an average age of 67 yrs (range: 45-95), BMI of 29 ± 4kg/m2. 47% of the patients were male. We retrospectively reviewed pre and post operative notes from 406 consecutive TKA patients from a single surgeon. Intraoperative data included the integrity of the three compartments and the ACL.Introduction
Methods
