Total knee arthroplasty (TKA) is one of the most successful and beneficial treatments for osteoarthritic knees. We have developed posterior-stabilized (PS) total knee prosthesis for Asian patients, especially Japanese patients, and have used it since November, 2010. The component was designed based on the CT images of osteoarthritic knees, aiming to achieve deep flexion and stability. The purpose of this study was to analyze We analyzed a total of 28 knees implanted with PS TKAs: Fourteen knees with the new PS prosthesis (group A), and the other fourteen knees with a popular PS prosthesis as a control group (group B). Preoperative data of both groups were not significantly difference. Flat-panel radiographic knee images were recorded during five static knee postures including full extension standing, lunge at 90° and maximum flexion, and kneeling at 90° and maximum flexion. The three-dimensional position and orientation of the implant components were determined using model-based shape matching techniques. The results of this shape-matching process have standard errors of approximately 0.5° to 1.0° for rotations and 0.5 to 1.0 mm for translations in the sagittal plane. Unpaired t-tests were used for statistical analysis and probability values less than 0.05 were considered significant.INTRODUCTION
METHODS
Discrepancies in patient outcomes after total knee arthroplasty have encouraged the development of different treatment options including early preventive interventions. In addition, improvements in surgical techniques and instrumentation have increased the accuracy of the surgeries. In this case study, we review the first robotic-arm assisted modular tricompartmental knee arthroplasty in which bone and soft tissues are conserved by employing a precise planning and execution technique. A 63 year old Caucasian female with a Body Mass Index (BMI) of 27 presented to the surgeon (SK) with knee pain and a varus mechanical alignment. The patient received modular tri-unicompartmental arthroplasty performed with robotic-arm assistance; (see figure 1 for post-op radiograph). Range of Motion (ROM), Knee Society Score (KSS) and Knee Injury and Osteoarthritis Outcomes Score (KOOS) were measured pre-operatively and post-operatively at 6, 16, and 23 months. At 6 months post-op an in-depth in vivo kinematic analysis was conducted by using a validated fluoroscopic assessment technique [1]. The patient simulated stair climbing, kneeling activity, and deep lunge while under single plane fluoroscopy. Three dimensional models were created from CT scans and were matched to 2D fluoroscopic images for kinematic assessment.Background
Materials and Methods
There is strong current interest to provide reliable treatments for one- and two-compartment arthritis in the cruciate-ligament intact knee. An alternative to total knee arthroplasty is to resurface only the diseased compartments with discrete compartmental components. Placing multiple small implants into the knee presents a greater surgical challenge than total knee arthroplasty, and it is not certain natural knee mechanics can be maintained. The goal of this study was to compare functional kinematics in cruciate-intact knees with either medial unicondylar (mUKA), mUKA plus patellofemoral (mUKA+PF), or bi-unicondylar (biUNI) arthroplasty using discrete compartmental implants with preparation and placement assisted by haptic robotic technology. Nineteen patients with 21 knee arthroplasties consented to participate in an I.R.B. approved study of knee kinematics with a cruciate-retaining multicompartmental knee arthroplasty system. All subjects presented with knee OA, intact cruciate ligaments, and coronal deformity ranging from 7° varus to 4° valgus. All subjects received multicompartmental knee arthroplasty using haptic robotic-assisted bone preparation an average of 13 months (6–29 months) before the study. Eleven subjects received mUKA, five subjects received mUKA+PF, and five subjects received biUKA. Subjects averaged 62 years of age and had an average body mass index of 31. Combined Knee Society Pain/Function scores averaged 102 ± 28 preoperatively and 169 ± 26 at the time of study. Knee range of motion averaged −3° to 120° preoperatively and −1° to 129° at the time of the study. Knee motions were recorded using video-fluoroscopy while subjects performed step-up/down, kneeling and lunging activities. The three-dimensional position and orientation of the implant components were determined using model-image registration techniques (Fig. 1). The AP locations of the medial and lateral condyles were determined by computing a distance map between the femoral condyles and the tibial articular surfaces.INTRODUCTION
METHODS
Adjusting joint gaps and establishing mediolateral (ML) soft tissue balance are considered essential interventions for better outcomes in total knee arthroplasty (TKA). However, the relationship between intraoperative laxity measurements and weight-bearing knee kinematics has not been well explored. The goal of this study was to establish how intraoperative joint gaps and ML soft tissue balance affect postoperative kinematics in posterior-stabilized (PS)-TKA. We investigated 44 knees with 34 patients who underwent primary PS-TKA. Subjects averaged 71 ± 7 years at the time of surgery, included 8 male and 36 female knees with a preoperative diagnosis of osteoarthritis in 38 knees and rheumatoid arthritis in 6 knees. A single surgeon performed all the surgeries with mini-midvastus approach. After independent bone cutting, soft tissues were released on a case-by-case basis to obtain ML balance. The femoral trial and a tensor were put in place, and the patella was reduced to the original position. A joint distraction force of 40 lb was applied by the tensor, and the central joint gaps and ML tilting angles were measured at 0°, 10°, 30°, 60°, 90°, 120° and 135° flexion (Fig. 1). We defined a “gap difference” as a gap size difference between one gap and another, which represents the gap change between the two knee flexion positions. ML soft tissue balance was assessed by measuring the mean joint gap tilting angle over all flexion angles for each patient. Based on the tilting angle, the 44 knees were classified into three groups: The knees with the mean joint gap tilting of less than −1.0° (13 knees), between −1.0 and 1.0° (14 knees), and over 1.0° (17 knees). At least 1.5 year after surgery, a series of dynamic squat radiographs and 3 static lateral radiographs of straight-leg standing, lunge at maximum flexion, and kneeling at maximum flexion, were taken for each patient. The 3-dimensional position and orientation of the implant components were determined using model-based shape matching techniques (Fig. 2). Correlations between intraoperative measurements and knee kinematics were analyzed. The knee kinematics was also compared among three tilting groups.Introduction:
Methods:
The in vivo kinematics of squatting after total hip arthroplasty (THA) has remained unclear. The purpose of the present study was to elucidate range of motion (ROM) of the hip joint and the incidence of prosthetic impingement during heels-down squatting after THA. 23 primary cementless THAs using a computed tomography-based navigation system (CT-HIP, Stryker Navigation, Freiberg, Germany) were investigated using fluoroscopy. An acetabular component with concavities around the rim (TriAD HA PSL, Stryker Orthopaedics, Mahwah, NJ) and a femoral component with reduced neck geometry (CentPiller, Stryker Orthopaedics), which provided a large oscillation angle, were used. The femoral head size was 28mm (8 hips), 32mm (10 hips), and 36mm (5 hips). Post-operative analysis was performed within 6 months in 6 hips, and at 6 months to 2 years in 17 hips. Successive hip motion during heels-down squatting was recorded as serial digital radiographic images in a DICOM format using a flat panel detector. The coordinate system of the acetabular and femoral components based on the neutral standing position was defined. The images of the hip joint were matched to three-dimensional computer aided design models of the acetabular and femoral components using a two-dimensional to three-dimensional (2D/3D) registration technique. In the previous computer simulation study of THA, the root mean square errors of rotation was less than 1.3°, and that of translation was less than 2.3 mm. We estimated changes in the relative angle of the femoral component to the acetabular component, which represented the hip ROM, and investigated the incidence of prosthetic impingement during squatting. We also estimated changes in the flexion angle of the acetabular component, which represented the pelvic posterior tilting angle (PA), and the flexion angle of the femoral component, which represented the femoral flexion angle (FA). The contribution of the PA to the FA at maximum squatting was evaluated as the pelvic posterior tilting ratio (PA/FA). In addition, when both components were positioned most closely during squatting, we estimated the minimum angle (MA) up to theoretical prosthetic impingement. No prosthetic impingement occurred in any hips. The maximum hip flexion ROM was mean 92.7° (SD; 15.7°, range; 55.1°–119.1°) and was not always consisted with the maximum squatting. The maximum pelvic posterior tilting angle (PA) was mean 27.3° (SD; 11.0°, range; 5.5°–46.5°). The pelvis began to tilt posteriorly at 50°–70° of the hip flexion ROM. The maximum femoral flexion angle (FA) was mean 118.9° (SD; 10.4°, range; 86.4°–136.7°). At the maximum squatting, the ratio of the pelvic posterior tilting angle to the femoral flexion angle (pelvic posterior tilting ratio, PA/FA) was mean 22.9% (SD; 10.4%, range; 3.8%–45.7%). The minimum angle up to the theoretical prosthetic impingement was mean 22.7° (SD; 7.5°, range; 10.0°–37.9°). The maximum hip flexion of ROM in 36 mm head cases was larger than that in 32 mm or 28 mm head cases, while the minimum angle up to the prosthetic impingement in 36 mm head cases was also larger than that in 32 mm or 28 mm head cases. Three-dimensional assessment of dynamic squatting motion after THA using the 2D/3D registration technique enabled us to elucidate hip ROM, and to assess the prosthetic impingement, the contribution of the pelvic posterior tilting, and the minimum angle up to theoretical prosthetic impingement during squatting.
There is great interest to provide repeatable and durable treatments for arthritis localized to one or two compartments in the cruciate-ligament intact knee. We report a series of efforts to develop and characterize an implant system for partial knee resurfacing. We studied distal femoral morphology and found that the sagittal-plane relationships between the condylar and trochlear surfaces are highly variable (Figs 1 and 2). In response, we report the design of a multi-compartmental system of implants intended to anatomically resurface any combination of compartments (Fig 3). Finally, we report the results of a pilot fluoroscopic study of the in vivo knee kinematics in patients who received medial, medial plus patellofemoral and bi-condylar knee arthroplasty. The kinematic results suggest these treatments provide a stable knee with intact cruciate ligament function. This work shows various partial knee resurfacing treatments have the potential to provide excellent knee mechanics and clinical outcomes.
