As previous meta-analyses on the alignment outcomes of Computer-assisted orthopaedic surgery (CAOS) did not differentiate between CAOS systems, limited information is available on the accuracy of a specific CAOS system based on clinical cases. This study assessed the accuracy and precision of achieving surgical goals in approximately 7000 cases using a specific contemporary CAOS system. Alignment parameters were extracted from the technical logs of 6888 TKA surgeries performed between October 2012 and January 2017 using a contemporary CAOS system. The following surgical parameters were investigated: 1) planned resection defined by the surgeon prior to the bone cuts; 2) Checked resection defined as digitalisation of the bony cuts. Deviations in alignment between planned and checked resections were evaluated, with acceptable resections defined as no more than 3° of resection deviations. For the tibial resection, deviations in tibial varus/valgus angle and posterior tibial slope were 0.06 ± 0.94° and −0.09 ± 1.73°, respectively. For the femoral resection, deviations in femoral varus/valgus angle amd femoral flexion were 0.00 ± 0.97° and −0.17 ± 1.44°, respectively. High percentages of the resections were found to be acceptable (>94% of the cases). The CAOS system investigated was shown to provide accurate and precise intra-operative assistance to the surgeon in achieving targeted resections. The study summarised a large number of cases spanning the application history of the specific CAOS system, including both experienced users and new adopters of the technology. The data provided a complete clinical relevant evaluation demonstrating its high accuracy and precision in resection alignment.
Computer-assisted orthopaedic surgery (CAOS) has been demonstrated to increase accuracy to component alignment of total knee arthroplasty compared to conventional techniques. The purpose of this study was to assess if learning affects resection alignment using a specific CAOS system. Nine surgeons, each with >80 TKA experience using a contemporary CAOS system were selected. Prior to the study, six surgeons had already experienced with CAOS TKA (experienced), while the rest three were new to the technology (novice). The following surgical parameters were investigated: 1) planned resection, resection parameters defined by the surgeon prior to the bone cuts; 2) checked resection, digitalisation of the realised resection surfaces. Deviations in the alignment between planned and checked resections were compared between the first 20 cases (in learning curve) and the last 20 cases (well past learning curve) within each surgeon. Any significance detected (p < 0.05) with >1° difference in means indicated clinically meaningful impact on alignment by the learning phase. Both pooled and surgeon-specific analysis exhibited no clinically meaningful significant difference between the first 20 and the last 20 cases from both experienced and novice surgeon groups. The resections in both the first 20 and the last 20 cases demonstrated acceptable rates of over 95% in alignment (<3° deviation) for both experienced and novice surgeons. This study demonstrated that independent of the surgeon's prior CAOS experiences, the CAOS system investigated can provide an accurate and precise solution to assist in achieving surgical resection goals with no clinically meaningful compromise in alignment accuracy and outliers during the learning phase.
Despite that computer-assisted orthopaedic surgery (CAOS) has been shown to offer increased accuracy to the bony resections compared to the conventional techniques [1], previous studies of CAOS have mostly focused on alignment outcomes based on a small number of patients [1]. Although several recent meta-analyses on the CAOS outcomes have been reported [2], these analyses did not differentiate between systems, while system-dependency has been reported to influence alignment parameters [3]. To date, no study has benchmarked a specific CAOS system based on a large number of clinical cases. The purpose of this study is to assess the accuracy and precision of bony resection in more than 4000 cases using a specific contemporary CAOS system. Technical logs of 4292 TKAs performed between October 2012 and January 2016 using a contemporary CAOS system (ExactechGPS, Blue-Ortho, Grenoble, FR) were analyzed. The analyses were performed on: 1) planned resection, defined by the surgeon prior to the bone cuts. These parameters serve as inputs for the CAOS guidance; and 2) Checked resection, defined as digitalization of the actual resection surfaces by manually pressing an instrumented checker onto the bony cuts. Deviations in alignment and resection depths (on the referenced side) between planned and checked resections were calculated in coronal and sagittal planes for both tibia and femur (planned vs checked).INTRODUCTION
Materials and Methods
Although several meta-analyses have been performed on total knee arthroplasty (TKA) using computer-assisted orthopaedic surgery (CAOS) [1], understanding the inter-site variations of the surgical profiles may improve the interpretation of the results. Moreover, information on the global variations of how TKA is performed may benefit the development of CAOS systems that can better address geographic-specific operative needs. With increased application of CAOS [2], surgeon preferences collected globally offers unprecedented opportunity to advance geographic-specific knowledge in TKA. The purpose of this study was to investigate geographic variations in the application of a contemporary CAOS system in TKA. Technical records on more than 4000 CAOS TKAs (ExactechGPS, Blue-Ortho, Grenoble, FR) between October 2012 and January 2016 were retrospectively reviewed. A total of 682 personalized surgical profiles, set up based on surgeon's preferences, were reviewed. These profiles encompass an extensive set of surgical parameters including the number of steps to be navigated, the sequence of the surgical steps, the definition of the anatomical references, and the parameters associated with the targeted cuts. The profiles were compared between four geographic regions: United States (US), Europe (EU), Asia (AS), and Australia (AU) for cruciate-retaining (CR) and posterior-stabilized (PS) designs. Clinically relevant statistical differences (CRSD, defined as significant differences in means ≥1°/mm) were identified (significance defined as p<0.05).INTRODUCTION
Materials and Methods
While multiple factors contribute to the variability of prosthesis placement during total knee arthroplasty (TKA), the accuracy of the surgeon's resection planning (positioning of the cutting block) is arguably the most critical. One may postulate that proper training, including enabling the surgeon to passively receive quantitative feedback on the cutting block position, may help him/her improve resection accuracy. The purpose of this study was to test the hypothesis that passive reception of feedback on cutting block position improves the accuracy of the successive TKA resection planning. Five cadaveric knees (tibia and foot only) were studied. After arthrotomy, the tracker of an imageless navigation system (ExactechGPS®, Blue-Ortho, Grenoble, FR) was attached to the tibia. A navigated TKA procedure was initiated starting with registration of anatomical landmarks. Four surgeons then positioned the tibial cutting block (without pinning) on each knee using standard extramedullary mechanical instruments. The planned target resection was neutral varus/valgus, 3° posterior slope, and 10mm resection depth referencing the lateral plateau. Each surgeon performed 3 planning trials on each of the 5 knees, removing the cutting block between attempts. The planned resections were measured using an instrumented checker provided with the navigation system, referencing the cutting block. Surgeons were informed of the resection parameters measured by the navigation system after each planning trial. The deviations in resection parameters between the resection target and the cutting block position were calculated for each planning trial. The effect of receiving passive feedback on the accuracy of successive placement of the cutting block was assessed by comparing the deviations between each surgeon's 3 trials on the same cadaver (paired-t test). Statistical significance was defined as p<0.05.INTRODUCTION
Materials and Methods
The alignment of components in total knee arthroplasty (TKA) is perceived to be one of the most influential factors in determining the long-term outcomes. A contemporary debate exists regarding the choice of the alignment method. As a vast majority of the surgeons support the basis of the mechanical alignment philosophy (MA), others believe in the concept of anatomical alignment theory (AA) to closely match the anatomy of the femur and the tibia of the native knee [1]. This study was intended to evaluate the accuracy of achieving a planned tibial resection target using either the MA or AA methods. Five healthy cadaveric knees (tibia and foot only) were studied. Four surgeons were independently asked to position a tibial cutting block (without pinning) using conventional extramedullary mechanical instrumentation (Exactech LPI instrumentation, Gainesville, FL, USA). Surgeons were asked to target a predefined proximal tibial cut according to MA (Varus= 0°, posterior slope= 3°, resection level= 10 mm) or to AA (Varus= 3°, posterior slope= 6°, resection level= 9 mm). Once the surgeon expressed satisfaction with the achieved position of the tibial cutting block, the planned resection was recorded using an imageless guidance system (ExactechGPS®, Blue-Ortho, Grenoble, FR). Surgeons completed at least three positioning trial for each alignment method on each cadaver. The accuracy and outliers (deviated more than 2°/mm from the target [2]) of resection planning were compared between the MA and AA methods. Statistical significance was defined as p< 0.05.INTRODUCTION
Materials and Methods
Studies have reported that only 70–80% of the total knee arthroplasty (TKA) cases using conventional instruments can achieve satisfactory alignment (within ±3° of the mechanical axis). Computer-assisted orthopaedic surgery (CAOS) has been shown to offer increased accuracy and precision to the bony resections compared to conventional techniques [1]. As the early adopters champion the technology, reservation may exist among new CAOS users regarding the ability of achieving the same results. The purpose of this study was to investigate if there are immediate benefits in the accuracy and precision of achieving surgical goals for the novice surgeons, as compared to the experienced surgeons, by using a contemporary CAOS system. Two groups of surgeons were randomly selected from TKAs between October 2012 and January 2016 using a CAOS system (ExactechGPS, Blue-Ortho, Grenoble, FR), including:
All the surgeries from the INTRODUCTION
Materials and Methods
Total knee arthroplasty (TKA) can effectively treat end-stage knee osteoarthritis. For cruciate-retaining (CR) TKA, the posterior tibial slope (PTS) of the reconstructed proximal tibia plays a significant role in restoring normal knee kinematics as it directly affects the tension of the posterior cruciate ligament (PCL) [1]. However, conventional cadaveric testing of the impact of PTS on knee kinematics may damage/stretch the PCL, therefore impact the test reproducibility. The purpose of this study was to assess the reproducibility of a novel method for the evaluation of the effects of PTS on knee kinematics. Cemented CR TKAs (Logic CR, Exactech, Gainesville, FL, USA) were performed using a computer-assisted surgical guidance system (ExactechGPS®, Blue-Ortho, Grenoble, FR) on six fresh frozen non-arthritic knees (PCL presumably intact). The tibial baseplate was specially designed (Fig. 1) with a mechanism to modify the PTS in-situ. Knee kinematics, including anteroposterior (AP) translation, internal/external (IE) rotation, and hip-knee-ankle angles, were evaluated by performing a passive range of motion from extension up to ∼110° of flexion, three separate times at 5 PTSs: 10°, 7°, 4°, 1°, and then 10° again. The repeatability of the test was investigated by comparing the kinematics between the first and the last 10° tests. Any clinically relevant deviation (1.5° for the hip knee ankle angle, 1.5mm for anterior-posterior translation and 3° for internal-external rotation) would reflect damage to the soft-tissue envelope or the PCL during the evaluation. Potential damage of PCL was investigated by comparing the kinematic parameters from the first and last 10° slope tests at selected flexion angles (Table 1) by paired t-test, with statistical significance defined as p<0.05.Introduction
Materials and Methods
While total knee arthroplasty (TKA) improves postoperative function and relieves pain in the majority of patients with end stage osteoarthritis, its ability to restore normal knee kinematics is debated. Cadaveric studies using computer-assisted orthopaedic surgery (CAOS) system [1] are one of the most commonly used methods in the assessment of post-TKA knee kinematics. Commonly, these studies are performed with an open arthrotomy; which may impact the knee kinematics. The purpose of this cadaveric study was to compare the knee kinematics before and after (open or closed) arthrotomy. Kinematics of seven non-arthritic, fresh-frozen cadaveric knees (PCL presumably intact) was evaluated using a custom software application in an image-free CAOS system (ExactechGPS, Blue-Ortho, Grenoble, FR). Prior to the surgical incision, one tracker was attached to the diaphysis of each tibia and femur. Native intact knee kinematics was then assessed by performing passive range of motion (ROM) three separate times, from full extension to at least 110 degrees of flexion, with the CAOS system measuring and recording anatomical values, including flexion angle, internal-external (IE) rotation and anterior-posterior (AP) translation of the tibia relatively to the femur, and the hip-knee-ankle (HKA) angle. Next, an anterior incision with a medial parapatellar arthrotomy was performed, followed by acquisition of the anatomical landmarks used for establishing an anatomical coordinate system in which all the anatomical values were evaluated [2]. The passive ROM test was then repeated with closed and then open arthrotomy (patella manually maintained in the trochlea groove). The anatomical values before and after knee arthrotomy were compared over the range of knee flexion using the native knee values as the baseline.Introduction
Materials and Methods
Cemented total knee arthroplasty (TKA) is a widely accepted treatment for end-stage knee osteoarthritis. During this procedure, the surgeon targets proper alignment of the leg and balanced flexion/extension gaps. However, the cement layer may impact the placement of the component, leading to changes in the mechanical alignment and gap size. The goal of the study was to assess the impact of cement layer on the tibial mechanical alignment and joint gap during cemented TKA. Computer-assisted TKAs (ExactechGPS®, Blue-Ortho, Grenoble, FR) were performed by two fellowship trained orthorpaedic surgeons on five fresh-frozen non-arthritic pelvis-to-ankle cadaver legs. All the surgeries used a cemented cruciate retaining system (Optetrak Logic CR, Exactech, Gainesville, FL). After the bony resection, the proximal tibial resection plane was acquired by manually pressing an instrumented checker onto the resected tibial surface (resection plane). Once the prosthesis was implanted through standard cementing techniques, the top surface of the implanted tibial component was probed and recorded using an instrumented probe. A best fit plane was then calculated from the probed points and offset by the thickness of the prosthesis, representing the bottom plane of the component (component plane). The deviation of component alignment caused by the cement layer was calculated as the coronal and sagittal projection of the three-dimensional angle between the resection plane and the component plane. The deviation of the component height, reflecting a change in the joint gap, was assessed as the distance between the two planes calculated at the lowest points on the medial and lateral compartments of the proximal tibial surface. Statistical significance was defined as p≤0.05.INTRODUCTION
MATERIAL
Up to date there are only few reports in literature on the long term survival of uncemented stems. As for cemented THA, 10 year survival of at least 90% is required for any THA. We followed the first 354 consecutive implantations of an uncemented, straight femoral stem (CLS, Zimmer Inc, Warsaw, USA) in 326 patients. Mean time of follow-up evaluation was 17 years (range, 15-20 years).Introduction
Materials and methods
