Bone Resection Thickness Research Articles

Evaluating the accuracy of a new robotically assisted system in cadaveric total knee arthroplasty procedures

BackgroundRobot-assisted total knee arthroplasty (TKA) has been shown to facilitate high-precision bone resection, which is an important goal in TKA. The aim of this cadaveric study was to analyze the accuracy of the target angle and bone resection thickness of a recently introduced robotic TKA system.MethodsThis study used 4 frozen cadaveric specimens (8 knees), 2 different implant designs, navigation, and a robotic system. The 4 surgeons who participated in this study were trained and familiar with the basic principles and operating procedures of this system. The angle of the bone cuts performed using the robotic system was compared with the target angles from the intraoperative plan. For each bone cut, the resection thickness was recorded and compared with the planned resection thickness.ResultsThe mean angular difference for all specimens was less than 1°, and the standard deviation was less than 2°. The mean difference between the planned and measured angles was close to 0 and not significantly different from 0 except for the difference in the frontal tibial component angle, which was 0.88°. The mean difference in the hip-knee-ankle axis angle was − 0.21°± 1.06°. The mean bone resection difference for all specimens was less than 1 mm, and the standard deviation was less than 0.5 mm.ConclusionsThe results of the cadaveric experimental study showed that the new TKA system can realize highly accurate bone cuts and achieve planned angles and resection thicknesses. Despite the limitations of small sample sizes and large differences between cadaveric and clinical patients, the accuracy of cadaveric experiments provides strong support for subsequent clinical trials.

Robotic arm-assisted posterior-stabilised total knee arthroplasty reduces the amount of tibial bone resection thickness without increasing the rate of postoperative flexion contracture in varus knees in the short term: Comparison with image-free navigated total knee arthroplasty.

This study aimed to compare the bone resection thickness, rate of minimal thickness insert usage, and postoperative range of motion (ROM) between robotic and navigated total knee arthroplasty (TKA). Fifty consecutive posterior-stabilised (PS) robotic TKA and 50 case-controlled PS navigated TKA were enroled. Bone resection thickness, rate of minimal thickness insert usage, and postoperative flexion contracture over 5° were statistically compared. The tibial bone resection thickness was significantly thinner in robotic TKA. The insert thickness was significantly lower, and the rate of minimal thickness insert usage was significantly higher in robotic TKA. The ROM at 3months postoperatively and the rate of postoperative flexion contracture were comparable between the two groups. Robotic TKA can reduce the tibial bone resection thickness and increase the rate of minimal thickness insert usage without increasing postoperative flexion contracture as compared with navigated TKA.

Surgical procedures for the prevention of extension-flexion gap imbalance in total knee arthroplasty

The purpose of this study was to identify preoperative and intraoperative factors that influence extension-flexion gap imbalance in total knee arthroplasty (TKA). Ninety-three knees undergoing TKA with the modified gap balancing technique were included. Preoperative range of motion, intraoperative extension-flexion gap balance, thickness of the resected bone and radiological parameters were investigated. The preoperative flexion contracture, bone resection thickness in the medial proximal tibia, and the medial distal femur all correlated with the extension-flexion gap balance in TKA. Bone resection thickness in the medial proximal tibia and the medial distal femur were predictive of extension-flexion imbalance.

Decreasing Posterior Femoral Condyle Offset Improves Intraoperative Correction of Flexion Contracture in Total Knee Arthroplasty.

Multiple intraoperative strategies are described to achieve full extension in total knee arthroplasty, but only a few studies have assessed the effect of the flexion gap on intraoperative improvement in flexion contracture. The aim of this study was to determine whether posterior condylar offset, in isolation, independently affects extension at the time of total knee arthroplasty.Two hundred and seventy-eight patients who underwent total knee arthroplasty for knee osteoarthritis and flexion contracture ≥ 5 degrees between January 2008 and July 2018 were included in this study. Patients with other factors that could affect knee extension at the time of surgery were excluded. We recorded the thickness of posterior femoral condyle bone resected as well as the thickness of the posterior femoral component chosen for each patient. Patients' knee extension was recorded under anesthetic, prior to resection and intraoperatively after total knee replacement.Average thickness of bone resection for the posteromedial femur was 12.64 ± 1.65 mm and for the posterolateral femur was 10.38 ± 1.52 mm. Using a linear regression model, we found that changes in posterior offset and implant downsizing influenced correction of fixed flexion deformity at the time of surgery. When patients had a combined posteromedial and posterolateral offset 2 mm thinner than the thickness of bone resected, there was an average correction of 3.5 degrees of flexion contracture.Our study demonstrated that posterior femoral condyle offset is an independent variable affecting correction of flexion contracture at the time of surgery in a gap balanced cruciate-retaining total knee arthroplasty. This is a level IV evidence study.

MRI-based or CT-based patient-specific instrumentation in Total knee Arthroplasty: How do the two systems compare?

BackgroundPatient-specific instrumentation (PSI) has been introduced into total knee arthroplasty (TKA) to improve accuracy in restoration of alignment. PSI in TKA refers to custom-made cutting jigs manufactured according to anatomic configuration of the patient’s bone based on preoperative magnetic resonance imaging (MRI) or computed tomography (CT) scans. The purpose of this study was to compare the MRI- or CT-based PSI to see if they could reproduce accurate bone resection and postoperative outcomes.MethodsSeventy-one patients who received elective TKA using a PSI system for primary osteoarthritis with varus deformity were prospectively enrolled for this study. We randomly allocated those patients to MRI-based PSI group (36 patients) and CT-based PSI group (35 patients). The actual resection thickness and planned resection thickness by preoperative PSI electronic program were compared between the two groups. Radiographic findings of the postoperative limb alignment, three-dimensional position of the implants, and related complications were also evaluated. Clinical evaluation was also performed before and 2 years after the surgery.ResultsThere were no significant differences in the resection thickness in femur and tibia between actual resection and planned resection in both groups. Furthermore, there were no significant differences between two groups in terms of coronal, sagittal and rotational alignment of the components. All clinical assessments revealed no differences between two groups 2 years after the operation. No specific complication related to PSI was observed.ConclusionsAlthough MRI allows for visualization of cartilage, MRI-based PSI system did not show better accuracy in predicting the thickness of bone resection than CT-based PSI. Moreover, there were no differences in radiographic and clinical outcomes between the two groups.

Resection accuracy of patient-specific cutting guides in total knee replacement.

Patient-specific guides (PSGs) have been thoroughly investigated with regards to reconstitution of mechanical alignment in total knee arthroplasty (TKA). The ability to replicate the preoperative surgical plan is essential for optimal outcomes but intraoperative measurements to confirm accurate progression through the operation are limited. This leads to our clinical question: can PSGs replicate the planned bone resection depth during TKA? This is a prospective case series of 118 patients who underwent TKA using magnetic resonance imaging-based patient-specific cutting guides. Intraoperative bone resection thickness was measured and compared with the preoperative planned bone resections as a primary outcome. Secondary outcomes included the need for additional bone resections, the number of cases for which the PSG technique was abandoned, final component sizes and mechanical alignment. PSGs could not accurately recreate preoperative plan. PSGs resulted in over-resection in all bone cuts compared with the preoperative surgical resection plan. Secondary osteotomies were required in 37% of patients. PSGs had to be abandoned in 10.5% of cases, mostly due to suboptimal fit of the femoral block. The tibial component size was altered more frequently than the femoral. Intraoperatively, PSGs could not accurately recreate the preoperative plan. PSGs are marketed as user-friendly tools to simplify TKA but our research demonstrates the need for surgeons to monitor surgical progression and compensate for errors occurring during the use of PSGs.

The Effect of Patient-Specific Instrumentation Incorporating an Extramedullary Tibial Guide on Operative Efficiency for Total Knee Arthroplasty.

This retrospective study was to determine if patient-specific instrumentation (PSI) for total knee arthroplasty (TKA) leads to shortened surgical time through increased operating room efficiency according to different tibial PSI designs. 166 patients underwent primary TKA and were categorized into three groups as follows: PSI without extramedullary (EM) tibial guide (group 1, n = 48), PSI with EM tibial guide (group 2, n = 68), and conventional instrumentation (CI) group (group 3, n = 50). Four factors were compared between groups, namely, operative room time, thickness of bone resection, tibial slope, and rotation of the component. The mean surgical time was significantly shorter in the PSI with EM tibial guide group (group 2, 63.9 ± 13.6 min) compared to the CI group (group 3, 82.8 ± 24.9 min) (P < 0.001). However, there was no significant difference in the PSI without EM tibial guide group (group 1, 75.3 ± 18.8 min). This study suggests that PSI incorporating an EM tibial guide may lead to high operative efficiency in TKA compared to CI. This trial is registered with KCT0002384.

Assessment of patient-specific instrumentation precision through bone resection measurements.

In the present study, the precision of two patient-specific instrumentation (PSI) systems for total knee arthroplasty (TKA) was evaluated by comparing bony resection thicknesses of the pre-operative PSI planning and intra-operative measurements by a vernier calliper. It was hypothesized that the data provided by pre-operative planning were accurate within ±2mm of the bone resection thickness measured intra-operatively. Forty-one patient-specific TKAs were examined: 25 performed with Visionaire® technology and 16 with OtisMed® system. PSI accuracy was analysed comparing the resected bone thicknesses in the femoral and tibial cuts with pre-operatively planned resections. To determine pre-operative planning precision, the thickness values reported by the PSI planning were subtracted from the values reported intra-operatively by the calliper. The mean absolute differences between pre-operatively planned resections and corresponding intra-operative thickness measurements ranged from a minimum of 2.6mm (SD 0.8) to a maximum of 3.6mm (SD 1.3) in all three anatomical planes in both groups. In every plane, the mean absolute discrepancies between planned resections and measured cuts differed significantly from zero (p<0.0001). The proportion of differences within ±2mm between intra-operative measured resections and planned PSI cuts occurred in more than 90% of the cohort for femoral distal resections. Less precision was reported for the femoral posterior medial cuts (70.7% within ±2mm) and the tibial cuts (70.7% on the medial, 75.6% on the lateral side). Prosthetic component alignment on the coronal and transverse planes resulted in considerable deviations from the pre-operative planning. The two examined PSI technologies were accurate in femoral distal cuts, determining acceptable femoral component placement on the coronal plane. Posterior femoral and tibial cuts were less precise. Deviations from the pre-operative resection planning were reported in every plane. Inaccuracy was explained by ambiguous custom-made jigs placement on the bony surface. III.

Correction of coronal alignment correlates with reconstruction of joint height in unicompartmental knee arthroplasty.

Because there have been no standard methods to determine pre-operatively the thickness of resection of the proximal tibia in unicompartmental knee arthroplasty (UKA), information about the relationship between the change of limb alignment and the joint line elevation would be useful for pre-operative planning. The purpose of this study was to clarify the correlation between the change of limb alignment and the change of joint line height at the medial compartment after UKA. A consecutive series of 42 medial UKAs was reviewed retrospectively. These patients were assessed radiographically both pre- and post-operatively with standing anteroposterior radiographs. The thickness of bone resection at the proximal tibia and the distal femur was measured radiographically. The relationship between the change of femorotibial angle (δFTA) and the change of joint line height, was analysed. The mean pre- and post-operative FTA was 180.5° (172.2° to 184.8°) and 175.0° (168.5° to 178.9°), respectively. The mean δFTA was 5.5° (2.3° to 10.1°). The joint line elevation of the tibia (JLET) was 4.4 mm (2.1 to 7.8). The δFTA was correlated with the JLET (correlation coefficient 0.494, p = 0.0009). This study indicated that there is a significant correlation between the change of limb alignment and joint line elevation. This observation suggests that it is possible to know the requirement of elevation of the joint line to obtain the desired correction of limb alignment, and to predict the requirement of bone resection of the proximal tibia pre-operatively. Cite this article: Bone Joint Res 2015;4:128-133.

Correction of coronal alignment correlates with reconstruction of joint height in unicompartmental knee arthroplasty

ObjectivesBecause there have been no standard methods to determine pre-operatively the thickness of resection of the proximal tibia in unicompartmental knee arthroplasty (UKA), information about the relationship between the change of limb alignment and the joint line elevation would be useful for pre-operative planning. The purpose of this study was to clarify the correlation between the change of limb alignment and the change of joint line height at the medial compartment after UKA.MethodsA consecutive series of 42 medial UKAs was reviewed retrospectively. These patients were assessed radiographically both pre- and post-operatively with standing anteroposterior radiographs. The thickness of bone resection at the proximal tibia and the distal femur was measured radiographically. The relationship between the change of femorotibial angle (δFTA) and the change of joint line height, was analysed.ResultsThe mean pre- and post-operative FTA was 180.5° (172.2° to 184.8°) and 175.0° (168.5° to 178.9°), respectively. The mean δFTA was 5.5° (2.3° to 10.1°). The joint line elevation of the tibia (JLET) was 4.4 mm (2.1 to 7.8). The δFTA was correlated with the JLET (correlation coefficient 0.494, p = 0.0009).ConclusionsThis study indicated that there is a significant correlation between the change of limb alignment and joint line elevation. This observation suggests that it is possible to know the requirement of elevation of the joint line to obtain the desired correction of limb alignment, and to predict the requirement of bone resection of the proximal tibia pre-operatively.Cite this article: Bone Joint Res 2015;4:128–133

Posterior reference guides do not always maintain the size of posterior femoral condyles in TKA.

Posterior reference guides are provided by many manufacturers. However, the true posterior femoral condyle bone resection thicknesses using posterior reference guides are not stated by the manufacturers. The purpose of this study was to analyse the influence of the posterior reference guide designs on the posterior femoral condyle bone resection thickness. Thickness of posterior femoral condyle bone resection and thickness of prostheses were investigated in 8 types of total knee prostheses using the production drawings provided by the manufacturers. Posterior femoral condyle bone resection thickness differed between prostheses. Change in size of the medial posterior condyle ranged from -0.5 to 1.4mm at 0° external rotation, from -2.9 to 1.4mm at 3° external rotation, and from -5.3 to 1.4mm at 6° external rotation. Change in size of lateral posterior condyle ranged from -0.5 to 1.4mm at 0° external rotation, from -0.4 to 3.4mm at 3° external rotation, and from -0.4 to 5.3mm at 6° external rotation. This study showed that posterior femoral condyle bone resection thickness was different for each posterior reference guide. The rotation centre of posterior reference guides influenced the bone resection thickness in the posterior femoral condyle. The size of the posterior femoral condyles increased in some guides but decreased in other guides. The maximum differences in size changes of the posterior femoral condyles between the guides were 1.9mm at 0° external rotation, 4.1mm at 3° external rotation, and 6.3mm at 6° external rotation. To control the size of posterior femoral condyles, the posterior reference guide design should be checked before use.

Importance of the lateral anatomic tibial slope as a guide to the tibial cut in total knee arthroplasty in Japanese patients

Using three-dimensional computed tomography in 50 osteoarthritic knees, we simulated at various cutting angles the tibial cut for total knee arthroplasty. Cutting angles of 0°, 3°, 5°, 7°, 9°, and 11° were used. We then calculated the anterior and posterior thicknesses, the medial-lateral widths, and the medial and lateral condylar depths of the resected tibial bone at each cutting angle. Each set of measurements was evaluated according to a comparison between the cutting angle and the anatomic posterior slopes. The cutting angles showing the smallest anterior-posterior difference at the medial and lateral plateaus were 9° and 7°, respectively. The mean anatomic posterior slopes at the medial and lateral plateaus were 9.0° and 8.1°, respectively. When the tibia was cut at the cutting angle closest to the medial anatomical posterior slope in each knee, the thickness of the lateral posterior plateaus resected from 12 knees (24%) was more than 10 mm. Among these 12 knees, the cutting angle was more than 9° in 9 knees (75%). In contrast, when the tibia was cut at the cutting angle closest to the lateral anatomical posterior slope, only one resected medial posterior plateau was more than 10mm. The cutting angle of this case was 7°. Therefore, in consideration of the thickness of bone resection from anatomic posterior slope, we demonstrated the importance of using the lateral anatomic posterior tibial slope as a guide to the tibial cut. There was no significant difference with respect to resected bone morphology at any cutting angle.

Influence of prosthetic joint line position on knee kinematics and patellar position

Prosthetic joint line position after total knee arthroplasty (TKA) was investigated using sagittal roentgenograms obtained from six fresh frozen cadaver knees. A specially designed knee testing device was developed that allowed for a controlled flexion angle while maintaining a constant quadriceps force. Pre- and postoperative roentgenograms were obtained from 30° to 120° in 15° intervals. Steinman pins inserted into the medial femoral condyle and patella were used as reference points in the roentgenograms. A displacement vector between the medial femoral condyle and tibial plateau was used to analyze the tibiofemoral joint relationship. The functional patellar length (Insall-Salvati ratio), was used to determine correct patellar height. Another displacement vector was used to measure the patellofemoral joint relationship, and the angle between the patellar cut surface and femoral long axis was also calculated. Bone resection thickness from the femoral, tibial, and patellar surfaces was equal to the prosthetic thickness. This reconstructive scheme produced correct ligament balance and flexibility of the knee without the aid of tensioning devices or special measurements. Patellar tracking appeared to be identical before and after surgery. This accurate but simple surgical technique also reproduced normal knee extensor mechanisms that may influence longevity and long-term results of TKA.