Distal Femoral Cut Research Articles

Correlation Between Planned and Executed Bone Cuts Using Robotics in Total Knee Arthroplasty: A Prospective Study of 500 Patients.

This study evaluated the precision of robotic-arm-assisted total knee arthroplasty (RATKA) in performing bone resection, predicting component size, managing soft tissue tension, and determining postoperative range of motion (ROM). A total of 500 participants were enrolled in this prospective cohort research. The procedures were conducted at a single facility, with a uniform method and implant design. The Cuvis system, a fully automated robot, was utilized for the study. The precise removal of bone at both the tibial and femur sites, the positioning of the implant, and the release of soft tissue were documented and then compared to the preoperative plan. The distal (medial and lateral) femoral cuts had a mean absolute deviation from the plan of 0.23mm, while the posterior (medial and lateral) femoral cuts had a mean absolute difference of 1mm and 1.4mm, respectively. The absolute discrepancies in the medial and lateral tibial cuts are 0.93mm and -0.06mm, respectively. Out of 1000 bone resections, 980 (98%) were within < 1mm from the preoperative plan. The predictions for the sizes of the tibial and femoral components had accuracies of 100% and 98.9%, respectively. These findings collectively underscore the effectiveness of the fully automated Cuvis robotic system in achieving consistent and accurate results in bone resections and implant sizing, highlighting its potential as a valuable tool in orthopedic surgery.

The Trochlear Bisector as a New Landmark for Kinematic Alignment in Total Knee Arthroplasty: A Radiographic Study.

Background: In recent years, there has been considerable interest in prosthetic alignment techniques for total knee arthroplasty (TKA), particularly in the so-called kinematic alignment, which aims to restore the knee's native alignment. However, implementing this technique requires specialized instruments and procedural steps that can be laborious. This study introduces the bisector of the trochlear groove as a reliable landmark for performing the distal femoral cut while maintaining parallelism with the native femoral joint line. Methods: Three orthopedic specialists assessed 110 X-ray images of full-leg, weight-bearing lower limbs obtained from healthy individuals between January 2021 and December 2022. The bisector of the trochlear groove was identified on the X-ray images, and the angle between this bisector and the femoral joint line was measured. The consistency of these measurements across repeated assessments and different examiners was evaluated. Results: The bisector of the trochlear groove was found to be perpendicular to the femoral joint line, with a mean angle of 89.4°. The inter-rater reliability was 68% within ±1.3° from the mean, while the intra-rater reliability was 82% within ±1.5° from the mean. Conclusions: These results suggest that by performing a femoral cut perpendicular to the bisector of the trochlear groove, surgeons can inherently restore the femoral joint line of the native knee in patients where the native joint line is no longer identifiable due to the effect of osteoarthritis. This method may offer a viable and straightforward alternative to the standard surgical technique currently practiced for kinematic alignment in TKA.

Does Robotic Assistance Help with Bone Preservation in Total Knee Replacement?

This research paper investigates whether robotic total knee replacement (TKR) reduces bone resection compared to conventional TKR. While TKR is a successful procedure, revision surgery remains a challenge with up to 8.3% of all knee replacement procedures requiring revisions. The study retrospectively analyzed the tibial polyethylene inserts used and bone cuts made in 157 primary TKRs performed by a single surgeon. The results show that 93.3% of robotic TKRs used the base size tibial polyethylene of 9 mm, and the average distal femoral cut was 7.4 mm and the average tibial cut was 6.4 mm, with the minimum being 3 mm. The study suggests that robotic TKR reduces bone resection compared to conventional TKR.

Improving alignment in total knee arthroplasty: a cadaveric assessment of a surgical navigation tool with computed tomography imaging

Purpose To investigate the accuracy of an imageless, optical surgical navigation tool to assist with femoral and tibial bone cuts performed during TKA. Patients and methods Six board-certified orthopedic surgeons participated in a laboratory cadaver investigation, performing femoral and tibial bone cuts with the assistance of a computer navigation tool. Femoral and tibial varus/valgus, tibial slope, femoral flexion, and both femoral and tibial rotation measurements from the device were compared with angular measurements calculated from computed tomography (CT) images of the knees. Results Measurements with the navigation tool were highly correlated with those obtained from CT scans in all three axes. For the distal femoral cut, the absolute mean difference in varus/valgus was 0.83° (SD 0.46°, r = 0.76), femoral flexion was 1.91° (SD 1.16°, r = 0.85), and femoral rotation was 1.29° (SD 1.01°, r = 0.88) relative to Whiteside’s line and 0.97° (SD 0.56°, r = 0.81) relative to the posterior condylar axis. For the tibia, the absolute mean difference in varus/valgus was 1.08° (SD 0.64°, r = 0.85), posterior slope was 2.78° (SD 1.40°, r = 0.60), and rotation relative to the anteroposterior axis (posterior cruciate ligament to the medial third of the tibial tuberosity) was 2.98° (SD 2.54°, r = 0.79). Conclusion Utilization of an imageless navigation tool may aid surgeons in accurately performing and monitoring femoral and tibial bone cuts, and implant rotation in TKA and thus, more accurately align TKA components.

Total Knee Arthroplasty in a Patient with Ipsilateral Painless Hip Arthrodesis: Technical Surgical Tips and a Novel Method for Intraoperative Navigation-Assisted Planning.

Total knee arthroplasty (TKA) in the setting of a previous ipsilateral hip fusion/arthrodesis is an uncommon and challenging procedure. There is little information available in the literature on the challenges and techniques available to perform TKA in these patients. For a traditional TKA procedure, the patient is placed in the supine position and various knee-positioning devices are used to allow for adequate knee and hip flexion, which is required for surgical exposure and tibia preparation. Ipsilateral hip arthrodesis presents two major challenges: (1) Hip flexion is crucial for adequate knee flexion while the patient is supine during the TKA procedure, and (2) the use of advanced technology, specifically computer navigation and robotic-assisted surgery techniques, is limited due to the inability to acquire the hip center of rotation during surgery, due to the lack of hip motion. Therefore, equipment and positioning must be adjusted by the surgeon to facilitate TKA in these patients. This article reports the case of a 72-year-old male patient with a long-standing, painless right hip arthrodesis, presenting with end-stage osteoarthritis of the right knee, leg-length discrepancy, and an 11.6° difference between the mechanical and anatomical axes of the femur. We describe the unique surgical planning as well as the surgical positioning options that allow for adequate knee flexion and proper surgical exposure. Furthermore, we describe a novel method of computer-assisted navigation for intra-operative planning and execution utilizing a reflected tibia as a template for the distal femoral cut.

Bone Cut Accuracy in Total Knee Arthroplasty: Do Conventional Cutting Guides Stay True to the Planned Coronal Orientation of the Components?

Background: Total knee arthroplasty (TKA) has become the gold standard for the definitive treatment of knee osteoarthritis. One crucial aspect in the implantation of a TKA is the precise orientation of the femoral and tibial components. The main purpose of the present study is to assess, in patients undergoing total knee replacement, whether the difference between the planned angulation in the distal femoral cut and the angulation obtained in the postoperative radiological control is low enough to consider the conventional bone-cutting guides reliable. Methods: A retrospective study was designed with a consecutive series of patients who had undergone primary total knee arthroplasty using conventional instrumentation over one year. The authors analysed the main variable (bone cuts) while considering different variables (age, gender, surgeon, prosthesis, laterality, constraint, body mass index and alignment) to identify different patient patterns that justify the results in the main variable. Descriptive variables were analysed using the Mann–Whitney U and Kruskal–Wallis tests. Additionally, the correlation between continuous variables was explored in accordance with the Spearman correlation. Results: A total of 340 patients with a mean age of 75 ± 9.16 years were finally included in the present study. The mean absolute error of the main variable for the femoral coronal bone cut was 1.89° (SD 1.53). For the tibial coronal bone cut, it was 1.31° (SD 2.54). These values correspond to what remains after subtracting the radiological angulation obtained in the postoperative period from the planned intraoperative angulation of the distal femoral cut. No associations were observed between the main variable (the angulation of the proximal tibial cut and distal femoral cut) and the rest of variables for either the femur or tibia. Conclusion: A discrepancy between the planned angulation and the final radiological measure on the coronal plane of the femur and tibia using conventional cutting guides has been demonstrated. The degree of deviation is low enough that it probably does not affect clinical outcomes. Therefore, the use of conventional cutting guides will continue to be an appropriate tool to perform bone cuts in knee replacement surgery.

Is lateral femoral condyle hypoplasia a feature of genu valgum? A morphological computed tomography study of 200 knees

BackgroundYoung surgeons are taught that genu valgum deformity is associated with hypoplasia of the lateral femoral condyle, despite the absence of supporting evidence. The objective of this study was to determine whether the lateral condyle was hypoplastic in genu valgum, by assessing the morphological features of the distal femur and their variations according to the severity of the coronal deformity. HypothesisThe lateral femoral condyle is not hypoplastic in genu valgum deformity. Material and methodsThe 200 included patients treated by unilateral total knee arthroplasty were divided into five groups based on their preoperative hip-knee-ankle (HKA) angle. The HKA angle, valgus cut angle (VCA), and anatomical lateral distal femoral angle (aLDFA) were measured on long-leg radiographs. Computed tomography images were then used to measure the medial and lateral anterior-posterior condylar lengths (mAPCL and lAPCL) and condylar thicknesses (mCT and lCT), distal femoral torsion (DFT), medial and lateral posterior condylar heights (mPCH and lPCH), and medial and lateral condylar volumes (mCV and lCV). ResultsNo significant differences were demonstrated across the five mechanical-axis groups for mAPCL, lAPCL, mCT, lCT, mPCH, or lPCH. The groups differed significantly regarding the VCA (p<0.0001), aLDFA (p<0.0001), DFT (p<0.0001), and mCV/lCV ratio (p<0.0001). VCA and aLDFA were smaller when the valgus exceeded 10°. DFT was similar in all varus knees (2.2°–2.6°) but significantly greater for knees with moderate (4.0°) or severe (6.2°) valgus. Finally, lCV was greater than mCV in valgus knees compared to varus knees. ConclusionThe presence of lateral condyle hypoplasia in knees with genu valgum seems open to question. Apparent hypoplasia noted during the standard physical examination may be chiefly ascribable to distal valgus of the femoral epiphysis in the coronal plane and, with the knee flexed, to distal epiphyseal torsion, whose severity increases with the degree of valgus deformity. These considerations should be taken into account when performing distal femoral cuts for TKA, to ensure the restoration of normal anatomy in patients with genu valgus. Level of evidenceIV.

Fixed 6° distal femoral cut consistently achieves neutral alignment for Asians, Caucasians, and Native Hawaiian/Pacific Islanders.

Restoration of a neutral mechanical axis (MA) is important to the success of total knee arthroplasty (TKA). While known differences are present between Asians and Caucasians regarding native knee alignment, it is unknown whether such differences exist amongst Native Hawaiian/Other Pacific Islanders (NHPI) or if utilizing a fixed distal femoral cut of 6° can consistently achieve a neutral MA in these minority racial groups. This study examines the preoperative deformities presented by Asians, Caucasians, and NHPI, and the resulting knee alignment achieved following TKA when a fixed 6° distal femoral cut is targeted for all patients. Preoperative and postoperative MA was measured from 835 Asian, 447 Caucasian, and 163 NHPI hip-to-ankle radiographs. All patients underwent TKA in which a standard distal femoral cut of 6° valgus was targeted for all patients. Data were evaluated as continuous variables and by groupings of varus (MA < - 3°), valgus (MA > 3°), and neutral (- 3° ≤ MA ≤ 3°) alignment. Preoperative deformity ranged from 38° varus to 29° valgus. The proportion of Asian and NHPI presenting with varus alignment prior to surgery was significantly greater than Caucasian patients in both males (Asians: 80.6%; Caucasians: 67.0%; NHPI: 79.0%, p = 0.001) and females (Asians: 66.1%; Caucasians: 45.7%; NHPI: 63.2%, p < 0.001). There was no difference in the proportion of patients (72-79%) achieving a neutral MA amongst all three racial groups. NHPI appear to have similar preoperative deformities to Asians with both groups having significantly more varus alignment than Caucasians. Despite a wide range of preoperative deformity, application of a fixed distal femoral cut of 6° valgus successfully established a neutral MA equally in the majority of patients across all three racial groups.

Up to 4 millimeters excessive distal femoral resection in total knee arthroplasty has no significant effect on patellar height and functional score in patient with severe flexion contracture: a retrospective study

Background: Excessive distal femoral resection in patients with severe preoperative flexion contracture has been previously attributed to the joint line elevation after performing total knee arthroplasty (TKA). In this study, the authors investigated the effects of excessive distal femoral cut on the patellar height as well as the outcome of TKA. Methods: This retrospective study included patients with severe flexion contracture (&gt;30°) who underwent TKA. They were divided into two groups according to the size of distal femoral cut: group A (≤9 mm, n=27) and group B (&gt;9 mm, n=22). The functional and radiographic outcomes as well as radiographic indices of patellar height, including adductor ratio, Insall-Salvati index, Blackburne-Peel index, Caton-Deschamps index, and fibular height, were compared between these two study groups. Results: The baseline characteristics of the participants were comparable. The mean femoral cut was 8.3±0.8 in group A and 12.6±0.9 in group B. The mean changes of the adductor ratio, Insall-Salvati index, Caton-Deschamps index, Blackburne-Peel index, and fibular height were not significantly different between the two study groups. As well, the functional and radiographic outcomes of TKA were comparable. No revision surgery was required during the mean follow-up of 51.7±32.4 mo. No genu recurvatum was recorded, and no patient complained of knee instability. Conclusions: Excessive distal femoral cut does not seem to change patellar height in TKA patients, so it could be used safely for patients with a severe preoperative flexion deformity. Level of Evidence: Level IV.

Influence of the femoral entry point for intramedullary alignment in total knee arthroplasty: A computer-aided design approach.

Objectives The aim of this study was to simulate different entry points and investigate potential angulation errors of the intramedullary device and resulting changes in the distal femoral cut using a computer-aided design (CAD) approach.Materials and methods We used a CAD approach to simulate various distal femoral entry points for intramedullary instrumentation. Simulations were performed on (i) a commercially available three-dimensional (3D) CAD model of a human femur (DigitalFemur) and (ii) a digital 3D model of an analogue large femur model produced using a coordinate measuring machine (FaroFemur). Divergent insertion points medial, lateral, anterior and posterior to the ideal position were simulated. Angulation deviations of the resulting positions of the intramedullary rod were measured and changes in the anatomical-mechanical axis angle were calculated. Differences between the two simulation models were quantified.Results The ideal entry point in the FaroFemur was 9.9 mm anterior and 4.3 mm medial to the apex of the intercondylar notch, and 9.2 mm anterior and 3.6 mm medial in the DigitalFemur. A medial entry point increased the angle between the anatomical femoral axis and the alignment rod in the FaroFemur and DigitalFemur (with 5 mm displacement 2.510° and 2.363°, respectively; with 10 mm displacement 3.239° and 3.283°, respectively). In contrast, a lateral entry point decreased the angle between the anatomical femoral axis and the alignment rod (with 5 mm displacement 2.267° and 2.262°, respectively; with 10 mm displacement 3.158° and 3.731°, respectively). An anterior entry point changed the angle between the anatomical femoral axis and the alignment rod towards extension (1.802° in the FaroFemur; 2.142° in the DigitalFemur), while a posterior entry point generated a deviation toward flexion (2.045° in the FaroFemur; 2.055° in the DigitalFemur). The mean difference between the two models was 0.108±0.121° with the highest difference for anterior displacement.Conclusion Minor deviations of the entry point for intramedullary instrumentation during total knee arthroplasty can result in malalignment of several degrees.

Flip Autograft Technique for Anterolateral Femoral Deficiency in Total Knee Arthroplasty.

Anterolateral bone loss of the femur within the trochlear groove presents a unique and rare issue in primary total knee arthroplasty (TKA). Unlike distal and posterior femur bone loss for which most contemporary TKA systems have modular augments, the same does not exist for anterolateral bone loss. We present a technique in which a patient’s host bone from the standard distal femoral cuts was used to augment and provide a stable base for cementing of final femoral implants. Currently, the patient has 3-year follow-up with excellent results in terms of pain control with no evidence of component failure on the most recent radiographs. This technique provides a simple solution to a complex problem within primary TKA.

Accuracies of bone resection, implant position, and limb alignment in robotic-arm-assisted total knee arthroplasty: a prospective single-centre study

ObjectiveThis study assessed the accuracy of robotic-arm-assisted total knee arthroplasty (RATKA) for bone resection, component size prediction, implant placement, and limb alignment.MethodsThis prospective cohort study included 36 patients. All procedures were performed by a single experienced surgeon, using an identical approach and implant designs. The MAKO RIO Robotic Interactive Orthopaedic Arm (Stryker, Mahwah, NJ, USA) system was used. The actual bone resection, implant placement, component size, and postoperative mechanical alignment were recorded, then compared with the preoperative plan.ResultsThe mean absolute differences from the plan for the distal (medial and lateral) and posterior (medial and lateral) femoral cuts were 0.39 mm (0.62), 0.49 mm (0.70), 0.62 mm (0.79), and 0.65 mm (0.81), respectively, with 0.57° (0.65) varus. The mean absolute differences in the medial and lateral tibial cuts were 0.56 mm (0.75) and 0.58 mm (0.76), with 0.48° (0.16) varus and 0.54° (0.25) anterior/posterior slope. Of 192 bone resections, 176 (91.7%) were within ≤ 1 mm of the preoperative plan. The accuracies of femoral and tibial component size prediction were 100% and 97.22%, respectively. The mean absolute difference in final limb coronal alignment was 0.92° (0.65). Of the alignments, 18 (75.0%) were within ≤ 1.00° of the plan, and 100% were within ≤ 3.00° of the plan.ConclusionRATKA could accurately predict the component size and execute a preoperative plan to achieve precise bone resection, and implant placement, thereby reducing alignment outliers.

A rare case of bilateral medial femoral condylar cyst in OA knee managed with cruciate retaining TKA

Introduction: We report an osteoarthritic patient with huge sub-chondral cyst-like lesions in the medial femoral condyle of distal femur. This large bone defects due to advanced osteoarthritis was successfully treated with Cruciate retaining implant in total knee replacement. Case Report: A 60yrs old obese Female presented in our institution diagnosed with bilateral tricompartmental Osteoarthritis. The x-rays showed bone on bone Tricompartment OA Knee with Varus Malalignment. The left knee was operated first. After exposure, Distal Femoral Cuts where taken wherein a huge bony defect of about 2cm*1 cm was found in medial femoral condyle, but as lateral border of medial femoral condyle was intact the contained defect was managed with bone grafting and Hebert’s screw and a Cruciate retaining implant was done in femur. The right knee was the mirror image of left and managed similarly with bone grafting and Hebert’s screw and implanted a CR femur. Conclusion: Any cystic /defect management in knee replacement traditionally always require extra armamentariumin form of augments, rods, wedges, but sometimes reverse thinking can also work if we understand the intraoperative scenario objectively and CR femur, the least constraint implant also, if used judiciously can bail us out from such a difficult situation. Usually one should keep rods, augments, wedges and constrain implants ready for difficult cases. Read your x ray carefully, if suspected a Preoperative MRI /CT scan should be done to exclude any sub-chondral cysts osteochondral defects and good planning of the cases, which will avoid any surprise during surgery. No benefits or funds were received in the support of this study. The authors reports no conflict of interest.

A ligament tensor-guided extramedullary alignment technique for distal femoral cut in total knee replacement: results at a minimum 3 years follow-up

Femoral intramedullary canal referencing is used by most knee arthroplasty systems for distal femoral cut; to avoid the opening of the femoral canal different solutions have been presented such as navigation, patient-specific instruments (PSI) or the use of an extramedullary device. The FuZion® system is a tensor device, created to merge the two main techniques for performing a total knee arthroplasty: the ligament balancing and measured resection techniques. Our idea was to use the tensor as an extramedullary cutting guide for the distal femoral cut, based on a 90° tibial resection. A total of 110 patients were operated on with this technique. Patients were evaluated with weight-bearing long-standing X-rays, knee a-p and lateral views, validated PROMs (Oxford Knee Score, EQ-5D and EQ-VAS), the Knee Society Scoring System (KSS) and the Forgotten Joint Score (FJS). Minimum follow up was 3years (range 38-50months). Complete results were available for 104 patients (5 were lost in follow up and 1 died). Significant improvements were registered for all the evaluated scores from pre-op to the final follow up. Pre-op long-standing X-rays showed 21 valgus knees (20%) with a mean HKA of 187.6° (± 3.2°), 70 varus knees (62%) with a mean 172.2° (± 3.7°) HKA and 19 neutrally aligned knees, with a mean HKA of 179.5° (0 ± 2°). The radiographic evaluation at 3months post-op showed 20 valgus knees (mean HKA 183.7° ± 1.5°), 67 varus knees (mean HKA 176.1° ± 1.8°) and 23 neutrally aligned knees with a mean HKA of 179.3° (0 ± 2°). At final follow up the survival rate was 100% for revision of the implant as the endpoint. With any reoperation as the endpoint Kaplan-Meier survival estimate showed a survival rate of 95.1% at 3years. This technique for performing a ligament driven alignment in total knee arthroplasty showed encouraging clinical outcomes at mid-term follow up leaving a residual deformity on the coronal plane.

Concepts and techniques of a new robotically assisted technique for total knee arthroplasty: the ROSA knee system.

The ROSA (Robotic Surgical Assistant) Knee system (Zimmer Biomet, Warsaw, IN) for total knee arthroplasty (TKA) can be considered as collaborative robotics, where the surgeon remains in charge of the procedure and collaborates with a smart robotic tool, to perform the surgery with a high accuracy and reproducibility. The aim was to describe: (1) its concept and surgical technique; (2) its advantages and potential limits; (3) the early experience with this system. The goal during its development phase was to keep the surgeon active and at the center of the operation: the surgeon handles the saw and performs the cuts while the robotic arm places and holds the guide at the right place. The ROSA knee platform assists the surgeon for the distal femoral cut, the femoral component sizing and positioning, the tibial cut and the ligament balance. This robotic system has two options: image-based with 3D virtual model; or image-less, based on intraoperative landmarks acquisition. All the classic surgical techniques can be used: measured resection, gap balancing, functional alignment, kinematic alignment. Some techniques recently developed are more ROSA-specific: Robotic personalized TKA, ROSA-FuZion technique. Its advantages as compared to other available systems include: radiographs in standing position, collaborative robotic system where the robot completes the surgeon skills, "off-the-shelf" implants, predictive robotic with concept of machine learning incorporated into the system. Two cadaveric studies have reported the high accuracy and reproducibility of this device. This robotic system is recent and currently no clinical series has enough follow-up to report clinical outcomes. The ROSA knee system is a robotically assisted semi-autonomous surgical system with some specific characteristics. The aim of this collaborative robotic system is to improve the accuracy and reliability of the bone resections and the ligament balancing, without replacing the steps well performed by the surgeon.

Comparison with Navigation of a Novel Three-Step Technique for Improving Accuracy of the Distal Femoral Resection during Conventional TKA: A Case-Control Study.

Correct placement of the femoral component in the coronal plane during primary total knee arthroplasty (TKA) is related to long-term survival. The aim of this radiographic study was to determine the accuracy of a novel three-step technique for improving the accuracy of the distal femoral cut during conventional technique and compare it with computer navigation during TKA. A total of 458 TKAs were retrospectively analyzed (178 conventional TKAs with the novel technique and 280 navigated TKAs) for postoperative femoral component coronal alignment and compared between the two groups. Mean femoral component coronal alignment was not significantly different (p = 0.314) between the two groups. There was no significant difference in the mean femoral component coronal alignment between varus and valgus knees. The number of outliers (90 ± 3 degrees) for femoral component coronal alignment was not significantly different between the two groups when assessed separately for varus and valgus deformities. The mean value of femoral component alignment using the conventional technique in knees with varus deformity <10 degrees was 88.8 degrees, in knees with varus deformity 10 to 20 degrees was 89.4 degrees, and in those with varus deformity >20 degrees was 90.2 degrees. Femoral component alignment in knees with varus <10 degrees was significantly different from those >20 degrees (p = 0.006); there was no significant difference between knees with varus <10 degrees and those with 10 to 20 degrees varus (p = 0.251), nor between 10 and 20 degrees varus knees and those with varus >20 degrees (p = 0.116). Using the novel three-step technique during conventional TKA to perform the distal femoral cut can help achieve femoral component coronal alignment comparable to the navigation technique.

Posterior-Stabilized TKA in Patients With Severe Genu Recurvatum Achieves Good Clinical and Radiological Results at 5-year Minimum Follow-Up: A Case-Controlled Study

BackgroundGenu recurvatum is a rare knee deformity. Total knee arthroplasty (TKA) in severe preoperative recurvatum requires surgical adjustments. Few studies have assessed the clinical and radiological results of TKA in recurvatum. The aim was to compare the clinical and radiological outcomes, complications, and revision rates after posterior-stabilized TKA in severe recurvatum with those without recurvatum. MethodsBetween 1987 and 2015, 32 primary posterior-stabilized TKA were performed with a preoperative genu recurvatum greater than 10° and minimum follow-up of 60 months. In severe genu recurvatum, the extension gap needs to be decreased compared with flexion gap. To achieve this, the distal femoral cut is distalized, whereas the posterior femoral and tibial cuts are performed as usual. They were compared with 64 matched posterior-stabilized TKAs without recurvatum. The demographic data were similar between groups. The clinical and radiological outcomes, complications, and revision rates were assessed at the last follow-up. ResultsAt a mean follow-up of 7.4 years ± 1.9, there was no significant difference in International Knee Score functional score (77.5 vs. 73.4; P = .50) and knee score (86.6 vs. 89.5; P = .37) between the recurvatum group and the control group, respectively. 6 patients had a postoperative recurvatum equal or superior to 10° in the recurvatum group (18.8%). There was no difference between both groups in radiological outcomes, complication, or revision rates. No instability was found in the recurvatum group. ConclusionPosterior-stabilized TKA with controlled distalization of the femoral component in the setting of severe preoperative genu recurvatum achieves good clinical and radiological outcomes at a minimum follow-up of 5 years and similar to TKA without preoperative recurvatum. Level of EvidenceIII.

Evaluation of the accuracy of resected bone thickness based on patient-specific instrumentation during total knee arthroplasty.

In total knee arthroplasty (TKA) using patient-specific instrumentation (PSI), the correlation between the preoperative surgical plan and intraoperative resection size is unclear. The aims of this study were to evaluate whether the computed tomography (CT)-based PSI surgical plan can be executed accurately and to determine the accuracy of bone resection in TKA using PSI. Data of 45 consecutive knees undergoing TKA using CT-based PSI were retrospectively evaluated. The preoperative plan was prepared using three-dimensional CT acquisitions of the hip, knee, and ankle joints. Resected bone thicknesses of the femoral condyle of the distal medial, distal lateral, posterior medial, posterior lateral, and medial and lateral tibial plateaus were measured with a Vernier caliper intraoperatively. Then these respective measurements were compared with those in the preoperative CT-predicted bone resection surgical plan, and the measured thickness of resection was subtracted from the planned resection thickness. Errors were defined as: acceptable, ≤ 1.5mm; borderline, 1.5-2.5mm; and outliers, > 2.5mm. Overall, 22 (48.9%) knees had no outliers. There were 20 (44.4%) and 3 (6.7%) knees in which only 1 and 2 resection planes were outliers, respectively. The posterior medial tibial plateau had the lowest proportion of acceptable cuts (44.4%). Posterior femoral resection including the medial and lateral condyles had more outliers (n = 18/90 cuts, 20.0%) (p < 0.001) than the tibial condyles (n = 3/90 cuts, 3.3%) and distal femoral cuts (n = 6/90 cuts, 6.7%). The posterior surface of the femur, where the incidence of outliers was higher, tended to have a higher proportion of undercuts than other surfaces of the femur (> 80%). PSI showed only fair-to-moderate accuracy. The cutting guide for the posterior femur was less accurate than that for the tibia and distal femur. Specific attention is required when cutting the posterior femur. The PSI design needs to be improved to reduce errors.

Inter-Observer and Intra-Observer Reliability of 2D Radiograph-Based Valgus Cut Angle Measurement in Preoperative Planning for Primary Total Knee Arthroplasty.

BackgroundPreoperative planning is imperative for a successful total knee replacement. Determining the valgus angle for the distal femoral cut from the preoperative 2D radiograph is a very inexpensive method that can be used to achieve the native knee alignment during a total knee arthroplasty (TKA).ObjectiveThe aim of this study was to document the intra-observer and inter-observer reliability of the valgus angle determination for distal femur cut from a preoperative digital radiograph in a TKA.MethodsA total of 20 patients with bilateral grade 3-4 primary osteoarthritis were assessed independently by a medical student, five surgeons, of which one was a consultant with more than 20 years of experience, and four residents in varied levels of training. Full-length (pelvis to toes) weight-bearing radiographs of both lower limbs were obtained prior to the surgery. The measurements were made thrice at more than 24 hours interval without any possible knowledge of their own previous measurement or that of other surgeons. We assessed the angle between the mechanical and anatomical axis of both femurs.ResultsThe single measures intraclass correlation was found to be 0.733, showing that there is a moderate reliability among the six raters when single measures were considered, whereas the average measures intraclass correlation was found to be 0.943, showing that there is an excellent reliability among the six raters when average measures were considered.For intra-observer reliability, the single measures intraclass correlation showed that there is a good-to-excellent reliability between the three trials when single measures was considered. The averages measures intraclass correlation showed that there is an excellent reliability between the three trials when average measures was considered.ConclusionA very inexpensive method of determining valgus angle for distal femur cut was found to have a moderate-to-excellent inter-observer reliability and a good-to-excellent intra-observer reliability.

Kinematic alignment-management of deformities and flexion contractures

Kinematic alignment (KA) total knee arthroplasty (TKA) has proven to be aviable alternative to mechanical alignment (MA) TKA. Like any technique, its validity has to encounter challenges. Two of these are flexion contracture and large deformities of the knee. Flexion contracture is commonly treated with posterior capsular release. Often, however, this technique is not sufficient. Many surgeons accustomed to MA techniques and guided by traditional femoral instruments manage the problem by proximalizing the distal femoral cut. However, this has proven to be asurgical mistake that often leads to mid-flex knee instability. KA rules limit this mistake but leave the problem of flexion contracture. In these cases, the surgeon acts on the tibia distalizing the cut and, so as not to create instability in flexion, decreasing the slope. The technique is effective to obtain full extension but often leaves instability at 90°of knee flexion. To avoid this, it is useful to use the so-called "virtuous mistake" strategy, which strictly follows the KA guidelines but undercuts the posterior femoral condyles by 2 mm. Another problem that often limits the use of KA is large deformities. It is necessary to distinguish whether they are intra or extra-articular. In the first case, it is possible to decide whether to use the pure KA technique or to restrict the indication at the level of the tibial cut. In the latter, extraarticular osteotomies or combined procedures (osteotomy plus KA) have to be performed.