Robot-Assisted Total Knee Arthroplasty Accurately Restores the Joint Line and Mechanical Axis. A Prospective Randomised Study

Robot-assisted Total Knee Arthroplasty (TKA) improves the accuracy and precision of component implantation and mechanical axis (MA) alignment. Joint-line restoration in robot-assisted TKA is not widely described and joint-line deviation of > 5 mm results in mid-flexion instability and poor outcomes. We prospectively randomised 60 patients into two groups: 31 patients (robot-assisted), 29 patients (conventional). No MA outliers (> ± 3° from neutral) or notching was noted in the robot-assisted group as compared with 19.4% (P = 0.049) and 10.3% (P = 0.238) respectively in the conventional group. The robot-assisted group had 3.23% joint-line outliers (> 5 mm) as compared to 20.6% in the conventional group (P = 0.049). Robot-assisted TKA produces similar short-term clinical outcomes when compared to conventional methods with reduction of MA alignment and joint-line deviation outliers.     

Femoral Anterior Tangent Line of the Osteoarthritic Knee for Determining Rotational Alignment of the Femoral Component in Total Knee Arthroplasty

Several reference axes have been used to establish femoral rotational alignment during total knee arthroplasty. The current study examined the configuration of the anterior surface of the femur immediately proximal to the trochlea as an alternative rotational landmark. An analysis of computed tomographic images of 150 knees with osteoarthritis indicated that the configuration of the surface is mostly flat or slightly depressed, and the line tangential to the surface (femoral anterior tangent line; FAT line) was consistently determined to be 12.2° ± 3.6° internally rotated to the transepicondylar axis. This value was relatively constant and as reliable as the femoral anteroposterior axis for determining rotational alignment. In addition, the FAT line was not affected by the degree of the varus-valgus deformity of the osteoarthritic knees.     

Image-Free Robotic-Assisted Total Knee Arthroplasty Improves Implant Alignment Accuracy: A Cadaveric Study

BackgroundImproving resection accuracy and eliminating outliers in total knee arthroplasty (TKA) is important to improving patient outcomes regardless of alignment philosophy. Robotic-assisted surgical systems improve resection accuracy and reproducibility compared to conventional instrumentation. Some systems require preoperative imaging while others rely on intraoperative anatomic landmarks. We hypothesized that the alignment accuracy of a novel image-free robotic-assisted surgical system would be equivalent or better than conventional instrumentation with fewer outliers.MethodsForty cadaveric specimens were used in this study. Five orthopedic surgeons performed 8 bilateral TKAs each, using the VELYS Robotic-Assisted System (DePuy Synthes) and conventional instrumentation on contralateral knees. Pre-resection and postresection computed tomography scans, along with optical scans of the implant positions were performed to quantify resection accuracies relative to the alignment targets recorded intraoperatively.ResultsThe robotic-assisted cohort demonstrated smaller resection errors compared to conventional instrumentation in femoral coronal alignment (0.63° ± 0.50° vs 1.39° ± 0.95°, P < .001), femoral sagittal alignment (1.21° ± 0.90° vs 3.27° ± 2.51°, P < .001), and tibial coronal alignment (0.93° ± 0.72° vs 1.65° ± 1.29°, P = .001). All other resection angle accuracies were equivalent. Similar improvements were found in the femoral implant coronal alignment (0.89° ± 0.82° vs 1.42° ± 1.15°, P = .011), femoral implant sagittal alignment (1.51° ± 1.08° vs 2.49° ± 2.10°, P = .006), and tibial implant coronal alignment (1.31° ± 0.84° vs 2.03° ± 1.44°, P = .004). The robotic-assisted cohort had fewer outliers (errors >3°) for all angular resection alignments.ConclusionThis in vitro study demonstrated that image-free robotic-assisted TKA can improve alignment accuracy compared to conventional instrumentation and reduce the incidence of outliers.     

Are Gender-Specific Femoral Implants for Total Knee Arthroplasty Necessary?

The purpose of this study was to determine the effect of gender on epiphyseal morphology and using this information to determine if an implant product line with a single width provides sufficient bone coverage for the entire population of knees being replaced. Morphology of the distal femoral epiphysis from 420 continuous knees was acquired with a surgical navigation system during primary TKA. A three-dimensional model of the distal femur was generated and used to determine the anterioposterior (AP) and mediolateral (ML) dimensions on 19 different virtual knee sections. Female knees had smaller AP and ML dimensions than male knees. The ML width of the distal femoral epiphysis was associated with femur length, not gender. Measurements derived from surgical navigation confirm that distal femoral epiphysis dimensions are related to femur length only independently of gender.     

Distal Femoral Rotation Correlates With Proximal Tibial Joint Line Obliquity: A Consideration for Kinematic Total Knee Arthroplasty

Background

We hypothesized that there is a correlation between the distal femoral rotation and proximal tibial joint line obliquity in nonarthritic knees. This has significance for kinematic knee arthroplasty, in which the target knee alignment desired approximates the knee before disease.

Intraoperative Measurements of Femoral Anterior Tangent (FAT) Line for Determining the Rotational Alignment of Femoral Component of Total Knee Arthroplasty

Previously, we reported using CT images that the anterior surface of the femur immediately proximal to the trochlea and its tangent line (femoral anterior tangent line; FAT line) could be used as a good index of the femoral rotation. In this study, we developed a jig that allowed us to measure the FAT line during surgery, and we examine the relation between preoperative and intraoperative measurement values. The results indicated that the average intraoperative measurement value of the ‘surgical’ FAT line was 9.8° ± 3.2° internally rotated using surgical transepicondylar axis reference. This value significantly correlated to preoperative FAT line/clinical transepicondylar axis angle. These findings demonstrated that FAT line is a useful index for appropriate rotational alignment of femoral component, both before and during TKA.     

Distal Femoral Arthroplasty for the Treatment of Periprosthetic Fractures After Total Knee Arthroplasty

Periprosthetic fractures after total knee arthroplasty present substantial challenge if associated with poor bone stock, fracture comminution, and loose or damaged components. Revision total knee arthroplasty with distal femoral arthroplasty is often necessary in these injuries. We reviewed 20 patients (22 knees) with a mean age of 69.5 years who underwent revision with distal femoral arthroplasty fracture. Patients were followed for an average of 58.6 months. At the latest follow-up, the mean Knee Society knee and functional score were 82.8 and 40, and the Short Form 36 mean physical functioning and mental functioning scores were 55.8 and 65.6, respectively. There were 10 postoperative complications with 5 patients requiring additional surgery. Distal femoral arthroplasty seems to be a viable option for complex periprosthetic femoral fractures after total knee arthroplasty. However, considering the relatively high rate of complications, this procedure should be reserved for patients where alternative treatments are not possible.     

Plain Radiograph Fails to Reflect the Alignment and Advantages of Navigation in Total Knee Arthroplasty

The study purposed to determine if a navigation in total knee arthroplasty (TKA) leads to accurate limb alignment and component position than the conventional technique as measured by full length standing radiographs and to evaluate the correlation between navigation and radiographic measurements. A total of 160 knees underwent navigation (n = 80) or conventional (n = 80) TKAs. The frontal femoral alignment was more accurate in navigation TKAs, whereas mechanical axis and frontal tibial alignment were similar in both techniques. Although the intraoperative navigation alignment showed no outliers, postoperative radiographic measure resulted as much as 20% of outliers, and there was no correlation between the two measurements. This lack of correlation and inherent limitations in measuring TKA alignment may bring to question if plain radiograph are useful to determine if alignment achieved by navigation is accurate.     

Evaluation of Total Knee Arthroplasty Performed With and Without Computer Navigation: A Bilateral Total Knee Arthroplasty Study

Sequential bilateral total knee arthroplasty performed on 54 patients utilizing navigation (CAS-TKA) in one knee and traditional instrumentation (T-TKA) in the contralateral knee was reviewed at a mean follow-up duration of 2.5 years. There were no differences with regard to KSS, ROM, postoperative anatomic alignment, mechanical axis, or tibial angle. There was a statistically significant decrease in outliers for the CAS-TKA group with respect to anatomic alignment (3.7% vs. 17.0%, P = 0.024), mechanical axis (6.1 vs. 20.4%, P = 0.037) and tibial component alignment (0% vs. 7.5%, P = 0.042). There is no apparent benefit of CAS-TKA with regards to KSS, ROM, or alignment in the hands of fellowship-trained total joint specialists. The clinical relevance of reduced outliers in the CAS-TKA group is unknown with the current follow-up interval.     

Intraoperative Measurements of Joint Line Changes Using Computer Navigation Do Not Correlate With Postoperative Radiographic Measurements in Total Knee Arthroplasty

Background

The adverse effects of joint line (JL) changes on kinematics and outcomes of total knee arthroplasty (TKA) have been studied. Some authors have quantified JL changes using intraoperative data from computer navigation, despite no studies validating these measurements to date. We designed a prospective study to determine whether intraoperative measurements of JL changes using computer navigation correlate with measurements obtained on weight-bearing radiographs postoperatively.

Computer-Assisted Navigation Software Advancements Improve the Accuracy of Total Knee Arthroplasty

The purpose of this study was to evaluate the effectiveness of software advancements in improving total knee component positioning and limb alignment when using computer-aided navigation. A single total joint fellowship-trained surgeon performed unilateral total knee arthroplasty on 315 patients using conventional techniques or with assistance from computer navigation software. Preoperative and postoperative x-ray measurements were taken and analyzed. Our previous work demonstrated a statistically significant improvement (P < .02) in limb alignment (±3° of biomechanical neutral) when using version 2.0 software (93%) when compared with conventional techniques (82%). Further improvement was demonstrated with the version 3.1 software (99%, P < .03). The tourniquet times were recorded for each group and showed a significant improvement with the 3.1 software (conventional = 74 minutes, 2.0 navigation = 90 minutes, and 3.1 navigation = 73 minutes). The Stryker 2.0 software (Stryker Orthopedics, Mahwah, NJ) tourniquet time was statistically significantly longer than either the conventional or the 3.1 group (P < .001). Outcomes-based studies will be required to see if these factors will lead to improved patient function and/or prolonged prosthetic survival rates.     

Effect of Total Knee Arthroplasty on Coronal Alignment of the Ankle Joint

BackgroundThe effect of total knee arthroplasty (TKA) on the ankle joint is not entirely clear. The purpose of this study is to assess postoperative changes in the coronal alignment of the ankle joint in patients undergoing TKA for various degrees of knee deformity.MethodsThis retrospective study included 107 patients who had undergone TKA for primary osteoarthritis. In all cases, preoperative coronal alignment deformity of the knee was corrected in an attempt to restore the native mechanical axis of the knee. Patients were stratified into 3 groups according to the degree of knee coronal alignment correction achieved intraoperatively: group 1 (<10° varus/valgus correction, n = 60), group 2 (≥10° varus correction, n = 30), and group 3 (≥10° valgus correction, n = 17). Knee/ankle alignment angles were measured on full-length, standing anteroposterior imaging preoperatively and postoperatively and included the following: hip-knee-ankle angle, tibial plafond inclination (TPI), talar inclination (TI), and tibiotalar tilt angle.ResultsSignificant changes in ankle alignment, specifically with regard to TPI (9.5° ± 6.9°, P < .01) and TI (8.8° ± 8.8°, P = .03) were noted in the ≥10° valgus correction group compared to the other 2 groups. Regardless of the degree of knee deformity correction, TKA did not lead to significant changes in the tibiotalar tilt angle.ConclusionA correction of ≥10° in a genu valgum deformity can affect ankle joint alignment, leading to alterations in TPI and TI. These findings need to be taken into consideration in assessing candidates for TKA as a possible cause of postoperative ankle pain.     

Variability in the Relationship Between the Distal Femoral Mechanical and Anatomical Axes in Patients Undergoing Primary Total Knee Arthroplasty

Currently, an intramedullary (IM) guide is often used for performing the distal femoral resection in total knee arthroplasty (TKA). However, this method assumes that in most patients, the distal femoral mechanical–anatomical angle (FMAA) is 5°. Preoperative, standing, AP hip-to-ankle radiographs were reviewed in 493 patients undergoing primary TKA, and the FMAA was digitally measured. Correlation coefficients relative to several radiographic measurements, along with demographic variables, were performed. A significant number of patients (28.6%) had an FMAA outside the range of 5° ± 2° (range 2.0°–9.6°). The only measurement demonstrating a fair/moderate correlation with the FMAA was the neck–shaft angle (r = − 0.55). Using an IM resection guide, without obtaining AP hip-to-ankle radiographs to determine each patient's true FMAA, may lead to malalignment of the femoral component.     

Navigation-Assisted Total Knee Arthroplasty for the Knee Retaining Femoral Intramedullary Nail, and Distal Femoral Plate and Screws

Proper ligament balancing, restoration of the mechanical axis and component alignment are essential for the success and longevity of a prosthesis. In conventional total knee arthroplasty (TKA), an intramedullary guide is used to improve the alignment. An extramedullary guide can be used in cases of severe femoral bowing or intramedullary nailing but its use is more subjective and relies on the surgeon''s experience. This paper reports two successful cases of navigation-assisted TKA for severe right knee osteoarthritis retaining a femoral intrameullary nail, and left knee osteoarthritis retaining a distal femoral plate.     

Primary Total Knee Arthroplasty in Infection Sequelae About the Native Knee

The aim of this study is to assess the results of primary total knee arthroplasty (TKA) after bone or joint sepsis about the native knee and to analyze the risk factors of periprosthetic infection. Sixty-two patients (62 knees), considered to have prior sepsis history to be resolved, underwent primary TKA and were followed during a mean of 6.1 years (range, 2–10.4 years). Of the 62 patients, periprosthetic infection occurred in 6 after primary TKA (9.7%). Five of 6 patients grew the same organism as prior infection. The number of prior surgeries undertaken for deep infection was found to be an independent risk factor of periprosthetic infection.     

A Comparison of Classical and Anatomical Total Knee Alignment Methods in Robotic Total Knee Arthroplasty : Classical and Anatomical Knee Alignment Methods in TKA

The purpose of this study was to compare the clinical and radiological outcomes achieved using classical and anatomical alignment methods in primary total knee arthroplasty (TKA). One hundred and seventeen patients were randomly assigned to undergo robotic-assisted TKA using either the classical (56 patients) or the anatomical alignment method (61 patients). Clinical outcomes including varus and valgus laxities, ROM, HSS and WOMAC scores and radiological outcomes were evaluated after a minimum follow-up of 2 years. Varus and valgus laxity assessments showed no significant inter-group differences (P > 0.05). Moreover, no significant differences were observed in ROM, HSS and WOMAC scores (P > 0.05). We could not find any significant difference in mechanical alignment of the lower limb. The results of this study show that two alignment methods provide comparable clinical and radiological outcomes after primary TKA.     

Functional Outcome of Total Knee Arthroplasty After Periprosthetic Distal Femoral Fracture

A prospective matched cohort study was performed to compare functional outcomes between 28 patients with periprosthetic femoral fractures and 28 with primary total knee arthroplasties (TKA). The mean follow-up was 6.7 years (range, 5–9). Radiographic osteopenia was a predisposing factor, but not notching, body mass index, or preinjury knee scores or motion. At last follow-up, the Knee Society scores, knee motion, Womac, and SF-12 were significantly lower in the fracture group, and were significantly decreased compared to the preinjury status. We found that periprosthetic distal femoral fracture after TKA worsens functional outcomes at the medium term, but arthroplasty complication and survival rates were similar in both groups.     

Femoral Bow Predicts Postoperative Malalignment in Revision Total Knee Arthroplasty

Diaphyseal bowing may compromise axial alignment in revision total knee arthroplasty (TKA). 277 patients undergoing revision TKA were evaluated for coronal bowing and hip–knee–ankle (HKA) axis. The mean femoral bow was 1.52° ± 0.18° varus (− 10.1° to + 8.4°). The mean tibial bow was 1.25° ± 0.13° valgus (− 5.9° to + 10°). HKA axis averaged 3.08° ± 0.35° varus preoperatively compared to 0.86° ± 0.25° varus postoperatively. Inter-rater and intra-rater reliability was high. Femoral bow greater than 4° significantly correlated with postoperative HKA axis malalignment (r = 0.402, P = 0.008). 39.7% of patients deviated 3° or greater from a neutral mechanical axis with a significant difference in femoral bow (0.94° ± 0.31°, P = 0.003). Diaphyseal bowing clearly has an important effect on postoperative limb alignment in revision TKA.     

The Effect of Joint Line Elevation on Patient-Reported Outcomes After Contemporary Revision Total Knee Arthroplasty

BackgroundJoint line elevation in revision total knee arthroplasty (rTKA) is considered a risk factor for inferior outcomes, engendering a dogmatic protocol of joint line restoration. However, this precedent is based on historical data using rudimentary revision systems and unvalidated outcome measures. This study’s purpose was to evaluate the effect of joint line height elevation on validated patient-reported outcome measures (PROMs) using modern revision implants.MethodsA total of 327 rTKAs performed at a single institution were reviewed. Surgical technique prioritized flexion-extension gap balancing and accepted joint line elevation if necessary to achieve a balanced flexion space. Radiographic measurements included changes in joint line height (from preoperative and calculated “intended” anatomic/native) and change in posterior condylar offset. Prospectively collected PROMs were evaluated using multivariate regression.ResultsThe mean joint line elevation from preoperative and “intended” to postoperative joint line was 4.9 ± 5.7 mm and 7.2 ± 6.6 mm, respectively. The mean increase in posterior condylar offset was 1.0 ± 4.6 mm. Patients within ±5 mm of preoperative joint line height were 3.88× more likely to achieve the substantial clinical benefit for Knee Injury and Osteoarthritis Outcome Score for Joint Replacement (P = .004). An increase from intended joint line height >5 mm was not associated with differences in any other PROMs (P ≥ .165).ConclusionsIn contemporary rTKA, recreating the joint line within 5 mm of preoperative improves knee-specific health outcomes. These data support approximating native joint line height as a viable technique to optimize flexion gap balance and subsequent patient outcomes in rTKA.Level of EvidenceLevel III retrospective cohort study.     

The Impact of Mechanical and Restricted Kinematic Alignment on Knee Anatomy in Total Knee Arthroplasty

Background

Total knee arthroplasty (TKA), aiming at neutral mechanical alignment (MA), inevitably modifies the patient's native knee anatomy. Another option is kinematic alignment (KA), which aims to restore the original anatomy of the knee. The aim of this study was to evaluate the variations in lower limb anatomy of a patient population scheduled for TKA, and to assess the use of a restricted KA TKA protocol and compare the resulting anatomic modifications with the standard MA technique.