Medial Posterior Condylar Offset Research Articles

Measurement of femoral posterior condylar offset and posterior tibial slope in normal knees based on 3D reconstruction

BackgroundFemoral posterior condylar offset (PCO) and posterior tibial slope (PTS) are important for postoperative range of motion after total knee arthroplasty (TKA). However, normative data of PCO and PTS and the correlation between them among healthy populations remain to be elucidated. The purpose of this study was to determine PCO and PTS in normal knees, and to identify the correlation between them.MethodsEighty healthy volunteers were recruited. CT scans were performed followed by three-dimensional reconstruction. PCO and PTS were measured and analyzed, as well as the correlation between them.ResultsPTS averaged 6.78° and 6.11°, on the medial and lateral side respectively (P = 0.002). Medial PCO was greater than lateral (29.2 vs. 23.8 mm, P < 0.001). Both medial and lateral PCO of male were larger than female. On the contrary, male medial PTS was smaller than female, while there was no significant difference of lateral PTS between genders. There was an inverse correlation between medial PCO and PTS, but not lateral.ConclusionsSignificant differences exhibited between medial and lateral compartments, genders, and among individuals. An inverse correlation exists between PCO and PTS in the medial compartment. These results improve our understanding of the morphology and biomechanics of normal knees, and subsequently for optimising prosthetic design and surgical techniques.

Flexion First Balancer: description of new technique in TKA to reproduce joint line and pre-disease mechanical alignment

A considerable proportion of patients (19%) are dissatisfied after total knee arthroplasty (TKA). Possible factors contributing to this dissatisfaction are decreased posterior condylar offset (PCO) with subsequent joint line elevation, leading to mid-flexion instability. Secondly, the pre-disease mechanical alignment is changed into a neutral alignment. The Flexion First Balancer was developed to avoid these problems. This technique aims to maintain MCL isometry by restoring medial PCO and medial joint line to its pre-disease level. Also, to reconstruct the pre-disease mechanical alignment by adjusting the distal femoral angle. In this study we provide a detailed technical overview of the Flexion First Balancer technique.

What Is the Possible Impact of High Variability of Distal Femoral Geometry on TKA? A CT Data Analysis of 24,042 Knees.

Previous studies analyzing femoral components of TKAs have demonstrated the limited ability of these components to accommodate size variations seen in the patient population, particularly width and femoral offset. The purpose of this study was to use a large data set of knee CT scans (1) to determine the variations in the distal and posterior femoral geometries and to determine whether there is a correlation between distal condylar offset and posterior femoral offset as a potential parameter for symmetry/asymmetry; and (2) to evaluate what proportion of knees would have a substantial mismatch between the implant's size or shape and the patient's anatomy if a femoral component of a modern standard TKA of symmetric (sTKA) or asymmetric (asTKA) designs were to be used. A retrospective study was performed on 24,042 data sets that were generated during the design phase for a customized TKA implant. This data set was drawn from European and US-American patients. Measurements recorded for the femur included the overall AP and mediolateral (ML) widths, widths of the lateral condyle and the medial condyle, the distal condylar offset (DCO) between the lateral and medial condyles in the superoinferior direction, and the posterior femoral offset (PFO) as the difference between the medial and lateral posterior condylar offset (PCO) measured in the AP direction. A consecutively collected subset of 2367 data sets was further evaluated to determine the difference between the individual AP and ML dimensions of the femur with that of modern TKA designs using two commercially available implants from different vendors. We observed a high degree of variability in AP and ML widths as well as in DCO and PFO. Also, we found no correlation between DCO and PCO of the knees studied. Instances of a patient having a small DCO and higher PCO were commonly seen. Analysis of the DFOs revealed that overall, 62% (14,906 of 24,042) of knees exhibited DCO > 1 mm and 83% (19,955 of 24,042) of femurs exhibited a > 2-mm difference between the lateral and medial PCO. Concerning AP and ML measurements, 23% (544 of 2367) and 25% (592 of 2367) would have a mismatch between the patient's bony anatomy and the dimensions of the femoral component of ± 3 mm if they would have undergone a modern standard sTKA or asTKA design, respectively. Analysis of a large number of CT scans of the knee showed that a high degree of variability exists in AP and ML widths as well as in DCO and PFO. These findings suggest that it is possible that a greater degree of customization could result in surgeons performing fewer soft tissue releases and medial resections than now are being done to fit a fixed-geometry implant into a highly variable patient population. However, as an imaging study, it cannot support one approach to TKA over another; comparative studies that assess patient-reported outcomes and survivorship will be needed to help surgeons decide among sTKA, asTKA, and customized TKA.

Gender differences in morphology exist in posterior condylar offsets of the knee in Korean population.

This study aimed to analyze the morphometric data from magnetic resonance images of arthritic knees in Korean adults, and to identify the existence of morphological differences of femoral posterior condylar offset (PCO) between genders. The differences in anthropometric PCO data in 975 patients (825 female and 150 male) were evaluated. The distances from the anterior and posterior femoral shaft cortex line to the most posterior femoral condyle tangent line were defined as the anterior-posterior dimension (AP) and the PCO. The PCO ratio (PCOR) was calculated as PCO/AP. The medial PCO was greater than the lateral PCO (26.3 ± 2.2 vs. 24.3 ± 2.3mm, p < 0.01). This difference was observed in both female patients (medial: 26.2 ± 2.2mm vs. lateral: 24.2 ± 2.2mm, p < 0.01) and male patients (medial: 26.8 ± 2.3mm vs. lateral: 24.8 ± 2.4mm, p < 0.01). The medial and lateral PCO values were also greater in male patients than in female ones (p < 0.01). In contrast, PCOR was greater in female patients than in male ones, both in the medial and lateral femoral condyles (p < 0.01). It was shown that medial and lateral PCO and PCOR were asymmetric, and that there was gender difference in Korean population in our study. In addition, our data showed that the PCOR of contemporary TKAs may be small for Asian patients that may not be sufficient to meet the needs of the Korean patient population. These results confirm that a gender-specific femoral component design is necessary to recreate the PCO for male and female Asian populations. Non-consecutive patients, Level III.

Does medial-to-lateral femoral posterior condylar offset difference effect accuracy of established reference axes for determining femoral component rotation in total knee arthroplasty?

Aims and Objectives: The femoral posterior condylar offset (PCO) has been viewed with increased significance for knee joint movement patterns and has been discussed for its possible implication for femoral component rotation in total knee arthroplasty (TKA). However, a great inter-individual variability in medial and lateral PCO size has also been demonstrated. Though the medial and lateral PCO seem closely related to the functional flexion axis (fFA), determined by the radius curvature of the medial and lateral femoral condyle, the relationship of both parameters considering their impact on the accuracy of established reference axes for determining femoral component rotation in TKA remains unknown. The objective of this paper was, therefore, to compare the individual fFA with the anatomical and surgical transepicondylar axis (aTEA; sTEA) and with the posterior condylar axis (PCA) considering the medial and lateral PCO size. It was hypothesized that the disparity of the PCO influences the accuracy of the sTEA, aTEA, and PCA for determination of femoral component rotation in TKA. Materials and Methods: MRI investigations of 56 consecutive non-arthritic knee joints (male/female 28/28; mean age 22.8 years; range 16-59 years) were used for this study. Coronal, sagittal and transverse MRI images were used to measure the medial and lateral PCO and to determine the fFA, aTEA, sTEA, and PCA for each subject as described previously. A paired two-tailed t-test was used to test for differences between the medial and lateral PCO sizes. Deviation of the aTEA, sTEA and PCA from the fFA were analyzed with a one-sample t-test. Correlation analysis (Pearson r) was used to determine the relationship between the PCO ratio (medial-to-lateral PCO) and the deviation of the aTEA, sTEA and PCA from the fFA in each subject. The level of significance was set at 0.05. Results: The mean medial PCO was 34.0 mm (90%CI 28.72-30.55 mm; range 26.3 to 44.7 mm) and the lateral PCO averaged 29.64 mm (90%CI 30.3-31.4 mm; range 14.3 to 39.1 mm) (p<0.0001). The medial-to-lateral PCO ratio was 1.16 (90%CI 1.13 -1.19; range 0.93 to 1.85). The aTEA showed an increased external rotation in relation to the fFA throughout the whole PCO ratio range (mean deviation 4.2°; 95%CI 3.8°-4.6°; range -4.2° to 10.1°; p<0.0001), whereas the sTEA tends towards a slight but significant internal rotation throughout the PCO ratio range (mean deviation -1.6°; 95%CI -2.1°- -1.2°; range -8.1° to 4.8°; p<0.0001). The PCA showed the best conformity with the fFA (mean difference -0.2°; 95%CI -0.5°-0.2°; range -6° to 5.3°; p=0.36) and was most robust against medial-to-lateral PCO variations. A weak but significant positive correlation between the PCO ratio and the deviation from the fFA was solely found for the sTEA (r=0.28; p=0.042). Conclusion: Differences of the medial and lateral PCO size are a common finding. The PCA had the best match with the fFA, regardless of medial-to-lateral PCO disparity. Only the sTEA was influenced to a small extent by variation of the PCO-ratio.

Interactive effect of femoral posterior condylar offset and tibial posterior slope on knee flexion in posterior cruciate ligament-substituting total knee arthroplasty

BackgroundThis work aimed to evaluate the changes in the femoral posterior condylar offset (PCO) and tibial slope after posterior cruciate ligament (PCL)-substituting total knee arthroplasty (TKA), and to address the presence of any interactive effect between the two on knee flexion. MethodsFifty-two PCL-substituting TKAs were performed using a posterior referencing system. Three-dimensional reconstructed computed tomographic (CT) images were used to evaluate PCO and tibial slope before and after arthroplasty. Range of motion and clinical scores were evaluated at a mean of 3.1years postoperatively. Multivariate linear model with interaction terms was used to evaluate and compare the relationships among changes in PCO, tibial slope, and postoperative knee flexion angles. ResultsThe degree of change in PCO was greater in the lateral condyle than in the medial condyle (3.1±2.5mm and −0.5±2.8mm, respectively). Postoperative medial and lateral tibial slopes were 1.4°±1.8 and 1.4°±2.0, respectively. The mean degree of postoperative knee flexion was 125°. Analysis with interaction terms and covariate adjustment demonstrated that medial PCO and tibial slope were significantly related to knee flexion with interactive effect (P=0.011). In cases with <3° posterior tibial slope, the postoperative PCO was positively correlated to the degree of knee flexion angle. However, in cases with >3° tibial slope, PCO was negatively correlated to knee flexion. ConclusionMedial femoral PCO and tibial slope showed interactive effect on knee flexion after PCL-substituting TKAs. Reconstitution of the proper PCO and avoiding excessive tibial slope may be necessary.

Sagittal magnetic resonance imaging-scan orientation significantly influences accuracy of femoral posterior condylar offset measurement.

In total knee arthroplasty the femoral posterior condylar offset (PCO) may serve as a potential branch for correct femoral component positioning. The technique of adjusting the sagittal magnetic resonance imaging (MRI)-scan on which it is measured has not been investigated in previous literature, but may be subject to variances due to knee joint positioning or axial localizer scan angulation. The purpose of this study was to investigate the effect of simulated femur rotation on the accuracy of PCO measurement. Ten asymptomatic knee joints underwent MRI investigations. A sagittal plane perpendicular to the transepicondylar axis was defined as the true-sagittal plane (tsP). Sagittal images were reformatted in the tsP and angulated by 5° and - 5° in medial and lateral direction. In total each knee received three scans in 0°, 5° and - 5° axial localizer scan angulation. Medial and lateral PCO measurement was performed in each MRI-scan angulation. Simulated external rotation decreased medial PCO size by 1.7mm (95% CI 0.5994-3.127) (p = 0.012), and simulated internal rotation increased medial PCO size by 2.1mm (95% CI 1.142-2.994) (p = 0.001). Lateral PCO size increased by 1.9mm (95% CI 0.5660-3.412) and decreased by 2.1mm (95% CI 1.142-2.994) with simulated external and internal rotation, respectively (p = 0.011; p = 0.0007). This study shows the high sensitivity of medial and lateral PCO measurements to small changes of MRI axial localizer scan angulations simulating minor degrees of internal or external femur rotation. Thus, absolute PCO values should be interpreted with caution if the sagittal image acquisition is not standardized.

Important Differences Exist in Posterior Condylar Offsets in an Osteological Collection of 1,058 Femurs

Posterior condylar offset (PCO) has important implications in total knee arthroplasty (TKA) function and design. In an osteological study of 1,058 femurs, we measured PCO using two separate techniques with a 3D digitizer. Measurements were standardized for the size of the femur. The medial PCO was greater than lateral PCO (32.6mm vs. 31.2mm, P<0.0001). In 53% of individuals, the medial PCO differed between sides by more than 2mm. Age did not affect standardized medial or lateral PCO. Compared with African-Americans, Caucasians had a larger standardized medial (1.3mm vs. 1.2mm, P=0.006) and lateral (1.1mm vs. 1.0mm, P=0.004) PCOs. The standardized medial (1.2mm vs. 1.3mm, P=0.073), and lateral (1.1mm vs. 1.1mm, P=0.098), PCO did not differ between men and women, respectively.

Plain Radiographs Underestimate the Asymmetry of the Posterior Condylar Offset of the Knee Compared With MRI

Restoration of posterior condylar offset (PCO) during total knee arthroplasty is essential to maximize range of motion, prevent impingement, and minimize flexion instability. Previously, PCO was determined with lateral radiographs, which could not distinguish the asymmetries between the femoral condyles. MRI can independently measure both medial and lateral PCO. The purpose of this study is to determine the normal PCO of the knee, to establish the differences in medial and lateral PCO, and to compare PCO measurements obtained from radiographs versus those obtained from MRI. We identified 32 patients without a history of prior knee pathology who had both plain radiographs and MRI scans of the same knee performed. The PCO was measured on lateral radiographs and compared with MRI measurements using a novel three-dimensional protocol. By MRI, the mean medial PCO was 29 (± 3) mm and the mean lateral PCO was 26 (± 3) mm; both values were greater (p < 0.001 and p = 0.03, respectively) than the mean radiographic PCO of 25 (± 2) mm. The medial PCO, as measured by MRI, was significantly greater than the lateral PCO (p < 0.001). Plain radiographs underestimate PCO as well as the asymmetry of the medial and lateral PCO compared with MRI. This discrepancy is the result of both articular cartilage thickness and the anatomic differences between medial and lateral condyles. Designers of knee prostheses and instrumentation should take these differences into account.

Changes in the Medial and Lateral Posterior Condylar Offset in Total Knee Arthroplasty

The purpose of this study was to clarify the changes between preoperation and postoperation in each posterior condylar offset (PCO) using computed tomography (CT) and to compare them to conventional radiographic (x-ray) evaluation in total knee arthroplasty. One hundred nine knees in 97 patients were evaluated. The medial PCO was significantly larger before surgery. The lateral PCO was significantly larger after surgery. Changes in the PCO on x-ray showed no significant correlation with the changes observed in the CT-evaluated medial ( R = 0.028) and lateral PCO ( R = 0.190). Changes in PCO observed by x-ray did not reflect those of the medial or lateral condyles on CT. We recommend CT-based evaluation of PCO by condyle when assessing the influence of PCO on range of motion following total knee arthroplasty.