Reliability of the transepicondylar line as a parameter of femoral axial alignment

An assessment of femoral rotational alignment of mini-incision total knee arthroplasty: A comparison based on the transepicondylar line from the kneeling view and the intraoperative posterior condylar line

BACKGROUND

Rotational alignment of the distal femur is important in total knee arthroplasty. The purpose of this study is to use a roentgenographic technique to evaluate the accuracy of mini-incision total knee arthroplasty (MIS TKA) performed based on the transepicondylar line from the kneeling view.

METHODS

Totally 32 patients (aged from 64 to 80 years with an average of 70.9 years) with 46 cases of knee osteoarthritis received MIS TKA were registered. Before surgery, the condylar twist angle was measured from the kneeling view. The bone cut for the external rotation was completed, with regard to the condylar twist angle. The control group including 26 patients (aged from 50 to 89 years with an average of 69.7 years) with 42 cases of knee osteoarthritis underwent TKA with built-in cutting jig design 3 degrees of femoral external rotation. This study is a prospective continuous-time duration analysis study. The level of evidence is IIc.

RESULTS

The mean condylar twist angle was 5.1° in the experimental group and 5.4° in the control group. The mean postoperative angle between the clinical epicondylar axis and the posterior condylar line of the femoral component was 0.46°. The same postoperative angle of the built-in external rotation in the control group was 2.7°. The condylar twist angle was significantly more accurate than the built-in design.

CONCLUSION

Our result substantiates that the kneeling view is practicable and reproducible as the cutting reference for femoral external rotation. The accuracy of the kneeling view shows that the epicondylar axis can be used in smaller wound surgery, such as MIS TKA.

LEVEL OF EVIDENCE

Level IIc.

Influence of posterior lateral femoral condyle geometry on patellar dislocation

INTRODUCTION

Patellar instability is a condition with multifactorial aetiology, potentially involving soft tissue characteristics, the bony anatomy of the patella, femur and tibia, and alignment of the lower limb. The shape of the distal femur and patellofemoral joint has been frequently studied using plain orthogonal and skyline radiographs. We investigated a possible contribution of hypoplasia of the lateral femoral condyle in the axial plane to patellar instability.

METHODS

The geometry of the distal femur and alignment of the lower limb on plain radiographs and MRI scans in 25 young adult patients with patellar instability was measured, and compared to a control group of 75 age-matched patients. Measurements were validated by intra-observer and inter-observer reliability studies, and multivariate analysis was used to compare the groups. Cases with and without high Beighton score or knee hyperextension were also compared.

RESULTS

The anatomical posterior condylar angle, anterior condylar angle and sulcus angle on axial MRI scans showed insignificant differences between groups. The Blackburne-Peel ratio, anatomical femoro-tibial angle and femoral joint angle showed significant differences between groups, but not the tibial plateau angle. There was a significant correlation between posterior condylar angle and valgus knee alignment. In cases with joint hypermobility, femoral joint angle was significantly increased and posterior condylar angle was significantly decreased.

CONCLUSIONS

Multiplanar hypoplasia of the lateral femoral condyle resulting in a valgus knee is a risk factor for patellar instability in young patients without osteoarthritis or joint hypermobility. Isolated posterior lateral condyle hypoplasia appears to be unrelated to patellar instability.

The application of a three-column internal fixation system with anatomical locking plates on comminuted fractures of the tibial plateau

AIM

The purpose of this study was to describe the operative procedures and clinical outcomes of a new three-column internal fixation system with anatomical locking plates on the tibial plateau to treat complex three-column fractures of the tibial plateau.

METHODS

From June 2011 to May 2015, 14 patients with complex three-column fractures of the tibial plateau were treated with reduction and internal fixation through an anterolateral approach combined with a posteromedial approach. The patients were randomly divided into two groups: a control group which included seven cases using common locking plates, and an experimental group which included seven cases with a new three-column internal fixation system with anatomical locking plates.

RESULTS

The mean operation time of the control group was 280.7 ± 53.7 minutes, which was 215.0 ± 49.1 minutes in the experimental group. The mean intra-operative blood loss of the control group was 692.8 ± 183.5 ml, which was 471.4 ± 138.0 ml in the experimental group. The difference was statistically significant between the two groups above. The differences were not statistically significant between the following mean numbers of the two groups: Rasmussen score immediately after operation; active extension-flexion degrees of knee joint at three and 12 months post-operatively; tibial plateau varus angle (TPA) and posterior slope angle (PA) immediately after operation, at three and at 12 months post-operatively; HSS (The Hospital for Special Surgery) knee-rating score at 12 months post-operatively. All fractures healed.

CONCLUSION

A three-column internal fixation system with anatomical locking plates on tibial plateau is an effective and safe tool to treat complex three-column fractures of the tibial plateau and it is more convenient than the common plate.

Finite element analysis of the effect of cannulated screw placement and drilling frequency on femoral neck fracture fixation

BACKGROUND

Positioning of the implanted cannulated screw is paramount for stable femoral neck fracture fixation. To avoid overdrilling, the aim of this study is to determine the optimum configuration of three cannulated screws employed in femoral neck fracture fixation.

METHODS

Using a CT scan from a 28 year old healthy male, several models of femoral neck fracture fixation were developed using finite element analysis. After drilling small holes (in either fixed or random patterns) for screw insertion, the mechanical stresses on the screws were compared for three fracture types.

RESULTS

The inverted isosceles triangle was found to be the best screw configuration. Using finite element analysis, the upper limit of drilling frequency and the maximum stress on the screws for 30°, 50°, and 70° drilling were 14, 16, and 19 times and 46.1MPa, 61.9MPa, and 51.0MPa, respectively. The upper limit of drilling frequency and the maximum stress on the screws for subcapital type, transcervical type, and basicervical type were 14, 16, and 40 times and 24.7MPa, 61.9MPa, and 113.5MPa, respectively.

CONCLUSIONS

Results of this study had supported the use of the inverted isosceles triangle as the best screw configuration for femoral neck fracture fixation. Screw position, Pauwels angle, and drilling frequency can all affect the mechanical strength of femoral neck fracture fixation.

The effect of intra-operative knee flexion angle on determination of graft location in the anatomic double-bundle anterior cruciate ligament reconstruction

Graft tunnel placement is the factor with most influence on the outcome of double-bundle anterior cruciate ligament (ACL) reconstruction. However the final decision for the graft location has to be decided subjectively under arthroscopy, and can be misplaced due to the effect of the knee flexion angle. The displacement of the estimated placement by surgeons from the ACL anatomical attachment is due to the knee's differing knee flexion angle. Eight cadaveric knees and an electromagnetic position recording system were employed. After digitizing the anatomical location of AM and PL bundle center, four experienced surgeons estimated the graft placement repeatedly at 70 degrees , 90 degrees and 110 degrees of knee flexion. The displacements between these two positions were calculated and analyzed separately in antero-posterior and disto-proximal directions. The displacements of the estimated AM bundle placements were 4.7 +/- 3.4 mm at 70 degrees , 4.3 +/- 2.2 mm at 90 degrees , and 6.0 +/- 2.6 mm at 110 degrees , while those of the PL bundle were 4.0 +/- 2.2 mm at 70 degrees , 3.4 +/- 1.9 mm at 90 degrees , and 4.2 +/- 2.5 mm at 110 degrees . The best results were obtained at 90 degrees of knee flexion. Additionally, the estimated placements for both AM and PL bundle were located more distally as the flexion angle increased. Our results imply that the knee should be set at 90 degrees when determining the graft placement in double-bundle reconstruction to prevent misplacement of the graft usually in a disto-proximal direction.

Intraoperative assessment of femoral component rotational alignment in total knee arthroplasty

Poor clinical results following total knee arthroplasty like flexion gap instability or anterior knee pain may be related to femoral component rotational malalignment. The transepicondylar axis has been recommended as a landmark to consistently recreate a balanced flexion gap. However, the reproducibility to identify the transepicondylar axis intraoperatively is low. In this feasibility study we wanted to find out whether fluoroscopy-based CT scans obtained by a motorized mobile C-arm (Iso C 3D) may be useful to asses the transepicondylar axis intraoperatively. Following the femoral resections the Iso C 3D was used intraoperatively in ten knees with mild to severe deformities. On multiplanar reconstructions of the distal femur the clinical epicondylar axis as well as the angle to the posterior cut (condylar twist angle) could be easily measured. The scanning time was 40 s and the extra time needed for the whole setup about five to ten minutes. The Iso C 3D was helpful to intraoperatively identify the transepicondylar axis and the condylar twist angle, especially in cases with severe deformity or dysplasia when standard landmarks are difficult to determine.

Goodness-of-fit determination of femoral knee prosthesis using computer segmentation

35 patients undergoing Total Knee Arthroplasty (TKA) were examined with Computerized Tomography (CT). 3D computer models were created through segmentation of the CT scan data with Materialize MIMICS. Morphological dimensions of ten selected parameters were measured and then compared to two commercial femoral prosthesis design ranges. All measuring techniques were validated and the reproducibility of measuring morphological dimensions with points and planes from landmarks were investigated. The chi2 test was used as a goodness-of-fit parameter to determine which femoral component would achieve the best geometric fit for a specific patient. After establishing a database of geometric values, the method can be used to calculate the dimensions of a customized femoral knee prosthesis to achieve a perfect geometric fit for a TKA patient.

Reference axes for reconstruction of the knee

Knee alignment is an essential problem in reconstructive surgeries of the knee. Quite a number of reference parameters have been suggested to help the surgeons to get proper alignment during operations. In this article, most commonly used reference axes, both for the axial and the rotational, are reviewed, in an attempt to highlight their reliabilities and clinical relevance.

Transepicondylar line and condylar line as parameters for axial alignment in knee arthroplasty

In order to investigate the reliability of the transepicondylar line and the condylar line as indicators for lower limb alignment in knee arthroplasty, the femorotibial angle (FTA), and the angle between the transepicondylar line and the tangential line of tibial plateau (angle epsilon) and condylar-plateau angle (CPA) were measured in 107 (78 patients) full-length standing X-ray films of lower limbs. The mean FTA was measured to be 178.0+/-9.3 degrees, the CPA 1.5+/-8.5 degrees and angle epsilon -0.8+/-8.5 degrees. The correlation between FTA and the CPA was analyzed to be significant with a correlation coefficient of 0.63, while another correlation between FTA and angle epsilon was calculated to be significant with a correlation coefficient of 0.81 at the same time. As a result, the correlation of the latter one was highly significant, having a R2 value of 0.648 (P<0.001), while the R2 of the former was only 0.397 (P<0.001). In conclusion, the transepicondylar line could be considered as a more reliable indicator for lower limb alignment, which may play an important role in ligament balancing and improvement of the guiding system in knee arthroplasty.