Influence of Patellar Tilt Angle in Merchant View on Postoperative Range of Motion in Posterior Cruciate Ligament-Substituting Fixed-Bearing Total Knee Arthroplasty

BACKGROUND: We investigated whether the patellar tilt angle influences the maximum knee flexion after total knee arthroplasty (TKA) performed by using a posterior cruciate ligament-substituting (PS) fixed-bearing prosthesis in patients with relatively loose or tight flexion gap. METHODS: In this prospective cohort study, we followed up 169 patients for at least 2 years after TKA using PS fixed-bearing prosthesis. The patients were divided into two groups according to the flexion gap value—calculated by subtracting the thickness of the final bearing from the flexion gap measured intraoperatively under 200-cN·m force after patellar reduction and insertion of the final femoral and tibial components—into a relatively tight group (group T; 3–6.5 mm) and a relatively loose group (group L; 7–11 mm). Patellar tilt angles and maximum non–weight-bearing active knee flexion angles were assessed postoperatively. Group T was further divided into subgroup Tn if the patellar tilt angle was < 5° and subgroup Tw if the angle was ≥ 5°. Pearson correlation test was used for the correlation analysis of the flexion gap, patellar tilt angle, and postoperative flexion range. RESULTS: The mean postoperative flexion was 137.3° in group T and 137.5° in group L. The mean patellar tilt angle was 6.5° in group T and 6.9° in group L. In group T, a strong negative correlation (r = −0.78, p < 0.05) was observed between the patellar tilt and postoperative flexion range. However, further analysis revealed that only the subgroup Tw showed a strong negative correlation (r = −0.76, p < 0.05). Significant correlations were not found in the subgroup Tn and group L. CONCLUSIONS: In TKA where a relatively tight flexion gap (≤ 6.5 mm) is created because of concerns about postoperative flexion instability due to a loose flexion gap, the patellar tilt angle should be < 5° for maximal postoperative knee flexion.

Flexion Gap Measured in 45 Degrees and 90 Degrees of Hip Flexion Positions during Total Knee Arthroplasty: Measurement by Navigation System

PURPOSE: To evaluate the influence of thigh weight in different hip flexion positions on the knee flexion gap in total knee arthroplasty (TKA). MATERIALS AND METHODS: We evaluated 20 patients (25 knees) with osteoarthritis of the knee that underwent TKA using a navigation system from May 2010 to April 2011. After posterior cruciate ligament sacrificing, complete soft tissue balancing, and fixation of all components with cement, the flexion gaps were measured with the patello-femoral joint reduced. Medial and lateral flexion gaps were measured separately in both the 90degrees-90degrees and 45degrees-90degrees flexion positions of the hip-knee joints. RESULTS: The medial and lateral flexion gaps in the 45degrees-90degrees flexion position of the hip-knee joints were 13.02+/-2.17 mm and 13.12+/-2.21 mm, respectively. The medial and lateral flexion gaps in the 90degrees-90degrees flexion position were 12.92+/-2.03 mm and 13.08+/-2.29 mm, respectively. The flexion gaps showed no significant (p>0.05) differences between the two different hip flexion positions. CONCLUSIONS: Flexion gaps in TKA were not influenced by hip flexion positions (45degrees or 90degrees of flexion). Therefore, soft tissue balancing and polyethylene thickness should not be affected by hip flexion positions during TKA.

Anatomical Assessment of the Distal Femur and Tibia for Optimal Femoral Rotational Alignment in Total Knee Arthroplasty

PURPOSE: This study aimed 1) to identify the rotational axis of the femur that provides a balanced 90degrees flexion space in TKA, 2) to assess the changes in the flexion space in deep flexion, and 3) to assess the changes in rotational alignment, with using the posterior condylar axis (PCA) as a guide, and as the changes are related to asymmetric cartilage erosion of the posterior condyle. MATERIALS AND METHODS: The axial MR images of the distal femur in knee extension and the coronal images of the distal femur and the entire tibia at 90 and 130degrees were examined in 40 healthy adults. RESULTS: The clinical transepicondylar axis (TEA) provides a balanced 90degrees flexion space on average. The balanced flexion space in 90degrees became an asymmetrical space with relative narrowing of the medial side in 130degrees. Every 1 mm of asymmetrical cartilage erosion between the posterior condyles changed the femoral rotation by approximately 1degrees when using the PCA as a guide. CONCLUSION: This study suggests that the clinical TEA is the rotational reference that provides a balanced flexion space. When using the PCA as a rotational reference, a surgeon should consider the potential change in the rotational angle that is caused by asymmetrical cartilage erosion.

Effects of a Posterior Cruciate Ligament Resection on the Flexion-Extension Gap in Total Knee Arthroplasty / 대한정형외과학회잡지

PURPOSE: To assess the effects of a posterior cruciate ligament resection on the tibiofemoral joint gap in total knee arthroplasty. MATERIALS AND METHODS: The effect of a PCL resection on the tibiofemoral joint gap was analyzed prospectively in 58 patients (69 knees) who had undergone TKA between May 2003 and April 2006. The knee was exposed using a modified subvastus approach. The medial soft tissue was released and a tibial cutting was made first. The tibial insertion of a PCL was protected during the tibial resection by inserting a thin osteotome in front of the posterior spine. An extension and flexion gap were measured using a balancer/tensor device (Stryker Howmedica Osteonics(R), Allendale, NJ, USA) under manual maximal stress before and after the PCL resection. The change of the joint line and the posterior inclination on preoperative and postoperative lateral roentgenograms was also assessed. RESULTS: After the PCL resection, the flexion gap and extension gap increased by an average of 3.6+/-1.5 mm and 2.0+/-1.0 mm, respectively. Although the PCL resection resulted in an increasing a flexion gap and extension gap, the increase in the flexion gap was larger than that of the extension gap by 1.6 mm. CONCLUSION: A PCL resection resulted in an increase in the flexion and extension gaps by 3.6 mm and 2.0 mm, respectively. Therefore, a PCL resection would be a good alternative method for controlling the flexion-extension gap in TKA.

Gap Discrepancy in Posterior Cruciate Ligament-Sacrificing Total Knee Joint Arthroplasty

PURPOSE: To evaluate the effects of PCL (posterior cruciate ligament) resection on the flexion and extension gap during TKA (total knee joint arthroplasty). MATERIALS AND METHODS: From December 2002 to August 2003, we quantitatively measured and ana-lyzed prospectively the flexion and extension gap before and after PCL resection during TKA in 26 cases among 23 patients of osteoarthritis. A tensioning device was used to measure the gap and a torque wrench attached to the device was used to apply constant force. RESULTS: Before resection, the average flexion gap was 24.9 mm and the average extension gap was 25.3 mm. After resection, the average flexion gap was 29.8 mm and average extension gap was 27.6 mm. The extension gap was increased 2.2 mm and the flexion gap was increased 4.9 mm which implies that using a thicker polyethylene insert would be favorable after PCL resection. CONCLUSION: After PCL resection, both flexion and extension gaps were increased but the flexion gap was increased more than the extension gap.