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

Gerdy's tubercle as a novel anatomical landmark for the proximal tibial cut in total knee arthroplasty

OBJECTIVES

This study aimed to explore the use of Gerdy's tubercle (GT) as an innovative and dependable anatomical landmark for the proximal tibial cut in total knee arthroplasty (TKA) in cases with extensive knee degeneration.

MATERIALS AND METHODS

One hundred dry tibia bones and 10 formalin-fixed cadaveric knee specimens of both sexes were examined. A Zimmer NexGen tibial cutting guide and a Mitutoyo digital caliper were utilized to align the guide with the tibia's mechanical axis. The procedure was replicated on cadaver knees using a standardized medial parapatellar arthrotomy approach. Measurements included the distance from GT superior border to the resection line and the length of the tibia. A radiological study involving magnetic resonance imaging examinations of 48 patients, which were evaluated focusing on the upper border of GT and the least degenerated segment of the posterolateral part of the lateral tibial condyle, was conducted.

RESULTS

Anatomical measurements of GT and proximal tibial areas in 110 specimens showed slight but consistent variations with cadaver measurements. Magnetic resonance imaging analysis of 48 patients revealed notable sex differences in the distance between the superior border of GT and the tibia's posterolateral surface. There was also a significant negative correlation between the distance from GT to the posterolateral corner and cartilage thickness.

CONCLUSION

Proper alignment in TKA is crucial for success, but identifying an extra-articular landmark for horizontal tibial resection remains challenging, particularly in severely arthritic knees. This study introduces GT as a novel anatomical landmark for TKA, offering a more reliable reference for achieving desired joint levels in knees with significant degenerative changes.

Phenotyping of the Turkish population according to Coronal Plane Alignment of the Knee classification: A retrospective cross-sectional study

OBJECTIVES

This study aimed to phenotype healthy individuals and patients with arthritic knees in the Turkish population according to the Coronal Plane Alignment of the Knee (CPAK) classification.

PATIENTS AND METHODS

The retrospective cross-sectional study included 207 healthy individuals (109 males, 98 females; mean age: 32.9±8.4 years; range, 20 to 45 years) with a total of 414 knees (Group 1) and 296 patients (155 females, 141 males; mean age: 54.5±7.9 years; range, 43 to 80 years) with a total of 408 arthritic knees (Group 2) who met the inclusion criteria and underwent evaluation using digital long-leg radiographs between January 2019 and July 2023. Mechanical lateral distal femoral angle and medial proximal tibial angle were measured. Subsequently, the arithmetic hip-knee-ankle angle (aHKA) and joint line obliquity (JLO) were calculated. Based on the results obtained, participants in both groups were categorized according to the CPAK classification.

RESULTS

In Group 1, the mean aHKA was 0.3°±2.5°, and the mean JLO was 175.2°±3.5°. In Group 2, the mean aHKA was -1.4°±3.9°, and the mean JLO was 174.6°±3.7°. The most common CPAK type in healthy individuals (Group 1) was type 2 (41.5%), followed by type 3 (14.7%) and type 1 (14.5%). In arthritis patients (Group 2), the most common CPAK type was type 2 (31.6%), followed by type 1 (28.2%) and type 3 (13.5%).

CONCLUSION

The CPAK classification serves as an important guide for categorizing lower extremity alignment. In the Turkish population, healthy individuals most commonly exhibited CPAK type 2, 3, and 1 alignments, respectively, while osteoarthritic patients predominantly displayed CPAK type 2, 1, and 3 alignments.

Does sagittal alignment of the femoral component have an impact on radiological loosening and functional results in revision knee arthroplasty?

OBJECTIVES

In this study, we aimed to investigate the effect of sagittal alignment of the femoral component on both radiological loosening and functional results in revision total knee arthroplasty (rTKA), as well as the anterior condylar offset (ACO) and posterior condylar offset (PCO).

PATIENTS AND METHODS

Between December 2005 and November 2020, a total of 47 patients (12 males, 35 females; mean age: of 67.1±8.4 years; range, 52 to 90 years) who underwent rTKA due to aseptic prosthesis failure were retrospectively analyzed. Demographic data including age, sex, body mass index (BMI), and clinical outcomes of the patients were recorded. Early postoperative sagittal alignment of the femoral component, ACO, and PCO were measured. Radiological loosening of patients was evaluated using the modified Knee Society Score, while the functional outcomes were assessed using the Knee Injury and Osteoarthritis Outcome Score (KOOS).

RESULTS

The mean follow-up was 55.4±28.0 (range, 24 to 142) months. While there was a moderate and inverse correlation between the sagittal alignment of the femoral component and ACO (p=0.002), there was no significant correlation between the sagittal alignment of the femoral component and PCO (p=0.980). There was a weak and inverse correlation between BMI and KOOS (p=0.024). There was no significant relationship between the sagittal alignment of the femoral component, ACO, PCO, age, and sex with radiological loosening (p=0.241) or KOOS (p=0.894).

CONCLUSION

In rTKA, sagittal alignment of the femoral component does not affect radiological loosening and functional results. The sagittal alignment of the femoral component exhibits a moderate and inverse correlation with ACO, while it has no significant correlation with PCO.