A Retrospective Cross-Sectional Observational Study on the Distribution of Coronal Plane Alignment Classifications in Chinese Osteoarthritic and Healthy Populations

Research Background

Neutral mechanical alignment (MA) of the knee is considered the cornerstone of successful and durable total knee arthroplasty (TKA). However, the existence of “constitutional varus” knees suggests that restoring neutral alignment may be abnormal and undesirable in these cases, often requiring some degree of medial soft tissue release. Therefore, restoring native alignment rather than neutral alignment in TKA has gained interest among knee surgeons. Kinematic alignment (KA) aims to align the articular surfaces of the femoral and tibial components with the normal or preoperative joint lines of the knee. With the development of navigation or robotic-assisted systems, restricted KA, reverse KA, and functional KA have emerged from KA, compromising the principles of restoring native alignment and safe mechanical alignment zones [1].

Paper Source

This paper is authored by Yu-Hang Gao, Yu-Meng Qi, Pei-Hong Huang, Xing-Yu Zhao, and Xin Qi, among others, primarily from the Orthopedic Center of the First Hospital of Jilin University. The paper was published in the International Journal of Surgery on February 13, 2024.

Research Process

In this study, long-leg radiographs of 246 osteoarthritic (OA) patients (477 knees) and 107 healthy individuals (214 knees) were retrospectively reviewed to analyze the distribution of the coronal plane alignment (CPAK) classifications. The specific research process is as follows:

1. Study Subjects and Design

   • OA Group: Data from consecutive OA patients undergoing primary TKA by a senior surgeon from August 2021 to July 2023 were retrospectively analyzed. After excluding 27 patients, 246 patients (15 unilateral, 231 bilateral, totaling 477 knees) were included in the study.
   • Healthy Group: Data from consecutive visitors who underwent long-leg radiographs at the same institution’s outpatient clinic from January 2023 to July 2023 and had no signs of cartilage degeneration or history of lower limb disease were analyzed. After excluding 29 visitors, 107 visitors (214 knees) were included in the study.

2. Radiographic Measurements

   • All participants underwent standard digital long-leg radiography to measure the mechanical hip-knee-ankle angle (MHKA), lateral distal femoral angle (LDFA), medial proximal tibial angle (MPTA), and joint line convergence angle (JLCA).
   • The definition of the CPAK classification involved matching patients to nine possible CPAK alignment groups based on AHKA and JLO calculations.

3. Data Analysis

   • Age, gender, radiographic measurements, and CPAK classifications were compared between the OA and healthy groups. Independent sample t-tests and paired sample t-tests were used for data analysis. Pearson’s χ2 test was used for comparing categorical data.

Main Research Findings

1. Most Common Distribution

   • In the OA group, the most common CPAK type was Type I (43.6%), while in the healthy group, Type II was the most common (44.9%).

2. Radiographic Measurements and CPAK Classifications at Different Kellgren-Lawrence Grades

   • For patients undergoing unilateral TKA, the most common distribution in Kellgren-Lawrence grade 3-4 knees was Type I. In contrast, the most common distribution in the contralateral Kellgren-Lawrence grade 0-2 knees was Type I and Type II.

3. Clinical Outcomes of Patients with Different Coronal Alignment Strategies

   • For CPAK Type I OA patients, there were no significant differences in clinical outcomes at 3 months postoperatively between the mechanical alignment and restricted kinematic alignment groups.

Research Conclusions

This study found that the most common CPAK classifications were Type I and Type II in the Chinese osteoarthritic and healthy populations, respectively. Additionally, the progression of osteoarthritis may lead to changes in the CPAK classification. These findings have important clinical implications for designing and implementing personalized knee replacement surgeries.

Research Highlights

1. Significant Findings

   • The differences in CPAK classifications between the OA and healthy populations, suggesting that the progression of OA can affect the alignment classification of the knee.

2. Novelty

   • The introduction of a method to measure joint alignment using radiographic parameters (e.g., AHKA and JLO), and the validation of differences in their distributions between healthy and pathological states.

3. Clinical Application Value

   • The research findings can aid in guiding the selection of coronal alignment strategies in TKA surgeries, with practical implications for improving postoperative recovery outcomes.