During knee replacement surgery, known as total knee arthroplasty, physicians generally aim to align the hip, knee, and ankle in a straight line for a neutral posture, instead of matching the patient’s initial alignment. Recent research from Kyushu University offers compelling evidence that maintaining the patient’s natural alignment may be advantageous. This study appeared in The Bone & Joint Journal on October 1, 2024.
When the knee suffers damage from injuries or arthritis, routine activities such as walking, sitting, and running can become extremely painful. In cases of significant impairment, orthopedic surgeons advise knee replacement surgery to repair the damaged joint and alleviate pain by achieving a neutral alignment.
However, a neutral alignment does not always correspond to the patient’s original positioning, leading to differing opinions among orthopedic specialists about whether restoring the patient’s natural alignment leads to better postoperative results. This study aims to clarify this issue and develop comprehensive guidelines for preoperative planning and the handling of knee replacement surgeries.
The research primarily focuses on a classification system known as Coronal Plane Alignment of the Knee (CPAK). This system classifies potential knee joint alignments based on two key factors. The first factor is the hip-knee-ankle angle; large negative angles result in knees being angled outward, while significant positive angles lead to inward positioning. The second factor is the joint line angle, which describes the angle formed between a horizontal line at ground level and an imaginary line running across where the femur and tibia meet.
The research team, including MD Toshiki Konishi and Associate Professor Satoshi Hamai from the Department of Orthopedic Surgery at Kyushu University Hospital, aimed to investigate whether variations in CPAK categorization before and after the surgery were linked to significant differences in recovery outcomes. They gathered data from 231 patients who underwent knee replacement for osteoarthritis at Kyushu University Hospital between 2013 and 2019. Using X-ray images, the team assessed CPAK classifications and knee alignment parameters before and after the operations. They also distributed a questionnaire to the patients, which generated standardized scores reflecting symptoms, overall satisfaction, physical activity, and quality of life in the postoperative phase.
Upon conducting statistical analysis, the researchers found that patients whose knee alignment shifted after surgery—according to CPAK classifications—experienced significantly poorer long-term recovery results. Notably, patients whose joint line angle tilted outward post-surgery (away from the other leg) also reported worse overall outcomes.
This study underscores the importance of accurately mirroring a patient’s natural alignment during surgery to promote optimal recovery and enhance quality of life. These findings could significantly influence knee replacement surgical practices around the globe.
“Our results may assist surgeons in future clinical scenarios in strategizing preoperative planning and execution of total knee arthroplasty. By focusing on restoring the patient’s original alignment, superior outcomes may be achieved post-surgery,” remarks Konishi. He further adds, “This approach could help tackle the variability in recovery experiences observed after total knee arthroplasty, paving the way for a more personalized strategy regarding knee alignment, potentially establishing a new benchmark in orthopedic procedures.”
Recognizing that this was a retrospective study, the research team intends to pursue a prospective approach in their future efforts. “We aim to integrate the CPAK classification into preoperative planning, with each patient’s natural knee alignment serving as the surgical objective. Thanks to robot-assisted technologies employed at our center, we can now perform total knee arthroplasty with exceptional accuracy, ensuring we closely adhere to the preoperative plan,” states Konishi.
The researchers are optimistic that these initiatives will elevate the standard of knee replacement surgery, enabling patients to enjoy healthier, pain-free, and more active lives post-operation.
