Mid-level constraint may correct coronal plane imbalance without compromising patient function in patients with...

Area of Science:

• Orthopedic Surgery
• Biomedical Engineering

Background:

• Mid-level constraint (MLC) implants in Total Knee Arthroplasty (TKA) aid in achieving varus-valgus balance for slight ligamentous instability.
• Evaluating MLC versus posterior stabilized (PS) prostheses is crucial for optimizing patient outcomes.

Purpose of the Study:

• To compare patient-reported outcome measures (PROMs), alignment correction, and revision rates between MLC and PS knees in patients with preoperative degenerative arthritis.

Main Methods:

• A retrospective review of 57 MLC and 96 PS knees from a single manufacturer, implanted by one surgeon.
• Comparable demographic data (age, BMI, gender) and follow-up duration between the two groups.

Main Results:

• Both implant types achieved similar postoperative alignment despite differing preoperative deformities.
• The MLC group showed significantly better Knee Injury and Osteoarthritis Outcome Score (KSCRS-Total) results (163.9 vs. 132.8, p=0.003).
• No significant differences were observed in Range of Motion (ROM), anterior knee pain, Pain VAS, revision rates, or manipulation rates.

Conclusions:

• MLC implants in TKA can correct preoperative deformities with functional outcomes equal to or better than PS knees.
• Surgeons should prioritize knee balancing, using the least constraint necessary, and consider MLC implants when balancing is challenging.