Medially stabilized TKA device had superior outcomes vs posterior-stabilized device
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Use of a medially stabilized implant system in patients undergoing total knee arthroplasty yielded superior clinical outcomes compared with a posterior-stabilized implant system, according to results.
David F. Scott, MD, and colleagues randomly assigned patients undergoing elective primary TKA to receive either a posterior-stabilized implant system (n=100) or a medially stabilized implant system (n=101). Researchers assessed and compared clinical and radiographic outcomes preoperatively and at 6 weeks, 6 months and annually postoperatively between the two groups.
Results showed patients in the posterior-stabilized device group had a 7.24% longer tourniquet time compared with the medially stabilized device group. Researchers found the medially stabilized device group had better 1- and 2-year postoperative forgotten joint scores, Knee Society Scores and flexion. At 2 years postoperatively, patients in the medially stabilized group had an average forgotten joint score of 70.06 and an average Knee Society Score of 182.97, according to results. This was compared with an average forgotten joint score of 57.87 and an average Knee Society Score of 170.91 in the posterior-stabilized group at 2 years, researchers noted. Results showed the medially stabilized group had an average maximum active flexion of 132.18° vs. 124.18° in the posterior-stabilized group. However, researchers found no differences between the two groups in alignment as measured in the coronal plane with long-standing radiographs both preoperatively and postoperatively.
“At the minimum 2-year follow-up for all 201 subjects in this study, the results demonstrate superiority of the medially stabilized device in terms of multiple clinical outcomes, including patient satisfaction as measured by the forgotten joint score and Knee Society Score, as well as substantially better range of motion,” Scott told Healio Orthopedics. “These findings support the use of a medially stabilized knee implant system and support the conclusion that this design, in conjunction with a modified kinematic alignment surgical technique, offers improved biomechanics and kinematics of that obtained with a [posterior-stabilized] PS knee implant.” – by Casey Tingle
Reference:
Scott DF, et al. Poster 652. Presented at: American Academy of Orthopaedic Surgeons Annual Meeting; March 24-28, 2020 (meeting canceled).
Disclosure: Scott reports he receives IP royalties from Innomed; is on the editorial or governing board for the Journal of Arthroplasty; is a paid consultant and paid presenter or speaker for Medacta International; and receives research support from Medacta International, Microport, OMNI LifeScience and Stryker.
Perspective
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Thomas J. Barrett, MD
A variety of knee implant designs, balancing techniques and resection methodologies have been used to optimize the outcomes of total knee reconstruction. Medial stabilized designs have gained popularity as these attempt to reproduce native knee kinematics. David F. Scott, MD, and colleagues compared traditional posterior stabilized to a medial stabilized knee, using kinematic alignment, in reference to functional outcome scores. This is one of the few randomized control studies that compare medial stabilized to posterior stabilized designs.
The findings of this study are encouraging. At 2-year follow-up, the patients treated with the medial stabilized design had better forgotten joint scores and Knee Society Scores. They also showed better range of motion than the posterior stabilized group, with an average of 8° more maximum flexion. Medially stabilized knee designs and the kinematic alignment technique are complementary in their focus on restoring pre-arthritic alignment rather than mechanical alignment. Nevertheless, kinematic alignment has been shown to significantly increase contact stresses and wear on the medial compartment of the knee which may limit implant longevity. Long-term studies are necessary to evaluate the wear characteristics of the added medial constraint.
Warren Alpert Medical School
East Greenwich, Rhode Island
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Scott DF, et al. Poster 652. Presented at: American Academy of Orthopaedic Surgeons Annual Meeting; March 24-28, 2020 (meeting canceled).
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