- A recently introduced bi-cruciate retaining total knee arthroplasty demonstrated significantly reduced posterior contact excursions of the lateral condyle and reduced femoral external rotation during functionally strenuous activities
- Medial pivoting was observed in only about half the cohort
- Preservation of the anterior cruciate ligament alone may not be sufficient to restore native knee motion and medial pivot rotation during functionally strenuous high-flexion activities
An estimated 8%-25% of patients remain dissatisfied after total knee arthroplasty (TKA). One potential contributing factor is the removal of the anterior and/or both cruciate ligaments, which substantially alters the kinematics of the joint.
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A recently introduced bi-cruciate retaining (BCR) TKA was designed to allow preservation of both the anterior and posterior cruciate ligaments, and in some studies, it has shown several potential advantages over conventional posterior cruciate retaining and posterior stabilized TKA. However, there is limited information about the articular contact kinematics during functionally strenuous high-flexion activities.
Young-Min Kwon, MD, PhD, program director of the Adult Reconstructive Surgery Fellowship Program and director of the Bioengineering Laboratory, and colleagues studied this question in patients after BCR TKA and observed asymmetric femoral rollback plus medial translation in only about half the cohort. They published their findings in the Journal of Arthroplasty.
The patients in the study were 15 women and 14 men who had undergone unilateral BCR TKA. The same BCR knee system was used in all patients. Their average age was 66 (range, 47–76). No patient had a surgical complication during the average follow-up of 12.7 months (range, 10.9–21.3 months).
The patients were asked to perform sequential step-ups, single-leg deep lunges and sit-to-stand movements as they were imaged by a validated method of combined computer tomography and dual fluoroscopic system. The mean contact positions of the operated and non-operated knees were projected on the tibial plateau surfaces and measured using the mediolateral and anterior-posterior axes.
Articular contact kinematics were analyzed from full extension to 50°, 90° and 100° of knee flexion during step-ups, sit-to-stand movements and lunges, respectively.
The researchers found that contact excursions of the lateral condyle were significantly more anteriorly located in operated knees than in non-operated knees:
- Sit-to-stand: −4.9 vs. −9.7 mm
- Deep lunges: −5.7 vs. −10.0 mm
- Step-ups: −4.8 vs. −9.1 mm
Contact points of operated knees indicated significantly reduced femoral external rotation, compared with non-operated knees:
- Sit-to-stand: 2.1° vs. 7.7°
- Deep lunges: 1.8° vs. 7.0°
- Step-ups: 0.1° vs. 6.2°
All of the above differences were statistically significant at < .05.
There was pronounced variability in pivot position. Medial pivoting was observed in only 59%, 56% and 48% of the operated knees for step-ups, sit-to-stand movements and lunges, respectively, while the remaining patients showed lateral pivoting.
The researchers concluded that anterior cruciate ligament preservation alone may be inadequate to restore native knee motion and medial pivot rotation during functionally strenuous high-flexion activities, as in vivo kinematics is influenced by multiple factors including implant orientation and alignment as well as the articular surface design of the TKA system.
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