Long-Term Clinical Performance of an Uncemented, Mobile Bearing, Anterior Stabilized Knee System and the Impact of Previous Knee Surgery

Traumatic anterior tibiofemoral dislocation of mobile-bearing total knee arthroplasty: Two cases

Background

Anterior tibiofemoral dislocation is a severe complication of a total knee arthroplasty. It is rare, and it is distinctly different from bearing spinout. Most tibiofemoral dislocations are posterior. Anterior dislocation has previously been described in various prosthesis designs, but not in mobile-bearing prostheses. We present two cases and provide recommendations for the management of this rare and severe injury.

Case description

Two cases of complete anterior tibiofemoral dislocation were brought on by trauma, fifteen and eight years after initial implantation of mobile-bearing total knee arthroplasties in 71-year-old and 73-year-old female patients. One was managed with closed reduction and made a full recovery. In the other, closed reduction failed, open reduction was performed, and there was a need for revision surgery for instability after her initial recovery. There were no neurovascular complications. Follow-up was 23 and 14 months respectively.

Conclusion

Anterior tibiofemoral dislocation is a severe injury with a risk of concomitant complications. Early management should include prompt reduction, serial neurovascular exams and CT angiography for all cases. Late management should include assessment of joint stability.

5-year migration and inducible displacement of the uncemented LCS and ATTUNE rotating platform knee systems: a secondary report of a randomized controlled RSA trial

BACKGROUND AND PURPOSE

 Early migration of the uncemented cruciate-sacrificing rotating platform ATTUNE and Low Contact Stress (LCS) tibial components was classified as at-risk for aseptic loosening rates exceeding 6.5% at 15 years based on recent fixation-specific migration thresholds. In this secondary report of a randomized controlled trial (RCT) we aimed to evaluate whether the 5-year migration, inducible displacement, and the clinical outcome of the ATTUNE components were comparable to those of the LCS.

METHODS

 Patients from the initial 2-year radiostereometric analysis (RSA) RCT were recruited for a 5-year follow-up. At 5 years, participants underwent 2 supine and 1 loaded RSA examination, clinical assessments, and questionnaires. Migration was analyzed using maximum total point motion (MTPM), translations, and rotations, focusing on 5-year migration, continuous migration (> 0.10 mm/year), and inducible displacement. Revisions, along with clinical and functional outcomes, were also evaluated.

RESULTS

 At 5 years, 24 ATTUNE and 24 LCS implants were analyzed. The mean MTPM was similar for tibial components (ATTUNE 1.13mm [confidence interval (CI) 0.94-1.33]; LCS 1.24 mm [CI 1.05-1.46]) but significantly lower for the ATTUNE femoral component (1.14 mm [CI 0.92-1.39]) than LCS 1.87 mm [CI 1.57-2.21]). 2-to-5-year migration rates were comparable, but 11 ATTUNE and 7 LCS exceeded 0.10 mm MTPM/year, indicating a higher risk of loosening. Inducible displacement was similar, although 1 patient with a tibial ATTUNE showed excessive displacement (3.34 mm MTPM) with focal osteolysis but no symptoms. 1 revision 10 days post-surgery was performed for an ATTUNE insert spinout, resolved with an isolated insert exchange. Clinical and functional outcomes were comparable.

CONCLUSION

 At the 5-year follow-up, ATTUNE tibial components showed similar migration, while the femoral component migrated significantly less than the LCS, which mainly occurred during the first 2 years. 2-to-5-year migration rates, inducible displacement, and clinical and functional outcomes were comparable. These findings suggest a comparable long-term risk of aseptic loosening between the uncemented ATTUNE and LCS knee systems.

Association Between Surface Modifications for Biologic Fixation and Aseptic Loosening of Uncemented Total Knee Arthroplasties

BACKGROUND

Various surface modifications are used in uncemented total knee arthroplasties (TKAs) to enhance bony ingrowth and longevity of implants. This study aimed to identify which surface modifications are used, whether they are associated with different revision rates for aseptic loosening, and which are underperforming compared to cemented implants.

METHODS

Data on all cemented and uncemented TKAs used between 2007 and 2021 were obtained from the Dutch Arthroplasty Register. Uncemented TKAs were divided into groups based on their surface modifications. Revision rates for aseptic loosening and major revisions were compared between groups. Kaplan-Meier, Competing-Risk, Log-rank tests, and Cox regression analyses were used. In total, 235,500 cemented and 10,749 uncemented primary TKAs were included. The different uncemented TKA groups included the following: 1,140 porous-hydroxyapatite (HA); 8,450 Porous-uncoated; 702 Grit-blasted-uncoated; and 172 Grit-blasted-Titanium-nitride (TiN) implants.

RESULTS

The 10-year revision rates for aseptic loosening and major revision of the cemented TKAs were 1.3 and 3.1%, and for uncemented TKAs 0.2 and 2.3% (porous-HA), 1.3 and 2.9% (porous-uncoated), 2.8 and 4.0% (grit-blasted-uncoated), and 7.9% and 17.4% (grit-blasted-TiN), respectively. Both type of revision rates varied significantly between the uncemented groups (log-rank tests, P < .001, P < .001). All grit-blasted implants had a significantly higher risk of aseptic loosening (P < .01), and porous-uncoated implants had a significantly lower risk of aseptic loosening than cemented implants (P = .03) after 10 years.

CONCLUSION

There were 4 main uncemented surface modifications identified, with different revision rates for aseptic loosening. Implants with porous-HA and porous-uncoated had the best revision rates, at least equal to cemented TKAs. Grit-blasted implants with and without TiN underperformed, possibly due to the interaction of other factors.

Mobile medial pivot (lateral slide) type total knee arthroplasty exhibits a medial pivot pattern: three-dimensional motion analysis using cadaveric knees

PURPOSE

The purpose of this study was to analyze the dynamic kinematics of the mobile medial pivot-type total knee arthroplasty (MMPTKA) using the three-dimensional (3D)-to-2D registration technique.

METHODS

Cadaveric knees from five humans were used. Computed tomography of the lower limb and preoperative 3D planning for MMPTKA were performed. After performing TKA, passive motion of the knee was observed from a fully extended position to maximum flexion using a flat panel detector. The following parameters were determined: (1) anteroposterior (AP) translations of the medial and lateral most distal points (estimated contact point) of the femoral component, (2) rotational femoral component's X-axis (FCX) angle, and (3) rotational insert angle. Paired t-tests were used to analyze differences in the AP translation between the medial and lateral most distal points of the femoral component as well as differences in the changes in the rotational angle between the FCX and X-axis of the insert on the tibial component's axial plane.

RESULTS

The AP translations of the femoral component's medial and lateral most distal points were 8.4 ± 2.5 and 13.6 ± 3.3 mm, respectively (p = 0.001). The rotational angles of the FCX and insert were 10.7° ± 4.9° external rotation and 8.9° ± 4.1° internal rotation, respectively (p = 0.004).

CONCLUSIONS

The posterior translation of the lateral side of the femoral component was greater than that of the medial in all cases. Hence, a medial pivot pattern was identified. The femoral component exhibited external rotation throughout knee flexion in all subjects, whereas the mobile insert exhibited internal rotation (opposite pattern relative to the femoral component). This study provides valuable kinematical information of MMPTKA that has not been clear yet.