Posterior Tibial Slope Increases Anterior Cruciate Ligament Stress in Bi-Cruciate Retaining Total Knee Arthroplasty: In Vivo Kinematic Analysis

In vivo kinematic comparison of bi-cruciate retaining total knee arthroplasty between mechanical alignment and functional alignment methods

Background/objective

This study aimed to clarify the kinematics of bi-cruciate-retaining (BCR) total knee arthroplasty (TKA) by comparing the mechanical alignment (MA) and functional alignment (FA) methods and to evaluate differences between the two alignment methods.

Methods

The in vivo kinematics of 20 MA TKA and 20 FA TKA knees were investigated under fluoroscopy during squatting using a two-to three-dimensional registration technique. Accordingly, knee flexion angle, axial rotational angle, varus-valgus angle, anteroposterior translation of the medial and lateral low contact points of the femoral component relative to the tibial component and kinematic pathway were evaluated.

Results

No difference in the knee flexion angle was observed between the MA and FA TKA groups. Femoral external rotation was observed in both groups and no significant difference was observed. Significant varus alignment from extension to early flexion range was observed in the FA TKA group. The posterior translation of the medial side was smaller in the FA TKA group than in the MA TKA group. Conversely, no significant difference in the anteroposterior translation of the lateral side was observed. In the kinematic pathway, a medial pivot motion from 0° to 20° of flexion and a lateral pivot motion beyond 20° of flexion were observed in both groups.

Conclusion

During squatting in BCR TKA, the FA TKA group significantly showed varus alignment and smaller posterior translation of the medial side than the MA TKA group from extension to early flexion range.

Evaluating axial alignment and knee phenotypes in a young Indian population, using X-rays converted to three-dimensional bone models, and their relevance in total knee arthroplasty

PURPOSE

The standard principle of total knee arthroplasty (TKA) targeted by most orthopaedicians is the alignment of the lower limb in a neutral mechanical axis. However, for several patients the neutral mechanical alignment is not normal. Aligning these patients to a neutral mechanical axis may not result in desirable outcomes as it may feel unnatural. This study aimed to discover what percentage of the young healthy Indian population have a neutral hip-knee-ankle angle (HKA = 180°) and what percentage of this population have a deviation from the neutral HKA. We also studied the distribution of knee phenotypes in this non-arthritic population.

SUBJECTS AND METHODS

A total of 196 lower limbs were evaluated from 100 subjects, between the ages of 20 and 35 years, without any history of lower limb pathology, of which 50 were males and 50 were females. All volunteers were subjected to full-leg standing anteroposterior and lateral digital radiographs on which various alignment parameters were analysed. Three-dimensional bone models were generated using a validated software.

RESULTS

125 limbs (63.7%) from the total population lay in the range of 180 ± 3°; 7.14% (14/196) of the total limbs had an HKA angle of 180°; 29.5% (58/196) of the total population had a varus alignment, i.e., HKA angle of ≤176° and 6.6% (13/196) had knees in valgus alignment, i.e., HKA angle of ≥184°. Thirty-four percent (33/96) of limbs in men and 25% (25/100) of limbs in women had constitutional varus knees with an alignment of ≤176°; 5.2% (5) of limbs in men and 8% (8) of limbs in women had constitutional valgus knees with an alignment of ≥184°; 67/96 knees in males and 58 knees in females were in the range of 180 ± 3°.

CONCLUSIONS

A significant portion of the normal population had limbs that deviated from the neutral HKA. If these subjects were to need TKA in the future, it would not be desirable to restore their alignment to its neutral.

Bi-cruciate retaining total knee arthroplasty is here to stay: A consecutive series transitioning from manual instrumentation to enabling technologies

BACKGROUND

Bicruciate-retaining (BCR) total knee arthroplasty (TKA) has seen renewed interest due to the potential for more natural knee kinematics with anterior cruciate ligament (ACL) retention.

OBJECTIVE

The present study attempts to determine differences in the 2-year survivorship and patient-reported outcomes between two surgical strategies (traditional instrumentation versus robotics) applied to the extensive use of a modern, 2nd generation BCR TKA design.

METHODS

We performed a retrospective study with prospectively collected data of 113 patients who underwent primary TKA between 2018 and 2020 using a 2nd generation BCR TKA implant. Patient demographics, PROMS, and intra/post-operative complications were collected. Patients were also evaluated according to the use or not of robotics. A Kaplan-Meier analysis was used to evaluate revision-free survival at follow up.

RESULTS

102 patients were enrolled: 90 received traditional surgery and 12 robotic-assisted surgery. The mean age was 68 years (SD 7.76) with an average BMI of 29.6 kg/m2 (SD 3.56). The mean follow up (FU) was 32.4 ± 6.2 months (range 24-45 months). Survivorship at 2 years was 98% (95% CI: 92.4-99.5). Revisions/reoperations were performed for anterior cruciate ligament (ACL) tear (1/4), pain (1/4), arthrofibrosis (1/4) and acute periprosthetic joint infection (PJI) (1/4). At final FU, 92 patients (90.2%) considered themselves satisfied, showing a mean OKS of 40.6 (SD 5.1) and a mean FKS of 76.7 (SD 11.8). No differences in the outcome were found between traditional and robotic-assisted procedures.

CONCLUSION

The modern BCR design evaluated in this study achieved excellent results in terms of implant survivorship, low rate of reoperation and clinical results, independently from the use of enabling technologies.

Short-term clinical results of bicruciate-retaining total knee arthroplasty using personalized alignment

BACKGROUND

Bicruciate-retaining (BCR) prosthesis has been introduced to recreate normal knee movement by preserving both the anterior and posterior cruciate ligaments. However, the use of BCR total knee arthroplasty (TKA) is still debatable because of several disappointing reports. We have been performing BCR TKAs with personalized alignment (PA). This study aimed to reveal the limb alignment and soft tissue balance of FA-BCR TKAs and compare the clinical outcomes of FA-BCR TKAs with those of unicompartmental knee arthroplasty (UKA).

METHODS

Fifty BCR TKAs and 58 UKAs were included in this study. The joint component gaps of BCR TKA were evaluated intraoperatively and the postoperative hip-knee-ankle (HKA) angle, medial proximal tibial angle (MPTA), and lateral distal femoral angle (LDFA) were measured using full-length standing radiography. The short-term clinical outcomes of BCR TKAs were compared with those of UKA using the scoring system of 2011 Knee Society Scoring (KSS) and the knee injury and osteoarthritis outcome score (KOOS) at an average of 2 years postoperatively (1-4yeras).

RESULTS

The coronal alignment values of PA-BCR TKA were as follows: HKA angle, 177.9° ± 2.3°; MPTA, 85.4° ± 1.9°; and LDFA, 87.5° ± 1.9°. The joint component gaps at flexion angles of 10°, 30°, 60°, and 90° were 11.1 ± 1.2, 10.9 ± 1.4, 10.7 ± 1.3, and 11.2 ± 1.4 mm for the medial compartment and 12.9 ± 1.5, 12.6 ± 1.8, 12.5 ± 1.8 and 12.5 ± 1.7 mm for the lateral compartment, respectively. The patient expectation score and maximum extension angle of PA-BCR TKA were significantly better than those of UKAs.

CONCLUSIONS

The short-term clinical outcomes of PA-BCR TKA were comparable or a slightly superior to those of UKAs.

Comparison of the joint laxity of total knee arthroplasty evaluated by the distraction force and the varus-valgus force

BACKGROUND

Component gap (CG) measurement help surgeons evaluate intraoperative soft-tissue balance. One technique is measuring the CG using tensioner devices with distraction force. Another is to evaluate the laxity under a varus-valgus force using navigation or robotics. The aim was to compare the JL evaluated by CG and varus-valgus force between the different types of total knee arthroplasties.

METHODS

Forty-three bi-cruciate stabilized (BCS) knees and 33 bi-cruciate retaining (BCR) knees were included. After bone resection and soft tissue balancing, the CG was measured and after the final implantation and capsule closure, JL under a maximum varus-valgus stress was recorded with navigation. JL evaluated by the CG (JLCG) was defined as CG minus selected thickness of the tibial component and JL under varus-valgus force (JLVV) was defined as difference between varus-valgus angles without stress and maximum varus-valgus angles under varus-valgus force. The evaluations were performed at flexions of 10°, 30°, 60° and 90°.

RESULTS

Although JLCGs of lateral compartment of BCS were larger than those of BCR, no difference was found between JLVVs of BCS and BCR. Although JLCGs of lateral compartment did not change at each knee flexion angle in both BCS and BCR, JLVVs of lateral compartment increased by 3° from 10° to 90° knee flexion.

CONCLUSION

JLVVs of BCS and BCR were equivalent, whereas BCS showed larger JLCGs of lateral compartment. JLVVs of lateral compartment increased by 3° in the range from 10° to 90° knee flexion whereas JLCGs remained stable.