Bone cement solidifiliation influence the limb alignment and gap balance during TKA

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.

Navigation-based analysis of associations between intraoperative joint gap and mediolateral laxity in total knee arthroplasty

BACKGROUND

No data have demonstrated how joint gap measured under a distraction force is actually associated with mediolateral laxity evaluated under a varus-valgus force during total knee arthroplasty (TKA). This study aimed to investigate the correlations between them using a navigation system.

METHODS

A total of 113 primary navigated TKAs were included. After bone resection and soft-tissue balancing, the component gap was measured with a distraction force of 60 N and 80 N for both the medial and lateral compartment (i.e. a total of 120 N and 160 N) at 0°, 10°, 30°, 60°, 90°, and 120° knee flexion. After the final prosthetic implantation and capsule closure, mediolateral laxity under a maximum varus-valgus stress was recorded with image-free navigation at each knee flexion angle. The correlation between joint gap laxity (total differences between component gap and insert thickness in the medial and lateral compartment) and mediolateral laxity was analyzed using Spearman's rank correlation coefficient.

RESULTS

The joint gap laxity under both distraction forces showed significant positive correlations with mediolateral laxity at 10°, 30°, 60°, and 90° flexion, whereas no correlation was observed at extension and 120° flexion. The correlations were stronger in gap measurement under 80 N than 60 N at all examined ranges. In patients with body mass indexes (BMIs) ≥ 30 kg/m², the correlation became non-significant.

CONCLUSION

Intraoperative joint gap laxity was associated with mediolateral laxity after TKA, especially at mid-flexion angles. The factors weakening the correlations were a lower applied distraction force for gap measurement and a larger BMI.

How Much Bone Cement Is Utilized for Component Fixation in Primary Cemented Total Knee Arthroplasty?

BACKGROUND

No scientific evidence exists regarding the amount of bone cement used and discarded in primary cemented Total knee arthroplasty (TKA). The aim of this study was to identify the exact amount of bone cement utilized for component fixation in primary TKA.

METHODS

In a prospective study carried out at five centers, 133 primary cemented TKAs were performed. One pack of 40g Palacos bone cement (PBC 40) was hand mixed and digitally applied during the surgery. After fixation of the TKA components, the remaining bone cement was methodically collected and weighed on a digital weighing scale. The actual quantity of cement utilized for component fixation was calculated.

RESULTS

On an average, 22.1 g of bone cement was utilized per joint, which accounted to 39 % of 57 g, the solidified dry weight of PBC 40. Among 133 knees, the cement usage was 20 % to 50% in 109 knees, more than 50% in 20 knees and less than 20% in 4 knees. Knees which received larger sized femoral implant required more cement compared to medium and small sizes. Knees which had pulse lavage had more cement utilization compared to knees which had simple syringe lavage before implantation.

CONCLUSION

Large quantity of bone cement was handled than actual requirements in primary TKA when a standard 40g pack was used with the digital application technique, resulting in sizeable discard of bone cement. Customizing cement pack according to the implant size can potentially avoid this cement wastage. Future research is required to study the utility and economic impact of smaller packs (20 g or 30 g) of bone cement in primary TKA.

Three-dimensional analysis of accuracy of patient-matched instrumentation in total knee arthroplasty: Evaluation of intraoperative techniques and postoperative alignment

BACKGROUND

It is questionable that the accuracies of patient-matched instrumentation (PMI) have been controversial, even though many surgeons follow manufacturers' recommendations. The purpose of this study was to evaluate the accuracy of intraoperative procedures and the postoperative alignment of the femoral side using PMI with 3-dimensional (3D) analysis.

METHODS

Eighteen knees that underwent total knee arthroplasty using MRI-based PMI were assessed. Intraoperative alignment and bone resection errors of the femoral side were evaluated with a CT-based navigation system. A conventional adjustable guide was used to compare cartilage data with that derived by PMI intraoperatively. Postoperative alignment was assessed using a 3D coordinate system with a computer-assisted design software. We also measured the postoperative alignments using conventional alignment guides with the 3D evaluation.

RESULTS

Intraoperative coronal alignment with PMI was 90.9° ± 1.6°. Seventeen knees (94.4%) were within 3° of the optimal alignment. Intraoperative rotational alignment of the femoral guide position of PMI was 0.2° ± 1.6°compared with the adjustable guide, with 17 knees (94.4%) differing by 3° or less between the two methods. Maximum differences in coronal and rotation alignment before and after bone cutting were 2.0° and 2.8°, respectively. Postoperative coronal and rotational alignments were 89.4° ± 1.8° and -1.1° ± 1.3°, respectively. In both alignments, 94.4% of cases were within 3° of the optimal value. The PMI group had less outliers than conventional group in rotational alignment (p = 0.018).

CONCLUSIONS

Our 3D analysis provided evidence that PMI system resulted in reasonably satisfactory alignments both intraoperatively and postoperatively. Surgeons should be aware that certain surgical techniques including bone cutting, and the associated errors may affect postoperative alignment despite accurate PMI positioning.

Analysis of different bicruciate-retaining tibial prosthesis design using a three dimension finite element model

The recent interest in bicruciate-retaining prostheses has aimed to address the need for an implant that can mimic a natural knee. Arguments have always existed about survivorship, including loosening and subsidence, as well as tibial preparation in bicruciate-retaining tibial prostheses. The aim of this study was to investigate the biomechanics of a new modular design and other bicruciate-retaining designs using a three-dimensional finite element model under different load conditions to discover which prosthesis was more suitable. We also evaluated related parameters (the third principal stress, shear stress, micromotion, and von Mises stresses) to compare the characteristics of different bicruciate-retaining designs. The biomechanics of the bicruciate-retaining tibial prosthesis can be influenced by the style of the designed prosthesis and gait loading. The new modular design showed stability and moderated the third principal stress, leading to less shear stress and stress shield, suggesting that this type of design can avoid knee prosthesis loosening and subsidence. Therefore, the new design may be used as a more suitable prosthesis for future bicruciate-retaining implant application.

Effects of Cementing on Ligament Balance During Total Knee Arthroplasty

Complications related to joint imbalance may contribute to some of the most predominant modes of failure in total knee arthroplasty (TKA). These complications include instability, aseptic loosening, asymmetric component wear, and idiopathic pain. Fixation may represent a step that introduces unchecked variability into the procedure and may contribute to the incidence of joint imbalance-related complications. The ability to quantify in vivo loading in the medial and lateral compartments would allow for the ability to confirm balance after fixation and prior to wound closure. This retrospective study sought to capture any variability and imbalance associated with cementing technique. A total of 93 patients underwent sensor-assisted TKA. All patients were confirmed to have quantifiably balanced joints prior to cementation. After cementing and final component placement, the sensor was reinserted into the joint to capture any cementation-induced changes in loading. Imbalance was observed in 44% of patients after cementation. There was no difference in the proportion of imbalance due to surgeon experience (P=.456), cement type (P=.429), or knee system (P=.792). A majority of knees exhibited loading increase in the medial compartment. It was concluded that cementation technique contributes to a significant amount of balance-related variability at the fixation stage of the procedure. The use of the sensor in this study allowed for the correction of all instances of imbalance prior to closure. More objective methods of balance verification may be important for ensuring optimal surgical outcomes. [Orthopedics. 2017; 40(3):e455-e459.].