How are we addressing ligament balance in TKA? A literature review of revision etiology and technological advancement

The in-vivo medial and lateral collateral elongation correlated with knee functional score and joint space following unicompartmental knee arthroplasty

BACKGROUND

The medial collateral ligament (MCL) and lateral collateral ligament (LCL) are paramount for joint stability. Their elongation patterns may change during fixed-bearing and mobile-bearing unicompartmental knee arthroplasty (FB and MB UKA). This study aims to explore the relationship between the elongation of MCL, LCL, and changes in joint space, as well as their correlation with functional scale scores during FB and MB UKA.

HYPOTHESIS

We hypothesize that MCL and LCL have different elongation patterns in UKA patients, and there is a correlation between elongation and joint space and functional scores.

MATERIALS AND METHODS

The study recruited 24 patients undergoing UKA on a unilateral knee (13 FB and 11 MB). A dual fluoroscopic imaging system was employed to assess in-vivo knee kinematics during static standing and single-leg lunge. The superficial and deep MCL (sMCL, dMCL) and LCL were divided into anterior, medium, and posterior portions. The virtual ligament method quantified in-vivo ligament lengths. Analysis focused on the correlation of normalized ligament lengths with functional scores and joint space.

RESULTS

1. LCL Elongation in FB UKA: There is a significant increase in LCL elongation during early and mid-flexion of the single-leg lunge (p < 0.05). 2. MCL Elongation in MB UKA: Both sMCL and dMCL exhibit significant elongation during early and mid-flexion of the single-leg lunge (p < 0.05). 3. Correlation with Functional Scores: Differences in collateral ligament elongation in FB UKA are significantly correlated with the OKS and KSS, highlighting the impact on functional outcomes. In MB UKA, differences in ligament elongation are significantly correlated with the FJS. 4. Joint Space Correlation: There is a significant correlation between the elongation of the anterior and medium portions of dMCL and joint space in the surgical compartment during mid- and deep flexion (30-100°, p < 0.05, r > 0.64).

CONCLUSION

The study reveals distinct ligament elongation patterns between UKA and native knees in LCL for FB UKA and MCL for MB UKA. These patterns are associated with knee functional scores. Moreover, dMCL elongation correlates significantly with the joint space for MB UKA during middle and deep flexion phases.

LEVEL OF EVIDENCE

III; prospective retrospective cohort study.

Can a Total Knee System Providing 1 mm Increment of Polyethylene Insert Thickness Offer a Clinical Benefit?

Background and Objectives: The purpose of this study was to compare clinical outcomes and polyethylene (PE) insert thickness between total knee arthroplasty (TKA) systems providing 1 mm and 2 mm increments. Materials and Methods: In this randomized controlled trial, 50 patients (100 knees) undergoing same-day or staggered bilateral TKA were randomized to receive a TKA system providing 1 mm increments in one knee (1 mm group) and a TKA system providing 2 mm increments in the other knee (2 mm group). At 2 years postoperatively, Knee Society Score (KSS), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score, Forgotten Joint Score (FJS), range of motion (ROM), and insert thicknesses were compared between the groups. Results: A total of 47 patients (94 knees) participated in follow-up analysis. In each group, patient-reported outcomes improved significantly after TKA (all, p < 0.05). There were no significant differences in patient-reported outcomes. The mean ROM was not significantly different between groups at preoperative and 2-year points. The rate of postoperative flexion contracture ≥ 5° was 2.1% and 4.3%, and the rate of postoperative recurvatum ≥ 5° was 4.3% and 2.1% in the 1 mm group and 2 mm, respectively (all, p = 1.000). Mean insert thickness was significantly thinner in the 1 mm group than the 2 mm group (p = 0.001). The usage rate of a thick insert (≥14 mm) was 12.7% and 38.3% in the 1 mm group and 2 mm group (p = 0.005). Conclusions: The use of a TKA system providing 1 mm PE insert thickness increments offered no clinical benefit in terms of patient reported outcomes over systems with 2 mm increments at 2 years of follow-up. However, the TKA system with 1 mm increments showed significantly thinner PE insert usage. As a theoretical advantage of 1 mm increments has yet to be proven, the mid- to long-term effects of thinner PE insert usage must be determined.

Can a robot help a surgeon to predict a good total knee arthroplasty?

AIMS

Neither a surgeon's intraoperative impression nor the parameters of computer navigation have been shown to be predictive of the outcomes following total knee arthroplasty (TKA). The aim of this study was to determine whether a surgeon, with robotic assistance, can predict the outcome as assessed using the Knee Injury and Osteoarthritis Outcome Score (KOOS) for pain (KPS), one year postoperatively, and establish what factors correlate with poor KOOS scores in a well-aligned and balanced TKA.

METHODS

A total of 134 consecutive patients who underwent TKA using a dynamic ligament tensioning robotic system with a tibia first resection technique and a cruciate sacrificing ultracongruent TKA system were enrolled into a prospective study. Each TKA was graded based on the final mediolateral ligament balance at 10° and 90° of flexion: 1) < 1 mm difference in the thickness of the tibial insert and that which was planned (n = 75); 2) < 1 mm difference (n = 26); 3) between 1 mm to 2 mm difference (n = 26); and 4) > 2 mm difference (n = 7). The mean one-year KPS score for each grade of TKA was compared and the likelihood of achieving an KPS score of > 90 was calculated. Finally, the factors associated with lower KPS despite achieving a high-grade TKA (grade A and B) were analyzed.

RESULTS

Patients with a grade of A or B TKA had significantly higher mean one-year KPS scores compared with those with C or D grades (p = 0.031). There was no difference in KPS scores in grade A or B TKAs, but 33% of these patients did not have a KPS score of > 90. While there was no correlation with age, sex, preoperative deformity, and preoperative KOOS and Patient-Reported Outcomes Measurement Information System (PROMIS) physical scores, patients with a KPS score of < 90, despite a grade A or B TKA, had lower PROMIS mental health scores compared with those with KPS scores of > 90 (54.1 vs 50.8; p = 0.043). Patients with grade A and B TKAs with KPS > 90 were significantly more likely to respond with "my expectations were too low", and with "the knee is performing better than expected" compared with patients with these grades of TKA who had a KPS score of < 90 (40% vs 22%; p = 0.004).

CONCLUSION

A TKA balanced with robotic assistance to within 1 mm of difference between the medial and lateral sides in both flexion and extension had a higher KPS score one year postoperatively. Despite accurate ligament balance information, a robotic system could not guarantee excellent pain relief. Patient expectations and mental status also significantly affected the perceived success of TKA. Cite this article: Bone Joint J 2021;103-B(6 Supple A):67-73.

Sensor-guided technology helps to reproduce medial pivot kinematics in total knee arthroplasty

METHODS

Two cohorts of 50 patients each were preoperatively matched to receive the same TKA, having a J-curve femoral design with an adapted "medially congruent" polyethylene insert; the second cohort (group B) underwent the intraoperative sensor-check. Intraoperative sensor data were recorded as tibiofemoral load at 10°, 45°, and 90°. We considered stable knees those with a pressure <50 lbs on the medial compartment, <35 lbs on the lateral, and a mediolateral inter-compartmental difference <15 lbs. Clinical outcomes were evaluated according to the Oxford Knee Score (OKS) and Knee Society Score (KSS).

RESULTS

All patients (group A: no sensor; group B: sensor) were available at 2-year minimum follow-up (FU; min. 24 months, max. 34 months); no preoperative statistical differences existed between groups in the average range of motion (ROM), OKS, KSS, and body mass index. There were no statistical differences at final FU between groups in the average OKS (group A: 41.1; group B: 41.5), in the average KSS (group A: 165.7; group B: 166.3), or in final ROM (group A: 123°; group B: 124°). One patient in each group required a manipulation under anesthesia. In the sensor group, an accessory soft tissue release/bone recut was necessary after sensor testing with trial components in 24% to obtain the desired loads; in the same group, the level of constraint in the final components was increased to posterior-stabilized in 12% because of an inter-compartmental difference >40 lbs. Surgical time was 8 min longer in the sensor group.

CONCLUSION

The use of this sensing technology did not improve the clinical outcome but supported multiple intraoperative decisions aimed to better reproduce the medial pivot kinematic of the normal knee.

Soft-Tissue Balancing Technology for Total Knee Arthroplasty

» Improperly balanced total knee arthroplasties are at increased risk for complications including residual pain and/or instability, which are often corrected by a revision surgical procedure. » Because of the morbidity and financial burden associated with revision total knee arthroplasty, different technological applications, such as tibial insert sensors and computer-assisted gap balancing, are being used to assist with soft-tissue balancing during primary total knee arthroplasty. » Computer-assisted gap balancing increases the accuracy of mechanical alignment and improves the precision of balancing flexion and extension gaps during total knee arthroplasty. It is unclear whether this translates to improved short-term or long-term outcome measures. Considerations of this technology include increased cost, increased operative time, and a steep learning curve. » Intraoperative sensors increase the accuracy of balancing by quantifying the mediolateral intercompartmental load distribution through the range of motion, which may lead to improved outcome scores, patient satisfaction, higher activity levels, and decreased pain. The advantages of this technology compared with computer assistance include decreased cost and no disruption of operative time or workflow. Limited availability with constrained implants, limited implant choices, and a lack of long-term follow-up data have reduced utilization of intraoperative sensors. » Computer-assisted gap balancing and intraoperative sensors are not yet universally accepted, and the cost-benefit ratio associated with their use remains a consideration in today’s cost-conscious health-care environment. Future research should focus on longer-term follow-up to evaluate implant survivorship, cost-effectiveness, and clinical outcomes.

Evaluating distal femoral torsion and posterior condylar line reliability for adjusting femoral component rotation in TKA, Egyptian population radiographic study

BACKGROUND

Femoral component rotational alignment is critical for successful TKA. The primary study objective is to measure the preoperative distal femoral torsion (DFT) of an Egyptian patient's cohort using a seated posteroanterior (PA) knee radiograph. The secondary objectives are to check the intraoperative reliability of using the posterior condylar line (PCL) as a reference for rotation and to measure postoperative component rotation using the same radiographic technique.

METHODS

100 arthritic knees, 22 males, 78 females, 95 Varus and five valgus. A long anteroposterior radiograph [Hip to knee to ankle (HKA)] for coronal alignment assessment, and the anatomical posterior condylar angle (aPCA) between the anatomical transepicondylar axis (aTEA) and the PCL was measured in the seated PA knee radiographs for evaluating the DFT and component rotation. Intraoperative rotation was adjusted to 3° external rotation to the PCL.

RESULTS

HKA improved from a preoperative mean 170.4° ± 6.2 to a postoperative mean 178.3° ± 1.5 (p < 0.005). DFT was internal in all knees; the mean aPCA was -4.5 ± 2.4 (0° to -9°), femoral component rotation significantly changed to a mean aPCA of -3.6 ± 2.3 (0° to -7°) (p = 0.005). Acceptable intraoperative patellar tracking in 94%, and patellar subluxation needed a lateral retinacular release in 2% (two valgus knees). The preoperative DFT was not affected by sex or direction of coronal deformity; more external DFT noticed in severe varus deformity.

CONCLUSIONS

All keens had an internal DFT not affected by sex, or coronal deformity direction. Using PCL as a guide to adjust femoral component rotation is a valid technique in our population.

Advances in Computer-Aided Technology for Total Knee Arthroplasty

Technology such as computer-assisted navigation systems, robotic-assisted systems, and patient-specific instrumentation has been increasingly explored during the past decade in an effort to optimize component alignment and improve clinical outcomes. Computer-assisted navigation accurately restores mechanical-axis alignment, but clinical outcome data are inconsistent. Computer-assisted navigation gap balancing has shown early promise in establishing mechanical-axis alignment with improved functional outcomes. Robotic-assisted systems more accurately restore component alignment when compared with computer-assisted navigation, but clinical outcomes have yet to be determined. Patient-specific instrumentation does not consistently improve alignment, accuracy, or patient outcomes. Studies demonstrating implant survivorship, cost-efficiency, and improved clinical outcomes and patient satisfaction are needed. [Orthopedics. 2017; 40(6):338-352.].