Comparison of cruciate retaining and PCL sacrificing TKA with respect to medial and lateral gap differences in varus knees after medial release

Preoperative Factors Predicting the Preservation of the Posterior Cruciate Ligament in Total Knee Arthroplasty

Objective

Predicting the successful preservation of posterior cruciate ligament (PCL) in total knee arthroplasty (TKA) is an important step for preoperative planning to secure the satisfactory outcomes. We aimed to examine the preoperative factors predicting the successful preservation of the PCL in cruciate‐retaining TKA and the outcome of sacrificing the PCL.

Methods

In this retrospective study, we analyzed TKAs consecutively performed by a single surgeon between January 2019 and August 2021 who had been preoperatively planned to undergo implantation of cruciate‐retaining (CR) prostheses. The outcome of the current study was whether the PCL was retained or sacrificed. Anterior‐stabilized (AS) tibial bearings when the PCL was sacrificed as needed were used intraoperatively. Age, sex, body mass index (BMI), and preoperative diagnosis from the patients' medical records were obtained. The medial‐lateral width of epicondyle (MLW), the medial posterior condyle height (MPCH), the lateral posterior condyle height (LPCH), the ratio of MLW and MPCH, the ratio of MLW and LPCH, the Insall–Salvati index, and the severity of the varus or valgus deformity were measured using preoperative radiographs. Univariate and multivariate regression were fitted to assess the association of these factors with the successful retention of PCL. To examine the influence of sacrifice of the PCL on the surgical procedure, the size of the tibial and femoral components, the thickness of the polyethylene insert, and the rate of patella replacement between the CR group and AS group were also compared using t tests or chi‐square tests.

Results

Among 307 TKAs included, PCL was sacrificed with concurrent use of AS prostheses in 89 (29.0%) procedures. Knees with rheumatoid arthritis (P < 0.01), lower Insall–Salvati index (P < 0.01), and more severe varus deformity (P = 0.011) were at a higher risk of sacrificing the PCL intraoperatively. There was no significant difference in age, sex, BMI, MLW, MPCH, LPCH, ratio of MLW and MPCH, ratio of MLW and LPCH, size of the tibial and femoral components, or replacement of the patella between the CR and AS groups. Converting from CR to AS was associated with a higher risk of using a thicker polyethylene insert (P < 0.01).

Conclusion

Rheumatoid arthritis, lower Insall–Salvati index, and more severe varus deformity were associated with an increased risk of sacrificing the PCL in TKAs planned to undergo implantation CR prostheses. Converting to AS tibial bearing may result in a thicker polyethylene insert. These factors should be carefully considered for the appropriate selection of prosthesis type preoperatively.

Effects of the posterior cruciate ligament and tibia insert thickness on tibiofemoral joint pressure in total knee arthroplasty: a cadaveric study

Background

Emerging knowledge has highlighted the significant role of the posterior cruciate ligament (PCL) in total knee arthroplasty (TKA). However, few studies have reported how the PCL affects tibiofemoral joint pressure (TFP), and differences in the effects of the PCL and the effects of tibial insert thickness on TFP remain unknown. Thus, this study used the sensor technique to analyze and compare the effects of PCL and tibial insert thickness on TFP during knee flexion.

Methods

Cruciate-retaining total knee arthroplasty (CR-TKA) was performed in 8 cadaveric knees. The PCL was partially released and completely resected sequentially while the tibial insert thickness was increased from 10- to 12-mm at 1-mm intervals. With the optimal tibial insert in place, the effects of PCL release and resection on medial and lateral TFP during knee flexion were analyzed. Medial tibiofemoral joint pressure (MTFP) with PCL retention and a 12-mm tibial insert was set as the baseline. The effects of PCL resection without tibial insert thickness reduction on MTFP were compared to the effects of PCL retention with a 1- or 2-mm thinning of the tibial insert on MTFP during knee flexion.

Results

PCL resection significantly reduced MTFP at 90° and 120° of knee flexion (P=0.01 and P=0.03, respectively). Partial release and complete resection of the PCL did not significantly reduce lateral tibiofemoral joint pressure (LTFP) at 10°, 30°, 60°, 90° and 120° of knee flexion (P=0.68, P=0.60, P=0.62, P=0.21 and P=0.12, respectively). At 10°, 30°, and 60° of knee flexion, a 1-mm reduction in the tibial insert had a greater effect on MTFP than did the resection of the PCL. In contrast, at 90° of knee flexion, MTFP was more affected by PCL resection than by a 2-mm reduction of the tibial insert.

Conclusions

The PCL predominantly affects MTFP at 90° and 120° of knee flexion. The impact of PCL resection on MTFP at 90° flexion was higher than the impact of a 2-mm thinning of the tibial insert.

Cruciate-Retaining vs Posterior-Stabilized Primary Total Arthroplasty. Clinical Outcome Comparison With a Minimum Follow-Up of 10 Years

BACKGROUND

Controversy continues regarding whether the posterior cruciate ligament should be retained or removed during total knee arthroplasty (TKA) procedure. The objective was to compare the clinical outcomes with a minimum follow-up of 10 years between patients who received contemporary cruciate-retaining or posterior-stabilized primary TKA.

METHODS

Case-control study of 268 patients who underwent cruciate-retaining TKA vs 211 to posterior-stabilized design, with the same arthroplasty system, and a minimum follow-up of 10 years. Clinical assessment was performed by Knee Society scores, Western Ontario and MacMasters Universities and Short-Form 12 questionnaires, range of motion, and patient satisfaction.

RESULTS

Successful outcomes were found for both designs. No significant differences in functional scores, range of motion, patient-related scores, or patient satisfaction. Between the 5-year and last postoperative follow-up, there were a significant decrease of all clinical scores in both groups. In addition, complication rate and implant survival were similar between groups.

CONCLUSION

The superiority of one design over the other was not found. Both designs can be used expecting long-term successful outcomes and high survival. The choice of the design depended on the status of the posterior cruciate ligament and surgeon preference.

Posterior cruciate-retaining versus posterior-stabilized total knee arthroplasty for osteoarthritis with severe varus deformity

Objective

The aim of this study was to compare the radiological and functional results of posterior cruciate ligament (PCL) – retaining and posterior-stabilized total knee arthroplasties in patients with severe varus gonarthrosis.

Methods

Medical records of 112 knees of 96 patients who underwent total knee arthroplasty for severe varus (≥15°) were reviewed. PCL-retaining and PCL-stabilizing groups consisted of 58 and 54 knees, respectively. Mean follow-up time was 56.6 months (range: 24–112 months). Knee Society (KS) clinical rating system was used in clinical evaluation. Range of motion, degree of flexion contracture, postoperative alignment, and complication rates were compared between the groups.

Results

Mean preoperative mechanical tibiofemoral angle was 20.1° in varus alignment, and was restored to 4.6° in valgus postoperatively. No statistically significant differences were found between PCL-stabilizing and PCL-retaining groups when KS knee scores, function scores, and flexion arc were evaluated. Two patients in PCL-retaining group underwent revision surgery due to aseptic loosening of tibial component. One patient in PCL-stabilizing group needed arthrotomy due to patellar clunk syndrome.

Conclusion

There were no notable differences between the 2 groups and PCL-retaining design had outcomes as good as PCL-stabilizing total knee implant in osteoarthritic knees with severe varus deformity.

Level of evidence

Level III, Therapeutic study.

Distinctions of introarticular force distribution between genesis-II posterior stabilized and cruciate retaining total knee arthroplasty: An intraoperative comparative study of 45 patients

BACKGROUND

Although both the posterior stabilized and cruciate retaining total knee arthroplasty have been proven to effectively relieve pain and restore basic functions, the joint gap width during flexion was reported to be different due to the presence or absence of posterior cruciate ligament, which may lead to different intra-articular force distribution. In this study, we investigated the distinctions in intra-articular force distribution between the two types of TKA designs in patients with varus knee osteoarthritis.

METHODS

Forty five patients (50 knees) with varus knee osteoarthritis were prospectively included, with each 25 knees receiving cruciate retaining and posterior stabilized total knee arthroplasty, respectively. With an intra-articular force measurement system, the intra-articular force distribution with knee flexion at 0°, 30°, 45°, 60°, 90°, and 120° were recorded in all patients.

FINDINGS

The total force was similar for posterior stabilized and cruciate retaining knees at all flexion degrees. However, force in the medial compartment accounted for 59.8%-84.0% of total force in posterior stabilized knees, while 27.4%-65.7% in cruciate retaining knees. In cruciate retaining knees, no significant difference was found between forces in the two compartments at 30° flexion (P=0.444), but force was significantly concentrated in the lateral side during 45°-120° flexion (P=0.000-0.028).

INTERPRETATION

Although the entire intra-articular forces were similar between CR and PS knees at different flexion angles, medial part had higher force than lateral part when PS knee was used. The posterior cruciate ligament do a role in soft balance, and make the force more evenly distributed.

The superficial medial collateral ligament is the primary medial restraint to knee laxity after cruciate-retaining or posterior-stabilised total knee arthroplasty: effects of implant type and partial release

PURPOSE

The aim of this study was to quantify the contributions of medial soft tissues to stability following cruciate-retaining (CR) or posterior-stabilised (PS) total knee arthroplasty (TKA).

METHODS

Using a robotic system, eight cadaveric knees were subjected to ±90-N anterior-posterior force, ±5-Nm internal-external and ±8-Nm varus-valgus torques at various flexion angles. The knees were tested intact and then with CR and PS implants, and successive cuts of the deep and superficial medial collateral ligaments (dMCL, sMCL) and posteromedial capsule (PMC) quantified the percentage contributions of each structure to restraining the applied loads.

RESULTS

In implanted knees, the sMCL restrained valgus rotation (62 % across flexion angles), anterior-posterior drawer (24 and 10 %, respectively) and internal-external rotation (22 and 37 %). Changing from CR TKA to PS TKA increased the load on the sMCL when resisting valgus loads. The dMCL restrained 11 % of external and 13 % of valgus rotations, and the PMC was significant at low flexion angles.

CONCLUSIONS

This work has shown that medial release in the varus knee should be minimised, as it may inadvertently result in a combined laxity pattern. There is increasing interest in preserving constitutional varus in TKA, and this work argues for preservation of the sMCL to afford the surgeon consistent restraint and maintain a balanced knee for the patient.