No difference in anterior tibial translation with and without posterior cruciate ligament in less invasive total knee replacement

Cruciate-retaining total knee arthroplasty: How much of the PCL is really retained?

PURPOSE

It is questionable how much of the PCL is really preserved following a complete transverse tibial cut during a cruciate-retaining (CR) total knee arthroplasty (TKA). It is hypothesized that a complete transverse tibial cut jeopardizes the PCL tibial insertion during a common CR TKA. Thus, the aim of the present study was to assess intraoperatively the amount of PCL tibial attachment damage following a standard complete tibial cut technique.

METHODS

Thirty consecutive female patients suffering from degenerative knee osteoarthritis were included. Two measurements were performed on preoperative MRI images. On sagittal plane, the PCL facet of tibia and the PCL tibial attachment were measured. All 30 patients underwent a TKA using a common CR prosthesis. Postoperatively, the amount of PCL facet resection was measured on the resected tibial plateau using a digital sliding caliper.

RESULTS

In preoperative MRI images, the length of the PCL facet of tibia was found 25.5 ± 2.1 mm and the length of the PCL tibial attachment was 14.5 ± 1.3 mm. The amount of PCL facet resection following TKA was 20.6 ± 2.2 mm on average. This result corresponds to an average resection of 65.1 ± 15.9 % of the PCL tibial attachment following TKA.

CONCLUSION

The hypothesis that a complete transverse tibial cut during a conventional CR TKA jeopardizes the PCL tibial insertion was confirmed. According to measurements performed on preoperative knee MRI scans and surgical specimens of resected tibial plateaus, a significant amount of the PCL insertion on the tibia is actually removed in the majority of cases. Surgeons should be aware that when resecting the tibial plateau without using a technique that spares the PCL tibial attachment, there is a high risk of considerable damage to the PCL that may, in turn, increase the likelihood of potential complications due to PCL deficiency.

LEVEL OF EVIDENCE

IV.

Patient-related factors influence stiffness of the soft tissue complex during intraoperative gap balancing in cruciate-retaining total knee arthroplasty

PURPOSE

How much force is needed to pre-tension the ligaments during total knee arthroplasty? The goal of this study was to determine this force for extension and flexion, and for both compartments, and to identify predicting patient-related factors.

METHODS

Eighty patients [55 females, mean age 71 (SD 9.7)] were recruited and had a navigated cruciate-retaining total knee arthroplasty. Distraction of the medial and lateral compartments of the extension and flexion gap (90°) with an instrumented bi-compartmental double-spring tensioner took place after finishing the bone cuts. Applied forces and resulting gap distances were recorded by the navigation system, resulting in a force-elongation curve. Lines were fitted with the intersection defined as the stiffness transition point. The slopes (N/mm) represented the stiffness of the ligamentous complex. Linear multiple regression analysis was performed to identify predicting factors.

RESULTS

The amount of force at the stiffness transition point was on average 52.3 (CI₉₅ 50.7-53.9), 54.5 (CI₉₅ 52.7-56.3), 48.3 (CI₉₅ 46.2-50.2), and 59.3 (CI₉₅ 57.0-61.6) N for the medial and lateral extension and flexion gap, respectively, and varied considerably between patients. The force at the stiffness transition point was significantly different between extension and flexion and both compartments (P < 0.05). Stiffness of the ligaments statistically significantly helped to predict the amount of force at the stiffness transition point, as well as body mass index, gender, and varus-valgus alignment.

CONCLUSION

The amount of force at the stiffness transition point varies between 48 and 59 N, depending on flexion/extension and compartment. Patient-related factors influence the stiffness transition point and can help predict the stiffness transition point. When forces higher than 60 N are used for gap distraction, the ligamentous sleeve of the knee might be over-tensioned.

LEVEL OF EVIDENCE

Prognostic study, Level I-high-quality prospective cohort study with >80 % follow-up, and all patients enrolled at same time point in disease.

Deep-dished highly congruent tibial insert in CR-TKA does not prevent patellar tendon angle increase and patellar anterior translation

PURPOSE

Starting from the hypothesis that a deep-dished highly congruent tibial insert in cruciate-retaining total knee arthroplasty would prevent the increase in patellar tendon angle and anterior patellar translation by reducing the paradoxical anterior femoral translation, the main purpose of the present study was to investigate the effect of this prosthesis design, and secondary to assess the clinical outcomes at 6-month follow-up.

METHODS

Twenty patients treated with cruciate-retaining total knee arthroplasty with navigation technique were enrolled and prospectively followed up at 6 months. The median value of age was 71 years (57-83). Before and after surgery, the following parameters were calculated: patellar tendon angle, anterior-posterior and medio-lateral patellar translation, patellar height and range of motion. All patients were assessed with the SF-36 Physical Functioning and the Knee injury and Osteoarthritis Outcome Score ADL scores.

RESULTS

Patellar tendon angle and anterior patellar translation significantly increased in post-operative conditions (p < 0.0001); a statistically significant medial patellar translation was found (p < 0.0001), while patellar height did not show any difference between pre- and post-operative conditions (n.s). A significant correlation was found between patellar tendon angle and anterior patellar translation and the clinical scores (p < 0.0417). There was a significant post-operative decrease (p < 0.0033) in the range of motion.

CONCLUSIONS

The present study failed to demonstrate that deep-dished highly congruent tibial insert prevents the anterior translation of the patella in cruciate-retaining total knee arthroplasty, thus causing inferior clinical scores. It provided useful information about the biomechanical role of the patella in total knee arthroplasty, allowing to choose the most appropriate surgical approach.

LEVEL OF EVIDENCE

Case series, Level IV.

How much of the PCL is really preserved during the tibial cut?

PURPOSE

There are two different techniques for retaining the posterior cruciate ligament (PCL) in total knee arthroplasty. The attachment of the PCL can be spared during resection of the tibial plateau, so that a small posterior bone block remains. In contrast to this, many surgeons resect the tibial plateau completely and detach a part of the tibial PCL attachment from the resected material. The objective of this study was to determine how big this part is in an anatomical resection of the tibial plateau with 0° and 7° slope and whether it is gender-dependent.

METHODS

Two hundred consecutive patients who had undergone MRI of a knee joint were included. Patients were excluded if they were younger than 18 years or had dysplasia of the knee joint or injuries of the posterior cruciate ligament. The MRIs of 182 knees that fulfilled the inclusion criteria were analysed. For each knee, an anatomical tibial resection with 0° and 7° posterior slope was simulated, and the parts of the tibial PCL attachment that were resected and retained were determined.

RESULTS

Given a measured tibial resection with 0° slope, 45 ± 28% of the tibial PCL attachment was removed in the men, compared with 46 ± 30% in the women (n.s.). Given a resection with 7° slope, 69 ± 24% of the tibial PCL attachment was removed in the men and 67 ± 25% in the women. This corresponded to a complete resection in 19 men (20%) and 16 women (24%).

CONCLUSIONS

Independently of gender, the anatomical resection of the tibia leads to the removal of a considerable part of the tibial PCL attachment, if this is not spared in the form of a bone block during resection. This becomes increasingly relevant with higher posterior slope of the resection plane. In the case of a cruciate-retaining surgical technique, the retention of the posterior tibial cortical bone in the area of attachment of the PCL is therefore strongly recommended.

LEVEL OF EVIDENCE

II.