Posterior cruciate ligament recruitment affects antero-posterior translation during flexion gap distraction in total knee replacement: An intraoperative study involving 50 patients

Background and purpose

Because of the oblique orientation of the posterior cruciate ligament (PCL), flexion gap distraction could lead to anterior movement of the tibia, which would influence the tibiofemoral contact point. This would affect the kinematics of the TKR. We assessed the flexion gap parameters when the knee is distracted during implantation of a PCL-retaining TKR. Furthermore, the effects of PCL elevation (steep or flat) and collateral ligament releases on the flexion gap parameters were determined.

Methods

During a ligament-guided TKR procedure in 50 knees, the flexion gap was distracted with a double-spring tensor with 200N after the tibia had been cut. The flexion gap height, anterior tibial translation, and femoral rotation were measured intraoperatively using a CT-free navigation system.

Results

During flexion gap distraction, the greatest displacement was seen in anterior-posterior direction. Mean ratio between increase in gap height and tibial translation was 1 to 1.9, and was highest for knees with a steep PCL (1 to 2.3). Knees with a flat PCL and knees with a ligament release had a larger increase in PCL elevation when the gap was distracted.

Interpretation

When the PCL is tensioned, every extra mm that the flexion gap is distracted can be expected to move the tibia anteriorly by at least 1.7 mm (flat PCL), or more if there is a steep PCL. This changes the tibiofemoral contact point, which may have consequences for polyethylene wear.     

Posterior cruciate ligament balancing during total knee arthroplasty

This study was undertaken to describe and evaluate the use of a posterior cruciate ligament balancing technique in total knee arthroplasty. Two hundred sixty total knee arthroplasties in 156 patients were performed between January 1984 and December 1985 using the described technique of posterior cruciate ligament balancing when necessary. Seventy-eight arthroplasties (30%) required ligament balancing to obtain a smooth flexion arc. At 1-year minimum follow-up evaluation, no knee was found to be unstable in the anterior-posterior plane. Average flexion arc for the posterior cruciate ligament balanced knees was 2 degrees - 114 degrees and for the standard arthroplasty was 2 degrees - 107 degrees. Posterior cruciate ligament balancing is a useful adjunct in total knee arthroplasty surgery when flexion gap tightness occurs.     

Posterior cruciate ligament effects on the flexion space in total knee arthroplasty

Twelve fresh frozen anatomic specimen knees were used in this study to measure changes in the tibiofemoral joint gaps after sacrificing the posterior cruciate ligament. Joint gap changes were measured using a motion tracking device in full extension and at 45 degrees and 90 degrees flexion. Tibiofemoral gaps were measured with no external compressive loads and under tension to define the flexion gap, the space available to be filled by components. After initial anterior cruciate ligament removal, meniscectomy, and a 1-cm tibial plateau cut, sacrifice of the posterior cruciate ligament caused significant differences in the flexion gap. At 90 degrees flexion the tibia distracted from the femur 5.26 +/- 1.9 mm (range, 3.2-9.1 mm) at rest and 6.4 +/- 2.5 mm under tension. No differences in the joint space were calculated in full extension under either loading case. The authors conclude that a major result of posterior cruciate ligament sacrifice is the creation of a larger flexion gap. This result provides insight into relative joint line changes that can occur after posterior cruciate ligament sacrifice. It also suggests the need for greater attention to flexion stability when sacrificing the posterior cruciate ligament and rethinking the role of posterior cruciate ligament release in the management of pure, primary flexion contracture.     

Factors affecting flexion gap tightness in cruciate-retaining total knee arthroplasty

With the exception of flexion gap tightness, which is common in cruciate-retaining (CR) total knee arthroplasty (TKA), the risk factors of flexion gap tightness have not been described. This retrospective study characterized factors that are associated with flexion gap tightness in CR TKA. Data on 203 consecutive knees that underwent CR TKA were reviewed. The prevalence rate of flexion gap tightness was 21.1%. By logistic regression analysis after adjusting for age, preoperative flexion contracture, and referencing method used for femoral sizing, insufficient tibial slope remained a significant independent risk factor of flexion gap tightness. Although excessive tibial slope should be avoided, the findings of the present study demonstrate that the risk of flexion gap tightness can be reduced by increasing the tibial slope in CR TKA.     

Total knee arthroplasty ligament balancing and gap kinematics with posterior cruciate ligament retention and sacrifice

This cadaver study was undertaken to gain insight into the effects that posterior cruciate ligament retention and sacrifice would have on the amount of deformity correction obtained with medial and lateral structure release during total knee arthroplasty. Twenty-seven cadaveric specimens were used to sequentially release medial and lateral structures with and without posterior cruciate support. Each release sequence was tested in full extension and 90 degrees flexion. In full extension, the resulting change into valgus after release of the posterior cruciate ligament, posteromedial capsule/oblique ligament complex, superficial medial collateral ligament, and pes anserinus and semimembranosus tendons was 6.9 degrees, and it increased to 13.4 degrees in 90 degrees flexion. With preservation of the posterior cruciate ligament this decreased to 5.2 degrees in extension and 8.7 degrees in flexion. Changes seen in 90 degrees flexion were significantly greater than those in full extension. For the valgus knee model with release of the posterior cruciate ligament, posterolateral capsule, lateral collateral ligament, iliotibial band, popliteus tendon, and lateral head of the gastrocnemius, 8.9 degrees of change into varus was seen in extension and 18.1 degrees in 90 degrees flexion. With posterior cruciate ligament retention 5.4 degrees and 4.9 degrees of change into varus was seen in extension and flexion, respectively. Significantly less change with retention of the posterior cruciate ligament was seen with both medial and lateral release and more opening of the flexion gap was seen on the release side of the joint for all groups except those with lateral release with sacrifice of the posterior cruciate ligament.     

The role of the posterior cruciate ligament in total knee replacement

We randomised 129 knees which were to be replaced using a standard posterior-cruciate-ligament (PCL)-retaining cemented total knee replacement into two groups. In one the PCL was retained in the normal way and in the other it was resected. They were well matched, with a predominance of women, and a mean age of 67 years. There was no statistically significant difference in the Hospital for Special Surgery scores at a mean of 57 months (56 to 60) between the two groups although 21 patients (24 knees) were lost to follow-up. Relief from pain, correction of deformity, range of movement, stability and strength were comparable in both. Radiological assessment showed femoral rollback in approximately 20% of knees with a slightly higher incidence in the PCL-resected group. There was no significant loosening detected in either group at review at two years. At five years, one knee in the PCL-retained group had been revised because of infection and one patient in each group was awaiting revision for loosening. Our findings have shown no significant difference in the five-year results for a PCL-retaining total knee replacement if the PCL is excised or preserved. This suggests two important points. First, the PCL is not functional in most patients with a total knee replacement even when retained. Secondly, patients with an excised PCL show a good result with a PCL-retaining implant, thereby questioning the need for a posterior stabilised design in such a situation.     

Effects of posterior condylar osteophytes on gap balancing in computer-assisted total knee arthroplasty with posterior cruciate ligament sacrifice

Objective

Gap planning in navigated total knee arthroplasty (TKA) is a critical concern. Osteophytes are normally removed prior to gap planning, with the exception of posterior condylar osteophytes of the femur, which are removed after posterior condylar resection. This study investigated how posterior condylar osteophytes affect gap balancing during surgery.

Methods

This prospective study was conducted on 40 primary varus osteoarthritic knees with a posterior condylar osteophyte that underwent TKA navigation. For all knees, computed tomography (CT) was performed to evaluate osteophyte position. The extension gap and flexion gap were determined under navigation using a tension device with a distraction force of 44 lb. The extension gap and flexion gap were measured before and after osteophyte removal.

Results

This study revealed that the average osteophyte thickness after removal was 7.75 ± 5.34 mm. The average extension gap change was 0.64 ± 0.80 mm, and the average flexion gap change was 0.85 ± 1.12 mm. With respect to increases in the medial extension gap, lateral extension gap, medial flexion gap and lateral flexion gap, the average effects of posterior condylar osteophyte removal were 0.74 ± 0.81 mm, 0.53 ± 0.96 mm, 0.71 ± 0.97 mm and 1.00 ± 1.41 mm, respectively. Posterior condylar osteophyte thickness was also significantly associated with increases in the lateral extension gap (R² = 0.107, p = 0.03), medial flexion gap (R² = 0.101, p = 0.04) and lateral flexion gap (R² = 0.107, p = 0.04).

Conclusion

These results indicated that posterior condylar osteophytes of the femur affect gap balancing during TKA navigation.

     

Anterior cruciate ligament integrity in osteoarthritis of the knee in patients undergoing total knee replacement

Background  

Anterior cruciate ligament (ACL) rupture has been implicated in the development of knee osteoarthritis (OA). This study aimed at determining the incidence of prior ACL deficiency in patients undergoing total knee replacement (TKR), the effect of prior ACL deficiency on function and the macroscopic and microscopic appearance of the ligament.     

Skin incision translation in total knee arthroplasty: the difference between flexion and extension

Scar location and point loading of the scar after total knee arthroplasty are common postoperative concerns for patients and physicians. A frequent problem is discomfort associated with the incision. We evaluated 40 knees to better understand the association of the tibial tubercle with the overlying skin in both flexion and extension. Our results revealed lateral translation of the skin overlying the tibial tubercle in 100% of our volunteers as the knee is flexed and the tibia internally rotates. The average amount of lateral translation measured 9.7 mm. This could have a significant impact on point loading of the scar if an anterior midline incision for total knee arthroplasty is planned in extension.     

The posterior cruciate ligament during flexion of the normal knee

The posterior cruciate ligament (PCL) was imaged by MRI throughout flexion in neutral tibial rotation in six cadaver knees, which were also dissected, and in 20 unloaded and 13 loaded living (squatting) knees. The appearance of the ligament was the same in all three groups. In extension the ligament is curved concave-forwards. It is straight, fully out-to-length and approaching vertical from 60 degrees to 120 degrees, and curves convex-forwards over the roof of the intercondylar notch in full flexion. Throughout flexion the length of the ligament does not change, but the separations of its attachments do. We conclude that the PCL is not loaded in the unloaded cadaver knee and therefore, since its appearance in all three groups is the same, that it is also unloaded in the living knee during flexion. The posterior fibres may be an exception in hyperextension, probably being loaded either because of posterior femoral lift-off or because of the forward curvature of the PCL. These conclusions relate only to everyday life: none may be drawn with regard to more strenuous activities such as sport or in trauma.     

Posterior cruciate ligament and coupled posterolateral instability of the knee

We wanted to investigate the role of the posterior cruciate ligament (PCL) in the knee's posterolateral stability and the magnitude of the coupled posterolateral instability with the knee examined at 90 degrees of flexion. The coupled posterolateral instability of the knee was studied by selective ligament cutting in cadaver knees set at 90 degrees. The coupled posterolateral displacement after cutting the PCL was 173% of the intact knee. With an intact PCL, the coupled posterolateral displacement after cutting the popliteus tendon and lateral collateral ligament with the knee at 90 degrees of flexion was 299% of the intact knee. When the PCL was cut together with the popliteus tendon and lateral collateral ligament, the coupled posterolateral displacement was 367%. The PCL plays an important role in the posterolateral stability of the knee, and its injury may cause mild (< 5 mm) to moderate (5-10 mm) posterolateral instability. Thus, in a knee with posterolateral instability, injury of the PCL must be considered. With an intact PCL, the posterolateral instability was very recognizable with the knee at 90 degrees of flexion, and injury to the PCL further increased the posterolateral instability and caused posterior translation of the knee. Therefore, examination for posterolateral instability of the knee should also be performed with the knee at 90 degrees of flexion, which is much easier to perform in a clinical setting. A positive posterior translation rather than posterolateral instability at different knee positions differentiates knees with combined PCL and posterolateral instability from knees with isolated posterolateral instability.     

Decreased posterior tibial slope increases strain in the posterior cruciate ligament following total knee arthroplasty

The purpose of this study was to measure the strain in the posterior cruciate ligament as a function of knee flexion angle and posterior tibial slope following total knee arthroplasty with a posterior cruciate ligament-retaining design. Posterior cruciate ligament strain was measured in seven fresh-frozen cadavers for posterior tibial slopes of 10°, 8°, and 5°. For all three levels of tibial slope tested, strain in the posterior cruciate ligament increased with increasing flexion angle to approximately 100° and then decreased with increasing flexion. The strain measured at 8° posterior tibial slope was greater than that measured at 10°, but the difference was not significant. The strain measured at 5° posterior slope was significantly greater than strain measured at both 8° and 10°. This increased strain may result in altered knee kinematics and reduced range of motion at higher flexion angles.     

Posterior cruciate ligament replacement with a two-strand quadriceps tendon-patellar bone autograft and a tibial inlay technique

BACKGROUND: Complete ruptures of the posterior cruciate ligament alter knee kinematics and may result in functional limitations with sports and daily activities. We prospectively evaluated the functional results and knee stability after posterior cruciate ligament replacement with use of a two-strand quadriceps tendon-patellar bone autograft and a tibial inlay technique. METHODS: Nineteen patients were followed for a mean of thirty-five months postoperatively. All had a chronic knee injury, and eight had additional ligament reconstructions. The results were measured with stress radiography, arthrometric testing, and two validated knee-rating instruments. RESULTS: Eighteen patients rated the knee condition as improved. Before surgery, eleven patients had pain with daily activities, but only one had such pain at the time of the latest follow-up. Significant improvements were noted for pain, swelling, giving-way, walking, climbing stairs, squatting, running, jumping, and twisting and turning (all p < or = 0.05). Eleven patients returned to low-impact sports, and two patients were able to participate in strenuous sports without problems. At the time of the latest follow-up, stress radiography revealed that fourteen knees had < or =5 mm of increased posterior tibial translation between the reconstructed and the contralateral side, three knees had 6 to 10 mm, and two knees had >10 mm. No knee had an infection, permanent limitation of knee motion, or patellar fracture. CONCLUSIONS: Posterior cruciate ligament replacement produced reasonable subjective, functional, and objective results in this group of complex, chronic knee injuries. The tibial inlay approach was useful in nine revisions in which prior tibial tunnels had to be avoided.     

Posterior-stabilized versus cruciate-retaining total knee arthroplasty: balancing the gap

A prospective, randomized, double-blind trial was carried out to compare cruciate-retaining (CR) and posterior-stabilized (PS) total knee arthroplasties (TKAs). A total of 40 knees were randomized to receive either a NexGen CR (Zimmer, Warsaw, IN) or a Legacy PS (Zimmer, Warsaw, IN) TKA. All knees were implanted with identical surgical technique, making sure to balance precisely the flexion-extension gaps before implantation of the components. At 2-year follow-up, there was no difference between the CR and the PS TKAs with respect to their Knee Society clinical, functional, and radiographic scores. These findings suggest that with careful attention to surgical technique and balancing the knee, orthopaedic surgeons should expect similar results whether they use a CR or PS TKA.     

Precision of Ci-navigated extension and flexion gap balancing in total knee arthroplasty and analysis of potential predictive variables

Introduction  

The aim of this study was to evaluate the accuracy of final limb alignment and flexion–extension and medial–lateral gap balancing in computer navigated total knee arthroplasty and to analyze various possible predictive variables that may affect the gaps in computer navigated knee arthroplasty.     

Preparation of the flexion gap affects the extension gap in total knee arthroplasty

Changes in the extension gap caused by the preparation of the flexion gap were measured in 50 varus osteoarthritic knees undergoing total knee arthroplasty. The extension gap was first prepared and then measured before and after preparation of the flexion gap. The extension gap increased significantly on both the medial and lateral sides (19.3 +/- 0.3 to 22.0 +/- 0.3 and 21.9 +/- 0.3 to 24.0 +/- 0.3 mm, respectively, mean +/- SE, both P < .0001). The increase was greater medially (P = .0014), and in the knees with more varus deformities (> or = 10 degrees, P = .0075). Thus, preparation of the flexion gap resulted in significant widening of the extension gap, especially on the medial side. The medial release should be stepwise and conservative to achieve adequate soft tissue balance.     

The relationship between the intercondylar roof and the tibial plateau with the knee in extension: relevance for tibial tunnel placement in anterior cruciate ligament reconstruction.

The relationship between the intercondylar roof and the tibial plateau with the knee in full extension was studied in 100 patients with a unilateral anterior cruciate ligament (ACL) lesion. A lateral view of both knees in full extension with superimposition of the femoral condyles was obtained with the fluoroscope. We found that, in the normal knee, the roof line intersects the tibial plateau (roof-plateau intersection ratio) at 31.5% (SD +/- 5%) of its width and at 33.9% (+/- 5.4%) in the ACL deficient knee (P < .001). The difference was attributable to a subtle anterior tibial displacement in the ACL-deficient knee. Multiple regression analysis showed a direct relationship between roof-plateau intersection ratio and the angle between roof line and tibial plateau (P = .0006). A direct relationship of borderline significance (P = .06) was present with the knee recurvatum measured clinically. In conclusion, the roof-plateau intersection ratio has a wide range of variability (22% to 41%). The larger the roof-plateau angle the more posterior the roof-plateau intersection ratio.     

Long-term results of retention of the posterior cruciate ligament in total knee replacement in rheumatoid arthritis

We analysed the long-term results with a mean follow-up of 10.2 years, of 66 total knee replacements in 42 patients with rheumatoid arthritis. In all cases the posterior cruciate ligament was retained. There were only three complications (4.5%). Revision surgery was necessary in five knees (7.6%), including one (1.5%) with infection. At the final follow-up, 75.8% of knees were rated excellent clinically. Only 15% had an excellent function score. The survival rate of the implant was 90.7% at 19 years. The clinical, radiological and survivorship analysis shows that the posterior-cruciate-retaining knee arthroplasty performs well in rheumatoid arthritis.