Observations of femoral rollback in cruciate-retaining knee arthroplasty

The current study evaluated kinematics of the knee during a stair-climbing activity after total knee arthroplasty. All patients received a posterior cruciate ligament retaining prosthesis of the same design, having an anatomically shaped femoral component and an unconstrained tibial insert. All patients had the same surgical technique done by two experienced surgeons. Patients had some posterior femoral rollback and screw-home type axial rotations during weightbearing activities. However, patients treated by different surgeons had different patterns of tibiofemoral motions. In Group 1, rollback occurred early in the flexion range and was maintained until 80 degrees flexion. In Group 2, the lateral condyle had rollback in early flexion, but both condyles translated forward as flexion increased to 80 degrees. An anatomic femoral component seems to be necessary to produce consistent early femoral rollback. However, soft tissue balance can have a significant effect on the kinematics of sagittally unconstrained posterior cruciate retaining total knee arthroplasty, because it may vary among surgeons.     

Anterior cruciate-retaining total knee arthroplasty

Fifty patients underwent bilateral total knee arthroplasty retaining both cruciate ligaments on one side and only the posterior cruciate ligament on the other. Patients were questioned about pain, instability, “feel,” and ability to climb stairs. Seventy percent of patients stated that their anterior and posterior cruciate-retaining knee was their better knee overall. Ten percent stated that their posterior cruciate-only knee was better. Twenty percent could find no difference. There were no meaningful differences in inpatient care, physical therapy requirements, strength, range of motion, or component positioning. Fourteen patients handled stairs using each knee equally. Twenty-nine climbed stairs leading with the anterior and posterior cruciate-retaining knee and seven patients led with the posterior cruciate-only knee. Complaints of clunks, pops, and clicks occurred in 11 patients with posterior cruciate-only knee arthroplasties and in 4 patients retaining both anterior and posterior cruciate ligaments. Retaining the anterior cruciate ligament can provide a knee that subjectively “feels” better.     

Fixed-bearing cruciate-retaining total knee arthroplasty

Whether to retain, sacrifice, or substitute the posterior cruciate ligament remains controversial. There are advantages to each technique and the excellent long-term clinical results of each ensures that this controversy will continue. This article will review the indications, technique, and results of cruciate-retaining fixed-bearing total knee arthroplasty.     

Kinematic factors affecting postoperative knee flexion after cruciate-retaining total knee arthroplasty

Purpose

The purpose of this study was to investigate kinematic factors affecting postoperative knee flexion after cruciate-retaining (CR) total knee arthroplasty (TKA) by analysing pre- and postoperative knee kinematics.

Methods

We retrospectively analysed 58 patients with osteoarthritis who received the same implant series. Pre- and postoperative kinematics were measured intraoperatively using a navigation system. As a clinical outcome, we measured the knee flexion angle before and one year after surgery. Correlations among pre- and postoperative kinematics and postoperative flexion were analysed using simple linear regression analyses.

Results

Preoperative knee kinematics, including tibial internal rotation and anterior translation (R?=?0.87, P?<?0.001; R?=?0.53, P?<?0.001, respectively), were significantly correlated with postoperative kinematics. Preoperative varus–valgus movements improved significantly postoperatively; however, tibial internal rotation remained unchanged. Furthermore, postoperative knee flexion angle was significantly correlated with postoperative tibial internal rotation (R?=?0.45, P?<?0.001).

Conclusions

Preoperative knee kinematics were unchanged even after CR-TKA. Postoperative tibial internal rotation is one of the most important factors affecting postoperative knee flexion.     

Complete anterior knee dislocation 16 years after cruciate-retaining total knee arthroplasty

Anterior dislocation after total knee arthroplasty (TKA) is rare; 9 cases have been reported in the English literature. Five patients sustained subluxation, with recurvatum as the clinical manifestation, and 4 patients sustained complete dislocation, usually accompanying other serious complications.This article describes a case of complete dislocation that developed atraumatically 16 years after TKA and was characterized by dislocation in extension and spontaneous reduction in flexion. Revision TKA was planned, with several alternative procedures under consideration, ranging in degree of invasiveness from simple polyethylene exchange to conversion to a hinge-typed prosthesis. Intraoperatively, extensive areas of blackened synovium and posterior-dominant polyethylene wear existed medially and laterally. Considering the patient's age of 82 years, low activity level in activities of daily living, edematous skin, and number of stable components, we performed simple polyethylene exchange to a cruciate-retaining component that left the partial metal defect in the tibial plate untouched. Successful outcome was achieved for >2 years. The dislocation mechanism was polyethylene thinning, leading to relative valgus and anteroposterior instability that aggravated the anterior cruciate ligament dysfunction, which is speculated as the inherent key causative factor in every TKA.Complete dislocation, usually accompanying other complications, requires prompt treatment because the possibility of serious consequences exists. Due to the absence of a gold standard, the treatment of choice needs to be made on a case-by-case basis.     

In vivo determination of posterior femoral rollback for subjects having a NexGen posterior cruciate-retaining total knee arthroplasty

This study determines the in vivo kinematics during a deep-knee bend activity for subjects implanted with a posterior cruciate-retaining total knee arthroplasty having asymmetric geometries. Of 20 subjects, 19 experienced posterior femoral rollback (PFR) of the lateral condyle (average -3.9 mm), and 13 subjects experienced PFR of the medial condyle (average -3.1 mm). As a result of the lateral condyle rolling further posterior than the medial condyle, on average, subjects experienced 1.4 degrees of normal axial rotation. Of 20 subjects, 10 experienced normal axial rotation, whereas 10 experienced an opposite rotation pattern. Condylar lift-off occurred predominantly with the lateral condyle. Contrary to previous in vivo studies, the subjects in this study experienced consistent PFR of the posterior cruciate-retaining total knee arthroplasty. It can be hypothesized that having asymmetric femoral condyles may lead to PFR with increasing knee flexion.     

Femoral rollback of cruciate-retaining and posterior-stabilized total knee replacements: in vivo fluoroscopic analysis during activities of daily living.

Restoration of the physiological flexor/extensor mechanism at the knee in terms of appropriate muscular lever arms, proper required quadriceps force, and suitable patellofemoral compressive force, is fundamental for the success of total knee replacement. Therefore, measurements of anteroposterior translation of the femoral component over the tibial base-plate against joint flexion during daily living activities are essential for the assessment of the in vivo performance of current prosthesis designs. Patients treated with posterior stabilized and cruciate retaining prostheses with excellent clinical scores were evaluated during stair climbing, sitting and rising from a chair, and step up and down, using a three-dimensional pose reconstruction technique based on videofluoroscopy. The posterior stabilized patients experienced a fairly consistent and physiological rollback specific of each motor task, demonstrating proper function of the spine-cam mechanism. Rollback was somehow inconsistent among subjects in the cruciate retaining group, accompanied with a smaller range of knee flexion. In this group, more posterior locations of the condyles correlated significantly with higher clinical and functional scores. Articular surface conformity restores physiological rollback in the presence of a spine-cam mechanism, but not coherently in the presence of the posterior cruciate ligament.     

Twelve years' experience with posterior cruciate-retaining total knee arthroplasty

The posterior cruciate ligament can be retained with advantage during routine total knee arthroplasty. This ligament is virtually always intact and functioning, even in rheumatoid patients. It is an important biologic stabilizer of the knee, capable of absorbing anterior-posterior shearing forces that otherwise must be borne by a constrained prosthesis and hence by the bone-cement interface. Its presence allows maintenance of the normal kinematics of the knee. Roll-back of the femur on the tibia can occur, enhancing flexion and improving the quadriceps moment. Substitution of the posterior cruciate ligament with the addition of prosthetic constraint will increase bone-cement reaction forces. These prostheses also require significant intercondylar femoral bone stock resection. The average range of motion of the early cruciate sacrificing design used in Insall's series was 94 degrees, 10 degrees or more less than now routinely seen with cruciate preservation. The bone-cement interface of the early total condylar knee with limited range of motion absorbed less force than it potentially might encounter with greater range of motion and increased function. Predictably, at long-term follow-up examination the newer cruciate-substituting prostheses that allow more physiologic range of motion might show higher radiolucent line rates and higher loosening rates than their cruciate-preserving counterparts. Only this information can settle the argument over whether the posterior cruciate ligament should be preserved, and if the objective is a knee with maximum flexion and maximum functional capability.     

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.     

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.     

Results of posterior cruciate-retaining unconstrained total knee arthroplasty after proximal tibial osteotomy for osteoarthritis

The purpose of the study was to investigate the results of posterior cruciate ligament (PCL)-retaining total knee arthroplasty (TKA) after previous proximal closed wedge tibial osteotomy for degenerative arthritis according to the technique recommended by Coventry and Insall. Thirty-five patients with previous proximal tibial osteotomy were matched to 35 patients without previous osteotomy according to age, sex, and Knee Society patient category. TKA after osteotomy was technically more difficult, often requiring a more extensive exposure. Complications were similar in the two groups, but an extended hematoma was more common in patients with previous osteotomies (2 patients) than in those with primary arthroplasty (1 patient). Knee Society scores were significantly lower in those with previous osteotomy, primarily because of decreased anteroposterior stability and pain. No significant differences were found in function scores, range of motion, or alignment. However, overall results of this PCL-retaining unconstrained TKA did not match those reported after PCL-substituting TKA.     

Femoral component loosening in total knee arthroplasty

From experience with over 1600 condylar-type total knee arthroplasties performed between 1974 and 1981, the authors identified 15 knees in which the femoral component had loosened and shifted into flexion on the end of the femur. This mode of failure was related to inadequate support of the prosthetic posterior condyle, which resulted from inaccurate surgical cuts, poor cementing technique, or deficient bone stock either primary or secondary to persistent rheumatoid synovitis. Newer prosthetic designs that allow for greater range of motion and maximal function will further test the critical posterior condylar bone interface, as a result of which a higher incidence of femoral component loosening with flexion shift may be seen. Femoral component design changes and surgical techniques that sustain the posterior femoral condyle metal-bone interface may thus be necessary. Femoral components with intramedullary stems may be appropriate for high-risk patients.     

Three-dimensional tibiofemoral articular contact kinematics of a cruciate-retaining total knee arthroplasty

BACKGROUND: Accurate knowledge of the location of tibiofemoral articular contact following total knee arthroplasty is important in order to understand polyethylene wear and the mechanisms of component failure. The present study was performed to determine the three-dimensional tibiofemoral articular contact patterns of a posterior cruciate ligament-retaining total knee replacement during in vivo weight-bearing flexion. METHODS: Nine osteoarthritic patients who were managed with a single design of a posterior cruciate ligament-retaining total knee implant were investigated with the use of an innovative dual orthogonal fluoroscopic imaging system. The position of the components during in vivo weight-bearing flexion was measured from full extension to maximum flexion in 15 degrees intervals. Tibiofemoral articular contact was determined by the overlap of the tibiofemoral articular surfaces. The centroid of the surface intersection was used to report the point of contact location. The average tibiofemoral contact points on both the medial and lateral tibial component surfaces were reported as a function of flexion. RESULTS: The average maximum weight-bearing flexion angle was 113.3 degrees +/- 13.1 degrees (range, 96 degrees to 138 degrees ). In the anteroposterior direction, the contact location was relatively constant in the medial compartment and moved posteriorly by 5.6 mm in the lateral compartment as the knee flexed from full extension to 90 degrees of flexion. The range of the contact location in the mediolateral direction was 3.7 mm in the medial compartment and 4.8 mm in the lateral compartment. For both compartments, posterior translation of the contact point was significant from 90 degrees to maximum flexion, but the contact point at maximum flexion was not observed to reach the posterior edge of the polyethylene tibial insert articular surface. CONCLUSIONS: While the minimum anteroposterior translation of the contact point on the medial side might be interpreted as a medial pivot rotation during knee flexion, the contact point did move in the mediolateral direction with flexion. Beyond 90 degrees , both medial and lateral contact points were shown to move posteriorly but stopped before reaching the posterior edge of the polyethylene tibial insert articular surface. It seemed that the current component design did not allow the femoral condyle to roll off the polyethylene edge at high degrees of flexion because of the geometry at the posterior lip.     

Joint line changes in cruciate-retaining versus posterior-stabilized computer-navigated total knee arthroplasty

Introduction

This study compared joint line changes and functional outcomes between cruciate-retaining (CR) and posterior-stabilized (PS) computer-navigated total knee arthroplasties (TKAs). With the increased precision offered by computer navigation, we hypothesized that there should be minimal differences in the joint line changes between the groups and thus no significant differences in the clinical outcomes.

Materials and methods

A retrospective study of 195 patients with a minimum of 2-year follow-up following primary surgery was conducted. The patients were stratified into two groups: the CR group and the PS group. The joint line changes of both groups were then compared using the Student t test. Multivariate analysis and regression modelling were then utilized to analyze the functional outcomes of both groups.

Results

CR knees had a significantly lesser mean joint line change of 1.70 mm as compared to 2.34 mm in PS knees (p = .04) but the absolute difference was only 0.64 mm. The PS group had significantly better final range of motion of 122° (±9.9°) as compared to 114° (±15.0°) in the CR group (p < .0001). There were no significant differences in the final outcome scores.

Conclusion

Although there is a significant difference statistically in the joint line changes between the groups, this difference is less than 1 mm and probably has no significant clinical impact. This is further affirmed by the fact that there was no significant difference in the clinical outcomes. The increased range seen in PS knees is probably not related to joint line changes.

Level of evidence

III.     

Functional comparison of posterior cruciate-retaining versus posterior stabilized total knee arthroplasty

A prospective, randomized comparison of posterior cruciate-retaining (PCR) and posterior stabilized (PS) total knee arthroplasties (TKAs) was conducted in 20 patients who underwent bilateral TKAs for osteoarthritis. All procedures were performed by a single surgeon. One knee was implanted with a PCR TKA, and a contralateral knee with a PS TKA. Both prosthetic designs were of the same TKA series, with comparable surface geometries. Patients had a clinical and radiographic evaluation at a mean of 31.7 months for PCR TKAs and 30.6 months for PS TKAs postoperatively. There were no significant differences between the PCR and PS TKAs in postoperative knee scores. However, postoperative improvement in range of motion was significantly superior in the PS group.     

Proprioception, kinesthesia, and balance after total knee arthroplasty with cruciate-retaining and posterior stabilized prostheses

BACKGROUND: The effect of total knee arthroplasty on proprioception, kinesthesia, and postural control remains controversial. It is argued that retaining the posterior cruciate ligament may help to preserve these sensorimotor functions and improve the longevity of the prosthesis and the functional outcome. We performed a prospective, randomized study to assess proprioception, kinesthesia, and balance following total knee arthroplasty with cruciate-retaining and posterior stabilized prostheses. METHODS: Twenty patients scheduled to undergo total knee arthroplasty were randomly assigned to receive either a cruciate-retaining or a posterior stabilized prosthesis. Joint-position sense, the threshold to detect joint motion, and the subject's ability to balance on an unstable platform were assessed prior to and at least six months after the operation. Paired two-tailed t tests (with a level of significance of p < 0.05) were used to assess the effect of the arthroplasty on the preoperative measures for all subjects. Analysis of covariance was performed to identify the effects of prosthetic design. RESULTS: Following total knee arthroplasty, patients detected motion significantly faster and reproduced joint position with less error. The balance index also improved significantly from the preoperative to the postoperative evaluation. The group treated with the posterior stabilized prosthesis more accurately reproduced joint position when the knee was extended from a flexed position. CONCLUSIONS: Total knee arthroplasty results in mild improvements in proprioception, kinesthesia, and balance. These changes may result from the retensioned capsuloligamentous structures and reduced pain and inflammation. Retention of the posterior cruciate ligament does not appear to significantly improve proprioception and balance compared with those functions in patients with a posterior stabilized total knee design.     

后交叉韧带保留型和后稳定型全膝关节置换术后早期临床疗效比较

目的评价后交叉韧带保留（PCR）型和后稳定（PS）型全膝关节置换（TKA）的早期临床疗效，探讨两种不同假体置换术的临床相关问题。方法回顾2000年4月～2005年10月139例（166膝）初次行TKA的患者资料，比较PCR型（PCR组）58例（69膝）和PS型（PS组）81例（97膝）的早期疗效，结合文献分析两种不同假体的优缺点及相关技术问题。结果术后随访1年，患者对手术的满意率PCR组为94.2％，PS组为93．8％，两组比较差异无统计学意义（P〉0．05）。HSS评分PCR组平均为93．9分，PS组平均为94．3分，两组比较差异无统计学意义（P〉0．05）。膝关节活动度PCR组平均为105．8°，PS组平均为107．4°，两组比较差异无统计学意义（P〉0．05）。患者主诉患膝有轻微疼痛者，PCR组有7膝（占10．1％），PS组有10膝（占10，3％），均不需特殊治疗。有明显髌骨弹响征者PCR组2例，PS组4例，但对功能活动无影响。结论PCR型或PS型TKA后早期随访疗效满意；对膝关节畸形较轻，术中探查后交叉韧带结构完整者，可考虑采用PCR型假体，但应松解PCR，原则上宁松勿紧；对于PS型假体，手术技术要求相对较低，容易掌握，临床适用范围更广。     

The effects of early rollback in total knee arthroplasty on stair stepping

We investigated the effects of early compared with late (ie, in flexion) rollback on quadriceps efficiency during stair stepping. We studied 10 patients with the IB II (Zimmer, Warsaw, IN) total knee arthroplasty (TKA), designed to enforce rollback at 73 degrees of knee flexion; 9 patients with the Maxim PS (Biomet, Inc, Warsaw, IN) TKA, designed to enforce rollback between 20 degrees and 30 degrees of flexion; 8 patients with the TRAC PS (Biomet, Inc, Warsaw, IN) mobile bearing TKA, designed to enforce rollback at 8 degrees of flexion; and 21 healthy control subjects during stair stepping. We measured the external knee flexion moments, which must be largely balanced by quadriceps force acting over the quadriceps lever arm, as indicators of quadriceps efficiency. The peak external knee flexion moment generated by the IB II patients during stair stepping was 12.4% and occurred at 65 degrees of knee flexion. This moment was significantly less (P=.006) than the peak moment, 17.6%, generated by the healthy controls. Knee flexion for the IB II patients did not reach 73 degrees, and rollback was not enforced until after the peak moment (ie, maximum demands on the quadriceps) had been attained. The peak moments generated by the TRAC PS patients, 14.2%, and Maxim patients, 14.8%, were not significantly different from that of the controls. These results suggest that early as compared with late rollback returns more normal quadriceps efficiency during stair stepping.     

Femoral fracture through a previous pin site after computer-assisted total knee arthroplasty

Computer-assisted total knee arthroplasty has been gaining popularity given the proposed benefits of increased accuracy of the femoral and tibial cuts, quantitative feedback on soft tissue balancing, and the potential for performing the procedure through smaller incisions with decreased soft tissue trauma. Most navigation systems require femoral and tibial threaded pin insertion for placement of guidance trackers, which when removed leave behind defects in the bone that may act as stress risers. We present 2 cases of a femoral fracture through a previous pin site where a guidance tracker had been placed for computer-assisted total knee arthroplasty. Both patients were informed that data concerning the cases would be submitted for publication. To our knowledge, this complication has not previously been reported for this procedure.