Femoral rollback after cruciate-retaining and stabilizing total knee arthroplasty

Limited data comparing the kinematics of posterior cruciate ligament-retaining or substituting total knee arthroplasty with its own intact knee under identical loadings is available. In the current study, posterior femoral translation of the lateral and medial femoral condyles under unloaded conditions was examined for intact, cruciate-retaining, cruciate ligament-deficient cruciate-retaining and posterior-substituting knee arthroplasties. Cruciate-retaining and substituting total knee arthroplasties behaved similarly to the cruciate-deficient cruciate-retaining total knee arthroplasty between 0 degrees and 30 degrees flexion. Beyond 30 degrees, the posterior cruciate-retaining arthroplasty showed a significant increase in posterior translation of both femoral condyles. The posterior cruciate-substituting arthroplasty only showed a significant increase in posterior femoral translation after 90 degrees. At 120 degrees, both arthroplasties restored approximately 80% of that of the native knee. Posterior translation of the lateral femoral condyle was greater than that observed in the medial condyle for all knees, indicating the presence of internal tibial rotation during knee flexion. The data showed that the posterior cruciate ligament is an important structure in posterior cruciate-retaining total knee arthroplasty and proper balancing is imperative to the success of the implant. The cam-spine engagement is valuable in restoring posterior femoral translation in posterior cruciate-substituting total knee arthroplasty.     

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.     

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.     

The influence of femoral rollback on patellofemoral contact loads in total knee arthroplasty

Increasing femoral rollback in flexion is thought to reduce patellofemoral contact load in total knee arthroplasty (TKA). The objectives of this study were to quantify the dependence of patellar load on rollback and to assess the effectiveness of posterior cruciate ligament (PCL)-retaining, PCL-sacrificing, and PCL-substituting TKA types in generating rollback. Nine cadaver knees were tested in simulated squatting. Six TKAs that were expected to produce varying amounts of femoral rollback were evaluated: PCL-retaining TKA, PCL-sacrificing TKA, a commercially available PCL-substituting TKA, and 3 modified PCL-substituting TKAs in which the anteroposterior position of the tibial post was varied. Kinematics, quadriceps loads, and patellofemoral contact loads were recorded. Significant differences in rollback were observed in the 30 degrees to 90 degrees flexion range. PCL-sacrificing TKAs generated the least rollback. PCL-retaining TKAs produced greater rollback but had the most variability. PCL-substituting TKAs produced the greatest and most reproducible rollback. Moving the tibial post posteriorly further increased rollback. Increased rollback correlated with reduced patellar load (-2.2%/mm). Reductions in patellar load of 17.6% were observed. Quadriceps loads were reduced by increasing rollback but to a smaller degree (-0.9%/mm). Rollback primarily affects patellar load rather than quadriceps load or efficiency.     

保留后交叉与不保留后交叉韧带人工膝关节置换术术后效果的Meta分析

目的对人工膝关节置换术保留后交叉韧带与不保留后交叉韧带术后效进行评价。方法按照Cochrane系统评价的方法,计算机检索下列数据库：Medline（1995／2012435）、Pubmed（1995／2012435）、SPINGER（1995／2012435）、JohnWiley（1995／2012435）、ScienceDirect（1995／2012-05）、EBSCO（1995／2012435）、CNKI（1995／2012435）、万方数数据库（1995／2012435）,并采用手工检索等方法收集会议文献。收集所有相关随机对照试验,采用Cochrane协作网提供的软件Revman4．2进行Meta分析。结果经过筛选,共纳入5个临床随机对照实验共685个患者。Meta分析结果显示两组患者术后疼痛评分均降低,但保留后交叉组比不保留后交叉组下降更明显[RR=-1．07,95％a为（-1．86,-0．29）,P〈0．01]。两组患者术后功能评分较术前明显增高,但是保留后交叉组与不保留后叉组术后无统计学差异[RR=-3．34,95％CI为（-7．18,0．50）,P〉0．05]。两组患者术后SF生理评分无统计学差异[RR=-1．26,95％CI为（-3．72,1．21）,P〉0．05]。两组患者术后SF心理评分无统计学差异[RR=-1．53,95％CI为（-3．88,0．83）,P〉0．05]。两组患者术后关节僵硬发生率比较无统计学差异[RR=3．08,95％C／为（0．81,11．65）,P〉0．05]。两组患者术后并发症发生率比较无统计学差异[RR=0．77,95％CI为（0．26,2．35）,P〉0．05]。结论保留后交叉较不保留后交叉韧带人工膝关节置换术更能减轻疼痛评分、而两者术后膝关节功能评分、SF心理评分、SF生理评分、术后并发症都无明显差异。     

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.     

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.     

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 using cruciate-retaining kinematic condylar prosthesis.

The purpose of the current study was to evaluate the long-term results of the Kinematic I condylar prosthesis with retention of the posterior cruciate ligament. One hundred sixty-eight total knee arthroplasties in 118 patients (mean age, 65.2 years; range, 21-88 years) were inserted with cement, an all-polyethylene patella, metal-backed tibia, and posterior cruciate ligament retention. Sixty-one patients (86 knees) died, one patient had an above-knee amputation, and three patients (five knees) were lost to followup; therefore, 66 knees (excluding revisions) in 50 patients were available for followup at a mean of 15.7 +/- 1.1 years (range, 14-20 years). Of the entire cohort of 168 knees, 13 have been revised: one for medial femoral condyle fracture, one for tibiofemoral instability, one for femoral and two for tibial component aseptic loosening, four for tibial polyethylene wear, and four for patellar component aseptic loosening. The 15-year survivorship free of any component revision excluding infections was 88.7% (confidence interval, 82%-95%). The 15-year survivorship free of radiographic loosening and/or revision of any component was 85.1% (confidence interval, 78%-92%). The current study shows good function and survivorship of the posterior cruciate-sparing Kinematic I condylar prosthesis at a mean of 15.7 +/- 1.1 years.     

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.     

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.     

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.     

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.     

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.     

The effect of preoperative knee deformity on the initial results of cruciate-retaining total knee arthroplasty

Between November 1985 and June 1987, 751 posterior cruciate-sparing total knee arthroplasties were performed on 523 patients who exhibited fixed varus or valgus deformities. Patients excluded from this study included the following: those with a postoperative follow-up period of less than 2 years (including patients who had died), patients who became infected, and patients with previous failed total knee arthroplasty in the same knee. A total of 473 knees left for evaluation. All arthroplasties were measured using anatomic axis for alignment measurement. The Hospital for Special Surgery scoring system was used to determine the clinical scores prior to the end of each follow-up examination. All ligament releases were performed sequentially, including balancing of the posterior cruciate ligament. All arthroplasties were divided into six separate groups depending upon the degree of varus or valgus deformity. Kaplan-Meier curves were constructed using three methods of failure definition. Curves were then compared between groups. The mean Hospital for Special Surgery score was no different between any of the groups, except for the group of 6 degrees-10 degrees varus, which was significantly higher than the mean score of the 11 degrees and higher valgus group. All other groups were the same statistically. It is concluded that severe varus and valgus deformities may be satisfactorily corrected with the use of a cruciate-retaining type of total knee arthroplasty.     

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。