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° 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.     

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.     

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 comparison of knee kinematics for subjects having either a posterior stabilized or cruciate retaining high-flexion total knee arthroplasty

The objective of this study was to determine the in vivo kinematics for subjects having either a fixed posterior stabilized (PS) or cruciate retaining (CR) high-flexion total knee arthroplasty (TKA). Three-dimensional kinematics from full extension to maximum flexion were determined for 30 subjects (15 PS, 15 CR) using fluoroscopy. On average, the PS subjects demonstrated 112 degrees of weight-bearing (WB) flexion, -6.4 mm of posterior femoral rollback, and 2.9 degrees of axial rotation. The CR subjects averaged 117 degrees of WB flexion, -4.9 mm of posterior femoral rollback, and 4.8 degrees of axial rotation. Posterior femoral rollback of the lateral condyle occurred for all PS TKAs and in 93% of the CR TKAs. Only 2 subjects in each group experienced greater than 1.0 mm of condylar lift-off. Subjects in both TKA groups demonstrated excellent WB ranges of motion and kinematic patterns similar to the normal knee, but less in magnitude.     

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.     

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.     

In vivo determination of total knee arthroplasty kinematics: a multicenter analysis of an asymmetrical posterior cruciate retaining total knee arthroplasty

The objective of this study was to determine if consistent posterior femoral rollback of an asymmetrical posterior cruciate retaining (PCR) total knee arthroplasty was mostly influenced by the implant design, surgical technique, or presence of a well-functioning posterior cruciate ligament (PCL). Three-dimensional femorotibial kinematics was determined for 80 subjects implanted by 3 surgeons, and each subject was evaluated under fluoroscopic surveillance during a deep knee bend. All subjects in this present study having an intact PCL had a well-functioning PCR knee and experienced normal kinematic patterns, although less in magnitude than the normal knee. In addition, a surprising finding was that, on average, subjects without a PCL still achieved posterior femoral rollback from full extension to maximum knee flexion. The findings in this study revealed that implant design did contribute to the normal kinematics demonstrated by subjects having this asymmetrical PCR total knee arthroplasty.     

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.     

In vivo determination of knee kinematics for Japanese subjects having either a low contact stress rotating platform or an anteroposterior glide total knee arthroplasty

The objective of this study was to work with a consecutive series of patients having Hospital for Special Surgery scores higher than 90 to evaluate kinematic patterns, under in vivo conditions, for 20 Japanese subjects implanted with 2 different mobile-bearing (MB) total knee arthroplasties (TKAs). Femorotibial contact paths for the medial and lateral condyles were then determined using a computer-automated model-fitting technique. This present study has shown that kinematic patterns for subjects having 2 different MB TKA designs differed but were not statistically different. Subjects implanted with a rotating platform (RP) MB TKA experienced minimal anteroposterior (AP) motion and larger axial rotation (RP). Subjects implanted with an anterior glide MB TKA experienced both femoral rotation and femoral translation (AP glide). There was minimal variability in the kinematic patterns for subjects implanted with an RP, whereas subjects implanted with an AP glide experienced more variable kinematic patterns. Key words: total knee arthroplasty, in vivo, fluoroscopy, kinematics.     

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.     

In vivo comparison of femorotibial contact positions for press-fit posterior stabilized and posterior cruciate-retaining total knee arthroplasties

The objective of this study was to determine the in vivo medial and lateral femorotibial condyle contact positions for 20 subjects having either a posterior cruciate-retaining (PCR) or posterior-stabilized (PS) total knee arthroplasty (TKA) while sitting and kneeling. The two-dimensional radiographic images were converted into three-dimensional images using an iterative computer model-fitting technique. Anteroposterior contact positions, axial rotation, and condylar lift-off were assessed for each subject. In a seated position, the femorotibial contact points were, on average, posterior for both TKA groups (PCR: medial = -2.4 mm, lateral = -3.4 mm; PS: medial = -5.1 mm, lateral = -8.9 mm; medial, P=.21; lateral, P=.08). In a kneeling position, the contact position shifted anteriorly for the PCR TKA group (medial = 0.9 mm, lateral = -0.8 mm), whereas the contact positions in the PS TKA group remained posterior (medial = -5.6 mm, lateral = -8.3 mm; medial, P=.002; lateral, P=.0004). It is hypothesized that while in a kneeling position, the posterior cruciate ligament has less resistance to the anterior thrust of the femur relative to the tibia than in a PS TKA, in which this force is absorbed in the cam-and-post mechanism.     

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。     

In vivo kinematic analysis of cruciate-retaining total knee arthroplasty during weight-bearing and non-weight-bearing deep knee bending

The purpose of the present study was to evaluate the in vivo kinematics of the posterior cruciate ligament-retaining total knee arthroplasty during weight-bearing and non-weight-bearing deep knee bending and compare these 2 different conditions. We evaluated the in vivo kinematics of the knee using fluoroscopy and femorotibial translation relative to the tibia tray by 2-dimensional/3-dimensional registration. In the weight-bearing state, the femoral component showed central pivot and bicondylar posterior rollback pattern. During non-weight-bearing, the movement anteriorly occurred on both the medial and lateral side during early flexion, whereas bicondylar femoral component rollback occurred after that. During non-weight-bearing, both the medial and lateral condyle significantly moved anteriorly compared with the weight-bearing state during early flexion. However, bicondylar femoral rollback occurred under both these conditions.     

In vivo kneeling biomechanics after posterior stabilized total knee arthroplasty

Background Kneeling is one of the activities sought by patients after total knee arthroplasty (TKA). This study investigated the six degrees of freedom (DOF) kinematics and three-dimensional (3D) contact during weight-bearing kneeling. Methods A total of 16 South Korean female patients (22 knees) after posteriorly stabilized (PS) TKA (LPS-Flex) were randomly recruited and had the same surgeon. The patients were imaged using a dual fluoroscopic technique while they kneeled from initial to maximum flexion. The acquired images and 3D models were then used to recreate the in vivo pose of the components. Contact was determined by locating the surface intersections in the tibiofemoral and cam/post (between the femoral cam and tibial post) articular compartments. Results Patients flexed, on average, from 107.3° to 128.0° during the kneeling activity. Changes in kinematics included 1.0 mm of proximal, 0.9 mm of medial, and 7.6 mm of posterior translation and 1.7° of varus rotation (P < 0.04). A difference in internal tibial rotation was not detected. Articular contact moved posteriorly by 5.9 mm and 6.4 mm in the medial and lateral compartments, respectively. Contact also moved medially by 3.2 mm and 5.8 mm in the medial and lateral compartments. A decrease in articular contact was observed in both condyles, and lateral condylar lift-off increased with flexion (P = 0.0001). More than 80% of the patients demonstrated cam/post engagement, which always occurred in the distal portion of the post. Conclusions In this patient cohort, the knee joint was constrained during the weight-bearing activity such that femoral subluxation and dislocation were not observed. Furthermore, posterior cam/post engagement occurred only in the distal portion of the tibial post, which may improve the longevity of the post. The tibiofemoral and cam/post articular contact data presented in this study further suggest that kneeling may be performed by patients after clinically successful PS TKA who feel comfortable with the activity and are free of pain.     

In vivo determination of knee kinematics for subjects implanted with a unicompartmental arthroplasty

Femorotibial contact positions for 20 subjects implanted with a unicompartmental knee arthroplasty (UKA) were analyzed using videofluoroscopy. Femorotibial contact paths were determined using a computer-automated model-fitting technique. Subjects having a medial UKA experienced on average -0.8 mm of posterior femoral rollback, whereas subjects having a lateral UKA experienced -2.5 mm of posterior femoral rollback. Twelve of 17 subjects having a medial UKA and 2 of 3 subjects having a lateral UKA experienced normal axial rotation (average, 3.3 degrees and 11.2 degrees ). The results for some subjects suggest that the anterior cruciate ligament was unable to thrust the femur anteriorly at full extension. These results support the findings that the anterior cruciate ligament plays a significant role in knee kinematics, which may contribute to UKA longevity.     

Primary posterior cruciate-retaining total knee arthroplasty: a comparison of American and Japanese cohorts

Excessive polyethylene wear is recognized as one of the most important factors affecting the durability of total knee arthroplasty; however, bearing surface wear is a multifactorial problem. The purpose of this study was to identify factors for polyethylene wear and failure in primary posterior cruciate-retaining (PCR) total knee arthroplasty (TKA) in two disparate cohorts (American and Japanese). Seventy-three total knee arthroplasty operations were performed on 48 Japanese patients, and 76 on 63 American patients with noninflammatory arthritides. All patients were evaluated clinically and radiographically using a total joint arthroplasty database. Age, weight, diagnosis, Knee Society patient category, prosthesis size, insert thickness, alignment, polyethylene wear, osteolysis, Knee Society knee score, Knee Society pain score, and radiographic and clinical survivorship were evaluated. Seventy-three Japanese TKAs were followed for a mean of 6.6 years (range, 2.0-10.6). Three (4.1%) Japanese patients required revision. Seventy-six American TKAs were followed for a mean of 9 years (range, 2-10.2). Two (2.6%) American patients required revision. The American patients were significantly older, heavier, male predominant, and required larger size implants. The Japanese patients were significantly more female predominant and had a significantly less postoperative arc of motion. Knee Society knee and pain scores, survivorship, average total polyethylene wear, and annual wear rates were not different among the two cohorts. PCR TKA had similar survivorship in disparate cohorts of Japanese and American total knee arthroplasty patients despite smaller stature patients in the Japanese cohort. Cultural, gender-specific, and morphologic differences need to be considered for knee implant design. However, survivorship and polyethylene wear rates appear to be independent of these factors in disparate populations.     

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.     

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.     

In vivo kinematic comparison of posterior cruciate-retaining and posterior stabilized total knee arthroplasties under passive and weight-bearing conditions

An in vivo comparison of flexion kinematics for posterior cruciate-retaining (PCR) and posterior stabilized (PS) total knee arthroplasty (TKA) was performed. Twenty patients who underwent bilateral paired TKAs were included in this prospective study. Both PCR and PS prostheses were from the same TKA series with comparable surface geometries, and all were implanted by a single surgeon. Of these 20 patients, 3-dimensional kinematics during flexion could be analyzed using a computer model fitting technique in 18 patients. The follow-up period ranged from 18 to 53 months. In the PCR TKA, an anterior femoral translation from 30 degrees to 60 degrees of flexion was observed in the weight-bearing condition. In contrast, flexion kinematics for the PS TKA was characterized by the maintenance of a constant contact position under weight-bearing conditions and posterior femoral rollback in passive flexion.