Effect of femoral component design on patellofemoral crepitance and patella clunk syndrome after posterior-stabilized total knee arthroplasty

The purpose of this study was to determine if recent changes to the femoral component of a particular posterior-stabilized total knee prosthesis would affect the incidence of postoperative patellofemoral crepitance and patella clunk syndrome. One hundred eight total knee arthroplasties were performed with the conventional design; 136 were performed after the femoral component was changed. Complications were compared between the groups with an average follow-up of 17.7 months and 12.4 months, respectively. Thirteen knees with the conventional design (12%) were found to have patellofemoral complications; no complications were noted with the new design (P < .0001). Femoral components with a deep trochlear groove and smooth transition of the intercondylar box appear to better accommodate any peripatellar fibrous nodule that may form after total knee arthroplasty.     

Incidence of patellar clunk with a modern posterior-stabilized knee design

Patellar clunk is an uncommon complication of posterior-stabilized total knee arthroplasty (TKA), though the incidence has been reported to be as high as 7.5% with some posterior-stabilized implants, and the etiology is multifactorial. Femoral component design has been implicated as a major cause of this complication. This series compares the incidence of patellar clunk with 2 different knee prostheses, the Insall-Burstein II (IB) and the NexGen Legacy PS (NG), both manufactured by Zimmer (Warsaw, Ind). One-hundred fifty consecutive posterior-stabilized TKAs were in each group, and the groups were similar in surgical approaches and techniques. Insall-Salvati (IS) ratios and joint-line positions were measured on preoperative and postoperative x-rays. Knee Society Clinical and Functional scores were calculated. Incidence of patellar clunk was reduced from 4% with the IB design to 0% with the NG design. IS ratios, joint-line positions, and clinical outcomes were no different between the groups. It appears that femoral component design may play a substantial role in development of patellar clunk after posterior-stabilized TKA.     

Incidence of patellar clunk with a modern posterior-stabilized knee design.

Patellar clunk is an uncommon complication of posterior-stabilized total knee arthroplasty (TKA), though the incidence has been reported to be as high as 7.5% with some posterior-stabilized implants, and the etiology is multifactorial. Femoral component design has been implicated as a major cause of this complication. This series compares the incidence of patellar clunk with 2 different knee prostheses, the Insall-Burstein II (IB) and the NexGen Legacy PS (NG), both manufactured by Zimmer (Warsaw, Ind). One-hundred fifty consecutive posterior-stabilized TKAs were in each group, and the groups were similar in surgical approaches and techniques. Insall-Salvati (IS) ratios and joint-line positions were measured on preoperative and postoperative x-rays. Knee Society Clinical and Functional scores were calculated. Incidence of patellar clunk was reduced from 4% with the IB design to 0% with the NG design. IS ratios, joint-line positions, and clinical outcomes were no different between the groups. It appears that femoral component design may play a substantial role in development of patellar clunk after posterior-stabilized TKA.     

Patellar clunk in total knee arthroplasty using modified Sigma posterior stabilized femoral component

Aim

The purpose of this study was to evaluate the efficacy of the enhanced PS femoral component design released in 2008 by DePuy. The patellar clunk syndrome has been reported in a significant number of patients following total knee arthroplasty. Design modifications of the implant have been made to reduce the incidence of the patellar clunk, especially in the posterior substituted designs.

Methods

130 total knee replacements performed using the enhanced PS femoral components were followed-up with clinical and radiographic evaluations.

Results

Patellar clunk was seen in 3 of the 130 knees (2%). This is much less than the incidence of patellar clunk reported until now.

Conclusions

Removal of the sharp ridge in the intercondylar groove in the newer implant seems to have been effective in reducing the incidence of the patellar clunk. It also indicates that the sharp ridge was the most probable cause of the clunk.     

The effect of patellar button placement and femoral component design on patellar tracking in total knee arthroplasty.

The effects of patellar button position and femoral component design on patellar tracking were investigated roentgenographically and arthroscopically using fresh-frozen adult anatomic specimen knees. Patellar tracking was evaluated for medial/lateral position and tilting angle deviation by comparing preoperative normal values to total knee replacement performance with the following variables: (1) femoral component design; symmetrical total condylar type with a 3-mm central patellar groove and a component with a 3-mm raised lateral patellar flange and 1-mm deepened patellar groove; and (2) patellar button placement; central insertion; and 10-mm medialized insertion. In the roentgenographic study, medialized position of the patellar button allowed the bony portion of the patella to assume its normal lateral position and tilt throughout the knee range of motion. A combination of medialized position of the patellar button and deepening of the patellar groove provided the most anatomically correct position and the most normal tilting of the bony structure of the patella. In the arthroscopic study, the centralized patellar position caused significant lateral tracking and subluxation relative to the femoral component, whereas the medialized position eliminated this tracking disorder. Deepening the patellar groove minimized the intraarticular tracking abnormality and constrained the patellar button in the patellar groove. These results show that the position of the patellar button and femoral component design exert a major influence on patellar tracking.     

Patellar clunk syndrome in total knee arthroplasty without patellar resurfacing

In a series of 647 total knee arthroplasties, the patella was not resurfaced if bony geometry of the patella was good enough to maintain good congruency of the patella undersurface to the femoral component and the patella was tracking normally at the femoral component groove at the time of surgery. Three hundred seventy-two total knee arthroplasties were done with a femoral component that had the same geometry as the original total condylar prosthesis. None of these knees resulted in patellar catching, whether the patella was resurfaced or not. Two hundred seventy-five total knee arthroplasties were done with a more contemporary femoral component with wider intercondylar space and shorter posterior extension of the intercondylar notch. Eleven of these 275 knees demonstrated catching of the patella at 60° to 90° of flexion when the knee was tested from flexion to extension during the surgery. All of these 11 knees did not have patellar resurfacing during surgery at first. Of these 11 knees with patellar catching noted during surgery, at first, patellar catching was eliminated with patellar resurfacing in 4 and by shaving of the superior pole of the patella in 7. None of the knees with the patella resurfacing in this series showed patellar catching.     

The effect of femoral component rotation on patellar tracking in total knee arthroplasty

Rotational adjustment of the femoral component in total knee arthroplasty influences patellar tracking. Sixty patients underwent TKA; the femoral component was placed parallel to the epicondylar axis in 30 patients and the femoral component was placed in 3 degrees external rotation to the posterior condylar axis in 30 patients. The epicondylar axis was identified using an image-guided navigation system. Mean patellar shift was 2.65 degrees for the computer assisted group and 3.50 degrees for the control group. Mean patellar tilt was 4.88 degrees for the computer assisted group and 6.68 degrees for the control group. Aligning the femoral component parallel to the epicondylar axis leads to significantly better patellar tracking.     

The influence of component alignment on patellar kinematics in total knee arthroplasty

Background and purpose — Postoperative anterior knee pain is one of the most frequent complications after total knee arthroplasty (TKA). Changes in patellar kinematics after TKA relative to the preoperative arthritic knee are not well understood. We compared the patellar kinematics preoperatively with the kinematics after ligament-balanced navigated TKA.

Patients and methods — We measured patellar tracking before and after ligament-balanced TKA in 40 consecutive patients using computer navigation. Furthermore, the influences of different femoral and tibial component alignment on patellar kinematics were analyzed using generalized linear models.

Results — After TKA, the patellae shifted statistically significantly more laterally between 30° and 60°. The lateral tilt increased at 90° of flexion whereas the epicondylar distance decreased between 45° and 75° of flexion. Sagittal component alignment, but not rotational component alignment, had a significant influence on patellar kinematics.

Interpretation — There are major differences in patellar kinematics between the preoperative arthritic knee and the knee after TKA. Combined sagittal component alignment in particular appears to have a major effect on patellar kinematics. Surgeons should be especially aware of altering preoperative sagittal alignment until the possible clinical relevance has been investigated.     

Gap measurement in posterior-stabilized total knee arthroplasty with or without a trial femoral component

Purpose

To investigate the effects of a trial femoral component on the intraoperative joint gap and intraoperative joint gap kinematics throughout the range of knee motion in minimally invasive surgery–total knee arthroplasty (MIS–TKA) with the gap technique.

Materials and methods

A total of 103 patients [15 men (15 knees) and 89 women (89 knees)] aged 50–88 years (mean 74.8 years) who received MIS–TKA with the gap technique were included. The intraoperative joint gap differences (90° flexion gap distance minus 0° extension gap distance) with and without the trial femoral component were compared. Subsequently, the intraoperative joint gap kinematics at 0°, 45°, 90°, and 120° with the trial femoral component were investigated.

Results

The intraoperative component gap difference (4.4 ± 2.7 mm) was larger than the estimated joint gap difference (1.2 ± 1.9 mm) (p < 0.01). The mean intraoperative component gap distances at 0°, 45°, 90°, and 120° of knee flexion were 14.7 ± 2.6, 19.0 ± 3.2, 19.2 ± 3.4, and 16.6 ± 3.3 mm, respectively. The intraoperative component gap distance increased significantly from 0° extension to 90° of knee flexion (p < 0.01), and then decreased significantly toward deep knee flexion at 120° (p < 0.01).

Conclusions

The trial femoral component influenced the intraoperative gap measurements, and increased the intraoperative gap difference. The joint gap kinematics with the trial femoral component were not constant throughout the range of knee motion, even if the appropriate joint gaps in extension and flexion were achieved. For acquisition of constant stability throughout the knee motion, the present results should be taken into account by surgeons performing MIS–TKA with the gap technique.     

The effect of femoral component position on patellar tracking after total knee arthroplasty

In a laboratory study, seven fresh anatomic knee specimens were evaluated to define the three-dimensional motions of the patella before and after total knee arthroplasty (TKA) with the AMK knee. The patella was displaced medially by an average of 4 mm and tilted medially by an average of 4 degrees after standard TKA. Medial translation or internal rotation of the femoral component further displaced and tilted the patella medially, but lateral translation or external rotation of the femoral component produced less predictable changes in patellar tracking. The patterns of patellar tracking after external rotation of the femoral component came closer to reproducing those of the intact knee than any other femoral component position. The high lateral ridge on the femoral component effectively prevents patellar dislocation but may produce abnormally high stresses on the patellar implant, especially if the implant is medially displaced or internally rotated. This could lead to accelerated wear or loosening of the patellar component.     

The patellar clunk syndrome. A complication of posterior stabilized total knee arthroplasty

Patellofemoral pain due to an unusual suprapatellar fibrous nodule developed in three patients after posterior stabilized total knee arthroplasty. Each patient had a "catch" or "clunk" associated with pain on extension of the knee. At revision, a prominent fibrous nodule was found at the junction of the proximal patellar pole and the quadriceps tendon. The pathogenesis of this proximal fibrous nodule may involve impingement of the anterosuperior edge of the intercondylar notch area of the femoral component into the proximal quadriceps tendon or may involve impingement of the patellar prosthesis itself on the quadriceps tendon. Roentgenographic examination revealed an abnormally proximal placement of the patellar prosthesis on the patella. Surgical removal of the fibrous nodule resolved the symptoms. Revision of the patellar prosthesis may be necessary.     

The influence of the position of the patellar component on tracking in total knee arthroplasty

Summary The position of the patellar component and patellofemoral symptoms were assessed in a series of 72 cemented polyethylene patellar components in total condylar arthroplasties. A small (25 mm) component was used. The minimum follow up was 2 years and maximum 3 years. A lateral retinacular release was carried out in 22 knees. Clinical results were assessed by questionnaire and 86% had no patellofemoral symptoms. The mean postoperative patellar height was not changed compared to the preoperative height. Lateral placement of the patellar component was associated with both increased medial tilt and lateral subluxation. The component should be inserted so that its centre is slightly medial to the centre of the bone.

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Résumé Etude de la fonction fémoro-patellaire et de la position de la prothèse rotulienne dans une série de 72 prothèses totales de genou à pièce rotulienne en polyéthylène cimentée (prothèse sans conservation des croisés de Johnson and Johnson). Dans la plupart des cas, un petit composant (25 mm) a été utilisé. Le minimum de suivi est 2 ans. Une section de l'aileron rotulien externe a été faite pour 22 genoux (30%). Les résultats fonctionnels ont été étudiés au moyen d'un questionnaire. 86% des patients ont une articulation fémoropatellaire asymptomatique. L'épaisseur moyenne de la rotule n'a pas été modifiée de fa?on significative par l'intervention. L'inclinaison frontale moyenne du composant patellaire est de moins 2°, l'inclinaison de la coupe osseuse est de moins de 5° et l'inclinaison de l'ensemble osprothèse est en moyenne de 3°. La position latérale du composant patellaire s'accompagne d'une fa?on significative d'une augmentation de l'inclinaison patellaire interne et d'un déplacement externe de la rotule. La prothèse patellaire doit donc être placée avec son centre légèrement plus médial que le centre de la rotule. L'utilisation d'une prothèse patellaire de petite taille n'est pas un facteur de douleur fémoro-patellaire.

     

Arthroscopic management of the patellar clunk syndrome following posterior stabilized total knee arthroplasty

The patellofemoral articulation in total knee arthroplasty can give rise to postoperative complications, such as patellar fracture, subluxation, or dislocation. The accumulation of hypertrophic fibrous tissue at the superior margin of the patellar button can give rise to catching or "clunking" of the extensor mechanism. Open surgical excision of this mass is successful in alleviating symptoms but runs the risk of infection and wound complications and delays postoperative mobilization. Arthroscopic resection with motorized instrumentation is highly successful, offers less risk of infection, and allows rapid postoperative mobilization.     

The stability of the cemented tibial component of total knee arthroplasty: posterior cruciate-retaining versus posterior-stabilized design

Micromotion of the tibial component in 40 knee arthroplasties for gonarthrosis was studied using Roentgen stereophotogrammetric analysis. The stability of this component was assessed for 2 years' postoperatively. In all arthroplasties, an attempt was made to reconstruct the preoperative posterior slope. Posterior cruciate-retaining (CR) and posterior-stabilized (PS) components showed at 2 years a maximum total point motion of 0.6 +/- 0.4 mm and 0.7 +/- 0.5 mm, respectively. Whereas 92.5% of the implants were determined to be stable, 1 of the CR group and 2 of the PS group displayed migration between the first and the second year of at least 0.2 mm. A negative correlation between subsidence of the tibial component at 2 years of follow-up and the difference between preoperative and postoperative tibial slope was found. Consequently, we suggest that restoring the original posterior slope of the tibial plateau must be a goal of tibial component implantation.     

Femoral component design and patellar clunk syndrome

The effect of patellar design of the femoral component on the prevalence of patellar clunk was examined by comparing 179 consecutive Insall-Burstein II posterior-stabilized total knee replacements with 210 consecutive primary Advanced posterior-stabilized total knee replacements. In the Advanced posterior-stabilized knee replacements, the patellofemoral groove had been extended posteriorly 7.5 mm compared with the Insall-Burstein II implant. At a minimum followup of 2 years, the prevalence of patellar clunk syndrome in the patients with a Insall-Burstein II knee replacement was 3.9% (seven of 179) compared with 0% in the patients with an Advanced posterior-stabilized knee replacement. Based on these data, it seems that the design change in patellofemoral groove of the Advanced posterior-stabilized knee replacement has eliminated the problem of patellar clunks.     

The effect of femoral component design on patellar tracking in total knee arthroplasty: Genesis II prosthesis versus Vanguard prosthesis

Introduction

The Genesis II knee system incorporates 3° of external rotation into the femoral component and the femoral component is implanted in neutral rotation to the femur. The purpose of this study was to compare patellar tracking of the Genesis II knee system with that of the Vanguard knee system, in which the femoral component is routinely implanted in a 3° externally rotated position to the posterior condylar axis (PCA) of the femur.

Materials and methods

One hundred consecutive knees scheduled to undergo total knee arthroplasty (TKA) were enrolled. Fifty knees underwent TKA with the posterior-stabilized (PS) Genesis II prosthesis and 50 knees underwent TKA with the PS Vanguard prosthesis. Rotation of the femoral component was calculated by measuring the acute angle between the transepicondylar axis (TEA) and the PCA on axial computed tomography (CT) images. The postoperative patellar tilt and displacement were compared between groups. The range of motion and Knee Society scores were also compared.

Results

Forty-eight knees in each group were followed up for 2 years. There was no difference in the angle between the PCA and the TEA on postoperative CT scans between the two designs. There was also no difference in patellar tracking between groups. Both the Genesis II and Vanguard knee systems showed good clinical results at 2 years postoperatively.

Conclusion

The patellar tracking of the Genesis II prosthesis was comparable to that of the Vanguard prosthesis.

Level of evidence

Prospective cohort study, Level II.