Computer-Assisted Navigation in Patellofemoral Arthroplasty: a New Technique to Improve Rotational Position of the Trochlea

Background

Maltracking or subluxation is one of the complications of patellofemoral arthroplasty.

Questions/Purposes

We questioned whether the computed navigation system can improve patellar tracking in patients with patellofemoral arthroplasty (PFA).

Methods

Between 2007 and 2010 we performed 15 patellofemoral arthroplasties using the Ceraver PFA and navigation assistance. Fifteen other patients underwent surgery without navigation during the same period and acted as a control group. The rotation of the native trochlea as measured using the epicondylar line as a reference before surgery and the rotation of the trochlear component and the trochlear twist angle were assessed with computed tomography (CT) scan after surgery.

Results

The mean follow-up was 3 years (range, 2–5 years). The group with navigation had no patellofemoral complications and better clinical scores. The group without navigation had abnormal patellofemoral tracking in 5 of the 15 patients. CT scan demonstrated excessive internal component rotation, as compared with patients without complications. This excessive internal rotation was proportional to the severity of the patellofemoral maltracking.

Conclusions

The short-term results suggest that navigation can lead to better trochlear rotation which, in our hands, is associated with fewer cases of patellar maltracking and better overall clinical scores.

Electronic supplementary material

The online version of this article (doi:10.1007/s11420-013-9328-x) contains supplementary material, which is available to authorized users.     

Association between measures of trochlear morphology and structural features of patellofemoral joint osteoarthritis on MRI: The MOST study

The sulcus angle has been widely used in the literature as a measure of trochlear morphology. Recently, lateral trochlear inclination and trochlear angle have been reported as alternatives. The purpose of this study was to determine the association between measures of trochlear morphology and patellofemoral joint (PFJ) cartilage damage and bone marrow lesions (BMLs). Nine hundred seven knees were selected from the Multicenter Osteoarthritis Study, a cohort study of persons aged 50–79 years with or at risk for knee OA. Trochlear morphology was measured using lateral trochlear inclination, trochlear angle, and sulcus angle on axial MRI images; cartilage damage and BMLs were graded on MRI. We determined the association between quartiles of each trochlear morphology variable with the presence or absence of cartilage damage and BMLs in the PFJ using logistic regression. The strongest associations were seen with lateral trochlear inclination and lateral PFJ cartilage damage and BMLs, with knees in the lowest quartile (flattened lateral trochlea) having more than two times the odds of lateral cartilage damage and BMLs compared to those in the highest quartile (p < 0.0001). Lateral trochlear inclination may be the best method for assessment of trochlear morphology as it was strongly association with structural damage in the PFJ. © 2011 Orthopaedic Research Society Published by Wiley Periodicals, Inc. J Orthop Res 30:1–8, 2012     

Revision patellofemoral arthroplasty: three- to seven-year follow-up

In this series, a failed first-generation patellofemoral arthroplasty was revised to a second-generation prosthesis. Fourteen knees were prospectively followed up for a mean of 60 months. Primary procedure failure was due to component malposition, subluxation, polyethylene wear, or overstuffing. Mean Bristol knee scores improved from 58 (range, 36-86) to 79 (range, 38-100) (P < .001). Mild femorotibial arthritis (Ahlbach stage I) was present in 5 knees and predicted a poorer outcome. At most recent follow-up, there was no evidence of wear, loosening, or subluxation. Significant improvement can be obtained when revising the failed patellofemoral arthroplasty, provided there is no femorotibial arthritis.     

Long-Term Outcomes of Patellofemoral Arthroplasty

The purpose of this study was to correlate the long-term survival of patellofemoral arthroplasty with primary diagnosis, age, sex, and body mass index. One hundred eighty-five consecutive Richards type II patellofemoral arthroplasties were performed in 161 patients with isolated patellofemoral osteoarthritis. Diagnoses included primary patellofemoral osteoarthritis, posttraumatic patellofemoral osteoarthritis, and patellofemoral osteoarthritis with a previous realignment procedure for patellar subluxation or trochlear dysplasia. Median time to follow-up was 13.3 (range, 2.0-30.6) years. Patellofemoral arthroplasty survival was 84% at 10 years and 69% at 20 years. Primary diagnosis, sex, or age at patellofemoral arthroplasty did not significantly affect the rate of revision (P = .35, P = .24, and P = .65, respectively). The rate of revision in obese patients (body mass index >30 kg/m²) was higher than that in nonobese patients (P = .02).     

Medial Unicompartmental Knee Arthroplasty in Patients Less Than 55 Years Old: Minimum of Two Years of Follow-Up

Eighty-five fixed bearing medial unicompartmental arthroplasties were performed in 42 men and 33 women with a mean age of 49 years (range, thirty-three to fifty-five years old) at the time of surgery. At a mean of 4.0 years (range two to twelve years), the mean pre-operative Knee Society score improved from 49 to 95.1 points (P< 0.0001) and the mean UCLA activity score was 7.5 (range 5 to 9). Three knees underwent revision to a total knee arthroplasty; two for arthritic progression in the lateral compartment and one for pain. At the time of final follow-up, two knees (2.4%) demonstrated progressive Grade 4 arthritis of the patellofemoral compartment but were asymptomatic. There was no radiographic evidence of loosening, osteolysis, or premature polyethylene wear. Estimated survivorship was 96.5% at 10 years. UKA offered excellent early outcomes in this cohort of younger, active patients.     

Reconstruction of medial patellofemoral ligament for chronic patellar instability

Background:

Disruption of the capsule, medial patellar retinaculum, and/or vastus medialis obliqus has been associated with recurrent patellar instability. Biomechanical studies have shown that the medial patellofemoral ligament (MPFL) is the main restraint against lateral patella displacement and reconstruction of the MPFL has become an accepted surgical technique to restore patellofemoral stability in patients having recurrent patellar dislocation. We report a prospective series of patients of chronic patellar instability treated by reconstruction of medial patellofemoral ligament.

Materials and Methods:

Twelve patients (15 knees) with recurrent dislocation of patella, were operated between January 2006 and December 2008. All patients had generalised ligament laxity with none had severe grade of patella alta or trochlear dysplasia. The MPFL was reconstructed with doubled semitendinosus tendon. Patients were followed up with subjective criteria, patellar inclination angle, and Kujala score.

Results:

The mean duration of followup after the operative procedures was an average of 42 months (range 24–60 months) 10 knees showed excellent results, 3 knees gave good results, and 2 knees had a fair result. The average patellar inclination angle decreased from 34.3° to 18.6°. The average preoperative Kujala functional score was 44.8 and the average postoperative score was 91.9.

Conclusion:

MPFL reconstruction using the semitendinosus tendon gives good results in patients with chronic patellar instability without predisposing factors like severe patella alta and high-grade trochlear dysplasia, and for revision cases.     

Fixed-Bearing Medial Unicompartmental Knee Arthroplasty in Patients Younger Than 55 Years of Age at 4-19 Years of Follow-Up: A Concise Follow-Up of a Previous Report

BackgroundUnicompartmental knee arthroplasty (UKA) is an effective alternative to total knee arthroplasty (TKA) in isolated unicompartmental disease; however, mid-term to long-term results in young patients are unknown. The purpose of this study is to determine the mid-term outcomes of fixed-bearing medial UKA in patients less than 55 years of age.MethodsSeventy-seven fixed-bearing medial UKAs in patients less than 55 years of age (mean 49.9, range 38-55) from a previously published report were retrospectively reviewed at a mean follow-up of 11.2 years (range 4.1-19.2).ResultsEleven knees were converted to TKA (14.3%) at 0.7-13.8 years postoperatively. The indications for revision included 7 for unexplained pain (9.1%), 2 for grade 4 arthritic progression (1 isolated lateral and 1 lateral and patellofemoral compartments; 2.6%), 1 for polyethylene wear (1.3%), and 1 for femoral component loosening (1.3%). Predicted survivorship free from component revision was 90.4% (95% confidence interval 86.9-93.9) at 10 years and 75.1% (95% confidence interval 66.2-84.0) at 19 years. The mean Knee Society Score improved from a mean of 51.9-88.6 points (P < .001). Of the 52 knees with 4-year minimum radiographs, 3 (5.8%) developed isolated grade 4 patellofemoral arthritis that was asymptomatic, and no knees had evidence of component loosening or osteolysis.ConclusionFixed-bearing medial UKA is a durable option for young patients with unicompartmental arthritis, with good clinical outcomes at mid-term follow-up. Unexplained pain was the most common reason for revision to TKA.     

Are Current Total Knee Arthroplasty Implants Designed to Restore Normal Trochlear Groove Anatomy?

Biomechanical studies have shown that external rotation of the femoral TKA component improves patellar tracking but does not restore it to physiologic values. We hypothesized that this could be due to differences in the trochlear groove geometry of TKA and normal knees. This was investigated via a virtual TKA procedure that mounted femoral components on to 3-dimensional models of healthy femurs, followed by measurement of the trochlear geometry before and after the simulated TKA. The results showed that (1) external rotation of the component brought the trochlear groove closer to normal anatomy than no external rotation; (2) however, even with external rotation, the trochlear anatomy was only partially restored to normal. Further work is needed to determine implications for patellofemoral complications observed with current TKA designs.     

Differences in Trochlear Surface Damage and Wear Between Three Different Total Knee Arthroplasty Designs

Introduction

Trochlear design plays a role in patellofemoral kinematics. Little is known regarding differences in the contact properties between modern designs. The purpose of the present study was to analyze patellofemoral joint contact by identifying areas of joint surface damage and wear in retrieved femoral components of 3 modern designs.

Linkage guide for rotational alignment during total knee arthroplasty

A linkage guide was devised for use in conjunction with knee arthroplasty instruments to achieve proper component rotation. The femoral component was rotationally aligned to the surgical epicondylar axis using one guide. The other guides were used after all bone surfaces were cut and soft tissue balancing was completed. A Kirschner wire was guided into the proximal tibial aspect parallel to the sagittal plane of the femoral component with the patella in its normal position and the knee in full extension. The wire was used as a reference to determine tibial component rotation. The relative rotational alignment of 21 knees in 19 patients who had undergone cruciate-retaining total knee arthroplasty utilizing this guide was assessed using the modified Eckhoff method. The results of radiographic analysis were compared with those in a control group of 25 knees where the guide was not employed. The external rotation of the femoral component relative to the tibial component was 1.3° ± 2.0° (mean ± SD) in the guided group and 1.1° ± 4.4° in the control group. The relative rotational angle was significantly more consistent using the guide. Implant malrotation can be reduced using our technique.     

Rotational Alignment of the Femoral Component Using Trochlear Navigation During Total Knee Arthroplasty: A Dual-Center Study of 145 Cases

Rotational alignment of the femoral component during TKA is critical. Here we propose a technique using navigation of the femoral trochlea to determine the rotation of the femoral component. The rotation is considered “ideal” when the component position leads to the arthroplasty trochlea being perfectly superimposed over the native trochlea. Thus the arthroplasty trochlea will be aligned on the trochlear groove axis, which itself is perpendicular to the transepicondylar axis. This was a prospective, non-randomized, dual-center study involving 145 knees. In all knees, the rotation of the femoral component was determined intraoperatively by trochlear navigation. The alpha angle obtained with this method was compared to the one calculated on a preoperative or postoperative CT scan. There was excellent agreement between the results obtained with the CT scan method and the ones obtained with trochlear navigation.     

Minimum Two-Year Outcomes of Modular Bicompartmental Knee Arthroplasty

The purpose of this study was to determine the results of modular unlinked bicompartmental knee arthroplasty (BiKA) for medial (or lateral) and patellofemoral arthritis. Twenty-nine modular BiKAs were followed prospectively, for a mean of 31 months (range, 24–46 months). Outcome measures included Knee Society Knee and Function Scores, KOOS, SF-12, and WOMAC, as well as radiographic assessments and implant survivorship. Two tail paired Student's t test was used to determine statistical differences between preoperative and postoperative scores. Mean range of motion (ROM) improved from 122° to 133° (P < 0.001). There was a statistically significant improvement across all functional scores. One patient underwent conversion to total knee arthroplasty at 3 years for knee instability. There were no cases of patellar instability, implant loosening or wear, or progressive arthritis.     

In vivo sagittal plane kinematics of the Avon patellofemoral arthroplasty

Isolated patellofemoral osteoarthritis can be treated with patellofemoral arthroplasty (PFA). In contrast to total knee arthroplasty, the effect of PFA on knee joint kinematics is not known. A study was performed to identify the kinematic changes after PFA. The sagittal plane kinematics was examined in 12 patients who had undergone Avon PFA. An established fluoroscopic method was used to examine the patellar tendon angle (PTA)/knee flexion relationship during functional activities. No significant difference existed between the kinematics of PFA knees compared with normal, except for a uniform elevation in PTA throughout the range. This increase in PTA in the PFA joint represents a 1.6-mm anterior displacement of the patella. The kinematic profile after PFA is close to normal and suggests that the knee is exhibiting more normal loading characteristics than those of the total knee arthroplasty joint.     

The influence of preoperative deformity on intraoperative soft tissue balance in posterior-stabilized total knee arthroplasty

Using a tensor for total knee arthroplasty (TKA) enabling soft tissue balance measurements with a reduced patellofemoral joint and femoral component in place, we examined the influence of preoperative deformity on intraoperative soft tissue balance during posterior-stabilized TKA at 0°, 10°, 45°, 90°, and 135° of flexion in 60 varus-type osteoarthritic patients. Despite more than 20° of preoperative varus deformity influencing intraoperative ligament balance in varus, joint gap showed no significant difference regardless of the amount of preoperative varus deformity. Accordingly, even in pre-operative severe varus deformed knees, gap balancing can be adjusted during PS TKA.     

The Lubinus patellofemoral arthroplasty: a series of 17 cases

Introduction The Lubinus patellofemoral arthroplasty was introduced in our institution in 1994. The first 17 patients were followed-up in order to identify the short-term outcome for this prosthesis.Materials and methods The average age at surgery was 66 years (range 37–82 years). The mean follow-up was 19 months. The indications for surgery were strictly limited to radiographically proven primary osteoarthritis affecting only the patellofemoral joint (13) and secondary arthritis due to maltracking, subluxation (3) or trauma to the patella (1). At review, the range of movement and Lysholm and Tegner scores were recorded and radiographs obtained. Patients were also asked if their outcome was satisfactory or unsatisfactory.Results At review, only 9 (53%) knees were classified as satisfactory by the patients. Further surgery had been carried out in 6 cases (35%) including revision to total knee arthroplasty in 4 (24%). Other complications included clicking and subluxation in 3 cases (18%), extension block in 3 (18%) and infection in 1 (6%). Progression of osteoarthritis to involve other compartments occurred in 2 cases (12%).Conclusions Many of these early problems are related to the unforgiving nature of the prosthesis on insertion. These poor early results have led us to stop using the prosthesis.     

Mid-Term Clinical,Functional, and Radiographic Outcomes of 105 Gender-Specific Patellofemoral Arthroplasties,With or Without the Association of Medial Unicompartmental Knee Arthroplasty

Background

The purpose of this study is to evaluate clinical and radiographic outcomes after gender-specific patellofemoral arthroplasty (PFA) either isolated or combined with unicompartmental knee arthroplasty (UKA).

Correction of Patellofemoral Malalignment With Patellofemoral Arthroplasty

Background

The goal of patellofemoral arthroplasty (PFA) is to replace damaged cartilage and correct underlying deformities to reduce pain and prevent maltracking. We aimed to determine how PFA modifies patellar height, tilt, and tibial tuberosity-trochlear groove (TT-TG) distance. The hypothesis was that PFA would correct trochlear dysplasia or extensor mechanism malalignment.

Optimizing femoral component rotation in total knee arthroplasty.

Femoral component rotation is important in total knee arthroplasty to optimize patellofemoral and tibiofemoral kinematics. More recently, the epicondylar axis has been cited as the definitive landmark for femoral component rotation. However, there are few studies to support the validity of this rotational landmark and its effect on the patellofemoral and tibiofemoral articulations. In the current study, a total knee arthroplasty was done in 11 knees from cadavers. The knees were tested with various femoral component rotations from 5 degrees internal rotation to 5 degrees external rotation referenced to the epicondylar axis and to the posterior femoral condyles. Each knee acted as its own internal control. The knees were actively ranged from 0 degrees to 100 degrees by a force on the quadriceps tendon in an Oxford knee simulator. Three-dimensional kinematics of all three components were measured whereas a multiaxial transducer imbedded in the patella measured patellofemoral forces. Femoral component rotation parallel to the epicondylar axis resulted in the most normal patellar tracking and minimized patellofemoral shear forces early in flexion. This optimal rotation also minimized tibiofemoral wear motions. These beneficial effects of femoral rotation were less reproducibly related to the posterior condyles. Rotating the femoral component either internal or external to the epicondylar axis worsened knee function by increasing tibiofemoral wear motion and significantly worsening patellar tracking with increased shear forces early in flexion. Based on the current study, the femoral component should be rotationally aligned parallel to the epicondylar axis to avoid patellofemoral and tibiofemoral complications.     

Reliability of the anteroposterior axis and the posterior condylar axis for determining rotational alignment of the femoral component in total knee arthroplasty

We examined the reliability of the anteroposterior and posterior condylar axes for determining rotational alignment of the femoral component in total knee arthroplasty (TKA). A computed tomography scan was taken at the level of the femoral epicondyle in 84 knees (27 varus knees with medial femorotibial arthritis (FT-OA) in 26 patients, 17 knees with patellofemoral arthritis in 14 patients, and 40 normal knees in 40 volunteers). On the image, an anteroposterior axis, a line perpendicular to the anteroposterior axis, an epicondylar axis and a posterior condylar axis were drawn, and the relationship between the three axes was assessed. The mean values for the 84 knees were evaluated, and the posterior condylar axis was 6.0°± 2.4° internally rotated relative to the epicondylar axis, while the line perpendicular to the anteroposterior axis was 1.4°± 3.3° internally rotated relative to the epicondylar axis. The internal rotation angle of the posterior condylar axis relative to the epicondylar axis was 6.2°± 1.9° in the knees with medial femorotibial arthritis, 6.4°± 2.4° in the knees with patellofemoral arthritis, and 5.8°± 2.7° in the normal knees, showing consistent values in normal and osteoarthritic knees. The internal rotation angle of the line perpendicular to the anteroposterior axis relative to the epicondylar axis was 0.1°± 3.3°, 1.3°± 3.3°, and 2.3°± 3.1° in the three groups, respectively (i.e., there were significant differences between the medial FT-OA knees and the normal knees). The results demonstrated that the anteroposterior axis was rotated externally to a significant degree in medial FT-OA knees and was less reliable than the posterior condylar axis for use in alignment for TKA on medial FT-OA knees. Received for publication on July 30, 1997; accepted on Feb. 3, 1998     

Femoral Rotation in Ligament Balanced Knee Arthroplasty : A Prospective Clinical Study

Rotational alignment of the femoral component is an important factor to achieve beneficial results in total knee arthroplasty. Femoral rotation pre versus post surgery was prospectively assessed in 40 patients who underwent ligament balanced knee arthroplasty. Computerized tomography of the knee was performed before and after the surgery to determine the femoral rotation. In 36 out of 40 patients the rotation of the femoral implants differed compared to the preoperative femur (P > 0.001). After surgery the rotational alignment of the femoral component ranged from − 3° (internal rotation) to 7° (external rotation). Increased external rotation was found in 33 out of 40 patients ranging from 1° to 7°. These results highlight the importance of individually determined femoral rotation in ligament balanced knee arthroplasty.