Coronal alignment of patellofemoral arthroplasty

The Influence of Patello-Femoral Overstuffing After Modular Unlinked Bicompartmental Knee Arthroplasty (BiKA) for Medial Tibio-Femoral and Patello-Femoral Osteoarthritis of the Knee

BACKGROUND

The factors affecting results after bicompartmental knee arthroplasty (BiKA) have not been fully elucidated. This major ligament-preserving procedure may be more susceptible to overstuffing of the patello-femoral (PF) joint than the major ligament-sacrificing total knee arthroplasty. Currently, we investigated the effect of PF overstuffing after BiKA on its clinical outcome.

METHODS

There were 71 patients (74 knees) who underwent modular unlinked BiKA at our clinic who had a follow-up of 5 to 9 years. Final follow-up results were assessed by evaluating knee range of motion, the 2011 Knee Society Score (2011KSS), Japanese Knee Osteoarthritis Measure, and radiological findings. The degree of postoperative PF overstuffing was evaluated by computed tomography and magnetic resonance images for 55 knees, and the correlation between the degree of overstuffing and postoperative clinical results were examined.

RESULTS

Overall clinical results improved significantly after surgery without any revision cases. The X-ray measurements showed the improved coronal alignments and the appropriate implant installation angles. Higher degree of postoperative PF overstuffing caused by insufficient amount of osteotomy on the anterior surface of the femur correlated with worse postoperative total 2011KSS at 2 years after surgery (Spearman's rank correlation coefficient (rs) = -0.387, P = .004), as opposed to no correlation at the time of the final follow-up (Spearman's rank correlation coefficient = 0.068, P = .623).

CONCLUSION

Modular unlinked BiKA provided patients with a high level of satisfaction and functional improvement over 5 to 9 years postoperatively. However, because PF overstuffing affects initial patient satisfaction, the amount of osteotomy should be determined carefully during the surgery.

Modern Patellofemoral Arthroplasty

INTRODUCTION

The ideal procedure for isolated patellofemoral arthritis is a controversial topic. Patellofemoral arthroplasty (PFA) is an option that aims to restore normal kinematics to the knee while preserving bone. PFA has been shown to have benefits compared with total knee arthroplasty (TKA) in this patient population but has historically had a high failure rate. Revision rates are improving with modern implants and tight indications but still remain higher than TKA. This review summarizes current thinking around PFA using modern implants and techniques in 2023, provides an implant-specific analysis, and assesses how we can improve outcomes after PFA based on the current literature. The aim was to provide an outline of the evidence around PFA on which surgeons can make decisions to optimize patient outcome in this young and active population.

METHODS

Four databases (MEDLINE, Embase, Scopus, and SPORTDiscus) were searched for concepts of patellofemoral joint arthroplasty. After abstract and text review, a screening software was used to assess articles based on inclusion criteria for studies describing indications, outcomes, and techniques for isolated PFA using modern implants, with or without concomitant procedures.

RESULTS

A total of 191 articles were included for further examination, with 62 articles being instructional course lectures, systematic reviews, technique articles, narrative reviews, expert opinions, or meta-analyses. The remaining articles were case reports, trials, or cohort studies. Articles were used to create a thorough outline of multiple recurrent topics in the literature.

CONCLUSIONS

PFA is an appealing option that has the potential to provide a more natural feeling and functioning knee for those with isolated PF arthritis. The high rate of revision is a cause for concern and there are several technical details that should be stressed to optimize results. The uncertain outcome after revision to TKA also requires more investigation. In addition, the importance of strict selection criteria and firm indications cannot be stressed enough to optimize longevity and attempt to predict those who are likely to have progression of tibiofemoral osteoarthritis. The development of new third-generation implants is promising with excellent functional outcomes and a much lower rate of maltracking and implant complications compared with earlier generations. The impact of these implants and improvement in surgical techniques on the revision rate of PFA will be determined from longer-term outcomes.

Deep Learning for Automated Measurement of Patellofemoral Anatomic Landmarks

BACKGROUND

Patellofemoral anatomy has not been well characterized. Applying deep learning to automatically measure knee anatomy can provide a better understanding of anatomy, which can be a key factor in improving outcomes.

METHODS

483 total patients with knee CT imaging (April 2017-May 2022) from 6 centers were selected from a cohort scheduled for knee arthroplasty and a cohort with healthy knee anatomy. A total of 7 patellofemoral landmarks were annotated on 14,652 images and approved by a senior musculoskeletal radiologist. A two-stage deep learning model was trained to predict landmark coordinates using a modified ResNet50 architecture initialized with self-supervised learning pretrained weights on RadImageNet. Landmark predictions were evaluated with mean absolute error, and derived patellofemoral measurements were analyzed with Bland-Altman plots. Statistical significance of measurements was assessed by paired t-tests.

RESULTS

Mean absolute error between predicted and ground truth landmark coordinates was 0.20/0.26 cm in the healthy/arthroplasty cohort. Four knee parameters were calculated, including transepicondylar axis length, transepicondylar-posterior femur axis angle, trochlear medial asymmetry, and sulcus angle. There were no statistically significant parameter differences (p > 0.05) between predicted and ground truth measurements in both cohorts, except for the healthy cohort sulcus angle.

CONCLUSION

Our model accurately identifies key trochlear landmarks with ~0.20-0.26 cm accuracy and produces human-comparable measurements on both healthy and pathological knees. This work represents the first deep learning regression model for automated patellofemoral annotation trained on both physiologic and pathologic CT imaging at this scale. This novel model can enhance our ability to analyze the anatomy of the patellofemoral compartment at scale.

Internal Rotation, Varus, and Anterior Femoral Component Malalignments Adversely Affect Patellofemoral Joint Kinematics in Patellofemoral Arthroplasty

Background

Patellofemoral arthroplasty (PFA) is reported to provide nearly normal PF joint kinematics but only with adequate surgical techniques. This study evaluated the effects of various femoral component settings on patellar component biomechanics.

Methods

A dynamic musculoskeletal computer simulation analyzed normal knee and standard PFA models, as well as 8 femoral component malposition models: 5° internal or external rotation, 5° valgus or varus, 5° extension or flexion, and 3-mm or 5-mm anterior positioning. Mediolateral patellar translation, lateral patellar tilt, and contact force and stress at the PF joint were measured in each model during gait.

Results

The patella in the standard PFA model was shifted up to 5.0 mm laterally near heel off and was tilted up to 3.0° laterally at heel strike compared to the normal knee model. The patella in the external rotation model translated more laterally in the direction of the femoral component setting than in the standard model. However, in the internal rotation and varus alignment models, the patellar lateral shift occurred largely in the opposite direction of the femoral component setting. The patella in most models was tilted in the same direction as the femoral component setting. The PF contact force was increased, especially in the anterior femoral position models, by up to 30 MPa compared with 20 MPa in the standard model.

Conclusions

Internal rotation, varus, and anterior femoral component settings during PFA should be avoided to reduce postoperative complications, whereas external rotation might be appropriate only for cases with lateral patellar instability.

Patellofemoral Arthroplasty Is an Efficient Strategy for Isolated Patellofemoral Osteoarthritis with or without Robotic-Assisted System

There is relative paucity in the literature concerning outcomes after robotic-assisted Patellofemoral Arthroplasty (PFA). The aims were (1) to evaluate outcomes in patients undergoing PFA with inlay or onlay components, with or without robotic arm assistance and (2) to identify risk factors of poor outcomes after PFA. This retrospective study included 77 PFA for isolated patellofemoral joint osteoarthritis, assigned to three groups (18 conventional technique, 17 image-free robotic-assisted system and 42 image-based robotic-assisted system). The demographic data were comparable between the three groups. The clinical outcomes assessed were: Visual Analogue Scale, Knee Society Score, Kujala score and satisfaction rate. The radiological measures were: Caton Deschamps index, patellar tilt and frontal alignment of the trochlea. Functional outcomes, satisfaction rate and residual pain were comparable between the three groups. Patellar tilt improvement was superior when a robotic device was used (either image-based or image-free) compared to the conventional technique. There were three revisions (3.9%) at the last follow-up related to femorotibial osteoarthritis progression. Multivariate analysis found no significant risk factors for poor outcomes, with respect to the surgical technique or implant design. Functional outcomes and revisions rate after PFA were comparable between the surgical techniques and implants. Robotic-assisted systems were associated with a superior improvement of the patellar tilt compared to the conventional technique.

The lack of retropatellar resurfacing at index surgery is significantly associated with failure in patients following patellofemoral inlay arthroplasty: a multi-center study of more than 260 patients

PURPOSE

To evaluate the clinical outcomes of patients with a minimum 2-year follow-up following contemporary patellofemoral inlay arthroplasty (PFIA) and to identify potential risk factors for failure in a multi-center study.

METHODS

All patients who underwent implantation of PFIA between 09/2009 and 11/2016 at 11 specialized orthopedic referral centers were enrolled in the study and were evaluated retrospectively at a minimum 2-year follow-up. Clinical outcomes included the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score, the Knee Injury and Osteoarthritis Outcome Score (KOOS), the Tegner Scale, the visual analogue scale (VAS) for pain, and subjective patient satisfaction. Pre- and perioperative risk factors were compared among failures and non-failures to determine potential risk factors.

RESULTS

A total of 263 patients (85% follow-up rate) could be enrolled. The mean age at the time of index surgery was 49 ± 12 years with a mean postoperative follow-up of 45 ± 18 months. The overall failure rate was 11% (28 patients), of which 18% (5 patients) were patients with patella resurfacing at index surgery and 82% (23 patients) were patients without initial patella resurfacing. At final follow-up, 93% of the patients who did not fail were satisfied with the procedure with a mean transformed WOMAC Score of 84.5 ± 14.5 points, a mean KOOS Score of 73.3 ± 17.1 points, a mean Tegner Score of 3.4 ± 1.4 points and a mean VAS pain of 2.4 ± 2.0 points. An increased BMI was significantly correlated with a worse postoperative outcome. Concomitant procedures addressing patellofemoral instability or malalignment, the lack of patellofemoral resurfacing at the index surgery and a high BMI were significantly correlated with failure in our patient cohort.

CONCLUSION

Patellofemoral inlay arthroplasty shows high patient satisfaction with good functional outcomes at short-term follow-up and thus can be considered a viable treatment option in young patients suffering from isolated patellofemoral arthritis. Patellar resurfacing at index surgery is recommended to decrease the risk of failure.

LEVEL OF EVIDENCE

Retrospective case series, Level IV.

[When nothing else works: patellofemoral joint arthroplasty]

Patellofemoral joint replacement is the best treatment option available for isolated patellofemoral arthritis. Especially young patients should be operated on with bone-sparing techniques that also preserve the soft tissues, since these patients are very likely to be revised at some point in their lifetime. Correct patient selection is important for the success of surgery and should include a meticulous clinical examination and imaging. Special attention should be paid to additional pathologies that may also need to be addressed. For the trochlea, there are two different options for treatment with the inlay and onlay system. The retropatellar surface should be replaced. Patellofemoral joint replacement is still rarely performed, so treatment in specialised centres is recommended. National joint registry data show high revision rates, while data from centres show promising results.

Pre-operative patella alta does not affect midterm clinical outcomes and survivorship of patellofemoral arthroplasty

PURPOSE

The purpose of this study was to evaluate the effect of preoperative patella alta on clinical outcomes, survivorship, and complication and reoperation rates on patellofemoral arthroplasty (PFA).

METHODS

All patients who underwent PFA for isolated patellofemoral arthritis by a single surgeon at our institution were identified. Preoperative radiographs were measured by two independent observers for patellar height using the Caton Deschamps (CD), Insall-Salvati (IS), and Blackburne-Peele (BP) methods. Patients were classified as either "patella alta" or "non-patella alta" for all three measurement methods. Clinical scores including KSS Pain, KSS Function, and Tegner Activity Scores were collected pre- and post-operatively. Failure was defined as conversion to total knee arthroplasty (TKA). Clinical outcomes and survivorship were compared between patients with "patella alta" and "non-patella alta" height measurements.

RESULTS

There were 119 patients with 153 knees (86% female) included in the study with a mean age of 55.8 years. Outcome scores improved from pre-operative to post-operative for both patella alta and non-patella alta patients for Tegner, KSS pain and KSS function scores. The mean change in Tegner scores for patella alta and non-patella alta patients were not significantly different for CD (p = 0.24), IS (p = 0.25) or BP measurements (p = 0.39). The mean change in KSS pain scores between groups were not significantly different for CD (p = 0.33) or IS measurements (p = 0.22), but was improved more significantly in patella alta patients vs non-patella alta patients (21.2 and 14.4; p = 0.02) for BP measurement. The mean change in KSS function scores between groups was not significantly different for CD (p = 0.61) IS (p = 0.90) or BP measurements (p = 0.79). The overall survivorship from conversion to total knee arthroplasty (TKA) was 94.1% at a mean follow-up time of 5.0 (SD 2.6) years. There were no significant differences in survivorship from TKA between patella alta and non-patella alta groups (CD: p = 0.72, IS: p = 0.63, BP: p = 0.66).

CONCLUSIONS

This study suggests that there are no significant differences in clinical outcome scores or survivorship from TKA between patella alta and non-patella alta patients who underwent onlay design PFA. Both patella alta and non-patella alta patients demonstrated excellent improvement in outcome scores from pre-operative to post-operative.

LEVEL OF EVIDENCE

IV.

Contemporary knee arthroplasty: one fits all or time for diversity?

INTRODUCTION

Total knee arthroplasty (TKA) has historically been the preferred solution for any type of knee osteoarthritis, independently of the number of compartments involved. In these days of patient-specific medicine, mono-compartmental disease could also be approached with a more individualized treatment, such as partial knee arthroplasty (PKA). Off-the-shelf (OTS) implants are often the compromise of averages and means of a limited series of anatomical parameters retrieved from patients and the pressure of cost control by limited inventory. Personalized medicine requires respect and interest for the individual shape and alignment of each patient.

MATERIALS AND METHODS

A Pubmed and Google Scholar search were performed with the following terms: "patient-specific knee" and "arthroplasty" and "custom implant" and "total knee replacement" and "partial knee replacement" and "patellofemoral knee replacement" and "bicompartmental knee replacement". The full text of 90 articles was used to write this narrative review.

RESULTS

Unicondylar, patellofemoral and bicompartmental knee arthroplasty are successful treatment options, which can be considered over TKA for their bone and ligament sparing character and the superior functional outcome that can be obtained with resurfacing procedures. For TKA, where compromises dominate our choices, especially in patients with individual variations of their personal anatomy outside of the standard, a customized implant could be a preferable solution.

CONCLUSION

TKA might not be the only solution for every patient with knee osteoarthritis, if personalized medicine wants to be offered. Patient-specific mono-compartmental resurfacing solutions, such as partial knee arthroplasty, can be part of the treatment options proposed by the expert surgeon. Customized implants and personalized alignment options have the potential to further improve clinical outcome by identifying the individual morphotype and respecting the diversity of the surgical population.

Aiming for anatomical femoral axis on the coronal plane leads to good-to-excellent short-term outcomes in isolated patellofemoral arthroplasty

BACKGROUND

In patellofemoral replacement (PFR) coronal alignment is mostly influenced by local condylar anatomy. However, there is still a lack of consensus regarding references to follow intraoperatively for the optimal positioning of the trochlear component. The aim of this study was to assess whether aiming for the anatomical femoral axis on the coronal plane leads to improved clinical outcomes and whether coronal alignment correlates with clinical outcomes.

METHODS

Forty-two patients who underwent PFR were retrospectively evaluated at a minimum one-year follow-up using Kujala and Knee Society Score (KSS). Moreover, patients underwent an anteroposterior hip-to-knee X-ray to evaluate the coronal alignment of the trochlear component with respect to the femoral anatomic and mechanical axis. Prosthesis coronal alignment, Kujala, and KSS were assessed for possible correlation.

RESULTS

Mean follow-up time: 29.1 months. Mean KSS for pain: 90 (±8.9), for function: 93.7 (±15.9); mean Kujala: 89.2 (±13.6). Mean prosthesis coronal alignment was 3.3 ± 2.3° in valgus with respect to the femoral anatomic axis and 7.4 ± 2.6° in valgus with respect to the femoral mechanical axis. No correlations were found between coronal alignment and KSS or Kujala scores.

CONCLUSIONS

Results from the current study showed that PF replacement with a third-generation implant led to good-to-excellent outcomes. In addition, the surgical technique used for aligning femoral component in this study resulted in reduced coronal alignment variability and achieved good short-term clinical outcomes.

Patella alta and patellar subluxation might lead to early failure with inlay patello-femoral joint arthroplasty

PURPOSE

With the growing interest in resurfacing procedures, several new implants have been recently introduced for isolated patello-femoral joint arthroplasty (PFA). However, not much data are available for these new techniques or about the right indications for each type of implant.

METHODS

Out of a retrospective cohort of 20 inlay PFA, 11 PFA with an elevated Insall-Salvati index and an increased patello-femoral congruence angle showed an initial satisfactory result, but presented thereafter with recurrent pain and "clunk" phenomena. They were all revised after a median time of 25 months (range 8-28 months) into an onlay technique PFA and analyzed for their failure mode and revision technique.

RESULTS

Clinical symptoms such as clunking, as well as abraded areas craniolateral of the inlay implant found intraoperatively, were the main observations of this study. The modified Insall-Salvati index (mISI) was significantly higher in the revised knees compared to the unrevised (median 1.8 versus 1.6; p = 0.041). VAS and KSS significantly improved after revision (median VAS reduction in pain of 4.0 points, median KSS improvement of 20.0 points; p < 0.05).

CONCLUSION

Patients with high-normal patellar height index or patella alta, as well as a craniolateral type of arthritis with additional lateralization, should be considered contra-indicated for an inlay technique PFA. They could be considered for a PFA system reaching further proximal into the distal femur. An onlay PFA can be an option for early revision of failed inlay implants. The clinical relevance of this study is that patella alta and patellar subluxation are more difficult to adjust for with an inlay PFJ component.

LEVEL OF EVIDENCE

Level IV.

Surgical technique in patellofemoral arthroplasty

Patellofemoral arthroplasty (PFA) has seen its role validated over the last decade as a treatment for severe Iwano III or IV patellofemoral osteoarthritis (PFOA). The ideal indication is PFOA with femoral trochlear dysplasia. The accumulation of data on factors influencing the likelihood of PFA failure or success when using first- or second-generation implants has led to design changes, which have been incorporated into modern third-generation implants. These implants are positioned using anatomic cuts, with instrumentation kits that ensure accurate and reproducible alignment. Their design corrects the femoral trochlear dysplasia. Refinements in the indications of PFA, together with advances in prosthetic kinematics and improved understanding of the surgical technique, have strengthened the role for PFA. Although either a lateral or a medial approach can be used, the lateral approach deserves preference. Proper orientation of the femoral and patellar implants is crucial and can be achieved in an accurate and reproducible manner. Orientation of the coronal femoral cut is the only modifiable variable. The cut should be performed with the knee in neutral rotation to minimise both the tibial tuberosity-trochlear groove distance and the amount of extensor apparatus valgus. In the coronal plane, the femoral component must be positioned in valgus, to align the distal part of the trochlear implant with the lateral condylar cartilage. Medial positioning of the patellar component finalises the match between the femur and the patella. This coronal alignment of the two components promotes patellar engagement at the beginning of knee flexion. Thus, the technique brings the trochlea towards the patella and the patella towards the trochlea, thereby ensuring optimal patellofemoral tracking and ensuring a good final outcome. When these requirements are met, the functional and radiographic outcomes are predictable, of good quality, and sustained over time, provided the patient remains free of tibio-femoral osteoarthritis.

Femoral component rotation in patellofemoral joint replacement

BACKGROUND

Clinical outcomes in patellofemoral joint replacement may be related to femoral component rotation. Assessment of rotational alignment is however difficult as patients with isolated patellofemoral osteoarthritis often have trochlear dysplasia. The use of the medial malleolus as a landmark to guide rotation has been suggested. The purpose of our study was to evaluate this technique with regard to femoral component rotation, and to correlate rotation with clinical outcomes at one-year follow-up.

METHODS

Forty-one knees in 39 patients had patellofemoral joint replacement using the Zimmer Gender-Solutions patellofemoral prosthesis. Intraoperatively, we determined femoral component rotational alignment using an extramedullary rod aimed at the inferior tip of the medial malleolus. Postoperatively, we measured the angle between the femoral component and the anatomical transepicondylar axis using CT. The amount of rotation was correlated with clinical outcomes at one-year follow-up.

RESULTS

Forty knees in 38 patients were available for one-year follow-up. Mean femoral component rotation relative to the anatomical transepicondylar axis was 1.4° external rotation (range, -3.8 to 5.7°). We found no statistically significant correlation between femoral component rotation and change from baseline KOOS subscales at one-year follow-up.

CONCLUSIONS

Our findings show that when using the medial malleolus as a landmark to guide rotation, the femoral component of the patellofemoral prosthesis was oriented in external rotation relative to the anatomical transepicondylar axis in 80% of knees. Our study did not show a relation between the amount of external rotation and clinical outcomes.

LEVEL OF EVIDENCE

Level III.

Inadequacy of computed tomography for pre-operative planning of patellofemoral arthroplasty

PURPOSE

To evaluate the accuracy of preoperative planning for patellofemoral arthroplasty (PFA) by comparing: (1) virtual implant positioning simulated on pre-operative images versus (2) real implant positioning from post-operative images.

METHODS

The authors prospectively studied 15 patients that received a PFJ implant (Tornier, Montbonnot France). A pre-operative planning software was established to determine the size and position of the trochlear component. Pre-operative scans were used to perform virtual implantations by two different operators, which were then compared to the post-operative scans to calculate errors (ε) in implant positioning and intra-class correlation coefficients (ICC) for intra- and inter-observer repeatability.

RESULTS

Analysis was performed for 13 patients, for whom agreement between virtual and real surgery was excellent for anteroposterior (AP) position (ICC = 0.84; ε _max = 3.5 mm), fair for proximodistal (PD) position (ICC = 0.50; ε _max  = 9.5 mm), and poor for mediolateral (ML) position (ICC = 0.07; ε _max = 9.0 mm). It was fair for flexum-recurvatum (FR) alignment (ICC = 0.53; ε _max = 8.2°), poor for varus-valgus (VV) alignment (ICC = 0.34; ε _max = 10.0°), and internal-external (IE) rotation (ICC = 0.34; ε _max = 10.6°).

CONCLUSIONS

Pre-operative planning was insufficiently accurate to follow intra-operatively, the greatest errors being angular alignment (VV and FR). The clinical relevance of these findings is that PFA is difficult to plan pre/operatively due to non-visibility of cartilage on CT scans and to trochlear dysplasia in most cases.

LEVEL OF EVIDENCE

Prospective evaluation of operative tools on consecutive patients, Level III.

PATELLOFEMORAL ARTHROPLASTY CHANGES THE TROCHLEAR GROOVE ANGLE

High early failure rates occur in the treatment of isolated symptomatic patellofemoral arthritis with commercially available patellofemoral arthroplasty (PFA) prostheses. We postulate that PFA changes the trochlear groove angle, thereby causing patellar maltracking, catching and pain. We examined the extent of this change in trochlear groove angle by virtually implanting five commercially available patellofemoral prostheses into two 3D reconstructed knees, one with a normal and the other with a dysplastic trochlea. The axial and coronal trochlear groove angles were measured pre- and post PFA for the five different prostheses in both the normal and the dysplastic knee. Post PFA, the trochlear groove angle changed from the original in both the axial and coronal planes for all the prostheses in both the normal and the dysplastic knee. The trochlear groove change is dependent on the design of the specific prosthesis. To avoid excessive changes post PFA, both the wide variation of changes between different generic PFA prostheses, as well as the wide variation in patient femoral anatomy should be considered.

The effect of axial rotation of the anterior resection plane in patellofemoral arthroplasty

BACKGROUND

Patellofemoral arthroplasty (PFA) has a small but definite place in replacement surgery of the knee, especially in young patients. The main surgical considerations in PFA are the patient's anatomy, the type of prosthesis and the surgical technique. The surgical technique and PFA success rely heavily on the anterior resection. In this study we investigate the effect of axial rotation of the anterior resection plane.

METHODS

We tested the outcome of PFA fit based on resection footprint measurements, axial and coronal groove angles, and lateral trochlear inclination (LTI) angle in a virtual PFA model. The range of anterior resection plane axial rotations was from five degree internal to five degree external with an increment of one degree.

RESULTS

Axial rotation of anterior resection plane changes the resection footprint dimension, which leads to coronal rotation of the femoral component. External rotation of the resection plane results in valgus rotation of the trochlear groove and decreased LTI after PFA and the opposite was observed for internal rotation.

CONCLUSION

Our study showed that by changing the axial rotation of the anterior cut, the coronal groove of the prosthesis can be altered to lie more closely with the native groove line without compromising the prosthesis-cartilage transition.

A cadaveric investigation into the demographic and bony alignment properties associated with osteoarthritis of the patellofemoral joint

BACKGROUND

Patellofemoral joint osteoarthritis is common, although circumstances dictating its evolution and pathogenesis remain unclear. Advances in surgical technique have improved the ability to modify long-bone alignment in the coronal, sagittal, and axial planes. However, to our knowledge, there is no significant long-term data available in regard to the relationship between anatomic alignment parameters most amenable to surgical modification and patellofemoral joint osteoarthritis.

METHODS

Five-hundred and seventy-one cadaveric skeletons were obtained from the Hamann-Todd osteological collection. Mechanical lateral distal femoral angle, medial proximal tibial angle, tibial slope, femoral version, tibial torsion, the position of the tibial tubercle relative to the width of the tibial plateau, trochlear depth, and patellar size were measured using validated techniques. A previously published grading system for patellofemoral joint arthritis was used to quantify macroscopic signs of degenerative joint disease.

RESULTS

Increasing age (standardized beta 0.532, p<0.001), female gender (standardized beta 0.201, p=0.002), and decreasing mechanical lateral distal femoral angle (standardized beta -0.128, p=0.025) were independent correlates of increased patellofemoral joint osteoarthritis. A relatively more laterally positioned tibial tubercle trended towards predicting patellofemoral joint osteoarthritis (standardized beta 0.080, p=0.089).

CONCLUSIONS

These findings confirm that patellofemoral joint osteoarthritis is strongly associated with increasing age and female gender. Valgus alignment of the distal femur, a relatively more lateral location of the tibial tubercle, and a shallower trochlear grove appear to have modest effects on the development of patellofemoral joint osteoarthritis.

Significant Functional Improvement at 2 Years After Isolated Patellofemoral Arthroplasty With an Onlay Trochlear Implant, But Low Mental Health Scores Predispose to Dissatisfaction

INTRODUCTION

We reviewed the clinical and radiographic outcomes of a consecutive series of patients who underwent patellofemoral arthroplasty (PFA) using a modern onlay-style trochlear design and all-polyethylene patellar component. An additional goal of the study was to elucidate, for the first time, the extent to which patients were satisfied with their implant and whether expectations were met after undergoing PFA.

METHODS AND MATERIALS

We identified a consecutive series of 70 knees (53 patients) treated with primary isolated PFA between October 2007 and May 2012. For our clinical outcomes analysis, we included patients with a minimum follow-up of 2 years and available preoperative original Knee Society scores.

RESULTS

At an average 4.9 years of follow-up, the mean range of motion and Knee Society Knee and Function scores improved significantly, and less than 4% of patients required revision arthroplasty. There was no radiographic evidence of component loosening or wear. Despite these improvements, new Knee Society scores indicated that fewer than two-thirds of patients were satisfied or had their expectations met. Dissatisfied patients and those whose expectations were not met had significantly lower Mental Health scores according to the Short Form-36 following PFA.

CONCLUSIONS

Despite the clinical and radiographic success of this implant, patient satisfaction remained low, which may be partially explained by poor mental health.