Are modern knee outcomes scores appropriate for evaluating anterior knee pain and symptoms after total knee arthroplasty?

Patellofemoral arthroplasty provides similar long-term survival rate and complications with better clinical outcomes compared to facetectomy for the treatment of isolated patellofemoral osteoarthritis

Purpose

This study aimed to analyse the clinical outcomes and survival of patellofemoral arthroplasty (PFA) in treating isolated patellofemoral osteoarthritis (IPFOA) at our centre. The secondary objective was to compare these results with a historical cohort treated with partial lateral facetectomy plus Insall realignment (PLFIR). We hypothesised that clinical outcomes and survival with PFA are superior to PLFIR and comparable to the literature.

Methods

A retrospective analysis of 120 patients with IPFOA was conducted. The PFA series included 33 patients treated between 2012 and 2019 with a minimum follow-up of 5 years (range 1.2-12.1 years). The PLFIR historical cohort treated between 1995 and 2002 (range 4.1-15.7 years) consisted of 87 patients. Preoperative and post-operative clinical outcomes were assessed using the Knee Society Score (KSS) and Kujala score, and survivorship was evaluated via Kaplan-Meier analysis. Cox regression analysis was used to identify factors influencing surgical failure.

Results

The PFA group demonstrated a 75.8% survival rate at 10 years, with a 24.2% failure rate requiring conversion to total knee arthroplasty (TKA). In the PLFIR group, the 10-year survival rate was 79.3%, although 26.4% required TKA. Both groups exhibited significant improvements in KSS and Kujala score, with PFA showing superior Kujala score improvement (p = 0.012). No statistically significant difference in survival between the two groups was observed at 10 years (p = 0.056), but PFA showed better long-term clinical outcomes.

Conclusions

PFA demonstrated comparable survival rates to PLFIR in the treatment of IPFOA. Despite a higher initial failure rate, PFA showed a potential for greater improvement in the long term, particularly in terms of anterior knee pain.

Level of Evidence

Level IV, retrospective case series analysis compared with a historical cohort.

Does inverse kinematic alignment coupled with robot-assisted TKA optimize patellofemoral clinical and radiological results?

INTRODUCTION

With a satisfaction rate of 80%, total knee arthroplasty (TKA) surgery has seen significant improvements in recent decades. The 20% of poor results may be explained by the alignment technique used for implant placement, which can influence patellofemoral kinematics. The objective of this study was to demonstrate that the use of inverse kinematic alignment makes it possible to obtain satisfactory clinical and radiological patellar scores in robotic TKA.

HYPOTHESIS

The inverse kinematic alignment technique coupled with robotic surgery makes it possible to restore the native kinematics of the patella.

MATERIALS AND METHODS

This prospective study including 100 TKAs with a primary TKA performed using the Stryker Mako™ robotic surgery system, and the inverse kinematic alignment technique. Patients who underwent patella resurfacing were excluded. Clinical and radiological scores were recorded preoperatively and 1 year postoperatively.

RESULTS

At one year, the specific patellar clinical scores were excellent with an average Kujala score of 85.69 and an average HSS Patellar score 88.15. The average patellar lateralization index was 0.15 and the average patellar tilt was 5.1°, showing no significant difference compared to preoperation (p=0.45 and p=0.18). The average external rotation of the femoral implant was 0.47±0.6° [-1.9; 2.1].

DISCUSSION

The patellofemoral clinical results were excellent. The use of the robotic arm coupled with this alignment technique makes it possible to obtain a controlled external rotation of the femoral implant as well as an optimized orientation of the tibial component, favoring good restitution of the alignment of the extensor apparatus. This study did not demonstrate any radiological correction of patellar tilt and lateralization.

CONCLUSION

The combined use of robotic surgery with the inverse kinematic alignment technique seems effective on specific clinical results of the patellofemoral joint.

LEVEL OF EVIDENCE

II; prospective cohort.

Patellar resurfacing might not be mandatory in contralateral second total knee replacement even if performed during replacement of the first knee

INTRODUCTION

The appropriateness or necessity of patellar resurfacing in total knee arthroplasty (TKA) is not clearly established. The objective of the present study was to compare the clinical and functional results of patients with bilateral involvement, operated on in one knee by TKA with patellar resurfacing and in the other knee by TKA without resurfacing. The hypothesis was that there was no difference in results between the two sides.

METHOD

This was a retrospective cohort of patients operated on by TKA without patellar resurfacing in a second osteoarthritic knee after contralateral TKA with patellar resurfacing. Twenty consecutive patients who underwent second primary TKA constituted their own control group (40 knees). Iwano scores were comparable. Mean age was 75.9±6.2years. Mean time between the two procedures was 20.6±11.9months.

RESULTS

There were no differences in SF-36, KOOS or Lille patellofemoral scores between the right and left knees. Sixty-five percent of patients were unable to differentiate the performance of their knees in activities of daily living.

CONCLUSION

The present study did not differentiate results according to patellar resurfacing, showing the limitations of resurfacing for early functional gain after primary TKA. Resurfacing might thus not be essential, even if it was performed in replacement of the first knee.

LEVEL OF EVIDENCE

IV; retrospective cohort study.

Outcomes of isolated patellofemoral arthroplasty

Osteoarthritis of the patellofemoral compartment can cause significant functional impairment. Isolated patellofemoral osteoarthritis affects greater than 10% of males and females over the age of 60. Patellofemoral arthroplasty (PFA) was developed as a joint-preserving procedure that maintains natural knee kinematics in those with isolated patellofemoral disease. First-generation implants were fraught with complications, a high rate of revision, and early conversion to total knee arthroplasty (TKA). Second-generation implants have demonstrated significant improvements in patient-reported outcome measures, complication rates and implant survivorship. Factors that can affect outcomes include surgical indications, patient selection, and PFA prosthesis design. Modern PFA for isolated patellofemoral osteoarthritis has comparable outcomes to TKA for isolated patellofemoral osteoarthritis. In this article, we discuss the use of PFA, implant design, the indications and factors affecting outcomes, and comparison to TKA.

Distal femoral megaprosthesis fracture treated by RescueSleeve MEGASYSTEM-C

Escalating revision surgery after megaprosthesis knee replacement sometimes raises the question of "limb salvage". Here we present a salvage technique for megaprosthesis fracture at the junction between the stem and the metaphyseal component. In this young active patient, the short residual proximal femur was not loose and was difficult to extract without prosthetic escalation. The technique described here conserved the well-fixed primary stem and used a custom-made RescueSleeve MEGASYSTEM-C connection sleeve (Link, Hamburg, Germany) plus spacer and a standard epiphyseal implant. This semi-conservative procedure avoided femorotomy or larger morbid segmental femoral resection. It conserved maximal bone stock and achieved rapid functional recovery. To our knowledge, this is the first reported case of this technique using a custom-made connecting part to manage megaprosthesis fracture. LEVEL OF EVIDENCE: IV.

Cruciate-substituting and posterior-stabilised total knee arthroplasties had similar gait patterns in the short term

PURPOSE

Surgeons want to achieve native kinematics in primary total knee arthroplasty (TKA). Cruciate-substituting (CS) implants could restore the knee kinematics more efficiently than posterior-stabilised (PS) TKA. This study aimed to compare gait patterns in patients with CS or PS TKA at 6 months. The hypothesis was that CS implants would demonstrate comparable gait parameters to PS implants at 6 months.

METHODS

In this prospective case-control study, 38 primary TKA without coronal laxity were divided into 2 groups: 19 cruciate-substituting (CS) and 19 posterior-stabilised (PS) implants. The type of prosthesis was determined according to the surgical period. Exclusion criteria were TKA revision, associated procedures and inability to walk on a treadmill. Gait analysis was conducted on a treadmill 6 months postoperatively for each patient with a knee assessment device (KneeKG®). Gait characteristics included analysis in three spatial dimensions (flexion-extension, abduction-adduction, internal-external rotation, anterior-posterior translation). Clinical outcomes (Knee Society Score and Forgotten Joint Score) were compared between both groups at 6 months postoperatively.

RESULTS

At 6 months, the gait analysis did not demonstrate any significant difference between CS and PS implants. The range and the maximum anteroposterior translation were similar in both groups (9.2 ± 6.5 mm in CS group vs. 8.1 ± 3 mm in PS group (n.s.); and - 5.2 ± 5 mm in CS group vs. - 6.3 ± 5.9 mm in PS group (n.s.), respectively). The internal/external rotation, the flexion, and the varus angle were similar between CS and PS implants. The KSS Knee score was higher at 6 months in the CS group than in the PS group (92.1 ± 5.6 vs. 84.8 ± 8.9 (p < 0.01)).

CONCLUSION

Cruciate-substituting and posterior-stabilised TKA had similar gait patterns at 6 months postoperatively, despite a non-equivalent posterior stabilisation system. CS prostheses were an interesting option for primary TKA for knee kinematics restoration without requiring a femoral box.

LEVEL OF EVIDENCE

Prospective, case-control study; Level II.

Evolution of body mass index and complications rate in severely or morbidly obese patients undergoing total knee arthroplasty

INTRODUCTION

Associations between obesity and knee osteoarthritis or complications after total knee arthroplasty (TKA) are well established. The procedure can significantly improve knee function, favoring weight loss, despite the risk of surgical complications. The main objective of the present study was to assess change in body mass index (BMI) after TKA in patients with severe or morbid obesity (BMI≥35kg/m2). The secondary endpoint was the rate of surgical revision. The hypotheses were that there is no significant change in BMI after TKA and that there is a significant rate of revision.

METHODS

This retrospective descriptive study was conducted for the period June 2009 to December 2019. Thirty-three patients (48 knees) were included: 27 women, 6 men; mean age, 66.5 years (range, 55-80). Preoperatively, 11 patients had BMI 35-39.9kg/m2 and 22 BMI≥40 (including 11 with BMI≥45kg/m2). The preoperative axis was in varus for 35 patients (73%, including 54%≥10°) and in valgus for 13 (27% including 33%≥10°). Radiological and clinical evaluation was carried out at 3 months and 1 year postoperatively. At≥2 years, change in BMI and EQ5D functional score were established by telephone survey; >5% change in BMI was considered significant.

RESULTS

Mean follow-up was 6.9±2.3 years (range, 2.9-10.5). Twenty-five patients (38 knees) were included for analysis. Mean postoperative BMI was 41±5kg/m2, with a mean decrease of 1.2±3.6kg/m2. At the last follow-up, BMI had increased in 8 patients (32%), including 3 by >5% (12%), and decreased in 16 (64%), including 7 by >5% (28%). The higher the baseline BMI, the greater the decrease: for BMI [35-39.9], -0.81 (range, -6.8; +4.3); for BMI [40-44.5],-1 (range, -9; +5.22); and for BMI>45, -1.54 (range, -3.97; +1.3). EQ5D averaged 0.75 at last follow-up. The higher the preoperative BMI, the more satisfactory the postoperative EQ5D: EQ5D for BMI [35-39.9]=0.71 (range, 0.36; 1); for BMI [40-44.5]=0.75 (range, 0.45; 1); and for BMI>45=0.80 (range, 0.48; 1). Four early surgical site infections (10.5%) and 2 isolated changes of the tibial component for early loosening (5.2%) required surgical revision.

CONCLUSION

Patients with severe or morbid obesity had a low tendency to lose weight after TKA, but this does not appear to us to be clinically relevant: the functional results were good. Nevertheless, this series showed a significant rate of revision (15%). TKA was feasible in patients with BMI≥35kg/m2, but requires appropriate patient information.

LEVEL OF EVIDENCE

IV.

Validation of a novel finite-element model for evaluating patellofemoral forces and stress during squatting after posterior-stabilized total knee arthroplasty

INTRODUCTION

Several studies have documented the relationship between patellofemoral pain and patient dissatisfaction after total knee arthroplasty (TKA). However, few computer simulations have been designed to evaluate the patellofemoral joint during flexion. The aim of this study was to validate a new computational simulation, driven by forces and moments, and to analyze patellofemoral reaction forces and stress under squat loading conditions after TKA implantation.

HYPOTHESIS

This computational simulation of a squat using a model driven by forces and moments is comparable to in vitro and in silico data from the literature.

MATERIAL AND METHODS

We developed a finite element model of the lower limb after implantation of a fixed-bearing posterior-stabilized TKA. To simulate squat loading conditions when standing on both legs, an initial load of 130N was applied to the center of the femoral head. Quadriceps force, patellofemoral contact force and Von Mises stress on the patellar implant, tibiofemoral contact forces and pressure on the tibial insert, and post-cam contact force were evaluated from 0° to 100° of knee flexion.

RESULTS

Quadriceps force increased during flexion, up to 6 times the applied load. Von Mises stress on patellar implant increased up to 16MPa at 100° flexion. Tibiofemoral contact forces increased up to 415 N medially and 339 N laterally, with 64% distributed medially on the tibial insert. Post-cam contact started slightly before 70° of flexion.

DISCUSSION

In this simulation, tibiofemoral, patellofemoral and post-cam contact forces, and pressure distribution on the tibial insert were consistent with various published studies. This agreement suggests that computational simulation driven by forces and moments can reproduce squat loading conditions during knee flexion after TKA, without experimental kinematic data used to drive the simulation.

CONCLUSION

This study represents an initial step towards validating tibiofemoral and patellofemoral mechanical behavior under squat conditions, from this computational simulation driven by forces and moments. This model will help us better understand the influence of various implantation techniques on patellofemoral forces and stress during flexion.

LEVEL OF EVIDENCE

IV, biomechanical computational study.

Does Choice of Patellar Implant in Total Knee Arthroplasty Matter?: A Randomized Comparative Trial of 3 Commonly Used Designs

BACKGROUND

There is currently a lack of evidence to identify the optimal patellar implant design in total knee arthroplasty (TKA). The aim of this study was to assess clinical, intraoperative, radiographic, and scintigraphic differences between inlay (IN), onlay round (OR), and onlay oval (OO) patellar implants.

METHODS

A parallel-group, double-blinded, randomized trial compared IN, OR, and OO patellar implants using the same posterior-stabilized TKA prosthesis for each. Patient outcomes were prospectively followed for a minimum of 2 years, with survivorship outcomes followed for a mean of 5 years. The primary outcome was the between-group differences in the mean Kujala score change from preoperatively to 2 years postoperatively. The secondary outcomes included differences in other knee-specific and general health outcomes, intraoperative characteristics, radiographic parameters, patellar vascularity, and implant survivorship.

RESULTS

A total of 121 participants (40 in the IN group, 41 in OR group, 40 in the OO group) were allocated to 1 of 3 implant designs. At 2 years postoperatively, there were no significant differences in Kujala score changes between groups (p = 0.7; Kruskal-Wallis test). Compared with the IN group, the OR group showed greater improvements in Knee injury and Osteoarthritis Outcome Score (KOOS) Activities of Daily Living and in KOOS Quality of Life compared with the OO group. However, the OO design exhibited better bone coverage and lower lateral facetectomy rates compared with the IN and OR designs. The IN group had more lateral contact compared with the OO group (p = 0.02; Fisher exact test), but the overall value for lateral contact was not significant (p = 0.09; chi-square test). There were no differences in postoperative scintigraphic vascularity (p = 0.8; chi-square test). There was 1 revision for infection at 3 years postoperatively in the OO group, and no revision in the other groups.

CONCLUSIONS

Patellar design did not influence patellofemoral outcomes or survivorship. However, OR implants showed improvements in some secondary patient-reported outcome measures, and OO implants exhibited superior bone coverage and improvements in several intraoperative, radiographic, and scintigraphic outcomes. These findings, combined with superior long-term implant survivorship from previous studies, add support for the use of onlay designs in TKA.

LEVEL OF EVIDENCE

Therapeutic Level I. See Instructions for Authors for a complete description of levels of evidence.