Varus-Valgus Constraint in Primary Total Knee Arthroplasty: A Short-Term Solution but Will It Last?

Long-term results (after a mean 11.3years, and up to 22years, of follow-up) of the Legacy Constrained Condylar Knee (LCCK™) in primary total knee arthroplasty

INTRODUCTION

The use of a sliding prosthesis in total knee arthroplasty (TKA) with increased stress is an intermediate solution in primary surgery, between posteriorly stabilized prostheses and hinged prostheses, in cases of ligamentous laxity and/or loss of bone substance. Favorable results have been reported in the medium term but to our knowledge, this type of prosthesis has not been evaluated in Europe beyond 10 years of follow-up. We therefore conducted a retrospective study in order to carry out: 1) the study of the survival of the Legacy Constrained Condylar Knee (LCCK™) prosthesis in primary surgery, 2) the analysis of complications, functional scores and radiographic data, 3) the analysis of the link between the diaphyseal filling rate and prosthetic loosening.

HYPOTHESIS

The LCCK™ sliding prosthesis with increased constraint has equivalent long-term survival and clinical results to standard posteriorly stabilized TKA and superior to hinged TKA.

MATERIAL AND METHOD

A retrospective series of 141 LCCK™ implanted in 134 patients between 1997 and 2010 was analyzed. Survival was assessed with censoring through an evaluation of partial or total revision of the implants. The functional results were evaluated using the IKS and Oxford 12 scores. Data regarding the Canal Fill Ratio (CFR) and the presence of pathological periprosthetic lines were also collected.

RESULTS

The average follow-up was 11.3±5.3years with a maximum follow-up of 22.7years. Survival at 20years was 90.8% [95% CI: 83.7-95.7]. The rate of early complications was 13.5% (19/141), predominantly comprised of venous thrombosis (6/141), hematomas (3/141 including two requiring surgical drainage), stiffness (3/141) and early infections (3/141). The rate of late complications was 17% (24/141), led by stiffness (4.4%; 6/141), infections (2.9%; 4/141) and hardware failure (2. 2%; 3/141). Ten of the 141 patients (7.1%) had LCCK failure, including 3 (2.1%) for stiffness, 3 (2.1%) for hardware failure, 2 (1.4%) for infection, 1 (0.7%) for laxity and 1 (0.7%) for a periprosthetic fracture. No aseptic loosening was found. The total IKS score went from 65 [0-116] to 143 [79-200] at follow-up, the IKS knee score went from 30 [0-66] to 85 [44-100], and the IKS function score went from 35 [0-70] to 57 [0-100]. The Oxford score went from 14 [2-25] to 34 [15-48] at follow-up. Only two patients (1.4%) presented with a partial periprosthetic line. The tibial CFR was 0.81 and the femoral CFR was 0.76. The influence of the CFR could not be analyzed due to the absence of loosening.

DISCUSSION

The LCCK™ prosthesis in primary surgery has good medium-term survival, a significant improvement in functional scores and a complication rate comparable to posteriorly stabilized prostheses. The complication rate is lower than that of hinged prostheses.

LEVEL OF EVIDENCE

IV; single-center retrospective study.

Knee valgus deformity and lateral bone defects affect the function of superficial medial collateral ligament: A finite element analysis

Purpose

The superficial medial collateral ligament (sMCL) is the primary restraint to valgus laxity of the knee, which is one of the significant indicators of implant selection in valgus knee. Our purpose is to explore the influence of knee valgus deformity and lateral bone defects in the function of sMCL.

Methods

the right knee joint of a healthy male volunteer was subjected to CT and MRI scans. The scanned data were imported into Mimics, Geomagic, Solidworks and Ansys software to establish a three-dimensional finite element model of the human knee joint. Femorotibial angle (FTA)5°,10°,15°,20°,25°,30°,35° and lateral bone defect 0,0.5,1,1.5,2 cm are controlled in Solidworks. Tensile test in vitro of maximum load on sMCL was simulated in Ansys.

Results

The peak stress of sMCL is raising with valgus deformity while there is no lateral defect. Increasing lateral bone defect can lessen the augmentation of the stress of sMCL caused by the valgus deformity. The peak stress of sMCL when it is in maximum load is 35.252 MPa. While valgus 35°, the peak stress of sMCL exceeds the value, with or without bone defect; the same is true for the valgus 30° with 0, 0.5, 1 cm bone defect and valgus 25° without defect.

Conclusion

Our findings allow for preoperative evaluation of sMCL function in the valgus knee, which would play an instructive role to some extent for implant selection in total knee arthroplasty.

Constraint in complex primary total knee arthroplasty: rotating hinge versus condylar constrained implants

INTRODUCTION

Condylar constrained knee arthroplasties (CCKAs) and rotating hinge knee arthroplasties (RHKAs) achieved good outcomes in complex primary total knee arthroplasties (TKAs); however, long-term comparative studies are few. Using an arthroplasty registry, we sought to assess and compare in CCKAs and RHKAs: (1) the intra-operative rates of complications, (2) the survival rates, (3) the reasons for revision, and (4) the adjusted hazard ratios for failure.

MATERIALS AND METHODS

1432 constrained implants in primary TKAs performed for non-oncological indications were included: 703 RHKAs, 729 CCKAs. The two groups were comparable regarding age and gender. Kaplan-Meier curves were used to compare survival rates, multivariate analyses to assess the hazard ratios for failures.

RESULTS

The mean follow-up was 4.1 years (range 0-16.3) for CCKAs and 6.8 years (0-18.1) for RHKAs. The intra/peri-operative complications were similar in both the cohorts, with similar rates of femoral and tibial fractures. 10-year implant survival rates were similar in both the cohorts (91.9%, CI 95% 89.2-93.9% in RHKAs; 93.4%, CI 95% 90.3-95.6% in CCKAs). Periprosthetic infection was the most common reason for revision in the two cohorts, followed by aseptic loosening. Breakage occurred in 3 RHKAs (0.4%). CCKAs and RHKAs had a similar distribution of revision causes. Males aged less than 60 had significantly more failures, regardless the constraint degree. Unstemmed CCKAs significantly failed more than RHKAs and stemmed CCKAs.

CONCLUSIONS

Both modern CCKAs and RHKAs are viable long-term solutions in complex primary TKAs. More failures should be expected in males aged less than 60.

LEVEL OF EVIDENCE

IV, Therapeutic study.

Kinematic Alignment in Total Knee Arthroplasty Reduces Polyethylene Contact Pressure by Increasing the Contact Area, When Compared to Mechanical Alignment—A Finite Element Analysis

Unrestricted Kinematic alignment (KA) in total knee arthroplasty (TKA) replicates the joint line of each patient by adjusting the cuts based on the anatomy of the patient. Mechanical alignment (MA) aims to restore a neutral mechanical axis of the leg, irrespective of the joint line orientation. The purpose of the present study was to compare contact pressure and contact areas of the polyethylene (PE) bearing surface as well as von Mises stress of the PE-tibial tray interface for MA and KA in the same patient, using CT data and finite element analysis. Finite element models were created from lower leg CT scans of 10 patients with knee osteoarthritis with different phenotypes. Mechanical PE properties were experimentally determined by tensile tests on dumbbell specimens. For numerical simulation purposes an adjusted non-linear material model with the maximum load to failure of 30.5 MPa, was calibrated and utilized. Contact pressure points were the deepest parts of the polyethylene inlay. Contact pressures were either very similar or were increased for MA knees throughout the gait cycle. KA either increased or had a comparable contact area, compared to MA. KA and MA produced comparable von Mises stresses, although both alignments breached the failure point of 30.5 MPa in all 3 valgus knees. This might indicate a higher probability of failure at the inlay-tibial baseplate interface. By maintaining the joint line orientation, KA reduces or has comparable contact pressures on the PE bearing surface by increasing or maintaining the contact area throughout one gait cycle in a validated finite element analysis model in 10 different knee phenotypes. The von Mises stress on the PE-tibial component interface was comparable, except for the valgus knees, where the load to failure was achieved in both alignment strategies and slightly higher stresses were observed for KA. Further studies for different knee phenotypes are needed to better understand the pressure changes depending on the alignment strategy applied.

Fixed-bearing posterior-stabilized implant versus constrained condylar knee in one-stage bilateral primary arthroplasty of the varus knee: A randomized controlled trial with minimum 2-year follow-up

Background:

Severe varus deformity of the knee poses a technical challenge in balancing the flexion–extension gaps. The use of a varus–valgus constrained prosthesis is a solution to achieve coronal plane stability. The results of constrained condylar knee (CCK) implants in primary total knee arthroplasty are not well known. This study aims to compare the functional outcomes of posterior-stabilized (PS) and CCK implants for primary arthroplasty of the varus knee.

Materials and Methods:

Twenty patients with bilateral severe osteoarthritis and genu varum of more than 10° were enrolled in this study. One knee was randomly implanted with a fixed-bearing PS implant, whereas the other was implanted with a CCK prosthesis. Pre- and postoperative Knee Society Score (KSS) and Oxford Knee Score (OKS) questionnaires were completed, and knee flexion was measured and compared.

Results:

The patients were followed for 32 months on average (24–36 months). On the KSS and OKS, both the groups improved significantly, but the difference between them was not statistically significant. Postoperative knee flexion was also not different between the two groups. Furthermore, 18 patients could not distinguish the difference between the two prostheses, whereas two patients preferred the PS one.

Conclusion:

We demonstrated that a PS prosthesis can achieve comparable functional results to the CCK one in the short term.

Good to excellent long-term survival of a single-design condylar constrained knee arthroplasty for primary and revision surgery

PURPOSE

The purpose of the study was to determine the long-term survivorship, functional outcomes of a single-design condylar constrained (CCK) TKA in primary and revision cases as well as to assess specific risk factors for failure. It was hypothesized that primary CCK TKA had a better survival than revision knees.

METHODS

One hundred and forty three patients who underwent revision TKA (n = 119) or complex primary TKA (n = 24) using a single-design condylar constrained knee system (Genesis CCK, Smith & Nephew) performed at a single institution between 1999 and 2008 were retrospectively included. The median follow-up amounted to 11.8 years (IQR 10.3-14.4). Implant survivorship was analyzed using Kaplan-Meier survival estimates and multivariate Cox regression analysis to identify risk factors for failure. Function was determined using the Oxford Knee Score (OKS).

RESULTS

The implant survival was 86.4% after five, 85.5% after ten and 79.8% at 15 years. A reduced implant survivorship was found in males (HR 5.16, p = 0.001), smokers (HR 6.53, p = 0.004) and in obese patients (HR 2.26, p = 0.095). Patients who underwent primary TKA had a higher revision-free implant survivorship compared to revision TKA at 15 years (100% vs. 76%, p = 0.036). The main cause for re-revision was infection in 10% of all revision TKA performed with the CCK design included, while no case was revised for instability. The median OKS was 39 (IQR 35-44) in 102 patients available for long-term functional outcome.

CONCLUSION

CCK implants are associated with excellent long-term survival when used in primary TKA; however, survival was worse when used during revision TKA. Males, smokers, obese patients and are at higher risk for revision. While instability and aseptic loosening were rare, infection remains a major concern.

LEVEL OF EVIDENCE

Level IV, retrospective observational study.

Varus-valgus constrained insert with posterior-stabilized femoral components in complex primary total knee arthroplasties

Aims

Varus-valgus constrained (VVC) devices are typically used in revision settings, often with stems to mitigate the risk of aseptic loosening. However, in at least one system, the VVC insert is compatible with the primary posterior-stabilized (PS) femoral component, which may be an option in complex primary situations. We sought to determine the implant survivorship, radiological and clinical outcomes, and complications when this VVC insert was coupled with a PS femur without stems in complex primary total knee arthroplasties (TKAs).

Methods

Through our institution’s total joint registry, we identified 113 primary TKAs (103 patients) performed between 2007 and 2017 in which a VVC insert was coupled with a standard cemented PS femur without stems. Mean age was 68 years (SD 10), mean BMI was 32 kg/m² (SD 7), and 59 patients (50%) were male. Mean follow-up was four years (2 to 10).

Results

The five-year survivorship free from aseptic loosening was 100%. The five-year survivorship free from any revision was 99%, with the only revision performed for infection. The five-year survivorship free from reoperation was 93%. The most common reoperation was treatment for infection (n = 4; 4%), followed by manipulation under anaesthesia (MUA; n = 2; 2%). Survivorship free from any complication at five years was 90%, with superficial wound infection as the most frequent (n = 4; 4%). At most recent follow-up, two TKAs had non-progressive radiolucent lines about both the tibial and femoral components. Knee Society Scores improved from 53 preoperatively to 88 at latest follow-up (p < 0.001).

Conclusion

For complex primary TKA in occasional situations, coupling a VVC insert with a standard PS femur without stems proved reliable and durable at five years. Longer-term follow-up is required before recommending this technique more broadly.

Cite this article: Bone Jt Open 2021;2(11):921–925.

Mid-Term Clinical Outcomes and Survivorship of a Second-Generation Modular Revision Knee System

INTRODUCTION

Revision knee systems have adapted to the challenges of revision knee arthroplasty with offset stems, augments, cones, and various levels of constraint. The purpose of this study is to review the mid-term outcomes of a second-generation modular knee revision system.

MATERIALS AND METHODS

A retrospective review was conducted from 2011 through 2014 on all patients who underwent knee arthroplasty with the Vanguard® 360 revision knee system (Zimmer Biomet, Warsaw, Indiana). Patients were included in the study if they were eligible for five-year minimum follow up and had signed a general research consent. The initial query revealed 253 patients (267 knees) that met inclusion criteria. Complications assessed were manipulation under anesthesia (MUA) and revision of any component. Statistical analysis using paired t-test was performed to evaluate changes in clinical outcomes and Kaplan-Meier survival analysis.

RESULTS

Mean follow up was 6.6 years. The Vanguard® 360 knee system was used in four (1.5%) primary total knee arthroplasties (TKAs), 66 (24.7%) second-stage reimplantation TKAs after infection, and 197 (73.8%) aseptic revisions. There were significant improvements in knee range of motion and Knee Society Scores (all p<0.05). Manipulations under anesthesia were performed in 17 knees (6.4%). A total of 41 knees (15.4%) failed for any cause and required re-revision surgery. Of these, 11 (4.1%) failed due to aseptic loosening. Kaplan-Meier analysis revealed overall survival to endpoint of aseptic loosening to be 96.4% (95% CI: ±1.2%) at five years and 95.2% (95% CI: ±1.4%) at 9.5 years. When comparing survivorship in patients who underwent initial revision for aseptic indications compared with those whose underwent revision for second-stage reimplantation after infection, Kaplan-Meier survival to endpoint of revision for any cause at 9.5 years was higher for patients with aseptic than septic indication for TKA (87.0% [95% CI: ±2.4%] vs. 75.3% [95% CI: ±5.4%], p=0.0156).

CONCLUSION

The findings of this study demonstrate greater than 95% aseptic survivorship with the use of the Vanguard® revision knee system at mid-term follow up.

Concurrent Surgical Management of Advanced Osteoarthritis of the Knee and Proximal Tibiofibular Joint With Compressive Peroneal Neuropathy: 3-Year Follow-Up On a Complex Case

The proximal tibiofibular joint (PTFJ) is susceptible to osteoarthritis (OA), making it a rare but potential source of lateral knee pain. Because PTFJ OA is a rare presentation of knee pain, no first-line treatment has been established and it can be missed in evaluation before total knee arthroplasty. We report an unusual case of a 59-year-old man who presented with advanced OA of both the knee and PTFJ, along with a progressive peroneal nerve palsy due to a large compressive ganglion cyst from the PTFJ. He was treated with concurrent total knee arthroplasty, peroneal nerve decompression, and resection of the fibular head and ganglion cyst, resulting in full recovery from his arthritic pain and resolution of his peroneal neuropathy. He remains free of symptoms without instability 3 years from the index surgery.

Satisfactory mid-term outcomes of condylar-constrained knee implants in primary total knee arthroplasty: clinical and radiological follow-up

Background

The purpose of this study was to evaluate (1) the reoperation rates and survivorship for septic and aseptic causes, (2) radiographic outcomes, and (3) clinical outcomes of condylar-constrained knee (CCK) implants used in primary total knee arthroplasty (TKA) with severe coronal deformity and/or intraoperative instability.

Materials and methods

A consecutive series of CCK implants in primary TKA was retrospectively evaluated in patients with severe coronal deformities. Forty-nine patients (54 knees) were included with a mean follow-up of 9 years (range 6–12). All patients were treated with a single-design, second-generation CCK implant. The primary diagnosis was osteoarthritis in 36 knees, post-traumatic arthritis in 7 knees, and rheumatoid arthritis in 4 knees. Preoperatively, standing femorotibial alignment was varus in 22 knees and valgus in 20 knees.

Results

At a mean follow-up of 9 years, overall survivorship was 93.6%. Two knees (4.3%) required revision for periprosthetic joint infection. One knee (2.1%) required subsequent arthroscopy due to patellar clunk syndrome. At final follow-up, no evidence of loosening or migration of any implant was reported, and the mean Knee Society knee scores improved from 43 to 86 points (p < 0.001). The mean Knee Society function scores improved to 59 points (p < 0.001). The average flexion contracture improved from 7° preoperatively to 2° postoperatively and the average flexion from 98° to 110°. No knees reported varus–valgus instability in flexion or extension.

Conclusion

CCK implants in primary TKA with major coronal deformities and/or intraoperative instability provide good midterm survivorship, comparable with less constrained implants. In specific cases, CCK implants can be considered a viable option with good clinical and radiographic outcomes. However, a higher degree of constraint should be used cautiously, leaving the first choice to less constrained implants.

Level of evidence Therapeutic study, level IV.