Partially loaded plain radiographic measurement to evaluate rotational alignment in total knee arthroplasty

Femur rotational alignment in total knee arthroplasty: Delphi consensus statements from European knee society (EKS)

Proper rotational alignment of the femur components represents one of the key factors for the functional outcome of patients after total knee arthroplasty (TKA). Recent 3-D imaging data have shown a wide variability of the distal femur bony anatomy in the axial plane. The identification and intraoperative correction of these bony torsional deformities remain controversial. During the last decades various bony landmarks and surgical techniques have been proposed for proper femur rotational alignment but there is no consensus or evidence which method will be the best.This study employs a Delphi consensus methodology among European Knee Society (EKS) experts to address key questions regarding femur rotational alignment in TKA. Through a systematic literature review and expert discussions, a strong consensus was achieved on three main points: (1) Proper femoral rotational alignment must establish a balanced flexion gap and ensure proper patella tracking through the 3-D positioning of the trochlear groove. There is no consensus or evidence indicating whether the transepicondylar or trans-cylindric axis is the best compromise for the TKA flexion/extension axis. (2) For the three main techniques (measured resection, balanced flexion gap and combined/hybrid) and the new personalized alignment philosophies, no agreement on the best femoral rotational alignment exist. (3) Computer-Assisted Surgery (CAS) techniques using 3-D imaging preoperatively can help to identify the key rotational bony landmarks. Until now CAS has not delivered conclusive data to link these pre- and intraoperative findings to the clinical outcome to allow any recommendation for proper rotational alignment of the femur.This Delphi consensus statement summarizes the controversies, current practices, and evidence on the three key questions regarding proper femoral rotational alignment. There is a need for further high-level studies to identify the correct individual femoral rotational alignment to achieve better TKA outcomes.

Third-generation posterior-stabilised cemented system for total knee arthroplasty: Survivorship and outcomes after 20-year follow-up

Purpose

Total knee arthroplasty is a common procedure due to increased life expectancy and ageing populations, necessitating implants with long-term efficacy. After some initial designs, the third-generation modular posterior-stabilised NexGen® prosthesis aimed to enhance kinematics and reduce complications. This study evaluates the long-term outcomes, survivorship, revision rates and complications of this implant. With promising results observed up to 15 years in previous studies, this investigation aims to assess the implant's performance over extended follow-up periods, aiding in optimal implant selection for improved patient outcomes.

Methods

We carried out a retrospective study on 263 total knee arthroplasties performed in our centre between 1998 and 2002. Statistical analysis of complications was performed and study of survival using the Kaplan-Meier method and competing risk analysis were calculated. Description of reinterventions and complications were also included.

Results

Results show a 20-year prosthesis survival rate of 90.8% for revision due to any reason, with an estimated survival of 92.3% considering competitive events. Estimated survivorship at 20 years is 98% for aseptic loosening as the end point, and an estimation of 98.80% considering competitive events. Twenty revisions were performed, with 10 cases due to infection and 10 for noninfectious reasons and three of them due to aseptic loosening. Radiographic analysis revealed radiolucent lines, but no clinical evidence of loosening was observed in these cases.

Conclusion

This study offers survivorship data from longer follow-up periods, what is difficult to find in the reported literature and showed excellent results of this implant in terms of survivorship and low rates of revision in our cohort.

Level of Evidence

Level IV.

Three-dimensional color map: a novel tool to locate the surgical transepicondylar axis

Background

Accurate localization of the surgical transepicondylar axis (sTEA) in total knee arthroplasty (TKA), the most reliable anatomical reference for femoral rotation, has long been a challenge, primarily because it is intractable to locate the center of the sulcus of the medial epicondyle. This study aimed to introduce and verify a novel method to locate the sTEA more precisely.

Methods

This study included 26 adult femoral specimens and 80 adult patients with computed tomography (CT) scan data. Three dimensions (3D) models based on CT scans of the distal femurs were reconstructed with Mimics and imported into Geomagic Studio. The 3D color map method was applied to locate the sTEA. To further verify the accuracy of the method, the identified sTEA was transferred to the femoral specimens and compared with the points identified by the total station machine. We further compared the recognition rate of sTEA between 3D color map method and two-dimensional (2D) CT slices method. The repeatability of this novel method was also evaluated.

Results

The 3D color map method located the centers of the sulcus of the medial epicondyle and the most prominent point of the lateral epicondyle of all the femoral specimens, which were further identified and confirmed by patient-specific guide plates and total station machine on femoral specimens. The 3D color map method achieved a recognition rate of up to 96.23%, while the recognition rate of the 2D CT slices method was only 68.87%. The repeatability of this objective method was excellent.

Conclusions

The results of this study indicated that the 3D color map method could be used to accurately and objectively locate the sTEA, with high repeatability and recognition rate. However, the proposed novel method requires further validation in clinical applications.

Methods of intra- and post-operative determination of the position of the tibial component during total knee replacement

AIM OF THE STUDY

To identify the most reliable anatomical landmarks and imaging techniques for assessing the rotation of the tibial component in total knee arthroplasty (TKA).

METHODS

An extensive literature review (from January 2016 to March 2019) was performed. We included studies about primary TKA with details concerning the anatomical landmarks used for implanting the tibial component and also imaging studies assessing tibial component rotation. The final selection comprises only thirty-five articles consistent with the inclusion criteria.

RESULTS

Extra-articular landmarks are not always reliable (even though the tibial tubercle is one of the most popular extra-articular landmarks used to assess the rotation of the tibial component), mainly because they vary and can lead to malrotation of the tibial component. Akagi's line (an intra-articular landmark) is considered to be the most reliable and easy to find during surgery and likewise is not affected by articular deformities. The anterior tibial cortex (intra-articular landmark) also proved to be accurate and reliable with the main advantage being that is palpable after tibial resection. Radiography provides a good and inexpensive option for imaging, but it is insufficient. Magnetic resonance imaging (MRI) is used in some cases but not routinely for assessing TKA components or their orientation. Computed tomography (CT), used together with a well-defined protocol (Berger's method being the preferred choice), remains the "gold standard" for evaluating the rotation of the tibial component after TKA.

CONCLUSION

Currently, the most accurate and reliable anatomical landmarks are represented by Akagi's line and the anterior cortex of the tibia. Post-operatively, through CT and well-established protocols, the rotation of the tibial component can be accurately determined.

Three dimensional gait analysis in patients with symptomatic component mal-rotation after total knee arthroplasty

PURPOSE

Purpose of the present cohort study was the determination of lower body function and rotation in patients with symptomatic component mal-rotation after total knee arthroplasty using instrumented 3D gait analysis.

METHODS

A consecutive series of 12 patients (61.3 years ± 11.4 years) were included suffering under remaining pain or limited range of motion at least six months after total knee arthroplasty. A CT-scan according to the protocol of Berger et al. and instrumented 3D gait analysis were carried out including clinical examination, videotaping, and kinematic analysis using a Plug-in Gait model. Outcome variables were temporospatial parameters as well as kinematics in sagittal and transversal plane. Data for reference group were collected retrospectively and matched by age and gender.

RESULTS

Temporospatial parameters of the study group showed decreased velocity, cadence, and step length as well as increased step time. Single limb support was reduced for the affected limb. In sagittal plane, maximum knee flexion during swing phase was reduced for the replaced knee joint. In transverse plane, there was hardly any difference between affected and non-affected limb. Compared to the reference group, both limbs show significant increased internal ankle rotation and external hip rotation. There were significant strong linear correlations between ankle rotation and hip rotation as well as ankle rotation and radiological tibial mal-rotation.

CONCLUSIONS

Patients with symptomatic component mal-rotation after total knee arthroplasty showed typically functional deficits. The affected and non-affected limb showed significant increased internal ankle rotation and external hip rotation, while only the affected, replaced knee showed reduced internal knee rotation. Identification of rotational abnormalities of hip and ankle joints seems to be mandatory in TKA to identify the patient group with external hip rotation, internal ankle rotation, and an elevated risk for symptomatic rotational TKA component mal-alignment.

Long-term follow-up of a non-randomised prospective cohort of one hundred and ninety two total knee arthroplasties using the NexGen implant

PURPOSE

The purpose of this study was to retrospectively analyse the clinical, functional and radiological outcomes, and the long-term survivorship of the NexGen Legacy Posterior Stabilised (LPS) knee prosthesis (Zimmer Biomet, Warsaw, IN, USA).

METHODS

Between 1996 and 2001, 197 primary NexGen LPS total knee arthroplasties (TKAs) were implanted by a single surgeon; 132 prostheses in 124 patients with a minimum follow-up of 15 years were included in the study. Surgical procedure and post-operative care were the same for all patients. All patients were assessed through the International Knee Society (IKS) scores and range of motion (ROM). A complete radiological study was performed for all patients. Failure was defined as revision of at least one prosthetic component for any cause.

RESULTS

IKS knee and function scores, as well as ROM and leg alignment, significantly improved at the latest follow-up (p ≤ 0.05). No significant differences were found between fixed- and mobile-bearing groups. Seven implant failures were reported; the implant survival rate (overall) was 94.7% at the latest follow-up.

CONCLUSIONS

This study showed optimal survivorship of the NexGen LPS, associated with a significant improvement in overall outcomes at a minimum follow-up of 15 years.

Presence of rotational errors in long leg radiographs after total knee arthroplasty and impact on measured lower limb and component alignment

PURPOSE

Rotation of the lower limb in weight bearing long leg radiographs has a great impact on measured component and lower limb alignment parameters. We asked which rotational errors of long leg radiographs are present in a high volume centre and which radiological and clinical consequences arise regarding measured coronal component and lower limb alignment after total knee arthroplasty.

METHODS

In 100 long leg radiographs coronal femoral and tibial component alignment and hip knee ankle angle (HKA) were measured. Present rotational errors in long leg radiographs were determined by fibular overlap and its impact on alignment parameters calculated.

RESULTS

A mean internal rotation of 8.1° (9.3 SD) with a range between 36° of internal and 16° of external rotation was found in long leg radiographs. This resulted in mean differences between measurements before and after rotational correction regarding femoral and tibial component alignment and HKA of 0.6-0.8° (range 3.5° valgus and 1.6° varus error). Clinically, 11 out of 100 patients were wrongly assigned to either mal- or well-alignment (neutral mechanical alignment within ±3° varus or valgus).

CONCLUSION

Surgeons should be aware of potential rotational errors in long leg radiographs after total knee arthroplasty resulting in wrong measurements. In case of rotational errors, radiographs should be repeated or rotational corrections calculated. For study purposes only radiographs after rotational correction should be accepted.