Anthropometric measurements of the femur change with component positioning in total knee arthroplasty

Improved Knee Function with Customized vs. Off-the-Shelf TKA Implants-Results of a Single-Surgeon, Single-Center, Single-Blinded Study

BACKGROUND

Recent studies have been able to show certain benefits of Customized, Individually Made (CIM) compared to Off-the-Shelf (OTS) total knee arthroplasties (TKAs), but evidence is still lacking regarding the benefits of these implant systems. This study aimed to find differences in scores and functional outcome by comparing CIM and OTS implants, using Patient-Reported Outcome Measures (PROMs) and functional tests for activities of daily living in a single-surgeon setup.

METHODS

A total of 48 patients (16 CIM vs. 32 OTS) were consecutively enrolled and blindly examined. Functional testing was performed using four timed functional tests (TUG, WALK, TUDS, and BBS) and the VAS for pain. The Aggregated Locomotor Function (ALF) score was then calculated based on the addition of the average times of the three functional tests.

RESULTS

The CIM group showed significantly faster times in all functional tests and significantly better ALF scores. There were remarkable differences in the assessment of maximum pain sensation between the two groups, with superiority in the CIM group. The PROMs analysis revealed a higher proportion of excellent and good ratings for the items objective and function (KSS) in the CIM group.

CONCLUSION

The study showed that time-limited activities of daily living (ADLs) can be completed significantly faster with a CIM prosthesis and that a significantly higher percentage in this group reports freedom from pain during certain loads. Partial aspects of the PROM scores are also better in this group; however, this superiority could not be shown with regard to most PROM scores collected in this study.

Periprosthetic fractures after medial unicompartmental knee arthroplasty: a narrative review

INTRODUCTION

On rare occasions, fractures of the tibial plateau may occur after uni-compartmental knee arthroplasty (UKA) and account for 2% of total UKA failures. The purpose of this narrative review is to identify and discuss potential risk factors that might lead to prevention of this invalidating complication.

MATERIALS AND METHODS

Electronic database of Pubmed, Scopus, Cochrane and Google Scholar were searched. A total of 457 articles related to the topic were found. Of those, 86 references were included in this narrative review.

RESULTS

UKA implantation acts as a stress riser in the medial compartment. To avoid fractures, surgeons need to balance load and bone stock. Post-operative lower limb alignment, implant positioning, level of resection and sizing of the tibial tray have a strong influence on load distribution of the tibial bone. Pain on weight-bearing signals bone-load imbalance and acts as an indicator of bone remodeling and should be a trigger for unloading. The first three months after surgery are critical because of transient post-operative osteoporosis and local biomechanical changes. Acquired osteoporosis is a growing concern in the arthroplasty population. Split fractures require internal fixation, while subsidence fractures differ in their management depending of the amount of bone impaction. Loose implants require revision knee arthroplasty.

CONCLUSION

Peri-prosthetic fracture is a rare, but troublesome event, which can lead to implant failure and revision surgery. Better knowledge of the multifactorial risk factors in association with a thorough surgical technique is key for prevention.

Sexual dimorphism and racial diversity render bone-implant mismatch inevitable after off-the-shelf total knee arthroplasty: a systematic review and meta-analysis

PURPOSE

The purpose of this systematic review and meta-analysis was to investigate the variability in femoral geometric ratios among knees of different sexes and races, and to appreciate whether the observed variability is accommodated by commonly implanted total knee arthroplasty (TKA) components. The hypothesis was that the anthropometric studies report considerable variability of femoral geometric ratios among sexes and races.

METHODS

This systematic review and meta-analysis was performed according to the Preferred Reporting Items for Systematic reviews and Meta-analyses (PRISMA) criteria. Two authors independently conducted an electronic search using MEDLINE^® and Embase^® on 6 July 2020 for clinical studies reporting on femoral geometric ratios among sexes and races. Femoral geometric ratios were graphically represented as means and 2 standard deviations, and compared to those of 13 commonly implanted femoral components.

RESULTS

A total of 15 studies were identified that reported on a combined total of 2627 knees; all reported the aspect ratio, and 2 also reported the asymmetry ratio and trapezoidicity ratio. Men had wider knees than women, and compared to Caucasian knees, Arabian and Indian knees were wider, while East Asian were narrower. There were no differences in asymmetry ratio between men and women, nor among Caucasian and East Asian knees. Men had more trapezoidal knees than women, and East Asian knees were more trapezoidal than Caucasian knees. The commonly implanted femoral components accommodated less than a quarter of the geometric variability observed among sexes and races.

CONCLUSION

Anthropometric studies reported considerable sexual dimorphism and racial diversity of femoral geometric ratios. Since a surgeon generally only uses one or a few TKA brands, bone-implant mismatch remains unavoidable in a large proportion of knees. These findings support the drive towards personalized medicine, and accurate bone-implant fit may only be achievable through customisation of implants, though the clinical benefits of custom TKA remain to be confirmed.

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.

Popliteus impingement after TKA may occur with well-sized prostheses

PURPOSE

To determine the mechanisms and extents of popliteus impingements before and after TKA and to investigate the influence of implant sizing. The hypotheses were that (1) popliteus impingements after TKA may occur at both the tibia and the femur, and (2) even with an apparently well-sized prosthesis, popliteal tracking during knee flexion is modified compared to the preoperative situation.

METHODS

The location of the popliteus in three cadaver knees was measured using computed tomography, before and after implantation of plastic TKA replicas, by injecting the tendon with radiopaque liquid. The pre- and post-operative positions of the popliteus were compared from full extension to deep flexion using normosized, oversized, and undersized implants (one size increments).

RESULTS

At the tibia, TKA caused the popliteus to translate posteriorly, mostly in full extension: 4.1 ± 2 mm for normosized implants, and 15.8 ± 3 mm with oversized implants, but no translations were observed when using undersized implants. At the femur, TKA caused the popliteus to translate laterally at deeper flexion angles, peaking between 80° and 120°: 2 ± 0.4 mm for normosized implants and 2.6 ± 0.5 mm with oversized implants. Three-dimensional analysis revealed prosthetic overhang at the posterosuperior corner of normosized and oversized femoral components (respectively, up to 2.9 mm and 6.6 mm).

CONCLUSIONS

A well-sized tibial component modifies popliteal tracking, while an undersized tibial component maintains more physiologic patterns. Oversizing shifts the popliteus considerably throughout the full arc of motion. This study suggests that both femoro- and tibio-popliteus impingements could play a role in residual pain and stiffness after TKA.