[Medial unicondylar knee replacement]. Orthopade. 2014;43:875-876, 878-882. [PMID: 25227530 DOI: 10.1007/s00132-014-3012-9]

Concentration-Dependent Effects of Cobalt and Chromium Ions on Osteoarthritic Chondrocytes

OBJECTIVE

Cobalt and chromium (CoCr) ions from metal implants are released into the joint due to biotribocorrosion, inducing apoptosis and altering gene expression in various cell types. Here, we asked whether CoCr ions concentration-dependently changed viability, transcriptional activity, and inflammatory response in human articular chondrocytes.

DESIGN

Human articular chondrocytes were exposed to Co (1.02-16.33 ppm) and Cr (0.42-6.66 ppm) ions and cell viability and early/late apoptosis (annexin V and 7-AAD) were assessed in 2-dimensional cell cultures using the XTT assay and flow cytometry, respectively. Changes in chondrocyte morphology were assessed using transmitted light microscopy. The effects of CoCr ions on transcriptional activity of chondrocytes were evaluated by quantitative polymerase chain reaction (qPCR). The inflammatory responses were determined by measuring the levels of released pro-inflammatory cytokines (interleukin-1β [IL-1β], IL-6, IL-8, and tumor necrosis factor-α [TNF-α]).

RESULTS

CoCr ions concentration-dependently reduced metabolic activity and induced early and late apoptosis after 24 hours in culture. After 72 hours, the majority of chondrocytes (>90%) were apoptotic at the highest concentrations of CoCr ions (16.33/6/66 ppm). SOX9 expression was concentration-dependently enhanced, whereas expression of COL2A1 linearly decreased after 24 hours. IL-8 release was enhanced proportionally to CoCr ions levels, whereas IL-1β, IL-6, and TNF-α levels were not affected by the treatments.

CONCLUSIONS

CoCr ions showed concentration- and time-dependent effects on articular chondrocytes. Fractions of apoptotic articular chondrocytes were proportional to CoCr ion concentrations. In addition, metabolic activity and expression of chondrocyte-specific genes were decreased by CoCr ions. Furthermore, exposure to CoCr ions caused a release of pro-inflammatory cytokines.

The learning curve of patient-specific unikondylar arthroplasty may be advantageous to off-the-shelf implants: A preliminary study

Introduction

Introducing a new arthroplasty system into clinical routine is challenging and could have an effect on early results. Since UKA are known to have failure mechanisms related to technical factors, reliable results and easy adoption are ideal. The question remains whether there are differences in objective procedure parameters in the early learning curve of different UKA systems.

Methods

two different UKA implants (Biomet Oxford[BO] followed by Conformis iuni[CI]) were introduced consecutively into clinical routine. We retrospectively analyzed the first 20 cases of each implant for one arthroplasty surgeon regarding operating time, correction of the mechanical axis, learning curve parameters, and revision rate of implants for 1.5 years postoperatively.

Results

Operating time (BO:98.3 ± 26.3min, CI:83.85 ± 21.8min (p < 0.078)), and tourniquet time differed in favor of the CI implant (BO:97.5 ± 29.5min; CI:73.5 ± 33.2 min; p < 0.017)). Mechanical alignment was restored in boths (preop:BO:mean 2.9°varus, CI:2.7°varus, postop:BOmean1.3°varus, CI:1°varus), while one BO patient and two CI patients were overcorrected. Operating time decreased from the first five implants to implants 16-20 for CI (95.2 ± 18.5min to 69 ± 21.5min, p < 0.076) and BO (130.6 ± 27.6min to 78 ± 17.3min, p < 0.009). Within 18 months of follow-up, 2 BO and 1 CI implants were revised.

Conclusion

The introduction of an UKA implant was associated with longer surgery in both implants. Procedure time seems to differ between implants, while a learning curve was observed regarding instrumentation. CI implants seem to be reliable and adaptable in a medium-volume practice. The early results of this retrospective single-surgeon study were in favor of the individualized implant. Certainly, further studies encompassing larger cohorts with various implants are needed.

Arthroscopy combined with unicondylar knee arthroplasty for treatment of isolated unicompartmental knee arthritis: A long-term comparison

BACKGROUND

Knee osteoarthritis is the most prevalent form of osteoarthritis and is becoming the main reason for progressive pain in knee joints. Arthroscopy combined with unicondylar knee arthroplasty (UKA) is one of the effective methods for the treatment of severe unicompartmental knee arthritis. This surgical approach gives us the capacity to explore all the articular cavities and plays a vital role in UKA patient selection. However, some scholars think that the surgical procedure is traumatic and may increase the rate of surgical infection, and its clinical efficacy needs further study.

AIM

To compare the clinical effect of arthroscopy combined with UKA and UKA alone for patients suffering from unicompartmental osteoarthritis (OA).

METHODS

A retrospective study was conducted on patients who were diagnosed with unicompartmental OA (Kellgren–Laurence grade ≥ III) and underwent UKA between October 2012 and November 2006. The patients were followed at 3, 6, and 12 mo and every 2 years thereafter. During each follow-up, the radiographic materials, the range of motion of knee and hospital for special surgery (HSS) score, knee society score and knee function score as recorded, and the modes and time of failure and revision details were collected as well.

RESULTS

Data on 104 patients (118 knees), including 54 patients (60 knees) in the arthroscopy combined with UKA group (group A) and 51 (58 knees) in UKA alone group (group B) were collected during an average follow-up duration of 7.25 years, excluding the cases who were lost to follow-up. At the final follow-up, 3 (5.0%) of 60 knees in group A compared with 4 (6.9%) of 58 knees in group B failed and converted to total knee arthroplasty, with no statistically significant difference between the two groups (P = 0.933). The percentage of patients receiving blood transfusion was 40% in group A, significantly lower than that in group B (67.2%; P = 0.003). Total volume of blood transfusion in group A was also significantly lower than that of group B (P = 0.001). Both groups improved significantly after operation in clinical symptoms and functions. HSS score, knee society score, and knee function score increased significantly at the latest follow-up compared to pre-operation in group A, from 59.6 ± 10.9 to 82.7 ± 9.3 (mean difference [MD], 23.2; 95%CI: 19.3-27.0; P = 0.000), 47.3 ± 6.3 to 76.2 ± 13.1 (MD, 28.9; 95%CI: 25.1-32.7; P = 0.000), and 57.5 ± 6.3 to 75.1 ± 19.6 (MD, 17.5; 95% CI: 12.1-23.0; P = 0.000); and in group B, from 59.3 ± 15.6 to 84.3 ± 10.1 (MD, 23.7; 95%CI: 18.9-28.5; P = 0.000), 49.1 ± 9.2 to 75.1 ± 13.2 (MD, 24.7; 95%CI: 19.9-29.5; P = 0.000), and 59.3 ± 9.0 to 77.4 ± 13.8 (MD, 17.2; 95%CI: 12.8-21.6; P = 0.000).

CONCLUSION

Arthroscopy combined with UKA and UKA alone both provide benefits in clinical symptom improvement and alignment correction. Arthroscopy combined with UKA does not increase the infection probability and surgical complications, and has an advantage in reducing the total volume of blood transfusion and the percentage of patients receiving blood transfusion.

Effects of Loading Conditions on Articular Cartilage in a Metal-on-Cartilage Pairing

The aim of this in vitro study was to investigate the response of articular cartilage to frictional load when sliding against a metal implant, and identify potential mechanisms of damage to articular cartilage in a metal-on-cartilage pairing. Bovine osteochondral cylinders were reciprocally slid against metal cylinders (cobalt-chromium-molybdenum alloy) with several variations of load and sliding velocity using a microtribometer. The effects of different loads and velocities, and the resulting friction coefficients on articular cartilage, were evaluated by measuring histological and metabolic outcomes. Moreover, the biotribocorrosion of the metal was determined. Chondrocytes stimulated with high load and velocity showed increased metabolic activity and cartilage-specific gene expression. In addition, higher load and velocity resulted in biotribocorrosion of the metal implant and damage to the surface of the articular cartilage, whereas low velocity and a high coefficient of friction increased the expression of catabolic genes. Articular cartilage showed particular responses to load and velocity when sliding against a metal implant. Moreover, metal implants showed tribocorrosion. Therefore, corrosion particles may play a role in the mechano-biochemical wear of articular cartilage after implantation of a metal implant. These findings may be useful to surgeons performing resurfacing procedures and total knee arthroplasty. © 2019 The Authors. Journal of Orthopaedic Research® published by Wiley Periodicals, Inc. on behalf of Orthopaedic Research Society J Orthop Res 37:2531-2539, 2019.