Focal resurfacing of the knee - A systematic review and meta-analysis

PURPOSE

In order to assess the published validity of focal resurfacing of the knee, a systematic review and meta-analysis were conducted to (i) evaluate revision rates and implant survival of focal resurfacing of the knee; (ii) explore surgical complications; and (iii) evaluate patient reported clinical outcome measures.

METHODS

PubMED, Cochrane Library and Medline databases were searched by 2 independent reviewers in February 2022 for prospective and retrospective cohort studies evaluating any of the following implant types: HemiCAP®, UniCAP®, Episealer® or BioBoly®. Data on incidence of revision, complications and various patient reported outcome measures, such as Knee Society Score (KSS) or Knee Injury and Osteoarthritis Outcome Score (KOOS) was sourced.

RESULTS

A total of 24 published studies were identified with a total of 1465 enrolled patients. A revision rate of 12.97% over a 5.9 year weighted mean follow-up period was observed across all implant types. However, in one series a Kaplan-Meir survival as high as 92.6% at a 10-year follow-up period was noted. A statistically significant improvement was documented across multiple subjective clinical outcomes scores, for example a mean 4.56 point improvement of the VAS (0-10) pain score. The Kellgren-Lawrence score was used to evaluate the radiological progression of osteoarthritis and showed a small significant reduction in all anatomical locations, hence not supporting the hypothesis that focal femoral implants can lead to the progression of osteoarthritis in the affected compartment. There was a low reported incidence of post-operative complications such as aseptic loosening or deep wound infection.

CONCLUSIONS

Focal femoral resurfacing appears to be a viable treatment option for focal symptomatic chondral lesions in patients beyond biological reconstruction, with low revision rates and high patient satisfaction especially at short and medium length follow-up.

Influence of material heterogeneity on the mechanical response of articulated cartilages in a knee joint

Structurally, the articular cartilages are heterogeneous owing to nonuniform distribution and orientation of its constituents. The oversimplification of this soft tissue as a homogeneous material is generally considered in the simulation domain to estimate contact pressure along with other physical responses. Hence, there is a need for investigating knee cartilages for their actual response to external stimuli. In this article, impact of material and geometrical heterogeneity of the cartilage is resolved using well known material models. The findings are compared with conventional homogeneous models. The results indicate vital differences in contact pressure distribution and tissue deformation. Further, this study paves way for standardizing material models to extract maximum information possible for investigating knee mechanics with variable geometry and case specific parameters.

Chondral Defects Cause Kissing Lesions in a Porcine Model

OBJECTIVE

To assess the development of kissing lesions 12 months after the generation of full-thickness chondral defects.

DESIGN

Eight minipigs were randomized into 2 groups: the Φ8.5 mm full-thickness chondral defect group (8.5FT group) and the Φ6.5 mm full-thickness chondral defect group (6.5FT group). The Φ8.5 mm or Φ6.5 mm full-thickness chondral defects were prepared in the medial femoral condyle. Knee magnetic resonance imaging (MRI) was performed before sacrifice. India ink staining was performed to macroscopically assess kissing lesions. Histologic staining (hematoxylin-eosin [HE], safranin O/fast green, toluidine blue staining) and immunohistochemistry (collagen I, collagen II, collagen X, MMP-3) were performed. Microcomputed tomography analysis was completed to assess subchondral bone alterations.

RESULTS

Obvious kissing lesions were observed on the tibial plateau. Knee MRI demonstrated high cartilage signal intensity in the medial femoral condyle and opposite tibial plateau. HE staining demonstrated cartilage fibrillation and prominent cell death. The depletion of safranin O, toluidine blue staining, and collagen II was observed in the kissing lesion areas. The kissing lesion areas demonstrated increased collagen I, Collagen X, and MMP-3 expression. The 8.5FT group showed a significantly lower mean trabecular number (2.80 1/mm) than the control group (3.26 1/mm). The 6.5FT group showed a significantly increased mean trabecular thickness (0.54 mm) and a decreased mean trabecular number (2.71 1/mm) compared to the control group (0.32 mm; 3.26 1/mm).

CONCLUSIONS

Obvious kissing lesions were observed on the tibial plateau. Knee MRI demonstrated high cartilage signal The presented findings support the development of kissing lesions caused by full-thickness chondral defects.

The Influence of Anterior Cruciate Ligament Matrix Mechanical Properties on Simulated Whole-Knee Biomechanics

Knee finite element (FE) models are used to study tissue deformation in response to complex loads. Typically, ligaments are modeled using transversely isotropic, hyperelastic material models fitted to tension data along the predominant fiber direction (longitudinal) and, less commonly, to tension data orthogonal to the fiber direction (transverse). Currently, the shear and bulk responses of the anterior cruciate ligament (ACL) are not fitted to experimental data. In this study, a newly proposed material model was fitted to longitudinal tension, transverse tension, and shear experimental data. The matrix transverse tensile, shear, and bulk stiffnesses were then varied independently to determine the impact of each property on knee kinematics and tissue deformation in a whole-knee FE model. The range of values for each parameter was chosen based on published FE studies of the knee. For a knee at full extension under 134 N anterior tibial force (ATF), increasing matrix transverse tensile stiffness, shear stiffness, or bulk stiffness decreased anterior tibial translation (ATT), ACL longitudinal strain, and ACL shear strain. For a knee under 134 N ATF and 1600 N compression, changing the ACL matrix mechanical properties caused variations in ATT and thus changed cartilage deformation contours by changing the point of contact between the femoral and the tibial cartilage. These findings indicate that material models for the ACL must describe matrix material properties to best predict the in vivo response to applied loads.

Clinical Application of the Basic Science of Articular Cartilage Pathology and Treatment

The joint is an organ with each tissue playing critical roles in health and disease. Intact articular cartilage is an exquisite tissue that withstands incredible biologic and biomechanical demands in allowing movement and function, which is why hyaline cartilage must be maintained within a very narrow range of biochemical composition and morphologic architecture to meet demands while maintaining health and integrity. Unfortunately, insult, injury, and/or aging can initiate a cascade of events that result in erosion, degradation, and loss of articular cartilage such that joint pain and dysfunction ensue. Importantly, articular cartilage pathology affects the health of the entire joint and therefore should not be considered or addressed in isolation. Treating articular cartilage lesions is challenging because left alone, the tissue is incapable of regeneration or highly functional and durable repair. Nonoperative treatments can alleviate symptoms associated with cartilage pathology but are not curative or lasting. Current surgical treatments range from stimulation of intrinsic repair to whole-surface and whole-joint restoration. Unfortunately, there is a relative paucity of prospective, randomized controlled, or well-designed cohort-based clinical trials with respect to cartilage repair and restoration surgeries, such that there is a gap in knowledge that must be addressed to determine optimal treatment strategies for this ubiquitous problem in orthopedic health care. This review article discusses the basic science rationale and principles that influence pathology, symptoms, treatment algorithms, and outcomes associated with articular cartilage defects in the knee.