Cadaveric Classification of the Genicular Arteries with Implications for the Interventional Radiologist

Society of Interventional Radiology Research Reporting Standards for Genicular Artery Embolization

Genicular artery embolization (GAE) is an emerging, minimally invasive therapy to address the global burden of knee osteoarthritis (OA) and the unmet needs for medically refractory disease. Although total knee arthroplasty has been a standard intervention for severe cases, GAE is developing into a promising alternative, particularly for patients ineligible for or unwilling to undergo surgery. GAE targets the inflammatory cascade underlying OA pathophysiology by arresting neoangiogenesis and preventing pathological neoinnervation, offering potential pain relief. Although early studies have established safety and short-term effectiveness, ensuing studies are needed to validate long-term safety, durability, and comparative effectiveness and to optimize patient selection, embolic agent selection, and administration techniques. Standardized reporting guidelines are therefore essential to enhance transparency and reproducibility across clinical trials, facilitating data aggregation and comparison. This Society of Interventional Radiology (SIR)-endorsed reporting standards consensus document provides a framework to harmonize future research efforts and to improve the interpretation of outcomes.

Genicular Artery Embolization: A Review of Essential Anatomic Considerations

Genicular artery embolization is increasingly recognized as a safe and effective treatment option for symptomatic knee osteoarthritis and recurrent hemarthrosis after total knee arthroplasty. Genicular arteries are an essential contributor to vascular supply for the knee joint and demonstrate considerable variability. Familiarity with the anatomy and common variations is critical for preprocedural planning, accurate target selection, and minimizing adverse events in transarterial embolization procedures. This review aimed to provide a detailed discussion of the genicular artery anatomy that is relevant to interventional radiologists performing genicular artery embolization.

Added Value of Cone-Beam CT to Identify Arterial Supply during Genicular Artery Embolization for Knee Osteoarthritis

PURPOSE

To evaluate if the addition of cone-beam computed tomography (CT) to digital subtraction angiography (DSA) improves the identification of the genicular arteries during genicular artery embolization (GAE) for knee pain secondary to osteoarthritis (OA).

MATERIALS AND METHODS

This single-center study retrospectively analyzed 222 patients who underwent GAE for painful knee OA between May 2018 and April 2022. Intraprocedural cone-beam CT and DSA images were reviewed independently by 2 sets of interventional radiologists. DSA was performed for all patients. Technically adequate cone-beam CT was available for 205 patients (92.3%). The presence of the genicular arteries identified by cone-beam CT and DSA was compared using Φ coefficients. Embolization targets identified by both cone-beam CT and DSA were evaluated against those identified by DSA alone.

RESULTS

Genicular arteries with the highest concordance between cone-beam CT and DSA were the inferior lateral (196 vs 198; Φ = 0.3530; P < .0001), superior lateral (197 vs 200; Φ = 0.3060; P < .0001), and superior medial genicular (186 vs 161; Φ = 0.2836; P < .0001) arteries. Cone-beam CT demonstrated higher rates of detection of the inferior medial (195 vs 178; Φ = 0.04573; P = .5150) and median genicular arteries (200 vs 192; Φ = 0.04573; P = .5150). Meanwhile, genicular arteries less frequently identified by cone-beam CT were the descending genicular (197 vs 200; Φ = -0.03186; P = .6502), superior patellar (175 vs 184; Φ = 0.1332; P = .0569), and recurrent anterior tibial (156 vs 186; Φ = 0.01809; P = .7969) arteries. Cone-beam CT in combination with DSA identified 13.4% (372 vs 328) more targets compared to DSA alone.

CONCLUSIONS

Based on the results of the current study, cone-beam CT serves as a valuable adjunct for visualizing the genicular arteries during GAE, and together with DSA, it identifies more potential embolization targets.

Genicular Artery Embolization for Knee Osteoarthritis: A Comprehensive Review

» Genicular artery embolization (GAE) is a promising treatment option for patients with knee osteoarthritis who are unresponsive to nonsurgical treatments and not yet candidates for surgery.» Current evidence supports the effectiveness of GAE in reducing pain and synovitis, with few reported major adverse events.» The cost-effectiveness and long-term results of GAE compared with other treatment options require further investigation.» Limitations of existing studies include small sample sizes, single-center trials, and lack of comparison between embolic agents and other treatments.» Future research should focus on larger, multicenter trials with longer follow-up periods and head-to-head comparisons with alternative treatment modalities to establish the role of GAE in the management of knee osteoarthritis.

Classification of Genicular Artery Anatomic Variants Using Intraoperative Cone-Beam Computed Tomography

PURPOSE

Genicular artery embolization (GAE) is a new treatment option for symptomatic knee osteoarthritis. Genicular arterial anatomy is complex with limited published reports. This study describes the genicular artery anatomy utilizing intraprocedural cone-beam computed tomography (CBCT) during GAE.

MATERIALS AND METHODS

This retrospective single-center study was approved by the institutional review board. All patients who underwent GAE between May 2018 and April 2022 were reviewed. Patients with a technically adequate CBCT were included in the analysis. CBCTs were analyzed to determine the presence, course, and branching patterns of the genicular arteries.

RESULTS

A total of 222 patients underwent GAE and 205 (92%) were included for analysis. The descending genicular artery was present in 197 (96%) CBCTs with two branches in 152 (77%). The superior medial genicular artery (SMGA) was present in 186 (91%), superior lateral genicular artery (SLGA) in 203 (99%), inferior medial genicular artery (IMGA) in 195 (95%), inferior lateral genicular artery (ILGA) in 196 (95%), and median genicular artery (MGA) in 200 (97%). Four unique branching patterns were identified: common origin of SLGA and MGA (115, 56%), unique origins (45, 22%), trifurcation of SLGA, SMGA, and MGA (32, 15.5%), and common origin of SMGA and MGA (12, 6%). The recurrent ascending tibial was identified in 156 (76%) CBCTs and superior patellar artery in 175 (85%) CBCTs.

CONCLUSION

Genicular artery anatomy is complex with numerous common variants. CBCT is a powerful adjunct in GAE to rapidly identify target vessels for embolization and potentially decrease the risk of nontarget embolization.

Knee and Shoulder Vascular Anatomy

In the past decade, angiographic studies have demonstrated neovessels in or in the vicinity of affected joints in many musculoskeletal conditions that used to be considered wear and tear joint disease, such as knee osteoarthritis, frozen shoulder, and overuse injuries. The novelty of this finding is showing the presence of neovascularity at an angiographically detectable level, as compared to histologically evident neovessels that had been discovered years ago. These neovessels have now become the target of interventions in a growing field called muscoskeletal embolotherapy. An in-depth and all-encompassing understanding of the vascular anatomy that could specifically assist performing of these procedures is paramount. Such an understanding will help ensure success in clinical outcomes and avoid much dreaded complications. This review discusses the vascular anatomy relevant to the 2 most commonly performed musculoskeletal embolotherapies, genicular artery embolization and transarterial embolization for frozen shoulder.

Emerging Targets for the Treatment of Osteoarthritis: New Investigational Methods to Identify Neo-Vessels as Possible Targets for Embolization

Osteoarthritis (OA) is the major cause of disability, affecting over 30 million US adults. Continued research into the role of neovascularization and inflammation related to osteoarthritis in large-animal models and human clinical trials is paramount. Recent literature on the pathogenetic model of OA has refocused on low-level inflammation, resulting in joint remodeling. As a result, this has redirected osteoarthritis research toward limiting or treating joint changes associated with persistent synovitis. The overall goal of this review is to better understand the cellular and tissue-specific mechanisms of inflammation in relation to a novel OA treatment modality, Genicular Artery Embolization (GAE). This article also assesses the utility and mechanism of periarticular neovascular embolization for the treatment of OA with a particular emphasis on the balance between pro-angiogenic and anti-angiogenic cytokines, inflammatory biomarkers, and imaging changes.

Discovery and Characterization of Intercondylar Transphyseal Complexes and their Oncological Significance in Transphyseal Extension of Pediatric Osteosarcoma

Objective

To explore whether there exist undiscovered transphyseal vasculature‐canal compound structures in immature femurs and tibias, and reveal their potential oncological impact.

Methods

This investigation was divided into a morphological study and a clinical study. In the morphological part, a new‐identified anatomic structure was investigated by using radiographical, anatomical, and histological methodologies. Twenty‐eight 1‐mm‐slice thickness magnetic resonance images of pediatric knees were generated and 10 pediatric knees were dissected to verify the existence and universality, observe the radiographic and anatomic characteristics, and determined the located region of this structure. Hematoxylin–eosin staining, immunofluorescence, and angiography procedures were performed to illustrate its histological feature, molecular identification, and vascular origination, respectively. In the clinical part, 38 pediatric osteosarcoma patients were enrolled from January 2014 to December 2020. A descriptive clinical study including 13 typical participants was conducted to investigate the oncological significance of this new‐identified structure. Meanwhile, the discrepancy in transphyseal osteosarcoma extension between different physeal regions was evaluated in a cross‐sectional study.

Results

In the morphological study, we discovered a new‐found vasculature‐canal compound structure, intercondylar transphyseal complex (ITC), which originated from the middle genicular vessels, traversed the whole epiphysis, and breached the intact open physis in the immature proximal tibia or distal femur. The components of ITC included the juxta‐articular, epiphyseal, and transphyseal segments of vessels, the canals that traverse the entire epiphysis and physis and enclosed the vessels, vascular foramina on articular facet and foramina‐covered synovium. Depending on the location, ITCs can be divided into three types: femoral ITC, anterior tibial ITC, and posterior tibial ITC. Clinically, the ITC may facilitate intercondylar transphyseal sarcomatous dissemination without damaging the adjacent physeal cartilage. Compared to bilateral condylar physes, more osteosarcomas transgressed the open growth plates through intercondylar regions in which ITC was located (P = 0.022).

Conclusion

As the “gap” on intact open physis, ITC, which is a new‐identified compound structure in intercondylar regions of immature femur or tibia, may promote intercondylar transphyseal tumor extension. Moreover, the identification and characterization of ITC subvert some traditional comprehensions about physis and may provide novel perspectives for pediatric osteosarcomas.