Predictors of cartilage degeneration in patients with subchondral insufficiency fracture of the femoral head: a retrospective study

Molecular biomarker approaches to prevention of post-traumatic osteoarthritis

Up to 50% of individuals develop post-traumatic osteoarthritis (PTOA) within 10 years following knee-joint injuries such as anterior cruciate ligament rupture or acute meniscal tear. Lower-extremity PTOA prevalence is estimated to account for ≥12% of all symptomatic osteoarthritis (OA), or approximately 5.6 million cases in the USA. With knowledge of the inciting event, it might be possible to 'catch PTOA in the act' with sensitive imaging and soluble biomarkers and thereby prevent OA sequelae by early intervention. Existing biomarker data in the joint-injury literature can provide insights into the pathogenesis and early risk trajectory related to PTOA and can help to elucidate a research agenda for preventing or slowing the onset of PTOA. Non-traumatic OA and PTOA have many clinical, radiological and genetic similarities, and efforts to understand early risk trajectories in PTOA might therefore contribute to the identification and classification of early non-traumatic OA, which is the most prevalent form of OA.

Osteoporosis, Osteoarthritis, and Subchondral Insufficiency Fracture: Recent Insights

The increased incidence of osteoarthritis (OA), particularly knee and hip OA, and osteoporosis (OP), owing to population aging, have escalated the medical expense burden. Osteoarthritis is more prevalent in older women, and the involvement of subchondral bone fragility spotlights its association with OP. Notably, subchondral insufficiency fracture (SIF) may represent a more pronounced condition of OA pathophysiology. This review summarizes the relationship between OA and OP, incorporating recent insights into SIF. Progressive SIF leads to joint collapse and secondary OA and is associated with OP. Furthermore, the thinning and fragility of subchondral bone in early-stage OA suggest that SIF may be a subtype of OA (osteoporosis-related OA, OPOA) characterized by significant subchondral bone damage. The high bone mineral density observed in OA may be overestimated due to osteophytes and sclerosis and can potentially contribute to OPOA. The incidence of OPOA is expected to increase along with population aging. Therefore, prioritizing OP screening, early interventions for patients with early-stage OA, and fracture prevention measures such as rehabilitation, fracture liaison services, nutritional management, and medication guidance are essential.

Subchondral fatigue fracture of the femoral head with acetabular dysplasia treated by transposition osteotomy of the acetabulum: a case report

Introduction

Subchondral insufficiency fracture of the femoral head commonly occurs in older women with osteoporosis. However, subchondral fatigue fracture of the subchondral femoral head is rare. We present a rare case of fatigue fracture of the subchondral femoral head with acetabular dysplasia.

Case Report

The patient was a 16-year-old male, height 180 cm, weight 112 kg, and body mass index 34.6 kg/m2. Continuous right hip pain appeared after club activity of table tennis a month before admission to our department. Pain was observed on deep flexion of the right hip joint. The FADIR test was positive. X-ray images showed a depressed deformity of the right femoral head loading portion. In addition, the center-edge angle was 10° on the right and 21° on the left, tear drop distance was 12 mm on the right and 8 mm on the left, and bilateral acetabular dysplasia was noted. In magnetic resonance imaging, the T1-weighted image shows low-intensity signal and the T2-weighted image shows high-intensity signal, indicating a fatigue fracture of the femoral head with subchondral depression. Thus, transposition osteotomy of the acetabulum was performed in this case. Postoperatively, the depression portion showed gradual remodeling, and the patient returned to sports after 6 months. Because this patient was highly obese with acetabular dysplasia, a large shear force was applied to the loading portion of the femoral head relative to the acetabular rim. The femoral head was repeatedly forced, resulting in a fatigue fracture. We believe that the stress applied to the depressed portion was dispersed by the transposition osteotomy of the acetabulum, resulting in remodeling.

Conclusion

This is the first report of the transposition osteotomy of the acetabulum for a subchondral fatigue fracture of the femoral head with acetabular dysplasia. Thus, this may serve as a reference in the management of such rare occurrences and pave the way for further understanding of this condition.

Current Research on Subchondral Insufficiency Fracture of the Femoral Head

Subchondral insufficiency fracture (SIF) of the femoral head is one of the predominant etiologies of rapidly progressive osteoarthritis of the hip (RPOH). SIF is a rare disease that causes acute pain in the hip joint. It is most frequently found in elderly women with osteoporosis. It is often underdiagnosed or misdiagnosed as osteonecrosis of the femoral head. SIF is currently a well-established cause of RPOH; however, the deeper etiology of SIF is not clear. Good clinical outcomes have been reported for hip preservation therapy and hip replacement. SIF is not obvious radiologically in the early stage, and a T1-weighted magnetic resonance imaging shows a discontinuous low-intensity band under the articular cartilage convex to the articular surface as its characteristic manifestation. Some patients will lose the opportunity to preserve the hip joint due to symptoms such as progressive joint space narrowing and subchondral collapse within a very short period. Patients with progressive hip space narrowing and subchondral collapse on X-ray should be converted to total hip arthroplasty. Based on the characteristics of the disease, surgeons need to master the clinical and radiological characteristics of SIF and strive for early diagnosis and treatment.

Inflammasome Activation in the Hip Synovium of Rapidly Destructive Coxopathy Patients and Its Relationship with the Development of Synovitis and Bone Loss

Rapidly destructive coxopathy (RDC), a rare disease of unknown etiology, is characterized by the rapid destruction of the hip joint. In the current study, the potential involvement of inflammasome signaling in the progression of RDC was investigated. Histopathologic changes and the gene expression of inflammasome activation markers in hip synovial tissues collected from patients with RDC were evaluated and compared with those of osteoarthritis and osteonecrosis of the femoral head patients. The synovial tissues of patients with RDC exhibited remarkable increases in the number of infiltrated macrophages and osteoclasts, and the expression of inflammasome activation markers was also increased compared with those of osteoarthritis and osteonecrosis of the femoral head patients. To further understand the histopathologic changes in the joint, a co-culture model of macrophages and synoviocytes that mimicked the joint environment was developed. Remarkably, the gene expression levels of NLRP3, GSDMD, IL1B, TNFA, ADMTS4, ADMTS5, MMP3, MMP9, and RANKL were significantly elevated in the synoviocytes that were co-cultured with activated THP-1 macrophages, suggesting the association between synovitis and inflammasome activation. Consistent with these findings, osteoclast precursor cells that were co-cultured with stimulated synoviocytes exhibited an increased number of tartrate-resistant acid phosphatase-positive cells, compared with cells that were co-cultured with non-stimulated synoviocytes. These findings suggest that the activation of inflammasome signaling in the synovium results in an increase in local inflammation and osteoclastogenesis, thus leading to the rapid bone destruction in RDC.

Rapid Destructive Arthropathy of the Knee in Parkinson's Disease with Pisa Syndrome: A Case of Knee-Spine Syndrome

The changes occurring in knee osteoarthritis often cause alterations in the spinal loading condition, which further lead to degenerative changes. This close relationship of the knee and spine has been reported as knee-spine syndrome. A 60-year-old woman with Parkinson's disease (PD; Hoehn-Yahr stage IV) had severe knee pain with moderate lateral osteoarthritis of the knee (Kellgren-Lawrence classification grade II). Conservative therapy had no effect at all, and the knee developed destructive osteoarthritis rapidly without any traumatic episodes. The radiographic findings progressed to Kellgren-Lawrence grade IV within a month. Magnetic resonance imaging revealed partial depression of the joint surface, including shredded ossicles and substantial amounts of synovial fluid. The imaging findings were considered to be caused by a subchondral insufficiency fracture (SIF). Total knee arthroplasty was performed using a semiconstrained prosthesis. The alignment of her lower extremity improved, and the patient could walk without knee pain. The patient had Pisa syndrome, a lateral flexion of the trunk, which is a postural deformity of the trunk secondary to long-standing PD. The postural deformity in PD is not based on spinal deformity itself but on the loss of postural reflexes and the imbalance of muscle tonus. Her left knee pain appeared 1 month after L1-L4 posterior lumbar interbody fusion (PLIF) as the Pisa syndrome to her left side worsened. The more the trunk tilts to the lateral side, the center of the gravity axis will shift and pass through more lateral points of the knee and result in higher knee load. The stress concentration from the spine to the lateral joint of the knee caused lateral knee osteoarthritis, namely, knee-spine syndrome. When patients undergo correction surgery for adult spinal disorder with impairment of postural reflexes, they need to be followed up carefully regarding not only the spinal alignment but also the lower extremities.