Pathophysiology and Management of Subchondral Insufficiency Fractures of the Knee

Subchondral Fracture of the Femoral Head in a High School Badminton Player: A Case Report.

The purpose of this article is to verify the hypothesis that osteonecrosis and subchondral insufficiency fracture of the femoral head can be differentiated on the basis of their appearance on MRI. Between May 1998 and February 2009, we reviewed 30 consecutive hips in 30 patients, 60 years old or older at the time of onset of hip pain, with radiologic evidence of subchondral collapse of the femoral head and with both MR images and histologic results available. Both clinical and radiologic appearances were investigated. The patients were divided into two groups according to the shape of low-intensity bands on T1-weighted images. The first group showed concavity of the articular surface, which is characteristic of osteonecrosis, and the second group showed an irregular convexity of the articular surface, which is characteristic of subchondral insufficiency fracture. Sixteen hips (53.3%) showed evidence of osteonecrosis, and 14 (46.7%) showed evidence of subchondral insufficiency fracture, which was consistent with the corresponding histopathologic diagnoses. In all cases of osteonecrosis, the patient had a history of either corticosteroid intake or alcohol abuse. Among patients with subchondral insufficiency fracture, the proportion of women was significantly higher than that among patients with osteonecrosis. A crescent sign (subchondral fracture) was present radiographically in about half of all cases in both groups. The results of the present study suggest that the shape of the low-intensity band on MRI is useful for the differentiating subchondral insufficiency fracture from osteonecrosis. In addition, among osteoporotic elderly women without any history of corticosteroid intake or alcohol abuse, a diagnosis of subchondral insufficiency fracture should be considered.

Spontaneous osteonecrosis of the knee is a superficial subchondral lesion classically seen in the medial femoral condyle; in general, it is markedly different in its clinicopathological presentation from the classic wedge-shaped subchondral osteonecrotic lesions seen in the hip, knee, and other joints. Recent reports on subchondral insufficiency fracture of the femoral head, which has marked morphological similarities with spontaneous osteonecrosis of the knee, led us to reevaluate a series of patients who had had operative treatment because of a clinical and pathological diagnosis of spontaneous osteonecrosis of the knee. We reviewed the cases of fourteen patients who had had operative treatment of spontaneous osteonecrosis of the knee in order to reevaluate the gross and histological morphology of this lesion. The patients included eight women and six men who ranged in age from fifty-nine to eighty-eight years. In all patients, the diagnosis of spontaneous osteonecrosis of the knee had been based on clinical presentation, imaging studies, and pathological findings. The appearance of the lesion on plain radiographs was categorized into four stages, which corresponded to the gross and histological findings. In stage 1, the radiographic appearance is normal; in stage 2, a radiolucent oval area is seen subchondrally or there is slight flattening of the convexity of the condyle, or both; in stage 3, the radiolucent area is expanded and is surrounded by a sclerotic halo; and in stage 4, secondary osteoarthritic changes are apparent. No patient had a stage-1 lesion. Three patients, all of whom had a stage-2 lesion, were considered to have a subchondral insufficiency fracture of the medial femoral condyle. Another six patients, all of whom had a stage-3 lesion, were considered to have a subchondral fracture and associated focal osteonecrosis that was confined to the area between the fracture line and the articular surface. The remaining five patients, three of whom had a stage-3 lesion and two of whom had a stage-4 lesion, had indeterminate findings because the lesion had become detached from the condyle. Our histopathological findings suggest that the primary event leading to spontaneous osteonecrosis of the knee is a subchondral insufficiency fracture and that the localized osteonecrosis seen in association with this disease is the result of a fracture.

The purpose of our study was the clinical characteristics, radiographic appearance, and outcomes after treatment in patients with rapid destructive arthrosis (RDA) due to subchondral insufficiency fracture (SIF) of the shoulder. Twenty-two cases of RDA of the shoulder were retrospectively reviewed. Clinical outcomes for 15 cases who underwent shoulder arthroplasty were evaluated at an average of 41.4 months. The mean age of patients was 73.7 years (range 50–83 years), and there were 20 women and 2 men. The mean time from onset of symptoms to head collapse was 6.8 months (range 1–12 months). The mean t-score of bone mineral density was −3.1. Nine patients had pseudoparalysis. Based on radiographic appearance, a diversity of types of head destruction with subchondral fracture, bone marrow edema, joint effusion, and synovitis were observed in all cases. In conclusion, RDA due to SIF of the shoulder, presenting with severe short-term pain and functional disability, commonly occurred in elderly women with bone fragility. MRI revealed bone marrow edema, extensive joint effusion, and synovitis as well as a diversity of types of head destruction with subchondral fracture within several months from onset of symptoms.

Subchondral insufficiency fracture (SIF) represents a potentially severe condition that can advance to osteoarthritis, with collapse of the articular surface. SIF manifests as a fracture in bone weakened by non-tumorous disease, precipitated by repetitive physiological stress, without a clear history of major trauma. It is observed along the central weight-bearing region of the femoral condyle, with a higher incidence in the medial femoral condyle, but also in other large weight-bearing synovial joints, such as the femoral head, tibial plateau, or talus.A review of the literature from the past six years was performed by searching PubMed and ScienceDirect databases, using the keywords "subchondral insufficiency fracture" and "spontaneous osteonecrosis of the knee". The inclusion criteria were scientific papers presented in the English language that reported on the magnetic resonance imaging (MRI) aspects of SIF of the lower limb.Detecting SIF at the level of the hip, knee, and ankle may present challenges both clinically and radiologically. The MRI appearance is dominated by a bone marrow edema-like signal and subchondral bone changes that can sometimes be subtle. Subchondral abnormalities are more specific than the pattern of bone marrow edema-like signal and are best shown on T2-weighted and proton-density-weighted MR images. MRI plays an important role in accurately depicting even subtle subchondral fractures at the onset of the disease and proves valuable in follow-up, prognosis, and the differentiation of SIF from other conditions. · Subchondral insufficiency fractures may affect the hip, knee, and ankle.. · Subchondral insufficiency fractures may heal spontaneously or progress to collapse.. · MRI is important for the detection, follow-up, and prognosis of subchondral insufficiency fractures.. · Differential diagnosis may include transient osteoporosis and osteonecrosis of systemic origin.. · Buturoiu MM, Ghiea S, Weber M. Subchondral insufficiency fractures: overview of MRI findings from hip to ankle joint. Fortschr Röntgenstr 2024; 196: 1143 - 1154.

The role of torsional stress in the development of subchondral insufficiency fracture of the femoral head: A finite element model analysis

Subchondral insufficiency fractures (SIFs) and SIFs with osteonecrosis (SIF-ONs) of the knee (previously misnamed spontaneous osteonecrosis of the knee (SONK)) are bone lesions that appear without prior traumatic, tumoral, or inflammatory event.Both conditions are characterized in the early stages by epiphyseal bone marrow edema (BME)-like signal at MRI. However, while SIFs usually heal spontaneously, they can also evolve to osteonecrosis (i.e., SIF-ON), which may progress to an irreversible collapse of the articular surface. Careful analysis of other MRI signs may help differentiate the two conditions in the early phase. In SIFs, the BME edema-like signal extends to the area immediately adjacent to the subchondral plate, while in SIF-ONs, this subchondral area shows low signal intensity on fluid-sensitive MR images due to altered bone marrow. The thickness and length of subchondral areas with low fluid-sensitive signal intensity are important factors that determine the prognosis of SIF-ONs. If they are thicker than 4 mm or longer than 14 mm, the prognosis is poor. The differential diagnosis of SIFs and SIF-ONs include bone lesions associated with the “complex regional pain syndrome” (CRPS), epiphyseal osteonecrosis of systemic origin, and those related to cartilage pathology.Clinical relevance statement Imaging plays an essential role in diagnosing subchondral insufficiency fractures (SIFs) from subchondral insufficiency fractures with osteonecrosis (SIF-ONs) and collapse, as well as in distinguishing them from other spontaneous knee subchondral bone lesions presenting with bone marrow edema-like signal.Key points• Subchondral insufficiency fractures may affect the knee, especially in older adults.• Subchondral insufficiency fractures usually heal spontaneously.• Sometimes, subchondral osteonecrosis and collapse may complicate subchondral insufficiency fractures.• Bone marrow-like edema is an aspecific sign seen in all these lesions.• Degraded marrow in osteonecrosis complicating fractures is hypointense on fluid-sensitive sequences.Graphical

Subchondral stress insufficiency fracture of the knee is a new type of fracture that occurs in people of the older age group (from 50–55 years old) when exposed to a normal load on weakened bone trabeculae. In Russian sources, there is few information about this type of fracture. This is primarily due to the fact that initially the world and domestic medical communities designated this type of pathology as “spontaneous osteonecrosis of the knee”. In recent years, this term has been revised abroad and replaced by a more suitable one – “subchondral insufficiency fracture”. The etiology of insufficiency fracture is based on many diseases and conditions that lead to bone tissue weakening (osteoporosis, collagenosis, rheumatoid arthritis, post-radiation changes in bones, etc.). The main method for diagnosing this type of fracture is magnetic resonance imaging, since it is able to detect a fracture at any stage (especially at an early one). According to modern concepts, the terms “osteonecrosis” and “subchondral insufficiency fracture” require completely different approaches to the treatment. In the presence of complications, a fracture of insufficiency of the knee joint condyles threatens with subchondral collapse and secondary osteoarthritis, which leads to disability of a patient. Given the relevance of this medical problem, the aim of the review is to show the current state of literature data on the issue.

Spontaneous osteonecrosis of the knee (SONK) was first described by Ahlbäck et al. in 1968. However, subsequent studies revealed that subchondral fractures, rather than necrosis, are the most common histopathological finding in bone samples from patients diagnosed with SONK. This has led to ongoing debate regarding the accuracy of the term "SONK." Therefore, SONK is an inappropriate definition for this condition since the absence of necrosis in most histopathological samples of patients with such diagnosis. A PRISMA-compliant scoping review was conducted using PubMed, Scopus, and Cochrane databases. All original research studies reporting histological analyses of bone samples from patients who underwent surgery following a diagnosis of SONK were considered for inclusion. Extracted data included general study characteristics, radiographic and magnetic resonance imaging (MRI) findings, time elapsed between arthroscopy and histological sampling, and the results of histological examinations of bone samples. Eight articles met the inclusion criteria, comprising 90 patients (91 knees), of which 87 bone samples were analyzed histologically. Of these, 7 showed undetermined outcomes. Among the remaining 80 samples, necrosis was identified in 35 cases and absent in 45. Subchondral insufficiency fractures (SIFs) were detected in 41 cases, with 19 of these also showing necrosis. The histopathological evidence suggests that the term "SONK" is inappropriate, as SIFs, rather than necrosis, are the predominant finding. We therefore recommend adopting "SIF" as a more accurate descriptor for this condition.

To clarify the clinical application of the disease terms "subchondral insufficiency fracture of the knee (SIFK)" and "osteonecrosis of the knee (ONK)", and to review the research progress on this pathological condition. The research literature in the field of SIFK and ONK both domestically and internationally in recent years was widely reviewed, and the research progress of SIFK and ONK was summarized from the aspects of the current conceptual frameworks, etiological factors and pathogenic mechanisms, clinical and imaging manifestations, therapeutic approaches, and prognostic outcomes. The exact etiology of SIFK remains controversial, and its specific pathogenesis has not been fully elucidated. Subchondral fracture has been identified as the primary pathological feature of this disease entity. SIFK predominantly affects the females over 65 years old, presenting with sudden onset of severe and persistent pain. MRI serves as the gold standard for diagnosis of early-stage SIFK. The characteristic MRI findings include bone marrow edema-like signals and a subchondral low-signal line in the affected femoral condyle. Generally, if bone morphology is preserved without subchondral bone collapse, conservative management is typically the first-line treatment approach. Surgical intervention should be considered if there is no clinical or radiographic improvement after 3 to 4 months of conservative therapy. Considering the pathological features of bone specimens, adopting the SIFK for ONK demonstrates greater appropriateness in diagnosis and management of these disorders. Early diagnosis and management are important for improving the prognosis of SIFK patients.

Background. Subchondral insufficiency fracture of the knee (SIFK) is a frequent cause of knee joint pain in patients over 55 years of age. Diagnosis of this pathology at an early stage has certain difficulties, as it requires magnetic resonance imaging (MRI). Aim of the study. To determine the relationship between the size of the lesion in subchondral insufficiency fracture of the knee joint, the patient's body mass index and the risk of articular surface collapse. Material and Methods. In 35 female patients with subchondral insufficiency fracture the size of the lesion in frontal and sagittal planes, as well as its volume according to MRI were determined. The obtained results made it possible to assess the risk of articular surface collapse. Results. The study revealed a relationship between the size of the lesion and the risk of articular surface collapse in subchondral insufficiency fracture of the knee. An anteroposterior size of the lesion of more than 14.1 mm, a transverse size of more than 10.2 mm, and a craniocaudal size of more than 1.22 mm are risk factors for subsequent articular surface collapse and progression of osteoarthritis of the knee joint. The analysis of the correlation between body mass index (BMI) and the development of articular surface collapse found no specific BMI value associated with articular surface collapse. Conclusions. A risk factor for articular surface collapse in patients with subchondral bone insufficiency fracture of the knee joint was determined, which allows predicting the outcomes of the disease treatment. Body mass index and the development of articular surface collapse do not correlate with each other.

Subchondral insufficiency fractures (SIF) occur without adequate trauma to the weight-bearing joint surfaces due to repeated physiological loading and occur predominantly in older people. Magnetic resonance imaging (MRI). Radiographs. MRI is the best method for the detection, follow-up, and assessment of the prognosis of subchondral insufficiency fractures. The typical MRI findings of SIF are bone marrow edema, asubchondral hypointense fracture line, and possibly asubchondral hypointense area on T2-weighted sequences. Subchondral cortical deformity and afluid-filled cleft indicate advanced SIF with apoor prognosis. Subchondral insufficiency fractures can heal spontaneously or progress to collapse. The task of radiology is to distinguish between lesions that heal (simple subchondral insufficiency fractures) and lesions that progress unfavorably (subchondral insufficiency fractures with osteonecrosis).

Subchondral insufficiency fracture of the femoral head may be confused with osteonecrosis, mainly because of radiological overlap. SPECT/CT with Tc-99 m hydroxymethylene diphosphonate images in 7 patients with subchondral insufficiency fracture were retrospectively reviewed and compared with those from 11 patients with symptomatic early osteonecrosis. In all of the hips with subchondral insufficiency fracture, SPECT/CT showed increased uptake at the subchondral lesions of the femoral head. On the other hand, in all of the hips with osteonecrosis, absence of uptake was confirmed at the subchondral lesions. SPECT/CT may assist in differentiating subchondral insufficiency fracture from osteonecrosis.

Avascular necrosis of the femoral head (AVN) describes an ischemia-induced necrosis of the subchondral bone of the femoral head. Early diagnosis is crucial to initiate appropriate treatment and achieve the longest possible preservation of the native joint. Pathophysiologically, AVN results from impaired blood supply to the subchondral bone, promoted by various risk factors or underlying pathologies. The most relevant include prolonged or high-dose corticosteroid therapy and chronic alcohol abuse. Magnetic resonance imaging (MRI) is regarded as the key modality for early detection, enabling identification of characteristic changes before radiographic abnormalities become apparent. The earliest MRI finding is aband-like, T1-hypointense line demarcating the necrotic area from surrounding viable bone. The characteristic double-line sign-comprising an outer hypointense and an inner hyperintense rim-reflects reparative processes at the necrosis margin. Bone marrow edema occurs only after the development of asubchondral fracture and thus indicates an advanced stage, rather than, as previously assumed, an early manifestation of AVN. Differential diagnosis should primarily include transient bone marrow edema syndrome and subchondral insufficiency fracture. The Association Research Circulation Osseous (ARCO) classification provides amultimodal, internationally established system for standardized staging. It distinguishes four clinically relevant stages: isolated MRI detection (stageI), radiographic changes without fracture (stageII), subchondral fracture (stageIII), and secondary osteoarthritis (stageIV). This system allows reproducible stage-based assessment, supports therapeutic planning, and facilitates interdisciplinary communication. Consequently, radiologic imaging plays apivotal role in diagnosis, disease monitoring, and treatment decision-making for patients with AVN.

Introduction:Osteonecrosis of knee is classified as primary spontaneous osteonecrosis of knee (SPONK) and secondary osteonecrosis of knee. Primary SPONK usually involves medial femoral condyle (MFC). Incidence of medial tibial plateau (MTP) is only 2% among the patients with SPONK and simultaneous involvement of MFC and MTP is very rare.Case Report:We report a very rare case of 45-year-old female with SPONK affecting both MFC and MTP simultaneously with subchondral insufficiency fractures. She presented with pain in both the knees and difficulty in walking since 1 year. Physical examination revealed decreased range of motion and local tenderness over MFC and medial tibial condyle. Subchondral fracture with articular surface collapse of MFC with joint space narrowing and varus deformity was seen on X-ray in both the knees. Sclerosis was seen in the medial tibial condyle bilaterally. Magnetic resonance imaging showed characteristic focal hyperintense areas surrounded by band like hypointense areas in both MFC and MTP which was suggestive of subchondral collapse with ill-defined bone marrow changes. X-ray of both knees revealed SPONK in Koshino’s Stage IV and Carpintero’s Stage IV. Bilateral total knee replacement (TKR) was planned. First left knee was operated. A cruciate retaining type of TKR was done. Two weeks, later right side TKR was operated. MFC of right side also had a large osteochondral fragment which was excised to leave defect with depth more than 2 cm. Defect was reconstructed with bone graft obtained from posterior condylar cuts. Posterior stabilized type of knee replacement component was used along with femoral extender stem. Histopathological examination revealed necrotic bone surrounded by an area of fibrovascular granulation tissue on both the femoral and tibial sides. Patient has good functional outcome at 2 years follow-up.Conclusion:Concomitant SPONK of MFC and MTP in bilateral knee is very rare and in advanced stages TKR can provide good radiological and functional outcome. Furthermore, pre-operative assessment of bone defects is necessary and appropriate use of augments (extender stem or metal wedges) is crucial.