Femoral condyle insufficiency fractures: associated clinical and morphological findings and impact on outcome

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.

High-resolution magnetic resonance imaging can predict osteoarthritic progression after medial meniscus posterior root injury: randomized in vivo experimental study in a rabbit model

IMPORTANCE

The field of meniscal root preservation has undergone significant advancement over the past decades; however, the challenge remains to fully understand whether meniscal root repair can ultimately arrest or delay osteoarthritic changes.

OBJECTIVE

To assess longitudinal changes in articular cartilage, subchondral bone, and progression to meniscal extrusion (ME) using high-resolution magnetic resonance imaging (MRI).

METHODS

Medial meniscus posterior root tear was surgically induced in 39 New Zealand white rabbits. Animals were randomly assigned into three experimental groups: partial meniscectomy after root tear (PM, n ​= ​13); root tear left in situ (CT, n ​= ​13); and transtibial root repair (RR, n ​= ​13). Contralateral limbs were used as healthy controls. High resolution 4.7 Tesla MRI of the knee joint was performed at baseline, after 2-, and 4-months of post-surgery. Cartilage thickness was calculated in medial and lateral compartments. In addition, the evaluation of ME, subchondral bone edema and healing potential after root repair were assessed too.

RESULTS

Progressive cartilage thinning, ME, and subchondral bone edema were evident in all 3 study groups after 4-months of follow-up. The mean cartilage thickness in the PM group was 0.53 ​mm (±0.050), 0.57 ​mm (±0.05) in the CT group, and 0.60 ​mm (±0.08) in the RR group. The PM group exhibited significantly higher cartilage loss when compared to the CT and RR groups (p ​< ​0.001). Moreover, progressive ME and subchondral bone edema were associated with a more severe cartilage loss at the final follow-up.

CONCLUSION

Meniscal root repair did not halt but rather reduced the progression of osteoarthritis (OA). Degenerative changes worsened at a rapid rate in the PM group compared to the RR and CT groups. Early cartilage swelling, persistent subchondral edema, and progressive ME predicted a more severe progression to knee OA in the CT and RR groups.

LEVEL OF EVIDENCE

II.

Risk of Arthroplasty in Patients with Subchondral Insufficiency Fractures of the Knee: A Matched Study of the Implantable Shock Absorber using a Validated Predictive Model

Subchondral insufficiency fractures of the knee (SIFK) can result in high rates of osteoarthritis and arthroplasty. The implantable shock absorber (ISA) implant is a titanium and polycarbonate urethane device which reduces the load on the medial compartment of the knee by acting as an extra-articular load absorber while preserving the joint itself. The purpose of this study was to evaluate whether partially unloading the knee with the ISA altered the likelihood of progression to arthroplasty utilizing a validated predictive risk model (SIFK score). A retrospective case-control (2:1) study was performed on patients with SIFK without any previous surgery and on those implanted with the ISA with the primary outcome being progression to arthroplasty compared with nonoperative treatment at 2 years. Baseline and final radiographs, as well as magnetic resonance imagings, were reviewed for the evaluation of meniscus or ligament injuries, insufficiency fractures, and subchondral edema. Patients from a prospective study were matched using the exact SIFK Score, a validated predictive score for progression to arthroplasty in patients with SIFK, to those who received the ISA implant. Kaplan-Meier analysis was conducted to assess survival. A total of 57 patients (38 controls:19 ISA) with a mean age of 60.6 years and 54% female were included. The SIFK score was matched exactly between cases and controls for all patients. The 2-year survival rate of 100% for the ISA group was significantly higher than the corresponding rate of 61% for the control group (p < 0.01). In ISA, 0% of the patients converted to arthroplasty at 2 years, and 5% (one patient) had hardware removal at 1 year. When stratified by risk, the ISA group did not have a significantly higher survival compared with low-risk (p = 0.3) or medium-risk (p = 0.2) controls, though it had a significantly higher survival for high-risk groups at 2 years (100 vs. 15%, p < 0.01). SIFK of the medial knee can lead to significant functional limitation and high rates of conversion to arthroplasty. Implants such as the ISA have the potential to alter the progression to arthroplasty in these patients, especially those at high risk.

Subchondral Insufficiency Fractures of the Knee: A Clinical Narrative Review

» Subchondral insufficiency fractures of the knee (SIFKs) are subchondral plate fractures with a prevalence of 2% to 4% of all knee injuries.» Magnetic resonance imaging is the gold standard for evaluating SIFK, while plain radiographs have limited the use in the diagnosis of SIFK.» Among patients with SIFK, 50% to 100% have meniscal pathology.» Medical therapies and standard treatments traditionally used in the management of knee osteoarthritis differ from recommended management of SIFK patients.» Randomized controlled trials and cohort studies with long-term follow-up are needed to determine the optimal rehabilitation protocol, interventional therapy, and prognosis of SIFK patients.

Proximal fibular osteotomy relieves pain in spontaneous osteonecrosis of the knee: A retrospective study

Spontaneous osteonecrosis of the knee (SONK) causes knee pain and joint motion limitation. Ischemia or insufficiency fracture may be the cause, but no consensus has been developed. Proximal fibular osteotomy (PFO) has been reported to relieve pain from osteoarthritis through medial compartment decompression. We reviewed the effect of this procedure on medial compartment SONK patients and explored clinical and radiological results. Since January 2018 to January 2020, the data of 12 knees (8 right and 4 left) from 11 SONK patients (9 women and 2 men) who received PFO were analyzed. The average age was 61.5 years. The diagnosis of SONK was established through weight-bearing anterior-posterior radiographs or magnetic resonance imaging (MRI). Visual analog scale (VAS) scores, Oxford knee score (OKS), Femorotibial angle (FTA), medial joint space, and lateral joint space were documented preoperatively and at follow up visits. Outcome assessment for the clinical and radiographic data was reviewed at 12- and 24-month follow-up visits. The mean follow up period was 33 months. All patients were able to walk with or without cane assistance the day after surgery. Both VAS score and OKS (preoperative: 6.6 ± 0.9 and 24.7 ± 3.8, respectively) improved significantly at the 12-month follow-up, and to 24-month follow-up (3.6 ± 1.3 and 35.6 ± 4.5, respectively, P < .05). Medial joint space ratio increased from 0.36 to 0.50 (P < .05). Changes of FTA were insignificant at any point of follow up. Four patients underwent follow-up MRI, and a decrease in the osteonecrotic area was clearly observed in 2 patients. By achieving medial knee decompression, PFO allowed quick weight-bearing recovery, pain relief, and improvement in knee function in SONK patients.

Subchondral insufficiency fracture of the knee: review of current concepts and radiological differential diagnoses

Subchondral insufficiency fracture of the knee (SIFK) is a common cause of knee joint pain in older adults. SIFK is a type of stress fracture that occurs when repetitive and excessive stress is applied to the subchondral bone. If the fracture does not heal, the lesion develops into osteonecrosis and results in osteochondral collapse, requiring surgical management. Because of these clinical features, SIFK was initially termed "spontaneous osteonecrosis of the knee (SONK)" in the pre-MRI era. SONK is now categorized as an advanced SIFK lesion in the spectrum of this disease, and some authors believe the term "SONK" is a misnomer. MRI plays a significant role in the early diagnosis of SIFK. A subchondral T2 hypointense line of the affected condyle with extended bone marrow edema-like signal intensity are characteristic findings on MRI. The large lesion size and the presence of osteochondral collapse on imaging are associated with an increased risk of osteoarthritis. However, bone marrow edema-like signal intensity and osteochondral collapse alone are not specific to SIFK, and other osteochondral lesions, including avascular necrosis, osteochondral dissecans, and osteoarthritis should be considered. Chondral lesions and meniscal abnormalities, including posterior root tears, are also found in many patients with SIFK, and they are considered to be related to the development of SIFK. We review the clinical and imaging findings, including the anatomy and terminology history of SIFK, as well as its differential diagnoses. Radiologists should be familiar with these imaging features and clinical presentations for appropriate management.

Medial meniscus posterior root repair prevents the progression of subchondral insufficiency fracture of the knee

BACKGROUND

Medial meniscus posterior root tear (MMPRT) causes medial meniscus extrusion (MME) and leads to subchondral insufficiency fracture of the knee (SIFK). However, the progression of SIFK after MMPRT pullout repair remains unknown. This study aimed to investigate the progression of SIFK and compare clinical outcomes in patients with SIFK to those without SIFK after MMPRT pullout repair. We hypothesized that the progression of SIFK would be prevented by MMPRT pullout repair, and clinical outcomes would improve in all patients.

METHODS

The SIFK grade (1-4) was evaluated using T2-fat suppression magnetic resonance imaging. Thirty-eight patients without SIFK (n = 22) and with low-grade SIFK (1 and 2; n = 16) who underwent MMPRT pullout repair were included. Preoperative factors, such as the duration from injury to the time of magnetic resonance imaging/surgery (weeks), femorotibial angle (degree), MME (mm), and clinical outcomes were evaluated, as well as the progression of SIFK.

RESULTS

SIFK was identified in only 9 patients (grade 1) postoperatively. Significantly improved clinical outcomes were observed in all patients. Preoperative femorotibial angle, MME, and duration from injury to the time of magnetic resonance imaging/surgery were 177.1 ± 1.5°, 3.2 ± 1.6 mm, and 6.4 ± 7.0/10.1 ± 7.5 weeks, respectively. No significant difference in preoperative factors and clinical outcomes was observed between patients with SIFK and those without SIFK.

CONCLUSIONS

MMPRT pullout repair prevented the progression of low-grade SIFK and improved clinical outcomes in all patients, although bone contusions (grade 1 SIFK) were not completely healed within 1 year. MMPRT pullout repair could be a good treatment option for optimizing clinical outcomes in patients with low-grade SIFK.

Edema-like marrow signal intensity: a narrative review with a pictorial essay

The term edema-like marrow signal intensity (ELMSI) represents a general term describing an area of abnormal signal intensity at MRI. Its appearance includes absence of clear margins and the possibility of exceeding well-defined anatomical borders (for example, physeal scars). We can define "ELMSI with unknown cause" an entity where the characteristic MR appearance is associated with the absence of specific signs of an underlying condition. However, it is more often an important finding indicating the presence of an underlying disease, and we describe this case as "ELMSI with known cause." It presents a dynamic behavior and its evolution can largely vary. It initially corresponds to an acute inflammatory response with edema, before being variably replaced by more permanent marrow remodeling changes such as fibrosis or myxomatous connective tissue that can occur over time. It is important to study ELMSI variations over time in order to evaluate the activity state and therapeutic response of an inflammatory chronic joint disease, the resolution of a trauma, and the severity of an osteoarthritis. We propose a narrative review of the literature dealing with various subjects about this challenging topic that is imaging, temporal evolution, etiology, differential diagnoses, and possible organization, together with a pictorial essay.

Lateral femoral condyle insufficiency fractures: imaging findings, demographics, and analysis of outcomes

OBJECTIVE

To describe imaging characteristics and demographics of lateral femoral condyle insufficiency fractures (LFCIFs) and identify characteristics associated with progression to epiphyseal collapse.

MATERIALS AND METHODS

A retrospective review of 105 consecutive patients with LFCIF was performed (mean age 58.1 years) after excluding post-traumatic and pathological fractures. Lesion size and location, presence of bone marrow edema-like signal, soft tissue edema, chondrosis grade, and meniscus pathology were documented. Demographics were recorded from the electronic patient record. Follow-up MRI and/or radiographs were evaluated for healing/stability or progression to epiphyseal collapse. Bone mineral density was assessed from dual-energy x-ray absorptiometry (DEXA) scans and/or radiographs.

RESULTS

Fifty-six female and 49 male subjects were included. Female subjects were older at presentation (60.5 versus 56.3 years, p = .02). A total of 61.7% of the subjects with available DEXA and/or radiographs had osteopenia/osteoporosis. The central weight-bearing (61%) and outer condyle (54.3%) were most involved. High-grade chondrosis was present in ≥ 1 compartment in 70.5% including 42% in the lateral compartment. A total of 67.6% had ≥ 1 meniscus tear with similar frequency of medial and lateral tears (47.6% versus 41%). Bone marrow edema-like signal was present in all cases; soft tissue edema was present in 83.8%. Fifty-three subjects had available follow-up MRI (n = 24) and/or radiographs (n = 29). Increased age, fracture dimensions, presence of medial meniscus tears, and high-grade patellofemoral chondrosis were associated with progression (p ≤ .05).

CONCLUSION

LFCIFs are associated with meniscus tears, high-grade chondrosis, and osteopenia/osteoporosis with more global knee pathology present when compared with medial femoral condyle insufficiency fracture. Increased age, medial meniscus tears, fracture dimensions, and high-grade patellofemoral chondrosis were associated with progression.

The SIFK score: a validated predictive model for arthroplasty progression after subchondral insufficiency fractures of the knee

PURPOSE

The purpose of this study was to create a predictive model utilizing baseline demographic and radiographic characteristics for the likelihood that a patient with subchondral insufficiency fracture of the knee will progress to knee arthroplasty with emphasis on clinical interpretability and usability.

METHODS

A retrospective review of baseline and final radiographs in addition to MRIs were reviewed for evaluation of insufficiency fractures and associated injuries. Patient and radiographic factors were used in building predictive models for progression to arthroplasty with Train: Validation: Test subsets. Multiple models were compared with emphasis on clinical utility.

RESULTS

Total of 249 patients with a mean age of 64.6 (SD 10.5) years were included. Knee arthroplasty rate was 27% at mean of 4 years of follow-up. Lasso Regression was non-inferior to other models and was chosen for ease of interpretability. In order of importance, predictors for progression to arthroplasty included lateral meniscus extrusion, Kellgren-Lawrence Grade 4, SIFK on MFC, lateral meniscus root tear, and medial meniscus extrusion. The final SIFK Score stratified patients into low-, medium-, and high-risk categories with arthroplasty rates of 8.8%, 40.4%, and 78.9% (p < 0.001) and an area under the curve of 82.5%.

CONCLUSION

In this validated model, lateral meniscus extrusion, K-L Grade 4, SIFK on MFC, lateral meniscus root tear, and medial meniscus extrusion were the most important factors in predicting progression to arthroplasty (in that order). This model assists in patient treatment and counseling in providing prognostic information based on patient-specific risk factors by classifying them into a low-, medium-, and high-risk categories. This model can be used both by medical professionals treating musculoskeletal injuries in guiding patient decision making.

LEVEL OF EVIDENCE

Level III.

Spontaneous Osteonecrosis/Subchondral Insufficiency Fractures of the Knee: High Rates of Conversion to Surgical Treatment and Arthroplasty

BACKGROUND

Spontaneous osteonecrosis of the knee has recently been termed subchondral insufficiency fracture of the knee (SIFK) to appropriately recognize the etiology of mechanical overloading of the subchondral bone. The purpose of this study was to assess clinical outcomes of SIFK based on progression to surgical treatment and arthroplasty, and to evaluate the risk factors that increase the progression to arthroplasty.

METHODS

A retrospective review was performed on patients with a diagnosis of SIFK, as confirmed with use of magnetic resonance images (MRIs). Baseline and final radiographs were reviewed. Baseline MRIs were also reviewed for injury characteristics. Failure was defined as progression to surgical treatment or conversion to arthroplasty.

RESULTS

Two hundred twenty-three patients (71% female) with a mean age of 65.1 years were included. SIFK affected 154 femora (69%) and 123 tibiae (55%), with medial compartment involvement in 198 knees (89%); 74% of medial menisci had root or radial tears, with a mean extrusion of 3.6 mm. Varus malalignment was identified in 54 (69%) of 78 knees. Seventy-six (34%) of all patients progressed to surgical intervention at 2.7 years, and 66 (30%) underwent arthroplasty at 3.0 years. The rates of conversion to surgical intervention and arthroplasty increased to 47% (37 of 79; p = 0.04) and 37% (29 of 79; p = 0.09), respectively, in patients with >5 years of follow-up. The 10-year survival rate free of arthroplasty for patients with SIFK on the medial femoral condyle (p < 0.01), SIFK on the medial tibial plateau (p < 0.01), medial meniscal extrusion (p = 0.01), varus alignment (p = 0.02), and older age (per year older; p = 0.003) was significantly higher than the survival rates of those without each respective condition.

CONCLUSIONS

Subchondral insufficiency fractures predominantly involve the medial compartment of the knee and commonly present with medial meniscal root and radial tears. Approximately one-third of patients progressed to total knee arthroplasty. Baseline arthritis, older age, location of the insufficiency fracture on both the medial femoral condyle and medial tibial plateau, meniscal extrusion, and varus malalignment were all associated with progression to arthroplasty.

LEVEL OF EVIDENCE

Prognostic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Longitudinal MRI structural findings observed in accelerated knee osteoarthritis: data from the Osteoarthritis Initiative

OBJECTIVE

To analyze structural, longitudinal MRI findings during the development of accelerated knee osteoarthritis (AKOA) over 4 years.

MATERIALS AND METHODS

From the Osteoarthritis Initiative (OAI), knees with no radiographic osteoarthritis (KL 0/1) developing advanced-stage osteoarthritis (KL 3/4; AKOA) within a 4-year (y) timeframe were selected. MRIs were graded using the modified Whole-Organ Magnetic Resonance Imaging Score (WORMS) at the beginning of the 4-year timeframe (index visit), at 2-year, and 4-year follow-up. Morphological and clinical findings associated with KL 3/4 onset within 2 years compared to 4 years were assessed using generalized estimating equations.

RESULTS

AKOA was found in 162 knees of 149 subjects (age 63.25 ± 8.3; 103 females; BMI 29.4 ± 3.9). Moderate to severe meniscal lesions WORMS ≥ 3 were present in 25% (41/162) at the index visit, 64% (104/162) at 2-year and 93% (151/162) at 4-year follow-up. Meniscal extrusion was the most prevalent finding (ranging from 18% at the index visit, 45% at 2-year and 94% at 4-year follow-up) and root tears were the most common types of tears (9% at the index visit; 22% at 2 years and 38% at 4 years). Risk factors associated with KL 3/4 onset within 2 years included root tears at the index visit (adjusted OR, 2.82; 95% CI: 1.33, 6.00; p = 0.007) and incident knee injury (42%, 49/116 vs. 24%, 11/46, p = 0.032).

CONCLUSIONS

Meniscal abnormalities, in particular extrusion and root tears, were the most prevalent morphological features found in subjects with AKOA. These results suggest that meniscal abnormalities have a significant role in accelerated progression of OA.

The role of radiography and MRI for eligibility assessment in DMOAD trials of knee OA

Currently, no disease-modifying osteoarthritis drugs (DMOADs) have been approved. Past clinical trials have failed for several reasons, including the commonly applied definition of eligibility based on radiographic assessment of joint structure. In the context of precision medicine, finding the appropriate patient for a specific treatment approach will be of increasing relevance. Phenotypic stratification by use of imaging at the time of determining eligibility for clinical trials will be paramount and cannot be achieved using radiography alone. Furthermore, identification of joints at high risk of rapid progression of osteoarthritis is needed in order to enable a more efficient DMOAD trial design. In addition, joints at high risk of collapse need to be excluded at screening. The use of MRI might offer advantages over radiography in this context. Technological advances and simplified image assessment address many of the commonly perceived barriers to the application of MRI to assessment of eligibility for DMOAD clinical trials.

Prayer's fracture: rare cases of knee insufficiency fracture in non-weight-bearing femoral condyle

Insufficiency fractures are a relatively common sub-type of stress fractures and occur as a result of decreased bone resistance due to underlying conditions such as osteoporosis. Insufficiency fractures of the knee most commonly occur at the central weight-bearing zone of the medial femoral condyle. We present five unusual cases of insufficiency fractures occurring at the posterior non-weight-bearing zone of condyles. After investigating commonalities between these patients, we discovered that all of these patients performed the daily practice of prayer rituals that include high knee flexion. We have chosen to coin this type of fracture a "Prayer's fracture". Considering the mechanics of high knee flexion, transient changes in the weight-bearing zone of knee explain the unusual location of this fracture. We describe these cases, the characteristic imaging appearance, and the probable biomechanics that we believe predispose patients to this type of injury.

The Role of Meniscal Tears in Spontaneous Osteonecrosis of the Knee: A Systematic Review of Suspected Etiology and a Call to Revisit Nomenclature

BACKGROUND

The cause of spontaneous osteonecrosis of the knee (SONK) and postarthroscopic osteonecrosis of the knee is unknown, and the mechanisms involved have been poorly characterized.

HYPOTHESIS/PURPOSE

The purpose of this study was to perform a detailed systematic review of the literature to examine proposed etiological mechanisms for SONK in order to establish an improved understanding of the processes involved. We hypothesized that the etiology of SONK would be multifactorial.

STUDY DESIGN

Systematic review.

METHODS

A systematic review of the literature was performed by searching PubMed, Medline, Cochrane Database of Systematic Reviews, and the Cochrane Central Register of Controlled Trials. Inclusion criteria were all original research articles presented in the English language that reported on the suspected etiology of SONK. Reviews, case reports with fewer than 3 patients, cost-effectiveness studies, technical reports, editorial articles, surveys, special topics, letters to the editor, personal correspondence, and studies that only proposed factors for the progression of SONK were excluded.

RESULTS

After a comprehensive review of 255 articles, 26 articles were included for final analysis. Twenty-one (80.7%) of 26 articles implicated the role of the meniscus in the development of SONK, in an association with either meniscal tears or its development after meniscectomy. The medial meniscus and posterior meniscal root tears were implicated more frequently. All 4 studies incorporating histological findings supported the insufficiency fracture hypothesis as a pathological basis of SONK.

CONCLUSION

Physicians should be cognizant of the high prevalence of medial meniscus root tears in patients with SONK. Meniscectomy and meniscal tears, particularly of the medial meniscus posterior root, increase contact pressures and create an environment from which insufficiency fractures can emanate. We believe the term SONK is a misrepresentation of the etiology and pathogenesis of the condition and should be replaced with subchondral insufficiency fractures of the knee. Further elucidation of the etiology is required.

[Analysis of medial unicompartmental knee arthroplasty for patients with spontaneous osteonecrosis of the knee]

Objective

To analyse the effectiveness of unicompartmental knee arthroplasty (UKA) for the patients with spontaneous osteonecrosis of the knee (SONK).

Methods

Between January 2012 and December 2016, 31 patients with SONK was admitted and treated with medial UKA. All patients were examined by both plain radiography and magnetic resonance images. The patients were composed of 5 men and 26 women with an average age of 64.3 years (range, 48-79 years), and with 16 left joints and 15 right joints. The average disease duration was 14.7 months (range, 6-26 months). Preoperative visual analogue scale (VAS) was 6.00±1.15, Hospital for Special Surgery (HSS) score was 55.77±11.03, and knee range of motion (ROM) was (114.68±10.40)°. The imaging examinations showed that all the lesions were located in the medial compartment of the knee joint and there were 19 patients with Aglietti stage Ⅳ and 12 patients with Aglietti stage Ⅴ. Preoperative femorotibial angle (FTA) was (177.39±1.63)° and posterior tibial slope (PTS) was (84.05±1.39)°.

Results

All the incisions healed by first intention. All patients were followed up 14-46 months (mean, 25 months). At last follow-up, VAS score was 2.06±0.72 and HSS score was 86.45±3.67, which both improved significantly when compared with preoperative scores ( t=22.73, P=0.00; t=-14.72, P=0.00). ROM was (118.06±3.80)° with no significant difference when compared with preoperative ROM ( t=-1.78, P=0.08). The X-ray films showed there was no severe adverse events, such as periprosthetic infection, aseptic loosening, bearing dislocation, and so on. At last follow- up, PTS was (85.30±1.19)° with significant difference compared with preoperative one ( t=-4.07, P=0.00); while FTA was (177.51±1.98)° with no significant difference when compared with preoperative FTA ( t=-0.38, P=0.71).

Conclusion

UKA may be an optional management for SONK with minimally invasive, bone-preserving, and rapid recovery.

Osteochondral Lesions of the Knee: Differentiating the Most Common Entities at MRI

Several pathologic conditions may manifest as an osteochondral lesion of the knee that consists of a localized abnormality involving subchondral marrow, subchondral bone, and articular cartilage. Although understanding of these conditions has evolved substantially with the use of high-spatial-resolution MRI and histologic correlation, it is impeded by inconsistent terminology and ambiguous abbreviations. Common entities include acute traumatic osteochondral injuries, subchondral insufficiency fracture, so-called spontaneous osteonecrosis of the knee, avascular necrosis, osteochondritis dissecans, and localized osteochondral abnormalities in osteoarthritis. Patient demographics, the clinical presentation, and the role of trauma are critical for differential diagnosis. A localized osteochondral defect can be created acutely or can develop as an end result of several chronic conditions. MRI features that aid in diagnosis include the location and extent of bone marrow edema, the presence of a fracture line, a hypointense area immediately subjacent to the subchondral bone plate, and deformity of the subchondral bone plate. These findings are essential in diagnosis of acute traumatic injuries, subchondral insufficiency fracture, and its potentially irreversible form, spontaneous osteonecrosis of the knee. If the lesion consists of a subchondral region demarcated from the surrounding bone, the demarcation should be examined for completeness and the presence of a "double-line sign" that is seen in avascular necrosis or findings of instability, which are important for proper evaluation of osteochondritis dissecans. Subchondral bone plate collapse, demonstrated by the presence of a depression or a fluid-filled cleft, can be seen in advanced stages of both avascular necrosis and subchondral insufficiency fracture, indicating irreversibility. Once the diagnosis is established, it is important to report pertinent MRI findings that may guide treatment of each condition. ^©RSNA, 2018 An earlier incorrect version of this article appeared online. This article was corrected on August 23, 2018.

Bone Marrow Lesion: Image, Clinical Presentation, and Treatment

In this article, the cause, histology, imaging characteristics, clinical presentation, and treatment of these lesions are thoroughly discussed. Bone marrow edema is the generic term classically used to describe the high-signal-intensity alterations detected on magnetic resonance fluid-sensitive sequences. The significance of bone marrow edema for the patient’s clinical condition and the prognosis of the affected joint is being increasingly investigated and discussed, and situations characterized by subchondral insufficiency are receiving increasing attention. More recent studies found some important correlations between bone marrow lesions and patient’s pain and osteoarthritis progression. Conservative treatment is based on anti-inflammatory and analgesic uses according to the patient’s pain, combined with reduced load on the affected limb. Regarding surgical treatment, subchondroplasty is an option still in development, albeit with promising initial results.

Subchondral insufficiency fracture of the knee: A recognizable associated soft tissue edema pattern and a similar distribution among men and women

OBJECTIVE

Primary: to describe the presence and pattern of soft tissue edema in subchondral insufficiency fractures of the knee (SIFK). Secondary: to investigate the gender distribution and identify factors associated with disease progression.

METHODS

MR images of 74 SIFKs in 74 patients were retrospectively reviewed for soft tissue edema presence and location, meniscal tears and extrusion and synovitis. The clinical records were reviewed for age, gender, and BMI. Follow up examinations were reviewed to assess for progression. Data were analyzed for gender distribution and for association between each imaging finding as a predictor of SIFK location and progression.

RESULTS

Soft tissue edema was present in 89% (66/74) of SIFK. It was located around the MCL in 78% (58/74), posterior to and abutting on the posterior distal femur in 68% (50/74), around to the tibia in only 18% (13/74), but when present it strongly predicted the presence of a medial tibial plateau SIFK (p=5.6×10^-12). Edema extended to the vastus medialis fascia in 51% (38/74) and vastus lateralis fascia in 24% (18/74). Gender distribution was 1:1 (males=38, females=36), most common in the 6th decade (29/74, 39%). Lesion progression showed a trend towards being more common in females (8/9, 89%) compared to males (9/16, 56%), and in patients with meniscal extrusion (≥3mm) (13/14, 93%) compared to those with no extrusion (2/7, 29%).

CONCLUSION

A recognizable soft tissue edema pattern is seen in SIFK and may have an important role in early diagnosis. Also, SIFK may affect equally males and females in the 6th decade and may progress more in females. Meniscal extrusion may predispose to disease progression.