Early MRI diagnosis and non-surgical management of spontaneous osteonecrosis of the knee

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.

Bilateral trochlear subchondral insufficieny fracture of the knee in a professional cyclist

This case report presents a rare case of subsequent ipsilateral and contralateral subchondral insufficiency fracture of the knee (SIFK) in the trochlea of the femur within months, manifested in a professional cyclist. SIFKs in the trochlea have not yet been reported in the literature; however, their appearance in a professional cyclist might be explained by the amount of repetitive pressure on the patellofemoral joint when cycling. In both instances, atraumatic anterior knee pain occurred, resolving after conservative treatment for 6-9 weeks. The patient reached their previous activity level. The authors believe SIFK in the younger population may be more common than currently perceived due to its self-limiting behaviour and a lack of performing immediate MRIs in this younger group whenever an overload injury is suspected.

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.

Inflammation and subsequent nociceptor sensitization in the bone marrow are involved in an animal model of osteoarthritis pain

AIMS

This study aimed to determine whether pathological changes in the bone marrow cause Osteoarthritis (OA) pain based on magnetic resonance imaging (MRI), immunohistochemistry, and electrophysiology.

MAIN METHODS

Adjuvant-induced arthritis (AIA) was achieved by injecting 150 μL of complete Freund's adjuvant into the right knee joints of male Sprague-Dawley rats. AIA rats were compared with saline-injected rats.

KEY FINDINGS

AIA significantly induced mechanical hyperalgesia and spontaneous pain in the right hind paw 1-14 days after induction. Intratibial injection of 50 μL of 1 % lidocaine significantly suppressed AIA-induced mechanical hyperalgesia (p = 0.0001) and spontaneous pain (p = 0.0006) 3 days after induction. In T2-weighted MRI, AIA induced high-signal intensity within the proximal tibial metaphysis, and the mean T2 values in this area significantly increased on days 3 (p = 0.0043) and 14 (p = 0.0012) after induction. AIA induced intraosseous edema and significantly increased the number of intraosseous granulocytes on days 3 (p < 0.0001) and 14 (p < 0.0001) after induction. The electrophysiological study on days 3-7 after induction showed significantly increased spontaneous firing rates (p = 0.0166) and evoked responses to cutaneous stimuli (brush, p < 0.0001; pinching, p = 0.0359) in the right hind paw plantar surface and intratibial stimuli (p = 0.0002) in wide-dynamic-range neurons of the spinal dorsal horn.

SIGNIFICANCE

Intraosseous changes caused by OA induce hypersensitivity in the sensory afferents innervating bone marrow may be involved in OA pain. Novel bone marrow-targeted therapies could be beneficial for treating OA pain.

Mosaicplasty With High Tibial Osteotomy for Knee Subchondral Insufficiency Fracture Had Better Magnetic Resonance Observation of Cartilage Repair Tissue Scores With Less Bone Marrow Edema and Better Plug Union and Less Plug Necrosis Compared With Mosaicplasty Alone

PURPOSE

To determine the magnetic resonance imaging (MRI) findings after mosaicplasty (MOS) for knee subchondral insufficiency fracture (SIFK), and to analyze the relationship between MRI findings and clinical outcomes.

METHODS

We retrospectively reviewed the cases of consecutive patients who underwent MOS for SIFK with/without high tibial osteotomy (HTO) between January 1998 and December 2015. The MRI findings at 12 months after the surgery were assessed by the modified magnetic resonance observation of cartilage repair tissue (MOCART) score to determine the degree of bone marrow edema (BME), plug union, and plug necrosis. The clinical outcomes were assessed by Lysholm score to clarify the minimal clinically important difference (MCID) and patient acceptable symptom state analysis.

RESULTS

In total, 58 patients (17 men and 41 women) were enrolled in this study. Among them, 30 knees were treated by MOS alone and 28 knees were treated by MOS with HTO. The MOCART scores of patients who received MOS alone were significantly lower in BME score (P = .0060), plug union score (P = .0216), and in plug necrosis score (P = .0326) than patients who received MOS with HTO. BME lesion was less likely to persist among elderly (odds ratio 1.20, P = .0248) and female (OR 41.8, P = .0118) patients. The MCID of Lysholm score was 6.6 in MOS alone and 8.4 in MOS with HTO cases, but there were no significant association between MRI findings and the postoperative Lysholm score.

CONCLUSIONS

The MOS with HTO cases had better MOCART scores with less BME, better plug union, and less plug necrosis compared with MOS alone cases. Female and older patients had better resolution of BME, but there was no significant correlation between MRI findings and the postoperative Lysholm score. All cases in both groups showed improvement of Lysholm score exceeding MCID; thus, MOS may be effective as a joint preserving surgery for SIFK.

LEVEL OF EVIDENCE

Level IV, clinical case series.

Osteonecrosis of the Knee: Not all Bone Edema is the Same

Knee pain is among the most common complaints that an orthopedic surgeon may see in practice. It is often worked up with X-rays and MRI, leading to a myriad of potential diagnoses ranging from minimal edema patterns to various types of osteonecrosis. Similarities in certain causes can pose diagnostic challenges. The purpose of this review was to present the 3 types of osteonecrosis observed in the knee as well as additional causes to consider to help aid in the diagnosis and treatment..

A Case of Subchondral Insufficiency Fracture of the Knee at Lateral Femoral Condyle Treated With Unicompartmental Knee Arthroplasty

Spontaneous insufficiency fracture of the knee is a potentially devastating yet poorly understood disease entity that can lead to secondary osteoarthritis. Most cases involve the medial femoral condyle, and the lateral femoral condyle is rarely affected. The optimal treatment for spontaneous insufficiency fracture of the lateral femoral condyle remains undetermined, and there are no previous dedicated reports on treatment outcome with unicompartmental knee arthroplasty. A middle-aged lady presented with subacute left knee pain and a locked knee. Subsequent imaging studies revealed a spontaneous insufficiency fracture of the lateral femoral condyle. In view of the isolated compartment involvement, unicompartmental knee arthroplasty was performed with satisfactory outcome. At 1 year postoperatively, the patient had complete resolution of knee pain and was able to resume working.

Treatment options for secondary osteonecrosis of the knee

Knee osteonecrosis is a debilitating progressive degenerative disease characterized by subchondral bone ischemia. It can lead to localized necrosis, tissue death, and progressive joint destruction. For this reason, it is essential to diagnose and treat this disease early to avoid subchondral collapse, chondral damage, and end-stage osteoarthritis, where the only solution is total knee arthroplasty. Three types of knee osteonecrosis have been documented in the literature: spontaneous or primitive, secondary, and post arthroscopy. Spontaneous osteonecrosis is the most common type studied in the literature. Secondary osteonecrosis of the knee is a rare disease and, unlike the spontaneous one, involves patients younger than 50 years. It presents a particular set of pathological, clinical, imaging, and progression features. The management of secondary osteonecrosis is determined by the stage of the disorder, the clinical manifestation, the size and location of the lesions, whether the involvement is unilateral or bilateral, the patient's age, level of activity, general health, and life expectancy. This review aims to present the recent evidence on treatment options for secondary osteonecrosis of the knee, including conservative treatment, joint preserving surgery, and knee replacement.

Minimally invasive cell-based therapy for symptomatic bone marrow lesions of the knee: A prospective clinical study at 1 year

Bone Marrow Lesions (BMLs) are typical findings in magnetic resonance imaging (MRI) present in different pathologies, such as spontaneous insufficiency fractures, osteonecrosis, transient BML syndromes, osteoarthritis, and trauma. The etiology and evolution of BMLs in multiple conditions remain unclear. There is still no gold standard protocol for the treatment of symptomatic BMLs in the knee. The biologic augmentation by Osteo Core Plasty is a new treatment modality showing promising results reducing pain with the aim to stop the progression of the disease. The purpose of this prospective study is to report the clinical outcomes and safety of Osteo Core Plasty for the treatment of symptomatic BMLs in the knee. Fifteen patients with symptomatic BMLs of the knee treated with the Osteo Core Plasty technique were included and followed prospectively for a minimum of 12 months. Each patient was evaluated before the surgery and respectively at 6 and 12 months using the Tegner Score, Marx Score, the International Knee Documentation Committee (IKDC), the Knee Injury and Osteoarthritis Outcome Score (KOOS) divided in pain, activity daily living (ADL) and Quality of Life (QOL) subscale and the Visual Analogue Scale (VAS) for pain. All clinical scores except Tegner and Marx score showed an overall statistically significant improvement through the entire follow-up (p<0.05) and a significant improvement (p<0.05) between each follow-up period (T0 versus T1; T0 versus T2; T1 versus T2). No complications were reported. These preliminary results confirm that biological subchondral bone augmentation by Osteo Core Plasty technique is a safe and effective minimally invasive treatment option for symptomatic BMLs in the knee at 1-year follow-up. There is still a need for high-quality RCTs studies and systematic reviews in the future to enhance further treatment strategies in preventing or treating BMLs of the knee.

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.

Effects of Light on Attention and Reaction Time: A Systematic Review

BACKGROUND

Accuracy, speed, efficiency, and applicability of activities in the workplace are among the most important effective factors on people's productivity, which is in turn affected by environmental factors, such as light. Therefore, the present research aimed to review the studies performed about the effects of light on attention and reaction time.

METHODS

This review study systematically searched articles from 2000-2019 in databases of Google Scholar, ISC, SID, Magiran, Web of Science, Science Direct, PubMed, and Scopus using keywords of light, lighting, attention, and reaction time. The titles and abstracts of articles containing relevant results over the past 20 years were extracted. Thereafter, they were categorized and analyzed according to the title, author name, publication year, study method, study type, and evaluation results.

RESULTS

Based on the results, the light with shorter wavelengths, higher intensity, and higher color temperature led to suppressed melatonin, higher consciousness, less somnolence, increased attention, and faster reaction time. Simultaneous exposure to harmful levels of environmental factors affects cognitive and physiological parameters, acting independently with a separate mechanism or synergistically with a similar mechanism. The best light in the regulation of psychological, biological, and cognitive processes is bright daylight in the morning with a short wavelength, high intensity, and more lasting effects.

CONCLUSION

As evidenced by the obtained results,  light is a powerful modulator of non-visual performance in cognitive tasks. The wavelength, color temperature, and light intensity modulate brain responses to cognitive tasks, including attention and reaction time. Therefore, these parameters, along with personal and environmental factors, should be considered in designing and using light.

Medial meniscus extrusion as a predictor for a poor prognosis in patients with spontaneous osteonecrosis of the knee

BACKGROUND

Risk factors for the progression of spontaneous osteonecrosis of the knee (SONK) remain unclear. The purpose of this study was to investigate the association between magnetic resonance imaging (MRI) findings of the meniscus and the prognosis of SONK.

METHODS

A total of 78 consecutive patients (female 85%; mean age 75.6 ± 7.2 years old) diagnosed with SONK were included. Of these, 30 patients did not receive surgery within 1 year from the onset of SONK (conservative group), while the remaining 48 patients underwent unicompartmental knee arthroplasty due to worsening of symptoms (UKA group). Using MRI findings obtained within 3 months of the onset, we compared the types of meniscus tear and medial meniscus extrusion between the conservative group and UKA group. We performed a receiver operating characteristics (ROC) analysis to estimate the cut-off value.

RESULTS

Patients in the UKA group showed greater medial meniscus extrusion (absolute value, 4.2 mm ± 1.9 vs. 2.8 mm ± 1.2, P = 0.001; relative percentage of extrusion (RPE), 45.7% ± 21.5 vs. 30.7% ± 12.9, P = 0.001) and a higher prevalence of radial tear (P = 0.021) than those in the conservative group. In the multivariate analysis, RPE remained a relevant independent factor (P = 0.035) for future UKA. An ROC analysis found that the cut-off point of RPE was 33% (sensitivity, 81.2%; specificity, 63.3%).

CONCLUSION

RPE was a predictor of the prognosis of patients who underwent UKA within 1 year after the onset of SONK. Our results suggest that patients with RPE ≥ 33% are at high risk for progression.

Subchondroplasty in the Treatment of Bone Marrow Lesions of the Knee: Preliminary Experience on First 15 Patients

Purpose  The aim of this prospective study was to assess the effectiveness in terms of pain relief and functional improvement of the Subchondroplasty procedure in the treatment of osteoarthritis-related bone marrow lesions (BMLs) of the knee. Methods  The study included first 15 consecutive patients undergone to Subchondroplasty procedure for the treatment of chronic degenerative BMLs in which previous conservative treatment have failed. Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) scores, Knee Injury and Osteoarthritis Outcome Scores (KOOS), and visual analog scale (VAS) pain scores were obtained preoperatively and at 1, 6, and 12 months of follow-up. Results  WOMAC scores significantly improved from 39.7 ± 20.2 before surgery to 26.8 ± 16.1 at the 1-month follow-up ( p  = 0.045). A further significant improvement to 15.5 ± 12.7 ( p  = 0.02) and to 8.6 ± 3.1 ( p  < 0.01) was obtained both at 6-month and at 1-year follow-up. KOOS scores improved significantly from 47.5 ± 16.6 before surgery to 65.4 ± 14.9 at 1 month ( p  = 0.013) and to 80.4 ± 15.1 at 6-month follow-up ( p  = 0.01). A further improvement to 85.6 ± 15.1 was recorded 1 year postoperatively, although nonsignificant. VAS score showed a significant improvement from 55.8 ± 20.5 preoperatively to 36.2 ± 16.9 at 1 month ( p  = 0.008) and to 18.2 ± 17.3 at 6-month follow-up ( p  = 0.005). This further improved to 12.8 ± 17.9 at 1-year follow-up, although not significantly. Conclusion  Subchondroplasty procedure represents a safe and valid surgical option in the treatment of osteoarthritis-related BMLs of the knee, providing an improvement in terms of pain relief and functional recovery. Longer studies are required to evaluate how long these improvements may last. Level of Evidence  Therapeutic case-series, Level IV study.

A Retrospective Study of Unicompartmental Knee Arthroplasty Functional Outcome and the Incidence of Medial Meniscus Posterior Root Tear in Spontaneous Osteonecrosis of the Knee

Background

Spontaneous osteonecrosis of the knee (SONK) can lead to severe knee osteoarthritis predominantly localized to the medial compartment. We aimed to determine whether unicompartmental knee arthroplasty was an effective treatment for primary SONK.

Methods

We analyzed the functional outcomes in 23 patients with SONK (with a magnetic resonance imaging- (MRI-) confirmed diagnosis) who underwent UKA at a single center. The mean follow-up time was 67 months post-UKA.

Results

Significant improvements in function were indicated by reduced Oxford Knee and Visual Analogue Scale scores after UKA, and there were no specific complications after the procedures. The incidence of MRI-identified medial meniscus posterior root tear (MMPRT) was 69.6% (16/23).

Conclusion

Unicompartmental arthroplasty for SONK is less destructive to the native knee structure than total knee arthroplasty but can achieve comparable prognosis with strict patient selection. While the precise etiology of SONK is unknown, one theory posits that a MMPRT may change the biomechanical circumstances of the knee joint, leading to osteonecrosis. Although not confirmatory, the high prevalence rate suggests that MMPRT may have a key role in the development of SONK. UKA is an effective treatment option for SONK, resulting in significant functional improvement. Long-term (>10 years) outcomes should be investigated.

Spontaneous osteonecrosis of the knee (SONK): The role of MR imaging in predicting clinical outcome

Background/aim

We try to investigate the association between patterns of imaging findings in patients who had a diagnosis of subchondral fracture around the knee, formerly known as SONK and their clinical outcome.

Materials and methods

We retrospectively identified 43 knees of 37 patients (28 males, 15 females) who had diagnosis of subchondral fractures around the knee. The mean age is 56-year-old (range 17-83). Musculoskeletal fellowship trained radiologist evaluated all 43 knee MRI in: 1)location of marrow edema 2)peri-osseous edema; 3) subchondral fracture line; 4) subchondral articular surface contour; 5)meniscal tear and extrusion; 6)adjacent soft tissue edema; 7) joint effusion. Independent clinical chart review was performed for clinical outcome with follow up time average of 13.3 months (range 0-88 months). Bad outcome was defined as worsening on imaging, continued complaint with surgical management and knee replacement or another episode of SONK. Chi-square analysis and Student's T tests were conducted to test the statistical significance of association between MR findings and outcomes. Statistical significance was set at p = 0.05 level.

Results

Of 43 knees, 6 patients had another episodes of SONK (14%), 11 patients were not improving or needed injection vs arthroscopy (26%), 4 patients required arthroplasty (9%), 22 patients had no negative outcome (51%). Gender, age, diabetic status, and location of the subchondral fracture show no influence on outcome. Worse outcome group had a significantly higher average BMI (31.7 vs. 28.0, P = 0.02). Positive change of subchondral articular surface contour is the only imaging finding with positive association with worse outcome (80% vs. 39.9%, P = 0.02). Presence of positive findings of above 3), 4), 5) and 6) had higher percentage of bad outcome (77.8%) compared to those with less positive findings (47.2%).

Conclusion

MR imaging findings may help at identifying SONK patient with potential risk of developing bad outcome.

Spontaneous osteonecrosis of the knee: what do we know so far? A literature review

PURPOSE

Spontaneous osteonecrosis of the knee (SONK) is said to be a relatively common disease which may lead to an end-stage osteoarthritis of the knee. The aim of this paper was to review the literature on this field published until now, discuss the results of both conservative and surgical treatment options, as well as to introduce new methods of treatment, which may be applicable in SONK treatment.

METHODS

We searched the PubMed and Cochrane databases until November 2019 and presented the most recent findings in this work.

RESULTS

The exact aetiology of SONK still remains unclear; however, recent studies suggested that early stage of SONK is rather a result of the subchondral fracture than primary osteonecrosis. So far described conservative treatment includes non-weight bearing or protected weight bearing with a knee brace, nonsteroidal anti-inflammatory drugs, analgesics, and bisphosphonates. Surgical management includes arthroscopic debridement, core decompression, osteochondral autograft, high tibial osteotomy, and unicompartmental knee arthroplasty or total knee arthroplasty.

CONCLUSIONS

Although the aetiology of SONK remains unknown, there are many treatment options, and the choice of the most suitable one is challenging. We think that subchondroplasty may be one of the effective methods.

Treatment of spontaneous osteonecrosis of the knee by daily teriparatide: A report of 3 cases

RATIONALE

Although the treatment of femoral head necrosis has already been established with the adoption of daily teriparatide, a clear consensus on the treatment of spontaneous osteonecrosis of the knee (SONK) has yet to be reached. Therefore, we focused on the treatment of SONK with daily teriparatide administration (20 μg, subcutaneous) and confirmed its effects to determine whether it is a valid option.

PATIENTS' CONCERNS

Three osteoporotic patients who were diagnosed with SONK complained of knee pain.

DIAGNOSIS

SONK was diagnosed on magnetic resonance imaging in all cases.

INTERVENTIONS

All patients took daily teriparatide as a treatment for SONK.

OUTCOMES

There was a significant and dramatic reduction in the visual analog scale score 1 month after treatment. After 6 months of treatment, the sizes of the affected SONK lesions were smaller than in the initial phase, and plain X-rays showed no further signs of progression.

LESSONS

Daily teriparatide might be an effective treatment for SONK.

Medial Unicompartmental Knee Arthroplasty for the Treatment of Focal Femoral Osteonecrosis

BACKGROUND

Previous research has indicated that unicompartmental arthroplasty may be an effective treatment for focal osteonecrosis in the knee; however, these reports have been composed of small patient cohorts and without characterization of the osteonecrotic lesions. Therefore, the purpose of this study was to investigate the effectiveness of unicompartmental arthroplasty for the treatment of focal osteonecrosis within the medial femoral condyle including an assessment of lesion size.

METHODS

A consecutive series of >5,000 unicompartmental knee arthroplasties performed at a single institution was retrospectively reviewed to identify cases of medial femoral condyle osteonecrosis with a minimum 2-year follow-up. Lesion size was classified according to the ratio of lesion width to condylar width, as well as lesion depth relative to condylar depth. Patient-reported outcome measures and need for a revision procedure were studied.

RESULTS

Sixty-four patients (32 males, 32 females; 65 knees) with a mean age of 64 years were included. The mean patient follow-up was 5.3 years (range, 2 to 12 years). The mean ratio of lesion width to condylar width was 64%, the mean lesion depth was 1.11 cm, and 82% of cases demonstrated subchondral collapse. At the time of the latest follow-up, patients demonstrated substantial improvements in the pain, function, and clinical components of the Knee Society Score, by 36, 25, and 51, respectively. Four patients (6%) required a revision, of which only 1 was for aseptic loosening of the femoral component.

CONCLUSIONS

Unicompartmental arthroplasty is an effective treatment for advanced-stage focal osteonecrosis of the medial femoral condyle. Loss of component fixation to the femoral condyle did not appear to be a substantial concern because there was only 1 femoral failure as a result of aseptic loosening, despite lesions affecting a significant portion of the femoral condyle.

LEVEL OF EVIDENCE

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

Clinical Characteristics and Treatment of Spontaneous Osteonecrosis of Medial Tibial Plateau: A Retrospective Case Study

Background:

In a small proportion of cases, spontaneous osteonecrosis of the knee (SONK) involves the medial tibial plateau (MT). Here, we introduced the clinical characteristics of spontaneous osteonecrosis of the MT and unicompartmental knee arthroplasty (UKA) as the favorable treatment for this situation based on a retrospective case study.

Methods:

Patients with spontaneous osteonecrosis of the MT, confirmed by magnetic resonance imaging (MRI) at Guangdong Provincial Hospital of Chinese Medicine (China) from March 2015 to June 2016, were included as a case serial and analyzed retrospectively. All patients underwent Oxford Medial UKA. The characteristics of their lesions, corresponding treatment, and results of follow-up were presented. The lesion scores and grade were determined according to the criteria of Ficat and Arlet.

Results:

In total, 22 patients (5 men, 17 women; mean age, 64.1 years) with spontaneous osteonecrosis of the MT were analyzed. The lesion stages assessment showed that 3 (14%) were Stage II, 10 (45%) were Stage III, 7 (32%) were Stage IV, and 2 (9%) were Stage V. In the sagittal plane, 7 (32%) were in the anterior region (MTa) and 15 (68%) were central (MTc). The lesion volume averaged 2.24 ± 0.79 cm³ (range: 1.57–3.08 cm³). Seventeen patients (77%) had Level III posterior medial meniscus root tears (MMRTs). All the patients underwent UKA. Average follow-up was 30.0 ± 6.4 months with a range of 23.0–38.0 months. The visual analog scale score was 7.78 ± 0.67 before surgery while decreased to 2.22 ± 1.09 at the final follow-up (P < 0.001). The Hospital for Special Surgery scores of pre-/post-surgery were 65.67 ± 5.45 and 84.10 ± 4.20, respectively (P < 0.001).

Conclusions:

SONK often occurs in the anterior and central tibial plateau due to abnormal stresses. Most of the patients had Level III posterior medial meniscus root tears. MRI is recommended for suspected cases to identify SONK at an early stage. The use of the Oxford Medial UKA for SONK of the MT is reliable both immediately and at follow-up.

Metaphyseal burst sign: A secondary sign on MRI of subchondral insufficiency fracture of the knee

INTRODUCTION

To describe a novel secondary sign of subchondral insufficiency fracture of the knee, metaphyseal burst sign (soft tissue oedema in the meta-epiphyseal region of the affected condyle).

METHODS

An electronic database research of 7926 knee MRI examinations was performed. Forty-eight scans were included in the study. The diagnosis of subchondral insufficiency fracture (SIF) was confirmed in a consensus review by one fellowship trained musculoskeletal (MSK) radiologist and one radiology fellow. The presence of metaphyseal burst sign was evaluated in the cohort.

RESULTS

Forty-one patients were included in the study (21 males, 20 females). The mean age was 61.5 years (range 41-80 years). The anatomical location was medial femoral condyle (n = 28), the lateral femoral condyle (n = 5) and medial tibial condyle (n = 8). The metaphyseal burst sign was present in 45 of the 48 scans reviewed. The average craniocaudal length of the soft tissue oedema defined as metaphyseal burst sign was 7 cm (range 10.5 to 4.5).

CONCLUSION

The metaphyseal burst sign is an early, indirect sign of SIF.

Fresh Osteochondral Allograft Transplantation for Spontaneous Osteonecrosis of the Knee: A Case Series

Background:

Spontaneous osteonecrosis of the knee (SONK) is a clinical entity identified by acute knee pain usually associated with joint effusion, with radiographic findings of a radiolucent defect on the weightbearing area of the femoral condyle. Conservative treatment is initially undertaken; however, surgical procedures are often necessary. Historically, surgical options have included core decompression, cartilage repair, high tibial osteotomy, or joint arthroplasty. Few studies in the literature have reported the use of fresh osteochondral allograft (OCA) for the treatment of SONK lesions.

Hypothesis:

OCA transplantation is an effective treatment for SONK lesions on the medial femoral condyle.

Study Design:

Case series; Level of evidence, 4.

Methods:

A case series was analyzed of 7 patients treated with OCA for large SONK lesions of the medial femoral condyle with a minimum 4-year follow-up. All patients experienced failure of at least 6 months of conservative treatment and declined arthroplasty as the form of definitive treatment for medial femoral condyle lesion. All patients underwent OCA of the medial femoral condyle. Mean lesion size was 4.6 cm² (range, 3.24-6.25 cm²), with a mean condylar width of 41.7 mm (range, 35.4-48.6 mm), resulting in a median proportion (lesion size/condylar width) of 56.8% (range, 32.7%-62.6%). The median surface allograft area was 5.1 cm² (range, 3.2-6.3 cm²).

Results:

The median follow-up was 7.1 years (range, 4.5-14.1 years). No patient had additional surgery following OCA transplant; the allograft failure rate was 0%. Subjective outcome scores from the International Knee Documentation Committee, Knee injury and Osteoarthritis Outcome Score, and modified Merle d’Aubigné-Postel scale improved from preoperative assessment to the latest follow-up. All patients were extremely satisfied with the results of the OCA transplant.

Conclusion:

Fresh OCA transplantation demonstrated excellent efficacy, durability, and satisfaction in this group of patients with isolated stage 2 and 3 SONK lesions who had experienced failure of conservative treatment. Fresh osteochondral allografts are an attractive method for surgical management of selected patients with spontaneous osteonecrosis of the knee.

Annual trends in knee arthroplasty and tibial osteotomy: Analysis of a national database in Japan

BACKGROUND

Various nationwide studies have reported differing annual trends in utilization of knee arthroplasty and tibial osteotomy. Using the Diagnosis Procedure Combination database in Japan, the present series examined annual trends and demographics in total knee arthroplasty (TKA), unicompartmental knee arthroplasty (UKA) and tibial osteotomy.

METHODS

All patients were identified who underwent TKA, UKA or tibial osteotomy for osteoarthritis, osteonecrosis or rheumatoid arthritis of the knee between July 2007 and March 2015.

RESULTS

A total of 170,433 cases of TKA, 13,209 cases of UKA and 8760 cases of tibial osteotomy were identified. The proportion of patients undergoing UKA rose from 4.0% in 2007 to 8.1% in 2014 (P<0.001), and that of tibial osteotomy from 2.6% in 2007 to 5.5% in 2014 (P<0.001); the proportion undergoing TKA fell from 93.4% in 2007 to 86.3% in 2014 (P<0.001). Between 2007 and 2014 the proportions of patients with osteonecrosis who underwent UKA and tibial osteotomy increased from 34.7% and 11.6% to 38.6% and 16.2%, respectively (P=0.001 for UKA and P=0.004 for tibial osteotomy). The proportions of patients with osteonecrosis undergoing UKA or tibial osteotomy were significantly greater than those with other diagnoses (P<0.001 for both).

CONCLUSIONS

The popularity of UKA and tibial osteotomy in Japan increased during the period 2007-2014 at the expense of TKA. The proportions of UKA and tibial osteotomy in patients with osteonecrosis also increased, and were larger than those in patients with other causative diseases.

Diseases of Subchondral Bone 2

Osteonecrosis of the knee can be divided into the following 3 categories: primary or Spontaneous osteonecrosis of the knee (SONK), secondary osteonecrosis (ON), and postarthroscopic osteonecrosis. Patient characteristics as well as underlying risk factors can help categorize the type of osteonecrosis and guide treatment. SONK was &filig;rst described by Ahlback et al in 1968. It is described as a disease of subchondral bone that leads to focal ischemia and bone marrow edema, necrosis, and possible subsequent structural collapse. SONK typically presents in the older women with frequent involvement of the medial femoral condyle. Secondary osteonecrosis is typically present in patients below 55 years of age. Unlike SONK, secondary ON presents multiple foci of bone marrow involvement with extension into the metaphysis and diaphysis. Postarthroscopic ON has been described after arthroscopic meniscectomy, shaver-assisted chondroplasty, anterior cruciate ligament reconstruction, and laser or radiofrequency-assisted debridement.

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.

Predictive factors for the progression of spontaneous osteonecrosis of the knee

PURPOSE

To assess potentially predictive factors that were evaluated 1 year after the onset of symptoms in patients with spontaneous osteonecrosis of the knee (SONK) and to determine receiver operating characteristic (ROC) curve cut-off values.

METHODS

Within 1 year of symptom onset, patients with SONK-selected treatment options, mainly based on severity of pain, chose either conservative treatment (n = 27 knees) or operative treatment (n = 27 knees). Knee and whole-leg radiographs, knee MRIs and bone mineral density scans of the lumbar spine, femoral neck and femoral condyles were obtained. The parameters measured were: (1) anatomical angle on whole-leg radiograph and (2) lesion size and medial meniscus extrusion on MRI.

RESULTS

The anatomical angle and lesion size in the sagittal section (depth) on MRI were markedly larger in the operative treatment group than those in the conservative treatment group. The anatomical angle and depth on MRI of SONK at Stages 1-3 were significantly different between groups, with odds ratios (95 % confidence intervals) of 1.16 (1.18-2.34) and 1.11 (1.01-1.23). One year after symptom onset, ROC curve cut-off value for anatomical angle was 180° and depth on MRI was 20 mm.

CONCLUSION

An anatomical angle >180° and depth >20 mm on MRI were predictive factors for a poorer prognosis 1 year after symptom onset in patients with SONK. Our results on radiographs and MRI provided a predictive prognosis for patients with SONK at the initial visit to their orthopaedic surgeons.

LEVEL OF EVIDENCE

III.

Spontaneous Osteonecrosis of the Knee: A Retrospective Analysis by Using MRI and DEXA

Objective:

Although there are many etiology and prediction for prognosis of spontaneous osteonecrosis of the knee (SONK) by using radiological examinations, these issue have not been clarified yet. Furthermore, most of the studies evaluated them by only radiological examination such as magnetic resonance imaging (MRI), bone mineral density (BMD) in dual-energy X-ray abosorptiometry (DEXA) or plain X-ray. Therefore, we focused our investigation on the measurements of the affected área in MRI and BMD in DEXA, and whether these results were conected with the cause and prognosis of SONK or not.

Method:

A consecutive case series of two groups composed of ten osteoporotic patients who were suffering from SONK was considered. Based on the severity or duration of pain, one group was treated with surgical procedure which was unicompartmental knee arthroplasty (UKA), the other received conservative treatment. Both groups underwent DEXA in their distal fêmur and próximal tíbia and all patients who took MRI measured the affected lesion in low and high intensity área on T2 weighted images. This data was analyzed from these areas and units.

Results:

Significant decrease in regional boné density of the affected femoral condyle compared to the unaffected side was observed. However, the boné mineral density in the affected side was similar in the non-operative and surgical group. The área of the lesion which showed in both low and high intensity indicated that the operation group was significantly larger than the conservative group on T2 weighted images.

Conclusion:

The cause and prognosis of SONK have a close relationship with the size of the affected lesion and decreased boné mineral density

The importance of early diagnosis in spontaneous osteonecrosis of the knee - A case series with six year follow-up

BACKGROUND

Spontaneous osteonecrosis of the knee has an unknown aetiology. Management options include conservative, surgical and pharmacological interventions. The aim of this study was to report the experience of the authors in conservative management of SONK using non-operative measures by analysing the functional outcome and need for surgical intervention.

MATERIALS AND METHODS

All patients treated for SONK between 1st August 2001 and 1st April 2014 were retrospectively reviewed. Treatment consisted of touch-down weight bearing for around six weeks. MR imaging was evaluated for size of lesion, the condyles involved and the time taken for resolution. Tegner Activity Scale, VAS pain, Lysholm, WOMAC and IKDC scores were recorded at presentation and final follow-up (mean six years, range six months to 13years).

RESULTS

Forty cases were included; the mean age of the group was 55.3years and 67.5% were male. The medial femoral condyle was the most commonly affected (52.5%). A statistically significant improvement was reported in all functional outcome measures (p<0.001). Only one patient required arthroscopic surgical intervention and no patients required arthroplasty during the follow-up period.

CONCLUSION

Early stage spontaneous osteonecrosis of the knee can be managed successfully without surgery if diagnosed early. Thus early investigation of acute knee pain with MRI scanning is recommended.

Bone marrow lesions and subchondral bone pathology of the knee

Bone marrow lesions (BMLs) around the knee are a common magnetic resonance imaging (MRI) finding. However, despite the growing interest on BMLs in multiple pathological conditions, they remain controversial not only for the still unknown role in the etiopathological processes, but also in terms of clinical impact and treatment. The differential diagnosis includes a wide range of conditions: traumatic contusion and fractures, cyst formation and erosions, hematopoietic and infiltrated marrow, developmental chondroses, disuse and overuse, transient bone marrow oedema syndrome and, lastly, subchondral insufficiency fractures and true osteonecrosis. Regardless the heterogeneous spectrum of these pathologies, a key factor for patient management is the distinction between reversible and irreversible conditions. To this regard, MRI plays a major role, leading to the correct diagnosis based on recognizable typical patterns that have to be considered together with coexistent abnormalities, age, and clinical history. Several treatment options have been proposed, from conservative to surgical approaches. In this manuscript the main lesion patterns and their management have been analysed to provide the most updated evidence for the differential diagnosis and the most effective treatment.

Analysis of risk factors for poor prognosis in conservatively managed early-stage spontaneous osteonecrosis of the knee

BACKGROUND

Management guidelines for early-stage spontaneous osteonecrosis of the knee (SONK) have not been established. The purposes of this study were to review the outcome of conservative treatment for patients with early-stage SONK and to examine clinical factors affecting the prognosis.

METHODS

Diagnosis of early-stage SONK was made based on the criteria consisting of specific clinical features including magnetic resonance imaging (MRI) findings. During the study period, all patients with this diagnosis underwent standardized conservative treatment. The study population comprised 38 knees in 36 patients with a mean age at presentation of 66.4years. The mean follow-up period was 34.9months. During the treatment course, progressive joint space narrowing or collapse of bony contours identified in serial follow-up radiographs was regarded as indicating a poor prognosis. The significance of potential prognostic factors such as age, gender, obesity, coronal alignment, lesion size, and MRI findings was analyzed using a multivariate logistic regression analysis.

RESULTS

The prognosis was defined to be poor in eight knees (21.1%). The multivariate logistic regression analysis for potential risk factors revealed that only varus alignment with a femorotibial angle (FTA) of 180° or more on the initial radiograph was significantly associated with the poor prognosis (P=0.01, odds ratio 28.1) while no other factors significantly correlated with the prognosis.

CONCLUSIONS

Approximately 80% of patients with early-stage SONK could be managed successfully with conservative treatment without progression of the disease process. The presence of varus deformity (FTA of 180° or more) was significantly associated with poor prognosis complicated with progressive deformity and prolonged disability.

LEVEL OF EVIDENCE

Level IV, case series.

Osteonecrosis of the knee: review

Osteonecrosis is a devastating disease that can lead to end-stage arthritis of various joint including the knee. There are three categories of osteonecrosis that affect the knee: spontaneous osteonecrosis of the knee (SONK), secondary, and post-arthroscopic. Regardless of osteonecrosis categories, the treatment of this disease aims to halt further progression or delay the onset of end-stage arthritis of the knee. However, once substantial joint surface collapse has occurred or there are sign of degenerative arthritis, joint arthroplasty is the most appropriate treatment option. Currently, the non-operative treatment options consist of observation, non-steroidal anti-inflammatory drugs (NSAIDs), protected weight bearing, and analgesia as needed. Operative interventions include joint preserving surgery, unilateral knee arthroplasty (UKA), or total knee arthroplasty (TKA) depending on the extent and type of disease. Joint preserving procedures (i.e., arthroscopy, core decompression, osteochondral autograft, and bone grafting) are usually attempted in pre-collapse and some post-collapse lesions, when the articular cartilage is generally intact with only the underlying subchondral bone being affected. Conversely, after severe subchondral collapse has occurred, procedures that attempt to salvage the joint are rarely successful and joint arthroplasty are necessary to relieve pain. The purpose of this article is to highlight the recent evidence concerning the treatment options across the spectrum of management of osteonecrosis of the knee including lesion observation, medications, joint preserving techniques, and total joint arthroplasties.

MRI of subchondral fractures: a review

Several authors have recently emphasized the role of magnetic resonance imaging (MRI) in the diagnosis of subchondral fractures. There is increasing interest about this type of fractures, mostly because they have been implicated in the genesis of some well-known destructive articular conditions whose cause was previously undetermined, such as distal clavicular osteolysis, rapidly progressive osteoarthritis of the hip, spontaneous osteonecrosis of the knee and adult-type Freiberg's infraction. Subchondral fractures may ultimately lead to bone collapse, secondary osteonecrosis and severe articular damage, and there may be rapid progression of joint destruction over a period of weeks to months. It has been suggested that timely diagnosis might potentially improve the outcome and avoid the onset of destructive joint disease, making MRI even more important in this setting. The fracture line usually appears as a band of low signal intensity in the subchondral bone plate, adjacent to the articular surface, most often surrounded by bone marrow edema. In this article the authors review the most relevant imaging features of subchondral fractures in several joints, stressing the importance of early recognition for a better outcome.

The natural course of spontaneous osteonecrosis of the knee (SPONK): a 1- to 27-year follow-up of 40 patients

BACKGROUND AND PURPOSE

Spontaneous osteonecrosis of the knee (SPONK) is a painful lesion in the elderly, frequently leading to osteoarthritis and subsequent knee surgery. We evaluated the natural course and long-term consequences of SPONK in terms of need for major knee surgery.

METHODS

Between 1982 and 1988, 40 consecutive patients were diagnosed with SPONK. The short-term outcome has been reported previously (1991). After 1-7 years, 10 patients had a good radiographic outcome and 30 were considered failures, developing osteoarthritis. In 2012, all 40 of the patients were matched with the Swedish Knee Arthroplasty Register (SKAR) and their medical records were reviewed to evaluate the long-term need for major knee surgery.

RESULTS

At the 2012 review, 33 of the 40 patients had died. The mean follow-up time from diagnosis to surgery, death, or end of study was 9 (1-27) years. 17 of 40 patients had had major knee surgery with either arthroplasty (15) or osteotomy (2). All operated patients but 1 were in the radiographic failure group and had developed osteoarthritis in the study from 1991. 6 of 7 patients with large lesions (> 40% of the AP radiographic view of the condyle) at the time of the diagnosis were operated. None of the 10 patients with a lesion of less than 20% were ever operated.

INTERPRETATION

It appears that the size of the osteonecrotic lesion can be used to predict the outcome. Patients showing early signs of osteoarthritis or with a large osteonecrosis have a high risk of later major knee surgery.

Spontaneous osteonecrosis of the knee (SONK)

PURPOSE

Spontaneous osteonecrosis of the knee (SONK/Morbus Ahlback) mainly affects the medial condyle of elderly women. It is assumed that localized vascular insufficiency leads to necrosis of the subchondral bone with subsequent disruption of the nutrition supply to the cartilage above. The aetiology remains unclear in detail. Operative treatment procedures compete against non-operative strategies, whereas the outcome is unpredictable in many cases.

METHOD

A consecutive case series of five patients suffering from SONK was analysed. All patients underwent a clinical examination, magnetic resonance imaging (MRI) and dual-energy X-ray absorptiometry scan, as well as laboratory analyses and visual analogue scale (VAS) evaluation. Our treatment regime is based on high-dose vitamin D administered orally and intravenous application of 3 mg ibandronate two times within 8 weeks. Another 8 weeks later, all patients were followed up including a follow-up MRI.

RESULTS

Within 4 weeks, all patients were free of symptoms. The MRI follow-up showed remission of the bone marrow oedema in every case studied. VAS decreased significantly from 7.4 ± 1.0 pre-interventional to 0.8 ± 1.0 post-interventional. No allergic reactions or other side effects were documented.

CONCLUSION

We showed that our treatment regime not only eliminated the pathological findings in the MRI of all cases studied, but also decreased the pain level and functional limitations within a short-time period.

LEVEL OF EVIDENCE

IV.

Low bone mineral density is associated with the onset of spontaneous osteonecrosis of the knee

BACKGROUND AND PURPOSE

The primary event preceding the onset of symptoms in spontaneous osteonecrosis in the medial femoral condyle (SONK) may be a subchondral insufficiency fracture, which may be associated with underlying low bone mineral density (BMD). However, the pathogenesis of SONK is considered to be multifactorial. Women over 60 years of age tend to have higher incidence of SONK and low BMD. We investigated whether there may be an association between low BMD and SONK in women who are more than 60 years old.

METHODS

We compared the BMD of 26 women with SONK within 3 months after the onset of symptoms to that of 26 control women with medial knee osteoarthritis (OA). All the SONK patients had typical clinical presentations and met specified criteria on MRI. The BMDs measured at the lumbar spine, ipsilateral femoral neck, and knee condyles and the ratios of medial condyle BMD to lateral condyle BMD (medial-lateral ratios) in the femur and tibia were compared between the two groups. The medial-lateral ratios were used as parameters for comparisons of the BMDs at both condyles.

RESULTS

The mean femoral neck, lateral femoral condyle, and lateral tibial condyle BMDs were between x% and y% lower in the SONK patients than in the OA patients (p < 0.001). The mean femoral and tibial medial-lateral ratios were statistically significantly higher in the SONK patients than in the OA patients.

INTERPRETATION

A proportion of women over 60 years of age have low BMD that progresses rapidly after menopause and can precipitate a microfracture. These findings support the subchondral insufficiency fracture theory for the onset of SONK based on low BMD.

SPONTANEOUS OSTEONECROSIS IN AN ATHLETE'S KNEE TREATED USING A HYPERBARIC CHAMBER: CASE REPORT AND REVIEW OF THE LITERATURE

Osteonecrosis is a clinical syndrome characterized by osseous necrosis of a load-bearing portion of the femoral condyle, followed by subchondral fracturing, subsequent segmental collapse and arthrosis. It most frequently affects obese women over the age of 55 years. Its treatment is still a matter of controversy in the literature. The authors report the case of a 24-year–old male patient who was a professional soccer player, who presented with a complaint of knee pain one day after physical activity. Imaging examinations performed early on already demonstrated the start of the lesion. The treatment, which was successful, used the following: withdrawal of support, physiotherapy, medications (such as NSAIDs and bisphosphonates) and a hyperbaric chamber. Although hyperbaric chamber therapy is new, its use in association with drug therapy and withdrawal of support may bring good results in treating idiopathic osteonecrosis, even for athletes with high physical demands. However, there is a need for further reports and studies with greater evidence, in order to demonstrate the validity of this treatment.

Autogenous osteochondral graft transplantation for steroid-induced osteonecrosis of the femoral condyle: A report of three young patients

Steroid-induced osteonecrosis of the femoral condyle is a relatively uncommon condition and is often difficult to select appropriate treatment especially in young patients. Three young men (aged 25, 18, and 24) presented with severe pain and dysfunction of the knee diagnosed as steroid-induced osteonecrosis of the femoral condyle by magnetic resonance imaging (MRIs). Full-thickness cartilage defects sized 20 × 10, 15 × 10, and 30 × 20 mm respectively were classified as International Cartilage Repair Society Grade IV lesions and treated with osteochondral autograft transplantation. They were treated successfully with osteochondral autograft transplantation certificated by post-operative MRI and second look arthroscopy.

Increase in posterior tibial slope would result in correction loss in frontal plane after medial open-wedge high tibial osteotomy

PURPOSE

The purpose of this study was to clarify the causes of the increase in the posterior tibial slope during open-wedge high tibial osteotomy (HTO) and to investigate whether its changes influenced the correction angle in frontal plane.

METHODS

We retrospectively reviewed 20 patients (26 knees) treated with open-wedge HTO. They were divided into the following two groups. Group A consisted of the knees whose opening gaps were fixed using a spacer plate having the trapezoidal block with a 2° posterior slope. In Group B, anterior and posterior opening gaps were fixed separately. The posterior tibial slope and the hip-knee-ankle angle were measured based on CT data. The relationship between the correction rate in frontal plane and the changes of posterior tibial slope was investigated.

RESULTS

Increase in the posterior tibial slope was 2.1 ± 2.5° in Group A and 0.2 ± 1.2° in Group B, which showed a statistical difference (P = 0.02). The difference between the hip-knee-ankle angles before and after operation was 5.2 ± 2.3° in Group A and 5.5 ± 2.5° in Group B. The correction rate was statistically correlated with the changes of posterior tibial slope (R = -0.55, P = 0.003).

CONCLUSION

To avoid increase in the posterior tibial slope, the trapezoidal block with a only 2° posterior slope in a spacer plate was not sufficient, and it was necessary to fix anterior and posterior gaps separately. The correction angle in frontal plane had a trade-off relationship with the changes in posterior tibial slope. Thus, we thought that increase in the posterior tibial slope might result in correction loss.

LEVEL OF EVIDENCE

Therapeutic study, Retrospective comparative study, Level III.

Osteonecrosis of the knee and related conditions

Osteonecrosis (ON) of the knee is a progressive disease that often leads to subchondral collapse and disabling arthritis. Recent studies have identified three distinct pathologic entities, all of which were previously described as knee ON: secondary ON, spontaneous ON of the knee, and postarthroscopic ON. Radiographic and clinical assessment is useful for differentiating these conditions, predicting disease progression, and distinguishing these conditions from other knee pathologies. The etiology, pathology, and pathogenesis of secondary ON of the knee are similar to those found at other sites (eg, hip, shoulder). Spontaneous ON is a disorder of unknown etiology. Postarthroscopic ON has been described as an infrequent but potentially destructive complication. Various treatment modalities (eg, core decompression, bone grafting, high tibial osteotomy, arthroplasty), have been used with varying degrees of success for each type of ON. Secondary ON frequently progresses to end-stage disease, and early surgical intervention is recommended. Initial management of spontaneous ON of the knee and postarthroscopic ON is typically nonsurgical, with observation for clinical or radiographic progression.

UKA after spontaneous osteonecrosis of the knee: a retrospective analysis

PURPOSE

Safety and efficacy of unicompartmental knee arthroplasty (UKA) in unicompartmental osteoarthritis (OA) has been shown in large patient series. It has been matter of discussion whether or not spontaneous osteonecrosis of the knee (SONK) can successfully be treated with UKA.

PATIENTS AND METHODS

A retrospective approach included 52 cases of UKA for SONK of the femoral condyles. Four implants were revised (7.7%), and seven patients had died. Nine patients were interviewed by telephone, 28 followed the invitation for clinical examination including clinical scores (KSS and WOMAC) and radiographs. Satisfaction of patients was recorded in four categories. Four patients (7.7%) were lost to follow-up.

RESULTS

Average follow-up was 10.9 ± 4.8 years (4-25). Average age at operation was 66.6 ± 9.7 years. The KSS score increased from a preoperative 85 ± 30 to 173 ± 27 (p < 0.0001) at latest follow-up. WOMAC was 7.7 ± 11.4 at latest follow-up. Of the patients with implants still in place, most patients were satisfied (21.6%) or very satisfied (75.7%) with the outcome of this surgical procedure. One patient was dissatisfied (2.7%). Kaplan-Meier analysis with implant revision as endpoint revealed a survival rate of 93.1% at 10 years and 90.6% at 15 years.

DISCUSSION

This study shows that spontaneous osteonecrosis of the knee (SONK) can successfully be treated with UKA at a good mid- to long-term follow-up.

[Can MRI determine whether acute or chronic processes predisposing conditions are present in spontaneous osteonecrosis of the knee?]

OBJECTIVE

To analyze possible underlying causes of spontaneous osteonecrosis of the knee in adults in function of the lesion's behavior on magnetic resonance imaging (MRI): acute lesion (insufficiency fractures) or chronic lesion (osteoarthritic degeneration).

MATERIAL AND METHODS

We retrospectively evaluated knee MRI studies in 48 patients who fulfilled criteria for spontaneous osteonecrosis. A total of 51 subchondral lesions were included and classified in two groups: those in which linear images were present (Group A) and those in which linear images were not present (Group B). We recorded the location and size of the lesions, their signal intensity, their relation with bone edema, ipsilateral meniscal tear and abnormalities in the adjacent cartilage, as well as the presence of osteoarthritis.

RESULTS

We studied 28 men and 20 women (mean age, 55.1+/-18.0 years). Linear images were present in 58.5% of lesions (group A) and absent in 41.2% (group B). The most common location in both groups was the internal femoral condyle (56.7% in group A and 52.4% in group B), and 88.2% of lesions were hypointense on T1-weighted and fat suppressed proton density sequences. The mean size of the anteroposterior and transversal diameters was 11.9+/-3.6 x 9.4+/-3.9 mm in group A and 10.9+/-5.1 x 10.5+/-4.5 mm in group B. The predominant bone edema was severe (grade 2-3) in group A and mild (grade 0-1) in group B (p=0.033). Defects in the cartilage ipsilateral to the subchondral lesion were more common in group B than in group A, although this difference was not significant (76.2% and 56.7%, respectively; p=0.33). The frequency of ipsilateral meniscal tear was similar in the two groups (56.7% in group A and 57.1% in group B; p=0.97).

CONCLUSION

Knowing the MRI findings for spontaneous osteonecrosis and evaluating other data (type of lesion, bone edema, meniscal tear, and ipsilateral cartilage defects) can help determine the primary predisposing process. Linear lesions might be related to an acute process (insufficiency fractures) and non-linear lesions might be related to a chronic process (osteoarthritis).

Bicondylar spontaneous osteonecrosis of the knee: A case report

Spontaneous osteonecrosis of the knee was originally described as a distinct disorder in 1968. Characteristic imaging findings and distinctive demographic and clinical factors help distinguish this disease from other osteonecrotic conditions, with which it can be confused. This report presents a rare, atypical case of bicondylar spontaneous osteonecrosis of the knee in a young patient, and highlights the importance of a clear understanding of the clinical and radiographic characteristics of this condition to accurately diagnose and treat it when evaluating osteonecrotic lesions of the knee.

Joint-preserving surgical treatment of spontaneous osteonecrosis of the knee

BACKGROUND

To date, reports of surgical treatment of spontaneous osteonecrosis of the knee (SPONK) refractory to non-operative treatment have primarily focused on knee arthroplasty. This report presents an overview of the characteristics of SPONK and reports our experience with joint-preserving surgical treatment of this condition.

METHODS

Fifteen patients who had joint-preserving surgery after failed non-operative modalities were studied. These patients were treated at a single center between January 1998 and September 2006 with a combination of arthroscopy and core decompression, or osteochondral autograft transfers.

RESULTS

Thirteen of the 15 knees (87%) had knee joint survival with a mean Knee Society Score of 81 points (range 45–100 points) at a mean follow-up of 40 months (range 9–120 months). Five of seven knees treated with core decompression had a successful clinical outcome. One of the patients who failed core decompression later underwent osteochondral autograft transfer, and eight of nine knees treated with this modality had a successful outcome.

CONCLUSION

Overall, these results demonstrate that joint-preserving surgical treatment can successfully postpone the need for knee arthroplasty in selected patients with pre-collapse SPONK.

Transient osteoporosis of the hip and spontaneous osteonecrosis of the knee: a common aetiology?

INTRODUCTION

The aetiologies of transient osteoporosis of the hip (TOH) and spontaneous osteonecrosis of the knee (SONK) are still unknown. Both entities present with pain and extensive bone marrow oedema is seen on magnetic resonance imaging.

METHODS AND MATERIALS

We describe a patient who presented with TOH and later also developed SONK. Initial magnetic resonance imaging findings of both the hip and the knee showed extensive bone marrow oedema and a subchondral fracture line suggesting that subchondral fractures might be of importance to the aetiology of both conditions.

CONCLUSION

To our knowledge, this is the first case report that describes the occurrence of TOH and SONK in the same patient and introduces the possibility of a common aetiology.

Osteonecrosis of the knee: a review of three disorders

Osteonecrosis of the knee is a debilitating disease that is poorly understood. Originally described as a single disorder, it encompasses three distinct conditions: spontaneous osteonecrosis of the knee (SPONK), secondary osteonecrosis of the knee, and post-arthroscopic osteonecrosis of the knee. This article reviews the current knowledge of these distinct conditions by describing their etiology, pathology, and pathogenesis, as well as their clinical and radiographic presentations. The various treatment options available for each condition are reviewed, with a discussion of their rationale and indications, and a summary of results with various techniques. A thorough understanding of these conditions and their distinguishing features is critical to selecting the best treatment option for an individual patient.

Histological evaluation of spontaneous osteonecrosis of the medial femoral condyle and short-term clinical results of osteochondral autografting: a case series

Although many surgical modalities for spontaneous osteonecrosis of the knee (SONK) of the medial femoral condyle have been reported, few reports have described these treatment options from the etiological point of view. Recently, osteochondral autografting has gained popularity for use in small cartilage injuries. The aims of this study were to characterize the SONK lesion histopathologically and to report on preliminary clinical results of autogenous osteochondral grafting for SONK. Six patients with SONK of the medial femoral condyle underwent osteochondral autografting. Average age was 54.2 years (range, 50-57 years). Using Koshino's classification, three patients' lesions were classified as stage III and three as stage IV. Classical histological investigation of the lesions was performed in all cases. All the patients achieved favorable pain relief after osteochondral autografts. The mean duration of follow-up was 27.7 months (range, 23-45 months). An increase in the average Lysholm score was found, ranging from 54.7 preoperatively to 92.3 postoperatively. Histological investigation of the lesions revealed articular bone plate fracture with enchondral ossification, reactive cartilage tissue formation, and proliferation of fibrous tissue. An area of osteonecrosis was observed in detached or fragmented osteochondral lesions. Osteochondral autografting was performed on six patients for the SONK and the short-term clinical results were favorable. Histological results give support to subchondral fracture as the etiological mechanism underlying SONK.