Predictive factors for the progression 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.

An AI-Based Image Quality Control Framework for Knee Radiographs

Image quality control (QC) is crucial for the accurate diagnosis of knee diseases using radiographs. However, the manual QC process is subjective, labor intensive, and time-consuming. In this study, we aimed to develop an artificial intelligence (AI) model to automate the QC procedure typically performed by clinicians. We proposed an AI-based fully automatic QC model for knee radiographs using high-resolution net (HR-Net) to identify predefined key points in images. We then performed geometric calculations to transform the identified key points into three QC criteria, namely, anteroposterior (AP)/lateral (LAT) overlap ratios and LAT flexion angle. The proposed model was trained and validated using 2212 knee plain radiographs from 1208 patients and an additional 1572 knee radiographs from 753 patients collected from six external centers for further external validation. For the internal validation cohort, the proposed AI model and clinicians showed high intraclass consistency coefficients (ICCs) for AP/LAT fibular head overlap and LAT knee flexion angle of 0.952, 0.895, and 0.993, respectively. For the external validation cohort, the ICCs were also high, with values of 0.934, 0.856, and 0.991, respectively. There were no significant differences between the AI model and clinicians in any of the three QC criteria, and the AI model required significantly less measurement time than clinicians. The experimental results demonstrated that the AI model performed comparably to clinicians and required less time. Therefore, the proposed AI-based model has great potential as a convenient tool for clinical practice by automating the QC procedure for knee radiographs.

Early aseptic loosening of primary total knee arthroplasty in patients with osteonecrosis of the knee: A case series

The cause of early aseptic loosening in total knee arthroplasty (TKA) is uncertain, although several possibilities could be offered. We report that osteonecrosis of the knee should be considered as a possible cause or contributing etiologic factor for early aseptic loosening following primary TKA.

Extrusion of the medial meniscus is a potential predisposing factor for post-arthroscopy osteonecrosis of the knee

Background

Post-arthroscopic osteonecrosis of the knee (PAONK) is a rare condition. No studies have analyzed the relationship between the meniscus extrusion and PAONK. The purpose of this retrospective study is to test a hypothesis that the degree of the medial meniscus (MM) extrusion might be significantly greater in the knees with PAONK than in the matched control knees both before and after the meniscectomy.

Methods

Ten knees with PAONK were detected out of a total of 876 knees which had undergone arthroscopic partial meniscectomy of the MM. Ten matched control knees were randomly selected out of the remaining 866 knees without PAONK. The clinical data of these 20 patients were retrospectively collected from the medical records. To evaluate the location of the menisci on the joint line, Extrusion width and Inner width were defined on a coronal section of magnetic resonance imaging (MRI). The intra- and inter-rater reliability was evaluated by calculating the intra- and inter-class coefficients. Statistical comparisons between the 2 groups were made using the 3 non-parametric tests.

Results

Before the meniscectomy, the Extrusion width of the MM (mean 4.7 ± 1.4 mm) was significantly greater than that (3.0 ± 1.3 mm) in the Control group (P = 0.0195). In the MRI taken in a range from 3 to 50 weeks after the meniscectomy, the Extrusion width of the MM (5.9 ± 1.1 mm) in the PAONK group was significantly greater than that (3.4 ± 1.4 mm) in the Control group (P = 0.0009), and the Inner width of the MM (0.6 ± 1.7 mm) in the PAONK group was significantly less than that (3.9 ± 1.0 mm) in the Control group (P = 0.0001).

Conclusion

A significant relationship was found between the degree of the MM extrusion and the onset of PAONK. This study suggested that the extrusion of the MM is a potential predisposing factor for PAONK.

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.

Post-arthroscopic Subchondral Insufficiency Fractures of the Knee Yield High Rate of Conversion to Arthroplasty

PURPOSE

To evaluate both the potential causes and resultant outcomes in patients in whom subchondral insufficiency fracture of the knee (SIFK) develops after arthroscopy.

METHODS

We performed a retrospective review of all patients with a magnetic resonance imaging diagnosis of SIFK after arthroscopic meniscectomy and chondroplasty over a 12-year period.

RESULTS

A total of 28 patients were included, with a mean age of 61 years and mean follow-up period of 5.7 years. SIFK showed a predilection for the medial compartment (n = 25, 89%), specifically the medial femoral condyle (n = 21, 75%). In 7 patients (25%), SIFK developed in both the femoral condyle and tibial plateau in the ipsilateral compartment. Fifteen patients (54%) went on to conversion to arthroplasty at a mean of 0.72 years. The rate of survival free of conversion to arthroplasty was 57%, 45%, and 40% at 1 year, 2 years, and 5 years, respectively. Furthermore, 63% of patients with a meniscal tear and SIFK in the same compartment went on to arthroplasty (P = .04). There was an increased risk of conversion to arthroplasty if SIFK was present in both the femur and tibia in the same compartment (P = .04). A higher Kellgren-Lawrence grade at the time of the SIFK diagnosis increased the likelihood of eventual arthroplasty (P = .03). The presence of SIFK in both the femur and tibia in the ipsilateral compartment, an increased Kellgren-Lawrence grade, and a meniscal tear or prior meniscectomy in the same compartment as SIFK were associated with an increased risk of eventual arthroplasty.

CONCLUSIONS

Post-arthroscopic SIFK most commonly occurs in the medial compartment, particularly in patients who underwent a prior meniscectomy. The presence of meniscal root and radial tears in these patients is notable (75%). Ultimately, there is a high rate of progression of arthrosis (33%) and eventual conversion to arthroplasty.

LEVEL OF EVIDENCE

Level IV, case series.

The Fate of Bone Marrow Lesions After Open Wedge High Tibial Osteotomy: A Comparison Between Knees With Primary Osteoarthritis and Subchondral Insufficiency Fractures

BACKGROUND

Subchondral insufficiency fracture of the knee (SIFK) is characterized by a subchondral lesion that may lead to end-stage osteoarthritis (OA). In patients who have SIFK in a precollapse state with varus malalignment, a joint-preserving technique such as open wedge high tibial osteotomy (OWHTO) should be considered.

PURPOSE

To evaluate the efficacy of OWHTO in primary OA and SIFK-dominant OA by clinical and radiological evaluations including magnetic resonance imaging (MRI).

STUDY DESIGN

Cohort study; Level of evidence 3.

METHODS

A total of 33 SIFK-dominant OA knees and 66 with primary OA that underwent biplanar OWHTO between March 2014 and February 2016 were included after 1:2 propensity score matching. The MRI Osteoarthritis Knee Score was used to assess bone marrow lesions (BMLs) preoperatively and at follow-up. The weightbearing line ratio, the hip-knee-ankle angle, and the joint line convergence angle were measured. The clinical outcomes assessed were range of motion, the American Knee Society Score, and the Western Ontario and McMaster University (WOMAC) score.

RESULTS

The mean follow-up period was 41.2 ± 12.6 months. The distribution of preoperative BML grade in the SIFK-dominant OA group was significantly higher in both the femur and tibia (P < .001 and <.001, respectively) than that in the primary OA group. However, the difference was not significant postoperatively (femur, P = .425; tibia, P = .462). In both groups, postoperative BMLs showed significant improvement compared with preoperative BMLs (primary OA [femur, P < .001; tibia, P = .001] and SIFK-dominant OA [femur, P < .001; tibia, P < .001]). The WOMAC pain score was higher in the SIFK-dominant OA group preoperatively (primary OA, 7.0 ± 3.73; SIFK-dominant OA, 9.17 ± 2.6; P = .032) even though it was not different at the final follow-up (primary OA, 2.11 ± 1.7; SIFK-dominant OA, 1.79 ± 1.32; P = .179).

CONCLUSION

OWHTO is an effective procedure not only for primary OA but also for SIFK-dominant OA. OWHTO can improve BMLs, which represent the main pathological feature of SIFK. Therefore, in patients who have SIFK with varus malalignment, OWHTO can be an attractive treatment option for preserving the joint and enhancing subchondral bone healing.

Radiographic deformities of the lower extremity in patients with spontaneous osteonecrosis of the knee

BACKGROUND

Spontaneous osteonecrosis of the knee (SONK) is one of the acute knee pain disorders arising in elderly patients. The presence of knee varus alignment and the size of necrotic area have been reported as the negative prognostic factors in prior studies. However, no previous study has yet clarified the radiological analysis of the lower extremity in SONK compared with that in osteoarthritis. The purpose of this study was therefore to identify the radiographic findings of the lower extremity in SONK.

METHODS

Sixty-three knees of Kellgren-Lawrence classification grade 1 or 2 without any trauma treated between April 2012 and March 2014 were enrolled in this study. These knees were divided into two groups according to their magnetic resonance imaging (MRI) findings: SONK group (31 knees) and OA group (32 knees). Using a long leg standing X-ray, femorotibial angle (FTA), mechanical axis deviation (MAD), mechanical lateral distal femoral angle (mLDFA), medial proximal tibial angle (MPTA) and joint line convergent angle (JLCA) were compared between groups. Correlation between each parameter and the width ratio (WR) of the necrotic lesion were analyzed.

RESULTS

FTA, MAD, MPTA and JLCA showed significant differences between the SONK and OA groups. In the SONK group, FTA was positively correlated with WR, and, MAD and MPTA was negatively correlated with WR.

CONCLUSIONS

Compared with OA, SONK is associated with a significantly larger varus deformity at the proximal tibia, and larger joint play in the coronal plane.

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.

Reliable outcomes and survivorship of primary total knee arthroplasty for osteonecrosis of the knee

AIMS

Knee osteonecrosis in advanced stages may lead to joint degeneration. Total knee arthroplasty (TKA) for osteonecrosis has traditionally been associated with suboptimal results. We analyzed outcomes of contemporary TKAs for osteonecrosis, with particular emphasis on: survivorship free from aseptic loosening, any revision, and any reoperation plus the clinical outcomes, complications, and radiological results.

PATIENTS AND METHODS

In total, 156 patients undergoing 167 primary TKAs performed for osteonecrosis between 2004 and 2014 at a single institution were reviewed. The mean age at index TKA was 61 years (14 to 93) and the mean body mass index (BMI) was 30 kg/m² (18 to 51) The mean follow-up was six years (2 to 12). A total of 110 TKAs (66%) were performed for primary osteonecrosis and 57 TKAs (34%) for secondary osteonecrosis. Overall, 15 TKAs (9%) had tibial stems, while 12 TKAs (7%) had femoral stems. Posterior-stabilized designs were used in 147 TKAs (88%) of TKAs. Bivariate Cox regression analysis was conducted to identify risk factors for revision and reoperation.

RESULTS

Survivorship free from aseptic loosening, any revision, and any reoperation at ten years was 97% (95% confidence interval (CI) 93 to 100), 93% (95% CI 85 to 100), and 82% (95% CI 69 to 93), respectively. No factors, including age, sex, BMI, primary versus secondary osteonecrosis, stem utilization, and constraint, were identified as risk factors for reoperation. Four TKAs (2%) underwent revision, most commonly for tibial aseptic loosening (n = 2). Excluding revisions and reoperations, there was a total of 11 complications (7%), with the most common being a manipulation under anaesthesia (six TKAs, 4%). Mean Knee Society Scores (Knee component) significantly improved from 57 (32 to 87) preoperatively to 91 (49 to 100) postoperatively (p < 0.001). No unrevised TKAs had complete radiolucent lines or radiological evidence of loosening.

CONCLUSION

Contemporary cemented TKAs with selective stem utilization for osteonecrosis resulted in durable survivorship, a low complication rate, and reliable improvement in clinical outcomes. Cite this article: Bone Joint J 2019;101-B:1356-1361.

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.

Reliable outcomes and survivorship of unicompartmental knee arthroplasty for isolated compartment osteonecrosis

Aims

Primary (or spontaneous) and secondary osteonecrosis of the knee can lead to severe joint degeneration, for which either total or unicompartmental arthroplasty may be considered. However, there are limited studies analyzing outcomes of unicompartmental knee arthroplasties (UKAs) for osteonecrosis involving an isolated compartment of the knee. The aims of this study were to analyze outcomes of UKAs for osteonecrosis with specific focus on 1) survivorship free of any revision or reoperation, 2) risk factors for failure, 3) clinical outcomes, and 4) complications.

Patients and Methods

A total of 45 patients underwent 46 UKAs for knee osteonecrosis between 2002 and 2014 at our institution (The Mayo Clinic, Rochester, Minnesota). Twenty patients (44%) were female; the mean age of the patients was 66 years, and mean body mass index (BMI) was 31 kg/m². Of the 46 UKAs, 44 (96%) were medial UKAs, and 35 (76%) were fixed-bearing design. Mean mechanical axis postoperatively was 1.5° varus (0° to 5° varus); 41 UKAs (89%) were performed for primary osteonecrosis. Mean follow-up was five years (2 to 12).

Results

Survivorship free of any revision in the cohort was 89% (95% CI 77 to 99) and 76% (95% CI 53 to 99) at five and ten years, respectively. In patients undergoing UKA for primary osteonecrosis survivorship free of any revision was 93% (95% CI 83 to 100)at both five and ten years. Secondary osteonecrosis was a significant risk factor for poorer survivorship free of any revision or reoperation (hazard ratio 7.7, p = 0.03). Three medial UKAs (6.5%) were converted to total knee arthroplasties (TKAs): two for lateral compartment degeneration and one for development of lateral osteonecrosis. No implants were revised for loosening, fracture, or wear. Knee Society scores improved from a mean of 60 (44 to 72) preoperatively to a mean of 94 postoperatively (82 to 100) (p < 0.001). There were no surgical complications.

Conclusion

When done for primary osteonecrosis of the knee, UKA resulted in reliable clinical improvement, minimal complications, and durable estimated implant survivorship free of revision at ten years. UKA done for secondary osteonecrosis was substantially less durable at mid-term follow-up. Progression of knee degeneration, rather than implant failure or loosening, was most common indication for conversion to TKA. Cite this article: Bone Joint J 2018;100-B:450-4.

Characteristics, management, and outcomes of spontaneous osteonecrosis of the knee in Indian population

PURPOSE

Spontaneous osteonecrosis of the knee affects the medial femoral condyle in patients above 55 years of age. Many reports and studies are available from western countries. But there is a gross paucity of literature on spontaneous osteonecrosis of the knee (SPONK) in the Indian subcontinent, either it is under-reported or detected at a later stage. The aim of our study was to detect SPONK in Indian population and describe its characteristics, treatment, and outcome.

MATERIAL AND METHOD

A prospective study was conducted over a period of three years. All patients above 18 years with knee pain at rest and medial condyle tenderness without joint laxity were evaluated with plain radiographs and MRI. Further tests were done if radiological signs of osteonecrosis were present. Various parameters were recoded like Visual Analog Scale (VAS), Knee Society Score (KSS), and MRI Osteoarthritis Knee Score. Conservative treatment consisted of a combination of NSAIDs and bisphosphonates. Decompression with bone grafting was done if there was no improvement or deterioration at three month follow-up.

RESULTS

Ten patients were diagnosed with SPONK. The mean age was 50 years with male predominance (60%) with the involvement of medial femoral condyle (80%) or left knee (70%). Most cases were in Koshino stage 1. Mean VAS was 6.5 and mean KSS was 59. All clinical parameters showed improvement at one year.

DISCUSSION

A study with a bigger sample size and longer follow-up is needed to fill the lacunae of literature on this topic from the Indian subcontinent. In spite of the limitations, we did observe that in our population, males were more commonly affected than females, which is contrary to most studies on the subject. Also, the disease had an early age of onset (50 years) in Indian population as compared to Western and East Asian populations.

CONCLUSION

Combined therapy of NSAIDs and bisphosphonates shows excellent results over a period of one year. Joint-preserving surgeries are effective even in Koshino stage 3 SPONK.

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.

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.