Development of a Novel Rat Knee Osteoarthritis Model Induced by Medial Meniscus Extrusion.

OBJECTIVE: The medial meniscus extrusion (MME) is associated with increased stress on the knee joint, which leads to cartilage degeneration. To evaluate the etiology of knee osteoarthritis, it is extremely important to create animal models of the disease that more closely resemble actual clinical conditions in terms of symptomatology, molecular biology, and histology. This study aimed to create a clinically relevant model of MME in rats. DESIGN: Behavioral, molecular biological, and histological changes in the newly developed rat MME model were compared with those in sham and medial meniscus transection and medial collateral ligament transection (MMT) models to examine the characteristics of this model. RESULTS: In the MME rat model, behavioral evaluation shows abnormalities in gait compared with the other 2 groups, and molecular biological evaluation of the infrapatellar synovia of rats shows that gene expression of inflammatory cytokines, matrix-degrading enzymes, and pain-related nerve growth factor was increased compared with the sham group. Furthermore, histological evaluation reveals that cartilage degeneration was the most severe in the MME group. CONCLUSIONS: The newly developed MME model reproduced the characteristic pathology of MME in clinical practice, such as severe pain, inflammation, and rapid progression of osteoarthritis. The MME model, which might more closely mimic human knee osteoarthritis (OA), could be a useful model for elucidating the pathophysiology and considering therapeutic management for knee OA.

Transient receptor potential ankyrin 1 in the knee is involved in osteoarthritis pain.

Transient receptor potential families play important roles in the pathology of osteoarthritis (OA) of the knee. While transient receptor potential ankyrin 1 (TRPA1) is also an essential component of the pathogenesis of various arthritic conditions, its association with pain is controversial. Thus, we researched whether TRPA1 is involved in knee OA pain by in vivo patch-clamp recordings and evaluated the behavioral responses using CatWalk gait analysis and pressure application measurement (PAM). Injection of the Trpa1 agonist, allyl isothiocyanate (AITC), into the knee joint significantly increased spontaneous excitatory synaptic current (sEPSC) frequency in the substantia gelatinosa of rats with knee OA, while injection of the Trpa1 antagonist, HC-030031, significantly decreased the sEPSC. Meanwhile, AITC did not affect the sEPSC in sham rats. In the CatWalk and PAM behavioral tests, AITC significantly decreased pain thresholds, but no difference between HC-030031 and saline injections was observed. Our results indicate that Trpa1 mediates knee OA-induced pain. We demonstrated that Trpa1 is activated in the knee joints of rats with OA, and Trpa1 activity enhanced the pain caused by knee OA.

Erratum for Lumbar Fusion including Sacroiliac Joint Fixation Increases the Stress and Angular Motion at the Hip Joint: A Finite Element Study.

[This corrects the article DOI: 10.22603/ssrr.2021-0231.].

Lumbar Fusion including Sacroiliac Joint Fixation Increases the Stress and Angular Motion at the Hip Joint: A Finite Element Study.

Introduction: Adult spinal fusion surgery improves lumbar alignment and patient satisfaction. Adult spinal deformity surgery improves saggital balance not only lumbar lesion, but also at hip joint coverage. It was expected that hip joint coverage rate was improved and joint stress decreased. However, it was reported that adjacent joint disease at hip joint was induced by adult spinal fusion surgery including sacroiliac joint fixation on an X-ray study. The mechanism is still unclear. We aimed to investigate the association between lumbosacral fusion including sacroiliac joint fixation and contact stress of the hip joint. Methods: A 40-year-old woman with intact lumbar vertebrae underwent computed tomography. A three-dimensional nonlinear finite element model was constructed from the L4 vertebra to the femoral bone with triangular shell elements (thickness, 2 mm; size, 3 mm) for the cortical bone's outer surface and 2-mm (lumbar spine) or 3-mm (femoral bone) tetrahedral solid elements for the remaining bone. We constructed the following four models: a non-fusion model (NF), a L4-5 fusion model (L5F), a L4-S1 fusion model (S1F), and a L4-S2 alar iliac screw fixation model (S2F). A compressive load of 400 N was applied vertically to the L4 vertebra and a 10-Nm bending moment was additionally applied to the L4 vertebra to stimulate flexion, extension, left lateral bending, and axial rotation. Each model's hip joint's von Mises stress and angular motion were analyzed. Results: The hip joint's angular motion in NF, L5F, S1F, and S2F gradually increased; the S2F model presented the greatest angular motion. Conclusions: The average and maximum contact stress of the hip joint was the highest in the S2F model. Thus, lumbosacral fusion surgery with sacroiliac joint fixation placed added stress on the hip joint. We propose that this was a consequence of adjacent joint spinopelvic fixation. Lumbar-to-pelvic fixation increases the angular motion and stress at the hip joint.

S2 alar-iliac screw loosening as a preventive factor for hip joint osteoarthritis after adult spinal deformity surgery: a case-control study.

PURPOSE: This study aimed to evaluate the progression of hip pathology and risk factors after ASD surgery. METHODS: This case-control study enrolled 123 patients (246 hips); seven hips underwent hip arthroplasty were excluded. We measured the center-edge (CE) angle, joint space width (JSW), and Kellgren-Lawrence (KL) grade. We defined a CE angle˂25° as developmental dysplasia of the hip (DDH). We evaluated S2 alar-iliac (AI) screw loosening at final follow-up. RESULTS: The annual decrease in the JSW was 0.31 mm up to 1 year, and 0.13 mm after 1 year (p = 0.001). KL grade progression occurred in 24 hips (10.0%; group P), while no progression occurred in 215 (90.0%; group N) hips. Nonparametric analysis between groups P and N revealed that significant differences were observed in sex, DDH, KL grade, ratio of S2AI screw fixation at baseline, and ratio of S2AI screw loosening at final follow-up. Multiple logistic regression analysis revealed that DDH (p = 0.018, odds ratio (OR) = 3.0, 95%CI = 1.2-7.3), baseline KL grade (p < 0.0001, OR = 37.7, 95%CI = 7.0-203.2), and S2AI screw fixation (p = 0.035, OR = 3.4, 95%CI = 1.1-10.4) were significant factors. We performed sub-analysis to elucidate the relationship between screw loosening and hip osteoarthritis in 131 hips that underwent S2AI screw fixation. Non-loosening of the S2AI screw was a significant factor for KL grade progression (p < 0.0001, OR = 8.9, 95%CI = 3.0-26.4). CONCLUSION: This study identified the prevalence and risk factors for the progression of hip osteoarthritis after ASD surgery. Physicians need to pay attention to the hip joint pathology after ASD surgery.

A Prospective, 3-year Longitudinal Study of Modic Changes of the Lumbar Spine in a Population-based Cohort: The Wakayama Spine Study.

STUDY DESIGN: Large-scale, prospective, population-based, longitudinal observational study. OBJECTIVE: The aim of this study was to investigate the rate of incidence, transformation, and reverse transformation of Modic changes (MCs) using T1-weighted (T1W) and T2-weighted (T2W) lumbar magnetic resonance images (MRI) over a 3-year period. SUMMARY OF BACKGROUND DATA: Although MCs in populational study are considered significant, existing epidemiological evidence is based on cross-sectional studies only. METHODS: Overall, 678 subjects (208 men, 470 women, mean age 62.1 ± 12.8 years in 2013) in both 2013 and 2016 surveys were included. The rate of change in Modic Type I (T1W: low-intensity, T2W: high-intensity), Type II (T1W: high, T2W: high), and Type III (T1W: low, T2W: low) at five endplates was analyzed over a 3-year period. An incidence of MC at each level and in the lumbar region was defined as no MC at baseline with signal changes at follow-up. Transformation was defined as Type I or II MC at baseline with conversion at follow-up Type II from Type I or Type III MC from Type I and II. Furthermore, reverse transformation was defined as Type I, II, or III MC at baseline, with at least one endplate showing a reversion in Modic type (no MC for baseline Type I; no MC and Type I for baseline Type II; no MC, Type I or Type II for baseline Type III) at follow-up. RESULTS: Overall, 3390 endplates were included. For 3 years, the incidence, transformation, and reverse transformation of MCs were seen in 395 (11.7%), 84 (2.5%), and 11 (0.3%) endplates, respectively. The highest levels of incidence, transformation, and reverse transformation were at L2/3 (96 [14.2%] endplates), L5/S1 (32 [4.7%] endplates), and L2/3 (5 [0.7%] endplates), respectively. CONCLUSION: This study revealed a high incidence of MCs at the upper lumbar levels and transformation at the lower lumbar levels. Reverse transformation of MCs occurs but are rare.Level of Evidence: 2.

Detailed Subphenotyping of Lumbar Modic Changes and Their Association with Low Back Pain in a Large Population-Based Study: The Wakayama Spine Study.

INTRODUCTION: To examine the association between the five types of Modic changes and low back pain (LBP) in a large population-based cohort. METHODS: Of the 952 participants in the second Wakayama Spine Study, 814 (men, 246; women, 568; mean age, 63.6 years) were included in this study. Endplate changes on magnetic resonance imaging were classified according to the Modic classification system. Low back pain (LBP) was defined as continuous back pain for at least 48 h in the past month that is currently present. The prevalence of Modic changes in the lumbar region was assessed. Multivariate logistic regression analysis was conducted to determine the association between detailed subphenotype of Modic change and LBP comparing no Modic change in the lumbar spine and each level, respectively. RESULTS: Modic changes throughout the lumbar spine were noted in 63.5% (n = 516) of all participants, with types I, I/II, II, II/III, and III observed in 7.8% (n = 63), 10.8% (n = 88), 40.0% (n = 326), 2.1% (n = 17), and 2.7% (n = 22), respectively. Modic types I/II were associated with LBP [odds ratio (OR): 3.26; 95% confidence interval (CI) 1.9, 5.5]. Furthermore, Modic type I/II changes at L2/3 and L4/5 were significantly associated with LBP (odds ratio: 2.77; 95% CI 1.04, 7.39 at L2/3; odds ratio: 2.86; 95% CI 1.39, 5.90 at L4/5). CONCLUSIONS: Type I/II Modic changes in the lumbar region are significantly associated with LBP. To the best of our knowledge, this is the first large population-based study on the association between various Modic changes and LBP.

Adjacent segment disease on hip joint as a complication of spinal fusion surgery including sacroiliac joint fixation.

PURPOSE: Recently, the number of adult spinal deformity surgeries including sacroiliac joint fixation (SIJF) by using an S2 alar iliac screw or iliac screw has increased to avoid the distal junctional failure. However, we occasionally experienced patients who suffered from hip pain after a long instrumented spinal fusion. We hypothesized that long spinal fusion surgery including SIJF influenced the hip joint as an adjacent joint. The aim of this paper was to evaluate the association between spinal deformity surgery including SIJF and radiographic progression of hip osteoarthritis (OA). METHODS: This study was retrospective cohort study. In total, 118 patients who underwent spinal fusion surgery at single center from January 2013 to August 2018 were included. We measured joint space width (JSW) at central space of the hip joint. We defined reduction of more than 0.5 mm/year in JSW as hip OA progression. The patients were divided into two groups depending on either a progression of hip osteoarthritis (Group P), or no progression (Group N). RESULTS: The number of patients in Group P and Group N was 47 and 71, respectively. Factor that was statistically significant for hip OA was SIJF (p = 0.0065, odds ratio = 7.1, 95% confidence interval = 1.6-31.6). There were no other significant differences by the multiple logistic regression analysis. CONCLUSION: This study identified spinal fixation surgery that includes SIJF as a predictor for radiographic progression of hip OA over 12 months. We should pay attention to hip joint lesions after adult spinal deformity surgery, including SIJF.

Association between types of Modic changes in the lumbar region and low back pain in a large cohort: the Wakayama spine study.

PURPOSE: The clinical significance of Modic changes in low back pain (LBP) is yet to be clarified. Thus, this study aimed to examine the association between Modic changes and LBP after adjustment for confounding factors. METHODS: We evaluated participants in the second Wakayama Spine Study. The degree of endplate changes as measured using magnetic resonance imaging was classified based on the Modic classification system. The prevalence of the types of Modic change in the lumbar region and at each level was assessed. Multivariate logistic regression analysis was conducted to determine the association between the types of Modic changes and LBP with adjustment for age, sex, body mass index, disc degeneration score, and disc displacement score. The LBP intensity was also compared according to the Visual Analogue Scale (VAS) score among the three types of Modic change. RESULTS: Overall, 814 subjects were evaluated. Type II Modic changes were the most prevalent (41.9%). Only type I Modic changes were significantly associated with LBP (odds ratio): 1.84, 95% confidence interval [CI]: 1.1-2.9). The LBP VAS score was significantly higher in subjects with type I Modic change than that in those with no Modic change (23.9 ± 26.3 vs. 9.9 ± 19.4, p < 0.05). CONCLUSION: Type I Modic changes in the lumbar region are significantly associated with LBP. Profiling Modic changes may be helpful to improve targeted treatment of LBP.