The impact of type 2 diabetes on bone metabolism and growth after spinal fusion

Analysis of risk factors for non-fusion of bone graft in anterior cervical discectomy and fusion: A clinical retrospective study

BACKGROUND

Bone graft fusion is a major concern among surgeons after Anterior Cervical Discectomy and Fusion (ACDF) surgery as non-fusion may lead to further physical and drug therapies.

METHODS

The related risk elements of non-fusion of bone graft in ACDF surgery were retrospectively assessed. Patients receiving ACDF operation in our hospital from January 2015 to December 2019 were retrospectively analyzed. According to the criteria, 107 study subjects were recruited with a total of 164 surgical segments. The general information of patients, bone graft materials, imaging parameters, and clinical efficacy was recorded. T-test, chi-square test and binary logistic regression evaluation were employed to explore the risk factors of bone graft nonunion.

RESULTS

Low housefield unit (HU) value, diabetes, allogeneic bone, and hydroxyapatite (HA) artificial bone could be risk factors for bone graft fusion in ACDF surgery. Further multivariate analysis was performed and confirmed those related factors of bone graft non-fusion including low HU value (non-fusion rate: 32.53% [27/83], OR = 5.024, p = 0.025), diabetes (non-fusion rate: 53.33% [8/15], OR = 4.776, p = 0.031), allogeneic bone (18.57% [13/70], OR = 3.964, p = 0.046), and artificial bone (68.29% [28/41], OR = 50.550, p < 0.01).

CONCLUSION

By looking at bone graft fusion, selecting autologous iliac bone is an ideal selection to avoid non-fusion of bone graft in ACDF. Diabetes was more important predictor of bone graft nonunion than low HU value. Larger sample size and longer follow-up are required to further confirm these findings in the future.

Clinical efficacy and complications of MIS-TLIF and TLIF in the treatment of upper lumbar disc herniation: a comparative study

BACKGROUND

The optimal treatment modality for upper lumbar disc herniation remains unclear. Herein, we compared the clinical efficacy and application value of minimally invasive transforaminal lumbar interbody fusion (MIS-TLIF) and transforaminal lumbar interbody fusion (TLIF) for upper lumbar disc herniation. We aimed to provide new evidence to guide surgical decisions for treating this condition.

METHODS

We retrospectively analyzed the clinical data of 81 patients with upper lumbar disc herniation admitted between January 2017 and July 2018, including 41 and 40 patients who underwent MIS-TLIF and TLIF, respectively. Demographic characteristics, preoperative functional scores, perioperative indicators, and postoperative complications were compared. We performed consecutive comparisons of visual analog scale (VAS) scores of the lumbar and leg regions, Oswestry disability index (ODI), Japanese Orthopaedic Association scores (JOA), and MacNab scores at the final follow-up, to assess clinical outcomes 5 years postoperatively.

RESULTS

VAS scores of the back and legs were significantly lower in the MIS-TLIF than the TLIF group at 3 months and 1 year postoperatively (P < 0.05). Intraoperative bleeding and postoperative hospitalization time were significantly lower, and the time to return to work/normal life was shorter in the MIS-TLIF than in the TLIF group (P < 0.05). The differences in JOA scores and ODI scores between the two groups at 3 months, 1 year, and 3 years postoperatively were statistically significant (P < 0.05).

CONCLUSION

The early clinical efficacy of MIS-TLIF was superior to that of TLIF, but no differences were found in mid-term clinical efficacy. Further, MIS-TLIF has the advantages of fewer medical injuries, shorter hospitalization times, and faster postoperative functional recovery.

Radiological and Clinical Outcomes comparing 2-level MIS Lateral and MIS Transforaminal Lumbar Interbody Fusion in Degenerative Lumbar Spinal Stenosis

STUDY DESIGN

Retrospective Cohort Study.

OBJECTIVES

To compare early postoperative radiological and clinical outcomes between 2-level minimally invasive (MIS) trans-psoas lateral lumbar interbody fusion (LLIF) and MIS transforaminal lumbar interbody fusion (TLIF) for degenerative lumbar spinal stenosis.

METHODS

Fifty three consecutive patients undergoing 2-level lumbar interbody fusion from L3-L5 for degenerative lumbar spinal stenosis were enrolled. Twenty four patients underwent LLIF and 29 underwent TLIF.

RESULTS

Operative time and length of stay were similar between LLIF and TLIF (272.8 ± 82.4 vs 256.1 ± 59.4 minutes; 5.5 ± 2.8 vs 4.7 ± 3.3 days, P > .05), whereas blood loss was lower for LLIF (229.0 ± 125.6 vs 302.4 ± 97.1mls, P = .026). Neurological deficits were more common in LLIF (9 vs 3, P = .025), whereas persistent deficits were rare for both (1 vs 1, P = 1). For both groups, all patient reported outcomes visual analogue scale (VAS back pain, VAS leg pain, ODI, SF-36 physical) improved from preoperative to 2-years postoperative (P < .05), with both groups showing no significant differences in extent of improvement for any outcome. Lateral lumbar interbody fusion demonstrated superior restoration of disc height (L3-L4: 4.1 ± 2.4 vs 1.2 ± 1.9 mm, P < .001; L4-L5: 4.6 ± 2.4 vs .8 ± 2.8 mm, P < .001), foraminal height (FH) (L3-L4: 3.5 ± 3.6 vs 1.0 ± 3.6 mm, P = .014; L4-L5: 3.0 ± 3.5 vs -.1 ± 4.4 mm, P = .0080), segmental lordosis (4.1 ± 6.4 vs -2.1 ± 8.1°, P = .005), lumbar lordosis (LL) (4.1 ± 7.0 vs -2.3 ± 12.6°, P = .026) and pelvic incidence-lumbar lordosis (PI-LL) mismatch (-4.1 ± 7.0 vs 2.3 ± 12.6°, P = .019) at 2-years follow-up.

CONCLUSION

The superior radiological outcomes demonstrated by 2-level trans-psoas LLIF did not translate into difference in clinical outcomes compared to 2-level TLIF at the 2-years follow-up, suggesting both approaches are reasonable for 2-level lumbar interbody fusion in degenerative lumbar spinal stenosis.

Conditioned Medium of Intervertebral Disc Cells Inhibits Osteo-Genesis on Autologous Bone-Marrow-Derived Mesenchymal Stromal Cells and Osteoblasts

Low back pain (LBP) is associated with the degeneration of human intervertebral discs (IVDs). Despite progress in the treatment of LBP through spinal fusion, some cases still end in non-fusion after the removal of the affected IVD tissue. In this study, we investigated the hypothesis that the remaining IVD cells secrete BMP inhibitors that are sufficient to inhibit osteogenesis in autologous osteoblasts (OBs) and bone marrow mesenchymal stem cells (MSCs). A conditioned medium (CM) from primary human IVD cells in 3D alginate culture was co-cultured with seven donor-matched OB and MSCs. After ten days, osteogenesis was quantified at the transcript level using qPCR to measure the expression of bone-related genes and BMP antagonists, and at the protein level by alkaline phosphatase (ALP) activity. Additionally, cells were evaluated histologically using alizarin red (ALZR) staining on Day 21. For judging ALP activity and osteogenesis, the Noggin expression in samples was investigated to uncover the potential causes. The results after culture with the CM showed significantly decreased ALP activity and the inhibition of the calcium deposit formation in alizarin red staining. Interestingly, no significant changes were found among most bone-related genes and BMP antagonists in OBs and MSCs. Noteworthy, Noggin was relatively expressed higher in human IVD cells than in autologous OBs or MSCs (relative to autologous OB, the average fold change was in 6.9, 10.0, and 6.3 in AFC, CEPC, and NPC, respectively; and relative to autologous MSC, the average fold change was 2.3, 3.4, and 3.2, in AFC, CEPC, and NPC, respectively). The upregulation of Noggin in residual human IVDs could potentially inhibit the osteogenesis of autologous OB and MSC, thus inhibiting the postoperative spinal fusion after discectomy surgery.

Murine models of posterolateral spinal fusion: A systematic review

BACKGROUND

Rodent models are commonly used experimentally to assess treatment effectiveness in spinal fusion. Certain factors are associated with better fusion rates. The objectives of the present study were to report the protocols most frequently used, to evaluate factors known to positively influence fusion rate, and to identify new factors.

METHOD

A systematic literature search of PubMed and Web of Science found 139 experimental studies of posterolateral lumbar spinal fusion in rodent models. Data for level and location of fusion, animal strain, sex, weight and age, graft, decortication, fusion assessment and fusion and mortality rates were collected and analyzed.

RESULTS

The standard murine model for spinal fusion was male Sprague Dawley rats of 295g weight and 13 weeks' age, using decortication, with L4-L5 as fusion level. The last two criteria were associated with significantly better fusion rates. On manual palpation, the overall mean fusion rate in rats was 58% and the autograft mean fusion rate was 61%. Most studies evaluated fusion as a binary on manual palpation, and only a few used CT and histology. Average mortality was 3.03% in rats and 1.56% in mice.

CONCLUSIONS

These results suggest using a rat model, younger than 10 weeks and weighing more than 300 grams on the day of surgery, to optimize fusion rates, with decortication before grafting and fusing the L4-L5 level.

Semaphorin 3A delivered by a rapidly polymerizing click hydrogel overcomes impaired implant osseointegration in a rat type 2 diabetes model

Semaphorin 3A (sema3A) is an osteoprotective factor that enhances bone formation while inhibiting osteoclast bone resorption. It is produced by rat calvarial osteoblasts cultured on grit-blasted/acid-etched microtextured (SLA) titanium surfaces at higher levels than on tissue culture polystyrene, suggesting that it may improve performance of titanium implants in vivo, particularly in conditions characterized by compromised bone quality. To test this, we established a clinically relevant type 2 diabetes mellitus (T2DM) rat model and used a non-toxic click hydrogel that rapidly polymerizes in situ (GEL) to provide localized controlled delivery of sema3A. In vitro studies confirmed that sema3A released from GEL was biologically active, increasing osteoblast differentiation of a pre-osteoblast cell-line. Whereas increased sema3A production was not observed in T2DM calvarial osteoblasts cultured on SLA, exogenous sema3A enhanced surface-induced osteoblast differentiation, indicating that it would be a viable candidate for in vivo use. Delivery of sema3A either by GEL or by local injection to bone defects enhanced osseointegration of SLA implants in the T2DM rats. Trabecular bone mass and bone-to-implant contact were decreased in T2DM rats compared to normal rats; sema3A delivered locally improved both parameters. These findings suggest that reduced trabecular bone contributes to poor osseointegration in T2DM patients and support GEL as a promising treatment option for sustained release of therapeutic doses of sema3A. Moreover, using this clinically translatable T2DM model and developing a biocompatible, Cu-free click chemistry hydrogel platform for the non-invasive delivery of therapeutics has major implications for regenerative medicine as a whole. STATEMENT OF SIGNIFICANCE: Osseointegration is compromised in patients with poor bone quality due to conditions like type 2 diabetes mellitus (T2DM). Previously, we showed that semaphorin 3A (sema3A) production is increased when human bone marrow stromal cells are cultured on titanium substrates that support osseointegration in vivo, suggesting it may enhance peri-implant osteogenesis in diabetes. Here we established a spontaneously developing T2DM rat model with clinical translatability and used it to assess sema3A effectiveness. Sema3A was delivered to the implant site via a novel copper-free click hydrogel, which has minimal swelling behavior and superior rheological properties. Osseointegration was successfully restored, and enhanced compared to burst release through injections. This study provides scientific evidence for using sema3A to treat impaired osseointegration in T2DM patients.

Endothelium dysfunction in hind limb arteries of male Zucker Diabetic-Sprague Dawley rats

Endothelium dysfunction produces peripheral vascular disease comorbidities in type 2 diabetes, including hypertension, and critical limb ischemia. In this study we aimed to test endothelial dysfunction, the vasodilator effects of a proteinase-activated receptor 2 (PAR2) agonist (2fLIGRLO), and thromboxane A₂ synthase inhibitor (ozagrel) on PAR2 vasodilation in hind limb arteries ex vivo, using Zucker Diabetic-Sprague Dawley (ZDSD) rats, a model of type 2 diabetes. Male Sprague Dawley rats (SD) and ZDSD were fed a high-fat content 'Western diet' from 16 to 20 weeks of age (wks) then fed a standard laboratory diet. We identified diabetic ZDSD rats by two consecutive blood glucose measurements > 12.5 mM, based on weekly monitoring. We used acetylcholine, 2fLIGRLO, and nitroprusside with wire-myograph methods to compare relaxations of femoral, and saphenous arteries from diabetic ZDSD (21-23 wks) to age-matched normoglycemic SD. All arteries showed evidence of endothelium dysfunction using acetylcholine (reduced maximum relaxations, reduced sensitivity), and higher sensitivities to 2fLIGRLO, and nitroprusside in ZDSD vs SD. Ozagrel treatment of ZDSD distal segments, and end-branches of saphenous arteries decreased their sensitivities to 2fLIGRLO. We tested aortas for altered expression of endothelium-specific gene targets using PCR array and qPCR. PAR2, and placental growth factor gene transcripts were 1.5, and 4-times higher in ZDSD than SD aortas. Hind limb arteries of ZDSD exhibit endothelium dysfunction having less GPCR agonist induced vasodilation by endothelial NO-release. Different expression of several endothelial genes in ZDSD vs SD aortas, including PAR2, suggests altered inflammatory, and angiogenesis signaling pathways in the endothelium of ZDSD.

Zucker Diabetic Sprague Dawley rat (ZDSD): type 2 diabetes translational research model

New Findings

What is the topic of this review?

The Zucker Diabetic‐Sprague Dawley (ZDSD) rat is in the early adoption phase of use by researchers in the fields of diabetes, including prediabetes, obesity and metabolic syndrome. It is essential that physiology researchers choose preclinical models that model human type 2 diabetes appropriately and are aware of the limitations on experimental design.

What advances does it highlight?

Our review of the scientific literature finds that although sex, age and diets contribute to variability, the ZDSD phenotype and disease progression model the characteristics of humans who have prediabetes and diabetes, including co‐morbidities.

Abstract

Type 2 diabetes (T2D) is a prevalent disease and a significant concern for global population health. For persons with T2D, clinical treatments target not only the characteristics of hyperglycaemia and insulin resistance, but also co‐morbidities, such as obesity, cardiovascular and renal disease, neuropathies and skeletal bone conditions. The Zucker Diabetic‐Sprague Dawley (ZDSD) rat is a rodent model developed for experimental studies of T2D. We reviewed the scientific literature to highlight the characteristics of T2D development and the associated phenotypes, such as metabolic syndrome, cardiovascular complications and bone and skeletal pathologies in ZDSD rats. We found that ZDSD phenotype characteristics are independent of leptin receptor signalling. The ZDSD rat develops prediabetes, then progresses to overt diabetes that is accelerated by introduction of a timed high‐fat diet. In male ZDSD rats, glycated haemoglobin (HbA1c) increases at a constant rate from 7 to >30 weeks of age. Diabetic ZDSD rats are moderately hypertensive compared with other rat strains. Diabetes in ZDSD rats leads to endothelial dysfunction in specific vasculatures, impaired wound healing, decreased systolic and diastolic cardiac function, neuropathy and nephropathy. Changes to bone composition and the skeleton increase the risk of bone fractures. Zucker Diabetic‐Sprague Dawley rats have not yet achieved widespread use by researchers. We highlight sex‐related differences in the ZDSD phenotype and gaps in knowledge for future studies. Overall, scientific data support the premise that the phenotype and disease progression in ZDSD rats models the characteristics in humans. We conclude that ZDSD rats are an advantageous model to advance understanding and discovery of treatments for T2D through preclinical research.

Macrophage Control of Incipient Bone Formation in Diabetic Mice

Both soft and hard tissue wound healing are impaired in diabetes. Diabetes negatively impacts fracture healing, bone regeneration and osseointegration of endosseous implants. The complex physiological changes associated with diabetes often manifest in immunological responses to wounding and repair where macrophages play a prominent role in determining outcomes. We hypothesized that macrophages in diabetes contribute toward impaired osseous wound healing. To test this hypothesis, we compared osseous wound healing in the mouse calvaria defect model using macrophages from C57BL/6J and db/db mice to direct osseous repair in both mouse strains. Initial analyses revealed that db/db mice macrophages showed an inflamed phenotype in its resting state. Incipient bone regeneration evaluated by μCT indicated that bone regeneration was relatively impaired in the db/db mouse calvaria and in the calvaria of C57BL/6J mice supplemented with db/db macrophages. Furthermore, osteogenic differentiation of mouse mesenchymal stem cells was negatively impacted by conditioned medium from db/db mice compared to C57BL/6J mice. Moreover, miR-Seq analysis revealed an altered miRNA composition in db/db macrophages with up regulated pro-inflammatory miRNAs and down regulated anti-inflammatory miRNAs. Overall, this study represents a direct step toward understanding macrophage-mediated regulation of osseous bone regeneration and its impairment in type 2 diabetes mellitus.

Advanced Glycation End Product Inhibitor Pyridoxamine Attenuates IVD Degeneration in Type 2 Diabetic Rats

Type 2 diabetes mellitus (T2DM) is associated with advanced glycation end product (AGE) enrichment and considered a risk factor for intervertebral disc (IVD) degeneration. We hypothesized that systemic AGE inhibition, achieved using pyridoxamine (PM), attenuates IVD degeneration in T2DM rats. To induce IVD degeneration, lumbar disc injury or sham surgery was performed on Zucker Diabetic Sprague Dawley (ZDSD) or control Sprague Dawley (SD) rats. Post-surgery, IVD-injured ZDSD rats received daily PM dissolved in drinking water or water only. The resulting groups were SD uninjured, SD injured, ZDSD uninjured, ZDSD injured, and ZDSD injured + PM. Levels of blood glycation and disc degeneration were investigated. At week 8 post-surgery, glycated serum protein (GSP) levels were increased in ZDSDs compared to SDs. PM treatment attenuated this increase. Micro-MRI analysis demonstrated IVD dehydration in injured versus uninjured SDs and ZDSDs. In the ZDSD injured + PM group, IVD dehydration was diminished compared to ZDSD injured. AGE levels were decreased and aggrecan levels increased in ZDSD injured + PM versus ZDSD injured rats. Histological and immunohistochemical analyses further supported the beneficial effect of PM. In summary, PM attenuated GSP levels and IVD degeneration processes in ZDSD rats, demonstrating its potential to attenuate IVD degeneration in addition to managing glycemia in T2DM.

Anterior cervical discectomy and fusion for cervical myelopathy using stand-alone tricortical iliac crest autograft: Predictive factors for neurological and fusion outcomes

PURPOSE

The purpose of this article is to investigate the outcomes after anterior cervical discectomy and fusion (ACDF) surgery with stand-alone tricortical iliac crest autograft and to determine predictive factors for poor neurological recovery, non-union, graft collapse and loss of C2-C7 sagittal alignment.

METHODS

This was a retrospective study involving patients with cervical myelopathy who underwent ACDF surgery with stand-alone tricortical iliac autograft between 2006 and 2016, with a minimum 2-year postoperative follow-up. Outcomes included the change in Japanese Orthopaedic Association (JOA) scores clinically and timing of fusion, graft height and C2-7 angle measured on lateral radiographs. Any complication such as neurological deterioration, non-union, graft collapse or loss of angle was recorded. Delayed union was considered as radiological union identified only beyond postoperative 6 months. Risk factors including age, smoking, drinking, comorbidities and operative levels were analysed through a multivariate regression for their respective influences on the various outcomes.

RESULTS

Of the 69 patients studied, none of the patients had non-union, while 33 (47.1%) achieved fusion in 6 months. The most common complications were anterior protrusion of graft (5.8%) and hoarseness (2.9%). The 1-year mean change in JOA score was 3.9 ± 2.7. The C2-7 angle gradually became more kyphotic, despite an initial lordosis correction intraoperatively. The graft height also gradually collapsed during subsequent follow-ups. Multivariate regression model suggested that diabetics (cumulative odds ratio 7.4) and drinkers (cumulative odds ratio 8.6) were associated with delayed union.

CONCLUSION

ACDF using tricortical iliac crest autograft has satisfactory outcomes with low occurrence of complications. Diabetics and drinkers were predictors of delayed union.

The effect of insulin dependent diabetes on bone metabolism and growth after spinal fusion

STUDY DESIGN

Experimental animal model.

OBJECTIVE

The purpose of this study was to evaluate the hypothesis that insulin dependent diabetes mellitus (IDDM) will inhibit the formation of a solid bony union after spinal fusion surgery via an alteration of the microenvironment at the fusion site in a rat model.

SUMMARY OF BACKGROUND DATA

Previous studies report diabetes mellitus (DM) and specifically IDDM as a risk factor for complications and poor surgical outcomes following spinal fusion.

METHODS

Twenty control and 22 diabetic rats were obtained at 5 weeks of age. At 20 weeks of age, all animals underwent posterolateral lumbar fusion surgery using a tailbone autograft with diabetic rats receiving an implantable time release insulin pellet. A subset of rats was sacrificed 1-week postsurgery for growth factor (PDGF, IGF-I, TGF-β, and VEGF) and proinflammatory cytokine ELISA analysis. All other rats were sacrificed 3-months postsurgery for fusion evaluation via manual palpation and micro CT. Glycated hemoglobin (HbA1c) was measured at surgery and sacrifice on all animals.

RESULTS

Compared with healthy rats undergoing spinal fusion, rats with IDDM demonstrated a significant reduction in manual palpation fusion rates (16.7% vs. 43%, p<.05). Average bone mineral density, bone volume, and bone volume fraction were also significantly reduced and negatively correlated to blood glucose levels. IL-1B, IL-5, IL-10, TNF-α, and KC/GRO were significantly elevated in fusion beds of IDDM rats.

CONCLUSIONS

This study demonstrates that rats with IDDM demonstrate a reduced rate and quality of spinal fusion with increased local levels of inflammatory cytokines. Targeted modalities are required to improve bone healing in this growing, high-risk population.

CLINICAL SIGNIFICANCE

This is the first translational animal model of IDDM to evaluate the rate and quality of spinal fusion while controlling for other surgical and patient-related risk factors. Our findings demonstrate the complex nature by which IDDM impairs bone healing and highlight the need for additional basic science research to further elucidate this mechanism in order to develop more effective therapeutic interventions.