Obesity significantly impacts spinal health, primarily through increased biomechanical loading and systemic inflammation. Patel et al reported that patients with a BMI of 40 have a 36% probability of encountering significant perioperative complications, emphasizing the critical need for effective nonsurgical management in obese patients.2 This elevated risk is due to both direct mechanical stress on the spine and a proinflammatory state characterized by elevated adipokine levels, such as leptin, which exacerbate degenerative spinal conditions.3

Weight management strategies, including dietary modifications and physical therapy, play a pivotal role to treat obesity. Exercise programs tailored to strengthen core musculature can mitigate the mechanical load on the spine, reducing pain and disability.4 Furthermore, dietary interventions that reduce caloric intake and modulate inflammation are crucial, as they directly address the inflammatory mediators involved in degenerative spinal processes.5

Medical management often involves using anti-inflammatory medications to reduce systemic inflammation, which is particularly pronounced in obese individuals.3 Medication management also includes GLP-1 (Glucagon-like peptide-1) agonists. The current literature explores potential adverse effects associated with the use of GLP-1 agonists during the preoperative period.

These medications have a longer half-life than endogenous GLP-1, which results in a prolonged effect on delaying gastric emptying and consequently may increase the risk of aspiration. This needs to be considered when discussing the timing of discontinuing these medications prior to surgery, time for fasting and use of a clear liquid diet.6 Alongside pharmacological interventions, nonpharmacological approaches like cognitive-behavioral therapy have been reported to help manage chronic pain and improve adherence to lifestyle modifications.

Educational programs that integrate information on the relationship between obesity, spinal health, and overall wellness are essential. These programs encourage patient participation in their treatment and emphasize the importance of maintaining a healthy weight for spinal health. Regular follow-ups which include clinical evaluations and imaging studies are helpful to monitor the progression of spinal conditions and adjusting treatments as needed.2 AAOS Risk Tool suggests reasonable BMI for elective surgery is <= 40. Good strategies include a set BMI target, discussion of reasonable goals with the patient, consideration of verbal or written contrasts for weight loss goals and referral for nutritional services.7

While obesity may increase the technical difficulty and potential for certain complications associated with spinal injections and anesthesia, it should not be considered a strict contraindication to the procedure. Careful consideration of the patient's individual circumstances, including BMI and other comorbidities, and a thorough discussion of the risks and benefits are crucial for providing safe and effective care.

There have been numerous investigations over the years regarding the risk of smoking related to spinal surgery. Recent literature on the subject strongly suggests that smoking can have negative effects on spinal surgical patients. Multiple systematic reviews8,9,10,11 linked smoking with pseudarthrosis in spinal fusion surgery, both cervical and lumbar. Li et al presented pooled results of 26 studies showing the fusion rate of smokers after spinal fusion was significantly lower than that of nonsmokers.11

Several studies reported higher infection rates in smokers8,9,12 and association with increased risk for reoperation.13 In 2021, Harrop et al likewise concluded that smoking is associated with increased risk of reoperation.14 Berman et al linked smoking with dysphagia following cervical spine surgery and increase in adjacent segment pathology.9 Mohamed et al found that smoking was associated with an increased risk of postoperative pneumonia and was a leading cause of postoperative intubation.15

Smoking cessation recommendations are controversial. Harrop et al found that there was insufficient evidence that cessation of smoking before spine surgery decreases the risk of reoperation.14 Berman et al concluded that the most important recommendation is smoking cessation for four weeks after surgery and suggested that preoperative smoking cessation should be recommended as a method to reduce comorbidities and improve overall patient health.9 The AAOS suggests stopping smoking at least 4-6 weeks prior to surgery and 6 weeks following the surgery. They suggest checking blood nicotine level prior to surgery; some insurance companies require nicotine testing prior to fusion surgery.16

The World Health Organization broadly defines anemia as a hemoglobin concentration <13 g/dL for men and <12 g/dL for women.17 Spine surgery is commonly associated with increased perioperative blood loss, which is attributed to the long duration of surgery and rich blood supply to the spine.18

Seicean et al concluded that all levels of anemia (mild, moderate and severe) were significantly associated with prolonged length of hospitalization and poorer operative outcome in spine patients.19

Perioperative anemia reduces transfusion threshold thereby increasing the rate of blood transfusion and its potential risks which could affect overall surgical outcomes. Estimates of blood loss in spine surgery range from 100 to 4700 ml. Higher blood loss is significant in patients with presence of perioperative anemia.20 Other complications that could arise from anemia include implant failure, surgical site infections, deep vein thrombosis and pulmonary embolism.

As a result of these challenges, anemia is considered an independent risk factor for preoperative and postoperative complications in elective spine surgery.19 It is therefore clinically important to understand potential perioperative risks of anemia in spine surgery and aim at correcting anemia preoperatively.

Furthermore, surgeons should maximize the use of available minimally invasive techniques coupled with meticulous surgical dissection to minimize intra and post-operative blood loss.

Only one review addressed nutrition as a risk factor.21 In all 13 articles included in the review, malnutrition was assessed using albumin as a surrogate for nutritional status. On this basis, “malnutrition” was associated with an increased rate of postop complications including surgical site infections (SSI), other wound complications, non-unions, hospital readmissions, and other medical complications.

However, the authors did not find sufficient evidence to support the use of a perioperative multimodal nutrition management protocol. Albumin alone may not be adequate as a measure of nutrition; nutritional status is affected by multiple factors.22 No studies in our search have identified a single reliable measure of nutrition and its impact on surgical outcomes, as malnutrition is a multifactorial and multi-system process disorder.

The AAOS Toolkit suggests several laboratory tests to consider when evaluating for malnutrition including albumin, prealbumin, total protein, total lymphocyte count and serum transferrin levels. A suitable nutritional screening checklist should include low BMI, diabetes, anemia, inflammatory disease and obesity. If malnutrition is suspected, patients should receive nutritional counselling and supplementation, particularly with protein and vitamin D.23

However, as stated above, these labs, especially albumin and prealbumin, should be interpreted with caution to assess the underlying cause as they can reflect a sign of physiologic stress, potentially resulting from disease or trauma-related inflammation, rather than solely a reflection of nutrition status.

Vitamin D deficiency was addressed in a systematic review by Kerezoudis et al. They included five articles and found that patients presenting with vitamin D deficiency had lower fusion rates and higher rates of recurrent-persistent low back pain compared with patients with normal vitamin D levels.24 Within the Kerezoudis review, the studies examining the effect of postoperative vitamin D supplementation in deficient patients reported significant improvements in low back pain intensity, patient-reported outcomes scores and fusion rates compared with baseline and with control groups. Patients presenting for spinal fusion may benefit from correction of vitamin D deficiency to maximize the chance of a successful arthrodesis and to achieve optimal surgical outcomes.

Uncontrolled Diabetes Mellitus is a well-established risk factor associated with diminished long-term patient-reported outcomes, increased readmission rates and an increased incidence of surgical site infections (SSI) following spine surgery.29-32

Glycated hemoglobin A1c serves as a serum biomarker to measure diabetic control with several studies establishing the relationship between preoperative HbA1c values and postoperative outcomes.

In a systematic review by Tao et al, the authors concluded that preoperative HbA1c at values > 8.0% was associated with an increased risk in all-cause postoperative complications.33 Specifically, Cancienne et al showed in patients undergoing anterior cervical discectomy that there is a significant correlation between elevated HbA1c levels (> 7.5mg/dL) and both the reoperation rate and SSI.34

In a retrospective review, Hikata et al noted that patients undergoing thoracolumbar procedures with an HbA1c > 7.0% tended to have a significantly higher incidence of SSI in comparison to patients with HbA1x < 7.0%.29 Overall, there is a strong association between elevated HbA1c and worsened postoperative outcomes following spine surgery29-34; however there is insufficient data to assess the particular risk of SSI in Spinal Cord Stimulator implantation.35

HbA1c testing, and if needed, optimization in the preoperative period of diabetic patients undergoing spine surgery should be performed to minimize complications and improve patient outcomes.

Injection therapy that includes steroids as part of the injectate have a direct, short-term effect on blood sugar levels.36,37 Patients should be counseled on the risk and benefits of receiving exogeneous corticosteroids. While there is no standardized cutoff for blood glucose levels prior to performing interventional procedures, clinicians should be aware of the potential of increased blood glucose as a result of corticosteroid administration in the immediate post-procedure period.36,37

Osteoporosis is defined as low bone mineral density and altered bone quality that places the patient at risk of fragility fractures and associated morbidity. Traditional methods of diagnosis are DEXA scanning and T-score calculation. The World Health Organization classifies osteoporosis as a T score <= -2.5.38 Osteopenia has a T-score -1.0 to -2.4. Osteoporosis may also be clinically diagnosed with a T-score above -2.5 if the patient has a concomitant fragility fracture or a risk of fracture based on the FRAX score. A FRAX score of >3% risk of hip fracture or >20% risk of major osteoporotic fracture (MOF) supports a clinical diagnosis of osteoporosis.

Alternative options to evaluate bone quality in the absence of a DEXA scan would be a CT scan of the spine.39 Greater than or equal to 150 Hounsfield Units (HU) at L1 is normal, less than 100 HU is considered osteoporosis and 100-150 HU is considered osteopenia.

Poor bone health has been linked to worse outcomes in spine surgery including junctional problems, screw loosening and hardware failure.40 Treatment options include optimization of calcium and vitamin D in all patients.40 For patients with osteoporosis or high FRAX scores, antiresorptive agents (bisphosphonates and denosumab) or anabolic agents are also treatment options.40

Anderson has suggested risk stratification based on assessment of bone health and complexity of surgery into normal or low risk, intermediate risk, high risk and very high risk.41 All patients should have optimization of their calcium and vitamin D. Normal or low risk patients typically have normal bone density and low FRAX scores. These patients should optimize calcium and vitamin D, without delay in surgery.38,42 Intermediate-risk patients are those with osteopenia but no fractures and a FRAX MOF of <20%; they should have calcium and vitamin D optimized, and no delay of surgery.40,43

High-risk patients are those with osteoporosis, fractures within the last two years, and a FRAX MOF of 20-30%. In addition to optimizing calcium and vitamin D, they should be treated with an antiresorptive agent or an anabolic agent. Delaying surgery should be considered in cases of multilevel or revision fusion. Very high-risk patients have osteoporosis, multiple fractures, and a FRAX MOF >30% with recent fractures. Optimization of calcium and vitamin D, prescription of an anabolic agent and delay of surgery 3-9 months are strongly recommended.44,45

Basivertebral nerve ablation (BVNA) offers promising treatment for chronic vertebrogenic low back pain. However, its interaction with bone quality requires careful consideration particularly in the elderly and osteoporotic population, where it may temporarily increase the risk of vertebral compression fractures. Recent research suggests that while BVNA appears to have a strong long-term safety profile and may not have a long-term adverse impact on vertebral bone, a transient weakening period should be acknowledged and managed.46

A recent retrospective review by Bellow et al found no post-procedure vertebral compression fractures even in patients with osteoporosis and osteopenia.47 While the sample size was small (N=32), this is one of the few studies evaluating the safety of BVNA in patients with low bone density. Overall, the findings contribute to the growing body of literature supporting the safety and effectiveness of basivertebral nerve ablation in patients with reduced bone density.