Postoperative opioid administration inhibits bone healing in an animal model

Exogenous Opioids and the Human Endocrine System: An Endocrine Society Scientific Statement

The use and misuse of opioids are a growing global problem. Although the effects of these drugs on the human endocrine system have been studied for decades, attention on their related clinical consequences, particularly on the hypothalamic-pituitary system and bone health, has intensified over recent years. This Statement appraises research data related to the impact of opioids on the gonadal and adrenal function. Whereas hypogonadism is well recognized as a side effect of opioids, the significance of their inhibitory actions on the hypothalamic-pituitary-adrenal system and the occurrence of clinically relevant adrenal insufficiency is not fully elucidated. The often-inconsistent results of studies investigating how opioids affect the secretion of GH, prolactin, arginine vasopressin, and oxytocin are assessed. The accumulating evidence of opioid actions on bone metabolism and their negative sequelae on bone mineral density and risk of fracture are also reviewed. In each section, available data on diagnostic and management approaches for opioid endocrine sequelae are described. This Statement highlights a plethora of gaps in research associated with the effects and clinical consequences of opioids on the endocrine system. It is anticipated that addressing these gaps will improve the care of people using or misusing opioids worldwide. The Statement is not intended to serve as a guideline or dictate treatment decisions.

Vagus nerve stimulation rescues persistent pain following orthopedic surgery in adult mice

ABSTRACT

Postoperative pain is a major clinical problem imposing a significant burden on patients and society. In a survey 2 years after orthopedic surgery, 57% of patients reported persisting postoperative pain. However, only limited progress has been made in the development of safe and effective therapies to prevent the onset and chronification of pain after orthopedic surgery. We established a tibial fracture mouse model that recapitulates clinically relevant orthopedic trauma surgery, which causes changes in neuropeptide levels in dorsal root ganglia and sustained neuroinflammation in the spinal cord. Here, we monitored extended pain behavior in this model, observing chronic bilateral hindpaw mechanical allodynia in both male and female C57BL/6J mice that persisted for >3 months after surgery. We also tested the analgesic effects of a novel, minimally invasive, bioelectronic approach to percutaneously stimulate the vagus nerve (termed percutaneous vagus nerve stimulation [pVNS]). Weekly pVNS treatment for 30 minutes at 10 Hz for 3 weeks after the surgery strongly reduced pain behaviors compared with untreated controls. Percutaneous vagus nerve stimulation also improved locomotor coordination and accelerated bone healing. In the dorsal root ganglia, vagal stimulation inhibited the activation of glial fibrillary acidic protein-positive satellite cells but without affecting microglial activation. Overall, these data provide novel evidence supportive of the use of pVNS to prevent postoperative pain and inform translational studies to test antinociceptive effects of bioelectronic medicine in the clinic.

The Inhibitory Effect of NSAIDs and Opioids on Spinal Fusion: An Animal Model

STUDY DESIGN

Translational research.

OBJECTIVE

To evaluate the relative effects of NSAIDs, opioids, and a combination of the two on spinal fusion inhibition in a rodent model.

SUMMARY OF BACKGROUND DATA

Nonsteroidal anti-inflammatory drugs (NSAIDs) and opioids are common postoperative analgesic agents. Since NSAIDs inhibit the cyclooxygenase (COX) pathway, they are seldom prescribed following spinal fusion. Opioids may be given instead, but recent evidence suggests opioids also adversely affect spinal fusion quality and success.

METHODS

Eighty male Sprague-Dawley rats underwent L4-5 posterior lumbar fusion and were given one of the following analgesia regimens: saline, morphine (6 mg/kg), ketorolac (4 mg/kg), or morphine (3 mg/kg) and ketorolac (2 mg/kg). Serum samples were drawn to evaluate systemic pro-osteoblastic cytokines and vascular endothelial growth factor-A (VEGF-A) levels, which were measured through enzyme-linked immunosorbent assays (ELISA). After six weeks, the rats were sacrificed, and the operated spinal segments underwent manual palpation, microCT, and histologic analysis.

RESULTS

Manual palpation scores were significantly diminished in the opioid, NSAID, and multimodal groups when compared with control ( P <0.001). MicroCT fusion scores ( P <0.001) and fusion rates (control: 75% vs . NSAID: 35% vs . opioid: 0% vs . combination: 15%, P <0.001) were significantly diminished in the treatment groups. The bone volume (BV) to tissue volume (TV) ratio (BV/TV) ( P <0.001) and bone mineral density (BMD) ( P <0.001) were all lower in the treatment groups, with the opioid and combined groups having the lowest BMD. Although statistically insignificant ( P <0.09), the concentration of VEGF-A was greater in the control group compared with opioids, NSAIDs, and the combined group.

CONCLUSION

Opioids and NSAIDs, both independently and combined, inhibited spinal fusion and caused inferior bony callus. Administration of opioids resulted in the lowest rate of spinal fusion. We propose this may be due to the inhibition of VEGF-A, which limits angiogenesis to the burgeoning fusion mass.

Opioid Use Increases the Rate of Pseudarthrosis and Revision Surgery in Patients Undergoing Anterior Cervical Discectomy and Fusion

STUDY DESIGN

Retrospective Cohort.

OBJECTIVES

To (1) quantify the risk opioids impart on pseudarthrosis development, (2) analyze the effect of pseudarthrosis on clinical outcomes, and (3) identify if the amount of opioids prescribed are predictive of pseudarthrosis revision.

METHODS

Patients who underwent ACDF at a single institution between 2017-2019 were retrospectively identified. Postoperative dynamic cervical spine radiographs were reviewed to assess fusion status. Logistic regression models measured the effect of morphine milligram equivalents (MME) prescribed on the likelihood of pseudarthrosis development. Receiver operating characteristic (ROC) curves were generated to predict the probability of surgical revision based on MME prescribed.

RESULTS

Of 298 included patients, an average of 2.01 ± 0.82 levels were included in the construct and 121 (40.9%) patients were diagnosed with a pseudarthrosis. However, only 14 (4.7%) required a pseudarthrosis revision. Patients requiring pseudarthrosis revision had worse one-year postoperative Δ PCS-12 (-1.70 vs. 7.58, P = 0.004), Δ NDI (3.33 vs. -15.26, P = 0.002), and Δ VAS Arm (2.33 vs. -2.48, P = .047). Multivariate logistic regression analyses found the three-month postoperative (OR=1.00, P = .010), one-year postoperative (OR=1.001, P = 0.025), and combined pre- and postoperative MME (OR=1.000, P = .035) increased the risk of pseudarthrosis. ROC analysis identified cutoff values to predict pseudarthrosis revision at 90.00 (area under the curve (AUC): 0.693, confidence interval (CI): 0.554-0.832), 132.86 (0.710, CI: 0.589-0.840), 224.76 (0.687, CI: 0.558-0.817) and 285.00 (0.711, CI: 0.585-0.837) MME in the preoperative, three-month postoperative, one-year postoperative, and combined pre-and postoperative period.

CONCLUSION

Increased prescription of opioid medications following ACDF procedures may increase the risk of pseudarthrosis development and revision surgery.

LEVEL OF EVIDENCE

Therapeutic Level III.

Comparing the efficacy of intravenous morphine versus ibuprofen or the combination of ibuprofen and acetaminophen in patients with closed limb fractures: a randomized clinical trial

INTRODUCTION

This study aims to investigate the effectiveness of intravenous ibuprofen or intravenous ibuprofen plus acetaminophen compared to intravenous morphine in patients with closed extremity fractures.

METHODS

A triple-blinded randomized clinical trial was conducted at a tertiary trauma center in Iran. Adult patients between 15 and 60 years old with closed, isolated limb fractures and a pain intensity of at least 6/10 on the visual analog scale (VAS) were eligible. Patients with specific conditions or contraindications were not included. Participants were randomly assigned to receive intravenous ibuprofen, intravenous ibuprofen plus acetaminophen, or intravenous morphine. Pain scores were assessed using the visual analog scale at baseline and 5, 15, 30, and 60 min after drug administration. The primary outcome measure was the pain score reduction after one hour.

RESULTS

Out of 388 trauma patients screened, 158 were included in the analysis. There were no significant differences in age or sex distribution among the three groups. The pain scores decreased significantly in all groups after 5 min, with the morphine group showing the lowest pain score at 15 min. The maximum effect of ibuprofen was observed after 30 min, while the ibuprofen-acetaminophen combination maintained its effect after 60 min. One hour after injection, pain score reduction in the ibuprofen-acetaminophen group was significantly more than in the other two groups, and pain score reduction in the ibuprofen group was significantly more than in the morphine group.

CONCLUSION

The study findings suggest that ibuprofen and its combination with acetaminophen have similar or better analgesic effects compared to morphine in patients with closed extremity fractures. Although morphine initially provided the greatest pain relief, its effect diminished over time. In contrast, ibuprofen and the ibuprofen-acetaminophen combination maintained their analgesic effects for a longer duration. The combination therapy demonstrated the most sustained pain reduction. The study highlights the potential of non-opioid analgesics in fracture pain management and emphasizes the importance of initiation of these medications as first line analgesic for patients with fractures. These findings support the growing trend of exploring non-opioid analgesics in pain management.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT05630222 (Tue, Nov 29, 2022). The manuscript adheres to CONSORT guidelines.

Vagus nerve stimulation rescues persistent pain following orthopedic surgery in adult mice

Postoperative pain is a major clinical problem imposing a significant burden on our patients and society. Up to 57% of patients experience persistent postoperative pain 2 years after orthopedic surgery [49]. Although many studies have contributed to the neurobiological foundation of surgery-induced pain sensitization, we still lack safe and effective therapies to prevent the onset of persistent postoperative pain. We have established a clinically relevant orthopedic trauma model in mice that recapitulates common insults associated with surgery and ensuing complications. Using this model, we have started to characterize how induction of pain signaling contributes to neuropeptides changes in dorsal root ganglia (DRG) and sustained neuroinflammation in the spinal cord [62]. Here we have extended the characterization of pain behaviors for >3 months after surgery, describing a persistent deficit in mechanical allodynia in both male and female C57BL/6J mice after surgery. Notably, we have applied a novel minimally invasive bioelectronic approach to percutaneously stimulate the vagus nerve (termed pVNS) [24] and tested its anti-nociceptive effects in this model. Our results show that surgery induced a strong bilateral hind-paw allodynia with a slight decrease in motor coordination. However, treatment with pVNS for 30-minutes at10 Hz weekly for 3 weeks prevented pain behavior compared to naïve controls. pVNS also improved locomotor coordination and bone healing compared to surgery without treatment. In the DRGs, we observed that vagal stimulation fully rescued activation of GFAP positive satellite cells but did not affect microglial activation. Overall, these data provide novel evidence for the use of pVNS to prevent postoperative pain and may inform translational studies to test anti-nociceptive effects in the clinic.

Role of macrophage autophagy in postoperative pain and inflammation in mice

BACKGROUND

Postoperative pain and inflammation are significant complications following surgery. Strategies that aim to prevent excessive inflammation without hampering natural wound-healing are required for the management of postoperative pain and inflammation. However, the knowledge of the mechanisms and target pathways involved in these processes is lacking. Recent studies have revealed that autophagy in macrophages sequesters pro-inflammatory mediators, and it is therefore being recognized as a crucial process involved in regulating inflammation. In this study, we tested the hypothesis that autophagy in macrophages plays protective roles against postoperative pain and inflammation and investigated the underlying mechanisms.

METHODS

Postoperative pain was induced by plantar incision under isoflurane anesthesia in mice lacking macrophage autophagy (Atg5flox/flox LysMCre +) and their control littermates (Atg5flox/flox). Mechanical and thermal pain sensitivity, changes in weight distribution, spontaneous locomotor activity, tissue inflammation, and body weight were assessed at baseline and 1, 3, and 7 days after surgery. Monocyte/macrophage infiltration at the surgical site and inflammatory mediator expression levels were evaluated.

RESULTS

Atg5flox/flox LysMCre + mice compared with the control mice exhibited lower mechanical and thermal pain thresholds and surgical/non-surgical hindlimb weight-bearing ratios. The augmented neurobehavioral symptoms observed in the Atg5flox/flox LysMCre + mice were associated with more severe paw inflammation, higher pro-inflammatory mediator mRNA expression, and more monocytes/macrophages at the surgical site.

CONCLUSION

The lack of macrophage autophagy augmented postoperative pain and inflammation, which were accompanied by enhanced pro-inflammatory cytokine secretion and surgical-site monocyte/macrophage infiltration. Macrophage autophagy plays a protective role in postoperative pain and inflammation and can be a novel therapeutic target.

"High ankle block" for surgery at the ankle joint

BACKGROUND

Surgery around the ankle is increasingly embedded in outpatient treatment concepts. Unfortunately, the classic "ankle block" as a concept of regional anesthesia is inappropriate for surgery around the ankle because the injection sites are too distal to block this specific region.

METHODS

The "high ankle block" avoids this disadvantage by dislocating the injection points 15 cm proximal to the malleoli. Three of five peripheral nerves necessary to perform the block can be reached by a circumferential subcutaneous wall. The Posterior Tibial Nerve and the Deep Peroneal Nerve are addressed by an ultrasound guided approach.

RESULTS

The efficacy of the technique is highlighted by a case series (3 cases) in which the new blockade was used as a stand-alone procedure, i.e. without additional general anesthesia.

CONCLUSIONS

The "high ankle block" may serve as an ultrasound guided expansion to the classic techniques, extending the operative spectrum to the ankle region.

Chronic Pain after Bone Fracture: Current Insights into Molecular Mechanisms and Therapeutic Strategies

Bone fracture following traumatic injury or due to osteoporosis is characterized by severe pain and motor impairment and is a major cause of global mortality and disability. Fracture pain often originates from mechanical distortion of somatosensory nerve terminals innervating bones and muscles and is maintained by central sensitization. Chronic fracture pain (CFP) after orthopedic repairs is considered one of the most critical contributors to interference with the physical rehabilitation and musculoskeletal functional recovery. Analgesics available for CFP in clinics not only have poor curative potency but also have considerable side effects; therefore, it is important to further explore the pathogenesis of CFP and identify safe and effective therapies. The typical physiopathological characteristics of CFP are a neuroinflammatory response and excitatory synaptic plasticity, but the specific molecular mechanisms involved remain poorly elucidated. Recent progress has deepened our understanding of the emerging properties of chemokine production, proinflammatory mediator secretion, caspase activation, neurotransmitter release, and neuron-glia interaction in initiating and sustaining synaptogenesis, synaptic strength, and signal transduction in central pain sensitization, indicating the possibility of targeting neuroinflammation to prevent and treat CFP. This review summarizes current literature on the excitatory synaptic plasticity, microgliosis, and microglial activation-associated signaling molecules and discusses the unconventional modulation of caspases and stimulator of interferon genes (STING) in the pathophysiology of CFP. We also review the mechanisms of action of analgesics in the clinic and their side effects as well as promising therapeutic candidates (e.g., specialized pro-resolving mediators, a caspase-6 inhibitor, and a STING agonist) for pain relief by the attenuation of neuroinflammation with the aim of better managing patients undergoing CFP in the clinical setting.

Fracture-induced pain-like behaviours in a femoral fracture mouse model

This study is the first comprehensive characterisation of the pain phenotype after fracture using both evoked and naturalistic behaviours in adult male and ovariectomised female mice. It also shows that an anti-nerve growth factor (NGF) therapy could be considered to reduce pain after fracture surgery.

INTRODUCTION

Bone fractures are common due to the ageing population and very painful even after healing. The phenotype of this pain is still poorly understood. We aimed to characterise it in a femoral fracture model in mice.

METHODS

We employed both adult male, and female ovariectomised (OVX) mice to mimic osteoporotic fractures. Mice underwent a unilateral femoral fracture maintained by an external fixator or a sham surgery. Pain behaviours, including mechanical and thermal sensitivity, weight bearing and LABORAS, were measured from baseline to 6 weeks after fracture. The effect on pain of an antibody against nerve growth factor (anti-NGF) was assessed. Changes in nerve density at the fracture callus were analysed by immunohistochemistry.

RESULTS

Following surgery, all groups exhibited high levels of invoked nociception. Mechanical and thermal hyperalgesia were observed from 1 week after surgery, with nociceptive sensitization in the fracture group maintained for the 6 weeks, whereas it resolved in the sham group after 3 weeks. OVX induced reduction in pain thresholds, which was maintained after fracture. The frequency of naturalistic behaviours did not change between groups. Anti-NGF administered before and weekly after surgery alleviated fracture-induced mechanical nociception. The density of nerve fibres in the fracture callus was similar in all groups 6 weeks after surgery.

CONCLUSIONS

Fractures in rodent models are highly painful in both sexes. This pain-like phenotype is prolonged and should be routinely considered in fracture healing studies as it can affect the study outcome. The anti-NGF alleviates fracture-induced mechanical pain.

A Machine Learning Algorithm to Identify Patients at Risk of Unplanned Subsequent Surgery After Intramedullary Nailing for Tibial Shaft Fractures

OBJECTIVES

In the SPRINT trial, 18% of patients with a tibial shaft fracture (TSF) treated with intramedullary nailing (IMN) had one or more unplanned subsequent surgical procedures. It is clinically relevant for surgeon and patient to anticipate unplanned secondary procedures, other than operations that can be readily expected such as reconstructive procedures for soft tissue defects. Therefore, the objective of this study was to develop a machine learning (ML) prediction model using the SPRINT data that can give individual patients and their care team an estimate of their particular probability of an unplanned second surgery.

METHODS

Patients from the SPRINT trial with unilateral TSFs were randomly divided into a training set (80%) and test set (20%). Five ML algorithms were trained in recognizing patterns associated with subsequent surgery in the training set based on a subset of variables identified by random forest algorithms. Performance of each ML algorithm was evaluated and compared based on (1) area under the ROC curve, (2) calibration slope and intercept, and (3) the Brier score.

RESULTS

Total data set comprised 1198 patients, of whom 214 patients (18%) underwent subsequent surgery. Seven variables were used to train ML algorithms: (1) Gustilo-Anderson classification, (2) Tscherne classification, (3) fracture location, (4) fracture gap, (5) polytrauma, (6) injury mechanism, and (7) OTA/AO classification. The best-performing ML algorithm had an area under the ROC curve, calibration slope, calibration intercept, and the Brier score of 0.766, 0.954, -0.002, and 0.120 in the training set and 0.773, 0.922, 0, and 0.119 in the test set, respectively.

CONCLUSIONS

An ML algorithm was developed to predict the probability of subsequent surgery after IMN for TSFs. This ML algorithm may assist surgeons to inform patients about the probability of subsequent surgery and might help to identify patients who need a different perioperative plan or a more intensive approach.

LEVEL OF EVIDENCE

Prognostic Level II. See Instructions for Authors for a complete description of levels of evidence.

Negative pharmacological effect on spine fusion: A narrative review of the literature of evidence-based treatment

Spine fusion surgery is commonly performed for diverse indications, the most frequent one being degenerative spine diseases. Despite the growing importance of this surgery, there is limited evidence concerning the effects of drugs on the process of spine fusion and healing. While asymptomatic sometimes, nonunion of the spine can have tremendous repercussions on the patients' quality of life and the healthcare system rendering it an "expensive complication". This literature review identifies the role of some perioperative drugs in spine fusion and reveals their potential role in pseudarthrosis of the spine. This review also benefits spine surgeons looking for current evidence-based practices. We reviewed the data related to nonsteroidal anti-inflammatory drugs (NSAIDs), corticosteroids, vancomycin, bisphosphonates, proton pump inhibitors (PPIs), pregabalin, and opioids. From the available experimental and clinical studies, we conclude that bisphosphonates might positively influence the process of spine fusion, while steroids and vancomycin have shown variable effects, and the remaining medications likely disturb healing and union of the spine. We recommend spine surgeons be cautious about the drugs they resort to in the critical perioperative period until further clinical studies prove which drugs are safe to be used.

The Effect of Nonsteroidal Anti-inflammatory Drugs and Selective COX-2 Inhibitors on Bone Healing

A recently published study, "Risk of Nonunion With Nonselective NSAIDs, COX-2 Inhibitors, and Opioids" by George et al (J Bone Joint Surg Am. 2020;102:1230-1238), assesses whether the use of nonselective nonsteroidal anti-inflammatory drugs (NSAIDs), selective cyclooxygenase 2 (COX-2) enzyme inhibitors, or opioids was associated with a risk of long bone fracture nonunion in Optum's deidentified private health database. This review analyzes the study, including strengths, weaknesses, and areas for future research. The study found an association between COX-2 inhibitor and opioid use with fracture nonunion but not with nonselective NSAID use. Although the literature on this topic is varied, these results are at least partially aligned with several animal studies that show COX-2 inhibitors to be associated with fracture nonunion. The George et al study design has several important limitations, indicating that further research is needed on this topic.

Effects of maternal consumption of morphine on rat skeletal system development

Background

Opioid abuse is among the most ubiquitous issues world-wide, and when it happens in mothers, it puts them at risk of diseases that can be transferred to the next generation. Previous studies have indicated that morphine addiction during pregnancy could inhibit development in rat embryos and infants.

The present study focused on the effects of maternal consumption of morphine on rat skeletal system development and also investigate the molecular pathway of chondrogenesis and osteogenesis of infants from control and addicted rat groups.

Methods

Thirty-two female rats were randomly assigned to four groups. The groups consisted of one- and seven-day-old female infants which were born of morphine-dependent mothers and a control group for each of them. Experimental groups received oral morphine at the final dose of 0.4 mg/ml/day. Withdrawal signs were confirmation of morphine dependency. Female rats were crossed with male rats and coupling time was recorded. Fixed bones of all groups were processed and then stained by hematoxyline-eosin method. Thickness and cell number of proximal and distal growth plate of bones were measured. The cartilage and bone cells were stained by alcian blue/alizarin red method. Additionally, the gene expression of alkaline phosphatase, osteocalcin, and COLL2 and SOX9 gene expression were studied immuno-histochemically.

Results

Unfavorable effects of morphine on histological measurements were observed in one-day and seven-day infants, with more effects on seven-day infants. The thickness and cell number of the proximal and distal growth plate of morphine-dependent rat offsprings were reduced significantly. Furthermore, morphine reduced growth of primary and secondary ossification centers, and thus, longitudinal bone growth was reduced. Moreover, a decrease in the alkaline phosphatase, osteocalcin, COLL2 and SOX9 gene expression, and the number of stained cells was observed. More adverse effects of morphine in seven-day infants compared to one-day infants which showed the time dependent of morphine to the time length of administration.

Conclusion

Histochemistry and immunohistochemistry findings on cartilage and bone matrix formation, as well as protein expression of chondrogenic and osteogenic markers suggest that morphine dependence in pregnant mothers may impair intra-cartilaginous osteogenesis in post-natal rats.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12891-021-04321-6.

Chronic Preoperative Opioids Are Associated With Revision After Rotator Cuff Repair

PURPOSE

We sought to clarify the relationship between chronic preoperative opioids and complications following rotator cuff repair. Specifically, we assessed revision, a definitive postoperative end point for surgical outcome.

METHODS

This study used PearlDiver, a United States national insurance claims database. All patients undergoing rotator cuff repair from 2008 to 2018 were identified and stratified based on a minimum of 2 opioid prescriptions within the 6 months before surgery, with 1 prescription occurring within 0 to 3 months before surgery and a second prescription within 4 to 6 months before surgery. Univariate logistic regressions of risk factors were conducted, followed by multivariate analysis of comorbidities, including ongoing preoperative opioids, any preoperative nonsteroidal anti-inflammatory drug (NSAID) prescriptions, age, sex, diabetes, tobacco, and obesity.

RESULTS

In total, 28,939 patients undergoing rotator cuff repair were identified, of whom 10,695 had opioid prescriptions within both 0 to 3 months and 4 to 6 months before index rotator cuff repair, whereas 18,244 had no opioid prescriptions within the 6-month preoperative period. In total, 977 (3.4%) patients underwent revision within 6 months, which increased to 1311 (4.5%) within 1 year of the index procedure. In the multivariate analysis controlling for age, preoperative NSAID prescriptions, tobacco, diabetes, obesity, and sex, we observed a significant association between chronic preoperative opioid prescriptions and rotator cuff repair revision (6-month odds ratio 1.12; P = .021, 1-year odds ratio 1.43; P < .001) following index procedure.

CONCLUSIONS

We report increased rates of revision within both 6 months and 1 year in patients with prolonged preoperative opioid prescriptions. The opioid cohort had greater rates of preoperative NSAID use and tobacco use, which also were observed to be independent risk factors for revision at both timepoints.

LEVEL OF EVIDENCE

III; Retrospective comparative study.

The Altered Migration and Distribution of Systemically Administered Mesenchymal Stem Cells in Morphine-Treated Recipients

Mesenchymal stem cells (MSCs) have the ability to migrate to the site of injury or inflammation, and to contribute to the healing process. Since patients treated with MSCs are often users of analgesic drugs, to relieve their uncomfortable pain associated with the tissue disorder, there is a possibility of negative effects of these drugs on the migration of endogenous and exogenous MSCs. Therefore, we tested the impact of acute and chronic treatment with morphine on the migration and organ distribution of exogenous adipose tissue-derived MSCs in mouse models. Firstly, we showed that the incubation of MSCs with morphine significantly reduced the expression of adhesive molecules CD44 (HCAM), CD54 (ICAM-1) and CD106 (VCAM-1) on MSCs. Using a model of systemic administration of MSCs labeled with vital dye PKH26 and by the application of flow cytometry to detect living CD45^-PKH26⁺ cells, we found a decreased number of labeled MSCs in the lung, spleen and bone marrow, and a significantly increased number of MSCs in the liver of morphine-treated recipients. A skin allograft model was used to study the effects of morphine on the migration of exogenous MSCs to the superficial wound. Intraperitoneally administered MSCs migrated preferentially to the wound site, and this migration was significantly decreased in the morphine-treated recipients. The present results showed that morphine significantly influences the distribution of exogenous MSCs in the body, and decreases their migration to the site of injury.

Expression of Opioid Receptors in Cells of the Immune System

The observation of the immunomodulatory effects of opioid drugs opened the discussion about possible mechanisms of action and led researchers to consider the presence of opioid receptors (OR) in cells of the immune system. To date, numerous studies analyzing the expression of OR subtypes in animal and human immune cells have been performed. Some of them confirmed the expression of OR at both the mRNA and protein level, while others did not detect the receptor mRNA either. Although this topic remains controversial, further studies are constantly being published. The most recent articles suggested that the expression level of OR in human peripheral blood lymphocytes could help to evaluate the success of methadone maintenance therapy in former opioid addicts, or could serve as a biomarker for chronic pain diagnosis. However, the applicability of these findings to clinical practice needs to be verified by further investigations.

The Effects of Chronic Preoperative Opioid Use on Single-level Lumbar Fusion Outcomes

STUDY DESIGN

A retrospective study using a national insurance claims database.

OBJECTIVE

The objective of this study was to assess the relationship between chronic preoperative opioids and the outcomes of revision surgery and nonunion after single-level lumbar fusion.

SUMMARY OF BACKGROUND DATA

Opioids are widely utilized for pain management before spine procedures. Studies have associated opioids with unfavorable postoperative outcomes, and animal models have also linked opioid administration with unstable bone healing.

METHODS

Single-level lumbar fusion patients were identified. Patients with any fracture history within 1 year before surgery were excluded. A chronic preoperative opioid cohort was defined by opioids prescriptions within 3 months prior and within 4-6 months before surgery. The rates of revision surgery within 6 months and nonunion within 6-24 months after surgery were assessed. Univariate analyses of chronic preoperative opioid prescriptions and various comorbidities for revision and nonunion were conducted followed by multivariate analyses controlling for these factors. Individual analyses were run for each of the 3 single-level lumbar fusion procedures.

RESULTS

A total of 8494 single-level lumbar fusion patients were identified. Of the 3929 (46.3%) patients filled criteria for the chronic preoperative opioid cohort, while 3250 (38.3%) patients had no opioid prescriptions within 6 months before surgery. The opioid cohort experienced significantly higher rates of both revisions (3.92% vs. 2.71%, P=0.005) and nonunion (3.84% vs. 2.89%, P=0.027) relative to the opioid-naive cohort. In the multivariate analyses, chronic preoperative opioids were identified as an independent risk factor for revision (odds ratio: 1.453, P=0.006).

CONCLUSIONS

We report that chronic opioid prescriptions before lumbar fusion may increase the risk of revision. Although these prescriptions were also associated with increased nonunion, the comparisons did not achieve statistical significance in the multivariate model. Chronic preoperative opioid use may be considered a potential risk factor in arthrodesis populations.

The Life of a Fracture: Biologic Progression, Healing Gone Awry, and Evaluation of Union

New knowledge about the molecular biology of fracture-healing provides opportunities for intervention and reduction of risk for specific phases that are affected by disease and medications. Modifiable and nonmodifiable risk factors can prolong healing, and the informed clinician should optimize each patient to provide the best chance for union. Techniques to monitor progression of fracture-healing have not changed substantially over time; new objective modalities are needed.

Opioid-free spine surgery: a prospective study of 244 consecutive cases by a single surgeon

BACKGROUND CONTEXT

There have been no reported efforts to eliminate opioid use for elective spine surgery, despite its well-known drawbacks.

PURPOSE

We sought to test the hypothesis that opioid-free elective spine surgery, including lumbar fusions, can be performed with satisfactory pain control.

STUDY DESIGN/ SETTING

This study analyzes prospectively collected data from a single surgeon's patients who were enrolled into an institutional spine registry.

PATIENT SAMPLE

We enrolled every consecutive surgical patient of author RAB between January 1, 2018 and July 13, 2019.

OUTCOME MEASURES

The postsurgical opioid use, pain scores, emergency room visits, and readmissions were tracked.

METHODS

We developed a comprehensive program for opioid-free pain control after elective spine surgery. In the initial stage, opioids were given "PRN" only, while in the second stage, they were avoided altogether. Student's t tests were performed to compare pain scores, and regression analyses were performed to understand drivers of opioid use and pain.

RESULTS

Two hundred forty-four patients were studied, a third of whom underwent lumbar fusions. In the initial stage, 47% of patients took no opioids from recovery room departure until 1-month follow-up. During the second stage, 88% of patients took no opioids during that period. Pain scores were satisfactory, and there was no association between postoperative opioid use and either procedural invasiveness or pain scores. However, preoperative opioid use was associated with a nearly fivefold increased risk of postoperative use. Ninety-three percent of lumbar fusion patients who were opioid-free before surgery did not take a single opioid in the postoperative period.

CONCLUSION

Opioid-free elective spine surgery, including lumbar fusions, is feasible and effective. We suggest that opioid-free spine surgery be offered to patients who are opioid-naïve or who can be weaned off before the operation.

Risk of Nonunion with Nonselective NSAIDs, COX-2 Inhibitors, and Opioids

BACKGROUND

Cyclooxygenase-2 (COX-2) has been found to be important for fracture-healing in animal models, raising concerns about use of nonsteroidal anti-inflammatory drugs (NSAIDs) and selective COX-2 inhibitors after fractures. We evaluated associations of NSAIDs, COX-2 inhibitors, and opioids with nonunion after long-bone fracture.

METHODS

Using private health insurance claims data from Optum's de-identified Clinformatics Data Mart database from January 1, 2000, to September 30, 2015, we identified adults with a single long-bone fracture or commonly paired long-bone fractures who had 1 year of available follow-up data. Using multivariable logistic regression models, we examined associations between NSAID, COX-2-inhibitor, or opioid prescription fills after the fracture and the risk of nonunion within 1 year, defined as a nonunion diagnosis with a procedure to treat the nonunion.

RESULTS

A nonunion diagnosis with a procedure to treat the nonunion was identified after 2,996 (0.9%) of the 339,864 fracture episodes, with rates varying by fracture site. The risk of that outcome was greater in patients who had filled COX-2-inhibitor prescriptions (adjusted odds ratio = 1.84 [95% confidence interval = 1.38 to 2.46]) or opioid prescriptions (1.69 [1.53 to 1.86]), but not in patients who had filled nonselective-NSAID prescriptions (1.07 [0.93 to 1.23]) after the fracture. Results were similar when the outcome definition was changed to just a nonunion diagnosis.

CONCLUSIONS

COX-2 inhibitors, but not nonselective NSAIDs, were associated with a greater risk of nonunion after fracture. Opioids were also associated with nonunion risk, although patients filling prescriptions for opioids may have had more severe fractures.

LEVEL OF EVIDENCE

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

The Effect of Opiates on Bone Formation and Bone Healing

PURPOSE OF REVIEW

Opioids have been shown to be associated with an increased risk of fracture. The purpose of this paper is to review recent research into the effects of opioids on bone formation and bone healing in animal models and in human studies.

RECENT FINDINGS

Most opioids, such as morphine and fentanyl, negatively affected bone remodeling and bone healing in animal models. Conversely, remifentanil has been recently shown to promote in vitro osteoblast differentiation and to inhibit differentiation and maturation of osteoclasts, therefore reducing bone resorption. According to the possible negative role of opioids in bone healing, opioid antagonists have been shown to enhance bone mineralization, suggesting a possible therapeutic role in the future for osteoporosis. Other neuropeptides, such as the vasoactive intestinal peptide (VIP) and the neuropeptide Y (NPY), have been proved to promote osteogenesis. The increased risk of fractures among opioid users may be related to their central nervous system side effects or to the reduced bone density, partly due to their endocrine effects, and partly to their direct activity on bone cells. Clinical data strongly suggested a potential negative effect of opioids in bone healing. The risk of nonunion fracture is significantly increased in opioid users, and bone mass density was reduced in patients under long-term opioid treatment. The direct effects of opioids on bone remodeling appears evident from these reports. Not all opioids have the same potential for negatively impacting bone healing. Opioid antagonists may increase bone density and could represent a possible future treatment for low bone mass density pathologies. However, further trials are warranted to clarify the clinical relevance of these emerging findings from animal studies.

Cross-Cultural Comparison of Nonopioid and Multimodal Analgesic Prescribing in Orthopaedic Trauma

BACKGROUND

After musculoskeletal injury, US providers prescribe opioids more frequently and at higher dosages than prescribers in the Netherlands and Haiti; however, the extent of variation in nonopioid analgesic prescribing is unknown. The aim of our study was to evaluate how nonopioid prescribing by orthopaedic residents varies by geographic context.

METHODS

Orthopaedic residents in three countries in which residents are the primary prescribers of postoperative analgesia in academic medical centers (Haiti, the Netherlands, and the United States) responded to surveys using vignette-based musculoskeletal trauma case scenarios. The residents chose which medications they would prescribe for postdischarge analgesia. We quantified the likelihood and dose of acetaminophen or a nonsteroidal anti-inflammatory drug prescription. We constructed multivariable regressions with generalized estimating equations to describe differences in nonopiate prescription according to country, the resident's sex and training year, and the injury site and age in the test cases.

RESULTS

Compared with residents from the United States, residents from Haiti were more likely to prescribe nonopioids (odds ratio, 3.22 [confidence interval, 1.94 to 5.34], P < 0.0001) and residents from the Netherlands nearly always prescribed nonopioids. Of those cases where one or more opioid was prescribed, providers also prescribed a nonopioid (acetaminophen or nonsteroidal anti-inflammatory drug) in 345/603 (57.2%) of US, 152/152 (100%) of Dutch, and 69/97 (71.1%) of Haitian cases (Fisher exact test P value <0.0001). Finally, providers prescribed only nonopioids for pain control in 3/348 (0.86%) of US, 32/184 (17.4%) of Dutch, and 107/176 (60.8%) of Haitian cases (Fisher exact test P < 0.0001).

CONCLUSIONS

When comparing multimodal analgesic patterns, US prescribers prescribed nonopioid analgesics less frequently than prescribers in two other countries, one low income and one high income, either in isolation or in conjunction with opioids.

An understanding of bone pain: A narrative review

Skeletal pathologies are often accompanied by bone pain, which has negative effects on the quality of life and functional status of patients. Bone pain can be caused by a wide variety of injuries and diseases including (poorly healed) fractures, bone cancer, osteoarthritis and also iatrogenic by skeletal interventions. Orthopedic interventions are considered to be the most painful surgical procedures overall. Two major groups of medication currently used to attenuate bone pain are NSAIDs and opioids. However, these systemic drugs frequently introduce adverse events, emphasizing the need for alternative therapies that are directed at the pathophysiological mechanisms underlying bone pain. The periosteum, cortical bone and bone marrow are mainly innervated by sensory A-delta fibers and C-fibers. These fibers are mostly present in the periosteum rendering this structure most sensitive to nociceptive stimuli. A-delta fibers and C-fibers can be activated upon mechanical distortion, acidic environment and increased intramedullary pressure. After activation, these fibers can be sensitized by inflammatory mediators, phosphorylation of acid-sensing ion channels and cytokine receptors, or by upregulation of transcription factors. This can result in a change of pain perception such that normally non-noxious stimuli are now perceived as noxious. Pathological conditions in the bone can produce neurotrophic factors that bind to receptors on A-delta fibers and C-fibers. These fibers then start to sprout and increase the innervation density of the bone, making it more sensitive to nociceptive stimuli. In addition, repetitive painful stimuli cause neurochemical and electrophysiological alterations in afferent sensory neurons in the spinal cord, which leads to central sensitization, and can contribute to chronic bone pain. Understanding the pathophysiological mechanisms underlying bone pain in different skeletal injuries and diseases is important for the development of alternative, targeted pain treatments. These pain mechanism-based alternatives have the potential to improve the quality of life of patients suffering from bone pain without introducing undesirable systemic effects.

Influence of Pain and Analgesia on Orthopedic and Wound-healing Models in Rats and Mice

The surgical stress response and resulting physiologic changes can lead to postoperative complications and negatively impact animal welfare. Although appropriate pain management is crucial to reduce the pain and stress response to surgery, analgesic choice can significantly affect bone and wound healing. This review aims to summarize data from rat and mouse studies and to provide recommendations for integrating analgesia into orthopedic and wound healing models in these species. Data from other species, such as humans, rabbits and other rodents, is included, where available. From these data, we conclude that for orthopedic surgical models, opioids, local anesthetics and dissociative agents have minimal impact on fracture healing; cyclooxygenase 2 (COX2) selective nonsteroidal antiinflammatory drugs (NSAID) may be used in the shortterm; and steroids should be avoided. For wound healing models, short-term systemic or topical opioids have negligible impact on wound healing; NSAID or local anesthetics may be used short-term; and systemic steroids should be avoided. Alternative analgesics such as tramadol, gabapentin, ketamine, and acetaminophen warrant consideration and further evaluation for both orthopedic and wound healing models. In all cases, researchers and veterinarians should work together to determine the appropriate analgesic plan to minimize pain, as well as to minimize unwanted effects on the orthopedic and wound healing models themselves.

Clinical Practice Guidelines for Pain Management in Acute Musculoskeletal Injury

PURPOSE

We aimed to produce comprehensive guidelines and recommendations that can be utilized by orthopaedic practices as well as other specialties to improve the management of acute pain following musculoskeletal injury.

METHODS

A panel of 15 members with expertise in orthopaedic trauma, pain management, or both was convened to review the literature and develop recommendations on acute musculoskeletal pain management. The methods described by the Grading of Recommendations Assessment, Development, and Evaluation Working Group were applied to each recommendation. The guideline was submitted to the Orthopaedic Trauma Association (OTA) for review and was approved on October 16, 2018.

RESULTS

We present evidence-based best practice recommendations and pain medication recommendations with the hope that they can be utilized by orthopaedic practices as well as other specialties to improve the management of acute pain following musculoskeletal injury. Recommendations are presented regarding pain management, cognitive strategies, physical strategies, strategies for patients on long term opioids at presentation, and system implementation strategies. We recommend the use of multimodal analgesia, prescribing the lowest effective immediate-release opioid for the shortest period possible, and considering regional anesthesia. We also recommend connecting patients to psychosocial interventions as indicated and considering anxiety reduction strategies such as aromatherapy. Finally, we also recommend physical strategies including ice, elevation, and transcutaneous electrical stimulation. Prescribing for patients on long term opioids at presentation should be limited to one prescriber. Both pain and sedation should be assessed regularly for inpatients with short, validated tools. Finally, the group supports querying the relevant regional and state prescription drug monitoring program, development of clinical decision support, opioid education efforts for prescribers and patients, and implementing a department or organization pain medication prescribing strategy or policy.

CONCLUSIONS

Balancing comfort and patient safety following acute musculoskeletal injury is possible when utilizing a true multimodal approach including cognitive, physical, and pharmaceutical strategies. In this guideline, we attempt to provide practical, evidence-based guidance for clinicians in both the operative and non-operative settings to address acute pain from musculoskeletal injury. We also organized and graded the evidence to both support recommendations and identify gap areas for future research.

The Impact of Morphine on the Characteristics and Function Properties of Human Mesenchymal Stem Cells

Morphine is an analgesic drug therapeutically administered to relieve pain. However, this drug has numerous side effects, which include impaired healing and regeneration after injuries or tissue damages. It suggests negative effects of morphine on stem cells which are responsible for tissue regeneration. Therefore, we studied the impact of morphine on the properties and functional characteristics of human bone marrow-derived mesenchymal stem cells (MSCs). The presence of μ-, δ- and κ-opioid receptors (OR) in untreated MSCs, and the enhanced expression of OR in MSCs pretreated with proinflammatory cytokines, was demonstrated using immunoblotting and by flow cytometry. Morphine modified in a dose-dependent manner the MSC phenotype, inhibited MSC proliferation and altered the ability of MSCs to differentiate into adipocytes or osteoblasts. Furthermore, morphine rather enhanced the expression of genes for various immunoregulatory molecules in activated MSCs, but significantly inhibited the production of the vascular endothelial growth factor, hepatocyte growth factor or leukemia inhibitory factor. All of these observations are underlying the selective impact of morphine on stem cells, and offer an explanation for the mechanisms of the negative effects of opioid drugs on stem cells and regenerative processes after morphine administration or in opioid addicts.

Prediction of tibial nonunion at the 6-week time point

INTRODUCTION

Intramedullary (IM) nail fixation is a common operative treatment, yet concerns regarding the frequency of complications, such as nonunion, remain. Treatment of tibial shaft fractures remains a challenge, and little evidence of prognostic factors that increase risk of nonunion is available. The aim of this study was to develop a predictive model of tibial shaft fracture nonunion 6 weeks after reamed intramedullary (IM) nail fixation based on commonly collected clinical variables and the radiographic union score for tibial fractures (RUST).

METHODS

A retrospective case-control study was conducted. All tibial shaft fractures treated at our level I trauma center from 2007 to 2014 were retrospectively reviewed. Only patients with follow-up until fracture healing or secondary operation for nonunion were included. Fracture gaps ≥3 mm were excluded. A total of 323 patients were included for study.

RESULTS

Infection within 6 weeks of operation, standard RUST, and the Nonunion Risk Determination (NURD) score had statistically significant associations with nonunion (odds ratio > or < 1.0; p < 0.01). The NURD score was increasingly predictive of nonunion with decreasing RUST. All patients in the high RUST group (RUST ≥ 10), achieved union regardless of NURD score. In the medium RUST group (RUST 6-9), 25% of patients with a NURD score ≥7 experienced nonunion. In the low RUST group (RUST <6 or infection within 6 weeks), 69% of patients with a NURD score ≥7 experienced nonunion.

CONCLUSION

Three variables predicted nonunion. Based on these variables, we created a clinical prediction tool of nonunion that could aid in clinical decision making and discussing prognosis with patients.

Sequestration of artemin reduces inflammation-induced activation and sensitization of bone marrow nociceptors in a rodent model of carrageenan-induced inflammatory bone pain

BACKGROUND

Pathologies that affect the bone marrow have a significant inflammatory component; however, it is not clear how inflammatory mediators affect nociceptive nerve terminals within the marrow cavity.

METHODS

In this study, an in vivo bone-nerve preparation was used to directly record the physiological response properties of bone marrow nociceptors innervating the tibial marrow cavity of rats, before and after application of the inflammatory agent carrageenan. In addition, endogenous artemin was sequestered by application of an artemin neutralizing antibody to determine if this could prevent the inflammation-induced physiological changes observed.

RESULTS

A single injection of carrageenan administered into the tibial marrow cavity produced rapid changes in weight bearing (pain-like behaviour) in conscious animals. Carrageenan, but not saline, activated bone marrow nociceptors in whole-nerve recordings and sensitized a subtype of Aδ-bone marrow nociceptors to mechanical stimulation. The activation and sensitization had a rapid time course that matched that of pain-like behaviours. Sequestration of endogenous artemin significantly reduced carrageenan-induced increases in ongoing activity and completely abolished sensitization of bone marrow nociceptors to mechanical stimulation.

CONCLUSIONS

These observations indicate that inflammation affects the activity and sensitivity of bone marrow nociceptors; that artemin plays a role in these changes; and that artemin might be a promising target for pharmacological manipulations in the treatment of inflammatory bone pain.

SIGNIFICANCE

Most pathologies that affect the bone marrow have an inflammatory component. We have used a model of carrageenan-induced inflammation to show that sequestration of artemin reduces inflammation-induced activation and sensitization of bone marrow nociceptors. Our findings suggest that artemin signalling is a target for the treatment of inflammatory bone pain.

Opioids delay healing of spinal fusion: a rabbit posterolateral lumbar fusion model

BACKGROUND CONTEXT

Opioid use is prevalent in the management of pre- and postoperative pain in patients undergoing spinal fusion. There is evidence that opioids downregulate osteoblasts in vitro, and a previous study found that morphine delays the maturation and remodeling of callus in a rat femur fracture model. However, the effect of opioids on healing of spinal fusion has not been investigated before. Isolating the effect of opioid exposure in humans would be limited by the numerous confounding factors that affect fusion healing. Therefore, we have used a well-established rabbit model to study the process of spinal fusion healing that closely mimics humans.

PURPOSE

The objective of this work was to study the effect of systemic opioids on the process of healing of spinal fusion in a rabbit posterolateral spinal fusion model.

STUDY DESIGN/SETTING

This is a preclinical animal study.

MATERIALS AND METHODS

Twenty-four adult New Zealand white rabbits were studied in two groups after approval from the Institutional Animal Care and Use Committee (IACUC). The opioid group (n=12) received 4 weeks' preoperative and 6 weeks' postoperative transdermal fentanyl. Serum fentanyl levels were measured just before surgery and 4 weeks postoperatively to ensure adequate levels. The control group (n=12) received only perioperative pain control as necessary. All animals underwent a bilateral L5-L6 posterolateral spinal fusion using iliac crest autograft. Animals were euthanized at the 6-week postoperative time point, and assessment of fusion was done by manual palpation, plain radiographs, microcomputed tomography (microCT), and histology.

RESULTS

Twelve animals in the control group and 11 animals in the opioid group were available for analysis at the end of 6 weeks. The fusion scores on manual palpation, radiographs, and microCT were not statistically different. Three-dimensional microCT morphometry found that the fusion mass in the opioid group had a lower bone volume (p=.09), a lower trabecular number (p=.02), and a higher trabecular separation (p=.02) compared with the control group. Histologic analysis found areas of incorporation of autograft and unincorporated graft fragments in both groups. In the control group, there was remodeling of de novo woven bone to lamellar organization with incorporation of osteocytes, formation of mature marrow, and relative paucity of hypertrophied osteoblasts lining new bone. Sections from the opioid group showed formation of de novo woven bone, and hypertrophied osteoblasts were seen lining the new bone. There were no sections showing lamellar organization and development of mature marrow elements in the opioid group. Less dense trabeculae on microCT correlated with histologic findings of relatively immature fusion mass in the opioid group.

CONCLUSIONS

Systemic opioids led to an inferior quality fusion mass with delay in maturation and remodeling at 6 weeks in this rabbit spinal fusion model. These preliminary results lay the foundation for further research to investigate underlying cellular mechanisms, the temporal fusion process, and the dose-duration relationship of opioids responsible for our findings.

Complexities of Perioperative Pain Management in Orthopedic Trauma

PURPOSE OF REVIEW

This review discusses both obvious and hidden barriers in trauma patient access to pain management specialists and provides some suggestions focusing on outcome optimization in the perioperative period.

RECENT FINDINGS

Orthopedic trauma surgeons strive to provide patients the best possible perioperative pain management, while balancing against potential risks of opioid abuse and addiction. Surgeons often find they are ill-prepared to effectively manage postoperative pain in patients returning several months following trauma surgery, many times still dependent on opioids for pain control. Some individuals from this trauma patient population may also require the care of pain management specialists and/or consultation with drug addiction specialists. As the US opioid epidemic continues to worsen, orthopedic trauma surgeons can find it difficult to obtain access to pain management specialists for those patients requiring complex pain medication management and substance abuse counseling. The current state of perioperative pain management for orthopedic trauma patients remains troubling due to reliance on only opioid analgesics, society-associated risks of opioid medication addiction, an "underground" prescription drug marketplace, and an uncertain legal atmosphere related to opioid pain medication management that can deter pain management physicians from accepting narcotic-addicted patients and discourage future physicians from pursuing advanced training in the specialty of pain management. Additionally, barriers continue to exist among Medicaid patients that deter this patient population from access to pain medicine subspecialty care, diminishing medication management reimbursement rates make it increasingly difficult for trauma patients to receive proper opioid analgesic pain medication management, and a lack of proper opioid analgesic medication management training among PCPs and orthopedic trauma surgeons further contributes to an environment ill-prepared to provide effective perioperative pain management for orthopedic trauma patients.

The Advantages of Bilateral Osteotomy Over Unilateral Osteotomy for Osteoporotic Bone Healing

Most models of osteoporotic bone fractures are performed unilaterally (UL). We investigated healing of tibia osteotomy performed either UL or bilaterally (BL) in ovariectomized rats. Behavior of animals and muscle structure were assessed. Three-month-old female Sprague-Dawley rats were ovariectomized (n = 32). After 10 weeks, half the rats underwent UL osteotomy of tibia metaphysis (right limb) with plate osteosynthesis. The other rats were osteotomized BL. Half of the rats in each group received either standard pain treatment with carprofen (5 mg/kg body weight (BW), 1x/day for 2 days) or carprofen and buprenorphine (5 mg/kg BW, 1x/day and 0.03 mg/kg BW, 2x/day for 5 days) after osteotomy. The UL rats started to load the injured limb from day 27 ± 9; BL rats did this from day 4 ± 4 onward. The UL rats more frequently loaded only one hind limb; BL rats more often loaded both hind limbs. Osteotomy was not bridged in 20% of UL rats and in 4% of BL rats. Callus volume and bone volume fraction were lower in UL group. Weight and fiber size of UL-intact limb muscles were enhanced, compared to the osteotomized limb and those in BL group. Most of the other parameters which assess physiology, activity, body posture, head, or coat were not different. The effect of two pain therapies was not significant on any variable studied. Welfare of the animals was acceptable in all rats. In UL rats, bone healing was delayed. The more advanced healing in BL rats suggested a positive effect of earlier loading. In studies on bone healing, it is advisable to perform BL osteotomy.

Positives and negatives of nonsteroidal anti-inflammatory drugs in bone healing: the effects of these drugs on bone repair

Tissue damage following injury triggers the processes of coagulation, inflammation and healing. In tissues surrounding the bone, the result of the healing process is a scar, while bone tissue has a unique ability to achieve shape, strength and pre-injury function. Bone healing is a process of regeneration rather than classic recovery. The result of this process is the formation of new, healthy bone tissue instead of a scar. Many factors can inhibit or impair the bone healing process, and their influence is critical during the stages of inflammation and angiogenesis and finally on the clinical outcome. Nonsteroidal anti-inflammatory drugs (NSAIDs) play an essential role associated with their analgesic potency and anti-inflammatory effects. NSAIDs are also the most often used drugs in patients who require pain control and inflammation reduction due to musculoskeletal diseases or injures. Although their analgesic effect is well documented, NSAIDs also interfere with bone healing; therefore, the relative benefits and disadvantages connected with their administration should be taken into consideration. Despite the negative effect, NSAIDs have beneficial properties, but their clinical benefits in relation to dose and time of use are still unclear. Therefore, in this review, we focus on bone healing with relation to the impact of NSAIDs.

Opioid Consumption Following Foot and Ankle Surgery

Background Orthopedic surgeons frequently prescribe pain medications during the postoperative period. The efficacy of these medications at alleviating pain after foot/ankle surgery and the quantity of medication required (and conversely, leftover) are unknown.

METHODS

Patients undergoing foot/ankle surgery during a 3-month period who met inclusion criteria were surveyed at their first postoperative visit. Information collected included gender, number of prescribed pills remaining, satisfaction with pain control, and willingness to surrender leftover opioids to a Drug Enforcement Administration (DEA) disposal center. Additional data, including utilization of a perioperative nerve block and type (bony versus nonbony) and anatomic region of procedure, were collected through review of the medical record. All data were analyzed in a retrospective fashion. A total of 171 patients with a mean age of 53.1 ± 15.5 years (range, 18-81 years) were included in the study.

RESULTS

The mean number of opioids taken was 27.2 ± 17.5 pills (range, 0-70). The mean number of short-acting opioids and long-acting opioids taken was 21.4 ± 14.8 and 9.2 ± 5.0 pills, respectively. Most (73.5%) patients were satisfied with their pain control. Patients who underwent ankle/hindfoot surgery took more long-acting opioids on average than others ( P = .047). There was not a significant difference in opioid usage between bony and nonbony procedures. Of those with leftover opioids, 63% were willing to surrender them to a DEA disposal center. Patients willing to surrender leftover medications had both more short-acting ( P < .001) and long-acting ( P = .015) opioids leftover than those not willing to surrender them.

CONCLUSION

Most patients undergoing foot/ankle surgery had opioids leftover at the first postoperative visit, and most were willing to surrender them. We can adequately treat patients' pain and decrease the number of opioid pills available in the community by decreasing the number of pills prescribed and encouraging disposal of leftovers.

LEVEL OF EVIDENCE

Level IV, retrospective case series.

GDNF, Neurturin, and Artemin Activate and Sensitize Bone Afferent Neurons and Contribute to Inflammatory Bone Pain

Pain associated with skeletal pathology or disease is a significant clinical problem, but the mechanisms that generate and/or maintain it remain poorly understood. In this study, we explored roles for GDNF, neurturin, and artemin signaling in bone pain using male Sprague Dawley rats. We have shown that inflammatory bone pain involves activation and sensitization of peptidergic, NGF-sensitive neurons via artemin/GDNF family receptor α-3 (GFRα3) signaling pathways, and that sequestering artemin might be useful to prevent inflammatory bone pain derived from activation of NGF-sensitive bone afferent neurons. In addition, we have shown that inflammatory bone pain also involves activation and sensitization of nonpeptidergic neurons via GDNF/GFRα1 and neurturin/GFRα2 signaling pathways, and that sequestration of neurturin, but not GDNF, might be useful to treat inflammatory bone pain derived from activation of nonpeptidergic bone afferent neurons. Our findings suggest that GDNF family ligand signaling pathways are involved in the pathogenesis of bone pain and could be targets for pharmacological manipulations to treat it.SIGNIFICANCE STATEMENT Pain associated with skeletal pathology, including bone cancer, bone marrow edema syndromes, osteomyelitis, osteoarthritis, and fractures causes a major burden (both in terms of quality of life and cost) on individuals and health care systems worldwide. We have shown the first evidence of a role for GDNF, neurturin, and artemin in the activation and sensitization of bone afferent neurons, and that sequestering these ligands reduces pain behavior in a model of inflammatory bone pain. Thus, GDNF family ligand signaling pathways are involved in the pathogenesis of bone pain and could be targets for pharmacological manipulations to treat it.

Effects of freshwater clam extract on fracture induced inflammation at early stage

The inflammatory process after traumatic fracture and soft tissue injury includes release of inflammatory cytokines and activated polymorph nuclear cells (PMN) that can cause subsequent affected limbs delayed healing and vital organ complications. Analgesics have good effect on relief of the symptom but may cause further burden for hepatic and renal metabolism. Freshwater clam extract (FCE) has been demonstrated to suppress the release of the pro-inflammatory cytokine tumor necrosis factor-α production after hemorrhagic shock, and decrease the level of liver injury marker in rats. The aim of the present study was to determine whether FCE is able to affect the inflammation induced by unilateral tibial fracture in a rat model. The rats were randomly divided into control, fracture, FCE and fracture with FCE groups. The fracture group received left tibia and fibula shaft fractures using a consistent three point bending method. For the fracture with FCE group, FCE (40 mg/kg) was administered orally after fracture. Their physiological changes were continuously monitored for 48 h. Blood samples were extracted from the femoral arterial catheter at 1, 3, 6, 9, 12, 18, 24 and 48 h after fracture. In comparison with fracture group, those whom were fed with FCE had more stable heart rate frequency, lower central temperature at the initial h, and lower serum level of the proinflammatory cytokines and muscle damage markers induced by fracture. FCE was also associated with decreased recruitment of inflammatory cells in the adjacent soft tissue. Thus, the present results suggest that FCE could decrease fracture induced inflammation reaction and have beneficial regulatory effect on post inflammatory response.

Leading the Way to Solutions to the Opioid Epidemic: AOA Critical Issues

BACKGROUND

In the past 2 decades, overdoses and deaths from prescription opioids have reached epidemic proportions in the United States. The widespread use of opioids complicates management of the orthopaedic surgery patient in the acute and chronic settings. Orthopaedic surgeons are some of the top prescribers of opioids in the complex setting of chronic use, abuse, and diversion.

METHODS

The literature regarding the basic science of pharmacologic options for pain management (e.g., opioids and nonsteroidal anti-inflammatory drugs), the impact of strategies on bone and soft-tissue healing, and pain relief are summarized as they relate to the management of orthopaedic injuries and conditions. Additionally, a section on designing solutions to address the current opioid crisis is presented.

RESULTS

The mechanism of action of different classes of analgesic medications is discussed, as well as the basic scientific evidence regarding the impact of narcotic and nonnarcotic analgesic medications on bone-healing and on other organ systems. Differences between pain and nociception, various treatment strategies, and clinical comparisons of the effectiveness of various analgesics compared with opioids are summarized. Finally, options for addressing the opioid crisis, including the description of a large system-wide intervention to impact prescriber behavior at the point of care using health-information solutions, are presented.

CONCLUSIONS

Orthopaedic leaders, armed with information and strategies, can help lead the way to solutions to the opioid epidemic in their respective communities, institutions, and subspecialty societies. Through leadership and education, orthopaedic surgeons can help shape the solution for this critical public health issue.

Risk Factors for Failure of Bone Grafting of Tibia Nonunions and Segmental Bone Defects: A New Preoperative Risk Assessment Score

OBJECTIVE

To develop a clinically useful prediction model of success at the time of surgery to promote bone healing for established tibial nonunion or traumatic bone defects.

DESIGN

Retrospective case controlled.

SETTING

Level 1 trauma center.

PATIENTS

Adult patients treated with surgery for established tibia fracture nonunion or traumatic bone defects from 2007 to 2016. Two hundred three patients met the inclusion criteria and were available for final analysis.

INTERVENTION

Surgery to promote bone healing of established tibia fracture nonunion or segmental defect with plate and screw construct, intramedullary nail fixation, or multiplanar external fixation.

MAIN OUTCOME MEASURES

Failure of the surgery to promote bone healing that was defined as unplanned revision surgery for lack of bone healing or deep infection. No patients were excluded who had a primary outcome event.

RESULTS

Multivariate logistic modeling identified 5 significant (P < 0.05) risk factors for failure of the surgery to promote bone healing: (1) mechanism of injury, (2) Increasing body mass index, (3) cortical defect size (mm), (4) flap size (cm), and (5) insurance status. A prediction model was created based on these factors and awarded 0 points for fall, 17 points for high energy blunt trauma (OR = 17; 95% CI, 1-286, P = 0.05), 22 points for industrial/other (OR = 22; 95% CI, 1-4, P = 0.04), and 28 points for ballistic injuries (OR = 28; 95% CI, 1-605, P = 0.04). One point is given for every 10 cm of flap size (OR = 1; 95% CI, 1-1.1, P < 0.001), 10 mm of mean cortical gap distance (OR = 1; 95% CI, 1-2, P = 0.004), and 10 units BMI, respectively (OR = 1.5; 95% CI, 1-3, P = 0.16). Two points are awarded for Medicaid or no insurance (OR = 2; 95% CI, 1-5, P = 0.035) and 3 points for Medicare (3; 95% CI, 1-9, P = 0.033). Each 1-point increase in risk score was associated with a 6% increased chance of requiring at least 1 revision surgery (P < 0.001).

CONCLUSIONS

This study presents a clinical score that predicts the likelihood of success after surgery for tibia fracture nonunions or traumatic bone defects and may help clinicians better determine which patients are likely to fail these procedures and require further surgery.

The Effect of Opioids, Alcohol, and Nonsteroidal Anti-inflammatory Drugs on Fracture Union

The estimated rate of fracture nonunion is between 5% and 10%, adding significant cost to the health care system. The cause of fracture nonunion is multifactorial, including the severity of the injury, patient factors resulting in aberrancies in the biology of fracture, and the side effects of pain control modalities. Minimizing surgeon-controlled factors causing nonunion is important to reduce the cost of health care and improve patient outcomes. Opioids, alcohol, and nonsteroidal anti-inflammatory drugs have been implicated as risk factors for fracture nonunion. Current literature was reviewed to examine the effects of opioids, alcohol, and nonsteroidal anti-inflammatory drugs on fracture union.

Molecular Mechanisms That Contribute to Bone Marrow Pain

Pain associated a bony pathology puts a significant burden on individuals, society, and the health-care systems worldwide. Pathology that involves the bone marrow activates sensory nerve terminal endings of peripheral bone marrow nociceptors, and is the likely trigger for pain. This review presents our current understanding of how bone marrow nociceptors are influenced by noxious stimuli presented in pathology associated with bone marrow. A number of ion channels and receptors are emerging as important modulators of the activity of peripheral bone marrow nociceptors. Nerve growth factor (NGF) sequestration has been trialed for the management of inflammatory bone pain (osteoarthritis), and there is significant evidence for interaction of NGF with bone marrow nociceptors. Activation of transient receptor potential cation channel subfamily V member 1 sensitizes bone marrow nociceptors and could contribute to increased sensitivity of patients to noxious stimuli in various bony pathologies. Acid-sensing ion channels sense changes to tissue pH in the bone marrow microenvironment and could be targeted to treat pathology that involves acidosis of the bone marrow. Piezo2 is a mechanically gated ion channel that has recently been reported to be expressed by most myelinated bone marrow nociceptors and might be a target for treatments directed against mechanically induced bone pain. These ion channels and receptors could be useful targets for the development of peripherally acting drugs to treat pain of bony origin.

Lengthening and deformity correction about the knee using a magnetic internal lengthening nail

Introduction: The introduction of the internal lengthening nail (ILN) has changed the treatment of complex malalignment and shortening about the knee. Acute correction of the deformity and gradual lengthening through this osteotomy site has greatly simplified postoperative recovery. This manuscript is a review of the techniques that are currently being used in surgery.

Methods: The article is broken into two sections: distal femur osteotomy and tibia osteotomy. Each is addressed separately since they have different personalities. Also included are topics of particular interest that surface in ongoing conferences regarding the ILN. This work is a mix of expert opinion and best practice supported by peer reviewed publications on the topic.

Results: Most published series demonstrate excellent results with the ILN. Certain precautions are reiterated including avoiding mechanical failure, need for a percutaneous osteotomy, need for over-reaming, and the need for blocking screws.

Discussion: Current controversies will be brought to light and discussed. The reader should find this aspect particularly helpful in navigating this rapidly evolving field.

Chronic Osteoporotic Pain in Mice: Cutaneous and Deep Musculoskeletal Pain Are Partially Independent of Bone Resorption and Differentially Sensitive to Pharmacological Interventions

Although the pathological changes in osteoporotic bones are well established, the characterization of the osteoporotic pain and its appropriate treatment are not fully elucidated. We investigated the behavioral signs of cutaneous and deep musculoskeletal pain and physical function; time-dependent changes in bone mineral density (BMD) and the emergence of the behavioral phenotype; and the effects of pharmacological interventions having different mechanisms of action (chronic intraperitoneal administration of pamidronate [0.25 mg/kg, 5x/week for 5 weeks] versus acute treatment with intraperitoneal morphine [10 mg/kg] and pregabalin [100 mg/kg]) in a mouse model of ovariectomized or sham-operated mice 6 months following surgery. We observed reduced BMD associated with weight gain, referred cutaneous hypersensitivity, and deep musculoskeletal pain that persisted for 6 months. Chronic bisphosphonate treatment, 6 months after ovariectomy, reversed bone loss and hypersensitivity to cold, but other behavioral indices of osteoporotic pain were unchanged. While the efficacy of acute morphine on cutaneous pain was weak, pregabalin was highly effective; deep musculoskeletal pain was intractable. In conclusion, the reversal of bone loss alone is insufficient to manage pain in chronic osteoporosis. Additional treatments, both pharmacological and nonpharmacological, should be implemented to improve quality of life for osteoporosis patients.

Opioid receptor agonists may favorably affect bone mechanical properties in rats with estrogen deficiency-induced osteoporosis

The results of epidemiological, clinical, and in vivo and in vitro experimental studies on the effect of opioid analgesics on bone are inconsistent. The aim of the present study was to investigate the effect of morphine (an agonist of opioid receptors), buprenorphine (a partial μ opioid receptor agonist and κ opioid receptor antagonist), and naloxone (an antagonist of opioid receptors) on the skeletal system of female rats in vivo. The experiments were carried out on 3-month-old Wistar rats, divided into two groups: nonovariectomized (intact; NOVX) rats and ovariectomized (OVX) rats. The bilateral ovariectomy was performed 7 days before the start of drug administration. Morphine hydrochloride (20 mg/kg/day s.c.), buprenorphine (0.05 mg/kg/day s.c.), or naloxone hydrochloride dihydrate (2 mg/kg/day s.c.) were administered for 4 weeks to NOVX and OVX rats. In OVX rats, the use of morphine and buprenorphine counteracted the development of osteoporotic changes in the skeletal system induced by estrogen deficiency. Morphine and buprenorphine beneficially affected also the skeletal system of NOVX rats, but the effects were much weaker than those in OVX rats. Naloxone generally did not affect the rat skeletal system. The results confirmed the role of opioid receptors in the regulation of bone remodeling processes and demonstrated, in experimental conditions, that the use of opioid analgesics at moderate doses may exert beneficial effects on the skeletal system, especially in estrogen deficiency.

Will My Tibial Fracture Heal? Predicting Nonunion at the Time of Definitive Fixation Based on Commonly Available Variables

BACKGROUND

Accurate prediction of tibial nonunions has eluded researchers. Reliably predicting tibial nonunions at the time of fixation could change management strategies and stimulate further research.

QUESTIONS/PURPOSES

We asked (1) whether data from medical records, fracture characteristics, and radiographs obtained at the time of fixation would identify features predictive of tibial fracture nonunion; and (2) whether this information could be used to create a model to assess the chance of nonunion at the time of intramedullary (IM) nail fixation of the tibia.

METHODS

We retrospectively reviewed all tibial shaft fractures treated at our center from 2007 to 2014. We conducted a literature review and collected data on 35 factors theorized to contribute to delayed bone healing. Patients were followed to fracture healing or surgery for nonunion. Patients with planned prophylactic nonunion surgery were excluded because their nonunions were anticipated and our focus was on unanticipated nonunions. Our cohort consisted of 382 patients treated with IM nails for tibial shaft fractures (nonunion, 56; healed, 326). Bivariate and multivariate regression techniques and stepwise modeling approaches examined the relationship between variables available at definitive fixation. Factors were included in our model if they were identified as having a modest to large effect size (odds ratio > 2) at the p < 0.05 level.

RESULTS

A multiple variable logistic regression model was developed, including seven factors (p < 0.05; odds ratio > 2.0). With these factors, we created the Nonunion Risk Determination (NURD) score. The NURD score assigns 5 points for flaps, 4 points for compartment syndrome, 3 points for chronic condition(s), 2 points for open fractures, 1 point for male gender, and 1 point per grade of American Society of Anesthesiologists Physical Status and percent cortical contact. One point each is subtracted for spiral fractures and for low-energy injuries, which were found to be predictive of union. A NURD score of 0 to 5 had a 2% chance of nonunion; 6 to 8, 22%; 9 to 11, 42%; and > 12, 61%.

CONCLUSIONS

The proposed nonunion prediction model (NURDS) seems to have potential to allow clinicians to better determine which patients have a higher risk of nonunion. Future work should be directed at prospectively validating and enhancing this model.

LEVEL OF EVIDENCE

Level III, diagnostic study.

The Physiology of Bone Pain. How Much Do We Really Know?

Pain is associated with most bony pathologies. Clinical and experimental observations suggest that bone pain can be derived from noxious stimulation of the periosteum or bone marrow. Sensory neurons are known to innervate the periosteum and marrow cavity, and most of these have a morphology and molecular phenotype consistent with a role in nociception. However, little is known about the physiology of these neurons, and therefore information about mechanisms that generate and maintain bone pain is lacking. The periosteum has received greater attention relative to the bone marrow, reflecting the easier access of the periosteum for experimental assessment. With the electrophysiological preparations used, investigators have been able to record from single periosteal units in isolation, and there is a lot of information available about how they respond to different stimuli, including those that are noxious. In contrast, preparations used to study sensory neurons that innervate the bone marrow have been limited to recording multi-unit activity in whole nerves, and whilst they clearly report responses to noxious stimulation, it is not possible to define responses for single sensory neurons that innervate the bone marrow. There is only limited evidence that peripheral sensory neurons that innervate bone can be sensitized or that they can be activated by multiple stimulus types, and at present this only exists in part for periosteal units. In the central nervous system, it is clear that spinal dorsal horn neurons can be activated by noxious stimuli applied to bone. Some can be sensitized under pathological conditions and may contribute in part to secondary or referred pain associated with bony pathology. Activity related to stimulation of sensory nerves that innervate bone has also been reported in neurons of the spinoparabrachial pathway and the somatosensory cortices, both known for roles in coding information about pain. Whilst these provide some clues as to the way information about bone pain is centrally coded, they need to be expanded to further our understanding of other central territories involved. There is a lot more to learn about the physiology of peripheral sensory neurons that innervate bone and their central projections.