Heterotopic Ossification: Basic-Science Principles and Clinical Correlates

Prediction of heterotopic ossification on the cervical spine with offset of the artificial disc - A finite element study

Heterotopic ossification (HO) is a significant complication of cervical total disc replacement (TDR), often leading to fusion and negating the intended benefits of motion preservation. Although clinical factors associated with HO formation are known, the exact biomechanical mechanism remains unclear. This study aims to predict HO formation after Mobi-C disc replacement at the C5-C6 level using a validated finite element model (FEM) of the cervical spine (C2-T1) under physiological loading. The results revealed that the Mobi-C disc increased the range of motion (ROM) at the implanted level by 52 % under flexion and extension, while adjacent levels exhibited a 2-5 % reduction. Following HO formation, ROM at the implanted level decreased by 67-76 % in flexion and extension, respectively, while adjacent levels showed a moderate increase of 5-8 %. Additionally, intradiscal pressure at the adjacent levels increased by up to 60 % in extension, mimicking fusion-like behavior. HO volume was 678 mm³ for the ideal implant position, to 760 mm³ (+12 %) for a 0.5 mm offset and 800 mm³ (+17 %) for a 1 mm offset. This study highlights the importance of Mobi-C placement to minimize HO formation, preserve motion, and mitigate complications, providing insights for clinical practice.

Ossification in Normal and Pathological Contexts: The Key Role of Static Osteogenesis vs. Dynamic Osteogenesis in the Etiopathology of Some Skeletal Alterations

This Commentary is intended to start a discussion in the field of calcification/ossification related to osteogenesis. It highlights that two types of bone formation, static osteogenesis (SO) and dynamic osteogenesis (DO), are temporally followed by each other in bone histogenesis and bone lesion repair. Moreover, they also represent the common denominator in the pathological processes of both calcification and peculiar ossifications, such as heterotopic ossification and the formation of supernumerary skeletal segments. The final objective is to propose a different interpretation of certain bone alterations/pathologies, attributable to the two peculiar osteogenesis patterns (SO and DO), occurring in both physiological and pathological conditions. From these reflections, new approaches in the definition of diagnosis and therapies of certain alterations could be derived.

Heterotopic ossification following total wrist arthroplasty: a case report

BACKGROUND

Total wrist arthroplasty as a procedure in patients with advanced osteoarthritis has gained more popularity in recent years. As early implants had high rates of complications and newer implants have only slowly gained traction, some sequelae have not been reported yet.

CASE PRESENTATION

This study presents the case of a male German patient, 57 years old, with advanced osteoarthritis who received arthroplasty and presented with severely restricted range of motion 6 weeks after surgery. Radiographs revealed signs of heterotopic ossification that could be confirmed during the revision surgery. Intraoperatively, ossifications were removed and the mobile parts of the implant were changed. In the further course of the healing process, no further signs of ossifications have been reported for 1 year, but range of motion remains reduced.

CONCLUSION

This is the first reported case of heterotopic ossification of the wrist following arthroplasty. Heterotopic ossification should be taken into consideration in cases of restricted range of motion after arthroplasty to be able to handle this complication adequately.

Ethnicity does not change burn resuscitation and time to first excision

Health and racial disparities can limit access to preventative, trauma, and chronic disease care but have not been addressed in burn resuscitation. Over- and under-resuscitation contribute to increased overall hospital costs, and morbidity and mortality rates. The primary objective of this study was to identify potential racial disparities that may exist during the initial fluid resuscitation after burn injury. This was a retrospective review of all burn patients > 14 years of age admitted between January 1, 2020 and December 31, 2022 to a county safety net hospital. Patients were excluded if they transitioned to comfort care within 24 hours of admission. Data collected included baseline demographics, relevant burn injury information, and laboratory parameters. Outcomes included hospital and ICU length of stay, duration of mechanical ventilation, payor status, and mortality. Patients were divided into white (59 %) vs. African American-Hispanic (AA-HIS) (41 %) and included 105 patients. The median age (IQR) was 44.5(30) for whites vs 34(36) for AA-HIS. There were no statistically significant differences in severity of burn injury, cause of burn injury, rates of inhalation injury, or ICU or hospital lengths of stay. In both groups 55 % of the patients required mechanical ventilation while 18 % required renal replacement therapy. Overall mortality was not higher in the AA-HIS group at 32.6 % vs 17.7 % (p = 0.081). There were no differences in amount of fluid administered, urine output, laboratory values during resuscitation, or patient outcomes between the groups. The use of protocols for burn resuscitation can be instrumental in protecting against racial and ethnic disparities.

Myositis Ossificans of the Piriformis Muscle: First Reported Case of Non-Traumatic Sciatic Nerve Injury Requiring Surgical Decompression

There are only scarce reports of other presentations of non-traumatic myositis ossificans (MO). We describe the first reported case of non-traumatic MO of the piriformis muscle causing irretractability neuropathic pain in the sciatic nerve territory and signs of severe motor and sensory deficit, requiring surgical decompression. The patient presented a complete resolution of pain and partial resolution of neurological deficits. The surgical images and protocol, imaging tests, and post-surgical follow-up were reviewed, using validated scales and rating systems. We concluded that MO is an infrequent condition, but high suspicion is required because early treatment reduces the development of permanent neurological deficits.

Clinical outcomes following total hip arthroplasty for bony ankylosed hips: a propensity score-matched analysis

BACKGROUND

Total hip arthroplasty (THA) is one of the most effective treatments for hip arthritis. However, postoperative outcomes of THA in patients with bony ankylosed hips remain inconclusive. We aimed to examine the postoperative results of THAs for bony ankylosed hips using propensity score matching.

METHODS

A propensity score was calculated using logistic regression analysis for a bony-ankylosed group (40 hips, 38 patients) and a non-ankylosed (control) group (829 hips, 729 patients). Patients were followed up for more than 10 years after primary THA. The propensity score used five covariates: age, sex, height, weight, and body mass index. Propensity matching was performed, with each bony ankylosed hip being matched to a non-ankylosed control hip. The clinical outcomes of the Japanese Orthopaedic Association (JOA) hip scores and complications were investigated.

RESULTS

The propensity-matched population consisted of 40 bony ankylosed hips (38 patients) and 40 hips (40 patients) of matched controls. In both groups, the postoperative JOA hip scores at the last follow-up significantly improved compared to the preoperative scores. The JOA hip scores at the last follow-up for all components in the bony-ankylosed group were significantly lower than those in the control group. The number of hips with postoperative complications was significantly higher in the bony-ankylosed group than that in the control group.

CONCLUSIONS

THA for patients with bony ankylosed hips achieved positive results, including improved JOA hip scores; however, these scores were inferior to those observed in patients with non-ankylosed hips. This should be preoperatively communicated to patients with bony ankylosed hips who undergo THA.

Heterotopic ossification: Current developments and emerging potential therapies

ABSTRACT

This review aimed to provide a comprehensive analysis of the etiology, epidemiology, pathology, and conventional treatment of heterotopic ossification (HO), especially emerging potential therapies. HO is the process of ectopic bone formation at non-skeletal sites. HO can be subdivided into two major forms, acquired and hereditary, with acquired HO predominating. Hereditary HO is a rare and life-threatening genetic disorder, but both acquired and hereditary form can cause severe complications, such as peripheral nerve entrapment, pressure ulcers, and disability if joint ankylosis develops, which heavily contributes to a reduced quality of life. Modalities have been proposed to treat HO, but none have emerged as the gold standard. Surgical excision remains the only effective modality; however, the optimal timing is controversial and may cause HO recurrence. Recently, potential therapeutic strategies have emerged that focus on the signaling pathways involved in HO, and small molecule inhibitors have been shown to be promising. Moreover, additional specific targets, such as small interfering RNAs (siRNAs) and non-coding RNAs, could be used to effectively block HO or develop combinatorial therapies for HO.

A mouse coccygeal intervertebral disc degeneration model with tail-looping constructed using a suturing method

BACKGROUD

Intervertebral disc degeneration (IDD) is one of the common degenerative diseases. Due to ethical constraints, it is difficult to obtain sufficient research on humans, so the use of an animal model of IDD is very important to clarify the pathogenesis and treatment mechanism of the disease.

METHODS

In this study, thirty 2-month-old mice were selected for operation to establish a coccygeal IDD model. The distal tail portion of the tail (beyond the 17th coccygeal vertebra) and a small piece of skin above the 8th coccygeal vertebra were excised, and the two incisions were brought together after flexion, and secured with sutures. The heights and signal intensities of the intervertebral discs (IVDs) were assessed using microcomputed tomography (μCT) and magnetic resonance imaging (MRI) at 0, 6, 12 weeks postoperatively. The overall tissue morphology, cell distribution and density, and extracellular matrix of the IVDs were also assessed using Hematoxylin and Eosin (HE), Safranin O-Fast Green and immunohistochemical staining.

RESULTS

All mice in the experimental group survived after the operation, and there were no complications such as wound infection, tail necrosis and suture shedding. The experimental results demonstrated that the suturing method can successfully initiate IDD. Different severity levels of IDD can be induced by controlling the bending angle of the IVDs within the tail loop; however, for consistency, histologic and imaging results should be obtained at the same bending angle and looping period.

CONCLUSIONS

This IDD model is an effective method for studying the etiology and treatment of degenerative IVD disease.

Denervation‑induced NRG3 aggravates muscle heterotopic ossification via the ErbB4/PI3K/Akt signaling pathway

Peripheral nerve injury exacerbates progression of muscle heterotopic ossification (HO) and induces changes in expression of local cytokines in muscle tissue. The objective of the present study was to assess the impact of peripheral nerve injury on muscle HO development and the mechanism of cytokine modulation. A mouse model of gastrocnemius muscle HO was established and the sciatic nerve cut to simulate peripheral nerve injury. To evaluate the underlying factors contributing to the exacerbation of muscle HO resulting from denervation, fresh muscle tissue was collected and micro‑computed tomography, histochemical staining, RNA‑sequencing, reverse transcription‑quantitative PCR, Western blot, muscle tissue chip array were performed to analyze the molecular mechanisms. Sciatic nerve injury exacerbated HO in the gastrocnemius muscle of mice. Moreover the osteogenic differentiation of nerve‑injured muscle tissue‑derived fibro‑adipogenic progenitors (FAPs) increased in vitro. The expression of neuregulin 3 (NRG3) was demonstrated to be increased after nerve injury by muscle tissue chip array. Subsequent transcriptome sequencing analysis of muscle tissue revealed an enrichment of the PI3K/Akt pathway following nerve injury and an inhibitor of the PI3K/Akt pathway reduced the osteogenic differentiation of FAPs. Mechanistically, in vitro, peripheral nerve injury increased secretion of NRG3, which, following binding to ErbB4 on the cell surface of FAPs, promoted expression of osteogenesis‑associated genes via the PI3K/Akt signaling pathway, thus contributing to osteogenic differentiation of FAPs. In vivo, inhibition of the PI3K/Akt pathway effectively protected against muscle HO induced by peripheral nerve injury in mice. The present study demonstrated that the regulatory roles of NRG3 and the PI3K/Akt pathway in peripheral nerve injury exacerbated muscle HO and highlights a potential therapeutic intervention for treatment of peripheral nerve injury‑induced muscle HO.

Distal Biceps Tendon Repair: An Arthroscopic-Assisted Technique With Suture Anchors

Distal biceps tendon ruptures are rare injuries that can lead to significant limitations in forearm supination strength and elbow flexion. Although conservative treatment leads to satisfactory results in many cases, surgical treatment is indicated in high-demanding patients, heavy workers, and athletes. Many different surgical techniques have been described, but the percentage of complications after surgery remains high (almost 25%). The purpose of this article is to describe our preferred surgical approach for acute distal biceps tendon ruptures with an arthroscopic-assisted technique and suture anchor fixation method. We believe that this technique can be easily reproducible and that it might lead to a reduction in the complication rate because it is less invasive.

Exploring the role of peripheral nerves in trauma-induced heterotopic ossification

Recent studies have linked pain and the resultant nociception-induced neural inflammation (NINI) to trauma-induced heterotopic ossification (THO). It is postulated that nociception at the injury site stimulates the transient receptor potential vanilloid-1 (the transient receptor potential cation channel subfamily V member 1) receptors on sensory nerves within the injured tissues resulting in the expression of neuroinflammatory peptides, substance P (SP), and calcitonin gene-related peptide (CGRP). Additionally, BMP-2 released from fractured bones and soft tissue injury also selectively activates TRVP1 receptors, resulting in the release of SP and CGRP and causing neuroinflammation and degranulation of mast cells causing the breakdown the blood-nerve barrier (BNB), leading to release of neural crest derived progenitor cells (NCDPCs) into the injured tissue. Parallel to this process BMP-2 initiates the NCDPCs toward osteogenic differentiation. CGRP has direct osteogenic effects on osteoprogenitor cells/mesenchymal stem cells, by activating BMP-2 via canonical Wnt/β-catenin signaling and cAMP-cAMP-response element binding protein signaling. BMP-2 binds to TGF-βRI and activates TGF-β-activated kinase 1 (TAK1) leading to phosphorylation of SMAD1/5/8, which binds to the co-activator SMAD4 and translocates to the nucleus to serve as transcription factor for BMP responsive genes critical in osteogenesis such as Runx2 and others. Thus, NINI phenotypes, and specifically CGRP induction, play a crucial role in THO initiation and progression through the activation of the BMP pathway, breakdown of the BNB, leading to the escape of NCDPCs, and the osteogenic differentiation of the latter.

Artificial intelligence in predicting postoperative heterotopic ossification following anterior cervical disc replacement

OBJECTIVE

This study aimed to develop and validate a machine learning (ML) model to predict high-grade heterotopic ossification (HO) following Anterior cervical disc replacement (ACDR).

METHODS

Retrospective review of prospectively collected data of patients undergoing ACDR or hybrid surgery (HS) at a quaternary referral medical center was performed. Patients diagnosed as C3-7 single- or multi-level cervical disc degeneration disease with > 2 years of follow-up and complete pre- and postoperative radiological imaging were included. An ML-based algorithm was developed to predict high grade HO based on perioperative demographic, clinical, and radiographic parameters. Furthermore, model performance was evaluated according to discrimination and overall performance.

RESULTS

In total, 339 ACDR segments were included (61.65% female, mean age 45.65 ± 8.03 years). Over 45.65 ± 8.03 months of follow-up, 48 (14.16%) segments developed high grade HO. The model demonstrated good discrimination and overall performance according to precision (High grade HO: 0.71 ± 0.01, none-low grade HO: 0.85 ± 0.02), recall (High grade HO: 0.68 ± 0.03, none-low grade HO: 0.87 ± 0.01), F1-score (High grade HO: 0.69 ± 0.02, none-low grade HO: 0.86 ± 0.01), and AUC (0.78 ± 0.08), with lower prosthesis‑endplate depth ratio, higher height change, male, and lower postoperative-shell ROM identified as the most important predictive features.

CONCLUSION

Through an ML approach, the model identified risk factors and predicted development of high grade HO following ACDR with good discrimination and overall performance. By addressing the shortcomings of traditional statistics and adopting a new logical approach, ML techniques can support discovery, clinical decision-making, and intraoperative techniques better.

Heterotopic Ossifications Following Intramedullary Stabilization of Femoral Fractures in Polytraumatized Patients

INTRODUCTION

Heterotopic ossifications (HOs) are a well-known complication following total hip arthroplasty. Yet only little is known about the development of HOs following a femoral fracture and intramedullary stabilization in polytraumatized patients. Thus, the present study aimed to investigate whether the development of HOs is being observed more frequently in patients suffering polytrauma compared to those with single-extremity trauma.

MATERIALS AND METHODS

The retrospective outcome study was conducted at our level I trauma center. All patients admitted from 2010 to 2020 were included if they (1) presented with multiple injuries (≥2 body regions), (2) had an Injury Severity Score ≥16, (3) suffered a femoral fracture, and (4) were treated with intramedullary stabilization. Furthermore, a control group was established to match the polytrauma group (sex, age), who were suffering from single-extremity trauma (femoral fracture) which was treated with intramedullary stabilization. Subsequently, X-rays of the hip were performed and evaluated for up to one-year post-trauma.

RESULTS

Our study group consisted of 36 patients in total (91.7% male; mean age 39.4 ± 17.4 years, range: 18-82 years). The polytrauma (PT) group included 12 patients (mean age 39.5 years, median ISS 28), whereas the control group (single-extremity-trauma) included 24 patients (mean age 39.3 years). We documented HOs in nine (75%) patients in the PT group vs. five (20.8%) patients in the single-extremity group (p = 0.03).

CONCLUSION

In this study, we were able to demonstrate that heterotopic ossifications are being observed significantly more frequently in patients suffering from polytrauma in comparison to patients with single-extremity trauma following intramedullary stabilization after a femoral fracture.

Role of hedgehog signaling in the pathogenesis and therapy of heterotopic ossification

Heterotopic ossification (HO) is a pathological process that generates ectopic bone in soft tissues. Hedgehog signaling (Hh signaling) is a signaling pathway that plays an important role in embryonic development and involves three ligands: sonic hedgehog (Shh), Indian hedgehog (Ihh) and desert hedgehog (Dhh). Hh signaling also has an important role in skeletal development. This paper discusses the effects of Hh signaling on the process of HO formation and describes several signaling molecules that are involved in Hh-mediated processes: parathyroid Hormone-Related Protein (PTHrP) and Fkbp10 mediate the expression of Hh during chondrogenesic differentiation. Extracellular signal-regulated kinase (ERK), GNAs and Yes-Associated Protein (YAP) interact with Hh signaling to play a role in osteogenic differentiation. Runt-Related Transcription Factor 2 (Runx2), Mohawk gene (Mkx) and bone morphogenetic protein (BMP) mediate Hh signaling during both chondrogenic and osteogenic differentiation. This paper also discusses possible therapeutic options for HO, lists several Hh inhibitors and explores whether they could serve as emerging targets for the treatment of HO.

Comparative analysis of 'functional excision' of heterotopic ossification around the hip - computed tomography (CT) navigation guided versus conventional excision

PURPOSE

We aim to analyse and compare the efficacy of the excision of HO around the hip with and without CT-guided navigation. We also aim to compare the functional outcome between CT navigation guided versus conventional excision of HO.

PATIENTS AND METHODS

This study is a retrospective analysis of prospectively collected data from 2015 to 2022. There were 23 patients (24 hips) in the final cohort. Intraoperative CT navigation guided excision was performed in 7 hips and conventional excision of HO was done in 17 hips. The HO was classified by Brooker's grading in radiographs. CT scan was taken preoperatively in all patients to exactly identify the volume, location and preoperative planning. The functional outcome was analysed according to Harris Hip Score (HHS) and International Hip Outcome Tool (iHOT) for self-ambulatory patients and improvement in the sitting or nursing care was assessed in patients mobilising with wheelchair or walker support. Any complications or recurrence noted postoperatively and in follow-up were recorded.

RESULTS

The mean follow-up was 41.2 months in the CT navigation-guided excision group and 55 months in the conventional excision group. According to Brooker's grading, grade IV was present in 20 hips and grade III in four hips. Twelve patients were self-ambulatory and the other 12 patients were requiring support for mobilisation. There was a significant improvement in the HHS from 21.3 ± 3.7, 18.3 ± 2.5 preoperatively to 75.2 ± 8.3, 72.2 ± 4.3 postoperatively in the CT navigation guided and conventional group respectively (p < 0.001) in the self-ambulatory group. There was one anterior wall and one partial posterior wall fracture in the conventional group. One patient in the conventional group had a deep infection and recurrence. One patient had a superficial infection and another had superficial vein thrombosis in the CT guided excision group.

CONCLUSION

Intraoperative CT navigation helps to exactly localize the HO and facilitates safe excision. Functional excision of the HO leads to better nursing care and functional outcomes between both groups.

Dual and opposing role of retinoic acid receptor signaling in mesenchymal stem cells for tendon ossification in mice

Heterotopic ossification is abnormal bone formation in soft tissues that occurs primarily after injury and major surgery. This condition often causes local pain and limits joint motion in the affected limb. Currently, there is no effective treatment or prophylaxis for this condition other than surgical removal of the lesion. Recent studies suggest that retinoic acid receptor (RAR) agonists are effective in suppressing heterotopic ossification in patients with Fibrodysplasia Ossificans Progressiva, a congenital disorder characterized by progressive ossification of soft tissue, by suppressing the aberrant differentiation of mesenchymal stem cells in muscle. In this study, we aimed to elucidate the potential use of RAR agonists in suppressing injury-induced ectopic tendon ossification using a mouse Achilles tenotomy model. Contrary to our initial hypothesis, administration of RAR agonists throughout the experimental period (5 weeks) accelerated ectopic tendon ossification in our model. Of note, in vitro differentiation experiments using tendon-derived mesenchymal stem cells revealed that RAR agonists play opposing roles in osteogenic and chondrogenic differentiation, promoting the former and suppressing the latter. Indeed, we found that RAR agonists suppressed tendon ossification when administered before cartilage nodule formation, but promoted it when administered after. These results suggest that RAR agonists have a dual and opposing effect on tendon ectopic ossification, depending on the duration and timing of their administration. Our data may provide a basis for further investigation of the potential use of RAR agonists in the treatment of injury-induced heterotopic ossification.

Heterotopic mesenteric ossification caused by trauma: A case report

BACKGROUND

Heterotopic mesenteric ossification (HMO) is a clinically rare condition characterized by the formation of bone tissue in the mesentery. The worldwide reporting of such cases is limited to just over 70 instances in the medical literature. The etiology of HMO remains unclear, but the disease is possibly induced by mechanical trauma, ischemia, or intra-left lower quadrant abdominal infection, leading to the differentiation of mesenchymal stem cells into osteoblasts. Here, we present a rare case of HMO that occurred in a 34-year-old male, who presented with left lower quadrant abdominal pain.

CASE SUMMARY

We report the case of a 34-year-old male patient who presented with left lower abdominal pain following trauma to the left lower abdomen. He subsequently underwent surgical treatment, and the postoperative pathological diagnosis was HMO.

CONCLUSION

We believe that although there is limited literature and research on HMO, when patients with a history of trauma or surgery to the left lower abdomen present with corresponding imaging findings, clinicians should be vigilant in distinguishing this condition and promptly selecting appropriate diagnostic and therapeutic interventions.

A rare mass with atypical localization: Heterotopic ossification associated with flexor hallucis longus

Heterotopic ossification (HO), characterized by the formation of ectopic bone, is a benign mass observed in soft tissues. Depending on its location, it can cause symptoms beyond compression, such as mechanical blockage when associated with joints, leading to limitations in joint movements. In the majority of cases, involvement of the hip and elbow joints is common, while HO can sometimes be observed in atypical locations. Trauma, head injury, and spinal cord injuries are well-recognized risk factors for HO development. However, on rare occasions, in non-traumatic cases are identified without any known risk factors. Herein, we present a rare non-traumatic HO case associated with the flexor hallucis longus (FHL) tendon in a 58-year-old female patient. She complained of pain under the first toe of her right foot while wearing shoes for a year, and a mass was detected on the plantar surface of the foot along with limitation of movement in the first metatarsophalangeal joint. Further examinations revealed that the identified mass was a mature HO lesion. Surgical treatment was performed, and during one-year follow-up, the pain subsided, and joint movements returned to normal, resulting in a satisfactory outcome. In conclusion, although many cases of HO are associated with traumatic injuries, it can sometimes be idiopathic, as in our case, and rarely it is accompanied tendon such as FHL in the foot.

Heterotopic ossification of the elbow joint in a child: Successful surgical resection - A case report

Background

This case report describes the occurrence of a rare heterotopic ossification of the elbow joint in a child, caused by inappropriate movement after trauma. A successful operation to remove heterotopic ossification was described in the report with satisfactory results.

Case presentation

A 7-year-old boy suffered a supracondylar fracture of the humerus after an accidental fall, and after immobilization with a cast, improper movement resulted in heterotopic ossification of the elbow joint, which severely affected joint function. The heterotopic ossification was surgically removed and a complete recovery was demonstrated at 18 months follow-up. The heterotopic ossification was successfully removed with good elbow function and no recurrence at 18 months follow-up.

Conclusions

The purpose of this report is to show the good results with surgical treatment of heterotopic ossification of the elbow joint in children,when conservative treatment does not work.

Single-cell RNA sequencing uncovers cellular heterogeneity and the progression of heterotopic ossification of the elbow

Heterotopic ossification of the elbow (HOE) is a complicated pathologic process characterized by extra bone formation in the elbow. Bone formation is a complex developmental process involving the differentiation of mesenchymal stem cells into osteoblasts. The aim of this study was to explore the cellular origin and progression of HOE by single-cell RNA sequencing. We identified 13 clusters of cells in HOE and further analyzed the subclusters for 4 of the main cell types. Six subclusters of osteoblasts, nine subclusters of chondrocytes, six subclusters of fibroblasts, and five subclusters of mononuclear phagocytes (MPs) were identified and analyzed. The new findings on osterix (OSX) and SOX9 expression in osteoblast subclusters and chondrocyte subclusters indicate that HOE is mediated through endochondral ossification. Further identification of the corresponding signature gene sets of distinct subclusters indicated that subclusters of osteoblasts_3, osteoblasts_4, osteoblasts_5, and osteoblasts_6 are relatively more mature during the osteoblastic progression of HOE. The trajectory analysis of the osteoblasts demonstrated that some genes were gradually downregulated, such as CRYAB, CCL3, SFRP4, WIF1, and IGFBP3, while other critical genes were upregulated, such as VCAN, IGFBP4, FSTL1, POSTN, MDK, THBS2, and ALPL, suggesting that these factors may participate in HOE progression. Cell-cell communication networks revealed extensive molecular interactions among the 13 HOE clusters. Ligand-receptor pairs for IL6, COL24A1, COL22A1, VWF, FZD6, FGF2, and NOTCH1 were identified, suggesting that multiple signaling pathways may be involved in HOE. In conclusion, this study provided the cellular atlas for HOE. We have established a greater extent of the heterogeneity of HOE cells than previously known through transcriptomic analysis at the single-cell level. We have observed gradual patterns of signature gene expression during the differentiation and maturation progression of osteoblasts from stem cells in HOE with higher resolution. The cell heterogeneity of HOE deserves further investigation to pave the way for identification of potential targets for HOE early diagnosis and therapeutic treatment.

Fulminant Heterotopic Ossification of the Lower Extremity After Gunshot Injury and Blunt Trauma: A Case Report

Traumatic heterotopic ossification (HO) of the lower extremity is relatively rare but is of major importance in clinical practice. They are defined as posttraumatic abnormal formations of bone within soft tissue outside of the skeletal system. This article describes the clinical case of a 31-year-old male patient who suffered 2 traumatic events within 12 months-a gunshot wound in the lumbar spine/gluteal region followed by a severe traumatic brain injury with intracranial hemorrhage in a traffic accident as a pedestrian. Clinically, the patient was bedridden because of complete stiffening of the lumbar spine, both hip joints, and the left knee joint. After preoperative diagnosis, 3 surgical ablations of the HO were performed on both the hip joints and the left knee joint. In addition, physiotherapeutic exercise, postoperative nonsteroidal anti-inflammatory drug administration (25 mg of indomethazine for 6 weeks, 3 times a day), and perioperative radiation with 7 Gy for each operation were advised. After 4 years of follow-up, the patient showed significant improvement. In HO treatment, prophylactic local radiotherapy (pre- and postoperative radiation with a local single dose of 7 Gy) and postoperative administration of nonsteroidal anti-inflammatory drugs are often recommended. For therapeutic purposes, surgical resection is still indicated for pronounced cases.

The Role of Neuromodulation and Potential Mechanism in Regulating Heterotopic Ossification

Heterotopic ossification (HO) is a pathological process characterized by the aberrant formation of bone in muscles and soft tissues. It is commonly triggered by traumatic brain injury, spinal cord injury, and burns. Despite a wide range of evidence underscoring the significance of neurogenic signals in proper bone remodeling, a clear understanding of HO induced by nerve injury remains rudimentary. Recent studies suggest that injury to the nervous system can activate various signaling pathways, such as TGF-β, leading to neurogenic HO through the release of neurotrophins. These pathophysiological changes lay a robust groundwork for the prevention and treatment of HO. In this review, we collected evidence to elucidate the mechanisms underlying the pathogenesis of HO related to nerve injury, aiming to enhance our understanding of how neurological repair processes can culminate in HO.

Excision of Intra-articular Knee Heterotopic Ossification Using a 70° Arthroscope

Heterotopic ossification is ectopic lamellar bone formation within soft tissue and can result in significant functional limitations. There are multiple underlying etiologies of HO including musculoskeletal trauma and traumatic brain injury. Intra-articular HO of the knee is rare and is typically located within the cruciate ligaments. We report a case of a 24-year-old female who presented with worsening right knee pain and limited knee extension two and a half years after a motor vehicle crash with multiple lower extremity fractures. Physical examination of the knee revealed anterior pain, limited extension, and a palpable infrapatellar prominence. Imaging showed a retropatellar tendon, intra-articular excrescence of bone proximal to the anterior tibial plateau. Diagnostic arthroscopy with a 70° arthroscope identified HO at the proximal anterior tibial plateau, which was excised with a high-speed burr under direct visualization. At the three-month follow-up, the patient remained asymptomatic and returned to sport. Retropatellar tendon, intra-articular anterior knee HO is a rare but debilitating clinical entity that can be successfully and safely managed with excision under direct visualization using a 70° arthroscope.

A scoping review on active vs. passive range of motion approaches to treat heterotopic ossification at the elbow

Objective

The objective of this scoping review is to synthesize and clarify literature on the effectiveness of active and passive range of motion therapy techniques to address range of motion in people with heterotopic ossification (HO), and to provide guidance to therapists in clinical decision-making based on current evidence.

Method

To find articles that included therapeutic interventions to maintain or improve range of motion in people with heterotopic ossification, the authors searched the following databases: Cochrane Database of Systematic Reviews, PubMed, CINAHL, PsychINFO, Web of Science, and OTSeeker. To ensure that the search was comprehensive, the authors also searched Burns and Trauma, Burns Journal, Burns Open, and the Journal of Hand Therapy. Searches were limited to peer-reviewed articles published in the English language. No publication date limits were set. The Physiotherapy Evidence Database PEDro scale was utilized to measure the validity of the methodological quality of each article.

Results

Five studies met the inclusion criteria.. Two studies emphasized that passive range of motion was effective in less than 50% of their subjects, while the other three studies utilized active range of motion only, reporting 50% of patients did not require surgery.

Discussion/conclusion

There is insufficient evidence to determine effective therapeutic management of HO and the literature that does exist is contradictory and inconclusive. Future research is necessary to determine if any effectiveness of manual therapeutic approaches exists for patients with HO.

Activation of BMP4/SMAD pathway by HIF-1α in hypoxic environment promotes osteogenic differentiation of BMSCs and leads to ectopic bone formation

OBJECTIVE

Heterotopic ossification (HO), also known as ossifying myositis, is a condition that produces abnormal bone and cartilage tissue in the soft tissues. Hypoxia inducible factor lα (HIF-lα) regulates the expression of various genes, which is closely related to the promotion of bone formation, and Drosophila mothers against decapentaplegic protein (SMAD) mediates the signal transduction in the Bone morphogenetic protein (BMP) signaling pathway, which affects the function of osteoblasts and osteoclasts, and thus plays a key role in the regulation of bone remodeling. We aimed to investigate the mechanism by which HIF-1α induces osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) in a hypoxic environment.

METHODS

A cellular hypoxia model was constructed to verify the expression of HIF-1α, while alizarin red staining was performed to observe the osteogenic differentiation ability of bone marrow mesenchymal stem cells (BMSCs). Alizarin red staining was used to analyze the late mineralization ability of the cells. Western blot analysis was performed to analyze the expression levels of osteogenesis-related factors OCN, OPN proteins as well as the pathway proteins BMP4, p-Smad1/5/8, and Smad1. We also constructed a rat model of ectopic bone formation, observed ectopic ossification by X-ray, and verified the success of the rat model by ELISA of HIF-1α. HE staining was used to observe the matrix and trabecular structure of bone, and Masson staining was used to observe the collagen and trabecular structure of bone. Immunohistochemistry analyzed the expression of OCN and OPN in ectopic bone tissues, and WB analyzed the expression of pathway proteins BMP4, p-Smad1/5/8 and Smad1 in ectopic bone tissues to verify the signaling pathway of ectopic bone formation.

RESULTS

Our results indicate that hypoxic environment upregulates HIF-1a expression and activates BMP4/SMAD signaling pathway. This led to an increase in ALP content and enhanced expression of the osteogenesis-related factors OCN and OPN, resulting in enhanced osteogenic differentiation of BMSCs. The results of our in vivo experiments showed that rats inoculated with BMSCs overexpressing HIF-1α showed bony structures in tendon tissues, enhanced expression of the bone signaling pathways BMP4 and p-Smad1/5/8, and enhanced expression levels of the osteogenic-related factors OCN and OPN, resulting in the formation of ectopic bone.

CONCLUSIONS

These data further suggest a novel mechanistic view that hypoxic bone marrow BMSCs activate the BMP4/SMAD pathway by up-regulating the expression level of HIF-1α, thereby promoting the secretion of osteogenic factors leading to ectopic bone formation.

Heterotopic ossification following COVID-19 infections: systematic literature review of case reports and case series

BACKGROUND

This review aims to study the clinical characteristics, diagnostic results, treatments, and outcomes in patients with heterotopic ossification following COVID-19 infection.

METHODS

A literature search for eligible articles was conducted using MEDLINE/Pubmed, Global Health, and Scopus databases (January 12th, 2023), including all case reports and case series from any country and language. The criteria for inclusion in this review were cases of COVID-19 infection subsequently developing heterotopic ossification.

RESULTS

This systematic review analysed 15 reports (n = 20 patients) documenting cases of heterotopic ossification following COVID-19 infection. 80% of the patients were male, with a median age of 59 years. All patients required intensive care unit stay with an average duration of 48.5 days. Mechanical ventilation was necessary for all patients and 30% of them underwent tracheostomy. Common symptoms included stiffness and pain, most frequently affecting multiple locations (70%), with the hips and shoulders being predominantly involved. X-rays were the most commonly used imaging modality, followed by computed tomography. Although treatment was given, some of the patients continued to experience symptoms, particularly stiffness.

CONCLUSION

20 patients who developed heterotopic ossification after COVID-19 have been reported, the majority of which had at least two independent risk factors for this condition. The link between those two clinical entities is therefore uncertain, requiring further investigation. It is nonetheless important to suspect heterotopic ossification in patients with severe COVID-19 infection, prolonged immobilisation, mechanical ventilation, who develop joint pain and stiffness, as this condition can significantly impact patients' quality of life.

PROTOCOL REGISTRATION

CRD42023393516.

Case report: Focal heterotopic ossification in paravertebral muscles as a cause of neurogenic lameness in a dog

This case report describes a 17-month-old Pudelpointer with recurring motor impairment localized to the left thoracic limb. A neurological exam highlighted lameness in that limb, accompanied by pre-scapular swelling. Radiographs and magnetic resonance imaging detected an osseous structure in soft tissues close to the fifth cervical vertebra, and subsequent surgery uncovered adjacent cervical spinal nerve impingement. Histology of the bony structure revealed heterotopic ossification in paravertebral muscles. Mild bone re-formation at the operating site was detected after a 2-year period, but the patient was asymptomatic. This article reports the first case of heterotopic ossification with spinal nerve entrapment in a dog and adds a new differential diagnosis to the causes of neurogenic lameness in dogs.

Incidence of heterotopic ossification following total hip arthroplasty by approach: a systematic review

BACKGROUND

Heterotopic ossification (HO) formation has been increasingly recognized as a complication of major orthopedic surgeries, particularly total hip arthroplasty (THA). Though, the overall incidence of HO following THA has been well-documented, it is often not reported by severity or by surgical approach.

QUESTIONS/PURPOSES

(1) What are the demographics of patients with HO? (2) What is the severity of HO following THA using the Brooker classification? (3) What is the incidence and class of HO following different THA approaches (anterior, posterior, posterolateral, anterolateral, superior, lateral, trans-gluteal)? (4) What are the number and training level of surgeons who performed each procedure?

METHODS

The PubMed, Embase, and Web of Science databases were queried, and PRISMA guidelines were followed. Qualitative and quantitative analyses were performed using Microsoft Excel.

RESULTS

We isolated 26 studies evaluating 6512 total hip arthroplasties (THA). The mean HO percentage overall was 28.8%, mostly Class I (54.2%) or Class II (29.6%). The highest percentage of HO was associated with the modified direct lateral (57.2%) and the traditional lateral (34.6%) approaches. The lowest HO percentages were identified following posterolateral (12.8%) and direct superior approaches (1%). Most studies reported a singular senior surgeon operating within the same approach for all patients.

CONCLUSIONS

The traditional lateral and modified direct lateral approaches to THA resulted in the highest percentage of HO postoperatively. However, most ossification cases were not clinically significant and did not strongly affect overall patient morbidity. Further studies are warranted to identify an association between severity of ossification and different arthroplasty approaches.

Genetic regulation of injury-induced heterotopic ossification in adult zebrafish

Heterotopic ossification is the inappropriate formation of bone in soft tissues of the body. It can manifest spontaneously in rare genetic conditions or as a response to injury, known as acquired heterotopic ossification. There are several experimental models for studying acquired heterotopic ossification from different sources of damage. However, their tenuous mechanistic relevance to the human condition, invasive and laborious nature and/or lack of amenability to chemical and genetic screens, limit their utility. To address these limitations, we developed a simple zebrafish injury model that manifests heterotopic ossification with high penetrance in response to clinically emulating injuries, as observed in human myositis ossificans traumatica. Using this model, we defined the transcriptional response to trauma, identifying differentially regulated genes. Mutant analyses revealed that an increase in the activity of the potassium channel Kcnk5b potentiates injury response, whereas loss of function of the interleukin 11 receptor paralogue (Il11ra) resulted in a drastically reduced ossification response. Based on these findings, we postulate that enhanced ionic signalling, specifically through Kcnk5b, regulates the intensity of the skeletogenic injury response, which, in part, requires immune response regulated by Il11ra.

Musculoskeletal Issues in Pediatric Burn Patients

A burn injury affects virtually every organ system. The purpose of this article is to review musculoskeletal issues in children with burn injuries. Both acute and long-term problems will be discussed. A low threshold to consult a pediatric orthopaedist is recommended.

Vegfc-expressing cells form heterotopic bone after musculoskeletal injury

Heterotopic ossification (HO) is a challenging condition that occurs after musculoskeletal injury and is characterized by the formation of bone in non-skeletal tissues. While the effect of HO on blood vessels is well established, little is known about its impact on lymphatic vessels. Here, we use a mouse model of traumatic HO to investigate the relationship between HO and lymphatic vessels. We show that injury triggers lymphangiogenesis at the injury site, which is associated with elevated vascular endothelial growth factor C (VEGF-C) levels. Through single-cell transcriptomic analyses, we identify mesenchymal progenitor cells and tenocytes as sources of Vegfc. We demonstrate by lineage tracing that Vegfc-expressing cells undergo osteochondral differentiation and contribute to the formation of HO. Last, we show that Vegfc haploinsufficiency results in a nearly 50% reduction in lymphangiogenesis and HO formation. These findings shed light on the complex mechanisms underlying HO formation and its impact on lymphatic vessels.

Idiopathic cardiac ossification with Chiari mesh in the right atrium: a case report and literature review

Background

Idiopathic cardiac osseous metaplasia in the right atrium of a 9-year-old boy, accompanied by right atrial Chiari network and right pulmonary artery embolism. This case is rare and can easily be misdiagnosed.

Case Description

We encountered a case of a 9-year-old boy with a 3.5 cm diameter neoplasm in the right atrium. Preoperative imaging diagnosis could not determine the nature of the tumor, and the initial clinical suspicion of cardiac myxoma. After admission, a cardiotomy to remove foreign bodies and a pulmonary artery thrombectomy were performed.

Conclusions

Idiopathic cardiac osseous metaplasia is relatively rare, and it is even rarer to be accompanied by a Chiari network in the right atrium. Due to the location and characteristics of the lesion in this case, it is easy to be misdiagnosed as atrial myxoma in clinical practice. Whether it is idiopathic osseous metaplasia or myxoma, it needs to be performed surgical treatment and pathological examination can easily rule out the diagnosis of myxoma. However, as idiopathic cardiac metaplasia is difficult to encounter in clinical work and there are few reports in the literature, clinicians and pathologists need to consult more relevant literature. Learn to understand and master the disease through multi-party consultation.

Heterotopic Ossification Secondary to Motor Vehicle Collision Trauma Leading to Femoroacetabular Impingement Syndrome: A Case Report

Introduction

A patient presented for recalcitrant right hip pain secondary to femoroacetabular impingement (FAI) after blunt motor vehicle trauma and following the development of a 12 cm heterotopic ossification (HO). FAI is an increasingly recognized diagnosis where the hip joint is exposed to repeated femoral microtrauma from high-level physical activity or trauma, often causing labral ossification, and perhaps underlying a similar biological mechanism to HO.

Case Report

In this case report, we have an otherwise healthy 49-year-old male who was involved in a high-speed motor vehicle collision who was diagnosed with right hip FAI secondary to HO (Brooker's Class IV) and indicated for surgical excision of the HO anterior to the right proximal femur. The care team and patient initially trialed non-operative conservative treatment with non-steroidal anti-inflammatories drugs (NSAIDs) and hypothesized therapeutic success using a non-surgical approach. Surgical resection was pursued with the patient after a failure of conservative measures. The patient reported a zero out of ten on a ten-point numerical rating scale for pain, he also stated improved quality of life, satisfaction with the procedure, and subsequent rehabilitation at 1-month post-operative follow-up.

Conclusion

HO with near complete ankylosis of the hip joint may be causative of FAI when untreated. Although this case demonstrates a rarely studied traumatic etiology of impingement secondary to HO, initial standard conservative anti-inflammatory treatment can still be pursued. By analyzing the periarticular impact of HO secondary to non-surgical trauma, we can utilize and make inferential correlations from the literature, studying HO and impingement in the setting of prior hip surgery to guide treatment and prognosis in those presenting with FAI symptoms secondary to blunt force trauma.

Regional distribution prevalence of heterotopic ossification in the elbow joint: a 3D study of patients after surgery for traumatic elbow injury

BACKGROUND

Heterotopic ossification (HO) is a common complication after elbow fracture surgery and can lead to severe upper extremity disability. The radiographic localization of postoperative HO has been reported previously. However, there is no literature examining the distribution of postoperative HO at the three-dimensional (3D) level. This study aimed to investigate 1) the distribution characteristics of postoperative HO and 2) the possible risk factors affecting the severity of postoperative HO at a 3D level.

METHODS

A retrospective review was conducted of patients who presented to our institution with HO secondary to elbow fracture between 13 January 2020 and 16 February 2023. Computed tomography scans of 56 elbows before elbow release surgery were reconstructed in 3D. HO was identified using density thresholds combined with manual identification and segmentation. The elbow joint and HO were divided into six regions according to three planes: the transepicondylar plane, the lateral ridge of the trochlear plane, and the radiocapitellar joint and coronoid facet plane. The differences in the volume of regional HO associated with different initial injuries were analyzed.

RESULTS

Postoperative HO was predominantly present in the medial aspect of the capsule in 52 patients (93%), in the lateral aspect of the capsule in 45 patients (80%), in the medial supracondylar in 32 patients (57%), and in the lateral supracondylar, radial head, and ulnar region in the same number of 28 patients (50%). The median and interquartile range volume of total postoperative HO was 1683 (777-4894) mm3. The median and interquartile range volume of regional postoperative HO were: 584 (121-1454) mm3 at medial aspect of capsule, 207 (5-568) mm3 at lateral aspect of capsule, 25 (0-449) mm3 at medial supracondylar, 1 (0-288) at lateral supracondylar, 2 (0-478) at proximal radius and 7 (0-203) mm3 at the proximal ulna. In the subgroups with Injury Severity Score > or = 16, Gustilo-Anderson II, normal uric acid levels, elevated alkaline phosphatase, and body mass index > or = 24, the median HO volume exceeds that of the respective control groups.

CONCLUSION

The medial aspect of the capsule was the area with the highest frequency and median volume of postoperative HO among all initial elbow injury types. Patients with higher Gustilo-Anderson grade, Injury Severity Score, alkaline phosphatase or Body Mass Index had higher median volume of postoperative HO.

Exosome MiR-21-5p Upregulated by HIF-1α Induces Adipose Stem Cell Differentiation to Promote Ectopic Bone Formation

Heterotopic bone occurs after burns, trauma and major orthopedic surgery, which cannot be completely cured by current treatments. The development of new treatments requires more in-depth research into the mechanism of HO. Available evidence suggests that miR-21-5p plays an important role in bone formation. However, its mechanism in traumatic HO is still unclear. First, we identified exosomes extracted from L6 cells using TEM observation of the structure and western blotting detection of the surface marker CD63. Regulation effect of HIF-1α to miR-21-5p was confirmed by q-PCR assay. Then we co-cultured L6 cells with ASCs and performed alizarin red staining and ALP detection. Overexpression of miR-21-5p upregulated BMP4, p-smad1/5/8, OCN and OPN, which suggests the BMP4-smad signaling pathway may be involved in miR-21-5p regulation of osteogenic differentiation of ASCs. Finally in vivo experiments showed that miR-21-5p exosomes promoted ectopic formation in traumatized mice. This study confirms that HIF-1α could modulate miR-21-5p exosomes to promote post-traumatic ectopic bone formation by inducing ASCs cell differentiation. Our study reveals the mechanisms of miR-21-5p in ectopic ossification formation after trauma.

Cutaneous burn injury represents a major risk factor for the development of traumatic ectopic bone formation following blast-related extremity injury

Blast-related traumatic heterotopic ossification (tHO) impacts clinical outcomes in combat-injured patients, leading to delayed wound healing, inflammatory complications, and reduced quality of life. Blast injured patients often have significant burns. This study investigated whether a partial thickness thermal burn injury exacerbates blast-related tHO in a clinically relevant polytrauma animal model. Adult male Sprague Dawley rats were subjected to an established model involving a whole-body blast overpressure exposure (BOP), complex extremity trauma followed by hind limb amputation (CET) followed by the addition of a 10 % total body surface area (TBSA) second degree thermal burn (BU). Micro-CT scans on post-operative day 56 showed a significant increase in HO volume in the CET + BU as compared to the CET alone injury group (p < .0001; 22.83 ± 3.41 mm3 vs 4.84 ± 5.77 mm3). Additionally, CET + BU concomitant with BOP significantly increased HO (p < .0001; 34.95 ± 7.71 mm3) as compared to CET + BU alone, confirming BOP has a further synergistic effect. No HO was detectable in rats in the absence of CET. Serum analysis revealed similar significant elevated (p < .0001) levels of pro-inflammatory markers (Cxcl1 and Il6) at 6 h post-injury (hpi) in the CET + BU and BOP + CET + BU injury groups as compared to naïve baseline values. Real-time qPCR demonstrated similar levels of chondrogenic and osteogenic gene expression in muscle tissue at the site of injury at 168 hpi in both the CET + BU and BOP+CET + BU injury groups. These results support the hypothesis that a 10 % TBSA thermal burn markedly enhances tHO following acute musculoskeletal extremity injury in the presence and absence of blast overpressure. Furthermore, the influence of BOP on tHO cannot be accounted for either in regards to systemic inflammation induced from remote injury or inflammatory-osteo-chondrogenic expression changes local to the musculoskeletal trauma, suggesting that another mechanism beyond BOP and BU synergistic effects are at play. Therefore, these findings warrant future investigations to explore other mechanisms by which blast and burn influence tHO, and testing prophylactic measures to mitigate the local and systemic inflammatory effects of these injuries on development of HO.

Calcified apoptotic vesicles from PROCR+ fibroblasts initiate heterotopic ossification

Heterotopic ossification (HO) comprises the abnormal formation of ectopic bone in extraskeletal soft tissue. The factors that initiate HO remain elusive. Herein, we found that calcified apoptotic vesicles (apoVs) led to increased calcification and stiffness of tendon extracellular matrix (ECM), which initiated M2 macrophage polarization and HO progression. Specifically, single-cell transcriptome analyses of different stages of HO revealed that calcified apoVs were primarily secreted by a PROCR+ fibroblast population. In addition, calcified apoVs enriched calcium by annexin channels, absorbed to collagen I via electrostatic interaction, and aggregated to produce calcifying nodules in the ECM, leading to tendon calcification and stiffening. More importantly, apoV-releasing inhibition or macrophage deletion both successfully reversed HO development. Thus, we are the first to identify calcified apoVs from PROCR+ fibroblasts as the initiating factor of HO, and might serve as the therapeutic target for inhibiting pathological calcification.

Intersections of Fibrodysplasia Ossificans Progressiva and Traumatic Heterotopic Ossification

Heterotopic ossification (HO) is a debilitating pathology where ectopic bone develops in areas of soft tissue. HO can develop as a consequence of traumatic insult or as a result of dysregulated osteogenic signaling, as in the case of the orphan disease fibrodysplasia ossificans progressiva (FOP). Traumatic HO (tHO) formation is mediated by the complex interplay of signaling between progenitor, inflammatory, and nerve cells, among others, making it a challenging process to understand. Research into the pathogenesis of genetically mediated HO (gHO) in FOP has established a pathway involving uninhibited activin-like kinase 2 receptor (ALK2) signaling that leads to downstream osteogenesis. Current methods of diagnosis and treatment lag behind pre-mature HO detection and progressive HO accumulation, resulting in irreversible decreases in range of motion and chronic pain for patients. As such, it is necessary to draw on advancements made in the study of tHO and gHO to better diagnose, comprehend, prevent, and treat both.

Suppression of Overactive Insulin-Like Growth Factor 1 Attenuates Trauma-Induced Heterotopic Ossification in Mice

Heterotopic ossification (HO) is the ectopic bone formation in soft tissues. Aside from hereditary HO, traumatic HO is common after orthopedic surgery, combat-related injuries, severe burns, or neurologic injuries. Recently, mammalian target of rapamycin (mTOR) was demonstrated to be involved in the chondrogenic and osteogenic processes of HO formation. However, its upstream signaling mechanism remains unknown. The current study used an Achilles tendon puncture-induced HO model to show that overactive insulin-like growth factor 1 (IGF-1) was involved in the progression of HO in mice. Micro-computed tomography imaging showed that IGF-1 not only accelerated the rate of osteogenesis and increased ectopic bone volume but also induced spontaneous ectopic bone formation in undamaged Achilles tendons. Blocking IGF-1 activity with IGF-1 antibody or IGF-1 receptor inhibitor picropodophyllin significantly inhibited HO formation. Mechanistically, IGF-1/IGF-1 receptor activates phosphatidylinositol 3-kinase (PI3K)/Akt signaling to promote the phosphorylation of mTOR, resulting in the chondrogenic and osteogenic differentiation of tendon-derived stem cells into chondrocytes and osteoblasts in vitro and in vivo. Inhibitors of PI3K (LY294002) and mTOR (rapamycin) both suppressed the IGF-1-stimulated mTOR signal and mitigated the formation of ectopic bones significantly. In conclusion, these results indicate that IGF-1 mediated the progression of traumatic HO through PI3K/Akt/mTOR signaling, and suppressing IGF-1 signaling cascades attenuated HO formation, providing a promising therapeutic strategy targeting HO.

Heterotopic hip ossification resection: monocentric experiences of associated factors, outcomes, and complications

PURPOSE

The exponential increase in total hip arthroplasty (THA) has led to acute and chronic surgery-related complications. Common chronic and local complications are represented by hip ossification (HO). The aim of our study was to assess the clinical and radiological correlates of patients undergoing surgical removal of heterotopic ossifications after THA and the possible association between HO and prosthetic joint infection.

METHODS

Data of 26 patients who underwent surgical removal of periprosthetic calcifications after THA from 2000 to 2022 were analyzed and compared with characteristics of 156 subjects without HO.

RESULTS

The preoperative radiographs of patients showed a high-grade Brooker, 3 or 4, later reduced to 1 or 2 in the postoperative radiographs. Ten (38.5%) patients underwent radiotherapy prophylaxis, administered as a single dose 24 h before surgery. In 19 (73%) patients, pharmacological prophylaxis with indomethacin was added in the 30 postoperative days. Only one patient who underwent radiotherapy had a recurrence, while new ossifications were found in three patients without prophylaxis (11.5%). Intraoperative cultures were performed for suspected periprosthetic infection in 8 study group patients. In logistic regression, the presence of HO was significantly and inversely associated with the ASA score (OR = 0.27, 95% CI = 0.09-0.82; P = 0.021) after adjusting.

CONCLUSION

Surgical HO removal in symptomatic patients with high-grade disease produces good clinical and radiographic results. Radiotherapy was a good perioperative and preventive strategy for recurrence, also associated with NSAIDs and COX-2 inhibitors.

Nontraumatic Myositis Ossificans After Spontaneous Subarachnoid Hemorrhage: A Case Report

Myositis ossificans is uncommon in patients with nontraumatic brain injuries. This report presents a challenging case in which myositis ossificans was diagnosed and treated by medical management in a patient who was unable to complain of any symptoms due to akinetic mutism that occurred after nontraumatic subarachnoid hemorrhage. The patient had intermittent high-grade fever, and laboratory tests showed elevated C-reactive protein and D-dimer levels without clinical signs of infection two months after subarachnoid hemorrhage. Lower-extremity venography using computed tomography was performed to rule out deep venous thrombosis. There was no thrombus, but right vastus medialis muscle showed inflammatory change with faint multilayered curvilinear hyperdense rims. The administration of indomethacin helped prevent abnormal bone formation. For the early detection of myositis ossificans, careful observation of clinical presentation and a high index of clinical suspicion is necessary in brain-injured patients. Further, elevated serum inflammatory markers accompanied by elevated alkaline phosphatase can be a critical clue. Early computed tomography helps identify early 'string sign' prior to characteristic ossification. Our report highlights that the myositis ossificans is remediable by early detection and appropriate nonsurgical management.

Symptomatic Treatment of Myelopathy

OBJECTIVE

This article discusses the effects of myelopathy on multiple organ systems and reviews the treatment and management of some of these effects.

LATEST DEVELOPMENTS

Recent advances in functional electrical stimulation, epidural spinal cord stimulation, robotics, and surgical techniques such as nerve transfer show promise in improving function in patients with myelopathy. Ongoing research in stem cell therapy and neurotherapeutic drugs may provide further therapeutic avenues in the future.

ESSENTIAL POINTS

Treatment for symptoms of spinal cord injury should be targeted toward patient goals. If nerve transfer for upper extremity function is considered, the patient should be evaluated at around 6 months from injury to assess for lower motor neuron involvement and possible time limitations of surgery. A patient with injury at or above the T6 level is at risk for autonomic dysreflexia, a life-threatening condition that presents with elevated blood pressure and can lead to emergent hypertensive crisis. Baclofen withdrawal due to baclofen pump failure or programming errors may also be life-threatening. Proper management of symptoms may help avoid complications such as autonomic dysreflexia, renal failure, heterotopic ossification, and fractures.

MEK-inhibitors decrease Nfix in muscular dystrophy but induce unexpected calcifications, partially rescued with Cyanidin diet

Muscular dystrophies (MDs) are incurable genetic myopathies characterized by progressive degeneration of skeletal muscles. Dystrophic mice lacking the transcription factor Nfix display morphological and functional improvements of the disease. Recently, we demonstrated that MAPK signaling pathway positively regulates Nfix in muscle development and that Cyanidin, a natural antioxidant molecule, strongly ameliorates the pathology. To explore a synergistic approach aimed at treating MDs, we administered Trametinib, a clinically approved MEK inhibitor, alone or combined with Cyanidin to adult Sgca null mice. We observed that chronic treatment with Trametinib and Cyanidin reduced Nfix in myogenic cells but, unexpectedly, caused ectopic calcifications exclusively in dystrophic muscles. The combined treatment with Cyanidin resulted in histological improvements by preventing Trametinib-induced calcifications in Diaphragm and Soleus. Collectively, this first pilot study revealed that Nfix is modulated by the MAPK pathway in MDs, and that Cyanidin partly rescued the unexpected ectopic calcifications caused by MEK inhibition.

Traumatic bilateral acetabular fracture secondary to high-energy trauma in healthy adults

BACKGROUND

Bilateral acetabular fracture is a very rare presentation among the trauma patients, as the pattern and the degree of the forces required to fracture both acetabula is very unique. The primary purpose of this study is to report a series of adult patients presenting with post-traumatic bilateral acetabular fracture without any history of pathological or metabolic bone disease.

PATIENTS AND METHODS

In this retrospective study, 18 cases of traumatic bilateral acetabular fracture were included. There was predominance of both column (four patients on left and six on right) followed by anterior column (two patients left and four on right) and posterior wall (three patients left and right). They were treated surgically through open reduction and internal fixation. All cases were followed up for at least 13 months. Matta's criteria were used for radiological evaluation on plain radiographs. Functional outcome was evaluated using the Merle d'Aubigne and postel score at final follow-up.

RESULTS

No patients were lost during the follow-up period; there was one case of surgical site infection. There were three cases of postoperative osteoarthritis, one case of heterotrophic ossification, one case of persistent sciatic nerve palsy and one case of lateral femoral cutaneous nerve palsy. The radiological evaluation according to Matta's criteria revealed anatomic reduction in 12 patients, imperfect reduction in three patients while other three patients had poor reduction. According to modified Merle d'Aubigne and Postel score, 10 cases were rated as excellent, five cases as good and three cases presented fair (one case) to poor (two cases) results.

CONCLUSION

We report an unusual case series of bilateral acetabular fracture successfully managed surgically with good clinical outcome. With the increasing incidence of route traffic accidents, such cases would probably be recurrent in the upcoming years.

Embolization followed by resection of the heterotopic hip joint ossification with spinal cord injury

BACKGROUND

Heterotopic ossification of large joints, such as knees and hips, has been reported after spinal cord injury, possibly leading to decreased activity of daily living due to a limited range of motion of the affected joint. Therefore, heterotopic ossification resection is performed to improve the range of motion, but it might cause massive bleeding as a complication.

METHODS

In this case, the patient had a history of spinal cord injury and developed heterotopic ossification after the left hip injury. He had left hip ankylosis and could not transfer to a wheelchair by himself; therefore, heterotopic ossification resection was planned. On conducting contrast-enhanced computed tomography, the supplying arteries extending to the heterotopic ossification could be identified. A day before the surgery, embolization of the branches by interventional radiology was performed.

RESULTS

Heterotopic ossification resection was performed with an 820-ml blood loss. Postoperative rehabilitation was continued, and range of motion continued to improve without heterotopic ossification recurrence 2 years post-surgery.

CONCLUSIONS

The combination of preoperative contrast-enhanced computed tomography and embolization was useful in treating heterotopic ossification.

3D-Printed Model in Preoperative Planning of Sciatic Nerve Decompression Because of Heterotopic Ossification: A Case Report

CASE

A 31-year-old patient presented with an encapsulated sciatic nerve secondary to extensive hip heterotopic ossification (HO), which prevented visualization of a safe osteotomy site to avoid nerve damage. The 3D-printed model demonstrated an easily identifiable osseous reference point along the inferior aspect of the heterotopic mass, allowing for a vertical osteotomy to be safely performed.

CONCLUSION

HO is associated with loss of normal anatomic topography. The current case report illustrates the use of a 3D-printed model to identify pertinent anatomic landmarks required for safe decompression of an encapsulated sciatic nerve within the anatomic region of the hip.

Pristimerin suppresses AIM2 inflammasome by modulating AIM2-PYCARD/ASC stability via selective autophagy to alleviate tendinopathy

Macroautophagy/autophagy plays an important role in regulating cellular homeostasis and influences the pathogenesis of degenerative diseases. Tendinopathy is characterized by tendon degeneration and inflammation. However, little is known about the role of selective autophagy in tendinopathy. Here, we find that pristimerin (PM), a quinone methide triterpenoid, is more effective in treating tendinopathy than the first-line drug indomethacin. PM inhibits the AIM2 inflammasome and alleviates inflammation during tendinopathy by promoting the autophagic degradation of AIM2 through a PYCARD/ASC-dependent manner. A mechanistic study shows that PM enhances the K63-linked ubiquitin chains of PYCARD/ASC at K158/161, which serves as a recognition signal for SQSTM1/p62-mediated autophagic degradation of the AIM2-PYCARD/ASC complex. We further identify that PM binds the Cys53 site of deubiquitinase USP50 through the Michael-acceptor and blocks the binding of USP50 to PYCARD/ASC, thereby reducing USP50-mediated cleavage of K63-linked ubiquitin chains of PYCARD/ASC. Finally, PM treatment in vivo generates an effect comparable to inflammasome deficiency in alleviating tendinopathy. Taken together, these findings demonstrate that PM alleviates the progression of tendinopathy by modulating AIM2-PYCARD/ASC stability via SQSTM1/p62-mediated selective autophagic degradation, thus providing a promising autophagy-based therapeutic for tendinopathy.Abbreviations: 3-MA: 3-methyladenine; AIM2: absent in melanoma 2; AT: Achilles tenotomy; ATP: adenosine triphosphate; BMDMs: bone marrow-derived macrophages; CHX: cycloheximide; Col3a1: collagen, type III, alpha 1; CQ: chloroquine; Cys: cysteine; DARTS: drug affinity responsive target stability; DTT: dithiothreitol; DUB: deubiquitinase; gDNA: genomic DNA; GSH: glutathione; His: histidine; IL1B/IL-1β: interleukin 1 beta; IND: indomethacin; IP: immunoprecipitation; LPS: lipopolysaccharide; MMP: mitochondrial membrane potential; NLRP3: NLR family, pyrin domain containing 3; PM: pristimerin; PYCARD/ASC: PYD and CARD domain containing; SN: supernatants; SOX9: SRY (sex determining region Y)-box 9; SQSTM1: sequestosome 1; Tgfb: transforming growth factor, beta; TIMP3: tissue inhibitor of metalloproteinase 3; TNMD: tenomodulin; TRAF6: TNF receptor-associated factor 6; Ub: ubiquitin; USP50: ubiquitin specific peptidase 50; WCL: whole cell lysates.