Comparison of the Outcomes of Anterior Cervical Discectomy and Fusion and Cervical Disc Replacement for Cervical Disc Disease.

OBJECTIVE: To compare the radiological outcome and development of heterotopic ossification (HO) following single-segment anterior cervical discectomy and fusion (ACDF) and cervical disc replacement (CDR) for cervical disc herniation and evaluate their impact on surgical success. STUDY DESIGN: Descriptive comparative study. Place and Duration of the Study: Neurosurgery Department at Bozyaka Education and Research Hospital, Izmir, Turkiye, between January 2020 and June 2022. METHODOLOGY: Patients aged 18-70 years with radicular neck pain unresponsive to conventional medical treatment and an MRI-confirmed diagnosis were included. Patients with osteoporosis (OP) were excluded. Patients were randomised into two treatment groups (ACDF and CDR) and stratified by age and symptom severity. Radiographic assessments and HO classification according to McAfee were performed. RESULTS: Among the included patients, 56 underwent ACDF and 45 underwent CDR. The mean patient age was 48.29 ± 9.530 and 41.84 ± 7.239 years in the ACDF and CDR groups, respectively (p <0.001). The postoperative disc height increased in both groups. The T1 slope was significantly higher preoperatively and in the early postoperative period in the CDR group than in the ACDF group (p = 0.001). HO was graded as 1, 2, 3, and 4 in 28 (27.7%), 6 (5.9%), 7 (6.9%), and 4 (3%) patients, respectively. CONCLUSION: ACDF and CDR provided similar improvements in radiological measurements and pain relief. Although both procedures significantly enhanced the patient's quality of life and disability scores, HO was more prevalent following CDR during long-term follow-up. KEY WORDS: Cervical disc replacement, Anterior cervical discectomy and fusion, Spinal surgery techniques, Heterotopic ossification.

Trauma patient heterotopic ossification diagnosis is associated with increased hospital length of stay.

BACKGROUND: Traumatic heterotopic ossification (tHO) refers to the development of extra-skeletal bone in muscle and soft tissues following tissue insult secondary to surgery or trauma. This presents a persistent clinical concern associated with significant patient morbidity and expense to diagnose and treat. Traumatic HO is a substantial barrier to rehabilitation for trauma-injured patients. As such, the development of tHO after burn and other trauma is hypothesised to prolong inpatient length of stay (LOS) and thus increase health care costs. OBJECTIVE: To investigate the association between an inpatient tHO diagnosis and hospital LOS in trauma patients. METHODS: A retrospective audit of trauma patients over a 14-year period was completed using data from four WA hospitals. Burn and neurological trauma patients diagnosed with tHO as an inpatient (tHO+) and control subjects (tHO-), matched (1:3) by age, gender, and injury severity factors, were identified using medical diagnostic codes. Data relating to patient and injury-related determinants of LOS from tHO+ and tHO- subjects were analysed to model the association of tHO on total hospital length of stay. RESULTS: 188 identified patients were hospitalised due to traumatic injury; 47 patients with tHO following burn injury (n = 17), spinal cord injury (n = 13) and traumatic brain injury (n = 17), and 141 control patients. Those who developed tHO during hospitalisation had a significantly higher median LOS than matched trauma patients who did not develop tHO (142 days vs. 61 days). Multivariate regression analyses identified the following independent predictive factors of a prolonged hospital LOS: tHO diagnosis, mechanical ventilation hours, injury to the hip region and thigh area, other ossification disorder, pressure injury, admission to intensive care unit and deep vein thrombosis. Trauma patients diagnosed with tHO during their hospital admission stayed 1.6 times longer than trauma patients matched for injury severity without a tHO diagnosis (IRR 1.56, 95% CI 1.35-1.79, p<0.001). CONCLUSION: Traumatic heterotopic ossification is an independent explanatory factor for increased hospital LOS in patients following burns, spinal cord, and traumatic brain injury. Early diagnosis may assist in reducing the impact of tHO on acute hospital stay after trauma.

Heterotopic bone formation in a case of clear cell renal cell carcinoma: A case report.

Renal cell carcinoma (RCC) with heterotopic formation has been reported very rarely. We report this rare entity in a 33-year-old female patient who came to the out-patient department after complaining of pain in the lumbar region of the left side for 2 years. A computed tomography scan showed a heterogeneously enhancing lesion originating from the posterior cortex of the left kidney in the upper pole. It had many chunky calcification foci and was treated with left robotic partial nephrectomy. Histo-pathological examination revealed clear cell RCC with the heterotopic bone formation with a tumor size measuring 5 × 4 × 2.5 cm; the tumor was limited to the kidney, and the tumor resection margin were free of tumor, WHO/ISUP Grade 2. The pathological stage (AJCC 8th edition PTNM) was p T1b p NX p MX. The prognostic implications regarding calcification are poorly addressed in the literature. Patients suffering from osseous metaplasia are often in their early stages of the disease and have a favorable prognosis.

Differences in the Demographics and Clinical Characteristics between the Ossification of the Posterior Longitudinal Ligament and Ossification of the Ligamentum Flavum in Patients Who Underwent Thoracic Spinal Surgery for Compressive Myelopathy.

Ossification of the posterior longitudinal ligament (OPLL) and ossification of the ligamentum flavum (OLF) are related diseases associated with the ossification of spinal ligaments that can occasionally lead to thoracic myelopathy. We retrospectively analyzed the clinical data of 34 consecutive patients who underwent thoracic spinal surgeries for OPLL and/or OLF at our hospital between July 2010 and June 2022, and statistically compared data between patients with thoracic OPLL (TOPLL; n = 12) and those with thoracic OLF (TOLF; n = 22). The mean age of the TOPLL group was significantly lower than that of the TOLF group (53.7 vs. 68.4 years). The TOPLL group exhibited a greater female predominance than the TOLF group (58.3% vs. 18.2%). The median body mass index of the TOPLL group was significantly higher than that of the TOLF group (33.0 vs. 26.0 kg/m2). Patients with TOPLL significantly required instrumented fusion and repetitive surgical intervention more than those with TOLF (83.3% vs. 9.1%; 50.0% vs. 0.0%). Although neurological deterioration just after the intervention was more common in patients with TOPLL (41.7% vs. 4.6%), no difference was observed in thoracic Japanese Orthopaedic Association score and recovery rate in the chronic phase between TOPLL and TOLF. The TOPLL group had a younger onset, female dominance, and a greater degree of obesity when compared with the TOLF group. The surgery for TOPLL is challenging, considering that it requires long-range decompression and fusion, subsequent operations, careful management, and long-term follow-up, when compared to TOLF, which necessitates only simple decompression.

Treatment and rehabilitation of post-traumatic elbow stiffness with heterotopic ossification.

AIM: To investigate surgical treatment, postoperative rehabilitation and prevention of heterotopic ossification (HO) in patients with post-traumatic elbow stiffness. METHODS: We performed a retrospective review of patients with post-traumatic elbow stiffness combined with HO between 2007 and 2021. This study was performed on a total of 15 patients (18 elbows) admitted to our hospital, consisting of 12 males and 3 females, with post-traumatic stiffness of the elbow combined with HO, where elbow function could not be recovered by rehabilitation and orthosis treatment. Fifteen patients were treated by surgical excision of heterotopic bones and release of elbow contracture combined with postoperative rehabilitation and orthosis-wearing. Comprehensive treatments, including radiation, oral ibuprofen medication, and manipulation techniques to improve range of motion, were used to prevent HO recurrence. The flexion-extension arc and functional score of the elbow were measured after treatment and compared with the preoperative measurements. Roentgenography was used to observe HO recurrence. RESULTS: After surgical treatment and postoperative rehabilitation, the patients' range of motion improved, and the functional score improved considerably. The postoperative flexion-extension arc and The Hospital for Special Surgery (HSS) functional score were statistically significantly higher than the preoperative values (p < 0.01). Roentgenographic examination showed no HO recurrence during the follow-up period. CONCLUSION: Surgical excision of heterotopic bones and elbow contracture release combined with postoperative rehabilitation and preventative HO measures can be an effective treatment for cases of post-traumatic elbow stiffness combined with HO, for which conservative treatment is ineffective.

Transoral robotic styloidectomy for Eagle syndrome: A systematic review.

OBJECTIVES: The aim of the study is to conduct a systematic review of the existing literature on styloidectomy performed through transoral robotic surgery (TORS) in Eagle syndrome (ES). DESIGN AND SETTING: Two independent reviewers (RC and AC) conducted a systematic review of PubMed and Embase databases, seeking articles on TORS performed for ES treatment. The search was conducted in July 2023. The review was carried out in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. PARTICIPANTS: The review included a total of 17 adult patients, comprising 12 females and 5 males, with an average age of 52.2 years, all diagnosed with ES. MAIN OUTCOME MEASURES: For each patient, we assessed the overall length of the styloid process, the affected side, total intervention duration, hospitalization duration, pre and postoperative Visual Analogue Scale (VAS) scores, and the presence of minor and major complications. RESULTS: We identified 4 articles describing 17 instances of TORS as a surgical treatment for ES in the literature, totaling 18 styloidectomies. The mean age of the patients was 52.2 years, with 12 females and 5 males. The average operation time, inclusive of the docking phase, was 68.8 minutes. Sixteen patients (94.1% of the total) experienced complete symptom disappearance or near-complete resolution after surgery. One patient (5.9%) showed improvement categorized as 'non-meaningful.' Only one case of minor complication was reported among the 17 procedures (5.9%).

Eagle Syndrome: An Unusual Cause of Axial Neck Pain: A Case Report.

CASE: A 42-year-old woman presented with left-sided axial neck pain with radiation behind left ear of 3 months unresponsive to conservative treatment. As clinical examination revealed tenderness anterior to the mastoid process, she was referred to an otolaryngologist. Computed tomography showed an elongated left styloid process. Diagnostic local anesthetic infiltration provided complete pain relief confirming the diagnosis of Eagle syndrome (ES) after which a transoral excision of the left styloid process was performed. She was asymptomatic till the final follow-up of 15 months. CONCLUSION: ES should be considered in differential diagnosis of axial neck pain radiating to ear, and excision of the styloid process in resistant cases provides complete pain relief.

Bony encasement of the ulnar nerve secondary to heterotopic ossification of the elbow: an evaluation of long-term outcomes.

BACKGROUND: Ulnar neuropathy at the elbow caused by heterotopic ossification (HO) is a rare condition. This retrospective study aims to report on 32 consecutive cases of ulnar nerve encasement caused by elbow HO and evaluate long-term outcomes of operative management and a standardized postoperative rehabilitation regimen. METHODS: A retrospective case series was conducted on 32 elbows (27 patients) that underwent operative management of bony ulnar nerve encasement. All procedures were performed in the inpatient setting at an Academic Level 1 Trauma Center from September 1999 to July 2021 by one of 3 fellowship-trained shoulder and elbow. Postoperatively, all patients received formal physical therapy, HO prophylaxis (30 received indomethacin, 2 received radiation), and a structured continuous passive motion machine regimen. Patient demographics, age, gender, type of injury, history of tobacco use, and medical comorbidities were obtained to include in the analysis. Long-term follow-up examinations were performed to evaluate elbow flexion-extension arc of motion, Mayo Elbow Performance Score, and visual analog scale pain scores. RESULTS: Thirty-two elbows with complete bony ulnar nerve encasement secondary to HO were identified (14 from burns, 15 from trauma, 3 closed head injuries). Following surgery, the mean flexion-extension arc of motion improved significantly, increasing from 21° to 100° at long-term follow-up (average 8.7 years, range 2-17 years), with statistically significant improvements in preoperative vs. long-term postoperative elbow extension (P < .001), flexion (P < .001), and total arc of motion (P < .001). There was a statistically significant improvement in pre- vs. postprocedure ulnar nerve function, as demonstrated by a decrease in average McGowan grade (1.2-0.7; P = .002). Additionally, 63% of patients with preoperative ulnar neuropathy symptoms (20/32) had either complete resolution or subjective improvement after surgery. The mean time from injury to surgery was 518 days (range 65-943 days). Age, gender, time to surgery, and medical comorbidities were not associated with outcomes. The complication rate was 9% (3/32). Patients had an average flexion-extension arc of motion of 97° and average Mayo Elbow Performance Score of 80 ("good") at long-term follow-up. CONCLUSIONS: The combination of operative management, postoperative HO prophylaxis, and a regimented rehabilitation program has proven to be a durable solution for treating and ensuring good long-term functional outcomes for patients with elbow HO and bony ulnar nerve encasement. This treatment approach leads to superior range of motion, improved or resolved ulnar neuropathy, and good to excellent long-term functional outcomes.

Peri-articular bone formation involving the temporomandibular joint: a narrative summary and Delphi consensus of a new classification system.

Heterotopic ossification (HO) is defined as 'bone where it does not belong'. Given the historical variety of nomenclature and eponyms, there is significant confusion about the etiology, pathogenesis, classification, and treatment of HO related to the temporomandibular joint (TMJ). The existing classifications for TMJ HO have shortcomings: they relate to specific populations, use differing imaging studies and demographic data, do not universally include alloplastic/autologous replacements, are based variously on radiological and/or clinical presentations that cannot always be combined, and were largely developed to assist oral and maxillofacial surgeons in surgical management. These deficiencies make it problematic to compare studies, draw valid conclusions, and pursue research. The aim of this study was to develop a new, more inclusive classification for TMJ HO. Currently available classifications were evaluated and a Delphi-type system used to build consensus from clinicians and researchers to develop a new system. Fourteen unique classifications for TMJ ankylosis/HO were identified. In light of the biological specifics related to heterotopic calcification of extracellular matrix versus heterotopic formation of actual bone, the group recommends a more unambiguous term - peri-articular bone formation - and proposes a new classification. This will help clinicians and researchers to study, describe, and manage various types of ectopic bone associated with the TMJ.

Elbow stiffness: Interview with professor Bernard Morrey.

Stiff elbow is a complex condition whose diagnosis and management are sometimes quite a challenge. Compared to the other joints, the elbow is disproportionately affected by loss of motion following trauma or surgery. It is unclear why the elbow tends to develop stiffness; its anatomical complexity, namely the presence of three highly congruent joints in the same capsule and synovial space, the tautness of the lateral and medial collateral ligaments through the whole range of motion, and the very close relationship among tendons, muscles, and skin 2 may account for this characteristic. In a stiff elbow, it is critical to assess the possible involvement of articular and periarticular tissues, particularly the degree of preservation of the articular surfaces and joint congruency. Morrey et al have classified post-traumatic stiff elbow into three types: 1) extrinsic contracture, which involves the soft tissue around the joint (capsule, ligaments, muscles) and heterotopic ossification across the joint, 2) intrinsic contracture, secondary to intra-articular fractures that have altered the anatomy of the articular surface, and 3) mixed contracture, combining intrinsic and extrinsic contracture. In the preoperative clinical assessment, we assume capsule contracture to be present in all patients with a stiff elbow. Two main associated lesions can affect prognosis and surgical management: heterotopic ossification and an altered bone joint anatomy. According to Morrey et al, most activities of daily living can be accomplished within an arc of motion from 30° to 130° in extension and flexion and of 50° in pronation and supination. The elbow arc of motion is not compensated for by the wrist and shoulder, thus loss of extension impairs the use of the hand in the space around the body and loss of flexion limits its use for grooming and self-care. The elbow should carefully be tested for deformity of the axial bone alignment (varus and valgus deformity) and rotational stability. Several treatment options are available for stiff elbow, from conservative management with a dedicated rehabilitation program to surgical treatment and from arthroscopic capsulectomy to joint replacement.

Safety and Efficacy Outcomes Following Spinal Endoscopic Procedures for Thoracic Ligamentous Ossification: A Systematic Review and Meta-Analysis.

STUDY DESIGN: A systematic review and meta-analysis. OBJECTIVE: This study systematically reviewed and evaluated the safety and efficacy of spinal endoscopic techniques as a treatment for thoracic ligamentum flavum ossification (TOLF). SUMMARY OF BACKGROUND DATA: The use of spinal endoscopic techniques for the treatment of TOLF has increased in recent years. The present study is the first comprehensive systematic review and meta-analysis focused on the use of spinal endoscopic techniques for TOLF. MATERIALS AND METHODS: The Cochrane Central, PubMed, Web of Science, and Embase databases were systematically searched for studies focused on patients undergoing spinal endoscopic techniques to treat symptomatic TOLF. RESULTS: This meta-analysis included 23 studies. We included 323 patients (177 males, 146 females) with a mean age of 58.40±10.06 years, with 304 total recorded lesion locations of which 245 were located in the lower thoracic spine. Complications affected 35/323 patients, and the mean operative duration for 305 patients was 108.15±47.34 minutes. For 187 patients, the mean operative bleeding was 25.13±12.54 mL, while for 87 patients the mean duration of hospitalization was 4.59±1.93 days. At last follow-up, functional assessment was performed for 260 patients, of whom 200 were in excellent condition, visual analog scale (VAS) scores were assessed for 160 patients, with a mean improvement of 4.40 (3.95, 4.86) Japanese Orthopedic Association (JOA) scores were recorded for 115 patients, with a mean improvement of 3.49 (2.79,4.18), and modified Japanese Orthopedic Association (mJOA) scores were recorded for 208 patients, with a mean improvement of 3.62 (2.89,4.35). CONCLUSIONS: These results support several advantages of spinal endoscopic techniques for the treatment of symptomatic TOLF. These include low complication rates, rapid postoperative recovery, and good functional recovery when used for single-segment, non-nodular ossification and no combined dural ossification.

A postoperative heterotopic ossification leading to radial palsy.

We report the case of a 58-year-old man who developed radial palsy three months after surgical reinsertion of the distal biceps brachii through a single anterior approach. Radiographs and ultrasound examinations revealed heterotopic ossification compressing the deep branch of the radial nerve. Surgical excision and neurolysis were performed. At the two-month follow-up, the patient was asymptomatic. Practitioners and orthopedic surgeons should be aware of the risk of heterotopic ossification after distal biceps reinsertion and its possible atypical clinical presentation.

Tranexamic acid in patients with post-traumatic elbow stiffness: protocol for a randomised, double-blind, placebo-controlled trial investigating the effectiveness of tranexamic acid at reducing the recurrence of heterotopic ossification after open elbow arthrolysis.

INTRODUCTION: Exaggerated inflammatory response is one of the main mechanisms underlying heterotopic ossification (HO). It has been suggested that the antifibrinolytic drug tranexamic acid (TXA) can exert a significant anti-inflammatory effect during orthopaedic surgery. However, no prospective studies have yet investigated the effects of TXA on HO recurrence in patients following open elbow arthrolysis (OEA). METHODS AND ANALYSIS: Here, we present a protocol for a single-centre, randomised, double-blind, placebo-controlled trial to investigate the effectiveness of TXA on HO recurrence after OEA in a single hospital. A minimum sample size of 138 eligible and consenting participants randomised into treatment and control groups in a 1:1 manner will be included. Patients will receive 2 g of intravenous TXA (experimental group) or placebo (normal saline, control group) administered before skin incision. The primary outcome is HO recurrence rate within 12 months after surgery. The secondary outcomes are the serum immune-inflammatory cytokines including erythrocyte sedimentation rate, C reactive protein, interleukin (IL)-6, IL-1ß, IL-13 at the first and third day postoperatively, and elbow range of motion and functional score at 1.5, 6, 9 and 12 months after surgery. After completion of the trial, the results will be reported in accordance with the extensions of the Consolidated Standards of Reporting Trials Statement for trials. The results of this study should determine whether TXA can reduce the rates of HO occurrence after OEA. ETHICS AND DISSEMINATION: Ethical approval has been granted by the Medical Ethics Committee of the Shanghai Sixth People's Hospital Affiliated to Shanghai Jiao Tong University School of Medicine (reference number 2022-123-(1)). The results of this study will be disseminated through presentations at academic conferences and publication in peer-reviewed journals. TRIAL REGISTRATION NUMBER: ChiCTR2300068106.

Heterotopic Ossification Remodeling After Acetabular Surgery: A Natural History Case Report.

CASE: A 30-year-old woman presented with a transverse plus posterior wall acetabular fracture and underwent operative fixation through a Kocher-Langenbeck approach. Shared decision was made for no heterotopic ossification (HO) prophylaxis. The patient developed symptomatic HO and was scheduled for resection, which was delayed because of the pandemic. She returned with interval remodeling of HO and symptom resolution. No surgery was required. CONCLUSION: HO is a common complication after acetabular injury. Resection is the treatment of choice for symptomatic HO. We are not aware of other reports of spontaneous remodeling of symptomatic HO such that it no longer required surgery.

Learning Curve and Clinical Outcomes of Ultrasonic Osteotome-based En Bloc Laminectomy for Thoracic Ossification of the Ligamentum Flavum.

OBJECTIVE: Despite rapid advances in minimally invasive surgery, en bloc laminectomy remains the most common surgical approach for treating thoracic ossification of the ligamentum flavum (TOLF). However, the learning curve of this risky operation is rarely reported. Therefore, we aimed to describe and analyze the learning curve of ultrasonic osteotome-based en bloc laminectomy for TOLF. METHODS: Among 151 consecutive patients with TOLF who underwent en bloc laminectomy performed by one surgeon between January 2012 and December 2017, we retrospectively analyzed their demographic data, surgical parameters, and neurological function. Neurological outcome was evaluated with the modified Japanese Orthopaedic Association (mJOA) scale, and the Hirabayashi method was used to calculate the neurological recovery rate. The learning curve was assessed with logarithmic curve-fitting regression analysis. Univariate analysis methods were used for statistical analysis, including t-test, rank sum test, and chi-square test. RESULTS: A total of 50% of learning milestones could be reached in approximately 14 cases, and the asymptote in 76 cases. Therefore, 76 of the 151 enrolled patients were defined as the "early group," and the remaining 75 were delimitated as the "late group" for comparison. There was a significant intergroup difference in the corrected operative time (94.80 ± 27.77 vs 65.93 ± 15.67 min, P < 0.001) and the estimated blood loss (median 240 vs 400 mL, P < 0.001). The overall follow-up was 83.1 ± 18.5 months. The mJOA significantly increased from a median of 5 (IQR: 4-5) before the surgery to 10 (IQR: 9-10) at the last follow-up (P < 0.001). The overall complication rate was 37.1%, and no significant intergroup difference was found, except for the incidence of dural tears (31.6% vs 17.3%, p = 0.042). CONCLUSION: Initially, mastering the en bloc laminectomy technique using ultrasonic osteotome for TOLF treatment can be challenging, but the surgeon's experience improves as the operative time and blood loss decrease. Improved surgical experience reduced the risk of dural tears but was not associated with the overall complication rate or long-term neurological function. Despite the relatively long learning curve, en bloc laminectomy is a secure and valid technique for TOLF treatment.

Do Clinical Parameters Reflect Local Bone Metabolism in Heterotopic Ossification After Septic or Aseptic THA?

BACKGROUND: Heterotopic ossification (HO) is a common complication after THA. Although current research primarily focuses on treatment and prevention, little is known about the local bone metabolism of HO and clinical contributing factors. QUESTIONS/PURPOSES: We aimed to assess bone remodeling processes in HO using histomorphometry, focusing on the effects of inflammation and prior NSAID treatment. Specifically, we asked: (1) Are HO specimens taken from patients with periprosthetic joint infection (PJI) more likely to exhibit active bone modeling and remodeling than specimens taken at the time of revision from patients without infection? (2) Do clinical or inflammatory serum and synovial parameters reflect the microstructure of and remodeling in both HO entities? (3) Is NSAID treatment before revision surgery associated with altered local bone mineralization or remodeling properties? METHODS: Between June 2021 and May 2022, we screened 395 patients undergoing revision THA at two tertiary centers in Germany. Of those, we considered all patients with radiographic HO as potentially eligible. Based on that, 21% (83 of 395) were eligible; a further 43 were excluded because of an inability to remove the implant intraoperatively (16 patients), insufficient material (11), comorbidities with a major effect on bone metabolism (10), or bone-specific drugs (six), leaving 10% (40) for analysis in this retrospective, comparative study. HO specimens were collected during aseptic (25 patients: 18 male, seven female, mean age 70 ± 11 years, mean BMI 29 ± 4 kg/m 2 ) and septic (15 patients: 11 male, four female, mean age 69 ± 9 years, mean BMI 32 ± 9 kg/m 2 ) revision THA at a mean of 6 ± 7 years after primary implantation and a mean age of 70 ± 9 years at revision. Septic origin (PJI) was diagnosed based on the 2018 International Consensus Meeting criteria, through a preoperative assessment of serum and synovial parameters. To specify the local bone microstructure, ossification, and cellular bone turnover, we analyzed HO specimens using micro-CT and histomorphometry on undecalcified sections. Data were compared with those of controls, taken from femoral neck trabecular bone (10 patients: five female, five male, mean age 75 ± 6 years, mean BMI 28 ± 4 kg/m 2 ) and osteophytes (10 patients: five female, five male, mean age 70 ± 10 years, mean BMI 29 ± 7 kg/m 2 ). The time between primary implantation and revision (time in situ), HO severity based on the Brooker classification, and serum and synovial markers were correlated with HO microstructure and parameters of cellular bone turnover. In a subgroup of specimens of patients with NSAID treatment before revision, osteoid and bone turnover indices were evaluated and compared a matched cohort of specimens from patients without prior NSAID treatment. RESULTS: Patients with aseptic and septic HO presented with a higher bone volume (BV/TV; aseptic: 0.41 ± 0.15, mean difference 0.20 [95% CI 0.07 to 0.32]; septic: 0.43 ± 0.15, mean difference 0.22 [95% CI 0.08 to 0.36]; femoral neck: 0.21 ± 0.04; both p < 0.001), lower bone mineral density (aseptic: 809 ± 66 mg HA/cm 3 , mean difference -91 mg HA/cm 3 [95% CI -144 to -38]; septic: 789 ± 44 mg HA/cm 3 , mean difference -111 mg HA/cm 3 [95% CI -169 to -53]; femoral neck: 899 ± 20 mg HA/cm 3 ; both p < 0.001), and ongoing bone modeling with endochondral ossification and a higher proportion of woven, immature bone (aseptic: 25% ± 17%, mean difference 25% [95% CI 9% to 41%]; septic: 37% ± 23%, mean difference 36% [95% CI 19% to 54%]; femoral neck: 0.4% ± 0.5%; both p < 0.001) compared with femoral neck specimens. Moreover, bone surfaces were characterized by increased osteoblast and osteoclast indices in both aseptic and septic HO, although a higher density of osteocytes was detected exclusively in septic HO (aseptic: 158 ± 56 1/mm 2 versus septic: 272 ± 48 1/mm 2 , mean difference 114 1/mm 2 [95% CI 65 to 162]; p < 0.001). Compared with osteophytes, microstructure and turnover indices were largely similar in HO. The Brooker class was not associated with any local bone metabolism parameters. The time in situ was negatively associated with bone turnover in aseptic HO specimens (osteoblast surface per bone surface: r = -0.46; p = 0.01; osteoclast surface per bone surface: r = -0.56; p = 0.003). Serum or synovial inflammatory markers were not correlated with local bone turnover in septic HO. Specimens of patients with NSAID treatment before revision surgery had a higher osteoid thickness (10.1 ± 2.1 µm versus 5.5 ± 2.6 µm, mean difference -4.7 µm [95% CI -7.4 to -2.0]; p = 0.001), but there was no difference in other osteoid, structural, or cellular parameters. CONCLUSION: Aseptic and septic HO share phenotypic characteristics in terms of the sustained increase in bone metabolism, although differences in osteocyte and adipocyte numbers suggest distinct homeostatic mechanisms. These results suggest persistent bone modeling or remodeling, with osteoblast and osteoclast indices showing a moderate decline with the time in situ in aseptic HO. Future studies should use longitudinal study designs to correlate our findings with clinical outcomes (such as HO growth or recurrence). In addition, the molecular mechanisms of bone cell involvement during HO formation and growth should be further investigated, which may allow specific therapeutic and preventive interventions. CLINICAL RELEVANCE: To our knowledge, our study is the first to systematically investigate histomorphometric bone metabolism parameters in patients with HO after THA, providing a clinical reference for evaluating modeling and remodeling activity. Routine clinical, serum, and synovial markers are not useful for inferring local bone metabolism.

Navigation-Assisted Micro-Window Excision of Thoracic Ossification of Ligamentum Flavum (Mishima Surgery) in Professional Baseball Pitchers: A Case Report and Technical Note.

Background and Objectives: Thoracic ossification of the ligamentum flavum (OLF) often causes myelopathy and/or radiculopathy. The disease is frequently observed in East Asian populations. Although thoracic OLF in young athletes who have underwent decompression surgery has been reported, the removal of posterior spinal bony elements and ligamentous complex may often cause postoperative thoracolumbar instability. We established a novel surgical technique that preserves the posterior spinal elements, including the spinous processes, facet joints, and supraspinous and interspinous ligaments for thoracic OLF. This is the first case report to describe a navigation-assisted micro-window excision of thoracic OLF. Case: A 32-year-old male right-handed professional baseball pitcher with significant weakness and numbness in the left leg was referred to our hospital. The patient was diagnosed with thoracic OLF at T10-11 based on radiographic and magnetic resonance images in August 2022. After exposure of the left T10-11 laminae via a small unilateral incision, the location of T10-11 OLF was detected over the lamina by O-arm navigation. Then, the micro-window was made directly above the OLF using a navigated air drill, and the OLF was removed on the ipsilateral side. The contralateral side of OLF was also resected through the same micro-window, achieving complete spinal cord decompression. Results: The next day of the surgery, his leg weakness and numbness were significantly improved. Six weeks after the surgery, he started pitching. Three months after surgery, his symptoms had gone completely, and he pitched from the mound. Approximately 6 months after surgery, he successfully pitched in a professional baseball game. Conclusions: A navigation-assisted micro-window excision of thoracic OLF effectively preserved the spinal posterior bony elements and ligamentous complex. However, long-term clinical outcomes should be evaluated in future studies.

Uniportal Thoracic Endoscopic Unilateral Laminotomy with Bilateral Decompression of Thoracic Ossification of Ligamentum Flavum: A Systematic Review of Current Literature.

BACKGROUND: Thoracic ossification of ligamentum flavum (TOLF) is a rare disease that often results in worsening neurologic sequelae if left untreated. Although the gold standard treatment for TOLF is open posterior laminectomy, it is often accompanied by high rates of complications and perioperative morbidity. There have been studies looking into feasibility of endoscopic posterior decompression for TOLF, citing potential for lower perioperative morbidity and achieving similar functional outcomes to its open laminectomy counterparts. We provide an up-to-date systematic review of clinical outcomes after endoscopic posterior decompression for TOLF from the latest assemblage of evidence. METHODS: A systematic review of the technique was conducted from May 2000 to May 2023. Articles were selected based on PRISMA guidelines. Eligibility of studies was independently by 2 reviewers, with disagreements resolved by a third author. RESULTS: Nineteen primary references comprising 337 patients with TOLF who underwent endoscopic posterior decompression were included in the systematic review. Mean follow-up time across all studies ranged from 8.9 to 65.3 months. Mean age ranged from 51.2 to 63 years, with mean intraoperative blood loss ranging from 15 to 62 mL. There is significant improvement in visual analog scale (VAS) score, VAS back, VAS leg, modified Japanese Orthopaedic Association score, and Oswestry Disability Index compared with preoperative recorded values across all studies, with low rates of complications reported. CONCLUSIONS: Endoscopic posterior spinal decompression is a safe and effective technique for treatment of TOLF, with a low rate of complications and improvement in pain and function.