Complications of Hardware Removal in Pediatric Orthopaedic Surgery.

BACKGROUND: Hardware removal (HR) is one of the most common surgical procedures in pediatric orthopaedics. Surgeons advocate for HR for a variety of reasons, including to limit peri-implant fracture risk, restore native anatomy for adult reconstruction surgery, permit bone growth and development, and mitigate implant-related pain/irritation. To our knowledge, no recent study has investigated the characteristics and complications of HR in pediatric orthopaedics. The goal of this study is to report the prevalence and complications of hardware removals across all of pediatric orthopaedic surgery. METHODS: A retrospective case series was conducted of all hardware removals from 2012 to 2023 performed at a single urban tertiary-care children's hospital. Cases were identified using CPT codes/billing records. Spinal hardware and cases for which hardware was either implanted or explanted at an outside hospital were excluded. Patient demographic and clinical data were recorded. For patients with multiple hardware removals, each case was recorded independently. RESULTS: A total of 2585 HR cases for 2176 children met study criteria (57.7% male; mean age 12.3±4.4 y). The median postoperative follow-up time was 1.7 months (interquartile range: 0.6 to 6.9). The most common sites of hardware removal were the femur/knee (32.7%), tibia/fibula/ankle (19.3%), and pelvis/hip (18.5%). The most common complications included sustained, new-onset postoperative pain (2.6%), incomplete hardware removal (1.6%), and perioperative fracture (1.4%). The overall complication rate of hardware removal was 9.5%. Eighty-eight percent of patients who underwent hardware removal for pain experienced pain relief postoperatively. HR >18 months after insertion had a 1.2x higher odds of overall complication (P=0.002) and 3x higher odds of incomplete removal/breakage (P<0.001) than hardware removed 9 to 18 months after insertion. CONCLUSIONS: The overall complication rate of hardware removal across a large series in the pediatric population was 9.5%. Despite hardware removal being one of the most common and often routine procedures in pediatric orthopaedics, the complication rate is not benign. Surgeons should inform patients and families about the likelihood of success and the risks of incomplete removal during the informed consent process. LEVEL OF EVIDENCE: IV.

Management of osteonecrosis of the humeral head in the pediatric population: A systematic review.

Purpose: Humeral head osteonecrosis in the pediatric patients most often occurs in patients with underlying hemoglobinopathies, exposure to chronic corticosteroids, or after trauma. The purpose of this study was to perform a systematic review evaluating the prevalence, clinical characteristics, and management of humeral head osteonecrosis in the pediatric population. Methods: PubMed, Ovid MEDLINE, and Scopus were screened with the terms "osteonecrosis," "avascular necrosis," "pediatric," and "proximal humerus" on January 10, 2024. A total of 218 studies were screened, and 74 studies were evaluated for eligibility. Studies that reported on the prevalence and/or management of pediatric humeral head osteonecrosis were included. The systematic review was conducted according to the Preferred Reporting Items for Systematic Review and Meta-Analyses guidelines. Results: Twelve studies met inclusion criteria: four retrospective case series, three prospective case series, one retrospective cohort study, one retrospective case-control study, and three case reports. A majority of the studies (67%) discussed chemotherapy-induced osteonecrosis of the humeral head. A total of 77 patients (106 shoulders) with humeral head osteonecrosis were identified. The overall prevalence of osteonecrosis of the humeral head across eight studies examining at-risk populations (underlying hemoglobinopathies or undergoing chemotherapy) was 2%. Intra-articular steroid injections, physical therapy, and activity modification are effective conservative management strategies. Additionally, core decompression and hemiarthroplasty are surgical treatment options. Conclusions: The prevalence of osteonecrosis of the humeral head is low even among at-risk populations with associated medical conditions. A variety of conservative and surgical treatment options have been described, but no comparative evaluations of these modalities has been conducted. Level of evidence: IV.

Rib-on-Pelvis Deformity and Reported Pain in Neuromuscular Early-Onset Scoliosis.

BACKGROUND: Neuromuscular early-onset scoliosis (N-EOS) often presents with a long sweeping thoracolumbar scoliosis and pelvic obliquity. With severe pelvic obliquity, the ribs come into contact with the high side of the pelvis, termed rib-on-pelvis deformity (ROP). The goal of this study is to evaluate whether ROP is associated with reported pain and other health-related quality of life (HRQOL) measures. We hypothesize that ROP is associated with increased pain and negative HRQOL. METHODS: A multicenter international registry was queried for all nonambulatory patients with N-EOS from 2012 to 2022. Both surgical and nonsurgical patients were included. ROP was classified as a binary radiographic assessment of preoperative (surgical patients) and most recent follow-up (nonsurgical patients) upright radiographs. Reported pain and other HRQOL measures were assessed through the 24-Item Early Onset Scoliosis Questionnaire (EOSQ-24). Patients with nonupright radiographs or EOSQ-24 questionnaires and corresponding radiographs >4 months apart were excluded. RESULTS: Totally, 225 patients (8.4±3.1 y, 55% female) were included. The median major curve was 63.3 (IQR: 40.6 to 81.2) degrees and median pelvic obliquity was 15.5 degrees (IQR: 8.8 to 26.4). Eighty-three patients (37%) had ROP. ROP was associated with both frequency (P<0.001) and severity (P<0.001) of pain. ROP was associated with worse general health (P=0.01), increased difficulty with vocalization (P=0.02), increased frequency of shortness of breath (P=0.002), and increased difficulty sitting upright (P=0.04). Regarding overall EOSQ-24 domains, ROP was associated with worse general health, pain/discomfort, pulmonary function, and physical function (P<0.01). In a subanalysis of 76 patients who underwent surgical intervention with at least 2 years of follow-up, patients with preoperative ROP experienced significantly greater improvements in both frequency (P=0.004) and severity (P=0.001) of pain than the patients without preoperative ROP at 2 years postoperatively. CONCLUSIONS: The overall incidence of ROP in N-EOS is about 37%. ROP is associated with greater pain and worse HRQOL through the EOSQ-24 questionnaire. Furthermore, these patients experienced a greater reduction in pain after surgery. Clinicians and parents must be aware that ROP is possibly a pain generator, but responds positively to surgical intervention. LEVEL OF EVIDENCE: Level III.

Predicting brace holiday eligibility in juvenile idiopathic scoliosis.

PURPOSE: The psychological effects of scoliosis bracing can be difficult, and thus clinicians sometimes recommend a brace holiday when the curve corrects to less than 25°. However, the clinical indications for taking a break from the brace before reaching maturity have yet to be described. We hypothesized there would be a relationship between brace holiday eligibility and degree of curve at presentation, change in curve magnitude while bracing, and level of bracing compliance. METHODS: A retrospective cohort study at a single institution was performed from 2016 to 2022. Objective brace compliance I-button data were collected on patients aged 3-9 years old. Patients with other etiologies besides idiopathic scoliosis before the age of 10 were excluded. Binary logistic regression was performed to determine the effect of significant variables on the likelihood of brace holiday. RESULTS: Fifty-six patients met inclusion criteria. Of these, 20 were able to get a brace holiday. Patients with higher brace compliance and larger in-brace curve correction were more likely to get a brace holiday (P = 0.015, 0.004). Patients with higher BMIs and larger curves at initial presentation were less likely to get a brace holiday (P = 0.002, 0.014). CONCLUSION: Compliant brace wearers with good in-brace correction are most likely to be eligible for a brace holiday. While some elements remain immutable, others are modifiable, such as bracing compliance. Understanding how outcomes differ between patients who do and do not take a brace holiday will be crucial to elucidating if the psychological benefit of taking a break from the brace can be justified.

Prevalence and Risk Factors for Stiffness Following Open Reduction for Developmental Dysplasia of the Hip.

OBJECTIVE: Most prior investigations on adverse outcomes after open reduction (OR) for developmental dysplasia of the hip (DDH) have focused on avascular necrosis, redislocation, and residual dysplasia. To our knowledge, no previous study has investigated risk factors for stiffness, an underappreciated source of postoperative morbidity. The goals of this study were to define the entity more clearly and evaluate the prevalence and risk factors for arthrofibrosis after OR for DDH. METHODS: A retrospective study was conducted, including all open hip reductions for DDH performed by a single surgeon from 2009 to 2022. Preoperative anteroposterior pelvic radiographs were used to calculate superior displacement, which was defined as the distance from the highest point of the proximal femoral metaphysis to the Hilgenreiner line, normalized by pelvic width. Cases treated with premature postoperative bracing cessation and/or referral to physical therapy with a resolution of stiffness within 6 months were categorized as mild arthrofibrosis. Cases that required >6 months of formal physical therapy for persistent range of motion concerns, manipulation under anesthesia, and/or inpatient rehabilitation admission were categorized as significant arthrofibrosis. RESULTS: This study included 170 hips with a mean age of 21.6 months (range: 6.1 to 93.6 mo) and a mean follow-up of 46.8 months. 156 ORs (91.8%) were done through an anterior approach. Sixty-four patients (37.6%) had a concomitant isolated pelvic osteotomy, and 34 (20.0%) had both pelvic and femoral osteotomies. During the postoperative course, 109 patients (64.1%) had no arthrofibrosis, 38 (22.4%) had mild stiffness, and 23 (13.5%) had significant arthrofibrosis. On multivariable analysis, older age, superior displacement, and concomitant pelvic osteotomy were associated with any degree of arthrofibrosis (P< 0.05). Children older than 18 months or with dislocations higher than 16% of pelvic width had a 4.7 and 2.7 times higher risk, respectively, of experiencing some degree of stiffness postoperatively. CONCLUSIONS: Older age, high dislocations, and concomitant pelvic osteotomy without femoral shortening are risk factors for stiffness after OR for DDH. Surgeons should counsel families about the risk of postoperative stiffness, which occurred to some degree in 36% of our patients. LEVEL OF EVIDENCE: Level IV.

Patient Characteristics and Postoperative Outcomes of Surgically Treated Inferior Pole Patellar Sleeve Fractures.

BACKGROUND: Despite representing over half of all pediatric patella fractures, inferior pole patellar sleeve fractures (PSFs) are a relatively uncommon pediatric injury. As a result, existing literature on PSFs is limited to case reports and small case series. The purpose of this study was to evaluate the radiographic and clinical characteristics of operatively treated PSFs as well as outcomes following surgical management. METHODS: A retrospective review of all inferior pole PSFs requiring surgery from 2007 to 2023 was performed at a single urban tertiary care children's hospital. Cases were identified using diagnostic and billing codes. Patient demographics, injury characteristics, surgical techniques, and postoperative rehabilitation practices were recorded. Regional skeletal maturity, fracture characteristics, and postreduction patellar height were recorded. Postoperative complications were recorded and categorized using the modified Clavien-Dindo Classification System (CDS). RESULTS: Thirty-eight inferior pole PSFs were identified meeting study criteria. The majority of patients were male (86.8%), and the mean age at injury was 11.0 years (range: 7.2 to 15.0). Mean BMI was 21.1. Radiographically, the majority of patients were Epiphyseal Fusion Stage 0 (nonunion), with a median postreduction Caton-Deschamps index (CDI) of 1.2 (IQR: 1.1 to 1.3). These fractures were predominantly treated with suture-based fixation (84%). Postoperative immobilization varied within the cohort, and the initiation of knee ROM was permitted at a median of 3.5 (IQR: 2.0 to 4.6) weeks. All patients regained full range of motion and straight leg raise without extensor lag, and return-to-sport was achieved by a median of 17.6 weeks (IQR: 12.8 to 30.3). Complications occurred in 10 (26.3%) patients, with 3 (7.9%) requiring a return to the OR (CDS Grade III). CONCLUSIONS: Inferior pole PSFs appear to occur most commonly among prepubertal males of normal BMI and normal patellar height. Despite variable rehabilitation protocols, operative management resulted in restoration of extensor mechanism function. Eight percent of patients experienced complications requiring unplanned surgery. This large series improves our understanding of the epidemiology, injury characteristics, and postoperative outcomes of an operatively treated cohort of a rare injury pattern. LEVEL OF EVIDENCE: Level IV.

Predictors of Reoperation and Survival Experience (Minimum 1 Year) for Primary Versus Conversion Total Hip Arthroplasty in Young Patients.

BACKGROUND: Total hip arthroplasty (THA), including primary and conversion procedures, is commonly used for many types of joint disease in patients aged below 65 years, though few studies have evaluated THA outcomes in young patients (≤ 40 years old). This study examined a large cohort of patients who underwent THA at a young (≤ 40 years old) age to identify predictors of reoperation and compare survivorship between primary and conversion THAs. METHODS: A retrospective study was conducted on 497 patients who underwent 612 primary and conversion THAs at 40 years old or younger between 1990 and 2020. Medical records were reviewed to collect patient/surgical data. A multivariable logistic regression model identified independent predictors of reoperation, and Kaplan-Meier analysis with log-rank tests was used to compare survival curves by THA type. RESULTS: The median age at surgery (interquartile range) was 31 years (25 to 36). The median follow-up time was 6.6 years (range, 3.8 to 10.5). Conversion THAs had an increased rate of both revisions (12.3 versus 5.6%, P = 0.02) and nonrevision reoperations (8.9 versus 3.2%, P = 0.03) compared to primary THAs. A ceramic-on-ceramic articulation (odds ratio: 5.17; P = 0.03) and a higher estimated blood loss (odds ratio: 1.0007; P = 0.03) were independent predictors of reoperation for primary and conversion THA, respectively. Conversion THAs had a lower 15-year survival (77.8 versus 90.8%, P = 0.009) compared to primary THAs. CONCLUSIONS: Patients ≤ 40 years old who underwent primary and conversion THAs demonstrated an impressive 15-year survival comparable to that of older populations (74 to 93%), while conversion procedures had a higher reoperation rate. Although primary THA may be more ideal, there are promising outcomes for patients who need THA at a younger age than typically implemented, especially for those who are very young (≤ 30 years old).

Predictors of reoperation and survival experience for primary total knee arthroplasty in young patients with degenerative and inflammatory arthritis.

INTRODUCTION: While total knee arthroplasty (TKA) is typically implemented in patients > 65 years old, young patients may need to undergo TKA for pain relief and functional improvement. Current data are limited by older cohorts and short-term survival rates. This study aimed to examine a large sample size of patients with degenerative and inflammatory conditions who underwent primary TKA at a young (≤ 40) age to identify predictors of reoperation, as well 15-year survivorship. MATERIALS AND METHODS: A retrospective study was performed on 77 patients (92 surgeries) who underwent primary TKA at ≤ 40 years old, between January 1990 and January 2020. Patient charts were reviewed and a multivariable logistic regression model identified independent predictors of reoperation. Kaplan-Meier analysis was employed to build survival curves and log-rank tests analyzed survival between groups. RESULTS: Of the 77 patients, the median age at the time of surgery was 35.7 years (IQR: 31.2-38.7) and median follow-up time was 6.88 years. Twenty-one (22.8%) primary TKAs underwent 24 reoperations, most commonly due to stiffness (n = 9, 32.1%) and infection (n = 13, 46.4%) more significantly in the OA group (p = 0.049). There were no independent predictors of reoperation in multivariable analysis, and 15-year revision-free survivorship after TKA did not differ by indication (77.3% for OA/PTOA vs. 96.7% for autoimmune, p = 0.09) or between ≤ 30 and 31-40 year age groups (94.7% vs. 83.6%, p = 0.55). CONCLUSIONS: In this cohort of patients ≤ 40 years old, revision-free survival was comparable to that reported in the literature for older TKA patients with osteoarthritis/autoimmune conditions (81-94% at 15-years). Though nearly a quarter of TKAs required reoperation and causes of secondary surgery differed between degenerative and inflammatory arthritis patients, there were no significant predictors of increased reoperation rate. Very young patients ≤ 30 years old did not have an increased risk of revision compared to those aged 31-40 years.

What Is the Most Effective Treatment for Periprosthetic Joint Infection After Total Joint Arthroplasty in Patients with Rheumatoid Arthritis?: A Systematic Review.

BACKGROUND: Rheumatoid arthritis (RA) is a risk factor for periprosthetic joint infection (PJI) after total joint arthroplasty (TJA). The purpose of this study was to perform a systematic review comparing the failure rates of debridement, antibiotics, and implant retention (DAIR), one-stage exchange arthroplasty/revision (OSR), and 2-stage exchange arthroplasty/revision (TSR) for RA patients with PJI and identify risk factors in the RA population associated with increased treatment failure rate. METHODS: PubMed, Ovid MEDLINE, and Ovid Embase databases were screened with the terms "rheumatoid arthritis," "total joint arthroplasty," "prosthetic joint infection," and "treatment for PJI" on August 29, 2021. Four hundred ninety-one studies were screened, of which 86 were evaluated. The primary outcome evaluated was failure of surgical treatment for PJI. RESULTS: Ten retrospective cohort studies were included after full-text screening, yielding 401 patients with RA. Additional demographic and PJI management data were obtained for 149 patients. Patients with RA who underwent TSR demonstrated a lower failure rate (26.8%) than both DAIR (60.1%) and OSR (39.2%) (χ2 = 37.463, p < 0.00001). Patients with RA who underwent DAIR had a 2.27 (95% CI, 1.66-3.10) times higher risk of experiencing treatment failure than those who underwent TSR. Among risk factors, there was a significant difference in the C-reactive protein of patients who did vs. did not experience treatment failure (p = 0.02). CONCLUSION: TSR has a higher rate of success in the management of PJI patients with RA compared with DAIR and OSR. The complete removal of the infected prosthesis and delayed reimplantation may lower the treatment failure rate. LEVEL OF EVIDENCE: Level III. See Instructions for Authors for a complete description of levels of evidence.

Multicenter Evaluation of Radiation and Immune Checkpoint Inhibitor Therapy in Mucosal Melanoma and Review of Recent Literature.

Purpose: Optimal integration of local therapy and systemic immune therapy for patients with mucosal melanoma (MM) is uncertain. We evaluated treatment patterns and outcomes following radiation therapy (RT) in combination with immune checkpoint inhibition (ICI) in MM. Methods and Materials: Thirty-seven patients with localized (n = 32, 87%) or node-positive (n = 5, 14%) MM were treated across 4 institutions with RT to the primary tumor with or without oncologic resection (n = 28, 76%) and ICI from 2012 to 2020. Recurrence rates were estimated using cumulative incidence in the presence of the competing risk of death. Results: Mucosal sites were head/neck (n = 29, 78%), vaginal (n = 7, 19%), and anorectal (n = 1, 3%). Patients received ICI prior to or concurrent with RT (n = 14, 38%), following RT (n = 5, 14%), or at recurrence (n = 18, 49%). The objective response rate for evaluable patients was 31% for ICI as initial treatment (95% CI, 11%-59%) and 19% for ICI at recurrence (95% CI, 4%-46%). Median follow-up was 26 months for living patients; median overall survival (OS) was 54 months (95% CI, 31 months-not reached). Two-year OS was 85%; distant metastasis-free survival 44%. The 2-year cumulative incidence of local recurrence (LR) was 26% (95% CI, 13%-41%). For 9 patients with unresectable disease, 2-year OS was 88% (95% CI, 35%-98%); LR was 25% (95% CI, 3%-58%). For 5 patients with positive nodes at diagnosis, 2-year OS was 100%; LR was 0%. Conclusions: High rates of local control were achieved with RT with or without oncologic resection and ICI for localized and locally advanced MM. In particular, favorable local control was possible even for patients with unresectable or node-positive disease. Although risk of distant failure remains high, patients with MM may benefit from aggressive local therapy including RT in the setting of immunotherapy treatment.

What Is the Clinical Benefit of Common Orthopaedic Procedures as Assessed by the PROMIS Versus Other Validated Outcomes Tools?

BACKGROUND: Patient-reported outcome measures (PROMs), including the Patient-reported Outcomes Measurement Information System (PROMIS), are increasingly used to measure healthcare value. The minimum clinically important difference (MCID) is a metric that helps clinicians determine whether a statistically detectable improvement in a PROM after surgical care is likely to be large enough to be important to a patient or to justify an intervention that carries risk and cost. There are two major categories of MCID calculation methods, anchor-based and distribution-based. This variability, coupled with heterogeneous surgical cohorts used for existing MCID values, limits their application to clinical care. QUESTIONS/PURPOSES: In our study, we sought (1) to determine MCID thresholds and attainment percentages for PROMIS after common orthopaedic procedures using distribution-based methods, (2) to use anchor-based MCID values from published studies as a comparison, and (3) to compare MCID attainment percentages using PROMIS scores to other validated outcomes tools such as the Hip Disability and Osteoarthritis Outcome Score (HOOS) and Knee Disability and Osteoarthritis Outcome Score (KOOS). METHODS: This was a retrospective study at two academic medical centers and three community hospitals. The inclusion criteria for this study were patients who were age 18 years or older and who underwent elective THA for osteoarthritis, TKA for osteoarthritis, one-level posterior lumbar fusion for lumbar spinal stenosis or spondylolisthesis, anatomic total shoulder arthroplasty or reverse total shoulder arthroplasty for glenohumeral arthritis or rotator cuff arthropathy, arthroscopic anterior cruciate ligament reconstruction, arthroscopic partial meniscectomy, or arthroscopic rotator cuff repair. This yielded 14,003 patients. Patients undergoing revision operations or surgery for nondegenerative pathologies and patients without preoperative PROMs assessments were excluded, leaving 9925 patients who completed preoperative PROMIS assessments and 9478 who completed other preoperative validated outcomes tools (HOOS, KOOS, numerical rating scale for leg pain, numerical rating scale for back pain, and QuickDASH). Approximately 66% (6529 of 9925) of patients had postoperative PROMIS scores (Physical Function, Mental Health, Pain Intensity, Pain Interference, and Upper Extremity) and were included for analysis. PROMIS scores are population normalized with a mean score of 50 ± 10, with most scores falling between 30 to 70. Approximately 74% (7007 of 9478) of patients had postoperative historical assessment scores and were included for analysis. The proportion who reached the MCID was calculated for each procedure cohort at 6 months of follow-up using distribution-based MCID methods, which included a fraction of the SD (1/2 or 1/3 SD) and minimum detectable change (MDC) using statistical significance (such as the MDC 90 from p < 0.1). Previously published anchor-based MCID thresholds from similar procedure cohorts and analogous PROMs were used to calculate the proportion reaching MCID. RESULTS: Within a given distribution-based method, MCID thresholds for PROMIS assessments were similar across multiple procedures. The MCID threshold ranged between 3.4 and 4.5 points across all procedures using the 1/2 SD method. Except for meniscectomy (3.5 points), the anchor-based PROMIS MCID thresholds (range 4.5 to 8.1 points) were higher than the SD distribution-based MCID values (2.3 to 4.5 points). The difference in MCID thresholds based on the calculation method led to a similar trend in MCID attainment. Using THA as an example, MCID attainment using PROMIS was achieved by 76% of patients using an anchor-based threshold of 7.9 points. However, 82% of THA patients attained MCID using the MDC 95 method (6.1 points), and 88% reached MCID using the 1/2 SD method (3.9 points). Using the HOOS metric (scaled from 0 to 100), 86% of THA patients reached the anchor-based MCID threshold (17.5 points). However, 91% of THA patients attained the MCID using the MDC 90 method (12.5 points), and 93% reached MCID using the 1/2 SD method (8.4 points). In general, the proportion of patients reaching MCID was lower for PROMIS than for other validated outcomes tools; for example, with the 1/2 SD method, 72% of patients who underwent arthroscopic partial meniscectomy reached the MCID on PROMIS Physical Function compared with 86% on KOOS. CONCLUSION: MCID calculations can provide clinical correlation for PROM scores interpretation. The PROMIS form is increasingly used because of its generalizability across diagnoses. However, we found lower proportions of MCID attainment using PROMIS scores compared with historical PROMs. By using historical proportions of attainment on common orthopaedic procedures and a spectrum of MCID calculation techniques, the PROMIS MCID benchmarks are realizable for common orthopaedic procedures. For clinical practices that routinely collect PROMIS scores in the clinical setting, these results can be used by individual surgeons to evaluate personal practice trends and by healthcare systems to quantify whether clinical care initiatives result in meaningful differences. Furthermore, these MCID thresholds can be used by researchers conducting retrospective outcomes research with PROMIS. LEVEL OF EVIDENCE: Level III, therapeutic study.

Automatic proximal airway volume segmentation using optical coherence tomography for assessment of inhalation injury.

BACKGROUND: Acute respiratory distress syndrome (ARDS) is a severe form of acute lung injury with a mortality rate of up to 40%. Early management of ARDS has been difficult due to the lack of sensitive imaging tools and robust analysis software. We previously designed an optical coherence tomography (OCT) system to evaluate mucosa thickness (MT) after smoke inhalation, but the analysis relied on manual segmentation. The aim of this study is to assess in vivo proximal airway volume (PAV) after inhalation injury using automated OCT segmentation and correlate the PAV to lung function for rapid indication of ARDS. METHODS: Anesthetized female Yorkshire pigs (n = 14) received smoke inhalation injury (SII) and 40% total body surface area thermal burns. Measurements of PaO2-to-FiO2 ratio (PFR), peak inspiratory pressure (PIP), dynamic compliance, airway resistance, and OCT bronchoscopy were performed at baseline, postinjury, 24 hours, 48 hours, 72 hours after injury. A tissue segmentation algorithm based on graph theory was used to reconstruct a three-dimensional (3D) model of lower respiratory tract and estimate PAV. Proximal airway volume was correlated with PFR, PIP, compliance, resistance, and MT measurement using a linear regression model. RESULTS: Proximal airway volume decreased after the SII: the group mean of proximal airway volume at baseline, postinjury, 24 hours, 48 hours, 72 hours were 20.86 cm (±1.39 cm), 17.61 cm (±0.99 cm), 14.83 cm (±1.20 cm), 14.88 cm (±1.21 cm), and 13.11 cm (±1.59 cm), respectively. The decrease in the PAV was more prominent in the animals that developed ARDS after 24 hours after the injury. PAV was significantly correlated with PIP (r = 0.48, p < 0.001), compliance (r = 0.55, p < 0.001), resistance (r = 0.35, p < 0.01), MT (r = 0.60, p < 0.001), and PFR (r = 0.34, p < 0.01). CONCLUSION: Optical coherence tomography is a useful tool to quantify changes in MT and PAV after SII and burns, which can be used as predictors of developing ARDS at an early stage. LEVEL OF EVIDENCE: Prognostic, level III.

Automated 3D segmentation of methyl isocyanate-exposed rat trachea using an ultra-thin, fully fiber optic optical coherence endoscopic probe.

Development of effective rescue countermeasures for toxic inhalational industrial chemicals, such as methyl isocyanate (MIC), has been an emerging interest. Nonetheless, current methods for studying toxin-induced airway injuries are limited by cost, labor time, or accuracy, and only provide indirect or localized information. Optical Coherence Tomography (OCT) endoscopic probes have previously been used to visualize the 3-D airway structure. However, gathering such information in small animal models, such as rat airways after toxic gas exposure, remains a challenge due to the required probe size necessary for accessing the small, narrow, and partially obstructed tracheas. In this study, we have designed a 0.4 mm miniature endoscopic probe and investigated the structural changes in rat trachea after MIC inhalation. An automated 3D segmentation algorithm was implemented so that anatomical changes, such as tracheal lumen volume and cross-sectional areas, could be quantified. The tracheal region of rats exposed to MIC by inhalation showed significant airway narrowing, especially within the upper trachea, as a result of epithelial detachment and extravascular coagulation within the airway. This imaging and automated reconstruction technique is capable of rapid and minimally-invasive identification of airway obstruction. This method can be applied to large-scale quantitative analysis of in vivo animal models.