Mechanical loading of bone-anchored implants during functional performance tests in service members with transfemoral limb loss.

Introduction: For individuals with limb loss, bone-anchored implants create a direct structural and functional connection to a terminal prosthesis. Here, we characterized the mechanical loads distal to the abutment during several functional performance tests in Service members with transfemoral (TF) limb loss, to expand on prior work evaluating more steady-state ambulation on level ground or slopes/stairs. Methods: Two males with unilateral TF limb loss and two males with bilateral TF limb loss participated after two-stage osseointegration (24 and 12 months, respectively). Tri-directional forces and moments were wirelessly recorded through a sensor, fit distal to the abutment, during six functional tests: Timed Up and Go (TUG), Four Square Step Test (FSST), Six Minute Walk Test (6MWT), Edgren Side-Step Test (SST), T-Test (TTEST), and Illinois Agility Test (IAT). Additionally, participants performed a straight-line gait evaluation on a 15 m level walkway at a self-selected speed (0.93-1.24 m/s). Peak values for each component of force and moment were extracted from all six functional tests; percent differences compared each peak with respect to the corresponding mean peak in straight-line walking. Results: Peak mechanical loads were largest during non-steady state components of the functional tests (e.g., side-stepping during SST or TTEST, standing up from the ground during IAT). Relative to walking, peak forces during functional tests were larger by up to 143% (anterior-posterior), 181% (medial-lateral), and 110% (axial); peak moments were larger by up to 108% (flexion-extension), 50% (ab/adduction), and 211% (internal/external rotation). Conclusions: A more comprehensive understanding of the mechanical loads applied to bone-anchored implants during a variety of activities is critical to maximize implant survivability and long-term outcomes, particularly for Service members who are generally young at time of injury and return to active lifestyles.

Thighplasty at the Time of Stage-1 Bone-Anchored Osseointegration Surgery.

Background: For patients with transfemoral amputations and difficulty tolerating conventional socket-based prostheses, osseointegrated (OI) implants have enabled increased prosthetic use, improved patient satisfaction, and shown promising functional outcomes1,2. Although the use of OI implants effectively eliminates the soft-tissue-related challenges that have plagued socket-based prostheses, the presence of a permanent, percutaneous implant imparts a host of new soft-tissue challenges that have yet to be fully defined. In patients undergoing OI surgery who have redundant soft tissue, we perform a thighplasty to globally reduce excess skin and fat, tighten the soft-tissue envelope, and improve the contour of the residual limb. Description: First, the orthopaedic surgical team prepares the residual femur for implantation of the OI device. After the implant is inserted, the residual hamstrings and quadriceps musculature are closed over the end of the femur, and the subcutaneous tissue and skin are closed in a layered fashion. Although the anatomic location and amount of excess soft tissue are patient-dependent, we perform a standard pinch test to determine the amount of soft tissue that can be safely removed for the thighplasty. Once the proposed area of resection is marked, we proceed with longitudinal, sharp dissection down to the level of the muscular fascia. At this point, we use another pinch test to confirm the amount of soft-tissue resection that will allow for adequate resection without undue tension3. Excess subcutaneous fat and skin are carefully removed along the previously marked incisions, typically overlying the medial compartment of the thigh in the setting of patients with transfemoral amputations. The thighplasty incision is closed in a layered fashion over 1 or 2 Jackson-Pratt drains, depending on the amount of resection. Alternatives: Depending on the amount of redundant soft tissue, thighplasty may not be necessary at the time of OI surgery; however, in our experience, excess soft tissue surrounding the transcutaneous aperture can predispose the patient to increased shear forces at the aperture, increased drainage, and increased risk of infection4. Rationale: Although superficial infectious complications are most common following OI surgery, the need for soft-tissue refashioning and excision is one of the most common reasons for reoperation1,5. Our group has been more aggressive than most in our use of a vertical thighplasty procedure to globally reduce soft-tissue motion in the residual limb to avoid reoperation. Expected Outcomes: Although much of the OI literature has focused on infectious complications, recent studies have demonstrated reoperation rates of 18% to 36% for redundant soft tissue following OI surgery1,5. We believe that thighplasty at the time of OI not only reduces the likelihood of reoperation but may also decrease infectious complications by reducing relative motion and inflammation at the skin-implant interface4,6. Important Tips: The thighplasty procedure is ideally performed as part of the first stage of the OPRA (Osseointegrated Prosthesis for the Rehabilitation of Amputees) procedure to limit the likelihood of problematic ischemia-related complications.We utilize a confirmatory pinch test both before and throughout the thighplasty procedure to ensure adequate resection without undue tension.The thighplasty excision pattern utilizes a long vertical limb designed to decrease the circumferential laxity of the residual limb. Maximal tension is borne on the vertical limb and not on the transverse extensions, as these are prone to scar widening and distortion of surrounding tissues.Closed-suction drainage is utilized liberally to decrease the likelihood of a symptomatic seroma. Acronyms and Abbreviations: OI = osseointegratedOPRA = Osseointegrated Prosthesis for the Rehabilitation of AmputeesPVNS = pigmented villonodular synovitisT-GCT = tenosynovial giant-cell tumor.BMI = body mass indexPMH = past medical history.

The influence of microbial colonization on inflammatory versus pro-healing trajectories in combat extremity wounds.

A combination of improved body armor, medical transportation, and treatment has led to the increased survival of warfighters from combat extremity injuries predominantly caused by blasts in modern conflicts. Despite advances, a high rate of complications such as wound infections, wound failure, amputations, and a decreased quality of life exist. To study the molecular underpinnings of wound failure, wound tissue biopsies from combat extremity injuries had RNA extracted and sequenced. Wounds were classified by colonization (colonized vs. non-colonized) and outcome (healed vs. failed) status. Differences in gene expression were investigated between timepoints at a gene level, and longitudinally by multi-gene networks, inferred proportions of immune cells, and expression of healing-related functions. Differences between wound outcomes in colonized wounds were more apparent than in non-colonized wounds. Colonized/healed wounds appeared able to mount an adaptive immune response to infection and progress beyond the inflammatory stage of healing, while colonized/failed wounds did not. Although, both colonized and non-colonized failed wounds showed increasing inferred immune and inflammatory programs, non-colonized/failed wounds progressed beyond the inflammatory stage, suggesting different mechanisms of failure dependent on colonization status. Overall, these data reveal gene expression profile differences in healing wounds that may be utilized to improve clinical treatment paradigms.

Lifetime cost-effectiveness analysis osseointegrated transfemoral versus socket prosthesis using Markov modelling.

Aims: Prior cost-effectiveness analyses on osseointegrated prosthesis for transfemoral unilateral amputees have analyzed outcomes in non-USA countries using generic quality of life instruments, which may not be appropriate when evaluating disease-specific quality of life. These prior analyses have also focused only on patients who had failed a socket-based prosthesis. The aim of the current study is to use a disease-specific quality of life instrument, which can more accurately reflect a patient's quality of life with this condition in order to evaluate cost-effectiveness, examining both treatment-naïve and socket refractory patients. Methods: Lifetime Markov models were developed evaluating active healthy middle-aged male amputees. Costs of the prostheses, associated complications, use/non-use, and annual costs of arthroplasty parts and service for both a socket and osseointegrated (OPRA) prosthesis were included. Effectiveness was evaluated using the questionnaire for persons with a transfemoral amputation (Q-TFA) until death. All costs and Q-TFA were discounted at 3% annually. Sensitivity analyses on those cost variables which affected a change in treatment (OPRA to socket, or socket to OPRA) were evaluated to determine threshold values. Incremental cost-effectiveness ratios (ICERs) were calculated. Results: For treatment-naïve patients, the lifetime ICER for OPRA was $279/quality-adjusted life-year (QALY). For treatment-refractory patients the ICER was $273/QALY. In sensitivity analysis, the variable thresholds that would affect a change in the course of treatment based on cost (from socket to OPRA), included the following for the treatment-naïve group: yearly replacement components for socket > $8,511; cost yearly replacement parts OPRA < $1,758; and for treatment-refractory group: yearly replacement component for socket of > $12,467. Conclusion: The use of the OPRA prosthesis in physically active transfemoral amputees should be considered as a cost-effective alternative in both treatment-naïve and treatment-refractory socket prosthesis patients. Disease-specific quality of life assessments such as Q-TFA are more sensitive when evaluating cost-effectiveness.

Utility of Thermal Imaging in Predicting Superficial Infections in Transfemoral Osseointegrated Implants.

Background: Superficial infection is a common minor complication of transcutaneous implants that can be challenging to predict or diagnose. Although it remains unclear whether superficial infections progress to deep infections (which may require implant removal), predicting and treating any infection in these patients is important. Given that flap thinning during stage II surgery requires compromising vascularity for stability of the skin penetration aperture, we hypothesized that early skin temperature changes predict long-term superficial infection risk. Methods: We obtained standardized thermal imaging and recorded surface temperatures of the aperture and overlying flaps 2 weeks postoperatively for the first 34 patients (46 limbs) treated with the Osseointegrated Prosthesis for the Rehabilitation of Amputees transfemoral implant system. We used two-sided t tests to compare temperatures surrounding the aperture and adjacent soft tissues in patients with and without subsequent infection. Results: During median follow-up of 3 years, 14 limbs (30.4%) developed 23 superficial infections. At patients' initial 2-week visit, mean skin temperature surrounding the aperture was 36.3ºC in limbs that later developed superficial infections and 36.7ºC in uninfected limbs (P = 0.35). In four patients with bilateral implants who later developed superficial infection in one limb, average temperature was 1.5ºC colder in the infected limb (P = 0.12). Conclusions: Superficial infections remain a frequent complication of transfemoral osseointegration surgery. We did not find differences in early heat signatures between limbs subsequently complicated and those not complicated by superficial infection. Further research should explore more objective measures to predict, diagnose, and prevent infections after osseointegration surgery.

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.

Technical Trick: Cryoneurolysis for Subacute Pain Mitigation in Patients With Limb Loss.

SUMMARY: Pain after amputation is often managed by target muscle reinnervation (TMR) with the added benefit that TMR also provides improved myoelectric terminal device control. However, as TMR takes several months for the recipient muscles to reliably reinnervate, this technique does not address pain within the subacute postoperative period during which pain chronification, sensitization, and opioid dependence and misuse may occur. Cryoneurolysis, described herein, uses focused, extreme temperatures to essentially "freeze" the nerve, blocking nociception, and improving pain in treated nerves potentially reducing the chances of pain chronification, sensitization, and substance dependence or abuse.

The Scope and Distribution of Upper Extremity Nerve Injuries Associated With Combat-Related Extremity Limb Salvage.

PURPOSE: Chronic pain and functional limitations secondary to nerve injuries are a major barrier to optimal recovery for patients following high-energy extremity trauma. Given the associated skeletal and soft tissue management challenges in the polytraumatized patient, concomitant nerve injuries may be overlooked or managed in delayed fashion. Whereas previous literature has reported rates of peripheral nerve injuries at <10% in the setting of high-energy extremity trauma, in our experience, the incidence of these injuries has been much higher. Thus, we sought to define the incidence, pain sequelae, and functional outcomes following upper extremity peripheral nerve injuries in the combat-related limb salvage population. METHODS: We performed a retrospective review of all patients who underwent limb salvage procedures to include flap coverage for combat-related upper extremity trauma at a single institution between January 2011 and January 2020. We collected data on patient demographics; perioperative complications; location of nerve injuries; surgical interventions; chronic pain; and subjective, patient-reported functional limitations. RESULTS: A total of 45 patients underwent flap procedures on 49 upper extremities following combat-related trauma. All patients were male with a median age of 27 years, and 96% (n = 47) of injuries were sustained from a blast mechanism. Thirty-three of the 49 extremities (67%) sustained associated nerve injuries. The most commonly injured nerve was the ulnar (51%), followed by median (30%) and radial/posterior interosseous (19%). Of the 33 extremities with nerve injuries, 18 (55%) underwent surgical intervention. Nerve repair/reconstruction was the most common procedure (67%), followed by targeted muscle reinnervation (TMR, 17%). Chronic pain and functional limitation were common following nerve injury. CONCLUSIONS: Upper extremity peripheral nerve injury is common following high-energy combat-related trauma with high rates of chronic pain and functional limitations. Surgeons performing limb salvage procedures to include flap coverage should anticipate associated peripheral nerve injuries and be prepared to repair or reconstruct the injured nerves, when feasible. TYPE OF STUDY/LEVEL OF EVIDENCE: Therapeutic IV.

Consensus and Equipose in the Management of Military Trainee Femoral Neck Stress Fractures: A Survey of Military Surgeons.

BACKGROUND: Femoral neck stress fractures (FNSFs) are a unique injury pattern not commonly treated in the civilian trauma population; however, it is particularly high with military trainees engaged in basic combat training. To date, no study has surveyed a population of military orthopedic surgeons on treatment preferences for military service members (SMs) with FNSF. QUESTIONS: We aim to evaluate the extent of clinical equipoise that exists in the management of these injuries, hypothesizing that there would be consensus in the factors dictating surgical and non-surgical intervention for FNSF. PATIENTS AND METHODS: A 27-question survey was created and sent to U.S. military orthopedic surgeon members of the Society of Military Orthopaedic Surgeons. The survey was designed in order to gather the experience among surgeons in treating FNSF and identifying variables that play a role in the treatment algorithm for these patients. In addition, seven detailed, clinical vignettes were presented to further inquire on surgeon treatment preferences. Binomial distribution analysis was used to evaluate for common trends within the surgeon's treatment preferences. RESULTS: Seventy orthopedic surgeons completed the survey, the majority of whom were on active duty status in the U.S. Military (82.86%) and having under 5 years of experience (61.43%). Majority of surgeons elected for a multiple screw construct (92.86%), however the orientation of the multiple screws was dependent on whether the fracture was open or closed. Management for compression-sided FNSF involving ≥50% of the femoral neck width, tension-sided FNSF, and stress fractures demonstrating fracture line progression had consensus for operative management. Respondents agreed upon prophylactic fixation of the contralateral hip if the following factors were involved: Complete fracture (98.57%), compression-sided fracture line >75% (88.57%), compression-sided fracture line >50-75% with hip effusion (88.57%), contralateral tension-sided fracture (87.14%), and compression-sided fracture line >50-75% (84.29%). An FNSF < 50% on the contralateral femoral neck or a hip effusion was indeterminate in surgeons indicating need for prophylactic fixation. Majority of surgeons (77.1%) utilized restricted toe-touch weight-bearing for postoperative mobility restrictions. CONCLUSIONS: Consensus exists for surgical and non-surgical management of FNSF by U.S. military orthopedic surgeons, despite the preponderance of surgeons reporting a low annual volume of FNSF cases treated. However, there are certain aspects in the operative and non-operative management of FNSF that are unanimously adhered to. Specifically, our results demonstrate that there is no clear indication on the management of FNSF when an associated hip effusion is involved. Additionally, the indications for surgically treating contralateral FNSF are unclear. LEVEL OF EVIDENCE: IV.

Inhibition of focal adhesion kinase 2 results in a macrophage polarization shift to M2 which attenuates local and systemic inflammation and reduces heterotopic ossification after polysystem extremity trauma.

Introduction: Heterotopic ossification (HO) is a complex pathology often observed in combat injured casualties who have sustained severe, high energy polytraumatic extremity injuries. Once HO has developed, prophylactic therapies are limited outside of surgical excision. Tourniquet-induced ischemia injury (IR) exacerbates trauma-mediated musculoskeletal tissue injury, inflammation, osteogenic progenitor cell development and HO formation. Others have shown that focal adhesion kinase-2 (FAK2) plays a key role in regulating early inflammatory signaling events. Therefore, we hypothesized that targeting FAK2 prophylactically would mitigate extremity trauma induced IR inflammation and HO formation. Methods: We tested whether the continuous infusion of a FAK2 inhibitor (Defactinib, PF-573228; 6.94 µg/kg/min for 14 days) can mitigate ectopic bone formation (HO) using an established blast-related extremity injury model involving femoral fracture, quadriceps crush injury, three hours of tourniquet-induced limb ischemia, and hindlimb amputation through the fracture site. Tissue inflammation, infiltrating cells, osteogenic progenitor cell content were assessed at POD-7. Micro-computed tomography imaging was used to quantify mature HO at POD-56. Results: In comparison to vehicle control-treated rats, FAK2 administration resulted in no marked wound healing complications or weight loss. FAK2 treatment decreased HO by 43%. At POD-7, marked reductions in tissue proinflammatory gene expression and assayable osteogenic progenitor cells were measured, albeit no significant changes in expression patterns of angiogenic, chondrogenic and osteogenic genes. At the same timepoint, injured tissue from FAK-treated rats had fewer infiltrating cells. Additionally, gene expression analyses of tissue infiltrating cells resulted in a more measurable shift from an M1 inflammatory to an M2 anti-inflammatory macrophage phenotype in the FAK2 inhibitor-treated group. Discussion: Our findings suggest that FAK2 inhibition may be a novel strategy to dampen trauma-induced inflammation and attenuate HO in patients at high risk as a consequence of severe musculoskeletal polytrauma.

A Data-Driven Method to Discriminate Limb Salvage from Other Combat-Related Extremity Trauma.

INTRODUCTION: The aim of this study was to address and enhance our ability to study the clinical outcome of limb salvage (LS), a commonly referenced but ill-defined clinical care pathway, by developing a data-driven approach for the identification of LS cases using existing medical code data to identify characteristic diagnoses and procedures, and to use that information to describe a cohort of US Service members (SMs) for further study. METHODS: Diagnosis code families and inpatient procedure codes were compiled and analyzed to identify medical codes that are disparately associated with a LS surrogate population of SMs who underwent secondary amputation within a broader cohort of 3390 SMs with lower extremity trauma (AIS > 1). Subsequently, the identified codes were used to define a cohort of all SMs who underwent lower extremity LS which was compared with the opinion of a panel of military trauma surgeons. RESULTS: The data-driven approach identified a population of n = 2018 SMs who underwent LS, representing 59.5% of the combat-related lower extremity (LE) trauma population. Validation analysis revealed 70% agreement between the data-driven approach and gold standard SME panel for the test cases studied. The Kappa statistic (κ = 0.55) indicates a moderate agreement between the data-driven approach and the expert opinion of the SME panel. The sensitivity and specificity were identified as 55.6% (expert range of 51.8-66.7%) and 87% (expert range of 73.9-91.3%), respectively. CONCLUSIONS: This approach for identifying LS cases can be utilized to enable future high-throughput retrospective analyses for studying both short- and long-term outcomes of this underserved patient population.

In situ forming biomaterials as muscle void fillers for the provisional treatment of volumetric muscle loss injuries.

Volumetric muscle loss (VML) represents a devastating extremity injury which leads to chronic functional deficits and disability and is unrecoverable through normal healing pathways. When left untreated, the VML pathophysiology creates many challenges towards successful treatment, such as altered residual muscle architecture, excessive fibrosis, and contracture(s). As such, innovative approaches and technologies are needed to prevent or reverse these adverse sequelae. Development of a rationally designed biomaterial technology which is intended to be acutely placed within a VML defect - i.e., to serve as a muscle void filler (MVF) by maintaining the VML defect - could address this clinical unmet need by preventing these adverse sequelae as well as enabling multi-staged treatment approaches. To that end, three biomaterials were evaluated for their ability to serve as a provisional MVF treatment intended to stabilize a VML defect in a rat model for an extended period (28 days): polyvinyl alcohol (PVA), hyaluronic acid and polyethylene glycol combination (HA + PEG), and silicone, a clinically used soft tissue void filler. HA + PEG biomaterial showed signs of deformation, while both PVA and silicone did not. There were no differences between treatment groups for their effects on adjacent muscle fiber count and size distribution. Not surprisingly, silicone elicited robust fibrotic response resulting in a fibrotic barrier with a large infiltration of macrophages, a response not seen with either the PVA or HA + PEG. Taken together, PVA was found to be the best material to be used as a provisional MVF for maintaining VML defect volume while minimizing adverse effects on the surrounding muscle.

Long-Term Health Outcomes of Limb Salvage Compared with Amputation for Combat-Related Trauma.

BACKGROUND: There are little long-term health data, particularly in terms of body composition and development of metabolic syndromes, to help surgeons to guide the decision between limb salvage and amputation in patients with limb-threatening trauma. The purpose of this study was to compare long-term health outcomes after high-energy lower-extremity trauma between patients who underwent attempted flap-based limb salvage or amputation. METHODS: We performed a retrospective review of servicemembers with a minimum 10-year follow-up who underwent flap-based limb salvage followed by unilateral amputation or continued limb salvage after combat-related, lower-extremity trauma between 2005 and 2011. Patient demographic characteristics, injury characteristics, and health outcomes including body mass index (BMI) and development of metabolic disease (e.g., hyperlipidemia, hypertension, heart disease, and diabetes) were compared between treatment cohorts. Adjusted BMIs were calculated for the amputation cohort to account for lost surface area. We performed multivariable and propensity score analysis to determine the likelihood of developing obesity or metabolic disease. RESULTS: In this study, 110 patients had available long-term follow-up (mean, 12.2 years) from the time of the injury. Fifty-six patients underwent limb salvage and 54 patients underwent unilateral amputation. There was no difference in preinjury BMI (p = 0.30). After adjusting for limb loss, the amputation cohort had a trend toward higher BMIs at ≥1 years after the injury, a higher rate of obesity, and a greater increase in BMI from baseline after the injury. The development of metabolic comorbidities was common after both amputation (23 [43%] of 54) and limb salvage (27 [48%] of 56). With the numbers available, we were unable to demonstrate a difference in risk for the development of hypertension, hyperlipidemia, diabetes, heart disease, or any comorbidity other than obesity (p > 0.05). CONCLUSIONS: Amputations may be medically necessary and may decrease pain, improve mobility, and/or expedite return to activity compared with limb salvage after similar injuries. However, limb loss may negatively impact metabolic regulation and may contribute to a higher risk of obesity despite beneficial effects on mobility. LEVEL OF EVIDENCE: Therapeutic Level III . See Instructions for Authors for a complete description of levels of evidence.

Effect of Targeted Cytokine Inhibition on Progression of Post-Traumatic Osteoarthritis Following Intra-Articular Fracture.

Intra-articular fractures (IAF) result in significant and prolonged inflammation, increasing the chances of developing post-traumatic osteoarthritis (PTOA). Interleukin-one beta (IL-1ß) and Tumor Necrosis Factor-alpha (TNF-α) are key inflammatory factors shown to be involved in osteochondral degradation following IAF. As such, use of targeted biologics such as Infliximab (INX), a TNF-α inhibitor, and Anakinra (ANR), an interleukin-one (IL-1) receptor antagonist (IL1RA), may protect against PTOA by damping the inflammatory response to IAF and reducing osteochondral degradation. To test this hypothesis, IAFs were induced in the hindlimb knee joints of rats treated with INX at 10 mg/kg/day, ANR at 100 g/kg/day, or saline (vehicle control) by subcutaneous infusion for a period of two weeks and healing was evaluated at 8-weeks post injury. Serum and synovial fluid (SF) were analyzed for soluble factors. In-vivo microcomputed tomography (µCT) scans assessed bone mineral density and bone morphometry measurements. Cationic CA4+ agent assessed articular cartilage composition via ex vivo µCT. Scoring according to the Osteoarthritis Research Society International (OARSI) guidelines was performed on stained histologic tibia sections at the 56-day endpoint on a 0-6 scale. Systemically, ANR reduced many pro-inflammatory cytokines and reduced osteochondral degradation markers Cross Linked C-Telopeptide Of Type II (CTXII, p < 0.05) and tartrate-resistant acid phosphatase (TRAP, p < 0.05). ANR treatment resulted in increased chemokines; macrophage-chemotractant protein-1 (MCP-1), MPC-3, macrophage inhibitory protein 2 (MIP2) with a concomitant decrease in proinflammatory interleukin-17A (IL17A) at 14 days post-injury within the SF. Microcomputed tomography (µCT) at 56 days post-injury revealed ANR Treatment decreased epiphyseal degree of anisotropy (DA) (p < 0.05) relative to saline. No differences were found with OARSI scoring but contrast-enhanced µCT revealed a reduction in glycosaminoglycan content with ANR treatment. These findings suggest targeted cytokine inhibition, specifically IL-1 signaling, as a monotherapy has minimal utility for improving IAF healing outcomes but may have utility for promoting a more permissive inflammatory environment that would allow more potent disease modifying osteoarthritis drugs to mitigate the progression of PTOA after IAF.

Hounsfield Unit-Calculated Bone Mineral Density Loss Following Combat-Related Lower Extremity Amputations.

BACKGROUND: After combat-related lower extremity amputations, patients rapidly lose bone mineral density (BMD). As serial dual x-ray absorptiometry (DXA) scans are rarely performed in this setting, it is difficult to determine the timeline for bone loss and recovery or the role of interventions. However, a strong correlation has been demonstrated between DXA BMD and computed tomography (CT) signal attenuation. We sought to leverage multiple CT scans obtained after trauma to develop a predictive model for BMD after combat-related lower extremity amputations. METHODS: We reviewed amputations performed within the United States military between 2003 and 2016 in patients with multiple CT scans. We collected pertinent clinical information, including amputation level(s), complications, and time to weight-bearing. The primary outcome measure was the development of low BMD, estimated in Hounsfield units (HU) from CT scans with use of a previously validated method. One hundred and twenty-eight patients with 613 femoral neck CT scans were available for analysis. A least absolute shrinkage and selection operator (LASSO) multiple logistic regression analysis was applied to determine the effects of modifiable and non-modifiable variables on BMD. A random-effects model was applied to determine which factors were most predictive of low BMD and to quantify their effects. RESULTS: Both amputated and non-amputated extremities demonstrated substantial BMD loss, which stabilized approximately 3 years after the injury. Loss of BMD followed a logarithmic pattern, stabilizing after 1,000 days. On average, amputated limbs lost approximately 100 HU of BMD after 1,000 days. Other factors identified by the mixed-effects model included nonambulatory status (-33.5 HU), age at injury (-3.4 HU per year), surgical complications delaying weight-bearing (-21.3 HU), transtibial amputation (20.9 HU), and active vitamin-D treatment (-19.7 HU). CONCLUSIONS: Patients with combat-related lower extremity amputations experience an initially rapid decline in BMD in both intact and amputated limbs as a result of both modifiable and non-modifiable influences, including time to walking, amputation level, surgical complications, and age. The paradoxical association of vitamin-D supplementation with lower HU likely reflects this treatment being assigned to patients with low BMD. This model may assist with clinical decision-making prior to performing lower extremity amputation and also may assist providers with postoperative decision-making to optimize management for prophylaxis against osteoporosis. LEVEL OF EVIDENCE: Therapeutic Level III . See Instructions for Authors for a complete description of levels of evidence.

Preventing biological waste: Effective use of viable tissue in traumatized lower extremities.

Severe open lower extremity trauma requires debridement to remove contamination and devitalized tissues. Aggressive debridement should be balanced with preservation of viable tissue. These often damaged but preserved viable tissues are "spare parts" that augment the options available for reconstruction. The long-term goal of reconstruction should be functional limb restoration and optimization. Injury patterns, levels, and patient factors will determine whether this endeavor is better accomplished with limb salvage or amputation. This article reviews the rationale and strategies for preserving spare parts throughout debridement and then incorporating them as opportunistic grafts in the ultimate reconstruction to facilitate healing and maximize extremity function. Level of Evidence: 5.

Systemic inflammation induced from remote extremity trauma is a critical driver of secondary brain injury.

Blast exposure, commonly experienced by military personnel, can cause devastating life-threatening polysystem trauma. Despite considerable research efforts, the impact of the systemic inflammatory response after major trauma on secondary brain injury-inflammation is largely unknown. The aim of this study was to identify markers underlying the susceptibility and early onset of neuroinflammation in three rat trauma models: (1) blast overpressure exposure (BOP), (2) complex extremity trauma (CET) involving femur fracture, crush injury, tourniquet-induced ischemia, and transfemoral amputation through the fracture site, and (3) BOP+CET. Six hours post-injury, intact brains were harvested and dissected to obtain biopsies from the prefrontal cortex, striatum, neocortex, hippocampus, amygdala, thalamus, hypothalamus, and cerebellum. Custom low-density microarray datasets were used to identify, interpret and visualize genes significant (p < 0.05 for differential expression [DEGs]; 86 neuroinflammation-associated) using a custom python-based computer program, principal component analysis, heatmaps and volcano plots. Gene set and pathway enrichment analyses of the DEGs was performed using R and STRING for protein-protein interaction (PPI) to identify and explore key genes and signaling networks. Transcript profiles were similar across all regions in naïve brains with similar expression levels involving neurotransmission and transcription functions and undetectable to low-levels of inflammation-related mediators. Trauma-induced neuroinflammation across all anatomical brain regions correlated with injury severity (BOP+CET > CET > BOP). The most pronounced differences in neuroinflammatory-neurodegenerative gene regulation were between blast-associated trauma (BOP, BOP+CET) and CET. Following BOP, there were few DEGs detected amongst all 8 brain regions, most were related to cytokines/chemokines and chemokine receptors, where PPI analysis revealed Il1b as a potential central hub gene. In contrast, CET led to a more excessive and diverse pro-neuroinflammatory reaction in which Il6 was identified as the central hub gene. Analysis of the of the BOP+CET dataset, revealed a more global heightened response (Cxcr2, Il1b, and Il6) as well as the expression of additional functional regulatory networks/hub genes (Ccl2, Ccl3, and Ccl4) which are known to play a critical role in the rapid recruitment and activation of immune cells via chemokine/cytokine signaling. These findings provide a foundation for discerning pathophysiological consequences of acute extremity injury and systemic inflammation following various forms of trauma in the brain.

Development and characterization of an intra-articular fracture mediated model of post-traumatic osteoarthritis.

PURPOSE: This study aimed to develop and characterize a closed intra-articular fracture (IAF) mediated post-traumatic osteoarthritis (PTOA) model in rats to serve as a testbed for putative disease modifying interventions. METHODS: Male rats were subject to a 0 Joule (J), 1 J, 3 J, or 5 J blunt-force impact to the lateral aspect of the knee and allowed to heal for 14 and 56 days. Micro-CT was performed at time of injury and at the specified endpoints to assess bone morphometry and bone mineral density measurements. Cytokines and osteochondral degradation markers were assayed from serum and synovial fluid via immunoassays. Histopathological analyses were performed on decalcified tissues and assessed for evidence of osteochondral degradation. RESULTS: High-energy (5 J) blunt impacts consistently induced IAF to the proximal tibia, distal femur, or both while lower energy (1 J and 3 J) impacts did not. CCL2 was found to be elevated in the synovial fluid of rats with IAF at both 14- and 56-days post-injury while COMP and NTX-1 were upregulated chronically relative to sham controls. Histological analysis showed increased immune cell infiltration, increased osteoclasts and osteochondral degradation with IAF relative to sham. CONCLUSION: Based on results from the current study, our data indicates that a 5 J blunt-forced impact adequately and consistently induces hallmark osteoarthritic changes to the articular surface and subchondral bone at 56 days after IAF. Marked development of PTOA pathobiology suggest this model will provide a robust testbed for screening putative disease modifying interventions that might be translated to the clinic for militarily relevant, high-energy joint injuries.

Bone Homeostasis and Physiology in Normal and Orthopaedic Disease Conditions.

Some of the most common human systemic diseases-both benign and malignant-affect bone regulation, formation, and homeostasis (the cellular balance regulated by osteocytes, osteoblasts, and osteoclasts). This review discusses our current understanding of the molecular components and mechanisms that are responsible for homeostasis and interactions resulting in dysregulation (dysfunction due to the loss of the dynamic equilibrium of bone homeostasis). Knowledge of key pathways in bone biology can improve surgeon understanding, clinical recognition, and treatment of bone homeostasis-related diseases.