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.

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.

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.

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.

Bilateral Chronic Quadriceps Tendon Ruptures Treated with Hamstring Autograft Reconstruction: A Case Report.

CASE: A 30-year-old semiprofessional football player presented with chronic bilateral quadriceps tendon ruptures. Both quadriceps tendon ruptures were unsuitable for isolated primary repair because of tendon retraction and immobility. A novel reconstruction technique using semitendinosus and gracilis tendon autografts was performed to restore both lower extremities' disrupted extensor mechanisms. At the final follow-up, the patient regained excellent motion of both knees and returned to high-intensity activity. CONCLUSION: Chronic quadriceps tendon ruptures present challenges related to tendon quality and mobilization. Reconstruction with hamstring autograft using a Pulvertaft weave through the retracted quadriceps tendon in a high-demand athletic patient represents a novel approach for treating this injury.

An Anatomic Study of the Proximal Tibial Epiphysis With Relevance to Percutaneous Epiphysiodesis Using Transphyseal Screws (PETS).

BACKGROUND: Percutaneous epiphysiodesis using transphyseal screws (PETS) is a common procedure to correct lower extremity limb-length discrepancies in the pediatric population. A potential complication of this procedure is development of tibial valgus deformity, which may occur secondary to decreased screw purchase in the thinner medial proximal tibial epiphysis. The thickness of the proximal tibial epiphysis has not yet been well quantified, which was the aim of this study. METHODS: Three-dimensional surface scans of 32 cadaveric proximal tibial epiphyses in specimens aged 3 to 17 years old were obtained and computer modeling software was utilized to measure the thickness of the proximal tibial epiphysis at 20 standardized potential screw insertion points according to a generated 5×4 map. RESULTS: When normalized to the total width of the proximal tibial epiphysis, the lateral side is thicker compared with the medial side. The positions with the greatest thickness are located at the midline in the sagittal plane and 33% of the total physeal width away from the medial and lateral edges in the coronal plane (0.265 and 0.261 normalized thickness, respectively). The proximal tibial epiphysis is particularly thin 25% from the medial edge (normalized thickness range: 0.196 to 0.221). Multiple regression analysis revealed a significant relationship between increasing age and female sex with thinner normalized medial and lateral heights. CONCLUSIONS: During PETS, areas for greater screw purchase are located centrally in the sagittal plane and 33% of the total width away from the medial and lateral edges of the proximal tibial epiphysis in the coronal plane. Caution should be taken when inserting screws in the medial 25% of the proximal tibial epiphysis as it is thinner relative to the lateral edge, particularly in females. CLINICAL RELEVANCE: This study provides quantitative, anatomic data on the thickness of the proximal tibial epiphysis, which can direct screw placement during PETS for correcting limb-length discrepancies. These data may help lessen the risk of developing tibial valgus deformity although future clinical studies are necessary to fully evaluate this possibility.

Optimal Fluoroscopic Angulation to Determine Intercondylar Notch Violation during Pediatric Medial Patellofemoral Ligament Reconstruction.

Previous anatomic data has suggested that during pediatric medial patellofemoral ligament (MPFL) reconstruction, the femoral tunnel must be angled distally and anteriorly to avoid damage to the distal femoral physis and then intercondylar notch. The purpose of this study was to determine the optimal degree of fluoroscopic angulation necessary to radiographically determine the presence of intercondylar notch violation. Fourteen adult cadaveric human femora were disarticulated and under fluoroscopic guidance, Schöttle's point was identified. A 0.62-mm Kirschner wire was then drilled through the condyle to create minimal notch violation. The femur was then placed on a level radiolucent table and coronal plane radiographs angled from -15 to 60 degrees were obtained in 5-degree increments to determine the fluoroscopic angle at which intercondylar notch violation was most evident. Grading of optimal fluoroscopic angle between two authors found that violation of the notch was the best appreciated at a mean angle of 43 ± 15 degrees from neutral. Results from this study emphasize the importance of angling the beam to essentially obtain a notch view to assess for a breech.

Incidence and Risk Factors of Acute Patellar Tendon Rupture, Repair Failure, and Return to Activity in the Active-Duty Military Population.

BACKGROUND: Patellar tendon ruptures have a reported incidence of 0.68 per 100,000 person-years in the general population. The epidemiology of surgically treated patellar tendon ruptures in the US military has yet to be reported, which would provide opportunity for identification of risk factors for these otherwise healthy and active patients. PURPOSE: To determine the incidence of patellar tendon rupture in the Military Health System (MHS) population and to analyze demographic patterns, surgical fixation methods, and rerupture rates. STUDY DESIGN: Case-control study; Level of evidence, 3. METHODS: We utilized the MHS Data Repository (MDR) to identity active-duty military servicemembers surgically treated for patellar tendon rupture between 2010 and 2015. Records were reviewed for demographic information, injury characteristics, fixation technique, and occurrence of rerupture. Risk factors for rupture were calculated using Poisson regression based on population counts and demographic data obtained in the MDR. Risk factors for rerupture and return to duty were analyzed via univariate analysis and multivariate regression. RESULTS: A total of 504 operatively treated primary patellar tendon repairs in 483 patients were identified, with an overall incidence of 6 per 100,000 person-years. Mean age was 33.6 years (range, 17-54 years) and 98% of patients were male. Fixation method was 81% bone tunnels and 7% suture anchors, and 12% were unknown. Black race had a higher relative rate ratio for rupture compared with the race categories White (9.21; P < .0001) and Other (3.27; P < .0001). The rupture rate was higher in 35- to 44-year-old patients compared with those aged 18 to 24 years (P < .0001), 25 to 34 years (P < .0001), and 45 to 64 years (P = .004). Return to full previous level of activity occurred in 75.8% of patients, 14.6% returned to activity with limitations, and 9.5% were medically separated. The rerupture rate was 3%. Fixation method, tobacco usage, body mass index, and race were not significant risk factors for rerupture. CONCLUSION: The incidence of patellar tendon rupture in the US military population is substantially higher than has been reported in the civilian population. Among military personnel, men, Black servicemembers, and those aged 35 to 44 years were at highest risk for patellar tendon rupture. Three-quarters of patients were able to return to full activity without limitations. The rerupture rate was low and unaffected by fixation method.

Internal tibial torsion is related to syndesmosis injury in a large osteological collection.

BACKGROUND: The long-term consequences of tibial torsion remain unclear. This study evaluated whether syndesmotic injuries are associated with tibial torsion. METHODS: A collection of over 3000 cadaveric skeletons was screened for irregular bony prominence along the lateral distal tibia, consistent with previous syndesmosis injury. Tibial torsion was measured and compared to 1034 control cadaveric tibiae. RESULTS: Mean torsion of 236 specimens with syndesmotic injury was 6.2±8.9 degrees, while that of control specimens was 7.9±8.8 degrees (P = 0.008). Multiple regression analysis showed a non-statistically significant trend toward internal torsion and syndesmotic injury (standardized beta=-0.051, P=0.059). Syndesmosis injury was present in 48/200 specimens (24.0%) with internal torsion and 31/199 specimens (15.6%) with external torsion (P=0.035). CONCLUSION: This association between internal tibial torsion and syndesmotic injury suggests that internal tibial torsion might not be an entirely benign condition and merits further study.

Type-V Median Nerve Entrapment in a Pediatric Medial Condyle Fracture: A Case Report.

CASE: A 30-month-old boy with a displaced medial condyle fracture and no history of an elbow dislocation was found to have an entrapped median nerve. CONCLUSION: Entrapment of the median nerve is a potential consequence of a displaced medial condyle fracture, even when there are no neurologic deficits on presentation. This provides additional support for open reduction of these fractures rather than percutaneous treatment or nonoperative management. Prompt identification and extraction of an interposed ulnar or median nerve is imperative to prevent the catastrophic consequences of an upper-extremity nerve palsy in children, as well as to optimize fracture-healing and elbow growth and development.