Heterotopic ossification (HO) refers to ectopic bone formation, typically in residual limbs following trauma and injury. A review of injuries from Operation Iraqi Freedom (OIF) and Operation Enduring Freedom (OEF) indicated that approximately 70% of war wounds involved the musculoskeletal system, largely in part from the use of improvised explosive devices (IED) and rocket-propelled grenades (RPG). HO is reported to occur in approximately 63%–65% of wounded warriors from OIF and OEF. Symptomatic HO may delay rehabilitation regimens since it often requires modifications to prosthetic limb componentry and socket size. There is limited evidence indicating a mechanism for preventing HO. This may be due to inadequate models, which do not produce HO bone structure that is morphologically similar to HO samples obtained from wounded warfighters injured in theatre. We hypothesized that using a high-power blast of air (shockwave) and simulated battlefield trauma (i.e. bone damage, tourniquet, bacteria, negative pressure wound therapy) in a large animal model, HO would form and have similar morphology to ectopic bone observed in clinical samples. Initial radiographic and micro-computed tomography (CT) data demonstrated ectopic bone growth in sheep 24 weeks post-procedure. Advanced histological and backscatter electron (BSE) analyses showed that 5 out of 8 (63%) sheep produced HO with similar morphology to clinical samples. We conclude that not all ectopic bone observed by radiograph or micro-CT in animal models is HO. Advanced histological and BSE analyses may improve confirmation of HO presence and morphology, which we demonstrated can be produced in a large animal model.

Journal of Medical Internet Research - International Scientific Journal for Medical Research, Information and Communication on the Internet #Preprint #PeerReviewMe: Warning: This is a unreviewed preprint. Readers are warned that the document has not been peer-reviewed by expert/patient reviewers or an academic editor, may contain misleading claims, and is likely to undergo changes before final publication, if accepted, or may have been rejected/withdrawn. Readers with interest and expertise are encouraged to sign up as peer-reviewer, if the paper is within an open peer-review period. Please cite this preprint only for review purposes or for grant applications and CVs (if you are the author). Background: Heterotopic ossification (HO) is a significant complication for wounded warriors with traumatic limb loss. Although this pathologic condition negatively impacts the general population, ectopic bone has been observed with higher frequency for those injured in theatre. Several factors including a traumatic blast, bioburden, tourniquet and wound vacuum usage, and/or bone fractures/fragments have been associated with the increased HO formation for service members. The first step in assessing the effect of these factors on HO formation in a large animal model was to establish a repeatable and reproducible high pressure air system that could simulate a battlefield-relevant blast Objective: N/A Methods: The repeatability and reproducibility of a high-power air delivery system was determined by collecting force data across a spectrum of PSI settings. In addition, the ability of the higher power air delivery system to affect host tissue, displace metal particulate and disperse bone chips was assessed in cadaveric sheep limbs. Results: Data demonstrated that the air delivery setup could generate battlefield-relevant blast forces. Dispersion data likewise indicated that the delivery system would have the ability to cause host tissue trauma and effectively disperse metal particulate and/or host bone chips in local musculature. Conclusions: Taken together, data showed that a high pressure air impact device will have the ability to function as a simulated battlefield blast scenario and allow factors including blast trauma to translate toward a large animal model. Clinical Trial: N/A

Case: We present a case report documenting the retrieval and histological analysis of a porous tantalum (P-Ta) total ankle replacement (TAR) from a 50-year-old woman after a below-knee transtibial amputation. This rare opportunity to examine an intact TAR may help to better understand the implant-bone relationship because it would be in situ. Conclusion: In this case study, we demonstrate bone ingrowth to the first layer of the P-Ta and organized trabecular orientation, suggesting that equal bone load was achieved on the base and the rails in both components using a transfibular surgical approach.

During articular fracture reconstruction, orthopedic surgeons are frequently faced with the dilemma of retaining small articular fragments versus discarding these fragments. The purpose of this study was to compare post-traumatic osteoarthritis (PTOA) development between tibial plafond fractures and plafond fractures with a missing articular fragment (MF) in a porcine model. High-energy tibial plafond fractures in skeletally mature Yucatan mini pigs (n ​= ​12) were created. During surgery, a 3 ​× ​3 mm section of the articular surface was removed in six animals (MF group). Ankle synovial fluid was analyzed for IL-1β, IL-1Ra, IL-6, IL-8, and IL-10 concentrations obtained at initial surgery and 12 weeks post-surgery. Plafond and talus sections were evaluated for subchondral bone porosity and stained with Sanderson's Rapid Bone Stain and blindly evaluated to determine the Osteoarthritis Research Society International (OARSI) grade and vascular invasion. Fractured ankles had greater concentrations of IL-1β, IL-1Ra, IL-6, IL-8, and IL-10 compared to control ankles. There was no difference in cytokine concentrations between fractured and fractured ​+ ​MF ankles. Fractured ankles had significantly greater bone porosity, vascular invasion, and OARSI grade as compared to the control group. In comparing tibial plafonds, the MF group had significantly more bone porosity, more vascular invasion, and a higher average OARSI grade than the anatomically reconstructed group. In comparing the talus, the MF group had higher average OARSI grade and similar bone porosity. Articular fractures with a MF had worse PTOA development as measured by bone porosity, vascular invasion, and OARSI grade than the anatomically reconstructed fractures.