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Purpose: Osseointegration (OI) is the direct attachment of an external prosthesis to the skeleton. These implants are well-suited for patients with combat-related amputations, especially those who do not tolerate conventional socket prostheses. However, transdermal implants are at risk for complications, particularly infection. The Transhumeral Amputee Osseointegration Study (TAOS) is an ongoing clinical trial sanctioned by Food and Drug Administration (FDA) to study the safety of the Osseointegrated Prostheses for the Rehabilitation of Amputees (OPRA) implant in transhumeral amputees. The purpose of this preliminary report is to (1) evaluate the frequency and severity of surgical, medical, and mechanical complications, and (2) evaluate the changes in functional ability and pain. Method: Under an FDA Early Feasibility Study, we performed 2-stage OI surgery using the OPRA Implant. Included patients were transhumeral amputees between 22 and 65 years old who could not tolerate or had poor function with conventional socket prosthetics. Contraindications include concurrent diseases that interfere with wound healing, such as peripheral vascular disease or diabetes. Stage-1 consists of implanting a titanium fixture into the medullary canal and bone graft augmentation of the distal bone. Patients also underwent concurrent targeted muscle reinnervation (TMR) during the Stage-1 surgery. Following a three-month interval, the distal soft tissue is fashioned into a thin cutaneous flap and a transdermal abutment is attached to the underlying fixture during Stage-2 surgery. We collected pre-operative shoulder range of motion, applicable Patient Reported Outcomes Measurement Systems (PROMIS) modules, and other outcome measures at 3, 6, 12, and 24 months after Stage-2. Results: Six patients with transhumeral amputations have completed graduated load-bearing rehabilitation, and have increased their prosthetic wear time by an average of 72% from baseline. The 12-month post Stage-2 PROMIS Pain Interference and Pain Behavior scores averaged 45.2 and 48.9 points respectively. All patients showed improvement in these modules. Twelve-month post Stage-2 PROMIS Upper Extremity (UE) scores averaged 34.8, which was a 1.6-point improvement from preoperative scores. There were no surgical, medical, or mechanical complications, and fixtures remain intact radiographically without evidence of loosening, stress shielding, or infection.Conclusion: The OPRA system shows promising early results for combat-related transhumeral amputations. Improvements in PROMIS pain scores demonstrate that pain is less of a hindrance on life following OI. Improvements in PROMIS functional scores may indicate that patients achieve more independence with OI compared to conventional prostheses. We also observed a low rate of early complications. These results should be taken with caution as transdermal implants remain in their early stages and warrant further study.

246 Background: Development of prostate cancer (PCa) metastasis, while uncommonly observed in US men, typically occurs to bone and ultimately leads to disease-specific death. The goal of this study was to estimate OS in a racially diverse cohort of military health care beneficiaries diagnosed with metastatic PCa to bone, to enhance understanding of factors such as patient race and receipt of palliative treatment, that potentially affect OS in advanced PCa patients. Methods: A retrospective cohort study was conducted, examining men consented to participate in the CPDR multi-center national database who underwent biopsy for suspicion of prostate cancer between 1989-2017 and subsequently diagnosed with bone metastasis, confirmed by bone scan, bone biopsy and/or MRI. Multivariable Cox proportional hazards (PH) analysis was used to model OS as a function of race and palliative treatment, controlling for clinical covariates. Hazard ratios (HR) and 95% Confidence intervals (CI) are reported. Results: Among 17,356 patients diagnosed with prostate cancer (PCa) between 1989 and 2017, 869 (5.0%) developed bone metastasis. Median patient age was 67 years; median follow-up time following diagnosis with bone metastasis was 2.4 years. Over one-fifth of patients (22.5%) self-reported as African American. Only 11.5% of all patients with metastasis received palliative treatment (radiation (RT) only, RT+ hormone therapy (HT), RT+HT, or RT+HT+chemotherapy). While race did not predict OS, receipt of palliative treatment was strongly predictive of better OS (p

This article was updated on July 22, 2015, because the name of one of the authors, Victor W. Wong, was listed incorrectly. The name, which previously read “Victor C. Wong,” on pages 1101 and 1108, now reads “Victor W. Wong.” An erratum has been published: J Bone Joint Surg Am. 2015 Sep 2;97(17):e59. ➤ Heterotopic ossification occurs most commonly after joint arthroplasty, spinal cord injury, traumatic brain injury, blast trauma, elbow and acetabular fractures, and thermal injury. ➤ The conversion of progenitor cells to osteogenic precursor cells as a result of cell-mediated interactions with the local tissue environment is affected by oxygen tension, pH, availability of micronutrients, and mechanical stimuli, and leads to heterotopic ossification. ➤ Radiation and certain nonsteroidal anti-inflammatory medications are important methods of prophylaxis against heterotopic ossification. ➤ Well-planned surgical excision can improve patient outcomes regardless of the joint involved or the initial cause of injury. ➤ Future therapeutic strategies are focused on targeted inhibition of local factors and signaling pathways that catalyze ectopic bone formation.

BACKGROUND Heterotopic ossification most commonly occurs after burn injury, joint arthroplasty, and trauma. Male gender has been identified as a risk factor for the development of heterotopic ossification. It remains unclear why adult male patients are more predisposed to this pathologic condition than adult female patients. In this study, the authors use their validated tenotomy/burn model to explore differences in heterotopic ossification between male and female mice. METHODS The authors used their Achilles tenotomy and burn model to evaluate the osteogenic potential of mesenchymal stem cells of male and female injured and noninjured mice. Groups consisted of injured male (n = 3), injured female (n = 3), noninjured male (n = 3), and noninjured female (n = 3) mice. The osteogenic potential of cells harvested from each group was assessed through RNA and protein levels and quantified using micro-computed tomographic scan. Histomorphometry was used to verify micro-computed tomographic findings, and immunohistochemistry was used to assess osteogenic signaling at the site of heterotopic ossification. RESULTS Mesenchymal stem cells of male mice demonstrated greater osteogenic gene and protein expression than those of female mice (p < 0.05). Male mice in the burn group formed 35 percent more bone than female mice in the burn group. This bone formation correlated with increased pSmad and insulin-like growth factor 1 signaling at the heterotopic ossification site in male mice. CONCLUSIONS The authors demonstrate that male mice form quantitatively more bone compared with female mice using their burn/tenotomy model. These findings can be explained at least in part by differences in bone morphogenetic protein and insulin-like growth factor 1 signaling.