Radiographic and histologic effects of bone morphogenetic protein-2/hydroxyapatite within bioabsorbable magnesium screws in a rabbit model.

BACKGROUND: Hydrogen gas formed by magnesium (Mg) screw corrosion can accumulate around the implant and create bone cysts, long-term osteolysis lesions, and bone healing delay. Thus, several authors currently do not recommend Mg implants for clinical use. In contrast, bone morphogenetic proteins (BMP)-2 have a very strong osteoinductive activity. The purpose of this study was to evaluate the effect of rhBMP-2/hydroxyapatite (HA) inside specially designed Mg cannulated screws in a rabbit femur model for hydrogen gas formation avoidance. METHODS: Fifteen rabbits underwent randomly different cannulated Mg screw implantation in both distal femora; 30 femora were divided into three groups depending on the materials fill in the cannulated Mg screw: control group (Mg screw with no treatment), HA group (Mg screw with HA), and BMP-2/HA group (Mg screw with a composite BMP-2/HA). Plain radiography, micro-CT, and histological analysis were accomplished, and the ability to release BMP-2 of the screws was evaluated by immersion of both the screw with no treatment and screw with a composite BMP-2/HA into the SBF for up to 7 days. RESULTS: X-ray assessment found the gas shadow around the implant was slightly smaller in the BMP-2/HA group than the HA and control groups at 8 weeks. Micro-CT analysis demonstrated statistically significant higher new bone formation in the BMP-2/HA group than the other groups, respectively, which also correlated with a decreased gas volume. Histological analysis showed higher osteointegration between implants and host femurs in the BMP-2/HA group than the HA and control groups at 12 weeks. CONCLUSIONS: This study indicates that the combination of BMP-2/HA within Mg screws enhances new bone formation and therefore has the potential to decrease the complications of hydrogen gas formation around these implants.

Orthopedic Trauma: Extremity Fractures.

Fractures continue to account for a large proportion of combat-related injuries. The basic tenets of irrigation, debridement, soft tissue care, and vigilant monitoring/fasciotomy for acute compartment syndrome persist. Closed management of fractures with splinting or casting is acceptable. If time and facility allow, external fixation of fractures offer many advantages over closed treatment but require knowledge, experience and skill in the safe placement of pins. The care of host nationals presents unique challenges and deployed surgeons must be flexible and resourceful in these situations.

Gas formation and biological effects of biodegradable magnesium in a preclinical and clinical observation.

Magnesium alloys are biodegradable metals receiving increasing attention, but the clinical applications of these materials are delayed by concerns over the rapid corrosion rate and gas formation. Unlike corrosion, which weakens mechanical properties, the gas formation issue has received little attention. Therefore, we evaluated the gas formation and biological effects for Mg implants through preclinical (immersed in Earle's balanced salt solution and in vivo) and clinical studies. The immersion test examined the gas volume and composition. The in vivo study also examined gas volume and histological analysis. The clinical study examined the gas volume and safety after Mg screw metatarsal fixation. Gas was mainly composed of H2, CO and CO2. Maximum volumes of gas formed after 5 days for in vivo and 7 days in clinical study. Within the clinical examination, two superficial wound complications healed with local wound care. Osteolytic lesions in the surrounding metaphysis of the Mg screw insertion developed in all cases and union occurred at 3 months. Mg implants released gas with variable volumes and composition (H2, CO, and CO2), with no long-term toxic effects on the surrounding tissue. The implants enabled bone healing, although complications of wound breakdown and osteolytic lesions developed.

Operative and nonoperative treatment approaches for lumbar degenerative disc disease have similar long-term clinical outcomes among patients with positive discography.

OBJECTIVE: It remains unclear whether fusion for lumbar degenerative disc disease with positive discography produces better outcomes compared with nonoperative treatment. The aim of this study was to compare outcomes of patients with discography-concordant lumbar degenerative disc disease electing for fusion versus nonoperative treatment. METHODS: We retrospectively reviewed consecutive patients with back pain and concordant lumbar discogram who were offered fusion. Follow-up questionnaires included pain score, Oswestry disability index, short form-12, and satisfaction scale. Patients were stratified based on whether they elected for fusion or nonoperative treatment. RESULTS: Overall follow-up was 48% (96/200). Patients lacking follow-up were slightly older (P = 0.021) and less likely to be smokers (P = 0.013). Between patients with and without follow-up, there were no significant differences in pain score at initial visit, body mass index, or gender (P ≥ 0.40). The 96 patients for whom follow-up was obtained included 53 in the operative and 43 in the nonoperative groups. At baseline, there were no significant differences between these groups based on age, pain score, body mass index, smoking, or gender (P ≥ 0.25). Mean follow-up was 63 months for operative and 58 months for nonoperative patients (P = 0.20). The mean pain score at last follow-up improved significantly for operative and nonoperative patients (P < 0.001). At follow-up, operative and nonoperative groups did not differ significantly with regard to pain scores, Oswestry disability index, short form-12, or satisfaction scale. CONCLUSIONS: Comparison of long-term outcomes for patients with back pain and concordant discography did not demonstrate a significant difference in outcome measures of pain, health status, satisfaction, or disability based on whether the patient elected for fusion or nonoperative treatment.

Biomechanics of subdural hemorrhage in American football: review of the literature in response to rise in incidence.

The number of catastrophic head injuries recorded during the 2011 football season was the highest since data collection began in 1984--the vast majority of these cases were secondary to subdural hemorrhage (SDH). The incidence of catastrophic head injury continues to rise: the average yearly incidence from 2008 to 2012 was 238% that of the average yearly incidence from 1998 to 2002. Greater than 95% of the football players who suffered catastrophic head injury during this period were age 18 or younger. Currently, the helmet industry utilizes a standard based on data obtained at Wayne State University approximately 50 years ago that seeks to limit severity index--a surrogate marker of translational acceleration. In this manuscript, we utilize a focused review of the literature to better characterize the biomechanical factors associated with SDH following collisions in American football and discuss these data in the context of current helmet standard. Review of the literature indicates the rotational acceleration (RA) threshold above which the risk of SDH becomes appreciable is approximately 5,000 rad/s(2). This value is not infrequently surmounted in typical high school football games. In contrast, translational accelerations (TAs) experienced during even elite-level impacts in football are not of sufficient magnitude to result in SDH. This information raises important questions about the current helmet standard--in which the sole objective is limitation of TA. Further studies will be necessary to better define whether helmet constructs and quality assurance standards designed to limit RA will also help to decrease the risk of catastrophic head injury in American football.