ABSTRACT: BACKGROUND: Heterotopic ossification (HO) occurs most commonly after trauma and surgery about the hip and may compromise subsequent function. Currently available animal models describing the cellular progression of HO are based on exogenous osteogenic induction agents and may not reflect the processes following trauma. QUESTIONS/PURPOSES: We therefore sought to characterize the histologic progression of heterotopic bone formation in an animal model that recapitulates the human condition without the addition of exogenous osteogenic material. METHODS: We used a rabbit model that included intramedullary instrumentation of the upper femur and ischemic crush injury of the gluteal muscle. Bilateral surgical induction procedures were performed on 30 animals with the intention of inciting the process of HO; no supplemental osteogenic stimulants were used. Three animals were sacrificed at each of 10 predetermined times between 1 day and 26 weeks postoperatively and the progression of tissue maturation was graded histologically using a five-item scale. RESULTS: Heterotopic bone reliably formed de novo and consistently followed a pathway of endochondral ossification. Chondroid elements were found in juxtaposition with immature woven bone in all sections that contained mature osseous elements. CONCLUSIONS: These results establish that HO occurs in an animal model mimicking the human condition following surgical trauma about the hip; it is predictable in its histologic progression and follows a pathway of endochondral bone formation. CLINICAL RELEVANCE: By showing a consistent pathway of endochondral ossification leading to ectopic bone formation, this study provides a basis for understanding the mechanisms by which HO might be mitigated by interventions.
Clinical Orthopaedics and Related Research 01/2013; · 2.53 Impact Factor
ABSTRACT: Postoperative spine infections cause considerable morbidity. Patients are subjected to long-term antibiotic regimens and may require further surgery. Delivery of electric current through instrumentation can detach biofilm, allowing better antibiotic penetration and assisting in eradicating infection. QUESTION/PURPOSES: We asked (1) whether capacitive coupling treatment in combination with a single dose of antibiotics would reduce infection rates when compared with antibiotics alone in a rabbit spine infection model, (2) whether it would decrease the overall bacterial burden, and (3) whether there was a time-dependent response based on days treated with capacitive coupling.
Thirty rabbits were subjected to a well-established spine infection model with a single dose of intravenously administered systemic ceftriaxone (20 mg/kg of body weight) prophylaxis. Two noncontiguous rods were implanted inside dead space defects at L3 and L6 challenged with 10(6) colony-forming units of Staphylococcus aureus. Rabbits were randomly treated with a capacitive coupling or control device. Instrumentation and soft tissue bacterial growth were assessed after 7 days.
Sites treated with capacitive coupling showed a decrease in the incidence of positive culture: 36% versus 81% in the control group. We observed no difference in the soft tissue's infectious burden. Overall bacterial load was not decreased with capacitive coupling.
Capacitive coupling in conjunction with antibiotics reduced the instrumentation-related infection rate compared with antibiotics alone.
Capacitive coupling noninvasively delivers an alternating current that may detach biofilm from instrumentation. Treatment of infection may be successful without removal of instrumentation, allowing for improved stability and overall decreased morbidity.
Clinical Orthopaedics and Related Research 01/2012; 470(6):1646-51. · 2.53 Impact Factor
ABSTRACT: To create an animal survival model for heterotopic ossification (HO) in the residual limb of the rat after extremity blast amputation. The hypothesis was that extremity blast amputation spontaneously stimulates development of HO in the residual limb.
Twelve Sprague-Dawley rats underwent localized exposure to a controlled, high-energy blast. Seven rats were designated for hind limb amputation and five for forelimb amputation. Our protocol produced extremity amputation through detonation of an explosive while protecting the animal proximal to the specified amputation level. Immediately after injury, the rat underwent wound management and primary surgical closure. Radiographs of the amputated limbs were obtained every 2 weeks. Heterotopic bone was radiographically classified as periosteal growth (Type A) or noncontiguous growth (Type B). A kappa statistic was calculated for interobserver strength of agreement on the presence of HO. Fisher exact test was conducted to assess the significance of the difference in hind limb and forelimb HO rates.
Nine of 12 animals survived the procedure. The three nonsurvivors were all hind limb amputees, and each died of various related causes. All four surviving hind limb amputees exhibited Type A HO, and three of four also exhibited Type B HO within the injured stump. One of five forelimb amputees exhibited Types A and B HO.
We have developed a reproducible model for HO in the residual limbs of blast-amputated rats without addition of exogenous osteogenic stimulus. Hind limb amputation demonstrated a predilection for HO formation in comparison with forelimb amputation (P < 0.05).
Journal of orthopaedic trauma 08/2011; 25(8):506-10. · 1.78 Impact Factor