Current Animal Models of Postoperative Spine Infection and Potential Future Advances.

Implant related infection following spine surgery is a devastating complication for patients and can potentially lead to significant neurological compromise, disability, morbidity, and even mortality. This paper provides an overview of the existing animal models of postoperative spine infection and highlights the strengths and weaknesses of each model. In addition, there is discussion regarding potential modifications to these animal models to better evaluate preventative and treatment strategies for this challenging complication. Current models are effective in simulating surgical procedures but fail to evaluate infection longitudinally using multiple techniques. Potential future modifications to these models include using advanced imaging technologies to evaluate infection, use of bioluminescent bacterial species, and testing of novel treatment strategies against multiple bacterial strains. There is potential to establish a postoperative spine infection model using smaller animals, such as mice, as these would be a more cost-effective screening tool for potential therapeutic interventions.

Operant serial feature-positive conditional discrimination with composite features and different topography responses.

In a serial feature-positive conditional discrimination procedure the properties of a target stimulus A are defined by the presence or not of a feature stimulus X preceding it. In the present experiment, composite features preceded targets associated with two different topography operant responses (right and left bar pressing); matching and non-matching-to-sample arrangements were also used. Five water-deprived Wistar rats were trained in 6 different trials: X-R-->Ar and X-L-->Al, in which X and A were same modality visual stimuli and the reinforcement was contingent to pressing either the right (r) or left (l) bar that had the light on during the feature (matching-to-sample); Y-R-->Bl and Y-L-->Br, in which Y and B were same modality auditory stimuli and the reinforcement was contingent to pressing the bar that had the light off during the feature (non-matching-to-sample); A- and B- alone. After 100 training sessions, the animals were submitted to transfer tests with the targets used plus a new one (auditory click). Average percentages of stimuli with a response were measured. Acquisition occurred completely only for Y-L-->Br+; however, complex associations were established along training. Transfer was not complete during the tests since concurrent effects of extinction and response generalization also occurred. Results suggest the use of both simple conditioning and configurational strategies, favoring the most recent theories of conditional discrimination learning. The implications of the use of complex arrangements for discussing these theories are considered.

Operant serial feature-positive conditional discrimination with composite features and different topography responses

In a serial feature-positive conditional discrimination procedure the properties of a target stimulus A are defined by the presence or not of a feature stimulus X preceding it. In the present experiment, composite features preceded targets associated with two different topography operant responses (right and left bar pressing); matching and non-matching-to-sample arrangements were also used. Five water-deprived Wistar rats were trained in 6 different trials: X-R arrow right Ar and X-L arrow right Al, in which X and A were same modality visual stimuli and the reinforcement was contingent to pressing either the right (r) or left (l) bar that had the light on during the feature (matching-to-sample); Y-R arrow right Bl and Y-L arrow right Br, in which Y and B were same modality auditory stimuli and the reinforcement was contingent to pressing the bar that had the light off during the feature (non-matching-to-sample); A- and B- alone. After 100 training sessions, the animals were submitted to transfer tests with the targets used plus a new one (auditory click). Average percentages of stimuli with a response were measured. Acquisition occurred completely only for Y-L arrow right Br+; however, complex associations were established along training. Transfer was not complete during the tests since concurrent effects of extinction and response generalization also occurred. Results suggest the use of both simple conditioning and configurational strategies, favoring the most recent theories of conditional discrimination learning. The implications of the use of complex arrangements for discussing these theories are considered.

Accessory soleus muscle as a cause of resistance to correction in congenital club foot: a case report.

A 14-month-old female with bilateral clubfeet was initially treated by serial casting and percutaneous tenotomy of the Achilles tendon, bilaterally. Both clubfeet subsequently underwent surgical treatment with a posteromedial release through a Cincinnati incision. At surgery on one clubfoot, an accessory Soleus muscle was found anterior to the Achilles tendon with a distinct insertion on the upper surface of calcaneus, anterior and medial to the insertion of Achilles tendon. This accessory Soleus muscle may have been the cause of resistance to correction in this congenital clubfoot.

Symptomatic osteonecrosis of the hip after orthotopic liver transplantation.

Patients who require long-term steroid use for immunosuppression after organ transplantation are at risk for the development of osteonecrosis. The purpose of this study was to determine the prevalence of symptomatic osteonecrosis of the hip in patients who were managed with corticosteroids for immunosuppression after orthotopic liver transplantation. We reviewed the relationship of the administration and dosage of steroids in 203 patients who underwent orthotopic liver transplantation. Overall, 29 of the 203 patients (14%) complained of hip pain, but only 3 patients (2%) developed symptomatic osteonecrosis of the hip. The osteonecrosis was diagnosed an average of 31 months after transplantation (range, 26-38 months). There was no association noted between steroid dose and the development of osteonecrosis. Routine screening for osteonecrosis of asymptomatic liver transplant patients is not necessary.

Lacerations and ruptures of the flexor or extensor hallucis longus tendons.

Lacerations and ruptures of the flexor hallucis longus or extensor hallucis longus tendon are frequently managed with operative repair. Tendon injuries of the hallux are not all alike; careful consideration should be given to the mechanism and site of injury, the timing of presentation, and the presence of other injuries. Not all tendon injuries of the hallux require repair. The effectiveness of a repair will depend on the goals of surgery, which may include pain relief, active joint motion, or correction of deformity. When goals are clearly defined, a satisfactory result can be expected in most patients.

Gene therapy for osteoinduction.

One application of gene therapy that holds great promise is the stimulation of bone formation. Gene therapy offers several potential advantages over other methods of osteoinduction and current research suggests that it may be a feasible treatment option for the orthopedic surgeon in the near future. This article reviews the basic concepts and strategies of gene therapy and evaluates the current research using gene therapy to induce bone formation and enhance healing.