Impact of Biomechanical Forces on Antibiotics Release Kinetics from Hydroxyapatite Coated Surgical Fixation Pins

This work investigates the impact of biomechanical wear and abrasion on the antibiotic release profiles of hydroxyapatite (HA) coated fixation pins during their insertion into synthetic bone. Stainless steel fixation pins are coated with crystalline TiO2 by cathodic arc evaporation forming the bioactive layer for biomimetic deposition of Tobramycin containing HA. Tobramycin is either introduced by co-precipitation during HA formation or by adsorption-loading after HA deposition. The samples containing antibiotics are inserted into bone mimicking polyethylene foam after which the drug release is monitored using high performance liquid chromatography. This analysis shows that HA coating wear and delamination significantly decrease the amount of drug released during initial burst, but only marginally influence the sustained release period. Spalled coating fragments are found to remain within the synthetic bone material structure. The presence of HA within this structure supports the assumption that the local release of Tobramycin is not only expected to eliminate bacteria growth directly at the pin interface but as well at some distance from the implant. Furthermore, no negative effect of gamma sterilization could be observed on the drug release profile. Overall, the observed results demonstrate the feasibility of a multifunctional implant coating that is simultaneously able to locally deliver clinically relevant doses of antibiotics and an HA coating capable of promoting osteoconduction. This is a potentially promising step toward orthopaedic devices that combine good fixation with the ability to treat and prevent post-surgical infections.

Clinical significance of Baumann's angle in the percutaneous pinning fixation for supracondylar fractures of the humerus in children

To evaluate the clinical significance of Baumann’s angle in the closed reduction and percutaneous pinning fixation for supracondylar fractures of the humerus in children.Methods There were 97 children (male 59,female 38,mean age of 6.8 years) with displaced supracondylar fracrtures of the humerus were treated in this hospital.Under fluoroscopy guidance,three-dimensional displacement of fractures was corrected by closed reduction.The percutaneous Kirschner wire pinning was applied only if the radiographs demonstrated that Baumann’s angle was less than 4 degree compared to that on the normal side.All of them were followed up for 34.5 months (range,12 to 48 months).Results There was one case with ulnar nerve palsy associated with the pinning.There were no Volkmann’s contracture in this group.X-ray examinations revealed an average 73.7 degrees of Baumann angle on the injured and 72.8 on uninjured side.An average 7.6 degrees of the carrying angle on the injured and 9.7 on uninjured side were also demonstrated by radiography.Five patients developed slight cubitus varus deformity.The result according to Flynn criteria were excellent in 85 patients (87.6%),good in 12 patients (12.4%).Conclusion The satisfactory results can be gained in children with displaced supracondylar fractures of the humerus by restoration of the normal Baumann angle and percutaneous pinning fixation.18 refs,2 figs.

Percutaneous fixation of neonatal humeral physeal fracture: A case report and review of the literature

BACKGROUND Neonatal distal humeral physeal fractures are rare and difficult to diagnose.Thus,missed diagnoses and delayed healing are possible.Few studies have reported surgical treatment,because a callus may develop at the fracture site 5 d after the fracture,resulting in difficult reduction,and reduction of the limb may cause further physeal injury.Other surgical challenges include the provision of adequate anesthesia and complexity of the operation.However,without appropriate reduction and fixation,a varus elbow deformity may develop.Manual reduction and percutaneous pin fixation are ideal treatment options.CASE SUMMARY A 4-day-old neonate with left elbow pain accompanied by limited movement for 4 d was admitted,and diagnosed with delayed physeal fracture of the distal humerus based on physical examination,ultrasonography,and magnetic resonance imaging.The patient was treated by manual reduction combined with percutaneous pin fixation under arthrography.Postoperatively,the reduction was successful.The upper limbs could have been lifted and the fingers could have been moved freely on the second day after the operation.CONCLUSION The techniques of manual reduction and percutaneous pin fixation,to treat neonatal distal humeral physeal fractures,are safe and reliable.