Effect of malpositioned anterior cruciate ligament replacement on knee joint structures: a biomechanical model.

Any sort of malpositioning of anterior cruciate ligament (ACL) replacement leads to an overload of single fibers of the ACL replacement. As long as this does not result in a tear of these fibers so that isometry of the ACL replacement is restored, the abnormal forces acting in and on the ACL replacement are transmitted from the ACL replacement to the remainder of the knee joint structures. We assumed that the posterior cruciate ligament (PCL) is notably affected. The present biomechanical model illustrates the relevant force vectors and reveals the extent of the effect of malpositioned ACL replacement on knee joint structures, particularly the PCL. Further investigations are needed to find out if the presumably occurring overload of a malpositioned ACL replacement can be calculated from its position on an individual basis. This may help deduce recommendations for ACL replacement procedures in the future.

Arthroscopic fixation of posterior cruciate ligament avulsion fractures: a new minimally invasive technique.

We present a new all-inside technique for the reduction and fixation of posterior cruciate ligament avulsion fractures. Two suture discs and a mersilene band are used to continuously exert even pressure on the avulsion fragment, thereby maintaining reduction during healing. The risk of a loss of reduction and further fragmentation is minimized.

Orthotic management of Charcot feet after external fixation surgery.

The authors use a total contact cast (TCC), Charcot restraint orthotic walker (CROW), or prefabricated diabetic walker (DW) for the treatment of neuroarthropathy, depending on the medical, social, and economic circumstances. There is not one single orthosis for the treatment of Charcot feet, but there are several models with advantages and disadvantages the physician should be aware of. In a retrospective study of 200 Charcot feet, the ankle foot orthosis (AFO) built in the authors' workshop turned out to be an efficient and comfortable appliance for orthotic treatment after reconstructive surgery. They prefer this type of orthosis because of its versatility and its safe application in a compliant patient.

The effects of combined gentamicin-hydroxyapatite coating for cementless joint prostheses on the reduction of infection rates in a rabbit infection prophylaxis model.

Infections remain a critical issue in total joint arthroplasty. Addition of antibiotics to bone cement was shown to significantly improve antimicrobial prophylaxis in cemented joint arthroplasty. In cementless joint arthroplasty a comparable prophylaxis by local antibiotics has not been possible yet. The aim of the current study was to investigate the antimicrobial effect of two different gentamicin-hydroxyapatite (HA) coatings for cementless prostheses in a rabbit infection model. Staphylococcus aureus with a dose of 10(7) CFUs was inoculated into the intramedullary canal of the tibia of 30 rabbits followed by the implantation of standard steel HA K-wires (n=10), steel K-wires coated with a gentamicin-HA combination (n=10), and steel K-wires coated with a gentamicin-RGD-HA combination (n=10), respectively. The animals were sacrificed after 28 days and clinical, histological and microbiological assessment on the bone and on the removed K-wire itself by agar plating and DNA-pulsed field gel electrophoresis were carried out to detect infection. There was a statistically significant reduction of infection rates by both gentamicin-coating types (0 infections in both groups) compared to standard HA coating (7 infections in 8 animals; 2 animals were lost due to acute diarrhea) (p<0.001). An excellent correlation between agar plating testing results of the K-wires and of the bone samples was found. Detailed histology showed cortical lysis, abscess and sequester formation in the infected animals. Both gentamicin-coating types showed significant improvement of infection prophylaxis compared to standard HA coating and, therefore, this coating technology could help to improve infection prophylaxis in cementless total joint arthroplasty. In further studies biocompatibility of the coatings has to be assessed.

Radiology-pathology conference: osteosarcoma in a cartilaginous exostosis of the femur.

Osteochondromas are common lesions in the metaphyseal segments of the long bones and are known to be able to degenerate into chondrosarcoma. We present the case of a 20-year-old patient with an osteosarcoma at the base of a cartilaginous exostosis and discuss the causal relationship between the two lesions on the basis of the radiologic and pathologic findings.