[Mega-prostheses in revision knee arthroplasty]. / Megaprothesen in der Knierevision.

BACKGROUND: Due to a predicted increase in primary total knee arthroplasty (TKA), revision TKA will gain importance over the following years. Because the average age of patients receiving a TKA is decreasing the possible need for multiple revisions might increase as well. Despite efforts to minimize bone and soft tissue damage, the resulting bone and soft-tissue loss increases with each revision and will make the use of megaprostheses indispensable in the future. COMPLICATIONS: The implantation of a mega-prosthesis must be carefully considered and planned, since mega-prostheses in particular are associated with an increased risk of infection and loosening. Mechanical complications, patient-specific problems and periprosthetic infections can be either the cause for or the result of revision surgery of a mega-prosthesis. In the case of a complication, only a salvage procedure, namely an arthrodesis, amputation or-if necessary-the installation of a permanent fistula is commonly recommended.

Extensor hallucis longus-transfer for tibialis anterior tendon rupture repair.

OBJECTIVE: Restore the function of the tibialis anterior muscle, which is responsible for dorsiflexion and inversion of the foot. INDICATIONS: Spontaneous or traumatic rupture of the tibialis anterior tendon. CONTRAINDICATIONS: Patients with multimorbidity or lack of functional demands. SURGICAL TECHNIQUE: Direct repair of the tibialis anterior tendon with fiber-wire suture and augmentation with extensor hallucis longus tendon, potentially in combination with reinsertion of the tibialis anterior tendon in the medial cuneiform. POSTOPERATIVE MANAGEMENT: Six weeks of non-weight-bearing: 3 weeks of cast immobilization with ankle in 10° dorsiflexion, followed by 3 weeks of splint immobilization and passive mobilization. Then stepwise increase in weight-bearing over a period of 2-3 weeks. RESULTS: In 8 patients postoperative results with a mean follow-up of 13.5 months were available. One patient showed a rerupture of the augmented tendon. The mean American Orthopaedic Foot and Ankle Society (AOFAS) hindfoot score was 81.0 (range 67-88). The median ankle dorsiflexion muscle strength was 67% (range 29.3-85.5%) compared to the nonoperated leg. All patients, except the one that experienced rerupture, were very satisfied or satisfied with the result.

A checklist for streamlining organ donation after cardiac death.

There is currently a shortage of organ donors to meet the demands of transplantation waiting lists. In recent years there has been renewed interest in donation after cardiac death in order to increase the pool of potential donors. The Organ and Tissue Authority has recently developed a national policy for donation after cardiac death. We describe here a checklist that is used by our hospital-based staff for organ donation which outlines important steps in the donation after cardiac death process.

Synergistic interactions between two skeletal mutations in mice: individual and combined effects of the semidominants cleidocranial dysplasia (Ccd) and short digits (Dsh).

Heterozygotes for cleidocranial dysplasia (Ccd) and short digits (Dsh) were crossed to test whether synergistic interactions occur between different dominant mutations whose individual pleiotropic phenotypic effects exhibit a common feature. These unlinked mutations are homozygous lethal, and they are congenic on the C57BL/10 background. Each mutation caused more than 10 different anomalies and showed variable expressivity. Each mutation produced several malformations that were present in every heterozygote. Seven different synergistic interactions were found, including one that yielded an entirely new abnormality not predicted from any abnormalities found in either of the single heterozygotes. Although synergistic interactions between dominant mutations have not, to our knowledge, been described in humans, these findings in mice increase the probability that they occur in humans. Under certain circumstances in human populations, the segregation of mutations causing synergistic interactions of the type demonstrated might be confused with recessive inheritance. It will be important to learn whether synergistic interactions can occur between other mutations. If they can, it will probably become important to take synergistic interactions into account when estimating the genetic hazards to humans from mutagens. Three antagonistic interactions were also found.

A comparison of stem cell populations and hemoglobin switching in normal versus beta-thalassemic mice.

The hematopoietic stem cell concentrations in tissues of homozygous beta-thalassemic and non-thalassemic fetuses and neonates were compared by using the spleen colony-forming units (CFU-S) assay. The relative quantities of embryonic and adult hemoglobins were also determined for fetuses. Beta-thalassemic fetuses had a reduced incidence of CFU-S in the liver throughout gestation, but after birth the beta-thalassemic neonates maintained a greater number of CFU-S in the liver for an extended period. The incidence of CFU-S in the bone marrow was not different for the two groups. The beta-thalassemic mice exhibited a significant expansion of CFU-S in the spleen beyond 11 days after birth. The switch from the synthesis of primarily embryonic to primarily adult hemoglobins in circulating erythrocytes in beta-thalassemic fetuses appeared later than the switch in normal fetuses. These observations establish that the developmental timing and expansion of hematopoiesis are perturbed in beta-thalassemic mice.