Applications of surface-surface matching algorithms for determination of orthodontic tooth movements.

Orthodontic tooth movements are described as the differences between initial and final tooth positions. A computer based method for determination of tooth movements for different treatment methods was developed. A total of 20 casts of the upper jaw of patients treated with tooth positioners or fixed appliances were used as a basis for this study. Tooth movement was analysed on casts before (Ci) and after treatment (Cf). The casts were digitized either with a COMT or 3D laser scanning systems. After digitization, the models were superimposed in the palate by using a surface-surface matching algorithm. Tooth surfaces of the orthodontically moved teeth were segmented and determination of tooth movement was accomplished by matching the moved teeth from Ci to Cf. The resulting transformations delivered three dimensional information on translations and rotations. An accuracy of 0.2 mm in translations and 1 degree in rotations could be demonstrated, showing the different efficiency of treatment schemes.

[Is surgical education associated with additional costs? A controlled economic study on the German DRG System for primary TKA]. / Kostet operative Ausbildung Geld? Eine kontrollierte gesundheitsökonomische Studie auf Grundlage des deutschen DRG-Systems am Beispiel der primären Knieendoprothetik.

AIM: Total knee arthroplasty (TKA) is one of the most common procedures in orthopaedic surgery, the cost of surgical training has as yet not been quantified. In a pilot study, we investigated the economic impact of surgical training under DRG system influences, analysing the cost-proceeds structure in surgical training for orthopaedic residents. METHODS: Consecutive TKAs were performed by the most educated surgeon (Group A) having implanted ≥ 1000 TKAs, another attending (Group B) with ≥ 200 TKAs and a resident (Group C) having assisted in 25 TKAs (n = 30 patients per Group A-C). All patients were embedded in a standardised clinical pathway. By analysing the costs parameters such as numbers of blood transfusions, the operating time and the length of stay in the hospital we investigated the health care-related costs matched to the DRG-based financial refunding. Data were analysed after undergoing a analysis of variance followed by a post-hoc Scheffé procedure. RESULTS: On the one hand the resident generated additional costs of 1111,7 ± 97 € in comparison to the Group A surgeon and 1729,8 ± 152 € compared to the attending Group B (p > 0,05), these were generated by longer stay in hospital, longer operation time and higher need of resources. On the other hand there were significantly higher proceeds of the Group C in comparison to the attending Group B and also to Group A: 474,78 ± 82 € vs. A and 150,54 ± 52 € vs. Group B (p < 0,05). This was generated both by a higher patient clinical level of complexity (PCCL) and increased complication rates resulting in a consecutively augmented profit by grouping these patients to a more lucrative DRG. Overall the deficit per patient treated by the resident is 637 ± 77 € vs. Group A and 1579,3 ± 137 € vs. Group B (p > 0,05). CONCLUSION: The German DRG matrix results in higher profits accounted to the learning surgeon by increased PCCL relevant status and grouping the case to a more profitable DRG. Hereby, the additional costs are only partly redeemed. Surgical education of residents is associated with additional costs for the hospital. These costs have to be redeemed to allow good surgical training for hospitals having good teaching conditions.