[Validity of digital templating in total hip arthroplasty: impact of stem design and planner's experience].

INTRODUCTION: Preoperative planning in total hip arthroplasty decreases the risk of implant oversizing and facilitates intraoperative orientation. The size of the acetabular and femural components can be estimated. The aim of the present study was to determine the validitiy of digital templating. Furthermore, we compared the accuracy of three planners with different clinical experience and the effect of two different femoral component designs on planning accuracy.

METHODS: On 60 a. p. pelvis radiographs, 60 unilateral, non-cemented total hip arthroplasties using the planning tool "AGFA-Orthopaedic-Tools Version V2.10®" (Fa. Agfa Health Care, Mertsel, Belgium) were repeatedly planned by three orthopaedic surgeons (planner A fifth year, planner B third year, planner C second year of training). All 60 patients received pressfit acetabular components, a straight stem was implanted in 28 (CLS-Spotorno™, Fa. Zimmer) and a short stem (Fitmore™, Fa. Zimmer) in 32 patients. The planned sizes of the components and the offset-variations were compared to the implanted sizes.

RESULTS: The percental accuracy and ICC planning for the straight stem were 42.9 %/0.906 for planner A, 39.3 %/0.833 for planner B, and 28.6 %/0.836 for planner C. Planning the short stem, the percental accuracy and ICC were 34.4 %/0,886 for planner A, 21.9 %/0.708 for planner B, and 12.5 %/0.681 for planner C. The accuracy and ICC of templating the acetabular components were 35 %/0.796 for planner A, 30 %/0.725 for planner B, and 26.8 %/0.511 for planner C. Planning the sizes of both femoral components showed significant differences between planner A and C and planner B and C in Wilcoxon's signed-rank test.

CONCLUSION: A lower level of experience showed no effect on the planning results of the acetabular components, but there were considerable and significant differences on planning the femoral components. Furthermore, the design of the femoral component had an impact on planning accuracy.