Fluoroscopy Improves Femoral Stem Placement

Prospectively two groups of patients with hip osteoarthritis were included in the study. Hip osteoarthritis was classified according to the Croft classification. The investigators primary goal is to evaluate T+ 2 ( 2 cm above trochanter minor) results between the two groups. Standard effect sizes (standard effect size) assumed to be at least 0.75. 30 cases for each group took power with 80% margin of 5% error. Patients with malignant tumors, previously known bone disease, drug consumption affecting bone mineralization or Crowe type III hip dislocations with greater than 4 cm of limb length discrepancy (LLD) were excluded. Prior to the operation, all patients underwent an X ray investigation to exclude any bone abnormalities. All patients were operated by the same team, which was composed of two senior surgeons and 2 fellows. Patients with odd-numbered were the first group and even numbers were the second group in order of receipt surgery. All patients were operated on the lateral decubitus position with a posterior approach and a metaphyseal locking femoral stem (Depuy Synthess SUMMIT Tapered Hip System, US). In the first group, no preoperative templating was performed, and the final conformation of the stem size and position was decided freehand intraoperatively based on anatomic landmarks. In the second group, there was also no preoperative templating, but after both senior surgeons agreed on the final stem size intraoperatively, C-arm fluoroscopy images were obtained with the last rasp size before stem implantation. The alignment and stem fitting of the femoral canal were evaluated. While evaluating the limb leg discrepancy anterior - posterior fluoroscopy image must include both hips and both lesser trochanters. Once this was achieved, the interteardrop line was used and vertical distance between interteardrop line and lesser trochanters measured for limb length discrepancy. Horizontal distance between tip of trochanter major and center of rotation was evaluated as lateral offset. For stem alignment, the femoral stem axis being parallel with the axis of the femoral canal was assessed. Also centralization of femoral stem tip in the femoral canal was assessed. Determination of stem was assessed according to full contact of broach teeth in sub trochanteric region. The stem was size changed unless all criteria above was achieved on fluoroscopy. After the operation, all patients were evaluated with X ray and CT(computerized tomography).

Medial canal flare index (MCFI) can be used for metaphyseal lacking femoral stems. The alignment of the femoral stem with the femoral canal, the limb length discrepancy ( LLD) and the lateral offsets were evaluated on X ray. The stem/endosteal areas at 2 cm above the trochanter minor (T+2) and 2 cm below the trochanter minor (T-2) and the deviation of the stem tip from the center of the femoral canal were evaluated on CT(Computerized tomography) images.

Inclusion criteria

• patients with hip osteoarthritis

Exclusion criteria

• malignant tumors, previously known bone disease, drug consumption affecting bone mineralization or Crowe type III hip dislocations with greater than 4 cm of LLD were excluded