Article
Influence of the reaming diameter on failure loads of human femora
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Published: | November 6, 2018 |
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Objectives: Treatment of large bone defects is still related to unsolved problems in orthopedic trauma surgery. Currently, the use of autologous bone graft harvested from the iliac crest is the gold standard to fill such defects. However, this procedure is associated with complications and postoperative morbidities. Recently, a new minimally-invasive technique for intramedullary reaming and autograft harvesting of large bone graft amounts from the medullary canal of the femur with the use of the Reamer-Irrigator-Aspirator (RIA) device was introduced.
The aim of this study was to investigate the influence of RIA diameter on femoral bone strength and to determine the amount of harvested graft in a human cadaveric model in relation to the reaming diameter.
Methods: Fourty-five pairs fresh-frozen human femora were randomized to 3 paired groups with 15 pairs each. One femur of each pair was reamed with RIA at a diameter of either 1.5 mm (group 1), 2.5 mm (group 2) or 4.0 mm (group 3) larger than its isthmus, whereas its contralateral femur was left intact without reaming. Following, all specimens were destructively tested in internal rotation to determine their torsional stiffness and torque at failure (Figure 1 [Fig. 1]).
The harvested graft was weighted and the wall thickness decrease determined by means of CT-scanning.
Furthermore the endosteal isthmus diameter was determined on radiographs and from the CT-data and checked for correlation.
Statistical evaluation was performed at level of significance P=0.05.
Results and conclusion: Torsional stiffness (Nm/°) of reamed/non-reamed femora in groups 1-3 was on average 9.2/10.2, 9.0/9.7 and 8.0/9.2. It decreased significantly after reaming in group 3, but not in groups 1 and 2. Torque at failure (Nm) of reamed/non-reamed femora (126/144, 105/133 and 102/126 for groups 1-3) revealed significant decrease after reaming in all 3 groups. Collected bone graft volume (gram) was significantly bigger in group 3 (26) compared to groups 1 (7) and 2 (14).
The endosteal isthmus diameter determined on the radiographs correlated well with the endosteal diameter calculated from the CT data according to the formula y = 0.8463x + 1.6214 and R² = 0.8695.
RIA diameter which is up to 4mm larger than the isthmus of the femur influences its torsional stability but results in a considerable amount of harvested bone. Further investigations are still necessary in order to determine the maximum permissible reaming diameter. The determination of endosteal isthmus diameter and hence of the adequate reamer head diameter on radiographs seems so far still adequate.