{'fraction_non_alphanumeric': 0.02942694889003614, 'fraction_numerical': 0.0123902942694889, 'mean_word_length': 5.1916932907348246, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Screw Pullout Strength: A Biomechanical Comparison of Large-fragment and Small-fragment Fixation in the Tibial Plateau

Objectives To compare the pullout strengths of 6.5-millimeter diameter partially threaded cancellous screws and 4.5-millimeter diameter fully-threaded cortical screws versus 3.5-millimeter diameter cortical screws in the proximal tibia. Design Three screws were inserted in the lateral tibial plateau of each leg of fifteen paired cadaveric tibias. In one tibia, large-fragment fixation was used, consisting of a unicortical 6.5-millimeter screw in the subchondral bone, and bicortical 4.5-millimeter screws in the metadiaphyseal and diaphyseal bone. In the contralateral tibia, small-fragment fixation consisting of three 3.5-millimeter screws was used, placing the screws in the same positions as described above. Main Outcome Measurements A materials-testing machine was used to determine axial pullout strengths of each screw. The mean pullout strengths of large-fragment and small-fragment screws in each position were compared. Results No significant difference in pullout strengths was found between the large-fragment and small-fragment screws in subchondral and metadiaphyseal bone. A statistically significant difference was found between pullout strengths of large-fragment and small-fragment screws in diaphyseal bone. Conclusions In human proximal tibial bone, the data from this study do not suggest that the pullout strength of 3.5-millimeter screws differs from that of 6.5-millimeter screws in subchondral bone, or that the pullout strength of 3.5-millimeter screws differs from that of 4.5-millimeter screws in metadiaphyseal bone. However, the pullout strength of 3.5-millimeter screws is significantly less than that of 4.5-millimeter screws in diaphyseal bone. The authors of the present study believe this supports the use of small-fragment fixation in the treatment of tibial plateau fractures.