Background: When performing arthroscopic ankle arthrodesis for end-stage ankle arthritis, internal fixation is\nperformed using bone screws after appropriate preparation.\nHowever, optimal characteristics of bone screws have not been examined in terms of pressure force. Objective\ncomparisons of bone-screw performance may provide information on procedures for arthroscopic ankle arthrodesis.\nThe study objectives were to determine whether it was possible to measure compressive force changes using the\nnewly developed device and to infer all screw characteristics from measurement results when used in actual\nsurgeries. In addition, we performed experiments on cadavers to verify whether the experimental results could be\napplied to the joints of living subjects.\nMethods: Three types of screws (S1, S2, and S3) were inserted into the unique measurement device, and the\nchanges in pressure were measured for each 45�° turn. Changes in pressure and maximum pressure force were\nrecorded after the application of the screws. After reaching the maximum pressure in the simulated bone, further\nscrew rotations were accompanied by a gradual pressure decrease to 0 MPa. We also measured pressure changes\nin a similar manner by inserting a miniature pressure sensor into the talocrural joints of cadavers.\nResults: The mean maximum pressure �± standard deviation for S1, S2, and S3 were 0.832 �± 0.164 MPa, 0.434 �± 0.\n116 MPa, and 0.414 �± 0.127 MPa, respectively. Pressure slopes to the maximum did not significantly differ between\nthe screws in the simulated bone, and a subsequent pressure decrease to 0 MPa was significantly more rapid for S1\nthan for S2 and S3. Although pressure failure after the overtightening of screws was only observed in the simulated\nbone, patterns of pressure vs. rotation angle were similar in simulated and cadaveric bones. The pressure profile\ncharacteristics of three different screw types were determined.\nConclusions: We were able to measure the compressive force changes using the newly developed device when\nthe screws were inserted. On the basis of the measurement results, we were able to infer the characteristics of all\nscrews when used in actual surgery.
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