Pengaruh Lebar Pelat Lower Profile Tibial Shaft Terhadap Kekuatan Bending

ARIF WIBOWO, Dr Rahadyan Magetsari, dr, SpOT(K)., PhD., FICS

2013 | Tesis | S2 Orthopaedik dan Traumatologi

Latar belakang : Kekuatan pelat tergantung pada bahan, desain dan dimensi pelat. Uji mekanik preklinik membandingkan pelat desain baru dengan pelat standar yang telah diakui dan dipakai secara luas. Permukaan medial diafisis tibia bersifat subcutaneous, sehingga desain pelat tipis (lower profile) dapat mengurangi penonjolan pelat. Penambahan lebar pelat lower profiel tibial shaft akan meningkatkan kekuatan pelat tersebut. Metode Penelitian : Penelitian ini merupakan studi eksperimental melalui tahapan penentuan tebal, lebar pelat dan tes bending. Lebar terkecil permukaan medial diafisis dari x-ray posisi lateral tibia dextra orang Indonesia (n=60) diukur rataratanya. Pelat lower profile tibial shaft dan narrow DCP AO Synthes dianalisis dengan metode finite element. Tebal pelat lower profile tibial shaft ditentukan berdasarkan momen inersia. Pelat lower profile tibial shaft dan narrow DCP AO Synthes dibandingkan dengan menggunakan tes bending standar ISO 9585 dan ASTM F382-99. Hasil dan Diskusi : Selisih lebar narrow DCP AO Synthes dan rata-rata (23,04 mm) lebar terkecil permukaan medial diafisis tibia dextra adalah 11,04 mm. Dari tes bending didapatkan nilai stress pelat lower profile tibial shaft lebar 14 mm sebesar 100,94 N/mm^2 (80%) dibanding pelat AO Synthes. Karena nilai strain pelat AO Synthes lebih kecil dari lower profile tibial shaft DCP, menyebabkan nilai modulus young`s paling besar. Modulus young`s pelat lower profile tibial shaft lebar 14 mm sebesar 26.428,2 N/mm^2 (90%) dibanding pelat AO Synthes. Modulus young`s menunjukkan derajat kekakuan pelat. Kesimpulan : Dengan menambah ukuran lebar pelat menjadi 14 mm, stiffness pelat lower profiel tibial shaft mendekati stiffness pelat narrow DCP AO Synthes sebesar 90%.

Background: Stiffness of the plate depends on the materials, design and dimensions. Preclinical mechanical testing comparing the new design implant with standard implants that have been recognized and widely used. Medial surface of the tibial shaft is widening subcutaneous, so the designing of lower profile plate can reduce the protrusion of the plates. The addition of wide lower profile tibial shaft plate would generate strength. Research Methods: This study is an experimental study with the stage of determining the width of the plates and bending test. The shortest width of the medial surface of the Indonesian right tibial X-ray (n = 60) were measured. Both lower profile tibial shaft plates and AO Synthes plates were performed finite element analysis. The thickness of the lower profile tibial shaft plates were detemined using moment of inertia. The lower profile tibial shaft plates and AO Synthes plates were compared by conducting bending tests using 4 point bending configuration design that is based on the standard ISO 9585 and ASTM F382-99 Results and Discussion: The difference between the plate width of 12 mm and the average (23.04 mm) shortest width of the right medial tibial shaft is 11.04 mm. From the results obtained from the bending tes, stress value of the lower profile tibial shaft plates is 100.94 N/mm^2 (80%) for 14 mm width plates compared to the AO Synthes plates. The Young`s modulus of the lower profile tibial shaft plates is 26428.2 N/mm^2 (90%) for 14 mm width plates compared to the AO Synthes plates. The Young`s modulus indicates the degree of stiffness of the plates. Conclusion: The highest of stifness of the lower profile tibial shaft plates can be achieved by the width to 14 mm and the thickness to 3.5 mm. The stiffness of lower profile tibial shaft plates is closest to 90% of the AO Synthes plates stiffness.

Kata Kunci : Permukaan medial diafisis tibia, Pelat lower profile tibial shaft, Lebar pelat, Tes Bending, Stiffnes