title: Use of simple algorithms to predict screw length facilitates navigation-controlled medial opening-wedge osteotomy using the TomoFix HTO system.
abstract: This study was performed to establish simple algorithms to predict proper screw lengths for the 4 proximal holes of TomoFix plates (Synthes GmbH; Solothurn, Switzerland) based on radiographic mediolateral (ML) and anteroposterior (AP) dimensions of the proximal tibia and to determine how well these algorithms function for navigation-controlled medial opening-wedge high tibial osteotomy (HTO) using TomoFix. Experimental HTO surgery was performed in proximal tibial models manufactured for 30 patients undergoing HTO to determine the longest screw lengths for the 4 proximal holes of TomoFix plates. Eight algorithms were created for the 4 proximal screws by investigating the relationships between measured screw lengths and radiographic dimensions and were used for 30 navigation-controlled medial opening-wedge HTOs. The algorithms used to predict screw length were: screw A=ML width-20 mm and AP length+5 mm; screw B=ML width-25 mm and AP length; screw C=ML width-35 mm and AP length-10 mm; and screw D=ML width-40 mm and AP length-15 mm. All 30 surgeries were performed with no perioperative adverse events. Mean operative time was 47.1 minutes, and no far cortex perforation of more than 3 mm was observed for any of the 4 proximal screws. Mean mechanical tibiofemoral angle and weight load line coordinate at the knee joint were valgus 3.7° and 62.9%, respectively. Targeted alignment was achieved in 28 (93%) knees for a mechanical tibiofemoral angle between valgus 2° and 6°, and in 25 (83%) knees for a weight load line coordinate between 55% and 70%. The authors propose the use of the developed algorithms to select proper screw lengths for medial opening wedge HTO using the TomoFix HTO system.
authors.affiliation: Joint Reconstruction Center, Seoul National University Bundang Hospital, Seongnam-si, Gyeonggi-do 463-707, Republic of Korea. osktk@snubh.org
authors.forename: Tae Kyun
authors.initials: TK
authors.lastname: Kim
authors.forename: Chong Bum
authors.initials: CB
authors.lastname: Chang
authors.forename: Kyung Hag
authors.initials: KH
authors.lastname: Lee
authors.forename: Hyung June
authors.initials: HJ
authors.lastname: Cho
authors.forename: Min Soo
authors.initials: MS
authors.lastname: Je
authors.forename: Ho Hyun
authors.initials: HH
authors.lastname: Won
authors.forename: Yeon Gwi
authors.initials: YG
authors.lastname: Kang
mesh_terms: D000328:Adult; D000465:Algorithms; D001182:Arthroscopy; D017760:Bone Malalignment / Q000503:physiopathology / Q000601:surgery*; D001860:Bone Plates; D001863:Bone Screws; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000503:physiopathology / Q000601:surgery; D007720:Knee Prosthesis; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000503:physiopathology / Q000601:surgery*; D010027:Osteotomy / Q000009:adverse effects / Q000295:instrumentation / Q000379:methods*; D020127:Recovery of Function; D025321:Surgery, Computer-Assisted / Q000295:instrumentation / Q000379:methods*; D013977:Tibia / Q000473:pathology / Q000601:surgery; D016474:Weight-Bearing