Selection of fixation devices in proximal femur rotational osteotomy: clinical complications and finite element analysis.
OBJECTIVE
To compare the postoperative stability between large cancellous screws fixation and dynamic hip screws fixation in transtrochanteric rotational osteotomy.


METHODS
Finite element analysis was designed to validate the clinical outcomes of fixation failure in transtrochanteric rotational osteotomy.


BACKGROUND
From 1997 to 2000, transtrochanteric rotational osteotomy had been done in 20 osteonecrotic hips. Fixation with large cancellous screws as suggested by Sugioka had been used in the first five hips. Unfortunately, fixation failures were encountered in all of the five cases. The fixation mode was then shifted to a combination of plate and screws, no fixation failure had been observed postoperatively. A finite element analysis was designed to investigate the causes of fixation failure.


METHODS
Finite element models for four dynamic hip screw instrumented femora and four large screws instrumented femora simulating four different levels of bone cut were created. The von Mises stress distributions of each model were analyzed and compared for a loading condition simulating single-legged stance.


RESULTS
Analysis results confirmed our clinical observation that fixation with screws had higher stress concentration on the proximal femur. Improper bone cut, especially those that are too distal from the intertrochanteric line, had higher risks of fixation failure.


CONCLUSIONS
Transtrochanteric rotational osteotomy is a technically demanding procedure such that surgical principles should be abided carefully to avoid catastrophic complications.


CONCLUSIONS
Finite element analysis results demonstrated that dynamic hip screw fixation provides better stability and prevents fixation failure that corresponds with the clinical observation.
Department of Biomedical Engineering, Chung Yuan Christian University, Chungli 320, Taiwan.
Weng-Pin
WP
Chen
Ching-Lung
CL
Tai
Chun-Hsiung
CH
Shih
Pang-Hsin
PH
Hsieh
Menq-Chiang
MC
Leou
Mel S
MS
Lee
D000328:Adult; D001863:Bone Screws; D005260:Female; D005271:Femur Head Necrosis / Q000000981:diagnostic imaging / Q000601:surgery*; D020342:Finite Element Analysis; D006801:Humans; D008297:Male; D008875:Middle Aged; D010027:Osteotomy / Q000295:instrumentation* / Q000379:methods; D011859:Radiography; D013314:Stress, Mechanical