Influence of resection geometry on fracture risk in the treatment of femoroacetabular impingement: a finite element study.
BACKGROUND
A fracture is the most serious complication of surgical resection of the femoral head-neck junction in the treatment of cam-type femoroacetabular impingement (FAI).


OBJECTIVE
To investigate the influence of resection length, width, and depth on postoperative fracture risk in activities of daily living.


METHODS
Descriptive laboratory study.


METHODS
The femoral anatomy used for the finite element model was based upon a publicly available standardized model. For descriptive validation, the fracture location was compared with radiographs of patients who had suffered from a femoral neck fracture after surgical treatment of FAI in our institution. Additionally, a 2-part quantitative validation against previously published experimental data was performed. To simulate surgery, round resections were made in which length and width were varied at 10%, 20%, and 30%. The fracture loads were compared with published in vivo loads measured during activities of daily living with telemetric hip implants.


RESULTS
Validation showed that the model predicted fracture locations comparable with clinical cases and fracture loads within published experimental values. Femoral fracture loads were 325% more sensitive to resection deepening and 70% more sensitive to widening than lengthening.


CONCLUSIONS
Although resection depth is the most important determinant of bone resistance, it should be considered in combination with resection length and width. Even a resection depth as low as 10% may lead to a fracture in case of stumbling.


CONCLUSIONS
We show that for resection depths of 20% or less and resection length of less than 35% of the femoral neck, normal activities of daily living are safe. Resection widths typically achieved in practice did not induce fractures during activities of daily living. Patients who have undergone surgical resection should be counseled on how to try to avoid stumbling.
Department of Orthopedics, Balgrist University Hospital, University of Zurich, 8008 Zurich, Switzerland. Esin.Rothenfluh@me.com
Esin
E
Rothenfluh
Patrick
P
Zingg
Claudio
C
Dora
Jess G
JG
Snedeker
Philippe
P
Favre
D000328:Adult; D057925:Femoracetabular Impingement / Q000601:surgery*; D005265:Femoral Neck Fractures / Q000209:etiology* / Q000503:physiopathology; D005270:Femur Head / Q000601:surgery*; D005272:Femur Neck / Q000601:surgery*; D020342:Finite Element Analysis; D006801:Humans; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D019637:Orthopedic Procedures / Q000009:adverse effects*