Abstract
BackgroundNonunion following treatment of supracondylar femur fractures with lateral locked plates (LLP) has been reported to be as high as 21 %. Implant related and surgeon-controlled variables have been postulated to contribute to nonunion by modulating fracture-fixation construct stiffness. The purpose of this study is to evaluate the effect of surgeon-controlled factors on stiffness when treating supracondylar femur fractures with LLPs:Does plate length affect construct stiffness given the same plate material, fracture working length and type of screws?Does screw type (bicortical locking versus bicortical nonlocking or unicortical locking) and number of screws affect construct stiffness given the same material, fracture working length, and plate length?Does fracture working length affect construct stiffness given the same plate material, length and type of screws?Does plate material (titanium versus stainless steel) affect construct stiffness given the same fracture working length, plate length, type and number of screws?MethodsMechanical study of simulated supracondylar femur fractures treated with LLPs of varying lengths, screw types, fractureworking lenghts, and plate/screw material. Overall construct stiffness was evaluated using an Instron hydraulic testing apparatus.ResultsStiffness was 15 % higher comparing 13-hole to the 5-hole plates (995 N/mm849N vs. /mm, p = 0.003). The use of bicortical nonlocking screws decreased overall construct stiffness by 18 % compared to bicortical locking screws (808 N/mm vs. 995 N/mm, p = 0.0001). The type of screw (unicortical locking vs. bicortical locking) and the number of screws in the diaphysis (3 vs. 10) did not appear to significantly influence construct stiffness (p = 0.76, p = 0.24). Similarly, fracture working length (5.4 cm vs. 9.4 cm, p = 0.24), and implant type (titanium vs. stainless steel, p = 0.12) did also not appear to effect stiffness.DiscussionUsing shorter plates and using bicortical nonlocking screws (vs. bicortical locking screws) reduced overall construct stiffness. Using more screws, using unicortical locking screws, increasing fracture working length and varying plate material (titanium vs. stainless steel) does not appear to significantly alter construct stiffness. Surgeons can adjust plate length and screw types to affect overall fracture-fixation construct stiffness; however, the optimal stiffness to promote healing remains unknown.
Highlights
Nonunion following treatment of supracondylar femur fractures with lateral locked plates (LLP) has been reported to be as high as 21 %
The purpose of this study is to evaluate the effect of surgeon-controlled factors on overall fracture-fixation construct stiffness when applying lateral locked plates in the treatment of supracondylar femur fractures: 1. Does plate length affect construct stiffness given the same plate material, fracture working length and type of screws?
Does screw type and number of screws affect construct stiffness given the same material, fracture working length, and plate length? The use of bicortical nonlocking screws decreased overall construct stiffness by 18 % compared to bicortical locking screws (808 N/mm vs. 995 N/mm, p = 0.0001) (Fig. 4b)
Summary
Nonunion following treatment of supracondylar femur fractures with lateral locked plates (LLP) has been reported to be as high as 21 %. Does plate length affect construct stiffness given the same plate material, fracture working length and type of screws?. 2. Does screw type (bicortical locking versus bicortical nonlocking or unicortical locking) and number of screws affect construct stiffness given the same material, fracture working length, and plate length?. 3. Does fracture working length affect construct stiffness given the same plate material, length and type of screws?. 4. Does plate material (titanium versus stainless steel) affect construct stiffness given the same fracture working length, plate length, type and number of screws?. Distal femur fractures are a common orthopaedic problem with an overall incidence of approximately 37 per 100,000 person-years [1] These injuries occur in younger patients with high-energy trauma, and increasingly in older patients after low-energy mechanisms. Patients and injury related factors such as obesity, diabetes, smoking and open fracture have been associated with increased rates of nonunion [22]
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