|Year : 2016 | Volume
| Issue : 2 | Page : 48-51
Femur nail-cortex contact length and aging
Ahmet A Karaarslan1, Eyad Skiak2, Hakan Aycan1, Ahmet Ascioglu1, Erhan Sesli1
1 Department of Orthopaedics and Traumatology, Sifa University, Izmir, Turkey
2 Department of Orthopaedics and Traumatology, Ozel Gazikent Hastanesi, Izmir, Turkey
|Date of Web Publication||9-May-2016|
Ahmet A Karaarslan
Department of Orthopaedics and Traumatology, Faculty of Medicine, Sifa University, Kaz?m Dirik Mah. Sanayi Cad. No: 7, Bornova, Izmir
Source of Support: None, Conflict of Interest: None
Aims: For prevention of interfragmentary shear motion in intramedullary nailing, the nail-cortex contact (N-CC) length should be long enough. This study was designed to assess the N-CC length changes related to the aging process. Materials and Methods: Femur anteroposterior (AP) radiograms of 204 patients older than 20 years were reamed virtually to be 13-mm, 14-mm, and 15-mm diameter artificial medullary cavities. Patients were divided into two major groups (males and females). Each group was subdivided into four subgroups - 20-39 years, 40-59 years, above 60 years, and above 70 years. The N-CC lengths of the femur diaphysis were measured in all groups and changes were compared between the groups. Results: For the 13-mm diameter artificial medullar cavity in female groups, the mean N-CC length value in the 20-39 years age group was 13.8 ± 4 cm, mean N-CC length value in the 40-59 years group was 11.6 ± 4.3 cm, mean N-CC length value in the above 60 years group was 9.4 ± 5.3 cm, and mean N-CC length value in the above 70 years age group were 8.8 ± 3 cm. A significant 48.6% decrease of N-CC length between 20-39-year and 40-59-year aged female groups was noticed (Z = −2.423; P = 0.015), whereas in the male groups, the significant N-CC length decrease (86%) was between the 40-59 years age group and above 70 years age group (Z = −4.279; P = 0.001). Conclusion: As N-CC length decreases after the age of 40 years in women and after the age of 70 years in men, thicker intramedullary nails should be used in these age groups for long N-CC area.
Keywords: Femur fracture, femoral nailing, nail-cortex contact length
|How to cite this article:|
Karaarslan AA, Skiak E, Aycan H, Ascioglu A, Sesli E. Femur nail-cortex contact length and aging. Sifa Med J 2016;3:48-51
| Introduction|| |
Mechanical stability is a very important factor for fracture healing. Ample interfragmentary shear motion may delay and prevent fracture healing. Fracture fixation of long bones with thin intramedullary unreamed nails may not prevent interfragmentary shear motion. ,,
The femoral bone medullary canal is cylindrical in shape in the midshaft level; however, it becomes like a funnel when reaching both the proximal and distal ends. In a press-fit intramedullary femoral nails, the nail-cortex contact (N-CC) area is maximum at the cylindrical midshaft portion, whereas in the proximal and distal femoral ends due to the funnel shape-like internal structure the N-CC is absent, and this will make the shear motion unavoidable, which may lead to complications such as delayed union and nonunion.
Many studies have focused on the proximal femoral internal medullary architecture because of the frequent use of proximal femur prosthesis ,,,,,,, while other anthropological works studied only one-level measurement at the midshaft of the femur bone. ,,
The aim of this study was to assess the N-CC area lengths and the medullary canal changes of the femoral bone in relation to the aging process. For this purpose, we created artificial medullary cylinders by a virtual digital reamerization of the femoral diaphysis with 13-mm, 14-mm and 15-mm diameter artificial cavities on the digital radiograms of 204 patients divided into two major groups (females and males) and four minor subgroups according to age (20-39 years, 40-59 years, older than 60 years, and older than 70 years).
Before starting our study, we assumed that the N-CC length might change with the aging process. The main questions of our study were: Does femur N-CC length change with age? At which age do N-CC lengths decrease in women and men?
| Materials and Methods|| |
Femoral bone true anterior-posterior x-rays of 204 patients were obtained from our hospital out-clinic between October 2011 and August 2013. There were 97 males (47.5%) and 107 females (52.5%). All digital radiograms were examined retrospectively. In the male group, 32 (33%) out of the 97 were of 20-39-year-old, 32 (33%) were of 40-59-year-old, 33 (34%) were older than 60 years, and 13 (13, 4%) were older than 70 years, whereas in the female group 30 (28%) out of the 107 were 20-39-year-old, 45 (42%) were 40-59-year-old, 32 (30%) were older than 60 years, and 13 (12%) were older than 70 years. Whereas, in the female group 30 (28%) out of 107 were 20-39 years old, 45 (42%) were 40-59 years old, 32 (30%) were older than 60 years and 13 (12%) were older than 70 years. The mean age was 50 ± 7 with an age range of 21-89 years. Ninety-two right and 112 left femur digital radiograms were included in the study.
All the patients who were included in this study had bone maturation. All radiograms with bone pathology were excluded from the study, and all radiograms were involving the whole femur from the greater trochanter proximally to the femoral condyles distally. All radiological measurements were done using Siemens Axiom Aristos FX (Berlin, Germany).
X-rays were taken by 66-KV, 125-mA, and 10.0-mA exposure values, anterior to posterior in a true anteroposterior (AP) position from 108-cm distance; the patient was positioned to include femur diaphysis. 43 × 43 cm cassettes were used. For standardizing of the measurements, a metal ruler was positioned parallel to the femoral shaft in a foam material. The software measurements were done with Wizard (Siemens). The metal ruler measurements and software measurements were set to be the same. Measuring from proximal to distal, we determined and marked the first level with a 13-mm medullary canal diameter. Also, measuring from the distal femur to proximal femur, we determined and marked the first level with a 13-mm medullary canal diameter. We measured the distance between these two levels as "the N-CC length" for a 13-mm medullary artificial cavity. We performed the same process for 14-mm and 15-mm canal diameters too [Figure 1].
|Figure 1: Demonstration of the femur AP radiogram measurement with the first levels from proximal and distal 13-mm and 15 mm-canal diameters|
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All of the measurements on radiograms were performed by the same researcher. The differences of measurement between the age groups were statistically analyzed with Mann-Whitney U test. P < 0.05 values were accepted as significant.
| Results|| |
For a 13-mm diameter artificial medullar cavity in female groups, we found out that while the mean N-CC length value in the 20-39 years age group was 13.8 ± 4 cm, the mean N-CC length value in the 40-59 years age group was 11.6 ± 4.3 cm, the mean N-CC length value in those older than 60 years age group was 9.4 ± 5.3 cm, and the mean N-CC length value in those older than 70 years age group was 8.8 ± 3 cm [Table 1]. The decrease in N-CC length in female patients between 20-39 years and 40-59 years was 46.8%; the difference was statistically significant (Z = −2.423; P = 0.015).
|Table 1: Nail-cortex contact lengths (N-CC) in women's age groups (cm) (mean ± SD, 95% CI)|
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For 13-mm diameter artificial medullar cavity in male groups, we found out that while the mean N-CC length value in the 20-39 years age group was 11.1 ± 3.8 cm, the mean N-CC length value in the 40-59 years age group was 10.6 ± 3 cm and the mean N-CC length value in above 60 years age group was 9.1 ± 4.3 cm and the mean N-CC length value in the above 70 years group was 5.7 ± 1.2 cm [Table 2]. The decrease of mean N-CC lengths is not statistically significant between the 20-39 years age group and the above 60 years age group (Z = −0.920; P = 0.357); on the other hand, the decrease of mean N-CC length value between the 40-59 years age group and the above 70 years group was 86% and the difference was statistically significant (Z = −4.279; P = 0.001) [Table 2].
|Table 2: Nail-cortex contact (N-CC) lengths in men's age groups (cm) (mean ± SD, 95% CI)|
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We obtained similar results for 14-mm and 15-mm diameter artificial medullar cavities in females and males [Table 1] and [Table 2], [Figure 2]. We detected long N-CC lengths with large intramedullary cavities of nail in females and males [Table 1] and [Table 2], [Figure 2].
|Figure 2: Nail-cortex contact (N-CC) lengths (cm, mean) in male and female age groups for 13-mm, 14-mm, and 15-mm artifi cial canal diameters (ACDs)|
Click here to view
| Discussion|| |
For a stable intramedullary fixation in femur diaphysis fractures, a maximum N-CC is required to prevent the undesired interfragmentary shear motion. As the N-CC length increases, the stress that the distal locking screws bear will decrease. ,,
We found that in females, the N-CC length decreases after 40 years of age and in males the N-CC length decreases after 70 years of age. However, in male patients the changes of the N-CC length with age was found to be not significant before 70 years of age.
We had some limitations in our study, one of which was the lack of measurement with computed tomography (CT) scanning. However, CT scanning exposes patients to more radiation and it is of course a more expensive imaging method. Furthermore, on radiograms taken at different rotation degrees at the femoral neck region, the possibility of different medullary diameter measurements was reported.  It was reported that 2 cm distal to the lesser trochanter to the distal femur metaphysis, the femoral canal becomes round therefore, the AP and lateral canal diameters are nearly the same, which makes only AP measurement enough to determine the canal diameter. ,
It was reported that while the roentgen graphic method is more accurate, measurements in the CT method is technically easier to conduct. 
We couldn't find any study about the resulting medullary diameters after 13 mm, 14 mm and 15 mm reamer. For this reason, we used the term "diameter of artificial medullary cavity" instead of the diameter of reamer.
This study implied that the decrease of the N-CC length after 40 years of age in females may be due to the relevant menopause because subtrochanter region osteoporosis and endosteal bone resorption were reported.  It had been reported that metaphysis has a more bone turnover than the diaphysis and is more sensitive to osteoporosis after the age of 50 years.  N-CC length decrease in females may be the result of the increase of the intramedullary canal diameter. It had been demonstrated that the femoral diaphysis had a wider diameter in older age than in young adulthood and this geometric difference may compensate for the decreased bone mass with aging. 
Our study revealed that males have shorter N-CC lengths compared to that of female N-CC lengths, which can be explained by the wider canal of male femur diaphysis with the same diameter of cylindrical cavity. Previous researchers reported that the male femur has a wider intramedullary canal comparing to that of females. 
We found out that N-CC length increases when the artificial cylindrical cavity diameter increases. It is reported that high shear movements of about 4 mm may occur during gait and these shear movements can be reduced by about 30% by the use of 1-mm thicker nail.  Clearance of the implant within the medullary canal and flexibility of the implant itself determine the extent of interfragmentary movement and the majority of the movement is related to the clearance of the nail within the bone.  It was reported that the largest possible nail should be used to maximize N-CC for minimum fracture site movement. 
| Conclusion|| |
N-CC length starts to decrease in females after 40 years of age, whereas in males it starts to decrease after 70 years. In order to obtain a longer N-CC area, thicker intramedullary nails should be used in order to prevent shear motion in femur diaphysis fractures after certain age.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2]
[Table 1], [Table 2]