Gender and Side-to-Side Differences of Femoral Condyles Morphology: Osteometric Data from 360 Caucasian Dried Femori

The purpose of the present study was to conduct direct measurements in a large sample of dried femori in order to record certain morphometric parameters of the femoral condyles and determine whether there are gender and side differences. Three hundred sixty (Greek) Caucasian dried femori (180 left and 180 right), from 192 males and 168 females, were measured using a digital caliper. The mean age was 67.52 years. The mean bicondylar width of the femur was 8.86 cm ± 0.42 cm in men and 7.85 cm ± 0.30 cm in women (P < 0.01). The relative values for the medial condylar depth were 6.11 cm ± 0.34 cm and 5.59 cm ± 0.29 cm (P < 0.05); for the lateral condylar depth were 6.11 cm ± 0.33 cm and 5.54 cm ± 0.21 cm (P < 0.01); for the intercondylar width were 2.20 cm ± 0.18 cm and 1.87 cm ± 0.10 cm (P < 0.001); for the intercondylar depth were 2.78 cm ± 0.16 cm and 2.37 cm ± 0.12 cm (P < 0.001). No significant side-to-side difference was observed in any parameter. The femoral condyles differences in anatomy between genders might be useful to the design of total knee prostheses. The contralateral healthy side can be safely used for preoperative templating since there were no significant side differences.


Introduction
Quantitative anatomy of the distal femur is important for the design of total joint replacement and internal fixation material. Recent studies emphasize on differences between genders and among ethnic groups [1][2][3][4][5]. Preoperative templating for a total knee arthroplasty usually involves the contralateral, healthy side, based on the assumption that there are no side-to-side differences [6]. Furthermore, it has been found that certain osteometric parameters of the femur, such as the femoral intercondylar notch width, differ between genders and are associated with both the volume and the incidence of anterior cruciate ligament (ACL) rupture [7][8][9]. However, this association has been questioned by other researchers [10,11].
Most morphometric large sample size studies of the distal femur include measurements on radiographs, computerized tomography or magnetic resonance imaging [1,9,11,12]. A study on 1207 dried femora was published recently, where authors performed measurements using a microscribe digitizer for 3D analysis [13]. In the present study, certain osteometric parameters of the femoral condyles were recorded and the existence of gender and side-to-side difference was examined in 360 Caucasian dried femori.

Materials and Methods
The sample consisted of 360 paired dried femori (180 left and 180 right) from 192 males and 168 females. The mean age was 67.52 years (range 40-94 years). Femori that belonged to individuals other than Greeks were excluded. Femori that on gross inspection had evidence of fracture, postmortem damage or arthritis were excluded from the study, as well. All measurements were performed with a digital sliding caliper. The osteometric parameters were defined as follows: (1) bicondylar width: the maximum distance across the femoral condyles in the transverse plane ( Figure 1); 2 Anatomy Research International  Data analysis was conducted using SPSS for Windows version 18.0. One way ANOVA was used to test for significant differences between genders and sides of the body. A P-value less than 0.05 was considered statistically significant. A single author performed all measurements for consistency. Each measurement was repeated three times and the mean value was recorded. Measurement error was assessed for every anatomical parameter according to the method described by White and Folkens for osteometric studies [14]. All measurements were rounded to two decimal places.

Discussion
In the present study, five morphometric parameters were recorded in dried bones with a direct method using digital sliding caliper. In the literature most anatomic morphometric studies have been conducted with indirect methods including radiography, computerized tomography, magnetic resonance imaging, and 3D modelling. Given the fact that cadaveric material is scarce, these methods offer the advantage of describing anatomy in large samples since they can be performed in living subjects. However, indirect methods have been found to be inaccurate even after correction for magnification, technique, and projection [14][15][16].
The bicondylar width of the femur was found 8.39 cm±0.63 cm on average. It was significantly (P < 0.01) greater in men than in women, but there was no significant difference between the two sides of the body. The bicondylar width is the most frequently measured anatomic parameter of the distal femur. However, there is great variability between studies regarding the definition of measuring points as well as the measurement techniques and the type of sample [1, 4-7, 9-13, 17-19]. As a result, any comparison would provide unreliable conclusions. We measured the bicondylar width of the femur according to the definition of Farrally and Moore which is the maximum distance across the condyles in the transverse plane. [18]. They reported an average of 8.31 cm in 27 Caucasian femori, which is very close to the present study result, and 7.95 cm in 32 Negro femori (P < 0.01). Regardless of the measurement method, most studies have demonstrated a greater bicondylar width in men than in women and no statistically significant difference between left and right side [1, 4-7, 9, 10, 12, 13, 17, 19].
The mean medial condylar depth of the femur was 5.87 cm ± 0.41 cm. Men had a significantly (P < 0.05) greater depth than women. The average lateral condylar depth of the femur in our sample was 5.85 cm ± 0.4 cm and it was also significantly (P < 0.01) greater in men than in women. No significant difference was found between the left and right femori for both measurements. In the literature, the condylar depth was uniformly defined as the maximum anteroposterior diameter of each femoral condyle, but differences in measurement techniques and sample material were consistent. Farrally and Moore (1975) reported the "anteroposterior width of femoral condyles", but they did not clarify which condyle was measured [18]. The greater depth of both femoral condyles in men than in women and the absence of side differences, which were noticed in the present study, are in accordance with most literature studies [1, 4-6, 17, 20, 21]. However, Gillespie et al. [13] measured the medial and lateral flange height and found no difference between men and women.
The bicondylar width as well as the medial and lateral condylar depths of the femur are important parameters for the design of total knee prostheses. Differences in anatomy between genders have led to the design of gender-specific implants. Lateral condyle depth of the femur has been associated with osteoarthritis, but it remains unclear whether the increased depth of the lateral condyle is a predisposing factor or the effect of knee osteoarthritis [20].
The intercondylar width of the femur was 2.05 cm ± 0.22 cm on average, while the mean intercondylar depth was 2.59 cm ± 0.20 cm. Both intercondylar notch dimensions were significantly (P < 0.001) greater in men than in women. No significant difference was found between the left and right femori. Intercondylar notch dimensions have a clinical impact since smaller intercondylar notches have been associated with smaller ACL width and more frequent ACL ruptures [7,9,20,22,23]. However, other studies questioned this association [8,11,24,25]. This controversy led to the publication of morphometric studies of the intercondylar notch with the use of imaging techniques [7-11, 20, 22-24]. Wada et al. reported that there is an association between intercondylar width and knee osteoarhritis but this observation needs further investigation [20].
The intercondylar width has been studied extensively but this is not the case for the intercondylar depth of the femur. [7-11, 20, 22-25]. Herzog et al. compared intercondylar width measurements obtained with imaging techniques and the direct method [24]. There was no statistical significant difference between measurements obtained with calipers and MRI but there was a significant difference between calipers and X-ray [24]. Based on their observation, we compared our results with those mentioned in the literature and we noticed that they are within the range of the values reported [7-11, 20, 22-25]. The larger intercondylar notch in men Anatomy Research International 5 and the absence of side-to-side differences, which were found in the present study, have been verified by many authors [7,9,10,22,23].
In conclusion, in the present study direct measurements of the femoral condyles were conducted in a large sample of Caucasian (Greek) subjects. The differences in anatomy between genders might add to the design of prostheses. However, recent studies have shown that gender differences of distal femur morphometry depend on other morphometric measurements of femur, such as the femur length and width [4]. In the study by Dargel et al. 2011, which included 26 measurements of the knee joint, when gender differences were corrected for differences in femur length, medial-lateral dimensions of knees were still significantly larger in men than in women; however, matched paired analysis did not prove those differences to be consistent [17]. Therefore, they proposed that new implant design might rather take into account interindividual variations in the knee joint anatomy instead of gender-specific variations. Based on the results of the present study, the contralateral healthy side can be used safely for preoperative templating in total knee reconstruction since there was no statistical significant difference.