Gender-Related Anatomic Differences of the Middle Genicular Artery: A Comparative Cadaveric Analysis

Joshua A. Tuck, D.O., Steven Habusta, D.O., M.Ed, Michael Bradbury, Ph.D. Investigation performed at Lake Erie College of Osteopathic Medicine

Background

Anterior cruciate ligament, (ACL), injuries account for approximately half of all isolated knee ligament injuries, with an estimated 100,000 new cases occurring annually. An estimated 70% of these injuries occur during participation in sports.

Female athletes are two to eight times more likely to sustain an ACL injury than male athletes.

Although several causes have been explored to explain the disparity of ACL injuries between males and females, no study to date has looked specifically at potential gender-related differences in the chief blood supply to the ACL, the middle genicular artery. Graph 1: Combined male and female left middle genicular artery (MGA) lengths (cm) This study sought to utilize cadaveric dissection of the middle genicular artery to discover if gender-related vascular anatomic plotted against widths (mm). As the length of the vessel increased, so too did the width, differences exist, which in turn may help explain the increased incidence of anterior cruciate ligament injury in the female regardless of gender. population.

Figure 1: Dissection of right knee demonstrating middle genicular artery arising from origin off popliteal artery and diving between the anterior and posterior cruciate ligaments. The blue pin marks the posterior cruciate ligament.

Hypothesis Results

The average length and width of the female middle genicular arteries will be less than that of the male arteries, while the average course of the vessel will be similar. The mean length of the female right middle genicular artery, (MGA), was 3.63 cm with an average width of 1.69 mm. In the male specimens, the average length of the right MGA was 4.08 cm, with an average width of 2.0 mm, (see Table 1).

. The left MGA was available for analysis in all 19 specimens. The mean length of the left MGA in the female specimens was 3.45 cm with a width of 1.63 mm. The mean length of the male left MGA was Methods 4.0 cm, with a mean width of 2.19 mm, The course of each MGA was similar among the specimens, with the vessel arising from the anterior aspect of the popliteal artery within the popliteal fossa, 3 to 5 cm proximal to the joint line, as previously described The artery was found to course anterior to the popliteal artery and posterior to the joint capsule, until it pierced the capsule and became intra-articular through the substance of the oblique popliteal ligament.

Regardless of gender, the course of the vessel from its origin to its insertion followed the same posterolateral to anteromedial path, with entry into the posterior joint capsule at its’ posteromedial aspect.

Graph 2: Regardless of gender, as height (in) increased, so too did left middle genicular Utilizing the gross anatomy lab of the Lake Erie College of Osteopathic Medicine, 19 cadavers, (10 female, 9 male), ranging in age The differences in age between the two genders was insignificant, (P value 0.7070). However, the gender differences in height, (P value 0.0002), right MGA width, (P value 0.0118), left MGA length, (P artery, (MGA), length (cm) and width (mm). from 41 to 99 years, were used for anatomic dissection. Two lacked fossae = 36 fossae available for analysis. value 0.0048), and left MGA width (P value 0.0003), were all found to be significant. The differences in right MGA length, (P value 0.1138), were found to be insignificant between the genders, (see Graphs 1 & 2). This lack of significant difference is likely the result of a single point outlier in the data, (specimen #1), with an apparently longer right MGA of 5.1 cm. As such, comparative analysis was limited to the more representative data obtained from the left MGA. Macroscopic dissection of the middle genicular artery was carefully performed from its origin off the popliteal artery to its insertion, (via ligamentous branches), diving between the cruciates and into the dorsal aspect of the ACL, (see Figure 1). Conclusion

Initial vessel identification was confirmed and photodocumentation was utilized to record the course of each middle genicular artery within each specimen

When corrected for height, no significant anatomical differences were noted in the course of the MGA between males and females The vessel was then measured in length from it’s origin to its insertion, and a luminal width was measured using the central third of in our study. Regardless of gender, as height increased, so too did left MGA length and width. the vessel as a standardized reference point. Each measurement was performed by the same principle investigator to eliminate investigator reliability issues. Vessel size and length were recorded and compared. This data confirms that taller subjects will generally have longer and wider middle genicular arteries. This larger vessel size may confer a relatively greater blood supply to the anterior cruciate ligament, thus potentially altering its vulnerability to injury. Taller The heights from each cadaver were also measured and recorded, using a standard reference point from the most superior aspect of athletes may have less ACL injuries than their shorter counterparts. the calvarium to the heel.

The average difference in height between males and females, (thus difference in MGA size), may play a role in the disparity of Statistical analysis was used to determine if statistically significant differences existed between each of these measured variables. ACL injuries. To this investigator’s knowledge, no study has been published that has compared differences in height with frequency of ACL injuries. The information obtained through this study and the possible clinical implications lend the subject to further investigation. Table 1: Table of male and female heights, ages and right and left middle genicular artery lengths and widths. Ht: height. R length: Right middle genicular artery length. R Width: Right middle genicular artery width. L Length: Left middle genicular artery length. L Width: Left middle genicular artery width.

Erie, Presque Isle