No Sex Differences Exist in Posterior Condylar Offsets of the Knee

Abstract

Background Restoration of posterior condylar offset during TKA is believed to be important to improving knee kinematics, maximizing ROM, and minimizing flexion instability. However, controversy exists regarding whether there are important anatomic differences between sexes and whether a unisex knee prosthesis can restore the anatomy of knees in males and females. Questions/purposes The purposes of our study were to determine if sex differences exist in (1) absolute posterior condylar offset size, (2) relative posterior condylar offset size in relation to total condylar height, and (3) posterior condylar articular cartilage thickness.Methods We identified 100 patients (50 men and 50 women) without a history of arthritis, deformity, dysplasia, osteochondral defect, fracture, or surgery about the knee who had MRI of the knee performed. All MR images were ordered by primary care medical physicians for evaluation of nonspecific knee pain. Using a previously described three-dimensional MRI protocol, we measured posterior condylar offset, total condylar height, and articular cartilage thickness at the medial and lateral femoral condyles and compared values to evaluate for potential sex differences. We performed an a priori power calculation using a 2-mm posterior condylar offset difference as the minimum clinically important difference; with 2n = 100, our power to detect such a difference was 99.8%.

Important Differences Exist in Posterior Condylar Offsets in an Osteological Collection of 1,058 Femurs

“…We suspect this is due to the variable nature of the intercondylar fossa. We identified that the medial and lateral PCOs are not symmetrical, corroborating early work suggesting medial PCO is greater than lateral PCO [6,22,23]. While the significance of this is unclear, some authors have suggested that existing arthroplasty systems do not adequately account for a non-uniform PCO [2].…”

“…Wang et al studied 50 male and 50 female Chinese patients and demonstrated that the average PCO of Chinese females (25.80 mm ± 2.71 mm) was significantly smaller than that of Chinese males (27.32 mm ± 2.34 mm), but these authors did not standardize their measurements using the width of the femoral diaphysis and had a very limited population [26]. Our results support those and suggest that PCO is relatively independent of sex, substantiating an MRI study that used standardized measurements [22]. While genderbased knee systems remain a controversial and heavily researched topic, more recent outcome studies have found no difference in genderbased implants [8,10,27].…”

“…In accord with earlier studies, we would argue that the use of a unisex prosthesis to recreate posterior condylar anatomy is likely sufficient [22]. Other custom implants have attempted to account for differences in PCO by varying the size of medial and lateral posterior condyles; most authors agree that more longterm follow-up is needed to determine the potential benefits of such systems [28][29][30].…”

“…Other purposes of our study included the assessment of the range of PCO within the general population, as well as within individuals. Comparisons of laterality, race, and gender are not as susceptible to error based on the absence of articular cartilage, which has not been shown to vary systematically based on the parameters we measured [22]. Although MRI has been demonstrated to accurately measure PCO [15], a large-scale study such as ours could not be efficiently performed in this manner.…”

“…However, the normative population data can be interpreted within the context of previous reports on articular cartilage. Shepherd et al [32] and Voleti et al [22] found no difference in posterior condylar articular cartilage thickness between medial and lateral sides, and no difference between genders. Other purposes of our study included the assessment of the range of PCO within the general population, as well as within individuals.…”