Regional variation in distal femur subchondral bone mineral density: An in vitro human cadaveric model

Background

Osteochondral defects of the knee are a frequent cause of pain that often require surgical intervention. Restorative procedures such as osteochondral autograft transplantation (OAT) and osteochondral allograft transplantation (OCA) aim to replace cartilage lesions with healthy autologous tissue or cadaveric tissue from the distal femur, respectively. Osteochondral graft donor sites are selected to optimize donor-recipient site congruity by assessing factors such as surface topography, cartilage thickness, and contact pressures. However, few studies have evaluated subchondral bone mineral density (BMD) when selecting an osteochondral graft donor site.

Purpose

To examine bone morphology and characterize variation in subchondral BMD of the human distal femur.

Study design

Descriptive Laboratory Study.

Methods

18 human cadaveric distal femurs were utilized in the current study. All soft tissue and ligaments of the distal femur were removed. Dual-energy X-ray absorptiometry (DEXA) scans were performed on each femur to determine BMD of five regions of interest (ROI). ROIs included the entire distal femur, medial condyle, lateral condyle, posterior condyles, and trochlea. Subsequently, 90 osteochondral bone plugs (10 mm diameter, 10 mm depth) were harvested collectively from the medial and lateral trochlea of included specimens. DEXA scans of each osteochondral graft were then performed. Statistical analysis was performed via Welch Two-Sample t-test. Significance was defined as p < 0.05.

Results

All specimens were included for analysis. There were no significant differences in the dimensional characteristics or BMDs of corresponding ROIs across distal femurs. There was no significant difference in the BMD of the medial condyle compared to the lateral condyle, and the posterior condyle compared to the trochlea. Also, there was no significant difference in BMD of grafts extracted from the medial and lateral trochlea (all p > 0.05).

Conclusion

No significant difference was found in BMD between the medial and lateral condyles, trochlea and posterior condyles, or osteochondral grafts harvested from the medial and lateral trochlear ridges of the distal femur.

Clinical relevance

Similar BMD between common osteochondral donor and recipient sites may provide surgeons with added confidence that fewer adjustments must be made to optimize congruity with respect to bone density.