The aim of our study was to investigate whether mechanical pressure plays an important role in cartilage degeneration in patients with developmental dysplasia of the hip. Here we compare glycosaminoglycan (GAG) content of neoacetabular cartilage (region subjected to mechanical pressure) and acetabular cartilage (region that is under no pressure) of patients with secondary hip osteoarthritis induced by developmental dysplasia of the hip (DDH), using delayed-gadolinium enhanced MRI of cartilage (dGEMRIC).
Samples of osteochondral unit were obtained from neoacetabular (NA) and acetabular (Ac) region of the hip from patients (N=10) with DDH-induced secondary hip osteoarthritis undergoing total hip arthroplasty, with a 10 mm diameter cylindrical chisel. Samples were scanned on a 7.0T micro-MRI machine (BioSpec 70/20 USR, Bruker Biospin, Germany) immediately following the surgery. T1 relaxometry was performed. Samples were then immersed in 0.5mM gadolinium solution for 16h and scanned using dGEMRIC protocol. T1 relaxation times before (T1preGd) and after gadolinium application (T1Gd) were calculated. ΔR was calculated as (1/T1Gd -1/T1preGd). Results obtained from different anatomical regions were compared using a t-test, with a significance level set at 0.05.
Mean T1 relaxation times after gadolinium application of Ac and NA were 609.671 ms and 552.800 ms, respectively. Calculated ΔR values of Ac and NA were 0.00114 ms-1 and 0.00141 ms-1. Statistical analysis showed no significant differences between different anatomical regions.
No significant difference was found between GAG content of neoacetabular and acetabular cartilage of DDH patients, indicating that no weight bearing does not have a positive effect on GAG content of acetabular cartilage in DDH. However, both T1 relaxation times after gadolinium application and ΔR values show that neoacetabular cartilage tends to be more degenerated. To fully understand the extent of tissue damage caused by DDH, more research needs to be done, with the emphasis on neoacetabular region.