ARTICULAR CARTILAGE THICKNESS IN PEDIATRIC AND ADOLESCENT KNEES DECREASES WITH AGE AND SKELETAL MATURITY: IMPLICATIONS FOR OSTEOCHONDRAL GRAFTING PROCEDURES

Abstract

Background:

Quantifying native cartilage thickness in pediatric and adolescent knees can help match donor and recipient sites for articular cartilage restoration procedures such as osteochondral autograft transplantation (OATS) and osteochondral allograft transplantation (OCA).

Hypothesis/Purpose:

The purpose of the current study was to quantify articular cartilage thickness in pediatric and adolescent knees using magnetic resonance imaging (MRI). We hypothesized that cartilage thickness is inversely correlated with skeletal maturity and age.

Methods:

One hundred and twenty MRI scans were evaluated in a cohort of patients 9 to 18 years old without osteochondral lesions, chondral wear or pathology, intraarticular fractures, history of knee surgery, or inflammatory arthropathy. Measurements of articular cartilage thickness at the medial femoral condyle, lateral femoral condyle, lateral trochlea, and patella were made on axial, coronal, and sagittal MRI scans (Figure 1). Skeletal maturity was categorized as ‘open’, ‘closing’, or ‘closed’ based on the status of the proximal tibial and distal femoral growth plates. Descriptive statistics was used to evaluate cartilage thickness by age and sex. Independent samples t-test, analysis of variance (ANOVA), and linear regression were performed to investigate for associations with sex, skeletal maturity, and age.

Results:

On the femur, cartilage was thickest at the lateral trochlea with mean articular thickness of 4.2 ± 1.4 mm in males and 3.6 ± 1.3 mm in females (p=0.015) (Table 1). Skeletally immature patients with open physes had significantly thicker cartilage at the medial femoral condyle, lateral femoral condyle, and lateral trochlea compared to patients with closing and closed physes (Figure 2). Linear regression analysis also revealed a significant association between femoral cartilage thickness and age (Figure 3). Age explained 63% of the variance at the medial femoral condyle (B=6.1, p<0.001), 64% of the variance at the lateral femoral condyle (B=4.9, p<0.001), and 68% of the variance at the lateral trochlea (B=8.2, p<0.001) (Table 2). In contrast, cartilage thickness at the patella did not significantly vary by age, sex, or skeletal maturity (Figures 2 and 4).

Conclusion:

There is a strong inverse association between increasing age and cartilage thickness of the femoral condyles and lateral trochlea. In particular, pediatric knees demonstrate relatively thick cartilage at the lateral trochlea that decreases with age. This information will help surgeons understand recipient site anatomy and identify appropriate donor site tissue for articular cartilage restoration procedures such as OATS and OCA in children and adolescents.

Tables:

Table 1.

Mean articular cartilage thickness of the femur and patella

	Combined (n=120)	Male(n=40)	Female(n=60)	p value
Medial femoral condyle	3.2 ± 1.0	3.5 ± 1.0	2.9 ± 0.8	0.001
Lateral femoral condyle	2.8 ± 0.7	2.9 ± 0.7	2.7 ± 0.7	0.056
Lateral trochlea	3.9 ± 1.4	4.2 ± 1.4	3.6 ± 1.3	0.015
Median ridge of patella	4.2 ± 0.9	4.4 ± 0.9	4.1 ± 0.9	0.080
Medial facet of patella	4.7 ± 1.0	4.8 ± 1.0	4.6 ± 0.9	0.320
Lateral facet of patella	4.6 ± 0.8	4.7 ± 0.8	4.5 ± 0.8	0.185

Table 2.

Linear regression of articular cartilage thickness of the femur and patella by age

	R²	B	p value
Medial femoral condyle	0.63	6.1	<0.001
Lateral femoral condyle	0.64	4.9	<0.001
Lateral trochlea	0.68	8.2	<0.001
Median ridge of patella	0.02	4.8	0.090
Medial facet of patella	0.04	5.5	0.032
Lateral facet of patella	0.001	4.5	0.741

Figures:

Figure 1.

Measurements of patellofemoral articular cartilage thickness

Figure 2.

Mean articular cartilage thickness of the femur and patella by growth plate status

Figure 3.

Mean articular cartilage thickness of the femur by age

Figure 4.

Mean articular cartilage thickness of the patella by age