Figure 1. The patients’ demographics.

Figure 2. A radiograph revealing a pedunculated osteochondroma at the proximal tibia (left). The thickness of the cartilage cap is 2.83 mm upon MRI examination (middle). After 6 years, the tumor vanished, as depicted by a radiograph (right).

Figure 3. Radiographs revealing a pedunculated-type osteochondroma of the proximal humerus (left). At initial diagnosis, the thickness of the cartilage cap is 2.25 mm (circle) on MRI (middle). Two years later, regression of osteochondroma was observed (right).

Table 1. Definition of tumor regression.

Table 1. Definition of tumor regression.

Tumor Regression Vanished>70% decrease from baselineRegressedA 30–70% decrease from baselineAssessment Method for Mode of Tumor Regression IncorporationThe height of the tumor AbsorptionThe stalk of the tumorFractureHistory of fracture

Table 2. The characteristics of the patients with spontaneous regression.

Table 2. The characteristics of the patients with spontaneous regression.

Age (Years)SexThickness of Cartilage Cap (mm)TypeSiteAge at Shrinkage (Years)2Female3.84SessileTibia87Male2.83PedunculatedTibia119Male4.57SessileHumerus139Female1SessileFemur158Male1SessileTibia93Male1.61SessileFemur1210Female2.25PedunculatedHumerus1410Male1.91PedunculatedFemur1111Female1.37SessileHumerus127Female1Sessilephalanx9

Table 3. The variables for predicting tumor shrinkage.

Table 3. The variables for predicting tumor shrinkage.

VariablesCategoryRegressionStable or Progressionp-ValueSexMale5101.0Female58AgeMean (range)9 (2–12)10 (2–16)0.346Tumor siteLong bone9120.362Flat bone16Shape of tumorPedunculated 340.674Sessile714Cartilage capMean (range)2.29 mm
(1.0–4.57)3.65 mm
(1.6–7.65)0.038

Table 4. The relationship between cartilage cap and clinical variables.

Table 4. The relationship between cartilage cap and clinical variables.

Clinical VariablesCategoryMean Cartilage Capp-ValueSexMale2.860.351Female2.09Age10>2.930.16210≤2.01Tumor siteLong bone2.70.362Flat bone1.35Shape of tumorPedunculated 3.240.674Sessile2.26