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Table 4 Subgroup analysis of the included studies by different influential factors

From: Does hydroxyapatite coating have no advantage over porous coating in primary total hip arthroplasty? A meta-analysis

Factors Harris hip score Survival Incidence of thigh pain Radiolucent lines Femoral osteolysis Polyethylene wear
  Subgroups (numbers) WMD (95% CI) Subgroups (numbers) RR (95% CI) Subgroups (numbers) OR (95% CI) Subgroups (numbers) OR (95% CI) Subgroups (numbers) OR (95% CI) Subgroups (numbers) WMD (95% CI)
Study design RCT (10) 1.41 (0.30, 2.52) RCT (10) 1.01 (0.99, 1.02) RCT (4) 0.73 (0.42, 1.28) RCT (4) 0.95 (0.65, 1.39) RCT (2) 1.37 (0.45, 4.17) RCT (4) N.A.
Non-RCT (5) 2.29 (0.50, 4.07) Non-RCT (6) 1.00 (0.99, 1.00) Non-RCT (2) 0.14 (0.04, 0.49) Non-RCT (2) 0.96 (0.41, 2.24) Non-RCT (3) 0.39 (0.22, 0.70) Non-RCT (0)
  p = 0.42   p = 0.27   p = 0.02   p = 0.98   p = 0.05  
Study quality High (9) 1.41 (0.30, 2.52) High (8) 1.01 (0.99, 1.02) High (3) 1.29 (0.57, 2.88) High (4) 0.95 (0.65, 1.39) High (2) 1.24 (0.38, 4.13) High (4) N.A.
Moderate (6) 2.28 (0.50, 4.07) Moderate (8) 1.00 (0.99, 1.00) Moderate (3) 0.30 (0.15, 0.57) Moderate (2) 0.96 (0.41, 2.24) Moderate (2) 0.42 (0.24, 0.74) Moderate (0)
  p = 0.42   p = 0.27   p = 0.006   p = 0.98   p = 0.11  
Thickness of HA 50–80 μm (8) 0.76 (−0.63, 2.15) 50–80 μm (10) 1.00 (0.99, 1.00) 50–80 μm (3) 0.71 (0.40, 1.27) 50–80 μm (5) N.A. 50–80 μm (3) N.A. 50–80 μm (2) 0.00 (−0.01, 0.01)
<50 μm or >80 μm (3) 2.03 (0.41, 3.64) <50 μm or >80 μm (4) 1.02 (0.98, 1.06) <50 μm or >80 μm (2) 0.19 (0.06, 0.58) <50 μm or >80 μm (0) <50 μm or >80 μm (0) <50 μm or >80 μm (2) −0.03 (−0.03, −0.03)
  p = 0.24   p = 0.23   p = 0.04     p < 0.00001
Purity of HA >90% (4) −0.09 (−3.04, 2.86) >90% (7) 1.00 (0.99, 1.00) >90% (2) 0.68 (0.36, 1.26) >90% (3) 0.73 (0.31, 1.71) >90% (2) 0.66 (0.27, 1.62) >90% (1) 0.01 (−0.06, 0.08)
<90% (3) 0.82 (−0.77, 2.42) <90% (3) 1.00 (0.98, 1.02) <90% (3) 0.23 (0.08, 0.65) <90% (2) 0.93 (0.61, 1.40) <90% (1) 1.24 (0.38, 4.13) <90% (1) 0.00 (−0.01, 0.01)
  p = 0.59   p = 0.72   p = 0.08   p = 0.63   p = 0.4   p = 0.79
Implant design Anatomic (5) 1.65 (0.15, 3.16) Anatomic (4) 1.02 (0.99, 1.05) Anatomic (2) 0.19 (0.06, 0.58) Anatomic (1) 0.32 (0.07, 1.47 Anatomic (2) 0.66 (0.27, 1.62) Anatomic (2) −0.03 (−0.03, −0.03)
Non-anatomic (10) 1.66 (0.44, 2.87) Non-anatomic (12) 1.00 (1.00, 1.00) Non-anatomic (4) 0.72 (0.41, 1.28) Non-anatomic (5) 1.01 (0.71, 1.45) Non-anatomic (3) 0.46 (0.25, 0.85 Non-anatomic (2) 0.00 (−0.01, 0.01)
  p = 1.00   p = 0.24   p = 0.04   p = 0.15   p = 0.52   p < 0.00001
Follow-up duration >6 years (9) 2.21 (1.05, 3.37) >6 years (10) 1.01 (0.99, 1.03) >6 years (4) 0.56 (0.29, 1.08) >6 years (2) 0.58 (0.24, 1.43) >6 years (4) 0.44 (0.24, 0.77) >6 years (3) −0.02 (−0.02, −0.01)
<6 years (6) 0.58 (−1.04, 2.20) <6 years (6) 1.00 (0.99, 1.00) <6 years (2) 0.50 (0.24, 1.05) <6 years (4) 1.04 (0.71, 1.52) <6 years (1) 1.00 (0.32, 3.15) <6 years (1) 0.01 (−0.06, 0.08)
  p = 0.11   p = 0.11   p = 0.82   p = 0.25   p = 0.2   p = 0.46
  1. Study design and study quality would affect the incidence of thigh pain and study design has influence on femoral osteolysis. When the thickness of HA is <50 or >80 μm, it has less thigh pain incidence and polyethylene wear. The anatomic implant has less incidence of thigh pain and polyethylene wear.
  2. WMD weighted mean difference, N.A. not available. HA hydroxyapatite.