Study selection
We initially obtained 969 studies and included 7 randomized controlled trials with 600 participants into the meta-analysis after screening for eligibility[18-20, 28-31]. The PRISMA study flow diagram is shown in Figure 1.
Study characteristics
A total of 7 randomized controlled trials with 600 participants were included. one study showed statistical significance in gender[28], one study did not state the BMI data[19]. All the studies were not learning cases, The demographic characteristics of patients are shown in Table 1.
Risk of bias
All the studies included in the meta-analysis were randomized controlled trials with high quality. It's hard to achieve blindness for doctors in surgery, but we think the detection bias outcome is unlikely to be affected by the absence of blindness. The risk of bias graph of each study and the risk of bias summary are shown in Figure 2 and figure 3.
Clinical outcomes
Length of incision
Five studies[18-20, 28, 31] with a total of 503 patients were eligible to compare the length of incision between DAA and PA in primary THA. We failed to find a significant difference between the DAA group and PA group with significant statistical heterogeneity among study groups (MD=-2.79 cm, 95%CI -5.77 to 0.18, p = 0.07, I2=100%, Fig. 4).
Surgery time
Six studies[18-20, 28, 30, 31] with a total of 549 patients were eligible to compare the surgery time between DAA and PA in primary THA. DAA inclined to a significantly longer surgery time (13.74 min, 6.88 to 20.61, p<0.0001, Fig.5), but there was significant statistical heterogeneity among the study groups(I2=93%).
Blood loss
Four studies[20, 28, 30, 31] with a total of 357 patients were eligible to compare the perioperative blood loss between DAA and PA in primary THA. We failed to find a significant difference between the DAA group and PA group with significant statistical heterogeneity among study groups. (MD=58.96 ml, 95% CI -4.46 to 122.38, p = 0.07, I2=97%, Fig. 6).
Transfusion rates
Three studies[19, 20, 31] with a total of 344 patients were eligible to compare the Transfusion rates between DAA and PA in primary THA. We failed to find a significant difference between the DAA group and PA group with significant statistical heterogeneity among study groups. (OR=0.35, 95%CI 0.04 to 3.15, p = 0.35, I2=87%, Fig. 7).
Length of stay (LOS)
Six studies[18, 19, 28-31] with a total of 496 patients were eligible to compare the LOS between DAA and PA in primary THA. There was no significant difference between the DAA group and PA group in terms of the LOS (MD=-1.52 day, 95%CI -3.75 to 0.71, p = 0.18, Fig. 8). There was significant statistical heterogeneity among the study groups(I2=100%).
Complication
Five studies[18-20, 28, 31] were eligible to compare the complication between DAA and PA in primary THA. Three studies[18, 20, 28] reported postoperative dislocation. And there was no significant difference between the two groups in terms of the dislocation (OR=0.52, 95%CI 0.09 to 3.08, p = 0.48, I2=0%, Fig. 9). Three studies[18, 28, 31] reported postoperative fracture. And there was no significant difference between the two groups in terms of the fracture (OR=1.45, 95%CI 0.27 to 7.66, p = 0.67, I2=0%, Fig. 10). Three studies[18-20] reported postoperative DVT. And there was no significant difference between the two groups in terms of DVT (OR=0.43, 95%CI 0.08 to 2.45, p = 0.34, I2=0%, Fig. 11). Two studies[18, 20] reported postoperative LCNT neuropraxia. And there was no significant difference between the two groups in terms of LCNT neuropraxia (OR=43.20, 95%CI 0.70 to 2654.71, p = 0.07, I2=74%, Fig. 12). Four studies[18-20, 28] reported overall postoperative complications. And there was no significant difference between the two groups in terms of overall postoperative complications (OR=1.39, 95%CI 0.72 to 2.66, p = 0.32, I2=0%, Fig. 13).
Functional outcomes
VAS Score
Three studies[20, 28, 31] with a total of 311 patients were eligible to compare the VAS Score between DAA and PA in primary THA. There was no significant difference between the two groups in terms of the preoperative VAS score (MD=-0.08, 95%CI -0.41 to 0.25, p = 0.62, I2=42%, Fig.14). Two studies[28, 31] followed-up the VAS score postoperative 1 day and 2 days. DAA inclined to a significantly higher VAS Score postoperative 1 day (MD=-0.65, -0.91 to -0.38, p<0.00001, I2=0%, Fig.15). DAA showed a significantly higher VAS Score postoperative 2 days (MD=-0.67, -1.34 to -0.01, p=0.05, I2=88%, Fig.16), but there was significant statistical heterogeneity among the study groups(I2=88%). Two studies[20, 28] followed-up the VAS score postoperative 12 months. There was no significant difference between the two groups in terms of the VAS score postoperative 12 months (MD=-0.01, 95%CI -0.47 to 0.50, p = 0.96, I2=72%, Fig.17).
Harris Hip Score (HHS)
Five studies[19, 20, 28, 30, 31] with a total of 477 patients were eligible to compare the HHS Score between DAA and PA in primary THA. There was no significant difference between the two groups in terms of the preoperative HHS score (MD=-0.61, 95%CI -2.15 to 0.93, p = 0.44, I2=12%, Fig.18). Two studies[28, 30] followed-up the HHS score postoperative 6 weeks. DAA inclined to a significantly higher HHS Score postoperative 6 weeks (MD=6.05, 1.14 to 10.95, p=0.02, I2=52%, Fig.19). Three studies[19, 28, 31] followed-up the HHS score postoperative 3 months. There was no significant difference between the two groups in terms of the HHS score postoperative 3 months (MD=6.30, 95%CI -1.70 to 14.31, p = 0.12, I2=89%, Fig.20). Two studies[28, 31] followed-up the HHS score postoperative 6 months. There was no significant difference between the two groups in terms of the HHS score postoperative 6 months (MD=0.67, 95%CI -1.87 to 3.21, p = 0.60, I2=0%, Fig.21). Two studies[20, 28] followed-up the HHS score postoperative 12 months. There was no significant difference between the two groups in terms of the HHS score postoperative 12 months (MD=0.65, 95%CI -1.16 to 2.46, p = 0.48, I2=0%, Fig.22).
Radiographic outcomes
According to the Lewinnek safe zone (anteversion angle of 15°±10° and abduction angle of 40°±10°)[32], we estimated the radiographic outcomes of DAA and PA. Five studies[18-20, 28, 31] with a total of 503 patients were eligible to compare the radiographic outcomes between DAA and PA in primary THA. There was no significant difference between the two groups in terms of the preoperative anteversion angle (MD=-0.01, 95%CI -4.21 to 4.20, p = 1.00, I2=96%, Fig.23). Besides, There was no significant difference between the two groups in terms of the preoperative abduction angle (MD=1.06, 95%CI -0.95 to 3.07, p = 0.30, I2=82%, Fig.24).