Study Characteristics
We identified 2186 studies, of which nine studies met the inclusion criteria[8, 20, 22, 23, 29-33]. Four of them were the same as one of the studies, but with different follow-up[23, 30, 31, 33] (Fig. 1). During study selection, we excluded some RCTs, including five studies that incorporated patients younger than 75 years old[7, 34-37] and two studies included patients unable to live independently[38, 39], and two studies included patients unable to live independently[40, 41]. There were a total of 631 participants in the nine trials included in the study. Of these, 301 patients underwent a THA procedure, and 330 patients underwent a HA procedure. The nine trials were published between 2006 and 2017 (Table 1). The range of the duration of follow up was from 24.0 months to 194.0 months. One of these studies also included a third arm (internal fixation), but the data from these arms were not taken into account[32].
Risk of bias assessment
All nine Randomized Controlled Trials were assessed and found to have used adequate randomisation procedures, including the sealed-envelope technique, computer randomisation programs, and systemic random sampling[8, 20, 22, 23, 29-33]. Only one of the studies utilised blinding of outcome measurements, which had the interviewers blinded to the patient recruitment and randomisation or the type of surgery performed[32]. There was no blinding of participants in any of the included studies. Four of the studies were multi-centre studies[22, 23, 30, 32]. One of the studies was funded by a commercial entity[20]. The results of the risk of bias assessment were summarized in Fig.2.
Operative time
Three studies assessed the operative time in both the THA and the HA groups (117 with THA and 123 with HA)[20, 22, 30]. The operative time was significantly longer in the THA group (MD 18.20, 95%CI 9.99-26.41, Fig.3) and heterogeneity across the studies was 46%.
Study Characteristics
We identified 2186 studies, of which nine studies met the inclusion criteria[8, 20, 22, 23, 29-33]. Four of them were the same as one of the studies, but with different follow-up[23, 30, 31, 33] (Fig. 1). During study selection, we excluded some RCTs, including five studies that incorporated patients younger than 75 years old[7, 34-37] and two studies included patients unable to live independently[38, 39], and two studies included patients unable to live independently[40, 41]. There were a total of 631 participants in the nine trials included in the study. Of these, 301 patients underwent a THA procedure, and 330 patients underwent a HA procedure. The nine trials were published between 2006 and 2017 (Table 1). The range of the duration of follow up was from 24.0 months to 194.0 months. One of these studies also included a third arm (internal fixation), but the data from these arms were not taken into account[32].
Risk of bias assessment
All nine Randomized Controlled Trials were assessed and found to have used adequate randomisation procedures, including the sealed-envelope technique, computer randomisation programs, and systemic random sampling[8, 20, 22, 23, 29-33]. Only one of the studies utilised blinding of outcome measurements, which had the interviewers blinded to the patient recruitment and randomisation or the type of surgery performed[32]. There was no blinding of participants in any of the included studies. Four of the studies were multi-centre studies[22, 23, 30, 32]. One of the studies was funded by a commercial entity[20]. The results of the risk of bias assessment were summarized in Fig.2.
Operative time
Three studies assessed the operative time in both the THA and the HA groups (117 with THA and 123 with HA)[20, 22, 30]. The operative time was significantly longer in the THA group (MD 18.20, 95%CI 9.99-26.41, Fig.3) and heterogeneity across the studies was 46%.
General complication
Four studies assessed the general complication rates in both groups (261 with THA and 289 with HA), with the mean follow up being 14.5m[20, 23, 30, 32]. Although the HA group had lower rates of general complications, there was no significant difference from the THA group (RR 1.38, 95% CI 0.86-2.21, Fig.5), There was low heterogeneity (I2=0%) among the studies.
Wound Infection
Three studies assessed the wound infection rates of both groups (169 with THA and 170 with HA)[20, 22, 32]. Pooling the data of the included studies elicited no significant statistical difference between the THA and HA groups (RR 1.54, 95% CI 0.54-4.41, Fig.6), and heterogeneity across the studies was 0%.
VTE
Three studies assessed the venous thromboembolism (VTE) prevalence in both groups (169 with THA and 170 with HA) with the mean follow up of 9.66m[20, 22, 32]. No significant difference was found between the groups (RR 1.80, 95% CI 0.61-5.3, Fig.7). There was low heterogeneity (I2=6%) among studies.
Peri-prosthetic fracture
Two studies assessed the rate of peri-prosthetic fracture in both groups (82 with THA and 82 with HA)[20, 22]. There was no significant statistical difference between both groups (RR 0.59, 95% CI 0.08-4.60, Fig.8) and no significant between-study heterogeneity (I2=0%).
Erosion
Three studies reported the erosion rates in both groups (189 with THA and 202 with HA) during the follow up periods (mean 45.3m)[20, 22, 23]. The erosion rates were 0.48% in the THA group and 13.7% in the HA group with a significant difference (RR 0.05, 95% CI 0.01-0.20, Fig.9) and no significant between-study heterogeneity (I2=0%).
Re-operation rate
Four studies assessed the relative risk of re-operation rate in both two groups (375 with THA versus 396 with HA)[20, 22, 23, 32]. We divided the data into two subgroups according to follow up durations (within five years and more than five years). Four studies assessed the re-operation rate within five years of follow up(I2=0%)[20, 22, 23, 32]. Pooling the data revealed no significant difference (RR 1.12, 95%CI 0.49-2.54, Fig.10) in outcomes between the THA and HA groups. Two studies assessed the re-operation rate after five years of follow up(I2=0%)[22, 23]. The re-operation rate was 3.5% in the THA group and 5.6% in the HA group, however, there was no significant difference (RR 0.45, 95%CI 0.14-1.39, Fig.10) between the two techniques. If we added the patients with painful symptoms to the group of patients revised, the re-operation rate was significantly lower in the THA group after five years of follow up than in the HA group (RR 0.26, 95%CI 0.09-0.82, Fig.11). Heterogeneity across the studies was 0%[22, 23].
Dislocation rate
Five studies reported the dislocation rate in both groups (301 with THA and 300 with HA). We divided the data into three subgroups according to follow up duration(within three years and more than three years)[20, 22, 23, 30, 32]. There was a significant statistical difference between dislocation rates in the THA group(4.0%) and the HA group(0.61%)(RR 4.40, 95% CI 1.35-14.37, Fig.12). There were no dislocations reported in the subgroups that had more than three years of follow up[20, 23].
Total HHS
Three studies assessed the total Harris Hip Score (HHS) in both groups (190 with THA and 218 with HA)[20, 23, 30]. We divided the data into two subgroups according to the follow up duration (within one year and more than one year). Two studies assessed the total HHS within 1 year(I2=0%)[20, 30]. Pooling the data showed a significantly higher total HHS in the THA group compared to the HA group (MD 4.63, 95% CI 0.44-8.82, Fig.12). Two studies assessed the total HHS after more than one year of follow up (I2=32%), and the data favoured the THA group (MD 5.00, 95% CI 1.74-8.26, Fig.12)[20, 30].
Pain HHS
Two studies assessed the HHS pain in both groups (175 with THA and 197 with HA)[20, 23]. We divided the data into two subgroups according to the follow up duration (within one year and more than one year). Two studies assessed the HHS pain within one year(I2=0%)[20, 23]. Patients in the THA group experienced significantly less pain than patients in the HA group (MD 2.28, 95% CI 0.93-3.64. Fig.13). Two studies assessed the HHS pain after more than one year of follow up (I2=84%), and the data favoured the THA group (MD 3.09, 95% CI 1.78-4.40, Fig.13)[20, 23].
Function HSS
Two studies assessed the HHS function in both groups (171 with THA and 192 with HA)[20, 23]. We divided the data into two subgroups according to the follow up duration (within one year and more than one year). Two studies assessed the HHS function within one year(I2=56%) and the data tended to favour the THA group (MD 1.37, 95% CI -1.54-4.27, Fig,14)[20, 23]. Two studies assessed the HHS function after more than one year of follow up (I2=0%), and the data favoured the THA group (MD 3.48, 95% CI -0.7-6.26, Fig,14)[20, 23].
Eq-5Dindex
Two studies assessed the Eq-5D in both groups with a mean follow up duration of 18m (122 with THA and 120 with HA)[20, 32]. THA group had better Eq-5Dindex score (MD 0.13, 95% CI 0.03-0.22, Fig.15). There was no significant heterogeneity (I2=3%).
Hospital stay
Two studies assessed the length of hospital stay in both groups (132 with THA and 160 with HA). The data trended to favour the HA group (MD 1.30, 95% CI -0.43-4.57, Fig.16)[23, 30]. Heterogeneity across the studies was 0%.