To explore the learning curve of SuperPATH minimally invasive total hip arthroplasty and evaluate its clinical application value.

A retrospective study was conducted of consecutive 85 osteoporotic femoral neck fracture patients who had been treated with SuperPATH minimally invasive total hip arthroplasty from August 2014 to December 2018 at Department of Orthopedic, Affiliated Hospital/Clinical Medical Collage of Chengdu University. There were 24 males and 61 females, with an average age of (62±3.3) years (57-70 years). All operations were completed by the same medical group.The patients were divided into 4 groups (n=85) according to the date of operations: group A (n=21), group B (n=21), group C (n=21) and group D (n=22). The operative time, incision length, intraoperative hemorrhage, perioperative complications, anteversion of acetabular prosthesis and Harris hip score at 6 weeks were statistically analyzed and compared between 4 groups. The Log curve regression analysis was used to reflect the change trend of operation time with the number of operation cases. [y=aln(x)+b, x indicating the number of surgical cases, y operation time].

85 patients were fully followed up, with a follow-up rate of 100%. The follow-up time was 5 to 12 months, with a median follow-up time of 8 months. The 4 groups were comparable due to insignificant difference in age, gender, fracture type, time from injury to operation. There was no sciatic nerve injury in the four groups (n=0) but one hip prosthesis dislocation in group A and one incision infection in group B showing no significant difference in each group (9.5%, 4.7%, 0%, 0%) (P>0.05). There was no significant difference in Harris hip score between 4 groups at six weeks after operation. The operation time for the 4 groups respectively (122.05±6.13)min,(115.43±9.22)min, (106.71±7.23)min, (98.64±4.46) min showing significant differences between 4 groups (P<0.01) and significant differences between group A and B versus group C and D (P<0.01) but no significant differences between group C and D (P>0.05). The Log curve regression analysis showed that the operation time [y=8.778ln(x)+141.11, r²=0.5158, P<0.01] decreased significantly with the increase of operation number but stable in group C and D. There were significant differences among the four groups in the intraoperative hemorrhage (ML), incision length (CM) and the anteversion of acetabular prosthesis (P<0.01).

The perioperative complications rate and postoperative hip Harris score of SuperPATH minimally invasive total hip arthroplasty does not change with the number of cases increased but the operation time, incision length and intraoperative hemorrhage decreased significantly with the increase of the number of cases.The anteversion angle of acetabulum prosthesis was close to the ideal anteversion angle of 20° with the increase of the number of cases. The SuperPATH minimally invasive total hip arthroplasty has learning curve but becomes stable very fast, indicating the technique is easy to learn.