Various approaches are described in the literature for implanting a total hip replacement (THR), without scientific evidence to support the superiority of one type of approach over the others, and with good long-term radiological and clinical results.1 The choice of the surgical approach to use is influenced by the surgeon's experience, patient-related factors and even geographical trends.2 Proper management of soft tissues parts needs to be one of the orthopaedic surgeon's objectives in order to achieve a satisfactory short-term result, regardless of the type of approach used for implanting a THR. Minimally invasive surgery (MIS) approaches were developed to achieve rapid recovery and reincorporation to daily living and work activities.3

In 2011, Dr Chow developed the MIS approach to THR using the supercapsular percutaneously assisted total hip (SuperPath®, MicroPort Orthopedics Inc., Arlington, TN, USA) approach,4 which combines elements of 2 posterior MIS approaches: the percutaneously assisted approach of Path® (MicroPort Orthopedics Inc., Arlington, TN, USA)5 and the superior capsular THR (SuperCap®, MicroPort Orthopedics Inc., Arlington, TN, USA) approach.6 Recent studies have shown satisfactory short-term results, correct radiological position of the prosthetic components, and a low rate of complications.7–10

The objective of our study was to determine the short-term results of a cohort of patients that had undergone a THR intervention using the SuperPath approach, and compare the results with a cohort of patients operated for THR using conventional posterior approach. Our working hypothesis was that the SuperPath approach would make it possible to obtain results similar to those of the posterior approach.

Our hip function results during the learning curve of the SuperPath approach have been similar to the short-term results of the posterior approach in the surveys used, except for the iHOT-12 questionnaire at 3 months, and the SF-12 physical and SF-12 mental at 12 months, with a higher score and a significant difference in the SuperPath cohort. In another comparative study on 46 hips operated using the SuperPath approach and 46 hips with the posterior approach, Xie et al.10 report significantly greater values at 1 week, 1 month and 3 months in the Harris Scale and Barthel Index; a lower pain level on a visual analogue scale (VAS); shorter time to get up from a chair, walk 3m and return to the chair (Timed Up and Go [TUG] test); and less time to go up and come down 12 steps (Timed Stair Climb [TSC] test); and there were no differences at 12 months. Our findings coincide in that there are statistically significant differences in 1 of the surveys at 3 months, but not in detecting differences at 12 months. Preserving the external rotators might facilitate a quicker functional recovery of the operated hip, as a greater score at 3 months in the iHOT-12 survey shows. However, it would be logical for functional outcomes to be similar with the follow-up. The statistically significant differences in the SF-12 questionnaire at 12 months are produced by a decrease in the values in the posterior cohort, while they remain the same in the SuperPath cohort. A longer patient follow-up would allow us to confirm whether the differences increase or decrease.

The posterior approach is the one most used in prosthetic hip surgery, allowing wide exposure of the joint through muscular-capsular detachment of the external rotators, facilitating implant insertion and preserving the gluteal musculature. The SuperPath approach is close to the posterior approach, allowing preservation of the external rotators, respecting the iliotibial band, and requiring specific instruments; but it is performed on a conventional operating table for orthopaedic surgery and allows changing to the posterior approach if necessary.

Preserving the external rotators should be an advantage in reducing the incidence of prosthetic dislocation. Xie et al.10 report a dislocation in their series of 46 hips operated using the SuperPath approach (2.1%). Gofton et al.7 publish 4 dislocations in 479 hips operated (.8%). Rasuli and Gofton9 indicate a dislocation in 50 hips (2%). In our series, there were no cases of dislocation. A future line of research might be the use of the SuperPath approach in patients with a greater risk of prosthetic dislocation, such as elderly patients with subcapital fracture of the femur. Han et al.22 share the outcomes of 2 cohorts of patients older than 65 years with subcapital fracture of the femur and associated neurological disorder that were operated using the posterior approach preserving the rotators compared with the conventional posterior approach: there are 0% of dislocations in the group in which the rotators are preserved compared with 7.7% in the group in which the conventional approach is used.

Blood loss in prosthetic hip surgery is related to the bleeding at the level of the osteotomy and the medullary cavity. Smaller soft tissue dissection in the SuperPath approach should be linked to less bleeding and fewer transfusions. Gofton et al.7 report a 3.3% need for transfusion in their series of 479 hips; Rasuli and Gofton,9 4% in 50 hips; Chow and Fitch,23 1.9% in 419 hips; and Cardenas-Nylander,2 9.5% in 21 hips. Xie et al.10 indicate 4.3% compared with 11% in the posterior approach cohort, and a blood loss of 303.6ml compared with 326.4ml; the differences were not statistically significant. In our series, the decreases in Hb and Hto, and the blood loss were significantly greater in the SuperPath cohort, possibly because of a greater operative time. In spite of this, no patient required autologous blood transfusion.

The correct position of the prosthetic components is essential for medium- and long-term implant survival. The smaller exposure in el SuperPath approach might, theoretically, be associated with improper implant position. Della Torre et al.8 report an acetabular inclination angle of 40.1° in their series of 66 hips, with properly implanted femoral components. Carlomagno2 indicate an acetabular angle of 44.0°, while that of Rasuli and Gofton9 is 39.0°. Xie et al.10 publish an acetabular angle of 43.6° and 93.4% of neutral femoral alignment, without statistically significant differences with the posterior cohort. In our series, the acetabular angle was 47.6°, with no statistically significant differences with the posterior cohort, and the alignment of the femoral component was neutral in all the cases. To determine acetabular orientation, using the transverse acetabular ligament as a guide is recommended, as well as using the intraoperative radioscopy to align the femoral stem correctly.

Some authors report a shorter hospital stay in patients operated using the SuperPath approach. Gofton et al.7 indicate a mean admission of 1.6 days in their series, with 50% fewer days than the data published by the National Agency for Healthcare Research and Quality. Rasuli and Gofton9 report a mean stay of 2.2 days. Carlomagno2 indicates a mean stay of 4.7 days, with a mean reduction of 1.4 days compared with a posterior approach cohort. And Xie et al.10 publish a mean hospital stay of 8.3 days, as against the 11.4 days for the posterior cohort. In our series, the mean stay in the SuperPath cohort was 2.2 days, with a mean reduction of 0.2 days, although the differences were not statistically significant.

Operative time usually increases in the learning curve for a new surgical approach. Chow and Fitch23 report a mean operative time of 142.7min, compared with the 102.8min indicated by Carlomagno.2 Xie et al.10 relate a mean time of 103.6min, similar to the 106.5min in the posterior cohort. With 69.5min, our operative time was less than that published in the literature, but significantly longer than in the posterior cohort (56.1min). This fact might have played a role in the greater bleeding in the SuperPath cohort, even though it is an approach that preserves the soft tissues better.

Periprosthetic fracture is another problem associated with using the SuperPath approach. Chow and Fitch4 report 3 intraoperative fractures: 2 femoral and 1 acetabular. The 3 occurred in patients with a prior history of osteoporosis. Carlomagno2 indicates 1 intraoperative femoral fracture. Xie et al.10 do not communicate this complication. In our series, we had 1 intraoperative acetabular fracture, likewise in a patient with a history of osteoporosis, and possibly due to excessive acetabular reaming.

The need for hospital readmission during the first month after the THR raises the cost of the healthcare process by up to 40%.7 Two recent studies indicate a lower readmission rate in the patients operated using the SuperPath approach. In their multicentre study on 479 THR implanted using the SuperPath approach, Gofton et al.7 report 2.3% of readmissions during the first 30 days after surgery, which represents a reduction of 1.9% over the national mean in the USA. And Chow and Fitch23 indicate, in a comparative study between 419 THR using the SuperPath approach and 1673 THR implanted using other approaches, 0.4% of readmissions as against 2.9%. In our series, no readmissions were registered during the first month after surgery in the SuperPath cohort.

Our study presents limitations as far as the number of cases in the SuperPath approach group, although it should also be remembered that the learning curve for the technique is considered in the series. There is also the fact that different stem-stem models were used in the 2 cohorts, although we consider that they are similar cementless prosthesis models without any differences in friction torques or femoral head size used. Another limitation is the surgeon-dependent distribution of the patients into the SuperPath or posterior approaches. However, the study also has various strengths. It is a cohort-paired prospective analytical study, with 6 evaluation tools (2 that were objective and 4, subjective) applied to all the patients. In addition, no patients were lost in the follow-up.

The learning curve for the SuperPath approach presents radiological and clinical results similar to those of the posterior approach during the first year after the THR. It should be pointed out that the SuperPath approach requires a longer skin-to-skin operative time and has greater patient bleeding.

Level of evidence III.

The authors have no conflicts of interest to declare.