Introduction We believe minimally invasive surgery should be defined by the extent of soft tissue dissection rather than incision length. We describe a new technique that is truly soft-tissue sparing and report our early results.

The surgical approach The landmarks for the incision are identified and an incision is made over the posterior aspect of the greater trochanter. Piriformis is preserved. A capsular repair is performed through drill holes into bone. There are no restrictions to mobility. No specialised instruments are required.

Method The standard posterior approach (group 1) was compared with the PSMI approach (group 2) in a prospective cohort study of 200 consecutive patients over 60 years of age. Patients were scored pre-operatively and followed up prospectively, by a blinded observer.

Results Mean operation time was about 1 hour in both groups. Mean incision length was 21.5 cm in group 1 and 8.4cm in group 2. Mean blood loss in group 1 was significantly higher than group 2 (P< 0.0001). Mean inpatient stay was significantly higher in group 2 (P< 0.0001).

Minimum follow-up was 3 years in group 1 and 1.5 years in group 2. There were 3 dislocations in group 1, and none in group 2. There were 2 re-operations in both groups. The relative improvement in WOMAC scores was significantly greater in group 2 at 3 months and 1 year (P< 0.05).

Conclusion: This is the first study to suggest the benefits of minimally invasive surgery may be prolonged. Cosmesis is a by-product rather than primary objective.