Comparison of posterolateral and direct anterior approach in uncemented total hip arthroplasty with a short stem prosthesis

The purpose of this randomized controlled study is to compare posterolateral approach (PLA) and direct anterior approach (DA) in total hip arthroplasty with the NANOS short stem for subsidence, functional outcome, quality of life and isometric hip abduction force over a follow-up period of 2 years.

- The NANOS short stem prosthesis will show less subsidence if placed by means of the direct anterior approach (DAA) compared to the posterolateral approach (PLA) at two years follow-up

- The NANOS short stem prosthesis will show better stem position if placed by means of the DAA compared to the PLA at two years follow-up

- The NANOS short stem prosthesis will show better off-set if placed by means of the DAA compared to the PLA at two years follow-up

- The NANOS short stem prosthesis will show lower pain scores if placed by means of the DAA compared to the PLA

- The NANOS short stem prosthesis will show a better functional outcome and range of motion if placed by means of the DAA compared to the PLA

- The NANOS short stem prosthesis will show higher maximum isometric hip abductor muscle force if placed by means of the DAA compared to the PLA

- The NANOS short stem prosthesis will show a better gait pattern in terms of hip joint angles and hip joint moments in the frontal plain if placed by means of the DAA compared to the PLA

Demographic characteristics - pre-operative



Clinical outcome:

HOOS - pre-operative, 8 weeks, 3 months, 6 months, 12 months, 24 months

VAS - pre-operative, day 1-3, 8 weeks, 3 months, 6 months, 12 months, 24 months

Hospital stay - day 1-3

EQ-5D - pre-operative, 8 weeks, 3 months, 6 months, 12 months, 24 months

Complications - pre-operative, day 1-3, 8 weeks, 3 months, 6 months, 12 months, 24 months



Functional outcome:

HOOS - pre-operative, 3 months, 6 months, 12 months, 24 months

HHS - pre-operative, 8 weeks, 12 months

Quality of balance and walking - pre-operative, 8 weeks, 12 months



Surgical outcome:

Operation parameters - Operation

Pelvic radiography - pre-operative, day 1-3, 8 weeks, 12 months, 24 months

The NANOS short stem femoral component (Smith & Nephew, Memphis, Tennessee, United States of America) in combination with the R3 acetabular component (Smith & Nephew, Memphis, Tennessee, United States of America) will be placed. Both components are ODEP rated. The NANOS stem has previously been placed in the hospital in a research setting investigating short to medium survivorship and function and showed excellent results.

All patients will be submitted to standard postoperative physical therapy and analgesia protocols.

The prosthesis will be placed using a direct anterior or posterolateral approach. Both approaches are regularly performed in hospitals and clinics in the Netherlands and in Noordwest Ziekenhuisgroep location Alkmaar specifically. The two surgeons involved in the study have extensive experience with both approaches and perform at least 40 total hip replacements each year. Therefore, no specific surgical learning curve is expected for either of the procedures.

For the DAA, the patient is placed in a supine position. The hip capsule is reached from the front, utilizing the internervous plane, located between the sartorius muscle and tensor fascia latae muscle superficially, and between the rectus femoris muscle and gluteus medius muscle more profoundly.

The PLA is the most commonly used approach overall in the Netherlands. For the PLA, the patient is placed in the lateral position. The hip capsule is reached from the back, after incising the tensor fascia lata muscle and gluteal fascia, blunt dissection of the gluteus maximus muscle, and releasing the insertions of the piriformis, gemelli and obturator externus tendons.

Intra- and postoperatively patients will be treated according to the standard clinical hip replacement protocol implemented in the NWZ.