The primary purpose of this study is to measure the postoperative changes in bone mineral density, comparing the Taperloc Complete Reduced Distal Microplasty stem and the standard length Taperloc Complete Reduced Distal stem.

The Taperloc Microplasty cementless stem is designed to transmit load to the proximal femur, thereby preserving bone density, and preventing long term instability and loosening secondary to proximal bone resorption. The primary aim of this study is therefore to compare the postoperative changes in bone density with the Taperloc Microplasty stem, using the standard length Taperloc stem as a control.

In addition, the Taperloc stem has historically had a neck angle of 138°. There have been criticisms that this neck angle is too high for the typical Korean population. The newer Taperloc Complete system (both Microplasty and standard length) has a neck angle of 133°. A secondary aim is Occurrence ratio of thigh pain difference between Microplasty and standard stem in Korean Population

Inclusion Criteria:

• Patients suitable for primary Total Hip Replacement

Patients with degenerative joint disease (inflammatory or non-inflammatory) or any of the composite diagnoses of:

1. Osteoarthritis
2. Avascular necrosis
3. Legg Perthes
4. Rheumatoid Arthritis
5. Diastrophic variant
6. Fused hip
7. Sequelae of Slipped capital epiphysis
8. Traumatic arthritis
9. Patients aged over 20
10. Patients must be able to understand instructions and be willing to return for follow-up

Exclusion Criteria:

• Absolute contraindications include: infection, sepsis, and osteomyelitis.

Relative contraindications include:

1. uncooperative patient or patient with neurologic disorders who are incapable of following directions,
2. Small Femoral canal

2) Severe osteoporosis (Patients over 65 years old) 3) metabolic disorders which may impair bone formation, 4) osteomalacia, 5) distant foci of infections which may spread to the implant site, 6) rapid joint destruction, marked bone loss or bone resorption apparent on roentgenogram, and 7) vascular insufficiency, muscular atrophy, or neuromuscular disease. 8) pregnancy 9) Fracture of the pelvis 10) Subcapital fractures