Total Hip Arthroplasty Using the Miniature Anatomic Medullary Locking Stem

We report the outcome of a prospective consecutive series of 52 primary total hip arthroplasties using the miniature porous-coated Anatomic Medullary Locking stem in patients with small anatomic proportions because of hip dysplasia or juvenile chronic arthritis. The mean age of the patients at the time of surgery was 28.7 years (range, 14-56 years). The average body weight and height of the patients were 51.8 kg (range, 38.5-78.3 kg) and 157.1 cm (range, 142.2-183 cm), respectively. The stem was cementless in 40 hips and cemented in 12 hips because of poor bone stock. A cementless acetabular cup with screws was used in all hips. The average followup was 7.1 years (range, 3-15.6 years). The Harris hip scores improved from an average of 31.2 points (range, 3.1-68.8 points) preoperatively to 82.8 points (range, 61.1-96.6 points) at latest followup. Three of 12 (25%) cemented and two of 40 (5%) cementless stems were revised. Four of seven 42-44-mm cups were revised. The miniature Anatomic Medullary Locking cementless femoral stem provides a satisfactory outcome in patients with small anatomic proportions. However, wear and osteolysis with the use of a small cementless polyethylene liner remain challenges.

Level of Evidence: Therapeutic Study, Level II (prospective comparative study). See the Guidelines for Authors for a complete description of levels of evidence.