Total Hip Arthroplasty Using the Miniature Anatomic Medullary Locking Stem

Abstract

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 screw 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 stem 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.

Developmental hip dysplasia treated by total hip arthroplasty using a cementless Wagner cone stem in young adult patients with a small physique

“…Although no precise definition of a small physique and narrow femoral canal have been developed in previous studies [6, 25–28], most cementless standard stems in small-proportioned patients are also limited [26] because current cementless stems are designed to extend to the isthmus of the medullary canal to stabilize component alignment and prevent varus migration [7]. When such patients undergo hip arthroplasty, standard cementless femoral stems always encounter this difficulty in insertion, and extensive reaming and rasping are used to obtain safe implantation [29]; however, more vigorous reaming may easily cause perforation or fracture during the operation. Meanwhile, dysplastic hips usually present with excessive anteversion of the femoral head, and anatomical reconstruction of the correct antetorsion should be achieved by rotating the stem in the medullary canal.…”

“…Although several prostheses have been used for treating DDH [8, 26, 28, 29, 31–33], only a few studies have considered the Wagner stem as a possibility [1, 7, 13, 30]. Based on its 5° tapered stem with a circular cross-section, the Wagner cone prosthesis stem can be placed in any anteversion orientation by the surgeon.…”

Three-dimensional custom-designed cementless femoral stem for osteoarthritis secondary to congenital dislocation of the hip

“…Huo et al 17 There are reports of conventional femoral cementless components used in THR for hip dysplasia. [47][48][49][50][51] In a series of 121 THRs with a straight cementless stem with a 9.3-year survival rate of 97.5%, 20 hips required an additional osteotomy and seven femoral fractures occurred. 49 Oh et al 48 studied the outcome of THR in 12 cemented and 40 cementless hips using miniature anatomical medullary locking stems for hip dysplasia or juvenile arthritis, observing that proximal stress shielding occurred in 39 of the 40 femora that underwent cementless fixation.…”

Statistical fallacies in orthopedic research

“…Modern medicine indeed seems to have fragmented human being into a conglomerate of different parts-organs, tissues, etc. An orthopedic surgeon may count the average number of vertebrae in a group of cases of spinal tuberculosis9 or number of knees10 or number of replaced hips 11. Although this might be adequate in some instances, it may be inadequate to assess the magnitude of the problem.…”