Abstract
Objective
This study shows the radiographic results of total hip arthroplasty (THA) using the Revelation hip system® for hip joint disease.
Methods
We performed THA for hip disease using the Revelation Hip System®. From July 2007 to May 2009, 30cases (35 hips) were available for this study. Radiographic evaluation was performed at the last follow-up. Evaluation items included the presence or absence of subsidence, spot welds, demarcation line, cortical hypertrophy and stress shielding. The stem was designed to be implanted without cement and to be combined to the femur bone at the proximal portion to avoid stress shielding. Zone of Gruen zone 1 was divided into 1A or 1B, above and below the outermost tip of the lateral flare of the stem.
Results
In total, 35 hips had spot welds at zones 1B and 7, and many hips had demarcation lines in zone 4 or 5, but not in zones 1B or 7. Cortical hypertrophy was detected in 6 cases in zone 3, the lateral edge of the stem. Stress shielding was first degree or second degree in 29 hips; however, no cases were identified with more than third-degree stress shielding.
Discussion
At the proximal portion of the stem, spot welds were detected but demarcation lines were not, suggesting that bone ingrowth to the stem and combination of the stem and femur may have been completed in this area. Loading at the medial proximal end may not have occurred with a collarless cementless stem. First-degree stress shielding was thus considered a natural phenomenon that should not be seen as usual stress shielding. Cortical hypertrophy was detected in 17.1% of hips. Although no complaints such as thigh pain were identified, Revelation microMax®, in which the unnecessary distal portion of the stem was shortened, was designed to address this problem.
