Abstract
Purpose
CentPillar GB HA stem (stryker®) is developed as the stem fitting the Japanese femur, and now there is CentPillar TMZF HA stem (stryker®) as the improvement type of the stem by coating the PureFix HA with plasma spray. We observed the factors which influenced on the stem subsidence between the two-type stems.
Materials and Methods
We intended for 26 hips 23 patients that we performed total hip arthroplasty (THA) during the period between January 2005 and June 2009 and were able to follow up more than three years. 10 males 11 hips and 13 females 15 hips, the mean age at the time of surgery was 56.5 (range, 29–74) years old, and primary diseases were osteoarthritis (OA) in 17 hips, Idiopathic Osteonecrosis of Femoral Head (ION) in six hips, and rheumatoid arthritis (RA) in three hips. 16 hips were treated with the CentPillar GB HA stem (G group), and 10 hips were performed with the CentPillar TMZF HA stem (T group). The examination items are the stem size, the canal fill ratio of the stem (the top of lesser trochanter, the bottom of lesser trochanter, the distal portion of the stem) and the stem alignment (on anteroposterior radiograph and Lauenstein view).
Results
The mean stem subsidence was 1.75 mm (range, 0–8.9 mm) in the G group, and 0.87 mm (range, 0–2.9 mm) in the T group. Although there was no significant difference, it accepted the tendency that the stem subsidence in the G group was larger than its in T group. The case in which the stem subsidence more than 2 mm was found at were 7 hips in the G group, whereas it was only one hip in the T group. The stem size, the canal fill ratio of the stem and the stem alignment were no meaningful effect on the stem subsidence. In F-test, the stem subsidence of the G group had significantly large dispersion compared with the T group (P<0.01).
Discussion and Conclusion
Although there were no significant differences in the stem subsidence between the two groups, the variation of the stem subsidence was significantly small in the T group. We examined the factor which affected the stem subsidence, but neither item recognized meaningful relation, and the influence such as differences of the surface processing was considered. In fact, the strength of the TMZF HA stem improved for the GB HA stem with TMZF titanium alloy, the contact area with the bone spread by coating the PureFix HA with plasma spray, the elasticity of TMZF became closer to the bone, and the strong proximal fixation were enabled. In THA with the GB HA stem, variation of the stem subsidence was significantly large, so considerable attention for the excessive stem subsidence was required.
