Purpose: To evaluate the clinical and radiographic mid-term results of short-stem total hip arthroplasty (THA) in patients with osteonecrosis of the femoral head (ONFH). Methods: We reviewed 83 cases that underwent Metha stem between November 2010 and November 2012. The appearance of bone trabeculae development and radiolucent line were reviewed and HHS was recorded at 6 months postoperatively then yearly to evaluate the clinical results. Results: The mean age of patients was 43.8 years with the mean follow-up 69.3 (60–84) months. Harris Hip Score improved significantly from 44.7 preoperatively to 99.6 at the last follow-up ( p < 0.0001). There were 4 cases (4.8%) of intraoperative femoral fractures. There was 1 case (1.2%) of distal stem perforation that had stable bone ingrowth and there was 1 case (1.2%) of 5-mm subsidence, which was then stable at 3 months postoperatively. Bone trabecular development was detected at zone 1 (65.1%), 2 (69.9%), 3 (14.4%), 4 (1.2%), 6 (97.6%) and 7 (81.9%). There was 1 case (1.2%) where radiolucent lines were observed in zones 1 and 7. There was 1 femoral stem revision from periprosthetic fracture 4 years after index surgery and 1 cup revision from aseptic loosening. Kaplan-Meier survivorship with the end point of stem revision for any reason was 98.8% and for aseptic loosening it was 100% at 7 years. Conclusions: The mid-term clinical and radiographic results of the Metha stem in patients with ONFH were promising. Its design enables preservation of the bone stock and the bone trabeculae appear to confirm the assumption of proximal force transmission.

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Background: Cup malalignment increase impingement, dislocation, cup migration, and polyethylene wear. Screw fixation for enhanced stability is the preferred option in cases of doubtful primary cup stability. There have been few studies about alignment changes after screw fixation, which may be another cause of cup malalignment. This study aimed to evaluate cup alignment change after screw fixation. Materials and Methods: Patients undergoing imageless navigation total hip arthroplasty using screws fixation for acetabular cup were corrected. After the press-fit cup was fully seated, the cup orientation was recorded. After screws were inserted, the cup orientation was recorded again to calculate the alignment change. Results: There were 99 cases with a mean age 63.7 years (25–93). Alignment change after screw fixation was found in 73 cases (73.7%). There were 56 cases (56.6%) with inclination angle change and the mean change was 2.21° (0°–8°). The inclination angle increased in 47 cases (47.5%) with 9 cases (9.1%) increased by 5° or more and decreased in 9 cases (9.1%). There was statistically significant difference between patients using one screw and patients using two or more screws in inclination angle change, 1.56° (0°–5°) and 3.4° (0°–8°), respectively ( P = 0.0039). There was statistically significant correlation between inclination angle change and number of screws ( r = 0.5401, P < 0.01). There were 49 cases (49.5%) with anteversion angle change and the mean change was 1.67° (0°–5°). The anteversion angle increased in 31 cases (31.3%), decreased in 18 cases (18.2%) with two cases (2%) decreased by 5° or more. There was significant difference between patients using one screw and patients using two or more screws in anteversion angle change, 1.46° (0°–5°) and 2.21° (0°–5°), respectively ( P = 0.009). There was significant correlation between anteversion angle change and number of screws ( r = 0.284, P = 0.048). Conclusions: Changes in cup alignment after screw fixation were detected in most cases. It is one possible cause of cup malalignment.

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