Tapered wedge stems decrease early postoperative subsidence following cementless total hip arthroplasty in Dorr type C femurs compared to fit-and-fill stems

Background: To compare the degree of stem subsidence between two different femoral component designs and to determine the risk factors associated with stem subsidence after cementless total hip arthroplasty (THA) in Dorr type C femurs. Methods: We retrospectively reviewed 91 consecutive hips in 87 patients with Dorr type C proximal femoral morphology who underwent primary cementless THA using a fit-and-fill stem or a tapered wedge femoral stem at our institution between January 2013 and June 2020. A fit-and-fill stem was used in 48 hips and a tapered wedge stem was used in 43 hips. Radiologically, the distance between the apex of the major trochanter and the stem shoulder were measured at three different time points (immediately [0W], one week [1W], and six weeks [6W] after surgery) and the degrees of stem subsidence were assessed by comparing the distance between 0W and 1W, 1W and 6W, and 0W and 6W, respectively. Results: The mean degree of stem subsidence (0W vs. 1W) was 0.25 mm (standard deviation [SD] 0.58) in the fit-and-fill stem group, and 0.24 mm (SD 0.43) in the tapered wedge stem group. There was no significant difference between the two groups (P = 0.4493). However, the mean degrees of subsidence were significantly higher in the fit-and-fill stem group (1W vs. 6W, 0.38 mm [SD 0.81]; 0W vs. 6W, 0.64 mm [SD 1.17]) than in the tapered wedge stem group (1W vs. 6W, 0.17 mm [SD 0.29]; 0W vs. 6W, 0.25 mm [SD 0.35]) (P < 0.05 for both). In addition, the rates of >3 mm subsidence (in which instability can be observed) were 16.7% (8 of 48 hips) and 2.3% (1 of 43 hips), respectively. There was also a significant difference between the two stems (P = 0.0324). Multivariate analysis demonstrated that higher age and fit-and-fill stem were risk factors for >3 mm subsidence after THA in Dorr type C femurs (P = 0.0396 and 0.0227, respectively). Conclusion: Our findings suggest that the tapered wedge stem is more suitable for Dorr type C femurs than the fit-and-fill stem to avoid early postoperative subsidence in cementless THA.

Uncemented Custom-Made Femoral Components

We present our experience of total hip replacement (THR) in younger patients using a custom-made smooth titanium alloy femoral prosthesis. Measurements made from pre-operative marker radiographs allowed creation of templates and subsequent computer analysis to mill the stem prior to surgery. Fifty-one such cementless implants were carried out in 43 patients between January 1993 and June 1996 with follow-up to an average of 47 months. Sixteen hips have required revision to date; 13 of these operations were for aseptic loosening. Two more were awaiting revision, giving an overall failure rate of 35.3 %. The average duration from primary operation to revision was 47 months. Thus, even though the concept of an uncemented custom-made femoral component is attractive, the failure rate was found to be unacceptably high. This device may achieve “fit and fill”, but adequate bone on- or in-growth was not achieved. On the basis of these data we have discontinued the use of this implant since 1996.