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Background: Mechanically assisted crevice corrosion (MACC) has been associated with the compromised durability and fixation of modular total hip implants, adverse reaction of local tissue, and other undesirable clinical outcomes in total hip arthroplasty (THA). MACC is primarily caused by the relative motion between the femoral head and stem. To minimize the relative motion the taper connection between the two components must be strong enough. The current study addressed the following questions: (1) Does increasing the mass of the femoral stem improve the taper connection strength intraoperatively? (2) Does increasing the mass of the femoral stem reduce the risk of periprosthetic tissue damage intraoperatively?, Hypothesis: Increasing the mass of the femoral stem improve the taper connection strength intraoperatively., Materials and Methods: During the experiment, femoral heads were impacted onto the stem tapers with and without an additional weight attached to the stem. The femoral heads were then pulled off to investigate the strength of the taper connection. The stem displacement and acceleration at impaction were also measured to evaluate the risk of periprosthetic tissue damage., Results: The results showed that the pull-off force was increased by 24% (p=0.011, n=6) when an additional weight was attached to the stem. The additional weight also reduced the maximum stem acceleration and maximum stem displacement by 37% (p<0.001, n=6) and 14% (p=0.094, n=6), respectively., Discussion: These findings suggest that the femoral head and stem taper connection strength can be significantly improved and the risk of periprosthetic tissue damage significantly reduced intraoperatively by attaching an additional weight to the stem to increase its mass., Level of Evidence: III, comparative in vitro mechanical investigation., (Copyright © 2022 Elsevier Masson SAS. All rights reserved.)

While revision of total hip arthroplasty (THA) is being performed with increasing frequency, outcomes of repeated revisions have been rarely reported in the literature. The purpose of this study was to report mid-term outcomes of re-revision of failed revision THA acetabular components. We performed at least two revisions of the failed acetabular component in 57 patients (57 hips) between August 1996 and April 2008. Of these, 15 patients with infection were excluded and one died before 4-year evaluation. The final study cohort consisted of 41 patients (41 hips) with a mean age of 55.5 years (range, 37 to 82). Preoperative acetabular bone defects was classified as Paprosky Type IIA in 4 hips, Type IIB in 6, Type IIC in 9, Type IIIA in 16, and Type IIIB in 6. The mean duration of follow-up was 7.2 years (range, 4 to 15). Mean Harris hip score improved 45 points preoperatively to 83 points postoperatively. Six hips (14.6%) required additional revision procedure: 3 for aseptic loosening, 2 for deep infection, and 1 for recurrent instability. Complications included 2 dislocations and 1 peroneal nerve palsy. Kaplan-Meier survivorship with an end point of reoperation for any reason was 88.5% (95% CI, 78.0% to 100%) at 7.2 years. For aseptic loosening of the acetabular component, the survival was 91.8% (95% CI, 80.8% to 100%) at 7.2 years. Rerevision with contemporary uncemented cup or antiprotrusio cage for failed revision THA acetabular components showed encouraging mid-term outcomes for this technically challenging condition.

Objective: The ROBODOC system offers the theoretical advantage of providing better fit and mechanical stability of the stem in total hip arthroplasty. However, there has been no previous study on short metaphyseal-fitting stem implantation using the ROBODOC system. The aim of the present study was to compare the implant position and primary stability of short metaphyseal-fitting stems implanted by robotic milling and manual rasping in a human cadaveric femoral model., Methods: Eight matched pairs of human cadaveric femora were randomly assigned to a robotic milling group or manual rasping group. Operative time and intraoperative femoral fractures were monitored, and radiographic evaluation of stem alignment was performed by comparison of preoperative planning and postoperative CT data. Stability testing was performed on six matched pairs of femora, excluding two specimens in which intraoperative fractures occurred., Results: The robotic milling procedures took an average of 27 minutes longer than the manual rasping procedures (p < 0.001). The robotic milling group exhibited significantly better anteroposterior alignment and vertical seating, and also showed a significantly reduced variability in both alignment and vertical seating. No intraoperative femoral fracture was detected in the robotic milling group, whereas two femoral fractures and one femoral stem tip perforation were detected in the manual rasping group. Stability testing showed no significant difference in translational and rotational migrations between the two groups, although the robotic milling group showed a trend towards reduced variability of stability., Conclusions: Our cadaveric study suggests that the use of the ROBODOC system for short metaphyseal-fitting stem implantation may have advantages in improving implant fit and reducing the risk of intraoperative femoral fractures without compromising primary stability.

We present our experience of contemporary cementless total hip arthroplasty (THA) conducted at a single institution to treat advanced avascular necrosis (AVN) in renal transplant patients. Between October 1997 and October 2008, 45 consecutive primary cementless THAs were performed in 30 patients with advanced AVN after renal transplantation. There were 18 males (27 hips) and 12 females (18 hips) (patient group) with an overall mean age 44 years (22 to 68). The clinical and radiographic results were compared with those of 96 sex and age-matched osteonecrotic hips in 72 patients that had not undergone organ transplantation or long-term steroid therapy (the control group). Patients were evaluated at surgery and at a mean of 7.2 years (2 to 13 years) postoperatively. The mean Harris hip score of patients improved from 48 points preoperatively to 94 points at last follow-up (p<0.05). Three hips in the patient group had massive osteolysis with polyethylene wear requiring revision surgery. One hip in the patient group underwent revision surgery because of recurrent dislocation at 11 years postoperatively. No intergroup differences in overall rates of complications or revisions were observed. However, transplant patients had a significantly higher rate of ectopic ossification. Despite diffuse osteopenia and chronic immunosuppression in renal transplant patients with osteonecrotic hips, cementless THA showed durable implant fixation to bone and no increased risk of complications.

Purpose: Although isolated revision of the acetabular component has become an increasingly common option for revision hip surgery, opinions differ regarding the ideal surgical approach for reducing postoperative instability. The purpose of this study was to compare the clinical and radiographic results of isolated acetabular revision performed using a posterolateral and an anterolateral approach., Materials and Methods: The authors retrospectively compared the clinical and radiographic results of isolated acetabular revision performed in 33 hips using a posterolateral approach with those performed in 36 hips using an anterolateral approach. All procedures were performed by a single surgeon and all patients received the same postoperative protocol. Mean duration of follow-up was 4.6 years (range 2-13.2)., Results: Mean postoperative Harris hip scores were similar in the posterolateral and anterolateral groups (86.5 and 87.2 points, respectively). In the entire series of 69 hips, 6 (9%) underwent re-revision of the acetabular component because of aseptic cup loosening in 4, recurrent dislocation in 1, and deep infection in 1. No significant difference was found between the two groups with respect to complication or re-revision rates, but the dislocation rate in the anterolateral approach group was significantly lower than that in the posterolateral group (0 vs. 12%, p = 0.047)., Conclusion: Isolated acetabular revision performed using an anterolateral approach seems to be the more viable option in selected patients, and in particular, it has a significantly lower postoperative dislocation rate than posterolateral acetabular revision.