Thru purpose of this study was to evaluate the clinical outcomes of a consecutive series of conversion total hip arthroplasty (cTHA) following previous hip fractures.

A retrospective chart review of patients who underwent cTHAs from 2008–2017 at an urban academic teaching institution was performed.

Eighty-eight patients were included in this study. The mean age at the cTHA was 66 years (range 27 to 89). 67% of the patients wre women. The mean BMI was 28 kg/m² (range 17 to 41). The mean Charlson Comorbidity Index was 3 (range 0 to 9). The mean follow-up was 49 months (range 24 to 131). The mean duration from the hip fracture fixation to the cTHA was 51 months (range 10 to 144). The mean operating time was 188 minutes, (range 71 to 423) with a mean estimated blood loss of 780 ml (range 300 to 2500). Revision-type (long-stem) designs were used in 65% of the cases. The mean length of hospital stay was 8 days (range 2 to 61). The readmission rate was 37% within 90 days after the CTHAs. Of these, 57% were due to non-orthopaedic complications. There were 10 orthopaedic complications: 7 PJIs, all of which required I&D and 3 required staged revision. There were 2 dislocations treated with closed reduction and 1 case of intraoperative periprosthetic femur fracture during femoral component insertion. There was no revision for aseptic loosening within the follow-up period. The one-year mortality rate was 0%.

cTHAs were associated with longer operating time, more blood loss, longer length of hospital stay, and higher readmission rates than the primary THAs in our institutional database. We believe utilizing a multi-disciplinary care protocol to optimize these patients is needed to reduce the high rate of readmissions, and the complications in this patient population.

Modular tapered stems have become increasingly popular in femoral revisions and stem subsidence remains a reported clinical problem. Computer modeling and biomechanical testing demonstrated a minimum initial line-to-line fit of 25 mm was required to reduce the risk of subsidence. We examined XR imaging of 110 consecutive femoral revisions by a single surgeon using two different modular tapered stems to determine if this biomechanical threshold was of clinical relevance. 72% of the revisions were done for aseptic loosening and 28% for periprosthetic fracture or infection. Stem subsidence of any degree was observed in 24 (21.8%), while 12 (10.9%) demonstrated substantial subsidence of > 10 mm. We matched this cohort to 12 patients who had no stem subsidence. The average age of patients with subsidence was 59 years (43 to 79 years). The average of patients without subsidence was 66 years (41 to 77 years). Each group had 7 men and 5 women. Stem subsidence was observed in the first 3 months post-surgery. The demographics, bone deficiency, stem design, and stem diameter were similar between groups.

83% of patients with substantial stem subsidence had less than 25 mm of line-to-line fit compared to 17% of patients without subsidence. The 12 cases of no stem subsidence had a mean line-to-line fit of 48 mm (25 to 55 mm). 75% of patients with substantial stem subsidence had also undergone an extended trochanteric osteotomy (ETO) compared to 33% of patients without subsidence.

We conclude that there is a positive correlation with the biomechanical testing parameters and substantial stem subsidence. ETO was found to be associated with higher stem subsidence.