Osteoporotic Patients Undergoing Total Hip Arthroplasty Have a Similar 5-Year Cumulative Incidence Rate of Periprosthetic Fracture Regardless of Cemented Versus Cementless Femoral Stem Fixation

BACKGROUND

In osteoporotic patients, surgeons may utilize cemented femoral fixation to minimize risk of fracture. The purpose of this study was to compare 5-year implant survivability in patients who have osteoporosis who underwent elective total hip arthroplasty (THA) with cementless versus cemented fixation.

METHODS

A retrospective analysis of patients who have osteoporosis undergoing THA with either cemented or cementless femoral fixation was conducted using a national administrative claims database. Of the 18,431 identified THA patients who have osteoporosis, 15,867 (86.1%) underwent cementless fixation. The primary outcome was a comparison of the 5-year cumulative incidences of aseptic revision, mechanical loosening, and periprosthetic fracture (PPF). Kaplan-Meier and Multivariable Cox Proportional Hazard Ratio analyses were used, controlling for femoral fixation method, age, sex, a comorbidity scale, use of osteoporosis medication, and important comorbidity.

RESULTS

There was no difference in aseptic revision (Hazard's Ratio (HR): 1.13; 95% Confidence Interval (CI): 0.79 to 1.62; P value: .500) and PPF (HR: 0.96; 95% CI: 0.64 to 1.44; P value: .858) within 5 years of THA between fixation cohorts. However, patients who had cemented fixation were more likely to suffer mechanical loosening with 5 years post-THA (HR: 1.79; 95% CI: 1.17 to 2.71; P-value: .007).

CONCLUSIONS

We found a similar 5-year rate of PPF when comparing patients who underwent cementless versus cemented femoral fixation for elective THA regardless of preoperative diagnosis of osteoporosis. While existing registry data support the use of cemented fixation in elderly patients, a more thorough understanding of the interplay between age, osteoporosis, and implant design is needed to delineate in whom cemented fixation is most warranted for PPF prevention.

Does Femoral Morphology Predict the Risk of Periprosthetic Fracture After Cementless Total Hip Arthroplasty?

BACKGROUND

Periprosthetic femur fracture remains a leading mode of early failure following cementless total hip arthroplasty (THA). The purpose of this study is to determine if a specific femoral morphology is associated with an increased risk of acute, periprosthetic fracture after cementless THA.

METHODS

An institutional arthroplasty registry was used to identify 32 primary, cementless THAs revised for acute, postoperative periprosthetic fracture ("fracture" cohort) within 3 months of the index procedure. Patients were matched 1:2 to 64 THAs without fracture ("control" cohort) for age, body mass index, gender, and stem design. Preoperative radiographic measurements performed on anteroposterior pelvis and femur radiographs included the neck-shaft angle, endosteal width at 4 locations, and external cortical diameter at 2 locations. These measurements were used to calculate the morphological cortical index, canal flare index, canal calcar ratio, and canal bone ratio. Postoperative measurements included canal fill and stem alignment. Statistical analyses included clustered regressions, Fisher's exact test, and Student's t-test.

RESULTS

The mean endosteal width at 10 cm distal to the lesser trochanter was greater in fracture patients, although not statistically significant (P = .1). However, this resulted in differences in the canal flare index (P = .03), canal calcar ratio (P = .03), and canal bone ratio (P = .03) between the 2 cohorts. These ratios indicate decreased meta-diaphyseal taper in fracture patients. Preoperative femoral neck-shaft angle was more varus in fracture patients (P = .04).

CONCLUSION

Patients sustaining an acute, periprosthetic fracture with cementless femoral fixation after THA had thinner distal cortices and a decreased meta-diaphyseal taper.

Reliability and Validity of the Vancouver Classification in Periprosthetic Fractures Around Cementless Femoral Stems

BACKGROUND

The Vancouver classification of periprosthetic femur fractures divides B1 and B2 subtypes based on the stability of the femoral stem. However, this classification was described and validated with cemented femoral stems. We sought to assess reliability and validity of the Vancouver classification in patients with cementless femoral stems.

METHODS

This is a blinded radiographic study which included patients treated for Vancouver B cementless periprosthetic femur fractures between February 2007 and December 2017. Adult reconstruction-trained and trauma fellowship-trained orthopedic surgeons graded all preoperative radiographs using the Vancouver classification on 3 separate occasions. Interobserver and intraobserver reliability was assessed via the Fleiss' kappa statistic. Validity was assessed via accuracy between radiographic and intraoperative assessments. The Landis and Koch criteria were used to interpret the kappa values.

RESULTS

Fifty-three patients with Vancouver B fractures (B1, 8; B2, 45) around a cementless femoral stem were included in the study. Five reconstruction-trained and 5 trauma-trained orthopedic surgeons graded all radiographs. The interobserver reliability kappa value was 0.45 (moderate agreement), with all raters agreeing on only 43% of radiographs. Validity analysis showed demonstrated 79% agreement. Overall, 20% (range, 14%-24%) of unstable B2 fractures were misread as B1 fractures. Intraobserver reliability was 0.71 between readings.

CONCLUSION

The reliability of the Vancouver classification for cementless total hip arthroplasty is lower than previously described in cemented femoral stems. Radiographic assessment alone may be inadequate for determination of stability of cementless stems in periprosthetic femur fractures.

LEVEL OF EVIDENCE

Level III therapeutic study: retrospective comparative study.