Total Hip Replacement Failure Calculator

This calculator estimates the chance that you may need a second surgery (called a revision) on your replaced hip at some point during the rest of your life. It is built on data from a large US Medicare study (Katz et al., 2012) that tracked hip replacement patients over many years. The results shown are conservative, which means the actual risk could be lower than what is displayed.

Demographics

Age at surgery

40 to 90 years

Biological sex

Body Measurements

Height 5′ 4″

Weight 155 lbs

BMI 26.6

Medical History

Inflammatory arthritis Rheumatoid arthritis or similar autoimmune joint condition

Prior hip surgery Any previous orthopedic surgery on this hip

Complicated diabetes Perioperative factor (year 0–1 only): diabetes with eye, kidney, nerve, or vascular complications

Moderate Risk

Adjust the inputs above to calculate your estimated lifetime reoperation risk.

Important: This estimate is anchored to US Medicare registry data and models revision surgery (component replacement or removal) as the primary endpoint. It is intended for educational purposes only and should be discussed with your surgeon. It cannot predict any individual outcome.

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Technical Appendix

1. Evidence Extraction & Model Rationale

Primary baseline: piecewise cause-specific hazard schedule anchored to Katz et al. (2012), a US Medicare cohort study of 12-year revision risk after primary THA with competing-risk methodology. The hazard is time-varying: elevated in year 0–1 (infection, dislocation, periprosthetic fracture), low in years 2–5, then gradually rising (polyethylene wear, aseptic loosening).
Evans et al. (2019) context: a multinational registry meta-analysis (non-US; late follow-up driven primarily by the Finnish Arthroplasty Register) reporting 25-year revision-free survivorship of 57.9 %. This estimate is not used as the model baseline but provides a long-term plausibility reference.
Endpoint: revision surgery (component replacement or removal). Short-term complication endpoints (irrigation & debridement alone) are excluded from the baseline hazard schedule.
MA ascertainment correction: a ×1.15 hazard multiplier applied only from year 13 onward corrects for under-ascertainment in Traditional Medicare claims as patients transition to Medicare Advantage plans, calibrated to the reported 92 % vs 90 % survivorship divergence at 15 years (Lacny et al. 2023).

2. Model Coefficients

Variable	Source	Functional Form	Effect Size
Age at surgery (continuous)	Bayliss et al., 2017	exp(−0.025 × [age − 70])	HR ≈ 2.0 at age 42; ≈ 0.61 at age 90 (vs ref 70)
Male sex (year 0–1)	Katz et al., 2012	Constant HR, time-varying	1.35
Male sex (year 1+)	Katz et al., 2012	Constant HR, time-varying	1.15
BMI (continuous, above 25)	Meta-analytic synthesis	exp(0.030 × max(0, BMI − 25))	HR ≈ 1.16 at BMI 30; ≈ 1.35 at BMI 35
Inflammatory arthritis	Bozic et al., 2014	Constant HR	1.32
Prior orthopedic surgery	Wright et al., 2012	Constant HR	1.35 (from OR 1.45)
Complicated diabetes	SooHoo et al., 2010	Year 0–1 only	1.50 (down-weighted; short-term endpoint)

PVD was removed: SooHoo (2010) reports only short-term complication risk, not long-term revision. Height and weight are replaced by continuous BMI derived from user-entered measurements.

3. Statistical Method

A cause-specific hazard competing-risk model (1-year steps, Beyersmann et al. formulation) calculates the Cumulative Incidence Function (CIF) for revision:

Revision hazard (h_R): time-varying baseline λ(t) × composite HR. The baseline follows a piecewise schedule: 1.20 % year 0–1, 0.45 % year 1–2, 0.35 % years 2–5, 0.45 % years 5–10, rising to 1.05 % for years 25+. A ×1.15 MA correction is applied from year 13 onward.
Death hazard (μ_D): derived from US Life Tables 2023 via μ = −ln(1 − q_x), providing the proper cause-specific (continuous-time) mortality hazard rate rather than using raw q_x probabilities directly.
CIF increment: CIF_R(t+1) = CIF_R(t) + S(t) × [1 − exp(−(h_R + μ_D))] × h_R / (h_R + μ_D).
Overall survival: S(t+1) = S(t) × exp(−(h_R + μ_D)).
Terminal age: recursion runs to age 100; for ages beyond the life table a default high-mortality rate is applied.

4. Plausibility Checks

Reference patient (Female, age 70, BMI 25, no comorbidities): 12-year CIF ≈ 5 % (consistent with Katz lower-bound reference); remaining-lifetime CIF ≈ 10 %.
Younger patient (Female, age 50, BMI 25): remaining-lifetime CIF ≈ 35 %, which is higher due to ~50 years at risk.
Elderly patient (Female, age 80, BMI 25): remaining-lifetime CIF ≈ 4 %, bounded by competing mortality.
High-risk combination (Male, age 50, BMI 40, RA + prior surgery + diabetes): remaining-lifetime CIF ≈ 65 %.

These figures represent the remaining-lifetime probability of revision surgery, not a fixed-horizon rate.