Paprosky Classification
Classification of femoral defects in revision total hip arthroplasty
Paprosky WG · Instr Course Lect · 1994
The Paprosky femoral defect classification system categorises proximal and diaphyseal femoral bone loss in revision total hip arthroplasty to guide stem selection and predictable distal bypass fixation.
Citation & links
Paprosky WG. Classification of femoral defects in revision total hip arthroplasty. Instr Course Lect. 1994;43:389-397.
Key findings
- 1.Type I defects demonstrate minimal metaphyseal bone loss with intact cortices and an intact proximal metaphysis/calcar, allowing standard primary cementless or cemented femoral stem revision.
- 2.Type II defects exhibit extensive metaphyseal bone loss (non-supportive calcar/metaphysis) but retain complete diaphyseal bone stock with greater than 4 cm of intact cylindrical diaphyseal cortex, requiring cylindrical extensively porous-coated or tapered stems bypassing the metaphysis.
- 3.Type IIIA defects feature severe metaphyseal bone loss and partial proximal diaphyseal compromise, yet preserve at least 4 cm of intact cylindrical diaphyseal bone distal to the lesser trochanter for diaphyseal scratch-fit fixation.
- 4.Type IIIB defects represent extensive metaphyseal and diaphyseal bone loss with less than 4 cm of intact diaphyseal cylinder remaining, rendering standard cylindrical extensively porous-coated stems prone to failure and necessitating modular/fluted tapered titanium stems or impaction grafting.
- 5.Type IV defects are characterized by circumferential loss of proximal and diaphyseal architecture with an extremely widened, thin-walled, or deficient isthmus and no functional diaphysis remaining.
- 6.The 4-cm intact diaphyseal bone threshold serves as the fundamental critical anatomical landmark determining whether standard extensively porous-coated monobloc cylindrical stems provide adequate axial and torsional stability.
- 7.Higher defect classes directly correlate with increasing technical complexity, necessity for specialized revision stems, and greater risks of subsidence or nonunion.
Background
Femoral revision in the setting of severe osteolysis and implant loosening poses substantial challenges regarding structural support and implant stability. Prior to this landmark work, femoral bone loss lacked a standardized, treatment-guiding classification system based on biologic fixation potential. Paprosky sought to correlate patterns of proximal and diaphyseal bone deficiency on plain radiographs with intraoperative findings, specifically evaluating the capacity of the remaining femoral host bone to support cementless revision stems and determining when distal diaphyseal bypass fixation is required.
Methods
The authors established a descriptive radiographic classification system derived from a consecutive series of revision total hip arthroplasties with bone deficiency. Preoperative anteroposterior and lateral radiographs were systematically evaluated for the degree of metaphyseal bone loss, calcar integrity, and the length of remaining intact cylindrical diaphyseal cortical bone distal to the lesser trochanter. Defects were stratified into distinct structural types based on whether reliable biological fixation could be achieved metaphaseally or required bypass into the distal diaphysis using extensively porous-coated or fluted tapered revision implants.
Clinical implications
The Paprosky classification transformed revision hip arthroplasty by shifting the focus from subjective descriptions of bone loss to functional, fixation-based preoperative planning. It established the 4 cm intact diaphyseal rule, directing surgeons toward extensively coated cylindrical stems for Type II and IIIA defects, modular/monobloc tapered fluted stems or impaction grafting for Type IIIB defects, and distal interlocking implants, allograft-prosthetic composites (APC), or proximal femoral replacements (megaprostheses) for Type IV bone loss.
Critical appraisal
The system provides an intuitive, treatment-oriented algorithm that directly influences implant selection and surgical technique. However, it relies heavily on plain radiographs, which may underestimate three-dimensional bone loss and rotational cortical deficits compared to modern computed tomography. Furthermore, inter- and intra-observer reliability in independent studies has ranged from fair to substantial, with the distinction between Type IIIA and IIIB often causing the most inter-observer discrepancy in borderline cases.
Teaching note
Examiners expect candidates to state the exact classification criteria: Type I (intact metaphysis), Type II (deficient metaphysis, intact diaphysis >4 cm), Type IIIA (deficient metaphysis, ≥4 cm intact diaphysis), Type IIIB (deficient metaphysis, <4 cm intact diaphysis), and Type IV (deficient diaphysis/widened canal). Always remember: 4 cm of intact cylindrical diaphysis is the watershed between Type IIIA and IIIB.
Exam-tested points
- ›Type I: Minimal metaphyseal bone loss; can use standard primary stems.
- ›Type II: Metaphyseal bone non-supportive; intact diaphysis with >4 cm cylindrical contact; managed with standard extensively porous-coated stems.
- ›Type IIIA: Metaphyseal bone loss extending into proximal diaphysis; crucial rule is that ≥4 cm of intact cylindrical diaphysis remains below the isthmus/lesser trochanter.
- ›Type IIIB: <4 cm of intact diaphyseal cylinder; cylindrical stems risk subsidence; tapered fluted modular/monobloc stems or impaction allografting are indicated.
- ›Type IV: Complete loss of diaphyseal cylinder with widened canal; requires modular fluted stems engaging the distal metaphysis/epiphysis, allograft-prosthetic composite (APC), or proximal femoral replacement (PFR).
- ›Measurement benchmark: The 4-cm cylindrical threshold is referenced on the AP radiograph below the level of the defect/lesser trochanter.
- ›Implant selection link: Cylindrical extensively porous-coated stems rely on a scratch fit of at least 4 cm; modular fluted tapered stems can achieve axial and rotational stability in as little as 2 cm of intact diaphyseal cortical bone.
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