Cementless vs Cemented Fixation in Arthroplasty

The mode of fixation of total hip and total knee arthroplasty components — cemented, cementless (biological), or hybrid — is one of the most debated topics in arthroplasty surgery. Cemented fixation uses polymethylmethacrylate (PMMA) bone cement to interlock the implant with the host bone, providing immediate fixation. Cementless fixation relies on bone ingrowth or ongrowth into a porous or roughened implant surface, achieving durable biological fixation over weeks to months. Hybrid fixation (cemented tibial and cementless acetabular cup, or vice versa) is used in specific situations. The optimal choice depends on patient age, bone quality, implant design, and joint.

• Bone cement (PMMA): polymethylmethacrylate is an acrylic polymer that polymerises exothermically after mixing; it does not bond chemically to bone — it achieves fixation by mechanical interdigitation into the cancellous bone interstices; the interface between cement and bone (the cement mantle) is the site of most stress and the origin of aseptic loosening over time; modern cementing technique (second and third generation) significantly reduces early aseptic loosening rates: pulse lavage, drying the canal, retrograde cement filling, cement pressurisation, and avoidance of cement voids
• Cementless fixation surfaces: the implant surface must provide a scaffold for bone ingrowth; porous surfaces (sintered beads — titanium or cobalt-chrome; fibre mesh — titanium; trabecular metal — tantalum with ~80% porosity mimicking cancellous bone; 3D-printed titanium lattice — TiOblast, Tritanium); hydroxyapatite (HA) coating — applied to porous or grit-blasted surfaces; HA is osteoconductive and promotes early bone-implant bonding (HA gradually resorbs as bone grows in); press-fit stability (initial mechanical stability from impaction fit) is essential for cementless fixation — the implant must be stable immediately after insertion to allow bone ingrowth without micromotion (<150 µm micromotion threshold for ingrowth; >150 µm → fibrous tissue ingrowth → failure)
• Bone ingrowth biology: osteoblasts from the host bone migrate into the porous surface; bone bridges the gap over 6–12 weeks; the final biological fixation is potentially more durable than cemented fixation in young active patients; however, immediate fixation is less strong than cemented — partial weight-bearing may be required in the early post-operative period for cementless TKA (though most modern cementless TKA series allow immediate full weight-bearing)

• Cemented TKA — the historical gold standard: cemented TKA has the most long-term survival data of any arthroplasty procedure; registry data (NJR, Swedish Knee Arthroplasty Register) consistently show >95% 10-year survival and >90% 15-year survival for cemented TKA; cemented TKA works well across all age groups and bone quality levels; it remains the most widely performed fixation method globally; the tibial component is the weakest link — tibial component aseptic loosening is the most common mechanical failure mode in cemented TKA
• Cementless TKA — growing evidence: cementless TKA has historically had higher early failure rates (aseptic loosening) than cemented TKA, particularly for the tibial component; however, modern cementless tibial components with improved porous surfaces (trabecular metal, 3D-printed porous titanium) have demonstrated improving medium-term survival; the ATTUNE Cementless (DePuy) and Vanguard (Zimmer Biomet) cementless TKA systems have 5–7 year survival data approaching cemented equivalents; the NJR is now showing equivalent 5–7 year revision rates for modern cementless vs cemented TKA in patients <65 years
• The CANOE RCT (Bonutti et al.) and subsequent trials: early RCTs comparing cemented vs cementless TKA showed superior outcomes for cemented fixation; more recent RCTs comparing modern cementless designs to cemented TKA (including the CANOE trial — the largest contemporary RCT) showed equivalent functional outcomes (OKS, WOMAC) and revision rates at 2–5 years; the evidence is converging towards equivalence for modern cementless designs in appropriately selected patients
• Hybrid TKA: a cemented tibial component + cementless femoral component (`hybrid` or `reverse hybrid`); the tibial baseplate is cemented (historically the weaker component for cementless fixation) while the femoral component is cementless (femoral bone quality is generally better and cementless femoral fixation is reliable); hybrid TKA may represent a pragmatic approach combining the proven tibial stability of cement with the potential biological longevity of a cementless femoral component
• Bone quality assessment for cementless TKA: adequate cancellous bone density at the tibial cut surface is essential for cementless tibial baseplate ingrowth; poor bone quality (osteoporosis, Paget`s, prior steroid use) is a relative contraindication for cementless tibial fixation; the `paper test` (a folded paper inserted between the trial tibial baseplate and the cut tibial surface — if the paper does not grip securely, cemented fixation is used) is a practical intraoperative bone quality assessment tool

• First generation cementing technique (1960s–70s): cement hand-mixed and finger-packed into the femoral canal; high rates of cement voids, inadequate pressurisation, and early aseptic loosening; the Charnley THA using first-generation technique had revision rates of approximately 10% at 10 years from aseptic loosening; no longer used
• Second generation: introduction of intramedullary canal plug (restricts cement to the metaphyseal-diaphyseal zone), pulse lavage (removes fat and blood from the cancellous bone interstices, improving cement penetration), and cement gun (retrograde filling of the canal); significant improvement in cement mantle quality
• Third generation (current standard): all second generation steps PLUS cement pressurisation (a proximal seal allows the cement to be pressurised into the cancellous interstices under pressure — `cement gun under pressure`); vacuum mixing of cement (eliminates air bubbles and cement voids, improving cement mantle homogeneity and fatigue strength by up to 30%); centraliser on the stem tip (ensures a uniform cement mantle around the stem, preventing direct stem-bone contact); modern third-generation technique has reduced 10-year aseptic loosening rates to approximately 1–3% for well-designed cemented stems

• Cemented fixation: PMMA mechanical interdigitation (not chemical bond); immediate stability; excellent long-term data; 3rd generation technique essential (pulse lavage, retrograde fill, pressurisation, vacuum mixing, centraliser); risk of BCIS
• Cementless fixation: press-fit + bone ingrowth; <150 µm micromotion for ingrowth; >150 µm → fibrous tissue; porous surfaces (sintered beads, trabecular metal, 3D-printed Ti); HA coating promotes early bonding
• BCIS (Bone Cement Implantation Syndrome): fat + air + cement monomer + marrow emboli during canal pressurisation; cardiovascular collapse; warn anaesthetist; raise FiO2 to 1.0; Grade 0–3; higher risk in osteoporotic elderly + cardiorespiratory disease; cementless avoids BCIS
• THA age guidance (NJR): cemented or hybrid stem preferred >70 years (osteoporotic bone, immediate stability regardless of ingrowth); cementless preferred <65–70 years (biological durability for longer expected implant life)
• Acetabular cup: almost universally cementless press-fit hemispherical cup in modern THA; cemented all-poly cup retained for elderly frail patients, complex deformity, or when press-fit not achievable
• Cemented TKA: historical gold standard; >95% 10-year survival (NJR); tibial loosening = most common mechanical failure; works across all ages and bone quality
• Cementless TKA: improving evidence with modern porous surfaces; NJR showing equivalent revision rates to cemented at 5–7 years in patients <65; hybrid TKA (cemented tibia + cementless femur) is a pragmatic option
• 3rd generation cement technique: pulse lavage + canal plug + cement gun retrograde fill + pressurisation + vacuum mixing + centraliser; 10-year loosening rate ~1–3%
• Taper-slip principle (Exeter stem): cemented polished taper stem subsides within cement mantle under load, increasing hoop stress and strengthening the cement-bone interface; DO NOT use with bone graft or impaction grafting without understanding this principle