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37 visible knowledge nodes in arthroplasty
Arthrofibrosis after Arthroplasty
Defined as knee stiffness after TKA, usually 10° extension loss. Incidence: 3–6% after TKA. Causes: poor rehab, malposition, infection, scar tissue formation. Management: early manipulation under anesthesia (MUA), arthrolysis, revision if mechanical cause. Prevention: adequate pain control, early physiotherapy, correct alignment.
Open topicAseptic Loosening in Arthroplasty
Most common cause of late arthroplasty failure. Pathophysiology: particle-induced macrophage activation → cytokine release → osteolysis. Risk factors: polyethylene wear, malalignment, micromotion, poor cementing technique. Clinical: pain, progressive radiolucent lines, migration. Management: revision arthroplasty with improved fixation and bearing surfaces.
Open topicBearing Surfaces in Hip Arthroplasty (MoM, MoP, CoC, CoP)
Main bearing couples: Metal-on-Polyethylene (MoP), Metal-on-Metal (MoM), Ceramic-on-Ceramic (CoC), Ceramic-on-Polyethylene (CoP). MoP: gold standard; risk of wear/osteolysis; improved with highly crosslinked PE. MoM: large heads, low wear but metal ions, ALTR, pseudotumors; largely abandoned. CoC: lowest wear; risk of squeaking, fracture. CoP: good compromise — low wear, no squeaking; increasingly preferred.
Open topicCementless vs Cemented Fixation in Arthroplasty
THA: cementless acetabular components standard; femoral fixation cemented (elderly) vs cementless (younger). TKA: tibial components commonly cemented; cementless options increasing with porous coatings in the young. Cemented: immediate fixation, proven longevity; risks include cement implantation syndrome. Cementless: biologic ingrowth; risk of early micromotion if poor bone stock. Choice individualized by bone quality, age/activity, and surgeon expertise.
Open topicComplications of Total Hip Arthroplasty (THA)
Early complications: dislocation, infection, nerve injury, DVT/PE. Late complications: aseptic loosening, periprosthetic fracture, heterotopic ossification, osteolysis, implant wear. Dislocation risk factors: posterior approach, malposition, neuromuscular disorders. Nerve injuries: sciatic > femoral; incidence ~1%. Infection: incidence 0.5–2%; requires DAIR or revision.
Open topicComputer-Assisted / Navigation-based Arthroplasty
Computer-assisted surgery (CAS) improves component alignment in TKA/THA. Techniques: imageless and CT-based navigation. Benefits: improved mechanical axis alignment, reduced outliers, useful in deformity. Limitations: longer OR time, cost, learning curve; functional/survivorship benefits inconsistent. Adjunct tool especially in complex anatomy.
Open topicDislocation after THA — Risk Factors & Management
Incidence 1–3% after primary THA; higher in revision. Risk factors: posterior approach, malpositioned cup (anteversion 25°, inclination >60°). Patient factors: neuromuscular disease, dementia, noncompliance. Management: closed reduction, bracing; revision for recurrent instability. Prevention: proper cup position, posterior repair, large femoral heads.
Open topicExtensor Mechanism Failure after TKA
Includes quadriceps tendon rupture, patellar fracture, patellar tendon rupture, patellar component failure. Risk factors: previous surgery, patellar resurfacing, malalignment, steroid use. Presentation: extensor lag, inability to extend knee, palpable gap. Management: direct repair (acute), augmentation with graft/allograft (chronic). High failure rates with chronic repairs — need reinforcement.
Open topicHemiarthroplasty Hip — Indications
Most common indication: displaced femoral neck fracture in elderly. Types: unipolar (Austin-Moore, Thompson) vs bipolar prostheses. Advantages: shorter surgery, less blood loss vs THA. Disadvantages: acetabular erosion, groin pain in long term. Choice depends on age, activity, acetabular status.
Open topicHeterotopic Ossification after Hip Arthroplasty
HO = abnormal bone formation in periarticular soft tissues after surgery or trauma. Incidence after THA: 20–50%; clinically significant in 5–10%. Risk factors: male sex, hypertrophic OA, ankylosing spondylitis, previous HO. Classification: Brooker I–IV (X-ray based). Prophylaxis: NSAIDs, radiotherapy; treatment = excision if severe functional limitation.
Open topicHip Resurfacing Arthroplasty
Bone-conserving alternative to THA; resurfaces femoral head with metal cap. Indicated in young, active patients with OA, good bone stock, large femoral head size. Advantages: bone preservation, easier conversion to THA, lower dislocation risk. Complications: femoral neck fracture, aseptic loosening, metal ion release (cobalt/chromium). Decline in popularity due to metal-on-metal concerns; selected patients may still benefit.
Open topicInstability after TKA
Accounts for ~20% of TKA revisions. Types: extension instability, flexion instability, mid-flexion instability, recurvatum. Causes: ligament imbalance, component malposition, polyethylene wear, PCL incompetence. Diagnosis: clinical exam, stress radiographs, CT for component position. Management: revision TKA with constrained implants as per instability type.
Open topicModular Taper Junctions & Trunnionosis
Trunnionosis = corrosion/wear at head–neck modular junction of THA. Mechanism: fretting + crevice corrosion, leading to metal ion release. Clinical: unexplained pain, swelling, adverse local tissue reaction (ALTR). Diagnosis: ESR/CRP to rule out infection; elevated cobalt/chromium; MRI (MARS) for pseudotumor. Management: revision with ceramic heads, titanium sleeves; avoid further corrosion.
Open topicOsteolysis & Wear in Arthroplasty
Biologic response to wear particles (polyethylene > metal/cement) drives periprosthetic osteolysis via macrophage cytokine cascade. Risk factors: conventional PE, thin liners, malalignment, edge-loading, high activity, third-body wear. Radiology: progressive radiolucent lines, endosteal scalloping, cystic defects; CT helpful for pelvic osteolysis; metal artifact reduction MRI. Prevention: highly crosslinked PE (HXLPE), ceramic heads, proper component position, larger heads with caution for trunn...
Open topicOutpatient / Day-care Joint Replacement — Safety & Protocols
Enhanced recovery protocols (ERAS) enable same-day/next-day discharge in selected patients. Selection: ASA I–II, motivated, good support, no major comorbidities or bleeding risks. Protocol: multimodal anesthesia/analgesia, tranexamic acid, early mobilization, standardized discharge criteria. Benefits: lower cost, reduced infection risk, high satisfaction; challenges include safety in high-risk groups. Telemonitoring and home PT expand feasibility.
Open topicPatellar Resurfacing in TKA — Controversies
Controversial: to resurface or not during TKA. Resurfacing: reduces anterior knee pain, avoids secondary resurfacing procedures. Non-resurfacing: avoids patellar complications (fracture, maltracking, loosening). Selective resurfacing based on patellar status increasingly practiced. Registry data show mixed outcomes; no universal consensus.
Open topicPatellofemoral Complications in TKA
Commonest source of dissatisfaction after TKA. Includes anterior knee pain, maltracking, subluxation/dislocation, fracture, loosening of patellar component. Risk factors: malrotation of femoral/tibial components, improper patellar preparation, soft tissue imbalance. Investigation: clinical exam, skyline view radiographs, CT for malrotation. Management: physiotherapy, lateral release, component revision, patellar resurfacing as indicated.
Open topicPatient-Specific Instrumentation in Arthroplasty
PSI uses preop MRI/CT to fabricate custom cutting jigs. Goal: improve accuracy, reduce OR time/inventory; evidence shows marginal accuracy gains without clear functional benefit. Limitations: cost, imaging/manufacture time, error propagation if imaging off. Best reserved for complex deformity or limited instrument settings. Distinguish PSI (custom guides) from custom implants (rare).
Open topicPeriprosthetic Fractures — Classification & Management
Classification guides treatment by considering fracture location, implant stability, and bone stock. THA femur: **Vancouver** (A: trochanteric; B1: around stem-stable; B2: around stem-unstable; B3: poor bone stock; C: distal). TKA periprosthetic femur: **Lewis–Rorabeck** (I: nondisplaced, stable; II: displaced, stable; III: loose component). Principles: fix stable implants; revise loose stems; restore alignment and biology with locking plates/cables/strut grafts or long-stem revision. Risk...
Open topicPeriprosthetic Fractures after TKA — Classification & Management
Incidence rising with aging population and expanding TKA volumes. Common sites: distal femur (supracondylar), tibia (around keel/stem), patella (resurfaced patella). Classifications: Lewis–Rorabeck & Su (femur), Felix (tibia), Ortiguera–Berry (patella). Stable components → fixation; loose components/poor bone → revision with stems/augments ± megaprosthesis. Avoid iatrogenic risk factors (anterior femoral notching, malalignment, osteolysis).
Open topicPeriprosthetic Joint Infection — Principles
Diagnosis uses consensus criteria (MSIS/ICM) combining major and minor criteria. Classify by timing: early (24 mo) — guides biofilm maturity and strategy. Treatment options: DAIR (debridement, antibiotics, implant retention), one‑stage or two‑stage revision; chronic suppression in poor hosts. Principles: radical debridement, exchange modular parts, biofilm‑active antibiotics (e.g., rifampicin combinations for staph). Prevention bundle: laminar flow, antibiotic prophylaxis, skin prep, glycemic co...
Open topicPeriprosthetic Osteolysis — Imaging & Management
Periprosthetic osteolysis = bone loss from wear particle-induced inflammation. Detected on radiographs as radiolucencies, cystic defects; CT useful for mapping, MRI (MARS) for soft tissue. Must exclude infection before labeling aseptic osteolysis. Management: debridement of granuloma, bone grafting, bearing exchange, revision arthroplasty if components loose. Prevention: use of HXLPE, ceramics, optimal component position.
Open topicPolyethylene Wear in TKA
Primary driver of late osteolysis and aseptic loosening in TKA. Wear modes: adhesive/abrasive; delamination & pitting with high contact stress/oxidation in older PE. Risk factors: malalignment/malrotation, thin inserts, tibial backside micromotion, third-body debris. Prevention: HXLPE, polished tibial trays, correct alignment, adequate insert thickness. Management: exclude PJI; bearing exchange + synovectomy vs full revision depending on fixation and bone loss.
Open topicReverse Shoulder Arthroplasty
Indicated for cuff tear arthropathy, pseudoparalysis, massive irreparable cuff tears. Developed by Grammont: medialized & lowered center of rotation. Deltoid substitutes for deficient rotator cuff. Requires intact deltoid and axillary nerve. Complications: scapular notching, instability, acromial stress fracture.
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