Arthroplasty

Definition and Types

Indications

General Indications

• End-stage arthritis (osteoarthritis, rheumatoid arthritis, post-traumatic arthritis)
• Kellgren-Lawrence (KL) Grades 3-4 radiographic changes
• Debilitating pain affecting activities of daily living
• Failed conservative management (physiotherapy, NSAIDs, intra-articular injections)
• Avascular necrosis (osteonecrosis) with collapse involving >30% of the femoral head
• Certain acute fractures - especially displaced intracapsular femoral neck fractures in older patients

Arthroplasty vs. Internal Fixation in Hip Fractures

• Physiologically younger patients (<65 years): prefer anatomic reduction and internal fixation
• Older patients with displaced femoral neck fractures: prefer arthroplasty
• Total hip arthroplasty is preferred over hemiarthroplasty in select patients (women <75; ASA I/II) - better functional outcomes with lower revision rates (6% vs. 20%)
• Unipolar vs. bipolar hemiarthroplasty: similar outcomes; bipolar may slightly lower revision rates

Campbell's Operative Orthopaedics 15th Ed 2026; Miller's Review of Orthopaedics 9th Edition

Total Hip Arthroplasty (THA)

Surgical Approaches

Implant Fixation

• Microinterlock between cement and endosteal bone
• Preferred for: elderly females, Dorr Type C femur ("stovepipe"), poor bone quality, hip fractures
• Cemented cups fail at a higher rate than cemented stems (shear/tension forces at the cup-cement interface vs. mostly compression at the stem)
• Cemented stems have lower risk of periprosthetic fracture in osteoporotic bone
• Rare complication: intraoperative cardiac collapse during cementation

• Preferred for the acetabular cup - porous-coated cementless cups have superior long-term results
• Both cementless and cemented stems give durable results for the femoral component
• Preferred in high-activity young males (cement fatigues with cyclic loading)
• Two mechanisms: bone ingrowth (porous coating, 50-200 μm pore size) and bone ongrowth (grit/textured surface)

• Pore size 50-200 μm; bone will not grow deeper than 150 μm
• Metal porosity of 40-80%
• Gap between prosthesis and bone <50 μm
• Micromotion <50 μm (>150 μm leads to fibrous fixation)
• Press-fit technique: cup 1 mm oversized; femoral stem 0.5-1 mm oversized

• Proximal femoral bone density loss from modulus mismatch between the stiff stem and femoral cortex
• Most pronounced with extensively porous-coated diaphyseal-filling stems (distal bone loading)
• Proximal porous-coated stems preserve proximal bone density better

Bearing Surfaces

Submicron PE particles are phagocytized by macrophages → RANKL-mediated osteolysis via osteoclast activation.

Templating

• Uses standardized radiographs with calibration markers
• Goals: restore limb length and femoral offset
• Dorr classification guides femoral component choice (Type A = champagne flute, young male; Type C = stovepipe, elderly female - usually cemented)

Total Knee Arthroplasty (TKA)

Design Categories

TKA Complications

• Infection (Periprosthetic Joint Infection, PJI): #1 reason for painful TKA within the first year
  • Diagnosis: serum CRP, ESR + joint aspiration; ICM-18 criteria
  • Two major criteria (only one required): draining sinus communicating to joint (absolute diagnosis) OR two positive cultures of the same organism
  • Chronic PJI = biofilm on implant; bone erosive changes on XR = chronic
  • Acute PJI = signs/symptoms present ≤3 weeks
  • Treatment: radical debridement +/- staged exchange arthroplasty
• Peroneal nerve palsy: most commonly from combined valgus-flexion deformity; first treatment = remove compressive wraps and flex the knee
• Lateral retinacular release: artery at risk = lateral superior genicular artery → osteonecrosis of the patella
• Arthrofibrosis: manipulation should be performed between 4-12 weeks post-op
• Osteolysis (aseptic loosening): manifests at 7-15 years; round lytic lesions, most common behind posterior femoral condyle

Gap Balancing

• Symmetric gap problem → adjust tibia first
• Asymmetric gap problem → adjust femur first

Perioperative Nerve Blocks

• Femoral nerve block: motor AND sensory block (knee buckles on walking → needs knee immobilizer)
• Adductor canal block: sensory only (knee does not buckle; preferred for early mobilization)

Revision Arthroplasty

Revision THA

• Start-up pain = most common presentation of implant loosening
• Acetabular revision: hemispheric porous cup with multiple screws is the most common solution; modular metal constructs for severe bone loss; custom triflange cups for massive defects
• "Zone of death": anterior-superior quadrant of acetabulum - screws here risk the external iliac artery and veins (can be fatal)
• Pelvic discontinuity (superior pelvis separated from inferior): addressed with cup-cage constructs, custom triflange, or distraction
• Femoral revision: tapered fluted modular titanium stems are now the mainstay (preferred over cylindrical extensively porous-coated stems)

Revision TKA

• Indications: infection, aseptic loosening, instability, stiffness, periprosthetic fracture
• PS TKA with "closed box" femur: do NOT use retrograde IM nail (blocked by metal)
• Elderly with osteoporosis and significant comminution: distal femoral replacement
• For stable implants with distal femur fracture: ORIF with submuscular distal lateral locking plate (preferred)

Other Joint Arthroplasties

Shoulder Arthroplasty

• Hemiarthroplasty: used when glenoid cartilage is intact but rotator cuff is intact
• Total Shoulder Arthroplasty (TSA): both glenohumeral surfaces replaced; requires an intact rotator cuff
• Reverse Total Shoulder Arthroplasty (RTSA): glenoid = ball, humerus = socket; used for cuff-deficient shoulders, proximal humeral fractures/malunions with rotator cuff insufficiency; pain relief in 75-85% of patients
• Greater tuberosity osteotomy complications: nonunion/malunion/resorption in ~41% in some series

Elbow Arthroplasty

• Total elbow arthroplasty (TEA) used for rheumatoid arthritis, complex distal humeral fractures in elderly, and post-traumatic arthritis
• Activity restrictions post-TEA: no lifting >5 lbs (lifetime restriction with most designs)

Ankle Arthroplasty

• Total ankle arthroplasty (TAA) as an alternative to ankle arthrodesis
• Advantages over fusion: preserved motion, less adjacent joint arthrosis
• Revision TAA has higher complication rates

Key Contraindications to Arthroplasty

• Active joint or systemic infection
• Neuropathic (Charcot) joint (relative)
• Insufficient bone stock/severe osteoporosis
• Medically unfit for surgery
• Non-compliant patient (relative)

Summary of High-Yield Points

1. Cemented cup fails faster than cemented stem (shear/tension vs. compression forces)
2. Cementless cup is the preferred acetabular choice in primary THA
3. Cemented femoral stem preferred in hip fractures and Dorr C anatomy
4. PJI is the #1 cause of painful TKA within the first year
5. AAOS strongly supports arthroplasty for displaced (unstable) femoral neck fractures
6. Dual-mobility cups reduce dislocation risk
7. Highly cross-linked PE reduces wear/osteolysis
8. For MOM concerns: check serum cobalt and chromium + MRI with MARS
9. Zone of death (anterior-superior acetabulum) risks external iliac vessel injury
10. Reverse TSA is the solution for rotator-cuff-deficient shoulders

Sources: Campbell's Operative Orthopaedics 15th Ed 2026, Miller's Review of Orthopaedics 9th Edition, Bailey and Love's Short Practice of Surgery 28th Edition, Rockwood and Green's Fractures in Adults 10th Ed 2025