Adult Reconstruction and Arthroplasty
Concepts
Adult reconstruction questions test indications, implant selection, complications and the workup of the painful arthroplasty. Arthroplasty is indicated for end-stage disease after failed nonoperative care - pain limiting function, night pain, deformity - not for isolated radiographic findings.
Hip: know the approaches and their trade-offs. Posterior approach carries higher dislocation risk; direct anterior risks lateral femoral cutaneous nerve injury and wound problems. Highly cross-linked polyethylene with ceramic or metal heads is standard; metal-on-metal has adverse local tissue reactions and is largely abandoned. Dislocation is the most common early complication, followed by leg-length discrepancy, periprosthetic fracture and sciatic nerve injury with posterior approach and lengthening.
Knee: alignment and gap balancing, and avoiding overstuffing of the patellofemoral joint.
Periprosthetic joint infection is high yield. Diagnosis uses major criteria (sinus tract communicating with the joint, or two positive cultures with the same organism) or minor criteria including elevated CRP/ESR, synovial white cell count and neutrophil percentage, leukocyte esterase, alpha-defensin and purulence. Aspirate before antibiotics. DAIR suits acute infection with a well-fixed implant; chronic infection usually needs two-stage exchange.
Vancouver periprosthetic femur fracture: A trochanteric, B around the stem (B1 stable, B2 loose, B3 loose with poor bone), C below the stem.
Rule of thumb: a sinus tract means infection until proven otherwise - never call it aseptic loosening.