Periprosthetic Fractures Around Total Hip Arthroplasty

Distinguishing a stable B1 from a loose B2 is this topic's single most important decision, and the IMPLANT mnemonic lists the signs — but they are read against a standard map, the Gruen zones, using defined loosening criteria.

• Gruen zones. The femoral component is divided into seven zones on the AP film (1-7, starting at the lateral shoulder/greater trochanter, running down the lateral cortex to the stem tip and back up the medial cortex), with matching zones on the lateral view. They give a reproducible language for where a lucency, osteolysis or debonding sits.
• Cemented-stem loosening (Harris criteria). Definite = stem migration/subsidence or a fractured cement mantle; probable = a continuous radiolucent line at the cement-bone interface around the entire stem; possible = a lucent line over 50 to 100% of the interface. A progressive or circumferential lucency is the key signal.
• Uncemented-stem loosening. Suggested by subsidence or migration on serial films, a continuous reactive line around a porous surface, and a distal pedestal with no proximal bone ongrowth; conversely, spot-welds (endosteal bone bridging to the porous coating) and absence of migration indicate a stable, osseointegrated stem.
• The practical rule. Compare against serial and immediate-postoperative films whenever possible; if the radiographs stay equivocal, test the stem directly at operation before committing — a loose stem fixed as a B1 fails.

The painful THA with a possible fracture must be distinguished from other causes of acute or progressive hip/thigh pain. The two errors that fail candidates are missing infection (septic loosening masquerading as fracture) and missing occult loosening in an apparently intact femur.

The exam pearls warn to "STOP, assess and stabilise immediately" for an intraoperative fracture, and the epidemiology shows it complicates roughly 1.7% of primary and 12% of revision stems — so the on-table response deserves spelling out.

• When and where. Most occur during stem insertion/impaction (press-fit), typically at the calcar in primaries and the diaphysis in revisions; uncemented stems carry roughly a 3-fold (revision) to 14-fold (primary) higher risk than cemented. Highest risk in osteoporotic older women, with undersized broaching, or a sclerotic revision canal.
• Recognise it. A change in the pitch of impaction, a visible or palpable crack, unexpected stem subsidence, or an intraoperative fluoroscopic lucency. If suspected, stop and image the whole femur before proceeding.
• Manage by pattern (the same location logic as the Vancouver scheme):
  • Calcar crack (proximal, undisplaced): a single cerclage cable/wire around the proximal femur before seating the stem — the rationale for a prophylactic cable in an at-risk femur.
  • Diaphyseal split at the stem tip: cerclage, plus — if stability is doubtful — bypass with a longer diaphyseal-fitting stem by at least two cortical diameters.
  • Fracture distal to the intended stem: may need a longer stem, a plate, or both, before or after final component placement.
• Prevention and aftercare. Canal-appropriate gentle broaching, prophylactic cables in fragile bone, and protected weight-bearing afterwards. Undisplaced diaphyseal fractures recognised and cabled on the table generally heal well.

Global epidemiology. Periprosthetic femoral fracture complicates roughly 1% of primary and up to ~5% of revision THAs over the implant lifetime, and is consistently among the top reasons for revision in every major registry. Risk is concentrated in elderly women, osteoporotic/inflammatory-arthritis bone, and uncemented femoral fixation. As the global volume of primary arthroplasty rises, absolute fracture numbers are increasing worldwide.