Periprosthetic Fracture

Periprosthetic fracture is a fracture around a joint replacement, most often the hip (femur or acetabulum), knee (distal femur, tibia, patella) and shoulder. It is increasing because of more joint replacements and an older, osteoporotic population.

Femoral periprosthetic fractures occur in about 1 to 4% of primary hip replacements and up to 4 to 11% of revisions, with a 1-year mortality of 10 to 20%.

Risk factors:

• Osteoporosis, rheumatoid arthritis, female sex and age over 70.
• Loosened implants and osteolysis.
• Cementless stems (intraoperative fracture) and revision surgery.
• Stress risers (cortical defects) and anterior femoral notching in knee replacement.
• Falls.

The Vancouver classification (hip) is based on fracture site, implant stability and bone quality.

• Type A is in the trochanteric region (AG greater and AL lesser trochanter).
• Type B is around or at or just distal to the stem: B1 with a well fixed stem, B2 with a loose stem and good bone, B3 with a loose stem and poor bone stock.
• Type C is well distal to the stem.

For the knee, the Rorabeck classification applies:

• Type I: undisplaced with an intact prosthesis.
• Type II: displaced with an intact prosthesis.
• Type III: loose or failed prosthesis.

Complications are nonunion, malunion, infection, implant loosening, dislocation, venous thromboembolism, loss of mobility and independence, and death.

Pathophysiology.

Intraoperative fractures follow forceful stem insertion, cementless press fit and bone fragility. Postoperative fractures follow low energy falls on osteoporotic bone around stress risers, or loosening with osteolysis from wear debris. The stem stability decides whether the implant can be retained (fixation) or must be revised.

Pain in the thigh, groin or around the knee after a fall (sometimes minor), inability to bear weight, deformity, shortening and swelling. Prodromal thigh pain before the fracture suggests a loose implant or stress reaction. Examine the leg for open wounds, neurovascular state, the hip and knee range, and the surgical scar.

Check the patient's general condition: delirium, comorbidities, anticoagulants, frailty, nutrition and the cause of the fall (cardiac, neurological, medication). Previous surgical records identify the implant type (needed for revision planning).

• Radiographs: anteroposterior and lateral views of the whole prosthesis and the entire bone, including both adjacent joints. Assess fracture pattern, stem or component stability (subsidence, lucent lines, change in position compared with earlier films), bone quality and osteolysis.
• CT (with metal artefact reduction) for stem stability, bone stock, acetabular fractures and planning.
• Blood tests: full blood count, C-reactive protein, erythrocyte sedimentation rate, creatinine, calcium, 25-hydroxyvitamin D and group and crossmatch. Aspirate the joint in a loose implant to exclude infection.
• Preoperative medical optimisation and anaesthetic assessment.

Differential diagnosis.

• Implant loosening or osteolysis without fracture.
• Periprosthetic joint infection.
• Pathological fracture from metastasis.
• Native bone fracture (acetabular, femoral neck) and stress fracture.

Management follows the type and stability, and the patient's fitness. Early surgery within 48 hours reduces complications.

Vancouver type A. Trochanteric fragments: non-operative if undisplaced; fixation with cable, wire or claw plate if displaced over 2 cm or with a loose component.

Vancouver type B1 (stable stem). Open reduction and internal fixation with a locking plate and cables, often spanning the stem with bicortical screws around it, and allograft strut grafts if needed. Aim for biological fixation and spanning of the fracture past the stem.

Vancouver type B2 and B3 (loose stem). Revision arthroplasty with a long, cementless, distally fixed stem that bypasses the fracture by at least 2 cortical diameters (or 4 to 6 cm). Use cables or plates and allograft for proximal bone loss. Type B3: proximal femoral replacement, allograft prosthesis composite or revision with extensive bone grafting.

Vancouver type C. Plate or nail fixation (retrograde nail, locking plate) with overlap of the stem.

Knee. Distal femur: locking plate or retrograde nail (if the implant has an open box and the nail clears it) for stable prostheses. Use revision with a distal femoral replacement for loose components or poor bone stock. Tibial and patella: fixation or revision as indicated.

Non-operative. Unfit patients, undisplaced fractures with a stable implant (type I): protected weight bearing, with higher risk of nonunion and immobility complications.

Rehabilitation. Orthogeriatric care. Allow weight bearing as tolerated if the construct is stable, or protected weight bearing (toe touch) for 6 to 12 weeks if not. Early mobilisation and physiotherapy.

Operative antibiotic prophylaxis. Cefazolin 2 g intravenously (3 g when weight is 120 kg or over) within 60 minutes before incision as a single dose (repeat after 4 hours or blood loss over 1500 mL). With severe penicillin allergy, give vancomycin 15 mg/kg intravenously starting 90 to 120 minutes before incision as a single dose, with levels and creatinine checked in prolonged cases. Take multiple deep samples in revision surgery to exclude infection.

Thromboprophylaxis. Enoxaparin 40 mg subcutaneously once daily, started within 12 hours after surgery and continued for 28 to 35 days. Use 20 mg once daily at creatinine clearance under 30 mL/min, adjust by anti-Xa level in obesity and renal impairment, and check the platelet count on days 5 to 14 for heparin induced thrombocytopenia. Use mechanical prophylaxis until then. For patients on long term anticoagulants, bridge as advised by haematology.

Analgesia.

• Paracetamol 1 g orally or intravenously every 6 hours (maximum 4 g daily; 3 g daily when weight is under 50 kg, with chronic alcohol use or hepatic impairment).
• Oral morphine 2.5 to 5 mg every 4 hours as needed for severe pain in older adults, for up to 5 days. Avoid exceeding 60 mg in 24 hours without senior review; start 2.5 mg with age over 75 or eGFR under 30 mL/min/1.73 m2. Monitor sedation and respiration, and prescribe a laxative.
• Fascia iliaca block with ropivacaine 0.2% 30 to 40 mL as a single injection by a skilled operator (maximum 3 mg/kg of ropivacaine), with monitoring for toxicity; avoid with infection at the site.
• Avoid NSAIDs in older adults with kidney impairment or heart failure.

Secondary prevention after a fragility fracture. Alendronate 70 mg orally once weekly, taken fasting with a full glass of water and kept upright for 30 minutes, for 5 years then reassess (maximum 70 mg weekly). Check calcium, 25-hydroxyvitamin D and creatinine before starting and yearly. Avoid with eGFR under 35 mL/min/1.73 m2, uncorrected hypocalcaemia or oesophageal stricture.

Zoledronic acid 5 mg intravenously over at least 15 minutes once yearly (for 3 years, then reassess) when oral therapy is not tolerated and eGFR is 35 mL/min/1.73 m2 or over, with creatinine and calcium checked before each dose. Colecalciferol 800 to 2000 IU orally daily with dietary calcium to a total of 1000 to 1200 mg daily (maximum total 2000 mg daily); correct vitamin D deficiency first.

Monitoring. Radiographs after surgery, at 2 weeks, 6 weeks, 3 months, 6 months and 12 months. Wound, neurovascular state and function at each visit. Delirium, nutrition and renal function in the first week. Bone health and falls assessment before discharge.

Referral and escalation. Refer every periprosthetic fracture to the arthroplasty service or a revision capable centre within 24 hours. Emergency referral for an open fracture, vascular compromise, suspected infection or an unstable patient. Early orthogeriatric review.

Special groups.

• Older adults: combined orthogeriatric care reduces mortality and complications; treat anaemia, delirium and malnutrition.
• Anticoagulated patients: reverse as indicated before surgery.
• Rheumatoid arthritis and long term corticosteroids: poor bone quality needs longer constructs and grafts.
• Kidney impairment: avoid NSAIDs and bisphosphonates at eGFR under 35 mL/min/1.73 m2, and reduce morphine doses.