Periprosthetic Fractures of the Lower Extremity

Periprosthetic Fractures Around Hip Arthroplasty

Periprosthetic fractures around THA can affect the acetabulum or the proximal femur.

Periprosthetic Fractures Around Knee Arthroplasty

Periprosthetic fractures around TKA can also be observed intraoperatively and during the postoperative time course. The overall incidence of intraoperative periprosthetic fractures is estimated to be 0.4%, most commonly involving the distal femur in primary TKA and the proximal tibia in revision TKA. The overall incidence of postoperative fractures is up to 0.3% to 5.5% for primary TKA and up to 30% in revision TKA.

Patient-Related Risk Factors

Patient-related risk factors for periprosthetic fractures are listed in the Key Points box.

The role of antiresorptive medication as a risk factor for periprosthetic fractures is controversially discussed.

Implant-Related Risk Factors

Malpositioning of orthopaedic implants, prosthetic loosening, and the presence of revision arthroplasty, as well as local osteolysis, drill-holes after internal fixation, and bony defects (e.g., cortical perforation), represent general implant-related risk factors.

Implant-related risk factors stratified for intraoperative versus postoperative fractures and for the different anatomic sites around hip and knee arthroplasty are summarized in Tables 69.1 and 69.2 .

Periprosthetic Fractures Around UKA

Current literature focuses on medial UKA as it is far more commonly performed than lateral UKA. Fractures around UKA are rare but almost always occur intraoperatively at the tibial plateau. Risk factors include uncemented implants, intraoperative damage to the proximal tibia, and low-volume surgeons. The use of press-fit uncemented implants is increasing due to concerns with radiolucent lines under cemented tibial trays. However, they are associated with an increased fracture risk as the load to fracture is lower than with cemented implants. Finite element analysis studies have shown that increased strain occurs at the proximal tibia as a direct result of an excessive tibial resection, increased valgus inclination of the tibial component, and an extended vertical saw cut that damages the posterior tibial cortex. This reflects the fact that UKA is a technically demanding procedure that is often performed through a minimally invasive approach. Accordingly, complication rates including intraoperative fracture are reported to significantly reduce with increased surgeon experience and high-volume surgery.

Clinical Examination

All patients with periprosthetic fractures of the lower extremity require detailed medical assessment as they may have complex comorbidities with anesthetic and surgical implications. A thorough history must include age, occupation, mechanism of injury, functional status, past medical history, and medication history. A history of pain before injury may be suggestive of implant loosening, osteolysis, or infection, and these factors will often dictate surgical treatment. Details regarding the primary arthroplasty must be recorded, including date, indication, treating institute, and any postoperative complications. Previous operation notes should be carefully reviewed to determine surgical approach and implant specifications to allow the appropriate extraction kit to be ordered if required for revision surgery. A thorough clinical assessment should be performed, concentrating primarily on initial resuscitation maneuvers that may be required due to blood loss and hemodynamic instability. Life-threatening injuries should be prioritized in the case of multiply injured patients or those involved in high-energy trauma. A complete neurovascular examination should be performed and documented accurately.

Laboratory Examination

Hematologic investigations should include full blood count, urea and electrolytes, clotting screen, blood group screening, and cross matching. Urinalysis should be performed to rule out a urinary tract infection, which may need treating before surgery. An infection screen must be performed, including inflammatory markers (erythrocyte sedimentation rate and C-reactive protein) and blood cultures. However, elevated inflammatory markers often occur as consequence of trauma and have been shown to be a poor indicator for infection in this context. If infection is clinically or radiologically suspected, joint aspiration with synovial fluid analysis is mandatory to establish whether a two-stage process for treating periprosthetic joint infection is required.

Radiologic Examination

Radiographs of the affected limb to include the entire femur or tibia in two orthogonal planes must be performed. Imaging of the whole orthopaedic implant is mandatory, especially in interprosthetic fractures and long-segment fractures. Implant loosening can be confirmed by comparing serial radiographs, and every effort should be made to obtain these. Computed tomography (CT) can be useful in outlining the extent of bone loss when planning surgery and for complex fracture types such as periprosthetic acetabular fractures. Importantly, if calf pain is reported by the patient, a duplex ultrasound scan is warranted to investigate the presence of deep vein thrombosis, which will need medical treatment before surgery. If present, consideration should be given to prophylactic insertion of a vena cava filter before surgery to minimize the risk of pulmonary embolism. Further imaging, such as magnetic resonance imaging (MRI), scintigraphy, and positron emission tomography (PET), is normally not necessary.

Unified Classification System

Periprosthetic fractures can affect any joint replacement within the musculoskeletal system. Numerous classification schemes have been proposed that both define the fracture pattern as well as guide treatment. The principles behind these systems are fairly constant, and to improve clinical application, registry-level reporting, and research methodology, the Unified Classification System has been developed ( Table 69.3 ). It describes fracture patterns based on their anatomic location and proximity to specific implants. Type A fractures are apophyseal and are often the result of an avulsion injury (e.g., greater trochanter or tibial tubercle). Type B fractures occur directly adjacent to the implant and are further subdivided into B1, with a well-fixed implant; B2, where the implant is loose; and B3, where the implant is loose with poor surrounding bone stock due to osteolysis, osteopenia, or fracture comminution. Type C fractures occur distant to the implant but within the same bone (e.g., tibial shaft fracture below a TKA). Type D fractures occur in a long bone supporting two joint replacements at either end and are commonly termed interprosthetic fractures (e.g., femoral shaft fracture in between a THA and TKA). Type E fractures involve two bones supporting one joint replacement (e.g., a combined acetabular and femur fracture around a THA). Type F fractures occur at a native joint surface that directly articulates with an implant (e.g., acetabular fracture next to a hip hemiarthroplasty). This system has been shown to have substantial intraobserver and interobserver reliability when used to classify periprosthetic fractures around THA and TKA.

Periprosthetic Fractures Around Hip Arthroplasty