Periprosthetic Fracture: Prevention, Diagnosis, and Treatment

Introduction

Periprosthetic fracture in association with total hip arthroplasty (THA) is an uncommon but potentially devastating complication. It can occur during or after the procedure. The reported intraoperative risk is 0.3% to 1.7% and postoperative risk is up to 1.6% in primary total hip replacements at 10 years. The cumulative probability of suffering a postoperative fracture at 20 years is 7.7%, which makes it one of the most common long-term complications of THA. The risk of a periprosthetic fracture in revision hip arthroplasty is even higher for intraoperative fractures at 12% and 20-year cumulative probability of 11% for postoperative fractures. These fractures can lead to considerable morbidity due to loss of fixation of the components, loss of bone stock, and subsequent functional deficit. Most patients with these fractures require surgical management either in the form of open reduction internal fixation or a revision arthroplasty. Overall, 9.5% of reoperations after THA are attributed to periprosthetic fractures. These procedures have high surgical complication and readmission rates and compromised functional outcomes. The reoperation rate following stem revision for periprosthetic fracture has been recorded to be as high as 24%. Periprosthetic fractures are also associated with a 30-day mortality rate of 10% and considerable costs. This chapter focuses on principles of assessment, classification, and treatment of these challenging complications of arthroplasty.

Epidemiology and Risk Factors

The number of THAs performed has steadily risen over the years. This is due to the excellent results from THA, which has led to extended indications in the young as well as in the elderly and to an increase in life expectancy. Hence, there are higher numbers of elderly patients with THA in situ with ongoing risk of postoperative fracture due to poor bone quality, periprosthetic bone loss, and risk of falls.

A comprehensive review of the all-payer data from the National Inpatient Sample from the states participating in the Healthcare Cost and Utilization Project in the United States revealed a total of 4571 periprosthetic hip fractures between 2006 and 2010. Total hospital charges steadily increased through the study period from $66,531 in 2006 to $94,214 in 2010.

Periprosthetic fractures of the acetabulum are less common than those of femur, but they are often severe and warrant careful evaluation of the posterior column for its integrity. Intraoperative acetabular fractures can occur during preparation of the acetabulum but more commonly during impaction of a cementless acetabular component. The risk is highest with shells of elliptical shape.

A single-center series of 32,644 patients who underwent primary hip arthroplasties over 40 years with a median follow-up of 7.9 years has reported a rate of intraoperative periprosthetic femoral fractures of 1.7% (564/32,644), with statistically greater risk in female patients (2.0% vs. 1.4%, P < .001) and those older than 65 years (2.5% vs. 1.0%, P < .001). Of note, 93.8% of these fractures were undergoing cementless hip replacement and accounted for a complication rate of 3% versus 0.2% in cemented hip arthroplasty. In the same series, the cumulative probability of postoperative periprosthetic femoral fracture was 0.4% at 1 year, 0.8% at 5 years, 1.6% at 10 years, and 3.5% at 20 years. At 20 years, the cumulative probability of suffering a postoperative fracture after experiencing an intraoperative fracture was 7.2%. Of the 557 postoperative periprosthetic femur fractures, 335 of 17,466 (1.9%) occurred after uncemented implants and 222 of 15,178 (1.5%) after cemented implants ( P < .001; Fig. 107.1 ). The 20-year cumulative probabilities of femur fractures after cementless and cemented stems were 7.7% (95% confidence interval [CI] 6.2–9.1) and 2.1% (95% CI 1.8–2.0), respectively, which makes it one of the most common long-term complications of THA. When stratified based by gender, there was no increased risk of postoperative femur fractures in females (hazard ratio [HR] = 1.0; 95% CI 0.8–1.2; P = .98). Likewise, patients greater than 65 years old at operation also did not have an increased risk when compared with a patient less than or equal to 65 years of age (HR = 1.0; 95% CI 0.8–1.1; P = .59).

In a separate series from the same institute over 40 years, 668 intraoperative periprosthetic fractures of the femur were reported during revision arthroplasty, with an incidence of 12%. Fractures were 3 times more common with cementless stems (19%) than with cemented stems (6%, P < .001). They also reported 281 postoperative periprosthetic fractures of the femur with a 20-year probability of 11%.

Periprosthetic fractures have an overall mortality risk within 12 months of the complication of 11% to 25%. In a retrospective study of 151 periprosthetic fractures of the femur, 25.2% died within the study period. A significant effect was seen in patients with increasing age, cardiovascular problems, hypothermia, and renal failure.

Diagnosis

The diagnosis of periprosthetic fracture is generally not difficult and is based primarily on radiographic examination ( Fig. 107.2A ). Intraoperative periprosthetic fractures can be diagnosed by direct observation, but this requires circumferential exposure of the calcar or on intraoperative radiographs if a fracture is suspected and, more rarely, on postoperative radiographs if a fracture was not suspected intraoperatively. These are likely to occur during 1 of the 3 stages of reconstruction: removal of fixation hardware or previous implants, bone preparation, or implant insertion. Signs that alert the surgeon to this possibility include a change in pitch while using instruments, a sudden reduction in the force required when a broach or rasp is used, or advancement of the implant beyond the planned level of placement, either in the socket or in the canal. In acetabular fractures, a sudden loss of cup stability should alert the surgeon to this possibility. Exposure of the superior portion of the posterior column is necessary to ensure safe reaming and the lack of an intraoperative fracture.

Postoperative periprosthetic fractures are typically associated with acute onset of pain and deformity that may or may be associated with a fall. Radiographs prior to the fracture should be examined for evidence of osteolysis and loosening. The authors of 2 large data reports attributed many of these fractures to implant loosening or osteolysis and highlighted the importance of regular radiographic follow-up of all patients with primary and revision THAs.

Radiographic evaluation of all suspected fractures should be comprehensive, including full-length views of the femur in 2 planes, an anteroposterior (AP) pelvic radiograph, and Judet views when required to evaluate the floor, roof, and columns of the acetabulum. Comparison with previous radiographs is valuable when available. This comparison also allows assessment of implant migration. More specialized imaging, such as computed tomography (CT), may be helpful in selected circumstances of unusual complexity, especially around the acetabulum, and can be combined with 3-dimensional reconstruction to assist with preoperative planning. Metal artifact reduction sequences (MARS) in CT and magnetic resonance imaging scanners help to improve image quality. If the acetabular component is intrapelvic, CT angiography is recommended for preoperative planning to evaluate the risk of potential vascular injuries. Sporadic cases of death from vascular injury have been reported with acute protrusion of the acetabular component.

Confirming stability of the implant is critical in the management of periprosthetic fractures, using implant exposure and interface assessment when needed. Failure to appreciate implant loosening and inadvertent management of the fracture without implant revision has been attributed to a high failure rate.

Classification

A number of classification systems have been described for periprosthetic fractures around the hip. The Vancouver Classification System (VCS) for fractures involving the femur described by Duncan and Masri in 1995 has been widely adopted. It is based on the location of the fracture, stability of the stem, and quality of the surrounding bone. Its reliability and validity have been established ( Table 107.1 ). The classification was subsequently expanded so that it could be applied to intraoperative femoral fractures. The anatomic types A, B, and C are subdivided into 3 types: subtype 1 represents a simple cortical perforation; subtype 2, an undisplaced linear fracture; and subtype 3, a displaced or unstable fracture.

The principles of the VCS have been more recently expanded so that they can be applied to other joint replacements, as the Unified Classification System (UCS). The UCS is now applied to fractures following replacement of the shoulder, elbow, wrist, hip, knee, and ankle. A simple mnemonic has been proposed to assist with recall of the fracture type ( Table 107.2 ). The high interobserver and intraobserver reliability of the UCS has been established.

Femoral Fractures

The objective of the VCS was successful assessment and management of these complex complications of THA (see Table 107.1 ). It takes into consideration 3 core principles: the location of the fracture (whether the fracture involves the bone supporting the implant or is distant to it); stability of the implant (whether the bone-implant interface was stable prior to fracture and remained so after the injury); and the adequacy of the bone stock supporting the implant (whether it is sufficient to permit revision without requiring additional major reconstruction).

The 3 major anatomic types defined by this classification system depend on the location of the fracture: type A refers to the trochanteric area (one or both trochanters and proximal metaphysis, not extending to the diaphysis) and has little influence on implant fixation. These fractures are subdivided into greater trochanter (A _G ; Figs. 107.3 and 107.4 ) and lesser trochanter (A _L ; Fig. 107.5 ) depending on the location of the fracture. Type B refers to a fracture around or just distal to the femoral stem (metaphysis and/or diaphysis) and has been subdivided into B ₁ , B ₂ , and B ₃ on the basis of stability of the implant and adequacy of bone. Type C refers to fractures that are sufficiently distal to the tip of the stem that their treatment can be considered independent of the presence of the implant (the diaphysis and/or metaphysis; Fig. 107.6 and see Table 107.1 ). If a fracture occurs through the cement mantle distal to an otherwise well-fixed cemented stem, this would be classified as a B ₁ . When the fracture passes through the cement mantle around the stem, it leads to a B ₂ fracture, irrespective of whether the stem was well fixed before the fracture. In both of these categories, the bone stock is usually good. In some cases, the distinction between type B ₁ and B ₂ will require further radiologic investigation, such as MARS CT scan or fluoroscopy), a review of prior radiographs, or examination of the bone-implant interface at the time of the operation. However, it is best to make this differentiation preoperatively given the differences in the surgical approach between a revision procedure and fixation of a femoral fracture in which there is no need to dislocate the hip.

Extending the principles of the VCS, in the UCS for periprosthetic femoral fractures (see Table 107.2 ), type A fractures in the femur are also subdivided into greater trochanter (A _G ) and lesser trochanter (A _L ). Type B has been subdivided into those in which the implant is stable (B ₁ ), those in which the implant is loose (B ₂ ), and those in which the bone stock is poor and the implant is loose (B ₃ ). In type C, the fracture is distant to the arthroplasty (see Fig. 107.6 ). In type D, the fracture has divided a femur that supports 2 implants (hip and knee replacement; Fig. 107.7 ); these are also known as intraprosthetic fractures. In type E, the fractures involve 2 bones that support 1 joint replacement, such as both the acetabulum and femur after hip replacement ( Fig. 107.8 ).

A single-center series of 32,644 patients over 40 years old with a median follow-up of 7.9 years identified Vancouver A _G fractures as the most common, followed by Vancouver B ₂ fractures. A more in-depth analysis revealed that Vancouver A _G , A _L , B ₁ , and B ₂ fractures were more common with cemented stems, while Vancouver B ₃ and C fractures were more common with uncemented stems. In addition, Vancouver A _G fractures mostly occurred with no known trauma, were avulsion-type fractures, and were treated nonoperatively. On the other hand, Vancouver B fractures were mostly due to a fall from standing height, were oblique or spiral-pattern fractures, and were treated with open reduction internal fixation or revision.

Treatment and Results