1.1 Periprosthetic hip fractures

Periprosthetic hip fractures can involve the acetabulum or the femur. Fractures at these sites can occur either intraoperatively or postoperatively. Intraoperative periprosthetic acetabular fractures are rare and almost always are secondary to the impaction forces if press-fit noncemented acetabular components are used. Unpublished review data from the Mayo clinic in the Unites States involving 32,684 primary total hip arthroplasties showed that of 78 (0.24%) identified acetabular fractures, 70 (0.43%) were noncemented components and 8 (0.05%) were cemented. In the setting of revision surgery of the acetabular component, the fractures increased to 39 (0.68%) of 5,720 with 0.74% for noncemented and 0.53% for cemented socket placement.

Fractures around the femoral component are far more common. The rate of intraoperative periprosthetic femoral fractures varies depending if it is a primary or a revision total hip arthroplasty and if a noncemented (press-fit) or cemented technique is used [2]. In the current literature [2], primary total hip arthroplasties with cemented femoral stems have the lowest rate of femoral fractures with 0.1–2.5%. In the revision surgery setting this rate goes up to 3.0–3.6% if the femoral stem is cemented. But this is still lower than a noncemented (press-fit) technique with 3.7–5.4% in primary and 6.3–20.9% in revision total hip arthroplasties [2]. The incidence of intraoperative femoral fractures is so much higher in the revision setting due to the frequency of osteolysis and the additional surgical steps that have a risk of fracture ( Table 6.6.4-1 ). Such fractures can occur during exposure, hip dislocation, implant removal, cement removal, canal preparation, implant insertion, and hip reduction.

Postoperative periprosthetic fractures show an increasing prevalence. Similar to intraoperative fractures, we see higher rates after revision (2.1–4.2%) than after primary (0.4–3.5%) total hip arthroplasty ( Table 6.6.4-1 ) [6]. It is still unclear if the technique (cemented or noncemented) of the femoral component has an influence on the rate of postoperative fractures.

1.2 Periprosthetic knee fractures

Periprosthetic fractures associated with total knee replacement are less common than the hip but the absolute numbers are rising as total knee replacement becomes more common and patient activity and lifespan rise. Most of these fractures occur around the femoral component. Intraoperative fractures are less common than postoperative fractures but are likely to be underestimated, as some remain undetected. The current literature identifies 0.1–0.4% of intraoperative femoral fractures in primary total knees and 0.8% in revision surgeries [2]. Intraoperative tibial fractures are generally lower but reach almost the same levels in the revision setting.

Postoperative fractures are more common than intraoperative fractures and are far more common in the femur [2, 7]. Most occur in the supracondylar region of the femur [7].

Patellar fractures are more common than periprosthetic tibial fractures but less common than those occurring in the femur [2, 8]. Resurfacing of the patella is the main risk factor for periprosthetic patellar fracture. Revision surgery again increases the likelihood of a fracture (1.4% vs 2.7%).

1.3 Periprosthetic fractures of the upper limb

Due to the reduced mechanical forces, periprosthetic fractures are less common in the upper limb. Again, we differentiate intraoperative and postoperative fractures. Studies for periprosthetic fracture around shoulder arthroplasties have shown that revision surgery, noncemented implantation, and the female gender seem to be risk factors [9].

The incidence of postoperative humeral fractures associated with shoulder arthroplasty is around 0.6–3%. Intraoperative fractures seem to be less common at about 1.5% [9].

2.1 Orthogeriatric medical condition

Most patients who have joint arthroplasty are elderly and demographic shifts together with increased life expectancy mean that a significant number of the population are now at risk of periprosthetic fracture. Most patients who undergo joint arthroplasty for arthritis are relatively fit for their age but as the ageing process continues, they may develop osteopenia, sarcopenia, and multiple medical comorbidities that are accompanied by the intake of multiple medications. Thus, many patients with a periprosthetic fracture present similar challenges to the elderly with a hip fracture. It is important to assess the patient thoroughly before surgery to address all necessary aspects of their physical and mental health. Important aspects that need to be checked are:

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  Anemia

  
  
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  Platelets/coagulation

  
  
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  Metabolic disorders

  
  
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  Cardiovascular disease

  
  
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  Pulmonary disease

  
  
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  Diabetes mellitus

  
  
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  Renal function

  
  
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  Malnutrition

  
  
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  Parkinson disease

  
  
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  Neurological disorders

  
  
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  Polypharmacy

The availability of social support is also an important factor. Within the geriatric population, patients with frailty are at highest risk of developing postoperative complications. The frailty syndrome is characterized by an increased vulnerability to external and internal stress factors due to impairment of multiple, interrelated physiological systems. This vulnerability leads to a decline in homeostatic reserve and resilience and implies an increased risk for different adverse health-related problems. Components of the frailty syndrome include sarcopenia, osteoporosis, and muscle weakness [10–14].

2.2 Arthroplasty technique

Precise arthroplasty technique can help to reduce the risk of periprosthetic fractures. Careful preoperative planning, good surgical technique, and implant considerations are paramount. It is important to recognize patient-related risk factors for periprosthetic fractures such as:

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  Inflammatory arthropathy

  
  
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  Osteoporosis

  
  
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  Metabolic bone disease

  
  
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  Female gender

  
  
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  Advanced age

  
  
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  Osteolysis

  
  
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  Infection

  
  
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  Axial malalignment

  
  
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  Previous surgical interventions

It is also important to be aware of biomechanical problems like stress shielding and stress risers. The difference in stiffness between implant and bone is an important factor and the presence of an implant alters the strain distribution in the surrounding bone: reduced strain contributes to osteopenia around the implant [15, 16] while increased strain may eventually result in stress fracture. The coating of the prosthesis also has an influence on bone resorption with extensively coated devices inducing the most pronounced bone loss [17]. A further important cause of osteolysis is the formation of polyethylene wear debris, causing aseptic loosening—this is the most common mode of implant failure.

Intraoperative fractures are most often sustained during removal of an existing prosthetic stem or cement, medullary canal preparation or insertion of the prosthesis. Certain strategies can be applied to reduce the risk:

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  Obtaining adequate surgical exposure, which may require trochanteric/tibial osteotomy

  
  
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  Overreaming to reduce hoop stress and fracture during insertion of noncemented press-fit stems and acetabular cups

  
  
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  Avoiding eccentric or varus reaming

  
  
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  Removing cement carefully

  
  
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  Preventing propagation of the fracture by using prophylactic cerclage cables or wires

  
  
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  Using the image intensifier during revision surgery

3.1 Case history and physical examination

The assessment should diagnose the periprosthetic fracture, evaluate the patient′s fitness and level of function, and determine the stability of the prosthetic component. All of these are key factors in decision making and help to recommend the optimal treatment for the patient.

Patients often present with onset of pain, instability, deterioration in function, or recent history of trauma. A simple fall from standing height is a common mechanism but up to half of all patients report no history of a fall or trauma before diagnosis. If the fracture occurred without a clear traumatic event or if the x-ray shows signs of osteolysis around the prosthesis, three key factors should be considered before embarking on revision surgery:

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  Coexisting infection

  
  
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  Identification of the implants to be extracted

  
  
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  Bone stock

The identification of infection is important and its incidence is probably underestimated. Every patient presenting with pain, instability, and suspected fracture should be considered infected until proven otherwise. There are multiple diagnostic tests available to investigate for infection, each one with different sensitivity, specificity, and costs. The diagnostic pathway in each patient will be determined by the clinical index of suspicion (see chapter 5.4).

3.2 Imaging

Diagnostic imaging is a fundamental part of the assessment of a symptomatic patient following arthroplasty. Typically, it should be a step-by-step approach including plain film x-rays, cross-sectional imaging, bone density measurement, and nuclear medical examination in certain situations. Plain film x-rays are the first-line investigation. The comparison over time with previous images reveals loosening, subsidence, alignment change, and information regarding osteolysis. Bone cement should be carefully evaluated for cracks.

Computed tomography is useful to detect implant loosening and to diagnose periprosthetic fractures. It can help for preoperative planning of revision cases and to evaluate bone stock. It is highly reproducible in the evaluation of rotational alignment and reveals the presence of osteolysis or an occult fracture ( Fig 6.6.4-1 ).

Magnetic resonance imaging (MRI) used to be limited due to metal-related artefact. Technical advancements in signal processing have made MRI a diagnostic tool for the bone-prosthesis interface and the soft-tissue envelope [18]. A tremendous advantage is its ability to provide high-definition images of the prosthesis-fixation interface and in detecting bone cement in the femoral canal.

For revision surgery, dual-energy x-ray absorptiometry scanning can indicate the likelihood of adequate fixation of the new revision implant. There is strong evidence to suggest that it is highly sensitive for predicting failure of underlying bone [19].