7.12 Management of total hip replacement periprosthetic fractures

Periprosthetic fracture of the femur after total hip arthroplasty (THA) surgery was first described in 1954 and the experience with periprosthetic femoral fractures was limited during this period.

Nowadays, the reconstructive orthopaedic surgeon deals with periprosthetic fractures quite frequently. Periprosthetic femoral fracture is a devastating complication after THA that can result in poor clinical outcome. They are challenging to treat, as they require the skills of both a revision surgeon and a trauma specialist. In this review we summarize the epidemiology, aetiology, classification, and various modalities of management.

The Swedish Hip Registry data have shown that periprosthetic femoral fractures were the third commonest reason for reoperation (9.5%) after total hip replacement, after aseptic loosening (60.1%), and recurrent dislocation (13.1%). Periprosthetic femoral fractures can be classified as intraoperative and postoperative. The cumulative prevalence of periprosthetic femoral fractures is 1.0% in primary total hip replacements and 4% in revision total hip replacements (Mayo Clinic Joint Registry). The incidence of intraoperative fractures is 0.3% in primary cemented and up to 5.4% in uncemented THAs whereas in revision surgeries the incidence is 3.6% in cemented and 20.9% in uncemented revision THAs. There is an increasing incidence of late postoperative periprosthetic femoral fractures that is attributable to many factors, including an increasing number of elderly patients at risk for falls, increasing numbers of young patients with total hip replacements at risk for high-energy trauma events, and the increasing numbers of revision procedures using cementless press-fit fixation or bone impaction allograft techniques. Periprosthetic femoral fractures usually occur with low-energy events, either after falls or spontaneously during activities of daily living. Patients may present with insidious pain and fracture with no history of fall or trauma. It should be borne in mind that osteolytic lesions often occur in asymptomatic hips.

Continuous surveillance of THR patients, especially younger ones with higher activity levels, may help in timely intervention and reduce the incidence of osteolytic-related fractures. In primary and revision hip arthroplasty, femoral fractures can occur after dislocation of the existing prosthetic stem, cement removal, during femoral canal preparation, and during insertion of the prosthesis.

Acetabular fractures occur during component insertion or removal. Postoperative acetabular fractures are associated with uncemented acetabular component insertion because of bone loss in a failed THA. The first description of acetabular fractures around THA was in 1972. The reported incidence of intraoperative acetabular periprosthetic fracture is less than 0.2%.The prevalence of such fractures has increased since the introduction of uncemented components. The prevalence of periacetabular fracture with pelvic discontinuity at acetabular revision is 0.9%.These fractures are attributed to trauma, osteolysis, under-reaming and oversizing of the components, osteopenia, and Paget’s disease.

Various classification systems have been in and out of favour in the past based on site and pattern of fracture or implant instability. Some of the commonly used classification systems are given in Table 7.12.1.The Vancouver classification system for both intraoperative and postoperative femoral fractures has gained universal acceptance (Table 7.12.2). This is the only periprosthetic classification system that has been subjected to psychometric testing for its reliability and validity. The factors that determine treatment are fracture location, stability of the implant and fracture, quality of host bone stock, patient physiology and age, and surgeon experience. This classification consolidated the three most important factors, i.e. the site of the fracture, the stability of the implant, and the quality of the surrounding bone stock.

Periprosthetic femoral fractures are classified into:

Intraoperative fractures are subclassified into:

The postoperative fracture type A is subdivided into A_L (involves lesser trochanter) and A_G (greater trochanter). Type B is subdivided into B1, B2, and B3 based on implant stability and bone stock quality. B1 fractures have a solidly fixed implant. B2 fractures describe those in which there is a unstable implant and B3 fractures have a unstable implant and a compromised bone stock.

Figures 7.12.1 and 7.12.2 shows comprehensive treatment algorithms for periprosthetic femoral and acetabular fractures which were described in 2004.

The conservative treatment of periprosthetic fractures has become obsolete. These methods are fraught with complications. For example, revision rates as a result of prosthesis loosening have been reported in the range of 19–100%; reports of pseudoarthrosis rates range from 25–42%, and abnormal varus positioning of the femur occurs at an average rate of 45%. Subsequent revision is fraught with difficulties due to malunion. We no longer recommend the use of non-operative methods such as traction or cast immobilization as they increase the risk of thrombosis, embolism, pneumonia, pressure ulceration, and knee joint contractures. The goals of treatment are: to achieve early union; anatomical alignment and length; a stable prosthesis; early mobilization; a return to premorbid function; and maintenance of bone stock.

In type A1, the cortical perforations are easily accessible and can be treated with simple bone grafting. In type A2, undisplaced linear cracks, the surgeon should assess the stability of the fracture and the stability of the implant and these fractures can be treated with cerclage wire or cable fixation. In type A3, displaced or unstable fracture of the proximal femur or greater trochanter, disruption of the integrity of the metaphyseal region of the proximal femur necessitates the use of a diaphyseal fitting uncemented femoral stem. Fracture of the greater trochanter can be fixed with wires, cables, or a trochanteric fixation claw and cables.

Type B1 (diaphyseal cortical perforation) most commonly occur during canal preparation and should be bypassed by two cortical diameters with a longer stem. Cerclage wiring of the bone at or below the perforation, before stem insertion, to prevent crack propagation is advisable. A combination of bone graft and cortical strut should be used to bypass the perforation if it is at the tip of the stem. Amplified hoop stresses created while inserting the prosthesis can cause undisplaced linear cracks (type B2). When recognized intraoperatively, they should be treated with cerclage wires or cables and the fracture should be bypassed. If unable to bypass the fracture with a longer stem, supplement with a cortical strut, or a plate and screws. Cortical onlay allograft struts increase cortical strength and are associated with good clinical results. Most of type B2 fractures are diagnosed only on the postoperative radiographs and they are treated with protected weight bearing for 6 weeks to 3 months until there are signs of healing. Type B3 (displaced fracture of the mid femur) occur during dislocation of the femur, broaching, femoral cement removal, canal preparation, and insertion of the prosthesis. The fracture should be adequately exposed, reduced, and fixed, with either cerclage wires or with one or two cortical struts. The continuity of femoral canal should be re-established and a femoral stem that bypasses the fracture by at least two cortical diameters should be inserted. For a stable implant, retain the stem augment with cables and cortical struts. Type C1 (cortical perforations) should be bone grafted and bypassed with a cortical strut. Type C2 (undisplaced linear crack extending just above the knee), if recognized intraoperatively and if fracture is potentially unstable, cerclage wires with or without an onlay cortical strut allograft should be used. Whereas in type C3 (displaced fracture of the distal femur that cannot be bypassed by a femoral stem) should be treated with open reduction and internal fixation. For intraopertive acetabular fracture, the surgeon needs to assess for component stability, augment fixation with screws, buttress plating, or graft, and if loosening present, revision is inevitable.

The main aim of treatment is provision of bony columns to support an acetabular component. If the fracture pattern is more extensive with a transverse component or if there is displacement, the surgeon should stabilize the posterior column and fix anteriorly with lag screws and graft if required.

Type A_G are stable fractures treated with protected weight bearing up to 3 months and active abduction is avoided until union is achieved. Displacement greater than 2.5cm, trochanteric non-union, instability, or weakness of abduction are indications for internal fixation. When Type A_L fractures involve a large portion of the medial buttress, they may result in loss of implant stability and may warrant revision arthroplasty. These fractures are becoming more common with the increasing use of anatomical and tapered cementless stems.

The type B subgroup in the Vancouver system are probably the most crucial as they involve the bone in the vicinity of the femoral stem. They comprise more than 80% of late periprosthetic femoral fractures. There is a consensus that most fractures associated with a well-fixed stem (type B1 fractures) can be treated with open reduction and internal fixation whereas The mainstay of treatment for B2 type is revision of the femoral component using cemented or uncemented prostheses augmented with cerclage wires and strut grafts where indicated (Figures 7.12.3 and 7.12.4). Revision with a long-stem prosthesis permits stabilization of the fracture similar to that achieved when using an intramedullary nail, but the proximal femur may be a poor environment for recementing or proximal porous ongrowth if the index procedure was cemented. Uncemented prostheses help provide axial and rotational control in the diaphysis of the femur distal to the bone loss and comminution. In addition, they alleviate the potential concerns of cement inhibition or interposition on fracture healing. Fractures associated with a loose stem and extremely poor proximal bone quality (type B3 fractures), are treated with resection of the proximal femur and substitution with either a tumour prosthesis or an allograft prosthetic composite or a custom made implant (Figure 7.12.5). Every effort is made to preserve the abductor mechanism and reattach it to the implant or wrap the proximal femur around the implant.

Type C fractures are treated with open reduction and internal fixation.

The intramedullary blood supply is already compromised in periprosthetic fractures around THR. To add on to this the extraosseous blood supply is interfered due to dissection involved with open reduction and internal fixation (ORIF) with or without wiring. Bone grafting of all periprosthetic femoral shaft fractures treated with ORIF is recommended. Percutaneous fixation of periprosthetic fractures with dynamic compression plating (DCP) is a good alternative. In locking plates the screw locks onto the plate, providing additional angular stability; the plates are designed for minimally invasive insertion, allowing extraperiosteal application, preserving the periosteal blood supply and reducing soft tissue damage. The plates allow unicortical screw placement which makes it useful when dealing with periprosthetic fractures, as screws may be placed without damaging the cement mantle. However, some fracture configurations may affect the outcome of internal fixation even when the stem is stable; for example, transverse fractures at the tip of the stem are very difficult to treat with plates alone, and in these cases revision of the stem may be preferred. The other common implant systems used are the cable plate fixation devices. The third-generation systems allow cable retightening which is particularly useful.

Cortical onlay strut grafting, first described for the treatment of femoral periprosthetic fractures, is an attractive option because it combines fixation with the potential to restore the bone stock and increase cortical strength. Excellent union rates with this technique have been reported. Through union with the host bone, the allograft also may enhance the host bone stock and strength.

Impaction grafting with long cemented femoral prostheses, bypassing the most distal fracture line, together with structural cortical grafts and/or plates, has also been attempted with encouraging results. An alternative of cement-in-cement revision to a longer stem is available for unfit patients providing the cement mantle is well preserved. This is particularly useful with tapered stems.

In acetabular fractures, the aim is to regain structural integrity of the columns and restoration of bone stock so that it allows stable fixation. All patients who are suspected of acetabular fractures after THAs should get standard and Judet views of the pelvis and a computed tomography scan to make an accurate diagnosis. These images are also used to define the anatomy. Patients with stable acetabular fractures are initially treated with 6–8 weeks of touch-toe weight bearing. In the presence of significant displacement revision surgery is necessary. Initial conservative treatment is justified to allow union and avoid stripping of the posterior column for late presenting fractures around cemented acetabular components with significant osteolysis and minimal displacement. If pelvic discontinuity is present at revision surgery they should be treated with tantalum sockets, cup cage constructs, or antiprotrusio cages (APC), with bone grafting and plating as necessary.

Further classification of periprosthetic fractures around endoprostheses with epiphyseal or metaphyseal fixation has been proposed into EM-B and EM-C. EM-B fractures are found with surface replacement endoprostheses, which occur at the boundary of the cup endoprosthesis and the neck of the femur, or which occur in the metaphysis in the case of metaphyseal-fixed prostheses. The implant should be exchanged for a stem endoprosthesis in cases of EM-B fractures. The EM-C1 fractures are infrequent fractures that occur at some distance away from a stable cup endoprosthesis or below stable metaphyseal anchored prostheses. Internal fixation is the ideal treatment for these cases.

The indication of osteosynthesis should depend on the location of the fracture, quality of the osteosynthesis, and on whether polyethylene wear is radiologically detectable or not. If wear is present, these fractures should be managed like EM-C2 fractures and treated primarily by complete exchange of the prosthesis. The EM-C2 fractures are fractures that occur at some dis-tance below a loosened implant and are treated by prosthetic exchange.

Interprosthetic fracture is also proposed as an extension of the classification of periprosthetic fractures. Type IA are the fractures that occur between a stemmed endoprosthesis of the hip and surface replacement prosthesis of the knee joint, and type IB are those that occur between two stem prostheses (hip and knee) The type IA fractures are subclassified according to the implant stability: fractures with stable implant as type IA1 and loose implants as type IA2. Type IA1 fractures are treated with internal fixation techniques. Type IA2 require exchange of the implant at the same time with a prosthesis that bridges the fracture by at least two diaphysis diameters. Type IB fractures usually require a total femur prosthesis, whereby a stable stem implant can be integrated into a special prosthesis in the form of a pin prosthesis.

Surgical decision-making in this complex group is influenced by various factors such as the patient’s age, gender, femoral anatomy, bone stock quality, type and size of the prosthesis, surgical approaches, and techniques. The main strategies of management are: 1) identify the high-risk group, e.g. recurrent dislocation, loosening, subsidence and osteolysis; 2) perform revision arthroplasty before extensive bone loss results in periprosthetic femoral fracture; 3) in revision arthroplasties, it is prudent to obtain adequate surgical exposure, which may involve a trochanteric osteotomy, avoid eccentric or varus reaming, over-ream to avoid hoop stresses and fracture during the insertion of press fit stems, remove cement safely (by splitting it radially and at several levels or by ultrasound), and finally prevent propagation of fracture with the aid of prophylactic cerclage cables or wires.