Traditionally, before 2014, the classification described by Rorabeck was used for the periprosthetic distal femur fracture (PDFF) associated with total knee arthroplasty (TKA)1; and the Vancouver classification associated with total hip arthroplasty (THA).2 Several other classification systems exist for fractures above a TKA (Neer, DiGioa, Chen, and Su).3–6 Duncan and Haddad introduced the more comprehensive Unified Classification System (UCS) for periprosthetic fractures, which is used for fractures associated with both THA and TKA and is a valuable tool in the management of these injuries.7,8
Risk factors for distal femur periprosthetic fractures include osteopenia and osteoporosis, advanced age, inflammatory arthritides (such as rheumatoid arthritis), stress shielding and osteolysis, chronic corticosteroid use, stiffness, neurological disorders, revision arthroplasty, implant loosening, and infection.9 Anterior notching was believed to increase the risk of fractures, but biomechanical studies have not translated to increased incidences in clinical practice.10
High-quality plain x-rays are the mainstay of diagnosis and surgical planning of PDFF management. Anterior-posterior and lateral x-rays of the knee centered over the joint and the whole femur in 2 planes are required to assess the fracture pattern, extent of the fracture, and stability of the prosthesis. Full-length femur x-rays are also required to assess the femoral bow when considering intramedullary fixation. Regarding uncemented THA, early (first few weeks after implantation) PDFFs should be considered as having loose stems because they would not have the chance to become integrated.
Although not essential, computed tomography (CT) scans can be used to assess the stability of the femoral component. Major osteolysis is clearly visible on x-ray; however subtler osteolysis is more evident on CT scans. CT scans can also assist in assessing the location of the fracture around the stem or box, which may have an impact on the choice of fixation device.11 Metal artifact reduction magnetic resonance imaging can be used if implant stability is unclear from x-ray and/or CT scans but is not often accessible in resource-limited and constrained settings.
In general, PDFFs are treated operatively. Conservative management is associated with significantly higher rates of nonunion, malunion, and secondary surgical episodes.12,13 Nonoperative management, in the form of hinge bracing or casting and non–weight-bearing until union, may be considered in cases where the patient is anesthetically unfit for surgery, refuses surgical intervention, or if there are severe financial constraints. UCS type A can be treated conservatively (with a brace) based on the degree of displacement, with the provision that knee stability has not been compromised. If conservative treatment fails, fixation of the avulsed fragment may be necessary.
Fractures below a well-fixed THA are classified as UCS type C fractures. These fractures are often spiral fractures of the distal metaphyseal or diaphyseal part of the femur and are rarely intra-articular. By definition, they do not involve the femoral stem. Thus, the implant does not need to be revised, but the fracture needs to be fixed with consideration given to the implant above it. The workhorse of type C fracture treatment is open reduction internal fixation (ORIF). As most periprosthetic fractures occur in older individuals with poor bone stock, locking plates are preferred over nonlocking plates, to reduce cut-out rates.14 To avoid stress risers and to allow sufficient working length for the plate, it is recommended that the plate span the entire femur, from the lateral condyle to the greater trochanter. Cerclage wires are commonly used in the proximal part of the femur because regular screw placement may be challenging in the presence of a femoral stem. Unicortical or bicortical screws missing the implant can be considered as alternative options. Cables are preferred over unicortical screws, which are more prone to pull-out.15 Yet, with certain types of stems, such as tapered “blade” stems, it may be possible to place a variable-angle locking screw either anterior or posterior to the stem. In addition, a cemented stem may allow screw placement through the cement mantle behind or in front of the stem (Fig. 1). Because plate fixation may require nontouch or toe-touch weight-bearing postoperatively, patients may need to be discharged to a rehabilitation facility or a nursing home. Gausden et al examined the outcomes of these fractures and noted a nonunion rate of 10% at 2 years and a mortality rate of 31% at the same time frame.14
The UCS divides these fractures into those that involve only the epicondyles (type A), those that involve the distal femur at, or just proximal to, the level of the implant (Type B), and those that involve the femoral shaft well proximal to the TKA (Type C).8 Type B fractures are further subdivided into: B1—femoral component is well-fixed; B2—femoral component is loose; B3—femoral component is loose and there is poor bone stock. Type B fractures are treated in a fashion similar to type B fractures of the hip. The treatment algorithm for type B PDFFs is summarized below in Fig. 2. Type B1 fractures are treated with ORIF, where fixation can be performed with either a plate or a retrograde nail (Fig. 3). If choosing a retrograde nail, one must be sure that the nail can pass through the femoral component. This is usually not a problem in cruciate retaining implants, in which the posterior aspect of the implant is open. Posterior-stabilized implants have a posterior cam that creates a “box” between the cam and the condyles. One must confirm that the box has an open design (can be entered through the implant) and that it is large enough to allow passing a nail of the appropriate size. A guide has been published to assist in this decision-making process.16 It is important to verify that there are enough locking screw options in the distal part of the nail to ensure sufficient mechanical stability of the distal fragment. In addition, one must be cognizant of the fact that the shape of the femoral component may force the final construct into an inevitable extension deformity (Fig. 4). With modern anatomical lateral locking femoral plates, polyaxial screw placement allows the screws to be directed to areas with good bone stock and miss the femoral component. If plate fixation is used, a lateral locking plate spanning the length of the femur through open or minimally invasive plate osteosynthesis (MIPO) can be used. A dual plating technique with the use of a proximal humerus or contoured reconstruction plate on the medial side and distal locking lateral plate is useful in osteopenic bone. Both plates are placed using the MIPO technique and held with a single proximal and distal fixation point. A clamp is then placed on both the medial and lateral plates to maintain axial and sagittal alignment, therefore avoiding disruption or further comminution at the supracondylar level.17
Type B2 fractures are treated with revision of the femoral component. If the fracture involves the epicondyles, consideration must be given to using a hinged component (Fig. 5). In type B3 fractures, the condylar bone stock is very poor, and thus, it is very difficult to position a stable femoral component on the femur. In such cases, a distal femoral replacement (DFR) or tumor prosthesis should be considered.
Type C fractures are treated as isolated femoral shaft fractures. They may be nailed in an antegrade or retrograde fashion, depending on the location of the fracture. In antegrade nailing, the nail should end distal to the anterior flange of the femoral component to prevent a stress riser and a possible interimplant fracture (Fig. 6).
Interprosthetic fractures between a THA and a TKA (type D in the UCS) are expected to be on the rise, with an increasing number of knee and hip arthroplasties performed annually. In these cases, “block out analysis” is recommended, where the effect of the fracture is analyzed separately for each implant.7 For example, a simple spiral fracture well above a primary TKA and well below a primary THA is a type C fracture, to be treated with ORIF. A type D fracture, involving any of the 2 implants, will be treated as a type B fracture for that specific implant, with consideration given to the presence of the other one. If the femoral component of a TKA is revised and a femoral stem is used, the stem should end at least 2 cortical diameters below the tip of the ipsilateral THA femoral component to prevent another interprosthetic fracture. If that is not possible, a plate spanning both implants and the fracture should be considered. In extreme cases of multiple revised hips and knees, a total femoral replacement may be considered (Fig. 7).
It is clear that these complex fractures require careful assessment and consideration of the management protocol. The available resources and surgical technical skill and training may dictate the chosen protocol or plan. This article is prepared as a collaborative effort with the perspectives from both developed and developing world economies. The 3 countries participating in this collaborative report, Israel, South Africa, and South Sudan, differ in their health care systems, their population comorbidities and life expectancy, their rehabilitation facilities, and the resources available.
2. Israeli Perspective
Israel does not have a national total joint registry, and thus, it is difficult to comment on a nation-wide policy in treating these fractures. The one common issue facing most hospitals is the Israeli payment system, which prevents, for example, appropriate utilization of DFR when needed. Israel enjoys universal health care so that all citizens are automatically insured by 1 of 4 insurers. Since 2002, the Israeli Ministry of Health (MoH) has included TJR in a procedure-related group (PRG) payment model, setting a fixed price for the entire episode of care. The MoH acts as a regulator only, and thus, each of the 4 abovementioned insurers negotiates a rate of its own with each hospital for a given PRG, often for a sum much lower than the original price set by the MoH. This makes procedures that use an expensive implant unprofitable for the hospital because it narrows its profit margin for each procedure or may even cost the hospital more than the reimbursement it would receive from the insurer. Thus, type B3 fractures are often treated with ORIF and a prolonged period of nontouch or toe-touch weight-bearing, whereas a DFR could have provided the patient immediate weight-bearing, minimizing rehabilitation costs, and preventing complications related to long-term immobility.
3. South African Perspective
South Africa has recently implemented a national orthopaedic registry; however, it is not mandatory, and data are slowly being collected. Regarding periprosthetic fractures, ICD-10 coding is not always consistent, with some surgeons coding for a distal femur fracture, rather than a periprosthetic fracture. These teething problems need to be resolved to determine the national incidence of PDFFs. South Africa has 2 health care systems, both with their own challenges that affect access to resources and in some cases, dictate the management of PDFFs. The state sector, which is accessed by many citizens, is funded by the state and limited by access to theatre time and budget constants that need to be distributed equally. As for Israel, often when a more expensive implant would ensure quicker return to function and potentially lower complication or reoperation rates for an individual patient, a more inexpensive implant must be used. Within the private sector, a similar problem exists with health care funders (insurance companies) placing prosthesis limits and more recently implementing a global fee for a surgical event in which all stakeholders are compensated from a set amount. This includes the prosthesis, and therefore, compromise must be made to ensure adequate fees to each party. Access to rehabilitation, step-down facilities, and home-based care is a very limited resource in both the public and private sectors and affects the functional recovery of patients. Regarding management of type B1 fractures, there has been a trend toward using lateral locking plates rather than retrograde intramedullary nails. The technique of dual plating is gaining traction currently. However, each patient and fracture is managed on their merits. Type B3 fractures are often managed with ORIF and constrained femoral prostheses rather than DFR for the above-mentioned reasons.
4. South Sudanese Perspective (East Africa)
Both THA and TKA are gaining traction in this region, but there is little published literature on PDFFs regarding the management approach based on the available resources. In South Sudan, retrograde intramedullary nails are the implants of choice for UCS types B and C.18–20 Compared with distal femur periarticular locking plates, intramedullary nails are a more cost-effective solution. Periarticular distal femur locking plates are sparsely available in some areas in South Sudan. These are considered optimal options in distally located fractures and with femoral components that are not compatible with intramedullary nails. Although inferior implants,20 nonlocking plates are still in use where access to better options is limited. Angular plates and dynamic condylar screws are the fixation methods applied in such scenarios. The complication rates are high with these implants however, and they are particularly hard to use in posterior stabilized knees. Fracture patterns where any part of the fracture line extends distal to the upper edge of the anterior flange of the femoral component (Su type III) are preferably treated with periarticular distal femur locking plates. Fractures that compromise the stability of the femoral components are most often referred for revision arthroplasty or DFR. Both options are not available in most of the countries in the East Africa region.
While this report discusses the literature and defines the current preferred protocols for each classification type, ultimately resource availability and surgical training will influence the management plans in these 3 regions. Israel can be considered a developed world, South Africa a combination of developed and developing world, and South Sudan a developing world environment. The management protocols in all 3 countries are an interesting study of the evolution of health care. Interference by funders is a problem in both Israel and South Africa, and adequate registry data are needed if the physicians would like to challenge these financially motivated protocols. This initiative has been undertaken by the South African Orthopaedic Association, but time is required to collect and collate the data meaningfully. Israel offers universal health care, but there are “stealth” obstacles in the provision of this care. The South African private health system is tiered so that the affluent patients who can afford elite health insurance have unlimited access, and as the insurance plan changes so does the implant choice and surgery access. The South African public health system is largely constrained by resource limitation. Within this system, tertiary academic hospitals can offer care in line with the developed world protocols, while the outlying secondary hospitals in smaller communities are not as well resourced. These dichotomies can exist within a few kilometers of each other, and a referral system has evolved to care for the complex case. Referral however relies on recognition by the primary treating doctor. East Africa is a developing region. The orthopaedic surgeons in South Sudan manage according to their resource limitations, and referral across borders can be arranged if needed. Optimization and management of modifiable risk factors is part of both a preventative strategy and fracture management.
Surgical management of PDFFs should ideally include orthopaedic surgeons with both trauma and arthroplasty expertise. A multidisciplinary team approach includes, but is not limited to, geriatric physicians, endocrinologists, rheumatologists, physiotherapists, occupational therapists, and home-based care teams. PDFFs are challenging injuries. The UCS helps classify and guide treatment of these fractures. Financial constraints often limit treatment options, and innovative strategies need to be adopted for each individual patient.
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