Current evidence and new challenges in periprosthetic hip and knee fractures| Lo Scalpello - Journal

Abstract

Periprosthetic fractures (PPF) constitute an issue of increasing importance for orthopedic surgeons. With the continuous advancement of less invasive surgery techniques and the progressively ageing population, prosthetic replacement procedures have become routine. PPF are complex conditions that can compromise the outcome of surgery and the patient’s quality of life. However, in some cases, revision surgery is required. In this article we will analyze the epidemiology, risk factors, different classi ications, management, and evolution of treatment of hip and knee periprosthetic fractures.

Introduction

The overall number of periprosthetic fractures (PPF) is rising, due to three main risk factors: the increasing number of total hip and knee replacements being performed in Western countries and the global median age combined with the prevalence of bone weakening pathologies in elderly patients ¹.

Intraoperative periprosthetic fractures occur 14 times more frequently with un-cemented implants than with cemented ones, especially in patients over 65 years of age. Much more often, however, fractures occur in un-cemented prostheses because of low-energy trauma, regardless of gender ². The difficulty of treatment depends not only on fracture management, but above all on the stability of the prosthesis.

Furthermore, general and local factors can play an important role. General conditions, functional requests, patient compliance, and comorbidities are extremely important and must be taken into account. Local factors consist in the intraoperative stability of the implant, bone stock, and biology of the bone. In case of elderly patients with other pathologies, who poorly comply with their therapeutic and rehabilitative plan, choosing the least invasive type of procedure is preferred. Very often, however, in order to avoid complications due to extended bed rest and allow early load, prosthetic replacement is the surgical choice. For young patients, bone stock preservation is imperative, in consideration of their long-life expectancy and the high probability of a revision ³.

Epidemiology

In total hip arthroplasty (THA) the incidence of PPF varies from about 1 to 2.3% and is higher when using un-cemented prostheses instead of cemented ones (3 vs 0.2%); for women, compared to men, these percentages increase over the years. In THA revisions, the total incidence is even higher at 12.3% ^2,4.

In total knee arthroplasty (TKA), the incidence of PPF varies between 0.3 and 2.5% for the first implants and increases up to 38% after revision, with an average of 25.5 months between the TKA and possible fracture ^5,6.

The mortality rate following a femur PPF is significantly higher compared to a simple femur fracture. The increase in mortality affects both THA and TKA and is higher after surgery, reaching 8% in the first post-operative month and 27% after the first year. Survival decreases in older patients ^2,7.

Risk factors

Numerous factors can predispose to PPF. Patient-associated factors include advanced age, female gender, neurological and walking disorders, and more generally all conditions causing a depletion of bone mass such as osteoporosis, osteomalacia, Paget’s disease, and osteopenia due to corticosteroid therapy ¹. Prosthetic-related factors include local bone resorption and osteolysis phenomena, which can occur as a result of implant mobilization and bone defects ⁸.

Classification

PPF are generally categorized and classified based on the fracture site, but the classification can also take into account other criteria. For instance, how long after the prosthetic replacement surgery the fracture occurred and the stability of the implant ⁹.

The Vancouver classification for Periprosthetic Hip Fractures is the universal reference and is based on the fracture site and type, stability of the implant, quality of the periprosthetic bone stock (Tab. I) ^10,11.

There are several classifications for periprosthetic knee fractures and the most widely used is Rorabeck and Taylor. It evaluates fractures of the femoral component and takes into account bone fragment displacement and stability of the prosthetic components, but does not evaluate bone stock quality (Tab. II) ¹².

Felix’s classification concerns PPF of the tibial component, although less frequent, and divides them into four categories (Tab. III).

Patella fractures are categorized following the Goldberg classification, which is based on the integrity of the extensor apparatus and stability of the patella surface ¹⁴.

Periprosthetic hip fracture

There are currently no defined guidelines for the treatment of hip PPF. The choice of treatment depends on the type of fracture according to the Vancouver classification ².

In general, the loss of bone stock and the general conditions of the patient, often compromised, makes surgery more difficult. Revision surgery is basically inevitable in case of high comminution fracture or loosened prostheses ^15,16.

The implant stability is evaluated both by CT scan and intraoperatively. The proposed treatments are, therefore, open reduction and internal fixation (ORIF) or revision ⁷.

Generally speaking, there is unanimity in defining internal fixation as the treatment of choice for B1 fractures and revision as the best treatment for B2, B3, and C fractures, whereas most AG-type fractures are avulsions of the greater trochanter which are treated conservatively ^2,17,18.

After the surgery, the aim is to reduce bed rest time in order to minimize complications, allowing fast functional recovery. The most frequent complications are: non-union, fracture recurrence, aseptic loosening, recurrent dislocations, local infections, post-surgical stiffness, and limping ^2,17,19.

Periprosthetic knee fracture

As for fractures of the proximal femur, there are no precise indications regarding management of distal femur fractures in patients with TKA ⁶. The conservative treatment of supracondylar fractures is based on skeletal traction and immobilization of the limb. Skeletal traction is hard to implement because it requires prolonged immobilization and can lead to local and systemic complications, such as pressure ulcers and thromboembolic events. For these reasons, it is no longer in use ²⁰.

The most used surgical osteosynthesis techniques for supracondylar fractures are plate and screw synthesis and intramedullary nailing ⁶. In this case, early patient mobilization is essential to minimize complications associated with internal fixation, among which non-union stands out ^21,22.

In patients with low bone stock or significant bone loss, obtaining a stable fracture synthesis is not possible, and therefore the use of megaprostheses should be considered. The use of this technique allows the patient to gain early weight bearing, recovery of an acceptable range of motion, and a better long-term result, despite an increased rate of post-operative complications and mortality ^23,24.

Tibial fractures are a minority of periprosthetic knee fractures with a prevalence of 0.07-0.1% ²⁵. Tibial plateau fractures generally cause loss of implant stability and are treated with revision arthroplasty, while fractures without mobilization can be treated with open reduction and internal fixation (ORIF) ²⁶.

Methods

For the purpose of this study, we searched the PubMed and Cochrane databases with “periprosthetic fractures, femur, tibia, hip, knee, revision, megaprosthesis” as keywords. We crossed referenced the current insights on periprosthetic fracture treatment with our personal experience, to produce a review of the existing literature about treatment and management of PPF.

Results

By analysis of literature data about treatment of proximal femur PPF, the most common fracture is the Vancouver B1 type. The average age of patients according to Cox et al is 76.6 years; 1-2% of periprosthetic hip fractures were treated conservatively, 70% with ORIF and 27% with revision. Hospital mortality rate was 2.6% ⁴.

According to Abdel et al., the rate of PPF is much higher in cases treated with un-cemented implants than with cemented ones (7.7 vs 2.1%). 82% of AG-type fractures are avulsion fractures of the greater trochanter and 89.7% of these cases were treated conservatively. Among B1 fractures, 77% are treated with ORIF. Among fractures of types B2, B3, and C, 94.2% of cases were treated with THA revision ^2,28. In cases of type B2 and B3 fractures, the most recent studies show that ORIF and the prosthetic revision are comparable in terms of results ²⁷. It should be noted that a prosthetic replacement of the proximal femur, with massive bone loss, brings about an infection rate of around 2% and a percentage of instability close to 19% ²⁹.

For periprosthetic knee fractures, the average age is 70-76 years. Rorabeck type II fracture is the most frequent, followed by Rorabeck III and I ³⁰. According to Herrera et al, angular-stable plates give better long-term results than traditional plates. The medullary nail provides better fracture reduction but, in long-term follow-up, has a higher rate of pseudo-arthrosis than plate fixation ³¹. Several studies have observed that, the surgical treatment success rates of Rorabeck Type II fractures for patients treated with locking plate systems are similar to that of patients treated with intramedullary nail, respectively reaching 87 and 84% ^32-34. Other studies, however, have shown better results when using locking plate system ³⁵. Megaprostheses are a valid choice in distal femur PPF, especially if comminuted with bone stock loss; periprosthetic infections are the main complication ³⁶.

Analyzing comminuted fractures of the distal femur, Darrit B. et al pointed out that there is no significant difference in terms of blood loss between ORIF and prosthetic replacement. Moreover, multivariate analyses showed that the mortality rate of the two groups appeared to be overlapping ³⁷. However, Saidi et al. concluded in their study that blood loss and recovery time are reduced when revision surgery was performed ³⁸.

Discussion

Considering the increased incidence, long-term consequences, and increased mortality rate, hip and knee PPF constitute an issue of increasing importance for orthopedic surgeons. Currently used osteosynthesis systems represent an evolution in the treatment of this type of fracture. Locking plate systems preserve periosteal vascularization, allow minimally invasive techniques, and give better stability in poor bone stock compared to conventional plating systems. Low contact plates respect bone biology and minimize soft tissue damage. The load is distributed from the screw to the plate allowing for both compression and/or angular stability (depending on the surgeon’s choice and the fracture type). However, callus formation is sometimes inconsistent and asymmetrical, so that their use can cause delayed union and pseudo-arthrosis. As stated by Bottlang et al., the high stiffness of the angularly stable plates reduces micro-movements around the fracture site, reducing callus formation ³⁹.

Far cortical locking (FCL) screws can be seen as a new frontier in traumatology. Combined with locking plates, FCL screws show greater elasticity of the construct, promoting callus formation ⁴⁰. Moazen et al. demonstrated in 2016 that FCL screws guarantee and increase fracture site micro-movements, but also the stability of the PPF synthesis under axial and torsional loads. Therefore, their use is recommended in case of stable fractures (possibly with 1 mm gaps between each fracture fragment). However, other methods of synthesis such as long revision stems are advisable in case of PPF with unstable implant ⁴¹.

Prevention is a continuous process, starting from the first implant surgery, and then with post-operative radiographic checks to be repeated over the following months. When PPF occur, the primary objective of treatment must be functional rehabilitation for rapid recovery of the patient, in order to ensure implant stability and reduce mortality.

Although the literature does not present a precise and defined management algorithm for these cases, the use of classifications that take into account various aspects is crucial.

When choosing to proceed with ORIF, the principles that must be respected are stable fixation, preservation of soft tissues, and careful pre-operative planning (Fig. 1).

The use of resection prostheses or megaprostheses, in cases with large bone loss and highly comminuted fractures, is a possible choice. However, we would like to point out the importance of having a team of experienced surgeons, accustomed to using this type of implant and to filling large segmental defects (for example in oncological orthopedic surgery) (Fig. 2) ⁴².

For the distal femur, there is no significant difference in terms of function, considering the Knee Society Score ³⁷, for fractures treated with prosthesis instead of ORIF. Very often, distal femur fractures, or in any case of fractures involving the joint component, even when treated with ORIF, the result is a severe osteoarthritis which in most cases subsequently requires a prosthetic implant.

The complexity of using resection prostheses or megaprosthesis is complex, and many cases of severe complications are described in the literature, which are often hard to manage. There is a high incidence of dislocations in proximal femur replacements. On the contrary, a high rate of infections is reported in distal femur replacements ³⁶. Choosing replacement surgery with this type of implant means having to deal with very severe complications to which traumatologists are often not accustomed.

Taking into account to all the above, choosing the right course of action among all the available surgical treatment options is a difficult task, since conservative treatment is not always to be preferred and, in selected cases, it would be appropriate to consider using megaprosthesis.

In addition to improving megaprosthetic skills, the current challenges involve treating fractures in patients who have already undergone treatment of a PPF using ORIF; for example, patients with THA and proximal plate and screws. Our experience has led us to treat cases such as the aforementioned through the use of classic plates modeled preoperatively on the anatomy of the bone segment to be synthesized (Fig. 3).

In other cases, when inter-prosthetic fracture occurs combined with the presence of an ipsilateral THA and TKA, Patel NK et al. suggest to proceed with a reconstruction technique, by using a custom-made megaprosthesis that allows direct attachment to the stem of the retained knee prosthesis ⁴³.

Conclusions

The management of PPF represents a complex challenge. In fact, there is currently no clear boundary between synthesis and revision. The choice is influenced by several factors and the various classifications constitute a valid support, but are not completely sufficient to choose the most suitable surgical procedure. The use of megaprostheses in multi-fragmented and comminuted fractures with bone loss is a viable option, but surgeons must be familiar with surgical techniques and implants. Nowadays, the types of treatment for standard fractures have reached unambiguous indications, as opposed to PPF which require further advancement in terms of approach and treatment. In the most complex cases, such as fractures adjacent to prior PPF, the new perspective should include megaprostheses or, alternatively, advanced and patient-specific techniques of synthesis.

Figures and tables

Figure 1.Revision surgery in a failed ostheosynthesis of a periprosthetic fracture.

Figure 2.Distal femur replacement with a megaprosthesis in a failed osteosynthesis of periprosthetic fracture.

Figure 3.Classic plates modeled preoperatively on the anatomy of the bone segment to be synthesized.

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