Do we bridge the femur to prevent interprosthetic fractures? A survey of 118 consultant orthopaedic surgeons

Introduction

Interprosthetic fractures (IPF) between ipsilateral hip and knee arthroplasties present a complex and increasingly relevant challenge for orthopaedic surgeons, both in terms of prevention and management. Although the true incidence of IPFs remains uncertain, they are estimated to account for up to 5–7% of all periprosthetic femoral fractures (PFFs). ¹ With rising arthroplasty volumes, an ageing population, and the increasing prevalence of periprosthetic fractures,^2,3 the burden of IPFs is expected to grow substantially.

Prophylactic strategies to reduce the risk of IPFs have been proposed, including the use of a spanning femoral plate to bridge adjacent implants—particularly when interprosthetic distance is short, such as in the presence of a stemmed total knee arthroplasty (TKA). However, clinical evidence supporting prophylactic bridge plating remains limited. In a series of proximal femoral fractures with stemmed TKAs, Peiró et al. advocated lateral plating to overlap the constructs, reporting no major complications. ⁴ Similarly, Sato et al. described “whole-span plating” in 10 patients with PFFs, observing no refractures but a 90% transfusion rate, highlighting the potential physiological burden of such interventions. ⁵

Biomechanical investigations have sought to clarify the mechanisms underlying IPFs and the factors that increase fracture risk. Soenen et al. demonstrated, using 3D femoral models, that interprosthetic distances below 110 mm markedly increase the risk of shaft fractures, particularly in osteoporotic bone. ⁶ Mühling et al. found that maintaining a minimum 10 mm interprosthetic gap mitigated strain peaks in synthetic bone models. ⁷ Conversely, Weiser et al. reported that cortical thickness, rather than implant spacing, was the dominant factor influencing fracture risk. ⁸ This finding was supported by Lipoff et al., who identified thin cortices, wide medullary canals, and an increased canal-to-cortex ratio as key risk factors. ⁹ Similarly, Mühling et al. and Iesaka et al. observed that reduced cortical thickness and the presence of a loose stem tip both act as stress risers, increasing peak strain between implants.^7,10

Unfortunately, there is a paucity of real-world clinical data on risk factors for IPFs. As such, our aim was to conduct a survey to assess current practice among lower limb arthroplasty surgeons to determine how surgeons manage cases of ipsilateral total hip arthroplasty (THA) and TKA, and whether surgeons feel there is merit to prophylactically bridging the implants to reduce the risk of IPF. We also wanted to investigate the factors which may influence a surgeon's decision to prophylactically bridge.

Methods

The senior authors (tertiary centre revision lower limb arthroplasty surgeons) met to discuss the pertinent factors associated with decision-making on interprosthetic fractures in patients with stemmed THA and TKAs. A questionnaire was created and distributed within multiple departments across England and also publicised on social media. Responses were collated in a data collection spreadsheet and analysed quantitively and qualitatively.

Results

Demographics of survey respondents

One hundred thirty-seven orthopaedic surgeons responded, of which 118 were consultants and 19 were fellows, associate specialists, or registrars. Of the 118 consultants, 67 (57%) practice both elective and trauma surgery, 41 (35%) elective only and 10 (8%) trauma only. Of the 109 consultants practicing electively, 67 (61%) work in a tertiary centre, 41 (38%) in secondary care/district general hospitals and 1 (1%) privately only. Of the 77 consultants practicing trauma, 40 (52%) work in a major trauma centre and 37 (48%) in a trauma unit.

Of the respondents, there were high numbers of primary and revision hip surgeons, and surgeons performing open reduction internal fixations for femoral periprosthetic fractures. There were lower, but still commendable, numbers of surgeons performing revision knees and endoprosthetic replacements (Figure 1).

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Figure 1.

Operative practice of consultant surgeons. THR, performs over 50 primary total hip replacements per year; TKR, performs over 50 primary total knee replacements per year; Rev THR, performs over 10 revision hip replacements per year; Rev TKR, performs over 10 revision total knee replacements per year; ORIF, performs over 10 femur periprosthetic fracture open reduction internal fixations per year; EPR, performs over 5 endoprosthetic replacements per year.

When would you prophylactically bridge the femoral implants?

With respect to millimetre (mm) of unprotected diaphyseal bone; 12% of surgeons would never bridge, 40% would prefer to use number of cortical diameters to make this decision. Of those that would use mm to decide, 41/55 (75%) would bridge if less than 60 mm (Figure 2).

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Figure 2.

When would you bridge the femur with respect to mm of unprotected diaphyseal bone?.

With respect to number of cortical diameters between implants; 12% of surgeons would never bridge, 17% would prefer to use mm between implants to make this decision. Of those that would use cortical diameters, 51/82 (62%) would bridge if less than 2 cortical diameters (Figure 3).

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Figure 3.

When would you bridge the femur with respect to number of cortical diameters between implants?.

Discussion

This survey of lower limb arthroplasty consultants demonstrates that most surgeons would consider prophylactic bridge plating of the femur to reduce the risk of IPFs when the distance between hip and knee implants is less than 60 mm or two cortical diameters. However, there remains substantial variation in practice, with 12% of respondents indicating they would never bridge the femur. The decision to prophylactically plate is clearly multifactorial and influenced by both patient- and implant-related factors.

The incidence of IPF is expected to rise as a result of an ageing population and the increasing number of total hip and knee arthroplasties, including revision procedures, being performed in the UK. ² IPF represent a devastating complication, often associated with prolonged morbidity and significant technical challenges. Management options depend on fracture configuration and implant stability, ranging from internal fixation to complex revision or endoprosthetic reconstruction. ¹¹ These interventions are associated with high complication rates, including prosthetic joint infection, re-fracture, non-union and hardware failure, with 2-year survivorship from reoperation reported as only 71%. ¹² Furthermore, the physiological impact of both the initial injury and subsequent reconstruction must be carefully considered in this typically elderly, frail patient group.

Prophylactic bridge plating to span the diaphysis between hip and knee implants has been proposed as a means of reducing the risk of IPF. Despite its theoretical benefit, the evidence base supporting this approach is limited, which is reflected in the considerable variability in clinical practice demonstrated by this survey. Prophylactic plating is not without potential drawbacks: additional surgical time, soft-tissue dissection, and the risk of further complications must be weighed against the anticipated benefit. Indeed, Taniguchi et al. reported a femoral fracture occurring despite prophylactic plating between a hip hemiarthroplasty and hinged knee prosthesis. ¹³ An alternative strategy to bridge the interprosthetic gap is to fill the femoral canal with cement; 29% of respondents in our study considered this an acceptable technique.

Identifying patients at highest risk of IPF remains challenging. Although biomechanical studies have demonstrated that reduced interprosthetic distance and narrow cortical width increase fracture risk,^6–10 clinical decision-making is influenced by many additional factors. In our cohort, 60% of surgeons reported they were more likely to prophylactically plate in the presence of poor bone quality, defined variably as osteoporosis, osteopenia, prior fragility fracture, or radiographic cortical thinning. Half of respondents were more likely to plate when the indication for arthroplasty was trauma—patients who typically have compromised bone stock. Additionally, 31% indicated they would consider bridging when a constrained knee prosthesis was used, likely reflecting concern regarding increased force transmission at the bone–implant interface. Other factors influencing decision-making included patient frailty, activity level, falls risk, equipment availability, and the technical feasibility of fixation around an existing femoral stem.

Despite the variation in individual practice, the majority of surgeons in this survey would bridge implants with a prophylactic plate when the interprosthetic gap was less than 60 mm or two cortical diameters. This highlights a general concern among surgeons regarding the risk of IPFs, despite the lack of robust clinical evidence to guide practice. Notably, 88% of respondents agreed that this remains an important and under-researched area. The multifactorial nature of the decision-making process and the heterogeneity of patient and implant variables make the design of a definitive clinical trial particularly challenging. Even seemingly simple parameters—such as how interprosthetic distance should be measured—lack consensus among surgeons.

Further biomechanical and clinical research is therefore warranted to better define thresholds for intervention, identify patients at greatest risk, and evaluate the true efficacy and cost–benefit of prophylactic bridging in the prevention of interprosthetic femoral fractures.

Conclusion

This national survey of 118 consultant lower limb arthroplasty surgeons highlights substantial variability in the use of prophylactic bridge plating to mitigate the risk of IPFs between ipsilateral total hip and knee arthroplasties. While most respondents favoured bridging when the interprosthetic distance was less than two cortical diameters or 60 mm, a notable minority (12%) reported they would never employ this technique. Decision-making was influenced by multiple factors, underscoring the multifactorial and complex nature of this clinical problem. Further clinical studies are warranted to establish evidence-based guidelines for the prevention of IPFs in this challenging cohort.