Non prosthetic peri-implant femur fracture classification system and treatment algorithm: a systematic review

INTRODUCTION

Fragility fractures of the femur remain one of the most common causes of orthopaedic hospital admission worldwide. Between 2004 and 2014, 27% of all fractures requiring hospitalisation were hip fractures, accounting for 58% of orthopaedic bed occupancy in the UK National Health Services, with a further 10% attributed to femoral shaft and subtrochanteric fractures.¹ An increasingly recognised complication of fracture fixation is the NP-PIFF, with an incidence ranging from 0.5% to 2.7% and significant one-year mortality.^2-5

NP-PIFFs represent a distinct clinical challenge, occurring in femora that contain retained osteosynthesis hardware following primary fixation or osteotomy.⁶ Historically, these have been grouped under the broader category of “periprosthetic fractures,” which occur around joint replacements; however, the biological and mechanical considerations of NP-PIFFs differ markedly.⁴

The main difficulty in treating NP-PIFFs arises from the presence of a pre-existing fixation device, which alters the mechanical environment of the bone, interferes with healing, and restricts options for further fixation.^6,7 Although principles derived from periprosthetic fracture management may be partially applicable, a dedicated classification and treatment algorithm is needed to address the specific challenges of NP-PIFFs.²

In recent years, several authors have proposed implant-specific classification systems and management strategies. This systematic review aims to evaluate the existing literature on NP-PIFFs, synthesise data on classification systems and treatment algorithms, and propose a novel integrated framework. Secondary objectives include assessing key outcomes, such as union rates, one-year mortality, and post-operative complications.

METHODS

This systematic review followed the PRISMA guidelines and was prospectively registered with PROSPERO (CRD420251102564).

Eligibility criteria

Included studies reported on NP-PIFFs, described a classification system and/or treatment algorithm, and documented at least one of the following outcomes: union rate, one-year mortality, or postoperative complications. Eligible study designs included retrospective or prospective cohort studies and case series published in English. Exclusion criteria were case reports, studies limited to periprosthetic fractures, reviews, editorials, or conference abstracts.

Search strategy

A comprehensive search was conducted in Medline and Google Scholar, with assistance from hospital librarians. Keywords and MeSH terms included peri-implant fracture, femur, classification, internal fixation, and treatment algorithm. The search included all literature published up to July 2025. Reference lists of included articles were manually screened to identify additional relevant studies.

Study selection and data extraction

Two independent reviewers screened titles and abstracts. Full texts were assessed for eligibility, with disagreements resolved by consensus or a third reviewer. Data was extracted using a standardised spreadsheet, capturing study characteristics, patient demographics, classification systems, treatment strategies, union and mortality rates, and postoperative complications.

Quality assessment and synthesis

Methodological quality was assessed using the National Heart, Lung and Blood Institute (NHLBI) Quality Assessment Tool for case series and cohort studies. Studies were rated as good, fair, or poor. Due to heterogeneity in study design and outcomes, a narrative synthesis was undertaken.

Preferred reporting items for systematic reviews and meta-analyses (PRISMA) 2020 flow diagram.

RESULTS

Study characteristics

The search yielded 2,424 unique articles; 19 studies met inclusion criteria after screening. These included 12 retrospective studies, five case series, one validation study, and one consensus review, comprising a total of 984 patients. Mean age was 82.2 years (range 22-105 years). The incidence of NP-PIFF ranged from 1.4% to 5.1% across studies.

Classifications identified

Seven distinct classification systems for NP-PIFF were identified, highlighting the lack of standardisation. The most frequently cited system was Videla-Cés et al used in five studies, categorising fractures by anatomical location and implant type.⁸ Although comprehensive, it does not incorporate the healing status of the primary fracture.

Egol et al’s classification simplifies fracture description to three main patterns but excludes distal implants and original fracture status.⁹ The NPPIF/Chan classification adds a functional dimension by categorising primary fracture healing (A: healed, B: not healed, C: failing).^10,11 A modified version by Kruse et al expands this to include screws/pins and non-weightbearing fractures.¹²

The AO/OTA, Müller, and Skala-Rosenbaum systems provide varying degrees of anatomical detail but lack implant-specific parameters and biological context.^4,13-15 Four studies did not use any formal classification system.

The review suggests that an ideal classification should combine the structural specificity of Videla-Cés et al with the biological insight of the NPPIF/Chan framework, enabling clinicians to integrate fracture morphology with functional healing status.

Treatment strategies identified

Despite variability, management approaches shared consistent biomechanical principles. Most authors emphasised constructs spanning the entire femur, minimisation of stress risers, and retention of previous implants where feasible.^6,11,16,20

For fractures distal to cephalomedullary nails, options included long-nail exchange or plate augmentation, particularly when the original fracture was unhealed.^2,10 Plate-related fractures were managed with nail-plate constructs or plate-on-plate fixation.¹³ Distal femoral fractures were typically treated with locking plate osteosynthesis, such as LISS systems.⁴

Consensus guidelines, including the PISCO recommendations, reinforce the application of biological fixation principles-employing minimally invasive techniques, maintaining load-sharing constructs, and protecting the femoral neck.⁶ Technical refinements, such as reconstruction nails for dual-segment protection and intentional valgus alignment to mitigate varus collapse, were also noted.^16,17

Clinical outcomes and complications

One-year mortality was reported in 11 studies and ranged from 2.7% to 36%, highest in patients over 75 years with comorbidities. The most frequent causes of death were pneumonia, sepsis, and cardiovascular events.^2,18

Union rates were consistently high-95-100% across 14 studies-with follow-up periods up to 43 months.^10,16,19 Reported complications included implant failure (plate breakage, screw pull-out, nail breakage), loss of fixation, and peri-implant fracture propagation.^5,17 Malalignment, including varus collapse and rotational malreduction, was observed in multiple series.

Medical complications such as pneumonia, delirium, urinary tract infections, and acute kidney injury were common, often prolonging hospital stay.^2,11,18 Thromboembolic events-notably deep vein thrombosis and pulmonary embolism-occurred predominantly in the early postoperative phase.^5,16,19

These findings emphasise the dual importance of sound surgical technique and comprehensive perioperative care, requiring collaboration among orthopaedic, geriatric, and rehabilitation teams.

DISCUSSION

This systematic review synthesises the current literature on classification systems, treatment strategies, and clinical outcomes for NP-PIFFs-a challenging and increasingly recognised complication following fracture fixation in the elderly population.^3,20,21 The findings demonstrate marked heterogeneity in how NP-PIFFs are defined, classified, and managed, underscoring the absence of a universally accepted framework to guide clinical practice and research.

Classification systems: persistent heterogeneity

A consistent theme across the literature is the lack of a standardised, validated classification system for NP-PIFFs. Seven distinct classifications were identified among the 19 included studies, each addressing different aspects of fracture morphology, implant characteristics, or bone healing status. The most widely applied system-Videla-Cés et al’s classification-categorises fractures by anatomical location and implant type; however, it omits consideration of the primary fracture’s healing status, a key determinant of biomechanical stability and treatment planning.^3,8,22 In contrast, the NPPIF/Chan classification incorporates the healing status (healed, unhealed, or failing), which is clinically relevant but lacks comprehensiveness for distal and mixed-implant scenarios.^10,11

The frequent omission of the original fracture’s healing status-a factor with clear biomechanical and prognostic implications-represents a critical gap.^3,23-25 The coexistence of multiple systems limits the comparability of published data and obstructs the development of robust treatment algorithms. The trend toward hybrid or modified systems, such as the integration of Videla-Cés’ structural classification with the NPPIF’s functional component, reflects an evolving understanding that future classifications must integrate anatomical, mechanical, and biological dimensions. A unified, validated classification-incorporating implant type, fracture morphology, and healing status of original fracture-would provide a common language for the research, facilitate prognostic stratification, as well as the improve clinical decision-making.

Treatment strategies: convergence on core principles

Despite variations in fracture configuration and implant construct, treatment strategies across studies converged on several biomechanical principles. Authors consistently emphasised the importance of constructs spanning the entire femur, minimising stress risers, and retaining previous implants when feasible to avoid additional surgical trauma.^6,11,16,20 These tenets were reinforced by consensus recommendations from the PISCO group, which advocate biological fixation principles, implant overlap or bridging, and femoral neck protection.⁶

For fractures distal to a cephalomedullary nail, two dominant strategies emerged: long-nail exchange or supplementary plate fixation. For plate-related fractures, plate-on-plate fixation or combined nail-plate constructs were used to optimise load sharing. Distal femoral fractures were most often managed with long locking plate osteosynthesis, such as LISS systems, while retrograde nailing was reserved for select cases due to concerns of joint violation and implant interference.^4,10,16

A recurring emphasis on biological fixation-using minimally invasive reduction, preservation of soft-tissue integrity, and respect for the healing environment-reflects a paradigm shift from rigid fixation to functional stability. The increasing use of overlapping constructs to protect the entire femur reflects growing awareness that stress concentration between implants predisposes to secondary fractures.^3,20

Clinical outcomes and complications

Union rates were consistently high, often exceeding 95% across included studies, suggesting that predictable healing can be achieved when stable fixation and biological integrity are preserved.^10,16,19 Nonetheless, one-year mortality ranged widely from 2.7% to 36%, mirroring the frailty, multimorbidity, and advanced age typical of this patient group.^2,18

Mortality was most frequently attributed to postoperative medical complications such as pneumonia, sepsis, and thromboembolic events.

Mechanical complications were also prominent, including implant failure (plate or nail breakage, screw pull-out), loss of fixation, and fracture propagation around existing implants.^5,17 Malalignment, particularly varus collapse and rotational malreduction, was described in several reports and may be associated with suboptimal construct length or inadequate overlap.

Equally significant were systemic complications-pneumonia, delirium, urinary tract infections, and acute kidney injury-which were strongly correlated with prolonged hospitalisation and delayed mobilisation.^2,11,16,18 The early postoperative period was also associated with a notable incidence of deep vein thrombosis and pulmonary embolism, highlighting the need for aggressive thromboprophylaxis and early mobilisation strategies.^5,16,19 Collectively, these data reinforce that NP-PIFF management requires a multidisciplinary approach integrating orthogeriatric, anaesthetic, and rehabilitation expertise to optimise outcomes and reduce systemic morbidity.

Evidence limitations and future directions

The current evidence base remains limited by methodological heterogeneity. Most studies were retrospective case series with small sample sizes, inconsistent follow-up durations, and variable outcome definitions. Only one prospective, multicentre study (the PIPPAS study) systematically evaluated mortality predictors in a large cohort, underscoring the need for higher-level evidence.² Furthermore, no randomised trials have directly compared fixation constructs or investigated the functional outcomes of differing surgical strategies.

Future research should prioritise the development of multicentre registries and prospective validation studies of unified classification systems. Standardised outcome measures-including functional recovery, health-related quality of life, and reoperation rates-are essential to advance the evidence base. Comparative biomechanical and clinical studies examining overlapping constructs, implant materials, and biological augmentation techniques will also be crucial in the defining optimal surgical strategies.

CONCLUSION

Non-prosthetic peri-implant femoral fractures represent a growing challenge in orthopaedic trauma, reflecting the increasing use of internal fixation devices and the aging population. This review highlights the heterogeneity in classification systems and treatment strategies and underscores the urgent need for a unified framework integrating implant type, fracture morphology, and original fracture status.

Despite limited high-level evidence, several consistent principles emerge: fixation constructs should span the entire femur, stress risers must be minimised, and existing implants should be preserved whenever possible to reduce surgical trauma. High union rates are achievable with these strategies, but the overall prognosis remains guarded due to patient frailty and systemic complications.

Future efforts should focus on prospective, multicentre validation of classification systems, comparative trials of fixation constructs, and integrated multidisciplinary care pathways aimed at optimising both surgical and systemic outcomes in this complex patient population.

Funding: No funding sources

Conflict of interest: None declared

Ethical approval: Not required

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