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. 2025 May 1;14(5):368-375.
doi: 10.1302/2046-3758.145.BJR-2024-0278.R2.

Decreased femoral fracture load after cephalomedullary nail removal : a biomechanical ex vivo study

Gilbert M Schwarz  1   2   3 , Alexander Synek  4 , Stephanie Huber  2   3 , Jochen G Hofstaetter  3   5 , Dieter Pahr  4   6 , Andreas Reisinger  6 , Sylvia Nürnberger  1 , Lena Hirtler  2
Affiliations

Decreased femoral fracture load after cephalomedullary nail removal : a biomechanical ex vivo study

Gilbert M Schwarz et al. Bone Joint Res. .

Abstract

Aims: Spontaneous neck fractures are feared complications of cephalomedullary nail removal after successful healing of per- and subtrochanteric fractures. To date, the initial postoperative stability as well as the correct weightbearing regimen remain unclear. The aim of this biomechanical ex vivo study was to evaluate the initial postoperative failure load after hardware removal of specimens, which received cephalomedullary nails during their lifetime.

Methods: A total of 20 specimens of voluntary body donors were included in this study. Group 1 (n = 10) consisted of specimens that received cephalomedullary nails during their lifetime due to per- or subtrochanteric fractures. Each individual was matched for age, sex, femur size, and neck-shaft angle (Group 2 = control, n = 10). Biomechanical testing was performed in a single-leg stance setting, and volumetric bone mineral density (vBMD) was measured proximally at the femoral neck and distally at the epicondyles.

Results: Groups 1 and 2 differed significantly in terms of failure loads (p = 0.002), fracture types, and ratios of proximal and distal vBMD (p = 0.035). Femora after nail removal were significantly weaker (1,835.0 N vs 4,523.0 N) and showed lower ratios of proximal to distal vBMD (0.74 vs 1.18), which indicated altered stress distributions at the femoral neck in presence of femoral neck screws. They were further characterized by predominantly subcapital buckle-type fractures, while the control Group 2 showed predominantly transcervical fractures.

Conclusion: Altered stress distribution in presence of femoral neck screws leads to changes in biomechanical properties of the proximal femur, resulting in potentially unstable situations after nail removal in clinical settings. Elective removal of cephalomedullary nails should be undertaken with caution in view of the potentially increased fracture risk.

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Conflict of interest statement

G. M. Schwarz and L. Hirtler report funding from the Medical Scientific Fund of the Mayor of the City of Vienna (MA 40-GMWF-21072), and a Scientific Research Grant from DePuy Synthes, Johnson & Johnson (8205 (213871)), both related to this study.

Figures

Fig. 1
Fig. 1
Overview of included specimens. Upper row: DePuy Synthes Proximal Femur Nail Antirotation (PFNA) (USA). Lower row: Stryker Gamma3 (USA). L = long. Specimen 2 showed cement present within the femoral head surrounding the PFNA blade, and specimen 5 was excluded from biomechanical testing due to a nonunion at the pertrochanteric region. m, months.
Fig. 2
Fig. 2
Workflow of the study protocol. BMD, bone mineral density; PFNA, Proximal Femur Nail Antirotation; vBMD, volumetric bone mineral density.
Fig. 3
Fig. 3
Force-displacement curves of all tested specimens. Group 1 (femora after nail removal) = black, Group 2 (intact control group) = grey. Mean failure load was 1,835.0 N (SD 669.5) for Group 1 and 4,523.0 N (SD 2,161.0) for Group 2. Differences were statistically significant (p = 0.002, independent-samples two-sided t-test).
Fig. 4
Fig. 4
Left: Diagram of fracture types at the proximal femur – subcapital fracture (dotted line), transcervical fracture (dashed line), and pertrochanteric fracture (xxx-line). The subcapital fracture was classified as a buckle-type fracture, i.e. an undisplaced complete subcapital fracture with a varus tilt of the femoral head and a medial impaction zone. Right: 3D volume renderings (upper row) and coronal CT reconstructions (lower row) of subcapital (left), transcervical (middle), and pertrochanteric (right) fractures found in this study.
See this image and copyright information in PMC

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