Summary

The proximal fascia lata (PFL) graft used for arthroscopic superior capsular reconstruction is openly harvested, whereas the mid-thigh (MFL) graft is minimally invasively harvested. The purpose of this study was to compare their biomechanical properties. We hypothesized that, despite their different morphological characteristics, their biomechanical properties would not significantly differ.

Abstract

Background

The proximal fascia lata graft construct (PFL) used for arthroscopic superior capsular reconstruction (ASCR) is openly harvested, whereas the mid-thigh fascia lata graft construct (MFL) is minimally invasively harvested. Knowledge of how the MFL compares biomechanically with the PFL may assist orthopedic surgeons in the choice of the location, harvesting technique, and type of graft construct for ASCR. The purpose of the current study was to compare the biomechanical properties of PFLs and MFLs used for ASCR. The hypothesis was that, despite the different morphological characteristics of the PFL and MFL used for ASCR, their biomechanical properties would not significantly differ.

Methods

Forty fascia lata (FL) specimens, twenty proximal-thigh and twenty mid-thigh, were harvested from the lateral thighs of ten fresh human cadavers (6 male, 4 female; average age, 58.60±17.20 years). The thickness of each 2-layered proximal- and 6-layered mid-thigh FL final graft construct was measured. Each construct was mechanically tested in the longitudinal direction, and the stiffness and Young’s modulus (YM) were computed. Data were compared by Welch’s independent t-test and analysis of variance. Statistical significance was set at P < 0.05.

Results

The average thickness of the PFL (7.17±1.97 mm) was significantly higher than that of the MFL (5.54±1.37 mm) [F (1,32)=7.333, p =0.011]. The average YM of the PFL and MFL was 32.85±19.54 MPa (range, 7.94–75.14 MPa; 95% CI, 23.71–42.99) and 44.02±31.29 MPa (range, 12.53–120.33 MPa; 95% CI, 29.38–58.66), respectively. The average stiffness of the PFL and MFL was 488.96±267.80 N/mm (range, 152.96–1086.49 N/mm; 95% CI, 363.63–614.30) and 562.39±294.76 N/mm (range, 77.46–1229.68 N/mm; 95% CI, 424.44–700.34), respectively. There was no significant difference in the average YM or stiffness between the PFL and MFL (p=0.185 and p =0.415, respectively). The main findings of this study were that the average values of the stiffness and YM did not significantly differ between the two types of FL graft constructs, despite the greater average thickness of the PFL. This study has several strengths: the PFL and MFL groups were equally sized with regard to the sex and age of the subjects, thereby avoiding the confounding influence of the sex- and age-dependent morphological and mechanical properties of the FL on the results; and the specimens were harvested from fresh cadavers, avoiding the significant influence of the fixation methods used to preserve fresh-frozen or embalmed cadaveric specimens on the mechanical properties of the FL. This study validates the biomechanical equivalence of the two types of FL graft constructs with regard to the stiffness and YM, and orthopedic surgeons and patients may find the mid-thigh harvesting of the graft advantageous versus the open harvesting technique because the MFL can be minimally invasively harvested using a reproducible technique, with a low donor site morbidity. This study defines material properties of PFLs and MFLs that can be used in computational studies regarding the role of the FL graft in ASCR.

Conclusion

Despite the different morphological characteristics of the PFL and MFL used for ASCR, their YM and stiffness did not significantly differ.