Biomechanical Testing Of Three Techniques Of Suspensionplasty Following Trapeziectomy
Hayman Lui, MD, PhD1,2; John Galbraith, MD3; Kathleen N. Meyers, MS4; Randy Bindra, FRCS5; Steve K. Lee, MD6
1Griffith University, Gold Coast, QLD, Australia; 2Mayo Clinic, Rochester, MN; 3University Hospital Galway, Galway, Ireland; 4Hospital for Special Surgery, New York, NY; 5Orthopaedic Surgery, Griffith University and Gold Coast University Hospital, Southport, Australia; 6Hand and Upper Extremity Surgery, Hospital for Special Surgery, New York, NY
INTRODUCTION The abductor pollicis longus (APL) suspensionplasty and Delsignore suture suspensionplasty techniques will have comparable biomechanical strength to the traditional Burton and Pellegrini ligament reconstruction and tendon interposition (LRTI).
METHODS 18 below-elbow cadaveric forearms were used for this study with 6 specimens per surgical technique. Each specimen was randomly assigned to receive the LRTI, APL suspensionplasty or suture suspensionplasty post-trapeziectomy. The APL suspensionplasty involved the use of a distally based APL tendon slip, passage through an osseous tunnel in the first metacarpal and fixation using a 3.5mm tenodesis screw into the base of the index metacarpal. Biomechanical testing was adopted from previously validated studies. A physiological lateral pinch model was simulated to assess maintenance of trapezial space height for each surgical technique (Figure 1). Following pinch simulation, the thumb metacarpal was axially loaded in increments of 5lb, tensioning statically for 5 minutes on each weight from 5lb to 25lb or until failure. Metacarpal subsidence was measured on fluoroscopy images as per previously described methods. One-way ANOVA with Tukey’s multiple comparisons test were used for determining significance (p<0.05) in the 3 experimental groups.
RESULTS There was no significant difference between the mean trapezial space height of the specimens pre-surgery compared to unloaded post-trapeziectomy with suspensionplasty (p>0.05). After simulation of the physiological lateral pinch, there was a significant difference in mean trapezial space height between both the APL suspensionplasty (6.8±1.3mm) and the suture suspensionplasty (8.1±2.3mm) when compared to the LRTI group (2.1±1.2mm) (Figure 2, p<0.05). After axial loading, there was significantly greater metacarpal subsidence in the LRTI group when compared to the APL and suture suspensionplasty groups (Figure 2, p<0.05).
CONCLUSIONS Both the APL suspensionplasty and suture suspensionplasty technique demonstrated superior biomechanical strength in resisting trapezial space collapse when compared to the LRTI group.The use of the APL tendon decreases the deforming force of the APL that pulls the first metacarpal into dorsal subluxation while also allowing for the reconstruction of the transverse carpal ligament. The suture technique is a quick and cost-effective method for metacarpal suspensionplasty with no tendon graft requirement resulting in decreased donor morbidity. The APL and suture suspensionplasty techniques may provide an alternative to current techniques of metacarpal suspensionplasty and facilitate earlier mobilization post-surgery.
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