Absorbable scaphoid screw development: a comparative study on biomechanics

Figures & data

Figure 1 ASS design.

Notes: (A) ASS parameters. (B) Side-by-side comparison to show the actual ASS size. L represents length; R represents radius; and Φ represents diameter. Units are given in millimeters.
Abbreviation: ASS, absorbable scaphoid screw.

Figure 2 Surgical procedure for scaphoid fixation using an ASS.

Notes: (A) A standard dorsal wrist incision of 5 cm was made, after which the wrist capsule was opened by using a ligament-sparing capsulotomy. (B) ASS was screwed into the scaphoid.
Abbreviation: ASS, absorbable scaphoid screw.

Figure 3 CT imaging of a scaphoid fixed with ASS with fracture gap measurement.

Notes: (A) horizontal plane. Arrowhead indicates the ASS. (B) Coronal plane. Numbers indicate fracture gap displacement. Arrows indicate the fracture gaps and their associated distances. (C) Sagittal plane. Arrows indicate the fracture gaps and their associated distances. Numbers indicate fracture gap displacement.
Abbreviations: CT, computerized tomography; ass, absorbable scaphoid screw.

Figure 4 CT scanning to measure fracture gap displacement after fatigue testing.

Notes: (A) Horizontal plane. Arrowheads indicate the ASS. (B) Coronal plane. Numbers indicate fracture gap displacement. Arrows indicate the fracture gaps and their associated distances. (C) Sagittal plane. Arrows indicate the fracture gaps and their associated distances. Numbers indicate fracture gap displacement.
Abbreviations: CT, computerized tomography; ASS, absorbable scaphoid screw.

Figure 5 3D palm reconstruction image after fatigue testing.

Notes: (A) 3D reconstruction showing carpal bone positions. (B) 3D reconstruction of the scaphoid (blue), lunate (green), and capitate (pink). Arrows indicate drill openings where the ASS was inserted into the scaphoid.
Abbreviations: 3D, three dimensional; ASS, absorbable scaphoid screw.

Table 1 Comparisons of fracture gap displacements before and after fatigue testing

Groups	Measured by CT (mm)
	Before	After
ASS group (n=10)	0.16±0.02	0.21 ±0.03*
K-wire group (n=10)	0.22±0.02	1.52±0.07*,**

Notes: Values are mean ± standard deviation.

* P<0.05, compared with the same group before fatigue testing.

** P<0.05, compared with the ASS group after fatigue testing.

Abbreviations: CT, computerized tomography; ASS, absorbable scaphoid screw; K-wire, Kirschner wire.

Table 2 Comparisons of tensile and flexural strengths

	Tensile strength (MPa)	Flexural strength (MPa)
ASS group (n=10)	0.95±0.02	2.71 ±0.20
K-wire group (n=10)	0.63±0.02*	2.5±0.52

Notes: Values are mean ± standard deviation.

* P<0.05, compared with the ASS group.

Abbreviations: ASS, absorbable scaphoid screw; K-wire, Kirschner wire.