Short title: Interfacial biochemical bond strength
An in vivo method for quantifying the interfacial biochemical bond strength of
bone implants
Short title: Interfacial biochemical bond strength
Young-Taeg Sul*, DDS, PhD1, Carina Johansson, PhD2 and Tomas Albrektsson, MD, PhD3
1
Associate professor, Department of Biomaterials/Handicap Research, Institute for Clinical
Sciences, Sahlgrenska Academy, Gothenburg University, Gothenburg, Sweden.
2
Professor, School of Health and Medical Sciences, Department of Clinical Medicine, Örebro
University, Örebro, Sweden.
3
Professor, Department of Biomaterials/Handicap Research, Institute for Clinical Sciences,
Gothenburg University, Gothenburg, Sweden.
Corresponding author information
Dr. Young-Taeg Sul.
Mailing address: Department of Biomaterials/Handicap Research, Institute for Clinical
Sciences, The Sahlgrenska Academy, Gothenburg University, Box 412, SE 405 30,
Gothenburg, Sweden.
Tel: +46 31 786 2950
Fax: +46 31 786 2941
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Short title: Interfacial biochemical bond strength
SUPPLEMENTARY METHODS
Design details of the TBS implant device
All dimensions of the TBS components were detailed in Supplementary Fig. 1. The disc
implant (Supplementary Fig. 1b) had a
45 degree and a 0.5 mm long bevelended functional surface of 8 mm
diameter and a cylindrical transducer
with a 2 mm hole for connecting to the
sample holder. To reduce shear and
tilting forces, the pin hole was tapered
and connected by a pin and pinhole
connection.
The
housing
frame
(Supplementary Fig. 1c) consisted of
the bevel seat for the fit of the disc
implant, a cylindrical lip at the bottom, two
arms, and necks and holes for the retention
screw. The cylindrical lip was designed to
stabilize the TBS implant device by pressfitting into the bone bed at the same
dimension of 10 mm diameter, 0.5 mm
depth. The cover screw (Supplementary
Fig. 1d) fit in the chamber of the housing
and held the disc implant in a desired bevel
seat position through point contact with the
conical apex of the cylindrical transducer of
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Short title: Interfacial biochemical bond strength
the
disc
implant.
The
retention
screw
(Supplementary Fig. 1e) was 3.3 mm wide and 7
mm long, with 10 tapered threads for obtaining
good retention of the TBS implant device in bone.
For possible adaptation of the TBS frame to
individual variance of the tibia contour, we
designed a notched neck along the arm and a
tolerance between the retention screw and screw
hole (3.3 mm vs. 4.0 mm).
Surgical protocol for stress-free stabilization of
the TBS implant device on bone
The animals were anesthetized with intramuscular
injections of fentanyl and fluanison (Hypnorm Vet,
Janssen, Saunderton, England) of 0.5 ml per kg body
weight and intraperitoneal injections of diazepam
(Valium, Roche, France) of 2.5 mg per animal. The
skin and fascial layers were opened separately. The
periosteal layer was gently pulled away from the
surgical area. To prepare the precise bone bed for
stabilizing the TBS implant device, we used a
custom-made 3 flute end mill set of 2, 4, 6, 8 and 10
mm diameters with a stopper of 0.5 mm height and a
central guide pin of 2 mm diameter. The desired position of the TBS device was marked on
the tibia cortical bone plate with assistance of a surgical guide template, followed by twist
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Short title: Interfacial biochemical bond strength
drills to make a 2.0 mm bone hole for the functional disc implant and the 3.0 mm holes for the
fixation screws.
When consecutively milling, care must be taken to ensure
the bone bed floor is flattened and parallel to the tibia
contour without perforating the floor of the bone bed
through the marrow cavity as the tibia cortex of the surgical
site of interest was thin, approximately 1.8 mm to 2.0 mm.
The drill stopper and central guide pin allowed the surgeon
to prepare the precise bone bed for stabilizing the TBS
implant device. The housing was positioned by fitting the
cylindrical lip on the flat-bottomed bone, stabilizing the TBS
implant device. The disc implant was fitted into the bevel
seat of the housing by screwing down the cover screw.
Alternatively, the housing, disc implant, and cover screw can be put together prior to
surgery. This can save operation time and confirm the high precision of the bevel seat fitting
between the disc implant and the housing. Stabilization of the TBS device was finished with
final adjustment of the retention screws. The skin and fascial layers were closed but the
periosteal layer was not resutured. During all surgical drilling and milling, low rotary drill
speeds and saline cooling were used. After surgery, the animals were kept in separate cages
and allowed full weight-bearing. The animals were sacrificed by intravenous injections of an
overdose of Pentobarbital® (Apoteksbolaget, Uppsala, Sweden).
Supplementary captions
Supplementary Figure 1. Detailed dimensions of the TBS implant devices in vertical crosssection view taken along the middle line. (a) Top and cross-section view of TBS implant
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Short title: Interfacial biochemical bond strength
assembly, (b) top and cross-section view of the housing frame (a-①), (c) top and lateral view
of functional disc implant (a-②), (d) top and cross-section view of cover screw (a-③), and (e)
top and lateral view of retention screw (a-④).
Supplementary Figure 2. Test set-up: (a) test machine, (b) a three-dimensionally adjustable
sample mount at the micrometer scale, and (c) the functional disc implant coupled to the load
transducer after measurement. The test machine was calibrated with a measurement accuracy
of better than 0.4 % using a load cell of 10 N at a constant load rate of 10 mm/min.
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Short title: Interfacial biochemical bond strength
Supplementary Table 1. Interfacial bond strength of the implants, MPa.
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