Symptomatic flatfoot deformity in adults often occurs as a result of dysfunction of the
Tibialis posterior tendon (TPTD), with a prevalence of 3.3%. Structured non-surgical
treatment programs with orthotics and physiotherapy can achieve a high level of long-term
subjective and functional satisfaction, with surgery being avoided in 70-89% of cases.
Surgical intervention is indicated for progressive or uncontrolled symptoms. Flexible
flatfoot deformity, stage II classified by Johnson and Strom, can be treated with a
joint-preserving strategy, which usually includes a medializing calcaneal osteotomy,
debridement of the tibialis posterior tendon, and transfer of the flexor digitorum longus
(FDL) tendon. 87% satisfaction after ten years was observed in both pain relief and foot
function and alignment.
Metal screws have been used for decades to treat bone fractures. The removal is the major
disadvantage of conventional osteosyntheses and requires a second operation, with all the
resulting risks of complications for each patient. The use of the bone screw from
allogeneic cortical bone would reduce costs substantially, with a significant reduction
in the average complication rate to 0.3%.
The idea of stabilizing fractures using compact bone instead of metal is not new.
Obwegeser published the clinical use of 796 screw implants of allogeneic bone and
reported that the only complication was the fracture of 6 screws (<1%) and three screw
loosening (<0,5%).
Since 2016, the human, allogeneic cortical bone screw(Shark Screw®) has been used by two
tissue banks, the Austrian Austrian tissue bank Surgebright-GmbH and the German Institute
for Cell and Tissue Replacement (DIZG). The Shark Screw® graft was approved by the
competent Austrian authority (AGES) in 2016. The bone graft immediately creates a solid,
purely bony connection. This leads to bone remodeling, bone incorporation and optimal
reparation in the surgical area. Depending on the loads and requirements, the bone
connection adapts for the future. The bone grafts undergo a certified sterilization
procedure at the DIZG, which was developed in 1985 at the Berlin Charité.
Due to the lack of further systematic investigations to objectively confirm the
theoretically given and subjectively experienced product advantages, this observational
study is now being conducted.
The aim of the present study is to evaluate the application of the human allogeneic
cortical bone screw (Shark Screw®) and the metal/Bio-Tenodesis screw in the surgical
treatment (medializing calcaneus osteotomy with FDL transfer) of symptomatic flatfoot and
to systematically document corresponding clinical and radiological parameters before and
after surgery.