Orthopedic screws insertion simulation with immediate feedback enhances surgical skill.

BACKGROUND: Screw insertion to bones is a fundamental skill in orthopedic, spine and cranio-maxillofacial surgery. Applying the correct tightening torque is critical when compressing and fixating bone fragments. Overtightening yields in plastic deformation of the bone and destruction of the screw-bone interface, damaging the construct's stability. The surgeon is required to achieve sufficient hold and compression without stripping the bone. Several studies have investigated these skills, demonstrating much potential to enhance the future surgeons' capabilities. This study presents a novel training module, combining direct tightening followed by deliberate striping with immediate feedback suggested to enhance the surgeon's tactile perception and improve skill. METHODS: A prospective single-blinded cohort study was run. Twenty surgeons from various disciplines, excluding orthopedic and maxillo-facial surgeons, were trained using an orthopedic screws insertion model, comprised of synthetic bones. Training sessions considered inserting 40 screws into normal and osteoporotic bone models, experiencing deliberate stripping of the screws and feedback for their performance in three different sessions. FINDINGS: Success rate increased between sessions - by 24% to 48% in normal bone, and by 37% to 52% in osteoporotic bone. Stripping rate decreased between sessions - by 37.5% to 18.5% in normal bone, and by 29% to 14% in osteoporotic bone. Average ratio between tightening torque and maximum possible torque before bone stripping improved gradually and consistently from 67.3% to 81.6% in normal bone (p < 0.001), and slightly from 76.4% to 77.5% in osteoporotic bone (p = 0.026). INTERPRETATION: Immediate feedback with deliberate stripping and external feedback using a digital torque measuring screwdriver may improve cortical screw insertion technique in the surgeons' community.

Is initial interfragmentary compression made to last? An ovine bone in vitro study.

Interfragmentary compression, a major principle of fracture treatment, is clinically not quantified and might be lost quickly even without functional loads. We designed an experimental study hypothesizing that (1) compression can be controlled using either lag screw or compression plate, and expecting similar initial compression, (2) loss of interfragmentary compression through relaxation within one hour is reduced with neutralization locking plate next to lag screw compared to compression plate. Twelve ovine femora (N=6) and humeri (N=6) were assigned into groups: Group 1 received a 45° oblique osteotomy at mid-diaphysis and was fixated using a 3.5 mm interfragmentary lag screw and locking compression plate (3.5 mm LCP, DePuy Synthes) as neutralization plate. Group 2 received a transverse osteotomy and was fixated with dynamic compression using compression plate (LCP). Interfragmentary pressure and relative bone fragment displacements were recorded over one hour. Median loss of compression over one hour time (relaxation) were 0.52% in Group 1, and 0.17% in Group 2 (p>0.05). Median rotational displacements amounted to 0.46° for Group 1, and 0.31° for Group 2, and axial displacement to a median of -20 µm in Group 1 and 25 µm in Group 2. Ovine bone interfragmentary stress relaxation maintains compression over the first hour for lag screw with neutralization plate for an oblique fracture line or compression plate for a transverse fracture line. Measured compression forces around 100 N could be overcome by physiological tension loading in bending or torsion, necessitating for instance tension band plating, additional lag screws or absolutive stability.