PURPOSE: A new device for intraoperative pedography was developed. The purpose of this study was to validate the introduced method with standard dynamic pedography, and to analyze the clinical benefit.

Methods: For an intraoperative introduction of standardized forces to the footsole, a device named Kraftsimulator Intraoperative Pedographie was developed.

The validation was performed in two steps: Step 1. Comparison of standard dynamic pedography (three trials, walking, third step, three trials, mid stance force pattern), static pedography in standing position (three trials) and pedography with KIOP in healthy volunteers (three trials, total force 400 N).. Step 2. Comparison between pedography in standing position, pedography with KIOP in awake and anaesthesized patients (three trials, total force 400 N).

A randomized prospective controlled study comparing treatment with and without intraoperative pedography has started on November 1, 2005. The subjects are randomized into two groups,

a) use of intraoperative pedography, versus

One-year-follow-up including standard dynamic pedography is planned. The following scores are used: American Orthopaedic Foot and Ankle Society (AOFAS), Visual-Analogue-Scale Foot and Ankle (VAS FA), Short-Form 36 (SF36, standardized to 100-point-maximum). Intraoperative consequences after the use of intraoperative pedography were recorded.

Results: Validation Step 1: 30 individuals were included (age, 26.1±8.6 years; gender, male: female = 24: 6). Step 2: 30 individuals were included (age, 55.3±30.3 years; gender, male: female = 24: 6). No significant differences between all measurements of step 1 and 2 were found for step 1 and 2 without the dynamic platform measurements of step 1.

Clinical use: 16 patients were included until January 31, 2006 (ankle correction arthrodesis, n=2; subtalar joint correction arthrodesis, n=4; arthrodesis midfoot, n=4, correction forefoot, 4; Lisfrcan-fracture-dislocation, n=2). 9 patients were randomized for the use of intraoperative pedography. The mean preoperative scores were: AOFAS: 49.6±23.7; VAS FA: 42.2±13.1; SF36: 48.1±23.2. The mean interruption of operative procedure for the intraoperative pedography was 359±34 seconds. In 4/9 cases changes were made after intraoperative pedography during the same operative procedure (correction modified, n=3; screw tightened, n=1). The follow-up has not been completed so far.

Conclusion: Since no statistical significant differences were found between the measurements of intraoperative pedography in anaesthesized individuals and the standard static pedography, the introduced method can be considered to be valid for intraoperative static pedography.

During the clinical use, in 44% of the cases a modification of the surgical correction were made after intraoperative pedography in the same surgical procedure.

Different calcaneal plates with locked screws were compared in an experimental model of a calcaneal fracture. Four plate models were tested, three with uniaxially-locked screws (Synthes, Newdeal, Darco), and one with polyaxially-locked screws (90° ± 15°) (Rimbus). Synthetic calcanei were osteotomised to create a fracture model and then fixed with the plates and screws. Seven specimens for each plate model were subjected to cyclic loading (preload 20 N, 1000 cycles at 800 N, 0.75 mm/s), and load to failure (0.75 mm/s).

During cyclic loading, the plate with polyaxially-locked screws (Rimbus) showed significantly lower displacement in the primary loading direction than the plates with uniaxially-locked screws (mean values of maximum displacement during cyclic loading: Rimbus, 3.13 mm (sd 0.68); Synthes, 3.46 mm (sd 1.25); Darco, 4.48 mm (sd 3.17); Newdeal, 5.02 mm (sd 3.79); one-way analysis of variance, p < 0.001).

The increased stability of a plate with polyaxially-locked screws demonstrated during cyclic loading compared with plates with uniaxially-locked screws may be beneficial for clinical use.