Kirschner wires are commonly used in paediatric fractures, however, the requirement for removal and the possibility of pin site infection provides opportunity for the development of new techniques that eliminate these drawbacks. Bioabsorbable pins that remain in situ and allow definitive closure of skin at the time of insertion could provide such advantages.

Three concurrent studies were performed to assess the viability of bioabsorbable pins across the growth plate. (1) An epidemiological study to identify Kirschner wire infection rates. (2) A mechanical assessment of a bioabsorbable pin compared to Kirschner wires in a simulated supracondylar fracture. (3) The insertion of the implants across the physis of sheep to assess effects of the bioabsorbable implant on the growth plate via macroscopic, pathohistological and micro-CT analysis.

An infection rate of 8.4% was found, with a deep infection rate of 0.4%. Mechanically the pins demonstrated comparable resistance to extension forces (p=) but slightly inferior resistance to rotation (p=). The in vivo component showed that at 6 months: there was no leg length discrepancy (p=0.6), with micro-CT evidence of normal physeal growth without tethering, and comparable physeal width (p=0.3).

These studies combine to suggest that bioabsorbable pins do not represent a threat to the growth plate and may be considered for physeal fracture fixation.

The suture properties associated with a successful tendon repair are: high tensile strength, little tissue response, good handling characteristics and minimal plastic deformation. Plastic deformation contributes to gap formation at a tendon repair site. Gaps greater than 4mm are prone to failing. This study investigates whether the plastic deformation demonstrated by two commonly used suture materials can be reduced by manual pre-tensioning.

Twenty sutures of both Prolene 3/0 (Ethicon, UK) and Ethibond 3/0 (Excel, Johnson and Johnson, UK) were tested. Half of the sutures in each group were manually pre-tensioned prior to knot tying and half were knotted without pre-tensioning. All knots were standard surgical knots with six throws. The suture lengths were measured before and after a standardised cyclical loading regime on an Instron tensile tester. The regime was designed to represent the finger flexion forces produced in a typical rehabilitation programme. All sutures were subsequently tested to their ultimate tensile strength.

After cyclical loading the pre-tensioned sutures demonstrated a mean increase in suture length of 0.7% (range 0.1-1.9%). The sutures not pre-tensioned showed a mean increase of 5.4% (range 3.3-7%). This equates to 87% less plastic deformation (p <0.05 Students' T-test) upon pre-tensioning. There were no differences with Ethibond. Pre-tensioning had no effect on ultimate tensile strength for either group.

Manual pre-tensioning reduces plastic deformation in Prolene 3/0 sutures without affecting the ultimate tensile strength. This simple technique could theoretically diminish gap formation at the site of a tendon repair.