Soft Tissue Internal Fixation


Background for STIF in human medicine

The 1980s saw a growing enthusiasm for synthetic material ligament reconstruction, by the 1990s the popularity of artificial implants had declined due to high failure rates. The ligaments of the first generation were extremely brittle, ruptured early, shed lubricants or were not resistant to abrasions causing synovitis. Although the newer synthetic ligaments of the second generation were a marked improvement over the previous ones, they also caused early failures due to a lack of tissue in-growth and low resistance to abrasion and fraying.

The LARS Ligament Augmentation & Reconstruction System (manufactured by LARS, Surgical Implants and Devices, Arc-sur-Tille, France) represents a third generation synthetic ligament. It incorporates a design, which takes into account the causes of earlier synthetic ligament failures. LARS has been developed with a more accurate understanding of the functional anatomy of joints, muscle-tendon units and ligaments. Combined with advanced surgical techniques, medical technologies and materials. This new generation of synthetic ligaments have been used successfully for more than 19 years in a wide variety of patients, from elite athletes to the general population. The intra-articular reconstruction is used as the technique of choice in humans for returning the knee joint as close to preoperative functional status as possible.

STIF has used the experience and technology of LARS to provide a viable option to treat tendon and muscle defects in animals.


The construction of the STIF ligament is the result of many years detailed research; due to the LARS success, not only in finding a suitable biocompatible material which corresponds to the material properties of native structures, but also in identifying the best way to apply this material to produce the various ligaments available. STIF are constructed from polyethylene terephthalate (PET), an industrial-strength polyester fibre that has been selected for its characteristics for ligament scaffold applications. There are over 500 different types of PETs, each with their own specific physical and mechanical characteristics. In contrast to previous generation synthetic ligaments, STIF are extensively treated to remove residual processing aids, which were found to inhibit soft tissue in-growth, providing a more fibroblastic friendly environment (see graph below). The intra-articular portion of the STIF ligament consists of longitudinal fibres without transverse or crossing components.


STIF reflects a third generation of ligament design

The free fibres are oriented to the ligament they are intended to be used with, mimicking the normal anatomic fibres. This patented structure allows a high resistance to fatigue, especially in flexion, as well as providing a porosity favouring fibroblastic ingrowth, which then isolates the synthetic fibres.

In the extra-articular portion the same parallel fibres are kept united by a process of warp knitting. This knitting process minimises secondary elongation (as opposed to braided or woven fibres).

Regardless of the tissue or implant used for cruciate reconstruction, all are avascular at the point of implantation, this is why preserving any native remnants and the free fibres of the STIF, encourage fibroblastic in-growth and graft remodelling, without compromised mechanical strength during the initial healing phase.