The biological response to a failed extra-articular polyester ligament used for AC Joint reconstruction at the shoulder girdle: a retrieval analysis of five cases.

The LockDown device (previously called Surgilig) is a braided polyester mesh which is mostly used to reconstruct the dislocated acromioclavicular joint. More than 11,000 have been implanted worldwide. Little is known about the tissue reaction to the device nor to its wear products when implanted in an extra-articular site in humans. This is of importance as an adverse immunological reaction could result in osteolysis or damage to the local tissues, thereby affecting the longevity of the implant. We analysed the histology of five LockDown implants retrieved from five patients over the last seven years by one of the senior authors. Routine analysis was carried out in all five cases and immunohistochemistry in one. The LockDown device acts as a scaffold for connective tissue which forms an investing fibrous pseudoligament. The immunological response at the histological level seems favourable with a limited histiocytic and giant cell response to micron-sized wear particles. The connective tissue envelope around the implant is less organised than a native ligament.