Arthroscopic Thermal Shrinkage for Scapholunate Ligament Injuries

Published on 11/04/2015 by admin

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Last modified 11/04/2015

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CHAPTER 10 Arthroscopic Thermal Shrinkage for Scapholunate Ligament Injuries

Biomechanical Effects of Thermal Shrinkage

The aim of thermal shrinkage is to improve joint stability when the ligaments or capsular tissue are lax or incompetent. There is, however, some conflicting data with regard to the biomechanical properties of thermally treated soft tissue. Some of these inconsistencies may be accounted for by differences in experimental protocols, which do not allow for direct comparison between studies. Only a few (but important) basic concepts may be extrapolated from these studies as they pertain to shrinkage of the scapholunate ligament.

Experimental studies have shown that (1) ligaments and joint capsular tissue can be modified significantly (shortened) by thermal energy at the temperature range of 70 to 80° C, (2) thermal energy causes immediate deleterious effects such as loss of the mechanical properties, collagen denaturation, and cell necrosis, (3) thermally treated tissue is repaired actively by a residual population of fibroblasts and vascular cells, with concomitant improvement of mechanical properties, (4) the shrunken tissue stretches with time if the tissue is subjected to physiologic loading immediately after surgery, and (5) leaving viable tissue between treated regions significantly improves the healing process.10,11

Near- and long-term biomechanical effects of thermal energy treatment are different, and the result will depend on the final tissue composition of the scapholunate complex (ligament SL and dorsal capsular ligament). Thus, the postoperative program should maintain the surgically achieved stability for enough time for cellular invasion matrix formation and healing.

Rationale for Shrinkage of Scapholunate Ligament Injuries

Our concept for the use of thermal shrinkage for the treatment of instability of the carpus with scapholunate ligament injuries arose from previous published work on the use of thermal shrinkage on other articulations, as well as the favorable results that were achieved following mechanical debridement of partial SL ligament tears.12,13 We were also influenced by the biomechanical importance of the SL ligament for stability of the carpus and the paucity of treatment methods for carpal instability, as well as the relative ease of performing an arthroscopic shrinkage of the SL ligament.

The SL ligament is not a homogeneous structure. It is divided into three parts: dorsal, proximal, and palmar (Figure 10.1). The dorsal part is the strongest subregion of the SL ligament. It meets all criteria for the definition of an articular ligament in that it is composed of collagen fascicles surrounded by connective tissue with intertwined neurovascular bundles.1416 It has a thickness of 2 to 3 mm and a length of 4 to 5 mm (Figure 10.2), and it merges with the dorsal capsule (Figure 10.3).

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