J Wrist Surg 2021; 10(06): 465-466
DOI: 10.1055/s-0041-1739184
Editorial

The Scapholunate Dilemma

Stephen K. Tham
1   Hand Surgery Unit, St Vincent's Public Hospital and Dandenong Hospital, Melbourne, Australia
,
Eugene T. Ek
2   Department of Orthopaedic Surgery, University of Melbourne and at Dandenong Hospital, Monash University, Austin Hospital, Melbourne, Australia
› Author Affiliations

The evolution of techniques used in anterior cruciate ligament reconstruction in the knee over a 50-year period highlights the importance of reconstruction based on anatomical principles and understanding the biomechanical properties of the graft material.[1] The inadequacy of extra-articular techniques became apparent, and anatomical reconstruction techniques followed. As a consequence, graft positioning became important. The free patellar tendon became the gold standard for anatomical reconstruction. The biomechanical properties of the graft material used then gained importance. A double bundle reconstruction was seen to more closely resemble an anatomical reconstruction, potentially correcting residual instability. Synthetic devices such as Dacron, Kevlar, and carbon fiber met with some initial clinical success but ultimately failed because of inappropriate initial biomechanical properties, material fatigue profiles, and material shedding.[2] [3] [4] [5] The abraded synthetic particles collected in the joint space, lymph nodes, and other tissues and led to a chronic inflammatory response.[6] Xenograft attempt also failed and was abandoned. Although the mechanism of failure for the bovine-based devices were mixed, poor biocompatibility attributed to excess glutaraldehyde, improper preimplantation biomechanical properties, the lack of host integration,[7] and immunological rejection were key variables leading to poor clinical results.[8]

In the wrist, the primary and secondary stabilizers that contribute to scapholunate (SL) stability and the kinematic consequences of sequential sectioning of these structures[9] are well documented. Numerous techniques have been described[10] [11] to address the SL injured wrist where primary repair is not possible, and the radiological measures of reconstructive success was based on the approximation of the SL interval and reestablishment of scaphoid and lunate alignment. However, static radiological realignment does not necessarily result in reestablishment of normal carpal kinematics, and the kinematic consequence of the described procedures have not been determined. It may be that the alterations to joint contact loading,[12] particularly at the scaphoid fossa and midcarpal joint, may become a more important measure. More recently, the importance of taking into account the lessons learned from cadaveric studies have gained popularity, and reconstructive techniques that address both the primary and secondary stabilizers anatomically, including the dorsal and volar components of the SL to control the rotatory stability of the scaphoid and lunate, have been described.[13] [14] [15] [16] [17] [18] [19]

Nonetheless, the material used for reconstruction must allow the differential motion[20] [21] that exists between the scaphoid and lunate. It is influenced by the biomechanical characteristics of the graft material used. The process of ligamentization is more prolonged in humans than animals, and the biomechanical characteristics of different donor tendons differ.[22] [23] More importantly, the biomechanical characteristics of the donor tendon is significantly reduced at the conclusion of the maturation phase of ligamentization. Stiffness and load to failure measures quoted on graft material do not take into account the biomechanical consequences and the physiological changes that occur as a result of ligamentization. Other variables that may also influence the results of a reconstructive technique are the size of the graft used and the degree of tensioning. Reconstructive techniques that use a combination of autologous tendon, to provide a biological graft material, and a ligament substitute, for immediate biomechanical strength, go against the “law of functional adaptation,” as the ligament substitute will protect the biological graft material, preventing it from undergoing changes in its mechanical and biological properties that occur when tendon grafts are exposed to different mechanical loading in a suitable biological environment.

The purpose of this special review edition is to throw the spotlight not on the techniques used for scapholunate reconstruction, but on the graft material, as reestablishing the soft-tissue anatomy is the foundation from which normal joint kinematics, and contact pressures, can be regained, and the graft material used is an important building block.



Publication History

Article published online:
01 December 2021

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