Treatment for Kienbock's Disease (KD) has certainly benefitted from these advances. In KD, the lunate has lost its intrinsic (coming from within the bone, internal) or extrinsic (coming from outside the bone, external) blood supply. The myriad revascularization procedures all attempt to address this problem, but they differ in approach.

Vascular (arteriovenous) pedicle implantation with a free bone graft, pedicled vascularized bone graft, fully vascularized bone flap ,and variations of these, are all currently being used in KD.

The following information will help you to understand how these terms come together to describe revascularization techniques used in treating the earlier stages of Kienbock's Disease.

A pedicle is "the stem that attaches a new growth."

A graft is any piece of tissue that is transferred from one site to another and relies on the recipient site to rebuild the blood supply.

Almost any type of tissue can be transferred as a graft. Bone grafts may be autografts (taken from the recipient himself) or allografts (taken from cadavers). Autografts may be cortical (hard bone), cancellous (soft, marrow-rich bone), or both, and may be transferred either without vascular supply (conventional bone graft, BG) or as a vascularized bone graft (VBG) and either on a pedicle or as a free graft.

A flap is any piece of tissue that is transferred to another site and retains its own vascularity rather than relying on the recipient site for blood supply.

Flaps are classified by the tissue type (ie, skin, muscle, bone) or types (myocutaneous - muscle and skin, osteocutaneous - bone and skin) transferred. A free flap is composed of any type of tissue (or several types in the case of a composite flap) that can be transferred by microvascular anastomosis (surgical joining) of its vascular pedicle.

Free bone grafts involve bone only, with no vascular pedicle, soft tissue, or muscle component. Free grafts can be divided into autograft, such as calvarial (skull), rib, and iliac (hip) bone; or allograft, which includes irradiated, freeze dried, and demineralized bone from a donor patient.

Free bone grafts placed in contact with a vascularized muscle flap have the theoretical advantage of increased survival. The vascularized bone flap has the best survival and function because the native blood supply remains in direct contact with the graft.

Very generally speaking, there seem to be two "popular" revascularization procedures in KD: a vascular pedicle implant with a free graft or a fully vascularized flap. Undoubtedly there are more and certainly each individual has had some unique variation.

Again, generally speaking, in the vascular pedicle implant, one of the metacarpal (finger) arteries - a pedicle - is plugged into a hole that has been drilled into the lunate after necrotic (dead) tissue is removed. Then cancellous (the soft, spongy inside bone, rich in marrow) bone chips (most likely from the radius, but could be from other sites such as the iliac crest) are stuffed into the hole to secure the pedicle and, hopefully, help the lunate retain and/or regain shape/height. This is a free bone graft as it does not retain its own blood supply; the new vascular source is the arteriovenous pedicle.

In a vascularized bone graft, the necrotic tissue is drilled out of the lunate and a chunk of cancellous bone is removed from the radius while attached to the quadrator pronatus (a muscle in the forearm) and stuffed into the lunate. This is a fully vascularized bone flap as it retains its own vascular supply from the muscle.

Contributed by Phyllis Walker

Sources for the above include Rockwood & Green's Fractures in Adults, 4th ed. and Canale: Campbell's Operative Orthopaedics, 9th ed.