Selection of appropriate treatment for Keenbox disease remains a difficult problem for clinicians today. Treatment options generally have been directed at altering mechanical load. These methods include intercarpal fusion, adjustment of the relative length of the radius or ulna, shortening the capitate, or increasing or decreasing the slope of the distal radius. Another logical method, however, is to directly revascularize the lunate, solving the underlying problem of Keenbox disease. Vascularized bone grafts have been described as well as use of arteriovenous pedicles for this purpose. Revascularization is logical in that it attempts to improve the vascular supply, and if grafts are used, may also allow restoration of lunate shape, hopefully preventing progressive collapse during the revascularization process. We prefer to use dorsal radius grafts harvested from a dorsal approach which allows placement and harvest of the graft through the same incision. The anatomy is based on a description of the blood supply published in the Journal of Hand Surgery by Sheets Bishop et al. Two deep vessels lie on the floor of the 4th and 5th extensor compartments. These vessels arising from the posterior division of the anterior interosseous artery are termed the 4th and 5th extensor compartment arteries respectively. They have distal anastomoses which allow the creation of a retrograde flow vascular pedicle based on flow through the dorsal radiocarpal and dorsal intercarpal arches. The dorsal intercarpal arch is the most important. The most commonly used graft at our institution utilizes retrograde flow through the 5th ECA vessel and then orthograde in direction through the 4th compartment artery with a graft harvested from the floor of the 4th compartment. The approach is dorsal. We use a longitudinal incision slightly ulnar to the midline. The incision is directed through the skin and subcutaneous tissues to expose the extensor retinaculum. The extensor retinaculum will be opened through the 5th dorsal compartment overlying the extensor digiti minimi. Here the tendon is identified distal to the retinaculum and confirmed with traction. The 5th compartment is then opened sharply to expose the vessel. The retinaculum will be hinged open on a radially based flap allowing exposure of the entire dorsum of the wrist capsule from the 3rd through the 5th extensor compartments. With the incision made and the extensor digiti minimi retracted, the vessel is seen on the radial aspect of the 5th compartment. Vessel dissection is easily accomplished by dissection with scissors superficial to the vessel. A natural plane allows exposure of the vessel without injuring it. As the vessel is exposed, one can identify venacomatons running with the vessel allowing it to be used as a source of retrograde flow. Once the vessel has been adequately mobilized from the septum between the 4th and 5th compartments, the septum is divided to expose the extensor digitorum communis and extensor indicis tendons. Small perforating vessels supplying the dorsal supraretinacular arch may be identified and cauterized during this dissection. On the radial aspect of the 4th compartment, the 4th extensor compartment artery will be identified and will need to be protected. Next, the 3rd is exposed by division of its septum. The extensor tendons may then be retracted to widely expose the dorsal wrist capsule and dorsal surface of the distal radius and ulna. Here you can see the posterior division of the anterior osseous artery dividing into its terminal branches including the 5th extensor compartment artery and the 4th extensor compartment artery. Again, illustrated diagrammatically. The 5th extensor compartment artery is then progressively mobilized by blunt dissection beneath it, placement of a VESI loop, and then careful dissection raising the artery and venacomatons with a small cuff of normal tissue for safety. Proximally, one can identify the oblique dorsal artery of the distal ulna which may be ligated or cauterized and divided. The posterior interosseous vessels will also need to be divided. Dissection continues with mobilization of the proximal aspect of the 4th compartment and by division of the 4th compartment artery at the point where it crosses the wrist capsule. Here the posterior interosseous nerve is also identified and divided. The next step is to ligate the posterior division of the anterior interosseous artery. This is done well proximal to the separation of the 4th and 5th compartment arteries to ensure that flow may occur in a retrograde fashion through the 5th compartment and then orthograde into the 4th extensor compartment artery. The 5th extensor compartment artery must be immobilized distally sufficient to allow capsulotomy without endangering the vessel. Capsulotomy is performed with a ligament sparing technique that involves division of the dorsal radiocarpal and dorsal intercarpal ligaments through their mid-substance parallel to their fibers. This capsulotomy may be truncated slightly on the ulnar aspect to avoid endangering the vessels. The 4th extensor compartment vessels are cauterized at the wrist joint capsule level. Here you see diagrammatically the capsulotomy which allows direct exposure of the lunate, scapholunate ligament and lunotricuitral ligament. The capsulotomy is being outlined. Again notice that it does not come to a point at the triquetrum as is usually the case but terminates to the radial side of the 5th extensor compartment artery. Here the capsule is retracted, the vessel under direct vision and protected from harm. Use of the 5th extensor compartment artery as the source of blood flow is convenient for this purpose as it lies ulnar to the lunate and thus need not be disturbed or excessively mobilized. The lunate is identified in this case somewhat soft in appearance with palpation. Lunate preparation involves using a high-speed burr under image intensification control to remove necrotic bone and if necessary later expansion of the lunate. A high-speed burr is used initially. Placement is directed with a fluoroscope used in two planes to allow gradual removal of the necrotic bone. The procedure is contraindicated when there is a sagittal fracture through the cartilage shell of the lunate. Bony fractures are not contraindications in our opinion provided the cartilage shell is intact. Once all of the necrotic bone has been removed, the dimensions of the graft are noted. A typical graft would be 2 centimeters in depth and approximately 5 millimeters in width. With careful palpation of the lunate fossa, the graft is marked on the radius taking care not to place the graft distal, thereby endangering the articular surface. The graft is centered over the fourth extensor compartment artery pedicle. In general, it is safer to raise the graft slightly larger than anticipated and trim it with a bone-cutting forcep at a later stage. We use sharp osteotomes to raise the graft. The proximal cut is made first, followed by the distal osteotomy. As the cuts are made, the graft is again measured and the articular surface palpated and protected. The radial-sided cut is then made followed by the final ulnar-sided osteotomy. Once it is done, it is then possible to carefully pry the graft from the radius, taking with it not only cortical but also cancellous bone. The vascular pedicle is freed up to complete the dissection, creating a long vascular pedicle which will reach easily anywhere in the carpus but most especially into the lunate with no tension. Here again is a diagrammatic representation of the graft elevated. Graft placement is important. We prefer to orient the graft, as you see in this diagram, with the cortical bone oriented in an anterior-posterior dimension. This allows a bony strut to prevent lunate collapse during the subsequent healing and revascularization process. The long axis of the graft is placed vertically into the lunate to completely fill the two centimeter previously burred and curetted defect. The graft may need to be trimmed and adjusted in size prior to this step with trial fitting. It is important not to compress or damage the vessels and to leave some room on the ulnar side of the lunate where the vessels run vertically along with the bone into the lunate. Once placement appears satisfactory, the graft is impacted with a small impactor and mallet. Once completed, one can see the vascular pedicle with no tension and the bone fully placed inside the lunate. The lateral view demonstrates satisfactory lunate expansion. On the AP view you can see the cortical strut. The next step is to temporarily unload the lunate with two scapho-capitate Kirschner wires placed with the wrist under distraction. This temporarily unloads the capitate lunate and lunate radius articulations and protects the lunate and the graft while allowing some motion early postoperatively. The capsular flap is then closed, taking care not to damage the vascular pedicle which must be visualized and protected during this process. The retinaculum may then be closed. Here you see the retinaculum replaced with the suture line over the fifth compartment here. The extensor digiti minimi and extensor digitorum tendons are replaced beneath the retinaculum while the EPL tendon here is left transposed dorsally. Skin closure then completes the procedure. The Kirschner wires are left penetrating the skin. Postoperative management includes immobilization of the wrist for three weeks, instituting active range of motion at three weeks. The pins are removed at six weeks following surgery. Vascularized bone grafting from the dorsal distal radius is an alternative to mechanical load altering for the treatment of lunate avascular necrosis. It is indicated in stages 1 to 3A provided the articular cartilage shell is intact. It may be the procedure of choice in ulna neutral wrists. The ability to place vessels as well as expand the collapsed lunate with a living bone graft are significant advantages to this revascularization method. Thanks for watching!

Keenbox disease

treatment selection

revascularization

vascularized bone grafts

dorsal radius grafts