There are many treatment that are currently available for aseptic lunate bone necrosis6. Simple lunate bone resection can cause carpal bone disarrangement, capitate bone depression, and intractable pain of the wrist joint7; therefore, lunate bone resection and replacement becomes a good therapeutic option for lunate bone necrosis. Many implantable substitutes are available following lunate bone resection, such as capitate bone displacement, lentiform bone displacement,metal ball,tendon ball,titanium alloy prosthesis, and so on8, but the replacement surgeries for capitate bone displacement and lentiform bone displacement are complicated to perform, and they may damage the structures and partial functions of the wrist joint9. The hard metal ball easily wears out based on the adjacent carpal bone, while the soft tendon ball and arc transparent cartilage easily result in the instability of the wrist joint after implantation10. Moreover, a titanium alloy prosthesis is expensive and must be customized in advance; its size is difficult to adjust, and there is difficulty associated with its simulation11. Conversely, bone cement is characterized by its stable physical and chemical properties; its shape and size can be adjusted during the operation. Bone cement can be shaped and sized in such a way that it is basically coincident to the patient’s original lunate; it also matches the physiological characteristics of the wrist joint. In addition, bone cement can maintain its original elasticity for a long period of time, and it prevents itself from deformation, corrosion, and absorption12.
The surgical replacement of lunate bone using bone cement prosthesis has the following advantages: (1) one can replace the original necrotic lunate bone with bone cement, which restores the normal anatomy of the wrist joint; (2) this surgery is simple to perform, so it can be used in all hospitals; (3) the fixation time of the wrist joint is short (it does not exceed six weeks), so patients can promptly return to work; and (4) the lunate prosthesis is an important support structure for avoiding the collapse of proximal row carpal bones, thus it can play a role in preventing the collapse of wrist joint and proximal row carpal bones. It should be noted that during the operation, one must pay attention to the design of the prosthesis, and one should also design the width, height, and concave side of the lunate bone according to the geometric shape of a healthy lunate bone, so as to maintain the original size as much as possible. During the heating of bone cement, we avoid the contact between bone cement and the adjacent joints as possible mainly by retracting the articular space, and wash the bone cement prosthesis with the ice physiological saline to prevent the adjacent structures from the heat damage caused by bone cement. After implantation of lunate bone cement prosthesis, mainly the total repair of articular joint was performed, without the repair and reconstruction of SL and LT ligaments. This is because the prosthetic stabilization is predominantly determined by two factors: the mutual gomphosis of the prosthetic concave structure and the adjacent bony structure; and the resistance from the adjacent articular capsule and tendons. To prevent the detachment of lunate prosthesis in the early stage, attention shall be paid to the repair and suturing of articular capsule during operation; after operation, the plaster immobilization in the functional position shall be performed to avoid the detachment of lunate prosthesis caused by wrist movement and facilitate the repair of articular capsule and adjacent soft tissues. After operation, the wrist joint was fixed at the functional position with plaster for four weeks, because we believed that soft tissues surrounding lunate bone nearly healed to prevent the prolapse of lunate bone at four weeks postoperatively, and the removal of plaster at this time point could facilitate early functional exercise of wrist joint. If the fixation was kept for six weeks, the wrist joint would lose most of its function.
Swanson13 replaced lunate bone with a silicone rubber prosthesis, long-term prosthesis fractures and detachments from other carpal bone easily occurred, this was accompanied by serious foreign-body inflammatory reactions and synovitis. Daecke et al 14 treated 21 patients with Lichtman stage III–IV ischemic lunate bone necrosis by lunate bone resection and lunate fossa filling with a vascularized bone flap, and during follow-up period, the authors found that the imaging examination indicated lentiform bone atrophy and flattening in five patients, lentiform bone sclerosis in ten patients, lentiform bone dislocation in two patients, lentiform bone fracture in one patient, and osteoarthritis or carpal bone collapse in ten patients. We treated 19 patients of advanced lunate bone necrosis using a individualized bone cement prosthetic replacement .these patients were followed up for mean 37.8 months At the last visit, wrist joint pain was markedly relieved, and the range of motion and grasp force were both increased. As confirmed by imaging examinations (X-ray examination and 3D CT), the bone cement prosthesis of the lunate bone had good anatomic suitability and was not broken or detached from other carpal bone, and there was no heat-induced damage to the cartilage in the lunate fossa. If wrist joint pain was observed during follow-up, local immobilization or motion reduction was the preferred treatment, followed by oral non-steroidal anti-inflammatory drugs. We found no surgical failure in the patients followed up, so we could not earn the relevant experience. If a surgical failure happens, we will remove the prosthesis and then perform proximal row wrist arthrodesis for serious damage to wrist joint, or simply remove the prosthesis and/or then perform other surgeries for slight damage to wrist joint. However, this preliminary study did not include a control group, and the follow-up period only encompassed a hot period of time.