kienbck s disease , defined as avascular necrosis of the lunate , is a relatively rare condition with a poorly understood etiology . the disease is a relatively rare condition in which the etiology and natural history of this condition are poorly understood and even more poorly documented in the literature . a wide array of treatment recommendations is available , and reported results vary , which may hinder consistent treatment recommendations . conservative and invasive treatments for kienbck s disease include the following : wrist immobilization with a splint during early disease stages , surgical joint - leveling procedures to attempt to reduce loading on the joint and to promote revascularization and increased blood flow , vascularized bone grafting , proximal row carpectomy , and total wrist arthrodesis . proximal row carpectomy and total wrist arthrodesis attempt to alleviate arthritis pain due to carpal collapse ; however , these 2 interventions greatly limit range of motion . none of these treatments effectively address the chronic pain , loss of range of motion , and decreased grip strength associated with kienbck s disease . the staging distinguishes only the  state of collapse  in an ordinal classification scheme and does not allow localization or indicate partial involvement of the lunate , which the image contrast from mri may provide . osteochondral transfer for treatment of kienbck s disease may be possible for individuals with segmental or incomplete avascular necrosis of the lunate . previous investigators have acknowledged the importance of donor site cartilage thickness to aid in minimizing postoperative abnormal stresses and resulting poor function . selection of donor cartilage with an appropriate thickness may be difficult due to source availability and donor site location relative to the load - bearing region of a joint , which may lead to donor site morbidity . an alternative to matching cartilage thickness is the matching of curvature of the articular surface . matching the curvature of donor and recipient sites has been shown to maintain preoperative contact stresses for a given loading regimen . in this short communication , we report the treatment of a patient s kienbck s disease by combining mri with mathematical modeling to optimize the congruency between the curvature of donor and recipient sites of an autologous osteoarticular plug transfer . the purpose of this study was to describe the feasibility of a novel surgical technique . the results indicate that donor site selection for autologous osteoarticular transfer using a quantitative evaluation of articular surface curvature may be beneficial for optimizing the likelihood for restoring the radius of curvature and thus joint articulation following cartilage repair . a 48-year - old , right hand  dominant woman had left wrist pain associated with decreased wrist flexion since september 2009 . in november 2009 , the patient experienced severe wrist pain after falling on her hand . after acquiring standard radiographs , the woman was diagnosed with kienbck s disease , and a proximal row carpectomy was recommended by an initial orthopedic surgeon . the patient sought a second opinion after understanding that the carpectomy would not only reduce pain during activities of daily living but would also limit range of motion . upon presentation to our institution , physical examination of the left wrist revealed no focal swelling , dystrophic changes , or evidence of muscular atrophy . the left wrist range of motion was 20 of flexion and 30 of extension ; the patient had full , painless range of motion in her right wrist . grip strength in her left hand was 111.2 n as compared with 333.6 n in her right hand . mri of the wrist was performed utilizing a clinical superconducting 3-t imaging unit ( sigma hdx , general electric healthcare , waukesha , wi ) and a dedicated wrist coil . pulse sequencing included a 3-dimensional gradient - recalled sequence with tr / te of 39/14 milliseconds , field of view of 9 cm , slice thickness of 1 mm with no gap , flip angle of 10 , and band width of 41.7 khz . coronal , sagittal , and axial cartilage  sensitive fast spin echo sequences were obtained with a long tr ( 4,000 - 5,500 milliseconds ) , moderate te ( 31 - 38 milliseconds ) , field of view of 8 to 9 cm , slice thickness of 2 to 3 mm , acquisition matrix of 512  512 ( 320 - 352 ) , 2 excitations , a band width of 14.7 to 41.7 khz , and echo train length of 10 to 12 . coronal fast inversion recovery sequence was performed with a tr of 5200 milliseconds , te of 23 milliseconds , inversion time of 170 milliseconds , field of view of 9 cm , slice thickness of 2.5 mm , matrix of 288  192 , 2 excitations , band width of 31.2 khz , and echo train length of 12 . the examination demonstrated collapse of the proximal pole of the lunate , with subchondral sclerosis and a mild bone marrow edema pattern ( fig . 1 ) . foci of completely devitalized marrow were noted in the proximal pole with an associated intense synovitis . moderate partial wear of cartilage was seen over the collapsed lunate with preservation over the radial side of the lunate fossa . a best - fit circle was manually placed on the lunate with its articulation with the distal radius to determine the joint curvature . preoperative coronal ( a ) and fat - suppressed ( b ) fast spin echo images of the wrist demonstrate sclerosis and partial collapse of the lunate ( arrows ) with hyperintensity in the adjacent cartilage . one - year postoperative sagittal ( d ) and fat - suppressed ( e ) fast spin echo images and computerized tomographic evaluation ( f ) demonstrate partial bony incorporation expected for the time interval . computerized tomographic examination was performed utilizing axial acquisition with a slice resolution of 0.8 mm , subsequently reformatted into sagittal and coronal reformations . concurrent computerized tomography was performed to quantify the extent of subchondral collapse , which measured up to 1 mm . mri of the left knee was subsequently acquired to provide a digital template for the planned osteochondral transplantation . a 3-dimensional t1-weighted spoiled gradient echo data set with frequency - selective fat suppression was acquired for cartilage segmentation : tr of 13.6 milliseconds , te of 3.0 milliseconds , field of view of 16 cm , flip angle of 20 , slice thickness of 1.5 mm , matrix of 512  512 , receiver bandwidth of 41.7 khz , and 1.2 excitations . the cartilage was segmented from the image data using custom - written semiautomated software ( general eelectric healthcare ) , with minimal manual editing performed as needed . a 3-dimensional mesh representation of the segmented lateral condyle image data was constructed and smoothed for curvature calculations . curvature calculations were performed on the 3-dimensional surface mesh using a custom - written matlab ( mathworks , natick , ma ) program . 2a ) , and a best - fit paraboloid ( z(x , y ) = ax + bxy + cy ) was fit to each vertex and the surrounding 2-ring neighborhood ( fig . 2b ) . the analytical solutions for maximum curvature ( max ) and minimum curvature ( min ) were determined from the best - fit paraboloid ( fig . this process is repeated for each vertex on the 3-dimensional surface mesh to generate max and min maps . regions with large values of min display concavities on a surface , and regions with large values of max display convexities of a surface . the model of a paraboloid was chosen due to the computational efficiency as well as the verified accuracy of the curvature calculation as compared to other numerical methods . ( a ) each mesh vertex ( red point ) had a 2-ring neighborhood ( blue points ) calculated . ( b ) the coefficients of a best - fit paraboloid through the vertex and 2-ring neighborhood were used to calculate the maximum and minimum curvatures . the directions of maximum curvature ( red arrow ) and minimum curvature ( green arrow ) were also calculated . ( c ) the direction and magnitude of the maximum curvature and minimum curvature at the vertex are shown by the orientation and radius of the pink and green circles , respectively . the radius of each circle (  ) is the inverse of the calculated curvature (  = 1/ ) . at the indicated vertex ( red dot ) , the anterolateral femoral condyle had the maximum curvature in the mediolateral direction and minimum curvature in the anteroposterior direction . the patient underwent osteochondral transfer from her left femoral condyle to her left lunate . using a tourniquet to control bleeding , the necrotic area of the lunate , which measured approximately 8 mm  1 mm  1 cm , was debrided . after thorough debridement of the avascular necrotic bone , intraoperative fluoroscopy was used to identify and better assess the defect in the lunate . the donor site was filled with a synthetic acellular biphasic copolymer plug ( trufit , smith and nephew , andover , ma ) . using the digital template acquired from the algorithm , an osteochondral plug from the left femoral condyle that closely matched the radius of curvature of the lunate , 12.7 mm from the manual measurement , was harvested during knee arthroscopy ( fig . the location of the plug was assessed from the previously constructed 3-dimensional model of the articular surface , relative to the local anatomy . a 10 blade and rongeur were used to fit the dimensions of the osteochondral plug with those of the lunate . 2 fiberwire ( arthrex , naples , fl ) stitch was placed through the scapholunate ligament . internal fixation was performed with a 1-mm drill , drilled antegrade through the lunate to fix the osteochondral plug ; a 1.5-mm  8-mm screw was then compressed across the plug with fixation in the distal aspect of the lunate . there was no block in flexion , extension , or radial deviation , and the osteochondral fragment remained stable through a full range of motion . the patient was placed in a sling and discharged with instructions to return for regular follow - up visits . maximum ( left ) and minimum ( right ) principal curvature maps of the anterior portion of the lateral femoral condyle . postoperative radiographs demonstrated that the wrist was in good alignment and the hardware was intact . follow - up radiographs and physical examinations were performed at 2 , 4 , 6 , 8 , and 10 weeks ; 3 , 4 , 7 , and 10 months ; and 1 year postoperatively . we treated kienbck s disease with the aid of a 3-dimensional model of femoral articular surface and calculated the principal curvatures of the surface . this was performed to determine the optimal congruency of the chondral donor and recipient sites . surgical challenges for autologous osteoarticular transfer include restoration of the articular surface as well as the tidemark . koh et al . have shown in a preclinical model that plugs left elevated or angled result in increased contact pressures , thus presenting potential risk to the cartilage on the opposite side of the joint . the mesh model created in the knee allowed for objective assessment of the articular surface to ensure more optimal plug alignment , provide reconstitution of joint architecture , and promote biologic incorporation of the plug into the recipient site . we did not seek to evaluate the functional outcome of the surgical procedure in this short report but to introduce the feasibility of this novel surgical planning technique for osteochondral repair . this case report presents the unique application of mri and mathematical modeling when applying the autologous osteoarticular transfer procedure to the lunate . these techniques require only an additional limited 3-dimensional model of the knee with minimal scan time beyond the routine examination of the wrist for assessment of marrow viability and the integrity of the articular surfaces . additional applications would include osteochondral lesions of the distal femur , capitellum , talus , and potentially , over the femoral head . future studies will refine the image acquisition and 3-dimensional modeling processes for optimal selection of the osteochondral plug based on local tissue morphology .
kienbck s disease , defined as avascular necrosis of the lunate , is a relatively rare condition with a poorly understood etiology . 
 conservative and invasive treatments for kienbck s disease exist , including wrist immobilization , surgical joint - leveling procedures , vascularized bone grafting , proximal row carpectomy , and total wrist arthrodesis . 
 staging kienbck s disease using radiography assumes near complete avascularity of the lunate . 
 the staging distinguishes only the  state of collapse  in an ordinal classification scheme and does not allow localization or indicate partial involvement of the lunate , which the image contrast from mri may provide . in this short communication , we report the treatment of a patient s kienbck s disease by combining mri with mathematical modeling to optimize the congruency between the curvature of donor and recipient sites of an autologous osteoarticular plug transfer . follow - up mri and radiographs at 1 year postoperatively demonstrated gradual graft incorporation and bone healing . 
 the purpose of this study was to describe the feasibility of a novel surgical technique . 
 the results indicate that donor site selection for autologous osteoarticular transfer using a quantitative evaluation of articular surface curvature may be beneficial for optimizing the likelihood for restoring the radius of curvature and thus joint articulation following cartilage repair .