Biomechanical Analysis And Long-term Follow-up Outcomes After Vascularized Capitate Transposition

Kienbock's disease is a form of bone necrosis. Its etiology remains unclear. Morphological changes, such as negative ulnar variance, ulnar over-exposure, abnormal radial inclination and / or trapezoid bone, and the particular pattern of its vascularity may be predisposing factors. The history of trauma is also common. The diagnosis is made on plain radiographs, but MRI diagnosis can be helpful early in the disease. A CT scan may prove beneficial aspects of bone fracture and collapse. Lichtman divided Kienbock's disease into four stages. History of the disease incidence is. not very clear, and the symptoms do not correlate well with the changes of bone shape and isn't proportional to the degree of carpal collapse. There is no strong evidence to support any kind of special treatment. Many patients are improved by being fixed the wrist, but this does not prevent the further collapse of the wrist.The treatment options for Kienbock's disease are mainly based on the severity of the disease. Surgical methods used are mainly revascularization, radial shortening, ulnar lengthening, lunate excision and prosthetic replacement surgery, limited wrist arthrodesis, proximal row carpal resection, total resection of the wrist joint and nerve cut surgery and so on. The surgical treatment of Kienbock's disease is still controversal.Since 1985, we have performed the vascularized capitate transposition in patients with the advanced Kienbock's disease, which includes excision of the necrotic lunate and proximally shifted vascularized capitate bone graft to reconstruct the radiocarpal joint,and achieved satisfactory clinical results. But the structure of the reconstructed wrist joint is different from the normal anatomical wrist, so whether these anatomical changes in the structure will become secondary to traumatic arthritis, and what's the the long-term follow-up result? These are to be solved.Objective:In this study, we tried to measure the contact pressures in the radiocarpal and triquetrohamate joints in a cadaveric wrist model before and after surgery, and compared the differences between the two, and analysed the way of load conduction and the influence on the biomechanics of the articular surface. At the same time follow-up applied to the surgical cases in order to provide more accurate experimental basis and clinical basis.Method:We documented the contact pressures in the radiocarpal and TH joints using the Fuji prescale film before and after operation, measure the contact pressures in the radiocarpal and triquetrohamate joints in a cadaveric wrist model before and after surgery, and compare the differences between the two. Twelve patients were follow-up.Patients were seen, examined, and queried regarding their wrists.Range of motion,grip strength,and subjective patients satisfaction were all obtained and quantified using a clinical outcomes scale.Radiographs were obtained to assess the radiocapitate articulation.Results:No significant change occurred in the average contact pressures of scaphoid fossa, TFC and TH articulation between the intact and postsurgical wrists in each wrist position. The results indicated that there was no significant. When the wrist was in the neutral position, dorsal extension, and ulnar deviation, no statistically significant difference existed in the average lunate fossa contact pressures between the intact and postsurgical wrists. However, when the wrist was in the palmar flexion and radial deviation, there existed statistically significant difference between the intact and postsurgical wrists. By LSD test, we noticed that the difference derived from comparison between the intimate contact and nonintimate contact groups. In the intimate contact group, the average lunate contact pressure was 0.983±0.12 MPa, greater than that in the nonintimate contact group (0.782±0.04 MPa), which indicated a decreased load transmitted by the central column in the nonintimate contact group.The decreased load transmission of the lunate fossa in the nonintimate contact group was the effect of capitate shortening. Twelve patients demonstrated good or fair results based on the clinical outcomes scale used (7 good,5 fair, and none poor). Total arc of motion averaged 67% of the uninvolved side. Grip strength averaged 59% of the uninvolved side. At the most recent follow-up, all patients remained employed. No patients demonstrated radiographic degeneration.Conclusion:No statistically significant difference existed in the average contact pressures of the scaphoid fossa, lunate fossa, triangular fibrocartilage, and triquetrohamate articulation in each wrist position between pre-and postoperation. These results suggested that this procedure did not necessarily result in increased rate of postsurgical arthritis.This study demonstrated that vascularized capitate transposition was a reliable motion-preserving procedure with good clinical results and maintained out to a long-term postoperatively.