Objective To explore the influence of discectomy and artificial disc replacement on the upper lumbar facet joint and to provide the evidence for use of artificial disc replacement. Methods Under the loads of 200-2 000 N axis pressure and 1-10 Nm back-extending/side-bending pressure on the 7 fresh adult corpses, the pressure of L3,4facet joint was measured in the case of L4,5disc integrity, discectomy and artificial disc replacement and the statistical analysis was done.ResultsUnder the same load (axis, back-extending/side bending), there were significant differences (Plt;0.01) in the pressure of upper lumbar facet jointboth between disc integrity and discectomy and between discectomy and artificial disc replacement, and there was no difference(Pgt;0.05) between disc integrity and artificial disc replacement. Conclusion The stress ofupper lumbar facet joint reduced after discectomy, it implies that simply discectomy may change biomechanics of lumbar and lead to secondary lumbar structure degeneration. The stress of upper lumbar facet joint is close to the normal value after artificial disc replancement, it implies that artificial disc replacement may protect lumbar structure. It provides some biomechanics foundation and evidence for artificial disc replacement.
Objective To evaluate the mid-term effectiveness of two-stage hip prosthesis revision in the treatment of infection after hip arthroplasty. Methods Between April 2002 and November 2006, 12 cases of infection after hip arthroplasty were treated. There were 5 males and 7 females, aged from 47 to 72 years (mean, 59.8 years). The femoral head arthroplasty wasperformed in 2 cases and total hip arthroplasty in 10 cases. Infection occurred 1 to 67 months after arthroplasty. According to the Segawa classification criteria, infections included type 2 in 1 case, type 3 in 2 cases, and type 4 in 9 cases. The preoperative Harris score was 36.7 ± 6.1. Nine cases had elevated C reactive protein and 10 cases had elevated erythrocyte sedimentation rate. The results of bacterial culture were positive in 8 cases and negative in 4 cases. After the removal of the infected prosthesis and thorough debridement, antibiotic-loaded cement spacers or infected therapeutic temporary prosthesis were used as placeholders, and then the anti-infection treatments were given after operations; two-stage hip prosthesis revisions were performed 3 to 10 months after debridement. Results In 1 patient who failed to control infection after debridement, infection was controlled after the second debridement and the antibiotic-loaded cement spacer as placeholder. Other patients achieved heal ing of incision by first intention, and no compl ication such as deep venous thrombosis and nerve injury occurred. All patients were followed up 3 to 8 years after revision (mean, 5.4 years). During the follow-up, no infection recurrence and joint dislocation occurred. Dull pain was present in 2 cases during activity and mild claudication in 3 cases at last follow-up. The Harris score was 81.6 ± 4.5, showing significant difference (t=52.696, P=0.000) when compared with preoperative score. The X-ray films showed that noprosthesis loosening and obvious subsidence were observed, and bone graft healed. Conclusion The two-stage hip prosthesis revision has good infection control rate and mid-term effectiveness in treatment of infection after hip arthroplasty.