Osteoprotegerin (OPG) has been reported to be a novel protein that can suppress osteoclast differentiation and activation. This study examined the therapeutic effects of OPG on established periprosthetic osteolysis in a rat model.

A bone cement prosthesis was inserted into the rat femur and polyethylene particles were continuously infused into the knee joint using an osmotic pump. After osteolysis was established in four weeks, rats were intravenously injected with vehicle (control group) or 1 mg/kg of OPG (OPG-1 group) or 10 mg/kg of OPG (OPG-10 group) every week until they were sacrificed at 8 weeks. Effects of direct injections of OPG into the knee joint were also investigated. Periprosthetic bone resorption was evaluated with bone mineral density and histomorphometric analysis of membranes composed of total area of interface membrane and inflammatory grading. Radiographs were evaluated for focal osteolysis with a blind manner.

Periprosthetic bone resorption was significantly suppressed in OPG-10 group compared to the other groups (p < 0.05). Histomorphometric analyses showed less total area as well as less inflammatory grading of the interface membrane in OPG-10 group compared to other groups (p < 0.01). Radiographic osteolysis appeared to decrease in number in OPG-10 group. Direct injections of OPG into the knee joint appeared to be more effective compared to intravenous injections.

The present study demonstrates that OPG has significantly restored the established periprosthetic osteolysis in our animal model. OPG may be a possible agent to retain the bone stock before revision surgery for failed prostheses. Conclusion: This study demonstrates that osteoprotegerin suppresses the progression of periprosthetic osteolysis and restores bone stock in a rat model.

Percutaneous radiofrequency neurotomy of the lumbar medial branch is a widely accepted treatment for pain of the lumber intervertebral joints. However its success rate has varied among authors. One reason for this inconsistency is the lack of method for objective evaluation of whether the nerve has been sufficiently denervated or not. This study has made possible real time and accurate monitoring of whether electrocauterization is properly executed or not.

The subjects were 50 patients with law back pain persisting for 3 months or longer in whom facet block or medial branch block of posterior ramus was only temporarily effective. They ranged in age from 19 to 76 years (mean 54 years) and were followed up for 1 year to 7 years and 1 month (mean 2 years and 9 months). In our percutaneous radiofrequency neurotomy, the target point of denervation is defined as the groove between the mammillary process and accessory process (1) and complex muscle action potentials (CMAPs) of multifidus muscles are used as an index for objective evaluation of the effects of denervation.

Improvements were observed immediately after the treatment in 39 patients (78%). The effects of this treatment, once attained, remained over a long period, and the duration of effects was 18–20 months as estimated by the cumulative success rate calculated using the Kaplan-Meyer method.

Patients must be carefully selected for percutaneous radiofrequency neurotomy to be consistently effective, all the more because the procedure is simple. However, it is a reliable method for denervation of the lumbar medial branch and long-term relief from pain can be expected. This therapy, therefore, is an effective alternative for the treatment of chronic pain due to lumbar intervertebral arthropathy that resists conservative treatments and disturbs daily living.

The purpose of this study is to evaluate the relationship between the clinical results and the angle of the reconstructed ligament measured radiographically.

We also describe the comparison of the results by the fixation technique of the femoral tunnel. We retrospectively evaluated 90 patients who had arthroscopy assisted ACL reconstruction using middle-third middle-third bone patellar tendon autograft. There were 67 men and 23 women. Their average age at surgery was 23.9 years. The average follow up periods was 28.0 months. We used interference fit screw for grafted ligament fixation of the femoral and tibial tunnel. 71 patients received inside out technique and on 19 patients outside in technique as for the fixation of the femoral funnel.

The lateral angle and A-P angle of the reconstructed ligament were measured roentgenographically. Data from KT-2000 arthrometer testing with side to side difference and Lachman test were used to assess postoperative anterior knee laxity.

Pivot shift tests were also used for rotational knee laxity. Data from roentgenograms reflected the correlation with clinical testing.

Mean value of the side to side difference was 1.3mm. In pivot shift test, the average lateral angle of the reconstructed ligament of negative group was 73.2o , while positive group was 77.2 o , it was statistically significant. The average lateral angel and A-P angle of the reconstructed ligament with inside out technique group was larger than those of outside in technique group.

Recent recommendations placing the tibial tunnel more posterior results in a lower incidence of graft impingement, but we found a relationship between the angle of the reconstructed ligament and rotational stability of the knee.

Anterior-posterior stability can be obtained by achieving posterior placement of the reconstructed ligament. More vertical graft angle caused by posterior placement of tibial tunnel should affect rotational stability. Inside out as the way of fixation technique for the femoral tunnel showed a tendency of more vertical graft angle.