The Accuracy of Lower Extremity Alignment in Total Knee Arthroplasty Using Navigation System: Data Analysis of 661 Cases / 대한정형외과학회잡지

PURPOSE: We wanted to evaluate the accuracy of the alignment of the lower extremity in 661 cases of total knee arthroplasty (TKA) with using a navigation system. MATERIALS AND METHODS: We evaluated 661 cases (431 patients) that underwent TKA using a navigation system from June 2006 to September 2008. To analyze the mechanical axis, the weight bearing full length lower extremity radiographs were taken preoperatively and the again at3 weeks after the operation. The results from a well- experienced surgeon (423 cases) were compared with those from a less-experienced surgeon (238 cases), and they both used the navigation system. RESULTS: The mean of the mechanical axis was -13.3degrees (range: -33.3degrees-10.6degrees) preoperatively, but it was corrected to -2.0degrees (range: -14.3degrees-7.5degrees) after TKA using a navigation system. There was no significant difference between the mean of, -1.8degrees (range: -13.4degrees-6.8degrees) by a well-experienced surgeon and the mean of, -2.2degrees (range: -14.3degrees-7.5degrees) by a less-experienced one. CONCLUSION: According to the radiologic results, the navigation system is beneficial for the accuracy of the mechanical axis in TKA. The navigation system helps a less-experienced surgeon increase the accuracy of the lower extremity alignment.

Effects of the Amount of Proximal Tibia Resection on the Bone Strength of Prepared Bone Surface: A FEM Study / 대한정형외과학회잡지

PURPOSE: We wanted to evaluate the mechanical strength of proximal tibia as resection distance increased from the joint surface. MATERIALS AND METHODS: We obtained the CT images of twenty knee osteoarthritis patients undergoing total knee arthroplasty. The finite element models were created based on the computed tomography images. The 8-node hexahedron element was made from BIONIX(TM) (CANTIBio. Co, Suwon, Korea), which is automatic mesh generation software program. The finite element model of the proximal tibia was resected at 6 mm, 8 mm, 10 mm, 12 mm, 15 mm and 18 mm from the lateral joint surface. A 1% strain rate was applied to a model by using HyperMesh(TM) software (Altair Engineering. Inc, Seattle, USA). The ultimate stress was calculated from the finite element analysis with using ANSYS 9.0 (ANSYS. Inc, Orlando, USA). RESULTS: The mean ultimate stress was 906.84 MPa, 877.22 MPa, 895.93 Mpa, 852.70 MPa, 742.90 Mpa and 585.51 Mpa at the 6 mm, 8 mm, 10 mm, 12 mm, 15 mm and 18 mm resection levels. As compare to the 6 mm resection level, the bone strengths at 15 mm and 18 mm were decreased with statistical significance (15 mm: p=0.005, 18 mm: p=0.000). CONCLUSION: The ultimate stress was decreased as the resection distance increased from the joint surface. But within a 12 mm resection distance from the lateral condyle articular surface of the tibia, the ultimate stress was not significantly decreased (p>0.05).

Intramuscular Pressure of the Deltoid and the Efficacy of Cryotherapy in the Shoulder Arthroscopy / 대한정형외과학회잡지

During the arthroscopic surgery of the shoulder, there was extravasation of fluid into the surrounding soft tissue due to the use of pressure pump irrigator. Clinically, the shoulder region became tense and intramuscular pressure of the deltoid could be elevated. To analyze the change of the intramuscular pressure of the deltoid and the efficiency of cryotherapy in the shoulder arthroscopy with pressure pump, we studied 35 consecutive patients who underwent various arthroscopic shoulder procedures at the Dankook University Hospital. We monitored intramuscular pressure using spinal needle connected to the patient monitoring system during arthroscopic procedures and postoperative period until return to preoperative pressure level. Twenty-seven patients were fitted with a cryotherapy. device in the operating room, and 8 were not according to the patient opinions. We evaluated the effect of cryotherapy with visual analog scales and amounts of analgisics for 3 days postoperatively. The results were followed; 1. Intraoperative highest intramuscular deltoid pressure was 293mmHg (average 169+/-68mmHg, 71293mmHg). 2. Immediate postoperative deltoid pressure was average 58.3+/-28.1mmHg (24-145mmHg). 3. Average time that the pressure had returned to the preoperative level was 114.3+/-38.6 minutes (p<0.05). There were no statistically significant between two groups, 113.9+/-41.1 min in the cryotherapy group and 115.7+/-32.6 min in the non-cryotherapy group. 4. Shoulder pain was less in the cryotherapy cases until second postoperative day. In conclusion, arthroscopic surgery of the shoulder can be performed with minimal complication in spite of high intramuscular deltoid pressure. More than 60 minutes may be needed for returning to normal intramuscular deltoid pressure. Cryotherapy is eftective in the pain relief but cannot minimize swelling postoperatively.