【Abstract】 Objective To explore the cause of the perioprative period compl ication of scandinavian total anklereplacement(STAR) and to summarize the experience in the treatment and prevention. Methods From March 1999 toNovember 2006, 35 patients were given total ankle replacement(TAR) with STAR system. There were 19 males and 16 femaleswith an average age of 50.5 years (27 to 68 years), including 12 cases of posttraumatic arthritis, 8 cases of osteoarthritis and 15cases of rheumatoid arthritis. All patients had pain of ankle joint, swell ing and l imitation of joint motion. The disease coursewas 9-64 months. The curative effect was estimated by Kofoed total ankle scoring system. The mean preoperative ankle scorewas 29(6-48); the mean pain score was 18.3(0-35); the mean function score was 11.7(6-18); and the mean activity score was9.2(3-12). The type of all compl ications were record, and its cause, prevetion and treatment were analyszed. Results Thirtythreepatients achieved heal ing by first intention, 2 achieved delayed union because of infection. Twenty-eight patients werefollowed up 3-80 months (mean 43.5 months). Medial malleolus fracture occurred in 2 cases, unstable ankle joint introversion in2 cases, l imitation of ankle dorsiextension in 1 case and 1 case had hypoesthesia at intermediate dorsal skin of foot and 3rd-5thmetatarsal skin without obvious dysfunction; all were treated with symptomatic medication. The postoperative mean ankle scorewas 85.5 (58-95); the mean pain score was 48.3(35-50); the mean function score was 20.7(18-30); the mean activity score was17.2(16-20). There were statistically significant differences when compared with preoperative score(P lt; 0.01). The cl inical resultswere excellent in 16 patients, good in 9 patients and fair in 3 patients. The X-ray films showed no loosening and subsidence ofprosthesis. Conclusion Although STAR can retain the functions of the operated joint, it has its special compl ications. It isimportant to obey operation principle with proficient operative technique, to strictly control surgical indication and to intensifyperioperative period treatment so as to decrease the compl ications.
ObjectiveTo discuss the influence of artificial ankle elastic improved inserts (hereinafter referred to as “improved inserts”) in reducing prosthesis micromotion and improving joint surface contact mechanics by finite element analysis. Methods Based on the original insert of INBONE Ⅱ implant system (model A), four kinds of improved inserts were constructed by adding arc or platform type flexible layer with thickness of 1.3 or 2.6 mm, respectively. They were Flying goose type_1.3 elastic improved insert (model B), Flying goose type_2.6 elastic improved insert (model C), Platform type_1.3 elastic improved insert (model D), Platform type_2.6 elastic improved insert (model E). Then, the CT data of right ankle at neutral position of a healthy adult male volunteer was collected, and finite element models of total ankle replacement (TAR) was constructed based on model A-E prostheses by software of Mimics 19.0, Geomagic wrap 2017, Creo 6.0, Hypermesh 14.0, and Abaqus 6.14. Finally, the differences of bone-metal prosthesis interface micromotion and articular surface contact behavior between different models were investigated under ISO gait load. Results The tibia/talus-metal prosthesis interfaces micromotion of the five TAR models gradually increased during the support phase, then gradually fell back after entering the swing phase. The improved models (models B-E) showed lower bone-metal prosthesis interface micromotion when compared with the original model (model A), but there was no significant difference among models A-E (P>0.05). The maximum micromotion of tibia appeared at the dome of the tibial bone groove, and the micromotion area was the largest in model A and the smallest in model E. The maximum micromotion of talus appeared at the posterior surface of the central bone groove, and there was no difference in the micromotion area among models A-E. The contact area of the articular surface of the insert/talus prosthesis in each group increased in the support phase and decreased in the swing phase during the gait cycle. Compared with model A, the articular surface contact area of models B-E increased, but there was no significant difference among models A-E (P>0.05). The change trend of the maximum stress on the articular surface of the inserts/talus prosthesis was similar to that of the contact area. Only the maximum contact stress of the insert joint surface of models D and E was lower than that of model A, while the maximum contact stress of the talar prosthesis joint surface of models B-E was lower than that of model A, but there was no significant difference among models A-E (P>0.05). The high stress area of the lateral articular surface of the improved inserts significantly reduced, and the articular surface stress distribution of the talus prosthesis was more uniform. Conclusion Adding a flexible layer in the insert can improve the elasticity of the overall component, which is beneficial to absorb the impact force of the artificial ankle joint, thereby reducing interface micromotion and improving contact behavior. The mechanical properties of the inserts designed with the platform type and thicker flexible layer are better.