| ObjectiveTo analyze the curative effect of total hip arthroplasty(THA)in patients with hip ankylosis caused by ankylosing spondylitis(AS)Optimum implantation range of anteverted angle to assess the risk of prosthesis loosening after operation.MethodThrough retrospective research+computer simulation analysis,this study included 9 cases(13 hip joints)from our department who met the diagnostic criteria of ankylosing spondylitis and the study inclusion criteria from June 2019 to December 2022,The follow-up time ranged from 11 to 31 months,with an average of(24.08±5.95)months.General data such as age,gender,and follow-up time of patients were collected,and AS disease activity and function were evaluated before operation and at the last follow-up:ankylosing spondylitis disease activity score(ASDAS),Bath Ankylosing spondylitis function index(BASFI),ankylosing spondylitis quality of life(ASQOL),Bath ankylosing spondylitis imaging index(BASRI-hip),related to hip joint function evaluation:hip flexion range of motion,Harris hip score(HHS),visual analogue scale(VAS)and other evaluations were statistically analyzed,and the patients in this group were evaluated.Surgical efficacy of THA.According to the preoperative average patient pelvic tilt angle(PT)=28.85±8.22° as a reference,the CT data of healthy adult male pelvis was used for three-dimensional modeling with PT=30°,and the artificial acetabular cup was used to model the model.The left acetabular model was implanted at 5 angles of 0°,5°,10°,15°,and 20° to obtain 5 acetabular side models,which were assembled with the same femoral model implanted with the femoral side prosthesis to obtain 5 A hip model after THA.Set the material properties of each part in the model,and set the parameters of the material properties.A static standing load of 320N and an instantaneous maximum load of 1480N were applied to the five models respectively,and the stress/strain distribution nephogram and maximum stress(MPa)/strain(mm)value.Analyzing the range and degree of stress/strain concentration of different acetabular cup anteversion angles after application of load,the acetabular side prosthesis with the best stress range and stress/strain performance in the three-dimensional model was obtained.Angle range.The simulated results were compared with the average acetabular side prosthesis anteversion angle of this group of patients after surgery,and the effect of the prosthesis implantation angle on the long-term stability of the prosthesis in this group of patients during surgery was evaluated.Result1 General information1.1 Gender composition:7 males and 2 females1.2 Age distributionThe age ranged from 21 to 72 years old,with an average of 41.08±15.86 years old.1.3 Follow-up time Average follow-up 24.08±5.95 months.2 Preoperative and final follow-up results of patients2.1 Related evaluation of AS disease activity and functionBASRI-hip score:Except for 2 cases of grade 3 in this group,the others were all grade 4;the ASDAS score at the last follow-up was significantly improved compared with preoperative,and the improvement was statistically significant(P<0.001);BASFI score:the last follow-up was compared with preoperative There was a significant decrease,which was statistically significant(P<0.001);ASQOL score:the last follow-up was significantly lower than that before operation,which was statistically significant(P<0.001).2.2 Evaluation of hip joint function Flexion range of motion:A total of 10 hip joints lost their range of motion before surgery,and only 3 hip joints had range of motion.The average pelvic tilt angle was 28.85±8.22°;the postoperative average acetabular cup anteversion angle was 11.23±3.56°,and the HHS score:the average score of the last re-examination was significantly higher than that before operation,and the result was statistically significant(P<0.001);VAS score:the average score of the last re-examination was significantly higher than that before operation,and the result was statistically significant(P<0.001).3 Finite element analysis results3.1 Stress and strain of bony acetabulumThe stress ranges of the artificial acetabular cup 0° and 20° models were relatively concentrated,and the peak stress occurred when the acetabular cup anteversion was 0°.When the artificial acetabular cup was tilted forward by 10°,the stress range was relatively scattered,and the static and gait peak stresses were the lowest among the five groups.In the 10 working conditions,the strain was mainly distributed in the upper medial and anterior edge of the bony acetabulum.In standing and gait,the acetabular strain was significantly greater than that of the other three groups when the acetabular cup anteversion was 0° and 20°,and the strain was the most dispersed and the strain value was the lowest among the five groups when the acetabular cup anteversion was 10°.3.2 Stress and strain of the acetabular cupThere was no significant difference in the stress distribution area and range in different acetabular cup anteversion models under the same loading conditions.Peak stresses were greatest at 0° and 20° of acetabular cup anteversion.The peak stresses of the 5°,10°,and 15° anteversion groups were similar,and were significantly smaller than those of the 0° and 20° acetabular anteversion models under both loads.The acetabular cup strain was greatest at cup anteversion angles of 0° and 20°.The maximum strains of the 5°,10°,and 15° anteversion groups were similar,and were significantly smaller than those of the 0° and 20° acetabular anteversion models under both static and gait loads.3.3 Stress and strain of ceramic liner and ceramic femoral headUnder 10 working conditions of artificial liner and femoral head,the stress distribution range,maximum peak stress,and maximum strain did not show any correlation with the acetabular cup antever si on angle.4 Comparison of patient clinical data and finite element analysis resultsThe average pelvic inclination angle of patients in this group was 28.85±8.22°.The average postoperative acetabular cup prosthesis anteversion angle measured by Pradhan measurement method was 11.23±3.56°.It is consistent with the optimal acetabular cup anteversion angle range(10±5)° for the pelvic tilt angle of 30° in the finite element analysis.The optimal acetabular cup anteversion angle during THA for AS patients with retroverted pelvis is smaller than the Lewinnek safety zone standard commonly used in conventional THA.Conclusion1.THA is an effective treatment for AS combined with hip ankylosis to improve joint function and quality of life.2.According to the finite element simulation analysis,when PT=30°,when the acetabular cup is implanted with an anteversion angle of 10±5°,the risk of loosening due to stress on the contact surface between the prosthesis and the bony acetabulum is the lowest.3.The average acetabular cup anteversion angle of this group of patients after operation is within the best range of finite element simulation results,and the risk of long-term prosthesis loosening is predicted to be low in this group of patients. |
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