| Objective:With the rapid development and generalization of total hip arthroplasty, techniques of operative procedure have been gradually improved, the survival term of total hip arthroplasty also have been prolonged, and the quality of patients'life have been conspicuously increased.In cemented and cementless total hip arthroplasty, ten years after operation,the satisfaction rate of surgery can also reach to 90%.However, with more operations and longer follow-up period, complication after total hip arthroplasty are acquired more attentions. After surgery, some patients are still suffered from pain and slightly limitation of motion.Apart from aseptic loosening of prostheses, inflammation and other factors, the shape of ischium also has a significant influence on the postoperative effects of total hip arthroplasty. In clinical practice, we have detected that the various shapes of ischium may have influences on the length within lesser trochanter of femur and ischium, it could be a reason for impingement or soft tissue squeezing, paining, and the stability of hip after total hip arthroplasty. This point is usually been neglected by surgeon. We did not found any reports on the influences of ischium shape on total hip arthroplasty. We tested the angulations of the body of ischium and sagittal axis, and the length between the lesser trochanter of femur and ischial tuberosity, in three different positions within neutral position, 15°posterior extension and 30°posterior extension. The purpose is to analyze the morphological difference of ischium in Chinese and the relationship between lesser trochanter of femur and ischium, and to find weather the shape of ischium have influences on total hip arthroplasty. We also gave a description that the restored offset had an effect on the relationship between lesser trochanter of femur and ischium in total hip arthroplasty, in order to guide preoperative plans, then enhance the stability of hip, avoid impingement and finally improve the patients'quality of life.Methods:1 Measurement of angulations between the body of ischium and sagittal axis200 pelycograms(114 males and 86 females)were collected randomly from the radiology department in Third Hospital of Hebei Medical University from Feb.2005 to April 2006,Inclusion age was above 18 years old.Mean age of males and females were 41 and 49 respectively.Main inclusion criteria of the pelycograms which we collected are as follows: there should be no fracture, no congenital deformities or no unusual bony change in body of ischium. Apex of coccyx lies oppositely to the upper margin of pubic symphysis, both obturator foramen are symmetrical and similar.Angulations between the body of ischium and sagittal axis were measured on the pelycograms by Image Processing Software Photoshop.The angulations we measured were analyzed statistically by SAS 8.0 software to see the sides differences and sex differences in male and female respectively.2 Measurement of distance between the lesser trochanter of femur and ischial tuberosity in different body positionsTwenty adult formalin-fixed cadaver specimens in scientific research(14 males and 6 females) were collected from the department of anatomy of Hebei Medical University. Main inclusion criteria of the cadaver specimens which we collected are as follows: the cadaver specimens should be antiseptic fixed and there should be intact and no fracture ,no congenital deformities or no pathological changes in the pelvis, hip joint and femur. The cadaver specimens that lay in prone position were given an opography posterior to hip joint.We dissected the cadaver specimens layer by layer from skin to subcutaneous tissue and muscle, rejected the muscle tendon adherent to the lesser trochanter of femur and ischial tuberosity to let them to be exposed. Then we set the lower limbs in three different positions with the trans-articular external fixator, three different positions involve neutral position, 15°posterior extension and 30°posterior extension. The distances between the lesser trochanter of femur and ischial tuberosity were measured by sliding caliper and then analyzed statistically.Results:1 The angulations between the body of ischium and sagittal axis: Angulations between the body of ischium and sagittal axis in the 200 pelycograms were analyzed for test of normality with SAS 8.0 statistical software. According to standard a=0.1,angulations of both sides between the body of ischium and sagittal axis in male obey normal distribution(left side W=0.99,P=0.94>0.1;right side W=0.99 , P=0.83>0.1).Angulations of both sides between the body of ischium and sagittal axis in female obey normal distribution(left side W=0.98,P=0.24>0.1;right side W=0.99,P=0.96>0.1).1.1 Comparison of angulations between the body of ischium and sagittal axis in two sidesAngulations between the body of ischium and sagittal axis were analyzed for T-tests in compare two group means.Mean angulations of the left side in males was 28.38°±4.77°; Mean angulations of the right side in males was 27.87°±4.88°,According to standard a=0.05,no significant difference was found in associated with the angulations between the body of ischium and sagittal axis of both sides in males(t=0.80,P>0.05).Mean angulations of the left side in females was 23.18°±5.39°; Mean angulations of the right side in females was 22.90°±5.91°,According to standard a=0.05,no significant difference was found in associated with the angulations between the body of ischium and sagittal axis of both sides in females(t=0.33,P>0.05)1.2 Comparison of angulations between the body of ischium and sagittal axis in different sexMean angulations of the left side in males was obviously larger than those in females.A significant difference was found in the left side between males and females (t=7.22,P<0.01). Mean angulations of the right side in males was obviously larger than those in females.A significant difference was found in the right side between males and females (t=6.34,P<0.01).2 The distance between the lesser trochanter of femur and ischial tuberosity in three different positions:The mean distance between the lesser trochanter of femur and ischial tuberosity in neutral position, 15°posterior extension and 30°posterior extension in the left were 2.04cm,1.77 cm and 1.60 cm respectively;in the right were 2.00cm,1.80 cm and 1.65 cm respectively. The distance between three different positions were carried out for analysis of variance in randomized block design. According to standard a=0.05,significant differences were found in both sides in the distance from lesser trochanter of femur to ischial tuberosity among neutral position,15°posterior extension, and 30°posterior extension.(left side F=101.98,P<0.01;right side F=120.92,P<0.01;).Conclusion:1 There is an significant sex difference in the angulations between the ischiadic body and sagittal axis in Chinese,the angulations of female are lesser than that of male.2 The distance between the lesser trochanter of femur and ischial tuberosity is significantly diminished with the inceased posterior extension angle of the hip.3 There would be a likelihood of squeeze or impingement which caused pain between the lesser trochanter of femur and ischial tuberosity in whose angulations were justo minor(<15°) with the hip posterior extension concomitantly adduction if the offset was not fully restored in total hip arthroplasty.4 Pelviradiography is a simple and economical examination with which we judge the shapes of ischium and infer the likelihood of impingement or squeeze between the lesser trochanter of femur and ischial tuberosity preliminary. In order to avoid impingement or squeeze between the lesser trochanter of femur and ischial tuberosity, great emphases should be put on preoperative templating accuratly,restoring offset appropriately which furthermore enhances the stability of hip after total hip arthroplasty. |
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