The Study On The Anatomy Of The Transverse Acetabular Ligament And Its Clinical Reference Value In THA

PART ?The Anatomical Study of the Anteversion of the Transverse Acetabular Ligament and the AcetabulumPurpose: Reported in the literatures,both the acetabular rim and the transverse acetabular ligament (TAL) could be used as landmarks for aligning cup anteversion in total hip arthroplasty (THA).However,in the previous anatomical studies,both the anteversion value of the acetabulum and the anteversion value of the TAL were different in different literatures. An anatomical study on the anteversion of the TAL and acetabulum in normal adults was performed in this paper in order to clarify whether they could be used to position the cup anteversion in THA.Materials and methods: From January 2014 to January 2015, 66 adults (132 hips)without acetabular osteophytes and dysplasia were enrolled in the study, among which 16 cases (16 hips) underwent THA. The acetabulum was equally divided into five cross-sections and the three cross-sections in the middle were respectively defined as the superior, middle and inferior cross-section from the superior edge to the inferior edge. Then some angles were measured and analyzed as follow: (1) The radiographic inclination (RI) of the acetabulum was measured in computed tomography (CT) scout image; the anatomical anteversions (AAs) in the superior, middle and inferior cross-section of the acetabulum were measured in CT. The anatomical anteversion(AA) of the TAL was measured by the horns of the acetabular notch in 3-dimensional reconstruction CT. Then the difference among these AAs of the acetabulum in different section and the TAL were compared respectively. (2) The ratios of the AAs of the acetabulum and the TAL located in the "safe zone" defined by Lewinneck were counted respectively and the difference among them was compared. The ratio of the RI of the acetabulum located in the "safe zone" was counted. (3) The gender difference and lateral difference of the AAs of the acetabulum and the TAL were compared. The gender difference and lateral difference of the RI of the acetabulum were compared. (4) The difference value in all patients between the AA of the TAL and the middle cross-section of the acetabulum were statistically analyzed. In the 16 patients who underwent THA surgery, the preoperative difference value between the AAs of the TAL and the middle cross-section of the acetabulum were counted and the intraoperative difference values between them were counted. Then the difference between preoperation and intraoperation was statistically analyzed. (5) The correlations between the AA of the TAL and the AA of the middle cross-section of the acetabulum were statistically analyzed.The correlations between the RI of the acetabulum and the AAs of the acetabulum and the TAL were statistically analyzed.Results: (1) The mean RI of the acetabulum was 42.4±3.8 degrees; the mean AAs in the superior, middle and inferior cross-section of the acetabulum and the mean AA of the TAL were 19.1±7.2 degrees,21.7±5.8 degrees, 21.0± 5.9 degrees and 14.3±3.5 degrees respectively. There were significant differences between any two of them(t test, P<0.05). (2) 95% of the RI of the acetabulum was in the "safe zone". The ratios of the AAs in the superior, middle and inferior cross-section of the acetabulum and the TAL in the "safe zone" were 94%, 98%, 98% and 97% respectively. The differences between them were all not statistically significant (Chi-square test, P>0.05). The ratio of the AA in the "safe zone" was 100% if the anteversion of the TAL increased by 8.3 degrees,but there was no significant difference in the ratios of the AA in the "safe zone" between before and after the increased 8.3 degrees (Chi-square test, P> 0.05). (3) The mean RI of the acetabulum was 41.8± 4.4 degrees in male and 43.0 ± 3.0 degrees in female. The mean AAs in the superior, middle and inferior cross-section of the acetabulum were 20.2±6.3 degrees,21.1±4.9 degrees and 20.4± 5.4 degrees respectively in male, and 17.9 ± 7.8 degrees, 22.3± 6.6 degrees and 21.7 ± 6.3 degrees in female; the mean AA of the TAL was 14.3 ±2.3 degrees in male,and 14.2±4.6 degrees in female. There were no statistically significant differences between male and female in the RI of the acetabulum , the AA of the acetabulum and the AA of the TAL (t test, P> 0.05). (4) The radiographic inclinations (RIs) of the left and right acetabulum were 42.0 ± 3.6 degrees and 42.7±4.0 degrees respectively.The left AAs in the superior, middle and inferior cross-section of the acetabulum were 19.2±6.8 degrees,21.8± 8 degrees and 20.9±5.9 degrees respectively. The right AAs in the superior, middle and inferior cross-section of the acetabulum were 18.9±7.6 degrees,21.6±5.9 degrees, 21.2± 5.9 degrees respectively. The AAs of the left and right TAL were 14.2 ± 3.8 degrees and 14.3 ±3.3 degrees respectively. There were no significant differences between the left side and right side in the RI of the acetabulum, the AA of the acetabulum and the AA of the TAL (t-test, P> 0.05). (5)The mean difference value between the AA of the TAL and the AA of the middle cross-section of the acetabulum was 7.4±4.7 degrees in all patients. For the 16 cases who underwent THA, the mean preoperative difference value between the AA of the TAL and the AA of the middle cross-section of the acetabulum was 6.4± 5.6 degrees and the mean intraoperative difference value between the AA of the TAL and the AA of the middle cross-section of the acetabulum was 6.3 ±5.1 degrees. The difference between preoperation and intraoperation was not statistically significant (t test, P>0.05). (6) There was a moderate positive correlation between the AA of the TAL and the AA of the middle cross-section of the acetabulum (Pearson correlation analysis, P<0.05, r = 0.589).There were weak positive correlations between the RI of the acetabulum and the AAs of the middle and inferior cross-section of the acetabulum(Pearson Correlation Coefficient, P <0.05, r = 0.245, 0.258 respectively),while there were no correlations between the RI of the acetabulum and the AA of the superior cross-section of the acetabulum and the AA of the TAL(Pearson Correlation Coefficient, P> 0.05).Conclusion: For the patients without osteophytes around the acetabulum and acetabular dysplasia (1)Both the anteversion of the transverse acetabular ligament and the anteversions in the superior, middle and inferior cross-section of the acetabulum can be used to position the anteversion of the cup in total hip arthroplasty. Among these anteversions , the anteversion of the middle cross-section of the acetabulum is the closest to the mean value of the "safe zone" and the anatomical anteversion of the transverse acetabular ligament is about 8 degrees smaller than the mean value of the"safe zone".(2) The inclination of the acetabulum can be used to position the inclination of the acetabular cup in total hip arthroplasty.PART ?The Clinical Study of the Reference Value of the Transverse Acetabular Ligament in THACHAPTER ?The Clinical Study of the Exposing Method of the Osteophyte-covered Transverse Acetabular Ligament in THAPurpose: Both the acetabular rim and the transverse acetabular ligament (TAL)could be used to position the anteversion of the acetabular cup in total hip arthroplasty(THA). The accuracy of positioning the cup anteversion referring to the acetabular rim might be affected by the osteophytes around the acetabulum while the accuracy referring to the TAL was not affected by the osteophytes. In addition, the TAL was also used as a reference to position the height and inclination of the cup in some literatures. Therefore, the TAL played an important reference role in THA.However,the ability to find the TAL varied greatly in reported literatures because the TAL might be very hard to be exposed when it was completely covered by osteophytes. How to expose the TAL completely covered by osteophytes wasn't described in detail in previous literatures.In the present study, we introduced two methods and made a comparison between them to identify the easier procedure for finding an osteophyte-covered TAL.Materials and Methods: During the primary THA operations conducted from January 2012 to June 2015, a total of 100 patients (100 hips) were confirmed to have an completely osteophyte-covered TAL. These 100 patients were enrolled in this study.Two methods were used to identify the TAL: using a bone chisel(the bone chisel group) or a small reamer(the reamer group), and the patients were allocated randomly to one of these two groups. The proportion of the patients in whom the TAL was identified was compared between the two groups using a chi-square test.Results: The percentage of patients in whom the TAL was found using a bone chisel was 54.1% (26/48), whereas the percentage was 94.2% (49/52) among patients for whom a small reamer was used. The difference between the two methods was statistically significant (chi-square test, P<0.05).Conclusions: The TAL can be found more easily with a small reamer than with a bone chisel.CHAPTER ?The Clinical Study of the Reference Value of the Transverse Acetabular Ligament in Positioning the Cup AnteversionPurpose: It had been reported that the transverse acetabular ligament (TAL) could be used as a reference to position the cup anteversion in total hip arthroplasty(THA)without being affected by osteophytes around the acetabulum. However, there were still different opinions on its clinical effect.The clinical effect of positioning the cup anteversion referring to the TAL was compared with the traditional positioning method in this study in order to evaluate the clinical reference value of the TAL in positioning the cup anteversion.Materials and Methods: From July 2015 to March 2016, 80 patients (80 hips) were enrolled in this study and randomly divided into two groups: the transverse acetabular ligament group (TAL group) and the control group. The cup was positioned parallel to the TAL in the TAL group and by traditional method in the control group. The postoperative standard anteroposterior radiographs and computed tomography (CT) of the bilateral hip joint were used to evaluated the postoperative anteversion of the cup:The short and long axes of the cup opening plane were measured on the standard plain film and then the radiographic anteversion (RA) of the cup on plain film was calculated by a formula. The anatomical anteversion(AA) and the radiographic inclination(RI) of the cup were measured on postoperative CT of the hip and then the RA of the cup on CT was calculated by a formula. (1) The accuracy of measuring the RA of the cup on plain film and CT was compared. (2) The RA of the cup, the proportions of the patients in whom the RA of the cup were in the "safe zone" defined by Lewinneck and the dislocation rate within 1 year after THA operation were compared between the two methods of positioning the acetabular cup.Results: (1) In the TAL group, the radiographic inclinations(RIs) of the cup on plain film and CT were 10.8 ± 3.0 degrees (2.8?17.8 degrees) and 10.5±3.3 degrees (3.2?19.2 degrees) respectively and the difference between the plain film and CT was not statistically significant (paired t-test, P>0.05). The proportions of the patients in whom the RA of the cup were in the "safe zone" on plain film and CT were 97.6%(40/41) and 95.1% (39/41) respectively and the difference between the plain film and CT was not statistically significant(chi-square test, P>0.05). (2) In the control group,the Rls of the cup on plain film and CT were 18.6± 4.8 degrees (6.6 ?29.6 degrees)and 18.9 ± 5.1 degrees(5.4?29.2 degrees) respectively and the difference between the plain film and CT was not statistically significant (paired t-test, P>0.05) .The proportions of the patients in whom the RA of the cup were in the "safe zone" on plain film and CT were 92.3% (36/39) and 89.7% (35/39) respectively and the difference between the plain film and CT was not statistically significant(chi-square test, P>0.05). (3)The RA of the cup on plain film in the TAL group was smaller than the RA in the control group(10.8±3.0 degrees VS 18.6±4.8 degrees, t-test, P<0.05).There was no statistical difference between the proportion of the patients in whom the RA of the cup was in the "safe zone" in the TAL group and the proportion in the control group on plain film (97.6% VS 92.3%,t-test, P>0.05). (4) The RA of the cup on CT in the TAL group was smaller than the RA in the control group(10.5±3.3 degrees VS 18.9±5.1 degrees,t-test, P <0.05). There was no statistical difference between the proportion of the patients in whom the RA of the cup were in the "safe zone" in the TAL group and the proportion in the control group on CT (95.1% VS 89.7%,t-test, P>0.05).(5) The AAs of the cup measured on CT in the TAL group and in the control group were 14.9±15.0 degrees (5?30 degrees) and 25.9±6.6 degrees (8?42 degrees) respectively and the difference between the two groups was statistically significant (t test, P<0.05). The RIs of the cup measured on CT in the TAL group and in the control group were 44.9± 6.3 degrees (35?56 degrees) and 44.8±5.0 degrees(37?54 degrees) respectively and the difference between the two groups was not statistically significant(t test, P<0.05). (6) The dislocation rate was 0% both in the TAL group and the control group within 1 year after THA. Therefore, there was no significant difference between the two groups(chi-square test, P>0.05).Conclusion: (1)Through a standard anteroposterior radiograph of the bilateral hip joint and reasonable mathematical calculations,the accuracy of evaluating the radiographic anteversion of the acetabular cup by plain film is comparable to CT.(2)For the patients without acetabular dysplasia or abnormal TAL caused by acetabular fracture, the TAL is a good reference for positioning the cup anteversion in THA and the accuracy of positioning the cup anteversion referring to TAL is similar to or better than that of an experienced doctor.But a too small anteversion of the cup should be avoided if the anteversion of the cup is placed referring to the TAL.CHAPTER ?The Clinical Study of the Reference Value of the Transverse Acetabular Ligament in Managing the Leg LengthPurpose: The leg length discrepancy(LLD) after total hip arthroplasty (THA) was very often. It could lead to limping, pain, increased wear, etc. and then reduced the patients' satisfaction.In this paper,a novel method of leg length management by measuring the cup height referring to the transverse acetabular ligament(TAL) in THA operation, combined with preoperative contralateral leg length measurement was introduced. The clinical effect was compared with the traditional method in order to evaluate the reference value of the TAL in managing the leg length.Materials and Methods: From June 2014 to June 2015, 80 hips were enrolled in this study and their leg length were managed by the new method(the new method group)or the traditional method randomly(the control group). The new method was performed as follow: A straight line connecting the bilateral lower edge of acetabular posterior wall was drawn. Then the height of acetabular rotation center(the height from the rotation center of the acetabulum on the healthy side to the straight line) and the height of femoral head rotation center(the height of the femoral head on the healthy side to the straight line) was measured on the preoperative X-ray. During THA operation, the anteversion and height of the cup were positioned referring to the TAL and then the height of the acetabular prosthesis rotation center(the height from the rotation center of the cup to the posterior horn of the TAL in the acetabular posterior wall) was measured. A proper stem and femoral head prosthesis were selected according to the formula: the height of the acetabular prosthesis rotation center - the height of acetabular rotation center = the height of the femoral head prosthesis rotation center - the height of femoral head rotation center (in other words,the height change of the acetabular side = the height change of the femoral side).Then the rotation center of the femoral head prosthesis was adjusted in order to decrease the LLD after THA. The traditional method: This method mainly relied on the surgeon's experience. The leg length was evaluated mainly by the soft tissue tension around the hip joint, Shuck test and leg-to-leg comparison. (1)The LLD was measured on the postoperative X-ray. (2)The difference of LLD after THA between the two methods was compared by t test. The difference was statistically significant if P<0.05. (3)The ratios of the patients whose postoperative LLD were more than 1 cm in the two groups were counted and compared. The difference was statistically significant if P<0.05 (chi-square test).Results: (1 )In the new method group,the postoperative mean LLD was 4.8±2.6 mm. While in the control group,the postoperative mean LLD was 6.6±3.1 mm. The postoperative LLD in the new method group was smaller than that in the traditional group(t test ,P<0.05). (2)In the new method group, the postoperative LLD was more than 1 cm in 2.6% (1/38) of patients and the postoperative maximum LLD was 11 mm.While in the control group, the postoperative LLD was more than 1 cm in 16.7%(7/42)of patients and the postoperative maximum LLD was 13 mm. The ratio of patients whose LLD were more than 1 cm in the new method group was lower than that in the traditional group(P<0.05,chi-square test)Conclusion: The new method introduced in this paper can reduce the leg length discrepancy after THA better than the traditional method.