Postoperative Stem Anteversion Research Articles

A New Method to Predict Postoperative Stem Anteversion in Total Hip Arthroplasty for Developmental Dysplasia of the Hip.

Preoperative evaluation of femoral anteversion to predict postoperative stem anteversion aids the selection of an appropriate prosthesis and optimizes the combined anteversion in total hip arthroplasty (THA) for developmental dysplasia of the hip (DDH). The conventional prediction methods are based on the femoral anteversion measurement at the location of the femoral head and/or neck. However, varied differences between femoral anteversion and postoperative stem anteversion were demonstrated. This study investigated the predictive role of a new method based on the principle of sagittal three-point fixation. From January 2017 to December 2018, a total of 133 DDH hips that underwent THA were retrospectively analyzed. There were 76 Crowe type I, 27 type II, and 30 type III hips. The single-wedge stem was used in 49 hips, and the double-wedge stem was used in 84 hips. Preoperative native femoral anteversion at the femoral head-neck junction, anterior cortex anteversion at 2 levels of the lesser trochanter, posterior cortex anteversion at 5 levels of the femoral neck, and postoperative stem anteversion were measured using two-dimensional computed tomography. Predictive anteversion by the new method was calculated as the average anteversion formed by the anterior cortex at the lesser trochanter and the posterior cortex at the femoral neck. For hips with different neck heights, different Crowe types, different stem types, or different femoral anteversions, native femoral anteversion showed widely varied differences and correlations with stem anteversion, with differences ranging from -1.27 ± 8.33° to -13.67 ± 9.47° and correlations ranging from 0.122 (p = 0.705, no correlation) to 0.813. Predictive anteversion formed by the anterior cortex at the lesser trochanter proximal base and posterior cortex 10 mm above the lesser trochanter proximal base showed no significant difference with stem anteversion, with less varied differences (0.92 ± 7.52°) and good to excellent correlations (r = 0.826). Adopting our new method, predictive anteversion, measured as the average anteversion of the anterior cortex at the lesser trochanter proximal base and posterior cortex 10 mm above the lesser trochanter proximal base, predicted postoperative stem anteversion more reliably than native femoral anteversion.

The midcortical-line is more reliable than the T-line in predicting stem anteversion in patients with developmental hip dysplasia after total hip arthroplasty.

BackgroundPrecise preoperative planning improves postoperative outcomes in total hip arthroplasty (THA), especially in developmental dysplasia of the hip (DDH) cases. Previous studies used the T-line and midcortical-line as preoperative landmarks to predict postoperative stem anteversion (PSA). However, the most reliable landmark in predicting PSA in DDH patients remains unclear. To find the most reliable measurement to predict the PSA in DDH patients, this study compared the midcortical-line and T-line at different femoral neck levels.MethodsPre- and postoperative Computed Tomography (CT) scans of 28 hips in 21 DDH patients who received THA were obtained for three-dimensional femoral models. The preoperative CT scan was used to measure the anteversion of the midcortical-line on the axial cross-sectional plane images (AM-CT), the anteversion of the midcortical-line from 3D models (AM-3D), and the T-line from 3D models (AT-3D) at simulated osteotomy planes at 5 and 10 mm heights proximal to the base of the lesser trochanter. The correlation between the preoperative femoral anteversion (AM-CT, AM-3D, AT-3D) and the PSA was assessed to evaluate the prediction accuracy.ResultsThe correlations between the AM-CT and the PSA were 0.86 (mean difference (MD) = 1.9°) and 0.92 (MD = −3.0°) at 5 and 10 mm heights, respectively. The correlation between the AM-3D and the PSA were 0.71 (MD = −11.6°) and 0.61 (MD = −12.9°) at 5 and 10 mm heights. The AT-3D was significantly greater (MD = 15.4°) than the PSA (p-value <0.01) at 5 mm cutting height, and the correlation between the AT-3D and the PSA was 0.57 (MD = 7.8°) at 10 mm cutting height.ConclusionsThe AM-CT at the 10 mm height had the strongest correlation with the PSA and was more reliable in predicting the PSA when compared with the AM-3D and the AT-3D in DDH patients.

Higher femoral anteversion restoration accuracy after total hip arthroplasty with a proximally fixed anatomic stem than with a generic straight double-tapered stem.

Femoral antetorsion in uncemented hip replacement hardly can be modified and the restoration of the anatomic anteversion might be difficult with standard stems. We compared femoral anteversion restoration of a generic straight stem with a proximally fixed anatomic stem that included a dual sagittal curvature and a proximal torsion. It was hypothesised that the restoration of the anteversion was more accurate with the anatomic stem. In this comparative study data were collected prospectively of 80 consecutive patients with total hip arthroplasty for primary osteoarthritis. In the first 40 patients (Group I) a cementless proximally fixed anatomic stem with 15° antetorsion of the shaft and a dual sagittal curvature was used. Its design was based on a database of 3D CT images of 600 hips. For comparison a cementless generic straight double-tapered stem was implanted in the next 40 patients (Group II). All operations were performed by one experienced surgeon. All patients had a preoperative 3D planning. A low-dose CT scan was performed at 3 months postoperatively to determine the postoperative stem anteversion. The demographics were similar in both groups. In group I the mean postoperative femoral anteversion was similar to the preoperative one (22.1° ± 10.2° vs. 20.4° ± 9°; p = 0.2). In Group II, the mean postoperative femoral anteversion was lower (12.9° ± 10.8°, vs. 18.3° ± 12°; p = 0.02). Uncemented standard femoral stems tend to reduce femoral anteversion. The used anatomic stem restored femoral anteversion better. The clinical impact of this finding has to be proven.

Difference in tapered wedge stem alignment between supine and lateral position in cementless total hip arthroplasty via modified Watson-Jones anterolateral approach.

Whether different body positions during surgery affect postoperative stem alignment in total hip arthroplasty (THA) remains unclear. The purpose of this study was to clarify differences in tapered wedge stem alignment between supine and lateral positions in THA under the modified Watson-Jones anterolateral approach. We reviewed 242 consecutive, primary cementless THAs performed with ceramic-on-cross-linked polyethylene via the modified Watson-Jones approach in either supine or lateral positions between 2009 and 2015 (supine group: 113 cases; lateral group: 129 cases). No specific reasons to select supine or lateral positions for the surgery were given during the study period. Computed tomography was performed pre- and postoperatively to measure preoperative femoral anteversion and postoperative stem anteversion, respectively. Stem alignment in coronal and sagittal planes was also evaluated. Mean difference in stem anteversion and femoral anteversion was 8.6±9.4 in the supine position and 13.0±11.4 in the lateral position (p = 0.0013). Although no significant difference was seen between groups for stem alignment in the coronal plane, flexed implantation was more likely in the supine group (46/113, 40.7%) than in the lateral group (20/129, 15.5%). A significant correlation was found between femoral anteversion and stem anteversion in both the supine and lateral groups (r = 0.68, p <0.0001 and r = 0.52, p <0.0001, respectively). Although stem anteversion was more strongly correlated with femoral anteversion in the supine position than in the lateral position, neutral position in the sagittal plane was more likely to be found with the lateral position than with the supine position. Surgeons can achieve ideal stem positioning by considering these results in the modified Watson-Jones approach in both the supine and lateral positions.

Optimal Level of Femoral Neck for Predicting Postoperative Stem Anteversion in Total Hip Arthroplasty for Crowe Type I Dysplastic Hip.

ObjectiveThis study aimed to investigate the optimal level of femoral neck for measuring femoral anteversion to predict postoperative stem anteversion in Crowe type I developmental dysplasia of the hip.MethodsThis retrospective study analyzed 108 Crowe type I hips that underwent THA between January 2016 and December 2017, including 70 women and 19 men with a mean age of 63.08 ± 9.13 (range, 41–83) years. The single‐wedge stem was used in 37 hips, the double‐wedge stem was used in 71 hips. Computed tomography scans were performed pre‐ and post‐operation. Femoral anteversion at six levels of the proximal femur were measured via preoperative two‐dimensional computed tomography. Femoral anteversion at the level of the femoral neck osteotomy plane and postoperative stem anteversion were measured via three‐dimensional reconstructed models.ResultsThe mean follow‐up period was 18.5 months (range, 12–27). The mean preoperative Harris Hip Score was 51.5 ± 8.7 and improved to 90.4 ± 7.8 (P < 0.001) by the last follow‐up. There were no intraoperative fractures, and no infections occurred during the follow‐up period. Two patients developed deep venous thrombosis. There was no sign of prosthetic loosening in all hips. No significant correlations were found between the height of the femoral neck osteotomy plane and postoperative stem anteversion (r = −0.119, P = 0.220). Femoral anteversion decreased gradually from 64.00° ± 10.51° at the center of lesser trochanter to 15.21° ± 13.31° at the head–neck junction, which was changed from more to less than stem anteversion (24.37° ± 13.86°). The femoral anteversion at femoral head–neck junction (15.21° ± 13.31°) was significantly less than postoperative stem anteversion (P = 0.000), with a difference of −9.16° ± 9.27°. The femoral anteversion at the level of the osteotomy plane (28.48° ± 15.34°) was significantly more than the postoperative stem anteversion (P = 0.000), with a difference of 4.11° ± 9.56°. Among all six levels and the level of osteotomy, femoral anteversion at the 10‐mm level above the proximal base of lesser trochanter (22.65 ± 12.92) displayed the smallest difference (−1.72° ± 8.90°) and a good correlation (r = 0.764) with postoperative stem anteversion for all 108 hips, with a moderate correlation of 0.465 for single‐wedge stem hips and an excellent correlation of 0.821 for double‐wedge stem hips.ConclusionFor Crowe type I hips, femoral anteversion would be different if it was measured via different levels of the femoral neck. The 10‐mm level above the proximal base of the lesser trochanter could be an optimum choice for measuring femoral anteversion to predict postoperative stem anteversion.

A simple angle-measuring instrument for measuring cemented stem anteversion during total hip arthroplasty

BackgroundDuring total hip arthroplasty (THA), the accurate placement of the femoral components is an important determinant of the success of the procedure. This study assessed the accuracy of cemented stem placement using a new angle-measuring instrument. The primary objective was to investigate the accuracy of the intraoperative measurements of cemented stem anteversion obtained using the angle-measuring instrument. Our secondary objective was to evaluate the accuracy of stem positioning performed using the angle-measuring instrument.MethodsWe compared the intraoperative stem anteversion measurements obtained using the angle-measuring instrument with postoperative stem anteversion measurements obtained using computed tomography in 149 hips (measurement accuracy). We also compared the target angle and postoperative stem anteversion in 105 hips (implantation accuracy).ResultsThe mean amount of intraoperative stem anteversion was 37.9° ± 10.1°, and the mean amount of postoperative stem anteversion was 37.0° ± 10.4°. The mean measurement accuracy was 0.9° ± 6.1°, and the absolute measurement accuracy was 4.9° ± 3.7°. The correlation coefficient for the relationship between the intraoperative and postoperative stem anteversion measurements was 0.824 (p = 0.000). The mean amount of target angle was 37.4° ± 7.6°, and the mean amount of postoperative stem anteversion was 35.9° ± 9.1°. The mean implantation accuracy was 1.4° ± 5.6°, and the mean absolute implantation accuracy was 4.3° ± 3.6°. The correlation coefficient for the relationship between the target angle and postoperative stem anteversion was 0.795 (p = 0.000).ConclusionsThe angle-measuring instrument measured intraoperative stem anteversion accurately, and cemented stem was implanted accurately during THA with the angle-measuring instrument.

Effect of altered proximal femoral geometry on predicting femoral stem anteversion in patients with developmental dysplasia of the hip

BackgroundThe deformity of the proximal femur and acetabular in patients with developmental dysplasia of the hip (DDH) renders an intraoperative decision for ideal component placement challenging. We hypothesized that the altered morphology of calcar femorale (CF) in DDH patients changed the fixation mechanism of the cementless metaphyseal-filling stem and aimed to predict stem anteversion using proximal femoral anatomical parameters from preoperative CT.MethodsPreoperative and postoperative CT scans of 34 DDHs with a metaphyseal-filling stem in THA were retrospectively analyzed. Proximal femoral anatomical parameters, including the femoral anteversion (FA) and the CF angles at the low femoral neck (LFN) and the center of the lesser trochanter (CLT) levels (FA-LFN, FA-CLT, CF-LFN, and CF-CLT) were measured. The dysplastic hips were divided into the CF group (n = 21) and the non-CF group (n = 13) according to the presence of the CF-LFN. The association between the anatomical parameters and the postoperative stem anteversion was statistically analyzed, and the predicted stem anteversion was compared with postoperative stem anteversion.ResultsIn the CF group, the combination of the CF-LFN and FA-CLT exhibited a strong positive correlation (R = 0.870, p < 0.001) with the postoperative stem anteversion. In the non-CF group, only the FA-LFN had a strong positive correlation (R = 0.864, p < 0.001). Average prediction errors were 5.9° and 6.4° in the CF and non-CF groups.ConclusionsThe presence of CF-LFN is related to the press-fit mechanism of the metaphyseal-filling stem, and the preoperative measurements from CT images can be employed as a tool to predict postoperative stem anteversion in DDH patients.

Antéversion du pivot fémoral avec tiges sans ciment effilé dans les dysplasies de hanche : comparaison selon la voie d’abord postérolatérale ou antérolatérale

BackgroundIn total hip arthroplasty (THA), the concept of combined anteversion is accepted as one of best indicators of prosthetic joint stability. Technical parameters may influence the stem and cup anteversion. We therefore investigated if stem anteversion could be influenced by surgical approaches in cementless THA using a tapered wedge stem with stem-first technique. HypothesisWe postulated that the type of approach, posterolateral (PLA) or anterolateral approach (ALA), would influence stem anteversion in dysplastic hip patients. We asked: (1) whether stem anteversion was higher in the PLA group and (2) how postoperative stem anteversion was correlated to preoperative femoral anteversion in each group. Patients and methodsWe retrospectively compared two groups of hips that underwent THA using a tapered wedge stem with the posterolateral (PLA group; 154 hips) or anterolateral (ALA group; 81 hips) approaches. Computed tomography was utilized to measure femoral neck and stem anteversion. To investigate related factors that affect stem anteversion, a stepwise regression analysis was performed. ResultsThe stem anteversion in the PLA and ALA groups was 43.7°±9.8° and 34.0°±12.3°, respectively (p<0.01). The stepwise selection process resulted in a model involving femoral neck anteversion and surgical approach (p<0.01). The stem anteversion of the ALA group (r=0.75, p<0.01) was better correlated to femoral neck anteversion than that of the PLA group (r=0.52, p<0.01). DiscussionThe stem implantation through the ALA is thought to be more restricted than that through the PLA due to the difference of difficulty in femoral exposure. Tapered wedge stems, which are relatively thin and flat, have a high degree of freedom in the femoral canal. Consequently, in cementless THA using a tapered wedge stem, the surgical approaches affected stem anteversion differently. Stem anteversion was more anatomically restored to femoral neck anteversion through the ALA than through the PLA. Level of evidenceIII, retrospective case-control study.

Comparative study of stem anteversion using a cementless tapered wedge stem in dysplastic hips between the posterolateral and anterolateral approaches

BackgroundIn total hip arthroplasty (THA), the concept of combined anteversion is accepted as one of best indicators of prosthetic joint stability. Technical parameters may influence the stem and cup anteversion. We therefore investigated if stem anteversion could be influenced by surgical approaches in cementless THA using a tapered wedge stem with stem-first technique. HypothesisWe postulated that the type of approach, posterolateral (PLA) or anterolateral approach (ALA), would influence stem anteversion in dysplastic hip patients. We asked (1) whether stem anteversion was higher in the PLA group and (2) how postoperative stem anteversion was correlated to preoperative femoral anteversion in each group. Patients and MethodsWe retrospectively compared two groups of hips that underwent THA using a tapered wedge stem with the posterolateral (PLA group; 154 hips) or anterolateral (ALA group; 81 hips) approaches. Computed tomography was utilized to measure femoral neck and stem anteversion. To investigate related factors that affect stem anteversion, a stepwise regression analysis was performed. ResultsThe stem anteversion in the PLA and ALA groups was 43.7°±9.8° and 34.0°±12.3°, respectively (p<0.01). The stepwise selection process resulted in a model involving femoral neck anteversion and surgical approach (p<0.01). The stem anteversion of the ALA group (r=0.75, p<0.01) was better correlated to femoral neck anteversion than that of the PLA group (r=0.52, p<0.01). DiscussionThe stem implantation through the ALA is thought to be more restricted than that through the PLA due to the difference of difficulty in femoral exposure. Tapered wedge stems, which are relatively thin and flat, have a high degree of freedom in the femoral canal. Consequently, in cementless THA using a tapered wedge stem, the surgical approaches affected stem anteversion differently. Stem anteversion was more anatomically restored to femoral neck anteversion through the ALA than through the PLA. Level of evidenceIII, retrospective case-control study.

Prediction of Postoperative Stem Anteversion in Crowe Type II/III Developmental Dysplasia of the Hip on Preoperative Two-Dimensional Computed Tomography

BackgroundPreoperative planning is fundamental for total hip arthroplasty. This study investigated the optimal femoral neck level for measuring femoral anteversion to predict postoperative stem anteversion in developmental dysplasia of the hip and determined the predictive role of average anteversion based on the sagittal 3-point fixation. MethodsSixty-two Crowe type II/III dysplastic hips that underwent total hip arthroplasty were retrospectively analyzed. Preoperative and postoperative anteversion was measured via 2-dimensional computed tomography. Anterior and posterior cortex anteversions were measured at 6 levels of the proximal femur. Femoral anteversion at each level was calculated. Average anterior (lesser trochanter) and posterior cortex anteversions (femoral neck) were calculated based on the sagittal 3-point fixation. ResultsFrom the lesser trochanter to head-neck junction, femoral anteversion decreased gradually from more to less than stem anteversion. For hips with femoral neck height ≥10 mm, femoral anteversion at the 10-mm level above the lesser trochanter proximal base showed no significant difference with stem anteversion, with a good correlation for the single-wedge and an excellent correlation for the double-wedge stem. Average anterior (lesser trochanter proximal base) and posterior cortex anteversions (femoral neck at 10 mm above the lesser trochanter proximal base) showed no significant difference from stem anteversion, with excellent correlations. ConclusionFor Crowe type II/III hips with femoral neck height ≥10 mm, the 10-mm level above the lesser trochanter proximal base is an optimal choice for measuring femoral anteversion to predict postoperative stem anteversion. The average of anterior cortex anteversion at the lesser trochanter and posterior cortex anteversion at the femoral neck has a predictive role.

Total hip arthroplasty using stem-first technique with navigation: the potential of achievement of the optimal combined anteversion being a risk factor for anterior cup protrusion.

In the combined anteversion (CA) technique for total hip arthroplasty (THA) with a cementless stem, cup anteversion is strongly influenced by the native femoral anteversion. It is hypothesized that in cases with large native femoral anteversion, cup anteversion can be decreased, and anterior cup protrusion from the anterior edge of the acetabulum could occur due to the achievement of optimal CA. In this study, the accuracy of CA in THA with the CA technique using imageless navigation and the relationship between the protrusion of the anterior edge of cup and optimum CA was retrospectively evaluated. Ninety-seven patients (104 hips) who underwent primary THA by the CA technique using image-free navigation were enrolled in the study. The femoral stem was placed following the individual femoral anteversion so that the target cup anteversion could be determined following a mathematical formula (37 = femoral stem anteversion × 0.7 + cup anteversion). Results The resulting CA values effectively achieved accurate CA with 39.49 ± 5.03° postoperatively. On the other hand, anterior cup protrusion was measured by computed tomography image. A cup protrusion length of more than 3mm was indicated for 60 cases (57.7%). All included patients were divided into two groups: Group 1 as protrusion positive and Group 2 as protrusion negative. In Group 1, preoperative femoral anteversion and postoperative stem anteversion were significantly higher, while postoperative cup anteversion was significantly lower. However, the postoperative CA value indicated no significant difference between the groups. The CA (stem-first) technique with image-free navigated THA could effectively achieve accurate CA. On the other hand, a large number of cases revealed anterior cup protrusion due to the low cup anteversion.

Factors that Affect Version of the J-Taper Stem

Background: The appropriate combination of acetabular component and stem anteversion is needed to reduce implant impingement and dislocation of total hip arthroplasty (THA). J-Taper is a tapered wedge stem with a relatively shorter small area of arc spray coating compared with conventionally tapered wedge stems. We examined the factors that affect postoperative version of J-Taper. Methods: A total of 59 patients who underwent primary THA were assessed by computed tomography. Preoperative femoral neck and postoperative stem anteversion, stem sagittal alignment, and stem coronal alignment were measured. Results: Mean femoral neck anteversion was 26.1° ± 12.2°. Mean stem version was 32.3° ± 9.0°. Multiple linear regression analysis showed that femoral neck anteversion (p<0.01), stem sagittal alignment (p=0.045), and body height (p=0.048) were positively correlated with stem aversion. The stem version was significantly increased compared with that of native femoral anteversion (6.3° ± 10.9°). Multiple linear regression analysis showed that femoral neck anteversion was negatively correlated with an increased angle of stem version, body height, and stem sagittal alignment was positively correlated. Conclusions: Our findings are helpful for surgeons during preoperative planning to achieve the appropriate combined anteversion.

Cementless Hip Stem Anteversion in the Dysplastic Hip: A Comparison of Tapered Wedge vs Metaphyseal Filling

BackgroundAppropriate stem anteversion is important for achieving stability of the prosthetic joint in total hip arthroplasty. Anteversion of a cementless femoral stem is affected by the femoral canal morphology and varies according to stem geometry. We investigated the difference and variation of the increase in anteversion between 2 types of cementless stems, and the correlation between each stem and the preoperative femoral anteversion. MethodsWe retrospectively compared 2 groups of hips that underwent total hip arthroplasty using a metaphyseal filling stem (78 hips) or a tapered wedge stem (83 hips). All the patients had osteoarthritis due to hip dysplasia. Computed tomography was used to measure preoperative femoral anteversion at 5 levels and postoperative stem anteversion. ResultsThe increase in anteversion of the tapered wedge stem group (22.7° ± 11.6°) was more than that of the metaphyseal filling stem group (17.2° ± 8.3°; P = .0007). The variation of the increase in the tapered wedge stem group was significantly larger than that in the metaphyseal filling stem group (P = .0016). The metaphyseal filling stem group was more highly and positively correlated with femoral anteversion than the tapered wedge stem group. ConclusionFemoral anteversion affects stem anteversion differently according to stem geometry. The tapered wedge stems had greater variation of the increase in anteversion than did the metaphyseal filling stems. Based on the results of this study, it is difficult to preoperatively estimate the increase in stem anteversion for tapered wedge stems.

Novel measurement method on plain radiographs to predict postoperative stem anteversion in cementless THA

Preoperative knowledge of femoral stem anteversion can reduce instability and impingement especially using the standard "cup first" technique in cementless total hip arthroplasty (THA). In this study, we asked whether stems at risk of retroversion or high anteversion (>20°) can be detected preoperatively using hip radiographs in two planes (anteroposterior and Lauenstein). In 123 patients undergoing cementless THA using a non-anatomic, non-modular, straight stem, low centered hip radiographs in two planes were obtained preoperatively and three-dimensional computed tomography (3D-CT) 6 week postoperatively. The novel developed Isthmus Ratio (iRatio) as the relation between canal isthmus and calcar isthmus in the anteroposterior and Lauenstein view was calculated by two observers twice in a 6-week interval. iRatio was compared to postoperative 3D-CT stem version measured by an independent and blinded, external institute. We found a correlation between mean radiographic iRatio and 3D-CT stem torsion of r = 0.578 (p < 0.0001). The observers had excellent agreements within (ICC ≥0.918) and between (mean CCC = 0.967) radiographic iRatio measurements. Eighty-one percent (21/26) of the retroverted cementless stems had a preoperative iRatio below 0.35 and 91% (10/11) of stems with an anteversion exceeding 20° an iRatio above 0.55, respectively. The novel iRatio represents a feasible and reliable method for analyzing anteversion of the final stem on plain radiographs before cementless THA with a straight, tapered stem. iRatios below 0.35 and above 0.55 represent a warning of retroversion and anteversion more than 20° of the final stem, respectively. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:2025-2030, 2016.

Utility of Preoperative Femoral Neck Geometry in Predicting Femoral Stem Anteversion

This study investigated the relationships between the preoperative femoral anteversions and the femoral stem anteversion using CT scans and CT-based 3D models to determine whether any preoperative anteversion measurement correlates with the postoperative stem anteversion. Pre-operative and post-operative CT scans of 19 hips with THAs were evaluated. Five preoperative anatomical femoral anteversion measurements (CT-Head, CT-Below Head, CT-Neck, 3D-Head, and 3D-Neck) were compared with the postoperative femoral stem anteversion. The preoperative CT-Neck anteversion measurement was most correlated with the postoperative stem anteversion (r=0.761, P=0.002) with the narrowest ranges of the differences (−10.2° to 11.0°). The preoperative anteversions using the femoral neck geometry from CT scans can be used for the estimation of the postoperative femoral stem anteversion in THA.

Effects of coordinate-system construction methods on postoperative computed tomography evaluation of implant orientation after total hip arthroplasty

Objective: In total hip arthroplasty, it is important to assess postoperative implant orientation. The computed tomography-based (CT-based) three-dimensional (3D) templating method using 3D preoperative planning software is generally recommended. In this method, postoperative implant orientation within a bony coordinate system can be measured by overlaying a 3D computerized model of the implant on a real postoperative CT image of the implant. The bony coordinate system consists of several reference points (RPs) marked on a CT image of the bone surface. Therefore, preoperative and postoperative coordinate systems do not always match. We investigated how the difference between coordinate systems constructed from RPs chosen by manual methods (M1 and M2) and those constructed by the computer matching method influences the results of measurement validation.Methods: In M1, postoperative RPs were chosen without a specific tool in a single planning module. In M2, postoperative RPs were chosen with as little deviation as possible from preoperative RPs, verifying preoperative RPs on another monitor.Results: M1 and M2 produced mean errors in acetabular cup inclination of 0.7° ± 0.5° and 0.5° ± 0.3°, respectively, and mean errors in cup anteversion of 1.3° ± 1.2° and 0.5° ± 0.4°, respectively, which were statistically significant differences. M1 and M2 produced mean errors in femoral stem anteversion of 2.4° ± 2.0° and 2.7° ± 2.1°, respectively, not a significant difference, but these errors were larger than errors in cup orientation.Discussion: We recommend referring to preoperative RPs when choosing postoperative RPs. Surgeons must be aware that for evaluation of postoperative stem anteversion, manual methods may produce considerable error.

Value of computed tomography-based three-dimensional surgical preoperative planning software in total hip arthroplasty with developmental dysplasia of the hip

IntroductionPreoperative planning with computed tomography (CT)-based three-dimensional templatinghas been expanded to achieve more precise placement of hip components. However, few reports have addressed the utility of three-dimensional surgical planning software for secondary osteoarthritis cases. This study therefore investigated the value of CT-based three-dimensional templating software for preoperative planning in primary total hip arthroplasty (THA), with an emphasis on developmental dysplasia of the hip. Materials and methodsWe performed a retrospective review of 65 hips in 57 patients who underwent cementless primary THA. The preoperative diagnosis was secondary osteoarthritis in all cases due to developmental dysplasia of the hip. All preoperative planning and postoperative evaluations were completed using CT-based three-dimensional templating software. We analyzed the accuracy of stem size prediction and cup size prediction, the reproducibility of preoperative and postoperative stem anteversion, and the absolute error in preoperative and postoperative stem anteversion using CT-based three-dimensional templating software. ResultsThe sizes of 65 % of the femoral stems (42/65) were estimated exactly, and 98 % (63/65) were accuratelyestimated to within one stem size. The final acetabular cup sizes corresponded exactly to the preoperatively planned size in 92 % of all cases (62/65). 100 % of the cup size estimates were accurate to within one cup size. There was strong reproducibility of preoperative and postoperative stem anteversion (r = 0.88, P < 0.05). The absolute error in stem anteversion was 4.0° ± 3.6°. ConclusionsUsing CT-based three-dimensional templating software made it possible to achieve reproducible stem anteversion and choose accurate stem and cup sizes in patients with developmental dysplasia of the hip.

The importance of adequate stem anteversion for rotational stability in cemented total hip replacement

Progressive retroversion of a cemented stem is predictive of early loosening and failure. We assessed the relationship between direct post-operative stem anteversion, measured with CT, and the resulting rotational stability, measured with repeated radiostereometric analysis over ten years. The study comprised 60 cemented total hip replacements using one of two types of matt collared stem with a rounded cross-section. The patients were divided into three groups depending on their measured post-operative anteversion (< 10°, 10° to 25°, > 25°). There was a strong correlation between direct post-operative anteversion and later posterior rotation. At one year the < 10° group showed significantly more progressive retroversion together with distal migration, and this persisted to the ten-year follow-up. In the < 10° group four of ten stems (40%) had been revised at ten years, and an additional two stems (20%) were radiologically loose. In the 'normal' (10° to 25°) anteversion group there was one revised (3%) and one loose stem (3%) of a total of 30 stems, and in the > 25° group one stem (5%) was revised and another loose (5%) out of 20 stems. This poor outcome is partly dependent on the design of this prosthesis, but the results strongly suggest that the initial rotational position of cemented stems during surgery affects the subsequent progressive retroversion, subsidence and eventual loosening. The degree of retroversion may be sensitive to prosthetic design and stem size, but < 10° of anteversion appears deleterious to the long-term outcome for cemented hip prosthetic stems.