Femoral Stem Anteversion Research Articles

Impact of surgical approaches on stem position and hidden blood loss in total hip arthroplasty: minimally invasive vs. posterolateral

BackgroundThe surgical approach impacts the outcomes and recovery after total hip arthroplasty (THA), and approaches may affect the stem positioning. Contrary to the general concept of minimally invasive surgery, the direct anterior approach (DAA) results in more intraoperative blood loss. Therefore, the objective of this study was to compare stem positioning and hidden blood loss (HBL) among three surgical approaches: the minimally invasive DAA, Orthopadische Chirurgie Munchen (OCM), and the traditional posterolateral approach (PLA).MethodsA total of 201 patients undergoing their first non-cemented THA using the DAA, OCM, and PLA were included in the study. General demographic data, stem alignment, and blood loss were evaluated. Specific comparison measurements included femoral neck anteversion, femoral stem anteversion, alignment of the stem in coronal and sagittal planes, proximal and distal medullary ratios, and femoral offset. Blood loss was measured by calculating Intraoperative Blood Loss ( IBL), visible blood loss (VBL), and hidden blood loss (HBL).ResultsThere were no significant differences in age, gender, body mass index, preoperative diagnosis, or femoral Dorr classification among the three groups. The mean surgical time was longer for the DAA and OCM compared to the PLA (P < 0.01). IBL was highest in the DAA group and lowest in the PLA (P < 0.05). Postoperative stem anteversion were significantly different among the groups, with the DAA showing the greatest anteversion difference (P < 0.05). There was no difference in the stem coronal alignment. However, there were more valgus and varus implants in the sagittal plane for the DAA and OCM. The femoral offset reduction was less optimal in the DAA and OCM groups (P < 0.05). The proximal and distal medullary ratios were lower in the DAA and OCM (P < 0.05). HBL was significantly lower in the DAA and OCM compared to the PLA (P < 0.05).ConclusionMinimally invasive approaches such as DAA and OCM offer advantages in muscle and soft tissue preservation, leading to reduced HBL compared to the conventional PLA. However, these approaches present challenges in femoral stem positioning and longer surgical times.

Is AI 3D-printed PSI an accurate option for patients with developmental dysplasia of the hip undergoing THA?

BackgroundIn traditional surgical procedures, significant discrepancies are often observed between the pre-planned templated implant sizes and the actual sizes used, particularly in patients with congenital hip dysplasia. These discrepancies arise not only in preoperative planning but also in the precision of implant placement, especially concerning the acetabular component. Our study aims to enhance the accuracy of implant placement during Total Hip Arthroplasty (THA) by integrating AI-enhanced preoperative planning with Patient-Specific Instrumentation (PSI). We also seek to assess the accuracy and clinical outcomes of the AI-PSI (AIPSI) group in comparison to a manual control group.MethodsThis study included 60 patients diagnosed with congenital hip dysplasia, randomly assigned to either the AIPSI or manual group, with 30 patients in each. No significant demographic differences between were noted the two groups. A direct anterior surgical approach was employed. Postoperative assessments included X-rays and CT scans to measure parameters such as the acetabular cup anteversion angle, acetabular cup inclination angle, femoral stem anteversion angle, femoral offset, and leg length discrepancy. Functional scores were recorded at 3 days, 1 week, 4 weeks, and 12 weeks post-surgery. Data analysis was conducted using SPSS version 22.0, with the significance level was set at α = 0.05.Results and conclusionThe AIPSI group demonstrated greater prosthesis placement accuracy. With the aid of PSI, AI-planned THA surgery provides surgeons with enhanced precision in prosthesis positioning. This approach potentially offers greater insights and guidelines for managing more complex anatomical variations or cases.

Variety of femoral anteversion and its measurement in cementless total hip arthroplasty: Does robotic technology improve accuracy?

BackgroundHigh-performance total hip arthroplasty (THA) depends on the accurate position of components. However, femoral anteversion is variable, and current studies only used traditional instruments to evaluate it, such as protractor and spirit level with limited cases. This study aimed to identify the variability in the measured femoral native anteversion and intraoperative stem anteversion under different measurement methods, including intraoperative robotic method. We hypothesized that robotic technology was more accurate than traditional instruments for femoral anteversion evaluation.MethodsThis study included 117 hips of patients who underwent robotic-assisted THA between November 2019 and March 2021. Preoperative native femoral anteversion was measured using a robotic system. Intraoperative femoral stem anteversion was evaluated visually, and then measured with a goniometer and a robotic system, respectively. Variability in the measured femoral native anteversion and intraoperative femoral stem anteversion was calculated and compared. Intraclass correlation coefficient (ICC) and Pearson correlation analysis were used to assess the consistency and correlation of anteversion of different measurements and postoperative CT-measured stem anteversion, respectively.ResultsThe result of measurement for preoperative native femoral anteversion was more variable than the intraoperative robotic-measured stem anteversion. Intraoperative robotic-measured stem version showed the highest correlation with postoperative CT measurement of stem version (r = 0.806, P < 0.001), while intraoperative surgeon estimation had the lowest correlation coefficient (r = 0.281, P = 0.025). As for the consistency with postoperative CT measurement of femoral stem anteversion, the intraoperative robotic-measured femoral stem version also had the highest value (ICC = 0.892, P < 0.001).ConclusionNative femoral anteversion was variable preoperatively. Using cementless stems, anteversion was also highly variable. Robotic assessment for stem anteversion during surgery was more consistent with the final position than the preoperative assessment and conventional intraoperative estimation.

Analysis of factors associated with the influence of femoral stem anteversion after total hip arthroplasty

To explore the related factors of femoral stem anteversion (FSA) after total hip arthroplasty (THA), so as to provide reference for clinical design of FSA before operation and reduce the risk of hip dislocation after arthroplasty. Ninty-three patients (103 hips) who underwent THA between October 2021 and September 2022 and met the selection criteria were selected as the study subjects. Among them, there were 48 males and 45 females with an average age of 58.5 years (range, 25-88 years). Body mass index was 18.00-37.84 kg/m 2, with an average of 24.92 kg/m 2. There were 51 cases (57 hips) of osteonecrosis of femoral head, 35 cases (39 hips) of hip osteoarthritis, and 7 cases (7 hips) of congenital hip dysplasia. Based on CT images, the following indicators were measured: preoperative femoral neck anteversion (FNA), preoperative femoral rotation angle (FRA), preoperative acetabular anteversion (AA), and preoperative combined anteversion (CA; the sum of preoperative FNA and AA); postoperative FSA and the change in femoral anteversion angle (the difference between postoperative FSA and preoperative FNA). Based on preoperative X-ray films, the following indicators were measured: femoral cortical thickness index (CTI) and canal flare index (CFI), the proximal femoral medullary cavity was classified according to Noble classification (champagne cup type, normal type, chimney type), neck-shaft angle (NSA), and femoral offset (FO). Pearson correlation analysis, one-way ANOVA, and Point-biserial correlation analysis were used to investigate the correlation between postoperative FSA, postoperative change in femoral anteversion angle, and patient diagnosis, proximal femoral medullary cavity anatomy type, gender, age, as well as preoperative FNA, FRA, AA, CA, NSA, FO, CTI, and CFI. FSA was used as the dependent variable and the independent variables that may be related to it were included for multiple linear regression analysis. Based on CT image measurement, preoperative FNA was (15.96±10.01)°, FRA (3.36±10.87)°, AA (12.94±8.83)°, CA (28.9±12.6)°, postoperative FSA (16.18±11.01)°, and postoperative change in femoral anteversion angle was (0.22±9.98)°. Based on preoperative X-ray films measurements, the CTI was 0.586±0.081; the CFI was 4.135±1.125, with 23 hips classified as champagne cup type, 68 hips as normal type, and 12 hips as chimney type in the proximal femoral medullary cavity anatomy; NSA was (132.87±7.83)°; FO was (40.53±10.11) mm. There was no significant difference between preoperative FNA and postoperative FSA ( t=-0.227, P=0.821). Pearson correlation analysis showed that postoperative FSA was positively correlated with preoperative FNA, preoperative CA, postoperative change in femoral anteversion angle, and age ( P<0.05), while negatively correlated with preoperative FRA ( P<0.05). The postoperative change in femoral anteversion angle were positively correlated with preoperative FRA and postoperative FSA ( P<0.05), and negatively correlated with preoperative CA and FNA ( P<0.05). One-way ANOVA analysis showed that the above two indicators were not correlated with diagnosis and the proximal femoral medullary cavity anatomy type ( P>0.05). Multiple linear regression analysis showed a linear correlation between FSA and FNA, CA, age, and FRA ( F=10.998, P<0.001), and the best fit model was FSA=0.48×FNA-2.551. The factors related to FSA after THA include patient's age, preoperative FNA, CA, FRA and postoperative femoral anteversion, of which preoperative FNA is the most closely related. When designing a surgical plan before surgery, attention should be paid to the patient's preoperative FNA, and if necessary, CT around the hip joint should be scanned to gain a detailed understanding of the proximal femoral anatomical structure.

Does Individualization of Cup Position Affect Prosthetic or Bone Impingement Following Total Hip Arthroplasty?

BackgroundSpinopelvic (SP) mobility patterns during postural changes affect three-dimensional acetabular component position, the incidence of prosthetic impingement, and total hip arthroplasty (THA) instability. Surgeons have commonly placed the acetabular component in a similar “safe zone” for most patients. Our purpose was to determine the incidence of bone and prosthetic impingement with various cup orientations and determine if a preoperative SP analysis with individualized cup orientation lessens impingement. MethodsA preoperative SP evaluation of 78 THA subjects was performed. Data were analyzed using a software program to determine the prevalence of prosthetic and bone impingement with a patient individualized cup orientation versus 6 commonly selected cup orientations. Impingement was correlated with known SP risk factors for dislocation. ResultsProsthetic impingement was least with the individualized choice of cup position (9%) versus preselected cup positions (18%-61%). The presence of bone impingement (33%) was similar in all groups and not affected by cup position. Factors associated with impingement in flexion were age, lumbar flexion, pelvic tilt (stand to flexed seated), and functional femoral stem anteversion. Risk factors in extension included standing pelvic tilt, standing SP tilt, lumbar flexion, pelvic rotation (supine to stand and stand to flexed seated), and functional femoral stem anteversion. ConclusionProsthetic impingement is reduced with individualized cup positioning based on SP mobility patterns. Bone impingement occurred in one-third of patients and is a noteworthy consideration in preoperative THA planning. Known SP risk factors for THA instability correlated with the presence of prosthetic impingement in both flexion and extension.

Reliability and validity of the functional combined anteversion measurement method using standing lateral radiography after total hip arthroplasty.

The functional safe zone of combined anteversion (CA) shows a superior predictive value for dislocation after total hip arthroplasty (THA) compared to that of the Lewinnek safe zone. Thus, it is necessary to establish a feasible and accurate method for assessing CA for the evaluation of dislocation risk. We aimed to evaluate the reliability and validity of using standing lateral (SL) radiographs for determining CA. Sixty-seven patients who underwent SL radiography and computed tomography (CT) scans after THA were included. Radiographic CA values were obtained via the calculation of the sum of the acetabular cup and femoral stem anteversion (FSA) measurements as obtained from the SL radiographs. Acetabular cup anteversion (AA) was measured based on the tangential line to the face of the cup, whereas FSA was calculated using the developed formula based on the neck-shaft angle. The intra-observer and inter-observer reliabilities for each measurement were examined. Radiological CA values were compared with the CT scan measurements to evaluate their validity. The intra-observer and inter-observer agreements of the SL radiography were excellent [intraclass correlation coefficient (ICC) ≥0.90]. The radiographic measurements correlated well with the CT scan measurements (r=0.869, P<0.001). The mean difference between the radiographic and CT scan measurements was -0.55°±4.68° and ranged from 0.3° to 2.2° in terms of the 95% confidence interval (CI). SL radiography is a reliable and valid imaging tool for the assessment of functional CA.

Achieving Target Cemented Femoral Stem Anteversion Using a 3-Dimensional Model

BackgroundTotal hip arthroplasty aims to provide patients with a pain-free and stable hip joint through optimization of biomechanics such as femoral anteversion. There are studies evaluating the limits of cementless stem version, however, none assessing the range of version achieved by a cemented collarless stem. A computed tomography (CT)–based study was performed, utilizing a contemporary robotic planning platform to assess the amount of rotation afforded by a cemented collarless stem, whilst maintaining native biomechanics. MethodsThe study utilized 36 cadaveric hips. All had CT scans of the pelvis and hip joints. The CT scans were then loaded into a contemporary robotic planning platform. A stem that restored the patients native femoral offset was selected and positioned in the virtual femur. The stem was rotated while checking for cortical contact at the level of the neck cut. Cortical contact was regarded as the rotation limit, assessed in both anteversion and retroversion. Target range for stem anteversion was 10°-20°. Failure to achieve target version triggered a sequence of adjustments to simulate surgical decisions. ResultsNative femoral offset and target version range was obtained in 29 of 36 (80.5%) cases. Following an adjustment sequence, 4 further stems achieved target anteversion with a compromise in offset of 2.3 mm. Overall 33 of 36 (91.7%) stems achieved the target anteversion range of 10°-20°. ConclusionsTarget femoral stem anteversion can be achieved using a cemented, collarless stem in a CT-based 3-dimensional model in 80.5% of hips. With a small compromise in offset (mean 2.3 mm), this can be increased to 91.7%.

A Simple Device to Determine Ante-Version During Femoral Prosthesis Insertion in Total Hip Replacement

Introduction: Good outcomes in Total Hip Replacement (THR) depend upon correct component alignment. This is influenced by the surgeon’s capacity to recreate a geometrically normal and biomechanically stable hip joint. Mal-positioining of components can lead to various complications and the surgeons have to make vital decisions intra-operatively based on their experience. Materials and Methods: This study describes a simple instrument to aid alignment of femoral stem insertion and hence achieve the normal range of ante-version between 10 º-20 º. Experiments performed on a saw bone model by twenty orthopaedic surgeons, each making six attempts to insert a prosthesis demonstrated improved positioning when compared to unaided insertion. Results: The mean average femoral stem ante-version unaided was 18.3 º (range, 4.9 º to 36.6 º). Device aided ante-version was 14.4 º (range, 9.8 º to 18.9 º) (p&lt;0.001). We also report the practicality of the use of the device which was assessed by use on cadavers. Conclusion: Precise assessment of stem ante-version can be achieved in non-navigated THR if such a device is available intra-operatively.

The impact of increasing femoral offset and stem anteversion on postoperative dislocation in bipolar hemiarthroplasty.

Femoral offset and anteversion have been reported to affect the incidence of dislocation following bipolar hemiarthroplasty, although the magnitudes of contributions of the femoral offset and stem anteversion on dislocation, both singly and in combination is not fully understood. Using the CT data of 61 patients (61 hips), including 30 male and 31 female who underwent bipolar hemiarthroplasty, three-dimensional dynamic motion analysis was performed using a modular implant that enabled adjustment of femoral offset and stem anteversion independently. The pattern of impingement and relationship between femoral offset/stem anteversion and range of motion were evaluated using the software. We found that a higher femoral offset and stem anteversion correlate with a greater range of motion of flexion and internal rotation. Furthermore, an increased femoral offset has a great effect on increasing range of motion of flexion than stem anteversion, and increased both femoral offset and stem anteversion have fewer effect on the flexion, whereas increasing stem anteversion has a great impact on internal rotation than offset, especially in the case with lower femoral anteversion. However, a higher stem anteversion decrease the range of motion of external rotation, whereas a higher femoral offset leads to an increased range of motion of external rotation. We demonstrated that both a higher femoral offset and stem anteversion substantially affected the range of motion in flexion, internal rotation and external rotation. However, these are not independent, but rather mutually confounding, the surgeons should consider retaining femoral/anterior offset in bipolar hemiarthroplasty.

Distribution and outliers of anteversion of short-length cementless stem.

Inadequate stem version might lead to impingement and instability after cementless total hip arthroplasty (THA). We evaluated (1) the distribution of short-stem anteversion, (2) the proportion of stems with an anteversion less than 5° or larger than 25°, (3) combined cup and stem anteversion, and (4) dislocation rate. We evaluated the native femoral anteversion and stem anteversion in 340 patients (340 THAs): 144 men and 196 women. Their mean age was 56.2 (22-87) years and mean body mass index was 25.1 (15.2-40.7) kg/m2. The femoral neck anteversion was measured on pre-operative CT scan and the stem anteversion was obtained during the operation. The safe zone of the stem anteversion was defined as 5 to 25°. The femoral neck anteversion ranged from -15 to 61° (mean, 15.0°; SD, ±10.6°). The stem anteversion ranged -7 to 50° (mean, 15.7°; SD, ±9.5°). It was optimal (5-25°) in 71.2% (242/340), insufficient (<5°) in 13.3% (45/340), and excessive (>25°) in 15.6% (53/340). The stem anteversion had a medium correlation with the femoral neck anteversion (correlation coefficient = 0.449). The combined anteversion was 42.0° (range, 35.2-52.3°; SD, ±2.8°). During two to fouryear follow-up, no hip dislocated. Short-length stem had a great variability in the anteversion and considerable portion (28.9%, 98/340) of stems had an anteversion outside the safe zone. Surgeons should be aware of this variability of stem anteversion to compensate for abnormal stem anteversion, which might lead to impingement and instability after THA.

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.

3D Printed Guides and Preoperative Planning for Uncemented Stem Anteversion Reconstruction during Hip Arthroplasty: A Pilot Study.

Objective To investigate if 3D printed guides and preoperative planning can accurately control femoral stem anteversion. Methods A prospective comparative study was carried out from 2018 to 2020, including 53 patients who underwent hip arthroplasty for femoral neck fracture. The target rotation center of the femoral head is determined by three-dimensional planning. In group A, planning was made by 2D templates. In group B, preoperative 3D planning and 3D printed osteotomy/positioning guides were performed. After the operation, 3D model registration was performed to calculate the accuracy of anteversion restoration. Results We screened 60 patients and randomized a total of 53 to 2 parallel study arms: 30 patients to the group A (traditional operation) and 23 patients to the group B (3D preoperative planning and 3D printed guide). There were no significant differences in demographic or perioperative data between study groups. The restoration accuracy of group A was 5.42° ± 3.65° and of group B was 2.32° ± 1.89°. The number and rate of abnormal cases was 15 (50%) and 2 (8.7%), respectively. Significant statistical differences were found in angle change, restoration accuracy, and number of abnormal cases. Conclusion Three-dimensional preoperative planning and 3D printed guides can improve the accuracy of the restoration of femoral anteversion during hip arthroplasty.

Is Combined Anteversion Equally Affected by Acetabular Cup and Femoral Stem Anteversion?

BackgroundTo create a safe zone, an understanding of the combined femoral and acetabular mating during hip motion is required. We investigated the position of the femoral head inside the acetabular liner during simulated hip motion. We hypothesized that cup and stem anteversions do not equally affect hip motion and combined hip anteversion. MethodsHip implant motion was simulated in standing, sitting, sit-to-stand, bending forward, squatting, and pivoting positions using the MATLAB software. A line passing through the center of the stem neck and the center of the prosthetic head exits at the polar axis (PA) of the prosthetic head. When the prosthetic head and liner are parallel, the PA faces the center of the liner (PA position = 0, 0). By simulating hip motion in 1-degree increments, the maximum distance of the PA from the liner center and the direction of its movement were measured (polar coordination system). ResultsThe effect of modifying cup and stem anteversion on the direction and distance of the PA’s change inside the acetabular liner was different. Stem anteversion influenced the PA position inside the liner more than cup anteversion during sitting, sit-to-stand, squatting, and bending forward (P = .0001). This effect was evident even when comparing stems with different neck angles (P = .0001). ConclusionCup anteversion, stem anteversion, and stem neck-shaft angle affected the PA position inside the liner and combined anteversion in different ways. Thus, focusing on cup orientation alone when assessing hip motion during different daily activities is inadequate.

Accuracy of intraoperative estimation of femoral stem anteversion in cementless total hip arthroplasty by using a digital protractor and a spirit level

BackgroundThe femoral component anteversion during surgery is traditionally assessed by a visual assessment of the surgeon and has proven to be imprecise. We sought to determine the accuracy of a digital protractor and a spirit level to measure the stem anteversion during cementless THA.MethodsA prospective study was conducted among 107 patients (114 hips) who underwent primary cementless THA via posterolateral approach. A pipe with a spirit level was attached to the tibial tubercle and intermalleolar midpoint. While the leg was held perpendicularly to the floor, stem anteversion was estimated by 3 methods: method A by visual assessment; method B by a digital protractor alone; and method C by a digital protractor combined with a spirit level. The angles were compared with the true anteversion measured by postoperative CT scan.ResultsThe average anteversion by method C (22.8° ± 6.9°, range -2° to 40°) was significantly lower than method A (24.6° ± 5.2°, range 0° to 30°) (p=0.033), but not different from the true anteversion (22.1° ± 8.2°, range -5.4° to 43.1°) (p=0.445). There were no significant differences between method B (23.2° ± 8.2°, range -4° to 45°) and method A, C or the true anteversion. The mean deviation of the intraoperative estimation from the true anteversion was 0.8° ± 3.7° (range -7.1° to 8.0°) by method C; 1.2° ± 5.1° (range -8.8° to 14.3°) by method B; and 2.5° ± 7.4° (range -19.0° to 16.0°) by method A. Estimation error within 5° was found in 107 hips (93.9%) with method C; 86 hips (75.4%) with method B; and 59 hips (51.8%) with method A.ConclusionAccurate estimation of stem anteversion during cementless THA can be determined intraoperatively by the use of a digital protractor and a spirit level.Trial registrationThai Clinical Trials Registry (TCTR 20180326003). Registered on 20 March 2018. Retrospectively registered.

Impact of Cementless Zweymüller Stem Anteversion on Resistance to Periprosthetic Fracture in Total Hip Arthroplasty

SUMMARYTotal hip arthroplasty implies proper orientation of both acetabular and femoral components with a range of 25-40° of combined anteversion. The aim of the study was to examine resistance to periprosthetic fracture of the axially loaded cross section rectangular femoral stem (Zweymüller) with respect to different degrees of anteversion, implanted in the artificial bone model, in laboratory conditions. Femoral bone models with implanted femoral stems were divided into 3 groups depending on the degree of stem anteversion (A, control group 13-17°; B, stem retroverted 0°-4°; and C, stem anteverted 26-30°). The amount of axial load leading to periprosthetic fracture (PPFx) of the artificial bone model was determined experimentally for each construct. The results showed that the load at which the PPFx occurred significantly increased with the increase of the endoprosthesis anteversion angle. In our clinical practice, we are often unable to place the acetabular component in an ideal grade of anteversion for intraoperatively determined reasons. The results of this experimental study suggested that increasing rectangular femoral (Zweymüller) stem anteversion lowered the risk of PPFx. This study was limited by experimental design (laboratory conditions, artificial bone) and should be clinically verified.

Comparison of 5-year postoperative results between standard-length stems and short stems in one-stage bilateral total hip arthroplasty: a randomized controlled trial.

Short stems have recently become popular in total hip arthroplasty. Previous studies aimed at elucidating the efficacy of short stems did not eliminate the influence of other factors aside from stem length. This study aimed to evaluate the usefulness of short stems compared with that of standard-length stems that have the same proximal morphology, surface coating, and material. This was a prospective randomized study comparing 5-year midterm outcomes in 29 patients who underwent one-stage bilateral total hip arthroplasty with short and standard-length stems inserted in each of the two femurs. Clinical, radiographical, and dual-energy X-ray absorptiometry outcomes were compared. No significant differences were found in perioperative and radiographic characteristics (femoral neck anteversion, flare index, operation sequence, operation side, operation time, stem anteversion, and stem alignment). The number of joints with complications, appearance of radiopaque lines around the stems, or bone mineral density changed in stem regions 5 years postoperatively. However, greater micromotion of the stem was seen on the side of the short stem. Satisfactory improvement in hip function was seen on both sides. Based on the 5-year midterm outcomes, both stems obtained satisfactory clinical outcomes despite the greater micromotion with short stems. Both stems attained bone ingrowth fixation. Moreover, the stems were not significantly different in terms of stress shielding; however, further long-term studies (> 5 years) are required to validate our findings related to stress shielding.

Combined Anteversion Technique for the Modified Hardinge Approach in Cementless Total Hip Arthroplasty

Objective: To define the combined anteversion (CA) angle in the modified Hardinge approach, which created an impingement-free range of motion (ROM) and prevented dislocation. Materials and Methods: The femoral stem was prepared first, the anteversion of the femoral stem was determined and recorded. The target angle for acetabular cup abduction was 40 degrees in all cases. Cup anteversion angle was targeted individually close to but not exceed the native acetabular anteversion angle in each case. The hip joint was tested for impingement-free ROM and stability intraoperatively. Results: There were 120 cases with a mean age of 58.7 years (29 to 91, 14.1) and the mean follow-up of 21.8 months (18 to 37). The mean native acetabular anteversion angle was 11.9 degrees (3 to 28 degrees, 5.1). The mean femoral stem anteversion angle was 13.7 degrees (2 to 35 degrees, 7.7) and the mean acetabular cup anteversion angle was 10.2 degrees (−4 to 21 degrees, 3.6). The mean CA angle was 24.2 degrees (9 to 48 degrees, 7.9). The CA angle was within 10 to 40 degrees for 114 of 120 cases (95%). The acetabular cup anteversion angle was within the Lewinnek safe zone for 113 of 120 cases (94.2%). The mean femoral anteversion angle for male and female individuals was 12.16 degrees (2 to 30 degrees, 6.75) and 14.62 degrees (2 to 35 degrees, 8.17) respectively, there was no significant difference (P=0.094). The mean CA angle for male and female individuals was 23.21 degrees (15 to 42 degrees, 6.37) and 24.72 degrees (9 to 48 degrees, 8.6), respectively, which was not significantly different (P=0.310). There was no dislocation. Conclusions: The mean CA angle in the modified Hardinge approach was 24.2 degrees and the effective CA angle for impingement-free ROM and preventing dislocation was between 10 and 40 degrees.

The difference of femoral stem anteversion required for preventing postoperative dislocation in bipolar hip arthroplasty: conventional approach vs. CPP approach

The difference of femoral stem anteversion required for preventing postoperative dislocation in bipolar hip arthroplasty: conventional approach vs. CPP approach

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.

New combined anteversion technique in hybrid THA: cup-first procedure with CT-based navigation

Combined anteversion (CA) technique (stem-first procedure) is generally accepted as the optimal technique to attain an appropriate CA value in total hip arthroplasty (THA). However, cup anteversion is strongly influenced by the native femoral anteversion. Accordingly, anterior protrusion of the cup in the acetabulum might occur. The purpose of the present study is to investigate the achievement of the optimal CA while avoiding anterior cup protrusion and examine the significance of our new CA technique with cup-first procedure in hybrid THA. Seventy-nine hybrid THAs with the cup-first procedure used a CT-based navigation system for cup positioning. In the preoperative planning, cup anteversion was aimed at approximately 20°. However, in actuality, sufficient cup coveragein the original acetabulum based onindividual anatomy is given priority over cup placement based on CT-based planning to ensure adequate cup coverage. The target stem anteversion was determined following Widmer's mathematical formula (37.3 = femoral stem anteversion × 0.7 + cup anteversion). Cemented stem was inserted according to the target stem anteversion angle. Regarding the assessment of overall alignment, the calculated Widmer's CA values during surgery and postoperative CT evaluation were 34.1° ± 6.0° (range 20.7°-51.2°) and 35.1° ± 6.7° (range 21.6°-50.7°). There were 72 hips (91.1%) within 25°-50° of CA. Cup protrusion length averaged 2.0mm ± 2.6mm (0-8.8mm) in the axial view and 0.4mm ± 1.0mm (0-3.6mm) in the sagittal view. Cup protrusion length of more than 5mm was indicated in 10 hips, and no hips observed more than 10mm. Our new CA technique (cup-first procedure) with hybrid THA was able to achieve optimal CA value while avoiding anterior cup protrusion.