Acetabular cup positioning in revision total hip arthroplasty with Paprosky type III acetabular defects: Martell radiographic analysis

Purpose

This study evaluates acetabular cup position in the setting of revision total hip arthroplasty (THA) with severe acetabular bone defects.

Methods

With a definition of safe zone of abduction (30–50°) and anteversion (5–25°), acetabular cup position was measured by a digital image analysis program for 34 patients with Paprosky type III acetabular bone defects.

Results

There were 24 cups (71 %) for abduction and 26 cups (76 %) for anteversion located in the safe zone. Nineteen cups (56 %) were within the safe zone for both abduction and anteversion. There was no dislocation, however one cup out of the safe zone resulted in early cup failure due to aseptic loosening.

Conclusions

The acetabular cup positioning in patients with Paprosky type III defects was 'optimal' in half of the cases. The prevalence of optimal acetabular cup position was similar to those reported in primary THA, suggesting that the presence of a large acetabular bone defect may not be a significant risk factor for suboptimal acetabular cup positioning in the setting of revision THA.     

Effect of screw fixation on acetabular component alignment change in total hip arthroplasty

Purpose

The use of screws can enhance immediate cup fixation, but the influence of screw insertion on cup position has not previously been measured. The purpose of this study was to quantitatively evaluate the effect of intra-operative screw fixation on acetabular component alignment that has been inserted with the use of a navigation system.

Methods

We used a navigation system to measure cup alignment at the time of press-fit and after screw fixation in 144 hips undergoing total hip arthroplasty. We also compared those findings with factors measured from postoperative radiographs.

Results

The mean intra-operative change of cup position was 1.78° for inclination and 1.81° for anteversion. The intra-operative change of anteversion correlated with the number of screws. The intra-operative change of inclination also correlated with medial hip centre.

Conclusion

The insertion of screws can induce changes in cup alignment, especially when multiple screws are used or if a more medial hip centre is required for rigid acetabular fixation.     

Use of an ultrasound-based navigation system for an accurate acetabular positioning in total hip arthroplasty: a prospective, randomized, controlled study

The purpose of this study was to compare an ultrasound-based navigation system with an imageless navigation system with surface registration in the postoperative acetabular cup position. A prospective randomized controlled study of 2 groups of 40 patients each was performed. In the first group, cup positioning was assisted by an ultrasound-based navigation system, and in the second group, the cup was assisted by imageless navigation system with surface registration. There was significantly more outliers in the imageless navigation group. In addition, there was statistical significance in the anteversion angles and in the anteversion error between the imageless navigation and ultrasound-based navigation groups. Ultrasound-based navigation improves cup positioning in total hip arthroplasty better than an imageless navigation system by reducing the outliers, achieving a higher accuracy of anteversion.     

Image-free cup navigation inaccuracy: a two-study approach.

The present study tested the accuracy of an image-free navigation system used for total hip arthroplasty (THA). Two parallel, prospective studies were performed: one on real patients and the other on pelvic phantoms. We used a comparison between the intra-operative cup orientation, as displayed by the navigation system, and the post-operative cup position, as measured on CT data. The mean intrinsic overall error (+/- standard deviation) found in the phantom study was 2.6 +/- 1.1 degrees (range: 1.5-4.4 degrees ) for cup abduction, and 0.9 +/- 0.7 degrees (range: 0-2.5 degrees ) for cup anteversion. The system was less accurate in the clinical operative setting. The evaluation model was able to identify, and more importantly quantify, the clinically induced error. Ameliorating this would improve the clinical accuracy of the system.     

Poor accuracy of freehand cup positioning during total hip arthroplasty

Several studies have demonstrated a correlation between the acetabular cup position and the risk of dislocation, wear and range of motion after total hip arthroplasty. The present study was designed to evaluate the accuracy of the surgeon’s estimated position of the cup after freehand placement in total hip replacement. Peroperative estimated abduction and anteversion of 200 acetabular components (placed by three orthopaedic surgeons and nine residents) were compared with measured outcomes (according to Pradhan) on postoperative radiographs. Cups were placed in 49.7° (SD 6.7) of abduction and 16.0° (SD 8.1) of anteversion. Estimation of placement was 46.3° (SD 4.3) of abduction and 14.6° (SD 5.9) of anteversion. Of more interest is the fact that for the orthopaedic surgeons the mean inaccuracy of estimation was 4.1° (SD 3.9) for abduction and 5.2° (SD 4.5) for anteversion and for their residents this was respectively, 6.3° (SD 4.6) and 5.7° (SD 5.0). Significant differences were found between orthopaedic surgeons and residents for inaccuracy of estimation for abduction, not for anteversion. Body mass index, sex, (un)cemented fixation and surgical approach (anterolateral or posterolateral) were not significant factors. Based upon the inaccuracy of estimation, the group’s chance on future cup placement within Lewinnek’s safe zone (5–25° anteversion and 30–50° abduction) is 82.7 and 85.2% for anteversion and abduction separately. When both parameters are combined, the chance of accurate placement is only 70.5%. The chance of placement of the acetabular component within 5° of an intended position, for both abduction and anteversion is 21.5% this percentage decreases to just 2.9% when the tolerated error is 1°. There is a tendency to underestimate both abduction and anteversion. Orthopaedic surgeons are superior to their residents in estimating abduction of the acetabular component. The results of this study indicate that freehand placement of the acetabular component is not a reliable method. No benefits or funds were received in support of this study.     

Portable Accelerometer-Based Navigation System for Cup Placement of Total Hip Arthroplasty: A Prospective,Randomized, Controlled Study

BackgroundMalposition of the acetabular component during total hip arthroplasty (THA) is associated with increased risk of dislocation, reduced range of motion, and accelerated wear. The purpose of this study is to compare cup positioning with a portable, accelerometer-based hip navigation system and conventional surgical technique.MethodsIn a prospective, randomized, clinical study, cups were implanted with a portable, accelerometer-based hip navigation system (navigation group; n = 55) or conventional technique (conventional group; n = 55). THA was conducted in the lateral position and through posterior approach. The cup position was determined postoperatively on pelvic radiograph and computed tomography scans.ResultsAn average cup abduction of 39.2° ± 4.6° (range, 27° to 50°) and an average cup anteversion of 14.6° ± 6.1° (range, 1° to 27.5°) were found in the navigation group, and an average cup abduction of 42.9° ± 8.0° (range, 23° to 73°) and an average cup anteversion of 11.6° ± 7.7° (range, −12.1° to 25°) in the conventional group. A smaller variation in the navigation group was indicated for cup abduction (P = .001). The deviations from the target cup position were significantly lower in the navigation group (P = .001, .016). While only 37 of 55 cups in the conventional group were inside the Lewinnek safe zone, 51 of 55 cups in the navigation group were placed inside this safe zone (P = .006). The navigation procedure took a mean of 10 minutes longer than the conventional technique.ConclusionUse of the portable, accelerometer-based hip navigation system can improve cup positioning in THA.     

Evaluation of component positioning in primary total hip arthroplasty using an imageless navigation device compared with traditional methods

Acetabular orientation affects the success of total hip arthroplasty. Computer-assisted navigation systems may reduce positional errors. Total hip arthroplasty results were analyzed using an imageless navigation system. We hypothesized that reliability and accuracy would improve. One hundred forty-nine total hip arthroplasties were performed using minimally invasive surgical techniques in 3 cohorts: manual (n = 53), initial navigation cases (n = 49), navigation second series (n = 47). Manual patients' cup orientation variation from desired range was -19 degrees to +18 degrees anteversion (SD, 9.1 degrees ), -11 degrees to +25 degrees abduction (SD, 6.7 degrees ). Navigation variation from desired was -18 degrees to +15 degrees (SD, 7.3 degrees ) in group 1 and -15 degrees to +9 degrees (SD, 5.9 degrees ) in group 2 in anteversion and -15 degrees to +13 degrees (SD, 6.1 degrees ) in group 1 and -15 degrees to +11 degrees (SD, 4.7 degrees ) in group 2 in abduction. Results were statistically significant. There were significant differences for operating room time and estimated blood loss, but not incision size or body mass index. Navigation provided controlled, reproducible acetabular alignment; but a learning curve existed in terms of accuracy, estimated blood loss, and operating room time.     

计算机导航系统辅助下全髋关节表面置换的初步经验

目的 初步评估计算机辅助下行全髋关节表面置换的手术方法及假体植入的精确性.方法 对40例患者分成导航组(20例)和对照组(20例),分别采用计算机导航系统辅助和标准常规技术完成全髋关节表面置换术.比较两组手术时间、术中失血量、Harris髋关节评分(HHS),以及髋臼杯外展角和前倾角的偏移度及股骨假体柄干角和前倾角的偏移度.结果 手术时间导航组较对照组长38.7min(P＜0.05),术中平均出血量导航组较对照组多109.4 ml(P＜0.05).随访平均14.5个月,HHS评分两组比较差异无统计学意义(P＞0.05).对照组髋臼杯外展角偏移度(7.3°±4.3°)大于导航组(1.9°±1.3°)(P＜0.05),对照组髋臼杯前倾角偏移度(3.9°±2.3°)大于导航组(2.4°±1.5°)(P＜0.05).导航组股骨假体柄干角偏移度(1.5°±1.0°)小于对照组(11.3°±1.3°)(P＜0.05),导航组股骨假体前倾角偏移度(1.8°±2.3°)小于对照组(6.5°±5.3°)(P＜0.05).结论 计算机导航系统辅助下行全髋关节表面置换术可以提高假体植入的精确性,避免股骨颈皮质骨切迹,降低股骨颈骨折的风险.     

Understanding acetabular cup orientation: the importance of convention and defining the safe zone

Understanding acetabular cup orientation is important in all aspects of total hip arthroplasty including preoperative planning, intraoperative positioning, and postoperative analysis. New concepts in ideal cup orientation such as 'combined anteversion' have emerged. Using computer navigation and three-dimensional imaging, the potential for accuracy and precision of implantation have improved. Nevertheless, the varying manner in which the terms "anteversion" and "abduction" are often used in the literature is indicative of a nebulous understanding of the complex spatial anatomy of acetabular cup orientation.     

Comparison of conventional versus computer-navigated acetabular component insertion

This retrospective study compared the efficacy of computer navigation and conventional freehand techniques to place acetabular component orientation in the target position of acetabular cup inclination of 45 degrees and anteversion of 20 degrees . We selected 69 patients who had undergone total hip arthroplasty with freehand cup insertion who had computed tomography (CT) to plan for acetabular cup placement of the contralateral side. This group was compared with 98 patients who underwent CT-based cup insertion, and all had postoperative CT. After CT-based cup placement, average cup position was 43 degrees inclination (95% confidence interval [CI], 0.97; range, 30 degrees -58 degrees ) and 22.2 degrees anteversion (95% CI, 1.72; range, 5 degrees -38 degrees ). For freehand, average cup position was 45.7 degrees inclination (95% CI, 2.63 degrees ; range, 26 degrees -64 degrees ) and 28.5 degrees anteversion (95% CI, 3.80 degrees ; range, 9 degrees -53 degrees ). F ratio was 5.56 for inclination and 3.67 for anteversion (P < .0001). This study demonstrated substantial statistical improvement in accuracy of cup placement using CT-based navigation compared with freehand methods.     

The area method for measuring acetabular cup anteversion: An accurate and autonomous solution

Several radiological methods of measuring anteversion of the acetabular component after total hip arthroplasty have been described, all time-consuming and with varying reproducibility. This study aimed to compare the recently proposed Area method to true cup anteversion as determined by an accelerometer. This study further applied this method programmatically to autonomously determine radiographic cup orientation using two computer programs, then compared these results to hand and accelerometer measurements. 160 anteroposterior pelvis radiographs were taken of a standard Sawbones® pelvis fitted with a total hip arthroplasty system. The acetabular cup was re-oriented between each radiograph, with anteversion ranging from 0° to 90°. An accelerometer was mounted to the cup to measure true cup anteversion. Radiographic anteversion was independently measured via three methods: by hand, linear image processing, and machine learning. Measurements were compared to triaxial accelerometer recordings. Coefficient of determination (R2) was found to be 0.997, 0.991, and 0.989 for hand measurements, the machine learning, and linear image processing, respectively. The machine learning program and hand measurements overestimated anteversion by 0.70° and 0.02° respectively. The program using linear techniques underestimated anteversion by 5.02°. Average runtime was 0.03 and 0.59 s for the machine learning and linear image processing program, respectively. The machine learning program averaged within 1° of cup orientation given a true cup anteversion less than 51°, and within 2° given an anteversion less than 85°. The Area method showed great accuracy and reliability with hand measurements compared to true anteversion. The results of this study support the use of machine learning for accurate, timely, autonomous assessment of cup orientation.     

New method for measuring acetabular component positioning with EOS imaging: feasibility study on dry bone

Purpose

Malposition of the acetabular cup is the most common cause of total hip arthroplasty (THA) dislocation. The position of a total hip implant is usually analysed on computed tomography (CT) scan. We aim to prove it is possible to measure, with good accuracy, the position of an acetabular cup using the low-dose irradiation (EOS) imaging.

Material and methods

We implanted an acetabular cup in a pelvic dry bone and measured cup anteversion and inclination with scanography. We performed 14 series of EOS acquisitions with different inclination, rotation and pelvic tilt, which were analysed by five observers. Two observers repeated angle measurements. We then calculated measurement inter- and intrareproducibility and accuracy.

Results

Using a confidence interval (CI) of 95 %, inter- and intra-observer reproducibility were ±1.6, and ±1.4°, respectively, for cup inclination; accuracy in comparison with CT was ±2.6°. Using a 95 % CI, inter- and intra-observer reproducibility for cup anteversion were ±2.5° and ±2.3°, respectively. Measurement accuracy compared with CT was ±3.9°.

Conclusion

EOS imaging system is superior to standard radiography in terms of measuring acetabular anteversion and inclination.     

髋臼假体定位准确性的研究进展

为了防止全髋关节置换(total hip arthroplasty,THA)术后的脱位和降低假体磨损率,THA术中进行髋臼假体的定位非常重要。但由于受到多种潜在因素的影响,在手术中髋臼假体的准确植入目前仍具有一定的挑战性。Lewinnek安全区定位臼杯前倾(15±10)°,外展(40±10)°,一直被当作髋臼假体安装的标准范围,以图降低不稳定的风险。基于Lewinnek安全区,Ha提出的利用髋臼解剖标志。依据患者特异性的形态定位髋臼假体位置的方法利用患者特异性的形态确定其特异性的目标区域,从而减少髋关节置换术后的撞击,保持较低的内衬磨损率。计算机辅助导航系统可以提高髋臼杯的定位,但受到费用高,操作困难等诸多因素的影响。     

Computer-assisted cup placement techniques in total hip arthroplasty improve accuracy of placement

Malposition of the acetabular component during hip arthroplasty increases the occurrence of impingement, reduces range of motion, and increases the risk of dislocation and long-term wear. To prevent malpositioned hip implants, an increasing number of computer-assisted orthopaedic systems have been described, but their accuracy is not well established. The purpose of this study was to determine the reproducibility and accuracy of conventional versus computer-assisted techniques for positioning the acetabular component in total hip arthroplasty. Using a lateral approach, 150 cups were placed by 10 surgeons in 10 identical plastic pelvis models (freehand, with a mechanical guide, using computer assistance). Conditions for cup implantations were made to mimic the operating room situation. Preoperative planning was done from a computed tomography scan. The accuracy of cup abduction and anteversion was assessed with an electromagnetic system. Freehand placement revealed a mean accuracy of cup anteversion and abduction of 10 degrees and 3.5 degrees, respectively (maximum error, 35 degrees). With the cup positioner, these angles measured 8 degrees and 4 degrees (maximum error, 29.8 degrees), respectively, and using computer assistance, 1.5 degrees and 2.5 degrees degrees (maximum error, 8 degrees), respectively. Computer-assisted cup placement was an accurate and reproducible technique for total hip arthroplasty. It was more accurate than traditional methods of cup positioning.     

A Validation Model for Measurement of Acetabular Component Position

There is no agreement on a standard approach to evaluating acetabular cup orientation, ideal target orientation, or a standardized measurement method for cup orientation in total hip arthroplasty. The purpose of this study was to investigate a simple method for validating measurements of acetabular orientation obtained using computer navigation and computed tomography scans. This study validated the imageless navigation system to be accurate with a precision of 1° and a bias of 0.02° for inclination and a precision of 1.3° and a bias of 0° for anteversion measurements. From this study, we propose that acetabular cup alignment is accurately assessed using computer navigation. We suggest acetabular orientation be reported in the radiographic plane (coronal plane), which incorporates pelvic tilt and therefore is more functional definition of cup position.     

Accuracy and potential pitfalls of fluoroscopy-guided acetabular cup placement.

Using a total of 30 cadaveric hips, the accuracy of a fluoroscopy-based computer navigation system for cup placement in total hip arthroplasty (THA) was investigated and an error analysis was carried out. The accuracy of placing the acetabular component within a predefined safe zone using computer guidance was compared to the precision that could be achieved with a freehand approach. Accurate control measurements of the implanted cup were obtained using fiducial-based matching to a pre-operative CT scan with respect to the anterior pelvic plane. A significantly higher number of cups were placed in the safe zone with the help of the navigation system. The variability of cup placement could be reduced for cup abduction but not substantially for cup version. An error analysis of inaccurate landmark reconstruction revealed that the registration of the mid-pubic point with fluoroscopy was a potential source of error. Keeping this pitfall in mind, fluoroscopy-based navigation in THA is a useful tool for registration of the pelvic coordinate system, particularly those points that cannot be reached by direct pointer digitization with the patient in the lateral decubitus position.     

Evaluation of the accuracy of acetabular cup orientation using the accelerometer-based portable navigation system

BackgroundAccurate orientation of acetabular and femoral components is important during total hip arthroplasty (THA). In recent years, several navigation systems have been developed. However, these navigation systems for THA are unpopular worldwide because of their high cost. We assessed the orientation accuracy of cups inserted using a disposable accelerometer-based portable navigation system for THAs.MethodsThis was a prospective cohort study. We analyzed 63 hips with navigation prospectively and 30 hips without navigation retrospectively as historical control. The patients underwent THA via the mini anterolateral approach in the supine position using an accelerometer-based portable navigation system. We compared the preoperative target angles, intraoperative cup angles using navigation records, postoperative angles using postoperative CT data, measurement errors of cup angles, and clinical parameters such as sex, treated side, age at surgery, and body mass index (BMI).ResultsThe average absolute error (postoperative CT-navigation record) was 2.7 ± 2.1° (inclination) and 2.7 ± 1.8° (anteversion), and the absolute error (postoperative CT-preoperative target angle) was 2.6 ± 1.9° (inclination) and 2.7 ± 2.2° (anteversion). The absolute error between postoperative CT and target angle with navigation was significantly lower than the error without navigation (inclination; p = 0.025, anteversion; p = 0.005). Cup malalignment (absolute difference of inclination or anteversion between postoperative CT and preoperative target angle of over 5°) was significantly associated with BMI value (OR: 1.3, 95% CI: 1.1–1.7). The absolute measurement error of cup inclination and anteversion was significantly correlated with patients’ BMI (inclination error: correlation coefficient = 0.53, p < 0.001, anteversion error: correlation coefficient = 0.58, p < 0.001).ConclusionsThe clinical accuracy of accelerometer-based portable navigation is precise for the orientation of cup placement, although accurate cup placement was affected by high BMI. This is the first study to report the accuracy of accelerometer-based portable navigation for THA in the supine position.     

Reduced variability in cup positioning: the direct anterior surgical approach using navigation

Background and purpose Correct positioning of the acetabular component is important in total hip arthroplasty (THA). We evaluated the effect of an imageless navigation system on the accuracy of cup positioning using a minimally invasive direct anterior approach.

Methods Hip replacements were performed in 44 cadaveric hips (22 cadavers) that were divided randomly into 2 groups. In the study group, THA was performed using an imageless navigation system. In the control group, no navigation system was used. CT scans were taken postoperatively. Using 3D reconstructions, the cup position was determined in relation to the frontal pelvic plane. The goal was to place each cup at 45° of inclination and 20° of anteversion, as recommended by the manufacturer.

Results In the navigated group, there was a statistically significantly smaller range of deviation from the target angles of inclination and anteversion relative to the control group.

Interpretation We conclude that imageless navigation improves the accuracy of cup placement in minimally invasive THA using the direct anterior approach.     

C-arm based navigation in total hip arthroplasty-background and clinical experience

After experimental and preclinical evaluation of a CT-free image guided surgical navigation system for acetabular cup placement, the system was introduced into clinical routine. The computation of the angular orientation of the cup is based on reference coordinates from the anterior pelvic plane concept. A hybrid strategy for pelvic landmark acquisition has been introduced, involving percutaneous pointer-based digitization with the noninvasive bi-planar landmark reconstruction using multiple registered fluoroscopy images. From January 2001 to October 2003, a total of 236 consecutive patients (mean age 66 years, 144 male, 92 female, 124 left and 112 right hip joints) were operated on with the hybrid CT-free navigation system. During each operation, the angular orientation of the inserted implant was recorded. To determine the placement accuracy of the acetabular components, the first 50 consecutive patients underwent a CT scan 7-10 days postoperatively to analyze the cup position relative to the anterior pelvic plane. This procedure was done blinded and with commercial planning software. There was no significant learning curve observed for the use of the system. Mean values for postoperative inclination read 42 degrees (SD 3.6, range (37-49)) and anteversion 21 degrees (SD 3.9, range (10-28)). The resulting system accuracy, ie, the difference between intraoperatively calculated cup orientation and postoperatively measured implant position shows a maximum error of 5 degrees for the inclination (mean 1.5 degrees, SD 1.1) and 6 degrees for the anteversion (mean 2.4 degrees, SD 1.3). An accuracy of better than 5 degrees inclination and 6 degrees anteversion was achieved under clinical conditions, which implies that there is no significant difference in performance from the established CT-based navigation methods. Image-guided CT-free cup navigation provides a reliable solution for future total hip arthroplasty (THA).     

A Novel Method for Accurate and Reproducible Functional Cup Positioning in Total Hip Arthroplasty

Cup positioning is an important variable for short and long term function, stability, and durability of total hip arthroplasty (THA). This novel method utilizes internal and external bony landmarks, and the transverse acetabular ligament for positioning the acetabular component. The cup is placed parallel and superior to the transverse ligament and inside the anterior wall notch of the true acetabulum, then adjusted for femoral version and pelvic tilt and obliquity based on weight bearing radiographs. In 78 consecutive THAs, the mean functional anteversion and abduction angles were 17.9 ° ± 4.7 ° and 41.7 ° ± 3.8 °, respectively. 96% of the functional anteversion measurements and 100% of the functional abduction angles were within the safe zone. This technique is an easy, reproducible, and accurate method for functional cup placement.