A novel system of four-dimensional motion analysis after total hip arthroplasty.

We have developed a novel system of four-dimensional motion analysis after total hip arthroplasty (THA) that can aid in preventing dislocation by assessing safe range of motion for patients in several daily activities. This system uses skeletal structure data from CT and motion capture data from an infrared position sensor. A 3-D model reconstructed from CT data is combined with the motion capture data. Using this system, we analyzed hip motion when getting up from and sitting down in a chair or picking up an object while sitting in a chair in 17 patients (26 hips) who underwent THA. To assess the accuracy of this system's measurements, open MRI was used to evaluate positions of skin markers against bones in five healthy volunteers in various postures. No impingement between bones and/or implants was found in any subjects during any activities. However, mean angle at the point of maximum hip flexion was different for each patient. The open MRI results indicated that average error in hip angle of the present system was within 5 degrees for each static posture. The functional position of the pelvis during daily activities must be taken into account when assessing the real risk of dislocation. The present system enables dynamic analysis involving not only alignment of components and bones of each patient, but also individual differences in characteristics of daily motions. Further investigation using this system can help determine safe ranges of motion for preventing hip dislocation, improving the accuracy of individualized guidance for patients regarding postoperative activities.     

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.     

Bony impingement affects range of motion after total hip arthroplasty: A subject‐specific approach

Hip range of motion after total hip arthroplasty has been shown to be dependent on prosthetic design and component placement. We hypothesized that bony anatomy would significantly affect range of motion. Computer models of a current generation hip arthroplasty design were virtually implanted in a model of pelvis and femur in various orientations ranging from 35° to 55° cup abduction, 0° to 30° cup anteversion, and 0° to 30° femoral anteversion. Four head sizes ranging from 22.2 to 32 mm and two neck sizes ranging from 10‐mm and 12‐mm diameter were tested. Range of motion was recorded as maximum flexion–extension, abduction–adduction, and axial rotation of the femur before any contact between prosthetic components or bone was detected. Bony impingement preceded component impingement in about 44% of all conditions tested, ranging from 66% in adduction to 22% in extension. Range of motion increased as head size increased. However, increasing head size also increased the propensity for bony impingement, which tended to reduce the beneficial effect of increased head size on range of motion. Reducing neck diameter had a greater effect on prosthetic impingement (mean, 3.5° increase in range of motion) compared to bone impingement (mean, 1.9°). This model allowed for a clinically relevant assessment of range of motion after total hip arthroplasty and may also be used with patient‐specific geometry [such as that obtained from preoperative computed tomography (CT) scans] for more accurate preoperative planning. © 2007 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 26:443–452, 2008     

Intraoperative pelvic motion in total hip arthroplasty

In total hip arthroplasty (THA) in which the posterolateral approach is used, the pelvis can be easily inclined to roll both backward or forward on the operating table during the procedure. We prospectively studied 30 posterolateral-approach primary THA cases in which the surgeon used a specially devised goniometer that measured motions of the pelvis in the horizontal, frontal, and sagittal planes. We found that the pelvis primarily tilted forward during surgery, averaging 14.57 degrees of anterior tilt in the horizontal plane. The pelvic motion primarily occurred while the Hohman retractor was being applied to the femur to expose the acetabulum. Assessment of pelvic motion during surgery is an important component for successful positioning and placement of the acetabular cup with the posterolateral-approach THA.     

Anatomic hip range of motion after implantation during total hip arthroplasty as measured by a navigation system

Simulation of prosthetic impingement is important for preventing complications after total hip arthroplasty (THA). Although the anatomical hip range of motion (ROM) in patients after THA is an essential parameter for these simulations, previous simulation studies substituted various clinical hip ROMs for the anatomical hip ROM. Using a navigation system, anatomical hip ROM was accurately assessed after implantation during primary THA in 30 patients. We found that the hip could be passively moved to 113 degrees of flexion, 34 degrees of extension, 46 degrees of abduction, 75 degrees of internal rotation, and 36 degrees of external rotation. Almost all reference hip ROMs used in previous simulations were smaller than these values. Therefore, wider hip ROM values should be used as parameters for such simulations.     

Dual mobility cups in total hip arthroplasty

Total hip arthroplasty (THA) is considered one of the most successful surgical procedures in orthopaedics. With the increase in the number of THAs performed in the world in the next decades, reducing or preventing medical and mechanical complications such as post-operative THA instability will be of paramount importance, particularly in an emerging health care environment based on quality control and patient outcome. Dual mobility acetabular component (also known as unconstrained tripolar implant) was introduced in France at the end of the 1970s as an alternative to standard sockets, to reduce the risk of THA dislocation in patients undergoing primary THA in France. Dual mobility cups have recently gained wider attention in the United States as an alternative option in the prevention and treatment of instability in both primary and revision THA and offer the benefit of increased stability without compromising clinical outcomes and implant longevity. In this article, we review the use of dual mobility cup in total hip arthroplasty in terms of its history, biomechanics, outcomes and complications based on more than 20 years of medical literature.     

基于惯性测量单元的全髋关节置换术中髋关节活动度智能测量系统的体外验证

目的开展一项体外验证研究,评估基于惯性测量单元的智能测量系统(IMUHST)在全髋关节置换术中测量髋关节活动度的准确性。方法IMUHST系统由股骨头测量元件及电脑终端组成。采用不透X线的人工骨右侧髋臼磨锉后置入直径60 mm的臼杯,股骨髓腔内置入股骨柄,模拟全髋关节置换术,将IMUHST系统直径36 mm的试模股骨头装配于股骨侧股骨柄上。将CT图像数据测量的髋关节活动度作为参照标准,分析IMUHST系统测量结果(观察组)与参照标准(对照组)之间的差异,并计算组内相关系数(ICC)值。结果观察组与对照组在髋关节屈伸、内收外展、内旋外旋轴线上测量的活动度差异无统计学意义(P>0.05),ICC值均为0.982。结论体外研究证实IMUHST系统测量全髋关节置换术中髋关节活动度具有较高的准确性,该智能辅助系统具有广阔的临床应用前景。     

Dynamic measurements of hip movement in deep bending activities after total hip arthroplasty using a 4-dimensional motion analysis system

Although deep hip bending activities are often required in Asian populations because of traditional lifestyles and religious practices, few have examined the required hip range of motion (ROM) in these activities after total hip arthroplasty (THA). We performed postoperative motion analysis to evaluate the differences in required ROMs between Japanese-style and Western-style deep hip bending activities, to investigate whether prosthetic impingement would occur during these activities and to clarify the necessity for precautions in these activities after THA. Japanese-style activities did not require larger hip ROMs than Western-style ones, and all required hip flexion angles were less than 120°. Prosthetic impingement was not observed, with a safety margin 10° or higher until impingement in any directions of flexion, adduction, or internal rotation for any activities. Thus, particular postoperative precautions for Japanese-style activities are not required.     

Pelvic motion during total hip arthroplasty with translateral and posterolateral approaches

We devised a special instrument to assess intraoperative pelvic motion and used this device to measure intraoperative pelvic motion in three dimensions. A total of 100 total hip arthroplasties (THAs) were performed using this device. Two approaches were utilized: 52 THAs were performed with the posterolateral approach and the remaining 48 with the translateral approach. The average angle of pelvic tilt in the THAs with the translateral approach was less than that with the posterolateral approach. The average internal rotation angle was 1.75° with the translateral approach and 14.25° with the posterolateral approach. With the posterolateral approach, the internal rotation of the pelvis frequently occurred during retraction of the femur using a Hohmanns retractor placed at the anterior rim of the acetablum, with flexion and internal rotation of the affected hip.     

Factors affecting range of flexion after total knee arthroplasty

Many factors affect postoperative range of flexion after total knee arthroplasty (TKA). The purpose of this study was to identify the most important factors that affect range of knee flexion after TKA. Sixty-five patients (73 knees) were treated with Genesis II knee replacements. Minimum follow-up was 2 years. Patient demographics (sex, age, body mass index, previous surgery, component type, patella resurfacing, preoperative Knee Society score preoperative range of motion) and radiographic measurements (preoperative tibiofemoral varus/valgus angle, height of the joint line, length of the patellar tendon, shift and tilt angle of the patella) were analyzed statistically. Among these factors, preoperative range of flexion, positively, and preoperative varus/valgus tibiofemoral angle, negatively, affected postoperative range of flexion. The tilt angle of the patella and the tilt angle of the patellar button approached statistical significance in revealing a negative relation with postoperative range of flexion. TKAs in which the patella was not resurfaced tended to lose range of flexion, whereas TKAs in which the patella was resurfaced tended to have no loss of flexion, although the number of TKAs in which the patella was not resurfaced was small. In conclusion, preoperative range of flexion and preoperative varus/valgus tibiofemoral angle affected postoperative range of flexion. The tilt angle of the patella and tilt angle of the patellar button may be factors that affect postoperative range of flexion. Received: September 28, 2000 / Accepted: January 9, 2001     

CT image evaluation of the internal rotation limit prior to bony impingement after total hip arthroplasty

 This study evaluated the internal rotation limit prior to bony impingement of the proximal femur on the pelvis after total hip arthroplasty (THA). Reconstructed computed tomography (CT) images of 90° hip flexion were used to simulate the internal rotation limit against safety limits measured intraoperatively. Ninety joints in 86 subjects (12 men and 74 women) underwent THA for the treatment of secondary coxarthrosis. The correlation between the internal rotation limit prior to the bony impingement intraoperatively and the simulated internal rotation angle on the reconstructed CT image was statistically significant. We provide a new method to simulate the internal rotation limit prior to bony impingement based on postoperative CT. Received: October 8, 2001 / Accepted: March 19, 2002     

不同股骨头颈直径比与髋臼角对人工髋关节活动的影响

目的：探讨不同股骨头颈直径比和髋臼安置方位对人工全髋关节活动范围的影响。方法：应用计算机模拟技术建立人工全髋关节三维计算机模型，模拟测试三种不同头颈直径比全髋假体在体外不同安置方位的活动范围。结果：全髋关节置换术后的活动范围不仅取决于假体设计的某些参数，如头颈直径比，还取决于假体安置的某些参数，如臼杯的外展角和前倾角，假体柄的前倾角，以及臼杯和柄的相互方向等等。人工全髋关节在合适的安置方位内产生最佳的活动范围。头颈比越大，同一安置方位同一方向的活动范围越大。结论：人工全髋关节相对较大的头颈直径比在合适的安置方位内产生最佳的活动范围，可减少全髋关节置换术(THA)后假体撞击机会。国产镁硅玉全髋假体由于头颈比太小，在任何安置方位内其活动范围都较小，将难于满足日常生活需要。     

The continuum of hip range of motion: From soft-tissue restriction to bony impingement

Traditional studies of hip kinematics have not identified which anatomic structures limit the range of motion (ROM) when the hip is placed in different maneuvers. In this study, we attempted to answer two questions: (a) During which maneuvers is the motion of the hip limited by bony impingement between the femur and pelvis? (b) When is hip ROM determined by the constraint of soft tissues and to what extent? ROM of eight cadaveric hips was measured in 17 maneuvers using a motion capture system. The maneuvers were recreated in silico using 3D CT models of each specimen to detect the occurrence of bony impingement. If bony impingement was not detected, the variable component of 3D hip motion was increased until a collision was detected. The difference between the virtual ROM at the point of bony impingement and the initial ROM measured experimentally was termed as the soft-tissue restriction. The results showed that bony impingement was present in normal hips during maneuvers consisting of high abduction with flexion, and high flexion combined with adduction and internal rotation. At impingement-free maneuvers, the degree of soft tissue restriction varies remarkably, ranging from 4.9° ± 3.8° (internal rotation) at 90° of flexion to 80.0° ± 12.5° (internal rotation) at maximum extension. The findings shed light on the relative contributions of osseous and soft tissues to the motion of the hip in different maneuvers and allow for a better understanding of physical exams of different purposes in diagnosing bone- or soft tissue-related diseases.     

Computer-assisted cup positioning in total hip arthroplasty: usefulness, limits and future

The basic hypothesis for computer-assisted placement of the cup in total hip arthroplasty (THA) is that navigation will improve cup positioning around the targeted values previously defined in the literature as the gold standard for cup placement and reduce the number of outliers. Reducing the outliers will theoretically reduce the number of dislocation, improve range of motion and reduce wear. We will present the surgical technique, and the results of a prospective randomized study comparing computer-assisted cup positioning with free-hand placement. Furthermore we will outline some limitations of the navigation systems in hip surgery observed during our early experience through the results of complementary anatomical and clinical studies. Finally we will discuss the potential for future development of computer-assisted THA.     

Computed tomographic measurement of acetabular and femoral component version in total hip arthroplasty

Purpose

The purposes of the present study were (1) to investigate the variation and accuracy of both acetabular and femoral component version on the axial computed tomographic (CT) images, and (2) to better define the associations between the components version and clinical factors.

Methods

We investigated acetabular and femoral component orientation in 1,411 primary total hip arthroplasties that had been performed without computer-assisted navigation. Version of the acetabular and femoral components was measured on the axial CT images.

Results

The component version was significantly greater than the native version in both acetabular and femoral version. There was a significant correlation between the stem and native femoral versions, but not between the acetabular component and native acetabular versions.

Conclusion

This study identifies several features that might help analyse the effect of pre-operative native acetabular and femoral version on the variation of component alignment.     

Variability in hip range of motion on clinical examination

The goal of this study was to determine the interobserver and intraobserver reliability of physical examination in determining hip range of motion. Twenty normal hips, 21 hips with osteoarthritis, and 21 hips of patients more than 12 months after a total hip arthroplasty were examined for visual passive range of motion. These 62 hips were examined by 2 experienced surgeons and by 3 trainees. The 2 experienced examiners repeated their clinical examinations in 19 patients to determine the intraobserver reliability. Intraclass correlation coefficients (ICCs) indicated moderate interobserver agreement in estimates of clinical hip motion (ICC for hip flexion, 0.56 +/- 0.12; for hip abduction, 0.48 +/- 0.13). Intraclass correlation coefficients also suggest only moderate intraobserver reliability in measurements of hip motion (ICC for hip flexion, 0.62 +/- 0.14; hip abduction, 0.44 +/- 0.20). More reliable and accurate methods are needed to measure clinical hip motion before and after total hip arthroplasty.     

Combined anteversion technique reduced the dislocation in cementless total hip arthroplasty

Purpose

The combined anteversion (CA) technique is a method in which the cup is placed according to the stem anteversion in total hip arthroplasty (THA). We examined whether the CA technique reduced the dislocation rate, and the distribution of CA with the manual placement of the cup.

Methods

We retrospectively reviewed 634 hips in 579 patients with primary cementless THA. In 230 hips using the CA technique [CA(+)], a CA of 50 ± 10° was the aim. In the remaining 404 hips [CA(−)], the cup was first placed targeting 20° of anteversion. The post-operative CA was measured using the computed tomography (CT) images in 111 hips.

Results

One hip (0.4 %) had a dislocation in the CA(+) group, whereas ten hips (2.5 %) had a dislocation in the CA(−) group. A multivariate analysis showed that primary diagnosis, head size and CA technique significantly influenced the dislocation rate. Patients in the CA(−) group were 5.8 times more likely to have a dislocation compared to the CA(+) group. In the 111 hips with CT images, 81 hips (73.0 %) achieved the intended CA.

Conclusions

Although the manual placement of the cup resulted in 27 % of outliers from the intended CA, the CA technique significantly reduced the dislocation after primary THA.     

Improving acetabular cup orientation in total hip arthroplasty by using smartphone technology

Acetabular cup placement in total hip arthroplasty is often difficult to assess, especially in the lateral position and using the posterior approach. Conventional techniques and computer-assisted surgery are the 2 most popular methods for proper placement of the acetabular cup in Lewinnek's safe zone of orientation (anteversion 15° ± 10° and lateral inclination 40° ± 10°). We developed a system that uses the accelerometer and camera function of the iPhone. A level indicator application and protractor application were downloaded to the iPhone and used to improve acetabular cup placement. This system has proven to be accurate and quick. Our series of 50 prospective cases showed good results with all our acetabular cups being placed within a narrow range in the safe zone and with less than 5% difference between the preoperative, intraoperative, and postoperative acetabular inclinations.     

髋臼假体角度与全髋关节置换术后脱位的关系

目的研究人工全髋关节置换术（THA）髋臼假体安装固定角度与术后髋关节脱位的关系。方法在X线片测量236例（248髋）THA术后的髋臼外展角和前倾角,将外展角设定为〈30°、30-50°、〉50°3组,前倾角设定为〈0°、0-25°、〉25°3组。分析以上2个因素与术后髋关节脱位的关系。结果脱位组外展角平均（39±11．88）°,非脱位组为（38．98±8．65）°,两组之间外展角差异无统计学意义（P=0．449）;脱位组前倾角平均（12．33±14．89）°,非脱位组为（13．21±11．52）°,两组之间前倾角差异无统计学意义（P=0．131）°外展角在〈30°、30-50°、〉50°不同范围的脱位率差异无统计学意义（P〉0．05）,前倾角在〈0°、0～25°、〉25°不同范围内的脱位率差异无统计学意义（P〉0．05）。结论髋臼假体外展角在14～58°范围内、前倾角在-15～350范围内与THA术后脱位之间不存在相关性。     

全髋关节置换术治疗化脓性髋关节炎后遗关节畸形的临床研究

目的探讨人工全髋关节置换术（THA）治疗化脓性髋关节炎后遗关节畸形的近期临床疗效。方法 21例（22髋）化脓性髋关节炎后遗关节畸形行THA治疗。比较术前与末次随访时髋关节功能Harris评分,并随访观察假体稳定性。结果所有患者均获得平均45（24-58）个月随访。手术切口均一期愈合,无关节脱位、深静脉血栓形成、坐骨神经损伤或感染复发等并发症。所有患者均未出现〉2 mm的透亮带,无假体松动。临床症状及髋关节功能明显改善,末次随访时髋关节功能Harris评分平均89.5（73-97）分,较术前平均45.3（25-62）分明显提高,差异有统计学意义（t=13.642,P〈0.001）。结论 THA治疗化脓性髋关节炎后遗关节畸形的近期疗效良好。