The three-dimensional pattern of the pelvis movement in standarized gait cycle in patients before and after knee arthroplasty--leading article]

The main goal of this study was to estimate the influence of knee arthroplasty on angular changes of pelvis movement in three planes. The three-dimensional analysis of locomotion was carried out with 13 patients afer total knee replacement aged 47-74, using Vicon system. The first examination took place before knee operation and the second examination 6 months after arthroplasty. The results were represented at the background of biomechanical gait parameters of 30 healthy people aged 50-70. The angular changes of pelvis movement in each gait phase were taken into consideration. After knee arthroplasty the results of patients examinations were similar to the biomechanical norm in sagittal and transversal plane. In the sagittal plane the difference between the results of the first and the second research was 15 degrees. The first examination of pelvis movement in transversal plane showed that the distinction between patients results and biomechanical norm was 17 degrees in initial contact and terminal swing; after total knee replacement the movement amplitude was similar to the biomechanical norm. The biggest change of the hip joint movement after knee replacement was noticeable in transversal plane but there was only slight improvement in sagittal and frontal plane. There was also noticeable change in the knee movement in frontal plane and the results of the two research sessions in sagittal and transversal plane was similar to the biomechanical norm.     

How correctly does an intramedullary rod represent the longitudinal tibial axes?

In a robot-assisted procedure for preparing the tibia in total knee arthroplasty, developed in the authors' laboratory, an intramedullary rod is used to register the tibia. In 18 formalin-fixed tibias, the difference in orientation was calculated between the intramedullary rod and several longitudinal tibial axes used in clinical practice. This was done using roentgenstereophotogrammetric analysis. Three tibial axes and two insertion techniques were considered. In three-dimensional space, small differences between the axes are observed. The results showed a high standard deviation, indicating the importance of anatomic differences. In the frontal plane, the difference in orientation between rod and tibial axes never exceeded +/- 2 degrees. In the sagittal plane, the observed differences were larger. Significant differences between the considered axes appeared. The results of the two insertion techniques were not significantly different. Because an intramedullary rod frequently is used for alignment of the tibia in conventional surgery, these results also are valuable for conventional surgery. In the current study, the accuracy of the intramedullary alignment is examined, without influences of the sawing procedure. Moreover, the study is not limited to the frontal plane; the total accuracy in three-dimensional space, and the accuracy in the frontal and the sagittal planes were studied.     

Anatomy of the abductor muscles of the hip as studied by computed tomography

Computed tomography provides a non-invasive method for studying anatomy in live subjects. The abductor muscles of the hip were studied by using computed tomography to describe their position, size, and orientation. The outlines of the muscles were clearly identifiable; patterns that are associated with trauma, arthritis, and so on, differed from normal. The patterns in eighteen normal hips in twelve adults were mapped in detail. The cross-sectional areas of the abductor muscles were measured and vectors representing the total pull of the abductor muscle in the frontal and sagittal planes were constructed for each hip. The variations in individual and composite muscular anatomy were recorded. The inclination of the axis of the abductor muscle ranged from 17 to 26 degrees (standard deviation, 2.9 degrees) in the frontal plane and from -2 to 14 degrees (standard deviation, 4.2 degrees) in the sagittal plane.     

A prospective, randomized study of computer-assisted and conventional total knee arthroplasty. Three-dimensional evaluation of implant alignment and rotation

BACKGROUND: Despite the use of modern instruments in total knee arthroplasty, component malalignment remains a problem. Whether a computer-assisted implantation technique can improve the accuracy of the spatial positioning of an implant is a matter of debate. The objective of this study was to determine whether computer-assisted total knee arthroplasty is superior to the conventional surgical method with regard to the precision of implant positioning. METHODS: The spatial positioning of the implant in sixty total knee arthroplasties (thirty-two imageless computer-assisted and twenty-eight conventional implantations) was determined three-dimensionally with use of computed tomographic measurement, which allowed derotation and full extension of the knee in order to avoid projection-related imaging errors. RESULTS: The overall mechanical axis showed a range of between 4.8 degrees of valgus and 6.6 degrees of varus alignment in the frontal plane for conventionally implanted arthroplasty components compared with a significantly smaller range of between 2.9 degrees of valgus and 3.1 degrees of varus alignment for computer-assisted implantations (p = 0.004). In relation to the tibial implant, the mean deviation (and standard deviation) from the mechanical axis was 2.0 degrees +/- 1.7 degrees for the conventional surgical method and 1.4 degrees +/- 0.9 degrees for the navigated implantation. The rotational deviation from the referenced axis of the femoral component was between 3.3 degrees of internal rotation and 5.0 degrees of external rotation for the conventional implantation method, with a mean deviation of 0.1 degrees +/- 2.2 degrees. Femoral components implanted with computer assistance showed a deviation of between 4.7 degrees of internal rotation and 2.2 degrees of external rotation, with a mean deviation of 0.3 degrees +/- 1.4 degrees. CONCLUSIONS: In this study, with our technique of filtering out projection-related imaging errors, computer-assisted implantation of total knee replacements improved the frontal and sagittal alignment of the femoral component but not of the tibial component. We found that the rotational alignment of the component was not improved through navigation by solely referencing to the epicondylar axis for the femur and the tuberosity for the tibia.     

Bone cutting errors in total knee arthroplasty

Although achieving precise implant alignment is crucial for producing good outcomes in total knee arthroplasty, the contribution of the bone-cutting process to overall variability has not been measured previously. Eight orthopaedic surgeons with varying amounts of total knee arthroplasty experience performed 85 resections on 19 cadaver femora and tibiae, and the planes of the resulting cut surfaces were compared with the guide planes. Varus-valgus alignment variability ranged from 0.4 degrees to 0.8 degrees SD for expert and trainee surgeons. Sagittal variability was approximately 1.3 degrees SD for both surgeon groups. Slotted cutting guides reduced the variability and eliminated the bias in the sagittal plane for experienced surgeons but did not improve significantly frontal plane alignment variability. Guide movement contributed 10% to 40% of the total cutting error, depending on cut and guide type.     

Robotic total knee arthroplasty: the accuracy of CT-based component placement

BACKGROUND: Accurate alignment of the components in total knee arthroplasty is important. By use of postoperative CT controls, we studied the ability of a robotic effector to accurately place and align total knee arthroplasty (TKA) components according to a purely CT-based preoperative plan. PATIENTS AND METHODS: Robotic TKA was performed in 13 patients (6 men) with primary gonarthrosis. Locator screws were placed into femur and tibia under spinal anesthesia. A CT-scan including the femoral head, knee and ankle was performed. In the preoperative planning software, virtual components were positioned into the CT volume. In a second operation, the robot milled femur and tibia with a high-speed milling tool according to the preoperative plan. On the 10th day, CT controls were performed following the same protocol as preoperatively. RESULTS: The mean deviation of the postoperative from the preoperatively planned mechanical axis was 0.2 degrees (95% CI: -0.1 degrees to 0.5 degrees ). The accuracy of angular component placement in frontal, sagittal and transverse planes was within +/-1.2 degrees , and the accuracy of linear component placement in mediolateral, dorsoventral and caudocranial directions was within +/-1.1 mm. INTERPRETATION: Robotic TKA allows placement of components with unparalleled accuracy, but further development is mandatory to integrate soft-tissue balancing into the procedure and make it faster, easier and cheaper.     

Joint Motions of the Lower Limb during Ergometer Cycling

The purpose of the study was to study the utilization of range of motion at the hip, knee, and ankle joints during exercise on a bicycle ergometer. Six healthy subjects biked at different workloads, pedaling rates, saddle heights, and pedal foot positions. The subjects were filmed in the sagittal plane with a cine-film camera at 60 frames/sec. The mean hip range of motion (ROM) during normal cycling was 38 degrees ranging from 32-70 degrees hip flexion. The mean knee ROM was 66 degrees ranging from 46-112 degrees knee flexion, and the ankle ROM was 24 degrees ranging from 2 degrees plantarflexion to 22 degrees dorsiflexion. The hip, knee, and ankle joint motions were influenced by changes of the saddle height or pedal foot position. Different workloads had a small but statistically significant influence on the joint motions while different pedaling rates did not significantly change the lower limb joint motions. The range of motion utilized during cycling is approximately equal to, but more flexed compared to level walking and stair walking. The most effective way of increasing the ROM and obtaining more extension of the lower limb joints is to change the saddle height.J Orthop Sports Phys Ther 1988;9(8):273-278.     

Total knee arthroplasty for arthritis of the knee with extra-articular deformity

BACKGROUND: Simultaneous corrective osteotomy of angular deformity and total knee arthroplasty has been considered the treatment of choice for patients with arthritis of the knee associated with ipsilateral extra-articular deformity. However, this procedure is technically demanding, and the functional outcome of the total knee arthroplasty may be jeopardized if the osteotomy fails. This retrospective study was performed to evaluate the clinical results of total knee arthroplasty combined with intra-articular bone resection, without osteotomy, in patients with extra-articular deformity and arthritis of the knee. METHODS: Fifteen patients with arthritis of the knee and extra-articular deformity underwent total knee arthroplasty with bone resection and soft-tissue balancing. All deformities had resulted from fracture malunion. There were ten uniplanar, three biplanar, and two triplanar deformities. The deformity was in the tibia in eight patients and in the femur in seven. The average angle of the femoral deformities was 15.1 degrees in the coronal plane and 8.1 degrees in the sagittal plane. Two femora had a rotational deformity, consisting of 20 degrees of internal rotation in one and 10 degrees of external rotation in the other. The average angle of the tibial deformities was 19 degrees in the coronal plane. RESULTS: The duration of follow-up averaged thirty-eight months. The average Knee Society knee score improved from 22.3 points preoperatively to 91.7 points at the time of the last follow-up, and the average Knee Society function score improved from 28.0 points preoperatively to 87.3 points at the time of the last follow-up. The average arc of knee motion improved from 77.7 degrees preoperatively to 103.7 degrees postoperatively. The average mechanical axis of the knee improved from 22.7 degrees of varus preoperatively to 0.3 degrees of varus at the time of the last follow-up. Two patients had an unsatisfactory clinical result, which was not related to the total knee arthroplasty. There were no complications such as infection, ligament instability, or component loosening. CONCLUSIONS: Total knee arthroplasty in conjunction with intra-articular bone resection is an effective procedure for patients with arthritis of the knee and extra-articular varus deformity of <20 degrees in the femur or 30 degrees in the tibia in the coronal plane.     

不同程度屈膝挛缩畸形人工全膝关节置换的早期疗效比较

目的探讨不同程度屈膝挛缩畸形行人工全膝关节置换术(totalkneearthroplasty,TKA)后的早期疗效。方法回顾性分析2000年1月～2003年12月行TKA的65例97膝屈膝挛缩畸形患者资料。其中骨关节炎51例74膝,类风湿关节炎14例23膝。单膝置换33例33膝,双膝同时置换32例64膝。按屈膝挛缩畸形程度不同将患者分成A、B两组,A组屈曲挛缩<20°(0～15°)32例49膝,B组屈曲挛缩≥20°(20～60°)33例48膝。A、B两组膝关节术前屈曲挛缩度数、活动度(rangeofmotion,ROM)、KSS(kneesocietyscore)评分及功能评分分别为10.7±8.0°、104.6±20.0°、29.1±18.0、32.6±20.7和28.2±7.8°、60.8±26.6°、12.1±13.2、26.8±18.1,各指标组间比较差异均有统计学意义(P<0.05)。术中均采用Scorpio后稳定型骨水泥固定假体,行初期置换。术后3～4d在同一康复师指导下行CPM及主动功能锻炼。结果患者获随访8个月～3年6个月,平均2年7个月。A、B组术后膝关节屈曲挛缩度数、ROM、KSS评分和功能评分分别为0.4±2.1°、108.6±19.0°、82.1±13.8、72.3±29.1和1.3±3.2°、98.6±16.4°、75.9±8.2、81.4±26.9,组间比较差异均无统计学意义(P>0.05)。术后患者总满意度为94.6%,无深部感染及再翻修者。结论膝关节屈膝挛缩畸形严重与否对TKA的早期疗效无明显影响;TKA后ROM有“趋中”现象;术后早期行膝关节功能锻炼也是获得功能改善的重要环节之一。     

Use of a Guide Instrument for Compartmental Knee Arthroplasty

To improve the positioning of the tibial component in compartmental knee arthroplasty a guide instrument was introduced. With the guide instrument the position in the frontal plane significantly improved from a mean medial slope of 10 degrees to 2 degrees. In the sagittal plane the change from a mean posterior slope of 5 degrees to 3 degrees was insignificant. The mean value for the Hip-Knee-Ankle angle (HKA) (ideal 180 degrees) was 186 degrees after “free-hand” operation and 183 degrees with the modified operative technique. Thus, it is possible with the aid of a guide instrument to improve the precision in compartmental knee arthroplasty.     

Active range of motion of the head and cervical spine: a three-dimensional investigation in healthy young adults.

PURPOSE: To define reference values for head-cervical range of motion (ROM) in healthy young adults, to assess the effect of sex, and to quantify the separate contribution of other body districts. METHODS: Thirty women and 30 men performed maximal head and cervical spine flexion-extension, lateral bending, and axial rotation. Movements were detected using a digital optoelectronic instrument. Maximum head-cervical spine and thoracic motions were separated. RESULTS: Flexion and extension were performed mainly in the sagittal plane. The movement was larger in women (136 degrees) than in men (130 degrees). During flexion, both sexes moved the head-neck and the thorax in the same direction. During extension, men moved only the head-cervical spine, while women moved the two analyzed districts in the opposite directions. Lateral bending was nearly symmetric, associated with head-cervical rotation and extension, and larger in women (91 degrees) than in men (77 degrees). Adjunctive thoracic motion was limited in the sagittal and frontal planes, but larger in the horizontal plane (opposite motions of about 20 degrees). Head-neck rotation was symmetric, and associated with concomitant movements in both the sagittal and frontal planes. It was larger in women (162 degrees) than in men (155 degrees), and performed with limited adjunctive thoracic motions. CONCLUSIONS: The present values can be used as a first group of normative data for head-cervical ROM in young men and women.     

Cutting and implanting errors in minimally invasive total knee arthroplasty using a navigation system

Purpose

The purpose of this study was to evaluate the accuracy of bone cutting and implantation in minimally invasive total knee arthroplasty with image-free navigation.

Methods

The alignment of the tibial and femoral bone resection was measured in 40 knees during surgery. The alignment measurement was repeated after cementing the tibial and femoral components. We evaluated the cutting error and the implanting error.

Results

The mean tibial cutting errors were 0.5 and 0.7° in the frontal and sagittal planes, respectively. The mean femoral cutting errors were 0.5 and 0.9° in the frontal and sagittal planes, respectively. The mean tibial implanting errors were 1.0 and 0.9° in the frontal and sagittal planes, respectively. The mean femoral implanting error was 0.7° in the frontal plane.

Conclusions

Computer-assisted navigation was useful in checking the alignment of both bone cut and cementation.     

Test bed for assessment of the kinematical determination of navigation systems for total knee arthroplasty. Does a limited range of motion of the hip joint influence the accuracy of the determination?

OBJECTIVE: To locate the rotational center of the hip joint, CT-less navigation systems for artificial knee-joint replacement use movements of the femur with a rigid body attached. It cannot be assumed that the hip joint provides free mobility at all times. The purpose of the present study was: 1) To build a mechanical model to assess the system's accuracy in locating the rotational center of the hip by simulating a step-wise reduction of the range of motion (ROM) of the hip joint. 2) To determine the system's resolution by assessing a critical distance between two positions of the same femoral rigid body during the process of locating the rotational center of the hip. 3) To determine the sensitivity of the navigation system to the rotation of a femoral rigid body relative to the femoral bone while locating the rotational center of the hip joint. MATERIAL AND METHODS: To assess the impact that a limited ROM of the hip joint has on the accuracy of determination of the hip joint's rotational center, a test bed was built. This enables validation of the algorithm used by a CT-less navigation system. RESULTS: In the first part of the study, it was shown that a reduction of the ROM of the hip joint to 30% of its initial value had no evident influence on the accuracy of locating the rotational center of the joint. In the second part of the study, it was determined that the limit of resolution between two spatial points of the pivoting process is between 4.4 and 8.7 cm. The third part of the study showed that the examined system rejected the determination of the hip center even when the rigid body was only rotated through 22.5 degrees . CONCLUSIONS: The results show that osteoarthritis of the hip with a limited ROM, for example, cannot be taken as a contraindication for the use of the evaluated CT-less navigation system. However, the surgeon should ensure that the pivoting of the femur is performed without hindrance within the free range of motion of the hip joint. In accordance with the vendor's recommendation, a minimum distance of 10 cm should be maintained between two spatial points. To ensure safe and unconstrained operation, the rigid body must be firmly attached to the bone and must not be dislocated.     

术前活动度对人工全膝关节置换术后功能影响的观察

目的回顾性分析患者手术前的活动度对人工全膝关节置换(TKA)术后功能的影响。方法随访2000年1月—2003年12月在我科行TKA的患者65例(97膝),年龄64．8±9．9岁(35～85岁)。其中骨性关节炎55例(81膝),类风湿关节炎10例(16膝)。单膝置换33例,双膝同时置换32例。所有患者按术前膝关节活动度数(ROM)分成两组,≤90°(5°～90°)49膝,>90°(95°～140°)48膝。对两组患者进行疗效(最大屈膝度、活动度、KSS评分及功能评分)对比。所有患者均采用Scorpio后稳定型骨水泥固定的假体,均为初期置换,全部手术由同一组医师完成。术后3 d在同一康复师指导下行患肢CPM及主动功能锻炼至出院。结果平均随访时间29个月(10～44个月)。所有膝关节的活动度从术前的平均84．2°(5°～140°)提高到术后的平均101．6°(40°～140°) (P=0．000);而最大屈膝度数术前的平均103．5°(25°～140°)与术后的平均101．6°(40°～140°)无显著差异(P=0．439);KSS膝关节评分从术前平均19．5分(-24～62分)提高到术后平均78．8分(50～95分)(P=0．000)。所有患者的总满意度为93．8％(61／65)。两个分组比较,ROM≤90°的膝关节ROM及最大屈膝度术后均较术前有提高,而ROM>90°的膝关节平均最大屈膝度术后反而下降。没有翻修及深部感染。结论(1)在影响TKA术后膝关节功能的多种因素中,手术技术是关键因素。(2)在其他因素相同的情况下,术前膝关节的活动度对TKA术后的功能也有很大的影响,术前活动度大的膝关节比那些术前活动度小的膝关节术后能获得更好的功能。     

Accuracy of a computer-assisted navigation system in resurfacing hip arthroplasty

We developed a method to assess the accuracy of an image-free resurfacing hip arthroplasty navigation system in a proximal femur with normal and abnormal anatomy. A phantom lower limb allowed deformation in varus/valgus and ante-retroversion. At specific points during the simulated surgical procedure, information was compared between a digital caliper and the computer navigation system angular measurements. Repeated serial tests were undertaken. In the setting of normal anatomical alignment of the proximal femur, the mean error of the system characterised as the difference between the measured computer navigation and caliper angles was 0.6 degrees in the frontal plane and 3.4 degrees in the lateral plane. In the setting of abnormal anatomical alignment, the mean error was 0.4 degrees in the frontal plane and 2.1 degrees in the lateral plane. This is the first study designed to assess the accuracy of a femoral navigation system for resurfacing hip arthroplasty in normal settings and in the presence of angular deformity. The study demonstrates satisfactory in-vitro accuracy.     

Natural progression of gait in children with cerebral palsy

Twenty-eight children with cerebral palsy had two gait analyses an average of 4.4 years apart with no surgical intervention between the tests. The effects of growth and age were examined using three-dimensional kinematics, temporal and stride parameters, and clinical examination measures. Kinematic changes showed decreases in hip, knee, and ankle sagittal plane ranges of motion (ROM), peak hip flexion in swing, and peak knee flexion over time. Temporal and stride parameters showed declines in timing of toe off, cadence, and walking velocity. Clinical measures showed declines in hip abduction ROM (knees flexed and extended), popliteal angle, and sagittal plane ankle ROM (knees flexed and extended). Overall results showed that gait function in these individuals with cerebral palsy decreased longitudinally with respect to temporal/stride measures, passive ROM, and kinematic parameters compared with a group of individuals who had had orthopaedic intervention.     

Effects of kyphosis and lordosis on the remaining lumbar vertebral levels within a thoracolumbar fusion: an experimental study of the multisegmental human spine

This study was done to determine the motion of the whole lumbar spine after internal fixation and the effect of kyphosis and lordosis on the remaining vertebral levels. Baseline motion analysis of sagittal, frontal, and transverse planes was done to determine the intact range of motion. Three fusion configurations were tested: neutral position (0 degrees), 4.6 degrees +/- 2.0 kyphosis, and -6.2 degrees +/- 3.6 lordosis. The sagittal and frontal plane relative rotation of the instrumented segments (T12/L2) decreased an average of 74% and 60%, respectively, as compared with intact testing. Sagittal plane motion at the remaining segments increased for all fusion configurations when compared with intact motion and reached statistical significance at the L4/L5 level. No significant differences were found between fusion configurations (ie, fused neutral, kyphosis, and lordosis).     

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.     

Accuracy of Computer-assisted Navigation for Femoral Head Resurfacing Decreases in Hips with Abnormal Anatomy

Computer-assisted navigation systems for hip resurfacing arthroplasty are designed to minimize the chance of implant malposition. However, there is little evidence computer navigation is useful in the presence of anatomical deformity. We therefore determined the accuracy of an image-free resurfacing hip arthroplasty navigation system in the presence of a pistol grip deformity of the head and femoral neck junction and of a slipped upper femoral epiphysis deformity. We constructed an artificial phantom leg from machined aluminum with a simulated hip and knee. The frontal and lateral plane implant-shaft angles for the guide wire of the femoral component reamer were calculated with the computer navigation system and with an electronic caliper combined with micro-CT. There was a consistent disagreement between the navigation system and our measurement system in both the frontal plane and lateral plane with the pistol grip deformity. We found close agreement only for the frontal plane angle calculation in the presence of the slipped upper femoral epiphysis deformity, but calculation of femoral head size was inaccurate. The use of image-free navigation for the positioning of the femoral component appears questionable in these settings. One or more of the authors have received funding from the Wishbone Trust New Zealand (RPP) and from DePuy International, Leeds, UK (RPP).