The role of flexion contracture on outcomes in primary total knee arthroplasty

This study examined the role that flexion contracture plays in postoperative outcomes after total knee arthroplasty using a retrospective database review. The relationships between preoperative and postoperative knee extension, walking ability, stair climbing ability, Knee Society scores, pain scores, and knee function scores were studied in 5,622 knees. A preoperative flexion contracture was associated with an increased incidence of a persistent postoperative flexion deformity. A postoperative flexion contracture was associated with poorer postoperative results. Furthermore, a postoperative hyperextension deformity of greater than 10 degrees was associated with an increased risk of suboptimal pain and Knee Society scores. Knee extension deformities play a substantial detrimental role in the functional outcome of primary total knee arthroplasty.     

Magnetic resonance image analysis of meniscal translation and tibio‐menisco‐femoral contact in deep knee flexion

The purpose of this study was to clarify meniscal displacement and cartilage–meniscus contact behavior in a full extension position and a deep knee flexion position. We also studied whether the meniscal translation pattern correlated with the tibiofemoral cartilage contact kinematics. Magnetic resonance (MR) images were acquired at both positions for 10 subjects using a conventional MR scanner. Subjects achieved a flexion angle averaging 139° ± 3°. Both medial and lateral menisci translated posteriorly on the tibial plateau during deep knee flexion. The posterior translation of the lateral meniscus (8.2 ± 3.2 mm) was greater than the medial (3.3 ± 1.5 mm). This difference was correlated with the difference in tibiofemoral contact kinematics between medial and lateral compartments. Contact areas in deep flexion were approximately 75% those at full extension. In addition, the percentage of area in contact with menisci increased significantly due to deep flexion. Our results related to meniscal translation and tibio‐menisco‐femoral contact in deep knee flexion, in combination with information about force and pressure in the knee, may lead to a better understanding of the mechanism of meniscal degeneration and osteoarthritis associated with prolonged kneeling and squatting. © 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 26:673–684, 2008     

Fluoroscopic analysis of knee arthroplasty kinematics during deep flexion kneeling

Achieving deep knee flexion >145 degrees is a goal of many patients receiving knee arthroplasty in Asia and the Middle East, yet it is unknown whether knees with implants move similar to the natural knee in these postures. We studied 18 of 36 consecutively operated knees that were able to flex >145 degrees using fluoroscopic analysis during kneeling to maximum flexion. An average of 9 degrees tibial internal rotation was observed in deep flexion. Posterior condylar translations were observed from 80 degrees to 120 degrees flexion, and the condyles translated forward in flexion beyond 120 degrees. Separation of the condyles from the tibial surface was observed in 9 knees at flexion >130 degrees. Very deep flexion can be achieved and is well accommodated using contemporary posterior-stabilized knee arthroplasty, but the kinematics differ from the intact natural knee.     

Kneeling kinematics after total knee arthroplasty: anterior-posterior contact position of a standard and a high-flex tibial insert design

Deep flexion activities including kneeling are desired by patients after total knee arthroplasty. This in vivo radiographic study sought to reveal the effect of tibial insert design on tibiofemoral kinematics during kneeling. One group of patients received standard posterior stabilized tibial inserts, whereas the other group received posterior stabilized tibial inserts (Flex inserts) that were designed to allow more flexion. The patients with the Flex inserts achieved greater range of motion without different tibiofemoral contact behavior.     

In‐vivo patellar tendon kinematics during weight‐bearing deep knee flexion

This study quantified in‐vivo 3D patellar tendon kinematics during weight‐bearing deep knee bend beyond 150°. Each knee was MRI scanned to create 3D bony models of the patella, tibia, femur, and the attachment sites of the patellar tendon on the distal patella and the tibial tubercle. Each attachment site was divided into lateral, central, and medial thirds. The subjects were then imaged using a dual fluoroscopic image system while performing a deep knee bend. The knee positions were determined using the bony models and the fluoroscopic images. The patellar tendon kinematics was analyzed using the relative positions of its patellar and tibial attachment sites. The relative elongations of all three portions of the patellar tendon increased similarly up to 60°. Beyond 60°, the relative elongation of the medial portion of the patellar tendon decreased as the knee flexed from 60° to 150° while those of the lateral and central portions showed continuous increases from 120° to 150°. At 150°, the relative elongation of the medial portion was significantly lower than that of the central portion. In four of seven knees, the patellar tendon impinged on the tibial bony surface at 120° and 150° of knee flexion. These data may provide useful insight into the intrinsic patellar tendon biomechanics during a weight‐bearing deep knee bend and could provide biomechanical guidelines for future development of total knee arthroplasties that are intended to restore normal knee function. © 2012 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 30:1596–1603, 2012     

下颈椎在屈伸运动时的应力分布研究

目的探讨下颈椎屈伸运动对其应力分布的影响。方法取5具成人新鲜尸体颈椎标本(C2-C7),通过施加最大载荷为2.34N.m的纯扭矩,使颈椎产生前屈和后伸运动,记示C4、C5、C6前柱,中柱和后柱的应变。结果颈椎前屈时,前柱和中柱承受压应力,后柱承受拉应力,且前柱的应力大于中柱和后柱(P<0.05);后伸时,前柱受拉应力,中柱和后柱承受压应力,且前柱的应力最大(P<0.05)。前柱的应力前屈小于后伸(P<0.01),中柱的应力在前屈和后伸时相差不大,后柱的应力前屈大于后伸(P<0.01)。对于三个椎体相比较而言,前屈和后伸时前柱的应力最大(P<0.01),而C4-6前柱的应力在屈伸时无差别。中柱的应力在前屈时C4、C5较大,与C6有差别(P=0.03),而后伸时无差别。后柱的应力在前屈时,三个椎体无差别(P=0.02)。结论下颈椎屈伸运动过程中应力的变化情况可能与颈椎病的发病机制有一定的关系。     

In vivo comparison of knee kinematics for subjects having either a posterior stabilized or cruciate retaining high-flexion total knee arthroplasty

The objective of this study was to determine the in vivo kinematics for subjects having either a fixed posterior stabilized (PS) or cruciate retaining (CR) high-flexion total knee arthroplasty (TKA). Three-dimensional kinematics from full extension to maximum flexion were determined for 30 subjects (15 PS, 15 CR) using fluoroscopy. On average, the PS subjects demonstrated 112 degrees of weight-bearing (WB) flexion, -6.4 mm of posterior femoral rollback, and 2.9 degrees of axial rotation. The CR subjects averaged 117 degrees of WB flexion, -4.9 mm of posterior femoral rollback, and 4.8 degrees of axial rotation. Posterior femoral rollback of the lateral condyle occurred for all PS TKAs and in 93% of the CR TKAs. Only 2 subjects in each group experienced greater than 1.0 mm of condylar lift-off. Subjects in both TKA groups demonstrated excellent WB ranges of motion and kinematic patterns similar to the normal knee, but less in magnitude.     

In vivo flexion/extension of the normal cervical spine

Twenty-two women (age range 25-49 years, average 30.9 years) and twenty-two men (age range 23-42 years, average 31.6 years), all healthy and asymptomatic, underwent passive flexion/extension examinations of the cervical spine. Functional x-rays were taken and analyzed using a computer-assisted method that quantified intervertebral rotations, translations, and locations of the centers of rotation for each level C1-C2-C6-C7. The aim of the study was to establish values for these parameters for a normal population as related to age and gender. In the process, a statistically significant difference was found in the average value of rotation between male and female groups at the C5-C6 level. A new parameter, the ratio between translation and rotation, was also established and may prove useful for clinical diagnoses. This parameter has a smaller error associated with it than do pure translations and may aid the clinician by helping to account for the large variation in rotatory ranges of motion within the population. This translation/rotation ratio indicated highly significant differences in the lower segments of the cervical spine between gender groups.     

Monolateral external fixation for the progressive correction of neurological spastic knee flexion contracture in children

The purpose of this study was to report the results of the surgical treatment of spastic knee flexion contracture using tenotomy and progressive correction by external fixator–distractor devices. The study design involved a prospective observational study of 16 knees in nine patients with spastic flexion contracture greater than 30°. Treatment was indicated for both ambulatory and nonambulatory patients; and, in the latter group when sitting or personal hygiene was compromised. The average age was 11.6 years (range 10–17). Five of the patients were male and four female. There was one case of hemiplegia (11.1%), two cases of paraplegia (22.2%), and six cases of quadriplegia (66.7%). Six patients retained some walking capacity, while three had none. In all cases, distal lengthening of the hamstrings was carried out. A monolateral fixator with a gradual correction device was applied for a period of 4.8 weeks. The average follow-up was 26.6 months. The preoperative straight-leg raise was 55°. The popliteal angle was 58° preoperatively (range 30–80°), 8.5° on removal of the fixator, and 20° at the end of the follow-up. Complications: There were no superficial or deep infections, and no fractures or distal sensory–motor alterations. There was one case of arthrodiatasis of the knee (6.3%) which was resolved when the fixator was removed, and 11 cases of pin-track infection (68.7%) which were resolved with local care and oral antibiotics. To conclude, spastic knee flexion contracture can be treated gradually with monolateral external fixator with distraction devices, and with distraction modules which prevent acute stretching of the posterior neurovascular structures of the knee.     

Three‐dimensional patellar motion at the natural knee during passive flexion/extension. An in vitro study

Patellar maltracking may result in many patellofemoral joint (PFJ) disorders in the natural and replaced knee. The literature providing quantitative reference for normal PFJ kinematics according to which patellar maltracking could be identified is still limited. The aim of this study was to measure in vitro accurately all six‐degrees‐of‐freedom of patellar motion with respect to the femur and tibia on 20 normal specimens. A state‐of‐the‐art knee navigation system, suitably adapted for this study aim, was used. Anatomical reference frames were defined for the femur, tibia, and patella according to international recommendations. PFJ flexion, tilt, rotation, and translations were calculated in addition to standard tibiofemoral joint (TFJ) kinematics. All motion patterns were found to be generally repeatable intra‐/interspecimens. PFJ flexion was 62% of the corresponding TFJ flexion range; tilt and translations along femoral mediolateral and tibial proximodistal axes during TFJ flexion were found with medial, lateral, and distal trends and within 12°, 6 and 9 mm, respectively. No clear pattern for PFJ rotation was observed. These results concur with comparable reports from the literature and contribute to the controversial knowledge on normal PFJ kinematics. Their consistence provides fundamental information to understand orthopedic treatment of the knee and for possible relevant measurements intraoperatively. © 2009 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 27:1426–1431, 2009     

A Comparative Study on the Long-Term Outcome of Total Knee Arthroplasty Performed for Knees Stiff in Extension and Those Stiff in Flexion

Background

Patients with chronic stiff knee with extremely restricted arc of motion (AOM ≤ 20°) may present with stiffness either in extension (stiff in extension [SE]) or in flexion (stiff in flexion [SF]). The difference in the functional outcome after total knee arthroplasty between these 2 groups has not been elaborated in literature.

In vivo knee kinematics during stair and deep flexion activities in patients with bicruciate substituting total knee arthroplasty

Orthopedic surgeons and their patients continue to seek better functional outcomes after total knee arthroplasty. The bicruciate substituting (BCS) total knee arthroplasty design has been introduced to achieve more natural knee mechanics. The purpose of this study was to characterize kinematics in knees with BCS arthroplasty during deep flexion and stair activities using fluoroscopy and model-image registration. In 20 patients with 25 BCS knees, we observed average implant flexion of 128° during kneeling and consistent posterior condylar translations with knee flexion. Tibial rotations were qualitatively similar to those observed in the arthritic natural knee. Knee kinematics with BCS arthroplasty were qualitatively more similar to arthritic natural knees than knees with either posterior cruciate-retaining or posterior-stabilized arthroplasty.     

全膝人工关节股骨假体屈曲原因分析及其对疗效影响

目的:探讨全膝人工关节置换(TKR)术中股骨假体屈曲的原因及其对疗效的影响。方法:回顾性分析全膝人工关节置换手术123膝(78例),发现17膝股骨假体发生不同程度的屈曲,106膝无屈曲。比较股骨假体屈曲组和非屈曲组手术前后的HSS评分、膝关节活动范围和屈曲挛缩畸形等情况,并测量屈曲角(∠CAB)和屈曲距离(BC)。结果:∠CAB为7°~19°,平均11.3;°BC为2~4 mm,平均2.6 mm。经过平均38个月(15~50个月)的随访,HSS评分和膝关节活动范围,术前屈曲组与非屈曲组均无显著性差异(P>0.05),但术后屈曲组明显低于非屈曲组(P=0.01或P<0.01);术后均显著高于术前(P=0.02或P<0.01)。术后屈曲挛缩例数和角度均具有显著性差异(P<0.01),屈曲组明显多于和大于非屈曲组,两组术后与术前相比均有显著差异(屈曲组P<0.05,非屈曲组P<0.01),即各组术后屈曲挛缩均有明显改善。结论:在TKR术中发生股骨假体屈曲的主要原因是非水平安装、股骨后髁截骨量不足、前后髁屈曲位截骨和股骨后髁骨赘清除不彻底等,而股骨假体屈曲对TKR手术疗效的主要影响是增加术后膝关节屈曲挛缩发生率,造成伸膝功能障碍。     

In vivo flexor tendon forces increase with finger and wrist flexion during active finger flexion and extension.

The effects of different hand motions and positions used during early protected motion rehabilitation on tendon forces are not well understood. The goal of this study was to determine in vivo forces in human flexor digitorum profundus (FDP) and flexor digitorum superficialis (FDS) tendons of the index finger during active unresisted finger flexion and extension. During open carpal tunnel surgery (n = 12), flexor tendon forces were acquired with buckle force transducers, and finger positions were recorded on video while subjects actively flexed and extended the fingers at two different wrist angles. Mean in vivo FDP tendon forces varied between 1.3N +/- 0.9 N and 4.0 N +/- 2.9 N while mean FDS tendon forces ranged from 1.3N +/- 0.5 N to 8.5 N +/- 10.7 N. FDP force increased with active finger flexion at both wrist angles of 0 degrees or 30 degrees flexion. FDS force increased with finger flexion when the wrist was in 30 degrees flexion, but was unchanged when the wrist was in 0 degrees of flexion. Tendon forces were similar regardless of whether the fingers were moving in the flexion or extension direction. Active finger flexion and extension with the wrist at 0 degrees and 30 degrees flexion may be used during early rehabilitation protocols with limited risk of repair rupture. This risk can be further decreased for a FDS tendon repair by reducing wrist flexion angle.     

In vivo medial and lateral tibial loads during dynamic and high flexion activities.

Though asymmetric loading between the medial and lateral compartments of total knee replacements may contribute to implant loosening and failure, the in vivo contact force distribution during dynamic daily activities remains unknown. This study reports in vivo medial and lateral contact forces experienced by a well-aligned knee implant for a variety of activities. In vivo implant motion and total axial load data were collected from a single knee replacement patient performing treadmill gait (hands resting on handlebars), step up/down, lunge, and kneel activities. In vivo motion was measured using video fluoroscopy, while in vivo axial loads were collected simultaneously using an instrumented tibial component. An elastic foundation contact model employing linear and nonlinear polyethylene material properties was constructed to calculate medial and lateral contact forces based on the measured kinematics, total axial loads, and centers of pressure. For all activities, the predicted medial and lateral contact forces were insensitive to the selected material model. The percentage of medial to total contact force ranged from 18 to 60 for gait, 47 to 65 for step up/down, and 55 to 60 for kneel and lunge. At maximum load during the motion cycle, medial force was 1.2 BW for gait and 2.0 BW for step up/down, while the corresponding lateral forces were 1.0 and 1.5 BW, respectively. At mean load in the final static pose, medial force was 0.2 BW for kneel and 0.9 BW for lunge, with corresponding lateral forces of 0.1 and 0.7 BW, respectively. For this patient, a constant load split of 55% medial-45% lateral during loaded activity would be a reasonable approximation for these test conditions.     

Treatment of fixed knee flexion deformity and crouch gait using distal femur extension osteotomy in cerebral palsy

Purpose

The purpose of this study was to evaluate the results of distal femur extension osteotomy and medial hamstring lengthening in the treatment of fixed knee flexion deformity in patients with spastic diparetic cerebral palsy.

Methods

A retrospective study was done in a group of 12 diparetic cerebral palsy patients. A distal femur extension osteotomy was performed as part of multilevel surgery on lower limbs. The fixed knee flexion deformity was measured during physical examination, whereas hip and knee flexion in the stance phase and anterior pelvic tilt were both analyzed at kinematics. The pre- and post-surgery results were compared and analyzed statistically. A medical record review was done in order to identify the complications. The mean follow-up was 28 months.

Results

A significant reduction of fixed knee flexion deformity at physical examination and knee flexion in the stance phase at kinematics was observed, but with no decrease in hip flexion. As a non-desired effect, there was an increase in anterior pelvic tilt after surgical procedures. With regard to complications, a single patient had skin breakdown at a calcaneous area on one side and the recurrence of deformity was seen in 27% of cases.

Conclusions

In this study, in which fixed knee flexion deformity did not exceed 40° before surgery, the distal femur extension osteotomy was effective in increasing knee extension in the stance phase. However, an increase in anterior pelvic tilt, deformity recurrence and necessity for walking aids are possible complications of this procedure.     

In vivo kinematics of the ACL during weight-bearing knee flexion.

No study has investigated the three-dimensional morphological changes of the anterior cruciate ligament (ACL) during functional activities in vivo. The purpose of this study was to analyze the elongation, rotation (twist), and orientation of the ACL during weight-bearing flexion in five human subjects using dual-orthogonal fluoroscopic images and MR image-based computer models. The ACL consistently decreased in length with flexion. At 90 degrees , the length decreased by 10% compared to its length at full extension. The ACL twisted internally by only 20 degrees at 30 degrees of flexion. The ACL was oriented more vertically (approximately 60 degrees ) and slightly laterally (approximately 10 degrees ) at low flexion angles. These data on in vivo ligament elongation demonstrate that the ACL plays a more important role in lower flexion angles than at higher flexion angles during weight-bearing flexion. These data also suggest that successful ACL reconstruction should not only restore the ligament's elongation behavior, but also its rotational and orientation characteristics, so that normal ACL biomechanics are restored.     

Coda Motion运动分析系统测量健康人颈椎侧屈活动度的准确性分析

目的:探讨Coda Motion运动分析系统测量颈椎侧屈活动度的准确性,为临床及科研实践探索一种新的测量工具。方法:选择43名健康志愿者作为研究对象,采用Coda Motion运动分析系统和"金标准"X线两种工具同时测量其颈椎侧屈活动度。运用散点图、皮尔森相关系数r评估Coda Motion运动分析系统测量颈椎侧屈活动度的准确性。结果:Coda Motion运动分析系统与X线测量出的颈椎侧屈活动度差异无统计学意义(P0.05)。两种工具在测量右侧屈、左侧屈以及总侧屈活动度呈正相关,皮尔森相关系数分别为0.72、0.85和0.90。结论:Coda Motion运动分析系统测量颈椎侧屈活动度的准确性好,可能作为一种新型测量工具用于临床及科研测量颈椎侧屈活动度的实践中。