增加胫骨平台后倾角度、后交叉韧带部分松解对全膝关节置换术后膝关节运动影响的实验研究

目的通过增加胫骨平台后倾角度或后交叉韧带（PCL）部分松解对全膝关节置换术（TKA）中屈曲间隙过紧进行处理,分析这两种方法对TKA术后膝关节运动学的影响。方法测量6例新鲜尸体膝关节标本在完整状态下、正常TKA、屈曲间隙过紧、增加胫骨平台后倾角以及PCL部分松解TKA术后膝关节屈曲0°、30°、60°、90°、120°时的前后松弛度、内外翻松弛度、旋转松弛度及最大屈曲度。结果屈曲过紧TKA与正常TKA相比,在屈曲30°、60°、90°和120°时前后松弛度、内外翻松弛度及旋转松弛度均显著较小（P〈0．05）。与屈曲过紧TKA相比,增加胫骨后倾角后,在屈曲30°、60°、90°和120°时前后松弛度、内外翻松弛度和旋转松弛度均明显增大（P〈0．05）。PCL部分松解与屈曲过紧TKA相比,在屈曲30°、60°、90°和120°时前后松弛度明显增加（P〈0．05）;旋转松弛度在屈曲30°、60°、90°时明显增加（P〈0．05）。与PCL部分松解相比,增加胫骨后倾角的内外翻松弛度在屈曲30°、60°、90°时明显较大（P〈0．05）;旋转松弛度在屈曲0°、30°、60°和90°时明显较大（P〈0．05）。屈曲过紧TKA的最大屈曲度（120．4°）与正常TKA（130．3°）及增加胫骨后倾角（131．1°）相比明显较小（P〈0．05）。增加后倾角与PCL部分松解（124．0°）相比,最大屈曲度较大,但差异无统计学意义（P=0．0816）。结论屈曲间隙过紧TKA术后膝关节的前后松弛度、内外翻松弛度、旋转松弛度和最大屈曲度均减小;增加胫骨平台后倾角后,前后松弛度、内外翻松弛度、旋转松弛度和最大屈曲度均明显增大;PCL部分松解仅能明显增大前后松弛度。因此对于TKA术中屈曲紧张的膝关节,增加胫骨平台后倾角比PCL部分松解能更好地改善膝关节的运动学。     

Tests for posterolateral instability of the knee in normal subjects. Results of examination under anesthesia

An apparently normal knee was examined in each of 100 subjects while they were under general or epidural anesthesia for an unrelated operation. The Lachman, anterior drawer, posterior drawer, and pivot-shift tests were negative in all knees. All knees were stable to varus and valgus stress at both 0 and 30 degrees of flexion. The external-rotation recurvatum test also was negative in all knees. A positive reversed pivot-shift sign was present in 35 per cent of the knees, suggesting that it may not signify abnormality, at least not without a negative test on the contralateral knee. The results of the posterolateral drawer test were variable, difficult to quantify, and did not always have a firm end-point. The amount of maximum external rotation of the tibia, measured from the reference line of the medial border of the foot, was extremely variable at both 30 and 90 degrees of flexion of the knee. External rotation, as determined by this reference, was slightly greater (averaging 9 degrees) at 90 than at 30 degrees of flexion. The normal range of maximum external rotation of the foot was 10 to 45 degrees at 30 degrees of flexion of the knee and 15 to 70 degrees at 90 degrees of flexion. The presence of a large angle of external rotation and a positive reversed pivot-shift sign correlated strongly with increased ligamentous laxity and mild varus alignment of the knee.     

内减张技术辅助前交叉韧带重建的运动学分析

目的观察关节镜下内减张技术辅助解剖单束重建前交叉韧带(ACL)患膝术后膝关节运动学恢复情况。 方法将2017年1月至2018年12月于昆明医科大学第一附属医院运动医学科就诊共80例ACL断裂的患者纳入研究，其中40例采用内减张技术辅助ACL解剖单束重建(实验组)，40例采用常规术式(对照组)。采用Opti_Knee膝关节三维运动分析系统，记录术后3、6、12月膝关节在步态过程中三维6自由度(屈伸角、内外翻角、内外旋角、前后位移、上下位移及内外位移)活动范围(最大值与最小值的差值)，同时与40例正常成人测量数据进行对比。计数资料比较采用卡方检验，两两比较采用配对t检验，多组间比较采用SNK分析。 结果术后3、6、12个月实验组与对照组患者最大步长、最小步长、步频差异无统计学意义(P >0.05)，与正常成人差异无统计学意义(P>0.05)。实验组术后3、6月内外旋角(F＝51.141、13.204)和前后位移(F＝51.246、12.207)活动范围均小于对照组(P<0.05)，且与正常成人相近(P>0.05)，两组间屈伸角、内外翻角、上下位移及内外位移活动范围均差异无统计学意义(P>0.05)，与正常成人差异无统计学意义(P>0.05)。术后12月两组间6个自由度活动范围相比差异无统计学意义(P>0.05)，均与正常成人相近(P>0.05)。 结论与传统术式相比，采用内减张技术重建ACL可早期获得更满意的膝关节运动学恢复疗效，膝关节运动学分析可更客观评价膝关节功能及稳定性。     

Limits of movement in the human knee. Effect of sectioning the posterior cruciate ligament and posterolateral structures

We applied specific forces and moments to the knees of fifteen whole lower limbs of cadavera and measured, with a six degrees-of-freedom electrogoniometer, the position of the tibia at which the ligaments and the geometry of the joint limited motion. The limits were determined for anterior and posterior tibial translation, internal and external rotation, and varus and valgus angulation from zero to 90 degrees of flexion. The limits were measured in the intact knee and then the changes that occurred with removal of the posterior cruciate ligament, the lateral collateral ligament, the popliteus tendon at its femoral attachment, and the arcuate complex were measured. The cutting order was varied, allowing us to determine the changes in the limits that occurred when each structure was cut alone and the amount of motion of the joint that was required for each structure to become taut and to limit additional motion when the other supporting structures had been removed. Removal of only the posterior cruciate ligament increased the limit for posterior tibial translation, with no change in the limits for tibial rotation or varus and valgus angulation. The additional posterior translation was least at full extension and increased progressively, reaching 11.4 millimeters at 90 degrees of flexion. The progressive increase in posterior translation with flexion was apparently due to slackening of the posterior portion of the capsule, as the translation nearly doubled when the posterolateral structures subsequently were removed. Removal of only the posterolateral extra-articular restraints increased the amount of external rotation and varus angulation. The average increase in external rotation depended on the angle of flexion; it was greatest at 30 degrees of flexion and decreased with additional flexion. At 90 degrees of flexion, the intact posterior cruciate ligament limited the increase in external rotation to only 5.3 degrees, less than one-half of the 13.0-degree increase that occurred at 30 degrees of flexion. Subsequent removal of the posterior cruciate ligament markedly increased external rotation at 90 degrees of flexion, resulting in a total increase of 20.9 degrees. The limit for varus angulation was normal as long as the lateral collateral ligament was intact. When the lateral collateral ligament was cut, the limit increased 4.5 degrees (approximately 4.5 millimeters of additional joint opening) when the knee was partially flexed (to 15 degrees).(ABSTRACT TRUNCATED AT 400 WORDS)     

Effect of frontal plane tibiofemoral angle on the stress and strain at the knee cartilage during the stance phase of gait

Subject‐specific three‐dimensional finite element models of the knee joint were created and used to study the effect of the frontal plane tibiofemoral angle on the stress and strain distribution in the knee cartilage during the stance phase of the gait cycle. Knee models of three subjects with different tibiofemoral angle and body weight were created based on magnetic resonance imaging of the knee. Loading and boundary conditions were determined from motion analysis and force platform data, in conjunction with the muscle‐force reduction method. During the stance phase of walking, all subjects exhibited a valgus–varus–valgus knee moment pattern with the maximum compressive load and varus knee moment occurring at approximately 25% of the stance phase of the gait cycle. Our results demonstrated that the subject with varus alignment had the largest stresses at the medial compartment of the knee compared to the subjects with normal alignment and valgus alignment, suggesting that this subject might be most susceptible to developing medial compartment osteoarthritis (OA). In addition, the magnitude of stress and strain on the lateral cartilage of the subject with valgus alignment were found to be larger compared to subjects with normal alignment and varus alignment, suggesting that this subject might be most susceptible to developing lateral compartment knee OA. © 2010 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 28:1539–1547, 2010     

In vivo strain patterns in the four major canine knee ligaments

Using mercury gauges, we measured strains in vivo in the four major ligaments of the canine knee joint as the tibia was loaded in valgus or varus at fixed angles of knee flexion. Free axial rotation of the tibia on the femur was allowed. Forces up to 78.4 N were applied to the tibia, producing moments of approximately 9 N-m. We found that with valgus loading, significant strains were observed in the medial collateral ligament at extension. At 45 degrees of flexion, the medial collateral, posterior cruciate, and anterior cruciate were strained. At 90 degrees of flexion, all four ligaments were strained. With varus loading, significant strains were found in the lateral collateral and anterior cruciate at extension. The lateral collateral and anterior cruciate ligaments were strained at 45 degrees of flexion. At 90 degrees of flexion, the lateral collateral, anterior cruciate, and posterior cruciate ligaments were strained. With valgus loading, the tibia rotated internally and the degree of axial rotation increased with flexion. External rotation of the tibia resulted from varus loading, and was relatively constant through the range of flexion. Thus when axial rotation is allowed, stability of the knee in response to valgus and varus loads is maintained by the cruciates as well as the collaterals, and the role of the cruciates increases with flexion and axial rotation.     

Somatosensory Function Influences Aberrant Gait Biomechanics Following Anterior Cruciate Ligament Reconstruction

Osteoarthritis is common following anterior cruciate ligament reconstruction (ALCR), and aberrant gait biomechanics are considered a primary contributor. Somatosensory dysfunction potentially alters gait biomechanics, but this association is unclear. Therefore, the purposes of this investigation were to compare somatosensory function between limbs and evaluate associations between somatosensory function and gait biomechanics linked to osteoarthritis development in individuals with ALCR. Seventy-three volunteers with ALCR participated. Gait biomechanics (peak vertical ground reaction force magnitude and loading rate, peak internal knee extension and valgus moments, peak knee flexion and varus angles, and quadriceps/hamstrings co-activation) were assessed as subjects walked at their preferred speed. The somatosensory function was assessed via joint position sense error (knee flexion) and vibratory perception threshold (femoral epicondyles, malleoli, and first metatarsal). Though somatosensory function did not differ between the ACLR and contralateral limbs, poorer joint position sense in the ACLR limb was associated with lower loading rates and internal knee extension moments, and greater co-activation. Poorer vibratory perception at the medial and lateral malleoli and first metatarsal head in the ACLR limb was associated with lower loading rates, greater internal knee valgus moments and varus angles, and greater co-activation. Poorer vibratory perception at the medial malleolus and first metatarsal head in the contralateral limb was associated with greater peak knee varus angles and internal knee valgus moments. These results suggest that future research evaluating rehabilitation approaches for improving somatosensory function is warranted as a potential approach for restoring normal gait biomechanics and reducing osteoarthritis risk. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 38:620–628, 2020     

Distribution of bone mineral density at the proximal tibia in knee osteoarthritis

One hundred and thirteen knees with osteoarthritis (OA) were studied to assess the distribution of bone mineral density (BMD) in the proximal tibia and the potential relation between osteoarthritis and osteoporosis in evaluating hip BMD. All patients had severe knee pain and were diagnosed with Kellgren and Lawrence grade IV osteoarthritis. According to the magnitude of the axial deformity, four categories were created: varus>10 degrees ( 28.3%), varus 4-10 degrees (38.9%), aligned 180 +/- 3 degrees (13.3%), and valgus>4 degrees (19.5%). For each category, the medial and lateral proximal tibial density were assessed. BMD was measured at the femoral neck and at 14 regions of interest (ROI) in the proximal part of the tibia using dual X-ray absorptiometry. Based on the femoral neck BMD, patients were classified according to the World Health Organization (WHO) definition of osteoporosis. The mean knee BMD was positively correlated with the hip BMD value (knee BMD m = 0.38 + 0.73 x hip BMD, r = 0.60, P<0.001). The knee BMD distribution of the 113 patients was negatively correlated with the axial deformity (BMD MT-LT = 5.15 - 0.027 x HKA, r = 0.77, P<0.0001). In the varus deformity, BMD of the medial side was higher than that of the lateral side with an important asymmetry (0.587 g/cm2). This asymmetry was also found in the valgus deformity for the lateral side but was less important (-0.112 g/cm2). With equal deformity, the asymmetry of BMD was higher in varus deformity (0.587 g/cm2) than in valgus deformity (-0.112 g/cm2). Asymmetry of the knee BMD distribution revealed that progression of the deformity (either varus or valgus) with joint space narrowing led to an increase in the medio-lateral difference of the proximal tibia density. Lesser severity of Kellgren and Lawrence grades may reveal different results. Twenty patients with osteoporosis developed knee osteoarthritis (OA) and the relation between osteoporosis and knee OA remains unclear.     

Biomechanical stability of intramedullary nailed high proximal third tibial fractures with cement augmented proximal screws

OBJECTIVE: Intramedullary nailing of nonarticular proximal tibia fractures can be affected by bone density resulting in loss of stability, fixation, and malalignment in osteopenic bone. This study was designed to quantify the biomechanical effects of augmenting proximal screws with cement in intramedullary nailing of high proximal third tibial fractures. DESIGN: In vitro biomechanical study using anatomic specimens. METHODS: Reamed nails were inserted into seven pairs of fresh-frozen cadaveric proximal tibiae and secured using two oblique and two transverse proximal screws. Paired tibiae were randomly assigned into two groups: cemented and noncemented proximal screw-holes. Bone cement was injected into the screw-holes before screw insertion in the cemented tibiae. Specimens were then tested in flexion/extension and varus/valgus to 12 Nm and in torsion to 7 Nm. Physical measurements of bone density were obtained to determine the effect of density on stability. MAIN OUTCOME MEASURES: Stability of the construct in both groups was analyzed and compared statistically using paired t tests. RESULTS: Cement augmentation of the proximal screws significantly increased mechanical stability in torsion and varus/valgus load configurations, with average decreases in rotational motion of 5.4 degrees +/- 1.6 degrees and 5.1 degrees +/- 5 degrees respectively. No change in stability was observed in flexion/extension loading. A trend toward decreased stability was seen in the uncemented construct in varus/valgus; cement augmentation of the proximal screws eliminated this effect. CONCLUSIONS: Lower bone density decreased the stability of the uncemented construct; however, cement augmentation of the proximal screws showed a trend to eliminate this effect in the varus/valgus loading configuration and should be considered when nailing proximal third tibial fractures in osteoporotic patients.     

How accurate are orthopaedic surgeons in visually estimating lower limb alignment?

This study aimed to determine the accuracy and reliability of visual estimation of limb alignment and knee flexion by orthopaedic surgeons when compared to recordings done by computed navigation. Orthopaedic surgeons attending a national conference were asked to place a lower limb synthetic bone model in 6 positions of the knee in the coronal and sagittal planes. These were simultaneously quantified and recorded by a computer navigation system. In the sagittal plane, 44%, 54% and 60% of the surgeons deviated by more than 5 degrees when positioning the knee in 0 degrees flexion, 10 degrees flexion and 90 degrees flexion respectively. In the coronal plane, 15%, 12% and 8% of the surgeons deviated by more than 5 degrees when positioning the knee in 0 degrees varus/valgus, 5 degrees varus and 5 degrees valgus respectively. Only 25% of the surgeons could position the knee both within 3 degrees of neutral varus/valgus and within 5 degrees of neutral flexion. Accuracy of visual estimation was not different when surgeons were compared based on time since residency, experience with TKA and experience with computer-assisted TKA. Visual estimation of knee alignment in both the sagittal and coronal plane is prone to error and may lead to inaccurate limb alignment during procedures such as TKA.     

Effect of tibial slope or posterior cruciate ligament release on knee kinematics

An experimental study using fresh human cadaver knees was designed to evaluate the effect of partial posterior cruciate ligament release or posterior tibial slope on knee kinematics after total knee arthroplasty. Varus and valgus laxity, rotational laxity, anteroposterior laxity, femoral rollback, and maximum flexion angle were evaluated in a normal knee, an ideal total knee arthroplasty, and a total knee arthroplasty in which the ligaments were made to be too tight in flexion. The total knee arthroplasty specimens then were subjected to either partial posterior cruciate ligament release or increased posterior tibial slope, and the tests were repeated. Posterior tibial slope increased varus and valgus laxity, anteroposterior laxity, and rotational laxity in the knee that had flexion tightness. Posterior cruciate ligament release corrected only anteroposterior tightness, and had no effect on the abnormal collateral ligament tightness. Increased posterior tibial slope significantly improved varus and valgus laxity and rotational laxity in the knee that was tight in flexion more than with release of the posterior cruciate ligament. Therefore increasing posterior tibial slope is preferable for a knee that is tight in flexion during total knee arthroplasty.     

Primary and coupled motions in the intact and the ACL-deficient knee: an in vitro study in the goat model.

Quadrupeds are commonly used as animal models to study healing of anterior cruciate ligament (ACL) reconstructions. While rabbits, dogs, goats, and sheep have been used, goats and sheep are increasingly being employed because of the larger joint size that facilitates surgery, ease of availability, and lower expense to maintain in the farm environment. In spite of this, little is known about the function of the ACL in controlling primary and coupled motions in the quadruped. We report here on the measurements of these motions in goats, with the application of anterior-posterior forces, varus-valgus moments, and internal-external moments in the intact and ACL-deficient knee. Sectioning the ACL caused significant increases in primary anterior translation, and in varus-valgus and internal rotations. The increases in anterior translation were similar in amount and dependence on flexion angle to those seen in human knees. The increase in varus averaged 7 degrees and did not depend on flexion angle, whereas the increase in valgus was significant only in the flexed knee. The increases in internal tibial rotation were greatest in extension, whereas the increases in external rotation were small and independent of flexion angle. When the ACL was cut, coupled internal rotation increased with an anterior force as well as a valgus moment. Large increases were seen in coupled anterior translation with the application of varus and valgus moments, whereas smaller increases were seen with internal and external moments. These findings demonstrate that the ACL restrains multiple motions in the goat knee. This study also provides baseline data for future studies of ACL reconstruction.     

Lower limb alignment and foot angle are related to stance phase knee adduction in normal subjects: A critical analysis of the reliability of gait analysis data

Anatomic and mechanical factors that affect loading in the knee joint can contribute to pathologic changes seen at the knee in degenerative joint disease and should be considered in treatment planning. The objectives of this study were to quantify the relationships between the alignment of the bones of the lower extremity, foot progression angle, and knee adduction moment, and to determine the reliability of our gait measurements. Gait analysis and complete radiographic evaluation of the lower extremity were performed on 11 healthy subjects. The gait measurements were recorded with an optoelectronic digitizer and a multicomponent force plate. The subjects who had radiographic measurements indicative of varus alignment of the lower extremity had statistically higher peaks in knee adduction moment in early stance. Conversely, those with valgus alignment of the lower extremity had statistically lower peaks in knee adduction moment in early stance. The subjects who had a large toe-out angle and low ankle inversion moment peaks in late stance had significantly lower peaks in knee adduction moment in late stance. These significant (low to moderate) correlations suggest that the limbs with more valgus alignment and those with a toe-out gait exhibited a reduced peak adduction moment at the knee. To verify the reproducibility of the data, gait analysis testing was performed on each lower limb on 2 separate days for each subject. Analysis of variance showed that there was no significant difference between test limbs or test days for each subject. Our results suggest that the alignment of the lower limb and the foot progression angle, which can be readily measured in a clinical setting, can serve as predictors of knee joint loading in healthy individuals. These findings may have important implications for both surgical and nonsurgical treatment of abnormalities of the knee joint.     

Outcomes and complications of fibular head resection

The fibular head is often used as donor graft material for reconstruction of defects of the distal radius. However little is known on the safety of such a procedure. This report describes the long-term donor-site morbidity following the procedure. Fourteen patients who underwent simple or marginal resections of the proximal fibula between 1990 and 2007 were reviewed. Subjective donor-site morbidity, knee and ankle range of motion and instability, presence of sensory or motor function loss, gait and fibular regeneration were assessed. The mean age at surgery was 25 years; six were male, eight were female and the mean follow-up was 11 years. Abnormal clinical findings were present in 10 patients (71.4 %): nine patients (64.3 %) had Grade 2 varus laxity at the knee confirmed by stress radiographs; one had sensory loss in the distribution of the superficial peroneal nerve. Patients with varus laxity had significantly higher mean age at surgery than those without varus laxity (p = 0.001). None had deformity at the knee or ankle. The range of joint movements was normal. All had a normal tibiotalar angle and none had proximal migration of the fibula. One patient demonstrated near-complete regeneration of the fibula. Donor-site morbidity following simple and marginal resection of the proximal fibula is acceptable. Older patients had a higher risk of demonstrable varus laxity at the knee but proximal fibula resection in children appears to be safe.     

Custom-fit total knee arthroplasty (OtisKnee) results in malalignment

We report on 4 patients who underwent total knee arthroplasty with OtisKnee system (OtisMed, Hayward, Calif). An image-free computer navigation system was used to evaluate the deformities and the recommended cuts. The recommended custom cuts were as follows: valgus/varus cuts on the femur (5.5 degrees valgus to 0.5 degrees varus) in reference to the mechanical axis, flexion cuts on the femur (4 degrees -9 degrees of flexion); femoral rotation was within 1 degrees of the epicondylar axis; valgus/varus cut on the tibia (3 degrees of valgus to 7.5 degrees of varus); tibial slope (5.5 degrees of anterior slope to 0.5 degrees of posterior slope). The custom OtisKnee system guides recommended alignment of the components that was more than 3 degrees off of mechanical axis. The potential for malalignment with this system places implants at high risk of early failure.     

Shape of the joint gap for 90° and 120° knee flexion after total knee arthroplasty

BACKGROUND: The joint gap is set rectangular at 90 degrees flexion during total knee arthroplasty (TKA). However, the condition of the joint gap in deep knee flexion is obscure. METHODS: The method for obtaining a posteroanterior view radiograph of the knee at 90 degrees flexion (the epicondylar view) was modified, and a method to obtain an anteroposterior view radiograph at 120 degrees flexion (deep flexion view) was established. With this method, subjects lie on the radiography table with their thighs placed on a device so their lower legs hang down in neutral rotation with a 1.5-kg weight attached to the ankle. The joint gap angle and medial and lateral joint space widths were measured on epicondylar view and deep flexion view radiographs in 20 normal male subjects, 20 normal female subjects, and 20 subjects after TKA. RESULTS: The joint gap was almost rectangular at two flexion angles in normal subjects. In the implanted knees, the gap angle was 1.4 degrees varus +/- 3.3 degrees (mean +/- standard deviation), and no significant difference was found between medial and lateral joint space widths at 90 degrees flexion. In contrast, the gap angle was 2.5 degrees varus +/- 2.5 degrees and the lateral joint space width was significantly wider than the medial joint space width at 120 degrees flexion (P < 0.001). The gap angle was more varus with a significant difference in the implanted knees than that in the normal subjects at 120 degrees flexion (P < 0.001). CONCLUSIONS: The joint gap was trapezoidal with a wider lateral side at 120 degrees flexion even though it was almost rectangular at 90 degrees flexion after TKA.     

Selective ligament release in total knee arthroplasty of the knee in valgus.

An approach to the valgus knee based on anatomic function of ligaments in flexion and extension consistently yields a knee that is balanced in flexion and extension when the implants have been positioned correctly. Two hundred thirty-one knees had a valgus deformity (range, 12 degrees-45 degrees) and were corrected with valgus alignment to 5 degrees by resecting the intact joint surfaces to match implant thickness. Femoral joint surfaces were aligned in 5 degrees valgus to the long axis of the femur and parallel to the epicondylar axis of the femur in flexion and extension. The tibial surfaces were aligned perpendicular to the long axis of the tibia. For knees that were tight in flexion and extension, the lateral collateral ligament and popliteus tendon were released. Those knees that remained tight only in extension had release of the iliotibial band. Posterior capsular release was done only when necessary for persistent lateral ligament tightness. Neither ligament advancement procedures nor varus or valgus stabilized implant systems were needed to achieve stability with this procedure. The knees with ligament releases all fell within a range of 4 degrees to 7 degrees mean varus and valgus laxity, and were not significantly different from one another. No cases of clinical instability occurred, and joint stability did not deteriorate with time.     

Recurrent knee valgus deformity in Ellis-van Creveld syndrome

We report a case of recurrent knee valgus deformity in a patient with Ellis-van Creveld syndrome. Varus osteotomy, distraction osteogenesis, or epiphyseal stapling is one treatment option for valgus malalignment to improve appearance, gait, and function. However, surgical correction of valgus knee deformity by varus osteotomies of the proximal tibia was not maintained postoperatively, necessitating additional varus osteotomies of the distal femur in this case. The main cause of recurrence was attributed to large bony defect of the anterior segment of the proximal tibia, in addition to depression of the lateral tibial plateau.     

Intraoperative passive kinematics of osteoarthritic knees before and after total knee arthroplasty.

Total knee arthroplasty is a successful procedure to treat pain and functional disability due to osteoarthritis. However, precisely how a total knee arthroplasty changes the kinematics of an osteoarthritic knee is unknown. We used a surgical navigation system to measure normal passive kinematics from 7 embalmed cadaver lower extremities and in vivo intraoperative passive kinematics on 17 patients undergoing primary total knee arthroplasty to address two questions: How do the kinematics of knees with advanced osteoarthritis differ from normal knees?; and, Does posterior substituting total knee arthroplasty restore kinematics towards normal? Osteoarthritic knees displayed a decreased screw‐home motion and abnormal varus/valgus rotations between 10° and 90° of knee flexion when compared to normal knees. The anterior–posterior motion of the femur in osteoarthritic knees was not different than in normal knees. Following total knee arthroplasty, we found abnormal varus/valgus rotations in early flexion, a reduced screw‐home motion when compared to the osteoarthritic knees, and an abnormal anterior translation of the femur during the first 60° of flexion. Posterior substituting total knee arthroplasty does not appear to restore normal passive varus/valgus rotations or the screw motion and introduces an abnormal anterior translation of the femur during intraoperative evaluation. © 2006 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 24:1607–1614, 2006     

Dynamic lower extremity alignment in children with achondroplasia

The purpose of this study is to analyze lower extremity dynamic malalignment during gait using a 3-dimensional kinematics and kinetics in 13 children (3-17 years old) with achondroplasia and to compare measurements of alignment and malrotation between gait, radiographic, and clinical measures. Gait analysis in the coronal plane showed a varus malalignment of the knee (19 +/- 13 degrees) and variable tibial torsion abnormalities (13 [internal] +/- 15.7 degrees). Radiographs also showed knee varus malalignment (16 +/- 9 degrees); however, there was poor correlation with gait analysis measures (P > 0.05). In the sagittal plane, radiographs showed genu recurvatum deformity (23.5 +/- 13.2 degrees), although the sagittal plane knee kinematics were normal. Kinetic analyses of the knee showed high internal knee valgus moments (external varus moments, 0.48 +/- 0.25 N m/kg), which were significantly different from the normal population (P < 0.05). In conclusion, there is a 3-dimensional, complex, dynamic deformity of the lower extremity present in children with achondroplasia. We recommend a very careful assessment of the limb focusing on both the static and dynamic varus deformity and tibial torsion using a combination of radiographic, clinical, and gait analysis.