Q-angle influences tibiofemoral and patellofemoral kinematics.

Numerous surgical procedures have been developed to correct patellar tracking and improve patellofemoral symptoms by altering the Q-angle (the angle between the quadriceps load vector and the patellar tendon load vector). The influence of the Q-angle on knee kinematics has yet to be specifically quantified, however. In vitro knee simulation was performed to relate the Q-angle to tibiofemoral and patellofemoral kinematics. Six cadaver knees were tested by applying simulated hamstrings, quadriceps and hip loads to induce knee flexion. The knees were tested with a normal alignment, after increasing the Q-angle and after decreasing the Q-angle. Increasing the Q-angle significantly shifted the patella laterally from 20 degrees to 60 degrees of knee flexion, tilted the patella medially from 20 degrees to 80 degrees of flexion, and rotated the patella medially from 20 degrees to 50 degrees of flexion. Decreasing the Q-angle significantly tilted the patella laterally at 20 degrees and from 50 degrees to 80 degrees of flexion, rotated the tibia externally from 30 degrees to 60 degrees of flexion, and increased the tibiofemoral varus orientation from 40 degrees to 90 degrees of flexion. The results show that an increase in the Q-angle could lead to lateral patellar dislocation or increased lateral patellofemoral contact pressures. A Q-angle decrease may not shift the patella medially, but could increase the medial tibiofemoral contact pressure by increasing the varus orientation.     

The influence of altered lower-extremity kinematics on patellofemoral joint dysfunction: a theoretical perspective

Although patellofemoral pain (PFP) is recognized as being one of the most common disorders of the lower extremity, treatment guidelines and underlying rationales remain vague and controversial. The premise behind most treatment approaches is that PFP is the result of abnormal patellar tracking and/or patellar malalignment. Given as such, interventions typically focus on the joint itself and have traditionally included strengthening the vastus medialis oblique, taping, bracing, soft tissue mobilization, and patellar mobilization. More recently, it has been recognized that the patellofemoral joint and, therefore, PFP may be influenced by the interaction of the segments and joints of the lower extremity. In particular, abnormal motion of the tibia and femur in the transverse and frontal planes may have an effect on patellofemoral joint mechanics. With this in mind, interventions aimed at controlling hip and pelvic motion (proximal stability) and ankle/foot motion (distal stability) may be warranted and should be considered when treating persons with patellofemoral joint dysfunction. The purpose of this paper is to provide a biomechanical overview of how altered lower-extremity mechanics may influence the patellofemoral joint. By addressing these factors, better long-term treatment success and prevention may be achieved.     

中国人膝关节跑步运动学性别差异研究

目的探讨中国人正常膝关节跑步运动学并比较性别差异。 方法对40名健康成年人(22名男性和18名女性)进行膝关节6-自由度(6-DOF)跑步运动学研究。应用SPSS v16.0软件进行统计分析,用单因素方差分析比较不同性别的运动学参数差异。 结果正常人跑步运动学存在性别差异,主要出现在内/外翻角度上,女性平均外翻角度大于男性(F＝5.563,P<0.05),摆动期最大外翻角度(F＝6.476,P<0.05)及平均角度(F＝12.397,P<0.01)大于男性,而男性的最大内翻角度大于女性(F＝8.425,P<0.01)。女性在摆动期内外旋活动度(F＝7.220,P<0.01)和前位移最大值(F＝5.966,P<0.05)大于男性。膝关节屈/伸、胫骨内/外位移和远/近位移等差异无统计学意义(P>0.05)。 结论跑步时膝关节运动学与性别相关,运动学差异主要存在于冠状面和横截面上。本研究提供了不同性别的正常青年中国人跑步运动学参数,可为预防伤害、疾病治疗及康复训练提供有价值的信息。     

Influence of lunate type on scaphoid kinematics

PURPOSE: To assess the influence of lunate type on scaphoid kinematics. METHODS: One hundred normal wrists had fluoroscopic assessment of the wrist in maximal radial, neutral, and ulnar deviation. The shortest distance in a neutral position between the capitate and triquetrum, C-T distance, determined lunate type. A type I lunate had a C-T distance of < or =2 mm, a type II lunate > or =4 mm, and an intermediate group lay between these values. Scaphoid flexion and translation in radial and ulna deviation was measured. RESULTS: There were 18 subjects with a type I lunate, 19 with an intermediate lunate, and 63 with a type II lunate. There was no statistically significant difference between lunate type, subject age, or hand dominance. There was a statistically significant higher proportion of women with a type I lunate. Subjects with a type II lunate had a statistically greater amount of flexion during radioulnar deviation as determined by CR index (0.79 vs 0.91) and scaphoid flexion index (0.21 vs 0.09). Subjects with a type II lunate had statistically less translation during radioulnar deviation as determined by translation ratio (0.22 vs 0.31) and scaphoid inclination index (0.18 vs 0.23). The average scaphoid kinematic index in subjects with a type II lunate was 1.24, intermediate 0.86, and type I 0.42. A scaphoid kinematic index of greater than 1 indicates the scaphoid has more flexion during radioulnar deviation than translation. CONCLUSIONS: Wrists with a type I lunate show statistically greater scaphoid translation with radial deviation. Wrists with a type II lunate show statistically greater scaphoid flexion with radial deviation. Intermediate lunates have intermediate scaphoid mechanics. This allows the surgeon to determine the likely wrist scaphoid mechanics based on the lunate type determined from a single posterior-anterior x-ray.     

Influence of total knee arthroplasty on patellar kinematics and contact characteristics

Purpose  

Femoro-patellar complications are one of the most common problems after total knee arthroplasty (TKA). TKA components that reduce patellar loads and preserve physiological patellar kinematics should reduce these problems. Therefore, we evaluated the patellar kinematics and the retro-patellar contact characteristics in both the intact knee and in the TKA-knee.     

Influence of prosthetic joint line position on knee kinematics and patellar position

Prosthetic joint line position after total knee arthroplasty (TKA) was investigated using sagittal roentgenograms obtained from six fresh frozen cadaver knees. A specially designed knee testing device was developed that allowed for a controlled flexion angle while maintaining a constant quadriceps force. Pre- and postoperative roentgenograms were obtained from 30 degrees to 120 degrees in 15 degrees intervals. Steinman pins inserted into the medial femoral condyle and patella were used as reference points in the roentgenograms. A displacement vector between the medial femoral condyle and tibial plateau was used to analyze the tibiofemoral joint relationship. The functional patellar length (Insall-Salvati ratio), was used to determine correct patellar height. Another displacement vector was used to measure the patellofemoral joint relationship, and the angle between the patellar cut surface and femoral long axis was also calculated. Bone resection thickness from the femoral, tibial, and patellar surfaces was equal to the prosthetic thickness. This reconstructive scheme produced correct ligament balance and flexibility of the knee without the aid of tensioning devices or special measurements. Patellar tracking appeared to be identical before and after surgery. This accurate but simple surgical technique also reproduced normal knee extensor mechanisms that may influence longevity and long-term results of TKA.     

Diagnosis of chronic lower-extremity ischemia

The noninvasive vascular laboratory provides critically important objective and cost-effective information to supplement a careful history and physical examination in the evaluation of patients with CLEI. Optimal cost-effective ordering and interpretation of vascular tests will always depend on a sophisticated knowledge of vascular disease and detailed knowledge of the individual patient. A keen awareness of the limitations of each form of testing and potential sources of error is mandatory. Noninvasive vascular testing allows quantitative, physiologic assessment of lower extremity ischemia and provides the scientific basis for our modern therapeutic approaches to the care of patients with arterial occlusive disease. Clearly, the vascular lab provides much of the objective diagnostic data on which the modern practice of vascular surgery is built.     

Q-angle and J-sign: Indicative of Maltracking Subgroups in Patellofemoral Pain

Mechanical factors related to patellofemoral pain syndrome and maltracking are poorly understood. Clinically, the Q-angle, J-sign, and lateral hypermobility commonly are used to evaluate patellar maltracking. However, these measures have yet to be correlated to specific three-dimensional patellofemoral displacements and rotations. Thus, we tested the hypotheses that increased Q-angle, lateral hypermobility, and J-sign correlate with three-dimensional patellofemoral displacements and rotations. We also determined whether multiple maltracking patterns can be discriminated, based on patellofemoral displacements and rotations. Three-dimensional patellofemoral motion data were acquired during active extension-flexion using dynamic MRI in 30 knees diagnosed with patellofemoral pain and at least one clinical sign of patellar maltracking (Q-angle, lateral hypermobility, or J-sign) and in 37 asymptomatic knees. Although the Q-angle is assumed to indicate lateral patellar subluxation, our data supported a correlation between the Q-angle and medial, not lateral, patellar displacement. We identified two distinct maltracking groups based on patellofemoral lateral-medial displacement, but the same groups could not be discriminated based on standard clinical measures (eg, Q-angle, lateral hypermobility, and J-sign). A more precise definition of abnormal three-dimensional patellofemoral motion, including identifying subgroups in the patellofemoral pain population, may allow more targeted and effective treatments.