[Rotational Laxity of the Knee Joint - In Vivo MRI Study]. / Rotacní laxita kolenního kloubu ­ in vivo NMR studie.

PURPOSE OF THE STUDY The purpose of the study was to evaluate tibio-femoral rotation during a simulated squat and to investigate the relationship between the rotational position of the femur in full extension and the amount of external rotation of the femur on the tibia during flexion. MATERIAL AND METHODS Part 1: MRIs of volunteers Data on healthy knees of 10 volunteers were obtained using 2D MRI measurements. The foot and the ankle were fixed to prevent rotation and adduction/abduction movements. Sagittal MRIs of the knees have been performed in 4 positions of flexion. The amount of longitudinal rotation in each position of flexion was calculated. Part 2: Mathematical model experiment a) The model of the femur has been positioned in the 3D coordinate system in full extension and at 12.8° of internal rotation and then flexed to 90° without longitudinal rotation. The distance between the centre of the femoral head and the sagittal plane passing through the centre of the knee was then measured. b) Subsequently, the femur was flexed and rotation allowed to retain femoral head within the sagittal plane. The amount of femoral rotation was then calculated. RESULTS Part 1: In full extension the femur was on average in 12.8° of IR relative to the tibia. By 90° flexion femur rotated on average 12.2° externally. Part 2: a)From full extension to 90° flexion the femoral head moved 93.1 mm laterally from the sagittal plane. b)Between full extension and 90° flexion the femur rotated 12.8° externally, a degree which corresponds to the amount of initial internal rotation of the femur in full extension. DISCUSSION The most important finding of the presented in vivo study lies in the fact that in normal knees with tibia rotationally fixed flexion is always coupled with femoral external rotation in order to keep the femoral head in the acetabulum. This rotation is obligatory. CONCLUSIONS We have demonstrated that if the tibia is rotationally fixed, the knee flexion is possible only when accompanied by femoral external rotation to keep the femoral head in the acetabulum. A mathematical description of the experiment has been proposed, the results of which confirm the stated premise. This finding can be explained by initial internal rotation of the femur in full extension of the knee and is allowed by the shape of articulating bones and tension of soft tissues Key words: knee, terminal extension, knee rotation, knee movement, MRI, hip joint.

[Anterior Cruciate Ligament Tears - Influence on Terminal Extension]. / Ruptury predního zkrízeného vazu ­ vliv na terminální extenzi.

PURPOSE OF THE STUDY The aim of this paper was to compare terminal extension in normal and anterior cruciate ligament (ACL) deficient knees, and therefore to determine the role of the ACL during this motion. MATERIAL AND METHODS Ten knees with ACL tears (7 knees with recent ACL tears, 3 knees with long-standing tears) and 10 normal contralateral knees have been examined using MRI in passive hyperextension, 20° flexion and 20° flexion with a 9 kg posteriorly directed load on the femur. Movements of the femoral condyles on the tibia were calculated using previously described methods. RESULTS 1. Under the load at 20° flexion, knees with ACL tear showed posterior femoral subluxation (equivalent to a Lachman test), chronic tears being more unstable. Contralateral normal knees were antero-posteriorly stable. In hyperextension, both femoral condyles subluxed posteriorly in ACL tears but not in normal knees. 2. In all knees with ACL tear, the lateral femoral condyle moved posteriorly from hyperextension to 20°, equating to femoral external rotation. 3. The longitudinal rotation axis during terminal extension in normal knees was medial but in ACL tears it was central causing the medial femoral condyle to move forward from hyperextension to 20°. In normal knees, the medial femoral condyle did not move antero-posteriorly from hyperextension to 20° flexion. DISCUSSION Internal rotation of the femur during terminal extension has been recognized for 150 years. The question remains: what causes the usual combination of longitudinal rotation and extension? In the current literature ACL is considered to be responsible for internal rotation of the femur during terminal extension of the knee. So far, as we are aware, the kinematics of terminal extension, including hyperextension, have not been reported after ACL tear in the living knee. CONCLUSIONS Results of this study imply that: 1. The ACL prevents anterior tibial subluxation in hyperextension. 2. The ACL does not cause rotation in terminal extension. 3. The ACL locates the axis of longitudinal rotation in terminal extension. We hope that by studying living knees with and without ACL tear we may not only clarify the nature and mechanism of rotation in terminal extension, and hence the role of the ACL, but do so in a context of direct clinical relevance. Key words: knee, terminal extension, ACL tear, axis of longitudinal rotation, antero-posterior instability, MRI.

[Two-Stage Revision for Periprosthetic Infection of the Total Hip Arthroplasty: a Comparison of Two Methods]. / Srovnání klinických výsledku skupiny pacientu neartikulovaného a artikulovaného spaceru pri dvoudobé reimplantaci TEP kycelního kloubu pro periprotetický infekt.

PURPOSE OF THE STUDY The purpose of the study is a retrospective comparison of results of the two-stage revision total hip arthroplasty using a non-articulating and an articulating spacer to treat periprosthetic joint infection (PJI). Two basic hypotheses are evaluated: (1) the clinical outcomes of the patients treated with "hand made" articulating cement spacer are better than in non-articulating patient's group in two-stage revision for PJI of the total hip arthroplasty and (2) PJI recurrence is higher in the group of patients treated with an articulating spacer group. MATERIAL AND METHODS The evaluated group consists of a total of 57 patients (23 women, 34 men) with the mean age of 61.2 years. Group A of 39 patients were treated by two-stage revision using the "hand-made" articulating cement spacer and Group B of 18 patients were treated using the non-articulating spacer. Both the groups were evaluated retrospectively in the reference period: preoperatively and two years after the surgery using the Harris Hip Score (HHS) clinical assessment. The revision surgery for acute and chronic complications of treatment, length of hospitalization, and the PJI recurrence were evaluated for both the groups. RESULTS The resulting HHS clinical reviews were pre-operatively 43.59 points in both the groups with postoperative improvement up to 81.74 points. The mean preoperative HHS scores were 41.67 points (Group A) and 47.77 points (Group B) and two years after the surgery they were 83.43 points (Group A) and 78.08 points (Group B) (two-tailed t-test, p-value = 0.042). In Group A a total of seven revisions were performed in the interval between the two-stage revision (4x recurrent dislocation, 2x persistent infection, 1x spacer fracture). In Group B one patient was revised for persistent infection. In the two-year period after the operation, a relapse of PJI was recorded in 5 patients in Group A (12.8%) and in 1 patient in Group B (5.6%) (Chi-square test, p-value = 0.41). The average time of hospitalization was 51.58 days, whereby 49.72 days and 55.61 days on average for Group A and B respectively (p-value = 0.53). DISCUSSION According to recent studies, the advantage of motion preservation in articulating cement spacers can be complicated by recurrent dislocations, implant migration, periprosthetic fractures or recurrent joint replacement infections, which can further prolong the treatment and worsen the final clinical results. An alternative treatment option is the application of a nonarticulating spacer maintaining the advantage of local administration of antibiotics and reducing the dead space formed by the infected implant removal. Discussed is mainly the choice of the method in case of muscle disorder or presence of segmental bone defects. CONCLUSIONS The results demonstrate the better clinical outcomes and the higher revision rate of patients with an articulating cement spacer in two stage revision. We didn't find any differences between the risk of PJI recurrence in both groups. Key words:periprosthetic infection, total hip replacement, cement spacer, two stage revision, articulating spacer, nonarticulating spacer.

Risk factors for football injuries in young players aged 7 to 12 years.

Football (soccer) is very popular among children. Little is known about risk factors for football injuries in children. The aim was to analyze potential injury risk factors in 7- to 12-year-old players. We collected prospective data in Switzerland and the Czech Republic over two seasons. Coaches reported exposure of players (in hours), absence, and injury data via an Internet-based registration system. We analyzed time-to-injury data with extended Cox models accounting for correlations on team- and intra-person levels. We analyzed injury risk in relation to age, sex, playing position, preferred foot, and regarding age-independent body height, body mass, and BMI. Further, we analyzed injury risk in relation to playing surface. In total, 6038 player seasons with 395 295 hours of football exposure were recorded and 417 injuries occurred. Injury risk increased by 46% (Hazard Ratio 1.46 [1.35; 1.58]; P < .001) per year of life. Left-footed players had a higher injury risk (Hazard Ratio 1.53 [1.07; 2.19]; P = .02) for training injuries compared to right-footed players. Injury risk was increased in age-adjusted taller players (higher percentile rank). Higher match-training ratios were associated with a lower risk of match injuries. Injury risk was increased on artificial turf (Rate Ratio 1.39 [1.12; 1.73]; P < .001) and lower during indoor sessions (Rate Ratio 0.68 [0.52; 0.88]; P < .001) compared to natural grass. Age is known as a risk factor in older players and was confirmed to be a risk factor in children's football. Playing surface and leg dominance have also been discussed previously as risk factors. Differences in injury risks in relation to sex should be investigated in the future.

Autologous structural iliac bone grafts in reconstructions of short bone defects in the hand and foot after primary bone tumor resections: a single-institution retrospective study.

The use of structural autografts from the iliac crest for reconstruction of bony defects in the hand and foot was described by Wilson and Lance in 1965. However, very few series of this technique are published and long-term results are unknown. We present a single-institution series of 23 patients with a mean follow-up of 92 months. We also describe a novel modification of this technique using the anterior superior iliac spine for reconstruction of the adjacent joint. Failure rate was 13% at mean of 17.3 months. All patients had a firm grip in the hand and walked without support. Bony fusion was achieved in all cases regardless of the type of fixation used. The use of ASIS for joint reconstruction was successful, particularly in low-demand joints. We encountered 1 case of instability and progressive stiffness in weight-bearing joints. This is a reliable method of reconstructing bony defects in the hand or foot following tumor resections.

Gender differences in the morphology of the trochlea and the distal femur.

PURPOSE: The objective of this study was to provide a morphologic description of the distal femur and to determine whether there are any gender differences in the shape that might have an important consequence for the design of a femoral component of a total knee prosthesis. METHODS: Anthropometric data on the distal femur of 200 normal knees were obtained using two-dimensional MRI measurements. In all 18 parameters of the distal femur were measured including the anteroposterior (AP) dimension of femoral condyles, the mediolateral (ML) width of the distal femur at four levels, and the AP dimension and ML width of the trochlea. The aspect ratios between the AP and ML dimensions were calculated to determine whether there is a shape difference between genders. RESULTS: The female distal femur is significantly smaller in all measured parameters. The mean AP/ML aspect ratio of the female distal femur is significantly larger (p<0.05) at all measured ML levels except that of the anterior edge of the anterior chamfer. The AP dimensions of both the medial and lateral trochlea were significantly greater in men (p<0.001), but AP/ML aspect ratio did not differ between genders. CONCLUSIONS: We have found that although the female distal femur is relatively narrower (larger AP/ML aspect ratio) than the male in three of the four measured levels, there is no significant difference between genders at the level of the anterior edge of the anterior chamfer. It is at this level that it has been suggested that impingement between soft tissues and an overhanging prosthesis is most likely to be painful. Equally, there were no gender-related differences in the shape of the trochlea. These data therefore do not support the provision of narrow femoral components for TKA for women.

The effect of nimodipine, fentanyl and remifentanil intravenous products on the stability of propofol emulsions.

Nimodipine is used parenterally to treat ischemic neurological deficits caused by subarachnoid haemorraghe. Infusion of nimodipine should be continued during anaesthesia, surgery or angiography. In this context a simultaneous administration of nimodipine, propofol and fentanyl or remifentanil could be of great advantage. So the aim of this study was to evaluate the physical stability (droplet size) of propofol emulsions in combination with nimodipine and fentanyl/remifentanil. Droplet size of intravenous emulsions is of particular relevance as the administration of larger droplets to patients may cause pulmonary embolism. So the number of oil droplets > 10 microm was determined in combinations of propofol emulsion with nimodipine and fentanyl/remifentanil immediately after mixing and after 20 hours by using microscopy. The experiments showed that all combinations of propofol (1 and 2%) with nimodipine infusion solution resulted in coalescence of oil droplets, which finally caused a visible phase separation. Macrogol (polyethylene glycol 400) was identified as the component in nimodipine infusion solution which induced the physicochemical incompatibility with propofol lipid emulsions.