[Positive and negative predictors of long-term results after an osteotomy around the knee joint]. / Positive und negative Prädiktoren für das Langzeitresultat nach kniegelenknaher Osteotomie.

A frequently asked question in the context of any surgical procedure, including an osteotomy around the knee joint, is "which parameters are in favor of a therapeutic success in this special case?" If the analysis of the leg geometry is in favor of an osteotomy, then the patient must be assessed further, taking into account the joint status and patient's condition. Positive outcome predictors for long-term success of an osteotomy around the knee, especially for a valgus osteotomy at the tibia are a tibial bone varus angle (TBVA) > 3-5°, knee joint range of motion > 100° flexion, male sex, and a BMI < 30. It is unclear whether the degree of degeneration of the affected (medial) compartment is of special relevance. The severity of malalignment, the patient's sex, and psychopathological comorbidities are not important.

Alignment does not influence cartilage T2 in asymptomatic knee joints.

PURPOSE: To investigate whether the static knee alignment affects articular cartilage ultrastructures when measured using T2 relaxation among asymptomatic subjects. METHODS: Both knee joints (n = 96) of 48 asymptomatic volunteers (26 females, 22 males; 25.4 ± 1.7 years; no history of major knee trauma or surgery) were evaluated clinically (Lysholm, Tegner) and by MRI (hip-knee-ankle angle, standard knee protocol, T2 mapping). Group (n = 4) division was as follows: neutral (<1° varus/valgus), mild varus (2°-4° varus), severe varus (>4° varus) and valgus (2°-4° valgus) deformity with n = 12 subjects/group; n = 24 knees/group. Regions of interest (ROI) for T2 assessment were placed within full-thickness cartilage across the whole joint surface and were divided respecting compartmental as well as functional joint anatomy. RESULTS: Leg alignment was 0.7° ± 0.5° varus among neutral, 3.0° ± 0.6° varus among mild varus, 5.0° ± 1.1° varus among severe varus and 2.5° ± 0.7° valgus among valgus group subjects and thus significantly different. No differences between the groups emerged from clinical measures. No morphological pathology was detected in any knee joint. Global T2 values (42.3 ± 2.3; 37.7-47.9 ms) of ROIs placed within every knee joint per subject were not different between alignment groups or between genders, respectively. CONCLUSION: Static frontal plane leg malalignment does not affect cartilage ultrastructure among young, asymptomatic individuals as measured by T2 quantitative imaging. LEVEL OF EVIDENCE: Cross-sectional study, Level II-III.

Age does not influence the clinical outcome after high tibial osteotomy.

PURPOSE: Valgus high tibial osteotomy (HTO) is an established procedure for the medial gonarthrosis. In several studies, many negative influencing factors were evaluated. However, until now, the factor "age" was examined only insufficiently. The aim of our study was to evaluate the factor age in predicting the functional outcome after HTO, and we hypothesized that valgus HTO leads to equal results in the treatment of varus osteoarthritis independent of the patient's age. METHODS: We could generate 13 pairs of patients with a median age at operation of 57 (55-63) years (group A) versus patients 15 years younger with a median age of 42 (39-47) years (group B). The patients were matched according to the following criteria: age, gender, operation/osteosynthesis method, body mass index, same additional operations, and follow-up time. Evaluation of the patients was done by use of the Tegner and Lysholm score and visual analogue scale (VAS) as well as by subjective satisfaction of the patients. RESULTS: The Lysholm score showed a significant improvement in group A from 41 (SD ± 12.3) to 65 (SD ± 23.8) points (p = 0.01) and in group B from 33 (SD ± 16.7) to 70 (SD ± 31.8) points (p = 0.007). Moreover, the VAS decreased significantly in group A from 77 (SD ± 15.3) to 36 (SD ± 21.3) points (p = 0.003) and in group B from 73 (SD ± 22.7) to 41 (SD ± 33.7) points (p = 0.02). However, there was no significant difference for both groups regarding the activity of the patients evaluated by the Tegner score (group A: preop.: 5 (1-9), follow-up: 3.5 (1-6); group B: preop.: 6 (3-9), follow-up: 4 (2-7)). Furthermore, there was no significant difference between both groups in view of the Lysholm, Tegner and VAS. CONCLUSION: Valgus high tibial osteotomy is an effective procedure for the treatment of medial gonarthrosis independent of the patient's age. As a consequence, the age of the patient does not have to be taken into consideration for the indication of high tibial osteotomy. LEVEL OF EVIDENCE: III.

[Femoral osteotomy for patellofemoral instability]. / Femorale Osteotomien bei patellofemoraler Instabilität.

Axis and torsion malalignment of the femur has been widely recognized as a primary reason for patellofemoral instability and pain. In this article we explain the current concepts of biomechanics and describe the radiological findings in computed tomography (CT) examination. We describe the technique of a biplanar varus and/or external rotation distal femoral osteotomy in detail. Existing clinical studies describe this technique as part of a multimodal treatment concept with good to excellent results. We present our current technique and clinical results.

[Winter sports and shoulder arthroplasty]. / Schulterprothese und Wintersportfähigkeit.

Nowadays, a general negative evaluation of sportive activity regarding different kinds of sport following arthroplasty is at present no more scientifically supported. However, at present no valid guidelines regarding sportive activity of patients after implantation of shoulder joint arthroplasty exist. The question regarding the ability of performing winter sports activities of patients treated with shoulder joint endoprothesis has not been answered so far. Therefore the aim of the presented work was to identify winter sports-specific risks for patients treated with shoulder joint endoprothesis as well as to critically discuss the actual literature in refer to winter sport activities. Criteria for the education of patients with shoulder joint endoprothesis as well as consultation regarding winter sport activities will be provided for the orthopaedic surgeon.

A new model to predict in vivo human knee kinematics under physiological-like muscle activation.

Although a number of approaches have attempted to model knee kinematics, rarely have they been validated against in vivo data in a larger subject cohort. Here, we assess the feasibility of four-bar linkage mechanisms in addressing knee kinematics and propose a new approach that is capable of accounting for lengthening characteristics of the ligaments, including possible laxity, as well as the internal/external rotation of the joint. MR scans of the knee joints of 12 healthy volunteers were taken at flexion angles of 0 degrees , 30 degrees and 90 degrees under both passive and active muscle conditions. By reconstructing the surfaces at each position, the accuracy of the four-bar linkage mechanism was assessed for every possible combination of points within each cruciate ligament attachment area. The specific set of parameters that minimized the deviation between the predictions and the in vivo pose was derived, producing a mean error of 1.8 and 2.5 on the medial and 1.7 and 2.4mm on the lateral side at 30 degrees and 90 degrees flexion, respectively, for passive motion, significantly improving on the models that did not consider internal/external rotation. For active flexion, mean medial errors were 3.3 and 4.7 mm and lateral errors 3.4 and 4.8 mm. Using this best parameter set, a generic predictive model was created and assessed against the known in vivo positions, producing a maximum average error of 4.9 mm at 90 degrees flexion. The accuracy achieved shows that kinematics may be accurately reconstructed for subject specific musculoskeletal models to allow a better understanding of the load distribution within the knee.

Operative treatment of greater tuberosity fractures of the humerus--a biomechanical analysis.

BACKGROUND: Fractures of the greater tuberosity of the humerus present with increasing frequency. However, no biomechanical data about the optimal fixation technique of greater tuberosity fractures is available. This biomechanical cadaver study compares the stability of three standard fixation techniques used for the treatment of greater tuberosity fractures of the proximal humerus. METHODS: In 21 fresh frozen proximal humeri, standardized fractures of the greater tuberosity were created. The specimens were randomly assigned to one of three operation techniques: wire tension banding, two cancellous screws and transosseous sutures. These constructs were mechanically tested by applying an increasing force to the supraspinatus tendon. Load to 5mm displacement (load to 5mm yield point) and load to failure (maximum stretch strength) were measured in Newton (N). FINDINGS: Load to 5mm yield point values showed no significant differences between tension banding (498 N, SD 153) and two cancellous screws (400 N, SD 174) (P>0.01). Both techniques showed significantly higher values than transosseous sutures (185 N, SD 132) (P<0.01). Load to failure values were significantly higher for tension banding (1054 N, SD 125) than screws (842 N, SD 140) and sutures (480 N SD 101) (P<0.01). The difference between screws and sutures was also significant (P<0.01). INTERPRETATION: Tension banding and two cancellous screws provided the strongest fixation for isolated fractures of the greater tuberosity.

[Distal femoral osteotomy using a lateral opening wedge technique]. / Distale Femurosteotomie in lateraler Open-wedge-Technik.

OBJECTIVE: To shift the weight-bearing axis of the lower limb medially by opening a lateral-based metaphyseal osteotomy at the distal femur. INDICATIONS: Femoral-based valgus malalignment and symptomatic lateral unicompartimental osteoarthritis, lateral hyperpression syndrome, cartilage therapy of the lateral compartment, lateral meniscal replacement/transplantation, medial instability with valgus thrust, reconstruction of the medial collateral ligament, patellar instability and/or maltracking. CONTRAINDICATIONS: Advanced cartilage damage (>grade 2) or subtotal meniscal loss of the medial compartment, age >65 years (relative), nicotine abuse, body mass index >30, flexion contracture >25°, corrections with a wedge base >10 mm in case of congenital deformities, inflammatory or septic arthritis, severe osteoporosis. SURGICAL TECHNIQUE: Lateral approach to the distal femur; biplanar osteotomy (frontal + axial osteotomy), gradual opening of the osteotomy, osteotomy fixation with a locking plate. POSTOPERATIVE MANAGEMENT: Free range of motion. Partial weight bearing with 20 kg for 2 weeks, followed by progressive weight bearing thereafter. RESULTS: Mean improvement of knee scores from 20-30 points and mean 10-year survival rate of 80% in patients with lateral unicompartimental osteoarthritis. Mean complication rate of 9%.

Functional outcome after transphyseal anterior cruciate ligament reconstruction in young patients with open growth plates.

BACKGROUND: This study evaluates sports ability, rotational laxity and potential growth changes in children after transphyseal ACL reconstruction with metaphyseal fixation technique, considering physis biology by placing drill holes vertically in the femoral anatomic origin in order to reduce volumetric injury to the physis. METHODS: In this retrospective trial of 42 patients data were collected. Thirty-seven were reviewed measuring rotational laxity and anteroposterior tibial translation using the Laxitester (ORTEMA Sport Protection, Markgroeningen, Germany) and the KT1000. Clinical examination was evaluated with the IKDC 2000 knee examination form. Leg axis was determined with digital photography and leg length was assessed clinically. Sports ability was assessed with questionnaires including subjective IKDC, Tegner Activity Scale, Activity Rating Scale and a questionnaire on sports and level of sports. RESULTS: Mean follow-up was 24.9months. Mean age at surgery was 13.2years in boys and 13.1years in girls. IKDC 2000 grading was A or B in 28 patients and C in nine patients. Significant increased anterior tibial translation was observed in neutral position and in external tibia rotation. No growth abnormalities were seen. Fifty-seven percent of the patients were able to participate in competitive sports at follow-up. CONCLUSION: Transphyseal ACL reconstruction with metaphyseal fixation in children with open growth plates can be done with low risk of growth changes. Return to competitive sports is possible although low rotational laxity still exists. LEVEL OF EVIDENCE: IV.

Effect of abducting and adducting muscle activity on glenohumeral translation, scapular kinematics and subacromial space width in vivo.

It is currently unknown in which ways activity of the ab- and adductor shoulder muscles affects shoulder biomechanics (scapular kinematics and glenohumeral translation), and whether these changes are relevant for alterations of the subacromial space width. The objective of this experimental in vivo study was thus to test the hypotheses that potential changes of the subacromial space width (during antagonistic muscle activity) are caused by alterations of scapular kinematics and/or glenohumeral translation. The shoulders of 12 healthy subjects were investigated with an open MRI-system at 30 degrees, 60 degrees, 90 degrees, 120 degrees and 150 degrees of arm elevation. A force of 15N was applied to the distal humerus, once causing isometric contraction of the abductors and once contraction of the adductors. The scapulo-humeral rhythm, scapular tilting and glenohumeral translation were calculated from the MR image data for both abducting and adducting muscle activity. Adducting muscle activity led to significant increase of the subacromial space width in all arm positions. The scapulo-humeral rhythm (2.2-2.5) and scapular tilting (2-4 degrees) remained relatively constant during elevation, no significant difference was found between abducting and adducting muscle activity. The position of the humerus relative to the glenoid was, however, significantly (p < 0.05) different (inferior and anterior) for adducting versus abducting muscle activity in midrange elevation (60-120 degrees). These data show that the subacromial space can be effectively widened by adducting muscle activity, by affecting the position of the humerus relative to the glenoid. This effect may be employed for conservative treatment of the impingement syndrome.

In vivo contact areas of the knee in patients with patellar subluxation.

OBJECTIVE: Ex vivo studies have suggested that cartilage contact areas and pressure are of high clinical relevance in the etiology of osteoarthritis in patients with patellar subluxation. The aims of this study were therefore to validate in vivo measurements of contact areas with 3D open magnetic resonance imaging (MRI), and to study knee joint contact areas in patients with patellar subluxation at different angles of knee flexion in comparison with healthy subjects. METHODS: 3D-MRI data sets of 12 healthy volunteers and eight patients with patellar subluxation were acquired using a standard clinical (1.5 T) and an open (0.2 T) MRI scanner. We compared femoro-patellar and femoro-tibial contact areas obtained with two different sequences from open MRI [dual-echo-steady-state (DESS) and fast-low-angle-shot (FLASH) sequences] with those derived from standard clinical 1.5 T MRI. We then analyzed differences in joint contact areas between healthy subjects and patients with patellar subluxation at 0 degree, 30 degrees, and 90 degrees of knee flexion using open MRI. RESULTS: The correlation of the size of contact areas from open MRI with standard clinical MRI data ranged from r = 0.52 to 0.92. Open-MRI DESS displayed a smaller overestimation of joint contact areas (+21% in the femoro-patellar, +12% in the medial femoro-tibial, and +19% in the lateral femoro-tibial compartment) than FLASH (+40%, +37%, +30%, respectively). The femoro-patellar contact areas in patients were significantly reduced in comparison with healthy subjects (-47% at 0 degree, -56% at 30 degrees, and -42% at 90 degrees of flexion; all p < 0.01), whereas no significant difference was observed in femoro-tibial contact areas. CONCLUSIONS: Open MRI allows one to quantify joint contact areas of the knee with reasonable accuracy, if an adequate pulse sequence is applied. The technique permits one to clearly identify differences between patients with patellar subluxation and healthy subjects at different flexion angles, demonstrating a significant reduction and lateralization of contact areas in patients. In the future, application of this in vivo technique is of particular interest for monitoring the efficacy of different types of surgical and conservative treatment options for patellar subluxation.

The management of leg-length discrepancy in Ollier's disease with a fully implantable lengthening nail.

Ollier's disease is characterised by severe deformity of the extremities and retarded growth because of multiple enchondromas. For correction of deformity, the Ilizarov method has been used although it has many complications. A 17-year-old boy with Ollier's disease had a limb-length discrepancy of 17.4 cm, with a valgus deformity of the right knee and recurvatum of the femur of 23 degrees . He had undergone three unsuccessful attempts to correct the deformities by using external fixators. We used a fully implantable, motorised, lengthening and correction nail (Fitbone) to achieve full correction of all the deformities without complications. We decided to carry out the procedure in three stages. First, we lengthened the femur by 3.6 cm and the tibia by 4 cm. We then exchanged the femoral nail for a longer implant and achieved a further 6 cm of length. This reduced the shortening to 3.8 cm. When the boy has finished secondary school we will adjust the remaining discrepancy.

Reduction of high dislocation of the hip using a distraction nail before arthroplasty.

We report the case of a 22-year-old woman who underwent plate and screw fixation for a traumatic left acetabular fracture and fixation with cancellous screws for an associated femoral neck fracture. Two months later, the internal fixation became infected and was removed. This resulted in a painful high dislocation of the hip. We solved the problem with continuous soft-tissue distraction using a fully implantable motorised distraction nail in order to reduce the proximal femur prior to total hip arthroplasty. To our knowledge, this is the first time that reduction of a high dislocation of the hip has been performed using such a system.

Influence of a mono-centric knee brace on the tension of the collateral ligaments in knee joints after sectioning of the anterior cruciate ligament--an in vitro study.

OBJECTIVE: To analyze the influence of knee bracing on the tension of the medial and lateral collateral ligaments in anterior cruciate ligament deficiency. DESIGN: The tension of the collateral ligaments in anterior cruciate ligament deficient knees was measured with and without knee bracing using an in vitro model. BACKGROUND: Anterior cruciate ligament deficiency increases the tension in both collateral ligaments at the knee joint. Therefore knee braces should reduce that tension increase. However, that effect has never been proven quantitatively. METHODS: After anterior cruciate ligament-transection, the forces of the medial (anterior/posterior part) and lateral collateral ligament were measured in ten fresh human cadaver knees at 0 degrees, 20 degrees, 40 degrees, 60 degrees, 80 degrees and 100 degrees of flexion, with and without application of a mono-centric knee brace. To quantify the ligament forces, strain gauges were fixed at the bony origins of the ligaments. RESULTS: Bracing led to a significant decrease of ligament forces (20-100 degrees: P < 0.0001) in the anterior part of the medial collateral ligament in all joint positions. In the posterior aspect, this effect was observed only at 40 degrees (P < 0.0001) and 80 degrees (P = 0.001) of flexion. In the lateral collateral ligament, bracing caused a strain reduction from 60 degrees to 100 degrees of flexion (P < 0.0001). Therefore a flexion angle dependent effect of knee bracing on the strain was seen in the posterior aspect of the medial and in the lateral collateral ligament in anterior cruciate ligament deficient knee joints. CONCLUSIONS: Application of a mono-centric knee brace leads to a significant position dependent reduction of collateral ligament tension after anterior cruciate ligament-rupture.

Patella kinematics and patello-femoral contact areas in patients with genu varum and mild osteoarthritis.

BACKGROUND: Patients with genu varum of the knee and moderate to severe osteoarthritis often suffer from additional symptoms of the patello-femoral joint. These patients have a poor prognosis following high tibial osteotomy. It is unclear whether varus knees with only mild femoro-tibial osteoarthritis are also associated with alterations of patella biomechanics, and affect the prognosis of intended high tibial osteotomy. METHODS: Fifteen patients with genu varum and mild osteoarthritis and 15 healthy volunteers were assessed in an open MRI-scanner. 3D-GRE sequences of the knee were obtained in 0 degrees, 30 degrees and 90 degrees with and without activity of the extensor muscles. After segmentation of patella, femur, tibia and the adjacent cartilage, a patella-based local coordinate system was established. Femoral and tibial reference points allowed definition of the spatial position of the patella. Contact areas were defined by intersection of opposing cartilage volumes. FINDINGS: No significant differences in patella kinematics and patello-femoral contact areas could be found (P > 0.05) between varus knees with mild osteoarthritis and healthy knees either at different flexion angles or under extending muscle activity. INTERPRETATION: In knees with genu varum and mild medial osteoarthritis we could detect no alterations in patello-femoral kinematics. Since the alterations of patients with genu varum and mild osteoarthritis are restricted to the medial femoro-tibial joint high tibial osteotomy might be successful.

Strain measurement at the knee ligament insertion sites.

We describe the modification of an existing method of ligament strain measurement at the knee joint in detail. At ten fresh joint specimens we used that technique where strain gauges are attached to the ligamentous insertions and origins. We both improved the preparation of the attachment site and the application of the strain gauges. In a special apparatus the specimens were moved from 0 degree extension to 100 degrees flexion while simulating muscle strength and axial force. Testing was performed at the posterior cruciate ligament with both intact and transsected anterior cruciate ligament. In contrast to other existing techniques it does not affect the motion of the joint or the integrity and the function of the ligaments. Unlike the original description of that method we could register a loading behaviour of the posterior cruciate ligament that is similar to those reported in the literature.

[Central cable system--fully automatic, continuous distraction osteogenesis for the lengthening treatment of large bone defects]. / Zentrale Zugseilsysteme--vollautomatische, kontinuierliche Kallusdistraktion zur Behandlung langstreckiger Knochendefekte.

Distraction osteogenesis involving bone transport enables the reconstruction of large bone defects. The main bone fragments are usually stablilised externally, an intermediate bone segment is separated and moved through the defect at a rate of about 1 mm/day. New high-quality bone is built up in the constantly enlarging osteotomy gap. A major problem associated with the method is the fact that the fixation pins are also moved over the same distance, and cut through the soft tissue, often resulting in painful pin tract infections and ugly scars. An automatic motorized bone transport system employing a single central cable now eliminates this problem. The system can be combined with any external fixateur, since the relevant implanted parts for bone transport are independent of the external stabilizer. The surgical procedure, which is easy on the patient, consists of bone segment separation, central cable fixation, and stabilisation of the main fragments, and requires the use of numerous special tools. The distraction itself results in significantly less soft tissue irritation and pain. Pin tract infections are rare, so that changeover to internal fixation after completion of bone transport carries little risk of infection. This article details the technical features of the stabilizing system and the transport and the control systems, and describes the clinical application in a patient.

[Measuring ligament elasticity of the knee joint--elasticity measuring strip and its alternatives]. / Banddehnungsmessung am Kniegelenk--Der Dehnungsmessstreifen und seine Alternativen.

Those techniques for measuring ligament tension at the knee joint that are most commonly cited and easiest to carry out are discussed. These include four techniques based on the use of strain gauges. Apart from the Omega transducer and the buckle transducer, there is also the tendon force transducer, and the application of strain gauges to the bony ligament insertion sites. Other indirect measuring methods considered are the mercury strain transducer and the Hall effect transducer. The parameter measured with all of these methods is fluctuating current or voltage, which is then correlated with ligament tension. Three direct measurements are also discussed: the separation distances of marked fibres of the ligaments, replacement of fibres by threads, and a load cell/bone plug construction. The measured value is equated with the effective change in ligament length.

[Tractive force measurement in bone transport--an in vivo investigation in humans]. / Zugkraftmessungen beim knöchernen Segmenttransport--in vivo Untersuchungen am Menschen.

Bone transport applying the principle of distraction osteogenesis makes it possible to reconstruct long bone defects caused by trauma or resection of bone tumors. The method employing a central cable, developed in Munich, is especially suitable for such applications. The main bone fragments are stabilized by an external fixateur, and bone transport is effected with a single central cable fixed to the tip of the segment, and driven by an external, programmable motor. In 15 patients the tractive forces during the entire bone transport were measured with a strain gauge incorporated within the cable. On the basis of the force profiles characteristics normal bone transport (forces between 150-250 N) can be distinguished from a critical transport (forces > 250 N) with the risk of premature consolidation. There is some evidence that at a very high level of force, just before premature consolidation a very effective form of bone transport with good bone neoformation can be achieved. Transport systems employing a central cable allow this special form of distraction osteogenesis, since there is continuous force monitoring, and there is the option of employing the traction force as a control factor in a loop.