The natural initiation and progression of osteoarthritis in the anterior cruciate ligament deficient feline knee.

OBJECTIVE: The aim of this study was to document the natural history of development and long-term progression of osteoarthritis (OA) in the feline knee after minimally invasive anterior cruciate ligament (ACL) transection. DESIGN: ACL transections of the left knee joint of 14 skeletally mature cats were performed. Radiographic scores, tibiofemoral and patellofemoral joint space and anterior tibial translation were assessed before, immediately and every 3 months after ACL transection (longest follow-up: 93 months). RESULTS: After 26 months, all ACL transected knees had developed definite OA. The earliest changes were observed on the tibia plateau starting as early as 2 months after ACL transection, and at 12 months signs of OA were present in more than 80% of cats in the medial and in almost 80% of cats in the lateral compartment. In the first 24 months, medial tibiofemoral joint space decreased by 0.88 mm (95% confidence interval [-0.55;-1.21] mm) and lateral tibiofemoral joint space by 0.55 mm ([-0.26;-0.85] mm). In the same interval, the joint space in the patellofemoral joint increased by 0.98 mm ([0.59; 1.37] mm). Throughout the entire observation period, the anterior tibial translation was on average 5.3 mm greater than in the contralateral knee ([4.5; 6.0]mm). CONCLUSIONS: Immediate changes in anterior tibial translation during an anterior drawer test clearly showed joint instability that persisted throughout the lifetime of the animals. Degenerative changes were observed on radiographs within 4 months of the injury only in the transected but not the contralateral limb suggesting the role of mechanical instability for the development and progression of knee OA.

[Malleolar osteotomy--osteotomy as approach]. / Knöchelosteotomie--Die Osteotomie als Zugang.

Both arthroscopic and open surgical techniques may be used for treatment of osteochondral lesions of the ankle joint. Osteotomy around the ankle joint is a well established technique to extend the approach in cases where the osteochondral lesions are located more posteriorly. Medial, oblique, monoplanar malleolar osteotomy should be used in patients with lesions of the medial talus shoulder. The posterolateral ostechondral lesions are less frequent and in such cases distal fibular osteotomy is recommended. In this study the indications for different forms of osteotomy are discussed and the surgical techniques are described.

Computed tomography analysis of knee pose and geometry before and after total knee arthroplasty.

Using a three-dimensional (3D) modality to image patients' knees before and after total knee arthroplasty (TKA) allows researchers and clinicians to evaluate causes of pain after TKA, differences in implant design, and changes in the articular geometry as a result of surgery. Computed tomography (CT) has not been fully utilized to date for evaluating the knee after TKA due to metal artifacts obscuring part of the image. We describe an accurate, validated protocol, which has been implemented in vivo, that improves visibility of the patellofemoral joint, matches implant models automatically in 3D, segments preoperative bone semi-automatically, detects and sets coordinate systems automatically, determines the six degrees of freedom of knee pose and geometry, and allows for multiple other measurements that are clinically relevant. Subjects are imaged at 0° and 30° knee flexion, while pushing on a custom-made knee rig to provide partial loadbearing. With some modifications, the protocol can be adopted by any group with access to a CT scanner and image analysis software, allowing for the investigation of numerous clinical and biomechanical questions.

Altered cell metabolism in tissues of the knee joint in a rabbit model of Botulinum toxin A-induced quadriceps muscle weakness.

Quadriceps muscle weakness is frequently associated with knee injuries in sports. The influence of quadriceps weakness on knee joint homeostasis remains undefined. We hypothesized that quadriceps weakness will lead to tissue-specific alterations in the cell metabolism of tissues of the knee. Quadriceps weakness was induced with repetitive injections of Botulinum toxin A in six 1-year-old New Zealand White rabbits for 6 months. Five additional animals served as controls with injections of saline/dextrose. Muscle weakness was assessed by muscle wet mass, isometric knee extensor torque, and histological morphology analysis. Cell metabolism was assessed for patellar tendon, medial and lateral collateral ligament, and medial and lateral meniscus by measuring the total RNA levels and specific mRNA levels for collagen I, collagen III, MMP-1, MMP-3, MMP-13, TGF-ß, biglycan, IL-1, and bFGF by reverse transcription and polymerase chain reaction. While the total RNA levels did not change, tissue-specific mRNA levels were lower for relevant anabolic and catabolic molecules, indicating potential changes in tissue mechanical set points. Quadriceps weakness may lead to adaptations in knee joint tissue cell metabolism by altering a subset of anabolic and catabolic mRNA levels corresponding to a new functional and metabolic set point for the knee that may contribute to the high injury rate of athletes with muscle weakness.

[Total ankle arthroplasty in valgus ankle osteoarthritis]. / Sprunggelenkprothese bei Valgusarthrose.

Ankle osteoarthritis (OA) is often associated with deformities. Valgus OA is less frequent than varus OA and causes of valgus OA include medial ligament instability, flat foot and posttraumatic situations, e.g. fractures of the fibula or lateral tibial plafond. The importance of the mechanical axis is generally accepted in orthopedic surgery. In cases of implantation of total ankle replacements the normal biomechanics need to be restored in order to have a correct and pain-free functioning total ankle replacement both in the short and long-term. The two most important criteria are (1) an anterior tibio-talar angle of about 90° and (2) a neutral hindfoot position. The hindfoot position is measured with the hindfoot alignment view according to Saltzman. In this view, healthy feet are in neutral or minimal varus position of 1-2° and not in a valgus position as generally assumed. The following operative steps are performed depending on the degree and localization of the valgus deformity: (1) total ankle replacement, (2) supramalleolar or (3) inframalleolar osteotomy/arthrodesis, (4) medial ligament repair, (5) fibula osteotomy and (6) syndesmotic reconstruction.

A novel method for determining articular cartilage chondrocyte mechanics in vivo.

Work relating the mechanical states of articular cartilage chondrocytes to their biosynthetic responses is based on measurements in isolated cells or cells in explant samples removed from their natural in situ environment. Neither the mechanics nor the associated biological responses of chondrocytes have ever been studied in cartilage within a joint of a live animal, and no such measurements have ever been performed using physiologically relevant joint loading through muscular contractions. The purpose of this study was to design and apply a method to study the mechanics of chondrocytes in the exposed but fully intact knee of live animals, which was loaded near-physiologically through muscular contraction. In order to achieve this purpose, we developed an accurate and reliable method based on two-photon laser excitation microscopy. Near-physiological knee joint loading was achieved through controlled electrical activation of the knee extensor muscles that compress the articulating surfaces of the femur, tibia and patella. Accuracy of the system was assessed by inserting micro-beads of known dimensions into the articular cartilage of the mouse knee and comparing the measured volumes and diameters in the principal directions with known values of the beads. Accuracy was best in the plane perpendicular to the optical axis (average error = 1%) while it was slightly worse, but still excellent, along the optical axis (average error = 3%). Reliability of cell volume and shape measurements was 0.5% on average, and 2.9% in the worst-case-scenario. Pilot measurements of chondrocyte deformations upon sub-maximal muscular loading causing a mean articular contact pressure of 1.9 ± 0.2 MPa showed an "instantaneous" decrease in cell height (17 ± 4.5%) and loss of cell volume (22.3 ± 2.4%) that took minutes to recover upon deactivation of the knee extensor muscles.

[Achilles tendon ruptures and tibialis anterior tendon ruptures]. / Achillessehnen- und Tibialis-anterior-Sehnenruptur.

Achilles tendon ruptures (ATR) are becoming the most frequent tendon rupture of the lower extremity, whereas less than 100 cases of tibialis anterior tendon ruptures (TATR) have been reported. Common in both tendons are the degenerative causes of ruptures in a susceptible tendon segment, whereas traumatic transections occur at each level. Triceps surae and tibialis anterior muscles are responsible for the main sagittal ankle range of motion and ruptures lead to a distinctive functional deficit. However, diagnosis is delayed in up to 25% of ATR and even more frequently in TATR. Early primary repair provides the best functional results. With progressive retraction and muscle atrophy delayed tendon reconstruction has less favourable functional results. But not all patients need full capacity, power and endurance of these muscles and non-surgical treatment should not be forgotten. Inactive patients with significant comorbidities and little disability should be informed that surgical treatment of TATR is complicated by high rates of rerupture and surgical treatment of ATR can result in wound healing problems rarely necessitating some kind of transplantation.

SPECT-CT imaging in degenerative joint disease of the foot and ankle.

The precise localisation of osteoarthritic changes is crucial for selective surgical treatment. Single photon-emission CT-CT (SPECT-CT) combines both morphological and biological information. We hypothesised that SPECT-CT increased the intra- and interobserver reliability to localise increased uptake compared with traditional evaluation of CT and bone scanning together. We evaluated 20 consecutive patients with pain of uncertain origin in the foot and ankle by radiography and SPECT-CT, available as fused SPECT-CT, and by separate bone scanning and CT. Five observers assessed the presence or absence of arthritis. The images were blinded and randomly ordered. They were evaluated twice at an interval of six weeks. Kappa and multirater kappa values were calculated. The mean intraobserver reliability for SPECT-CT was excellent (kappa = 0.86; 95% CI 0.81 to 0.88) and significantly higher than that for CT and bone scanning together. SPECT-CT had significantly higher interobserver agreement, especially when evaluating the naviculocuneiform and tarsometatarsal joints. SPECT-CT is useful in localising active arthritis especially in areas where the number and configuration of joints are complex.

[Ossification in chronic Achilles tendinosis: a third calf bone]. / Ossifikation bei chronischer Achillessehnentendinose: ein dritter Unterschenkelknochen.

Ossification of the Achilles tendon is a rare complication of chronic Achilles tendinosis. This case report discusses a 59-year-old man who experienced Achilles tendon lengthening in early childhood due to a congenital clubfoot disorder with a record-breaking ossification of a length of 10 cm. Because of persistent symptoms and the risk of fracture, the choice of treatment after unsuccessful conservative therapy depends on surgical reconstructive criteria.

[Chronic ankle instability]. / Chronische Instabilität des oberen Sprunggelenks.

Chronic ankle instability represents a typical sports injury. After an acute ankle sprain 20-40% of the injured develop chronic ankle instability. From an orthopaedic point of view chronic ankle instability can be subdivided into lateral and medial instability or a combination of both, the so-called rotational ankle instability. From a pathophysiological point of view, chronic ankle instability can be either mechanical with a structural ligament lesion or functional with loss of neuromuscular control. For the physician chronic ankle instability is a difficult entity as the diagnosis is usually complex and the therapy often surgical. This review on chronic ankle instability deals with the pathomechanisms, diagnostics, indications for conservative and surgical treatments, and possible long-term sequelae, such as ligamentous osteoarthritis.

[Chronic ankle instability in sports -- a review for sports physicians]. / Chronische Instabilität des oberen Sprunggelenks im Sport -- ein Review für Sportärzte.

Chronic ankle instability represents a typical sports injury which can mostly be seen in basketball, soccer, orienteering and other high risk sports. 20 to 40 % of the acute ankle sprains develop into chronic ankle instability. From a sports orthopaedic point of view, chronic ankle instability can be subdivided into a lateral, medial or a combination of both so called rotational ankle instability. From a pathophysiological point of view, chronic ankle instability can be either mechanical with a structural ligament lesion or functional with loss of the neuromuscular control. For the sports physician, the chronic ankle instability is a difficult entity as the diagnosis is usually complex and the therapy usually surgical. This review on chronic ankle instability addresses pathomechanism, diagnostics, indications for conservative and surgical treatments, and possible long-term sequelae, as ligamentous osteoarthritis.