Tribocorrosion of a CoCrMo alloy sliding against articular cartilage and the impact of metal ion release on chondrocytes.

Partial knee replacement and hemiarthroplasty are some of the orthopedic procedures resulting in a metal on cartilage interface. As metal implant material, CoCrMo based alloys are commonly used. The aim of the present study is to assess the role of biotribocorrosion on the CoCrMo-cartilage interface with an emphasis on metal release during sliding contact. The biotribocorrosion experiments were performed under controlled electrochemical conditions using a floating cell with a three electrode set up coupled to a microtribometer. Throughout the experiment the coefficient of friction and the open circuit potential were monitored. Analyses of the electrolyte after the experiment show that metal release can occur during sliding contact of CoCrMo alloy against articular cartilage despite the extraordinary low coefficient of friction measured. Metal release is attributed to changes in passive layer caused at the onset of sliding. The released metal was found to be forming compounds with potential cytotoxicity. Since the presence of metal ions in the cartilage matrix can potentially lead to cell apoptosis, the metabolic activity of human osteoarthritic chondrocytes (2D-cultures) was investigated in the presence of phosphate buffered saline containing metal ions using XTT-assay. The experiments indicate that critical concentrations of Co ions lead to a significant decrease in chondrocyte metabolic activity. Therefore, biotribocorrosion is a mechanism that can occur in partial replacements and lead to chondrocyte apoptosis thus playing a role in the observed accelerated degradation of the remaining cartilage tissue after the mentioned orthopedic procedures. STATEMENT OF SIGNIFICANCE: Partial replacements provide an alternative to total joint replacements. This procedure is less invasive, allows a faster rehabilitation and provides a better function of the joint. However, the remaining native cartilage experiences accelerated degradation when in contact with metallic implant components. This work investigates the role of tribocorrosion at the metal-cartilage interface during sliding. Tribocorrosion is a degradation process that can alter significantly the wear rates experienced by metallic implants and lead to the release of metal ions and particles. The released metal can form compounds with potential cytotoxicity on cartilage tissue. The knowledge gained in this work will serve to understand the mechanisms behind the failure of partial replacements and develop future biomaterials with an enhanced lifetime.

Comparison of a resorbable magnesium implant in small and large growing-animal models.

Fracture treatment in children needs new implant materials to overcome disadvantages associated with removal surgery. Magnesium-based implants constitute a biocompatible and bioresorbable alternative. In adults and especially in children, implant safety needs to be evaluated. In children the bone turnover rate is higher and implant material might influence growth capacity, and the long-term effect of accumulated particles or ions is more critical due to the host's prolonged post-surgery lifespan. In this study we aimed to investigate the degradation behavior of ZX00 (Mg-0.45Zn-0.45Ca; in wt.%) in a small and a large animal model to find out whether there is a difference between the two models (i) in degradation rate and (ii) in bone formation and in-growth. Our results 6, 12 and 24 weeks after ZX00 implantation showed no negative effects on bone formation and in-growth, and no adverse effects such as fibrotic or sclerotic encapsulation. The degradation rate did not significantly differ between the two growing-animal models, and both showed slow and homogeneous degradation performance. Our conclusion is that small animal models may be sufficient to investigate degradation rates and provide preliminary evidence on bone formation and in-growth of implant materials in a growing-animal model. STATEMENT OF SIGNIFICANCE: The safety of implant material is of the utmost importance, especially in children, who have enhanced bone turnover, more growth capacity and longer postoperative lifespans. Magnesium (Mg)-based implants have long been of great interest in pediatric orthopedic and trauma surgery, due to their good biocompatibility, biodegradability and biomechanics. In the study documented in this manuscript we investigated Mg-Zn-Ca implant material without rare-earth elements, and compared its outcome in a small and a large growing-animal model. In both models we observed bone formation and in-growth which featured no adverse effects such as fibrotic or sclerotic encapsulation, and slow homogeneous degradation performance of the Mg-based implant material.

[Arthroscopically assisted osteosynthesis of intraarticular distal radius fractures]. / Arthroskopisch gesteuerte Osteosynthese der dislozierten intraartikulären distalen Radiusfraktur.

OBJECTIVE: Anatomical reconstruction of the distal radius after intra-articular fractures with special consideration of the articular surface and treatment of concomitant ligament injuries. INDICATIONS: Intra-articular distal radius fractures in adults under 65 years of age. CONTRAINDICATIONS: Osteoporotic deterioration of metaphyseal bone, radiocarpal fracture dislocation and open fractures. SURGICAL TECHNIQUE: Conventional palmar approach for plate fixation of the fracture with a fixed angle locking plate. Arthroscopy of the wrist is performed for reduction of the articular fracture component using the standard 3­4 and 6R portals. Following temporary Kirschner (K) wire fixation of the fracture, angle stable locking screws are inserted into the most distal portion of the plate. Finally, the intercarpal ligaments and the triangular fibrocartilage complex (TFCC) are checked for concomitant lesions and if necessary subsequent treatment within the same operation. POSTOPERATIVE MANAGEMENT: Plaster cast fixation for 4 weeks followed by a physiotherapy program. RESULTS: After arthroscopically assisted reduction of an intra-articular distal radius fracture, 17 out of the 23 patients were available for follow-up examination an average of 31 months after the procedure. The mean disabilities of the arm, shoulder and hand (DASH) score was 4.9 and the mean patient-rated wrist evaluation (PRWE) score was 6.0 at final follow-up. Except for wrist flexion, an active range of motion at the wrist as well as forearm rotation of more than 90 % was achieved compared with the uninjured contralateral side. Grip strength averaged 96 % compared with the contralateral side and pain levels under stress varied between 1 and 3 on a visual analog scale (range 0-10).

[Arthroscopically assisted osteosynthesis of dorsally tilted intraarticular distal radius fractures--technique and results]. / Arthroskopisch assistierte Versorgung dorsal dislozierter distaler intraartikulärer Speichenfrakturen--Technik und Ergebnisse.

The present paper describes the indication and application of an arthroscopically assisted osteosynthesis for distal radius fractures. Visualisation of articular incongruency is emphasised with special regard to articular fracture fragment reduction. In addition to that, classification of soft tissue injuries and treatment options are discussed. The final clinical and radiological results of 17 patients are presented: DASH and PRWE averaged 4.9 and 6.0 respectively. Active range of motion measured 123° for flexion/extension, 51° for radial and ulnar deviation and 163° for pronosupination, which is 87%, 98% and 97%, respectively, compared with the opposite wrist. Radial inclination at final follow-up was 23°, palmar tilt measured 6° and ulnar variance averaged -1.2 mm. The scapholunate gap at follow-up was 1.6 mm, and the scapholunate angle measured 57°.

Migration of two different cementless hip arthroplasty stems in combination with two different heads: a biomechanical in vitro study.

The aim of the present in vitro study was to evaluate migrational characteristics of cementless primary hip arthroplasty stems in combination with a diameter 50 mm head (hemiarthroplasty) and a diameter 28 mm head in and with a polyethylene cup (total hip arthroplasty) in fresh-frozen human specimens. Two different types (Endo SL, FMT) were implanted into seven pairs of fresh-frozen human femoral specimens. The implanted stems were combined with a diameter 50 mm head (hemiarthroplasty) on one side and with a polyethylene cup and a 28 mm head (total hip arthroplasty) on the other side. Dynamic mechanical loading was applied for 50,000 cycles while recording relative motions between stem and bone stock using a 3-D motion analysis system. The Endo SL stem showed a significantly higher amplitude of relative motion in all translational and rotational components regardless of the head used. In both stem types a strong tendency for higher axial migration with the diameter 50 mm head in comparison to the THA head was found. The lowest axial migration was found in the FMTstem in combination with the small head and a PE cup. The highest axial migration was found in the Endo SL stem combined with the diameter 50 mm head. Our results indicate that the head might play an important role for axial migration of cementless stems.

Cementless hemiarthroplasty in femoral neck fractures: evaluation of clinical results and measurement of migration by EBRA-FCA.

Aim of the present study was to evaluate migration rates of cementless primary hemiarthroplasty in acute femoral neck fractures. In a longitudinal, prospective study 46 patients were treated by cementless hemiarthroplasty. Clinical follow up was correlated with the EBRA-FCA method. In 30% of all patients stem migration amounted to more than 2 mm; further, these patients were seen to have a high level of activity. A high degree of migration in more than 30% of all patients requires critical scepticism toward further use of the investigated cementless stem as hemiarthroplasty. According to literature, migration of more than 2 mm suggests a high probability of early aseptic loosening. In patients with a low degree of activity good results could be observed; nevertheless, in patients with a high level of activity the combination of the investigated cementless stem with a solid fracture head cannot be recommended.

[Total endoprosthesis of the upper ankle joint after post-traumatic arthrosis]. / Totalendoprothese des oberen Sprunggelenks nach posttraumatischer Arthrose.

In 1997 six patients with posttraumatic ankle arthritis aged 54 (45-71) years were treated with a LINK S.T.A.R. ankle prothesis. The average follow up was 29 (21-36) months. Results were evaluated according to the ankle score of H. Kofoed [7]. Two patients had an excellent outcome and 1 patient had a fair result. In three patients secondary arthrodesis had to be performed, due to loosening of the implant. Based on our experiences we cannot recommend this implant for patients with posttraumatic arthritis at this time.

[A new classification for standardizing nomenclature in wound closure by microvascular flap-plasty]. / Eine neue Klassifizierung für die Standardisierung der Nomenklatur beim Wundverschluss durch mikrovaskuläre Lappenplastiken.

The profusion of terms currently used to describe microvascular flap wound closure according to the time of reconstruction makes reliable comparisons of outcomes between institutions difficult if not impossible. To address the issue, a consistent terminology applicable to microvascular flap wound closure in general was formulated with respect to our experience with a total of 197 microvascular tissue transplantations. The nomenclature presented divides microvascular flap closure into three categories: "primary microvascular flap closure" (within 24 hours). "delayed primary microvascular flap closure" (two to seven days), and "secondary microvascular flap closure" (after seven days). This is consistent with known biological, microbiological, and surgical principles of wound closure in general and should provide a simple basis for classifying microvascular flap wound closure. Sample cases are selected to illustrate the categories within this new classification scheme.

Free flap reconstruction of the foot.

Free flap reconstruction of the foot has been widely performed in the last 20 years, but choice of a free transferred substitute for the soft tissue of the particular defect remains controversial. The authors present a series of 77 free flaps to the foot performed in 68 patients during October 1976 and September 1997. Long-term follow-up ranged from 12 months to 18 years (median, 44.4 months). Seventy-three flaps were transferred successfully (95%). The indications for a specific flap depended on the localization and extension of the foot defect. In weight-bearing areas the authors favored the use of a muscle flap covered with a split-thickness skin graft; the latissimus dorsi muscle was used primarily. This study shows a lower ulceration rate in muscle flaps covered with split-thickness skin grafts than in fasciocutaneous flaps in weight-bearing areas (27% vs. 60%). In nonweight-bearing areas, fasciocutaneous flaps were the best choice. In this series, the lateral arm flap was applied most often. The authors recommend free fascial flaps (serratus fascial flap or radial forearm fascial flap) covered by split- or full-thickness skin grafts for coverage of the malleolar region as well as coverage of exposed tendons of nonweight-bearing regions. Proper tailoring of the flap and postoperative care are very important to maintain a result without ulceration, as is avoiding having the suture line cross a weight-bearing area. Tactile sensation does not seem to be essential.

Bone bruise of the knee: histology and cryosections in 5 cases.

We evaluated the histopathologic and cryosectional appearance of bone bruise injuries of the knee detected on MRI. Histologic evaluation of bone biopsies from 3 patients revealed microfractures of cancellous bone, edema and bleeding in the fatty marrow. Between intact lamellar bone trabecules, fragments of hyaline cartilage mixed with highly fragmented bone trabecules were found. Postmortem specimens were obtained from 2 more patients, killed in motor vehicle accidents. MRI revealed bone bruise injuries of the lateral femoral condyle and of the lateral tibial plateau in 1 knee and anterior cruciate ligament disruption, a medial meniscus tear and bone bruise injury of the tibial plateau and of the lateral femoral condyle in the other specimen. The specimens were embedded in physiologic saline solution and frozen to -30 degrees C. By rotationcryotomy, 1 mm slices were removed from the surface of the specimens and documented on photographs. Subchondral lesions and bleeding were found, corresponding to the MR images.

Partial meniscectomy and osteoarthritis. Implications for treatment of athletes.

The biphasic ultrastructure of the meniscus and of articular cartilage provides their function in the complex biomechanics of the knee joint including load distribution, shock absorption, viscoelasticity, a smooth low friction gliding surface and resilience to compression. Meniscectomy may lead to destruction of cartilage and to osteoarthritis of the knee joint. Osteoarthritic changes after meniscectomy have been reported in up to 89% of patients. Retrospective analysis after open or arthroscopically assisted meniscectomy revealed restriction in sports to be between 2 and 50% and cessation of sports to be between 2 and 25%. Generally, patients with degenerative changes at the time of surgery are reported to have lower knee joint function and to resume sports activities later. Pharmalogical measures to treat osteoarthritis following previous meniscectomy include pain medication and intra-articular drug administration. Additionally, range of motion and strengthening exercises and moderate athletic activities are recommended. When surgery is considered, correctional osteomies and unicompartmental or total knee arthroplasty depending on the degree of osteoarthritis are preferred.

Surgical treatment of neuropathic scoliosis: morphologic and functional outcome.

We evaluated the morphologic and functional outcome as well as the extent of satisfaction following surgical treatment in 41 patients with progressive neuropathic scoliosis. The mean follow-up time was 5.6 years (range 2.5-20 years), and follow-up rate was 97.6%. Posterior spine fusion was performed with new instrumentation techniques (Luque/Luque-Galveston, CD, ISOLA) in 29 patients, with extension onto the sacrum in 16 patients, and Harrington instrumentation in 12. In 20 patients we did an additional intervertebral disc excision and fusion. Mean correction of the thoracic spine deformity, as assessed by comparing the Cobb angles on pre- and postoperative X-rays, was 53%, and of the lumbar spine 55.2%, in patients classified as Lonstein I. Scolioses classified as Lonstein II evidenced an average correction of 46.2%. Functional improvement according to the Rancho-Los Amigos scheme could be demonstrated in 20 patients. Seventeen patients remained unchanged, whereas 4 patients showed deterioration. Cosmetic results were rated as excellent by 25 patients, good by 7, and poor by 1. For 8 patients the appearance was unimportant. Pain relief was experienced in all cases (n = 4) of the preoperative low-back or abdominal pain. The major complications were deep wound infection in 3 patients which led to revision surgery, and removal of instrumentation in 1 patient.

[The conservative and surgical therapy of traumatic humeral shaft fractures]. / Konservative und operative Therapie traumatischer Oberarmschaftbrüche.

Sixty-three patients with humeral shaft fractures were evaluated clinically and radiographically 18 months after injury; 27 patients were treated surgically (group A) and 36 patients conservatively (group B). Analysis of the results according to a score by Kwasny revealed 6.2 points in group A and 2.2 points in group B (P < 0.0001; F = 46.9). The results of these two comparable groups suggest that conservative treatment of humeral shaft fractures is superior regarding mobility of the shoulder and elbow, strength, the incidence of neurological complications, pain, subjective rating and cosmesis. There were no differences on roentgenograms between the two groups (P = 0.48).

Influence of magnetic resonance imaging on indications for arthroscopy of the knee.

In a prospective study, magnetic resonance imaging was performed before arthroscopy for all patients (n = 121) with a meniscal tear (n = 125). Criteria of the study were stable cruciate and collateral ligaments, absence of pathologic radiographic findings, and absence of prior surgical interventions of the involved knee joint. In 43 knees (34%), the clinical diagnosis of a meniscal tear was discarded because of the results of the magnetic resonance imaging examination. Synovitis was diagnosed in 16 patients (13%), articular cartilage damage in 10 patients (8%), bone bruise injuries in 10 patients (8%), osteochondritis dissecans in 3 patients (2%), disruption of the inner layer of the medial collateral ligament in 3 patients (2%), and osteonecrosis in 1 patient. The use of magnetic resonance imaging in establishing diagnosis of disorders of the knee joint altered treatment in a significant proportion of patients. Magnetic resonance imaging should be done before arthroscopy of the knee in all cases in which the clinical diagnosis has been reduced to a suspected meniscus injury.

The effect of ultrasonographic screening on the incidence of developmental dislocation of the hip.

The effect of ultrasonographic screening and treatment with a Pavlik harness on the incidence of developmental dislocation of the hip has been studied retrospectively. Observations were made at three different consecutive periods; in the first, clinical screening was carried out, in the second, ultrasonography was added for children up to 3 months of age, and in the third ultrasonography was used within the first few days of birth. A significantly decreased dislocation rate was demonstrated in each group, suggesting that early ultrasonography was of value in the early detection of dislocation.

Rotation cryotomy: medical and scientific value of a new serial sectioning procedure.

Preparation of thin serial sections for comparative macromorphologic investigations has always represented a grave technical problem, especially in the case of regions in which bone as well as soft tissue are to be documented within their natural relations to each other in any desired sectional plane. Non-decalcified specimens up to the size of a whole cadaver are embedded in physiologic medium, precisely positioned, and deep-frozen to a specimen-ice block. A newly developed device, working on the basis of blades rotating at high speed, allows quick, successive removal of sections from the surface of the specimen block, with a thickness of each section infinitely variable between 0.1 and 5 mm. Following each cut, the new surface of the block can be documented photographically or on videotape for macromorphologic evaluation. So far more than 1,000 human, animal, and botanical specimens have been sectioned and evaluated with this method. In none of the cases were specimens damaged. Furthermore, any desired sectional plane could be adjusted: consequently a definite correlation between these sections and previous sonography, magnetic resonance (MR), or computed tomography (CT) images could be established. As serial cryosectioning becomes available to a far wider circle of medical and natural scientists, high-quality results should be obtained at lower costs.

[Problems in removal of a broken unreamed tibial nail]. / Das Problem der Entfernung eines gebrochenen unaufgebohrten Tibianagels.

A solid AO unreamed tibial nail was found to be broken at the revision operation for a pseudoarthrosis following open tibial fracture treatment in a 17-year-old girl. The nail breakage had not been detectable in the roentgenograms. Access to the broken nail was achieved through a longitudinal osteotomy via the tibial tuberosity. A metal drill was used to drill a 5-mm hole proximally into the medial aspect of the nail. There the tip of an elevatorium could be inserted, which allowed force to be applied along the longitudinal axis of the nail. Additionally, another longitudinal osteotomy had to be performed immediately distal to the pseudoarthrosis, and a bone distractor was applied in between. Thus, the nail loosened and could be removed completely. The bony defect was filled with autologous bone graft and a 9-hole AO tibial plate was applied to stabilize the tibia. We report on the breakage of this system and the surgical management of this complication.

Osteoarthritis after arthroscopic partial meniscectomy.

The purpose of this study was radiologic assessment of osteoarthritis after arthroscopic partial meniscectomy. At an average followup of 53.5 months, 284 consecutive patients were retrospectively evaluated clinically and radiologically. Two hundred forty-seven patients had been treated for medial (Group I) and 37 for lateral meniscal tears (Group II). Preoperative radiographs were compared with those at followup and were classified. The results were analyzed statistically. Osteoarthritic changes were classified as being worse in 38% of the patients after medial and in 24% of the patients after lateral arthroscopic partial meniscectomy. Further subclassification and comparison of patients with or without already existing articular surface damage at the time of arthroscopy were not found to have significant impact on the prevention of osteoarthritic changes. Patients who were older than 40 years of age and who had undergone arthroscopic partial medial meniscectomy were radiologically classified with a significantly higher rate of osteoarthritis than patients who were younger than 40 years. Partial medial or lateral meniscectomy leads to a significant increase of osteoarthritic changes, even when this intervention is performed arthroscopically.