[Periprosthetic knee fractures]. / Periprothetische Frakturen des Kniegelenkes.

BACKGROUND: The cumulative incidence of periprosthetic fractures around the knee is increasing further because of an extended indication for knee replacement, previous revision arthroplasty, rising life expectancy and comorbidities. AIM OF THE WORK: The relevance of local parameters such as malalignment, osseous defects, neighbouring implants, aseptic loosening and low-grade infections may sometimes be hidden behind the manifestation of a traumatic fracture. A differentiated diagnostic approach before the treatment of a periprosthetic fracture is of paramount importance, while the physician in-charge should also have particular expertise in fracture treatment and in advanced techniques of revision endoprosthetics. The following work gives an overview of this topic. RESULTS: Valid classifications are available for categorising periprosthetic fractures of the femur, the tibia and the patella respectively, which are helpful for the selection of treatment. CONCLUSIONS: With the wide-ranging modern treatment portfolio bearing in mind the substantial rate of complications and the heterogeneous functional outcome, the adequate analysis of fracture aetiology and the corresponding transformation into an individualised treatment concept offer the chance of an acceptable functional restoration of the patient at early full weight-bearing and prolonged implant survival. The management of complications is crucial to the final outcome.

[Post-treatment rehabilitation after autologous chondrocyte implantation: State of the art and recommendations of the Clinical Tissue Regeneration Study Group of the German Society for Accident Surgery and the German Society for Orthopedics and Orthopedic Surgery]. / Nachbehandlung bei der autologen Chondrozytentransplantation: Eine Bestandsaufnahme und Empfehlung der AG Klinische Geweberegeneration der DGU/DGOOC.

BACKGROUND: Over the course of the past two decades autologous chondrocyte implantation (ACI) has become an important surgical technique for treating large cartilage defects. The original method using a periostal flap has been improved by using cell-seeded scaffolds for implantation, the matrix-based autologous chondrocyte implantation (mb-ACI) procedure. MATERIAL AND METHODS: Uniform nationwide guidelines for post-ACI rehabilitation do not exist. A survey was conducted among the members of the clinical tissue regeneration study group concerning the current rehabilitation protocols and the members of the study group published recommendations for postoperative rehabilitation and treatment after ACI based on the results of this survey. RESULTS: There was agreement on fundamentals concerning a location-specific rehabilitation protocol (femoral condyle vs. patellofemoral joint). With regard to weight bearing and range of motion a variety of different protocols exist. Similar to this total agreement on the role of magnetic resonance imaging (MRI) for postsurgical care was found but again a great variety of different protocols exist. CONCLUSIONS: This manuscript summarizes the recommendations of the members of the German clinical tissue regeneration study group on postsurgical rehabilitation and MRI assessment after ACI (level IVb/EBM).

Autologous chondrocyte implantation (ACI) for cartilage defects of the knee: A guideline by the working group "Clinical Tissue Regeneration" of the German Society of Orthopaedics and Trauma (DGOU).

BACKGROUND: Autologous chondrocyte implantation (ACI) is an established and well-accepted procedure for the treatment of localised full-thickness cartilage defects of the knee. METHODS: The present review of the working group "Clinical Tissue Regeneration" of the German Society of Orthopaedics and Trauma (DGOU) describes the biology and function of healthy articular cartilage, the present state of knowledge concerning therapeutic consequences of primary cartilage lesions and the suitable indication for ACI. RESULTS: Based on best available scientific evidence, an indication for ACI is given for symptomatic cartilage defects starting from defect sizes of more than three to four square centimetres; in the case of young and active sports patients at 2.5cm(2), while advanced degenerative joint disease needs to be considered as the most important contraindication. CONCLUSION: The present review gives a concise overview on important scientific background and the results of clinical studies and discusses the advantages and disadvantages of ACI. LEVEL OF EVIDENCE: Non-systematic Review.

Analysis of forces of ACL reconstructions at the tunnel entrance: is tunnel enlargement a biomechanical problem?

Bone tunnel enlargement is a common phenomenon following reconstruction of the anterior cruciate ligament (ACL). Biomechanical and biological factors have been reported as potential causes of this problem. However, there is no analysis of forces between the graft and bone, as the graft changes direction at the bone tunnel entrance. The purpose of this study was to study these 'redirecting forces'. Magnetic resonance images of 10 patients with an ACL reconstruction (age: 26+/-6.8 years) were used to determine the angle between graft and drill holes. Vector analysis was used to calculate the direction and magnitude of the perpendicular component of the force between the bone tunnel and the graft at the entrance of the bone tunnel. Force components were projected into the radiographically important sagittal and coronal planes. Tension of ACL reconstructions was recorded during passive knee motion in 10 cadaveric knee experiments (age: 28.9+/-10.6 years) and the tension multiplied with the force component for each plane. Results are reported for the coronal and sagittal planes, respectively: For -10 degrees of extension, the percentages of graft tension were determined to be 17+/-7 (max: 26; min: 7%) and 26+/-9 (max: 39; min: 16%) for the tibia. They were 59+/-6 (max: 66; min: 48%) and 99+/-1 (max: 1.00; min: 99%) for the femur. Force components were 14.68+/-6.54 and 25.73+/-12.96 N for the tibial tunnel. For the femoral tunnel, they were 52.48+/-19.03 and 90.77+/-32.06 N. Percentages of graft tension and force components were significantly higher for the femoral tunnel compared with the tibial tunnel. Moreover, in the sagittal direction, force components for the femoral tunnel were significantly higher compared with the coronal plane (Wilcoxon test, p < 0.01). The differences in force components calculated in this study corresponds with the amount of tunnel enlargement in the radiographic planes in the literature providing evidence that biomechanical forces play a key role in postoperative tunnel expansion.

[Capacity for sport and the sensorimotor system after stabilization of the shoulder in overhead athletes]. / Sportfähigkeit und Sensomotorik nach Schulterstabilisierung beim Uberkopfathleten.

The anterior capsulolaboral reconstruction according to Jobe is a modification of the Bankart operation, performing the capsular shift via a subscapularis-split approach avoiding any incision into the musculature. A total of 24 overhead athletes with posttraumatic, chronic anterior shoulder instability underwent surgery. Twenty-two patients were examined after an average follow-up of 2.8 +/- 0.7 years. On average, a Constant-Murley-Score of 93.7 +/- 5.3 points and an ASES-Score of 95.0 +/- 5.1 points were achieved. The relaxation rate was 9 %. The study demonstrated, that despite the good clinical results, only 12 out of 22 (55 %) of patients were able to return to their previous sports activity level. This relevant problem is in agreement with other similar studies so that it was further addressed by determination of proprioception and electromyographic muscle activity. Postoperatively, a persisting proprioceptive deficit as well as an altered EMG pattern was found with a significant reduction in activity of the deltoideus muscle on the operated side. The analysis of the data of each patient showed that there was a significant relation between the restitution of proprioception and ability to return to the previous sports activity level. In contrast, the relation between EMG pattern and full recovery to completely unrestricted shoulder function was not significant.

Changes in the extracellular matrix of the autogenous patellar tendon graft after posterior cruciate ligament reconstruction: a biochemical study in sheep.

The left knee joints of female German sheep were operated, replacing the posterior cruciate ligament by the central third of the patellar tendon. After 2, 6, 16, 26 and 52 weeks the graft of the operated leg as well as the contralateral central third of the patellar tendon and the posterior cruciate ligament were dissected and used for biochemical analysis. The total glycosaminoglycan content in grafts increases within the first year up to 5 fold and is higher than that of the patellar tendon, but is lower than that of the cruciate ligament. The distribution pattern of glycosaminoglycans differ in the posterior cruciate ligament and the patellar tendon. In cruciate ligament the main components are chondroitin sulfate (76%) and hyaluronan (15%). In the patellar tendon a higher portion of dermatan sulfate (approx. 16%) was found, next to 52% chondroitin sulfate and 22% hyaluronan. During the examination time the grafts show changes in the concentration and the distribution pattern of glycosaminoglycans. The chondroitin sulfate content increases during the experimental period from 1.4 +/- 1.2 mumol/g dry weight (d.w.) to 8.7 +/- 2.9 mumol/g d.w. After 1 year the chondroitin sulfate content in the graft does not differ significantly from that of the cruciate ligament. In the grafts the concentration of chondroitin (non sulfated) increases after 6 weeks up to 1.3 +/- 0.6 mumol/g d.w. in comparison to the value after 2 weeks (0.2 +/- 0.1 mumol/g d.w.) and also in the other groups (16, 26 and 52 weeks) it remains significantly increased. After 1 year the dermatan sulfate content in the graft has increased up to the fifth-fold compared to the value after 2 weeks and is higher than in the patellar tendon and in the cruciate ligament. In graft the hyaluronan content (1.0 +/- 0.4 mumol/g d.w. does not differ significantly in the groups 2, 6, 16, 26 and 52 weeks after operation, but in all five groups it is lower than in the cruciate ligament (2.4 +/- 1.0 mumol/g d.w.). Dermatan and heparan sulfate are not or only little detected in all three tissues. The distribution pattern of glycosaminoglycans in graft shows chondroitin sulfate and dermatan sulfate being the major parts of glycosaminoglycans with a slight increase of these components in the different groups during the experimental period. Hyaluronan makes up to 24 +/- 5% of the whole content of glycosaminoglycans after 2 weeks and decrease to 8 +/- 1% after 52 weeks.(ABSTRACT TRUNCATED AT 400 WORDS)

Histochemical aspects of the proteoglycans of patellar tendon autografts used to replace the posterior cruciate ligament.

In the female German black-faced sheep the posterior cruciate ligament was replaced by a free patellar tendon autograft and after 2, 6, 16, 26 and 52 weeks tissue samples of the graft's center (axial region far from bones) were removed for histochemistry and electron microscopy. To localize the proteoglycans Alcian Blue and 0.3 M MgCl2 were added to the fixative solution. The distribution of the proteoglycans in the graft was compared to that of a normal patellar tendon and of a normal posterior cruciate ligament. In the patellar tendon spindle-shaped cells predominated and proteoglycans appeared as short filaments at regular intervals between the collagen fibrils. In the posterior cruciate ligament chondroid cells and long filaments in a net-work-like arrangement were seen. In the patellar tendon autografts short interfibrillar filaments prevailed after 2, 6 and 16 weeks. After 26 weeks and particularly after 52 weeks long filaments also appeared. Digestion with Chondroitinase ABC, AC and Hyaluronidase suggested that the short filaments were PGs containing dermatan sulfate. In grafts, in the early phases the fibroblasts predominated, while in the late phases mainly chondroid cells were observed. The grafts showed aspects of the normal posterior cruciate ligament. However, differences remained, for example the thin collagen fibrils, which could represent one of the reasons for a secondary graft failure.

Comparison of human bone marrow stromal cells seeded on calcium-deficient hydroxyapatite, beta-tricalcium phosphate and demineralized bone matrix.

The aim of this study was to compare three resorbable biomaterials regarding seeding efficacy with human bone marrow stromal cells (BMSCs), cell penetration into the matrix, cell proliferation and osteogenic differentiation. Calcium-deficient hydroxyapatite (CDHA), beta-tricalcium phosphate (beta-TCP), and demineralized bone matrix (DBM) were seeded with human BMSCs and kept in human serum and osteogenic supplements for 3 weeks. Morphologic and biochemical evaluations were performed on day 1, 7, 14 and 21. The allograft DBM and CDHA exhibited both an excellent seeding efficacy while the performance of beta-TCP was lower when compared. The total protein content and the values for specific alkaline phosphatase (ALP) increased on all matrices and no significant difference was found for these two markers. BMSCs in monolayer had a significant increase of protein, but not of ALP. Osteocalcin (OC) values increased significantly higher for BMSC in cultures on DBM when compared to CDHA and beta-TCP. The OC levels decreased significantly in the BMSC monolayer culture. BMSCs were found inconsistently within the synthetic materials, whereas in DBM they were found more homogeneously distributed throughout the matrix. All three matrices promoted BMSC proliferation and differentiation to osteogenic cells. DBM allografts seem to be more favorable with respect to cell ingrowth tested by histology, and osteogenic differentiation ascertained by an increase of OC. CDHA with its high specific surface area showed more favorable properties than beta-TCP regarding reproducibility of the seeding efficacy.

Effects of cyclic longitudinal mechanical strain and dexamethasone on osteogenic differentiation of human bone marrow stromal cells.

The aim of the study was to investigate the effect of cyclic mechanical strain on differentiation markers in the presence or absence of dexamethasone. Human bone marrow stromal cells (BMSC) from seven donors (32.5+/-6.2 years) were cultivated with (D+) or without (D-) dexamethasone. A cyclic mechanical strain with an elongation of 2% (D+2; D-2) or 8% (D+8; D-8) was applied for three days with a stimulation time of three times two hours each day. Levels of alkaline phosphatase (ALP) and osteocalcin (OC) were compared after time intervals of four and seven days. mRNA expression of Collagen I, III and Cbfa1 was investigated after one, four, and seven days. ALP levels were significantly increased in the D+8 group after four and seven days (147.1+/-6.3%; p<0.05 and 168.6+/-6,5%; p<0.03) and in the D-8 group after 7 days (197.4+/-10.4; p<0.04). Cyclic strain had a significant influence on ALP-secretion (F=7.5; p<0.01). In the D-8 group there was a significant increase in OC secretion after 4 days (140.9+/-12.5%; p<0.05).; p<0.01). The effect of stretching was significantly stronger than that of dexamethasone (F=17.2 vs. 1.8). Collagen I (Col I) expression was upregulated in D+8 cultures after 4 days (215.0+/-53.3 p<0.04) and after seven days (166.7+/-55.7; p<0.04). Collagen III (Col III) expression was upregulated in D+2 and D+8 cultures after 4 days (200.7+/-16.3 and 185.9+/-12.7; p<0.04) and after seven days (154.4+/-10.1 and 118.8+/-16.4; p<0.04). There was a significant increase of Cbfa1 expression in D+8 cultures at all investigated time intervals (day 1: 105.5+/-3.7%; day 4: 104.7+/-3.0%; day 7: 104.4+/-2.1%; p<0.03). Stretching (F=20.0; p<0.01) was a stronger contributor to Cbfa-1 expression than dexamethasone (F=12.1; p<0.01). Cyclical mechanical stimulation with 8% elongation increases ALP and OC levels and upregulates Col I and III synthesis and Cbfa1 expression. In the short term, cyclical stretching is a stronger differentiation factor than dexamethasone. Cyclical stretching and dexamethasone both enhance the osteogenic commitment of hBMSC.

The relationship of mechanical properties to morphology in patellar tendon autografts after posterior cruciate ligament replacement in sheep.

In a sheep model the posterior cruciate ligament (PCL) was replaced by a patellar tendon autograft (PTAG) using the central one-third of the ipsilateral patellar tendon (PT). The sheep were sacrificed at 16, 26, 52 and 104 weeks postoperation. The PTAG, and, as controls, the contralateral PCL and PT were harvested. These were examined using biomechanical testing as well as light and transmission electron microscopy, including immunohistological techniques. The material properties (maximum stress, elastic modulus) were compared to the morphological features. The cellular distribution, the distribution of glycosaminoglycans (GAGs), the collagen fibril diameter and the occurrence of Type III collagen were studied. Prior to transplantation, the PTAG was shown to be superior in maximum stress (57.2 +/- 5.5 MPa vs 41.3 +/- 1.9 MPa) and elastic modulus (368.8 +/- 49.3 MPa vs 172.3 +/- 14.6 MPa) to the PCL. The early decline in material properties of the PTAG (maximum stress 22% and elastic modulus 42% of the control) after free grafting paralleled a cell- and capillary-rich PTAG tissue with remnants of necrosis and a poorly organized extracellular matrix. Two years after implantation, with progressive alignment of the tissue matrix, maximum stress and elastic modulus acquired approximately 60 and 70% of the control, respectively. However, there was also an evidence of degenerative changes characterized by acellular areas, loss of the normal bundling pattern of collagen fibers and abnormal accumulation of GAGs. Ultrastructurally, there was a predominant shift to thin collagen fibrils in the PTAG compared to PCL and PT, both consisting of thick and thin collagen fibrils. Thin fibrils were demonstrated to be, in part, split thick fibrils as well as newly formed fibrils. Most of these thin fibrils revealed a positive reaction with antibodies to Type III collagen.

Healing of the patellar tendon autograft after posterior cruciate ligament reconstruction--a process of ligamentization? An experimental study in a sheep model.

Forty-eight skeletally mature sheep underwent posterior cruciate ligament reconstruction with free patellar tendon autografts in one knee; the contralateral knee served as a control. Immediate rehabilitation without immobilization followed. Autograft healing was evaluated by histologic, roentgenographic, and biomechanical techniques up to 2 years postoperatively. After implantation, the autograft tissue underwent necrosis and degeneration, followed by a gradual healing process comprising revascularization, cellular migration, and formation of an extracellular matrix. The autograft bone pegs were osseously incorporated by 6 weeks. After an initial loss of strength, the material properties of the operated knee recovered to only about one-third that of the control. Better alignment of the collagen fiber bundles resulted in increased material properties, up to approximately 50% of the control at 52 weeks. After 2 years, the autograft tissue was found to differ structurally and mechanically from a ligament, suggesting that the autograft may never approach normal ligament characteristics. Degenerative alterations, the wide-spread presence of type III collagen, and abnormal accumulations of glycosaminoglycans in the autograft correlated with a maximum stress of 60% and an elastic modulus of 70% of the control. Although ligamentization was not seen, the staging of autograft healing into different phases based on distinct morphologic manifestations (necrosis, revitalization, collagen formation, and remodeling) and correlating with changing mechanical properties may provide a rationale for rehabilitation protocols with a realistic evaluation of the loading capacity of the replacement tissue.

Alterations of glycosaminoglycans during patellar tendon autograft healing after posterior cruciate ligament replacement. A biochemical study in a sheep model.

In each of 30 skeletally mature sheep, the posterior cruciate ligament was replaced in one knee by a free patellar tendon autograft using the central third of the ipsilateral patellar tendon. The healing autograft was compared with the contralateral posterior cruciate ligament and the patellar tendons and posterior cruciate ligaments of nonoperated animals. The content of glycosaminoglycans, chondroitin sulfate disaccharides, and dermatan sulfate disaccharides was assessed biochemically at six periods during the 2 years after surgery. The total glycosaminoglycans and chondroitin sulfate disaccharides in the native posterior cruciate ligament was threefold that in the native patellar tendon. In contrast, the amount of dermatan sulfate disaccharides was similar in both the native tendon and native ligament. In the autograft, glycosaminoglycans and chondroitin sulfate disaccharides increased significantly to about 144% and 172%, respectively, of the contralateral posterior cruciate ligament at Week 104. The dermatan sulfate disaccharides in the autograft also showed a significant increase up to Week 26, followed by a remarkable but not significant decrease until the end of the study. In the contralateral posterior cruciate ligament, the dermatan sulfate disaccharides increased significantly between Weeks 52 and 104. Thus, the amount of dermatan sulfate disaccharides was similar in both the autograft and the contralateral posterior cruciate ligament after 2 years. This study suggests that the patellar tendon autograft did not completely assume the biochemical properties of the posterior cruciate ligament.

Collagen fibril organization in the patellar tendon autograft after posterior cruciate ligament reconstruction. A quantitative evaluation in a sheep model.

We replaced the posterior cruciate ligament in 30 skeletally mature sheep with a patellar tendon autograft using the central third of the ipsilateral patellar tendon. The healing autograft was compared with the contralateral posterior cruciate ligament and the patellar tendons and posterior cruciate ligaments of nonoperated animals. The collagen fibril diameters were analyzed using transmission electron photomicrographs of fibril cross sections taken at six periods during the 2 years after surgery. The patellar tendon and posterior cruciate ligament were characterized by a broad, nongaussian distribution of collagen fibril diameters. The autografts shifted to a unimodal distribution by an increase of small-diameter collagen fibrils. The frequency of small-diameter fibrils measuring up to 100 nm was 99% after 2 years. At that time, these small-diameter fibrils represented 91.6% of the area covered by collagen fibrils. The mean diameter of the collagen fibrils in the autografts significantly decreased to 45% of the controls at Week 26 and remained at this level until the end of this study. The percentage of area covered by collagen fibrils per 1 micron 2 was 78% of the controls 2 years post-operatively. This study suggests that the patellar tendon autograft could not reproduce the collagen fibril organization of the posterior cruciate ligament. This may be a biologic factor responsible for inconsistent results in posterior cruciate ligament replacement.

Proprioception after rehabilitation and reconstruction in knees with deficiency of the anterior cruciate ligament: a prospective, longitudinal study.

We assessed proprioception in the knee using the angle reproduction test in 20 healthy volunteers, ten patients with acute anterior instability and 20 patients with chronic anterior instability after reconstruction of the anterior cruciate ligament (ACL). In addition, the Lysholm-knee score, ligament laxity and patient satisfaction were determined. Acute trauma causes extensive damage to proprioception which is not restored by rehabilitation alone. Three months after operation, there remained a slight decrease in proprioception compared with the preoperative recordings, but six months after reconstruction, restoration of proprioception was seen near full extension and full flexion. In the mid-range position, proprioception was not restored. At follow-up, 3.7 +/- 0.3 years after reconstruction, there was further improvement of proprioception in the mid-range position. There was no difference between open and arthroscopic techniques. The highest correlation was found between proprioception and patient satisfaction. After reconstruction of the ACL reduced proprioception may explain the poor functional outcome in some patients, despite restoration of mechanical stability.

Ultrastructural changes of the patellar tendon as a cruciate ligament substitute (one year and two year results).

In four black-faced sheep, the posterior cruciate ligament was replaced with a free autogenous patellar tendon transplant. Tissue samples from the transplants were investigated by light and electron microscopy 1 year and 2 years after surgery. The normal contralateral posterior cruciate ligament and the normal contralateral patellar tendon were used as controls. The structural differences concerned cells, collagen fibrils, elastic tissue and proteoglycans. Most of the cells of the contralateral patellar tendon were spindle-shaped, whereas those of the transplant were frequently chondroid. In the central region of the transplant as well as in the area far from the bone, cell degenerations, and occasionally hypo- or even acellular zones were found. Measurements of the diameter of collagen fibrils in both contralateral patellar tendon and posterior cruciate ligament showed a more or less pronounced bimodal distribution. A unimodal distribution with mainly thin fibrils (20-60 nm) was demonstrated in the transplant tissue which also revealed some morphological alterations of the collagen fibrils. Thin elastic fibers (microfibrils and amorphous material) were randomly scattered among the collagen fibrils of the control samples, bundles of microfibrils (without amorphous material) characterized the transplant. Staining with Alcian blue in the presence of 0.3 M MgCl2 demonstrated a close relationship between proteoglycans and collagen fibrils as well as elastic components in patellar tendon. This arrangement was lost in the transplant where abundant proteoglycans were revealed which, however, composed a tight irregular network between the collagen fibrils. The results serve as a baseline for understanding the impaired biochemical properties of a free autogenous patellar tendon transplant.

[Nonunion of the humeral diaphysis - operative and nonoperative treatment]. / Diaphysäre Oberarmpseudarthrosen - operative und konservative Behandlung.

Operative treatment of acute humeral shaft fractures represents a major source of nonunions. The analysis of the biomechanical and biological causes of diaphyseal nonunions of the humerus is a prerequisite for the successful treatment of ununited humeral shaft fractures. Biologically active nonunions heal after debridement and correction of deformities with an improvement of mechanical stability, preferably by fixation with a compression plate. In atrophic nonunions, the restoration of the biologic capacity to restore osteogenesis by bone grafting is additionally necessary. The treatment of synovial pseudarthrosis and infected nonunion requires removal of bone and debridement of synovial and infected avascular tissues, respectively. Intramedullary nails to improve mechanical stability and nonoperative treatment with extracorporeal shock waves should only be used in a few special cases which do not have any severe deformities.

[Significance of lung contusion in mortality following polytrauma. Possibilities for therapeutic influence]. / Die Bedeutung der Lungenkontusion für die Letalität nach Polytrauma. Möglichkeiten der therapeutischen Beeinflussung.

Multiple trauma is often associated with blunt thoracic injuries. Especially lung contusion can result in respiratory insufficiency and therefore a higher mortality rate. In our prospective study comparing 8 multiple trauma patients with and without associated lung contusion, we found that respiratory function was already significantly disturbed (decrease of paO2/FiO2 and increase of AaDO2, a rise in extravascular lung water (EVLW) both early after trauma and also with a second peak following the 4th day. This group (LK) developed significantly more cases of respiratory distress (ARDS). The disturbance of respiratory function seen initially was interpreted as a consequence of the direct mechanical impact, leading to the formation of interstitial fluid and hematoma. The frequent development of ARDS in the LK-group probably results from a pronounced activation of cellular and humoral mechanisms and therefore an enforced injury of the pulmonary capillary bed. A significant increase of pulmonary infections or the development of sepsis was not seen in the LK-group and is probably not responsible for the higher ARDS-rate in this group.

[Minimally invasive screw fixation of the intracapsular femoral neck fracture in elderly patients]. / Die minimal-invasive Schraubenosteosynthese der medialen Schenkelhalsfraktur bei betagten Patienten.

INTRODUCTION: Increasing life expectancy is associated with an increase of geriatric fractures such as intracapsular femoral neck fractures. Their treatment by arthroplasty imposes a significant burden on our health care system. METHODS: In an open clinical study we investigated the complication rate of a less expensive and less invasive, femoral head saving operative procedure. Between June 1997 and June 2000, 205 intracapsular femoral neck fractures of elderly patients (mean age 78.1 +/- 11.8 years) were fixed with cannulated screws. RESULTS: Seventy-seven percent were displaced fractures and 15.6% were impacted Garden I fractures. Reoperation after internal fixation occurred in 38 patients. The most frequent cause of reoperation was secondary arthroplasty due to redisplacement (14x), femoral head necrosis (10x) and non-union (7x). Implant removal (4x), wound hematoma (1x) and femoral head penetration by screws (2x) were other causes for reoperation. CONCLUSION: Less invasive cannulated screw fixation of intracapsular femoral neck fractures should be considered as a treatment option, because it is a smaller and less expensive operation than prosthetic replacement. Adequate reduction and screw placement, however, are a prerequisite for successful outcome.

The patellar tendon graft for PCL reconstruction. Morphological aspects in a sheep model.

Surgical reconstruction of the PCL has not yet gained the acceptance that ACL reconstruction has achieved. However, in selecting an autograft to restore PCL function in symptomatic posterior knee instability, the free patellar tendon autograft is commonly used at present. Knowledge of the basics in graft healing and of factors regulating this healing process are still limited. It is of interest to determine the biologic response and final morphology of a patellar tendon autograft after PCL replacement. Based on morphological studies in PCL replacement in a sheep model the patellar tendon autograft under-goes necrosis and degeneration followed by a gradual healing process comprising revitalization (i.e. revascularization and cellular proliferation), formation of extracellular matrix components and remodeling. The autograft bone pegs become osseointegrated by 6 weeks. After 2 years, the autograft tissue differs structurally from a ligament, suggesting that the autograft may never approach normal ligament characteristics. Degenerative alterations in the core region of the autograft, the widespread presence of type III collagen and fibronectin, as well as the predominance of thin collagen fibrils do not favor a ligamentization process. The understanding of the autograft healing process remains the prerequisite for a realistic assessment of the biologic PCL replacement and will be a baseline of studies with the goal of influencing the healing process and thus improving the clinical results.