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.

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.

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.

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.

Successful resuscitation of a child with severe hypothermia after cardiac arrest of 88 minutes.

A 4-year-old boy broke through the ice of a frozen lake and drowned. The boy was extricated from the icy water by a rescue helicopter that was dispatched shortly after the incident. Although the boy was severely hypothermic, no cardiac response could be induced with field resuscitation measures, including intubation, ventilation, suction, and cardiopulmonary resuscitation. On admission, the primary findings included fixed, nonreacting pupils and asystole. The first core temperature measured was 19.8 degrees C (67.6 degrees F). During active, external warming, the first ventricular beats were observed 20 minutes after admission, and changed 10 minutes later to a sinus rhythm. Continuous monitoring included repeated arterial blood gas and electrolyte tests; prophylaxis for cerebral edema was performed with hyperventilation and administration of sodium Brevimytal and dexamethasone. Seventy minutes after admission, hemodynamics stabilized and the boy was transferred to the pediatric intensive care unit (PICU), where active external warming was continued to raise the core temperature at a rate of 1 degree C/hour. Adult respiratory distress syndrome developed, and the boy had to be ventilated in the PICU for 10 days. He was discharged home after another two weeks. He recovered fully. The rapid heat loss with the induction of severe hypothermia (< 20 degrees C; 68 degrees F) was the main reason for survival in this rare event of a patient with cardiac arrest lasting 88 minutes after accidental hypothermia.

[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.

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.

[The healing process after cruciate ligament repair in the sheep model]. / Heilungsvorgänge nach Kreuzbandplastik am Schafsmodell.

The patellar tendon autograft is widely used in cruciate ligament replacement. Knowledge of the basic processes involved in graft healing and of factors regulating the healing process is still limited. The patellar tendon and cruciate ligament are morphologically and biochemically distinct, which reflects the different mechanical forces acting on them. Based on morphological studies in posterior cruciate ligament replacement in a sheep model, the patellar tendon autograft undergoes a remarkable transformation process during healing. Distinct healing phases similar to those in would healing can be differentiated. During the phase of necrosis and degeneration the graft tissue becomes disorganized and mechanically weak. During the following phase of revitalization, which is characterized by revascularization, cellular proliferation and formation of collagen and other components of the extracellular matrix, the mechanical properties gradually improve. Even after the phase of remodeling the autograft tissue differs structurally and mechanically from a ligament, suggesting that the autograft only heals to a scar-like replacement tissue. The lack of a fascicular structure, the widespread presence of type III collagen and fibronectin, and the predominance of thin collagen fibrils correlate with a maximum stress of 60% and an elastic modulus of 70% compared with control values. In the sheep model cartilage alterations in the treated knees are similar to those in controls even though reconstruction of the posterior cruciate ligament cannot restore joint stability of controls.(ABSTRACT TRUNCATED AT 250 WORDS)

[Perioperative hygiene in trauma surgery]. / Perioperative Hygiene in der Unfallchirurgie.

Wound infection is the most significant nosocomial infection in trauma surgery. The acceptance of hygiene measures in the operational sector is generally high with a good educational level of personnel involved. In spite of this, inappropriate hygienic behavior can be observed repeatedly. The cause of this lies, in part, in a mental state of mind and is therefore not accessible to routine discussion. Several routinely relevant psychological aspects of hygiene behavior and motivation are shown. In addition, hygienic measures in the operating theater as they apply to the patient, the personnel and the surgical procedure are discussed. The authors opinion is stated.