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.

[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.

[4-fragment fracture of the proximal upper arm]. / Die 4-Fragment-Fraktur des proximalen Oberarms.

Four-fragment fractures have to be accorded great importance because they are so severe. The morphology allows differentiation of two types, the dorsolateral fracture type and the impacted fracture type. Over a 4-year time span, 13 of these fractures were treated with minimal osteosynthesis. This involve the open anatomical reduction and allogeneic spongiosa grafting and retention of the fracture with screws and, if necessary, K-wires and tension banding. After an average of 26.3 months the shoulder function was evaluated using the CONSTANT score. The dorsolateral fractures were scored of 87.2 while the impacted fractures were scored at 88.8. No necrosis of the humeral head was found. These good results show that after four-fragment fractures primary reconstruction of the humeral head should be preferred over primary prosthetic replacement.

[Diaphyseal pseudarthroses. Epidemiology and outcome]. / Diaphysäre Pseudarthrosen. Epidemiologie und Outcome.

From 1971 to 1993, a total of 759 cases of nonunion of both the upper and lower extremities were treated. In recent years the frequency of these cases of nonunion has clearly declined. Analysis of patient data shows a positive trend particularly for nonunion in the lower arm and leg while at the same time nonunion in the upper arm and leg remained essentially constant. Moreover, the proportion of aseptic to septic manifestations has shifted towards the aseptic forms in a ratio of 1:0.5. The treatment results of a representative, randomly chosen group (n = 107 out of a total of 392) from 1981 to 1993 are satisfactory with little statistical deviation for the upper extremity. The least pleasing results were seen in nonunion of the lower leg, which differed from the somewhat better results for the upper leg on the OLERUD score, with a statistical significance of P < 0.05. This study shows a very interesting development in clinical results.

[Age, activity and strength of knee ligaments]. / Alter, Aktivität und die Belastbarkeit von Kniebändern.

The cruciate ligaments of older persons are thought to have diminished biomechanical properties. On the other hand, joint immobilization also leads to similar functional losses in ligaments. It can be difficult to differentiate between these factors in older and immobile persons. The anterior and posterior cruciate ligaments of six younger (average age 30 years) and six older (average age 64.7 years) donors with similar levels of activity were subjected to biomechanical testing. Each sample had to meet the following conditions: appropriate age, no chronic vascular and cardiopulmonary disease found on autopsy, no signs of osteoarthrosis and no knee injuries. The material properties of maximum stress (e.g. ACL: young/old 24/21N/mm2), elastic modulus (e.g. ACL: young/old 144/129 MPa), and strain (e.g. ACL: young/old 25/28%), did not differ significantly (p less than 0.05). This indicates that older persons who are active do not necessarily show functional losses in the cruciate ligaments. Other data found in the literature can be ascribed to immobilization influences. In this data many of the older test persons had chronic vascular insufficiency, cardiopulmonary disease or malignancies.

Influence of immobilization on autograft healing in the knee joint. A preliminary study in a sheep knee PCL model.

The influence of immobilization on patellar tendon autograft healing was investigated in 12 sheep with replaced posterior cruciate ligaments of the knee (PCLs). In one group achillotomy immobilized the operated knee joint. In another group initial reduced weight-bearing was obtained by hanging the sheep in a special trapeze. In the third group no protection at all was given to the operated knee. The sheep in this group went within 8 weeks from partial use of the operated leg to unrestricted weightbearing and mobility. Biomechanical testing 16 weeks after the operation demonstrated a considerable decrease in the maximum force, ligament stiffness, and strain values in the achillotomy group, as well as an increase in posterior laxity. The best data were observed in the no-protection group. This study demonstrates the negative effect of immobilization on autograft healing in a sheep PCL model. Even early in the healing process tissue may be extremely sensitive to stress and strain.

Staging of patellar tendon autograft healing after posterior cruciate ligament reconstruction. A biomechanical and histological study in a sheep model.

The prerequisite for adequate rehabilitation after cruciate ligament reconstruction with a patellar tendon autograft is a thorough knowledge of the biologic healing processes. It is of interest to determine whether distinct phases similar to those in wound healing can be differentiated. It is also important to assess the magnitude of the biomechanical loading capacity and the duration of the healing processes. One posterior cruciate ligament in each of 48 skeletally mature sheep was replaced with a free patellar tendon autograft. Immediate rehabilitation without immobilization followed. Four phases of healing were demonstrated using the histologic condition of the autograft as a guide. The biomechanical data were correlated with the morphologic data. During the necrotic phase, a maximum of necrotic tissue was seen two weeks postoperatively. The strength of the graft is initially limited by the surgical fixation strength; however, later the intraarticular portion becomes the strength-limiting factor. During the revitalization phase, which is characterized by revascularization and proliferation of fibroblasts, and during the following phase, collagen formation, an increase in maximum stress is seen while the elastic modulus remains constant. Only in the remodeling phase is an increase in elastic modulus seen, owing to longitudinal alignment of the collagen bundles. One year after implantation, the autograft achieves approximately 50% of the material properties of the control. Even after two years, the autograft reaches only a maximum stress of 60% and an elastic modulus of 70% of the control. Ligamentization of the autograft could not be demonstrated in this study, but degeneration was seen in the core region of the graft during late remodeling.

The morphological effects of synthetic augmentation in posterior cruciate ligament reconstruction: an experimental study in a sheep model.

The treatment of posterior cruciate ligament (PCL) injuries remains controversial. Due to various problems, PCL reconstruction has not consistently produced the knee stability desired. Biological graft tissue undergoes a remarkable healing process comprising different phases. The strength of autogenous graft material decreases soon after operation. During this early healing phase synthetic augmentation could protect the graft tissue from overloading or overstretching, supporting the tissue revitalization and remodeling process. In order to evaluate the morphological effects of the ligament augmentation device (LAD) on a free patellar tendon autograft in PCL reconstruction, a comparative study in sheep was conducted. In 24 mature sheep, the PCL was replaced with either a patellar tendon autograft alone or a patellar tendon autograft augmented by the LAD. The LAD was fixed at both ends. After the operation the animals were not immobilized. Tibial fixation was released 8 weeks postoperation. The autografts of both groups were histologically evaluated after 2, 6, 16, 26, 52, and 104 weeks. In addition to necrotic and degenerative alterations, a remarkable inflammatory reaction could be seen in the LAD-augmented autografts early postoperation. Compared with the nonaugmented autografts, tissue formation and remodeling were delayed in the augmented group. After 1 and 2 years, the morphology of the autograft tissue was similar in both the augmented and nonaugmented group and differed from that of a normal PCL. The LAD was surrounded by a chronic inflammatory reaction, and collagen fiber ingrowth into the LAD was not observed. Using transmission electron microscopy, small diameter collagen fibrils were predominant in the graft tissue of both groups. Thus, a better remodeling of the autograft tissue in the presence of the LAD could not be demonstrated in this particular study. The value of synthetic augmentation of biological grafts in PCL reconstruction seems to be questionable at present.

[Morphologic aspects of alloplastic augmentation in replacement of the posterior cruciate ligament. An experimental study on the sheep]. / Morphologische Aspekte der alloplastischen Augmentation beim Ersatz des hinteren Kreuzbandes. Eine experimentelle Studie am Schaf.

The treatment of injuries to the posterior cruciate ligament (PCL) remains controversial. Various problems have prevented PCL reconstruction from consistently producing the knee stability desired. Biological graft tissue undergoes a remarkable healing process comprising different phases. The strength of autogenous graft material decreases soon after the operation. During this early healing phase synthetic augmentation could protect the graft tissue from overloading or overstretching, supporting the tissue restoration process. In order to evaluate the morphological effects of the ligament augmentation device (LAD) on a free patellar tendon autograft in PCL reconstruction a comparative study in sheep was conducted. In 24 mature sheep the PCL was replaced with either a patellar tendon autograft alone or a patellar tendon autograft augmented by the LAD. The LAD was fixed at both ends. The animals were not immobilized after the operation. Tibial fixation was released 8 weeks after the operation. The autografts of both groups were histologically evaluated after 2, 6, 16, 26, 52 and 104 weeks. In addition to necrotic and degenerative alterations a pronounced inflammatory reaction could be seen in the LAD-augmented autografts soon after the operation. Compared with the non-augmented autograft, tissue formation and remodeling was delayed in the augmented group. After 1 and 2 years, the morphology of the autograft tissue was similar in the augmented and the non-augmented group and was different from that of a normal PCL. The LAD was surrounded by a chronic inflammatory reaction, and collagen fiber ingrowth into the LAD was not observed. Transmission electron microscopy showed that small-diameter collagen fibrils were predominant in the graft tissue of both groups. Thus, better remodeling of the autograft tissue in the presence of the LAD was not demonstrable in this particular study. The value of synthetic augmentation of biological grafts of PCL reconstruction seems to be questionable at present.

[Healing phases in autogenous posterior cruciate ligament replacement. A decision aid for after-care. A biomechanical and histologic study]. / Die Einheilungsphasen beim autogenen hinteren Kreuzbandersatz. Entscheidungshilfe für die Nachbehandlung. Eine biomechanische und histologische Studie.

In a sheep model for reconstruction of the posterior cruciate ligament using the central one-third of the autogenous patellar tendon and immediate mobilization, the incorporation course was studied biomechanically, histomorphometrically and radiographically at eight different points in time up to 1 year after surgery. Four different phases of autograft healing were demonstrated on the basis of the histological events. The biomechanical data were correlated with the morphological findings. Phase 1--necrosis--was characterized by a maximum of necrotic autograft tissue 2 weeks postoperatively. Initially, graft strength was determined by the surgical fixation strength. During phase 2--revitalization--the autograft showed cellular proliferation and revascularization, starting from the periphery. The autograft was determined to be weakest during this phase. Phase 3--collagen formation--revealed a marked increase in newly formed collagen tissue between weeks 12 and 16. A significant increase in maximum load and stress was measured. In phase 4--remodeling--the longest phase, the collagen tissue appeared more compact and less cellular. The fiber bundles were arranged more longitudinally. However, the biomechanical properties remained clearly below that of a normal posterior cruciate ligament.

[The AIDS problem in accident surgery]. / AIDS-Problematik in der Unfallchirurgie.

In trauma surgery there is a particularly high proportion of patients in the age group most at risk of infection with AIDS. The result of an epidemiological study in our patients (HIV screening of all patients scheduled for surgery at a trauma center over 18 months) showed a prevalence of 0.1%. Specific therapeutic strategies must be developed to deal with the weakened immunity of HIV-infected patients. Fracture treatment in HIV-infected hemophiliacs is a special problem. Homogenous bone transplantation is described with reference to HIV. The particular danger of injury in trauma surgery is also investigated. The chain of infection is illustrated and used to demonstrate the precautions that can be taken against nosocomial HIV infections. Following infection with fluids containing HIV, specific measures must be taken. The legal aspects of HIV-antibody testing in the Federal Republic of Germany are elucidated. Finally, the problems of general preoperative HIV-antibody testing are discussed.