Biomedical subjects
Publications and source records attributed to C Krenkel.
The case of a 30 year old man with acatalasemia is presented. The congenital disorder is charaterized by a lack or major reduction of catalase, an enzyme that catalyzes the decomposition of hydrogen peroxide to oxygen and water. The defect is inherited in an autosomal recessive fashion. Occasionally the defect manifests as progressive oral gangrene or Takahara's, disease.
For osteosynthesis and for bone transplant fixation in particular, a lag screw with a biconcave washer, the so called "Anchor Screw" (AS) has been introduced in maxillo-facial surgery. Using 2D-finite element analysis (FEA), the v. Mises and the circumferential stresses induced in underlying bone by this AS are analysed and compared to those under a conventional lag screw. The stress distributions below the biconcave washer of the AS were correlated with histomorphological bone reactions after AS osteosynthesis in two tumor patients, retrieved 12 weeks and 19 months after tumor surgery, respectively. Depending on the thickness of cortical bone, the v. Mises stress concentrations below the biconcave washer were lower than under the head of the conventional lag screw (CLS), but with a higher stress maximum concentrated around the rim of the washer. The circumferential stresses were only half as high around the AS, and thus the deformation of bone was reduced. As predicted by FEA, histology showed microcrack formation, but then after minimal resorption, remodelling of bone below the biconcave washer. Stable osteosynthesis could be demonstrated by bony union already after 12 weeks, and, while bone remodelling continued in the healed osteotomy, it had decreased around the screws after 19 months. It can be concluded from the biomechanical principles and the histomorphological findings that the AS appears superior to the CLS.
Particularly with true dislocation fractures, nonoperative treatment with maxillomandibular fixation followed by physiotherapeutic exercises leads to poor results, as was proved with axiography and clinical examinations. The main reason for this is the shortening and scarring of the condyloid process and the lack of function of the lateral pterygoid muscle. The condyle with its insertion of the muscle is usually displaced medially and anterially and nearly in touch with the origin on the pterygoid process so that protrusion by the muscle is no longer possible. The physiologic relationship of the lateral pterygoid muscle is restored after reduction of the condyle and osteosynthesis of the condylar neck fracture and the original distance between origin and insertion of the muscle is re-established and is a fundamental necessity for regaining function (Fig. 40). The anchor screw osteosynthesis is a most effective technique with low limitations for its indication. A comparison with plates shows this technique to be very economic because one anchor screw has the effect of at least one five-hole plate with five plating screws. That means a reduction of osteosynthesis implants of up to 80%, which saves a lot of money. On the other hand, the sophisticated technique of an anchor screw osteosynthesis needs some training on the part of the surgeon to get the best results possible. In general, we could realize that the anchor screw osteosynthesis gives a perfect adaptation of the fracture ends with compression also on the inner cortical layer, which with plates is only possible in rare cases. After an osteosynthesis of mandibular condyle neck fractures with an axial anchor-screw there are a few cases with an absorptive process in the fracture interface where the screw migrates in an axial direction with loosening of the osteosynthesis. This effect can be compared with the effect of a dynamic hip screw, which leads to compression of the callus, which speeds up bony union at the expense of shortening the bone. When the same absorption happens using a plate, the fracture ends cannot become sintered and the plate is in danger of fracturing as a result of metal fatigue. Ceipek evaluated 136 patients with mandibular condylar neck fractures treated with axial anchor screw osteosynthesis. Thirty-six of these screws showed signs of migration, but only 3.7% for more than 4 mm. For the migration process there are some important risk factors: difficult repositioning of the proximal fragment, dorsal luxation fracture, indirect method of anchor screw osteosynthesis, narrow condyle neck, no intercuspation in the molar region, no compliance, and disturbance of bone healing. Another stable technique of osteosynthesis should be used if patients show more risk than one risk factor.
The principle of the functionally dynamic bridging plate can be compared with the construction of a double bridge. The first bridge, which performs a protective function, is established by means of a plate which extends from one stump of the mandible to the other. The homogeneous, square-sectioned, central bar of the plate tolerates micromovements when stressed and demonstrates no predetermined breaking points. The second bridge ist established with the aid of the primary or secondary bone transplants, which are fixed to each other separately and to the stumps of the mandible with supplementary gracile implants. An adequate degree of functional stress on the bone transplant, i.e. the transmission of functional dynamical forces, is essential for the remodelling of the bone and must extend from one resected stump to the other. The choice of a square cross-section for the functionally dynamic bridging plate bar simplifies the three-dimensional bending and shaping of the plate on a template or the bone, thereby stressing the plate material uniformly and protecting it accordingly. This considerably facilitates the intraoral fixation of the plate. The functionally dynamic bridging plate system has proved successful in cases of partial mandibular resections, after tumour resections or in cases of defects following traumas and inflammations. It is suitable for cases with or without immediate bone reconstruction. It can be placed on the buccal side of the mandible, the caudal side or a combination of both. Positioning bone transplants can thus be carried out by a direct approach without obstruction and is consequently technically simpler.(ABSTRACT TRUNCATED AT 250 WORDS)
During autopsy, a reconstructed partial mandibular resection was recovered and subjected to histological examination. The mandible had been reconstructed 12 weeks earlier with a caudal plate and autologous cancellous bone from the iliac crest. Undecalcified microsections showed that the plate was firmly anchored by screws on both sides and on one side there was bony union. However, most of the free transplant bone had undergone 'unreplaced resorption.' Nevertheless, this method offers advantages over the conventional method of seating the plate on the buccal aspect and has interesting potential for further development.
Almost a quarter of all mandibular fractures are located in the condylar neck region and generally lead to disturbances of occlusion. Because they still possess active growth centres, children and adolescents can take advantage of the joint's remodelling capacity following conservative treatment of these fractures. Fractures with displacement of the condylar head in adults can interfere with function if they are not surgically reduced (Krenkel and Strobl, 1989). In addition, a compensatory overloading of the non-fractured side, which originally goes unnoticed, can bring about disc pathology and chronic pain years later. For this reason, a surgical technique was developed for the management of mandibular condylar neck fractures. A new axial/oblique-axial lag screw (anchor screw) with biconcave washers (anchor washer) makes it possible to carry out standardized osteosynthesis in the region of the thin mandibular condyle neck. Functional exercises can be initiated immediately after the operation. There are three operative procedures using an extraoral approach (1-3) and two using an intraoral approach (4-5), depending on the type and severity of the fracture: 1. Direct anchor screw osteosynthesis with closed gliding hole. 2. Indirect anchor screw osteosynthesis with open gliding groove and safety plates. 3. Osteosynthesis with a 'slanted-screw' plate for longer oblique fractures. 4. Intraoral anchor screw method. 5. Intraoral anchor screw method with intraoral 'slanted-screw' plate. The functional long-term results of conservatively and surgically treated mandibular condylar neck fractures were objectively documented by means of mechanical and electronic axiography. The functional long-term results of the condylar neck fractures treated surgically were significantly better than those treated conservatively.(ABSTRACT TRUNCATED AT 250 WORDS)
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The University of Innsbruck, Department of Dentistry, analysed the cephalograms of 23 prognathic patients whose dysgnathia was corrected by an osteotomy of the mandible only. The obtained results were compared with an analysis of the respective models. Documentation was obtained prior to surgery, post-operatively and during follow-up examinations over a period of at least six years. Evaluation of the results focused on occlusion and the WITS-appraisal. Prior to surgery 21 patients presented with a macromandibulosis which in 50 percent of the cases was combined with a micro- or retromaxillosis. As a rule, there were also dento-alveolar compensations with retrusion of the lower front teeth and protrusion of the anterior maxillary teeth. Surgical results remained stable in 14 cases, three patients incurred a slight partial relapse while six patients had a significant relapse, though the original extend of the malocclusion with anterior crossbite reoccurred in two cases only. It was possible to prove the relationship between relapse and the existence of myofunctional disturbances. Consequently, safe long-term results may only be obtained by means of interdisciplinary planning and treatment.
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On conventional radiographs, the morphology and position of the condyles in an axial view are best seen in the submentovertex projection. The foramina spinosa, which are used by the middle meningeal arteries as passages and are clearly outlined in this view, serve as landmarks for a co-ordinate system that permits precise measurements of various angles and distances. One hundred and twenty-six submentovertex views were used for measuring the condyles. Results presented as means and standard deviations suggest condylar variables to be related to the function of the stomatognathic system. Practical applications include surgical, orthodontic or prosthetic manipulations of the mandible resulting in transverse or sagittal displacement of the condyles.
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The conservative procedures widely used to treat fractures of the condylar neck seem to provide positive short-term benefits, but on long-term observation the results sometimes are not consistent with the early prognosis. We observed a patient (adult female) from the time of the accident for a period of 7 years. The patient suffered from a high double-sided fracture of the condylar neck combined with a multiple fracture in the frontal region of the mandible. The treatment plan was: 1. primary osteosynthesis of the fracture in the frontal-region, 2. intermaxillary fixation for 14 days, 3. functional post-operative treatment using monoblock. Up to the first month it looked like a normal recovery. However, after three months the expected recovery became questionable. After 7 years it was obvious that the recovery had reached its peak between 3 months and 1 year after the operation. The patient experienced chronic pain and progressive loss of function. Such results are unsatisfactory and new operative procedures using osteosynthesis have to be developed.
In a follow-up study of 24 patients with mesial bite operated on at the Department of Oral and Maxillofacial Surgery, University of Innsbruck Medical School, relations between the outcome of sagittal splitting and myofunctional disorders were investigated. Orofacial imbalances of variable extent were found to be present in 16 of the patients followed up. Effects of myofunctional factors on occlusal position, occlusion, overbite and overjet are reviewed. Five patients with particularly severe myofunctional disorders underwent detailed logopedic and myofunctional evaluation. Results are presented. As myofunctional factors may profoundly affect the late results of surgery, it is concluded that patients with myofunctional disorders should undergo adjuvant myofunctional rehabilitation before or at least after surgery in order to prevent relapses.
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