[Surgical treatment of kyphosis in children and adolescents]. / Operative Therapie von Kyphosen im Kindesalter.

OBJECTIVE: Correction of a pathological kyphosis to restore a balanced, low-pain or pain-free and load-bearing spine. INDICATIONS: Pronounced sagittal imbalance, progressive kyphosis despite conservative therapy, and neurological deficits are indications for surgery. Further surgical indications are severe therapy-resistant complaints and/or psychologically burdening cosmetic impairment. The guidelines for surgical indications are kyphosis angles of 75-80° thoracic and 30-50° lumbar. CONTRAINDICATIONS: No specific, but general contraindications for surgical treatment. SURGICAL TECHNIQUE: Depending on the characteristics of the kyphosis, different surgical techniques are used. Rod-screw systems are mainly used, and surgery is primarily performed by shortening the spinal column from posterior using a wide variety of techniques. In individual cases, this can be combined with ventrally mobilizing, resecting, or straightening techniques. POSTOPERATIVE MANAGEMENT: The aim of surgical treatment is to achieve a primarily stable and weight-bearing spine. Regular wound control as well as stabilizing physiotherapy during follow-up are essential. Postoperatively, initially abstaining from sports; later physical activity is encouraged under professional guidance. RESULTS: The literature shows very good corrective results in children and adolescents. The technical procedures are associated with a low and acceptable complication rate. Over the course of time, these patients must be monitored in order to detect possible long-term complications such as junctional kyphosis or pseudarthrosis.

Does the intraoperative 3D-flat panel control of the planned implant position lead to an optimization and increased in safety in the anatomically demanding region C1/2?

BACKGROUND: The aim of this study was to evaluate the applicability and advantages of intraoperative imaging using a 3D flat panel in the treatment of C1/2 instabilities. MATERIALS: Prospective single-centered study including surgeries at the upper cervical spine between 06/2016 and 12/2018. Intraoperatively thin K-wires were placed under 2D fluoroscopic control. Then an intraoperative 3D-scan was carried out. The image quality was assessed based on a numeric analogue scale (NAS) from 0 to 10 (0 = worst quality, 10 = perfect quality) and the time for the 3D-scan was measured. Additionally, the wire positions were evaluated regarding malpositions. RESULTS: A total of 58 patients were included (33f, 25 m, average age 75.2 years, r.:18-95) with pathologies of C2: 45 type II fractures according to Anderson/D'Alonzo with or without arthrosis of C1/2, 2 Unhappy triad of C1/2 (Odontoid fracture Type II, anterior or posterior C1 arch-fracture, Arthrosis C1/2) 4 pathological fractures, 3 pseudarthroses, 3 instabilities of C1/2 because of rheumatoid arthritis, 1 C2 arch fracture). 36 patients were treated from anterior [29 AOTAF (combined anterior odontoid and transarticular C1/2 screw fixation), 6 lag screws, 1 cement augmented lag screw] and 22 patients from posterior (regarding to Goel/Harms). The median image quality was 8.2 (r.: 6-10). In 41 patients (70.7%) the image quality was 8 or higher and in none of the patients below 6. All of those 17 patients the image quality below 8 (NAS 7 = 16; 27.6%, NAS 6 = 1, 1.7%), had dental implants. A total of 148 wires were analyzed. 133 (89.9%) showed a correct positioning. In the other 15 (10.1%) cases a repositioning had to be done (n = 8; 5.4%) or it had to be drawn back (n = 7; 4.7%). A repositioning was possible in all cases. The implementation of an intraoperative 3D-Scan took an average of 267 s (r.: 232-310 s). No technical problems occurred. CONCLUSION: Intraoperative 3D imaging in the upper cervical spine is fast and easy to perform with sufficient image quality in all patients. Potential malposition of the primary screw canal can be detected by initial wire positioning before the Scan. The intraoperative correction was possible in all patients. Trial registration German Trials Register (Registered 10 August 2021, DRKS00026644-Trial registration: German Trials Register (Registered 10 August 2021, DRKS00026644- https://www.drks.de/drks_web/navigate.do?navigationId=trial.HTML&TRIAL_ID=DRKS00026644 ).

Patient-Matched 3-D-Printed Guides for the Insertion of Cervical Pedicle Screws in Tumor Surgery.

BACKGROUND: Pedicle screw fixation in the cervical spine provides biomechanical advantages compared to other stabilization techniques. However, pedicle screw insertion in this area is challenging due to the anatomical conditions with a high risk of breaching the small pedicles and violating the vertebral artery or neural structures. Today, several techniques to facilitate screw insertion and to make the procedure safer are used. 3-D-printed patient-matched guides based on a CT reconstruction are a helpful technique which allows to reduce operation time and to improve the safety of pedicle screw insertion at the cervical spine. CASES: 3-D-printed patient-matched drill guides based on a CT scan with a 3-D reconstruction of the spine were used in two challenging cervical spine surgical tumor cases to facilitate the implantation of the pedicle screws. The screw position was controlled postoperatively by means of the routinely performed CT scan. RESULTS: Postoperative imaging (conventional radiographs and CT scan) revealed the correct position of the pedicle screws. The time needed for screw insertion was short, and the need for intraoperative fluoroscopy could be reduced. There was no intra- or postoperative complication related to the pedicle screw implantation. Both tumors could be removed completely. CONCLUSION: These preliminary results show that 3-D-printed patient-specific guides are a promising tool to support and facilitate the implantation of cervical pedicle screws. The time needed for insertion is short, and intraoperative fluoroscopy time can be reduced. This technique allows for both a meticulous preoperative planning and a correct and therefore safe intraoperative positioning of cervical spine pedicle screws.

[Spinal deformity in neurofibromatosis type 1]. / Wirbelsäulendeformitäten bei Neurofibromatose Typ 1.

BACKGROUND: With a prevalence of up to 60%, spinal deformity represents the most common skeletal manifestation of neurofibromatosis type 1. The deformity can occur as a non-dystrophic or as a less common dystrophic type. This distinction is of great relevance because the therapeutic strategy is completely different in each case. NON-DYSTROPHIC TYPE: The non-dystrophic type can be treated like idiopathic scoliosis due to the comparable behavior of both entities. However, care must be taken regarding the so-called modulation. Modulation describes the formation of dysplasias of the spine. This will result in a progression behavior as known from the dystrophic type. DYSTROPHIC TYPE: For the dystrophic type, different spinal dysplastic changes are typical. These lead to a rapid progression of deformity and a lack of response to conservative treatment. If untreated, severe and grotesque deformities can arise. This type of deformity requires early surgical intervention, even in childhood. The knowledge about the peculiarities of this disease in general, as well as the typical changes of the spine are prerequisites to managing these often-challenging situations.

[Cost coverage for complex paediatric spinal deformities with preoperative halo traction-an economic problem?] / Kostendeckung bei komplexen pädiatrischen Wirbelsäulendeformitäten mit präoperativer Halotraktion ­ ein wirtschaftliches Problem?

BACKGROUND: Spinal surgery is largely reimbursed in a differentiated manner via the DRG system. For treatments of complex paediatric deformities with increased pre and postoperative effort due to special treatment approaches, it seems that the costs for the treatment are not fully covered. MATERIALS AND METHODS: All paediatric cases with surgical treatment of the spine that were treated in a single spine centre from 2018-2020 were considered. The subgroup of patients with inpatient halo-gravity traction (halo group) before surgery was compared with all other cases treated in terms of economic and demographic factors. RESULTS: There were 86 cases that were treated surgically without halo traction and 6 cases with halo traction. The groups did not differ significantly in age (p = 0.41) or Patient Clinical Complexity Level (PCCL, p = 0.76). The average length of hospital stay in the halo group was significantly longer than in the other cases (84.2 ± 40.1 d vs. 11.0 ± 6.4 d; p = 0.001). Due to DRG grouping and long-stay surcharges, the mean revenue per case was significantly higher in the halo group than in the other cases (€ 63,615 ± 45,138 vs. € 16,836 ± 9356) (p = 0.003). The contribution margin for the period of the long-term surcharges varied between 11,394 and 9766 €. The high additional costs due to the necessary medical devices of halo traction were not sufficiently reflected in the reimbursement. CONCLUSION: Paediatric spine surgery can be challenging in special cases. In particular, severe deformities of the spine may require additional procedures. The subgroup of patients requiring preoperative halo traction is not adequately compensated by the DRG system.

Comparison of three different screw trajectories in osteoporotic vertebrae: a biomechanical investigation.

BACKGROUND: Pedicle screw insertion in osteoporotic patients is challenging. Achieving more screw-cortical bone purchase and invasiveness minimization, the cortical bone trajectory and the midline cortical techniques represent alternatives to traditional pedicle screws. This study compares the fatigue behavior and fixation strength of the cement-augmented traditional trajectory (TT), the cortical bone trajectory (CBT), and the midline cortical (MC). METHODS: Ten human cadaveric spine specimens (L1 - L5) were examined. The average age was 86.3 ± 7.2 years. CT scans were provided for preoperative planning. CBT and MC were implanted by using the patient-specific 3D-printed placement guide (MySpine®, Medacta International), TT were implanted freehand. All ten cadaveric specimens were randomized to group A (CBT vs. MC) or group B (MC vs. TT). Each screw was loaded for 10,000 cycles. The failure criterion was doubling of the initial screw displacement resulting from the compressive force (60 N) at the first cycle, the stop criterion was a doubling of the initial screw displacement. After dynamic testing, screws were pulled out axially at 5 mm/min to determine their remaining fixation strength. RESULTS: The mean pull-out forces did not differ significantly. Concerning the fatigue performance, only one out of ten MC of group A failed prematurely due to loosening after 1500 cycles (L3). Five CBT already loosened during the first 500 cycles. The mean displacement was always lower in the MC. In group B, all TT showed no signs of failure or loosening. Three MC failed already after 26 cycles, 1510 cycles or 2144 cycles. The TT showed always a lower mean displacement. In the subsequent pull-out tests, the remaining mean fixation strength of the MC (449.6 ± 298.9 N) was slightly higher compared to the mean pull-out force of the CBT (401.2 ± 261.4 N). However, MC (714.5 ± 488.0 N) were inferior to TT (990.2 ± 451.9 N). CONCLUSION: The current study demonstrated that cement-augmented TT have the best fatigue and pull-out characteristics in osteoporotic lumbar vertebrae, followed by the MC and CBT. MC represent a promising alternative in osteoporotic bone if cement augmentation should be avoided. Using the patient-specific placement guide contributes to the improvement of screws' biomechanical properties.

[Injuries of the thoracolumbar spine in children]. / Verletzungen der kindlichen thorakolumbalen Wirbelsäule.

BACKGROUND: Injuries of the thoracolumbar spine in children are rare and challenging for the treating physician. Besides knowledge of fracture treatment, the anatomical particularities of the spine in children are of great importance. METHODS: The article gives an overview of the diagnosis and therapy with the most common classification of injuries of the thoracolumbar spine. RESULTS: Taking into account the children's age and the fracture morphology most cases can be treated conservatively, especially because the young spine has great potential for remodelling. The older the child becomes, the more smoothly the transition to adult treatment occurs; thus, unstable fractures should be treated with surgery. CONCLUSION: The difficult indication and the specific characteristics of surgery necessitate treatment in a spine centre with experience with surgery on children.

[Chronic recurrent multifocal osteomyelitis of the spine : Children and adolescent]. / Chronische rekurrierende multifokale Osteomyelitis der Wirbelsäule : Kindes- und Jugendalter.

Chronic non-bacterial osteomyelitis (CNO) in childhood and adolescence is a non-infectious autoinflammatory disease of the bone with partial involvement of adjacent joints and soft tissue. The etiology is unknown. The disease can occur singular or recurrent. Individual bones can be affected and multiple lesions can occur. Chronic recurrent multifocal osteomyelitis (CRMO) shows the whole picture of CNO. Accompanying but temporally independent of the bouts of osteomyelitis, some patients show manifestations in the skin, eyes, lungs and the gastrointestinal tract. The article gives an overview of the clinical manifestations, diagnostic procedures, and treatment options for CRMO involvement of the spine based on the current literature and our own cases.

[Delayed indications for additive ventral treatment of thoracolumbar burst fractures : What correction loss is to be expected]. / Zeitverzögerte Indikationsstellung zur additiv ventralen Versorgung thorakolumbaler Berstungsfrakturen : Welcher Korrekturverlust ist zu erwarten.

INTRODUCTION: There is a general consensus that unstable vertebral body fractures of the thoracolumbar junction with a B type fracture or a high load shear index need to be surgically stabilized, primarily by a dorsal approach. The authors believe that there are indications for an additional ventral spondylodesis in cases of reduction loss or a relevant intervertebral disc lesion in magnetic resonance imaging (MRI) 6 weeks after dorsal stabilization. However, in cases of unstable vertebral fractures it remains unclear if a delayed anterior spondylodesis will lead to unacceptable loss of initial reduction. MATERIAL AND METHODS: A total of 59 patients were included in this study during 2013 and 2014. All patients suffered from a traumatic vertebral fracture of the thoracolumbar junction and were initially treated with a dorsal short segment stabilization. All vertebral body fractures had a load shear index of at least 5 or were B type fractures. An x-ray control was carried out after 2 and 6 weeks and MRI was additionally performed after 6 weeks. An additional ventral spondylodesis was recommended in patients showing a reduction loss of at least 5° and in patients with relevant intervertebral disc lesions. The extent of the reduction loss was analyzed. Other parameters of interest were the fracture level, fracture classification, patient age and surgical technique (e.g. implant, index screw, laminectomy and cement augmentation). RESULTS: The patient collective consisted of 23 women and 36 men (average age 51 years ± 17 years). The mean reduction loss was 5.1° (± 5.2°) after a mean follow-up of 60 days (± 56 days). The reduction loss was significantly higher when polyaxial implants were used compared to monoaxial dorsal fixators (10.8° versus 4.0°, p < 0.001). There was a significantly higher reduction loss in those patients who received a laminectomy (11.3° versus 4.3°, p = 0.01) but there were no significant differences if an index screw was used (4.5° versus 5.3°). Additionally, there was a significantly lower reduction in the subgroup of patients 60 years or older who were stabilized using cement-augmented screws (3.9° versus 11.3°, p = 0.02). The mean reduction loss was 2.8° (± 2.5°) in patients treated with a monoaxial implant, cement-augmented if 60 years or older and without laminectomy (n = 39). There was no significant correlation between reduction loss and the other parameters of interest, such as fracture morphology with classification according to the working group on questions of osteosynthesis (AO) and McCormack or fracture level. CONCLUSION: Delayed indications for an additional ventral spondylodesis in patients with unstable thoracolumbar vertebral fractures and initial dorsal stabilization will cause no relevant reduction loss if monoaxial implants are used and laminectomy can be avoided. Additionally, cement augmentation of the pedicle screws seems to be beneficial in patients 60 years of age or older.

[Pavlik harness for the treatment of congenital hip dysplasia types D III and IV]. / Pavlik-Bandage zur Therapie der kongenitalen Hüftdysplasie Typ D, III und IV.

BACKGROUND: Up to 4% of all neonates in Central Europe are born with congenital hip dysplasia (CHD), the most common congenital disease of the musculoskeletal system. However, in this retrospective analysis the outcomes of infants with CHD (type D, III or IV according to Graf) have been considered, with Pavlik therapy starting within the first 12 weeks of life. Connections between the start of therapy or the first finding according to Graf`s classification and the ultrasound result achieved, as well as the X-rays taken after 1 and 2 years, were evaluated. No repositioning under Pavlik treatment or side effects and their relevance have been evaluated, especially with regard to avascular necrosis (AVN) of the femoral head. MATERIALS AND METHODS: All infants treated using Pavlik treatment for CHD between 2010 and 2012 in our clinic were determined. A total of 62 patients with 79 pathological hips were included. The infants were classified into three groups to evaluate the influence of the start of therapy on the result: group I with the first investigation and start of treatment within the first 10 days of life, group II between the 11th day and the end of week 3, group III within preventive general examinations (U3) after the 4th week. Clinical examinations and the usual ultrasound scans were performed at an average of 1, 3, and 6 months. Furthermore, after 1 and 2 years clinical and radiological investigations were carried out, as well as further examinations depending on the findings. RESULTS: A failure of repositioning of the Pavlik treatment occurred in group I in 1 case (2.2%), in group II in 1 case (7.1%), and in group III in 2 cases (10%). This occurs in hips type D and type III in 1 case each (3.3%) and type IV in 2 cases (10.5%). Maturation disorders of the hips were found in 1 case (2.2%) in group I, 1 case (7.1%) in group II, and 3 cases (15%) in group III. Avascular necrosis of the femoral head was proven in 2 cases (4.4%) in group I, 0% in group II, and in 1 case (5%) in group III. All patients initially had femoral head necrosis of Graf type IV . All necrosis and maturation disorders were no longer visible on subsequent examinations after 2 years at the most. CONCLUSIONS: In summary, the study shows that even with a late treatment start (U3) good results could be achieved, but with a rising number of repositioning failures and femoral necroses. Ultrasound screening on U3 seems to be sufficient; however, for high-risk groups an additional screening in the first week of life should be performed, which does not replace a second evaluation at U3 if there are normal findings.

[Spondylosclerosis hemispherica: a rare radiological syndrome of the spine]. / Spondylosclerosis hemispherica: Ein seltenes bildmorphologisches Syndrom der Wirbelsäule.

BACKGROUND: Spondylosclerosis hemispherica is a rare syndrome of the spine and was described first by Dihlmann. The typical radiographic appearance is a hemispherical sclerosis of the vertebral body, which is accompanied by pain in the affected region. Usually it appears at the lower lumbar spine. The etiology varies and includes degenerative disk diseases, scoliosis, bacterial infections, ankylosing spondylitis, osteoid osteoma, and malignant diseases.The radiological findings of 2 patients with spondylosclerosis hemispherica are presented and the current literature discussed. MATERIAL AND METHODS: Two women (33 and 60 years old) with spondylosclerosis hemispherica of the lower spine suffered from low back pain and fulfilled all criteria of Dihlmann's description. Malignant disease was excluded in both cases with a broad diagnostic workup (lab values, x-ray, CT scan, MRI) and in one case a biopsy from the affected vertebra was taken. RESULTS: In both cases all radiological findings demonstrated the typical changes of spondylosclerosis hemispherica with sclerosis of the vertebra body and erosions at the upper and inferior end plates. Malignant disease was excluded in one case with a biopsy and in the other case with noninvasive diagnostic procedures. Both patients were treated nonsurgically. During clinical follow-up, the patients were in a good condition with decreasing regional low back pain and no ongoing radiological changes in the affected vertebral bodies. CONCLUSION: Spondylosclerosis hemispherica is a syndrome with a typical radiographic appearance. The etiology of spondylosclerosis hemispherica is manifold; however, malignancy must be excluded. In most cases, noninvasive diagnostics are sufficient to rule out malignant growth even in cases with concomitant degenerative changes of the affected segment. Thus, there is no need for a biopsy except in cases with ambiguous results. Subsequently, close clinical and radiological follow-up of the patients with spondylosclerosis hemispherica is necessary.

[Superinfected epidermal inclusion cyst of the thigh with development of squamous cell carcinoma--case report of a rare complication]. / Superinfektion einer epidermalen Inklusionszyste des Oberschenkels mit Ausbildung eines Plattenepithelkarzinoms--Fallbericht einer seltenen Komplikation.

Epidermal cysts (atheroma) are the most common benign tumours of the skin with ubiquitous localisation all over the body. However, rupture of the atheroma and formation of an inclusion cyst with additional superinfections are frequently seen. Malignant transformations have rarely been reported. Presented here is the unusual case of a 65-year-old woman with multiple atheromas and a distinctive tumour of the upper limb. Imaging diagnostics showed malignant deformation. Contrary to the imaging findings the histological/microbiological examination showed an enormous superinfected and ruptured epidermoid cyst with multiple abscess formation in the ventral upper limb. Radical surgical restoration with salvage of the limb was frustrated because of honey-combed anterior soft tissue and the changing bacterial spectrum. After resection of the complete ventral compartment, remission was realised approximately. In the follow-up there was a recurring infection with spontaneous fistula formation that histologically impressed as a squamous cell carcinoma. After proximal ablation of the upper limb, total rehabilitation of the infection as well as the malignoma could be achieved.

[Results-adapted operative treatment options for spinal metastases]. / Befundadaptierte operative Versorgungsmöglichkeiten bei Wirbelsäulenmetastasen.

The current operative approaches and technical possibilities in the operative treatment of spinal metastases are manifold which enables an individual operative strategy adapted to the patient's condition. Maintaining quality of life is the primary goal in the treatment of these patients. The therapeutic goals, such as pain control, avoidance of neurological deficits and the achievement of spinal stability have to be attained with as little morbidity as possible. From this perspective the available operative techniques ranging from minimally invasive approaches to complex reconstructive surgery will be addressed and discussed in this article.

[Prognosis scores for spinal metastases]. / Prognostische Scores bei Wirbelsäulenmetastasen.

Advances in early detection and therapy of spinal metastasis have improved life expectancy of patients with various tumor entities. However, this and the demographic development have led to an increased risk for developing spinal metastases. Numerous prognostic factors have been determined to allow an assessment of outcome and survival time of patients with metastatic spinal tumors. The implementation of these factors into different scoring systems has been encouraging in the decision making process of spinal surgery. This overview highlights some of the most important prognostic factors and scores which may facilitate surgical considerations.

[Ex vivo microCT analysis of possible microfractures of the femoral head during implantation of a cementless hip resurfacing femoral component]. / Ex-vivo-microCT-Untersuchungen zu möglichen Mikrofrakturierungen des Hüftkopfs bei der Implantation eines zementfreien Oberflächenersatzes am Hüftgelenk.

AIM: Microfractures of the femoral head during implantation of the femoral components are suspected to be a cause of fractures at the implant/neck junction which represent a common failure mode in hip resurfacing arthroplasty. Callus formation observed in femoral head retrievals suggests the occurrence of microfractures inside the femoral head, which might be inadvertently caused by the surgeon during implantation. The aim of this biomechanical study was to analyse whether or not the implantation of a cementless femoral component hip resurfacing system causes microfractures in the femoral head. METHOD: After the preparation of 20 paired human cadaveric femoral heads, the cementless femoral component ESKA Typ BS (ESKA Implants GmbH & Co., Lübeck) was implanted on 9 specimens with an impaction device that generates 4.5 kN impaction force. On 9 specimens the femoral component was implanted by hand. One head was used as a fracture model, 1 specimen served as control without manipulation. The femoral component used for impaction was equipped with hinges to enable its removal without further interfering with the bone stock. Specimens were scanned with a microCT device before and after impaction and the microCT datasets before and after impaction were compared to identify possible microfractures. RESULTS: Twenty strikes per hand or with the impaction device provided sufficient implant seating. Neither the macroscopic examination nor the 2-dimensional microCT analysis revealed any fractures of the femoral heads after impaction. CONCLUSION: At least macroscopically and in the 2-dimensional microCT analysis, implantation of the cementless hip resurfacing femoral component ESKA Typ BS with 4.5 kN or by hand does not seem to cause fractures of the femoral head.

[Influence of different surface machining treatments of resorbable implants made from different magnesium-calcium alloys on their degradation--a pilot study in rabbit models]. / Einfluss der Oberflächenbearbeitung von resorbier- baren Implantaten aus verschiedenen Magnesium- Calciumlegierungen auf die Degradation - Erste Ergebnisse einer Pilotstudie am Kaninchenmodell.

To examine the influence of different surface machining treatments of resorbable implants 3x5 mm cylinders of magnesium-calcium-alloys with plane, rough or sand blasted surface and different concentrations of calcium (0.4 %, 0.8 %, 1.2 % und 2.0 %) were implanted into the distal femur condylus of 18 New Zealand White Rabbits. They were placed into the spongy-cortical passage. During six weeks the animals were examined daily and x-rayed weekly. After euthanasia the bone was explanted and scanned in a microcomputed tomograph. The implants were well tolerated by the rabbits, neither lameness nor signs of pain occured. Wound healing was mostly without complications. Eight of 36 implants (22 %) showed dehiscence of suture within first ten days, whereby implants made of 1,2 % MgCa were mainly affected (six of 12 cases, 50 %). At the place of insertion all implants induced obvious callus genesis which could be seen in MgCa 1,2-cylinders with plane surface and MgCa 0,8-cylinders with rough and sand blasted surface the most. Influence of different calcium concentrations on degradation behaviour could not be discovered. They showed different stages of resorption. Concerning the different surface machining treatments sand blasted implants showed the highest degree of degradation which could be seen by the totally loss of structure in micro-computed examinations. These implants also showed in six of 36 cases a clinical occurrence of gas production. Rough implants showed an irregular degradation with high degree of resorption of some implants and signs of degradation only in the border area of others. Cylindricity maintained in plane implants. They showed loss of structure only in border areas.

Ecological effects of linezolid versus amoxicillin/clavulanic acid on the normal intestinal microflora.

Twelve healthy subjects (6 females, 6 males; age range 18-40 y) participated in this trial. Linezolid was given as 600 mg tablets b.i.d. for 7 d and amoxicillin/clavulanic acid as 1000 mg tablets o.d. for 7 d. The washout period between the administration of the 2 antibacterial agents was 4 weeks. Faecal samples were collected prior to administration (Days -2 and -1), during administration (Days 4 and 8) and after administration (Days 14, 21 and 35) for microbiological analyses. The samples were diluted in pre-reduced media and inoculated aerobically and anaerobically on non-selective and selective media. Different colony types were identified to genus level by morphological, biochemical and molecular analyses. During the administration of linezolid, enterococci in the intestinal aerobic microflora were markedly suppressed while Klebsiella organisms increased in number. In the anaerobic microflora, the numbers of bifidobacteria, lactobacilli, clostridia and Bacteroides decreased markedly while no impact on the other anaerobic bacteria was observed. The microflora was normalized in all volunteers after 35 d. Amoxicillin/clavulanic acid administration caused increased numbers of enterococci and Escherichia coli in the aerobic intestinal microflora while numbers of bifidobacteria, lactobacilli and clostridia decreased significantly. Clostridium difficile strains were recovered from 3 of the volunteers. At the last visit, the intestinal microflora of the volunteers had returned to normal levels. The administration of linezolid mainly had an impact on the gram-positive bacteria and linezolid thus had an ecological profile different from that of amoxicillin/clavulanic acid.