[Arch-shaped approach : New modified medial approach for the treatment of talus fractures]. / Bogenförmiger Zugang : Neuer modifizierter medialer Zugang zur Versorgung von Talusfrakturen.

OBJECTIVE: Anatomical reduction and fixation of complex talar fractures (Hawkins type III and IV, Marti type III and IV) using a medial approach. INDICATIONS: Displaced talar fractures (Hawkins type III and IV, Marti type III and IV) with the need for a medial malleolar osteotomy or the simultaneous treatment of a medial malleolus fracture. CONTRAINDICATIONS: High perioperative risk, severe soft tissue injuries in the medial approach area, infected soft tissues. SURGICAL TECHNIQUE: Medial arch-shaped approach about 12 cm in length over the medial malleolus using a simultaneous medial malleolus fracture or via an additional medial malleolar osteotomy. Dissection and retraction of the terminal branches of the saphenous vein and the saphenous nerve. Protection of the blood supply in the area of the medial talus and in the sinus tarsi. Reduction of the talar joint surfaces and reconstruction of the anatomical axes according to the preoperative planning by means of native radiological and computed tomographic imaging. Osteosynthesis adapted to the fracture type using Kirschner wires, conventional screws, cannulated screws, double-threaded screws, resorbable pins, magnesium screws, small fragment plates. POSTOPERATIVE MANAGEMENT: Lower leg splint or orthesis for 6 weeks, partial weight-bearing with 20 kg for 10-12 weeks. Early range of motion exercise of the ankle, subtalar and mid-tarsal joints. RESULTS: In the past 5 years, 11 patients with either Hawkins type III and IV or Marti type III and IV fractures were treated operatively using the arch-shaped approach. No soft tissue problems were seen related to the arch-shaped approach. Of the 7 patients who could be followed up after an average of 2 years, the mean American Orthopedic Foot and Ankle Score was 73. Avascular necrosis occurred in 3 cases (43%). These were partial necroses of less than one third of the talar body with asymptomatic course at the time of examination. In 4 patients (57%) radiographic signs of osteoarthritis occurred within 2 years, whereby in two of those cases (29%) an arthrodesis of the upper ankle was performed.

Implementation of a multidisciplinary infections conference affects the treatment plan in prosthetic joint infections of the hip: a retrospective study.

INTRODUCTION: Establishing a systematic multidisciplinary approach in the treatment of prosthetic joint infections (PJI) of the hip and analyzing its effect on clinical decision-making. PATIENTS AND METHODS: Forty-six patients diagnosed with PJI of the hip were included in the retrospective study. The treatment plan was either established by a single-discipline approach (n = 20) or by a weekly multidisciplinary infections conference (n = 26) consisting of at least an orthopedic surgeon, microbiologist and pathologist. Recorded data included the length of hospital stay, number and type of surgeries, medical complications, recovered organisms as well as the number of applied antibiotics. RESULTS: Patients discussed in the multidisciplinary infections conference showed a significantly shorter in-hospital stay (29 vs 62 days; p < 0.05), a significant reduction in surgeries (1.8 vs 5.1; p < 0.05) and a smaller number of antibiotics required (2.8 vs 4.2; p < 0.05). No significant difference could be found comparing inpatient complications between the two groups. Staphylococcus aureus and coagulase-negative staphylococci were the most frequently recovered organisms in both patient groups. CONCLUSION: This study demonstrates the successful implementation of a weekly infections conference as an instrument to introduce a multidisciplinary approach to PJI of the hip. Implementation of these conferences significantly improves the treatment plan compared to a single-discipline approach, which we therefore highly recommend for other institutions. Multidiscipline may even affect clinical outcome which needs to be further investigated.

Incidence and severity of malreduction of the tibiofibular syndesmosis following surgical treatement of displaced ankle fractures and impact on the function -Clinical study and MRI evaluation.

PURPOSE: To compare tibiofibular reduction quality in different types of operatively treated ankle fractures and the impact on clinical and functional outcome at mid-term follow-up. PATIENTS AND METHODS: One hundred patients with an acute ankle fracture who had undergone open reduction and internal fixation were included. Eighty-eight patients who suffered from ligamentous ankle injury with neither fracture nor syndesmotic lesions served as a control group. Tibiofibular alignment was measured on MR images in all 188 patients. In case of tibiofibular malreduction tibiotalar positioning was determined as well. Clinical and functional outcome was assessed using the AOFAS hindfoot score as well as the SF-36. RESULTS: No tibiofibular malreduction was found in type Weber B fractures, irrespective of syndesmotic instability followed by syndesmotic screw placement, as compared to the control group. A significant tibiofibular malreduction was detected in bimalleolar/trimalleolar/dislocated type Weber B fractures and in isolated type Weber C fractures with syndesmotic screw, in comparison to the control group. Tibiotalar displacement could not be detected. Clinical and functional outcome analysis revealed no significant differences between the treatment groups. CONCLUSION: Three-dimensional imaging may improve tibiofibular malreduction visualization in bimalleolar/trimalleolar/dislocated type Weber B fractures and in isolated type Weber C fractures with syndesmotic transfixation. The clinical impact of improving tibiofibular positioning remains highly questionable since there was no correlation between tibiofibular alignment and the clinical outcome at mid-term follow-up.

Significance of clinical examination, CT and MRI scan in the diagnosis of posterior pelvic ring fractures.

INTRODUCTION: Patients with a fracture in the anterior pelvic ring often simultaneously demonstrate pain in the posterior pelvic ring. The aim of the present prospective study was to assess the sensitivity of CT, MRI and clinical examination in the detection of fractures in the posterior pelvic ring in patients with fractures of the anterior pelvic ring diagnosed in conventional radiographs. METHODS: Sixty patients with radiographic signs of an anterior pelvic ring injury were included in this prospective analysis. Following a focused clinical examination of the posterior pelvis, all patients underwent both a CT and then a MRI scan of their pelvis. Two board certified radiologists evaluated the CT and MRI scans independently. To estimate the presence of osteoporosis the Hounsfield units of the vertebral body of L5 were measured in each case. RESULTS: Fifty-three women and seven men, with a mean age of 74.7+/-15.6 years were included into the study. A fracture of the posterior pelvic ring was found in fourty-eight patients (80%) patients using MRI. Fractures of the posterior pelvic ring would have been missed in eight cases (17%), if only CT had been used. Eighty-five percent of the patients with a posterior fracture had an osteoporosis. The majority of the cases suffered from a low energy trauma. Thirty-eight patients (83%) with positive clinical signs at the posterior pelvic ring actually had a fracture of the posterior pelvic ring in the MRI. The clinical examination proved to be equally effective to CT in detecting posterior pelvic ring fractures. CONCLUSION: The significance of both, clinical examination and CT was confirmed in the detection of fractures in the posterior pelvic ring. MRI examination of the pelvis however, was found to be superior in detecting undislocated fractures in a cohort of patients with a high incidence of osteoporosis. Using MRI may be beneficial in select cases, especially when reduced bone density is suspected.

Isolated syndesmotic injury in acute ankle trauma: comparison of plain film radiography with 3T MRI.

OBJECTIVES: To determine cut-off values and the accuracy of plain film measurements for the detection of isolated syndesmotic injury after acute ankle trauma and to investigate MRI findings of concomitant ankle injury. METHODS: Eighty-four consecutive patients with absent fracture in plain film radiographs were prospectively evaluated for isolated syndesmotic injury after acute ankle trauma. The tibiofibular clear space (TFCS), the tibiofibular overlap (TFO), and the medial clear space (MCS) were independently assessed in plain radiographs by two readers. MRI performed at 3T within 24h served as the reference standard. MRI was evaluated for syndesmotic injury, using a four-scale grading system (0=normal syndesmosis, 1a=periligamentous edema, 1b=intraligamentous edema, 2=partial rupture, 3=complete rupture), and for concomitant ankle injury. Inter-observer variability for x-ray measurements was assessed using Bland-Altman diagrams. ROC analyses were performed to determine cut-off values and sensitivity and specificity for TFCS, TFO, and MCS. RESULTS: Eleven of 84 patients (13.1%) revealed syndesmotic injury (Grade 2 or 3) according to MRI. Between patients with and without syndesmotic injury significantly different measurements were obtained for TFCS (p=0.003) and MCS (p=0.04). ROC derived cut-off values were 5.3mm for TFCS, 2.8mm for TFO, and 2.8mm for MCS. Sensitivity and specificity was 82% and 75% for TFCS, 36% and 78% for TFO, and 73% and 59% for MCS. The bias and limits of agreement were -0.04 mm and [-1.54; 1.53] for TFCS, 0.8mm and [-2.5; 2.5] for TFO, and 0.05 mm and [-1.42; 1.43] for MCS. Patients with syndesmotic injury had a 5-fold increased risk of concomitant ankle injury (p=0.07). CONCLUSIONS: The determined cut-off values aid in the evaluation of syndesmotic integrity in patients with absent fracture in plain radiographs. In case of increased distances MRI is recommended to assess severity of SI and to reveal associated ankle injuries.

[Surgical treatment of posterior shoulder dislocation: importance of arthroscopy]. / Operative Versorgung der posterioren Schulterluxation: Stellenwert der Arthroskopie.

OBJECTIVE: Posterior dislocations of the shoulder represent a rare injury with frequently occurring soft tissue and/or bony concomitant lesions such as the reverse Hill-Sachs lesion and the dorsal labrum tear. For the combination of these injuries, no evidence-based therapeutic recommendations exist. AIM OF STUDY: Reflecting on two clinical cases and the current literature data, options for the treatment of combined osseous and soft tissue injuries due to posterior dislocation of the shoulder are presented. METHODS: We report two cases of fresh traumatic first-time posterior dislocations that were each explored arthroscopically and subsequently operated using an open technique. In the first case, we performed refixation of the labrum, followed by open osteosynthesis with bone substitution. Treatment of the second case included diagnostic arthroscopy and - after a frustrating attempt to elevate the defect in an arthroscopically assisted retrograde technique - open reconstruction of the humeral head with an allograft. RESULTS: In both cases good clinical outcomes with Constant scores of 79 and 86 points at the 16- and 12-month follow-ups, respectively, were achieved. Radiologically complete integration of the used materials was found. CONCLUSION: These cases show that for the operative treatment of fresh, traumatic posterior shoulder dislocation, it is useful to explore the joint arthroscopically to identify concomitant injuries of the labrum and if necessary treat them. The bony pathology of the humeral head can subsequently be addressed in an open technique, whereby the appropriate treatment should be chosen based on the size of the defect.

[Beyond the horizon of health-care delivery - medical marketing]. / Neue Wirklichkeiten - Marketing und Chirurgie.

BACKGROUND: The progress in medical health care and demographic changes cause increasing financial expenses. The rising competitive environment on health-care delivery level calls for economisation and implementation of a professional marketing set-up in order to ensure long-term commercial success. METHODS: The survey is based on a questionnaire-analysis of 100 patients admitted to a trauma department at a university hospital in Germany. Patients were admitted either for emergency treatment or planned surgical procedures. RESULTS: Competence and localisation represent basic criteria determing hospital choice with a varying focus in each collective. Both collectives realise a trend toward economisation, possibly influencing medical care decision-making. Patients admitted for planned surgical treatment are well informed about their disease, treatment options and specialised centres. The main source of information is the internet. Both collectives claim amenities during their in-hospital stay. CONCLUSION: Increasing economisation trends call for a sound and distinct marketing strategy. The marketing has to be focused on the stakeholders needs. Concomitant factors are patient satisfaction, the establishment of cooperation networks and maintenance/improvement of medical health-care quality.

[Posterior approaches to the pelvic ring]. / Posteriore Zugänge zum Beckenring.

The posterior pelvic ring is critical for the mechanical stability of the pelvis. There is considerable variability in the degree of traumatic injury to the posterior pelvis which results in damage to the ligaments, the bones or a combination of these two functional structures. For management of combined posterior and anterior pelvic ring injuries it is crucial to decide which side has to be treated with priority. Surgical approaches for the posterior pelvic ring include transiliacal plate osteosynthesis, local plate osteosynthesis, iliosacral screw ostheosynthesis and spinopelvic stabilization. The degree of soft tissue damage represents an important criterion that should be considered when determining the surgical approach because extensive soft tissue damage often prevents enlarged explorative surgical access. Especially in posterior pelvic ring injuries, soft tissues should be preserved as much as possible because long periods of immobilization in severely injured patients can compromise wound healing. The aim of this paper is to provide an overview of the most commonly used posterior surgical approaches for pelvic ring injuries.

[Clinical findings and treatment of perilunar dislocations and dislocation fractures]. / Diagnostik und Therapie von perilunären Luxationen und Luxationsfrakturen.

Perilunate dislocations, dislocation fractures and lunate dislocations are rare injuries predominantly resulting from hyperextension of the wrist during high-energy trauma. Early recognition and treatment of these injuries usually results in good functional outcome despite degenerative changes on radiographs. Immediate reduction and adequate restoration of normal alignment are the key to successful healing. Surgical intervention with open reduction and ligament repair aims at stable reconstruction of the carpus. It requires broad surgical experience and a profound knowledge of normal anatomy.

Comparison of diagnostic accuracy of Magnetic Resonance Imaging and Multidetector Computed Tomography in the detection of pelvic fractures.

OBJECTIVE: To compare diagnostic accuracy and interobserver reliability of Magnetic Resonance Imaging (MRI) and Multidetector Computed Tomography (MDCT) in the detection of acute pelvic fractures. MATERIALS AND METHODS: In 38 consecutive patients (mean age 74.7 years) with a positive finding of anterior pelvis fracture in the conventional X-rays, pelvic MRI and MDCT were performed for further evaluation of pelvic ring fractures. Two radiologists independently read all data sets. Sensitivity and specificity were calculated based on mean scores for each method. Sensitivities of CT and MRI were compared using a paired proportion test (McNemar). Diagnostic validity of both methods was assessed by the interobserver variability using kappa statistics. Combined clinical data and findings from all imaging studies served as the reference standard. RESULTS: 122 fractures were identified in the reference standard (37 sacral, 58 pubic, 22 acetabular, 1 ischial, 4 ilial). On average, MRI detected 96.3% whereas CT detected 77% of all fractures. With regard to sensitivity, MRI proved to be significantly better compared to MDCT (observer 1, p=0.0009; observer 2, p=0.0003 by observer 2). In particular, MRI performed better in the depiction of sacral fractures, reaching a sensitivity of 98.6% compared to 66.1% at CT. The interobserver variability was determined to be very good (k=0.955 for MRI and 0.902 for MDCT). CONCLUSION: MRI reaches a significantly higher sensitivity than CT in the detection of acute pelvic fractures, particularly of the sacrum. Especially in elderly patients with suspicion of a sacral fracture and negative results at MDCT, MRI may be considered as the next step in diagnostic workup.

Management of traumatic spinopelvic dissociations: review of the literature.

PURPOSE: Spinopelvic dissociation is a rare high-energy injury pattern in adults associated with high morbidity and an increased rate of neurological deficits. The purpose of this article is the conception of fracture type-associated treatment recommendations. METHODS: This article is based on our own experience with spinopelvic dissociations and a review of the current literature. RESULTS: Bilateral vertical plus an optional transverse fracture component configures spinopelvic dissociations as "U"- or "H"-shaped, with the result of a spinopelvic dissociation. "Y"-, "T"- or "II"-shaped fractures do not necessarily belong to this entity but can be subsumed to this entity in a wider sense. The surgical treatment of these injuries remains challenging. Initial haemodynamic stabilisation represents the main goal of primary care until definitive treatment can be performed. Anatomical reduction is demanding and even more complex in fracture areas with large comminution. Surgical treatment options depend on the fracture type, including transsacral screws, sacral banding and spinopelvic fixation, plus combinations of these procedures. CONCLUSIONS: Spinopelvic dissociations remain highly complex injuries. "U"- and "H"-shaped fractures usually require triangular fixation, whereas "II"-, "Y"- and "T"-shaped fractures might be sufficiently stabilised with transsacral screws.

[Subtrochanteric renal cell carcinoma metastasis: implantation of a femoral head preserving prosthesis]. / Subtrochantäre Nierenzellkarzinommetastase: Hüftkopferhaltender Femurteilersatz.

A 60-year-old man presented to our institution with a singular subtrochanteric renal cell carcinoma metastasis of the right femur. Tumor resection and implantation of a cemented femoral head preserving prosthesis was considered as the best treatment option to obtain a good hip joint function. After successful surgery (R0 resection) the patient was immediately mobilized with full weight-bearing. One year postoperatively the patient presented with good joint function and absolute mobility. X-ray examinations revealed a good position of the implanted prosthesis without signs of tumor recurrence or femoral head necrosis. Implantation of a femoral head preserving prosthesis is a good option for the treatment of subtrochanteric/diaphyseal tumors of the femur.

[Refixation of sternoclavicular luxation with a suture anchor system]. / Refixation der sternoklavikulären Luxation mit einem Fadenankersystem.

Luxations of the sternoclavicular joint are rare injuries. We present a case of anterior dislocation which was caused by a minor fall onto the right shoulder. Diagnosis was delayed by 2 weeks which prevented treatment by closed reduction. As an alternative surgical treatment a PDS cord around the clavicle and the first rib was used to stabilize the clavicle at the vertical level. Subsequently, fixation to the medial side was achieved by a suture anchor that was placed into the manubrium. The presented case highlights this simple and safe method to treat dislocations of the sternoclavicular joint in which standard treatment cannot be performed. A detailed description for each operation step is given and our experience in terms of aftercare and outcome is reported.

Sacroplasty in a cadaveric trial: comparison of CT and fluoroscopic guidance with and without balloon assistance.

Sacral insufficiency fractures can cause severe, debilitating pain to patients concerned. The incidence of this fracture type correlates with the appearance of osteoporosis in the elderly population. A polymethylmethacrylate (PMMA) cement injection procedure called sacroplasty has been recently described as an optional method for the treatment of this fracture type. However, the correct cement placement in the complex anatomical structure of the sacrum is a surgical challenge. The aim of the study is to compare the precision, safety, and radiation exposure of standard multiplanar fluoroscopy and computed tomography (CT) guidance for PMMA application to the sacrum using both balloon-assisted sacroplasty and conventional sacroplasty. A controlled experimental investigation in a human cadaver trial has been performed. Two imaging and two application modalities to monitor percutaneous PMMA injection to the sacrum were examined. The application forms were randomized from side to side of the pelvis. We found less cement extravasation in the CT-guided groups, but also a significant higher radiation exposure (P < 0.05) by using CT guidance. The conventional fluoroscopy-guided sacroplasty revealed the shortest procedure time (incision to closure time) of all treatment groups (P < 0.01). These findings show no difference regarding cement extravasation between ballon-assisted and conventional sacroplasty. Further, in comparison to fluoroscopy-assisted technique, the CT-guided cement injection seems to decrease the risk of cement extravasation, irrespective of the use of an additional balloon assistance. However, we have to consider a greater radiation exposure using CT guidance. Further investigations will proof the suitability in the normal course of clinical life.

[Periprosthetic fractures. Long-term results after plate osteosynthesis stabilization]. / Periprothetische Femurfrakturen. Langzeitergebnisse nach plattenosteosynthetischer Stabilisierung.

BACKGROUND: Due to the increasing age of patients and the rising number of joint replacements, the incidence of periprosthetic fractures (PPF) is also increasing. The treatment should be selected with knowledge of the prefracture interface status and the type of fracture involved. The aim of this study was to evaluate our treatment of PPF with long-term follow-up. PATIENTS AND METHODS: From 1988 to 2006, 99 patients with PPF were treated in our department. In 86 cases a plate osteosynthesis was used. After a mean time of 7.3+/-2.8 years, we studied 56 patients and monitored their complications. RESULTS: The most diagnosed fracture was Johansson type III (44%). Seventy-one patients were treated with a conventional and 15 with locking-plate osteosynthesis. In 15 cases (17.5%) we found severe complications (3 breaks and 3 dislocations of the plates, 6 cases of pseudarthrosis, 2 deep wound infections, and 1 case of postoperative bleeding). CONCLUSION: Due to the minor frequency of severe complications, plate osteosynthesis of a periprosthetic fracture with a loosened interface is a good therapeutic option for individual patients, particularly for geriatric patients and those without disorders specific to a loosened interface.

Comparison of open versus percutaneous pedicle screw insertion in a sheep model.

Minimally invasive surgery has become more and more important for the treatment of traumatic spine fractures. Besides, some clinical studies, objective data regarding the possible lower damage to the surrounding tissue of the spine is still missing. Here we report a sheep model where we compared a percutaneous versus an open approach for dorsal instrumentation with pedicle screws to the spine. Twelve skeletally mature sheep underwent bilateral pedicle screw fixation at the L4-L6 level. Forty-eight pedicle screws were bilaterally inserted into the pedicles and connected with rods using either an open dorsal standard or a percutaneous approach. Operation time, blood flow, compartment pressure, radiation time, loss of blood, laboratory findings and EMG were evaluated to objectify possible advantages for the percutaneous operation technique. Loss of blood and the distribution of CK-MM as a marker for muscle damage were significantly lower in the percutaneous group. However, radiation time was significantly longer in the percutaneous group. Other parameters like compartment pressure, blood flow and also measurement of the EMG at different time points did not reveal significant differences. Based on the results we found in the present study, percutaneous screw insertion can bring moderate advantages but it should be noted that essential functional deficits to the muscle could not be detected.

[CT-guided balloon-assisted sacroplasty. Preliminary results of a feasibility study]. / CT-gesteuerte Sakroplastie unter Verwendung insufflierbarer Ballons. Ergebnisse einer Machbarkeitstudie.

OBJECTIVE: The procedure of sacroplasty was introduced recently and involves the percutaneous application of cement to the sacral bone. Currently there are no standardized data available reflecting clinical results such as leakage rates or other complications. The aim of this study was to evaluate the feasibility and results of a balloon-assisted, CT-guided cement application in a controlled experimental approach. MATERIAL AND METHODS: The trials were conducted on preserved human cadaveric specimens (n=6). The cement application was supported by kyphoplasty balloons (Kyphon) on the right hand side, and was performed without balloons on the opposite side. CT scans were obtained for preoperative planning and postoperative assessment, while CT fluoroscopy was used for intraoperative guidance (Philips Brilliance 64). RESULTS: The procedure revealed a good feasibility with an average procedure time of 36.9+/-2.4 min (range 33.1-38.9). The chosen scan protocol produced the following effective doses: 0.99 mSv in females and 0.63 mSv in males per scan and 0.33 mSv (females) and 0.25 mSv (males) per CT fluoroscopy image. Extraosseous cement spreading was not observed after both balloon-assisted and conventional application. CONCLUSION: The CT-guided technique presented in this study enables surgeons to perform sacroplasty with high precision and moderate radiation exposure. Further clinical studies are necessary to show if the balloon-assisted cement application can promote lower leakage rates than the conventional technique in patients with sacral fractures.

[Consequences of occult insufficiency fractures of the sacrum]. / Folgen der okkulten Insuffizienzfraktur des Os sacrum.

Low back pain disorders of the elderly can potentially be caused by sacral insufficiency fractures due to osteoporosis, radiation necrosis or seldom malignant processes. In our institution an increasing numbers of patients suffering from osteoporotic sacral insufficiency fractures could recently be observed. In a case report study clinical symptoms, diagnostic procedures as well as therapeutic options are discussed.

Red cell glucose-6-phosphate dehydrogenase status and pyruvate kinase activity in a Nigerian population.

Glucose-6-phosphate dehydrogenase A- (G6PD A-) deficiency is a common enzymopathy in Africa that sporadically leads to manifest haemolytic anaemia. It is not exactly known how far the haematological status of individuals with either homozygous or heterozygous G6PD A- deficiency differs from that of individuals with normal G6PD activity. In a field study in Nigeria, we determined G6PD gene variants, the corresponding G6PD and pyruvate kinase (PK) activities, and basic haematological parameters in clinically healthy individuals, who were, in part, asymptomatically infected by malaria parasites. Red blood cell counts and haemoglobin levels were lower in G6PD A- deficient than in G6PD normal subjects. PK activities were higher in G6PD deficients, indicating a younger red cell population in these individuals. These findings suggest that G6PD A- deficiency is accompanied by chronic subclinical haemolysis. As a consequence, the reduced life span of red cells leads to an impaired diagnosis of G6PD heterozygosity when applying routine biochemical methods.

Concentrations of chloroquine and malaria parasites in blood in Nigerian children.

Consumption of chloroquine (CQ) and subtherapeutic drug levels in blood are considered to be widespread in areas where malaria is endemic. A cross-sectional study was performed with 405 Nigerian children to assess factors associated with the presence of CQ in blood and to examine correlations of drug levels with malaria parasite species and densities. Infections with Plasmodium species and parasite densities were determined by microscopy and PCR assays. Whole-blood CQ concentrations were measured by high-performance liquid chromatography. Plasmodium falciparum, P. malariae, and P. ovale were observed in 80, 16, and 9% of the children, respectively, and CQ was detected in 52% of the children. CQ concentrations were >17 and <100 nmol/liter in 25% of the children, 100 to 499 nmol/liter in 14% of the children, and > or =500 nmol/liter in 13% of the children. Young age, attendance at health posts, and absence of parasitemia were factors independently associated with CQ in blood. With increasing concentrations of CQ, the prevalence of P. falciparum infection and parasite densities decreased. However, at concentrations corresponding to those usually attained during regular prophylaxis (> or =500 nmol/liter), 62% of children were still harboring P. falciparum parasites. In contrast, no infection with P. malariae and only one infection with P. ovale were observed in children with CQ concentrations of > or =100 nmol/liter. These data show the high prevalence of subcurative CQ concentrations in Nigerian children and confirm the considerable degree of CQ resistance in that country. Subtherapeutic drug levels are likely to further promote CQ resistance and may impair the development and maintenance of premunition in areas where malaria is endemic.