Low-field magnetic resonance imaging offers potential for measuring tibial component migration.

BACKGROUND: Roentgen stereophotogrammetric analysis (RSA) is used to measure early prosthetic migration and to predict future implant failure. RSA has several disadvantages, such as the need for perioperatively inserted tantalum markers. Therefore, this study evaluates low-field MRI as an alternative to RSA. The use of traditional MRI with prostheses induces disturbing metal artifacts which are reduced by low-field MRI. The purpose of this study is to assess the feasibility to use low-field (0.25 Tesla) MRI for measuring the precision of zero motion. This was assessed by calculating the virtual prosthetic motion of a zero-motion prosthetic reconstruction in multiple scanning sessions. Furthermore, the effects of different registration methods on these virtual motions were tested. RESULTS: The precision of zero motion for low-field MRI was between 0.584 mm and 1.974 mm for translation and 0.884° and 3.774° for rotation. The manual registration method seemed most accurate, with µ ≤ 0.13 mm (σ ≤ 0.931 mm) for translation and µ ≤ 0.15° (σ ≤ 1.63°) for rotation. CONCLUSION: Low-field MRI is not yet as precise as today's golden standard (marker based RSA) as reported in the literature. However, low-field MRI is feasible of measuring the relative position of bone and implant with comparable precision as obtained with marker-free RSA techniques. Of the three registration methods tested, manual registration was most accurate. Before starting clinical validation further research is necessary and should focus on improving scan sequences and registration algorithms.

Computed tomography determined femoral torsion is not accurate.

INTRODUCTION: Computed tomography (CT) is considered the method of choice for detecting rotational malalignment of the femur. However, it is unclear how reliable the method is, and what the causes are of potential inaccuracies. MATERIALS AND METHODS: To address these issues three observers measured the CT images of the femur of 76 patients on two separate occasions. The images were made during follow-up of a unilateral femoral shaft fractures. Rotational malalignment was determined by comparing the torsion angle of the injured to the noninjured leg. RESULTS: The pooled intraobserver variance was 3.9 degrees and interobserver variance 4.1 degrees. Of the two measurements of one observer 95% were up to 10.8 degrees different, and between observers 95% of the measurements were up to 15.6 degrees different. CONCLUSIONS: CT measurements of rotational malalignment of the femur are not accurate. This is due principally to the difficulty in defining a line through the axis of the femoral neck. The accuracy can be improved by taking the average of two measurements.

Rotational malalignment after intramedullary nailing of femoral fractures.

OBJECTIVES: Intramedullary nailing has been accepted as the treatment of choice for femoral shaft fractures. The aim of our study was to determine the incidence and implications of rotational malalignment after intramedullary nailing using computed tomography measurements. DESIGN: Cohort study. SETTING: Patients who postoperatively visited the orthopaedic outpatient and radiology clinics. PATIENTS: Seventy-six patients, 59 men and 17 women, with a mean age of 28.4 years (15-88). INTERVENTION: Patients treated on a fracture table with an antegrade reamed AO nail (n = 46) or Grosse Kempf nail (n = 30) for a unilateral femoral shaft fracture between 1988 and 1998 were included in the study. MAIN OUTCOME MEASUREMENTS: Patients filled out a questionnaire concerning pain, daily activities, and sport. Oxford, Western Ontario and McMaster University osteoarthritis index, and Harris Hip and Knee Society scores were obtained. Physical exams and computed tomography measurements were established. RESULTS: Twenty-one patients (28%) were found to have a rotational malalignment of 15degrees or more. There was no significant difference in rotational deformity with either the AO or Grosse Kempf nail. The incidence of malrotation was independent of the fracture level. Patients with a torsional deformity had difficulties with more demanding activities like running, sports, and climbing stairs. Patients with an external rotational malalignment (n = 12) have more functional problems than patients with an internal rotational malalignment (n = 9). Clinically determined rotation differences are not accurate (+/-20degrees) compared with the established computed tomography measurements. CONCLUSIONS: Rotational malalignment after intramedullary nailing for femoral fractures is found in 28% of the patients in this study. These patients have difficulties with more demanding activities, especially when they have an external torsional deformity.

[Limb-length measurements using wooden boards: an accurate and experience-independent method]. / Bepaling van beenlengteverschil met de plankjesmethode: nauwkeurige uitkomsten, onafhankelijk van ervaring van de onderzoeker.

OBJECTIVE: To determine the precision and reliability of the indirect limb-length measurement, and the inter-observer variance between doctors differing in level of experience. DESIGN: Descriptive. METHOD: Indirect limb-length measurement by placing 0.5 cm-thick wooden boards under the foot of the shorter leg until the difference in length was corrected, was performed by 3 observers differing in experience (medical student, resident and orthopaedic surgeon) on 66 patients with unilateral femoral-shaft fractures treated with a femoral nail. The group of patients consisted of 51 men and 15 women with a median age of 30 years (range: 18-90). In total 17 observers participated and 177 limb-length measurements were performed. The measurements obtained were compared with limb-length measurements obtained by orthoradiograms of the entire leg. RESULTS: Of the 177 indirect limb-length measurements, 144 (81%) differed by 0-1.0 cm compared with the limb length obtained by orthoradiogram. There was no statistically significant difference in the limb-length measurements obtained by the three groups of observers with different experience levels. There was a certain degree of correlation between values measured by medical students and residents (r = 0.7). When comparing the measurements carried out by staff members with those of residents and medical students, respectively, a lower degree of correlation was found (r = 0.6 and 0.5, respectively). CONCLUSION: Indirect limb-length measurement with wooden boards was accurate. Experience did not play an essential role.

Long-term results after laparoscopic Thal procedure in children.

As the laparoscopic approach to gastroesophageal reflux disease (GERD) was introduced in pediatric surgery in the last decade of the 20th century, it became apparent that this approach was beneficial. The favorable results have led to a more general acceptance and implementation of this type of surgery at the beginning of the 21st century. We give an overview of the first decade of laparoscopic antireflux procedures in children with an emphasis on the laparoscopic Thal fundoplication and its implication on morbidity and cure of GERD in the long term both for normal and mentally handicapped children. Between 1993 and 2002, 149 children with GERD underwent 157 laparoscopic antireflux procedures, of whom 48% were mentally handicapped. Follow-up ranged from 6 months to 9 years (median age 4.5 years). Nineteen children died. All but one were not related to the antireflux procedure. Immediate relief of symptoms occurred in 120 children (80.5%). In 29 children, the results were less than optimal. Eight patients underwent a laparoscopic redo procedure (5.4%). However, none of the children with a follow-up of more than 5 years show any symptoms anymore. In conclusion, the laparoscopic Thal fundoplication is a safe procedure, and results in the long term are favorable, irrespective of the nature of the cause, ie, mental retardation.