Large articulations do not increase wear rates of thin second-generation highly cross-linked polyethylene liners at ten years

Aims

Radiostereometric analysis (RSA) is the most accurate radiological method to measure in vivo wear of highly cross-linked polyethylene (XLPE) acetabular components. We have previously reported very low wear rates for a sequentially irradiated and annealed X3 XLPE liner (Stryker Orthopaedics, USA) when used in conjunction with a 32 mm femoral heads at ten-year follow-up. Only two studies have reported the long-term wear rate of X3 liners used in conjunction with larger heads using plain radiographs which have poor sensitivity. The aim of this study was to measure the ten-year wear of thin X3 XLPE liners against larger 36 or 40 mm articulations with RSA.

Methods

We prospectively reviewed 19 patients who underwent primary cementless THA with the XLPE acetabular liner (X3) and a 36 or 40 mm femoral head with a resultant liner thickness of at least 5.8 mm. RSA radiographs at one week, six months, and one, two, five, and ten years postoperatively and femoral head penetration within the acetabular component were measured with UmRSA software. Of the initial 19 patients, 12 were available at the ten-year time point.

Results

The median proximal, 2D, and 3D wear rates calculated between one and ten years were all less than 0.005 mm/year, with no patient recording a proximal wear rate of more than 0.021 mm/year. Importantly, there was no increase in the wear rate between five and ten years.

Conclusion

The very low wear rate of X3 XLPE liners with larger articulations remains encouraging for the future clinical performance of this material.

Comparison of Sacroiliitis Grade Readings on the Same Plain Radiographs by the Same Observer at Different Periods

BACKGROUND

 This study aimed to investigate whether there is a difference between the readings of plain sacroiliac radiographs of patients with sacroiliitis by the same observer.

MATERIALS AND METHODS

 In the study, we included patients diagnosed with sacroiliitis through sacroiliac MRI who had undergone plain radiographs at our center between 2015 and 2022. The radiographic grading of patients was conducted by transferring their demographic and clinical information into a computerized environment so that these details would not be identifiable. The plain radiographs were numbered, and the responses were graded as grade 0, 1, 2, 3, or 4 for the right and left sacroiliac joints. The next day, using the same procedure, the same clinician re-evaluated the same plain radiographs in a different order without viewing the previous responses. This method was employed to prevent bias. The results (kappa value) were evaluated (0.00-0.20: slight agreement, 0.21-0.40: fair agreement, 0.41-0.60: moderate agreement, 0.61-0.80: substantial agreement, 0.81-1.00: perfect agreement).

RESULTS

 The study population included 478 patients and 956 sacroiliac joints from plain radiographs, both on the right and left. Following the observer's classification of the sacroiliac joints into 0, 1, 2, 3, and 4, a moderate level of agreement was found in the second evaluation of the same observer a day later with the same grades (p<0.001, kappa: 0.576). When categorized as grade 0-1 and grade 2-4, there was moderate agreement (p<0.001, kappa: 0.519), and categorization into grades 0-2 and 3-4 showed substantial agreement (p<0.001, kappa: 0.715). Analyzing the categorization into grades 0-3 and grade 4 revealed a higher kappa value, indicating substantial agreement (p<0.001, kappa: 0.766).

CONCLUSION

Intraobserver interpretation of radiographs may be more accurate than the interpretation of different specialists. While interpreting plain radiographs, we observed variability between adjacent grades but less variability between distant grades. However, these results need to be validated.

Prevalence of lumbosacral transitional vertebra in patients with chronic low back pain: a descriptive cross-sectional study

BACKGROUND

Numerous causes of low back pain have been identified like spondylosis, spondylolysis, spondylolisthesis, facet lesions, discal abnormalities, vertebral instability, degenerative osteoarthritis, etc., These causes of low back pain are seen commonly in >50 years of age. Lumbosacral transitional vertebra (LSTV) is a common congenital anomaly with multitude of intermediate morphologic manifestations between the typical sacral and lumbar vertebra reported by some authors as a cause of low back pain. There are racial differences reported in the literature on the prevalence of LSTV. There is no common consensus in literature about the association between LSTV and low back pain. There is a paucity of literature on the subject in the Indian population, hence the current study was conducted.

MATERIAL AND METHODS

60 cases of low back pain and 60 controls were included in the study. Patients between 18-50 years of age with low back pain of >12 weeks duration who were fulfilling the inclusion criteria were included in the study. The plain radiographs were screened by two observers (one Orthopaedician and one Radiologist) for the presence or absence of lumbosacral transitional vertebra (LSTV) and classification was determined by consensus. The incidence of LSTV was calculated in both the groups (cases and controls) and evaluated for statistical significance.

RESULTS

Prevalence of lumbosacral transitional vertebra (LSTV) was found to be 38.33% in cases group as compared to control group (21.66%) and was statistically significant (p value <0.05). Prevalence of lumbarisation was higher in case group (10%) in comparison to control group (5.0%) but not found to be statistically significant. Prevalence of sacralisation was also found to be higher in case group (28.33%) as compared to control group (16.67%). This was not found to be statistically significant.

CONCLUSION

The present study showed a higher prevalence of lumbosacral transitional vertebra (LSTV) in case group (38.33%) as compared to control group (21.66%) which was found to be statistically significant. Prevalence of lumbarisation and sacralisation were both found to be higher in the case group in comparison to control group, but the difference was not statistically significant. However, further studies with larger sample would be needed to conclusively determine any association between low back pain and subtypes of LSTV.

Evaluation of Spinal Fusion in Thoracic and Thoracolumbar Spine on Standard X-Rays: A New Grading System for Spinal Interbody Fusion

STUDY DESIGN

Retrospective evaluation of prospectively collected data.

OBJECTIVE

Analyzing time course and stages of interbody fusion of a uniformly operated cohort, defining a grading system and establishing diagnosis-dependent periods of bone healing.

METHODS

Sequential lateral radiographs of 238 patients (313 levels) with interbody fusion operated thoracoscopically were analyzed.

RESULTS

Evaluation of 1696 radiographs with a mean follow-up of 65.19 months and average numbers of 5.42 (2-18) images per level was performed. Diagnoses were Pyogenic Spondylitis (74), Fracture (96), Ankylosing Spondylitis (38) and Degenerative Disease (105). No case with Grade 2 deteriorated to Grade 5. On average, Grade 4 persisted for 113 days, Grade 3 for 197 days, Grade 2 for 286 days and Grade 1 for 316 days. The first 95% of levels ("Green Zone", ≤ Grade 2) fused at 1 year, the remaining 4% levels fused between 12 and 17 months ("Yellow Zone") and the last 1% ("Red Zone") fused after 510 days.

CONCLUSION

Sequential lateral radiographs permit evaluation of interbody fusion. Grade 2 is the threshold point for fusion; once accomplished, failure is unlikely. If fusion (Grade 2,1 or 0) is not reached within 510 days, it should be regarded as failed. The 510-day-threshold could reduce the necessity of CT scanning for assessing fusion.

An Evaluation of the Quality of Plain Radiograph Interpretations by Radiology Trainees: A Single Institution Experience

Introduction: The primary communication between the radiologist and referrer is through the radiological report. However, there are incidents of misinterpretation during radiologist training. Therefore, the present study aimed to evaluate the accuracy level and incidence of interpretation errors for plain radiographs among radiology trainees at our institution. Materials and Methods: The present study retrospectively reviewed 508 reported plain radiographs for one year, and two radiologists subsequently evaluated these plain radiographs. The initial diagnosis by the trainee was compared with the radiologists’ evaluation, and the results were categorized as either ‘accurate’, ‘minor discrepancy’, or ‘major discrepancy’. The data were analyzed concerning the overall performance, year of trainee, anatomic area, patient age group, and radiograph type. A chi-square test was performed, with p < 0.05 indicating statistical significance. Results: The overall accuracy rate was 69%, with minor and major discrepancy rates of 21% and 10%, respectively. There was an insignificant increase in overall accuracy with increased years of training, despite a reduction to 58% accuracy among Year 3 trainees. The accuracy level increased between Year 1, Year 2 and Year 4 by 70%, 71% and 75%, respectively (p > 0.05). The accuracy rates for both the adult and pediatric age groups were not statistically significant. The mobile radiographs showed lower accuracy rate of reporting than the plain radiographs. Conclusion: The radiological trainee interpretations for plain radiographs had an average rating with low discrepancy rates. The Year 3 trainees had the lowest accuracy compared to the other trainee groups. However, the present study suggests the need for further research to determine if the current outcomes are outliers or are indicative of a real phenomenon.

Incidence and Predictors of Lateral Hinge Fractures Following Medial Opening-Wedge High Tibial Osteotomy Using Locking Plate System: Better Performance of Computed Tomography Scans

BACKGROUND

This study compared the rates of plain radiographs and computed tomography (CT) for detecting lateral hinge fractures and to evaluate factors affecting lateral hinge fractures in patients following medial opening-wedge high tibial osteotomy (MOWHTO).

METHODS

This prospective study included 59 patients (65 knees) undergoing MOWHTO for primary medial compartment osteoarthritis with a 2-year follow-up between 2013 and 2016. Clinical and radiographic evaluations were performed using Knee Society Score and Western Ontario and McMaster Universities Arthritis Index, and we calculated the hip-knee-ankle angle, weight-bearing line ratio, lateral distal femoral angle, medial proximal tibial angle, posterior tibial slope, osteotomy gap height, and osteotomy gap filling rate. Immediate plain radiographs and CT were used to detect lateral hinge fractures according to Takeuchi's method.

RESULTS

Among 65 knees, the incidence of lateral hinge fractures was 13.8% (Type I: 7, Type II: 2). Only 6 knee fractures (9.2%) were detected on postoperative plain radiographs, including 5 Type I fractures and 1 Type II fracture. An additional 3 knees (4.6%) were detected on postoperative CT scans, including 2 Type I fractures and 1 Type II fracture. Furthermore, osteotomy gap height (adjusted odds ratio = 1.831, P = .016) was the only predictor of lateral hinge fractures.

CONCLUSION

The incidence of lateral hinge fractures after MOWHTO was 13.8%. CT (13.8%) afforded higher detection rates for lateral hinge fractures than did plain radiographs (9.2%) despite a marginal difference with uncertain significance. Osteotomy gap height was the only predictor of lateral hinge fractures.

LEVEL OF EVIDENCE

Prospective cohort study (Level II).

Medical Imaging and Laboratory Analysis of Diagnostic Accuracy in 107 Consecutive Hospitalized Patients With Diabetic Foot Osteomyelitis and Partial Foot Amputations

The primary aim of our study was to compare the preoperative diagnostic accuracy of plain radiographic findings with the accuracy of magnetic resonance imaging (MRI) findings for diabetic foot osteomyelitis in hospitalized patients who underwent first-time partial foot amputations with confirmed histopathological specimens positive for osteomyelitis. Second, it was desired to determine whether certain variables within the initial clinical presentation and preoperative laboratory findings were associated with more accurate diagnosis of diabetic foot osteomyelitis in this study population. Finally, it was desired to determine the most common bacterial organisms found in bone and soft-tissue cultures taken intraoperatively and to determine how often the same organism was found in both. After applying the inclusion and exclusion criteria to the initial 329 patients identified through chart review, the final sample size for further analysis was n =107. In this study, after adjusting for the effects of covariates such as age, erythrocyte sedimentation rate (ESR) and C-reactive protein, plain radiographs seemed to have statistically more significant power than MRI in predicting and diagnosing diabetic foot osteomyelitis. In addition, higher ESR values were confirmed to predict a higher chance of positive diagnosis for diabetic foot osteomyelitis. Furthermore, the presence of positive bacterial identification from intraoperative bone cultures did not always indicate true osteomyelitis on histopathological examination.

LEVELS OF EVIDENCE

Level II: Diagnostic study.

Emergency Physicians Choose Wisely When Ordering Plain Radiographs for Low Back Pain Patients

Objectives

The Choosing Wisely Canada (CWC) Emergency Medicine group recommends avoidance of lumbosacral radiographs for patients with non-traumatic low back pain (LBP) in the absence of red flags. The objective of this study was to evaluate imaging practices of emergency physicians (EPs) in four Calgary emergency departments (EDs) and identify patient, physician, and environmental factors associated with over-ordering of radiographs for low-risk LBP patients.

Methods

Data was retrospectively collected from patients, ages 18–50 and Canadian Triage and Acuity Scale (CTAS) codes 2–5, who presented with non-traumatic LBP to Calgary EDs from April 1, 2014 to March 31, 2016. Patients considered high risk, specifically with partial thromboplastin time (PTT) > 40 seconds or international normalized ratio (INR) > 1.2 seconds, any consult, admission to hospital, and history of cancer, were excluded. The primary outcome was to establish the overall usage of lumbosacral radiographs. The secondary outcome was to identify factors that influenced lumbosacral spine imaging.

Results

Data from 2128 low-risk patients showed that 14.8% of the patients received lumbosacral radiographs. Variation among 132 physicians in X-ray ordering ranged from 0% to 90.9%. There were site-specific differences in ordering patterns [Rockyview General Hospital (RGH) = 21.6% > South Health Campus (SHC) = 15.6% > Peter Lougheed Centre (PLC) = 13.1% > Foothills Medical Centre (FMC) = 9.7%, p < 0.001]. Canadian College of Family Physicians-Emergency Medicine (CCFP-EM) licensed physicians ordered more X-rays compared to Fellow of the Royal College of Physicians of Canada (FRCPC) licensed physicians (16.6% vs. 11.1%, p < 0.001). Older physicians and physicians with more experience ordered more X-rays than their younger and less experienced colleagues.

Conclusion

Considerable variation exists in the ordering practices of Calgary EPs. Overall, EPs seem to be choosing wisely in terms of ordering plain radiographs for non-traumatic LBP.

Lesser Trochanter Size on Plain Anteroposterior Radiographs Correlates With Native Femoral Anteversion

BACKGROUND

Assessing femoral version in orthopedic surgery is important for preoperative planning of total hip arthroplasty, especially for recognizing excessive anteversion or retroversion. The present study addressed the following: (1) Is the position of the lesser trochanter correlated to the femoral neck axis? (2) If so, may femoral version be assessed by means of plain pelvic radiographs?

METHODS

Three-dimensional computed tomography scans of 60 patients undergoing minimally invasive cement-free total hip arthroplasty were retrospectively analyzed, particularly with regard to the relation between the femoral neck axis and the lesser trochanter, the femoral version, and the size of the projected lesser trochanter in different rotational positions. Based on linear regression, a biomathematical formula was developed to assess femoral anteversion on plain radiographs depending on the visible part of the lesser trochanter.

RESULTS

The mean difference between the location of the lesser trochanter axis and the femoral neck axis was 43.3° ± 6.2°. Eighty-seven percent of patients (52 of 60) had a deviation of <10° from the mean value of 43.3°. By virtual rotation of the femur in steps of 10°, the visible part of the lesser trochanter linearly increased with anteversion of the femur: femoral version = (lesser trochanter size - 5.57) × 4.17. There was a high correlation between the visible part of the lesser trochanter and femoral version (R² = 0.75; P < .001). The lesser trochanter was no longer visible with femoral retroversion in each of the 60 data sets.

CONCLUSION

The projected size of the lesser trochanter as available on plain pelvic AP radiographs correlates with native femoral anteversion.

Leg lengthening and femoral-offset reduction after total hip arthroplasty: where is the problem - stem or cup positioning?

Background Restoration of femoral offset (FO) and leg length is an important goal in total hip arthroplasty (THA) as it improves functional outcome. Purpose To analyze whether the problem of postoperative leg lengthening and FO reduction is related to the femoral stem or acetabular cup positioning or both. Material and Methods Between September 2010 and April 2013, 172 patients with unilateral primary osteoarthritis treated with THA were included. Postoperative leg-length discrepancy (LLD) and global FO (summation of cup and FO) were measured by two observers using a standardized protocol for evaluation of antero-posterior plain hip radiographs. Patients with postoperative leg lengthening ≥10 mm (n = 41) or with reduced global FO >5 mm (n = 58) were further studied by comparing the stem and cup length of the operated side with the contralateral side in the lengthening group, and by comparing the stem and cup offset of the operated side with the contralateral side in the FO reduction group. We evaluated also the inter-observer and intra-observer reliability of the radiological measurements. Results Both observers found that leg lengthening was related to the stem positioning while FO reduction was related to the positioning of both the femoral stem and acetabular cup. Both inter-observer reliability and intra-observer reproducibility were moderate to excellent (intra-class correlation co-efficient, ICC ≥0.69). Conclusion Post THA leg lengthening was mainly caused by improper femoral stem positioning while global FO reduction resulted from improper positioning of both the femoral stem and the acetabular cup.

Persistent proatlas with additional segmentation of the craniovertebral junction - The Tsuang-Goehmann-Malformation

Case study description and analysis of a complex craniovertebral dysplasia in an 8-year-old male patient, in which conventional cervical spine radiographs demonstrated a regularly differentiated occipital base, as well as the presence of two lateral masses of the proatlas vertebra and two lateral masses of the atlas vertebra. Further assessment included computed tomography of the occipital base and the upper cervical spine as well as three-dimensional reconstruction. Malsegmentation of the fourth occipital vertebra can result in various anomalies that are known as 'manifestation of the proatlas'. The occurrence of a persistent proatlas with additional segmentation of the craniovertebral junction represents an extremely rare dysplasia. To our knowledge, it is the second report concerning the persistence of a complete human proatlas vertebra. We consider the biomechanical and embryological particularities of this complex dysplasia to represent sufficient basis for future differentiation from other malformations of the fourth occipital vertebra. Comprehensive literature review and discussion about the entity will be provided.

Uncommon Causes of Acute Abdominal Pain - A Pictorial Essay

Acute abdomen is one of the most common clinical conditions requiring a radiological investigation. Ultrasound is the primary modality of choice which can diagnose some of the common causes of acute abdomen. However, sometimes the underlying cause for the pain is far more complicated than expected mandating a high degree of suspicion to suggest further investigation with contrast enhanced computed tomography or magnetic resonance imaging. Here, we have compiled a comprehensive series of selected cases to highlight the conditions which can be easily overlooked unless carefully sought for. This article also emphasizes the importance of multimodality approach to arrive at the final diagnosis with an increased overall diagnostic accuracy which in turn improves patient management and prognosis.

Talofibular Bony Impingement in the Ankle

BACKGROUND

Talofibular bony impingement has not previously been reported, since it is difficult to detect on plain radiograph, similar to the spur on the anterior border of the medial malleolus and anterior portion of the medial talar facet. We hypothesized that talofibular bony impingement can cause limited dorsiflexion of the ankle. The aim of this study was to evaluate talofibular bony impingement as a distinct form of impingement that limits dorsiflexion of the ankle.

METHODS

This study included 20 consecutive patients (21 ankles) with talofibular impingement and 19 consecutive patients (19 ankles) with lateral ankle instability without talofibular impingement. Presence or absence of talofibular impingement was confirmed under direct intraoperative visualization. Dorsiflexion before and after excision of the impinging spurs was measured. Findings on plain radiographs and computed tomography were compared between the groups. Pre- and postoperative clinical assessments were done with Foot Function Index, visual analog scale for pain, and American Orthopaedic Foot & Ankle Society ankle-hindfoot score at a mean follow-up of 1.4 years.

RESULTS

After removal of the bony impingement, the range of dorsiflexion increased by a mean 7.9 degrees (range, 2.5 to 11.0 degrees) in the impingement group. The mean distance between the fibula and lateral process of the talus on weight- bearing anteroposterior radiograph of the ankle was 1.2 mm (range, 0 to 4.5) in the impingement group and 3.2 mm (range, 1 to 4.5) in the control group. On axial computed tomography image, bony protrusion of the lateral process of the talus was frequently present in the impingement group, and the mean amount of protrusion was more than that of the control group. Clinical findings improved overall.

CONCLUSIONS

Talofibular impingement was a cause of limited dorsiflexion, and the diagnosis was confirmed intraoperatively.

LEVEL OF EVIDENCE

Level III, retrospective comparative study.

Acute nonsteroidal anti-inflammatory drug-induced colitis

Resulting from direct toxicity on the bowel mucosa, nonsteroidal anti-inflammatory drug (NSAID)-induced colitis is an underestimated although potentially serious condition. Plain abdominal radiographs and multidetector computed tomography allow to identify a right-sided acute colitis with associated pericolonic inflammation, progressively diminished changes along the descending and sigmoid colon, and rectal sparing, consistent with the hypothesized pathogenesis of NSAID colitis. Increased awareness of this condition should reduce morbidity through both prevention and early recognition. High clinical suspicion and appropriate patient questioning, together with consistent instrumental findings, negative biochemistry, and stool investigations should help physicians not to miss this important diagnosis.

Retrospective evaluation of exposure index (EI) values from plain radiographs reveals important considerations for quality improvement

INTRODUCTION

Following X-ray exposure, radiographers receive immediate feedback on detector exposure in the form of the exposure index (EI).

PURPOSE

To identify whether radiographers are meeting manufacturer-recommended EI (MREI) ranges for routine chest, abdomen and pelvis X-ray examinations under a variety of conditions and to examine factors affecting the EI.

METHODS

Data on 5000 adult X-ray examinations including the following variables were collected: examination parameters, EI values, patient gender, date of birth, date and time of examination, grid usage and the presence of implant or prosthesis. Descriptive statistics were used to summarize each data set and the Mann-Whitney U test was used to determine significant differences, with P < 0.05 indicating significance for all tests.

RESULTS

Most examinations demonstrated EI values that were outside the MREI ranges, with significantly higher median EI values recorded for female patient radiographs than those for male patients for all manufacturers, indicating higher detector exposures for all units except for Philips digital radiography (DR), where increased EI values indicate lower exposure (P = 0.01). Median EI values for out of hours radiography were also significantly higher compared with normal working hours for all technologies (P ≤ 0.02). Significantly higher median EI values were demonstrated for Philips DR chest X-rays without as compared to those with the employment of a grid (P = 0.03), while significantly lower median EI values were recorded for Carestream Health computed radiography (CR) chest X-rays when an implant or prosthesis was present (P = 0.02).

CONCLUSIONS

Non-adherence to MREIs has been demonstrated with EI value discrepancies being dependent on patient gender, time/day of exposure, grid usage and the presence of an implant or prosthesis. Retrospective evaluation of EI databases is a valuable tool to assess the need of quality improvement in routine DR.

Early diagnosis of vertebral fractures

Vertebral fractures are a common clinical entity, caused by trauma or related to osteoporosis (benign). Their recognition is especially important in the post-menopausal female population but also important is their differentiation from pathological (malignant) fractures (1). A vertebral fracture is evidenced by vertebral body deformity or reduction in vertebral body height beyond a certain threshold value in the absence of bone discontinuity. For prognosis and treatment it is extremely important to recognize the cause of the fracture. In contrast to fractures that occur in other locations, vertebral fractures often go unrecognized in the acute phase as the pain may be transient and radiographic and evaluation of the spine may be difficult (2). Objective measurement of the vertebral deformity provides invaluable information to the interpreting physician and helps grade fracture severity. The recognition and diagnosis of vertebral fractures can be performed using additional diagnostic tools.

The value of a CT scan compared to plain radiographs for the classification and treatment plan in tibial plateau fractures

This study aimed to evaluate the intra- and interobserver agreement for both fracture classification according to Schatzker and treatment plan of tibial plateau fractures using plain radiographs alone and with computed tomography (CT) scans. The study was carried out prospectively to assess the impact of an advanced radiographic study on the agreement of treatment plan and fracture classification of tibial plateau fractures. Eight experienced observers (six surgeons and two radiologists) classified 15 tibial plateau fractures with plain radiographs and CT scans and set up a treatment plan. Agreement was measured using kappa coefficients. Using plain radiographs alone, the mean interobserver kappa coefficient for classification was 0.47, which decreased to 0.46 after addition of CT scans. Using plain films alone for formulating a treatment plan, the mean interobserver kappa coefficient was 0.40, which decreased to 0.30 after addition of CT scans. The mean intraobserver kappa coefficient for fracture classification using plain radiographs was 0.60, which decreased to 0.57 with addition of CT scans. The mean intraobserver kappa coefficient for treatment plan based on plain radiographs alone was 0.53, which decreased to 0.45 after addition of CT scans. In contrast with other recent publications, there is no increase in inter- and intra-agreement of a CT scan compared to plain radiographs for the classification and treatment plan in tibial plateau fractures. Routine CT scanning of the knee for tibial plateau fractures is not supported by this study.

Comparison of plain radiographs with CT scan to evaluate interbody fusion following the use of titanium interbody cages and transpedicular instrumentation

The availability of lumbar interbody cages has fuelled renewed interest in interbody fusion. Despite this, there is no consensus regarding the best non-invasive method for evaluation of interbody fusion, especially where cages have been used. The purpose of this study was to determine whether high-quality thin-slice (1- to 3-mm) computed tomography (CT) scans allow proper evaluation of interbody fusion through titanium cages. Patients undergoing lumbar interbody fusion were prospectively evaluated with CT scan and plain radiographs 6 months following surgery. These images were blindly and independently evaluated by a consultant radiologist and a spine research fellow, for bridging bony trabeculation both through and surrounding the cages as well as for changes at the cage endplate interface. Fifty-three patients (156 cages) undergoing posterior lumbar interbody fusion using titanium interbody cages were evaluated. Posterior elements were used to pack the cages and no graft was packed outside the cages. The outcome data were analysed using the Kappa co-efficient and chi-squared analysis. On CT scan, both observers noted bridging trabeculation in 95% of the cages (Kappa 0.85), while on radiographs this was present in only 4% (Kappa 0.74). Both observers also identified bridging trabeculation surrounding the cages on CT scan in 90% of cages (Kappa 0.82), while on the radiographs this was 8% (Kappa 0.86). Radiographs also failed to demonstrate all the loose cages. The results of the study show that high-quality CT scans show images suggesting bridging bony trabeculae following the use of titanium interbody cages. They also appear to show consistent bone outside the cages in spite of no bone graft having been used, and they appear to be better than plain radiographs in the early detection of cage loosening.

Reliability of pedicle screw assessment utilizing plain radiographs versus CT reconstruction

The position of 119 pedicle screws was assessed on plain antero-posterior and lateral radiographs taken immediately post-operatively and at 3 months' follow-up. The readings of five independent observers were compared with the "gold standard" of CT reconstructions. The position of only 41% of implants (range 14%-56%) was assessed correctly on the plain radiographs (47% on follow-up films). Two-thirds of CT-detectable perforations were missed. As shown with perforations of the anterior cortex, detectability increased significantly with magnitude of perforation. No specifically difficult anatomic level or direction of malplacement could be identified. Interobserver variation was considerable. Plain radiographs were shown to be of limited use in assessing the position of pedicle screws.