We aim to assess the value of patellofemoral Computed Tomography in assessing patients with anterior knee symptoms. Anterior knee symptoms are often due to patellar malalignment. Plain axial radiography or (CT) can be used to investigate these abnormalities. We have evaluated the use of patellofemoral CT scanning in 63 patients and compared the CT findings with the patients’ symptoms. We compared patellar centralisation and patellar tilt angle with the symptom described for each of 126 knees. No difference could be detected in the CT appearances of affected and unaffected knees in those patients with unilateral symptoms (all patients have both knees scanned). A significant association between maltracking and osteoarthiritic changes was demonstrated

Aim of the study: To define the dimensions of the radial head, as well as the radiocapitellar and proximal radio-ulnar joints. The most congruent portions of the radial head articulations were determined. Materials & Methods: Computed tomography scans of twenty-two cadaveric adult elbows were obtained in three forearm positions – supination, neutral, pronation. The radial head dimensions, the radiocapitellar joints, and the proximal radioulnar joints were also measured. Multivariate analysis of variance was used to determine which portions of each articulation were the most congruent. Results: At the level of the radial trough, the maximum diameter was 22.3 mm, the minimum diameter was 20.9 mm, and the diameter difference was 1.4 mm. This difference represented only 6.3% of the overall maximum diameter. The depth of curvature of the radial head trough was 2.3 mm, the radial head length was 9.8 mm, and the radial neck length was 10.7 mm. At the isthmus of medullary canal, the maximum diameter was 9.7 mm, the minimum diameter was 8.2 mm, and the diameter difference was 1.5 mm. This difference represented 15.6% of the maximum diameter. The average radiocapitellar distance at the radial lip was 4.0 mm, the trough 2.4 mm, and the ulnar lip 2.2 mm. Thus, the radial head tended to become uncovered at the radial lip (p < 0.0001). The radiocapitellar joint was tighter in pronation than in supination (p = 0.0008). The proximal radioulnar joint was most congruent at the MPRUJ (middle proximal radioulnar joint), at the midportion and posterior aspects, rather than the anterior aspect (p < 0.0001). The PRUJ coverage was between 69.0 and 79.2 degrees. Conclusions: Prosthesis trial sizing should be judged by the articulations providing the most congruency –. 1) the ulnar lip or trough of the radiocapitellar joint in pronation and. 2) the posterior or midportion of the MRPUJ

Purpose: We analysed outcome of 106 Latarjet-Patte procedures at 7.5 years mean follow-up. Computed tomography of 80 bone blocks provided further details. Material and methods: One hundred two patients (106 bone blocks), mean age 34 years, were reviewed at a mean 7.5 years follow-up. The sex ratio was 5/1 M/F. The accident had occurred at a mean age of 22 years, by trauma in 87% of the cases, generally involving the dominant limb. Eighty-seven patients practised sports, a high-risk sport in 48% of the cases. Clinical outcome was assessed with the Duplay and Row score, radiographs and a bilateral computed tomography scan in 80 cases. Results: Postoperative morbidity was 12% and only required revision surgery in 2.8% of the cases. Posterior pain required screw ablation in 6% of the cases. Global outcome was excellent or good in 66% of the patients and 60% of the patients who practised sports were able to resume their activities at the same level. Painless shoulders were achieved for 70% of the patients. There was one post-traumatic recurrence and residual apprehension in 13% of the cases. Grade 3 or 3 osteoarthritis was present in 15% of the cases with a clear narrowing of the joint space in 3.5%. The CT scans were less favourable, showing global or posterior joint space narrowing in 17.5% of the cases. Monocortical screwing led to nonunion in 7%. Advanced osteolysis led to pain with alteration of the functional score. Discussion: Postoperative complications deteriorated the global result. Overly long malleolar screws led to posterior pain with fatty degeneration of the infraspinatus. Osteoarthritis and “inverted L” subscapularis were the main factors related to loss of rotation. Persistent apprehension was not related to technical error, but to exaggerated anteversion of the humeral cap, basically due to the presence of a notch. Revision scans clearly contributed to the evaluation of the bone block and its position. It allowed a more objective assessment of the osteoarthritis, showing that plain radiographs underestimated both incidence and gravity related to delay after surgery, patient age and the overhanging property of the joint stop. Conclusion: The Latarjet-Patte procedure has given satisfactory results that can be improved with rigorous technique. Computed tomography provides a more objective analysis of the results

Normal acetabular development in developmental dysplasia of the hip (DDH) depends upon early and maintained congruent reduction. Computed tomography is an accepted method for evaluating this and attempts to quantify hip reduction, by various angular and linear measurements, have been reported. The aim of this study was to assess initial CT scans, following open reduction in the older child with DDH, with comparison of outcome to evaluate prognostic value. Method: Thirty consecutive patients underwent open reduction for DDH, with a mean age of 25.9 months at the time of operation. Acetabular morphology and the position of the femoral head were evaluated on the initial CT scan, taken on the first postoperative day, and AP pelvic radiograph taken at the latest follow-up. Results: The acetabulae of the dislocated hips were found to be significantly more anteverted than the normal. The dislocated hips also had significantly increased lateral displacement both initially and at latest follow-up. Posterior displacement of the proximal femoral metaphysis should raise concern due to an association with the need for further surgical intervention. These results did not however correlate with outcome. In conclusion, despite the significant differences noted between DDH and normal hips they did not predict acetabular development or persistent acetabular dysplasia

Analyzing shoulder kinematics is challenging as the shoulder is comprised of a complex group of multiple highly mobile joints. Unlike at the elbow or knee which has a primary flexion/extension axis, both primary shoulder joints (glenohumeral and scapulothoracic) have a large range of motion (ROM) in all three directions. As such, there are six degrees of freedom (DoF) in the shoulder joints (three translations and three rotations), and all these parameters need to be defined to fully describe shoulder motion. Despite the importance of glenohumeral and scapulothoracic coordination, it's the glenohumeral joint that is most studied in the shoulder. Additionally, the limited research on the scapulothoracic primarily focuses on planar motion such as abduction or flexion. However, more complex motions, such as internally rotating to the back, are rarely studied despite the importance for activities of daily living. A technique for analyzing shoulder kinematics which uses 4DCT has been developed and validated and will be used to conduct analysis. The objective of this study is to characterize glenohumeral and scapulothoracic motion during active internal rotation to the back, in a healthy young population, using a novel 4DCT approach.

Eight male participants over 18 with a healthy shoulder ROM were recruited. For the dynamic scan, participants performed internal rotation to the back. For this motion, the hand starts on the abdomen and is moved around the torso up the back as far as possible, unconstrained to examine variability in motion pathway. Bone models were made from the dynamic scans and registered to neutral models, from a static scan, to calculate six DoF kinematics. The resultant kinematic pathways measured over the entire motion were used to calculate the ROM for each DoF.

Results indicate that anterior tilting is the most important DoF of the scapula, the participants all followed similar paths with low variation. Conversely, it appears that protraction/retraction of the scapula is not as important for internally rotating to the back; not only was the ROM the lowest, but the pathways had the highest variation between participants. Regarding glenohumeral motion, internal rotation was by far the DoF with the highest ROM, but there was also high variation in the pathways. Summation of ROM values revealed an average glenohumeral to scapulothoracic ratio of 1.8:1, closely matching the common 2:1 ratio other studies have measured during abduction.

Due to the unconstrained nature of the motion, the complex relationship between the glenohumeral and scapulothoracic joints leads to high variation in kinematic pathways. The shoulder has redundant degrees of freedom, the same end position can result from different joint angles and positions. Therefore, some individuals might rely more on scapular motion while others might utilize primarily humeral motion to achieve a specific movement. More analysis needs to be done to identify if any direct correlations can be drawn between scapulothoracic and glenohumeral DoF. Analyzing the kinematics of the glenohumeral and scapulothoracic joint throughout motion will further improve understanding of shoulder mechanics and future work plans to examine differences with age.

A primary goal of revision Total Knee Arthroplasty (rTKA) is restoration of the Joint Line (JL) and Posterior Condylar Offsets (PCO). The presence of a native contralateral joint allows JL and PCO to be inferred in a way that could account for patient-specific anatomical variations more accurately than current techniques. This study assesses bilateral distal femoral symmetry in the context of defining targets for restoration of JL and PCO in rTKA.

566 pre-operative CTs for bilateral TKAs were segmented and landmarked by two engineers. Landmarks were taken on both femurs at the medial and lateral epicondyles, distal and posterior condyles and hip and femoral centres. These landmarks were used to calculate the distal and posterior offsets on the medial and lateral sides (MDO, MPO, LDO, LPO respectively), the lateral distal femoral angle (LDFA), TEA to PCA angle (TEAtoPCA) and anatomic to mechanical axis angle (AAtoMA). Mean bilateral differences in these measures were calculated and cases were categorised according to the amount of asymmetry.

The database analysed included 54.9% (311) females with a mean population age of 68.8 (±7.8) years. The mean bilateral difference for each measure was: LDFA 1.4° (±1.0), TEAtoPCA 1.3° (±0.9), AAtoMA 0.5° (±0.5), MDO 1.4mm (±1.1), MPO 1.0mm (±0.8). The categorisation of asymmetry for each measure was: LDFA had 39.9% of cases with <1° bilateral difference and 92.4% with <3° bilateral difference, TEAtoPCA had 45.8% <1° and 96.6% <3°, AAtoMA had 85.7% <1° and 99.8% <3°, MDO had 46.2% <1mm and 90.3% <3mm, MPO had 57.0% <1mm and 97.9% <3mm.

This study presents evidence supporting bilateral distal femoral symmetry. Using the contralateral anatomy to obtain estimates for JL and PCO in rTKA may result in improvements in intraoperative accuracy compared to current techniques and a more patient specific solution to operative planning.

Summary Statement. It is now possible to diagnose osteoporosis using incidental abdominal CT scans; applying this approach to fractures of the cervical spine demonstrates levels of osteoporosis in patients over 65. Introduction. Recently published data now makes it possible to screen for osteoporosis in patients who, in the course of their hospital stay, have had Computed Tomography (CT) scans of their abdomen for reasons other than direct imaging. This is as a result of CT derived bone mineral density (BMD) in the first lumbar vertebra (L1) being correlated BMD derived from Dual-energy X-ray absorptiometry (DEXA) scans. The advantage of this is the reduction in both cost and radiation exposure. Although age has a detrimental effect on BMD, relatively few patients have formal DEXA studies. The aims of this study were to evaluate the utility of this new technique in a cohort of patients with acute fractures of the cervical spine and to compare relative values for BMD in patients aged over 65 with those aged under 65, and thus define the role of osteoporosis in these injuries. Methods & Patients. Following Institutional review board approval, we performed a retrospective study of patients who presented to a level I trauma center with acute fractures of the cervical spine between 2010 and 2013; patients also had to have had a CT scan of their L1 vertebra either during the admission or within 6 months of their admission (for any other clinical reason). Using a picture archiving and communication (PACS) system, we generated regions of interest (ROI) of similar size in the body of L1 (excluding the cortex), in line with the publication by Pickhardt et al., and computed the mean values for Hounsfield units (HU). These values were compared against established threshold values which differentiate between osteoporosis and osteopenia; for a balanced sensitivity and specificity, <135 HU is the threshold and for 90% sensitivity a HU threshold of <160 HU is set. Comparisons were also performed between age stratified groups. Results. A total of 187 patients were reviewed for eligibility, 91 patients met the criteria with 53 patients aged 64 years or younger (range 23–64) and 38 patients aged above 65 years (range 65–98). In the younger cohort, 6/53 (11% were osteoporotic, using the lower threshold, while the higher threshold indicated 5/53 (17%) of patients under 65 years were osteoporotic; mean HU for the group was 195.8 (SD 43.3). In the older cohort, 24/38 (63%) were osteoporotic using the lower threshold, whereas 34/38 (89%) were osteoporotic using the higher threshold. Mean HU for the cohort aged over 65 years was 118.7 (SD 38.4). Age based comparison of the mean values, regardless of threshold, was statistically significant (p<0.001) in both cases. Discussion and Conclusions. This study demonstrates, for the first time in the cervical spine (including C2), the role of age related osteoporosis in acute fractures of the cervical spine. This new technique harnessing the presence of opportunistic CT scans of the abdomen saves on the extra cost and radiation exposure that may be associated with DEXA scanning. In younger patients, the higher threshold indicated 17% were osteoporotic – in the setting of an opportunistic scan, this may afford them the opportunity to commence prophylactic treatment to prevent future fractures. We believe these result have the potential to significantly impact future clinical practice

Our aim was to use CT Scanogram to evaluate fibular growth, and thus calculate normal growth velocity, which may aid in determining the timing of epiphysiodesis. Current understanding of normal lower limb growth and growth prediction originates in the work of Anderson et al published in the 1960s. There now exist several clinical and mathematical methods to aid in the treatment of leg length discrepancy, including the timing of epiphysiodesis. Early research in this area provided limited information on the growth of the fibula. It is now well recognized that abnormal growth of paired long bones may evolve into deformity of clinical significance. Existing work examining fibular growth used plain film radiography only. Computed Tomography (CT) scanogram is now the preferred method for evaluating leg length discrepancy in the paediatric population. We calculated fibular growth for 28 children (n = 28, 16 girls and 12 boys) presenting with leg length discrepancy to our unit. Mean age at presentation was 111.1 months (range 33 – 155 months). For inclusion, each child had to have at least five CT scanograms performed, at six monthly intervals. Fibular length was calculated digitally as the distance from the proximal edge of the proximal epiphysis to the most distal edge of the distal epiphysis. For calculation purposes, mean fibular length was determined from two measurements taken of the fibula. A graph for annual fibular growth was plotted and fibular growth velocity calculated. CT Scanogram may be used to calculate normal fibular growth in children presenting with leg length discrepancy

In cases of severe postdysplastic coxarthosis, it seems to be impossible to recognize acetabular geometry and the real femoral position on a plain X-ray because the real diameters and angles can be disfigured when projected. Computed tomography (CT) provides important information to the surgeon about the concavity, shape and stereotomy of the acetabulum. It is quite difficult to correctly evaluate severely changed hips. CT displays more precise acetabular diameters and angles than a plain radiograph. Because of the high density of bony tissue, the CT makes it easy to produce a three-dimensional display of the hip. From September 1995 to December 1998, 224 patients (148 female, 76 male) underwent arthroplasty using a non-cemented prosthesis according to Zweymüller. A total of 236 hip joints were operated and classified as Crowe Group I (76 hips), Crowe Group II (149 hips), and Crowe Group III (11 hips). There were no Crowe Group IV hips. A total of 96 patients were examined by 3D CT in preoperative planning. Based on CT results, four joints were not recommended for an operative solution. CT protocol: scanner Elscint TWIN II, slice 2.5 mm, 120 kV, 285 mAs, matrix 3402,. No. of slices: 40–50, incremental dual acquisition. Postprocessing: axial images, multiplanar reconstructions, 3D SSD. Acetabular stereometry: superoinferior diameter, anteroposterior diam., depth, bottom thickness, femoral neck anteversion angle and subtrochanteric marrow diameter. A three-dimensional CT of the hip is a very effective tool for preoperative assessment

Summary Statement. Using abdominal CT scans to evaluate bone mineral density following acute fractures of the thoracic and lumbar spine demonstrates significant levels of osteoporosis in older patients; this approach may help save on time and resources, and reduce unnecessary radiation exposure. Introduction. While a reduction in bone mineral density (BMD) is associated with aging, relatively few patients have formal dual-energy X-ray absorptiometry (DXA) to quantify the magnitude of bone loss, as they age. This loss of bone may predispose to fractures. Recent data, which correlates mean Hounsfield units (HU) in an area of the L1 vertebra with BMD, now makes it possible to screen for osteoporosis using incidental abdominal Computed Tomography (CT) scans to measure bone density. This innovation has the potential to reduce both cost and radiation exposure, and also make it easier to identify patients who may be at risk. The aims of this study were to evaluate the utility of this approach in patients with acute thoracic and lumbar spine fractures and to evaluate the impact of aging on BMD, using CT screening. Patients & Methods. Following institutional review board approval, we performed a retrospective study of patients who presented to a level I trauma center with acute fractures of the thoracic and lumbar spine between 2010 and 2013; patients also had to have had an abdominal (or L1) CT scan either during the admission or in the 6 months before or after their injury. Using a picture archiving and communication (PACS) system, we generated regions of interest (ROI) of similar size in the body of L1 (excluding the cortex) and computed mean values for HU. Values derived were compared against threshold values which differentiate between osteoporosis and osteopenia - for specificity of 90%, a threshold of 110 was set; for balanced sensitivity and specificity, a threshold of <135 HU was set and for 90% sensitivity a threshold of <160 HU was set. A student's t test was used to compare the age stratified mean HU (younger than 65yrs; 65yrs and older), while Fisher's exact test was used to perform aged stratified comparisons between the proportions of patients above and below the thresholds outlined (in each of the three threshold groups). Results. A total of 124 patients were evaluated, with 74 having thoracic and 50 having lumbar fractures. Among those with thoracic fractures, there were 33patients in the younger cohort, who also had a mean BMD of 196.51HU and 41 in the older cohort, who had mean BMD of 105.90HU (p<0.001). In patients with lumbar fractures, 27 patients were in the younger cohort, with mean BMD of 192.26HU and 23 patients in the older cohort with mean BMD of 114.31HU (p<0.001). At the threshold of 110 HU, set for specificity, the magnitude of difference between the age stratified cohorts was greater in the thoracic spine (p<0.001 vs. p=0.003). At the other thresholds: 135HU (balanced for sensitivity and specificity) and 160 HU (90% sensitivity), age of 65 years or older was significantly associated with reduction in CT derived measure of BMD (p<0.001 in all cases). Discussion. This study demonstrates the relative frequency of osteoporosis in acute fractures of the thoracic and lumbar spine, and how this changes with age; it is also the first study to do this using opportunistic CT scans. There seems to be a strong association between a reduction in bone mineral density and advanced age, in patients presenting with acute fractures of the spine. This approach may save on the extra cost and additional radiation exposure that may be associated with DXA scanning; in addition, it may help provide clinicians and patients with an approach to monitor developing problems with BMD before it becomes clinically apparent, especially in younger patients

PURPOSE. Osteochondral talar defects (OCDs) are sometimes located so far posteriorly that they may not be accessible by anterior arthroscopy, even with the ankle joint in full plantar flexion, because the talar dome is covered by the tibial plafond. It was hypothesized that computed tomography (CT) of the ankle in full plantar flexion could be useful for preoperative planning. The dual purpose of this study was, firstly, to test whether CT of the ankle joint in full plantar flexion is a reliable tool for the preoperative planning of anterior ankle arthroscopy for OCDs, and, secondly, to determine the area of the talar dome that can be reached by anterior ankle arthroscopy. METHODS. In this prospective study, CT-scans with sagittal reconstructions were made of 46 consecutive patients with their affected ankle in full plantar flexion. In the first 20, the distance between the anterior border of the OCD and the anterior tibial plafond was measured both on the scans and during anterior ankle arthroscopy as the gold standard. Intra- and interobserver reliability of CT as well as agreement between CT and arthroscopy were assessed by intraclass correlation coefficients (ICCs) and a Bland and Altman graph. Next, the anterior and posterior borders of the talar dome as well as the anterior tibial plafond were marked on all 46 scans. Using a specially written computer routine, the anterior proportion of the talar dome not covered by the tibial plafond was calculated, both lateral and medial, indicating the accessible area. RESULTS. The distance between the anterior border of the OCD and the anterior tibial plafond ranged from −3.1 to 9.1 mm on CT and from −3.0 to 8.5 on arthroscopy. The intra- and interobserver reliability of the measurements made on CT-scans were excellent (ICC > 0.99, p < 0.001). Likewise, agreement between CT and arthroscopy was excellent (ICC=0.97; p < 0.001); only one patient showed a difference of more than 2.0 mm. The anterior 47.3 ± 6.8% (95%CI, 45.2–49.3) of the lateral talar dome, and 47.7 ± 7.0% (95%CI, 45.7–49.8) of the medial talar dome was not covered by the tibial plafond. CONCLUSIONS. Computed tomography of the ankle joint in full plantar flexion is an accurate preoperative planning method to determine the arthroscopic approach for treatment of OCDs of the talus. Almost half of the talar dome is directly accessible by anterior ankle arthroscopy

Introduction. A femoral rotational alignment is one of the essential factors, affecting the postoperative knee balance and patellofemoral tracking in total knee arthroplasty (TKA). To obtain an adequate alignment, the femoral component must be implanted parallel to the surgical epicondylar axis (SEA). We have developed “a superimposable Computed Tomography (CT) scan-based template”, in which the SEA is drawn on a distal femoral cross section of the CT image at the assumed bone resection level, to determine the precise SEA. Therefore, the objective of this study was to evaluate the accuracy of the rotational alignment of the femoral component positioned with the superimposed template in TKA. Patients and methods. Twenty-six consecutive TKA patients, including 4 females with bilateral TKAs were enrolled. To prepare a template, all knees received CT scans with a 2.5 mm slice thickness preoperatively. Serial three slices of the CT images, in which the medial epicondyle and/or lateral epicondyle were visible, were selected. Then, these images were merged into a single image onto which the SEA was drawn. Thereafter, another serial two CT images, which were taken at approximately 9 mm proximal from the femoral condyles, were also selected, and the earlier drawn SEA was traced onto each of these pictures. These pictures with the SEA were then printed out onto transparent sheets to be used as potential “templates” (Fig. 1-a). In the TKA, the distal femur was resected with the modified measured resection technique. Then, one template, whichever of the two potential templates, was closer to the actual shape, was selected and its SEA was duplicated onto the distal femoral surface (Fig. 1-b). Following that, the distal femur was resected parallel to this SEA. The rotational alignment of the femoral component was evaluated with CT scan postoperatively. For convention, an external rotation of the femoral component from the SEA was given a positive numerical value, and an internal rotation was given a negative numerical value. Results. The subjects were 4 knees in 4 males and 26 knees in 22 females. A mean age (for 30 knees) at the operation was 76.7 ± 6.1 years (range from 66.4 to 88.3). The posterior condylar angle was −0.27 ± 1.43, and the outlier, more than 3 degrees, was 1 case. Discussion. Conventionally, the SEA is palpated intraoperatively, however, the sulcus of the medial condyle sometimes cannot be identified precisely in osteoarthritic degeneration at the medial condyle. Also, the SEA is determined from the posterior condylar axis (PCA) by calculating the posterior condylar angle, which is between the SEA and the PCA, with the measurements from the preoperative CT scan. However, the residual cartilage thickness is not considered in this method, and thus, the SEA is possible to be inaccurate. The simple technology of our template allowed us to determine the SEA directly on the femoral surface, without any influence from bone degeneration. The femoral components could be implanted accurately, and therefore, the superimposed template was considered to improve TKA outcomes with the accurate SEA

Abstract

Summary Statement. It is now possible to diagnose osteoporosis using incidental CT scans; this approach has been used to objectively demonstrate the role of osteoporosis in fracture in ankylosing spondylitis patients. Background. In advanced disease, Ankylosing Spondylitis (AS) is frequently associated with a reduction in bone mineral density (BMD), this contributes to pain and predisposes to fractures. Quantifying this reduction in BMD is complicated by the simultaneous processes occurring, in which there is both an overgrowth of bone (syndesmophytes) and a concurrent loss of trabecular bone. Traditional methods such as dual-energy X-ray absorptiometry (DXA) struggle to generate accurate estimates for BMD in these patients. It has recently become possible to diagnose osteoporosis, with a high sensitivity and specificity, using incidental CT scans of the L1 vertebra. The purpose of this study was to evaluate the use of opportunistic CT screening in the diagnosis of osteoporosis in patients with AS who had sustained vertebral fractures. Patients & Methods. Following Institutional review board approval, patients with AS who presented, with acute fractures of the spine, to our facility between 2004 and 2013 were reviewed to assess whether or not they had a Computed Tomography (CT) scan of the abdomen on admission or in the 6 months before or after injury. In addition, patients were also required to have signs of advanced AS such as the presence of syndesmophytes and syndesmophyte bridging; patients with fractures through L1 were excluded. Of those fitting the criteria, a region of Interest (ROI) was generated over the body of L1, Hounsfield unit (HU) were then measured. Results. Of the 42 patients reviewed, a total of 17 AS patients fit the above criteria. 15 were male and 2 were female, mean age of the whole cohort was 69.9years (range 22–85; SD 15.9). Using a threshold balanced for sensitivity and specificity (<135 HU) which differentiates between osteopenia and osteporosis, 14 (82%) patients were found to have a BMD less than 135HU; a higher threshold (<160 HU) with 90 % sensitivity for differentiating osteoporosis from osteopenia was applied to the group, and 15 patients (88%) were found to be osteoporotic. Of note all the females in the study were osteoporotic. Discussion and Conclusion. This study demonstrates, for the first time, using opportunistic CT screening, that a high proportion of AS patients who sustain fractures have osteoporosis; this overcomes the difficulties that have been encountered with the use of DXA in this unique group of patients. This simple and accessible method saves on excess cost and exposure to radiation. With a high sensitivity, patients identified using this method can then be managed more proactively. We believe these data have the potential to significantly impact the day to day management of patients with spondyloarthropathies

Anterior lumbar inter-body fusion (ALIF) is a surgical procedure that is available to chronic lower back pain patients who fail to respond to conservative treatments. Failure to achieve fusion may result in persistence of pain. Fusion of the lumber vertebral segment is more accurately assessed using fine-cut helical Computed tomography (CT) scans (0.25 mm thickness slices). Unfortunately this technique exposes the body to high radiation dose with hazard of increase risk of late malignancy. An alternative imaging tool is radiostereometry (RSA) which developed as a means to determine the magnitude of relative motion between two rigid bodies. In this study we used RSA to detect movement at the fused lumbar segment (ALIF site) during flexion and extension and compare the results obtained with fine-cut helical CT scan using histopathology as final gold standard assessment tool. ALIF of three levels of lumbar spine (L1-L2, L3-L4, and L5-L6) was done in 9 sheep. The sheep divided into three groups (3sheep each). The first group had RSA assessment immediately, 3, and 6 months after surgery. The second group had RSA immediately, 3, 6, 9 months after surgery. The third group had an RSA immediately, 3, 6, 9, 12 months after surgery All the animals were humanly killed immediately after having the last scheduled RSA (group1, group2, and group 3 sheep were killed 6 month, 9month and 12 months after surgery respectively). This followed by in vitro fine cut CT and histopathology after the animals are scarified. Micro CT scan has been also used to identify the area where histopathology slide should be made to pick up fusion. Fine cut CT scan assessment for all sheep were done. The CT scan has been reported by two independent radiologists. Histopathology has been started and will finish in 2 weeks. RSA showed there was significant increasing stiffness of the spine though the fused segments as the time pass on compare to immediate postoperative assessment. CT scan were done and showed variable fusion though out the spinal segments. Histopathology of all sheep has been started and the results will be available in 2 weeks which will be followed by statistical assessment to decide how accurate RSA compare to CT scan in assessment of fusion

Aim: To determine the quantity and the quality of the bone bridge between the bone tunnels, in both the femoral and tibial side, after double-bundle anterior cruciate ligament (ACL) reconstruction. Material and methods: Twenty-seven patients undergoing primary double-bundle ACL reconstruction with hamstring tendon autograft were included in this prospective study. Computed tomography (CT) was performed in all patients at a mean of 13 months postoperatively. The amount of the bone bridge between the bone tunnels was measured, in both the femoral and tibial side, on an axial plane at three locations:. at the level of the joint line. at the mid-portion of the bone bridge and. at the base of the bone bridge. In addition, the bone density of the bone bridge was measured in Hounsfield units (HU) in the same locations. Bone density of the anterior tibial cortex lateral femoral condyle, and adjacent cancellous area, and were measured for comparisons. Results: CT confirmed that the bone bridge was triangular in shape in all cases in both the femoral and tibial side. On the femoral side, at the level of joint line (apex of the bone bridge) the mean thickness of the bone bridge was 1.7 mm, at the mid-portion the mean thickness of the bone bridge was 3.7 mm and at the base of the bone bridge the mean thickness was 7.1 mm. On the tibal side, at the level of joint line (apex of the bone bridge) the mean thickness of the bone bridge was 1.5 mm, at the mid-portion the mean thickness of the bone bridge was 3.2 mm and at the base of the bone bridge the mean thickness was 6.5 mm. Bone density at the mid-portion and at the base of the bone bridge was similar to the cancellous bone for both the femoral and tibial side. However, the bone density of the bone bridge, at the level of the joint line, for the femoral side was 860 HU and this was not statistically significant in comparison to the density of the lateral femoral cortex (960 HU). Similarly, the bone density of the bone bridge, at the level of the joint line, for the tibial side was 885 HU and this was not statistically significant in comparison to the density of the anterior tibial cortex (970 HU). Conclusions: Our study demonstrated one year after double-bundle ACL reconstruction the thickness of the triangular bone bridge between the bone tunnels is sufficient at the mid-portion and at the base of the triangle but is thin at the level of the joint line. However, the bone bridge at the apex of the triangle is very strong since its density is similar to that of cortical bone. We believe that the “corticalization” of the bone bridge at the level of the joint line on both the femoral and tibial side is important and contributes significantly to avoid communication of the bone tunnels

Introduction. Malrotation following total knee replacement is directly related to poor outcome. The knowledge of proximal and distal rotational axes and angles of the femur is therefore of high importance. The aim of the study was to determine whether the most used proximal and distal femoral angles; femoral anteversion angle (FAA) and posterior condylar angle (PCA) were different within individuals, between right, left and gender. As well, we studied whether the “inferior condylar angle” is correlated to the PCA and therefore useful in determining the rotation of the distal femur. Material and Methods. From 36 cadavers the femora were obtained and after removing the soft tissue a Computed Tomography (CT) scan was made. Three angles were measured: (i) the FAA between femoral columnar line (FHNL) and posterior condylar line (PCL), (ii) the PCA between anatomical transepicondylar line (TEL) and PCL, (iii) the inferior condylar angle (ICA) between the TEL and inferior condylar line (ICL). Statistical analysis of comparative relationships between the different angles was examined by calculating correlation coefficients and a paired t-test. Results. The mean FAA, PCA and ICA for the whole group were respectively 12.0 degrees (range 0.2–31.6, SD 8.3, 95% CI 9.6–14.4), 4.8 degrees (range 0.9–9.6, SD 2.3, 95% CI 4.1–5.4) and 4.5 degrees (range 0.1–9.8, SD 2.1, 95% CI 3.9–5.1). A strong correlation of the FAA was found within the total group and left versus right (r = 0.82; p = 0.00). A weaker relationship was found for the total group of the PCA measurements (r = 0.59; p = 0.00). When FAA compared to the PCA subdivided in only sexes, there is a weak correlation for the female group (r = 0.54; p = 0.00) Despite the small mean difference of the mean ICA and PCA, there was no correlation between these two angles. Conclusion. Considering the weak correlation of the FAA and PCA within the group but also individuals, the importance of development of more individual approaches for determining the optimal rotation of the components in total knee surgery is essential. As a result, one should be aware that the widely used, current guidelines for knee rotation of 3 degrees of external rotation in placing total knee arthroplasties shows variation between individuals. A more individual approach in total knee arthroplasty seems essential for future knee prosthesis implantations

Robotic-assisted technology in total knee arthroplasty (TKA) aims to increase implantation accuracy, with real-time data being used to estimate intraoperative component alignment. Postoperatively, Perth computed tomography (CT) protocol is a valid measurement technique in determining both femoral and tibial component alignments. The aim of this study was to evaluate the accuracy of intraoperative component alignment by robotic-assisted TKA through CT validation. A total of 33 patients underwent TKA using the MAKO robotic-assisted TKA system. Intraoperative measurements of both femoral and tibial component placements, as well as limb alignment as determined by the MAKO software were recorded. Independent postoperative Perth CT protocol was obtained (n.29) and compared with intraoperative values. Mean absolute difference between intraoperative and postoperative measurements for the femoral component were 1.17 degrees (1.10) in the coronal plane, 1.79 degrees (1.12) in the sagittal plane, and 1.90 degrees (1.88) in the transverse plane. Mean absolute difference between intraoperative and postoperative measurements for the tibial component were 1.03 degrees (0.76) in the coronal plane and 1.78 degrees (1.20) in the sagittal plane. Mean absolute difference of limb alignment was 1.29 degrees (1.25), with 93.10% of measurements within 3 degrees of postoperative CT measurements. Overall, intraoperatively measured component alignment as estimated by the MAKO robotic-assisted TKA system is comparable to CT-based measurements.

In total knee arthroplasty, polyethylene wear has been a major cause of revision surgery. However, it is sometimes difficult to determine the time of revision surgery in elderly people due to their concomitant diseases. Therefore, the brace for measuring polyethylene wear under computed tomography was developed.

Surgical navigation requires an accurate, stable transformation between the tracking system and reference images. This study was the design and evaluation of an additively manufactured calibrator with an integrated verification tool, used to register cone-beam computed tomography (CBCT) image volume to electromagnetic (EM) tracking.

An Aurora EM system was used to track both the calibrator and a surgical probe. Intraoperative CBCT images were acquired with a GE Innova 4100 scanner. The calibrator incorporated 7 tantalum beads, a 6DOF EM sensor, and 7 through-holes for calibrator verification. The calibrator was characterised using the beads and averaged EM reading in 10 poses.

Target Registration Error (TRE) estimation used a device with 14 beads and 18 through-holes. For verification, the probe was placed in each path and the axis and tip location measured relative to the calibrator. This verification task took about 45s. Axial error was the angle between the probed paths and designed axes; translation error was the shortest distance between these lines.

The translation TRE was 3.14±0.96 mm and the angular TRE was 1.7±0.7 degrees, which is consistent with published EM evaluations. The validation axes had an inter-line distance of 0.9±0.78 mm and an axial difference of 1.1±0.7 degrees. The verification errors were smaller than TRE because of the different mathematical formulation. Although the verification calculation was not exactly a tracking error, it provided an alternative quantitative assessment of registration accuracy. This integrated intra-operative registration verification minimises modifications to the surgical workflow and these results demonstrated highly accurate orientation tracking in a surgical environment.

Aim

To asses the accuracy of total knee replacements performed using CT based patient specific instrumentation by postoperative CT scan.

Introduction

The number of complex revision total hip arthroplasties (THA) is predicted to rise. The identification of acetabular bone defects prior to revision THA has important implications on technique and complexity of acetabular reconstruction. Paprosky et al. proposed a classification system including 3 main types with up to 3 subtypes focused on the integrity of the superior rim of the acetabulum and medial wall. However, the classification system is complex and its reliability has been questioned. The purpose of this study was to evaluate the effectiveness of different radiologic imaging modalities (plain radiographs, 2-D CT, 3-D CT reconstructions) in classifying acetabular defects in revision hip arthroplasty cases and their value of at different levels of orthopaedic training.

Introduction

Histology remains the gold standard in morphometric and pathological analyses of osteochondral tissues in human and experimental bone and joint disease. However, histological tissue processing is laborious, destructive and only provides a two-dimensional image in a single anatomical plane. Micro computed tomography (μCT) enables non-destructive three-dimensional visualization and morphometry of mineralized tissues and, with the aid of contrast agents, soft tissues. In this study, we evaluated phosphotungstic acid-enhanced (PTA) μCT to visualize joint pathology in spine osteoarthritis.

Osteophytes are bony spurs on normal bone that develop as an adaptive reparative process due to excessive stress at/near a joint. As osteophytes develop from normal bone, they are not always well depicted in common imaging techniques (e.g. CT, MRI). This creates a challenge for preoperative planning and image-guided surgical methods that are commonly incorporated in the clinical routine of orthopaedic surgery.

The study examined the accuracy of osteophyte detection in clinical CT and MRI scans of varying types of joints.

The investigation was performed on fresh-frozen ex-vivo human resected joints identified as having a high potential for presentation of osteophytes. The specimens underwent varying imaging protocols for CT scanning and clinical protocols for MRI. After dissection of the joint, the specimens were subjected to structured 3D light scanning to establish a reference model of the anatomy. Scans from the imaging protocols were segmented and their 3D models were co-registered to the light scanner models. The quality of the osteophyte images were evaluated by determining the Root Mean Square (RMS) error between the segmented osteophyte models and the light scan model.

The mean RMS errors for CT and MRI scanning were 1.169mm and 1.419mm, respectively. Comparing the different CT parameters, significance was achieved with scanning at 120kVp and 1.25mm slice thickness to depict osteophytes; significance was also apparent at a lower voltage (100kVp).

Preliminary results demonstrate that osteophyte detection may be dependent on the degree of calcification of the osteophyte. They also illustrate that while some imaging parameters were more favourable than others, a more accurate osteophyte depiction may result from the combination of both MRI and CT scanning.

Introduction: The successful outcome from metal-on-metal hip resurfacing is partly dependent on the restoration of the natural biomechanics of the hip joint. Valid measurement of the geometry of the reconstructed hip is challenging using plain radiographs. CT is more accurate and precise yet rarely used to assess hip geometry. Our aims were 1) to quantify the agreement between radiographic and CT measurement of horizontal femoral offset (HFO); 2) to determine the relationship between HFO and patient gender and size; and 3) To compare HFO of the reconstructed hip to the contralateral hip.

Method: We used plain radiograph and CT data from 42 patients (23 male and 19 female) from a consecutive series with unilateral metal-on-metal hip resurfacings. We measured HFO of both hips (component and contralateral) using plain radiographs (with PACS) and CT (with Robin 3D software). Pelvic width and radial head sizes were measured on CT. Measurements were made in triplicate by 2 observers.

We graded the contralateral hip for severity of joint space narrowing on plain radiographs.

Results: There was considerable disagreement between CT and plain radiographs for HFO. HFO was statistically different between genders (p=0.0004). HFO correlated with femoral head radius (0.57, p=0.0002), but not patient size (for height (0.29, p=0.13), or pelvic width (0.25, p=0.11). There was a wide range of HFO of the contralateral hips that was comparable to the reconstructed hip.

Conclusion: To our knowledge this is the first study to show the importance of measuring HFO using CT. HFO was found to be correlated to gender and femoral head radius, but not with any other parameters of patient size. The wide range of offset was considerably greater than is available from current total hip replacement designs. Hip resurfacing may overcome this.

Objective

In total hip arthroplasty (THA), the femoral component influences leg length inequality and gait, and is associated with poor muscle strength and other unsatisfactory long-term results. We have therefore used intraoperative radiographs to acquire accurate measurements of femoral component size and position. At the last meeting of this society, we reported that accurate positioning was successfully achieved in 68 cases (87.2%) as a consequence of taking intraoperative radiographs. However, we have little understanding as regards to the accuracy of X-ray measurements. We accordingly undertook an examination of the accuracy of such measurements. The purpose of this study was to evaluate the difference between leg length discrepancy (LLD) measured using X-ray and computed tomography (CT).

The authors are not aware of any research comparing computed tomography (CT) and avascular necrosis (AVN) of the scaphoid bone. The primary aim of our study was to investigate the use of longitudinal CT in predicting AVN of the proximal pole of the scaphoid, and subsequent fracture nonunion following internal fixation.

Thirty-two patients operated on by the senior author for scaphoid fracture were included. Preoperative CT scans were independently assessed for deformity, comminution, fracture position, proximal pole sclerosis, and bridging trabeculae. Intra-operative biopsy of the proximal pole was assessed independently by a blinded musculoskeletal histologist. AVN was determined by histology of a proximal pole biopsy, using the criteria described by Ficat. Post-operative CT scan was utilised to determine fracture union.

Preoperative CT features which significantly correlated with AVN were, increased radiodensity of the proximal pole, the absence of any bridging trabeculae comminution, dorsal cortical angle, proximal fracture and age less than 20. Features predictive of subsequent nonunion were fractures of the proximal, increased radiodensity of the proximal pole, and AVN.

Preoperative CT scan findings are significantly correlated with histologically confirmed AVN and fracture union. Preoperative longitudinal CT scan is of significant prognostic value and should be considered to assist in predicting outcome and assessing treatment options.

[Hong Kong Orthopaedic Association, Travelling Fellow]

Glenoid bone loss predisposes to further dislocation and failure of arthroscopic Bankart repair in patients with recurrent shoulder dislocation. This study investigates quantification of glenoid bone loss in anterior shoulder dislocation using computerized tomography (CT).

CT was performed in 40 patients (average age 31 years, range 16–82 years) with anterior shoulder dislocation. Of this group, 42 shoulders with anterior dislocation and 38 contralateral normal shoulders were examined. In addition, twenty shoulders in ten normal subjects were examined. CT technique comprised 1mm acquisition, pitch 1.0, simultaneously of both shoulders. Reformatted images en face to the glenoid fossa were obtained. Ten different measures of the glenoid fossa were obtained including cross sectional area, maximum height, and width and flattening of the anterior curvature of the glenoid.

In normal subjects, maximum side to side difference in cross-sectional area was 14% and maximum glenoid width 4.1mm. For dislocating shoulders, flattening of the anterior edge of the glenoid fossa and a reduction in maximum glenoid width were the best objective criteria of bone loss. Flattening of the anterior glenoid curvature was a feature of 95% dislocated shoulders though was only seen in 1.5% of normal shoulders. Glenoid cross-sectional area was not a useful measure of glenoid bone deficiency.

Variable glenoid bone loss is a measurable feature of anterior shoulder dislocation. CT can be used to objectively assess this preoperatively. This should help when deciding on whether to perform an arthroscopic Bankart repair or open bone block procedure.

Background

Humeral retroversion is variable among individuals, and there are several measurement methods. This study was conducted to compare the concordance and reliability between the standard method and 5 other measurement methods on Twodimensional (2D) computed tomography (CT) scans.

Introduction and Aims: There is a relationship between the anatomy of the hip joint and the development of arthritis. A common cause of hip pain in the young adult that can lead to arthritis is acetabular dysplasia. More recently, femoroacetabular impingement has been described as another cause of hip pain. The purpose of our study was to evaluate the applicability of pelvic computed tomography (CT) with three-dimensional surface rendering to evaluate femoro-acetabular impingement.

Method Thirty-six hips (30 patients; 17 males; 13 females) with persistent hip pain, mean age 41 (37–52), underwent three-dimensional CT of the pelvis, as well as MRI arthrography with gadolinium enhancement. On 3D CT, the concavity of the femoral head-neck junction (offset), alpha angle as described by Notzli was calculated to depict the anterior femoral neck contour. The concavity of the posterior aspect of the head neck junction was measured as the beta angle. The same measurements were made in 20 hips, consisting of randomly selected patients with no prior history of hip pathology or pain (mean age 37; 13 males; eight females).

Results The mean alpha angle for the symptomatic group was 66.4 (39–94) and 43.8 (39.3–48.3) for the control group (p=0.001). All symptomatic hips had abnormal findings on MRA: labral tears in all; cartilage delamination/ulceration in 14 hips; herniation pits in six hips. The majority of labral tears and delamination were located in the antero-superior quadrant. In the surgical treated group, all MRA findings were confirmed. The mean beta angle was significantly smaller (increase concavity) in the symptomatic versus the controls: 40.2 versus 43.8 (p=0.011). Interestingly in the symptomatic group the beta angle was significantly lower than the alpha angle (p< 0.02), but not in the controls.

Conclusion: 3D CT with surface rendering and multiplanar reformation is useful to determine degree of bone buttressing of the anterior femoral head-neck junction quantitatively assessed by alpha angle measurement, which is elevated in patients with femoro-acetabular impingement. With a greater posterior concavity i.e. small beta angle in the symptomatic group versus the control, subclinical slipped femoral epiphysis remains a plausible cause of this deformity.

Introduction and Aims: Little is known about peri-acetabular bone remodelling after insertion of the acetabular cup in total hip arthroplasty. This study was designed to analyse retroacetabular bone changes using quantitative CT-assisted osteodensitometry. This is a new method for a detailed measurement of bone density (BD) changes around the implants.

Method: Prospective cohort study. Operations were performed on 26 consecutive hips (26 patients) using an uncemented prosthesis with alumina-alumina pairing (Cerafit, Ceraver Osteal, France). The average age of patients was 58.4 years. There were 15 men and 11 women. CT investigations were performed within two weeks of surgery and then one year and three years post-operatively. Cancellous, cortical and total bone density (mgCaHA/ml) were assessed using specific software (Impact-Hip, VAMP, Moehrendorf, Germany).

Results: All 26 hips were available for follow-up at one year, seven patients were available at three years. At three-year follow-up we found an 18.4% decrease of cancellous BD proximal to the upper rim of the cup. Cortical BD increased by + 5.2% in this region. Cortical BD decreased ventral to the cup by −5.0% and by −2.3% dorsal to the cup. Of more interest, cancellous BD was observed to decrease by −40.9% in the ventral region and −32.2% in the dorsal region.

Conclusion: We have observed a progressive decrease of cancellous BD after insertion of an uncemented ace-tabular component. These phenomenon could explain the onset of late migration and implant failure of pressfit cups. Only minor changes have been observed in cortical BD. Further investigations are required to define the role of implant design and material in periprosthetic bone remodelling of the acetabulum.

Introduction

Fixation patterns of cementless stem were known as proximal or distal part. Distal fixation was seen in fully porous coated stem and stress shielding of the proximal femur was indicative. These phenomena did not lower the clinical results, but technical difficulties were more and more in revision surgery because of infection or dislocation. There was lot of reports that alendronate was effective for treatment of osteoporosis by induction of apoptosis in osteoclasts. We can expect alendronate to modify the bone quality around the stem after cementless THA.

Introduction

The treatment of trochanteric femoral fractures with the use of short femoral nails has become an established method. The fixation is required that lag screw be centered to prevent complications. But correct positioning of the device may difficult because of anatomical feature. This study evaluated the femoral morphology three-dimensionally using computed tomography (CT) images.

The orientation of the acetabular component in metal-on-metal hip resurfacing arthroplasty affects wear rate and hence failure. Correct assessment of acetabular orientation is key in assessing the painful hip resurfacing. This study aimed to establish if interpretation of pelvic radiographs with TraumaCad software can provide a reliable alternative to computed tomography (CT) in measuring the acetabular inclination and version.

TraumaCad was used to measure the acetabular orientation on AP pelvis radiographs of 14 painful hip resurfacings. Four orthopaedic surgeons performed each measurement twice. These were compared with measurements taken from CT reformats performed by an experienced musculoskeletal radiologist. The correlation between TraumaCad and CT was calculated, as was the intra- and inter-observer reliability of TraumaCad.

There is strong correlation between the two techniques for the measurement of inclination and version (p<0.001). Intra- and inter-observer reliability of TraumaCad measurements are good (p<0.001). Mean absolute error for measurement of inclination was 2.1°. TraumaCad underestimated version compared to CT in 93% of cases, by 12.6 degrees on average.

When assessing acetabular orientation in hip resurfacing, the orthopaedic surgeon may use TraumaCad in the knowledge that it correlates well with CT and has good intra- and inter-observer reliability but underestimates version by 12° on average. This underestimation may be contributed to by the natural divergence of the X-ray beam, the short arc of the ellipse left exposed by the large diameter head, and the non-hemispherical resurfacing cup.

Introduction: It has been proposed that rotational gait abnormalities in the normal child are usually reflections of the anatomic deformity. A decreased acetabular and femoral anteversion have been recognized as a predisposing factor for osteoarthritis of the hip and the McKibbin instability index was introduced to quantify this relationship. Additionally, an increased femoral anteversion has been associated with osteoarthritis of the knee. However, it is well known that compensatory factors influence the dynamic rotational profile during gait. We compared rotational computed tomography data with gait analysis to evaluate their correlation and to elucidate the influence of compensatory mechanisms.

Materials and Methods: In a prospective study conducted between 2001 and 2005 patients presenting with rotational malalignment were sent for 3D gait analysis. Main exclusion criterion was any kind of neurological affection. Patients in whom surgery was considered were referred to rotational computed tomography. The rotational alignment of the pelvis, hip and knee at different times during the gait cycle as evaluated in the 3D gait analysis was compared to the angular values derived from the rotational computed tomography for the femur and tibia and statistically analyzed and correlated.

Results: There were 12 female and 16 male patients with a mean age of 16 (± 9.7) years at the time of gait analysis. After a first evaluation of data 8 limb segments were excluded to increase the quality of data. The mean anteversion of the femur was 29 degrees (2 degrees of retrotorsion to 56 degrees of anteversion) and the mean tibial torsion was 31 degrees (1 to 66 degrees of external torsion). The calculation of the Pearson correlation showed that an increase of femoral anteversion resulted in an increase of pelvic range of motion. An increase of femoral anteversion resulted in an increase of the internal rotation of the hip. Highly significant correlations were found between the rotational–CT values for the tibia and the all parameters describing rotation of the knee. The determination coefficient was high for tibial torsion versus knee rotation (R2 = 0.64), but showed a low value for femoral anteversion versus hip rotation (R2 = 0.2).

Conclusion: The rotation of the hip as found in the gait analysis showed only weak correlation with rotational CT data. This is not surprising as the hips segment offers many possibilities for compensation. The torsion of the tibia was found to correlate very strongly with the gait analysis. The McKibbin index seems questionable as a prognostic factor for the individual patient in the light of a multitude of dynamic compensatory influences. Effort should be made to integrate the static instability index with dynamic gait analysis data.

Introduction: Concern remains in loosening of glenoid component reversed prostheses. This study is to analyze glenoid location of stem and 4 screws of glenoid component.

Material and method: 34 reversed prostheses included. Mean age 74,10, 33 females/1 male. Preoperative CT study : glenoid version; measure of anterior-posterior osteophytes. Postoperative CT study: central stem location and superior, inferior, anterior, posterior screws location. Study of influence of glenoid version and presence of osteophytes in location of glenoid implant.

Results: 27 retroverted glenoids (mean 6,5°); 7 ante-verted (mean 5,3°). 17 cases with anterior osteophyte and 12 of posterior. In 52% the central stem was centered inside glenoid, 33% anterior end was outside glenoid and 14% the posterior end. When central stem was anteriorly outside 85% presented retroverted glenoid (mean 8,33°). When the central stem was posteriorly outside 66% presented anteverted glenoid (mean 9,5°). Inferior screw was fully in place in 38%, ¾ part inside in 19%, 2/4 part in 23%, ¼ part in 19%. Superior screw was fully in place in 47%, ¾ part inside in 23%, 2/4 part in 19%, ¼ part in 9%. Anterior screw was fully in place in 66%, ¾ part in 23% and 2/4 part in 9%. Posterior screw was fully in place in 38%, ¾ part in 42%, 2/4 part in 14%, ¼ part in 4%. The correct positioning of superior screw correlates with less coverture of inferior screw. Anterior and posterior osteophytes did not correlated with stem nor screw positioning.

Conclusions: Positoning of central stem correlates with glenoid version. Anteriorly extruded stems correlate with higher retroverted glenoids and posteriorly extruded stems correlate with higher anteversion.

Positioning the inferior screw fully inside the lateral border of the scapula correlates with lower bony coverture of superior screw.

The purpose of this study was to evaluate in vivo fit and fill analysis of tapered wedge-type stem in total hip arthroplasty (THA) with computed tomography (CT)-based navigation system. 100 THAs were all performed through the posterolateral approach, with patients in the lateral decubitus position. Each cohort of 50 consecutive primary cementless THAs with was compared with and without CT-based navigation system. The post-operative antero-posterior (AP) hip radiographs were obtained two weeks after the operation. All radiographic fit and fill measurements in the proximal and distal areas were analyzed by two of the authors who were both blinded to the use of CT-based navigation system. The type of the fit in the cementless stem was divided into three types. The fit of the stem was classified as Type I, if there was both proximal and distal engagement (maximum proximal to distal engagement difference of 2 mm or greater), Type II when there was proximal engagement only, and Type III when there was distal engagement only. The fill parameters such as mean stem-to-canal ratios and mean minimum and maximum gaps between the stems to the cortical bone in proximal and distal sections were compared. There was a significantly better overall canal fit obtained by THA with CT-based navigation system compared to without the navigation system (p<0.01). With CT-based navigation system, 42 of 50 stems (84%) were categorized as Type I fit compared to 31 of 50 stems (62%) without the navigation system. As to Type II fit, There are significantly more stems without the navigation system (26%) compared to with it (12%). There were better canal fills of the stems obtained by THA with CT-based navigation system both in proximal (94%) and distal sections (88%) of the femur compared to without the navigation system (proximal 88%/distal 82%) (p<0.05). Excellent radiographic fit and fill has been previously reported to potentially correlate with improved clinical outcomes. The stems obtained by THA with CT-based navigation system had a significantly better canal fit demonstrated by higher proportion of Type I and lower proportion of Type II fits, compared to without the navigation system. The stems with the navigation system had also significantly better proximal and distal canal fill.

Introduction: Loss of the cervical lordosis is a common finding on the emergency department in patients who have been involved in a car accident as well as in those who have suffered head and neck injury. The difficult circumstances, under which the plain films are usually taken, make the use of CT indispensable. Our study presents the CT findings from the cervical spine in patients with loss of the cervical lordosis.

Method-Patients We studied 120 patients from February 2003 to January 2004. Their mean age was 37 years old. Our protocol included the lateral-AP view, while in the absence of findings, except loss of cervical lordosis, from the plain films, the patients underwent spiral CT within 24 h.

Results: Fractures of the cervical spine were found in 7 patients (5,8%). In 5 of them these involved the A1–A2 level. In two patients fractures of the occipital condyles were found. One A7 fracture coexisted with an A2 fracture. No patient had neurological symptoms.

Conclusions: The complete investigation of the cervical spine at the emergency department is often quite difficult. The possible underlying injuries can be potentially life threatening. The percentage of positive findings in our study is quite high to justify the routine use of spiral CT for the detailed investigation of such patients.

Articular cartilage has a limited regeneration capacity, and damage of cartilage often results in the onset of degenerative disease such as osteoarthritis (OA). MRI and CT imaging of cartilage and subchondral bone are becoming increasingly important in early detection and treatment of OA as well as for quantifying quality of tissue-engineered samples. Non-invasive CT scanners have been used to image cartilage tissue with the help of contrast agents. However, since only one energy source is available, imaging information of multiple soft and hard tissues is lost given that the overall x-ray attenuation is measured. Medipix All Resolution System (MARS) CT offers the possibility of applying more than one energy source. It is able to measure the energy of each photon individually and therefore determines the characteristics of attenuation.

In this study, an ionic contrast agent (Hexabrix) was used to image the negatively charged extra-cellular matrix component, glycosaminoglycan (GAG), which is abundantly found in the middle and lower layers of healthy cartilage tissue. GAG distribution in the cartilage tissue could be imaged using an inverse relationship with Hexabrix signal (i.e. high signal represents low GAG content). Eight bovine cartilage-bone explants (3mm × 5mm) were incubated in 4 different Hexabrix concentrations ranging from 20% to 50% in PBS. Sections were imaged using the MARS scanner at high and low energies (13.32 keV and 30.84 keV). Images were pre-processed, reconstructed and colour-coded using different enhancement techniques and virtual experimental software. Histological (Safranin-O) staining and quantitative biochemical analysis of GAG content (DMMB dye assay) was performed to correlate GAG distribution and content with MARS-CT images.

High resolution images of both cartilage and bone regions were obtained, with contrast enhanced CT of cartilage correlating well with histological staining. X-ray attenuation was high in regions poor in GAG content, whereas attenuation was low in GAG rich regions. Furthermore, there was a direct inverse correlation between Hexabrix signal and GAG content as measured in superficial (2.9 μg/mg) and middle/deep regions (10.6 μg/mg) in cartilage explants.

It can be concluded that the MARS technique can be used to image GAG distribution and GAG content, and therefore could be used clinically to assess quality of healthy or osteoarthritic cartilage, as well as non-destructive imaging of GAG content in engineered tissues.

Introduction: Compared with open instrumented anterior spinal fusion for adolescent idiopathic scoliosis (AIS), endoscopic surgery offers clinical benefits that include reduced pulmonary morbidity and improved cosmesis. However, quantitative data on the radiological improvement of vertebral rotation using this method is limited. The aim of this study was to measure pre-operative and postoperative axial vertebral rotational deformity at the curve apex in endoscopic anterior instrumented scoliosis surgery patients using computed tomography (CT), and assess the relevance of these findings to clinically measured chest wall rib hump deformity correction.

Methods: Between November 2002 and August 2005, twenty patients with right-sided thoracic curves underwent endoscopic single-rod anterior instrumented fusion. Pre and post surgical axial vertebral rotation was measured at the curve apex on preoperative and two-year postoperative CT using Aaro and Dahlborn’s method. Rib hump deformity correction was retrieved from a surgical database and correlated to the CT findings. Linear regression was used to investigate the correlation between apical vertebral rotation measured on CT and rib hump measured using a scoliometer.

Results: The mean angle of correction achieved in axial vertebral body derotation at the apical vertebra as measured by CT was 7.9°. This equated to a 43% improvement (range 20–90%). The preoperative and postoperative clinical measurements i.e. rib hump deformity correction, correlated significantly with CT measurements using regression analysis (p=0.03) and the mean improvement in rib hump deformity was 55%.

Conclusion: To our knowledge, this is the first quantitative CT study to confirm that endoscopic anterior instrumented fusion for AIS substantially improves the axial vertebral body rotational deformity at the apex of the curve. The margin of correction of 43% compares favourably historically published figures for all-hook-rod constructs in posterior spinal fusion. In addition, the CT measurements obtained significantly correlated to the clinical outcome of rib hump deformity correction.

Background: Complex fractures of the tibial plateau can be difficult to characterize on plain radiographs and two-dimensional computed tomography scans. We tested the hypothesis that three-dimensional computed tomography reconstructions improve the reliability of tibial plateau fracture characterization and classification.

Methods: Forty-five consecutive intra-articular fractures of the tibial plateau were evaluated by six independent observers for the presence of six fracture characteristics that are not specifically included in currently used classification schemes:

posteromedial shear fracture;

In addition, fractures were classified according to the AO/OTA Comprehensive Classification of Fractures, the Schatzker classification system and the Hohl and Moore system. Two rounds of evaluation were performed and then compared. First, a combination of plain radiographs and two-dimensional computed tomography scans (2D) were evaluated, and then, four weeks later, a combination of radiographs, two-dimensional computed tomography scans, and three-dimensional reconstructions of computed tomography scans (3D) were assessed.

Results: Interobserver agreement improved for all classification systems after the addition of three-dimensional reconstructions (AO/OTA κ2D = 0.536 versus κ3D = 0.545; Schatzker κ2D = 0.545 versus κ3D = 0.596; Hohl and Moore κ2D = 0.668 versus κ3D = 0.746).

Three-dimensional computed tomography reconstructions also improved the average intraobserver reliability for all fracture characteristics, from κ2D = 0.624 (substantial agreement) to κ3D = 0.687 (substantial agreement). The addition of three-dimensional images had limited infiuence on the average interobserver reliability for the recognition of specific fracture characteristics (κ2D = 0.488 versus κ3D = 0.485, both moderate agreement). Three-dimensional computed tomography images improved interobserver reliability for the recognition of coronal plane fractures from fair (κ2D = 0.398) to moderate (κ3D = 0.418) but this difference was not statistically significant.

Conclusions: Three-dimensional computed tomography is helpful for;

individual orthopaedic surgeons for preoperative planning (improves intraobserver reliability for the recognition of fracture characteristics), and for

Background: This study tested the null hypothesis that computed tomography (CT) and magnetic resonance imaging (MRI) have the same diagnostic performance characteristics for triage of suspected scaphoid fractures.

Methods: Thirty-four consecutive patients with a suspected scaphoid fracture (post-injury tenderness of the scaphoid and normal radiographs) underwent CT and MRI within ten days after trauma. CT-reconstructions were made in planes defined by the long axis of the scaphoid. The reference standard for a true fracture of the scaphoid was 6-week follow-up radiographs in four views, based on current literature. A panel including surgeons and radiologists came to a consensus diagnosis for each type of imaging considered in a randomized and blinded fashion, independent of the other types of imaging. We calculated sensitivity, specificity and accuracy as well as positive (PPV) and negative predictive values (NPV) for both imaging modalities.

Results: According to the reference standard there were six true fractures of the scaphoid (prevalence 18%). CT diagnosed fracture of the scaphoid in five patients (15%), with one false positive, two false negative and four true positive results. MRI diagnosed a fracture in seven patients (21%), with three false positive, two false negative and four true positive results. Sensitivity, specificity and accuracy for CT were 67%, 96% and 91%; and for MRI 67%, 89% and 85% respectively. According to the McNemar test for paired binary data for each imaging modality these differences were not significant. The positive predictive values using Bayes’ formula were 76% for CT and 54% for MRI. Negative predictive values were 94% for CT and 93% for MRI.

Conclusions: CT and MRI had comparable diagnostic characteristics. Both were subject to both false positive and false negative interpretations. They were better to rule out a fracture than to rule one in. The best reference standard for a true fracture is debatable

Apert’s syndrome (or acrocephalosyndactyly type 1) is a rare condition characterized by anomalies of the skull (craniosynostosis) in conjunction with complex syndactyly of the hands and feet. There are many studies involving the description and management of hand deformities in Apert’s syndrome. The study of foot anomalies however in children with Apert’s syndrome has been limited to individual case reports and small series. Plain radiographic studies have shown that during childhood, progressive fusion of the bones of the feet occurs. The management of these children’s feet has never been addressed in the literature.

Seven patients with Apert’s syndrome were included in our study. The study group consisted of 2 girls and 5 boys, age range 4–16 years. We performed plain radiography, 3-D computed tomography and paedobarographic studies on all seven children based on our observation that some children with Apert’s had prominent metatarsal heads with symptomatic callosities under the first and second metatarsal heads. Five of the seven children studied demonstrated a specific pattern both on paedobarographic studies and 3D computed tomography of an excessively plantar flexed, fused first and second rays.

A corrective extension osteotomy of the fused first and second rays were then carried out in one patient with an excellent post-operative result. We propose that by early recognition and correction of the pattern of an excessively plantar flexed first and second ray would improve both function and footwear.

Purpose: We report the operative technique and preliminary results for percutaneous osteosynthesis in the supine position with computed tomography guidance for acetabular fractures without joint displacement.

Material and methods: This prospective study conducted in a single unit included a consecutive non-randomised series of 55 patients who underwent surgery for an unstable pelvic injury between June 1996 and December 2000 under computed tomography guidance. In ten cases, the radiographic and computed tomographic analysis demonstrated a coronal fracture of one of the columns without joint displacement accessible for anteroposterior screw fixation. There were eight men and two women, mean age 35 years.

Surgery: the ten patients were operated on in the supine position, in the scanner room under the same aseptic conditions as in the operation room. The reference computed tomography slice was the Corse slice. The femoral vasculo-nervous bundle was identified. A threaded guide wire was inserted perpendicuallary to the fracture line, anteriorly to posteriorly (Cap Corse technique). A perforated screw with a 7.3 mm diameter was used to fix the fracture. Minimal post-surgical surveillance was 48 hours. Weight bearing was not authorised for six weeks to three months. Al patients were followed prospectively, and mean follow-up ws 16 months (12–36).

Results: Traction was lifted immediately after surgery in all cases. All the patients got up the day after surgery. Mean hospital stay was less than five days postoperatively in all cases. There were no complications (vascular, neurologic, infectious) and no secondary displacement. At last follow-up, he Postel Merle d’Aubigné score was 18 for eight patients, 16 for one and 14 for one. Two patients showed radiographic signs of degenerative hip disease.

Discussion: This percutaneous osteosynthesis method using computed tomographic guidance is reliable (100% well positioned screws) and avoids the need for traction in bed. Morbidity is low (no complications). Even though these eight patients did not present clinical and radiographic signs of osteoarthritis, this technique did not avoid the risk of degenerative hip disease in two patients.

Conclusion: An alternative to traction, percutaneous osteo-synthesis with computed tomographic guidance performed in the supine position for acetabular fractures is a cost-effective procedure.

Purpose of the study: Two principle angles describe the orientation of the acetabular reconstruction of hip arthroplsty: lateral inclination and anteversion. Lateal inclination is easily determined on the plain x-ray but the measurement of anteversion generally requires axial computed tomography (CT). The values measured for acetabular anteversion depend on the planes chosen as reference. Similarly the measurement of acetabular inclination using conventional radiographs is often considered imprecise due to the large number of variables involved. Several reference planes are described in the literature. The purpose of this work was to characterise the values obtained using two reference planes, the anterior pelvic plan (APP) used for navigation and the pelvic axis (proposed by other authors).

Materials and Methods: We used the Hip-Plane-Sympios^® software to determine lateral inclination and anteversions using each reference plane. The APP was defined by three points: the anterosuperior border of the pubic symphysis, the anterior border of the two antero-superior iliac spines. The pelvic axis was defined by three points: the centre of the S1 plateau and the centres of the two femoral heads. A control reference plane (the plane of the CT table which corresponds to the conventional radiographic plane) was also used. Seventy-six patients scheduled for total hip arthroplasty for osteoarthritis were included in this protocol.

Results: Values measured for the APP were: mean acetabular inclination 52.5°± 4.1° (40–62°), mean acetabular anteversion 24.1°±5.8° (14–35°). Values measured for the pelvic axis were: mean acetabular inclination 47.6°± 4.5° (37–59°), mean acetabular anteversion 12.9°±7° (2–31°). In the plane of the CT table: mean acetabular inclination was 50.6°±4.2° (38–57°) and mean acetabular anteversion 20.2°±702° (1–40°). All of these values were significantly different from the others (p< 0.001). Use of the APP yields values higher than conventional values and those obtained using the pelvic axis, yet the distributions remained identical.

Discussion: The APP is used for total hip arthroplasty navigation systems. It is important to recognised that the angles measured in reference to this plane are greater than the classical radiographic values measured for acetabular inclination. The pelvic plane produces angles closer to the generally accepted anatomic values. Angles measured relative to the radiographic table are intermediary.

Aims

The primary aim of this study was to address the hypothesis that fracture morphology might be more important than posterior malleolar fragment size in rotational type posterior malleolar ankle fractures (PMAFs). The secondary aim was to identify clinically important predictors of outcome for each respective PMAF-type, to challenge the current dogma that surgical decision-making should be based on fragment size.

Introduction: Open instrumented anterior spinal fusion for adolescent idiopathic scoliosis (AIS) is a proven technique for vertebral derotation that, compared with posterior spinal fusion procedures, invariably requires fewer distal fusion levels to be performed. With the advent and evolution of endoscopic anterior instrumentation, further clinical benefits are possible such as reduced pulmonary morbidity, improved cosmesis and less postoperative pain. However, quantitative data on the radiological improvement of vertebral rotation using this method is limited. The aim of this study was to measure preoperative and postoperative axial vertebral rotational deformity at the apex of the curve in endoscopic anterior instrumented scoliosis surgery patients using computed tomography (CT), and assess the relevance of these findings to clinically measured chest wall rib hump deformity correction.

Methods: Between November 2002 and August 2005, adolescent idiopathic scoliosis patients with right-sided thoracic major curves were selected for endoscopic single-rod anterior fusion by the senior authors. Low-dose pre-operative CT was performed as described previously (1) and two-year postoperative CT was also performed on consenting patients in accordance with local ethical committee approval. The pre and post surgical axial vertebral rotation was measured at the curve apex using Aaro and Dahlborn’s method (2). Intraobserver and interobserver variability was assessed. Additional clinical information such as rib hump deformity correction and change in the Cobb angle was retrieved from a surgical database and correlated to the CT findings. Least squares linear regression was used to investigate the correlation between apical vertebral rotation measured on CT and rib hump measured using a scoliometer.

Results: Twenty patients were included in the study. The mean angle of correction achieved in axial vertebral body derotation at the apical vertebra measured by CT was 7.9° (median preoperative angle 17.3° [range 12.5° to 27.3°] and median postoperative angle 10.3° [range 1.8° to 18.1°]. This equated to a 43% improvement (range 20–90%). The preoperative and postoperative clinical measurements i.e. rib hump deformity correction, correlated significantly with CT measurements using regression analysis (p=0.03) and the mean improvement in rib hump deformity was 55% (median preoperative 15.0° [range 10° to 30°] and median postoperative 7.0° [range 4° to 10°]). 95% confidence intervals for intraobserver and interobserver validity were within the ranges ±4.5° to ±6.4°.

Discussion: We believe this is the first quantitative CT study to confirm that endoscopic anterior instrumented fusion for AIS substantially improves the axial vertebral body rotational deformity at the apex of the curve. The margin of correction of 43% compares more favourably than the historically published figure of 24% in a cohort of patients with all-hook-rod constructs used for posterior spinal fusion (3). Patient age and gender demographics, curve magnitude and curve types in the historical study were similar to our group, and an identical CT protocol for measuring vertebral derotation was utilised. In addition, the CT measurements obtained significantly correlated to the clinical outcome of rib hump deformity correction.

Periprosthetic osteolysis is a serious medium to long-term complication of total hip arthroplasty. Interobserver reliability of detecting osteolysis around cementless ace-tabular components is reported to be poor using plain radiographs. Quantitative computed tomography (CT) provides sensitive and accurate measures of osteolytic lesion volume, however, there may remain a role for plain radiographs in monitoring progression of osteolysis. The aim of this study was to use quantitative CT to monitor the progression of osteolytic lesions around cementless acetabular components and to compare plain radiographs and CT in determining the progression of osteolysis.

A high-resolution multi-slice quantitative CT scanner with metal artefact suppression was used to determine the volume of osteolysis around 18 cementless acetabular components. The mean time since arthroplasty was 14 years (range 10–15 years) at the initial CT. Repeat scans of the hip were undertaken over a five-year period to determine progression of osteolysis with time. A second blinded observer examined anteroposterior and lateral plain radiographs taken at the same time as the CT scans and measured the location and area of osteolytic lesions.

CT measurements determined that in ten of 18 hips (56%), osteolytic lesions progressed by more than 1cm3/yr. Progression in size of osteolytic lesions was significantly associated with hips with larger osteolytic lesions at the initial CT (p=0.0005). The mean volume of osteolysis progression was 4.9cm3/year (range 2.8–7.5cm3/yr) for cases with osteolysis volumes greater than 10cm3 at the initial CT, and 0.7cm3/yr (range 0–2.3cm3/yr) for cases with osteolysis volumes smaller than or equal to 10cm3 at the initial CT (p=0.002). Importantly, the rate of osteolysis progression between CT scans varied greatly in some hips. In contrast, using plain radiograph assessment, progression in the area of osteolytic lesions was only detected in 10% of hips.

In conclusion, quantitative CT provides new insights into the natural history of periacetabular osteolysis. Total osteolysis volume greater than 10cm3 is associated with a high risk of progression and progress, on average, at a greater rate than those less than 10cm3. Plain radiographs, including a lateral view, are an unreliable clinical diagnostic tool to predict substantial progression of periacetabular osteolytic lesions.

Introduction: Symptomatic osteochondral lesions of the talus have been managed with a variety of operative techniques involving open or arthroscopic approaches to the ankle joint. The purpose of this study is to report our technique of drilling stable osteochondral lesions of the talus via a percutaneous retrograde approach using computed tomography for guidance.

Materials and Methods: Seven adult patients with Berndt and Harty Stage 2 or 2A/5 (subchondral cyst positive) talar osteochondral lesions, confirmed by magnetic resonance imaging, had retrograde drilling with CT guidance performed under local anaesthesia. Follow-up MR imaging was performed to investigate radiological evidence of healing.

Results: All retrograde drillings performed were technically successful.

Discussion: The concept of retrograde drilling is to preserve intact articular cartilage while encouraging revascularisation of the osteochondral fragment. The use of CT allowed drilling without conventional direct visualisation of the articular surface via arthrotomy or arthroscopy. The procedure can therefore potentially be performed in an outpatient setting. Suggestions are made from review of the literature as to improve further the technique for future studies.

We usually plan surgery for total hip arthroplasty (THA)using pre-operative X-ray templates. However, the technique provides only two dimensional (2D) images and therefore has limitations for planning three-dimensional (3D) objects. Recently it has become possible to describe 3D images using computer programs that use free down loaded computer software (Hip-op) that enable comparison between 3D templates obtained by computed tomography (CT) and 2D conventional X-ray templates.

Six hip joints in 6 patients (1 male, 5 females; age range at the time of operation, 49–77 years) were evaluated. Five of the patients suffered from secondary osteoarthritis of the hip (secondary OA), while the remaining patient suffered from osteonecrosis of the femoral head (ONFH). All the patients underwent THA using a cement less femoral stem (ANCA-FIT Wright Medical Technology, Arlington, Tennessee, USA). Pre-operative planning was performed using Hip-op software (Rizzoli Institute, Bologna, Italy). After the THA surgery, we carried out a repeat CT scan that was used to analyze stem fitting in the femur.

In all the patients it proved easy to obtain the pre-operative template. In 4 patients, the correct stem size was selected pre-operatively, while in the other 2 patients, the planned stem size was one size smaller than that actually implanted. In the 4 patients in whom the correct stem was selected, 2 had their template correctly assessed by conventional 2D images, 1 patient’s template was one size smaller than the implant, while the remaining patient’s template was two sizes smaller than the implant. In the 2 patients who received implants one size smaller than the CT template, 1 patient had the stem inserted in the virus position while in the other patient a fracture occurred during implantation

Preoperative planning for THA using a CT-based computer templating system proved to be a useful technique for the orthopedic surgeons.