Nonunion From Head to Toe

Transcription

1 Nonunion From Head to Toe Poster No.: C-1645 Congress: ECR 2013 Type: Educational Exhibit Authors: B. Geerts, K. L. Verstraete ; Brugge/BE, Ghent/BE Keywords: Bones, Musculoskeletal bone, Musculoskeletal joint, Digital radiography, CT, MR, Education, Trauma DOI: /ecr2013/C Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. Page 1 of 57

2 Learning objectives To define nonunion. To define the causes of nonunion. To illustrate the range of different nonunion types, 'from head to toe'. To describe the most efficient evaluation methods. Page 2 of 57

3 Background Definition: Nonunion is defined as a fracture which fails to heal without further intervention, in a period of 6 to 9 months after injury [1]. Whereas bones have an extensive capacity to heal, the majority of fractures will heal without complication in case of appropriate treatment. However, sometimes difficulties arise in the healing process of fractured bones. It has been estimated that nearly 5% of all fractures become nonunions [2]. While a fracture that does not heal approximately 6 to 9 months post injury is called a 'nonunion', a fracture that is slow in its healing process is called a 'delayed union'. Delayed union is witnessed when an adequate period of time has elapsed since the initial injury and a considerable slow healing is observed. Delayed union does not automatically result in a nonunion. Nonunion should be regarded as one possible outcome of a delayed union [1,3]. Nonunion eventually can result in the development of pseudarthrosis. A false synoviumlined cavity separates the ends of a bone at the fracture site. Typically synovial fluid is related to persistent motion at the nonunion site [1]. It's sometimes difficult to differentiate with hypertrophic nonunion. When CT-scan is not conclusive, a technetium bone scan will show increased uptake at the fracture site with a cold center as seen in pseudarthrosis [3,4]. In general, fracture union is a continuous evolution in which the broken bone is rebuilt by a process of bone regeneration, Fig. 6 on page 6. Fracture healing encompasses three phases: [1] (1) Inflammatory respons (10% of healing time) (2) Reparative phase (40% of healing time) (3) Remodeling phase (50-70% of healing time) Yet, in case of nonunion, a malfunction occurs in the fracture healing process. The Weber and Cech's classification is still the most appreciated classification system. They classified nonunions in two main groups, based on the vitality of the fracture Page 3 of 57

4 site, whether they have a good blood supply [3,4]. We distinguish the hypertrophic, oligotrophic and atrophic nonunion. The hypertrophic and oligotrophic nonunions are vascular nonunion types, Fig. 7 on page 6. Atrophic nonunions have a poor or even absent blood supply. Fracture sites with a good blood supply will often show callus formation. Callus formation normally occurs with external bridging callus at the periosteal surface, intramedullary callus and primary callus at the ends of the fracture fragments [1]. It's difficult to differentiate the oligotrophic nonunion from the atrophic nonunion [3,4]. We were not able to demonstrate the degree of blood supply by radioisotope studies, Fig. 8 on page 7. Therefore, in this educational exhibit, we use the term 'hypotrophic' for both oligotrophic and atrophic nonunion types. Hypertrophic nonunions are characterized by the formation of callus and rich blood supply in the ends of the fragments. They result from insufficient mechanical stability due to insecure fixation, insufficient immobilization or premature weight bearing [6]. Hypertrophic nonunion can be observed in the pattern of an elephant foot (a) or horse hoof (b). The radiographic image of a hypotrophic nonunion shows a persistent fracture line, without clearly demonstrable callus formation (c). Causes of Nonunion: Nonunion has many causes: Fractures (open, comminuted, segmental, pathological) Insufficient immobilization osseous fragments Infection Inadequate blood supply Poor nutritional status Metabolic bone disease, such as osteoporosis Radiation (irradiated bone unites at slower rate) [1,3,5] Relevance of this Research: Nonunion is a challenging problem, often difficult to manage. Although nonunion frequently occurs in femur, tibia and humerus, other locations may not be overlooked. In Page 4 of 57

5 the patient's interest, it is important to be very well aware of the existence of nonunion and its related consequences. Imaging plays a key role in diagnosis, as well as followup. Radiologists need to consult previous images and compare these images with initial documentation. Detecting delayed union in an early stage can play a significant role in the patients rehabilitation or treatment possibilities. Page 5 of 57

6 Images for this section: Fig. 6: Shows the different phases in the normal fracture healing process Pearson Education. Inc. Publishing as Benjamin Cummings. Fig. 7: Schematic representation of hypervascular nonunions with vascular supply and morphologic appearance: a 'Elephant foot' nonunion, b 'Horse hoof' nonunion, c 'Oligotrophic' nonunion. Page 6 of 57

7 Weber BC, Cech O. Pseudarthrosis, Pathology,Biomechanics, Therapy, Results. Bern: Hans Huber Medical Publisher; Fig. 8: (a)nonunion of the forearm, the biological activity at the nonunion site is difficult to asses. (b) Tc 99 Scintigraphy is very useful to show biological activity. Mora R. Nonunion of the long bones: Diagnosis and Treatment with CompressionDistraction Techniques. Italy: Springer; Page 7 of 57

8 Imaging findings OR Procedure details Method We performed a retrospective data analysis ( ) in the imaging files of the Ghent University Hospital, Belgium. We applied a specific designed search tool and compiled our sample through the inclusion of patients by using the following key words: 'nonunion', 'non-union', 'pseudarthrosis' and 'pseudartrosis'. Our search task matched with 745 results. Patients were excluded when there were no images available or a wrong diagnosis was given. In addition, we omitted multiple matches of 1 patient. Our final sample consisted of 182 patients. We found 188 different nonunions. The studied patients had an average age of 45.2 year. 68% of the patients with nonunion were male (n=122), 32% were female (n=60). We developed a working file in which the following parameters were determined: age, gender, specific location of the fracture, elapsed time after injury, imaging modality and conspicuity on the imaging study. We performed a descriptive analysis and evidenced our descriptive findings with relevant images. Imaging findings Fig. 9 on page 16 Figure 1. shows the incidence of different nonunion locations found in our database of 188 patients. The tibia, scaphoid bone, humerus and femur are the most common nonunion locations. TIBIA Fig. 10 on page 16, Fig. 11 on page 17, Fig. 12 on page 18. The tibia is a common location for the development of nonunion. We found nonunion in 36 patients (19%) with a mean age of 44.6 year. The male-female ratio was 72% versus 28%. We distinguish the hypertrophic nonunion type with its typical horse hoof or elephant foot pattern from the hypotrophic type. The majority of the patients had a hypertrophic nonunion. Conventional radiography was performed in each patient. In 8 cases additional CTimaging was performed and one MR-scan. Page 8 of 57

9 Table 1. Prevalence of Nonunion in Tibia (N=188) Hypertrophic Hypotrophic Total Prevalence in Tibia 30 (83%) 6 (17%) 36 (19%) Table 2. Tibia Location Number of Patients (%) Proximal diaphysis 9 (25%) Mid-diaphyseal 6 (17%) Distal diaphysis 20 (55%) Mid-diaphyseal + distal diaphysis 1 (3%) HUMERUS Fig. 13 on page 19, Fig. 14 on page 20, Fig. 15 on page 21. The humerus is another common nonunion location. We observed nonunion in 25 patients (13.4%) with a mean age of 57 year. The male-female ratio was 60% versus 40%. Most nonunions occurred in the proximal diaphysis. The majority of the patients had a hypotrophic type of humerus nonunion. 40% of the patients underwent additional CT imaging. Table 3. Prevalence of Nonunion in Humerus Hypertrophic Hypotrophic Total Prevalence Humerus 10 (40%) 15 (60%) 25 (13.4%) in Table 4. Humerus Location Number of Patients (%) Proximal diaphysis 16 (64%) Mid-diaphyseal 7 (28%) Distal diaphysis 2 (8%) FEMUR Fig. 16 on page 22, Fig. 17 on page 23, Fig. 18 on page 24. Page 9 of 57

10 The femur is a vulnerable bone structure for developing nonunion. We found 22 patients (11.7%) with an isolated nonunion of the femur. The mean age of 38.2 year is considerably younger in comparison to the group of humeral nonunion. The majority of the patients had a hypertrophic nonunion, which can have a horse hoof pattern or a more explicit elephant foot configuration. The male-female ratio was 55% versus 45%. Radiography was inconclusive in 7 patients (32%) in whom additional CT-scan imaging was performed. Table 5. Prevalence of Nonunion in Femur. Hypertrophic Hypotrophic Total Femur Prevalence 16 (73%) 6 (27%) 22 (11.7%) in Table 6. Femur Location Number of Patients (%) Proximal diaphysis 8 (36%) Mid-diaphyseal 6 (27%) Distal diaphysis 7 (32%) Proximal + Distal diaphysis 1 (5%) FIBULA Fig. 19 on page 25, Fig. 20 on page 26, Fig. 21 on page 27. The fibula was a less common nonunion location. Only six patients (3.2%) had a fibula nonunion. The mean age of this group was 52.5 year. The male - female ratio was 83% versus 17%. Remarkably, the majority of these patients showed no callus formation at all. Table 7. Prevalence of Nonunion in Fibula Hypertrophic Hypotrophic Total Fibula 2 (33%) 4 (67%) 6 (3.2%) Prevalence in Table 8. Fibula Location Page 10 of 57

11 Number of Patients (%) Proximal diaphysis 1 (17%) Mid-diaphyseal 1 (17%) Distal diaphysis 4 (67%) CLAVICULA Fig. 22 on page 28, Fig. 23 on page 29, Fig. 24 on page 30. We found 7 patients (3.7%) in our database with an isolated nonunion of the clavicula. The mean age was 36.1 year. Nonunion of the clavicula concerns a younger population compared to the tibia, femur and fibula nonunion group. The male-female ratio was 57% versus 43%. Most patients had a hypertrophic nonunion. The midclavicular portion was most vulnerable to nonunion. Noteworthy: only one clavicula nonunion was clearly visible on radiography. CT and/or MRI was performed in 6 patients. Table 9. Prevalence of Nonunion in Clavicula Hypertrophic Hypotrophic Total Prevalence Clavicula 5 (71%) 2 (29%) 7 (3.7%) in Table 10. Clavicula Location Number of Patients (%) Pars sternalis 2 (29%) Midclavicular 4 (57%) Pars acromialis 1 (14%) FOREARM: ULNA Fig. 25 on page 31, Fig. 26 on page 32. We found four patients (2.1%) in our database with an isolated nonunion of the ulna. Two male and two female patients. There were two hypertrophic nonunions and two hypotrophic types. The mean age was 54 year. In two patients an additional CT-scan was performed to assess the fracture site more clearly. Table 11. Prevalence of Nonunion in Forearm: Ulna Page 11 of 57

12 Hypertrophic Hypotrophic Total Prevalence in Ulna 2 (50%) 2 (50%) 4 (2.1%) Table 12. Forearm: Ulna Location Number of Patients (%) Pars olecrani 1 (25%) Mid-diaphyseal 2 (50%) Distal ulna 1 (25%) FOREARM: RADIUS Fig. 27 on page 33, Fig. 28 on page 34, Fig. 29 on page 35. Our database contained three patients (1.6%) with an isolated nonunionf of the radius. Two hypertrophic nonunion and only one hypotrophic type. The mean age was 47 year and all the patients were male. Radiography was performed in case of all three patients. Despite the moderate to good visualization on radiography, two patients underwent a supplementary CT-scan. Table 13. Prevalence of Nonunion in Forearm: Radius Hypertrophic Hypotrophic Total Prevalence Radius 1 (33%) 2 (67%) 3 (1.6%) in Table 14. Forearm: Radius Location Number of Patients (%) Distal diaphysis 2 (67%) Mid-diaphyseal 1 (33%) SCAPHOID BONE: Fig. 31 on page 37, Fig. 32 on page 37, Fig. 33 on page 38. Page 12 of 57

13 We found 32 patients (17%) in our database with a nonunion of the scaphoid bone. The mean age of 32.2 year refers to a much younger population compared to other nonunion sites. Surprisingly, 94% of the patients were male and only 6% female. All scaphoid nonunions were hypotrophic types which might be due to the impaired blood flow. Radiographic evaluation of the scaphoid bone is useful to determine if a fracture is present (sens 65%-70%). Remarkably 27 patients (84%) underwent an additional CT-scan. Table 15. Prevalence of Nonunion in Scaphoid Bone Hypertrophic Hypotrophic Total Prevalence Scaphoid Bone 0 (0%) 32 (100%) 32 (17%) in Table 16. Scaphoid bone location Number of Patients (%) Proximal diaphysis 3 (9%) Mid-diaphyseal 27 (85%) Distal diaphysis 2 (6%) DENS AXIS (C2): Fig. 34 on page 39, Fig. 35 on page 40, Fig. 36 on page 41. Isolated dens axis nonunion occurred in 5 patients (2.7%). The mean age was 62 year. Remarkably, all patients were male. There was a lack of callus formation at the fracture site of every single patient, leading to a hypotrophic nonunion. Eventually, a loose bone fragment is persisting, often called 'os odontoideum'. There was a moderate to bad visibility on conventional radiography. In all 5 cases supplementary CT and/or MRI was performed. In our series the dens axis was the most frequent fracture site of the cervical vertebrae. Table 17. Prevalence of Nonunion in Dens Axis Page 13 of 57

14 Hypertrophic Hypotrophic Total Prevalence in Dens axis 0 (0%) 5 (100%) 5 (2.7%) RARE NONUNION LOCATIONS - METACARPAL BONES Fig. 37 on page 41, Fig. 38 on page 42. We found one patient with a mid-diaphyseal nonunion of a metacarpal bone. RARE NONUNION LOCATIONS - STERNUM Fig. 39 on page 43, Fig. 40 on page 44. Four patients (2.1%) in our database had a sternal nonunion. The mean age was 61 year. There is an obvious relationship with CABG surgery. All nonunions were hypotrophic types in which the fracture line persists. There was a poor conspicuity on conventional radiography. Consequently, a CT-scan was performed in all four cases. RARE NONUNION LOCATIONS - COSTAE - RIBS Fig. 41 on page 45, Fig. 42 on page 46. There was one patient in our database with nonunion formation of a rib. RARE NONUNION LOCATIONS - PUBIC BONE Fig. 43 on page 47. Three patients (1.6%) in our database had a pubic bone nonunion all of which were hypertrophic nonunion types. The mean age was 40 year, two women and one male patient. RARE NONUNION LOCATIONS - SCAPULA Fig. 44 on page 48. We observed one female patient of 69 year old with a rare scapular nonunion. RARE NONUNION LOCATIONS - FOOT: METATARSAL BONES Fig. 45 on page 49. Three patients in our sample developed a metatarsal nonunion. Two women and one male. In all three cases a hypotrophic nonunion is present. Two patients had typical Page 14 of 57

15 th nonunion of the 5 metatarsal, following a common 'Jones- fracture'. The mean age was 71.3 year old, an obvious older population. In all three cases good visualization was achieved by conventional radiography. No additional imaging was needed. RARE NONUNION LOCATIONS - FOOT: HALLUX Fig. 46 on page 50. Two male patients had a nonunion of the hallux. Both were hypotrophic nonunions. Initial radiography was not conclusive, additional CT-imaging was needed. RARE NONUNION LOCATIONS - FOOT: CALCANEUS Fig. 47 on page 51, Fig. 48 on page 52. Four patients in our database had a nonunion of the calcaneus. The male- female ratio was 50%. The mean age was 57 year. There were 3 hypotrophic nonunions and 1 hypertrophic type. Radiography was the initial imaging technique used in all four patients. In two cases an additional CT-scan was performed. RARE NONUNION LOCATIONS - SACRUM Fig. 49 on page 53. One patient in our database had a nonunion of the sacrum. Page 15 of 57

16 Images for this section: Fig. 9: Nonunion Locations - Incidence Rate (N=188). Page 16 of 57

17 Fig. 10: Lateral radiograph of a 16 year old male patient with hypertrophic tibia nonunion. Page 17 of 57

18 Fig. 11: Anteroposterior radiograph of a 74 year old female patient with hypotrophic tibia nonunion. Page 18 of 57

19 Fig. 12: CT- scan in sagittal plane shows no endosteal or periosteal bone formation, a clear example of hypertrophic nonunion. (a) Pre-operative (b) Endomedullary nail. Same patient as in Figure 11. Page 19 of 57

20 Fig. 13: AP radiographs of a 43 year old male patient with a mid-diaphyseal humerus nonunion. Remark the complete hypertrophic helaing of the mid-diaphyseal humerus fracture. Page 20 of 57

21 Fig. 14: Radiograph in AP view of a 43 year old male patient with a mid-diaphyseal nonunion of the humerus. Note the sclerotic borders and hypertrophic callus formation at the fracture site. Page 21 of 57

22 Fig. 15: (a) Radiograph in AP view of a 53 year old female patient, suggesting hypotrophic nonunion. (b) CT-scan in axial plane confirmed the hypotrophic aspect of the fracture site. Page 22 of 57

23 Fig. 16: AP radiographs of a 66 year old female patient with a mid-diaphyseal femur nonunion. Page 23 of 57

24 Fig. 17: AP radiographs of a 40 year old male patient with a mid-diaphyseal femur fracture and complete healing after three year. Page 24 of 57

25 Fig. 18: Lateral radiographs of the 40 year old male patient with a mid-diaphyseal femur fracture and subsequent hypertrophic callus formation. Obvious endosteal and periosteal bone formation. Page 25 of 57

26 Fig. 19: AP radiographs of a 60 year old male patient with combined tibia and fibula fracture. Note the complete lack of callus formation around the fracture site, hypotrophic nonunion (a), two years later (b). Page 26 of 57

27 Fig. 20: CT - scan in coronal plane of a 23 year old male patient with hypotrophic nonunion of the proximal part of the fibula. Note the obvious sclerotic fracture margins. Page 27 of 57

28 Fig. 21: AP radiographs of a 53 year old female patient with hypertrophic tibia and fibula nonunion. Radiograph (a) shows incomplete healing that resulted in a hypertrophic nonunion, type elephant hoof. (b) Shows an increased endosteal and periosteal bone formation at both fracture sites with eventually complete consolidation. Page 28 of 57

29 Fig. 22: AP radiograph of a 29 year old female patient with clavicula nonunion after resection of a hemangio-endothelioma in the pars sternalis. Remark the poor visibility on radiography. Page 29 of 57

30 Fig. 23: CT-scan of the 29 year old female patient with nonunino of the clavicula after resection of a hemangio-endothelioma in the pars sternalis. Due to the poor visibility on plain radiography, a CT scan was performed. Page 30 of 57

31 Fig. 24: MRI T2 FS in axial plane of the 29 year old female patient with nonunion of the clavicula after resection of a hemangio-endothelioma in the pars sternalis. Notice the hyperintense fluid in the neo joint at the fracture site. Page 31 of 57

32 Fig. 25: Anteroposterior radiograph of a 66 year old male patient mentioning the plate and screw osteosynthesis and a conspicuous hypertrophic nonunion of the ulna. Page 32 of 57

33 Fig. 26: Radiograph in lateral view of the 66 year old male patient discussed in figure 18. Note the distinct translucency at the fracture site. Incomplete healing process. Page 33 of 57

34 Fig. 27: AP radiograph of a 66 year old male with nonunion of the distal radius. Poor visibility due to superposition of osteosynthetic material. Page 34 of 57

35 Fig. 28: Lateral radiograph of the 66 year old male with distal radius nonunion, suggesting a hypotrophic nonunion. Due to artifacts, a CT-scan is performed (see Figure 23). Page 35 of 57

36 Fig. 29: CT-scan in coronal and sagittal plane of the 66 year old male with nonunion of the distal radius, confirming the hypotrophic aspect of the nonunion. Page 36 of 57

37 Fig. 30: Exceptional case, a 56 year old female patient develops a hypotrophic nonunion of the ulna and a mid-diaphyseal hypertrophic nonunion of the radius. Fig. 31: Plain radiograph (a,b) and CT-scan (c) in coronal plane of a 27 year old male patient with a mid-diaphyseal nonunion of the scaphoid bone. Note the sclerotic margins and absence of callus formation at the fracture site. Page 37 of 57

38 Fig. 32: Radiograph in ¾ view of the 27 year old male patient with a mid-diaphyseal hypotrophic nonunion of the scaphoid. Page 38 of 57

39 Fig. 33: AP radiograph (a, b) of a 37 year old male patient treated with bone grafts from the distal radius and osteosynthesis. One year post-operative (c, d) there is a persistant mid-diaphyseal nonunion of the scaphoid bone. Page 39 of 57

40 Fig. 34: Lateral radiograph (a) of a 62 year old male patient shows a detachment of the dens axis. AP open mouth view (b) demonstrates the nonunion of the dens axis type 2 leading to an os odontoideum. Page 40 of 57

41 Fig. 35: CT- scan in sagittal (a) and coronal (b) plane of the a 62 year old male patient confirms the diagnosis and more clearly shows the sclerotic margins of the fracture site. There is a lack of callus formation. Fig. 36: An example of dens axis nonunion. (a) CT scan in sagittal plane, (b) MR T1 sequence, and (c) MRI T2 sequence. Note the hyperintense fluid signal at the fracture site on the T2 sequence, indicative for pseudo joint formation. Page 41 of 57

42 Fig. 37: Plain radiograph (a) of a 16 year old female patient with nonunion of the third metacarpal. (b) Magnified radiograph in AP view (b). Oblique view (c). Page 42 of 57

43 Fig. 38: Plain radiograph (a, b) and oblique view (c) of the 16 year old female patient with nonunion of the third metacarpal, six months after osteosynthesis. Page 43 of 57

44 Fig. 39: CT-scan in coronal plane of a 42 year old male patient with nonunion of the sternal manubrium. Page 44 of 57

45 Fig. 40: CT Topogram in a 62 year old female with hypotrophic nonunion of the sternum (a), CT-scan in axial plane (b), magnified CT-scan image in axial plane (c). Note the plate and screw osteosynthesis after sternotomy for cardiac surgery. Page 45 of 57

46 Fig. 41: CT- scan in coronal plane of a 53 year old male patient with a subtle nonunion of rib 7 on the left side. Page 46 of 57

47 Fig. 42: CT-scan in coronal plane, slice 81 (a) - 83 (b) - 8(c) of a 53 year old male patient with a subtle nonunion of rib 7 on the left side. Note the irregular shape of rib 7 (b). Page 47 of 57

48 Fig. 43: Plain radiograph of a 48 year old female patient with hypertrophic nonunion of the right sided ischiopubic bone. There is a total hip prosthesis with acetabular cup fixation. Page 48 of 57

49 Fig. 44: CT-scan in axial plane of the right scapula of a 69 year old female patient. Remark the irregular nonunion formation with absence of bony bridging. Page 49 of 57

50 Fig. 45: AP radiograph of a 76 year old female with nonunion of the second metatarsal head. Page 50 of 57

51 Fig. 46: CT-scan in sagittal plane shows hypotrophic nonunion of the distal phalanx of the hallux in a 30 year old male patient. Page 51 of 57

52 Fig. 47: Lateral radiograph of a 51 year old female patient showing status after calcaneal osteotomy (a). 1 year later, there is an obvious nonunion formation of the calcaneus (b). Page 52 of 57

53 Fig. 48: CT-scan in the same patient as above in sagittal plane show obvious sclerotic margins and nonunion of the calcaneus after an osteotomy was performed one year earlier (3 osteosynthesis screws). Page 53 of 57

54 Fig. 49: CT-scan in coronal (a, b) and sagittal plane (c) of a 53 year old male patient with an obvious example of sacral bone nonunion. Page 54 of 57

55 Conclusion 1. Nonunion appears in all different types of bones. The most affected sites are the humerus, femur, tibia and scaphoid bone. However, nonunion can also occur elsewhere in the skeleton, and be less conspicuous. The Weber and Cech's classification is currently the most suitable system. Nonunion is classified according to radiographic appearance. In our study however we distinguished two main types of nonunion: hypertrophic nonunion, in which a horse hoof or elephant foot formation can be seen, and hypotrophic nonunion which shows a persistent fracture line without demonstrable callus formation. Nonunion occurs in all different age categories. Some remarkable differences are observed when considering the average age of nonunion occurrence in particular locations. For example, scaphoid and clavicula nonunion appear in an obvious younger population compared to humeral nonunion. 2. In the patient's interest, it is important to be very well aware of the existence of nonunion and its related consequences. One should keep in mind the different mechanisms that can lead to delayed union and eventually nonunion formation. Imaging plays a key role in diagnosis as well as follow-up. Detecting delayed union in an early stage can play a significant role in the patient's rehabilitation or treatment possibilities. Consulting previous imaging and comparing these with current documentation plays a key role in diagnosing nonunion. 3. The most appropriate initial imaging technique is plain radiography. X-ray enables to distinguish between a hypertrophic and hypotrophic nonunion type. CT-scan is useful in case of ambiguous radiography. More specifically this imaging technique can determine any existing bridging and evaluate if the fracture healing is complete or incomplete. CT-scan can also be performed in case of superposition (other bone structures, plates, screws ). MR imaging can be useful in doubtful cases with soft tissue involvement (nerve entrapment, spinal cord ), infection, necrosis (alternative bone scintigraphy shows no Tc uptake). Page 55 of 57

56 References Resnick D. Diagnosis of Bone and Joint Disorders. 4th ed. Philadelphia (PA): Saunders; Heppenstall RB: Fracture Treatment and Healing. Philadelphia, WB Saunders, Frölke JPM., Patka P. Definition and classification of fracture non-unions. Injury, Int. J. Care Injured. 2007; 38S, S19-S22. Weber BG, Cech O. Pseudarthrosis, Pathology, Biomechanics, Therapy, Results. Bern: Hans Huber Medical Publisher; Chapman MW, Szabo RM,Marder R, Vince KG, Mann RA, Lane JM, McLain RF, Rab G. Chapman's orthopaedic surgery. 3th ed. Lippincott Wiliams & Wilkins Kocaoglu M, Bilen FE. (2011) Armed conflict injuries to the extremities. In Lerner A, Soudry M (eds.) Delayed union and nonunion a treatment manual. Springer; P Mora R. Nonunion of the long bones: Diagnosis and Treatment with Compression-Distraction Techniques. Italy: Springer; Page 56 of 57

57 Personal Information No conflict of interest. Page 57 of 57