Br. J. Surg. Vol. 66 (1979) 640-642
The incidence of deep vein thrombosis in Hong Kong Chinese after hip surgery for fracture of the proximal femur C . K. M O K , F. T. H O A G L U N D , S . M . R O G O F F , S . P. C H O W , A. M A A N D A. C. M . C. Y A U * SUMMARY
Fgiy-three Hong Kong Chinese patients with fractures of the proximal femur have been studied after hip surgery using functional ascending phlebograms for evaluating deep vein thrombosis. There was an incidence of deep vein thrombosis oJ’S3.1 per cent in the jiactured limbs and 14.3 per cent in the uninjured limbs. The majority of thrombi (84-6per cent) were located in the calJ No clinical or Jatal pulmonary embolism was observed. A NUMBER of clinical reports, 12T-labelledfibrinogen uptake studies and autopsy reviews suggest that there are differences in the incidence of thromboembolism between different geographical regions and different ethnic groups, with low incidences among Asian and African populations (Thomas et al., 1960; Franz et al., 1961; Dodd, 1964; Gore et al., 1964; Horn and Wang, 1964; Srivastava, 1964; Tinckler, 1964; Sevitt, 1965; Sandritter and Felix, 1967; Hwang, 1968; Baker and Houlder, 1973; Baker and Prajapat, 1974; Chumnijarakij, 1974; Cunningham and Yong, 1974; Hassan et al., 1974; Chumnijarakij and Poshyachinda, 1975; Bong and Chow, 1977; Talalak, 1976). However, Joffe (1974) from Cape Town and Colin et al. (1975) from Nairobi reported that European, Coloured, African and Indian patients were at a similar high risk of venous thromboembolism. True geographical and ethnic differences in the incidence of thromboembolism are of importance, because they might shed some light on the pathogenesis of the condition. A study on the incidence of thromboembolism in clinical practice amongst Chinese patients has never been reported. Clinical observations indicated that venous thromboembolisni is a rarity even among ‘high risk’ Chinese patients (Horn and Wang, 1964; Bong and Chow, 1977). In an autopsy review (Hwang, 1968), the incidence of pulmonary embolism among Chinese in Singapore was found to be low. This article reports the use of phlebography to determine the incidence of deep vein thrombosis in a group of Hong Kong Chinese patients after hip surgery for fracture of the proximal femur.
Patients and methods Fifty-three Hong Kong Chinese patients (19 males, 34 females), aged 40-83 years, with fractures of the proximal femur, were randomly selected for prospective study for deep vein thrombosis. Informed consent to perform the phlebography was given in writing by each patient. There were 19 intracapsular fractures and 34 pertrochanteric fractures. Pinning alone was performed in 6 patients, a pin and plate was used in 34 and a Moore’s prosthesis was inserted in 13. Patients were not treated with aspirin or other antithrombotic medications during their care. Functional ascending phlebography was performed principally according to the technique described by Rogoff and DeWeese (1960). After being reassured and coached in details of the procedure, the patient was placed semi-erect on an X-ray
table raised to 45” from the horizontal. Percutaneous puncture or cut down was made into any convenient vein on the dorsum of the foot with a 20-gauge scalp vein needle. Infusion of isotonic saline was begun through a three-way stopcock to keep the needle patent. With a rubber tourniquet placed tightly around the ankle, 50 ml of Conray 280 (60 per cent meglumine iothalamate) were injected into the foot vein over a period of 1 min. At the end of the injection, the first exposure was made on a 14x 34 in. (350 x 855 mm) film at 56 in. ( 1 4 m) target-film distance. The tourniquet was removed and the patient was instructed to pump up and down on the balls of his feet ten times. A second long radiograph was then exposed. The time lapse between the first and second radiographs was 35-40 s. A third 14 x 17 in. (350x 427 mm) film centred under the pelvic region was exposed about 45 s after the second radiograph. The patient was then returned to a horizontal position and about 50 ml of saline were rapidly flushed through the needle. The phlebographic examinations were carried out 5-15 days after surgery and 7-28 days after the fracture. The timing of the examinations depended simply upon the availability of the patients and access t o the radiological facilities. All the phlebograms were read and interpreted by one of the authors (S. M. R.) who was unaware of the clinical status of the patients. The criteria for the diagnosis of venous thrombosis were based on those reported by DeWeese and Rogoff (1963), namely: (a)the recognition, in at least two radiographs, of well-defined defects in clearly visualized veins; ( b ) lack of opacification of the popliteal, superficial femoral or common femoral veins with good delineation of the proximal and distal veins, and the presence of collaterals. Absence of contrast medium in the calf veins was not considered diagnostic of thrombosis. Examination for clinical evidence of deep vein thrombosis and pulmonary embolism was made daily by two of the authors (C. K. M. and A. M.). The patients’ temperature charts were examined at the same time and attention was paid t o any unexplained pyrexia. In the presence of any clinical signs which might suggest pulmonary embolism, a chest X-ray, an electrocardiogram, blood gases, serum bilirubin, serum glutamicoxaloacetic transaminase and lactic acid dehydrogenase estimations were performed and repeated on subsequent days. Perfusion lung scan was only performed when there was a strong suspicion of pulmonary embolism.
Results The phlebographic technique proved to be practical and relatively simple to perform. The films were of diagnostic quality, either excluding or demonstrating thrombus. A few patients experienced some discomfort in the foot and calf during the injection of the contrast medium. The discomfort rapidly disappeared after returning the patient to a horizontal position when saline was infused through the veins. There was no allergic reaction to the Conray 280. Forty-five of the 53 patients who were being studied had bilateral phlebograms. The remaining 8 patients had unilateral phlebograms, 4 on the fractured side alone and 4 on the uninjured limb alone. Thus, there were 49 sets of phlebograms
* Departments of Surgery and Orthopaedic Surgery, University of Hong Kong, Hong Kong.
DVT in Chinese after hip surgery
641
Table I: DEEP VEIN THROMBOSIS IN CASES O F FRACTURE OF THE PROXIMAL FEMUR* Incidence of DVT (%) Site of thrombi (%) Detection No. in Overall Injured limb Uninjured limb Calf Above knee methodst study Author(s) Johnsson et al. (1968) Stevens et al. (1968)
PG PG
Culver et al. (1970) Hamilton et al. (1970) Field et al. (1972) Kakkar et al. (1972) Present series
PG PG FUT FUT PG
25 71
NA 40
52 NA
NA NA
NA NA
100
NA
40 49 54 48 53.1
50 26 34 34 14.3
41.3 53.8 NA NA 84.6
76 50 50
53
60 54 53.3
NA More frequent than calf 58.7 46.2 NA NA 15.4
* Only studies using objective diagnostic criteria are included. t PG, phlebography; FUT, 1Z51-labelledfibrinogen uptake test. NA, Not available.
performed upon injured limbs and another 49 sets upon uninjured limbs. On reviewing the 49 sets of phlebograms from the injured limbs, thrombi involving the soleal veins were found in 8 patients, the posterior tibial vein in 2, the peroneal vein in another 2 and combinations of these veins in 9. Two patients had isolated clots in the common femoral and superficial femoral veins without calf involvement, and 3 other patients had involvement of both the femoral and calf systems. An incidence of 53.1 per cent of venous thrombosis was diagnosed on the injured limb phlebograms. Seven (14.3 per cent) of the 49 sets of phlebograms of uninjured limbs were positive for venous thrombosis. There was one case each of soleal and peroneal vein thrombi, 2 patients had posterior tibial vein thrombi and a combination of calf vein involvement was present in 3 other patients. Fifteen patients with phlebographic thrombi had clinical evidence of deep vein thrombosis; 1 1 other patients had clinical features of phlebothrombosis but showed no evidence of it on the phlebograms. Fourteen patients who showed evidence of a phlebographic defect had no clinical evidence of thrombosis. There was no diagnosed pulmonary embolism. Clinical features which remotely suggested pulmonary embolism were observed in 2 patients. Investigations, including perfusion lung scans, excluded the diagnosis. There was no hospital mortality in this group of patients. Discussion A group of patients with fracture of the proximal femur was selected for the study of venous thromboembolism among Chinese because the inhabitants of Western countries have a high incidence of venous thromboembolism. Despite the clinical observations of ‘absence of thromboembolic complications’ among Chinese patients with fractures of the proximal femur managed by non-operative (Horn and Wang, 1964) and operative (Bong and Chow, 1977) treatment, an overall incidence of 53.3 per cent of deep vein thrombosis was disclosed by the present phlebographic study. This is similar to that reported in the West (Table I ) . When confinement to bed is taken as a risk factor, our patients were at a greater risk than similar patients in Western countries. In the present series, because of the lack of operating time, hip surgery was performed 2-14 days after the injury. Although clinical evidence of deep vein thrombosis was carefully sought, a confident clinical diagnosis of deep vein thrombosis was made on only two occasions in this prospective
survey. An analysis of the clinical data collected and the phlebographic findings revealed no correlation between them. Inadequacy of the clinical methods probably explains the failure to recognize deep vein thrombosis in Chinese patients with fracture of the proximal femur by both Horn and Wang and Bong and Chow. Two unique observations of these authors remain, i.e. a low mortality rate (5.5 and 3.6 per cent respectively) and the absence of fatal pulmonary embolism. In the present study, when the sites of the thrombi are analysed and compared with similar studies in the West (Table I), the following points of difference are evident: (a) involvement of the uninjured limb is far less common; (b) the majority of thrombi are located in the calf; (c) extensive venous thrombosis is not observed. In the autopsy study on pulmonary embolism by Hwang in Singapore (19681, the incidence among Chinese was found to be low and massive emboli were rare. The low incidence of ‘clots at risk’ (Kakkar et al., 1969) among Chinese patients with fractures of the proximal femur probably explains the absence of clinical and fatal pulmonary embolism observed by us and others. It is felt that the differences demonstrated in this study merit further investigation. References
w. and HOULDER A. (1973) Deep vein thrombosis in Bantu and Indian patients. S. Afr. Med. J. 47, 16891692. BAKER L. w. and PRAJAPAT D. K. (1974) Deep vein thrombosis in African and Indian patients. S. Afr. J. Surg. 12, 127131. BONG s. c. and CHOW s. P. (1977) Mortality in fractures of the proximal end of femur in Hong Kong Chinese. J. West Pacific Orthop. Assoc. 14, 1-8. CHUMNIJARAKIJ T. (1974) Incidence of postpartum thromboembolism in Thai women: comparison with Western experience. J. Med. Assoc. Thailand 51, 592-594. CHUMNIJARAKIJ T. and POSHYACHINDA v. (1975) Postoperative thrombosis in Thai women. Lancet 1, 1357-1358. COLIN J. F., ROTTCHER K. H. and HALL D. P. (1975) Venous thrombosis in Africans. Lancet 1, 408. CULVER D., CRAWFORD J. s., GARDINER I. H. et al. (1970) Venous thrombosis after fractures of the upper end of the femur. J. Bone Joint Surg. 52B,61-69. C U N N I N G H A M I. G. E. and YONG N. K. (1974) The incidence of post-operative deep vein thrombosis in Malaysia. Br. J. Surg. 61, 432-433. DEWEESE I. A. and ROGOFF s. M. (1963) Phlebographic patterns of acute deep venous thrombosis of the leg. Surgery 53, 99108. DODD H. (1964) The cause, prevention and arrest of varicose veins. Lancet 5 , 809-81 1. FIELD E. s., NICOLAIDES A. N., and K A K K A R v. v. (1972) Deep vein thrombosis in patients with fractures of the femoral neck. Br. J. Surg. 59, 377-379. BAKER L.
642
C. K. Mok et al.
c., KARK A. E. and HATHOKN M. (19611 Postoperative thrombosis and plasma fibrinolytic activity. A comparative study in Africans, Indians and Whites. Lancet 1, 195- 197. GORE I., HIRST A. E. and TANAKA K. (1964) Myocardial infarction and thromboembolism. A comparative study in Boston and in Kyushu, Japan. Arch. Intern. Men. 113, 323330. HAMILTON H. w., CRAWFORD J . s., OARDINER I. H. et al. (1970) Venous thrombosis in patients with fracture of the upper end of the femur. A phlebographic study of the effect of prophylactic anticoagulation. J . Bone Joint Surg. 52B, 268-289. HASSAN M. A., RAHMAN E. A. and RAHMAN I. A. (1974) Prostatectomy and deep vein thrombosis in Sudanese patients. Er. J . Surg. 61, 650-652. HOKN I. s. and W A N G Y . c. (1964) The mechanism, traumatic anatomy and non-operative treatment of intertrochanteric fracture of the femur. Br. J . Surg. 51, 574-580. HWANG w. s. (1968) The rarity of pulmonary thromboembolism in Asians. Singapore Med. J. 9, 276-279. JOFFE s. N. (1974) Racial incidence of postoperative deep vein thrombosis i n South Africa. Br. J . Surg. 61, 982983. J O H N S O N 9. R., BYGDEMAN S. and ELIASSON R. (1968) Effect Of dextran on postoperative thrombosis. Acra Chir. Scunrl. Suppl. 387, pp. 80-82. FRANZ K.
v. v., HOWE c. T., FLANC c. et al. (1969) Natural history of postoperative deep vein thrombosis. Lancet 2 , 230-232. K A K K A K v. v. (1972) The diagnosis of deep vein thrombosis KAKKAR
fibrinogen test. Arch. Surg. 104, 152-159. DEWEESE I. A. (1960) Phlebography of the lower extremity. J A M A 172, 1599-1606. SANDRITTER W. and FELIX H. (1967) Geographical pathology Of fatal lung embolism. Puthol. Microhiol. 30, 742. SEVITT s. (1965) Postoperative prophylactic anticoagulants in gynaecology. Lancet 1, 217. SRIVASTAVA s. c. (1964) Absence of pulmonary embolism in Asians. Br. Med. J. 1, 772-773. STEVENS I., FARDIN R. and FREEARK R. J. (1968) Lower extremity thrombophlebitis in patients with femoral neck fractures. J . Trauma 8, 527-534. TALAI-AK P. (1976) Thromboembolism in Thailand. Incidence, coagulogram and its significance in therapeutic implication and prognosis. J . Med. Assoc. Timifund 59, 6-1 1. THOMAS w. A., DAVIES J . N., O'NEAL R. M. et al. (1960) Incidence of myocardial infarction correlated with venous and pulmonary thrombosis and embolism. A geographic study based on autopsies in Uganda, East Africa and St. Louis. Am. J . Cardiol. 5 , 41-47. TINKLER L. F. (1964) Abscence of pulmonary embolism in Asians? Br. Med. J . 1, 502. using the
ROGOFF
lZsI
s. M. and
Paper accepted 3 April 1979.
The average medical book is predominantly textual and illustrations are needed for two reasons: first, to represent something which the reader needs to be able to interpret by sight and not by a verbal descriptionsomething he will see in his work and recognize because he has seen it before, such as a measles rash as opposed to smallpox, a radiograph shadow, or a pathological cross-section; secondly, to clarify something which is obscure when expressed in words alone. Medical illustrations are not designed primarily as decoratioii. The extent to which pictures are used instead of words can be a reflection of the author's verbal skills, but by and large it is he who originates the thought-the substance-of the book, and it is he who should decide whether it can be expressed best in words or in pictures. Journal ojdudiovisual Media in Medicine (1978) 1, 89.
The incidence of deep vein thrombosis in Hong Kong Chinese after hip surgery for fracture of the proximal femur C . K. M O K , F. T. H O A G L U N D , S . M . R O G O F F , S . P. C H O W , A. M A A N D A. C. M . C. Y A U * SUMMARY
Fgiy-three Hong Kong Chinese patients with fractures of the proximal femur have been studied after hip surgery using functional ascending phlebograms for evaluating deep vein thrombosis. There was an incidence of deep vein thrombosis oJ’S3.1 per cent in the jiactured limbs and 14.3 per cent in the uninjured limbs. The majority of thrombi (84-6per cent) were located in the calJ No clinical or Jatal pulmonary embolism was observed. A NUMBER of clinical reports, 12T-labelledfibrinogen uptake studies and autopsy reviews suggest that there are differences in the incidence of thromboembolism between different geographical regions and different ethnic groups, with low incidences among Asian and African populations (Thomas et al., 1960; Franz et al., 1961; Dodd, 1964; Gore et al., 1964; Horn and Wang, 1964; Srivastava, 1964; Tinckler, 1964; Sevitt, 1965; Sandritter and Felix, 1967; Hwang, 1968; Baker and Houlder, 1973; Baker and Prajapat, 1974; Chumnijarakij, 1974; Cunningham and Yong, 1974; Hassan et al., 1974; Chumnijarakij and Poshyachinda, 1975; Bong and Chow, 1977; Talalak, 1976). However, Joffe (1974) from Cape Town and Colin et al. (1975) from Nairobi reported that European, Coloured, African and Indian patients were at a similar high risk of venous thromboembolism. True geographical and ethnic differences in the incidence of thromboembolism are of importance, because they might shed some light on the pathogenesis of the condition. A study on the incidence of thromboembolism in clinical practice amongst Chinese patients has never been reported. Clinical observations indicated that venous thromboembolisni is a rarity even among ‘high risk’ Chinese patients (Horn and Wang, 1964; Bong and Chow, 1977). In an autopsy review (Hwang, 1968), the incidence of pulmonary embolism among Chinese in Singapore was found to be low. This article reports the use of phlebography to determine the incidence of deep vein thrombosis in a group of Hong Kong Chinese patients after hip surgery for fracture of the proximal femur.
Patients and methods Fifty-three Hong Kong Chinese patients (19 males, 34 females), aged 40-83 years, with fractures of the proximal femur, were randomly selected for prospective study for deep vein thrombosis. Informed consent to perform the phlebography was given in writing by each patient. There were 19 intracapsular fractures and 34 pertrochanteric fractures. Pinning alone was performed in 6 patients, a pin and plate was used in 34 and a Moore’s prosthesis was inserted in 13. Patients were not treated with aspirin or other antithrombotic medications during their care. Functional ascending phlebography was performed principally according to the technique described by Rogoff and DeWeese (1960). After being reassured and coached in details of the procedure, the patient was placed semi-erect on an X-ray
table raised to 45” from the horizontal. Percutaneous puncture or cut down was made into any convenient vein on the dorsum of the foot with a 20-gauge scalp vein needle. Infusion of isotonic saline was begun through a three-way stopcock to keep the needle patent. With a rubber tourniquet placed tightly around the ankle, 50 ml of Conray 280 (60 per cent meglumine iothalamate) were injected into the foot vein over a period of 1 min. At the end of the injection, the first exposure was made on a 14x 34 in. (350 x 855 mm) film at 56 in. ( 1 4 m) target-film distance. The tourniquet was removed and the patient was instructed to pump up and down on the balls of his feet ten times. A second long radiograph was then exposed. The time lapse between the first and second radiographs was 35-40 s. A third 14 x 17 in. (350x 427 mm) film centred under the pelvic region was exposed about 45 s after the second radiograph. The patient was then returned to a horizontal position and about 50 ml of saline were rapidly flushed through the needle. The phlebographic examinations were carried out 5-15 days after surgery and 7-28 days after the fracture. The timing of the examinations depended simply upon the availability of the patients and access t o the radiological facilities. All the phlebograms were read and interpreted by one of the authors (S. M. R.) who was unaware of the clinical status of the patients. The criteria for the diagnosis of venous thrombosis were based on those reported by DeWeese and Rogoff (1963), namely: (a)the recognition, in at least two radiographs, of well-defined defects in clearly visualized veins; ( b ) lack of opacification of the popliteal, superficial femoral or common femoral veins with good delineation of the proximal and distal veins, and the presence of collaterals. Absence of contrast medium in the calf veins was not considered diagnostic of thrombosis. Examination for clinical evidence of deep vein thrombosis and pulmonary embolism was made daily by two of the authors (C. K. M. and A. M.). The patients’ temperature charts were examined at the same time and attention was paid t o any unexplained pyrexia. In the presence of any clinical signs which might suggest pulmonary embolism, a chest X-ray, an electrocardiogram, blood gases, serum bilirubin, serum glutamicoxaloacetic transaminase and lactic acid dehydrogenase estimations were performed and repeated on subsequent days. Perfusion lung scan was only performed when there was a strong suspicion of pulmonary embolism.
Results The phlebographic technique proved to be practical and relatively simple to perform. The films were of diagnostic quality, either excluding or demonstrating thrombus. A few patients experienced some discomfort in the foot and calf during the injection of the contrast medium. The discomfort rapidly disappeared after returning the patient to a horizontal position when saline was infused through the veins. There was no allergic reaction to the Conray 280. Forty-five of the 53 patients who were being studied had bilateral phlebograms. The remaining 8 patients had unilateral phlebograms, 4 on the fractured side alone and 4 on the uninjured limb alone. Thus, there were 49 sets of phlebograms
* Departments of Surgery and Orthopaedic Surgery, University of Hong Kong, Hong Kong.
DVT in Chinese after hip surgery
641
Table I: DEEP VEIN THROMBOSIS IN CASES O F FRACTURE OF THE PROXIMAL FEMUR* Incidence of DVT (%) Site of thrombi (%) Detection No. in Overall Injured limb Uninjured limb Calf Above knee methodst study Author(s) Johnsson et al. (1968) Stevens et al. (1968)
PG PG
Culver et al. (1970) Hamilton et al. (1970) Field et al. (1972) Kakkar et al. (1972) Present series
PG PG FUT FUT PG
25 71
NA 40
52 NA
NA NA
NA NA
100
NA
40 49 54 48 53.1
50 26 34 34 14.3
41.3 53.8 NA NA 84.6
76 50 50
53
60 54 53.3
NA More frequent than calf 58.7 46.2 NA NA 15.4
* Only studies using objective diagnostic criteria are included. t PG, phlebography; FUT, 1Z51-labelledfibrinogen uptake test. NA, Not available.
performed upon injured limbs and another 49 sets upon uninjured limbs. On reviewing the 49 sets of phlebograms from the injured limbs, thrombi involving the soleal veins were found in 8 patients, the posterior tibial vein in 2, the peroneal vein in another 2 and combinations of these veins in 9. Two patients had isolated clots in the common femoral and superficial femoral veins without calf involvement, and 3 other patients had involvement of both the femoral and calf systems. An incidence of 53.1 per cent of venous thrombosis was diagnosed on the injured limb phlebograms. Seven (14.3 per cent) of the 49 sets of phlebograms of uninjured limbs were positive for venous thrombosis. There was one case each of soleal and peroneal vein thrombi, 2 patients had posterior tibial vein thrombi and a combination of calf vein involvement was present in 3 other patients. Fifteen patients with phlebographic thrombi had clinical evidence of deep vein thrombosis; 1 1 other patients had clinical features of phlebothrombosis but showed no evidence of it on the phlebograms. Fourteen patients who showed evidence of a phlebographic defect had no clinical evidence of thrombosis. There was no diagnosed pulmonary embolism. Clinical features which remotely suggested pulmonary embolism were observed in 2 patients. Investigations, including perfusion lung scans, excluded the diagnosis. There was no hospital mortality in this group of patients. Discussion A group of patients with fracture of the proximal femur was selected for the study of venous thromboembolism among Chinese because the inhabitants of Western countries have a high incidence of venous thromboembolism. Despite the clinical observations of ‘absence of thromboembolic complications’ among Chinese patients with fractures of the proximal femur managed by non-operative (Horn and Wang, 1964) and operative (Bong and Chow, 1977) treatment, an overall incidence of 53.3 per cent of deep vein thrombosis was disclosed by the present phlebographic study. This is similar to that reported in the West (Table I ) . When confinement to bed is taken as a risk factor, our patients were at a greater risk than similar patients in Western countries. In the present series, because of the lack of operating time, hip surgery was performed 2-14 days after the injury. Although clinical evidence of deep vein thrombosis was carefully sought, a confident clinical diagnosis of deep vein thrombosis was made on only two occasions in this prospective
survey. An analysis of the clinical data collected and the phlebographic findings revealed no correlation between them. Inadequacy of the clinical methods probably explains the failure to recognize deep vein thrombosis in Chinese patients with fracture of the proximal femur by both Horn and Wang and Bong and Chow. Two unique observations of these authors remain, i.e. a low mortality rate (5.5 and 3.6 per cent respectively) and the absence of fatal pulmonary embolism. In the present study, when the sites of the thrombi are analysed and compared with similar studies in the West (Table I), the following points of difference are evident: (a) involvement of the uninjured limb is far less common; (b) the majority of thrombi are located in the calf; (c) extensive venous thrombosis is not observed. In the autopsy study on pulmonary embolism by Hwang in Singapore (19681, the incidence among Chinese was found to be low and massive emboli were rare. The low incidence of ‘clots at risk’ (Kakkar et al., 1969) among Chinese patients with fractures of the proximal femur probably explains the absence of clinical and fatal pulmonary embolism observed by us and others. It is felt that the differences demonstrated in this study merit further investigation. References
w. and HOULDER A. (1973) Deep vein thrombosis in Bantu and Indian patients. S. Afr. Med. J. 47, 16891692. BAKER L. w. and PRAJAPAT D. K. (1974) Deep vein thrombosis in African and Indian patients. S. Afr. J. Surg. 12, 127131. BONG s. c. and CHOW s. P. (1977) Mortality in fractures of the proximal end of femur in Hong Kong Chinese. J. West Pacific Orthop. Assoc. 14, 1-8. CHUMNIJARAKIJ T. (1974) Incidence of postpartum thromboembolism in Thai women: comparison with Western experience. J. Med. Assoc. Thailand 51, 592-594. CHUMNIJARAKIJ T. and POSHYACHINDA v. (1975) Postoperative thrombosis in Thai women. Lancet 1, 1357-1358. COLIN J. F., ROTTCHER K. H. and HALL D. P. (1975) Venous thrombosis in Africans. Lancet 1, 408. CULVER D., CRAWFORD J. s., GARDINER I. H. et al. (1970) Venous thrombosis after fractures of the upper end of the femur. J. Bone Joint Surg. 52B,61-69. C U N N I N G H A M I. G. E. and YONG N. K. (1974) The incidence of post-operative deep vein thrombosis in Malaysia. Br. J. Surg. 61, 432-433. DEWEESE I. A. and ROGOFF s. M. (1963) Phlebographic patterns of acute deep venous thrombosis of the leg. Surgery 53, 99108. DODD H. (1964) The cause, prevention and arrest of varicose veins. Lancet 5 , 809-81 1. FIELD E. s., NICOLAIDES A. N., and K A K K A R v. v. (1972) Deep vein thrombosis in patients with fractures of the femoral neck. Br. J. Surg. 59, 377-379. BAKER L.
642
C. K. Mok et al.
c., KARK A. E. and HATHOKN M. (19611 Postoperative thrombosis and plasma fibrinolytic activity. A comparative study in Africans, Indians and Whites. Lancet 1, 195- 197. GORE I., HIRST A. E. and TANAKA K. (1964) Myocardial infarction and thromboembolism. A comparative study in Boston and in Kyushu, Japan. Arch. Intern. Men. 113, 323330. HAMILTON H. w., CRAWFORD J . s., OARDINER I. H. et al. (1970) Venous thrombosis in patients with fracture of the upper end of the femur. A phlebographic study of the effect of prophylactic anticoagulation. J . Bone Joint Surg. 52B, 268-289. HASSAN M. A., RAHMAN E. A. and RAHMAN I. A. (1974) Prostatectomy and deep vein thrombosis in Sudanese patients. Er. J . Surg. 61, 650-652. HOKN I. s. and W A N G Y . c. (1964) The mechanism, traumatic anatomy and non-operative treatment of intertrochanteric fracture of the femur. Br. J . Surg. 51, 574-580. HWANG w. s. (1968) The rarity of pulmonary thromboembolism in Asians. Singapore Med. J. 9, 276-279. JOFFE s. N. (1974) Racial incidence of postoperative deep vein thrombosis i n South Africa. Br. J . Surg. 61, 982983. J O H N S O N 9. R., BYGDEMAN S. and ELIASSON R. (1968) Effect Of dextran on postoperative thrombosis. Acra Chir. Scunrl. Suppl. 387, pp. 80-82. FRANZ K.
v. v., HOWE c. T., FLANC c. et al. (1969) Natural history of postoperative deep vein thrombosis. Lancet 2 , 230-232. K A K K A K v. v. (1972) The diagnosis of deep vein thrombosis KAKKAR
fibrinogen test. Arch. Surg. 104, 152-159. DEWEESE I. A. (1960) Phlebography of the lower extremity. J A M A 172, 1599-1606. SANDRITTER W. and FELIX H. (1967) Geographical pathology Of fatal lung embolism. Puthol. Microhiol. 30, 742. SEVITT s. (1965) Postoperative prophylactic anticoagulants in gynaecology. Lancet 1, 217. SRIVASTAVA s. c. (1964) Absence of pulmonary embolism in Asians. Br. Med. J. 1, 772-773. STEVENS I., FARDIN R. and FREEARK R. J. (1968) Lower extremity thrombophlebitis in patients with femoral neck fractures. J . Trauma 8, 527-534. TALAI-AK P. (1976) Thromboembolism in Thailand. Incidence, coagulogram and its significance in therapeutic implication and prognosis. J . Med. Assoc. Timifund 59, 6-1 1. THOMAS w. A., DAVIES J . N., O'NEAL R. M. et al. (1960) Incidence of myocardial infarction correlated with venous and pulmonary thrombosis and embolism. A geographic study based on autopsies in Uganda, East Africa and St. Louis. Am. J . Cardiol. 5 , 41-47. TINKLER L. F. (1964) Abscence of pulmonary embolism in Asians? Br. Med. J . 1, 502. using the
ROGOFF
lZsI
s. M. and
Paper accepted 3 April 1979.
The average medical book is predominantly textual and illustrations are needed for two reasons: first, to represent something which the reader needs to be able to interpret by sight and not by a verbal descriptionsomething he will see in his work and recognize because he has seen it before, such as a measles rash as opposed to smallpox, a radiograph shadow, or a pathological cross-section; secondly, to clarify something which is obscure when expressed in words alone. Medical illustrations are not designed primarily as decoratioii. The extent to which pictures are used instead of words can be a reflection of the author's verbal skills, but by and large it is he who originates the thought-the substance-of the book, and it is he who should decide whether it can be expressed best in words or in pictures. Journal ojdudiovisual Media in Medicine (1978) 1, 89.
