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The monofixator in the primary stabilization of femoral shaft fractures in multiply-injured patients
Injury (1992) 23, (8), 525-528
Printti in
Greuf &ituin
525
The monofixator in the primary stabilization of femoral shaft fractures in multiply-injured patients P. L. Broos, M. J. Miserez and P. M. Rommens Department
of Traumatology
and Emergency
Surgery, University
In multiply-injured patienfs wifh femoral shuff jkfures, evidnzcegrows that a fast primay temporary stabilization a&co is preferable to a definitive method of stabilkation by intramedullay nailing or plate osteosynthek Conversion to intramedullay nailing is performed lafer, During a l&month period, we treated nine patients with 10 femoral shaft fractures in this way. ?Iere were two open fractures and six oGer fracfures were associated with severe soft tissue damage. The overall ftmcfion resulf is ercellenf and con.wlia&m was reached aftpr a relatively short time. The advantages are clear: a shorter operation time, earlier mobilimtion and rehabilitafion, and freer complications.
Introduction Early stabilization of fractures of the long bones has become a major component of acute care and is a well-established practice in many trauma centres. Not only does it improve the overall functional results, but it also greatly reduces mortality due to multiple-organ failure. When stabilizing long bone fractures in multiply-injured patients, one should preferably use minimal intervention. Since January 1989, we have been using the unilateral external fixator or so-called monofixator frame as a temporary fixation for femoral shaft fractures. Depending on the presence of associated lesions, the general condition of the patient and the severity of the accompanying soft tissue injury, the external fixator was removed and definitive fixation of the fracture was obtained by intramedullary nailing. Preliminary results show clearly that this is a safe method of stabilization.
Materials and methods Between January 1989 and April 1990, we treated nine patients with 10 femoral shaft fractures using an external monofixation device as primary fixation. All cases were followed up. There were seven men, average age 20 years, and two women, average age 46 years. They were all multiply-injured with associated lesions as illustrated in T&able I. Only two fractures were open, although six patients with closed fractures developed severe soft tissue damage classified 4 or 3 by Tscheme’s classification (Table N). There were two femoral artery injuries (Figure I). All fractures were stabilized within hours of arrival at the emergency department. The average theatre time was 0
1992 Butterworth-Heinema 0020-1383/92/080525-04
Ltd
Hospitals, Leuven, Belgium
21 min. In each case, two or three pins were placed above and below the fracture site. They were all fixed laterally. No additional lag screws were used because of the intended temporary nature of the stabilization (Figure 2). None of the patients died, two developed pulmonary infection, one complicated by ARDS and one with cardiac failure. There were no pin tract infections, according to the diagnostic criteria of Green and Nguyen, or other local complications (Green, 1983; Nguyen et al., 1986). In eight of nine patients, the external fixator was removed an average of 21 days later and subsequently replaced by an intramedullary nail. Timing and type of device depended on the general condition of the patient and local soft tissue disorders (Figure 3). The average theatre time to perform the second operation was 43 min. In one patient, the second operation was postponed due to soft tissue complications which resulted in a below-knee amputation. In this case, intramedullary nailing was performed 27 weeks after injury by which time an aseptic delayed union was present. Fracture healing occurred without complication. No infections were found deep in the femur. The mean time to
Table I. Associated lesions in femoral shaft fractures (N= IO) No associated lesions Associated lesions Lower extremity Upper extremity Craniocerebral trauma Abdominal trauma Vascular lesion Thoracic trauma Pelvic trauma Urogenital lesion Degloving injury Mean Injury Severity Score (ISS) = 35.5 (range 17-57)
N=O N=9 11 2 5 2 2 1 1 1 1
Table II. Fracture type in femoral shaft fractures (?V= 10) Type A Type B Type C
Subtype A2 Subtype A3 Subtype Bl Subtype 83 SubtypeC2 Subtype C3
1 3 1 1 1 3
Injury: the British Journal of Accident Surgery (1992) Vol. 23/No. 8
526
Figure 1. Left femoral shaft fracture before external fixation.
union was 14.6 weeks (range 9-23 weeks) (Figm4). Function was evaluated 6-12 months after injury according to the classification of Klemm and Bomer (1986). This involved assessing the mobility of the hip and knee joint, muscle atrophy and the radiological appearances. They were judged to be excellent in six patients and good in four patients (Table 111).
Discussion Initial stabilization of long bone fractures in multiply-injured patients is advantageous in comparison with long-term skeletal or skin traction for many reasons: 1. Better local wound control; 2. Earlier and easier mobilization and nursing; 3. Fewer complications such as pulmonary infection, sepsis, multiple-organ failure, and a considerable reduction in length of hospital stay (Laduca et al., 1980; Goris et al., 1982; Broos et al., 1987). There are three ways of stabilizing
a femoral shaft fracture:
1. Plating; 2. Intramedullary nailing; 3. External fixation. Recently, closed intramedullary fixation has become the treatment of choice in the presence of damaged soft tissue, since the haematoma around the fracture remains confined
Figure2. Left femoral shaft fracture 1 week after external fixation.
thus promoting fracture healing. Furthermore, this is a minimal traumatic intervention with a low infection risk (less than 1 per cent) and a good cosmetic result (Rush, 1984; Kempf et al., 1985; Klemm and Biimer, 1986). However, there are also disadvantages to this technique, particularly in the acute post-traumatic phase in the multiply-injured patient. Immediately after trauma, the severely injured patient is very likely to develop a state of shock due to hypovolaemia, hypoxia and pain with the subsequent release of shock-mediating factors in the blood. This situation will be aggravated by surgical trauma. It is therefore important to limit this stressful factor with a short, efficient procedure in those patients with severe associated lesions. Intrarnedullary nailing in particular is not ideal in these emergency situations, especially during the night and at weekends for several reasons: it takes time to place the patient on the orthopaedic table and, because of a worse alignment of the bone fragments immediately after trauma, a primary intramedullary fixation takes approximately 40 min longer (mean theatre time = 83 min) than a secondary elective intramedullary nailing. It is also necessary to have technically highly competent and experienced surgeons together with good radiological equipment, technicians and nurses (Browner, 1986). By far the most important disadvantage is the possible development of fat embolism during the procedure, which can result in ARDS, a major prognostic factor in morbidity and eventually mortality in the acute post-traumatic shock phase of multiply-injured patients (Wenda et al., 1990). In an experimental sheep model lung damage occurred after intramedullary femoral nailing in the
Broos et al.: Stab&&ion
of femoral shaft frachxres
Figure 3. Left femoral shaft fracture I day after intramedullary
527
Figure 4. Consolidated left femoral shaft fracture (i.e. 9 months after external fixation).
nailing (i.e. z weeks after external fixation).
presence of previous lung contusion and haemorrhagic shock (Pape et al., 1991). It has been stated that primary intramedullary nailing of femoral shaft fractures is not desirable in patients with a thoracic injury as well because of the increased risk of massive pulmonary embolism (Soldner, 1990). Moreover, Grosse and Kempf believe this method is not good for associated vascular lesions. Stabilization in these circumstances must be achieved as quickly as possible in order to perform the vascular repair without delay. Plating does not have these disadvantages but involves greater soft tissue damage. Devascularized bone fragments may increase infection, delayed union and blood loss (Rush, 1984; Cheng et al., 1985). There is a longer hospital stay and greater quadriceps muscle damage with a slower rehabilitation process and greater danger of refracture after removing the implant. The end result is not as good and cancellous grafting is sometimes necessary, either primarily or later (Breederveld et al., 1985; Cheng et al., 1985; Thompson et al., 1985; Klemm and B6mer, 1986; Heitemeyer et al., 1987). With external fixation, maintenance of leg length is of prime importance, but a perfect anatomical reduction is not necessary. Stability with external fixation is enough to allow early, i.e. on the day of operation, mobilization of the patient. Furthermore, there is no need to use a traction table; the external fixator is easy to install without additional soft tissue damage or blood loss and is well tolerated by the patients in every day life, with easy cleaning and dressing.
In conclusion, external fixation is not only the treatment of choice for severe open femoral fractures or infected pseudarthroses (Tidal, 1980), but it deserves a place in multiply-injured patients. Indeed, mobilization and rehabilitation of the patient, being of great importance in multiplyinjured patients, may be as early as with primary intramedullary nailing but, as a whole, the external fixator is much better tolerated in this group of patients. Furthermore, external fixation is enough to prevent multiple-organ failure in multiply-injured patients (Goris et al., 1982; Broos et al., 1987).
However, as delayed union may occur in adults, as illustrated by our case of one patient in whom there was no
Table III. Functional results after femoral fractures (N= IO) Excellent: Full hip and knee motion No muscular atrophy Normal radiographic alignment Good: Slight loss of hip or knee motion Less than 2 cm muscle atrophy Angular deformity less than 5 Fair: Moderate (25%) loss of hip or knee motion More than 2 cm muscle atrophy Angular deformity 5-40 (Klemm and Biirner, 1986)
N=6
N=4
N=O
52s
Injury: the British journal of Accident Surgery (1992)
bony bridging at 5 months, definitive treatment of the fracture has to be planned. The timing of the second operation depends on the general condition of the patient and the local state of the soft tissues. In most cases, this will involve conversion of the external fixator into an intramedullary nail. Intramedullary nailing provides not only a mechanical stimulus, enhancing the stability of the fractured region, but a biological stimulus as well, by means of the drilling procedure, which can be seen as a ‘closed autologous cancellous bone graft. In most cases, this leads to fast bony bridging. The fixator may be removed on the traction table. The disadvantage of undergoing two consecutive operations is not as great as the risks of pulmonary complications after primary intramedullary fixation in these severely injured patients. The latter in turn leads indirectly to an increase in morbidity, hospital stay and cost-effectiveness ratio.
References Breederveld R. S., Patka P. and Van Mourik J. C. (1985) Refractures of the femoral shaft. Neth. J. Surg. 37,114. Broos P. L. O., Stappaerts K. H., Luiten E. J. T. et al. (1987) The importance of early internal fixation in multiply-injured patients to prevent late death due to sepsis. Injuy 18, 235. Browner B. D. (1986) Pitfalls, errors, and complications in the use of locking Kiintscher nails. Clin. Orthup. 212, 192. Cheng J. C. Y., Tse P. Y. T. and Chow Y. Y. N. (1985) The place of the dynamic compression plate in femoral shaft fractures. Injury 16,529. Goris J. A., Gimbrere J. S. F., van Niekerk J. L. M. et al. (1982) Early osteosynthesis and prophylactic mechanical ventilation in the m&trauma patient. J. Traurrur 22, 895. Green S. A. (1983) Complications of external skeletal fixation. Clin. Orfhop. Rel. Res. 180, 109.
Vol. 23/No.
8
Heitemeyer U., Kemper F., Hierholzer G. et al. (1987) Severely comminuted femoral shaft fractures: treatment by bridgingplate osteosynthesis. Arch. Orthop. Trauma Surg. 106, 327. Kempf I., Grosse A. and Beck G. (1985) Closed locked intramedulJar-ynailing. J. BoneJoinf Surg. 67A, 709. Klemm K. W. and Biimer M. (1986) Interlocking nailing of complex fractures of the femur and tibia. C/in. O&rep. 212,89. Laduca J. N., Boone L. L, Seibel R. W. et al. (1980) Primary open reduction and internal fixation of open fractures. J. Trauma 20, 580. Nguyen V. D., London J. and Cone R. 0. (1986) Ring sequestmm: radiographic characteristics of skeletal fixation pin-tract osteomyelitis. Radio&y 158, 129. Pape H.-C., Dwenger A., Regel G. et al. (1991) Does intramedullary femoral nailing have an intluence on lung function in case of additional lung contusion and severe hemorrhagic shock? A sheep model. Unfulkhirurg 94, 381. Rush F. (1984) Intramedullary fixation. In: GaJaxo C. B. S. (ed) R+rci~les of Fracture ldmugemenf. Edinburgh: Churchill Livingstone, 101. Soldner E. (1990) Die Veniegelungsnagelung in Kombination mit dem Thoraxtrauma. Abstract ‘20 Jahre Verriegelungsnagelung’, Frankfurt am Main, 28-30 September 1990. Thompson F., O’Beime J., Gallagher J. et al. (1985) Fractures of the femoral shaft treated by plating. lnjuy 16,535. Wenda K., Ritter H., Ahlers J. et al. (1990) Detection and e#ects of bone marrow intravasation during operations in the region of the femoral cavity. Unfa~khinrrg 93, 56. Widal J. (1980) La fixufion e&me d’&@run. Geneve: Diffinco S. A. Paper accepted
7 April 1992.
Requestsfor reprints should be addressed to: P. L. Broos, Department of Traurnatology and Emergency Surgery, U.Z. Gasthuisberg, Herestraat 49, B-3000 Leuven, Belgium.
Printti in
Greuf &ituin
525
The monofixator in the primary stabilization of femoral shaft fractures in multiply-injured patients P. L. Broos, M. J. Miserez and P. M. Rommens Department
of Traumatology
and Emergency
Surgery, University
In multiply-injured patienfs wifh femoral shuff jkfures, evidnzcegrows that a fast primay temporary stabilization a&co is preferable to a definitive method of stabilkation by intramedullay nailing or plate osteosynthek Conversion to intramedullay nailing is performed lafer, During a l&month period, we treated nine patients with 10 femoral shaft fractures in this way. ?Iere were two open fractures and six oGer fracfures were associated with severe soft tissue damage. The overall ftmcfion resulf is ercellenf and con.wlia&m was reached aftpr a relatively short time. The advantages are clear: a shorter operation time, earlier mobilimtion and rehabilitafion, and freer complications.
Introduction Early stabilization of fractures of the long bones has become a major component of acute care and is a well-established practice in many trauma centres. Not only does it improve the overall functional results, but it also greatly reduces mortality due to multiple-organ failure. When stabilizing long bone fractures in multiply-injured patients, one should preferably use minimal intervention. Since January 1989, we have been using the unilateral external fixator or so-called monofixator frame as a temporary fixation for femoral shaft fractures. Depending on the presence of associated lesions, the general condition of the patient and the severity of the accompanying soft tissue injury, the external fixator was removed and definitive fixation of the fracture was obtained by intramedullary nailing. Preliminary results show clearly that this is a safe method of stabilization.
Materials and methods Between January 1989 and April 1990, we treated nine patients with 10 femoral shaft fractures using an external monofixation device as primary fixation. All cases were followed up. There were seven men, average age 20 years, and two women, average age 46 years. They were all multiply-injured with associated lesions as illustrated in T&able I. Only two fractures were open, although six patients with closed fractures developed severe soft tissue damage classified 4 or 3 by Tscheme’s classification (Table N). There were two femoral artery injuries (Figure I). All fractures were stabilized within hours of arrival at the emergency department. The average theatre time was 0
1992 Butterworth-Heinema 0020-1383/92/080525-04
Ltd
Hospitals, Leuven, Belgium
21 min. In each case, two or three pins were placed above and below the fracture site. They were all fixed laterally. No additional lag screws were used because of the intended temporary nature of the stabilization (Figure 2). None of the patients died, two developed pulmonary infection, one complicated by ARDS and one with cardiac failure. There were no pin tract infections, according to the diagnostic criteria of Green and Nguyen, or other local complications (Green, 1983; Nguyen et al., 1986). In eight of nine patients, the external fixator was removed an average of 21 days later and subsequently replaced by an intramedullary nail. Timing and type of device depended on the general condition of the patient and local soft tissue disorders (Figure 3). The average theatre time to perform the second operation was 43 min. In one patient, the second operation was postponed due to soft tissue complications which resulted in a below-knee amputation. In this case, intramedullary nailing was performed 27 weeks after injury by which time an aseptic delayed union was present. Fracture healing occurred without complication. No infections were found deep in the femur. The mean time to
Table I. Associated lesions in femoral shaft fractures (N= IO) No associated lesions Associated lesions Lower extremity Upper extremity Craniocerebral trauma Abdominal trauma Vascular lesion Thoracic trauma Pelvic trauma Urogenital lesion Degloving injury Mean Injury Severity Score (ISS) = 35.5 (range 17-57)
N=O N=9 11 2 5 2 2 1 1 1 1
Table II. Fracture type in femoral shaft fractures (?V= 10) Type A Type B Type C
Subtype A2 Subtype A3 Subtype Bl Subtype 83 SubtypeC2 Subtype C3
1 3 1 1 1 3
Injury: the British Journal of Accident Surgery (1992) Vol. 23/No. 8
526
Figure 1. Left femoral shaft fracture before external fixation.
union was 14.6 weeks (range 9-23 weeks) (Figm4). Function was evaluated 6-12 months after injury according to the classification of Klemm and Bomer (1986). This involved assessing the mobility of the hip and knee joint, muscle atrophy and the radiological appearances. They were judged to be excellent in six patients and good in four patients (Table 111).
Discussion Initial stabilization of long bone fractures in multiply-injured patients is advantageous in comparison with long-term skeletal or skin traction for many reasons: 1. Better local wound control; 2. Earlier and easier mobilization and nursing; 3. Fewer complications such as pulmonary infection, sepsis, multiple-organ failure, and a considerable reduction in length of hospital stay (Laduca et al., 1980; Goris et al., 1982; Broos et al., 1987). There are three ways of stabilizing
a femoral shaft fracture:
1. Plating; 2. Intramedullary nailing; 3. External fixation. Recently, closed intramedullary fixation has become the treatment of choice in the presence of damaged soft tissue, since the haematoma around the fracture remains confined
Figure2. Left femoral shaft fracture 1 week after external fixation.
thus promoting fracture healing. Furthermore, this is a minimal traumatic intervention with a low infection risk (less than 1 per cent) and a good cosmetic result (Rush, 1984; Kempf et al., 1985; Klemm and Biimer, 1986). However, there are also disadvantages to this technique, particularly in the acute post-traumatic phase in the multiply-injured patient. Immediately after trauma, the severely injured patient is very likely to develop a state of shock due to hypovolaemia, hypoxia and pain with the subsequent release of shock-mediating factors in the blood. This situation will be aggravated by surgical trauma. It is therefore important to limit this stressful factor with a short, efficient procedure in those patients with severe associated lesions. Intrarnedullary nailing in particular is not ideal in these emergency situations, especially during the night and at weekends for several reasons: it takes time to place the patient on the orthopaedic table and, because of a worse alignment of the bone fragments immediately after trauma, a primary intramedullary fixation takes approximately 40 min longer (mean theatre time = 83 min) than a secondary elective intramedullary nailing. It is also necessary to have technically highly competent and experienced surgeons together with good radiological equipment, technicians and nurses (Browner, 1986). By far the most important disadvantage is the possible development of fat embolism during the procedure, which can result in ARDS, a major prognostic factor in morbidity and eventually mortality in the acute post-traumatic shock phase of multiply-injured patients (Wenda et al., 1990). In an experimental sheep model lung damage occurred after intramedullary femoral nailing in the
Broos et al.: Stab&&ion
of femoral shaft frachxres
Figure 3. Left femoral shaft fracture I day after intramedullary
527
Figure 4. Consolidated left femoral shaft fracture (i.e. 9 months after external fixation).
nailing (i.e. z weeks after external fixation).
presence of previous lung contusion and haemorrhagic shock (Pape et al., 1991). It has been stated that primary intramedullary nailing of femoral shaft fractures is not desirable in patients with a thoracic injury as well because of the increased risk of massive pulmonary embolism (Soldner, 1990). Moreover, Grosse and Kempf believe this method is not good for associated vascular lesions. Stabilization in these circumstances must be achieved as quickly as possible in order to perform the vascular repair without delay. Plating does not have these disadvantages but involves greater soft tissue damage. Devascularized bone fragments may increase infection, delayed union and blood loss (Rush, 1984; Cheng et al., 1985). There is a longer hospital stay and greater quadriceps muscle damage with a slower rehabilitation process and greater danger of refracture after removing the implant. The end result is not as good and cancellous grafting is sometimes necessary, either primarily or later (Breederveld et al., 1985; Cheng et al., 1985; Thompson et al., 1985; Klemm and B6mer, 1986; Heitemeyer et al., 1987). With external fixation, maintenance of leg length is of prime importance, but a perfect anatomical reduction is not necessary. Stability with external fixation is enough to allow early, i.e. on the day of operation, mobilization of the patient. Furthermore, there is no need to use a traction table; the external fixator is easy to install without additional soft tissue damage or blood loss and is well tolerated by the patients in every day life, with easy cleaning and dressing.
In conclusion, external fixation is not only the treatment of choice for severe open femoral fractures or infected pseudarthroses (Tidal, 1980), but it deserves a place in multiply-injured patients. Indeed, mobilization and rehabilitation of the patient, being of great importance in multiplyinjured patients, may be as early as with primary intramedullary nailing but, as a whole, the external fixator is much better tolerated in this group of patients. Furthermore, external fixation is enough to prevent multiple-organ failure in multiply-injured patients (Goris et al., 1982; Broos et al., 1987).
However, as delayed union may occur in adults, as illustrated by our case of one patient in whom there was no
Table III. Functional results after femoral fractures (N= IO) Excellent: Full hip and knee motion No muscular atrophy Normal radiographic alignment Good: Slight loss of hip or knee motion Less than 2 cm muscle atrophy Angular deformity less than 5 Fair: Moderate (25%) loss of hip or knee motion More than 2 cm muscle atrophy Angular deformity 5-40 (Klemm and Biirner, 1986)
N=6
N=4
N=O
52s
Injury: the British journal of Accident Surgery (1992)
bony bridging at 5 months, definitive treatment of the fracture has to be planned. The timing of the second operation depends on the general condition of the patient and the local state of the soft tissues. In most cases, this will involve conversion of the external fixator into an intramedullary nail. Intramedullary nailing provides not only a mechanical stimulus, enhancing the stability of the fractured region, but a biological stimulus as well, by means of the drilling procedure, which can be seen as a ‘closed autologous cancellous bone graft. In most cases, this leads to fast bony bridging. The fixator may be removed on the traction table. The disadvantage of undergoing two consecutive operations is not as great as the risks of pulmonary complications after primary intramedullary fixation in these severely injured patients. The latter in turn leads indirectly to an increase in morbidity, hospital stay and cost-effectiveness ratio.
References Breederveld R. S., Patka P. and Van Mourik J. C. (1985) Refractures of the femoral shaft. Neth. J. Surg. 37,114. Broos P. L. O., Stappaerts K. H., Luiten E. J. T. et al. (1987) The importance of early internal fixation in multiply-injured patients to prevent late death due to sepsis. Injuy 18, 235. Browner B. D. (1986) Pitfalls, errors, and complications in the use of locking Kiintscher nails. Clin. Orthup. 212, 192. Cheng J. C. Y., Tse P. Y. T. and Chow Y. Y. N. (1985) The place of the dynamic compression plate in femoral shaft fractures. Injury 16,529. Goris J. A., Gimbrere J. S. F., van Niekerk J. L. M. et al. (1982) Early osteosynthesis and prophylactic mechanical ventilation in the m&trauma patient. J. Traurrur 22, 895. Green S. A. (1983) Complications of external skeletal fixation. Clin. Orfhop. Rel. Res. 180, 109.
Vol. 23/No.
8
Heitemeyer U., Kemper F., Hierholzer G. et al. (1987) Severely comminuted femoral shaft fractures: treatment by bridgingplate osteosynthesis. Arch. Orthop. Trauma Surg. 106, 327. Kempf I., Grosse A. and Beck G. (1985) Closed locked intramedulJar-ynailing. J. BoneJoinf Surg. 67A, 709. Klemm K. W. and Biimer M. (1986) Interlocking nailing of complex fractures of the femur and tibia. C/in. O&rep. 212,89. Laduca J. N., Boone L. L, Seibel R. W. et al. (1980) Primary open reduction and internal fixation of open fractures. J. Trauma 20, 580. Nguyen V. D., London J. and Cone R. 0. (1986) Ring sequestmm: radiographic characteristics of skeletal fixation pin-tract osteomyelitis. Radio&y 158, 129. Pape H.-C., Dwenger A., Regel G. et al. (1991) Does intramedullary femoral nailing have an intluence on lung function in case of additional lung contusion and severe hemorrhagic shock? A sheep model. Unfulkhirurg 94, 381. Rush F. (1984) Intramedullary fixation. In: GaJaxo C. B. S. (ed) R+rci~les of Fracture ldmugemenf. Edinburgh: Churchill Livingstone, 101. Soldner E. (1990) Die Veniegelungsnagelung in Kombination mit dem Thoraxtrauma. Abstract ‘20 Jahre Verriegelungsnagelung’, Frankfurt am Main, 28-30 September 1990. Thompson F., O’Beime J., Gallagher J. et al. (1985) Fractures of the femoral shaft treated by plating. lnjuy 16,535. Wenda K., Ritter H., Ahlers J. et al. (1990) Detection and e#ects of bone marrow intravasation during operations in the region of the femoral cavity. Unfa~khinrrg 93, 56. Widal J. (1980) La fixufion e&me d’&@run. Geneve: Diffinco S. A. Paper accepted
7 April 1992.
Requestsfor reprints should be addressed to: P. L. Broos, Department of Traurnatology and Emergency Surgery, U.Z. Gasthuisberg, Herestraat 49, B-3000 Leuven, Belgium.