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Experience with the A.O. locking femoral nail
Injury
(1988) 19,249-253
Printed in Great Britain
249
Experience with the A.O. locking femoral nail G. P. Graham Department
and I. G. Mackie
of Traumatic
and Orthopaedic
Surgery,
Summary
A series of 21 fractures of the femur unsuitable for ordinary closed nailing have been treated using the A.O. locking femoral nail. The results obtained have been good with one case of non-union and no cases of deep infection, despite the complex nature of the fractures. The procedure is technically demanding and exposes the surgeon to the risks of ionizing radiation. Practical points to simplify the procedure and reduce exposure to radiation are discussed. INTRODUCTION THE introduction
of locking medullary nails has greatly increased the scope for medullary nailing of difficult fractures of the femur. Traction, plating and open nailing with cerclage wiring are the main alternatives, but these methods all have drawbacks. The locking nail allows stable internal fixation of virtually all fractures between the lesser trochanter and the femoral condyles, without exposing the fracture site. Cornminuted, segmental, and rotationally unstable fractures may be treated using this method, provided there is enough bone proximally and distally to accept the screws (Wiss et al.. 1986). In practice this means that the lesser trochanter and the femoral condyles should be intact (Fig. 1). Much has been written in the last few years on the advantages of closed locking nailing (Johnson et al., 1984; Kempf et al., 1985; Thoresen et al., 1985; Wiss et al., 1986). Most of the discussion on the technical aspects have tended to concentrate on the Gross and Kempf nail and little has been written about the A.O. interlocking nail. The insertion of the A.O. nail is technically demanding and depends on fluoroscopic control, which exposes the surgeon to the risks of ionizing radiation (Levin et al., 1987). We would like to present the early results of our experience with the A.O. locking nail and discuss some practical points which facilitate its use and decrease the screening time. MATERIALS
Three of the fresh fractures were open. Two of the wounds were closed at the time of nailing, after lavage with copious amounts of betadine solution. The third,
r L
c
c (
AND METHODS
A total of 21 fractures of the femur in 21 patients have been treated with the A.O. interlocking nail. All the fractures were unsuitable for treatment with a nonlocking nail and would, in the past, have been treated by other methods. The procedures were performed for fresh traumatic fractures in 19 patients and for pathological fractures in two patients. The age range was 16 to 72 years. 0
Cardiff Royal Infirmary
1988 Butterworth 002G1383/88/040249-05
& Co (Publishers) $03TJO
Ltd
Fig. 1. Comminuted. segmental and rotationally unstable fractures which are unsuitable for ordinary closed nailing may be treated with the A.O. locking nail.
250
in which there was significant skin loss, was left open and grafted 3 days later. The open fractures were operated on within 3 h of the injury. Closed fractures were put on the next available operating list. Intravenous cefuroxime was used in all cases for prophylaxis. A dose of 1.5 g was given with induction of anaesthesia and a further 750mg was given 8 h and 16 h postoperatively. All procedures were performed using general anaesthesia and endotracheal intubation. A description of the technique used is given. Following induction of anaesthesia the length of the unfractured femur is measured from the tip of the greater trochanter to the lateral joint line of the knee. A tensioned wire is inserted through the femoral condyles. This is performed under image intensification and the wire is positioned as far distally and as far posteriorly in the femoral condyles as possible. The patient is placed in the lateral position on the fracture table with the hip flexed to 90”. The femur is distracted until the distance from the greater trochanter to the joint line is equal to the other side. The femur should be parallel to the floor and the leg should be in neutral rotation to avoid rotational deformity and to allow a true lateral view of the femur to be obtained. The image intensifier is positioned so that it will swing around the femur for the anteroposterior (AP) view without impinging on the table or leg. The beam of the image intensifier should be perpendicular to the floor for the lateral view and parallel to the floor for the AP view. It should be possible to screen the whole length of the femur except the top few centimetres. The limb and the C arm of the image intensifier are draped, so the whole of the lateral aspect of the femur is accessible. A short 7-Xcm incision is made over the greater trochanter and the femur is entered via the piriform fossa. It is important that the entry point is not too far forward as this may lead to difficulty when the nail is introduced due to its curvature. The guidewire is passed across the fracture in the usual way. A selection of guidewires with slight curves on the end is often helpful, particularly in segmental fractures. The tip of the guidewire should lie as far distally as possible and should be positioned so that it lies posteriorly in the condyles. The femur is reamed 0.5mm larger than the nail to be used. The reamer should be screened across the fracture to check that the femoral cortex is not reamed out or the fracture made more cornminuted. This is particularly important in older patients (Jenkins et al., 1987). The nail is inserted keeping the proximal aiming device vertical. If the nail does not pass easily down the femur it should be reamed another 0.5 mm. The nail is inserted flush with the neck of the femur and its tip should be adjacent to the subchondral bone of the knee. For insertion of the distal screws the image intensifier is positioned so that the more proximal of the two holes appears as a perfect circle in the centre of the screen (Fig. 2~). This is made easier if the proximal aiming device has been kept vertical as the nail is introduced. When this is achieved the intensifier is locked in position. A lead shield (supplied with the nail set) with a hole cut in it is used to protect the operator’s hands from radiation when positioning the aiming device. The
Injury: the British Journal of Accident Surgery (1988) Vol. 19/No. 3
a
t
e 0
0
0 ;
0
b
@
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J
C
63 0
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Fig. 2. ~1. Image seen on the screen when the intensifier is lined up correctly. h. Image seen on the screen when using the parallax aiming device as described in the A.O. literature. c. Image seen on the screen when the aiming device is correctly lined up using the method described in the text.
operator may wear sterile lead impregnated gloves over his normal gloves to decrease further the amount of radiation absorbed (supplied by Cardiological Surgical Ltd). We have found the distal aiming device difficult to use in the way described in the A.O. literature (Figs. 2h and 3) and have modified the technique. It is essential that an assistant is available for the next steps. Using a scalpel the position of the hole is identitied and a 2-cm incision is made over it. The aiming trocar and parallax aiming device are removed from the distal aiming device, leaving only the handle and the guide sleeve (Figs. 3 and 4). This is positioned over the hole until a perfect circle is seen through it (Fig. 2~). This is made easier if the intensifier is adjusted so that any movement of the aiming device is in the same direction on the screen. Once the device is in position it is gently
251
Graham and Mackie: A.O. locking femoral nail
a
a
b b
Fj,y. 3. The distal aiming device with the parnllax aiming attachment 21ssupplied in the A.O. locking nail set. We do not use the parallax attachment.
tapped into the bone to stop it slipping. With one surgeon holding the device perfectly still the other may drill the 4.5 and 3.2mm holes using the guides provided. tap the thread and insert the screw. The more distal screw may be inserted using the direction tinder supplied, but we have found it difficult to use and therefore use the method described above for inserting the distal screw. The proximal screw is inserted using the aiming device attached to the proximal end of the nail (Fig. 5). With this technique our average total operating time is l-1.5 h. Postoperatively the patient is placed on a continuous passive motion machine initially set between O-45”. Flexion is increased by IO” per day. If no CPM machine is available the leg is placed over pillows with the knee hexed 45-60”. Active motion is started on the first postoperative day. Sutures are removed on the 14th postoperative day. If the fracture is felt to be stable the patient is allowed to mobilize non-weight-bearing on crutches as soon as he is able-usually after 3 or 4 days if there are no other injuries. For fractures which are unstable with gross comminution or ;I gap, or where the bone quality is
Fj,q. 4. The dist:ll itiming device ;IS used by the authors.
poor. a femoral cast brace is applied when the wounds are healed. The brace is kept until there is radiological evidence of commencement of union. Full unprotected weight bearing is allowed when the patient is confident to do this and there is good callus formation evident on a radiograph. RESULTS All but one of the fractures of the femur treated with the A.O. interlocking nail have proceeded to satisfactory union as assessed both clinically and radiologically. All the fractures healed with callus. Due to the difficulty in distinguishing union and non-union clinically following femoral nailing. radiological consolidation of the fracture was taken as evidence of union. Callus was seen as early as 5 weeks and all except one fracture united within 20 weeks. The fracture which did not unite initially was in a multiply injured patient with a cornminuted open fracture of the distal femur where there was a gap between the bone fragments. This frncturc was unstable in the varus/valgus plane due to the play in the distal screws (XC below). The fracture was tinally bone grafted leaving the nail in G/u. There have been no mnjor intraoperative problems. In one case the fracture had to be opened as ;I piece of bone had lodged in the medullary canal of the distal
252
Fig. 5. The proximal aiming device attached to the nail.
and the guidewire could not be passed. This was removed through a small incision. There have been no cases of deep infection despite three of the fractures being open. Superficial wound infection at the entry site has not been a major problem and in the two patients in whom it did occur the infection settled after a short course of antibiotics. None of the three open wounds became infected. All wounds were healed at 2 weeks when the sutures were removed. All patients except the one who went on to nonunion have recovered a full range of movement in the affected knee and hip. The range of movement was measured by comparison with the other leg. Knee stiffness has been an initial problem in the patients who have not been put on to CPM machines postoperatively, but full function has returned in all cases by the time of radiological union. The patient who went on to non-union has only recently had his bone graft and it is too early to tell how much movement he will recover. One of the early cases was nailed with the leg in slight external rotation and has developed a 15” external rotation deformity which is noticeable when she walks. This problem has been avoided since then by attention to the way the leg is set up on the fracture table. There have been no leg length discrepancies of more than 5mm. Three of the patients have complained of discomfort in the buttock when they flex their hip due to prominence of the proximal end of the nail. This can be avoided by ensuring the nail is inserted flush with the piriform fossa. One patient has complained of pain at the lower screw site due to prominence of one of the screws. In two cases where the fracture was very distal it was noticed postoperatively that the fracture was unstable in the valgus/varus plane, despite the fact that the femur was nailed straight. The deformity produced was mild and was corrected in one case using a femoral cast brace. The other case went on to non-union and is discussed below. fragment
DISCUSSION
The advantages of closed locking nailing are well recognized. The benefits to the patient are great but the operation is technically demanding and exposes the
Injury:
the British Journal
of Accident
Surgery
(.1988) Vol. 19/No. 3
surgeon to the risks of ionizing radiation. The techniques described above have been found to make the operation easier and quicker, and to decrease the screening time. We have found the lateral position to be the most satisfactory. Although it is more time consuming to set the patient up in this position, it is in our view preferable to the supine position. Problems may arise in patients with short fat thighs who have proximal fractures of the femur, as it may be difficult to see the top of the femur with the intensifier. This difficulty can usually be overcome by tipping the intensifier towards the buttock to gain an oblique view which is adequate. Many American authors prefer the supine position. Its major disadvantage is that access may be limited at the upper end of the femur. The leg has to be adducted maximally in order to gain access to the piriform fossa and to avoid impingement of the reamers and nail against the pelvis. It is, however, easier to screen a very proximal fracture with the patient in the supine position. Some authors have reported leg length discrepancies and rotational deformities as complications of locking nailing. Shortening of the femur can be avoided if the length of the intact femur is measured and the fracture nailed at the correct length. Despite the fact that this may leave a gap we have had a problem with non-union in only one case. Rotation must be carefully controlled during the setting up of the patient as rotational deformities are impossible to correct without removing the screws. Most authorities are now in favour of the piriform fossa as the point of entry for the nail. The bone at this site is stronger than in the trochanter and it gives direct access to the medullary cavity. Because of the curvature of the nail the point of entry should be slightly posterior to the piriform fossa to allow the nail to follow the curve of the femur. In one case we made our point of entry too far forward and the nail would not pass down the femur until it had been over-reamed by 3mm. The entry point should not be too medial as there have been reports of fracture of the neck of the femur secondary to femoral nailing where the entry point was medially placed. The position of the guidewire is important. Its tip should lie as far distally as possible and it should be posterior in the condyles in order to avoid reaming out the front of the femur, particularly in older people with porotic bone. The reamer should be screened across the fracture each time it is passed, as it is possible for the reamer to penetrate the femur or for the guidewire to jump out of the distal femur, particularly when the fracture is very distal (Jenkins et al., 1987). When inserting the distal screws we have found in common with many American authors that the freehand method of aiming is the most satisfactory. We do not use the parallax aiming device supplied with the nail as it is difficult to use and it is quicker to use the handled guide alone (Fig. 3). It is important that there is an assistant to hold the aiming device. Positioning the aiming device over the hole is made easier if the skin incision is generous. However, the most valuable single factor is to set up the image intensifier so that the image of the femur is horizontal and any movement of the aiming device is in the same direction on the screen.
Graham and Mackie: A.O. locking femoral nail
253
This cuts out much of the difficulty in working out which way to move the device when centring it over the hole. We have found in the case of distal fractures which rely on the screws to hold their position that the A.O. nail allows a degree of valgus/varus movement at the fracture site. This is because the distal screws are not a perfect fit in the nail holes and therefore allow movement. The problem may be overcome by putting the patient in a femoral cast brace. The amount of radiation to which the surgeon is exposed during closed locking nailing is small but quantifiable. Levin et al. (1987) found that during interlocking nailing of the femur with the Gross and Kempf nail the average total screening time for the introduction of the nail and distal screws was 12~6min (3.1-31.4 min). The average dose of radiation to the dominant hand was O-0252 msieverts (2.52 mRems)/ min while introducing the nail and 0.0329mSieverts (3.29 mRems)/min while inserting the distal screws. During the procedure they found the average dose of radiation to the neck to be 0.0087mSieverts (0*87mRems)/min of deep radiation and O-01 msieverts (1.0 mRems)/min of shallow exposure. Our average total screening time for this procedure using the A.O. nail is 7min (5-15 min) which compares favourably with their results using the Gross and Kempf nail. These levels of radiation exposure are well below the guidelines laid down by the National Radiation Protection Board of 50 mSieverts/year to the whole body and 50OmSieverts/year to the skin. However, all possible precautions should be taken to reduce to a minimum the amount of radiation to which staff are exposed as these levels are only arbitrary and are at present under review (National Radiological Protection Board, 1987). Apart from keeping the screening time to a minimum other precautions should be taken. The surgeons and theatre staff should all wear protective lead aprons and should be as far away from the intensifier as possible when screening is in progress. Distance from the tube is important as radiation decreases with distance according to the inverse square law. Giachino and Chieng (1980) in a study on cadaver hips found that when the surgeon was 45.7 cm (18 in) away from the specimen the amount of radiation absorbed was reduced considerably. This was supported by Dosch et al. (1983) who also found that during interlocking nailing, the use of an image intensifier with a memory cuts down the screening time by more than 50 per cent. Modern
Requests Newport
fur reprinrsshould he addressed tot Mr Road,
Cardiff
CF2
ISZ.
G. P. Graham,
intensifiers allow the beam to be coned down accurately, thus reducing radiation scatter. The use of the lead shield which is supplied with the A.O. nail and the use of lead impregnated gloves further cuts down radiation absorbed by the surgeon. In conclusion the A.O. interlocking nail is an effective method of treatment for the majority of fractures of the femur which are unsuitable for ordinary closed nailing. The results from this series are very good, particularly when the severity of the fractures is considered. We have found that by modifying the technique of insertion the procedure may be simplified and the screening time reduced.
REFERENCES
Dosch J. C., Dupuis M. and Beck G. (1983) Strahlungsmessungen bei verriegelungsnagelungen. Hefte Unfallheilk. 161, 36. Giachino A. A. and Cheng M. (1980) Irradiation of the surgeon during pinning of femoral fractures. J. Bone Joint Surg. 62B. 227. Jenkins N. H.. Mintowt-Czyz W. J., Graham G. P. et al. (1987) New problems in old bones: closed nailing of the femoral shaft. fnjury 18, 274. Johnson K. D., Johnston D. W. C. and Parker B. (1984) Comminuted femoral shaft fractures: treatment by roller traction, cerclage wires and intramedullary nail, or an interlocking intramedullary nail. J. Bone Joint Surg. 66A, 1222. Kempf I.,
Gross A. and Beck G. (1985) Closed locked intramedullary nailing. It’s application to comminuted fractures of the femur. J. Bone Joint Surg. 67A, 709. Levin P. E., Schoen R. W. Jr. and Browner B. D. (1987) Radiation exposure to the surgeon during closed interlocking intramedullary nailing. J. Bone Joint Surg. 69A, 761. National Radiation Protection Board (1987) Statement from the 1987 Como meeting of the International Commission on Radiological Protection. Radiological Protection Bulletin (supplement), No. 86. Thoresen B. O., Alho A., Ekeland A. et al. (1985) Interlocking intramedullary nailing in femoral shaft fractures. J. Bone Joint Surg. 67A, 1313. Wiss D. A., Fleming C. H., Matta J. M. et al. (1986) Comminuted and rotationally unstable fractures of the femur treated with an interlocking nail. C/in. Orthop. 212,
35.
Paper accepted 20 November
Department
of Traumatic
and Orthopaedic
1987.
Surgery, Cardiff
Royal Infirmary,
(1988) 19,249-253
Printed in Great Britain
249
Experience with the A.O. locking femoral nail G. P. Graham Department
and I. G. Mackie
of Traumatic
and Orthopaedic
Surgery,
Summary
A series of 21 fractures of the femur unsuitable for ordinary closed nailing have been treated using the A.O. locking femoral nail. The results obtained have been good with one case of non-union and no cases of deep infection, despite the complex nature of the fractures. The procedure is technically demanding and exposes the surgeon to the risks of ionizing radiation. Practical points to simplify the procedure and reduce exposure to radiation are discussed. INTRODUCTION THE introduction
of locking medullary nails has greatly increased the scope for medullary nailing of difficult fractures of the femur. Traction, plating and open nailing with cerclage wiring are the main alternatives, but these methods all have drawbacks. The locking nail allows stable internal fixation of virtually all fractures between the lesser trochanter and the femoral condyles, without exposing the fracture site. Cornminuted, segmental, and rotationally unstable fractures may be treated using this method, provided there is enough bone proximally and distally to accept the screws (Wiss et al.. 1986). In practice this means that the lesser trochanter and the femoral condyles should be intact (Fig. 1). Much has been written in the last few years on the advantages of closed locking nailing (Johnson et al., 1984; Kempf et al., 1985; Thoresen et al., 1985; Wiss et al., 1986). Most of the discussion on the technical aspects have tended to concentrate on the Gross and Kempf nail and little has been written about the A.O. interlocking nail. The insertion of the A.O. nail is technically demanding and depends on fluoroscopic control, which exposes the surgeon to the risks of ionizing radiation (Levin et al., 1987). We would like to present the early results of our experience with the A.O. locking nail and discuss some practical points which facilitate its use and decrease the screening time. MATERIALS
Three of the fresh fractures were open. Two of the wounds were closed at the time of nailing, after lavage with copious amounts of betadine solution. The third,
r L
c
c (
AND METHODS
A total of 21 fractures of the femur in 21 patients have been treated with the A.O. interlocking nail. All the fractures were unsuitable for treatment with a nonlocking nail and would, in the past, have been treated by other methods. The procedures were performed for fresh traumatic fractures in 19 patients and for pathological fractures in two patients. The age range was 16 to 72 years. 0
Cardiff Royal Infirmary
1988 Butterworth 002G1383/88/040249-05
& Co (Publishers) $03TJO
Ltd
Fig. 1. Comminuted. segmental and rotationally unstable fractures which are unsuitable for ordinary closed nailing may be treated with the A.O. locking nail.
250
in which there was significant skin loss, was left open and grafted 3 days later. The open fractures were operated on within 3 h of the injury. Closed fractures were put on the next available operating list. Intravenous cefuroxime was used in all cases for prophylaxis. A dose of 1.5 g was given with induction of anaesthesia and a further 750mg was given 8 h and 16 h postoperatively. All procedures were performed using general anaesthesia and endotracheal intubation. A description of the technique used is given. Following induction of anaesthesia the length of the unfractured femur is measured from the tip of the greater trochanter to the lateral joint line of the knee. A tensioned wire is inserted through the femoral condyles. This is performed under image intensification and the wire is positioned as far distally and as far posteriorly in the femoral condyles as possible. The patient is placed in the lateral position on the fracture table with the hip flexed to 90”. The femur is distracted until the distance from the greater trochanter to the joint line is equal to the other side. The femur should be parallel to the floor and the leg should be in neutral rotation to avoid rotational deformity and to allow a true lateral view of the femur to be obtained. The image intensifier is positioned so that it will swing around the femur for the anteroposterior (AP) view without impinging on the table or leg. The beam of the image intensifier should be perpendicular to the floor for the lateral view and parallel to the floor for the AP view. It should be possible to screen the whole length of the femur except the top few centimetres. The limb and the C arm of the image intensifier are draped, so the whole of the lateral aspect of the femur is accessible. A short 7-Xcm incision is made over the greater trochanter and the femur is entered via the piriform fossa. It is important that the entry point is not too far forward as this may lead to difficulty when the nail is introduced due to its curvature. The guidewire is passed across the fracture in the usual way. A selection of guidewires with slight curves on the end is often helpful, particularly in segmental fractures. The tip of the guidewire should lie as far distally as possible and should be positioned so that it lies posteriorly in the condyles. The femur is reamed 0.5mm larger than the nail to be used. The reamer should be screened across the fracture to check that the femoral cortex is not reamed out or the fracture made more cornminuted. This is particularly important in older patients (Jenkins et al., 1987). The nail is inserted keeping the proximal aiming device vertical. If the nail does not pass easily down the femur it should be reamed another 0.5 mm. The nail is inserted flush with the neck of the femur and its tip should be adjacent to the subchondral bone of the knee. For insertion of the distal screws the image intensifier is positioned so that the more proximal of the two holes appears as a perfect circle in the centre of the screen (Fig. 2~). This is made easier if the proximal aiming device has been kept vertical as the nail is introduced. When this is achieved the intensifier is locked in position. A lead shield (supplied with the nail set) with a hole cut in it is used to protect the operator’s hands from radiation when positioning the aiming device. The
Injury: the British Journal of Accident Surgery (1988) Vol. 19/No. 3
a
t
e 0
0
0 ;
0
b
@
I
J
C
63 0
I
I
Fig. 2. ~1. Image seen on the screen when the intensifier is lined up correctly. h. Image seen on the screen when using the parallax aiming device as described in the A.O. literature. c. Image seen on the screen when the aiming device is correctly lined up using the method described in the text.
operator may wear sterile lead impregnated gloves over his normal gloves to decrease further the amount of radiation absorbed (supplied by Cardiological Surgical Ltd). We have found the distal aiming device difficult to use in the way described in the A.O. literature (Figs. 2h and 3) and have modified the technique. It is essential that an assistant is available for the next steps. Using a scalpel the position of the hole is identitied and a 2-cm incision is made over it. The aiming trocar and parallax aiming device are removed from the distal aiming device, leaving only the handle and the guide sleeve (Figs. 3 and 4). This is positioned over the hole until a perfect circle is seen through it (Fig. 2~). This is made easier if the intensifier is adjusted so that any movement of the aiming device is in the same direction on the screen. Once the device is in position it is gently
251
Graham and Mackie: A.O. locking femoral nail
a
a
b b
Fj,y. 3. The distal aiming device with the parnllax aiming attachment 21ssupplied in the A.O. locking nail set. We do not use the parallax attachment.
tapped into the bone to stop it slipping. With one surgeon holding the device perfectly still the other may drill the 4.5 and 3.2mm holes using the guides provided. tap the thread and insert the screw. The more distal screw may be inserted using the direction tinder supplied, but we have found it difficult to use and therefore use the method described above for inserting the distal screw. The proximal screw is inserted using the aiming device attached to the proximal end of the nail (Fig. 5). With this technique our average total operating time is l-1.5 h. Postoperatively the patient is placed on a continuous passive motion machine initially set between O-45”. Flexion is increased by IO” per day. If no CPM machine is available the leg is placed over pillows with the knee hexed 45-60”. Active motion is started on the first postoperative day. Sutures are removed on the 14th postoperative day. If the fracture is felt to be stable the patient is allowed to mobilize non-weight-bearing on crutches as soon as he is able-usually after 3 or 4 days if there are no other injuries. For fractures which are unstable with gross comminution or ;I gap, or where the bone quality is
Fj,q. 4. The dist:ll itiming device ;IS used by the authors.
poor. a femoral cast brace is applied when the wounds are healed. The brace is kept until there is radiological evidence of commencement of union. Full unprotected weight bearing is allowed when the patient is confident to do this and there is good callus formation evident on a radiograph. RESULTS All but one of the fractures of the femur treated with the A.O. interlocking nail have proceeded to satisfactory union as assessed both clinically and radiologically. All the fractures healed with callus. Due to the difficulty in distinguishing union and non-union clinically following femoral nailing. radiological consolidation of the fracture was taken as evidence of union. Callus was seen as early as 5 weeks and all except one fracture united within 20 weeks. The fracture which did not unite initially was in a multiply injured patient with a cornminuted open fracture of the distal femur where there was a gap between the bone fragments. This frncturc was unstable in the varus/valgus plane due to the play in the distal screws (XC below). The fracture was tinally bone grafted leaving the nail in G/u. There have been no mnjor intraoperative problems. In one case the fracture had to be opened as ;I piece of bone had lodged in the medullary canal of the distal
252
Fig. 5. The proximal aiming device attached to the nail.
and the guidewire could not be passed. This was removed through a small incision. There have been no cases of deep infection despite three of the fractures being open. Superficial wound infection at the entry site has not been a major problem and in the two patients in whom it did occur the infection settled after a short course of antibiotics. None of the three open wounds became infected. All wounds were healed at 2 weeks when the sutures were removed. All patients except the one who went on to nonunion have recovered a full range of movement in the affected knee and hip. The range of movement was measured by comparison with the other leg. Knee stiffness has been an initial problem in the patients who have not been put on to CPM machines postoperatively, but full function has returned in all cases by the time of radiological union. The patient who went on to non-union has only recently had his bone graft and it is too early to tell how much movement he will recover. One of the early cases was nailed with the leg in slight external rotation and has developed a 15” external rotation deformity which is noticeable when she walks. This problem has been avoided since then by attention to the way the leg is set up on the fracture table. There have been no leg length discrepancies of more than 5mm. Three of the patients have complained of discomfort in the buttock when they flex their hip due to prominence of the proximal end of the nail. This can be avoided by ensuring the nail is inserted flush with the piriform fossa. One patient has complained of pain at the lower screw site due to prominence of one of the screws. In two cases where the fracture was very distal it was noticed postoperatively that the fracture was unstable in the valgus/varus plane, despite the fact that the femur was nailed straight. The deformity produced was mild and was corrected in one case using a femoral cast brace. The other case went on to non-union and is discussed below. fragment
DISCUSSION
The advantages of closed locking nailing are well recognized. The benefits to the patient are great but the operation is technically demanding and exposes the
Injury:
the British Journal
of Accident
Surgery
(.1988) Vol. 19/No. 3
surgeon to the risks of ionizing radiation. The techniques described above have been found to make the operation easier and quicker, and to decrease the screening time. We have found the lateral position to be the most satisfactory. Although it is more time consuming to set the patient up in this position, it is in our view preferable to the supine position. Problems may arise in patients with short fat thighs who have proximal fractures of the femur, as it may be difficult to see the top of the femur with the intensifier. This difficulty can usually be overcome by tipping the intensifier towards the buttock to gain an oblique view which is adequate. Many American authors prefer the supine position. Its major disadvantage is that access may be limited at the upper end of the femur. The leg has to be adducted maximally in order to gain access to the piriform fossa and to avoid impingement of the reamers and nail against the pelvis. It is, however, easier to screen a very proximal fracture with the patient in the supine position. Some authors have reported leg length discrepancies and rotational deformities as complications of locking nailing. Shortening of the femur can be avoided if the length of the intact femur is measured and the fracture nailed at the correct length. Despite the fact that this may leave a gap we have had a problem with non-union in only one case. Rotation must be carefully controlled during the setting up of the patient as rotational deformities are impossible to correct without removing the screws. Most authorities are now in favour of the piriform fossa as the point of entry for the nail. The bone at this site is stronger than in the trochanter and it gives direct access to the medullary cavity. Because of the curvature of the nail the point of entry should be slightly posterior to the piriform fossa to allow the nail to follow the curve of the femur. In one case we made our point of entry too far forward and the nail would not pass down the femur until it had been over-reamed by 3mm. The entry point should not be too medial as there have been reports of fracture of the neck of the femur secondary to femoral nailing where the entry point was medially placed. The position of the guidewire is important. Its tip should lie as far distally as possible and it should be posterior in the condyles in order to avoid reaming out the front of the femur, particularly in older people with porotic bone. The reamer should be screened across the fracture each time it is passed, as it is possible for the reamer to penetrate the femur or for the guidewire to jump out of the distal femur, particularly when the fracture is very distal (Jenkins et al., 1987). When inserting the distal screws we have found in common with many American authors that the freehand method of aiming is the most satisfactory. We do not use the parallax aiming device supplied with the nail as it is difficult to use and it is quicker to use the handled guide alone (Fig. 3). It is important that there is an assistant to hold the aiming device. Positioning the aiming device over the hole is made easier if the skin incision is generous. However, the most valuable single factor is to set up the image intensifier so that the image of the femur is horizontal and any movement of the aiming device is in the same direction on the screen.
Graham and Mackie: A.O. locking femoral nail
253
This cuts out much of the difficulty in working out which way to move the device when centring it over the hole. We have found in the case of distal fractures which rely on the screws to hold their position that the A.O. nail allows a degree of valgus/varus movement at the fracture site. This is because the distal screws are not a perfect fit in the nail holes and therefore allow movement. The problem may be overcome by putting the patient in a femoral cast brace. The amount of radiation to which the surgeon is exposed during closed locking nailing is small but quantifiable. Levin et al. (1987) found that during interlocking nailing of the femur with the Gross and Kempf nail the average total screening time for the introduction of the nail and distal screws was 12~6min (3.1-31.4 min). The average dose of radiation to the dominant hand was O-0252 msieverts (2.52 mRems)/ min while introducing the nail and 0.0329mSieverts (3.29 mRems)/min while inserting the distal screws. During the procedure they found the average dose of radiation to the neck to be 0.0087mSieverts (0*87mRems)/min of deep radiation and O-01 msieverts (1.0 mRems)/min of shallow exposure. Our average total screening time for this procedure using the A.O. nail is 7min (5-15 min) which compares favourably with their results using the Gross and Kempf nail. These levels of radiation exposure are well below the guidelines laid down by the National Radiation Protection Board of 50 mSieverts/year to the whole body and 50OmSieverts/year to the skin. However, all possible precautions should be taken to reduce to a minimum the amount of radiation to which staff are exposed as these levels are only arbitrary and are at present under review (National Radiological Protection Board, 1987). Apart from keeping the screening time to a minimum other precautions should be taken. The surgeons and theatre staff should all wear protective lead aprons and should be as far away from the intensifier as possible when screening is in progress. Distance from the tube is important as radiation decreases with distance according to the inverse square law. Giachino and Chieng (1980) in a study on cadaver hips found that when the surgeon was 45.7 cm (18 in) away from the specimen the amount of radiation absorbed was reduced considerably. This was supported by Dosch et al. (1983) who also found that during interlocking nailing, the use of an image intensifier with a memory cuts down the screening time by more than 50 per cent. Modern
Requests Newport
fur reprinrsshould he addressed tot Mr Road,
Cardiff
CF2
ISZ.
G. P. Graham,
intensifiers allow the beam to be coned down accurately, thus reducing radiation scatter. The use of the lead shield which is supplied with the A.O. nail and the use of lead impregnated gloves further cuts down radiation absorbed by the surgeon. In conclusion the A.O. interlocking nail is an effective method of treatment for the majority of fractures of the femur which are unsuitable for ordinary closed nailing. The results from this series are very good, particularly when the severity of the fractures is considered. We have found that by modifying the technique of insertion the procedure may be simplified and the screening time reduced.
REFERENCES
Dosch J. C., Dupuis M. and Beck G. (1983) Strahlungsmessungen bei verriegelungsnagelungen. Hefte Unfallheilk. 161, 36. Giachino A. A. and Cheng M. (1980) Irradiation of the surgeon during pinning of femoral fractures. J. Bone Joint Surg. 62B. 227. Jenkins N. H.. Mintowt-Czyz W. J., Graham G. P. et al. (1987) New problems in old bones: closed nailing of the femoral shaft. fnjury 18, 274. Johnson K. D., Johnston D. W. C. and Parker B. (1984) Comminuted femoral shaft fractures: treatment by roller traction, cerclage wires and intramedullary nail, or an interlocking intramedullary nail. J. Bone Joint Surg. 66A, 1222. Kempf I.,
Gross A. and Beck G. (1985) Closed locked intramedullary nailing. It’s application to comminuted fractures of the femur. J. Bone Joint Surg. 67A, 709. Levin P. E., Schoen R. W. Jr. and Browner B. D. (1987) Radiation exposure to the surgeon during closed interlocking intramedullary nailing. J. Bone Joint Surg. 69A, 761. National Radiation Protection Board (1987) Statement from the 1987 Como meeting of the International Commission on Radiological Protection. Radiological Protection Bulletin (supplement), No. 86. Thoresen B. O., Alho A., Ekeland A. et al. (1985) Interlocking intramedullary nailing in femoral shaft fractures. J. Bone Joint Surg. 67A, 1313. Wiss D. A., Fleming C. H., Matta J. M. et al. (1986) Comminuted and rotationally unstable fractures of the femur treated with an interlocking nail. C/in. Orthop. 212,
35.
Paper accepted 20 November
Department
of Traumatic
and Orthopaedic
1987.
Surgery, Cardiff
Royal Infirmary,