- Email: [email protected]
Treatment of delayed- and non-union of fractures using pulsed electromagnetic fields
Treatment of delayed- and non-union of fractures using pulsed electromagnetic fields D.J. Colson, J.P. Browett *, N.J. Fiddiant and B. Watson Department of Medical Electronics, St Bartholomew’s Hospital, London ECl, Bartholomew’s and Homerton Hospitals, London ECl, UK and TPoole and Christchurch Dorset, UK Keceivcd
December
1987,
accepted
January
UK; *St Hospitals,
1988
ABSTRACT A prospective series of 32 consecutive patients, with 33 long-bone fractures suffering from delayed- or non-union were treated by pulsed electromagnetic fields (PEMF) or by PEMF with surgery. The management regime for the PEMF treatment was simpler and less rigid than that reported by Bassett et al.” and our stimulation waveform was also &$erent. Nineteen fractures (100%) treated with surgery and PEMF united within nine months of the commencement of PEMF treatment. Fourteen fractures were treated with PEMF alone. Twelve (86%) united within ten months and two failed to unite. The results of this study suggest that the stimulating waveform is less critical than is claimed by Bassett et al. and that a simpler- and easier management regime&r PEMF treatment can be just as effective. Alternatively PEMF may have no @ect onfracture healing. Keywords:
Electromagnetic
fields,
fractures,
non-united
INTRODUCTION There have been many reports on the use of direct current or pulsed electromagnetic fields (PEMF) in the treatment of fractures suffering from delayedor non-union. There is substantial anecdotal evidence supporting the use of these treatments, but pending the outcome of double-blind trials which we and their efficacy cannot be others arc undertaking, Due to the weight of anecdotal considered proven. evidence, however, many hospitals are using some form of electrical stimulation as a routine treatment for fractures suffering. from delayedor non-union whilst the results of trials are awaited. For a review of the literature and clinical applications of PEMF scv Barker and Lunt’. In St Bartholomew’s Hospital, London, UK, PEMF treatment has been chosen, because of its non-invasive nature, in preference to direct current that the techniques. Bassett el al. z3 have claimed stimulating waveform is critical and that the patient management must be carefully controlled for optimal results. Their stimulating waveform consists of a pulse train of quasi-rectangular pulses 200 pus wide lasting for about 5 ms. The pulse train itself is pulsed at lo-15 Hz. ‘The peak magnetic field strength is about 1.5 mT. Their management regime is complex, and coil size and placement are regarded as critical. X-rays are taken every 4-6 weeks. Axial compression exercises for tibia1 fractures are started when there is an increase in radiographic density of the tissues in the gap between the bone ends, and are gradually built up until partial weight bearing is introduced. We have, however, used a different stimulation waveform from that used by
Correspondencr to Dr D.J. C&on Rrprints from Mr J.P. Browett, St Bartholomew’s EC]. LIE;
I(‘: 1988 Butterworth &kCo [Publishers) 0l41~5425/88/040301~~4 $03.00
Hospital.
London
others’,” and a simpler patient management regime. The results of treatment of a prospective series of 32 consecutive patients with non-united long-bone fractures are presented, together with our conclusions on several aspects of the treatment. PATIENTS
AND METHODS
The PEMF unit and treatment
regime
At St Bartholomew’s Hospital, the routine use of PEMF treatment has been limited to patients with difficult fractures, usually of at least five months duration. Fractures of less than five months may be treated if it is felt that delayed or non-union would be the likely outcome of conventional treatment5. Surgical intervention is carried out when the surgeon feels that there is little chance of the fracture uniting, such as when there is sclerotic rounding of the bone ends indicative of a synovial joint; a large gap between the bone ends; or gross movement at the fracture site which cannot be overcome by conservative means. In these cases, PEMF treatment may be used as an adjunct to surgery. Our PEMF unit produces a peak magnetic field of 0.8 mT at a point midway on the axis between two coils (Figure I). The stimulating waveform consists of a train of five quasi-rectangular pulses, each of 300 ps duration, and separated by 1500 ps. The pulse train is itself pulsed at 50 Hz. The coil diameter is chosen to be equal to or greater than the diameter of the limb at the fracture site (including any cast) in order to give a reasonably uniform peak magnetic field in the region of the fracture. Using the most recent X-ray for guidance, the coils are applied to the limb, usually one medial and one lateral, and centred over the fracture site (Figure I). If the patient requires no form of immobilizing cast, a removable Plastazote splint is
Ltd J. Biomrd.
Eng. 1988. Vol. lO.July
301
8 Gauss U Figure
1 The position of PEMF treatment coils over a tibia1 fracture. The arrows indicate the direction of the magnetic field
produced made up with locating pads for the coils, which are held in place with velcro straps. If the limb is to be immobilized, the coils are attached to the cast. The patient uses the PEMF unit at home for between 12 and 15 hours a day until the fracture has united. Patients are instructed to check the coils daily with a transistor radio; interference is produced if the system is functioning correctly. Patients with lower limb fractures are kept strictly non-weight bearing until there are definite radiological signs of bridging. Then partial weight bearing is introduced and increased (within ache tolerance) as healing progresses. PEMF treatment is maintained, wherever possible, until there is full radiological and clinical evidence of union. If the fracture has not united within a year, PEMF treatment is discontinued. PATIENT
POPULATION
Thirty-two patients (nine female) with 33 fractures have completed their PEMF treatment. Their age range was from 18 to 84 years (mean 40 years). The fracture sites treated are shown in Table I. One patient with bilateral fractures of the tibiae had one
Table 1
Sites of fractures treated with PEMF
Femur Tibia Ulna Ulna/Radius Radius Humerus
4 22 1
Total
33
I 2 3
302 J. Biomcd. En,q. 1988, Vol. IO,July
f‘racture treated with PEMF and surgery and one fracture treated with PEMF alone. Nineteen of these 33 fractures had some form of surgery within the 3 months before PEMF treatment. Three required surgery during PEMF treatment for abscess drainage or for immobilization. The time between the date of the fracture and the commencement of’ PEMF treatment ranged from 3 to 120 months (mean 27 months, median 15 months). During this time the patients had undergone between one and six surgical procedures (mean 3, median 2). Five patients had active infections at the fracture site at the start of PEMF treatment and five had a history of infection. Two had had their fractures for less than nine months. One had sustained a severe compound cornminuted fracture of the left radius and ulna in a traffic accident which showed no sign of union after three months. The other had a closed spiral fracture of the right tibia which became infected four months later, after being plated. Delayed or non-union seemed the likely outcome in both cases. The other 14 fractures were treated by PEMF alone. The time between the date of fracture and the commencement of PEMF treatment ranged from 2 to 93 months (mean 25 months, median 12 months). The number of previous surgical procedures varied between zero and six, with a mean of two and a median of two. Two patients had active infection at the fracture site and two had a previous history of infection. Only one patient had a fracture of less than five months duration. This patient sustained a fracture of the lower end of the left radius in a fall and had an arthrodesis of the wrist 12 years previously following an injury. After four months of conservative treatment the fracture was still mobile and painful with no radiological signs of healing. In view of this history a delayed or non-union seemed the likely outcome, so PEMF was commenced. RESULTS All 19 fractures ( 100 %) treated by PEMF and surgery united within 9 months of the commencement of PEMF (mean and median 6 months). Twelve of the 14 fractures (86 “XJ) treated with PEMF alone united within 10 months of the commencement of treatment (mean and median 6 months). One of the failures was an open tibia1 fracture of 19 months duration in a grossly obese patient. Initial treatment had included traction followed by a cast and there had been problems with skin healing and infection at the fracture site. The patient was maintained in a cast and PEMF treatment was started. After four months there was no sign of union and it was clear that the plaster cast was failing to stabilize the fracture. PEMF treatment was discontinued and the patient put onto the waiting list for external fixation. However, the patient failed to attend and we have no record of her subsequent course. ‘l’he second failure was an overseas patient with an elephant’s foot type of non-union of the tibia of 45 months duration. He took the PEMF unit home with him, but did not check the coils. Although arrangements had been made for them to be
periodically double-checked by his local hospital, this was not done. When he finally returned to the UK 11 months later the coils were both found to be non-functional and therefore the number of hours of PEMF treatment received must be in doubt. In addition, he had also been weight-bearing. A chronic low-grade infection was present throughout most of his previous and subsequent treatment. This patient underwent excision of the non-union, plating and grafting. PEMF treatment was not resumed. A year later the union was sound. DISCUSSION We consider that the prerequisites for achieving union in difficult fractures (with or without PEMF) are: apposition of the bone ends, preferably with minimal gap and no intervening tissue; no movement at the fracture site; and patience. In the later stages of fracture healing no external callus is available and therefore recovery relies purely on medullary callus and primary bone healing’j. Obviously any significant movement at the fracture site could disrupt the bridging process. Some difficult non-united fractures will unite given apposition and immobilization, provided both patient and surgeon are prepared to wait long enough for vascularization to take place followed by bone union. PEMF treatment provides an incentive for patience and the maintenance of non-weight bearing and may well have some stimulatory effect upon vascularization or osteogenesis ‘-* . As yet, how e v er, there is no conclusive evidence to suggest that PEMF treatment is beneficial, and preliminary results from one double-blind trial have been negativeg. We have used the combined approach of surgery and PEMF when internal fixation was necessary for adequate immobilization; if there was a large gap between the bone ends or a synovial joint; if gross angulation required surgical correction; or, in some cases, when it was felt that surgery alone needed adjuvant therapy. All 19 cases treated with this combined approach went on to unite within 9 months. Definitions of delayed union, non-union and union are difficult. Some of the cases included here could be classified as delayed union in that union could be expected with the passage of time. Only difficult fractures in which the surgeon felt that there was severe doubt about the outcome were included in this study. The majority of cases presented with non-union, i.e. it was deemed that there was no prospect of eventual union. This is a subjective judgement and there is obviously some overlap between the two states. Union was said to have occurred when sound bony bridging could be seen on X-ray. The mean and median times between the commencement of PEMF and union was six months in both groups. This compares favourably with the time reported by Bassett et ~1.~ of just over five months from the cessation of PEMF at stage II healing. Our overall success with PEMF therapy has been high; 100 % for fractures treated in conjunction with surgery and 86% for fractures treated by PEMF
alone. This may be compared with the 87% reported by Bassett et aL3 for fractures treated with PEMF alone. Of our two failures, one fracture was deemed too mobile and the patient failed to attend for surgery. The other patient was weight-bearing and did not check the continued operation of the coil system. The stimulation waveform reported here is very different from that claimed by Bassett et aL2 as the only viable waveform. In contrast to the complex fitting procedure and patient management regime recommended in the same paper, our approach has been a simple one. Patient management is no different from that usually employed in St Bartholomew’s Hospital for the treatment of similar fractures which are not receiving PEMF treatment. No expert technical help is required in either fitting the coils or subsequent patient reviews. A selection of PEMF units and coils, with the magnetic field strength set up for a range ofcoil spacings, are kept in the fracture clinic ready for use. It is often claimed that the coils must be separated by their diameter to give a uniform magnetic field. In fact the coils would have to be separated by their radius (Helmholtz coils). However, coils of this size are not feasible for treating fractured limbs. Coils separated by their diameter are feasible, but it must be remembered that the resultant field is not as uniform. Any ‘critical’ values should therefore be treated with caution, especially as the limbs are not homogeneous and will therefore complicate the electrical fieIds produced. Many features of PEMF treatment may encourage fractures to unite. The importance of variables such as the stimulation waveform, coil geometry, electric and magnetic field strengths, patient management regime and the role of psychology in the treatment are, as yet, unknown and will remain so until the mechanisms involved in the treatment are fully understood. In the meantime many hospitals will continue to use PEMF. Our results suggest that the stimulating waveform is not as critical as has been claimed, and that both the stimulation waveform and the simple patient management regime we have adopted give as good a success rate in the healing of fractures as that recommended by Bassett et al.“. Whether these results are due to the effect of PEMF or to some other factor remains to be established.
ACKNOWLEDGEMENTS We gratefully acknowledge the assistance of Mr P. Byrne for suggesting the stimulating waveform. Thanks are also due to Mr K. Buffong for applying the coils to the plaster casts, and to the staff of the Orthopaedic Department at St Bartholomew’s Hospital for their assistance.
REFERENCES Barker AT, Lunt MJ. The effects of pulsed magnetic fields of the type used in the stimulation of bone fracture healing. Clin Phys Physiol Meas 1983.4:1-27.
,J, Biomed.
Lng.
1988, Vol.
lO..July
303
2. Bassett CAL, Pilla AA, Mitchell SN, et al. Repair of non-unions by pulsing electromagnetic fields. Acta O&~/J
Belgica 1978; 44: 706-24. 3. Bassett CAL, Mitchell SN,
Gaston SR. Treatment of ununited tibia1 diaphyseal fractures with pulsing electromagnetic fields. J Bone Jt Sung 1981; 63A: 51 l-23. 4. De Haas WG, Watson J, Morrison DM. Non-invasive treatment of ununited fractures of the tibia using electrical stimulation. J Bone Jt Surg 1980; 62B: 465-70. 5. Nicoll EA. Fractures of the tibia1 shaft: A survey of 705 cases. J Bone Jt Surg 1964; 46B: 373-87. 6. McKibben B. The biology of fracture healing in long bones.
304
J. Biomcd. hg.
1988, Vol. 10,July
J Bone Jt Surg 1978, 60B: 15(t62, 7. Luben RA, Cain CD, Chi-Yun Chen M, Rosen DM, Adey WR. Effects of electromagnetic stimuli on bone cells in vitro: inhibition of responses to parathyroid hormone by low-energy low-frequency fields Proc Nail Acad Sci USA 1982; 79: 4180-84. 8. Murray JC, Farndale RW. Modulations of collagen production in cultured fibroblasts by a low-frequency pulsed magnetic field. Biockim Biopkgs Acta 1985; 838: 98-105. 9. Barker AT, Dixon RA, Sharrard WJW, Sutcliffe MF. Pulsed magnetic field therapy for tibia1 non-union-Interim results of a double-blind trial. Lancet 1984; i: 994-6.
December
1987,
accepted
January
UK; *St Hospitals,
1988
ABSTRACT A prospective series of 32 consecutive patients, with 33 long-bone fractures suffering from delayed- or non-union were treated by pulsed electromagnetic fields (PEMF) or by PEMF with surgery. The management regime for the PEMF treatment was simpler and less rigid than that reported by Bassett et al.” and our stimulation waveform was also &$erent. Nineteen fractures (100%) treated with surgery and PEMF united within nine months of the commencement of PEMF treatment. Fourteen fractures were treated with PEMF alone. Twelve (86%) united within ten months and two failed to unite. The results of this study suggest that the stimulating waveform is less critical than is claimed by Bassett et al. and that a simpler- and easier management regime&r PEMF treatment can be just as effective. Alternatively PEMF may have no @ect onfracture healing. Keywords:
Electromagnetic
fields,
fractures,
non-united
INTRODUCTION There have been many reports on the use of direct current or pulsed electromagnetic fields (PEMF) in the treatment of fractures suffering from delayedor non-union. There is substantial anecdotal evidence supporting the use of these treatments, but pending the outcome of double-blind trials which we and their efficacy cannot be others arc undertaking, Due to the weight of anecdotal considered proven. evidence, however, many hospitals are using some form of electrical stimulation as a routine treatment for fractures suffering. from delayedor non-union whilst the results of trials are awaited. For a review of the literature and clinical applications of PEMF scv Barker and Lunt’. In St Bartholomew’s Hospital, London, UK, PEMF treatment has been chosen, because of its non-invasive nature, in preference to direct current that the techniques. Bassett el al. z3 have claimed stimulating waveform is critical and that the patient management must be carefully controlled for optimal results. Their stimulating waveform consists of a pulse train of quasi-rectangular pulses 200 pus wide lasting for about 5 ms. The pulse train itself is pulsed at lo-15 Hz. ‘The peak magnetic field strength is about 1.5 mT. Their management regime is complex, and coil size and placement are regarded as critical. X-rays are taken every 4-6 weeks. Axial compression exercises for tibia1 fractures are started when there is an increase in radiographic density of the tissues in the gap between the bone ends, and are gradually built up until partial weight bearing is introduced. We have, however, used a different stimulation waveform from that used by
Correspondencr to Dr D.J. C&on Rrprints from Mr J.P. Browett, St Bartholomew’s EC]. LIE;
I(‘: 1988 Butterworth &kCo [Publishers) 0l41~5425/88/040301~~4 $03.00
Hospital.
London
others’,” and a simpler patient management regime. The results of treatment of a prospective series of 32 consecutive patients with non-united long-bone fractures are presented, together with our conclusions on several aspects of the treatment. PATIENTS
AND METHODS
The PEMF unit and treatment
regime
At St Bartholomew’s Hospital, the routine use of PEMF treatment has been limited to patients with difficult fractures, usually of at least five months duration. Fractures of less than five months may be treated if it is felt that delayed or non-union would be the likely outcome of conventional treatment5. Surgical intervention is carried out when the surgeon feels that there is little chance of the fracture uniting, such as when there is sclerotic rounding of the bone ends indicative of a synovial joint; a large gap between the bone ends; or gross movement at the fracture site which cannot be overcome by conservative means. In these cases, PEMF treatment may be used as an adjunct to surgery. Our PEMF unit produces a peak magnetic field of 0.8 mT at a point midway on the axis between two coils (Figure I). The stimulating waveform consists of a train of five quasi-rectangular pulses, each of 300 ps duration, and separated by 1500 ps. The pulse train is itself pulsed at 50 Hz. The coil diameter is chosen to be equal to or greater than the diameter of the limb at the fracture site (including any cast) in order to give a reasonably uniform peak magnetic field in the region of the fracture. Using the most recent X-ray for guidance, the coils are applied to the limb, usually one medial and one lateral, and centred over the fracture site (Figure I). If the patient requires no form of immobilizing cast, a removable Plastazote splint is
Ltd J. Biomrd.
Eng. 1988. Vol. lO.July
301
8 Gauss U Figure
1 The position of PEMF treatment coils over a tibia1 fracture. The arrows indicate the direction of the magnetic field
produced made up with locating pads for the coils, which are held in place with velcro straps. If the limb is to be immobilized, the coils are attached to the cast. The patient uses the PEMF unit at home for between 12 and 15 hours a day until the fracture has united. Patients are instructed to check the coils daily with a transistor radio; interference is produced if the system is functioning correctly. Patients with lower limb fractures are kept strictly non-weight bearing until there are definite radiological signs of bridging. Then partial weight bearing is introduced and increased (within ache tolerance) as healing progresses. PEMF treatment is maintained, wherever possible, until there is full radiological and clinical evidence of union. If the fracture has not united within a year, PEMF treatment is discontinued. PATIENT
POPULATION
Thirty-two patients (nine female) with 33 fractures have completed their PEMF treatment. Their age range was from 18 to 84 years (mean 40 years). The fracture sites treated are shown in Table I. One patient with bilateral fractures of the tibiae had one
Table 1
Sites of fractures treated with PEMF
Femur Tibia Ulna Ulna/Radius Radius Humerus
4 22 1
Total
33
I 2 3
302 J. Biomcd. En,q. 1988, Vol. IO,July
f‘racture treated with PEMF and surgery and one fracture treated with PEMF alone. Nineteen of these 33 fractures had some form of surgery within the 3 months before PEMF treatment. Three required surgery during PEMF treatment for abscess drainage or for immobilization. The time between the date of the fracture and the commencement of’ PEMF treatment ranged from 3 to 120 months (mean 27 months, median 15 months). During this time the patients had undergone between one and six surgical procedures (mean 3, median 2). Five patients had active infections at the fracture site at the start of PEMF treatment and five had a history of infection. Two had had their fractures for less than nine months. One had sustained a severe compound cornminuted fracture of the left radius and ulna in a traffic accident which showed no sign of union after three months. The other had a closed spiral fracture of the right tibia which became infected four months later, after being plated. Delayed or non-union seemed the likely outcome in both cases. The other 14 fractures were treated by PEMF alone. The time between the date of fracture and the commencement of PEMF treatment ranged from 2 to 93 months (mean 25 months, median 12 months). The number of previous surgical procedures varied between zero and six, with a mean of two and a median of two. Two patients had active infection at the fracture site and two had a previous history of infection. Only one patient had a fracture of less than five months duration. This patient sustained a fracture of the lower end of the left radius in a fall and had an arthrodesis of the wrist 12 years previously following an injury. After four months of conservative treatment the fracture was still mobile and painful with no radiological signs of healing. In view of this history a delayed or non-union seemed the likely outcome, so PEMF was commenced. RESULTS All 19 fractures ( 100 %) treated by PEMF and surgery united within 9 months of the commencement of PEMF (mean and median 6 months). Twelve of the 14 fractures (86 “XJ) treated with PEMF alone united within 10 months of the commencement of treatment (mean and median 6 months). One of the failures was an open tibia1 fracture of 19 months duration in a grossly obese patient. Initial treatment had included traction followed by a cast and there had been problems with skin healing and infection at the fracture site. The patient was maintained in a cast and PEMF treatment was started. After four months there was no sign of union and it was clear that the plaster cast was failing to stabilize the fracture. PEMF treatment was discontinued and the patient put onto the waiting list for external fixation. However, the patient failed to attend and we have no record of her subsequent course. ‘l’he second failure was an overseas patient with an elephant’s foot type of non-union of the tibia of 45 months duration. He took the PEMF unit home with him, but did not check the coils. Although arrangements had been made for them to be
periodically double-checked by his local hospital, this was not done. When he finally returned to the UK 11 months later the coils were both found to be non-functional and therefore the number of hours of PEMF treatment received must be in doubt. In addition, he had also been weight-bearing. A chronic low-grade infection was present throughout most of his previous and subsequent treatment. This patient underwent excision of the non-union, plating and grafting. PEMF treatment was not resumed. A year later the union was sound. DISCUSSION We consider that the prerequisites for achieving union in difficult fractures (with or without PEMF) are: apposition of the bone ends, preferably with minimal gap and no intervening tissue; no movement at the fracture site; and patience. In the later stages of fracture healing no external callus is available and therefore recovery relies purely on medullary callus and primary bone healing’j. Obviously any significant movement at the fracture site could disrupt the bridging process. Some difficult non-united fractures will unite given apposition and immobilization, provided both patient and surgeon are prepared to wait long enough for vascularization to take place followed by bone union. PEMF treatment provides an incentive for patience and the maintenance of non-weight bearing and may well have some stimulatory effect upon vascularization or osteogenesis ‘-* . As yet, how e v er, there is no conclusive evidence to suggest that PEMF treatment is beneficial, and preliminary results from one double-blind trial have been negativeg. We have used the combined approach of surgery and PEMF when internal fixation was necessary for adequate immobilization; if there was a large gap between the bone ends or a synovial joint; if gross angulation required surgical correction; or, in some cases, when it was felt that surgery alone needed adjuvant therapy. All 19 cases treated with this combined approach went on to unite within 9 months. Definitions of delayed union, non-union and union are difficult. Some of the cases included here could be classified as delayed union in that union could be expected with the passage of time. Only difficult fractures in which the surgeon felt that there was severe doubt about the outcome were included in this study. The majority of cases presented with non-union, i.e. it was deemed that there was no prospect of eventual union. This is a subjective judgement and there is obviously some overlap between the two states. Union was said to have occurred when sound bony bridging could be seen on X-ray. The mean and median times between the commencement of PEMF and union was six months in both groups. This compares favourably with the time reported by Bassett et ~1.~ of just over five months from the cessation of PEMF at stage II healing. Our overall success with PEMF therapy has been high; 100 % for fractures treated in conjunction with surgery and 86% for fractures treated by PEMF
alone. This may be compared with the 87% reported by Bassett et aL3 for fractures treated with PEMF alone. Of our two failures, one fracture was deemed too mobile and the patient failed to attend for surgery. The other patient was weight-bearing and did not check the continued operation of the coil system. The stimulation waveform reported here is very different from that claimed by Bassett et aL2 as the only viable waveform. In contrast to the complex fitting procedure and patient management regime recommended in the same paper, our approach has been a simple one. Patient management is no different from that usually employed in St Bartholomew’s Hospital for the treatment of similar fractures which are not receiving PEMF treatment. No expert technical help is required in either fitting the coils or subsequent patient reviews. A selection of PEMF units and coils, with the magnetic field strength set up for a range ofcoil spacings, are kept in the fracture clinic ready for use. It is often claimed that the coils must be separated by their diameter to give a uniform magnetic field. In fact the coils would have to be separated by their radius (Helmholtz coils). However, coils of this size are not feasible for treating fractured limbs. Coils separated by their diameter are feasible, but it must be remembered that the resultant field is not as uniform. Any ‘critical’ values should therefore be treated with caution, especially as the limbs are not homogeneous and will therefore complicate the electrical fieIds produced. Many features of PEMF treatment may encourage fractures to unite. The importance of variables such as the stimulation waveform, coil geometry, electric and magnetic field strengths, patient management regime and the role of psychology in the treatment are, as yet, unknown and will remain so until the mechanisms involved in the treatment are fully understood. In the meantime many hospitals will continue to use PEMF. Our results suggest that the stimulating waveform is not as critical as has been claimed, and that both the stimulation waveform and the simple patient management regime we have adopted give as good a success rate in the healing of fractures as that recommended by Bassett et al.“. Whether these results are due to the effect of PEMF or to some other factor remains to be established.
ACKNOWLEDGEMENTS We gratefully acknowledge the assistance of Mr P. Byrne for suggesting the stimulating waveform. Thanks are also due to Mr K. Buffong for applying the coils to the plaster casts, and to the staff of the Orthopaedic Department at St Bartholomew’s Hospital for their assistance.
REFERENCES Barker AT, Lunt MJ. The effects of pulsed magnetic fields of the type used in the stimulation of bone fracture healing. Clin Phys Physiol Meas 1983.4:1-27.
,J, Biomed.
Lng.
1988, Vol.
lO..July
303
2. Bassett CAL, Pilla AA, Mitchell SN, et al. Repair of non-unions by pulsing electromagnetic fields. Acta O&~/J
Belgica 1978; 44: 706-24. 3. Bassett CAL, Mitchell SN,
Gaston SR. Treatment of ununited tibia1 diaphyseal fractures with pulsing electromagnetic fields. J Bone Jt Sung 1981; 63A: 51 l-23. 4. De Haas WG, Watson J, Morrison DM. Non-invasive treatment of ununited fractures of the tibia using electrical stimulation. J Bone Jt Surg 1980; 62B: 465-70. 5. Nicoll EA. Fractures of the tibia1 shaft: A survey of 705 cases. J Bone Jt Surg 1964; 46B: 373-87. 6. McKibben B. The biology of fracture healing in long bones.
304
J. Biomcd. hg.
1988, Vol. 10,July
J Bone Jt Surg 1978, 60B: 15(t62, 7. Luben RA, Cain CD, Chi-Yun Chen M, Rosen DM, Adey WR. Effects of electromagnetic stimuli on bone cells in vitro: inhibition of responses to parathyroid hormone by low-energy low-frequency fields Proc Nail Acad Sci USA 1982; 79: 4180-84. 8. Murray JC, Farndale RW. Modulations of collagen production in cultured fibroblasts by a low-frequency pulsed magnetic field. Biockim Biopkgs Acta 1985; 838: 98-105. 9. Barker AT, Dixon RA, Sharrard WJW, Sutcliffe MF. Pulsed magnetic field therapy for tibia1 non-union-Interim results of a double-blind trial. Lancet 1984; i: 994-6.