Br. J. Surg. Vol. 62 (1975) 147-150
Cervical spinal interbody fusion with Kiel bone P. S. R A M A N I , R. M . K A L B A G A N D R. P. S E N G U P T A * SUMMARY
Experience with the use of the Kiel bone graft in anterior cervical interbody fusion in cervical spondylosis is reported. The survey reviews the results of operations on 73 disc spaces in 65 consecutive patients, from 2 to 5 years after the operation. We have failed to confirm that any bony fusion in the true sense occurs with Kiel bone in anterior cervical interbody fusion. However, the aims of the operations are achieved, namely removal of the disc and osteophyte, fixation of the spine to prevent compression of the neural tissues, distraction of the adjacent uertebrat bodies providing increased room in the intervertebral foraminn and stabiiity of the spine.
INTERBODY fusion of the cervical spine by an anterior approach using the Cloward technique (Cloward, 1958) is now one of the standard operations in surgery. In the early stages of our experience of the operation, in common with that of others using autografts from the iliac crest, there was a higher degree of morbidity from the donor site than anticipated. Discomfort in the area involved, often amounting to pain, was a consistent factor delaying discharge from hospital and prolonging convalescence. Change to an alternative source for the graft was prompted for a reason peculiar to the Regional Neurological Centre, Newcastle upon Tyne, where a prospective study of the relative merits of the various methods of management of cervical spondylotic myelopathy is in progress (Kalbag, 1972). Serial functional assessment of the patients was one of the basic features in the study, and it was considered that pain from the donor site would introduce a bias by reducing the timed performance figures for the Cloward group. Commercially produced heterografts have been available for many years but are still viewed with reservation. It was, however, felt that as far as the treatment of degenerative disc disease was concerned, such grafts were worth consideration. Kiel bone is a processed animal bone prepared from young calves. It was introduced in 1957 (Maatz and Bauermeister, 1957). It is partially deproteinized and according to the authors it is substituted by living bone faster and more completely than any other bone grafts. Materials and methods We have used Kiel bone since June 1968 in over 150 patients, but this survey reviews the results in only 65 consecutive cases from 2 to 5 years after the operation, thus giving a follow-up period of at least 2 years. Seventy-three disc spaces were dealt with in these 65 cases, 8 of which required fusion at two levels. There were 55 males and 10 females and 77 per cent of the
cases were in the fifth or sixth decade. The operation was carried out using the standard Cloward technique (Cloward, 1958, 1962) with the patient in Halter traction. The drill hole straddling the disc was made with a 12.5-mm drill and the dowel inserted was 15.5 mm in diameter. A closed suction drain was left routinely in the prevertebral space for 24 hours. No collar was provided for postoperative immobilization of the neck. Apart from paraparetic patients who required intensive physiotherapy, patients were discharged home on the fifth day. Check X-rays of the cervical spine were taken the day after operation, at 6 weeks and then at 6-monthly intervals. We attempt to countersink the dowel slightly or make it flush with the bodies. In 9 patients, however, the first postoperative check X-rays showed the dowel to be slightly protruding forwards beyond the anterior surface of the vertebral bodies (Fig. la). Without immobilization in a collar, follow-up X-rays showed normal alignment and stability indistinguishable from that of a more satisfactorily placed dowel (Fig. lb, c).
Results Fifty-six (86 per cent) cases showed satisfactory alignment of the spine without abnormal mobility in flexion or extension at the time of final assessment. In 2 cases the dowel had to be removed because of infection, and the remaining 7 cases showed some complications as described below. Partial absorption of the Kiel bone dowel was noted in 4 patients at 6 weeks’ follow-up, but they had no symptoms. All the same, immobilization in a collar was carried out for 3 months. Partial resorption of the vertebral bodies adjacent to the graft was seen in 3 patients at the end of 6 weeks, but with a collar alone stability and fixation were obtained. Fracture of adjacent vertebral bodies was not a feature using autografts but occurred in 2 cases while a Kiel bone was being hammered in, when the anterior edge of one of the adjacent vertebrae was chipped off. Thiscomplication occurredinpatients withsomedegree of osteoporosis and marked spondylotic changes. The contributory factor was probably the hard consistency of Kiel bone. Perhaps with the extension of the neck, as recommended by Cloward, this complication could have been avoided, but in our series, where a narrow spinal canal and myelopathy were frequent, extension of the neck under general anaesthesia was considered undesirable because of the obvious hazards of such a manoeuvre.
* Regional Neurological Centre, Newcastle General Hospital, Newcastle upon Tyne. 147
P. S. Ramani et al.
n
b
c
Fig. 1. a , Lateral X-ray oC the cervical spine taken immediately after operation shows anterior protrusion of the dowels which is more marked at the upper level (C4/5). However, follow-up X-rays taken ( h ) 8 months and (c) 17 months after the operation show alignment and stability indistinguishable from that of a more satisfactorily placcd dowel.
148
Fig. 2. Anteroposterior X-ray of the cervical spine taken 2 ycars after operation shows a halo around thc dowel.
Cervical spinal interbody fusion
n
b
Fig. 3. u , Anteroposterior tomogram of the cervical spine 2 years after the operation and ( b ) lateral tomogram of the cervical spine nearly 5 years after operation showing a halo around the dowel and indicating the absence of fusion.
All cases with partial absorption of the dowel as well as the adjacent vertebral bodies also showed some later anterior protrusion of the dowel. In all these 7 cases immobilization in a collar was carried out. The end result was a stable spine although all of them showed some angulation of the spine. A radiological study of our cases does not show a single case in which one could say with any confidence that bony fusion had occurred. Some patients showed a halo around the dowel (Fin.. 2) even a t the end of 5 years. Those who did not show the halo on plain Xrays were submitted to tomography in two planes and all of them showed a distinct halo surrounding the dowel (Fig. 3). We have interpreted this halo as a zone of fibrous tissue encaging the graft. We cannot therefore confirm that fusion occurs with the use of Kiel bone. Discussion Cloward (1 962), reporting his experience with cadaver bone, thought that the common belief that autologous bone is superior t o homologous bone was untenable. Burwell (l969), in a most comprehensive review of the fate of bone grafts, concluded that the best bank bone for clinical use seemed to be the freeze-dried homologous cancellous bone sterilized by irradiation. However, Taheri andLGueramy (1972), reporting on 200 cases with cervical disc disease who were operated on using the Cloward technique, stated that with heterogenous bone the results are good, the operation time is shortened and complications are diminished. They graded their patients radiologically into ‘excellent’, defined as good fusion and no angulation, while ‘good’
implied sound fusion but minimal angulation; 85.5 per cent were considered excellent and 11.5 per cent good, indicating that fusion o r bony union had occurred in 97 per cent. This compares very favourably with the results quoted by Robinson et al. (1962). Admittedly, like the present series, this was a smaller series of 55 cases in which ileal autografts were used with an approximately 88 per cent fusion rate. A radiological study of our own cases does not show a single case in whom one could say with any confidence that bone fusion had occurred. However, the absence of true fusion does not show any material disadvantages in the particular situation that we are considering, namely cervical disc disease, where spinal instability such as in fracture dislocation is rare. Our series shows ‘satisfactory’ results in 86 per cent in that alignment and stability have been achieved without convincing evidence of ‘fusion. As designed for the spine, the Cloward operation using a dowel 3 mm larger than the drill hole provides firm splinting and with the resultant close approximation to a bed of vascular cancellous bone. Even with merely the splinting effect at the site of operation, the aims of the particular procedure are achieved, i.e. (1) removal of the disc and osteophyte, (2) fixation of the spine and (3) distraction of the adjacent vertebral bodies providing increased room in the intervertebral foramina. In this respect the results appear to be superior to those of autografts; Robinson et al. (1962) found abnormal mobility in flexion and extension in 9 out of the 56 patients reported. Mechanical damage to the adjacent vertebral bodies could be related to the consistency and size of the 149
P. S. Ramani et al. graft, which with a diameter of 15.5 mm seems too large for easy introduction into a drill hole 12.5 nim in diameter, especially where the spine shows gross osteophyte formation. Taheri and Gueraniy (1 972) use a 14-mm dowel where only one space is operated upon and a 12-mm dowel if more than one space warrants attention. The former size would seem preferable to the one we have used. In conclusion we have failed to confirm that any fusion in the true sense occurs with Kiel bone in cervical interbody fusion; nevertheless, we feel that except in fracture dislocation there is no practical disadvantage in its use and that the saving in operation time and morbidity more than counters any objections to its use in the particular context of cervical spondylotic disease.
Acknowledgement We wish to acknowledge the help of the Department of Neuroradiology, Newcastle General Hospital, for providing the X-rays.
150
References BURWELL R. G. (1969) The fate of bone grafts. In: APLEY A. G . (ed.) Recent Advances in Orthopaedics.
Baltimore, Williams & Wilkins, pp. 115-208. (1958) The anterior approach for renioval of ruptured cervical discs. J . Neurosurg. 15, 602-617. CLOWARD R . B. (1962) New method of diagnosis and treatment of cervical disc disease. Clin. Neurosurg. 8, 93-132. KALBAG R. M. (1972) Notes and comments on cervical spondylosis. Br. Med. J . 1, 563. MAATZ R. and BAUERMEISTER A. (1957) A method of bone maceration. Results in animal experiments. J. Bone Joint Surg. (Am.) 39, 153-166. ROBINSON R . A . , WALKER A. E., FERLIC D. c . and WIECKING D. K. (1962) The results of anterior interbody fusion of the cervical spine. J. Bone Joint Surg. (Am.) 44, 1569-1587. TAHERI z. E. and GUERAMY M. (1972) Experience with calf bone in cervical interbody fusion. J . Neurosurg. 36, 67-71. CLOWARD R. B.
Cervical spinal interbody fusion with Kiel bone P. S. R A M A N I , R. M . K A L B A G A N D R. P. S E N G U P T A * SUMMARY
Experience with the use of the Kiel bone graft in anterior cervical interbody fusion in cervical spondylosis is reported. The survey reviews the results of operations on 73 disc spaces in 65 consecutive patients, from 2 to 5 years after the operation. We have failed to confirm that any bony fusion in the true sense occurs with Kiel bone in anterior cervical interbody fusion. However, the aims of the operations are achieved, namely removal of the disc and osteophyte, fixation of the spine to prevent compression of the neural tissues, distraction of the adjacent uertebrat bodies providing increased room in the intervertebral foraminn and stabiiity of the spine.
INTERBODY fusion of the cervical spine by an anterior approach using the Cloward technique (Cloward, 1958) is now one of the standard operations in surgery. In the early stages of our experience of the operation, in common with that of others using autografts from the iliac crest, there was a higher degree of morbidity from the donor site than anticipated. Discomfort in the area involved, often amounting to pain, was a consistent factor delaying discharge from hospital and prolonging convalescence. Change to an alternative source for the graft was prompted for a reason peculiar to the Regional Neurological Centre, Newcastle upon Tyne, where a prospective study of the relative merits of the various methods of management of cervical spondylotic myelopathy is in progress (Kalbag, 1972). Serial functional assessment of the patients was one of the basic features in the study, and it was considered that pain from the donor site would introduce a bias by reducing the timed performance figures for the Cloward group. Commercially produced heterografts have been available for many years but are still viewed with reservation. It was, however, felt that as far as the treatment of degenerative disc disease was concerned, such grafts were worth consideration. Kiel bone is a processed animal bone prepared from young calves. It was introduced in 1957 (Maatz and Bauermeister, 1957). It is partially deproteinized and according to the authors it is substituted by living bone faster and more completely than any other bone grafts. Materials and methods We have used Kiel bone since June 1968 in over 150 patients, but this survey reviews the results in only 65 consecutive cases from 2 to 5 years after the operation, thus giving a follow-up period of at least 2 years. Seventy-three disc spaces were dealt with in these 65 cases, 8 of which required fusion at two levels. There were 55 males and 10 females and 77 per cent of the
cases were in the fifth or sixth decade. The operation was carried out using the standard Cloward technique (Cloward, 1958, 1962) with the patient in Halter traction. The drill hole straddling the disc was made with a 12.5-mm drill and the dowel inserted was 15.5 mm in diameter. A closed suction drain was left routinely in the prevertebral space for 24 hours. No collar was provided for postoperative immobilization of the neck. Apart from paraparetic patients who required intensive physiotherapy, patients were discharged home on the fifth day. Check X-rays of the cervical spine were taken the day after operation, at 6 weeks and then at 6-monthly intervals. We attempt to countersink the dowel slightly or make it flush with the bodies. In 9 patients, however, the first postoperative check X-rays showed the dowel to be slightly protruding forwards beyond the anterior surface of the vertebral bodies (Fig. la). Without immobilization in a collar, follow-up X-rays showed normal alignment and stability indistinguishable from that of a more satisfactorily placed dowel (Fig. lb, c).
Results Fifty-six (86 per cent) cases showed satisfactory alignment of the spine without abnormal mobility in flexion or extension at the time of final assessment. In 2 cases the dowel had to be removed because of infection, and the remaining 7 cases showed some complications as described below. Partial absorption of the Kiel bone dowel was noted in 4 patients at 6 weeks’ follow-up, but they had no symptoms. All the same, immobilization in a collar was carried out for 3 months. Partial resorption of the vertebral bodies adjacent to the graft was seen in 3 patients at the end of 6 weeks, but with a collar alone stability and fixation were obtained. Fracture of adjacent vertebral bodies was not a feature using autografts but occurred in 2 cases while a Kiel bone was being hammered in, when the anterior edge of one of the adjacent vertebrae was chipped off. Thiscomplication occurredinpatients withsomedegree of osteoporosis and marked spondylotic changes. The contributory factor was probably the hard consistency of Kiel bone. Perhaps with the extension of the neck, as recommended by Cloward, this complication could have been avoided, but in our series, where a narrow spinal canal and myelopathy were frequent, extension of the neck under general anaesthesia was considered undesirable because of the obvious hazards of such a manoeuvre.
* Regional Neurological Centre, Newcastle General Hospital, Newcastle upon Tyne. 147
P. S. Ramani et al.
n
b
c
Fig. 1. a , Lateral X-ray oC the cervical spine taken immediately after operation shows anterior protrusion of the dowels which is more marked at the upper level (C4/5). However, follow-up X-rays taken ( h ) 8 months and (c) 17 months after the operation show alignment and stability indistinguishable from that of a more satisfactorily placcd dowel.
148
Fig. 2. Anteroposterior X-ray of the cervical spine taken 2 ycars after operation shows a halo around thc dowel.
Cervical spinal interbody fusion
n
b
Fig. 3. u , Anteroposterior tomogram of the cervical spine 2 years after the operation and ( b ) lateral tomogram of the cervical spine nearly 5 years after operation showing a halo around the dowel and indicating the absence of fusion.
All cases with partial absorption of the dowel as well as the adjacent vertebral bodies also showed some later anterior protrusion of the dowel. In all these 7 cases immobilization in a collar was carried out. The end result was a stable spine although all of them showed some angulation of the spine. A radiological study of our cases does not show a single case in which one could say with any confidence that bony fusion had occurred. Some patients showed a halo around the dowel (Fin.. 2) even a t the end of 5 years. Those who did not show the halo on plain Xrays were submitted to tomography in two planes and all of them showed a distinct halo surrounding the dowel (Fig. 3). We have interpreted this halo as a zone of fibrous tissue encaging the graft. We cannot therefore confirm that fusion occurs with the use of Kiel bone. Discussion Cloward (1 962), reporting his experience with cadaver bone, thought that the common belief that autologous bone is superior t o homologous bone was untenable. Burwell (l969), in a most comprehensive review of the fate of bone grafts, concluded that the best bank bone for clinical use seemed to be the freeze-dried homologous cancellous bone sterilized by irradiation. However, Taheri andLGueramy (1972), reporting on 200 cases with cervical disc disease who were operated on using the Cloward technique, stated that with heterogenous bone the results are good, the operation time is shortened and complications are diminished. They graded their patients radiologically into ‘excellent’, defined as good fusion and no angulation, while ‘good’
implied sound fusion but minimal angulation; 85.5 per cent were considered excellent and 11.5 per cent good, indicating that fusion o r bony union had occurred in 97 per cent. This compares very favourably with the results quoted by Robinson et al. (1962). Admittedly, like the present series, this was a smaller series of 55 cases in which ileal autografts were used with an approximately 88 per cent fusion rate. A radiological study of our own cases does not show a single case in whom one could say with any confidence that bone fusion had occurred. However, the absence of true fusion does not show any material disadvantages in the particular situation that we are considering, namely cervical disc disease, where spinal instability such as in fracture dislocation is rare. Our series shows ‘satisfactory’ results in 86 per cent in that alignment and stability have been achieved without convincing evidence of ‘fusion. As designed for the spine, the Cloward operation using a dowel 3 mm larger than the drill hole provides firm splinting and with the resultant close approximation to a bed of vascular cancellous bone. Even with merely the splinting effect at the site of operation, the aims of the particular procedure are achieved, i.e. (1) removal of the disc and osteophyte, (2) fixation of the spine and (3) distraction of the adjacent vertebral bodies providing increased room in the intervertebral foramina. In this respect the results appear to be superior to those of autografts; Robinson et al. (1962) found abnormal mobility in flexion and extension in 9 out of the 56 patients reported. Mechanical damage to the adjacent vertebral bodies could be related to the consistency and size of the 149
P. S. Ramani et al. graft, which with a diameter of 15.5 mm seems too large for easy introduction into a drill hole 12.5 nim in diameter, especially where the spine shows gross osteophyte formation. Taheri and Gueraniy (1 972) use a 14-mm dowel where only one space is operated upon and a 12-mm dowel if more than one space warrants attention. The former size would seem preferable to the one we have used. In conclusion we have failed to confirm that any fusion in the true sense occurs with Kiel bone in cervical interbody fusion; nevertheless, we feel that except in fracture dislocation there is no practical disadvantage in its use and that the saving in operation time and morbidity more than counters any objections to its use in the particular context of cervical spondylotic disease.
Acknowledgement We wish to acknowledge the help of the Department of Neuroradiology, Newcastle General Hospital, for providing the X-rays.
150
References BURWELL R. G. (1969) The fate of bone grafts. In: APLEY A. G . (ed.) Recent Advances in Orthopaedics.
Baltimore, Williams & Wilkins, pp. 115-208. (1958) The anterior approach for renioval of ruptured cervical discs. J . Neurosurg. 15, 602-617. CLOWARD R . B. (1962) New method of diagnosis and treatment of cervical disc disease. Clin. Neurosurg. 8, 93-132. KALBAG R. M. (1972) Notes and comments on cervical spondylosis. Br. Med. J . 1, 563. MAATZ R. and BAUERMEISTER A. (1957) A method of bone maceration. Results in animal experiments. J. Bone Joint Surg. (Am.) 39, 153-166. ROBINSON R . A . , WALKER A. E., FERLIC D. c . and WIECKING D. K. (1962) The results of anterior interbody fusion of the cervical spine. J. Bone Joint Surg. (Am.) 44, 1569-1587. TAHERI z. E. and GUERAMY M. (1972) Experience with calf bone in cervical interbody fusion. J . Neurosurg. 36, 67-71. CLOWARD R. B.
