Management of scoliosis in Duchenne muscular dystrophy: a large 10-year retrospective study

Transcription

1 Management of scoliosis in Duchenne muscular dystrophy: a large 10-year retrospective study M Kinali MD; S Messina MD, Dubowitz Neuromuscular Centre, Department of Paediatrics, Hammersmith Hospital Campus, Imperial College London; E Mercuri MD PhD, Dubowitz Neuromuscular Centre, Department of Paediatrics, Hammersmith Hospital Campus, Imperial College London, UK; and Department of Child Neurology, Catholic University, Rome, Italy. J Lehovsky MD; G Edge MD PhD, Department of Orthopaedics, Royal National Orthopaedic Hospital, Stanmore; AY Manzur MD; F Muntoni* MD PhD, Dubowitz Neuromuscular Centre, Department of Paediatrics, Hammersmith Hospital Campus, Imperial College London, UK. *Correspondence to last author at Dubowitz Neuromuscular Centre, Department of Paediatrics, Hammersmith Hospital Campus, Imperial College London, Du Cane Road, London W12 ONN, UK. f.muntoni@imperial.ac.uk Scoliosis affects 75 to 90% of patients with non-ambulant Duchenne muscular dystrophy (DMD). Spinal surgery is the treatment of choice but the indication varies among centres. Some offer surgery to all non-ambulant patients, irrespective of scoliosis severity. Early surgery has the advantage of targeting DMD when cardiorespiratory function is preserved, but not all patients develop scoliosis. We report our 10-year experience of scoliosis management in 123 patients with DMD who were at least 17 years old at the time of the study. Scoliosis was absent in 10%, and mild, non-progressive (at least 30 ) in 13% of patients. Another 13% had moderate scoliosis (31 50 ) and were managed conservatively. Surgery was considered in 57% (70/123) of patients with scoliosis greater than 50 and eventually performed in 35%. The remaining patients either refused surgery (9%) or were unfit because of cardiorespiratory compromise (13%). In a further 7%, scoliosis (greater than 50 ), first noted after 14 years of age, was progressing slowly and surgery was not performed. At 17 years there was no difference in survival, respiratory impairment, or sitting comfort among patients managed conservatively or with surgery. One-third (44/123) of our patients were managed satisfactorily without receiving spinal surgery. We provide insight into the natural history of scoliosis in DMD that should help families and clinicians with decision-making when surgery is considered. See end of paper for list of abbreviations. Scoliosis is a frequent complication in Duchenne muscular dystrophy (DMD), which progresses rapidly with puberty in non-ambulant children (Gibson et al. 1978, Oda et al. 1993). In these patients, scoliosis causes discomfort and leads to compromise of respiratory function (Kennedy et al. 1995, Galasko 2001, Yamashita et al. 2001). The incidence of scoliosis in DMD varies between 75 and 90% (Rideau et al. 1984, Brooke et al. 1989, Oda et al. 1993, Yamashita et al. 2001). Attempts to prevent or delay scoliosis with spinal support systems are often insufficient to control deterioration. Thoracic orthoses are only capable of controlling curvatures of less than 25 (Hsu 1983). Standing and walking in callipers has been suggested to be of help in preventing the rapid progression of scoliosis in DMD (Rodillo et al. 1988). Spinal surgery is the treatment of choice for correcting DMD scoliosis (Sussman 1984). It improves sitting comfort, appearance, and quality of life (Miller et al. 1991, Kennedy et al. 1995, Granata et al. 1996, Bridwell et al. 1999). However, the effect of spinal surgery on respiratory function and longterm survival is controversial (Miller et al. 1991, Kennedy et al. 1995, Granata et al. 1996). Several centres worldwide perform spinal surgery in all patients with DMD, with even a mild scoliosis, soon after ambulation is lost (Gibson et al. 1978, Sussman 1984, Kennedy et al. 1995). The advantage of this approach is that, at this early stage, severe respiratory impairment is uncommon and the procedure is more easily performed (Sussman 1984, Ramirez et al. 1997, Bentley et al. 2001, Heller et al. 2001). Spinal surgery is indeed a major procedure with significant complications (Granata et al. 1994). However, is spinal surgery always necessary, considering that scoliosis is not an inevitable complication in DMD? Granata et al. (1996) suggested that up to 37% of individuals with DMD do not develop scoliosis by up to 16 years of age. Considering the beneficial effect of callipers, and the recently reported decreased incidence of scoliosis in patients treated with steroids (Alman et al. 2004), an approach to spinal surgery tailored only to those children needing it would be desirable. In other centres, and ours, surgery is not performed as a routine but only offered to patients after careful monitoring of cardiorespiratory function and documenting the progression of the spinal deformity. The risk of this more individualized approach, however, is that scoliosis might develop and progress rapidly when the cardiorespiratory function has deteriorated so that surgery can no longer be considered safe. With the effect of respiratory management and subsequent prolongation of survival (Eagle et al. 2002), it is also possible that mild to moderate scoliosis could continue to progress even after growth has ceased. In this retrospective study we reviewed data on 123 males with DMD, aged at least 17 years at the time of the study, and who had been followed at our centre for at least 10 years. Our aims were to: (1) identify the prevalence of scoliosis in our population at the age of 17 years; (2) identify the proportion of patients who did or did not undergo spinal surgery and the reasons for not having surgery; and (3) correlate various measures of outcome, such as respiratory function and survival, in our population. Method The study was approved by the Ethics Committee at the Hammersmith Hospital, London, UK. We reviewed case notes Developmental Medicine & Child Neurology 2006, 48:

2 of patients with DMD who were aged at least 17 years and who had been assessed at the Hammersmith Neuromuscular Centre from 1992 to This is a tertiary referral centre for children with neuromuscular disorders. The age of 17 years was chosen as the growth spurt is almost entirely completed, by then (Tanner 1989) and the risk in males of developing significantly progressive scoliosis is much lower. As a policy of our centre, we monitor patients with DMD at 4- to 6-month intervals and remobilize approximately 90% of them in lightweight knee ankle foot orthoses (callipers) at the time of loss of ambulation (Rodillo et al. 1988). If the clinical examination reveals the presence of scoliosis, sitting anteroposterior spinal radiographs are taken every 6 months. If the Cobb angle is greater than 20, polypropylene moulded thoracolumbar spinal orthoses (TLSOs) are offered. Patients are advised to wear their TLSOs for at least 6 to 8 hours daily, when sitting. During the study period, spinal surgery was offered to patients with rapidly progressive scoliosis (progress of at least 10 per 6 months) and to those with a Cobb angle greater than 50. The decision to offer surgery also took into account the patient s age, cardiorespiratory function, and level of ambulation. Patients who are still ambulant or stand daily in callipers are monitored at our centre every 4 months and offered scoliosis surgery later, especially if their curvatures are stable or only slowly progressive. Patients with more significant cardiorespiratory impairment and a clear curvature progression are offered scoliosis surgery earlier. Until 1996, most patients who were operated on had Luque fusion (a method of segmental spinal instrumentation in which loops of wire are slipped underneath the lamina at each vertebral level and then fixed on either side of the paravertebral rods; Luque 1982) and only few Harrington rods (this involved fixing paravertebral rods at their distal ends to a spine that had been maximally distracted by traction; Robin and Brief 1971). Since 1996 most patients have had universal spinal system instrumentation. (This is a new system designed to simplify the surgical treatment of scoliosis by providing the surgeon with a single set of instruments and implants that could be used to treat different conditions affecting the thoracolumbar spine via either an anterior or posterior approach; Laxer 1994.) With only a few exceptions, all patients had pelvic fixations. The following data were collected from the medical records: results of radiographic examination, performed at the onset of scoliosis; annual rate of deterioration of the curvature at 1-year intervals, always using the scoliosis X-ray in sitting without the TLSO on; maximum rate of deterioration of the curvature over a year and at what age this occurred; age at surgery, the preoperative Cobb angle, the correction achieved with surgery, and complications related to surgery; patient s subjective perception about sitting posture and the number of referrals to sitting clinics in each group; pulmonary function tests (forced vital capacity [FVC]) recorded in the sitting position and without the TLSO on, performed longitudinally, every 6 months; predicted FVC (%), calculated according to standing height or arm span in the non-ambulant patients; age at respiratory failure, and death; presence and severity of cardiomyopathy; information on longer follow-up, Table I: Age scoliosis was first noted, maximum annual deterioration in Cobb angle, age it occurred, mean forced vital capacity, age at onset of respiratory failure, and heart involvement at 17 years, in surgical and non-surgical groups Surgical group Non-surgical groups a (n=43) Group 1 Group 2 Group 3 Group 4 Group 5 (n=28) (n=16) (n=9) (n=11) (n=16) Age scoliosis first noted mean 12:2 No scoliosis, 13:3 12:4 11:5 12:5 (range), y:m (11:0 15:2) n=12 (10:0 15:0) ( 8:0 15:0) (10:0 13:0) (9:0 15:2) Mild scoliosis, n=16 Mean 14.1 (11:8 16:0) Maximum annual deterioration 29 NA in Cobb angle, mean (range) (15 56) (7 25) (10 23) (13 40) (15 40) Age maximum annual NA deterioration in Cobb angle observed, median y Forced vital capacity at 17y, mean (range) % predicted (6 51) (6 58) (16 40) (10 50) ( 8 39) (7 22) n=13/16 3/16 not recordable Number of patients on nocturnal 17/43 3/28 4/16 3/9 4/11 9/16 ventilation Heart involvement at 17y, n Abnormal 11/43 7/28 3/16 6/9 1/11 6/16 Don t know 3/43 12/28 4/16 1/9 6/11 2/16 Normal 29/43 9/28 9/16 2/9 4/11 8/16 NA, not applicable. a See Results section for group description. 514 Developmental Medicine & Child Neurology 2006, 48:

3 when available; and identification of patients who died during the study period and who would have been included had they been alive. Results A total of 123 patients with DMD were included in the study. Forty-three had undergone spinal surgery whereas 80 patients had not. SURGERY PATIENTS Of 43 patients who had surgery, mean age at development of scoliosis was 12 years 2 months (range 11y 15y 2mo) and mean age at surgery was 14 years 9 months (SD 1y 2mo). The mean preoperative Cobb angle was 62 (range ). Seven patients had a Cobb angle of not more than 50 (range ) but had surgery because of rapid decline of FVC. Information on bracing was available for 32 of 43 patients. Twenty-six patients were braced before surgery, four were not braced owing to obesity, and two did not tolerate bracing. Mean preoperative FVC was 40.2% (range 19 65%) and the mean postoperative FVC 33.6% (range 15 52%). Only one patient developed nocturnal hypoventilation and was started on non-invasive ventilation within 6 months of surgery. There was no death in the postoperative period. NON-SURGICAL PATIENTS Eighty patients did not have scoliosis surgery and were further classified into five subgroups (Table I). Group 1: patients with no or mild scoliosis (Cobb angle 30 ) at 17 years (n=28/80) Eight of 16 patients with mild scoliosis were managed with TLSOs for a maximum of 4 years (Table I). Group 2: patients with moderate scoliosis (31 50 ) at 17 years (n=16/80) Eleven of 16 patients were managed with TLSOs for a mean period of 3 years (range 1y 5y 4mo). One patient refused bracing; four could not be braced owing to obesity (Table I). Group 3: patients with severe scoliosis ( 50 ) at 17 years (n=9/80) These patients had late onset (at least 14y) and slow progression (not more than 10 per 6 months) of their curvatures (Figs 1 and 2). They were managed with TLSOs for a mean period of 3 years 1 month (range 1 7y) and their postural control with bracing was well tolerated and satisfactory (Table I). Group 4: patients who refused scoliosis surgery (n=11/80) Seven patients were managed with TLSOs, for a mean period of 4 years 5 months (range 3 7y). Three patients refused bracing; one was not braced owing to obesity (Table I). Group 5: patients unfit for surgery, owing to poor FVC ( 20% predicted) or cardiac insufficiency before the development of a significant scoliosis (n=16/80) One patient had severe dilated cardiomyopathy. Fifteen had Table II: Clinical findings of Duchenne muscular dystrophy patients from surgical and non-surgical groups followed after 17 years of age Surgical group Non-surgical groups a (n=43) Group 1 Group 2 Group 3 Group 4 Group 5 (n=28) (n=16) (n=9) (n=11) (n=16) Number of patients followed-up beyond 17y Length of follow-up 3:1 3:2 2:4 2:2 4:4 1:5 after 17y, mean (range) y:m (0:3 5:5) (0:3 9:0) (0:3 4:2) (0:2 4:7) (0:3 8:0) (0:3 2:3) Number of deceased patients 15/16 6/18 7/12 3/5 4/5 2/4 and age, mean (range) y:m 20:2 20:8 19:5 19:8 20:6 19:35 (17:3 22:5) (17:3 23:1) (18:5 21:7) (18:0 21:7) (17:3 24:6) (19:3 19:4) Number of living patients n=1/16 n=12/18 n=5/12 n=2/5 n=1/5 n=2/4 and age at last follow-up, mean At 22:0 19:75 20:2 18:6 At 25:0 17:7 (range) y:m (17:6 26:0) (17:3 23:2) (17:2 20:5) (17:2 18:1) Number of patients on 13/16 0 3/12 0 3/5 2/4 nocturnal ventilation Age of starting nocturnal, 19:7 0 20:3 0 20:6 20:5 ventilation, mean (range) y:m (17:1 22:5) (18:5 23:0) (19:0 22:5) (19:0 22:0) Length of follow-up n=7/18 n=12/12 n=5/5 scoliosis X-rays, mean 2:7 2:6 1:2 (range) y:m (1:0 5:0) (1:0 6:0) (1:0 7:0) One patient Five of 12 Three of 5 wearing brace patients patients for 1:0 wearing braces wearing braces for mean 2:3 mean 2:2 (0:7 4:0) (0:2 4:7) Nocturnal hypoventilation developed in 35% of surgical group and 25% of non-surgical group. a See Results section for group description. Management of Scoliosis in Duchenne Muscular Dystrophy M Kinali et al. 515

4 FVC<1L when scoliosis was first noted; nine patients had significantly reduced FVC at the time they had lost the ability to walk. In the other six, the low FVC coincided with scoliosis deterioration. Fifteen patients were managed with TLSOs for a mean period of 4 years 2 months (range 1y 2mo 8y); one patient could not tolerate bracing (Table I). MAXIMUM ANNUAL DETERIORATION IN COBB ANGLE Table I shows details of the maximum annual deterioration of the Cobb angle in each group and the age when this occurred. In groups 2 and 3, treated conservatively, the maximum annual deterioration exceeded 20 in only 25% of these patients and was never above 30. In contrast, 90% of the children who had surgery and 70% of those who were offered surgery but refused (group 4) had deterioration above 20. In the group of patients unfit for surgery the results were more variable (Fig. 1). The age when the maximum deterioration occurred was above 14 years in most of the children treated conservatively (80% in group 2 and 85% in group 3), whereas in all children who refused surgery, and in more than 80% of those who had surgery, these changes occurred before 14 years of age (Fig. 2). FVC AND CARDIAC IMPAIRMENT Table I shows details of the mean FVC, onset of respiratory failure, and cardiac involvement at 17 years of age. There was a tendency for patients who did not develop a marked scoliosis (groups 1 and 2) to have a better mean FVC than patients with marked scoliosis. The percentage of patients who developed nocturnal hypoventilation by the age of 17 years was lower in the groups who were treated conservatively (groups 1, 2, and 3) when compared with the groups considered for surgery. DISCOMFORT The percentage of patients who complained about discomfort and required a review of their sitting posture was much higher in the surgical group (14/43, 32.5%) and in the group who refused surgery (4/11, 36%) or were unfit for surgery (7/16, 43.8%), than in the patients with mild, moderate, or severe scoliosis (10/53, 18.8%), as suggested by the number of referrals to specialist sitting clinics. FOLLOW-UP Further progression of scoliosis Thirty-five patients treated conservatively (groups 1, 2, and 3) were followed beyond 17 years for a range of 1 to 7 years. Only one patient for whom we elected not to perform surgery (group 3) showed a deterioration of the Cobb angle of at least 10 over a period of 7 years. Survival and respiratory involvement beyond the age of 17 years Details of survival and respiratory impairment in the 60 of 123 patients who were followed-up beyond the age of 17 are shown in Table II. Survival data for adolescents followed up contemporaneously but not included in the study From 1992 to 2002, 51 patients with DMD aged 10 to 17 years were followed at our centre but not included in the study, because they were less than 17 years at the time of this study. They were classified into surgical and non-surgical groups (1a 5a). The number of deceased patients in each group was as follows: surgical group, 6/57; group 1a, 5/40; group 2a, 4/26; group 3a, 2/11; group 4a, 3/15; group 5a, 7/25. Discussion Scoliosis surgery for DMD has greatly improved the quality of life and sitting posture of the affected individuals. As this intervention is associated with significant complications it would be desirable to avoid unnecessary surgery. The difference of opinion in the timing and severity indication in scoliosis surgery may reflect not only the clinician s approach but also a different natural history of scoliosis in various centres, depending on their rehabilitation practices with callipers and corticosteroid use, both of which may delay scoliosis onset (Rodillo et al. 1988, Alman et al. 2004). Our findings expand previous observations related to the incidence of scoliosis at the end of puberty in a large population of patients with DMD, in whom we attempted a customized approach to the management of scoliosis. Approximately a quarter of our patients (28/123, 23%) did not have any scoliosis during the study period, or only had a minimal scoliosis, not more than 30 at age 17 years. In another 16 out of 123 (13%) there was mild to moderate scoliosis (31 50 ) that was successfully managed conservatively. In these patients quality of sitting, as indicated by patient satisfaction and referrals to sitting clinics, was good and, if anything, better than that of patients who had surgery. Our long-term Percentage of deterioration Group 2 Group 3 Group 4 Group 5 Surgical group Percentage of patients Group 2 Group 3 Group 4 Group 5 Surgical group < >30 <13y 13 14y 14y Figure 1: Maximum annual deterioration in Cobb angle in non-surgical and surgical groups. Figure 2: Age when maximum annual deterioration in Cobb angle occurred in non-surgical and surgical groups. 516 Developmental Medicine & Child Neurology 2006, 48:

5 data on further progression of scoliosis in this group of patients are limited; however, in only 1 of 35 patients (groups 1, 2, and 3) followed for 1 to 7 years beyond age 17 did scoliosis progress greater than 10. This is comparable to the mean loss of correction of the spinal curvature after surgery (Cervellati et al. 2004). Seventy-nine patients (64%, groups 3, 4, and 5) developed a curvature of at least 50. In 16 of 79 patients, scoliosis surgery was considered but could not be performed because of very poor cardiorespiratory function; this was already present when scoliosis was first noticed in 9 of 16. This group of patients probably represents the severe end of the DMD spectrum. Spinal surgery was offered to 54 patients but performed in 43, as 11 refused surgery. Spinal surgery was well tolerated, no patient died, and only one developed respiratory failure, 6 months after surgery. Nine patients (group 3) developed a curvature of at least 50 but were treated conservatively as sitting posture was good in the brace and the chances of further progression that would make sitting uncomfortable were considered small. The multidisciplinary team carefully monitored all these patients. In this group the maximum annual deterioration in Cobb angle was nearly always (8/9) less than 20 and tended to occur after 14 years of age, whereas in the surgical group the deterioration was greater than 20 and tended to occur well below 14 years. The follow-up was too short and this group of patients too small to establish whether survival and quality of life in this group is different from those treated with surgery. Mean and range of age of death was similar between patients who had surgery and those who did not. To avoid ascertainment bias we also collected information about patients who died younger than 17 years. These data suggest that there was a homogeneous distribution of deaths across the various groups, according to the severity of the disease s natural course and underlying scoliosis. Similarly, other authors have failed to find a significant effect of scoliosis surgery on mortality (Miller et al. 1991, Kennedy et al. 1995, Granata et al. 1996). This is probably not a surprising finding as most studies have failed to identify a protective role of spinal surgery on FVC (Miller et al. 1988, 1991; Kennedy et al. 1995), although some have (Rideau 1986). In our cohort, patients who had surgery had a 7% fall in FVC between the preoperative and postoperative period. Granata et al. (1996) also reported a fall of up to 10% in the FVC in the immediate postoperative period. Although our study did not evaluate all the types of spinal deformity (rigidity, kyphosis, lordosis), which can also affect posture quality, our results suggest that a significant number of patients can be managed conservatively and that scoliosis surgery can be safely avoided in an appreciable proportion of patients with DMD. In particular, 28 of 123 patients had scoliosis of not more than 30 which did not require any specific intervention. Another proportion of patients was managed conservatively, with bracing to improve sitting posture; all had curvatures less than 50 at age 17. In our experience, most of these patients could be managed conservatively and effectively with excellent results, at least in the medium term. Although spinal surgery could be performed safely even in patients with FVC less than 30% (Harper et al. 2004), the improved lifespan of patients with DMD means that further deterioration due to scoliosis in these patients cannot be excluded. This is a group of patients we would now follow more carefully and possibly counsel for future spinal surgery. Similarly, those patients who developed a curvature of at least 50 but were treated conservatively would now most likely be advised to have surgery. Although the outcome at 17 years does not appear to indicate that they would have benefited from surgery, longer follow-up is required to confirm that the curvature in these patients will fail to change significantly and to evaluate quality of life and survival beyond this age. Our results suggest, therefore, that an individualized multidisciplinary approach can help to identify patients at high risk of developing progressive scoliosis from those who do well without surgical intervention. In our experience, patients with onset of scoliosis under 14 years and a maximal annual deterioration in Cobb angle greater than 20 will invariably require surgery. In contrast, up to 88% (8/9 in group 3) of patients with onset of scoliosis after 14 years of age, and with maximal annual deterioration in Cobb angle of less than 20, may be successfully managed conservatively. Individualized management of patients with DMD is needed, not only because of increasing pressure for precise indication for intervention, but also because corticosteroids may change the natural history of the condition, reducing the chance of developing a curvature of the spine (Alman et al. 2004). In our present series only 30% of patients had received corticosteroids and were equally distributed in the different patient groups (data not presented here). In line with past practice, corticosteroids were given for short periods, towards the end of functional walking, and discontinued almost immediately afterwards; they did not influence age at loss of ambulation in these patients (Dubowitz 2000). This suggests that any effect of corticosteroids is likely to be small, if present; we plan to analyze this further in the context of the various risk factors for the development of scoliosis. In conclusion, our data show that an appreciable proportion of patients with DMD can be effectively managed without surgery. Although this is the largest series we are aware of including patients who did not receive surgical intervention, it is interesting to note that the percentage of patients not requiring surgery in our series is very similar to that of previously reported smaller series (Granata et al. 1996). Our data on patients with moderate scoliosis managed conservatively, nevertheless, have to be interpreted with caution, especially because of the improved long-term prognosis of individuals with DMD who are now expected to survive into their late 20s and beyond (Eagle et al. 2002). Although the follow-up of this group of patients for a period of up to 7 years has not shown a significant trend in deterioration of the scoliosis, longer observation will be needed to conclude that conservative management was the best option for these patients. DOI: /S Accepted for publication 3rd October Acknowledgements We thank Professor Victor Dubowitz for his comments. The financial support of the Muscular Dystrophy Campaign to the Hammersmith Hospital Neuromuscular Centre is gratefully acknowledged. During the initial part of this work MK was supported by the Dutch DMD parent support group. References Alman BA, Raza SN, Biggar WD. (2004) Steroid treatment and the development of scoliosis in males with Duchenne muscular dystrophy. J Bone Joint Surg Am 86-A: Management of Scoliosis in Duchenne Muscular Dystrophy M Kinali et al. 517

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