15 Complications of Growing Rod Treatment
The growing rod technique is the prototype of posterior distraction-based growing spine procedures used for the surgical treatment of progressive early onset scoliosis that is not controlled with nonoperative care. The standard course of treatment includes an initial growing rod implantation with limited fusion at the foundations sites, distraction procedures at regular intervals to maintain or stimulate growth of the nonfused segments, and a definitive final spinal fusion at skeletal maturity. 1 Planned and unplanned revisions may be at times necessary to address implant- or patient-related complications.
The surgical treatment of early onset scoliosis with contemporary techniques is inherently prone to adverse events. Frequent operations, young age at initial surgery, associated medical conditions and malnutrition, and complex underlying spinal deformities place these patients at increased risk for complications. Depending on the etiology of early onset scoliosis, the number of surgeries, and the length of follow-up, complications after growing rod surgery have been reported variably in different studies. This chapter reviews the complications that commonly develop after growing rod treatment.
15.1 Review of the Literature
The complication rates reported in the earlier literature on the first generation of growing rods (i.e., subcutaneous Harrington or Moe rods) were unacceptably high. In 2002, Mineiro and Weinstein reported the results of subcutaneous rodding and repeated distraction procedures in 11 patients. The most common complication was rod failure, which occurred in more than half of patients. The subcutaneous placement of Harrington or Moe rods achieved acceptable deformity correction and variable spinal height gain, but with an average of 1.5 complications per patient. 2
Klemme et al reviewed spinal instrumentation without fusion in 67 patients treated over a period of 21 years. They reported details of the complications, including implant-related problems, which occurred in 33 procedures in 25 patients (8%), and hook dislocations, which occurred on 21 occasions. Rod fracture was seen 12 times: seven times with Moe-modified Harrington rods, four times with Harrington rods, and one time with a pediatric Cotrel–Dubousset rod. Despite the frequency of the complications, the authors believed that instrumentation without fusion could be applied to a selected group of children with progressive scoliosis, but they also suggested that arthrodesis must be performed without delay in the event of suboptimal gain in length. 3
In 2010, Bess et al published a comprehensive review of complications after growing rod surgery in 140 patients with early onset scoliosis. 4 Their landmark study described complications of the classic growing rod construct, which was introduced in 2000 by Akbarnia and Marks. 5 The authors reviewed 140 cases of index growing rod surgery, 633 lengthening procedures, and 74 unplanned procedures. The total numbers of surgeries and lengthening procedures per patient were 6.4 and 4.5, respectively. Of the 140 patients, 81 (57%) had at least one complication. A total of 177 complications occurred after 897 surgeries (20%). An unplanned surgical procedure was needed to manage 74 of the 177 complications (42%). The patients were divided into treatment groups based on type of growing rods (51% single vs. 49% dual) and location of implants (37% subcutaneous vs. 63% submuscular). The complications were categorized as implant-related (45% of all patients), wound-related (16%), alignment-related (7%), neurologic (3%), or general medical and surgical (12%) complications. There were 94 complications in 43 patients with a single growing rod and 83 complications in 38 patients with dual growing rods. Superficial wound infections were more common in the patients with dual rods, whereas hook dislodgments and unplanned procedures due to other implant complications were more common in the patients with a single rod. Implant complications more often led to unplanned surgical procedures in patients with a single rod (45%) than in those with dual rods (24%; p < 0.05). Three patients (2%) had neurologic complications. Fifty-one patients (37%) had subcutaneous growing rods, and 88 patients (63%) had submuscular growing rods. Subcutaneous rod placement was associated with more frequent complications per patient, more frequent wound complications, and more prominent implants than submuscular rod placement (p < 0.05). Survival analysis of all patients showed that the rate of complications increased after a given number of surgeries. The authors concluded that complications could be reduced by delaying the initial implantation of growing rods if possible, using dual rods, and limiting the number of lengthening procedures. Submuscular placement reduced wound complications and implant prominence and reduced the number of unplanned operations. 4
15.2 Classification of Complications
Efforts have been made to classify complications after growth-friendly procedures and to reach a consensus for more efficient communication, the preparation of treatment guidelines, and prognostication. Smith et al recently developed a new, consensus-based classification system to report complications after growth-friendly procedures. 6 A complication was defined as an unexpected medical event that occurred during the course of treatment. Complications were classified as disease- or surgery-related and were graded according to severity. A surgery-related complication of severity grade I (SV-I) was defined as a complication that does not necessitate unplanned surgery. SV-II requires unplanned surgery: SV-IIA only one surgery and SV-IIB multiple surgeries. SV-III changes the course of planned treatment. A disease-related complication of SV-I does not necessitate hospitalization, but SV-II requires hospitalization for treatment. The authors tested the new classification system by using it to evaluate 65 patients from five centers with early onset scoliosis and at least 2 years of follow-up, including 14 with growing rods, 47 with a vertical expandable prosthetic titanium rod, and four with hybrid constructs. There were 57 surgery-related SV-I, 79 SV-IIA, 10 SV-IIB, and 6 SV-III complications. The authors concluded that although complications were common, only six were severe enough to change the course of planned treatment, and they suggested that this new system could be used to facilitate better communication among pediatric spine surgeons.
15.3 Implant-Related Complications
15.3.1 Rod Fracture
Rod fracture as a complication of nonfusion spinal instrumentation in the immature spine was first described by Moe et al. 7 Fracture of the longitudinal implants in a growing rod system is a common complication; however, its significance and effect on the ongoing care of a patient depend on the timing of the fracture and number of implanted rods. In our experience, if only one rod fractures and the patient is close to his or her next scheduled lengthening, the rod exchange can be planned at the next lengthening. However, if the patient has a single growing rod or a rod fractures soon after a lengthening procedure, unplanned revision should be performed so as not to lose curve correction and achieved spinal height gain.
Yang et al studied the risk factors for rod fracture after growing rod surgery. In a retrospective study of 327 patients who had undergone growing rod surgery, 86 rod fractures occurred in 49 patients (15%). The mean time to fracture after initial insertion was 25 ± 21 months, and it was 5.8 ± 3 months after the previous lengthening. Rod fractures occurred most commonly adjacent to tandem connectors and at thoracolumbar region (T11-L1). The incidence of rod fracture was highest in patients with syndromic early onset scoliosis (14%). Risk factors for rod fracture were prior rod fracture, single rod, stainless steel material, smaller diameter, proximity to the tandem connector (within 1 cm), short tandem connector, and preoperative ambulatory status. Patients with a single growing rod had a higher rate of fracture than those with dual growing rods. The repeated fracture always occurred on the same side and within one vertebral level of the original fracture. The authors suggested the use of dual growing rods with a maximal diameter whenever possible and of gradual rather than focal bends. They also suggested exchanging the entire section of the construct if one rod breaks. 8
David et al reviewed 413 lengthening procedures in every patient undergoing growing rod surgery at a single center from 1997 to 2012. They found 42 rod fractures in 22 patients (10%), with the first rod fracture occurring at a mean of 37 months after the primary surgery. Following a revision procedure combined with lengthening, there were 21 rod re-fractures (50%). In seven of the episodes (17%), the rod fractures were bilateral, requiring revision of both sides. Among fractures of a single rod in which revision on a single side was undertaken (n = 15), there were 8 re-fractures (53%), with a mean time to re-fracture of 17 months. When both sides were revised (n = 18) following failure of a single side, seven re-fractures occurred (39%; p = 0.32), with a mean time to re-fracture of 19 months. The majority of rod re-fractures (13 of 15) occurred on the same side as the initial fracture. In contrast to the usual belief, David et al advised against a bilateral exchange of rods in patients with a single-sided growing rod fracture. 9
We have continued to change both rods if one rod breaks in order to prevent fatigue of the other rod and an early failure.
15.3.2 Anchor Failure
Anchor failure is the second most common growing rod complication after rod fracture (29%), with hook dislodgment in 21% and screw dislodgement in 3% (Fig. 15.1). 5 Depending on the type and time of the anchor failure, treatment strategies are different. Unilateral anchor failure in a patient with no neurologic or vascular injury, an intact contralateral growing rod construct, and close to the next planned growing rod lengthening can be managed during planned revision at the next lengthening event.
Skaggs et al compared complications of hooks vs. screws in 247 patients who underwent growing rod treatment with a mean follow-up of 40 months. Among 896 pedicle screws, 22 complications (2.4%) were directly related to the screw, including acute loss of fixation (4), migration (14), breakage (1), skin breakdown (2), and unspecified loss of fixation (1). Among 867 hooks, there were 60 complications (6.9%), including acute loss of fixation (35), migration (22), and unspecified loss of fixation (3). There were no intraoperative pedicle screw–related issues, but two hooks plowed intraoperatively, resulting in bone damage. The average time to loss of fixation was 19 months for both implants. No complications involved neurologic or vascular injury directly related to hooks or screws. 10
The use of spine anchors on the proximal ribs as fixation points has recently received attention as an alternative growing rod technique, commonly referred to as a hybrid growing rod technique. Skaggs et al reviewed the result of the hybrid growing rod technique in 28 patients (23 with a single growing rod and five with dual growing rods) over a mean follow-up of 37 months. The mean primary coronal curve (measured by the Cobb method) at the time of index surgery was 69 degrees, which was corrected to 19 degrees, and the correction was maintained through the latest follow-up. The mean increase in T1-S1 length at the latest follow-up was 49 mm, with a mean increase of 13 mm per lengthening procedure. Complications occurred in seven patients (24%), all with congenital scoliosis. A nonsignificant trend was observed for complications to be associated with a younger age and a larger Cobb angle at index surgery. Patients who had complications included two with wound issues, nine with loss of fixation of the rib anchors, and one rod breakage. There were no neurologic complications. No loss of fixation occurred in any construct that had a proximal foundation of at least four up-going hooks on ribs, and no complications occurred in dual constructs. 11
Akbarnia et al compared the biomechanical properties of the four bilateral proximal anchors commonly used in growing rod technique in an in vitro porcine model and found that claw-fashioned rib hook constructs had a significantly higher load to failure compared with bilateral laminar hooks and bilateral transverse process–laminar hooks, but not with pedicle screw constructs. The authors suggested that rib anchors may serve as an alternative upper foundation in growing rod technique. 12
Related posts:
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
