Extraspinal ossifications after implantation of vertical expandable prosthetic titanium ribs (VEPTRs)

Abstract

IntroductionThough developed for thoracic insufficiency syndrome, the spinal growth-stimulating potential and the ease of placement of vertical expandable titanium ribs (VEPTRs) has resulted in their widespread use for early-onset spine deformity. Observation of implant-related ossifications warrants further assessment, since they may be detrimental to the function-preserving non-fusion strategy.Patients and methodsRadiographs (obtained pre and post index procedure, and at 4-year follow-up) and the records of 65 VEPTR patients from four paediatric spine centres were analysed. Ossifications were classified as type I (at anchor points), type II (along the central part) or type III (re-ossification after thoracostomy).ResultsThe average age at the index procedure was 6.5 years (min 1, max 13.7). The most prevalent spine problem was congenital scoliosis (37) with rib fusions (34), followed by neuromuscular and syndromic deformities (13 and 8, respectively). Idiopathic and secondary scoliosis (e.g. after thoracotomy) were less frequent (3 and 4, respectively). Forty-two of the 65 (65 %) patients showed ossifications, half of which were around the anchors. Forty-five percent (15/33) without pre-existing rib fusions developed a type II ossification along the implant. Re-ossifications of thoracostomies were less frequent (5/34, 15 %). The occurrence of ossifications was not associated with patient-specific factors.ConclusionsImplant-related ossifications around VEPTR are common. In contrast to harmless bone formation around anchors, ossifications around the telescopic part and the rod section are troublesome in view of their possible negative impact on chest cage compliance and spinal mobility. This potential side effect needs to be considered during implant selection, particularly in patients with originally normal thoracic and spinal anatomy.

Sagittal Distraction of the Sternum in a Juvenile Male with Severe Short Rib Syndrome and Thoracic Insufficiency Syndrome - A Case Report

“…Fusions of the ribs after VEPTR procedures have been documented and were found in our patient; this was likely the reason why the lengthening procedures failed to improve his thoracic volume. This finding is consistent with those of previous publications [12,13].…”

Biomechanical Evaluation of a Growth-Friendly Rod Construct

“…Ossifications at the attachment sites, along the implant, between ribs, and between vertebrae have been found with differeing level of incidence. [10–12, 30, 31, 34] These ossifications are thought to contribute to curve stiffening. [11, 12, 30, 35] Anchor point migration is a common occurrence with these devices,[6, 12, 30–35] and in some cases rib fracture or dislocation has occurred.…”

“…Ossifications most often occurred at attachments at the lumbar spine and were more prevalent when the construct had a high rate of load sharing and when the curve correctability was lower, indicating a stiffer thoracic curve. [10, 12] By design, repeated pressure is applied at attachment sites. This allows for flexibility of the construct, which mitigates rib fracture and dislocation, but leaves the periosteum suseptible to injury and subsequent ossification.…”

“…[10–13] Sankar described the law of diminishing returns with subsequent lengthening of growing rods, which was felt to likely be secondary to autofusion. [14] Cahill et al reported an 89% incidence of autofusion in their series of 9 patients treated with growing rods.…”

Vertical expandable prosthetic titanium ribs (VEPTR) in early-onset scoliosis: Impact on thoracic compliance and sagittal balance

“…7,8 These constrictive mechanisms on the thoracic mobility may reduce thoracic compliance which forces infants to use more energy for respiration.…”