Does the external remote controller's reading correspond to the actual lengthening in magnetic-controlled growing rods?

PURPOSE: Magnetic-controlled growing rods (MCGRs) are now routinely used in many centres to treat early-onset scoliosis (EOS). MCGR lengthening is done non-invasively by the external remote controller (ERC). Our experience suggests that there may be a discrepancy between the reported rod lengthening on the ERC and the actual rod lengthening. The aim of this study was to investigate this discrepancy. METHODS: This was a prospective series. Eleven patients who were already undergoing treatment for EOS using MCGRs were included in this study. RESULTS: One hundred and ninety-two sets of ultrasound readings were obtained (96 episodes of rod lengthening on dual-rod constructs) and compared to their ERC readings. Only 15/192 (7.8%) readings were accurate; 27 readings (14.9%) were false positive; and 8 readings (4.2%) were an underestimation while 142 readings (74.0%) were an overestimation by the ERC. Average over-reporting by the ERC was 5.31 times of the actual/ultrasound reading. When comparing interval radiographs with lengthening obtained on ultrasound, there was a discrepancy with an average overestimation of 1.35 times with ultrasound in our series. There was a significant difference between ERC and USS (p = 0.01) and ERC and XR (p = 0.001). However, there was no significant difference between USS and XR (p > 0.99). CONCLUSION: The reading on the ERC does not equate to the actual rod lengthening. The authors would recommend that clinicians using the MCGR for the treatment of early-onset scoliosis include pre- and post-extension imaging (radiographs or ultrasound) to confirm extension lengths at each outpatient extension. In centres with ultrasound facilities, we would suggest that patients should have ultrasound to monitor each lengthening after distraction but also 6-month radiographs. These slides can be retrieved under Electronic Supplementary Material.

Do magnetic growing rods have lower complication rates compared with conventional growing rods?

BACKGROUND CONTEXT: The main advantage cited for the use of the magnetic controlled growing rod (MCGR) system over the conventional growing rod (CGR) in early-onset scoliosis is avoiding repeated invasive surgical procedures for lengthening, thus reducing, complications. PURPOSE: The study aimed to evaluate the complications of the MCGR system against the CGR system in our center. STUDY DESIGN/SETTING: This is a retrospective case control series. PATIENT SAMPLE: The sample includes patients with early-onset scoliosis treated with MCGR or CGR. OUTCOME MEASURES: Complications and unplanned return to theater were the outcome measures. RESULTS: Of the 37 patients (MCGR, N=10; CGR, N=27) in our cohort, 28 patients (76%) had at least one complication. Taking into account the follow-up period, MCGR had a higher complication rate than CGR group (0.32 complication per patient per year vs. 0.15 complication per patient per year). The use of MCGR was associated with a lower risk of deep infection (odds ratio [OR]: 0.22; p=.22) and superficial infection (OR: 0.07, p=.017) but increased risk of metalwork problems (OR: 4.67; p=.045) and unplanned return to theater (OR: 2.92; p=.05) compared with CGR. CONCLUSIONS: Although MCGR has a lower rate of both deep and superficial infections when compared with CGR, it does not completely avoid repeated invasive surgical procedures as previously suggested. It does have a significant increased risk of metalwork problems and unplanned return to theater.

Magnetic controlled growing rods for early-onset scoliosis: a 4-year follow-up.

BACKGROUND CONTEXT: There have been no studies with medium-term follow-up of magnetic controlled growing rods (MCGRs). PURPOSE: This study aimed to report our single center experience of a magnetic growing rod system with an average of 4 years' follow-up. STUDY DESIGN/SETTING: A retrospective case series was carried out. PATIENT SAMPLE: The sample comprised patients with early-onset scoliosis treated with magnetic controlled growth rods who were operated in 2011. OUTCOME MEASURES: Cobb angle, spinal growth rate, complications, and revision were the outcome measures. METHODS: Clinical case notes and radiographs were reviewed. RESULTS: There were 8 patients (5 dual-rod construct, 3 single-rod construct) who had a minimum of 44 months' follow-up and average of 48 months (44-55 months). Mean age at surgery was 8.2 years (range 3-10). Mean preoperative Cobb angle was 60° (34-94), whereas mean postoperative Cobb angle was 42° (32-63). The average number of extensions was 13.8 (range: 12-20). There were 6 patients (75%) who required 8 revision surgeries: rod problems (N=4), proximal screw pull-out (N=3), and development of proximal junction kyphosis (N=1). All three patients who had single-rod construct underwent revision procedure. Currently, four patients (50%) still have the magnetic rods in situ. The mean duration of MCGR in the patient in the removed group was 39 months (range: 34-46). CONCLUSIONS: Medium-term results of MCGR are not as promising as previously reported early results. Hence, MCGRs should be used with caution. Single-rod constructs should definitely be avoided. The role of MCGRs in revision cases still remains unknown.

Spontaneous locking of the knee after anterior cruciate ligament reconstruction as a result of a broken tibial fixation device.

The Intrafix device (DePuy Mitek, Raynham, MA) is one of a number of recently developed products whose aim is to improve fixation of quadrupled hamstring grafts when used for anterior cruciate ligament reconstruction. We present a case of failure and intra-articular migration of the sleeve of an Intrafix device causing locking of the knee 10 weeks after anterior cruciate ligament reconstruction. We were unable to identify the cause of the failure or migration of the device. Rehabilitation had been progressing normally and without incident. The broken fragments were removed arthroscopically, and the reconstruction was found to be intact and healing well. Presumably, the device retained enough mechanical function to allow healing to progress, despite failure of the sleeve. This is, to our knowledge, the first reported case of such an event occurring with the new generation of hamstring graft fixation devices.