Growth modulation in the management of growing spine deformities

Three-dimensional vertebral shape changes confirm growth modulation after anterior vertebral body tethering for idiopathic scoliosis

PURPOSE

To evaluate three-dimensional (3D) vertebra and disk shape changes over 2 years following anterior vertebral body tether (AVBT) placement in patients with idiopathic scoliosis (IS).

METHODS

Patients with right thoracic IS treated with AVBT were retrospectively evaluated. 3D reconstructions were created from biplanar radiographs. Vertebral body and disk height (anterior, posterior, left and right) and shape (wedging angle) were recorded over the three apical segments in the local vertebral reference planes. Changes in height and wedging were measured through 2 years postoperatively. Change in patient height was correlated with changes in the spine dimensions.

RESULTS

Forty-nine patients (Risser 0-3, Sanders 2-4) were included. The mean age was 12.2 ± 1.4 years (range 8-14). The mean coronal curve was 51 ± 10° preoperatively, 31 ± 9° at first postoperative time point and 27 ± 11° at 2-year follow-up (p < 0.001). The mean patient height increased 8 cm by 2 years (p < 0.001). The left side of the spine (vertebra + disc) grew in height by 2.2 mm/level versus 0.7 mm/level on the right side (p < 0.001). This differential growth was composed of 0.5 mm/vertebral level and 1.0 mm/disk level. Evaluation of the change in disk heights showed significantly decreased height anteriorly (- 0.4 mm), posteriorly (- 0.3 mm) and on the right (- 0.5 mm) from FE to 2 years. Coronal wedging reduced 2.3°/level with 1.1°/vertebral level change and 1.2°/disk level. There was no differential growth in the sagittal plane (anterior/posterior height). Patient height change moderately correlated with 3D measures of vertebra + disk shape changes.

CONCLUSIONS

Three-dimensional analysis confirms AVBT in skeletally immature patients results in asymmetric growth of the apical spine segments. The left (untethered) side length increased more than 3 × than the right (tethered) side length with differential effects observed within the vertebral bodies and disks, each correlating with overall patient height change.

Percutaneous transphyseal screw induces varus proximal femoral growth modulation in a growing pig model-A three-dimensional analysis

Bone and joint angular deformities are common pediatric orthopedic problems that are often corrected surgically. Previous studies successfully demonstrated proximal femoral growth modulation in animal models, however outcome measurements were limited by two-dimensional analysis. In this study, six Yorkshire cross male piglets were treated with unilateral percutaneous transphyseal screw placement across the medial aspect of the proximal femoral physis and analyzed using three-dimensional (3D) techniques. Three primary outcome measures were considered-physis angle, version, and femoral length. Compared to paired controls, all treated femurs displayed varus correction and shortening after an average treatment period of 10 weeks. The amount of varus change was 11.6 ± 2.8° (mean ± SD) (p = 0.0002, 95% confidence interval [CI] [8.659, 14.589]) and shortening was 4.3 ± 1.6 mm (p = 0.0011, 95% CI [2.672, 5.942]). Four animals demonstrated retroversion and two demonstrated anteversion compared to controls (4.1 ± 5.4° retroversion, p = 0.1169, 95% CI [-1.483, 9.765]). The amount of varus correction was strongly correlated with the orientation of the screw relative to the medial/lateral axis of the physis (r = -0.887, p = 0.0183, 95% CI [-0.988, -0.271]). The amount and direction of version was strongly correlated with how eccentrically anterior or posterior the screw was placed relative to the center of the physis (r = -0.850, p = 0.0322, 95% CI [-0.983, -0.123]) as well as the angle of the screw relative to the posterior condylar axis of the femur (r = -0.980, p = 0.0006, 95% CI [-0.998, -0.822]). This study is the first to use 3D analysis to quantify proximal femur growth modulation and identify associations between the growth modulation outcomes and screw placement parameters.

Anterior Vertebral Body Tethering for Adolescent Idiopathic Scoliosis: Early Results and Future Directions

Anterior vertebral body tether (AVBT) is a nonfusion surgical procedure for correction of scoliosis in skeletally immature individuals. With US Food and Drug Administration approval in 2019, AVBT technology is spreading and early to midterm reports are being published. Early clinical reports are promising while precise indications, outcomes, complication profiles, and best practices are being established. Patients who are skeletally immature and wish to avoid a fusion surgery may benefit from this procedure. This article highlights the translational science foundation, early to midterm clinical reports, and future directions for this growing technique in pediatric spinal deformity surgery.

Contactless treatment for scoliosis by electromagnetically controlled shape-memory alloy rods: a preliminary study in rabbits

PURPOSE

To evaluate the safety and efficacy of a system aiming to correct scoliosis called "electromagnetically controlled shape-memory alloy rods" (EC-SMAR) used in a rabbit model.

METHODS

We heat-treated shape-memory alloy (SMA) rods to achieve a transition temperature between 34 and 47 °C and a C-shape austenite phase. We then developed a water-cooled generator capable of generating an alternating magnetic field (100 kHz) for induction heating. We next studied the efficacy of this system in vitro and determined some parameters prior to proceeding with animal experiments. We then employed a rabbit model, in which we fixed a straight rod along the spinous processes intraoperatively, and conducted induction heating postoperatively every 4 days for 1 month, while performing periodic X-ray assessments.

RESULTS

Significant kyphotic deformations with Cobb angles of about 45° (p < 0.01) were created in five rabbits, and no complications occurred throughout the experiment. The rabbits are still very much alive and do not show any signs of discomfort.

CONCLUSIONS

This is the first system that can modulate spinal deformation in a gradual, contactless, noninvasive manner through electromagnetic induction heating applied to SMA alloy rods. Although this study dealt with healthy spines, it provides promising evidence that this device also has the capacity to correct human kyphosis and even scoliosis in the future. These slides can be retrieved under Electronic Supplementary Material.

Utility of an allograft tendon for scoliosis correction via the costo-transverse foreman

Current convex tethering techniques for treatment of scoliosis have centered on anterior convex staples or polypropylene tethers. We hypothesized that an allograft tendon tether inserted via the costo-transverse foramen would correct an established spinal deformity. In the pilot study, six 8-week-old pigs underwent allograft tendon tethering via the costo-transverse foreman or sham to test the strength of the transplanted tendon to retard spine growth. After 4 months, spinal deformity in three planes was induced in all animals with allograft tendons. In the treatment study, the allograft tendon tether was used to treat established scoliosis in 11 8-week-old pigs (spinal deformity > 50°). Once the deformity was observed (4 months) animals were assigned to either no treatment group or allograft tendon tether group and progression assessed by monthly radiographs. At final follow-up, coronal Cobb angle and maximum vertebral axial rotation of the treatment group was significantly smaller than the non-treatment group, whereas sagittal kyphosis of the treatment group was significantly larger than the non-treatment group. In sum, a significant correction was achieved using a unilateral allograft tendon spinal tether, suggesting that an allograft tendon tethering approach may represent a novel fusion-less procedure to correct idiopathic scoliosis. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:183-192, 2017.

Sonographic Analysis of Changes in Skull Shape After Cranial Molding Helmet Therapy in Infants With Deformational Plagiocephaly

OBJECTIVES

-The purpose of this study was to investigate the changes in skull shape on sonography after cranial molding helmet therapy in infants with deformational plagiocephaly.

METHODS

-Twenty-six infants who were treated with cranial molding helmet therapy were recruited. Caliper and sonographic measurements were performed. The lateral length of the affected and unaffected sides of the skull and cranial vault asymmetry index were measured with calipers. The occipital angle, defined as the angle between lines projected along the lambdoid sutures of the skull, was calculated by sonography. The occipital angle difference and occipital angle ratio were also measured. All caliper and sonographic measurements were performed in each infant twice before and twice after treatment.

RESULTS

-The study group included 12 male and 14 female infants with a mean age ± SD of 6.2 ± 3.5 months. The mean treatment duration was 6.0 ± 2.5 months. The difference in lateral length before and after helmet therapy was significantly greater on the affected skull than the unaffected skull (16.7 ± 12.7 versus 9.0 ± 13.4 mm; P < .01). The difference in the occipital angle before and after helmet therapy was significantly greater on the affected skull than the unaffected skull (-5.7° ± 7.3° versus 4.2° ± 7.9°; P < .01). The cranial vault asymmetry index and occipital angle ratio were significantly reduced after helmet therapy (cranial vault asymmetry index, 9.3% ± 2.3% versus 3.5% ± 3.0%; occipital angle ratio, 1.07 ± 0.05 versus 1.01 ± 0.01; P < .05).

CONCLUSIONS

-These results suggest that occipital angle measurements using sonography, combined with cephalometry, could provide a better understanding of the therapeutic effects of cranial molding helmet therapy in infants with deformational plagiocephaly.

Bacterial colonization of VEPTR implants under repeated expansions in children with severe early onset spinal deformities

PURPOSE

Historically, severe spinal and thoracic deformities in children were treated with early long spinal fusions. This prevented further growth of the spine and thorax and often led to small stiff thoraces. Therefore, growth-retaining implants, like vertical expandable titanium ribs (VEPTR), were developed to stimulate thoracic and spinal growth. To accommodate growth, these implants have to be expanded every 6 months. Infection rates of up to 2 % per procedure are reported. Exchange of implant parts allows analyzing the development of implant-related infections and subclinical colonizations.

METHODS

In this prospective study, all patients undergoing repeat VEPTR expansion procedures at our institution were included. Preoperatively, clinical signs of infection were documented, and blood samples were taken. The removed implants were treated by sonication and microbiologically analyzed. The clinical follow-up was documented.

RESULTS

From January 2009 to May 2012, 39 children with 163 re-operations were included. Four of the 39 patients (10 %) developed clinical apparent infections and had implant removal. These were excluded and analyzed separately. Of 144 procedures, implant parts were eligible for analysis. Implant colonization was detected by sonication in 24 of 144 (16 %) operations in 18 out of 39 (46 %) patients. Repeated detection occurred in 5 (14 %) patients. No risk factors for colonization could be identified.

CONCLUSION

The rate of implant colonization is 4.5 times higher than the rate of manifest infections in VEPTR patients. Colonization may lead to a manifest infection over time. The knowledge of persistent implant colonization may change the treatment algorithm in patients with growth-retaining implants.

The effect of serial growing rod lengthening on the sagittal profile and pelvic parameters in early-onset scoliosis

STUDY DESIGN

Retrospective case series.

OBJECTIVE

To report the effect of repeated growing rod (GR) lengthenings on the sagittal and pelvic profile in patients with early-onset scoliosis.

SUMMARY OF BACKGROUND DATA

Posterior distraction-based GRs have gained popularity as a technique for the surgical management of early-onset scoliosis. However, there are no published studies on the effect of serial GR lengthenings on sagittal balance, thoracic kyphosis (TK), lumbar lordosis (LL), and pelvic parameters.

METHODS

We retrospectively reviewed data from a multicenter early-onset scoliosis database. Forty-three patients who were able to walk with minimum 2-year follow-up who underwent single- or dual-GR surgery were included for review. Mean number of lengthenings was 6.4 (range, 3-16). Mean preoperative age was 5.6 years (standard deviation, 2.4 yr), and mean follow-up was 3.5 years. Maximum TK, LL, and sagittal balance were assessed preoperatively, after index surgery, and at the latest follow-up.

RESULTS

There was a significant decrease both in TK and LL after index surgery, which then increased during the lengthening period. There was a significant increase in both proximal junctional kyphosis and distal junctional angle. Pelvic parameters (pelvic tilt, pelvic incidence, sacral slope) were unchanged during the treatment period. Significant improvement was observed in sagittal balance. There was a correlation between the change in TK and change in LL.

CONCLUSION

TK decreased after index surgery and increased between the index surgery and the latest follow-up, which was accompanied by an increase in LL. All-screw proximal constructs had mean 9° more proximal junctional kyphosis than all-hook proximal constructs. An increase in proximal junctional kyphosis and distal junctional angle was found during the treatment period. Although there was an independent effect of number of lengthenings on TK, there was no significant detrimental effect on other sagittal spinopelvic parameters. GRs had a positive effect on sagittal vertical axis, which returned patients to a more neutral alignment through the course of treatment.

LEVEL OF EVIDENCE

4.

A new ultrasound method for assessment of head shape change in infants with plagiocephaly

Objective

To compare a new ultrasound measurement method with calliper cephalometry in infants with deformational plagiocephaly (DP) and to assess the differences of two methods according to the severity of DP.

Methods

Fifty-two infants with DP were divided into two groups according to the degree of cranial vault asymmetry (CVA); group 1 included 42 infants with CVA over 10 mm, and group 2 included 10 infants with CVA under 10 mm. Cranial vault asymmetry index (CVAI) and occipital angle ratio (OAR) were measured by using calliper and ultrasound measurements, respectively. The occipital angle was defined as the angle between the lines projected along the lambdoid sutures of the skull.

Results

The occipital angles of the affected sides were significantly greater than those of unaffected sides in both groups. The CVAI and OAR were significantly greater in group 1 than in group 2 (CVAI, 9.3%±2.3% vs. 4.6%±1.5%; OAR, 1.05±0.4 vs. 1.01±0.0; p<0.05). The OAR was positively correlated with the CVAI in all infants (r=0.789) and in group 1 (r=0.784; p<0.05).

Conclusion

Our study revealed that OAR using the new ultrasound measurement was positively correlated with the CVAI in infants with DP. Therefore, the occipital angle measurement using ultrasound combined with cephalometry could provide better understanding about the characteristics of the overall cranial bone and lambdoid suture complex in infants with DP.

The Shilla growth guidance technique for early-onset spinal deformities at 2-year follow-up: a preliminary report

BACKGROUND

The Shilla growth guidance technique has been developed to treat spinal deformities without the necessity of repeated operative lengthenings. The dual stainless steel rods are fixed to the corrected apex of the curve by pedicle screws with limited fusion about the apex. Vertebral growth occurs in a cephalad and caudad direction through extraperiosteally placed sliding pedicle screws. A retrospective review of patients treated with the Shilla growth guidance technique for early-onset spinal deformity was performed to study patients with >2-year follow-up and describe outcome parameters.

METHODS

From a cohort of 38 patients, 10 patients with a mean age of 7 + 6 years were identified as qualifying for 2-year follow-up inclusion.

RESULTS

The average preoperative curve of 70.5 degrees was corrected to 27 degrees at 6 weeks follow-up and maintained at 2-year follow-up. The space available for lung improved an average of 13%. Truncal height (C7 to S1) increased an average of 12%. One patient required rod revision, 1 required rod change to a smaller size rod, and 1 required rod replacement. Two patients required wound debridement for low-grade infection in the early-postoperative period for a total of 5 procedures beyond the index correction. No patient had changes neurologically as a result of surgery. Patients were braced for the first 3 months postoperatively while the fusion was incorporating then not thereafter.

CONCLUSIONS

At 2-year follow-up, the Shilla procedure has allowed children correction of their spinal deformity with an acceptable complication rate and ability to grow brace free without repeated trips to the operating room for lengthenings. These patients would have had 49 scheduled lengthening procedures after their initial correction if treated by conventional distraction growing rod methods.

LEVEL OF EVIDENCE

IV case series of therapeutic study investigating results of treatment.

Convex short segment instrumentation and hemi-chevron osteotomies for Putti type 1 thoracic hemivertebrae: a simple treatment option for patients under 5 years old

STUDY DESIGN

A case series depicting the results of a novel surgical technique.

OBJECTIVE

To prove that a minimally invasive surgical technique can effectively control and even correct congenital scoliosis caused by a fully segmented hemivertebra.

SUMMARY OF BACKGROUND DATA

Congenital hemivertebrae have been treated by anterior and posterior growth arrest with/without fusion, anterior and posterior hemivertebrectomy, transpedicular hemivertebra excision, and transpedicular hemiepiphysiodesis. These approaches are complex and require experience. There is a need for a simple treatment method to treat these deformities.

METHODS

Twelve patients under 5 years of age with Putti type1 hemivertebrae were treated by posterior convex short segment instrumentation, partial chevron osteotomies, and fusion. Scoliosis, segmental scoliosis, kyphosis, segmental kyphosis, trunk shift were measured both preoperatively and postoperatively.

RESULTS

The mean correction of the segmental curve was 6 degrees (21%) which was maintained at the latest follow-up. The average final correction of the main curve was 23%. The trunk shift was 1.8 cm (range, 1-3 cm) preoperative and 1.4 cm (range, 0-2.5 cm) at the latest follow-up. The segmental angle of kyphosis averaged 11 degrees (range, -12 to 20 degrees) preoperative, and 14 degrees (range, 0-29 degrees) at the latest follow-up assessment. The values of the total thoracic kyphosis (T2-T12) were 29.5 degrees (range, 10-46 degrees) preoperative, 31 degrees (range, 10-44 degrees) postoperative, and 32 degrees (range, 16-45 degrees) at the last follow-up resulting in a mean improvement of 2 degrees. This improvement continued at the latest follow-up with a mean increase of 3 degrees.

CONCLUSIONS

Transpedicular instrumentation is ideal for early correction in young children. The new posterior approach is much less invasive than the combined approaches or other posterior vertebrectomies and is well tolerated even in very young patients. The fusion segment is kept short. The deformities seem to stop progressing and this can avoid development of severe local deformities and secondary curves.

Surgical epiphysiodesis indications and techniques: update

PURPOSE OF REVIEW

To present a summary of epiphysiodesis indications and to report most recent advances in the field, along with their clinical relevance.

RECENT FINDINGS

Percutaneous epiphysiodesis using transphyseal screws (PETS) and guided growth using eight plates represent the most recent techniques used for hemiepiphysiodesis.

SUMMARY

PETS and guided growth have yielded very good results and low rates of complications and are the current standard for the management of angular deformities of the lower extremities in children. Permanent percutaneous epiphysiodesis remains the preferred method for the treatment of limb length discrepancies.

Guided growth

Guiding growth by harnessing the ability of growing bone to undergo plastic deformation is one of the oldest orthopaedic principles. Correction of deformity remains a major part of the workload for paediatric orthopaedic surgeons and recently, along with developments in limb reconstruction and computer-directed frame correction, there has been renewed interest in surgical methods of physeal manipulation or ‘guided growth’. Manipulating natural bone growth to correct a deformity is appealing, as it allows gradual correction by non- or minimally invasive methods.

This paper reviews the techniques employed for guided growth in current orthopaedic practice, including the basic science and recent advances underlying mechanical physeal manipulation of both healthy and pathological physes.