Crankshaft phenomenon in congenital scoliosis: a preliminary report

Ten-year trends in surgical management of 1207 congenital scoliosis

PURPOSE

To report and analyze development trends in the surgical treatment of congenital scoliosis (CS) in a large CS cohort over a 10-year period.

METHODS

We retrospectively searched and extracted medical records of CS inpatients receiving posterior instrumented fusion surgery at our institute from January 2010 to December 2019. We analyzed information on demographics and surgical information, including the surgical approach, number of fused segments, use of osteotomy and titanium cage implantation, length of stay, intraoperative blood loss, and rates of complications and readmission.

RESULTS

1207 CS inpatients were included. In the past decade, the proportion of patients younger than 5 years increased from 15.5 to 26.9%. The average number of fused segments decreased from 9.24 to 7.48, and the proportion of patients treated with short-segment fusion increased from 13.4 to 30.3%. The proportion of patients treated with osteotomy and titanium cage implantation increased from 55.65% and 12.03% to 76.5% and 40.22%. The average length of stay and blood loss decreased from 16.5 days and 816.1 ml to 13.5 days and 501.7 ml. The complication and readmission rates also decreased during these ten years.

CONCLUSION

During this ten-year period, the surgical treatment of CS at our institute showed trends toward a younger age at fusion, lower number of fused segments, higher rate of osteotomy and titanium cage implantation, reduced blood loss, shorter length of stay and lower rate complications and readmission. These results suggest performing osteotomy combined with titanium cage implantation at an earlier age can achieve fewer fused segments and complications.

Hybrid Growing Rod Technique of Osteotomy With Short Fusion and Spinal Distraction: An Alternative Solution for Long-Spanned Congenital Scoliosis

STUDY DESIGN

Retrospective study.

OBJECTIVE

The current study aimed to evaluate the effectiveness of the hybrid growing rod (GR) technique for the treatment of young children with congenital scoliosis (CS).

SUMMARY OF BACKGROUND DATA

Congenital vertebral anomalies within long-spanned kyphoscoliosis were difficult to be managed by either definitive spinal fusion or standard GR technique. Hybrid technique of one-stage posterior osteotomy with short fusion and GR distraction was proposed in previous studies. There is, however, paucity of data regarding its effectiveness.

METHODS

Thirteen patients (mean age, 5.4 ± 2.0 yr) who had undergone hybrid GR treatment were retrospectively reviewed, including 8 patients treated with single GR and 5 patients with dual GR. All of their radiographic data were measured, and surgical complications were recorded.

RESULTS

On average, the current cohort had 4.1 ± 1.7 lengthening procedures. After the index surgery, the major curve improved remarkably from 86.4° ± 11.9° to 37.3° ± 12.4° (P < 0.001). The global kyphosis significantly decreased from 66.8° ± 16.1° to 33.3° ± 3.5° postoperatively. Both value remained steady during follow-up. There were no significant difference between single GR and dual GR groups in terms of the coronal deformity correction, whereas correction loss of global kyphosis in single GR group was significantly higher than that in dual GR group (P = 0.039). After the index surgery, T1-S1 height averagely gained 4.4 ± 0.8 cm and it grew at an average rate of 1.31 ± 0.24 cm/yr during the follow-up. Two complications were identified in two patients, including one with rod fracture and one with proximal junctional kyphosis.

CONCLUSION

The hybrid GR technique was effective in correcting spinal deformity and allowing continuous spinal growth. The optimal indications were young children with apical vertebrae anomalies and a long-spanned kyphoscoliosis.

LEVEL OF EVIDENCE

3.

A comprehensive review of the diagnosis and management of congenital scoliosis

PURPOSE

To provide the reader with a comprehensive but concise understanding of congenital scoliosis METHODS: We have undertaken to summarize available literature on the pathophysiology, epidemiology, and management of congenital scoliosis.

RESULTS

Congenital scoliosis represents 10% of pediatric spine deformity and is a developmental error in segmentation, formation, or a combination of both leading to curvature of the spine. Treatment options are complicated by balancing growth potential with curve severity. Often associated abnormalities of cardiac, genitourinary, or intraspinal systems are concurrent and should be evaluated as part of the diagnostic work-up. Management balances the risk of progression, growth potential, lung development/function, and associated risks. Surgical treatment options involve growth-permitting systems or fusions.

CONCLUSION

Congenital scoliosis is a complex spinal problem associated with many other anomalous findings. Treatment options are diverse but enable optimization of management and care of these children.

A re-evaluation of the effects of dual growing rods on apical vertebral rotation in patients with early-onset scoliosis and a minimum of two lengthening procedures: a CT-based study

OBJECTIVE This study aimed to evaluate the correction results of traditional dual growing rods (DGRs) on axial rotation using CT scans and to further explore the relationships between axial and torso deformities in patients with early-onset scoliosis (EOS). METHODS Patients with EOS who were treated with traditional DGRs between January 2006 and December 2014 were retrospectively reviewed. Plain radiographs were used to assess the degree of coronal and sagittal deformity. The apical vertebral rotation (AVR) and rib hump (RH) were measured on CT scans at the apical vertebra. Pearson or Spearman rank correlation analyses were used to analyze the associations between spinal and torso deformities. RESULTS A total of 27 patients (10 boys and 17 girls, average age 6.5 ± 1.7 years) were enrolled in this study. The average number of lengthenings per patient was 5.0 ± 1.9, with a mean follow-up duration of 52.9 ± 18.2 months. The apical vertebral translation, apical vertebral body-rib ratio (AVB-R), AVR, and RH parameters were significantly decreased after the initial surgery (p < 0.05) but showed notable progression at the latest follow-up evaluation (p < 0.05). The preoperative AVR and its correction after index surgery were significantly correlated with the preoperative values as well as with the corrections of the major Cobb angle, AVB-R, and RH. During the follow-up period, significant correlations were found between the deterioration of AVR and the AVB-R and also between the deterioration of AVR and the RH from the initial surgery to the latest follow-up. CONCLUSIONS Significant AVR correction can be achieved by DGR techniques after the initial surgery. However, this technique weakly prevents the deterioration of AVR during the follow-up period.

Serial derotational casting in congenital scoliosis as a time-buying strategy

BACKGROUND

Serial casting is an effective treatment modality in early-onset idiopathic scoliosis; however, the role of this method in congenital scoliosis is not well studied.

METHODS

A total of 11 patients with progressive congenital scoliosis were treated with serial cast application. Age at initial cast application, magnitudes of the congenital, compensatory and sagittal deformities, coronal balance, T1 to T12 height, number of casts and time-in cast per patient, subsequent surgical interventions, and complications were evaluated.

RESULTS

Mean age at the first cast application was 40 months, and the average number of cast changes was 6.2 per patient. There were no major complications. The average precasting curve magnitude was 70.7 degrees (range, 44 to 88 degrees) and was significantly reduced to 55.1 degrees (range, 16 to 78 degrees) at the latest follow-up (P=0.005). The average precasting compensatory curve was 55.8 degrees (range, 38 to 72 degrees) and was significantly reduced to 39.8 degrees (range, 23 to 62 degrees) at the latest follow-up (P=0.017). Average T1 to 12 height increased from 12.8 cm at post-first cast to a 14.6 cm at the latest follow-up (P=0.04). Average time in cast was 26.3 months (range, 13 to 49 mo). During the treatment period, none of the patients required surgery for curve progression.

CONCLUSIONS

Serial derotational casting is a safe and effective time-buying strategy to delay the surgical interventions in congenital deformities in the short-term follow-up.

LEVEL OF EVIDENCE

Level IV, case series.

[Prognostic factors of the crankshaft phenomenon in patients with scoliosis and open triradiate cartilage. Is the double approach the solution?]

OBJECTIVE

To study young patients after scoliosis surgery in order to determine risk and prevention factors for developing a crankshaft phenomenon (CP).

MATERIAL AND METHODS

Retrospective study of a cohort of 26 skeletally immature patients. Six were excluded due to progression of various conditions. Crankshaft was defined as an increase in the Cobb angle >10°, or an increase in the Mehta angle (DAVC) >10°, or any decrease in the apex-rib thoracic distance, or increase in the apical vertebral translation (AVT). Patients with and without CP development were compared in order to analyse preoperative, surgical and postoperative risk factors, as well as the influence of different surgical techniques.

RESULTS

The mean follow-up was 83.9 months. Nine patients (45%) developed the crankshaft phenomenon. Only immaturity parameters were associated with development of CP. No preoperative or postoperative radiographic parameters appeared to influence its development. The amount of correction may be a protective factor (41.4 vs. 61.4%; P=.06). The double approach was able to prevent the development of CP (0%) compared with single posterior instrumentation (44%), P=.02.

DISCUSSION

None of these preoperative factors seemed to predispose to CP: gender or aetiology, T5-T12 kyphosis or apical hypokyphosis, coronal Cobb, vertebral rotation, or DAVC. The residual postoperative Cobb, achieved kyphosis, or wired instrumentation versus hooks, also seemed to have no influence.

CONCLUSION

In patients with open triradiate cartilage under 11 years of age, it seems advisable to correct by double approach to avoid the appearance of the crankshaft phenomenon.

Evidence basis for management of spine and chest wall deformities in children

STUDY DESIGN

: Review of relevant studies, including levels of evidence.

OBJECTIVE

: To review research on growth of the spine and chest wall and treatment of deformities. To place this knowledge in context of evidence-based assessment.

SUMMARY OF BACKGROUND DATA

: Knowledge of the growth of the spine, chest wall, and lung in the normal and deformity states has evolved among independent specialties over the past 60 years. Interest in the interrelationship has blossomed as more tools for assessment and treatment have developed. Spine-based and chest wall-based treatment options now exist, as well as options of resection versus gradual distraction.

METHODS

: Peer-reviewed research published on the growth of the spine, lung, chest wall, and treatment of their deformities was reviewed. Treatment methods and outcomes were compared. Ranking of the levels of evidence was performed where possible.

RESULTS

: Most studies of these topics are Level III and IV studies, consisting of case-control studies and case series. This limitation arises because of the rarity and heterogeneity of the disorders affecting the growing spine and chest wall. The natural history of most types of spinal/chest wall deformities is not known with accuracy. Some experimental evidence informs the treatments which involve modulation of the growth of the spine. However, accurate models of the deformities themselves are lacking. Improvements in imaging and measurement offer options for more accurate patient comparison.

CONCLUSION

: The natural history and results of treatment of deformities of the spine and chest wall offer much opportunity for further evidence-based research.

Congenital scoliosis: a review and update

Vertebral anomalies causing congenital scoliosis are classified on the basis of failures of formation, segmentation, or both. The natural history depends on the type of anomaly and the location of anomaly. Patient evaluation focuses on the history and physical examination, followed by appropriate imaging modalities. The hallmark of surgical treatment is early intervention before the development of large curvatures. The surgical treatment of a congenital deformity mandates the use of neurological monitoring to minimize the risk of perioperative neurological deficit. Modern surgical techniques have evolved to include the routine use of spinal instrumentation. Patients with associated chest wall deformities or large compensatory curves may be candidates for vertical expansion prosthetic titanium rib placement or growing rods insertion to maximize growth.

Congenital scoliosis

Congenital scoliosis is caused by early embryologic errors in vertebral column formation. Defining the deformity, predicting the natural history, and applying the correct treatment can help ensure successful management. Most congenital spine anomalies can be classified, and many have a predictable natural history. Because the deformities are associated with other organ system anomalies in more than half of patients, the surgeon should look for cardiac, auditory, genitourinary, and renal anomalies. Intraspinal abnormalities are present in approximately one third of patients with congenital spine deformities. Curve progression is best documented by measuring identical landmarks on sequential radiographs. Magnetic resonance imaging is warranted when curve progression is established or when surgical intervention is planned. Management of progressive deformity is generally by early in situ fusion because orthotic treatment is rarely appropriate. Other surgical techniques include combined anterior and posterior epiphysiodesis, hemivertebra resection, and reconstructive osteotomies.

The crankshaft phenomenon after posterior spinal arthrodesis for congenital scoliosis: a review of 54 patients

STUDY DESIGN

Retrospective chart and radiographic reviews were conducted.

OBJECTIVE

To identify the incidence of and any possible risk factors for the crankshaft phenomenon after posterior spinal arthrodesis for congenital scoliosis.

SUMMARY OF BACKGROUND DATA

Studies have shown the crankshaft problem to be common after posterior arthrodesis for infantile and juvenile idiopathic scoliosis, but the few reports available show it to be much less common for congenital scoliosis.

METHODS

This study chose children fused before the pubertal growth spurt, all classified as Risser 0 and with open triradiate cartilages. These children were followed to the end of their growth (mean follow-up period 12 years). Several measurement parameters were used for evaluation.

RESULTS

The crankshaft problem, measured as a Cobb angle increase of more than 10 degrees, was seen in 15% of the 54 patients. There was a positive correlation with earlier surgery and larger (>50 degrees) curves. No other positive correlations could be identified.

CONCLUSIONS

Crankshafting was observed in 15% of the patients, more often with larger curves and earlier fusions.

Long-term results from in situ fusion for congenital vertebral deformity

STUDY DESIGN

Retrospective review of long-term outcome of fusion in situ for congenital vertebral anomaly with particular emphasis on cosmesis and the incidence of reoperation.

OBJECTIVE

Examination of the success rate of this procedure and of risk factors for failure.

BACKGROUND

Fusion in situ is the accepted prophylactic treatment to prevent deformity in congenital vertebral anomalies that have a high risk of progression or have been shown to be deteriorating.

METHODS

Records of patients who were at least 15 years of age at last examination were reviewed retrospectively. Consideration was given to cosmetic outcome and to the incidence of reoperation.

RESULTS

There were 43 patients in this category, 19 boys and 24 girls, who were at least 15 years of age when last seen. Reoperation had been performed in 11 cases (25.6%). The main finding was that, although the Cobb angle of the fused segment of spine remained constant after fusion, a curve sometimes developed in the whole spine, sometimes (but by no means always) centered on that fused segment. Cosmetic deformity continued to progress in a number of cases.

CONCLUSIONS

Localized fusion, whether posterior alone or anterior and posterior combined, was effective in preventing progression of the Cobb angle of the congenitally malformed area but did not control the overall deformity that developed or progressed with growth. Current concepts of the pathomechanism of deformity do not adequately explain the observations, and a more biologic approach is suggested.

Congenital scoliosis

Congenital scoliosis is a deformity of the developing spine that results from defects in vertebral development. The developmental etiologies may be classified as either a failure of formation, a failure of segmentation, or a mixture of these two modes of maldevelopment. Early detection and close surveillance of congenital scoliosis is critical, as a rapidly progressive curve may lead to significant deformity, pulmonary restriction, and neurologic problems if not treated. Early surgical treatment is often necessary for rapidly progressive curves.

Complications in spinal fusion

Complications in spinal fusion can lead to less than desirable results. The complications of spinal fusion in the cervical and lumbar spine are discussed. Methods of avoiding and correcting complications also are reviewed. Through a better understanding, it is hoped that complications can be prevented.

Congenital scoliosis caused by a unilateral failure of vertebral segmentation with contralateral hemivertebrae

STUDY DESIGN

The medical records and serial spine radiographs of 59 consecutive patients with congenital scoliosis caused by unilateral unsegmented bar with contralateral hemivertebrae were reviewed.

OBJECTIVES

To study the presentation, natural history, and treatment of these patients.

SUMMARY AND BACKGROUND DATA

This is the least common type of congenital scoliosis.

METHODS

The mean age at diagnosis was 4 years 1 month. Forty-three patients were observed without treatment for a mean of 6 years and 1 month. Prophylactic arthrodesis was performed in 10 patients before they were 5 years old. Thirty-five patients had a corrective procedure and arthrodesis after they were 5 years old.

RESULTS

Thoracolumbar curves had the worst prognosis. Without management all but two exceeded 50 degrees when the patients were 2 years old. All untreated curves exceeded 88 degrees. Midthoracic curves had only a slightly less severe prognosis, and all but one exceeded 40 degrees by the time the patient was 2 years old. All untreated curves exceeded 70 degrees. In eight of the 14 patients whose congenital curves had their apexes at T5, T6, or T7, a long secondary structural curve developed on the opposite side in the thoracolumbar region, and this contributed significantly to the overall deformity. Occult intraspinal anomalies were present in 24 patients (41%). Surgical treatment after the patient was 5 years old was not successful in producing significant correction of these severe rigid deformities.

CONCLUSION

These patients have the most rapidly progressive and severely deforming of all types of congenital scoliosis. All midthoracic, thoracolumbar, and lumbar curves require immediate prophylactic surgical treatment by anterior and posterior arthrodesis--preferably in the first year of life.

Posterior arthrodesis in the skeletally immature patient. Assessing the risk for crankshaft: is an open triradiate cartilage the answer?

STUDY DESIGN

Thirty-three skeletally immature patients younger than 12 years of age and having posterior arthrodesis and evidence of solid posterior fusion without "adding on" were retrospectively reviewed. All patients had a minimum of 5 years of follow-up.

OBJECTIVES

To ascertain factors associated with crankshaft and to determine how accurate a marker the triradiate cartilage was.

SUMMARY OF DATA

All patients had Risser Stage 0 curves and all of the girls were premenarchal preoperatively. The average age was 9 years 3 months (range, 2 years-11 years 11 months). Preoperative diagnoses consisted of 14 idiopathic, 11 congenital, five dysplastic, and three neuromuscular etiologies.

METHODS

Preoperatively, within 3 months after surgery, and at 2-year, 5-year, and final postoperative follow-up, the following radiographic parameters were reviewed: coronal Cobb, apical vertebral rotation, apical vertebral translation, rib vertebral angle difference, and trunkshift.

RESULTS

The triradiate cartilage was open in 24 patients at the time of operation. Of those 24, only nine (37.5%) had documented proof of crankshaft. Patients with closed triradiate cartilage had no significant postoperative increase in radiographic parameters (0 of 9). The subgroup of patients with idiopathic scoliosis had an average age of 11 years 3 months (range, 9 years 2 months-11 years 11 months). Five of 14 patients had an open triradiate cartilage. All were followed up to skeletal maturity. None had significant progression in postoperative radiographic parameters.

CONCLUSION

This study did not find an open triradiate cartilage to be an absolute prognostic indicator for the occurrence of crankshaft. Additional refinement of markers of maturity are needed to determine who requires anterior arthrodesis.

The crankshaft phenomenon after posterior Harrington fusion in skeletally immature patients with thoracic or thoracolumbar idiopathic scoliosis followed to maturity

STUDY DESIGN

This retrospective study evaluated the progression of deformity after posterior fusion by reviewing 63 consecutive patients with idiopathic scoliosis who were all in Risser sign 0 at the time of surgery. All patients were observed beyond the time of skeletal maturity. Average follow-up time was 9 years and 8 months (range, 5-16 years).

OBJECTIVES

To investigate the risk factors for the crankshaft phenomenon after posterior fusion and to build a model for predicting the probability of curve progression until maturation of growth.

SUMMARY OF BACKGROUND DATA

There remains considerable controversy concerning the incidence, risk factors, and necessity of combined anterior fusion to prevent the crankshaft phenomenon in patients who are skeletally immature.

METHODS

Serial radiographs were measured for Cobb angle, apical rotation according to Perdriolle, and apical rib-vertebra angle of Mehta. Multivariate and univariate logistic regression analysis was performed using seven potential predictors as independent variables and Cobb angle progression and rotational progression as dependent variables.

RESULTS

Average progression of deformity was 3 degrees Cobb angle (range, -8-16 degrees) and 3 degrees Perdriolle rotation (range, -9-17 degrees). Progression of deformity more than 5 degrees of either Cobb angle or rotation was observed in 22 (35%) of 63 curves with 7 (11%) of 63 curves greater than 10 degrees. Chronologic age and skeletal age were found to be significantly associated with progression of deformity in univariate analysis. In multivariate analysis, only skeletal age seemed to be independently prognostic. The authors tried to build the logistic model using the three factors of chronologic age, skeletal age, and apical rib-vertebra angle. This model correctly classified 81% of all patients as progressive or nonprogressive. The positive predictive value was 90%.

CONCLUSIONS

The results showed that patients with chronologic age of 11 years of younger, especially those with a skeletal age of 10 years or younger, had a high estimated probability of progression of deformity. The progression was fairly moderate, however, with an average Cobb angle of 9 degrees and average rotation of 7 degrees, which neither the patients nor the surgeon believed was of such magnitude as to warrant routine combined anterior fusion.

Overpowering the crankshaft mechanism. The effect of posterior spinal fusion with and without stiff transpedicular fixation on anterior spinal column growth in immature canines

STUDY DESIGN

This experimental study was designed to test the hypothesis that posterior spinal fusion and internal fixation, using a stiff transpedicular construct, would withstand additional anterior column growth without the need for an anterior procedure and would prevent the development of deformity secondary to asymmetric growth of the anterior column in the immature canine model.

OBJECTIVES

This model revealed that a mechanical epiphysiodesis of the anterior spinal column can be created through a posterior approach in an immature growing animal using a stiff transpedicular construct. These results were correlated to the crankshaft mechanism clinically to provide a possible rationale for transpedicular posterior spinal instrumentation and fusion, without a concomitant anterior procedure, in immature patients.

SUMMARY OF BACKGROUND DATA

All operative immature canines underwent posterior fusion of L1-L5 vertebral bodies with autogenous iliac crest bone graft. Instrumented canines underwent the additional placement of transpedicular screws at L1, L3, and L5 as well as 3/16-inch rods and a transverse connector. Previous studies have revealed that continued anterior spinal column growth after posterior arthrodesis causes a resultant deformity in quadrupeds. No previous study has assessed whether a transpedicular construct can overpower the anterior spinal growth plate in an immature growing model.

METHODS

Twenty-five skeletally immature canines were randomized into four groups: control, fusion only, screw and fusion, and instrumentation and fusion. Disc space growth, vertebral body growth, and sagittal plane angulation were the variables analyzed. Management response variables were visualized graphically and radiographically.

RESULTS

Posterior tethering and anterior column growth occurred in the noninstrumented fusion groups, producing substantial lordosis. Anterior column growth was arrested in the instrumented canines as demonstrated by decreased vertebral body length, disc space narrowing, and, most importantly, prevention of lordosis.

CONCLUSIONS

The present study confirmed that in immature canines anterior column growth continues after posterior fusion without instrumentation. The magnitude of this growth, combined with a posterior tether, is sufficient to cause significant lordosis. The results are the first to document that a stiff posterior spinal instrumentation system is sufficient to overpower the residual anterior growth centers, even in the presence of a posterior tether (fusion mass). This technique creates a mechanical epiphysiodesis evidenced by arresting vertebral body length, narrowing disc space, and preventing lordosis, thus thwarting the deformity-producing mechanism without an additional anterior procedure.