Reduced loosening rate and loss of correction following posterior stabilization with or without PMMA augmentation of pedicle screws in vertebral fractures in the elderly

Background

Therapy of vertebral fractures in the elderly is a growing challenge for surgeons. Within the last two decades, the use of polymethylmethacrylate (PMMA) in the treatment of osteoporotic vertebral fractures has been widely established. Besides vertebroplasty and kyphoplasty, the augmentation of pedicle screws with PMMA found widespread use to strengthen the implant–bone interface. Several studies showed an enhanced pullout strength of augmented screws compared to standard pedicle screws in osteoporotic bone models. To validate the clinical relevance, we analyzed postoperative radiologic follow-up data in regard to secondary loss of correction and loosening of pedicle screws in elderly patients.

Materials and methods

In this retrospective comparative study, 24 patients admitted to our level I trauma center were analyzed concerning screw loosening and secondary loss of correction following vertebral fracture and posterior instrumentation. Loss of correction was determined by the bisegmental Cobb angle and kyphosis angle of the fractured vertebra. Follow-up computed tomography (CT) scans were used to analyze the prevalence of clear zones around the pedicle screws as a sign of loosening.

Results

In 15 patients (mean age 76 ± 9.3 years) with 117 PMMA-augmented pedicle screws, 4.3 % of screws showed signs of loosening, whereas in nine patients (mean age 75 ± 8.2 years) with 86 uncemented screws, the loosening rate was 62.8 %. Thus, PMMA-augmented pedicle screws showed a significantly lower loosening rate compared to regular pedicle screws. Loss of correction was minimal, despite poor bone quality. There was significantly less loss of correction in patients with augmented pedicle screws (1.1° ± 0.8°) as compared to patients without augmentation (5° ± 3.8°).

Conclusion

The reinforcement of pedicle screws using PMMA augmentation may be a viable option in the surgical treatment of spinal fractures in the elderly.     

Role of thoracoscopy for the sagittal correction of hypokyphotic adolescent idiopathic scoliosis patients

Purpose

Thoracic adolescent idiopathic scoliosis (AIS) curves (Lenke 1–4) are often characterized by hypokyphosis. Sagittal alignment remains challenging to correct, even with recent posterior segmental instrumentation. Some authors recommend anterior endoscopic release (AER) to reduce anterior column height, and facilitate thoracic kyphosis correction. The aim of this study was to assess the contribution of AER to sagittal correction in hypokyphotic AIS.

Methods

Fifty-six hypokyphotic (T4T12<20°) AIS patients were included. In group 1 (28 patients), patients first underwent AER, followed by posterior instrumentation and correction 5–7 days later. In group 2 (28 patients), patients underwent the same posterior procedure without AER. Posterior correction was performed in all cases using posteromedial translation and hybrid constructs consisting of lumbar pedicle screws and thoracic sublaminar bands. From radiological measurements performed using low-dose EOS radiographs, the correction of thoracic kyphosis was compared between the two groups.

Results

Groups 1 and 2 were comparable regarding demographic data and preoperative thoracic kyphosis (group 1: 11.7° ± 6.9° vs group 2: 12.1° ± 6.3°, p = 0.89). Postoperative thoracic kyphosis increase averaged 18.3° ± 13.6° in group 1 and 15.2° ± 9.0° in group 2. The benefit of anterior release was not statistically significant (p = 0.35).

Conclusion

Although previous studies have suggested that thoracoscopic release improved correction compared to posterior surgery alone, the current study did not confirm this finding. Moreover, results of the current series showed that no significant benefit can be expected from AER in terms of sagittal plane improvement when the posteromedial translation technique is used, even in challenging hypokyphotic patients.     

Computed tomography morphometric analysis of C2 translaminar screw fixation of Wright’s technique and a modified technique in the pediatric cervical spine

Purpose

To establish reference data on the dimensions of C2 lamina to guide the use of translaminar screws with Wright’s technique and a modified technique for pediatric patients in different age groups.

Methods

113 pediatric patients were divided into six age groups, and their cervical vertebrae were studied on CT scans. Laminar height, width, length and screw angle were measured. Statistical analysis was performed using Student t tests, Pearson’s correlation and linear regression analysis.

Results

Mean laminar height was 10.95 ± 2.81 mm, and mean width was 6.01 ± 0.90 mm. For Wright’s technique, mean laminar length was 30.65 ± 3 mm, and the screw angle was 56.02° ± 3.62°. For the modified technique, mean laminar length was 22.07 ± 2.38 mm, and the screw angle was 67.40° ± 3.39°. 95.6 % (108/113) of the children could insert a screw into the lamina (laminar width ≥4.5 mm), 72.6 % (82/113) could accept bilateral translaminar screws (laminar width ≥4.5 mm and laminar height ≥9 mm).

Conclusion

Our investigation provides insight into the anatomy of C2 lamina in six pediatric age groups. Compared to adults, the benefits of C2 translaminar screws fixation are more obvious in the pediatric spine which has a large C2 lamina. Compared to Wright’s technique, the modified technique should insert a screw with bigger insert angle and shorter screw length.     

The results of closing wedge osteotomy with posterior instrumented fusion for the surgical treatment of congenital kyphosis

Purpose

There exist not much data regarding the surgical treatment of pure congenital kyphosis (CK) in the literature. The purpose of this study was to evaluate the results of closing wedge osteotomy with posterior instrumented fusion in patients with congenital kyphotic deformity.

Methods

We retrospectively evaluated the radiographical results of 10 patients who were subject to closing wedge vertebral osteotomy and posterior instrumented fusion due to CK. The mean age of the patients at surgery was 12.6 ± 3.72 years (range 8–18 years). Radiographical measurements including local kyphosis, correction loss, global kyphosis and sagittal balance values were noted for the preoperative, postoperative and final follow up periods, respectively. The data obtained from those periods underwent statistical analysis.

Results

Average follow-up period was 51.8 ± 29.32 months (range 26–96 months). The mean local kyphosis angle was 67.7° ± 15.64° (range 42°–88°) prior to the surgery, 31.5° ± 17.12 (range 14°–73°) following the surgery and 31.9° ± 15.98° (range 14°–71°) during the follow up-period, respectively (p < 0.05). A correction rate of 53.5 % was reported at the final follow up. Average sagittal balance was measured as 33.1 ± 24.48 mm (range 2–77 mm) prior to the surgery, 20.8 ± 15.46 mm (range 5–46 mm) following the surgery (p < 0.05) and 14.1 ± 9.2 mm (range 0–30 mm) during follow-up period (p > 0.05). Complications consisted of a rod fracture due to pseudoarthrosis, an implant failure with loosening of screws and a proximal junctional kyphosis. No neurological deficit or deep infection were encountered in any of the patients in the study group.

Conclusion

Closing wedge osteotomy with posterior instrumented fusion is an efficient method of surgical treatment in terms of sagittal balance restoration and deformity correction in patients with congenital kyphosis.     

Reversing the concept: correction of adolescent idiopathic scoliosis using the convex rod de-rotation maneuver

Purpose

To show the radiological results of adolescent idiopathic scoliosis (AIS) patients treated with posterior fusion using all-pedicle-screw construct with correction carried out using a convex rod reduction technique.

Methods

Between October 2004 and June 2007, 42 AIS patients were treated with posterior fusion using all-pedicle-screw construct with correction done through the convex side. Two patients were lost to follow-up and were not included in the study. Forty patients had a minimum follow-up of 2 years. Patients were evaluated for the deformity correction in coronal and sagittal planes and for spinal balance.

Results

The mean preoperative Cobb angle of the major curve and secondary minor curves was 60° and 41°, respectively. Immediate postoperative mean Cobb angle of the major curve and secondary minor curves was 17° and 13°, respectively. Postoperative 2-year average major curve loss of correction was 7 %. Postoperative 2-year average minor curve loss of correction was 5 %. Preoperative thoracic kyphosis of 28° was changed to 22° in 2-years follow-up. The loss of thoracic kyphosis was most noted in hyperkyphotic patients.

Conclusions

The correction of AIS by convex-sided pedicular screws yields a coronal correction comparable to what is described in the literature for segmental concave-sided screws.     

A five-step remedial screw placement method to treat severe spinal deformity with free-hand transpedicular screw placement

Purpose

Severe spinal deformity is a complex morphological deformation that occurs and develops in three-dimensional space combined with abnormal development and morphology of anatomical structures, which presents great difficulties in the process of transpedicular screw placement. This study tried to explore the methods of transpedicular screw placement in surgical correction of severe spinal deformities.

Methods

Surgical corrections through posterior approach were performed in all the 76 cases (mean age 20.4 years). The averaging preoperative Cobb’s angle of scoliosis was 108.2° ± 33.6° (range 100°–170°). Among these patients, 34 cases were combined with kyphosis; the average Cobb’s angle of kyphosis was 77.3° (range 63°–160°). During operation, the screw tract was first established with the regular free-hand pedicle screw placement method. When this failed, in order to adjust the screw trajectory, a five-step remedial method was performed in the following order: (1) the“funnel” method; (2) exploring the pedicle exterior edge through the costotransverse joint; (3) exploring the superior and inferior edges of pedicle through the nerve root canal; (4) the vertebral plate fenestration; and (5) hemilaminectomy.

Results

Among all 1,472 screws planned to be placed for the patients, 1,210 (82.2 %) were successfully placed after using the regular method, and 262 (17.8 %) failed in this stage. After applying the five-step remedial method, 256 of the failed 262 screws were successfully placed. Among them, 176 screws (68.8 %) were successfully placed after Step 1, 44 (17.2 %) after Step 2, 21 (8.2 %) after Step 3, 12 (4.7 %) after Step 4, and 3 (1.2 %) after Step 5. In only six, pedicles screws could not be placed eventually. No nerve or blood vessel damages occurred in all cases. All final screw positions were validated by CT.

Conclusion

The five-step remedial method proved to be an effective supplementary method for transpedicular screw placement to treat patients with severe spinal deformities. The key points include a detailed preoperative plan, a meticulous hand drilling sensation, and an experienced probing technique for screw tract.     

Effectiveness of pedicle screw-based ligamentotaxis in reducing preoperative kyphosis in thoracolumbar spinal fractures: a retrospective analytical study based on injury surgery interval

Objectives

Although there is an agreement of using long-level construct than short-level construct to correct the kyphosis, no literature mentioned the success of this treatment based on timing of surgery after the injury. Objective of this paper was to study the effect of ligamentotaxis on preventing the development of postoperative kyphosis in unstable thoracolumbar burst fractures based on injury surgery interval (ISI).

Study design

This is a retrospective analysis in 67 patients with unstable thoracolumbar burst fractures operated with posterior-only pedicle screw fixation.

Methods

A retrospective analytical study was conducted in 67 patients who had unstable thoracolumbar fracture and operated with posterior-only pedicle screw construct two levels above and one level below the fractured vertebra. Results were analyzed based on ISI: group 1 (34 patients) was operated within 7 days; group 2 (19 patients) operated between 7 and 14 days; and group 3(14 patients) operated after 14 days of injury. Immediate postoperative and final follow-up kyphotic angles were analyzed among all three groups using Kruskal–Wallis test. Complications regarding implant failure were also noted at final follow-up.

Results

Average follow-up was 37 ± 8.1 months. Average preoperative kyphosis at thoracolumbar junction was 26.3° ± 3.9°, 26.3° ± 2.9° and 26.3° ± 2.8° in groups 1, 2 and 3, respectively, which did not show any difference (P = 0.98). Immediate postoperatively kyphotic angle was improved to 4.3° ± 1.9°, 5.4° ± 1.7° and 10.1° ± 3.0° in groups 1, 2 and 3, respectively, which exhibited statistically significant difference (P < 0.001); and at final follow-up kyphotic angles were 5.4° ± 1.9°, 7.2° ± 1.7° and 15.0° ± 1.6° in groups 1, 2 and 3, respectively showing 1.1°, 1.7° and 4.9° loss in correction at final follow-up. Comparison of kyphotic angles and loss of kyphotic angles amongst the three groups showed statistically significant difference (P < 0.001). Two patients from group 3 had implant failure that required implant extraction.

Conclusion

Posterior-only pedicle screw fixation in unstable thoracolumbar fractures would correct and maintain the postoperative correction in kyphosis, at least at 3-year follow-up, without increasing implant failure if ISI is less than 2 weeks. While patients operated after 2 weeks of injury would require additional anterior procedure.     

Free-hand placement of occipital condyle screws: a cadaveric study

Purpose

Cranio-vertebral junction fixation is challenging due to the complex topographical anatomy and the presence of important anatomical structures. There are several limitations to the traditional occipital squama fixation methods. The purpose of this work is to assess the safety and feasibility of a new optimum trajectory of occipital condyle (OC) screws for occipitocervical fixation via a free-hand technique.

Methods

Eight different parameters of OC morphology were studied in fifty adult skulls. Free-hand placement of OC screws was performed in five cadavers using 3.5-mm titanium polyaxial screws and a 3-mm rod construct (C0–C1–C2). Postoperative computed tomography was performed to determine the success of the screw placement and their angulation, length and effect on hypoglossal canal volume.

Results

The average length, width and height of the OC were 24.2 ± 3.6, 14.2 ± 1.9, and 10.7 ± 2 mm, respectively. The average medio-lateral, hypoglossal canal and atlanto-occipital joint angles were 38.8° medially ±5°, 7.4° rostrally ±1.9° and 23.4° caudally ±3.5°, respectively. The ten screws were successfully inserted using a free-hand technique with bicortical purchase. There was no vertebral artery injury or breach of the hypoglossal canal in any specimen. The average screw length was 22.2 ± 3.9 mm. The average medio-lateral angle was 30° medially ±6.7°. The average cranio-caudal angle was 4° caudally ±6.2°.

Conclusions

The free-hand technique of OC screw placement is a safe and viable option for occipitocervical fixation and may be a preferred alternative in selected cases. However, further studies are needed to compare its safety and reliability to other more established methods.     

Does surgery for Scheuermann kyphosis influence sagittal spinopelvic parameters?

Purpose

To analyze changes in sagittal spinopelvic parameters (SSPs) after surgical treatment of Scheuermann’s Kyphosis (SK).

Methods

We analyzed 20 patients affected by SK and subjected to posterior correction of the kyphosis by facetectomy, Ponte osteotomy, fusion and multilevel instrumentation with pedicle screw system. Four spinal and three pelvic parameters were measured: sagittal vertical axis (SVA), thoracic kyphosis (TK), thoracolumbar kyphosis, lumbar lordosis (LL), pelvic incidence (PI), sacral slope (SS) and pelvic tilt (PT). Analysis of changes in postprocedural SSPs compared to preoperative values was performed.

Results

TK passed from 78.6° preoperatively to 45.8° (p = 0.003). LL passed from 74.5° preoperatively to 53.5° (p = 0.01). No significant changes occurred in SVA, SS, PT and PI compared to preoperative values.

Conclusion

We confirm the positive effect of surgery by Ponte osteotomy and posterior spinal fusion on TK and LL in patients with SK. In our experience, pelvic parameters did not change after surgery.

     

Minimally invasive fixation techniques for thoracolumbar fractures: comparison between percutaneous pedicle screw with intermediate screw (PPSIS) and percutaneous pedicle screw with kyphoplasty (PPSK)

Purpose

To assess and compare the efficacy of two minimally invasive techniques (percutaneous pedicle screw with intermediate screw vs. percutaneous pedicle screw with kyphoplasty) for spinal fracture fixation by comparing the segmental kyphosis and vertebral kyphosis angles after trauma before surgery, after surgery, and at 4-month and 12-month follow-up.

Methods

Data from 49 patients without neurological deficit treated by either percutaneous pedicle screw with intermediate screw or percutaneous pedicle screw with kyphoplasty were retrospectively analysed. The segmental kyphosis and vertebral kyphosis angles over time were calculated and correlated with the type of procedure, AO classification, lumbar or thoracic site and the age and sex of the patients.

Results

After surgery, both techniques were found to be efficacious means of bringing about a significant correction of the segmental kyphosis angle (p = 0.002) and a just significant correction of the vertebral kyphosis angle (p = 0.06), although less effectively in thoracic fractures (p = 0.004). At follow-up, the vertebral kyphosis angle was stable in both groups, while there was a significant loss of segmental kyphosis angle stability in the percutaneous pedicle screw with kyphoplasty group at 1 year (p = 0.004); fractured thoracic vertebrae maintained a greater vertebral kyphosis angle (p = 0.06) and segmental kyphosis angle (p < 0.001), than the lumbar.

Conclusion

At 1 year after surgery, the use of intermediate screws in fractured vertebrae seemed to maintain a more efficacious correction with respect to kyphoplasty, although thoracic fracture sites appear to be associated with greater post-traumatic segmental kyphosis and lesser stability in the long term after both percutaneous surgical techniques.

     

Skip pedicle screw fixation combined with Ponte osteotomy for adolescent idiopathic scoliosis

Purpose

This study aimed to determine whether Ponte osteotomy combined with skip pedicle screw fixation (SPSF) can improve the correction rate and restore thoracic kyphosis for patients with adolescent idiopathic scoliosis.

Methods

Surgical time, blood loss, preoperative Cobb angle of the main thoracic curve, flexibility, Cobb angle at 1 year after surgery, thoracic curve correction rate, and Cincinnati correction index (CCI) were determined for both the Ponte (n = 17) and non-Ponte (control; n = 21) groups. Furthermore, kyphotic angles at T5–T12 before and 1 year after the surgery were measured.

Results

The following measurements were obtained for the Ponte and control groups, respectively: surgical time, 236 ± 13 and 187 ± 9 min; blood loss, 1,141 ± 150 and 745 ± 120 g; preoperative Cobb angle of the main thoracic curve, 52.5° ± 10.4° and 51.5° ± 9.2°; flexibility, 31.7 ± 13.2 and 45.1 ± 12.3 % (p = 0.003); thoracic curve correction rate, 62.0 ± 2.5 and 63.6 ± 2.5 %; CCI, 2.2 ± 0.2 and 1.5 ± 0.1 (p = 0.003); preoperative kyphotic angle at T5–T12, 11.3° ± 11.2° and 13.0° ± 9.0°; and kyphotic angle at T5–T12 at 1 year after the surgery, 21.8° ± 1.7° and 24.2° ± 1.9°.

Conclusion

Ponte osteotomy was combined with SPSF in case of rigid curve. CCI was significantly greater in the Ponte group. Postoperative thoracic kyphotic angles were identical in both groups.     

Sagittal alignment of the cervical spine in adolescent idiopathic scoliosis treated by posteromedial translation

Purpose

To analyze postoperative changes in the cervical sagittal alignment (CSA) of patients with AIS treated by posteromedial translation.

Methods

49 patients with thoracic AIS underwent posterior arthrodesis with hybrid constructs, combining lumbar pedicle screws and thoracic universal clamps. Posteromedial translation was the main correction technique used. 3D radiological parameters were measured from low-dose biplanar radiographs. CSA was assessed using the C2C6 angle, and the central hip vertical axis (CHVA) was used as a reference axis to evaluate patients’ balance.

Results

Preoperatively, 58 % of patients had thoracic hypokyphosis, and 79 % had a kyphotic CSA. Significant correlation was found (r = 0.45, P = 0.01) between thoracic hypokyphosis and cervical kyphosis. Increase in T4–T12 thoracic kyphosis (average 14.5° ± 10°) was associated with significant decrease in cervical kyphosis in the early postoperative period. The CSA further improved spontaneously during follow-up by 7.6° (P < 0.0001). Significant positive correlation (r = 0.32, P = 0.03) was found between thoracic and cervical improvements. At latest follow-up, 94 % of the patients were normokyphotic and 67 % had a CSA in the physiological range. Sagittal balance of the thoracolumbar spine was not significantly modified postoperatively. However, the procedure significantly changed the position of C2 in regard to the CHVA (C2–CHVA), which reflects headposition (P = 0.012). At last follow-up, the patients sagittal imbalance was not significantly different from the preoperative imbalance (P = 0.34).

Conclusions

Thoracic hypokyphosis and cervical hypolordosis, observed in AIS, can be improved postoperatively, when the posteromedial translation technique is used for correction. The cervical spine remains adaptable in most patients, but the proportion of patients with physiological cervical lordosis at final follow-up remained low (24.5 %).     

Rod fracture after long construct fusion for spinal deformity: clinical and radiographic risk factors

Background

No reports have been published on detailed risk factors for rod fracture after spinal deformity correction and fusion. The purpose of this study was to analyze clinical and radiographic risk factors of rod fracture after long construct fusion for spinal deformity.

Methods

The survey subjects were 155 cases who were diagnosed with spinal deformity and underwent correction and fusion surgery with long construct instrumentation (>3 levels, average 10.3 levels) between July 2004 and June 2010. The subjects comprised 32 males and 123 females with a mean age of 19.0 (range 8–78) years. The mean Cobb angle was 61.0 ± 16.1° preoperatively and 25.7 ± 16.9° postoperatively. Univariate analysis and logistic regression analysis were performed.

Results

Rod fracture occurred in 8 of 155 cases (5.2 %). The mean period from surgery to rod fracture was 18.1 months (range 2–37). The level of fracture ranged from the thoracolumbar junction to the lumbosacral vertebrae. Six patients had fracture near the fused lower end and two patients had fracture at the thoracolumbar junction. Univariate analysis revealed that non-ambulatory status, preoperative kyphosis, small-diameter rods, multiple surgery, and use of iliac screws were significant risk factors for rod fracture. Sex, obesity, severity of preoperative scoliosis, and rod material were not significant risk factors. Logistic regression analysis revealed that use of iliac screws (odds ratio: 81.9, 95 % confidence interval: 7.2–935.0, p < 0.001) and small-diameter (<6 mm) rods (odds ratio: 16.3, 95 % confidence interval: 1.7–152.6, p = 0.015) were risk factors for rod fracture.

Conclusions

The incidence of rod fracture after long construct fusion for spinal deformity was 5.2 %. Iliac screw fixation and small-diameter rods were risk factors for rod fracture.     

Five-year clinical and radiographic outcomes using pedicle screw only constructs in the treatment of adolescent idiopathic scoliosis

Purpose

To determine the mid-term clinical and radiographic impact of pedicle screw fixation in patients with adolescent idiopathic scoliosis (AIS).

Methods

A multicenter AIS database was retrospectively queried to identify 99 consecutive patients who underwent posterior spinal fusion using an all pedicle screw construct with a minimum of 5-year follow-up. Radiographic and clinical parameters were reviewed at regular intervals up to 5 years.

Results

The mean age was 14.4 ± 2.0 years with 79 % being female. The mean preoperative major curve was 51.7 ± 14.2° with a mean correction of 66 and 64 % at 2 and 5 years (p = 0.16). Pre-op thoracic kyphosis averaged 22.3 ± 12.9° and was 18.4 ± 10.6° at 5 years with no significant change from 2 years (p = 0.33). SRS total and domain scores demonstrated significant improvements at 2 years, which were slightly decreased at 5 years (p = 0.06). SRS scores of self-image (p = 0.99) and satisfaction (p = 0.18) were significantly improved after surgery with minimal change by 5 years. The change in SRS total scores from 2 to 5 years was attributed to differences in SRS scores of pain and mental health (p < 0.05).

Conclusions

Intermediate follow-up of patients with AIS treated with an all pedicle screw construct demonstrates maintenance of their coronal, and sagittal plane correction between 2- and 5-year follow-up. At 5 years, improvements in SRS scores were consistent with 2-year values, except for a decline in pain and mental health scores.     

Accuracy of thoracic pedicle screw placement in adolescent patients with severe spinal deformities: a retrospective study comparing drill guide template with free-hand technique

Purpose

Patients with severe spinal deformities often have small pedicle diameters, and pedicle dimensions vary between segments and individuals. Free-hand pedicle screw placement can be inaccurate. Individualized drill guide templates may be used, but the accuracy of pedicle screw placement in severe scoliosis remains unknown. The accuracy of drill guide templates and free-hand technique for the treatment of adolescent patients with severe idiopathic scoliosis are compared in this study.

Methods

This study included 37 adolescent patients (mean age 16.4 ± 1.3 years) with severe idiopathic scoliosis treated surgically at a single spine center between January 2014 and June 2017. Spinal deformities were corrected using posterior pedicle screw fixation. Patients in group I were treated with rapid prototype drill guide template technique (20 patients; 396 screws) and patients in group II were treated with free-hand technique (17 patients; 312 screws). Outcomes that included operative time, correction rate, and the incidence and distribution of screw misplacement were evaluated.

Results

Operative time in group I was 283 ± 22.7 min compared to 285 ± 25.8 min in group II (p = 0.89). The scoliosis correction rate was 55.0% in group I and 52.9% in group II (p = 0.33). Based on both axial and sagittal reconstruction images, the accuracy rate of pedicle screw placement was 96.7% in group I and 86.9% in group II (p = 0.000).

Conclusion

The drill guide template technique has potential to offer more accurate and thus safer placement of pedicle screws than free-hand technique in the treatment of severe scoliosis in adolescents.

     

Two-level pedicle subtraction osteotomy for severe thoracolumbar kyphotic deformity in ankylosing spondylitis

Study design

A retrospective clinical study.

Objective

To evaluate the outcomes of two-level (T12 and L3) pedicle subtraction osteotomy (PSO) for severe thoracolumbar kyphosis in ankylosing spondylitis (AS), and to discuss the surgical strategies of this surgery.

Background

Cases were limited on the results of two-level PSO for correction of severe kyphosis caused by AS, nor on surgical strategies of this type of surgery.

Methods

From March 2006 to December 2010, nine consecutive AS patients with severe kyphotic deformity, underwent T12 and L3 PSOs. Chin-brow vertical angle (CBVA) and radiographic assessments which contain thoracic kyphosis (TK), lumbar lordosis (LL), global kyphosis (GK), and sagittal vertical axis were carefully recorded pre and postoperatively to evaluate the sagittal balance. Intra and postoperative complications were also registered. All patients were asked to fill out Oswestry Disability Index before surgery and at the last follow-up visit.

Results

All nine patients (8M/1F), averaged 41.4 years old (range 35–51 years), were received two-level (T12 and L3) PSO, and were followed up after surgery for a mean of 39.9 months (range 24–68 months). Good cosmetic results were achieved in all patients. Mean correction at two-level PSO was 67.9 ± 5.5°. All CBVA, TK, LL, and GK were changed significantly after surgery (P < 0.05), the mean amount of correction of which were 59.5 ± 13.8, 34.7 ± 3.8, 33.2 ± 2.4, and 54.0 ± 14.8 degrees, respectively, and with a small loss of correction at the last follow-up visit. Sagittal imbalance was significantly improved from 27.3 ± 4.4 to 3.4 ± 0.7 cm postoperatively. Neither mortalities nor any major neurological complications were found. The mean ODI score was significantly improved from 53.4 ± 15.5 before surgery to 8.2 ± 4.7 at the last visit.

Conclusion

The outcomes of follow-up showed that two-level (T12 and L3) PSO can effectively and safely correct severe thoracolumbar kyphosis in AS.     

3D rod shape changes in adolescent idiopathic scoliosis instrumentation: how much does it impact correction?

Purpose

Flattening of rods is known to reduce the correction capability of the instrumentation, but has not been studied in 3D. The aim is to evaluate the rods shape 3D changes during and immediately after instrumentation, and its effect on 3D correction.

Methods

The 5.5 mm CoCr rods of 35 right thoracic adolescent idiopathic scoliosis patients were measured from rod tracings prior to insertion, and reconstructed in 3D from bi-planar radiographs taken intra-operatively after the correction maneuvers and 1 week post-operatively. The rod bending curvature, maximal deflection and orientation of the rod’s plane of maximum curvature (RPMC) were computed at each stage. The relation between rod contour, kyphosis and apical vertebral rotation (AVR) was assessed.

Results

Main thoracic Cobb angle was corrected from 58° ± 10° to 15° ± 8°. Prior to insertion, rods were more bent on the concave side (curvature/deflection: 39° ± 8°/25 ± 6 mm) than the convex side (26° ± 5°/17 ± 3 mm). Only the concave rod shape changed after the correction maneuvers execution (flattening of 21° ± 9°/13 ± 7 mm; p < 0.001) and stayed unchanged post-operatively. After instrumentation, the RPMC was deviated from the sagittal plane (concave side: 27° ± 19°/convex side: 15° ± 12°). There was a significant association between kyphosis change and the relative concave rod to spine contour (rod curvature—pre-operative kyphosis) (R ² = 0.58) and between AVR correction and initial differential concave/convex rods deflection (R ² = 0.28).

Conclusions

Correction maneuvers induce a significant change of the concave rod profile. Both rods end in a plane deviated from the sagittal plane which is representative of the spinal curvature 3D orientation. Differential rod contouring technique has a significant impact on the resulting thoracic kyphosis and transverse plane correction.

     

Biomechanical advantage of C1 pedicle screws over C1 lateral mass screws: a cadaveric study

Purpose

The established technique for posterior C1 screw placement is via the lateral mass. Use of C1 monocortical pedicle screws is an emerging technique which utilizes the bone of the posterior arch while avoiding the paravertebral venous plexus and the C2 nerve root. This study compared the relative biomechanical fixation strengths of C1 pedicle screws with C1 lateral mass screws.

Methods

Nine human C1 vertebrae were instrumented with one lateral mass screw and one pedicle screw. The specimens were subjected to sinusoidal, cyclic (0.5 Hz) fatigue loading. Peak compressive and tensile forces started from ±25 N and constantly increased by 0.05 N every cycle. Testing was stopped at 5 mm displacement. Cycles to failure, displacement, and initial and end stiffness were measured. Finally, CT scans were taken and the removal torque measured.

Results

The pedicle screw technique consistently and significantly outperformed the lateral mass technique in cycles to failure (1,083 ± 166 vs. 689 ± 240 cycles), initial stiffness (24.6 ± 3.9 vs. 19.9 ± 3.2 N/mm), end stiffness (16.6 ± 2.7 vs. 11.6 ± 3.6 N/mm) and removal torque (0.70 ± 0.78 vs. 0.13 ± 0.09 N m). Only 33 % of pedicle screws were loose after testing compared to 100 % of lateral mass screws.

Conclusions

C1 pedicle screws were able to withstand higher toggle forces than lateral mass screws while maintaining a higher stiffness throughout and after testing. From a biomechanical point of view, the clinical use of pedicle screws in C1 is a promising alternative to lateral mass screws.     

Sagittal spinopelvic alignment in adolescents associated with Scheuermann’s kyphosis: a comparison with normal population

Purpose

Spinopelvic alignment is increasingly considered as a main factor in the energy-efficient posture of the individual in normal and pathological status. However, the spinopelvic characteristics in Scheuermann’s kyphosis (SK) are poorly defined in the literature. The purpose of this study was to determine whether differences of the spinopelvic parameters exist between adolescents with SK and age-matched normal controls.

Methods

In this study, 55 patients with SK and 60 healthy age-matched adolescents were recruited consecutively. Sagittal spinal and pelvic parameters were measured from the standing lateral radiograph, including global kyphosis, thoracic kyphosis (TK), cervical lordosis (CL), lumbar lordosis (LL), pelvic incidence (PI), sacrum slope (SS), pelvic tilt (PT) and sagittal vertical axis (SVA). According to the location of the kyphosis, patients were subdivided into Scheuermann’s thoracic kyphosis (STK) group and Scheuermann’s thoracolumbar kyphosis (STLK) group. The radiographic comparison and correlation analysis were further performed.

Results

SK patients had significantly lower PI and PT than normal controls (32.0° vs. 45.0°, P < 0.001 for PI; 0.2° vs. 11.9°, P < 0.001 for PT). The rate of a negative PT was 41.8 % (22/55) in SK patients, which was remarkably higher than in normal controls (10.0 %, 6/60). The CL, TK and LL were significantly increased in STK group when compared with STLK and control groups. A significant correlation was noticed between TK and CL and also between TK and LL in STK group. Both TK and LL were decreased in STLK patients, and a significant correlation was found between them (r = ?0.687, P < 0.001). A significantly strong correlation was also observed between LL and SS in STLK patients (r = ?0.641; P < 0.001).

Conclusion

Adolescents with SK have a significantly lower PI when compared with age-matched normal controls. Patients with different curve patterns (STK vs. STLK) could have distinct compensatory mechanisms to maintain the sagittal balance.