The current trend in kyphosis correction is for “every level” instrumentation to achieve intraoperative stability, correction, fusion and implant longevity. We evaluate the medium term follow up of a low implant density (LID) construct. All patients with adolescent kyphosis (idiopathic or Scheurmann's) on our deformity database were identified. Radiographs and records were analysed for neurological complications, correction and revision. The constructs included were all pedicle screw anchors with multiple apical chevron osteotomies and a proximal and distal “box” of 6 to 8 screws. A four rod cantilever reduction manoeuvre with side to side connectors completed the construct. Kyphosis for any other cause was excluded. Follow up less than 12 months was excluded. 23 patients were identified with an average follow up 27 months (72 to 12 months) and a mean implant density of 1.1 (53.5% of “available” pedicles instrumented). There was 1 false positive neurophysiological event without sequelae (4%). There were no proximal junctional failures (0%). There were no pseudarthroses or rod breakages (0%). There was 1 loss of distal rod capture (early set screw failure) (4%). This was revised uneventfully. There were 4 infections requiring debridement (early series). Average initial correction was 44% (77.7 degrees to 43.5 degrees) with a 1% loss of correction at final follow up (43.5 to 44.0 degrees). The fulcrum bending correction index was 107% (based on fulcrum extension radiographs). 85% of curves had a fulcrum flexibility of less than 50%. The average cost saving compared to “every level “instrumentation was £5700 per case. This paper shows that a LID construct for kyphosis has technical outcomes as good as high density constructs. The obvious limitation of the study is the small number of patients in the cohort. The infection rates have improved with changes to perioperative process in the later series of patients. We do not believe these are a consequence of the construct itself

Objectives: To evaluate the early coronal and sagittal correction of main thoracic adolescent idiopathic scoliosis using pedicle screw instrumentation and to determine whether implant density influences correction. Methods and results: 49 consecutive patients with Lenke I main thoracic adolescent idiopathic scoliosis underwent single stage posterior correction and instrumented spinal fusion with pedicle screw fixation between 2006 and 2008. All surgeries were performed in a single institution by a single surgeon using identical surgical technique and type of instrumentation. Pre- and postoperative radiographs were analyzed. The pre-operative main thoracic curve of 60.0 ± 13.4° was corrected to 17.4 ± 6.9° (69.9% correction) on the post-operative radiographs. The pre-operative thoracic kyphosis of 20.0 ± 10.2° decreased to 11.6 ± 4.9° post-operatively. There was a significant correlation between decrease in sagittal kyphosis and magnitude of coronal Cobb angle correction (P = 0.002). There was no correlation between implant density and magnitude of coronal or sagittal curve correction, with and without curve flexibility taken into consideration. Conclusions: Pedicle screw constructs provided excellent coronal correction of thoracic idiopathic scoliosis, however this was at the expense of sagittal contour. Decrease in sagittal kyphosis correlated with magnitude of coronal correction. Bilateral segmental pedicle screw fixation did not improve curve correction compared with unilateral or alternate segmental fixation. Ethics approval: None required. Caldicott and Data Protection Approval No. 661. Interest Statement: None

Introduction. Thoracic pedicle screws have been proven to be safe and effective in the treatment of adolescent idiopathic scoliosis (AIS). However, the effect of the instrumentation alloy has not yet been investigated. We aimed to compare segmental versus non segmental thoracic pedicle screw instrumentation in patients with AIS. Methods. A consecutive series of 143 patients with AIS (Lenke classification 1–4) surgically treated from 1998 to 2005 by means of thoracic pedicle screws were retrospectively reviewed. Considering implant density (number of fixation anchors placed per available anchors sites; segmental =60% [S], non-segmental =60% [NS]) and implant alloy used (titanium [Ti] vs stainless steel [SS]) we divided the cohort into four groups: Ti-S (48 cases); Ti-NS (34 cases); SS-S (35 cases); and SS-NS (26 cases). Groups were similar for preoperative mean age, sex distribution, Risser sign, main thoracic curve, and thoracic kyphosis. Pearson correlation coefficient and univariate analysis of variance were used. Results. At a mean follow-up of 6·2 years (range 3–10) the overall final main thoracic curve correction was a mean of 61·4% (20–89), whereas the implant density within the major curve was 71% (15–100%). We recorded a significant correlation between implant density and percentage major curve correction (r=0·41, p<0·002); when the four groups were compared we noted that the SS-S group showed the greatest average correction (75%), followed by the Ti-S, SS-NS, and Ti-NS groups. We detected no significant differences between SS-S versus Ti-S versus SS-NS (r=0·002, p>0·05; r=0·13, p>0·05; r=0·07, p>0·01, respectively), whereas the Ti-NS group showed a statistically significant inferior percentage correction when compared with all other groups (average 52%; p<0·001). Nevertheless, no significant difference between groups was recorded on the SRS-30 assessment, showing a postoperative improvement in both self-image and satisfaction. Conclusions. When an SS instrumentation is used, non-segmental pedicle screw constructs seem to be equally effective as segmental instrumentations in obtaining satisfactory results in patients with main thoracic AIS. When the implant alloy used is titanium, an implant density of greater than 60% should be guaranteed so as to achieve similar results to those recorded in this study

Aim:. The introduction of novel systems for correction of scoliosis should be subject to critical analysis and based on patient benefit. Methods:. Retrospective analysis of prospective data from a single surgeon consecutive series of Lenke 1 type curves. The two cohorts compared K2M and AOUSS2. Pre and Post operation Cobb angle, flexibility, absolute correction rate, implant related correction, levels fused, implant density, implant cost and cost per Cobb improvement analysis were collected. Results:. A total of 26 patients were analysed, 13 in each group. Both groups were similar in pre-operative parameters. The mean age was 14.62 and 14.23 respectively. The mean pre-operation Cobb angle was 71 (96–53) K2M and 70 (85–56) AOUSS2 bending to 45 in each. The flexibility was similar as was the correction in both. Post op Cobb 28 (42–16) K2M and Cobb 28 (44–16) AOUSS2. The implant density and number of screws used was similar. The average cost per construct was £6554 for K2M and £6140 AOUSS2. Discussion:. Using these simple and immediate outcome measures and a grossly simplified cost analysis there was a cost difference of £5382 with no measurable clinical advantage or disadvantage in curves of similar flexibility. The cost per case is determined by implant density and curve flexibility. In the least complex of scoliosis cases there needs to be evidence of benefit to justify the increased resource allocation in a health care system that is not fiscally driven. Conflict Of Interest Statement: No conflict of interest

Increasing health care costs, limited resources and increased demand makes cost-effective and cost-efficient delivery of Adolescent Idiopathic Scoliosis (AIS) management paramount. Rising implant costs in deformity surgery have prompted justification of high implant density. The objective of this study was to analyse the costs of thoracoscopic scoliosis surgery, comparing initial learning curve costs with those of the established technique and to the costs involved in posterior instrumented fusion from the literature. 189 consecutive cases from April 2000 to July 2011 were assessed with a minimum of 2 years follow-up using a prospective database covering perioperative factors, clinical and radiological outcomes, complications and patient-reported outcomes. The patients were divided into three groups to allow comparison; 1. A learning curve cohort, 2. An intermediate cohort and 3. A third cohort using our established technique. Hospital finance records and implant manufacturer figures were corrected to 2013 costs. A literature review of AIS management costs and implant density in similar curve types was performed. The mean pre-op Cobb angle was 53°(95%CI 0.4) and was corrected postop to mean 22.9°(CI 0.4). The overall complication rate was 20.6%, primarily in the first cohort, with a rate of 5.6% in the third cohort. The average total costs were $46,732, operating room costs of $10,301 (22.0%) and ICU costs of $4620 (9.8%). The mean number of screws placed was 7.1 (CI 0.04) with a single rod used for each case giving average implant costs of $14,004 (29.9%). Comparison of the three groups revealed higher implant costs as the technique evolved to that in use today, from $13,049 in Group 1 to $14577 in Group 3 (P<0.001). Conversely operating room costs reduced from $10,621 in Group 1 to $7573 (P<0.001) in Group 3. ICU stay was reduced from an average of 1.2 to 0 days. In-patient stay was significantly (P=0.006) lower in Groups 2 and 3 (5.4 days) than Group 1 (5.9 days). Our thoracoscopic anterior scoliosis correction has evolved to include an increase in levels fused and reduction in complication rate. Implant costs have risen, however, there has been a concurrent decrease in those costs generated by operating room use, ICU and in-patient stay with increasing experience. Literature review of equivalent curve types treated posteriorly shows similar perioperative factors but higher implant density, 69–83% compared to the 50% in this study. Thoracoscopic Scoliosis surgery presents a low density, reliable, efficient and effective option for selected curves

Aim:. To evaluate the effect of a stiffer rod in normalising thoracic hypokyphosis in adolescent idiopathic scoliosis (AIS). Methods:. A retrospective review of AIS cases performed at our institution was carried out. In order to reduce variability, the analysis included only Lenke 1 cases which had all pedicle screw constructs, with similar constructs and implant density. Cases that underwent anterior release were excluded. All cases had the same implant (Expedium 5.5, Depuy-Synthes, Raynham, USA). The rod material differed in that some cases had 5.5 titanium, whilst others had 5.5 cobalt chrome. The preoperative and postoperative sagittal Cobb angle was measured. Results:. 35 patients met the inclusion criteria. 15 had titanium rods and 20 had cobalt chrome rods. The mean fulcrum correction index was similar between groups. The preoperative coronal and sagittal Cobb was similar between the two groups. There was no statistically significant difference in the postoperative sagittal Cobb between the two groups (ANOVA one way test). Discussion:. Despite the theoretical advantage of a stiffer construct improving the sagittal profile in AIS, this study identified no such benefit despite closely matching the two groups. All pedicle screw constructs do not seem to improve the sagittal profile despite the use of a stiffer rod. Conflict of interest:. Depuy-Synthes fund a fellow in this unit. Conflict Of Interest Statement: No conflict of interest

To determine if the use of high density implants (i.e. high proportion of pedicle screws relative to number of spinal levels involved) causes significant loss of thoracic kyphosis and its effect on sagittal balance in adolescent idiopathic scoliosis. Retrospective analysis of pre and post-operative radiographs to assess sagittal balance and C7-L1 kyphosis angle. 17 patients (16 females, 1 male). All right sided single thoracic curves. All surgery performed by single surgeon (Senior author, ED). Comparison of pre and post operative sagittal balance and C7-L1 kyphosis angle. Assessment of implant density (i.e. proportion of pedicle screw relative to number of spinal levels involved in correction). 9 patients demonstrated improved sagittal balance following surgery. There was no significant difference (p value 0.83) between the pre and post op C7-L1 kyphosis angle. Mean angle pre op 28.9 (95% CI 20.3 to 37.5). Mean angle post op 29.6 (95% CI 22.2 to 37.0). No correlation identified between sagittal balance correction and kyphosis angle. Metal density ranged from 79-100%. Although the sample size in this series is modest, high density implants do not significantly affect the kyphosis angle in the operative management of adolescent idiopathic scoliosis in the thoracic spine

Objective. To determine if there is a differing effect between two spinal implant systems on sagittal balance and thoracic kyphosis in adolescent idiopathic scoliosis. Methods. Retrospective analysis of pre and post-operative radiographs to assess sagittal balance, C7-L1 kyphosis angles and metal implant density. Group 1 (Top loading system): 11 patients (9 females, 2 males) Single surgeon NB. Group 2 (Side loading system): 17 patients (16 females, 1 male) Single surgeon ED. Total 28 patients. All single right sided thoracic curves. Comparison of pre and postoperative sagittal balance and C7-L1 kyphosis angle for each spinal system. Assessment of implant density (i.e. proportion of pedicle screw relative to number of spinal levels involved in correction). Results. 16 patients demonstrated improved sagittal balance following surgery. There was no significant difference between the pre and post op C7-L1 kyphosis angle in either group (p value 0.06 and 0.83 respectively) although a greater discrepancy was noted in Group 1. In group 1, the mean angle pre op was 33.1 (95% CI 27.3 to 38.9) and post op was 26.2 (95% CI 22.5 to 29.9). In Group 2, the mean angle pre op was 28.9 (95% CI 20.3 to 37.5) and post op was 29.6 (95% CI 22.2 to 37.0). No correlation identified between sagittal balance correction and kyphosis angle. Metal density ranged from 60-100%. Conclusions. Although the numbers in this series are modest they do suggest that high density metal implants do not lead to a flatback deformity in the sagittal plane. There is no significant difference in the pre and post op kyphosis angles for either implant system used in this study although the results for Group 1 do approach statistical significance. Larger prospective multicentre studies are required to quantify the true significance of these results. Ethics Approval: Audit/Service Standard in Trust

Purpose of the study. To compare the effectiveness of unilateral and bilateral pedicle screw techniques in correcting adolescent idiopathic scoliosis. Summary of Background Data. Pedicle screw constructs have been extensively used in the treatment of adolescent patients with idiopathic scoliosis. It has been suggested that greater implant density may achieve better deformity correction. However, this can increase the neurological risk related to pedicle screw placement, prolong surgical time and blood loss and result in higher instrumentation cost. Methods. We reviewed the medical notes and radiographs of 139 consecutive adolescent patients with idiopathic scoliosis (128 female-11 male, prospectively collected single surgeon's series). We measured the scoliosis, thoracic kyphosis (T5-T12), and lumbar lordosis (L1-L5) before and after surgery, as well as at minimum 2-year follow-up. SRS 22 data was available for all patients. Results. All patients underwent posterior spinal arthrodesis using pedicle screw constructs. Mean age at surgery was 14.5 years. We had 2 separate groups: in Group 1 (43 patients) correction was performed over 2 rods using bilateral segmental pedicle screws; in Group 2 (96 patients) correction was performed over 1 rod using unilateral segmental pedicle screws with the 2. nd. rod providing stability of the construct through 2-level screw fixation both proximal and distal. Group 1. Mean Cobb angle before surgery for upper thoracic curves was 37°. This was corrected by 71% to mean 11° (p<0.001). Mean Cobb angle before surgery for main thoracic curves was 65°. This was corrected by 71% to mean 20° (p<0.001). Mean Cobb angle before surgery for thoracolumbar/lumbar curves was 60°. This was corrected by 74% to mean 16° (p<0.001). No patient lost >2° correction at follow-up. Mean preoperative thoracic kyphosis was 24° and lumbar lordosis 52°. Mean postoperative thoracic kyphosis was 21° and lumbar lordosis 50° (p>0.05). Mean theatre time was 5.5 hours, hospital stay 8.2 days and intraoperative blood loss 0.6 blood volumes. Complications: 1 transient IOM loss/no neurological deficit; 1 deep wound infection leading to non-union and requiring revision surgery; 1 rod trimming due to prominent upper end. Mean preoperative SRS 22 score was 3.9; this improved to 4.5 at follow-up (p<0.001). Pain and self-image demonstrated significant improvement (p=0.001, p<0.001 respectively) with mean satisfaction rate 4.9. Group 2. Mean Cobb angle before surgery for upper thoracic curves was 42°. This was corrected by 52% to mean 20° (p<0.001). Mean Cobb angle before surgery for main thoracic curves was 62°. This was corrected by 70% to mean 19° (p<0.001). Mean Cobb angle before surgery for thoracolumbar/lumbar curves was 57°. This was corrected by 72% to mean 16° (p<0.001). No patient lost >2° correction at follow-up. Preoperative scoliosis size for all types of curves correlated with increased surgical time (r=0.6, 0.4). Mean preoperative thoracic kyphosis was 28° and lumbar lordosis 46°. Mean postoperative thoracic kyphosis was 25° and lumbar lordosis 45° (p>0.05). Mean theatre time was 4.2 hours, hospital stay 8.4 days and intraoperative blood loss 0.4 blood volumes. Complications: 1 deep and 1 superficial wound infections treated with debridement; 1 transient brachial plexus neurapraxia; 1 SMA syndrome. Mean preoperative SRS 22 score was 3.7; this improved to 4.5 at follow-up (p<0.001). Pain, function, self-image and mental health demonstrated significant improvement (p<0.001 for all parameters) with mean satisfaction rate 4.8. Comparison between groups showed no significant difference in regard to age at surgery, preoperative and postoperative scoliosis angle for main thoracic and thoracolumbar/lumbar curves, as well as SRS scores and length of hospital stay. Better correction of upper thoracic curves was achieved in Group 1 (p<0.05), but upper thoracic curves in Group 2 were statistically more severe before surgery (p<0.05). Increased surgical time and blood loss was recorded in Group 1 (p<0.05, p=0.05 respectively). The implant cost was reduced by mean 35% in Group 2 due to lesser number of pedicle screws. Conclusion. Unilateral and bilateral pedicle screw instrumentation has achieved excellent deformity correction in adolescent patients with idiopathic scoliosis, which was maintained at follow-up. This has been associated with high patient satisfaction and low complication rates. The unilateral technique using segmental pedicle screw correction has reduced surgical time, intraoperative blood loss and implant cost without compromising surgical outcome for the most common thoracic and thoracolumbar/lumbar curves. The bilateral technique achieved better correction of upper thoracic scoliosis

Determine the detection rate of modern spinal implants using the current technology. There is a paucity of data regarding detection rates of modern spinal implants using modern walk-through pulsed archway metal detectors (AMDs). No published reports compare detection capability with hand-held metal detectors (HHMDs). ex-vivo & in-vivo comparison of detection rates using AMD & HHMD (set to maximum DoT sensitivities), in patients of varying Body Mass Index (BMI), implants, implant mass/density and alloys. 40 patients with: lumbar disc replacement (CoCr) (n=8), cervical disc replacement (CoCr) (1), posterior deformity instrumentation (17), anterior deformity instrumentation (2), anterior reconstruction (2), PLIF (6), interspinous distraction device (1), anterior cervical plate (2) ALIF (1), All implants were titanium unless indicated. Mean metal mass was 98g (range 6g-222g). The AMD did not detect any instrumentation individually or in combination up to a titanium mass totalling 215g. The HHMD detected all instrumentation at a distance of 5cm; with the minimum mass being 2g. No implants were detected in patients by the AMD. The HHMD did not detect any anterior lumbar or thoracic surgical implants. It detected anterior cervical implants. The HHMD detected all posterior surgical implants. There was no significant relationship between detection, BMI, total metal mass, and metal density/segment. AMD detectors do not detect modern spinal implants. HHMD detect all modern posterior spinal implants; this has implications for patient documentation

Purpose of the study: Acetabular bone loss and loosening after total hip arthroplasty has been evaluated on plain x-rays (Vives, 1988; D’Antonio, 1989; Paprosky, 1994). Experience has proven that intraoperative assessment of bone loss is more important than previously thought. Our main objective was to quantify, intraoperatively, the real volume of bone loss. A secondary objective was to measure, independently of the observer, the course of acetabular loosening. Material and method: This was a prospective series of acetabular loosenings (10 female, 4 male, mean age 68 years). Plain x-rays and computed tomography (CT) were obtained. A special image analysis software was used for the CT images after manual segmentation of the prosthetic acetabulum: automatic 3D volume and periprosthetic bone density were noted. Results: Bone loss was divided into three stages. At stage 1, the volume lost was from 10 to 20 cm3; at stage 2, the volume loss was 20 to 40 cm3; and at stage 3 the loss was greater than 40 cm3. At six months, two hips exhibited early stage acetabular loosening with 5% lucency. The corresponding volumes between the stages observed on the plain x-rays and those measured on the CT scan did not correlate significantly. Discussion: Compared with conventional x-ray methods for volume assessment, this computed tomography method is precise. The segmentation preparation was semi-automatic and took about 30 minutes. The prosthetic material did not hinder the image analysis. Results were produced automatically. The 3D representation enabled the operator to visualize intraopera-tively the acetabular zones the most affected, helpful for planning the procedure and choosing the implant. The density analysis gave the quality of the bone and the limit between healthy tissue, pathological tissue and the cement, increasing the volume of the bone loss. Conclusion: These automatic measurement tools reduce analysis time. The precision of the measurements is a supplementary factor for determining the stage of the bone loss and the amount of graft tissue or bone substitute needed. This method can be used for all joints

INTRODUCTION:. Clinical densitometry studies indicate that following TKR implantation there is loss of bone mineral density in regions around the implant. Bone density below the tibial tray has been reported to decrease 36% at eight years after TKR. This bone loss (∼5%/year) is substantially greater than osteoporosis patients in the same age group (∼1–2%/year) and could contribute the loss of mechanical support provided by the peri-implant leading to loosening of components in the long term. High patient mass and body mass index have also been implicated in increased loosening rates, and was thought to be due to high stress or strain on the tibial constructs. These findings suggest that peri-implant bone strain may be affected by time in service and patient factors such as body mass. The goal of this project was to assess the proximal tibial bone strain with biomechanical loading using en bloc retrieved TKR tibial components. Note that the implants were not obtained from revision surgery for a loose implant, but rather after death; thus the implants can be considered to be successful for the lifetime of the patient. We asked two research questions, guided by the clinical and laboratory observations: (1) are the peri-implant bone strain magnitudes for cemented tibial components greater for implants with more time in service and from older donors?, (2) is tibial bone strain greater for constructs from donors with high body weight and lower peri-implant BMD?. METHODS:. Twenty-one human knees with cemented total knee replacements were obtained from the SUNY Upstate Medical University Anatomical Gift Program. Clinical bone density scans were obtained of the proximal tibia in the anterior-posterior direction. Axial loads (1 body weight, 60/40% medial to lateral) were applied to the tibia through the contact patches identified on the polyethylene inserts. Strain measures were made using a non-contacting 3-D digital image correlation (DIC) system. Strain was measured over six regions of the bone surface (anterior (A), posterior (P), medial (M), lateral (L), postero-medial (PM), postero-lateral (PL)) (Figure 1). RESULTS:. For a donor population of 54 to 90 years (78 ave) with 0 to 22 years in service (ave 9 years), the peri-implant bone strains ranged from 119 to 791 ue. Maximum strains exceeded 3000 ue. Peri-implant bone strains were greater for implants with more time in service (p = 0.044), but not age of the donor (p = 0.333) (Figure 2). Peri-implant bone strains were greater for donors with greater mass (p = 0.028) and lower bone density (p = 0.0039) (Figure 3). DISCUSSION:. To the authors knowledge, these results show for the first time (using cemented tibial components) that bone remodeling after in-vivo service does not result in constant bone strain as would be expected for ‘homeostatic’ strain conditions. Even though loading was applied based on body weight, heavier donors had higher bone strains. Donors with more time in service also had higher bone strains. Combined, these results suggest that the supporting bone stock could diminish in some patients to the point at which bone failure occurs resulting in component migration

Objectives

Periprosthetic femoral fractures (PFFs) have a higher incidence with cementless stems. The highest incidence among various cementless stem types was observed with double-wedged stems. Short stems have been introduced as a bone-preserving alternative with a higher incidence of PFF in some studies. The purpose of this study was a direct load-to-failure comparison of a double-wedged cementless stem and a short cementless stem in a cadaveric fracture model.

Proximal tibial bone density (BD) is a key determinant in the migration of implants following total knee arthroplasty (TKA). CT-osteodensitometry offers three-dimensional, volumetric analysis of both cortical and cancellous regions and has been shown to be both accurate and reliable about the hip. The primary objective of this study is to assess differences in the bone remodelling pattern (tibial segment) of patients operated on using fixed or rotating platform, using CT-osteodensitometry. The hypothesis is that the presence of a rotating platform optimises stress distribution along the proximal tibia, resulting in reduced proximal bone remodelling of tibia. The secondary objective is to correlate the osteodensitometry and clinical data at follow-up. Following completion of the initial assessment and after obtaining written informed consent, the patients were randomly allocated to either a PFC Sigma fixed bearing or a PFC Sigma rotating platform (mobile bearing) total knee system (DePuy, Leeds, UK). Clinical follow-ups were performed at three months, one year, and two years after the index operation. CT scans were performed immediately post-operatively and at one and two years respectively. 52 knees (47 patients) were randomised for cemented TKR management using rotating or fixed tibia platform and followed up at one and two years. At the two year follow-up, the knee function and patellar scores were comparable in both groups. There were no radiographic signs of loosening, and no revision surgery was performed. Sequential BD measurement from post-operative baseline to two year follow-up showed minimal differences between the fixed and rotating platform implants. Bone density assessment showed a 20% mean loss of cancellous BD and minimal changes of cortical BD, with little differences between the two groups. Loss of cancellous BD appears progressive. In conclusion, this study shows that the mode of fixation of the TKR polyethylene liner does not influence bone remodelling of the proximal tibia after surgery. This is the first study performed to assess separately cortical and cancellous BD changes in THR. There are no data in the literature for comparison