Effect of alendronate on bone ingrowth into porous tantalum and carbon fiber interbody devicesAn experimental study on spinal fusion in pigs

Recent studies have reported that bisphosphonates reduce the resorption of grafted bone and inhibit bone resorption at a bone-implant interface. However, it is not known whether bisphosphonates affect bone ingrowth into porous biomaterial or spine fusion interbody devices with an autograft. In this study, 18 pigs (9 in each group) underwent anterior intervertebral lumbar arthrodeses at L2-3, L4-5 and L6-7. Each level was randomly allocated to one of the 3 implants: a solid piece of porous tantalum (Hedrocel), a porous tantalum ring or a carbon fiber cage both packed with an autograft. Alendronate was given orally to one of the groups. The radiographic and histological findings in the two groups 3 months after operation were similar in these devices. Histological examination showed that the original graft was entirely replaced by new trabecular bone in both groups. On histomorphometric analysis, the bone volume fraction, both inside the central hole of porous tantalum ring and in the porous tantalum, was larger in the pigs given alendronate than in the controls, but the fraction inside and around the central hole of the carbon fiber cage was not affected by this treatment. Short-term alendronate treatment, in a relatively low dose, does not impair the formation of new bone, but increases bone ingrowth into the central hole of the porous tantalum ring and the pores of the porous tantalum in this porcine model. This may be an effective way to enhance early biologic fixation of porous intervertebral implants.     

Effect of alendronate on bone ingrowth into porous tantalum and carbon fiber interbody devices: an experimental study on spinal fusion in pigs

Recent studies have reported that bisphosphonates reduce the resorption of grafted bone and inhibit bone resorption at a bone-implant interface. However, it is not known whether bisphosphonates affect bone ingrowth into porous biomaterial or spine fusion interbody devices with an autograft. In this study, 18 pigs (9 in each group) underwent anterior intervertebral lumbar arthrodeses at L2-3, L4-5 and L6-7. Each level was randomly allocated to one of the 3 implants: a solid piece of porous tantalum (Hedrocel), a porous tantalum ring or a carbon fiber cage both packed with an autograft. Alendronate was given orally to one of the groups. The radiographic and histological findings in the two groups 3 months after operation were similar in these devices. Histological examination showed that the original graft was entirely replaced by new trabecular bone in both groups. On histomorphometric analysis, the bone volume fraction, both inside the central hole of porous tantalum ring and in the porous tantalum, was larger in the pigs given alendronate than in the controls, but the fraction inside and around the central hole of the carbon fiber cage was not affected by this treatment. Short-term alendronate treatment, in a relatively low dose, does not impair the formation of new bone, but increases bone ingrowth into the central hole of the porous tantalum ring and the pores of the porous tantalum in this porcine model. This may be an effective way to enhance early biologic fixation of porous intervertebral implants.     

Effect of alendronate on bone ingrowth into porous tantalum and carbon fiber interbody devices

Recent studies have reported that bisphosphonates reduce the resorption of grafted bone and inhibit bone resorption at a bone-implant interface. However, it is not known whether bisphosphonates affect bone ingrowth into porous biomaterial or spine fusion interbody devices with an autograft. In this study, 18 pigs (9 in each group) underwent anterior intervertebral lumbar arthrodeses at L2-3, L4-5 and L6-7. Each level was randomly allocated to one of the 3 implants: a solid piece of porous tantalum (Hedrocel), a porous tantalum ring or a carbon fiber cage both packed with an autograft. Alendronate was given orally to one of the groups. The radiographic and histological findings in the two groups 3 months after operation were similar in these devices. Histological examination showed that the original graft was entirely replaced by new trabecular bone in both groups. On histomorphometric analysis, the bone volume fraction, both inside the central hole of porous tantalum ring and in the porous tantalum, was larger in the pigs given alendronate than in the controls, but the fraction inside and around the central hole of the carbon fiber cage was not affected by this treatment. Short-term alendronate treatment, in a relatively low dose, does not impair the formation of new bone, but increases bone ingrowth into the central hole of the porous tantalum ring and the pores of the porous tantalum in this porcine model. This may be an effective way to enhance early biologic fixation of porous intervertebral implants.     

Bone ingrowth characteristics of porous tantalum and carbon fiber interbody devices: an experimental study in pigs.

BACKGROUND CONTEXT: In preclinical and clinical joint replacement applications, porous tantalum has been shown to be osteoconductive and effective for biological fixation. Relatively little research has been undertaken to investigate the porous tantalum implants for potential application in intervertebral spinal fusion. PURPOSE: The current study was designed to assess the radiographic and histological performance of porous tantalum and carbon fiber devices in the porcine anterior lumbar interbody fusion (ALIF) model. STUDY DESIGN: A total of 10 Danish Landrace pigs underwent a three-level anterior intervertebral lumbar arthrodeses at L2-L3, L4-L5 and L6-L7. Each level was randomly allocated to one of three implants: a solid piece of porous tantalum, a porous tantalum ring packed with autograft or a carbon fiber cage, likewise packed with autograft. Two staples for fixation were supplemented in front of implant. METHODS: Pigs were sacrificed 3 months after operation. Specimens were evaluated by plain radiography, conventional tomography and histology. RESULTS: Bone graft filled into the central hole of the porous tantalum ring was less than that of the carbon fiber cage (p<.001). Radiolucencies around the porous tantalum solid were significantly higher than the carbon fiber cage (p=.02) and were not different between the porous tantalum ring and the carbon fiber cage. The bone volume in the hole of implants, within the pores of the porous tantalum and in the implant interface did not differ between implants. Bone volume in the hole of the porous tantalum ring did not differ from that of the adjacent vertebral bone; however, it was significantly different in the carbon fiber cage and the adjacent vertebral bone (p=.005). CONCLUSIONS: In this porcine ALIF model, the radiographic and histological appearances of the porous tantalum ring were equivalent to those of the carbon fiber cage. The high presence of radiolucencies and fibrous tissue layer at the vertebrae-implant interface suggests that an initial stabilizing biomechanical environment is important in order to achieve bone ingrowth in the interbody fusion devices in this ALIF model.     

Clinical and radiographic outcomes of the treatment of adolescent idiopathic scoliosis with segmental pedicle screws and combined local autograft and allograft bone for spinal fusion: a retrospective case series

Background

High morbidity has been reported with iliac crest bone graft harvesting; however, donor bone is typically necessary for posterior spinal fusion. Autograft bone combined with allograft may reduce the morbidity associated with iliac crest bone harvesting and improve the fusion rate. Our aim in this study was to determine the presence of complications, pseudarthrosis, non-union, and infection using combined in situ local autograft bone and freeze-dried cancellous allograft bone in patients undergoing posterior spinal fusion for the treatment of adolescent idiopathic scoliosis.

Methods

A combination of in situ local autograft bone and freeze-dried cancellous allograft blocks were used in 50 consecutive patients with adolescent idiopathic scoliosis treated by posterior fusion and Moss Miami pedicle screw instrumentation. Results were assessed clinically and radiographically and quality of life and functional outcome was evaluated by administration of a Chinese version of the SRS-22 survey.

Results

There were 41 female and 9 male patients included for analysis with an average age of 14.7 years (range, 12-17). All patients had a minimum follow-up of 18 months (range, 18 to 40 months). The average preoperative Cobb angle was 49.8° (range, 40° to 86°). The average number of levels fused was 9.8 (range, 6-15). Patients had a minimum postoperative follow-up of 18 months. At final follow-up, the average Cobb angle correction was 77.8% (range, 43.4 to 92.5%). There was no obvious loss in the correction, and the average loss of correction was 1.1° (range, 0° to 4°). There was no pseudarthrosis and no major complications.

Conclusions

In situ autograft bone combined with allograft bone may be a promising method enhances spinal fusion in AIS treated with pedicle screw placement. By eliminating the need for iliac crest bone harvesting, significant morbidity may be avoided.     

Early failures of porous tantalum osteonecrosis implants: a case series with retrieval analysis

Backgrounds

Porous tantalum osteonecrosis implants have been used in femoral head necrosis for several years, while the clinical outcomes were mixed. As a joint-preserving surgery, early necrosis deterioration and conversion to total hip arthroplasy failed our expectation. We hence investigate an observational study with retrieval analysis to find out the underlying reasons.

Methods

Thirteen patients were treated with core decompression and implantation of a tantalum rod. The cases were evaluated both functionally and radiologically. We retrieved and analyzed the micro-structural changes and the histopathologic features of four early failed femoral heads with scanning electron microscopy, histopathologic examination, and micro-CT scaning.

Results

All implants were placed in proper positions. One-year survival rate was 64.29 % with a HSS score of 81.11?±?15.62. Four patients converted to arthroplasty in a mean time of 305 days (0.84 years), with a HSS score of 43.75?±?7.5 at the last follow-up. A liquid layer surrounded the tantalum implant was noted on MRI in all four failed cases. Volume render CT remodeling revealed interspace between the metal and bone. Scanning electron microscopy and histopathologic examination indicated sparse and isolated bone ingrowth into the implants. The remodeled trabecular bone and the increased density around the peri-implant area were illustrated with micro-CT scaning.

Conclusions

The deterioration of early failed tantalum implant exceeds the nature of osteonecrosis progression. Rather than insufficient mechanical support resulting in improper position and invalid bone ingrowth, nullification of core decompression and consequential intra-osseous pressurization probably led to early failure of porous tantalum osteonecrosis implants.

     

Biological performance of a polycaprolactone-based scaffold plus recombinant human morphogenetic protein-2 (rhBMP-2) in an ovine thoracic interbody fusion model

Purpose

We develop a sheep thoracic spine interbody fusion model to study the suitability of polycaprolactone-based scaffold and recombinant human bone morphogenetic protein-2 (rhBMP-2) as a bone graft substitute within the thoracic spine. The surgical approach is a mini-open thoracotomy with relevance to minimally invasive deformity correction surgery for adolescent idiopathic scoliosis. To date there are no studies examining the use of this biodegradable implant in combination with biologics in a sheep thoracic spine model.

Methods

In the present study, six sheep underwent a 3-level (T6/7, T8/9 and T10/11) discectomy with randomly allocated implantation of a different graft substitute at each of the three levels: (a) calcium phosphate (CaP) coated polycaprolactone-based scaffold plus 0.54 μg rhBMP-2 (b) CaP-coated PCL-based scaffold alone or (c) autograft (mulched rib head). Fusion was assessed at 6 months post-surgery.

Results

Computed Tomographic scanning demonstrated higher fusion grades in the rhBMP-2 plus PCL-based scaffold group in comparison with either PCL-based scaffold alone or autograft. These results were supported by histological evaluations of the respective groups. Biomechanical testing revealed significantly higher stiffness for the rhBMP-2 plus PCL-based scaffold group in all loading directions in comparison with the other two groups.

Conclusion

The results of this study demonstrate that rhBMP-2 plus PCL-based scaffold is a viable bone graft substitute, providing an optimal environment for thoracic interbody spinal fusion in a large animal model.     

Adjuncts in posterior lumbar spine fusion: comparison of complications and efficacy

Purpose

The purpose of this study was to define the efficacy of recombinant human Bone Morphogenetic Protein-2 (rhBMP-2) and Demineralized Bone Matrix (DBM) compared to autograft in posterior lumbar spine fusion by comparing complication rates.

Methods

During a 7-year period (2003–2009), all patients undergoing posterior lumbar fusion were retrospectively evaluated within a large orthopedic surgery private practice. Patient demographics, comorbidities, number of levels, type of surgery, and types of bone void filler and osteobiologics were analyzed. Complications were defined as reoperation secondary to failed symptomatic fusion, hyper-reaction with fluid collections, bone overgrowth, and infections.

Results

1,398 patients were evaluated with 41.1?% males and 58.9?% females. Mean age was 60?years and BMI 30.6?kg/m2. Patients were subdivided in treatment groups: rhBMP-2, 947 (67.7?%), DBM 306 (21.9?%), and autograft 145 (10.4?%). The overall infection rate was 2.1?%. No significant differences were found between the three groups. The incidence of seroma formation was higher in the BMP group (3.2?%) than in the DBM or autograft group (2.0 and 1.4?%, respectively) but this was not significant (p?=?0.286 and p?=?0.245, respectively). 103 patients (7.4?%) underwent redo surgery for clinically significant nonunion. We found significantly fewer nonunions (4.3?%) in the rhBMP-2 group (p?Conclusion ICBG is the gold standard. DBM leads to comparable fusion rates and does not increase infection or seroma formation. rhBMP-2 supplementation instead of ICBG or bone marrow aspirate results in higher fusion rates compared to autograft alone or autograft plus DBM.     

Biomechanical comparison of alternative densities of pedicle screws for the treatment of adolescent idiopathic scoliosis

Purpose

The objective of this computational study was to compare the biomechanical effects of different implant densities in terms of curve reduction and the force levels at the implant–vertebra interface and on the intervertebral elements.

Methods

Eight cases were randomly picked among patients who have undergone a posterior spinal instrumentation for adolescent idiopathic scoliosis (AIS). For each case, two computer simulations were performed, one with the actual surgery implant pattern and another with the same fusion levels but an alternative implant pattern proposed by an experienced surgeon. The two implant patterns for each case were respectively put into higher and lower implant density group. The spinal correction and the force levels at bone–implant interface and on the intervertebral elements were analyzed and compared between the two groups.

Results

There were on average 13% more pedicle screws and 30% more bilaterally placed pedicle screws in the higher versus lower density group. The difference in the density of screws (92% vs. 79%) did not lead to significant difference in terms of the resulting main thoracic (MT) Cobb angle, and the MT apical axial vertebral rotation. The average and maximum implant-vertebra force levels were about 50 and 65%, respectively higher in the higher versus lower density group, but without consistent distribution patterns. The average intervertebral forces did not significantly differ between the two groups.

Conclusions

With the same fusion levels, lower density screws allowed achieving similar deformity correction and it was more likely to have lower screw–vertebra loads.     

Bone loss following knee arthroplasty: potential treatment options

Introduction

The management of bone loss is a crucial aspect of the revision knee arthroplasty. Bone loss can hinder the correct positioning and alignment of the prosthetic components, and can prevent the achievement of a stable bone–implant interface. There is still controversy regarding the optimal management of knee periprosthetic bone loss, especially in large defects for which structural grafts, metal or tantalum augments, tantalum cones, porous metaphyseal sleeves, and special prostheses have been advocated. The aim of this review was to analyze all possible causes of bone loss and the most advanced strategies for managing bony deficiency within the knee joint reconstruction.

Materials and methods

Most significant and recent papers about the management of bone defects during revision knee arthroplasty were carefully analyzed and reviewed to report the most common causes of bone loss and the most effective strategies to manage them.

Results

Modular metal and tantalum augmentation showed to provide more stable and durable knee revisions compared to allografts, limited by complications such as graft failure, fracture and resorption. Moreover, modular augmentation may considerably shorten operative times with a potential decrease of complications, above all infection which has been frequently associated to the use of allografts.

Conclusions

Modular augmentation may significantly reduce the need for allografting, whose complications appear to limit the long-term success of knee revisions.     

Airport metal detector activation is rare after posterior spinal fusion in children with scoliosis

Purpose

Since the September 11, 2001 terrorist attacks on the World Trade Center in New York City, travel security has become an ever-increasing priority in the United States. Frequent parent and patient inquiry and recent literature reports have generated interest in the impact of heightened security measures on patients with orthopaedic implants, and have indicated increasing rates of metal detector triggering. There are no reports to date, however, evaluating children and adolescents who have undergone posterior spinal fusion for scoliosis, so responses to patient and parent inquiries are not data-driven. The purpose of this study is to determine the frequency of airport metal detector triggering by patients who have had posterior-only spinal fusion and to characterise any potential predictors of metal detector activation.

Methods

A cross-sectional study was performed by interviewing 90 patients who underwent posterior-only spinal fusion for a diagnosis of juvenile or adolescent idiopathic scoliosis and have travelled by air in the past year. Demographic, clinical and surgical instrumentation data were collected and evaluated, along with patients’ reports of airport metal detector triggering and subsequent screening procedures.

Results

Five patients with stainless steel instrumentation (5.6 % of the cohort) triggered an airport walkthrough metal detector, and an additional five patients who did not trigger an airport detector triggered a handheld detector at a different venue. All patients who triggered an airport metal detector had stainless steel instrumentation implanted prior to 2008, and no patient with titanium instrumentation triggered any detector in any venue. All trigger events required subsequent screening procedures, even when an implant card was presented.

Conclusions

In this cohort of children and adolescents with posterior spinal instrumentation, airport walkthrough metal detector triggering was a rare event. Therefore, we advise patients and families with planned posterior scoliosis fusions using titanium instrumentation that airport detection risk is essentially non-existent, and only rare for those with planned stainless steel instrumentation. We no longer issue implant cards postoperatively, as these did not prevent further screening procedures in this cohort.

Level of evidence

Prognostic level 2. Study design: cross-sectional.     

Opioids delay healing of spinal fusion: a rabbit posterolateral lumbar fusion model

Background Context

Opioid use is prevalent in the management of pre- and postoperative pain in patients undergoing spinal fusion. There is evidence that opioids downregulate osteoblasts in vitro, and a previous study found that morphine delays the maturation and remodeling of callus in a rat femur fracture model. However, the effect of opioids on healing of spinal fusion has not been investigated before. Isolating the effect of opioid exposure in humans would be limited by the numerous confounding factors that affect fusion healing. Therefore, we have used a well-established rabbit model to study the process of spinal fusion healing that closely mimics humans.

Histological ex vivo analysis of retrieved human tantalum augmentations

Purpose

The characteristics of tantalum augment osseointegration in human ex vivo specimens from re-revision procedures are unknown and limited data in this regard is available. The purpose of this study was to investigate the osseointegration pattern into porous tantalum augmentations harvested during re-revision procedures.

Methods

Between 2007 and 2010 a total of 324 hip and knee revisions with a tantalum augmentation were performed in our institution. Out of this cohort, seven patients (2.2 %) had to be re-revised. To analyse the status of trabecular ingrowth in the retrieved cases (four hips, three knees), all specimens were analysed by contact radiography, subjected to undecalcified processing, histology, thin-section analysis and backscattered electron imaging.

Results

Trabecular and vascular ingrowth could be found along the bone-augment-interface in two of seven revised specimens, respectively. The depth of bone ingrowth reached up to 2.6 mm. However, the analysis of the remaining cases revealed no bony ingrowth into trabecular metal. Rather, large parts of the implants were embedded in cement or pores were filled with autologous bone.

Conclusions

Although the cause for the missing bony ingrowth seems to be multifactorial, some fundamental conditions, such as the provision of the greatest possible interface between the tantalum implant and the host bone, should be met and thus, bone cement and autologous bone grafts should be used with caution.     

Anterior cervical interbody fusion with rhBMP-2 and tantalum in a goat model.

BACKGROUND CONTEXT: Tricortical autogenous iliac crest has long served as the gold standard for arthrodesis after cervical discectomy. The added morbidity resulting from bone graft harvest may be eliminated by the use of a biocompatible synthetic bone graft substitute with osteoconductive abilities, and when used with an osteoinductive agent, such as recombinant bone morphogenic protein (rhBMP)-2, it may facilitate arthrodesis similar to autograft. PURPOSE: To determine by radiographic and histologic analysis whether tantalum with and without rhBMP-2 can facilitate bony ingrowth and arthrodesis in an animal model. STUDY DESIGN/SETTING: Single-level anterior cervical discectomy and fusion was performed using a tantalum bone graft substitute with and without rhBMP-2 in a previously established goat model for anterior cervical fusion. METHODS: Eight goats underwent single-level anterior cervical discectomy and stabilization with a porous tantalum implant. There were four goats in each experimental group. Group A underwent anterior cervical stabilization with tantalum alone, whereas in Group B rhBMP-2 was added to the tantalum implant. The goats were sacrificed at 12 weeks, and their cervical spines were removed for histologic and radiological analysis. RESULTS: Only one of four goats in Group A had any bony ingrowth into the tantalum. Three of four goats in Group B demonstrated bony ingrowth. The average extent of bony ingrowth at the perimeter of the tantalum in Group A was 2.5% compared with 12.5% in Group B. Similarly, the volume of bony ingrowth within the tantalum was 2.5% in Group A and 10% in Group B. The difference was not statistically significant. CONCLUSIONS: The data in this pilot study suggest that tantalum may function as a synthetic osteoconductive bone graft substitute. The addition of rhBMP-2 may facilitate osteoinduction within a synthetic osteoconductive implant. The sample size in this study was too small for statistical significance. The present animal model as used in this study was inadequate for cervical arthrodesis where rigid implant fixation is desired.     

Relation between radiological assessment and biomechanical stability of lumbar interbody fusion in a large animal model

Purpose

To relate the progress of vertebral segmental stability after interbody fusion surgery with radiological assessment of spinal fusion.

Methods

Twenty goats received double-level interbody fusion and were followed for a period of 3, 6 and 12 months. After killing, interbody fusion was assessed radiographically by two independent observers. Subsequently, the lumbar spines were subjected to four-point bending and rotational deformation, assessed with an optoelectronic 3D movement registration system. In addition, four caprine lumbar spines were analysed in both the native situation and after the insertion of a cage device, as to mimic the direct post-surgical situation. The range of motion (ROM) in flexion/extension, lateral bending and axial rotation was analysed ex vivo using a multi-segment testing system.

Results

Significant reduction in ROM in the operated segments was already achieved with moderate bone ingrowth in flexion/extension (71 % reduction in ROM) and with only limited bone ingrowth in lateral bending (71 % reduction in ROM) compared to the post-surgical situation. The presence of a sentinel sign always resulted in a stable vertebral segment in both flexion/extension and lateral bending. For axial rotation, the ROM was already limited in both native and cage inserted situations, resulting in non-significant differences for all radiographic scores.

Discussion

In vivo vertebral segment stability, defined as a significant reduction in ROM, is achieved in an early stage of spinal fusion, well before a radiological bony fusion between the vertebrae can be observed. Therefore, plain radiography underestimates vertebral segment stability.     

The Exeter method—acetabular impaction grafting with cemented reimplantation

Objective

Restoration of acetabular anatomy and biomechanics at revision hip surgery by replacing deficient acetabular bone through impaction of allograft and/or autograft bone chips.

Indications

Aseptic loosening of the socket due to osteolysis, bone loss from infection, iatrogenic bone loss due to implant removal, and in the primary setting protrusio acetabuli, dysplasia and previous acetabular fracture.

Contraindications

Large segmental peripheral acetabular defects which cannot be contained, the presence of untreated infection, unstable acetabular fractures, previous radiotherapy to the affected hip area.

Surgical technique

Sound exposure of the acetabulum with delineation of the bony defect. Creation of a host environment suitable for bone graft and containment of segmental defects using rim mesh or porous augments. Impaction grafting using layered allograft or autograft bone chips of 0.8–1 cm³, packed using hemispherical impactors, followed by cementing of a polyethylene acetabular component with pressurisation.

Postoperative management

Partial weight bearing 6 weeks, modified depending on level of containment and intra-operative findings.

Results

A successful and reproducible technique with survival up to 87?% at 20 years for aseptic loosening in the revision setting.     

Posterior spinal fusion to sacrum in non-ambulatory hypotonic neuromuscular patients: sacral rod/bone graft onlay method

Purpose

A retrospective study involving 65 non-ambulatory patients with hypotonic neuromuscular scoliosis has assessed the effectiveness of a sacral rod/bone onlay technique for extending spinal fusion to the sacrum.

Methods

To extend posterior spinal fusion to the sacrum, we used either 1 Harrington rod and 1 Luque L rod with sublaminar wires in 14 patients (Group 1) or two rods with sublaminar wires in 51 patients (Group 2) along with abundant autograft and allograft bone covering the ends of the rods.

Results

Diagnoses were Duchenne muscular dystrophy 53, spinal muscular atrophy 4, myopathy 3, limb girdle muscular dystrophy 2, infantile FSH muscular dystrophy 1, cerebral palsy 1, and Friedreich ataxia 1. Mean age at surgery was 14.3 years (±2.2, range 10.9–25.2). Radiographic follow-up (2 years post-surgery or greater) was 6.4 years (±4.4, range 2–25.3). Using the onlay technique, all patients fused with no rod breakage or pseudarthrosis. For the entire series, the mean pre-operative scoliosis was 54.7° (±31.1, range 0°–120°) with post-operative correction to 21.8° (±21.7, range 0°–91°) and long-term follow-up 24° (±22.9, range 0°–94°). For pelvic obliquity, pre-operative deformity was 17.3° (±11.3, range 0°–51°) with post-operative correction to 8.9° (±7.8, range 0°–35°) and long-term follow-up 10.1° (±8.1, range 0°–27°). Five required revision at a mean of 3.3 years post-original surgery involving rod shortening at the distal end. One of these had associated infection.

Conclusion

Lumbosacral stability and long-term sitting comfort have been achieved in all patients. Problems can be minimized by positioning the rods firmly against the sacrum at the time of surgery with a relatively short extension beyond the L₅–S₁ junction. The procedure is valuable in hypotonic non-ambulatory neuromuscular patients whose immobility enhances the success rate for fusion due to diminished stress at the lumbosacral junction. It is particularly warranted for those with osteoporosis and a small, deformed pelvis. Considerable weight loss and lengthy rods not closely apposed to the sacrum at the time of surgery played a major role in patients needing revision.     

One-stage anterior debridement,bone grafting and posterior instrumentation vs. single posterior debridement,bone grafting,and instrumentation for the treatment of thoracic and lumbar spinal tuberculosis

Purpose

The aim of this study was to compare single posterior debridement, interbody fusion and instrumentation with one-stage anterior debridement, interbody fusion and posterior instrumentation for treating thoracic and lumbar spinal tuberculosis.

Method

From January 2006 to January 2010, we enrolled 115 spinal tuberculosis patients with obvious surgical indications. Overall, 55 patients had vertebral body destruction, accompanied by a flow injection abscess or a unilateral abscess volume greater than 500 ml. The patients underwent one-staged anterior debridement, bone grafting and posterior instrumentation (group A) or single posterior debridement, bone grafting and instrumentation (group B). Clinical and radiographic results for the two groups were analyzed and compared.

Results

Patients were followed 12–36 months (mean 21.3 months), Fusion occurred at 4–12 months (mean 7.8 months). There were significant differences between groups regarding the post-operative kyphosis angle, angle correction and angle correction rate, especially if pathology is present in thoracolumbar and lumbar regions. Operative complications affected five patients in group A, and one patient in group B. A unilateral psoas abscess was observed in three patients 12 months postoperatively. In one of them, interbody fusion did not occur, and there was fixation loosening and interbody absorption. All of them were cured by an anterior operation.

Conclusion

Anterior debridement and bone grafting with posterior instrumentation may not be the best choice for treating patients with spinal tuberculosis. Single posterior debridement/bone grafting/instrumentation for single-segment of thoracic or lumbar spine tuberculosis produced good clinical results, except in patients who had a psoas abscess.     

The effect of posterior spinal fusion on respiratory function in Duchenne muscular dystrophy

Purpose

Posterior instrumented spinal fusion is indicated for progressive scoliosis that develops in Duchenne muscular dystrophy (DMD) patients. Whilst spinal fusion is known to improve quality of life, there is inconsistency amongst the literature regarding its specific effect on respiratory function. Our objective was to determine the effect of scoliosis correction by posterior spinal fusion on respiratory function in a large cohort of patients with DMD. Patients with DMD undergoing posterior spinal fusion were compared to patients with DMD not undergoing surgical intervention.

Methods

An observational study of 65 patients with DMD associated scoliosis, born between 1961 and 2001: 28 of which underwent correction of scoliosis via posterior spinal fusion (Surgical Group) and 37 of which did not undergo surgical intervention (Non-Surgical Group). Pulmonary function was assessed using traditional spirometry. Comparisons were made between groups at set times, and by way of rates of change over time.

Results

There was no correlation between the level of respiratory dysfunction and the severity of scoliosis (as measured by Cobb angle) for the whole cohort. The Surgical Group had significantly worse respiratory function at a comparable age pre-operatively compared to the Non-Surgical Group, as measured by per cent predicted forced vital capacity (p = 0.02) on spirometry. The rate of decline of forced vital capacity and per cent predicted forced vital capacity was not slowed following surgery compared to the non-operated cases. There was no significant difference in survival between the two groups.

Conclusions

Severity of scoliosis was not a key determinant of respiratory dysfunction. Posterior spinal fusion did not reduce the rate of respiratory function decline. These two points suggest that intrinsic respiratory muscle weakness is the main determinant of decline in respiratory function in DMD.