Harms Cage Research Articles

Biomechanical evaluation of a novel integrated artificial axis: A finite element study.

Various modified instruments are used for the anterior reconstruction of the tumor lesion affecting the second cervical vertebra, but there have been no reports regarding individual integrated artificial axis (IAA) prosthesis fabricated by selective laser melting. In the present work, a new type of IAA prosthesis has been designed with a 3-dimensional (3D) finite element model of normal occiput-the fourth cervical vertebra being established to assess its biomechanics. For easy comparison, another 3D finite element model is also established for the T-shaped Harms cage and an additional posterior fixation was performed on each model. The models are tested under a preliminary loading of 40 N to simulate cervical physical action including flexion, extension, lateral bending, and rotation. Under various loads from 4 different directions, the maximum stress and displacement of the IAA are less than those of the modified T-shaped Harms cage. Except for flexion, the maximum stress of the third cervical vertebra endplate of the IAA is smaller than that of the modified T-shaped Harms cage. The new prosthesis with axis is a good choice for upper cervical operation, which not only can greatly increase the operation stability of the upper cervical segment but also could significantly reduce the risk of fixation failure due to Harms cage subsidence.

A Novel Method to Fix Type C3 Distal Femur Fractures with Bone Defect Loss Using “Harms Cage”

A case of compound C3 distal femur fracture with 12 cm bone defect. After thorough debridement, the Harms cage was used to reconstruct the medial column and the fracture was fixed with the locking distal femur plate laterally. The Harms cage prevents the cantilever effect and eliminates the need for medial plating. This avoids another medial incision and preserves medial biology. At 18 months’ follow-up, plain radiographs demonstrated full reconstruction of the medial column with good range of motion at the knee joint. This technique avoids the need of dual plating in these fractures with good results.

Lateral mass lesions of the C1 vertebra: a modified “far lateral” approach

The surgical removal of lateral mass lesions is demanding due to their close anatomical relationship with the vertebral artery, upper spinal cord as well as overlying muscular structures. Usually a dorsal approach will be performed to reach the lateral mass. The disadvantage of this approach is the extensive mobilization of the neck muscles required to allow exposure of the lateral mass, which can be accompanied by severe muscular atrophy due to the damage of the local innervation. Additionally, management of the exposure of the vertebral artery is hindered by the dorsal approach. A modified "far lateral" approach with complete resection of the lateral mass of C1 followed by a substitute with a Harms cage is presented. A 54-year-old woman was suffering from severe neck pain accompanied by a progressive sliding of her head and the visual axis to the right hand side. MRI as well as CT scans showed an osteolytic destruction of the right lateral mass of C1. After occipito-cervical fusion the osteolytic lateral mass was removed using a far lateral approach to the upper cervical spine. The patient recovered immediately after surgery, the neck pain improved and the lateral bending of the head was balanced. This far lateral approach offers the advantage of direct visualization of the lateral aspect of the upper cervical spine with the opportunity for local stabilization at the center of rotation.

Auswanderung der PMMA-Zementplombe als seltene Komplikation der Kyphoplastie - Kasuistik und Übersichtsarbeit

For vertebral body fractures combined with strong back pain, the kyphoplasty is an established method for pain reduction. A balloon effects an excavation in the vertebral body, which will be filled up with cement. We distinguish between cements of polymethyl metacrylate (PMMA) and calcium phosphate. Their diverse chemical qualities enable different indications. A 72-year-old male patient with refractory back pain after a lumbar vertebral body fracture was treated with a kyphoplasty operation. After four days the patient went home with clearly less pain. After two months the patient had a bagatelle trauma at home, which caused an exacerbation of the back pain. In computered tomography we saw a disruption of the PMMA cement plombage forwards and also a kyphosis of the lumbar vertebrae. Therefore we had to operate on the patient two more times. The first time we stabilised the spine from dorsal via an internal fixator. The additive ventral fixation was at that time declined by the patient. Because of the persistency of the back pain after operation combined with a sense of instability, we were ten days after the first revision allowed to stabilise the patient from ventrally with a Harms cage. At the first-year follow-up the patient was still free of pain. Injuries of the vertebral body frame cannot be operated exclusively with kyphoplasty. The reason for this is the instability of the vertebral body despite the injection of the PMMA cement. We advise to stabilise the spine in such cases with a dorsal internal fixator additively.

Reamed Transacral Interbody Fusion for L5–S1 Pseudoarthrosis

A retrospective cohort study. To present the technique, radiographic, and clinical outcomes of a series of patients who underwent a novel method for revision L5-S1 interbody fusion. Pseudoarthrosis at L5-S1 is a relatively common problem after long fusion to the sacrum. Revision approach to L5-S1 for cage or graft removal by anterior lumbar interbody fusion, posterior lumbar interbody fusion, or transforaminal interbody fusion is challenging and potentially dangerous which makes salvage by a posterior reamed transacral technique appealing. Consecutive patients with symptomatic pseudoarthrosis at L5-S1, who underwent posterior reamed fluoroscopically guided fusion were identified over a 3-year period. Operative notes, medical records, preoperative and postoperative plain radiographs, computed tomography scans, Visual Analog Scores (VAS) (lower extremity and low back) preoperatively, and at most recent follow-up were studied. Ten patients (age, 53±2.8 y) with prior lumbar spinal operations (mean, 3.5±0.6) met the inclusion criteria. Prior procedures at L5-S1 were anterior lumbar interbody fusion (n=4), posterior lumbar interbody fusion (n=3), and posterolateral fusion (n=3). Mean Meyerding grade was 1.41 (range, 0-4). Reaming was performed between the S1 and S2 (n=9) or S2 and S3 (n=1) nerve roots and allowed fragmentation/removal of polyetheretherketone interbody grafts (n=3) or femoral ring allografts (n=3). Transacral Harms cage (n=8) or autograft (n=1) was passed through the reamed channel or a carbon fiber-reinforced polyetheretherketone directly into the interspace (n=1). VAS scores lower extremity (P=0.003) and low back (P=0.001) were improved at a mean follow-up of 13.5±3.6 months. No neurologic sequelae occurred and solid fusion was achieved in 9/10 (90%). We report a series of patients who underwent a novel revision technique for symptomatic lumbosacral pseudoarthrosis. Despite the small numbers in this cohort, a salvage technique is presented that permitted fusion as confirmed by computed tomography scan and improved VAS scores in the majority of patients. The data suggest that this technique should be considered as an alternative to the revision anterior or posterior approaches to L5-S1 and merits further investigation.

Spondilolistesi degenerativa lombare: trattamento chirurgico

The authors present a retrospective study on a consecutive series of 147 patients operated on for degenerative lumbar spondylolisthesis. All of them had at least one year of conservative treatment prior to surgery. The surgery was posterior bilateral decompression, reduction of the listhesis and instrumented PLIF using Harms cages and polyaxial pedicle screws, with segment compression. 22 patients were lost at follow-up. 85% of the followed-up patients were satisfied with the result of the surgery, while 15% had a poor or bad result.

A Comparative Study of the Anterior Cervical Fusion with Harms Cage versus Iliac Bone Block: Clinical and Radiological Outcomes

A Comparative Study of the Anterior Cervical Fusion with Harms Cage versus Iliac Bone Block: Clinical and Radiological Outcomes

In vivo experimental study of hat type cervical intervertebral fusion cage (HCIFC)

The purpose of this study was to compare the characteristics of interbody fusion achieved using the hat type cervical intervertebral fusion cage (HCIFC) with those of an autologous tricortical iliac crest graft, Harms cage and the carbon cage in a goat cervical spine model. Thirty-two goats underwent C3-4 discectomy and fusion. They were subdivided into four groups of eight goats each: group 1, autologous tricortical iliac crest bone graft; group 2, Harms cage filled with autologous iliac crest graft; group 3, carbon cage filled with autologous iliac bone; and group 4, HCIFC filled with autologous iliac graft. Radiography was performed pre- and postoperatively and after one, two, four, eight and 12 weeks. At the same time points, disc space height, intervertebral angle, and lordosis angle were measured. After 12 weeks, the goats were killed and fusion sites were harvested. Biomechanical testing was performed in flexion, extension, axial rotation, and lateral bending to determine the stiffness and range of motion. All cervical fusion specimens underwent histomorphological analyses. One week after operation, the disc space height (DSH), intervertebral angle (IVA) and lordosis angle (LA) of HCIFC and carbon cage were statistically greater than those of autologous iliac bone graft and Harms cage. Significantly higher values for DSH, IVA and LA were shown in cage-treated goats than in those that received bone graft over a 12-week period. The stiffness of Harms cage in axial rotation and lateral bending were statistically greater than that of other groups. Radiographic and histomorphological evaluation showed better fusion results in the cage groups than in the autologous bone group. HCIFC can provide a good intervertebral distractability and sufficient biomechanical stability for cervical fusion.

Harms titanium mesh cage fracture

Interbody fusion has become a mainstay of surgical management for lumbar fractures, tumors, spondylosis, spondylolisthesis and deformities. Over the years, it has undergone a number of metamorphoses, as novel instrumentation and approaches have arisen to reduce complications and enhance outcomes. Interbody fusion procedures are common and successful, complications are rare and most often do not involve the interbody device itself. We present here a patient who underwent an anterior L4 corpectomy with Harms cage placement and who later developed a fracture of the lumbar titanium mesh cage (TMC). This report details the presentation and management of this rare complication, as well as discusses the biomechanics underlying this rare instrumentation failure.

Biomechanical study of a hat type cervical intervertebral fusion cage

The purpose of this study was to evaluate the biomechanical effect of a hat type cervical intervertebral fusion cage (HCIFC). In this in vitro biomechanical study, 48 goat cervical spines (C2-5) were tested in flexion, extension, axial rotation, and lateral bending with a nondestructive stiffness method using a nonconstrained testing apparatus, and three-dimensional displacement was measured. Autologous iliac bone and cervical spine intervertebral fusion cage were implanted according to manufacturers' information after complete discectomy (C3-4). Eight spines in each of the following groups were tested: intact, autologous iliac bone graft, Harms cage, SynCage C, carbon cage, and HCIFC. The mean apparent stiffness values were calculated from the corresponding load-displacement curves. Additionally, cage volume and volume-related stiffness were determined. The stiffness of the SynCage C was statistically greatest in all directions. After implantation of the HCIFC, flexion stiffness increased compared with that of the intact motion segment. There was no significant difference in stiffness between the HCIFC and carbon cage. The stiffness of the HCIFC was statistically higher than that of the Harms cage in axial rotation and significantly lower in flexion, extension, and lateral bending. Volume-related stiffness of all cages was higher than that of iliac bone graft. The Harms cage was highest in volume-related stiffness in all directions. The HCIFC can provide enough primary stability for cervical intervertebral fusion.

In vivo experimental study of hat type cervical intervertebral fusion cage

To compare the characteristics of interbody fusion achieved using hat type cervical intervertebral fusion cage (HCIFC) with those of an autologous tricortical iliac crest graft, Harms cage and Carbon cage in a goat cervical spine model. Thirty-two goats underwent C(3, 4) discectomy and fusion in which the following were used: Group 1, autologous tricortical iliac crest bone graft (8 goats); Group 2, Harms cage filled with autologous iliac crest graft (8 goats); Group 3, Carbon cage filled with autologous iliac bone (8 goats); Group 4, HCIFC filled with autologous iliac graft (8 goats). Radiography was performed pre- and postoperatively and after 1, 2, 4, 8, and 12 weeks. At the same time points, disc space height, intervertebral angle, and lordosis angle were measured. After 12 weeks, the goats were killed and fusion sites were harvested. Biomechanical testing was performed in flexion, extension, axial rotation, and lateral bending to determine the stiffness and range of motion. All cervical fusion specimens underwent histomorphological analysis. One week after operation, the DSH, IVA and LA of HCIFC and Carbon cage were statistically greater than those of autologous iliac bone graft and Harms cage. Significantly higher values for disc space height, intervertebral angle and lordosis angle were shown in cage-treated goats than in those that received bone graft over a 12-week period. The stiffness of Harms cage in axial rotation and later bending were statistically greater than that of other groups. Radiographic and histomorphologic evaluation showed better fusion results in cage groups than in autologous bone group. HCIFC can provide a good intervertebral distractability and enough biomechanical stability for cervical fusion.

Biomechanical Evaluation of a Novel Lumbosacral Axial Fixation Device

Interbody arthrodesis is employed in the lumbar spine to eliminate painful motion and achieve stability through bony fusion. Bone grafts, metal cages, composite spacers, and growth factors are available and can be placed through traditional open techniques or minimally invasively. Whether placed anteriorly, posteriorly, or laterally, insertion of these implants necessitates compromise of the anulus--an inherently destabilizing procedure. A new axial percutaneous approach to the lumbosacral spine has been described. Using this technique, vertical access to the lumbosacral spine is achieved percutaneously via the presacral space. An implant that can be placed across a motion segment without compromise to the anulus avoids surgical destabilization and may be advantageous for interbody arthrodesis. The purpose of this study was to evaluate the in vitro biomechanical performance of the axial fixation rod, an anulus sparing, centrally placed interbody fusion implant for motion segment stabilization. Twenty-four bovine lumbar motion segments were mechanically tested using an unconstrainedflexibility protocol in sagittal and lateral bending, and torsion. Motion segments were also tested in axial compression. Each specimen was tested in an intact state, then drilled (simulating a transaxial approach to the lumbosacral spine), then with one of two axial fixation rods placed in the spine for stabilization. The range of motion, bending stiffness, and axial compressive stiffness were determined for each test condition. Results were compared to those previously reported for femoral ring allografts, bone dowels, BAK and BAK Proximity cages, Ray TFC, Brantigan ALIF and TLIF implants, the InFix Device, Danek TIBFD, single and double Harms cages, and Kaneda, Isola, and University plating systems. While axial drilling of specimens had little effect on stiffness and range of motion, specimens implanted with the axial fixation rod exhibited significant increases in stiffness and decreases in range of motion relative to intact state. When compared to existing anterior, posterior, and interbody instrumentation, lateral and sagittal bending stiffness of the axial fixation rod exceeded that of all other interbody devices, while stiffness in extension and axial compression were comparable to plate and rod constructs. Torsional stiffness was comparable to other interbody constructs and slightly lower than plate and rod constructs. For stabilization of the L5-S1 motion segment, axial placement of implants offers potential benefits relative to traditional exposures. The preliminary biomechanical data from this study indicate that the axial fixation rod compares favorably to other devices and may be suitable to reduce pathologic motion at L5-S1, thus promoting bony fusion.

P5. Acute kyphosis correction using expandable Synex cage implant

BACKGROUND CONTEXT: There are various implants used for vertebral body reconstructions after vertebral body resection for management of acute thoracolumbar fractures, posttraumatic deformity with cord compression, neoplastic disorders and vertebral body infection. Reconstruction is commonly performed using structural autograft or allograft bone or metallic implants, such as Harms cages. These implants can be further supplemented with anterior and/or posterior fixation. Although the structural bone and cage implants are successful in achieving stability, kyphosis correction with these static implants may be difficult.

The use of short and rigid anterior instrumentation in the treatment of idiopathic thoracolumbar scoliosis: a retrospective review of 24 cases.

The results of short anterior rigid rod instrumentation used to treat thoracolumbar scoliosis in 24 patients were reviewed retrospectively. To assess the safety and efficiency of anterior correction of thoracolumbar scoliosis using a single rigid rod with segmental fixation. This method of treatment results from the historical difficulties noted in obtaining adequate correction in both planes for this particular type of curve while saving as many segments as possible. This approach seems to combine the advantages and avoid the limitations of posterior segmental and previous anterior segmental techniques. For this study, 24 patients with thoracolumbar scoliosis underwent anterior spinal correction and fusion using a single rigid rod and segmental fixation. Additionally, in five patients, this construct was supplemented by interbody titanium cages. The patients were assessed for the amount of correction obtained in the main curve, and for the spontaneous correction of the compensatory curves above and below. Trunk balance was measured on standing radiographs. The average age of the patients was 17.3 years (range, 10-43 years), and the average follow-up period was 3.6 years (range, 2-4.5 years). Correction of the major curve at follow-up assessment was 54%, with a 73% correction of the instrumented area. The upper compensatory curve showed a 21% correction, and the lower curve a 59% correction. Over the duration of the follow-up period, the instrumented area showed kyphosis progression of 6.5 degrees. The five patients who had insertion of Harms cages tended to have a lower rate of correction. The average number of intervertebral mobile segments fused was 2.9 (range, 2-5 segments). No intraoperative complication occurred in relation to the anterior approach. A temporary sympathectomy effect on the side of the approach was noted in most patients. Two radiologic pseudarthrosis and one loss of fixation at the top of the construct were observed. Anterior correction and fusion using solid rod instrumentation constitute effective and safe treatment of thoracolumbar scoliosis. As compared with posterior systems, it provides correction and rebalance of the trunk through a shorter fusion segment.

Three-dimensional motion analysis with Synex

The authors present a new implant for vertebral body replacement in the thoracic and lumbar spine. Synex is a titanium implant designated for reconstruction of the anterior column in injury, post-traumatic kyphosis or tumour of the thoracolumbar spine and must be supplemented by a stabilizing implant. After positioning, the implant is distracted in situ, thus ensuring best contact with adjacent end-plates and three-dimensional (3D) stability, and minimizing the possibility of secondary dislocation or loss of correction. We compared the effectiveness of the Synex implant with that of the "Harms cage" (MOSS) in combination with two alternative stabilizing instrumentations: the USS and Ventrofix. In a 3D spinal loading simulator, we determined the bisegmental (T12-L2) neutral zone (NZ), elastic zone (EZ), and range of motion (ROM) of 12 human cadaveric spines. After corpectomy of L1, we tested the four possible combinations of stabilizing instrumentation and vertebral replacement implant: USS/Synex, USS/MOSS, Ventrofix/Synex, Ventrofix/MOSS. We analysed the differences between each of the instrumentations as well as differences compared to the intact spine. Comparing the two stabilizing implants, a significantly higher stability was achieved with the USS for flexion, extension, and lateral bending, regardless of whether Synex or MOSS was used as vertebral body replacement. No differences were observed for axial rotation. In addition, no implant combination was able to restore the rotational stability of the intact spine. Comparing the vertebral body replacing implants, significantly higher stability was noted with Synex in combination with USS for extension, lateral bending, and axial rotation. No differences between Synex and MOSS were observed in combination with Ventrofix. Posterior fixation was found to offer superior stability compared to anterior fixation. Synex was at least comparable to MOSS for suspensory replacement of the vertebral body in the thoracolumbar spine. The increased biomechanical stability demonstrated for Synex suggests that a more rigid construction would also be achieved in vivo. When using MOSS in combination with posterior stabilization, the induction of intervertebral compression via the posterior fixator is recommended. This surgical step was not necessary with Synex.

In vitro biomechanical investigation of the stability and stress-shielding effect of lumbar interbody fusion devices.

Interbody fusion devices are rapidly gaining acceptance as a method of ensuring lumbar interbody arthrodesis. Although different types of devices have been developed, the comparative reconstruction stability remains controversial. It also remains unclear how different stress-shielded environments are created within the devices. Using a calf spine model, this study was designed to compare the construct stiffness afforded by 11 differently designed lumbar interbody fusion devices and to quantify their stress-shielding effects by measuring pressure within the devices. Sixty-six lumbar specimens obtained from calves were subjected to anterior interbody reconstruction at L4-5 by using one of the following interbody fusion devices: four different threaded fusion cages (BAK device, BAK Proximity, Ray TFC, and Danek TIBFD), five different nonthreaded fusion devices (oval and circular Harms cages, Brantigan PLIF and ALIF cages, and InFix device); two different types of allograft (femoral ring and bone dowel) were used. Construct stiffness was evaluated in axial compression, torsion, flexion, and lateral bending. Prior to testing, a silicon elastomer was injected into the cages and intracage pressures were measured using pressure needle transducers. No statistical differences were observed in construct stiffness among the threaded cages and nonthreaded devices in most of the testing modalities. Threaded fusion cages demonstrated significantly lower intracage pressures compared with nonthreaded cages and structural allografts. Compared with nonthreaded cages and structural allografts, threaded fusion cages afforded equivalent reconstruction stiffness but provided more stress-shielded environment within the devices.

Substitution of Transpedicular Screws by Hook Claws in a Vertebrectomy Model

At times one pedicle screw cannot be used in a posterior construct because of morphometric reasons or when the pedicle is fractured intraoperatively. It is not clear from the literature whether and to what extent a construct's stability is compromised by substituting a hook claw for one pedicle screw. A synthetic vertebra model using a hook claw in lieu of a pedicle screw in a compressive and torsional mechanical study is evaluated. Isola screw-based constructs varying in the number of pedicle screws and hook claws were used. To recreate a realistic clinical scenario, transverse connectors and a Harms cage were used as well. In compression, substituting screws with claws did not substantially change the stiffness, whereas substituting one or two pedicle screws with one or two hook claws significantly reduced torsional stiffness. We conclude that using one or two hook claws is a viable alternative for pedicle screws when the latter cannot be used in a clinical situation, especially as an adjunct when the anterior column is reconstructed.