Autologous Tricortical Iliac Crest Bone Research Articles

A technical note on autologous iliac crest bone grafting for restoration of the distal tibial articular surface

PurposeThis technical note describes a reconstructive technique of the distal tibial articular surface using autologous iliac crest bone graft.MethodsFollowing curettage and high-speed burring of giant cell tumor of bone (GCTB) of the distal tibial articular surface, the resulting cavity was filled, and the articular surface was reconstructed using autologous tricortical iliac crest bone graft. The graft was fixed to the tibia with a plate.ResultsThe smooth congruent articulating surface of the distal tibia was restored. Full ankle range of motion was achieved. No recurrence was detected in the follow-up imaging.ConclusionsThe currently reported technique using autologous tricortical iliac crest bone graft is a viable option for reconstructing the articular surface of the distal tibia.

Open latarjet procedure versus all-arthroscopic autologous tricortical iliac crest bone grafting for anterior-inferior glenohumeral instability with glenoid bone loss.

The purpose of this study is to compare the open Latarjet procedure versus the all-arthroscopic autologous tricortical iliac crest bone grafting (AICBG) technique for recurrent anterior-inferior glenohumeral instability with glenoid bone loss. All open Latarjet and AICBG procedures for recurrent anterior-inferior shoulder instability with glenoid bone loss performed at two institutions between September 2015 and April 2019 were retrospectively analyzed. Inclusion criteria were a traumatic etiology, a glenoid surface deficiency >13.5%, and a minimum follow-up (FU) of 18months. Primary outcomes included the subjective shoulder value, the Western Ontario Shoulder Instability (WOSI), Rowe scores including subdomains, and the four subdomains of the Constant score (pain, activities of daily living, internal rotation, external rotation). Secondary outcomes were subjective shoulder instability, EQ-5D-3L, pain level on the VAS, level of overall satisfaction, operative time, return-to-work rate, and return-to-sports rate. Forty-three patients were available for final analysis (Latarjet: n = 21; AICBG: n = 22) at an average FU of 34.9months (range, 22-66months). Both techniques provided good outcomes and improved stability. The Rowe score, Rowe-range of motion, and CS-internal rotation (p = 0.008, p<0.001, p = 0.001) were slightly better in the AICBG group. Furthermore, the WOSI physical symptoms subdomain was significantly better (p = 0.04) in the AICBG group, while its total score did not reach statistical significance (p = 0.07). There was no statistically significant difference in the secondary outcomes besides operative time, which was significantly shorter in the Latarjet procedure group (p = 0.04). Overall complication rate was similar in both groups (Latarjet: 9.5% (n = 2), AICBG: 9.1% (n = 2)). Open Latarjet and AICBG procedures provide comparable clinical outcomes except for significantly better Rowe score, Rowe-range of motion, WOSI physical symptoms subdomain, and internal rotation capacity in the AICBG group. However, these results should be carefully interpreted in the context of known minimal clinically important differences of these scores.

Large segmental defects in midshaft clavicle nonunion treated with autologous tricortical iliac crest bone graft.

To evaluate the use of intercalary iliac crest bone graft in the treatment of clavicle nonunion with a large segmental bone defect (3-6 cm). This retrospective study evaluated patients with large segmental bone defects (3-6 cm) after clavicle nonunion, treated with open reposition internal fixation and iliac crest bone graft between February 2003 and March 2021. At follow-up the Disabilities of the Arm, Shoulder and Hand (DASH) questionnaire was administered. A literature search was performed to provide an overview of commonly used graft types per defect size. We included five patients treated with open reposition internal fixation and iliac crest bone graft for clavicle nonunion with a median defect size of 3.3 cm (range 3-6 cm). Union was achieved in all five, and all pre-operative symptoms resolved. The median DASH score was 23 out of 100 (IQR 8-24). An extensive literature search revealed that there are no studies describing the use of an used iliac crest graft for defects larger than 3 cm. Instead, a vascularized graft was typically used to treat defects sizes between 2.5 and 8 cm. An autologous non-vascularized iliac crest bone graft can be safely used and is reproducible to treat a midshaft clavicle non-union with a bone defect between 3 and 6 cm.

Evaluation of Bioabsorbable Multiamino Acid Copolymer/Nanohydroxyapatite/Calcium Sulfate Cage in a Goat Spine Model.

Currently, polylactide is the most popular material used to made bioabsorbable cages but too-quick degradation and osteolysis around the cage have been reported in the literature. This study evaluated the fusion effect, biomechanical stability, and histologic characteristics of a novel bioabsorbable multiamino acid copolymer/nanohydroxyapatite/calcium sulfate (MAACP/n-HA/CS) interbody cage in a goat model of anterior cervical discectomy and fusion. A total of 24 goats underwent C3/C4 discectomy and fusion with 3 groups of intervertebral implants: MAACP/n-HA/CS cage group (n= 8), titanium cage group (n= 8), and autologous tricortical iliac crest bone group (n= 8). Disc space height and lordosis angle were measured pre- and postoperatively and after 4, 12, and 24 weeks. Range of motion (ROM) was evaluated through biomechanical testing. Histologic analysis was performed to evaluate fusion status and to detect any foreign body reactions associated with the bioabsorbable cages. At 12 and 24 weeks, disc space height in MAACP/n-HA/CS cage group was greater than that of titanium cage group and tricortical iliac crest group (P < 0.05). Lordosis angle in MAACP/n-HA/CS cage group and titanium cage group were lower than that of tricortical iliac crest group (P < 0.05). Biomechanical test showed that ROM did not differ significantly between MAACP/n-HA/CS cage group and titanium cage group, whereas the value of ROM in bone graft group was the largest. Histologic evaluation showed a better interbody fusion in the MAACP/n-HA/CS cage group than in the other 2 groups. MAACP/n-HA/CS cage surface degraded and was absorbed at 24 weeks. All MAACP/n-HA/CS cages showed excellent biocompatibility. MAACP/n-HA/CS cages can provide good fusion effect, enough biomechanical stability, and integrate closely with the surrounding bone.

Arthroscopic Glenoid Reconstruction for Chronic Anteroinferior Shoulder Instability Using a Tricortical Iliac Crest Bone Graft.

Arthroscopic glenoid reconstruction using a tricortical iliac crest bone graft is performed to anatomically reconstruct the glenoid and reestablish glenohumeral stability in patients with chronic anteroinferior shoulder instability and substantial osseous defects1-3. Place the patient in the lateral decubitus position and prepare the arm and ipsilateral iliac crest. Perform a diagnostic arthroscopy via the posterior portal and establish an anteroinferior, an anterosuperior, and a deep anteroinferior portal. Depending on the pathology and morphology of the defect, release the capsulolabral complex from the scapular neck and prepare the glenoid rim and scapular neck with a motorized burr to ensure adequate osseous healing. Harvest an autologous tricortical iliac crest bone block from the ipsilateral side and contour it appropriately for an anatomic reconstruction of the glenoid. Enlarge the passage for the graft through the rotator interval, insert the bone block, and position it anatomically at the scapular neck. With the aid of a drill sleeve, temporarily stabilize the graft using Kirschner wires and then definitively attach it to the scapular neck using 2 Bio-Compression screws. Reattach the capsulolabral complex to the original glenoid, inferior and superior to the bone block, using 2 knotless suture anchors to complete the anatomic reconstruction of the glenoid. Immobilize the arm for 6 weeks postoperatively and limit flexion and external rotation during this time period. Fifteen patients with a mean age of 31.4 years (range, 17 to 49 years) with anteroinferior glenohumeral instability and substantial glenoid defects underwent arthroscopic iliac crest bone-grafting and were prospectively evaluated for an average period of 20.6 months (range, 12 to 65 months)12.

In Vivo Study of Hydroxyapatite-coated Hat Type Cervical Intervertebral Fusion Cage Combined With IGF-I and TGF-β1 in the Goat Model

An in vivo animal experimental study. To investigate the hydroxyapatite (HA) coating in a modified fusion cage in improving the results of cervical intervertebral fusion and the role of combination of IGF-I and TGF-β1 treatment in a goat cervical spine interbody fusion model. Thirty-two goats were divided into 4 groups (n=8 for each) and underwent C3-4 discectomy and intervertebral fusion by the following methods: group 1, autologous tricortical iliac crest bone graft; group 2, cage only; group 3, cage coated with HA; group 4, cage coated with HA+IGF-I and TGF-β1. Radiography was performed preoperatively, postoperatively, and after 1, 2, 4, 8, and 12 weeks. At the same time points, disk space height, intervertebral angle, and lordosis angle were measured. At 12 weeks postoperatively, the goats were killed and fused segments were harvested. Biomechanical study was performed in flexion, extension, axial rotation, and lateral bending with a nondestructive stiffness method to determine the range of motion and stiffness. All cervical fusion specimens underwent histomorphologic studies. All 3 cage-treated groups showed significantly higher values for disk space height, intervertebral angle, and lordosis angle compared with the autologous tricortical iliac group at 1, 2, 4, 8, and 12 weeks after surgery (P<0.05). The stiffness of hat-shaped cervical intervertebral fusion cage coated with HA+IGF-I and TGF-β1 in flexion, extension, and lateral bending was significantly greater than that of the other groups (P<0.05), and the stiffness of hat-shaped cervical intervertebral fusion cage coated with HA in extension, axial rotation, and lateral bending was significantly greater than that of fusion with the bone graft and cage-only groups (P<0.05). Histomorphologic evaluation showed better fusion in 3 cage groups than in the bone graft group. In group 4 of the cage coated with HA+IGF-I and TGF-β1, a slightly more advanced bone matrix formation was shown than in groups without coating. HA coating can improve the fusion effect of the cervical intervertebral cage, and IGF-I and TGF-β1 can enhance bone fusion.

Bioabsorbable interbody magnesium-polymer cage: degradation kinetics, biomechanical stiffness, and histological findings from an ovine cervical spine fusion model.

An experimental study using a sheep cervical spine interbody fusion model. First, to compare anterior cervical discectomy and fusion of an experimental bioabsorbable cage consisting of a magnesium alloy and a polymer (poly-ε-caprolactone, PCL) with an autologous tricortical iliac crest bone graft. Second, to determine the degradation kinetics of the cage, assess the 2 fusion devices for biomechanical stability, and determine their histological characteristics. Bioabsorbable cages are not routinely used in spine surgery at present, due to some undesirable effects such as cracks and foreign body reactions. This study involved the manufacture of a bioabsorbable cage from a magnesium alloy and the polymer PCL, which was then used as a device for anterior cervical discectomy and fusion in a sheep cervical spine fusion model. Twenty-four sheep had anterior cervical discectomy and fusion of C3-C4 and C5-C6 with an experimental bioabsorbable cage consisting of the magnesium alloy AZ31, which was infiltrated and covered with PCL at 1 level and with an autologous tricortical iliac crest bone graft at a second level. The sheep were divided into 4 groups. After 3, 6, 12, or 24 weeks postimplantation, the animals were killed and the cervical spines were harvested. The intervertebral spaces with the cage were investigated using μ-computed tomographic images to calculate degradation kinetics. Stiffness of all monosegments was determined through biomechanical testing. Histological analysis was performed to evaluate fusion status and to detect any foreign body reactions. The results from both implants were compared. The magnesium-PCL cage showed nonlinear degradation over time. Both implants demonstrated time-dependent increases in stability, with a significantly greater stiffness of the bone graft after 24 weeks in all directions of motion. Histologically, the cage showed no signs of fusion with progressive encapsulation over time. In comparison with the bone graft, the bioabsorbable cage showed inferior stiffness and fusion properties. Thus, further component modifications are necessary. N/A.

Arthroscopic anatomic glenoid reconstruction using an autologous iliac crest bone grafting technique

Open bone block procedures for glenohumeral stabilization have been used for a long time. With the advancement of arthroscopic techniques and the development of sophisticated instruments and implants, the insertion of the bone block can be performed by an all-arthroscopic approach. The purpose of this study was to evaluate the clinical and radiologic results after an arthroscopic anatomic glenoid reconstruction using an all-arthroscopic, autologous tricortical iliac crest bone grafting technique. Fifteen patients (1 female and 14 male patients; mean age, 31.4 years [range, 17-49 years]) underwent reconstruction of significant glenoid defects in cases of recurrent shoulder instability by the aforementioned technique. The patients were followed up clinically (range of motion, Constant score, Rowe score, Subjective Shoulder Value, and Western Ontario Shoulder Instability Index) and radiographically (with true anteroposterior and axillary views, as well as 2-/3-dimensional computed tomography [glenoid configuration, signs of graft resorption, bone consolidation, and glenoid index]). After a mean follow-up period of 20.6 months (range, 12-65 months), the Constant score averaged 85.0 points (range, 73-98 points; contralateral side, 89.6 points [range, 78-96 points]), the Rowe score averaged 88.0 points (range, 65-100 points), the Subjective Shoulder Value averaged 84.5% (range, 50%-100%), and the Western Ontario Shoulder Instability Index averaged 76.7% (range, 46%-93%). No recurrent subluxations or dislocations were observed. Radiographically, computed tomography imaging showed a consolidated autograft in all cases. The glenoid index increased from a mean of 0.77 preoperatively to 1.16 immediately postoperatively; at the time of last follow-up, the glenoid index decreased to 1.04. The arthroscopic reconstruction of anteroinferior glenoid defects re-creates the pear-shaped anatomy of the anteroinferior glenoid and leads to good to excellent early clinical results.

Biomechanical stability of a bioabsorbable self-retaining polylactic acid/nano-sized &amp;beta;-tricalcium phosphate cervical spine interbody fusion device in single-level anterior cervical discectomy and fusion sheep models

PurposeThe aim of this study was to investigate the biomechanical stability provided by a novel, polylactic acid/nano-sized, β-tricalcium phosphate, bioabsorbable, self-retaining cervical fusion cage (BCFC).MethodsQuasistatic nonconstraining torques (maximum 1.5 NM) induced flexion, extension, lateral bending (±1.5 NM), and axial rotation (±1.5 NM) on 32 sheep cervical spines (C2–C5). The motion segment C3–C4 was first tested intact; the following groups were tested after complete discectomy: autologous tricortical iliac crest bone graft, Medtronic–Wego polyetheretherketone (PEEK) cage, Solis PEEK cage, and BCFC. The autologous bone graft group was tested with an anterior plate. The mean range of motion (ROM) was calculated from the load-displacement curves.ResultsBCFC significantly decreased ROM in lateral bending and axial rotation compared to other implants, and no significant difference in ROM between two types of PEEK cages and BCFC could be observed in flexion and extension. Anterior cervical plate (ACP) significantly decreased ROM in flexion and extension, but no significant difference in ROM between BCFC and bone graft plus ACP could be determined in lateral bending and axial rotation.ConclusionThe BCFC device showed better stability to autologous tricortical iliac crest bone graft and PEEK cages in single-level anterior cervical discectomy and fusion models and thus may be a potential alternative to the current PEEK cages.

Evaluation of Bioabsorbable Multiamino Acid Copolymer/α-Tri-Calcium Phosphate Interbody Fusion Cages in a Goat Model

A study of cervical interbody fusion using polyamino acid-based bioabsorbable fusion cages in a goat model. To compare interbody fusion of a bioabsorbable multiamino acid copolymer/α-tri-calcium phosphate (MAACP/α-TCP) fusion cage with an autologous tricortical iliac-crest bone graft and a titanium cage. Polyamino acid is widely used as a carrier for drug delivery. To our knowledge, no study investigates interbody fusion cage made of polyamino acid. A total of 15 sheep underwent C3/C4 discectomy and fusion. The following stabilization techniques were used: group A, autologous tricortical iliac crest bone graft (n = 5); group B, MAACP/α-TCP cage filled with autologous cancellous bone graft (n = 5); group C, titanium cage filled with autologous cancellous bone graft (n = 5). Radiographic scans to determine disc space height were performed before and after surgery and after 4, 8, and 12 weeks, respectively. After 12 weeks, the C3/C4 motion segment was isolated and sectioned to create a 5-mm thick parasagittal section from which lateral radiographs were obtained. All the radiographs were encoded and reviewed in a blinded fashion to evaluate interbody fusion within the cage devices according to a three-point radiographic score. Biomechanical testing was performed in flexion, extension, axial rotation, and lateral bending to determine range of motion (ROM). Histomorphological and histomorphometrical analyses were performed to evaluate fusion and foreign-body reactions associated with the bioabsorbable cages. Radiographic results showed that the disc space height (DSH) in MAACP/α-TCP cage group was better than that of bone graft group and the best radiographic score was found in MAACP/α-TCP cage group. Biomechanical test showed that no significant difference was found in ROM between MAACP/α-TCP cage group and titanium cage group whereas the value of ROM in bone graft group was the largest. Histologic evaluation showed a higher intervertebral bone volume/total volume ratio and a better interbody fusion in the MAACP/α-TCP cage group than in the other two groups. Two MAACP/α-TCP cages showed microcracks and the other three cages had maintained their original geometry. All MAACP/α-TCP cages showed excellent biocompatibility. After 12 weeks, there was no significant difference between the MAACP/α-TCP cage and the titanium cage in distractive properties and biomechanical properties. Compared with titanium cages, MAACP/α-TCP cages showed an advanced interbody fusion. Although MAACP/α-TCP cages developed cracks after only 12 weeks, they showed significantly better distractive properties, biomechanical properties, and an advanced interbody fusion than the tricortical iliac crest bone graft. Improvement should be made to insure the strength of MAACP/α-TCP cage last at least 6 month after implantion.

The Use of Titanium Mesh Cages in the Reconstruction of Anterior Column Defects in Active Spinal Infections: Can We Rest the Crest?

Study DesignRetrospective clinical series.PurposeTo assess whether titanium cages are an effective alternative to tricortical iliac crest bone graft for anterior column reconstruction in patients with active pyogenic and tuberculous spondylodiscitis.Overview of LiteratureThe use of metal cages for anterior column reconstruction in patients with active spinal infections, though described, is not without controversy.MethodsSeventy patients with either tuberculous or pyogenic vertebral osteomyelitis underwent a single staged anterior debridement, reconstruction of the anterior column with titanium mesh cage and adjuvant posterior instrumentation. The lumbar spine was the predominant level of involvement. Medical co-morbidities were seen in 18 (25.7%) patients. A significant neurological deficit was seen in 32 (45.7%) patients. At follow up patients were assessed for healing of disease, bony fuson, and clinical outcome was assessed using Macnab's criteria.ResultsFinal follow up was done on 64 (91.4%) patients at a mean average of 25 months (range, 12 to 110 months). Pathologic organisms could be identified in 42 (60%) patients. Forty two (60%) patients had histopathological findings consistent with tuberculosis. Thirty of 32 (93.7%) patients showed neurological recovery. The surgical wound healed uneventfully in 67 (95.7%) patients. Bony fusion was seen in 60 (93.7%) patients. At final follow up healing of infection was seen in all patients. As per Macnab's criteria 61 (95.3%) patients reported a good to excellent outcome.ConclusionsInspite of the theoretical risks, titanium cages are a suitable alternative to autologous tricortical iliac crest bone graft in patients with active spinal infections.

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.

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.

Treatment of traumatic cervical spine instability with interbody fusion cages: A prospective controlled study with a 2-year follow-up

The purpose of this prospective cohort study was to define indications and analyze the clinical and radiographic results of using interbody cages to surgically treat traumatic cervical spine instability. 53 patients were treated by monosegmental anterior discectomy and interbody fusion using either autologous tricortical iliac crest bone graft and CSLP (cervical spine locking plate) (bone graft group, n=26) or Syncage-C filled with autologous cancellous bone grafts and CSLP (cage group n=27). Indications for surgery were traumatic cervical spine instability classified according to the AO classification as B1, B2, B3, C2, or C3. Intraoperative parameters such as blood loss and operation time were assessed. Prior to surgery and at follow-up (6,12, and 24 months), evaluation included measurement of neck pain, shoulder/arm pain, muscle strength, Neck Pain Disability Index (NPDI), and Cervical Spine Functional Score (CSFS). Neurological and overall outcome was assessed using the ASIA impairment scale and Odom's criteria, respectively. In addition, radiographic evaluation, including plain x-rays, flexion-extension views, and CT scans was performed. Fusion, segmental mobility, segmental lordosis/kyphosis and disc space height were determined. Operation time and hospital stay were significantly shorter (p<0.05) in the cage group than in the bone graft group. After 6,12, and 24 months there was no difference between either group in pain, muscle strength, NPDI, CSFS, neurological and overall outcome. Although the cage group showed a trend for prolonged fusion process, there was no statistically significant difference between the groups for all radiographic parameters. Under strict indications, cages offer a valid alternative to a tricortical iliac crest bone graft in the surgical treatment of monosegmental traumatic cervical spine instability. Although there was no significant difference between the cage and the bone graft group in the functional and radiographic outcome, less donor site morbidity, a shorter operating time, and a reduced hospital stay might result in cost-effectiveness of cages.

Bioabsorbable Interbody Cages in a Sheep Cervical Spine Fusion Model

An experimental study using a sheep cervical spine interbody fusion model. To compare interbody fusion of an autologous tricortical iliac crest bone graft with two bioabsorbable cages and to determine whether there are differences between the three interbody fusion techniques in 1) the ability to preserve postoperative distraction, 2) the biomechanical stability, and 3) the histologic characteristics of intervertebral bone matrix formation. Bioabsorbable cages would be beneficial compared with metallic cages; however, currently no suitable bioabsorbable interbody fusion cage is available. Twenty-four sheep underwent C3/C4 discectomy and fusion. The following stabilization techniques were used: Group 1) autologous tricortical iliac crest bone graft (n = 8); Group 2) bioabsorbable cage made of 70/30 poly(l-lactide-co-d,l-lactide) (experimental) filled with autologous cancellous bone graft (n = 8); Group 3) bioabsorbable cage made of a polymer-calciumphosphate composite (Biomet Europe, Dordrecht, The Netherlands) filled with autologous cancellous bone graft (n = 8). Radiographic scans to determine disc space height were performed before and after surgery and after 1, 2, 4, 8, and 12 weeks, respectively. After 12 weeks, animals were killed, and fusion sites were evaluated using functional radiographic views in flexion and extension. Quantitative computed tomographic scans were used to assess bone mineral density, bone mineral content, and bony callus volume. Biomechanical testing was performed in flexion, extension, axial rotation, and lateral bending to determine stiffness, ROM, and neutral and elastic zone. Histomorphological and histomorphometrical analysis were performed to evaluate fusion and foreign body reactions associated with the bioabsorbable cages. Over a 12-week period, the polymer-calciumphosphate composite cage showed significantly higher values for disc space height compared with the bone graft and the poly(l-lactide-co-d,l-lactide) cage. Additionally, the polymer-calciumphosphate composite cage demonstrated a significantly higher stiffness and lower ROM, neutral zone, and elastic zone in axial rotation and lateral bending than any other group. However, quantitative computed tomographic scans demonstrated cracks in six of the eight polymer-calciumphosphate composite cages after 12 weeks. Histologically, the highest bone volume/total volume ratio and the highest fusion rate were found in the polymer-calciumphosphate composite cage group. Although the poly(l-lactide-co-d,l-lactide) cage showed grade I through III foreign body reactions in all fusion areas, only two animals developed grade I foreign body reactions with the polymer-calciumphosphate composite cage. After 12 weeks, there was no significant difference between the bioabsorbable poly(l-lactide-co-d,l-lactide) cage and the tricortical bone graft. In comparison to the tricortical bone graft, the bioabsorbable polymer-calciumphosphate composite cage showed significantly better distractive properties, a significantly higher biomechanical stiffness, and an advanced interbody fusion; however, six of eight polymer-calciumphosphate composite cages cracked. Although the fate of the foreign body reactions and the cracks is currently unclear for both bioabsorbable cages, the early appearance of large osteolysis associated with use of the poly(l-lactide-co-d,l-lactide) cage allows skepticism regarding the value of this bioabsorbable implant.

Clinical experience with porous tantalum cervical interbody implants in a prospective randomized controlled trial

A prospective randomized study was undertaken to evaluate the radiological appearance and clinical effectiveness of two porous tantalum (Hedrocel) implants in achieving a stable cervical interbody fusion. A prerandomization protocol was used to allocate patients to the three arms of the study: a ring implant containing autologous cancellous bone graft, a solid block implant or autologous tricortical iliac crest bone graft. Patients were followed for 2 years with plain radiological studies, SF-36, and Neck Disability Index questionnaires and neurological assessment. Early in the study the postoperative radiographs of four patients receiving Hedrocel implants showed inferior end-plate lucency raising concerns about delayed or non-fusion. Recruitment to the study was halted by the investigators to allow longer-term follow-up of the implanted patients when only 24 patients had been recruited to the study. Although fusion was subsequently noted in all patients at 12 months there was no further enrolment to the study. At 2 years the radiological and clinical outcomes of the three groups appeared comparable, but the study numbers were too small for any statistical analysis. This study highlights the difficulties that can arise when clinical caution takes precedence over objective measures of clinical progress during a study. In the absence of an independent safety monitoring committee, the investigators were under an ethical obligation to suspend recruitment to this study, until it was clear that the radiological features were not associated with poor clinical outcomes. The use of safety monitoring committees and the clarification of stopping criteria in relation to outcome measures should be considered in open randomized trials of spinal surgical techniques and implants.

IGF-I and TGF-1 application by a poly-(D,L-lactide)–coated cage promotes fusion in the sheep cervical spine

Frank Kandziora, MD, N.P. Hass, Gerhard Schmidmaier, Georg Schollmeier, Herman Bail, Robert Pflugmacher, MD, Thomas Gorke, Martin Wagner, Thomas Mittlmeier, PhD, Michael Raschke, Berlin, GermanyStudy design: Growth factors such as bone morphogenetic protein (BMP)-2 have proven to promote spine fusion and to overcome the disadvantages of an autologous bone graft. The optimum growth factor to promote spinal fusion, as well as the optimum method to deliver such growth factors, is still a matter of discussion. A sheep cervical spine interbody fusion model was used to determine the effect of IGF-I and TGF-1 application by a biodegradable poly-(D,L-lactide) (PDLLA)–coated cage. The purpose of this study was to determine the safety and efficacy of a new PDLLA carrier system and to evaluate the safety and efficacy of combined IGF-I and TGF-1 application in a sheep cervical spine model.Methods: Thirty-two sheep underwent C3–4 discectomy and fusion: Group 1: autologous tricortical iliac crest bone graft (n=8); Group 2: titanium cage (n=8); Group 3: titanium cage coated with a PDLLA carrier (n=8); Group 4: titanium cage coated with a PDLLA carrier including IGF-I (5% w/w) and TGF-1 (1% w/w) (n=8). Blood samples, body weight and temperature were analyzed. Radiographic scans were performed pre- and postoperatively and after 1, 2, 4, 8 and 12 weeks, respectively. At the same time points, disc space height, intervertebral angle and lordosis angle were measured. After 12 weeks, animals were killed and fusion sites were evaluated using functional radiographic views in flexion and extension. Quantitative computed tomographic scans were performed to assess bone mineral density, bone mineral content and bony callus volume. Biomechanical testing was performed in flexion, extension, axial rotation and lateral bending. Stiffness, ranges of motion, neutral and elastic zone were determined. Histomorphological and histomorphometrical analysis was performed, and polychrome sequential labeling was used to determine the time frame of new bone formation.Results: There were no differences between the groups concerning blood counts, body weight and temperature. Over a 12-week period, the cage Groups 2, 3 and 4 showed significantly higher values for intervertebral angle compared with the bone graft. Functional radiographic assessment revealed significantly lower residual flexion/extension movement in Group 4 than in any other group. The PDLLA-coated cages with IGF-I and TGF-1 showed significantly highest values for bone mineral density, bone mineral content and bony callus volume. Average stiffness in rotation and bending was significantly higher, and range of motion, neutral and elastic zone in rotation were significantly lower in Group 4 than in any other group. Histomorphometrical evaluation showed a more progressed bone matrix formation in PDLLA-coated cages with IGF-I and TGF-1 than in any other group. Polychrome sequential labeling showed accelerated intervertebral fusion in Group 4.Conclusion: PDLLA coating of cervical spine interbody fusion cages as a delivery system for growth factors was effective and safe. The PDLLA coating showed no adverse effects. IGF-I and TGF-1 application by a PDLLA-coated interbody cage significantly increased results of interbody fusion in a sheep cervical spine model without adverse side effects. In this new combination (implant plus PDLLA plus growth factors) the cage represents a “real fusion” cage, because it does not only serve as a mechanical device for spine fixation but also as a local drug delivery system.