ABSTRACT: Comparison of feasibility and safety of the placement of short and long iliac screws by anatomic and biomechanical evaluations as they apply to lumbo-iliac fixation construct.
To compare the stability of the short and long iliac screw fixations for lumbo-iliac reconstruction by anatomic and biomechanical evaluations.
Spinopelvic reconstruction remains a challenge to spine surgeons. Despite the advent of many fixation methods, the use of iliac screws seems most favorable so far. Various lengths of iliac screws are applied in surgical treatments; however, no biomechanical comparison has been reported based on the screw length.
For anatomic observation, CT scan data of 60 Chinese adults were used to measure the details of the iliac spine structures. For biomechanical evaluation, 7 adult human cadavers (L3-pelvis) were observed. L4-S1 pedicle screw fixation was performed with posterior spinal fixation system. On the basis of the lengths of iliac screws, 2 groups were tested (short screw group using 70 mm screws and long screw group using 138 mm screws). In this study, short and long iliac screws were placed in the same specimen. Biomechanical testing was performed on a material testing machine under 800 N compression and 7 Nm torsion loading modes for stiffness evaluations. Finally, pullout testing was performed for all the iliac screws to measure the maximum pullout force.
The length of the line between posterior superior iliac spine and anterior inferior iliac spine was 140.6 +/- 1.1 mm, and the distance between this line and the greater sciatic notch was 18.3 +/- 0.8 mm. The length of the line between posterior superior iliac spine and the second narrowest point was 67.1 +/- 0.62 mm in men and 70.1 +/- 1.4 mm in women. Insertion lengths of the short and long iliac screws were 70 +/- 2 mm and 138 +/- 4 mm, respectively. The lumbo-pelvic reconstruction using short and long iliac screws restored 53.3% +/- 13.6% and 57.6% +/- 16.2% of the initial stiffness in compression testing respectively. In torsion testing, the use of short and long iliac screws harvested 55.1% +/- 11.9% and 62.5% +/- 9.2% of the initial stiffness, respectively. No significant difference was detected between the 2 reconstructions in terms of compressive and torsional stiffness (P > 0.05). However, the maximum pullout strength of long iliac screw group was significantly higher than the short screw group (P < 0.05).
The local stability is rather difficult to be restored to the original levels regardless the length of iliac screws. Obviously, long iliac screws resisted significantly greater axial pullout force. However, under physiologic, torsional, and compressive loading conditions, the mechanical stability of lumbo-pelvic fixation construct with short iliac screws was comparable with that of the long ones. Therefore, the use of short iliac screws, which are only about half the length of the long iliac screws, could reduce the implantation risk without significantly compromising on the stability of the construct.
Spine 07/2009; 34(16):E565-72. · 2.08 Impact Factor
ABSTRACT: To evaluate the efficacy of hBMP-4 gene modified tissue engineered bone graft in the enhancement of rabbit spinal fusion and find an ideal kind of substitute for the autograft bone.
Rabbit BMSCs were cultured and transfected with AAV-hBMP-4 using different MOI value. The optimal MOI value were determined by observing cell's morphology change. BMSCs were then transfected with AAV-hBMP4 and AAV-EGFP respectively, following which the transfected cells were evenly suspended in a collagen sponge I, and implanted to either side of the L5,6 intertransverse spaces posterolateral in the New Zealand rabbits to induce spinal fusion. Fourteen rabbits were randomly divided into 2 groups. Group 1: AAV-hBMP-4 transfected BMSCs in the right side (hBMP-4 side) and autograft bone in the left side. Group 2: AAV-hBMP-4 transfected BMSCs in the right side (hBMP-4 side) and AAV-EGFP transfected BMSCs in the left side (EGFP side). Radiographs and three-dimensional CT of the spine, manual palpation, gross and histological examination of the fusion masses for all the animals were performed subsequent to animals having been sacrificed at 12 weeks after surgery.
Evaluation has been taken in 12 New Zealand rabbits delivered into 2 groups which meet the criterion after operation. Eleven in 12 implemented sides involved hBMP-4 achieved bony fusion, to which 5 in 6 autografted sides was similar. But only 2 in 6 sides in EGFP-group achieved bony fusion meanwhile. Three-dimensional CT scan and palpation also evidenced the results. Bone formation was observed obviously on specimen both in hBMP4 sides and autografted ones. EGFP-group also got bony integration, but the quantity was small.
Tissue-engineered bone graft constructed from application of hBMP4 is a fine substitute for autograft. Effective enhancement of bony integration in spinal fusion surgery has been evidenced in vivo.
Zhonghua wai ke za zhi [Chinese journal of surgery] 03/2009; 47(3):197-201.
ABSTRACT: To biomechanically compare the stability of the short and long iliac screw fixation constructs in lumbo-iliac reconstruction.
Seven adult human embalmed cadavers (L(3)-pelvis) were used. Using posterior spinal fixation system, L(4)-S(1) pedicle screw fixation was performed. This was defined as intact state of the sacroiliac joint. After the intact test, total sacrum resection and L(4)-L(5)-pelvis reconstruction by pedicle screw and iliac screw with different lengths were performed as follow: short screw group (as the length of exceeding 2 mm over ischial notch) and long screw group (as the length of exceeding 2 mm over anterior inferior iliac spine). Using the 858 MTS material testing machine, biomechanical testing was performed under 800 N compression and 7 Nm torsion loading modes. At last, the axial pullout test of two iliac screws was executed. Construct stiffness in compression and torsion test, and maximum pullout force were analyzed.
Insertion lengths of the short and long iliac screw were (70 +/- 2) mm and (138 +/- 4) mm respectively. The lumbo-pelvic reconstruction using short and long iliac screw, respectively restored 53.3% +/- 13.6% and 57.6% +/- 16.2% of the initial stiffness in compression testing, and respectively harvested 55.1% +/- 11.9% and 62.5% +/- 9.2% of the initial stiffness in torsion testing. No significant difference was detected between the two reconstructions (P > 0.05), however, the compressive and torsional stiffness of the two techniques were markedly less than the intact condition (P < 0.05). The maximum pullout strength of long iliac screw was significantly higher than short screw (P < 0.05).
Under the physical loading, lumbo-pelvic fixation construct using the short iliac screw may obtain mechanical stability comparable to that by long iliac screw. The short iliac screw is only the half of the long iliac screw by length, could reduce the implantation risk. However, the long iliac screw behaves greater axial pullout force, should be applied as far as possible in the osteoporosis patient. The lumbo-pelvic reconstruction utilizing any length of iliac screw is difficult to restore the local stability.
Zhonghua wai ke za zhi [Chinese journal of surgery] 08/2008; 46(15):1179-82.
ABSTRACT: To observe the effect and safety of one-stage single balloon multiple expansions percutaneous kyphoplasty (PKP) in treatment of osteoporotic vertebral compressive fracture (OVCF) and spinal tumor.
One-stage single balloon multiple expansions PKP was performed on 18 patients, 5 males and 13 females, aged 68.77 (44 - 80), with 45 vertebrae, including 11 case of OVCF (with 29 diseased vertebrae), 11 cases of multiple vertebral fracture (with 19 diseased vertebrae), 5 cases of multiple myeloma (with 12 diseased vertebrae), and 2 case of spinal metastatic tumor (with 4 diseased vertebrae), the vital signs were record during operation. Pain relief and functional recovery were evaluated with visual analogue pain scale (VAS) and Oswestry disability index (ODI) scaling, and restoration of vertebral height and Cobb angle were evaluated by X-ray examination. Follow-up was conducted by telephone survey or clinic consults for 12.3 months (6 - 18 months).
Operation was successfully performed on all patients with an operative time of 29.3 min (55 - 127 min) per vertebra. The average pressure of the balloon expansion was 165 Psi (87 - 210 Psi), and the average balloon expanded volume was 3.25 ml (1.5 - 4 ml). A balloon was expanded 2 approximately 5 times in one operation with the average of 2.94 expanded times. The bone cement volume injected was 3.95 ml (2 - 8.5 ml) per vertebra. Epidural cement leakage was seen in 1 vertebra in 1 case and paraspinal leakage was seen in two vertebrae in 1 case. The VAS and ODI scoring of these patients were both decreased significantly after operation. Both the anterior height and midline height of vertebrae were significantly improved. The pain relief and functional recovery were substantial and maintained to the last follow-up without any re-collapse or adjacent level fracture.
one-stage single balloon multiple expansions PKP is effective, economic and safe in treatment of multi-level OVCF and spinal tumor.
Zhonghua yi xue za zhi 04/2007; 87(9):580-4.