The Effect of Bone Quality on Pedicle Screw Loading in Axial Instability

McLain, Robert F.; McKinley, Todd O.; Yerby, Scott A.; Smith, Tait S.; Sarigul‐Klijn, Nesrin

doi:10.1097/00007632-199707010-00006

Cited by 61 publications

(33 citation statements)

References 41 publications

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“…According to the previous studies, the injection of PMMA along the entire length of the screw results in the highest pullout strength [14]. The pedicle area provides approximately 60% of the pullout strength [6], which means the more zones (especially the pedicle area) that involve PMMA, the stronger the pull-out strength of the pedicle screw.…”

Section: Discussionmentioning

confidence: 93%

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Polymethylmethacrylate augmentation of the pedicle screw: the cement distribution in the vertebral body

Chang

et al. 2011

Eur Spine J

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Many studies have proven that the polymethylmethacrylate (PMMA) augmentation of the pedicle screw can significantly increase stiffness and strength of spinal fixation. Some major complications have also been reported. However, there are no reports discussing cement distribution and its morphology in the osteoporotic vertebral body, which is critical in the analysis of the biomechanical strength of the pedicle screw and the risk of cement leakage after pedicle screw augmentation. In this study, we used computed tomography (CT) to evaluate the cement distribution in the osteoporotic vertebral body after PMMA augmentation of a pedicle screw and to analyze the factors leading to cement leakage. Two groups of patients were studied. Group A consisted 25 osteoporotic patients (mean age of 73 years) with spinal instrumentation who had a total of 145 pedicle screws and cement augmentation with biopsy needles. Group B consisted of 23 osteoporotic patients (mean age of 74.6 years) with spinal instrumentation who had a total of 125 cannulated pedicle screws with cement augmentation. All patients had CT evaluation of the cement distribution in the vertebral body after the surgery. The cement distribution in the vertebrae was divided into four zones in the axial CT view: anterior onethird, middle third, and posterior third of vertebral body, and the pedicle. The morphology of the cement distribution around the pedicle screw was defined as scattered type or concentrate type. The leakage pattern was divided to anterior-lateral, posterior-lateral, and canal leakage. The correlations among bone mineral density (BMD), the cement leakage rate, and cement distribution morphology were also analyzed. The results showed that most augmented pedicle screws had cement extension into three of the four zones of the vertebral body (66.3%), followed by two zones (20%), all four zones (11.5%), and only one zone (2.2%). Overall, 123 screws (84.8%) in Group A and 108 screws (86.4%) in Group B had cement concentrate type distribution. The cement leakage rate in Group A is 18.3% and 13.6% in Group B. Patients with a BMD \0.6 g/cm 2 had significantly higher rates of cement leakage and tended toward a scattered cement distribution. There was only one patient who had a symptomatic leakage (sciatica) in Group B. We concluded that the cement distribution after pedicle screw augmentation with biopsy needle or cannulated screw technique was mostly localized in three zones of the vertebral body, and patients with lower BMD had a higher risk of cement leakage and scattered cement distribution.

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Section: Discussionmentioning

confidence: 93%

“…In some patients, surgical treatment is unavoidable. An osteoporotic spine presents a significant challenge for a spinal surgeon to manage [7,14].…”

Section: Introductionmentioning

confidence: 99%

Polymethylmethacrylate augmentation of the pedicle screw: the cement distribution in the vertebral body

Chang

et al. 2011

Eur Spine J

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“…These have been rightly classified as bony failure and not implant failure. Osteoporosis is one factor which should always be accounted in the preoperative planning [3,4]. As surgeons, we have the options of using sublaminar wires (unpublished data), hooks [5], or cement augmented screws [6,7] in severely osteoporotic cases.…”

Section: Discussionmentioning

confidence: 99%

Role of ‘low cost Indian implants’ in our practice: our experience with 1,572 pedicle screws

et al. 2011

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Purpose As Indian spine surgeons, we have to choose between 'foreign implants' and 'Indian implants'. An Indian four pedicle screw rod construct costs 330 US dollars (one-third that of a similar foreign construct). About 60% of patients cannot afford expensive foreign implants. There is little written data evaluating how these Indian implants fare. The purpose of our study was to evaluate implant failure rate with Indian implants and compare it to foreign implants. Methods We analysed results of 1,572 titanium pedicle screws used in 239 patients with a minimum 1-year followup. Patients were divided into Indian and foreign implant groups. Radiological failures were classified as (1) surgery and disease failure, (2) bone failure and (3) implant failure. The null hypothesis was that there is no difference between implant failure rate for Indian and foreign implants.

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“…[12][13][14][15][16] Most bony failure studies have focused on the influence of BMD. [17][18][19][20] However, no studies have reported on the change in the trabecular bone loading during screw placement or following pedicle screw removal. Routine implant removal following general fracture healing is still somewhat controversial due to the perceived risks and benefits.…”

Section: Discussionmentioning

confidence: 99%

“…[12][13][14][15][16] Most bony failure studies have focused on the influence of bone mineral density (BMD). [17][18][19][20] The specific aim of the current study is to investigate the trabecular strain behavior following pedicle screw placement. The authors hypothesized that the trabecular strain adjacent to the screw would be significantly greater than the strain of the same bone before screw placement.…”

Section: Introductionmentioning

confidence: 99%

The influence of pedicle screw placement on thoracic trabecular strain

et al. 2005

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The Effect of Bone Quality on Pedicle Screw Loading in Axial Instability

Abstract: Although small changes in pedicle morphometry can alter screw bending moments significantly, changes in cancellous modulus had no measurable impact on bending moments at these same loads. Bone density is likely to play a limited role in screw bending failure.

Cited by 61 publications

References 41 publications

Polymethylmethacrylate augmentation of the pedicle screw: the cement distribution in the vertebral body

Polymethylmethacrylate augmentation of the pedicle screw: the cement distribution in the vertebral body

Role of ‘low cost Indian implants’ in our practice: our experience with 1,572 pedicle screws

The influence of pedicle screw placement on thoracic trabecular strain

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