Harry Mai | University of California, Los Angeles (original) (raw)

Papers by Harry Mai

The Spine Journal, 2015

The use of a novel lumbar pedicle cortical bone trajectory (CBT) screw has recently gained popula... more The use of a novel lumbar pedicle cortical bone trajectory (CBT) screw has recently gained popularity allowing for a minimally invasive approach and potentially improved screw purchase. However, to date, no studies have identified the ideal patient population to utilize this technology. This study reports the bone mineral density using Hounsfeld units along a CBT screw pathway. Patients with a greater difference in density of bone in the lumbar vertebrae between the fixation points of the CBT and traditional pedicle screw may be optimal candidates to realize the advantages of this technique. Cross-sectional observational anatomic study PATIENT SAMPLE: 180 randomly selected patients with lumbar computed tomography imaging from L1-L5 spinal levels OUTCOME MEASURES: CT image-derived Hounsfield Units (HU) as a metric for bone mineral density METHODS: A total of 180 patients without previous lumbar surgery with computed tomography imaging of the lumbar spine met the inclusion criteria. Patients were chosen randomly from an institutional database based on age (evenly distributed by decade of life) and gender. HU were measured at the expected end fixation point for both a cortical (superior/posterior portion of the vertebral body) and traditional pedicle trajectory (midvertebral body). HU values measured at the end fixation point for the CBT screw were significantly greater than that of the traditional pedicle screw in all age groups. The relative difference in HU values significantly increased with each decade of age (p < 0.001) and caudal lumbar level (p < 0.001). In the osteoporotic group, as determined by well-established HU values, there was a significantly greater difference in the bone mineral density of the CBT fixation point compared to the traditional trajectory (p = 0.048 - < 0.001). Bone mineral density as measured by HU values for the fixation point of the CBT screw is significantly greater that of the traditional pedicle screw. This difference is even more pronounced when comparing osteoporotic and elderly patients to the general population. The data in this study suggests that the potential advantages from the CBT screw such as screw purchase may increase linearly with age and in osteoporotic patients.

Spine, Jan 17, 2015

Retrospective Cross-Sectional Study OBJECTIVE.: Identify the pathoanatomical features of the cerv... more Retrospective Cross-Sectional Study OBJECTIVE.: Identify the pathoanatomical features of the cervical spine associated with congenital stenosis SUMMARY OF BACKGROUND DATA.: Congenital cervical stenosis (CCS)describes a patient with a decreased spinal canal diameter at multiple levels of the cervical spine in the absence of degenerative changes. Despite recognition of CCS throughout the literature, the anatomical features that lead to this condition have not been established. Knowledge of the pathoanatomybehind CCS may lead to alterations in surgical technique for this patient population that may improve outcomes. From 1,000 cervical MRIs between January 2000 to Dec 2014, CCS was identified in 68 patients using a strict definition of age less than 50 years with mid-sagittal canal diameters (< 10 mm) at multiple sub-axial cervical levels (C3-C7). A total of 68 patients met the inclusion criteria for this group. Fourteen controls with normal SCDs (> 14 mm) at all cervical levels ...

Spine, 2015

Cross-sectional observational study OBJECTIVE.: To formulate a reliable method and modality for p... more Cross-sectional observational study OBJECTIVE.: To formulate a reliable method and modality for preoperative planning and to determine the effects of height, BMI and age on accessibility to the upper thoracic vertebrae through an anterior cervical approach. Various modalities have been proposed to determine the lowest spinal-level accessible through a traditional anterolateral cervical approach and the consequent need for manubriotomy. Past methods have routinely involved a variety of imaging studies such as plain radiographs and computed tomography but the reliability of these methods has not been assessed. The MRI images of 180 patients classified by age and gender were evaluated and the most caudal accessible intervertebral disc space was determined from an approach angle beginning at the suprasternal notch. Plain cervical radiographs were also reviewed when available. In patients with multiple imaging studies, the reliability of the measurements was compared. Rate of accessibili...

Journal of Cataract & Refractive Surgery, 2015

To compare the prediction error after toric intraocular lens (IOL) (Acrysof IQ) implantation usin... more To compare the prediction error after toric intraocular lens (IOL) (Acrysof IQ) implantation using corneal astigmatism measurements obtained with an IOLMaster automated keratometer and a Galilei dual rotating camera Scheimpflug-Placido tomographer. Jules Stein Eye Institute, University of California Los Angeles, Los Angeles, California, USA. Retrospective case series. The predicted residual astigmatism after toric IOL implantation was calculated using preoperative astigmatism values from an automated keratometer and the total corneal power (TCP) determined by ray tracing through the measured anterior and posterior corneal surfaces using dual Scheimpflug-Placido tomography. The prediction error was calculated as the difference between the predicted astigmatism and the manifest astigmatism at least 1 month postoperatively. The calculations included vector analysis. The study evaluated 35 eyes (35 patients). The preoperative corneal posterior astigmatism mean magnitude was 0.33 diopter (D) ± 0.16 (SD) (vector mean 0.23 × 176). Twenty-six eyes (74.3%) had with-the-rule (WTR) posterior astigmatism. The postoperative manifest refractive astigmatism mean magnitude was 0.38 ± 0.18 D (vector mean 0.26 × 171). There was no statistically significant difference in the mean magnitude prediction error between the automated keratometer and TCP techniques. However, the automated keratometer method tended to overcorrect WTR astigmatism and undercorrect against-the-rule (ATR) astigmatism. The TCP technique lacked these biases. The automated keratometer and TCP methods for estimating the magnitude of corneal astigmatism gave similar results. However, the automated keratometer method tended to overcorrect WTR astigmatism and undercorrect ATR astigmatism. Dr. Hamilton has received honoraria for educational lectures from Ziemer Ophthalmic Systems. No other author has a financial or proprietary interest in any material or method mentioned.

Cornea, 2013

To report the use of annular amniotic membrane transplantation as a host incorporated graft in th... more To report the use of annular amniotic membrane transplantation as a host incorporated graft in the management of Brown-McLean syndrome. Case report. An 87-year-old man underwent annular amniotic membrane transplantation with ethylenediaminetetraacetic acid chelation resulting in resolution of pain, irritation, and foreign body sensation, and resolution of recurrent peripheral epithelial defects. Annular amniotic membrane transplantation is a safe and effective treatment strategy for the management of Brown-McLean syndrome.

Although low-back pain is common in the general population, there are unique considerations when ... more Although low-back pain is common in the general population, there are unique considerations when athletes present with this complaint. The most common etiologies include degenerative disc disease, lumbar disc herniation, and spondylolysis. Genetic predisposition has recently been identified as a predominant determinant of degenerative disc disease but the intense physical loading and training demands of elite athletes may play a more significant role in athletes than in the general population. The evidence-based literature regarding lumbar disc herniation in athletes suggests that despite having career-ending potential, it would be reasonable for athletes to expect excellent clinical outcomes after both operative and nonoperative management. Spondylolysis, especially common in adolescent athletes, can often be successfully managed conservatively. If necessary, operative management with fusion or direct pars repair, combined with strict postoperative rehabilitation, can lead to successful return to sport. Oper Tech Orthop 25:164-176 C

The Spine Journal, 2015

The use of a novel lumbar pedicle cortical bone trajectory (CBT) screw has recently gained popula... more The use of a novel lumbar pedicle cortical bone trajectory (CBT) screw has recently gained popularity allowing for a minimally invasive approach and potentially improved screw purchase. However, to date, no studies have identified the ideal patient population to utilize this technology. This study reports the bone mineral density using Hounsfeld units along a CBT screw pathway. Patients with a greater difference in density of bone in the lumbar vertebrae between the fixation points of the CBT and traditional pedicle screw may be optimal candidates to realize the advantages of this technique. Cross-sectional observational anatomic study PATIENT SAMPLE: 180 randomly selected patients with lumbar computed tomography imaging from L1-L5 spinal levels OUTCOME MEASURES: CT image-derived Hounsfield Units (HU) as a metric for bone mineral density METHODS: A total of 180 patients without previous lumbar surgery with computed tomography imaging of the lumbar spine met the inclusion criteria. Patients were chosen randomly from an institutional database based on age (evenly distributed by decade of life) and gender. HU were measured at the expected end fixation point for both a cortical (superior/posterior portion of the vertebral body) and traditional pedicle trajectory (midvertebral body). HU values measured at the end fixation point for the CBT screw were significantly greater than that of the traditional pedicle screw in all age groups. The relative difference in HU values significantly increased with each decade of age (p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.001) and caudal lumbar level (p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.001). In the osteoporotic group, as determined by well-established HU values, there was a significantly greater difference in the bone mineral density of the CBT fixation point compared to the traditional trajectory (p = 0.048 - &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.001). Bone mineral density as measured by HU values for the fixation point of the CBT screw is significantly greater that of the traditional pedicle screw. This difference is even more pronounced when comparing osteoporotic and elderly patients to the general population. The data in this study suggests that the potential advantages from the CBT screw such as screw purchase may increase linearly with age and in osteoporotic patients.

Spine, Jan 17, 2015

Retrospective Cross-Sectional Study OBJECTIVE.: Identify the pathoanatomical features of the cerv... more Retrospective Cross-Sectional Study OBJECTIVE.: Identify the pathoanatomical features of the cervical spine associated with congenital stenosis SUMMARY OF BACKGROUND DATA.: Congenital cervical stenosis (CCS)describes a patient with a decreased spinal canal diameter at multiple levels of the cervical spine in the absence of degenerative changes. Despite recognition of CCS throughout the literature, the anatomical features that lead to this condition have not been established. Knowledge of the pathoanatomybehind CCS may lead to alterations in surgical technique for this patient population that may improve outcomes. From 1,000 cervical MRIs between January 2000 to Dec 2014, CCS was identified in 68 patients using a strict definition of age less than 50 years with mid-sagittal canal diameters (< 10 mm) at multiple sub-axial cervical levels (C3-C7). A total of 68 patients met the inclusion criteria for this group. Fourteen controls with normal SCDs (> 14 mm) at all cervical levels ...

Spine, 2015

Cross-sectional observational study OBJECTIVE.: To formulate a reliable method and modality for p... more Cross-sectional observational study OBJECTIVE.: To formulate a reliable method and modality for preoperative planning and to determine the effects of height, BMI and age on accessibility to the upper thoracic vertebrae through an anterior cervical approach. Various modalities have been proposed to determine the lowest spinal-level accessible through a traditional anterolateral cervical approach and the consequent need for manubriotomy. Past methods have routinely involved a variety of imaging studies such as plain radiographs and computed tomography but the reliability of these methods has not been assessed. The MRI images of 180 patients classified by age and gender were evaluated and the most caudal accessible intervertebral disc space was determined from an approach angle beginning at the suprasternal notch. Plain cervical radiographs were also reviewed when available. In patients with multiple imaging studies, the reliability of the measurements was compared. Rate of accessibili...

Journal of Cataract & Refractive Surgery, 2015

To compare the prediction error after toric intraocular lens (IOL) (Acrysof IQ) implantation usin... more To compare the prediction error after toric intraocular lens (IOL) (Acrysof IQ) implantation using corneal astigmatism measurements obtained with an IOLMaster automated keratometer and a Galilei dual rotating camera Scheimpflug-Placido tomographer. Jules Stein Eye Institute, University of California Los Angeles, Los Angeles, California, USA. Retrospective case series. The predicted residual astigmatism after toric IOL implantation was calculated using preoperative astigmatism values from an automated keratometer and the total corneal power (TCP) determined by ray tracing through the measured anterior and posterior corneal surfaces using dual Scheimpflug-Placido tomography. The prediction error was calculated as the difference between the predicted astigmatism and the manifest astigmatism at least 1 month postoperatively. The calculations included vector analysis. The study evaluated 35 eyes (35 patients). The preoperative corneal posterior astigmatism mean magnitude was 0.33 diopter (D) ± 0.16 (SD) (vector mean 0.23 × 176). Twenty-six eyes (74.3%) had with-the-rule (WTR) posterior astigmatism. The postoperative manifest refractive astigmatism mean magnitude was 0.38 ± 0.18 D (vector mean 0.26 × 171). There was no statistically significant difference in the mean magnitude prediction error between the automated keratometer and TCP techniques. However, the automated keratometer method tended to overcorrect WTR astigmatism and undercorrect against-the-rule (ATR) astigmatism. The TCP technique lacked these biases. The automated keratometer and TCP methods for estimating the magnitude of corneal astigmatism gave similar results. However, the automated keratometer method tended to overcorrect WTR astigmatism and undercorrect ATR astigmatism. Dr. Hamilton has received honoraria for educational lectures from Ziemer Ophthalmic Systems. No other author has a financial or proprietary interest in any material or method mentioned.

Cornea, 2013

To report the use of annular amniotic membrane transplantation as a host incorporated graft in th... more To report the use of annular amniotic membrane transplantation as a host incorporated graft in the management of Brown-McLean syndrome. Case report. An 87-year-old man underwent annular amniotic membrane transplantation with ethylenediaminetetraacetic acid chelation resulting in resolution of pain, irritation, and foreign body sensation, and resolution of recurrent peripheral epithelial defects. Annular amniotic membrane transplantation is a safe and effective treatment strategy for the management of Brown-McLean syndrome.

Although low-back pain is common in the general population, there are unique considerations when ... more Although low-back pain is common in the general population, there are unique considerations when athletes present with this complaint. The most common etiologies include degenerative disc disease, lumbar disc herniation, and spondylolysis. Genetic predisposition has recently been identified as a predominant determinant of degenerative disc disease but the intense physical loading and training demands of elite athletes may play a more significant role in athletes than in the general population. The evidence-based literature regarding lumbar disc herniation in athletes suggests that despite having career-ending potential, it would be reasonable for athletes to expect excellent clinical outcomes after both operative and nonoperative management. Spondylolysis, especially common in adolescent athletes, can often be successfully managed conservatively. If necessary, operative management with fusion or direct pars repair, combined with strict postoperative rehabilitation, can lead to successful return to sport. Oper Tech Orthop 25:164-176 C