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Levy J.C.,Orthopaedic Institute at Holy Cross | Gutierrez S.,Phillip Spiegel Orthopaedic Research Laboratory | Frankle M.A.,Florida Orthopaedic Institute
Journal of Shoulder and Elbow Surgery | Year: 2011

Hypothesis/background: Patients who are treated with reverse shoulder arthroplasty in the setting of proximal humeral bone loss present a technical challenge for humeral component fixation. The purpose of this study was to determine the effect of proximal humeral bone loss on fixation of reverse shoulder humeral implants. Materials and methods: Three reverse humeral designs (two modular and one monobloc) were cemented into twenty-four Sawbones humeri prepared to simulate intact and proximal humeral bone loss. Torque was applied to the humerus for 1,000 cycles in increments of 2.5 N-m to 25 N-m. Rotational micromotion of the implant was measured. Results: There was a significant decrease in rotational micromotion in the intact constructs when compared with the bone loss constructs (we found P < .01 when looking at torsion levels of 5 to 17.5 N-m). In the intact humerus, 10 of 12 implant constructs survived testing. The 2 that failed were modular implants. In the bone loss setting, 7 of 12 implant constructs survived testing. The 5 that failed were also modular implants. Conclusions: This is the first investigation on humeral component fixation in reverse shoulder arthroplasty. The proximal humerus adds stability to the fixation of a cemented humeral implant. Modular components in the presence of proximal humeral bone loss may be at increased risk of mechanical failure. Conversely, non-modular cemented humeral components can withstand greater loads before failure. © 2011.

Marulanda G.A.,Florida Orthopedic Institute | Nayak A.,Phillip Spiegel Orthopaedic Research Laboratory | Murtagh R.,University of Florida | Santoni B.G.,Phillip Spiegel Orthopaedic Research Laboratory | And 2 more authors.
Journal of Spinal Disorders and Techniques | Year: 2014

Study Design: Cadaveric Biomechanical and Radiographic Analysis. Objective: The Purpose of this study was to quantify the changes in intervertebral height and lateral and central recess areas afforded by lateral interbody fusion cages with 2 supplemental forms of internal fixation in cadaveric specimens. BACKGROUND DATA: When conservative treatment for symptomatic lumbar stenosis fails, traditional intervention has been direct posterior decompression. The minimally invasive, lateral transpsoas approach may be a viable alternative to direct decompression by providing restoration of the foraminal and intervertebral dimensions, yet few reports have examined the anatomic and radiographic changes that occur using this technique. Methods: Computed tomography (CT) scans were taken of 18 intact lumbar (L1-S1) cadaveric specimens under a 400 N preload. Intervertebral height, foraminal areas, and canal area were measured at L3-L4 and L4-L5. Thereafter, the cadaveric specimens were instrumented with lateral cages placed in the central or posterior third of the disk space at L3-L4 and L4-L5 and either (1) lateral plate (n=9) or (2) bilateral posterior pedicle screw fixation (n=9). All constructs were again subjected to a 400 N preload, postinstrumentation CT scans were taken, and changes in intervertebral height and lateral and central recess areas were calculated. Results: There was no effect of cage placement on any radiographic metric of indirect decompression for either fusion construct. In the lateral plate and pedicle screw groups, respectively, significant increases in average posterior disk height (30.9%, 60.1%), average right (35.3%, 61.5%) and left foraminal area (48.3%, 57.8%), and average canal area (32.3%, 33.3%) were observed. Pedicle screw instrumentation afforded a significantly greater increase in average posterior disk height and foraminal area compared with the lateral plate group, though there was no difference in the average increase in canal area afforded by either form of fixation. Conclusions: The radiographic results reported here using a cadaveric model add validity to the underlying rationale described for the minimally invasive lateral approach technique. Increases in disk height, foraminal and canal areas were not dependent on cage positioning within the disk space. As intraoperative placement of a cage in the central portion of the disk is an easier and safer technique, our results suggest that central placement may be preferable in a clinical setting. © 2014 by Lippincott Williams & Wilkins.

Santoni B.G.,Phillip Spiegel Orthopaedic Research Laboratory | Ehrhart N.,Colorado State University | Betancourt-Benitez R.,University of Rochester | Beck C.A.,University of Rochester | Schwarz E.M.,University of Rochester
Clinical Orthopaedics and Related Research | Year: 2012

Background: Allograft integration in segmental osseous defects is unpredictable. Imaging techniques have not been applied to investigate angiogenesis and bone formation during allograft healing in a large-animal model. Questions/purposes: We used dynamic contrast-enhanced (DCE)-MRI and cone beam (CB)-CT to quantify vascularity and bone volume in a canine femoral allograft model and determined their relationship with biomechanical testing and histomorphometry. Methods: Femoral ostectomy was performed in three dogs and reconstructed with a 5-cm allograft and compression plate. At 0.5, 3, and 6 months, we performed DCE-MRI to quantify vascular permeability (Ktrans) and perfused fraction and CB-CT to quantify bone volume. We also performed posteuthanasia torsional testing and dynamic histomorphometry of the grafted and nonoperated femurs. Results: DCE-MRI confirmed the avascular nature of allograft healing (perfused fraction, 2.08%-3.25%). CB-CT demonstrated new bone formation at 3 months (26.2, 3.7, and 2.2 cm 3) at the graft-host junctions, which remodeled down at 6 months (14.0, 2.2, and 2.0 cm 3). The increased bone volume in one subject was confirmed with elevated Ktrans (0.22) at 3 months. CB-CT-identified remodeled bone at 6 months was corroborated by histomorphometry. Allografted femurs recovered only 40% of their strength at 6 months. Conclusions: CB-CT and DCE-MRI can discriminate differences in angiogenesis and bone formation in the canine allograft model, which has potential to detect a small (32%) drug or device effect on biomechanical healing with only five animals per group. Clinical Relevance: These radiographic tools may have the potential to assess adjuvant effects on vascular invasion and new bone formation after segmental allograft transplantation. © 2012 The Association of Bone and Joint Surgeons®.

Pervaiz K.,Florida Orthopaedic Institute | Cabezas A.,Phillip Spiegel Orthopaedic Research Laboratory | Downes K.,University of South Florida | Santoni B.G.,Phillip Spiegel Orthopaedic Research Laboratory | Frankle M.A.,Florida Orthopaedic Institute
Journal of Shoulder and Elbow Surgery | Year: 2013

Background: Patients with osteoarthritis undergoing shoulder arthroplasty may suffer from osteoporosis. The purpose of this study was to determine whether computed tomography (CT)-derived Hounsfield unit (HU) measurements correlate with bone mineral density (BMD) and whether these data could predict implant size and fixation choice. Materials and methods: The study analyzed preoperative dual energy x-ray absorptiometry and shoulder CT scans for 230 patients who underwent total shoulder arthroplasty. Hip BMD and T scores and HU attenuation in the humerus were correlated. HU cutoff values were developed to aid in differentiating patients whose BMD values were within normal reference ranges from patients with osteopenia or osteoporosis. Risk factors associated with low BMD were correlated, and the effect of BMD on humeral stem size, and fixation method was investigated. Results: Significant correlations between HU and hip BMD and T score were identified (P < .001). HU value ranges were identified that may alert the surgeon of metabolic bone disease. Significant correlation (P < 0.05) was found between low BMD and certain osteoporosis risk factors. Age at time of surgery was a predictor of cemented stem fixation (P = .024). Patients with a lower BMD were statistically more likely to receive a larger-diameter humeral stem (P = .016). Conclusions: Orthopedic surgeons may be able to use data obtained from shoulder CT scans to predict the need for larger stem size or cement fixation during shoulder arthroplasty. In combination with the risk factor profile, these data may be useful in predicting the need for an osteoporosis workup and treatment. © 2013 Journal of Shoulder and Elbow Surgery Board of Trustees.

Simon P.,Phillip Spiegel Orthopaedic Research Laboratory | Gupta A.,Florida Orthopaedic Institute | Pappou I.,Florida Orthopaedic Institute | Hussey M.M.,Florida Orthopaedic Institute | And 3 more authors.
Journal of Shoulder and Elbow Surgery | Year: 2015

Background: Glenoid component loosening in total shoulder arthroplasty may be prevented by component placement on a congruent and adequate bony surface. Glenoid subchondral bone density (SBD) variability may be correlated with this concept. This study analyzed the 3-dimensional distribution of glenoid SBD in total shoulder arthroplasty patients with osteoarthritis. Materials and methods: Three-dimensional computed tomography osteoabsorptiometry (CT-OAM) was performed in 42 men (21 with eccentric and 21 with concentric wear patterns) with glenohumeral arthritis. Glenoid SBD was measured from the joint surface based on 5 clinically relevant topographic zones. The correlation of the wear pattern with the SBD distribution was investigated. Results: The glenoid subarticular layers could be separated into distinct regions: calcified cartilage (≤1.5mm), subchondral plate (2-4.5mm) and cancellous bone (≥5mm). There were significant differences in SBD among these layers within and between patients with concentric and eccentric wear patterns. In concentric glenoids, the SBD distribution was homogeneous, with greater mineralization in the central zone, 1,749.1±162.3 Hounsfield units (HU) (at 2.5mm), compared with the posterior, anterior, and superior zones (. P<.001). In the eccentric group, the SBD distribution was inhomogeneous. Mineralization was greatest in the posterior zone, 1,739.0±172.6 HU (at 2.5mm), followed by the inferior zone, 1,722.1±186.6 HU (at 3mm). Conclusion: This study represents the first study using CT-OAM to evaluate the 3-dimensional SBD distribution of the glenoid vault for different arthritic wear patterns. The study findings indicate that the SBD distribution is dependent on (1) depth from the articular surface, (2) topographic zone, and (3) wear pattern. CT-OAM may be an effective tool to assist in preoperative planning for shoulder arthroplasty. © 2015 Journal of Shoulder and Elbow Surgery Board of Trustees.

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