Variable Bone Density of Scaphoid: Importance of Subchondral Screw Placement

Background Ideal internal fixation of the scaphoid relies on adequate bone stock for screw purchase; so, knowledge of regional bone density of the scaphoid is crucial. Questions/Purpose The purpose of this study was to evaluate regional variations in scaphoid bone density. Materials and Methods Three-dimensional CT models of fractured scaphoids were created and sectioned into proximal/distal segments and then into quadrants (volar/dorsal/radial/ulnar). Concentric shells in the proximal and distal pole were constructed in 2-mm increments moving from exterior to interior. Bone density was measured in Hounsfield units (HU). Results Bone density of the distal scaphoid (453.2 ± 70.8 HU) was less than the proximal scaphoid (619.8 ± 124.2 HU). There was no difference in bone density between the four quadrants in either pole. In both the poles, the first subchondral shell was the densest. In both the proximal and distal poles, bone density decreased significantly in all three deeper shells. Conclusion The proximal scaphoid had a greater density than the distal scaphoid. Within the poles, there was no difference in bone density between the quadrants. The subchondral 2-mm shell had the greatest density. Bone density dropped off significantly between the first and second shell in both the proximal and distal scaphoids. Clinical Relevance In scaphoid fracture ORIF, optimal screw placement engages the subchondral 2-mm shell, especially in the distal pole, which has an overall lower bone density, and the second shell has only two-third the density of the first shell.

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Effect of Screw Perpendicularity on Compression in Scaphoid Waist Fractures

Journal of Wrist Surgery ◽

10.1055/s-0036-1596059 ◽

2016 ◽

Vol 06 (03) ◽

pp. 178-182 ◽

Cited By ~ 1

Author(s):

Morgan Swanstrom ◽

Kyle Morse ◽

Joseph Lipman ◽

Krystle Hearns ◽

Michelle Carlson

Keyword(s):

Compression Strength ◽

Scaphoid Fracture ◽

Three Dimensional ◽

Average Density ◽

Screw Placement ◽

Fracture Plane ◽

Fracture Angle ◽

Computed Tomography Scans ◽

Three Dimensional Models ◽

Shear Area

Background Central and perpendicular (PERP) screw orientations have each been described for scaphoid fracture fixation. It is unclear, however, which orientation produces greater compression. Questions/Purposes This study compares compression in scaphoid waist fractures with screw fixation in both PERP and pole-to-pole (PTP) configurations. PERP orientation was hypothesized to produce greater compression than PTP orientation. Methods Ten preoperative computed tomography scans of scaphoid waist fractures were classified by fracture type and orientation in the coronal and sagittal planes. Three-dimensional models of each scaphoid and fracture plane were created. Simulated Acutrak 2 (Acumed, Hillsboro, OR) screws were placed into the models in both PERP and PTP orientations. Engagement length and screw angle relative to the fracture were measured. Compression strength was calculated from the shear area, average density, and angle acuity. Results The PTP angle between screw and fracture ranged from 36 to 84 degrees. By definition, the PERP screw-to-fracture angle was 90 degrees. Perpendicularity of the PTP screw to the fracture was positively correlated to compression strength. PERP screws had greater compression than PTP screws when the PTP screw-to-fracture angle was < 80 degrees (106 vs. 80 N), but there was no difference in compression when the PTP screw-to-fracture angle was > 80 degrees, approximating the PERP screw. Conclusion Increasing screw perpendicularity resulted in higher compression when the screw-to-fracture angle of the PTP screw was < 80 degrees. Maximum compression was obtained with a screw PERP to the fracture. The increased compression gained from PERP screw placement offsets the decreased engagement length. Clinical Relevance These results provide guidelines for optimal screw placement in scaphoid waist fractures.

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Three Dimensional Fluoroscan is More Accurate and Repeatable Than Two Dimensional Fluoroscan for Measuring Central Scaphoid Screw Placement in a Cadaver Model

ASME 2010 Summer Bioengineering Conference, Parts A and B ◽

10.1115/sbc2010-19084 ◽

2010 ◽

Author(s):

Hyun Kyu Han ◽

W. Scott Green ◽

Jenni M. Buckley ◽

Lisa L. Lattanza

Keyword(s):

Three Dimensional ◽

Treatment Method ◽

Screw Placement ◽

Scaphoid Bone ◽

Ct Reconstruction ◽

Cast Immobilization ◽

Scaphoid Fractures ◽

Significant Difference ◽

Screw Malpositioning ◽

Fluoroscopic Imaging

A commonly accepted treatment method for scaphoid fractures is dorsal percutaneous fixation [1, 2]. This has been shown to decrease the need for cast immobilization and allow faster recovery [3, 4]. For this approach a central screw placement is critical as it provides greater stiffness and load to failure, and allows a longer screw to be inserted which increases screw compression. All of these factors aid in fracture union [5]. However, the complex shape of the scaphoid bone makes central screw placement difficult, as the main axis cannot be easily visualized. Currently, scaphoid screws are placed using K wires guided under 2D fluoroscopy; however, intra-operative 3D fluoroscopy, which can create a CT reconstruction, is becoming more readily available. The goals of this study are to see if there is a significant difference between 2D and 3D fluoroscopic imaging in measuring screw malpositioning (distance off-center) and if there is a difference in repeatability.

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Clinical Value of Computer-Assisted Taylor Three-dimensional External Fixation in the Treatment of Tibiofibular Fracture (Preprint)

10.2196/preprints.20711 ◽

2020 ◽

Author(s):

Hongfeng Sheng ◽

Weixing Xu ◽

Bin Xu ◽

Hongpu Song ◽

Di Lu ◽

...

Keyword(s):

Retrospective Study ◽

Internal Fixation ◽

External Fixation ◽

External Fixator ◽

Theoretical Basis ◽

New Technology ◽

Three Dimensional ◽

Computer Assisted ◽

Clinical Value

UNSTRUCTURED The retrospective study of Taylor's three-dimensional external fixator for the treatment of tibiofibular fractures provides a theoretical basis for the application of this technology. The paper collected 28 patients with tibiofibular fractures from the Department of Orthopaedics in our hospital from March 2015 to June 2018. After the treatment, the follow-up evaluation of Taylor's three-dimensional external fixator for the treatment of tibiofibular fractures and concurrency the incidence of the disease, as well as the efficacy and occurrence of the internal fixation of the treatment of tibial fractures in our hospital. The results showed that Taylor's three-dimensional external fixator was superior to orthopaedics in the treatment of tibiofibular fractures in terms of efficacy and complications. To this end, the thesis research can be concluded as follows: Taylor three-dimensional external fixation in the treatment of tibiofibular fractures is more effective, and the incidence of occurrence is low, is a new technology for the treatment of tibiofibular fractures, it is worthy of clinical promotion.

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How Do Parameters of Implant Primary Stability Correspond with CT-Evaluated Bone Quality in the Posterior Maxilla? A Correlation Analysis

Materials ◽

10.3390/ma14020270 ◽

2021 ◽

Vol 14 (2) ◽

pp. 270

Author(s):

Ji-Hyun Kim ◽

Young-Jun Lim ◽

Bongju Kim ◽

Jungwon Lee

Keyword(s):

Bone Density ◽

Bone Quality ◽

Objective Assessment ◽

Primary Stability ◽

Insertion Torque ◽

Hounsfield Units ◽

Stability Parameters ◽

Posterior Maxilla ◽

Different Types ◽

Edentulous Patients

The aim of the present study was to evaluate correlations between bone density and implant primary stability, considering various determinants such as age, gender, and geometry of implants (design, diameter). Bone density of edentulous posterior maxillae was assessed by computed tomography (CT)-derived Hounsfield units, and implant primary stability values were measured with insertion torque and resonance frequency analysis (RFA). A total of 60 implants in 30 partially edentulous patients were evaluated in the posterior maxilla with two different types of dental implants. The bone density evaluated by CT-derived Hounsfield units showed a significant correlation with primary stability parameters. The bone quality was more influenced by gender rather than age, and the type of implant was insignificant when determining primary stability. Such results imply that primary stability parameters can be used for objective assessment of bone quality, allowing surgical modifications especially in sites suspected of poor bone quality.

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Factors Associated with Scaphoid Nonunion following Early Open Reduction and Internal Fixation

Journal of Wrist Surgery ◽

10.1055/s-0039-3402769 ◽

2020 ◽

Vol 09 (02) ◽

pp. 141-149

Author(s):

Pooja Prabhakar ◽

Lauren Wessel ◽

Joseph Nguyen ◽

Jeffrey Stepan ◽

Michelle Carlson ◽

...

Keyword(s):

Internal Fixation ◽

Open Reduction ◽

Scaphoid Fracture ◽

Receiver Operating Curve ◽

Scaphoid Nonunion ◽

Retrospective Case ◽

Level Of Evidence ◽

Fracture Location ◽

Scaphoid Fractures ◽

Time From Injury

Abstract Background Nonunion after open reduction and internal fixation (ORIF) of scaphoid fractures is reported in 5 to 30% of cases; however, predictors of nonunion are not clearly defined. Objective The purpose of this study is to determine fracture characteristics and surgical factors which may influence progression to nonunion after scaphoid fracture ORIF. Patients and Methods We performed a retrospective case–control study of scaphoid fractures treated by early ORIF between 2003 and 2017. Inclusion criteria were surgical fixation within 6 months from date of injury and postoperative CT with minimum clinical follow-up of 6 months to evaluate healing. Forty-eight patients were included in this study. Nonunion cases were matched by age, sex, and fracture location to patients who progressed to fracture union in the 1:2 ratio. Results This series of 48 patients matched 16 nonunion cases with 32 cases that progressed to union. Fracture location was proximal pole in 15% (7/48) and waist in 85% (41/48). Multivariate regression demonstrated that shorter length of time from injury to initial ORIF and smaller percent of proximal fracture fragment volume were significantly associated with scaphoid nonunion after ORIF (63 vs. 27 days and 34 vs. 40%, respectively). Receiver operating curve analysis revealed that fracture volume below 38% and time from injury to surgery greater than 31 days were associated with nonunion. Conclusion Increased likelihood for nonunion was found when the fracture was treated greater than 31 days from injury and when fracture volume was less than 38% of the entire scaphoid. Level of Evidence This is a Level III, therapeutic study.

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Long-Term Results after Silicone Prosthesis Replacement of the Proximal Pole of the Scaphoid Bone in Advanced Scaphoid Nonunion

Journal of Hand Surgery (European Volume) ◽

10.1054/jhsb.2002.0758 ◽

2002 ◽

Vol 27 (5) ◽

pp. 417-423 ◽

Cited By ~ 11

Author(s):

P. HAUSSMANN

Keyword(s):

Scaphoid Fracture ◽

Long Term Results ◽

Partial Replacement ◽

Scaphoid Bone ◽

Proximal Fragment ◽

Carpal Collapse ◽

X Ray ◽

Silicone Prosthesis ◽

Prosthesis Replacement

The treatment of scaphoid fracture nonunion with a small proximal fragment with disturbed circulation and radioscaphoid arthrosis is difficult, and the result is often unsatisfactory. For this reason, in 1981 the replacement of the proximal fragment by a silicone lunate prosthesis was recommended for such cases. From 1980 to 1984, 11 patients (all male, average age 42 [range, 25–59] years) with the conditions described above were treated by silicone prosthesis partial replacement of the scaphoid. In one patient, the prosthesis had to be removed due to dislocation, and in another patient an arthrodesis of the wrist had to be carried out after 5 years due to increasing pain. All nine remaining patients were followed up after an average of 14 (range, 12–16) years, and were clinically and radiologically re-examined and assessed using the evaluation scheme proposed by Martini (1999) . The overall results were satisfactory. Specifically, the outcome was good in one case, satisfactory in six cases, and poor in two cases. Concerning the individual criteria, the best scores were observed in “subjective overall assessment” and in “work and sports”, whilst the worst were found in “movement” and “X-ray”. For all patients, X-ray examination revealed both postoperative arthrosis and extensive multiple cystoid osteolysis, presumably due to silicone synovitis. Nevertheless, most patients were free of symptoms. None of the patients felt that further treatment was necessary. Silicone prosthesis partial replacement of the scaphoid leads to long-term reduction in pain and adequate hand function. However, it is not capable of preventing carpal collapse and carpal arthrosis. Furthermore, since in several cases a progressive silicone synovitis developed, the method was rightly abandone d after 1984.

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Assessment of First Metatarsal Head Bone Density for Optimal Screw Placement in Minimally-Invasive Hallux Valgus Surgery

Foot & Ankle Orthopaedics ◽

10.1177/2473011420s00038 ◽

2020 ◽

Vol 5 (4) ◽

pp. 2473011420S0003

Author(s):

Katherine M. Dederer ◽

Patrick J. Maloney ◽

John T. Campbell ◽

Clifford L. Jeng ◽

Rebecca A. Cerrato

Keyword(s):

Bone Density ◽

Minimally Invasive ◽

Hallux Valgus ◽

Screw Fixation ◽

Weight Bearing ◽

Metatarsal Head ◽

Screw Placement ◽

Cannulated Screws ◽

First Metatarsal ◽

History Of

Category: Bunion; Basic Sciences/Biologics Introduction/Purpose: Minimally-invasive surgery (MIS) for hallux valgus correction has become increasingly common. This technique involves an osteotomy of the first metatarsal, followed by fixation with two cannulated screws. Since screws are typically not bicortical, they rely upon bone quality within the metatarsal head for fixation strength. However, bone mineral density (BMD) within different regions of the metatarsal head is unknown. Measuring the BMD in the target region may predict the strength of the bone-screw fixation. Similar to previous work which determined the optimal position for lag screw placement in the femoral head during hip fracture fixation, this study aimed to determine average BMD within four quadrants of the metatarsal head using CT and thus predict the optimal trajectories for cannulated screws during the MIS bunion procedure. Methods: All patients between 18-75 years of age scheduled to undergo MIS hallux valgus correction by one of two surgeons experienced in the MIS technique were eligible to participate. Patients were excluded if they had a prior first metatarsal surgery, pre-existing hardware, previous first metatarsal fracture, or a history of osteoporosis treatment. Patients were enrolled prospectively, and a weight-bearing CT scan of the affected foot was obtained pre-operatively. Demographic factors including age, sex, laterality, body mass index (BMI), comorbidities, and smoking status as well as standard three-view weight-bearing radiographs were collected for all patients.Using the coronal CT slice at maximal metatarsal head diameter, each head was divided into equal quadrants. Hounsfield units (HU) within each quadrant were measured independently by three study investigators using our hospital’s radiology viewing software (Merge PACS; IBM Corporation, Armonk, NY), and these density measurements were averaged. Statistical analysis was conducted using ANOVA and Student’s t-test. Results: Fifteen patients were included for preliminary analysis. All patients were female. The average age was 45.7 years. 9 of the 15 included feet were right feet. Average BMI was 28.0. One patient reported active smoking prior to surgery. Comorbidities included obesity in three patients; none were diabetic. One had a history of diplegic cerebral palsy. The average HVA on a weight- bearing AP foot x-ray was 28.2°, and the average IMA was 12.6°. The BMD within the metatarsal head varied by quadrant, with the two combined dorsal quadrants having higher average BMD than the two combined plantar quadrants (122 vs 85 HU; p<0.001). The dorsal lateral quadrant had the highest average BMD of any quadrant (132 HU, p<0.001; Table 1). Conclusion: The density of the metatarsal head did vary by region within the head. The highest BMD was found in the dorsal lateral quadrant, and the lowest in the plantar lateral and plantar medial quadrants, which did not differ significantly from each other. Because strength of screw fixation is predicated upon screw design as well as bone density, these results suggest that surgeons may wish to direct screws toward the dorsolateral region of the metatarsal head in order to achieve optimal fixation. Further work is needed to determine whether this varies with patient age, gender, or hallux valgus angle. [Table: see text]

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