Publications by authors named "Scott Telfer"

41 Publications

Quantification and visualization of anterior pelvis bone density to optimize screw fixation: A novel technique.

J Orthop Res 2022 Jun 30. Epub 2022 Jun 30.

Department of Orthopaedics and Sports Medicine, University of Washington, Seattle, Washington, United States.

Plate fixation of anterior pelvic ring fractures is often a vital component when surgically treating unstable pelvis fractures. Certain plate and screw configurations can have premature implant loosening, potentially in part due to insufficient pullout strength in lower density bone. This study sought to define densities about the anterior pelvic ring using a novel computer-based technique. Thirty-three patients who received a computed tomography (CT) of the abdomen/pelvis for reasons other than pelvis fracture in a 1-month time period were included. Three statistically distinct density regions of the anterior pelvis were identified based on the three-dimensional (3D) density map. The densest regions included both the anterior and posterior aspects of the superior pubic ramus, along with the region of bone along the inferior cotyloid fossa. The intermediate density region included the caudal and medial pubic body. The least dense region included the anterior aspect of the inferior pubic ramus (IPR), the posterior pubic body, and the posterior/inferior IPR. This study presents specific quantification of anterior pelvis bone density based on a novel technique using opportunistic CT scans. Clinical Significance: Anterior surgical fixation of unstable pelvic ring injuries may benefit from targeting areas of higher density as described in this novel technique.
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http://dx.doi.org/10.1002/jor.25409DOI Listing
June 2022

Anterior Cruciate Ligament Reconstruction with 4-Strand Hamstring Tendon Construct May be Biomechanically Superior to 5-Strand Hamstring Tendon Construct When Using Femoral Suspensory Fixation.

Arthrosc Sports Med Rehabil 2022 Jun 24;4(3):e1097-e1102. Epub 2022 May 24.

Department of Orthopaedics and Sports Medicine, University of Washington, Seattle, Washington, U.S.A.

Purpose: To compare stiffness, strain, and load to failure of 4- versus 5-strand hamstring anterior cruciate ligament reconstruction human tendon allografts with femoral suspensory and tibial interference screw fixation.

Methods: Allograft hamstring tendons were used to create 10 four-strand (4S) and 10 five-strand (5S) grafts. Grafts were fixed to a uniaxial electromechanical load system via a femoral cortical suspensory button and a bioabsorbable interference screw in bone analogue. Grafts were cycled from 100 Newtons (N) to 250 N for 1,000 repetitions at 0.5 hertz before load to failure testing. Cyclic displacement was defined as the difference in graft length from the first 20 to 30 cycles compared with the last 10 cycles. Trials were recorded on a high-definition camera to allow for digital image correlation analysis.

Results: Cyclic displacement more than 1,000 cycles was significantly lower in the 4S compared with the 5S group (0.87 vs 1.11 mm,  = .037). Digital image correlation analysis confirmed that the fifth strand elongated more than the other 4 strands in the 5S constructs (6.1% vs 3.9%,  = .032). Load to failure was greater in the 4S compared with the 5S group but not statistically significant (762 vs 707 N,  = .35). Stiffness was similar between constructs (138.5 vs 138.3 N/mm,  = .96).

Conclusions: Compared with cyclically loaded 4S hamstring grafts, the 5S grafts had significantly increased displacement over time in a model of femoral suspensory and tibial interference screw fixation.

Clinical relevance: Anterior cruciate ligament reconstruction with hamstring tendon autograft is a commonly performed surgery with excellent outcomes. It has been shown that graft diameter influences these outcomes. As surgeons use larger grafts, it is important to investigate how these constructs may affect the outcomes of surgery.
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http://dx.doi.org/10.1016/j.asmr.2022.03.008DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC9210479PMC
June 2022

A novel workflow to fabricate a patient-specific 3D printed accommodative foot orthosis with personalized latticed metamaterial.

Med Eng Phys 2022 06 14;104:103802. Epub 2022 Apr 14.

VA RR&D Center for Limb Loss and MoBility (CLiMB), VA Puget Sound Health Care System, Seattle, WA, United States; Department of Mechanical Engineering, University of Washington, Seattle, WA, United States.

Patients with diabetes mellitus are at elevated risk for secondary complications that result in lower extremity amputations. Standard of care to prevent these complications involves prescribing custom accommodative insoles that use inefficient and outdated fabrication processes including milling and hand carving. A new thrust of custom 3D printed insoles has shown promise in producing corrective insoles but has not explored accommodative diabetic insoles. Our novel contribution is a metamaterial design application that allows the insole stiffness to vary regionally following patient-specific plantar pressure measurements. We presented a novel workflow to fabricate custom 3D printed elastomeric insoles, a testing method to evaluate the durability, shear stiffness, and compressive stiffness of insole material samples, and a case study to demonstrate how the novel 3D printed insoles performed clinically. Our 3D printed insoles results showed a matched or improved durability, a reduced shear stiffness, and a reduction in plantar pressure in clinical case study compared to standard of care insoles.
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http://dx.doi.org/10.1016/j.medengphy.2022.103802DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC9210925PMC
June 2022

Assessment of regional sacral bone quality: A step towards patient-specific fracture fixation.

J Orthop Res 2022 Mar 17. Epub 2022 Mar 17.

Department of Orthopaedics and Sports Medicine, University of Washington, Seattle, Washington, USA.

Characterizing changes in sacral bone density could help us to inform instrumentation choices for procedures involving the sacrum. The aim of this study is to provide detailed maps of changes in sacral bone density across a series of patients using opportunistic quantitative computed tomography (QCT). We hypothesized that there would be significant differences in local cortical and trabecular bone density associated with age and sex. Fifty-four three-dimensional sacral models were segmented from routine clinical computed tomography scans, and detailed bone density estimates were derived for each bone using a calibrated opportunistic QCT approach. The effects of age and sex on cortical and trabecular bone density were determined across the sample. Overall cortical bone loss averaged 2.1 and 0.9 mg/cc per year, and trabecular bone loss was 1.6 and 0.7 mg/cc for female and males, respectively. Several regions had loss rates several times greater. Areas that were significantly affected by age included the vertebral bodies, bilateral ala, apex, and areas adjacent to both the anterior and posterior sacral foramina. Areas that were significantly affected by sex were the anterior sacral promontory, aspects of the ala. Bone density distribution across the sacrum changes nonuniformly due to factors including sex and age. Despite these overall trends, there remains significant variability between individuals. Clinical significance: This study provides detailed bone density information for both cortical and trabecular bone that could assist orthopaedic surgeons in planning surgical approaches to sacral fracture fixation.
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http://dx.doi.org/10.1002/jor.25329DOI Listing
March 2022

What happens at the L5/S1 facet joint when implants are placed across the sacroiliac joint?

Injury 2022 Jun 5;53(6):2121-2125. Epub 2022 Feb 5.

University of Washington Department of Orthopaedics & Sports Medicine, Seattle, WA, United States. Electronic address:

Background: Injuries to the posterior pelvic ring are often stabilized with fixation across the sacroiliac joint (SIJ). However, the compensatory changes at the neighboring L5/S1 facet joint are unknown. The objective of this study was to determine the compensatory change in pelvic kinematics and contact forces at the L5/S1 facet joint after fixation across the sacroiliac joint (SIJ) using a cadaveric model.

Methods: Five fresh-frozen cadaveric pelvis specimens were dissected to remove non-structural soft tissue. Retroreflective markers were fixed to the L5 body, S1 body and bilateral anterior superior iliac spines to represent the motion of L5, S1 and the ileum, respectively. Pressure sensors were inserted in both L5/S1 facet joints. Testing was performed using a robotic system that applied load to mimic ambulation. Testing was performed prior to SIJ fixation, after unilateral SIJ fixation and bilateral fixation.

Results: Contact force at the L5/S1 facet joint significantly increased by 55% from 48.4 N to 75.2 N following unilateral fixation (p = 0.0161) and increased by 100% to 96.9 N after bilateral fixation (p = 0.0038). Unilateral SIJ fixation increased flexion of the ilium relative to L5 from 1.2° to 2.0° (p = 0.01) and increased axial rotation of L5 relative to S1 from 0.7° to 1.6° (p = 0.001). Bilateral fixation increased flexion of the ilium relative to L5 to 2.0° from 1.2° prior to fixation (p = 0.001), increased axial rotation of L5 relative to S1 to 1.2° from 0.7° prior to fixation (p = 0.002) and increased flexion of L5 relative to S1 to 2.4° from 1.5° prior to fixation (p = 0.04).

Conclusion: The L5/S1 facet joint experiences compensatory increased motion under increased contact force after unilateral and bilateral SIJ fixation, possibly predisposing it to adjacent segment arthritis.

Level Of Evidence: V, cadaveric study.
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http://dx.doi.org/10.1016/j.injury.2022.02.011DOI Listing
June 2022

Sources of error in bone mineral density estimates from quantitative CT.

Eur J Radiol 2021 Nov 15;144:110001. Epub 2021 Oct 15.

Department of Orthopaedics and Sports Medicine, University of Washington. Seattle, WA, United States.

Bone mineral density (BMD) estimates from quantitative computed tomography (QCT) have proven useful for opportunistic screening of osteoporosis, treatment monitoring, and bone strength measurement. These estimates are subject to bias and variance from a variety of sources related to the imaging equipment, methods applied in the estimation procedure, and the patients themselves. In this article, we review the literature to describe the sources and sizes of error in spine and hip BMD estimates from single-energy QCT that can result from factors related to the scanner, imaging techniques, imaging subject, calibration phantom, and calibration approach. We also describe the baseline variance that can be expected based on repeatability and reproducibility studies. Though reproducible BMD estimates may be achievable with QCT, a thorough understanding of the potential sources of error and their size relative to the diagnostic task is essential to their appropriate and meaningful interpretation.
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http://dx.doi.org/10.1016/j.ejrad.2021.110001DOI Listing
November 2021

Does a Medial Malleolar Osteotomy or Posteromedial Approach Provide Greater Surgical Visualization for the Treatment of Talar Body Fractures?

J Bone Joint Surg Am 2021 12;103(24):2324-2330

Department of Orthopaedic Surgery, University of Washington, Seattle, Washington.

Background: Surgical management of talar body fractures is influenced by soft-tissue condition and fracture pattern. Two common surgical approaches for the treatment of talar body fractures are the medial malleolar osteotomy (MMO) and the posteromedial approach (PMA). The purpose of this study was to compare the observable talar body surface area with the MMO and the PMA. We hypothesized that visualization following a PMA improves with distraction and distraction with a gastrocnemius recession.

Methods: Five pairs of cadaver limbs were used. Each pair of specimens underwent both approaches to act as an internal control. The laterality of the PMA was determined by randomization, and the MMO was performed on the contralateral ankle. The PMA was performed to visualize the talus, and the talar surface area was recorded using a handheld 3D surface scanner. A distractor was then placed across the joint, and the surface area was remeasured. Finally, a gastrocnemius recession was performed, and the measured surface area under the distraction was recorded. The MMO was performed in standard fashion using fluoroscopy, and the observable talar surface area was recorded. Scans were performed twice for each approach, and the surface areas were averaged. The talus was excised and scanned after each approach in order to compare the visualized surface area with the total surface area of the native talus.

Results: The MMO and the PMA exposed a mean of 11.2 and 6.7 cm2, respectively, of the talar surface. Visualization with the PMA was improved with distraction, revealing 8.3 cm2 of the talus (p = 0.01 when compared with an isolated PMA). A PMA with distraction and gastrocnemius recession exposed 9.9 cm2 of the talar dome and body. There was no significant difference in exposure between the MMO and the PMA with distraction and gastrocnemius recession (p = 0.32).

Conclusions: The MMO and the PMA both afford excellent visualization for reduction and fixation of talar body fractures. Visualization using the PMA is improved with distraction and distraction with a gastrocnemius recession. The results of this study may assist surgeons in selecting the optimal approach for surgical repair of talar body fractures.
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http://dx.doi.org/10.2106/JBJS.21.00299DOI Listing
December 2021

The effect of proximal tibiofibular joint dislocation on knee mechanics: reduction and fixation matters.

Eur J Orthop Surg Traumatol 2022 Jul 18;32(5):821-826. Epub 2021 Jun 18.

Department of Orthopaedic Surgery, University of Washington, 325 9th Ave , Box # 359798, Seattle, WA, 98102, USA.

Purpose: Proximal tibiofibular joint (PTFJ) dislocations are under-investigated injuries. There is scant basic science or clinical evidence to direct management. The purpose of this study was twofold; first to investigate the pathomechanics of PTFJ dislocation on knee mechanics. The second purpose was to evaluate knee mechanics following reduction and fixation.

Methods: Six cadaveric legs were tested on a mechanical platform. A 5 Nm external rotation force was applied to each knee and the external rotation and fibular translation was measured for several study conditions at 0°, 30°, and 90° of flexion. Conditions included: the native state, transection of the posterior PTFJ ligament, transection of the anterior and posterior ligaments, screw fixation, and suspensory fixation. Screw fixation was performed using a single quadricortical 3.5 mm screw. Suspensory fixation was performed using an Arthrex TightRope device RESULTS: Transection of the anterior and posterior ligaments increased external rotation by 4.3°, 5.9°, and 5.6°, at 0°, 30°, and 90° (p ≤ 0.001), respectively. Screw and suspensory fixation returned external rotation to a near native state with mild overconstraint. Complete transection of anterior and posterior ligaments resulted in pathologic anterior fibular translation of 1.51 mm (p = 0.001), 1 mm, (p = 0.02) and 0.44 mm (p = 0.69) for 0°, 30°, 90° of knee flexion. Screw and suspensory fixation restored native translation at all points with a small degree of overconstraint.

Conclusion: Disruption of the PTFJ causes pathologic external rotation and anterior fibular translation. Fixation restores near native motion with minor overconstraint. Surgeons should consider reduction and fixation of PTFJ injuries to restore native knee mechanics.
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http://dx.doi.org/10.1007/s00590-021-03047-4DOI Listing
July 2022

Changes in scapular bone density vary by region and are associated with age and sex.

J Shoulder Elbow Surg 2021 Dec 9;30(12):2839-2844. Epub 2021 Jun 9.

Department of Orthopaedics and Sports Medicine, University of Washington, Seattle, WA, USA.

Background: Decreases in bone density of the scapula due to age and disease can make orthopedic procedures such as arthroplasty and fracture fixation challenging. There is limited information in the literature regarding the effect of age and sex on the patterns of these density changes across the bone. Characterizing these changes could assist the surgeon in planning optimal instrumentation placement.

Methods: Ninety-seven 3-dimensional models of the scapula were segmented from routine clinical computed tomography scans, and an opportunistic quantitative computed tomography approach was used to obtain detailed calibrated bone density measurements for each bone model. The effects of age and sex on cortical and trabecular bone density were assessed for the entire scapula. Specific regions (eg, scapular spine) where these factors had a significant effect were identified. Three-dimensional models were generated to allow clear visualization of the changes in density patterns.

Results: Cortical bone loss averaged 1.0 mg/cm and 0.3 mg/cm per year for female and male subjects, respectively, and trabecular bone loss averaged 1.6 mg/cm and 1.2 mg/cm, respectively. However, several regions had loss rates several times greater. Areas that were significantly affected by age included the acromion, scapular spine, base of the coracoid, inferior glenoid neck, and glenoid vault. Areas that were significantly affected by sex were the scapular spine and body.

Conclusions: These findings provide evidence that the bone density distribution across the scapula changes non-uniformly because of factors including sex and age. Despite overall trends of bone loss, there remains significant variability between individuals, and subject-specific tools for planning surgical procedures in which scapular fixation is required may be beneficial.
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http://dx.doi.org/10.1016/j.jse.2021.05.011DOI Listing
December 2021

The Effect of Forearm Shortening on Forearm Range of Motion.

J Hand Surg Am 2022 01 14;47(1):87.e1-87.e7. Epub 2021 May 14.

Department of Orthopaedics and Sports Medicine, University of Washington, Seattle, WA.

Purpose: Osseous shortening of the forearm is performed during forearm replantation; however, no large clinical reviews have discussed its effects on patient outcomes. A recent cadaver study demonstrated the progressive loss of forearm pronation/supination ranges of motion with increased shortening lengths using external fixation. Our study aimed to quantify the effects of shortening on passive forearm motion using internal fixation after 2, 4, and 6 cm of mid-forearm shortening.

Methods: A volar Henry approach and direct approach to the ulna were used on 8 cadaveric specimens. The forearms were sequentially shortened by 2, 4, and 6 cm. Fixation was performed on the volar surfaces of the radius and ulna. Pronation and supination of the forearms were tested by applying 1 Nm of torque at baseline and after the fixation of both the radius and ulna using osteotomy. Radiographs and measurements were obtained at each phase to determine the maximum radial bow and radioulnar gap. Data were analyzed using a linear mixed-effects model.

Results: Greater shortening of the radius and ulna led to progressively greater reductions in both pronation and supination range of motion. Larger differences were seen in supination at 2-4 cm of shortening and in pronation at 4-6 cm of shortening. Changes in supination were found to be associated with the radial bow and radioulnar gap; changes in pronation were found to be associated with the radial bow and radial bow's location.

Conclusions: This study demonstrates that quantifiable effects on passive forearm motion occur after osseous shortening of the forearm.

Clinical Relevance: This information may improve surgeons' and patients' understanding of the changes in forearm motion expected after shortening in the setting of replantation or tumor resection or in the setting of limb salvage of a mangled extremity.
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http://dx.doi.org/10.1016/j.jhsa.2021.03.017DOI Listing
January 2022

Using Wearable Technology to Measure the Association Between Neck Posture and Pain During Urologic Open and Robotic Surgery.

J Endourol 2021 11 17;35(11):1710-1715. Epub 2021 Sep 17.

Department of Orthopaedics and Sports Medicine and University of Washington School of Medicine, Seattle, Washington, USA.

Chronic neck pain is the most prevalent work-related musculoskeletal injury among surgeons. Urologists may be at higher risk of neck injury due to extended time spent operating in deep anatomical structures during open surgery. Our goal was to use wearable technology to quantify the relationship between neck posture and pain during open and robotic surgery. Urologic attendings and residents who spent at least 1 day per week performing surgery for >6 hours took part in this study. Neck posture was measured in real time during surgery using inertial measurement devices attached at the occipital protuberance and seventh cervical vertebrae. Self-reported neck pain scores were obtained throughout their workday. Thirty participants and 202 hours of surgery were included in the study (21 attendings, 9 residents). There was a significant association between neck posture and pain ( = 0.04). Surgeons performing open procedures spent on average 147 minutes with their head in neck flexion postures of 30° or greater compared with 68 minutes for those performing robotic procedures ( = 0.007). Surgeons performing open procedures reported a mean change in neck pain of 2.0 on the numeric analogue scale, compared with 1.3 for those performing robotic procedures ( = 0.04). Real-time measurements of neck flexion during urologic surgery shows that greater duration and higher degree of neck flexion were associated with increased neck pain. Raising awareness about ergonomics in the operating room during residency will enable future generations of surgeons to make conscious decisions regarding their neck posture in surgery.
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http://dx.doi.org/10.1089/end.2021.0260DOI Listing
November 2021

Biomechanical Effects of Blood Flow Restriction Training after ACL Reconstruction.

Med Sci Sports Exerc 2021 01;53(1):115-123

Department of Orthopaedics and Sports Medicine, University of Washington Medical Center, Seattle, WA.

Introduction: After anterior cruciate ligament reconstruction surgery, returning the knee to previous levels of strength and function is challenging, with the failure to do so associated with an increased risk of reinjury and long-term degenerative problems. Blood flow restriction (BFR) is gaining popularity as a rehabilitation technique; however, its effects on the mechanics of these exercises have not been fully explored. In this study, we aimed to determine the acute effects of BFR on the performance of a step-up exercise protocol and to assess the acceptability of the technique.

Methods: Twenty individuals (12 female/8 male; mean age, 30.6 yr) who had recently undergone anterior cruciate ligament reconstruction and 20 controls (11 female/9 male, mean age 28.0 yr) performed a step-up exercise protocol with and without BFR. Lower limb kinematics and kinetics were measured and compared between groups and conditions. Testing was completed in June 2019.

Results: Participants in both groups had increased external rotation of the tibia of 2° (P < 0.001) and reductions in knee flexion and rotation torques around the joint of around 50% (P < 0.001) when using BFR compared with nonrestricted step-up exercise. The intervention was found to increase the difficulty of the exercise and induce moderate levels of discomfort (P < 0.001).

Conclusion: The present study provides cautious support for the use of BFR, showing that there are minimal changes in knee joint mechanics when performing the same exercise without BFR, and that the changes do not increase joint torques at the knee. From an acute biomechanical perspective, the intervention appears safe to use under qualified supervision; however, effects of repetitive use and long-term outcomes should be monitored.
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http://dx.doi.org/10.1249/MSS.0000000000002437DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8191295PMC
January 2021

The effect of age and sex on pelvic bone density measured opportunistically in clinical CT scans.

J Orthop Res 2021 03 13;39(3):485-492. Epub 2020 Jul 13.

Department of Orthopaedics and Sports Medicine, University of Washington, Seattle, Washington.

Unstable pelvic ring fractures are severe and complex injuries, and surgical fixation is challenging and can be complicated by early failure due in part to difficulties with securely fixing screws in low-density bone. There is limited information in the literature about how the density distribution across the pelvic bones changes with age and sex. In this study, we used 60 sets of calibrated bone density measurements obtained opportunistically from clinical computed tomography scans of the pelvis. Three-dimensional models of the innominate bone were produced and the effects of age and sex on cortical bone density modeled. Overall trends and regions where these factors had a significant effect were identified, and the results visualized. Across the entire innominate bone, the mean loss of density was found to be 1.6 mg/cc per year, with several specific areas (pubic body, iliac fossa, posterior ilium, and anterior inferior iliac spine for example) showing significant rates of loss up to three times greater than the rest of the bone. Areas significantly affected by sex included the posterior pubic root, anterior aspect of the pubic body, and iliac crest. Despite overall trends of attenuation, there remains significant variability between individuals. This supports the need to further explore subject-specific planning tools for pelvic fracture repair. Statement of clinical significance: Bone density changes across the innominate bone due to age and sex tend to vary between individuals, although consistent effects were seen at specific regions. This information may help in surgical planning of unstable fracture repairs.
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http://dx.doi.org/10.1002/jor.24792DOI Listing
March 2021

Monitoring changes in knee surface morphology after anterior cruciate ligament reconstruction surgery using 3Dsurface scanning.

Knee 2020 Jan 26;27(1):207-213. Epub 2019 Dec 26.

Department of Orthopaedics and Sports Medicine, University of Washington Medical Center, Seattle, WA, United States of America.

Study Design: Prospective case series.

Background: After surgical reconstruction of the anterior cruciate ligament, recovery to pre-injury levels of knee function is challenging. Postoperative edema and muscle atrophy are common roadblocks to full function and are evident in changes to the surface morphology of the knee. There are currently few accessible objective tools to accurately track these morphological changes.

Objectives: We aimed to determine if 3D surface scanning can be used to monitor changes in the external shape of the knee after surgery and throughout the rehabilitation process.

Methods: Thirty participants had 3D surface scans taken of their knee, along with questionnaire-based functional outcomes prior to surgery (baseline), and at two-week, six-week, 12-week, and 26-week timepoints post-surgery. Volumetric changes relative to pre-op were assessed using generalized linear growth models for key anatomical regions and correlated with functional outcomes.

Results: Significant swelling of the patella region compared to baseline was evident immediately after surgery (14%, p < 0.001), before returning to pre-operative levels. Changes in volume at this region were significantly associated with patient-reported functional outcomes. Reductions in volume of the regions corresponding to the vastus medialis and lateralis muscles were significant at 12 weeks post-surgery (p = 0.018 and 0.01 respectively) but returned to baseline levels at six months.

Conclusion: We demonstrate the use of 3D surface scanning as a method for capturing detailed measurements of knee surface morphology after surgery. Significant changes in external morphology are evident during the rehabilitation process.
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http://dx.doi.org/10.1016/j.knee.2019.10.004DOI Listing
January 2020

THE USE OF MICROSOFT KINECT ™ FOR ASSESSING READINESS OF RETURN TO SPORT AND INJURY RISK EXERCISES: A VALIDATION STUDY.

Int J Sports Phys Ther 2019 Sep;14(5):724-730

University of Washington, Department of Orthopaedics and Sports Medicine, Seattle, WA.

Introduction: Assessing readiness of return to sport after procedures such as anterior cruciate ligament (ACL) reconstruction is a complex process, complicated by the pressures that athletes face in returning to sport as quickly as possible. Advances in motion analysis have been able to demonstrate movements that are risk factors for initial ACL injury and subsequent reinjury after reconstruction. An inexpensive, objective measure is needed to determine when athletes are ready to return to sport after ACL reconstruction.

Purpose: The aim of this study was to compare the use of a single camera, markerless motion capture technology to 3D motion capture during lower extremity movements that pose as risk factors for ACL injury.

Study Design: Cross Sectional Study.

Methods: This study assessed the validity of the Microsoft Kinect™ against an established 3-dimensional motion analysis system in 20 healthy subjects. Knee kinematics were assessed during impact activity in the coronal and sagittal plane specifically evaluating peak knee valgus and peak knee flexion during single leg hop and jump from box exercises. Intraclass correlation coefficients and 95% limits of agreement (LoA) were determined for each kinematic variable.

Results: For the single leg hop, the mean absolute difference in the sagittal plane was 10.4 ° (95% LoA [-11.7 °, 26.8 °]), and in the frontal plane was 5.31 ° (95% LoA [-8 °, 13.9 °]). Similarly, for the jump from box landing on one leg, there was a difference of 7.96 ° (95% LoA [-17.7 °, 21.3 °]) and 4.69 ° (95% LoA [-6.3 °, 12.6 °]) respectively. For the jump from box, two-foot land, turn and pivot, the mean absolute difference between the systems was 7.39 ° (95% LoA [-17.8 °, 19.7 °]) in the sagittal and 4.22 ° (95% LoA [-5.9 °, 11.6 °]) in the frontal plane respectively. Intraclass correlation coefficients for each activity ranged from 0.553 to 0.759.

Conclusion: The results from the Microsoft Kinect™ were found to be in poor agreement with those from a standard motion capture system. Measuring complex lower extremity movements with the Microsoft Kinect™ does not provide adequate enough information to use as an assessment tool for injury risk and return to sport timing.

Level Of Evidence: Level III.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6769275PMC
September 2019

Plantar pressures in identical and non-identical twins.

J Biomech 2019 03 12;86:247-250. Epub 2019 Feb 12.

Department of Orthopaedics and Sports Medicine, University of Washington Medical Center, Seattle, WA, United States.

Identifying environmental risk factors for musculoskeletal disorders is challenging due to the number of potential confounders. Twins are of particular interest for researchers interested in studying these types of problems due to their inherent control for the influence of genetic factors. In twin studies, this population can allow environmental risk factors to be more easily identified, and this type of study design may allow the role of biomechanics in injury and disease to be further explored. At present, it is unclear if foot function displays more similarity between certain types of twins. In this study, we hypothesized that the plantar pressures of monozygotic (identical) twins would be more similar between pairs than dizygotic (non-identical) twins. We measured static and dynamic plantar pressures from five pairs of each twin type. Statistical parametric modeling was used to compare pressure distributions at the sensor level. For >80% of stance phase, the pixel level analysis indicated that monozygotic twins had less variation in plantar pressure between pairs. The average z-statistic across the entire trial was 0.88 for the monozygotic group and 1.13 for the dizygotic group. In this study we provide evidence of greater similarity of plantar pressures in monozygotic twin pairs compared to dizygotic twins. This finding supports the use of co-twin studies investigating potentially modifiable environmental and biomechanical risk factors for musculoskeletal conditions that affect the foot and ankle.
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http://dx.doi.org/10.1016/j.jbiomech.2019.01.059DOI Listing
March 2019

Hind- and midfoot bone morphology varies with foot type and sex.

J Orthop Res 2019 03 16;37(3):744-759. Epub 2019 Jan 16.

RR&D Center for Limb Loss and MoBility, VA Puget Sound, Seattle, Washington.

Foot type has been associated with pain, injury, and altered gait mechanics. Morphological variations in foot bones due to foot type variation may impact surgical and therapeutic treatments. The purpose of this study was to utilize principal component analysis (PCA) to determine how morphology of the hind- and midfoot bones differs among foot types and sex. The calcaneus, talus, navicular, and cuboid were segmented using previously obtained computed tomography (CT) scans and converted to surface models. The CTs were sorted into four foot types-cavus, neutrally aligned, asymptomatic planus, and symptomatic planus. Morphometric shape analysis software (Geomorph) was used to perform a PCA to determine which components varied between foot types and between sexes. The calcaneus showed planus feet of both types to have calcanei that have decreased height and increased length compared to neutrally aligned feet. The talus demonstrated increased posterior mass for cavus feet compared to neutrally aligned feet. For the navicular, symptomatic planus had a more posteriorly positioned tuberosity and were wider than asymptomatic planus feet. The cuboid did not exhibit any differences between foot types. Sex differences, found only at the talus and navicular, were subtle. PCA is an objective technique that helped elucidate differences in bone morphology between foot types and sex without needing to determine the features of interest before comparing groups. Understanding these variations can help inform diagnosis of foot pathologies and surgical protocols as well as improve computer models of the foot. Published 2018. This article is a U.S. Government work and is in the public domain in the USA. J Orthop Res 9999:1-16, 2019.
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http://dx.doi.org/10.1002/jor.24197DOI Listing
March 2019

Factors influencing knee adduction moment measurement: A systematic review and meta-regression analysis.

Gait Posture 2017 10 24;58:333-339. Epub 2017 Aug 24.

Department of Orthopaedics and Sports Medicine, University of Washington, Seattle, WA, United States.

The external knee adduction moment has been identified as a key biomarker in biomechanics research, with associations with this variable and degenerative diseases such as knee osteoarthritis. Heterogeneity in participant characteristics and the protocols used to measure this variable may however complicate its interpretation. Previous reviews have focused on interventions or did not control for potential moderator variables in their analysis. In this meta-regression analysis, we aimed to determine the influence of factors including the cohort type, footwear, and walking speed on the measurement of knee adduction moment. We performed a systematic review of the literature, identifying articles that used the Plug-in-Gait inverse dynamics model to calculate the knee adduction moment during level walking, and used a mixed effect model to determine the effect of the previously described factors on the measurement. Results for 861 individuals were described in 19 articles. Walking speed had the largest influence on knee adduction moment (p<0.001), and participants with medial knee osteoarthritis had an increased knee adduction moment (p=0.008) compared to healthy subjects. Footwear was found to have a significant overall effect (p=0.024). Participants tested barefoot or wearing their own shoes had lower adduction moments than those tested in footwear provided by the researchers. Overall, the moderators accounted for 60% of the heterogeneity in the results. These results support the hypothesis that an increased knee adduction moment is associated with medial compartment knee osteoarthritis, and that footwear choice can influence the results. Gait speed has the largest effect on knee adduction moment measurement and should be carefully controlled for in studies investigating this variable.
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http://dx.doi.org/10.1016/j.gaitpost.2017.08.025DOI Listing
October 2017

Local weather is associated with rates of online searches for musculoskeletal pain symptoms.

PLoS One 2017 9;12(8):e0181266. Epub 2017 Aug 9.

Belfer Center for Science and International Affairs, Kennedy School of Government, Harvard University, Cambridge, United States of America.

Weather conditions are commonly believed to influence musculoskeletal pain, however the evidence for this is mixed. This study aimed to examine the relationship between local meteorological conditions and online search trends for terms related to knee pain, hip pain, and arthritis. Five years of relative online search volumes for these terms were obtained for the 50 most populous cities in the contiguous United States, along with corresponding local weather data for temperature, relative humidity, barometric pressure, and precipitation. Methods from the climate econometrics literature were used to assess the casual impact of these meteorological variables on the relative volumes of searches for pain. For temperatures between -5°C and 30°C, search volumes for hip pain increased by 12 index points, and knee pain increased by 18 index points. Precipitation had a negative effect on search volumes for these terms. At temperatures >30°C, search volumes for arthritis related pain decreased by 7 index points. These patterns were not seen for pain searches unrelated to the musculoskeletal system. In summary, selected local weather conditions are significantly associated with online search volumes for specific musculoskeletal pain symptoms. We believe the predominate driver for this to be the relative changes in physical activity levels associated with meteorological conditions.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0181266PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5549896PMC
October 2017

Knee joint kinetics in response to multiple three-dimensional printed, customised foot orthoses for the treatment of medial compartment knee osteoarthritis.

Proc Inst Mech Eng H 2017 Jun;231(6):487-498

1 Institute for Applied Health Research, School of Health and Life Sciences, Glasgow Caledonian University, Glasgow, UK.

The knee adduction moment is consistently used as a surrogate measure of medial compartment loading. Foot orthoses are designed to reduce knee adduction moment via lateral wedging. The 'dose' of wedging required to optimally unload the affected compartment is unknown and variable between individuals. This study explores a personalised approach via three-dimensional printed foot orthotics to assess the biomechanical response when two design variables are altered: orthotic length and lateral wedging. Foot orthoses were created for 10 individuals with symptomatic medial knee osteoarthritis and 10 controls. Computer-aided design software was used to design four full and four three-quarter-length foot orthoses per participant each with lateral posting of 0° 'neutral', 5° rearfoot, 10° rearfoot and 5° forefoot/10° rearfoot. Three-dimensional printers were used to manufacture all foot orthoses. Three-dimensional gait analyses were performed and selected knee kinetics were analysed: first peak knee adduction moment, second peak knee adduction moment, first knee flexion moment and knee adduction moment impulse. Full-length foot orthoses provided greater reductions in first peak knee adduction moment (p = 0.038), second peak knee adduction moment (p = 0.018) and knee adduction moment impulse (p = 0.022) compared to three-quarter-length foot orthoses. Dose effect of lateral wedging was found for first peak knee adduction moment (p < 0.001), second peak knee adduction moment (p < 0.001) and knee adduction moment impulse (p < 0.001) indicating greater unloading for higher wedging angles. Significant interaction effects were found for foot orthosis length and participant group in second peak knee adduction moment (p = 0.028) and knee adduction moment impulse (p = 0.036). Significant interaction effects were found between orthotic length and wedging condition for second peak knee adduction moment (p = 0.002). No significant changes in first knee flexion moment were found. Individual heterogeneous responses to foot orthosis conditions were observed for first peak knee adduction moment, second peak knee adduction moment and knee adduction moment impulse. Biomechanical response is highly variable with personalised foot orthoses. Findings indicate that the tailoring of a personalised intervention could provide an additional benefit over standard interventions and that a three-dimensional printing approach to foot orthosis manufacturing is a viable alternative to the standard methods.
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http://dx.doi.org/10.1177/0954411917691318DOI Listing
June 2017

Metatarsal Shape and Foot Type: A Geometric Morphometric Analysis.

J Biomech Eng 2017 Mar;139(3)

Department of Orthopaedics and Sports Medicine, University of Washington, Seattle, WA 98195; RR&D Center of Excellence, VA Puget Sound, Seattle, WA 98108; Department of Mechanical Engineering, University of Washington, Seattle, WA 98195.

Planus and cavus foot types have been associated with an increased risk of pain and disability. Improving our understanding of the geometric differences between bones in different foot types may provide insights into injury risk profiles and have implications for the design of musculoskeletal and finite-element models. In this study, we performed a geometric morphometric analysis on the geometry of metatarsal bones from 65 feet, segmented from computed tomography (CT) scans. These were categorized into four foot types: pes cavus, neutrally aligned, asymptomatic pes planus, and symptomatic pes planus. Generalized procrustes analysis (GPA) followed by permutation tests was used to determine significant shape differences associated with foot type and sex, and principal component analysis was used to find the modes of variation for each metatarsal. Significant shape differences were found between foot types for all the metatarsals (p < 0.01), most notably in the case of the second metatarsal which showed significant pairwise differences across all the foot types. Analysis of the principal components of variation showed pes cavus bones to have reduced cross-sectional areas in the sagittal and frontal planes. The first (p = 0.02) and fourth metatarsals (p = 0.003) were found to have significant sex-based differences, with first metatarsals from females shown to have reduced width, and fourth metatarsals from females shown to have reduced frontal and sagittal plane cross-sectional areas. Overall, these findings suggest that metatarsal bones have distinct morphological characteristics that are associated with foot type and sex, with implications for our understanding of anatomy and numerical modeling of the foot.
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http://dx.doi.org/10.1115/1.4035077DOI Listing
March 2017

The Glasgow-Maastricht foot model, evaluation of a 26 segment kinematic model of the foot.

J Foot Ankle Res 2016 8;9:19. Epub 2016 Jul 8.

NUTRIM, Department of Human Movement Sciences, Maastricht University Medical Centre +, PO 5800, 6202 AZ Maastricht, The Netherlands.

Background: Accurately measuring of intrinsic foot kinematics using skin mounted markers is difficult, limited in part by the physical dimensions of the foot. Existing kinematic foot models solve this problem by combining multiple bones into idealized rigid segments. This study presents a novel foot model that allows the motion of the 26 bones to be individually estimated via a combination of partial joint constraints and coupling the motion of separate joints using kinematic rhythms.

Methods: Segmented CT data from one healthy subject was used to create a template Glasgow-Maastricht foot model (GM-model). Following this, the template was scaled to produce subject-specific models for five additional healthy participants using a surface scan of the foot and ankle. Forty-three skin mounted markers, mainly positioned around the foot and ankle, were used to capture the stance phase of the right foot of the six healthy participants during walking. The GM-model was then applied to calculate the intrinsic foot kinematics.

Results: Distinct motion patterns where found for all joints. The variability in outcome depended on the location of the joint, with reasonable results for sagittal plane motions and poor results for transverse plane motions.

Conclusions: The results of the GM-model were comparable with existing literature, including bone pin studies, with respect to the range of motion, motion pattern and timing of the motion in the studied joints. This novel model is the most complete kinematic model to date. Further evaluation of the model is warranted.
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http://dx.doi.org/10.1186/s13047-016-0152-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4938906PMC
April 2017

Metatarsal Loading During Gait-A Musculoskeletal Analysis.

J Biomech Eng 2016 Mar;138(3):4032413

Detailed knowledge of the loading conditions within the human body is essential for the development and optimization of treatments for disorders and injuries of the musculoskeletal system. While loads in the major joints of the lower limb have been the subject of extensive study, relatively little is known about the forces applied to the individual bones of the foot. The objective of this study was to use a detailed musculoskeletal model to compute the loads applied to the metatarsal bones during gait across several healthy subjects. Motion-captured gait trials and computed tomography (CT) foot scans from four healthy subjects were used as the inputs to inverse dynamic simulations that allowed the computation of loads at the metatarsal joints. Low loads in the metatarsophalangeal (MTP) joint were predicted before terminal stance, however, increased to an average peak of 1.9 times body weight (BW) before toe-off in the first metatarsal. At the first tarsometatarsal (TMT) joint, loads of up to 1.0 times BW were seen during the early part of stance, reflecting tension in the ligaments and muscles. These loads subsequently increased to an average peak of 3.0 times BW. Loads in the first ray were higher compared to rays 2-5. The joints were primarily loaded in the longitudinal direction of the bone.
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http://dx.doi.org/10.1115/1.4032413DOI Listing
March 2016

Simplified versus geometrically accurate models of forefoot anatomy to predict plantar pressures: A finite element study.

J Biomech 2016 Jan 11;49(2):289-94. Epub 2015 Dec 11.

Department of Orthopaedics and Sports Medicine, University of Washington, Seattle, WA, USA.

Integration of patient-specific biomechanical measurements into the design of therapeutic footwear has been shown to improve clinical outcomes in patients with diabetic foot disease. The addition of numerical simulations intended to optimise intervention design may help to build on these advances, however at present the time and labour required to generate and run personalised models of foot anatomy restrict their routine clinical utility. In this study we developed second-generation personalised simple finite element (FE) models of the forefoot with varying geometric fidelities. Plantar pressure predictions from barefoot, shod, and shod with insole simulations using simplified models were compared to those obtained from CT-based FE models incorporating more detailed representations of bone and tissue geometry. A simplified model including representations of metatarsals based on simple geometric shapes, embedded within a contoured soft tissue block with outer geometry acquired from a 3D surface scan was found to provide pressure predictions closest to the more complex model, with mean differences of 13.3kPa (SD 13.4), 12.52kPa (SD 11.9) and 9.6kPa (SD 9.3) for barefoot, shod, and insole conditions respectively. The simplified model design could be produced in <1h compared to >3h in the case of the more detailed model, and solved on average 24% faster. FE models of the forefoot based on simplified geometric representations of the metatarsal bones and soft tissue surface geometry from 3D surface scans may potentially provide a simulation approach with improved clinical utility, however further validity testing around a range of therapeutic footwear types is required.
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http://dx.doi.org/10.1016/j.jbiomech.2015.12.001DOI Listing
January 2016

Let me Google that for you: a time series analysis of seasonality in internet search trends for terms related to foot and ankle pain.

J Foot Ankle Res 2015 3;8:27. Epub 2015 Jul 3.

Professor of Rehabilitation, Institute of Applied Health Research, Glasgow Caledonian University, Glasgow, UK.

Background: The analysis of internet search traffic may present the opportunity to gain insights into general trends and patterns in information seeking behaviour related to medical conditions at a population level. For prevalent and widespread problems such as foot and ankle pain, this information has the potential to improve our understanding of seasonality and trends within these conditions and their treatments, and may act as a useful proxy for their true incidence/prevalence characteristics. This study aimed to explore seasonal effects, general trends and relative popularity of internet search terms related to foot and ankle pain over the past decade.

Methods: We used the Google Trends tool to obtain relative search engine traffic for terms relating to foot and ankle pain and common treatments from Google search and affiliated pages for major northern and southern hemisphere English speaking nations. Analysis of overall trends and seasonality including summer/winter differences was carried out on these terms.

Results: Searches relating to general foot pain were on average 3.4 times more common than those relating to ankle pain, and twice as common as searches relating to heel pain. Distinct seasonal effects were seen in the northern hemisphere, with large increases in search volumes in the summer months compared to winter for foot (p = 0.004, 95 % CI [22.2-32.1]), ankle (p = 0.0078, 95 % CI [20.9-35.5]), and heel pain (p = 0.004, 95 % CI [29.1-45.6]). These seasonal effects were reflected by data from Australia, with the exception of ankle pain. Annual seasonal effects for treatment options were limited to terms related to foot surgery and ankle orthoses (p = 0.031, 95 % CI [3.5-20.9]; p = 0.004, 95 % CI [7.6-25.2] respectively), again increasing in the summer months.

Conclusions: A number of general trends and annual seasonal effects were found in time series internet search data for terms relating to foot and ankle pain. This data may provide insights into these conditions at population levels.
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http://dx.doi.org/10.1186/s13047-015-0074-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4490673PMC
July 2015

What has finite element analysis taught us about diabetic foot disease and its management? A systematic review.

PLoS One 2014 7;9(10):e109994. Epub 2014 Oct 7.

Department of Orthopaedics and Sports Medicine, University of Washington, Seattle, Washington, United States of America.

Background: Over the past two decades finite element (FE) analysis has become a popular tool for researchers seeking to simulate the biomechanics of the healthy and diabetic foot. The primary aims of these simulations have been to improve our understanding of the foot's complicated mechanical loading in health and disease and to inform interventions designed to prevent plantar ulceration, a major complication of diabetes. This article provides a systematic review and summary of the findings from FE analysis-based computational simulations of the diabetic foot.

Methods: A systematic literature search was carried out and 31 relevant articles were identified covering three primary themes: methodological aspects relevant to modelling the diabetic foot; investigations of the pathomechanics of the diabetic foot; and simulation-based design of interventions to reduce ulceration risk.

Results: Methodological studies illustrated appropriate use of FE analysis for simulation of foot mechanics, incorporating nonlinear tissue mechanics, contact and rigid body movements. FE studies of pathomechanics have provided estimates of internal soft tissue stresses, and suggest that such stresses may often be considerably larger than those measured at the plantar surface and are proportionally greater in the diabetic foot compared to controls. FE analysis allowed evaluation of insole performance and development of new insole designs, footwear and corrective surgery to effectively provide intervention strategies. The technique also presents the opportunity to simulate the effect of changes associated with the diabetic foot on non-mechanical factors such as blood supply to local tissues.

Discussion: While significant advancement in diabetic foot research has been made possible by the use of FE analysis, translational utility of this powerful tool for routine clinical care at the patient level requires adoption of cost-effective (both in terms of labour and computation) and reliable approaches with clear clinical validity for decision making.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0109994PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4188702PMC
December 2015

Dynamic plantar loading index detects altered foot function in individuals with rheumatoid arthritis but not changes due to orthotic use.

Clin Biomech (Bristol, Avon) 2014 Nov 27;29(9):1027-31. Epub 2014 Aug 27.

Institute for Applied Health Research, Glasgow Caledonian University, UK.

Background: Altered foot function is common in individuals with rheumatoid arthritis. Plantar pressure distributions during gait are regularly assessed in this patient group; however, the association between frequently reported magnitude-based pressure variables and clinical outcomes has not been clearly established. Recently, a novel approach to the analysis of plantar pressure distributions throughout stance phase, the dynamic plantar loading index, has been proposed. This study aimed to assess the utility of this index for measuring foot function in individuals with rheumatoid arthritis.

Methods: Barefoot plantar pressures during gait were measured in 63 patients with rheumatoid arthritis and 51 matched controls. Additionally, 15 individuals with rheumatoid arthritis had in-shoe plantar pressures measured whilst walking in standardized footwear for two conditions: shoes-only; and shoes with prescribed custom foot orthoses. The dynamic plantar loading index was determined for all participants and conditions. Patient and control groups were compared for significant differences as were the shod and orthosis conditions.

Findings: The patient group was found to have a mean index of 0.19, significantly lower than the control group's index of 0.32 (p>0.001, 95% CI [0.054, 0.197]). No significant differences were found between the shoe-only and shoe plus orthosis conditions. The loading index was found to correlate with clinical measures of structural deformity.

Interpretation: The dynamic plantar loading index may be a useful tool for researchers and clinicians looking to objectively assess dynamic foot function in patients with rheumatoid arthritis; however, it may be unresponsive to changes caused by orthotic interventions in this patient group.
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http://dx.doi.org/10.1016/j.clinbiomech.2014.08.009DOI Listing
November 2014

Simple finite element models for use in the design of therapeutic footwear.

J Biomech 2014 Sep 30;47(12):2948-55. Epub 2014 Jul 30.

Department of Orthopaedics and Sports Medicine, University of Washington, Seattle, WA, USA. Electronic address:

Therapeutic footwear is frequently prescribed in cases of rheumatoid arthritis and diabetes to relieve or redistribute high plantar pressures in the region of the metatarsal heads. Few guidelines exist as to how these interventions should be designed and what effect such interventions actually have on the plantar pressure distribution. Finite element analysis has the potential to assist in the design process by refining a given intervention or identifying an optimal intervention without having to actually build and test each condition. However, complete and detailed foot models based on medical image segmentation have proven time consuming to build and computationally expensive to solve, hindering their utility in practice. Therefore, the goal of the current work was to determine if a simplified patient-specific model could be used to assist in the design of foot orthoses to reduce the plantar pressure in the metatarsal head region. The approach is illustrated by a case study of a diabetic patient experiencing high pressures and pain over the fifth metatarsal head. The simple foot model was initially calibrated by adjusting the individual loads on the metatarsals to approximate measured peak plantar pressure distributions in the barefoot condition to within 3%. This loading was used in various shod conditions to identify an effective orthosis. Model results for metatarsal pads were considerably higher than measured values but predictions for uniform surfaces were generally within 16% of measured values. The approach enabled virtual prototyping of the orthoses, identifying the most favorable approach to redistribute the patient's plantar pressures.
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http://dx.doi.org/10.1016/j.jbiomech.2014.07.020DOI Listing
September 2014

Reproducibility of a peripheral quantitative computed tomography scan protocol to measure the material properties of the second metatarsal.

BMC Musculoskelet Disord 2014 Jul 19;15:242. Epub 2014 Jul 19.

Institute for Applied Health Research, Glasgow Caledonian University, Glasgow G4 0BA, UK.

Background: Peripheral quantitative computed tomography (pQCT) is an established technology that allows for the measurement of the material properties of bone. Alterations to bone architecture are associated with an increased risk of fracture. Further pQCT research is necessary to identify regions of interest that are prone to fracture risk in people with chronic diseases. The second metatarsal is a common site for the development of insufficiency fractures, and as such the aim of this study was to assess the reproducibility of a novel scanning protocol of the second metatarsal using pQCT.

Methods: Eleven embalmed cadaveric leg specimens were scanned six times; three times with and without repositioning. Each foot was positioned on a custom-designed acrylic foot plate to permit unimpeded scans of the region of interest. Sixty-six scans were obtained at 15% (distal) and 50% (mid shaft) of the second metatarsal. Voxel size and scan speed were reduced to 0.40 mm and 25 mm.sec(-1). The reference line was positioned at the most distal portion of the 2(nd) metatarsal. Repeated measurements of six key variables related to bone properties were subject to reproducibility testing. Data were log transformed and reproducibility of scans were assessed using intraclass correlation coefficients (ICC) and coefficients of variation (CV%).

Results: Reproducibility of the measurements without repositioning were estimated as: trabecular area (ICC 0.95; CV% 2.4), trabecular density (ICC 0.98; CV% 3.0), Strength Strain Index (SSI) - distal (ICC 0.99; CV% 5.6), cortical area (ICC 1.0; CV% 1.5), cortical density (ICC 0.99; CV% 0.1), SSI - mid shaft (ICC 1.0; CV% 2.4). Reproducibility of the measurements after repositioning were estimated as: trabecular area (ICC 0.96; CV% 2.4), trabecular density (ICC 0.98; CV% 2.8), SSI - distal (ICC 1.0; CV% 3.5), cortical area (ICC 0.99; CV%2.4), cortical density (ICC 0.98; CV% 0.8), SSI - mid shaft (ICC 0.99; CV% 3.2).

Conclusions: The scanning protocol generated excellent reproducibility for key bone properties measured at the distal and mid-shaft regions of the 2(nd) metatarsal. This protocol extends the capabilities of pQCT to evaluate bone quality in people who may be at an increased risk of metatarsal insufficiency fractures.
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http://dx.doi.org/10.1186/1471-2474-15-242DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4108224PMC
July 2014

An ultrasound based non-invasive method for the measurement of intrinsic foot kinematics during gait.

J Biomech 2014 Mar 25;47(5):1225-8. Epub 2013 Dec 25.

Institute for Applied Health Research, Glasgow Caledonian University, UK.

Soft tissue artefact (STA) and marker placement variability are sources of error when measuring the intrinsic kinematics of the foot. This study aims to demonstrate a non-invasive, combined ultrasound and motion capture (US/MC) technique to directly measure foot skeletal motion. The novel approach is compared to a standard motion capture protocol. Fourteen participants underwent instrumented barefoot analysis of foot motion during gait. Markers were attached to foot allowing medial longitudinal arch angle and navicular height to be determined. For the US/MC technique, the navicular marker was replaced by an ultrasound transducer which was secured to the foot allowing the skeletal landmark to be imaged. Ultrasound cineloops showing the location of the navicular tuberosity during the walking trials were synchronised with motion capture measurements and markers mounted on the probe allowed the true position of the bony landmark to be determined throughout stance phase. Two discrete variables, minimum navicular height and maximum MLA angle, were compared between the standard and US/MC protocols. Significant differences between minimum navicular height (P=0.004, 95% CI (1.57, 6.54)) and maximum medial longitudinal arch angle (P=0.0034, 95% CI (13.8, 3.4)) were found between the measurement methods. The individual effects of STA and marker placement error were also assessed. US/MC is a non-invasive technique which may help to provide more accurate measurements of intrinsic foot kinematics.
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http://dx.doi.org/10.1016/j.jbiomech.2013.12.014DOI Listing
March 2014
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