Aniruddh Nayak - Academia.edu (original) (raw)

Papers by Aniruddh Nayak

Journal of Orthopaedic Trauma, 2016

This study compared the stabilizing effect of 2 intertrochanteric (IT) fracture fixation devices ... more This study compared the stabilizing effect of 2 intertrochanteric (IT) fracture fixation devices in a cadaveric hemi-pelvis biomechanical model. Eleven pairs of cadaveric osteopenic female hemi-pelves with intact hip joint and capsular ligaments were used. An unstable IT fracture (OTA 31-A2) was created in each specimen and stabilized with a single lag screw device (Gamma 3) or an integrated dual screw (IDS) device (InterTAN). The hemi-pelves were inverted, coupled to a biaxial apparatus and subjected to 13.5 k cycles of loading (3 months) using controlled, oscillating pelvic rotation (0-90 degrees) plus cyclic axial femoral loading at a 2:1 body weight (BW) ratio. Femoral head rotation and varus collapse were monitored optoelectonically. For specimens surviving 3 months of loading, additional loading was performed in 0.25 × BW/250 cycle increments to a maximum of 4 × BW or failure. Femoral head rotation with IDS fixation was significantly less than the single lag screw construct after 3 months of simulated loading (P = 0.016). Maximum femoral head rotation at the end of 4 × BW loading was 7× less for the IDS construct (P = 0.006). Varus collapse was significantly less with the IDS construct over the entire loading cycle (P = 0.021). In this worst-case model of an osteopenic, unstable, IT fracture, the IDS construct, likely owing to its larger surface area, noncylindrical profile, and fracture compression, provided significantly greater stability and resistance to femoral head rotation and varus collapse.

Bulletin of the Hospital for Joint Disease (2013), 2015

Concomitant repair of the subscapularis with reverse shoul - der arthroplasty (rTSA) is controver... more Concomitant repair of the subscapularis with reverse shoul - der arthroplasty (rTSA) is controversial. To evaluate the biomechanical impact of subscapularis repair with rTSA, a cadaveric shoulder controller quantified the muscle forces required to elevate the arm during scapular abduction with the elbow flexed at 90°. The results of this study demonstrate that concomitant subscapularis repair with rTSA creates a biomechanically unfavorable condition during arm eleva - tion. Specifically, repair of the subscapularis significantly increased the force required by the deltoid and posterior rotator cuff and also significantly increased the joint reaction force relative to when the subscapularis was not repaired. These results also demonstrated that both the 42 mm Gram - mont and 42 mm Equinoxe ® rTSA prostheses significantly decreased the mean force required by the posterior rotator cuff and also significantly decreased the mean joint reaction force over the range of motion relative to t...

Journal of Shoulder and Elbow Surgery, 2015

The Journal of Hand Surgery, 2015

To determine repair site bulk, gliding resistance, work of flexion, and 1-mm gap formation force ... more To determine repair site bulk, gliding resistance, work of flexion, and 1-mm gap formation force in zone II flexor tendon lacerations repaired with knotless barbed or traditional braided suture. Transverse zone II lacerations of the flexor digitorum profundus (FDP) tendon were created in 36 digits from 6 matched human cadaveric pairs. Repair was performed with 2-0 barbed suture (n = 18) or 3-0 polyethylene braided suture (n = 18). Pre- and postrepair cross-sectional area was measured followed by quantification of gliding resistance and work of flexion during cyclic flexion-extension loading at 10 mm/min. Thereafter, the repaired tendons were loaded to failure. The force at 1 mm of gap formation was recorded. Repaired FDP tendon cross-sectional area increased significantly from intact, with no difference noted between suture types. Gliding resistance and work of flexion were significantly higher for both suture repairs; however, we identified no significant differences in either nondestructive biomechanical parameters between repair types. Average 1-mm gap formation force with the knotless barbed suture (52 N) was greater than that of the traditional braided suture (43 N). We identified no significant advantage in using knotless barbed suture for zone II FDP repair in our primary, nondestructive mechanical outcomes in this in vitro study. In vivo studies may be warranted to determine if one suture method has an advantage with respect to the parameters tested at 4, 6, and 12 plus weeks postrepair and the degree of adhesion formation. The combined laboratory and clinical data, in additional to cost considerations, may better define the role of barbed knotless suture for zone II flexor tendon repair.

Bio-medical materials and engineering, 2010

Dynamic stabilization systems are emerging as an alternative to fusion instrumentation. However, ... more Dynamic stabilization systems are emerging as an alternative to fusion instrumentation. However, cyclic loading and micro-motion at various interfaces may produce wear debris leading to adverse tissue reactions such as osteolysis. Ten million cycles of wear test was performed for PercuDyn™ in axial rotation and the wear profile and the wear rate was mapped. A validation study was undertaken to assess the efficiency of wear debris collection which accounted for experimental errors. The mean wear debris measured at the end of 10 million cycles was 4.01 mg, based on the worst-case recovery rate of 68.2%. Approximately 40% of the particulates were less than 5 μm; 92% less than 10 μm. About 43% of particulates were spherical in shape, 27% particulates were ellipsoidal and the remaining particles were of irregular shapes. The PercuDyn™ exhibited an average polymeric wear rate of 0.4 mg/million cycles; substantially less than the literature derived studies for other motion preservation dev...

International Journal of Spine Surgery, 2014

Mechanically replacing one or more pain generating articulations in the functional spinal unit (F... more Mechanically replacing one or more pain generating articulations in the functional spinal unit (FSU) may be a motion preservation alternative to arthrodesis at the affected level. Baseline biomechanical data elucidating the quantity and quality of motion in such arthroplasty constructs is non-existent.

Journal of Orthopaedic Trauma, 2015

The Journal of Hand Surgery, 2014

The International Journal of Spine Surgery, 2013

The Spine Journal, 2014

Despite an increase in the clinical use of no-profile anchored interbody cages (AIC) for anterior... more Despite an increase in the clinical use of no-profile anchored interbody cages (AIC) for anterior cervical discectomy and fusion (ACDF) procedures, there is little published biomechanical data describing its stabilizing effect relative to the traditional anterior plating technique over two contiguous levels. To biomechanically compare the acute stability conferred by a stand-alone interbody fusion device with three integrated fixation screws ("anchored cage") with a traditional six-hole rigid anterior plate in a two contiguous levels (C4-C5+C5-C6) fusion construct. We hypothesized that the anchored cage would confer comparable segmental rigidity to the cage and anterior plate construct. A biomechanical laboratory study using cadaveric human cervical spines. Seven (n=7) cadaveric human cervical spines (C3-C7) were subjected to quasistatic, pure-moment loading (±1.5 Nm) in flexion-extension (flex/ext), right/left lateral bending (RB/LB), and right/left axial rotation (RR/LR) for the following test conditions: intact; after discectomy and insertion of the AIC at C4-C5 and C5-C6 with anchoring screws engaged; after the removal of the integrated anchoring screws and instrumentation of an anterior locking plate (ALP) over both levels; and cage-only (CO) configuration with screws and anterior plate removed. Intervertebral range of motion (ROM) at the instrumented levels was the primary biomechanical outcome. Flex/ext, RB/LB, and RR/LR ROMs were significantly reduced (p<.001) over both levels by AIC and ALP constructs relative to the CO construct. Significant reduction in flex/ext motion was achieved with the ALP (6.8±3.7) relative to the AIC (10.2°±4.6°) (p=.041) construct. No significant differences were seen in ROM reductions over the two levels between the AIC and APL groups in lateral bending or axial rotation (p>.826). The anchored cage fusion construct conferred similar acute biomechanical stability in lateral bending and axial rotation ROMs relative to rigid anterior plating. We identified a statistically significant reduction (Δ=3.4°, combined over two levels) in sagittal plane ROM conferred by the ALP relative to the AIC construct. Our biomechanical findings may support the clinical use of no-profile integrated interbody devices over two contiguous levels in ACDF.

The spine journal : official journal of the North American Spine Society, 2013

The lateral transpsoas approach to interbody fusion is gaining popularity because of its minimall... more The lateral transpsoas approach to interbody fusion is gaining popularity because of its minimally invasive nature and resultant indirect neurologic decompression. The acute biomechanical stability of the lateral approach to interbody fusion is dependent on the type of supplemental internal fixation used. The two-hole lateral plate (LP) has been approved for clinical use for added stabilization after cage instrumentation. However, little biomechanical data exist comparing LP fixation with bilateral pedicle screw and rod (PSR) fixation. To biomechanically compare the acute stabilizing effects of the two-hole LP and bilateral PSR fusion constructs in lumbar spines instrumented with a lateral cage at two contiguous levels. Biomechanical laboratory study of human cadaveric lumbar spines. Eighteen L1-S1 cadaveric lumbar spines were instrumented with lateral cages at L3-L4 and L4-L5 after intact kinematic analysis. Specimens (n=9 each) were allocated for supplemental instrumentation with ...

Clinical Orthopaedics & Related Research, 2014

Clinical Orthopaedics & Related Research, 2014

The Spine Journal, 2014

No profile, integrated interbody cages are designed to act as implants for cervical spine fusion,... more No profile, integrated interbody cages are designed to act as implants for cervical spine fusion, which obviates the need for additional internal fixation, combining the functionality of an interbody device and the stabilizing benefits of an anterior cervical plate. Biomechanical data are needed to determine if integrated interbody constructs afford similar stability to anterior plating in single-level cervical spine fusion constructs. The purpose of this study was to biomechanically quantify the acute stabilizing effect conferred by a single low-profile device design with three integrated screws ("anchored cage"), and compare the range of motion reductions to those conferred by a standard four-hole rigid anterior plate following instrumentation at the C5-C6 level. We hypothesized that the anchored cage would confer comparable postoperative segmental rigidity to the cage and anterior plate construct. Biomechanical laboratory study of human cadaveric spines. Seven human cadaveric cervical spines (C3-C7) were biomechanically evaluated using a nondestructive, nonconstraining, pure-moment loading protocol with loads applied in flexion, extension, lateral bending (right+left), and axial rotation (left+right) for the intact and instrumented conditions. Range of motion (ROM) at the instrumented level was the primary biomechanical outcome. Spines were loaded quasi-statically up to 1.5 N-m in 0.5 N-m increments and ROM at the C5-C6 index level was recorded. Each specimen was tested in the following conditions: 1. Intact 2. Discectomy+anchored cage (STA) 3. Anchored cage (screws removed)+anterior locking plate (ALP) 4. Anchored cage only, without screws or plates (CO) RESULTS: ROM at the C5-C6 level was not statistically different in any motion plane between the STA and ALP treatment conditions (p>.407). STA demonstrated significant reductions in flexion/extension, lateral bending, and axial rotation ROM when compared with the CO condition (p<.022). In this in vitro biomechanical study, the anchored cage with three integrated screws afforded biomechanical stability comparable to that of the standard interbody cage+anterior plate cervical spine fusion approach. Due to its low profile design, this anchored cage device may avoid morbidities associated with standard anterior plating, such as dysphagia.

Journal of Spinal Disorders & Techniques, 2014

Journal of Orthopaedic Trauma, 2012

The purpose of this study was to determine if proximity of cannulated lag screws to the articular... more The purpose of this study was to determine if proximity of cannulated lag screws to the articular surface of the patella combined with the tension band technique affects resistance to fracture gap opening, and if an alternative locking nut and bolt device without a tension band behaves in a biomechanically similar fashion. Thirty-three cadaveric knees were allocated to 3 transverse patella fracture fixation groups: cannulated lag screw placement close to the articular (TBA) or non-articular (TBNA) surface with tension, and placement of a compressive locking nut and bolt device without tension band (CompresSURE) close to the articular surface. Knees were cycled through flexion-extension motion for 1000 cycles during which the fracture gap opening was quantified after the first flexion-extension cycle and after the 1,000 th cycle using an optoelectronic motion analysis system. After the first range of motion cycle, there was no significant difference in fracture gap opening between the 3 groups on the articular surface (P > 0.600). Total fracture gap displacement after the 1,000 th cycle was not significantly different between groups (P > 0.408). In general and irrespective of fixation technique, fractures opened in a wedge-like fashion with larger measured gap on the ventral surface relative to the articulating surface. When combined with the tension band, the proximity of cannulated lag screws to the articular surface did not affect resistance to fracture gap opening. Additionally, the stand-alone CompreSURE cannulated locking nut and bolt device without tension band was able to resist fracture gap opening in transverse fractures as effectively as the cannulated screw with tension band technique.

Clinical Biomechanics, 2014

Clinical Biomechanics, 2013

Background: Multiple classifications combine objective and subjective measures to predict fractur... more Background: Multiple classifications combine objective and subjective measures to predict fracture risk through a metastatic lesion. In our literature review, no studies have attempted to validate this predicted fracture risk from a biomechanical perspective. The study goal was to evaluate proximal femur strength after creating osteolytic defects. We report a standardized technique to re-create a metastatic lesion. Methods: Eight femoral matched pairs were procured and a standardized technique was used to create an osteolytic femoral neck defect in one femur with the contralateral specimen serving as the control. Femurs were loaded to failure in a material testing machine at 2 mm/s. Failure load (N) and location of failure were documented. 3D finite element (FE) femur models with and without the lesions were developed to predict von Mises stresses in the femoral neck and compare between the two models. Findings: Femurs containing the osteolytic defect failed at significantly lower loads than the intact specimens in a reproducible manner (intact: 10.69 kN (3.09 SD); lesion: 5.56 kN (2.03 SD), p b 0.001). The average reduction in failure load was 48%, and the fracture pattern was consistent in all specimens. FE model comparison similarly predicted significantly higher von Mises stress at the lesion. Interpretation: Our methods and pathologic fracture model represent the clinical parameters of metastatic bone disease and suggest a significant reduction in structural integrity of the lesion-containing femur. Prophylactic surgical fixation may be warranted clinically to reduce the risk of pathologic fracture. Our model technique is reproducible and may be used in future studies.

Journal of Orthopaedic Trauma, 2016

This study compared the stabilizing effect of 2 intertrochanteric (IT) fracture fixation devices ... more This study compared the stabilizing effect of 2 intertrochanteric (IT) fracture fixation devices in a cadaveric hemi-pelvis biomechanical model. Eleven pairs of cadaveric osteopenic female hemi-pelves with intact hip joint and capsular ligaments were used. An unstable IT fracture (OTA 31-A2) was created in each specimen and stabilized with a single lag screw device (Gamma 3) or an integrated dual screw (IDS) device (InterTAN). The hemi-pelves were inverted, coupled to a biaxial apparatus and subjected to 13.5 k cycles of loading (3 months) using controlled, oscillating pelvic rotation (0-90 degrees) plus cyclic axial femoral loading at a 2:1 body weight (BW) ratio. Femoral head rotation and varus collapse were monitored optoelectonically. For specimens surviving 3 months of loading, additional loading was performed in 0.25 × BW/250 cycle increments to a maximum of 4 × BW or failure. Femoral head rotation with IDS fixation was significantly less than the single lag screw construct after 3 months of simulated loading (P = 0.016). Maximum femoral head rotation at the end of 4 × BW loading was 7× less for the IDS construct (P = 0.006). Varus collapse was significantly less with the IDS construct over the entire loading cycle (P = 0.021). In this worst-case model of an osteopenic, unstable, IT fracture, the IDS construct, likely owing to its larger surface area, noncylindrical profile, and fracture compression, provided significantly greater stability and resistance to femoral head rotation and varus collapse.

Bulletin of the Hospital for Joint Disease (2013), 2015

Concomitant repair of the subscapularis with reverse shoul - der arthroplasty (rTSA) is controver... more Concomitant repair of the subscapularis with reverse shoul - der arthroplasty (rTSA) is controversial. To evaluate the biomechanical impact of subscapularis repair with rTSA, a cadaveric shoulder controller quantified the muscle forces required to elevate the arm during scapular abduction with the elbow flexed at 90°. The results of this study demonstrate that concomitant subscapularis repair with rTSA creates a biomechanically unfavorable condition during arm eleva - tion. Specifically, repair of the subscapularis significantly increased the force required by the deltoid and posterior rotator cuff and also significantly increased the joint reaction force relative to when the subscapularis was not repaired. These results also demonstrated that both the 42 mm Gram - mont and 42 mm Equinoxe ® rTSA prostheses significantly decreased the mean force required by the posterior rotator cuff and also significantly decreased the mean joint reaction force over the range of motion relative to t...

Journal of Shoulder and Elbow Surgery, 2015

The Journal of Hand Surgery, 2015

To determine repair site bulk, gliding resistance, work of flexion, and 1-mm gap formation force ... more To determine repair site bulk, gliding resistance, work of flexion, and 1-mm gap formation force in zone II flexor tendon lacerations repaired with knotless barbed or traditional braided suture. Transverse zone II lacerations of the flexor digitorum profundus (FDP) tendon were created in 36 digits from 6 matched human cadaveric pairs. Repair was performed with 2-0 barbed suture (n = 18) or 3-0 polyethylene braided suture (n = 18). Pre- and postrepair cross-sectional area was measured followed by quantification of gliding resistance and work of flexion during cyclic flexion-extension loading at 10 mm/min. Thereafter, the repaired tendons were loaded to failure. The force at 1 mm of gap formation was recorded. Repaired FDP tendon cross-sectional area increased significantly from intact, with no difference noted between suture types. Gliding resistance and work of flexion were significantly higher for both suture repairs; however, we identified no significant differences in either nondestructive biomechanical parameters between repair types. Average 1-mm gap formation force with the knotless barbed suture (52 N) was greater than that of the traditional braided suture (43 N). We identified no significant advantage in using knotless barbed suture for zone II FDP repair in our primary, nondestructive mechanical outcomes in this in vitro study. In vivo studies may be warranted to determine if one suture method has an advantage with respect to the parameters tested at 4, 6, and 12 plus weeks postrepair and the degree of adhesion formation. The combined laboratory and clinical data, in additional to cost considerations, may better define the role of barbed knotless suture for zone II flexor tendon repair.

Bio-medical materials and engineering, 2010

Dynamic stabilization systems are emerging as an alternative to fusion instrumentation. However, ... more Dynamic stabilization systems are emerging as an alternative to fusion instrumentation. However, cyclic loading and micro-motion at various interfaces may produce wear debris leading to adverse tissue reactions such as osteolysis. Ten million cycles of wear test was performed for PercuDyn™ in axial rotation and the wear profile and the wear rate was mapped. A validation study was undertaken to assess the efficiency of wear debris collection which accounted for experimental errors. The mean wear debris measured at the end of 10 million cycles was 4.01 mg, based on the worst-case recovery rate of 68.2%. Approximately 40% of the particulates were less than 5 μm; 92% less than 10 μm. About 43% of particulates were spherical in shape, 27% particulates were ellipsoidal and the remaining particles were of irregular shapes. The PercuDyn™ exhibited an average polymeric wear rate of 0.4 mg/million cycles; substantially less than the literature derived studies for other motion preservation dev...

International Journal of Spine Surgery, 2014

Mechanically replacing one or more pain generating articulations in the functional spinal unit (F... more Mechanically replacing one or more pain generating articulations in the functional spinal unit (FSU) may be a motion preservation alternative to arthrodesis at the affected level. Baseline biomechanical data elucidating the quantity and quality of motion in such arthroplasty constructs is non-existent.

Journal of Orthopaedic Trauma, 2015

The Journal of Hand Surgery, 2014

The International Journal of Spine Surgery, 2013

The Spine Journal, 2014

Despite an increase in the clinical use of no-profile anchored interbody cages (AIC) for anterior... more Despite an increase in the clinical use of no-profile anchored interbody cages (AIC) for anterior cervical discectomy and fusion (ACDF) procedures, there is little published biomechanical data describing its stabilizing effect relative to the traditional anterior plating technique over two contiguous levels. To biomechanically compare the acute stability conferred by a stand-alone interbody fusion device with three integrated fixation screws ("anchored cage") with a traditional six-hole rigid anterior plate in a two contiguous levels (C4-C5+C5-C6) fusion construct. We hypothesized that the anchored cage would confer comparable segmental rigidity to the cage and anterior plate construct. A biomechanical laboratory study using cadaveric human cervical spines. Seven (n=7) cadaveric human cervical spines (C3-C7) were subjected to quasistatic, pure-moment loading (±1.5 Nm) in flexion-extension (flex/ext), right/left lateral bending (RB/LB), and right/left axial rotation (RR/LR) for the following test conditions: intact; after discectomy and insertion of the AIC at C4-C5 and C5-C6 with anchoring screws engaged; after the removal of the integrated anchoring screws and instrumentation of an anterior locking plate (ALP) over both levels; and cage-only (CO) configuration with screws and anterior plate removed. Intervertebral range of motion (ROM) at the instrumented levels was the primary biomechanical outcome. Flex/ext, RB/LB, and RR/LR ROMs were significantly reduced (p<.001) over both levels by AIC and ALP constructs relative to the CO construct. Significant reduction in flex/ext motion was achieved with the ALP (6.8±3.7) relative to the AIC (10.2°±4.6°) (p=.041) construct. No significant differences were seen in ROM reductions over the two levels between the AIC and APL groups in lateral bending or axial rotation (p>.826). The anchored cage fusion construct conferred similar acute biomechanical stability in lateral bending and axial rotation ROMs relative to rigid anterior plating. We identified a statistically significant reduction (Δ=3.4°, combined over two levels) in sagittal plane ROM conferred by the ALP relative to the AIC construct. Our biomechanical findings may support the clinical use of no-profile integrated interbody devices over two contiguous levels in ACDF.

The spine journal : official journal of the North American Spine Society, 2013

The lateral transpsoas approach to interbody fusion is gaining popularity because of its minimall... more The lateral transpsoas approach to interbody fusion is gaining popularity because of its minimally invasive nature and resultant indirect neurologic decompression. The acute biomechanical stability of the lateral approach to interbody fusion is dependent on the type of supplemental internal fixation used. The two-hole lateral plate (LP) has been approved for clinical use for added stabilization after cage instrumentation. However, little biomechanical data exist comparing LP fixation with bilateral pedicle screw and rod (PSR) fixation. To biomechanically compare the acute stabilizing effects of the two-hole LP and bilateral PSR fusion constructs in lumbar spines instrumented with a lateral cage at two contiguous levels. Biomechanical laboratory study of human cadaveric lumbar spines. Eighteen L1-S1 cadaveric lumbar spines were instrumented with lateral cages at L3-L4 and L4-L5 after intact kinematic analysis. Specimens (n=9 each) were allocated for supplemental instrumentation with ...

Clinical Orthopaedics & Related Research, 2014

Clinical Orthopaedics & Related Research, 2014

The Spine Journal, 2014

No profile, integrated interbody cages are designed to act as implants for cervical spine fusion,... more No profile, integrated interbody cages are designed to act as implants for cervical spine fusion, which obviates the need for additional internal fixation, combining the functionality of an interbody device and the stabilizing benefits of an anterior cervical plate. Biomechanical data are needed to determine if integrated interbody constructs afford similar stability to anterior plating in single-level cervical spine fusion constructs. The purpose of this study was to biomechanically quantify the acute stabilizing effect conferred by a single low-profile device design with three integrated screws ("anchored cage"), and compare the range of motion reductions to those conferred by a standard four-hole rigid anterior plate following instrumentation at the C5-C6 level. We hypothesized that the anchored cage would confer comparable postoperative segmental rigidity to the cage and anterior plate construct. Biomechanical laboratory study of human cadaveric spines. Seven human cadaveric cervical spines (C3-C7) were biomechanically evaluated using a nondestructive, nonconstraining, pure-moment loading protocol with loads applied in flexion, extension, lateral bending (right+left), and axial rotation (left+right) for the intact and instrumented conditions. Range of motion (ROM) at the instrumented level was the primary biomechanical outcome. Spines were loaded quasi-statically up to 1.5 N-m in 0.5 N-m increments and ROM at the C5-C6 index level was recorded. Each specimen was tested in the following conditions: 1. Intact 2. Discectomy+anchored cage (STA) 3. Anchored cage (screws removed)+anterior locking plate (ALP) 4. Anchored cage only, without screws or plates (CO) RESULTS: ROM at the C5-C6 level was not statistically different in any motion plane between the STA and ALP treatment conditions (p>.407). STA demonstrated significant reductions in flexion/extension, lateral bending, and axial rotation ROM when compared with the CO condition (p<.022). In this in vitro biomechanical study, the anchored cage with three integrated screws afforded biomechanical stability comparable to that of the standard interbody cage+anterior plate cervical spine fusion approach. Due to its low profile design, this anchored cage device may avoid morbidities associated with standard anterior plating, such as dysphagia.

Journal of Spinal Disorders & Techniques, 2014

Journal of Orthopaedic Trauma, 2012

The purpose of this study was to determine if proximity of cannulated lag screws to the articular... more The purpose of this study was to determine if proximity of cannulated lag screws to the articular surface of the patella combined with the tension band technique affects resistance to fracture gap opening, and if an alternative locking nut and bolt device without a tension band behaves in a biomechanically similar fashion. Thirty-three cadaveric knees were allocated to 3 transverse patella fracture fixation groups: cannulated lag screw placement close to the articular (TBA) or non-articular (TBNA) surface with tension, and placement of a compressive locking nut and bolt device without tension band (CompresSURE) close to the articular surface. Knees were cycled through flexion-extension motion for 1000 cycles during which the fracture gap opening was quantified after the first flexion-extension cycle and after the 1,000 th cycle using an optoelectronic motion analysis system. After the first range of motion cycle, there was no significant difference in fracture gap opening between the 3 groups on the articular surface (P > 0.600). Total fracture gap displacement after the 1,000 th cycle was not significantly different between groups (P > 0.408). In general and irrespective of fixation technique, fractures opened in a wedge-like fashion with larger measured gap on the ventral surface relative to the articulating surface. When combined with the tension band, the proximity of cannulated lag screws to the articular surface did not affect resistance to fracture gap opening. Additionally, the stand-alone CompreSURE cannulated locking nut and bolt device without tension band was able to resist fracture gap opening in transverse fractures as effectively as the cannulated screw with tension band technique.

Clinical Biomechanics, 2014

Clinical Biomechanics, 2013

Background: Multiple classifications combine objective and subjective measures to predict fractur... more Background: Multiple classifications combine objective and subjective measures to predict fracture risk through a metastatic lesion. In our literature review, no studies have attempted to validate this predicted fracture risk from a biomechanical perspective. The study goal was to evaluate proximal femur strength after creating osteolytic defects. We report a standardized technique to re-create a metastatic lesion. Methods: Eight femoral matched pairs were procured and a standardized technique was used to create an osteolytic femoral neck defect in one femur with the contralateral specimen serving as the control. Femurs were loaded to failure in a material testing machine at 2 mm/s. Failure load (N) and location of failure were documented. 3D finite element (FE) femur models with and without the lesions were developed to predict von Mises stresses in the femoral neck and compare between the two models. Findings: Femurs containing the osteolytic defect failed at significantly lower loads than the intact specimens in a reproducible manner (intact: 10.69 kN (3.09 SD); lesion: 5.56 kN (2.03 SD), p b 0.001). The average reduction in failure load was 48%, and the fracture pattern was consistent in all specimens. FE model comparison similarly predicted significantly higher von Mises stress at the lesion. Interpretation: Our methods and pathologic fracture model represent the clinical parameters of metastatic bone disease and suggest a significant reduction in structural integrity of the lesion-containing femur. Prophylactic surgical fixation may be warranted clinically to reduce the risk of pathologic fracture. Our model technique is reproducible and may be used in future studies.