A Biomechanical Comparison Shows No Difference Between Two Knee Braces used for Medial Collateral Ligament Injuries.

PURPOSE: The purpose of this study was to assess the ability of 2 commonly used knee braces to control knee valgus motion and subsequent strain on the medial collateral ligament (MCL) in a laboratory-controlled environment. METHODS: Twenty healthy individuals (6 male, 14 female; mean age, 23 ± 3 years) with no history of knee injury or brace use performed a jump landing task while wearing either no brace or 1 of 2 braces: the Playmaker and Total Range of Motion . Three-dimensional joint kinematics and kinetics were measured in our biomechanics laboratory. RESULTS: Significantly less knee dynamic valgus angulation was noted when using either brace (-0.51° ± 3.9° and -1.3° ± 3.2°) compared no brace (4.8° ± 3.0°). Dynamic valgus angulation did not differ significantly between the 2 braces tested, which were both not statistically different from baseline alignment. There were significant differences seen in peak knee flexion angle between each brace (77.9° ± 8.8°and 83.1° ± 8.4°), as well as between both braces and no brace (90.6° ± 11.1°). There was no significant difference in knee frontal plane moment or peak vertical ground reaction force loading among all 3 testing conditions. CONCLUSIONS: Compared to no brace, both braces allowed significantly less dynamic valgus angulation of the knee under physiological vertical loads but were not significantly different from one another. CLINICAL RELEVANCE: Knee braces are commonly used to protect the MCL when placed under physiological loads. It is important to know which braces effectively reduce valgus stress to provide the best outcomes.

Biomechanical comparison of a 3.5-mm conical coupling plating system and a 3.5-mm locking compression plate applied as plate-rod constructs to an experimentally created fracture gap in femurs of canine cadavers.

OBJECTIVE To compare stiffness and resistance to cyclic fatigue of two 3.5-mm locking system plate-rod constructs applied to an experimentally created fracture gap in femurs of canine cadavers. SAMPLE 20 femurs from cadavers of 10 mixed-breed adult dogs. PROCEDURES 1 femur from each cadaver was stabilized with a conical coupling plating system-rod construct, and the contralateral femur was stabilized with a locking compression plate (LCP)-rod construct. An intramedullary Steinmann pin was inserted in each femur. A 40-mm gap then was created; the gap was centered beneath the central portion of each plate. Cyclic axial loading with increasing loads was performed. Specimens that did not fail during cyclic loading were subjected to an acute load to failure. RESULTS During cyclic loading, significantly more LCP constructs failed (6/10), compared with the number of conical coupling plating system constructs that failed (1/10). Mode of failure of the constructs included fracture of the medial or caudal aspect of the cortex of the proximal segment with bending of the plate and pin, bending of the plate and pin without fracture, and screw pullout. Mean stiffness, yield load, and load to failure were not significantly different between the 2 methods of stabilization. CONCLUSIONS AND CLINICAL RELEVANCE Both constructs had similar biomechanical properties, but the conical coupling plating system was less likely to fail than was the LCP system when subjected to cyclic loading. These results should be interpreted with caution because testing was limited to a single loading mode.

Does the novel lateral trauma position cause more motion in an unstable cervical spine injury than the logroll maneuver?

OBJECTIVE: Prehospital personnel who lack advanced airway management training must rely on basic techniques when transporting unconscious trauma patients. The supine position is associated with a loss of airway patency when compared to lateral recumbent positions. Thus, an inherent conflict exists between securing an open airway using the recovery position and maintaining spinal immobilization in the supine position. The lateral trauma position is a novel technique that aims to combine airway management with spinal precautions. The objective of this study was to compare the spinal motion allowed by the novel lateral trauma position and the well-established log-roll maneuver. METHODS: Using a full-body cadaver model with an induced globally unstable cervical spine (C5-C6) lesion, we investigated the mean range of motion (ROM) produced at the site of the injury in six dimensions by performing the two maneuvers using an electromagnetic tracking device. RESULTS: Compared to the log-roll maneuver, the lateral trauma position caused similar mean ROM in five of the six dimensions. Only medial/lateral linear motion was significantly greater in the lateral trauma position (1.4mm (95% confidence interval [CI] 0.4, 2.4mm)). CONCLUSIONS: In this cadaver study, the novel lateral trauma position and the well-established log-roll maneuver resulted in comparable amounts of motion in an unstable cervical spine injury model. We suggest that the lateral trauma position may be considered for unconscious non-intubated trauma patients.

Effect of investigator observation on gait parameters in individuals with and without chronic low back pain.

Despite the ubiquity of gait assessment in clinic and research, it is unclear how observation impacts gait, particularly in persons with chronic pain and psychological stress. We compared temporal spatial gait patterns in people with and without chronic low back pain (CLBP) when they were aware and unaware of being observed. This was a repeated-measures, deception study in 55 healthy persons (32.0±12.4 yr, 24.2±2.7kg/m2) and persons with CLBP (51.9±17.9 yr, 27.8±4.4kg/m2). Participants performed one condition in which they were unaware of observation (UNW), and three conditions under investigator observation: (1) aware of observation (AWA), (2) investigators watching cadence, (3) investigators watching step length. Participants walked across an 8.4m gait mat, while temporal spatial parameters of gait were collected. The Medical Outcomes Short Form (SF-12), Beck Depression Inventory (BDI), State Trait Anxiety Inventory (STAI), and Oswestry Disability Index (ODI) were completed. Significant condition by group interactions were found for velocity and step length (p<0.05). Main effects of study condition existed for all gait variables except for step width. Main effects of group (healthy, LBP) were significant for all variables except for step width (p<0.05). Regression analyses revealed that after accounting for age, sex, and SF-12 mental component score, BDI scores predict velocity changes during walking from the UNW to AWA conditions. These findings show that people change their gait patterns when being observed. Gait analyses may require additional trials before data can reliably be interpreted and used for clinical decision-making.

Detection of Intravascular Injection During Lumbar Medial Branch Blocks: A Comparison of Aspiration, Live Fluoroscopy, and Digital Subtraction Technology.

BACKGROUND CONTEXT: Medial branch blocks may have unrecognized vascular uptake potentially resulting in false- negative results. PURPOSE: To determine the rate of unintended vascular injection of contrast medium during medial branch blocks (MBB) with digital subtraction (DS) technology in the context of negative vascular uptake as determined by live fluoroscopy. STUDY DESIGN/SETTING: Prospective Study in an academic medical center. PATIENT SAMPLE: 344 consecutive MBBs in 80 subjects. OUTCOME MEASURES: The presence of vascular flow as determined by live fluoroscopy and DS technology. METHODS: Unintended vascular injection of contrast medium was determined on 344 consecutive MBBs in 84 subjects, first using live fluoroscopy followed by DS. If live fluoroscopy initially detected vascular uptake, the needle was repositioned until no vascular flow was detected. Once no vascular uptake was confirmed by live fluoroscopy, a contrast medium was then injected while being visualized with DS to again assess the presence or absence of vascular flow undetected by live fluoroscopy. RESULTS: Live fluoroscopy revealed inadvertent vascular uptake in 38 of the 344 blocks [11% (95% CI 8.0-15%)]. DS uncovered an additional 27 of the 344 blocks [7.8% (95% CI 5.3-11.4%)] with evidence of vascular uptake that were not detected with conventional live fluoroscopy. CONCLUSION: DS enhances the ability to detect inadvertent vascular flow during medial branch blocks. This study demonstrates that standard live fluoroscopy can miss a small percentage of cases with unintentional vascular uptake during MBB when compared with DS and may contribute to occasional false-negative responses.

Horizontal Slide Creates Less Cervical Motion When Centering an Injured Patient on a Spine Board.

BACKGROUND: A patient with a suspected cervical spine injury may be at risk for secondary neurologic injury when initially placed and repositioned to the center of the spine board. OBJECTIVES: We sought to determine which centering adjustment best limits cervical spine movement and minimizes the chance for secondary injury. METHODS: Using five lightly embalmed cadaveric specimens with a created global instability at C5-C6, motion sensors were anchored to the anterior surface of the vertebral bodies. Three repositioning methods were used to center the cadavers on the spine board: horizontal slide, diagonal slide, and V-adjustment. An electromagnetic tracking device measured angular (degrees) and translation (millimeters) motions at the C5-C6 level during each of the three centering adjustments. The dependent variables were angular motion (flexion-extension, axial rotation, lateral flexion) and translational displacement (anteroposterior, axial, and medial-lateral). RESULTS: The nonuniform condition produced significantly less flexion-extension than the uniform condition (p = 0.048). The horizontal slide adjustment produced less cervical flexion-extension (p = 0.015), lateral bending (p = 0.003), and axial rotation (p = 0.034) than the V-adjustment. Similarly, translation was significantly less with the horizontal adjustment than with the V-adjustment; medial-lateral (p = 0.017), axial (p < 0.001), and anteroposterior (p = 0.006). CONCLUSIONS: Of the three adjustments, our team found that horizontal slide was also easier to complete than the other methods. The horizontal slide best limited cervical spine motion and may be the most helpful for minimizing secondary injury based on the study findings.

Controlled Laboratory Comparison Study of Motion With Football Equipment in a Destabilized Cervical Spine: Three Spine-Board Transfer Techniques.

BACKGROUND: Numerous studies have shown that there are better alternatives to log rolling patients with unstable spinal injuries, although this method is still commonly used for placing patients onto a spine board. No previous studies have examined transfer maneuvers involving an injured football player with equipment in place onto a spine board. PURPOSE: To test 3 different transfer maneuvers of an injured football player onto a spine board to determine which method most effectively minimizes spinal motion in an injured cervical spine model. STUDY DESIGN: Controlled laboratory study. METHODS: Five whole, lightly embalmed cadavers were fitted with shoulder pads and helmets and tested both before and after global instability was surgically created at C5-C6. An electromagnetic motion analysis device was used to assess the amount of angular and linear motion with sensors placed above and below the injured segment during transfer. Spine-boarding techniques evaluated were the log roll, the lift and slide, and the 8-person lift. RESULTS: The 8-person lift technique resulted in the least amount of angular and linear motion for all planes tested as compared with the lift-and-slide and log-roll techniques. This reached statistical significance for lateral bending (P = .031) and medial-lateral translation (P = .030) when compared with the log-roll maneuver. The lift-and-slide technique was significantly more effective at reducing motion than the log roll for axial rotation (P = .029) and lateral bending (P = .006). CONCLUSION: The log roll resulted in the most motion at an unstable cervical injury as compared with the other 2 spine-boarding techniques examined. The 8-person lift and lift-and-slide techniques may both be more effective than the log roll at reducing unwanted cervical spine motion when spine boarding an injured football player. Reduction of such motion is critical in the prevention of iatrogenic injury.

Glenohumeral Joint Pain Referral Patterns: A Descriptive Study.

BACKGROUND: Pain diagrams are a useful tool to help physicians understand the varying presentation patterns of specific pain generators. This study is the first to describe the potential pain patterns of the glenohumeral joint (GHJ) based on responses to diagnostic image-guided GHJ injections. PURPOSE: To determine potential GHJ pain referral patterns. METHODS: 162 consecutive patients undergoing 168 GHJ injections recorded their preprocedure pain scores and drew accurate pain diagrams prior to undergoing fluoroscopically guided GHJ injections with local anesthetic. Postprocedure pain scores were recorded and those with complete relief were considered responders. Pain diagrams were overlaid via computer software to facilitate analysis and a composite pain map. A responder composite was also compared with a nonresponder composite. RESULTS: The GHJ was shown to cause pain in traditionally localized areas of the anterior and/or posterior shoulder and upper arm regions in 100% of patients who experienced complete pain relief after injection. Among 100% responders, 18% had neck pain and 6% had scapular pain. Pain was shown to radiate distally, with anterior forearm pain in 9%, posterior forearm pain in 8%, and hand pain in 9%. No patients with pain both in the medial neck and below the elbow were found to be 100% responders. Similarly, no patients were 100% responders if they had pain in the medial scapula and below the elbow, or medial scapula and medial neck. CONCLUSIONS: Anterior or posterior shoulder and upper arm pain, or a combination of the two, is the most common pain referral area from a symptomatic shoulder joint. Referral to the lateral neck, in combination with shoulder pain, was occasionally seen. Pain referral to the forearm and hand was less common. Rarely did a symptomatic shoulder joint refer pain to the scapula or to the medial neck.

Comparison of cannulated screws with FiberWire or stainless steel wire for patella fracture fixation: A pilot study.

PURPOSE: This pilot study tested whether FiberWire provides similar protection to steel wire against repair displacement in patella fractures. METHODS: Thirteen cadaver knees were cyclically loaded with 10 cycles (0-90° flexion) and fracture displacement was recorded. Fixation methods were also tested in load to failure (>3 mm displacement). RESULTS: There was no difference between wire types in fracture displacement (1.4 mm ± 0.33 mm vs 1.2 mm ± 0.34 mm, respectively; p = 0.418) or in the load to failure (714.7 N ± 110.9 N vs 744.5 N ± 92.8 N, respectively; p = 0.360). CONCLUSION: FiberWire provides similar protection to steel wire against repair displacement after fixation of patellar fractures.

In-vivo three-dimensional knee kinematics during daily activities in dogs.

The canine knee is morphologically similar to the human knee and thus dogs have been used in experimental models to study human knee pathology. To date, there is limited data of normal canine 3D knee kinematics during daily activities. The objective of this study was to characterize 3D in-vivo femorotibial kinematics in normal dogs during commonly performed daily activities. Using single-plane fluoroscopy, six normal dogs were imaged performing walk, trot, sit, and stair ascent activities. CT-generated bone models were used for kinematic measurement using a 3D-to-2D model registration technique. Increasing knee flexion angle was typically associated with increasing tibial internal rotation, abduction and anterior translation during all four activities. The precise relationship between flexion angle and these movements varied both within and between activities. Significant differences in axial rotation and coronal angulation were found at the same flexion angle during different phases of the walk and trot. This was also found with anterior tibial translation during the trot only. Normal canine knees accommodate motion in all planes; precise kinematics within this envelope of motion are activity dependent. This data establishes the characteristics of normal 3D femorotibial joint kinematics in dogs that can be used as a comparison for future studies.

Shoulder arthroplasty and its effect on strain in the subscapularis muscle.

BACKGROUND: Increasing the thickness of the prosthetic humeral head on subscapularis strain in patients undergoing total shoulder arthroplasty has not been elucidated. The optimal postoperative rehabilitation for total shoulder arthroplasty that does not place excessive strain on the subscapularis is not known. We hypothesize that the use of expanded non-anatomic humeral heads during shoulder replacement will cause increased tension in the repaired subscapularis. We identified a recommended passive range of motion program without invoking an increase in tension in the repaired subscapularis, and determined the impact of the thickness of the humeral head on subscapularis strain. METHODS: Eight fresh-frozen, forequarter cadaver specimens were obtained. An extended deltopectoral incision was performed and passive range-of-motion exercises with the following motions were evaluated: external rotation, abduction, flexion, and scaption. An optical motion analysis system measured strain in the subscapularis. The same protocol was repeated after performing a subscapularis osteotomy and after placement of an anatomic hemiarthroplasty of three different thicknesses. FINDINGS: For abduction and forward flexion, we observed a trend of decreasing strain of the subscapularis, as the laxity is removed with increasing humeral head component thickness. With the short humeral head, strain was similar to native joint with passive scaption and flexion but not with external rotation or abduction. INTERPRETATION: The passive range of motion that minimizes tension on the subscapularis is forward flexion and scaption. Therefore, passive forward flexion or scaption does not need to be limited, but external rotation should have passive limits and abduction should be avoided.

Metabolic, cardiopulmonary, and gait profiles of recently injured and noninjured runners.

OBJECTIVE: To examine whether runners recovering from a lower body musculoskeletal injury have different metabolic, cardiopulmonary, and gait responses compared with healthy runners. DESIGN: Cross-sectional study. SETTING: Research laboratory at an academic institution. METHODS: Healthy runners (n = 50) were compared with runners who were recently injured but had returned to running (n = 50). Both groups were participating in similar cross-training modalities such as swimming, weight training, biking, and yoga. Running gait was analyzed on a treadmill using 3-dimensional motion capture, and metabolic and cardiopulmonary measures were captured simultaneously with a portable metabolic analyzer. MAIN OUTCOME MEASURES: Rate of oxygen consumption, heart rate, ventilation, carbohydrate and fat oxidation values, gait temporospatial parameters and range of motion measures (ROM) in the sagittal plane, energy expenditure, and vertical displacement of the body's center of gravity (COG). RESULTS: The self-selected running speed was different between the injured and healthy runners (9.7 ± 1.1 km/h and 10.6 ± 1.1 km/h, respectively; P = .038). No significant group differences were noted in any metabolic or cardiopulmonary variable while running at the self-selected or standard speed (13.6 km/h). The vertical displacement of the COG was less in the injured group (8.4 ± 1.4 cm and 8.9 ± 1.4, respectively; P = .044). ROM about the right ankle in the sagittal plane at the self-selected running speed during the gait cycle was less in the injured runners compared with the healthy runners (P < .05). CONCLUSIONS: Runners with a recent lower body injury who have returned to running have similar cardiopulmonary and metabolic responses to running as healthy runners at the self-selected and standard speeds; this finding may be due in part to participation in cross-training modes that preserve cardiopulmonary and metabolic adaptations. Injured runners may conserve motion by minimizing COG displacement and ankle joint ROM during a gait cycle.

Glenoid fracture after arthroscopic Bankart repair: case series and biomechanical analysis.

To examine whether anchors used in arthroscopic Bankart repair increased the risk of subsequent fracture, six intact polyurethane scapulae and six with three 3.0-mm suture anchors placed along the anteroinferior glenoid were compared. An axial load of 1 mm/s was applied to the anteroinferior glenohumeral joint with a prosthetic humeral head. Outcome measures were force needed for initial fracture and catastrophic failure, percent of anterior glenoid bone loss, and fracture length. With the numbers available, no significant differences could be detected between groups in yield load or maximum load. The anchor group had a significantly larger percentage of bone loss (p < .01) and fracture length (p < .01) compared to the intact group. In this study, anchors did not decrease force needed to fracture but did lead to significantly larger fractures of the anterior glenoid during a simulated dislocation event. Further study using various anchors and techniques is warranted.

Motion produced in the unstable cervical spine by the HAINES and lateral recovery positions.

STUDY OBJECTIVE: To compare the amount of segmental vertebral motion produced with the lateral recovery position and the HAINES technique when performed on cadavers with destabilized cervical spines. METHODS: The cervical spines of 10 cadavers were surgically destabilized at the C5-C6 vertebral segment. Sensors from an electromagnetic tracking device were affixed to the vertebrae in question to monitor the amount of anterior/posterior, medial/lateral, and distraction/compression linear motion produced during the application of the two study techniques. RESULTS: The statistical analysis of linear motion data did not reveal any significant differences between the two recovery positions. CONCLUSION: At this time, no single version of the recovery position can be endorsed for the spine-injured trauma patient. More research is needed to fully ascertain the safety of commonly used recovery positions.

Trainee involvement in transforaminal epidural steroid injections associated with increased incidence of vasovagal reactions.

OBJECTIVES: To evaluate whether trainee involvement (resident and fellow) during transforaminal epidural steroid injections (TFESI) results in greater rates of vasovagal reactions. DESIGN: Retrospective study on consecutive patients. SETTING: Single academic medical center with multiple attending physicians and trainees. PARTICIPANTS: A total of 2642 consecutive subjects undergoing 4482 TFESI were analyzed from March 8, 2004, to January 30, 2009. MAIN OUTCOME MEASURES: The Pearson χ(2) test was used to determine the relationship between vasovagal reactions and level of trainee involvement. RESULTS: A total of 4482 TFESIs were performed, with 157 (3.5%) of procedures complicated by a vasovagal reaction. An attending physician performed 2884 (64.3%) procedures without trainee involvement, with only 79 (2.7%) vasovagal reaction noted. A fellow was involved in 723 (16.1%) procedures, with 30 (4.1%) noted to have a vasovagal reaction. A resident was involved in 875 (19.5%) procedures, with 48 (5.5%) having a vasovagal reaction. Overall, trainees were involved in 1598 (35.7%) cases, of which 78 (4.9%) were complicated by vasovagal reaction. When a trainee was involved in the case, there was a greater incidence of vasovagal episodes (P < .001, χ(2) = 16.047). Although there was a trend towards greater vasovagal rates with residents over fellows, this did not reach statistical difference. CONCLUSIONS: Vasovagal reactions can occur with spine injection procedures and may result in premature procedure termination or other adverse events. Although this retrospective study has significant potential for bias, it appears that trainee involvement in a TFESI is associated with a greater incidence of vasovagal reaction (P < .001, χ(2) = 16.047).

Accuracy of noninvasive, single-plane fluoroscopic analysis for measurement of three-dimensional femorotibial joint poses in dogs.

OBJECTIVE: To compare accuracy of a noninvasive single-plane fluoroscopic technique with radiostereometric analysis (RSA) for determining 3-D femorotibial poses in a canine cadaver with normal stifle joints. SAMPLE: Right pelvic limb from a 25-kg adult mixed-breed dog. PROCEDURES: A CT scan of the limb was obtained before and after metal beads were implanted into the right femur and tibia. Orthogonal fluoroscopic images of the right stifle joint were acquired to simulate a biplanar fluoroscopic acquisition setup. Images were obtained at 5 flexion angles from 110° to 150° to simulate a gait cycle; 5 cycles were completed. Joint poses were calculated from the biplanar images by use of RSA with CT-derived beaded bone models and compared with measurements obtained by use of CT-derived nonbeaded bone models matched to single-plane, lateral-view fluoroscopic images. Single-plane measurements were performed by 2 observers and repeated 3 times by the primary observer. RESULTS: Mean absolute differences between the single-plane fluoroscopic analysis and RSA measurements were 0.60, 1.28, and 0.64 mm for craniocaudal, proximodistal, and mediolateral translations, respectively, and 0.63°, 1.49°, and 1.58° for flexion-extension, abduction-adduction, and internal-external rotations, respectively. Intra- and interobserver repeatability was strong with maximum mean translational and rotational SDs of 0.52 mm and 1.36°, respectively. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that single-plane fluoroscopic analysis performed by use of CT-derived bone models is a valid, noninvasive technique for accurately measuring 3-D femorotibial poses in dogs.

Accuracy of noninvasive, single-plane fluoroscopic analysis for measurement of three-dimensional femorotibial joint poses in dogs treated by tibial plateau leveling osteotomy.

OBJECTIVE: To compare accuracy of a noninvasive single-plane fluoroscopic analysis technique with radiostereometric analysis (RSA) for determining 3-D femorotibial poses in a canine cadaver stifle joint treated by tibial-plateau-leveling osteotomy (TPLO). SAMPLE: Left pelvic limb from a 25-kg adult mixed-breed dog. PROCEDURES: A CT scan of the left pelvic limb was performed. The left cranial cruciate ligament was transected, and a TPLO was performed. Radiopaque beads were implanted into the left femur and tibia, and the CT scan was repeated. Orthogonal fluoroscopic images of the left stifle joint were acquired at 5 stifle joint flexion angles ranging from 110° to 150° to simulate a gait cycle; 5 gait cycles were completed. Joint poses were calculated from the biplanar images by use of a digitally modified RSA and were compared with measurements obtained by use of hybrid implant-bone models matched to lateral-view fluoroscopic images. Single-plane measurements were performed by 2 observers and repeated 3 times by the primary observer. RESULTS: Mean absolute differences between results of the single-plane fluoroscopic analysis and modified RSA were 0.34, 1.05, and 0.48 mm for craniocaudal, proximodistal, and mediolateral translations, respectively, and 0.56°, 0.85°, and 1.08° for flexion-extension, abduction-adduction, and internal-external rotations, respectively. Intraobserver and interobserver mean SDs did not exceed 0.59 mm for all translations and 0.93° for all rotations. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that single-plane fluoroscopic analysis by use of hybrid implant-bone models may be a valid, noninvasive technique for accurately measuring 3-D femorotibial poses in dogs treated with TPLO.

Application of the fulcrum axis to estimate the central scapular axis.

BACKGROUND: Glenoid resurfacing can be a challenging component of total shoulder arthroplasty when significant glenoid retroversion or deformity is present. The purpose of this study was to determine whether a newly designed glenoid-targeting guide using the parallel relationship between glenoid version and an anatomic fulcrum axis could accurately estimate the central axis of the scapula. MATERIALS AND METHODS: Three orthopaedic surgeons used a newly designed glenoid-targeting guide to place a guide pin into 6 normal Sawbones scapulae (Pacific Research Laboratories, Vashon Island, WA, USA), 6 retroverted Sawbones scapulae, 8 cadaveric scapular specimens, and 5 cadaveric shoulder specimens. Angles of deviation from the central scapular axis and from perpendicular to the fulcrum axis were measured. RESULTS: The mean pin deviation angle from the central scapular axis and the mean fulcrum deviation angle for the normal Sawbones scapulae were 1.7° (SD, 1.2°) and 2.1° (SD, 1.5°), respectively. For altered retroverted Sawbones scapulae, the mean deviation angles were 1.8° (SD, 1.2°) and 2.8° (SD, 1.6°), respectively. The combined mean pin deviation angle and mean fulcrum deviation angle for cadaveric shoulder specimens were 2.8° (SD, 3.3°) and 2.3° (SD, 2.3°), respectively. The surgeons' results did not differ significantly whether using Sawbones models, cadaveric scapular specimens, or cadaveric shoulder specimens. CONCLUSION: A glenoid-targeting guide based on the relationship of the fulcrum axis and glenoid version can be used to accurately estimate the central scapular axis. Such a tool can be accurate and reliable intraoperatively, aiding in glenoid component placement to within 5° of ideal version, irrespective of glenoid deformity.

Biomechanical comparison of two implants for the stabilization of incomplete ossification of the humeral condyle lesions in dogs.

OBJECTIVE: To compare biomechanical properties of (1) 4.5 mm cortical screws and Fitz Fenestrated Tubular Transcondylar (F2T2) screws; (2) normal humeri and humeri with an intracondylar osteotomy; and (3) humeri with an intracondylar osteotomy stabilized with either a 4.5 mm cortical screw or a F2T2 screw. STUDY DESIGN: Cadaveric biomechanical assessment. SAMPLE POPULATION: 4.5 mm cortical screws (n = 10), 5.85 mm F2T2 screws (n = 10), and paired dog humeri (n = 40). METHODS: Cortical and F2T2 screws were loaded to failure in 3-point bending. Ten pairs of humeri with or without an intracondylar osteotomy were axially loaded to failure. Ten additional pairs of humeri with an intracondylar osteotomy were alternately stabilized with a positional cortical or F2T2 screw and axially loaded to failure. RESULTS: Mean stiffness, yield load, and failure load was significantly greater (P < .001) for the F2T2 screws compared with cortical screws as well as for intact humeri compared with humeri with an intracondylar osteotomy (P < .001). There were no significant differences in mean stiffness (P = .59), yield load (P = .31), or failure load (P = .24) between humeri with stabilized intracondylar osteotomy. CONCLUSION: Isolated F2T2 screws have superior mechanical properties to 4.5 mm cortical screws when loaded in 3-point bending. Intracondylar osteotomy adversely affected humeral mechanical integrity. Osteotomized humeri stabilized by either screw had comparable mechanical properties.