OBJECTIVES: Comparison of range of motion measurements by 3 types of investigators with different levels and types of training using three different measurement techniques. The study hypothesis was that the accuracy and precision of range of motion measurements would vary based on (1) the level and type of experience of the investigator and (2) the measurement technique used. DESIGN/SETTING: Descriptive laboratory study. PARTICIPANTS: Ten fresh frozen cadavers (20 upper and 20 lower extremities). INTERVENTIONS: Shoulder, elbow, hip, and knee motion were measured using 3 different measurement techniques (digital photography, goniometry, and visual estimation) by 3 groups of investigators (attending orthopedic surgeons, physical therapists, and residents). Accuracy was defined by the difference from the reference standard (motion capture analysis), whereas precision was defined by the proportion of measurements within either 5 or 10 of the reference standard. Analysis of variance, t-tests, and chi-squared tests were used. RESULTS: Statistically significant (p < 0.05) differences in accuracy were found for hip flexion, abduction, internal rotation, external rotation, and knee flexion. However, none of these differences met the authors' defined clinical significance (maximum difference 3). Precision was significantly (p < 0.05) different for elbow extension, hip flexion, abduction, internal rotation, external rotation, and knee flexion. CONCLUSION: This study found that clinically accurate measurements of shoulder, elbow, hip, and knee motion are obtained regardless of technique used or the investigators' level and type of experience. Precision was equivalent for all shoulder motions, elbow flexion, and knee extension, but varied by as much as 7% to 28% between groups for all other motions.(C) 2017 Association of Program Directors in Surgery. Published by Elsevier Inc. All rights reserved.

Background: Accurate measurements of shoulder and elbow motion are required for the management of musculoskeletal pathology. The purpose of this investigation was to compare three techniques for measuring motion. The authors hypothesized that digital photography would be equivalent in accuracy and show higher precision compared to the other two techniques. Methods: Using infrared motion capture analysis as the reference standard, shoulder flexion/abduction/internal rotation/external rotation and elbow flexion/extension were measured using visual estimation, goniometry, and digital photography on 10 fresh frozen cadavers. These measurements were performed by three physical therapists and three orthopaedic surgeons. Accuracy was defined by the difference from the reference standard (motion capture analysis), while precision was defined by the proportion of measurements within the authors' definition of clinical significance (10 degrees for all motions except for elbow extension where 5 degrees was used). Analysis of variance (ANOVA), t-tests, and chi-squared tests were used. Results: Although statistically significant differences were found in measurement accuracy between the three techniques, none of these differences met the authors' definition of clinical significance. Precision of the measurements was significantly higher for both digital photography (shoulder abduction [93% vs. 74%, p < 0.001], shoulder internal rotation [97% vs. 83%, p = 0.001], and elbow flexion [93% vs. 65%, p < 0.001]) and goniometry (shoulder abduction [92% vs. 74%, p < 0.001] and shoulder internal rotation [94% vs. 83%, p = 0.008]) than visual estimation. Digital photography was more precise than goniometry for measurements of elbow flexion only [93% vs. 76%, p < 0.001]. Conclusions: There was no clinically significant difference in measurement accuracy between the three techniques for shoulder and elbow motion. Digital photography showed higher measurement precision compared to visual estimation for shoulder abduction, shoulder internal rotation, and elbow flexion. However, digital photography was only more precise than goniometry for measurements of elbow flexion. Overall digital photography shows equivalent accuracy to visual estimation and goniometry, but with higher precision than visual estimation. (C) 2017 Published by Elsevier B.V. on behalf of The Japanese Orthopaedic Association.

Background: Hip “microinstability” is commonly cited as the cause of symptoms that occur in the presence of translation of the femoral head away from conformity with the acetabular fossa. However, there is still no consistent objective criteria defining its presence and biomechanical basis. One hypothesis is that abnormal motion of the articular surfaces occurs because of capsular laxity, ultimately leading to clinical symptoms. Purpose: To determine the relationship between capsular laxity and abnormal rotation and translation of the hip. Study Design: Controlled laboratory study. Methods: Eight cadaveric hips were dissected down to the capsule and mounted in a customized multiaxial hip activity simulator. Each specimen was loaded with 5 N·m of internal and external rotational torque in full extension and 0°, 30°, 60°, and 90° of flexion. During testing, the relative position and rotation of the femur and the pelvis were monitored in real time with a 6-camera motion analysis system. The testing was repeated after capsular laxity was generated by placing a regular array of incisions (“pie crusting”) in the iliofemoral, pubofemoral, and ischiofemoral ligaments. Joint rotation and femoral head translation were calculated with specimen-specific models. A hip microinstability index was defined as the ratio between the length of the locus of the femoral head center and the radius of the femoral head during rotation from extension to 90° of flexion. Results: In intact hips, the components of femoral head translation were within 0.5 mm in positions close to neutral (<30° of flexion). Capsular modification led to significant increases in internal and external rotation ( P < .01) and in the translation of the femoral head center at different positions ( P < .05). Compared with intact hips, the femoral head was inferiorly displaced during external rotation and anteroinferiorly during internal rotation. The length of the locus of the femoral head center increased from 3.61 ± 1.30 mm to 5.35 ± 1.83 mm for external rotation ( P < .05) and from 6.24 ± 1.48 mm to 8.21 ± 1.42 mm for internal rotation ( P < .01). The correlations between rotational laxity and the total translation of the femoral head were not significant, with coefficients of 0.093 and 0.006 in external and internal rotation, respectively. In addition, the hip microinstability index increased from 0.40 ± 0.08 for intact hips to 0.55 ± 0.09 for modified hips ( P < .01). Conclusion: The native hip approximates a concentric ball-and-socket joint within 30° of flexion; however, beyond 30° of flexion, the femoral head translation reached as high as 4 mm. Capsular laxity leads to microinstability of the hip, as indicated by significantly increased joint rotations and femoral head translations and an abnormal movement path of the femoral head center. However, there was no correlation between rotational laxity and the increase in femoral head translation. Clinical Relevance: Capsular laxity alters normal kinematics (joint rotation and femoral head translation) of the hip, potentially leading to abnormal femoral-acetabular contact and joint degeneration.

IntroductionTribo-chemical damage of modular taper junctions is often observed at revision THR and may be a contributing factor to chronic inflammation of peri-prosthetic tissues through generation of chromium rich corrosion products. At the time of revision, surgeons may elect to leave the primary femoral stem in situ and replace the original femoral head with a new component. This decision is based on the assumption that the interface formed between the original trunnion and the new bore is capable of withstanding the loads and torques applied during use, without failure of the new interface. This study was performed to determine the extent to which the mechanical properties of the taper interface are degraded with varying degrees of tribo-chemical damage secondary to prior implantation.Materials and MethodsFifteen CoCr femoral heads (DePuy: 6, Smith & Nephew: 5; Zimmer: 4) were retrieved at revision THR and were examined with stereomicroscopy. The surface of each bore was scored for the presence of fre...

IntroductionMechanically-assisted corrosion of the head-neck junction present a dilemma to surgeons at revision THR whenever the femoral component is rigidly fixed to the femur. Many remove the dam...

INTRODUCTIONCementless tibial trays commonly fail through failure of fixation due to excessive interface motion. However, the specific combination of axial and shear forces precipitating implant fa...

Introduction:Despite all the attention to new technologies and sophisticated implant designs, imperfect surgical technique remains a obstacle to improving the results of total knee replacement (TKR...

This study demonstrates that digital photography does increase the accuracy of measuring range of motion in the upper extremity but no more than assessment with a goniometer. There is a similar statistically significant reduction in outliers with either photography or use of goniometer when compared to visual assessment alone.

Background Accurate measurements of knee and hip motion are required for management of musculoskeletal pathology. The purpose of this investigation was to compare three techniques for measuring motion at the hip and knee. The authors hypothesized that digital photography would be equivalent in accuracy and show higher precision compared to the other two techniques. Methods Using infrared motion capture analysis as the reference standard, hip flexion/abduction/internal rotation/external rotation and knee flexion/extension were measured using visual estimation, goniometry, and photography on 10 fresh frozen cadavers. These measurements were performed by three physical therapists and three orthopaedic surgeons. Accuracy was defined by the difference from the reference standard, while precision was defined by the proportion of measurements within either 5° or 10°. Analysis of variance (ANOVA), t-tests, and chi-squared tests were used. Results Although two statistically significant differences were found in measurement accuracy between the three techniques, neither of these differences met clinical significance (difference of 1.4° for hip abduction and 1.7° for the knee extension). Precision of measurements was significantly higher for digital photography than: (i) visual estimation for hip abduction and knee extension, and (ii) goniometry for knee extension only. Conclusions There was no clinically significant difference in measurement accuracy between the three techniques for hip and knee motion. Digital photography only showed higher precision for two joint motions (hip abduction and knee extension). Overall digital photography shows equivalent accuracy and near-equivalent precision to visual estimation and goniometry.

INTRODUCTION Cementless tibial trays commonly fail through failure of fixation due to excessive interface motion. However, the specific combination of axial and shear forces precipitating implant failure is unknown. This has led to generic loading profiles approximating walking to perform pre-clinical assessment of new designs, even though telemetric data demonstrates that much larger forces and moments are generated during other functional activities. This study was undertaken to test the hypotheses: (i) interface motion of cementless tibial trays varies as a function of specific activities, and (ii) the response of the cementless tibial interface to walking loading is not representative of other functional activities.MATERIALS and METHODS Six fresh-frozen cadaveric tibias were tested using a custom designed functional activity simulator after implantation of a posterior stabilized total knee replacement (NexGen LPS, Zimmer, Warsaw IN). Activity scenarios were selected using force (Fx, Fy, Fz) and moment (Mx, My, Mz) data from patients with instrumented tibial trays (E-tibia) published by Bergmann et al. A pattern of black and white spray paint was applied to the surface of the specimen including the tibial tray and bone. Each specimen was preconditioned through application of a vertical load of 1050N for 500 cycles of flexion-extension from 5–100°. Following preconditioning, each tibia was loaded using e-tibia values of forces and moments for walking, stair-descent, and sit-to-stand activities. The differential motion of the tibial tray and the adjacent bony surface was monitored using digital image correlation (DIC) (resolution: 1–2 microns in plane; 3–4 microns out-of-plane). Four pairs of stereo-images of the tray and tibial bone were prepared at sites around the circumference of the construct in both the loaded and unloaded conditions: (i) before and after pre-conditioning and (ii) before and after the 6 functional loading profiles. The images were processed to provide circumferential measurements of interface motion during loading. Differences in micromotion and migration were evaluated statistically using step-wise multivariate regression.RESULTS The average 3D motion of the tibial tray varied extensively with the loading conditions corresponding to the different activities (Figs 1,2). The largest 3D motion was seen during the first peak of stair descent (86.6±8.0µm) and the first peak of walking (83.1±10.2µm; p=0.5516), both of which were characterized by large adduction moments (18.5 and 19.1Nm respectively). The differences between 3D micromotion of all other pairs of activities were statistically significant (pu003c0.0001 to p=0.0127). Each of the 6 loading scenarios simulated elicited a different combination of components of implant displacement at the cementless interface. The largest differences in interface motion were observed between the first peak of walking and all of the other loading modes with reversal of the direction of the SI (p=0.3828), AP (pu003c0.0001) and ML (pu003c0.0001) components of tray displacement (Figs. 2,3).CONCLUSIONS 1. Magnitude and direction of interface motion between the tibia and a cementless tibial tray vary with specific loading patterns. 2. Interface motion observed during loading conditions representative of walking are not indicative of the stability of cementless implant fixation when exposed to loading conditions generated by other activities.For figures/tables, please contact authors directly.

Introduction Mechanically-assisted corrosion of the head-neck junction present a dilemma to surgeons at revision THR whenever the femoral component is rigidly fixed to the femur. Many remove the damaged femoral head, clean the femoral taper and fix a new head in place to spare the patient the risks associated with extraction and replacement of the well-functioning femoral stem. This study was performed to answer these research questions: Will new metal heads restore the mechanical integrity of the original modular junction after impaction on corroded tapers? Which variables affect the stability of the new interface created at revision THR? Materials and Methods Twenty-two tapers (CoCr, n=12; TiAlV, n=10) were obtained for use in this study. Ten stems were in pristine condition, while 12 stems had been retrieved at revision THR and with corrosion damage to the trunnion (Goldberg scale 4). Twenty-two new metal heads were obtained for use in the study, each matching the taper and manufacturer of the original component. The following test states were performed using a MTS Machine: 1. Assembly, 2. Disassembly, 3. Assembly, 4. Toggling and 5. Disassembly. All head assemblies were performed wet using 50% calf serum in accordance to ISO 7206-10. During toggling, each specimen9s loading axis was aligned 25° to the trunnion axis in the frontal plane and 10° in the sagittal plane (Figure 1). Toggling was performed at 1Hz for 2,000 cycles with a sinusoidal loading function (230N–4300N). During loading, 3D motion of the head-trunnion junction was measured using a custom jig rigidly attached to the head and the neck of each prosthesis. Relative displacement of the head with respect to the neck was continuously monitored using 6 high resolution displacement transducers with an accuracy of ±0.6µm. Displacement data was independently validated using FEA models of selected constructs. Results The average micromotion of the head vs trunnion interface was greatest at the start of loading and stabilized after approximately 50 loading cycles at an average of 30.6±3.2µm (Figure 2). For CoCr couples, interface motion dropped by 17% when a pristine head was mounted on a corroded stem compared to a new stem (25.7±2.7µm (pristine stem), vs. 30.1±4.6µm (corroded stem), p= 0.4023) (Figure 3). However, addition of a new CoCr head with a corroded titanium stem led to an 73% increase in interface motion after assembly with a new CoCr head (Corroded: 43.4±9.8µm, Pristine: 25.2±7.0µm, p=0.1661). The resistance to head-neck disruption was 15% higher in TIALV/CoCr couples compared to CoCr/CoCr (TiAlV: 2558 ±63N, CoCr: 2226±99N, p=0.0111) and was not affected by the presence of corrosion of the trunnion (1% loss of strength in each case). Discussion Corrosion at the trunnion does not disrupt the mechanical integrity of the junction when a CoCr head is replaced on a CoCr taper. We are less sure about the mechanical integrity of a TiAlV taper demonstrated by a trend towards increased micromotion at this junction. Further work is required to better elucidate the role of dissimilar metals in the mechanical integrity of the head-neck junction.

BACKGROUND:Meniscal root tears are an increasingly recognized subset of meniscal injury. The menisci are critical secondary stabilizers of the anterior cruciate ligament (ACL). The kinematic effect of lateral meniscus posterior root tear in the setting of ACL injury is not known.PURPOSE/HYPOTHESIS:The purpose of this study was to determine the effect of tear of the lateral meniscal root on stability of the ACL-deficient knee. The hypothesis was that disruption of the lateral meniscal root will further destabilize the ACL-deficient knee during a simulated pivot shift.STUDY DESIGN:Controlled laboratory study.METHODS:Pivot-shift testing of 8 fresh-frozen cadaveric knees was performed after attachment of photoreflective flags and preparation of CT scans. Each knee was mounted in a custom activity simulator and dynamically loaded from 15° to 90° of flexion with all the permutations of the following: iliotibial band force (50, 75, 100, 125, 150, and 175 N), internal rotation moments (1, 2, and 3 N·m), and valgus moments (5 and 7 N·m). In addition, anterior stability tests were performed by applying a 90-N anterior force to the tibia at flexion angles of 15°, 30°, 45°, 60°, and 90°. During each test, the anterior tibial translation and rotation of the tibia were measured with a high-resolution multiple infrared camera motion analysis system for the following 3 conditions: ACL-intact (ACL-I), ACL-deficient (ACL-D), and ACL-deficient/lateral meniscal posterior root avulsion (ACL-D/LMR-A).RESULTS:A pivot-shift phenomenon was observed in the ACL-D and ACL-D/LMR-A conditions. The mean tibial translation of the lateral tibial condyle during the pivot-shift maneuver was 2.62 ± 0.53 mm for the ACL-I knees, 6.01 ± 0.51 mm for the ACL-D knees (P value vs. intact: .0005), and 8.13 ± 0.75 mm for the ACL-D/LMR-A knees (P value vs intact: <.0001). During the pivot-shift maneuver, translation was significantly increased in the ACL-D/LMR-A condition compared with the ACL-D condition (P = .0146). Compared with the intact group, anterior tibial translation during the Lachman maneuver also increased at 30° and 90° of flexion in the ACL-D group (P < .0001) and the ACL-D/LM group (P < .0001). No statistically significant difference was found between the ACL-D and ACL-D/LMR-A groups during the Lachman maneuver at 30° and 90° (P = .16 and .72, respectively).CONCLUSION:A tear of the lateral meniscal posterior root further reduces the stability of the ACL-deficient knee during rotational loading.CLINICAL RELEVANCE:This study shows that lateral meniscal root injury further destabilizes the ACL-deficient knee and thus advances the concept that the lateral meniscus is a secondary stabilizer of the knee under pivot-shift loading. In the absence of stronger evidence, the study data suggest a rationale for surgical repair of lateral meniscal root tears encountered in the setting of ACL tears.

Background Flexor tendon repair in zone II remains a vexing problem. Repair techniques have been developed to strengthen and optimize the number of core strands crossing a repair. A polyamide looped suture doubles the number of core strands for every needle path. This simplifies repairs, but the knot remains a potential weakness. The purpose of our study was to create a biomechanical model used to evaluate the bulky knot of a looped suture as it may be weaker, resulting in greater deformation. Methods Using machined steel rods to hold our suture constructs, we compared four different knot configurations using looped and non-looped sutures in 3-0 and 4-0 varieties using a four-core strand technique. The constructs were tested under increased cyclic loading recording both forces applied and suture construct lengthening (“clinical gapping”) and ultimate breaking strength. Results During continuous periods of cyclic loading, we measured permanent deformation and ultimate breaking strength. Permanent deformation results when there is no recoverable change after force removal defined as a permanent rod separation (or gapping) of 2 mm. Four-strand 3-0 and 4-0 looped sutures failed at 39.9 and 27.1 N faring worse than a four-strand non-looped suture which reached a rod separation of 2 mm at 60.7 and 41.3 N. The ultimate breaking strength demonstrated absolute failure (construct rupture) with the 3-0 looped suture breaking at the knot at 50.3 N and the non-looped suture at 61.5 N. For the 4-0 suture, these values were 32.4 and 41.76 N. Conclusion Within the constraints of this model, a looped suture fared worse than a non-looped suture especially when comparing 4-0 and 3-0 sutures. However, two-knot 3-0 looped suture constructs did resist the force generally accepted as occurring with early non-resistive tendon motion protocols, while two-knot 4-0 looped suture constructs did not. Clinical Relevance This paper provides a description of a model to evaluate various suture materials and knot strengths in isolation of the tendon itself. This allowed us to evaluate mechanical differences between looped and non-looped sutures for polyamide, which are commonly used in flexor tendon repair. These differences between sutures may impact choices for a suture type selected for these repairs.

Introduction: Despite all the attention to new technologies and sophisticated implant designs, imperfect surgical technique remains a obstacle to improving the results of total knee replacement (TKR). On the tibial side, common errors which are known to contribute to post-operative instability and reduced function include internal rotation of the tibial tray, inadequate posterior slope, and excessive component varus or valgus. However, the prevalence of each error in surgeries performed by surgeons and trainees is unknown. The following study was undertaken to determine which of these errors occurs most frequently in trainees acquiring the surgical skills to perform TKR. Materials and Methods: A total of 43 knee replacement procedures were performed by 11 surgical trainees (surgical students, residents and fellows) in a computerized training center. After initial instruction, each trainee performed a series of four TKR procedures in cadavers (n = 2) and bone replicas (n = 2) using a contemporary TKR instrument set and the assistance of an experienced surgical instructor. Prior to each procedure, computer models of each cadaver and/or bone replica tibia were prepared by reconstructing CT scans of each specimen. All training procedures were performed in a navigated operating room using a 12 camera motion analysis system (Motion Analysis Inc.) with a spatial resolution in all three orthogonal directions of ± 0.15 mm. The natural slope, varus/valgus alignment, and axial rotation of the proximal tibial surface were recorded prior to surgery and after placement of the tibial component. For evaluation of all data, acceptable limits for implantation were defined as: posterior slope: 0–10°; varus/valgus inclination of tibial resection: ± 3°; and external rotation: 0–10°. Results: The tibial component was implanted with an average posterior slope of 3.4° ± 3.4°. In 83% of trials, the trainees cut the tibia with less posterior slope than intended (average shortfall: 2.0° ± 4.0°). In 14% of cases the tibial resection sloped anteriorly, whereas in another 5% the posterior slope exceeded 10°. The coronal alignment of the tibial osteotomy averaged 0.1° ± 2.9° of valgus, with 19% of components were implanted in more than 3° of valgus vs. 14% varus (>3°). The average rotational orientation of the tibial component was 5.4° ± 5.3° of external rotation. Overall, 21% of components were placed in internal rotation, and a further 29% in more than 10° of external rotation. Rotational malalignment of the tibial component was the most common error in technique encountered in the study population. Conclusion: 1.Tibial preparation still presents significant difficulty to many less experienced surgeons, despite the use of modern instrumentation and careful didactic instruction. 2.The most prevalent error in tibial preparation in TKR is malrotation of the tibial component, especially in internal rotation. 3.The errors measured in the computerized bioskills lab replicate clinical cases often presenting with symptoms necessitating early revision. 4.Greater attention is needed to training of surgical skills and intraoperative assessment of sources of technical error, such as component position to improve clinical outcomes of TKR.

Purpose: Current mandibular plating systems contain a wide range of plates and screws needed for the treatment of mandibular reconstruction and mandibular fractures. The authors' hypothesis was that a single diameter screw could be used in all applications in a plating system. Therefore, the purpose of this study was to test if the 2.0-mm locking screws could replace the 2.4-mm screws to stabilize a 2.5-mm-thick reconstruction plate in the treatment of mandibular discontinuity.Materials and Methods: Thirty-six fresh human cadaveric mandibles were used: 18 were plated using 2.0-mm locking screws (experimental) and the other 18 were plated using 2.4-mm locking screws (control). Each group was further divided into 3 subgroups based on the site of loading application: the ipsilateral (right) second premolar region, the central incisal region, and the contralateral (left) first molar region. The same ipsilateral (right) mandibular angular discontinuity was created by the same surgeon. The mandible was mounted on a material testing machine. The micromotions between the 2 segments, permanent and elastic displacements, were recorded after incremental ramping loads. The magnitude of screw back-out and the separation between plate and bone were recorded using a laser scanner (resolution, 0.12 mm) before and after the loading applications. The data were processed. Descriptive analyses and a general linear model for repeated measures analysis of variance were performed.Results: There was no statistically significant difference in permanent displacement (mean, 1.16 and 0.82 mm, respectively) between the 2.0-mm and 2.4-mm screw groups. There also was no statistically significant difference in elastic displacement between the 2 groups (mean, 1.48 and 1.21 mm, respectively). Finally, there were no statistically significant differences in screw back-out or separation between plate and bone between the 2 groups. All means for screw back-out and separation between screwand bone for each group were judged within the error of the laser scanning system (< 0.12 mm).Conclusion: One may anticipate that the mechanical functions of the 2.0-mm locking screws are not different from those of the 2.4-mm screws when a 2.5-mm-thick reconstruction plate is used to reconstruct mandibular angular discontinuity. However, further biomechanical studies (ie, fatigue of screws) are warranted before a randomized clinical trial can be conducted to definitively prove that the 2.4-mm screws can be replaced by 2.0-mm screws. (C) 2013 American Association of Oral and Maxillofacial Surgeons

Introduction Tribo-chemical damage of modular taper junctions is often observed at revision THR and may be a contributing factor to chronic inflammation of peri-prosthetic tissues through generation of chromium rich corrosion products. At the time of revision, surgeons may elect to leave the primary femoral stem in situ and replace the original femoral head with a new component. This decision is based on the assumption that the interface formed between the original trunnion and the new bore is capable of withstanding the loads and torques applied during use, without failure of the new interface. This study was performed to determine the extent to which the mechanical properties of the taper interface are degraded with varying degrees of tribo-chemical damage secondary to prior implantation. Materials and Methods Fifteen CoCr femoral heads (DePuy: 6, Smith & Nephew: 5; Zimmer: 4) were retrieved at revision THR and were examined with stereomicroscopy. The surface of each bore was scored for the presence of fretting and corrosion using the grading system of Goldberg et al. Nine additional heads in original (unimplanted) condition (3 per manufacturer) were also selected to act as controls. Each head was manually assembled on a matching unimplanted TiAlV trunnion in a mechanical testing machine (MTS Bionix) and loaded at 500N/sec to a maximum assembly load of 4000N. The head/trunnion specimen was then mounted in a torsional loading fixture and immersed in bovine serum. A cyclic torque was applied to the head with an initial maximum value of 2 Nm. The specimen was unloaded and held for a 30 sec wait period and the torsional loading was repeated to a peak value of 4 Nm. With each torsional cycle the peak torque was increased by 2 Nm until the taper junction underwent rotational failure. During testing, relative motion between the femoral head and the trunnion was measured with a displacement transducer (DVRT-3, MicroStrain, accuracy = ± 0.1%, resolution = 1.5 μm, hysteresis & repeatability = ± 1 μm). A separate disassembly test was performed by first assembling each specimen with 4000N and then applying a distraction force at 0.008 mm/sec until separation. Results The maximum torque applied at 3 μm permanent displacement of the taper junction averaged 13.2 ± 0.7 Nm. This value characterizes the resistance of each taper junction to slippage under repetitive loading. The relationship between the severity of taper corrosion and resistance to torsional displacement was not statistically significant (p = 0.1343). The ultimate torque capacity of the taper junctions averaged 17.1 ± 0.7 Nm and did not vary significantly with corrosion score (p = 0.2317). There was no difference between manufacturers in terms of resistance to torsional displacement, ultimate torque capacity, and disassembly force (1352 ± 114N). Conclusions 1.Slippage of 3 μm at the CoCr-TiAlV taper junction during cyclic loading requires peak torques of only 12–14 Nm. 2.The torsional properties of taper junctions are not significantly degraded in the presence of mild or moderate grades of corrosion damage on the Goldberg scale. 3.This supports the practice of retaining a TiAlV stem and replacing a CoCr head during a revision procedure to avoid disrupting the femoral component.

Twelve total hip arthroplasty procedures were performed in fresh cadaveric specimens via the anterolateral approach using straight 9-cm incisions placed in 2 different locations with respect to anatomical landmarks. During each procedure, the forces applied to the wound edges by each of the hip instruments and the pressures and strains generated along the wound edges were measured. Pressures ranging from 40 to 190 kPa were developed between the retractors and the wound edges during acetabular reaming and femoral rasping. The resulting strain along the wound edges averaged 28% during acetabular reaming and 34% during femoral broaching (P < .0001). Maximum strains were recorded at the ends of each incision and averaged 58% and 61%, respectively (P < .0001). These results were independent of the anatomical placement of the skin incision. In total hip arthroplasty, the mechanical trauma associated with the procedure is primarily determined by the surgical approach to the hip and the properties of the subcutaneous tissues, and not the anatomical location of the skin incision itself.

Purpose This study examined whether there is a difference in external rotation (ER) between type 2 SLAP repairs consisting of anchors placed only posterior to the biceps insertion compared with repairs with an additional anchor placed anterior to the biceps. Methods Seven cadaveric shoulders from donors with a mean age of 39.4 years were tested. Type 2 SLAP lesions were created, followed by a 3-anchor repair: a standard repair with 2 anchors posterior to the biceps plus an additional anchor anterior to the biceps. The specimens were placed on a material testing system machine and rotation was measured under a constant torque. The sutures were then removed sequentially from anterior to posterior during testing. Results The average ER of the intact shoulder was 115.7° ± 2.6°. After SLAP tear creation and cyclic loading, the ER was 118.5° ± 2.6°, which decreased to 116.5° ± 2.6° after repair. This corresponds to a reduction of 2.0° of ER (P < .0001) with the repair. After release of the anterior anchor, the ER increased to 117.9° ± 2.6°, which corresponds to an increase in shoulder motion of 1.4° of ER (P = .0011). Additional release of the middle anchor, leaving only the posterior anchor intact, resulted in 118.0° ± 2.7° of ER, which corresponds to an increase of only 0.1° of ER (P = .7667). Conclusions Following type 2 SLAP repair in the cadaveric shoulder, removing the effect of the anchor anterior to the biceps resulted in a small but statistically significant increase in ER. The anterior anchor had the greatest effect on ER. The presence of 1 or 2 anchors posterior to the biceps did not have a significant effect on rotation. Clinical Relevance When performing SLAP repairs on those in whom even a small loss of ER would be detrimental, such as baseball pitchers, avoidance of the use of an anchor anterior to the biceps should be considered.

Introduction Although the “learning curve” in surgical procedures is well recognized, little data exists documenting the accuracy of surgeons in performing individual steps of orthopedic procedures. In this study we have used a validated computer-based training system to measure variations instrument placement and alignment in TKA, specifically those relating to tibial preparation. Methods Eleven trainees (surgical students, residents and fellows) were recruited to perform a series of 43 knee replacement procedures in a computerized training center. After initial instruction, each trainee performed a series of four TKA procedures in cadavers (n=2) and bone replicas (n=2) using a contemporary TKA instrument set and the assistance of an experienced surgical instructor. The Computerized Bioskills system was utilized to monitor the placement and orientation of the proximal tibial osteotomy and the tibial tray. Results The tibial component was implanted with an average posterior slope of 3.2°±2.7°. In 14% of cases the tibial resection sloped anteriorly, and in another 5%, the posterior slope exceeded 10°. In 83% of trials, the trainees cut the tibia with less posterior slope than intended, ranging from −10.0° to +5.6° (average:−2.0°±4.0°). The average rotational orientation of the tibial component was 5.4°±5.3°of external rotation, however individual values ranged from 7.6°of int rot to 14.4°of ext rot. Overall, 19% of components were placed in internal rotation. Conclusions Tibial preparation still presents significant difficulty to many less experienced surgeons, despite the use of modern instrumentation and careful didactic instruction. The errors measured in the computerized bioskills lab unfortunately replicate clinical cases often presenting with symptoms necessitating early revision,. Greater attention is needed to training of surgical skills and intraoperative assessment of component position to improve clinical outcomes of TKA.

Injuries to the acetabular labrum have been seen in association with femoroacetabular impingement, but recent studies have reported labral pathology in patients with normal hip morphology. The hypothesis of the current study was that labral lesions could occur without femoroacetabular impingement but that labral pathology would occur more commonly and more severely in hip joints that exhibit reduced head-neck offset. The presence, location, and severity of labral injury were recorded in 22 cadaveric specimens. Computed tomography was used to define the anatomic parameters of proximal femoral morphology. Three-dimensional modeling was used to simulate hip positions that typically cause labral impingement, including high flexion and internal rotation. Femoral morphology was compared between specimens with and without labral pathology using descriptive statistics. Labral pathology was seen in 15 of 22 specimens and was located in the anterosuperior portion of the labrum. No difference existed in age, femoral neck shaft angle, anteversion, acetabular depth, head diameter, alpha angle, or beta angle between specimens with and without labral pathology. The severity of labral pathology correlated with the alpha angle of the proximal femur. This study demonstrates that damage to the labrum may occur in hips with normal proximal femur morphology. However, the findings also indicate that the presence of morphologic features that increase the risk of impingement may predispose the hip joint to a characteristic pattern or severity of labral pathology. The results confirm the importance of considering both femoral morphology and athletic-type activities of the hip when determining the mechanism responsible for injury of the acetabular labrum.