Assessing thoraco-pelvic covariation in Homo sapiens and Pan troglodytes: A 3D geometric morphometric approach.

OBJECTIVES: Understanding thoraco-pelvic integration in Homo sapiens and their closest living relatives (genus Pan) is of great importance within the context of human body shape evolution. However, studies assessing thoraco-pelvic covariation across Hominoidea species are scarce, although recent research would suggest shared covariation patterns in humans and chimpanzees but also species-specific features, with sexual dimorphism and allometry influencing thoraco-pelvic covariation in these taxa differently. MATERIAL AND METHODS: N = 30 adult H. sapiens and N = 10 adult Pan troglodytes torso 3D models were analyzed using 3D geometric morphometrics and linear measurements. Effects of sexual dimorphism and allometry on thoraco-pelvic covariation were assessed via regression analyses, and patterns of thoraco-pelvic covariation in humans and chimpanzees were computed via Two-Block Partial Least Squares analyses. RESULTS: Results confirm the existence of common aspects of thoraco-pelvic covariation in humans and chimpanzees, and also species-specific covariation in H. sapiens that is strongly influenced by sexual dimorphism and allometry. Species-specific covariation patterns in chimpanzees could not be confirmed because of the small sample size, but metrics point to a correspondence between the most caudal ribs and iliac crest morphology that would be irrespective of sex. CONCLUSIONS: This study suggests that humans and chimpanzees share common aspects of thoraco-pelvic covariation but might differ in others. In humans, torso integration is strongly influenced by sexual dimorphism and allometry, whilst in chimpanzees it may not be. This study also highlights the importance not only of torso widths but also of torso depths when describing patterns of thoraco-pelvic covariation in primates. Larger samples are necessary to support these interpretations.

Three-dimensional geometric morphometrics of thorax-pelvis covariation and its potential for predicting the thorax morphology: A case study on Kebara 2 Neandertal.

The skeletal torso is a complex structure of outstanding importance in understanding human body shape evolution, but reconstruction usually entails an element of subjectivity as researchers apply their own anatomical expertise to the process. Among different fossil reconstruction methods, 3D geometric morphometric techniques have been increasingly used in the last decades. Two-block partial least squares analysis has shown great potential for predicting missing elements by exploiting the covariation between two structures (blocks) in a reference sample: one block can be predicted from the other one based on the strength of covariation between blocks. The first aim of this study is to test whether this predictive approach can be used for predicting thorax morphologies from pelvis morphologies within adult Homo sapiens reference samples with known covariation between the thorax and the pelvis. The second aim is to apply this method to Kebara 2 Neandertal (Israel, ∼60 ka) to predict its thorax morphology using two different pelvis reconstructions as predictors. We measured 134 true landmarks, 720 curve semilandmarks, and 160 surface semilandmarks on 60 3D virtual torso models segmented from CT scans. We conducted three two-block partial least squares analyses between the thorax (block 1) and the pelvis (block 2) based on the H. sapiens reference samples after performing generalized Procrustes superimposition on each block separately. Comparisons of these predictions in full shape space by means of Procrustes distances show that the male-only predictive model yields the most reliable predictions within modern humans. In addition, Kebara 2 thorax predictions based on this model concur with the thorax morphology proposed for Neandertals. The method presented here does not aim to replace other techniques, but to rather complement them through quantitative prediction of a virtual 'scaffold' to articulate the thoracic fossil elements, thus extending the potential of missing data estimation beyond the methods proposed in previous works.

3D geometric morphometric analysis of variation in the human lumbar spine.

OBJECTIVES: The shape of the human lumbar spine is considered to be a consequence of erect posture. In addition, several other factors such as sexual dimorphism and variation in genetic backgrounds also influence lumbar vertebral morphology. Here we use 3D geometric morphometrics (GM) to analyze the 3D morphology of the lumbar spine in different human populations, exploring those potential causes of variation. MATERIAL AND METHODS: We collected 390 (semi) landmarks from 3D models of the CT scans of lumbar spines of seven males and nine females from a Mediterranean population (Spain, Israel) and seven males and either females from a South African population for geometric morphometric (GM) analysis. We carried out Generalized Procrustes Analysis, Principal Components, and Regression analyses to evaluate shape variation; and complemented these analyses with the Cobb Method. RESULTS: The Mediterranean sample was considerably more lordotic than the South African sample. In both populations, female lumbar spines showed proportionally narrower and more craniocaudally elongated lumbar segments than in males. In addition, the point of maximum curvature in females tended to be located more inferiorly than in males. DISCUSSION: Our results show that sexual dimorphism is an important factor of lumbar spine variation that mainly affects features of lumbar spine robustness (height proportions) and the structure-but not the degree-of its curvature. Differences in lordosis, however, are clearer at the inter-population level. This reflects previous conflicting studies casting doubts on pregnancy as an adaptive factor influencing lordosis. Other factors, for example, shape of the individual lumbar vertebrae and intervertebral discs and their relative proportions within the lumbar spine should be considered when exploring variation in vertebral column morphology.

Three-dimensional morphometrics of thoracic vertebrae in Neandertals and the fossil evidence from El Sidrón (Asturias, Northern Spain).

Well preserved thoracic vertebrae of Neandertals are rare. However, such fossils are important as their three-dimensional (3D) spatial configuration can contribute to the understanding of the size and shape of the thoracic spine and the entire thorax. This is because the vertebral body and transverse processes provide the articulation and attachment sites for the ribs. Dorsal orientation of the transverse processes relative to the vertebral body also rotates the attached ribs in a way that could affect thorax width. Previous research indicates possible evidence for greater dorsal orientation of the transverse processes and small vertebral body heights in Neandertals, but their 3D vertebral structure has not yet been addressed. Here we present 15 new vertebral remains from the El Sidrón Neandertals (Asturias, Northern Spain) and used 3D geometric morphometrics to address the above issues by comparing two particularly well preserved El Sidrón remains (SD-1619, SD-1641) with thoracic vertebrae from other Neandertals and a sample of anatomically modern humans. Centroid sizes of El Sidrón vertebrae are within the human range. Neandertals have larger T1 and probably also T2. The El Sidrón vertebrae are similar in 3D shape to those of other Neandertals, which differ from Homo sapiens particularly in central-lower regions (T6-T10) of the thoracic spine. Differences include more dorsally and cranially oriented transverse processes, less caudally oriented spinous processes, and vertebral bodies that are anteroposteriorly and craniocaudally short. The results fit with current reconstructions of Neandertal thorax morphology.

Comparative morphology of the hominin and African ape hyoid bone, a possible marker of the evolution of speech.

This study examines the morphology of the hyoid in three closely related species, Homo sapiens, Pan troglodytes, and Gorilla gorilla. Differences and similarities between the hyoids of these species are characterized and used to interpret the morphology and affi nities of the Dikika A. afarensis, Kebara 2 Neanderthal, and other fossil hominin hyoid bones. Humans and African apes are found to have distinct hyoid morphologies. In humans the maximum width across the distal tips of the articulated greater horns is usually slightly greater than the maximum length (distal greater horn tip to most anterior point of the hyoid body in the midline). A different pattern is usually found in the African ape hyoids, which have much greater maximum lengths. In humans, the hyoid body is also much more anteroposteriorly shallow in proportion to its height and width, and this is true for all age classes. The Dikika australopithecine hyoid body proportions are chimpanzeelike. A discriminant function analysis, using a larger subadult sample from the three extant species than that reported by Alemseged et al. (2006), confirms this finding. The Kebara hyoid dimensions (body alone, and articulated body and greater horns) are almost all within the observed range for human hyoids. Discriminant functions clearly distinguish human from African ape hyoids and classify the Kebara 2 hyoid as human (confirming the finding of Arensburg et al. 1989). Our virtual dissection of a chimpanzee air sac system shows its subhyoid extension into the dorsal hyoid body. Following Alemseged et al. (2006), the expanded bulla characteristic of the African ape and australopithecine hyoid body is therefore interpreted as refl ecting the presence of such a laryngeal air sac extension. Its absence in the human, Neanderthal, and H. heidelbergensis (Atapuerca SH) hyoids implicates the loss of the laryngeal air sacs as a derived Neanderthal and modern human trait, which evolved no later than the middle Pleistocene. If, as has been argued by de Boer (2012), the loss of the air sac helped to enhance perceptual discrimination of speech sounds, then this derived hyoid morphology can be added to the list of fossil markers of the capacity for speech.

Articulatory capacity of Neanderthals, a very recent and human-like fossil hominin.

Scientists seek to use fossil and archaeological evidence to constrain models of the coevolution of human language and tool use. We focus on Neanderthals, for whom indirect evidence from tool use and ancient DNA appears consistent with an adaptation to complex vocal-auditory communication. We summarize existing arguments that the articulatory apparatus for speech had not yet come under intense positive selection pressure in Neanderthals, and we outline some recent evidence and analyses that challenge such arguments. We then provide new anatomical results from our own attempt to reconstruct vocal tract (VT) morphology in Neanderthals, and document our simulations of the acoustic and articulatory potential of this reconstructed Neanderthal VT. Our purpose in this paper is not to polarize debate about whether or not Neanderthals were human-like in all relevant respects, but to contribute to the development of methods that can be used to make further incremental advances in our understanding of the evolution of speech based on fossil and archaeological evidence.

Reliability of a navigation system for intra-operative evaluation of antero-posterior knee joint laxity.

BACKGROUND: The purpose of this study was to investigate about the reliability of measuring antero-posterior laxity within-subjects for in-vivo studies using a navigation system. METHODS: The analysis was performed by enroling 60 patients undergoing anterior cruciate ligament ACL reconstruction, and assessing AP laxity during the Lachman and drawer tests. RESULTS: For the navigation system standard deviation for intra-trial measures was 0.7 mm, thus the intra-trial repeatability coefficient was 2.2 mm; standard deviation for intra-trial measure was 1.2 mm, while the reference inter-trial repeatability coefficient between expert surgeons was 3.4 mm. CONCLUSIONS: In conclusion, this study suggests that KIN-Nav may represent a new method to measure and document AP laxity intra-operatively with improved accuracy and test the effect of surgical treatment in-vivo with higher sensitivity than in the past and this study quantify its reliability for within-subjects studies performed by a single expert surgeon.

Intraoperative evaluation of total knee replacement: kinematic assessment with a navigation system.

Interest in the kinematics of reconstructed knees has increased since it was shown that the alteration of knee motion could lead to abnormal wear and damage to soft tissues. We performed intraoperative kinematic measurements using a navigation system to study knee kinematics before and after posterior substituting rotating platform total knee arthroplasty (TKA). We verified intraoperatively (1) if varus/valgus (VV) laxity and anterior/posterior (AP) laxity were restored after TKA; (2) if TKA induced abnormal femoral rollback; and (3) how tibial axial rotation was influenced by TKA throughout the range of flexion. We found that TKA improved alignment in preoperative osteoarthritic varus knees which became neutral after surgery and maintained a neutral alignment in neutral knees. The VV stability at 0 degrees was restored while AP laxity at 90 degrees significantly increased after TKA. Following TKA, the femur had an abnormal anterior translation up to 60 degrees of flexion, followed by a small rollback of 12 +/- 5 mm. TKA influenced the tibia rotation pattern during flexion, but not the total amount of internal/external rotation throughout whole range of flexion, which was preserved after TKA (6 degrees +/- 5 degrees ). This study showed that the protocol proposed might be useful to adjust knee stability at time zero and that knee kinematic outcome during total knee replacement can be monitored by a navigation system.

Does a lateral plasty control coupled translation during antero-posterior stress in single-bundle ACL reconstruction? An in vivo study.

The objective of this study was to quantify, in vivo, the reduction of knee laxity obtained by an extra-articular procedure, added to hamstring single-bundle (SB) anterior cruciate ligament (ACL) reconstruction in controlling coupled tibial translation during the Lachman and drawer tests. Twenty-eight patients were evaluated with a computer-assisted kinematic evaluation protocol; patients with associated ligament tears or meniscal damages were not included in the study. All patients underwent an hamstring ACL with an additional extra-articular procedure. During the intervention, tibia was tracked during the Lachman and drawer tests with ACL-deficient knee, after SB fixation and after extra-articular plasty fixation, performed with the remnant part of the hamstring tendons, from end of lateral condyle to Gerdy's tubercle. Statistical analysis was performed to see whether there was a difference in knee laxity after the tests in the three steps. At 30 degrees , the SB graft reduces AP translation of about 5 mm (P < 0.05) while the extra-articular procedure controls lateral tibial compartment, reducing translation by 1.6 mm (P < 0.05). At 90 degrees the SB graft reduces AP translation more in the lateral compartment (P < 0.05), while the extra-articular procedure contributes in controlling tibial translation reducing laxity by 1 mm (P < 0.05) in both compartments. Result shows that, in vivo, the addition of an extra-articular procedure to single-bundle ACL reconstruction may be effective in controlling coupled tibial translation during the Lachman test and reduces AP laxity at 90 degrees of flexion.

Knee stability before and after total and unicondylar knee replacement: in vivo kinematic evaluation utilizing navigation.

Surgical navigation systems are currently used to guide the surgeon in the correct alignment of the implant. The aim of this study was to expand the use of navigation systems by proposing a surgical protocol for intraoperative kinematics evaluations during knee arthroplasty. The protocol was evaluated on 20 patients, half undergoing unicondylar knee arthroplasty (UKA) and half undergoing posterior-substituting, rotating-platform total knee arthroplasty (TKA). The protocol includes a simple acquisition procedure and an original elaboration methodology. Kinematic tests were performed before and after surgery and included varus/valgus stress at 0 and 30 degrees and passive range of motion. Both UKA and TKA improved varus/valgus stability in extension and preserved the total magnitude of screw-home motion during flexion. Moreover, compared to preoperative conditions, values assumed by tibial axial rotation during flexion in TKA knees were more similar to the rotating patterns of UKA knees. The analysis of the anteroposterior displacement of the knee compartments confirmed that the two prostheses did not produce medial pivoting, but achieved a postoperative normal behavior. These results demonstrated that proposed intraoperative kinematics evaluations by a navigation system provided new information on the functional outcome of the reconstruction useful to restore knee kinematics during surgery.

Relationship between coracoacromial arch and rotator cuff analysed by a computer-assisted method.

BACKGROUND: In this paper we describe and assess the feasibility of a computer-assisted method which could be useful to investigate the mechanism of subacromial impingment of the shoulder. METHODS: The relationship between the infraspinatus and supraspinatus and the coracoacromial (CA) arch during passive elevation and abduction are described. The methodology is based on the use of a tracker for recording surfaces and passive movements and data elaboration using dedicated software. RESULTS: In four cadavers, we observed that the minimal distances between the rotator cuff insertions and CA arch were realized at 45 degrees abduction between the acromion and infraspinatus, at 50-90 degrees elevation between the acromion and supraspinatus and also at 45-70 degrees abduction between the CA ligament and supraspinatus. This study showed that the proposed method is able to provide repeatable kinematic data (ICC > or = 0.90), numerical anatomical data comparable with the literature and, moreover, individual measurements on the shoulder joint. CONCLUSIONS: This preliminary results support the extension of the methodology to an in vivo protocol to be used during computer-assisted arthroscopic surgery.

Double-bundle ACL reconstruction: influence of femoral tunnel orientation in knee laxity analysed with a navigation system - an in-vitro biomechanical study.

BACKGROUND: This paper reports an in-vitro study for evaluating the influence of the femoral tunnel orientation in anterior cruciate ligament (ACL) double-bundle reconstructions. METHODS: This work describes the experimental protocol and results obtained for six cadaver knees using the FlashPoint optical system (Image Guided, Boulder, Colorado, USA) and a computer-assisted technique for the elaboration of anatomical and kinematic data. Each specimen was examined by the same surgeon in the following steps: (1) intact knee stability was evaluated by performing antero-posterior displacement and internal-external rotation test at 90 degrees ; (2) the ACL was resected and the knee evaluated again; (3) the ACL was reconstructed using the gracilis semi-tendinous tendon (through horizontal tunnels in femur), and the new kinematics recorded; (4) the ACL was reconstructed again with the same tendon, but with a more vertical orientation of the femoral tunnel (vertical tunnel) and kinematics was once more recorded; (5) finally the knee was dissected to digitise the anatomical structures. RESULTS: Off-line computer analysis of the acquired anatomical and kinematic data showed that there was a significant statistical difference (Wilcoxon test with the Montecarlo method for small samples - p = 0.035) between horizontal tunnel (HT) and vertical tunnel (VT) reconstruction both in the antero-posterior test (median antero-posterior displacement in horizontal tunnel was 0.8 mm less than in vertical tunnel reconstruction) and in the internal-external (IE) rotation test (median internal-external rotation in horizontal tunnel reconstruction was 5 degrees less than in vertical tunnel reconstruction). CONCLUSION: The analysis of graft behavior in reconstructed knees compared with normal and ACL-deficient knees suggests that the most horizontal tunnel performed better than the vertical tunnel, thus constraining optimally both antero-posterior and internal-external rotations. This finding suggests that femoral tunnel direction may be an important issue in ACL surgery.

A protocol for clinical evaluation of the carrying angle of the elbow by anatomic landmarks.

The aim of this work was to present an in vivo protocol to estimate the carrying angle of the elbow in full extension. Forty-four arms were measured by using an electrogoniometer to acquire 3-dimensional coordinates of the landmarks. An algorithm based on the Cardan decomposition method was used to compute the carrying angle and the flexion and pronation angles of the elbow. The mean carrying angle was 12.42 degrees +/- 4.06 degrees , in agreement with the literature and with values obtained by a standard goniometer (r = 0.46; P = .000). Our protocol provided excellent repeatability (interclass correlation coefficient [ICC] = 0.85), greater than a goniometer (ICC = 0.76), and a standard error of measurement of only 1.62 degrees . Flexion was a significant factor (P = .01) in carrying angle estimation. This study suggests that the carrying angle cannot be estimated independently by the flexion angle, even when measured in apparently full extension, and it could be useful in elbow disorders, such as fractures or epicondylar disease management and evaluation of elbow reconstruction.

Description and validation of a navigation system for intra-operative evaluation of knee laxity.

This paper describes the features of KIN-nav, a navigation system specifically dedicated to intra-operative evaluation of knee laxity, and assesses the reliability of the system during surgery. The acquisition protocol for its intra-operative use, the original user interface, and the computational methods for elaboration of kinematic data are described in detail. Moreover, an extensive and specific validation of the system was performed in order to evaluate its intra-operative performance and usability. KIN-nav's reliability and accuracy were analyzed in a series of 79 patients undergoing ACL reconstruction. The intra-surgeon repeatability computed for ACL-deficient and reconstructed knees at different flexion angles was less than 0.6 degrees for varus-valgus (VV) rotation, less than 1 mm for AP translation, and less than 1.6 degrees for IE rotation. The inter-surgeon repeatability is less than 2 degrees for VV rotation, 5 degrees for internal-external rotation, and less than 3 mm for AP translation. The proposed method was fast (requiring an additional 10 minutes of surgical time on average), required only a short learning period (5 cases), was minimally invasive, and was robust from the numerical perspective. Our system clearly shows that the use of navigation systems for kinematic evaluation provides useful and complete information on the knee state and test performance, and is simple and reliable to use. The good repeatability in manual kinematic tests is an improvement on the present ability to discriminate knee kinematics intra-operatively, and thus offers the possibility of better discrimination between knee pathologies and the prospect of new surgical applications.

Validation of a new protocol for navigated intraoperative assessment of knee kinematics.

BACKGROUND: This study describes a novel method for accurate evaluations of knee kinematics during arthroscopic reconstructions of anterior cruciate ligament (ACL). METHODS: Quantitative evaluation of knee stability was estimated by experimental validation on 30 volunteers and by statistical analysis of test repeatability. RESULTS: Proposed method present short learning time, is minimally invasive and thus suitable for arthroscopic techniques. Computed laxity showed a repeatability of 1.5 degrees for varus-valgus, 3 degrees for internal-external, and 2mm for antero-posterior tests. CONCLUSIONS: This method represents a reliable quantification of knee kinematics in surgery, able to improve present intra-operative assessment of knee stability.

Does ACL reconstruction restore knee stability in combined lesions?: An in vivo study.

Treating anterior cruciate ligament (ACL) lesions combined with a torn medial collateral ligament (MCL) is controversial because residual laxity may lead to stretching of the ACL graft and eventual failure of the reconstruction. Few studies describe the in vivo translations of combined ACL and MCL injuries. We compared the preoperative and postoperative laxity between patients with combined ACL+MCL Grade II injuries and isolated ACL ruptures and tested whether an ACL reconstruction could restore all laxities in both groups. We evaluated knee kinematics during ACL reconstruction in 57 patients (37 ACL lesions and 20 ACL+MCL injury). Laxity tests were performed before and after graft fixation. Postoperatively, there was greater anteroposterior laxity and greater varus-valgus laxity in the group with MCL injury compared to the group with an ACL lesion only. This finding suggests residual laxities remain when ACL reconstruction is performed in patients with combined ACL+MCL lesion, and raises the question of addressing the MCL ligament when Grade II laxity is found.

Development and applications of a software tool for diarthrodial joint analysis.

This paper describes a new software environment for advanced analysis of diarthrodial joints. The new tool provides a number of elaboration functions to investigate the joint kinematics, bone anatomy, and ligament and tendon properties. In particular, the shapes and the contact points of the articulating surfaces can be displayed and analysed through 2D user-defined sections and fittings (lines or conics). Ligament behaviour can be evaluated during joint movement, through the computation of elongations, orientations, and fiber strain. Motion trajectories can be also analysed through the calculation of helical axes, instantaneous rotations, and displacements in specific user-chosen coordinate reference frames. The software has an user-friendly graphical interface to display four-dimensional data (time-space data) obtained from medical images, navigation systems, spatial linkages or digitalizers, and can also generate printable reports and multiple graphs as well as ASCII files that can be imported to spreadsheet programs such as Microsoft Excel.

Computerized protocol for anatomical and functional studies of joints.

This chapter describes a new methodology for the acquisition and computer elaboration of joint anatomy and motion data and the study of their correlation. The method uses a commercial industrial electrogoniometer, custom tools, and software designed and developed by the authors for interactive display of the anatomical structures during joint motion, numerical interpolations of the articular geometries, and kinematic analysis of motion. The original data acquisition protocol and computer elaboration software are described in detail, and a final subheading describes briefly previous studies and future developments.

Computer analysis of PCL fibres during range of motion.

An understanding of the orientation of posterior cruciate ligament (PCL) fibres can contribute to current knowledge of PCL biomechanics and potentially improve the effectiveness of PCL surgical reconstruction. In this paper, the orientation of PCL fibres with respect to the tibia and femur was analysed by means of a new computer method. The antero-lateral (AL) and postero-medial (PM) bundles of the PCL showed an increasing slope with respect to the tibial plateau during flexion and a statistically significant difference between them (AL: 37-65 degrees, PM: 47-60 degrees). PCL bundles showed similar orientation with respect to the femur and varied 14 degrees average during flexion. The study also measured 84 degrees twisting of PCL bundles during passive range of motion.