Electromyography of brachial muscles in Pan troglodytes and Pongo pygmaeus

Electromyographic recordings were taken from all heads of the triceps brachii and biceps brachii muscles and from the anconeus, brachialis, and brachioradialis muscles in a chimpanzee and an orangutan as they stood still and walked quadrupedally on horizontal and inclined surfaces, engaged in suspensory behavior, reached overhead, and manipulated a variety of foods and artifacts. Like the gorilla (Tuttle and Basmajian, 1974a), the chimpanzee and orangutan possess special close-packed positioning mechanisms that allow the bulky muscles that cross their elbow joints to remain silent during quiet pendant suspension. We found no major myological features that would dramatically separate the arms of knuckle-walking African apes from those of the orangutan. With a few exceptions, which could as well be attributed to individual variation as to interspecific differences, the brachial muscles acted similarly during quadrupedal positional behaviors, irrespective of whether the hands of the subjects were knuckled (African apes), fisted (chimpanzee and orangutan), or placed in modified palmigrade postures (orangutan). Evolutionary transformations, from brachial and elbow complexes like those of Pongo to ones like Pan, or vice versa, would probably be achieved quite readily as the species changed its substrate preferences and positional habits.     

Electromyography of knuckle-walking: results of four experiments on the forearm of Pan gorilla

Preliminary results of electromyographic (EMG) studies on the forearm of a gorilla provisionally support the hypothesis that special closepacked positioning mechanisms may characterize the wrist and metacarpophalangeal joints II–V in extant knuckle-walkers (chimpanzees and gorillas). We recommend that once the bony features, related to these close-packed positions are clearly identified, they may be employed strategically to discern evidence of a knuckle-walking heritage in the hands of extant hominoids, including man, and to trace the history of knuckle-walking in available fossils. This report contains results of the first successful employment of indwelling fine-wire electrode techniques to elucidate problems on the functional and evolutionary biology of great apes.     

Electromyography of pronators and supinators in great apes.

We obtained electromyographic recordings from the supinator, biceps brachii, pronator quadratus, and pronator teres muscles of a chimpanzee and a gorilla and from the supinator, pronator quadratus, and biceps brachii muscles of an orangutan as they stood and walked quadrupedally on horizontal and inclined surfaces, engaged in suspensory behavior, reached overhead, and manipulated a variety of foods and artifacts. In Pan troglodytes and Pan gorilla, as in Homo sapiens, the supinator muscle is the prime supinator, with the biceps brachii muscle serving to augment speed or force of supination. Primary of the pronator quadratus muscle over the pronator teres muscle during pronation is less clear in the African apes than in humans. Possibly, pongid radial curvature or forelimb elongation or both factors are related to the somewhat different patterns of activity that we observed in the pronator muscles of Pan versus those reported for Homo sapiens. In Pongo pygmaeus, as in P. troglodytes and P. gorilla, the pronator quadratus muscle acts as a pronator and the supinator muscle acts to supinate the hand at the radioulnar joints. The biceps brachii muscle is active at low levels as the orangutan supinates its hand with the elbow flexed.     

Knuckle-walking in Sivapithecus? The combined effects of homology and homoplasy with possible implications for pongine dispersals

Sivapithecus is a Miocene great ape from South Asia that is orangutan-like cranially but is distinctive postcranially. Work by others shows that the humerus resembles large terrestrial cercopithecoids proximally and suspensory hominoids distally, but most functional interpretations nevertheless situate Sivapithecus in an arboreal setting. We present a new quantitative analysis of the Sivapithecus capitate and hamate. Though the functional morphology of both bones suggests some degree of arboreality, the overall morphology is most similar to knuckle-walking African apes. Other features of the Sivapithecus humerus and hind limb are also functionally consistent with knuckle-walking, and we suggest that this locomotor behavior is a valid alternative functional interpretation of the postcranial morphology. We speculate that knuckle-walking in Sivapithecus would have evolved independently from African apes, perhaps for similar ecological reasons. The discovery of a possible pongine knuckle-walker challenges the hypotheses that (1) knuckle-walking evolved only once in hominoids and (2) knuckle-walking is too highly specialized to be the positional behavior from which human bipedalism evolved. The possibility of knuckle-walking in Sivapithecus may help to explain not only the curious combination of characters that typify the postcranium but also the unique postcranial morphology of extant Pongo. Furthermore, it may clarify the distribution of fossil pongines across many ecological zones in Eurasia in the Miocene and Pleistocene, as well as, independently, the spread of African apes across a diversity of environments in equatorial Africa.     

Shape of articular surface of crocodilian (Archosauria) elbow joints and its relevance to sauropsids

The determination of area and shape of articular surfaces on the limb bones of extinct archosaurs is difficult because of postmortem decomposition of the fibrous tissue and articular cartilages that provide the complex three‐dimensional joint surfaces in vivo. This study aims at describing the shape of the articular cartilages in the elbow joints of six crocodilian specimens; comparing its structure with that of four birds, three testudines, and five squamates; and comparing the shapes of the surfaces of the calcified and the articular cartilages in the elbow joints of an Alligator specimen. The shapes of the articular cartilages of crocodilian elbow joint are shown to resemble those of birds. The humerus possesses an olecranon fossa positioned approximately at the midportion of the distal epiphysis and bordering the margin of the extensor side of the articular surface. The ulna possesses a prominent intercotylar process at approximately the middle of its articular surface, and splits the surface into the radial and ulnar cotylae. This divides the articular cartilage into an articular surface on the flexor portion, and the olecranon on the extensor portion. The intercotylar process fits into the olecranon fossa to restrict elbow joint extension. Dinosaurs and pterosaurs, phylogenetically bracketed by Crocodylia and Aves (birds), may have possessed a similar olecranon fossa and intercotylar process on their articular cartilages. Although these shapes are rarely recognizable on the bones, their impressions on the surfaces of the calcified cartilages provide an important indication of the extensor margin of the articular surfaces. This, in turn, helps to determine the maximum angle of extension of the elbow joint in archosaurs. J. Morphol., 2010. © 2010 Wiley‐Liss, Inc.     

Inverse remodelling algorithm identifies habitual manual activities of primates based on metacarpal bone architecture

Previously, a micro-finite element (micro-FE)-based inverse remodelling method was presented in the literature that reconstructs the loading history of a bone based on its architecture alone. Despite promising preliminary results, it remains unclear whether this method is sensitive enough to detect differences of bone loading related to pathologies or habitual activities. The goal of this study was to test the sensitivity of the inverse remodelling method by predicting joint loading histories of metacarpal bones of species with similar anatomy but clearly distinct habitual hand use. Three groups of habitual hand use were defined using the most representative primate species: manipulation (human), suspensory locomotion (orangutan), and knuckle-walking locomotion (bonobo, chimpanzee, gorilla). Nine to ten micro-computed tomography scans of each species (\(n=48\) in total) were used to create micro-FE models of the metacarpal head region. The most probable joint loading history was predicted by optimally scaling six load cases representing joint postures ranging from \(-\,75^{\circ }\) (extension) to \(+\,75^{\circ }\) (flexion). Predicted mean joint load directions were significantly different between knuckle-walking and non-knuckle-walking groups (\(p<0.05\)) and in line with expected primary hand postures. Mean joint load magnitudes tended to be larger in species using their hands for locomotion compared to species using them for manipulation. In conclusion, this study shows that the micro-FE-based inverse remodelling method is sensitive enough to detect differences of joint loading related to habitual manual activities of primates and might, therefore, be useful for palaeoanthropologists to reconstruct the behaviour of extinct species and for biomedical applications such as detecting pathological joint loading.

     

Telemetered electromyography of flexor digitorum profundus and flexor digitorum superficialis in Pan troglodytes and implications for interpretation of the O. H. 7 hand.

The importance of knuckle-walking in the locomotor repertoire of African apes raises the possibility that the long digital flexors may be specially adapted more to meet the demands of ground quadrupedalism than those of suspension. To investigate this possibiltiy, the activities of the flexor digitorum superficialis and flexor digitorum profundus were studied by means of telemetered electromyography in three chimpanzees. Results clearly indicate that the fasciculi of the muscles to digits bearing weight in knuckle-walking are not called upon to contract in quadrupedal postures or in slow and moderately fast quadrupedal locomotion except to help clear the fingers from the ground as the forelimb begins its recovery stroke. At the most rapid speeds, a slight to moderate level of activity sometimes occurs in the latter half of stance phase. The long digital flexors display maximum and sustained activity during suspension. It is concluded that any role for these muscles in maintenance of stability at the metacarpophalangeal joints during knuckle-walking must be predominantly passive. Prominent markings for insertions of these muscles in a fossil hand (such as O.H. 7) suggest use of the forelimb in suspensory climbing behaviors.     

Articular morphology of the proximal ulna in extant and fossil hominoids and hominins

Extant hominoids share similar elbow joint morphology, which is believed to be an adaptation for elbow stability through a wide range of pronation-supination and flexion-extension postures. Mild variations in elbow joint morphology reported among extant hominoids are often qualitative, where orangutans are described as having keeled joints, and humans and gorillas as having flatter joints. Although these differences in keeling are often linked to variation in upper limb use or loading, they have not been specifically quantified. Many of the muscles important in arboreal locomotion in hominoids (i.e., wrist and finger flexors and extensors) take their origins from the humeral epicondyles. Contractions of these muscles generate transverse forces across the elbow, which are resisted mainly by the keel of the humeroulnar joint. Therefore, species with well-developed forearm musculature, like arboreal hominoids, should have more elbow joint keeling than nonarboreal species. This paper explores the three- and two-dimensional morphology of the trochlear notch of the elbow of extant hominoids and fossil hominins and hominoids for which the locomotor habitus is still debated. As expected, the elbow articulation of habitually arboreal extant apes is more keeled than that of humans. In addition, extant knuckle-walkers are characterized by joints that are distally expanded in order to provide greater articular surface area perpendicular to the large loads incurred during terrestrial locomotion with an extended forearm. Oreopithecus is characterized by a pronounced keel of the trochlear notch and resembles Pongo and Pan. OH 36 has a morphology that is unlike that of extant species or other fossil hominins. All other hominin fossils included in this study have trochlear notches intermediate in form between Homo and Gorilla or Pan, suggesting a muscularity that is less than in African apes but greater than in humans.     

Olecranon orientation as an indicator of elbow joint angle in the stance phase,and estimation of forelimb posture in extinct quadruped animals

Reconstruction of limb posture is a challenging task in assessing functional morphology and biomechanics of extinct tetrapods, mainly because of the wide range of motions possible at each limb joint and because of our poor knowledge of the relationship between posture and musculoskeletal structure, even in the extant taxa. This is especially true for extinct mammals such as the desmostylian taxa Desmostylus and Paleoparadoxia. This study presents a procedure that how the elbow joint angles of extinct quadruped mammals can be inferred from osteological characteristics. A survey of 67 dried skeletons and 113 step cycles of 32 extant genera, representing 25 families and 13 orders, showed that the olecranon of the ulna and the shaft of the humerus were oriented approximately perpendicular to each other during the stance phase. At this angle, the major extensor muscles maximize their torque at the elbow joint. Based on this survey, I suggest that olecranon orientation can be used for inferring the elbow joint angles of quadruped mammals with prominent olecranons, regardless of taxon, body size, and locomotor guild. By estimating the elbow joint angle, it is inferred that Desmostylus would have had more upright forelimbs than Paleoparadoxia, because their elbow joint angles during the stance phase were approximately 165° and 130°, respectively. Difference in elbow joint angles between these two genera suggests possible differences in stance and gait of these two mammals. J. Morphol. 2009. © 2009 Wiley‐Liss, Inc.     

Ontogenetic changes in limb bone structural proportions in mountain gorillas (Gorilla beringei beringei)

Behavioral studies indicate that adult mountain gorillas (Gorilla beringei) are the most terrestrial of all nonhuman hominoids, but that infant mountain gorillas are much more arboreal. Here we examine ontogenetic changes in diaphyseal strength and length of the femur, tibia, humerus, radius, and ulna in 30 Virunga mountain gorillas, including 18 immature specimens and 12 adults. Comparisons are also made with 14 adult western lowland gorillas (Gorilla gorilla gorilla), which are known to be more arboreal than adult mountain gorillas. Infant mountain gorillas have significantly stronger forelimbs relative to hind limbs than older juveniles and adults, but are nonsignificantly different from western lowland gorilla adults. The change in inter-limb strength proportions is abrupt at about two years of age, corresponding to the documented transition to committed terrestrial quadrupedalism in mountain gorillas. The one exception is the ulna, which shows a gradual increase in strength relative to the radius and other long bones during development, possibly corresponding to the gradual adoption of stereotypical fully pronated knuckle-walking in older juvenile gorillas. Inter-limb bone length proportions show a contrasting developmental pattern, with hind limb/forelimb length declining rapidly from birth to five months of age, and then showing no consistent change through adulthood. The very early change in length proportions, prior to significant independent locomotion, may be related to the need for relatively long forelimbs for climbing in a large-bodied hominoid. Virunga mountain gorilla older juveniles and adults have equal or longer forelimb relative to hind limb bones than western lowland adults. These findings indicate that both ontogenetically and among closely related species of Gorilla, long bone strength proportions better reflect actual locomotor behavior than bone length proportions.     

Moment distribution among human elbow extensor muscles during isometric and submaximal extension

To understand better how the central nervous system (CNS) distributes a joint moment among muscles, moment distribution among the three heads of the triceps and the anconeus muscles during isometric elbow extension was quantified in vivo and noninvasively. Electrical stimulation was used to activate an individual muscle selectively at various contraction levels, and the relationship between the peak M-wave amplitude and peak elbow extension moment was established across various contraction levels for each muscle. The relationship was then used to calibrate the corresponding EMG signal and determine moment distribution among the muscles during voluntary isometric elbow extension. Results showed that moment distribution among muscles was not proportional to the muscles' physiological cross-sectional areas (PCSA) and the CNS favored uniarticular muscles for the isometric task performed: the uniarticular lateral and medial heads of the triceps were dominant (contributing approximately 70-90% of the total elbow extension moment) and the anconeus contributed significantly, especially at the lower levels of elbow extension moment (up to approximately 15% of the extension moment). In contrast, the two-joint long head of the triceps contributed significantly less than the uniarticular heads of the triceps. While the absolute contributions of all the muscles increased with the total elbow extension moment, the relative contributions of the muscles may increase or decrease with the elbow extension moment. Cross-validation using fresh data (not used in determining the moment distribution) showed close match between the measured and predicted elbow extension moment except for trials in which fatigue became significant.     

Trabecular Bone Structure Correlates with Hand Posture and Use in Hominoids

Bone is capable of adapting during life in response to stress. Therefore, variation in locomotor and manipulative behaviours across extant hominoids may be reflected in differences in trabecular bone structure. The hand is a promising region for trabecular analysis, as it is the direct contact between the individual and the environment and joint positions at peak loading vary amongst extant hominoids. Building upon traditional volume of interest-based analyses, we apply a whole-epiphysis analytical approach using high-resolution microtomographic scans of the hominoid third metacarpal to investigate whether trabecular structure reflects differences in hand posture and loading in knuckle-walking (Gorilla, Pan), suspensory (Pongo, Hylobates and Symphalangus) and manipulative (Homo) taxa. Additionally, a comparative phylogenetic method was used to analyse rates of evolutionary changes in trabecular parameters. Results demonstrate that trabecular bone volume distribution and regions of greatest stiffness (i.e., Young''s modulus) correspond with predicted loading of the hand in each behavioural category. In suspensory and manipulative taxa, regions of high bone volume and greatest stiffness are concentrated on the palmar or distopalmar regions of the metacarpal head, whereas knuckle-walking taxa show greater bone volume and stiffness throughout the head, and particularly in the dorsal region; patterns that correspond with the highest predicted joint reaction forces. Trabecular structure in knuckle-walking taxa is characterised by high bone volume fraction and a high degree of anisotropy in contrast to the suspensory brachiators. Humans, in which the hand is used primarily for manipulation, have a low bone volume fraction and a variable degree of anisotropy. Finally, when trabecular parameters are mapped onto a molecular-based phylogeny, we show that the rates of change in trabecular structure vary across the hominoid clade. Our results support a link between inferred behaviour and trabecular structure in extant hominoids that can be informative for reconstructing behaviour in fossil primates.     

Muscle activity in rapid multi-degree-of-freedom elbow movements: solutions from a musculoskeletal model

The activity of certain muscles that cross the elbow joint complex (EJC) are affected by forearm position and forearm movement during elbow flexion/extension. To investigate whether these changes are based on the musculoskeletal geometry of the joint, a three-dimensional musculotendinoskeletal computer model of the EJC was used to estimate individual muscle activity in multi-degree-of-freedom (df) rapid (ballistic) elbow movements. It is hypothesized that this model could reproduce the major features of elbow muscle activity during multi-df elbow movements using dynamic optimal control theory, given a minimum-time performance criterion. Results from the model are presented and verified with experimental kinematic and electromyographic data from movements that involved both one-df elbow flexion/extension and two-df flexion/extension with forearm pronation/supination. The model demonstrated how the activity of particular muscles is affected by both forearm position and movement, as measured in these experiments and as previously reported by others. These changes were most evident in the flexor muscles and least evident in the extensor muscles. The model also indicated that, for specific one- and two-df movements, activating a muscle that is antagonistic or noncontributory to the movement could reduce the movement time. The major features of muscle activity in multi-df elbow movements appear to be highly dependent on the joint's musculoskeletal geometry and are not strictly based on neural influences or neuroanatomical substrates. Received: 9 May 1997 / Accepted in revised form: 8 December 1998     

Functional anatomy of the olecranon process in hominoids and plio-pleistocene hominins

This study examines the functional morphology of the olecranon process in hominoids and fossil hominins. The length of the bony lever of the triceps brachii muscle (TBM) is measured as the distance between the trochlear articular center and the most distant insertion site of the TBM, and olecranon orientation is measured as the angle that this bony lever makes with the long axis of the ulna. Results show that Homo, Pan, Gorilla, most monkeys, and the Australopithecus fossils studied have similar relative olecranon lengths. Suspensory hominoids and Ateles have shorter olecranons, suggesting, in some instances, selection for greater speed in extension. The orientation that the lever arm of the TBM makes with the long axis of the ulna varies with preferred locomotor mode. Terrestrial primates have olecranons that are more posteriorly oriented as body size increases, fitting general models of terrestrial mammalian posture. Arboreal quadrupeds have more proximally oriented lever arms than any terrestrial quadrupeds, which suggests use of the TBM with the elbow in a more flexed position. Olecranon orientation is not consistent in suspensory hominoids, although they are all characterized by orientations that are either similar or more posterior than those observed in quadrupeds. Homo and the fossils have olecranons that are clearly more proximally oriented than expected for a quadruped of their size. This suggests that Homo and Australopithecus used their TBM in a flexed position, a position most consistent with manipulatory activities.     

Tripedal knuckle-walking: a proposal for the evolution of human locomotion and handedness.

A comparative morphological analysis of human and non-human hominoids was conducted in an attempt to determine the mode of locomotion of the protohominid. Although the generalized hominoid anatomy permits variation of locomotion: brachiation, knuckle-walking, etc., minor variations in structure determine which behavior is favored. Arboreal arm swinging requires a flexible forelimb while terrestrial fist or knuckle-walking demands more rigidity of the hand and wrist. It is demonstrated that the large human thumb accompanied by the strong adduction of the thenar, hypothenar, and palmar interosseous muscles offer powerful rigidity to the hand, while fusion of the os centrale with the scaphoid during gestation permits the formation of an arch of carpals which imbue the wrist with the stability necessary for weight bearing. Fascialization of the contrahentes and dorsiepitrochlearis muscles in the human as well as depilation of the middle phalanges; the webbing (syndactyly) of the palm; the direction of the fibers of the interosseous membrane of the forearm; the shape of the puerile annular ligament, and the direction of the human glenoid fossa strongly suggest that the ancestor of man used a knuckle-walking form of locomotion prior to becoming bipedal. A model is presented that suggests that bipedalism was attained through an intermediate stage of tripedalism. The model is based on the fact that man's anatomy is much more asymmetric than that of the great apes. A presumption is made that due to the absence of trees for climbing in the transition from forest to open plain, the protohominid needed to carry tools (stones) at all times for protection. Stones could be carried for long distances on the posterior iliac crest since the weight would be shifted posteriorly over the legs. Pick up, medial rotation and adduction of the stone would employ a two-muscle chain of biceps brachii and latissimus dorsi. On the iliac crest, the stone is posterior to the coronal plane of the glenohumeral joint, and with the contraction of this two-muscle chain, the shoulder on one side is moved posteriorly effecting a semi-erect posture. It is proposed that tripedalism of the protohominid may be an explanation for the handedness unique to hominids.     

Effects of body size and social context on the arboreal activities of lowland gorillas in the Central African Republic

The objectives of this 27 month study were to document the positional behaviors used by lowland gorillas (Gorilla gorilla gorilla) in the Central African Republic and to compare the effects of body size dimorphism on the use of arboreal substrates. During this study, despite their great size, all gorillas used trees regularly. Predictions concerning the relationship of body size to arboreal behavior were generally upheld. Small branch and suspensory activities were rare for silverbacks. Females used smaller and multiple substrates and suspensory postures more frequently than males. Although females foraged in the periphery of trees, males stayed close to the cores and rarely used terminal branches. In addition to body size, this study found that party size, social rank, and tree structure all influence an animal's substrate choice and subsequent positional activities. Lone males typically remained in the cores of trees where substrates are large. Group males may have been forced to use all parts of trees because others were present. Lone males used small crown trees which provided easy access to terminal branch foods. Males and females foraging together used larger trees (containing more feeding sites) than single sex groups. Female positional behavior may have been affected by the presence of males. When apart from males, females used the cores of trees and larger substrates more than when foraging with males. As habitat and social context both influence substrate use, they should be considered essential components of body-sized based interpretations of the behavior of fossil or extant species. © 1995 Wiley-Liss, Inc.     

The reconstructive strategy for improving elbow function in late obstetric brachial plexus palsy.

Children with previously untreated obstetric brachial plexus palsy frequently have abnormal elbow function because of motor recovery with aberrant reinnervation, or because of paresis or paralysis. From 1988 to 1997 (9-year period), 62 children with obstetric brachial plexus palsy with resulting elbow deformity underwent various methods of palliative reconstruction to improve elbow function. For motor recovery with aberrant reinnervation, release of aberrantly reinnervated antagonistic muscles and augmentation of paretic muscles form the basis of surgical intervention. The surgical procedures included triceps-to-biceps transfer, biceps-to-triceps transfer, brachialis-to-triceps transfer, or combined biceps- and brachialis-to-triceps transfer. Choice of procedures was individualized and randomly determined on the basis of the degree and pattern of aberrant reinnervation between elbow flexors and extensors. In patients' motor recovery with paresis or paralysis, persistently weak elbow flexion was salvaged with a functioning free muscle transplantation or Steindler's flexorplasty, or regional shoulder muscle transfer. In addition, patients with aberrant reinnervation between shoulder abductors and elbow flexors underwent anterior deltoid-to-biceps transfer with a fascia lata graft. All patients had a minimum follow-up of 2 years. Results are assessed and discussed and a reconstructive algorithm is recommended. In general, reconstruction of elbow extension should precede that of elbow flexion. Biceps-to-triceps transfer with preservation of an intact brachialis muscle, or brachialis-to-triceps transfer with preservation of an intact biceps, allows 50 percent of these patients to achieve acceptable elbow flexion and extension in a single-stage procedure.     

Surgical strategy for improving forearm and hand function in late obstetric brachial plexus palsy

For the purpose of treatment, obstetric brachial plexus palsy can be subdivided into two distinct phases: initial obstetric brachial plexus palsy, and late obstetric brachial plexus palsy. In the latter, nerve surgery is no longer practical, and treatment often requires palliative surgery to improve function of the shoulder, elbow, forearm, and hand. Late obstetric brachial plexus palsy in the forearm and hand includes weakness or absence of wrist or metacarpophalangeal or interphalangeal joint extension; weakness or absence of finger flexion; forearm supination, or less commonly pronation contracture; ulnar deviation of the wrist; dislocation of the radial or ulnar head; thumb instability; or sensory disturbance of the hand. Palliative reconstruction for these forearm and hand manifestations is more difficult than for the shoulder or elbow because of the lack of powerful regional muscles for transfer. This report reviews the authors' experience performing more than 100 surgical procedures in 54 patients over a 9-year period (between 1988 and 1997) with a minimum of 2 years' follow-up. Surgical treatment is highly individualized, but the optimal age for forearm and hand reconstruction is usually later than for shoulder and elbow reconstruction because of the requirement for a preoperative exercise program. Multiple procedures for forearm and hand function were often performed on any given patient. Frequently, these were done simultaneously with reconstructive procedures for improving shoulder and/or elbow function. Traditional tendon transfer techniques do not provide satisfactory reconstruction for those deformities. Many of the authors' patients required more complex techniques such as nerve transfer and functioning free-muscle transplantation to augment traditional techniques of tendon and/or bone management. Sensory disturbance of the forearm and hand in late obstetric brachial plexus palsy seems a minor problem and further sensory reconstruction is unnecessary.