Fist position for skin grafting on the dorsal hand: II. Clinical use in deep burns and burn scar contractures

The fundamental problem in all types of hand burns is a loss of skin and subsequent deformities. The goal of skin grafting on the dorsal hand is to graft a sufficient amount of skin, as much as the original amount, and to restore normal hand function without secondary deformities. The safe, or Michigan, position commonly has been used for immobilizing the hand. However, this position is to protect hand function rather than to provide for adequate skin grafting. This institution has developed a new hand position (the fist position) for grafting the greatest amount of skin on the dorsal side of the hand. In the fist position, the hand is positioned flexing all joints of the wrist and the fingers and maximally stretching the dorsal surface of the hand before skin grafting. Ten hands with deep second- or third-degree burn (n = 6) and burn scar contracture (n = 4) of the dorsal hand in eight patients were treated with split-thickness skin grafting after immobilizing in the fist position. The burns and contractures involved nearly the total area of the dorsal hand. The hand was kept in the fist position for 7 to 9 days after skin grafting. Excellent functional and cosmetic results were observed in all cases during the follow-up period of 6 months to 2 years. Complications resulting from hand immobilization for a short period did not occur. The fist position may be a proper hand position for skin grafting to reconstruct the dorsal hand.     

Optimizing the correction of severe postburn hand deformities by using aggressive contracture releases and fasciocutaneous free-tissue transfers

Severe postburn hand deformities were classified into three major patterns: hyperextension deformity of the metacarpophalangeal joint of the fingers with dorsal contracture of the hand, adduction contracture of the thumb with hyperextension deformity of the interphalangeal joint, and flexion contracture of the palm. Over the past 6 years, 18 cases of severe postburn hand deformities were corrected with extensor tenotomy, joint capsulotomy, and release of volar plate and collateral ligament. The soft-tissue defects were reconstructed with various fasciocutaneous free flaps, including the arterialized venous flap (n = 4), dorsalis pedis flap (n = 3), posterior interosseous flap (n = 3), first web space free flap (n = 3), and radial forearm flap (n = 1). Early active physical therapy was applied. All flaps survived. Functional return of pinch and grip strength was possible in 16 cases. In 11 cases of reconstruction of the dorsum of the hand, the total active range of motion in all joints of the fingers averaged 140 degrees. The mean grip strength was 16.5 kg and key pinch was 3.5 kg. In palm reconstruction, the wider contact area facilitated the grasping of larger objects. In thumb reconstruction, key-pinch increased to 5.5 kg and the angle of the first web space increased to 45 degrees. Jebsen's hand function test was not possible before surgery; postoperatively, it showed more functional recovery in gross motion and in the dominant hand. Aggressive contracture release of the bone,joints, tendons, and soft tissue is required for optimal results in the correction of severe postburn hand deformities. Various fasciocutaneous free flaps used to reconstruct the defect provide early motion, appropriate thinness, and excellent cosmesis of the hand.     

Distal, dorsal superior extremity plasty

Multiple deep wrinkles and redundant skin over the dorsal hand, wrist, and forearm develop and become of cosmetic importance to some patients as they age. Distal, dorsal superior extremity plasty was performed in selected patients by excising redundant skin and wrinkles from the dorsal hands, wrists, and forearms. The area of skin to be excised is elliptical, with the long axis of the ellipse centered over the wrinkles on the dorsal wrist. The amount of skin to be excised (i.e., the short axis of the ellipse) is determined by grasping the dorsal wrist skin, hence advancing the dorsal forearm and hand skin, while the patient flexes the wrist. This maneuver is performed to avoid excessive excision of dorsal wrist skin, which would cause decreased wrist flexion. The surgical procedure is performed with use of magnification to avoid sensory nerve injury. A relatively large volume of lidocaine is injected subcutaneously to increase the distance between the skin and nerves and therefore decrease the risk of nerve injury. The skin edges are undermined for 1 to 1(1/2) cm, and the wound is closed in two layers. The wrist is splinted in 30 to 45 degrees of extension to decrease wound tension. The procedure produces long-lasting, good to excellent cosmetic improvement and patient satisfaction. The dorsal wrist, hand, and forearm appear smoother and more youthful, and scars are relatively inconspicuous. Potential significant complications include injury to the superficial branch of the radial nerve and dorsal branch of the ulnar nerve, wound dehiscence, and decreased range of motion of the wrist. Use of magnification, a bloodless field, injection of a relatively large volume of local anesthetic (10 to 12 cc), knowledge of regional anatomy, and careful surgical technique decrease the risk of nerve injury. Avoidance of injury to the superficial sensory branches of the radial and ulnar nerves is absolutely necessary for patient satisfaction. Avoidance of injury to the wound edges with good surgical technique, postoperative immobilization with the wrist in an extended position, and subsequent advancement of the wrist to a neutral position for several weeks decrease the risk of wound dehiscence. Avoidance of excessive skin excision and prolonged wrist immobilization lowers the risk of decreasing range of motion. There have been no complications in patients who underwent this procedure.     

Correction of first web space deficiency in congenital deformities of the hand with the pseudokite flap

The authors describe a new flap to enlarge or create a first web in patients with congenital deficiencies of the hand. This lozenge-shaped flap is harvested from the dorsoradial aspect of the index finger based on a narrow proximal skin bridge protecting its axial vascularization. A dorsal skin graft of the donor site is avoided by closure using a rhomboid flap. Procedures in 16 patients were performed and reviewed; the only complication was insertion of a small split-thickness graft in five patients to avoid tension at the metacarpophalangeal joint level. The flap lengthened the web fold an average of 3.2 cm without "pseudolengthening" the thumb.     

The use of skin grafts in postburn contracture release: a 10-year review

Postburn scarring and contracture affecting function remain the most frustrating late complications of burn injury. Various techniques are used to release contractures; the choice depends on their location and/or the availability of unaffected skin adjacent to the contracture or elsewhere. A retrospective review was carried out of the case notes of patients who had skin grafting for the release of postburn contracture at the Burns Unit, City Hospital, Nottingham between May of 1984 and August of 1994 to evaluate the experience over this period. Information was obtained about the burn injury, contracture site, interval between burn and release of contracture, indication, age at first release, intervals between releases, operative details (donor and graft sites), complications and nonoperative treatment, and follow-up to the end of the study period. A total of 129 patients underwent skin grafting for release of contractures as opposed to any other method of correction. Full-thickness skin grafts were used in 81 patients (63 percent) and split-thickness skin grafts in 26 (20 percent). Twenty-two patients (17 percent) had both types used on different occasions. Flame burns (41 percent) were the most common causes, followed by scalds (38 percent). Two hundred thirty-nine sites of contracture were released, with the axilla (59) and the hand/wrist (59) being the most common sites involved, followed by the head/neck region (42). It was found that for the same site, release with split-thickness skin grafts was associated with more rereleases of the contracture than with full-thickness skin grafts. Also, the interval between the initial release and first rerelease was shorter than with full-thickness skin grafts (p < 0.048). It was also noted that children required more procedures during growth spurts, reflecting the differential effect of the growth of normal skin and contracture tissue. Patients reported more satisfaction with texture and color match with the full-thickness skin grafts. There was comparable donor-site and graft morbidity with both graft types. The use of skin grafts is simple, reliable, and safe. Whenever possible, the authors recommend the use of full-thickness skin grafts in preference to split-thickness skin grafts in postburn contracture release.     

Rice cooker steam hand burn in the pediatric patient

Burn injuries often lead to significant cosmetic and functional deformity. In the Orient, household electric rice cookers have caused a significant number of steam burns to infant hands. The clinical course and treatment outcome of these burns have been studied retrospectively in a review of the medical records of 79 pediatric patients treated for acute hand steam burns and of 38 other patients who underwent correction for postburn contracture. Electric rice cookers caused all of the acute pediatric steam burns treated at our institute. Of the 81 hands treated between 1995 and 1998, 38.3 percent healed with conservative treatment and 61.7 percent required skin grafting. The volar aspects of the index and middle fingers were those most frequently involved. Eighteen of 36 hands (50 percent) grafted with split-thickness skin developed late contractures requiring additional procedures. Among the 38 patients who underwent correction for postburn deformity, initial treatment was split-thickness grafting for 60.5 percent, full-thickness skin grafting for 7.9 percent, and spontaneous healing for 31.6 percent. Awareness among medical personnel and continued public education should be promoted to help prevent this unique type of pediatric steam burn from occurring.     

The groin flap in reparative surgery of the hand

The historical literature of the use of axial vascular pattern flaps from the hypogastric and iliofemoral regions in reparative surgery of the hand is concisely reviewed. Thirty-six iliofemoral (groin) flaps were utilized for delayed primary resurfacing and secondary reconstruction of defects of the hand and forearm. Two flaps (6 percent) were complicated by partial necrosis. We caution against the immediate resurfacing (within 24 hours of injury) of acute crushed hand wounds by distant flaps. The immediate application of a healthy flap on a soiled or crushed wound invites complications of local tissue necrosis, infection, and subsequent loss of the flap. When distant flaps are indicated for coverage of acute hand wounds, delayed primary coverage following complete removal of all nonviable tissue is a safe and reliable regimen. It is advantageous to design the serviceable portion of the flap on the distal area of the vascular territory of the groin flap. Thoughtful yet "radical" defatting can be performed on the lateral portion of the groin flap territory. Constructed in this way, the long medial base of the groin flap allows freedom for movement at the wrist and metacarpophalangeal and interphalangeal joints, thus decreasing edema and stiffness. In the management of soft-tissue defects in the hand requiring distant flap coverage, we choose to utilize the conventional groin flap in preference to the microvascular free flap when both techniques will deliver equal results.     

Kinematic performance of a six degree-of-freedom hand model (6DHand) for use in occupational biomechanics

Upper extremity musculoskeletal disorders represent an important health issue across all industry sectors; as such, the need exists to develop models of the hand that provide comprehensive biomechanics during occupational tasks. Previous optical motion capture studies used a single marker on the dorsal aspect of finger joints, allowing calculation of one and two degree-of-freedom (DOF) joint angles; additional algorithms were needed to define joint centers and the palmar surface of fingers. We developed a 6DOF model (6DHand) to obtain unconstrained kinematics of finger segments, modeled as frusta of right circular cones that approximate the palmar surface. To evaluate kinematic performance, twenty subjects gripped a cylindrical handle as a surrogate for a powered hand tool. We hypothesized that accessory motions (metacarpophalangeal pronation/supination; proximal and distal interphalangeal radial/ulnar deviation and pronation/supination; all joint translations) would be small (less than 5° rotations, less than 2mm translations) if segment anatomical reference frames were aligned correctly, and skin movement artifacts were negligible. For the gripping task, 93 of 112 accessory motions were small by our definition, suggesting this 6DOF approach appropriately models joints of the fingers. Metacarpophalangeal supination was larger than expected (approximately 10°), and may be adjusted through local reference frame optimization procedures previously developed for knee kinematics in gait analysis. Proximal translations at the metacarpophalangeal joints (approximately 10mm) were explained by skin movement across the metacarpals, but would not corrupt inverse dynamics calculated for the phalanges. We assessed performance in this study; a more rigorous validation would likely require medical imaging.     

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.     

Reconstruction of the hand in Apert syndrome: a simplified approach

Children born with Apert acrocephalosyndactyly pose great challenges to the pediatric hand surgeon. Reconstructive dilemmas consist of shortened, deviated phalanges and extensive skin deficits following syndactyly release. We present a 10-year review of patients with Apert acrocephalosyndactyly who were treated with a simplified surgical approach. Between 1986 and 1996, 10 patients with Apert syndrome underwent reconstructive surgery of their hands. The overall strategy involved early bilateral separation of syndactylous border digits at 1 year of age, followed by sequential unilateral middle syndactyly mass separation with thumb osteotomy and bone grafting as needed. In these 10 patients, a total of 53 web spaces were released, 49 of which involved osteotomies for complex syndactyly. Only local flaps and full-thickness skin grafts from the groin were used in all cases to achieve soft-tissue coverage. To date, seven of the 53 web spaces have needed revision (revision rate, 13 percent). Eleven thumb osteotomies (nine opening wedge and two closing wedge) were performed. Bone grafts from the proximal ulna or from other digits were used in all cases. To date, none of these thumb osteotomies have needed revision. This early, simplified approach to the complex hand anomalies of Apert acrocephalosyndactyly has been successful in achieving low revision rates and excellent functional outcomes as measured by gross grasp and pinch and by patient and parent satisfaction.     

A kinematic model of the human hand to evaluate its prehensile capabilities.

A kinematic model has been developed for simulation and prediction of the prehensile capabilities of the human hand. The kinematic skeleton of the hand is characterized by ideal joints and simple segments. Finger-joint angulation is characterized by yaw (abduction-adduction), pitch (flexion-extension) and roll (axial rotation) angles. The model is based on an algorithm that determines contact between two ellipsoids, which are used to approximate the geometry of the cutaneous surface of the hand segments. The model predicts the hand posture (joint angles) for power grasp of ellipsoidal objects by 'wrapping' the fingers around the object. Algorithms for two grip types are included: (1) a transverse volar grasp, which has the thumb abducted for added power; and (2) a diagonal volar grasp, which has the thumb adducted for an element of precision. Coefficients for estimating anthropometric parameters from hand length and breadth are incorporated in the model. Graphics procedures are included for visual display of the model. In an effort to validate the predictive capabilities of the model, joint angles were measured on six subjects grasping circular cylinders of various diameters and these measured joint angles were compared with angles predicted by the model. Sensitivity of the model to the various input parameters was also determined. On an average, the model predicted joint flexion angles that were 5.3% or 2.8 degrees +/- 12.2 degrees larger than the measured angles. Good agreement was found for the MCP and PIP joints, but results for DIP were more variable because of its dependence on the predictions for the proximal joints.     

A musculoskeletal model of the hand and wrist: model definition and evaluation

Abstract

To improve our understanding on the neuromechanics of finger movements, a comprehensive musculoskeletal model is needed. The aim of this study was to build a musculoskeletal model of the hand and wrist, based on one consistent data set of the relevant anatomical parameters. We built and tested a model including the hand and wrist segments, as well as the muscles of the forearm and hand in OpenSim. In total, the model comprises 19 segments (with the carpal bones modeled as one segment) with 23 degrees of freedom and 43 muscles. All required anatomical input data, including bone masses and inertias, joint axis positions and orientations as well as muscle morphological parameters (i.e. PCSA, mass, optimal fiber length and tendon length) were obtained from one cadaver of which the data set was recently published. Model validity was investigated by first comparing computed muscle moment arms at the index finger metacarpophalangeal (MCP) joint and wrist joint to published reference values. Secondly, the muscle forces during pinching were computed using static optimization and compared to previously measured intraoperative reference values. Computed and measured moment arms of muscles at both index MCP and wrist showed high correlation coefficients (r?=?0.88 averaged across all muscles) and modest root mean square deviation (RMSD?=?23% averaged across all muscles). Computed extrinsic flexor forces of the index finger during index pinch task were within one standard deviation of previously measured in-vivo tendon forces. These results provide an indication of model validity for use in estimating muscle forces during static tasks.     

Roping injuries in the hand: mechanism of injury and functional results

Twenty-two patients with roping injuries to 38 digits, including 19 patients injured while team roping, are discussed. Ten digits in nine patients were successfully revascularized or replanted. Seven digits in three patients failed after initial success. One patient is included in both categories. The failure rate is 41 percent for all 17 digits. Average follow-up is 18 months. The dominant hand was injured in 83 percent of team roping injuries; the thumb is the most commonly injured digit. Average interphalangeal motion for thumb replants is zero; for revascularizations, it is 47 degrees. There was 43 percent return of pinch strength for thumb replants compared to 83 percent return for a single thumb revascularization. The most common mechanism of injury was catching the roping thumb in the "thumb up" position during dallying. There are good motion and pinch strength with thumb revascularizations provided tendons and the interphalangeal joint are intact. Reconstruction of the flexor pollicis longus in the replanted thumb gave poor results. Primary tenodesis or arthrodesis is recommended.     

The natural history of the growth of the hand: I. Hand area as a percentage of body surface area

The use of a patient's own hand as a tool to estimate the area of burn injury is well documented. The area of the palmar surface of one hand has been estimated to be 1 percent of the body surface area. The area of the palmar surface of the hand was measured to test the accuracy of this estimate and then compared with the body surface area as calculated by formulas in common use. This study also sought to determine the natural history of the growth of the hand to permit development of a readily available, bedside means of estimating hand area and body surface area. Bilateral hand tracings were obtained from 800 volunteers ranging in age from 2 to 89 years. The area of each tracing was determined using an integrating planimeter. The height and weight of each individual were measured, and his/her body surface area was calculated. The palmar hand's percentage of body surface area was determined by calculating the quotient for hand area divided by body surface area. Additionally, the width of the hand was measured from the ulnar aspect at the palmar digital crease of the small finger to the point where the thumb rested against the base of the index finger. The length of the hand was measured from the middle of the interstylon to the tip of the middle finger. These two figures were multiplied together to obtain a product which approximated the area of the hand. Based on the most commonly used DuBois formula for calculating body surface area, the area of palmar surface of the hand corresponds to 0.78 +/- 0.08 percent of the body surface area in adults. The percentage varies somewhat with age and reaches a maximum of 0.87 +/- 0.06 percent in young children. Multiplying the length of the hand by its width overestimates the area of the hand as determined by planimetry by only 2 percent. A patient's own hand may be used as a complementary, readily available template for estimation of burn area or other areas of disease or injury. In adults, the area of tracing of the outline of the hand is 0.78 percent of the body surface area, whereas in children, this number tends to be slightly higher. In the emergency room or on the wards, a simple product of length multiplied by width of the hand will closely approximate the area as determined by planimetry. This method allows a more accurate determination of the area of the palmar surface of the hand than the 1 percent estimate, which may lead to an overestimation of the size of a burn wound in adults.     

Intrinsic and extrinsic contributions to the passive moment at the metacarpophalangeal joint

The purpose of this investigation was to determine whether the passive range of motion at the finger joints is restricted more by intrinsic tissues (cross a single joint) or by extrinsic tissues (cross multiple joints). The passive moment at the metacarpophalangeal (MP) joint of the index finger was modeled as the sum of intrinsic and extrinsic components. The intrinsic component was modeled only as a function of MP joint angle. The extrinsic component was modeled as a function of MP joint angle and wrist angle. With the wrist fixed in seven different positions the passive moment at the MP joint of eight subjects was recorded as the finger was rotated through its range at a constant rate. The moment-angle data were fit by the model and the extrinsic and intrinsic components were calculated for a range of MP joint angles and wrist positions. With the MP joint near its extension limit, the median percent extrinsic contribution was 94% with the wrist extended 60° and 14% with the wrist flexed 60°. These percentages were 40 and 88%, respectively, with the MP joint near its flexion limit. Our findings indicate that at most wrist angles the extrinsic tissues offer greater restraint at the limits of MP joint extension and flexion than the intrinsic tissues. The intrinsic tissues predominate when the wrist is flexed or extended enough to slacken the extrinsic tissues. Additional characteristics of intrinsic and extrinsic tissues can be deduced by examining the parameter values calculated by the model.     

Rheumatoid arthritis and Dupuytren's contracture

Of four patients with rheumatoid arthritis and Dupuytren's contracture, two were not aware of the presence of Dupuytren's contracture. When both diseases coexist, the presence of rheumatoid hand deformities, especially flexion and ulnar deviation of the metacarpophalangeal joints, may mask the flexion deformity caused by Dupuytren's contracture. Careful clinical examination should rule out the presence of a pathologic fascial cord. When reconstructive surgery is indicated for the rheumatoid hand in the presence of advanced Dupuytren's contracture, staged surgery would be appropriate and reconstruction of Dupuytren's contracture should precede other surgery.     

Posterior interosseous free flap with extended pedicle for hand reconstruction

The anatomy of the posterior interosseous vessels makes them suitable as a donor area of free flap. The skin island can be designed on the perforating vessels of the distal third of the forearm, up to the dorsal wrist crease, to increase the pedicle length (7 to 9 cm). A series of nine flaps transferred to reconstruct hand defects is presented. All flaps were designed over the dorsal distal forearm, and dimensions permitted direct closure of the donor site (up to 4 to 5 cm wide). Apart from a linear scar, donor morbidity was negligible. All transfers were successful. Although its dissection is somewhat tedious, the anatomy of the vascular pedicle is suitable for microanastomosis and the skin island is thin, although hairy. The posterior interosseous free flap with extended pedicle may be a good choice when limited amounts of thin skin and a long vascular pedicle are needed.     

The surgical treatment of Dupuytren's contracture: a synthesis of techniques

Dupuytren's disease is an affliction of the palmar fascia. Selective fasciectomy is recommended once contracture has occurred. Alternatives for wound closure include tissue rearrangement, the open palm technique, and full-thickness skin grafting. In this prospective study, a new "synthesis" technique was used to treat a cohort of patients with advanced Dupuytren's disease. The results were then compared with those of a second cohort of patients who underwent the open palm technique. Thirty consecutive patients were selected. Ten patients (nine men and one woman; average age, 67 years) underwent the open palm technique, and 20 patients (18 men and two women; average age, 70 years) underwent the synthesis method. Follow-up was 3.5 years for the open palm group and 2.7 years for the synthesis group. All patients in both groups improved with respect to motion, function, appearance, and satisfaction. Objectively, for the open palm technique, metacarpophalangeal joint contracture decreased from 50 degrees to 0 degrees, and proximal interphalangeal joint contracture decreased from 40 degrees to 6 degrees. Using the synthesis method, metacarpophalangeal joint contracture decreased from 57 degrees to 0 degrees, and proximal interphalangeal joint contracture decreased from 58 degrees to 10 degrees. The Disabilities of the Arm, Shoulder, and Hand Test scores decreased from 37 to 30 in both groups. There were no significant differences between groups in these parameters. The two significant intergroup differences were healing time (40 days for the open palm technique versus 28 days for the synthesis method) and recurrence rate (50 percent for open palm versus 0 percent for synthesis). The synthesis technique combines with success the best features of current methods for the surgical treatment of advanced Dupuytren's disease.     

拇指背侧皮神经营养血管皮瓣修复对拇指远端软组织缺损的效果观察

目的:探讨拇指背侧皮神经营养血管皮瓣修复拇指远端软组织缺损的临床效果。方法:选取我院2014年1月至2016年12月收治的拇指远端软组织缺损患者100例,随机分为对照组和观察组。对照组采取腹部皮瓣对拇指远端软组织缺损进行修复,观察组采取拇指背侧皮神经营养血管皮瓣对其进行修复。通过随访患者,记录分析皮瓣的生存状况、感觉指标、外观以及手部功能的DASH评分比较两组的修复效果。结果:观察组50例患者皮瓣全部成活。对照组50例皮瓣全部成活。与对照组相比,观察组在触觉、温度觉、单丝、两点辨别觉、瘢痕挛缩方面明显优于对照组(P0.05),臃肿发生率明显低于对照组(P0.05)。观察组DASH评分为29.56±2.14分,对照组为38.13±3.12分,观察组的DASH评分明显低于对照组(P0.05)。结论:拇指背侧皮神经营养血管皮瓣修复拇指远端软组织缺损手术不破坏主要血管神经,对供区影响小,操作简单,修复的指腹感觉,拇指外形较佳,是较为理想的选择。     

Precision grips,hand morphology,and tools

This study asks whether there are discernable links between precision gripping, tool behaviors,

1 The term “tool behavior” has been variously used in the literature, in some cases implying exclusively tool making distinctive of humans (Susman, 1991) and in others referring variably to tool using and/or tool-making abilities, some shared with us by other animals (Susman, 1988a,b, 1994). In this paper the term is used to include both tool using and tool making behaviors of humans and non-humans; the term “tool making” is used in place of “tool behavior” whenever the discussion is focused upon distinguishing a capacity for removing flakes from stone preforms from a more general capacity to manipulate stone tools.

and hand morphology in modern hominoids, which may guide functional interpretation of early hominid hand morphology. Findings from a three-pronged investigation answer this question in the affirmative, as follows. (1) Experimental manufacture of early prehistoric tools provides evidence of connections between distinctive human precision grips and effective tool making. (A connection is not found between the “fine” thumb/index finger pad precision grip and early tool making.) (2) Manipulative behavior studies of chimpanzees, hamadryas baboons, and humans show that human precision grips are distinguished by the greater force with which objects may be secured by the thumb and fingers of one hand (precision pinching) and the ability to adjust the orientation of gripped objects through movements at joints distal to the wrist (precision handling). (3) Morphological studies reveal eight features distinctive of modern humans which facilitate use of these grips. Among these features are substantially larger moment arms for intrinsic muscles that stabilize the proximal thumb joints. Examination of evidence for these reveals that three of the eight features occur in Australopithecus afarensis, but limited thumb mobility would have compromised tool making. Also, Olduvai hand morphology strongly suggests a capacity for stone tool making. However, functional and behavioral implications of Sterkfontein and Swartkrans hand morphology are less clear. At present, no single skeletal feature can be safely relied upon as an indicator of distinctively human capabilities for precision gripping or tool making in fossil hominids. Am J Phys Anthropol 102:91–110, 1997. © 1997 Wiley-Liss, Inc.