Bilateral abductor pollicis longus muscle variation. Case report and review of the literature

An abnormal abductor pollicis longus muscle was encountered bilaterally during the dissection of the upper limb of a 26-year-old male cadaver. In the left side, the abductor pollicis longus had seven tendon slips. The medial two inserted into the abductor pollicis brevis, the other five inserted into the base of the first metacarpal bone. In the right side of the case, the abductor pollicis longus was consisted of three bellies. The lateral belly's tendon was the main abductor pollicis longus tendon and inserted into the base of the first metacarpal bone. The medial belly inserted into the abductor pollicis brevis. Between these muscle bellies, there was an intermediate belly. Its tendon was split into two thin slips and inserted into both the abductor pollicis brevis and the opponens pollicis muscles. The number of such accessory tendons has a functional significance in the development of de Quervain's stenosing tendovaginitis and possibly also has a practical significance. This paper is the first to describe seven tendons of the abductor pollicis longus and extensor pollicis brevis in the same compartment.     

Case of an abductor pollicis longus muscle: variation or differentiation?

A variation of the abductor pollicis longus muscle in a 65 year old cadaver was encountered during routine dissection in our department. The muscle was found to split into two bellies and give off two tendons, one of which inserted to the abductor pollicis brevis, opponens pollicis and flexor pollicis brevis muscles. The other tendon inserted to the first metacarpal bone which is considered a normal insertion site for the abductor pollicis longus muscle.     

拇短展肌双肌腹双起始变异1例

拇短展肌具有外展、外旋拇指及使拇指腕掌关节屈曲的作用.拇短展肌一般为单肌腹,双肌腹变异极为罕见.我们在新鲜标本的解剖中,发现拇短展肌存在双肌腹双起点变异,报道如下:该标本系青年男性前臂远端肢体标本,我们解剖发现拇短展肌具有两个肌腹,按其位置关系可分为尺侧肌腹和桡侧肌腹,其中足侧肌腹的桡侧被桡侧肌腹的尺侧部分覆盖.     

A variation in the organization of abductor pollicis longus

The abductor pollicis longus (APL) muscle has been studied bilaterally in 50 cadavers. A variation in the organization of the muscle was found bilaterally in 15 of the 50 specimens. The novel muscular arrangement gives the appearance of being an additional muscle belly arising from the lateral aspect of the distal portion of the typical abductor pollicis longus muscle belly. This variation in the arrangement also creates a retinacular-like tunnel which encases the tendons of the extensor carpi radialis longus and the extensor carpi radialis brevis muscles. To the authors' knowledge, this arrangement has not been cited in the recent medical literature. An understanding of this unusual finding may be clinically relevant in describing the dorso-lateral compartment of the distal forearm. © 1996 Wiley-Liss, Inc.     

The abductor pollicis longus: relation between innervation, muscle bellies and number of tendinous slips

The aim of this study was to assess the relation between the insertions of the distal tendinous slips, the muscle bellies and the innervation pattern of the abductor pollicis longus (APL) muscle and of the extensor pollicis brevis (EPB). The upper extremities of 31 frozen cadavers were dissected under magnifying lenses to describe the distribution of the posterior interosseous nerve (PION). The number and the distribution of distal tendinous slip insertions of the APL muscle were variable. Two superficial and deep distal tendon groups were noted. The separation into superficial and deep muscular parts of the APL was frequent (87%). The EPB muscle was generally constituted by one muscle belly and one tendinous slip (93.5%). The innervation by the PION to the APL and EPB muscles was classified into five types. The specific innervation between superficial and deep muscular parts of the APL muscle, the specific innervation of the deep muscle bellies and the independence of the superficial and deep distal tendon groups of the APL muscle are arguments in favor of a complex functional role of the APL motor unit in thumb mechanics. However, no independence of the tendinous slips in the two distal tendon groups and no correlation between the number of tendinous slips and muscle bellies or innervation were observed. These limit the functional role of the two independent superficial and deep musculotendinous APL motor units. The use of the APL tendon for interposition arthroplasty, for tendon transfer or tendon translocation seems logical, particularly if using one of the two distal tendon groups.     

Variant of the extensor pollicis tertius: a case report on a unique extensor muscle to the thumb

Variations on muscular and tendinous connections of the hand occur frequently in the human population and are often discovered during routine surgical procedures and cadaveric dissections. A knowledge of such anomalies is important to the physician in order to avoid unintentional damage to healthy tendons during surgical procedures. In addition, accessory tendons have the potential to be used in the repair or replacement of damaged tendons through surgical transfer or transplantation. Here we describe a unique variant of the extensor pollicis tertius muscle that has its origin at the proximal end of the extensor indicis muscle and inserts on the tendon of the extensor pollicis longus at the proximal shaft of the proximal phalanx of the thumb.     

Anatomical variations of the extensor pollicis brevis tendon and abductor pollicis longus tendon--relation to tenosynovectomy

Sufficient improvement in De Quervain disease, is not always archieved even by tenosynovectomy, and the reason for this appears to be anatomical variation in the first extensor compartment of the hand. In this study we examined the first extensor compartment of 159 hands of 80 human cadavers. Hiranuma and colleagues documented four anatomical types of first compartment, and in this study type A was observed in 76 (47.8%) of the 159 hands, type B in 49 (30.8%), and type C in 21 (13.2%). No type D compartments in which the extensor pollicis brevis tendon is absent, were observed. There were 13 hands that did not fit any of Hiranuma's categories, and we classified them into three new types: E, F, and G. The numbers of extensor pollicis brevis tendons in the first compartment varied from one to three, and the number of abductor pollicis longus tendons varied from one to seven. Successful tenosynovectomy in the treatment of De Quervain disease requires to pay close attention to accessory tendons of the extensor pollicis brevis tendon and abductor pollicis longus tendon, branching of the tendons, and the presence of an atypical septum in the first compartment.     

3D打印截骨导板辅助下的TKA手术在河西走廊地区的临床应用

目的　比较3D打印截骨导板辅助全膝关节置换（total knee arthroplasty,TKA）与传统手术方式行TKA的临床效果差异,探讨应用3D打印个性化截骨技术在TKA中的临床应用价值。 方法　将2015年10月~2018年6月间行TKA的120例（136膝）患者,随机分成3D组和传统组,3D组60例（70膝）采用3D打印截骨导板辅助膝关节置换手术,传统组60例（66膝）采用传统的膝关节置换方法。术前两组患者年龄、性别、KSS（knee society score）评分,均无统计学差异（P>0.05）。记录手术时间,术中实际股骨远端、胫骨近端截骨量,术后X线片测量平均股骨、胫骨机械轴夹角（MFTA）,矢状位胫骨平台后倾角（STCA）,并进行统计学分析,末次随访时行KSS评分。 结果　术后随访9~32个月,两组病例均未出现关节感染,假体松动、移位、下沉等并发症。3D导板组术前规划的股骨远端、胫骨近端截骨量与手术实际无统计学差异（P>0.05）;3D导板组的手术时间、MFTA值、STCA值与传统组相比差异有统计学意义（P<0.05）;末次随访3D导板组KSS临床及功能评分均高于传统组,两组间差异有统计学意义（P<0.05）。 结论　3D打印个性化截骨技术简化了TKA手术步骤,可提高手术的精准度与临床疗效,值得进一步推广应用。     

拇长屈肌变异2例

在制作上肢肌肉标本时,发现拇长屈肌变异2例,此类变异少见,现报道如下:变异1标本1为一成年男性左侧上肢肌肉标本.分开其肌间隙后,见指浅屈肌、指深屈肌、拇长屈肌均正常,在深层指深屈肌与拇长屈肌之间见一异常肌束.     

Fiber type composition of contiguous palmaris longus and abductor pollicis brevis muscles: Morphological evidence of a functional synergy

The palmaris longus (PL) tendon is used in surgical opponensplasty to restore functional hand movements in thenar paralysis. Although successful PL autologous tendon transfer has been attributed to an established synergistic relationship between the PL and abductor pollicis brevis (APB) muscles in vivo, this functional relationship may be dependent on the quality of their spatial relationship and properties of their constituent muscle fibers. The purpose was to compare the proportion of type I and type II muscle fibers in the APB based on its contiguous morphological relationship with the PL tendon for indirect insight into their functional synergy, contractile capacity, and digastric arrangement. Twenty-four contiguous PL and APB specimens were harvested from the upper limbs (12 right and 12 left) of twelve formalin-embalmed cadavers (mean age: 74 ± 10 years). The fiber type composition of these muscles was determined by labeling serial cross sections with myosin heavy chain (MyHC) type I and type II monoclonal antibodies. The PL consisted of a relatively heterogeneous fiber type composition irrespective of the presence of a discrete (type I: 41 ± 11%; type II: 55 ± 12%; hybrid: 4 ± 3%) or rudimentary (type I: 49 ± 10%; type II: 45 ± 9%; hybrid: 6 ± 4%) tendinous connection with the APB. The APB fascicles arranged contiguously with the PL through a discrete tendon had significantly greater proportions of type II fibers (41 ± 19%) compared to those with rudimentary PL connections (type II: 15 ± 8%). Therefore, the APB fascicles arranged in a digastric relationship with the PL may have the capacity to produce more powerful contractions than those with rudimentary PL tendons based on the known contractile properties of type II muscle fibers. Knowledge of the spatial relationship between the PL and thenar musculature prior to PL autologous tendon transfer may be a useful indicator of the quality of established synergy in vivo.     

Variant course of extensor pollicis longus tendon in the second wrist extensor compartment

Among the muscles involved in thumb movement, the extensor pollicis longus (EPL) tendon of the hand is considered the most consistent structure with the least variation among individuals. There have been a few reports regarding different types of supernumerary tendons; however, an abnormal course of the EPL tendon is extremely rare. We describe a case of a variant course of a single EPL tendon appearing in the second extensor compartment of the wrist. This case was observed incidentally during wrist surgery, and demonstrates a unique variation of tendon course, which has not been reported previously. The knowledge of this anatomic variation is helpful in surgical planning and for making accurate diagnoses.     

Three-headed reversed palmaris longus muscle: a case report and review of the literature

The palmaris longus muscle (PLM) is extremely variable both in number and form. We present the first reported case of three-headed reversed PLM in a 36-year old woman. The relevant literature is reviewed. Variations of the muscles of the forearm and specifically the PLM are not uncommon. However, different rates are given for the types and agenesis of PLM. In one study, the incidence of agenesis was 12.8% and other anomalies were 9%. 15 cases of reversed PLM have been reported in the literature. In our case, the three-headed PLM was resected. The patient’s symptoms resolved and at 1-year follow-up she remains symptom-free.     

An accessory belly of the abductor digiti minimi muscle: a case report and embryologic aspects

Accessory fasciculi of the hypothenar muscles have been involved in vascular and nerve compressions. During a routine dissection an accessory belly of the abductor digiti minimi muscle arising from the tendon of the palmaris longus muscle was found in the lower third of the forearm. The accessory fasciculus ran through Guyon’s canal enclosing the ulnar nerve and vessels. It was attached by means of two tendons where the fibres of the abductor digiti minimi muscle ended in a single pennate form. This anatomic variation was associated with a marked reduction of the caliber of the fourth tendon of the flexor digitorum superficialis muscle and a split of the median nerve. The nerve supply arose from the ulnar nerve. A fibrous band originating from this accessory muscular belly was found covering the median nerve. Based on the development of muscles and fibrous structures within the hand and forearm, as well as on our results, we consider the present anomalies as an unusual persistence of an undifferentiated group of mesenchymal cells. These belong to the superficial muscular anlagen layer of the hand, just between the flexor digitorum superficialis muscle blastema (which has the capacity of migration) and that for the abductor digiti minimi muscle.     

System identification of evoked mechanomyogram from abductor pollicis brevis muscle in isometric contraction

The purpose of this study is to verify the applicability of a sixth-order model to the mechanomyogram (MMG) system of the parallel-fibered muscle, which was identified from the MMG of the pennation muscle. The median nerve was stimulated, and an MMG and torque of the abductor pollicis brevis muscle were measured. The MMGs were detected with either a capacitor microphone or an acceleration sensor. The transfer functions between stimulation and the MMG and between stimulation and torque were identified by the singular value decomposition method. The torque and the MMG, which were detected with a capacitor microphone, DMMG, were approximated with a second- and a third-order model, respectively. The natural frequency of the torque, reflecting longitudinal mechanical characteristics, did not show a significant difference from that of the DMMG. The MMG detected with an acceleration sensor was approximated with a fourth-order model. The natural frequencies of the AMMG reflecting the muscle and subcutaneous tissue in the transverse direction were obtained. Both DMMG and AMMG have to be measured to investigate the model of the MMG system for parallel-fibered muscle. The MMG system of parallel-fibered muscle was also modeled with a sixth-order model.