Biomechanical evaluation of wrist motor tendons after fractures of the distal radius

We conducted a biomechanical study of changes in parameters of wrist motor tendons in fractures of the distal radius in 7 cadaveric extremities. Extra-articular distal radius fractures were simulated by distal radius osteotomy and fracture angulation was maintained by external fixators. Eight positions of the distal radius fractures were studied: dorsal angulation of 10 degrees, 20 degrees, 30 degrees, and 40 degrees and radial angulation of 5 degrees, 10 degrees, 15 degrees, and 20 degrees. Dorsal and radial angulation of the fractures were measured with respect to the shaft of the radius. Excursions of 5 principal wrist motor tendons extensor carpi radialis longus, extensor carpi radialis brevis, extensor carpi ulnaris, flexor carpi radialis, and flexor carpi ulnaris were recorded simultaneously with wrist joint angulation using a computer-assisted recording system. Data were collected from intact wrists and from wrists with fractures at each of 8 positions of angulation during wrist flexion and extension and radical and ulnar deviation. Moment arm of the wrist motor tendons was derived from tendon excursion and joint angulation. The results demonstrated that excursions and moment arms of principal wrist motor tendons are significantly affected by dorsal and radial angulation of distal radius fractures. Amplitude of changes in moment arms increased as the deformities became more severe. Statistical analysis revealed that dorsal angulation of 10 degrees or more significantly affected moment arms of all the prime wrist motors. Dorsal angulation of 30 degrees or 40 degrees changed the moment arms greatly. Radial angulation of 5 degrees did not affect moment arms of the tendons and angulation over 10 degrees had a statistically significant effect on the tendons. We conclude that deformities of distal radius fractures have a significant influence on the biomechanics of the wrist motors.     

Effect of radial shortening on muscle length and moment arms of the wrist flexors and extensors

The purpose of this study was to determine the effect of distal radial shortening on muscle length and moment arm of the wrist flexors and extensors. In eight cadaveric upper extremities, distal radius fractures were simulated by an ostectomy. The distal radius was progressively shortened by 2.5, 5.0, 7.5, and 10 mm. Changes in the resting length of the flexor carpi radialis and ulnaris, extensor carpi radialis longus and brevis, and extensor carpi ulnaris muscles were measured with rotary potentiometers at neutral position, flexion, extension, and radial and ulnar deviation of the wrists. The wrists were passively moved through flexion-extension and radioulnar deviation, and tendon excursions and wrist joint angulation were recorded simultaneously. Tendon moment arms were derived from tendon excursions and joint motion. The results showed that either muscle, length or moment arm of the principal wrist flexors and extensors was significantly affected by the radial shortening. Muscle length decreased significantly after radial shortening in all the wrist flexors and extensors except for the extensor carpi ulnaris. The moment arm of the extensor carpi ulnaris tendon decreased significantly during either wrist flexion-extension or radioulnar deviation. The extensor carpi radialis brevis and flexor carpi ulnaris tendons also showed a significant decrease in their moment arms during radioulnar deviation of the wrist. Radial shortening of only 2.5 mm caused statistically significant changes in muscle length and moment arm of the wrist flexors and extensors. Increasing the extent of radial shortening exaggerated the biomechanical changes in the wrist motors. These results validate the importance of normal radial length for wrist kinetics and, from a biomechanical perspective, support complete correction of radial shortening after distal radius fractures.     

Wrist kinetics after scapholunate dissociation: the effect of scapholunate interosseous ligament injury and persistent scapholunate gaps.

The purpose of this study was to investigate the effects of cutting of the scapholunate interosseous ligament (SLIL) and persistent widening of the scapholunate (SL) joint on changes in moment arms of the principal wrist motor tendons. In seven fresh frozen cadaveric upper extremities, excursions of the extensor carpi radialis longus (ECRL) and brevis (ECRB), extensor carpi ulnaris (ECU), flexor carpi radialis (FCR), and flexor carpi ulnaris (FCU) were recorded simultaneously with wrist joint angulation during wrist flexion-extension and radioulnar deviation. Tendon excursions were measured in intact wrists, then in the wrists with complete SLIL sectioning and in those with moderate or severe persistent SL joint widening. The data were converted to moment arms of the tendons. The results showed that moment arms of the ECRL and ECRB tendons after SLIL sectioning were, respectively, 110+/-6% and 105+/-3% of those in the intact wrist. In the wrists with moderate or severe SL joint widening, moment arms of the flexors significantly increased (P < 0.01 and P < 0.001, respectively). During radioulnar deviation, moment arms of the ECRL, ECRB, ECU, and FCU tendons decreased after SLIL sectioning and the SL joint widening. However, moment arms of the FCR tendon significantly increased 122+/-23% after the SLIL section, 133+/-28% after the moderate SL joint widening, and 138+/-24% after the severe SL joint widening compared with those of the intact wrists. This study demonstrated that integrity of the SLIL and appropriate SL joint space are important for mechanics of wrist motor tendons. Loss of integrity of the SLIL and persistent SL joint widening increase mechanical effects of the radial side wrist motor tendons, which may contribute to the pathomechanics of scaphoid malrotation, scapholunate advanced collapse, and early osteoarthritis in the radioscaphoid joint interface seen in SL dissociation. The results also suggest that reduction of the displaced SL joint is imperative to the recovery of wrist kinetics after SL dissociation.     

创伤性舟月骨分离的腕动力学研究

目的 通过生物力学研究,探讨腕创伤性舟月骨分离及临床并发症的生物力学机制和治疗要求。方法 采用７只新鲜冷冻尸体上肢,分别在腕关节完整、舟月骨间韧带切断、中度及重度舟月骨间隙增大四个实验测定腕关节屈伸和尺桡偏运动时,腕主要运动肌腱的滑动距离,并根据滑动距离和关节运动角度与力臂之间的关系计算机肌腱力臂。结果 在舟月骨间韧带切断后腕屈伸运动时桡侧伸腕肌腱的力臂明显增大;在舟月骨间韧带切断及舟月骨间隙增大     

月骨周围进行性不稳定的腕运动学研究

目的 探索腕月骨周围进行性不稳定的运动力学变化。方法 对１４具新鲜冷冻尸体腕关节，用计算机辅助测量了正常腕和各阶段月骨周围不稳定时腕动力肌腱在腕屈伸，尺桡偏时滑动幅度，根据肌腱滑动幅度和关节运动范围计算动力肌腱力臂。结果 月骨周围进行性不稳定时屈腕肌腱力臂明显增大，屈指肌腱力臂减小；桡侧腕动力肌腱力臂以增大为主，尺侧肌腱力臂以减小为主。桡侧腕屈肌在腕肌屈伸或尺桡偏时均显著增大，结论 腕运动力学变化     

Trapeziometacarpal joint instability affects the moment arms of thumb motor tendons

This study measured the changes in moment arm length of thumb motor tendons after simulated ligamentous instability and subsequent reconstruction of the trapeziometacarpal joint. Excursions of thumb motor tendons were measured simultaneously with the trapeziometacarpal joint angulation during flexion to extension and abduction to adduction motion. Tendon moment arms were calculated based on joint and tendon displacement techniques in the intact joint, after sequential sectionings of the capsuloligamentous restraints, and after the reconstruction procedure of Eaton and Littler. The results showed that moment arms of the abductor pollicis longus and extensor pollicis brevis tendons increased significantly as compared with those for normal joints during flexion to extension motion after sectioning the palmar capsuloligamentous components. After the ulnopalmar structures were cut, the moment arm of the extensor pollicis longus tendon had a statistically significant increase during abduction to adduction motion, and those of the extensor and flexor pollicis longus tendons decreased significantly during flexion to extension motion. Changed moment arms were restored to a normal level after the ligamentous reconstruction. These results indicate that ligamentous disruptions alter the mechanical balance of thumb motor tendons, which may contribute to joint deformities observed in trapeziometacarpal joint arthritis. Restoring joint stability is important to correct mechanical imbalance of the tendons.     

Isolated ischemic contracture of the mobile wad: a report of two cases

Two children with isolated ischaemic contractures of the mobile wad (extensor carpi radialis longus, extensor carpi radialis brevis and brachioradialis), which developed after treatment of a supracondylar fracture, are presented. Z-lengthening of the extensor carpi radialis longus and brevis tendons improved wrist flexion.     

Architecture of selected wrist flexor and extensor muscles

The architectural features of 25 wrist flexor and extensor muscles were studied. Muscles included the flexor carpi ulnaris, the flexor carpi radialis, the extensor carpi ulnaris, the extensor capri radialis brevis, and the extensor carpi radialis longus. Muscle length, mass, fiber pennation angle, fiber length, and sarcomere length (by use of laser diffraction techniques) were determined. In addition, physiological cross-sectional area and fiber length/muscle length ratio were calculated. The muscles were found to be highly specialized, with architectural features of same muscles very similar. The fiber length/muscle length ratio, muscle length, and pennation angle represented the major differences between muscles. Thus using these parameters in discriminant analysis permitted correct identification of each of the 25 muscles. In terms of size and intrinsic design, these individual muscles were highly specialized for their function.     

Complications of opponensplasty with transfer of extensor carpi ulnaris to extensor pollicis brevis

The extensor carpi ulnaris (ECU) was transferred to the extensor pollicis brevis, as described by Phalen and Miller, in 12 patients with hand deformities from high and low median and ulnar nerve injuries. Although no complications of this transfer have been reported by other surgeons, four of our 12 patients developed significant radial deviation and loss of power grip. This complication was corrected in two patients by transferring the extensor carpi radialis longus to the base of the fifth metacarpal to balance the wrist extensor forces. We believe that this complication may occur when the extensor carpi radialis inserts into the radial aspect of the second metacarpal and when the ECU inserts into the ulnar aspect of the base of the fifth metacarpal. The flexor carpi ulnaris must have normal strength if the wrist is to be balanced after the ECU is transferred.     

A modified technique of two-staged extensor tendon reconstruction in zones 6–8 in a patient with absent palmaris/plantaris tendons: A case report

IntroductionThe indications for two-staged extensor tendon reconstruction are rare and only 14 previously reported cases were found in the literature. In these cases, silicone rods are inserted in the first stage. Few months later, the palmaris longus / plantaris tendon grafts are usually used to replace the silicone rods.Case reportwe encountered a patient with major defects of the extensor tendons of all fingers extending from the proximal one third of zone 6 to zone 8. The patient had no palmaris or plantaris tendons. We utilized a modified technique of reconstruction using the split flexor carpi radialis as the tendon graft and the flexor carpi ulnaris as the motor tendon. At final follow-up, there was full active extension of the fingers. However, there was limitation of wrist flexion because of the harvesting of both wrist flexors.DiscussionWe describe a modified technique of two-staged extensor tendon reconstruction which may be used in patients with absent palmaris/ plantaris tendons.ConclusionIn patients with absent palmaris/ plantaris tendons and major defects of the extensor tendons of all fingers, the use of split flexor carpi radialis is an adequate alternative for reconstruction and gives a good functional outcome.     

Wrist kinetics after luno-triquetral dissociation: the changes in moment arms of the flexor carpi ulnaris tendon.

Wrist biomechanics after luno-triquetral (LT) dissociation is important for understanding the clinical sequelae of the disease and for determining its treatment options. The LT interosseous ligament plays an important role in stabilizing the joint and damage to the ligament would be expected to significantly increase moment arms of tendon of the flexor carpi ulnaris (FCU), the principal ulnar wrist flexor. We investigated the changes in moment arms of FCU tendon after various amounts of sectioning of the ligaments proven to be associated with LT dissociation. In six fresh frozen cadaveric upper extremities, excursions of the FCU tendon were recorded simultaneously with wrist joint angulation during wrist flexion-extension and radioulnar deviation. Tendon excursions were measured in intact wrists, in wrists with sectioning of the dorsal portion of the LT interosseous ligament, in wrists with sectioning of the entire LT interosseous ligament, and finally in wrists with further sectioning of the dorsal radiotriquetral and intercarpal ligaments. Moment arms of the tendon were calculated from tendon excursions and joint motion angulations and expressed as percentage changes from those in the intact wrist. During wrist flexion-extension, moment arms of the FCU tendon after sectioning of the entire LT interosseous ligament and after sectioning of the two capsular ligaments were 112 +/- 7% and 114 +/- 8%, respectively; these values were significantly greater than those in the intact wrist. During radioulnar deviation, the moment arms were 114 +/- 11% after sectioning of the dorsal portion of the LT interosseous ligament, 134 +/- 15% after sectioning of the entire ligament, and 153 +/- 18% after sectioning of the capsular ligaments, again being significantly greater than the normal wrist. Increase in moment arms of the FCU tendon after loss of integrity of the LT interosseous ligament and dorsal capsular ligaments may contribute to clinical sequelae of LT dissociation and difficulty in treating this disorder.     

The extensor carpi radialis intermedius tendon

I examined 312 arms from 156 cadavers in the anatomy laboratory of Loma Linda University to find the incidence of the extensor carpi radialis intermedius tendon. I found 29 bodies (12%) that had a good extensor carpi radialis intermedius. In 17 of these 29 bodies, an extra tendon was found bilaterally. Thirty-two extensor carpi radialis intermedius tendons were suitable for transfer operations, and seven were unacceptable. One must be careful to differentiate between a true extensor carpi radialis intermedius tendon and accessory tendinous bands. The relatively high incidence rate and percentage of tendons suitable for transfer operations make this tendon potentially valuable in treating severe quadriplegia with tendon transfers. It can be used successfully for thumb opposition, to motor the flexor pollicis longus, or as a motor for the extensor pollicis longus of the thumb.     

Moment arm and force-generating capacity of the extensor carpi ulnaris after transfer to the extensor carpi radialis brevis.

Tendon transfers to the extensor carpi radialis brevis (ECRB) are often performed to augment wrist extension. This study was conducted to analyze how transfer of the extensor carpi ulnaris (ECU) to the ECRB affects the moment arms, force-generating capacity, and moment-generating capacity of the ECU over a range of wrist flexion-extension. A graphics-based computer model was developed from anatomic measurements of the muscle-tendon paths before and after transfer. This model calculates the lengths and moment arms of the muscles over a range of wrist flexion-extension and represents the muscles' force-generating characteristics from previous measurements of their physiologic cross-sectional areas, fiber lengths, and pennation angles. Analysis of the computer model revealed that the maximum isometric extension moment of the ECU at the neutral wrist position increased from 0.50 N-m to 1.72 N-m after transfer to the ECRB. The deviation moment shifted from 2.72 N-m ulnar deviation to 1.42 N-m radial deviation. The extension moment generated by the ECU varied more with wrist flexion angle after transfer due to its broadened operating range on the muscle force-length relationship. The simulations highlight the need for proper intraoperative tensioning of the ECU to maximize the force-generating potential of the transferred muscle over the functional range of motion.     

肌肉再分布技术应用于智能仿生手的解剖学研究

目的:研究肌肉再分布技术中关键肌肉-肌腱运动单元的外科腱腹交界部位,为不同平面截肢病例选择合理的肌肉再分布手术方案提供解剖学依据。方法:取新鲜上肢标本6侧,对前臂关键肌肉-肌腱运动单元,包括拇长屈肌、示指指深屈肌、肱桡肌、桡侧腕屈肌、拇长伸肌、示指固有伸肌、桡侧腕长伸肌、尺侧腕伸肌,分别测量其外科腱腹交界部位距肱骨内上...     

腕管综合征内窥镜手术预防正中神经损伤的临床研究

目的 介绍腕管综合征内窥镜手术(endoscopic carpal tunnel release,ECTR)预防正中神经损伤并发症的方法.方法 利用彩色多普勒超声仪(B超)对37例74手患者术前进行检测.结果 71例正中神经走行在桡侧腕屈肌腱与掌长肌腱之间,3例走行在掌长肌腱与尺侧腕屈肌腱之间,并术中确认.结论 正中神经变异走行在掌长肌腱与尺侧腕屈肌腱之间是ECTR的禁忌证,B超能准确定位正中神经与掌长肌腱关系,避免内窥镜手术损伤正中神经,更具有简单、经济、方便可靠等优点.

Abstract：

Objective To introduce a method of preventing median never injury during endoscopic carpal tunnel release (ECTR). Methods Ultrasonography of both wrists was done to 37 patients of carpal tunnel syndrome who were going to undergo open release of the transverse carpal ligament. Structures in the carpal tunnel were visualized to guide surgical decision-making. Results Ultrasonography showed that median never lies between the tendon of flexor carpi radialis and palmaris longus in 71 patients and lies between the tendon of palmaris longus and flexor carpi ulnaris in 3 patients. These findings were confirmed during the surgeries. Conclusion It is a contraindication of ECTR if median never lies between palmaris longus and flexor carpi ulnaris. Ultrasonography can accurately reveal the relative position of median never to the palmaris longus tendon. Pre-operative ultrasonography of the wrist is a simple, inexpensive and convenient method to exclude these contraindications and thus prevent median never injuries in ECTR.     

Are tendon transfers justified in very old hand radial palsies?

There have been very few reports about results of tendon transfers carried out in very old radial palsies affecting the hand. We present two cases of radial palsy operated 52 and 30 years after the original injury, which also had after-effects in pronosupination due to elbow injuries. In the first patient, with high radial-nerve palsy, we made a triple transfer of the pronator teres to the extensor carpi radialis brevis, the flexor carpi ulnaris to the extensor digitorum communis and the palmaris longus to the extensor pollicis longus. In the second case, which had posterior interosseous nerve palsy, we transferred the flexor carpi radialis to the extensor digitorum communis, and the brachiorradialis to the extensor pollicis longus. The surgical findings showed a 'gelatinous degeneration' in some of the receiving tendons, which did not prevent the sutures from being resistant. The first patient, who had a stiff elbow, with pronosupination blocked since childhood, showed disuse atrophy of the pronator teres, which conditioned a late rupture of the tenomuscular junction and required a second surgery for wrist arthrodesis. Results after postoperative period of 30 months after surgery in the first patient, and 14 months after surgery in the second one, showed functional recovery in finger range of extension, grip and key-pinch strength and a significantly higher QuickDASH score, restoring the natural aesthetical appearance of the limb. This facilitated the return to professional and daily activities, re-establishing a fine ability to grab and release objects.     

The centralization of extensor tendons during wrist surgery

After a wrist surgery in patients with rheumatoid arthritis, the extensor tendons have a tendency to shift toward the ulnar side of the wrist. This is caused by the dorsal tenosynovectomy, disruption of extensor retinaculum, and exteriorization and anatomical orientation of the superficial group of forearm extensor tendons. This article describes a technique as an adjunct to the wrist surgery, which aims to stabilize and centralize tendons of the fourth dorsal wrist compartment over the midline of the wrist. This is achieved by creating a distally based sling, harvested from the extensor carpi radialis longus tendon, then wrapped around the extensor digitorum communis and the extensor indicis proprius tendons, and finally anchored onto the extensor carpi radialis brevis. This adjunctive procedure is recommended in situations when after the wrist surgery, particularly wrist arthroplasty, tendons of the fourth dorsal wrist compartment tend to lay ulnar to the central axis of the hand.     

Long-term results of tendon transfers in radial and posterior interosseous nerve paralysis

Eighteen cases of tendon transfer for isolated radial or posterior interosseous nerve palsy have been carried out in our unit over a period of 21 years. Fifteen patients were reviewed with a mean follow-up of 9.5 years. Nine had sustained high and six low radial nerve injury. We achieved 11 excellent, two good, one fair and one bad result. The main problems were loss of power of gripping and the occurrence of radial deviation, particularly in patients with flexor carpi ulnaris transfer to the extensor digitorum communis. During this time, our technique has evolved, including changes of the tendons transferred. Our final preference is a modified Tsuge procedure, using the pronator teres to restore extension of the wrist, the flexor carpi radialis for extension of the fingers and the palmaris longus for extension of the thumb. Abduction of the thumb is restored by a tenodesis of the abductor pollicis longus to the brachioradialis. This review justifies the final policy, in particular the preservation of flexor carpi ulnaris to maintain wrist stability and flexion.     

Anomalous palmar cutaneous branch of the median nerve in the distal forearm: case report

Variations exist in the anatomy of the palmar cutaneous branch of the median nerve about the wrist. We report an anatomic variation in the course of the palmar cutaneous branch of the median nerve identified in a 17-year-old girl undergoing surgery for a scaphoid nonunion. Instead of coursing ulnar to the flexor carpi radialis tendon, deep to the antebrachial fascia between the tendons of the flexor carpi radialis and palmaris longus, the palmar cutaneous branch of the median nerve was noted to cross volar to the distal aspect of the flexor carpi radialis to lie on its radial aspect. Knowledge of the anatomic variant described in this report should encourage surgeons to dissect carefully as they expose the flexor carpi radialis during the exposure of the distal radius or scaphoid.     

Intersynovial communication between the tendon sheaths of the extensor pollicis longus and extensor carpi radialis brevis muscles

A communication was found between the synovial sheaths of the extensor pollicis longus and the extensor carpi radialis brevis tendons. The opening was at the level of the proximal row of carpal bones and permits passage of synovial fluid between the sheaths of these muscles.