Investigation of radialization and rerouting of the extensor digiti minimi (EDM) in the abduction deformity of the little finger: a cadaver study

Modification of the Zancolli Lasso Procedure for Simultaneous Correction of Wartenberg's Sign

Ulnar nerve injury initiates an imbalance between the intrinsic muscles and extrinsic extensors of the ring and small fingers, which leads to the characteristic hyperextension of the metacarpophalangeal (MP) joints and flexion of the proximal interphalangeal joints of these 2 digits-commonly referred to as the ulnar claw hand. In addition to these changes in the static posture of the hand, ulnar nerve palsy severely impairs grasp due to deficient active MP joint flexion. In most cases, motor balance can be restored by preventing MP joint hyperextension and augmenting MP joint flexion using the Zancolli lasso procedure (ZLP). Ulnar neuropathy can cause a second motor imbalance between the ulnar intrinsics and the extensor digit minimi leading to an abduction deformity of the small finger known as Wartenberg's sign. The inability to adduct the small finger can be a great source of frustration to patients. Using a cadaveric biomechanical model, we have developed a simple modification of the Zancolli lasso procedure that simultaneously corrects claw deformity and Wartenberg's sign and we report its efficacy in 2 clinical cases.

New Insights into Boxer's Knuckle Injury of the Little Finger

BACKGROUND

The original description of boxer's knuckle injury of the fifth ray mentions that the injury occurs between the extensor digitorum communis (EDC) and the extensor digiti minimi (EDM). Subsequent reports claim similar findings. Anatomical studies show that the EDC of the fifth ray is absent in most patients, while the EDM is generally composed of two slips. We present a modification of the current description of boxer's knuckle injury of the little finger based on the correlation between advanced preoperative 3D imaging and intraoperative findings.

METHODS

Five patients were investigated preoperatively using high-resolution ultrasound and 3D tendon reconstruction-based MR arthrography. Surgical exploration identified the lesion site relative to the EDM and EDC.

RESULTS

All patients had two slips of the EDM and no EDC to the fifth ray. The injury appeared as a longitudinal tear of the EDM between its two slips. The mean gap was 7.8 mm (range 4.5-10 mm) on the pathological side vs. 1.3 mm (range 1-2 mm) on the healthy contralateral side.

CONCLUSIONS

We believe that previous descriptions of boxer's knuckle of the fifth ray are inaccurate. High-resolution ultrasound and 3D reconstructions based on MR arthrography are reliable diagnostic tools allowing to locate the injury with precision.

Repair Method for Complete High Ulnar Nerve Injury Based on Nerve Magnified Regeneration

PURPOSE

Complete high ulnar nerve injury can cause serious sequelae, including residual sensation and loss of movement and especially dysfunction of the intrinsic muscles of the hand. As a solution to treat complete high ulnar nerve injury, we proposed a new repair method for ulnar nerve injury based on nerve-magnified regeneration.

METHODS

Twenty-two patients with complete division of the ulnar nerve at a high level who were treated from May 2013 to December 2016 were divided into two groups. The proposed repair method for complete high ulnar nerve injury was performed in group I (11 patients), while the traditional repair method, ie, repair of the original injury site of the ulnar nerve, was used in group II (11 patients).

RESULTS

The results showed no significant difference in the mean sensory scores assigned by the Highet-Zachary scheme (the Highet Scale) between the two groups. The mean Highet Scale score of muscle strength for the first dorsal interosseus muscle was significantly better in group I than that in group II (p=0.010). In group I, 10 of 11 patients were graded as M4 or M5. Grip strength, pinch strength, and the Disabilities of the Arm, Shoulder, and Hand (DASH) score were significantly better in group I than those in group II (p<0.01).

CONCLUSION

Therefore, this method for complete high ulnar nerve injury based on nerve-magnified regeneration can shorten the path of motor nerve regeneration, effectively reduce atrophy of the intrinsic muscles of the hand, and provide better hand function.

Predicting Tendon Tissue Grafting Source From the Extensors of Long Fingers: A Systematic Review of Cadaveric Studies

Background: The use of tendon tissue for transfer and grafting is a common practice in hand surgery. Many local tendons are usually used, mainly that of the palmaris longus muscle. However, this tendon could be absent in up to 46%. Extra slips of the extensor digitorum communis (EDC) and extra tendons such as the extensor indicis (EI) and the extensor digiti minimi (EDM) could be valuable sources for tendon tissue. Methods: A systematic review was conducted to quantify the proportion of extra slips in relation to each tendon and extra tendons in relation to each long finger. The aim is to better predict the location of tendon tissue sources on the dorsum of the hand in reconstructive surgery. Results: Based on 39 studies including 7847 hands, the cumulative frequencies of extra slips and extra tendons and the association between double-slip frequency and ancestry were as follows: (1) the little finger showed the highest cumulative frequency of extra slips (96.54%), followed by the ring (37.5%), long (30.6%), and index (9.5%) fingers; (2) the index with its EI and its variants and the little finger with its EDM bear by far the highest cumulative frequency of extra tendons (≈100%); and (3) double slips are found to be rare in Indian populations, most prevalent in Japanese populations, more prevalent in the index and little fingers of Caucasians, and more prevalent in the ring fingers of Middle Eastern populations. Conclusions: Knowledge of the frequencies of extra slips for each long extensor tendon and extra tendons for each long finger along with their prevalence in different populations would improve: (1) location prevision of tendon source for tendon grafting; and (2) surgical planning while supporting a patient-centered approach. Evidence-based hand anatomy would have a major potential to contribute to the practice of an evidence-based hand surgery. Predicting the possible tendon sources that could be present on the dorsum of the hand is thought to be very valuable for hand surgeons. In addition and from an evolutionary perspective, we hypothesized that the observed significantly higher frequency values of the double-slip and triple-slip types of the EDC of the ring finger, EDC of the little finger, and EDM might indicate a natural selection tendency for a higher independence of the former digits in the future evolution of the human hand.

The Relative Contribution to Small Finger Abduction of the Ulnar Versus Radial Slip of the EDM: Implications for Tendon Transfers

BACKGROUND

The extensor digiti minimi (EDM) tendon is commonly divided into a radial slip (EDM-R) and an ulnar slip (EDM-U). To our knowledge, the degree to which each EDM slip concomitantly abducts the small finger with active extension has not been formally tested. This study sought to characterize the comparative contributions of finger abduction inherent to each slip of the EDM to observe the sequelae of active small finger extension following transfer of the contralateral slip.

METHODS

Eighteen fresh-frozen cadaveric hands were used in this study. Starting with the hand in resting position, a controlled traction of 10 N was applied to each slip of the EDM tendon. The range of small finger abduction with respect to the fixed ring finger was recorded utilizing infrared reflective markers tracked through the range of motion using a digital video camera.

RESULTS

The mean abduction of the small finger when the radial slip of the EDM tendon was tested was 13.33° (95% confidence interval [CI]: 10.10°-16.55°), which was significantly different ( P ≤ .001) than small finger abduction produced by the ulnar slip of the EDM, with a mean of 23.72° (95% CI: 19.40°-28.04°).

CONCLUSIONS

Given the fact that the ulnar slip of the EDM tendon is shown to be the major contributor of aberrant abduction with active small finger extension, as traction on this slip produces almost twice as much abduction as the radial slip, the EDM-U is the ideal donor graft with respect to tendon transfers of the EDM.

The prevalence of the extensor digiti minimi tendon of the hand and its variants in humans: a systematic review and meta-analysis

The extensor digiti minimi (EDM) is frequently used in the case of an abduction deformity of the little finger. It is also considered as a main resource for tendon transfer. However, it shows many variations in the human hand, which include splitting into two or more slips and sending a slip to the fourth finger, named the extensor digiti minimi et quarti (EDMQ). The aim of this systematic review is to perform an evidence synthesis on the prevalence of the EDM and its variants. Twenty-six cadaveric studies met the inclusion criteria with a total of 2247 hands. Meta-analysis results yielded an overall pooled prevalence estimate (PPE) of the EDM of 99.7% and PPEs of 11.5, 77.6, 7 and 0.6% for the single-, double-, triple- and quadruple-slip EDM, respectively. For the single-slip EDM, the frequencies were such that Indians > Middle Eastern > Europeans > Japanese > North Americans. For the double-slip EDM, the frequencies were such that Japanese > North Americans = Europeans > Middle Eastern > Indians. No significance was found with regard to hand side. The true EDMQ prevalence was found to be at 7.3%, whereas its crude prevalence was 8%. This artilce offers reference values on the prevalence of the EDM and its variants, which are thought to be highly relevant to both anatomists and clinicians.

The prevalence of the extensor digitorum communis tendon and its insertion variants: a systematic review and meta-analysis

The tendons of the Extensor Digitorum Communis (EDC) are frequently injured in hand trauma. Dislocation and spontaneous rupture can also occur during the course of wrist osteoarthritis and rheumatoid arthritis. The EDC exhibits many variations including splitting of its individual slips to the medial four fingers or their absence. The aim of this systematic review is to assemble evidence about the prevalence of the EDC and its variants on the dorsum of the hand. Twenty-four cadaveric studies met the inclusion criteria, providing data from a total of 2,005 hands. Meta-analysis yielded the following results: (a) for EDC-II (Index), the pooled prevalence estimates (PPEs) were 99.8, 98, 1.8, and 0.2% for the total, single, double, and triple slips, respectively; (b) for EDC-III (Middle), the PPEs were 100, 67.7, 24.2, 6, and 0.42% for the total, single, double, triple, and quadruple slips, respectively; (c) for EDC-IV (Ring), the PPEs were 100, 58.6, 29.1, 7.1, and 1.3% for the total, single, double, triple, and quadruple slips, respectively; (d) for EDC-V (Little), the PPEs were 63.2, 58.5, 10.4, 0.94, and 25% for the total, single, double, triple, and common 4th-5th slips, respectively. There were no significant differences in relation to hand side. Many EDC slip variants demonstrated some interaction with ancestry. A sound knowledge of EDC variants and their prevalences is paramount for assessing and treating hand injuries and disorders.