Biomedical subjects

Aymeric Y T Lim

Publications and source records attributed to Aymeric Y T Lim.

10 recordsLinked to original sources

PubMed2007

Case report: the split flexor carpi ulnaris as a local muscle flap.

The flexor carpi ulnaris is a useful local muscle flap in the forearm and elbow. It is, however, an important palmar flexor and ulnar deviator of the wrist, and functional loss may arise from the use of this muscle in its entirety. The flexor carpi ulnaris is made up of two distinct neuromuscular compartments. This arrangement allows for splitting of the muscle and the potential use of the larger ulnar compartment as a local muscle flap while maintaining the humeral compartment as an ulnar deviator and palmar flexor of the wrist. We report two cases illustrating the clinical use of the split flexor carpi ulnaris as a local muscle flap.

Action Potentials↗

PubMed2007

Bone marrow-derived mesenchymal stem cells influence early tendon-healing in a rabbit achilles tendon model.

BACKGROUND: A repaired tendon needs to be protected for weeks until it has accrued enough strength to handle physiological loads. Tissue-engineering techniques have shown promise in the treatment of tendon and ligament defects. The present study tested the hypothesis that bone marrow-derived mesenchymal stem cells can accelerate tendon-healing after primary repair of a tendon injury in a rabbit model. METHODS: Fifty-seven New Zealand White rabbits were used as the experimental animals, and seven others were used as the source of bone marrow-derived mesenchymal stem cells. The injury model was a sharp complete transection through the midsubstance of the Achilles tendon. The transected tendon was immediately repaired with use of a modified Kessler suture and a running epitendinous suture. Both limbs were used, and each side was randomized to receive either bone marrow-derived mesenchymal stem cells in a fibrin carrier or fibrin carrier alone (control). Postoperatively, the rabbits were not immobilized. Specimens were harvested at one, three, six, and twelve weeks for analysis, which included evaluation of gross morphology (sixty-two specimens), cell tracing (twelve specimens), histological assessment (forty specimens), immunohistochemistry studies (thirty specimens), morphometric analysis (forty specimens), and mechanical testing (sixty-two specimens). RESULTS: There were no differences between the two groups with regard to the gross morphology of the tendons. The fibrin had degraded by three weeks. Cell tracing showed that labeled bone marrow-derived mesenchymal stem cells remained viable and present in the intratendinous region for at least six weeks, becoming more diffuse at later time-periods. At three weeks, collagen fibers appeared more organized and there were better morphometric nuclear parameters in the treatment group (p < 0.05). At six and twelve weeks, there were no differences between the groups with regard to morphometric nuclear parameters. Biomechanical testing showed improved modulus in the treatment group as compared with the control group at three weeks (p < 0.05) but not at subsequent time-periods. CONCLUSIONS: Intratendinous cell therapy with bone marrow-derived mesenchymal stem cells following primary tendon repair can improve histological and biomechanical parameters in the early stages of tendon-healing.

Achilles Tendon↗

PubMed2006

The cut intramuscular nerve affects the recovery in the lacerated skeletal muscle.

The recovery of lacerated skeletal muscles are said to be slow and incomplete. Often the intramuscular (IM-) nerve is concomitantly cut, but never repaired. We questioned whether the IM-nerve should also be reanastamosed before repairing the skeletal muscle. Before answering this, it was necessary to know if the cut IM nerve would have an effect on the recovery of the segment of muscle distal to the level of the laceration. This study investigates the recovery of lacerated muscles after repair, and compares a complete muscle laceration where the main IM-nerve was concomitantly cut and an incomplete muscle laceration where the IM-nerve was preserved intact. The medial gastrocnemius (MG) of the adult male New Zealand White rabbit was used, with the contralateral muscle as a sham control. The laceration was at the proximal quarter of the muscle, distal to the entry point of the nerve branch from the tibial nerve into the muscle belly. Twenty-eight weeks post-repair, the lacerated MG with the IM-nerve intact showed improved muscle wet weight, near normal morphology and contractile properties, and return of muscle fiber type mix and size. The repaired lacerated MG with their IM-nerve concomitantly cut demonstrated loss of muscle wet weight, obvious fibrosis, mononuclear proliferation with fatty infiltration, increase in type-1 fibers and muscle fiber atrophy in the distal portion. We postulate that it might be important to repair the intramuscular nerve branch by microanastomosis when repairing a vital skeletal muscle that is lacerated.

Animals↗

PubMed2006

The role of intramuscular nerve repair in the recovery of lacerated skeletal muscles.

The repair of lacerated muscle often results in suboptimal recovery. An important cause of poor outcome is denervation of the distal segment. The rabbit medial gastrocnemius muscle laceration model was used to assess whether intramuscular nerve repair resulted in better recovery. Lacerated rabbit muscles were divided into three groups: group A had no muscle repair; group B underwent muscle repair; and group C had muscle repair with intramuscular nerve repair. At 7 months, groups A and B showed significantly greater muscle atrophy, replacement of muscle fiber with scar and adipose tissue, and change of muscle fiber type from a fast-twitch to a slow-twitch pattern compared to group C. A clinical case study subsequently demonstrated feasibility of intramuscular nerve repair; reinnervation of the distal belly led to rapid functional recovery. In conclusion, primary intramuscular nerve repair results in better functional outcomes following repair of lacerated muscles.

Adenosine Triphosphatases↗

PubMed2006

Split flexor carpi ulnaris transfer: a new functioning free muscle transfer with independent dual function.

BACKGROUND: A functioning free muscle transfer is a well-established modality of restoring upper limb function in patients with significant functional deficits. Splitting the neuromuscular compartments of the free muscle based on its intramuscular neural anatomy and using each compartment for a different function would allow for restoration of two functions instead of one at the new distant site. METHODS: The authors previously reported on the clinical use of a pedicled split flexor carpi ulnaris muscle transfer. They now report the use of this muscle as a functioning free split muscle transfer to restore independent thumb and finger extension in a patient with total extensor compartment muscle loss in the forearm and a concomitant high radial nerve avulsion injury. RESULTS: Nine months postoperatively, the patient was able to extend his thumb and fingers independent of each other. CONCLUSION: This is the first report of a functioning free split muscle transfer demonstrating two independent functions in the upper limb.

Accidents, Occupational↗

PubMed2006

Clinical assessment of absence of the palmaris longus and its association with other anatomical anomalies-- a Chinese population study.

INTRODUCTION: Ethnic variations in the prevalence of absence of the palmaris longus (PL) are well known. Many techniques for clinically determining the presence of the PL have been described. Studies have also attempted to correlate its absence with other anatomical anomalies. However, most studies have been done in Caucasian populations. MATERIALS AND METHODS: The presence of the PL was clinically determined in 329 normal Chinese men and women using the standard technique. In subjects with an absent PL, 4 other tests were performed to confirm absence and an Allen's test was done to assess the palmar arches. All subjects were examined for the presence of the flexor digitorum superficialis (FDS) to the little finger. RESULTS: The overall prevalence of absence of the PL was 4.6%. All techniques were equally effective in determining the absence of the PL. There was no significant difference in its absence with regard to the body side or sex. Absolute deficiency of FDS to the little finger was seen in 6.4%. No correlation could be detected between the absence of the PL and FDS of the little finger. CONCLUSIONS: The prevalence of absence of the PL and absence of FDS to the little finger in a Chinese population is much lower compared to previous reports in the literature. There is no association between absence of the PL and absence of the FDS to the little finger. Although all techniques of examining for the absence of the PL are equally effective, the method suggested by Mishra seems the best as it was easily understood by subjects and can be used even when thumb abduction is not possible.

Adolescent↗

PubMed2005

Microsurgical skills training: a new concept for simulation of vessel-wall suturing.

Initiation of training in basic microsurgical suturing technique usually involves placing sutures on incisions made on latex sheets, and then progressing to a live anastomosis in a rat model. A straight incision resembles a skin incision and does not mechanically simulate vessel wall suturing, and various modifications and innovative prosthetic models continue to be developed to bring the simulation closer to a live anastomosis. We developed two models which closely simulate vessel wall suturing and require the application of similar skills by the trainee. In the first model (the "I" model), the straight 1-cm incision is converted to an I-shaped incision which increases the instability of the edge to be sutured, depending on the length of the horizontal incision, putting greater demand on dexterity in suture placement similar to a vessel. The length (1 cm) of the edge does not constrain the spacing of the sutures and can be used for the beginner. The second model (the "double triangle" model) creates a narrow and unstable edge for placing sutures, and puts greater demand on bimanual coordination and instrument control for training in accuracy of suture placement as well as spacing between sutures. Both these models are cost-effective and simple to construct.

Anastomosis, Surgical↗

PubMed2004

Intramuscular innervation of upper-limb skeletal muscles.

We studied 150 skeletal muscles from 8 upper limbs using the modified Sihler's staining technique. Based on the pattern of the intramuscular innervation and shape, the muscles were grouped into trapezoidal-shaped (Class I), spindle-shaped (Class II), and muscles that were combinations of these two classes (Class III). Such distinctions are clinically important for limb reconstruction procedures. Bipennate, spindle-shaped muscles with the aponeurosis of the tendons of insertion extending proximally into the muscle belly and Class III muscles with multiple tendons of origin may be split for separate independent functional transfers.

Aged↗

PubMed2004

Independent function in a split flexor carpi radialis transfer.

In a patient requiring tendon transfer after radial nerve palsy, the flexor carpi radialis, a bipennate muscle, was split longitudinally into 2 compartments along the length of the aponeurosis extending proximally from the distal tendon to provide independent finger and thumb extension. This case report shows that the 2 compartments of a bipennate muscle in the forearm may have separate innervation, allowing transfer for independent functions.

Forearm↗

PubMed2004

Properties of the two neuromuscular compartments in a split bipennate muscle.

Bipennate muscles may be split along their distal aponeurosis, dividing each into two compartments. These sub-muscle units may be used in tendon transfers. This paper presents the contractile properties of the two sub-units of the flexor carpi ulnaris in a macaca fascicularis, after it was split by up to 80% of its length. The sub-muscle units were electrically stimulated and found to have independent isometric contraction, with minimal contraction recorded from the non-stimulated sub-unit. Also, the sum of the forces measured from each unit when stimulated individually, was found to be greater than the force of the whole muscle, given the same isometric conditions. The distal aponeurosis which is common allows force transmission between the compartments. Splitting the muscle along this distal aponeurosis alters this function and the force capacity of the muscle, providing a new potential for using the sub-units as grafts for tendon transfers.

Animals↗