Improvement of Schwann cell attachment and proliferation on modified hyaluronic acid strands by polylysine

Hyaluronic acid (HyA) has the intrinsic ability to promote cell proliferation and reduce scar formation. However, the clinical use of HyA has so far been limited because of its water solubility and nonadhesive characteristics. Increasing interest in HyA as a clinically useful biomaterial has prompted our study of altering HyA's physical properties to render it a potential component of nerve grafts. In this study, strands of HyA were cross-linked by glutaraldehyde (Glut), coated with polylysine, and then inoculated with Schwann cells (SCs). Results in vivo and in vitro demonstrated that cross-linked HyA strands were water insoluble and thus less biodegradable. Poly-D-lysine-resurfaced strands showed significant SC attachment of 350-400 cells/mm(2), compared to uncoated controls (0-10 cells/mm(2), p < 0.01). Fibroblast control groups showed an attachment of 40-100 cells/mm(2) on coated strands. Immunostaining for proliferating cells showed SCs as and fibroblasts as +. Cells neither adhered to nor proliferated on the modified HyA strands that were not resurfaced. The results suggest that polylysine promotes SC attachment and proliferation to glutaraldehyde-cross-linked HyA strands, the product being a three-dimensional composite with low solubility that may have potential application in nerve grafts.

Quantification of fingertip force reduction in the forefinger following simulated paralysis of extensor and intrinsic muscles

Objective estimates of fingertip force reduction following peripheral nerve injuries would assist clinicians in setting realistic expectations for rehabilitating strength of grasp. We quantified the reduction in fingertip force that can be biomechanically attributed to paralysis of the groups of muscles associated with low radial and ulnar palsies. We mounted 11 fresh cadaveric hands (5 right, 6 left) on a frame, placed their forefingers in a functional posture (neutral abduction, 45 degrees of flexion at the metacarpophalangeal and proximal interphalangeal joints, and 10 degrees at the distal interphalangeal joint) and pinned the distal phalanx to a six-axis dynamometer. We pulled on individual tendons with tensions up to 25% of maximal isometric force of their associated muscle and measured fingertip force and torque output. Based on these measurements, we predicted the optimal combination of tendon tensions that maximized palmar force (analogous to tip pinch force, directed perpendicularly from the midpoint of the distal phalanx, in the plane of finger flexion-extension) for three cases: non-paretic (all muscles of forefinger available), low radial palsy (extrinsic extensor muscles unavailable) and low ulnar palsy (intrinsic muscles unavailable). We then applied these combinations of tension to the cadaveric tendons and measured fingertip output. Measured palmar forces were within 2% and 5 degrees of the predicted magnitude and direction, respectively, suggesting tendon tensions superimpose linearly in spite of the complexity of the extensor mechanism. Maximal palmar forces for ulnar and radial palsies were 43 and 85% of non-paretic magnitude, respectively (p<0.05). Thus, the reduction in tip pinch strength seen clinically in low radial palsy may be partly due to loss of the biomechanical contribution of forefinger extrinsic extensor muscles to palmar force. Fingertip forces in low ulnar palsy were 9 degrees further from the desired palmar direction than the non-paretic or low radial palsy cases (p<0.05).

Hand and wrist injuries in young athletes

Successful treatments of musculoskeletal injuries in the pediatric population demand a thorough understanding of the basic anatomy and its biomechanics, and the physiology of growth and development of the immature skeleton. In addition, good treatment outcomes rely on the treating physician being an effective teacher to the young athlete and the patient's parents, coaches, and trainers. At the same time, the physician must be a good student in learning the nature of the patient's sports and each patient's athletic ability and aspirations. Most pediatric hand and wrist injuries can be treated nonoperatively with proper immobilization techniques and activity modification, but cases requiring surgical intervention must be recognized promptly to avoid long-term complications.

A virtual-reality-based telerehabilitation system with force feedback

A PC-based orthopedic rehabilitation system was developed for use at home, while allowing remote monitoring from the clinic. The home rehabilitation station has a Pentium II PC with graphics accelerator, a Polhemus tracker, and a multipurpose haptic control interface. This novel interface is used to sample a patient's hand positions and to provide resistive forces using the Rutgers Master II (RMII) glove. A library of virtual rehabilitation routines was developed using WorldToolKit software. At the present time, it consists of three physical therapy exercises (DigiKey, ball, and power putty) and two functional rehabilitation exercises (peg board and ball game). These virtual reality exercises allow automatic and transparent patient data collection into an Oracle database. A remote Pentium II PC is connected with the home-based PC over the Internet and an additional video conferencing connection. The remote computer is running an Oracle server to maintain the patient database, monitor progress, and change the exercise level of difficulty. This allows for patient progress monitoring and repeat evaluations over time. The telerehabilitation system is in clinical trails at Stanford Medical School (CA), with progress being monitored from Rutgers University (NJ). Other haptic interfaces currently under development include devices for elbow and knee rehabilitation connected to the same system.

Polypeptide resurfacing method improves fibroblast's adhesion to hyaluronan strands

Hyaluronic acid (hyaluronan, HyA) is a matrix component that takes part in cell adhesion and growth in normal and repaired tissues. Since it is soluble in water, HyA has been of limited use in tissue engineering of artificial matrices. Recent studies demonstrate that polypeptides have the twin advantages of reducing solubility of HyA and improving cellular attachment via cell surface adhesion molecule receptors. This paper describes a new approach of using a polypeptide resurfacing method to enhance the attachment of cells to HyA strands. HyA strands were crosslinked by glutaraldehyde and then resurfaced with poly-D-lysine, poly-L-lysine, glycine, or glutamine. After inoculation with fibroblasts in vitro, modified HyA was evaluated with histological and immunohistochemical staining methods for cell adhesion and proliferation. Modified HyA with fibroblast cells also were implanted in vivo. The results show that (1) both polylysines enhanced fibroblast adhesion to crosslinked HyA strands; (2) HyA strands were able to be crosslinked well by 3 days of treatment in glutaraldehyde, and as a biomaterial they could resist biodegradation; (3) modified HyA has good biocompatibility, both in vitro and in vivo. The results demonstrate that HyA material resurfaced by polypeptides has positive advantages for cellular adhesion. Resurfaced HyA has much potential as an improved biomaterial for clinical usage.

Fine-wire electromyographic recording during force generation. Application to index finger kinesiologic studies

When accurately placed, fine-wire electrodes (FWEs) permit selective electromyographic recording during kinesiologic studies; however, their potential to limit contraction of the index finger muscles has not previously been evaluated. Given that these electrodes cannot be reinserted, reliable techniques are necessary to achieve proper placement while minimizing subject discomfort and electrode waste. The small size, close arrangement, and anatomic variability of hand and forearm muscles create challenges to achieving these goals. In this study, we simultaneously measured maximal fingertip forces and fine-wire electromyographic signals from all seven muscles of the index finger. Forces in five directions, with and without FWEs in place, were not statistically different (repeated-measures analysis of variance, P < 0.46) in five healthy adult subjects. To guide electrode placement, we identified skin penetration landmarks, direction of needle advancement, and depth of muscle fibers. Fibers of flexor digitorum superficialis and flexor digitorum profundus to the index finger were more distal than depicted in textbooks, requiring electrode placement at or distal to the midpoint of the forearm. For these muscles and the extensor digitorum, locating the desired fibers first with a monopolar needle electrode facilitated subsequent FWE placement. For the dorsal and palmar interossei, lumbrical, and extensor indicis proprius, insertion was aided by concurrent monitoring of the electromyographic signals. We achieved a 93% success rate during FWE placement in a total of 60 muscles. Techniques for recording from each of the seven index finger muscles are described.

Enhancement of axon growth by detergent-extracted nerve grafts

BACKGROUND

The immunogenicity of nerve allografts is responsible for their rejection. We have developed a method for preparing cell-free nerve grafts using lysophosphatidylcholine to remove cells, axons, and myelin sheaths.

METHODS

The remaining intact nerve extracellular matrix is the extracted nerve graft (eNG). Cultured neonatal Schwann cells were micro-injected into the eNG to form recellularized nerve grafts (rNG). eNG, rNG, and normal isografts (15 mm long) were implanted in the peroneal nerves of F-344 rats. Ten rats were given an eNG on the right, and an isograft on the left. Ten rats were given an rNG on the right, and a sham operation on the left. Sham operation was used as the control and the isograft was used as the benchmark procedure. Walking track analysis was performed every 15 days after surgery to determine the peroneal functional index. Morphometric analysis of the distal peroneal nerve and extensor digitorum muscle weight were analyzed 3 months after surgery.

RESULTS

The three types of grafted legs had the classical effect observed after peripheral nerve repair, with decreased functional ability, decreased target muscle weight, fewer large nerve fibers, and more small nerve fibers. Isografts, eNG, and rNG all had similar patterns of peroneal functional index improvement after implantation. The extensor digitorum longus muscle weight and axon counts for the three types of graft were not statistically different. Hence, eNG and rNG can enhance nerve regeneration in the same way as isografts. The host Schwann cells that invaded the implanted eNG probably acted in the same fashion as the cultured Schwann cells injected into the rNG and the resident cells of isografts.

CONCLUSIONS

The great permeability of the longitudinally oriented matrix of eNG to cells is, therefore, a major advantage over the reported poor permeability of freeze-thawed nerve grafts.

Vascularized toe joint transfer to the hand

From 1984 to 1993, 36 vascularized toe joints were transferred in 33 patients. The present study group excludes 3 toe joint transfers to elbow and temporomandibular joints and 4 toe joint to hand transfers lost to follow-up. The final study group includes 29 vascularized toe joint transfers in 27 patients, 21 males and 6 females. All were performed for posttraumatic reconstruction, except one transfer for congenital deformity. Follow-up averaged 32.4 months. Mean range of motion was 34 degrees in toe metatarsophalangeal joint to hand metacarpophalangeal joint transfers, 32 degrees in toe proximal interphalangeal joint to hand metacarpophalangeal joint transfers, and 24 degrees in toe proximal interphalangeal joint to hand proximal interphalangeal joint transfers. Although vascularized toe joint transfer is an alternative to arthrodesis, in order to have a greater range of motion than average, the patient must have well-functioning muscle and associated tendons effecting joint motion. Good results were obtained in two immediate free vascularized toe joint transfers to complex injuries involving loss of the metacarpophalangeal joint. We encourage toe joint transfer in selected complex hand injuries.

Action potentials of curved nerves in finite limbs

Previous simulations of volume-conducted nerve-fiber action-potentials have modeled the limb as semi-infinite or circularly cylindrical, and the fibers as straight lines parallel to the limb surface. The geometry of actual nerves and limbs, however, can be considerably more complicated. This paper presents a general method for computing the potentials of fibers with arbitrary paths in arbitrary finite limbs. It involves computing the propagating point-source response (PPSR), which is the potential arising from a single point source (dipole or tripole) travelling along the fiber. The PPSR can be applied to fibers of different conduction velocities by simple dilation or compression. The method is illustrated for oblique and spiralling nerve fibers. Potentials from oblique fibers are shown to be different for orthodromic and antidromic propagation. Such results show that the straight-line models are not always adequate for nerves with anatomical amounts of curvature.

Short gracilis myocutaneous flaps for vulvoperineal and inguinal reconstruction

From October of 1990 to April of 1993, 16 short gracilis myocutaneous flaps and 1 short gracilis muscular flap were used to reconstruct vulvoperineal, inguinal, perineal, and ischial soft-tissue defects. Five of the 6 bilateral myocutaneous flaps were used for vulvoperineal reconstruction after radical vulvectomy combined with partial vaginectomy and one radical vulvectomy. Four unilateral myocutaneous flaps and one muscular flap were used for inguinal, suprapubic, ischial, and perineal reconstruction after release of contracted scar or excision of an ischial pressure sore. The immediate complications consisted of partial necrosis of the distal third of the cutaneous tissue in 6 patients, 1 superficial cutaneous necrosis, and superficial wound infection in 7 patients. The muscular portion of the flaps all survived. The follow-up period was from 6 to 27 months. The short gracilis flap has greater mobility than the classically described gracilis flap. On the basis of the functional and cosmetic results, the short gracilis flap is an excellent alternative to the more bulky classic gracilis flap.

Extensor digiti minimi tendon transfer to prevent recurrent ulnar drift

Thirty percent of patients with rheumatoid arthritis develop ulnar drift. Although numerous operations have been described, recurrence of the deformity is frequent. We recommend use of the extensor digiti minimi tendon transfer to prevent recurrent ulnar deviation. The tendon insertion is moved from a dorsal location to a dorsal-radial position. In this new location, the tendon produces both extension and radial deviation. Moreover, this transfer is maximally effective in extension when ulnar drift is greatest. We have used this transfer 28 times during the past 6 years. In evaluating patients more than 1 year after surgery, metacarpal phalangeal joint extension averaged 52 degrees and there was no evidence of recurrent ulnar drift of the little finger. The only problem was slight hyperextension of less than 5 degrees in approximately half of the patients. However, in no patient was this functionally a problem. We recommend the use of this tendon transfer in all patients with ulnar drift undergoing metacarpal phalangeal joint replacement for rheumatoid arthritis.

The nerve gap dilemma: a comparison of nerves repaired end to end under tension with nerve grafts in a primate model

The objective of this study was to compare, in a clinically relevant primate model, axon regeneration after epineurial repair under tension (15 mm gap) with interfascicular nerve grafts with the use of either standard microsuture techniques or a new interfascicular nerve graft technique termed fascicular tubulization that uses a hypoantigenic collagen membrane formed into a tube to approximate nerve ends. Electrophysiologic analysis demonstrated that the percentage of proximal axons that conducted across the repair site was greater in those nerves repaired under tension with epineurially placed sutures than in either of the tensionless repairs involving interfascicular graft techniques. The mean diameters of the regenerated axons repaired under tension with epineurial sutures were greater than those of the nerves repaired with interfascicular grafts, although the difference was not statistically significant. Interfascicular nerve grafting with tubulization using the current collagen tube resulted in regeneration equal to the sutured interfascicular nerve grafts. For modest defects (perhaps up to 3 to 4 cm in the adult), it seems advantageous to accept the modest tension associated with an epineurial repair rather than to use an autograft (or artificial graft) to achieve a tension-free repair.

Efficacy of immobilization following aspiration of carpal and digital ganglions

In a prospective study 69 carpal and digital ganglions were aspirated, multiply punctured, and digitally ruptured. Fifty percent of the wrists and digits were immobilized for 3 weeks and 50% were mobilized early. Follow-up was 1 year. Immobilization in our study did not significantly improve the results of treatment. During the course of the study, 51% of all ganglions did not recur. The outcome was successful in 52% of the wrists and digits that were immobilized and in 50% of those that were not. Forty-six percent of the dorsal carpal ganglions did not recur. Treatment was successful in 48% of dorsal carpal ganglions in which the wrists were immobilized and in 45% of those that were not. Similar percentages were found for palmar and digital ganglions. From our results, we conclude that immobilization does not significantly improve the successful treatment of ganglions over perforation and aspiration alone.

The pulp plasty: a composite graft for complete syndactyly fingertip separations

Composite grafts of skin and subcutaneous fat harvested from the glabrous non-weight-bearing areas of the foot were used to graft 34 fingertips after separation of 23 complete syndactyly webs in 13 patients. Simple complete syndactylies accounted for 17% and complex complete syndactylies accounted for 83%; synonychia was encountered in 70%. Follow-up averaged 13.9 months (minimum, 2 months, maximum 33 months). All patients had 100% take of the composite graft. Subjective gradings were 94% good, 6% fair, and there were no poor results. This technique provides a relatively normal contour and satisfactory pad to the fingertip.

A comparison of suture and tubulization nerve repair techniques in a primate

This study compared standard methods of nerve repair, epineurial or perineurial sutures with a technique termed fascicular tubulization using a biodegradable polyglycolic acid tube in a nonhuman primate model. Electrophysiologic analysis demonstrated that the percentage of proximal axons that conducted across the repair site did not significantly differ among the three techniques while epineurial suture repairs were associated with significantly longer conduction delays across the repair site compared with the other two techniques. Even though fascicular tubulization using the current polyglycolic acid tube resulted in regeneration equal to the currently perceived best suture repair technique, associated technical problems with the current tube design indicate that this fascicular tubulization technique cannot, at present, be considered as an alternative to present clinically used nerve suture techniques.

Brachial plexus microsurgery in children

From this review, the following points have emerged: 1. The typical obstetrical palsy is a traumatic lesion caused by forced lowering of the shoulder during delivery. 2. While the lesion may affect all the roots, the upper roots are usually ruptured, whereas the lower roots (if involved) are always avulsed. 3. Spontaneous recovery is possible, but its quality depends on how early recovery of previously paralyzed muscles begins. If the biceps have not started to recover by 3 months, the final result will be poor. It is at this time interval that a surgical decision should be made. 4. Surgical repair is always possible, usually by grafting, though repair can be difficult if significant numbers of avulsions have occurred. 5. The results of surgical reconstruction are better than are the results of spontaneous evolution, at least in those patients who reach the age of 3 months without evidence of recovery of the biceps. For example, more than half of the patients recover a nearly normal shoulder after grafting C5, C6 lesions in Gilbert's series, whereas in the same control population of patients, none achieved this result spontaneously. 6. Palliative treatment of the sequelae of birth palsies is difficult, and the results obtained are rarely totally satisfactory. It is for these reasons that the initial surgical intervention should be on the plexus itself in those instances meeting the criteria established above. It is important to make this decision as quickly as possible before neuroplasticity is diminished and joint contractions have occurred.