Complex traumatic injuries and degenerative conditions of the hand continue to lead to significant impairment and disability. From technical innovations to regenerative concepts, this article presents the latest advances in the dynamic field of hand surgery in which worldwide efforts are made around the globe to repair, regenerate, or restore each composite tissue forming the hand. The systematic method by which finger replantation is performed, from bony fixation to skin closure, provides a platform for discussion of the newest innovations available to reconstructive hand surgeons.
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The induced membrane, or Masquelet technique, has great potential in managing bone defects.
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Tendon tissue engineering is a an innovative solution for repairing extensive tendon deficits.
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Fibrin glue, laser activated chitosan, end-to-side neurorrhaphy, and nerve conduits are used for peripheral nerve repair, along with more novel and untested approaches of nerve regeneration with molecular and cell therapy.
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Sutureless anastomosis, a combination of Food and Drug Administration–approved thermoreversible poloxamer gel and cyanoacrylate glue is in use for microvascular anastomosis.
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Botulinum toxin may become a promising treatment of Raynaud syndrome.
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A dynamic stress-shielding polymer device is effective in reducing scar formation.
Introduction
In 1944, the pioneer hand surgeon, Sterling Bunnell, described the specialty in these words, “As the problem in hand surgery is composite, the surgeon must also be. There is no shortcut. The surgeon must face the situation and equip himself to handle any and all of the tissues in a limb.” Nearly 70 years later, this principle remains the same, but innovations in all composite tissues of the hand have given the hand surgeon advantages that did not previously exist. Concepts and technologies in reconstructive hand surgery continue to evolve, improving patient outcome and surgeon ease. Intelligently designed devices, bioengineered tissues, allografts, and tissue substitutes will soon be available. The systematic method by which perform finger replantation is performed, from bony fixation to skin closure, provides a platform for discussion of the newest innovations available to reconstructive hand surgeons.
Bone
Problem: Bone Reconstruction in Severely Mutilated Digits or Septic Conditions
High-energy trauma or osteomyelitis can lead to complex composite defects in fingers with extensive bone loss. When the finger can be salvaged, bone stabilization becomes the first step of the reconstruction. However, there is often a deficit of bone tissue required for adequate reconstruction. Classic solutions include the use of bone grafts or vascularized bone grafts to fill the bone defect. However, these procedures are not practical in the context of emergency hand situations in which salvage is the primary goal.
Innovative Solution
Initially described by Masquelet and Begue for large diaphyseal bone defects caused by tumor resection, trauma, or osteoarthritis, the induced membrane technique is a two-stage procedure allowing bone reconstruction. The concept is to place space-maintaining material in the region of the defect. This leads to a foreign body reaction, which creates a membrane mimicking the periosteum. Once this is formed, bone graft can be placed in the periosteal sleeve. Recently, Flamans and colleagues applied the Masquelet technique to the hand with promising results.
The first stage involves soft tissue and bone debridement followed by implantation of a polymethyl methacrylate cement spacer in the area of the bone deficit and/or defect. Bone stabilization is then provided with internal and/or external fixation. Soft tissue defects may need to be addressed with free flap coverage.
The second stage is performed 2 months later. The periosteal membrane is incised and the spacer is removed. Autologous cancellous bone graft is placed within the membrane.
The results in the hand are from studies with small numbers but are promising. There are over 15 other studies investigating this technique in bone reconstruction outside the hand.
Clinical results in the literature
For clinical results in the literature, see Table 1 .
| Study | N | Cause of Bone Defect | Results | Complications |
|---|---|---|---|---|
| Flamans et al | 11 | Trauma (n = 8) Infection (n = 3) | Bone union rate 82% | 2 Nonunion |
| Proubasta et al | 1 | Osteomyelitis | Bone union | None |
Advantages
The membrane induced by the Masquelet technique has been shown to secrete vascular endothelial growth factor, transforming growth factor beta-1, and bone morphogenetic protein-2. Therefore, it has more than a mechanical role—it induces angiogenesis and proliferation of osteoblasts and chondrocytes. Bone graft substitutes, such as hydroxyapatite or tricalcium phosphate, can be used instead or in addition to autologous cancellous bone grafts to increase osteoconduction.
Complications
Nonunion and infections have been noted. However, it is not clear at this time whether this technique has an increased rate of complications over other techniques of reconstruction in these complex cases. Loss of function and finger stiffness is also a risk, but this is often inherently due to the infection or trauma. Overall, the technique is simple and easy to perform. This technique can be used for reconstructive problems of the hand in which vascularized bone graft and flaps are not viable options.
Tendons
Problem: the Need for More Tendon Graft Material
Tendons are essential to hand function and are frequently involved in hand injuries. When tendon deficits exist, the current solution is to harvest expendable autologous tendon grafts (ie, palmaris, plantaris) or use tendon allograft. However, the extrasynovial nature of these tendons increases the resulting adhesions at the repair sites and often leads to a suboptimal functional outcome.
Innovative Solution
Tendon tissue engineering may be a future solution in cases requiring extensive tendon reconstruction. Neotendons would ideally have the capacity to reduce adhesions and have adequate tensile strength, allowing early active rehabilitation and normal mobility.
Bioengineered tendon constructs first consist of a scaffold—natural or synthetic. Some hand surgeons choose to follow Gillies’ reconstructive principle of replacing “like with like” and use decellularized human tendon scaffolds from a donor bank. Other surgeons choose collagen derivatives, polysaccharides, small intestine submucosa, or human umbilical veins as natural scaffolds; whereas the synthetic scaffold uses polymers such as poly(a-hydroxyl acid)s, polylactic acid, or polypropylene. The ideal candidate remains to be decided. Natural scaffolds have the advantage of a high affinity to host cells allowing tissue ingrowth, but they theoretically are associated with potential risks such as disease transmission. Synthetic scaffolds have the advantage of being free of disease transmission and are easier to manufacture on a large scale. Being synthetic, however, results in less binding with the host’s cells and, therefore, less tissue proliferation. In addition, both types of scaffolds are subject to rejection (immunologic or foreign body reaction). Considerable research is underway, dedicated to creating the ideal tendon scaffold to meet the requirements of biodegradability, biocompatibility, superior mechanical properties, and optimal processing.
The second aspect of tissue-engineered tendon constructs is the addition of cells with regenerative and differentiation potential that can be used to seed these scaffolds. Several lines of cells have been studied, such as tenocytes, adipose-derived stem cells, bone marrow stromal cells, and fibroblasts. No significant differences were found between these four cell types in their ability to populate the scaffold. To date, it is unclear whether reseeding improves the biomechanical properties of these constructs.
The third area of focus includes strategies to further enhance in vivo regeneration and incorporation of tissue-engineered tendons. The most promising concepts include growth factor supplementation, mechanical stimuli, and contact guidance.
Nerve
Problem: Peripheral Nerve Repair
Peripheral nerve injuries are common and 60% of these are reported to occur in the upper extremities. The current gold standard procedure for managing such injuries is a tensionless end-to-end nerve repair. When the defect is so great that an end-to-end suture will create tension, an autologous nerve graft is performed, creating donor site morbidity and uncertain outcomes depending on the host site vascularization and the level at which the injury occurs. The need for peripheral nerve repair and regeneration strategies is, therefore, high on the priority list in research.
Innovative Solutions
Many strategies have been tested, such as sutureless nerve repair using fibrin glue, laser activated chitosan, and end-to-side neurorrhaphy. Nerve conduits are also a popular solution for segmental nerve defects of up to 3 cm and have been studied since as early as the late nineteenth century. Different types of conduits exist from biologic (eg, vein, arteries) to synthetic materials (eg, collagen, caprolactone, polyglycolic acid), giving promising results in small series studies. However, randomized studies of a larger scale are needed. Brooks and colleagues report the clinical outcome of 132 nerve injuries in a multicenter study for processed nerve allografts with recovery and safety comparable to autografts and better than nerve conduits.
The latest development in nerve regeneration is molecular and cell therapy. The goal is to augment allografts or conduits by adding cells to lower immunogenicity and increase nerve regeneration. Several types of constructs combining allografts or synthetic conduits with cells have been tested, such as adipose-derived stem cells, bone marrow–derived stem cells, Schwann cells, or (more recently) dorsal root ganglion cells. However, all of these combinations are still in the early stages of experimentation.
Vessels
Problem: the Tedium of Multiple Microvascular Anastomoses
Since Carrel pioneered vascular surgery in the early twentieth century, many techniques have been described to allow suturing of increasingly smaller vessels in a minimal amount of time. Although patency and reliability are indispensable and still achieved in technically challenging anastomoses using round-bodied needles and fine monofilament nylon sutures, the need for increased efficiency and minimal manipulation of small vessels continues to stimulate new technologies.
Several devices are currently used as alternatives to classic sutures, such as couplers (Unilink-3M [3M Healthcare, St. Paul, MN]) or clips (VCS [VCS; LeMaitre Vascular, Boston, MA], U-clip [Medtronic, Inc, Minneapolis, MN]) with outcomes evidence supporting their use. Although these devices reduce the time of the procedure considerably, they remain traumatic for the vessels and can cause foreign body reactions. Their use in digits can also cause the specific problem of foreign body sensation. Other technologies, such as adhesive (eg, cyanoacrylate, fibrin glue) or laser and photochemical bonding, have been tested. However, none of them has proven superior to hand-sewn anastomosis in terms of reliability.
An ideal microvascular anastomotic technique should be fast, atraumatic for the vessel, and easily reproducible in even the smallest vessels. A new sutureless technique described by the Gurtner laboratory may be a promising solution to this common microsurgical problem.
Innovative Solution
A new technique, sutureless anastomosis, uses the combination of Food and Drug Administration–approved thermoreversible poloxamer gel and cyanoacrylate glue.
Indications
Indications include:
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Microvascular anastomosis on vessels as small as 0.5 mm
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End-to-end or end-to-side anastomosis.
Surgical technique
The surgical technique is:
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The poloxamer gel is introduced into the lumens of both ends of the vessel.
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A heating source is then used to create a temperature of 40°C, at which point the gel becomes solid.
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Vessels are approximated and cyanoacrylate applied at the junction to perform the sutureless anastomosis.
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The heating source is removed, allowing the poloxamer to return to its liquid phase and dissolve, leaving the vessel patent.
Clinical results in the literature
Clinical results in the literature include:
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2-year follow-up, control group of hand-sewn anastomoses in rat model only
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Equivalent patency, flow and burst strength
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Sutureless anastomoses were performed five times faster than hand-sewn anastomoses
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Decreased inflammation and fibrosis at 2 years
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Efficient in small vessels smaller than 1 mm.
Advantages
This technique is reproducible, more efficient, and seems to have less long-term inflammation than the gold standard hand-sewn anastomoses. In addition, it allows patent reconstruction of smaller vessels making it particularly valuable in hand surgery.
Complications
The main disadvantage is the initial foreign body reaction caused by the use of cyanoacrylate glue. However, the inflammation does not seem to be persistent.
Another potential complication is the transmission of diseases through the albumin-based poloxamer; however, albumin-free gels with the same properties are currently being developed. This innovation awaits translation to human clinical cases.
Problem: Distal Ischemia Caused by Raynaud Phenomenon
Plastic surgeons are occasionally confronted by Raynaud phenomenon in extremities. A variety of vasospastic disorders, including connective tissue or autoimmune diseases, are responsible for this problem. A myriad of medical treatments have been tested to ease the intolerable pain or reduce the vasospasm of these ischemic digits without great success. Surgical techniques are limited to wound management of distal ulceration, sympathectomy and/or adventiectomy, distal vascular bypass, and, finally, amputation of necrotic fingers.
Innovative Solution: Botulinum Toxin A Injections
A few studies in the literature have evaluated the use of botulinum toxin for the treatment of Raynaud syndrome with the aim of reducing vasocclusive pain, improving vascular inflow, and healing ulcers in Raynaud fingers. Even though these studies lack controls and include a wide variety of patients (ie, different underlying diseases, variable severity), they all suggest that botulinum toxin may become a promising treatment of these disorders. As summarized by Mannava and colleagues, “Based on preclinical data and limited case series, the palmar injection of botulinum toxins has been described to treat refractory Raynaud phenomenon with nonhealing ulcers or pre-gangrene.”
The mechanism through which the toxin improves the finger’s perfusion and alleviates pain is still unexplained and is likely more complex than just the expected induced vasodilatation. The need for better clinical trials including standardized injection procedures and controls is necessary.
Indication
The indication is ischemic digits.
Surgical procedure
No standardized procedure has been reported yet, but the technique usually involves:
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Targeted injection around each neurovascular bundle and superficial palmar arch
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Average of 100 units per hand
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Evaluation of tissue perfusion with Doppler.
Clinical results in the literature
For clinical results in the literature, see Table 2 .
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