Surgery of the Hand in Recessive Dystrophic Epidermolysis Bullosa




The underlying genetic abnormalities of epidermolysis bullosa (EB) cause destabilization at the dermo-epidermal junction. Patients with EB characteristically are subject to blistering following relatively minor trauma (the Nikolsky sign), and suffer from ulcers and erosions in all areas subject to persistent or repeated friction, such as the hand. Hand deformities occur in most patients with dystrophic EB (DEB), and include adduction contractures of the first web space, pseudosyndactyly, and flexion contractures of the interphalangeal, metacarpophalangeal, and wrist joints. All structures in the hand may be involved. The severity of the deformity worsens with age, and surgical correction becomes increasingly difficult. Recurrent deformity occurs within 2 to 5 years. Meticulous skin care and the use of well-fitted splints supervised within a multidisciplinary team setting are essential. To date there is no strong evidence base on which to plan surgical treatment of the hand in DEB.


Epidermolysis bullosa (EB) is the name given to a heterogeneous group of rare, inherited skin diseases, characterized by fragility of the epidermis. The underlying genetic abnormalities cause destabilization at the dermo-epidermal junction. Characteristically, therefore, patients with EB are subject to blistering following relatively minor trauma (the Nikolsky sign), and suffer from ulcers and erosions in all areas subject to persistent or repeated friction, such as the hand.


More than 20 clinically distinct phenotypes of EB have been described, but there are 3 main subtypes. In epidermolysis bullosa simplex (EBS) the defect causes blister formation within the basal keratinocytes; in junctional epidermolysis bullosa (JEB) the defect causes blister formation within the lamina lucida; and in dystrophic epidermolysis bullosa (DEB) the blistering occurs in the superficial papillary dermis, at the level of the anchoring fibrils. DEB may be transmitted as an autosomal dominant or recessive subtype. The severity of the disease is mainly determined by the particular form of disease from which the patient suffers, but it is useful to broadly categorize the disease into the nonscarring and scarring (dystrophic) types.


Epidermolysis bullosa and the hand


The typical hand deformities that develop in recessive DEB (RDEB) in particular, where there is reduced or absent collagen VII, include the following: adduction contracture of the thumb; pseudosyndactyly of the digits; flexion contractures of the interphalangeal (IP), metacarpophalangeal (MCP), and wrist joints; and, less frequently, extension contractures of the MCP joints from dorsal scarring. The “mitten” deformity develops when the hand becomes encased in an epidermal cocoon.


All structures in the hand may be affected. Cutaneous involvement results in dermal fibrosis, pseudosyndactyly, contractures, atrophic finger and thumb tips, nail loss (due to subungual blistering) and dermal cocooning. Musculotendinous involvement may result in shortening of the flexor tendons and intrinsic muscle contractures. With time, and lack of use, the IP and MCP joints develop flexion deformities, including contracture and fibrosis of the collateral ligaments. Secondarily, articular involvement produces stiff, subluxed, or even destroyed joints in older patients. Generalized osteoporosis and thinned, wedge-shaped distal phalanges may also be found.


With each episode of relatively minor trauma to the hand, ulceration produces fibrinous adhesions and scarring; this results in the web spaces being obliterated, progressing to the finger tips and causing pseudosyndactyly. The same process occurs in the first web space, initially causing an adduction contracture. This condition may also progress until the thumb is no longer independent. A grading system may be used to describe adduction deformity of the first web space and pseudosyndactyly.


Initially, despite the pain, patients may be able to separate the digits using thread or paper. However, if left untreated, the resulting pseudosyndactyly, together with trauma to, and scarring of, the flexion creases produces flexion contractures at the joints ( Fig. 1 ). Finally, the whole hand may become encased in an epithelial cocoon, producing the mitten deformity ( Fig. 2 ). The term “pseudosyndactyly” is used (as opposed to syndactyly) because the dermis of the adjacent, fused digits remains, with dermis abutting dermis. This abutment is exploited during release of pseudosyndactyly, although a distinct plane may be difficult to find in older children and adults.




Fig. 1


Patients may be able to separate the digits using thread or paper. However, if left untreated, the resulting pseudosyndactyly, together with trauma to, and scarring of, the flexion creases produces flexion contractures at the joints.



Fig. 2


The whole hand may become encased in an epithelial cocoon, producing the “mitten” deformity.


Patients with DEB suffer the worst form of the disease, with major implications on all activities of daily living. Those with RDEB have the greatest degree of blistering, ulceration, and deformity. The risk of the hand developing a mitten deformity is 98% in RDEB (generalized severe type) by the age of 20 years.


Finally, it is not uncommon for squamous cell carcinoma to develop in the hand, the limbs and bony prominences being especially susceptible. Consequently, tumors often develop over the dorsum of joints, making surgical excision challenging.




Surgical planning


The aim of surgery is to provide simple pinch grip and grasp, by releasing the first web space and flexion contractures; independent finger movement, by releasing pseudosyndactyly; and improved appearance of the hand. Patients are seen in a multidisciplinary clinic, allowing their condition to be optimized and their admission planned. Wounds are swabbed preoperatively, and active infection treated. Growth of β-hemolytic streptococcus is a contraindication to surgery. The hand therapist spends time with the patient, discussing the nature of the postoperative rehabilitation regime, and emphasizing the need for splintage to delay recurrent contractures for as long as possible.


Surgery is indicated when loss of hand function begins to compromise the patient’s independence, but the cosmetic appearance of the hand is also important. Surgery should be performed when the patient’s skin, medical, and nutritional condition have been optimized, and at a time when they will be able to attend regular postoperative hand therapy sessions.


Surgery needs careful planning, including: whether to separate the thumb separately from the digits; how to cover the soft tissue defects; whether K-wires will be used; what type of anesthesia is to be used; whether there is an absolute need for postoperative splinting; and close liaison with the hand therapist.




Surgical planning


The aim of surgery is to provide simple pinch grip and grasp, by releasing the first web space and flexion contractures; independent finger movement, by releasing pseudosyndactyly; and improved appearance of the hand. Patients are seen in a multidisciplinary clinic, allowing their condition to be optimized and their admission planned. Wounds are swabbed preoperatively, and active infection treated. Growth of β-hemolytic streptococcus is a contraindication to surgery. The hand therapist spends time with the patient, discussing the nature of the postoperative rehabilitation regime, and emphasizing the need for splintage to delay recurrent contractures for as long as possible.


Surgery is indicated when loss of hand function begins to compromise the patient’s independence, but the cosmetic appearance of the hand is also important. Surgery should be performed when the patient’s skin, medical, and nutritional condition have been optimized, and at a time when they will be able to attend regular postoperative hand therapy sessions.


Surgery needs careful planning, including: whether to separate the thumb separately from the digits; how to cover the soft tissue defects; whether K-wires will be used; what type of anesthesia is to be used; whether there is an absolute need for postoperative splinting; and close liaison with the hand therapist.




Anesthesia


There are multiple anesthetic problems encountered in patients suffering from EB. The reader is referred to the article elsewhere in this issue by Nandi and Howard.


Surgery may be performed under general or regional anesthesia. The latter may be supplemented with an infusion of propofol, particularly if the patient is anxious. Topical local anesthetic cream, or an injection, is used for skin graft harvesting. In children, it is more common to use a general anesthetic. A broad-spectrum antibiotic is given intravenously before surgery begins.




Surgery


Surgery is usually performed under tourniquet control, although not all surgeons do this. Provided the arm is carefully protected using a layer of Vaseline gauze, followed by cotton wool padding, problems with skin ulceration are avoided. The patient is lifted carefully onto the operating table, which has to be well padded to prevent pressure sores. The authors use the RIK Fluid Operating Table Pad (KCI Medical Ltd, Oxford, UK) and have encountered no problems since its use.


The skin is most safely prepared by using a “dabbing” technique or spraying the skin preparation fluid onto the arm, taking care to prevent fluid from running under the tourniquet, essential if the fluid contains alcohol as it can burn the skin if it seeps under the inflated tourniquet. Sutures are placed through the tips of the digits to act as retractors, preventing unnecessary trauma.


Separation of Digits


Most surgeons release all contractures and affected joints of one hand during the same operation. However, because the thumb contributes 50% to hand function, release of the first web space alone produces significant improvement and can be useful if either the surgeon or the patient prefers to limit the extent of the surgery. The adducted first web space is released by incising the scarred skin from the base of the first metacarpal dorsally, to the thenar muscles volarly. Release of the first dorsal interosseous and the adductor pollicis as well as the overlying fascia may be needed in severe cases, but intraoperative stretching of the muscles may be adequate. Care must be taken to avoid injury to the neurovascular bundles.


Next, the pseudosyndactyly between the fingers is addressed. Whereas some surgeons “decocoon” the hand to identify the web spaces, the authors have found this not to be necessary, and try to preserve the tissue on the finger tips. Starting distally, the interdigital space, lined on each side by dermis, can usually be identified and entered with the tips of scissors. The digits can then be teased apart, down to the web spaces. Sometimes, however, this is not possible, particularly if there has been previous surgery, and sharp dissection with a scalpel may be necessary, exposing subcutaneous tissue.


Division of Flexion Contractures


The flexion contractures are then released. This procedure can be done either using multiple transverse incisions in the IP and MCP joint creases, or with a cruciate incision. In children, gentle forced extension of the fingers may sometimes divide any fibrinous adhesions if they alone are causing the flexion contracture. Occasionally, intrinsic muscle contractures need to be released, and shortened flexor tendons may need to be lengthened in selected cases, although this is not common.


K-wires are often used when the IP joints are stiff or subluxed. Like others, the authors prefer not to use wires across the proximal IP joints, unless absolutely necessary, to avoid the complications of prolonged postoperative joint stiffness in extension, potential pin-tract infection, and damage to articular cartilage. Furthermore, forced extension of the IP joints may cause injury to the neurovascular bundles or subluxation of the joints. As has been noted by others, full release of the distal IP joints may not be possible or useful.


Recurrent flexion deformity of the wrist occurs for several reasons, including the stronger pull of the flexor tendons compared with extensor tendons, the powerful pull of flexor carpi ulnaris, and the complex carpal bone movements that favor ulnar deviation in wrist flexion. In early wrist flexion contractures, which are often ulnarly deviated, simple division of the scarred skin will produce full release of the wrist. In more advanced contractures, division of palmaris longus and flexor carpi radialis may be necessary. If the flexor musculotendinous units are contracted, they may require lengthening in the forearm, though this is not common. Although replacement of joints has been described, this procedure is rare: only 1 adult out of 45 patients required MCP joint replacements in the largest published series.


In the most extreme and neglected cases, the wrist joint is also involved and may need to be fused in a neutral position. In some cases, the potential amount of surgery may be too daunting, and the patient may have learned to function so well that the surgeon is unable to guarantee an improved or predictable outcome ( Fig. 3 ).


Feb 12, 2018 | Posted by in Dermatology | Comments Off on Surgery of the Hand in Recessive Dystrophic Epidermolysis Bullosa
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