Crab-like polydactyly is one of the more difficult types of polydactyly and belongs to the convergence type 4 of wassel’s typology. The two fingers are laterally curved in opposite directions, shaped like two pincers of a crab, hence the name crab-like polydactyly.
There are two main surgical approaches to crab-like polydactyly. One is to fuse the bones and skin of both fingers, which is a high-risk operation, with the possibility of non-healing of the fused finger bones and even necrosis of the finger body, and the fused joint often does not function well, with a thicker appearance than a normal thumb and split scarring of the nail. Another way is to remove the poorly developed radial finger and keep the ulnar finger for osteoarthrosis, which is safe and has a better shape and flexion/extension function after surgery, except for the thumb, which is slightly smaller, and the nail is also intact and smooth. Therefore, the latter surgical approach is increasingly advocated internationally.
Case 1, male, 5 years old, left thumb with crab-like polydactyly.
Preoperative
X-rays.
Postoperative
Case 2, male, 7 months old, left thumb with crab-like polydactyly.
Preoperatively, just after the hand was prepared to soak the hand, wet little hand
Because of the young age and the request for surgery, only joint capsule release, tendon transposition, no osteotomy, and transfer of the excised polydactyly flap to the preserved thumb to make it fuller in shape were performed. It was more than 1 month after surgery.
The only regret is that the nail is still a bit skewed, and it looks even more crooked when it grows too long. The only regret is that the nail is still a bit skewed and too long, which makes it more crooked.
The previous case is a previous surgery, but the current surgery has been improved.
Case 3: Female, 2 years and 10 months old, with crab-like polydactyly of the right thumb.
Preoperatively, the development of the ulnar side was better than the radial side, and the main trunk finger, but the metacarpophalangeal and interphalangeal joints were laterally curved and had a “Z” deformity.
Preoperative X-ray
Immediately after surgery, the curvature had been corrected, and the kyphoscopic pin was in the process of fixation, but the excess skin at the ulnar interphalangeal joint had not been removed and was slightly protruding, which would retract on its own later.
Three months after surgery, the excess skin at the ulnar aspect of the interphalangeal joint was significantly better than before, and the finger would appear straighter after continued contraction.
The interphalangeal joint mobility is good, the child is uncooperative and the range of joint motion can be seen by passive flexion.
Update 2013.10.24, 1 year postoperatively1, the child has good thumb straightening and good joint motion after release of the radial thumb scar contracture.
The previous procedure had a deficiency of skin bloating on the ulnar side of the thumb, although all improved significantly after a long period of self retraction. However, the immediate postoperative results were poor and also less satisfactory to the parents. In order to overcome this deficiency, the surgical approach was modified and the excess skin was removed intraoperatively.
Case 4, male, just turned 3 years old, with crab-like polydactyly of the right thumb.
Preoperative
X-rays, dated 2012-05-09
Intraoperative trimming to remove excess skin for better immediate postoperative results
This child was operated on 2012-05-11, interested parents can wait for the post-operative follow-up photos.
It’s been a long time since I read this post. This child came back six months after surgery and his fingers were straight and his activities were completely normal, but there was a small knot formed under the skin on the ulnar side of the interphalangeal joint, which was because the joint capsule was closed with non-absorbable sutures in the past and some children would have thread reactions. He was given a follow-up visit to remove the knot and has not returned since.
Update December 2013, the child came back for follow-up, 1 year after the removal of the thread knot and 1.5 years after the surgery, the result is very good.
Last year, there were some cases, because the parents asked for early surgery, we took the way of staged surgery, and half a year old to remove multiple fingers at the same time to correct the scoliosis of the metacarpophalangeal joint, after 1.5 years old need a second operation to correct the scoliosis of the interphalangeal joint. However, nowadays, it is still felt that the benefits of a single surgery are more, as the tendon of the polydactyly can be removed to correct the muscle imbalance of the ectopic stop point. Moreover, the age of one-time surgery is also mentioned to be about 2 years old, and mild crab-like fingers have recently been done in a case as young as 1 year and 0 months, which is now 3 months postoperative with good results, and is still being followed up, and I will upload pictures. Therefore, the recommended age for surgery for crab-like polydactyly is 2 years and older, and the procedure is a single-formation.
The child, male, 1 year and 0 months, has a right thumb crab finger. I forgot to take the preoperative x-ray, I will ask the parents to bring it to the next review.
This child was just 1 year old at the time of surgery, and the parents said that he did not cooperate at all with the postoperative splint fixation, so they had to stop when they got it on. However, the finger shape and function were fine. The child was very active and I observed him using this hand all the time, grasping things on my table, and his thumb was cooperating well.
Now just almost 3 months post-op, the incision scar is a little contracted, and the thumb will be straighter later when the scar softens and relaxes.
Finally the age of surgery for crabby fingers has been moved up to 1 year!
Added at the end of March 2013.
Since I haven’t updated the article for a long time, some of the above points may give a misunderstanding. For the crab finger, there are more options for the current approach. Now, for BC fusion, I think that with careful surgical manipulation, the two fingers can be fused in a way that they also have good function and appearance without finger necrosis and bone non-union. Of course, traditional BC fusion has been done less often because it is rare for the bone joints of the two fingers to be completely equal, and in most cases the bone joint planes of the two fingers are different. Therefore, in the last year, more modified BC fusions have been done with mostly satisfactory results, which are generally better than the above-mentioned way of removing one finger and preserving the finger straightening. It is worth reminding that modified fusion in also has its limitations, and although the postoperative function is good, it is not effective for scoliosis correction, and some need to correct scoliosis again in the second stage. However, I personally believe that it is worthwhile to preserve both the size of the appearance and the function of the joint through two surgeries. In addition, regardless of the type of fusion surgery, the appearance will be more swollen in the early stage, that is, six months after the surgery, and the nails will be untidy or even temporarily fall off. In particular, at 2 or 3 months after surgery, the finger may be bent due to scarring or contracture of the skin flap. Generally, after half a year, or at the latest one year, the results are better when the scar softens, the swelling completely subsides, and the joint movement is restored.
Many parents are now also torn as to what way their child should be done? My current recommendation is that if one side of the finger has a more obvious advantage, the size difference is not more than 1/3, especially the main finger nail development is good, the shape is positive without skew, the finger also tends to develop better, in this case it is recommended to remove the poor finger, keep the good finger and correct the scoliosis. If both fingers are poorly developed and differ by more than 1/3 from the healthy finger, the sign is often a crooked nail, in which case fusion is recommended. If the scoliosis is severe in both fingers and the osteoarticular surfaces are equal, a traditional BC fusion is done. If the scoliosis of the two fingers is not severe and the articular surfaces are not equal, it is good to do a modified BC fusion.
In this child, the nail is more square, so he chose to remove and correct the scoliosis.
5 months after surgery, the shape and function are also better
The joint function of the finger is a concern for many parents, and I would like to emphasize it here. The function of the joint is important, but there is a trade-off with aesthetic appearance. I have been in contact with some older children in their late teens, both boys and girls, who basically demanded appearance over function. I even had one older boy say to me directly, “I just want to make my fingers straight, even if I can’t move them!” . His mother told me that the child had low self-esteem because of his bent fingers and often hid his hands from showing them. I can understand this, this is a society that values visual effects, many people value appearance, the hand is the second face of a person, so the child will have such thoughts. In fact, it is in the interphalangeal joint, the joint near the nail, that the bending of the polydactyly is difficult to correct. There are ways to correct the lateral bending of the interphalangeal joint very well, but it may be at the cost of affecting the movement of the joint. I think the price is worth it. For very severe crab fingers, some doctors will even fuse the joint to death and not allow any movement at all. As long as the metacarpophalangeal and carpometacarpal joints can move, even if the interphalangeal joints cannot move at all, the function of the thumb can meet the needs of daily life, including writing, holding chopsticks, playing computer games, driving, etc. If you don’t look closely, it’s not easy to see the abnormalities in your fingers. Of course, complete immobility of the interphalangeal joints has an impact on fine manual work, such as watch repair, which can be limited. Therefore, I personally think that for a crab finger with severe lateral curvature, we can still do the classical traditional BC procedure of fusing half of the bones and half of the soft tissues, so that although the functional movement of the interphalangeal joint is poor (note that there is usually not no movement at all, but only poor movement), the appearance is better and can be made very straight.
I am always asked by parents about the results of fusion, especially when the two fingers are not of equal length. I have a lot of fusion cases on the Chinese hand surgery website, but some parents just can’t see them, so I’ll add them here.
The child, 1 year and 8 months old, has a right thumb crab finger with unequal lengths and lateral curvature, and both fingers are small, and a modified fusion was done.
The parents sent pictures more than 1 month after the surgery, of course, the swelling has not yet finished, and the new nail has not yet grown out, because it is a modified fusion, so I believe that the functional recovery is no problem, I will continue to send follow-up pictures later
3013.10.24 Update.
The choice of surgical procedure for crab finger has always been a problem that many parents struggle with and often ask me for advice. My principle is generally to look at the nail, if the nail is crooked, do the fusion, the nail is more positive recommended to remove the radial finger, retain the ulnar finger straightening.
Nowadays, the way to do post-excision straightening has been greatly improved, and most cases do not require a kyphoscope, which is in line with my principle of minimizing the pain of the child. This way, there is no need to remove stitches or change medications after surgery, and parents can remove the dressing themselves at home after 3 weeks. In addition, the operation completely corrected the lateral curvature of the interphalangeal and metacarpophalangeal joints, and all operations were basically patterned and procedural.
In this case, the nail was slightly small, but the nail was positive and the shape was acceptable. We chose to remove the radial finger and keep the ulnar finger, and at the same time, we did joint correction and tendon neutralization.
At the follow-up visit 2.5 months after surgery, the straightness was good and the movement was good. However, the child was uncooperative and cried and struggled, so I barely took a few pictures, but I did not take any pictures of the interphalangeal joint in flexion. It’s okay, it’s a local child, so I will come back for a follow-up visit and try to get a picture next time.
In this case, the nail difference was large and the nail was crooked, so a modified fusion was chosen, the two fingers were not the same length, the radial composite tissue flap was made into an island flap to advance, and the preserved ulnar osteoarthritis was still corrected for joint scoliosis.
The medication was changed three days after surgery, with a little swelling and good blood supply.
Because, more and more postoperative polydactyly does not require dressing changes, parents unpack the dressing at home after three weeks, from time to time, some parents are frightened by the swelling of the finger or the scab, thinking that there is a problem with the wound, in order to avoid having to explain one by one, I am sending the recovery process of a case with very obvious swelling three weeks after surgery. Of course, most of the postoperative cases are not so heavy, but the deformities are heavy, and the swelling is more serious if the surgery was done in a big way.
The child, half a year old, has a crab-like polydactyly of the right thumb, also known as type IV convergence.
Immediately after the surgery, he was not given any Kirschner injection after straightening.
3 weeks after surgery, because it is local, come to the clinic to open, indeed, the redness and swelling is obvious, the thread knot and blood scabs clotted together, very unattractive, but the wound is dry, no more bandages after opening, do not remove the thread, after a few days the sutures and scabs will fall off on their own.
8 months after the operation, the child came back for a follow-up visit, the shape and activities are okay, the child is only 1 year and 2 months, how do not cooperate with the activities, did not take pictures of the flexion position.
Oh, the ugly pictures of the three weeks after the surgery were taken out, just to reassure parents that the swelling of the wound is normal when it is opened three weeks after the surgery, as long as the wound is dry it is not a big problem. Especially when you have done a crab finger, the surgery is big and the swelling takes longer. Of course, it is correct to send me pictures if you are unsure, but don’t scare yourself with a start.
Update 2015
Currently, the surgery for crab-like polydactyly is basically fixed with a keratoplasty pin, usually for 3-4 weeks, so that you don’t have to worry about a recurrence of lateral deviation due to improper dressing when the child returns to the local area for a change of medication.
In addition, this type of polydactyly is generally not fused now, because the traditional fusion of bone and joint movement is not good, and the thickening of the finger is also more obvious, especially the thickening of the joint is not good to reduce the second-stage surgery. And modified fusion is not easy to correct the scoliosis, easy to recurrence of scoliosis need to operate again.
Therefore, my current criterion for fusion is: Is the nail crooked? If the nail is straight, even if it is a little smaller, the nail will still be removed and the thumb straightened.
Here are the cases where I think fusion must be done, usually type III.
Update 2015.3.7
Crab-like polydactyly is mainly a reverse scoliosis of the interphalangeal joint (the joint of the thumb near the nail) and the metacarpophalangeal joint (the joint at the base of the thumb). The difficulty of surgery is to correct the scoliosis of the interphalangeal joints. For cases with severe scoliosis (90 degrees), it is not easy to correct the interphalangeal joints to be straight at once.
Most of my cases are in infants and toddlers over the age of 1 year, and I do not fuse the interphalangeal joints or generally osteotomize the phalanges in order not to affect the development of the fingers, but to straighten the lateral collateral ligaments by neutralizing the flexor and extensor tendons and adjusting the tension. The first is the best, that is, after the joint is basically stabilized (usually six months after surgery) just to the fully straightened position; the second is that the correction is still a little less, that is, the interphalangeal joint is still a little radially curved; the third is that the correction is too much, the thumb is in turn a little bent to the ulnar side (against the index finger direction) after surgery.
The reasons for the three outcomes are: the severity of the scar contracture of the wound, the size of the tension of the flexor and extensor tendons, the position of the midpoint of the stop and the tension of the lateral collateral ligament on the radial and ulnar side all have an impact on the postoperative outcome, and it is indeed difficult to guarantee that every child will be just straight after surgery. The immediate intraoperative result may not be the same as the six-month postoperative result. Some children who are made straight immediately during surgery may not be corrected enough after surgery due to scar contracture of the wound. In some cases, the wound is overcorrected intraoperatively and the postoperative scar contracture is just straight, but in other cases, the wound is not contracted, resulting in overcorrection after surgery. Of course, by summing up the experience and following up the postoperative period, I have a better grasp in most cases, and most of the children belong to the first case and can be made very straight in one operation, but the latter two cases still cannot be eliminated. I would like to ask parents to understand that no surgeon can guarantee a straight result in every case of crab-like polydactyly.
In addition, the outcome of the surgery, apart from the doctor’s skill, also has a lot to do with whether the parents can cooperate with the doctor in the post-operative rehabilitation. Therefore, 3-4 weeks after the surgery, after the child’s thumb is not wrapped, the parents need to send me pictures in a timely and regular manner so that I can detect abnormalities and promptly guide the parents to give interventions at home.
In the first case, it is just corrected to a fully extended position.
In the second case, the correction was not enough and there was a bit of scoliosis, and this case had a second stage surgery one year later.
In the second case, there were some cases where the lateral curvature was not corrected enough at 3 months after surgery due to scar contracture, but over time, the scar slowly softened and the thumb was slowly straightened. Therefore, the final result is stable after one year.
In the third case, the thumb was overcorrected, and the thumb was slightly side-bent in the opposite direction
This case is also overcorrected and a little obvious, but the parents do not ask for treatment for the time being, and continue to observe, or operate again if necessary.
Some parents are very anxious and cannot wait. In fact, I think it is worth waiting for a doctor with more reliable skills than rushing to find one. I have had good results with older children, and this one is almost 14 years old before surgery.
This case is an adult, 24 years old, with a very severe scoliosis, and a largely straight thumb after surgery.