Vita Yu-Hsien TU, Occupational Therapist and Project Manager
Sunshine Social Welfare Foundation
Claw hand is one of the most common post-burn deformities of the hand, and it is very common in the little finger. Many therapists find that once claw hand has set in the little finger, it is quite challenging to manage. In part 1 of a series of two articles, we will explain how and why claw hand develops in the little finger, as well as explain specific considerations when designing interventions to deal with little finger claw hand deformity.
What is claw hand deformity?
Claw hand deformity refers to the abnormal hand position where MP hyperextension and PIP flexion are present at the same time.
There are two main causes of post-burn claw hand deformity: scar contracture on dorsal side of the hand, and chronic swelling leading to accumulation of protein on the dorsal side.
Dorsal scar contracture: Because scars contract towards the center, the force of dorsal scar contracture will pull MP joints in extension, and even hyperextension.
Edema: Accumulation of fluids during post-burn edema will create swelling. As the loose and thin skin on the dorsum of the hand becomes extended due to swelling, tension will literally pull the fingers into a claw hand shape, with MP in extension and IP in flexion. The accumulation of protein in edema fluids will also cause tissue adhesion, which then leads to tissue adaptive shortening. This will impact tendons, collateral ligaments and joint capsules.
In a previous article What makes the safe position safe? Part 1, we explained that the safe position for the MP joint is flexion, because the collateral ligament will be in a stretched state. This position prevents adaptive shortening of the collateral ligament, which would otherwise lead to hand deformity. When MP joints are in extension and IP joints are in flexion for a prolonged period, this will cause shortening of ligaments and other soft tissues, and this position is the same as the claw hand deformity position
Why pay attention to little finger claw hand deformity?
In our clinical experience, we frequently see claw hand deformity of the little finger, like the one pictured below.
Groenevelt (1986) noted that the little finger's posture and position at the hand's edge make it more vulnerable to flame burns. His study also indicated that the little finger often suffers from more frequent and severe complications, with MP hyperextension and PIP flexion being typical post-burn deformities [1].
At first glance, the little finger might seem to have little impact on hand function and can therefore be easily overlooked in rehabilitation, especially when other fingers are affected. However, the importance of the little finger should not be underestimated, particularly its impact on grip strength. Methot et al. found that excluding the ring and little fingers from a functional grip pattern decreased grip strength by 34% to 67%, with a mean decrease of 55%. Exclusion of the little finger alone decreased overall grip strength by 33% [2]. With proper and timely rehabilitation intervention, it is possible to improve the little finger’s claw hand issue.
What are the prioritization considerations when managing claw hand deformity of the little finger?
When establishing rehabilitation priorities for the management of claw hand deformity, we usually start dealing with MP joint issues first, followed by PIP joint issues.
From a functional perspective, the hand needs to perform grasping function, and the finger joints will tend toward flexion. If MP joint flexion can be increased, the hand can have basic grasping capabilities.
From an anatomical point of view, the MP joint and PIP joint of the finger are linked through the anatomical structure of tendons and ligaments. When the MP joint is pulled in flexion, the PIP joint tends to straighten. Therefore, priority should be given to improving the MP hyperextension problem. Increasing MP flexion will encourage PIP extension, which will help improve PIP flexion problem in claw hand deformity.
Conclusion
Claw hand deformity of the little finger should not be overlooked, because despite what we may think, it can still have a significant impact on hand function, particularly grip strength. Addressing this deformity requires a thorough understanding of its causes and a structured rehabilitation approach, prioritizing MP joint correction to facilitate overall hand functionality. With appropriate and timely intervention, it is possible to improve outcomes for individuals suffering from this challenging post-burn condition.
In part 2 of this series, we will discuss in more detail the types of interventions used to address claw hand deformity of the little finger, as well as the specific sequence of these interventions.
Reference:
[1] Groenevelt F. Some aspects of the burned little finger. Br J Plast Surg. 1986 Apr;39(2):225-8. https://www.jprasurg.com/article/0007-1226(86)90087-1/pdf
[2] Methot J, Chinchalkar SJ, Richards RS. Contribution of the ulnar digits to grip strength. Can J Plast Surg. 2010 Spring;18(1):e10-4. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2851460/
To learn more about rehabilitation interventions for post-burn hand deformities, check out our online course Rehabilitation of the Burned Hand - Management of Common Hand Deformities. After this course, you will be able to:
Explain the causes of various types of post-burn hand deformities.
Explain acute stage rehabilitation interventions to prevent post-burn hand deformities.
Explain rehabilitation interventions in the wound healing and rehabilitation stages to manage post-burn hand deformities.
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