Abstract
Dear Editor,
Kindly find enclosed our comments on the article entitled Improved comfort and function of arm prosthesis after implantation of a Humerus-T-Prosthesis in trans-humeral amputees by Witsø et al. published in the December 2006 issue of the journal.
We agree with the authors that difficulties with prosthesis suspension often hamper post-amputation care in trans-humeral amputees. Their novel approach to overcoming these difficulties has obvious advantage in comparison to other techniques involving direct anchorage of artificial limbs to the skeleton of the amputation stump. The fact that the implanted prosthesis is not left exposed or protruding through the skin confers protection from infection as it eliminates a potential entry portal for organisms.
However, this study raises a number of questions. In the introduction section, the authors state that 50% of trans-humeral amputees do not use their prosthesis (Heger et al. 1985; Sturup et al. 1988; Wright et al. 1995) and then imply that this is mainly due to problems with suspension and anchorage of the prosthesis. Whilst we agree that these difficulties play a part, there is evidence that other factors are also important in determining upper limb prosthetic limb use. These include hand dominance (Dulkiewicz et al. 2004) and (lack of) sensory feedback from the prosthesis (Kuiken et al. 2007).
Secondly, despite the title of the article, there were no outcome measures used to determine comfort and function of the upper limb prosthesis. Simply measuring pain with VAS (Visual analogue scale) from the contralateral shoulder does not give any measure of the comfort of fit of the new prosthesis and certainly not on the functional use.
Thirdly, could the authors clarify how the range of motion in the shoulder was measured? Accurate goniometric measurements in the shoulder are difficult to achieve, especially with regards to internal and external rotation.
The authors preceded their in vivo work with in vitro testing, but did not state the number of repetitions of axial and torsional loading applied to the implant till failure of the fixation. We believe this is crucial especially in a device that will be subjected to repetitive axial and torsional loading during use.
Finally, the cause of the amputation in the 3 volunteers was not stated. Others have shown that traumatic upper limb amputees are less satisfied with their prosthesis and their functional ability is poorer especially with myoelectric prostheses (Gaine et al. 1997). In view of the poor result noted in patient III, could this have been a factor?
Yours sincerely,
Dr Abayomi Salawu
Dr Vera Neumann
Department of Rehabilitation Medicine
Chapel Allerton Hospital
Leeds, UK