Difficulties in recruiting subjects with partial foot amputations for kinesiological research

Abstract

We are reporting the difficulties encountered in the recruitment of patients with partial foot amputations (PFA) following diabetic neuropathy (DMPN) for kinesiological research during an attempt to study the functional outcome following healed unilateral PFA in subjects with DMPN. Amputations of the hallux, ray and trans-metatarsal amputations were collectively classified as PFA for our study. This kinesiological study included kinetic (study of forces) and kinematic (study of motion irrespective of the forces which govern the motion) analyses of functional activities such as sit-to-stand, standing and walking. Therefore, it was necessary to exclude patients with bilateral lower extremity amputations (LEA), gross neurological and musculo-skeletal impairments apart from those related to DMPN and painful forms of DMPN to minimise any confounding bias in the interpretation of the results. Based on power calculations a minimum number of 23 subjects was required for this study (α = 0.05, 1 − β = 0.80). Patients from two major NHS Trust hospitals and three podiatry and two diabetic foot clinics were screened for recruitment. At the first hospital, 32 subjects underwent PFA over a 2-year period. PFA were performed as primary procedures on 25 (25/32) subjects, of those 9 had diabetes (DM). One (1/9) subject attained healing, 6 (6/9) subjects with DM did not heal and 2 subjects underwent ipsi-lateral TTA (76 and 80 weeks, respectively) later. Seven (7/32) subjects underwent PFA as a secondary procedure (the primary procedure in these patients was vascular reconstruction) and out of those four subjects had DM, of those four, three subjects did not heal and one refused to participate in the study. At the second hospital, 18 patients with diabetes related PFA were identified of which 2 subjects remained unhealed, 4 subjects developed contra-lateral LEA following PFA, 6 subjects developed ipsi-lateral DFU following PFA, 1 subject was severely affected by Osteoarthritis, 1 subject suffered from partial blindness and 4 subjects did not respond to the invitation. Effectively, between the two hospitals from the 50 patients identified over a 19-months period, one ended up participating in our study. Another 15 subjects with healed PFA were identified through the various clinics. This challenging recruitment process highlights the difficulty in finding diabetic subjects with healed unilateral PFA. This could be attributed to many factors: (i) very low incidence of PFA compared to major LEA among diabetic subjects in South Wales (unpublished data) which was concurrent with the low incidence of foot amputations reported previously in the UK and USA [1] and [2]. (ii) Prolonged period of wound healing demonstrated by diabetic subjects following PFA: one subject from our centre had a healing time of 24 weeks. Although, we did not have this information for the other 15 participants, the time duration was similar to the previously reported average healing time, i.e. 29 weeks [3]. (iii) Increased risk for ulceration and re-amputation in diabetic patients with PFA as reported earlier [4]. Of the 27 diabetic subjects from both the centres 22.2% underwent re-amputation (2/27 ipsi-lateral amputations, 4/27 contra-lateral amputations) and 22.2% of subjects developed ipsi-lateral DFU. Kinesiological studies involving people with PFA require complete healing following an amputation. The presence of a wound could confound the results since it can produce movement alterations in addition to the changes already produced by PFA. On the other hand, the challenge to recruit adequate numbers affects the statistical analysis of the results. Therefore two-to-one (Controls: PFA) matching of subjects and prudent use of statistical tools to accommodate for unequal group sizes appear to be appropriate strategies in such cases. However, the low percentage of diabetic people with healed PFA and the rapid succession of further complications raise serious concerns. These facts underline the need for further research into improving the healing process and preventing further complications.