Macro- and microcirculatory assessment of cold sensitivity after traumatic finger amputation and microsurgical replantation

Finger replantations after traumatic amputation are associated with good prognosis and acceptable functional results. However, cold sensitivity is a common and sometimes disabling sequelae after digital replantation. The exact causes of cold intolerance are still unclear; neural as well as vascular mechanisms have been discussed. We examined the macro- and microvascular performance of replanted fingers using high-resolution color-coded sonography for the assessment of skin vessel density of the fingertips as well as nailfold capillary microscopy and laser Doppler anemometry. Subsequently, we correlated these findings with the presence of cold sensitivity of the replanted digits.

Thirty-seven patients (mean age 45 years; range 19–72) with 40 traumatic finger amputations and microsurgical replantations were studied. The mean time interval between amputation and examination was 57.7 months (range 13–95). Macro- and microvascular examination consisted of electronic oscillograms of both arms, photoplethysmograms of all fingers before and after cold test, duplex ultrasound of the finger arteries, high-resolution color-coded sonography of the fingertips and nailfold capillary microscopy with laser Doppler anemometry.

Cold sensitivity was present in 33 (83%) of the 40 replanted fingers. Peripheral arterial disease of the upper extremity could be excluded as all oscillograms showed normal findings. A vasospastic reaction after cold test was documented in 74% (30 of 38) of the replanted fingers, compared to 24% (9 of 38) of the contralateral uninjured fingers. Raynaud’s phenomenon was restricted to replanted fingers and occurred in 10 of 40 patients (25%). Compared with the contralateral fingertips, reduced skin vessel density was found in 27 of 36 (75%) replants. Nailfold capillary microscopy revealed uncharacteristic morphologic patterns. The capillary flow velocity was 0.28 ± 0.12 mm/s in the replanted fingers and 0.48 ± 0.23 mm/s in their unaffected counterparts (P < 0.001). Correlating these findings with the presence of cold intolerance, reduced skin vessel density in the fingertips was significantly different between cold-sensitive replants and those without cold sensitivity (P = 0.05). Reduced skin vessel density was not related to the extent of reconstruction of nerves (P = n.s.), arteries (P = n.s.) and veins (P = n.s.).

Our results do not confirm hypotheses that cold sensitivity after finger replantations is caused by macrovascular problems nor do they support assumptions of a primary capillary microcirculatory failure. Our findings of reduced vessel density point towards diminished thermoregulatory capacities in the fingertips of cold-sensitive replanted digits.