Functional outcome after digit replantation versus amputation

Since the first successful thumb replantation, performed by Komatsu and Tamai in 1965, numerous replantations have been performed, and results have been compared based on the survival rates [2, 8, 9, 11, 12, 27]. However, indications for replantation have also been controversially discussed [27]. Replanted digits often result in stiffness [4, 28], immobility, and cold intolerance [29]. Brown suggested in 1982 that a well-healed stump may be the best solution for many patients [30]. Our study’s aim was to compare the objective and subjective results after replantation versus amputation.

Functional results (ROM, FTD, FPD, and grip and pinch strengths)

Urbaniak et al. reported a mean ROM of 206° for a replanted finger after avulsion injury [31], and Adani et al. reported a mean ROM of 185° after ring finger avulsion injury [8]. A meta-analysis from 2011 yielded a ROM of 174° after 75 finger replantations [32]. In our study, the mean ROM after finger replantation was less than the results mentioned above (mean 146°). This could be because six of the 14 examined patients with a successful finger replantation had an arthrodesis of either the PIP or DIP joint. After thumb replantation, the mean ROM in this study was 91° (median 87°). In Unglaub et al.’s study, a mean ROM of 56° was found after thumb replantation [13].

In our study population, the median FPD was better than the median FTD. This indicates a greater limitation on finger flexion than extension. Reasons for this could be tendon adhesions and, in some cases, patient compliance during postoperative treatment.

Unglaub et al. described a mean force of 70% in grip strength and 68% in pinch strength after thumb replantation compared to the uninjured side [13]. In this study, a mean force of 92% was achieved in the grip test and 60% in the pinch test after thumb replantation. After thumb or finger replantation, no statistically significant differences in grip or pinch force could be found between groups R and A. It should be kept in mind that differences are expected whether the dominant or nondominant hand is affected [33]. The contralateral uninjured hand served as the control, since amputation injuries are emergency cases and no preinjury assessment of the affected side is possible.

Recovery of sensibility

In this study, the measurable median 2-PD was 5 mm in group R compared with 6 mm in group A. These are excellent results compared to previous studies. In a meta-analysis in 2011, the results after replanting 2273 digits were evaluated. Sensibility recovery was measured in 12 out of 30 studies and showed a mean of 7 mm [34]. In 2013, Adani et al. reported a mean static 2-PD of 12 mm (range 9–15 mm) after complete avulsion amputation injuries [8]. In contrast to our results, the 2-PD was only described after successful replantation in the previously described publications. Hence, there are no comparable values after amputation.

While the 2-PD measures spatial discrimination, the SWM test quantifies the cutaneous pressure threshold [23]. Criticism of the 2-PD includes the fact that it is a nonobjective test since the force the examiner applied is not standardized [23, 35, 36]. In contrast to the 2-PD, the SWM test is more reliable and objective [35]. Sensibility recovery was mostly tested using the 2-PD test in previous studies. Only one study used the SWM test after 24 thumb replantations [13]. This group reported normal sensibility (N) in one patient (4%), diminished light touch (DLT) in six patients (25%), diminished protective sensation (DPS) in 13 patients (54%), and a loss of protective sensation (LPS) in three patients (12%). Significantly worse results were present in patients with crush and avulsion injuries [13]. In comparison, better results were present in our replantation group. Normal sensibility was present in 21.2%, DLT was found in 48.5%, 24.2% showed DPS, and only 6.1% had LPS.

The superior sensory results in this study may be due to the progress made in microsurgical skills in recent decades when compared to older studies. Exact coaptation with two or three epineural 10–0 or 9–0 nylon sutures of the digital nerves is mandatory for obtaining optimal results [35].

Pain level

Cold intolerance after successful replantation occurred twice as often as in the amputation group in a study published in 1990 [14]. Jones et al. also reported cold intolerance as being the most common symptom after replantation [29]. Our results demonstrated significantly more pain at rest and under strain after revision amputation than after successful replantation. Importantly, most patients reported no pain at rest at all after successful replantation, while 80% of the patients reported a pain intensity at rest ranging from 1 to 7 (median 2) after amputation, according to the NRS.

DASH score

In the current study, a similar DASH score was obtained for groups R and A. It should be considered that the DASH score has its limitations because it does not differentiate between the dominant and nondominant sides [37]. This could result in a more unsatisfactory outcome if the injury ended in a stump formation but the patient originally wished for a replantation, and vice versa. The fact that the DASH questionnaire contains questions concerning the whole upper extremity and not just the hand function must also be kept in mind.

Current aspects of digit replantation

Comparing our overall results with previous studies, it is notable that functional studies assessing diverse parameters, such as the present work, are rare in the literature. For instance, ROM was regularly reported in older studies [8, 32], but grip and pinch strengths were mainly reported after thumb replantation [13]. The excellent sensory recovery results in the replantation group but also the very good remaining sensibility at the stump sites are probably due to the evolution of microsurgical skills, as mentioned above. Similar comparisons of sensory results not only in replanted but also in amputated digits are scarce in the literature. In contrast to older studies (more than 20 years old) [14, 29], pain levels were significantly less in the replantation group, again illustrating the evolution in microsurgical techniques that has occurred in the last decade. Due to meticulous nerve coaptation and anastomosis of both digital arteries and at least two veins in most of the cases, less pain due to neuroma formation or ischemia is expected.

A recent problem in Western and especially American countries is a declining replantation rate, resulting in less experience in digit replantation among surgeons and worse results concerning replantation success. Some explanations for that could be a change in workplace safety, injury characteristics, economic aspects, the surgeon’s attitude, and a lack of technical skills [38, 39]. This is the reason why actual studies examining functional results after digit replantations became rare in the last decade. Our results in a European hand surgery trauma center illustrate the importance of performing digit replantation, if feasible.

Limitations of the study

The main limitation of the study is the small number of patients, particularly in the replantation group, due to loss to follow-up. However, it is not easy to obtain a larger number of patients who are willing to take part in a follow-up examination in a single-center study years after their treatment. It would be interesting to perform further group comparisons, for example, between primary and secondary amputation, the corresponding digits of each side separately, between injury types, between single or multiple replantations on the same hand, and between dominant and nondominant hands. Furthermore, the assessment of more long-term health-related quality of life outcomes could enrich the comparisons mentioned above [40].

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