Repair of thumb defect by using the toenail flap: biomechanical analysis of donor foot-a retrospective cohort study

Abstract

Background: The thumb accounts for 50% of the total hand function. This study reports the functional outcomes and complications of people with traumatic thumb amputations who underwent toe-to-thumb reconstruction.

Methods: From January 2013 to January 2018, 29 patients with second-degree thumb defect underwent thumb reconstruction with distal phalangeal braided toenail flap. The footscan foot pressure gait analysis system was used to measure the index changes of the same foot before and after 1, 3 and 6 months. The contact area, peak pressure, impulse value, contact time of each gait phase, centre of gravity coordinate and foot balance were analysed statistically.

Results: Twenty-nine cases of thumb reconstruction recovered well. After following up for 6-15 months, the appearance of the reconstructed thumb was close to normal, and the sensation was restored to S3+. The two-point discrimination was 6-8 mm, and the function of the thumb was good. The function of the donor foot was well restored, and no skin ulceration, pain and claudication were noted during walking. Compared with that before the operation, the biomechanical indices of the donor foot were basically restored to normal 6 months after the operation. Only the stress and impulse values of the third metatarsal head were significantly increased, forming a stress concentration area centred on the third metatarsal head.

Conclusions: This study confirmed that the toenail flap with distal phalangeal bone restored the second-degree thumb defect without destroying the main functional structure of the sole. The biomechanical indices of the donor foot were basically restored to normal 6 months after the operation. Only the stress concentration area centred on the third metatarsal head, and the pain on the forefoot was induced after the operation. Discomfort, callus formation, metatarsal fasciitis, etc., can lead to fatigue fracture of the third metatarsal bone in severe cases, which requires further follow-up and observation.

Trial registration: Clinicaltrials.gov , NCT03879941; registered on 10 March 2019, retrospectively.

Keywords: Amputation; Biomechanics; Foot morbidity; Thumb reconstruction; Toe transfer.

Conflict of interest statement

The authors declare that they have no competing interests.

Figures

Fig. 1

a The range of thumb defect. b A schematic diagram of the toenail flap with distal phalanx

Fig. 2

A 25-year-old male patient. The left thumb was amputated at the interphalangeal joint level. A toenail flap with distal phalanx was transferred to reconstruct the thumb. a, b Follow-up photograph 1 year postoperatively shows a good replica of the intact thumb. c Comparison of appearance with healthy thumb

Fig. 3

The same patient as in Fig. 2. a Foot incision. b Dorsal appearance of donor foot 1 year postoperatively. c Plantar appearance of the donor foot

Fig. 4

Gait analysis was performed using F-Scan system (Footscan software 7.0 Gait, RsScan International). a The location of eight anatomic important areas of the peak pressure footprint. b Four phases of the total foot contact. c The x-component and y-component of the centre of the pressure. The x-component is positive when positioned medially to the heel-M2/3 axis and negative when it is positioned. A normal case (before the operation)

Fig. 5

Compared with that before the operation, the contact area of the donor foot in M1–M5 and M2–M4 areas decreased significantly 1 and 3 months after the operation, respectively. No significant change was observed 6 months after the operation. *P < 0.05, ***P < 0.001; N = 29. P < 0.05 was considered significant

Fig. 6

Compared with that before the operation, the maximum pressure of M1–M3 decreased and that of M4 and M5 increased 1 month after the operation. Three months after the operation, the pressure of M1 decreased, and that of M5 increased. Six months after the operation, the pressure of M3 increased. The difference was statistically significant. *P < 0.05, ***P < 0.001; N = 29. P < 0.05 was considered significant

Fig. 7

One month after the operation, the impulse value of M3 decreased and those of M4, M5 and HL increased. However, 3 months after the operation, the impulse values of M4 and HL increased. The difference was statistically significant (P < 0.05). No significant change was observed 6 months after the surgery. *P < 0.05, **P < 0.01, ***P < 0.001; N = 29. P < 0.05 was considered significant

Fig. 8

One month after the operation, the contact time of FFPOP decreased, whereas those of ICP, FFP, M5, HM and HL increased. After 3 months, the contact time of ICP increased, whereas that of FFPOP decreased. The difference was statistically significant. *P < 0.05, ***P < 0.001; N = 29. P < 0.05 was considered significant

Fig. 9

A statistically significant difference was observed in the x-coordinate value of FFPOP 1 month after the operation. *P < 0.05, N = 29. P < 0.05 was considered significant

Fig. 10

The lateral pressure of the foot in the FFP and FFPOP periods increased 1 month after the operation, and the difference was statistically significant (P < 0.05). No significant change was observed in other comparisons. ***P < 0.001, N = 29. P < 0.05 was considered significant