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Corresponding author: Yongqing Xu, MD, Department of Orthopedics, 920 Hospital of the Joint Logistic Support Force, People’s Liberation Army of China, 212 Daguan Road, Xishan District, Kunming 650032, People’s Republic of China Or: Yonghui Zhao, MD, Department of Orthopedics, The First People’s Hospital of Yunnan Province, The Affiliated Hospital of Kunming University of Science and Technology, 157 Jinbi Road, Xishan District, Kunming, 650032, People’s Republic of China.
Department of Orthopedics, 920 Hospital of the Joint Logistic Support Force, People’s Liberation Army of China, Kunming, People’s Republic of ChinaDepartment of Orthopedics, The First People’s Hospital of Yunnan Province, The Affiliated Hospital of Kunming University of Science and Technology, Kunming, People’s Republic of China
Corresponding author: Yongqing Xu, MD, Department of Orthopedics, 920 Hospital of the Joint Logistic Support Force, People’s Liberation Army of China, 212 Daguan Road, Xishan District, Kunming 650032, People’s Republic of China Or: Yonghui Zhao, MD, Department of Orthopedics, The First People’s Hospital of Yunnan Province, The Affiliated Hospital of Kunming University of Science and Technology, 157 Jinbi Road, Xishan District, Kunming, 650032, People’s Republic of China.
Department of Orthopedics, The First People’s Hospital of Yunnan Province, The Affiliated Hospital of Kunming University of Science and Technology, Kunming, People’s Republic of China
To explore the results of using the mini-ring Ilizarov external fixator for thumb metacarpal lengthening and its compatibility with a simultaneous groin flap.
Methods
From May 2016 to June 2019, 17 adult patients with thumb loss were treated with metacarpal lengthening using a mini-ring Ilizarov device. The device was composed of 2 rings, threaded rods, nuts, and K-wires (diameter, 1.5 mm). Of these patients, 6 also underwent simultaneous groin flap transfer. Lengthening was started 3 days after surgery at a rate of 0.66 mm/d. The pedicle of the groin flap was divided 1 month after the surgery. The healing index (days per cm), which denotes the number of days the external fixator is attached to the bone per centimeter of length gained, was used to evaluate the lengthening efficiency.
Results
The patients were observed for 21.9 ± 9.0 months. The lengthening continued for 29.1 ± 4.5 days, resulting in an additional length of 1.9 ± 0.3 cm.
Conclusions
The mini-ring Ilizarov external fixator is a simple device for primary metacarpal lengthening. This device can be used with a groin flap for single-stage lengthening of injured thumbs with bone exposure.
Traumatic finger injuries are commonly encountered in hand surgery. Thumb function accounts for more than 40% of all hand functions, and thumb defects seriously affect the pinching and holding functions of the hand, leading to a major loss of hand function, causing psychological trauma, and impairing the patient’s life and work.
Replantation is usually the first choice for thumb amputations however, it requires microsurgical expertise. In cases of failed replantation or extensive damage contraindicating replantation, an osteocutaneous flap or toe-to-hand transfer can be used to recover hand function.
Reconstruction of combined thumb amputation at the metacarpal base level and index amputation at the metacarpal level with pollicization and bilateral double toe composite transfer.
However, these procedures are always time consuming, require advanced microsurgical techniques, and cause morbidity at the donor site, usually the foot.
Via continuous, stable, and slow traction, the Ilizarov technique lengthens bone and soft tissue and can be used to treat limb defects and deformities.
In our experience, unilateral devices and Ilizarov mini-fixators produce insufficient biomechanical force and will lead to distraction osteogenesis dysplasia (poor mineralization). This complication occurs when there is strong resistance in the lengthening site, such as in metacarpals or scarred fingers. In addition, after trauma, some fingers may have bulky flap coverage, and the pins or wires of these 2 types of devices may be too short and weak for such a situation. Although traditional Ilizarov devices produce sufficient force, they are too bulky for the hand. Based on the traditional Ilizarov fixation system, a custom-made Ilizarov mini-ring external fixator was designed and used in this case series. This system is not only delicate and versatile (components can be added or removed freely), but also strong enough for metacarpal lengthening.
Materials and Methods
General information
This study was approved by the Medical Ethics Committee of our hospital. All patients were informed and signed surgical consent forms before surgery. From May 2016 to June 2019, a mini-ring Ilizarov device was used at our center for metacarpal lengthening in 17 adults with posttraumatic thumb defects. The patients included 10 men and 7 women aged 40.6 ± 8.6 years. The thumb stump wounds of 11 patients had healed before lengthening. Six patients underwent simultaneous groin flap transfer for coverage of the exposed phalanx. The preoperative residual length of the proximal phalanx was 6.8 ± 1.9 mm (range, 3.9–9.6 mm). The healing index refers to the ratio of time (in days) to lengthening (in centimeters) when the external fixation device was removed after complete mineralization of the phalanx. This value was used to evaluate the lengthening efficiency of the metacarpal.
Surgical technique
The mini-ring Ilizarov external fixator can be custom-made in 3 sizes (Fig. 1). With the patient in the supine position and under general anesthesia, 2 C-rings connected by 3 threaded rods (diameter, 4 mm) were assembled. The rings were fixed at the base and neck of the first metacarpal using 2 crossed K-wires (diameter 1.5 mm) for each ring. The end of the residual phalanx was fixed to the metacarpal by a K-wire (diameter, 1.2 mm). The wire was bent and fixed to the distal ring. A 0.5-cm long incision was made on the anterolateral and proximal side of the first metacarpal. A 1.5-mm K-wire was used to drill 1–3 holes, and then a bone chisel was used to divide the bone. For those undergoing simultaneous groin flap transfer, the hand was kept under proper tension, with the groin region using a Hoffmann II (Shanghai Kaiwei Medical Technology Co., LTD., China) external fixator to connect the anterior iliac bone and the ulna (Fig. 2). The pedicle was divided 1 month after the surgery. In cases in which a bulky flap or scar deformity due to previous operations was noted, additional half rings and other components were added as needed to modify the diameter of the frame (Fig. 3).
Figure 1The mini-ring Ilizarov external fixation device. A Mini-rings with 3 diameters and 15, 18, or 25 holes. B The device is composed of 2 full rings or half rings connected by threaded rods. Additional rings, rods, and other components may be added if necessary. C Size compared with a hand.
Figure 2A 53-year-old man who was a renovation worker. A The right thumb was amputated by a paper-cutting machine and exposed. B Single-stage treatment with a mini-ring external fixator for metacarpal lengthening and a groin flap for wound coverage. C One month later, the pedicle was severed. The lengthening was finished (arrows show the changing position of the ring along the threaded rods). D A preoperative x-ray film. E A 2-month postoperative x-ray film. F A postoperative x-ray film obtained 5 months after device removal. G Appearance of the 2 hands 5 months after surgery. H The pinching and opposition functions of the reconstructed thumb.
Figure 3More rings and components can be added, if necessary (arrows show the connection of the rings). In this case, the bulky thumb flap required larger-diameter rings.
Lengthening of the thumb metacarpal bone began 3 days after surgery. The nut of the mini-ring system has 6 sides, and a full rotation corresponds to a lengthening of 0.66 mm. The device was lengthened 3 times per day by one-third of a complete turn each time (2 sides of the nut). The rate of lengthening was decreased if severe pain, numbness, or disturbance of the distal blood supply occurred. Radiographs were obtained once a week during lengthening and once a month after lengthening was complete, revealing the maximum recovered length of the treated thumb. The maximum length was expected to reach the level of the interphalangeal joint of the contralateral thumb. The device was removed in the outpatient department if visible tricortical bone formation was observed.
In the 6 patients who underwent groin flap transfer, the flap circulation was closely monitored until complete flap survival was observed, and the pedicle was divided. During the treatment, the patients were asked to exercise the wrist, metacarpophalangeal, and interphalangeal joints. Exercises for thumb opposition, gripping, and holding began after fixator removal.
Results
The patients were observed for 21.9 ± 9.0 months (range, 12–42 months) (Table 1). The 6 groin flaps survived uneventfully. The lengthening period was 29.1 ± 4.5 days (range, 20–38 days), resulting in an additional length of 1.9 ± 0.3 cm (range, 1.3–2.5 cm). The length was 71.6% ± 9.3% of the length of the contralateral thumb (first digital ray). All lengthened metacarpals achieved bony union. The healing index was 54.7 ± 8.1 d/cm (range, 40.6–65.7 d/cm).
Table 1Details of 17 Patients who Underwent Lengthening of the First Metacarpal
At the last follow-up, the pinching, gripping, holding, and opposition functions and the appearance of the hands were improved. All the hands showed mild contracture and edema of the first web space, which resolved after fixator removal and rehabilitation. Twelve reconstructed thumbs showed a stiff first metacarpophalangeal joint, which was painless and stable.
first reported the use of a unilateral mini-traction device to lengthen the thumb. Since then, this technique has been widely used for metacarpal and phalangeal lengthening to restore finger function.
These unilateral external fixation devices are small and suitable for phalangeal lengthening. However, in our experience, they are not strong enough for metacarpal lengthening owing to the off-axis loading design. The half pins (diameter, 1.5–2.0 mm) easily loosen and back out during distraction, leading to poor or deformed osteogenesis. When the pins and wires have the same diameter, full wires fixed by a 3-dimensional ring or multi-threaded rods theoretically produce more stability.
In addition, the pins (at least 4) must be positioned in a straight line, which may be difficult to achieve in a hand that has undergone many previous surgeries. The Ilizarov mini fixator is minimal in size and more stable than the unilateral fixators because of the multidirectional fixation of the half pins.
Although it is suitable for phalangeal lengthening and deformity correction, it is not strong enough for metacarpal lengthening because the resistance of the soft tissue envelope around the metacarpals is much stronger than that around the phalanges. The mini-ring device provides the advantages of stability, a miniature size, ease of use, and versatility. No patient in this study experienced loosening or failure of this device. We believe that this external fixator could play an important role in hand bone lengthening in complicated cases. C-rings are suitable for the first, second, and fifth metacarpals. However, this system could also be applied to the index finger at any level and the distal phalanges of the middle and ring fingers using full-ring frames (Fig. 4).
Figure 4Full or half rings can be chosen according to the affected site and status of the hand.
An important point regarding this surgical technique is to locate the osteotomy site at the metacarpal base. A more proximal osteotomy site will result in better blood circulation of the bone and better osteogenesis.
The periosteum of the site should not be fully divided; instead, K-wires should be used to drill holes through which the metacarpal can be manually fractured. The time before beginning lengthening varies in the literature from the fourth to tenth postoperative days.
A shorter time may increase the possibility of prolonged bone union, whereas a longer time may lead to premature union. In this series, although the lengthening process began earlier (third postoperative day), the lengthening rate was 0.66 mm/d—slower than most rates reported in the literature.
suggested that lengthening to 68% was also acceptable. In this study, the thumb was lengthened by 1.9 ± 0.3 cm, corresponding to 71.6% ± 9.3% of the length of the contralateral thumb. At this length, the other fingertips were able to reach the distal thumb easily, achieving good opposition function. Considering that the metacarpophalangeal joint is always stiff and that there is no interphalangeal joint motion in the reconstructed thumb, we believe that the best length for the opposition function of a lengthened thumb is in the range of 70% to 85%, although this assumption needs further study.
The healing index varies in the literature. Erdem et al
suggested that the healing index is not related to the traction rate but is closely related to the patient’s age, osteotomy position, and lengthening length, and we agree with this view. The healing index was 54.7 ± 8.1 d/cm in the present series. The causes of thumb amputations in this series were serious injuries, which could result in damage to the blood circulation of the first metacarpal and possibly lead to a larger healing index.
In our series, 6 patients underwent simultaneous groin flap transfer for phalanx coverage, including 2 patients with a crush injury and 4 patients with replantation failure. This method not only maximizes the preserved thumb length but also shortens the treatment time. Groin flap transfer is simple and can be performed by most hand or orthopedic surgeons. However, in recent years, the groin flap has become unpopular because of its bulky appearance and discomfort due to hand-to-groin fixation lasting for several weeks.
We have found that the bulkiness of this flap is very useful for thumb lengthening because the soft tissue within the flap provides a reserve for lengthening. Without residual soft tissue coverage, the distal phalanx could potentially be exposed through the skin during lengthening. Local flaps, reversed neurovascular island flaps, or pedicled flaps from neighboring fingers are more aesthetic; however, they are not suitable for finger lengthening because the thin flap skin may be easily disrupted by the lengthened phalanx.
Free perforator flaps for finger coverage require microsurgical expertise.
In summary, thumb metacarpal lengthening with a mini-ring Ilizarov fixation device is a simple method for thumb reconstruction, especially when there is no available expertise for toe-to-hand reconstruction. In cases of thumb bone exposure or replantation failure, groin flap transfer can be performed simultaneously to preserve the residual thumb length.
Acknowledgments
This study was funded by the Yunnan Clinical Center Program of Traumatic Orthopaedic (grant no. ZX20191001), Key Laboratory of Digital Orthopedics of Yunnan Province (grant no. 202005AG070004), Lv-Weijia Expert Workstation of Yunnan Province (grant no. 202005AF150038), Digital Orthopedics Innovation Team of Yunnan Province (grant no. 202105AE160015), and Orthopedics and Sports Rehabilitation Clinical Medical Research Center of Yunnan Province (grant no. 202102AA310068).
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Reconstruction of combined thumb amputation at the metacarpal base level and index amputation at the metacarpal level with pollicization and bilateral double toe composite transfer.
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