1.Etiology and symptoms
Metatarsal shortening can involve any metatarsal bone and can occur unilaterally or bilaterally, with bilateral onset accounting for about 72% of patients, and there is a clear tendency for women to be susceptible, with a male to female ratio of 1:25. It can also occur in patients with multiple exophytic bone defects. The growth is characterized by premature closure of the metatarsal plate, often spontaneous, and may be associated with Down syndrome, Turner syndrome, Larsen syndrome, Albright syndrome, dwarfism, and pseudohypoparathyroidism. The disease can also be secondary to trauma, neurotrophic dysfunction, poliomyelitis, and surgical injury during growth and development. The metatarsal bones of the normal foot vary in length, and the line connecting the apexes of the five metatarsal heads is rounded and parabolic. Statistics show that the first and second metatarsals are of equal length, while the third, fourth and fifth metatarsals are shortened in turn. Some studies have also shown that the length of the first metatarsal is 86% of the length of the second metatarsal. However, when the length of the first metatarsal is less than 75% of the length of the second metatarsal, the weight-bearing of the second and third metatarsals increases, resulting in the formation of a plantar callus, along with musculoskeletal pain and a consequent change in the weight-bearing mechanism of the foot. The appearance of metatarsal hypoplasticity is characterized by short toes, but the essence of the disease is metatarsal shortening, which can affect any metatarsal bone, with the fourth metatarsal being the most commonly affected, followed by the first metatarsal. In multiple metatarsal shortening, the first and fourth metatarsal bones are often involved at the same time. As a result of metatarsal shortening, the parabolic shape of the normal metatarsal head line is interrupted, resulting in corresponding dysfunction.
Metatarsal deformities are uncommon at birth and often occur after the age of 4 years with metatarsal growth or delay, followed by various symptoms with age, including deformity in appearance, metatarsalgia when walking, plantar callus, upturning of the short toe which affects shoe wear, arch collapse, bunion, soft tissue contracture, etc.; the normal toe will deviate from its original position to fill the gap created by the short adjacent metatarsal, causing the toe located on the inside of the short toe to become The normal toe will deviate from its original position to fill the gap caused by the short adjacent metatarsal bone, so that the toe located on the inner side of the short toe will have a valgus deformity and the toe located on the outer side of the short toe will have an inversion deformity.
2.Surgical treatment
The only treatment for metatarsal shortening is surgery, and massage and traction are not effective during the developmental period. Many literature reports on the indications for surgical treatment of metatarsal shortening, which can be summarized as follows: ① young female patients, requiring aesthetic foot, easy to participate in social activities, etc. ② metatarsal pain, plantar callus can not be relieved, short toes are often located between the adjacent two toe webbing, and even affect the wearing of shoes; ③ a foot multiple metatarsal shortening, so that the metatarsal head line parabolic shape interrupted, soft tissue contracture, arch collapse, dysfunction with foot bunion, anatomical axis deviation, claw toe and other deformities, resulting in walking impairment. (5) With other foot dysfunctions, etc.
The goal of surgical treatment of metatarsal agenesis is to improve the appearance of the toes, relieve pain, and restore the parabolic shape of the metatarsal heads. The first type is immediate lengthening of the metatarsal bone, which is suitable for mild metatarsal shortening, i.e., the shortened metatarsal bone is cut off and lengthened at once to restore the anatomical length of the metatarsal bone, and the secondary bone defect is filled with autologous or allogeneic bone graft; the second type is the length equalization of adjacent metatarsal bones, which is suitable for multiple metatarsal shortening of the same foot, i.e., the adjacent relatively long metatarsal bone is cut off and the normal metatarsal bone is removed. The second type is the length equalization of adjacent metatarsal bones, which is applicable to multiple metatarsal shortening in the same foot, that is, to amputate a segment of the adjacent relatively long metatarsal bone and graft it onto the shortened metatarsal bone to readjust the length of the five metatarsal bones, so that the metatarsal head line can reach a parabolic shape again; the third type is the gradual lengthening of the metatarsal bone. The third type is gradual lengthening of the metatarsal bones, which is more commonly used in clinical practice, in which the proximal medullary end of the shortened metatarsal bone is truncated and slowly and rhythmically retracted to lengthen the metatarsal bone by retracting the bone at the broken end of the truncated bone.
Immediate bone lengthening
Baek reported that in 21 patients with short metatarsal bones, 41 short toes (including short metatarsals and phalanges) were lengthened instantly with autogenous bone graft; a longitudinal skin incision was made on the dorsum of the foot to expose the short metatarsals, which were truncated transversely in the center of the shaft, the distal metatarsals and phalanges were fixed with a kerf pin, and the bone spreader slowly supported the metatarsals on both sides of the osteotomy site. The bone spreader was used to slowly open the metatarsal bones on both sides of the osteotomy site, and the bone graft was taken and placed in the distal and proximal metatarsal gaps, and the metatarsal, distal phalanx, and proximal phalanx were firmly fixed again with a Kirschner pin; the Kirschner pin was removed 8.5 weeks after surgery, and full weight training was performed 12 weeks after surgery; the results showed that 41 short toes lengthened by an average of 13 mm (35% increase), of which 34 metatarsals lengthened by an average of 14 mm (32% increase)}7 metatarsals lengthened by an average of 8 mm (54% increase). Uiannini et al. reported that in 29 patients (age >12 years, excluding patients with first and fifth short toes), 41 short toes were instantly lengthened and filled with allograft bone. The results showed that the average lengthening of the 41 metatarsal bones was 13 mm (23% increase), and most of the patients returned to a normal parabolic shape at the vertex of the metatarsal heads. The parabolic shape was not fully restored in a few patients with too short metatarsals to avoid excessive soft tissue tension.
The main advantages of immediate metatarsal lengthening are better patient compliance, no need for external braces, no need to care for pinholes, no need to consider whether osteogenesis is allowed, short bone healing time, and small surgical fetish marks. The disadvantages are that the lengthening of the metatarsal bone is limited and difficult to achieve at one time, sometimes leaving a residual deformity; over-distraction at one time can rapidly increase the soft tissue tension and damage the neurovascular, or even endanger the blood supply of the affected toe, limiting the lengthening; sometimes it is necessary to perform a “z” shaping procedure to lengthen the muscle leg at the same time; the toe joint needs to be fixed during the healing process of the grafted bone, which often leads to joint stiffness and the risk of reoccurrence. This often leads to joint stiffness and risk of re-fracture; reabsorption of the bone graft can cause re-shortening, etc.
In immediate metatarsal lengthening, graft selection plays a key role. Graft bone not only stimulates the proliferation of recipient mesenchymal cells and produces new bone, but also provides scaffolding support for new bone formation. Autologous fresh bone graft can provide a source of osteoblastic cells and has the advantages of rapid bone formation, no need for special equipment storage, and no immune rejection in immediate metatarsal lengthening, but it also has the disadvantages of adding a new surgical site, prolonging the operation time, increasing bleeding, and making the donor area prone to complications such as pain, infection, local hematoma formation, and nerve injury. For patients with bilateral or multiple short toes, the use of autologous bone grafting will undoubtedly increase the risk of complications in the donor area due to the limited amount of donor bone, and will also leave large fetish scars in the donor area after surgery. Allogeneic bone grafting can adapt to the needs of the recipient area in terms of bone graft size, shape and amount, without sacrificing the recipient’s own normal structure and without causing complications in the donor area, but its disadvantage is that it has a certain immune rejection reaction and is prone to premature bone resorption, resulting in surgical failure.
Length equalization of adjacent metatarsal bones
Lee et al. reported that metatarsal length equalization was performed on 47 short toes in 37 patients with metatarsal shortening, resulting in a mean shortening of the second and third metatarsals by 8.9 mm and 7.2 mm and a mean lengthening of the fourth metatarsal by 10.3 mm~. The percentage changes in the length of the second, third, and fourth metatarsals were 12.3%, 12.5%, and 19.9%, respectively, and the mean range of motion was 55°, 51.1°, and 40.9°, respectively. The average healing index was 74 d/cm; the rounded umbilical service under the second and third metatarsal heads improved significantly and severe pain was relieved, but some patients showed stiffness in the fourth toe joint. The results showed that the average percentage of metatarsal lengthening was 28.3%, the average healing index was 63 d/cm, and there was only one incision, which reduced the number of focal scars and achieved better foot appearance; shortened the length of the adjacent relatively long normal metatarsal and made the lengthening length of the short metatarsal shorter than the lengthening length of the short metatarsal in other procedures, which not only restored the parabolic shape of the vertex of the metatarsal head, but also effectively reduced the risk of neurovascular complications; the bone healing time was short, the impact on the patient was minimal, and there was no need to remove the metal implant again.
However, joint stiffness is the most common complication of this procedure due to simultaneous shortening and lengthening of different metatarsals, and Lee et al. reported that stiffness in the toe joint corresponding to the shortened metatarsal was due to laxity of the joint and insufficient contraction of the leg, whereas stiffness in the toe joint corresponding to the lengthened metatarsal was due to soft tissue scar formation in the lengthened area and fixation of the joint with a kyphotic pin.
Progressive metatarsal lengthening
Progressive lengthening of the metatarsal bone, also known as bone demented lengthening, is the most commonly used procedure in clinical practice. Currently, the Ilizarov principle has been successfully applied to the foot bone lengthening. Studies have shown that progressive metatarsal lengthening is the ideal treatment for short metatarsals.
Compared with immediate lengthening of the toe bone, progressive lengthening of the toe bone does not require bone grafting and has no complications related to bone grafting; the lengthening length is longer, the bone growth rate is faster, and the lengthening can be terminated immediately after the appropriate length is obtained; the bone and soft tissue are lengthened simultaneously, so that the soft tissue tension is minimized and neurovascular complications are minimized; it is easier to stretch the muscle leg and there is no need to perform the “z-word The length of lengthening is more accurate without the need for “z-formation”, and the correction of deformity is more thorough. However, this procedure also has shortcomings, such as poor patient compliance; slightly longer treatment time, pinhole infection, and pigmentation of the skin around the pinhole.
The choice of fixed stent in gradual toe lengthening is crucial in order to effectively distract the short toe bone and obtain a good lengthening effect.
1.Pre-operative preparation
(1) Informed consent Before surgery, according to the patient’s hand defect, explain to the patient and his family the nature of the short metatarsal bone, the degree of functional impairment, and the improvement of appearance and function after lengthening, and obtain understanding and cooperation.
(2) Radiographic examination of the affected limb to confirm the shortened part and length.
(3) Pre-operative skin traction training of the residual finger end is required to make the skin of the residual end loose and soft, which is conducive to post-operative traction lengthening.
2.Surgical method
After successful anesthesia, the patient a supine. Under the monitoring of the image intensifier, the 4th metatarsocuneiform joint and its intermetatarsal joint with the adjacent one are determined with an injection needle, and the body projection of the 4th metatarsophalangeal joint is determined with another injection needle, at which time the contour of one metatarsal can be determined by the positioned needle. The Orthofix miniature unilateral brace and a 2. 0 mm diameter threaded half-pin were selected as the extension external fixator, which was placed flat over the fourth metatarsal, and the threaded half-pin nail was directly clamped with an electric drill, passed through the nail clamp hole in the brace as a guide, and slowly tapped into the diaphysis after piercing the skin perpendicular to the dorsal aspect of the metatarsal. The two threaded half-pins at the most proximal and distal ends of the stent are tapped first to determine the position of the stent, and then the remaining two nails are tapped. The stent is firmly locked to the threaded half-pin, and the stent is kept at a distance of about 5 mm from the dorsal skin of the foot. on the dorsal side of the foot, the dorsal part of the 4th metatarsal is cut open to reveal the metatarsal bone, and the metatarsal bone is cut off with a small bone knife between the tips of the middle 2 nails. during the osteotomy, attention is paid to the direction of the bone knife as parallel to the threaded half-pin as possible. In order to prevent the metatarsal from splitting during the osteotomy, multiple holes should be pre-drilled in the osteotomy with 1.5 mm steel pins. Finally, an image intensifier is used to confirm that the external fixator half-pin is tapped into the proper position and to ensure the osteotomy result. To prevent dislocation of the metatarsophalangeal joint in the postoperative extension, a 1.2 mm kerf pin was used to retrograde through the interphalangeal and metatarsophalangeal joints.
3. Postoperative treatment
Postoperative antibiotics were routinely applied for 1 d. Postoperative lengthening was started on the 7th day, 0.15 mm each time, 4 times a day. When the lengthening is in place, the kerf pins fixing the metatarsophalangeal joint are removed at the same time. Radiographs were taken every 2 weeks, and the external fixation brace was removed when the lengthened bone was completely calcified. Care was taken to keep the dorsalis pedis nail eye dry during lengthening, and daily spotting of alcohol was not required.
Walking on the heel is allowed 2 weeks after surgery as long as the pain is tolerated. When the lengthening is in place and all screws on the brace are torqued, full weight-bearing walking is possible, and the distance walked should not be less than 2 h. When the kyphotic pins holding the metatarsophalangeal joint in place are removed, the metatarsophalangeal and interphalangeal joints are massaged and passively moved by hand daily to increase joint mobility and prevent stiffness. The metatarsal lengthening was able to maintain overall forward translation without sinking and upward movement.
4. Treatment of combined metatarsal shortening
It is not uncommon for the 4th metatarsal shortening to be combined with other metatarsal shortening, the most common being the 1st metatarsal. The technical requirements for the lengthening of the 2nd and 3rd metatarsals are the same as those for the 4th metatarsal lengthening, but the lengthening of the 1st and 5th metatarsals requires a higher level of technique, and the lengthened metatarsals must strive to restore the three-point weight-bearing requirements of the metatarsal heads. The 5 metatarsal heads of the normal foot form a smooth parabola, and the 1st metatarsal lengthening cannot exceed the edge of the parabola; if it is too long, a secondary bunion deformity will occur.
5.Prevention of complications
(1) Needle eye infection
Needle eye infection is not common, and preventive measures include: keeping the nail clip at a distance of 5 mm from the dorsal skin of the foot, keeping the local area dry, not soaking in water, not spotting alcohol in the needle eye too often, and absolutely prohibiting the application of various topical Chinese medicines to prevent the abuse of drug allergy. Once it happens, it is necessary to lift up the brace to increase the distance between it and the skin, and wrap the threaded half-needle hole with alcohol fine gauze. If the steel needle fixing the metatarsophalangeal joint is infected, it can be pulled out as early as possible.
(2) Lengthening too long or too short
Extending the metatarsal bone too short affects the appearance recovery, too long will break the integrity of the metatarsal arch, and the metatarsal head will form walking pain when landing on the ground. The key is to master the length of the extension, a reasonable metatarsal length should be the fourth metatarsal head is located in the arc parabola formed by the five metatarsal heads, a simple criterion is to be flush with the line of the 3rd and 5th metatarsal head apex. If it is too short but the bone is already hardened, generally do not deal with it, it only affects the appearance. If the length is too long, we can only wait for the bone to harden and then amputate a section of the metatarsal bone to restore its normal length. Of course, if the length is found to be inappropriate within 3 d after the lengthening has stopped, it can be readjusted, and the bone can still be recompressed or lengthened within a period of time.
(3) Stiffness of the metatarsophalangeal joint
This phenomenon is more common when the bone is lengthened, the flexor and extensor muscles do not do z-shaped lengthening, the shrunken muscles spring back to pull, so that the metatarsophalangeal joint compression, joint gap narrowing. In addition, the steel pins that are fixed to prevent dislocation can also lead to reduced mobility of the metatarsophalangeal and interphalangeal joints. Prevention and treatment measures include: when the lengthening length is satisfactory, remove the fixed kyphotic pins as early as possible and encourage early ground movement; after the lengthening brace is removed, use physiotherapy, massage and hydrotherapy and other comprehensive means of rehabilitation, joint function can be restored at any time with a lengthening.
(4) Metatarsophalangeal joint subluxation
It is common in patients with large lengthening ratio and obvious shortening, or the metatarsophalangeal joint is not fixed with steel pins during lengthening, and the muscle key pulling leads to joint subluxation. In the present group of cases, the metatarsophalangeal joint was fixed by using kerf pins throughout, and in those with a relatively large proportion of lengthening, the time of removing the steel pins was delayed, which effectively prevented the occurrence of dislocation.