Minimally Invasive Distal Metatarsal Osteotomy for Mild-to-Moderate Hallux Valgus

Hallux valgus occurs almost exclusively in shoe – wearing societies. Coughlin and Thompson (2) noting the extremely high prevalence of bunions in American women in the fourth, fifth or sixth decade of life, implicated constricting footwear as a cause of hallux valgus. Likewise, in Japan, Kato and Watanabe (3) noted that the prevalence of hallux valgus in women increased dramatically following the introduction of high – fashion footwear after World War II.


Contraindications
Specific contraindications of the SERI technique are patients older than 75 years, severe deformity with the intermetatarsal angle larger than 20°, severe degenerative arthritis or stiffness of the metatarsophalangeal joint, and severe instability of the cuneometatarsal or metatarsophalangeal joint. The technique is not indicated in hallux rigidus and in patients in whom a Keller's procedure unsuccessful . (35,36)

Preoperative assessment
The preoperative plan includes acquiring a complete history of the patient plus physical and radiographic examination. The patient's complaints of pain, limitation in the use of footwear, and cosmetic concerns should be considered. Moreover, the severity of the prominent medial eminence and the hallux valgus deformity, as well as the great toe mobility at the metatarso -phalangeal joint and the reducibility of the deformity should be evaluated. The latter is tested by pushing laterally the metatarsal head with one hand, and simultaneously the great toe medially with the other hand. Stability of the metatarsophalangeal and metatarso -cuneiform joints must be assessed. Combined rotational deformity of the great toe or callosities under the first or second and third metatarsal heads must be considered, as well as any associated deformities of the lesser toes. A standard radiographic examination, including anteroposterior and lateral weight-bearing views of the forefoot, allows the assessment of the arthritis and congruency of the joint; measurement of the hallux valgus angle and intermetatarsal angle. The hallux valgus angle was measured by the method of Piggot. (37) The intermetatarsal angle by the method of Coughlin et al . (38)

Surgical technique
This technique was described by the author in the study that was published in Acta Orthopaedica Belgica, Vol. 76 -4 -2010. The patient is placed in the supine position, with a below knee wedge bracket allowing 90° of knee flexion and a plantigrade position of the foot on the operating table. Pneumatic tourniquet was applied in all cases. The operation is performed with either general or ankle -block anesthesia. The fluoroscopic image intensifier must be positioned to the side of the patient while the surgeon stands in front of the patient at the end of the table. Normally with this technique, soft -tissue release is not needed because attenuation is achieved with the lateral offset of the metatarsal head itself. If a slight stiffness of the metatarsophalangeal joint is present, manual stretching of the adductor hallucis is performed, forcing the big toe into a varus position.
Step 1. Wire insertion. Under image intensifier a 2.0 mm K -wire is inserted starting from the proximal medial corner of the nail of the great toe. (fig. 3-A) The pin is manually driven along the medial border of the proximal phalanx in a distal -toproximal direction to end distal to the site of the planed osteotomy. It is mandatory to place the wire in an extraperiosteal position in order to allow lateral displacement of the capital fragment at the osteotomy site. ( fig. 3-B) The wire must be midway between the dorsal and plantar aspect of the great toe in order to engage the metatarsal head correctly. This represents one of the most important biomechanical aspects of the technique. If the metatarsal head should be shifted plantarward, the pin has to be inserted more dorsally. If the metatarsal head should be shifted dorsally, the K -wire has to be inserted more plantarward. Plantar translation is done more often. Step 2. Skin incision. A 1.5 cm skin incision was made and centered over the medial aspect of the first metatarsal neck. ( fig. 3-C) The incision was carried directly to the bone, cutting the periosteum, with care being taken to remain in the midline equally between the dorsal and plantar aspects of the metatarsal neck in order to avoid the neurovascular bundle.
www.intechopen.com Step 3. Periosteal detachment. Next, the periosteum around the osteotomy site is detached dorsally and then plantarly, with use of small scissors inserted through the skin incision. ( fig. 3-D) In this way, the soft tissues surrounding the metatarsal shaft can be kept away from the bone cutter (saw).    Step 7. Closure. The skin is sutured with two 2 -0 prolene stitches. The distal extremity of the K -wire is curved and cut out of the tip of the toe.

Follow-up
Postoperatively, Patients can walk immediately in a flat, rigid sole postoperative shoe, which allows not to put weight through the osteotomy, though in the beginning they are advised to walk for short times only, and to rest with the foot raised while supine or sitting.
The stitches were removed two weeks after surgery, while the K -wire was removed 6 weeks postoperatively.
Patients were allowed to bear weight with normal shoes, and range of motion exercises of the first metatarsophalangeal joint was carried out from then on.
The postoperative examinations included X -ray next day postoperative and then six weeks after the operation. The patient is then reviewed between two and three months later for the third radiological and clinical control. The future follow -up frequency is variable, and usually every 6 months.
Clinically the patients on each follow -up were questioned about the cosmetic appearance of the foot, pain over the metatarsal head and shoe -wear problems. Thorough clinical examination was done looking for appearance, calluses under second and third metatarsal heads (transfer lesions), sensory abnormalities, and the range of motion of first MTP joint.
Furthermore, the clinical rating system for foot and ankle function, established by Kitaoka et al (40) [American Orthopaedic Foot and Ankle Society (AOFAS) Hallux -Metatarsophalangeal -Interphalangeal Score] was used as a quantification of the clinical and subjective evaluation at follow -up. Additionally the patients have been asked whether they were satisfied with the result of the operation or not. During the examination, special attention was paid to the aspect of metatarsalgia. The assessment of the passive range of motion (ROM) of the first metatarsophalangeal joint was performed according to Okuda et al. (41) The preoperative and the follow -up radiographs were made with the patient in the weight -bearing position.
Quantitative data were described by mean ± standard deviation (SD) or if more appropriate by median and range. Statistical analyses were performed using SPSS software V. 16.0 (SPSS Inc., Chicago, IL, USA).

Results of our study
Twenty -six patients with symptomatic mild -to -moderate hallux valgus deformities were operated using minimally invasive distal metatarsal osteotomy. Two patients were lost to follow -up and could not complete the minimum follow -up period of 12 months. The study describes the results of 36 feet in 24 patients comprising 20 female and 4 male patients. Twelve patients had a bilateral involvement. The age of the patients ranged from 17 to 52 years, the mean age being 37.8 years. The average follow -up period was 21 months (range 12 -36 months).

Clinical results
Hallux -Metatarsophalangeal -Interphalangeal Scale proposed by the American Orthopaedic Foot and Ankle Society (AOFAS) was used for the clinical assessment. This

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The Role of Osteotomy in the Correction of Congenital and Acquired Disorders of the Skeleton 270 system provides a score ranging from 0 to 100 points, which takes into consideration both subjective and objective elements such as pain (maximum score, 40 points), functional capacity (maximum score, 45 points), and hallux alignment (maximum score, 15 points). For all patients were seen at the time of final follow -up, there was no case of worsening of pain and no patient who presented with shoe -wear restriction as primary symptom had such pain after surgery. Eighteen patients (thirty feet; 83.3 %) reported total disappearance of the pain, four patients (four feet; 11.1 %) had only mild occasional pain, two patients (two feet; 5.6 %) had daily moderate pain, and no patient had severe or constant pain. The mean overall pain score was 37.3 ± 4.7 points of the 40 point maximum on the AOFAS.
The functional capacity of the hallux, which was graded by summing the scores for the six different aspects of functional performance on the hallux -metatarsophalangealinterphalangeal scale, averaged 40.9 ± 3.6 points (maximum score on the scale, 45 points). The maximum score for hallux alignment (15 points, indicating excellent or good alignment) on the hallux -metatarsophalangeal -interphalangeal scale was recorded for thirty feet (83.3%) in 20 patients; mild, asymptomatic malalignment (a score of 8 points) was recorded for six feet (16.7%) in four patients; and symptomatic malalignment (a score of 0 points) was not recorded in our study. The overall mean score for hallux alignment was 12.9 ± 4.2 points.
The total scores at the time of final follow -up according to the system of the American Orthopaedic Foot and Ankle society was 91.2 ± 6.8 points. Motion of the first metatarsophalangeal joint was limited to < 30° in three feet (8.3%). Patients were satisfied with the results of 31 (86%) of the 36 procedures and dissatisfied with the results of five (14%). Satisfaction was evaluated as the patient's willingness to undergo surgery again or not.

Radiographic results
According to radiographic results of the 36 consecutive MIDMOs the mean HVA decreased from 27.7° preoperatively to 14.6° at the final follow -up (p < 0.001). The first IMA decreased from an average of 11.2° preoperatively to 5.8° at the final follow -up (p < 0.001).
Plantar displacement of the first metatarsal head (mainly a plantar translation, with some degree of plantar angulation) was found at the time of follow -up in 17 (47.3%) of the 36 feet, dorsiflexion of the head (mainly angular deformity) was seen in three feet (8.3%), and a position that can be defined as neutral (essentially similar to the preoperative position) was observed in sixteen feet (44.4%). The extent of lateral displacement of the first metatarsal head was 56.2% ± 18.4% of the diameter of the first metatarsal shaft in the immediate postoperative period and 36.1% ± 15.9% at the time of follow -up. The relative shortening of the first metatarsal was measured in 11 feet (30.6%). In the remaining 25 feet the shortening was not measured. The mean first metatarsal shortening was 2.2 ± 2.8 mm (range: -8 to 3.4 mm). All of the osteotomies healed well, with callus evidence after an average of 3 months. All of the metatarsal bones remodeled themselves over time ( fig. 4) even in cases with marked offset at the osteotomy (several millimeters of bony contact). In our experience, the healing of the osteotomy and remodeling capability of the metatarsal bone are not related to the offset at the osteotomy, but it is preferable to obtain a bony contact not less than one third of the metatarsal section.

Complications
No intraoperative complications occurred in our study except in one foot some comminution occurred at the osteotomy site but did not affect either the stability of fixation or the union of the osteotomy. After dressing removal, in 3 feet a mild skin inflammatory reaction was present around the outlet of the K -wire at the tip of the toe. There was no need to remove the K -wire before the scheduled time. There were no episodes of nonunion, malunion, transfer metatarsalgia or avascular necrosis of the metatarsal head. No cases of secondary hallux varus were observed despite the slight overcorrection that had been consistently achieved at the time of stabilization of the osteotomy site. No patient underwent a deep venous thrombosis.

Discussion
The goal of operative treatment is to offer relief of pain, correction of forefoot deformity and a biomechanically functional foot. For a long time, bunion surgery had a reputation for being very painful with a lengthy recovery period. Indeed, many people put up with their bunions for years rather than face surgery. This was because older techniques involved cutting the bone and not using any form of fixation. Newer techniques introduced during the past decade enabled surgeons to fix the bones into the correct position, reducing pain and promoting a better and more controlled recovery.
However, we are constantly exploring ways of moving from open surgery to minimally invasive techniques, replacing large incisions with small 'ports' through which the surgeon works. In doing so, we offer important benefits for the patient, removing or damaging less tissue, reducing scarring and the subsequent risk of infection.
Minimally invasive distal first metatarsal osteotomy with a percutaneous technique was first described by Bösch et al in 1990 , and a satisfactory result was reported in a 7 -10 year follow -up study. (30) Portaluri (42) achieved 89% satisfaction rate with the Bösch method and stated that the advantages of this technique included short operation time and low incidence of complications. Sanna and Ruiu (43) reported excellent results in a long -term follow -up study of percutaneous distal first metatarsal osteotomies. Magnan et al (44) reported that the patients were satisfied following 107 (91%) of 118 percutaneous distal first metatarsal osteotomies.
Numerous studies have revealed that minimally invasive hallux valgus surgery can achieve a good satisfaction rate similar to other open techniques. (45,46) The distal metatarsal osteotomy in our study was a minimally invasive, simple bony procedure without other advanced soft tissue procedures. We did not perform bunion resection, formal capsulorrhaphy, lateral release or capsulotomy.
Our study involved twenty -four adult patients (36 feet) in the age range of 17-52 years with mild -to -moderate hallux valgus managed with the minimally invasive distal metatarsal osteotomy (MIDMO). The mean overall pain score was 37. The results of other series using minimally invasive techniques also reported comparable results to that of our study as the mean overall pain score reported by Magnan et al (44) was ( 36.3 ± 6.2 points) and that reported by Yu-Chuan Lin et al (49) was (35.7 ± 5 points ).
In our study, the mean HVA and first IMA corrections were 13.1° and 5.4° respectively compared with 17.8° and 5.1° in Magnan et al's study and 11.8° and 6.3° in the study by Yu-Chuan Lin et al.
Our results indicate that this minimally invasive technique can achieve angular correction that is as good as that achieved using traditional techniques. It has been demonstrated that the mean HVA correction ranged from 8.8° to 26°, and the mean first IMA correction ranged from 3.8° to 11° in studies that used open techniques. (6,50,51) A limitation of this minimally invasive approach is that we were unable to control the magnitude of lateral translation. This method simply relied on the stiffness of the K -wire and the size of the capital fragment to achieve lateral translation. We believe that the magnitude of angular correction might limit the use of our approach to treat more severe hallux valgus deformities. This explains why the inclusive criterion in our study was set at first intermetatarsal angle ≤ 18°. The lack of soft tissue surgery does not appear to affect the prevalence of recurrent hallux valgus deformity, perhaps because reorientation of the metatarsal head and reduction of the head on the sesamoids were the consistently achieved primary surgical objectives. In other studies that used open techniques in association with soft tissue procedures, the recurrence rate ranged from 0% to 10%. (17,51,52,53) Although some of our cases had an increase in HVA after K -wire removal, the HVA and first IMA were significantly decreased at final follow -up. The Kirschner wire insertion level in the study of Yu-Chuan Lin et al was at the middle of the proximal phalanx. In our study and that of Magnan et al, the more distal percutaneous insertion level of the K -wire, might achieve a greater correction of the hallux valgus angle because of a longer level arm to abduct the big toe.
The mean extent of lateral displacement of the first metatarsal head in our study was 56.2% of the diameter of the first metatarsal shaft in the immediate postoperative period and 36.1% www.intechopen.com However, these patients did not regard the joint motion deficit as disabling, and the rigidity did not cause pain during walking.
We did not have any case of postoperative avascular necrosis of first metatarsal head. This is probably due to the preservation of soft tissues on the lateral side of the metatarsal. These structures on the lateral side are important for the blood supply of the distal fragment. In our study, there were no episodes of nonunion, malunion or deep infection.

Conclusions
The results of our study demonstrate that MIDMO with a percutaneous K -wire stabilization under fluoroscopic control, without removal of the eminence and without open lateral release, performing only a manipulation of the great toe is an effective, reliable method of treating mild -to -moderate hallux valgus deformity in adult patients. The results appear to be comparable with those reported following traditional open techniques. Good satisfaction, functional improvement, and low complication rates were achieved with this technique. Nevertheless, we think that this technique requires a long learning curve and should be learned through both theoretical and practical courses. A well -designed prospective randomized controlled study with long -term results of a large study population is needed to support general use of this minimally invasive technique.