THE OUTCOMES OF FIRST METATARSAL BONE OSTEOTOMY WITH USE OF BIODEGRADABLE IMPLANTS
Central State Medical Academy,
Nasonova Scientific Research Institute of Rheumatology,
Moscow, Russia
Hallux valgus is the most common statnamic deformation of the foot among adult population [1]. The pathology is characterized with lateral deviation of the great toe and medial displacement of the first instep bone. The disease etiology is unclear, but the great role is given to wearing of tight shoes, high-heel shoes, disbalance of the muscles abducting and adducting the toe, and associated deformations of the foot (pes planus, metatarsus primus varus, syndrome of joint hypermobility) [2].
The indications for surgical treatment are pain and progressing deformation of the first metatarsophalangeal joint and difficulties in wearing common shoes [1, 2].
The literature describes more than 400 surgical techniques for correcting hallux valgus which are oriented to elimination of various components of deformation, but the gold standard is absent. The most common technique for correction of valgus deformation of the great toe is diaphyseal and metaphyseal osteotomy of the first metatarsal bone [1].
Chevron osteotomy is metaphyseal osteotomy performed by Austin in 1962 and hereafter described by Austin and Leventen. It is used for correction of valgus deformation of mild and middle degrees. 60° V-shaped osteotomy of the head of the first metatarsal bone is performed in horizontal plane. The distal fragment is displaced laterally up to reaching a half of the width of the metatarsal bone [3].
SCARF osteotomy is the most common diaphyseal osteotomy of the first metatarsal bone. The term SCARF presents English translation of the phrase “le trait de Jupiter” (French, Jupiter’s arrow). SCARF osteotomy is Z-shaped osteotomy of the first metatarsal bone [11]. The technique was firstly described by M. Meyer (1926). But it became popular much later, after implementation of the principles of AO osteosynthesis [5, 13]. L.S. Barouk [5] and L.S. Weil [13] made the greatest contribution to development and improvement of such technique.
Because of high incidence in the population, the pathology bears both medical and economic meaning. The high incidence of the pathology has resulted in searching of ways for improving results of surgical treatment, reducing time of hospital stay and decreasing costs for treatment. The surgical techniques and the postosteotomy methods of fixation of the first metatarsal bone have been improving.
The ideal fixator for osteotomy should provide adequate stability of bone fragments, hold sufficient hardness up to achievement of bone union, and be absorbed after union, with prevention of need for recurrent surgery for removal of a fixator. The animal researches of biodegradable implants were initiated in the mid-60s of 20th century. Kulkarni et al. (1966, polyglycolic acid (PGA) implants) and Cutright et al. (1974, polylactic acid (PLA) implants) noted satisfactory union of fractures and absence of surrounding tissue response to the implant. Use of biodegradable implants for human was firstly described in 1984. They were used for fixation of ankle fractures that resulted in the age of the new “perfect” fixators [12]. Further multiple studies showed efficiency of fixation of the first metatarsal bone with use of biodegradable implants [7, 9, 10]. PGA and PLA were mainly used for production of synthetic biodegradable fixators. Some problems were found as result of usage of pure polyglycolide (PGA): too rapid degradation of the polymer, which caused such complications as aseptic synovitis, formation of granuloma and osteolysis [4-10]. Improving production of polylactide (PLA) implants resulted in weakening events of osteolysis, but significant amount of responses to a foreign body appeared because of long term degradation of polylactic acid (up to 5 years) [4, 10, 12].
The recent implants, which are made of combined polyglycolic and polylactic acids (PLGA), provide the same tight fixation as implants made of pure PLLA, but with more rapid degradation. The controlled period of degradation is 18 months. Some insignificant inflammatory responses are present [4, 6, 7, 10].
The main objective of the study was examination of the results of osteotomy of the first metatarsal bone with use of new biodegradable implants: correction of angle deformations, complications, recurrence, time of union, functional outcomes (AO FAS), quality of life in long term and short term periods after surgical treatment.
MATERIALS AND METHODS
The study included 42 patients (56 feet) with osteoarthrosis and hallux valgus who received treatment in the department of traumatology and orthopedics, Central Clinical Hospital with Polyclinic of Department for Presidential Affairs of the Russian Federation, and in the traumatology departments of City Clinical Hospital No.71, Moscow, from September 2011 to October 2014. The patients with the following inflammatory diseases of the joints were excluded: RA, psoriatic arthritis, ankylosing spondylitis, gouty arthritis.
At the stage of presurgical planning all patients received the clinical examination, lateral and frontal X-ray imaging of the feet under load, estimation of functional status of the foot (AOFAS) and quality of life (EQ-5D).
The clinical examination included collection of the data about complaints and anamnesis, estimation of the locomotor system (presence of concurrent longitudinal and transverse platypodia, deformation of the toes 2-5, foot deformation), identification of neurocirculatory pathology.
History taking included duration of the disease, patient’s ability to working activity, need for additional support, and an ability to wear fancy, common or orthopedic shoes. Pain intensity was estimated with VAS. It present a line of 0-100 mm, where 0 – absent pain, 100 – maximal pain.
The angle meter was used for measurement of the volume of active and passive motions and angle declinations in the examined foot. Also limited motions, presence of extension-flexion contracture in the first metatarsophalangeal articulation (the normal values are 70-90° for dorsal flexion and 30° for plantar flexion) and mobility in the phalangeal joint were noted. The accuracy of the values was ± 1º.
The values of M1P1, M1M2 and degrees of hallux valgus were estimated with the X-ray images. The values of the angles were very important for choice of osteotomy [5, 11].
SCARF osteotomy was made for M1P1 angle (hallux valgus angle) more than 25°, M1M2 within the range of 14-20° that corresponds to 3rd degree of hallux valgus. Chevron osteotomy was conducted for M1P1 = 11-24° and M1M2 < 15° (hallux valgus of degrees 1 and 2). If necessary, Akin osteotomy was additionally conducted for the proximal phalanx of the great toe (for 17 feet).
The study used the biodegradable implants LactoSorb (pins) which consist of 82 % of PLA polymers and 18 % of PGA polymers (Biomet Inc., Warsaw, IN). Each pin holds a cylindrical shape and transverse section of 2 mm diameter.
The complex estimation of the foot was realized with the scale from American Orthopaedic Foot and Ankle Society (AOFAS), which is a common tool for assessing outcomes of surgical treatment of the foot and the ankle. AOFAS (Hallux Metatarsophalangeal-Interphalangeal Scale) considers and estimates the clinical and functional parameters of the foot (the application 1). The questionnaire is divided into 3 sections: pain, foot functioning, adaptation to surface. The maximal 100 points are possible for patients without pain, with full range of motions in the joints of the first arm of the foot, without signs of instability of the joints, without limitations in daily and professional activity, without limitations in choice and wearing of shoes. The outcome of treatment is estimated with AOFAS as follows: excellent – 95-100 points, good – 75-94, satisfactory – 51-74, poor – 50 and lower [14].
Quality of life was estimated with the validated Russian version of the questionnaire EuroQol – 5D (EQ-5D). EQ-5D presents two-page form: a descriptive part of the questionnaire (EQ-5D-profile) and VAS-EQ-5D- thermometer. The first part (EQ-5D-profile) includes 5 sections relating to the following aspects of the patient’s life: mobility, self-care, daily activity, pain and discomfort, anxiety or depression. Each component is divided into 3 levels in dependence on a degree of intensity (1 – no problem, 2 – a minor problem, 3 – a significant problem). The combination of 5 components gives 243 variants of health state. EQ-5D-profile is presented in view of numerical expression for full health – 11111, for presence of evident disorders of health – 33333. The combination of the figures corresponds to a specified value of EQ-5D and is calculated with the special table. The index has meaning from -1 to 1; 1 means full health.
The second part of the questionnaire presents “the health thermometer”. It is a vertical line which graduated in millimeters, with 0, which designates the worst state, and 100 – the best state of health.
The 0.10 point difference in the values presents the minimal clinically significant change in EQ-5D before and after treatment.
The gradation of efficiency of treatment according to the index EQ-5D: ∆ EQ-5D < 0.10 – no improvement in life quality; 0.24 ≤ ∆ EQ-5D < 0.31 – moderate improvement; ∆ EQ-5D ≥ 0.31– moderate improvement of life quality [15].
The control examination, control X-ray imaging and the questionnaire survey were conducted 12 weeks after surgery and in the long term period.
SURGICAL TECHNIQUE
Osteotomy of the first metatarsal bone (SCARF and chevron) was conducted with spinal anesthesia, with back-lying position and use of the pneumatic cuff for the middle one-third of the leg.
A lineal skin incision (8 cm) was made along the medial surface of the foot in the plane of the distal one-third of the first metatarsal bone and the first metatarsophalangeal articulation. The soft tissues were dissected layer-by-layer. Lateral release was made through the dorsomedial approach. Capsulotomy was made by means of a lineal incision along the medial surface of the first metatarsophalangeal articulation. Osteochondroma of the head of the first metatarsal bone was removed. Hereafter, chevron and SCARF osteotomy of the first metatarsal bone was performed.
Chevron osteotomy. The oscillometric saw was used for V-shaped osteotomy of the epiphysis of the head of the first metatarsal bone. The distal fragment was displaced laterally, to 1/3 of the width of the metatarsal bone (4-6 mm) (Fig. 1).
Figure 1 Figure 2
The scheme of chevron osteotomy of the The scheme of SCARF-osteotomy
first metatarsal bone. The prick line shows
the direction of introduction of absorbable pins
A pin (the diameter of 2 mm) was used for creation of 2 holes in the bonesaw-lines. A special pusher (as a part of the kit) was used with the absorbable implants for fixation of osteotomy of the first metatarsal bone. The length of the pins LactoSorb was controlled from the plantar side. In case of displacement of the pins beyond the plantar cortical layer, the protruding part of the pin was removed by means of the special heater.
SCARF osteotomy. Osteotomy of the first metatarsal bone was initiated from longitudinal sawing of the diaphysis. Transverse sawing was made on the angle of 80° to the axis of the second arm of the foot in proximal direction. After completion of osteotomy the plantar segment was displaced in lateral direction. The fragments were fixed in the corrected position with 2 biodegradable pins LactoSorb. The length of the pins was controlled for prevention of screw penetration into the metatarso-sesamoid joint. The volume of motions in the metatarsophalangeal articulation was tested before wound suturing (Fig. 2).
Early postsurgical load (2nd day after surgery) with wearing of the special shoes Barouk (for 8 weeks) without weight bearing to the anterior part of the foot was allowed. The middle period of hospital stay was 7 days (4-10 days). Full weight bearing was permitted after 8 weeks according to the results of X-ray examination.
STATISTICAL ANALYSIS
Statistica 7.0 and Student’s test were used for estimation of the presurgical values of volume of motions, M1P1, M1M2, AOFAS, EQ-5D and the time trends of the above-mentioned values. P ≤ 0.05 was statistically significant value.
RESULTS
The study group included 42 patients (56 feet), with 90.5 % of the women (38 women and 4 men), the mean age – 47.3 (25-70). The mean duration of the disease was 7.4 ± 3.1. Hallux valgus of degree 1 was found in 10.7 %, degree 2 – in 75.2 %, degree 3 – in 41.1 %. 83.3 % of the cases included the comorbidity in view of flatfoot, hammer-shaped deformation of the toes 2-5 and longitudinal platypodia. Transverse platypodia was found in all patients of the study group. 30.3 % of the cases included deformation of the phalangeal joint of the great finger.
The mean time of the follow-up was 16.3 months (6-39 months). 3 months after surgery we could observe union of the first metatarsal bone with gradual decrease of osteotomy line without signs of disordered correction in all cases.
The control examination showed the evident decrease in the metatarsal angle (M1P1) from 20.8° ± 4.7° before surgery from 7.2° ± 5.3° (p ≤ 0.001); the decreasing value of the metatarsal angle (M1M2) from 14.9° ± 3.4° before surgery to 8.8° ± 3.8 (p ≤ 0.001). There were no statistically significant changes in dorsal flexion (64.4° ± 10.4°) after surgery – 59.4° ± 15.4° (p = 0.157). One could observe the insignificant decrease in plantar flexion from 21.7° ± 5.9° to 18.3° ± 5.9° (p = 0.038), but the result was not clinically significant.
The evident increase in AOFAS values was found: from 49.6 ± 15.1 to 89.4 ± 14.9 (p ≤ 0.001).
According to VAS, the level of pain increased from 72.3 ± 14.2 mm to 25.8 ± 8.7 mm (Fig. 3).
Figure 3
The time trends of functional and radiologic values after surgical treatment
According to EQ-5D, the low quality of life was noted in all patients (0.46 ± 0.28). EQ-5D was 0.81 ± 0.11 in the control examination. It corresponded to evident improvement in quality of life. The mean presurgical value of health thermometer was 53.88 ± 10.98, in the control examination – 87.4 ± 14.94.
COMPLICATIONS
After 3 months the follow-up showed some radiologic focal signs of osteolysis. However it did not influence on the clinical outcomes and union of the first metatarsal bone. The subsequent X-ray images showed that the square of the foci of osteolysis had not increased.
11 cases were associated with a hyperergic response (fever with body temperature up to 38.2°C) during 3-4 days after surgical treatment.
DISCUSSION
After appearance of chevron and SCARF osteotomy for surgical correction of hallux valgus many techniques for postsurgical fixation of the first metatarsal bone have appeared. Fixation was realized with pins, metal plates and screws, and during the recent years – with absorbable pins.
Use of biodegradable implants for fixation of the first metatarsal bone has such advantages as minimal risk of bacterial colonization (a common complication after pin fixation), prevention of hypersensitivity to metal (metallosis). Besides, their use does not require recurrent surgery for removal of a fixator that reduces economic costs, despite of high initial cost of the implant. Biodegradable implants are characterized with the rigidity modulus which is similar with a cortical bone. As result, they do not cause stress-shielding syndrome (osteolysis, resorption) around the fixator and provide some favorable conditions for union with gradual absorption. However some studies showed such complications as osteolysis, formation of sterile sinus, granuloma, a response to a foreign body, a mechanical injury to the implant. The rate of complications after use of polyglycolide is significantly higher (55 %) in comparison with polylactide (3 %). Copolymers are developed for combining the advantages of various absorbable materials. The advantages include high stability, appropriate rate of absorption and low allergenicity.
The control examination showed the decrease in M1P1 angle by 13.6° and M1M2 by 6.1°. It corresponds to other similar studies: 14.8° and 6.1° in the study by Caminear D.S., 13° and 5.3° in the study by Grill et al correspondingly. Barca et Busa described the decrease in M1P1 by 14°, M1M2 by 5°. Deorio conducted the study of 41 feet and found the changes of 9.5° and 4.3° correspondingly [4, 6, 7].
According to AOFAS (Δ AOFAS 49.8) the improvement in the functional status of the foot was similar with other studies (Δ AÎFAS = 42.8 in Caminear and Δ AÎFAS = 44 in Morandi et al.) [6, 10].
In comparison with other studies we could observe the significantly lower rate of complications. The similar studies showed formation of granuloma, recurrent hallux valgus within the short term period as result of early full weight bearing, infection in the place of surgery, a false joint in osteotomy region, aseptic necrosis of caput ossis metatarsalis and osteomyelitis [4, 6, 7, 8, 12].
CONCLUSION
1. The results of the study show that biodegradable implants (LactoSorb pins) are the appropriate fixators during chevron and SCARF osteotomy for the first metatarsal bone with hallux valgus of degrees 1-3.
2. LactoSorb pins show such advantages as stability of fixation while the first metatarsal bone unions, biocompatibility (absorbable synthetic polymer), low percentage of complications, low level of bacterial colonization, absence of need for removal of the fixator.
3. Osteotomy of the first metatarsal bone with LactoSorb pins allows normalizing the axial relationships of the first arm of the foot, improving foot functioning (AOFAS index) and quality of life (EQ-5D index) in patients with hallux valgus within short term and long term periods after surgical treatment.