Background: The Cotton procedure, also known as medial cuneiform dorsal sparing osteotomy implant, is highly competent in correcting persistent or stiff forefoot pronation due to flatfoot. Its primary role is to bring the medial column into plantarflexion and correct the residual pronation deformity of the forefoot after correction of the hindfoot in patients with flatfoot syndrome. In addition, it has a degree of restoration of the medial longitudinal arch. It also increases the actual length of the medial column, which, combined with its plantarflexion function, has a stabilizing effect on the first metatarsal cuneiform joint from a biomechanical point of view. Currently, this procedure is also used to treat tarsal coalition disease, overcorrection of high arched feet, first metatarsal elevation deformity, forefoot rotation posterior deformity, and bunion stiffness. Although biomechanical studies on this procedure are less reported, most scholars consider this procedure, safe, reliable, and corrective. The purpose of this article is to summarize this classic procedure and to understand its background, indications, and surgical technique.
Review of the literature: Riedl argued in 1908 that the medial cuneiform osteotomy could be used to treat bunion deformities, and he also argued that a closed wedge osteotomy of the medial cuneus could be used to treat retrolateral deformities of the cuneus. Two years later, Young published a report on the use of a medial cuneiform sparing osteotomy for the treatment of bunions. Cotton reported the first medial cuneiform dorsal cuneiform osteotomy and implant in the New England Journal of Medicine, and concluded that the procedure could be used in patients with flat feet who were unable to bear weight on the first metatarsal head (although he had presented this idea at the New England Surgical Conference on September 28, 1935). Cotton wrote that the procedure was simple, painless, and could be weight-bearing within 1 month. After some case attempts and follow-up, there was no difficulty in the operation and no loss of orthopedic results since I suggested the procedure. It was further suggested that other deformities of the foot, such as Achilles tendon contracture, can have an effect on foot valgus and bunion. In addition, he used the resected medial tuberosity of the first metatarsal as a bone graft and concluded that the resected tuberosity was a good source of bone for grafting.
Hirose and Johnson provided 15 pediatric and adult patients who underwent Cotton’s surgery (along with adjunctive other hindfoot bony and soft tissue surgery) for peer review, affirming Cotton’s own statement: no nonunion or malunion. The lateral talus first metatarsal angle, heel inclination angle and medial cuneiform distance from the ground were significantly altered from the preoperative position. It was further noted that the Cotton procedure was also superior to the first metatarsocuneiform fusion, most notably because it preserved the mobility of the first metatarsocuneiform joint, better predicted surgical outcomes, and better controlled the degree of orthosis. They also concluded that the only drawback of the procedure is the need for bone grafting. In the correction of flatfoot deformity, the effect of the cotton procedure on hindfoot orthosis is inconclusive because it is used as an adjunctive operation, so it is difficult to evaluate its surgical results alone; nevertheless, it is recommended to use this procedure in combination with heel osteotomy. At the same time, soft tissue surgery can also be used as an adjunct to the Cotton procedure. In addition, it is difficult to decide preoperatively whether to use the Cotton procedure because the evaluation criteria for the Cotton procedure are primarily based on whether there is residual stiffness of the forefoot after correction of the hindfoot. acobs and Oloff have treated 8 patients with this procedure with a mean follow-up of 18.4 years and showed excellent results in 7 cases. Recent studies such as Lutz and Myerson reported 101 patients who underwent the Cotton procedure for a complex flatfoot and showed no nonunion or malunion in all affected feet, again confirming the results of previous studies with large sample sizes. The first metatarsal angle of the talus decreased from -23° to -1° preoperatively. In terms of biomechanical studies, in 2007 scott et al. used a cadaveric foot to study plantar pressure changes after medially displaced heel osteotomy, lateral column lengthening, and the Cotton procedure and found that the Cotton procedure did increase the mean medial forefoot plantar pressure, but did not significantly change the lateral plantar pressure. In the same year Benthien et al. found in a cadaver foot study that cotton not only increased medial plantar forefoot pressures but also reduced lateral plantar pressures. in 2008 Alan C. League et al. came to the same conclusion as Benthien. In terms of surgical complications, a study by Hirose and Johnson found one patient with screw-induced symptoms and a study by Lutz and Myerson found 10 patients with complications or related to the cotton procedure: three with screw-induced symptoms, two with exophytic warts, one with seed bone pain, one with metatarsophalangeal tendonitis, two with lateral column excessive weight bearing, and one case of recurrence of flatfoot deformity.
To summarize, the literature on cotton is mainly a clinical retrospective study, biomechanical study (plantar pressure) and study in x-ray. There are only a dozen articles, but the procedure is highly evaluated, mainly for its ability to correct forefoot pronation deformity, bone healing ability and evaluation of various parameters on x-ray. This procedure is often used in combination with other procedures as an adjunct to the treatment of flatfoot deformity, such as posterior tibial muscle reconstruction (bunion, toe, or anterior tibial tendon) gastrocnemius release or Achilles tendon lengthening, medial displacement osteotomy of the heel, lateral column lengthening and subtalar joint braking.
Pathogenesis: Forefoot pronation is defined as the angle between the line of the first and fifth metatarsal heads of the forefoot opening inward to the horizontal plane after passive correction of the hindfoot to a neutral position, also referred to as forefoot rotation posterior in the literature. Currently in foot and ankle surgery, both terms can describe the same deformity. The forefoot pronation deformity can be classified as flexible or rigid by clinical examination: the examiner fixes the hindfoot with one hand and fixes the heel bone in a neutral position, the forefoot appears to be pronated or rotated backwards, the other hand pushes the fifth metatarsal head upwards from the metatarsal side, if the line between the first and fifth metatarsal heads is parallel to the horizontal plane, the deformity is flexible, otherwise it is rigid. If the deformity is not corrected clinically, the patient’s medial sequence cannot touch the bottom after surgery when the foot is placed flat, which can easily cause walking weakness. Regarding the mechanism of forefoot pronation formation in patients with flatfoot, most scholars believe that it is due to the compensation of excessive hindfoot pronation to accommodate the three-point weight-bearing principle, but this view only applies to the foot flattening phase. The author has another additional explanation for the compensatory mechanism of posterior rotation of the foot: patients with flat feet have plantarflexion due to excessive valgus of the heel bone. The movement of the talus in relation to this is excessive plantarflexion, pronation, and external rotation. In order to avoid or reduce the occurrence of pain, the forefoot is rotated and advanced, and the anterior tibial muscles compensate for the contraction, which is aggravated by the shortening of the tendons as the disease progresses.
Indications for surgery: According to previous literature the procedure is mainly used for: tarsal coalition disease, overcorrection of horseshoe foot, high medial forefoot deformity, bunion stiffness and other diseases in which the first metatarsal cannot bear weight. Currently, it is mainly used in patients with stage 2 posterior tibial tendon insufficiency, persistent stiff forefoot pronation deformity after correction of hindfoot deformity, and forefoot pronation after triple joint fusion for stage 3 posterior tibial tendon insufficiency. However, for medial serial imaging manifestations with arthritic signs and obvious joint instability (such as signs of vertical instability of the first metatarsal cuneiform joint or enlarged opening below the metatarsal cuneiform joint on lateral x-ray; horizontal instability of the first metatarsal cuneiform joint with bunion deformity; lateral x-ray showing: obvious signs of instability of the navicular cuneiform joint). However, the procedure is not easily used in patients with forefoot pronation >35° after hindfoot correction. The former is mainly due to the failure to treat the patient for the etiology and is easy to use the first metatarsal cuneiform joint fusion. In the latter case, if the Cotton procedure is used alone, there will be excessive plantarflexion of the first metatarsal, which will reduce the effective length of the first metatarsal and make the medial sequence relatively short, so that the expected surgical results cannot be achieved or new deformities will appear. Hoke-Miller fusion, etc.).
Surgical procedure: The patient is placed in the horizontal position, and a tourniquet is placed on the patient’s thigh with a pressure of 300 mmHg Hg. The incision was chosen to have a dorsal foot incision: a longitudinal incision was made in the plane of the medial cuneiform joint, the skin was incised, and the subcutaneous was bluntly separated to reveal the long thumb extensor tendon and the short thumb extensor muscle, which were drawn medially and laterally respectively, while ensuring the integrity of the dorsal foot artery and the deep peroneal nerve. The dorsal surface of the medial cuneiform bone was exposed. The periosteum is incised longitudinally and separated on both sides, at which point the midpoint of the medial cuneiform bone is determined under fluoroscopy using a hemostatic forceps, and this point is the osteotomy position. The osteotomy can also be performed with a micro-swing saw using a fluoroscopic needle driven vertically from the dorsal midpoint of the medial cuneus to the metatarsal side as a guide pin, taking care not to completely cut it off and to preserve the integrity of the metatarsal cortex. The bone is cut approximately 1/2 of the way and the bone is cut while cocking the bone towards the metatarsal side to see the extent of the orthosis. Then a special kerf pin spreader is used to spreader the foot to a satisfactory level (by dorsiflexion of the ankle joint to check that the first and fifth metatarsal heads are on a horizontal plane), mainly to restore the three-point support of the foot. The degree of orthosis can also be checked under fluoroscopy. And then the extent and depth of the dorsal opening of the medial cuneiform is measured. The width of the bottom edge of the wedge is usually 5 to 8 mm for orthopedic purposes. Next, the bone graft is prepared. Although several types of bone grafts are available, we recommend the use of iliac bone with three-sided cortical bone as the source of the graft, either homogeneous (iliac, heel, tibial or medial metatarsal head) or allogeneic (frozen iliac or femoral head). According to clinical reports, there is no significant difference between the two in terms of postoperative results, and their use depends on the surgeon’s custom. The graft is made into a triangle of appropriate size using a miniature swing saw so that the cancellous bone side of the graft faces the truncated bone side of the medial cuneiform bone, while the cortical bone side is placed dorsally, medially and laterally. After placement of the graft, the kerf pin spacers are loosened so that the osteotomy surface is tightly united with the graft, and internal fixation is generally not required. Most physicians are comfortable with internal fixation, which includes Kirschner pins, cancellous bone screws, compression plates, etc. We do not usually use internal fixation. We do not usually use internal fixation. If the pin is used, it is removed approximately 4 to 6 weeks after surgery. Recently, a wedge-shaped plate has emerged in the clinic, and there are different sizes of wedges that can be selected according to orthopedic needs, with which we have little experience. The postoperative rehabilitation program depends on the type of additional surgery. In general, postoperative non-weight-bearing cast immobilization for 6 weeks, with x-ray confirmation of bone healing and no local pressure pain. The patient is allowed to use a protective brace for weight bearing. Full weight-bearing is usually allowed at about 10 weeks postoperatively.
In conclusion, the Cotton procedure is used as an adjunct and the final operative step in surgery for persistent or stiff pronation deformities of the forefoot after correction of stage 2 hindfoot deformity with posterior tibial tendon insufficiency. Despite the lack of prospective studies and more in-depth biomechanical studies, it is still considered as one of the commonly used procedures for the treatment of correction of forefoot pronation in patients with flatfoot due to its high orthopedic capacity, good results, simplicity of operation and few complications.