Evans Lateral Column Lengthening and Cotton Osteotomy

26 Evans Lateral Column Lengthening and Cotton Osteotomy


Jonathan Deland and Mackenzie Jones


Abstract


Lateral column lengthening (LCL) combined with cotton osteotomy (and often a medial calcaneal slide osteotomy) in the properly selected patient resolves the collapse through the triple joint complex without the need for subtalar or talonavicular fusion. The patient must not be so collapsed in the triple joint complex that the foot cannot be tensioned by an LCL to accomplish good position of the talonavicular and subtalar joints when the patient stands. Such a patient most often preoperatively does not have subfibular impingement but can certainly have subtalar impingement. Success with an LCL and cotton osteotomy is defined by achieving the right amount of correction with good alignment of the talonavicular and subtalar joints, resolving subtalar impingement and abduction of the talonavicular joint yet avoiding an overly stiff adducted/lateral weight-bearing foot. The successful patient has near-normal eversion motion remaining in the hindfoot, and good alignment of the heel. If surgery has achieved these goals, the patient is likely to have a good functional outcome with minimal stiffness and minimal chance of recurrence of the collapsing foot.


Keywords: lateral column lengthening, cotton osteotomy, best functional outcome, alignment


26.1 Indications and Pathology


• Adolescent flexible flatfoot.


• Adult acquired flatfoot deformity 2B:


image Posterior tibial tendon (PTT) dysfunction.


26.1.1 Clinical Evaluation


• Flatfoot deformity with medial arch collapse.


• Usually will have pain over the PTT.


• Too-many-toe sign when foot observed from behind in standing position due to forefoot abduction.


• Hindfoot valgus.


• Inability to perform a single-leg heel raise (heel should invert).


26.1.2 Radiographic Evaluation


• Weight-bearing anteroposterior (AP), lateral and Saltzman’s view radiographs are performed to assess degree of planovalgus.


• Indication for this procedure is excessive eversion/abduction of the midfoot with collapse of the arch as evidenced by one of the following:


image Forty percent or more talonavicular uncoverage on a standing AP X-ray of the foot.


image Lateral incongruity of the talonavicular joint on a standing AP foot X-ray.


image Borderline X-ray findings of one or two, but the patient has excessive pronation (eversion and abduction) seen clinically by a severe flatfoot with sag in the arch just distal to the ankle but not at the level of the tarsometatarsal or naviculocuneiform joints. Standing plain X-rays can underestimate deformity if patient is not allowing the arch to collapse, the patient is leaning back, or the X-ray is not properly centered over the talonavicular joint.


• If available, obtain a standing computed tomography (CT) scan in cases of severe deformity. This is helpful to assess possible lateral impingement at the subtalar joint and subfibular impingement. Also, on the coronal views of the CT scan, look for lateral subluxation of the subtalar joint, which probably indicates the need for a subtalar fusion.


• A magnetic resonance imaging (MRI) scan is not essential, but it can be helpful to assess the condition of the spring ligament in cases with severe deformity.


26.1.3 Nonoperative Options


• Boot or hinged ankle–foot orthosis (AFO) brace.


• Ritchie (ankle-level hinged brace with plantar orthotic component).


• Arizona brace.


Note: Any of these options may help symptoms and possibly slow down progression, but they do not halt progression. This should be explained to the patient.


26.1.4 Contraindications


• Unable to passively bring the talonavicular joint into an adducted or inverted position.


• Moderate to severe osteoporosis. In an osteoporotic patient with significantly weak bone, an Evans procedure is preferable to a step-cut osteotomy (see section “Lateral Column Lengthening Alternative Procedure: Step-cut Osteotomy”) because of less chance of fracturing the bone with manipulation.


• Symptomatic arthritis of the subtalar, calcaneocuboid, or talonavicular joint.


26.2 Goals of Surgical Procedure


• Correct alignment so that each of the following is achieved:


image No remaining subtalar or subfibular impingement.


image Near-normal eversion motion of the hindfoot without excessive eversion motion (mild stiffness in eversion is acceptable).


image A simulated weight-bearing AP fluoroscopic view in the operating room showing a congruent talonavicular joint with no more than 30% uncoverage and minimal, if any, adduction at the joint.


image A clinically straight heel when viewed from the end of the operating table so that the heel is directly underneath the ankle and calf, not in varus or appreciable valgus. Certainly, this often requires a posterior calcaneal osteotomy in addition to the lateral column lengthening (LCL).


26.3 Advantages of Surgical Procedure


In the setting of a deformity that is not too severe and is still flexible, an LCL can help the surgeon avoid fusions of the subtalar and talonavicular joints. These joints are important for the patient being able to exercise on the foot and minimize the risk of ankle arthritis over time.


26.4 Key Principles of the Surgical Procedure


• Achieve the right amount of correction taking care not to overcorrect, which is the most common mistake.


• Perform compression fixation of the osteotomies, especially the LCL.


• Confirm that the heel alignment is good after temporary fixation of the LCL and the posterior calcaneal osteotomy. In cases with more than a little increased heel valgus, it is normally necessary to do a posterior calcaneal osteotomy as well as an LCL to obtain correct position of the heel.


• If the first metatarsal is elevated, it should be brought down to a good position in comparison to the second metatarsal head. Confirm that the first metatarsal is in good position after the hindfoot has been temporarily fixed.


26.5 Preoperative Preparation and Patient Positioning


• Use standing X-rays preoperatively, with the patient allowing the arch to collapse. Judge the abduction of the talonavicular joint on the AP foot X-ray and the plantar sag at the talonavicular joint on the lateral X-ray. Also, look for possible sags at naviculocuneiform and first tarsometatarsal joints on the standing lateral X-ray.


• Assess a standing AP view of the ankle to confirm no valgus of the talus in the ankle joint.


• Patient is positioned supine. A small bump can be placed under the ipsilateral hip to aid with the lateral column lengthening, although this may make the approach to the PTT more difficult during the tendon transfer procedure if the leg is rotated too internally. Best position is toes pointing to the ceiling with the foot at rest.


• A flexor digitorum longus tendon transfer is usually performed in combination with the osteotomies in adult acquired flatfoot deformity with associated PTT pathology.


26.6 Operative Technique


26.6.1 Lateral Column Lengthening: Evans Procedure


• Use a sinus tarsi incision extending from the tip of the fibula to the anterior process of the calcaneus (Fig. 26.1).


• Dissect at the midportion of the incision to find the floor of the sinus tarsi, taking care to avoid and stay above the peroneal tendons and sural nerve. Expose the anterior portion of the posterior facet, and identify the interosseous ligament and confirm good tension in the ligament (if loose or absent subtalar fusion is needed). Take care not to cut the ligament.


• Dissect laterally over the anterior calcaneus, from a point adjacent to the calcaneocuboid joint to the level of the posterior facet. Mobilize the peroneal tendons so that they can be retracted with a Bennett retractor to allow a saw cut into the lateral aspect of the anterior calcaneus.



• Place a K-wire 17 mm from the calcaneocuboid joint through the lateral cortex and into the medial cortex one-third the way down from the dorsal rim aiming in between the middle and posterior facets (Fig. 26.2). The interval between the facets can usually be identified bluntly with an elevator. Measure the depth of the K-wire when it has reached the medial cortex. This will give the surgeon a good idea of the depth for the saw blade cut. The depth of the saw cut can be marked on the saw with a marking pen.


• With the thin oscillating saw, make the osteotomy perpendicular to plantar aspect of the foot just distal to the K-wire into the medial cortex. Weaken the medial cortex so that the osteotomy can be hinged open with an osteotome (Fig. 26.3).


• Place a pin distractor with one pin right next to the calcaneocuboid joint and the other well posterior to the saw cut.


• Use an osteotome to hinge open the osteotomy. Use the pin distractor to hold open the osteotomy and try different amounts of lengthening to correct the deformity.


• Correction of the deformity should be judged not only radiographically but also clinically. Radiographically, the abduction should be corrected so that there is a normal amount of uncoverage of the talar head (30% or less), and no adduction of the talonavicular joint. Clinically, there should be near-normal eversion motion remaining, but mild stiffness is acceptable (Fig. 26.4).


• If, on a simulated AP weight-bearing view with the eversion stress, there is adduction at the talonavicular joint or there is almost no eversion in the hindfoot, the foot is overcorrected. Undercorrection is defined by excessive uncoverage with over 30% uncoverage of the talar head on the simulated weight-bearing view or by excessive eversion motion remaining in the hindfoot. Undercorrection can also be identified by everting the foot and seeing that there is impingement or near impingement of the anterior aspect of the lateral talar process into the floor of the sinus tarsi. Too much correction can result in a good-looking X-ray and no impingement, but the hindfoot still too stiff. That situation will lead to an unsatisfied patient with lateral weight bearing. Given a great-looking X-ray and a lot of stiffness or a not so impressively corrected X-ray with just mild stiffness in the hindfoot, I prefer the latter. The most common amounts of LCL are in the range of 6 to 8 mm.


• Hold the osteotomy open to the desired amount of lengthening and fashion a tricortical allograft to fit that space. Another method (my preferred method) is to use trial wedges in 1-mm increments or some instrument with the desired amounts of lengthening to judge the foot.1 Use the wedges or instrument inserted into the osteotomy to judge the correction. Fashion the graft according to the ideal amount of correction as shown by looking at the osteotomy held open to the desired amount. Take note of the shape of the opening, and replicate the shape. The wedge is usually trapezoidal in shape.


• Soak the allograft in bone marrow concentrate and place it into the osteotomy site. Make sure that the fit is good. If there is any space on either side between the graft and native bone, rotate or trim the graft slightly to achieve excellent apposition along the lateral and dorsal aspects of the osteotomy. When this is achieved, place a pin from the anterior calcaneus across the graft and into the posterior calcaneus.


• With the graft in place and pinned, confirm that the amount of correction is appropriate and that both clinical inspection and fluoroscopic views show good apposition of the graft to the native bone. Fix the osteotomy with two longitudinal 3.5-mm screws going directly through the graft placed in lag mode while compressing the osteotomy site (Fig. 26.5). Alternative fixation is with a lateral low-profile claw-type plate to provide compression.


Jul 19, 2019 | Posted by in SPORT MEDICINE | Comments Off on Evans Lateral Column Lengthening and Cotton Osteotomy
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