Current Concepts In Flatfoot Surgery
Symptomatic flexible flatfoot conditions are common entities in both the adolescent and adult populations. Ligamentous laxity and equinus play a significant role in most adolescent deformities. Posterior tibial tendon dysfunction (PTTD) is the most common cause of adult acquired flatfoot. One should consider surgical treatment for patients who have failed nonoperative therapy and have advancing symptoms and deformities that significantly interfere with the functional demands of daily life. The Evans anterior calcaneal osteotomy is indicated for late stage II (Johnson and Strom’s Classification) adult acquired flatfoot and the flexible adolescent flatfoot. This procedure will address midtarsal instability, restore the medial longitudinal arch and reduce mild hindfoot valgus. One will usually note clinical midtarsal joint instability and abduction deformities during the physical examination. The Evans anterior calcaneal osteotomy is contraindicated when there is radiographic evidence of degenerative changes within the tritarsal complex and with rigid, non-reducible deformities. The posterior calcaneal displacement osteotomy (PCDO) is indicated for late stage I and early stage II PTTD with reducible calcaneal valgus. This is often combined with a tendon transfer. A PCDO is also indicated as an adjunctive procedure in the surgical reconstruction of the severe flexible adolescent flatfoot. Forefoot varus must be reducible. There should be an acceptable degree of stability within the midtarsal joint with minimal to no transverse plane deformity. The PCDO is contraindicated when there is radiographic evidence of degenerative changes within the tritarsal complex, a rigid deformity and/or significant angular deformity on radiographs (i.e. an increased talo-first metatarsal angle). What Should You Assess In The Physical Examination? In order to determine appropriate treatment, there are keys to look for during the nonweightbearing and weightbearing evaluations. Is the deformity flexible? What are the primary components of deformity (i.e. soft tissue contractures or muscle/tendon weakness)? What is the function of the tibialis posterior tendon? Does the ankle joint contribute to or is it the primary origin of the deformity? The nonweightbearing exam includes evaluation of the ankle joint for possible instability, equinus, deformity or pain. Equinus is often present in a longstanding flatfoot deformity. Assess ankle joint dorsiflexion with the knee extended and flexed. If there is a contracture, you may want to consider a posterior muscle group lengthening as an adjunctive procedure. If the equinus appears to be osseous (i.e. procurvatum ankle), then a supramalleolar osteotomy may also be necessary as the primary or adjunctive procedure. When assessing the patient’s ankle joint, identify any pain, crepitus or ligamentous instability that may be present. For adult patients, be sure to evaluate the course of the tibialis posterior tendon for tenderness, edema, nodularity or gross attenuation. Test the nonweightbearing strength by having the patient plantarflex and invert against resistance. The tibialis posterior tendon is often unable to support the medial arch adequately in mid- to late-stage II PTTD and may need to be addressed following osseous realignment. Proceed to evaluate the tritarsal complex. One should observe the position of the hindfoot to the leg and the forefoot to the hindfoot in the nonweightbearing position. If the hindfoot is in rigid valgus, it should remain in the same position in weightbearing and nonweightbearing. In the more flexible deformities, you should be able to place the subtalar joint in neutral position and attempt to reduce any forefoot abduction or varus. One can accomplish the varus reduction in the flexible patient by loading the lateral column to simulate the effect of weightbearing. Keep in mind that you cannot address a fixed varus deformity of the forefoot with an isolated calcaneal osteotomy. Therefore, one must evaluate for these fixed deformities and consider correcting this osseous realignment if it is present. Next, place the subtalar joint in a neutral position and maximally load the lateral column to evaluate the midtarsal joint (MTJ) while the patient is nonweightbearing. If the MTJ is unstable during this maneuver, an Evans anterior calcaneal osteotomy is indicated to help stabilize and reduce the MTJ. A MTJ that is stable will lock during loading, thus leaving a valgus of the heel as the etiology of the deformity. In this instance, a PCDO may be sufficient to address this deformity. Sometimes, there may be a combination of both, indicating that a double osteotomy may be necessary to correct the malalignment. Key Indicators To Look For During The Weightbearing Exam During the weightbearing exam, one should evaluate the frontal plane position of the calcaneus to the ground from a posterior view and observe any collapse of the longitudinal medial arch as well as any forefoot abduction. Reassess the hindfoot and midfoot flexibility in the weightbearing position by performing a hallux raise test with the patient standing. Dorsiflexion of the hallux will recreate the longitudinal medial arch and reduce some calcaneal valgus as the tibia is forced to externally rotate in a reducible deformity. Evaluate the function of the tibialis posterior tendon in the weightbearing position via the double and single-toe heel rise. The patient may be unable to perform a single heel raise in late stage II PTTD. Calcaneal osteotomies are contraindicated if the subtalar joint is non-reducible. What The Diagnostic Imaging May Reveal Assess standard weightbearing views (AP, lateral and oblique of the foot and ankle) for degenerative changes and angular deformity. Evaluate ankle films to rule out a valgus deformity within the ankle joint. Measure the talo-first metatarsal angle on AP and lateral foot radiographs. Seeing a view of the hindfoot alignment view and long leg calcaneal axial views can help you determine the level of valgus deformity (STJ vs. AJ vs. calcaneus). One should rule out tarsal coalitions in the adolescent patient. A MRI can be helpful for ruling out fibrous or cartilaginous coalitions in adolescent patients. Advanced imaging is also beneficial for evaluating joint integrity when deciding between joint sparing procedures or an arthrodesis. Pearls For Conducting The Evans Anterior Calcaneal Osteotomy When the Evans anterior calcaneal osteotomy is indicated, one should begin by ensuring that the patient is in the supine position on the operating table with a large bump under the ipsilateral hip to allow easy access to the lateral hindfoot. You may use spinal or general anesthesia. Prep the leg to the knee and drape the limb so you may access the posterior leg if a gastrocnemius recession or Achilles tendon lengthening is required. Identify bony landmarks including the base of the fifth metatarsal, the lateral malleolus and the calcaneocuboid joint. Place an oblique or longitudinal incision just distal to the sinus tarsi and 1 to 1.5 cm proximal to the calcaneocuboid joint. Sometimes this can be deceiving if the plantar fat pad is laterally displaced. Taking a lateral X-ray, with the use of a periosteal elevator as a guide, and identifying the dorsal and plantar aspects of the calcaneus may help prevent errors. One must ensure careful dissection and preservation of the peroneal tendons and the sural nerve. You should identify the calcaneocuboid joint (CCJ) but do not dissect it. You should perform the osteotomy approximately 1 cm proximal to the CCJ. One may use an image intensifier to confirm location prior to executing the skin and periosteal incisions, and the osteotomy. Proceed to incise the periosteum in a vertical fashion. Avoid extensive plantar dissection and do not dissect the periarticular ligaments of the CCJ. This will prevent disruption of the long plantar ligament (LPL) and prevent development of an unstable distal fragment following the osteotomy, which is a common radiographic finding following this procedure. This can still occur depending on the size of the bone graft and stretch on the LPL. Have the sagittal saw blade oriented perpendicular to the lateral surface of the calcaneus and perpendicular to the weightbearing surface. Perform the osteotomy from lateral to medial. Use caution when approaching the medial cortex. Exiting too far medial may compromise vital medial structures. It can sometimes be difficult to appreciate the medial cortex in this subchondral region of the calcaneus. One can use an osteotome to finish the osteotomy. You may also consider using a lamina spreader to manipulate and distract the osteotomy. When it comes to distracting the osteotomy in order to place the bone graft, you can use the lamina spreader to hold the osteotomy open. Alternatively, many surgeons use a mini external fixator. Evaluate the foot with the subtalar joint in neutral position and the forefoot loaded. Distract the osteotomy to the desired position and assess this position under image intensification. This will also help determine the size of bone graft needed. We prefer freeze-dried or frozen allograft bone for distraction. The allograft should be a composite of cortical bone in order to maintain structural realignment and cancellous bone for the promotion of osteoconduction. Tricortical or bicortical iliac crest or patella grafts are ideal. Fashion the graft into a triangular shape with the base lateral. Use a mallet and tamper to place the graft into the osteotomy site. Tap the graft into position under tension. Increased tension will eliminate micro-motion at the host-graft interface and promote consolidation. One may use image intensification to verify the final placement of the graft. The graft size is usually 10 mm in width. However, you would use a larger graft for larger individuals or if there is a significant deformity. We occasionally use fixation. The tension within the osteotomy invariably provides inherent stability. However, you may apply a Kirschner wire, screw or small plate as a form of fixation to stabilize the sagittal plane position of the bone graft and the distal fragment. Distraction osteogenesis is another option. This involves placing an external fixator on opposing sides of the osteotomy and obtaining gradual correction. The target distraction is approximately 1 mm per day and you should instruct the patient on the operation of the fixator. Using serial radiographs to evaluate progress, one can remove the external fixator after achieving the desired amount of lengthening. What You Should Know About Post-Op Considerations And Potential Complications Following the procedure, a non-weightbearing short leg cast is recommended for six to eight weeks. You should obtain serial radiographs to evaluate the incorporation of the graft. Graft stability is the key factor in determining the transition to weightbearing, which usually takes place around five to six weeks in adolescents and six to eight weeks in adults. You will see this stability as trabeculation at the host-graft interface. The absence of warmth and edema indicate bone graft healing. The patient can progress to controlled weightbearing in a fracture brace for two to three weeks and then proceed to physical therapy. Patients may require physical therapy to maintain range of motion of the foot and ankle, and to strengthen the posterior muscle group. Potential complications following the Evans procedure include transient sural neuritis, graft resorption, dorsal displacement of the distal segment and calcaneocuboid joint changes. Many of these complications are radiographic and do not result in clinical symptoms. Sural neuritis is usually transient and will resolve uneventfully. A Stepwise Approach To The Posterior Calcaneal Displacement Osteotomy (PCDO) When the PCDO is indicated, one should begin by following the same patient positioning technique described for the Evans anterior calcaneal osteotomy. Make the incision from just inferior to the lateral malleolus at a 45-degree angle to the weightbearing surface and parallel to the peroneal tendons, and just distal to them. Incise the periosteum in the same fashion as the skin incision. Dissect enough periosteum from the lateral calcaneus in order to allow access for the sagittal saw. Dorsal dissection should reach just posterior to the posterior facet of the subtalar joint and inferiorly just anterior to the plantar tubercle. Hold the blade of the saw perpendicular to the lateral surface of the calcaneus. Perform the osteotomy from lateral to medial. Use both hands to control the depth of the saw when approaching the medial cortex. Alternatively, you may osteotomize the medial cortex with an osteotome or view it on a long leg calcaneal axial (LLCA) X-ray. Place an osteotome within the osteotomy and stretch the medial periosteum. You may also utilize a lamina spreader to open and close the osteotomy completely and stretch the medial periosteum. This maneuver will mobilize the tuber segment of the calcaneus and allow easy medial translation. Then displace the posterior tuber medially and obtain provisional fixation with a 0.062 Kirschner wire or the guide wires for cannulated screw fixation. Hold the foot in plantarflexion during displacement in order to relax the inferior muscles, Achilles tendon and plantar fascia. This avoids sagittal plane displacement and allows for easy medial manipulation of the posterior segment. Translate the calcaneus approximately 1 cm medial. Check the cortical shelf to ensure that adequate medial displacement has been achieved on the LLCA view. Achieve final fixation with one or two large diameter compression screws and do not violate the subtalar joint. You can do this percutaneously under image intensification. One may choose to perform an osteoplasty of the remaining cortical shelf to avoid prominence. Adolescents with an open apophysis will require two 5/64-inch or 7/64-inch Steinmann pins, in lieu of screws, for final fixation. One may place these percutaneously or buried. The most common complications following a PCDO are undercorrection and fixation irritation. Utilizing this procedure in more advanced PTTD with significant angular deformities may lead to failure of the procedure and exacerbation of symptoms. A New Approach To The PCDO: The Percutaneous Technique This patient is prepped and draped as one would do prior to any PCDO or Achilles lengthening procedure. One must evaluate the Achilles tendon to determine if a percutaneous lengthening is needed. Perform a lateral X-ray to determine the exact location for the osteotomy. This X-ray will also enable you to determine the amount of Achilles lengthening that has been achieved. Utilize an osteotome or periosteal elevator to identify the site of the osteotomy and then mark it with a skin marker. Place multiple drill holes in the calcaneus in the same linear fashion as the skin markings through a small stab incision. Be cautious in your approach. Use the LLCA X-ray to prevent invasion of the medial soft tissue structures. At this point, use an osteotome to “connect the dots” or finish the osteotomy. Then distract the osteotomy with an osteotome and displace it medially. Provide provisional fixation with the guide wires from the percutaneous screw fixation set. Place the screws as for any PCDO. This technique minimizes soft tissue and periosteal dissection, and should help soft tissue and osseous healing. However, you must be knowledgeable in fluoroscopy usage and percutaneous osteotomy techniques. As far as post-op considerations go, one should place the patient in a short leg nonweightbearing cast for four to six weeks. Consider progressing to weightbearing when radiographs demonstrate healing of the osteotomy. Progress the patient to controlled weightbearing in a fracture brace for two to three weeks. It is important to evaluate the need for physical therapy as this is often necessary to maintain range of motion of the foot and ankle as well as to strengthen the posterior muscle group. In Conclusion Although calcaneal osteotomies address most flexible flatfoot deformities, it is not the answer to all flatfoot deformities in the adolescent and adult. Thorough evaluation will help prevent performing an inappropriate procedure. The percutaneous technique is a new approach to the tendo-Achilles lengthening and posterior calcaneal osteotomy. However, one should be proficient in the open techniques before considering the percutaneous approach. Dr. Mendicino is Chief of the Division of Foot and Ankle Surgery at the Western Pennsylvania Hospital in Pittsburgh, Pa. He is a Clinical Professor of Surgery at the Western Campus of the Temple University School of Medicine. Dr. Mendicino is also a Fellow and Past President of the American College of Foot and Ankle Surgeons. Dr. Catanzariti is the Director of Residency Training Programs within the Division of Foot and Ankle Surgery at the Western Pennsylvania Hospital. He is a Fellow of the American College of Foot and Ankle Surgeons. Dr. Reeves is a Chief Surgical Resident within the Division of Foot and Ankle Surgery at the Western Pennsylvania Hospital in Pittsburgh, Pa.
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