78-year-old man with collapsing cavus foot
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A 78-year-old man with past medical history of asthma, hypertension, heart block and neuropathy presented to the orthopedic clinic with 10 years of atraumatic right foot pain, weakness and progressive loss of the arch.
He had diffuse pain throughout the foot, but was unable to localize a specific area. He noted with his progressive deformity he has had decreased function of the right ankle and foot limiting his gait to slow shuffling unless he is using assistive devices, such as a shopping cart or a walker. He has tried over-the-counter insoles. This deformity causes diffuse discomfort throughout the foot and decreased function, such as limiting his ability to pursue activities such as hiking or walking.
On exam of his right foot, he had forefoot abduction and hindfoot valgus. He was unable to perform standing heel raise. He had a “too many toes” sign. He had no focal areas of tenderness to palpation other than mild tenderness over the sinus tarsi. He had no open wounds or skin changes. His ankle range of motion was from 10° dorsiflexion to 20° plantarflexion. On Silfverskiöld testing, he had 0° of ankle dorsiflexion with the knee extended and 10° with the knee flexed. He had minimal subtalar motion. He had grade two motor strength with plantarflexion and inversion and grade five eversion strength. His sensation was intact to light touch throughout his leg, consistent with his baseline neuropathy. He had a shuffling gait.
Radiographs of the right foot and ankle demonstrated midfoot abduction, forefoot adduction, hindfoot valgus, midfoot collapse and 50% medial uncoverage of the talar head (Figure 1). The calcaneus is posteriorly subluxated resulting in a disrupted cyma line. Meary’s angle is 35°. Despite the dramatic midfoot collapse, the pitch angle remains in the normal range. Given the abnormal pattern of pes planus deformity with associated midfoot collapse, a weight-bearing CT scan was ordered. The CT scan demonstrated gapping at the navicular-cuneiform joint, lateral subtalar subluxation with subfibular impingement and relative maintenance of the posterior and middle facets of the talocalcaneal joints, but significant impingement at the angle of Gissane (Figure 2). This is atypical; a foot with a 35° alteration in Meary’s line would be expected to exhibit a flat pitch angle and subluxated facets.
Source: Pooja Prabhakar, MD
What are the best next steps in management of this patient?
See answer below.
Subtalar reduction, arthrodesis
This patient has had a progressive collapse (or flattening) of a cavus foot as evidenced by collapse of an elevated midfoot and Z-pattern of midfoot abduction and forefoot adduction, which are both not seen in a progressive collapsing foot (flatfoot) deformity (PCFD) alone. Our goal was to treat this patient’s progressive collapsed cavus deformity to better realign the foot to decrease his pain. He had a rigid deformity with peritalar subluxation with hindfoot valgus, minimal subtalar motion and equinus contracture. We discussed that he would be a candidate for subtalar reduction and arthrodesis, tendo-achilles lengthening, flexor digitorum longus (FDL) to posterior tibial tendon (PTT) transfer, as well as possible talonavicular arthrodesis, peroneus brevis to peroneus longus transfer and midfoot arthrodesis.
Surgical procedure
The patient was positioned supine on an operating table with a bump under the hip and a ramp under the operative leg. A tendo-Achilles lengthening by precautious triple hemisection was performed in the order of medial, lateral and medial hemisections of the Achilles tendon. Increased dorsiflexion of 15° was noted after the tendo-Achilles lengthening was completed.
On the lateral foot, an incision was made through the sinus tarsi approach, and the subtalar joint was visualized and entered. Joint prep of the subtalar joint was performed by removing cartilage with an osteotome and curette from the posterior and middle facets. After this was completed, a burr was used to further increase blood flow in this area for fusion. Then on the medial side of the foot, the subtalar joint was entered medially, and cartilage was removed from the middle and anterior facets. Autograft taken from the burred bone was replaced into the subtalar joint to facilitate healing. The subtalar joint was then reduced by bringing the calcaneus medially and anteriorly using a periosteal elevator to correct the hindfoot valgus, as well as the elongated medial column. Two K-wires were placed through the reduced subtalar joint under fluoroscopic guidance in an orientation to fuse the middle and posterior facets. Guidewires for the 6.5-mm cannulated screws were placed and measured, and the near cortices were over-drilled. A 90-mm screw was placed through the posterior facet followed by a 100-mm screw through the middle facet. Anteroposterior foot and Harris fluoroscopic views were taken and showed adequate coverage of the talar head with the navicular, so it was decided to not perform a talonavicular fusion. Another subtalar screw was placed from the plantar portion of the foot aiming toward the middle of the talar dome, and a 55-mm cannulated screw was placed in similar fashion. Osteophytes in the subfibular region were removed with an osteotome and mallet.
Back to the medial side of the foot, the posterior tibialis tendon was identified and found to be disrupted. FDL was identified and transferred to PTT using a Pulvertaft technique. This was performed by releasing the FDL, creating a split in the PTT remnant and placing the proximal FDL stump through the created PTT split. The tendons were then attached together with a running locked nonabsorbable braided suture. During this tendon transfer, the foot was positioned in inversion. Back to the lateral side of the foot, a peroneus brevis to peroneus longus tendon transfer was performed with a running locking nonabsorbable braided suture. Fluoroscopic images were taken of the anteroposterior foot, anteroposterior ankle, lateral ankle and axial heel view, and were satisfactory. All the incisions were closed with 2-0 absorbable braided suture for the subdermal closure followed by 3-0 nylon vertical mattress sutures for the skin closure. The patient was placed in a short leg plaster splint for 2 weeks. The postoperative plan was for transition to a controlled ankle motion boot at the 2-week follow-up visit, and non-weight-bearing to the right foot for 6 weeks.
Discussion
Cavovarus deformity and PCFD are complex foot deformities commonly seen in clinical practice. Cavovarus foot is characterized by midfoot cavus, hindfoot varus, plantarflexion of the first metatarsal and forefoot adduction. Patients with this deformity may present with lateral foot and ankle pain, difficulty with wearing shoes and ankle instability. Progressive collapsing foot deformity is characterized by a collapse of the medial longitudinal arch, forefoot abduction at the talonavicular joint and hindfoot valgus. Patients with this deformity may present with medial foot and ankle pain, and, in a later stage of the disease, may have lateral ankle pain from subfibular impingement. It is not typical for a cavus foot to collapse.
Peri-talar subluxation is a component of PCFD, which occurs due to collapse of the medial longitudinal arch. In peri-talar instability, the talus translates on the neighboring calcaneal and navicular, moving medially and anteriorly, resulting in arthritis. Subtalar joint reduction and fusion can reposition the talus over the calcaneus, however, a talonavicular fusion may be needed to reduce or stabilize the forefoot abduction that also occurs in PCFD. The FDL to PTT tendon transfer increases inversion force on the navicular, which can correct forefoot abduction.
In this patient’s case, there were radiographic signs of a cavus foot that had progressively collapsed. This type of deformity of a collapsed cavus foot has elements of a skew foot. Goals of operative correction in a PCFD are realignment and balancing of the foot and, secondarily, preservation of joint motion.
Key points:
- PCFD is not typical but can occur in patients with a prior cavus deformity.
- Peri-talar subluxation is a component of PCFD which can be corrected through a reduction and fusion of the subtalar joint and, as needed, talonavicular fusion.
- The extent of operative correction should be based on the degree of correction that is obtained through bony and soft tissue procedures, such as arthrodesis and tendon transfers.
- References:
- Ananthakrisnan D, et al. J Bone Joint Surg Am. 1999;doi: 10.2106/00004623-199908000-00010.
- Habbu R, et al. Foot Ankle Int. 2011;doi: 10.3113/FAI.2011.0764.
- Hintermann B, et al. Foot Ankle Int. 2020;doi: 10.1177/1071100720950738.
- Sangeorzan BJ, et al. Foot Ankle Int. 2020;doi: 10.1177/1071100720950759
- Van Boerum DH, et al. Foot Ankle Clin. 2003;doi: 10.1016/s1083-7515(03)00084-6.
- For more information:
- Pooja Prabhakar, MD, and Bruce Sangeorzan, MD, can be reached at the department of orthopedics and sports medicine at the University of Washington Medical Center. Prabhakar’s email: prabhaka@uw.edu.
- Edited by Andrew Bi, MD, and Pooja Prabhakar, MD. Bi is a chief resident in the department of orthopedic surgery at NYU Langone. He will pursue a fellowship in sports medicine at Rush University Medical center following residency completion. Prabhakar is a chief resident in the department of orthopaedic surgery at the University of Washington. She will pursue a fellowship in foot and ankle surgery at Baylor University Medical Center following residency completion. For more information on submitting Orthopedics Today Grand Rounds cases, please email orthopedics@healio.com.
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