STAR Ankle Replacement in Rheumatoid Arthritis
By James K. DeOrio, M.D.
The patient is an 86-year-old female with a history of joint pain and a diagnosis of rheumatoid arthritis since 1985. She has previously sustained a left hip fracture treated with fixation followed by a left total hip replacement and two revisions. She is also status post right hip replacement and right ankle fusion. Now she complains of severe pain in the left ankle/hindfoot.
On physical examination, she walks with an obvious limp on the left leg and has pain with no more than 5 degrees of motion in the left ankle and subtalar joints and tenderness to palpation in the left sinus tarsi. A posterior tibial pulse is palpable, but the dorsalis pedis pulse is only evident on Doppler examination.
(Authors Note: Please click on the X-rays for the full image.)
AP and Lateral Ankle X-rays
Left Foot X-rays
The patient was given the choice of fusing the left ankle or having a left STAR ankle replacement. Given the limited mobility in the right ankle post fusion, the patient and her daughter decided that the risk of ankle replacement was worthwhile in order to try to preserve some range of motion of the left ankle. Because the patient had obvious changes in the talonavicular (TN) and subtalar joints, with virtually no motion and evidence of pain on physical examination, a simultaneous TN and subtalar joint arthrodesis was planned.
The patient underwent surgery to include a left STAR ankle replacement with simultaneous TN and subtalar arthrodesis. First, with the tourniquet down, a guide pin followed by a 3.5 mm fully threaded screw was inserted through the medial malleolus for protection against breakage. Next, with a thigh-high tourniquet inflated, the subtalar joint was opened with a 3-cm incision just posterior to the sinus tarsi and cleaned of residual cartilage; the subchondral joint was drilled and broken up. The ankle was then opened and the TN joint was similarly cleaned and drilled. Alignment guides were applied, then cuts were made in the tibia and talus for the STAR ankle, the datum was positioned and checked on fluoroscopy, and the remainder of the cuts were made, followed by trialing with the window guide.
Intraoperatively, fluoroscopic images with the prosthesis subsequently inserted demonstrated 10 degrees of varus on the anterior-posterior X-ray.
The components were removed, the tibia was recut on the alignment guide, and the tibial barrel holes were re-drilled.
Reinsertion of the components now demonstrated satisfactory alignment.
The subtalar and TN joints were then grafted with the patient’s own bone, which had been mixed with a small amount of Vancomycin powder. (The same bone was added to fill barrel holes anteriorly.) Fully-threaded, 5.5-mm screws were inserted over guide wires placed across the subtalar and navicular calcaneal joint.
The patient was discharged to a nursing home. She returned to the clinic 3 weeks after surgery for a cast change and stitch removal and then returned to her home. She remained in a cast for 6 weeks, being as non-weight bearing as possible. When seen at 6 weeks post operative, she was placed in a short removable boot for 2 weeks and allowed to weight bear as tolerated, after which time she began wearing regular shoes. Postoperatively, the patient did well and returned for a last follow-up one year post surgery. Her left STAR ankle replacement was solidly seated and the TN and subtalar joints healed. She was “grateful she could now walk” without pain.
- With a palpable posterior tibial and Doppler-only detectable dorsal pedis pulse on the left, was it reasonable to proceed with surgery without vascular consultation?
- Should a CT scan of the ankle have been done preoperatively to confirm involvement of the TN and subtalar joints?
- Is the prophylactic medial malleolar screw necessary?
- Was it correct to recut the tibia during surgery to get a more accurate cut or should the ankle have been left in some varus?
- Would a staged procedure of subtalar and TN fusions have been more appropriate, rather than simultaneously arthrodesing them with the replacement?
- Is it necessary to autograft the TN and subtalar joints and is there any evidence to show adding Vancomycin powder to the bone graft is helpful?
- Should more extensive fixation have been employed in the TN and subtalar joints? Is there an advantage to using fully-threaded instead of compression screws? Should the calcaneocuboid joint have been fused? Is it acceptable to put the screws in from front to back?