Treatment of Ankle Osteoarthritis with Total Ankle Replacement Through a Lateral Transfibular Approach

Summary

We present our preoperative, operative, and postoperative protocols for the treatment of osteoarthritis of the ankle with total ankle replacement via lateral transfibular approach.

Abstract

Total ankle replacement (TAR) is a valid option for the treatment of ankle osteoarthritis. The traditional surgical approach for TAR is the anterior approach. Recently, the lateral transfibular approach to the ankle has gained popularity since a new TAR implant was designed to be performed via this approach that results in an ideal visualization of the center of rotation of the ankle and curved resections that allow for sparing bone cuts. The aim of the present paper is to present our preoperative, operative, and postoperative protocols for the treatment of the osteoarthritis of the ankle with TAR via lateral approach. We present our preoperative clinical and radiographic protocol. In addition, we describe our surgical technique with some technical tips. Finally, we report our follow-up schedule that includes the collection of clinical, functional, and radiographic data. The results of this procedure are encouraging: TAR through a lateral transfibular approach provides reliable pain relief and improvements in functional outcomes in patients with ankle osteoarthritis.

Introduction

The most frequent etiology of ankle osteoarthritis is the post-traumatic origin. In fact, it is often secondary to traumatic injuries that typically affect young patients^1,2. Ankle osteoarthritis influences patients' quality of life to the same degree as hip osteoarthritis and even more than knee osteoarthritis³. Ankle fusion has been considered the gold-standard for the treatment of ankle osteoarthritis, but some studies show that it confers augmented stress and increased risk of osteoarthritis of the adjacent joints^4,5,6,7; furthermore, there still exist a number of complications associated with ankle fusion, such as equinus or talipes deformity and painful non-union^8,9. With the evolution of surgical techniques and implant designs, total ankle replacement (TAR) has become an excellent alternative to ankle fusion for a surgeon with a proper learning-curve^10,11,12.

TAR allows the preservation of ankle range of motion and protects from adjacent joint degeneration¹³. The anterior approach permits an optimal visualization of the coronal alignment; at the same time, this approach is inclined to wound-healing complications^14,15. Recently, a novel TAR implant was designed to be performed via the lateral transfibular approach that results in an ideal visualization of the center of rotation and curved resections that allow for sparing bone cuts¹⁶; moreover, this approach permits the implantation of components perpendicular to the bone trabeculae, thus limiting the shear forces at the level of the bone-implant interface¹⁶. This prosthesis consists of a fixed-bearing implant; an alignment coordinate system guides the bone resections and facilitates addressing both coronal and sagittal deformities¹⁷. The early results of ankle arthroplasty using this TAR implant have been published ^12,16,17,18. The aim of the present paper is to present our preoperative, operative, and postoperative protocols for the treatment of the osteoarthritis of the ankle with TAR via the lateral approach.

Patient selection starts with a careful clinical examination and history. A medical history of inflammatory or vascular disease, neuropathy or neurologic disease and complicated diabetes may modify the indication. Poor soft tissue envelope of the ankle should be carefully evaluated because it may compromise the wound healing: skin and subcutaneous soft-tissue may already have been compromised from injury or previous surgery. The use of drugs that may influence healing must be considered. Muscle and tendon function, ankle and hindfoot alignment, and ankle range of motion should be evaluated: a detailed examination can indicate whether accessory procedures are needed at the time of surgery¹⁹.

We suggest always discussing the expectations of the patient concerning the outcomes of the procedure and the need for compliance with post-operative care. TAR is indicated for patients with an ankle joint disease due to post-traumatic, rheumatoid, or primary arthritis not responsive to conservative options that include physical therapy, activity modification, and non-steroidal anti-inflammatory drugs¹⁹. Also, lateral ankle instability may represent a cause of joint degeneration defined as ligamentous posttraumatic ankle osteoarthritis²⁰. In addition, secondary osteoarthritis can be associated with systemic diseases: avascular necrosis of the talus, gout, hemophilia, post-infectious arthritis, and hereditary hemochromatosis^21,22,23,24.

During the preoperative consultation, we routinely record the following clinical and functional scores: American Orthopaedic Foot & Ankle Society (AOFAS) ankle and hindfoot score^25,26,27, 12-Item Short Form Health Survey^27,28, and Visual Analogue scale (VAS) pain score²⁹.

Protocol

All methods described have been approved by our institutional review board and the local ethics committee and they have been performed in accordance with the ethical standards laid down in the 1964 Declaration of Helsinki and its later amendments.

1. Preoperative Radiographic Evaluation

1. Perform weight bearing radiographs of the ankle and the foot with antero-posterior, lateral, and rearfoot alignment views (Saltzman's view³⁰).
2. Perform a conventional computed tomography (CT) of the ankle and request any other diagnostic exams (such as magnetic resonance), if necessary, to better clarify the diagnosis.
3. Measure the following parameters on the preoperative weight-bearing radiographs.
   1. Measure the anterior distal tibial angle (ADTA, normal value 83.0 ± 3.6 °) on the lateral ankle view: measure the angle between the anatomic axis of the tibia and the line connecting the distal points on the anterior and posterior edge of the tibial articular surface (Figure 1)^30,31.
   2. Measure the lateral distal tibial angle (LDTA, normal value 89.0 ± 3.0 °) on the anteroposterior ankle view: measure the angle subtended between the anatomic axis of the tibia and the line connecting the distal points on the medial and lateral edge of the tibial articular surface (Figure 2)^32,33,34.
   3. Measure the tibio-talar ratio (TT ratio, normal value 34.8 ± 3.8%): measure this parameter on the lateral ankle view; it is the ratio between the posterior longitudinal talar length (the length between the posterior talar edge and the intercept of the anatomical tibial axis) and the full longitudinal talar length (Figure 1)^33,35,36.
   4. Measure the tibio-talar surface angle (normal value 89.0 ± 2.6 °) on the anteroposterior ankle view: measure the angle between the anatomic axis of the tibia and the line connecting the proximal point on the medial and lateral talar articular surface (Figure 2)³⁷.
4. Use the CT to assess the available bone stock and to evaluate the severity of the avascular necrosis of the talus, if present.

2. Surgical Technique¹⁷

NOTE: This procedure is performed under general or regional anesthesia (spinal anesthesia).

1. Place the patient in the supine position with a rigid board under the leg to sustain the alignment stand. Position a thick pad under the ipsilateral hip. Do not use a tourniquet.
2. Make a longitudinal incision with a scalpel over the lateral malleolus that curves under its tip toward the sinus tarsi (Figure 3). Dissect the fibula and the anterior side of the tibia subperiosteally with the scalpel and the periosteal elevator to obtain a complete view of the osteophytes and the joint.
3. Release the posterior capsule of the tibia and the fibula using a periosteal elevator.
4. Make an oblique lateral malleolus osteotomy with a sagittal saw blade: begin from the posterior edge of the fibula, 6-7 cm proximal to the joint line; end on the anterior side of the fibula, 2 cm proximal to the joint line. Rotate the fibular malleolus distally and use a 1.6 mm K-wire to fix it to the calcaneus.
5. Remove the anterior osteophytes with the sagittal saw blade and a rongeur until the ankle can be easily placed in a neutral position.
   NOTE: The medial gutter release can be performed later during the tibial preparation.
6. Measure the medial/lateral talar width with the manufacturer's sizer, choosing the largest size possible while avoiding overhang.
7. Place the leg in the alignment stand that is assembled at the beginning of the procedure.
8. Internally rotate the foot and use the trans-calcaneal pin to fix it to the foot plate. Use the 4.0 mm pin to fix the talus to the footplate: put the pin as distal as possible in the talar neck, thus facilitating further correction of talar tilt.
9. Check the tibial alignment with fluoroscopy using a bar that is parallel to the mechanical tibial axis. Use fluoroscopy with the following parameters: 55 kilovolts, 3 milliampere-seconds.
10. Insert two 5.0 mm pins on the medial border of the tibia while an assistant pushes the tibia anteriorly if an anterior sagittal talar shifting is present. To increase the rigidity of the construct, an adjunctive carbon fiber bar can be placed in a vertical position.
11. Verify the level of the desired joint line with the pointer located through the ''Position'' hole of the cutting guide of the selected size. Check the amount of bone resection with the pointer placed in the ''Talus'' and ''Tibia #1'' hole.
12. Use the 4.0 mm drill through the pre-cutting guide to pre-drill the talus and the tibia surfaces. Assemble the bone burr to the pneumatic handpieces and put the contralateral talar trial of the selected size between the bone burr and the cutting guide to assess the medial depth of the bone cut. Then, use the bone burr to make the definitive bone cuts through the ''Talus'' and the ''Tibia #1'' holes of the guide. Use the ''Tibia #2'' hole to reach the whole tibial cut on the medial side and to release osteophytes of the medial gutter
13. Position the rail drill guides. Utilize antero-posterior fluoroscopy to verify they are properly placed to avoid lateral overhang. Drill the rails and position the provisional implant, then choose the insert size.
14. Insert the definitive implants using the talar and tibial inserter.
15. Use fluoroscopy to check the positioning, and use two or three 3.5 mm lag screws to fix the fibula; alternatively, use a plate-fixation of the lateral malleolus, if the deformity requires a malleolar lengthening or shortening that does not leave sufficient contact for screw fixation.
16. Check the stability of the syndesmosis with a bone hookapplied to the lateral malleolus. Gently pull the fibula laterally to assess any residual tibiofibular instability. If a lateral movement of the lateral malleolus is present, stabilize it with a syndesmosis screw fixation across four cortices. Test the ankle range of motion.
17. Repair the anterior talofibular ligament with resorbable suture before routine wound-closure.

3. Postoperative Care

1. Place the leg into a cast and forbid weight-bearing for four weeks. Then allow weight-bearing with a walker-boot for two weeks.
2. Allow calf strengthening, proprioceptive training and stretching of the triceps surae six weeks after the surgery.

4. Clinical and Radiographic Follow-Up

1. Radiologically and clinically evaluate patients at one, two, six, and twelve months after the procedure and, afterward, every twelve months. The follow-up protocol consists of function and pain assessment with SF-12, VAS pain score, and AOFAS ankle and hindfoot scores collected at each time-point.
2. Perform radiographic examination: request weight-bearing radiographs of the ankle and of the foot with antero-posterior, lateral and Saltzman's view at each end-point.
3. Measure the following parameters on the postoperative radiographs at each end-point.
   1. Measure the alpha angle (α-angle) on the antero-posterior ankle view: measure the angle formed laterally by the anatomical axis of the tibia and the articular surface of the tibial component (Figure 4)³⁸.
   2. Measure the beta angle (β-angle) on the lateral ankle view: measure the angle subtended anteriorly by the anatomical axis of the tibia and the articular surface of the tibial component (Figure 5)^18,38.
   3. Measure the gamma angle (γ-angle) on the lateral ankle view: measure the angle between a line through the anterior and the posterior edge of the talar component and a line along the center of the talar neck (Figure 5)³⁹.
   4. Measure the Tibio-talar ratio.
   5. Measure the Tibio-talar surface angle.

Results

We collected the results of a consecutive series of 114 patients (114 ankles) who underwent TAR via lateral transfibular approach between May 2013 and July 2016. All operative procedures were carried out by the senior author.

Data were analyzed with a statistical software (see Table of Materials). The ANOVA and kappa tests were performed^40,41. For k-scor...

Discussion

We reported the methods and protocol we use performing TAR with lateral transfibular approach. The absolute contraindications for TAR are talar avascular necrosis involving more than 50% of the bone-stock, acute or active infection with or without osteomyelitis, diabetic syndrome with polyneuropathy, high anesthesiologic risks, neuromuscular disorders, peripheral vascular disease, and neuroarthropathy (Charcot arthropathy of the midfoot or hindfoot)^19,42. The rel...

Materials

Name	Company	Catalog Number	Comments
Zimmer Total Ankle	Zimmer, Inc.	82-0175-162-00	Total Ankle Replacement
Calcaneus pin	Zimmer, Inc.	00-4501-040-00	Trans-calcaneal pin
4.0 mm Pin	Zimmer, Inc.	00-4501-040-04	Talar pin
5.0 mm Pin	Zimmer, Inc.	00-4501-040-05	Tibial pins
1.6 mm k-wire	Zimmer, Inc.	00-4501-040-01	1.6 mm Kirschner wire
Moonray BlueLIne Dual	SIMAD		Mobile C-arm
Pre-Cut Guide Drill	Zimmer, Inc.	00-4501-059-00	Precutting bone drill
Bur	Zimmer, Inc.	00-4501-076-00	Bone resection burr
Micro 100 Drill	Conmed Corporation	5053-009	Pneumatic handpieces
3.5 mm ULS screws	Zimmer, Inc.		Fibular fixation screws
Matlab version 2008	The MathWorks Inc.		Statistical software