Mobile-bearing total ankle arthroplasty: A fundamental assessment of the clinical, radiographic and functional outcomes
Doets, H.C.
Citation
Doets, H. C. (2009, June 16). Mobile-bearing total ankle arthroplasty: A fundamental assessment of the clinical, radiographic and functional outcomes. Retrieved from https://hdl.handle.net/1887/13846
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The handle http://hdl.handle.net/1887/13846 holds various files of this Leiden University dissertation.
Author: Doets, H.C.
Title: Mobile-bearing total ankle arthroplasty: A fundamental assessment of the clinical, radiographic and functional outcomes
Issue date: 2009-06-16
Preoperative Evaluation of Patients with End-Stage Ankle Arthritis
and Recommended Surgical Technique of Total Ankle Arthroplasty
Chapter
12
170 Chapter 12
12.1 Preoperative Evaluation
A
good result of TAA starts with proper patient selection and an adequate pre- operative workup. Many inferior results of TAA could, at least in part, be at- tributed to improper patient selection and insufficient preoperative evaluation.Therefore, a complete medical history and physical examination, followed by an adequate preoperative imaging and planning are of paramount importance in order to obtain a good result. Any adverse phenomenon, such as a comorbidity influenc- ing the neurovascular function of the lower leg (e.g. smoking, hypertension, diabetes mellitus), a history of wound healing disturbance, or a history of latent or overt infec- tion should be recorded and thoroughly evaluated. A systematic assessment of the functional capacities should be done, preferably by filling out a commonly used ankle score like the American Orthopaedic Foot and Ankle Society score1. For research purposes, preferably a self-assessment instrument like the Foot Function Index2 or the from this index derived Ankle Osteoarthritis Scale3 should be used in addition to the physician assessment instruments.
Physical examination should start with an assessment of the alignment of both legs, with specific attention for the alignment of the ankle and hindfoot, followed by an evaluation of all the joints of lower leg. The active motion of the ankle and hind- foot should be recorded and the stability of the ankle joint should be tested. The skin condition should be evaluated, including scars from any previous surgery. Finally, the neurovascular status should be assessed, and in the event of abnormalities an evaluation by the neurologist and/or vascular surgeon is indicated.
After completion of the physical examination, adequate imaging is an es- sential next step. For preoperative imaging, standard anteroposterior and lateral weightbearing radiographs of the ankle and the whole foot are recommended. In the event of suspected or apparent bone loss a computer tomography (CT) scan with high-quality image reconstructions in the frontal and sagittal plane should be done, as only by this technique a trustworthy assessment of the osseous situation can be made. In the event of suspected or apparent tendon and/or muscular abnormalities a magnetic resonance imaging (MRI) scan should be done for a systematic assess- ment of these structures.
Contraindications for TAA are considered to be: neurovascular insufficiency (e.g. heavy smokers), a history of active or latent infection, gross deformity in the frontal or sagittal plane, substantial loss of bone stock, and patients who are non- compliant or are willing to function at a high level of physical activity.
171 Preoperative patient evaluation and recommended surgical technique
12
12.2 Disease-Specific Characteristics and Recommendations
In view of the causes of ankle arthritis, the main indications for reconstructive surgery are posttraumatic arthritis (either post-fracture or instability arthritis) and inflamma- tory joint disease. Each of these indications has its disease-specific characteristics.
Patients with post-fracture arthritis frequently have undergone previous sur- gery, resulting in the presence of scars and often a reduced range of motion. If the fracture has healed in malunion, this could influence the alignment of the ankle- hindfoot complex. Some shortening of the lateral malleolus can be acceptable and should not be regarded as a contraindication for arthroplasty. Gross malalignment should be corrected as a first step by for example a supra-malleolar osteotomy be- fore TAA is carried out. A widening of the ankle mortise due to syndesmotic injury should be corrected by performing a synostosis between fibula and tibia at the time of arthroplasty. In general, after an ankle fracture, the local bone stock has remained intact, so that implantation of the prosthetic components can be done without severe difficulty.
Instability arthritis is caused by chronic lateral ligament laxity. Due to this instability the talus has a tendency to tilt into varus. This persistent instability creates a problem when arthroplasty is considered, as for a good result of a mobile-bearing prosthesis stability in neutral alignment is a prerequisite. Restoration of alignment can be done by either a lateral ligament reconstruction or a medial ligament re- lease. As an alternative to medial ligament release we developed a medial malleolar lengthening osteotomy for the restoration of neutral alignment (described in chapter 6). Mid-term results with this medial malleolar lengthening technique are encourag- ing4. Furthermore, with instability arthritis there is a high preoperative incidence of anterior subluxation at the ankle joint (Fig. 1).
Fig. 1 Preoperative lateral weight- bearing radiograph showing anterior subluxation of the talus with respect to the longitudinal axis of the tibia in a patient suffering from instability ar- thritis
Fig. 1
172 Chapter 12
It is of paramount importance, that such an anterior subluxation is corrected. To achieve a proper alignment in the sagittal plane, we recommend implantation of the tibial component at 90 degrees to the vertical axis of the tibia in the sagittal plane, thus with no or only a minimal anterior slope (Fig. 2).
Fig. 2 Postoperative lateral radiograph of the same patient as in Fig. 1, showing correct axi- al position of the talus with respect to the distal tibia.
An increased anterior slope of the tibial component in an unstable ankle could lead to anterior subluxation of the replaced ankle, and thereby to edge-loading of the polyethylene bearing and/or to anterior tilting of the tibial component (Fig. 3).
Figs. 3-A and 3-B Lateral radiographs of a patient with instability arthritis. Fig. 3-A An in- creased anterior slope of the tibial component is visible, leading to anterior subluxation and eccentric loading of the tibial component. Fig. 3-B He developed early tilting and aseptic loosening of the tibial component, requiring revision of the tibial component.
Fig. 3-A Fig. 3-B
Fig. 2
173 Preoperative patient evaluation and recommended surgical technique
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Some stemmed tibial components have an anterior slope incorporated, and extra attention should be paid to a correct positioning of such a tibial component.
Also, a polyethylene bearing of sufficient thickness should be used as to adequately tension the stretched collateral ligaments.
Inflammatory joint disease (rheumatoid arthritis in particular) is character- ized by polyarticular joint destruction, by osteopenia and by moderate to severe im- pairments of the patient. Localized bone loss and the formation of bone cysts occurs frequently and should be evaluated by preoperative CT scan (Fig. 4).
Figs. 4-A and 4-B Preoperative radiographs of a 68-year old female patient with long-stand- ing rheumatoid arthritis. Fig. 4-A Lateral weightbearing view of the foot and ankle, showing severe arthritic changes in the ankle and hindfoot but no gross osseous pathology. Fig. 4-B Computer tomography with reconstruction in the sagittal plane, showing a large cyst in the talar body, probably not visible on the standard radiographs due to overprojection.
Furthermore, the hindfoot frequently develops a valgus deformity with a concomitant lowering of the longitudinal arch of the foot due to midfoot arthritis.
Correction of such foot deformities is mandatory for a good long-term result of TAA.
An elevated failure rate has been demonstrated in the event of a persistent hindfoot deformity5. Due to the osteopenia an increased risk of an intra-operative fracture ex- ists, necessitating a careful surgical technique.
12.3 Recommended Surgical Technique
After proper patient selection and informed consent, the patient can be scheduled for surgery. I prefer to position the patient supine with the thigh in a leg holder in order to flex the knee and to position the lower leg in neutral rotation (Fig. 5).
Fig. 4-A Fig. 4-B
174 Chapter 12
Fig. 5 Recommended positioning of the lower leg with the thigh supported by a leg holder.
The knee is flexed, the lower leg is in a neutral position and the calf muscles are relaxed.
Also, I prefer to start with the tourniquet deflated to reduce tourniquet time in an attempt to reduce wound healing complications and inflate the tourniquet usu- ally at the start of or during the osseous preparation. A midline anterior approach is recommended. After skin incision, branches of the superficial peroneal nerve should be identified, and, if necessary, mobilized to the lateral side. After incision of the ex- tensor retinaculum, the interval between the anterior tibial and the extensor hallucis tendons is used to reach the anterior capsule. Transverse vessels should be ligated.
The anterior capsule is opened medially and mobilized to the lateral side. Bone preparation starts with removal of osteophytes at the anterior aspects of the distal tibia and the talus. For a correct distal tibial resection it is recommended to start with a short vertical osteotomy with use of a reciprocating saw at the base of the medial malleolus (Fig. 6).
Fig. 6 This image shows the first step in the osseous preparation of the distal tibia. With aid of a reciprocating saw a small verti- cal osteotomy is made in the dis- tal tibia at the base of the medial malleolus.
Then a limited resection of the articulating surface of the distal tibia is carried out. Sizing of the distal tibia is done by measuring the AP distance of the resection plane, for example with a depth gauge, and by the use of templates. One should aim for full coverage of the tibial resection plane by the tibial component. Tibial and talar Fig. 5
Fig. 6
175 Preoperative patient evaluation and recommended surgical technique
12
preparation is done according to the specific recommendations of the manufacturer of the prosthesis. Special attention should be paid to a correct positioning of the prosthetic components, in order to prevent edge-loading of the polyethylene bearing and impingement with the malleoli. Furthermore, the talar component should not be oversized, as this also increases the risk of edge-loading and impingement. Optimal stability of the replaced joint should be aimed for by implanting a bearing of adequate thickness. Careful closure of the extensor retinaculum is an important final step to reduce the risk of wound healing problems. In the event of an equinus deformity, per- cutaneous achilles tendon lengthening should be done. Routine aftertreatment con- sists of 2-3 days of bed rest, followed by 4 weeks of immobilization in a below-knee plaster cast, with weightbearing to tolerance being allowed for. A major objective of cast immobilization is the promotion of proper wound healing. Cast immobilization is usually prolonged to 6 weeks in patients with inflammatory joint disease and instabil- ity arthritis. If the procedure is combined with a hindfoot fusion, cast immobilization usually is done for a period of 10 weeks. Delayed wound healing may also require prolonged immobilization in a cast.
A video demonstrating our surgical technique of TAA with use of the Buechel- Pappas prosthesis is available through Video Journal of Orthopaedics6. See their website for more information: www.vjortho.com.
References
1. Kitaoka HB, Alexander IJ, Adelaar RS, Nunley JA, Meyerson MS, Sanders M. Clini- cal rating system for the ankle-hindfoot, midfoot, hallux and lesser toes. Foot Ankle Int.
1994;15:349-53.
2. Kuyvenhoven MM, Gorter KJ, Zuithoff P, Budiman-Mak E, Conrad KJ, Post MW. The Foot Function Index with verbal rating scales (FFI-5pt): a clinimetric evaluation and comparison with the original FFI. J Rheumatol. 2002;29:1023-8.
3. Domsic RT, Saltzmann CL. Ankle osteoarthritis scale. Foot Ankle Int. 1998;19:466-71.
4. Doets HC, Van der Plaat LW, Klein J-P. Medial malleolar osteotomy for the correction of varus deformity during total ankle arthroplasty. Results in 15 ankles. Foot Ankle Int.
2008;29:171-7.
5. Doets HC, Brand R, Nelissen RGHH. Total ankle arthroplasty in inflammatory joint disease with use of two mobile-bearing designs. J Bone Joint Surg Am. 2006;88:1272-84.
6. Doets HC, Nelissen RGHH. Cementless mobile-bearing total ankle arthroplasty. Video J Orthopaedics 2006;21:4.
