Introduction

Chronic anterior ankle pain is commonly caused by formation of talotibial osteophytes at the anterior part of the ankle joint. This condition has also been named "athlete's" ankle or "footballer's" ankle. In subsequent studies this entity is described to occur in other athletes, such as runners, ballet dancers, high-jumpers and volleyball players. Since then the term "footballer's" ankle has been replaced by the anterior ankle impingement syndrome.

The pain from impingement lesions is caused by catching of the synovial tissue between part of the talus and part of the ankle mortise. Osteophytes or ossicles facilitate this process, since they limit the range of motion.
A differentiation can be made between soft tissue impingement and bony impingement lesions.

In general, osteophytes are the secondary manifestation of osteoarthritic changes. However, repetitive minor trauma in the ankle, as seen in athletes, can induce spur formation.

History & Physical Examination

The typical patient with an anterior ankle impingement is a relative young athlete with a history of recurrent inversion sprains. The patient presents with anterior ankle pain, sometimes there is some swelling after activity and often a (slightly) limited dorsiflexion. Since anterior impingement is a clinical diagnosis, it is based on findings during physical examination. Recognizable local tenderness on palpation is present over the anterior joint line. Osteophytes may be palpable with the ankle joint in slight plantarflexion.

A differentiation can be made between anteromedial and anterolateral impingement. On palpation of the anterior joint line, the patient is asked whether this recproduces the pain. Since the middle section is covered by neurovascular structures and tendons, this part of the joint is difficult to access by palpation. If a patient with a clinical anterior impingement syndrome experiences pain predominantly located anteromedially when palpated, the diagnosis is anteromedial impingement. If pain on palpation is predominantly located anterolaterally, the diagnosis is anterolateral impingement.

Forced hyper- dorsiflexion can provoke the pain, but this test is often false negative.

Diagnostic Imaging

Standard radiographs

Standard AP and lateral radiographs are used to detect the presence of osteophytes. In patients with anterior talar and/or tibial spurs, these spurs are regarded to be the cause of an anterior impingement syndrome. Due to their location they lead to a "kissing" phenomena and concomitant pinching of hypertrophic synovial tissue. Because of the anteromedial notch, anteromedial osteophytes are undetected by standard radiographs in a substantial number of patients with anterior impingement complaints. In a cadaver study it was shown that anteromedial tibial osteophytes up to 7.3 mm in size, originating from the anteromedial border, remain undetected due to superposition or overprojection of the more prominent anterolateral border of the distal tibia. Medially located talar osteophytes remain undetected due to overprojection or superposition of the lateral part of the talar neck and body.

Detection of these osteophytes is important for preoperative planning. Several authors have stated that surgical distinction between normal bony and soft tissue variants and pathologic conditions is difficult, because of subtle variations in joint anatomy. Especially in patients with accompanying synovial reflections, overlying the concealed osteophytes, anteromedial bony spurs are poorly visualized arthroscopically and can therefore be missed easily. Radiographic classification of spur formation correlates with surgical outcome.

AMI

An oblique radiograph was introduced to detect medially located tibial and talar osteophytes. In this oblique Antero Medial Impingement (AMI) view, the beam is tilted to a 45° craniocaudal direction with the leg in 30° external rotation and the foot in plantarflexion in relation to the standard lateral radiograph position.

The sensitivity of lateral radiographs for detecting anterior tibial and talar osteophytes is 40% and 32% respectively (specificity 70% and 82%). When the lateral radiograph is combined with an oblique AMI radiograph, the sensitivity increases to 85% for tibial and 73% for talar osteophytes. This increase is due to the high sensitivity of the oblique AMI radiographs for detecting anteromedial osteophytes (93% for tibial and 67% for talar osteophytes). A lateral radiograph is insufficient to detect all anteriorly located osteophytes and an oblique AMI radiograph is a useful adjunct to routine radiographs and recommended for the detection of anteromedial tibial and talar osteophytes.

Preoperative Considerations

The cause of the pain in impingement is compression of synovial tissue between the anterior margin of the tibia or fibula and the talar neck in the dorsiflexed position. Osteophytes reduce the anterior space thus making it more easy for the synovial tissue to get compressed. The rationale for removing osteophytes in a patient with anterior ankle impingement is to restore the anterior space thereby reducing the chance that the synovial tissue gets squeezed again and that symptoms recur.

Removal of secondary osteophytes (osteoarthritic osteophytes, 50% good/ excellent results) have a worse prognosis than removal of osteophytes without joint space narrowing (85% good/ excellent results). These primary osteophytes are not a manifestation of osteoarthrosis and subsequently a "normal" joint remains after removal of these spurs.

Over 90% of osteophytes are situated well within the attachment of the joint capsule. On the talar side the typical osteophyte is found proximal to the notch of the talar neck. Both tibial and talar osteophytes can easily be detected during an arthroscopic procedure with the ankle in forced dorsiflexion. The capsule does not have to be detached to locate and remove these osteophytes.

Post-operative rehabilitation

The patient can be discharged the same day of surgery and weightbearing is allowed as tolerated. The patient is instructed to perform active dorsiflexion of the ankle to the neutral position (knee slightly bent). This exercise should be performed 2 or 3 days times per hour for the first days after surgery. The patient is instructed to elevate the foot when not walking to prevent edema. The dressing is removed 3 days post-operative. Normal walking without crutches at 4 - 5 days post surgery. Patients with limited range of motion are directed to a physiotherapist. Running can be started when range of motion is normal and in absence of swelling. This can on avarage be expected at 3 weeks post surgery. Sport resumption can on average be expected at 6 weeks post surgery. 

Recommended literature

Van Dijk CN, Fievez AWFM, Heijboer MP, et al. Arthroscopy of the ankle. Acta Orthop Scand 1993;64(suppl. 253):9.

Van Dijk CN, Scholte D. Arthoscopy of the Ankle Joint. Arthroscopy: The journal of Arthroscopic and Related Surgery, 1997;13(1):90-96.

Van Dijk, Verhagen RAW, Tol JL. Arthroscopy for problems after ankle fracture. J Bone Joint Surg (Br) 1997;79B(2):280-284.

 Tol JL, van Dijk CN. Anterior ankle impingement. Foot Ankle Clin. 2006 Jun;11(2):297-310, vi.

Tol JL, Verhagen RA, Krips R, Maas M, Wessel R, Dijkgraaf MG, van Dijk CN. The anterior ankle impingement syndrome: diagnostic value of oblique radiographs. Foot Ankle Int. 2004 Feb;25(2):63-8.

Van Dijk CN, Wessel RN, Tol JL, Maas M. Oblique radiograph for the detection of bone spurs in anterior ankle impingement. Skeletal Radiol. 2002 Apr;31(4):214-21.

Tol JL, Verheyen CP, van Dijk CN. Arthroscopic treatment of anterior impingement in the ankle. J Bone Joint Surg Br. 2001 Jan;83(1):9-13.

Van Dijk CN, Tol JL, Verheyen CC. A prospective study of prognostic factors concerning the outcome of arthroscopic surgery for anterior ankle impingement. Am J Sports Med. 1997 Nov-Dec;25(6):737-45.