McMurray attributed to the knowledge about the formation of the talotibial osteophytes. According to him, repeated capsular-ligamentar traction by repetitive kicking with the foot in full plantar flexion (i.e., traction spurs) (McMurray 1950) induces this osteophyte formation. Traction to the anterior ankle capsule, during plantar flexion movements, was supposed to be an important etiological factor (McMurray 1950; Biedert 1991; Cutsuries et al. 1994; Ferkel and Scranton 1993; Ogilvie-Harris et al. 1993). This hypothesis is supported by the fact that these spurs are frequently found in athletes, who repetitively force their ankle in hyperplantarflexion actions, resulting in repetitive traction to the anterior joint capsule (Handoll et al. 2001). It assumes however that the capsular attachment is located at the anterior cartilage rim at the location where spurs originate.

A recent study demonstrated that the anterior joint capsule does not attach at the location where the osteophyte occurs. The anterior joint capsule attaches onto the tibia on an average of 6 mm proximal to the joint level (Tol and Van Dijk 2004) (Figs. 7.1 and 7.2). On the talar side the capsule attaches likewise approximately 3 mm from the distal cartilage border. The distance of capsule attachment to the location where the bony spurs are most frequently localized is thus relatively large. Based on these anatomic observations, the hypothesis of formation of talotibial spurs due to recurrent traction to the joint capsule (traction spurs) is not very plausible. This is supported by observations during arthroscopic surgery (Tol and Van Dijk 2004). In patients with bony impingement, the location of tibial spurs is reported to be at the joint level and always within the confines of the joint capsule (Tol and Van Dijk 2004; Tol et al. 2001). On the talar side, the typical osteophytes are found proximal to the talar neck notch. Tibial and talar osteophytes can easily be detected during an arthroscopic procedure with the ankle in forced dorsiflexion. The capsule does not need to be detached to locate these osteophytes.

O’Donoghue (1957) considered the osteophytes to be related to direct mechanical trauma associated with the impingement of the anterior articular border of the tibia and the talar neck, during forced dorsiflexion of the ankle joint. Here, bone formation is considered to be a response of the skeletal system to intermittent stress and injury, as evidenced by Wolff’s law of bone remodeling (Williams and Brandt 1984). According to Hawkins (1988), runners, dancers, and high jumpers are prime examples of athletes who are predisposed to sports-related repeated trauma. Even though this etiological factor is widely cited (Cutsuries et al. 1994; Ferkel and Fasulo 1994; Ogilvie-Harris et al. 1993; Hawkins 1988), experimental evidence-based support is scarce.

Along the distal tibia, the width of the non-weight-bearing cartilage rim extends up to 3 mm proximal to the joint line (Fig. 7.3). It is this non-weight-bearing anterior cartilage rim that undergoes the osteophytic transformation (Ferkel and Fasulo 1994; Tol and Van Dijk 2004). It has been postulated that chondral and bone cell stimuli initiate a repair reaction with cartilage proliferation, scar tissue formation, and calcification (Fig. 7.4). Additional damage by ankle sprains—recurrent instability—or forced dorsiflexion movements will further enhance this process (Biedert 1991). Recent studies have demonstrated that chronic ankle instability is indeed correlated with osteophytic formation in the medial ankle compartment (Van Dijk et al. 1996; Krips et al. 2000). After an ankle fracture, spur formation is a regular finding (Stufkens et al. 2009). Another etiological factor in the development of spurs is recurrent microtrauma. In soccer players it was demonstrated that spur formation is related to recurrent ball impact, which can be regarded as repetitive microtrauma to the anteromedial aspect of the ankle (Tol et al. 2002). Repetitive trauma to the anteromedial cartilage can probably be precluded by prevention of recurrent ankle sprains.

In the anterior ankle impingement syndrome, the cause of pain is hypothesized to be not the osteophyte itself but the inflamed soft tissue that is caught between the osteophytes (Tol et al. 2001) (Figs. 7.5 and 7.6). The tibial and talar spurs typically do not overlap each other (Berberian et al. 2001). Histopathological analysis of arthroscopic resected soft tissue reveals synovial changes and chronic inflammation (Ferkel et al. 1991). In cadaver specimens, a triangular soft tissue synovial fold, subsynovial fat and collagen tissue, was found along the entire anterior tibiotalar joint line (Fig. 7.3). This soft tissue component gets squeezed between the anterior distal tibia and the talus during forced dorsiflexion movements. Recurrent trauma to this soft tissue may lead to hypertrophy of the synovial layer, subsynovial fibrotic tissue formation, and infiltration of inflammatory cells. Talar and tibial osteophytes decline the anterior space, and compression of this soft tissue component is more likely to occur. It is therefore important to remove these osteophytes, restoring the anterior space and reducing the chance that symptoms recur.

The typical patient with an anterior ankle impingement is a relatively young athlete with a history of recurrent inversion sprains (Scranton and McDermott 1992). The patient presents with anterior ankle pain, swelling after activity, and (slightly) limited dorsiflexion (Cutsuries et al. 1994). Since anterior impingement is a clinical diagnosis, the diagnosis is based on findings during physical examination. Recognizable local tenderness on palpation is present on the anterior joint line, and osteophytes can be palpable with the ankle joint in slight plantar flexion.

A differentiation is made between anteromedial and anterolateral impingement (Fig. 7.7). On palpation of the anterior joint line, the patient is asked whether this recreates 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 tenderness on palpation is predominantly located anterolaterally, the diagnosis is anterolateral impingement. Forced hyperdorsiflexion can provoke the pain, but this test can be false negative.

Standard anteroposterior (AP) and lateral radiographs are used to detect the presence of osteophytes (Van Dijk et al. 1997a, b). In patients with anterior talar and/or tibial spurs, these spurs are regarded to be the cause of the anterior impingement syndrome. Due to their location, they lead to a “kissing” phenomena and concomitant pinching of hypertrophic synovial tissue (Fig. 7.6). Because of the anteromedial notch (Tol and Van Dijk 2004), anteromedial osteophytes are undetected by standard radiographs in the majority of patients with anterior impingement complaints (Tol et al. 2002). 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 (Tol et al. 2002). Medially located talar osteophytes remain undetected due to overprojection of superposition of the lateral part of the talar neck and body (Tol et al. 2002) (Fig. 7.8).

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 (Ferkel 1996; Ray et al. 1994; Vogler et al. 1994). Especially in patients with accompanying synovial reflections, overlying the concealed osteophytes (Ray et al. 1994), anteromedial bony spurs are poorly visualized arthroscopically and can therefore be missed easily. Radiographic classification of spur formation correlates with the surgical outcome (Ferkel and Fasulo 1994; Van Dijk et al. 1997a, b; Scranton and McDermott 1992). An oblique radiograph was introduced to detect medially located tibial and talar osteophytes. In this oblique anteromedial impingement (AMI) view, the beam is tilted a 45-degree craniocaudal direction with the leg in 30-degree external rotation and the foot in plantar flexion 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 %) (Tol et al. 2004). 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 to detect anteromedial tibial and talar osteophytes (Figs. 2.​8 and 7.8).

The size of spurs is measured on the lateral radiograph. In this projection both malleoli are positioned perpendicular to the surface of the film, and therefore the foot has to be placed in a sagittal angle that can be well over 45°. In this projection, it is the anterolateral part of the distal tibia that is visualized. If an osteophyte is present, it is located anterolateral. The most obscure part of the anterior distal tibial rim is the medial part where the anteromedial tibia border and the anterior rim of the medial malleolus connect. Medial osteophytes of up to 7 mm are undetected on the lateral X-ray. These anteromedially located osteophytes can be detected by means of the so-called AMI view. In this oblique anteromedial impingement (AMI) view, the beam is tilted in a 45-degree craniocaudal direction with the leg in 30° of external rotation and the foot in plantar flexion. The sensitivity of lateral radiographs for detecting anterior tibial and talar osteophytes was 40 and 32 %, respectively (specificity 70 and 82 %) (Ray et al. 1994). When the lateral radiograph was combined with an oblique AMI radiograph, the sensitivity increased to 85 and 73 %, respectively. This increase was 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 only sufficient to detect anterolateral osteophytes. An oblique AMI radiograph is a useful adjunct to routine radiographs and recommended to detect anteromedial tibial and talar osteophytes (Tol et al. 2004).