Fig. 47.1
Types of accessory navicular bone
The incidence and frequency of types varies according to geographical and age group population studies. Corkun et al. found 11 % of 650 Turkish adult displayed radiographic appearance of accessory navicular bone with similar distribution within the three types (33 %, 31 % and 46 % respectively) [2].
In a study of 148 patients younger than 18 year old with accessory navicular bone in Korea, there were more patients exhibiting Type 2 variant (76 % vs 15 % Type 1, 9 % Type 3) and 87 % of patients had bilateral accessory navicular bone [3].
Why Does It Become a Problem?
There are arguments for a traumatic origin with repetitive chronic stress. Histological examination showed areas of microfracture with acute and chronic inflammation and tissue cellular proliferation around the synchondrosis [4]. In this case, the accessory navicular bone is acting as an irritant. On the other hand, there are also proponents of an inbuilt anatomical anomaly or abnormal posterior tibialis tendon insertion with abnormal tissue between the accessory and navicular bones [5].
Accessory navicular bone can become symptomatic with or without trauma [6, 7]. Pain is usually over the enlarged area of accessory navicular on the medial aspect of foot just at the insertion of posterior tibialis tendon. Tight shoes, walking and exercise exacerbate pain. There is increased pain with resisted inversion of the foot.
External oblique (medial to lateral) plain radiograph complements the dorsoplantar view in diagnosing the accessory navicular bone. Magnetic resonance imaging is sensitive in showing marrow oedema in symptomatic adolescents. The marrow oedema also diminishes following the relief of symptoms after non-operative management [8]. Technetium bone scan is sensitive in showing increased tracer uptake but not specific because half of asymptomatic patients demonstrate the similar features of symptomatic patients [9].
How to Treat Symptomatic Accessory Navicular Bone
Non-operative Management
Non-operative management including symptomatic management in the form of soft pads between the foot and sole of shoe, footwear modification, physiotherapy, orthoses to off-load midfoot and oral anti-inflammatory can be effective even for active adolescent [10–12]. Non-operative treatments are usually individualised according to patient and provider factors and there is no known literature on the most effective or widely agreed non-operative protocol or comparison against operative treatment. Most authors tried at least three months of non-operative management before proceeding with surgery [6, 7, 12–17].
Injection
We could not find published English literature using digital search engines on the topic of efficacy of injection in the management of symptomatic accessory navicular bone.
Surgery
Surgery aims to improve pain by removing the accessory bone or stabilising the synchondrosis and protecting the posterior tibialis tendon. Most common accessory navicular bone requiring surgery was Type 2. Table 47.1 summarises the references discussed below.
Table 47.1
Surgical treatment of symptomatic accessory navicular bone
Studies | Study type | No. of patients | Age (Y) | Accessory navicular type | Onset to surgery (month) | Preop mx duration (month) | Surgery | Follow up | Outcomes | Notes |
|---|---|---|---|---|---|---|---|---|---|---|
Bennett 1990 | n/a | 50 (38F:12M) 75 ft (56F:19M) | 12.6 (8–18) | 2 (77 %) 3 | n/a | >6 | Excision of accessory bone or prominent cornuate navicular + postop cast 2 w in equinovarus | 2–22 y | 77 % ‘excellent’ 16 % ‘good’ 4 % ‘fair’ 3 % ‘poor’ All females able to wear high heels | 20 FFF 8 % residual prominence, 1 % neuroma, 5 % superficial inflammation, 7 % scar problems |
Kiter 2000 | n/a | 17 (13F: 4M) | 14–36 | 2 | Chronic | n/a | Excision and rasping of remaining bone + postop cast 2 w | 3 y (2–5 y) | 11 patient no pain, no restriction of activity, no shoewear modification | Inability to single-heel raise persist postop in flatfoot |
Jasiewicz 2008 | n/a | 22 (17F: 5M) 34 ft | 14 (9–22) | 1, 2 (50 %), 3 | n/a | 3 | Excision +/− PTT reattachment + supinating insoles 4 w | 5.6 y (1–13 y) 1 lost to f/u | Improved VAS in all except 1 pt. unchanged in pain and shoewear | Single heel rise test positive pre and post in all cases 2 prolonged wound healing |
Prichasuk 1999 | n/a | 28 (20F: 8M) 31 ft | 23 (11–38) | 2 | n/a | >6 | Kidner + cast 6 w + insoles 6 m | 3.2 y (1–14 y) | 27 pts ‘good’ results | 3/25 FFF improved arch |
Lee 2012 | Retrospective | 41 (8F: 33M) 50 ft | 20 (8–48) | 2 | n/a | 6, (7 athletes straight to surgery) | Modified Kidner +cast 6 w | 5 y | Improved AOFAS midfoot | |
Macnicol 1984 | Retrospective | 47 62 ft | 10–50 | n/a | 33 (3 m–19 y) | n/a | Kidner (bilateral), n = 26 + postop cast 6 w, vs. excision, n = 21 Both groups have FF | Kidner 10 y (3–19 y) Excision 12 y (3–20 y) | Kidner – 19/22 FFF pain relieved, 14 shape improve Excision – in those aged 11–12, 15 with normal feet pain free, 4/5 in FFF painfree | 4 recurrent AN in cases without trimming of navicular tuberosity with 1 persistent pain Kidner patient also report protracted medial pain postop |
Cha 2013 | Prospective, non randomised | 50 (29F:21M) 50 ft | 9–15 | Unilateral Type 2 +FFF | 9.3–10.4 | >6 | Excision, n = 25 + supinating insoles vs. Kidner, n = 25 + casting | 36–52 m | Improved AOFAS midfoot scale and VAS, both groups not statistically different | Similar restoration of medial longitudinal arch in two groups |
Pretell-mazzini 2014 | Retrospective | 27 (22F: 5M) 32 ft | 13.2 (9–16) | 1, 2 (75 %), 3 | 10 (2–36) | n/a | Excision, n = 14 vs. Kidner, n = 18 (both postop cast 4–6 w) Similar distribution FF both groups | n/a | 87.5 % (93 % excision, 83 % Kidner) Good-to-excellent function (no significant difference between 2 groups) | 1 tendon Achilles lengthening and lateral column lengthening More complications (painful scar, tendinitis) and reoperation after tendon advancement, but not statistically significant |
Scott 2009 | Prospective, non-randomised
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