Jones Tendon Transfer (EHL to First Metatarsal)

Indication. A symptomatic claw hallux (flexible IP hyperextension with MTP flexion) occurring together with weak ankle dorsiflexion — most commonly the Charcot-Marie-Tooth (CMT) cavovarus foot, but also anterior compartment syndrome sequelae or any partial tibialis anterior weakness — where a single functioning EHL can be sacrificed. Flexible hallux IP hyperextension greater than about 20 degrees causing painful callosities is the typical trigger. Why this transfer works. By moving the EHL insertion from the distal phalanx to the first metatarsal neck, the tendon's pull now dorsiflexes the ankle (and the first ray) instead of hyperextending the IP joint. Fusing the IP joint removes the deforming force entirely. One tendon therefore corrects two problems: the claw, and the weak dorsiflexion. Contraindications. A fixed MTP deformity (address with an osteotomy first), a non-functioning EHL (no donor tendon — consider a Bridle procedure or AFO), or normal tibialis anterior power with an isolated claw (use EHL lengthening or an EHL-to-MTP capsule transfer instead — see below). The Jones transfer is also only a partial dorsiflexion substitute and is inadequate for a complete anterior compartment palsy. The decision: which claw-hallux operation? Match the procedure to the deformity and to the tibialis anterior power.

In the CMT foot the Jones transfer is one component of a multi-level reconstruction, staged as needed: a Dwyer calcaneal osteotomy for hindfoot varus, a peroneus longus-to-brevis transfer for first-ray plantarflexion, the Jones transfer for the claw hallux and dorsiflexion, and lesser-toe flexor-to-extensor (Girdlestone-Taylor) transfers for claw toes. Counselling must stress that CMT is progressive — the operation balances the foot, it does not cure the neuropathy. Setup. Supine with a sandbag under the ipsilateral hip, foot at the end of the table for access; thigh tourniquet. Mark both incisions with the foot held in the corrected position before exsanguination, as the landmarks become harder to palpate once the limb is bloodless.

The goal: through two dorsal incisions that are never connected, harvest the EHL off the distal phalanx, fuse the IP joint, create a bone tunnel through the first metatarsal neck, pass the EHL through it, and set the tension at ankle neutral so the hallux rests corrected and dorsiflexion is augmented. The exposure and the tensioning are the two steps that decide whether the operation works.

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Rehabilitation | Phase | Timing | Immobilisation | Therapy | |-------|--------|----------------|---------| | 1 | 0-2 weeks | Below-knee cast, ankle neutral, hallux in 10-15 degrees plantarflexion, non-weight-bearing | Toe mobilisation only; elevation 48-72 hours | | 2 | 2-6 weeks | Cast, progressive weight-bearing | Wound check at 2 weeks; nothing active | | 3 | 6-10 weeks | CAM boot if IP fusion progressing on 6-week radiograph | Gentle ankle and MTP range of motion; IP stays fused | | 4 | 10-16 weeks+ | Stiff-soled shoe; night splint if needed | Dorsiflexion strengthening, gait training, proprioception | Most patients return to regular shoes at 3-4 months and to full unrestricted activity at 4-6 months once IP fusion is confirmed. Expect a permanent IP fusion (no IP motion), improved ankle dorsiflexion and a corrected claw deformity. CMT patients need yearly follow-up to monitor disease progression. If IP fusion is not evident at 12 weeks, consider a bone stimulator, prolonged immobilisation, or revision fusion with bone graft. Complications

Pathoanatomy of the CMT cavovarus foot. Charcot-Marie-Tooth disease is a hereditary motor sensory neuropathy (HMSN type I most common) with progressive distal weakness in a "dying-back" pattern. The selective muscle imbalance produces the classic cavovarus triad: hindfoot varus (tibialis posterior relatively preserved and unopposed), first-ray plantarflexion (peroneus longus preserved while peroneus brevis weakens, so the longus is unopposed), and claw hallux and lesser toes (intrinsic weakness). Peroneal weakness (tibialis anterior and EHL) produces the drop foot and the hallux clawing that the Jones transfer addresses. Tibialis posterior is relatively spared, which is why it can be harvested for a Bridle procedure in complete palsy. The EHL: anatomy and why it is expendable. The extensor hallucis longus arises from the middle two-fourths of the anterior fibula and adjacent interosseous membrane, is innervated by the deep peroneal nerve (L5), and inserts on the dorsal base of the distal phalanx of the hallux. Its primary action is IP extension, with secondary MTP extension and weak ankle dorsiflexion. The tendon is round in the leg, flattens distally, and runs between extensor digitorum brevis medially and extensor digitorum longus laterally on the dorsum of the foot. Once the IP joint is fused, the EHL's IP extension function is sacrificed without functional loss, the MTP and ankle extension is preserved by EDL and EDB, and moving the insertion to the metatarsal neck actually augments ankle dorsiflexion — which is precisely what makes it a suitable donor. Assessment — the Coleman block test. Flexibility is decisive. The Coleman block test assesses whether the hindfoot varus is driven by the plantarflexed first ray (flexible — the hindfoot corrects when the first ray is blocked) or is fixed. A Jones transfer is a soft-tissue-balancing operation suited to a flexible, correctable deformity; a rigid foot needs osteotomies or arthrodesis. Published outcomes. The Jones procedure is almost always reported as one component of a combined flexible-cavovarus reconstruction rather than in isolation, so outcome data reflect the package (plantar release, first metatarsal dorsiflexion osteotomy, peroneus longus-to-brevis transfer, and EHL-to-metatarsal transfer with IP fusion). The figures below are taken directly from the cited PubMed-verified studies. - Faldini, Giannini et al. (2015) — 24 feet in 12 CMT patients, mean follow-up 6 years: combined plantar fasciotomy, midtarsal osteotomy, Jones EHL transfer and first metatarsal dorsiflexion osteotomy in flexible feet. Maryland Foot Score improved from 72 to 86 (excellent in 50 percent, good in 42 percent, fair in 8 percent); Meary angle corrected from 25 degrees to 2 degrees and was maintained. The authors attribute the only modest score gain to residual motor imbalance, not loss of correction.

• Ward, Dolan et al. (2008) — 25 patients, 41 feet, mean follow-up 26.1 years: the longest follow-up of an EHL-to-first-metatarsal-based reconstruction. Cavus correction was well maintained; some radiographic recurrence of hindfoot varus was common but no patient required triple arthrodesis. Seven patients (8 feet) needed at least one further foot or ankle operation, with lower reoperation and degenerative-change rates than historical triple-arthrodesis series; smoking strongly predicted worse pain and disability scores.
• Sammarco and Taylor (2001) — 21 feet in 15 patients with neuromuscular cavovarus: a joint-sparing osteotomy strategy (calcaneal plus metatarsal) with which the Jones transfer is frequently combined. AOFAS ankle-hindfoot improved from 46 to 91 and midfoot from 41 to 89; all patients became brace-free; nonunion in 3 of 66 metatarsal osteotomies. The consistent message. In a flexible, arthritis-free CMT foot, the Jones transfer combined with joint-sparing osteotomies gives durable deformity correction and supports a joint-preserving, soft-tissue-balancing strategy over early arthrodesis — but it balances the foot, it does not cure the progressive neuropathy.

Further reading 1. Jones R. The soldier's foot and the treatment of common deformities of the foot. BMJ 1916;1:749-753. 2. Hansen ST. Functional reconstruction of the foot and ankle. Lippincott Williams and Wilkins; 2000. 3. Holmes JR, Hansen ST. Foot and ankle manifestations of Charcot-Marie-Tooth disease. Foot Ankle 1993;14:476-486. 4. Schwend RM, Drennan JC. Cavus foot deformity in children. J Am Acad Orthop Surg 2003;11:201-211. 5. Chan G, Sampath J, Miller F, et al. The role of the dynamic pedobarograph in assessing treatment of cavovarus feet in children with Charcot-Marie-Tooth disease. J Pediatr Orthop 2007;27:510-516.