Definitive correction of severe hallux valgus by arthrodesis of a hypermobile 1st TMT joint · advanced
- Primary indication: severe hallux valgus (intermetatarsal angle greater than 18 degrees) with a hypermobile first TMT joint (greater than 9mm of dorsoplantar translation).
- It corrects the deformity at its APEX — the TMT joint — so it is the most anatomically appropriate option for the hypermobile first ray and for metatarsus primus varus, and it eliminates the pathologic mobility that causes recurrence after distal procedures.
- A dorsomedial locking plate plus a plantar-based lag screw is the current gold-standard fixation; modern meta-analysis nonunion is roughly 1 to 5 percent for plated constructs versus about 5 percent for screw-only fixation (older teaching quoted 5 to 8 percent for plates and 10 to 15 percent for screws).
- DORSIFLEXION malunion is the most common technical error and causes devastating transfer metatarsalgia. The medial cuneiform is trapezoid (wider dorsally than plantarly) and gravity actively drives the fusion into dorsiflexion — consciously hold the ray neutral or slightly plantarflexed and ALWAYS check the lateral fluoroscopy view before plating.
- Stay MEDIAL to the EHL tendon: the dorsalis pedis artery and deep peroneal nerve lie 15 to 20mm lateral to the incision, between EHL and EHB.
When & Why
Indication. The Lapidus procedure — arthrodesis of the first tarsometatarsal (TMT) joint — is offered for severe hallux valgus driven by a hypermobile first ray, where a distal osteotomy would correct the toe but leave the apex of the deformity (the TMT joint) mobile and destined to recur. The classic combination is an intermetatarsal angle greater than 18 degrees, a hallux valgus angle greater than 40 degrees, and more than 9mm of dorsoplantar TMT translation, failed conservative care (wide toe-box footwear, orthoses, activity modification), and pain localised to the bunion and midfoot. Why it works where distal procedures fail. A chevron or scarf osteotomy corrects at the metatarsal head; in a hypermobile patient the TMT joint keeps drifting, so the deformity returns. Fusing the TMT removes that mobility entirely, corrects at the true apex, and also addresses metatarsus primus varus and any coexistent TMT arthritis in one step.
Severe hallux valgus (IMA greater than 18 degrees, HVA greater than 40 degrees) with TMT hypermobility greater than 9mm; metatarsus primus varus; revision after failed distal bunion surgery; young active patients (under 50) wanting definitive correction; degenerative TMT arthritis with hallux valgus.
Moderate deformity (IMA 15 to 18 degrees) with clearly demonstrated hypermobility; rheumatoid disease of the first ray; neuromuscular deformity with a dynamic component.
Absolute: active infection, severe peripheral vascular disease (non-palpable pulses, ABI less than 0.5), active Charcot inflammation, non-ambulatory patient. Relative: heavy smoking (nonunion 20 to 30 percent), uncontrolled diabetes (HbA1c greater than 8 percent), severe osteoporosis, spastic neuromuscular disorder, and mild deformity (IMA less than 15 degrees) where a distal procedure is preferable.
Assess the whole ray before committing. On every candidate: - TMT hypermobility test (the decision-critical sign). Stabilise the hindfoot and midfoot with one hand, grasp the first metatarsal head with the other, and dorsally and plantarly translate it. Less than 5mm is normal, 5 to 9mm is borderline, and greater than 9mm is pathologic — the threshold that justifies a Lapidus. Compare with the contralateral side.
- MTP joint. Range of motion (normal dorsiflexion 65 to 75 degrees), sesamoid position (subluxation signals severe soft-tissue imbalance), and hallux pronation.
- Vascular and neurological status — palpable dorsalis pedis and posterior tibial pulses, capillary refill under 2 seconds, and diabetic neuropathy screening. Imaging (weight-bearing AP and lateral are mandatory). Measure the intermetatarsal angle (normal less than 9 degrees; severe greater than 18 degrees) and hallux valgus angle (normal less than 15 degrees; severe greater than 40 degrees); assess TMT arthritis and sesamoid subluxation, and the DMAA (greater than 10 degrees suggests intra-articular deformity, for which an Akin is added). Stress radiographs can demonstrate the hypermobility when clinical findings are equivocal. Correction goals. IMA to less than 10 degrees (aim 5 to 8 degrees); HVA to less than 15 degrees; sesamoids reduced; sagittal alignment neutral or slightly plantarflexed (never dorsiflexed); and first-ray shortening minimised (under 5mm) to avoid transfer metatarsalgia. Consent specifically for: a 6-week strict non-weight-bearing period (10 to 12 weeks to full consolidation), nonunion (5 to 8 percent with a plate, higher in smokers), transfer metatarsalgia (10 to 15 percent if excessive shortening or dorsiflexion), hallux varus from overcorrection (2 to 5 percent), dorsomedial cutaneous nerve injury (5 to 10 percent), hardware removal for prominence (10 to 15 percent), and a 4 to 6 month return to unrestricted activity. Setup. Supine with a small bump under the ipsilateral hip for 15 to 20 degrees of external rotation, foot at the end of a radiolucent table for intra-operative imaging. General or regional anaesthesia (a popliteal block gives excellent post-operative analgesia). Ankle tourniquet at 250mmHg (or thigh at 300mmHg). Fluoroscopy (AP, lateral, oblique), a dorsomedial locking plate system, 3.5mm or 4.0mm lag-screw instrumentation, a sagittal saw with a narrow blade, smooth K-wires, and small curettes and rongeurs.
The Operation
The goal: correct the severe hallux valgus by arthrodesing the first TMT joint — preparing flat, congruent, bleeding surfaces; reducing the metatarsal with lateral translation, derotation and neutral-to-plantarflexed sagittal alignment; and fixing it rigidly with a dorsomedial locking plate and a compression lag screw. The exposure is laid out in full below — stay medial to EHL throughout, and let the lateral fluoroscopy view govern the sagittal plane.
Operative sequence
- Supine, ipsilateral hip bumped to 15 to 20 degrees external rotation; foot at the end of a radiolucent table; ankle tourniquet at 250mmHg after Esmarch exsanguination.
- Prep circumferentially to mid-calf; drape for full foot exposure and fluoroscopy access.
- Palpate the landmarks: the navicular tuberosity (about 3cm proximal to the joint) and the first metatarsal base / TMT joint (3 to 4cm distal to the navicular tuberosity). The EHL tendon is the key safety landmark — the incision stays medial to it.
- A 4 to 5cm dorsomedial longitudinal incision centred over the first TMT joint: start about 2cm proximal to the joint and extend 2 to 3cm distally, over the metatarsal shaft.
- Confirm the joint level by palpation and fluoroscopy if there is any doubt (the intercuneiform joint lies just proximal and is easily confused with the TMT joint).
- Under loupe magnification, incise the subcutaneous tissue carefully. Identify the dorsomedial cutaneous nerve branches — typically two to three small branches that cross dorsally within 2 to 3mm of the incision in about 70 percent of patients.
- Gently retract the branches medially or laterally with vessel loops; avoid aggressive retraction or electrocautery near them. This is the most commonly injured structure (5 to 10 percent).
- Incise the fascia longitudinally and identify the EHL tendon coursing distally and laterally — the safety barrier for the whole case.
- Develop the interval medial to the EHL tendon and retract EHL laterally with a small Hohmann retractor. This keeps you away from the dorsalis pedis artery and deep peroneal nerve, which lie 15 to 20mm lateral to the incision, between EHL and EHB.
- Open the capsule longitudinally along the dorsal and medial aspects, then add transverse limbs to make a T- or H-shaped capsulotomy for maximal exposure; tag the capsule for later repair.
- Place small Hohmann retractors medially and laterally (staying medial to EHL). Avoid excessive plantar retraction — the medial plantar neurovascular bundle sits 10 to 15mm plantar to the joint.
- Confirm the correct level on fluoroscopy (the intercuneiform joint is proximal and is the classic wrong-joint error). Perform a synovectomy to visualise the cartilage surfaces.
- The goal is flat, parallel, congruent surfaces with healthy bleeding cancellous bone and minimal bone resection (under 5mm total, to avoid transfer metatarsalgia).
- Preferred — flat cut technique. With a sagittal saw and narrow blade, make a perpendicular cut removing 2 to 3mm from the metatarsal-base surface and a matching perpendicular cut removing 2 to 3mm from the cuneiform surface, keeping the two surfaces parallel and flat. (A curved concave-convex technique increases surface area but is more demanding and risks instability if non-congruent.)
- Remove every last fragment of cartilage with small curettes; fenestrate the subchondral plate with a rongeur or burr until punctate bleeding from cancellous bone is visible. Use the burr intermittently with irrigation to avoid thermal necrosis — any retained cartilage is a nonunion risk.
- Grasp the first metatarsal distally and: translate it laterally toward the second metatarsal (narrows the IMA); derotate to correct pronation (the hallux should point straight, not rotated); and set the sagittal plane to neutral or slight plantarflexion — never dorsiflexion. Minimise shortening and maintain contact with the lesser metatarsals.
- Hold the reduction with one or two smooth K-wires inserted from the dorsal metatarsal into the cuneiform, aiming plantar-proximal; check the wires do not penetrate the plantar cortex (which would threaten the neurovascular bundle).
- Obtain AP, lateral and oblique fluoroscopy with the K-wires in place, BEFORE plating — correction is far harder after definitive fixation.
- AP: IMA narrowed to less than 10 degrees (aim 5 to 8 degrees), metatarsal base centred on the cuneiform, no varus overcorrection.
- LATERAL — the critical view: the first metatarsal must align with or sit slightly plantar to the lesser metatarsals. Any dorsiflexion seen here must be corrected now. This single view is where the most common technical error is caught.
- Oblique: confirm joint reduction with no interposition. If any malposition is identified, remove the K-wires and reposition.
- Apply a low-profile, anatomic, TMT-specific dorsomedial locking plate spanning the joint — typically a 6-hole plate (three screws proximally in the cuneiform, three distally in the metatarsal). Ensure it sits flush on bone with no medial overhang (a painful prominence is the common reason for later hardware removal).
- Insert the first (usually non-locking) screw in the cuneiform, check fluoroscopy, then the first screw in the metatarsal — this is the last chance to fine-tune position. Complete the remaining locking screws, alternating proximal and distal.
- Measure every screw carefully: proximal screws typically 16 to 22mm, distal 18 to 24mm. Penetration of the plantar cortex risks the neurovascular bundle; penetration of the adjacent joints (naviculocuneiform, intercuneiform, second TMT) must be excluded on imaging. Use bicortical purchase.
- Add a 3.5mm or 4.0mm partially threaded lag screw from the dorsal metatarsal base toward the plantar cuneiform, trajectory dorsolateral to plantarmedial and perpendicular to the fusion plane. Overdrill the near (metatarsal) cortex to generate the lag effect; tighten until the surfaces approximate and compression is felt.
- Place it outside the plate where possible for independent fixation. Measure depth carefully — too long threatens plantar structures, too short loses compression. (A plantar plate is biomechanically superior as tension-side fixation but needs a separate plantar incision; reserve it for revisions or when a dorsal plate is undesirable.)
- Grafting is not routine in primary cases with good bone, but is considered for revisions with a bone defect, osteoporotic bone, smokers (more than 10 cigarettes/day), diabetics, or a gap greater than 2mm after compression.
- Local bone (morselised resected TMT bone) is most common — pack it around the periphery of the fusion AFTER fixation. Iliac-crest autograft is the biologic gold standard for large revision defects but carries donor morbidity; allograft chips or DBM avoid a donor site.
- Never interpose graft between the fusion surfaces — it blocks compression and delays union.
- After TMT fixation, reassess the hallux. The Lapidus usually corrects the whole deformity, but add a distal procedure if residual HVA greater than 15 degrees, DMAA greater than 10 degrees, or hallux valgus interphalangeus persists.
- Akin osteotomy (the common adjunct): a medial closing-wedge osteotomy of the proximal phalanx through a small separate medial incision, fixed with a screw or K-wire.
- Lateral soft-tissue release is rarely needed (correction at the TMT eliminates the tension); extensive circumferential MTP dissection risks metatarsal-head AVN. Avoid excessive medial eminence resection, which weakens the medial column and contributes to hallux varus.
- Final fluoroscopy in three views: AP (IMA less than 10 degrees, hardware well-positioned, no intra-articular screws), lateral (no dorsiflexion, first ray aligned with or plantar to the lesser rays), oblique (reduction and compression confirmed, no interposition).
- Copious irrigation (at least 3L saline); deflate the tourniquet and achieve hemostasis with bipolar cautery.
- Repair the capsule with 2-0 or 3-0 absorbable suture (adds stability), close the subcutaneous layer with 3-0 absorbable, and skin with 4-0 or 5-0 monofilament (interrupted or subcuticular). Apply a non-adherent layer, fluffed gauze, Webril, and a well-padded posterior splint or CAM boot with the ankle neutral — leave room for swelling.
The medial cuneiform is trapezoid — wider dorsally (12 to 15mm) than plantarly (8 to 10mm) — and under anaesthesia gravity pulls the foot into dorsiflexion. Both forces conspire to dorsiflex the fusion. The result, dorsiflexion malunion, offloads the first ray and produces devastating transfer metatarsalgia. Counter it by consciously holding the ray neutral or slightly plantarflexed during reduction and plating, using K-wire provisional fixation, and ALWAYS checking the lateral fluoroscopy view before final fixation. If dorsiflexion is seen on the lateral view, remove the hardware and reposition now — it cannot be corrected once the fusion consolidates except by revision.
From most to least stable: dorsomedial locking plate (plus a plantar-based lag screw) is the modern default and resists dorsiflexion moments best; a plantar plate is biomechanically ideal as tension-side fixation but technically harder; crossed lag screws alone are the historical option with the highest nonunion (around 5 percent, older teaching 10 to 15 percent) and the least resistance to dorsiflexion.
The EHL tendon is the safety barrier for the whole exposure. The dorsalis pedis artery and deep peroneal nerve run 15 to 20mm lateral to the incision, between EHL and EHB. Working in the interval medial to EHL and never dissecting lateral to it protects both — injury to the dorsalis pedis can cause forefoot ischaemia.
Aftercare & Complications
Rehabilitation >
Evidence note on weight-bearing. The traditional 6-week strict non-weight-bearing protocol below remains the safest default and is appropriate for screw-only constructs, osteoporotic bone, smokers and revisions. With a rigid plate (especially plate-plus-plantar-lag-screw or plantar plating), modern series and a systematic review report acceptable nonunion rates (about 3.6 percent) with protected early weight-bearing within 2 weeks. The construct's rigidity — not the timing alone — is the key determinant of union. Tailor the protocol to fixation quality and patient biology. | Phase | Timing | Immobilisation | Milestones | |-------|--------|----------------|------------| | 1 | 0 to 2 weeks | Well-padded posterior splint or CAM boot, ankle neutral | Strict non-weight-bearing; elevation above heart level ~23 h/day; ankle/knee/hip ROM only, no hallux or forefoot motion | | 2 | 2 to 6 weeks | Removable CAM boot | Continue strict non-weight-bearing; wound review and suture removal at 10 to 14 days; 6-week AP/lateral/oblique radiographs (CT if equivocal) — advance only if union is progressing | | 3 | 6 to 12 weeks | CAM boot | Progressive weight-bearing (25 percent to 50 percent to full) in the boot; gentle passive hallux ROM from 8 to 10 weeks; stationary bike without resistance from 8 weeks | | 4 | 3 to 6 months | Supportive wide toe-box shoe | Strengthening (resistance band, heel raises), proprioception, gradual return to impact (walking then jogging then running); no high-impact sport until 4 months, no sport until 6 months | Most patients return to desk work by about 6 weeks and to unrestricted activity by 6 months. Expected long-term outcomes with modern fixation: union 92 to 95 percent, satisfaction 85 to 90 percent, recurrence under 5 percent (fusion eliminates TMT hypermobility), and about 90 percent return to pre-injury sport by 12 months. Consider hardware removal at 12 to 18 months only if it is symptomatic. Complications
- Recognition
- Transfer metatarsalgia under the second to third metatarsal heads developing 3 to 6 months post-op; lateral view shows the first metatarsal elevated relative to the lesser rays; plantar calluses
- Prevention
- Conscious awareness of the trapezoid cuneiform and gravity; mandatory lateral fluoroscopy before final fixation; aim neutral or 5 degrees plantarflexion; assistant holds plantarflexion during plating
- Management
- Mild (under 5 degrees): orthotic with a first-ray cutout. Moderate to severe with symptomatic transfer metatarsalgia: revision — dorsal closing-wedge osteotomy to plantarflex the ray, or revision TMT arthrodesis
- Recognition
- Pain at the TMT beyond 12 weeks, no bridging bone, hardware loosening or breakage; CT at 12 to 16 weeks shows persistent lucency without bridging trabeculae
- Prevention
- Adequate joint preparation (bleeding cancellous bone), rigid plate fixation, minimal resection, smoking cessation, diabetic optimisation (HbA1c under 7 percent), graft in high-risk patients, strict 6-week NWB
- Management
- Asymptomatic and aligned: observe. Symptomatic: revision — remove hardware, refresh sclerotic surfaces, rigid fixation (consider plantar plate), iliac-crest autograft, address risk factors; union after revision 80 to 90 percent
- Recognition
- Pain and calluses under the lesser (usually second to third) metatarsal heads, worse on push-off, as weight-bearing progresses
- Prevention
- Minimise first-ray shortening (under 5mm), avoid dorsiflexion, maintain lateral alignment; address pre-existing lesser-metatarsal overload
- Management
- Conservative first: metatarsal pad, orthotic with first-ray support, activity modification, NSAIDs. Persistent beyond 6 months: Weil osteotomy of the symptomatic lesser metatarsal(s), or first-ray revision if malpositioned
- Recognition
- Hallux deviated medially, shoe-wear difficulty, crossover with the second toe; negative HVA, IMA overcorrected to under 5 degrees
- Prevention
- Target IMA 5 to 8 degrees (not under 5 degrees), assess soft-tissue balance with retractors released, avoid excessive medial eminence resection and aggressive lateral release
- Management
- Flexible: abduction splinting, toe spacer, stretching. Rigid: reverse (lateral closing-wedge) Akin, medial release with lateral reconstruction, or MTP arthrodesis in severe cases
- Recognition
- Numbness or dysaesthesia over the dorsomedial foot, possible painful neuroma; Tinel sign over the scar
- Prevention
- Loupe magnification, identify branches early, gentle vessel-loop retraction, meticulous closure, no electrocautery near the nerve
- Management
- Neuropraxia (most): observe — 80 to 90 percent recover over 3 to 6 months; desensitisation, gabapentin for dysesthesia. Persistent painful neuroma beyond 6 months: excision with nerve burial
- Recognition
- Pain over the dorsomedial plate with shoe pressure, palpable hardware, overlying erythema or bursa
- Prevention
- Low-profile anatomic TMT plate, sit it flush on bone, no medial overhang, countersink screw heads, counsel the patient
- Management
- Shoe modification and donut padding for 3 to 6 months. Persistent: remove hardware only after union is confirmed (minimum 12 months, preferably 18), confirming solid fusion intra-operatively first
- Recognition
- Edge separation, drainage, erythema, delayed healing beyond 3 weeks; worse in diabetes, smoking, PVD
- Prevention
- Meticulous gentle tissue handling and layered closure, smoking cessation 4 to 6 weeks pre-op, diabetic optimisation, well-padded dressing with room for swelling
- Management
- Superficial: local wound care, delayed primary closure or secondary intention. Exposed hardware or deep infection: cultures, IV antibiotics, surgical debridement — retain hardware if fusion incomplete, remove once solid
- Recognition
- Persistent pain, fever, raised inflammatory markers and drainage (deep infection); calf pain/dyspnoea (DVT/PE); allodynia, vasomotor and trophic changes (CRPS)
- Prevention
- Antibiotic prophylaxis and sterile technique (infection); mechanical prophylaxis, early ankle ROM, consider aspirin 325mg in high risk (DVT); minimise trauma, multimodal analgesia, early mobilisation of uninvolved joints (CRPS)
- Management
- Deep infection: debridement, culture-directed IV antibiotics for 6 weeks. DVT/PE: standard anticoagulation. CRPS: multidisciplinary — therapy, sympathetic blocks, gabapentin/tricyclics
Adjacent-joint arthritis (intercuneiform, naviculocuneiform, second TMT) is a long-term concern from altered mechanics; it is usually mild and managed conservatively, with fusion extension reserved for severe symptomatic disease. Recurrent deformity is rare (under 5 percent with sound technique) and usually indicates nonunion or untreated concurrent pathology.
Viva & Exam Focus
LAPIDUSLAPIDUS — when to choose it over a distal procedure
DORSALDORSAL — why dorsiflexion is the most common error
Crosses the dorsal incision 2 to 3mm from the line, multiple branches. Protect with loupe-magnified subcutaneous dissection and vessel-loop retraction. Injury 5 to 10 percent — dorsal foot numbness or neuroma.
Runs between EHL and EHB, 15 to 20mm lateral to the incision, palpable pre-operatively. Stay medial to EHL and palpate the pulse before incision. Injury can cause forefoot ischaemia.
Accompanies the dorsalis pedis laterally, between EHL and EHB. Stay medial to EHL; no blind lateral dissection. Injury causes first-web-space numbness and EHB/EDL weakness.
Lies 10 to 15mm plantar to the TMT joint. Do not extend dissection plantarly past the joint line, avoid excessive plantar retraction, and prevent plantar screw penetration.
The landmark for the whole case. The incision stays medial to it; identify it early and retract laterally with a blunt retractor. Sharp dissection near it risks loss of hallux extension.
Clinical Decision Scenarios
Practise clinical reasoning and management decisions out loud
“A 38-year-old woman has recurrent hallux valgus 3 years after a chevron osteotomy. Her IMA is 22 degrees and you demonstrate 12mm of TMT hypermobility. She wants definitive correction. How do you manage her?”
“After applying your dorsomedial locking plate and obtaining final fluoroscopy, the lateral view shows the first metatarsal elevated 6 to 8 degrees relative to the lesser metatarsals; the AP shows an excellent IMA of 8 degrees. What is the problem, why did it occur, and how will you manage it?”
“What is the evidence comparing plate fixation with crossed lag screws for the Lapidus? If you had to choose one method, which would you use and why?”
Indication
- Severe hallux valgus (IMA greater than 18 degrees, HVA greater than 40 degrees) plus TMT hypermobility greater than 9mm
- Metatarsus primus varus; revision after failed distal surgery; young active patients; degenerative TMT arthritis with hallux valgus
Key anatomy
- First TMT: metatarsal base on the medial cuneiform, which is trapezoid (wider dorsally 12 to 15mm than plantarly 8 to 10mm)
- Dorsalis pedis and deep peroneal nerve: 15 to 20mm lateral to the incision, between EHL and EHB — stay medial to EHL
- Dorsomedial cutaneous nerve: crosses dorsally 2 to 3mm from the incision, multiple branches
- Medial plantar neurovascular bundle: 10 to 15mm plantar to the joint — no plantar dissection past the joint line
Critical steps
- Dorsomedial incision over the TMT; protect the dorsomedial cutaneous nerve; stay medial to EHL
- Flat cuts removing 2 to 3mm per surface, minimal resection (under 5mm), bleeding cancellous bone
- Reduce: translate the metatarsal laterally (IMA to 5 to 8 degrees), neutral or slight plantarflexion
- Provisional K-wires then MANDATORY lateral fluoroscopy before plating
- Dorsomedial locking plate (three-plus-three screws) plus a plantar-based lag screw for compression
The dominant risk
- DORSIFLEXION malunion — most common error, devastating transfer metatarsalgia
- Cause: trapezoid cuneiform plus gravity plus AP-focused correction
- Prevention: hold the ray neutral/plantarflexed, lateral fluoroscopy before final fixation
- Cannot be corrected post-op without revision — fix it on the table
Complications
- Nonunion 5 to 8 percent (plate), around 5 percent (screws, older 10 to 15 percent), 20 to 30 percent smokers
- Transfer metatarsalgia 10 to 20 percent (dorsiflexion or over 5mm shortening)
- Hallux varus 2 to 5 percent (overcorrection); hardware prominence 10 to 15 percent; nerve injury 5 to 10 percent
Post-op
- 0 to 6 weeks strict NWB in boot/splint
- 6 weeks: radiographs (CT if equivocal), advance if union progressing
- 6 to 12 weeks: progressive weight-bearing in the boot; full activity by 6 months
Background & Evidence
Anatomy of the first TMT joint. The first metatarsal base articulates with the medial cuneiform. The joint line runs at about 45 degrees dorsomedial to plantarlateral, and crucially the medial cuneiform is trapezoid — wider dorsally (12 to 15mm) than plantarly (8 to 10mm) — the geometric reason dorsiflexion is the default malposition. Stability comes from the capsule and the dorsal and plantar ligaments; the Lisfranc ligament attaches the medial cuneiform to the second metatarsal base (not to the first). Blood supply is from the dorsalis pedis (laterally), the medial plantar artery (plantarly) and periosteal vessels. Biomechanics and pathology. About half of body weight passes through the first ray at push-off. A hypermobile TMT (normal translation under 5mm; pathologic greater than 9mm dorsoplantar) lets the first metatarsal drift into varus (raising the IMA); the hallux then compensates into valgus. Because distal procedures leave this mobile apex untouched, they recur in the hypermobile patient — the rationale for correcting at the TMT. Hallux valgus angle severity
- Normal
- Less than 9 degrees
- Mild
- 9 to 13 degrees
- Moderate
- 13 to 18 degrees
- Severe
- Greater than 18 degrees
- Normal
- Less than 15 degrees
- Mild
- 15 to 30 degrees
- Moderate
- 30 to 40 degrees
- Severe
- Greater than 40 degrees
Hypermobility assessment. Stabilise the hindfoot and midfoot, grasp the first metatarsal head, and translate dorsally and plantarly: under 5mm normal, 5 to 9mm borderline, greater than 9mm pathologic. Stress radiographs are more reliable than clinical examination alone and confirm the indication when findings are equivocal. Key evidence. Modern meta-analysis (Waehner, 2024) pooled 1,176 first TMT arthrodeses and found construct type — not mobilisation timing — drove failure, with nonunion lowest for plantar plating (0.7 percent) and dorsomedial plating (1.4 percent) and higher for screw-only (5.3 percent); all techniques corrected the deformity equally. Cottom and Vora (2013) reported only 2 nonunions in 88 plate-plus-plantar-screw cases with early weight-bearing from a mean of 11 days. Klos (2010) showed in cadaveric cyclic loading that a medial locking plate plus compression screw resisted plantar gapping and outlasted two crossed screws. Crowell (2018) confirmed in systematic review that protected early weight-bearing within 2 weeks gave an acceptable nonunion rate of about 3.6 percent with a rigid construct — reframing the classic strict 6-week non-weight-bearing dogma. In the revision setting, Ellington (2011) reported union in 24 of 25 feet (96 percent) with good-to-excellent results in 87 percent and a mean first-ray shortening of only 2.9mm.
References
Lapidus Arthrodesis for Hallux Valgus: A Systematic Review and Meta-Analysis (fixation comparison)
- 16 studies, 1176 first TMT arthrodeses pooled across screw-only, dorsomedial plating, and plantar plating cohorts
- Nonunion: 0.7 percent plantar plate, 1.4 percent dorsomedial plate, 5.3 percent screw-only — construct type, not early mobilisation, drove failure
- Overall complication rate 13 percent plantar, 19.5 percent dorsomedial, 24.5 percent screw-only; hardware removal 3.6 percent plantar, 11.8 percent dorsomedial, 7.7 percent screw
- No difference between constructs in IMA or HVA correction or AOFAS score — all techniques correct the deformity reliably
Fixation of Lapidus Arthrodesis with a Plantar Interfragmentary Screw and Medial Locking Plate: 88 Cases
- 88 consecutive patients with a plantar-to-dorsal retrograde lag screw plus low-profile medial locking plate
- Radiographic union in all healed fusions at a mean of 51 days; only 2 nonunions (2 percent)
- Early weight-bearing started at a mean of 11 days post-operatively with satisfactory outcomes
- Hardware removal in 15 patients (17 percent); hallux varus 2 percent; radiographic recurrence 7 percent
Stability of Medial Locking Plate and Compression Screw Versus Two Crossed Screws for Lapidus Arthrodesis (cadaveric biomechanics)
- 8 matched pairs of fresh-frozen specimens tested in four-point bending under cyclic load
- Medial locking plate plus compression screw showed significantly less plantar gapping and more cycles to failure than two crossed screws (p=0.001)
- No difference in bone mineral density or initial stiffness between constructs — the difference emerged under cyclic loading
- Cycles to failure correlated with bone mineral density in both constructs (relevant to osteoporotic patients)
Early Weight-bearing After First Metatarsal-Medial Cuneiform Arthrodesis: Systematic Review of Nonunion
- 8 studies, 443 arthrodeses with a defined early-weight-bearing protocol (weight-bearing within 2 weeks)
- Nonunion in 16 of 443 (3.61 percent) — an acceptable rate despite early loading
- Challenges the historical teaching that Lapidus mandates prolonged non-weight-bearing
- Applies to rigid constructs with adequate fixation; not a blanket endorsement of early loading after suboptimal fixation
The Use of the Lapidus Procedure for Recurrent Hallux Valgus
- 25 feet with recurrent hallux valgus after prior osteotomy, mean follow-up 31.6 months; union in 24 of 25 (96 percent)
- HVA corrected 36.2 to 15.2 degrees and IMA 13.6 to 7.5 degrees (p less than 0.001); mean first-ray shortening only 2.9mm
- 87 percent reported good-to-excellent results; clinical first TMT hypermobility present in 96 percent of revision cases
- Post-operative HVA and change in first-ray length independently predicted quality of life
Hypermobility of the first tarsometatarsal joint: a critical analysis of measurement techniques
Defines pathologic hypermobility as greater than 9mm of dorsoplantar translation and shows stress radiography is more reliable than clinical examination alone — the basis for the greater-than-9mm threshold that underpins the Lapidus indication.
Modified Lapidus procedure for hallux valgus (classic description)
The classic description of the modified technique and indications, emphasising first-ray hypermobility as the key feature that distinguishes the Lapidus from distal realignment procedures.
Modified Lapidus arthrodesis: rate of nonunion in 227 cases
The largest single-series nonunion analysis — 12 of 227 feet (5.3 percent) with screw fixation and joint curettage — identifying smoking, advanced age and diabetes as patient-related risk factors for nonunion.
The modified Lapidus procedure for hallux valgus: a clinical and radiographic analysis
A 93 percent union rate with crossed-screw fixation, with dorsiflexion malunion (18 percent) the most common complication, causing transfer metatarsalgia — the series behind the emphasis on sagittal-plane control.
First metatarsocuneiform arthrodesis with crossed screws or locking plate: a comparative study
Nonunion 12 percent with screws versus 5 percent with plates; hardware removal more common with plates (15 percent) but union superior — direct clinical support for plate-based fixation.
Early weight-bearing after modified Lapidus arthrodesis: a multicenter review of 80 cases
Early weight-bearing (2 to 4 weeks) was safe with rigid plate fixation, with no increase in nonunion or malunion — an early demonstration that construct rigidity, not timing, governs union.
Percutaneous chevron osteotomy versus Lapidus arthrodesis for hallux valgus
The Lapidus was superior for severe deformity (IMA greater than 15 degrees) and the hypermobile first ray, with a lower recurrence rate than chevron osteotomy (2 percent versus 8 percent).