FHL Tendinitis - One Pager
Exam Warning
Examiners expect you to differentiate FHL tendinitis from posterior ankle impingement syndrome and recognize the association with os trigonum. Know the anatomical zones and surgical approaches. Be prepared to discuss the "dancer's tendinitis" and the unique demands of ballet en pointe.
Anatomy and Biomechanics
Clinical Imaging
Imaging Gallery
FHL Tendon Anatomy
The flexor hallucis longus tendon has a complex anatomical course that predisposes it to pathology at specific sites.
Origin and Course
- Origin: Posterior fibula (middle two-thirds) and adjacent interosseous membrane
- Muscle belly: Extends distally to posteromedial ankle, more distal than other deep flexors
- Myotendinous junction: Located at level of ankle joint, unique among flexors
- Fibro-osseous tunnel: Between medial and lateral tubercles of posterior talus
- Sustentaculum tali: Second constriction point under medial talar process
- Master knot of Henry: Tendon slip connection with FDL in midfoot
- Insertion: Base of distal phalanx of hallux (plantar surface)
Three Zones of Pathology
Posterior ankle - fibro-osseous tunnel between talar tubercles. Most common site of stenosis. Under sustentaculum tali - second constriction point with potential impingement. Knot of Henry - adhesions between FHL and FDL can cause triggering.
Biomechanical Considerations
- Excursion: FHL has greatest excursion of any tendon in foot (approximately 3 cm)
- Force transmission: Up to 8 times body weight during push-off phase of gait
- En pointe position: Extreme plantarflexion in ballet increases compression
- Compensatory function: Can augment FDL function for lesser toes
- Windlass mechanism: Contributes to medial longitudinal arch support
Three Tight TunnelsFHL Zones of Pathology
Memory Hook:Remember the THREE zones where FHL gets TIGHT in TUNNELS
Pathophysiology
Mechanisms of Injury
FHL tendinopathy develops through mechanical and inflammatory processes related to anatomical constraints and repetitive loading.
Mechanical Impingement
The fibro-osseous tunnel at the posterior ankle creates a potential site of compression:
- Stenotic tunnel: Congenital or acquired narrowing between talar tubercles
- Os trigonum: Present in 10-25% of population, reduces tunnel space
- Posterior talus anatomy: Prominent tubercles or spurs from impingement
- Sustained plantarflexion: En pointe position in ballet dancers (90+ degrees)
- Repetitive motion: Running push-off and toe flexion activities
Inflammatory Cascade
- Peritendinitis: Initial inflammation of paratenon from mechanical irritation
- Tenosynovitis: Synovial sheath inflammation with effusion
- Tendinosis: Chronic degenerative changes with failed healing response
- Adhesions: Scarring to surrounding structures limits gliding
- Nodular thickening: Focal tendon swelling creates triggering
Associated Pathology
Os Trigonum Syndrome
Accessory ossicle or elongated lateral tubercle causing posterior impingement. May coexist with FHL tendinitis or cause secondary compression of tendon.
Pseudohallux Rigidus
Restricted great toe motion from FHL adhesions rather than MTPJ arthritis. Positive passive but negative active flexion test differentiates from true rigidus.
DANCERS FEETRisk Factors for FHL Tendinitis
Memory Hook:Think of DANCERS and their FEET to remember FHL tendinitis risk factors
Clinical Presentation
History
The clinical presentation of FHL tendinitis has characteristic features that aid in diagnosis.
Symptom Pattern
- Location: Posteromedial ankle pain, may radiate to plantar midfoot
- Character: Deep, aching pain with activity; may have sharp component with triggering
- Timing: Worse with push-off activities, stair climbing, relevé in dancers
- Triggering: Catching or snapping sensation with great toe flexion-extension
- Morning stiffness: Common with inflammatory component
- Night pain: Suggests more severe tendinopathy or associated pathology
Functional Impact
- Ballet dancers: Inability to maintain en pointe position, loss of push-off power
- Runners: Pain during toe-off phase of gait cycle, reduced pace
- Daily activities: Difficulty with stairs, reduced walking tolerance
- Toe flexion weakness: Subjective weakness pushing off or gripping with great toe
- Footwear issues: Tight shoes or heels exacerbate symptoms
Activity-Specific Presentations
Sport-Specific Presentations
| category | keyFeatures | typicalOnset | functionalLoss |
|---|---|---|---|
| Ballet Dancers | En pointe pain, relevé weakness, posterior ankle catching | Gradual with increased rehearsal intensity | Cannot maintain en pointe, loss of elevation |
| Distance Runners | Push-off pain, medial ankle tenderness, reduced stride power | After mileage increase or speed work | Reduced pace, altered gait mechanics |
| Soccer Players | Kicking pain, plantarflexion weakness, shooting difficulty | After intensive kicking drills | Reduced shot power, altered technique |
| Gymnasts | Landing pain, vault push-off difficulty, beam work impaired | With increased tumbling volume | Cannot stick landings, reduced elevation |
Physical Examination
Systematic examination identifies FHL pathology and excludes differential diagnoses.
Inspection
- Swelling: Posteromedial ankle fullness from tenosynovitis
- Muscle atrophy: Rare unless chronic or ruptured
- Foot posture: Assess for cavus alignment or toe deformities
- Gait observation: Antalgic pattern with reduced push-off
Palpation
- Posteromedial ankle: Tenderness posterior to medial malleolus
- Sustentaculum tali: Point tenderness under medial ankle
- Knot of Henry: Plantar midfoot tenderness if zone 3 involvement
- Trigger point: Palpable nodule or thickening with active toe flexion
- Os trigonum: Posterior ankle tenderness if coexistent
Special Tests
Passive ankle dorsiflexion with hallux extension reproduces posterior ankle pain. Sensitivity approximately 75%. Active great toe flexion against resistance elicits pain. Weakness suggests advanced tendinopathy or rupture. Active toe flexion-extension produces palpable catching or audible snap. Indicates nodular thickening or adhesions. Restricted active but normal passive toe motion. Differentiates adhesions from MTPJ arthritis.
Neurovascular Assessment
- Tarsal tunnel signs: Exclude concurrent tibial nerve compression
- Pulses: Document dorsalis pedis and posterior tibial
- Sensation: Medial plantar nerve distribution to hallux
- Compartments: Rule out deep posterior compartment pathology
Exam Pearl
The combination of posterior ankle pain with toe flexion activities, positive FHL stretch test, and triggering with great toe motion is highly specific for FHL tendinitis. Always assess for coexistent os trigonum syndrome as management may require addressing both pathologies.
Investigations
Imaging Studies
A structured imaging approach confirms the diagnosis and identifies associated pathology.
Radiographs
Standard views (weight-bearing preferred):
- AP and lateral foot: Exclude hallux arthritis, sesamoid pathology
- Lateral ankle: Identify os trigonum, posterior talar spurs, soft tissue swelling
- Oblique views: Better visualization of sustentaculum tali anatomy
Key radiographic findings:
- Os trigonum (10-25% prevalence) or prominent lateral tubercle
- Posterior talar spurring from chronic impingement
- Sustentaculum tali abnormalities or calcification
- Cavus foot alignment if contributory
- Soft tissue fullness posteromedial ankle
Ultrasound
Advantages: Dynamic assessment, cost-effective, no radiation
Technique:
- High-frequency linear transducer (12-15 MHz)
- Long-axis and short-axis views of tendon
- Dynamic scanning with active toe flexion-extension
- Comparison with contralateral side
Findings:
- Tendon thickening (normal 3-4 mm diameter)
- Hypoechoic tendinosis or tears
- Peritendinous fluid indicating tenosynovitis
- Reduced gliding with dynamic assessment
- Triggering visible at sites of constriction
- Os trigonum relationship to tendon
MRI
Indications: Uncertain diagnosis, pre-operative planning, suspected rupture
Protocol: Ankle protocol with foot-ankle coil, T1, T2, STIR sequences
Findings:
- Tendinosis: Increased T2 signal within tendon substance
- Tenosynovitis: Fluid surrounding tendon in sheath
- Tear: Partial (high signal with intact fibers) or complete (tendon gap)
- Adhesions: Obliteration of fat planes between tendon and adjacent structures
- Os trigonum edema: Bone marrow edema if symptomatic impingement
- Associated pathology: FDL tendinopathy, tarsal tunnel syndrome
MRI is the gold standard for pre-operative planning when surgery is contemplated. It defines the extent of tendinopathy, identifies the zone(s) of involvement, and reveals associated posterior ankle impingement pathology requiring concurrent treatment.
Diagnostic Injection
- Technique: Ultrasound-guided peritendinous local anesthetic injection
- Purpose: Confirm FHL as pain generator versus other posterior ankle pathology
- Caution: Avoid intratendinous injection due to rupture risk
- Response: Significant pain relief supports diagnosis
- Steroid consideration: May be therapeutic but controversial due to rupture risk
FLARESMRI Findings in FHL Tendinopathy
Memory Hook:FHL tendon shows FLARES on MRI when pathologic
Differential Diagnosis
Conditions to Consider
Several pathologies present with similar posterior ankle or great toe symptoms.
Key Differential Diagnoses
| condition | clinicalFeatures | examination | imaging |
|---|---|---|---|
| Os Trigonum Syndrome | Posterior ankle pain with plantarflexion, nutcracker test positive | Posterior tenderness, pain with forced plantarflexion | Os trigonum on lateral XR, bone edema on MRI |
| Hallux Rigidus | 1st MTPJ pain and stiffness, osteophyte formation | Restricted passive motion, MTPJ tenderness, crepitus | Joint space narrowing, osteophytes on weight-bearing XR |
| Tarsal Tunnel Syndrome | Plantar numbness/tingling, night symptoms, Tinel sign | Tinel posterior to medial malleolus, sensory changes | MRI may show space-occupying lesion, NCS abnormal |
| Posterior Tibial Tendinitis | Posteromedial ankle pain, flatfoot progression, medial swelling | Tenderness posterior to MM, too-many-toes, heel rise weakness | PTT thickening/tear on US/MRI, flatfoot on XR |
| Achilles Tendinopathy | Posterior ankle pain 2-6 cm proximal to insertion | Tendon thickening, arc of pain, positive squeeze test | Tendon thickening, intratendinous signal on MRI |
| Deep Posterior Compartment | Exertional posteromedial leg pain, relieved with rest | Tenderness over deep flexors, reproduction with exercise | Compartment pressure testing diagnostic |
Non-Operative Management
Management Algorithm
Activity Modification
- Relative rest: Reduce or eliminate aggravating activities for 4-6 weeks
- Cross-training: Maintain fitness with low-impact alternatives (cycling, swimming)
- Gradual return: Progressive loading protocol over 8-12 weeks
- Technique modification: Address biomechanical errors (en pointe mechanics in dancers)
- Training load management: Avoid rapid increases in volume or intensity
Immobilization
- CAM boot: 2-4 weeks for severe cases to reduce tendon excursion
- Night splint: Maintain ankle-foot position preventing extreme plantarflexion
- Taping: Kinesiology tape or athletic strapping to limit motion
- Duration: Minimum immobilization necessary to avoid stiffness
Pharmacological Interventions
- NSAIDs: Oral (naproxen 500 mg BD) or topical for anti-inflammatory effect
- Duration: 2-4 week courses, monitor for GI or renal side effects
- Analgesics: Paracetamol or tramadol for pain control if NSAIDs contraindicated
- Topical treatments: Ice massage along tendon course for 15-20 minutes
Physical Therapy
Phase 1 (0-2 weeks): Pain and inflammation control
- Ice therapy, gentle range-of-motion exercises
- Soft tissue mobilization avoiding direct tendon pressure
- Intrinsic foot muscle strengthening to reduce FHL demand
Phase 2 (2-6 weeks): Progressive loading
- Eccentric strengthening program (proven efficacy in tendinopathy)
- Calf stretching to address equinus if present
- Tendon gliding exercises to prevent adhesions
- Progressive weight-bearing as tolerated
Phase 3 (6-12 weeks): Return to activity
- Sport-specific rehabilitation (en pointe progression for dancers)
- Plyometric exercises for runners
- Proprioceptive training on unstable surfaces
- Gradual return to full activity with load monitoring
Injection Therapy
Corticosteroid injections for FHL tendinopathy are controversial. While they may provide short-term symptomatic relief, they carry a risk of tendon rupture and should be used cautiously. Ultrasound guidance is essential to avoid intratendinous injection. Consider no more than 1-2 injections separated by at least 3 months.
Injection options:
- Peritendinous corticosteroid: Methylprednisolone 40 mg with local anesthetic
- Ultrasound guidance: Mandatory to ensure accurate placement
- Post-injection protocol: Relative rest 2 weeks, gradual return to loading
- Alternative: PRP or autologous blood injection (limited evidence)
Orthotic Management
- Custom orthotics: Control excessive pronation or cavus mechanics
- Heel lift: Reduce Achilles tightness and secondary FHL overload
- Metatarsal pad: Offload great toe if contributory deformity
- Footwear modification: Adequate toe box, rigid sole for dancers
Conservative Management Outcomes
Retrospective cohort of 87 patients with FHL tendinitis treated conservatively showed 73% good-to-excellent outcomes at 1 year with structured physiotherapy program including eccentric exercises. Success was higher in non-dancers (82%) versus professional ballet dancers (61%). Median time to return to sport was 14 weeks. Poor prognostic factors included duration of symptoms greater than 6 months and presence of triggering.
Operative Management
Surgical Indications
Surgery is indicated when conservative management fails after appropriate duration and compliance.
Indications for Surgery
- Failed conservative treatment: Minimum 3-6 months of appropriate non-operative care
- Persistent symptoms: Pain limiting activities of daily living or sport
- Triggering: Mechanical symptoms suggesting nodular thickening or adhesions
- Professional athletes: Earlier surgery for elite performers with career impact
- Structural pathology: MRI evidence of tendon tear, severe stenosis, or os trigonum requiring excision
Pre-Operative Assessment
- MRI review: Define zones of involvement, extent of tendinopathy, associated pathology
- Patient expectations: Realistic goals for return to high-level activity
- Optimize health: Address smoking, diabetes, inflammatory conditions
- Surgical planning: Open versus endoscopic approach based on pathology
Surgical Techniques
Posteromedial Approach
Patient Positioning:
- Supine with bump under ipsilateral hip for external rotation
- Tourniquet on thigh (controversial - may impair visualization)
- Ensure access to medial ankle and hindfoot
Surgical Steps:
1. Incision and Exposure:
- Longitudinal incision 8-10 cm along posteromedial ankle
- Centered between medial malleolus and Achilles tendon
- Identify and protect saphenous vein and nerve
- Incise flexor retinaculum to expose FHL tendon sheath
2. Tendon Identification:
- FHL is most posterior of the three tendons (Tom, Dick, and Harry)
- Confirm by passive hallux flexion-extension producing tendon excursion
- Open tendon sheath along entire zone of pathology
- Inspect for tenosynovitis, nodular thickening, partial tears
3. Decompression:
- Release fibro-osseous tunnel at posterior ankle (between talar tubercles)
- Excise thickened or diseased sheath tissue
- Perform synovectomy if significant inflammation present
- Release constriction at sustentaculum tali if zone 2 involvement
- Confirm smooth gliding with full passive toe motion
4. Os Trigonum Excision (if indicated):
- Identify os trigonum or prominent lateral tubercle
- Protect FHL tendon during dissection
- Excise ossicle with rongeur or osteotome
- Smooth bony surfaces to prevent recurrent impingement
5. Tendon Treatment:
- Debride partial tears (preserve greater than 50% width)
- Tubularize if significant longitudinal split
- Consider FDL transfer if greater than 50% tendon involved
- Repair tear with non-absorbable suture if acute
6. Closure:
- Do not repair tendon sheath (prevent recurrent stenosis)
- Close flexor retinaculum loosely
- Layered skin closure with absorbable sutures
- Soft dressing or posterior splint in neutral position
Post-Operative Protocol:
- 0-2 weeks: Posterior splint, non-weight bearing, gentle toe ROM
- 2-6 weeks: CAM boot, progressive weight-bearing, active toe flexion exercises
- 6-12 weeks: Wean from boot, progressive strengthening, gait normalization
- 3-6 months: Return to sport protocol, gradual return to full activity
- Professional dancers: 4-6 months before returning to en pointe work
The neurovascular bundle (tibial nerve, posterior tibial vessels) lies anterior to the FHL tendon sheath. Use meticulous dissection and avoid excessive retraction. The medial calcaneal branch of tibial nerve is at risk with distal extension. Protect neurovascular structures throughout the procedure.
Open versus Endoscopic FHL Release
Systematic review of 18 studies (412 patients) comparing open and endoscopic FHL release. Both techniques showed excellent outcomes with 90-95% good-to-excellent results. Endoscopic approach had faster return to sport (median 12 weeks vs 18 weeks for open) and lower complication rates (3.2% vs 8.1%). Open surgery allowed better treatment of multi-zone pathology and tendon tears. No significant difference in recurrence rates at minimum 2-year follow-up.
Complications
Surgical Complications
Understanding potential complications is essential for informed consent and management.
Intraoperative Complications
- Neurovascular injury: Tibial nerve or posterior tibial vessels (1-2% risk)
- Medial calcaneal nerve injury: Heel numbness, avoid distal dissection
- FHL tendon laceration: Can occur during release, requires immediate repair
- Incomplete release: Inadequate decompression leading to persistent symptoms
- Excessive bone removal: Over-aggressive os trigonum excision destabilizing ankle
Early Post-Operative Complications
Common Early Complications
| complication | incidence | management | prevention |
|---|---|---|---|
| Wound Infection | 2-3% open surgery, less than 1% endoscopic | Oral antibiotics for superficial, I&D for deep infection | Perioperative antibiotics, sterile technique, careful handling |
| Hematoma | 3-5%, higher without tourniquet | Observation if small, evacuation if large or expanding | Meticulous hemostasis, compressive dressing, elevation |
| DVT/PE | Less than 1% with standard prophylaxis | Anticoagulation per protocol, may require admission | Early mobilization, chemical prophylaxis if high risk |
| Sural Nerve Injury | 1-2% with posterolateral portal | Observation, most resolve within 3-6 months | Careful portal placement, avoid excessive dissection |
Late Complications
- Persistent pain: 5-10% of cases, may indicate incomplete decompression or adhesions
- Recurrent stenosis: Rare if sheath not repaired, may require revision surgery
- Tendon adhesions: Loss of excursion requiring repeat release
- FHL weakness: Typically improves with rehabilitation, persistent in severe tendinosis
- Stiffness: Ankle or toe stiffness from prolonged immobilization
- Complex regional pain syndrome: Rare but devastating complication (less than 1%)
- Keloid scar: Hypertrophic scar formation, more common in open approach
Failure Management
Diagnostic approach to failed surgery:
- Repeat MRI to assess adequacy of decompression
- Dynamic ultrasound for persistent triggering
- Consider alternative diagnoses (tarsal tunnel, posterior impingement)
- Assess rehabilitation compliance and technique
Revision surgery indications:
- Confirmed incomplete decompression on imaging
- Recurrent stenosis with objective evidence
- Persistent triggering from adhesions
- New or missed pathology (os trigonum, zone 2/3 stenosis)
Revision technique:
- More extensive release of all three zones
- Thorough debridement of scar and adhesions
- Consider FHL to FDL transfer if severe tendon damage
- Address any concurrent pathology
- Extended post-operative rehabilitation protocol
Complications of FHL Surgery
Retrospective review of 156 FHL surgical releases (78 open, 78 endoscopic) identified overall complication rate of 6.4%. Complications included transient nerve paresthesias (2.6%), wound healing problems (1.9%), persistent pain (1.3%), and infection (0.6%). Endoscopic surgery had lower overall complication rate (3.8% vs 8.9% for open). No cases of tendon rupture or neurovascular injury occurred. Most complications resolved with conservative management.
Return to Sport and Outcomes
Expected Outcomes
Prognosis for FHL tendinitis depends on treatment modality, sport demands, and chronicity.
Non-Operative Treatment Outcomes
- Success rate: 70-75% achieve good-to-excellent results with conservative care
- Time to improvement: 3-6 months for significant symptom reduction
- Return to sport: 60-70% return to pre-injury level by 6 months
- Recurrence: 10-15% develop recurrent symptoms, especially without technique modification
Surgical Outcomes
Good-to-excellent outcomes after surgical decompression in appropriately selected patients.
Time to return to full unrestricted sport activity after endoscopic release.
Persistent symptoms requiring revision surgery or ongoing conservative management.
Sport-Specific Return to Play
Return to Sport Timeline
| sport | nonOperative | openSurgery | endoscopic | prognosis |
|---|---|---|---|---|
| Ballet (Professional) | 4-6 months to full performance, technique modification essential | 6-9 months to en pointe, 9-12 months to full performance | 4-6 months to en pointe, 6-9 months to full performance | 61% return to pre-injury level (most challenging) |
| Distance Running | 3-4 months to full training volume | 4-6 months to competitive racing | 3-4 months to competitive racing | 85% return to pre-injury level |
| Soccer | 3-4 months to full team training | 4-5 months to competitive play | 3-4 months to competitive play | 80% return to pre-injury level |
| Recreational Athletes | 2-3 months to return to activity | 3-4 months to full activity | 2-3 months to full activity | Greater than 90% return to desired activity level |
Prognostic Factors
Favorable predictors:
- Symptom duration less than 6 months
- No triggering or mechanical symptoms
- Recreational athlete versus professional
- Good compliance with rehabilitation
- No associated pathology (os trigonum, tarsal tunnel)
Poor prognostic factors:
- Symptom duration greater than 12 months
- Professional ballet dancer requiring en pointe work
- Presence of triggering indicating nodular thickening
- Multiple zones of involvement
- Previous failed surgery
- Worker's compensation or litigation issues
Long-Term Outcomes After FHL Surgery
Prospective cohort study of 94 patients (102 feet) undergoing FHL surgery with minimum 5-year follow-up. AOFAS scores improved from mean 62 pre-operatively to 91 at final follow-up. 88% of patients returned to their desired sport, with 76% achieving pre-injury performance level. Professional dancers had lower return rates (64%) compared to other athletes (92%). Satisfaction was high with 91% stating they would undergo surgery again.
Exam Viva Scenarios
Practice these scenarios to excel in your viva examination
Scenario 1: Professional Ballet Dancer with FHL Tendinitis
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Scenario 2: Failed FHL Surgery
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FHL Tendinitis Exam Essentials
High-Yield Exam Summary
Must-Know Anatomy
- •FHL origin: posterior fibula middle two-thirds
- •Three zones: (1) talar tunnel, (2) sustentaculum, (3) knot of Henry
- •Greatest tendon excursion in foot: 3 cm
- •Myotendinous junction at ankle level (unique among flexors)
- •Neurovascular bundle anterior to FHL (tibial nerve, PT vessels)
Classic Presentation
- •Professional ballet dancer or distance runner
- •Posteromedial ankle pain with push-off activities
- •Triggering with great toe flexion-extension
- •Positive FHL stretch test (dorsiflexion + hallux extension)
- •May have pseudohallux rigidus from adhesions
Key Investigations
- •Clinical diagnosis primarily
- •XR: lateral ankle for os trigonum (10-25% prevalence)
- •Ultrasound: dynamic assessment shows triggering
- •MRI: gold standard pre-op - shows tendinosis, synovitis, zones involved
- •Os trigonum bone edema suggests concurrent impingement syndrome
Management Algorithm
- •Conservative first: 3-6 months activity modification, physio, NSAIDs
- •Eccentric strengthening proven effective in tendinopathy
- •Steroid injection controversial - rupture risk, max 1-2 injections
- •Surgery if failed conservative: endoscopic (zone 1) vs open (multi-zone)
- •FHL to FDL transfer salvage for irreparable tears greater than 50%
Surgical Pearls
- •Open approach: posteromedial, release all involved zones, DO NOT repair sheath
- •Endoscopic: prone position, posterolateral and posteromedial portals
- •Protect neurovascular bundle throughout procedure
- •Excise os trigonum if symptomatic impingement coexists
- •Post-op: early ROM to prevent adhesions, 4-6 months to en pointe work
Viva Traps
- •Don't promise quick return to sport - ballet dancers need 6-9 months minimum
- •Recognize endoscopic limitations for zone 2/3 pathology
- •Multiple steroid injections contraindicated - rupture risk
- •Professional dancers have lower success rates (61% vs 85% recreational)
- •Failed surgery: assess zone adequacy on MRI, may need open revision
Critical Numbers
- •Conservative success: 70-75% good-to-excellent outcomes
- •Surgical success: 90-95% with appropriate patient selection
- •Return to sport: 12-24 weeks endoscopic, 18-30 weeks open
- •Professional ballet: 6-9 months to full performance
- •Complication rate: 3-4% endoscopic, 8-9% open approach