High Yield Overview

MEDIAL OPENING WEDGE HIGH TIBIAL OSTEOTOMY

Varus correction osteotomy for medial compartment OA | Advanced

Ideal Candidate (FRCS Key Criteria)

Age: Less than 60-65 years (biological age matters)
Activity level: High demand, wishes to return to sport
BMI: Less than 30 (higher BMI = higher failure rates)
Arthritis: Isolated medial compartment (Ahlbäck grade 1-2)
Alignment: Varus malalignment with mechanical axis through medial compartment
ROM: Flexion greater than 90°, full extension (no fixed flexion deformity)
Stability: Intact or reconstructable ligaments
Meniscus: Present medial meniscus (ideally) or concomitant MAT

Specific Indications

Symptomatic medial compartment OA with varus alignment
Post-traumatic medial OA in young patient
Varus thrust gait from ACL deficiency
Combined with ACL reconstruction for chronic varus thrust
Cartilage restoration procedures requiring realignment

Exam Pearl

Examiner Question: "What is the ideal patient for a medial opening wedge high tibial osteotomy?"

Model Answer: "The ideal HTO candidate is a young, active patient (under 60) with isolated medial compartment OA (Ahlbäck grade 1-2) and varus malalignment. Key criteria include: BMI less than 30 (higher BMI has higher failure rates), ROM greater than 90° flexion with full extension (no fixed flexion deformity), stable or reconstructable ligaments, and an intact medial meniscus (or suitable for MAT). The mechanical axis should pass through the medial compartment. This patient typically wants to return to high-impact activities or sport, which makes them unsuitable for arthroplasty at this age. HTO preserves the native joint, allows full activity, and maintains future options for TKA if needed."

Indication Pitfalls

Lateral or patellofemoral OA - absolute contraindication; shifting load will worsen other compartments
Inflammatory arthritis - HTO does not address systemic disease; contraindicated
Overcorrection expectation - HTO improves, not eliminates symptoms; set realistic goals
Ignoring lifestyle - patient unwilling to comply with 3-4 month recovery is poor candidate

Critical Danger Structures

Lateral Hinge

Lateral tibial cortex. Must preserve 5-10mm of intact cortex as the hinge. Hinge fracture is the most common complication (10-30%) - leads to instability and loss of correction.

Saphenous Nerve

Infrapatellar branch. Crosses operative field 2-3cm below joint line posteriorly. Injury causes numbness over anteromedial knee/proximal tibia. Often unavoidable but warn patient.

Popliteal Vessels

Posterior to proximal tibia. Located 1-2cm posterior to posterior tibial cortex. Risk with posterior cortex penetration or aggressive posterior retraction. Catastrophic if injured.

Patellar Tendon

Tibial tubercle insertion. Must protect during osteotomy and plate insertion. Biplanar cut with ascending limb behind tubercle prevents patella baja.

MCL

Superficial MCL insertion. Releases with osteotomy opening - may need to protect/repair. Deep MCL should be preserved for stability.

Mnemonic

F-U-J-I-S-A-W-AFUJISAWA

Memory Hook:The Fujisawa point is the KEY exam concept - 62-66% across tibial width from medial edge (just lateral to center). This shifts the mechanical axis to the healthy lateral compartment.

Mnemonic

H-I-N-G-EHINGE

Memory Hook:Lateral hinge fracture is the most common complication (10-30%). If fracture occurs, may need lateral locking plate or change to alternative fixation strategy.

Surgical Anatomy

Surface Anatomy

Tibial tubercle: Palpable prominence, patellar tendon insertion
Medial tibial plateau: Palpable joint line
Pes anserinus: Insertion 5-7cm below joint line on anteromedial tibia (sartorius, gracilis, semitendinosus)
Gerdy's tubercle: Lateral tibial tubercle, ITB insertion

Key Anatomical Relationships

Structure	Location	Clinical Relevance
Osteotomy level	4-5cm below joint line	Above tibial tubercle, below weight-bearing zone
Lateral hinge	1cm from lateral cortex	Must preserve for stability
Saphenous nerve	Posterior to pes anserinus	Risk of injury with posterior dissection
Popliteal vessels	1-2cm behind posterior cortex	Never penetrate posterior cortex
Superficial MCL	Broad insertion 5-7cm below joint	Releases with opening - self-heals

Osteotomy Plane

Horizontal cut: Parallel to tibial plateau slope, from medial cortex toward fibular head
Ascending cut: Behind tibial tubercle, 135° angle anteriorly
Depth: Stop 10mm from lateral cortex (preserve hinge)
Direction: Aim at superior aspect of fibular head

Positioning and Preparation

Patient Position: Supine on radiolucent table. Sandbag under ipsilateral hip if needed for neutral rotation. Thigh tourniquet. Leg holder or bolster allowing full knee flexion/extension.

C-arm Position: From contralateral side for true AP and lateral views.

Prep and Drape: Entire lower limb from tourniquet to foot. Allow knee flexion during procedure.

Alignment Check: Before incision, verify anatomical landmarks and planned correction on long leg films.

Operative Technique

Step 1: Incision and Exposure

Longitudinal or oblique incision on anteromedial tibia, extending from joint line to 6-8cm distally. Identify and protect the pes anserinus tendons posteriorly. Incise periosteum and reflect anterior to tibial tubercle and posterior to pes anserinus.

Exam Pearl

Technical Pearl: "Anteromedial incision, midway between tibial tubercle and posteromedial border. I identify pes anserinus (remember: SGS - Sartorius, Gracilis, Semitendinosus from anterior to posterior) and keep my dissection anterior to these structures."

Critical Safety Point

Protect infrapatellar branch of saphenous nerve (runs with saphenous vein posteriorly)
Stay subperiosteal to protect soft tissue
Identify MCL for later reference

Step 2: Guide Wire Placement

Place first guide wire from medial cortex, 4-5cm below joint line, aiming toward the tip of the fibular head. Wire should be parallel to the tibial slope (posterior tilt). Confirm position on AP and lateral fluoroscopy - wire should stop 10mm from lateral cortex.

Exam Pearl

Technical Pearl: "My guide wire starts 4-5cm below the joint line on the medial cortex and aims at the fibular head tip. I check AP and lateral fluoro to confirm it's parallel to the joint slope and stops 10mm from the lateral cortex - this is my HINGE."

Critical Safety Point

Wire too proximal risks intra-articular fracture
Wire too distal creates stress riser
Anterior trajectory increases posterior slope
Must preserve 10mm lateral cortex for stable hinge

Step 3: Biplanar Osteotomy Cut

Perform the biplanar osteotomy using oscillating saw:

Horizontal cut: Along guide wire plane, stop 10mm from lateral cortex
Ascending cut: Behind tibial tubercle at 135° angle to horizontal cut, protecting patellar tendon

Complete the osteotomy with thin osteotomes, working carefully toward the hinge.

Exam Pearl

Technical Pearl: "I make a biplanar cut - horizontal along my guide wire stopping 1cm from lateral cortex, then an ascending cut behind the tibial tubercle. This ascending cut protects the patellar tendon and prevents patella baja. I complete the cut with thin osteotomes, never forcing the hinge."

Critical Safety Point

NEVER breach posterior cortex (popliteal vessels)
Keep saw blade cool with irrigation
Use thin, sharp osteotomes for final cut
Do not force opening - will fracture hinge

Step 4: Gradual Opening

Gradually open the osteotomy using calibrated wedge osteotomes. Insert sequentially larger sizes until reaching the planned correction. Monitor for hinge integrity - feel for sudden give indicating fracture.

Exam Pearl

Technical Pearl: "I open gradually with sequential wedges - 5mm, then 8mm, then 10mm, up to my planned opening. I feel for the hinge constantly - any sudden give means fracture. Slow controlled opening over 5 minutes allows viscoelastic stress relaxation."

Critical Safety Point

Rapid forced opening = hinge fracture
Allow 1-2 minutes between sequential wedge sizes
If hinge fractures, need alternative fixation strategy

Step 5: Alignment Verification

Insert alignment rod or cable from hip center (ASIS) through knee to ankle center (midpoint between malleoli). Verify rod passes through Fujisawa point (62-66% across tibial width). Adjust opening as needed.

Exam Pearl

Technical Pearl: "I check alignment with a rod from the hip center (I use the ASIS as proxy) to the ankle center. The rod should pass through the Fujisawa point - 62-66% across the tibial plateau, which is just lateral to center. This ensures I've transferred load to the healthy lateral compartment."

Critical Safety Point

Undercorrection = continued medial overload, early failure
Overcorrection = lateral compartment overload and cosmetic concerns
Document alignment on fluoroscopy

Step 6: Plate Fixation

Apply medial opening wedge locking plate (TomoFix or similar). Secure with proximal and distal locking screws. Insert bone graft if gap exceeds 10mm - autograft, allograft, or synthetic. Confirm final alignment and hardware position on fluoroscopy.

Exam Pearl

Technical Pearl: "I use a TomoFix locking plate with spacer block sized to my opening. Four proximal locking screws, four distal screws. For gaps greater than 10mm, I fill with either iliac crest autograft or allograft chips to promote healing. Final fluoro confirms alignment and screw lengths."

Critical Safety Point

Avoid screws into joint
Check lateral screw lengths (bicortical distally)
Ensure plate does not impinge patellar tendon
Confirm hinge integrity maintained

Step 7: Closure and Post-op Care

Release tourniquet and achieve hemostasis. Close pes anserinus fascia over plate for soft tissue coverage. Layered closure with absorbable deep sutures. Skin closure of choice. Apply compressive dressing and hinged knee brace locked in extension.

Exam Pearl

Technical Pearl: "I close the pes anserinus fascia over the plate for soft tissue coverage - this reduces hardware prominence. Hinged brace for 6 weeks. Protected weight bearing until radiographic healing confirmed at 6-8 weeks."

Closure and Post-op Pitfalls

Not covering plate with soft tissue - exposed hardware causes skin irritation and prominence requiring removal
Full weight bearing too early - before radiographic healing leads to loss of correction or hardware failure
Missing DVT prophylaxis - prolonged immobilisation increases VTE risk; follow local protocol
Ignoring wound complications - early infection requires aggressive treatment to save the osteotomy

Complications

Complications: Recognition and Management

Post-operative Protocol

Immediate Post-op (0-2 weeks)

Hinged knee brace locked in extension
Ice, elevation, analgesia
DVT prophylaxis (LMWH or aspirin per protocol)
Toe-touch weight bearing with crutches/frame
Gentle ROM exercises in brace (0-90°)

Early Rehabilitation (2-6 weeks)

Progressive ROM (target full ROM by 6 weeks)
Continued protected weight bearing
Quadriceps strengthening (straight leg raise, quads sets)
Stationary bike (when ROM permits)
X-ray at 6 weeks to assess healing

Late Rehabilitation (6-12 weeks)

Progress to full weight bearing when radiographic healing confirmed
Wean from brace
Progressive strengthening (closed chain exercises)
Proprioception and balance training
Walking program progression

Return to Activity

Return to sedentary work: 2-4 weeks
Return to physical work: 3-4 months
Return to recreational sport: 6-9 months
Return to competitive sport: 9-12 months

Exam Viva Scenarios

Practice these scenarios to excel in your viva examination

VIVA SCENARIOStandard

EXAMINER

"You suspect a lateral hinge fracture has occurred during opening. How would you manage this intraoperatively?"

EXCEPTIONAL ANSWER

I would stop further opening immediately and assess the situation. First, I'd obtain AP and lateral fluoroscopy to confirm the fracture pattern and assess displacement. If the fracture is stable and the correction is adequate, I would proceed with my planned medial plate fixation but would add a lateral buttress plate to support the hinge side. This typically involves a small lateral incision over the proximal fibula, taking care to identify and protect the common peroneal nerve, and applying a small fragment plate to the lateral proximal tibia. If the fracture is unstable or significantly displaced, I might need to abort the opening wedge and convert to a closing wedge osteotomy, which doesn't rely on an intact hinge. Post-operatively, I would extend the period of protected weight bearing to 10-12 weeks and follow radiographically more closely. I would counsel the patient that healing may be delayed and the risk of delayed union is higher. If the fracture was recognized late and the correction was lost, I would discuss revision options.

VIVA SCENARIOStandard

EXAMINER

"A 45-year-old active man with medial compartment OA and 12° varus asks about HTO vs UKA. How would you counsel him?"

EXCEPTIONAL ANSWER

This is an excellent question for a young active patient. I would explain both options and involve him in shared decision-making. For HIGH TIBIAL OSTEOTOMY: The advantages are preservation of the native joint with potential for cartilage healing, ability to return to high-impact activities and sport, and no restrictions on activity level. He can still convert to TKA later if needed, and the 10-year survivorship is 80-90% with good patient selection. The disadvantages are longer recovery (3-4 months to normal activities), risk of complications including hinge fracture and nonunion, need for crutches and protected weight bearing, and eventual hardware removal in some cases. For UNICOMPARTMENTAL KNEE ARTHROPLASTY: Advantages include faster recovery (typically 6-8 weeks), very reliable pain relief, lower blood loss and complication rates, and can also convert to TKA if fails. Disadvantages are activity restrictions (no high-impact sports recommended), polyethylene wear with time, and younger patients have higher revision rates (may need multiple revisions over lifetime). For this specific patient at 45 with 12° varus and high activity demands, I would RECOMMEND HTO as my first choice, because his age and activity level are ideal for HTO, the correction required is straightforward, and he preserves options for the future. However, if he has other factors like lateral meniscectomy, PFJ symptoms, or is unwilling to accept the longer rehabilitation, UKA would be reasonable.

VIVA SCENARIOStandard

EXAMINER

"Describe your approach to pre-operative planning for HTO. What is the Fujisawa point and how do you calculate your correction?"

EXCEPTIONAL ANSWER

Pre-operative planning for HTO is critical and I follow a systematic approach. IMAGING: I start with long-leg standing radiographs from hip to ankle - these are essential. I also obtain weight-bearing AP and lateral knee views, a Rosenberg view for posterior cartilage assessment, and patellofemoral views to rule out PFJ arthritis. MEASUREMENTS: On the long-leg films, I measure the mechanical axis deviation (MAD) - the perpendicular distance from the knee center to the line connecting hip center to ankle center. I measure the hip-knee-ankle angle and the medial proximal tibial angle (MPTA, normally 87°). THE FUJISAWA POINT: This is my correction target - 62-66% across the tibial width from the medial edge. This means the mechanical axis passes just lateral to center of the tibial plateau. The rationale is to shift load to the healthy lateral compartment while avoiding overcorrection that would overload the lateral side. CORRECTION CALCULATION using Miniaci method: I draw the current mechanical axis (hip center to ankle center). I then mark the Fujisawa point at 62-66% across the tibial plateau. I draw lines from the hip center and ankle center to intersect at this point - these lines meet at the osteotomy site and the angle between them is my required correction. RULE OF THUMB: 1mm of opening equals approximately 1° of correction. So for a typical case needing 10° correction, I plan a 10mm opening. I also plan to preserve the native posterior tibial slope, adjusting my cut direction to maintain this.

References

Fujisawa Y, Masuhara K, Shiomi S. The effect of high tibial osteotomy on osteoarthritis of the knee. An arthroscopic study of 54 knee joints. Orthop Clin North Am. 1979;10(3):585-608.
Lobenhoffer P, Agneskirchner JD. Improvements in surgical technique of valgus high tibial osteotomy. Knee Surg Sports Traumatol Arthrosc. 2003;11(3):132-138.
Staubli AE, De Simoni C, Babst R, Lobenhoffer P. TomoFix: a new LCP-concept for open wedge osteotomy of the medial proximal tibia. Injury. 2003;34 Suppl 2:B55-62.
Spahn G, Hofmann GO, von Engelhardt LV, et al. The impact of a high tibial valgus osteotomy and target mechanical axis realignment on the treatment of knee osteoarthritis: a systematic review. Knee Surg Sports Traumatol Arthrosc. 2013;21(1):96-112.
Brinkman JM, Lobenhoffer P, Agneskirchner JD, et al. Osteotomies around the knee: patient selection, stability of fixation and bone healing in high tibial osteotomies. J Bone Joint Surg Br. 2008;90(12):1548-1557.
Schröter S, Nakayama H, Ihle C, et al. Factors influencing accuracy in high tibial osteotomy. Knee Surg Sports Traumatol Arthrosc. 2019;27(7):2090-2097.
Kim JH, Kim HJ, Lee DH. Survival of opening versus closing wedge high tibial osteotomy: a meta-analysis. Sci Rep. 2017;7(1):7296.
Amendola A, Bonasia DE. Results of high tibial osteotomy: review of the literature. Int Orthop. 2010;34(2):155-160.
Coventry MB, Ilstrup DM, Wallrichs SL. Proximal tibial osteotomy. A critical long-term study of eighty-seven cases. J Bone Joint Surg Am. 1993;75(2):196-201.
Floerkemeier S, Staubli AE, Schroeter S, et al. Outcome after high tibial open-wedge osteotomy: a retrospective evaluation of 533 patients. Knee Surg Sports Traumatol Arthrosc. 2013;21(1):170-180.

Medial Opening Wedge HTO - Exam Summary

High-Yield Exam Summary

Medial Opening Wedge High Tibial Osteotomy