High Yield Overview

TOTAL KNEE ARTHROPLASTY FOR VALGUS DEFORMITY

Medial or lateral parapatellar approach | Systematic lateral release | Balance before resection

Mnemonic

LATERAL - Valgus Release Sequence

Mnemonic

TYPE - Krackow Classification

Critical Danger Structures

Danger 1

Common peroneal nerve. Location: Around fibular neck, 2-3cm from lateral joint line. At HIGH RISK with lateral releases and retraction. Protect with bent-knee positioning and gentle retraction.

Danger 2

Popliteal neurovascular bundle. Location: Posterior knee, 5mm from posterior capsule at 90° flexion. Protect with careful posterior capsule release and avoid deep retractors.

Danger 3

Lateral collateral ligament. Location: Lateral femoral epicondyle to fibular head. Release from femur if needed - preserve fibular attachment for some constraint.

Danger 4

Medial collateral ligament. Location: Medial femoral epicondyle to proximal tibia. PROTECT - attenuated in valgus knees. Avoid medial retraction and aggressive manipulation.

Danger 5

Lateral genicular artery. Location: Courses around lateral femoral condyle. May be injured with lateral release - have diathermy ready for hemostasis.

Classification and Indications

Krackow Classification of Valgus Deformity:

Type	Deformity	Characteristics	Management
I	10-15°	Correctable with varus stress, minimal lateral contracture	Minimal release, CR may be possible
II	15-25°	Partially correctable, moderate lateral contracture	Sequential lateral release, PS common
III	greater than 25°	Fixed, severe lateral contracture, MCL attenuated	Extensive release, often CCK required

Key Pathology in Valgus Knee:

Lateral side CONTRACTED: ITB, LCL, popliteus, posterolateral capsule
Medial side ATTENUATED: MCL stretched, may be incompetent
Lateral femoral condyle often hypoplastic
Lateral tibial plateau worn
Patella may be laterally subluxed

Exam Pearl

FRCS Key Point: Assess PASSIVE correctability - if deformity corrects to neutral with gentle varus stress, Type I or II. If fixed, Type III.

Positioning and Preparation

Patient Position:

Supine on standard operating table
Knee flexed over bolster or leg holder
Thigh tourniquet applied
Ensure full flexion and extension possible intraoperatively

Key Considerations:

Preoperative standing long-leg alignment views essential
Templating to assess bone loss laterally
Prepare constrained components (CCK, RHK) in room
Warn patient of potential for higher constraint preoperatively

Special Instrumentation:

Standard TKA instruments
Pie-crusting needle (18G or similar)
Laminar spreaders for gap assessment
Constrained implant options available

Operative Technique

Step 1: EXPOSURE AND DEFORMITY ASSESSMENT

Approach (medial or lateral parapatellar based on severity). Sublux or evert patella. Document fixed vs correctable deformity. Assess passive correction with gentle varus stress. Document Krackow Type.

Exam Pearl

Technical Tip: EXAM KEY: Assess deformity BEFORE bone cuts. If passively correctable to neutral = Type I/II. If fixed = Type III. This determines release strategy.

Dangers at this step

Excessive medial retraction damaging attenuated MCL
Forced correction causing MCL rupture

Step 2: INITIAL BONE CUTS - TIBIAL RESECTION

Perform tibial cut FIRST in valgus knees. Use extramedullary guide. Cut perpendicular to mechanical axis (0° varus/valgus). Avoid excessive resection - preserve bone stock. Reference off lateral (higher) plateau.

Exam Pearl

Technical Tip: EXAM KEY: In valgus, tibial cut FIRST allows better assessment of deformity. Cut perpendicular to mechanical axis. The medial plateau is LOWER - do not under-resect medially.

Dangers at this step

Varus tibial cut creating medial overload
Excessive medial resection

Step 3: DISTAL FEMORAL RESECTION

Intramedullary guide with appropriate valgus correction angle. In valgus knee, may need LESS valgus (3-5° instead of 5-7°) as anatomic valgus already present. Remove distal femoral bone. Check extension gap with laminar spreader.

Exam Pearl

Technical Tip: EXAM KEY: Valgus knees often have LESS anatomic valgus correction needed. If setting at standard 5-7°, may under-resect lateral and over-resect medial. Consider reducing valgus cut angle.

Dangers at this step

Over-resection of medial femoral condyle
Under-correction due to standard valgus angle

Step 4: EXTENSION GAP ASSESSMENT

With trials in place, assess extension gap balance. In valgus knee, expect LATERAL tightness. Document asymmetry (medial vs lateral gap difference). Plan lateral release based on gap asymmetry.

Exam Pearl

Technical Tip: EXAM KEY: Document gap asymmetry in mm. Rule of thumb: each 1mm of lateral release adds ~1° of correction. Plan releases systematically.

Dangers at this step

Underestimating lateral contracture
Proceeding without documenting gap asymmetry

Step 5: LATERAL RELEASE SEQUENCE - PHASE 1

ITB Pie-Crusting:

Make multiple percutaneous stab incisions through ITB at joint line level
Use 18G needle or #11 blade
Space stabs 5mm apart
Releases 2-3mm per puncture
Safe distance from CPN (remains proximal to fibular head)

Exam Pearl

Technical Tip: EXAM KEY: Pie-crusting = SAFE, CONTROLLED lengthening of ITB. Multiple small releases add up. Each puncture releases ~2-3mm. Recheck balance after each set.

Dangers at this step

CPN injury if stabs too distal/posterior
Over-release causing lateral instability

Step 6: LATERAL RELEASE SEQUENCE - PHASE 2

Posterolateral Capsule Release:

If ITB pie-crusting insufficient
Release posterolateral capsule from lateral tibial plateau
Use electrocautery staying on bone
Releases the arcuate complex

Popliteus Release:

Release popliteus tendon from FEMORAL origin
Preserves tibial attachment for some constraint
Releases tight lateral flexion gap

Exam Pearl

Technical Tip: EXAM KEY: Release from FEMUR first (LCL, popliteus) - preserves their tibial attachments which provide residual lateral constraint. Order: ITB → PLC → Popliteus → LCL.

Dangers at this step

Popliteal vessel injury with aggressive posterior release
CPN injury with lateral retraction

Step 7: LATERAL RELEASE SEQUENCE - PHASE 3

LCL Release (if needed):

Release LCL from FEMORAL epicondyle
Subperiosteal elevation with cautery
Preserves fibular attachment
Significant release - may create lateral laxity

Lateral Epicondylar Osteotomy (LAST RESORT):

Osteotomize entire lateral epicondyle with LCL/popliteus attached
Allow to slide distally
May require fixation or accept malunion
Indicates severe deformity - consider CCK

Exam Pearl

Technical Tip: EXAM KEY: Lateral epicondylar osteotomy = LAST RESORT. If needed, indicates severe deformity requiring CCK constraint. Release sequence is critical: ITB → PLC → Popliteus → LCL → Osteotomy.

Dangers at this step

Massive lateral instability requiring CCK/RHK
CPN at risk with epicondylar osteotomy

Step 8: FEMORAL ROTATION AND SIZING

Size femoral component. Set rotation using transepicondylar axis (most reliable in valgus). Posterior condylar axis UNRELIABLE in valgus (hypoplastic lateral condyle). Make anterior, posterior, chamfer cuts.

Exam Pearl

Technical Tip: EXAM KEY: In valgus, posterior condylar axis unreliable due to lateral condyle hypoplasia. Use TRANSEPICONDYLAR AXIS for rotation. Avoid internal rotation → patella maltracking.

Dangers at this step

Internal rotation from using posterior condylar axis
Patella maltracking

Step 9: GAP BALANCING AND CONSTRAINT SELECTION

Check flexion and extension gaps. Goal: symmetric rectangular gaps. If residual lateral laxity greater than 10°, consider CCK. If collateral incompetence bilateral, consider RHK.

Constraint Ladder for Valgus:

CR (cruciate-retaining) - Type I, balanced after minimal release
PS (posterior-stabilized) - Type II, balanced after moderate release
CCK (constrained condylar) - Type III, residual instability greater than 10°
RHK (rotating hinge) - Severe bilateral laxity, MCL incompetence

Exam Pearl

Technical Tip: EXAM KEY: Accept slight residual valgus (2-3°) rather than overcorrect to varus. Varus overcorrection causes rapid medial wear and poor outcomes.

Dangers at this step

Under-constraining → postoperative instability
Over-constraining → accelerated wear, loosening

Step 10: COMPONENT INSERTION AND CLOSURE

Cement components with standard technique. Final check of balance, ROM, and patellar tracking. Repair lateral retinaculum if lateral approach used. Layered closure. Consider hinged brace if borderline stability.

Post-operative:

Weight-bearing as tolerated
Hinged brace for 6 weeks if concern for instability
Standard DVT prophylaxis
Physiotherapy focusing on quadriceps strength

Exam Pearl

Technical Tip: EXAM KEY: If any concern about stability, use hinged brace for 6 weeks postoperatively. Document intraoperative stability clearly.

Dangers at this step

Patella maltracking - check no-thumb test
VTE without prophylaxis

Complications

Evidence and Outcomes

Key Studies:

Krackow et al. (1991): Original classification of valgus deformity - guides surgical planning
Whiteside (2002): Systematic lateral release sequence - established ITB → PLC → Popliteus → LCL order
Ranawat et al. (2005): Lateral epicondylar osteotomy technique for severe valgus

Registry Data (AOANJRR 2023):

TKA for valgus OA has similar survivorship to varus OA when properly balanced
Higher revision rate if inappropriate constraint selected
CCK has slightly higher loosening rates than PS - use only when required

Exam Pearl

FRCS Key Point: Valgus TKA has equivalent outcomes to varus TKA when properly balanced and appropriate constraint selected. Key is systematic release and protecting the attenuated MCL.

Exam Viva Scenarios

Practice these scenarios to excel in your viva examination

VIVA SCENARIOStandard

EXAMINER

"You are performing a TKA on a 65-year-old woman with rheumatoid arthritis and a fixed 20° valgus deformity. After bone cuts, the lateral extension gap is 15mm and medial is 22mm. Describe your approach to balancing."

EXCEPTIONAL ANSWER

This is a Krackow Type II valgus deformity with significant lateral contracture (7mm gap asymmetry). My approach would be systematic lateral release. First, I would perform ITB pie-crusting at the joint line level using an 18-gauge needle, making multiple stab incisions 5mm apart. I would reassess the gap after each set of punctures. If insufficient, I would release the posterolateral capsule from the lateral tibial plateau. Next, I would release the popliteus tendon from its femoral origin - this particularly addresses the tight flexion gap. If still unbalanced, I would release the LCL from the lateral femoral epicondyle. Throughout, I would protect the CPN by maintaining knee flexion and avoiding aggressive lateral retraction. My goal is symmetric gaps with neutral alignment. I would accept 2-3° residual valgus rather than risk overcorrection. If greater than 10° residual laxity persists after release, I would use a CCK design.

VIVA SCENARIOStandard

EXAMINER

"A patient develops foot drop on post-operative day 1 after TKA for severe valgus deformity. How do you assess and manage this?"

EXCEPTIONAL ANSWER

This is likely common peroneal nerve palsy, a recognized complication of valgus TKA due to the proximity of the CPN to the lateral structures being released. Immediate assessment includes: removing any compressive dressings, flexing the knee to 30-40° to reduce tension on the nerve, and performing a thorough neurological examination documenting motor function (ankle dorsiflexion, toe extension, eversion) and sensory distribution (lateral leg, dorsum of foot). I would differentiate from epidural-related weakness if regional anaesthesia was used. Management depends on findings. If complete palsy, I would arrange urgent MRI to exclude hematoma. If no compressive lesion, observation is appropriate as most peroneal palsies after TKA are neurapraxia and recover over 12-18 months. I would provide an AFO to prevent foot drop contracture and refer to physiotherapy. If no recovery by 12 months, nerve conduction studies and possible exploration/neurolysis would be considered.

VIVA SCENARIOStandard

EXAMINER

"During TKA for Type III valgus, you perform extensive lateral releases but there remains 15° of lateral laxity in extension. What is your management?"

EXCEPTIONAL ANSWER

With 15° of lateral laxity after extensive release, this represents significant collateral incompetence requiring increased constraint. I would first confirm the release was appropriate and not excessive - checking that releases were done systematically from ITB through to LCL from femur. If the MCL is competent, I would use a CCK (constrained condylar knee) design, which provides varus-valgus constraint through the tall post engaging the intercondylar housing. If there is also MCL incompetence (bilateral collateral laxity), I would consider a rotating hinge knee which provides complete coronal plane constraint. I would counsel the patient preoperatively about the possibility of needing constraint, and I always have constrained options available in theatre for severe valgus cases. Important to document the intraoperative instability and rationale for constraint level selected.

References

Krackow KA, et al. Primary total knee arthroplasty in patients with fixed valgus deformity. Clin Orthop Relat Res. 1991;273:9-18. (Original classification)
Whiteside LA. Selective ligament release in total knee arthroplasty of the knee in valgus. Clin Orthop Relat Res. 1999;367:130-140.
Ranawat AS, et al. The lateral femoral epicondyle osteotomy technique: a novel approach for correcting severe valgus deformity. Clin Orthop Relat Res. 2005;440:166-171.
Elkus M, et al. Total knee arthroplasty for severe valgus deformity. J Bone Joint Surg Am. 2004;86:2671-2676.
Mullaji AB, et al. Computer-assisted navigation in total knee arthroplasty for severe valgus deformity. J Arthroplasty. 2007;22:1028-1034.
Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR). Hip, Knee & Shoulder Arthroplasty Annual Report 2023.
Rossi R, et al. Total knee arthroplasty in the valgus knee: a systematic review. J Arthroplasty. 2014;29:1207-1211.
Clarke HD, et al. Valgus deformity in total knee arthroplasty: technique and results. J Knee Surg. 2004;17:94-101.
Favorito PJ, et al. Total knee arthroplasty in the valgus knee. J Am Acad Orthop Surg. 2002;10:16-24.
Lombardi AV Jr, et al. The knee in the valgus deformity: a historical review with a contemporary solution. J Arthroplasty. 2016;31:S34-S38.

TKA for Valgus Deformity - Exam Summary

High-Yield Exam Summary

Total Knee Arthroplasty for Valgus Deformity