High Yield Overview

PRIMARY TOTAL KNEE ARTHROPLASTY - STANDARD MEASURED RESECTION TECHNIQUE

Medial parapatellar approach (gold standard - 90% of primary TKA cases) | advanced

Critical Danger Structures - KNOW LOCATION AND PROTECTION

Popliteal Artery

LOCATION: 10-15mm posterior to posterior tibial cortex at joint line

AT RISK: Proximal tibial cut (posterior saw exit), posteromedial capsular releases, aggressive posterior osteophyte removal

PROTECTION: ALWAYS use broad posterior retractors (Hohmann or curved Bennett) during tibial cut, stay anterior to posterior cortex, gentle sequential releases staying extraperiosteal

Popliteal Vein

LOCATION: Accompanies popliteal artery in neurovascular bundle, 10-15mm posterior to tibial cortex

AT RISK: Same as artery - tibial cut, posterior releases. Venous injury MORE COMMON than arterial

PROTECTION: Same protection as artery - posterior retractors mandatory, stay anterior, controlled releases

Common Peroneal Nerve

LOCATION: Winds around fibular neck 2-3cm distal to fibular head laterally

AT RISK: Lateral post compression, correction of severe valgus (more than 20°), lateral collateral releases, tibial tubercle osteotomy

PROTECTION: Adequate lateral post padding, gradual valgus correction avoiding acute traction, cautious lateral releases, monitor nerve during correction

Tibial Nerve

LOCATION: Posterior to popliteal vessels, deep in popliteal fossa

AT RISK: Well-protected but at risk if saw violates posterior cortex or deep uncontrolled posterior releases

PROTECTION: Stay anterior during all tibial work, use posterior retractors, controlled extraperiosteal releases

Patellar Tendon Insertion

LOCATION: Inserts on tibial tubercle with broad attachment

AT RISK: During medial arthrotomy extension distal to tubercle - avulsion is CATASTROPHIC complication

PROTECTION: Stay DIRECTLY ON BONE when extending arthrotomy past tubercle, score periosteum sharply, NEVER undermine tendon insertion

Mnemonic

CAPPSTIBIAL CUT - Critical Parameters

Mnemonic

TEA-W-PFEMORAL ROTATION - Three References

Patient Positioning

Supine Position: Operative leg must be free to flex 120° and extend fully for alignment assessment

Drop foot of table 90° OR use leg positioner
Lateral thigh post at hip level (prevent leg adduction, well-padded for common peroneal nerve protection)
Small bump (towel roll) under ipsilateral hip for 15-20° external rotation
Tourniquet proximal thigh at 300mmHg or LOP + 100mmHg (typically 350-400mmHg)
Prepare and drape leg circumferentially including foot for ROM assessment and alignment checks

Surgical Approach - Medial Parapatellar

Gold Standard Approach: Used in 90% of primary TKA cases

Advantages:

Excellent exposure of femur, tibia, patella
Preserves extensor mechanism integrity
Allows patellar eversion safely
Familiar anatomy and reproducible
Can be extended proximally or distally if needed
Facilitates future revision surgery

Incision Planning:

Midline longitudinal skin incision 12-15cm length
Centered over patella
Extends from 5cm proximal to superior patellar pole to 2-3cm distal to tibial tubercle
Midline incision preserves blood supply to both medial and lateral skin flaps
Allows conversion to different exposures if needed
CRITICAL for revision surgery access

Exam Pearl

Positioning Pearl: Leg must be completely free to move through full ROM for accurate alignment assessment. I use lateral post at hip level to prevent varus sag, and hip external rotation with bump to facilitate patella eversion. Tourniquet at LOP + 100mmHg balances hemostasis with nerve palsy risk. I limit tourniquet time to under 90 minutes.

Positioning Dangers

Tourniquet longer than 2 hours increases nerve palsy and compartment syndrome risk exponentially
Common peroneal nerve compression from lateral post - ensure adequate padding (folded towels or gel pads)
Inadequate external rotation makes patella eversion difficult and risks avulsion
Exsanguination with Esmarch bandage in severe PVD can precipitate critical ischemia - use elevation only

Major Complications - Recognition, Prevention, Management

Exam Viva Scenarios

Practice these scenarios to excel in your viva examination

VIVA SCENARIOStandard

EXAMINER

"A 68-year-old woman with severe varus osteoarthritis undergoes primary TKA. You have performed the tibial and distal femoral cuts. Walk me through your approach to femoral component rotation."

EXCEPTIONAL ANSWER

Femoral component rotation is CRITICAL for patellar tracking and balanced flexion gap. I use THREE anatomic references that should align: (1) TRANSEPICONDYLAR AXIS - this is the GOLD STANDARD and most reproducible. I palpate the medial epicondylar sulcus which is posterior to the MCL origin, and the lateral epicondylar prominence. I draw a line connecting these two points. (2) WHITESIDE'S LINE - this is perpendicular to the anteroposterior axis, running from the deepest point of the trochlear groove anteriorly to the center of the intercondylar notch posteriorly. (3) POSTERIOR CONDYLAR AXIS PLUS 3 DEGREES EXTERNAL ROTATION - I reference the posterior condyles and add 3 degrees of external rotation. In a normal knee, all three references should align when properly positioned. However, in knees with severe wear or dysplastic condyles, these references may conflict. When this happens, I PRIORITIZE the transepicondylar axis because it is most accurate for preventing patellar maltracking. Internal rotation of the femoral component causes patellar maltracking, anterior knee pain, and medial-sided flexion gap tightness. Excessive external rotation beyond 5 degrees causes lateral patellar subluxation and lateral flexion gap tightness. My target is 3 degrees external rotation relative to the posterior condyles, verified by alignment with TEA.

VIVA SCENARIOStandard

EXAMINER

"During trial reduction, you notice the knee has 5mm medial opening with valgus stress in extension but is balanced in flexion. What is your diagnosis and how do you address this?"

EXCEPTIONAL ANSWER

This patient has EXTENSION GAP medial-sided laxity with balanced flexion gap. This is a challenging scenario because the gaps are UNEQUAL between flexion and extension, which indicates either: (1) excessive tibial or distal femoral bone resection creating a loose extension gap, (2) inadequate soft tissue balancing, or (3) flexion gap is actually TIGHT rather than extension gap loose. First, I assess the EXTENSION GAP size - if it measures significantly more than my planned polyethylene thickness (typically 9-10mm), I have over-resected bone. If the gap height is correct but opening medially, I have asymmetric medial laxity. My approach: STEP 1 - Verify my cuts are correct and I haven't over-resected. If cuts are correct, this is a medial soft tissue deficiency in extension. STEP 2 - Check lateral structures aren't overly tight by ensuring lateral soft tissue releases were not excessive. STEP 3 - For medial extension gap laxity with balanced flexion gap, my options are: (1) Use THICKER polyethylene insert to fill the extension gap - but this risks creating TIGHT flexion gap and limiting ROM, (2) ACCEPT slightly thicker poly and perform additional POSTERIOR femoral resection to open flexion gap equally, (3) Use semi-constrained or constrained condylar knee (CCK) implant if laxity is severe (more than 10mm opening), (4) Advanced technique: medial collateral ligament reconstruction or advancement, though rarely needed in primary TKA. The key principle is achieving EQUAL and RECTANGULAR gaps throughout ROM. UNEQUAL gaps lead to instability in one position.

VIVA SCENARIOStandard

EXAMINER

"You are performing gap balancing in an 80% varus knee. Walk me through your sequential medial release technique and how you assess balance."

EXCEPTIONAL ANSWER

Varus knee is the MOST COMMON deformity in primary TKA, representing 80% of cases. The pathology is medial structures are CONTRACTED and tight, while lateral structures are stretched and loose. My goal is to achieve RECTANGULAR balanced gaps in both extension and flexion through sequential, controlled medial releases. Before starting releases, I ensure I have: (1) removed ALL osteophytes completely - residual osteophytes cause persistent contracture, (2) performed accurate perpendicular tibial cut and appropriate distal femoral cut, (3) inserted spacer blocks equal to my planned polyethylene thickness. My SEQUENTIAL MEDIAL RELEASE technique: STEP 1 - DEEP MCL FIBERS from tibia. I use osteotome to release subperiosteally from proximal medial tibial plateau. I use laminar spreaders to assess medial and lateral gap tension after this release. STEP 2 - If still tight medially, I perform SUPERFICIAL MCL FIBERS release using 'PIE-CRUSTING' technique. I use 15-blade to make multiple small perpendicular cuts through superficial MCL, creating controlled lengthening without complete disruption. I reassess with spreaders. STEP 3 - If still tight, I release PES ANSERINUS TENDONS from their insertion on proximal medial tibia. Reassess. STEP 4 - If still tight, I release SEMIMEMBRANOSUS from posteromedial corner of tibia. Reassess. STEP 5 - If still tight, I release POSTEROMEDIAL CAPSULE from tibia staying extraperiosteal to protect popliteal vessels which are 10-15mm posterior. Throughout this process, I use laminar spreaders in both extension and flexion to assess: (1) MEDIAL vs LATERAL tension should be EQUAL - feels balanced, (2) GAP HEIGHT should equal spacer thickness, (3) Gaps should be RECTANGULAR not trapezoidal. CRITICAL POINT: I NEVER completely transect the MCL. Complete MCL release causes severe medial instability requiring constrained implant, which is a FAILURE of technique. My goal is controlled, incremental release with frequent reassessment.

Primary TKA - Standard Measured Resection - Exam Summary

High-Yield Exam Summary

References

Insall JN, Binazzi R, Soudry M, Mestriner LA. Total knee arthroplasty. Clin Orthop Relat Res. 1985;(192):13-22. PMID: 3967412. [Foundational work on total knee arthroplasty technique and alignment principles]
Berger RA, Crossett LS, Jacobs JJ, Rubash HE. Malrotation causing patellofemoral complications after total knee arthroplasty. Clin Orthop Relat Res. 1998;(356):144-153. PMID: 9917679. [Critical study establishing importance of femoral component rotation for patellar tracking]
Whiteside LA, Arima J. The anteroposterior axis for femoral rotational alignment in valgus total knee arthroplasty. Clin Orthop Relat Res. 1995;(321):168-172. PMID: 7497664. [Described Whiteside's line as reference for femoral rotation]
Berger RA, Rubash HE, Seel MJ, Thompson WH, Crossett LS. Determining the rotational alignment of the femoral component in total knee arthroplasty using the epicondylar axis. Clin Orthop Relat Res. 1993;(286):40-47. PMID: 8425366. [Established transepicondylar axis as gold standard for femoral rotation]
Ranawat CS, White PB, West S, Ranawat AS. Clinical and radiographic results of attune and PFC sigma knee designs at 2-year follow-up: a prospective matched-pair analysis. J Arthroplasty. 2017;32(2):431-436. PMID: 27665240. [Modern outcomes data for primary TKA with measured resection technique]
Fehring TK, Odum S, Griffin WL, Mason JB, Nadaud M. Early failures in total knee arthroplasty. Clin Orthop Relat Res. 2001;(392):315-318. PMID: 11716402. [Analysis of early complications including instability, stiffness, and infection]
Mihalko WM, Whiteside LA, Krackow KA. Comparison of ligament-balancing techniques during total knee arthroplasty. J Bone Joint Surg Am. 2003;85-A Suppl 4:132-135. PMID: 14652403. [Comparison of gap balancing versus measured resection techniques]
Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR). Hip, Knee & Shoulder Arthroplasty: 2023 Annual Report. Adelaide: AOA; 2023. [Australian-specific registry data on TKA outcomes, revision rates, and implant survivorship]
Therapeutic Guidelines Ltd. eTG Complete [digital]. Melbourne: Therapeutic Guidelines Limited; 2023. [Australian antibiotic prophylaxis and VTE prevention guidelines for arthroplasty]
Dennis DA, Komistek RD, Colwell CE Jr, et al. In vivo anteroposterior femorotibial translation of total knee arthroplasty: a multicenter analysis. Clin Orthop Relat Res. 1998;(356):47-57. PMID: 9917666. [Kinematic analysis demonstrating importance of gap balancing for proper knee function]

Primary Total Knee Arthroplasty - Standard Measured Resection Technique