High Yield Overview

OSTEOCHONDRAL ALLOGRAFT (OCA)

Fresh Cadaveric Transplant | Large Lesions | Hyaline Cartilage

Over 4cm²Typical lesion size

28 daysOptimal use from harvest

75-85%Survivorship at 10 years

Type IIHyaline collagen preserved

INDICATIONS BY LESION TYPE

Large defect over 4cm²

PatternExceeds OATS donor capacity

TreatmentFirst-line for OCA

Failed prior cartilage surgery

PatternOATS, microfracture, ACI failure

TreatmentSalvage with OCA

Bone loss present

PatternSubchondral bone deficiency

TreatmentOCA restores bone stock

Critical Must-Knows

Fresh allograft essential - chondrocyte viability decreases with storage
28 days optimal window from harvest to implantation
Size-matched graft from tissue bank critical for fit
Large lesions (over 4cm²) where autograft insufficient
Single-stage surgery with no donor site morbidity

Examiner's Pearls

"
Fresh (not frozen) graft maintains 70%+ chondrocyte viability
"
Disease transmission risk: rigorous donor screening required
"
Immune response minimal to cartilage (avascular, immune-privileged)
"
Shell or dowel techniques depending on lesion geometry

Clinical Imaging

Critical OCA Exam Points

Fresh vs Frozen

Fresh graft is essential. Frozen allografts have less than 1% chondrocyte viability. Fresh grafts stored at 4°C maintain 70%+ viability for up to 28 days. This is a key exam distinction.

Large Lesion Solution

OCA is first-line for lesions over 4cm² where OATS donor site availability is limiting. No donor site morbidity. Can address extensive bone and cartilage defects.

Bone Stock Restoration

Unlike OATS or ACI, OCA can restore subchondral bone. Ideal for defects with bone loss, osteonecrosis, or post-traumatic bone defects.

Availability Limitation

Limited availability in Australia. Requires tissue bank coordination. Size matching delays surgery. Storage window is narrow (28 days).

OCA vs Other Cartilage Procedures

Feature	OCA	OATS	ACI/MACI
Ideal lesion size	Over 4cm²	1-4cm²	Over 2cm²
Cartilage type	Hyaline (Type II)	Hyaline (Type II)	Hyaline-like
Stages	Single	Single	Two
Donor morbidity	None (allograft)	10-15%	None (biopsy only)
Bone stock	Restores bone	Transfers with plug	Requires intact bone
Availability	Limited (tissue bank)	Immediate (patient)	Requires culture

Mnemonic

FRESHFRESH - Why Fresh Matters

Frozen kills cells

Less than 1% viability after freezing

Refrigerated at 4°C

Optimal storage temperature

Eighteen to 28 days window

Use within this timeframe

Seventy percent viable

Chondrocyte viability maintained

Hyaline preserved

Type II collagen matrix intact

Memory Hook:Keep it FRESH - fresh allografts have living cells, frozen ones are dead!

Mnemonic

LARGELARGE - When to Use OCA

Large lesions (over 4cm²)

Exceeds autograft capacity

AVN or bone loss

Restores bone stock

Revision cartilage surgery

After failed OATS/microfracture

Geometric matching

Size-matched from tissue bank

Extensive defects

Hemicondylar or bipolar lesions

Memory Hook:OCA is for LARGE problems that need big solutions!

Mnemonic

SCREENGraft Processing

Serology testing

HIV, Hepatitis B/C, syphilis

Culture for bacteria/fungi

Swabs and culture

Review medical history

High-risk exclusion

Examine tissue grossly

Visual inspection

Ensure size match

CT/XR for sizing

NAT for viral nucleic acids

Nucleic acid testing

Memory Hook:SCREEN every graft thoroughly - safety first!

Overview and Epidemiology

Why This Topic Matters

OCA is the only cartilage restoration option that transfers large amounts of mature hyaline cartilage with subchondral bone in a single stage. It fills a critical niche for large defects, failed prior surgery, and lesions with bone loss. Understanding fresh vs frozen and the storage window is essential.

Indications

Large lesions over 4cm²
Failed OATS or microfracture
Osteonecrosis with cartilage damage
Post-traumatic defects with bone loss
Bipolar (kissing) lesions
Young patients not suitable for arthroplasty

Contraindications

Diffuse OA
Inflammatory arthropathy
Active infection
Uncorrected malalignment
Non-compliant patient
Unrealistic expectations

Pathophysiology and Mechanisms

Fresh vs Frozen - The Critical Distinction

Fresh OCA stored at 4°C maintains 70%+ chondrocyte viability for up to 28 days. Frozen OCA has less than 1% chondrocyte viability because freezing destroys cells. The matrix remains intact in frozen grafts but the cartilage is essentially dead. Fresh grafts are essential for cartilage restoration.

Fresh vs Frozen Allograft

Property	Fresh (4°C)	Frozen (-80°C)
Chondrocyte viability	70%+ at 28 days	Less than 1%
Matrix integrity	Preserved	Preserved
Storage window	14-28 days optimal	Years
Availability	Limited, requires coordination	Readily available
Use for cartilage	Yes - living cartilage	No - structural only

Why Cartilage is Immune-Privileged

Avascular - no blood vessel access for immune cells
Chondrocytes encased in matrix
Low immunogenicity of cartilage matrix
Bone is immunogenic - deeper grafts may generate response

Graft Integration

Bone-to-bone healing: 8-12 weeks
Cartilage: Minimal integration (fibrocartilaginous junction)
Subchondral bone remodels over 1-2 years
Deep grafts integrate more slowly

Classification Systems

Graft Geometry Classification

Type	Description	Best For
Dowel/Plug	Cylindrical grafts (like large OATS)	Contained circular/oval lesions
Shell graft	Thin cartilage-bone slice	Large surface lesions, good bone stock
Hemicondylar	Entire condylar surface	Massive defects, failed TKA salvage
Bipolar	Both articulating surfaces	Tibial + femoral kissing lesions

The choice of graft geometry depends on lesion size, location, and associated bone loss. Dowel grafts are most common for focal defects, while shell grafts preserve more bone stock.

Clinical Assessment

History

Prior cartilage surgery (failed OATS, microfracture, ACI)
Large traumatic defect history
Osteonecrosis symptoms (night pain, rest pain)
Mechanical symptoms (catching, locking, swelling)
Activity level and expectations

Examination

Joint effusion - often present
Crepitus - may indicate cartilage damage
Tenderness - localized to affected compartment
Alignment - assess for malalignment
Stability - rule out ligamentous insufficiency

Assess Contributing Factors

Before OCA, assess and address: malalignment (osteotomy), ligament insufficiency (reconstruction), meniscal deficiency (allograft or preserve). OCA alone will fail if mechanical factors are not corrected.

Investigations

Investigation Protocol

First LineX-rays

Weight-bearing AP, lateral, Rosenberg, skyline. Assess joint space, alignment, OA changes, subchondral bone status. Sizing X-rays for tissue bank matching.

EssentialMRI

Lesion size and location. Subchondral bone status (edema, cysts, AVN). Associated meniscal/ligament pathology. Bone marrow lesion extent.

For SizingCT

Precise sizing for tissue bank matching. 3D reconstruction may help with complex defects. Assessment of bone stock.

Size Matching

Tissue banks use CT or XR measurements to match donor-recipient size. The graft should be matched to within 2-3mm of recipient dimensions. Oversized grafts can be trimmed; undersized grafts cannot fill the defect adequately.

Management Algorithm

Treatment Selection

Choose OCA when:

Lesion over 4cm² (exceeds OATS capacity)
Failed prior cartilage surgery
Bone loss or AVN present
Bipolar lesions
Young patient unsuitable for arthroplasty

Choose OATS instead when:

Lesion 1-4cm² and single
No bone loss
Availability/timing is critical

Choose ACI instead when:

Large lesion but no bone loss
OCA unavailable
Patient preference for autologous

This decision framework helps guide treatment selection based on lesion characteristics and patient factors.

Pre-operative Planning

Pre-operative Steps

Weeks PriorTissue Bank Coordination

Contact tissue bank. Provide sizing imaging (CT/XR). Request size-matched graft. Confirm availability and timing.

Days PriorGraft Arrival

Confirm graft arrival and harvest date. Verify within storage window (under 28 days from harvest). Review donor screening documentation.

Day OfOperating Room

Prepare graft bench. Have backup plan if graft unsuitable intra-operatively. Standard arthroscopy and open equipment.

The 28-Day Window

Fresh OCA should be implanted within 28 days of harvest for optimal chondrocyte viability. Beyond this, viability drops significantly. This creates logistical challenges - patient and OR must be available when graft arrives. The window between harvest and surgery cannot be flexible.

Surgical Technique

Dowel/Plug Technique

Surgical Steps

Step 1Exposure

Mini-open approach typical. Medial or lateral parapatellar as needed. Adequate exposure for instrumentation.

Step 2Recipient Preparation

Mark lesion boundaries. Use recipient sizing corer to create cylindrical hole. Match depth to available graft depth. Create perpendicular hole with stable rim.

Step 3Graft Preparation

Harvest dowel from allograft using matching corer. Match curvature and orientation. Trim bone depth to match recipient.

Step 4Implantation

Insert graft into recipient site. Press-fit stability. Graft should be flush or 1mm proud. Never recessed.

Step 5Fixation

Press-fit often sufficient. Bioabsorbable pins if unstable. Avoid metal hardware if possible.

Maintain Cartilage Viability

Handle cartilage surface gently. Keep moist with saline throughout. Minimize tourniquet time. Do not compress or traumatize the cartilage surface during insertion.

Complications

Complication	Incidence	Risk Factors	Prevention/Management
Graft failure/collapse	10-15% at 10 years	Large/deep grafts, poor integration	Protect weight-bearing, optimize biology
Disease transmission	Very rare	Inadequate screening	Rigorous donor screening protocols
Non-union of bone	5-10%	Deep grafts, poor vascularity	Protected loading, avoid smoking
Subchondral collapse	5-10%	Early loading, poor bone quality	Extended NWB if deep graft
Immune response	Rare for cartilage	Deep bone grafts	Cartilage is immune-privileged

Disease Transmission Risk

While rare, disease transmission is possible with allografts. All donors undergo rigorous screening (serology, NAT, culture, medical history review). HIV and Hepatitis C transmission have been reported historically but are extremely rare with modern protocols.

Postoperative Care and Rehabilitation

Weight-Bearing Protocol

Progression

Non-weight-bearingWeeks 0-6

Strict NWB or toe-touch only. Longer protection than OATS due to deeper bone integration required.

Partial Weight-BearingWeeks 6-12

Progressive weight-bearing 25% to 75%. Crutches continued.

Full Weight-BearingWeeks 12-16

Wean from crutches. Full WB by 16 weeks. Continue avoiding impact.

Longer Protection for Deep Grafts

OCA rehabilitation is longer than OATS because deeper bone grafts require more time for integration. Hemicondylar grafts may need 3-4 months of protection before full weight-bearing.

Outcomes and Prognosis

Long-term Outcomes

Time Point	Survivorship	Considerations
5 years	85-90%	Good early results expected
10 years	75-85%	Progressive decline begins
15 years	65-75%	Consider bridge to TKA success

OCA as Bridge to Arthroplasty

In young patients unsuitable for arthroplasty, OCA can delay TKA by 10-15 years on average. Even if OCA eventually fails, it preserves bone stock and allows eventual arthroplasty. This "bridge" strategy is valuable in patients too young for definitive replacement.

Evidence Base and Key Trials

OCA Long-term Survivorship

Levy YD, Gortz S, Pulido PA, et al • AJSM (2013)

Key Findings:

82% survivorship at 15 years
Larger lesions had slightly lower survivorship
Age under 30 had better outcomes
Prior marrow stimulation did not affect results

Clinical Implication: OCA provides durable long-term results, especially in young patients with large lesions.

Limitation: Retrospective single-center series.

Fresh vs Prolonged Storage

Pallante AL, Bae WC, Chen AC, et al • JBJS Am (2009)

Key Findings:

Chondrocyte viability 70%+ at 28 days storage
Significant decline after 28 days
Matrix properties maintained longer than cell viability
Fresh storage essential for cartilage restoration

Clinical Implication: The 28-day storage window is evidence-based. Beyond this, chondrocyte viability compromises outcomes.

Limitation: Laboratory study, may not fully replicate clinical conditions.

OCA for Femoral Condyle AVN

Gortz S, Bugbee WD • CORR (2006)

Key Findings:

78% good/excellent results at average 5 years for AVN
OCA effective for osteonecrosis with cartilage damage
Bone stock restoration successful
Alternative to arthroplasty in young patients

Clinical Implication: OCA is particularly valuable for AVN where bone stock and cartilage both need restoration.

Limitation: Relatively short follow-up for AVN cases.

Return to Sport After OCA

Krych AJ, Robertson CM, Williams RJ III • AJSM (2012)

Key Findings:

79% returned to some sporting activity
Only 44% returned to same level
Larger lesions had lower return rates
Patient satisfaction high despite activity reduction

Clinical Implication: Counsel patients about realistic sport expectations. Return to high-level sport is not guaranteed, especially with large grafts.

Limitation: Heterogeneous patient population and activities.

Bipolar OCA

Gross AE, Shasha N, Aubin P • JBJS Am (2005)

Key Findings:

Bipolar OCA (tibial + femoral) has higher failure rate
65% survivorship at 10 years for bipolar
80%+ for unipolar OCA
Bipolar reserved for severe cases

Clinical Implication: Bipolar OCA has lower success but may still be worthwhile in severe cases as alternative to arthroplasty.

Limitation: Small numbers of bipolar cases.

Exam Viva Scenarios

Practice these scenarios to excel in your viva examination

VIVA SCENARIOStandard

Scenario 1: Large Femoral Condyle Lesion (~2-3 min)

EXAMINER

"A 28-year-old male has a 5cm² full-thickness cartilage defect on the medial femoral condyle after failed microfracture 2 years ago. What are your treatment options?"

EXCEPTIONAL ANSWER

This young patient with a large (5cm²) lesion after failed microfracture is an excellent candidate for osteochondral allograft. My rationale: At 5cm², this exceeds the safe donor capacity for OATS (maximum ~4cm²). ACI is an option but requires two stages. OCA provides mature hyaline cartilage in a single surgery without donor site morbidity. My approach would be: 1. Confirm alignment is normal - if malaligned, plan osteotomy 2. Assess associated pathology (meniscus, ligaments) - address concurrently 3. Coordinate with tissue bank for size-matched fresh femoral condyle allograft 4. Ensure surgery within 28 days of graft harvest for optimal chondrocyte viability 5. Dowel technique if lesion is circular/oval; shell graft if irregular For this MFC lesion, I would likely use a dowel technique with a large (15-20mm) allograft plug or potentially 2 plugs if irregular shape. Post-operatively: NWB 6 weeks, progressive to full WB by 12-16 weeks. Return to sport 12-18 months. I would counsel about 75-85% survivorship at 10 years, and that this may serve as a bridge to eventual TKA if needed.

KEY POINTS TO SCORE

Recognize lesion exceeds OATS capacity

Fresh allograft essential (under 28 days)

Single-stage procedure with no donor morbidity

Know realistic outcomes and limitations

COMMON TRAPS

✗Suggesting OATS for 5cm² lesion

✗Not mentioning fresh vs frozen distinction

✗Forgetting to assess alignment

✗Overpromising sport return

LIKELY FOLLOW-UPS

"What is the difference between fresh and frozen allograft?"

"What if there was associated varus malalignment?"

"How would you fix the graft?"

VIVA SCENARIOChallenging

Scenario 2: Fresh vs Frozen (~2-3 min)

EXAMINER

"An examiner asks: Why do we use fresh osteochondral allograft instead of frozen? What are the storage considerations?"

EXCEPTIONAL ANSWER

This is a fundamental principle of osteochondral allograft transplantation. **Fresh vs Frozen - The Key Difference:** Fresh allograft stored at 4°C maintains over 70% chondrocyte viability for up to 28 days. The living chondrocytes continue to maintain the cartilage matrix, providing durable cartilage function. Frozen allograft stored at -80°C has less than 1% chondrocyte viability because freezing destroys the cells. While the matrix structure remains intact, the cartilage is essentially dead tissue. Frozen allografts are used for structural bone grafting where living cartilage is not needed. **Storage Considerations:** 1. **Temperature**: 4°C (refrigerated, not frozen) 2. **Medium**: Nutrient culture medium to support chondrocytes 3. **Time window**: Optimal use within 14-28 days of harvest 4. **Testing**: Donor screening during this window (serology, cultures, NAT) 5. **Logistics**: Surgery must be scheduled when graft is ready, not vice versa **The 28-day window creates challenges:** - Patient must be available when graft arrives - Operating room scheduling flexibility needed - Cannot store graft indefinitely waiting for optimal timing - Size matching delays add pressure to the timeline This is why OCA requires more coordination than autograft procedures like OATS.

KEY POINTS TO SCORE

Fresh = 70%+ viability; Frozen = less than 1%

28 days is the optimal storage window

4°C storage in nutrient medium

Logistical challenges with timing

COMMON TRAPS

✗Not knowing the viability percentages

✗Confusing storage temperatures

✗Not understanding the clinical implications

✗Suggesting frozen allograft for cartilage restoration

LIKELY FOLLOW-UPS

"What testing is done during the storage window?"

"What happens if surgery is delayed beyond 28 days?"

"Is there any role for frozen allograft in the knee?"

VIVA SCENARIOCritical

Scenario 3: Bipolar Lesions (~2-3 min)

EXAMINER

"A 35-year-old has bipolar (kissing) lesions on the medial femoral condyle and tibial plateau after failed HTO. What are your options?"

EXCEPTIONAL ANSWER

Bipolar or kissing lesions are among the most challenging cartilage problems. This patient with both femoral and tibial involvement after failed HTO requires careful evaluation. **Assessment:** 1. Current alignment - did HTO fail mechanically or is alignment now acceptable? 2. Size of each lesion - femoral and tibial separately 3. Bone stock - any bone loss from prior surgery? 4. Associated pathology - meniscal status critical **Treatment Options:** **1. Bipolar OCA (femoral + tibial):** - Can address both surfaces - Lower success than unipolar (65% vs 80%+ at 10 years) - Complex surgery with higher risk - May still delay arthroplasty 5-10 years **2. Unipolar OCA + other treatment:** - OCA for larger lesion - Microfracture or debridement for smaller opposing lesion - Reduces complexity but may not address both fully **3. Meniscal allograft + cartilage treatment:** - If meniscal deficiency contributes, add meniscal allograft - Addresses load distribution **4. TKA:** - Definitive option at age 35 but young - Should be considered if biology fails - Patient may still need revision in lifetime Given her age (35), I would counsel toward attempting biological solution first. Bipolar OCA with meniscal allograft if meniscal deficient would be my preferred approach, with clear counseling about reduced success rates compared to unipolar disease.

KEY POINTS TO SCORE

Bipolar lesions have worse prognosis than unipolar

Multiple treatment options exist

Meniscal status is critical

TKA is the fallback but young age is concerning

COMMON TRAPS

✗Not knowing bipolar has worse outcomes

✗Jumping to TKA without biological attempt

✗Ignoring meniscal contribution

✗Not reassessing alignment

LIKELY FOLLOW-UPS

"What is the survivorship of bipolar OCA at 10 years?"

"How would you consent this patient?"

"What if they wanted to avoid any further surgery?"

MCQ Practice Points

Storage Temperature Question

Q: At what temperature should fresh osteochondral allograft be stored? A: 4°C (refrigerated) - Fresh OCA is stored at 4°C in nutrient medium. Frozen storage (-80°C) kills chondrocytes and is not used for cartilage restoration.

Viability Question

Q: What is the approximate chondrocyte viability of fresh OCA at 28 days? A: Greater than 70% - Fresh OCA maintains over 70% chondrocyte viability when stored at 4°C for up to 28 days. Beyond this, viability drops significantly.

Frozen Viability Question

Q: What is the chondrocyte viability of frozen osteochondral allograft? A: Less than 1% - Freezing destroys chondrocytes. Frozen allografts have essentially no living cartilage cells, making them unsuitable for cartilage restoration (used only for structural bone).

Lesion Size Question

Q: What is the typical lesion size indication for OCA? A: Greater than 4cm² - OCA is typically indicated for lesions over 4cm² where OATS donor capacity is exceeded. It fills the gap for large lesions that cannot be treated with autograft.

Survivorship Question

Q: What is the approximate 10-year survivorship of unipolar OCA? A: 75-85% - OCA provides durable medium-term results with 75-85% survivorship at 10 years. This may serve as a bridge to eventual arthroplasty in young patients.

Bipolar Outcomes Question

Q: How do bipolar OCA outcomes compare to unipolar? A: Worse - approximately 65% survivorship at 10 years vs 80%+ - Bipolar (kissing) lesions involving both articulating surfaces have lower success rates than single-surface OCA.

Australian Context and Medicolegal Considerations

Australian Practice

OCA availability limited in Australia
Requires tissue bank coordination
Some centers import from US tissue banks
Cost and logistics are barriers
Alternative: OATS or ACI when OCA unavailable

Documentation Standards

Document graft harvest date and storage duration
Record donor screening documentation
Document surgical technique and fixation
Consent must include disease transmission risk
Record size matching process

Medicolegal Considerations

Key documentation requirements:

Consent must include: disease transmission risk (very low but real), potential for failure and conversion to TKA, realistic sport expectations
Document graft arrival and harvest date (confirm within window)
Record donor screening documentation reviewed
If graft fails early, documentation of proper storage and surgical technique is protective

OSTEOCHONDRAL ALLOGRAFT (OCA)

High-Yield Exam Summary

Definition

•Fresh cadaveric osteochondral graft
•Bone + hyaline cartilage transplant
•Living chondrocytes preserved
•Single-stage procedure

Fresh vs Frozen

•Fresh (4°C) = 70%+ viability
•Frozen (-80°C) = under 1% viability
•Fresh essential for cartilage restoration
•28 days optimal storage window

Indications (LARGE)

•Large lesions over 4cm²
•AVN or bone loss present
•Revision after failed cartilage surgery
•Geometric matching from tissue bank
•Extensive defects (bipolar, hemicondylar)

Key Numbers

•Over 4cm² = typical size indication
•28 days = storage window
•70%+ = chondrocyte viability fresh
•75-85% = 10-year survivorship
•65% = bipolar 10-year survivorship

Advantages

•Mature hyaline cartilage (Type II)
•Single stage surgery
•No donor site morbidity
•Restores bone stock
•Large lesion capability

Disadvantages

•Limited availability
•Narrow storage window
•Disease transmission risk (rare)
•Logistical coordination required
•Cost higher than autograft

Feature

OCA

OATS

ACI/MACI

Ideal lesion size

Over 4cm²

1-4cm²

Over 2cm²

Cartilage type

Hyaline (Type II)

Hyaline-like

Stages

Single

Two

Donor morbidity

None (allograft)

10-15%

None (biopsy only)

Bone stock

Restores bone

Transfers with plug

Requires intact bone

Availability

Limited (tissue bank)

Immediate (patient)

Requires culture

Property

Fresh (4°C)

Frozen (-80°C)

Chondrocyte viability

70%+ at 28 days

Less than 1%

Matrix integrity

Preserved

Storage window

14-28 days optimal

Years

Availability

Limited, requires coordination

Readily available

Use for cartilage

Yes - living cartilage

No - structural only

Type

Description

Best For

Dowel/Plug

Cylindrical grafts (like large OATS)

Contained circular/oval lesions

Shell graft

Thin cartilage-bone slice

Large surface lesions, good bone stock

Hemicondylar

Entire condylar surface

Massive defects, failed TKA salvage

Bipolar

Both articulating surfaces

Tibial + femoral kissing lesions

Dowel/Plug Technique

Surgical Steps

Step 1Exposure

Mini-open approach typical. Medial or lateral parapatellar as needed. Adequate exposure for instrumentation.

Step 2Recipient Preparation

Mark lesion boundaries. Use recipient sizing corer to create cylindrical hole. Match depth to available graft depth. Create perpendicular hole with stable rim.

Step 3Graft Preparation

Harvest dowel from allograft using matching corer. Match curvature and orientation. Trim bone depth to match recipient.

Step 4Implantation

Insert graft into recipient site. Press-fit stability. Graft should be flush or 1mm proud. Never recessed.

Step 5Fixation

Press-fit often sufficient. Bioabsorbable pins if unstable. Avoid metal hardware if possible.

Maintain Cartilage Viability

Handle cartilage surface gently. Keep moist with saline throughout. Minimize tourniquet time. Do not compress or traumatize the cartilage surface during insertion.

Complication

Incidence

Risk Factors

Prevention/Management

Graft failure/collapse

10-15% at 10 years

Large/deep grafts, poor integration

Protect weight-bearing, optimize biology

Disease transmission

Very rare

Inadequate screening

Rigorous donor screening protocols

Non-union of bone

5-10%

Deep grafts, poor vascularity

Protected loading, avoid smoking

Subchondral collapse

5-10%

Early loading, poor bone quality

Extended NWB if deep graft

Immune response

Rare for cartilage

Deep bone grafts

Cartilage is immune-privileged

Time Point

Survivorship

Considerations

5 years

85-90%

Good early results expected

10 years

75-85%

Progressive decline begins

15 years

65-75%

Consider bridge to TKA success

Location	Considerations	Technique
Medial femoral condyle	Most common, good access	Dowel or shell
Lateral femoral condyle	Match curvature carefully	Dowel or shell
Trochlea	Requires precise contouring	Shell often better
Patella	Technically challenging	Shell graft
Tibial plateau	Uncommon, difficult access	Dowel or shell

Pathology	Procedure	Timing
Malalignment	HTO or DFO	Staged or concurrent
ACL deficiency	ACL reconstruction	Concurrent or staged
Meniscal deficiency	Meniscal allograft	Concurrent preferred
PCL deficiency	PCL reconstruction	Staged usually

Location	Considerations	Technique
Medial femoral condyle	Most common, good access	Dowel or shell
Lateral femoral condyle	Match curvature carefully	Dowel or shell
Trochlea	Requires precise contouring	Shell often better
Patella	Technically challenging	Shell graft
Tibial plateau	Uncommon, difficult access	Dowel or shell

Pathology	Procedure	Timing
Malalignment	HTO or DFO	Staged or concurrent
ACL deficiency	ACL reconstruction	Concurrent or staged
Meniscal deficiency	Meniscal allograft	Concurrent preferred
PCL deficiency	PCL reconstruction	Staged usually

Osteochondral Allograft (OCA)

OSTEOCHONDRAL ALLOGRAFT (OCA)

INDICATIONS BY LESION TYPE

Critical Must-Knows

Examiner's Pearls

Clinical Imaging

Critical OCA Exam Points

Fresh vs Frozen

Large Lesion Solution

Bone Stock Restoration

Availability Limitation

OCA vs Other Cartilage Procedures

FRESHFRESH - Why Fresh Matters

LARGELARGE - When to Use OCA

SCREENGraft Processing

Overview and Epidemiology

Indications

Contraindications

Pathophysiology and Mechanisms

Fresh vs Frozen - The Critical Distinction

Fresh vs Frozen Allograft

Why Cartilage is Immune-Privileged

Graft Integration

Classification Systems

Graft Geometry Classification

Common OCA Locations

Clinical Assessment

History

Examination

Assess Contributing Factors

Investigations

Investigation Protocol

Management Algorithm

Treatment Selection

Associated Procedures

Pre-operative Planning

Pre-operative Steps

Surgical Technique

Dowel/Plug Technique

Surgical Steps

Maintain Cartilage Viability

Shell Graft Technique

Hemicondylar/Large Segment Grafts

Complications

Disease Transmission Risk

Postoperative Care and Rehabilitation

Weight-Bearing Protocol

Progression

Return to Sport

Activity Progression

Outcomes and Prognosis

Long-term Outcomes

Evidence Base and Key Trials

OCA Long-term Survivorship

Fresh vs Prolonged Storage

OCA for Femoral Condyle AVN

Return to Sport After OCA

Bipolar OCA

Exam Viva Scenarios

Scenario 1: Large Femoral Condyle Lesion (~2-3 min)

Scenario 2: Fresh vs Frozen (~2-3 min)

Scenario 3: Bipolar Lesions (~2-3 min)

MCQ Practice Points

Australian Context and Medicolegal Considerations

Australian Practice

Documentation Standards

Medicolegal Considerations

OSTEOCHONDRAL ALLOGRAFT (OCA)

Definition

Fresh vs Frozen

Indications (LARGE)

Key Numbers

Advantages

Disadvantages

Osteochondral Allograft (OCA)

OSTEOCHONDRAL ALLOGRAFT (OCA)

INDICATIONS BY LESION TYPE

Critical Must-Knows

Examiner's Pearls

Clinical Imaging