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Osteochondral Lesions of the Talus – Allograft Repair


Co-Authors:  Milford H. Marchant Jr., M.D.; Mark E. Easley, M.D.; James A. Nunley II., M.D.


Osteochondral Lesions of the Talus Review

Etiology
- Primary Causes
- Trauma
- Ischemic Necrosis
- Embolic phenomenon
- Ossification Defects
- Predisposing Factors
- Endocrine Disorders
- Peripheral vascular disease
- Genetic Predisposition?
- 10-25% Bilateral Lesions

Evaluation
- Presentation
- Acute inversion injury
- Chronic Ankle pain
+/- history of trauma
+/- instability
- Known History of OLT +/- prior treatment
- Symptoms
- Pain
- Catching, grinding
- Feelings of instability and give-way episodes

Diagnosis and Staging
- Radiography
- X-ray – initial evaluation
- MRI – modality of choice for suspected lesions
- CT-Scan – modality of choice for known lesions
- Arthroscopy
- Gold standard for diagnosis and determining optimal treatment modality

Treatment Plan
- Acute vs. Chronic symptoms
- Radiographic Staging / Severity of Lesion
- Location of the Lesion
- Quality of Subchondral Bone
- Ankle Instability
- Prior Interventions

Treatment Modalities
- Non-Tissue Transplantation
- Activity Restriction
- Internal Fixation
- Arthroscopy
- Excision
- Curettage / Abrasion
- Drilling
- Micro-fracture

- Tissue Transplantation
- Modalities
- Autologous Bone Grafting
- Autologous Chondrocyte Transplantation
- Carticel
- Osteochondral Autograft Transplantation (OATs)
- Single Osteochondral Plug
- Mosaicplasty
- Osteochondral Allograft Transplantation
- Benefits
- Provides the ability to fill in a larger defect
- Provides an articulating surface
- Prevents excessive weight bearing loads on the remaining portion of the talus which would accelerate ankle joint arthritis


Osteochondral Allograft Transplantation
- Allograft Transplantation is proving to be beneficial for large osteochondral defects where duplication of the anatomy would be difficult with autologous tissue.
- Osteochondral Autograft Transplantation Limitations
- Lesion size = Limited “extra” cartilage
- Only Carticel can fill irregular shaped lesions
- Flat surface required
- Attempts at angular repairs have been challenging

- Allograft Talus is size matched = Custom fit
- Able to treat the “shoulder lesion”
- Defect involving more than one articulating plane (Figure 1)

- Allograft Benefits
- In Fresh Allografts, Viable Chondrocytes are present within an intact Hyaline Cartilage Structure
- Arthroscopy and Mosaicplasty rely on fibrocartilage ingrowth
- Shorter procedure
- No second operative site for harvest
- Compared to OATs or Mosaicplasty
- Single surgical procedure
- Compared to Autologous Chondrocyte Transplants (Carticel)

- Allograft Risks
- Transmission of Disease
- Immune Response
- Resorption and fragmentation of the graft
- Procedure-based risk
- Osteotomy Non-union
- Post-op Arthritis

- Specimens
- Tissue Banks uphold strict guidelines and protocol established by American Association of Tissue Banks
- Allograft procurement is performed in patients 18 - 45y within 24h
- Transplantation occurs with 72 hours for fresh grafts
- Extension for up to 5 - 7 days has been reported
- Donor patients are screened to eliminate possible disease transmission.
- Extensive medical and social histories
- Multiple Cultures and serologic studies are performed
- Articular cartilage is examined in a class-100 clean room
- Particle count < 100 particles per cubic foot of a size 0.5µ (micron) and larger.

- Fresh vs. Fresh-Frozen Allograft
- Storage
- Fresh grafts  = 4 degrees Celsius in Ringers lactate
+/- Antibiotics (Ancef, Bacitracin) added to the milieu
+/- Cryopreservative (dimethylsulfoxide DMSO, glycerol)
- Frozen Grafts  = -70  -80 degrees Celsius
+ Cryopreservative
- Differing Chondrocyte Viability

- Ohlendorf, et al (1996)
- Studied effects of Cryopreservation to -80 deg on Calf Cartilage using con-focal and conventional fluorescent microscopy
- Rapid freezing (2 deg/min)  = non-viable chondrocytes
- Slow freezing (0.5 deg/min)  = superficial chondrocyte layer viable only
- Slow freezing with cryopreservative  = superficial chondrocyte layer viable only
- Chondrocyte survival in cryopreserved osteochondral articular cartilage.

- Rodrigo, et al (1987)
- Compared rat chondrocyte viability in fresh vs. fresh-frozen osteochondral allografts
- Chondrocytes stored at 4 deg had 75% viability in 24 hours, and 47% at 48 hours
- Bone viability declined rapidly to 10% in 24 hours
- Significant decline in viable chondrocytes after freezing
- 8/10 specimens had 0% viability
- 2/10 showed almost 100% viability
- Immunogenicity also declined with freezing
- Deep-freezing versus 4 degrees preservation of avascular osteocartilaginous shell allografts in rats.

- Differing Immunogenic response
- Chondrocytes are imbedded in Hyaline Matrix
- By nature of location inside a synovial joint are somewhat immunopriveleged.1
- Presently, there are no requirements to immunologically match donor and host
- Acute rejection has thus far not been a clinical problem
- Marrow depletion is necessary via high pressure pulse lavage prior to implantation

- Stevenson, et al. (1989)
- Evaluated allograft cartilage implanted in dogs
- 4 categories based on Canine Leukocyte antigen matching and fresh vs. cryopreserved grafts
- Antigen mismatched Frozen
- Antigen mismatched Fresh
- Antigen matched Frozen
- Antigen matched Fresh
- No dog had any noticeable clinical abnormality
- All cartilage specimens were thinned
- Inflammatory response in synovium most severe in Fresh, Antigen mismatched allografts
- The worst specimen was seen in Frozen, antigen mismatched
- Both histologically & biochemically
- Fresh Antigen matched grafts performed the best
- The fate of articular cartilage after transplantation of fresh and cryopreserved tissue-antigen-matched and mismatched osteochondral allografts in dogs.

- Allograft Choice
- Most Literature is leaning towards the use of Fresh Osteochondral Allograft
- Based on the viability of the chondrocytes and the maintenance of the cartilage matrix
- Grafts that have shown to be most viable when they are slow cooled to 4 deg Celsius and preserved

- Outcomes
- Literature has cited its use in Berndt and Harty Stage II, III, and IV lesions.

- Thomas, et al (1997)
- Fresh-frozen Talar allograft
- Used during reconstruction for a benign osteochondral tumor of the talar dome.
- 18 months s/p surgery pt was participating in normal activity pain free.
- Repair of an osteochondral tumor of the talus utilizing a fresh-frozen cadaveric graft.

- Gross, et al (2001)
- Evaluated 9 cases Clinically and Radiographically
- Pre-op:  All subjects had an area of Fragmentation and Collapse that could not be reattached
- Lesion at least 1 cm in diameter / 5 mm in depth
- All patients had prior procedures
- Average graft life = 9 years (3 – 19)
- 3/9  patients required fusions at 3, 5, 9 years out for graft fragmentation and collapse
- 6 pts with intact grafts required no assistive device
- 5 / 6 had no pain; 1 /6 had mild intermittant pain
- Osteochondral defects of the talus treated with fresh osteochondral allograft transplantation.

- Caylor and Pearsall (2002)
- Case report:  16-year-old female with 3 years pain after ankle sprain
- 2 Allograft Bone plugs used to treat a 18mm x 18mm lesion on posteromedial talus
- Post – op Protocol
- Immobilized 2 weeks
- ROM exercise only from 2 – 6 weeks
- Partial weight bear 6 – 12 weeks
- Full weight bear from 12 – 20 weeks
- Unlimited activity at 20 weeks
- F/U at 1 year, patient had no pain or limitations
- Fresh osteochondral grafting in the treatment of osteochondritis dissecans of the talus.


Surgical Technique - Lateral
- Care to avoid damage to the Sural n. & Peroneal artery posteriorly, & superficial peroneal n. anteriorly.
- Removal of Osteophytes at Talofibular Joint
- Fibular Osteotomy - Pre drill holes for plate
- Removal of Osteochondral Lesion and Curettage
- Preparation of Graft Site
- Template (Figure 2)

- Allograft Placement (Figure 3)

- Articulation Testing and Screw Fixation with Countersinking
- Osteotomy Repair
- Intra-operative Radiographs (Figures 4 & 5)

Surgical Technique - Medial
- Utilizes Medial Malleolar Osteotomy (Figure 6)

 


Summary
- Cartilage injuries and Osteochondral Lesions of the talus remain a challenge within Orthopaedics
- MRI & CT scan is useful with identifying and defining pathology in patients with suspected lesion
- Arthroscopy is the Gold Standard for diagnosis and treatment planning
- For large, abnormally positioned lesions, or those that have failed prior intervention, Allograft Transplantation is a promising treatment modality
- Further investigation and research is still needed in regards to
- graft storage options
- long term immunologic reactions
- clinical outcomes