AUTOLOGOUS CHONDROCYTE TRANSPLANTATION

Melanie McNeal, PT, CSCS, CFT

DAVID LINTNER, MD

Articular cartilage (AC) provides a resilient surface for friction free movement of joints. It must bear loads of more than 5 times body weight during normal activities. With a compressive load, the cartilage deforms to increase contact area and spread the load over a greater area of the joint.

AC is composed of an extracellular matrix of mainly type II hyaline collagen and proteoglycan aggregate produced by a small population of chondrocytes. The chondrocytes are responsible for the synthesis, maintenance, degradation, and repair of articular cartilage. The arrangement of type II collagen fibrils gives AC its stiffness and strength whereas the proteoglycan acts to increase shock absorption and resist deformation. Articular cartilage has a maximum thickness of 3-4 mm because it depends on diffusion of nutrients from the synovial fluid for nutrition.

Articular cartilage injury can result from one of three types of trauma: compaction, shearing, or avulsion. It is commonly injured in conjunction with other knee injuries, such as cruciate ligament ruptures. Some studies show that 80% of those who sustained ACL tears had concomitant bone bruises (subchondral trabecular microfracture). The articular cartilage is avascular and aneural and unless subchondral bone has been penetrated with injury, no inflammatory response will occur. Patients may have pain, effusion, or mechanical symptoms and because of the inadequate healing response, joint mechanics can be altered and the adjacent cartilage can undergo degeneration.

When an osteochondral injury is sustained, a significant hemarthrosis results due to the highly vascularized subchondral bone. An inflammatory response ensues and a fibrin clot is formed. Mesenchymal stem cells are activated and differentiate into chondrocytes which produce type I and II collagen to fill the defect. The new articular cartilage that is formed, however, is more fibrous like and over time, degenerates and leaves exposed subchondral bone. This results in osteoarthritis and significant symptoms.

In the past, the surgical procedures utilized to treat chondral lesions include abrasion, drilling, and microfracture. The goal is to penetrate subchondral bone to stimulate a healing response. Because true hyaline cartilage is not capable of being formed over the injured area, however, over time, degeneration ensues and further damage can result.

Autologous chondrocyte transplantation (Carticel) was first performed to treat patellar defects in rabbits in 1984. The first Carticel procedure in humans was performed in Sweden in 1987 and the procedure has since become popular in the US.

Indications for Carticel: Patients between the ages of 15-55 who have symptomatic, full-thickness articular surface defects or for osteochondritis dissecans (OCD) of the medial/lateral femoral condyle with an unstable fragment. For patients older than 55 years, a TKR is the treatment of choice.

The patient will undergo two surgical procedures. The first is to harvest the articular cartilage from a minor weight-bearing area, usually the medial femoral condyle. Approximately 200-300mg of articular cartilage is necessary for enzymatic digestion and cell culturing. This cartilage is sent to a lab where cultures are grown.

The second procedure consists of the following procedures:

Radical excision of the injured area and debridement to subchondral bone but without bleeding
The defect is measured using a template
Periosteum from the upper medial tibia is taken – the same size as the defect- to be used as a periosteal flap
The flap is sutured over the defect with the cambium layer facing the subchondral bone; an opening in the superior aspect of the defect is left to inject the cells
The cells are injected into the defect and the site is closed.

Results of Swedish experiences with 2-10 year follow-up following isolated femoral condyle injuries are promising. At an average follow-up of 4 years, 89% of patients reported subjective good or excellent improvement. For isolated femoral condyle injury + ACL, at 4.3 years follow-up, 63% considered themselves better (85% if ACL revision patients were excluded). For patients with OCD at an average follow-up of 3.9 years, 88% felt significant improvement. Arthroscopic evaluation of these patients revealed 80% had hyaline cartilage filling the defect.

OSTEOCHONDRAL AUTOGRAFT PROTOCOL

PHASE ONE

Weeks 1-8

Patient will be in immobilizer or IROM brace locked in full extension. The brace is to be worn at all times except during exercise. Patient will be NWB with crutches for 6 weeks.

The ROM limitations and exercise prescription is slightly different based on the area of defect. Trochlear repairs can immediately bear partial weight but will be restricted more in regards to ROM initially and should avoid active knee motion initially to avoid compression at the repair site.

EXERCISES

ROM

PASSIVE ROM ONLY!!

Femoral condyle defect Trochlear defect

Week 1-2 0-45° 0-30°

Week 2-4 0-90° 0-90°

Week 4-6 0-110° 0-110°

Week 6-8 0-120° 0-120°

*Make sure to consult with Dr. Lintner regarding ROM limitations based on area of defect

*Patellar mobilization and scar massage are critical

*Heel slides can be performed seated or supine at wall

*Cycling can be initiated when 110° of flexion is reached

STRENGTH AND NM CONTROL

Quad sets (10 X 10sec)– the more the better – at least 100/day

SLR – 4 way

Seated hip flexion

SAQ (When ROM allows) and LAQ- ONLY IF FEMORAL CONDYLE DEFECT

NO ACTIVE MOTION ALLOWED FOR TROCHEAR REPAIRS

Multi-hip

STRETCHING

Hamstring stretch (not aggressive if HSG) – hold 30 seconds

Gastroc stretch with towel – hold 30 seconds

GAIT

Trochlear repair – PWB to FWB per MD orders (FWB 4-6 wks)

Femoral condyle defect – NWB 6 wks; Initiate PWB at 6 weeks with bilateral crutches if approved by MD

MODALITIES

EMS may be needed to facilitate quad if contraction cannot be voluntarily evoked

EGS may be needed to help control swelling and increase circulation

Ice should be used following exercise and initially every hour for 20 minutes

*Perform HEP 3X/Day

PHASE TWO

Weeks 8-16

By end of this phase, the patient should ambulate with N gait I, have good quad control, controlled swelling, and be able to ascend/descend stairs.

Closed chain and open chain activities are initiated in this phase in a limited range: 0-60° for closed chain and 90-30° for open chain activities

EXERCISES

ROM

Goal is 0-140° - full range

Perform scar massage aggressively at portals

Prone hangs (do not add weight to ankle) w/BF

Heel slides – seated and/or supine

STRENGTH

Quad sets are continued until swelling is gone and quad tone is good

SLR (4 way) add ankle weights when ready

Shuttle/Total gym (0-60°) bilateral and unilateral- focus on weight distribution more on heel than toes to avoid overload on Patella tendon

Multi-hip – increase intensity as able

Closed chain terminal knee extension (TKE) with theraband

Leg Press (0-60°)

Step-ups – forward, lateral

Step-overs

Wall slides

Mini-squats – focus on even distribution of weight

Calf raises

Hamstring curls

Knee extension (90-30°)

CARDIO

High intensity cycling

EFX

Treadmill

STRETCHING

Continue with HS and calf stretching

Initiate quad stretch when near full ROM achieved

BALANCE

Single leg stance – even and uneven surface – focus on knee flexion

Plyoball – toss

Lateral cone walking with single leg balance between each cone

Steamboats

GAIT

FWB with crutches

Cone walking – forward and lateral

D/C crutches when N gait

MODALITIES

Continue to use ice following exercise

*Continue with HEP

Pt will usually be measured for more functional brace during this period. Can D/C IROM around week 4, when crutches are no longer needed.

PHASE THREE

Weeks 16-36

Exercises will be advanced in intensity based on quad tone – a patient who continues to have poor quad tone must not be advanced to activities that require high quad strength such as squats and lunges

STRENGTH

Continue with above exercises, increasing intensity as able

Step-ups – forward and lateral; add dumbbells to increase I; focus on slow and controlled movement during the ascent and descent

Squats – Smith press or standing

Lunges –forward and reverse; add dumbbells or med ball

Swiss ball and foam roll hamstring exercises – supine bridge with knee flexion, bridge with HS curl

T-band hip flexion

Single leg squats

Russian dead lifts – bilateral and unilateral

Single leg wall squats

Cycle – increase intensity; single leg cycle maintaining 80 RPM

BALANCE

Plyoball – toss – even and uneven surface

Squats on balance board/foam roll/airex

Steamboats – 4 way; even and uneven surface

Strength activities such as step-ups and lunges on airex

MODALITIES

Continue to use ice after exercise

*Continue with HEP at least 3X/week

PHASE FOUR

Weeks 36-52

Exercises for strengthening should continue with focus on high intensity and low repetitions (6-10) for increased strength.

Biodex may be implemented at high speeds (³180°).

Initiate lateral movements and sports cord: lunges, forward, backward, or side-step with sports cord, lat step-ups with sports cord, step over hurdles.

Jogging/Plyos:

When cleared by Dr. Lintner, the patient can begin to jog at a slow to normal pace focusing on achieving normal stride length and frequency. Initiate jogging for 2 minutes, walking for 1 until this is comfortable for the patient and then progress the time as able. Jogging should first be performed on a treadmill or track (only straight-aways) and then progressed to harder surfaces such as grass and then asphalt or concrete. It is normal for the patient to have increased swelling as well as some soreness but this should not persist beyond one day or the patient did too much.

Jump rope and line jumps can be initiated when the patient is cleared to jog.

This can be done for time or repetitions and should be done bilaterally and eventually progressed to unilateral.

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