Candidates for treatment with autologous chondrocyte implantation (ACI) are those suffering clinically significant, symptomatic defects to the articular cartilage of the knee. Appropriate defects for treatment are typically found in a knee which presents with joint pain, swelling, catching or grinding. These symptoms may be independent of, accompany, or be secondary to injury of the cruciate ligament, meniscus or other associated musculoskeletal tissues.

Traditional diagnostic methods may be employed (MRI, x-rays, direct arthroscopic visualization) to identify clinically inappropriate patients, due to advanced degenerative articular changes. Currently, ACI is generally applied to patients aged 15-55 years, although it is ultimately the treating surgeon's assessment of the physiologic condition of the affected joint that will determine appropriateness for treatment.

Arthroscopic evaluation of the joint is generally employed for final determination of a candidate's appropriateness. Inherent in the decision to treat with ACI is an assessment of the candidate's motivation and ability to comply with a rigorous post-operative rehabilitation program; this factor is critical to a successful outcome. If a defect is deemed suitable for treatment, and if the patient is willing to comply with the rehabilitation program, a cartilage biopsy is generally performed at the time of arthroscopy for subsequent culturing.

BACKGROUND INFORMATION

Following extensive animal research performed in the early 1980's, autologous chondrocyte implantation for treatment of articular defects has been in clinical use in Sweden since 1987. Early outcomes of the technique were reported in the New England Journal of Medicine (NEJM 331:889-895, October 6, 1994). This study reviewed outcomes of the technique in the first 23 patients treated for full thickness articular defects of the knee. In 14 of the 16 patients treated for defects of the femoral condyles (thigh bone) good to excellent results were reported. The two remaining patients suffered poor results with further treatment required.

Seven patients were treated for patellar defects, with only two reporting good or excellent results. It was later determined that success in these patients would require correction of coexisting patellar tracking problems and joint instabilities; the surgical technique was subsequently modified to incorporate these changes.

Dr. Lars Peterson, one of the pioneers of this technique, recently reported on further outcome findings at the 1996 annual American Academy of Orthopedics meeting. Drawing on a 251 patient experience, Dr. Peterson reported on 59 patients with at least 2 years post-operative follow-up. Overall, improvement was noted in 83% of all patients treated with the technique. Specifically, successful application was reported in 81% of the defects located on the femoral condyles, 85% of the lesions due to osteochondritis dissecans and 87% of patients suffering patellar defects.¹ Data collection is ongoing to further document the long term patient experience. (For further information on outcome studies: TREATMENT RESULTS: JUNE, 1997.)

RATIONALE FOR TREATMENT

Use of autologous cartilage implantation provides new hope for the unfortunate patient suffering from an articular cartilage injury. It is well documented that significant full thickness damage to an articular cartilage surface will not heal, and will likely undergo further degenerative changes over time.

Traditional treatments for articular defects include, primarily, those which violate the integrity of the underlying subchondral bone plate through techniques of drilling, abrasion or microfracture. These techniques lead to the formation of a fibrous scar tissue which is notably less durable than the cartilage tissue it is intended to replace.² These treatments are palliative with effectiveness generally limited to several years, prior to the reoccurrence of symptoms.^3,4,5 Repeated surgical intervention is typically required, with patient rehabilitation including significant restriction of future activity levels.

Existing and ongoing research in the use of autologous cells to treat articular defects supports the clinical evidence that ACI results in a superior repair tissue. When examined grossly, microscopically and histochemically, the repair tissue more closely resembles hyaline cartilage: the basis of normal articular tissue. Evidence indicates that the resultant repair tissue is one which gradually matures over time forming a durable long lasting repair, and which preserves the integrity of the joint.

THE SURGICAL PROCEDURE

This is a staged surgical procedure. The first step, biopsy tissue harvesting, is performed during arthroscopic examination of the joint. A small 200 - 300 mg tissue sample is removed from a non-weight bearing area, typically from the femoral condyle. The tissue is then sent for culturing, generally requiring 4 to 5 weeks. The post-arthroscopic patient care is routine.

The second procedure involves implantation of the autologous cultured cells. A 4-8 inch arthrotomy is performed to expose the joint and prepare the defect area to receive the 5-10 million cultured autologous cells. A small patch of periosteal tissue is taken from the tibia through a second incision, 2 to 4 inches long, over the patient's shinbone. This tissue is sutured over the debrided defect, and the circumference sealed with fibrin glue (an autologous blood product). The cells are injected under a watertight patch into the defect. If surgical correction of joint alignment or stability is required, it may be performed prior to or at the time of this implantation procedure. The wound is then closed in routine fashion and a soft elastic dressing is applied.

ASSOCIATED RISKS

Precautions should be taken in using autoogous chondrocyte in patients with known histories of anaphylaxis to gentamycin. Currently, Genzyme Tissue Repair,the only company to provide cultured autologous chondrocytes, indicates that the biopsy medium used with chondrocytes (biopsy source material) contains DMEM with gentamycin. However, the transport medium for the cultured cells does not contain gentamycin.

Intra-operative and postoperative complications resulting from any open knee procedure may occur as a result of cultured autologous chondrocyte implantation. While no serious adverse events definitely related to the use of autologous chondrocytes have been reported, risks from the surgical procedure including infection and inflammatory responses must be taken under consideration.

PATIENT REHABILITATION PROTOCOL

The following protocol is recommended based on more than 8 years of experience gathered at the Gothenburg Medical Center, Gothenburg, Sweden.

Week 1-6

• Unload the operated leg with crutches. Allow a maximum load of 40 lbs. After 3 weeks, the load may be increased as recommended by the physician.

Week 7-12

• Gradually increase the weight load. Once full control of extension without limping is achieved, begin to decrease use of crutches. Start ambulating without crutches indoors, later adding short outdoor walks. Gradually increase the distance walked.

• Motion and circulation training should start immediately after the operation and be continued at short, frequent intervals.
• Continuous passive motion ( CONTINOUS PASSIVE MOTION - ORTHOLOGIC) will be started on day 1 postoperatively and continue for 3 weeks.
• Active, floor supported motion training is to be practiced. Isometric quadriceps training in knee extension, straight leg raises with the foot upright, and turned outward and inward respectively. All other leg muscles to be maintained.

• Active motion training against gravitational force on the leg only.
• 2-4 lbs leg weight for straight leg raises if the knee can be fully extended.
• Rubber band or pulley training: hamstring curls, straight standing leg pulls in all directions.
• Once 90 degrees flexion attained: stationary cycling with low resistance.
• If available, pool mobility training: swimming with straight leg kicks or use of kickboard, gradually change over to wet vest training.

• Start of functional training - closed chain exercises.
• Balance: quadriceps training if knee extensions can be performed without pain.
• Knee extensions from 45 to 0 degrees with 2-4 lbs weight. (Thigh may be supported by a table or a roll under the knee joint.)

  • a) for patella implants, isometric strength training at different angles. After 12 weeks, carefully start dynamic strength training - increase slowly.

  • b) for femoral or tibial implants: as above, but start dynamic strength training at week 9 and increase slowly.

• Most of the quadriceps training takes place isometrically.
• Modify training progression to overall condition of the leg.
• Walking, bicycling and swimming is recommended. (Caution: wait 6 months for use of breast stroke or side stroke.)
• The proper amount of motion and strength training combined with functional training gives the best results.
  • Light jogging: 4-6 months
  • Running: 6 months
  • Skating: 3-6 months
  • Cross country skiing: 3-6 months
  • Strength test:
    • patella implant: 12 months
    • femur or tibia implant: 9 months
• Motion training stimulates the healing and the cartilage adaptation to the joint area.
• Swelling and possible warmth of the joint may occur during the first few months. If swelling occurs during training, the weights should be reduced.
• Crepitation may develop in the knee. If it is not associated with pain, it may be interpreted as soft tissue hypertrophy. If a painful click or painful region is present, the dynamic quadriceps training should occur above and below the region; work without weights during full range of motion training.
• Cartilage heals slowly, and the late processes of maturation and tempering will occur between 12-18 months.

1. Presented at the American Academy of Orthopaedic Surgeons Annual Meeting, Atlanta, Ga., February, 1996.
2. Furukawa,T., Eyre, DR., Koide, S., Gilmcher, MJ, Biochemical studies on repair cartilage resurfacing experimental defects in the rabbit knee. J Bone Joint Surg AM 1980; 62 (1): 79-89.
3. Tippet and coworkers reported good to excellent results from drilling in about 85% of their patients at 62 months. However, this was in combination with high tibial valgus osteotomy.
4. Lanny Johnson reported on 399 patients undergoing abrasion arthroplasty (debridement) with an average of 60 years. Only 12% reported no complaints post operatively. By 4-6 months, the repair tissue had become fibrocartilage. Arthroscopy, 2:54-56, 1986.
5. Rodrigo and coworkers reported on the use of microfracture. However, this paper demonstrates the effectiveness of continuous passive motion (CPM) following microfracture. Of the 77 patients followed, 15% of the CPM group reported no improvement; 45% of the non-CPM group reported no improvement.

(Courtesy of Genzyme Tissue Repair)

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Last Update: 04/03/2003
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