Marrow stimulation techniques of which microfracture is the most popular depend on the ability of undifferentiated cells to transform in to cartilaginous repair tissue.

Full thickness chondral lesions can be unexpectedly noticed only at the time of arthroscopy.

Microfracture can be used as first line treatment and performed purely arthroscopically.

Techniques of preparing the chondral lesion as well as post-operative rehabilitation are important to achieve good outcomes with microfracture.

Microfracture could be performed for both traumatic and degenerative lesions.

The ideal patient should preferably be less than 45 years of age, not obese and with a lesion on the femoral condyle less than 4 cm2 in size.

The patient should be compliant with rehabilitation and have realistic expectations and activity levels.

Always remember alignment, meniscal deficiency and ligament deficiency when dealing with any chondral defect and with the patellofemoral joint tracking should be optimal.

Microfracture is contraindicated in inflammatory joint disease and if the articular cartilage surrounding the lesion is too thin.

The term ‘microfracture’ was coined and the technique developed by JR Steadman. It is a safe, effective, one stage, first line treatment for full thickness chondral defects.

Prognostic factors –

  • Age – younger age better prognosis
  • Lesion size less than 4cm2 show better prognosis
  • Activity level- High impact athletes have worse prognosis though still improved
  • Increased body weight- worse prognosis
  • Patello-femoral lesions worse
  • Better fill of defect on MRI correlated to better clinical results

Technique of Microfracture

Microfracture curettes and awls

Step 1 – arthroscopic visualisation of all compartments

Any other pathology in the knee other than ligament reconstruction is dealt with prior to microfracture. Steadman recommends doing the arthroscopy without a tourniquet but visualisation of bleeding points could be achieved otherwise by turning off the fluid inflow or by application of suction using the shaver.

Step 2 – debridement and preparation of defect base and edges.

This is achieved using a combination of shavers to deal with the calcific cap and loose flaps of cartilage and a sharp curette to prepare stable vertical edges.

 

Step 3 – calculating area of defect

Most defects are elliptical. Measure the length on the long and short axes. The formula for area of an ellipse is pab/4

area of the defect- long axis=a short axis=b pi=3.142

Step 4 – preparation of multiple holes 3-4 mm apart and about 2-4mm deep

Microfracture awls with suitably angled tips impacted gently so that vertical holes can be made with no thermal damage. Start making the holes right at the edge of the lesion.

 

Step 5 – visualisation of adequacy of holes by observing fat and blood seep through

Step 6 – knee flexion angle for patello-femoral lesion contact

This helps in the decision on locking the knee brace at the appropriate angle to prevent shearing of the clot

Arthroscopy showing microfracture repair tissue at six months –

 

Post-operative rehabilitation

Basic science evidence has demonstrated that compressive loading may have a positive impact on articular cartilage healing. Shear loading is detrimental. Rehabilitation for microfracture depends on lesion size, location and other concomitant surgery.

Reinold MM, Wilk KE, Macrina LC, Dugas JR, Cain EL. Current concepts in the rehabilitation following articular cartilage repair procedures in the knee. J Orthop Sports Phys Ther. 2006 Oct;36(10):774-94. Review
Irrgang JJ, Pezzullo D: Rehabilitation following surgical procedures to address articular cartilage lesions of the knee. J Orthop Sports Phys Ther 28:232-240, 1998.


Recommended programme for –

1 Femoral or tibial lesions

  • Regain full range of movements and patella mobilisation.
  • Continuous passive mobilisation 6-8 hrs per day or in the absence of CPM, passive flexion and extension of the knee with 500 repetitions three times per day
  • Touch-down (10% body weight) weight bearing for 6-8 weeks
  • Exercise bike without resistance at 2 weeks
  • Resistance exercises by 12 weeks
  • No free weights until 16 weeks
  • No return to contact/pivoting sport or jumping for 4-9 months

2 Patello-femoral lesions

  • Use knee brace restricting flexion to avoid lesion coming in to contact with patella/trochlea (usually 0-20) for 8 weeks
  • Continue passive mobilisation and start early weight bearing in brace
  • Avoid lesion contact point with resistance exercises for 4 months
  • Similar rehabilitation after 12 weeks

The rehabilitation could be altered for lesions smaller than 2 cm2 with earlier weight bearing and possibly avoid CPM.

Marder RA, Hopkins G Jr, Timmerman LA. Arthroscopic microfracture of chondral defects of the knee: a comparison of two postoperative treatments. Arthroscopy. 2005 Feb;21(2):152-8

Results of microfracture
Results from the Steadman Hawkins clinic

For the treatment of full thickness traumatic defects 80% of patients rated themselves as improved at 7 years. There were 71 of 75 knees followed up for an average of 11 years (range 7-17 years). Significant improvements were also seen in the Lysholm, Tegner, SF-36 and WOMAC scores. The Lysholm scores showed poorer results in patients aged greater than 35 years.

Steadman also shows good outcomes in knee scores for 81 patients at 2.6 years follow-up for isolated degenerate chondral defects.

In a study on National Football League players, 19/25 (76%) of players returned to professional football after microfracture the following season. 6/25 retired at average 4.5 years follow-up due to various reasons.
Steadman JR, Briggs KK, Rodrigo JJ, et al: Outcomes of microfracture for traumatic chondral defects of the knee: Average 11-year follow-up. Arthroscopy 19:477-484, 2003.
Miller BS, Steadman JR, Briggs KK, et al: Patient satisfaction and outcome after microfracture of the degenerative knee. J Knee Surg 17:13-17, 2004.
Steadman JR, Rodkey WG: Microfracture in the pediatric and adolescent knee. In Micheli LJ, Kocher M (eds): The Pediatric & Adolescent Knee. Philadelphia, WB Saunders, 2004.
Steadman JR, Rodkey WG, Briggs KK: Microfracture chondroplasty: Indications, techniques, and outcomes. Sports Med Arthrosc Rev 11:236-244, 2003.

Results from other centres

1. Brigham and Women’s Hospital, Boston, USA
Mithoefer K, Williams RJ 3rd, Warren RF, Potter HG, Spock CR, Jones EC, Wickiewicz TL, Marx RG. Chondral resurfacing of articular cartilage defects in the knee with the microfracture technique. Surgical technique. J Bone Joint Surg Am. 2006 Sep;88 Suppl 1 Pt 2:294-304.
Mithoefer K, Williams RJ 3rd, Warren RF, Wickiewicz TL, Marx RG.High-impact athletics after knee articular cartilage repair: a prospective evaluation of the microfracture technique. Am J Sports Med. 2006 Sep;34(9):1413-8.

In a prospective study, knee function was rated good to excellent for thirty-two patients (67%). Magnetic resonance imaging in twenty-four knees demonstrated good repair-tissue fill in the defect in thirteen patients (54%), moderate fill in seven (29%), and poor fill in four patients (17%). The fill grade correlated with the knee function scores. The best short-term results are observed with good fill grade, low body-mass index, and a short duration of preoperative symptoms.

In a study on high impact athletes, after an initial improvement, score decreases were observed in 47% of athletes. Forty-four percent of athletes were able to regularly participate in high-impact, pivoting sports, 57% of these at the preoperative level. Return to high-impact sports was significantly higher in athletes with age <40 years, lesion size <200 mm(2), preoperative symptoms <12 months, and no prior surgical intervention

2. A Gobbi, Milan, Italy
Gobbi A, Nunag P, Malinowski K. Treatment of full thickness chondral lesions of the knee with microfracture in a group of athletes. Knee Surg Sports Traumatol Arthrosc. 2005 Apr;13(3):213-21.

This is a prospective study on 53 athletes with average age of 38 years (range 19-55) and mean follow-up was 72 months (range 36-120). At final follow-up 70% scored IKDC A or B. Tegner improved at 2 years from 3.2 to 6 though 80% of patients had a decline in sports activity level.

3. Department of Orthopaedic and Trauma Surgery, Albert Ludwig University of Freiburg, Freiburg, Germany
Kreuz PC, Erggelet C, Steinwachs MR et al. Is microfracture of chondral defects in the knee associated with different results in patients aged 40 years or younger? Arthroscopy. 2006 Nov;22(11):1180-6.

85 patients (mean age, 39 years) with full-thickness chondral lesions underwent the microfracture procedure and were evaluated preoperatively and at 6, 18, and 36 months. The scores improved in all patients though patients aged 40 years or younger had significantly better results (P < .01). Between 18 and 36 months after microfracture, the ICRS score deteriorated significantly (P < .05) in patients aged over 40 years whereas younger patients with defects on the femoral condyles and on the tibia showed neither a significant improvement nor a significant deterioration in the ICRS score (P > .1). Magnetic resonance imaging 36 months after surgery revealed better defect filling and a better overall score in younger patients (P < .05).

Calcified healing tissue after microfracture

Comparative studies
1. Department of Orthopaedic Surgery, University of Tromsø, Norway.

Knutsen G, Drogset JO, Engebretsen L et al A randomized trial comparing autologous chondrocyte implantation with microfracture. Findings at five years. J Bone Joint Surg Am. 2007 Oct;89(10):2105-12.

This randomized trial was to compare autologous chondrocyte implantation with microfracture. Forty patients were treated with autologous chondrocyte implantation, and forty were treated with microfracture All lesions involved the femoral condyles and 64.5% were traumatic defects. Sizes ranged from 2-10 cm2. At the five-year follow-up interval, there were nine failures (23%) in both groups. None of the patients with predominantly hyaline cartilage repair tissue at the two-year mark had a later failure. There was no significant difference in the clinical and radiographic results between the two treatment groups. One-third of the patients had early radiographic signs of osteoarthritis five years after the surgery.

2. Department of Orthopaedics and Trauma, Kaunas University Hospital, Kaunas, Lithuania

Gudas R, Kalesinskas RJ, Kimtys V et al. A prospective randomized clinical study of mosaic osteochondral autologous transplantation versus microfracture for the treatment of osteochondral defects in the knee joint in young athletes. Arthroscopy. 2005 Sep;21(9):1066-75.

Prospective randomized clinical study comparing the outcomes of mosaic-type osteochondral autologous transplantation (OAT) and microfracture (MF) procedures for the treatment of the articular cartilage defects of the knee joint in young active athletes. total of 60 athletes with a mean age of 24.3 years (range, 15 to 40 years) Only those athletes playing in competitive sports at regional or national levels were included in the study.

Fifty-seven athletes (95%) were available for a follow-up. There were 28 athletes in the OAT group and 29 athletes in the MF group. The mean duration of symptoms was 21.32 +/- 5.57 months and the mean follow-up was 37.1 months (range, 36 to 38 months), and none of the athletes had prior surgical interventions to the affected knee.

Patients were evaluated using modified Hospital for Special Surgery (HSS) and International Cartilage Repair Society (ICRS) scores, radiograph, magnetic resonance imaging (MRI), and clinical assessment. An independent observer performed a follow-up examination after 6, 12, 24, and 36 months. 96% had excellent or good results after OAT compared with 52% for the MF procedure (P < .001). Younger athletes did better in both groups. No serious complications were reported. There was 1 failure in the OAT group and 9 in the MF group. The ICRS Cartilage Repair Assessment for macroscopic evaluation during arthroscopy at 12.4 months showed excellent or good repairs in 84% after OAT and in 57% after MF. MRI evaluation showed excellent or good repairs in 94% after OAT compared with 49% after MF Twenty-six (93%) OAT patients and 15 (52%) MF patients returned to sports activities at the preinjury level at an average of 6.5 months (range, 4 to 8 months).

Autologous Membrane Induced Chondrogenesis (AMIC)
This is one stage technique of microfracture with augmentation where a collagen membrane is implanted over a chondral defect that has been treated by microfracture technique. It is not clear whether this is likely to produce superior repair tissue but the technique may be useful in treating a large lesion with microfracture.

Breinan showed that use of a Type II collagen membrane to cover a defect after treatment with microfracture created superior tissue fill though the tissue was still predominantly fibrocartilage. Kramer (2006) reported that mesenchymal stem (MS) cells can in fact be recovered from matrix material saturated with cells from bone marrow after microfracture. This introduces a new technique for MS cell isolation during arthroscopic treatment.

However Dorotka showed that although the collagen matrix is an adequate environment for BMSC in vitro, the additionally implanted unseeded collagen matrix did not increase the repair response after microfracture in chondral defects. They showed the benefit of adding autologous cultured chondrocytes.

Breinan H.A., Hu-Ping Hsu, Martin S, and Spector M, Healing of canine articular cartilage defects treated with microfracture, a typeII collagen matrix, or cultured autologous chondrocytes; J Orthop Research 2000, 18,781

Kramer J, Bohrnsen F, Lindner U, Behrens P, Schlenke P, Rohwedel J In vivo matrix-guided human mesenchymal stem cells. Cell Mol Life Sci. 2006 Mar;63(5):616-26
Dorotka R, Windberger U, Macfelda K, Bindreiter U, Toma C, Nehrer S. Repair of articular cartilage defects treated by microfracture and a three-dimensional collagen matrix. Biomaterials. 2005 Jun;26(17):3617-29