Indications
Microfracture knee surgery, which is used to address chondral defects, was originally developed to decrease pain while restoring mobility to high-demand athletes. The procedure began to gain popularity with the general public after successful outcomes were seen with several prominent athletes.
By recognizing isolated full-thickness chondral defects, microfracture aims to restore knee function and decrease the pain associated with injury. Microfracture surgery is a single-stage procedure that is ideally suited for small, well-contained, cartilage lesions.1 The procedure itself, involves local stimulation to induce a fibrin clot containing pluripotent, marrow-derived mesenchymal stem cells that are able to differentiate into fibrochondrocytes, resulting in a fibrocartilage repair with varying amounts of type I, II, and III collagen content.2-4
Current studies have shown a success rate of 75-80% among patients age 45 or younger, even among professional athletes.4 Good candidates for the procedure include those with limited areas of cartilage damage, those who are active and cannot participate in their sport or activity because of symptoms, and those with pain or swelling caused by the damaged area of cartilage. Patients who are not good candidates for microfracture include those with widespread arthritis of the joint, those who are inactive, and those who are unwilling to participate in a lengthy rehabilitation program after the procedures.
Preoperative Planning
A thorough history and physical exam are essential in determining whether other knee pathology exists prior to making a diagnosis of chondral defect. Symptomatic articular cartilage defects are typically discovered with use of cartilage-sensitive magnetic resonance imaging (MRI). The presence of symptoms and a correlative MRI are necessary to identify the size, location, and nature of the defect. Once the decision has been made to proceed with a cartilage restorative procedure, microfracture should be considered as a first-line treatment. The ideal knee lesion should be isolated, well contained, and not exceed an area of 4 cm2 (2 × 2 cm).
Positioning
The patient is placed in a supine position on the operating room table, with the affected extremity positioned to allow knee motion without limitation. General anesthesia is then administered. A non-sterile tourniquet is placed on the proximal aspect of the thigh. The leg is then prepped and draped in the usual sterile fashion with use of an extremity drape and a stockinette covering the foot up to the level of the proximal tibia. The stockinette is then covered with coban adhesive dressing to keep the distal extremity sterile.
Approach
Our approach to microfracture is almost exclusively via an arthroscopic technique. A thorough examination with diagnostic arthroscopy is performed to identify any additional intra-articular abnormalities, such as meniscal tears, ligament disruption, patellar maltracking, or multiple cartilage defects. Intra-articular pathology determined using an MRI must be correlated clinically with the initial diagnostic study. Large cartilaginous defects may benefit from an enlarged exposure performed through a median parapatellar arthrotomy. For most defects, arthroscopic portals are positioned according to the location of the cartilage lesion to provide optimal access to the articular cartilage defect.5
Standard anterolateral and anteromedial parapatellar tendon portals can be used for lesions of the central femoral condyles. For defects of the posterior condyles, portals should be placed lower to facilitate access and visualization of the defects. Farther medial or lateral portals can be added if necessary. Superolateral portals can be helpful for patellar and trochlear lesions.
A meniscal abnormality is treated before microfracture, while ligament reconstruction is performed after microfracture to allow for better visualization of the cartilage lesion. This single-stage approach avoids the repetitive operative morbidity and associated prolonged rehabilitation.6
The cartilage defect is identified and existing cartilage flaps are débrided back to a stable and healthy peripheral margin with use of an arthroscopic shaver or ring curet.
The size of the articular lesion is measured with a calibrated probe and recorded. If debridement reveals that the lesion is not contained by an intact cartilage margin, microfracture cannot be used. The goal of preparing the region of defect for microfracture involves isolating and removing the calcified cartilage layer just above the subchondral bone. An awl or pick may then be used to perform the microfracture. Starting around the periphery and culminating in the center of the defect, the holes are separated by approximately 3-4 mm with an emphasis on making sure the holes do not become confluent. To ensure adequate penetration, the arthroscopic pump is stopped to confirm marrow elements flowing from the area of microfracture.
Postoperative Care
For most patients postoperatively, sterile dressings are kept clean, dry, and intact until the first postoperative visit. In the immediate postoperative period, patients are placed into a Bledsoe hinged brace locked in extension. They are then allowed to weight-bear on the extremity as tolerated, with the Bledsoe brace on at all times. Crutches and/or cane may also be used to support the individual with weight-bearing activities.
Early passive range of motion (ROM) is encouraged. The use of a controlled passive motion (CPM) device may also be utilized when the patient is sitting or resting to prevent loss of motion at the operative joint. Alternatively, in the absence of this device, patient-directed passive ROM exercises may be preformed as tolerated. A physical therapy regimen is often recommended and implemented 6 weeks postoperatively, focusing on controlled closed chain exercises. By 4 months, patients are permitted to begin open chain exercises, focusing on quadriceps and hamstring strengthening.
Outcome
Although several articles have reported outcomes for microfracture surgery and patients’ subsequent return to activity, there is a paucity of data on competitive performance after surgery, especially among professional athletes whose knees are subjected to high joint forces from running, jumping, landing, pivoting, and sliding laterally.
Recently, retrospective review by Cerynik et al7 reported quantitative return-to-play data on 24 National Basketball Association (NBA) players who underwent microfracture surgery during a 9-year period (1997-2006) and 24 randomly selected controls from the 2004-2005 season, using actual performance data as an outcome marker instead of decreased sports activity. Performance outcomes were evaluated using pre-injury and post-injury statistics, including games played, minutes played, points, rebounds, assists, steals, blocks, turnovers, field goals attempted and made, and free throws attempted and made. Age, position, years in the NBA, date of injury, and prior surgeries on the knee were also collected. To evaluate performance, the NBA player efficiency rating (PER) was used, computing an index number based on major performance statistics kept by the league. The PER was expressed as:
[(Points + Rebounds + Assists + Steals + Blocks) - ((Field goals attempted - Field goals made) + (Free throws attempted - Free throws made) + Turnovers)] / Games
The goal of this study was to create an objective outcome marker versus the subjective measures reported in other studies.
Five out of 24 NBA players (21%) were unable to return to competition in the league. Two players (8%) were only able to play for one season after surgery before retiring. The remaining 17 players (71%) were able to play longer than one season. On average, PER fell 3.5 points the first season after returning to competition. For the 17 players who continued to play two or more seasons after surgery, the average PER reduction decreased to 2.7. For players who returned to competition, the average decrease in minutes played per game the first season after injury was 4.9 minutes. Players who played one season or less demonstrated a decrease of 9.2 minutes per game. Of the 17 players who played two or more years after surgery, the average decrease in minutes played per game was 3.0 minutes.
This study may indicate that athletes who are able to mount a sustained comeback for longer than two seasons after surgery will return to near their pre-injury levels of playing time and performance.
Namdari et al8 performed a similar study analyzing 24 NBA players who had microfracture surgery between 1997 and 2006, using an index year of 2001 for the control arm of the study. The demographic data collected included age, position, pre-injury NBA season, body mass index (BMI), time from surgery to return to play, preoperative all star status using performance data of games played, average minutes played, points, assists, rebounds, steals, blocks per game, and field goal percentage.
Only 67% of players in the Namdari study were able to return to playing basketball competitively after surgery, with only 59% able to return to the NBA after microfracture surgery. Players who did not return to the NBA tended to be older and more experienced. Performance data showed a decrease in the minutes per game from 31.7 to 25.7 minutes, accounting for a decrease in points, rebounds, and assists per game. The field goal percentage dropped from 46.5% to 42.5% postoperatively.
Steadman et al reported on 25 National Football League players with full chondral defects repaired by microfracture.9 Of these, 19 players (76%) returned to pro football after surgery for an average of 4.6 years, with reported improvements in pain, swelling, running, cutting, and squatting, though no game performance data were analyzed.
While the percentage of players returning to play varies from 59% to 71% depending on the sport and study, the absence of a true control (ie, players with chondral lesions treated non-operatively) may confound these results. Since the outcomes on microfracture surgery vary, a study incorporating the size and location of the lesion, as well as a matched control arm, may better predict outcomes of the surgery within the high-demand athletic population.
Complications
Overall, adverse events and morbidity due to microfracture surgery are extremely rare. Possible complications include:
- Cartilage breakdown over time. The new cartilage made by microfracture surgery is not as strong as the body’s original cartilage and can, consequently, break down after a few years
- Increased stiffness of the knee
References
- Mithoefer K, Williams RJ, Warren RF, et al. High-impact athletics after knee articular cartilage repair: a prospective evaluation of the microfracture technique. Am J Sports Med 2006;34(9):1413--1418.
- Steadman JR, Rodkey WG, Rodrigo JJ. Microfracture: surgical technique and rehabilitation to treat chondral defects. Clin Orthop Relat Res 2001;(391 Suppl):362--369.
- Ritchie PK, McCarty EC. Surgical management of cartilage defects in athletes. Clin Sports Med 2005;24(1):163--174.
- Steadman JR, Briggs KK, Rodrigo JJ, et al. Outcomes of microfracture for traumatic chondral defects of the knee: average 11-year follow-up. Arthroscopy 2003;19(5):477-484.
- Sterett WI, Steadman JR. Chondral resurfacing and high tibial osteotomy in the varus knee. Am J Sports Med. 2004;32:1243-9.
- Mithoefer K, Williams RJ 3rd, Warren RF. 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.
- Namdari S, Baldwin K, Anakwenze O, et al. Results and performance after microfracture in National Basketball Association athletes. Am J Sports Med 2009 37(5):943-948.
- Cerynik DL, Lewullis GE, Joves BC, et al. Outcomes of microfracture in professional basketball players. Knee Surg Sports Traumatol Arthrosc 2009;17(9):1135-1139.
- Steadman JR, Miller BS, Karas SG, et al. The microfracture technique in the treatment of full-thickness chondral lesions of the knee in National Football League players. J Knee Surg 2003;16(2):83-86.
