Research suggests that more than three-quarters of professional basketball players return to play following microfracture surgery, but even the most diligent rehabilitation may not restore their previous level of athletic performance.
by Nirav H. Amin, MD, Martin J. Morrison III MD, Douglas L. Cerynik, MD, and James Tom, MD.
The concept of microfracture knee surgery was originally developed in the late 1980s by Richard Steadman, MD. Offering an opportunity to decrease pain while restoring mobility to high-demand, high-pay athletes, the procedure gained interest among those who cared for these elite competitors—most notably those in the National Basketball Association (NBA). While Steadman’s published work primarily focused on elite level competitors, the procedure also began to gain popularity with the general public after successful outcomes were seen with several prominent athletes.
By reconciling isolated full-thickness chondral defects, microfracture aims to restore knee function and decrease the pain associated with injury. The procedure is a “marrow stimulating” technique in that an awl is used to penetrate the subchondral bone in the cartilage defect. Disruption of the subchondral bone induces fibrin clot formation in the area of the chondral defect. This clot contains pluripotent, marrow-derived mesenchymal stem cells, which are able to differentiate into fibrochondrocytes, resulting in a fibrocartilage repair with varying amounts of type I, II, and III collagen content.1,2 Microfracture is a single-stage procedure that is ideally suited for small, well-contained, cartilage lesions.3
In addition, a strict rehabilitation protocol is as vital to successful microfracture surgery as the surgery itself. Each surgeon adheres to his or her own recipe, but most are a variation of a period of non-weightbearing, followed by progressive range of motion and weight-bearing exercises, and finally a return to full activity.
While specific rehabilitation protocols exist, the large number of variations in lesion size, lesion location and concomitant injuries requires a comprehensive review behind the scope of this article. As a representative overview, Yen et al describe a 36 week rehabilitation program highlighted by four phases.4 Phase I ensures protection of the recent microfracture site and subsequent clot with restoration of knee joint mobility, by adherence to strict non-weightbearing coupled with use of a continuous passive motion (CPM) machine. Phase II, initiated at week nine, allows the patient to progress to weight bearing as tolerated, with closed kinetic chain activities, and gradual addition of resistance to build up muscle endurance. At month four (Phase III), strengthening and lesion location-specific activities are added, and the patient may incorporate running into his or her rehabilitation in a controlled fashion. Return to full activities is the hallmark of Phase IV, with agility activities typically representing the limiting factor. The patient should be pain-free before returning to full activity, but clinical judgment and assessments of every individual patient should also come into play.
Steadman rehabilitation protocol1 is based upon the location of the defect, size of the defect, and any other surgical procedure done in simultaneously. Chondral defects on the femur or tibia are started with immediate passive range of motion. Depending on whether CPM is available, the patient is encouraged to perform flexion and extension exercises.
The size of the defect will determine when the patient is allowed to place full weight on the leg. Defects under 1 cm are allowed to weight bear sooner than larger lesions, as most patients are toe-touch weightbearing for six to eight weeks. After eight weeks, full weight bearing is encouraged along with exercises to increase the strength and stamina in the leg. Patients are not allowed to return to athletic activities until four to six months postoperatively.
The protocol following microfracture for patellofemoral chondral defects differs from femoral or tibial defects due to the extensor mechanism. Unlike femoral and/or tibal defects, which do not require bracing routinely, rehabilitation of a patellofemoral defect typically involves a brace set at 0° to 20° of flexion, for at least eight weeks. The rationale is to protect the marrow from clots while the patella is engaging in the trochlea during flexion. However, achieving full range of passive motion after surgery is still a key objective of rehabilitation. After eight weeks, the flexion in the brace is gradually increased over the course of about four weeks. After 12 weeks post-operatively, the brace is not needed. Again, around four to six months, the patient’s knee will be examined by the physician prior to return to full activity.
Irrespective of the type of surgery, act ivies such as cutting, pivoting, and jumping should not be performed until the physician has cleared the patient. The patient may start to run and perform strength exercise around 8 to 12 weeks post-operatively, however any movement in the lateral plane should be reserved until four to six months.
Initially, there was concern regarding the long term outcomes of microfracture surgery, but published reports have demonstrated the procedure to be an effective surgical treatment.5-10 As such, Steadman has continued to adapt this procedure to help reconnect torn ligaments, with future applications possible in hip and ankle joints.11
While symptom improvement has been reported in as many as 70% of patients,9 over time the fibrocartilaginous repair begins to deteriorate, potentially resulting in a decrease in activity. Additionally, Gobbi found that 80% those who previously reported improvement reported decreased sports activity at 72 months.10 Kreuz et al12 demonstrated deterioration of activity after 18 months in 85 patients treated with microfracture surgery. in mechanical knee alignment, partial thickness tears and immune diseases of the cartilage, age greater than 65, and non-compliance with rigorous rehabilitation protocols have been shown to be indicators of poor outcomes.8 Variation
Although several articles have reported the microfracture procedure and return to activity, little data has been published regarding competitive performance after surgery. While studies have reported on performance outcomes after anterior cruciate ligament and labral repairs in professional football and baseball players, respectively,13,14 there remains a paucity of information on performance after microfracture.15
Using acutal performance data as an outcome marker, instead of decreased sports activity, Cerynik et al reviewed 24 NBA basketball players who underwent microfracture surgery during a nine year period (1997-2006).16 Performance outcomes were evaluated using pre-injury and post-injury statistics. 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 goal of this study was to create an objective outcome marker versus the reported 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 year after surgery before retiring. The remaining 17 players (71%) were able to play longer than one year.
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 years after surgery will return to near their pre-injury levels of playing time and performance.
Limitations of this study approach are the inability to obtain data regarding the size or location of the lesion, body mass index data, the length of post-operative follow up and whether additional procedures were performed concurrently with the microfracture. In particular, the size and location of the defect may affect the long-term success of the procedure.
The benefits of this study method are in correlating surgical success with performance success. The study shows a clear relationship between the pre-injury and post-injury state of the player. It may allow the practitioner to explain the benefits of undergoing surgical repair with the odds of returning to pre-injury playing status.
Using professional athletes as a blueprint, one might be tempted to extrapolate that the expected outcome of microfracture surgery in “weekend warriors” or other extremely active individuals will have similar results. Steadman et al reported on 25 National Football League players with full chondral defects repaired by microfracture.17 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. By comparison, Cerynik et al reported that 79% of NBA returned to competition, but all demonstrated performance deficiencies.
This apparent discrepancy in objective performance numbers may be attributable to the enhanced demands that jumping, cutting, and pivoting place on the knees of NBA players, who also play many more games per season than NFL players do. Or the NBA findings may more clearly represent the actual decline in performance not analyzed in the Steadman report. Given that results for elite athletes in different sports cannot reliably be compared, using data from professional athletes to predict functionality after microfracture surgery in less-skilled athletes may not be ideal. However, if anything, weekend warriors are less likely to subject their knees to the type of rigorous physical demands required of elite athletes.
Adverse events and morbidity due to microfracture surgery are extremely rare for this minimally invasive procedure, lending itself to be a good option for qualified patients. Younger patients tend to fare better due to an increased ability to create fibrocartilage in response to the lesions with stronger surrounding articular cartilage than older individuals with similar injuries.7 Additionally, factors such as the size of the lesion and patient BMI may also play a role in the recovery and outcome of the surgery. Studies seem to conclude that the benefits of microfracture surgery significantly outweigh the risks and vast numbers of patients are able to return to competition.
Nirav Amin, MD, and Martin J. Morrison III, MD, are residents in the department of orthopedic surgery at Drexel University College of Medicine in Philadelphia. Douglas L. Cerynik, MD, is director of research, and James Tom, MD, is a clinical instructor in the same department.
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