Arthroscopic microfracture of chondral defects of the knee: A comparison of two postoperative treatments

Arthroscopic Microfracture of Chondral Defects of the Knee: A Comparison of Two Postoperative Treatments Richard A. Marder, M.D., Gail Hopkins, Jr., M.D., and Laura A. Timmerman, M.D.

Purpose: We hypothesized that the treatment of focal, full-thickness chondral defects by an identical method of arthroscopic microfracture but with different postoperative regimens would produce similar results. Type of Study: Case control study, retrospective cohort. Methods: Fifty patients treated over a 6-year period (1993 to 1999) with a focal, less than 2-cm2, full-thickness chondral defect of either the medial or lateral femoral condyle of the knee had arthroscopic surgery to debride loose adjacent cartilage flaps and abortive fibrocartilage from the crater in conjunction with microfracture of the subchondral plate using a hand awl. Postoperatively, 1 group was treated with non-weight bearing and continuous passive motion (CPM) for 6 weeks (group I), and the other group was allowed weight bearing as tolerated and did not use CPM (group II). Results of treatment were assessed by the Lysholm knee rating scale augmented by the Tegner method of activity evaluation. Results were analyzed by independent t test or ␹-square test with significance assumed for P ⬍ .05. Results: Forty-three of 50 patients were evaluated at a minimum of 2 years after surgery (mean, 4.2 years; range, 2 to 9 years). The mean age was 39.7 years (range, 16 to 66 years) and there were 19 female and 24 male patients. For group I, Lysholm scores were 37 preoperative, 81 postoperative, and Tegner scores were 3 and 6, respectively. Group II Lysholm scores were 33 preoperative, 85 postoperative, and Tegner scores 3 and 6, respectively. No significant differences between groups were noted. Conclusions: In relatively small full-thickness chondral defects of the femoral condyles treated by microfracture, this study found no differences in results comparing 2 rehabilitation regimens differing by weight-bearing status and use of CPM. Level of Evidence: Level III, Case Control Study. Key Words: Chondral defect—Microfracture—Continuous passive motion—Outcome.

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ull-thickness chondral defects are encountered in a significant number of patients undergoing knee arthroscopy. In a large, retrospective series, Curl et al. found that 19% of patients undergoing knee arthroscopy had grade IV chondral defects.1,2 Hjelle et al.3 found that nearly 80% of full-thickness articular defects in their prospective study were solitary and predominantly involved the medial femoral condyle. An untreated, full-thickness chondral defect does not possess intrinsic healing potential and often leads to wors-

From the Department of Orthopaedic Surgery, University of California Davis, Sacramento, California, U.S.A. Address correspondence and reprint requests to Richard A. Marder, M.D., 2805 J St, Suite 3400, Sacramento, CA 95816, U.S.A. © 2005 by the Arthroscopy Association of North America 0749-8063/05/2102-3955$30.00/0 doi:10.1016/j.arthro.2004.10.009

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ening symptoms and joint deterioration, notwithstanding the occasional study to the contrary.4-6 On the basis of experimental and clinical studies, the use of continuous passive motion (CPM) of the knee together with a period of non-weight bearing has been widely adopted for the management of chondral defects, especially after microfracture. Salter et al.7 have been, perhaps, the most influential investigators to advocate the use of CPM in conjunction with biologic resurfacing procedures, believing that the quality of chondral repair tissue was markedly improved by the “dynamic compression” that modulates the regenerative potential of chondrocytes.7,8 To date, interstudy comparisons of cartilage procedures have proved difficult owing to wide ranging differences in the nature, extent, and location of the chondral lesion, the postoperative regimen, and the method of follow-up evaluation.2,9-13 A prospective, comparative study such as that recently performed by

Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 21, No 2 (February), 2005: pp 152-158

MICROFRACTURE OF CHONDRAL DEFECTS Horas et al.14 addressing autologous chondrocyte implantation and osteoarticular plugs is the ideal study design. During the time that we practiced independently but in the same physical location, we developed separate approaches to the postoperative management of full-thickness chondral defects treated by arthroscopic microfracture. One of us routinely used nonweight bearing and CPM for all patients and the other allowed weight bearing as tolerated and did not use CPM as an adjunct. We conjectured that the postoperative treatment did not affect the results of microfracture. Our study, although retrospective, reports the experiences of 2 surgeons treating a single, focal chondral lesion of a femoral condyle using the same technique of arthroscopic microfracture with similar follow-up evaluation in which postoperative management was the major variable: 1 surgeon used CPM and touchdown weight bearing and the other surgeon allowed weight bearing as tolerated and did not use CPM. METHODS We reviewed all patients who had an arthroscopic microfracture for 1 or more full-thickness chondral defects of the knee between 1993 and 1999. There were 82 patients with multiple defects and 71 with solitary full-thickness defects of either the medial or lateral femoral condyle of the knee. Of these 71 cases, 53 defects were determined by review of arthroscopic photographs to have a surface area less than 2-cm2 with a circumferentially stable margin of intact cartilage. Twenty-eight patients had been operated on by one of us (R.A.M.) and 25 by the other (L.A.T.). We defined the study to include 25 patients in each group by limiting inclusion to those operated on after July 1993 and before March 1999. Thus, there were 25 patients who had been treated by one of us (R.A.M.) using arthroscopic microfracture followed by CPM and touchdown weight bearing for 6 weeks (CPM ⫹ TDWB, group I), and 25 patients who had been treated by the other of us (L.A.T.) using arthroscopic microfracture followed by weight bearing as tolerated without CPM (nonCPM ⫹ WBAT, group II). Arthroscopic surgery was performed in the same manner for all patients. Chondral defects were treated by debridement of loose adjacent cartilage flaps, removal of abortive fibrocartilage from the crater of the defect, and microfracture using hand awls to penetrate the subchondral plate at 3- to 4-mm intervals (Fig 1). Based on training and practice experience, 1 of the

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FIGURE 1. Chondral defect of medial femoral condyle after microfracture, with probe measuring defect size (dimensions, 2 ⫻ 1 cm, 2-cm2).

authors used CPM and touchdown weight bearing (group I), and the other of us allowed weight bearing as tolerated along with intermittent active motion instead of CPM (group II). CPM was used in an initial setting of 0° to 40° at a rate of 1 cycle per minute for 6 to 8 hours minimum per day, usually performed in 2 to 3 hour sessions. Flexion arc was increased in 5° intervals as tolerated. CPM and touchdown weight bearing were used in conjunction for 6 weeks. NonCPM patients were encouraged to begin heel-slide sessions 3 times per day. These patients used crutches initially with weight bearing allowed to progress based on level of discomfort. After initial postoperative treatment, most patients had formal physical therapy as well. Evaluation at follow-up was done using arthroscopic photographs from the surgical procedure to confirm operative records. A detailed history was obtained from each individual with specific subjective assessment of pain, swelling, giving-way, and functional and sporting activities. Objective evaluation of each patient included prone and supine range of motion, circumferential thigh measurement, presence of effusion, crepitus, joint tenderness, and laxity testing for the 4 patients with documented anterior cruciate ligament (ACL) injury, including Lachman and pivot shift tests, as well as instrumented laxity testing recorded as difference between injured and uninjured knees. When economically feasible, anteroposterior weight-bearing radiographs of the injured and unin-

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R. A. MARDER ET AL. TABLE 1.

Activity Causing Injury

Activity

No. of Patients

Skiing Soccer Basketball Football Martial arts Wrestling Motorized sport Fall or work injury Unknown

9 5 5 4 3 2 1 3 11

jured knees were performed at follow-up to assess radiographic evidence of joint degeneration. Pretreatment and posttreatment symptoms and findings were tabulated using Lysholm and Tegner knee scores.15,16 Results were compared using an independent t test or ␹-square test with significance assumed for P ⬍ .05. RESULTS The majority of patients reported an injury occurring with sports (Table 1). The level of preinjury activity was determined for each individual. Preinjury sports participation was recreational,17 competitive,9 and professional.1 Seven patients were lost to followup, leaving a study sample of 43 who were able to be evaluated at a mean period of 4.2 years with a range of 2 to 9 years (23 group I, 20 group II; Table 2). There were no differences between groups with respect to age, sex, size of lesion, or period of follow-up (␹square analysis). Subjective In group I, at follow-up, 1 patient had pain rated as worse than preoperative, 4 had pain that was unchanged, 12 had improvement in pain, and 6 had no pain. In addition, 3 patients complained of constant swelling and 5 reported swelling with activity. Although 3 patients complained of instability with activity, none of the 2 patients with a repaired meniscus or the 1 with an ACL reconstruction had any complaints of residual instability. In group II, no patient had postoperative pain worse than before surgery, 3 had pain that was unchanged, 9 had improvement in pain, and 8 had no pain. Seven patients had swelling: 3 constant and 4 with activity. One patient who did not have ligamentous laxity complained of instability limiting activity.

Objective An effusion was present in 4 patients in group I and in 3 patients in group II. Tenderness over the involved condyle was present in 11 of 23 patients in group I and 8 of 20 patients in group II. Five patients had a change in range of motion at follow-up: 2 patients had a 5° extension loss (1 in group I and 1 in group II), 1 group II patient had a 5° to 10° extension loss and 2 patients (1 in group I and 1 in group II) had loss of 5° to 10° flexion compared with preoperative examination. Thigh atrophy of 1 cm or greater was noted in 15 of 23 patients in group I and 11 of 20 patients in group II. Of the 3 patients with concomitant ACL reconstruction, Lachman and pivot-shift testing were negative in 2 and trace in 1. Radiographic Thirty-four patients had anteroposterior weightbearing radiographs that were evaluated. No changes were noted in 22 patients. Eight patients were noted to have sclerosis or notch changes, and 4 patients had joint narrowing not exceeding 2 mm. There was no statistical correlation with radiographic changes and type of postoperative management. Knee and Activity Scores Postoperative Lysholm scores were significantly improved from preoperative scores (P ⬍ .01) but were not statistically different from each other (Fig 2). Tegner activity scores improved from 3 ⫾ 1 preoperatively to 6 ⫾ 2 postoperatively for both groups I and II. Postoperative scores were significantly improved from preoperative (P ⬍ .01) but did not differ significantly between themselves. A breakdown of Lysholm postoperative scores by overall rating (excellent ⬎95, good ⬎84, fair ⬎65, and poor ⬍64) revealed 8 excellent, 18 good, 13 fair, and 4 poor scores. Complications and Reoperations There were no infections, although 1 patient 4 days after surgery developed increasing knee pain and effusion suggesting infection. Arthroscopic washout revealed intact clot filling the chondral defect and cultures were negative (Fig 3). A presumptive diagnosis of reaction to the arthroscopic soaking solution was made. One patient had a calf deep vein thrombosis that was treated with anticoagulation for 3 months. Five patients had reoperation for persistent symptoms.

MICROFRACTURE OF CHONDRAL DEFECTS TABLE 2.

CPM ⫹ TDWB

Patient Data Presurgery Scores: (Lysholm (L) and Tegner (T))

Postsurgery Scores: (Lysholm (L) and Tegner (T))

Age (yr)/(Sex)

Location of Defect

36/(F) 16/(M) 48/(M) 46/(F) 43/(M) 38/(F) 51/(M) 32/(M) 19/(M) 61/(F) 55/(M) 33/(F) 37/(F) 51/(F) 27/(F) 29/(M) 56/(F)

MFC 30° MFC 60° LFC 60° MFC 45° MFC 30° LFC 60° MFC 10° MFC 30° MFC 10° MFC 60° LFC 10° LFC 30° MFC 60° MFC 10° MFC 45° LFC 30° LFC 90°

None MMT (repaired) None Loose body None Partial ACL Tear None None MMT (repaired) None Medial plica None Loose body None None None None

N Y Y N N Y N Y N Y Y Y Y N N Y Y

52(L); 29(L); 36(L); 37(L); 27(L); 29(L); 48(L); 44(L); 19(L); 40(L); 38(L); 31(L); 20(L); 69(L); 21(L); 42(L); 29(L);

3(T) 4(T) 3(T) 2(T) 4(T) 3(T) 4(T) 3(T) 3(T) 2(T) 3(T) 3(T) 3(T) 4(T) 3(T) 1(T) 3(T)

95(L); 90(L); 62(L); 84(L); 88(L); 95(L); 75(L); 64(L); 80(L); 77(L); 85(L); 95(L); 61(L); 88(L); 93(L); 72(L); 84(L);

23/(M) 37/(F) 37/(M) 38/(F) 45/(F) 36/(M) 57/(F) 18/(M) 47/(M) 54/(M) 22/(M)

MFC 10° MFC 30° MFC 45° MFC 30° LFC 30° MFC 10° MFC 10° MFC 30° MFC 10° MFC 10° MFC 30°

N Y N N N Y Y N N N Y

37(L); 27(L); 36(L); 19(L); 31(L); 29(L); 24(L); 18(L); 39(L); 48(L); 19(L);

4(T) 3(T) 4(T) 3(T) 3(T) 4(T) 2(T) 1(T) 4(T) 2(T) 1(T)

95(L); 6(T) 84(L); 6(T) 65(L); 5(T) 70(L); 4(T) 79(L); 6(T) 88(L); 7(T) 77(L); 4(T) 93(L); 9(T) 84(L); 5(T) 68(L); 4(T) 100(L); 9(T)

41/(F) 30/(F)

LFC 10° MFC 60°

None None MMT (resected) None LMT (resected) MMT (resected) None ACL tear (repaired) None None ACL tear ⫹ MMT (repaired) None Loose bodies

N Y

37(L); 3(T) 54(L); 4(T)

91(L); 7(T) 86(L); 6(T)

66/(M) 49/(M) 39/(M) 41/(M) 35/(F) 42/(M) 35/(M) 17/(F) 59/(M) 42/(F) 31/(M) 43/(M) 37/(F)

MFC 45° MFC 10° MFC 45° LFC 45° MFC 10° MFC 70° MFC 10° MFC 30° MFC 10° MFC 10° MFC 30° MFC 10° MFC 45°

MMT (resected) None None None MMT (resected) None None ACL tear (repaired) None None MMT (resected) None Loose body

N Y Y Y N Y N N Y Y N Y Y

31(L); 68(L); 52(L); 41(L); 15(L); 60(L); 21(L); 35(L); 31(L); 37(L); 27(L); 40(L); 29(L);

78(L); 95(L); 93(L); 87(L); 91(L); 77(L); 85(L); 95(L); 69(L); 60(L); 95(L); 84(L); 78(L);

Associated Injury

155

4(T) 5(T) 5(T) 4(T) 2(T) 4(T) 4(T) 2(T) 4(T) 4(T) 2(T) 5(T) 4(T)

7(T) 9(T) 6(T) 5(T) 5(T) 6(T) 7(T) 3(T) 9(T) 4(T) 7(T) 7(T) 6(T) 7(T) 9(T) 2(T) 4(T)

4(T) 7(T) 7(T) 5(T) 7(T) 7(T) 4(T) 9(T) 6(T) 4(T) 9(T) 7(T) 8(T)

Radiograph Changes None None Not performed None 1-2 mm narrowing Increased sclerosis None None None Not performed None None Increased sclerosis None None Not performed 2 mm narrowing; tibial spine peaking None Not performed Sclerosis Not performed Not performed None Sclerosis; marginal spur None None Not performed Notch changes only None Tibial spine peaking; sclerosis; 1-2 mm narrowing None None None Sclerosis None None Not performed Increased sclerosis 1-2 mm narrowing None Increased sclerosis None Not performed

Follow-up (mo) 35 26 51 28 73 87 36 23 24 37 31 25 70 64 36 59 73 66 24 76 57 23 41 60 84 91 38 108 43 53

25 75 31 49 50 36 52 72 65 47 78 25 34

Abbreviations: LFC, lateral femoral condyle; LMT, lateral meniscus tear; MFC, medial femoral condyle; MMT, medial meniscus tear.

In 2 of these, the articular defect was healed with firm repair tissue; in 3 patients, the repair tissue was incomplete, fragmented, or absent. These patients sub-

sequently underwent osteoarticular plug grafts (2 patients) and autologous chondrocyte implantation (1 patient).

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FIGURE 2. Lysholm preoperative and postoperative scores for groups I and II (N ⫽ 43 patients). Postoperative scores for both groups were significantly improved from preoperative scores (P ⬍ .01), but no significant intragroup differences were noted before or after surgery.

DISCUSSION Overall, the success of microfracture in both groups of patients appears equivalent to other reported studies using marrow-stimulating techniques.17-19 The use of CPM and non-weight bearing did not appear to confer any improvement in clinical results in this study, which compared patients with less than 2-cm2 solitary chondral defects on the weight-bearing segment of the femoral condyles. Previous authors have treated chondral injuries without CPM. Dzioba18 did use nonweight bearing for 8 weeks in his patients, but Levy et al.19 used an aggressive postoperative regimen with early weight bearing and return to sports at an average of nearly 11 weeks. This is contrary to popular practice, which has incorporated CPM as an adjunct in the treatment of chondral defects.7-10 Salter’s advocacy of CPM is based on the improvement in quality of the repair tissue it induces.7,8 This was based on visual inspection as well as histologic examination. On histologic examination, CPM significantly increased the percentage of hyaline cartilage in the repair. However, the authors’ data show that, even with the use of CPM, only 44% of adult rabbits had true hyaline cartilage repair of the chondral defect.7 Thus, the majority of lesions healed with fibrocartilage filling the chondral defect. In a retrospective review, Rodrigo et al.10 found significantly greater improvement by classification grade of the chondral lesion at second-look arthroscopy in patients treated with CPM after microfracture. Their study included patients with multiple lesions not limited to the femoral condyles and re-

ported results in terms of gross appearance of the chondral lesion at follow-up arthroscopy without a detailed subjective and objective examination. Buckwalter et al.20 noted that regenerated cartilage deteriorates from hyaline to fibrous cartilage at 1 year. Thus, even if CPM did promote early healing with hyaline cartilage, follow-up after 1 year, as was used in this study, may show no subsequent differences. Certainly, patient selection, differences in rating systems, and lack of more objective data for followup, such as isokinetic testing and arthroscopic evaluation, could be factors that influenced the outcome in this study. However, the most likely explanation for our results, we believe, is found in the concept of containment as discussed by Mandelbaum et al.21 Located on the weight-bearing segment of the femoral condyle, a small lesion, which is well circumscribed, is protected during loading of the joint by the margins of the lesion that act as shoulders to maintain axial height of the tibiofemoral articulation. Presumably, in this instance, weight bearing would not deter the migration of undifferentiated mesenchymal cells into the clot filling the chondral defect or their subsequent proliferation and differentiation into fibrocartilage tissue at a minimum— or hopefully, predominantly hyaline-like tissue. On the contrary, when the lesion is too large or its margins not intact, joint loading leads to compression of the material filling the defect with disruption of the repair.

FIGURE 3.

Hematoma filling defect 4 days after microfracture.

MICROFRACTURE OF CHONDRAL DEFECTS Notwithstanding published opinions and studies, the issue of progression of chondral defects remains under investigation.4,5,20 Recently, Jackson et al.22 reported the results of chondral defects produced in goats, thought to be more anthropomorphic than rabbits or dogs, in which surgically induced lesions on the weight-bearing segment of the medial femoral condyle did not heal.22 Review of this study shows that the size of the defects exceeded one half of the diameter of the affected femoral condyle. Extrapolating to the human knee, the relative size of such a lesion would clearly be uncontained. However, a 2-cm2 defect in the human knee would occupy less than one quarter of the diameter of the condyle and, thus, would be contained. As relates to the type of surgical treatment for full-thickness chondral defects, irrespective of postoperative management, this study raises a concern regarding the long-term success of microfracture, especially in active patients. Although our sample size did not have the statistical power to evaluate patients in high-demand sports, our overall data showed only 26 of 43 patients (60%) with a good or excellent result. Given the higher success rates of osteoarticular grafting procedures and the expectation that results will not deteriorate with time, direct replacement of articular cartilage may be preferable in the younger, athletic patient, even with a small, full-thickness lesion.14,23 Lack of arthroscopic reassessment of the articular lesion, inclusion of patients with associated injuries, incomplete radiographic examination of the knee, and the brevity of follow-up are weaknesses of our study. We did not evaluate the lesions at follow-up with arthroscopic assessment, excepting 5 knees that underwent reoperation. Thus, we do not know the status of the tissue filling the chondral defect in the other 38 knees. This is certainly a limitation of our study whose endpoint evaluation was clinical and functional outcome. As regards additional intra-articular injuries, the preponderance of these were loose bodies and meniscus tears (Fig 4), which commonly occur in patients with chondral injuries of the knee.24-26 An additional weakness of this study was the inability to take radiographs of 9 of the 43 studied patients at follow-up because of insurance and economic factors beyond our control. Ideally, any study of articular cartilage injury would include an arthroscopic reassessment of the joint at a period of time greater than the midterm follow-up (4.2 years) in the present study. Despite the shortcomings of this study, we believe that our results warrant further study of the

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FIGURE 4. Chondral defect of medial femoral condyle with associated medial meniscus tear.

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