Rehabilitation after Articular Cartilage Procedures

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Chapter 37 Rehabilitation after Articular Cartilage Procedures

INTRODUCTION

Articular cartilage defects of the knee appear to be an increasing cause of pain and functional disability in orthopaedics and sports medicine. This pathology creates a significant challenge to the health care team, especially the physician who must decide on the appropriate treatment plan. The avascular nature of articular cartilage predisposes the individual to progressive symptoms and degeneration owing to the extremely slow and frequent inability to heal. Nonoperative rehabilitation and palliative care are frequently unsuccessful, and further treatment is required to alleviate symptoms. This presents a significant challenge for patients, particularly young and more active individuals. Traditional methods of treating these lesions have led to unfavorable results, stimulating the need for newer surgical procedures designed to facilitate the repair or transplantation of autogenous cartilage tissue. Postoperative rehabilitation programs vary greatly between patients and are individualized based on specifics of the lesion (size, depth, location, containment, quality of tissue), patient (age, activities, goals, quality of tissue, lower extremity alignment, body mass index (BMI), general health, and nutrition), and surgery (exact procedure, tissue involvement, and concomitant surgeries). Thus, the development of an appropriate rehabilitation program is challenging and must be highly individualized to ensure successful outcomes. These programs are designed according to the knowledge of basic science, anatomy, and biomechanics of articular cartilage as well as the biologic course of healing after surgery. The goal is to restore full function in each patient as quickly as possible without overloading the healing articular cartilage. In this chapter, the essential principles of rehabilitation after articular cartilage repair procedures are discussed as well as specific rehabilitation guidelines for débridement, abrasion chondroplasty, microfracture, osteochondral autograft transplantation (OATS), and autologous chondrocyte implantation (ACI).

PRINCIPLES OF ARTICULAR CARTILAGE REHABILITATION

Several principles exist that must be considered when designing a rehabilitation program after articular cartilage repair procedures (Table 37–1). These key principles have been designed based upon the authors’ understanding of the basic science and mechanics of articular cartilage. These principles include individualization, creating a healing environment, understanding the biomechanics of the knee, reducing pain and effusion, restoring soft tissue balance, restoring muscle function, restoring proprioception and neuromuscular control, controlling the application of loads, and team communication. Each of these principles is briefly described as they relate to the rehabilitation program after articular cartilage repair procedures.

TABLE 37-1 Key Principles to Consider when Designing Rehabilitation Programs after Articular Cartilage Repair Procedures

Critical Points PRINCIPLES OF ARTICULAR CARTILAGE REHABILITATION

Individualization

One of the most important principles involving rehabilitation after articular cartilage repair procedures is the need for an individualized approach for each patient. Several variables must be considered when developing a unique rehabilitation progression for each patient. These include specifics regarding the patient, lesion, and surgery (Table 37–2).

TABLE 37-2 Specific Variables that Must be Considered when Designing Postoperative Rehabilitation Protocols after Articular Cartilage Procedures

Lesion specifics

Patient specifics Surgical specifics

The quality of each individual’s articular cartilage is the result of several factors including age, BMI, general health, nutrition, history of previous injuries, and genetics. The composition of articular cartilage undergoes a gradual degeneration over time that results in a breakdown of tissue matrix and a reduction in the load-bearing capacity of the cartilage.8 The specific factors that contribute to this deterioration remain controversial, but it appears that age, obesity, poor nutrition, and a history of repetitive impact loading (through work or sport activities) may result in osteoarthritic changes.8 Thus, younger patients with isolated defects and relatively healthy surrounding articular cartilage will progress more rapidly than older individuals with more degenerative changes and less dense cartilage structure. Furthermore, the patient’s motivation and previous activity levels must be considered when determining the rehabilitation approach to ensure that the goals of each patient are addressed. The rehabilitation program should be individualized to the specific demands of each patient’s activities of daily living, work, and/or sport activities.

Several variables must be considered in regard to the lesion that may have a dramatic effect on the rehabilitation process. Most important are the exact location and size of the lesion. Lesions on a weight-bearing surface of a femoral condyle must avoid deleterious compressive forces and will require a different rehabilitation approach than those located within the trochlea or undersurface of the patella, where shear forces should be avoided. Furthermore, the size, depth, and containment of each lesion must be considered. Lesions that are large or deep or that have poor containment with healthy surrounding articular cartilage may require a slightly slower rehabilitation progression to ensure that the repair tissue or graft has an adequate amount of time to heal. In addition, the patient’s lower extremity alignment must be carefully considered. A patient’s knee in a genu varum alignment with a medial compartment lesion may also require a high tibial osteotomy or an osteoarthritis unloader brace.

BMI is another factor to consider. Mithoefer and coworkers30 reported a correlation between BMI and outcomes after microfracture, because the greater the BMI, the more likely the clinical outcome would be less favorable.

Lastly, the specifics of each surgical procedure will vary the rehabilitation process. Arthroscopic procedures such as chondroplasty or microfracture may progress at a different pace than those with larger incisions and greater tissue involvement, such as OATS or ACI, which require a slower rehabilitation process to protect the healing structures. Each specific surgical procedure has different biologic healing responses postoperatively, which are discussed in detail later in this chapter. Furthermore, any concomitant procedures to address alignment, stability, or meniscal function may also alter the rehabilitation program because of the need to protect other healing tissues. The importance of communication between the surgical team and the rehabilitation team cannot be overemphasized. Appropriate information regarding the specifics of each surgical procedure must be shared to ensure the highest quality of care for each individual.

Create a Healing Environment

The next principle of articular cartilage rehabilitation involves creating an environment that facilitates the healing process while avoiding potentially deleterious forces to the repair site. This involves a thorough knowledge of the physiologic repair process after surgery. Through animal studies, as well as closely monitoring the maturation of repair tissue in human patients via arthroscopic examination, the biologic phases of maturation have been identified after several articular cartilage repair procedures.4,5,16,36,38 Knowledge of the healing and maturation process after these procedures will ensure that the repair tissue is gradually loaded and that excessive forces are not introduced too early in the healing process. These are discussed in detail in regard to each specific surgical procedure.

Two of the most important modes of rehabilitation of articular cartilage procedures are weight-bearing restrictions and range of motion (ROM) limitations. Unloading and immobilization have been shown to be deleterious to healing articular cartilage, resulting in proteoglycan loss and gradual weakening.2,17,50 Therefore, controlled weight-bearing and ROM are essential to facilitate healing and prevent degeneration. This gradual progression has been shown to stimulate matrix production and improve the tissue’s mechanical properties.6,7,51

Controlled compression and decompression forces observed during weight-bearing may nourish the articular cartilage and provide the necessary signals to the repair tissue to produce a matrix that will match the environmental forces.2,17,50 A progression of partial weight-bearing with crutches is used to gradually increase the amount of load applied to the weight-bearing surfaces of the joint. The use of a pool or aquatic therapy may also be beneficial to initiate gait training and lower extremity weight-bearing exercises. The buoyancy of the water has been shown to decrease the amount of weight-bearing forces to approximately 25% of the individual’s body weight when submerged to the level of the axilla and 50% of the individual’s body weight when submerged to the level of the waist.20 Commercially available devices to unload the patient’s body weight during treadmill ambulation may also be useful.

A force platform is another useful tool during the early phases of rehabilitation when weight-bearing is limited. This can be used to monitor the percentage of weight-bearing on each extremity during closed kinetic chain (CKC) exercises such as weight-shifts, mini-squats, and leg press (Fig. 37–1).

The pool and force platforms may be used during early phases of rehabilitation to perform limited weight-bearing activities designed to facilitate a normal gait pattern and enhance strength, proprioception, and balance. The goal of these techniques is to initiate weight-bearing activities during the early protective phases of rehabilitation, rather than remain strictly non–weight-bearing and immobilized. The authors’ opinion is that beginning controlled weight-bearing activities is a critical component to the overall successful outcome of the procedure. Although the return to functional activities will differ for each patient, early initiation of controlled exercise enables the individual to return to functional activities sooner than those who are immobilized and non–weight-bearing. This may have a positive effect on patient satisfaction.

Passive range of motion (PROM) activities, such as continuous passive motion (CPM) machines or manual PROM, performed by a rehabilitation specialist are also begun immediately after surgery in a limited ROM to nourish the healing articular cartilage and prevent the formation of adhesions. Motion exercises may assist in creating a smooth low-frictional surface by sliding against the joint’s articular surface and may be an essential component in cartilage repair.44,45 The authors’ opinion is that PROM is a safe and effective exercise to perform immediately postoperatively, with minimal disadvantageous shear or compressive forces, if done with patient relaxation. This ensures that muscular contraction does not create deleterious compressive or shearing forces. Furthermore, the use of CPM has been shown to enhance cartilage healing and long-term outcomes after articular cartilage procedures.41,42 In a study comparing the outcomes of patients after microfracture procedures, Rodrigo and associates41 reported an 85% satisfactory outcome in patients who used a CPM machine for 6 to 8 hours per day for 8 weeks as compared with a 55% satisfactory outcome in patients who did not use a CPM machine. PROM may also be performed on an isokinetic device (Biodex Corporation, Shirley, NY) in the passive mode or with a bike with adjustable pedals that can alter the available ROM (Unicam Corporation, Ramsey, NJ) (Fig. 37–2). The authors advocate low-intensity (light-resistance) bicycling for long duration to stimulate articular cartilage regeneration.

Biomechanics of the Knee

The next rehabilitation principle involves the biomechanics of the tibiofemoral and patellofemoral joints during normal joint articulation. Articulation between the femoral condyle and the tibial plateau is constant throughout knee ROM. The anterior surface of each femoral condyle is in articulation with the middle aspect of the tibial plateau near full knee extension. With weight-bearing, as the knee moves into greater degrees of knee flexion, the femoral condyles progressively roll posteriorly and slide anteriorly causing the articulation to shift posteriorly on the femoral condyle and tibial plateaus.24,28

The articulation between the inferior margin of the patella and the trochlea begins at approximately 10° to 20° of knee flexion depending on the size of the patella and the length of the patella tendon.23 As the knee proceeds into greater degrees of flexion, the contact area of the patellofemoral joint moves proximally along the patella. At 30°, the area of patellofemoral contact (inferior facets) is approximately 2 cm2.23 The area of contact gradually increases as the knee is flexed. At 60° of knee flexion, the middle facets of the patella articulate with the trochlea. At 90° of knee flexion, the contact area increases up to 6 cm2 and the superior facets articulate.23

Using this knowledge of joint arthrokinematics, the rate of weight-bearing, PROM, and exercise progression may be based on the exact location of the lesion (Fig. 37–3).3,12,14,15 For example, a patient with a lesion on the anterior aspect of the femoral condyle may perform exercises into deeper degrees of knee flexion without causing articulation at the repair site. Conversely, lesions on the posterior condyle may require the avoidance of exercise in deep knee flexion owing to the rolling and sliding component of the articulation during deeper knee flexion. Furthermore, the rehabilitation program for lesions on a non–weight-bearing surface, such as the trochlea, may include immediate partial weight-bearing with a brace locked in full knee extension without causing excessive compression on the repair site.

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FIGURE 37-3 A, The lesion location diagram from the International Knee Documentation Committee evaluation form used to document the location of articular cartilage lesions on the patella, trochlea, and femoral condyles. This form may be used to correlate with the exact location of lesion articulation with the patella (B), trochlea (C), and femoral condyles (D). The diagrams represent the point of articulation of the patellofemoral and tibiofemoral joints at various degrees of knee range of motion. Surface displacements (mm) and surface stresses (MPa) at 45° and 90° of knee flexion are depicted on D.

(A, Reprinted with permission from the International Knee Documentation Committee; B and C, Reprinted with permission from McConnell, J.; Fulkerson, J.: The knee: patellofemoral and soft tissue injuries. In Zachazewski, J. E.; Magee, D. J.; Quillen, W. S. [eds.]: Athletic Injuries and Rehabilitation. Philadelphia: W. B. Saunders, 1996; pp. 693-729; D, Reprinted with permission from Blankevoort, L.; Kuiper, J. H.; Huiskes, R.; Grootenboer, H. J.: Articular contact in a three-dimensional model of the knee. J Biomech 24:1019–1031, 1991.)

Rehabilitation exercises are altered based on the biomechanics of the knee to avoid excessive compressive or shearing forces. Whereas the exact ROM in which articulation of the lesion occurs is the most important factor to consider when designing the rehabilitation program, the amount of compressive and shear forces observed at the joint also vary throughout the ROM. Open kinetic chain (OKC) exercises, such as knee extension, are commonly performed from 90° to 40° of knee flexion. This ROM provides the lowest amount of patellofemoral joint reaction forces while exhibiting the greatest amount of patellofemoral contact area,22,23,49 thus distributing the force along a greater surface area. CKC exercises such as the leg press, vertical squats, lateral step-ups, and wall-squats are performed initially from 0° to 30° and then progressed to 0° to 60° where tibiofemoral and patellofemoral joint reaction forces are lowered.22,23,49 Clinically, these exercises are begun using a leg press machine rather than the vertical mini-squat owing to the ability to control the amount of weight applied to the lower extremities in the horizontal position in comparison with the vertical squat. As the repair site heals and symptoms subside, the ROM in which exercises are performed is progressed to allow greater muscle strengthening in a larger arc of motion. Exercises are progressed based on the patient’s symptoms and the clinical assessment of swelling and crepitation.

Reduce Pain and Effusion

Numerous authors have studied the effect of pain and joint effusion on muscle inhibition. A progressive decrease in volitional quadriceps activity has been noted as the knee exhibits increased pain and distention.48,52 Therefore, the reduction in knee joint pain and swelling is crucial to minimize this reflexive inhibition and restore normal quadriceps activity. Furthermore, any increase in intra-articular joint temperature has been shown to stimulate proteoglytic enzyme activity, which has a detrimental effect on articular cartilage.21,34

Treatment options for swelling reduction include cryotherapy, elevation, high-voltage stimulation, and joint compression through the use of a knee sleeve or compression wrap (Fig. 37–4). Patients presenting with chronic joint effusion may also benefit from a knee sleeve or compression wrap to apply constant pressure while performing everyday activities in an attempt to minimize the development of further effusion (Fig. 37–5).

Pain can be reduced passively through the use of cryotherapy, transcutaneous electrical nerve stimulation, and analgesic medication. Immediately after injury or surgery, the use of a commercial cold wrap can be extremely beneficial. PROM may also provide neuromodulation of pain during acute or exacerbated conditions.43

Restore Soft Tissue Balance

One of the most important aspects of articular cartilage rehabilitation involves the avoidance of arthrofibrosis, particularly with the OATS and ACI procedures, owing to the large open incision and extensive soft tissue trauma. This is achieved through the restoration of full passive knee extension, patellar mobility, and soft tissue flexibility of the knee and entire lower extremity. The inability to fully extend the knee results in abnormal joint arthrokinematics and subsequent increases in patellofemoral and tibiofemoral joint contact pressure, increased strain on the quadriceps muscle, and muscular fatigue.35 Therefore, a drop-lock postoperative knee brace locked into 0° of extension is used during ambulation, and PROM out of the brace is performed immediately after surgery.

The goal is to achieve at least 0° of knee extension within the first few days after surgery. Specific exercises include manual PROM exercises performed by the rehabilitation specialist, supine hamstring stretches with a wedge under the heel, and gastrocnemius stretching with a towel. Overpressure of 6 to 12 pounds may be used for a low-load long-duration stretch as needed to achieve full extension (Fig. 37–6). Patients are instructed to perform low, long-duration stretches for 10 to 12 minutes several times each day (usually five to six times per day). Modalities such as moist heat and ultrasound may also be applied to facilitate greater ROM improvements before and/or during these stretching techniques.25,40

The loss of patellar mobility after surgery may be due to various reasons including excessive scar tissue adhesions from the incision anteriorly as well as along the medial and lateral gutters. The loss of patellar mobility may result in ROM complications and difficulty in recruiting a quadriceps contraction. Patellar mobilizations in the medial-lateral and superior-inferior directions are performed by the rehabilitation specialist and independently by the patient during his or her home exercise program.

Soft tissue flexibility and pliability are also important for the entire lower extremity. Soft tissue mobilization and scar management are performed to prevent the development of adhesions around the anterior, medial, and lateral aspects of the knee. In addition, flexibility exercises are performed for the entire lower extremity including the hamstrings, hip, and calf musculature. As ROM improves and the lesion begins to heal, quadriceps stretching may be performed as tolerated by the patient.

Restore Muscle Function

The next principle involves restoring muscle function of the lower extremity. As previously stated, inhibition of the quadriceps muscle is a common clinical enigma in the presence of pain and effusion during the acute phases of rehabilitation. Electrical muscle stimulation (EMS) and biofeedback are often incorporated with therapeutic exercises to facilitate the active contraction of the quadriceps musculature (Fig. 37–7A).

EMS and biofeedback on the quadriceps musculature appear to facilitate the return of muscle activation and may be valuable additions to therapeutic exercises.9,46 Clinically, EMS is begun immediately after surgery while the patient performs isometric and isotonic exercises such as quadriceps sets, straight leg raises, hip adduction and abduction, and knee extensions (see Fig. 37–7B). EMS is used before biofeedback when the patient presents acutely with the inability to activate the quadriceps musculature. EMS is useful to attempt to recruit a maximum amount of muscle fibers during active contraction and may be used throughout the rehabilitation process. Once independent muscle activation is present, biofeedback may also be incorporated to facilitate further neuromuscular activation of the quadriceps. The patient must concentrate on neuromuscular control to independently activate the quadriceps during rehabilitation. The quadriceps and the hip/core muscles are emphasized to assist in dissipating ground reaction forces.

Exercises that strengthen the entire lower extremity, such as machine weights and CKC exercises, may be included as the patient progresses to more advanced phases of rehabilitation. It is important that total leg strength be emphasized rather than concentrating solely on the quadriceps. Furthermore, the importance of incorporating core stability exercises cannot be overlooked. Training of the core, hip, and ankle located proximally and distally along the kinetic chain is emphasized to assist in controlling the production and dissipation of forces in the knee. In addition, the hip and ankle assist in controlling abduction and adduction moments at the knee joint.

REHABILITATION AFTER ARTICULAR CARTILAGE REPAIR PROCEDURES

The rehabilitation progression is designed based on the four biologic phases of cartilage maturation: proliferation, transitional, remodeling, and maturation.4,5,11,16,19,33,36,38 The length of each phase will vary depending on the lesion, patient’s age and general health, and surgical specifics discussed previously; however, the concepts of each phase are consistent. The following sections overview the generalized rehabilitation process during each of the four phases.

Phase I: Early Protection Phase

The first phase of cartilage healing is the proliferation phase, which typically involves the first 4 to 6 postoperative weeks. During this phase, the initial healing process begins. It is imperative to decrease swelling, gradually restore PROM, and enhance volitional control of the quadriceps during this period of rehabilitation.

Controlled active ROM and PROM and a gradual weight-bearing progression are critical components to the rehabilitation process. As previously discussed, PROM and controlled partial weight-bearing will help promote the nurturing of the cartilage through diffusion of synovial fluid as well as provide the proper stimulus for the cells to produce specific matrix markers. Individuals begin with partial weight-bearing activities using crutches. Progressive loading exercises using the pool and force platforms are gradually implemented to increase the amount of load applied to the weight-bearing surfaces of the joint. The use of a pool or aquatic therapy may be beneficial to begin gait training and lower extremity exercises once the incisions are well healed.

PROM activities, such as manual PROM performed by a rehabilitation specialist and CPM machines, are also begun immediately after surgery to nourish the healing articular cartilage and prevent the formation of adhesions. The use of a CPM typically begins 6 to 8 hours after surgery and is performed for at least 2 to 3 weeks, with recommended use up to 6 to 8 weeks. It is recommended that the CPM be used throughout the day for up to 6 to 8 hours. The patient is instructed to also perform active-assisted ROM frequently throughout the day. Patella mobilization, soft tissue mobilization, and soft tissue flexibility exercises are also performed to minimize scar tissue formation and avoid loss of motion. Low-intensity stationary cycling may be implemented in this phase.

Early strengthening exercises are performed to restore volitional quadriceps control and neuromuscular control through the use of concomitant EMS. Exercises performed during this phase are limited based on the specific weight-bearing status of each patient and typically include quadriceps sets, straight leg raises, and early baseline proprioception exercises such as weight-shifting.

Phase II: Transition Phase

The second phase is the transitional phase, which typically includes postoperative weeks 4 through 12. The repair tissue at this point is gaining strength, which will allow for the progression of rehabilitation exercises. During this phase, the patient progresses from partial to full weight-bearing, while full ROM and soft tissue flexibility are achieved. Continued maturation of the repair tissue is fostered through higher-level functional and ROM exercises. It is during this phase that patients typically resume most normal activities of daily living. The rehabilitation program will gradually progress strengthening activities to include machine weights and CKC exercises, such as leg press, front lunges, wall-slides, and lateral step-ups, as the patient’s weight-bearing status returns to normal.

At this time, the rehabilitation process involves the progressive application of therapeutic exercises designed to gradually increase function in the postoperative knee. The progression of weight-bearing activities and restoration of ROM, as previously discussed, involves the gradual advancement of activities to ensure that complications do not arise while facilitating healing. A principle of gradual progressive loading is implemented during this phase. Once weight-bearing is initiated, the clinician may consider an osteoarthritis unloader brace. Common complications include motion restrictions and scar tissue formation. Furthermore, an overaggressive approach early within the rehabilitation program may result in increased pain, inflammation, or effusion as well as graft damage. This simple concept may be applied to the progression of strengthening exercises, proprioception training, neuromuscular control drills, and functional drills. For example, exercises such as weight-shifts and lunges are progressed from straight-plane anterior-posterior or medial-lateral directions to involve multiplane and rotational movements. Exercises using two legs, such as leg press and balance activities, are progressed to single-leg exercises. Thus, the progression through the postoperative rehabilitation program involves a gradual progression of applied and functional stresses. This progression is used to provide a healthy stimulus for healing tissues while ensuring that forces are gradually applied without causing damage.

SPECIFIC POSTOPERATIVE GUIDELINES

Microfracture

Rehabilitation after a microfracture procedure progresses more cautiously than that of a débridement or chondroplasty (Table 37–3). The program is based on size, location, number of areas treated, and concomitant procedures. The early protection phase begins immediately after surgery and lasts until the 4th week postoperatively. During this time, defects begin to fill with a fibrin clot, although no fibrocartilage is present.11 A period of non–weight-bearing is applied for the first 2 to 6 weeks postoperatively for most lesions. A recent study by Marder and colleagues27 compared the results of patients with small focal lesions of less than 2.0 cm2 using two postoperative rehabilitation programs. Group I used touch-down weight-bearing and a CPM machine for 6 to 8 hours a day for 6 weeks. Group II was allowed weight-bearing as tolerated immediately after surgery and used active-assisted heel-slides for ROM (without the use of a CPM). The authors reported significant improvements in both groups and no significant differences in the subjective or objective outcomes between groups a minimum of 2 years postoperatively. Thus, it appears that it may be possible to begin early controlled weight-bearing for small, focal lesions without applying deleterious forces to the repair site. Initial controlled touch-down weight-bearing is initiated for lesions that are localized and smaller than 2.0 cm2 in patients with good tissue quality. For patients with patellofemoral lesions, immediate weight-bearing is performed owing to the lack of lesion articulation during weight-bearing; however, a drop-locked knee brace is worn to avoid deleterious sheer forces to the healing repair site.

TABLE 37-3 Rehabilitation after Microfracture Procedure

Phase I: Early Protection Phase (Weeks 0–4)
Goals

Brace No brace; may use elastic wrap to control swelling. WB

ROM Strengthening program Functional activities Swelling control Ice, elevation, compression, and effusion modalities as needed. Criteria to progress to phase II
Phase II: Transition Phase (Weeks 4–8)
Goals
WB
ROM
Strengthening exercises
Functional activities
Criteria to progress to phase III
Phase III: Remodeling Phase (Weeks 8–16)
Goals
ROM Patient should exhibit 125°–135°+ flexion.
Exercise program
Functional activities As patient improves, increase walking (e.g., distance, cadence, incline)
Maintenance program
Criteria to progress to phase IV
PHASE IV: MATURATION PHASE (WEEKS 16–26)
Goals Gradual return to full unrestricted functional activities.
Exercises
Functional activities Patient may return to various sport activities as progression in rehabilitation and cartilage healing allows. Generally, low-impact sports such as swimming, skating, rollerblading, and cycling are permitted at about 2 mo for small femoral condyle and patellofemoral lesions and at 3 mo for large femoral condyle lesions. Higher-impact sports such as jogging, running, and aerobics may be performed at 4 mo for small lesions or 5 mo for larger lesions. High-impact sports such as tennis, basketball, football and baseball are allowed at 6–8 mo.

CKC, closed kinetic chain; CPM, continuous passive motion; EMS, electrical muscle stimulation; OKC, open kinetic chain; Q/H, quadriceps/hamstring; ROM, range of motion; WB, weight-bearing.

Owing to the arthroscopic nature of the procedure, PROM is performed immediately without restrictions. Full PROM of at least 0° to 125° is achieved between weeks 3 and 4, often with little difficulty.

The transition phase begins at week 4 and progresses to week 8. During this phase, the patient may progress to full weight-bearing and more functional CKC exercises. At 6 weeks postoperatively, a thin layer of tissue covers the base of the lesion.13 Although the repair is still incomplete, fibrocartilagenous tissue is present, and by 8 weeks, some tissue with hyaline-like characteristics has been detected.11 By 12 weeks, the defect is completely filled and the quality of cartilaginous tissue improves significantly.13

Weight-bearing is thus progressed to full at week 8 for most lesions when the strength of the repair tissue is increasing. However, the progression to more advanced exercises, including impact loading, is delayed until the end of the remodeling phase when the defect is completely filled. The patient may gradually begin to return to former activities during the maturation phase between months 4 to 6; however, larger lesions may need to delay the progression to high-impact activities for up to 8 months.

Clinical outcome studies indicate that a significant number of patients will be able to return to sports after a microfracture procedure. Mithoefer and coworkers31 reported on 32 patients who routinely participated in high-impact and pivoting sports. At a minimum 2-year follow-up, 66% had good to excellent results and 44% had returned to high-impact sports. However, after initial improvement, scores decreased in 47% of athletes. Return to sports was significantly higher in athletes younger than 40 years of age, patients with a lesion size less than 200 mm2, those with preoperative symptoms less than 12 months’ duration, and patients who had no prior surgical intervention. Mithoefer and associates29 reported results of microfracture on isolated femoral chondral lesions. They reported that 67% of patients had a good to excellent result; 25%, a fair result; and 8%, a poor result. The investigators were able to obtain follow-up magnetic resonance imaging (MRI) on 50% of the patients. MRI revealed good tissue healing and filling in 54%, moderate tissue filling in 29%, and poor healing result in 17%. Successful outcomes correlated to a low BMI, good healing or lesion filling, and short duration of symptoms. The worst results were seen in patients with a BMI of 30 kg/m. Kreuz and colleagues26 compared the results of microfracture in patients older than 40 years of age and younger than 40 years of age. The authors reported superior outcomes in patients 40 years or younger. Between 18 and 36 months postoperatively, the investigators found a deterioration in International Cartilage Repair Society (ICRS) scores, which was significantly pronounced in older patients. Furthermore, MRI performed at 36 months after surgery indicated better fill in patients younger than 40 years of age.

OATS

Rehabilitation after OATS procedures requires the avoidance of early deleterious forces to avoid disrupting the healing transplanted bone plugs (Table 37–4). Currently, the pace of the rehabilitation program after OATS procedures is based not only on the size of the lesion but also on the amount of transplanted bone plugs. The program is progressed more cautiously when numerous bone plugs are used owing to the potential for a less congruent surface. The early protection phase lasts until the 8th week postoperatively. During this phase, an initial 44% reduction in the push-in and pull-out strength of the transplanted bone plugs has been observed (at 1 wk postoperatively),52 emphasizing the need for strict non–weight-bearing postoperatively. Partial weight-bearing is usually initiated 2 to 4 weeks after surgery based on the size of the lesion and the number of transplanted bone plugs. Although the original hyaline cartilage remains intact and viable,33 the strength of the bone plugs is the limiting factor when designing the postoperative rehabilitation program.

TABLE 37-4 Rehabilitation after Osteochondral Autograft Transplantation

Phase I: Early Protection Phase (Weeks 0–6)
Goals

Brace WB ROM Strengthening program Functional activities Swelling control Ice, elevation, compression, and edema modalities as needed to decrease swelling. Criteria to progress to phase II
Phase II: Transition Phase (Weeks 6–12)
Goals
Brace Discontinue brace at 6 wk, consider unloading brace for femoral condyle lesions.
WB
ROM
Strengthening exercises
Functional activities
Criteria to progress to phase III
Phase III: Remodeling Phase (Weeks 12–26)
Goals
ROM Patient should exhibit 125°–135° flexion—no restrictions.
Exercise program
Functional activities As patient improves, increase walking (e.g., distance, cadence, incline)
Maintenance program
Criteria to progress to phase IV
Phase IV: Maturation Phase (Weeks 26–52)
Goals Gradual return to full unrestricted functional activities.
Exercises
Functional activities Patient may return to various sport activities as progression in rehabilitation and cartilage healing allows. Generally, low-impact sports such as skating, rollerblading, and cycling are permitted at about 6–8 mo. Higher-impact sports such as jogging, running, and aerobics may be performed at 8–10 mo. High-impact sports such as tennis, basketball, and baseball are allowed at 12–18 mo.

CKC, closed kinetic chain; CPM, continuous passive motion; EMS, electrical muscle stimulation; OKC, open kinetic chain; Q/H, quadriceps/hamstring; ROM, range of motion; WB, weight-bearing.

By 4 weeks, the cancellous bone plugs have united,19 and by 6 weeks, there is full subchondral integration and 29% of grafts show bonding between the articular cartilage of the bone plugs and the surrounding articular cartilage.33 Although integration has occurred, a 63% decrease in graft stiffness is still observed at 6 weeks postoperative.33 During this time, weight-bearing is gradually progressed as the strength of the repair increases. At 8 weeks postoperative, fibrocartilage has been observed to grow to the surface and seal the recipient and donor site hyaline cartilage, and weight-bearing is progressed to full. Immediate weight-bearing is initiated for patellofemoral lesions with a drop-lock knee brace and progressed to full without the brace at approximately 6 to 8 weeks postoperative.

ROM during the early protective phase is gradually progressed to ensure that adhesion formation and loss of motion is avoided. Owing to the large incision and invasive nature of the procedure, motion is progressed gradually to minimize effusion formation.

Exercises are progressed from non–weight-bearing, such as quadriceps sets and multiangle straight leg raises, to gentle weight-bearing in a restricted weight tolerance after week 6.

During the transition phase, full ROM and weight-bearing are achieved typically between weeks 8 to 10, although larger lesions may need to further delay the progress to full weight-bearing for up to 12 to 14 weeks. At this point, the strengthening program is progressed to include weight-bearing CKC and machine exercises. Again, during this phase, patients return to low-impact functional activities.

During the remodeling and maturation phases, strength, proprioception, and neuromuscular control are enhanced while impact-loading stresses are gradually applied as tolerated without an increase in symptoms. Patient may return to various sport activities as progression in rehabilitation and cartilage healing allows, although this is more delayed than the previously discussed rehabilitation progressions. Generally, low-impact sports such as golf, swimming, cycling, and walking for exercise are permitted at 4 to 5 months postoperatively. Moderate-impact sports such as tennis and hiking are permitted at 6 to 8 months (depending on size and location of the lesion). The return to high-impact sports is controversial, although some clinicians allow sports such as jogging, running, and aerobics at 8 to 10 months and tennis, basketball, and baseball at 12 to 18 months. There are too few studies to indicate the long-term success in allowing the return to strenuous activities, which may risk deterioration of the reparative cartilage.

Clinical outcome results after mosaicplasty indicate good results. Hangody and Fules18 followed 831 patients and reported a good to excellent result in 92% of those who exhibited a lesion of the femoral condyle, and the same in 87% with a tibial plateau lesion. Lesions of the patella rendered the lowest outcomes, with only 79% exhibiting a good to excellent result. Furthermore, the authors reported a 3% rate of donor site morbidity. Lastly, 36 patients exhibited a painful postoperative hemarthroses. Bartha and coworkers1 reported on 89 patients who underwent second-look arthroscopy, 77% of whom exhibited congruent surfaces and healing of the lesion.

ACI

The rehabilitation program after ACI is vital to the success and long-term outcomes of patients (Table 37–5). Early controlled ROM and weight-bearing are necessary to stimulate chondrocyte development, although caution is placed on overaggressive activities that may result in cell damage or graft delamination.

TABLE 37-5 Rehabilitation after Autologous Chondrocyte Implantation

Phase I: Early Protection Phase (Weeks 0–6)
Goals

Brace WB ROM Strengthening program Functional activities Swelling control Ice, elevation, compression, and edema modalities as needed to decrease swelling. Criteria to progress to phase II
Phase II: Transition Phase (Weeks 6–12)
Goals
Brace
WB
ROM
Strengthening exercises
Functional activities
Criteria to progress to phase III
Phase III: Remodeling Phase (Weeks 12–26)
Goals
ROM Patient should exhibit 125°–135° flexion.
Exercise program
Functional activities As patient improves, increase walking (e.g., distance, cadence, incline)
Maintenance program
Criteria to progress to phase IV
Phase IV: Maturation Phase (Weeks 12–26)
Goals Gradual return to full unrestricted functional activities.
Exercises
Functional activities Patient may return to various sport activities as progression in rehabilitation and cartilage healing allows. Generally, low-impact sports such as swimming, skating, rollerblading, and cycling are permitted at about 6 mo. Higher-impact sports such as jogging, running, and aerobics may be performed at 8–9 mo for small lesions or 9–12 mo for larger lesions. High-impact sports such as tennis, basketball, football and baseball are allowed at 12–18 mo.

CKC, closed kinetic chain; CPM, continuous passive motion; EMS, electrical muscle stimulation; OKC, open kinetic chain; Q/H, quadriceps/hamstring; ROM, range of motion; WB, weight-bearing.

Knowledge of the biologic healing response is vital for the development of appropriate rehabilitation guidelines. Rehabilitation may begin as early as the recovery room in the form of CPM. At this time, the chondrocytes are aligned and attached to the underlying surface.47 It is imperative that the patient be appropriately positioned to allow for the effect of gravity to evenly distribute the chondrocytes on the base of the defect during these first 4 hours as the cells adhere to the surface. A study by Sohn and associates47 showed that the defect orientation during these first 4 hours can be an important factor in the uniformity of cell distribution in the ACI procedure. These authors advanced the hypothesis, which has not yet been proved clinically, that the effects of gravity within the first few hours of cell implantation could lead to localization of induced cells in one area of the graft but not in other areas, which may affect healing of the defects. This suggests two possibilities. First, that the position of the patient with a patellar defect in the prone position would contraindicate CPM, because it would produce an abnormal gravity effect. Second, that the use of CPM immediately after surgery is warranted to produce a “more even distribution of implanted cells within the defect.” At present, no in vivo or clinical studies have been published to support this hypothesis.

Proliferation of the chondrocytes occurs in the first 6 weeks after cell implantation. During the first 24 hours after cell implantation, the cells line the base of the lesion and multiply several times to produce a matrix that will fill the defect with a soft repair tissue up to the level of the periosteal cover.16,38 At this time, PROM and controlled partial weight-bearing will help to promote cellular nutrition through synovial fluid diffusion as well as provide the proper stimulus for the cells to produce specific matrix markers. During this initial phase, controlled PROM and a gradual weight-bearing progression are two of the most important components of the rehabilitation process.

Immediate toe-touch weight-bearing is performed in knees with smaller lesions, progressing to 25% body weight at weeks 2 to 4, 50% body weight at weeks 5 to 6, and full weight-bearing at week 8. This progression may be delayed approximately 2 weeks, with 2 weeks of non–weight-bearing, if the lesion is large, deep, or uncontained. For lesions within the patella or trochlea, the patient is allowed to bear weight as tolerated immediately after surgery with a brace locked in full extension. ROM is progressed cautiously to avoid swelling similar to the OATS procedure, with at least 90° of flexion at week 1, 105° at weeks 2 to 3, 115° at week 4, and 125° at week 6. Early strength and proprioceptive exercises are performed within the patient’s weight-bearing status.

During the transition phase, which includes weeks 7 through 12, the repair tissue is spongy and compressible with little resistance. Upon arthroscopic examination, the tissue may in fact have a wavelike motion when a probe is slid over the tissue.16,38 During this phase, the patient achieves full ROM and progresses from partial to full weight-bearing. Continued maturation of the repair tissue is fostered through higher level functional and motion exercises. CKC exercises, such as front lunges, step-ups, and wall-squats are performed as well as machine exercises for the entire lower extremity. Again, caution should be placed on exercises that produce sheer forces in patients with patellofemoral lesions.

The remodeling phase occurs from 12 weeks through 32 weeks postoperatively. During this phase, there is a continuous production of matrix with further remodeling into a more organized structural tissue. The tissue at this point has the consistency of soft plastic upon probing.16,38 As the tissue becomes more firm and integrated, it allows for more functional training activities to be performed as well as elliptical, bicycle, and a gradual walking program.

The final maturation phase can last up to 15 to 18 months depending upon the size and location of the lesion. During this phase, the repair tissue reaches its full maturation. The stiffness of the cartilage resembles that of the surrounding tissue.16,38 The duration of this phase varies based on several factors such as lesion size and location.

Basic science studies have shown that it may take up to 6 months for the graft site to become firm and at least 9 months to become as durable as the surrounding healthy articular cartilage.16,38 Thus, low-impact activities (such as golf, swimming, cycling, and walking) are initiated by months 5 to 6 and progressed to moderate-impact activities (such as tennis, hiking, skating) from months 7 to 9 as tolerated. Usually, high-impact activities such as running and skiing are permitted with a gradual return beginning at 11 to 12 months postoperative.

The results of clinical outcomes after ACI are encouraging. Mithofer and colleagues32 reported a 72% good to excellent result and return to play in competitive soccer players, with 80% returning back to the same level of play. Peterson and coworkers37 reported a 90% good to excellent result using ACI on osteochondritis dissecans lesions of the knee in patients with a mean age of 26.4 years (range, 14–52 yr).

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