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Treatment of Patellofemoral Cartilage Lesions in the Young, Active Patient Matthew R. Prince, DO1 Aaron J. Krych, MD1
Alexander H. King, BS1
Michael J. Stuart, MD1
1 Department of Orthopedic Surgery and Sports Medicine Center,
Mayo Clinic, Rochester, Minnesota
Diane L. Dahm, MD1
Address for correspondence Aaron J. Krych, MD, Department of Orthopedic Surgery, Mayo Clinic, 200 First Street SW, Rochester, MN 55905 (e-mail: [email protected]).
Abstract
Keywords
► patellofemoral ► cartilage ► osteochondral
Articular cartilage lesions of the patella and trochlea are commonly encountered in the young and active patient. These defects can be classified as chondral or osteochondral, and then further described according to size, location, and etiology. Early surgical intervention is often indicated for traumatic injuries resulting in osteochondral damage, including acute patellofemoral dislocation. For chronic lesions, initial treatment involves exhaustive nonoperative measures, and surgery is reserved for patients with persistent symptoms. A thorough history, physical examination, and imaging are essential to select the best surgical option. Cartilage restoration procedures are combined with optimization of background factors such as patellofemoral alignment and congruity to achieve success. Cell-based therapies have evolved into a reliable strategy for management of these lesions.
Chondral injuries of the patellofemoral joint are both a common and often challenging problem. Arthroscopic examination of athletes’ knees has shown the overall prevalence of full-thickness cartilage lesions to be 36%. The most prevalent site of these defects is the patellofemoral joint, with the patella more commonly involved than the trochlea (64 vs. 36%).1 Many of these lesions will go undetected because a large percentage of the injuries occur in asymptomatic individuals.
Classification of Articular Cartilage Lesions Classifying articular cartilage lesions is critical for guiding treatment and also for analyzing treatment outcomes. Outerbridge described four different grades of chondromalacia of the patella in 1961.2 Grade I describes softening and swelling of the cartilage. Grade II is defined by fragmentation and fissuring in an area less than half an inch in diameter. Grade III has the same characteristics as grade II but involves an area greater than half an inch in diameter; and lastly Grade IV is erosion of the cartilage down to bone. An additional classifi-
received October 1, 2014 accepted after revision January 6, 2015 published online April 19, 2015
cation system which has been used largely for research is the International Cartilage Repair Society (ICRS) classification, which also takes into account the subchondral bone damage.3 It is helpful to further classify these lesions by etiology into traumatic, atraumatic, or dysplastic.4 The defect should be further subdivided as either purely chondral or osteochondral in nature. Traumatic chondral lesions of the patella are most commonly the result of a lateral patellofemoral dislocation (►Fig. 1). Acute patellar dislocations occur in both contact injuries and a noncontact twisting mechanism. In a review of the literature, Farr et al found the incidence of medial patellar facet and lateral femoral condyle chondral defects following acute patellar dislocation to range from 70 to 93%.5 The most common site of injury is the medial facet of the patella.6 It has also been suggested that the pediatric population is more prone to osteochondral injury with dislocation due to a maturing calcified cartilage layer, which subsequently weakens the boundary between subchondral bone and cartilage.7 Risk factors for patellar dislocation include: patella alta, trochlear dysplasia, lateralized tibial tubercle, excessive femoral anteversion, external tibial
Copyright © 2015 by Thieme Medical Publishers, Inc., 333 Seventh Avenue, New York, NY 10001, USA. Tel: +1(212) 584-4662.
DOI http://dx.doi.org/ 10.1055/s-0035-1549018. ISSN 1538-8506.
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Fig. 1 Traumatic patella cartilage defect on T2 sagittal MRI and at time of arthroscopy ( , loose body; !, donor site). Notice the sharp, vertical borders are well defined in this acute lesion.
torsion, prior dislocation, and iatrogenic instability.8 The location a trochlear lesion is dependent on the direction of the force applied and the degree of knee flexion at the time of collision.9 Traumatic lesions can also occur from repetitive microtrauma, even in a patellofemoral joint with normal alignment and morphology. This occurs during repetitive loading in high-stress activities such as basketball, alpine skiing, weight training, and fencing.4 Chondrosis due to dysplasia is represented by a wide spectrum of malalignment and morphological abnormalities. The significance of these abnormalities is related to the alteration of contact forces about the patellofemoral joint.4 It is hypothesized that there is an individualized threshold for the stress an individual’s cartilage can endure before chondrosis will occur.4 This margin is limited for the patellofemoral joint due to the high forces and small contact area. Recognizing this subset is important, as treatment will need to optimize the contact area and decrease the force transmitted through the joint to maintain unique shear forces. Osteochondral injuries are most commonly from a traumatic dislocation, but osteochondritis dissecans (OCD) can . also occur in this location. Though OCD is rare in this location, it is an important subset of patellofemoral cartilage defects that are essential to recognize. Patellar-based defects are more commonly located over the central ridge, while trochlear lesions typically involve the lateral femoral condyle.10,11 Two of the largest studies involving treatment of these lesions demonstrated high rates of continued anterior knee pain and crepitus.10,11 However, the surgery consisted only of debridement and loose body removal without cartilage regeneration procedures. It is prudent to address any underlying structural predisposing factors, while also realizing that bony management in these defects is as important as addressing the chondral involvement.4
History and Physical Exam The key to accurate diagnosis and management is a detailed history. Patients will typically present with deep anterior knee pain often described as a band of pain located inferior to the patella. Pain stemming from the trochlea may rarely The Journal of Knee Surgery
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present as posterior knee pain.12 Deep squats, prolonged sitting, and stair climbing have been classically noted to aggravate knee pain in patients with chondral damage or patellofemoral arthritis. Clinicians must be inquisitive with patients having a history of patellar instability to determine if pain occurs during subluxation. If pain occurs when the knee is stable, it is possible that a chondral defect may be present. A patellar stabilization brace may help a patient discern if instability is playing a role in their knee pain. Overall, lower extremity alignment and gait analysis are two key components of the physical exam in patients with patellofemoral cartilage lesions. Evaluations of the lumbar spine and neurologic system are important for determining the source of referred pain. Lastly, a knee exam must include an assessment of hip and core function to rule out any hip abnormality or other source of referred pain to the knee.
Standing Exam A general inspection of the lower extremity for bruising, redness, swelling, and surgical scars should begin the standing exam. Following this, an overall assessment of limb alignment with the feet together should be conducted. Any varus or valgus malalignment should be noted. Further static examination in a standing position should include observation of leg-length discrepancies, patella height, and knee extension. Patella alta has been linked to instability, while patella baja can lead to chondral damage to the patella.13 A dynamic evaluation of patients is just as important as a static one. This observation is typically composed of single and double leg squats, as well as gait analysis. During the squat, dynamic malalignment must be noticed, as this has frequently been shown to have negative effects, particularly with patellofemoral pain syndrome.14,15 Additionally, a gait analysis should be performed from both the anterior and posterior views while walking forward and backward.
Supine Exam Again, any signs of swelling or skin abnormalities compared with the contralateral knee should be noted. Patellar position is a key component of this exam. A laterally tilted patella can
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show a high amount of laterally directed forces to the patella. Patella alta and baja are most easily assessed from the side of the knee. During active range of motion, the patella should be observed again for the presence of a J-sign. Patellofemoral crepitus or grinding can be assessed by placing a hand over the patella during active range of motion. Palpation of the knee is the best technique of localizing anterior knee pain. Key points of palpation include the quadriceps tendon, superior pole of the patella, patellar body, inferior pole of the patella, patellar tendon, tibial tubercle, medial and lateral joint lines, and the medial and later retinaculum.13 To test for instability, the patellar glide and apprehension tests are the most reliable method. With the knee flexed to 20 degrees, the patella is translated medially and laterally. Medial glide with less than one quadrant of the patellar width is a positive sign of lateral tightness, while glide of three quadrants in either direction is a sign of hypermobility of the patella.13,16 The patellar tilt test is also used for evaluating patellofemoral tightness. Patellofemoral chondral damage can be evaluated using the compression test.
Imaging Techniques Due to the complexity of the patellofemoral joint, a variety of imaging modalities should be used to confirm the diagnosis and identify background factors. Common techniques include conventional radiographs, magnetic resonance imaging (MRI), and computed tomography (CT). Radiographs are able to evaluate joint space narrowing, check standing hip to ankle coronal alignment, and provide information about dysplasia. MRI is used to assess subchondral edema, articular cartilage loss, and focal defects. CT provides a better evaluation of bone loss and measurement of the tibial tubercle– trochlear groove (TT-TG) distance, but may be undesirable in young patients due to radiation concerns. MRI has been shown to be an acceptable method for measuring TT-TG distance.17–20 Radiographs are the first-line imaging technique used in evaluating knee pain. Standing anteroposterior, 45-degree posteroanterior flexed view, lateral, Merchant, or Laurin views are all utilized. The lateral view should be obtained at 30 degrees of flexion to assess patellar height to determine if patella alta is present. Trochlear dysplasia can also be assessed by a lateral view radiograph. However, there must be perfect superimposition of the posterior aspects of the medial and lateral femoral condyles to confidently evaluate trochlear depth.21 Less than 5 mm between the anterior condylar borders and the intercondylar sulcus suggests a risk of instability.22 The Merchant view allows for assessment of patella size, sulcus angle, and morphology of the patella.21 The Laurin technique is an axial image obtained inferior to superior with the knee in 20 degrees of flexion which can be used to evaluate patella subluxation. This technique is superior to the Merchant view since patella subluxation usually occurs between 20 and 30 degrees of flexion.23 Patellar tilt can also be assessed on axial radiographs. The patellofemoral
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index is the ratio of medial joint space to lateral joint space. Normally, this value measures 1.6 or less, with a ratio greater than 1.6, indicating lateral patellar tilt.24 MRI is very useful in viewing the patellofemoral joint because of its ability to assess soft tissue structures and its multiplanar capability. A dedicated multichannel knee coil should be used with a minimum of 1.5 T field units. A fatsuppressed T2 sequence shows bone marrow edema and fluid collection within the joint. Axial T1 and T2 sequences are useful for evaluating the chondral surfaces of the patellofemoral joint.12 An intermediate echo-time two-dimensional non–fat-suppressed fast/turn spin-echo image shows a strong signal for synovial fluid, intermediate for articular cartilage, and weak for fibrocartilage. Link and colleagues25 showed that high-resolution MR sequences were more effective in detecting cartilage lesions at 3 T, but at lower resolutions no differences were found between 1.5 and 3 T. MRI can be very helpful in determining the size of chondral defect, but is not always accurate in this setting.26 CT imaging is helpful for evaluating bone loss and measuring the TT-TG distance. TT-TG is commonly used as a surgical decision-making tool for patellofemoral malalignment and instability. An increased TT-TG distance is a risk factor for patellar dislocations and subluxations. On CT, a TT-TG distance of 20 mm has been used as a general guideline for performing a tibial tubercle osteotomy (TTO). CT has long been validated as a successful means of measuring TT-TG distance18,20,27–29; however, recent studies used axial MRI as a means for measurement.17,19,28,30–33 Camp et al determined that TT-TG distance can be measured with excellent reliability on both MRI and CT; however, the values obtained from these two modalities may not be interchangeable.18 MRI has the potential to underestimate TT-TG distance compared with CT, though more research is needed to establish validity.
Treatment Options Repair/Debridement Chondral and osteochondral injury has been reported to occur frequently after acute patellar dislocation. When possible, repair of an acute, traumatic osteochondral defect is the preferred treatment. Numerous open and arthroscopic fixation techniques have been described. Metal compression screws and bioabsorbable screws are acceptable treatment options.34–38 If the defect is small, or repair is not possible, then debridement may be preferred. It is important to note that the outcomes of nonoperative treatment of these lesions have been poor.39 If fixation is not possible, then microfracture of intact subchondral bone may be considered along with a cartilage biopsy for future autologous chondrocyte implantation (ACI) if this is chosen over other cell-based options such as juvenile particulated cartilage.
Microfracture Marrow stimulation techniques serve an important role in the treatment of cartilage lesions. The most common technique, microfracture, was originally popularized by Steadman. It has shown to be a cost-effective, minimally invasive The Journal of Knee Surgery
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Fig. 2 Microfracture of a traumatic 2-cm patellar chondral defect in a 15-year-old male skier. He was able to return to skiing at 4 months following surgery and remains symptom free at 2 years from surgery.
technique for the treatment of cartilage lesions.40 In the short term, microfracture has demonstrated excellent results in regard to pain relief and function, especially in younger patients.41–43 Unfortunately, the fibrocartilage produced by microfracture has proven to have unfavorable long-term durability and clinical results.44 A study by Kreuz further emphasized these poor findings when specifically looking at microfracture of the patella and trochlea.41 In addition, there is also evidence to suggest possible detriment to the results of future cartilaginous procedures in the face of a failed microfracture.45 Microfracture has also been proven to have sub-
optimal results with lesions greater than 2 to 4 cm, adding to its limitations as a viable treatment option.46,47 In a systematic analysis of 28 clinical microfracture studies, Mithoefer et al found patients with lesions 2 cm2.48 Although the above-mentioned shortcomings exist, there are several advantages to using microfracture. This singlestage procedure is relatively affordable with overall low morbidity. This may be the best option for a young athlete with a small patellofemoral lesion who wants to return to play
Fig. 3 A 19-year-old female with history of recurrent lateral patella dislocation and symptomatic cartilage lesion. Intraoperative pictures demonstrating patella cartilage lesion, microfracture, and augmentation with micronized cartilage matrix (Biocartilage, Arthrex, Naples, FL). Postoperative radiograph showing that background factors were addressed with TTO for increased TT-TG with distal lateral maltracking and medial patellofemoral ligament reconstruction. The Journal of Knee Surgery
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as quickly as possible (►Fig. 2). It is important to follow the surgical principles as outlined by Mithoefer et al, by obtaining stable vertical borders, removing the calcified cartilage layer, and placing perforations that access marrow elements without compromising subchondral bone integrity.49 Patellofemoral alignment and morphology must be thoroughly defined and addressed as necessary. Currently, there are options to augment microfracture, to encourage more articular-like cartilage formation over fibrocartilage. One option is micronized cartilage matrix, but clearly more research and clinical results are needed in this area (►Fig. 3). We currently consider this method when treating a larger lesion when other options have been denied by insurance for the patient. Other augmentation options include collagen and polymer membranes, chitosan and fibrin gels, hyaluronan injections, as well as numerous growth factors.50
Autologous Chondrocyte Implantation ACI has become a reliable treatment option for patellofemoral cartilage lesions. Short- and long-term follow-up have demonstrated excellent results with modern ACI techniques.51–57 Recently, Gillogly demonstrated good to excellent results in 83% of cases with ACI of the patella after a mean follow-up of 7.6 years.51 Mandelbaum et al showed that ACI of isolated trochlear lesions has both functional and symptomatic benefits.55 The most recent studies involving ACI in the patellofemoral compartment have demonstrated improved success
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with anteromedialization (AMZ) of the tibial tubercle, along with ACI.51,53,54,58 ACI of the patella alone has demonstrated less favorable results.59,60 However, when individualizing treatment based on lesion location and patellar alignment, Gomoll et al did not find a difference in the subgroups of ACI alone and ACI with TTO.52 It is important to note that distal and lateral lesions of the patella are most likely to benefit from AMZ as a result of unloading of these areas. In addition, proximal and medial lesions may experience higher loads if AMZ is performed. Successful outcomes are more typical when all of the above parameters are accounted for when developing an individualized treatment plan. In a prospective randomized trial comparing ACI to mosaicplasty of the knee, Bentley et al published significantly better results with ACI. When specifically looking at patellarbased lesions, there was 85% good or excellent results with ACI compared with 60% following mosaicplasty.61 The authors also reported a poor arthroscopic result in all five patellar mosaicplasties due to differing thicknesses of donor and recipient cartilage. One decisive advantage for ACI in this setting is that the geometry of the patch in unconstrained, compared with cylinders for mosaicplasty. When comparing ACI to microfracture, there are no studies which have evaluated results isolated to the patellofemoral joint. In a randomized trial comparing ACI to microfracture at two- and five-year follow-up, no significant
Fig. 4 Intraoperative photos of large pan-patellar full-thickness cartilage lesion treated with juvenile particulated chondral allograft (DeNovo NT, Zimmer, Warsaw, IN) in fibrin glue matrix. Preoperative sagittal T2 MRI demonstrates cartilage lesion and subchondral bony edema (arrow). Twoyear comparison postoperative MRI demonstrates complete resolution of bony edema (arrow) with good fill and incorporation of the chondral graft, but slight hypertrophy of the neocartilage. The Journal of Knee Surgery
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differences were observed.46,62 Van Assche et al also found no functional difference in ACI versus microfracture of the femoral condyle at two years postprocedure.63 However, significant differences exist between these two methods when taking into account lesion size. Diminishing results are commonly seen with microfracture of lesions greater than 2 cm.2,48 In a meta-analysis looking at the clinical outcomes of ACI versus microfracture, Negrin64 concluded that the results of ACI in lesions greater than 4 cm2 are maintained in contrast to microfracture. The theoretical benefit of ACI over microfracture is the amount and percentage of hyaline cartilage present in lesions treated with ACI. Two years following ACI, Peterson et al found 80% hyaline cartilage after biopsy.65 In contrast, Gudas et al found 57% of the biopsies obtained after microfracture containing solely fibrocartilage.47 In contrast, Knutsen did not find a significant difference in hyaline composition of cartilage biopsies in a randomized controlled study comparing ACI and microfracture.46,62 While the optimal treatment for cartilage lesions of the patellofemoral joint has yet to be clearly defined, it is apparent that the large amount of newly published data show long-term favorable results with ACI, thereby making it a very desirable and promising treatment option.
Particulated Juvenile Articular Cartilage The use of particulated juvenile articular cartilage (PJAC) for articular cartilage defects is an exciting and evolving treatment option. The most commonly used product currently is DeNovo NT Natural Tissue Graft (Zimmer Inc, Warsaw, Indiana, USA) and it consists of allograft articular cartilage from donors less than 13 years old. PJAC implantation for the treatment of cartilage lesions is performed in a manner very similar to ACI. Lesion preparation is completed in an identical fashion to ACI and it is a single-step implantation, typically with fibrin glue used to secure the cartilage cells into the defect (►Fig. 4). A large advantage of this technique is that it is a onestage surgery. One major limitation to the use of PJAC is the lack of high-quality published outcome data. The few
studies that do exist regarding its use have demonstrated promising results. Tompkins et al reviewed 13 patients in which PJAC was used for patellar cartilage defects averaging 2.4 1.2 cm2 . At an average of 33-month follow-up, they found overall promising clinical results with excellent defect filling on repeat MRI.66 In a recent case series published by Farr et al,67 the authors reported similar results in regard to clinical outcomes and defect repair in comparison to analogous MACI studies. While early results are promising, randomized controlled studies are needed to further evaluate the efficacy of PJAC in comparison to other available cartilage restoration procedures. The possibility of a single-stage procedure with results similar to ACI is an attractive treatment option if additional research continues to demonstrate clinical efficacy.
Osteochondral Autograft Transplantation Currently, minimal literature is available on the use of osteochondral autograft transplantation (OATS) for patellofemoral defects. When bone loss is present, making cell-based cartilage implantation unwarranted, OATS may be considered. Early investigations by Bentley et al suggested that differences in cartilage thickness made OATS unreliable for patellar use.61 The authors demonstrated superior results with ACI compared with mosaicplasty. Recent reports have claimed good clinical results and imaging evidence of incorporation with autograft plugs in short-term follow-up.68–70 Osteochondral autograft appears to be a viable option for patellofemoral defects. The physician should be aware of the possible difficulties in cartilage congruence and the reality of donor-site morbidity compounded by the fact that harvest typically occurs at the already diseased patellofemoral compartment.
Osteochondral Allograft Osteochondral allografting procedures have been performed in the knee for several decades.71 The procedure involves transplanting donor cartilage and bone from a size-matched distal femur into an osteochondral defect of the recipient patient. A recently published review of young active patients,
Fig. 5 Intraoperative photo demonstrating lateral trochlea osteochondral lesion from an unstable, unsalvageable OCD progeny fragment in a 39year-old female. This was treated with a stacked fresh-stored osteochondral allograft transplantation to restore both the bone and articular cartilage. An anteromedialization TTO was performed to offload the lateral trochlea and also to treat partial thickness lateral facet patella cartilage lesion. The Journal of Knee Surgery
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Treatment of Patellofemoral Cartilage Lesions
Patellofemoral Arthroplasty Patellofemoral arthroplasty (PFA) is a procedure generally considered as a salvage procedure in the young active patient due to higher adverse outcomes in patients under 40.75,76 With the advent of newer implant designs and improved implantation techniques, more acceptable results have been reported.77–79 PFA in the young active patient may be considered as another salvage option for the treatment of patellofemoral cartilage defects. Currently, there is no reliable evidence to determine the natural history of PFA in a patient continuing to be active in sport.80 Catastrophic failure by fracture or dislocation and failure due to polyethylene wear are the two categories comprising the risk associated with PFA in the active patient.80 These risks may be more pronounced in sports where high eccentric extensor loads and direction-change forces are common, such as basketball and
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soccer. The probability of these events is less likely in sports such as golf, running, and cycling.80
Author’s Preferred Surgical Approach Once a treatment plan is established, the goals and expectations are discussed in detail with the patient. The most important part of planning the procedure is in identification and treatment of background factors. Instability is often addressed with medial patellofemoral ligament reconstruction, trochlear dysplasia with trochleoplasty, and distal malalignment with TTO. The patient is placed in the supine position and a tourniquet is applied. A diagnostic arthroscopy with standard inferomedial and inferolateral portals is always performed to assess the lesion and survey the remainder of the knee joint. We prefer to perform our ACI and PJAC cases in an open fashion through an anteromedial incision and a medial patellar arthrotomy. This technique is preferred due to ease of everting the patella. Once the lesion and surrounding unstable cartilage is defined, a number 15 blade and curettes are used to create a vertical cartilage border. Any remaining calcified cartilage in the defect bed is removed carefully to prevent penetration of the subchondral bone and bleeding. It is important to note that ACI is not FDA-approved currently in the United States for treatment of patellar lesions, or for treatment of bipolar patellofemoral lesions, despite its excellent clinical results in a recent multicenter trial.52 ACI requires an index arthroscopy with a cartilage biopsy of 200 to 300 μg or approximately 5 to 10 mm of cartilage, which is
Fig. 6 Intraoperative photo demonstrating full-thickness central cartilage defect of patella in a 25-year-old male basketball player. The type I/III collagen membrane (BioGide, Geistlich Pharma North America, Princeton, NJ) is cut to size and preloaded with autologous chondrocytes on back table, sewn into defect with 6–0 Vicryl absorbable suture, and remaining cells are injected under membrane, and the membrane is sealed with fibrin glue. The Journal of Knee Surgery
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who had received a distal femoral osteochondral allograft a mean of 20 years prior, demonstrated excellent long-term survival.72 Unfortunately, such favorable results have not been reproduced in the patellofemoral joint. Jamali et al73 published a 25% failure rate in the 20 knees they treated with osteochondral allografting, with only 60% good or excellent results in the surviving patients. Spak and Teitge reported a 42% failure rate at an average follow-up of 10 years for their patellofemoral osteochondral allograft series.74 For these reasons, osteochondral allografting of the patellofemoral joint is generally reserved as a salvage procedure in the young active patient or to address a true osteochondral lesion, such as in OCD (►Fig. 5).
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Table 1 Rehabilitation protocol for patellofemoral cartilage procedures Phase
Goals
Restrictions
Range of motion
Exercises
Healing phase (weeks 0–6)
(1) Reduce swelling (2) Reduce muscle atrophy (3) Gradual full ROM (4) Patella mobilization
(1) Knee immobilizer as needed (2) PWB with crutches, TTWB if TTO performed
CPM 8 h/d, 10–60 degrees ROM as tolerated out of CPMa
(1) SLR, quad sets (2) Gluteal and core strengthening
Transitional phase (weeks 7–12)
(1) Reduce swelling (2) FWB by 10 wk (3) Reduce pain (4) Full ROM (5) Minimize hip, core, LE atrophy
Progress to FWB increasing each week
Full ROM
(1) Full ROM (2) Core strengthening (3) Body weight squat, leg press 0–60 degrees, as WB allows (4) Stationary bike (5) Gentle closed-chain terminal knee extension
Remodeling phase (weeks 13 þ )
(1) Full active ROM (2) No effusion (3) Improved quad strength and endurance
Surgeons decision on return to sports
Full ROM, normal walking
(1) Closed-chain exercise to promote stability and proprioception (2) Cycling on level surfaces (3) Forward and reverse treadmill walking (4) Resisted open-chain exercise
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Treatment of Patellofemoral Cartilage Lesions in the Young, Active Patient Matthew R. Prince, DO1 Aaron J. Krych, MD1
Alexander H. King, BS1
Michael J. Stuart, MD1
1 Department of Orthopedic Surgery and Sports Medicine Center,
Mayo Clinic, Rochester, Minnesota
Diane L. Dahm, MD1
Address for correspondence Aaron J. Krych, MD, Department of Orthopedic Surgery, Mayo Clinic, 200 First Street SW, Rochester, MN 55905 (e-mail: [email protected]).
Abstract
Keywords
► patellofemoral ► cartilage ► osteochondral
Articular cartilage lesions of the patella and trochlea are commonly encountered in the young and active patient. These defects can be classified as chondral or osteochondral, and then further described according to size, location, and etiology. Early surgical intervention is often indicated for traumatic injuries resulting in osteochondral damage, including acute patellofemoral dislocation. For chronic lesions, initial treatment involves exhaustive nonoperative measures, and surgery is reserved for patients with persistent symptoms. A thorough history, physical examination, and imaging are essential to select the best surgical option. Cartilage restoration procedures are combined with optimization of background factors such as patellofemoral alignment and congruity to achieve success. Cell-based therapies have evolved into a reliable strategy for management of these lesions.
Chondral injuries of the patellofemoral joint are both a common and often challenging problem. Arthroscopic examination of athletes’ knees has shown the overall prevalence of full-thickness cartilage lesions to be 36%. The most prevalent site of these defects is the patellofemoral joint, with the patella more commonly involved than the trochlea (64 vs. 36%).1 Many of these lesions will go undetected because a large percentage of the injuries occur in asymptomatic individuals.
Classification of Articular Cartilage Lesions Classifying articular cartilage lesions is critical for guiding treatment and also for analyzing treatment outcomes. Outerbridge described four different grades of chondromalacia of the patella in 1961.2 Grade I describes softening and swelling of the cartilage. Grade II is defined by fragmentation and fissuring in an area less than half an inch in diameter. Grade III has the same characteristics as grade II but involves an area greater than half an inch in diameter; and lastly Grade IV is erosion of the cartilage down to bone. An additional classifi-
received October 1, 2014 accepted after revision January 6, 2015 published online April 19, 2015
cation system which has been used largely for research is the International Cartilage Repair Society (ICRS) classification, which also takes into account the subchondral bone damage.3 It is helpful to further classify these lesions by etiology into traumatic, atraumatic, or dysplastic.4 The defect should be further subdivided as either purely chondral or osteochondral in nature. Traumatic chondral lesions of the patella are most commonly the result of a lateral patellofemoral dislocation (►Fig. 1). Acute patellar dislocations occur in both contact injuries and a noncontact twisting mechanism. In a review of the literature, Farr et al found the incidence of medial patellar facet and lateral femoral condyle chondral defects following acute patellar dislocation to range from 70 to 93%.5 The most common site of injury is the medial facet of the patella.6 It has also been suggested that the pediatric population is more prone to osteochondral injury with dislocation due to a maturing calcified cartilage layer, which subsequently weakens the boundary between subchondral bone and cartilage.7 Risk factors for patellar dislocation include: patella alta, trochlear dysplasia, lateralized tibial tubercle, excessive femoral anteversion, external tibial
Copyright © 2015 by Thieme Medical Publishers, Inc., 333 Seventh Avenue, New York, NY 10001, USA. Tel: +1(212) 584-4662.
DOI http://dx.doi.org/ 10.1055/s-0035-1549018. ISSN 1538-8506.
Downloaded by: NYU. Copyrighted material.
J Knee Surg 2015;28:285–296.
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Prince et al.
Fig. 1 Traumatic patella cartilage defect on T2 sagittal MRI and at time of arthroscopy ( , loose body; !, donor site). Notice the sharp, vertical borders are well defined in this acute lesion.
torsion, prior dislocation, and iatrogenic instability.8 The location a trochlear lesion is dependent on the direction of the force applied and the degree of knee flexion at the time of collision.9 Traumatic lesions can also occur from repetitive microtrauma, even in a patellofemoral joint with normal alignment and morphology. This occurs during repetitive loading in high-stress activities such as basketball, alpine skiing, weight training, and fencing.4 Chondrosis due to dysplasia is represented by a wide spectrum of malalignment and morphological abnormalities. The significance of these abnormalities is related to the alteration of contact forces about the patellofemoral joint.4 It is hypothesized that there is an individualized threshold for the stress an individual’s cartilage can endure before chondrosis will occur.4 This margin is limited for the patellofemoral joint due to the high forces and small contact area. Recognizing this subset is important, as treatment will need to optimize the contact area and decrease the force transmitted through the joint to maintain unique shear forces. Osteochondral injuries are most commonly from a traumatic dislocation, but osteochondritis dissecans (OCD) can . also occur in this location. Though OCD is rare in this location, it is an important subset of patellofemoral cartilage defects that are essential to recognize. Patellar-based defects are more commonly located over the central ridge, while trochlear lesions typically involve the lateral femoral condyle.10,11 Two of the largest studies involving treatment of these lesions demonstrated high rates of continued anterior knee pain and crepitus.10,11 However, the surgery consisted only of debridement and loose body removal without cartilage regeneration procedures. It is prudent to address any underlying structural predisposing factors, while also realizing that bony management in these defects is as important as addressing the chondral involvement.4
History and Physical Exam The key to accurate diagnosis and management is a detailed history. Patients will typically present with deep anterior knee pain often described as a band of pain located inferior to the patella. Pain stemming from the trochlea may rarely The Journal of Knee Surgery
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present as posterior knee pain.12 Deep squats, prolonged sitting, and stair climbing have been classically noted to aggravate knee pain in patients with chondral damage or patellofemoral arthritis. Clinicians must be inquisitive with patients having a history of patellar instability to determine if pain occurs during subluxation. If pain occurs when the knee is stable, it is possible that a chondral defect may be present. A patellar stabilization brace may help a patient discern if instability is playing a role in their knee pain. Overall, lower extremity alignment and gait analysis are two key components of the physical exam in patients with patellofemoral cartilage lesions. Evaluations of the lumbar spine and neurologic system are important for determining the source of referred pain. Lastly, a knee exam must include an assessment of hip and core function to rule out any hip abnormality or other source of referred pain to the knee.
Standing Exam A general inspection of the lower extremity for bruising, redness, swelling, and surgical scars should begin the standing exam. Following this, an overall assessment of limb alignment with the feet together should be conducted. Any varus or valgus malalignment should be noted. Further static examination in a standing position should include observation of leg-length discrepancies, patella height, and knee extension. Patella alta has been linked to instability, while patella baja can lead to chondral damage to the patella.13 A dynamic evaluation of patients is just as important as a static one. This observation is typically composed of single and double leg squats, as well as gait analysis. During the squat, dynamic malalignment must be noticed, as this has frequently been shown to have negative effects, particularly with patellofemoral pain syndrome.14,15 Additionally, a gait analysis should be performed from both the anterior and posterior views while walking forward and backward.
Supine Exam Again, any signs of swelling or skin abnormalities compared with the contralateral knee should be noted. Patellar position is a key component of this exam. A laterally tilted patella can
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show a high amount of laterally directed forces to the patella. Patella alta and baja are most easily assessed from the side of the knee. During active range of motion, the patella should be observed again for the presence of a J-sign. Patellofemoral crepitus or grinding can be assessed by placing a hand over the patella during active range of motion. Palpation of the knee is the best technique of localizing anterior knee pain. Key points of palpation include the quadriceps tendon, superior pole of the patella, patellar body, inferior pole of the patella, patellar tendon, tibial tubercle, medial and lateral joint lines, and the medial and later retinaculum.13 To test for instability, the patellar glide and apprehension tests are the most reliable method. With the knee flexed to 20 degrees, the patella is translated medially and laterally. Medial glide with less than one quadrant of the patellar width is a positive sign of lateral tightness, while glide of three quadrants in either direction is a sign of hypermobility of the patella.13,16 The patellar tilt test is also used for evaluating patellofemoral tightness. Patellofemoral chondral damage can be evaluated using the compression test.
Imaging Techniques Due to the complexity of the patellofemoral joint, a variety of imaging modalities should be used to confirm the diagnosis and identify background factors. Common techniques include conventional radiographs, magnetic resonance imaging (MRI), and computed tomography (CT). Radiographs are able to evaluate joint space narrowing, check standing hip to ankle coronal alignment, and provide information about dysplasia. MRI is used to assess subchondral edema, articular cartilage loss, and focal defects. CT provides a better evaluation of bone loss and measurement of the tibial tubercle– trochlear groove (TT-TG) distance, but may be undesirable in young patients due to radiation concerns. MRI has been shown to be an acceptable method for measuring TT-TG distance.17–20 Radiographs are the first-line imaging technique used in evaluating knee pain. Standing anteroposterior, 45-degree posteroanterior flexed view, lateral, Merchant, or Laurin views are all utilized. The lateral view should be obtained at 30 degrees of flexion to assess patellar height to determine if patella alta is present. Trochlear dysplasia can also be assessed by a lateral view radiograph. However, there must be perfect superimposition of the posterior aspects of the medial and lateral femoral condyles to confidently evaluate trochlear depth.21 Less than 5 mm between the anterior condylar borders and the intercondylar sulcus suggests a risk of instability.22 The Merchant view allows for assessment of patella size, sulcus angle, and morphology of the patella.21 The Laurin technique is an axial image obtained inferior to superior with the knee in 20 degrees of flexion which can be used to evaluate patella subluxation. This technique is superior to the Merchant view since patella subluxation usually occurs between 20 and 30 degrees of flexion.23 Patellar tilt can also be assessed on axial radiographs. The patellofemoral
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index is the ratio of medial joint space to lateral joint space. Normally, this value measures 1.6 or less, with a ratio greater than 1.6, indicating lateral patellar tilt.24 MRI is very useful in viewing the patellofemoral joint because of its ability to assess soft tissue structures and its multiplanar capability. A dedicated multichannel knee coil should be used with a minimum of 1.5 T field units. A fatsuppressed T2 sequence shows bone marrow edema and fluid collection within the joint. Axial T1 and T2 sequences are useful for evaluating the chondral surfaces of the patellofemoral joint.12 An intermediate echo-time two-dimensional non–fat-suppressed fast/turn spin-echo image shows a strong signal for synovial fluid, intermediate for articular cartilage, and weak for fibrocartilage. Link and colleagues25 showed that high-resolution MR sequences were more effective in detecting cartilage lesions at 3 T, but at lower resolutions no differences were found between 1.5 and 3 T. MRI can be very helpful in determining the size of chondral defect, but is not always accurate in this setting.26 CT imaging is helpful for evaluating bone loss and measuring the TT-TG distance. TT-TG is commonly used as a surgical decision-making tool for patellofemoral malalignment and instability. An increased TT-TG distance is a risk factor for patellar dislocations and subluxations. On CT, a TT-TG distance of 20 mm has been used as a general guideline for performing a tibial tubercle osteotomy (TTO). CT has long been validated as a successful means of measuring TT-TG distance18,20,27–29; however, recent studies used axial MRI as a means for measurement.17,19,28,30–33 Camp et al determined that TT-TG distance can be measured with excellent reliability on both MRI and CT; however, the values obtained from these two modalities may not be interchangeable.18 MRI has the potential to underestimate TT-TG distance compared with CT, though more research is needed to establish validity.
Treatment Options Repair/Debridement Chondral and osteochondral injury has been reported to occur frequently after acute patellar dislocation. When possible, repair of an acute, traumatic osteochondral defect is the preferred treatment. Numerous open and arthroscopic fixation techniques have been described. Metal compression screws and bioabsorbable screws are acceptable treatment options.34–38 If the defect is small, or repair is not possible, then debridement may be preferred. It is important to note that the outcomes of nonoperative treatment of these lesions have been poor.39 If fixation is not possible, then microfracture of intact subchondral bone may be considered along with a cartilage biopsy for future autologous chondrocyte implantation (ACI) if this is chosen over other cell-based options such as juvenile particulated cartilage.
Microfracture Marrow stimulation techniques serve an important role in the treatment of cartilage lesions. The most common technique, microfracture, was originally popularized by Steadman. It has shown to be a cost-effective, minimally invasive The Journal of Knee Surgery
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Fig. 2 Microfracture of a traumatic 2-cm patellar chondral defect in a 15-year-old male skier. He was able to return to skiing at 4 months following surgery and remains symptom free at 2 years from surgery.
technique for the treatment of cartilage lesions.40 In the short term, microfracture has demonstrated excellent results in regard to pain relief and function, especially in younger patients.41–43 Unfortunately, the fibrocartilage produced by microfracture has proven to have unfavorable long-term durability and clinical results.44 A study by Kreuz further emphasized these poor findings when specifically looking at microfracture of the patella and trochlea.41 In addition, there is also evidence to suggest possible detriment to the results of future cartilaginous procedures in the face of a failed microfracture.45 Microfracture has also been proven to have sub-
optimal results with lesions greater than 2 to 4 cm, adding to its limitations as a viable treatment option.46,47 In a systematic analysis of 28 clinical microfracture studies, Mithoefer et al found patients with lesions 2 cm2.48 Although the above-mentioned shortcomings exist, there are several advantages to using microfracture. This singlestage procedure is relatively affordable with overall low morbidity. This may be the best option for a young athlete with a small patellofemoral lesion who wants to return to play
Fig. 3 A 19-year-old female with history of recurrent lateral patella dislocation and symptomatic cartilage lesion. Intraoperative pictures demonstrating patella cartilage lesion, microfracture, and augmentation with micronized cartilage matrix (Biocartilage, Arthrex, Naples, FL). Postoperative radiograph showing that background factors were addressed with TTO for increased TT-TG with distal lateral maltracking and medial patellofemoral ligament reconstruction. The Journal of Knee Surgery
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as quickly as possible (►Fig. 2). It is important to follow the surgical principles as outlined by Mithoefer et al, by obtaining stable vertical borders, removing the calcified cartilage layer, and placing perforations that access marrow elements without compromising subchondral bone integrity.49 Patellofemoral alignment and morphology must be thoroughly defined and addressed as necessary. Currently, there are options to augment microfracture, to encourage more articular-like cartilage formation over fibrocartilage. One option is micronized cartilage matrix, but clearly more research and clinical results are needed in this area (►Fig. 3). We currently consider this method when treating a larger lesion when other options have been denied by insurance for the patient. Other augmentation options include collagen and polymer membranes, chitosan and fibrin gels, hyaluronan injections, as well as numerous growth factors.50
Autologous Chondrocyte Implantation ACI has become a reliable treatment option for patellofemoral cartilage lesions. Short- and long-term follow-up have demonstrated excellent results with modern ACI techniques.51–57 Recently, Gillogly demonstrated good to excellent results in 83% of cases with ACI of the patella after a mean follow-up of 7.6 years.51 Mandelbaum et al showed that ACI of isolated trochlear lesions has both functional and symptomatic benefits.55 The most recent studies involving ACI in the patellofemoral compartment have demonstrated improved success
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with anteromedialization (AMZ) of the tibial tubercle, along with ACI.51,53,54,58 ACI of the patella alone has demonstrated less favorable results.59,60 However, when individualizing treatment based on lesion location and patellar alignment, Gomoll et al did not find a difference in the subgroups of ACI alone and ACI with TTO.52 It is important to note that distal and lateral lesions of the patella are most likely to benefit from AMZ as a result of unloading of these areas. In addition, proximal and medial lesions may experience higher loads if AMZ is performed. Successful outcomes are more typical when all of the above parameters are accounted for when developing an individualized treatment plan. In a prospective randomized trial comparing ACI to mosaicplasty of the knee, Bentley et al published significantly better results with ACI. When specifically looking at patellarbased lesions, there was 85% good or excellent results with ACI compared with 60% following mosaicplasty.61 The authors also reported a poor arthroscopic result in all five patellar mosaicplasties due to differing thicknesses of donor and recipient cartilage. One decisive advantage for ACI in this setting is that the geometry of the patch in unconstrained, compared with cylinders for mosaicplasty. When comparing ACI to microfracture, there are no studies which have evaluated results isolated to the patellofemoral joint. In a randomized trial comparing ACI to microfracture at two- and five-year follow-up, no significant
Fig. 4 Intraoperative photos of large pan-patellar full-thickness cartilage lesion treated with juvenile particulated chondral allograft (DeNovo NT, Zimmer, Warsaw, IN) in fibrin glue matrix. Preoperative sagittal T2 MRI demonstrates cartilage lesion and subchondral bony edema (arrow). Twoyear comparison postoperative MRI demonstrates complete resolution of bony edema (arrow) with good fill and incorporation of the chondral graft, but slight hypertrophy of the neocartilage. The Journal of Knee Surgery
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differences were observed.46,62 Van Assche et al also found no functional difference in ACI versus microfracture of the femoral condyle at two years postprocedure.63 However, significant differences exist between these two methods when taking into account lesion size. Diminishing results are commonly seen with microfracture of lesions greater than 2 cm.2,48 In a meta-analysis looking at the clinical outcomes of ACI versus microfracture, Negrin64 concluded that the results of ACI in lesions greater than 4 cm2 are maintained in contrast to microfracture. The theoretical benefit of ACI over microfracture is the amount and percentage of hyaline cartilage present in lesions treated with ACI. Two years following ACI, Peterson et al found 80% hyaline cartilage after biopsy.65 In contrast, Gudas et al found 57% of the biopsies obtained after microfracture containing solely fibrocartilage.47 In contrast, Knutsen did not find a significant difference in hyaline composition of cartilage biopsies in a randomized controlled study comparing ACI and microfracture.46,62 While the optimal treatment for cartilage lesions of the patellofemoral joint has yet to be clearly defined, it is apparent that the large amount of newly published data show long-term favorable results with ACI, thereby making it a very desirable and promising treatment option.
Particulated Juvenile Articular Cartilage The use of particulated juvenile articular cartilage (PJAC) for articular cartilage defects is an exciting and evolving treatment option. The most commonly used product currently is DeNovo NT Natural Tissue Graft (Zimmer Inc, Warsaw, Indiana, USA) and it consists of allograft articular cartilage from donors less than 13 years old. PJAC implantation for the treatment of cartilage lesions is performed in a manner very similar to ACI. Lesion preparation is completed in an identical fashion to ACI and it is a single-step implantation, typically with fibrin glue used to secure the cartilage cells into the defect (►Fig. 4). A large advantage of this technique is that it is a onestage surgery. One major limitation to the use of PJAC is the lack of high-quality published outcome data. The few
studies that do exist regarding its use have demonstrated promising results. Tompkins et al reviewed 13 patients in which PJAC was used for patellar cartilage defects averaging 2.4 1.2 cm2 . At an average of 33-month follow-up, they found overall promising clinical results with excellent defect filling on repeat MRI.66 In a recent case series published by Farr et al,67 the authors reported similar results in regard to clinical outcomes and defect repair in comparison to analogous MACI studies. While early results are promising, randomized controlled studies are needed to further evaluate the efficacy of PJAC in comparison to other available cartilage restoration procedures. The possibility of a single-stage procedure with results similar to ACI is an attractive treatment option if additional research continues to demonstrate clinical efficacy.
Osteochondral Autograft Transplantation Currently, minimal literature is available on the use of osteochondral autograft transplantation (OATS) for patellofemoral defects. When bone loss is present, making cell-based cartilage implantation unwarranted, OATS may be considered. Early investigations by Bentley et al suggested that differences in cartilage thickness made OATS unreliable for patellar use.61 The authors demonstrated superior results with ACI compared with mosaicplasty. Recent reports have claimed good clinical results and imaging evidence of incorporation with autograft plugs in short-term follow-up.68–70 Osteochondral autograft appears to be a viable option for patellofemoral defects. The physician should be aware of the possible difficulties in cartilage congruence and the reality of donor-site morbidity compounded by the fact that harvest typically occurs at the already diseased patellofemoral compartment.
Osteochondral Allograft Osteochondral allografting procedures have been performed in the knee for several decades.71 The procedure involves transplanting donor cartilage and bone from a size-matched distal femur into an osteochondral defect of the recipient patient. A recently published review of young active patients,
Fig. 5 Intraoperative photo demonstrating lateral trochlea osteochondral lesion from an unstable, unsalvageable OCD progeny fragment in a 39year-old female. This was treated with a stacked fresh-stored osteochondral allograft transplantation to restore both the bone and articular cartilage. An anteromedialization TTO was performed to offload the lateral trochlea and also to treat partial thickness lateral facet patella cartilage lesion. The Journal of Knee Surgery
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Patellofemoral Arthroplasty Patellofemoral arthroplasty (PFA) is a procedure generally considered as a salvage procedure in the young active patient due to higher adverse outcomes in patients under 40.75,76 With the advent of newer implant designs and improved implantation techniques, more acceptable results have been reported.77–79 PFA in the young active patient may be considered as another salvage option for the treatment of patellofemoral cartilage defects. Currently, there is no reliable evidence to determine the natural history of PFA in a patient continuing to be active in sport.80 Catastrophic failure by fracture or dislocation and failure due to polyethylene wear are the two categories comprising the risk associated with PFA in the active patient.80 These risks may be more pronounced in sports where high eccentric extensor loads and direction-change forces are common, such as basketball and
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soccer. The probability of these events is less likely in sports such as golf, running, and cycling.80
Author’s Preferred Surgical Approach Once a treatment plan is established, the goals and expectations are discussed in detail with the patient. The most important part of planning the procedure is in identification and treatment of background factors. Instability is often addressed with medial patellofemoral ligament reconstruction, trochlear dysplasia with trochleoplasty, and distal malalignment with TTO. The patient is placed in the supine position and a tourniquet is applied. A diagnostic arthroscopy with standard inferomedial and inferolateral portals is always performed to assess the lesion and survey the remainder of the knee joint. We prefer to perform our ACI and PJAC cases in an open fashion through an anteromedial incision and a medial patellar arthrotomy. This technique is preferred due to ease of everting the patella. Once the lesion and surrounding unstable cartilage is defined, a number 15 blade and curettes are used to create a vertical cartilage border. Any remaining calcified cartilage in the defect bed is removed carefully to prevent penetration of the subchondral bone and bleeding. It is important to note that ACI is not FDA-approved currently in the United States for treatment of patellar lesions, or for treatment of bipolar patellofemoral lesions, despite its excellent clinical results in a recent multicenter trial.52 ACI requires an index arthroscopy with a cartilage biopsy of 200 to 300 μg or approximately 5 to 10 mm of cartilage, which is
Fig. 6 Intraoperative photo demonstrating full-thickness central cartilage defect of patella in a 25-year-old male basketball player. The type I/III collagen membrane (BioGide, Geistlich Pharma North America, Princeton, NJ) is cut to size and preloaded with autologous chondrocytes on back table, sewn into defect with 6–0 Vicryl absorbable suture, and remaining cells are injected under membrane, and the membrane is sealed with fibrin glue. The Journal of Knee Surgery
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who had received a distal femoral osteochondral allograft a mean of 20 years prior, demonstrated excellent long-term survival.72 Unfortunately, such favorable results have not been reproduced in the patellofemoral joint. Jamali et al73 published a 25% failure rate in the 20 knees they treated with osteochondral allografting, with only 60% good or excellent results in the surviving patients. Spak and Teitge reported a 42% failure rate at an average follow-up of 10 years for their patellofemoral osteochondral allograft series.74 For these reasons, osteochondral allografting of the patellofemoral joint is generally reserved as a salvage procedure in the young active patient or to address a true osteochondral lesion, such as in OCD (►Fig. 5).
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Table 1 Rehabilitation protocol for patellofemoral cartilage procedures Phase
Goals
Restrictions
Range of motion
Exercises
Healing phase (weeks 0–6)
(1) Reduce swelling (2) Reduce muscle atrophy (3) Gradual full ROM (4) Patella mobilization
(1) Knee immobilizer as needed (2) PWB with crutches, TTWB if TTO performed
CPM 8 h/d, 10–60 degrees ROM as tolerated out of CPMa
(1) SLR, quad sets (2) Gluteal and core strengthening
Transitional phase (weeks 7–12)
(1) Reduce swelling (2) FWB by 10 wk (3) Reduce pain (4) Full ROM (5) Minimize hip, core, LE atrophy
Progress to FWB increasing each week
Full ROM
(1) Full ROM (2) Core strengthening (3) Body weight squat, leg press 0–60 degrees, as WB allows (4) Stationary bike (5) Gentle closed-chain terminal knee extension
Remodeling phase (weeks 13 þ )
(1) Full active ROM (2) No effusion (3) Improved quad strength and endurance
Surgeons decision on return to sports
Full ROM, normal walking
(1) Closed-chain exercise to promote stability and proprioception (2) Cycling on level surfaces (3) Forward and reverse treadmill walking (4) Resisted open-chain exercise
