Knee Arthroscopy and Preservation, Knee Reconstruction

Caitlin C. Chambers, MD

Derek Ward, MD

C. Benjamin Ma, MD

None of the following authors or any immediate family member has received anything of value from or has stock or stock options held in a commercial company or institution related directly or indirectly to the subject of this chapter: Dr. Chambers, Dr. Ward, and Dr. Ma.

ABSTRACT

Articular cartilage injury in the knee can impact a focal area, a single joint compartment, or the entire knee. Surgical options for knee cartilage injury include arthroscopic débridement, cartilage restoration procedures, meniscal preservation procedures, realignment osteotomy, and unicompartmental or total knee arthroplasty. Multiple implant designs and assistive technologies, such as patient-specific instrumentation, computer navigation, and robotic assistance, have been developed with the goal of improving unicompartmental and total knee arthroplasty outcomes. Choosing the correct intervention is dependent upon careful analysis of the patient’s physical examination, activity levels, plain radiographs, and advanced imaging findings.

Keywords: arthritis; cartilage injury; knee arthroplasty; knee arthroscopy; knee cartilage; osteochondral defect

Introduction

Articular cartilage injuries within the knee can be seen as a result of age-related degenerative changes, previous trauma or injury, congenital osteochondral defects, inflammatory conditions, infection, and other causes. The chronicity, severity, and focal versus generalized nature of a patient’s cartilage injury guides treatment, with surgical options including arthroscopic débridement, osteochondral grafting, realignment osteotomy, or knee arthroplasty. Physical examination along with radiographic or advanced imaging findings must be used concomitantly to determine the source of each patient’s symptoms, and to determine appropriate surgical intervention when nonsurgical measures such as activity modification, weight loss, nonsteroidal anti-inflammatory drugs (NSAIDs), corticosteroid injections, and physical therapy have failed.

This chapter summarizes the range of surgical options available to treat articular cartilage injuries in the knee, beginning with a review of indicated radiographic and advanced imaging modalities. The indications, surgical approach, and outcomes of knee arthroscopy for cartilage injury will then be discussed. Knee preservation techniques including cartilage restoration, meniscal preservation or transplantation, and realignment osteotomies are detailed followed by a summary of arthroplasty techniques, including recent advances in the design of unicompartmental and total knee arthroplasty.

Imaging

Weight-bearing flexion posterior-anterior, lateral, and merchant or sunrise view radiographs (Figure 1) allow for multiplanar assessment of joint space narrowing, subchondral bone defect or sclerosis, ossified loose bodies, and osteophyte formation that may guide treatment recommendations in the case of cartilage injury. The weight-bearing flexion posterior-anterior view allows for visualization of the entire tibial articular surface by accounting for the posterior tibial slope. Standard plain radiographs of the knee should be obtained along with long-standing cassette radiographs for evaluation of limb alignment when there is clinical concern for malalignment that may place increased load on the affected joint compartment (Figure 2). Any identified malalignment should be addressed before or concurrent with cartilage procedures to ensure that the region of interest is appropriately off-loaded. Coronal plane malalignment can be identified using the measurements described in Table 1.

MRI without contrast should be obtained in cases where patients report a mechanical block to motion, large effusion, or significant locking or catching in the knee. MRI allows for identification of loose bodies and meniscal, ligamentous, or focal articular cartilage injury that can contribute to such mechanical complaints that may be remedied with surgical intervention (Figure 3).
MRI is 78% to 89% sensitive and 88% to 95% specific for meniscal injury, and 83% sensitive and 94% specific for the detection of chondral injury.¹^,²

Figure 1 Radiographs of the knee: weight-bearing flexion posterior-anterior (A), lateral (B), and merchant view (C).

Although not currently practical for routine clinical use, there are multiple MRI compositional sequences that allow for evaluation of articular cartilage quality. These sequences focus on the collagen network and water content of cartilage (T2 mapping, T2* mapping) or changes in cartilage extracellular matrix and proteoglycan or glycosaminoglycan content (T1ρ, dGEMRIC, gagCEST).³ These specialized sequences have the potential to identify cartilage degeneration at an earlier stage than is possible with current morphologic MRI sequences. Increased T1ρ signal in the area of impaction laterally after anterior cruciate ligament (ACL) injury has been correlated with significantly worse postinjury and postreconstruction pain and functional outcomes, providing a valuable tool for identifying otherwise subtle cartilage injury and allowing for better prediction of patient outcomes⁴ (Figure 4). As feasibility studies are ongoing, these sequences are now most commonly used for research rather than clinical purposes.

Figure 2 Long-standing cassette alignment radiographs demonstrating: solid red line: mechanical axis of the limb; dashed red line: mechanical axes of the femur and tibia; green line: anatomic axes of the femur and tibia; blue arrow: tangent to the most distal part of the femoral condyles; the lateral angle between this line and the femur mechanical axis (dashed red line) is the mechanical lateral distal femoral angle (mLDFA). Purple arrow: tangent to the proximal tibial plateau; the medial angle between this line and the tibia mechanical axis (dashed red line) is the medial proximal tibial angle (MPTA); yellow line (right knee): mechanical axis deviation.

Knee Arthroscopy

Indications

Knee arthroscopy with procedures including débridement, chondroplasty, loose body removal, microfracture, and partial meniscectomy is an acceptable treatment for appropriately indicated patients after
failure of nonsurgical care. In the setting of nonfocal cartilage loss, arthroscopic intervention may be considered for alleviation of mechanical symptoms or significant effusion related to meniscal pathology, articular cartilage flaps, or loose bodies. These patients will typically present with complaints of knee swelling, locking, catching, or sudden giving way. Physical examination often reveals an effusion, joint line tenderness and positive meniscal signs including pain or palpable click with McMurray’s test, pain with Thessaly’s test or Apley’s test, or pain while performing a deep squat. Importantly, patients should be made to understand that while alleviation of mechanical symptoms is relatively consistent, they may continue to have pain related to existing chondral wear.⁵ In all cases, imaging findings should be diligently reviewed to determine the appropriate potential for improvement in each patient.

Table 1 Measurements of Lower Extremity Coronal Alignment

Measurement	How to Measure	Normal	Abnormal
Mechanical axis	Limb: A line drawn from the center of the femoral head to the center of the talar dome Femur: A line drawn from the center of the femoral head to the center of the knee Tibia: A line drawn from the center of the talar dome to the center of the knee	Limb mechanical axis passes immediately medial to the center of the knee, near medial tibial spine	Lateral location = genu valgum Medial location = genu varum
Anatomic axis	Line bisecting the medullary canal of the femur or tibia	Tibia: anatomic axis = mechanical axis Femur: anatomic axis is in 5°-7° valgus relative to mechanical axis
Mechanical lateral distal femoral angle (mLDFA)	Lateral angle between the mechanical axis of the femur and a line tangent to the most distal point on the femoral condyles	85°-90°	Increased mLDFA = genu varum
Medial proximal tibial angle (MPTA)	Medial angle between the tibial mechanical axis and a line tangent to the proximal tibial plateau	85°-90°	Increased MPTA = genu valgum
Tibiofemoral angle	Angle between anatomic axis of tibia and femur	6°-7° valgus
Mechanical axis deviation	Perpendicular distance between the limb’s mechanical axis and center of the intercondylar notch	1-15 mm medial of midline	Medial deviation = genu varum Lateral deviation = genu valgum
Data from Paley D: Principles of Deformity Correction, ed 2. Berlin, Germany, Springer-Verlag, 2002.

Surgical Approach

Palpable surface landmarks including the inferior pole of the patella, patellar tendon, and tibial plateau guide proper placement of arthroscopy portals. The anterolateral portal is established first, located directly adjacent to the lateral patellar tendon edge at the level of the joint line (below the inferior pole of the patella and proximal to the lateral tibial plateau). This primarily serves as a viewing portal. An anteromedial portal is established under direct visualization, first using a spinal needle to determine appropriate portal position and trajectory. Most basic arthroscopic procedures can be completed with these two portals, but occasionally, posteromedial and/or posterolateral portals may be necessary to retrieve loose bodies behind the cruciate ligaments or to treat injuries of the meniscal roots. Posteromedial and posterolateral portals should be placed under direct arthroscopic visualization using a spinal needle for localization, entering
the skin 1 cm proximal to the joint line and just posterior to the medial collateral ligament or lateral collateral ligament, respectively.

Figure 3 Magnetic resonance image of a displaced medial meniscus flap tear (arrows) abutting the medial collateral ligament in the following planes: coronal (A), sagittal (B), and axial(C).

Outcomes

A landmark study by Moseley et al comparing arthroscopic débridement with sham surgery in patients with knee arthritis found no difference in postoperative pain or functional outcomes between groups.⁶ Several subsequent studies specifically assessing outcomes after partial meniscectomy versus physical therapy for patients with knee osteoarthritis (OA) and a meniscal tear similarly have demonstrated no significant difference in outcomes between groups. However, about 30% of patients randomized to the physical therapy group crossed over and choose to undergo surgery because of continued pain, and good outcomes were achieved in patients who crossed over.⁷^,⁸ This suggests that while surgery should not be the initial recommendation for most patients with arthritis, even in the presence of meniscal tear, those who fail to improve with conservative measures can have good outcomes with delayed meniscectomy. Patients with mechanical symptoms in particular may benefit from arthroscopic débridement including partial meniscectomy and chondroplasty after failure of nonsurgical care.⁵

Figure 4 Select sagittal cuts of a T1ρ magnetic resonance image sequence showing focal cartilage breakdown over the posterior medial femoral condyle (red shading).

Knee Preservation

Cartilage Restoration Procedures

Patients with symptoms and physical examination findings localized to the site of focal full-thickness cartilage loss in the knee are candidates for cartilage restoration procedures. These procedures are not appropriate in the setting of multifocal cartilage loss, diffuse arthritis, or inflammatory arthropathy. Additionally, patients with unaddressed ligamentous instability, malalignment, or meniscal deficiency are not candidates for cartilage restoration procedures. Cartilage restoration procedures can be generally classified as bone marrow stimulation techniques, osteochondral autograft or allograft transplantation, and autologous or allogeneic cell-based therapies (Table 2).

Bone marrow stimulation techniques include abrasion chondroplasty and microfracture, which represent the most simple and cost-effective techniques. These are single-stage arthroscopic surgeries that fill the defect with nonhyaline fibrocartilaginous tissue and
present the risk of osseous overgrowth that can result in increased joint contact pressures.⁹ There are also worse outcomes with larger cartilage defects or in patients with high body mass indexes. Additionally, mesenchymal stem cell (MSC) concentration decreases with age, which may render these procedures less efficacious in older patients, and despite promising short-term improvements, clinical deterioration has been shown across patients of all ages with long-term follow-up after knee microfracture.¹⁰^,¹¹

Table 2 Cartilage Restoration Techniques

Category	Examples	Summary	Pros	Cons
Bone marrow stimulation techniques	Abrasion chondroplasty Microfracture	Subchondral bone is perforated to recruit mesenchymal stem cells (MSCs) from bone marrow into the cartilage defect, creating a fibrocartilaginous defect fill	Technically easy Cost-effective	Osseous overgrowth⁹ Low MSC concentration with age¹⁰ Deterioration in clinical benefit over time¹¹
Whole tissue transplantation	Osteochondral autograft transfer Osteochondral allograft transplantation	Osteochondral plugs from either allograft or autograft sources are used to replace areas of articular cartilage ± subchondral bone loss. Autologous grafts are harvested from a non-weight-bearing area of the knee (commonly superomedial/superolateral trochlea or intercondylar notch)	Single-stage surgery Fills subchondral bone defects Hyaline cartilage Good revision and large defects Precise surface contour matching (allograft)	Donor site morbidity (autograft) Risk of immunological rejection or disease transmission (allograft) Expensive Technically demanding
Autologous cell-based therapy	ACI (autologous chondrocyte implantation) MACI (autologous cultured chondrocytes on porcine collagen membrane)	Autologous chondrocytes are harvested and expanded in a laboratory, then reimplanted ± collagen scaffold	Hyaline cartilage Good outcomes in bipolar defects and patellofemoral joint¹² Good outcomes in large lesions¹³	Two-stage procedure Expensive Requires intact subchondral bone
Allograft cell-based therapy	Particulated juvenile cartilage Biocartilage	Fragmented cartilage allograft used to fill defect ± biologic adjuvant (ie, platelet-rich plasma), heals with hyaline-like cartilage^14,15	Single-stage surgery Technically easy	Cost Lacking long-term outcome data
Data from Brown WE, Potter HG, Marx RG, Wickiewicz TL, Warren RF: Magnetic resonance imaging appearance of cartilage repair in the knee. Clin Orthop Relat Res 2004:214-223; Tran-Khanh N, Hoemann CD, McKee MD, Henderson JE, Buschmann MD: Aged bovine chondrocytes display a diminished capacity to produce a collagen-rich, mechanically functional cartilage extracellular matrix. J Orthop Res 2005;23:1354-1362; Kreuz PC, Erggelet C, Steinwachs MR, et al: Is microfracture of chondral defects in the knee associated with different results in patients aged 40 years or younger? Arthroscopy 2006;22:1180-1186; Gomoll AH, Gillogly SD, Cole BJ, et al: Autologous chondrocyte implantation in the patella: A multicenter experience. Am J Sports Med 2014;42:1074-1081; Rosenberger RE, Gomoll AH, Bryant T, Minas T: Repair of large chondral defects of the knee with autologous chondrocyte implantation in patients 45 years or older. Am J Sports Med 2008;36:2336-2344; Hirahara AM, Mueller KW Jr: BioCartilage: A New biomaterial to treat chondral lesions. Sports Med Arthrosc Rev 2015;23:143-148; and Yanke AB, Tilton AK, Wetters NG, Merkow DB, Cole BJ: DeNovo NT particulated juvenile cartilage implant. Sports Med Arthrosc Rev 2015;23:125-129.

Autologous and allogeneic cell-based therapies allow for fill of cartilage-only defects (lesions with intact subchondral bone) with hyaline or hyaline-like cartilage, respectively. Autologous cell-based therapies, such as autologous chondrocyte implantation (ACI) and autologous cultured chondrocytes on porcine collagen membrane otherwise known as matrix-induced ACI (MACI), have demonstrated good clinical outcomes for treatment of large and even bipolar (abutting) lesions in the tibiofemoral and patellofemoral joints, with histology-proven
hyaline cartilage fill.¹²^,¹³ These are both two-stage procedures, as they require initial chondrocyte biopsy with subsequent in vitro cell proliferation before final implantation. Alternatively, allograft-based therapies such as particulated juvenile cartilage (DeNovo, Zimmer-Biomet, Warsaw, IN, USA) or acellular extracellular matrix (Biocartilage, Arthrex, Naples, FL, USA) allow for single-stage treatment of cartilage-only defects using fragmented cartilage allograft with or without a biologic adjuvant such as platelet-rich plasma.¹⁴^,¹⁵ These have been shown to heal with cartilage that is histologically similar to hyaline cartilage, but long-term clinical data are not yet available.¹⁵

Osteochondral autograft transfer and osteochondral allograft transplantation are ideal options for large osteochondral lesions and revision cases. They are also the preferred method to address lesions that include bone loss in addition to cartilage loss. Both are single-stage procedures. Osteochondral autograft transfer utilizes a bone and cartilage plug harvested from the superomedial or superolateral trochlea or the intercondylar notch of the knee. These donor sites provide viable hyaline surfaces, but an imprecise contour match. Use of autograft is generally limited by the size of the defect and availability of good articular cartilage from the donor sites. On the the hand, osteochondral allograft transplantation allows surgeons to address very large defects with precise contour matching, but size-matched donors take a variable time to become available, and the allograft is expensive (Figure 5). Additionally, while donor site morbidity is avoided with use of allograft, the risks of immunological response and disease transmission are introduced.¹⁶

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