Meniscectomy

Anatomy and Physiology

The meniscus contributes to both load distribution and stability of the knee joint. They are each crescent-shaped, with the medial meniscus being more “C” shaped and the lateral meniscus “U” shaped.[2] Their primary function is load transmission across the tibiofemoral joint by converting compressive forces to horizontal hoop stress.[3] This is achieved due to their wedge shape, their biochemical composition, and their attachments to the tibia.

The meniscus is predominantly comprised of type 1 and type 2 collagen. There are three distinct layers of fibers intertwined within both lateral and medial meniscus. The deepest layer consists of circumferential fibers that aid with resisting hoop stresses during axial loading through the knee. In the middle layer, there are radially oriented fibers that give additional resistance to hoop stresses. They also provide resistance against a longitudinal split. The last, most superficial layer is composed of fibers parallel to the meniscal surface that allow for smoother gliding of the knee during motion.[4]

The blood supply to the meniscus comes from the medial and lateral middle geniculate arteries. Classically the meniscus is divided into three zones in regards to vascular supply. The inner third is dubbed the white-white zone and is avascular. It receives nearly 100% of nutrition from diffusion through the synovial fluid. The middle third is the red-white zone, and the outer third is the red-red zone. This outer red-red zone is the only portion of the meniscus with a direct blood supply, which has implementation when discussing repair versus meniscectomy.[5]

The medial meniscus is more stable, with attachments to the deep medial collateral ligament and knee capsule in addition to the anterior and posterior horn attachments to the tibia. The lateral meniscus lacks the capsular attachment posterolaterally due to the popliteus tendon running intra-articularly between the meniscus and capsule.[6] Additionally, there are two meniscofemoral ligaments that connect the posterior horn of the lateral meniscus to the medial femoral condyle. They are the ligaments of Humphrey and Wrisberg. While only 42% to 46% of the general population has both ligaments, at least one is present in nearly all patients.[3]

Indications

Patients with meniscus tears will frequently complain of mechanical symptoms in the knee. They may describe a clicking, popping, or locking sensation during ambulation. In addition, they commonly have intermittent effusions with or without pain. When examining these patients, the most sensitive physical exam finding is tenderness along the medial and/or lateral joint lines. The range of motion is typically normal or slightly limited.

In the majority of patients with suspected or confirmed meniscus tear, non-operative management is the initial therapy, with goals of symptom relief. These modalities include anti-inflammatory drugs, ice, activity modification, and physical therapy.[7] Intra-articular corticosteroid injections are often used to help manage pain from meniscal tears as well. These non-operative management options do not serve to heal the meniscus; however, they are aimed to limit symptoms from the tear.[8]

Ideally, partial meniscectomy is saved for patients who have persistent pain and/or mechanical symptoms after a trial of non-operative management. In addition, any other pathology that could be causing their knee pain and symptoms should be ruled out through physical exam, clinical history, and imaging. Magnetic resonance imaging (MRI) has become the gold standard for diagnosing meniscus pathology.[7] When patients fail non-operative management (generally at least 6 months) and have a confirmed meniscus tear on MRI with associated physical exam findings, the decision to proceed with arthroscopic partial meniscectomy can be made.[9]

Contraindications

Patients who have a reparable tear pattern in a vascular zone of the meniscus should have repair attempted as opposed to partial meniscectomy. Although there is contradictory evidence, it is generally recommended that older patients with degenerative meniscal tears may not benefit from arthroscopic partial meniscectomy as opposed to those with more acute, traumatic tears.[10] Additionally, patients with significant osteoarthritis on imaging typically do poorly with partial meniscectomy. In these patients, knee arthroplasty is commonly the surgical procedure of choice.[11]

Equipment

Following are the requirements to perform a successful meniscectomy:

• Standard operating room table
• Lateral post for counter-traction (or circumferential leg holder)
• 30-degree arthroscopic camera
• Standard arthroscopic tower equipment, which includes:
  • Arthroscopic camera system
  • Arthroscopic shaver console
  • Arthroscopic light source
  • Fluid pump management
  • Radiofrequency ablation console
  • Photo printer for arthroscopic images
• Basic arthroscopic instruments (including grasper, meniscal biter)

Personnel

For a meniscectomy, regular operating room personnel is required including a surgeon, surgical assistant (additional surgeon, physician assistant, or resident physician), anesthesiologist, scrub technician, and circulating nurse.

Preparation

For meniscectomy, the patient is positioned supine on the operating room table. After general anesthesia induction, the patient’s leg is either positioned in the circumferential leg holder, or the lateral post is attached to the ipsilateral side of the operating table approximately 5 cm proximal to the superior pole of the patella. If using the leg positioner, the contralateral leg is placed in a well-padded leg holder and allowed to hang free over the side of the OR table. The arms are positioned on standard arm holders at 90-degrees of abduction and padded appropriately with foam supports.

Depending on surgeon preference, the administration of lidocaine (or other preferred local anesthetics) can be injected into the projected portal sites to help alleviate post-operative pain. Additionally, a diluted concentration of sterile normal saline with epinephrine can be injected intra-articularly to assist with limiting bleeding during the arthroscopy.

Technique or Treatment

Initial Diagnostic Arthroscopy

Once the patient is positioned, a basic knee exam is performed to evaluate the range of motion and any notable instability. Then palpate the inferior pole of the patella and mark the skin. Mark the medial and lateral borders of the patellar tendon from the inferior patella to the tibial tuberosity. The two most commonly used portals for basic knee arthroscopy with partial meniscectomy will be inferomedial and inferolateral. A spinal needle can be used to assist in localizing the initial portal placement. Using an 11-blade scalpel, a 1-cm vertical (or transverse) skin incision is made with the knee in flexion just lateral to the lateral border of the patellar tendon at the joint line. A blunt obturator is used to gain entry into the knee joint while simultaneously extending the leg. The arthroscopic camera is inserted through the trocar sleeve. Inflow and outflow are connected to the trocar to allow for constant circulation of fluid throughout the knee to increase intra-articular space as well as remove loose fragments of tissue and/or blood.

The supra-patellar pouch is examined first. The camera is taken distally to examine the patellofemoral joint followed by the lateral gutter and popliteal hiatus. Then the medial gutter is examined before passing the camera into the medial tibiofemoral compartment while applying a valgus force to the leg to diastase the joint. Any loose bodies are noted. The medial meniscus can be partially inspected at this point. The camera is then taken to the intercondylar notch to inspect the anterior cruciate and posterior cruciate ligaments. To gain entry to the lateral knee, a varus force is applied to the leg to open the lateral tibiofemoral compartment. If using a leg holder, the leg is positioned into the figure-of-four position. Once the diagnostic arthroscopy is complete, the camera is taken back to the medial compartment. A spinal needle is used to create the inferomedial portal under direct visualization with the arthroscopic camera.

Partial Meniscectomy

A probe is inserted through the inferomedial portal to assess the integrity of the meniscus. The tear pattern is identified. A meniscal biter instrument is then inserted into the inferomedial portal. The rim of the torn meniscus is trimmed to the portion of the healthy meniscus. It is important to create a uniform rim that blends with the remaining healthy meniscus to allow proper transmission of forces through the knee. Once the torn meniscus is resected sufficiently, the meniscal biter is replaced with an arthroscopic shaver. The shaver is used to broadly smooth out the meniscal rim while simultaneously removing pieces of meniscal tissue from the joint. Throughout the procedure, care should be taken to minimize damage to the cartilage of the femur and tibia with the arthroscopic camera and instruments. Proper leg positioning is helpful in creating adequate gapping of the joint to reduce iatrogenic injury. Once the surgeon is satisfied with the meniscal resection, the arthroscopic instruments are removed from the knee. The trocar is left inside, while suction is applied to properly remove any excess saline and loose bodies from the knee. A 3-0 nylon suture is used to close the two portal sites, which are then dressed appropriately.

Complications

Complications from partial meniscectomy can include iatrogenic cartilage damage, inadequate meniscal resection, and infection, among others. The overall complication rate varies from 0.5% to 1.7% with meniscectomy.[12][13] Surgeon-induced chondral damage is a reported complication; however, the true incidence and clinical outcomes are not well documented.[10] A recent study of over 700,000 arthroscopic partial meniscectomy cases had an overall complication rate of 0.61%.[14] The rate of infection was 0.135% within the first 90 days post-operatively, which is similar to previous rates published in prior studies.

Hemarthrosis is another complication seen after meniscectomy.[12] Insufficient suctioning of excess saline and/or blood at the conclusion of the procedure can contribute to this occurrence. In addition, failure to achieve hemostasis intra-operatively can allow a hematoma to develop. Post-operative deep vein thrombosis (DVT) can occur, and rates have been documented as high as 18%.[15] Despite this, pulmonary embolism is seen in less than 0.1% of cases. 

Long-term complications following partial meniscectomy include re-operation due to the development of osteoarthritis. In patients undergoing partial meniscectomy with degenerative meniscal tears, studies have shown the average delay to re-operation for total knee arthroplasty to be roughly 9 months.[16] This highlights the significance of the meniscus in regards to knee biomechanics and protecting the cartilage. Resecting too much meniscus can lead to earlier development of osteoarthritis and, thus, earlier time to re-operation.

Clinical Significance

Meniscectomy is a commonly performed and effective treatment for the symptomatic meniscal tear. It is important for the surgeon to properly identify a meniscus tear pattern that is irreparable before proceeding with a meniscectomy. Herrlin et al. compared outcomes up to 5 years of patients with atraumatic, degenerative meniscal tears between a non-operative group and an arthroscopic partial meniscectomy group. Both groups had improved outcome scores at the 5-year mark. However, one-third of patients initially treated non-operatively failed conservative management and converted to surgery with improved results.[17] For the acute, traumatic meniscal tear, patients also benefit from an arthroscopic partial meniscectomy. A recent study examining 154 patients undergoing partial meniscectomy for acute, traumatic meniscus tears had an improvement in outcome scores at 4 years.[18] Major predictors for poorer outcomes were increased body-mass index (BMI) and grade 3 or 4 Outerbridge chondral lesion pre-operatively. With the right patient selection and tear pattern, arthroscopic partial meniscectomy can provide favorable results.

Enhancing Healthcare Team Outcomes

Achieving satisfactory outcomes following meniscectomy can be accomplished with an interprofessional team approach. It remains one of the most commonly performed orthopedic surgeries. Reaching the correct diagnosis and identifying patients who would benefit from meniscectomy is the first step towards successful outcomes. This includes general practitioners, nurses, radiology technicians, and office staff working in conjunction with the appropriate referrals to orthopedic specialists. Developing a thorough preoperative plan is crucial and requires input from all members of the interprofessional team.

Having an efficient operating room staff working together allows for a safe and effective procedure to be performed. Post-operative rehabilitation is fundamental to the success of meniscectomy. A systematic review with meta-analysis analyzed eighteen randomized control trials evaluating the effectiveness of physical therapy following arthroscopic partial meniscectomy. They concluded that physical therapy with a concomitant home therapy regimen results in superior patient-reported knee function in addition to an increased range of motion.[19] [Level 1]. Patient success following meniscectomy requires an interprofessional team approach from the onset of patient presentation to post-operative rehabilitation.

Nursing, Allied Health, and Interprofessional Team Interventions

The nurse’s role post-operatively includes the transition of post-anesthesia care to discharge from the hospital. The majority of meniscectomy procedures are done in an outpatient setting, so this role includes the management of intravenous fluids, administering pain medication, assisting with ambulation, and instruction on the use of assistive devices (such as crutches). They also address any wound or dressing issues that may arise prior to discharge.

Nursing, Allied Health, and Interprofessional Team Monitoring

Postoperative monitoring of patient recovery is an important aspect of successful outcomes following meniscectomy. This includes monitoring portal site healing and early identification of any potential erythema or drainage from the surgical sites. In addition, recognizing deficits in range of motion or ambulation status is crucial early in the postoperative period to prevent future stiffness.