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Arthrosc Tech
Arthrosc Tech
Arthroscopy Techniques
2212-6287
Elsevier

S2212-6287(24)00126-9
10.1016/j.eats.2024.103020
103020
Technical Note
Knee
Arthroscopic Excision of a Deep Infrapatellar Cyst
Koh Jun Rui Don Mb.Ch.B, B.A.O. kohjrd92@gmail.com
∗
Thayaparren Rajendram M.B.B.S., M.D.
Moo Ing How M.B.B.S., M.R.C.S., M.Med., F.R.C.S.
Changi General Hospital, Singapore
∗ Address correspondence to Koh Jun Rui Don, Mb.Ch.B, B.A.O., Changi General Hospital, 2 Simei St 3, Singapore 529889. kohjrd92@gmail.com
04 5 2024
8 2024
04 5 2024
13 8 1030209 1 2024
9 3 2024
© 2024 The Authors
2024
https://creativecommons.org/licenses/by-nc-nd/4.0/ This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
The knee joint is surrounded by multiple bursae, which are fluid-filled sacs whose main function is to reduce friction during movement. Extrusion of fluid from the bursa sac due to trauma or overuse can lead to the formation of cysts in the adjacent region. Operative treatment for cysts involves excision, traditionally performed as open surgery, which is associated with complications such as poor wound healing or recurrence. This Technical Note describes the arthroscopic excision of a deep infrapatellar cyst as an alternative to open surgery.

Technique Video

Video 1

1. Title slide

2. Patient positioning for arthroscopic excision of an infrapatellar cyst of the right knee. Patient is positioned supine after administration of general or regional anesthesia. A sandbag is placed under the operated foot to flex the knee at 90°. A side support is also placed laterally to provide stability.

3. Anteromedial (AM) portal placement for arthroscopic excision of an infrapatellar cyst of the right knee. Surface landmarks of the right knee are first identified and marked out. Important landmarks include the border of the patella, the edges of the patella tendon, and the tibial tuberosity. The site for AM portal placement is identified by locating the intersection 1 cm above the joint line and just medial to the patella tendon at a palpable soft spot.

4. Accessory anterolateral (AL) working portal placement for arthroscopic excision of an infrapatellar cyst of the right knee. AM portal is the viewing portal. Accessory AL working portal placement is performed with direct visualization of the cyst. A spinal needle is first inserted to ensure optimal position of the AL portal with adequate working angles to facilitate excision.

5. Clinical photograph showing accessory AL working portal placement for arthroscopic excision of an infrapatellar cyst of the right knee. The spinal needle, which was previously placed under direct visualization, is then withdrawn and replaced with an arthroscopic shaver (DYONICS platinum 3.4 Blade; Smith & Nephew) after a skin incision is made and a tract created with an artery forceps.

6. Arthroscopic excision of an infrapatellar cyst of the right knee. The AM portal is the viewing portal, and the accessory AL portal is the working portal. An arthroscopic grasper is used to remove an intracystic loose body.

7. Arthroscopic excision of an infrapatellar cyst of the right knee. The AM portal is the viewing portal, and the accessory AL portal is the working portal. Debridement of the cyst wall is performed under direct visualization with an arthroscopic shaver (DYONICS platinum 3.4 Blade; Smith & Nephew). Debridement is performed in a medial to lateral manner with the shaver orientated away from the patella tendon to prevent iatrogenic injury.

8. Clinical photograph showing AM and AL portals as working and viewing portals, respectively. The viewing and working portals are interchangeable to provide better working angles to allow complete excision.

9. Arthroscopic excision of an infrapatellar cyst of the right knee. The AM portal is the viewing portal, and the accessory AL portal is the working portal.

10. Arthroscopic excision of an infrapatellar cyst of the right knee. The AM portal is the viewing portal, and the accessory AL portal is the working portal. Debridement of the cyst wall is performed under direct visualization with an arthroscopic shaver (DYONICS platinum 3.4 Blade; Smith & Nephew). A valgus force is also applied to the lateral aspect of the cyst wall to displace the cyst toward the arthroscopic shaver to facilitate excision.
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pmcA bursa is a fluid-filled sac, mostly located around joints, with the primary function of reducing friction during movement.1 The knee is one such joint surrounded by multiple bursae, which are further categorized based on their location in the knee.2 Bursae surrounding the patella are named according to their position with respect to the patella and include the prepatellar, suprapatellar, and infrapatellar bursae. The infrapatellar bursa is further divided into superficial and deep, with the superficial bursa lying between the tibial tubercle and overlying skin and the deep being located between the anterior aspect of the tibia and the patellar tendon.

Inflammation of these bursae can result in the formation of cyst-like lesions, which present as tender lumps,3 many of which have various eponymous names. Herniation of fluid from the bursal sac due to trauma or repetitive knee flexion can also lead to the formation of cysts in the adjacent region.4 Treatment of symptomatic cysts begins with a trial of nonsurgical management that includes the use of analgesia and rest. Surgical treatment, typically via open surgery, is indicated for those whose symptoms still persist despite the above.

In this Technical Note, we describe the use of arthroscopy for surgical excision of a deep infrapatellar cyst. Some of the pearls and pitfalls of this technique are displayed in Table 1.Table 1 Pearls and Pitfalls

Pearls	
 Standard operative setup	
 No contraindications for arthroscopic approach	
 Side support for stability	
 Arthroscopic approach provides direct visualization of cyst	
Pitfalls	
 Piecemeal removal of cyst	
 Incomplete removal of cyst wall	
 Directing the shaver anteromedially may increase risk of iatrogenic injury to the patella tendon	

Preoperative Assessment

Patient Evaluation

Initial assessment of patients presenting with a lump in a knee should include taking a thorough clinical history and performing an adequate physical examination. The patient's medical history must be evaluated for any existing conditions such as malignancy or those that predispose the patient to infections. Further clinical history should also exclude trauma, as well as screen for symptoms of infection or malignancy.

A thorough physical examination should subsequently be performed to characterize the lump as per standard examination practices, likewise paying specific attention to signs of infection or malignancy. The knee should also be ranged to assess any limitation in range of motion, as well as to determine the site of the knee from which the lump is potentially decompressing.

Investigations

Biochemical investigations to rule out infection should be performed. Baseline imaging with plain-film radiographs of the affected knee should be performed to assess for any abnormalities.

Further imaging should include either an ultrasonography scan of the lump or a magnetic resonance imaging (MRI) scan of the knee for characterization and delineation of the lump. An MRI scan of the knee is the preferred imaging modality of choice as it allows adequate anatomic localization of the cyst, identifies structures it decompresses into, and screens for concomitant pathologies in the affected knee.

Indications

Indications for the surgical removal of the cyst include large or persistent cysts, concerns of malignancy, and symptomatic treatment.

Surgical Technique

Patient Preparation and Positioning

The patient is administered general or regional anesthesia and positioned supine.

A sandbag is placed under the foot of the operated limb to provide support and hold the knee in flexion at 90°. Additionally, a side support can be positioned lateral to the proximal third of the thigh to prevent the hip from externally rotating (Fig 1). A triangular cushion can also be positioned beneath the knee as a substitute for the above to flex the knee.Fig 1 Clinical photograph showing patient positioning for arthroscopic excision of an infrapatellar cyst of the right knee. The patient is positioned supine after administration of general or regional anesthesia. A sandbag is placed under the operated foot to flex the knee at 90°. A side support is also placed laterally to provide stability.

A tourniquet is also applied to the limb and inflated after cleaning and draping as per standard procedure.

Portal Placement

For portal placement, anatomic surface landmarks are first identified. The border of the patella, the edges of the patella tendon, and the tibial tuberosity are palpated and marked out with the use of a skin marker. The site of anteromedial (AM) portal placement is identified by palpating the soft spot just medial to the medial edge of the patella tendon at a level of 1 cm above the joint line (Fig 2). The AM portal is created contralateral to the side affected by the cyst in order not to perforate the sac before visual confirmation.Fig 2 Clinical photograph showing anteromedial (AM) portal placement for arthroscopic excision of an infrapatellar cyst of the right knee. Surface landmarks of the right knee are first identified and marked out. Important landmarks include the border of the patella, the edges of the patella tendon, and the tibial tuberosity. The site for AM portal placement is identified by locating the intersection 1 cm above the joint line and just medial to the patella tendon at a palpable soft spot.

A vertical skin incision is made and the skin and joint capsule are stretched with an artery forceps. The blunt trocar is first introduced and then replaced with the arthroscope (30° 4-mm arthroscope LENS Integrated System; Smith & Nephew).

The AM portal is the viewing portal, and a diagnostic scope of the knee is first performed to diagnose any concomitant intra-articular pathologies. The scope is then withdrawn just outside the capsule and redirected inferolaterally toward the anterolateral aspect of the deep infrapatellar region where the cyst is located.

After the cyst is identified, a spinal needle is inserted under direct vision for creation of an accessory anterolateral (AL) working portal to provide access for the arthroscopic instruments for excision of the cyst. The needle serves as a guide to screen if the working angles for the instruments are sufficient to reach the deepest portion of the cyst (Fig 3). After an optimal position is found, a vertical skin incision is again made and the skin tract widened with an artery forceps to allow the introduction of an arthroscopic shaver (DYONICS platinum 3.5 Blade; Smith & Nephew) (Fig 4).Fig 3 Accessory anterolateral (AL) working portal placement for arthroscopic excision of an infrapatellar cyst of the right knee. The anteromedial (AM) portal is the viewing portal. The accessory AL working portal placement is performed with direct visualization of the cyst. A spinal needle is first inserted to ensure optimal position of the AL portal with adequate working angles to facilitate excision.

Fig 4 Clinical photograph showing accessory anterolateral (AL) working portal placement for arthroscopic excision of an infrapatellar cyst of the right knee. The spinal needle, which was previously placed under direct visualization, is then withdrawn and replaced with an arthroscopic shaver (DYONICS platinum 3.4 Blade; Smith & Nephew) after a skin incision is made and a tract created with an artery forceps.

Debridement

Decompression and excision of the cyst are performed under direct vision with the arthroscopic shaver. Debridement is performed in a medial to lateral manner with care made to face the shaver away from the patella tendon to prevent iatrogenic injury (Fig 5).Fig 5 Arthroscopic excision of an infrapatellar cyst of the right knee. The anteromedial portal is the viewing portal, and the accessory anterolateral portal is the working portal. Debridement of the cyst wall is performed under direct visualization with an arthroscopic shaver (DYONICS platinum 3.4 Blade; Smith & Nephew) or a coblation wand (Werewolf Flow 50; Smith & Nephew). Debridement is performed in a medial to lateral manner with the shaver orientated away from the patella tendon to prevent iatrogenic injury. A valgus force is also applied to the lateral aspect of the cyst wall to displace the cyst toward the arthroscopic shaver to facilitate excision.

A valgus force is applied to the lateral aspect of the cyst wall to displace the cyst toward the arthroscopic shaver to facilitate complete excision and reduce the risk of recurrence. A coblation wand (Werewolf Flow 50; Smith & Nephew) can also be used interchangeably to aid with excision.

The working and viewing portals can be exchanged for better working angles (Fig 6). Debridement is performed until the cyst wall can no longer be directly visualized. The knee can also be manually palpated to ensure adequate decompression. The surgical technique described is shown in Video 1.Fig 6 Clinical photograph showing the anteromedial (AM) and accessory anterolateral (AL) portals as working and viewing portals, respectively. The viewing and working portals are interchangeable to provide better working angles to allow complete excision.

Postoperative Protocol

The procedure is routinely less than a 24-hour inpatient stay, and the patient is reviewed by the physiotherapist and surgical team before discharge. The patient is allowed full weightbearing and active range of motion immediately postoperatively.

Discussion

The use of arthroscopy in the extra-articular region of the knee has been previously described for the surgical excision of other cysts in the knee, most notably for popliteal cysts. Open surgery for the removal of such cysts comes with known complications such as abscess formation and injury to neurovascular structures, including the saphenous nerve.5 An arthroscopic approach not only conveys a lower risk of complications but also allows a quicker recovery for patients due to its less invasive nature.6

Arthroscopy also allows direct visualization of the cyst, which facilitates better excision of the cystic wall. Good clinical outcomes have previously been reported, with reduced risk of recurrence compared with open surgery.7,8 Furthermore, a study by Park et al.9 has shown a high incidence of intra-articular pathologies in association with extra-articular cysts. An arthroscopic approach for cyst excision therefore also confers the ability to treat any concomitant pathology affecting the knee in the same surgical setting.

Certain challenges and disadvantages are faced with an arthroscopic approach. First is the need for more operative room equipment in terms of the arthroscopic setup compared with simple open surgery. Second is the potentially longer operative time taken with an arthroscopic approach compared with the more direct open surgery. The above is also surgeon dependent as arthroscopy is performed in a lesser discussed area of the knee and hence has a steeper learning curve. The advantages and disadvantages of an arthroscopic approach for this surgery are displayed in Table 2.Table 2 Advantages and Disadvantages

Advantages	
 Lower risks of complications compared with open surgery	
 Quicker recovery due to less invasive surgery	
 Allows concurrent treatment of concomitant intra-articular conditions	
 Reduced risk of recurrence	
Disadvantages	
 Steeper learning curve for arthroscopy in lesser discussed area of the knee	
 Longer operative time compared with open surgery	
 Increased surgical equipment required	

Our article aims to highlight the potential use of arthroscopy for excision of lesions in this region as an alternative to traditional open surgery. Although there is a steep learning curve, there are many advantages for the surgeon as they increase their familiarity with this arthroscopic approach.

Disclosures

All authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Supplementary Data

Video 1

1. Title slide

2. Patient positioning for arthroscopic excision of an infrapatellar cyst of the right knee. Patient is positioned supine after administration of general or regional anesthesia. A sandbag is placed under the operated foot to flex the knee at 90°. A side support is also placed laterally to provide stability.

3. Anteromedial (AM) portal placement for arthroscopic excision of an infrapatellar cyst of the right knee. Surface landmarks of the right knee are first identified and marked out. Important landmarks include the border of the patella, the edges of the patella tendon, and the tibial tuberosity. The site for AM portal placement is identified by locating the intersection 1 cm above the joint line and just medial to the patella tendon at a palpable soft spot.

4. Accessory anterolateral (AL) working portal placement for arthroscopic excision of an infrapatellar cyst of the right knee. AM portal is the viewing portal. Accessory AL working portal placement is performed with direct visualization of the cyst. A spinal needle is first inserted to ensure optimal position of the AL portal with adequate working angles to facilitate excision.

5. Clinical photograph showing accessory AL working portal placement for arthroscopic excision of an infrapatellar cyst of the right knee. The spinal needle, which was previously placed under direct visualization, is then withdrawn and replaced with an arthroscopic shaver (DYONICS platinum 3.4 Blade; Smith & Nephew) after a skin incision is made and a tract created with an artery forceps.

6. Arthroscopic excision of an infrapatellar cyst of the right knee. The AM portal is the viewing portal, and the accessory AL portal is the working portal. An arthroscopic grasper is used to remove an intracystic loose body.

7. Arthroscopic excision of an infrapatellar cyst of the right knee. The AM portal is the viewing portal, and the accessory AL portal is the working portal. Debridement of the cyst wall is performed under direct visualization with an arthroscopic shaver (DYONICS platinum 3.4 Blade; Smith & Nephew). Debridement is performed in a medial to lateral manner with the shaver orientated away from the patella tendon to prevent iatrogenic injury.

8. Clinical photograph showing AM and AL portals as working and viewing portals, respectively. The viewing and working portals are interchangeable to provide better working angles to allow complete excision.

9. Arthroscopic excision of an infrapatellar cyst of the right knee. The AM portal is the viewing portal, and the accessory AL portal is the working portal.

10. Arthroscopic excision of an infrapatellar cyst of the right knee. The AM portal is the viewing portal, and the accessory AL portal is the working portal. Debridement of the cyst wall is performed under direct visualization with an arthroscopic shaver (DYONICS platinum 3.4 Blade; Smith & Nephew). A valgus force is also applied to the lateral aspect of the cyst wall to displace the cyst toward the arthroscopic shaver to facilitate excision.
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References

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