Ultrasound guided arthroscopic meniscus surgery

Abstract

Ultrasound is a useful adjunctive intra-operative imaging modality for soft tissue pathologies. It is readily available in the operating theater and has the distinct advantage of being more portable than an MRI, with no harmful radiation. It is especially useful for determining if any extra articular cysts have been decompressed through arthroscopic surgery, if a parameniscal cyst has been removed completely or if extrusion has been reduced adequately in a meniscus root repair. In our series, intra-operative ultrasound was used for two cases of medial meniscus horizontal tear with meniscus cyst excision, one case of lateral parameniscal cyst without a communicating tear, and five cases of meniscus root repairs. Ultrasound has the potential to be an important intra-operative diagnostic modality not only in diagnosing pathologies but also accurately localizing the soft tissue pathology, which is critical in arthroscopic surgery where the incisions are small. It also has the added advantage of guiding portal placements, especially in areas where there are neurovascular structures, to avoid injuring them. However, training in its effective use by the surgeon is important.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40477-022-00680-5.

Introduction

Ultrasound is an excellent diagnostic modality for soft tissue lesions in the knee, especially meniscal pathologies like tears and cysts [1]. Intra-operative use of MRI is not possible as the machine is too large to be in an operating room (OR). Ultrasound is more easily accessible in the OR, occupies less space and is portable [2]. Its intra-operative use gives information about the pathology at the time of surgery. However, pre-operative imaging has a time lag between the imaging and the procedure. It also has the advantage of being able to assess if the soft tissue lesion has been adequately removed, decompressed or addressed at the end of the procedure and before the patient is out of anesthesia so that if there is any leftover pathology it can be addressed. This also helps in making lesion-specific portals, especially when neurovascular structures are in the vicinity, to make sure they are not disrupted. MRI is a static imaging modality and it is often very hard determine the exact location or confirm complete removal of a lesion/cyst. The C arm is a very useful modality in fractures to confirm if a fracture is adequately reduced even if done open. It also confirms proper placement of an implant on the bone. There is no equivalent for soft tissue lesions, especially in minimally invasive arthroscopic surgery. However, there are challenges in making it universally applicable. Orthopedic surgeons are not routinely trained to use ultrasound and they depend on radiologists to use it in diagnosing various lesions. With the advent of MRI and its easy availability, the use of ultrasound in orthopedics has declined. Ultrasound has distinct advantages: it is less expensive, it uses no harmful radiations, and it is a dynamic modality that can picture structures while moving them [3]. The other challenge is to make sure the probe and wiring are adequately protected with sterilized covers. Another challenge is to make sure the visualization is not hampered in any way by the jelly used as an interface. We have tried to provide solutions to these important issues in this paper. There is a gap in the literature on the use of intra-operative ultrasound in arthroscopic knee surgery. However, ultrasound has been used in pre-operative preparation and post-operative evaluation of ACL reconstructions [4].

In this paper we intend to present ultrasound use in (1) meniscus root repairs to check intra-operatively if the extrusion has been reduced, (2) meniscus tears with cysts wherein cyst decompression is required apart from the meniscus surgery, and (3) lateral meniscus parameniscal cysts not communicating with the joint.

Technique

Positioning in the OR: The patient is positioned supine on an operating table with the knee at 70° flexion and a side support. The arthroscope trolley is positioned opposite the affected limb. The ultrasound machine is placed on the same side as the affected limb. The Mayo stand with the arthroscope, shaver, radiofrequency device and trocar with cannula and tubing is kept in front of the arthroscope tower (Fig. 1a). A sterile arthroscope cover (sheath), the same as used over the arthroscope, camera and wiring, is used to cover the probe of the ultrasound and wiring (Fig. 1b). A pre-operative ultrasound of the knee is done to localize the lesion after the patient is anesthetized. This helps in localizing it easily and planning where to efficiently place the probe intra-operatively.

Fig. 1.

a Illustration of the positions of the ultrasound machine, arthroscopy tower, surgeon, mayo stand, screen, anesthesia machine and monitor in relation to the patient. b Ultrasound probe covered with a sterile sheath and secured with a tape with ultrasound monitor on the same side of the patients operted limb and arthroscopy. c Applying the sterile ultrasound probe dipped in Povidone Iodine 5% solution to the affected limb and image seen on the ultrasound screen

A solution of 5% povidone-iodine is used as the interface in place of the usual jelly (Fig. 1c). The probe covered with the plastic sleeve is dipped in the povidone-iodine solution and applied to the area of interest.

Medial meniscus horizontal tear with cyst

The arthroscope was introduced into the knee through a standard anterolateral portal and the medial meniscus tear was visualized. The tear was trimmed and the ultrasound probe was applied vertically against the medial aspect of the knee to visualize the cyst (Fig. 2a). The arthroscope was held with the left hand and the ultrasound probe with the right (Fig. 2b). The probe was placed perpendicular to the joint line and moved from the center in a more medial direction (Fig. 2c). Once the exact location was identified, the cyst that is communicated with the joint using an arthroscopic shaver (Fig. 2d). When the cyst was decompressed, one could see it disappear on the ultrasound image (Fig. 2e).

Fig. 2.

a Ultrasound image of medial meniscus cyst intra op before excision arthroscopically. b Applying the sterile ultrasound probe on the skin adjoining the cyst and arthroscope in the joint to localize the cyst accurately. c Arthroscopy rasp introduced into the horizontal tear in the meniscus and further into the cyst to decompress it. d Ultrasound image showing no cyst after arthroscopic decompression

Lateral meniscus cyst

The ultrasound probe was placed vertically, perpendicular to the lateral joint line such that the middle of the probe was at the joint line and moved laterally until the cyst was visualized (Fig. 3a). The arthroscope was introduced into the knee and no meniscus tear was found on the lateral side that could be communicating with the cyst. At the cyst location identified through the ultrasound, a mini incision of 4 cm was made and the cyst was excised completely (Fig. 3b). The wound was closed in layers. The ultrasound probe was applied over the lateral aspect of the knee to confirm that no cyst remained (Fig. 3c).

Fig. 3.

a Ultrasound image of lateral parameniscal meniscus cyst intra op before excision. b Mini open surgical image of the cyst seen. c Ultrasound image of decompressed cyst after open excision

Meniscus root tear

An ultrasound was done intra-operatively to quantify the meniscal extrusion by placing the probe perpendicular to the joint line just posterior to the MCL such that the center of the probe corresponded to the joint line and the extrusion of the meniscus was visualized (Fig. 4a). The root tear was repaired with a standard single-tunnel pullout sutures technique using suture tapes [5]. While tying the tapes over a suture disc, the root of the meniscus was visualized using the arthroscope (Fig. 4b). Once traction was applied and three knots were tied, the ultrasound probe was applied as described to the region of the medial meniscus just posterior to the medial collateral ligament to see if the extrusion had been reduced (Fig. 4c). If it had not been reduced, the knots could be loosened and tightened again to restore the normal extrusion.

Fig. 4.

a Ultrasound image of extruded medial meniscus Intra Op before repair. b Left shows open image of tightening the suture tapes over a suture disc and right shows concurrent visualization of the meniscus root sitting over its anatomic. c Intra Op ultrasound image of reduction in extrusion after tightening the sutures and tying them over a suture disc

Results

Two medial meniscus cysts were operated upon. They both had intra-articular tears that were communicating with the cyst. In the two cysts with complex tears in the meniscus, the cyst was approached from inside out and decompressed and the meniscus was debrided. The ultrasound was used to identify the location of the cyst and to check if it had been completely decompressed before ending the procedure. The cyst was not present at ultrasounds done at 2 weeks and 6 months with no recurrence of symptoms. The mean pre-op Knee Society Score (KSS) [6] was 44 and it improved to 85 at 6 months post-op. None of them had external tenderness on the skin over the cyst location at the 6-month follow-up.

For the lateral meniscus cyst where there was no communicating intra-articular meniscus tear, the cyst was approached by ultrasound-guided open surgery and decompressed. The mean pre-op KSS was 50 and it improved to 80 at 6 months post-op. There were no cysts in the immediate post-op and 6-month ultrasounds.

Five medial meniscus root tears were repaired with ultrasound guided surgery. The ultrasound revealed a reduction in extrusion from a mean 4 mm pre-op to 1.4 mm post-repair. On repeated ultrasound at 6 weeks, in one meniscus the extrusion had increased to 2.5 mm from 1 mm post-op, and the other four remained the same as they were after surgery. The KSS improved from a mean 54 pre-op to 74 post-surgery.

Discussion

Ultrasound, being dynamic, has the added advantage of visualizing structures in movement, which is relevant for structures in and around the knee whose positions may change as the knee moves. Ultrasound is used routinely and successfully for cyst aspirations and giving intra-articular injections in the knee.

Meniscus cysts occur more often than not as a consequence of a meniscus tear. They can cause mechanical symptoms and pain. Decompressing the cysts along with addressing the meniscus pathology is the key to success. Only aspirating the cyst may be just a short-term benefit as it may reform if the meniscus tear is not addressed [7].

The use of ultrasound can be extended to mini open excision of parameniscal cysts that do not communicate with the joint as the exact location can be marked exactly using ultrasound, thereby reducing the size of the incision used to excise it.

When soft tissue lesions in the knee are operated upon arthroscopically, especially when communicating outside the joint, it is difficult to know if the lesion has been removed/decompressed adequately. The C arm is useful if the lesions are bony. Also, in certain surgeries like meniscus root repairs, where the intention is to reduce the extrusion of the meniscus after repairing the root, it is impossible to quantify the reduction in extrusion to intra-operatively arthroscopically quantify the reduction in extrusion [8]. This is important as there is a possibility of slack in the sutures that prevents them from being tightened sufficiently over a button or an anchor. Using ultrasound during and after tightening the sutures, the surgeon can adjust the tightening in such a way that the extrusion is minimized. Current approaches to tackling meniscus cysts, popliteal cysts or meniscus root repairs do not use any intra-operative diagnostic modalities other than relying on cystic fluid extravasation into the joint. MRI is used as a pre-operative diagnostic test to identify the anatomic location and to guide the surgery. However, there is usually no intra-operative way of checking whether the cyst has been adequately depressed or excised. Ultrasound fills this void and is a useful intra-operative technique. Ultrasound has the added advantage of being safe without any radiation risks as compared to X rays. It is usually readily available in the operating room as anesthetists use it regularly to give nerve blocks. The challenges it poses are:

(A) Having a proper sterile interface, like a jelly normally used to visualize structures. This was circumvented in our technique by using a betadine solution, which forms a useful interface that is effective even with the probe covered by a plastic sheath. (B) The space constraint due to additional equipment in the OR. This is avoided by keeping the ultrasound machine next to the arthroscopic tower. The ultrasound machine is much smaller than the tower and can be moved around it for direct visualization of the screen. (C) Sterility of the wiring and probe. This is ensured by covering the probe and wiring with a sterile plastic sheath, the same as used for the arthroscope and light cable. (D) The technical expertise of the surgeon using the ultrasound and making sense of the imaging. These skills can be acquired with available musculoskeletal ultrasound workshops. We conclude that ultrasound is a useful intra-operative adjunct to arthroscopic soft tissue surgeries of the knee, such as meniscus surgeries. Two studies focused on its role in robotic assisted knee arthroscopy, where 4D ultrasound was used to map the knee to avoid inadvertent injury to cartilage and surrounding structures of the knee during instrument introduction [9, 10].

Supplementary Information

Below is the link to the electronic supplementary material.

Funding

The authors have not disclosed any funding.

Declarations

Conflict of Interest

No conflict of interest.

Ethical approval

All the research was conducted according to the Helsinki protocol.

Consent to participate

Written informed consent was taken from all the participants for usage of ultrasound intra operatively wherever required.