Arthroscopic Saucerization With Inside-Out Repair and Anterocentral Shift of a Discoid Lateral Meniscus With Retention of Adequate Volume of Residual Meniscus.

ABSTRACT: Preservation of the meniscus has been shown to influence the progression of osteoarthritic changes in the knee. Discoid lateral meniscus (DLM) is classified on the basis of the presence and location of instability resulting from deficient capsular attachments. Recently, meniscal stabilization after saucerization was recommended in cases of DLM to preserve the meniscus shape and avoid the progression of osteoarthritis. However, it is difficult to identify the accurate resection volume and residual meniscal width during surgery, especially when there is an anterocentral shift of the DLM. This Technical Note describes an arthroscopic technique for an anterocentral shift of the DLM in which we highlight the resection point and confirm the methods of retaining an adequate volume of residual meniscus to restore and maintain the shape and function of the meniscus. LEVEL OF EVIDENCE: Level 1, Knee; Level 2, Meniscus.

As the importance of preserving the meniscus in cases of discoid lateral meniscus (DLM) has been increasingly recognized, surgeons have frequently attempted to repair the meniscus. Modern techniques allow for the repair and stabilization of the peripheral rim of the meniscus to maintain the peripheral rim. Some satisfactory long-term clinical results following these treatments have been reported in children and adolescents. These techniques result in fewer degenerative changes than total or subtotal meniscectomy; however, they cannot completely prevent knee-joint degeneration. Although a 6-8 mm width of remaining meniscus was recommended in a previous study, the widths of the anterior, middle and posterior segments were reported to be significantly less 2 weeks to 6 months after surgery. In some reports, an anterocentral (AC) shift of the DLM on preoperative magnetic resonance imgaging (MRI) was a risk factor for osteoarthritic changes and residual meniscal width of the midbody less than 5 mm. Therefore, a surgical technique that retains an adequate and reproducible meniscal width during surgery should be developed. This Technical Note describes an arthroscopic technique for an AC shift of the DLM in which we show the resection point and preservation methods of the meniscus so it can be reshaped to the same size as the normal lateral meniscus. We also show how to confirm methods of stabilizing the meniscus.

Surgical Technique

This technique is indicated for an AC shift of the DLM that is peripherally detached from the posterior segment (Fig 1A and 2B). With the patient in the supine position, a nonsterile tourniquet is applied to the upper thigh of the operative leg. Arthroscopic evaluation is performed using anteromedial and anterolateral portals. After the DLM is confirmed by arthroscopic viewing through the anterolateral portal (Fig 2A and 2B) (Video 1) using a probe, the detached DLM is also confirmed by a lateral gutter view through the anterolateral portal (Fig 2C) (Video 1). Saucerization is started from the border between the anterior horn and central area of the DLM with a 45˚ punch parallel to the circumferential fibers of the anterior horn of the DLM from the anteromedial portal (Fig 3A) (Video 1). After measuring 1 cm of resection length (Fig 3B) (Video 1) with a depth gauge (TRUKOR Depth Gauge; Smith & Nephew, Memphis, TN, USA), saucerization of the central portion is performed (Fig 3C) (Video 1). After resecting the posterior portion to 10 mm from the hiatus (Fig 3D) (Video 1), meniscal instability is again confirmed by a probe after saucerization and the McMurray test as viewed through the anteromedial portal. After confirmation, an arthroscopic rasp is used to freshen the sites of tears in the meniscus to promote healing. In cases where a horizontal tear appears after resection of the central portion, the horizontal tear (Fig 3E) (Video 1) is closed with a meniscal repair. The skin incision is parallel to and just posterior to the lateral collateral ligament with the knee in 90˚ of flexion for a standard inside-out meniscal repair. The fascia are exposed and cut just posterior to the lateral collateral ligament. A retractor (Stryker; Kalamazoo, MI, US) is inserted into the interval between the lateral posterior capsule and the gastrocnemius to protect the neurovascular structures behind the knee. Once the retractor is in place, meniscal repair is performed through the anteromedial portal in the figure-of-4 leg-lock position. The dual meniscal repair needles loaded with 2-0 braided polyester sutures (Stryker) are penetrated through the unstable portion of the meniscus, including the horizontal tear (Fig 4A and 4B) (Video 1) and through a cannula (Stryker) positioned in the anteromedial portal. The suture needles are retrieved under direct visualization through the previously prepared lateral incision. The sutures are tied over the capsule after every 4 sutures have been passed. The technique is performed with stitches placed at 3 mm intervals using 2-0 nonabsorbable sutures. After repairing the posterior portion, the width of the repaired meniscus is confirmed through the hiatus (Fig 4C) (Video 1). After stabilization of the meniscus (Fig 4D) (Video 1), the stability of the meniscus is confirmed by the McMurray test through the anteromedial portal.

Fig 1

Sagittal (A) and coronal (B) MRI of the anterocentral (AC) shift of the discoid lateral meniscus (DLM) in right knee. The DLM is displaced anterocentrally on the coronal image, and the anterior horn appeared to be thick on the sagittal images (white arrow).

Fig 2

Arthroscopic findings of the right knee viewed from the anterolateral portal in the supine position. (A) The discoid lateral meniscus (DLM) (black asterisk) is confirmed with arthroscopic viewing from the anterolateral portal in the figure-4 position. (B) Meniscal instability is confirmed by pulling posterolateral corner of the meniscus using a probe. (C) From the lateral gutter view through the anterolateral portal, absence of a posterosuperior fascicle is confirmed (white star) in the extension position of the knee. (D) Schema of anterocentral (AC) type of DLM of right knee. Black asterisk: discoid lateral meniscus; white star, absence of a posterosuperior fascicle. Po, popliteal tendon.

Fig 3

Procedure of saucerization of right knee viewed from the anterolateral portal in the figure-4 position. (A) Saucerization is started from the border between the anterior horn and the central area of the discoid lateral meniscus (DLM) with a 45-degree punch from the anteromedial portal parallel to the circumferential fibers of the anterior horn of the DLM, viewing from anterolateral portal. (B) The measurement of the resection length is performed with a ruler from the anteromedial portal; 1 cm of resection length is confirmed. (C) Saucerization with removal of the central area (black arrow) is performed by a punch from the anteromedial portal. (D) Schema of starting point of meniscectomy of right knee. (E) Schema of saucerization of right knee.

Fig 4

Inside-out suture including horizontal suture of right knee, viewed from the anterolateral portal in the figure-4 position. (A) Resection of discoid lateral meniscus is performed until it is 10 mm from the hiatus. (B) A horizontal tear (black asterisk) sometimes appears after saucerization. (C) The dual meniscal repair needles loaded with 2-0 braided polyester sutures penetrate the unstable portion of the meniscus, including the horizontal tear, through a cannula positioned in the anteromedial portal. (D) Arthroscopic view from anterolateral portal after penetrating the dual meniscal repair needles. (E) After repairing the posterior portion, the width of the repaired meniscus is confirmed to be 10 mm from the hiatus. (F) Arthroscopic view after saucerization with inside-out repair from the anteromedial portal. (G) Schema of saucerization and meniscal repair using the inside-out technique in the right knee.

Patients are immobilized with a brace for 1 week and then limited to a knee-range motion of 0 to 90 degrees for 3 weeks, followed by protected weight bearing for 6 weeks. Finally, these patients are permitted to jog at 3 months after surgery and return to previous sports at 6 months after surgery.

Early postoperative MRI shows the width of the body of the lateral meniscus to be 11 mm, which is similar to the width of the normal lateral meniscus (Fig 5). This suggests that this method may restore normal meniscus morphology after saucerization with repair.

Fig 5

Postoperative coronal MRI after saucerization with inside-out repair for an anterocentral shift of the discoid lateral meniscus in the right knee. It resembled the normal meniscus. The width of the body of the lateral meniscus was 11 mm (white arrow).

Discussion

In children, the DLM is susceptible to tear or subluxation because of its thick and disc-like shape. The occurrence of peripheral rim instability is relatively common in the DLM., Ahn et al. proposed an MRI classification based on the concept of meniscal shift, which is determined by the anatomic location in the joint into which the meniscus is displaced. They considered this classification as being complementary and helpful in treatment algorithms. Some studies have shown that saucerization with repair for peripheral rim instability results in fewer degenerative changes compared with total or subtotal meniscectomy. Although the 6-8 mm widths of the remaining meniscus rims were treated in the previous study,1, 2, 3 the long-term results of saucerization involved progression of lateral-compartment arthritis in 68.5% of patients. Moreover, Matsuo et al. reported that the widths of the anterior, middle and posterior segments were significantly decreased at 2 weeks to 6 months after surgery. Yamasaki et al. reported that an AC shift on preoperative MRI was a risk factor for smaller residual meniscal widths and osteoarthritic changes. The width of the body of the lateral meniscus was reported to be 9.8 ± 1.9 mm. Therefore, more remaining residual meniscus width must be needed, especially for AC shifts of the DLM. The advantages of this technique are as follows: (1) accurate saucerization can be provided by defining the starting point and the length of the cutting width of 1 cm; (2) the risk of excessive resection of the posterior segment is reduced by this technique; (3) this technique requires only standard meniscectomy and repair skills (Table 1). However, this is only a preliminary report, and further follow-up is necessary to investigate the long-term width of the residual meniscus and clinical and radiologic outcomes. Nevertheless, this technique defined the starting point and volume of resection of the AC shift of the DLM that can possibly preserve the meniscal width and prevent the progression of osteoarthritis. The advantages and limitations, as well as the pearls and pitfalls, of our technique are summarized in Tables 1 and 2, respectively.

Table 1

Advantages and Limitations of the Procedure

Advantages	Limitations
• No special instrumentation is required. • Standard meniscectomy and repair skills are needed. • Uniform methods are used to preserve and stabilize the remainder of the DLM. • Direct visualization and confirmation of instability of the DLM are performed by using the McMurray test through the anteromedial portal view.	• The possibility of reinjury after meniscal stabilization is present because of the remaining low-quality tissue, including the horizontal tear. • It does not address a central shift with central displacement, and signal loss of the peripheral side was noticed because of the limited length of the shifted meniscal fragment.

DLM. discoid lateral meniscus.

Table 2

Pearls and Pitfalls of the Procedure

Pearls

Pitfalls

• Careful evaluation of meniscal instability should be performed from the anterolateral and lateral gutter views through the anterolateral portal. • A curved, narrow basket punch rather than a straight punch is recommended to remove the anterior margin of the DLM. • Careful central debridement will preserve tissue to establish normal morphology. • Use a rasp to gently debride the sites of tears in the meniscus, including a horizontal cleft to stimulate healing in the tissue. • The suture should be used to penetrate the unstable portion of the meniscus, including the horizontal tear. • Confirm by the McMurray test from the anteromedial portal after meniscal stabilization.

• Excessive debridement can eliminate the ability to create a normal meniscus shape. • Inadequate chondral clearance for suture passing may result in iatrogenic chondral injury. • After saucerization, checking the stability of the peripheral rim on both the anterior and the posterior sided is necessary. • Careful retraction should be performed to protect the neurovascular structures behind the knee.

DLM, discoid lateral meniscus.