A Modified Arthroscopic All-inside Repair for Lateral Meniscal Tears Anterior to the Popliteal Hiatus: A Retrospective Case Series with Minimum 2-Year Follow-Up

Background popliteal hiatus. Methods Patients who underwent modified arthroscopic all-inside repair for lateral meniscal tears anterior to the popliteal hiatus at our institution were identified. The clinical assessment consisted of the symptoms of meniscal tears, McMurray test, and patient-reported outcomes (Lysholm score, Tegner score, and International Knee Documentation Committee (IKDC) score). The status of meniscal healing was assessed using postoperative MRI scan. Twenty-five patients met the inclusion criteria. The mean age was 27.60 ± 8.37 years (range, 16 to 43 years). The mean follow-up period was 26.04 ± 2.88 months (range, 24 to 36 months). At final follow-up, the symptoms of meniscal tears disappeared in 23 patients with a negative McMurray test. The patient-reported outcomes of Lysholm, Tegner, and IKDC score improved significantly compared to the preoperative values (P = 0.001). No significant differences were observed in postoperative clinical outcomes between patients with or without concomitant ACL tears (P > 0.05). Postoperative MRI scan showed that the repaired lateral meniscus anterior to the popliteal hiatus obtained healing in 23 (92.0%) patients and no healing in 2 patients. tears anterior


Background
To determine the clinical and MRI outcomes after modified arthroscopic all-inside repair for lateral meniscal tears anterior to the popliteal hiatus.

Methods
Patients who underwent modified arthroscopic all-inside repair for lateral meniscal tears anterior to the popliteal hiatus at our institution were identified. The clinical assessment consisted of the symptoms of meniscal tears, McMurray test, and patient-reported outcomes (Lysholm score, Tegner score, and International Knee Documentation Committee (IKDC) score). The status of meniscal healing was assessed using postoperative MRI scan.

Results
Twenty-five patients met the inclusion criteria. The mean age was 27.60 ± 8.37 years (range, 16 to 43 years). The mean follow-up period was 26.04 ± 2.88 months (range, 24 to 36 months). At final follow-up, the symptoms of meniscal tears disappeared in 23 patients with a negative McMurray test.
The patient-reported outcomes of Lysholm, Tegner, and IKDC score improved significantly compared to the preoperative values (P = 0.001). No significant differences were observed in postoperative clinical outcomes between patients with or without concomitant ACL tears (P > 0.05). Postoperative MRI scan showed that the repaired lateral meniscus anterior to the popliteal hiatus obtained healing in 23 (92.0%) patients and no healing in 2 patients.

Conclusion
This modified arthroscopic all-inside repair technique was safe and effective to treat lateral meniscal tears anterior to the popliteal hiatus, resulting in significantly improved clinical outcomes with a high healing rate and low risk of adjacent structures injury.

Background
Over the past decades, the anatomy and function of the lateral meniscus have been well recognized.
The arthroscopic techniques for lateral meniscal repair have also evolved dramatically [1,2].
However, arthroscopic repair for lateral meniscal tears anterior to the popliteal hiatus still presents a clinical challenge for orthopedic surgeons. The reason for this is multifactorial. First, several important structures are immediately behind the lateral meniscus, such as popliteus tendon, inferior lateral genicular artery (ILGA), and common peroneal nerve. There is a consensus regarding the possibility of iatrogenic injury to these adjacent structures during surgical procedure [3][4][5][6][7]. Recently, Uchida et al. reported that the rate of popliteus tendon injury could be as high as 94% during lateral meniscal repair anterior to the popliteal hiatus using FasT-Fix system [7]. Secondly, the joint capsule around the popliteal hiatus is quite thin. Therefore, suture knots or anchors could not be placed securely over the capsule [3]. Thirdly, the connection between the lateral meniscus and the joint capsule in this region is interrupted by popliteal hiatus, resulting in poor vascular supply and low healing rate. In a previous study, Horibe et al. demonstrated that the lateral meniscus anterior to the popliteal hiatus had a significantly lower healing rate compared with lateral meniscal posterior horn (63% vs. 97%, P <0.05) [8]. Therefore, how to safely and effectively repair the lateral meniscal tears anterior to the popliteal hiatus and promote the healing are the main challenges in treating these lesions.
Although lateral meniscal tears anterior to the popliteal hiatus is quite common in clinical practice, to our best knowledge, there is still very limited data in the literature regarding optimal arthroscopic repair technique for these lesions [9][10][11]. Since July 2015, we started to perform a modified arthroscopic all-inside repair using spinal needle and suture hook for lateral meniscal tears anterior to the popliteal hiatus. This study aimed to determine the clinical and MRI outcomes after this procedure. We hypothesized that this procedure would yield satisfactory clinical and MRI outcomes with a high healing rate and low risk of adjacent structures injury.

Study design
From July 2015 to December 2017, the medical records of patients who underwent modified arthroscopic all-inside repair for lateral meniscal tears anterior to the popliteal hiatus at our institution were identified. The indication of this procedure was a lateral meniscal tear anterior to the popliteal hiatus which was full-thickness or nearly full-thickness, longitudinal, with a length of tear > 1cm, and located in red-red zone or red-white zone. The inclusion criteria were (1) patients who were diagnosed with lateral meniscal tears anterior to the popliteal hiatus and underwent modified arthroscopic allinside repair, and (2) patients with a minimum 2-year follow-up. The exclusion criteria were (1) age older than 45 years, (2) patients with concomitant medial meniscal tears, (3) significant osteoarthritis of the joint (Kellgren-Lawrence grade III or IV), or (4) previous surgery of the same knee.
A total of 39 patients (39 knees) were identified (Fig. 1). As 12 patients had concomitant medial meniscal tears, 1 patient had previous surgery and another patient was lost to follow-up, we studied This study received approval from our institutional review board. Informed consent was obtained from all individual participants included in the study.

Surgical technique
All surgeries were performed under general anesthesia. The patients were placed in a supine position.
A routine arthroscopic evaluation was conducted using two standard anterior knee arthroscopy portals. If the ACL was torn, the lateral meniscus was addressed before ACL reconstruction.
Once a lateral meniscal tear anterior to the popliteal hiatus was confirmed (Fig. 2a), the torn edge was refreshed using a meniscal rasp. An 18-gauge spinal needle could also be utilized to pierce the torn edge to encourage bleeding.
Then the arthroscopy was placed in anterolateral portal, and the anteromedial portal was used as working portal. Passed an 18-gauge spinal needle preloaded with a No. 2 polydioxanone suture (PDS; Ethicon, Somerville, NJ) through the skin approximately 1.5~2 cm anterosuperior to the tip of the fibular head, subcutaneous tissue, and capsule. The needle emerged from the inferior surface of the lateral meniscus. Advanced the PDS suture through the spinal needle and the end of PDS suture was pulled out via the anteromedial portal using a suture retriever (Fig. 2b). Pulled back the needle out of the skin and the other end of PDS suture was pulled out over the superior surface of the lateral meniscus.
A 45° suture hook preloaded with a suture loop was introduced via the anteromedial portal and pierced through the inner part of the meniscus approximately 5 mm away from the torn edge. The suture loop was used as a shuttle relay to transport the end of PDS suture (on the inferior surface of the lateral meniscus) to the superior surface of the lateral meniscus. Now both the ends of PDS suture were on the superior surface of the lateral meniscus and became a vertical mattress stitch ready to be tied (Fig. 2c). Tied the sutures with a knot-pusher and adjusted the knot into the popliteal hiatus to avoid knot impingement with articular cartilage (Fig. 2d). The same maneuver was repeated as necessary to provide a stable meniscal repair. According to our experience, two stitches were usually needed for lateral meniscal tears anterior to the popliteal hiatus. If the meniscal tears extended anteriorly to the meniscal body or posteriorly to the posterior horn, the extension part was repaired using FasT-Fix system (Smith & Nephew, USA). After completion of lateral meniscal repair, the suture tension was checked with a probe.

Postoperative rehabilitation
Postoperatively, a hinged brace was applied for 12 weeks. Quadricep-strengthening exercises were started on the second day. Flexion was limited to 90 degrees during the first 4 weeks and gradually increased to normal at 12 weeks. Toe-touch weight-bearing was permitted at 4 weeks and full weightbearing with the brace was permitted at 6 weeks. Squatting and swimming were started at 3 months.
Running and bicycling were started at 6 months. Full return to competitive sports was allowed at 12 months.

Assessment
Demographic data were collected from the database, including age, sex, side of injury, time from injury to surgery, and concomitant surgical procedures. Clinical outcomes were assessed preoperatively and at final follow-up. Lim's criteria, if there was no high-signal-intensity linear area extending to an articular surface of the meniscus, it was regarded as meniscal healing. Otherwise, it was regarded as no healing [12].

Statistical analysis
All statistical analyses were performed using SPSS software (IBM-SPSS statistics 22.0; New York, USA).
Continuous variables were presented as the mean ± standard deviation. A paired-samples t test was used to determine the differences between preoperative and postoperative quantitative variables. In order to assess the influence of concomitant ACL tears on postoperative patient-reported outcomes, an independent-samples t test was used to determine the differences in postoperative clinical outcomes between patients with or without concomitant ACL tears. The significance level was set at 0.05.

Demographic data
In the end, 25 patients met the inclusion criteria and were enrolled in this study. There were 16 males and 9 females with a mean age of 27.60 ± 8.37 years (range, 16 to 43 years). Among this group, 16 patients underwent concomitant ACL reconstruction for ACL tear. The demographic data of the patients are summarized in Table 1. The data are shown as mean ± standard deviation or n. ACL, anterior cruciate ligament.

Clinical outcomes
The   The data are shown as mean ± standard deviation. IKDC score, International Knee Documentation Committee score.

MRI outcomes
At final follow-up, postoperative MRI scan showed that the repaired lateral meniscus anterior to the popliteal hiatus obtained healing in 23 (92.0%) patients and no healing in 2 patients (Fig. 3).

Complications
No infection, arthrofibrosis, or injury of adjacent structures (including popliteus tendon, ILGA, and common peroneal nerve) occurred among this group. Although two patients occasionally felt slight activity-related pain, no reoperation was required.

Discussion
The main finding of this study was that this modified arthroscopic all-inside repair for patients with lateral meniscal tears anterior to the popliteal hiatus yielded favorable clinical and MRI outcomes at a mean follow-up of 26.04 months. A high rate of meniscal healing (92.0%) and low risk of adjacent structures injury were observed. In addition, patients with concomitant ACL tears had similar postoperative patient-reported outcomes compared to patients without concomitant ACL tears.
In 1979, Cohn was the first to report that the popliteal hiatus was a constant feature of normal knee anatomy, with an average length of 1.3 cm [13]. Similarly, Aman et al. described that the mean length of superior popliteal hiatus exceeded 12.1 mm and the mean length of inferior popliteal hiatus was up to 36.9 mm [3]. It is generally considered that a meniscal tear requires surgery for better stability if the length of tear exceeds 1cm [1]. Therefore, when a lateral meniscal tear anterior to the popliteal hiatus occurs and exceeds 1 cm, surgery should be considered. Currently, the surgical methods for meniscal tears mainly include meniscectomy and meniscal repair. As multiple studies have shown that meniscectomy would lead to decreased tibiofemoral joint contact area, increased cartilage stress load, and accelerate degenerative joint changes [14][15][16]. Therefore, meniscal repair should be considered a priority in managing meniscal tears, especially for young patients.
For lateral meniscal repair anterior to the popliteal hiatus, some authors suggested using the popliteus tendon for meniscal repair device placement, and preliminary data have been reported [10,11]. Nevertheless, this technique has several disadvantages. First, it provides a non-anatomical repair, which would close down the popliteal hiatus, reduce the normal mobility of lateral meniscus, and even cause iatrogenic lateral meniscus extrusion [17][18][19]. Second, it has a high risk of adjacent structures injury, including popliteus tendon, ILGA, and common peroneal nerve [4][5][6][7]. The ILGA has been reported to be the main source of blood supply for lateral meniscus anterior to the popliteal hiatus, so its injury would significantly influence the meniscal healing [20]. Third, the suture anchors placed within or outside the popliteus tendon was a risk factor for local irritation, as well as suture loosening because of the anterior movement of the anchors in popliteus tendon during knee motion [21,22].

Limitations
There are some limitations in this study. First, this study was a retrospective study with all the inherent limitations of a retrospective study. Second, this study did not involve any control group.
Future blinded comparative study is required to determine whether our technique is superior to other repair techniques. Third, successful healing of the repaired lateral meniscus was not confirmed by second-look arthroscopy. Second-look arthroscopy allows for direct inspection of the repair site.
However, since it is invasive and expensive, it is rarely performed at our institution.

Conclusions
Overall, this modified arthroscopic all-inside repair technique was safe and effective to treat lateral meniscal tears anterior to the popliteal hiatus, resulting in significantly improved clinical outcomes with a high healing rate and low risk of adjacent structures injury.  Flow chart of this study.

Figure 2
Modified arthroscopic all-inside repair for lateral meniscal tears anterior to the popliteal hiatus (right knee). a A lateral meniscal tear anterior to the popliteal hiatus was confirmed by a probe. b One end of PDS suture was pulled out from the inferior surface of the lateral meniscus. c Both the ends of PDS suture were on the superior surface of the lateral meniscus and became a vertical mattress stitch ready to be tied. d Adjusted the knot into the popliteal hiatus. Figure 3 a Prepostoperative MRI showed a lateral meniscal tear anterior to the popliteal hiatus (white arrow). b Postoperative MRI showed that the repaired lateral meniscus obtained healing.

Supplementary Files
This is a list of supplementary files associated with this preprint. Click to download. data.xlsx