Evaluation of Outcomes at Mean 4.8 Years After Repair of Types 3 and 4 Lateral Meniscal Oblique Radial Tears during ACL Reconstruction

Abstract

Background:

Lateral meniscal oblique radial tears (LMORTs) of the posterior horn typically occur in the setting of an acute anterior cruciate ligament (ACL) rupture. Despite publications pertaining to the prevalence, biomechanics, and surgical repair techniques of LMORTs, studies reporting mid-term outcomes after LMORT repair are lacking.

Purpose:

To examine both clinical and functional outcomes after the surgical repair of LMORTs.

Study Design:

Case series; Level of evidence, 4.

Methods:

A retrospective chart review was conducted on 845 patients who underwent a meniscal repair at The Ohio State University Sports Medicine Center from 2017 to 2019. Operative reports and images were manually reviewed to identify LMORTs occurring concomitantly with ACL rupture. Subsequent knee surgery, meniscal repair failure, and postoperative complications were identified, with failure defined as retear at the same meniscal site. Patients without at least 2 years of follow-up were excluded. Patients were contacted postoperatively for evaluation of patient-reported outcomes (PROs)—including the Knee injury and Osteoarthritis Outcome Score (KOOS), Marx activity rating scale (Marx), and pain on a visual analog scale (VAS).

Results:

A total of 25 patients were identified who underwent repair of an LMORT at the time of ACL reconstruction during the study period, with 18 patients available for a 2-year follow-up. The mean age was 21.3 ± 5 years, the mean body mass index was 26.7 ± 4.3 kg/m², and 56% of patients were men. The mean follow-up was 4.8 ± 1 years. There were no identified failures of LMORT repair. Postoperative complications were reported in 9 patients (50%), of whom 7 underwent repeat arthroscopy of the index knee for stiffness, pain, and/or repeat injury. The mean follow-up was 4.9 years from the initial date of surgery. The mean KOOS, Marx, and VAS scores were 86.5 ± 8.6, 7.1 ± 4.7, and 2.1 ± 1.4, respectively.

Conclusion:

LMORT repair is associated with a low risk of failure and favorable PRO measures at the mid-term follow-up. However, a complication rate of 50% was found within the cohort because of joint stiffness, postoperative pain, and reinjury of the index knee.

Meniscal tears have been shown to occur frequently in the setting of anterior cruciate ligament (ACL) tears.^2,11,13 In particular, recent studies have demonstrated that lateral meniscal oblique radial tears (LMORTs) occur in 11.8% to 15.3% of acute ACL tears.^10,11 LMORTs have varying morphology and were recently classified to help provide the criteria for reporting and clinical decision-making. ¹¹ The Krych et al ¹¹ classification system established 4 types of LMORTs. These include partial (type 1) and complete (type 2) radial oblique tears <10 mm from the posterior meniscal root attachment and partial (type 3) and complete (type 4) radial tears that extend >10 mm from the posterior root attachment. Furthermore, Jeon et al ¹⁰ described the inclusion of a type 4b tear, which is an LMORT type 4, with a longitudinal tear at the meniscocapsular junction.

Kinematic evaluation of LMORTs and lateral meniscal posterior root tears (LMPRTs) has been conducted, demonstrating that these tear patterns of the posterior lateral meniscus result in an altered tibiofemoral contact profile with increased contact pressure, increased knee laxity in the presence of anterior loading, and decreased joint stability.^9,12,17,19 Repair of LMORT and LMPRT tears has been demonstrated to restore joint stability, indicating the clinical importance of surgical repair for these tear profiles, especially in the setting of concomitant ACL reconstruction (ACLR).^9,12,16,19 Evaluation of LMORT-specific repair postoperatively via second-look arthroscopy is limited, but rates of failure consisted of 0% and 10% in cohorts of 79 and 99 patients, respectively.^7,10

Patients undergoing meniscal repair of these tear patterns with concomitant ACLR have demonstrated improved patient-reported outcome measures (PROMs) with ranges of 2 to 4 years postoperatively.^6,7,10,20 However, data on mid- and long-term outcomes are limited with respect to types 3 and 4 LMORT-specific repair. This study aimed to examine both clinical and functional outcomes after the surgical repair of types 3 and 4 LMORTs.

Methods

A retrospective chart review was conducted on patients who underwent meniscal repair at The Ohio State University Sports Medicine Center from 2017 to 2019 to identify patients who underwent repair of type 3 or 4 LMORTs (Figure 1). Given the retrospective data collection, surgical decision-making regarding the treatment for each meniscal tear was made by the attending surgeon intraoperatively. The overall approach was to leave stable tears in situ, repair any unstable meniscal tears deemed repairable, and perform partial meniscectomy only for unstable, degenerative tears that were not amenable to repair. With approval from the institutional review board of our institution, operative images, procedure notes, and operative reports were manually reviewed and verified to confirm repair of an LMORT. In total, 25 patients were identified who underwent LMORT repair during the review period, all of whom were identified to occur concomitantly with ACLR. Patients were excluded from further review if there was not at least 2 years of reported follow-up.

Figure 1.

Example of a type 3 LMORT tear in the lateral meniscus of a left knee. LMORT, lateral meniscal oblique radial tears.

Surgical Technique

Diagnostic knee arthroscopy was performed using standard anteromedial and anterolateral portals. After visualization of the lateral compartment of the knee, an LMORT tear was identified. Tears were repaired via an all-inside surgical technique in accordance with standard protocol. ⁶ LMORT repair was done using the Novostitch Pro device (Smith & Nephew) in 14 patients (78%), LMORT was done using the FasT-Fix meniscal repair system (Smith & Nephew) in 1 patient (5%), and the operative reports (16%) did not identify the specific device utilized in 3 patients. A rasp was utilized to prepare the tear before repair. Suture configurations varied across patients, but a combination of vertical and horizontal mattress sutures was used to achieve side-to-side repair and compression across the repair site with or without rip-stop sutures, depending on tear obliquity and according to surgeon preference. A minimum of 1 suture and a maximum of 5 sutures were implanted, depending on the tear pattern and extension. For ACLR, independent femoral tunnel drilling techniques were utilized with the goal of anatomic graft placement. ACLR was performed on 15 (83%) patients with hamstring autografts, 2 (11%) patients with patellar tendon autografts, and 1 patient (6%) with a quadriceps tendon autograft.

Postoperative Protocol

The postoperative protocol varied in this series of patients. All patients were kept either nonweightbearing or toe-touch weightbearing for at least 2 weeks postoperatively, and most were limited in weightbearing for at least 4 weeks. Patients were typically placed into a hinged knee brace after surgery, with range of motion generally allowed from full extension to 90° of flexion for 6 weeks. All patients received physical therapy postoperatively, consistent with post-ACLR protocol and early weightbearing and range of motion restrictions. Running was allowed at a minimum of 4 months postoperatively when cleared by their physical therapist (based on achievement of at least 80% quadriceps strength compared with the contralateral side and qualitative gait assessment).

Data Extraction

After identifying patients who underwent LMORT repair, a chart review was performed to identify subsequent knee surgery, meniscal repair failure, and the presence of postoperative complications— including reinjury, pain, stiffness, recurrent swelling, weakness, instability, or wound infections. Meniscal repair failure was defined as retear at the same meniscal site based on the need for meniscectomy or if evaluation occurred during second-look arthroscopy.

Repeat arthroscopy was conducted on patients who had persistent complications postoperatively or experienced reinjury of the index knee at the discretion of the treating surgeon and the patient. Operative images and reports were retrospectively reviewed for each repeat arthroscopy to determine the healing status of the previously repaired LMORT (Figure 2). Patients were contacted via telephone postoperatively to collect PROMs—including the Knee Injury and Osteoarthritis Outcome Score (KOOS) subscales, Marx activity rating scale (Marx), and pain with a visual analog scale (VAS).

Figure 2.

Example of a healed LMORT in a right knee at second-look arthroscopy. LMORT, lateral meniscal oblique radial tears.

Data Analysis

Statistical analysis was conducted using JMP Version 17 (SAS Institute). Tables and figures were generated with the assistance of JMP and Microsoft Word Version 16.89 (Microsoft Corp).

Results

A total of 25 patients were identified who underwent LMORT repair at the time of ACLR during the study period, with 18 patients (72%) reviewed at a minimum 2-year postoperatively. The mean age was 21.3 ± 5 years, the mean body mass index was 26.7 ± 4.3 kg/m², and 56% were men. The mean follow-up was 4.8 ± 1 years. Patient characteristics are reported in Table 1.

Table 1.

Patient Characteristics ^a

Characteristic
Age, years	21.3 ± 5
Sex
Male	10 (56)
Female	8 (44)
BMI, kg/m2	26.7 ± 4.3
Laterality
Left	8 (44)
Right	10 (56)
Meniscus repaired
Lateral only	16 (89)
Medial and lateral	2 (11)

^aData are represented as mean ± SD or n (%). BMI, body mass index.

All patients undergoing LMORT repair had an ACLR performed concomitantly, none of which were revision ACLRs. One patient underwent repair of the medial collateral ligament as well.

Other procedures performed included chondroplasty, loose body removal, microfracture, and bone grafting as part of a staged ACLR. A summary of concomitant procedures performed is presented in Table 2. Two patients also had a medial meniscal repair; 1 was a vertical tear, and 1 was a complex tear.

Table 2.

Concomitant Procedure Performed ^a

Procedure	Incidence (%)
ACLR	18 (100)
Chondroplasty	9 (50)
Medial compartment	5
Lateral compartment	1
Anterior compartment	3
Loose body removal	6 (33)
Microfracture	2 (11)
Medial only	0
Lateral only	1
Bilateral	1
MCL repair	1 (6)
Bone grafting of previous ACL tunnels	1 (6)

^aACL, anterior cruciate ligament; ACLR, anterior cruciate ligament reconstruction; MCL, medial collateral ligament.

There were no identified failures of LMORT repair. Postoperative complications were reported in 9 patients (50%) (Table 3). Four patients had ongoing postoperative pain, 2 had postoperative stiffness, and 3 had repeat injury of the ACL. Two of the 4 patients with pain eventually had repeat surgery performed, 1 due to a new medial meniscal tear and 1 for synovectomy and chondroplasty. Both patients with postoperative stiffness had a repeat arthroscopic procedure for synovectomy and manipulation under anesthesia. Furthermore, each patient who experienced reinjury to the ACL had an arthroscopic procedure performed for evaluation and treatment of new pathology. All but 1 of these patients had the repeat procedure performed at our same institution; thus, available records were reviewed. Each of these 6 patients who underwent repeat arthroscopy of the index knee demonstrated complete healing of the LMORT repair site and appeared stable to probing during arthroscopic evaluation, with none requiring repeat intervention on the meniscus.

Table 3.

Failure and Complication Rates ^a

Postop failure
Yes	0
No	18
Postop complication
Yes	9
Pain	4
Stiffness	2
Reinjury	3
Superficial wound infection	0
Recurrent swelling	0
Weakness	0
Instability	0
No	9
Repeat procedure
Yes	7
Pain	2
Stiffness	2
Reinjury	3
No	11

^aData are represented as frequency. Postop, postoperative.

Of the 18 patients with a minimum 2-year follow-up, 17 completed PROMs. The mean time from surgery of patients with the completion of PROMs was 4.9 years. The mean KOOS, Marx and VAS score were 86.5 ± 8.6, 7.1 ± 4.7, and 2.1 ± 1.4, respectively. KOOS subscales are shown in Figure 3.

Figure 3.

KOOS Subscales. KOOS, Knee injury and Osteoarthritis Outcome Score.

Discussion

The most important finding of this study was the absence of LMORT repair failure at a mean of 4.8 years postoperatively. It has been shown in cadaveric studies that leaving this tear untreated results in increased laxity of the knee even after ACLR. ¹⁶ Furthermore, meniscectomy has been shown to not only negatively affect knee kinematics after ACLR, ¹⁶ but also contribute to the progression of osteoarthritis.^4,5,8 Therefore, given the low failure rate at nearly 5 years postoperative, repairing LMORTs may serve as a reliable way to produce positive clinical outcomes, preserve joint mechanics, and lower the risk of osteoarthritic progression.

The risk of ipsilateral ACL reinjury is present in a younger patient population, with rates of reinjury leading to repeat operation shown ranging from 7% to 18%, and this risk increases in male athletes returning to high levels of activity.^23,25 The recommended postoperative protocol of meniscal repair differs from that of ACLR alone, with the protocol of post-meniscal repair being more restrictive in terms of early weightbearing and range of motion as opposed to ACLR alone.^8,14,26 However, despite the restriction, there is evidence that loss of strength or worse PROMs are not negatively affected by the meniscal repair protocol. ³

The rate of reoperation due to stiffness has also been demonstrated in the literature, with the 6-month postoperative rates of manipulation under anesthesia and lysis of adhesions secondary to arthrofibrosis after ACLR, with concomitant meniscal repair at 0.91% and 0.61%, respectively. ²⁴ However, the rate of joint stiffness as defined by documented ²² stiffness, range of motion deficits, or arthrofibrosis varies considerably, from <1% to as high as 71%. Both patients undergoing repeat arthroscopy for stiffness within our series were women, with 1 patient having tri-compartment scar tissue evident and the other demonstrating primarily anterior arthrofibrosis. While our cohort demonstrated an increased rate of repeat procedure due to stiffness, this may be an effect seen secondary to a smaller sample size or the restricted flexion and prolonged weightbearing of our postoperative protocol. It has been suggested that there is no increased risk of joint stiffness in patients who had ACLR and concomitant meniscal repair, but female sex could be seen as a risk factor. ²² Patients with this injury should be counseled appropriately about this risk.

Second-look arthroscopic evaluation in patients undergoing LMORT repair has been limited in the literature. Seven patients (39%) in our cohort underwent repeat arthroscopy after initial LMORT repair, and all but 1 of these repeat surgeries were available for review. Of these 6 available second-look arthroscopy cases, each repair demonstrated complete healing at the LMORT repair site. Two previous studies have evaluated LMORT-specific repairs via second-look arthroscopy.^7,10 Jeon et al ¹⁰ completed 61 second-look arthroscopies after LMORT repairs, including all types of LMORT, demonstrating a complete healing rate of 80.3% and a partial healing rate of 19.7%, with no failures reported. In an evaluation of 10 second-look arthroscopies by De Leissègues et al, ⁷ including LMORT types 2 to 4, a total of 9 repairs showed complete healing, while only 1 repair was classified as a failure. Moreover, in studies^1,21,27 evaluating posterior lateral meniscal radial and/or root tears, complete healing repair rates ranged from 60% to 88.9%, with partial healing rates ranging from 11.1% to 30%. A failure rate was only seen in 1 study ²¹ at 10%. Although limited in the number of second-look arthroscopies performed in our study, our findings support previous literature that LMORT and LMORT-like repairs demonstrate favorable healing rates.

Studies evaluating PROMs of patients undergoing LMORT repair have increased in recent years but remain limited overall. Several studies with a minimum of 2 years follow-up have evaluated PROs, including subjective International Knee Documentation Committee scores (sIKDC), Tegner Activity Scale scores, and Lysholm scores, specifically for LMORT pathology repair along with ACL repair (Table 4). Jeon et al ¹⁰ reported a mean sIKDC of 82.9 in a cohort of 79 patients, Daniel et al ⁶ reported a mean sIKDC of 87.3 with 15 patients, Therrien et al ²⁰ reported a mean sIKDC of 92.5 with 50 patients, and De Leissègues et al ⁷ reported a mean IKDC of 86.9 with 99 patients. Tegner scores were similarly favorable postoperatively in these studies, with Jeon et al ¹⁰ reporting a mean Tegner score of 6.4, Therrien et al ²⁰ reporting a mean Tegner score of 6.7, and De Leissègues et al ⁷ reporting a mean Tegner score of 6. The mean Lysholm scores obtained by Jeon et al, ¹⁰ Daniel et al, ⁶ and De Leissègues et al, ⁷ were 88.2, 91.3, and 90.7, respectively. Our study reflects the results described in these studies in that a low failure rate is identified along with favorable postoperative PROMs. Furthermore, in previous studies evaluating tear pathology (radial, root, etc) repairs in the setting of ACL repair, similar results have been established.^1,18,27

Table 4.

Outcomes in LMORT-Specific Repair Studies ^a

Study	Tear Type	Mean Follow-up, Mo	Cohort Size	sIKDC b	Tegner Activity Scale	Lysholm Score b	Second-Look Reoperations	Complete Healing Rate	Failure Rate
Jeon et al 10	LMORT1-4	31.8	79	82.9	6.4	88.2	61	80.3	0
Daniel et al 6	LMORT2-4	24	15	87.3	NR	91.3	NR	NR	NR
Therrien et al 20	LMORT3-4	49.2	50	92.5 ± 6.8	6.7 ± 1.8	NR	NR	NR	NR
De Leissègues et al 7	LMORT2-4	42	99	86.9 ± 7.6	6	90.7 ± 6.7	10	90	10

^aNR, not reported; LMORT, lateral meniscal oblique radial tears; sIKDC, International Knee Documentation Committee subjective score.

^bMean or mean ± SD.

Few studies have PROMs—including KOOS, MARX, and/or VAS—as included in the present study. Along with the sIKDC and Lysholm scores, Daniel et al ⁶ reported PROMs—including VAS, single assessment numeric evaluation, and KOOS subscales. Notably, improvement from pre- to postoperative scores was statistically significant across all PROMs, and the Patient Acceptable Symptom State (PASS) was obtained for all PROs in the majority of patients, except the KOOS-Activity of Daily Living subscale, as this PROM carries a PASS ⁶ of 100. The mean KOOS subscales within our cohort closely align with the scores demonstrated by Daniel et al ⁶ across each subscale.

There are several limitations of this study. A significant limitation is the lack of preoperative PROMs. This limitation does limit the assessment of improvement with surgery. In addition, not every patient was able to be reached for follow-up and PRO questionnaire results, limiting the data that could be retrieved. The patients were selected in a retrospective fashion, and therefore, evaluation of the operative reports, notes, and images was limited in fully evaluating the pathology to correctly categorize the different types of LMORTs. Further, standardized postoperative physical examinations were not performed, with results assessments limited to repeat surgery and PROs. Also worth noting is this study's focus exclusively on types 3 and 4 LMORT, as opposed to types 1 and 2. While types 1 and 2 LMORTs are very similar to root tears, types 3 and 4 LMORTs are repaired with a different technique and may yield different outcomes. Importantly, types 3 and 4 LMORTs make up the majority of LMORT tears.^6,10,11 Additional limitations of the study stem from the way in which the study population was identified. The chart review was focused on the identification of patients who underwent LMORT repair during the study period from a meniscal repair database. This methodology precludes an assessment of the incidence of LMORTs within patients undergoing ACLR during the study period. Perhaps more importantly, this methodology also excludes patients with LMORTs that were treated with methods other than repair, including stable tears left in situ and those treated with partial meniscectomy. This study, therefore, is unable to provide insight into these other treatment methods and is unable to compare outcomes of repair with other treatment methods. It is important to consider that previous literature has demonstrated good outcomes for posterior horn lateral meniscal tears that are left in situ at the time of ACLR, while also noting that these previous studies are not specific to LMORT tears, but they include a variety of posterior horn lateral meniscal tear types. ¹⁵ Further studies are required to identify which tears are best treated with repair, those best left in situ, and those best treated with partial meniscectomy.

Conclusion

LMORT repair is associated with a low risk of failure and favorable PRO measures at a mid-term follow-up. However, a complication rate of 50% was found within the cohort due to joint stiffness, postoperative pain, and reinjury of the index knee.