Establishing the Minimal Clinically Important Difference and Patient Acceptable Symptom State After Isolated Arthroscopic Posterior Medial Meniscal Root Repair

Abstract

Background:

Significant clinical improvements have been shown after a posterior medial meniscal root (PMMR) repair; however, there is a lack of understanding of their effect on patients’ perspectives.

Purpose:

To (1) define the minimal clinically important difference (MCID) and the Patient Acceptable Symptom State (PASS) for patient-reported outcome measures (PROMs) after isolated PMMR repair; (2) investigate the role of preoperative, demographic, and intraoperative variables in predicting achievement of these thresholds.

Study Design:

Case series; Level of evidence, 4.

Methods:

Patients who underwent arthroscopic PMMR with a minimum of 2-year postoperative follow-up were included. PROMs, demographic variables, intraoperative details, and postoperative complications were recorded. PROMs analyzed include the International Knee Documentation Committee (IKDC) Score, the Knee injury and Osteoarthritis Outcome Score Jr (KOOS Jr), and the Veterans RAND 12 Physical Function (VR12 PF). MCID and PASS thresholds were calculated. Multivariate logistic regression analyses were conducted to identify factors associated with the attainment of the MCID and the PASS.

Results:

A total of 75 patients were included, and 5 progressed to arthroplasty within 2 years. Of the remaining patients, the MCID thresholds and percentage achievements were as follows: the IKDC, 10.17 and 84.3%; the KOOS Jr, 10.42 and 71.4%; and the VR12 PF, 6.08 and 60%. The PASS thresholds and percentage achievements were as follows: the IKDC, 67.81 and 60%; the KOOS Jr, 71.95 and 55.7%; and the VR12 PF, 47.75 and 52.9%. For the IKDC, a lower body mass index (BMI) and a lower preoperative score were predictive of MCID achievement, whereas a lower BMI and a greater preoperative score were predictive of PASS achievement. For the KOOS Jr, a lower BMI was predictive of PASS achievement. For the VR12 PF, younger age, lower BMI, Kellgren-Lawrence (KL) grade 1, and a lower preoperative score were predictive of MCID achievement, whereas lower BMI, greater preoperative joint space, KL grade 1, and a higher preoperative score were predictive of PASS achievement.

Conclusion:

This study defines the thresholds for MCID and PASS achievement at a minimum 2-year follow-up for the IKDC, KOOS Jr, and VR12 PF scores in a cohort of 70 patients undergoing isolated PMMR repair (72.9% women, mean age, 55.2 years). A larger portion of patients achieved the MCID (84.3%, 71.4%, and 60%) compared with the PASS (60%, 55.7%, and 52.9%). The most common predictors of MCID and PASS achievement included lower BMI and preoperative scores. Furthermore, younger age emerged as an independent predictor of MCID achievement for VR12 PF.

Keywords

medial meniscal posterior root tear minimal clinically important difference Patient Acceptable Symptom State patient-reported outcome measure transtibial pull-out repair

Posterior medial meniscal root (PMMR) tears include avulsion injuries affecting the bony or soft tissue attachments of the meniscus to the tibial plateau, as well as radial tears occurring within 1 cm of these attachment points.^3,27,52,53 Detachment of the meniscus from the tibia leads to a loss of the ability to maintain meniscal hoop tension, ^19,29 and therefore the joint experiences increased pressure loads, which can lead to early and rapid degenerative changes, with similar consequences to a total meniscectomy.^{2,12,17,20,31,33,38} Recent insights from anatomic, biomechanical, and clinical studies have shifted the treatment approach from partial and total meniscectomy toward repair.^15,37 While nonoperative treatment has been considered a viable option for middle-aged patients with early-stage osteoarthritis, it does not consistently meet the clinical needs of patients.^39,41,46 Traditionally, meniscectomy has been the preferred method for treating PMMR tears because of its procedural simplicity and the immediate pain relief offered, although it does not offer a solution to halt the progression of osteoarthritis.^6,21,51 On the other hand, biomechanical studies have demonstrated that PMMR repair can restore joint peak contact pressure to normal levels,^8,36,38,55 which can potentially act as a preventative measure against the onset of osteoarthritis. Consequently, repair procedures are increasingly becoming the preferred treatment for root tears.

Numerous studies have highlighted the role of preoperative factors in determining postoperative clinical outcomes after repairing the PMMR. Moon et al⁴³ assessed 51 patients after PMMR transtibial repair, with a mean follow-up of 33 months. Their analysis of the postoperative visual analog scale, American Knee Society Score, and Lysholm scores revealed that varus alignment of >5° and cartilage lesions of Outerbridge grades 3 or 4 significantly correlated with worse outcomes. Similarly, Chung et al¹¹ identified lesions with Outerbridge grades of ≥3, varus alignment, and older age as independent risk factors for suboptimal results. Brophy et al⁷ found that patients with a body mass index (BMI) of >35 kg/m² had higher failure rates, more frequent subsequent surgeries (25% vs 0%, P = .049), and a higher incidence of clinical osteoarthritis progression (75% vs 29%; P = .035) than patients with a BMI of <35 kg/m², according to the Knee injury and Osteoarthritis Outcome Score (KOOS) scale.

Despite some of these identified risk factors for less clinical success, there remains a lack of literature describing the clinical significance of improvements in patient-reported outcome measures (PROMs) after meniscal root repair. The minimal clinically important difference (MCID) and the Patient Acceptable Symptom State (PASS) have been routinely employed to assess clinical effectiveness after orthopaedic procedures.^9,12,35,42 The MCID represents the smallest change in a patient's outcome measure after treatment that they perceive as beneficial.²² Moreover, the PASS establishes a benchmark for patients, defining a level of symptoms or functional state they find acceptable after treatment.^22,49 These methodologies prioritize and emphasize patient perspectives and contribute to understanding the meaningful effect of orthopaedic interventions, aside from imaging-based assessments that have been commonly evaluated after root repairs.

This study aimed to (1) define the MCID and the PASS for PROMs related to knee function and osteoarthritis after isolated PMMR repair and (2) investigate the role of preoperative, demographic, and intraoperative variables in predicting the achievement of these thresholds. We hypothesized that younger age and lower BMI would be associated with greater odds of achieving the MCID and the PASS after PMMR.

Methods

A retrospective study of prospectively collected data from a single, high-volume institution was performed. Previous institutional review board approval was obtained for database querying and for contacting patients for the follow-up (23083005-IRB01). Patients who had undergone primary arthroscopic PMMR transtibial pullout repair from 2017 to 2021 and had a minimum 2-year postoperative follow-up were included (Figure 1). All surgical procedures were performed by 4 fellowship-trained attending surgeons (B.J.C., A.B.Y., N.N.V., and J.C.). The exclusion criteria consisted of the Kellgren-Lawrence (KL) grades of >3 osteoarthritis and concomitant ligamentous procedures. Also, patients who had ipsilateral knee surgery, excluding root revision surgery (high tibial osteotomy, unicompartmental knee arthroplasty, total knee arthroplasty, etc) within 2 years of undergoing meniscal root repair, and patients with incomplete PROMs at the final follow-up were excluded.

Figure 1.

Arthroscopic images showing a transtibial PMMR repair. (A) PMMR tear. (B) First suture passing through the PMMR. (C) Repaired PMMR. PMMR, posterior medial meniscal root.

Surgical Technique and Rehabilitation

After induction of general anesthesia, diagnostic arthroscopy was performed through standard portals, confirming a PMMR tear with adequate tissue quality for repair. The term “adequate tissue” was defined by the surgical team as any meniscal tissue capable of securely holding sutures in the reduced anatomic site. For the repair, the anatomic medial meniscus posterior root (MMPR) footprint is prepared using a combination of curettes and a shaver, and 1 or 2 transtibial tunnels are created from the anteromedial tibial cortex to the footprint. Subsequently, 2 or 3 nonabsorbable sutures are passed through the posterior medial meniscus and brought through the tunnels. The sutures are then passed through either a suture anchor or cortical button, appropriately tensioned, and fixed on the anterior tibia to complete the repair.

A standardized postoperative rehabilitation protocol was implemented, which included 6 weeks of crutches and nonweightbearing status with a hinged knee brace. During the initial 4 weeks, knee range of motion was limited to 0° to 90°. Compliance with the nonweightbearing protocol was monitored through a structured follow-up process—including a postoperative day 1 telephone call and follow-up visits at 2 and 6 weeks. At the 6-week mark, patients were allowed to progress to weightbearing as tolerated, with discontinuation of the hinged knee brace and restoration of full range of motion. Closed-chain exercises were initiated at 8 weeks after surgery, and jogging activities could commence at the 3-month mark. In addition, patients were advised to utilize a medial unloader brace for the first 6 months to offload the medial compartment during the period of healing and rehabilitation.

Key demographic and clinical variables, as well as PROMs, were collected from January 2017 to September 2023. Electronic medical records were reviewed to gather patient characteristics—including age, sex, side of injury, BMI, diabetes status, workers’ compensation status, history of previous ipsilateral knee surgery, and chronicity of the PMMR tear (>3 months defined as chronic). Preoperative radiographs were evaluated, where KL grades and medial joint space height were calculated on the Rosenberg view, and the mechanical axis was evaluated on bilateral standing long limb radiographs, where angles >180° were defined as varus alignment and <180° as valgus alignment. Preoperative magnetic resonance images were also analyzed, and meniscal extrusion was measured at the midpoint of the medial tibial plateau coronal view. Intraoperative details—such as the number of tunnels, fixation type, and concomitant procedures—were also registered. In addition, postoperative complications were recorded. The preoperative and final follow-up PROMs analyzed in this study included the International Knee Documentation Committee (IKDC) Score, the Knee injury and Osteoarthritis Outcome Score Jr (KOOS Jr), and the Veterans RAND 12 Physical Function (VR12 PF). At the final follow-up, patients were asked if they considered their current state as “satisfactory” based on their daily life, level of pain, and functional impairment.

Statistical Analysis

Data analysis was performed using the R Foundation for Statistical Computing (8238 Big Sur ARM build; R Core Team). For continuous variables, means and standard deviations were reported, while categorical variables were described using frequencies and percentages. The analysis included comparing PROMs before surgery and at a minimum of 2 years after surgery using the paired 2-tailed Student t test. The threshold for statistical significance indicating clinical importance was set at P < .05. The MCID was calculated using a distribution method and was determined to be one-half the standard deviation of the difference from the baseline in PROM scores at a minimum 2-year follow-up. This approach is consistent with previous studies^4,42,56,59 and has been shown to be a reliable method for estimating the MCID. Research by Norman et al⁴⁸ found that the MCID across various studies typically aligns closely with this calculation, reinforcing its validity.⁴⁸ PASS thresholds were calculated using an anchor-based approach. The anchor question was asked at a minimum of 2 years postoperatively and required a binary response. It asked, “Taking into account all the activities you have during your daily life, your level of pain, and also your functional impairment, do you consider that your current state is satisfactory?” Receiver operating characteristic analysis for the calculation of the PASS was conducted and optimal thresholds were calculated using the Youden Index to maximize the sensitivity and specificity of threshold values. Based on previous evidence,⁴ the strength of association was considered acceptable if the area under the curve (AUC) exceeded 0.7 and excellent if >0.8. Moreover, multivariable logistic regression models were fitted to identify patient-related demographic and intraoperative factors associated with the attainment of the MCID and the PASS. Variables included in the multivariable analyses were selected using the forward-stepwise Akaike Information Criterion.⁵⁴ These variables included age, sex, BMI, laterality of injury, chronicity of the tear, preoperative mechanical axis, joint space height, KL grade, meniscal extrusion, as well as diabetes, workers' compensation status, preoperative PROMs values, fixation method, and the number of tunnels used during surgery. Finally, co-achievement rates within different PROMs were evaluated using Pearson correlation coefficients, and values <0.39 were defined as weak, between 0.4 and 0.69 as moderate, and >0.7 as strong.¹

Results

Patient Characteristics

There were 123 MMPR transtibial pullout repairs performed from January 2017 to August 2021. From those cases, 15 were excluded because of incomplete preoperative PROMs, and 3 were excluded because of concomitant anterior cruciate ligament reconstruction. Moreover, 30 cases were then excluded for incomplete minimum 2-year follow-up PROMs (Figure 2). A total of 75 patients were initially included in the study, and 5 of them underwent subsequent ipsilateral knee arthroplasty within 2 years after PMMR repair and were excluded from the PROMs data analysis. Ultimately, 70 patients (56 women, 74.7%) were included in the MCID and PASS analysis, with a mean follow-up time of 34.2 ± 12.1 months. The mean age at the time of surgery was 55.10 ± 10.66 years, and the mean BMI was 32.83 ± 5.95 kg/m². Of the total patients, 72.9% underwent PMMR repair >3 months after injury and were considered to have chronic PMMR.^25,57 From those, 18 cases (35.3%) were late initial consults, and 33 (64.7%) were initially treated nonoperatively at the patient’s request with rest, physical therapy, non-steroidal anti-inflammatory drugs, and steroid injections. One of the included patients had a history of a previous ipsilateral knee surgery consisting of partial meniscectomy of a flap at the medial meniscus posterior horn (Table 1).

Figure 2.

A flowchart depicting the patient selection process. ACLR, anterior cruciate ligament reconstruction; MMPR, medial meniscal posterior root; PROMs, patient-reported outcome measures.

Table 1

Intraoperative and Patient Characteristics^a

Patient Characteristics
Age, y	55.19 ± 10.66
BMI, kg/m²	32.83 ± 5.95
Mechanical axis, deg	183.19 ± 2.80
Preop extrusion, mm	3.11 ± 1.05
Preop joint space, mm	4.31 ± 0.84
KL grade (0/1/2/3/4)	0/27/37/6/0
Sex, male:female, % male	19:51 (27.1)
Laterality, right:left, % right	33:37 (47.1)
Diabetes, yes:no, % yes	5:65 (7.1)
Chronicity, chronic:acute, % chronic	51:19 (72.9)
Workers' compensation status, yes:no, % yes	3:67 (4.3)
Intraop characteristics
Fixation method, anchor:button, % anchor	55:15 (78.6)
No. of tunnels, 1:2, % 1 tunnel	42:28 (60)
Concomitant MCL trephination	27 (38.6)
Concomitant MFC chondroplasty	12 (17.1)

Continuous variables are presented as mean ± SD. Categorical variables are presented as counts (percentages). BMI, body mass index; Intraop, intraoperative; KL, Kellgren-Lawrence; MCL, medical collateral ligament; MFC, medial femoral condyle; postop, postoperative.

A total of 60% of repairs were performed using 1 transtibial tunnel. Most patients (78.6%) reported fixating the repair with an anchor on the anteromedial tibial cortex. A concomitant medical collateral ligament trephination was needed in 38.6% of patients, and concomitant chondroplasty was performed in 17.1% of the patients. A centralization stitch was not used in any of the patients. Moreover, biologic augmentation was not used in this cohort (Table 1).

Patient-Reported Outcome Measures

When compared with baseline measures, the mean postoperative IKDC, KOOS Jr, and VR12 PF scores significantly improved at the final follow-up (P < .01 for each score) (Table 2). MCID thresholds, PASS thresholds, and achievement rates are presented in Table 2. The predictive value for all PASS thresholds was good to excellent, with AUC values of 0.858. 0.864, and 0.755 for the IKDC, the KOOS Jr, and the VR12 PF, respectively (Figure 3). In our cohort, 54 of the 70 included patients gave a “satisfactory” response, with a 77.1% achievement rate of success.

Table 2

MCID and PASS Thresholds and Achievement Rates Among Patients^a

	Baseline	Follow-up	P	MCID Threshold	Number Achieved	PASS Threshold	Number Achieved
IKDC	36 ± 16.06	66.47 ± 21.48	<.01	+ 10.17	59 (84.3)	> 67.81	42 (60)
KOOS Jr	52.17 ± 16.57	74.84 ± 18.98	<.01	+ 10.42	50 (71.4)	> 71.95	39 (55.7)
VR12 PF	36.98 ± 9.52	45.83 ± 11.48	<.01	+ 6.08	42 (60)	> 47.75	37 (52.9)

Data are presented as mean ± SD or n (%). P values reflect the comparison of preoperative scores with mean postoperative scores within a given outcome score. Percentages are reflective of a sample size of 70. IKDC, International Knee Documentation Committee; KOOS, Knee injury and Osteoarthritis Outcome Score; MCID, minimal clinically important difference; PASS, Patient Acceptable Symptom State; VR12 PF, Veterans RAND 12 Physical Function.

Figure 3.

Sensitivity and specificity of PASS thresholds for VR12 PF, IDKC, and KOOS scores. IKDC, International Knee Documentation Committee; KOOS, Knee injury and Osteoarthritis Outcome Score; PASS, Patient Acceptable Symptom State; VR12 PF, Veterans RAND 12 Physical Function.

Pearson correlation coefficients for MCID and PASS co-achievement rates within different PROMs are depicted in Table 3. Both IKDC and KOOS Jr scores had a weak correlation with VR12 PF MCID co-achievement. Notably, KOOS Jr and IKDC scores had a strong correlation in PASS co-achievement. However, the correlation of MCID and PASS co-achievement in all other PROM combinations was moderate. The correlations between MCID and PASS co-achievement within IKDC, KOOS Jr, and VR12 PF scores were +0.449 (moderate), +0.455 (moderate), and +0.456 (moderate), respectively.

Table 3

Pearson Correlation Coefficients for MCID and PASS Co-achievement Rates Between the 2 PROMs^a

		VR12 PF	KOOS Jr
MCID achievement	IKDC	+0.369, weak	+0.422, moderate
	KOOS Jr	+0.258, weak
	VR12 PF
PASS achievement	IKDC	+0.514, moderate	+0.740, strong
	KOOS Jr	+0.541, moderate
	VR12 PF

IKDC, International Knee Documentation Committee; KOOS, Knee injury and Osteoarthritis Outcome Score; MCID, minimal clinically important difference; PASS, Patient Acceptable Symptom State; VR12 PF, Veterans RAND 12 Physical Function.

Factors Predictive of MCID/PASS Achievement

Multivariate logistic regression analyses were performed to identify patient-related factors at baseline and intraoperative variables associated with MCID (Table 4) and PASS (Table 5) achievement.

Table 4

Multivariable Logistic Regression Model for the Predictive Value of Pre and Perioperative Variables on Anchor-Based MCID Achievement^a

Predictive Variables	OR [95% CI]	P
IKDC
Lower BMI	0.73 [0.53-0.95]	.03
Lower preop score	0.94 [0.88-0.98]	.02
VR12 PF
Younger age	0.93 [0.86-0.99]	.04
Lower BMI	0.84 [0.73-0.95]	.01
KL grade 1	28.32 [4.27, 362.86]	<.01
Lower preop score	0.91 [0.84-0.95]	<.01

BMI, body mass index; IKDC, International Knee Documentation Committee; KL, Kellgren-Lawrence; MCID, minimal clinically important difference; OR, odds ratio; preop, preoperative; VR12 PF, Veterans RAND 12 Physical Function.

Table 5

Multivariable Logistic Regression Model for the Predictive Value of Pre- and Perioperative Variables on Anchor-Based PASS Achievement^a

Predictive Variables	OR [95% CI]	P
IKDC
Lower BMI	0.87 [0.78-0.95]	<.01
Higher preop score	1.04 [1.01-1.09]	.04
KOOS Jr
Lower BMI	0.83 [0.73-0.92]	.01
VR12 PF
Lower BMI	0.85 [0.75-0.94]	<.01
Greater preop joint space	2.03 [1.06, 4.31]	.04
KL grade 1	14.91 [2.94, 127.98]	<.01
Higher preop score	1.19 [1.02-1.36]	.02

BMI, body mass index; IKDC, International Knee Documentation Committee; KL, Kellgren-Lawrence; OR, odds ratio; Preop, preoperative; PASS, Patient Acceptable Symptom State; VR12 PF, Veterans RAND 12 Physical Function.

For the IKDC, lower BMI (OR, 0.73 [95% CI, 0.53-0.95]; P = .03) and a lower preoperative score (OR, 0.94 [95% CI, 0.88-0.98]; P = .02) were predictive of MCID achievement, whereas lower BMI (OR, 0.87 [95% CI, 0.78-0.95]; P < .01) and a higher preoperative score (OR, 1.04 [95% CI, 1.01-1.09]; P = .04) were predictive of PASS achievement.

For the KOOS Jr, lower BMI (OR, 0.83 [95% CI, 0.73-0.92]; P < .01) was predictive of PASS achievement.

For the VR12 PF, younger age (OR, 0.93 [95% CI, 0.86-0.99]; P = .04), lower BMI (OR, 0.84 [95% CI, 0.73-0.95]; P = .01), KL grade 1 (OR, 28.32 [95% CI, 4.27, 362.86]; P < .01), and a lower preoperative score (OR, 0.91 [95% CI, 0.84-0.95]; P < .01) were predictive of achieving MCID. In contrast, lower BMI (OR, 0.85 [95% CI, 0.75-0.94]; P < .01), greater preoperative joint space (OR, 2.03 [95% CI, 1.06, 4.31]; P = .04), KL grade 1 (OR, 14.91 [95% CI, 2.94, 127.98]; P < .01), and a higher preoperative score (OR, 1.19 [95% CI, 1.02-1.36]; P = .02) were predictive of PASS achievement.

Complications

One patient developed arthrofibrosis and required a second surgery with arthroscopic lysis of adhesions and mobilization under anesthesia at 5 months after surgery. Moreover, 1 patient underwent subsequent ipsilateral knee surgery 2 years and 7 months after his MMPR repair for recurrent pain and required a partial meniscectomy of a small flap on the midbody and posterior medial meniscus.

Furthermore, 5 patients (6.7%) underwent subsequent ipsilateral knee arthroplasty within 2 years after PMMR repair due to arthritic progression, and their treatment was considered a failure.

Discussion

This study analyzed outcomes in a large cohort of patients who underwent isolated PMMR transtibial pullout repair at a single, high-volume institution and established MCID and PASS thresholds for several PROMs. In addition, this study identified key pre- and intraoperative variables predictive of achieving MCID and PASS. Preoperative scores and lower BMIs remained a consistent predictor of better outcomes, which is in line with the authors’ hypotheses. At a mean follow-up of 34.2 ± 12.1 months, our cohort demonstrated significant improvements in IKDC, KOOS Jr, and VR12 PF scores.

For patients in our study, IKDC scores significantly improved at the 2-year follow-up, from 36 preoperatively to 66.5 postoperatively. Similar results have been reported in previous literature, with IKDC scores showing significant improvements from baseline after PMMR at 1 or 2 years of follow-up.^{5,23,24,30,44} A prospective, multicenter study by Krych et al³⁴ demonstrated that at the 2-year follow-up after transtibial PMMR repair, IKDC scores also significantly improved from 41.1 to 78.4 (P < .001). However, their study did not find any associations between age, BMI, cartilage status, and meniscal extrusion with IKDC outcomes, possibly because of their smaller and more variable samples (45 cases, including 29 PMMR and 16 PLMR).³⁴ In contrast, the present study found that lower BMIs (OR, 0.73; P = .03) and lower preoperative scores (OR, 0.94; P = .02) were predictive of MCID achievement, whereas lower BMIs (OR, 0.87; P < .01) and higher preoperative scores (OR, 1.04; P = .04) were predictive of PASS achievement.³⁴ Furthermore, a meta-analysis conducted by Wang et al,⁵⁸ including 13 studies evaluating IKDC improvements after PMMR repair, found a pooled improvement in IKDC scores of 31.73 (95% CI, 9.79-33.66), demonstrating similar rates of improvement to those shown in the present study (33.47). Additionally, our study demonstrated significant improvements in KOOS Jr scores (52.17 pre- to 74.84 postoperatively) and VR12 PF scores (36.98 pre- to 45.83 postoperatively). While there are fewer studies evaluating KOOS Jr or VR12 PF scores after PMMR repairs relative to those reporting IKDC, the findings of the present study are consistent with previous research.^13,18,24 These previous studies evaluated both scores pre- and postoperatively, showing that repairing the meniscus root is associated with significant improvements in both KOOS Jr and VR12 PF scores at 1 and 2 years postoperatively.^13,18,24 On the other hand, Krych et al³² evaluated patients with MMPR tears treated nonoperatively and reported 87% failure rates at 62 ± 30 months³³ and 95% at 14.1 ± 2 years follow-up,³² defined as conversion to arthroplasty or severely abnormal IKDC at the final follow-up. This aligns with the review performed by Eseonu et al,¹⁴ where MMPR repair also depicted better functional outcomes when compared with partial meniscectomy and nonoperative treatment.

The present study also calculated MCID and PASS thresholds for patients undergoing PMMR repair. The MCID threshold and percentage of patients achieving it were +10.2 and 84.3% for the IKDC, +10.4 and 71.4% for the KOOS Jr, and +6.1 and 60% for the VR12 PF, respectively. PASS threshold scores for the IKDC, the KOOS JR, and the VR12PF were established as >67.81, >71.95, and >47.75, respectively. A previous study by Maheshwer et al⁴² reported the MCID and PASS thresholds for meniscal repair without accounting for differences in repair types. They included 173 patients with various types of meniscal tears and repairs and reported thresholds of +10.9 for the MCID and >69 for the PASS when evaluating IKDC scores, which align with values found in the present study. However, to our knowledge, the present study is the first to report MCID and PASS scores for patients specifically undergoing PMMR transtibial pullout repair. The MCID and PASS thresholds established in the present study could serve as a reference point for clinicians in evaluating the success of PMMR. Of the PROMs evaluated, the lowest MCID and PASS achievement rates were seen for the VR12 PF. The authors believe this may be due to the nature of the questions on that survey, with a greater emphasis on more vigorous activities that may be more challenging for patients to achieve. Moreover, from our cohort’s baseline scores, we noticed that 4.3% started above the PASS for the IKDC, 11.4% for the KOOOS Jr, and 11.4% for the VR12 PF, and of those, none dropped below it at the final follow-up. Importantly, the rates of PASS achievement observed within our cohort were 60%, 55.7%, and 52.9% for the IKDC, the KOOS JR, and the VR12 PF, respectively. The absolute achievement of patients with acceptable symptomatic states of root repair may not be high; nonetheless, patients likely still fare better than with partial meniscectomy or observation in the long term.^5,13-15 This has important implications for patient counseling that root repair may not drastically enhance patients’ current symptoms, although it is better for preservation of the knee in the long term.

Moreover, the Pearson correlation coefficient showed weak to moderate association within different PROMs in MCID achievement. Also, the rates of co-achieving both MCID and PASS for each PROMS showed a moderate correlation. This highlights the importance of evaluating multiple PROMs simultaneously and utilizing independent calculations of MCID and PASS thresholds because the different PROMs are not necessarily related to each other. In addition, a strong association was found between the IKDC and the KOOS Jr in PASS co-achievement rates, which can be expected given that those patients are doing substantially well and are likely to show good results in multiple PROMs.

Just as important as the established MCID and PASS thresholds are factors that predict success. In the present study, we found that lower BMIs and preoperative scores all had frequent correlations with achievement of the clinically significant outcomes, and younger age and lower KL grade were associated with greater MCID achievement for the VR12 PF. These findings align with previous research, which has established a link between increased BMI (>35 kg/m²) to less favorable clinical outcomes, increased osteoarthritis progression, and higher rates of subsequent arthroplasty after PMMR.⁷ Furthermore, Nie et al⁴⁷ reported that younger age and BMI were significant and independent predictors of both proper correction and the maintenance of correction of medial meniscal extrusion (MME). Patients with maintained corrected MME showed significantly higher mean Lysholm and IKDC scores compared with those who exhibited relapsed MME after repair, with a mean follow-up of 27.2 months. The association of younger age with MCID achievement in the VR12 PF might be due to younger patients having higher activity demands and therefore a higher ceiling for improvement. Interestingly, younger patients did not have greater rates of achievement of clinically significant outcomes for the IKDC and the KOOS Jr, which may be related to the questions themselves, with a perhaps greater focus on symptoms than activity relative to the VR12 PF. The number of tunnels and fixation method used for the PMMR repair, sex, chronicity of the tear, diabetes, and workers’ compensation status were not associated with MCID or PASS achievement in this study.

Furthermore, several studies have associated varus alignment with an increased risk of worse clinical outcomes in patients presenting with MMPR tears,^10,28 and some even recommended addressing these cases with a high tibial osteotomy rather than an MMPR repair.^26,40 Nevertheless, in our study, varus alignment did not show a significant association with achievement of MCID or PASS thresholds after repairs, which might be attributed to the fact that our cohort had a mean alignment of 183.19° ± 2.80°, or possibly due to the use of an unloader brace 6 months after surgery. The study by Moon et al⁴⁵ has shown that mild to moderate varus alignment (between 5° and 10° of hip-knee angle [HKA]) presents comparable outcomes to neutral knees (<5° HKA). Moreover, even though we did not directly evaluate the International Cartilage Regeneration & Joint Preservation Society grade or meniscal degeneration status, we included variables such as KL grade, joint space height, and preoperative meniscal extrusion, which can indirectly provide insights into the degenerative status of the knee joint. Our study has shown that KL grade 1 was associated with higher MCID and PASS achievement rates for the VR12 PF, which has also been shown in previous studies.^16,50 Interestingly, our study identified a notably high odds ratio of 28 for achieving the VR12 PF score in patients with KL grade 1 arthritis. This may be due to the nature of the VR12 PF questionnaire, which includes items more attainable for physically active patients. KL grade 1 likely indicates healthier joints, enabling broader activity with fewer limitations. This combination could explain the higher likelihood of achieving MCID in this population and highlights the importance of considering patient activity levels and joint health when evaluating outcomes after MMPR repair.

The influence of preoperative scores on the MCID and PASS achievement is logical. In general, we found that patients with lower preoperative scores were more likely to obtain the MCID. Patients with a lower starting point have more to gain with treatment and, therefore, may have an easier time achieving the MCID, which has also been shown previously.⁴² On the other hand, patients with greater preoperative scores are closer to the absolute PASS cutoff and, therefore, are more likely to achieve it. Overall, more patients achieved the MCID than the PASS, which is also common. Identifying predictors of patients who will achieve both the MCID and the PASS may help optimize patient selection for surgical treatment.

Limitations

This study is not without its limitations. As a retrospective study, it carries inherent selection bias. Also, 30% of our patients presented incomplete postoperative PROMs and had to be excluded from our analysis, potentially compromising our results. Moreover, 5 of the 75 patients with 2-year follow-up data required ipsilateral knee arthroplasty due to osteoarthritic progression and were excluded from the PROMs analysis, which may have biased our results. Furthermore, this study was conducted in a single institution, potentially limiting the generalizability of its findings. There was heterogeneity in the specific surgical technique and implants utilized by the surgeons. Moreover, the study lacks diversity as most patients were middle-aged women, which may limit its generalizability to other populations. The MCID and the PASS were calculated according to the selected methods; however, other methods also exist, which may result in different thresholds. This study did not correlate PROMs with imaging-based findings, which are also important to evaluate in the context of patients undergoing root repair.

Conclusion

This study defines the thresholds for MCID and PASS achievement at a minimum 2-year follow-up for IKDC, KOOS Jr, and VR12 PF scores in a cohort of 70 patients undergoing isolated PMMR repair (72.9% women, mean age, 55.2 years). A larger portion of patients achieved the MCID (84.3%, 71.4%, and 60%) compared with the PASS (60%, 55.7%, and 52.9%). The most common predictors of MCID and PASS achievement included lower BMI and preoperative scores. Furthermore, younger age emerged as an independent predictor of MCID achievement for the VR12 PF.

Footnotes

Final revision submitted October 14, 2024; accepted November 18, 2024.

One or more of the authors has declared the following potential conflict of interest or source of funding: S.A. has received honoraria from Encore Medical; education payments from Smith & Nephew. B.J.C. has received consulting fees from Aesculap Biologics, Arthrex, Bioventus, DJO, Vericel Corporation, Acumed, Anika Therapeutics, OSSIO, and Pacira Pharmaceuticals Incorporated; nonconsulting fees from Terumo BCT; royalties from Arthrex; hospitality payments from GE Healthcare; and honoraria from Vericel Corporation. A.B.Y. has received consulting fees from Stryker, JRF Ortho, and Olympus America; nonconsulting fees from Arthrex; education payments from Medwest Associates; and honoraria from JRF Ortho. N.N.V. has received hospitality payments from Abbott Laboratories, Spinal Simplicity, and Relievant Medsystems; royalties from Arthrex, Smith & Nephew, and Graymont Professional Products IP; and consulting fees from Stryker and Arthrex. J.C. has received consulting fees from Smith & Nephew, RTI Surgical, Vericel, Arthrex, Depuy Synthes Products, and Linvatec; education payments from Medwest Associates, Arthrex, and Smith & Nephew; hospitality payments from Stryker and Medical Device Business Services; grant from Arthrex. AOSSM checks author disclosures against the Open Payments Database (OPD). AOSSM has not conducted an independent investigation on the OPD and disclaims any liability or responsibility relating thereto.

Ethical approval for this study was obtained from Rush University Medical Center (23083005-IRB01).

ORCID IDs

Felicitas Allende

Rodrigo Saad Berreta

Sachin Allahabadi

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