The most important finding of the study was that patients who underwent repair for acute BHMTs achieved good to excellent clinical outcomes along with postoperative healing at a minimum follow-up of two years postoperatively. More specifically, the clinical healing rate according to Barrett’s criteria was 83.3% at final follow-up, while the postoperative MR examination demonstrated 69.4% completely and 25.0% partially healed menisci following BHMT repair, respectively. Of all patients, 87.5% reached or exceeded the PASS criteria for the IKDC score at final follow-up. Further, no correlations were revealed between meniscal healing and demographic characteristics as well as injury patterns. These findings are consistent with previous studies reporting satisfying functional outcomes along with a failure rate ranging between 10.4 and 34.2% of cases [1, 7, 8, 11, 15,16,17,18,19, 21, 27].
BHMTs have been found to account for 10–26% of all meniscal lesions, thus presenting a challenging subgroup of these injuries [3,4,5,6]. As preservation of meniscal tissue is of great clinical importance for maintaining sufficient function as well as preventing cartilage degeneration and the premature development of osteoarthritis, BHMTs should undergo surgical repair whenever possible [7,8,9,10,11,12,13,14]. When evaluating clinical outcomes of 38 patients who underwent BMHT repair, Hupperich et al. reported a mean Lysholm score of 86.6 ± 13.5, IKDC of 86.5 ± 10.2, and Tegner activity scale of 6.2 ± 2.2 after an average of 44.4 months postoperatively . However, the authors also found a relatively high clinical failure rate, defined as meniscus re-tear, of 34.2% of patients, subsequently undergoing revision surgery . In contrast, the present study demonstrated a revision rate of 10% of patients who consequently underwent arthroscopic partial meniscectomy, while similar postoperative values in terms of patient-reported outcome scores were achieved. Further, a satisfactory clinical healing rate of 83.3% according to Barrett’s criteria was observed after a mean follow-up of 51.8 months, which is consistent with previous work by Feng et al. and Espejo-Reina et al., reporting clinical healing in 86.6% after 26 months and 83.0% after 48.0 months, respectively.
Although second-look arthroscopy has been reported to most accurately determine meniscal healing, MRI has also been found to demonstrate a high specificity in detecting healed meniscal repairs without need for additional surgery, emphasizing its use as a significant complement to the clinical assessment . However, compared to the clinical healing rate of 83.3% of cases in the present study, the postoperative MR evaluation revealed a slightly lower rate of 69.4% completely healed menisci at final follow-up, while 25.0% were only partially healed and 5.6% were unhealed. Studies evaluating radiological healing following repair of acute BHMTs are scarce. In the setting of chronic medial BHMTs, Espejo-Reina et al. observed a comparable radiographic healing rate of 70.8% at 48 months postoperatively . However, 29.2% of repaired menisci were unhealed at final follow-up, which may be due to large time interval between injury and surgery with a mean of 10 months and the patients’ high activity level . Uzun et al. showed that 5 of 43 (11.7%) all-inside repairs of the lateral meniscus failed after a mean period of 12.8 months postoperatively on MRI . Similarly, Goh et al. showed that 19 of 21 patients had a stable reduction after repair of BHMT on MRI 2 years postoperatively .
Failure rates following repair of BHMTs have been reported to vary between 10.4 and 34.2% of cases [1, 7, 8, 11, 15,16,17,18, 29], which is consistent with the overall failure rate of 15.0% observed in the present study, comprising four patients who had to undergo revision surgery due to re-tears and two patients who revealed radiographically unhealed meniscal repairs at final follow-up. As the probability for absence of failure has been shown to constantly decrease over time , the present findings can be considered as satisfactory results. More specifically, Ardizzone et al. recently found a significantly higher failure rate following BHMT repair in patients with a follow-up period of more than 30 months (34.4%) when compared to patients with a follow-up of less than 30 months postoperatively (23.4%) .
Several factors having an impact on failure rates after BHMT repair have been suggested, including patient age and sex, activity level, ACL laxity, concomitant ACL reconstruction, meniscus laterality, delayed surgery, and length of postoperative follow-up [1, 7, 8, 15,16,17,18]. Previous studies highlighted the correlation of male sex with significantly increased failure rates following BHMT repair when compared to female patients [1, 7]. Similarly, all of the six failures in the present study occurred in male patients, however, this finding did not reach statistical significance mainly due to the limited sample size, introducing the concern over a type II error. Further, meniscus laterality did not seem to influence postoperative healing with the medial (16.7%) and lateral (12.5%) meniscus showing similar failure rates, which is consistent with recent work . Smoking was identified as risk factor for meniscus healing in one study . Time from injury to surgery has no statistically significant effect in the presented cohort.
While most of these factors rather seem to have negligible impact on postoperative success, several previous studies found concomitant ACL reconstruction to result in a lower risk of failure when compared to isolated BHMT repairs [7, 8, 15]. Espejo-Reina et al. reported that patients with isolated BHMT repairs were 21.3 times more likely to fail compared to those who underwent concomitant ACL reconstruction . However, more recently published studies found that concurrent ACL reconstruction only trended toward being a factor associated with successful repair, without reaching statistical significance [1, 8, 11]. Similarly, the present study showed that concomitant ACL reconstruction was not correlated to meniscal healing. Further, a mean side-to-side difference in knee laxity of 2.1 mm was observed in the ACL reconstruction group, which is consistent with pervious results of Feng et al. with a mean difference of 1.8 mm compared to the healthy contralateral side .
As a clinical consequence, acute and traumatic BHMTs should be repaired, and meniscal tissue preserved whenever possible. Clinical and radiographic outcomes demonstrate good to excellent results with a low revision and non-healing rate along with high patient satisfaction.
There were several limitations to the study. Although data was collected prospectively, the chart review was performed retrospectively, potentially creating selection bias. Second, the sample size was limited because only patients with complete data collection comprising patient-reported outcome scores, clinical examination, and MR examination were included in the final analysis. In addition, with reporting outcomes of only a single institution’s practice, external validity may be limited in terms of both patient population and surgical technique. Lastly, sensitivity and specificity of native MR examination is limited regarding the postoperative assessment of meniscal healing.