Cartilage repair strategies in the knee according to Dutch Orthopedic Surgeons: a survey study

Articular cartilage defects in the knee occur frequently and may cause considerable pain and disability [1‐3]. Cartilage regeneration or repair techniques may be indicated when cartilage defects become symptomatic.

Current techniques used in clinical practice include marrow stimulating repair techniques such as microfracture (MF) and its augmentations, regenerative techniques such as autologous chondrocyte implantation (ACI) and regenerative osteochondral scaffolds, and bone-based repair techniques—i.e., depending on osseointegration—such as osteochondral grafting using autografts or allograft transplantations (OAT and OCA) and focal knee resurfacing implants (FKRIs) [4]. MF augmentations include interventions such as autologous matrix-induced chondrogenesis. Regenerative osteochondral scaffolds include treatments such as Trufit™ (Smith and Nephew), MaioRegen (Finceramica) amd Agili-C™ (CartiHeal). Non-degradable bone-based FKRIs include HemiCAP^® (Arthrosurface), Episealer^® (Episurf) and BioPoly^® RS Femoral Condyle (BioPoly).

In an attempt to provide guidance within the complex field of cartilage regeneration and repair, several international cartilage experts have composed guidelines or ‘treatment algorithms’. The Dutch Orthopedic Society (Nederlandse Orthopedie Vereniging—NOV) cartilage repair consensus statement for (osteo)chondral surgical repair (abbreviated Dutch Consensus Statement; DCS) was first published in 2011 and were updated in 2019 (Table 1) [5]. Although the Netherlands is known for its excellent healthcare quality and registration [6], there is no separate registration of cartilage repair, i.e., there are no cartilage specific procedural terminology (CPT) billing codes. There is consequently no information about the perception and adherence to the DCS.

The objective of this survey study was to provide insight in the applied cartilage repair techniques and adherence to the DCS in the Netherlands. In addition, this study emphasized the patient age-related considerations by orthopedic surgeons. With relatively little literature available related to the treatment of the middle-aged population, insights by orthopedic surgeons concerning their patient age-related considerations in cartilage repair aid in understanding this knowledge gap [3].

This was the first national survey on cartilage repair in the Netherlands. The response rate of 60% was considered to be adequate, given the typical response rate of 37–51% for e-mail-based surveys [8, 9]. Such response rate highlights the widely accepted challenge in addressing cartilage defects.

Debridement and MF were the treatments employed by most surgeons and most surgeons indicate to treat the medial femoral condyle with a single lesion. This is in accordance with the incidence of cartilage defects as reported from large epidemiologic database studies [10‐14]. For symptomatic ICRS I/II defects, no surgical intervention, debridement and to a lesser extend MF were most considered as treatment when correspondents were asked. Debridement and MF were also most considered for ICRS III/IV defects up to 3 cm²_. Similar trends were previously found in a German and Turkish survey [15, 16]. However, due to the mounting evidence of its ineffectiveness [17], both the 2011 and the 2019 DCS discouraged the use of MF in defects larger than 2 cm². Hence, Dutch orthopedic surgeons seem to deviate from the DCS on this point.

In accordance with the DCS, the BMI limit for cartilage repair was set at 30 kg/m² by 72% of the respondents. Although it has been well established that a BMI of 30 or larger is correlated with inferior outcomes after cartilage repair procedures [18], the prevalence of patients with such a BMI and the growth of this group is significant. [19].

Concomitant surgeries like meniscal repair and leg axis corrections were performed by a large majority of respondents. This is in accordance with recent German registry data [20]. Although the question related was asked from a symptomatic cartilage defect perspective, this survey did not scrutinize if cartilage repair could also have been concomitant to an anterior cruciate ligament (ACL) repair for instance. Such situation is conceivable when an unexpected cartilage defect is encountered during arthroscopy. The incidence of severe cartilage defects with ACL injuries for instance was previously found to be 16–46% [21]. On the other hand, there is also an increasing notion that combined treatments might decrease the risk for reoperation and improve outcomes [20, 22‐24]. With a leg axis corrections considered at 5°–6° malalignment, most correspondents follow the DCS. Similar cut-offs were found in a previous West European study [16]. Some experts in the field, however, have advocated to correct malalignment in the mechanical axis from 2 degrees or more to unload the treated compartment and enhance repair. [22, 25] In a recent German database study the cut-off for varus axis correction was 3° [23]. Emphasized by the obesity pandemic, it is of great relevance to further clarify the indication and cut-off values for alignment corrections or overcorrections since unloading is potentially beneficial for the repair [22, 26]. In addition, the large spread in the cut-off values indicated by the respondents further confirms that there is yet no consensus for when to perform a corrective osteotomy in cartilage repair.

In general, respondents indicated a low employment of more complex techniques such as ACI, MF augmentations, allografts and FKRIs. At the same time, when specifically asked, these very treatments were indicated by the respondents for larger defects with higher ICRS scores, or, in older patients. This discrepancy suggests that there is a lack of availability of treatments. In addition, the previous debate in the Netherlands concerning the cost-effectiveness and hence reimbursement of ACI is possibly related to this [27]. Similar issues were also previously reported by Elmali et al. [15] Other explanations include the availability of allografts in Europe which is—contrary to the US—hampered due to regulatory issues [28]. But perhaps the best explanation for this is the centralization of cartilage repair in the Netherlands, highlighted by a 95% referral rate on indication. Indeed, due to regulation in the Netherlands, more complex techniques such as ACI or combined surgeries are only allowed to be performed in expertise centers. Hence, the orthopedic surgeon working in the periphery may only use debridement, MF and small osteochondral autografts.

Only half of the respondents would treat patellofemoral defects, which is a surprising finding given the fact that over 1/3 of patients present with patellofemoral defects [29]. Perhaps surgeons are discouraged by the inferior outcomes in this compartment [30]. At the same time, respondents also indicated to treat tibial defects, which are considered expert level treatments with only limited evidence and often inferior outcomes [31]. Hence, the latest DCS discouraged the surgical treatment of tibial defects. In line with this is the 8% of respondents treating kissing lesions which is also discouraged. Perhaps the fact that 28% of respondents seeing patients with multiple or kissing lesions did not work in a tertiary center contributed to these unadvised treatment indications.

Loose cartilage bodies were only fixed by the majority of the respondents if there was residual bone present, i.e., osteochondral shells. This is a critically important finding since a recent study indicated that pure chondral loose bodies could in fact serve as a functional autograft, even without the need for anchoring biomaterials [32]. Moreover, the patients’ own cartilage could potentially also serve as chondrocyte or chondron source for ACI and the novel minced cartilage repair options [33].

The major limitation of present study are its subjective outcomes, which is inherent to the nature of a survey study [37]. In the absence of CPT codes to register individual cases and different repair techniques, we are unable to compare current results to objective epidemiologic values. The results of the present study should therefore be interpreted as Dutch orthopedic surgeons describing how they would treat a given patient and defect, not as a completely objective measure of how to they actually treat their patients. Nevertheless, with the assumption of relatively similar demographics, the results of present studies can be compared to large database studies [11‐14] and other survey studies [15, 16]. A nationwide registry system, analogous to or combined with the Dutch Arthroplasty Register, for different cartilage defects and prognostic factors could provide objective data, rather than relying merely on subjective data.

Since we restricted the inclusion to members of orthopedic knee associations we only included surgeons with affinity for knee surgery. The very low volume orthopedic surgeon operating in a small peripheral hospital may therefore not be included. However, only a small number of respondents indicated to work in an expertise center and the results of the non-experts could consequently be extrapolated to the general orthopedic surgeon. Perhaps the knowledge gaps in present study would be even more profound in those who are not a member of a knee association.

In the absence of a nationwide cartilage repair registry, this survey gives an impression of cartilage repair in the Netherlands. The present survey study showed that cartilage defects are treated by experts and many by non-experts. Both groups revealed a relative adherence to (inter)national guidelines. Small (< 2 cm²) and simple cartilage defects in the absence of additional injuries or malalignment may therefore be treated by general orthopedic surgeons if they follow the latest national recommendations. However, several knowledge gaps for specific defect and patient characteristics were shown, indicating that not everyone is fully aware of the latest insights. Caution should be exercised concerning the opportunistic use of MF, treating rare defects such as defects > 2 cm² or those in the presence of loose viable cartilage bodies. Particularly patients with suboptimal characteristics such as an increased age (> 40 years), high BMI or malalignment should be considered for referral. This survey indicated that the recently introduced centralization of cartilage care is widely adopted in the Netherlands, which potentially aids in better knowhow and availability of advanced treatments, consequently better outcomes, and perhaps, joint preservation. Future research should focus more on dominant demographics such as older patients with typical comorbidities. This study should encourage orthopedic surgeons to engage in (inter-) national cartilage registries. Combining these registries with the Dutch Arthroplasty Register could aid in understanding the conversions to arthroplasties. Structural support from both the government and industry is necessary to enable the proper registration of all cartilage surgeries and products.