Medial Prof. MD David Figueroa & MD Rodrigo Guiloff Facultad de Medicina Clinica Alemana- Universidad del Desarrollo Santiago, Chile

Why is this topic important?

Injuries to the medial side of the knee are the most frequent knee reported in sports1,2. Historically, these have been treated in a conservatively with a high rate of beneficial results; however, a better understanding of the and of the different structures of the medial side of the knee have led to different opinions about the correct way of managing them. There is a variety of inconsistent concepts that may create confusion in the current literature leading to controversies and the lack of consensus in the management of these injuries.

The purpose of this presentation is to give an evidence and clinic base clarification of the controversies regarding the injuries to medial side of the knee and propose an algorithm for their management.

1st Controversy: Structures of the Posteromedial Corner (PMC)?

The study by Robinson et al. divided the medial side of the knee into thirds3. Everything posterior to the medial collateral ligament (MCL) was described as the “posterior third” which recent studies have described as the PMC which includes: the posterior oblique ligament (POL), the semimembranosus tendon and its expansions, the oblique popliteal ligament (OPL), the posteromedial capsule, and the posterior horn of the medial meniscus4,5.

A contemporary study by Cinque et al., also describe the PMC by 5 structures; however, they include the MCL with its superficial and deep portions as individual structures, without considering the semimembranosus and the posteromedial joint capsule6. They argue that the nomenclature of the medial side structures has been inconsistent, leading to confusion.

Answer to the controversy: We think of a holistic way of approaching, by including all the possible injured structures as the “medial side of the knee” (MSK), which is a functional unit for the restraint of valgus and rotation, understanding the superficial MCL (sMCL) as its core structure. We divide injuries as those which manifests as an isolated sMCL rupture or those combined with other medial structures (sMCL injury plus other medial structures), which are not to be confused with multiligamentary injuries, which would include the sMCL plus another core knee ligament of the knee. This categorization is a critical factor for making an accurate diagnosis and management decisions.

2nd Controversy: Which Clinical Classification Should be Use?

Different classifications have been used in the reported evidence for MSK injuries. This variation is of great trouble when trying to group all studies for analyzing and giving general conclusions.

Most of the reported results after MSK injuries come from studies which address MCL injuries with the original classification of the American Medical Association (AMA), which categorize them through the valgus opening at 30º. It has been proven of low inter and intraobserver agreement, due to its subjective value. For this reason, Hughston et al., modified it by including the sensation after the opening to differentiate as grade 2 those with a firm end and as a more severe injury, grade 3, those without it. However, it is important to question if these classifications, with or without the modification, really helps for the management decisions. We already stated that it is imperative for an accurate treatment to define if the injury is an isolated sMCL or a combined MKS injury. Some authors have argued that a Hughston grade 3 with more than 10mm of valgus opening should be considered as mixed injuries; nevertheless none of these classifications evaluate other components of the MSK.

Fetto and Marshal classification differentiate grade 2 injuries as those opening at 30º and as grade 3, those opening at 0º and 30º7. They recognized the importance of other medial knee structures for the kinematics of the knee and categorized as a more severe injury those in which the knee is also opened at 0º, which can be translated as those in which the POL is also injured.

Answer to the controversy: We think that a classification for MSK injuries should differentiate between isolated injuries to the sMCL and those combined. For this reason, from the existing classification, we advocate for the developed by Fetto and Marshal.

3rd Controversy: Does combined MSK injuries (MCL + Other Medial Structures) have a Lower Healing Capacity?

The historical indication of conservative treatment for MCL injuries is supported by the results of the study of Indelicato in 1984, in which a comparison between primary repair and conservative treatment for complete MCL injuries (grade III AMA) showed that both groups had good and excellent results8. The paper states that the key to treatment success is to establish that there is an isolated lesion with no associated damage of other vital structures.

There is an actual trend to recommend when there is a combined MSK injury4,6,9,10. A recent JBJS review, argues that MSK injuries with valgus gaping in extension or classified as grade III (modified AMA), meaning combined MSK injuries, have a higher risk of not healing. These injuries would result in a residual valgus and rotational instability, and thus they recommend with a grade A of recommendation (based on Level I studies with consistent findings) that these injuries should be considered for surgery6. Nevertheless, after a thorough review of the cited evidence11–16, some of them do not address combined MSK injuries and those that do, should not be considered of Level I evidence. To our knowledge, the only study to demonstrate that combined MSK injuries have a worse prognosis than isolated injuries when treated conservative is the one by Kannus17, in which MCL with valgus instability at 0º showed significantly worse outcome than those without instability at 0º by means of persistent valgus, secondary ACL deficiency, muscle weakness, and post-traumatic arthritis. This study reinforces the answer to the 2nd controversy and the importance of the POL for knee kinematics.

An associated injury of the deep medial collateral ligament (dMCL) to the sMCL has also been described as worsening the prognosis. Narvani et al2., described a case series of 17 high-level athletes with MCL injuries who failed non-operative treatment and required surgical intervention. The intraoperative finding was a failure of healing of a tear of the deep MCL at its femoral origin which could be repaired.

Answer to the controversy: Even though the recent literature advocates for surgery in combined MSK injuries, it is essential to recognize that this recommendation lacks of scientific evidence. In lights of the few existent studies and that there is a consistent theoretical explanation, we support the actual recommendation of operating those combined MSK injuries.

4th Controversy: Does AMRI implies a torn ACL?

As a combined MSK injury is often an indication for surgical management, great attention should be placed in the diagnostic workup for finding associated injured structures to the sMCL. Hughston et al., in 1976, introduced the concept of antero-medial rotatory instability (AMRI) as an abnormal excess opening of the medial joint space in abduction at 30º of knee flexion, with a simultaneous anteromedial rotatory subluxation of the medial tibial condyle on the central axis2. The presence of an AMRI indicates that there is combined MSK injury12,18.

The presence of an AMRI becomes critical as well because it is commonly related to the presence of an ACL tear. Halinen et al., reported that 96,3% of the MCL and ACL injuries had an associated POL injury. However, as Hughston describes in his AMRI series, patients had an injury to the midportion of the superficial and deep MCLs or the POL, often (but not always) with an associated ACL injury12. The biomechanical study of Robinson et al. supports this idea. At 90° of flexion, sectioning of sMCL, dMCL and the posteromedial capsule caused a significant increase in mean tibial external rotation translation, even with the ACL left intact.

Answer to the controversy: AMRI does not necessarily imply a torn ACL; however, it is highly probable. Despite this, it should be addressed and registered, because it indicates a severe MSK injury.

5th Controversy: Should MCL Associated in Multiligamentary Injuries be operated?

It has already been stated the importance of recognizing combined MSK injuries because of the premise that they have lower healing potential. The same argument has been given for MCL associated in multiligamentary injuries. Anderson et al. showed in an animal study the base of this assumption by demonstrating that in associated injuries of the MCL, ACL and , the MCL does not heal. However, after ACL reconstruction, the varus-valgus stability was reduced to the same as an isolated MCL injury.

Different strategies have been proposed, all agree in operating the other injured , and they can be grouped into those in which MCL in treated conservative and those treated with surgery. Each group can be subdivided according to the time in which the other injured ligaments are operated. Strategy 1A: Conservative MCL and acute surgery (<3 weeks) for the other injured ligaments. This approach has been highly discredited19–24 because the other ligaments reconstructions need a specific rehabilitation that is prejudicial for MCL healing. Besides, with a medial side unaddressed injury, other reconstructions can fail. Strategy 2A: Conservative MCL and delayed surgery (6 weeks) for the other injured ligaments. A resting period for giving the MCL the chance to heal and then reconstruct the other injuries was frequently recommended and was the consensus no long ago1,10,25. Many argued that it was important to wait because it diminishes the chances of . However, even the same authors that have supported this recommendation have recently questioned this premise and advocate for Strategy 3: surgery of MCL and the other ligaments, because it leads to better functional outcomes with low risk of arthrofibrosis and a higher rotational stability4,6,26. Nevertheless, it is important to remark that the cited evidence of these results has only been demonstrated in multiligamentary injuries involving the lateral side of the knee and not specifically for those of the MSK.

Answer to the controversy: In 2009, a systemic review about the management of MSK injuries concluded that there was lack of evidence for recommendation. Ten years later, we argue against strategy 1A, because with a medial side unaddressed injury, other acute reconstructions can fail and/or the MCL might not heal. However, we still agree that there is insufficient evidence for a recommendation between waiting for the MCL to heal and operating the MCL and other ligaments. An exception for this would be the case scenario in which a bony avulsion or entrapment is present in the MCL injury, in which we recommend for surgery of the MCL and the other injured ligaments.

6th Controversy: When surgery is indicated, what should be done? Repair, Augment or Reconstruct?

Answer to the controversy: We have developed an evidence-based management algorithm, including the different stated strategies. Five questions should be answered: 1) Is it an acute or chronic injury?; 2) Is it an injury that benefits from an acute repair? (bony avulsion and entrapment); 3) Is it an injury that has a low healing prognosis? (combined MSK and multiligamentary injuries); 4) Is there any other structure that must be surgically addressed? (ligament, menisci, cartilage); 5) Is it a patient with a high demand activity?

We recommend: repairing those amenable injuries that benefit from acute repair; augmenting those repairs in injuries with lower healing prognosis to protect and favor an early rehabilitation; reconstructing the MCL in chronic injuries.

References

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