Repair versus reconstruction of proximal anterior cruciate ligament tears

Historical overview

The first documented surgical treatment of an anterior cruciate ligament (ACL)
consisted of open primary repair in 1895 when Mayo Robson repaired a proximally
avulsed ACL and posterior cruciate ligament (PCL) back to the femur in a
41-year old male with good outcomes at six-year follow-up [1]. In the twentieth
century, Ivar Palmar [2, 3] and Don O*Donoghue [4, 5] further reported on open
primary repair as a treatment of ACL injuries, and in the early 1970s open
primary repair became a popular treatment for ACL injuries [6-9].

Feagin and Curl were the first to present the outcomes of open primary repair
at the AAOS in 1972 and noted good outcomes at short-term follow-up [8]. A few
years later in 1976, however, they noted a deterioration of outcomes at
mid-term follow-up in their cohort [10]. Several other surgeons similarly noted
good short-term [11-16] but disappointing mid-term outcomes [17-21]. With these
disappointing mid-term results and the promising early results of ACL
reconstruction, several (randomized) prospective studies were started in the
1980s comparing open primary repair with open ACL reconstruction [19, 22-24].
These prospective studies noted more reliable outcomes with ACL reconstruction
when compared to primary ACL repair, which led to an abandonment of open
primary repair and to the current gold standard of ACL reconstruction for all
patients [9].

In 1991, Sherman et al. were the first attempting to understand the
disappointing mid-term outcomes of open primary repair by performing an
extensive subgroup analysis [21]. The authors noted a trend towards better
outcomes in selected patients: outcomes were better in patients with proximal
avulsion type tears and good tissue quality and were inferior in midsubstance
tears and/or with poor tissue quality. Unfortunately, the inclusion of the
aforementioned prospective trials was already completed before the study by
Sherman et al., and thus the prospective trials contained all tear types
including midsubstance tears that had inferior results: this may explain the
unreliable results of open primary repair in these trials (as none of these
studies assessed tear location)

When critically reviewing the historical literature, and learning from these
findings by Sherman et al., it can be noted that the results of open primary
repair of proximal tears were good. Van der List and DiFelice performed a
systematic review of all historical studies on open primary repair and noted
outcomes were indeed better in studies with proximal tears [25]. The outcomes
of open primary repair of proximal tears were very good, even compared to
modern standards, with 83 to 90% clinical stability, 80% return to sports, 79%
good to excellent Lysholm score and 86% satisfaction in 539 patients in 11
studies. These findings indicate that primary repair may have been prematurely
abandoned for all tear types and perhaps should have been maintained as a good
treatment option for proximal tears. This would have led to a *tear type
dependent approach* in which primary repair can be performed for proximal tears
and reconstruction for midsubstance tears rather than our current *one size
fits all* approach. Furthermore, outcomes of primary ACL repair can be expected
to even be better when benefiting from modern development, such as arthroscopy
and modern rehabilitation.

Advantages

Arthroscopic primary ACL repair has some potential advantages over ACL
reconstruction. Firstly, with primary ACL repair the native tissue can be
preserved along with proprioception, which is not the case with ACL
reconstruction. Secondly, primary ACL repair is a less invasive surgery when
compared to ACL reconstruction as no tunnels need to be drilled and no graft
tissues need to be harvested, leading to less surgical morbidity [26-28],
faster return of range of motion and fewer complications [29]. Thirdly, in case
of failure of both treatments, revision surgery following primary repair can be
considered a primary reconstruction surgery, whereas revision of reconstruction
surgery is often complicated and leads to inferior outcomes compared to primary
reconstruction [30, 31]. Finally, primary ACL repair, with the preservation of
native tissues and minimal invasiveness, leads in experimental and long-term
follow-up studies to a lower incidence of osteoarthritis when compared to ACL
reconstruction [32-35]. This is important as there is large consequence for the
patient and a high economic burden for society with the occurrence of
osteoarthritis following ACL reconstruction.

Disadvantages

There are also potential disadvantages of primary ACL repair. First, it can be
expected that there is a higher rerupture and instability rate following repair
versus reconstruction when looking at the studies from the 1970s and 1980s.
Although current studies with only proximal tears do not show this [36-41],
this should be take into account. Second, there is a possibility that too many
patients will be operated with this technique (see section J). In the
Netherlands, patients are currently first treated conservatively for 6 weeks to
evaluatie which patients will become symptomatic and need to undergo surgical
reconstruction. Because a part of the ACL patients do not develop symptoms
(often these are less active patients or patients that prefer to stop sports
participation over surgery), there is with the ACL repair treatment the risk
that too many patients will undergo surgery (it is not evaluated which patients
will be symptomatic). It is attempted to decrease this risk by only treating
active patients (age 15 - 50 years and only patients who want to continue
sports participation), but this risk cannot be excluded.

Recent literature

Recently there has been a renewed interest in primary ACL repair. Learning from
past experiences (i.e. only treating proximal tears), and benefiting from
modern developments (i.e. arthroscopic surgery, modern rehabilitation), several
authors have performed arthroscopic primary repair of proximal ACL tears
[36-39]. DiFelice et al. were the first to perform arthroscopic primary ACL
repair tears and noted excellent short-term outcomes in their retrospective
case-series [36]. As opposed to the disappointing historical mid-term outcomes,
the mid-term outcomes of their case series were maintained at mid-term 6.0-year
follow-up with excellent patient reported outcomes and 1 clinical failure (9%).
The same group has presented the results of their first 56 patients (Jonkergouw
et al, KSSTA 2017, PMID 30612165) and reported a 10.7% failure rate, 7.1%
reoperation rate and all patient-reported outcome measures (PROMs) above 90% of
the maximum score. Achtnich et al. have recently assessed the outcomes in a
comparative study in which they retrospectively compared the outcomes in
patients with proximal avulsion type tears who were willing to undergo ACL
repair (n = 20) versus who were not willing to undergo repair and thus
underwent ACL reconstruction (n = 20) [37]. The authors noted similar outcomes
following repair and reconstruction in functional outcomes, failure rates and
stability examination in a small cohort. Three other small cohorts have
reported excellent outcomes of arthroscopic primary ACL repair in level IV case
series [38-41].

The current gold standard of surgically treating ACL injuries is ACL
reconstruction. As all new surgical techniques, the outcomes of arthroscopic
primary ACL repair need to be compared to the current gold standard of ACL
reconstruction in order to assess if this treatment can be used for standard
patient care, but the current literature only consists of level III or level IV
studies. The ACL study group in the Netherlands agrees with the need for this
study and has recently declared that *the application of primary ACL repair
could be considered in an IRB-approved study until there is high

The objective of this prospective randomized controlled trial is to compare the
outcomes of arthroscopic primary repair of proximal ACL tears with the current
gold standard of ACL reconstruction.

This study is a multi-center national prospective randomized controlled trial
(RCT) with randomization into four treatment arms. All patients are first
classified in a low and high-risk patient group.

In case a proximal (reparable) tear is present during surgery, the patient will
be randomized into one of these treatment arms, and will be followed at short-,
mid- and long-term follow-up.

In case a proximal (reparable) tear is not present during surgery, the patient
will undergo standard reconstruction and be excluded from this study.

High-risk patients are defined as those with a higher risk for treatment
failure (i.e. high-grade rotational laxity, patients with gross hypermobility,
younger patients, and/or patients performing sports at high activity level). In
both groups, all patients will then be randomized into repair or
reconstruction. For patients in the high-risk group, a modified lateral
extra-articular tenodesis (LET) will be performed to lower the risk of
treatment failure. Therefore, there will ultimately be four arms (isolated
repair vs. isolated reconstruction and repair combined with LET vs.
reconstruction combined with LET).

This study is a non-inferiority study with the hypothesis that arthroscopic
primary ACL repair is non-inferior to arthroscopic ACL reconstruction. A
non-inferiority design is chosen as it is expected that the primary repair
procedure is less invasive, shorter, has less complications and has easier
rehabilitation when compared to ACL reconstruction [29].

Randomization

All patients will be consented preoperatively for the study and will sign a
consent form if they wish to participate. The operation starts with a standard
knee arthroscopy. It will be assessed what type of ACL tear is presented, if a
proximal tear is present (i.e. if the distal remnant of the ACL is of
sufficient length to be reattached to the anatomical footprint of the ACL) and
if good tissue quality is present (i.e. if the anteromedial (AM) and
posterolateral (PL) bundles are of sufficient quality to withhold suture
passage and can be tensioned towards the femur). If these conditions are
present, patients are randomized on a computer in the operating room between
both treatment arms. If these conditions are not present, the patient is
excluded and standard ACL reconstruction will be performed.

Surgical techniques

The surgical technique of arthroscopic primary ACL repair has been more
extensively described in the literature [42-44, 52]. In brief, the ACL is
sutured in alternating and interlocking Bunnel-type patterns towards the
avulsed end of the ligament using FiberWire, such that the suture exits the
avulsed ligament at the femoral side. Then a femoral tunnel is drilled,
followed by drilling a tibial tunnel. A cortical button is then preloaded with
both the repair sutures as well as a FiberTape. This construct is then
retrieved through both tunnels. Distally, the FiberTape is first fixated on the
tibial cortex using a second cortical button, after which it is fixated at the
femoral cortex in near full extension. Finally, the repair sutures are fixated
proximally over the same femoral cortical button using alternating hitches in
90 degrees flexion.

For ACL reconstruction, autograft hamstring tendon ACL reconstruction surgery
is performed. First, autologous hamstrings (semitendinosus and gracilis tendon)
are harvested and will be prepared for graft usage with a minimum graft
diameter of 8mm. Then, the femoral and tibial sockets are independently drilled
using a FlipCutter (Arthrex) and the graft is fixated on the femoral side and
tibial side using a cortical button.

For high-risk patients, a LET procedure will be performed. With this procedure,
a central strip of the proximal iliotibial band (ITB) is harvested while
leaving the distal attachment at Gerdy's tubercle intact. The ITB graft is then
passed under the lateral collateral ligament (LCL) and fixated on the lateral
femoral condyle using an interference screw or an anchor.

Rehabilitation

Both treatment arms undergo the same rehabilitation program, and consists of a
milestone based program. Early range of motion exercises are started directly
postoperatively, and patients will wear a brace locked in extension during full
weight bearing until quadriceps control is regained. Crutches are used for 1 to
3 weeks up to the preference of the patient. Closed kinetic chain exercises
will be started immediately postoperatively. In case of meniscus repair, the
first 6 weeks patients are partial weight bearing and range of motion is
restricted to 0-90°. Although rehabilitation is milestone based and no strict
time goals can be set, generally cycling on a bike is allowed at 3-4 weeks,
running at 6-8 weeks and return to sports at 6-9 months postoperatively
depending on the rehabilitation progress, muscle atrophy and return to sports
battery tests with physical therapy. Patients will be under guidance of a
physical therapist and undergo a criterion-based rehabilitation which is
equivalent to the Dutch standard [45]. The patient and treating physician will
determine the time of return to activities.

By participating in this study, patients will be treated for their ACL injury
within 12 weeks of injury by either the gold standard of ACL reconstruction or
primary ACL repair. Several studies have shown that there is no risk in early
treatment of ACL injury by primary repair or reconstruction.

For this study patients will visit the clinic a total of 7 times of which the
last 3 visits is of additional burden to the patient when compared to normal
care. They will have to complete questionnaires (estimated time 10 minutes),
undergo physical examination (estimated time 5 minutes), and in the last two
visits they will also undergo bilateral knee radiographs to assess the
incidence of osteoarthritis.

The treatment of primary ACL repair has the aforementioned risk of rerupture of
the repaired ligament in which case the patient has to undergo an additional
surgery to remove the repaired ligament and perform a standard ACL
reconstruction. Small cohort studies have shown that the risk of rerupture with
primary ACL repair is equivalent to slightly higher when compared to the risk
of rerupture with ACL reconstruction, which needs to be examined by this study.


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