Diploma Thesis Allograft versus Allograft with Internal Bracing in Anterior Cruciate Ligament Reconstruction in Revision Cases after ACL re-tear Submitted by Andrea Baltic In partial Fulfilment of the Requirements for the Degree Doctor of Medicine (Dr. med. univ.) At the Medical University of Graz Conducted at the Department of Orthopaedics and Trauma Under Supervision of Priv.-Doz. Dr.med.univ. Gerwin A. Bernhardt, MBA and Priv.-Doz. Dr.med.univ. Gerald Gruber, MBA Graz, 07.11.2019
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Diploma Thesis
Allograft versus Allograft with Internal Bracing in Anterior Cruciate Ligament Reconstruction in Revision
Cases after ACL re-tear
Submitted by
Andrea Baltic
In partial Fulfilment of the Requirements for the Degree
Doctor of Medicine
(Dr. med. univ.)
At the
Medical University of Graz
Conducted at the
Department of Orthopaedics and Trauma
Under Supervision of
Priv.-Doz. Dr.med.univ. Gerwin A. Bernhardt, MBA and
Priv.-Doz. Dr.med.univ. Gerald Gruber, MBA Graz, 07.11.2019
i
Statutory Declaration
I hereby declare that this thesis is my own original work and that I have fully acknowledged by name all of those individuals and organizations that have contributed to the research for this thesis. Due acknowledgements have been made in the text to all other material used. Throughout this thesis and in all related publications I followed the guidelines of “Good Scientific Practice”. Graz, 07.11.2019 Andrea Baltic eh
ii
Danksagungen
Zuallererst möchte ich mich hiermit bei PD Dr. Gerwin A. Bernhardt und PD Dr. Gerald
Gruber für die Möglichkeit bedanken, bei dieser Studie mitzuarbeiten. Ein großes
Dankeschön gilt dabei Dr. Bernhardt, der mir als Ansprechperson stets zur Seite stand und
mir mit seinem Wissen und Ratschlägen von Anfang bis zum Ende immer weitergeholfen
hat. Ein weiterer Dank gilt dem Klinikvorstand der Universitätsklinik für Orthopädie und
Traumatologie Univ.-Prof. Dr. Andreas Leithner für die Möglichkeit, an der Studie
mitgearbeitet und beim internationalen SICOT Kongress in Montreal vorgestellt zu haben.
Der größte Dank gilt jedoch meinen Eltern und Geschwistern, welche schon immer an mich
geglaubt und mich in allen Lebenslagen unterstützt haben. Ohne sie wäre mein
Studienabschluss niemals möglich gewesen.
Ein großer Dank gilt auch meinen zahlreichen Freunden, von denen jeder einzelne für mein
geistiges Wohl während der langen Studienzeit gesorgt hat. Besonders erwähnen möchte ich
meine Mädels, welche seit der Schulzeit an meiner Seite stehen, sowie meine zwei
Freundinnen Sandra und Isabella, durch die die Studienzeit erst so schön geworden ist, wie
sie letztendlich war.
Meinem guten Freund Tobias möchte ich noch danke sagen, da er mir bei allem Freud und
Leid die Diplomarbeit (und auch andere Lebensereignisse) betreffend zur Seite stand und
diesen doch recht langen Weg mit mir gegangen ist.
Mein allerherzlichster Dank gilt auch meinem Freund Jan, der immer für mich da ist und
immer an mich glaubt.
Vielen Dank!
iii
Abstract
Introduction:
Anterior cruciate ligament (ACL) ruptures are one of the most common sports-associated
injuries. Increasing numbers of ACL reconstructions result in higher re-tear rates after
return-to-sport and in a higher number of revisions. Allograft transplants may be a good
alternative in complex revision cases. The use of so-called internal brace augmentation might
help graft ingrowth by providing higher primary stability. This study aimed to investigate
the outcome of patients with versus patients without internal brace augmentation in ACL
revision cases with allografts.
Material and Methods:
This is a blinded, randomized controlled pilot study with 30 patients planned. All patients
were treated with Achilles tendon allografts with bone blocks either with or without internal
brace. Data (clinical outcomes, 6- and 13-month MRI scan, SF-36, VAS, IKDC, Lysholm
Knee questionnaire, TAS and KOOS) were collected preoperatively as well as 6, 12 weeks,
6 and 13 months after surgery. Data of the 12-week follow-up results were included in this
thesis.
Results:
There were 18 patients included in the study (16,7% female). Eight patients were treated
with internal bracing (44.4%). The mean age was 29.4±7.8. There was no graft-failure in
either group. The outcome scores did not differ between the two groups after 12 weeks,
except for the IKDC being significantly better in the group without IB. The results of the
scores were KOOS 82.6±9.8, IKDC 74.7±8.8 and a median Lysholm score of 94 (65-100)
for the group without internal bracing versus KOOS 74.8±6.3, IKDC 63.9±8.7 and median
Lysholm score of 67 (62-100) in the bracing group.
Discussion:
The results show satisfactory short-term outcomes in both groups. There were no re-
ruptures or other complications in either group. There were no relevant clinical differences
between the two groups. If internal bracing might support the allograft healing process and
reduce re-ruptures has to be examined in the long term of this pilot study. Future studies then
iv
need to confirm the results in a larger cohort with adequate power and sample size
calculation.
v
Zusammenfassung
Einleitung:
Mit zunehmend steigenden Fallzahlen und guten return-to-sport Ergebnissen steigt auch die
Häufigkeit von neuerlichen Verletzungen des vorderen Kreuzbands. Die Revisionsoperation
nach einer Re-ruptur stellt jedoch häufig eine erhebliche Herausforderung für
Chirurgin/Chirurg und Patientin/Patient dar. Aufgrund der zum Teil limitierten
Entnahmemöglichkeiten von körpereigenen Sehnen sind Allografttransplantate in der
Revision von besonderem Interesse. Eine vorübergehende Fixierung (‚internal bracing‘) des
frisch transplantierten Allografts könnte durch Verminderung des Belastungsstresses zu
einer besseren Einheilung führen und somit zu einer Reduktion der Re-rupturraten.
Material und Methoden:
Bei dieser Studie handelt es sich um eine prospektiv, randomisiert, kontrollierte Pilotstudie.
Insgesamt 30 Patientinnen/Patienten wurden in eine Gruppe mit Augmentation durch
internal-bracing und ohne Augmentation randomisiert. Alle Patientinnen/Patienten wurden
mit einem Achillessehnenallograft mit Knochenblock in gleicher Operationstechnik
versorgt. Die Daten der Patientinnen/Patienten (Klinische Untersuchung, 6- und 13-Monats
MRT, SF-36, VAS, IKDC, Lysholm Knee questionnaire, TAS, KOOS) wurden präoperativ
und im Rahmen von Nachuntersuchungen (nach 6 und 12 Wochen, 6 und 13 Monaten)
prospektiv erhoben und ausgewertet. Die folgende Arbeit behandelt die 12-Wochen
Ergebnisse der ersten 18 Patientinnen/Patienten.
Ergebnisse:
Es wurden 18 Patientinnen/Patienten in die Studie eingeschlossen (16.7% weiblich). Acht
wurden mit internal bracing versorgt (44.4%). Das Durchschnittsalter der
Patientinnen/Patienten lag bei 29.4±7.8. Es gab in beiden Gruppen keine Reruptur.
Hinsichtlich des Outcomes unterscheiden sich die beiden Gruppen nach 12 Wochen nicht
signifikant, bis auf den IKDC, welcher in der Gruppe ohne internal brace signifikant besser
war. In der Gruppe ohne Internal-Brace zeigten sich 12 Wochen postoperativ für KOOS
82.6±9.8; IKDC 74.7±8.8 und im Lysholm Score 94 im Median (65-100). Die Gruppe mit
Internal-Brace zeigte mit KOOS 74.8±6.3, IKDC 63.9±8.7 und Lysholm 67 im Median (62-
100) sehr ähnliche Werte.
vi
Diskussion:
Die ersten Kurzzeitergebnisse zeigen für die verwendeten Techniken in komplizierten
Revisionssituationen in beiden Studiengruppen sehr zufriedenstellende Ergebnisse. Es gab
keine Re-rupturen oder andere Komplikationen in keiner der zwei Gruppen. Es gab auch
keine relevanten klinischen Unterschiede zwischen den beiden Gruppen. Ob das Internal-
Brace die Einheilung verbessern oder die Re-rupturraten verringern kann, kann erst nach
längerem Follow-up gesagt werden und muss in zukünftigen Studien mit größeren
Populationen evaluiert werden.
vii
Table of Contents
List of Figures ................................................................................................................. VIII
List of Tables ...................................................................................................................... X
Abbreviations .................................................................................................................... XI 1 Introduction ..................................................................................................................... 1
2 Theoretical Background.................................................................................................. 3 2.1 Anatomy of the knee joint ........................................................................................... 3
3 Material and Methods ................................................................................................... 29 3.1 Hypothesis of the Study ........................................................................................... 29
3.2 Study Population ...................................................................................................... 30 3.2.1 Inclusion Criteria ............................................................................................... 30
3.3 Study Design ............................................................................................................. 31
3.3.1 General Information .......................................................................................... 31 3.3.2 Ethics ................................................................................................................. 31
3.3.3. Data Protection ................................................................................................. 32
3.3.4 Revision ACL Reconstruction Surgery ............................................................. 32
3.4.1 Case Report Form (CRF) .................................................................................. 35 3.4.2 International Knee Documentation Committee (IKDC) .................................... 35
4.2.3 Clinical Scoring Systems ................................................................................... 40
4.2.4 Short-Form 36 Health Survey ........................................................................... 40
4.3 Surgical Data ............................................................................................................ 42 4.4 12-Week-Follow-Up Data ....................................................................................... 43
Figure 10: Ligaments of the knee joint, a: medial view, b: lateral view .............................. 7
Figure 11: Cruciate Ligaments ............................................................................................. 9 Figure 12: Vascular supply of the knee joint ...................................................................... 10
Figure 13: Innervation of the knee joint ............................................................................. 11
Figure 14: Moving axis during flexion and extension ........................................................ 12
Figure 15: Range of motion (ROM): a: flexion and extension, b: internal and external rotation ................................................................................................................................ 12 Figure 16: Dynamic Valgus ................................................................................................ 15
Figure 17: Lachman Test .................................................................................................... 17
Figure 18: Pivot Shift Test ................................................................................................. 17
Figure 19: Anterior Drawer Test ........................................................................................ 18 Figure 20: Lever Sign Test ................................................................................................. 19
Figure 21: Frontal and sagittal radiograph of a 23-year old patient with recent ACL re-rupture, drill holes from previous ACL surgery can be seen.............................................. 20
Figure 22: Sagittal T2 weighted MRI of a 22-year old patient with recent ACL rupture .. 20
Figure 33: SF-36 Comparison With US Normal Population .............................................. 47 Figure 34: Preoperative X-Ray Case I ................................................................................ 48
Figure 35: 6-Week Follow-Up X-Ray Case I ..................................................................... 48
Figure 36: 6-Month Follow-Up MRI Case I ...................................................................... 49
Figure 37: 13-Month Follow-Up MRI Case I .................................................................... 49 Figure 38: Preoperative X-Ray Case II .............................................................................. 51
Figure 39: 6-Week Follow-Up X-Ray Case II ................................................................... 52
Figure 40: 6-Month Follow-Up MRI Case II ..................................................................... 52
Figure 41: 13-Month Follow-Up MRI Case II ................................................................... 53
Table 2: Sensitivity and Specificity of ACL Tests ............................................................. 17 Table 3: Indications for conservative and surgical treatment of ACL ruptures ................. 21
Table 4: Advantages and disadvantages of available autografts ........................................ 23
Table 5: Advantages and disadvantages of allografts ........................................................ 25
Table 6: Complications associated with ACL reconstruction ............................................ 25 Table 7: Total patient population, total group without IB and total group with IB .......... 30
Table 8: Follow-Up Time and Performed Evaluations ...................................................... 31
Table 18: Questionnaire Results Case I .............................................................................. 50
Table 19: SF-36 Summary Scores Case I ........................................................................... 50 Table 20: Questionnaire Results Case II ............................................................................ 53
Table 21: SF-36 Summary Scores Case II ......................................................................... 53
xiii
Abbreviations
ACL Anterior Cruciate Ligament
AP Anterior-Posterior
AWMF The Association of the Scientific Medical Societies in Germany
BP Bodily Pain
CM Centimeter
CRF Case Report Form
FCL Fibular Collateral Ligament
GH General Health
HRQOL Health-Related Quality Of Life
IB Internal Brace
IKDC International Knee Documentation Committee
ITT Iliotibial Tract
KG Kilogram
KOOS Knee Injury and Osteoarthritis Outcome Score
LARS Ligament Advanced Reinforcement System
MAX Maximum
MH Mental Health
MIN Minimum
MM Millimeter
MRI Magnetic Resonance Imaging
MCS Mental Component Summary (SF-36)
OA Osteoarthritis
OC Oral Contraceptives
PCL Posterior Cruciate Ligament
PCS Physical Component Summary (SF-36)
PF Physical Functioning
PPI Proton Pump Inhibitor
PRP Platelet-Rich Plasma
QOL Quality of Life
RE Role Emotional
ROM Range of Motion
RP Role Physical
xiv
RR Relative Risk
RTS Return-To-Sports
SF Social Functioning
SF-36 Short Form – 36
TAS Tegner Activity Score
TCL Tibial Collateral Ligament
VAS Visual Analog Scale
VT Vitality
1
1 Introduction
Nowadays sports are a very important part of most people’s lives, despite the benefits
however, this change in western lifestyle also brings an increased rate of injuries.
Anterior cruciate ligament (ACL) ruptures are one of the most common injuries related to
sports. The ACL is involved in approximately two-thirds of all ligamentous injuries, which
make up about 40 % of all knee traumas. (1)
This also leads to an increase in ACL reconstruction surgery. Reconstruction is indicated in
patients who suffer from complex knee injuries (combination of ligament, meniscal and
chondral damages) or instability and meniscal lesions (in case of meniscal resection joint
instability increases). Likewise, patients who want to maintain their activity level and still
have athletic ambitions are considered for reconstruction. (2) These facts simultaneously
lead to an increase in additional ACL injuries after return-to-sport and therefore a higher
number of revisions. These present a particularly challenging situation for the surgeon as
they display higher complication rates than first-time reconstructions. (3) In these situations,
allografts may be a good alternative to the usually used autografts. Further muscle and tissue
damage due to tendon harvest could be avoided. In Central Europe, allografts are less
commonly used than in Anglo-American countries, similarly in primary ACL
reconstructions.
Studies comparing autografts and allografts have shown different results depending on study
design and number of patients. The majority show that autografts and allografts have no
differences in rupture rates and clinical outcomes. (4, 5) Some show that autografts display
an earlier functional recovery and lower rates of graft failure, at least compared to irradiated
allografts. (6-8) Young and active patients have the highest risk of requiring revisional
ACL47%
Complex6%
ACL + MCL12%
MCL29%
PCL4%
LCL2%
Ligament injuries
Ligament injury40%
Meniscus injury11%
Patella injury24%
Miscellaneous25%
Knee injuries
Figure 1: Knee injuries, adopted from (1) Figure 2: Ligament injuries, adopted from (1)
2
surgery. To improve allograft outcome in these cases there have been attempts to strengthen
the allogenic tissue using internal brace augmentation with a polyethylene tape which is
integrated seamlessly into the graft construct. (9) This technique was successfully used in
primary ACL repairs using the polyethylene bridging to maintain the ruptured ACL tissue.
(10)
To the best of our knowledge so far no one performed a study investigating if allografts with
additional internal bracing improve the outcome of patients compared to those using
allografts alone.
3
2 Theoretical Background
2.1 Anatomy of the knee joint The knee joint is the largest synovial joint in the human body. It allows a wide range of
motion and is composed of a complex construct of bones, muscles, soft tissue and cartilage.
(11)
2.1.1 Bones / Articulating Surfaces The knee joint is formed by three bones – the femur, tibia, and patella (the fibula is not
involved). The articulating surfaces are characterized by their incongruent shapes which
make the joint comparatively weak in a mechanical way. Therefore the stability depends on
the muscles and ligaments surrounding and strengthening the joint. (12, 13)
Figure 3: Bones of the knee joint (14)
4
Femur and tibia form the tibiofemoral joint. The proximal tibial surface (also tibial plateau)
slopes posteriorly 3 to 7° and its lateral and medial articular surfaces, which are slightly
concave, interact with the corresponding femoral condyles, which are almost completely
convex. The area between the articular surfaces of the tibia displays an eminence with medial
and lateral tubercles in the center. (14) This joint can be considered a trocho-ginglymus joint.
(16)
The second component of the knee joint is the patellofemoral joint, which is formed by the
posterior surface of the patella and the anterior surface of the femur. During flexion and
extension, the patella glides on the femoral surface, however, in full extension, only the
lowest patellar facets are in contact with the femur. (14)
2.1.2 Menisci The two menisci are C- or rather semilunar-shaped fibrocartilaginous discs that equalize the
and neutrophil recruitment. This is followed by a chronic phase in which fibroblasts
synthesize new extracellular matrix (tissue scar) and then a remodeling phase in which
collagen is produced and re-organized. Osteointegration between tendon and bone occurs in
six to 15 weeks after surgery and tight contact between bone and graft (for example achieved
by an interference screw) is crucial for graft integration. The process of the graft turning into
an adapted ligamentous structure appears to take place within the first three years following
reconstruction. (23)
The ACL graft develops no recognizable blood supply during the first two years of
implantation, which leads to the assumption that revascularization is not required for graft
stabilization and function, leaving synovial diffusion as the main nourishment source. (30)
However, in contrast, the periligamentous soft tissue is highly vascularized and covers the
graft. (30)
15
In summary, the success of graft integration is determined by the balance between resorption
of local blood clots, removal of cellular debris by the synovial fluid, collagen production and
growth factor expression from both, graft and host tissue. (23)
2.3 Risk Factors for ACL rupture Many genetic and lifestyle factors have been investigated with regards to a first time ACL
rupture, but only two relate to the risk of injury: gender and sport. Other risk factors such as
young age, meniscal and chondral injuries and tendon harvest are either consequential
because of other factors or not proven to have an impact. (31, 32)
2.3.1 Gender The risk of suffering an ACL injury in high-risk sports is three to six times greater for female
than for male athletes. (31, 32)
One reason for this may be the slightly different geometry seen in female knees. A decreased
femoral intercondylar notch width, decreased height of the posterior medial meniscus,
increased quadriceps angle and increased posterior tibial slope could predispose women for
ACL injuries. (32, 33)
Knee motion and loading is also a predicting factor concerning ACL injury. Landing in
inadequate flexion and increased valgus (“dynamic valgus”) and external rotation, as is often
seen in female athletes, leads to increased ACL strain and therefore higher risk of future
ACL ruptures. (31, 32)
Figure 16: Dynamic Valgus (30)
16
However, these movement biomechanics as well as lower-extremity muscle strength and
recruitment are possible to be positively adjusted applying neuromuscular training. 15
minutes of neuromuscular warm-up program twice a week significantly reduces ACL injury
rate by targeting core stability, balance, and proper knee alignment. (31, 34)
The ACL is an estrogen targeted tissue. (35) Collagen synthesis is reduced in the presence
of high estrogen levels, therefore the ligament matrix is affected. There is a protective
association between the use of oral contraceptives (OC) and the risk of sustaining an ACL
injury. However, prophylactic use of OCs to minimize injury risk in at-risk women is not
recommended until further studies have investigated the relationship between estrogen level
and ACL injuries. (35)
2.3.2 Sport ACL ruptures commonly occur during non-contact movements, usually while participating
in sports. An athlete’s risk of having a first-time ACL injury is influenced by level of
competition, gender, and type of sport. Especially knee demanding sports such as soccer,
volleyball, handball, judo etc., including stop-and-go and rotational movements during
flexion are associated with a higher injury risk. (36, 37)
2.4 Diagnostic Methods In case of an acute trauma or chronic complaints regarding the knee, there are several steps
needed to determine the right diagnosis. (2)
2.4.1 Anamnesis Asking about previous traumas or knee pathologies is essential to exclude differential
diagnoses and to distinguish acute from chronic complaints. Also, letting the patient explain
in which situations pain or instability occur, and what quality of pain is experienced, helps
gaining a lot of information before even examining the knee. Special attention should be
paid to activity level, type of sport practiced and current occupation. (2)
2.4.2 Physical Examination Diagnosing an ACL rupture based on a physical examination remains a challenge. There are
3 physical examination tests commonly used to evaluate the ACL, and a new one showing
promising results: the Lachman test, the pivot-shift test, the anterior drawer test and the
Lever sign test. (38)
17
Sensitivity Specificity
Lachman Test 81-86 % 81-94 % Pivot Shift Test 18-48 % 81-99 % Anterior Drawer Test 38-82 % 67-91 % Lever Sign Test 86-100 % 91 %
Table 2: Sensitivity and Specificity of ACL Tests (36)
2.4.2.1 Lachman Test The Lachman Test is the most valid test of the following to determine an ACL rupture. It
has a high sensitivity and specificity especially in acute injury cases and is not dependent in
other associated ligamentous or meniscal injuries being present. (39, 40)
The Lachman Test is performed by holding the knee between full extension and 15 degrees
of flexion. One hand is stabilizing the femur, while applying anterior pressure with the other
hand, holding the proximal tibia. The test is positive if an anterior translation of the tibia
with a “soft” end point is seen or felt. (40)
2.4.2.2 Pivot Shift Test Specificity of the Pivot Shift Test is very high (particularly under anesthesia), but sensitivity
rather poor. A positive Pivot Shift Test result is associated with a clinical “giving way”
symptomatology. (39, 40)
Figure 17: Lachman Test (picture taken by author)
Figure 18: Pivot Shift Test (pictures taken by author)
18
For the Pivot Shift Test, the examiner picks up the leg at the ankle and places the other hand
behind the fibula. Under a strong valgus force of the upper hand and an internal rotation of
the tibia, the knee is slowly flexed. If the ACL is torn, this position subluxates the tibia
anteriorly. At about 30 degrees of flexion the tibia suddenly reduces back to its normal
position due to tightening of the ITT. This reduction is seen and felt by patient and examiner
and indicates a positive test. (40)
2.4.2.3 Anterior Drawer Test The Anterior Drawer Test shows low sensitivity especially in acute settings. There are many
reasons for a possible false negative result:
- Due to hemarthrosis and reactive synovitis, knee flexion may be prevented.
- Joint pain may cause protective muscle action of the hamstrings which leads to an
alternate force.
- The posterior horn of the medial meniscus could be pressed against the posterior
margin of the medial femoral condyle and inhibits anterior translation of the tibia.
Also, false positive results are possible if a PCL insufficiency exists, which leads to a
posterior sagging of the tibia simulating a false neutral position. (39, 40)
For the Anterior Drawer Test the hip needs to be flexed to 45° and the knee to 90°. The
examiner sits on the patient’s foot with both hands around the proximal tibia, thumbs on the
tibial tuberosities. Then anterior force is applied. If increased tibial displacement (compared
to the other side) is seen, an ACL tear is likely.(40)
Figure 19: Anterior Drawer Test (picture taken by author)
19
2.4.2.4 Lever Sign Test The Lever Sign Test is a relatively new clinical test designed by Alessandro Lelli. The Lever
Sign Test is as sensitive as the three clinical tests presented before (2.4.2.1 – 2.4.2.3),
concerning chronic and total ACL tears. (41) But, different to the other common manual
tests, the Lever Sign Test also shows a high sensitivity regarding both acute and partial tears
of the ACL, which makes it a better alternative in these situations than the usually used
clinical tests.(41)
To perform the Lever Sign Test, a point of leverage, e.g. the examiners fist, is placed under
the supine patient’s calf and a downward force is applied on the quadriceps with the other
hand. If the ACL is intact, the patient’s heel will rise off the table, as seen in Figure 20 – a.
If the ACL is insufficient, the patient’s heel will remain on the examination table as seen in
Figure 20 – b. (41)
2.4.3 Radiology
2.4.3.1 Radiography Anterior-posterior (AP) and sagittal knee radiographs are easily available and obtained. They
are important to identify fractures or dislocations requiring emergent care. However, if only
an ACL rupture was sustained, the radiograph shows no pathologies. Nonetheless, it is an
important diagnostic tool to rule out some differential diagnosis. (42)
Figure 20: Lever Sign Test (39)
20
2.4.3.2 Magnetic Resonance Imaging (MRI) MRI is the only non-invasive diagnostic tool which can provide guaranteed certainty of an
ACL rupture and it can help to identify concomitant ligament, meniscal and/or cartilage
injuries. (42)
Figure 21: Frontal and sagittal radiograph of a 23-year old patient with recent ACL re-rupture, drill holes (white arrows) from previous ACL surgery can be seen (LKH Universitätsklinikum Graz)
Figure 22: Sagittal T2 weighted MRI of a 22-year old patient with recent ACL rupture (white arrow) (Diagnostikzentrum Graz für Computertomographie und Magnetresonanztomographie)
21
However, MRI is not only helpful with diagnosing an ACL tear, but also with verifying graft
healing after operative reconstruction. Graft volume combined with median signal intensity
of the graft, measured using MR-images, can predict clinical tests and also correlate with
common questionnaires used to analyze patient’s outcome. (43) These findings suggest, that
with the help of MRI, in combination with other follow-up methods, clinicians could better
determine the appropriate timing for patients to return to sport. (43)
2.5 Treatment There are various treatment options for ACL ruptures. The choice depends on type of injury,
patient factors, symptoms, and patient’s expectation. Some indications whether to pick a
conservative or surgical treatment are shown in Table 2. (2)
Conservative Management Surgical Treatment
• Contraindication for surgery
• Minimal knee instability
• No high activity ambitions
• Pre-existing arthrosis
• No concomitant injuries, isolated
ACL injury
• Complex concomitant injuries
(collateral ligament injuries,
meniscal injuries)
• Objective and subjective knee
instability (“giving-way”)
• Recurrent swelling
• Knee-demanding sports, activities Table 3: Indications for conservative and surgical treatment of ACL ruptures (2)
2.5.1 Conservative Management According to the current guidelines put out by the Association of the Scientific Medical
Societies in Germany (AWMF) (2), there are some individual aspects which point to
conservative management rather than surgical reconstruction. For instance, a nonsurgical
approach is suggested in patients who have other health issues making them not fit for an
operation, as well as patients who show minimal knee instability and have no high activity
ambitions. Also, pre-existing arthrosis and a lack of concomitant injuries endorses a
nonsurgical treatment. Either way, if conservative management is chosen, this does not mean
that the patient is left on their own. Muscle strengthening, physiotherapy, as well as the use
of walking aids in combination with increasing loads and clinical follow-up examinations
are essential. (2)
22
The views on conservative management of an ACL injury show broad variation, but if
patients are willing to lower their activity level, nonsurgical treatment can lead to
comparable clinical results to surgical reconstruction. (44) In moderately active patients (not
athletes), the clinical results between early or late surgically reconstructed knees or those
treated with rehabilitation alone, do not differ at all.(45, 46) The overall exception are
children and adolescents. Within this cohort, early surgical stabilization is preferred.
Nonoperative treatment in these patients results in a persistently unstable knee and therefore
further intra-articular damage. Also, the inability to return to previous activity levels,
especially in young patients, has a great impact in everyday-life. (47)
2.5.2 Surgical Treatment Surgical treatment is indicated if patients report “giving-way”-sensations in daily living or
if they want to resume knee-straining activities/sports such as football, basketball, volleyball,
tennis, and skiing. (48) Other indications can be seen in Table 2.
There is no guaranteed report of the right time for a surgical intervention after an ACL
rupture. (2) However, moderate evidence supports reconstruction within five months after
surgery, to avoid cartilage and meniscal damage. (42) The official guideline by the AWMF
favors surgery 48 hours within injury or after the acute inflammatory phase passes and ROM
is regained. (2) Early (<two weeks) and late (four to six weeks after injury) reconstruction
lead to a similar clinical and functional outcome. (49)
If surgery is not performed immediately, injury management should focus on the reduction
of hemarthrosis with rest, ice, compression, and elevation. Sometimes the administration of
nonsteroidal anti-inflammatory agents can be helpful. (48)
There is no age limitation for a surgical approach. Patients older than 40 years even achieve
comparable clinical outcomes to younger patients. (50)
ACL reconstruction is an arthroscopically performed procedure. The ruptured ACL is
replaced by a suitable graft, which is anatomically implanted in the original femoral and
tibial footprint area. (2) In children and adolescents traditional reconstruction techniques
may disrupt the growth plates, leading to leg-length discrepancies, axis disturbances or
physeal disruptions. In these cases, special procedures sparing or avoiding the physis must
be considered. (47)
23
2.5.3 Alternative Treatment Besides these two most common approaches to treat a ruptured ACL, there are also other
procedures being investigated at the moment.
Currently, there is no attempt to repair the torn ligament because isolated repair has met only
moderate success in history. (10) The main inhibitor of intrinsic ACL healing being the lack
of clot formation between the two torn ends of the ACL.(51) However, in most cases,
sufficient tissue remains for a repair to be considered. (10) Using an Internal Brace
Augmentation system to protect ACL repair may offer an advantage over previous ACL
repair techniques. (10)
On the other side, there has been growing interest on regenerative approaches to stimulate
ACL healing during procedures of reconstruction or repair, using platelet-rich plasma (PLP)
or stem cells. (52) Although some studies showed promising short-term outcomes, there is
still insufficient evidence to support the use of these biological agents systematically. (52,
53)
2.6 Grafts There are a lot of options when it comes to graft choice in ACL reconstruction. There is no
such thing as the ideal graft that fits every patient in every situation. Deciding on which graft
to use is always an individual patient (activity level, comorbidities, tissue availability, prior
surgeries, preference) and surgeon-dependent (experience, preference) choice. (54)
The ideal graft should have structural and biomechanical qualities similar to those of the
native ligament, allow secure fixation and rapid biologic incorporation, and limit donor site
morbidity. (54)
2.6.1 Autografts Autografts are most commonly used when it comes to primary ACL reconstructions.
However, there is no ‘gold standard’ graft in these procedures, as none has clearly shown a
faster return-to-sports than the other ones. (54) The individual advantages and disadvantages
of the available autograft choices can be seen in Table 3. (55)
Bone – Patellar Tendon-
Bone
+ bone-to-bone
healing in both
tunnels
- risk of anterior
kneeling pain
- invasive, large
incision
24
+ comparable stiffness
to native ACL
- risk of patellar
fracture
- fixed length
- weaker than native
ACL
Hamstring Tendon + easy to harvest
+ cosmetics
+ minimal donor site
morbidity
+ comparable strength
to native ACL
- soft tissue healing
- unpredictable graft
size
- not for athletes who
rely on their
hamstring muscles
- less stiffness than
native ACL
Quadriceps Tendon + large graft
+ option of a one-sided
bone block
- invasive, large
incision
- risk of patellar
fracture Table 4: Advantages and disadvantages of available autografts (53)
2.6.2 Allografts Another option besides autologous grafts are allografts. At first mostly used in revision or
multiple ligament rupture cases, primary use of allografts is getting more common.
Particularly when the native tissue is insufficient for repair or donor site morbidity presents
a problem, allografts are a suitable choice. (56)
Regarding the clinical outcome of allograft in comparison to reconstruction with autografts,
there is no clear opinion. A lot of studies show poorer clinical outcome and higher failure
and revision rates regarding allografts, but mostly in irradiated grafts. (57, 58) When
comparing autografts and non-irradiated allografts there is no significant difference in
results. (59)
The most often mentioned disadvantage of allografts is the commonly known inferior
remodeling and healing process. Autografts show a more advanced remodeling progress at
early stages of recovery than allografts. However, after one year both groups return to an
ACL-similar structure. (60) Despite the disadvantages, there are also a lot of positive aspects
regarding allograft use, which can be found in Table 4. (56)
25
Advantages and disadvantages of allografts
+ faster postoperative recovery
+ less postoperative pain
+ no graft harvest needed shorter surgery
time
+ no donor site morbidity
+ length and diameter available as needed
- lower stability rate
- higher graft failure rate
- slower graft incorporation
- concerns of disease transmission
Table 5: Advantages and disadvantages of allografts (54)
2.6.3 Synthetic Grafts Artificial grafts have long been under consideration as they represent a type of graft which
is easily available and would simplify the surgery as there is no preparation time involved
as in allografts or even graft harvesting as in autografts. However, most of them have showed
high failure rates in the past. (61) The new generation synthetic ‘Ligament Advanced
Reinforcement System’ (LARS) has gained more popularity than its predecessors and
showed comparable complication rates to traditional surgical techniques in short-term follow
up. (62) Nevertheless, first long-term results indicate that the LARS system should not be
considered as a potential graft for ACL reconstruction in a primary setting, because of high
failure rates and poor patient satisfaction. (63)
2.7 Complications A list of general and ACL-Reconstruction-specific complications associated with ACL
reconstruction can be found in Table 6. (64)
Complications associated with ACL reconstruction
General Complications
Vascular Damage Rare
Nerve Damage Occurs in 8.2% of arthroscopic knee
surgeries (64)
Infection Occurs in 0.8% of ACL reconstructions
(64)
26
Thrombosis and Embolism Occurs in 1.5-17.9% of arthroscopic knee
surgeries without thromboembolic
prophylaxis (64)
Osteoarthritis See 2.7.1
ACL-Reconstruction-Specific Complications
Graft Damage Not reported
Wrong Drill Hole Placement Not reported, leads to Graft Failure
Graft Failure See 2.7.2 Table 6: Complications associated with ACL reconstruction (64)
The general complications mentioned in Table 6 occur in every arthroscopic knee surgery.
Vascular damages can be avoided by properly flexing the knee while drilling the femoral
and tibial tunnels to protect the popliteal vessels. Nerve damages are one of the most
common intraoperative complications. They occur mostly during graft harvest and
arthroscopic portal incisions and result in paresthesia and dysesthesia. However, the sensory
deficit most commonly regresses a short time after the procedure. Infections occur only in
rare cases. Additional procedures such as meniscal-resection or sutures increase the risk of
intraarticular infections, as well as previous knee surgeries. An infection occurs most
commonly 3-5 days after surgery and should be treated with arthroscopic rinses,
synovectomy, debridement and intra venous antibiotics. To prevent postoperative
thrombosis and embolism, a prophylaxis using low molecular weight heparin should be
administered until full loading. (64)
An ACL reconstruction specific complication is graft damage. It occurs mostly during graft
harvest or graft fixation. The preparation and harvest of the hamstring-graft showed to be
more complicated and riskier than the patellar-tendon graft. However, harvesting of the
patellar tendon with a proximal and distal bone block can, in rare cases, lead to patella
fracture. Another cause for complications can be the drill hole placement. Wrong placement
of the femoral drill hole is considered the most common cause for reconstruction failure. In
most cases the drill hole is placed more anterior then it should, leading to graft laxity. (64)
2.7.1 Osteoarthritis (OA) OA in injured joints is caused by pathogenic processes initiated at the time of injury, and
long-term changes in biomechanical joint loading. (65) At 10 to 20 years after diagnosis,
about 50% of those with a diagnosed ACL tear have OA with associated pain and functional
impairment. (65) ACL injury predisposes to OA, while ACL reconstruction surgery reduces
the risk of developing degenerative changes. (66) The relative risk (RR) of developing OA
27
in nonoperatively treated ACL injuries is significantly higher (4.98) compared with those
treated with reconstruction (3.62). (66) However, even after reconstruction surgery, patients
with ACL injuries in the past show a three-fold increased prevalence of OA compared with
the contralateral healthy knee. (67)
2.7.2 Graft Failure Graft failure is a rare, but dreaded complication after ACL reconstruction. Estimated revision
rates vary from three to nine percent depending on source and follow-up. (68-70)
There are many possible reasons for an ACL re-tear after reconstruction. The graft may fail
as a result of traumatic overload, poor surgical technique, untreated concurrent knee injuries,
or poor biological incorporation of the graft. (69) Possible predictors of revision surgery are
young age at time of reconstruction and competitive activity level, especially in soccer
players. (70) There are no associations regarding sex, height, weight, or body mass index.
(71)
2.8 Revision Up to 20% of patients experience complications like knee laxity and/or instability during
athletic activities or daily life after primary reconstruction due to graft failure. (72) Revision
surgery is performed in order to stabilize the knee joint, prevent further cartilage and menisci
damage, and allow the patient to resume normal daily and/or sports activities. (72)
Revision surgery poses several diagnostic and technical challenges compared to primary
reconstructions. Due to the complexity of this procedure, preoperative planning is essential.
It begins with determining the cause of failure for the primary reconstruction. Furthermore,
a thorough history regarding the initial surgery, associated injuries, used graft type, fixation
method, as well as other prior procedures performed are necessary to obtain. (73)
Widening of the tibial and femoral tunnels presents a substantial obstacle during revision
surgery because of the bone loss and poor graft fixation leading to delayed graft
incorporation and decreased stability. There are many mechanical and biologic factors
responsible for tunnel widening, including graft position, fixation method, graft type, graft
donor, synovial fluid, and implant material and preparation. (74) Sometimes, a two-stage
procedure with initial tunnel bone grafting followed by ACL reconstruction four to six
months later is necessary. (73) Another solution would be the use of an allograft with large
bone block, which can be constructed and tailored to the specific deficit. (74) Radiography,
28
CT, and MRI can be used to determine the extent of widening, which should be about 10
Millimeters in diameter normally, but often exceeds 15 Millimeters. (74)
Another unique problem in revision reconstruction is preexisting hardware. Biodegradable
hardware is prone to fragmentation and cannot be removed easily. Therefore, it should be
left in place. In contrast, metal interference screws must be removed when interfering with
proper tunnel placement. (73)
The outcome of revision reconstructions is worse compared with primary reconstruction.
The failure rate is nearly three to four times higher. (3) Return-To-Sport (RTS) rates after
revision are similar to those after primary reconstruction in individual patients, but still lower
than those of patients who did not need revision surgery in the first place. (75) Patients need
to know, that a return to their previous level of performance before their first ACL
reconstruction cannot be expected. (73)
2.9 Rehabilitation Numerous factors have an impact on an optimum return to function after ACL reconstructive
surgery, one of them being the impact of external and internal forces over the course of the
postsurgical period. Precisely, the degree of joint force that rehabilitation exercises produce,
the nature of performed exercises in terms of intensity, mode, frequency, and duration; and
their impact on knee joint proprioception are very important. One cause for graft failure may
involve overloading of the reconstructed knee as a result of inappropriate dosage or
performance of various exercises. (76)
Movements applied to the knee joint postoperatively extending 30° of knee flexion increase
joint swelling, but if performed in the final degrees of extension, there is a noted decrease in
quadriceps inhibition, as well as an improved healing rate. (76)
Appropriate initiation of non-weightbearing exercises designed to reduce knee extensor
muscle atrophy is the primary goal of a lot of ACL rehabilitation programs. However,
anatomical research has shown that when the knee extensors contract, they can cause anterior
tibial displacement, especially if performed in an ‘open’ kinetic chain mode. When
performed in a ‘closed’ kinetic chain mode ACL stress is minimized and additionally, more
specific and sensory feedback is stimulated. (76)
The quantity of exercises an individual performs in a given period after ACL reconstruction
surgery similarly impacts recovery. For example, even low workload exercises can increase
the anterior laxity of both normal and ACL reconstructed knees.
29
On the other side, an inappropriate exercise dosage that results in muscle atrophy may not
only lead to knee joint instability, it also may prevent appropriate healing of the newly
constructed graft. (76)
One important factor of rehabilitation after ACL reconstruction is RTS. A return to the
preinjury level of activity is commonly assumed to take between 6 and 12 months. However,
only one third of active patients make it by this time. After two years, two out of three
patients return to their preinjury level sport. This suggests that some patients simply need
more time to recover than initially suggested. (77)
Unlike previously expected, RTS does not depend exclusively on physical function, but is
multifactorial. A lot of psychological factors like fear of reinjury or pain, recovery
expectations, and the feeling of uncontrollability during sports predict RTS outcomes. Male
and young patients are more likely to return to their previous level of sport than older patients
and women. (77)
The second important part of rehabilitation presents the Quality of Life (QOL) level after
surgery. Measured with the Short Form-36 (SF-36) ACL reconstruction resulted in a
relatively high gain of quality-adjusted life years. In the physical component summary (PCS)
score large improvements were noted at two years and maintained at six years after ACL
reconstruction, showing that physical benefits are durable throughout many years. The
mental component summary (MCS) score, as well as the general health subscale are both
well above population norm in patients undergoing ACL reconstruction and do not change
dramatically over time. (78)
3 Material and Methods
3.1 Hypothesis of the Study The hypothesis of this study was that the clinical outcome of patients with internal brace
(IB) augmentation in ACL revision cases is better than without, because of improved healing
conditions. Furthermore, we wanted to evaluate the difference in QOL and RTS.
Therefore, the study objectives were:
• Visual Analog Scale (VAS) for Pain in patients treated without and with IB
augmentation
• Knee specific clinical scores in patients treated without and with IB augmentation
• QOL in patients treated without and with IB augmentation
• RTS in patients treated without and with IB augmentation
30
3.2 Study Population
3.2.1 Inclusion Criteria All patients (n=18) who underwent ACL revision reconstruction while this study took place
at the University Hospital of Graz (Austria) and who matched following criteria were
included in the study:
• MRI verified re-tear of the ACL and
• Clinical and patient-reported instability of the knee joint and
• Signed informed consent
Table 7 gives an overview of the patients’ characteristics of the total study population.
Gender Total Without IB With IB
Patients (n)
All 18 10 8
Male 15 10 5
Female 3 0 3
Age (years, mean ± SD)
All 29.4 ± 7.8 28.2 ± 7.7 30.9 ± 8.3
Male 28.6 ± 7.4 28.2 ± 7.7 29.4 ± 7.6
Female 33.3 ± 10.5 / 33.3 ± 10.5
BMI (mean ± SD)
All 24.83 ± 2.0 25.1 ± 1.8 23.3 ± 1.8
Male 24.5 ± 2.0 25.1 ± 1.8 23.3 ± 1.9
Female 23.1 ± 2.0 / 23.1 ± 2.0 Table 7: Total patient population, total group without IB and total group with IB, SD= standard deviation
3.2.2 Exclusion Criteria Patients were excluded if they:
• suffered from an advanced stage of OA
• had an ongoing infection
• had cancer
• suffered from any immunosuppressant disease
• had a diagnosed neuromuscular disease
• suffered from a psychiatric disease, which made them unfit to consent
• had a writing and/or reading disability
• could not speak German or English and there was no interpreter available
31
3.3 Study Design
3.3.1 General Information This study was designed as a prospective, randomized pilot study starting on the 14th
February, 2017 (date of ethic votum). Various questionnaires, physical examination and
imaging evaluations at different study timepoints were planned (Table 8). We collected
general information using a self-designed Case Report Form (CRF). The data collection was
performed by the operators of the survey.
Before
Surgery
After 6
weeks
After 12
weeks
After 6
months
After 13
months
Clinical
Examination X X X X X
VAS of Pain X X X X X
IKDC X X X X X
KOOS X X X X X
Lysholm Knee
Scoring Scale X X X X X
TAS X X X X X
SF-36 X X X X X
Radiography X X X X X
MR-Imaging X X X Table 8: Follow-Up Time and Performed Evaluations
The patients were blinded and randomly categorized into two groups (with and without IB
augmentation), The surgeon and the survey staff were unblended. The study was planned as
a single-surgeon study.
30 patients have been planned to be included, 15 in each group, over the course of three
years. In this diploma thesis the patients included until 31st January, 2019 and their
preliminary results are analyzed.
3.3.2 Ethics All participants of the study had to sign an informed consent before inclusion, confirming
their approval of usage of their data. The informed consent can be found in the appendix of
this thesis (see chapter: 8. Appendix - Informed Consent, Case Report Form, Questionnaire).
32
The ethics committee of the medical university of Graz authorized this study with the project
number 29-136 ex 16/17.
3.3.3 Data Protection For this survey, protected medical information was needed: patients’ names, dates of birth,
phone numbers, addresses, operation dates, and other personal information. This data is
available in the hospital information system openMEDOCS (KAGES group).
The collected data is registered in a Microsoft Excel datasheet. The datasheet is password
protected, only members of the study staff have access to it. For the statistical analysis and
publication, patient sensitive data is anonymized.
3.3.4 Revision ACL Reconstruction Surgery We used a modified all-inside technique for our revision ACL reconstruction. (79) In
primary ACL repairs this technique shows the advantage of lower bone loss and
determination of tunnel length even before drilling. Therefore, length of the graft must not
be too long, because this would lead to increased laxity of the graft construct. (79, 80) The
femoral tunnel is drilled approximately 2 cm proximal and 1 cm anterior of the epicondylus
lateralis, stopping 1 cm before reaching the cortex. The tibial tunnel is drilled starting from
the ACL insertion point up until 40 mm before reaching the cortex. With a shuttle-thread the
graft is inserted femorally through the anteromedial portal, and then tibially. In a nearly-
extension position the graft is then tightened. (79, 81) In revision cases the tibial tunnel is
drilled from the outside and the emerging bone defect is preoperatively measured and filled
with the achilles tendon bone block. In 8 patients (44%) an additional tibial screw was used
IB, showed less pain and improved function two years postoperatively. However, due to the
lack of a control group it is not possible to say if the results of a possible reconstruction
surgery would have been better. (85) Jonkergouw et al. (87) conducted a study comparing
ACL repair with IB and without IB. They found no significant differences in outcomes
between the two groups and no failures related to the hardware. There were also no clinical
benefits, but they stated that the use of an IB could possibly be beneficial and larger cohorts
are needed to clearly answer this question. (87) In an animal study Seitz et al. (88)
demonstrated, that an augmented repair led to superior biomechanical results 16 weeks
postoperatively compared to a primary repair. (88) IB was also used in pediatric patients as
a temporary augmentation when performing an ACL repair. Smith et al. (86) used it in three
children with an ACL rupture, and removed the IB after 3 months. They reported complete
healing and stability in all three patients two years postoperatively. (86)
To our knowledge no study examining the effects of an IB augmentation in allografts used
in a revision ACL reconstruction was yet conducted. Our results show overall satisfactory
outcomes in both groups, with no relevant clinical difference. We used Achilles tendons in
both groups. The advantage of using the Achilles tendon is the availability of a bone block.
Compared to other allografts the failure rate is lower (101), it shows lower displacement,
and higher stiffness. (102) Further, the use of a bone block made a two-time approach with
56
previous bone building redundant, and the osseous fixation of the graft in the femoral tunnel
increased the overall stability of the graft. (103)
The use of an additional IB did not interfere with surgery time, being 115.9 minutes without
IB and 117.6 minutes with IB. The length of hospital stay did also not differ between the
two groups, being 5 days without IB and 5.5 days with IB. So, the use of an IB did not
lengthen surgery time or shorten hospital stay.
The lower IKDC and SF-36 subscale score for Physical Functioning in the group with IB
compared to the group without IB could be attributed to over-constriction of the graft. Smith
et al. (9) already described this phenomenon, which ultimately leads to loss of motion if the
IB is fixed too tight. (9) However, ROM in our study population was 139.5 degrees without
IB and 135.7 degrees with IB, and no patient showed relevant flexion or extension deficits
in the physical examination. No patient-reported signs of constriction of the affected knee.
The lower IKDC result in the IB group could, therefore, be just coincidental and disappear
with longer follow-up.
Our results show a mean Lysholm score of 94 without IB and 67 with IB. In current
literature, Lysholm scores ranged from 89 to 91 in autografts (92, 93) and 84.7 to 99 in
allografts (91). Respectively, these outcomes were reported after a minimum follow-up of
2-years in much larger cohorts. Although the results of the IB group seem lower, they were
not statistically significant and are likely to increase over time.
Similar results can be seen regarding the Tegner Activity Scale, ranging from 4.8 to 7.9 in
autografts and from 4.5 to 7.8 in allografts published in the meta-analysis of Wang et al.
(93). The mean TAS scores in our study were 4 in the group without IB and 3 in the group
with IB. The lower results can be easily explained, as the patients are not capable to return
to sport after just three months.
The IKDC ranges from 77.2 to 90 in autografts and 73.7 to 90 in allografts as described by
Wang et al. (93), compared to 74.7 without IB and 63.9 with IB in our study population. As
the IKDC mainly focuses on symptoms, function and sports activities (83), the low scores
after 12 weeks are not surprising. Respectively, all of our results evaluated after three months
are likely to increase over time. (see 4.5 Case Presentation).
The overall good SF-36 results in both groups could be explained by our study group being
generally healthier and younger than the compared US norm population. Considering that
the majority of ACL injuries occur to a young athletic population, and the SF-36 addresses
topics such as tiredness, sadness, and nervousness, which are more often found in a less
57
active population, these results should be viewed with caution and only be compared to
similar cohorts. (104)
5.1 Limitations and Strengths One drawback of our study is the short follow-up period of three months. The 13-month
follow-up of all included patients is supposed to deliver more detailed results. Another
drawback is the relatively small size of the study population, however this is due to the study
design of a pilot study. After sample size calculation based on our results further adequately
powered RCT will be planned. Still, based on the limited data regarding internal bracing in
current literature and lack of similar studies, our study cohort is still one of the largest.
Lifestyle factors have not been taken into consideration when forming the two study groups,
one of them being smoking habits. There was no statistically significant difference between
the two groups regarding packyears, but smoking itself interferes with healing processes,
making the study results impressionable. The activity level was also not considered during
the inclusion of the patients. Even though the difference in activity level was not statistically
significant, and there were no professional athletes included, the inter-patient differences
could affect the results.
The most prominent strength of this study is that it is the first prospective, randomized, and
blinded study regarding the use of internal braces in allografts in revision cases in current
literature. There are just a few other prospective, randomized, and blinded studies regarding
the use of allografts in revision cases, and none regarding the use of internal bracing in
allografts. Another strength is that we used the same allograft with the same processing in
all patients. Most other studies used differently processed allografts, thus making the data
hard to compare. Also, the relatively similar population in the two compared groups
regarding age and BMI strengthens the informative value of the study.
5.2 Conclusion This study provides the first HRQOL data and clinical results in patients treated with IB in
revision ACL reconstructions using allografts.
Revision ACL reconstruction using allografts with, as well as without IB, show good results
in short-term follow-up. There were no graft failures after 12 weeks in any of the groups.
The advantage of IB regarding outcome and failure rate could not yet be proven in this short
period of time. Prospective studies with larger cohorts and longer follow-up are needed.
58
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7 Appendix – Informed Consent, Case Report Form, Questionnaires