Dr Quang Dao

Information for orthopaedic surgeons

Some patients still report rotatory instability following well performed anterior cruciate ligament reconstructions. This may be due to neglected concomitant injuries to the anterolateral structures of the knee. 

In the last two decades there have been much research to provide anatomical and biomechanical data about these anterolateral structures. Surgical techniques have been developed to provide additional knee rotational stability.

The two main parts of the anterolateral aspect of the knee which provide rotational stability are the anterolateral ligament (ALL) and the iliotibial tract (ITT).

Anterolateral Ligament

Steven Claes (J Anat 2013) identified the ALL in 40 of 41 cadaveric knees. He pointed out that from its origin at the lateral femoral epicondyle (LFE), the anterolateral ligament (ALL) runs superficial to the lateral collateral ligament (LCL).  It then bifurcates, with one attachment to the lateral meniscus and the other into the proximal tibia about halfway between Gerdy’s tubercle and the fibular head.

The lateral inferior genicular artery (LIGA) runs between the lateral meniscus and the ALL. 

Helito et al (OJSM 2015) identified to femoral origin of the ALL is at the centre of the lateral femoral epicondyle and slightly anterior and distal to the FCL attachment point. It bifurcates and attach to the lateral meniscus and lateral tibial plateau.

In his dissection study, Sonnery-Cottet showed that the ALL is a thin structure and it fans out to its tibial insetion.

The tibial attachment of the ALL is consistent reported as between Gerdy’s tubercle and the fibular head. However, different authors have reported slight variations in its femoral origin. It is usually described as either anterior and distal to the femoral attachment point of the fibular collateral ligament (FCL) (Claes,Vincent, Caterine, Helito) or slightly proximal and posterior to it (Kennedy, Caterine, Spencer, Dodds, Kittl).

Spencer et al (AJSM 2015) showed in their dissection study that the ALL is superficial to the FCL. It originates from just proximal and posterior to the FCL origin. They found that the ALL assists the ACL in anterolateral rotation. 

Kennedy et al (AJSM 2015) examined 15 nonpaired cadaveric knees. The ALL was identified in all the specimens. Its point of origin is proximal and posterior to the FCL femoral attachment. Its tibial attachment was between the centre of Gerdy’s tubercle and the anterior margin of the fibular head. 

Anterolateral Ligament Foetal Cadaveric Dissection

There is evidence that the ALL is present in foetal cadaver dissection and histologic examination.

Anterolateral Ligament Histology

Claes et al have shown that the ALL is biomechanically and histologically different to the anterolateral joint capsule of the knee. He believes that it is not just a thickening of the capsule but rather a distinct ligament similar to the inferior glenohumeral ligament (IGHL) of the shoulder.

Anterolateral Ligament X-rays and MRI

Kennedy et al (AJSM 2015) provided radiographic landmarks of the ALL as well as attachment points of the other lateral structures.

The ALL can be seen on MRI scans. However, for best visualisation,  the slice thickness should be less than 1.5mm with no spaces in between. Proton density (PD) is the best sequence.

Claes found almost 80% of ACL injured knees have MRI findings of an injured ALL. Most of these occur at the tibial insertion or mid-substance.

Helito et al (KSSTA 2017) found ALL injuries in 39.5% of MRI scans in knees with ACL ruptures. Only 6% had a Segond fracture. This indicates that only a small proportion of ALL injuries will have a bony avulsion.

Anterolateral Ligament Biomechanics

Claes showed that additional cutting of the ALL after the ACL has been transected, increases the amount of tibial internal rotation. It also produces a high grade pivot shift test. Isolated sectioning of the ALL also increases the tibial internal rotation but produces a less explosive pivot shift.

Noyes et al (JBJS 2017) used a robotic simulator on 14 cadaveric knees. Their sequential sectioning study showed that the ALL and Iliotibial band (ITB) are secondary restraints to tibial internal rotation. Cutting these 2 structures increase the amount of internal rotation after the ACL has been sectioned.  In 8 of their 14 specimens, cutting of these 2 structures in addition to the ACL increases the lateral compartment translation to beyond 20mm, which is a value necessary for a grade 3+ pivot shift. Also note that a grade 3+ pivot shift test is absent in 4 cases even after cutting of all 3 structures.

Kennedy et al (AJSM 2015) recorded the mean maximum load to failure of the ALL was 175N. Six of the cases demonstrated avulsing the tibial attachment, representing a Segond fracture.

Iliotibial Tract

Kittl et al (AJSM 2015) reported that the deep fibres of the iliotibial tract (ITT) provided the most restraint to internal tibial rotation at low knee flexion angles. The superficial fibres provided more restraints to internal rotation at higher flexion angles. Overall the entire ITT is most important at 0-90 degrees flexion. In their dissection and robotic simulation study, the anterolateral ligament only had a minor role in restraining tibial internal rotation.

Lording et al (KSSTA 2017) have shown in their cadaveric dissection study that cutting the superficial and deep parts of the iliotibial tract increases tibial anterior translation, adduction and internal rotation.

Sonnery-Cottet et al (AJSM 2016) performed sequential sectioning of the ACL, ALL and ITB in one knee and then in the reverse order in the contralateral knee. Sectioning of the ALL after sectioning the ACL or ITB, increases tibial internal rotation.

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Dr Quang Dao

Information for orthopaedic surgeons (ACL Anatomy)

The anterior cruciate ligament (ACL) is composed of collagen fibres that connects the tibia to the femur. Currently there are two popular theories to describe the anatomy of the ACL. They are the Double Bundle Theory and the Ribbon Theory. 

The Double Bundle Theory

The anterior cruciate ligament (ACL) is composed of two bundles – the anteromedial (AM) bundle and the posterolateral (PL) bundle. Their names are based on their tibial insertion points. The size of each bundle varies in different individuals. The Double Bundle Theory has been popularised by Dr Freddie Fu. 

The ACL is formed at about 8 weeks of gestation. The distinction of two bundles can be seen at 16 weeks gestation. The two bundles are separated by a septum. The foetal ACL is cellular and vascular.

The ACL is an intra-articular but extrasynovial structure. It is composed of dense connective tissues, mostly Type I collagen and some Type III collagen. The adult ACL is less cellular. The two bundles are separated by a vascular septum.

The ACL receives its blood supply from a synovial plexus which covers the ligament. The proximal contribution to the plexus is from the middle genicular artery. The distal contribution is from the medial and lateral genicular arteries.

Nerve fibres from the tibial nerve can be found within the ACL and in the perivascular synovium. They function in vasomotor, transmit pain impulses and act as mechanicoreceptors for proprioception.

The ACL transitions from ligament in its midsubstance, to cartilage, to mineralised cartilage and then bone at both femoral and tibial insertions. This transition allows the ACL to dissipate the forces at its insertion points.

The intra-articular length of the ACL is between 22-41mm (average 32mm). The midsubstance cross sectional area is 44mm2. It reaches about 3 times at its femoral origin and tibial insertion.

The femoral origin occupies the medial wall of the lateral femoral condyle. It is bordered anteriorly by the lateral intercondylar ridge (resident’s ridge) and posteriorly by the articular cartilage of the lateral femoral condyle. It measures 18mm in length and 11mm in width. The AM bundle is located in the proximal half and the PL in the distal half (with the knee in the extended position). The 2 bundles are separated by the bifurcate ridge. During arthroscopy with the knee at 90 degrees of flexion, the PL bundle is shallow to the bifurcate ridge and the AM bundle is deep to this ridge. The lateral intercondylar ridge can be identified arthroscopically in 88% of ACL injured knees and the lateral bifurcate ridge in 48%. 

The tibial insertion is between the medial and lateral tibial spines. The medial-lateral diameter is 9-13mm (average 11mm). The anteroposterior diameter is 14-20mm (average 17mm). The AM bundle is located more anterior and medial. The PL bundle is located more posterior and lateral. The PL bundle is very close to the posterior root of the lateral meniscus.

As the knee is in extension, the femoral insertion areas of the 2 bundles are vertical to each other. In this knee position the bundles run parallel to each other.

When the knee is flexed to 90 degrees, the femoral insertion sites move so that they are more horizontal with the AM bundle insertion portion more deep and the PL bundle more shallow. This relative change in femoral insertion locations causes the 2 bundles cross.

The Ribbon Theory

Robert Smigielski and his group popularised the Ribbon theory describing the ACL as a flat “ribbon-like” structure. Other authors have also reported similar findings.

They dissected 111 fresh frozen cadaver knees, analysed them using photography, videography, CT scans, MRI scans and histology techniques. They found that the midsubstance of the ACL was flat like a ribbon. 

The direct fibres of the ACL insert just posterior to the lateral intercondylar ridge. This ridge is an anterior extension of the posterior femoral cortex. The indirect fibres expand and insert posteriorly towards the articular cartilage of the posterior aspect of the lateral femoral condyle.

Smigielski outlined the femoral ACL insertion area with ball bearings and radio-opaque sutures. Radiographs confirm that the direct fibres insertion points onto the lateral intercondylar ridge is a direct extension of the posterior femoral cortex.

Their dissections could not identify a separation of the ACL into 2 bundles.

They postulate that this double bundle appearance is due to the twisting of the ribbon structure as it spans from the femoral origin to its tibial insertion.

Their measurements showed 

• Mean width 2 mm from femoral insertion: 16.0 mm (12.7–18.1)
• Mean thickness 2 mm from femoral insertion: 3.54 mm (2–4.8)
• Mean cross-sectional area 2 mm from femoral insertion: 56.6 mm²
• Mean width at midsubstance of ACL: 11.4 mm (9.8–13.8).
• Mean thickness at midsubstance of ACL: 3.4 mm (1.8–3.9).
• Mean cross-sectional area at midsubstance of ACL: 39.8 mm²

Histologic examination demontrates that the fibres are oriented obliquely to the bone surface. The bone is denser at the direct fibres insertion points (thick arrows). The indirect fibres take up a larger area towards the articular cartilage of the posterior lateral femoral condyle (thin arrows).

In another dissection study of 20 cadaver knees, Rainer Siebold et al confirmed the ribbon-like midsubstance structure of the ACL. They also described the C-shaped tibial insertion footprint. The tibial insertion runs along the medial tibial spine to the anterior border of the anterior root lateral meniscus. The centre of the “C” is the bony insertion of the anterior root lateral meniscus. In some cases, the fibres of the ACL and meniscus blend in. In other cases, they are separate.

The most anterior part of the C is 9.3mm in the mediolateral direction. The central portion of the C, along the medial tibial spine is 11.4mm in the anteroposterior direction.

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Dr Quang Dao

Discoid meniscus is a congenital variant of the meniscus which can affect its size, shape and stability. Most often, it affects the lateral meniscus.

Incidence

It is a frequent finding in the Asian population with an incidence of up to 20%. In Caucasians, the incidence is 3-5%. It is slightly more common in females.

Pathoanatomy

A discoid meniscus is thicker and have a poorer blood supply than the normal meniscus. It is also larger and covers more of the underlying tibial plateausurface. This exposes it to more load between the femoral condyle and tibial plateau. Electron microscopy have demonstrated that a discoid meniscus hasdecreased number of collagen fibres and which are also disorganised. These factors make a discoid meniscus more fragile, easier to tear and less likely to heal following repairs.

Classification

There are 3 types of discoid menisci according to the Watanabe classificationwhich is based on arthroscopic findings.

Type I – complete and stable. The meniscus is very thick and appears like a block of tissue. It covers the entire tibial plateau. It is stable to probing during surgery.

Type II – partial and stable. The meniscus covers up to 80% of the tibial plateau. It is not as thick as type I. It is also stable to probing.

Type III – unstable Wrisberg variant. It is unstable when probed. This instability is due to the lack of the normal meniscotibial ligaments. These are fibres which normally attach the meniscus to the rim of the tibial plateau and thus provides stability. These type III menisci have the Wrisberg ligament present. This is a band of tissue connecting the back part of the meniscus to the medial femoral condyle.

Presentation

The classic presentation of a discoid meniscus is bulging of the joint line in flexion, clunking or popping of the knee in extension (snapping knee syndrome) and an inability to fully extend the knee. Pain, swelling and mechanical symptoms such as painful clicking, locking and giving way can occur when there is a tear. Discoid menisci can tear with minimal trauma, unlike its normal counterpart which often tears with sporting injuries.

https://www.youtube.com/watch?v=bIo7mKW5ZZk

https://www.youtube.com/watch?v=f_Ihf4RmZ4k

https://www.youtube.com/watch?v=uxvd3O7_5qg

Investigation

Radiographs are often normal. Sometimes with the type I complete discoid meniscus, x-rays may demonstrate a widened joint space, squaring of the femoral condyle, cupping of the tibial plateau and hypoplastic lateral tibial spine.
MRI is the preferred investigation tool for discoid menisci. On the coronal images, the meniscus is wider than 15mm or greater than 20% of the entire tibial plateau. On three consecutive 5mm thick sagittal images, there is continuity between the anterior and posterior horns (bowtie sign).

Arthroscopic Findings

https://www.youtube.com/watch?v=c0QJcaUFJzQ

https://www.youtube.com/watch?v=i_0Ne6QPvZI

https://www.youtube.com/watch?v=lBzUykD9Ma4

https://www.youtube.com/watch?v=Pv1JnuE-G-E

Treatment

Conservative management with observation is indicated for asymptomatic discoid menisci. This approach is still appropriate even for those knees which are clunking but has minimal pain and absence of locking or giving way. It is advisable that these patients avoid high impact activities to reduce the risk of meniscal tears.

Symptomatic knees can be treated surgically by saucerisation, repair and stabilisation.

Saucerisation is reshaping of the discoid meniscus. Usually the excess central portion is excised, leaving a peripheral rim of 6-8mm. Often the torn part is located in the central portion and it gets removed in the process of saucerisation. If there is still a tear in the remaining peripheral portion, it can be repaired. In the unstable discoid meniscus, this remaining peripheral portion is sutured to the capsule.

It has been reported that meniscal resection in adolescents causes three times the rate of radiographic changes consistent with osteoarthritis after 30 years. Therefore, complete resection of the meniscus is avoided if possible.

https://www.youtube.com/watch?v=1ReBffds8p4

https://www.youtube.com/watch?v=orB-9rptXE0

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Dr. Quang Dao

Introduction

Intra-substance tears of the anterior cruciate ligament (ACL) in children were rarely reported in the past. Historically, most ACL injuries involved an avulsion of the tibialeminence at the site of the tibial ACL insertion.

However , mid-substance ACL injuries in children and adolescents are becoming more common. This is due to increased participation in competitive sports at a much younger age, combined with the higher pressure placed on these young athletes to excel. With better knowledge of the condition and improved diagnostic tools, clinicians are now more accurately diagnosing this injury.

Traditionally, paediatric ACL injuries have been managed non-operatively due to the fear of damage to the open physis (growth plate). However, with improved technical understanding, more reconstructive surgeries have been performed to prevent further meniscal and chondral damage.

Anatomy

The Anterior Cruciate Ligament (ACL) is a band of dense connective tissue connecting the distal femur and proximal tibia.  It is like a rope or ribbon with one end attached to the medial surface of the lateral femoral condyle and the other end, to the central part of the tibial plateau. It is one of the main stabilisers of the knee.  It prevents anterior translation of the tibia on the femur. It also provides rotational stability of the knee.

MFC – medial femoral condyle
LFC – lateral femoral condyle
AM – anteromedial bundle of the ACL
PL – posterolateral bundle of the ACL

The ACL is composed of 2 bundles, the anteromedial bundle (AMB) and the posterolateralbundle (PLB). They are named according to their insertion points into the tibia. Histologically, there is a vascularized fibrous septum that separates the two bundles.

Histology examination demonstrates a septum (black arrows) dividing the anteromedial (AM) and posterlateral (PL) bundle

The 2 bundles are present at 16 weeks of gestation. The AMB is tighter in flexion and the PLB is tighter in extension.  The AMB is more important in anterior translation while the PLB is more important in rotational stability. The distance from the femoral origin to the femoral physis remains consistent from gestation to maturity and averages about 3 mm.

The femoral intercondylar notch continues to develop throughout skeletal maturity. However at age eleven years, the width of the anterior notch ceased to increase in size. The male notch is usually larger by this age.

ACL in a fetus with anteromedial (AM) and posterolateral (PL) bundles

Epidemiology

There is still lack of proper demographic data to reflect true rates of ACL injuries. However, there are a few small studies which convincingly demonstrate a rapid rise in the treatment of these injuries. Paediatric ACL injuries now form approximately 3% of all ACL injuries. Dodwell et al used a billing and discharge database in New York State from 1990 to 2009, to show an increase in the rate of ACL reconstructions in patients aged 3 to 20 years from 17.6 to 50.9 per 100,000 population. They also showed the highest rate was in patients aged 17 years. Souryal and Freeman reported an annual incidence rate of 16 per 1000 for ACL tears in a cohort of high school athletes. Stracciolini et al. found that 9.4% of presentations to the Division of Sports Medicine of a large, academic paediatric medical centre were ACL tears.

Risk Factors For ACL Injuries

Injury risk factors are either intrinsic or extrinsic. The intrinsic factors are inherent to the patient such as age, gender, hormonal differences, mechanical alignment, anatomic variation of the ligament and femoral notch, previous reconstruction and ligamentous laxity.  The patient’s playing style, skills, preparation and ability are all intrinsic factors. They have a significant bearing on the risk of ACL tears.

ACL injuries are more common in boys due to the higher number of boys participating in at risk sports. However, girls have a higher relative risk per athlete of sustaining ACL tears. Some of the proposed factors for this difference include sex hormone receptors located on the ACL, excessive femoral anteversion, increased Q-angle, decreased intercondylar notch width, smaller ACL size relative weakness in core strength, higher quadriceps to hamstrings ratio and deficient neuromuscular control.

Extrinsic risk factors are those extrinsic to the patient. The most important of these is the type of sports they play. High risk sports include soccer, netball, football, basketball and skiing. Other factors include hard and dry playing surfaces such as synthetic surfaces with high friction. Boots with higher number of studs (cleats) also pose increased risk. Increased number of cleats provide more traction with the ground but can cause the foot to be stuck while the remainder of the body is twisted on the knee. Using the right type of shoe for different surfaces can help reduce the risk of injury.

Studs of one of the most popular soccer boots

Injury Patterns

Injuries to the ACL can occur as a bony avulsion, mid-substance tear, complete, partial, in isolation or associated with other injuries.

Avulsion injuries tend to occur in younger patients. Most avulsions are at the tibialinsertion, rarely are they found on the femoral side. Kellenberger found that in a group of 63 skeletally immature patients with ACL injuries, 80% of those less than 12 years of age involved tibial eminence fracture, while 90% of those over 12 years of age had intrasubstance tears. Staninitski et al found in a review of 70 patients aged 7-18 years old, the rate of tibial spine fractures was three times more common in those aged 7-12 years when compared to those 13-18 years of age. Detectable laxity on clinical examination after healed avulsion injuries suggest that there was intra-substance stretch of the ligament at the time of the avulsion. Undisplaced Type I injuries can be managed conservatively in a cast or brace. Displaced avulsions Type II and III are managed with reattachment of the fragment and fixed with sutures, wires or screws.

Midsubstance tears can be complete or partial. The partial tears tend to affect either the anteromedial or posterolateral bundle. Patients with partial tears can still be managed conservatively if their knees remain stable.

Anteroposterior (A) and lateral (B) views showing a Type III tibial eminence fracture.

Presentation

The presentation of ACL tears in children is similar to that in adults. It usually resultsfrom an indirect sporting injury. The player suddenly changes direction causing a pivoting load on the knee. Abrupt deceleration or off-balance landing from a jump can also tear the ACL. Usually the player feels a “popping” or tearing sensation in the knee. The knee gives way and the player falls to the ground. There is immediate severe pain. Swelling is usually not seen until several hours later. Stanitski et al. found 47% of the preadolescent group and 55% of the adolescents with acute haemarthrosishad partial or complete ACL tears. It can be painful to weight bear for the first 2 weeks. Significant pain suggests other associated injuries such as torn menisci, osteochondral fracture or injuries to other ligaments.

Swollen right knee due to a large haemarthrosis

Initially, the knee will be swollen with restricted motion.  Special tests such as anterior drawer, Lachman, and pivot shift can be positive.

Tap on image to play video. Lachmann and Pivot Shift tests.

Investigation

X-rays can show a tibial eminence avulsion or a Segond fracture.
MRI is the best tool to diagnose a ruptured ACL and to detect associated injuries.

Management Controversies

MRI showing normal ACL     MRI showing ruptured ACL

The management of ACL injuries in the children can be controversial. There are differing views of what to do and when to do it.

Concerns with reconstructing

Traditionally, ACL injuries in children were treated with activity avoidance, bracing and delaying reconstructive surgery. The main reason for this approach is the concern of causing a growth disturbance in the operated leg of these skeletally immature patients. Surgery in these patients was usually delayed until their growth plates have fused. This is approximately 14 years for girls and 16 years for boys.

When growth arrest occurs it usually causes shortening, lengthening or angular deformity. The posterolateral position of the femoral tunnel or the over-the-top groove is very close to the femoral physis and can cause either valgus or flexion deformity of the distal femur. Injury to the anterior tibial physis can result in recurvatum of the knee.

Full length radiograph showing an increased valgus right knee following physeal sparing ACL reconstruction using ITB

The evidence for physeal injury in ACL reconstructions mainly come through animal studies, case reports or surgeons’ questionnaires.

Previous animal experiments have shown that the risks to growth arrests are higherwhen the physeal defect is greater than 7-9% of the total physeal area. Pananwala et al. showed in their MRI study of 39 knees in patients aged between 11 and 16 yearsthat a 9mm drill of the proximal tibia only created a 2.76% defect in the proximal tibia. Some researchers also showed that placing a soft tissue graft across the physealtunnel in the rabbit model was protective from causing an arrest. It has been shown by Edwards et al. that placing an overtensioned fascia lata graft in the canine model can cause valgus femoral and varus tibial deformities without having radiological or histological evidence of physeal bar formation.

In a survey of the Herodicus Society (an international sports medicine society) and the Anterior Cruciate Ligament Study Group, 15 of 140 respondents reported a growth disturbance following ACL reconstructions in skeletally immature patients. Of these 15 cases, 12 were on the femoral side and 3 were on the tibial side. Angular deformities consisted of 10 distal femoral valgus and 3 tibial recurvatum. Of the 2 cases with leg length discrepancy, one was 2.5 cm short and the other was 3 cm long. Most of these growth disturbance can be explained by surgical error such as placing a staple or suture across the physis, using the patellar tendon as graft with the bone plug across the physis, drilling a very large tunnel of 12mm and using extraarticular lateral tenodesis.

Koman reported a valgus deformity following ACL reconstruction using bone-patellar tendon-bone graft with femoral fixation hardware placed across the lateral femoral physis. This valgus deformity required a corrective osteotomy.

Concerns with not reconstructing

The problem with not reconstructing these ACL deficient knees is they often result in recurrent knee instability, meniscal and chondral damage as well as sports related instability. These younger patients are usually non-compliant with activity modification and brace wearing. Away from organized sports, they still perform running and pivoting maneuvers especially during breaks at school.

Millet found that medial meniscal tears were more common (36% versus 11%) in those patients who underwent reconstruction beyond 6 weeks from the time of injury compared to those who had surgery within 6 weeks. Graf studied 8 patients (average age 14.5 years) who underwent conservative management for ACL tears and found that 7 patients developed new meniscal tears at an average of 15 months following their injuries. Lawrence et al. reviewed 70 patients with average age 12.9 years and showed that there was an increased rate of meniscal tear and high grade chondraldefects (Outerbridge grades II to IV) if time from injury to surgery was delayed for more than 12 weeks. They also showed that rates of irreparable meniscal repairs were three times more frequent (24% vs. 7%). McCarroll et al reported 37 of 38 adolescent patients, at mean follow-up of 29 months, had recurrent instability. New symptomatic meniscal tears were observed in 27 patients. Only 16 attempted to return to sports, but all experienced instability. Kannus et al. observed good to excellent results in patients with partial, grade II tears who were managed non-surgically for 8 years. However, they reported poor results with chronic instability and arthritis in the complete grade III tears. Angel and Hall reported the majority of their 27 patients had pain and activity limitations. At average follow-up of 51 months, 4 patients had arthroscopic surgery, 4 had ACL reconstructions and another 3 had reconstruction recommended.Kocher and co-authors reported that up to one third of patients (mean age 13.7 years) with a partial ACL tear who were managed in a hinged knee brace and appropriate rehabilitation still eventually requires reconstruction for instability. They recommended surgery for patients with greater that 50% tears, tear of the posterolateral bundle and grade 2 pivot shift test.

There are also laboratory and clinical evidence that demonstrate delays in surgery cancause clinical instability and damage to the menisci and cartilage. Most paediatricknee surgeons these days tend to recommend early reconstruction to their patients.They utilize various techniques to minimize the risk of growth disturbance.

Tear of the posterior horn medial meniscus following a neglected ACL rupture

Assessing Patient’s Age

The patient’s age is one of several important factors in determining timing of the surgery. A patient’s chronologic age (based on their birthdate) does not always correlate with their development. In a classroom with students of the same age, there is wide spectrum of height and physiologic maturity.

Children of the same age can develop at different rates and resulting in different heights

There are several ways to determine how old a patient is and when to expect their growth to cease.

X-ray of the left hand is used to predict bone age

Tanner staging

Surgical Options

There are various methods to reconstruct the ACL in a skeletally immature patient. The most appropriate method is dependent on the patient’s age and physiologic maturity. The goal is to anatomically reconstruct the ligament without compromising growth. The surgical options include transphyseal, physeal sparing and hybrid techniques.

Transphyseal techniques involve drilling through one or both the tibial and femoral physis. Physeal sparing techniques include drilling tunnels only in the epiphysis or without drilling any tunnels by passing the graft in the over-the-top position of the femur and under the anterior intermeniscal ligament of the tiba.

Combined intra-articular and extra-articular reconstruction using iliotibal band (modified MacIntosh) technique

Micheli et al. described a modification of the MacIntosh and Darby technique. The iliotibal band is harvested via a single or double lateral incision technique. Approximately 15-20cm of the band is required depending on the patient’s size. It is detached proximally and left attached to Gerdy’s tubercle distally. The graft is tubularised with nonabsorbable sutures. The ruptured ACL remnant is minimally debrided and utmost care is taken to avoid damage to the perichondral ring around the posterior aspect lateral femoral condyle. Using a curved clamp, the graft is passed around the lateral femoral condyle, over-the top position and into the joint. Proximally the graft is fixed to the lateral femoral condyle by sutures at the insertion of the lateral intermuscular septum. This is performed with the knee at 90 degrees and neutral rotation. The graft is then passed under the intermeniscal ligament at the front of the tibia, into a rasped trough of the tibial epiphysis and attach to the proximal tibia via an elevated periosteal sleeve. Additional fixation to the proximal tibia can be achieved by a post, staple or suture anchor.

Kocher et al. reported on 44 patients who underwent reconstructive surgery using this technique. There were two ruptures occurring at 4.7 and 8.3 years postoperatively. No growth disturbance was identified. The International Knee Documentation Committee (IKDC) score was 96.7 and Lysholm score was 95.7.

Although this technique does not reproduce an anatomic ACL, it has been shown by Kennedy et al. that in a cadaveric model it most closely restore the native ACL kinematics when compared to the all-epiphyseal or transtibial over-the-top reconstruction.

Transepiphyseal anterior cruciate ligament reconstruction

In 2003, Anderson described a technique where the tunnels are placed entirely within the femoral and tibialepiphysis, without crossing the physis. The principle behind this technique is to achieve anatomical reconstruction of the ACL without compromising the physis.

This procedure uses fluoroscopy to ensure that drilling remains in the epiphysis. Both gracilis and semitendinosus tendons are harvested and doubled to form the graft. The graft is passed through the epiphyseal tunnels and fixed on the femoral side using an Endobutton and washer. It is fixed to the proximal tibia using a screw post.

Transphyseal anterior cruciate ligament reconstruction

This technique is very similar to the one used in adult ACL reconstruction. Its principle is to anatomically reconstruct the ruptured ACL by drilling tunnels through the physis and entering the joint at the injured ACL footprints. There are a few special considerations to minimize the risk of growth arrest. They include

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MFC – medial femoral condyle
LFC – lateral femoral condyle
AM – anteromedial bundle of the ACL
PL – posterolateral bundle of the ACL

The ACL is covered by a vascularised layer of synovium

How is the ACL injured?

The ACL is usually ruptured during sporting, work or motor vehicle accidents.  The most common sports causing ACL tears are soccer, football, netball and skiing. It is usually due to non-contact mechanisms where the foot is planted in the ground and the rest of the body continue to move or twist causing an abnormal force through the knee. Sometimes the injury is by direct contact such as in a football tackle.

Double click on the image to PLAY video showing injuries causing ACL tears

How Do Patients Present?

At the moment of injury, patients often hear or feel a popping sound in the knee. The knee usually collapses and the patient falls to the ground. There is significant immediate pain. The patient struggles to get up and walk. The knee would give way immediately in those that try to resume their sporting activity. There is often swelling in the knee over the next 24 hours.

Why is There Pain?

The ruptured ACL itself causes minimal pain. Pain is due to injuries of the surrounding tissues such as meniscal tears, fractures to bone and cartilage, ruptures of other ligaments, bleeding and inflammation.

Why is There Swelling?

Swelling usually occurs within 24 hours of the injury. It is due to disruption of the blood vessels which run along the ACL. It can also be the result of bleeding from a fracture of the thighbone or shinbone or tears of the capsule.  If an aspiration were to be performed acutely to suck out the fluid, it would yield blood. Swelling which occurs later is a result of inflammation within the joint. Its appearance is more straw colour and can be blood stained.

What to Expect in the First Few Days?

With the significant pain and swelling, patients find it difficult to walk on the injured leg. They cannot fully straighten or bend the knee. The knee feels unstable when walking, especially while climbing the stairs.

What to Expect in the Next Few Weeks?

In isolated ACL injuries, pain and swelling will slowly improve and settle after 3-4 weeks. The knee has more movement and the patient experiences less instability when weight bearing during normal walking. Persistence of symptoms suggests other pathologies.

Patients may experience giving way or instability when they return to sports. Again, these episodes can cause pain and swelling.

How Should the Knee be Managed Initially?

Patients should be assessed by a doctor or experienced physiotherapist following any major knee injury. The doctor will thoroughly take your medical history and perform clinical examination. Radiographs will exclude any obvious fracture. The knee will then be managed according to the RICE principles – Rest, Ice, Compression and Elevation. A compression bandage will be applied and the knee will be placed in a brace. Frequent ice packing will help control pain and swelling. Patients are advised to use crutches and to elevate the injured knee as much as possible. Painkillers and anti-inflammatory medications will be prescribed. Based on the history, examination and x-ray results, MRI scans will be organised. An orthopaedic referral is usually required.

Once the diagnosis of an isolated ACL injury is confirmed, the brace is removed and early motion is encouraged. In multi-ligament injuries or if fractures are present, brace wearing may be prolonged.

How is the Ruptured ACL diagnosed?

The diagnosis is based on the symptoms and signs. The clinical examination may reveal a joint effusion, muscle wasting, positive Lachmann’s, anterior drawer and pivot shift tests. These are special tests to assess the integrity of the ACL. There may be localised tenderness due to other structural injuries such as meniscal tears or cartilage damage. Patients may also experience reduced motion.

Double click on image to PLAY video showing Lachmann, anterior drawer and pivot shift tests

X-rays may, on the rare occasion, demonstrate a small avulsion flake of bone from the outer and upper part of the tibia (shin bone). This lesion is called a Segond fracture. It is highly suggestive of a ruptured ACL. It is caused when there is excessive rotation of the tibia, stretching the joint capsule and pulling away a small flake of bone.

MRI scans are used to confirm the diagnosis. These scans can also detect other injuries.

MRI scans showing an intact ACL

MRI scans showing a ruptured ACL

Should All Patients Have Knee Reconstruction?

Not all patients will require surgery. ACL reconstruction is indicated if patients experience giving way with simple daily activities. It should also be considered in those planning on returning to cutting, pivoting or contact sports. Another indication is in patients with other pathologies such as meniscal tears requiring repair or those with more that one ligament ruptures.

Therefore, patients with isolated ACL injury, whose knee is currently stable and are not planning on any future strenuous activity, do not require reconstructive surgery.

What Happens if the Ruptured ACL is Not Reconstructed?

Many, but not all knees with ruptured ACL will experience instability. Several factors determine this. Knees are more likely to give way if there is additional ligament, meniscal or cartilage damage. The type of activity will also dictate the likelihood of instability. Cutting or pivoting sports and labor intensive work increases the risk, as well as poor neuromuscular control and being non-compliant with a well-planned rehabilitation program.

Instability prohibits patients from participating in their usual activity. Each time the knee gives way, it can potentially cause more damage to other structures such as the meniscus or articulating cartilage.

How is the Surgery Performed?

The surgery can be performed open or arthroscopically (keyhole).  Usually, the patient is given general anaesthetics.

The injured ligament is removed and replaced by a graft. This graft can come from the patient’s own tissue, such as the hamstrings, patellar tendon, quadriceps tendon or iliotibial band. It can also come from a live or deceased donor. It can also be a synthetic material. The choice of graft is dependent on your surgeon’s preference as well as what is available. Graft harvesting is performed open or through a small incision with the assistance of special instruments. The graft is prepared. Its length and width are measured.

Hamstring graft

Bone-patellar-bone graft

Synthetic graft

Arthroscopic examination of the knee is performed to assess the ACL tear and other structures such as the meniscus and cartilage. Surgery to address these other pathologies is performed before ACL bony tunnels are created.  In most cases one femoral and one tibial bony tunnel is drilled. The size of the tunnels is appropriate to receive the graft that was prepared earlier. The graft is passed through these tunnels and secured with special devices such as a button, screw or staple. These devices are made of metal, inert plastics or bio-absorbable material.

Local anaesthetics are infiltrated into the wound, along the harvested tendon, around the femoral nerve or adductor canal to provide good pain relief immediately after surgery.

What is the Post-operative Care?

Some surgeons allow their patients to go home on the same day as the surgery. Others may elect to keep them overnight to provide closer observation and pain control.

Pain and swelling management are most important in the immediate post-operative period. Compression bandage, ice and elevation are essential in the first few days. In isolated ACL reconstructions, most surgeons allow their patients to commence early full weight bearing. In those cases where ACL reconstruction is combined with meniscal repair or cartilage surgery, some surgeons will keep their patients non-weight bearing for the initial period. This is usually 6 weeks.

Early range of motion exercises and muscle activation are encouraged during the initial period. Strengthening, balance training, and return to function are some other important aspects of the rehabilitation process. Physiotherapy plays a crucial role in this rehabilitation process.

When Can Patients Return to Sports?

The surgeon will determine when patients can return to sports. There are specific goals that must be met.

• Completed the rehabilitation program
• Pain free
• Full motion
• Stable knee
• Full strength when compared to other knee
• Adequate hamstrings to quadriceps strength ratio
• Agility T test
• Hop test

This usually takes 12 months to achieve.

What are the Risks and Complications of Surgery?

Some of the more common complications include

• Reactions to general and local anaesthetics
• Infection
• Injuries to nerves and blood vessels
• Bleeding
• Blood clots
• Pain
• Stiffness
• Graft failure
• Persistent instability

What I Do for You, as My Patient?

After a thorough history taking and clinical examination, I will arrange for MRI scans of your knee. Having your MRI scans organised by your family doctor before the consultation would definitely speed up the process. Please remember to bring the actual films of your scans (in addition to the report) for assessment.

If we decide that non-surgical treatment is best for you, then I will arrange for a formal referral to a local physiotherapist. I will review you over the next few months to ensure that you can safely return to your normal daily activities.

If we feel that surgery is required, then an in depth discussion about the surgery takes place.

I use your hamstrings as the source of graft. Most of the time we take your semitendinosis tendon. We quadruple the tendon using the Arthrex Graftlink technique. Tunnels are created arthroscopically in the femur and tibia. The graft is passed through the tunnels and into the knee joint. It is fixed at both cortical surfaces using Tightrope buttons.

Quadrupled semitendinosis tendon as graft

Graft secured with Tightropes & buttons

I keep my patients overnight for pain management, close observation and early physiotherapy.

I review you at 2 weeks, 6 weeks, 6 months, 12 months and sometimes 2 years.

The post Anterior Cruciate Ligament appeared first on The Knee Specialist - Adult & Paediatric Knee Surgery.

Patellar dislocation occurs when there is total loss of contact between the patellar and the femoral groove.

Patellar subluxation is defined as partial loss of contact between the patellar and femoral groove.

Both these disorders belong to the spectrum known as patellofemoral instability (PFI). The incidence of PFI in children and adolescents is 43 per 100 000. It is most common in the age group 10-14 years old.

Almost all patellar dislocations and subluxations are lateral and most reduce spontaneously.

Photograph showing lateral dislocation of the left patella

Radiograph showing a laterally subluxed and tilted patella. There is a small fracture of the patella.

Radiograph showing a lateral dislocation of the patella. There is a small avulsion fracture of the medial patella

Pathomechanics

Patellar stability relies on three factors

1. Static

• Size, contour and height of the patella & femoral trochlea
• Varus & valgus alignment of the lower limb
• Bony rotation

2. Passive

• Ligament (medial patellofemoral ligament)
• Joint capsule & retinaculum
• Iliotibial band

3. Dynamic

• Muscle (vastus medialis obliquus)

As the knee reaches full extension, the patella tracks slightly superior and lateral to the trochlea. During early flexion (0-30 degrees) the medial patellofemoral ligament (MPFL) guides the patella into the trochlea. It is the most important medial restraint in early flexion. Beyond 30 degrees, the bony anatomy of both patella and trochlea is the main stabiliser. Past 90 degrees, the patella engages into the notch.

The vastus medialis obliquus (VMO) is the most important dynamic stabiliser of the patella. It acts throughout the range of motion but plays more a significant role beyond 60 degrees of flexion when its fibres run perpendicular to the line patellar tracking.

Mechanism of Injury

Patellar instability can result from traumatic or non-traumatic events.

During traumatic dislocations the force can be direct or indirect. With direct mechanisms, the patella experiences a laterally directed force causing it to dislocate laterally. It can also result from a medially directed force on femorotibial joint of the knee, causing the knee into valgus and leaving the patella behind in the dislocated position. This type of direct injury usually occurs during a football tackle.

Indirect injuries result from a twisting knee when the foot is planted on the ground and the rest of the body changes direction. Most indirect injuries causing patellar dislocations occur in cutting and pivoting sports such as soccer, football, basketball and skiing.

Non-traumatic dislocations tend to occur with activities of daily living, requiring minimal force and often reduce spontaneously. These patients also report recurrent subluxations between episodes of true dislocations.

Risk Factors

There are several major risk factors for patellar dislocations. They can be classified as general or limb specific factors.

The general factors are

1. Sports which involve pivoting and cutting manoeuvres such as soccer, football, basketball, netball and skiing.
2. Previous patellar dislocation

• 20-30% after first time dislocation
• Rate is higher when the physis is still open
• Rate is 0% if patient is older than 40 years

3. Family history
4. Female

• Unclear if female sex is a risk factor as there are conflicting evidence

5. Ligamentous laxity

• Ehlers-Danlos syndrome
• Marfan syndrome
• Down syndrome

The limb specific risk factors can be subdivided into static, passive and dynamic. It can be further stratified into above, at and below the patella.

1. Static

• Genu valgum
• Excessive internal femoral torsion
• Excessive external tibial torsion
• Increased Q angle
• Patella and trochlea dysplasia
• Patella alta

2. Passive

• Ruptured or stretched MPFL
• Tight lateral retinaculum
• Tight iliotibial band

3. Dynamic

• Weak VMO

Classification

There are several classification systems but the following is most popular.

1. Single

• Patients present for the first time with a dislocation.
• Usually traumatic

2. Recurrent

• This is the second or subsequent dislocation
• Can be traumatic or non-traumatic

3. Habitual or Obligatory

• The patella dislocates with each cycle of knee motion
• Usually dislocates when the knee is flexed and reduces when the knee extends. The reverse can also occur.

4. Permanent

• Congenital
• Acquired following infection or surgery

Video clip showing habitual dislocation

 Closed Reduction

Most dislocations are lateral and reduce spontaneously. However some will require a closed reduction.

Following a patellar dislocation, the knee is usually held flexed. Due to the lateral & posterior position of the dislocated patella, the extensor mechanism of the knee now becomes a knee flexor. Pain and spasm of the thigh muscles, namely the hamstrings and quadriceps keep the knee in the flexed position.

The most important part of the reduction procedure is to relax the patient in a supine position. Slowly extend the knee. Only push and guide the patella back into place once the knee is fully extended. This should require minimal force. Forcing the patella to reduce while the knee is still flexed can cause osteochondral injuries to either the patella or lateral femoral condyle.

Once the patella is reduced, immobolise the knee in extension either with a brace or cast. Immobilastion is limited to a maximum of two weeks. Longer periods will cause stiffness, weakness and dysfunction of the dynamic stabiliser of the patellofemoral joint. Radiographs are performed to confirm reduction and to exclude any fracture.

Clinical Examination

Following an acute traumatic dislocation the knee is assessed to ensure that the patella is reduced. A large effusion or significant pain and tenderness should raise suspicion of a fracture and will require further investigation. The knee might be too painful to allow for a thorough examination. But when possible assess for ligamentous and meniscal pathologies.

Once the pain and swelling have settled, a comprehensive examination is carried out to detect the risk factors for patellar instability as well as excluding other injuries.

Important signs to look out for are

1. Genu valgum

• Genu valgum increases the risk of patellar instability

2. Knee hyperextension and planovalgus feet suggesting ligamentous laxity
3. Squinting patella

• Reflects excessive internal femoral rotation

4. In-toeing gait

• Reflects excessive internal femoral rotation

5. J-tracking of patella

• Abrupt lateralisation of the patella in terminal knee extension

6. Patellofemoral crepitations

• Can be due to chondral damage in the patellofemoral cartilage

7. Quadriceps weakness

• Focus on VMO size and activation

8. Effusion

• Indicates recent instability or osteochondral injury

9. Patellar tilt

• Normally the patella should be able to be tilted horizontally
• Inability to horizontalise the patella indicates tight lateral retinaculum

10. Patellar translation

• In extension the patella should be translated 1-2 quadrants medially or laterally

11. Q angle

• Upper limit is 10 degrees in males & 15 degrees in females

12. Rotational profile

• Assess for excessive femoral anteversion (internal torsion) and external tibial torsion

13. Ligamentous laxity

• At least 3 of 5 Wynn-Davies criteria
• Passively touching the thumb to the forearm with wrist flexed
• Fingers parallel to forearm with passive wrist extension
• Elbow hyperextension
• Knee hyperextension
• Passive ankle dorsiflexion greater than 45 degrees
• At least 6 of 9 Beighton Hypermobility Score

Investigation

Radiographs are performed initially to ensure that the patella has been reduced and to exclude any fracture. Due to pain in the acute period following a dislocation, it may be possible just to get the anteroposterior (AP) and lateral images. Once pain and swelling have settled, a skyline view is important to detect any fracture, assess patellar position, tilt as well as trochlear dysplasia.

AP X-ray showing a lateral patellar dislocation

Skyline x-ray showing a fracture of the patellar apex following a dislocation

Photograph of a patellar osteochondral fracture

CT scans are good for detecting fractures. They can also be used to calculate the tibial tuberosity – trochlear groove distance (TT-TG). The normal value is 13mm. A TT-TG of 20mm is pathological and indicates that tibial tubercle transfer should be part of the surgical plan.

Calculating TT-TG Distance

Axial CT image through the most prominent part of the tibial tubercle is superimposed on the image of the deepest part of the trochlea. Line 1 joins the posterior femoral condyles. Line 2 runs perpendicular to line 1 and through the trochlea. Line 3 is perpendicular to line 1 and through the centre of the tubercle. TT-TG is the perpendicular distance between line 2 & line 3.

TT-TG distance can also be calculated on MRI scans. The normal value is 10mm.

Patellar height measurement

Patella alta (high riding patella) is a risk factor for patellar instability. There are several methods to measure patellar height.

Insall-Salvati Ratio

The lateral radiograph is taken with the knee flexed at 30 degrees.

Two lengths are required to calculate the ratio.

1. TL = tendon length (red) which is the distance from the inferior pole of the patella to the point of insertion at the tibial tuberosity
2. PL = patellar length (yellow) which is the distance from superior to inferior pole of patella

Insall-Salvati ratio = TL (red)/ PL (yellow)

A normal value = 0.8 -1.2

Patellar alta > 1.2

Patella baja <0.8

Caton Deschamps index (CDI) requires two measurements.

1. A = distance from patellar inferior articulating edge to top of tibial plateau
2. B = length of patellar articulating surface

CDI = A/B

Normal = 0.8 – 1.2

Patella alta > 1.2

Patella baja < 0.8

Blackburn-Peel Index (BPI)

A horizontal line is drawn along the tibial plateau.

Perpendicular to this line, the distance is measured to the inferior aspect of the patellar articulating cartilage (1).

A second measurement is made along the patellar articulating surface (2).

BPI = (1) / (2)

Normal value = 0.8 - 1.0

Patella alta > 1.0

These days MRI scans are performed routinely in many centres for all patellar dislocations. It should at least be performed for those cases associated with a high energy trauma, persistent pain, swelling or fractures identified on radiographs. MRI scans have the ability to detect chondral injuries, tears of the MPFL, calculate the TT-TG distance and exclude other internal derangements such as meniscal tears or ligamentous ruptures.

Common MRI findings following a traumatic patellar dislocation include

• Haemarthrosis
• Bony contusions or osteochondral fractures involving the medial patellar facet and lateral femoral condyle
• Rupture of the medial patellofemoral ligament (MPFL)

Features on MRI scans which are risk factors for patellar dislocation

• Dysplastic femoral groove
• Dysplastic patella
• Patella alta
• Subluxed patella
• Laterally tilted patella
• Deficient vastus medialis obliquus (VMO)

Axial MRI scans demonstrating an effusion, bony contusions of the medial patella and lateral femoral condyle, rupture of the MPFL from its femoral insertion.

Coronal MRI showing bony contusion of the lateral femoral condyle

The post Patellar Dislocation appeared first on The Knee Specialist - Adult & Paediatric Knee Surgery.