Brief overview to this section...main content below...
In Part 1 we considered the option of not operating until the growth plates have closed. The evidence for following a conservative route was weak. Many surgeons would agree that the potential for years of instability, with a high probability of secondary damage to the internal structures, supports a decision to consider surgery. So in Part 2 we will look at the issues surrounding surgery for ACL injury in children.
The main concern about surgery is growth disturbance and this is a really important complication - but it’s extremely rare and certainly a lot more manageable if it does occur than if we see secondary damage to the joint surface or the meniscus in a developing adolescent.
So the consensus and the evidence is to treat, but there is no consensus over how we should carry out the surgery:
The potential growth disturbance on the femur is angular deformity - usually valgus - meaning that the knee can assume a 'knock-knee' appearance. If any growth disturbance is seen on the tibia, it is usually in the form of leg-length discrepancy or the leg bending backwards - what we call 'recurvatum'.
There are also some issues about what grafts we should use in children, particularly small children.
We use a scoring system called the Tanner Scale to help with decisions about how to tackle the surgery. The Tanner Scale is based mainly around the secondary sexual characteristics of puberty. For the very young - boys of less than 14 and girls less than 13 who have not entered puberty - it is recommended to use a tunnel that does not go through the growth plate on the femur, but to stay below it.
Let's look at the options for graft and tunnel placement in a bit more detail:
The strip of ITB is fed over-the-top, back into the notch, and under the intermeniscal ligament, to be fixed by a screw on the tibia below the growth plate.
The first option is to try to stabilise the knee without going through the joint cavity or the growth plates - what we call an ‘extra-articular’ approach’. Early work at extra-articular stabilisation focused on techniques where tissue could be used in the so-called 'over-the-top' position. In these techniques there was no tunnel in the femur whatsoever.
A strip of the iliotibial band (ITB) is taken from the side of the thigh, preserving its lower attachment on the tibia. This strip of strong material is fed around the rear of the knee and back to the front of the joint without putting a tunnel through either femur or tibia. The free end of the ITB is secured below the growth plate on the tibia, so the growth plates are totally avoided.
Papers have been published to show good results, but this is not a technique that is currently undertaken by many surgeons.
The next option is that of drilling right through the growth plates - what we call the ‘trans-physeal’ option. The vast majority of angular deformities and growth disturbances after ACL surgery in children have been associated with bone plugs or fixation devices deployed across the growth plate. It is also considered that drilling may cause heat damage and implants may have a pressure effect. Despite these risks, trans-physeal ACL reconstruction is frequently performed in skeletally immature patients with good outcomes, no or minimal growth disturbance and a high rate of return to previous activity levels. Tunnel positions generally need to be compromised, though, because although oblique tunnels are biomechanically favourable, they effectively increase the cross-sectional area of growth plate disruption.
The illustration is demonstrating 'tunnels' but a less invasive option is to use 'sockets', where there is a narrow portion that accommodates a suspensory thread and a wider portion that accommodates the ligament. That will be discussed in more detail in Part 3.
One of the real innovations in ACL surgery in general has been the development of what we call the 'all-inside' technique. This involves drilling the bone tunnels (or the newer 'sockets') from within the joint cavity, using 'retro-drills' such as the 'FlipCutter'. With this approach and the associated instrumentation, guided if necessary by fluoroscopic imaging, surgeons can go 'all-epiphyseal' - staying inside the ends of the bones without penetrating the growth plate.
In this option, the surgeon keeps the tunnels or sockets within the ends of the bone - that is within the epiphysis - and does not go anywhere near the growth plate. Gauges and fluoroscopic imaging ensure that the surgeon hits the target and does not compromise the growth plates.
If necessary the surgeon can perform a hybrid all-inside procedure, staying under the growth plate in the femur, but creating a tiny 3.5 mm drill hole through the growth plate on the tibia, using it to retro-drill from inside the joint a short but wider tunnel big enough to accommodate the graft.
As well as options for the placement of the tunnels, there are options for the kind of graft tissue or other material used for the stabilisation procedure.
The first option is that of an autograft. An autograft is a graft using the patient's own tissue - usually hamstrings tendons. The tendon that we can harvest from these small patients and use for reconstruction can be really quite weedy, a little pathetic. The reconstructed ligament remains vulnerable. A 2009 paper by Shelbourne  reports a 17% failure of primary ACL reconstruction in patients under the age of 18 compared with 4% of those over the age of 25. In other words there is a significantly higher re-rupture rate in children. From the Danish registry [2,3], also, the numbers given for revision risk is more than 2½ times higher in those under the age of 20 than in those over the age of 20. Because of the high failure rate that we see with reconstruction in this group, surgeons have considered alternative graft sources.
The second option is an allograft. An allograft is a graft using donor material. As an alternative to using the child's own hamstrings we can use adult donor tissue for the graft. Usually this material is harvested from a cadaver - from someone who has passed away but who had donated their body to medicine.
Our young patients in general don’t do quite as well with cadaver allograft but an allograft from a living person is something that is gaining attention. This was a topic that was presented by Justin Roe on behalf of him and Leo Pincewszki at the ISAKOS meeting in Toronto 2013 - and it won a prize. The obvious living donor for a child is the parent. Although either parent may prove suitable on tissue matching, it is probably the mother who will more commonly be the donor.
The third graft option is to use the native ACL and do a repair rather than a reconstruction. A 'repair' means that the old ligament is not cut away, but is retained. This is in contrast to 'reconstruction' where the old ligament tissue is removed and replaced. Repair is an old technique that fell out of favour, but it is being reconsidered for children.
In a child the ligament itself may still be intact, but may have simply torn off from the attachment site at the femur or avulsed from the tibia, where a small fragment of bone commonly breaks away with the ligament. Even if there is damage to the ligament itself, it may be only partly torn. Repair may be an alternative in all these cases.
Advantages of retaining what one can of the patient’s native ACL include -
Excellent outcomes of repair in children have been observed thus far, and the technique continues to evolve. Repair is possible via an all-inside all-epiphyseal approach, and tunnel diameter can be reduced from 3.5 mm to 2.4 mm which is significant in this population group.
Because of the flimsy nature of the native ACL in most small children, the repair may be augmented by adding graft tissue to bulk up the construct or by the use of a temporary internal brace.
We are suggesting the term 'hybrid' to describe the combination of the native ligament and the parental allograft, but it might also be used to describe augmenting the native ligament with the child's own hamstrings tendon or parental allograft. By augmenting in this way, concerns regarding adequate graft dimensions are eliminated.
A different but related concept is that of an 'internal brace' to support the native ligament while the repair heals. A tape of braided polyethylene FibreTape, for example, can provide temporary support for the healing repair, and it can then be electively removed after some months to prevent any tethering which could impair physis growth.
Timing of the surgical intervention in the child is critical. Early ACL reconstruction in children (within 6 weeks) is associated with improved results and threefold fewer medial meniscal tears , whereas delayed operative intervention leads to higher rates of meniscectomy and lower subjective outcome scores .
However, the high re-rupture rate in this population group continues to be a factor, and we hope you will find the ideas offered in the remainder of this course relevant in this respect.
1. Incidence of subsequent injury to either knee within 5 years after anterior cruciate ligament reconstruction with patellar tendon autograft. Shelbourne KD et al. Am J Sports Med. (2009): doi: 10.1177/0363546508325665. Epub 2008 Dec 24.
2. Incidence and outcome after revision anterior cruciate ligament reconstruction: results from the Danish registry for knee ligament reconstructions.Lind M, Menhert F, Pedersen AB.Am J Sports Med. 2012 Jul;40(7):1551-7. doi: 10.1177/0363546512446000. Epub 2012 May 4.PMID: 22562791
3. Risk for Revision After Anterior Cruciate Ligament Reconstruction Is Higher Among Adolescents: Results From the Danish Registry of Knee Ligament Reconstruction.Faunø P, Rahr-Wagner L, Lind M.Orthop J Sports Med. 2014 Oct 8;2(10):2325967114552405. doi: 10.1177/2325967114552405. eCollection 2014 Oct.PMID: 26535272
4. Millett PJ, Willis AA, Warren RF (2002) Associated injuries inpediatric and adolescent anterior cruciate ligament tears: doesa delay in treatment increase the risk of meniscal tear? Arthros-copy 18:955–959
5. Henry J, Chotel F, Chouteau J, Fessy MH, Berard J, Moyen B(2009) Rupture of the anterior cruciate ligament in children: earlyreconstruction with open physes or delayed reconstruction to skel-etal maturity? Knee Surg Sports Traumatol Arthrosc 17:748–755
The Tanner Scale
An autograft is tissue, usually tendon, taken from the patient him/herself, and used to replace (or augment) the native tissue, in this case the ACL ligament.
An allograft is tissue taken from a donor, and used to replace or (augment) the native tissue, in this ase the ACL ligament. The donor is usually deceased (cadaveric allograft) but may be living (eg parental allograft).