Part 4: Proximal Detachment from Femur - case example

Interview with the young patient and her father...

Proximal Detachment from Femur

In this Part we will briefly outline the management of a young patient with a proximal detachment of the ACL from the notch of the femur. The approach was a 'hybrid' one rather than 'all-epiphyseal', that is the tunnel on the femur was confined to the epiphysis and under the growth plate, but on the tibia the tunnel passed through the growth plate. This is not a standard procedure but one that we want to emphasise because the technical approach minimises the damage to the femur and causes very little damage to the tibia or the tibial growth plate.

In addition, an 'internal brace' was used to augment the repair for some months before the brace and its fixation were removed, giving the repair itself time to heal but avoiding later complications from the presence of the polyethylene tape.

Patient 'R'

This young girl suffered a knee injury at the age of 5 while jumping on a trampoline. Unseen by her, a friend threw a hard ball onto the trampoline, and the young patient inadvertently landed from a height onto the ball with her knee bent.

If you have not yet watched the video interview with the parent, scroll up to the top of the page and you will hear the story there. What is interesting is that the initial excruciating pain settled after a few days, and the parents only continued to be concerned because although she was getting around she was doing so with a rather strange gait.

The growth plates are quite clearly seen on the MRI, and the area where one would expect a clear outline of the ACL is indistinct, suggesting damage to the ACL.

Examination-under-Anaesthesia

In this clip the surgeon examines the knee for laxity while the young patient is under anaesthesis and fully relaxed.

A point to note is that pivot shift and anteroposterior translation are higher (for operated and normal knees) in children than adults, but this may be due to constitutional increased joint mobility present in children.

Arthroscopic Examination

Arthroscopy was performed via standard portals, revealing that the ACL had torn away from its femoral origin, but that the body of the ligament was intact - a perfect situation for a repair.

There was also a partial tear of the meniscus. You can see this as a very feint white line on the top of the meniscus.

The tear did not actually require any attention.

The empty notch at top end should have been filled up with ACL where it normally originates on the femur, but the ligament has come away from the bone here and left a gap.

The ACL itself is otherwise intact.

The ACL Repair Procedure

The first step of the procedure is to lasso the free end of the ACL, so that the surgeon can pull it out of the way to prepare the repair site, and then eventually pull it right back into its original position and fix it there. This lassoing is performed via the arthroscopy portals using an instrument called a 'mini-scorpion'. 

A small incision is made through the skin on the lateral side of the femur, and gauges and fluoroscopic imaging are used, to carefully drill a 2.4mm drill hole through the epiphysis, taking care to stay under the growth plate:

A double-stranded 'passing suture' is passed through the femoral tunnel. This will eventually be used to pass the FibreTape internal brace through both femur and tibia. A second 'repair suture' is passed through to hook the lasso and tension the ligament.

The lasso (on the left of the video) is pulled up through the femoral tunnel and the ACL is re-approximated on the side wall. The FibreTape for the internal brace is ready on the right, waiting for the drilling of the tibial tunnel.

Because the surgeon elected to do a hybrid approach for the internal brace, that is avoiding the growth plate on the femur but passing through it on the tibia, the tibial tunnel - again 2.4 mm - was drilled through the growth plate. The sutures holding the remnant are tied onto the suspensory fixation tightrope button which sits against the lateral femoral cortex. The FibreTape is secured and tensioned at the tibial end with a 4.75mm SwiveLock anchor​, with a button at the femoral end.

Second-look arthroscopy at 3 months

Three months later - immediately pre-op for the second-look arthroscopy, the patient demonstrated how well she was running around and pain free

During the arthroscopy the hardware was removed fairly easily, and with a clip on the FibreTape the internal brace just slid out really very easily. The rationale for removing the polyethylene braid was so that it would not tether the growth plate.

Examination of the joint was completely normal. There was no synovitis, the joint surfaces appeared normal, menisci were intact and the ACL healed. The ligament at the femur had really incorporated nicely, and was synovialised. It was not over tensioned..

Follow-up at 2 years

At two years the child was assessed for range-of-motion, limb length and ligament laxity. All of these were normal.

This is the device that we found useful to check the laxity in this small knee - the KIRA. This recorded a less than 2mm side to side difference.

Additional Resources (Click to view)

Is triaxial accelerometer reliable in the evaluation and grading of knee pivot-shift phenomenon?

FAQ

Here are answers to some frequently asked questions:

What is a KIRA?

Why was the surgeon watching out for synovitis?

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