Slope-changing osteotomy for a difficult problem

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Susan had a left slope-changing anterior osteotomy with bone graft for a recurvatum injury.

Susan is a really interesting case. She came up from the West Country to see me. She had had many opinions over three years as to how to help her with the severe instability of her left knee after an injury, but no-one could really find the problem and she was told that nothing could be done and that she would have to live with things as they were.

When she came to see me, which was back in February 2018 she was on two crutches and had this severe instability and pain. She had twisted her knee in September 2015 getting out of the shower and had such a significant injury that there was severe swelling and bruising afterwards and the knee never felt right after this - constant aching, and she was limping and constantly felt that the knee was hyperextending significantly more on the left compared to the right. On the right, she had just a few degrees of hyperextension and on the left as much as 20°. This made the knee unstable.

She had two or three very nasty falls because of the instability and that was why when she came to see me she was on two crutches.

The main problem was hyper-extension - she had obviously sustained a posterior capsular injury which was giving her hyperextension or recurvatum.

The external ligaments medially, laterally and over the front of the knee were fine, and on stress X-rays the ligaments were normal. We investigated also with an arthroscopy and actually the inside of the joint was really very good with the joint surfaces, menisci and cruciate ligaments also intact.

Managing recurvatum and instability like this is a very difficult problem to treat, but an effective way we have developed is to change the slope at the top of the tibia to the point where on the operating table the knee goes flat and not beyond flat. Usually it requires a change of slope of between 5-10° and an opening of approximately 10-15mm. This opening at the front of the knee is filled with femoral head allograft (bone graft). This is of course a significant and complex intervention and I explained that to both Susan and her husband in my office. I went through some cases that I have done before and showed videos of patients both before the surgery, an intra-operative video of how the surgery works as well as post-operative images. I explained the significant risk associated with invasive surgery such as this.

Slope-changing osteotomy

Once the dates were agreed we went ahead with an examination under anaesthesia and proceeded via a direct anterior approach to a slope changing osteotomy. I proceeded to increase her tibial slope such that I removed her hyperextension and this was done through a biological plating technique developed by my good friend Ronald van Heerwaarden. She was admitted to the Wellington Hospital back in June. We came from the front, did a tubercle osteotomy and then changed the slope by 12 degrees using a femoral head allograft to fit into the anterior wedge that we created and I am delighted to say that all her instability symptoms have now settled over the last month or so and the knee no longer gives way. She has healed up beautifully on the X-rays and the plan is to remove the hardware at some point next year.

She is a really interesting case and a good example of how our specialist centre in London for osteotomy can benefit patients because of our expertise in these rather niche procedures.

Her range of motion at 4 weeks post-operative was limited to 0 to 30° but that was no surprise given that she had been doing very little since the surgery. We talked today about doing exercises to 90° to get the knee moving and she should do these 3 or 4 times a day and I recommended a CPM.

Follow-up

Despite early stiffness, Susan progressed extremely well. By 10 weeks after surgery, she had regained full extension with just a very minor degree of hyper-extension, perhaps a degree or two compared to the other side where she has 10° plus. She had good flexion to 110 °. The knee felt nice and stable. The x-rays looked spot on and in particular, there is no posterior callus to suggest there was a hinge fracture and it all looked to be in perfect continuity. She was healing up very nicely.

She is going to wean out of her brace and off her crutches as she feels she can and I am going to review her in 3 months with further X-rays. I said she can go to full weight bearing now.

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