RE: THR luxation

Dinu Catilina — Sat, 18 Apr 2020 18:22:46 GMT

Thank you Malcolm!

RE: THR luxation

Malcolm Ness — Sat, 18 Apr 2020 12:56:46 GMT

Hi Dinu,

Sorry I am late to this one. You have done what I would have suggested!

While the radiographic study is incomplete, two things are apparent to me. First, the acetabular prosthesis is not well-positioned and that will almost certainly be contributing to, even causing, the luxation. Second, there seems to be a marked size mis-match between the femoral head component and the acetabulum. Your post-amputation photographs confirm that - the degree fo wear is massive and presumably due to inappropriate sizing, selection and positioning of the implants.

THR surgery is technically challenging and, in my opinion, should be done ONLY by those surgeons who have had extensive procedure specific training (my residents would do at least 50 cases as 'second surgeon' before leading a case of their own) AND have a caseload in excess of 25 operation annually. Too many bad THRs are available in the veterinary world. Once complications appear (they are almost always the consequence of the surgeon's earlier technical error) they are challenging to deal with. Almost all laxations are related to poorly positioned implants.

In a chronic case like this, you are left with few options and none of them are good - if the prostheses had been well positioned then capsular tightening of the kind you suggest might have helped. But it probably wouldn't! The massive implant wear/destruction here left you with two options - amputation or an attempt to explant the metalwork and give effectively an excision arthroplasty. You chose the more sensible option - while removal of the acetabular component is relatively straight forward, explantation of the femoral stem is a nightmare - the bonding between bone and the beaded surface of the stem will be extremely robust and matters made more complex by the fact that there is often proximal bone loss due to stress-shielding - there is evidence of that on your radiographs.

I hope that this is helpful.

Malcolm

RE: THR luxation

Dinu Catilina — Sat, 18 Apr 2020 09:43:56 GMT

Update, the leg was amputated, cup was loose and eroded on the dorsal aspec.

Photos below.