Cruciate and patella luxation issues

RE: Cruciate and patella luxation issues

Beats — Wed, 22 Jul 2020 19:45:23 GMT

[quote userid="3607" url="~/001/veterinary-clinical/small-animal/orthopaedics/f/discussions/29233/cruciate-and-patella-luxation-issues/224408#224408"]Aplogies for flooding vetsurgeon with verbose replies over the last few days - I am midway through some research and writing the is not holding my attention and I am finding vetsurgeon to be a ready distraction!![/quote]

We love your comprehensive replies, Malcolm!

Hope your research and writing goes well for you this week.

RE: Cruciate and patella luxation issues

Malcolm Ness — Wed, 22 Jul 2020 13:09:57 GMT

[quote userid="3094" url="~/001/veterinary-clinical/small-animal/orthopaedics/f/discussions/29233/cruciate-and-patella-luxation-issues/224312#224312"]Any thoughts or comments on my nots here?[/quote]

Certainly, it is not uncommon to find that the patella is palpably unstable following cranial cruciate (CCL) failure. That is not the same as patellar luxation, which I take to be the spontaneous luxation or subluxation during normal locomotion. The CCL limits cranial translation of the tibia relative to femur (as felt in the cranial draw test) but it also limits the internal rotation of the tibia relative to the femur. When this happens, or is induced during palpation/manipulation, there is a tendency for the patella to displace medially.

For me, the key question is whether or not there was evidence of lameness attributable to patellar luxation BEFORE the CCL failed. If not, or if there is any doubt, I will treat the CCL in isolation. I don't like these surgeries to be called 'stabilisations' - first the stifle joint is defined by the fact that the components move - it is never truly 'stable'. Second none of the surgeries are effective in abolishing the passive 'instability' - the osteotomies don't try and the lateral suture techniques don't achieve.

If clinically significant patellar luxation persists after CCL treatment (or if it appears - medial patella luxation can be seen as a result of technical error during TPLO or TTA surgery) then further surgery might be indicated.

In practice, clinically significant medial patella lunation is usually obvious in dogs around the time of skeletal maturity while CCL failure tends to be a feature of somewhat older dogs so only rarely do we encounter the two as significant clinical problems in the same dog. That said, beware the Westie. In my experience it is not unusual to see Westie's with low-grade patella laxations that are well-tolerated until the dog's CCL fails. In referral practice I saw these presenting following "failed" patella surgery with the CCL failure having gone un-noticed. Some of those improved with lateral suture surgery but I prefer TPLO or TTA in such cases because the standard osteotomy can be modified to effectively lateralise the tibial tuberosity thereby addressing the patella luxation at the same time as the CCL failure.

I hope that this makes sense.

Aplogies for flooding vetsurgeon with verbose replies over the last few days - I am midway through some research and writing the is not holding my attention and I am finding vetsurgeon to be a ready distraction!!

RE: Cruciate and patella luxation issues

Andrew Mellor — Wed, 22 Jul 2020 09:51:58 GMT

Thank you so much for such a comprehensive reply.

I will speak with the owner and follow your advise, finances allowing.

RE: Cruciate and patella luxation issues

Julian Earl — Sat, 18 Jul 2020 10:25:04 GMT

Regarding the combination of the two problems, which is not rare, do you find that stabilising the cruciate aspect first reduces the tendency for the patella to dislocate? That was my experience due, presumably to the increased stability ensuring that the patella was effectively pushed deeper into the groove or at least held there with more force. Plus the quadriceps is more effective with a stable joint as well. Repairing both at the same time is tricky so I tried to prioritise the surgeries I would expect that the cruciate lesion is the far more painful of the two and certainly heads to far more osteoarthritis within the joint. In this respect I think a luxating patella is probably over-rated as a case of arthritis.

Any thoughts or comments on my notes here? I am far, far from an orthopaedic expert like Malcom but have seen very many cruciates in particular i my forty years in practice!

Thanks in anticipation.

RE: Cruciate and patella luxation issues

Malcolm Ness — Sat, 18 Jul 2020 08:57:50 GMT

As with anything cruciate related, things are confused and controversial!

Some thoughts:

The signs of pain may, or may not be related directly to the cruciate.

The meniscal injury is almost certainly clinically insignificant.

The failed lateral suture is probably insignificant - there is a very poor correlation between palpable "stability" and good clinical outcome. Many (probably most) dogs that do well clinically after lateral suture surgery have demonstrably 'unstable" stifles.

It is not possible to make much sensible comment without recent radiographs and ideally the post op pictures. Any orthopaedic surgery that involves implants or the drilling/cutting of bone should include post op radiographs. Omission is a high-risk strategy.

Poor clinical outcome is not unusual with lateral suture techniques, especially in a larger, obese dog.

The radiograph shows considerable joint effusion/synovitis and that is almost certainly the cause of the patella being elevated from the trochlea. That in turn will allow the patella to be easily displaced laterally and medially. That is not the same as "Patella Luxation" by which I understand a patella that luxates during normal locomotion. The patella laxity detected in this case will have been exacerbated by the CCL ruptured (the normal cruciate controls internal tibial rotation) and also perhaps by the disruption of the joint capsule associated with surgical stifle explorations. If there was no clinically significant patella luxation before the CCL incident, then I wouldn't worry about it too much now.

The tibia on this radiograph is cranially sub-luxated and that is consistent with a failed CCL. The statements above about tibial thrust are incorrect - cranial tibial thrust is a force that can be neither defined nor inferred radiographically.

The presumption that TTA would make things worse because of cranially moving the tibial tuberosity is wrong. The various tibial osteotomies described for treating the lameness associated with CCL rupture/failure depend upon modifications to the biomechanics of the stifle joint. Those mechanics require that the normal forces are acting across the joint (muscle pulls; gravity; ground reaction forces etc etc). Simplistic conclusions and extrapolations from radiographs cannot be made.

Cranial wedge osteotomies of the tibia (CTWO etc) are simply TPLO procedures, they offer no advantages over the 'conventional' radial osteotomy TPLO and in fact, the opposite is true. Notably, the original USA patent filed by Dr Slocum for TPLO featured a wedge osteotomy. The mechanics of these procedures is complex and incompletely understood. The version implied in the earlier posts is over-simplified and not complete correct.

Rob raises the question of patella alta. In my experience that is very rarely of clinical significance and in this case there is a degree of radiographic artefact - the patella is displaced somewhat proximally because the distal femur is displaced somewhat caudally.

Where to go with this case?

First, a detailed clinical exam to confirm the stifle as the seat of pain. Next, a good radiographic study. If that reveals nothing necessitating urgent treatment then I would look to a lengthy course of NSAID (8 weeks+) during which time the dog should be gradually returned to full activity. If lameness or other signs persist and can be confidently attributed to CCL failure then further surgery should be considered. Either a conventional (Slocum) TPLO (the other wedge and triple osteotomy techniques are inferior) or one of the TTA techniques. Beware that these are challenging techniques, especially in a dog of this type.

RE: Cruciate and patella luxation issues

Rob Loxley — Sat, 18 Jul 2020 07:47:57 GMT

Is there a view of the other stifle; is there patella alta?

RE: Cruciate and patella luxation issues

Andrew Mellor — Fri, 17 Jul 2020 10:59:02 GMT

Sorry none were taken

RE: Cruciate and patella luxation issues

Malcolm Ness — Fri, 17 Jul 2020 10:27:54 GMT

Are any of the later 'post-op' pictures available?

RE: Cruciate and patella luxation issues

Andrew Mellor — Fri, 17 Jul 2020 09:39:58 GMT

this is only one I can get a half reasonable image of . Tibia looks to have sponge wedge pushing it caudally for TTA measurements. My colleague then chose lateral suture after discussion with owner I think mainly re finance

RE: Cruciate and patella luxation issues

Malcolm Ness — Fri, 17 Jul 2020 09:22:30 GMT

Hi Andrew. Do you have the radiographs available to post?

RE: Cruciate and patella luxation issues

Tafara Mapuvire — Thu, 16 Jul 2020 19:48:02 GMT

Thanks for the reply. Sounds truly tricky. If lateral suture is still intact then you shouldn't have cranial tibial thrust. TPLO and CTWO will only counter CTT during weight bearing which might help with the patellar luxation. If TPA is steep then I would suggest CTWO. Some surgeons combine TPLO with lateral suture to counter internal rotation of tibia, CTT during non weight bearing phase, and pivot shift phenomenon.

RE: Cruciate and patella luxation issues

Andrew Mellor — Thu, 16 Jul 2020 19:37:30 GMT

Thanks for your reply but patella is luxating laterally and medially because insertion of patella tendon is so far forward because of tibial thrust. Perhaps if tibial plateau angle was more normal with a tplo or cwo then thrust would be reduced and patella could sit into its groove.

RE: Cruciate and patella luxation issues

Tafara Mapuvire — Thu, 16 Jul 2020 19:12:09 GMT

Hi Andrew.

I am a GP with a bit of experience in orthopaedics especially cruciate ligament disease. Would be interesting to know what's causing the patellar luxation since groove is deep enough. I suspect excessive internal rotation of the tibia due to CrCL deficiency and or malalignment of quadriceps mechanism due to genu varus common in this breed. TTA with tibial tuberosity lateralisation might help if luxation is unilateral (most likely medial?) & groove deep enough. Would also make sure lateral suture hasn't snapped again as excessive internal rotation of tibia relative to the femur can precipitate medial patellar luxation. Also consider a CTWO as it also allows you to correct any angular limb deformities of the proximal tibia, which are common in this breed and can contribute to patellar luxation.

Cheers,

Tafara