VCOT March 2026 – Ortho Part 2: THR Cup Impactors & Patient-Specific Feline Spinal Guides

In this Simini Small Animal Surgery Podcast episode, we conclude our orthopedic coverage from the March 2026 issue of Veterinary and Comparative Orthopaedics and Traumatology (VCOT) by examining how better surgical instrumentation can improve precision, consistency, and patient safety. 

One study evaluates an ergonomically redesigned cup impactor for canine total hip replacement, while the second demonstrates how patient-specific 3D-printed drill guides may transform feline spinal stabilization.

In this episode:

✅ Mancusi et al. — A cadaveric study comparing a prototype ergonomic acetabular cup impactor with a conventional impactor during Zurich cementless total hip replacement. Among novice surgeons, the prototype significantly improved the angle of lateral opening (ALO), reducing the mean placement from 48.9° with the standard impactor to 43.2°, much closer to the ideal 45° target. However, the improved instrument did not improve cup retroversion, reinforcing that while better tools can reduce mechanical errors, accurate interpretation of anatomic landmarks remains essential for successful THA. 

✅ Rigo et al. — Evaluated patient-specific 3D-printed drill guides for thoracolumbar pedicle screw placement in cats. Across 126 pilot holes, the guides achieved an overall 91.2% safe placement rate, including 100% accuracy within the thoracic spine. Importantly, all breaches occurred laterally, with zero medial breaches or spinal canal violations, demonstrating that patient-specific guides can substantially improve safety while allowing a less invasive dorsal surgical approach. The study also reports the first successful clinical application of this technique in a feline patient, highlighting its potential for future spinal stabilization procedures. 

Together, these studies demonstrate that the future of orthopedic surgery isn't simply better implants—it's smarter instrumentation that helps surgeons consistently perform at a higher level.

🎓 Journal Articles Discussed

• Mancusi et al. — Comparison between Two Zurich Cementless Total Hip Replacement Cup Impactor Types in the Accuracy of Cup Positioning: An In Vitro Study
• Rigo et al. — Feasibility and Accuracy of Pedicle Screws in the Feline Thoracolumbar Spine

📚 From the March 2026 issue of VCOT

🎁 Want to learn more about Simini Protect Lavage or request a sample?

Learn More:
 www.simini.com

Request a Sample:
 https://www.simini.com/evaluation-kit

Transcript

SPEAKER_02 0:04

Hi, I'm Carl Damiani, and this is the Simony Small Animal Surgery Podcast, your fast focused update on what matters most from the latest small animal surgical literature. In each episode, we break down key articles from the veterinary journals and translate them into surgical insight you can use. Today, not someday. This episode continues our orthopedic coverage from issue 2, 2026, of veterinary and comparative orthopedics and traumatology with two studies exploring how better surgical tools and technology can improve precision in orthopedic surgery. First, we'll look at a study by Mencusi et al. comparing two different cup impactor designs for Xurix cementless total hip replacement. Can a better instrument help surgeons achieve more accurate acetabular cup positioning? We'll explore what the data show, particularly for surgeons early in their learning curve, and what that could mean for reducing complications such as postoperative luxation. Then we turn to feline spinal surgery with Rigo et al., who investigated the use of patient-specific three D printed drill guides for pedicle screw placement in the thoricolumbar spine. We'll discuss the remarkable accuracy achieved in their experimental model, the first successful clinical application in a cat, and whether this technology could open the door to less invasive and more reliable vertebral stabilization. Two studies, one common theme, improving surgical precision through better instrumentation and thoughtful innovation, because in orthopedic surgery, small improvements in accuracy can make a big difference in patient outcomes. Let's dive in.

SPEAKER_01 1:45

Four degrees. I mean, in canine total hip replacement, being off by just four degrees, uh it can be the difference between a textbook recovery and a completely devastating prosthesis luxation.

SPEAKER_00 1:57

Yeah, it's a terrifyingly small margin to work with.

SPEAKER_01 2:00

Right. So you know when you buy a premium tennis racket thinking it'll magically fix your swing, we're asking if but better surgical hammer can actually fix a beginner's technique, or if it really just comes down to, you know, anatomical mastery. Welcome to today's deep dive.

SPEAKER_00 2:15

Glad to be here. And well, we're pulling the data today from a recent cadaveric study, uh, Mencusi et al. 2026. They looked at exactly this problem. Oh, right.

SPEAKER_01 2:24

Testing prosthetic cups, I think.

SPEAKER_00 2:26

Yeah, they tested 80 prosthetic cups across 40 canine acetabula. And the focus was really comparing a standard cup impactor against this uh new ergonomic prototype.

SPEAKER_01 2:36

And that prototype, it has size-matched cup holders and a specifically widened hammering surface, right?

SPEAKER_00 2:41

Exactly. But the really critical part of the design wasn't just the tools themselves, it was who was actually holding them. They pitted a senior surgeon with 20 years of experience against a complete beginner.

SPEAKER_01 2:51

Which is brilliant, because we all know that standard impactors are incredibly unforgiving. I mean, it's like trying to drive a nail while balancing it on a golf deep.

SPEAKER_00 2:59

Yeah, that's a great way to put it.

SPEAKER_01 3:01

If your wrist drops even a fraction of an inch during the strike, you just drive the cup entirely off center.

SPEAKER_00 3:07

And that wrist drop is precisely what causes the excessive angle of lateral opening or ALO. And the data from this study completely proves it. For the beginner, using the standard impactor, uh, their mean ALO drifted way out to 48.9 degrees.

SPEAKER_01 3:24

Wow, 48.9, which immediately puts the patient in the danger zone, right?

SPEAKER_00 3:28

Absolutely.

SPEAKER_01 3:29

Because the ideal ALO is around 45 degrees, and the moment you creep up toward 49, your risk of craniodorsal dislocation just skyrockets. So, how exactly did the prototype fix this for the beginner?

SPEAKER_00 3:40

Well, it comes down to the physics of that wider hammering surface. By expanding the strike zone and matching the cup holder exactly to the implant size, the prototype acts almost like um like bowling bumpers.

SPEAKER_01 3:52

Bowling bumpers, I like that.

SPEAKER_00 3:53

Yeah, it physically forces the surgeon's strike to remain perpendicular. It restricts the hand from dropping during the impaction. And because of that mechanical constraint, the beginners mean ALO corrected to 43.2 degrees.

SPEAKER_01 4:06

Oh wow. 43.2 is a highly secure margin. So it just physically overrides the human tendency to drift.

SPEAKER_00 4:13

That's brilliant. But uh, what about the senior surgeon? Let me guess. Muscle memory trumped the tool.

SPEAKER_01 4:19

You nailed it. The tool made absolutely zero difference for the senior surgeon. I mean, 20 years of calibrating that wrist angle meant they hit the ideal trajectory regardless of the impactor's design.

SPEAKER_00 4:31

Makes sense. So the prototype is a massive safety net for beginners struggling with ALO, but that's really only half the alignment battle. Did this wider striking surface do anything to help the beginner orient the angle of cup retroversion?

SPEAKER_01 4:43

Not at all. It offered no advantage whatsoever for retroversion. The beginner consistently placed the cup in a much less retroverted position than the senior surgeon, no matter which tool they were using. Which makes sense mechanically. An impactor can force a perpendicular strike to control the lateral opening, but retroversion relies entirely on reading the patient's specific bone morphology.

SPEAKER_00 5:05

Right, exactly.

SPEAKER_01 5:05

I mean, the hammer can't tell you where the dorsal acetabular rim is.

SPEAKER_00 5:08

Yeah.

SPEAKER_01 5:09

You still need the anatomical mastery to visualize the alignment in 3D space.

SPEAKER_00 5:13

It's so true. The overarching lesson for your OR tomorrow is really about layering safety nets. We use specialized ergonomic tools to eliminate the mechanical variables we can control like a beginner's wrist drop.

SPEAKER_01 5:26

Aaron Powell Right, so they can focus on the hard stuff.

SPEAKER_00 5:28

Exactly. It frees up all their mental bandwidth for the variables they can't mechanize, like anacomical landmark recognition.

SPEAKER_01 5:34

Aaron Powell It's the core philosophy of modern surgery, really. Just systematically mitigating risks at the surgical site before they become post-operative complications. You upgrade your impactor to mechanically prevent alignment errors, and well, you upgrade your biological protocols for the exact same reason.

SPEAKER_00 5:50

100%.

SPEAKER_01 5:51

Like we know standard saline leaves about 42% of bacteria behind in the surgical site. So integrating a non-antibiotic, flush-like Semini Protect Livage into your closure protocol, it isn't just an add-on. It's a calculated safeguard.

SPEAKER_00 6:06

It removes that 42% that saline misses.

SPEAKER_01 6:09

Exactly, leaving 0% behind. You're systematically closing the gaps where human error or biological chance can creep in.

SPEAKER_00 6:16

And layering those safeguards is what separates a good outcome from a great one. So to summarize the findings from Ancusi et al. 2026, upgraded ergonomic impactors will significantly improve lateral opening accuracy for your less experienced surgeons. But uh teaching precise anatomical landmark recognition that remains absolutely non-negotiable for proper retroversion.

SPEAKER_01 6:38

You still have to know the anatomy, which leaves you with something to chew on before your next procedure. If mechanical tool design can already correct physical alignment errors for a beginner, how long until we see, you know, smart impactors?

SPEAKER_00 6:49

Oh, that's an interesting thought.

SPEAKER_01 6:51

Right. Tools that offer real-time haptic feedback to actively guide retroversion mid-surgery. Think about it. Turning the page. But if you told them they had to do it, like while reaching through a keyhole entirely by feel and avoiding live power cable well, they'd probably just walk off the job. Welcome to today's deep dive. If you're a busy veterinary surgeon, this one is tailored specifically for you.

SPEAKER_00 7:32

Yeah, we're looking at a fundamentally new approach to feline spine stabilization today. We're extracting all the clinical intelligence from a single paper, which is uh Rego Ital 2026.

SPEAKER_01 7:43

Aaron Powell Right, because the clinical environment for feline thoracolumbar vertebral fractures is just incredibly demanding. I mean, the standard approach requires exposing the lateral aspect of the vertebral body.

SPEAKER_00 7:54

Aaron Powell, which means dissecting through those really bulky costal attachments, and that just, you know, gets up so much valuable OR time.

SPEAKER_01 8:01

Oh, absolutely. And the historical dogma has always been that feline pedicles are just simply too tiny for safe screw replacement. Hence that uh carpentry through a keyhole problem I mentioned. You have virtually zero margin for error there.

SPEAKER_00 8:12

Aaron Powell Exactly. You really don't. But Rego at all. 2026, they bypassed that assumption entirely. They introduced custom 3D printed drill guides paired with 1.7 millimeter screws.

SPEAKER_01 8:25

Wow, 1.7 millimeters? That's tiny.

SPEAKER_00 8:28

It is. And they didn't just theorize this either. The team designed a really rigorous study. They first tested these customized guides across, I think it was 126 drilled holes on multiple 3D printed cat spines.

SPEAKER_01 8:42

Okay, so a lot of reps on the models first.

SPEAKER_00 8:44

Right, yeah. And then they validated the mechanics on an actual live clinical case.

SPEAKER_01 8:48

Aaron Powell, which makes perfect sense mechanically, because rather than relying on a surgeon's freehand angle, these custom guides act like a, well, like a bespoke lock and key mechanism.

SPEAKER_00 8:58

Aaron Powell Yeah, they essentially snap right onto the unique, really complex topography of that specific patient's vertebrae.

SPEAKER_01 9:04

Aaron Powell So it creates a physical jig that just locks the drill into the exact required trajectory.

SPEAKER_00 9:09

Aaron Powell Precisely. And the results actually reflect that level of control. The study demonstrated an impressive 91.2% overall safety rate.

SPEAKER_01 9:16

Aaron Powell That's massive. So over 90% of those screws were perfectly placed.

SPEAKER_00 9:20

Yeah. Meaning over 90% of those 1.7 millimeter screws were completely contained within those incredibly narrow feline pedicles.

SPEAKER_01 9:28

Aaron Powell But let's look a little closer at that remaining percentage, though, because the data isn't, you know, uniform across the spine, is it?

SPEAKER_00 9:34

Aaron Powell No, it's not. There's a split. So the thoracic segment saw a flawless 100% success rate, but the lumbar segment dropped to an 88% success rate.

SPEAKER_01 9:44

Aaron Powell Okay, wait. As a surgeon, a 12% chance of breaching a lumbar pedicle that immediately raises a red flag for me regarding the spinal canal. Doesn't that put the cord at risk?

SPEAKER_00 9:55

Aaron Powell Well, the anatomy actually dictates that outcome because thoracic pedicles in cats are slightly thicker than the lumbar ones. But to address your concern, the crucial reassurance for the surgeon here is that every single one of those lumbar breaches was strictly lateral.

SPEAKER_01 10:09

Oh, interesting. So there was no medial penetration at all?

SPEAKER_00 10:12

Zero. There was zero medial penetration and absolutely no spinal canal invasion across the entire study.

SPEAKER_01 10:17

Aaron Powell So the drill guide essentially forces any margin of error outwards, like into the muscle rather than inward toward the cord. That has to be a highly intentional safety buffer.

SPEAKER_00 10:27

It absolutely is. If the drill bit deflects off the dense cortical bone, the trajectory of least resistance is forced away from the nervous system.

SPEAKER_01 10:35

Aaron Powell Right. So because we know the spinal canal is safe, even with that 12% lateral breach rate in the lumbar spine, that really fundamentally changes our approach angle.

SPEAKER_00 10:44

It really does. We no longer need to dissect down laterally at all. Surgeons can rely solely on a dorsal exposure.

SPEAKER_01 10:51

Which biomechanically is a massive procedural advantage. I mean, if you can work entirely dorsally and just bypass the costal attachments completely, then a single cement pour can incorporate the screw heads bilaterally.

SPEAKER_00 11:04

Yes, exactly. And that directly opposes the main axis of flexion and extension. It's a much easier, potentially much stronger stabilization.

SPEAKER_01 11:12

Aaron Powell And I'd imagine that significantly reduces surgical trauma and uh time under anesthesia, too.

SPEAKER_00 11:18

Oh, for sure. The take-home message for your practice is really clear here. Feline pedicle screws are a highly feasible, safe alternative, but only if you utilize patient-specific 3D printed drill guides.

SPEAKER_01 11:30

Right. Free handing 1.7 millimeter screws into a cat's pedicle is still firmly off the table. Do not try that.

SPEAKER_00 11:36

Please don't, yeah, definitely off the table.

SPEAKER_01 11:37

Aaron Powell It really makes you evaluate the logistics of the modern veterinary ER, though.

SPEAKER_00 11:41

Yeah.

SPEAKER_01 11:42

I mean, we are probably only a few years away from every specialty hospital having a 3D printer running overnight, like right next to the CT scanner.

SPEAKER_00 11:50

Oh, I totally agree. It's moving that way fast.

SPEAKER_01 11:52

Just imagine scanning a trauma patient at admission and printing a custom surgical roadmap for the next morning. That might soon shift from, you know, cool research novelty to the mandatory standard of care for every complex case you face. Something to think about. You can find the full link to Rego et al. 2026 in our show notes. Until next time.

SPEAKER_02 12:15

That's it for this episode of the Simony Small Animal Surgery Podcast. This show is brought to you by Semini Protect Livage, our interoperative lavage developed to target resistant bacteria and biofilms where traditional solutions of saline and post op antibiotics fall short. If you're interested in learning more or trying out your own procedures, you'll find information and links in the show notes. Thanks for listening, and we'll see you in the next episode.