Navigating the Waters: DVT Risk After Knee Osteotomy Surgery

Hey there! Let’s chat about something pretty common in the world of orthopedics, specifically when folks are dealing with that pesky knee osteoarthritis, especially the kind that makes your knee bow outwards (that’s ‘varus deformity’ for you). One go-to surgery to help realign things and hopefully save the knee joint for a while is called Medial Opening-Wedge High Tibial Osteotomy, or MOWHTO for short. It’s a solid procedure, widely used, particularly for younger, active people.

But, like with any surgery, there are potential bumps in the road. One that gets talked about, but maybe not always fully understood in the context of MOWHTO, is Deep Venous Thrombosis (DVT). You know, those blood clots that can form in the deep veins, usually in your legs. They can be serious business, sometimes leading to bigger problems like a pulmonary embolism, which is definitely something we want to avoid.

So, even though doctors use standard preventative measures (like blood thinners or compression stockings), the risk is still there. And honestly, the studies out there haven’t always painted a super clear or consistent picture of just how often DVT happens after MOWHTO, or who is most likely to get it. This is partly because different studies use different methods, look at different groups of people, and even detect DVT in various ways.

That’s where this particular study comes in. A team of researchers decided to take a closer look, specifically at patients who had MOWHTO for that varus knee osteoarthritis. They wanted to nail down the actual incidence rate of DVT and figure out which factors might put someone at higher risk.

Taking a Look Back: The Study Setup

The researchers conducted a retrospective study, which means they looked back at existing patient records. They reviewed data from patients who underwent MOWHTO at a single center between January 2019 and September 2023. They included patients with medial compartment knee osteoarthritis and varus deformity who had a specific type of plate fixation.

They had some criteria for who *not* to include, like patients with a history of blood clots, bleeding disorders, those already on blood thinners, or those having other knee surgeries at the same time. This helped them focus specifically on new DVT cases after this particular procedure.

Crucially, all patients in this study had mandatory postoperative ultrasound screenings for DVT. This is a key point because it helps catch clots that might not be causing symptoms (which, spoiler alert, many in this study didn’t!). Based on the ultrasound findings, patients were sorted into groups: those who developed DVT and those who didn’t.

They then compared a whole bunch of stuff between these groups: demographics (age, sex), lifestyle (smoking, alcohol), other health issues (diabetes, hypertension, etc.), details about the surgery itself (duration, blood loss), and even some lab test results taken the day after surgery. They used statistical methods to see which factors were significantly different between the groups and, more importantly, which ones were independently associated with DVT risk.

The Findings: What Did They Discover?

Alright, let’s get to the numbers. The study included 421 patients. The median age was 56, and about two-thirds were female.

Here’s the headline: A significant number of patients developed DVT *after* the surgery. Out of the 421 patients, 55 (which is about 13.1%) had a new DVT detected postoperatively.

Now, where were these clots located? This is interesting. Most of them, a whopping 81.8% of the DVT cases (or 10.7% of all patients), were in the calf muscle veins (that’s called ICMVT). Clots in the deeper calf veins (DCVT) were less common (1.9%), and proximal DVT (the ones higher up, like in the popliteal or femoral veins, which are generally considered more serious) were quite rare, only occurring in 2 patients (0.5%). Most of these DVTs were found on the operative side, but some were on the non-operative side, and a few were even bilateral. And notably, nearly all of these DVT cases were *asymptomatic* – meaning the patients didn’t feel anything was wrong. Only one patient developed a pulmonary embolism, and they also had a calf DVT.

What about those lab tests? The researchers looked at various blood markers the day after surgery to see if any could predict DVT. Things like D-dimer (often used to screen for clots), hemoglobin, platelet count, etc. The results here weren’t super promising. Most of the lab indexes didn’t show a significant ability to predict DVT. A couple did (AT III and FDP), but their predictive power was considered poor. So, relying solely on these routine blood tests right after surgery might not be the best way to screen for DVT in this group.

Identifying the Risk Factors

This is a crucial part. By comparing the DVT group to the non-DVT group, and using statistical modeling, the researchers pinpointed factors that were *independently* associated with a higher risk of developing DVT after MOWHTO. The big three they found were:

• Female sex: Women were found to be more than twice as likely (OR 2.23) to develop DVT compared to men.
• Diabetes: Patients with diabetes had about a 2.5 times higher risk (OR 2.47) of DVT.
• Hyperlipidemia (high levels of fats/cholesterol in the blood): Patients with hyperlipidemia had almost twice the risk (OR 1.91) compared to those without it.

Other factors like age, BMI, smoking, hypertension, or even the details of the surgery itself didn’t come out as independent risk factors in this study’s final model.

What Does This Mean for You?

These findings are pretty important for both patients and doctors. First off, the 13.1% incidence rate, even with standard prophylaxis, tells us that DVT after MOWHTO is not a rare event, although thankfully, most clots were in the calf veins and asymptomatic. This highlights the importance of routine screening, like the mandatory ultrasounds used in this study, to catch these silent clots.

Secondly, knowing *who* is at higher risk is key. If you’re a woman, or if you have diabetes or hyperlipidemia and are considering MOWHTO, this study suggests you might be in a higher-risk group for DVT. This doesn’t mean you can’t have the surgery, but it *does* mean your doctor might want to be extra vigilant about DVT prevention and monitoring.

This could involve:

• More intensive or longer-duration blood thinner prophylaxis.
• Ensuring consistent use of mechanical methods like compression stockings or devices.
• Potentially closer monitoring with ultrasound after surgery.

The study also points out that standard lab tests right after surgery might not be the best predictors, suggesting a need to look at clinical factors and patient history more closely, and perhaps explore other, newer markers in the future.

A Few Caveats

It’s worth remembering that this was a retrospective study from a single center. While it included a good number of patients, looking back at records can sometimes miss details or introduce biases. For example, they relied on documented medical conditions, which might be underestimated. Also, while diabetes was a risk factor, the study couldn’t tell if it was the high blood sugar itself or the medications used to treat it that contributed to the risk. And the timing of the postoperative ultrasound (between days 3 and 7) means they might have missed clots that formed earlier or later.

Despite these limitations, the study provides valuable insights. It confirms a notable incidence of DVT after MOWHTO, primarily in the calf, and importantly, identifies female sex, diabetes, and hyperlipidemia as significant risk factors.

Wrapping It Up

So, the takeaway? MOWHTO is a great option for many, but it’s important to be aware of the potential for DVT. This study helps shine a light on the actual incidence and, crucially, points towards specific patient characteristics – being female, having diabetes, or having hyperlipidemia – that seem to increase the risk. This knowledge can help doctors and patients have better conversations about risk, plan more targeted prevention strategies, and hopefully make the recovery process safer for everyone.

Source: Springer