Patient-specific mechanical navigation system addresses hip replacement problems

More than half of acetabular components placed are malpositioned, according to a recent study from Massachusetts General Hospital.

Component malposition is associated with the most common reasons for revision surgery including instability, wear and wear-associated loosening, and impingement.

The HipSextant Navigation System (Surgical Planning Associates Inc., Boston) is a mechanical instrument, adjusted on a patient-specific basis, designed to achieve appropriate component alignment. The method was invented and developed by Stephen B. Murphy, MD, of Boston.

New technology to track movement, durability of hip, knee implants

A new tracking system enables physicians to determine how a hip or knee implant is interacting with their patients' bodies through use of a radiostereometric analysis device.

The device can help physicians monitor if a replacement implant is wearing down or moving. The implant procedure, according to a Midwest Orthopaedics at Rush news release, also provides a radiostereometric analysis (RSA) registry for implants — allowing researchers to collect data on materials and designs used for hip and knee replacement prostheses.

Scott Sporer, MD, is one of the first physicians in the country to use the new device in all compliant patients, according to the release.

Cementless straight stem proved bone preserving and less invasive

Belgian and French orthopedists determined a new bone-preserving straight, cementless hip stem proved less invasive, preserved bone and performed as well as other hip stems, according to a recently presented study.

Didier Mainard, MD, presented findings from the prospective study at the SICOT XXV Triennial World Congress 2011 in Prague.

“Uncemented stems can have the same good results as the cemented stem,” Mainard told Orthopedics Today in an interview.

Merits of the new stem

Mainard and colleagues theorized a stem coated with a special calcium phosphate called brushite would better preserve bone biology and invented a new uncemented stem that used the material, the Excia implant (B. Braun; Tuttlingen, Germany). The femoral prosthesis is coated proximally with titanium plasma and brushite.

Computer navigation unnecessary for proper component positioning in THA

Although computer navigation can increase accuracy in total hip arthroplasty (THA), surgeons using conventional instruments can achieve proper component positioning without additional costs and time, according to a presentation at Orthopedics Today Hawaii 2012.

“Ideal component position can be achieved with conventional instruments and a consistent surgical technique, so I see no reason to use computer navigation, at least on a regular basis,” Michael D. Ries, MD, said during his presentation.

Templating and positioning

Proper component positioning, Ries said, starts with patient positioning. He noted that the most important thing is to have the pelvis in a secure position.

Analysis examines rate of in-hospital blood clots following hip, knee replacement

A recently published review found that approximately 1 in every 200 patients undergoing hip replacement will develop a venous thromboembolism before hospital discharge when current venous thromboembolism preventive medications are used.

The findings were recently published in the Journal of the American Medical Association and also revealed that 1 in every 100 patients undergoing knee replacement will develop a venous thromboembolism (VTE).

“These estimates are of value to individuals and organizations seeking to evaluate institutional VTE event rates against contemporary benchmarks,” Jean-Marie Januel, RN, MPH, and colleagues wrote in their review. “Our above-mentioned rate estimates provide these contemporary benchmarks.”

Low Cost Orthopedic Implants: 5 Things to Know About Buying at Wholesale Price

Until recently, the cost of orthopedic and spine devices weren't inhibitory for providers, even though 700 percent mark-ups on these devices were the norm. Surgeons were able to select their preferred implants and payor reimbursement would cover the cost. However, with a recession at hand and incentives for lowering the cost of care, more surgeons are looking for high quality implants at the lowest cost; that's where small orthopedic and spine device companies like The Orthopaedic Implant Company come in, which offers implants to providers at their retail price.

"We founded the company about a year ago to meet the needs of surgeons who were frustrated with the high cost of orthopedic implants and our healthcare system's inability to pay for [them]," says Itai Nemovicher, president and co-founder of The Orthopaedic Implant Company. "If we tried to do this five years ago, it probably wouldn't have worked out, but now as physicians and hospitals are forced to align their interests, part of which is cost containment, there is a lot more care on the surgeon's side to use cost-effective implants."

Modular acetabular cup system provides versatility and positive results

The Pinnacle® Hip System (DePuy Orthopaedics, Inc.) was the first cementless acetabular cup to feature a design allowing varying combinations of acetabular liners. Though other designs have since mimicked this approach, Pinnacle has been established as a class leader and an extremely reliable clinical device. Within my clinical practice over the past 10 years, I have implanted more than 3,000 of these acetabular cups, and I continue to use it for all total hip arthroplasty (THA) patients, both primary and revision.

The variable liner cup system allows surgeons to use Pinnacle on almost every patient that requires a THA. In older patients, for example, a polyethylene liner may be the most appropriate bearing choice. In high-demand patients, a hard-on-hard bearing (ceramic-on-ceramic, ceramic-on-metal, metal-on-metal [MoM]) may be the best choice. The variable liner cup also allows for simplified reoperations in the event a revision is required. In fact, there is no need to replace the entire cup when a liner can easily be switched out to accommodate other designs—lipped, lateralized or face-changing liners—in cases of instability. The Pinnacle Hip System uses Variable Interface Prosthesis taper technology to allow for multiple liner options. Additionally, Pinnacle enables me to refine a single surgical technique with which I am very familiar, and one that has provided consistently positive results for my patients. This has the potential to minimize any variability in outcomes that could be introduced by adopting different implant systems, which I would use less frequently, for different patients.

Best of Both Worlds: Stanmore’s Patient-Specific Implant Meets Robotics

In 2012, UK-based Stanmore Implants is preparing to take on part of the world (the UK, Europe, and the United States) with a patient-specific knee system that integrates robotics. Although there are technologies that address patient-specific implant creation, the twist on the Savile Row system is that it integrates such an implant with robotics. “Everything from the planning phase through to the implant manufacture and surgical execution is personalized to the patient,” says Graeme Brookes, managing director of computer-assisted surgery and integrated technologies at Stanmore Implants. As a result, accuracy and reproducibility is introduced into the surgical procedure. The implant is a unicondylar knee replacement, which means it preserves more tissue than a total knee replacement.

Hip Implant Bearing Report Shows Little Difference Among Bearing Combinations

As metal-on-metal hip implants continue to be scrutinized, here's the latest from Jim Dickinson in MD+DI's Washington Wrap-Up:

"A review of clinical trials, observational studies, and registries produced limited evidence on comparative effectiveness of various hip implant bearing combinations, according to an open source British Medical Journal report by researchers from CDRH and universities in the United States and Australia. “Results do not indicate any advantage to metal-on-metal or ceramic-on-ceramic implants compared with traditional metal-on-polyethylene or ceramic-on-polyethylene bearings,” the study concludes....They say they systematically reviewed the evidence as part of that project to determine the short- and long-term outcomes reported by patients undergoing hip replacement and the rates of revision after using implants with various bearings."

Recovery of Orthopaedics Companies Remains Slow

In a daily letter from Canaccord Genuity, analysts reiterated a statement made last summer about the end of the glory days in orthopaedics. That is not to say that things won’t get better, but don’t expect to see improvements until the economy as a whole recovers.

Three Manufacturers Who Look Good:

• China Kangui Holdings. The China-based orthopaedics company continues to grow through its strong product pipeline.
• NuVasive. The acquisition of Impulse Medical could help strengthen NuVasive’s business strategy.
• OrthoFix. The company already surpassed analyst revenue expectations for Q4 2011.

Two Takeaways from the Canaccord Analysts: