0
    519
    views

    Evaluating Implant Survival and Outcomes in Young THA Patients

    In a study presented at the AAOS Annual Meeting, researchers from Hospital for Special Surgery examined a cohort of patients who had undergone total hip arthroplasty at age 35 and younger to determine characteristics of implant longevity and long-term outcomes as reported by the patients.

    Not that long ago, hip fusion was the primary surgical option for young patients with hip conditions such as developmental dysplasia of the hip (DDH) or juvenile idiopathic arthritis (JIA). Now, with improvements in implants and surgical techniques, the options have expanded to include total hip arthroplasty (THA) – and it’s being offered to younger and younger patients as a viable procedure to restore their mobility and reduce pain.

    Little is known, however, about long-term outcomes in these younger patients. Researchers from the Hospital for Special Surgery in New York sought to bring some clarity to the issue with a study of implant survival and long-term patient-reported outcomes in 400 patients who underwent THA at age 35 or younger. The authors believe this is the largest study of implant survival and patient-reported outcomes in these young THA patients.

    They presented their findings at the 2018 Annual Meeting of the American Academy of Orthopaedic Surgeons in New Orleans.

    A total of 548 THAs were performed in this patient cohort between 1982 and 2011. Most of the patients had osteonecrosis of this hip; DDH and JIA were other common reasons for the surgery. The researchers retrospectively collected demographics and clinical, surgical, and implant data on these patients, and then prospectively evaluated outcomes by sending surveys to the patients to ask about implant survival and outcomes. Outcomes were evaluated using the patient-reported hip disability and osteoarthritis outcome score (HOOS).

    Looking at Implant Survival

    Overall, implant survival at 10 years was 87% (95% Confidence Interval [CI]: 84% – 90%) and 61% (95% CI: 55% – 67%) at 20 years. Patients who were age 25 or older at the time of surgery did better than younger patients, as did male patients compared with female patients (both P<0.01).

    Bearing surface played a role in implant survival, the researchers found. Patients with ceramic-on-polyethylene bearings had greater implant survival than those with metal-on-polyethylene bearings (P=0.02). The patient’s primary diagnosis was also factor, with the worst implant survival seen in patients with a primary diagnosis of JIA (P=0.05). No differences were seen in survival between cemented and cementless implants.

    The implant survival numbers were a bit of a surprise for senior study author Mark P. Figgie, MD, Chief of the Surgical Arthritis Service at Hospital for Special Surgery. “I expected the durability of the implants to be better than it was,” he said. “Survivorship at 15 years was at a lower point than expected. Younger patients are not getting the same survivability as older patients, which may be due to greater activity and sizing and fit issues.”

    What wasn’t a surprise was the impact of primary diagnosis on implant survival. Dr. Figgie noted that historically, there have not been enough implant options for younger patients, particularly those with hip conditions like JIA and DDH. “They have early closure of the growth plates, which leads to high anteversion of the proximal femur,” he said. Surgeons “can’t always get the implant to fit without causing damage.”

    Looking at Implant Fit Issues

    Given that implant fit is critical to implant survivorship, are custom-fitted implants the answer for patients with challenging anatomy or deformities? Yes and no, Dr. Figgie said. For many younger patients with hip conditions, standard, off-the-shelf implants are too big. The surgeon could remove more bone to get the implant to fit properly, but that’s not a good solution for these young patients, in whom minimizing bone loss is the goal.

    In the study, Dr. Figgie and his colleagues found that overall, implant survival was not better for custom versus standard implants. “That’s because the custom implants were going into patients who had the worst deformities and worst bone, often bilateral disease, often involvement of the hips and knees,” Dr. Figgie said. “Standard implants go into fairly healthy patients.”

    Patients who received custom implants did okay, but not better than patients who received standard implants. “Custom implants are useful,” Dr. Figgie said, “but we need better answers and better implants that are economical and can be used by a wider number of surgeons.

    The solution, Dr. Figgie believes, is an implant that is customizable, but not completely custom. Custom implants have drawbacks: They’re expensive and take time to manufacture, and if there are fit issues in the OR, the surgeon is stuck and will have to find a way to make it work in that patient, much as with a standard implant.

    “One thing I think is going to help is coming up with a modular system that corrects for anteversion and offset,” Dr. Figgie said. Step-by-step guidelines are also needed to “virtually walk surgeons through the particulars of the procedure so they understand how to fit the implant without violating the patient’s bone,” he added. Robotics might also be incorporated to increase precision.

    Looking at the HOOS Scores

    Besides implant survival, the researchers wanted to gain insight into how patients were doing, with follow-up from a few years to about 30 years after patients had undergone THA (mean of 14 years). Patients reported the following mean HOOS scores:

    • 86 (95% CI: 84 – 88) for pain
    • 84 (95% CI: 82 – 86) for symptoms
    • 86 (95% CI: 85 – 88) for ADLs
    • 77 (95% CI: 75 – 80) for sports

    HOOS-Symptom and HOOS-ADL scores were worse in patients who had a single-staged bilateral THA compared with those who had unilateral THA, based on regression analysis (P= 0.02 and P=0.03, respectively). Patients who needed a custom implant had worse HOOS-ADL scores than patients with standard implants (P=0.03).

    Patients with ceramic-on-polyethylene implants had significantly better HOOS scores than patients with metal-on-polyethylene implants (P<0.01). Patients who had needed a revision THA by the follow-up had significantly worse HOOS scores than patients who had not undergone revision procedures, regardless of implant type (P< 0.01).

    Looking at Next Steps

    After evaluating the data and patient-reported outcomes, Dr. Figgie and his colleagues concluded that THA is a viable option for patients age 35 or younger. Implant survival is good, with favorable long-term patient-reported outcomes.

    The next step, Dr. Figgie said, is to further evaluate the reasons for revision THA in these patients. They’re just getting started with a study that will dig deeper into that data to find answers to these questions:

    • What type of revision was done: acetabular, femoral, or both?
    • Why was the patient revised?
    • What was the outcome of the revision?

    The answers may help define the next iteration of surgical management for younger patients with hip conditions who need THA.

    Source

    Swarup I, Lee Y-Y, Sutherland RT, Shields M, Figgie MP. Implant Survival and Patient-Reported Outcomes after Total Hip Arthroplasty in Young Patients (Paper 659). Presented at the 2018 Annual Meeting of the American Academy of Orthopaedic Surgeons, March 6-10, 2018, New Orleans, Louisiana.

    Disclosures

    The study authors have no disclosures relevant to this article.