Rare Case of Staphylococcus Caprae Periprosthetic Hip Infection with Unusual Clinical Presentation: A report

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Total hip arthroplasty (THA) surgeries are rapidly increasing due to an aging population, leading to an increase in degenerative hip osteoarthritis. However, 1% of these patients go through prosthetic joint infection (PJI), which gives rise to implant failure with prolonged periods of patient incapacitation and higher mortality risk.

Case Report

A 62-year-old male patient underwent a primary uncemented THA by direct anterior approach inn June 2020 due to the left hip end-stage osteoarthritis. After 4 days, the patient was discharged home without complications.

In January 2021, the patient presented with groin and buttock pain at rest and during walking, with limited range of motion (R.O.M) but with no symptoms of inflammation. MRI examination showed the presence of a voluminous three-lobed fluid-filled cyst around the implant. Synovial fluid was aspirated (23 ml) and four samples were collected for cultures, all of them yielding negative results.

In February 2021, the patient underwent arthroscopic synovectomy. After 1 month of follow-up, he underwent a new MRI, which showed the presence of a new voluminous cyst around the implant surrounding the nervous-vascular bundle causing paresthesia on the medial side of the thigh, and showed the same characteristics as the previous one. Subsequently, he was admitted to the hospital and a complete open resection was performed with femoral and obturator nerves neurolysis.

Several samples were collected for cultures, all of them yielding negative results. The patient presented good hip function, but complained of persistent groin pain. After 7 months, he underwent 111 Indium-labeled white blood cell bone scan which documented a high leukocyte uptake around the greater trochanter. In October 2021, he underwent a new ultrasound which showed the presence of a new voluminous cyst (50 mm ×15 mm) around the implant with the same characteristics as the previous one. Synovial fluid was aspirated (20 ml) and sent for cultures. Cultures were negative. In November 2021, he was admitted for further examinations. PET-CT showed presence of increased uptake around the ileo-psoas and vastus lateralis muscles. A new ultrasound showed the presence of a voluminous cyst (42 mm × 10 mm) around the implant, and blood test revealed ESR of 42 mm, and C-reactive protein (CRP) level of 0.58 mg/dl. In January 2023, he underwent triple phase bone scan that showed increased activity isolated to the proximal femur around the femoral stem. Since there were no clear signs of infection, an isolated single stage femoral stem revision was performed in February 2023. During the surgery, several swabs were collected and sent for culture. All three samples came positive for S. caprae.

As per infectious disease consultant’s recommendations, the patient was treated with 100 mg oral minocycline twice a day for 4 weeks. Two months after surgery, the patient complained of groin and buttock pain. Inflammatory markers were elevated (CRP 47.30 mg/dL), and a pelvis MRI showed a fluid containing formation with the same characteristics as the previous MRI.

In June 2023, he underwent a new ultrasound which showed the presence of a new voluminous cyst around the implant with the same characteristics as the previous one. Synovial fluid was aspirated (18 ml) and sent for cultures. Cultures revealed the presence of S. caprae; susceptibility to rifampin and minocycline was confirmed, which prompted the infectious disease consultant to initiate these antibiotics. The patient started taking 100 mg oral minocycline twice a day and 600 mg oral rifampin once a day. At this time, the decision was made to opt for the two-stage revision prosthesis.

In July 2023, he underwent explant and spacer placement. During the operation, synovial and tissue samples were collected for cultures that were positive for the same pathogen. The femoral stem and acetabular component were removed, and thorough debridement and irrigation with pulse lavage were performed. Vancomycin-Gentamicin loaded bone cement was used, and a new intraoperatively molded articulating hip spacer was placed.

The patient was hospitalized for 10 days and treated with 100 mg IV minocycline twice a day, 600 mg IV rifampin once a day in addition 850 mg IV daptomycin once a day was given since CRP levels remained persistently elevated despite therapy with minocycline and rifampin. The day before discharge daptomycin was discontinued and a single 1500 mg IV infusion of dalbavancin was administered to achieve comprehensive coverage and an appropriate duration of therapy, considering that dalbavancin is a long-acting antibiotic.

This was followed by outpatient 100 mg oral minocycline twice a day and 600 mg oral rifampin once a day. Ten days after beginning oral antibiotic therapy, minocycline was discontinued due to adverse side effects (dyspepsia and asthenia), 750 mg oral levofloxacin once a day was initiated as replacement therapy. In October 2023, the patient was readmitted for the second-stage. A spacer removal and a revision hip arthroplasty was performed using an uncemented multiholes titanium cup and a modular tapered titanium revision stem.

During the hospitalization, he continued the therapy with levofloxacin, rifampin, and daptomycin. At the time of the surgery, several swabs were taken and sent for culture which came out negative. The patient was discharged after 8 days without complication. Total oral antibiotic therapy with levofloxacin and rifampin was continued for 10 additional days.

The last follow-up 6 months after the revision showed no sign of loosening or persistent infection.

The authors commented – ‘S. caprae represents an extremely rare cause of hip PJI. There is paucity of data on the best surgical and antibiotic management in literature. We report the 11th case successfully treated with a two-stage exchange protocol.’

Further reading:

A Rare Case of Staphylococcus Caprae Periprosthetic Hip Infection with Unusual Clinical Presentation Daniele Grassa et al Journal of Orthopaedic Case Reports 2025 January:15(1):Page 51-55 DOI: https://doi.org/10.13107/jocr.2025.v15.i01.5122