Targeting the safe zones for cup position without fluoroscopic guidance in total hip arthroplasty: does the surgical approach affect the outcomes?

• Published in: European journal of orthopaedic surgery & traumatology Vol. 31; no. 7; pp. 1471 - 1476
• Main Authors: Trevisan, Carlo, Rocca, Antonio, Gallinari, Gianluca, Piscitello, Stefano, Klumpp, Raymond
• Format: Journal Article
• Language: English
• Published: Paris Springer Paris 01-10-2021; Springer Nature B.V
• Subjects: Accuracy; Acetabulum - diagnostic imaging; Acetabulum - surgery; Arthroplasty, Replacement, Hip; Fluoroscopy; Hip Prosthesis; Humans; Joint replacement surgery; Joint surgery; Medicine; Medicine & Public Health; Original Article; Orthopedics; Patients; Retrospective Studies; Software; Statistical analysis; Surgeons; Surgical Orthopedics; Transplants & implants; Traumatic Surgery; THA; Safe zone; Approach; Dislocation
• ISSN: 1633-8065; 1432-1068
• DOI: 10.1007/s00590-021-02909-1

Background
Proper acetabular cup positioning is crucial for achieving implant longevity and stability in total hip arthroplasty (THA). One of the elements that may affect the accuracy and precision of the positioning of the cup is the type of surgical approach used. This study compares the accuracy and the precision of conventional free-hand acetabular cup positioning relative to different “safe zones” in two groups of patients operated with THA using two different surgical approach.
Methods
Retrospective radiological comparative matched-pair controlled study of two groups of patients operated with primary THA: the first group was operated in supine decubitus with a mini-invasive direct anterior approach (DA group), the second group was operated in lateral decubitus with a conventional posterolateral approach (PL group). Cup inclination and anteversion were assessed using the digital planning software TraumaCad. Cup position in the two groups were compared in terms of accuracy and precision.
Results
Forty four patients were enrolled for each group. The DA group showed a less inclined and less anteverted cup compared to the PL group (respectively 38.5 ± 5.2 vs. 49.6 ± 5.6 and 16.2 ± 3.6 vs. 22.9 ± 6.4; p < 0.01). The DA group showed a significantly higher percentage of cups within the “safe zone” in 4 out of 6 reference zones and a significantly lower variance in anteversion (12.96 vs. 40.96, p < .01). There was no difference in the variance for inclination.
Conclusions
Our study found greater accuracy and precision in the positioning of the cup when surgery was performed through a direct anterior approach compared to the posterolateral approach due to the supine position of the patient which allows greater stability of the pelvis during surgery and makes it easier to target the desired angular references for cup positioning.