Subspinal impingement: clinical outcomes of arthroscopic decompression with one year minimum follow up

  • Frankl Michal
  • Eyal Amar
  • Ran Atzmon
  • Zachary Sharfman
  • Barak Haviv
  • Gilad Eisenberg
  • Ehud Rath



This study was designed to (1) evaluate the clinical outcomes after arthroscopic subspinal decompression in patients with hip impingement symptoms and low AIIS, and to (2) assess the presence of low anterior inferior iliac spine on the pre-operative radiographs of patients with established subspinal impingement diagnosed intra-operatively.


Retrospective analysis of patients who underwent arthroscopic subspinal decompression has been performed. The indications for surgery were femoroacetabular impingement (FAI), or subspinal impingement. Pre-operative radiographs were assessed for anterior inferior iliac spine type. Intra-operative diagnosis of low anterior inferior iliac spine was based on the level of anterior inferior iliac spine extension relative to the acetabulum and the presence of reciprocal labral and chondral lesions. In patients where low anterior inferior iliac spine was not diagnosed on pre-operative radiographs, the pre-operative radiographs were re-read retrospectively to assess missed signs of low anterior inferior iliac spine.


Thirty-four patients underwent arthroscopic subspinal decompression between 2012 and 2015. The patients were followed for a median of 25 months (13–37 months). Intra-operatively, grade 2 anterior inferior iliac spine was found in 27 patients and grade 3 anterior inferior iliac spine was found in 7 patients. MHHS, HOS, and HOSS scores increased from median (range) pre-operative scores of 55 (11–90), 48 (20–91) and 20 (0–80) to 95 (27–100), 94 (30–100) and 91 (5–100), respectively (p < 0.0001, p = 0.001, p < 0.0001, respectively). Pre-operative diagnosis of low AIIS was made in 6/34 patients via AP radiographs. On retrospective analysis of pre-operative radiographs, signs of low AIIS were still not observed in 21/34 (61.8%) patients.


Arthroscopic subspinal decompression of low AIIS yielded significantly improved outcome measures and high patient satisfaction at a minimum of 13 months follow-up. Low AIIS is often under-diagnosed on AP pelvis and lateral frog radiographs and if left untreated, may result in unresolved symptoms and failed procedure.

Level of evidence



Hip arthroscopy Hip impingement Subspinal impingement Low AIIS 


Author contributions

MF participated in acquisition of data, analysis and interpretation of data, and wrote the manuscript. EA is an equal contributor to this paper. He participated in the design of the study and performed the statistical analysis, and helped with writing the manuscript. RA participated in acquisition of data, analysis and interpretation of data. ZS participated in acquisition of data, analysis and interpretation of data, and helped with writing the manuscript. BH participated in acquisition of data, analysis and interpretation of data. GE participated in acquisition of data, analysis and interpretation of data. ER conceived of the study, and participated in its design and coordination and helped to draft the manuscript. All authors read and approved the final manuscript.


No external source of funding was used.

Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflict of interest.

Ethical approval

All procedures performed in the study were in accordance with the ethical standards of the institutional research committee and with the 1964 Helsinki declaration and its later amendments.

Informed consent

Informed consent was obtained from all individual participants included in the study.


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Copyright information

© European Society of Sports Traumatology, Knee Surgery, Arthroscopy (ESSKA) 2018

Authors and Affiliations

  1. 1.Assaf HaRofe Medical Center, Sackler Faculty of MedicineTel-Aviv UniversityZriffinIsrael
  2. 2.Sourasky Medical Center, Sackler Faculty of MedicineTel-Aviv UniversityTel-AvivIsrael
  3. 3.Rabin Medical CenterHasharon HospitalPetach-TikvaIsrael

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