Study identifies vascular ‘safe zones’ for hip arthroscopy
SAN DIEGO – A study presented here has reportedly located vascular safe zones in hip arthroscopy, providing an intraoperative guide to reduce the risk of damage to the femoral head blood supply during femoral neck osteoplasty and psoas tendon release.
Frank McCormick shared his findings at the 2011 Annual Meeting of the American Academy of Orthopaedic Surgeons.
“Hip arthroscopy has grown in incidence, indications, and invasiveness,” McCormick said. “Thus, it is important for the surgeon to be cognizant of the vessel proximities to avoid damage in the femoral head blood supply, which for our current understanding is based on cadaveric studies.”
The study aimed to identify the safe zones using anatomic and intra-capsular landmarks.
Visualizing the vasculature
McCormick said he and his group analyzed 76 consecutive contrast-enhanced MRI scans. High-resolution 3D scans were reconstructed to help visualize the vasculature.
The researchers traced the medial femoral circumflex artery course from the anterior thigh to the femoral head, paying specific attention to its proximity to the psoas tendon at the site of release and the associated retinacular vessels in relation to the course of the femoral neck.
According to McCormick, MRI revealed the medial femoral circumflex artery is “just posterior to the lateral synovial fold,” inserting on the posterior-superior femoral neck and diverging medially via two to five retinacular vessels located on the superior femoral head-neck junction.
This then dives, he added, into subcondral bone around 5.0 mm lateral to the osteochondral junction.
The safe zones
The group reported an average medial femoral circumflex artery location approximately 15 mm medial to the medial cortex of the femoral neck. This was reportedly at a mean 50% distance between the lesser trochanter and the inferior femoral head and acetabular junction.
The findings indicate that the safe zone for the femoral neck is on the anterior half of the femoral neck, with the psoas tendon release safe zone being proximal or distal to the middle third of the medial hip capsule.
“There are exceptions to every rule, and this study is included,” McCormick noted. “We cannot account for gross abnormal vasculature.”
- McCormick F, et al. Vascular safe zones in hip arthroscopy. Paper 639. Presented at the 2011 Annual Meeting of the American Academy of Orthopaedic Surgeons. Feb. 15-19, 2011. San Diego.
This was a very nice presentation with valuable anatomic information that has practical significance to both arthroscopic and open surgeons managing conditions, such as, femoroacetabular impingement (FAI), internal snapping hip and psoas impingement (which may be a cause of labral tears). The described safe zones permit resection of CAM deformities, which typically occur in the anterior, anterolateral and/or lateral (superior) femoral head- neck regions. Although there is only one reported case of iatrogenic femoral head osteonecrosis following primary arthroscopic FAI surgery, remaining anterior to the mid-coronal plane (in the safe zone) during femoral osteochondroplasty should minimize this risk. Hip internal rotation, often used to enter the central compartment using arthroscopic techniques, alters the relative positioning of this mid-coronal landmark (bringing it more anterior), so one should be cognizant of the mid-coronal plane relative to the degree of hip rotation at the time of osteochondroplasty.
The vascular safe zone is a good rule of thumb. That being said, there may be exceptions. I have performed CAM decompressions posterior to the mid-coronal plane, however only for significant posterosuperior dysmorphisms under strict arthroscopic visualization with CAM decompression of the proximal extent (away from the major arterial feeder vessels) of these less common deformities.
The safe zone for iliopsoas release also has practical significance in that whether released from the lesser trochanter or from a trans-capsular approach, vascular safe zones are accessed. My preference is the arthroscopic trans-capsular release (in the proximal safe zone) as it is relatively quick, permits intra-articular assessment and treatment of concurrent pathology, and releases only the adjacent iliacus portion of the iliopsoas tendon, theoretically minimizing early hip flexor weakness (compared to a complete release off of the lesser trochanter) while minimizing heterotopic ossification that has been reported with the latter method.
- Dean K. Matsuda, MD
Orthopedics Today Editorial board member