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Source of Blood Supply to the Hip Labrum

Posted on: 12/29/2010
There are plenty of studies and reports on the soft tissue structure known as the hip labrum. This may be the first published on the blood supply to the labrum. Several other studies have reported on the location of blood vessels inside and around the labrum. Now we have clear photos of the precise pattern of those blood vessels.

The labrum is a thick rim of fibrous cartilage around the edge of the hip acetabulum (socket). It is there to increase the depth of the hip socket. The labrum also provides a seal to help protect the hip articular (joint surface) cartilage.

The average person on the street isn't going to think much about the blood supply to the hip labrum. That's okay so long as the surgeon operating on that person's labrum sits up and takes notice. Understanding the labral blood supply is important when performing surgery to repair a torn labrum.

Orthopedic surgeons from the Iran University of Medical Sciences teamed up with researchers from the Department of Anatomy at the Legal Medicine Research Center in Tehran (Iran) to perform this study. They examined the hips of 35 cadavers (hips preserved after death for study). They used a special colored silicone that was injected into the blood vessels around the hip labrum.

The donor hips came from 28 cadavers ranging in age (at the time of death) from 20 to 50 years old. Cause of death was unknown but there was no damage to the hips and no sign of previous surgeries to the area.

Twenty-four hours after the silicon injections, they carefully took the hips apart and examined the blood vessels (now clearly visible from the injected dye). They found the beginning point (source) of the blood supply to the labrum and followed it to its insertion site into the hip joint capsule.

Beautiful color photos are provided to show the structures of the hip (e.g., bone, capsule, labrum). The blood vessels throughout the area show up as a green color in full detail. For the first time ever, the vascular ring pattern around the labrum is clearly seen. The authors describe the location and pattern of these blood vessels.

For those readers who find the photos difficult to understand, there is a schematic drawing to outline the ring of vessels around the labrum. Each blood vessel is labeled by name. This structure has been given the name: periacetabular vascular ring. Peri- means "around" and acetabular refers to the hip socket. So, periacetabular gives us the sense that we are looking at the blood vessels around the hip socket.

Seven of the hips had a visible labral tear. All specimens came from males. The presence of these labral injuries made it possible for the researchers to answer another big question. Is the blood supply to the labrum disrupted when the labrum is injured?

In all seven cases, the answer was No. The periacetabular ring was fully intact despite damage to the labrum.

By finding the source of the blood supply to the hip acetabular labrum, these researchers were able to show that the blood vessels do NOT come from the joint capsule or the subchondral bone (layer of bone just underneath the cartilage).

Instead, there is a special layer of loose connective tissue between the hip joint capsule and the surface of the labrum (next to the capsule). This tissue lining contains a separate blood supply to the labrum now referred to as the periarticular vascular ring.

Knowing that injury to the labrum does not include damage to the blood vessels is an important finding for surgeons attempting to repair a torn labrum. This knowledge is essential as studies have also shown that repair (rather than removal) of a torn labrum yields the best results for patients with this type of injury.

Further studies are needed in this area. For example, the authors did not see exactly how the blood vessels enter the labrum. They know it comes from outside the hip joint through the ring described. But they did not dissect the cadavers in such a way as to show this additional detail.

On the basis of their findings, the researchers suggest taking a closer look now at current techniques used to repair a torn labrum. Every effort should be made to avoid damaging the periacetabular vascular ring.

It appears that if the loose connective tissue containing the vascular ring is not disrupted, then no damage is done to the labrum's vascular supply. Labral repair with preservation of this capsular-sided connective tissue will enhance healing.

Morteza Kalhor, MD, et al. Vascular Supply to the Acetabular Labrum. In The Journal of Bone and Joint Surgery. November 3, 2010. Vol. 92A. No. 15. Pp. 2570-2575.

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