The hip capsule is attached proximally to the acetabular rim and distally to the base of the femoral neck, and the intra-articular structures include all of the femoral neck in addition to the acetabulum and femoral head. During hip surgery, all structures of the hip joint need to be fully exposed in order to visualize and manage intra-articular deformities and pathologies such as femoral head fractures, femoral acetabular impingement (FAI), slipped femoral epiphysis (SCEF), and choroidal nodular synovitis. However, blood flow damage to the femoral head and femoral head necrosis are common after hip dislocation, and are the most feared surgical complications for joint surgeons. This paper focuses on the topic of surgical dislocation of the hip joint and introduces the clinical application of this surgical dislocation technique access.
I. Major vascular anatomy of the femoral head
The main blood supply to the femoral head was thought to come from the medial and lateral rotor femoral arteries, which surround the basilar artery ring at the femoral head-neck junction, and from which several lateral epiphyseal arteries and the round ligament artery emanate.
It was also found that the femoral artery was well perfused when the femoral head-neck junction was severed 90% from the bottom up, leaving only the femoral head-neck continuous at the upper end; when the femoral head-neck junction was severed at the upper end, there was a complete loss of blood flow to the femoral head, indicating the importance of the vessels at the upper end of the femoral head-neck junction for blood flow to the femoral head.
It has been found that the medial femoral artery (MFCA) originates from the femoral artery between the iliopsoas muscle and the pubococcygeus muscle, and reaches the back of the hip joint via the intersection of the external foramen ovale and the short retractor muscle, with its terminal branch on the deep side of the femoral square muscle along the inferior border of the external foramen ovale muscle outward to the rotor fossa, and finally continues directly across the superficial or deep surface of the external foramen ovale tendon as the deep branch of the MFCA.
The deep branch of the MFCA enters the femoral head at the femoral head-neck junction through the lateral superior femoral neck (Figure 1). the deep branch of the MFCA is the lifeline of the blood supply to the femoral head, and the blood supply to the femoral head can be ensured by the deep branch of the MFCA alone. if the lateral deep branch of the MFCA entering the femoral head at the femoral head-neck junction is injured for any reason, the blood supply to the femoral head is basically lost. Therefore, the protection of the penetrating branch of this vessel into the femoral head is the core of hip surgical dislocation technique.
II. Surgical techniques
Surgical dislocation access to the hip joint.
(1) The blood supply to the femoral head mainly comes from the deep branch of the MFCA, and enters the femoral head from above the femoral head-neck junction.
(2) The greater trochanter is osteotomized and turned forward to maintain the integrity of the posterior external rotators of the greater trochanter, so that the MFCA that travels through it can be protected.
(3) The joint capsule is incised and dislocated anterolaterally at the hip to avoid injury to the penetrating branch of this vessel into the femoral head
. (4) If a more extensive area such as the femoral neck needs to be exposed, the cancellous bone in the upper 1/3 of the posterior aspect of the base of the greater trochanter can be resected and subperiosteal dissection performed to preserve the integrity of the periosteum to protect the external rotator muscle group at the posterior attachment point of the greater trochanter and the deep branches of the MFCA that penetrate it from being disturbed, forming a soft tissue vascular flap.
This soft-tissue vascular flap, which is completely dissected from the bone tissue, allows the blood vessels traversing it to be both protected by the soft tissue and protected by the soft-tissue vascular flap from the bony attachment, thus creating a safe operating space of less than 11 cm between the femoral head and acetabulum, especially in the femoral neck area, providing a complete view of the femoral head and neck as well as the acetabulum at approximately 360°.
This technique, known as the “soft tissue vascular flap lengthening” technique, is an expansion of the surgical dislocation technique for the hip joint and is a key technique that must be mastered for intra-articular procedures such as slipped femoral epiphysis repositioning, femoral neck osteotomy, and femoral reduction surgery.
(I) Conventional surgical dislocation technique
The patient is placed in the lateral position, and a Kocher-Langenbeck incision is selected to dissect the broad fascia. The thigh is then internally rotated to locate the posterior border of the gluteus medius and the posterior superior rotator fossa of the greater trochanter. An osteotomy of the greater trochanter of approximately 1.5 cm in thickness is made with a swing saw, taking care to maintain the integrity of the bone tissue adjacent to the greater trochanteric fossa and avoiding damage to the deep branches of the MFCA that travel beneath it (Figure 2). The separated greater trochanter is pushed anteriorly to the hip joint along with the gluteus medius (Fig. 3).
The gluteus minimus is dissected anteriorly and superiorly from the posterior inferior aspect of the joint capsule, taking care to protect or carefully sever the pear-shaped tendon, which is underlain by the deep branch of the MFCA that innervates the femoral head. The anterior, superior and posterior portions of the joint capsule are exposed. In order to avoid damage to the MFCA penetration in the femoral head, the capsule is incised longitudinally along the long axis of the femoral neck anterior to the greater trochanter, followed by a “Z” shaped incision and extension of the capsule at the medial appendage of the femoral neck, and a posterior incision of the capsule at the acetabular junction turning posterior to the superior posterior aspect of the femoral head (Figure 4).
Care should be taken to protect the femoral cartilage and glenoid labral structures below the incision when incising the capsule. The femoral head can be dislodged by extreme flexion and external rotation of the femur and clipping of the round ligament (Figure 5). Since the round ligament artery is not the main source of blood supply to the femoral head, the residual portion of the round ligament in the femoral head should be removed without affecting the blood flow to the femoral head.
The bone sled was placed anteriorly and inferiorly to the transverse ligament in the acetabulum, at which point the entire acetabular and femoral neck structures were completely exposed, allowing for surgical removal of the intra-acetabular lesion, glenoid lip revision, and revision of the femoral head cam.
To demonstrate the presence of blood supply to the femoral head, a small hole can be drilled in the dislocated femoral head. Blood oozing from the cancellous bone surface after revision of the femoral neck junction or the cam can also indicate a good blood supply to the femoral head. During the surgical operation, the use of Doppler flowmetry allows for a dynamic distribution map of blood perfusion to the femoral head. To prevent the articular cartilage from drying out, it can be continuously flushed with Ringer’s lactate solution.
After the intra-articular surgical operation of the hip is completed, the hip joint can be reset by traction on the lower limb, knee flexion and internal rotation. The sutures should not be too tight, as they can increase the tension of the supporting band vessels, which can lead to decreased blood perfusion to the femoral head. Two to three 3.5 or 4.5 mm cortical screws can be used to fix the greater trochanteric osteotomy block.
(B) Surgical dislocation of the hip joint, soft tissue vascular flap lengthening technique
For complex operations in the hip joint, such as reduction of the flattened hip, repositioning of the slipped femoral head and osteotomy of the femoral neck, the above-mentioned revealing method gives the operator limited space to operate because the small rotator muscle is completely attached to the bone of the greater trochanter and the blood vessels penetrating it are bounded by bone and muscle tissue.
The solution is to continue the oblique osteotomy in the posterior upper 1/3 of the osteotomy surface after the greater trochanter osteotomy and to perform a subperiosteal dissection of the external rotator muscle at the posterior attachment point of the greater trochanter, maintaining the integrity of the periosteal tissue and the attachment of the external rotator muscle, the integrity of the periosteum protects the integrity of the perforating vessels, and the detachment of the external rotator muscle from the bony attachment increases its mobility considerably (Figure 6).
As the relaxation of the deep branch of the MFCA penetrating the external rotator muscle is significantly increased, the space for surgical manipulation of the femoral neck and surrounding structures is increased, and the degree of safety is subsequently increased.
III. Indications for surgical dislocation of the hip joint
The limitation of hip arthroscopy technique is that it can only deal with glenoid labral injury, FAI, intra-articular free body, synovial lesions, etc. It cannot observe the impingement of femoral acetabulum under dynamic situation, and the operation technique is more complicated, and complications of nerve pull injury and articular cartilage injury are reported from time to time.
Surgical dislocation combined with femoral neck soft tissue vascular flap lengthening technique can handle complex deformity orthopedic surgery such as SCFE, flat hip and other femoral head deformities (reduction) and femoral neck osteotomy. In the future, we can also perform cartilage transplantation, etc. through this technique.
IV. Clinical applications of surgical dislocation of the hip joint in recent years
(I) Femoral acetabular impingement (FAI)
Clinically, FAI is an important cause of osteoarthritis of the hip joint. For patients with cam-type impingement, the dislocation can be treated by adequately trimming the acetabular glenoid lip and removing the bony prominence at the femoral head neck to eliminate the impingement factor, while patients with pincer-type impingement sign can be treated by removing part of the bony acetabular rim and trimming and refixing the glenoid lip. The hip joint can also be moved at any time during the operation to observe whether the impingement is completely released.
(B) Slipped capital femoral epiphysis (SCFE) resection and internal fixation
SCFE in adolescents has received increasing attention from pediatric orthopedics and hip surgery. The deformity of the head and neck caused by SCFE leads to FAI, which can lead to articular cartilage damage and premature osteoarthritis. Since slipped femoral epiphysis can form bone scabs at the slipped intersection and seriously affect the repositioning of the head and epiphysis, removing the bone scabs and shortening the femoral neck while ensuring blood flow to the femoral head is the key to correcting the head and epiphysis deformity and achieving anatomical repositioning of the slipped head and epiphysis.
(C) Osteotomy of the femoral neck
Intertrochanteric and subtrochanteric inversion, exostosis or rotational osteotomy is a common surgical method to treat proximal femoral deformities. However, in patients with intra-articular deformities of the hip, such as reverse slipped femoral epiphysis, an osteotomy at the femoral neck or the base of the femoral head would be more accurate and simpler. This procedure is possible with the guarantee of the soft tissue vascular flap lengthening technique. By doing subtrochanteric osteotomy, the lateral slipped epiphysis is repositioned and the force line of the femoral head neck is restored to normal.
In some patients with femoral head necrosis the necrosis is limited to the weight-bearing area of the femoral head and the anterior aspect of the head, while the bone behind the femoral head is normal. Inter-rotator femoral head forward rotational osteotomy rotates the normal femoral head posteriorly to the weight-bearing area and the necrotic area is rotated out of the weight-bearing area. Since the osteotomy site of this procedure is in the rotor question, rotation is not easy during the procedure.
(iv) Femoral head reduction
Congenital or secondary deformities such as femoral head macrosomia and flattened hip deformity cause the femoral head to become large or flattened, and some femoral heads show mushroom head-like changes with/without poor coverage of the hip joint. Even if the poor coverage of the acetabulum can be corrected, it is difficult for the oversized or flattened femoral head to be accommodated by the relatively small acetabulum to obtain satisfactory coverage.
Based on the understanding of the blood supply to the femoral head, the lateral half of the femoral head is innervated by the deep branches of the MFCA and the medial half of the femoral head is supplied by the medial branches of the MFCA. Therefore, it is safe and feasible to split the femoral head and then close it back together with the medial and lateral vessels intact. This technique is often performed in combination with periprosthetic osteotomy and inferior femoral greater trochanteric transposition (also known as relative lengthening of the femoral neck).
(E) Incisional resurfacing capsuloplasty for hip dislocation in children and adolescents over 8 years of age
The long-standing treatment option for children and adolescents over 8 years of age with complete unilateral dislocation of the hip has been to wait for future artificial arthroplasty because of the poor results of surgical resurfacing.
Ganz et al. modified the Colonna capsuloplasty with a surgical dislocation of the hip technique to completely avoid the postoperative complications of femoral head necrosis and the acetabular revision with an acetabular file, resulting in a perfect acetabular formation and a good surgical outcome for up to 20 years.
V. Complications of surgical dislocation of the hip joint
Ischemic necrosis of the femoral head is the most important complication of hip dislocation, which also includes postoperative complications such as non-union of the greater trochanteric fracture, failure of internal fixation, heterotopic ossification and sciatic nerve injury.