Surgical Approach

Craniolateral approach: most commonly used hip join approach. Indications include: capital physeal fractures, stabilization of coxofemoral luxation, femoral head and neck ostectomy, total hip replacement.

Key points: 1) incise along cranial edge of Greater Trochanter; 2) partial tendonectomy of deep gluteal muscle; 3) incise joint capsule along longitudinal axis of femoral neck; 4) continue capsular incision laterally through origin of vastus lateralis; incision is proximal just underneath the incised deep gluteal tendon.

Make a craniolateral skin incision is centered over the hip joint. The incision begins 5cm above the joint, courses slightly cranial to the greater trochanter, and extends distally 5 cm below the joint. Incise the subcutaneous tissues along the same line exposing the tensor facia lata muscle and cranial border of the biceps femoris muscle. Make an incision through the fascia lata along the cranial edge of the biceps muscle. At the region of the greater trochanter the incision curves cranially to follow the cranial border of the superficial gluteal muscle. Dorsal reflection of the superficial gluteal muscle and caudal retraction of the biceps femoris muscle exposes the middle gluteal muscle. With dorsal retraction of this muscle the tendon of insertion of the deep gluteal muscle can be seen. Use a periosteal elevator to separate the deep gluteal muscle from the coxofemoral fibrous joint capsule and perform a partial tendonotomy of the deep gluteal muscle near the greater trochanter. Incise through the fibrous joint capsule parallel to the longitudinal axis of the femoral neck. The incision is begun medially at the lateral rim of the acetabulum and extended laterally through the origin of the vastus lateralis muscle. Reflect the vastus lateralis muscle is distally to expose the site where the femoral neck joins the femoral metaphysis. To close, reposition the vastus lateralis and deep gluteal muscles with absorbable suture using a simple interrupted pattern. Suture the fascia lata is with absorbable suture using a simple continuous pattern and the skin with non-absorbable suture using a simple interrupted pattern.

Hip Dysplasia

Surgical intervention is divided into techniques useful in the younger population and those useful in mature dogs. Techniques useful in the younger population include Triple Pelvic Osteotomy (TPO), Double Pelvic Osteotomy (DPO), femoral head ostectomy, and possibly total hip replacement. My preference in this aged dog is either a DPO or conservative management. In the older dogs, my preference is total hip replacement or conservative management. Femoral head ostectomy is a good option in cases where conservative management is no longer effective of practical and financial constraints preclude total hip replacement.

Coxofemoral Luxation

Dislocation of the hip is usually due to violent injury, e.g., vehicular trauma or a significant fall. If there is hip dysplasia, however, the hip can be dislocated by relatively minor trauma eg. catching the foot in a closing door. Dislocation of the joint requires rupture of the teres ligament and severe damage to the joint capsule. It generally requires significant trauma to dislocate a normal hip and there will often be additional injuries eg. other musculoskeletal injuries, thoracic or abdominal trauma. As usual in trauma patients, it is important to examine and assess the whole patient rather than concentrating on an obvious orthopedic injury immediately.

The hip may be dislocated craniodorsally (most common), caudally, ventrally or cranioventrally. Craniodorsal displacement of the femoral head relative to the acetabulum is the most frequently seen hip dislocation. The majority of these patients have undergone a significant traumatic episode such as a motor vehicle accident. The round ligament of the femoral head always completely fails; it may be an interstitial rupture or an avulsion of the ligament from the fovea capitus. The fibrous joint capsule must also be completely torn to permit dislocation of the femoral head. The tear in the joint capsule may be a small rent through which the femoral head is dislodged or may be a complete fraying of the entire capsule. The diagnosis of hip luxation is confirmed with ventrodorsal and lateral radiographs. Careful evaluation of the radiographs for avulsion of the fovea capitus, associated fractures of hip joint, and the presence of degenerative changes secondary to poor joint conformation are necessary before deciding on a treatment method.

There are two methods to manage a hip luxation: closed manipulation to replace the femoral head within the acetabulum and open surgical manipulation. Open reduction is indicated in cases where avulsion of the capital fovea is present or when closed reduction has failed to maintain hip reduction. Open reduction is approached as an exploratory of the hip joint to assess the degree of soft tissue injury and the likelihood of maintaining reduction with a reconstructive procedure. Initially, the hip joint is approached through a craniolateral exposure; this may be expanded to a trochanteric osteotomy if more exposure is necessary.

Removal of the remnants of round ligament and debris from the femoral head and acetabulum is performed to allow complete seatage of the femoral head within the acetabulum. Once the hip is reduced, stability is assessed by viewing the acetabular coverage of the femoral head and placing the hip joint through a complete range of motion. If one assess that stability of the hip joint can be achieved through a reconstructive procedure, there are a number of techniques from which to choose. If the dorsal joint capsule is intact, replacing the femoral head within the acetabulum and suturing the capsule may suffice. One may choose to axially rotate the acetabulum to capture the femoral head as with a TPO. The majority of the cases, 20 axial rotation is all that is necessary. One may choose to supplement this with a second reconstructive procedure but it is not often necessary to do so. A second procedure which is effective for revision surgery is the use of prosthetic sutures. Heavy non-absorbable suture is secured at the 10 and 1 o'clock position (left hip) or 11 and 2 o'clock position (right hip) using screws or suture anchors. Use a trochanteric osteotomy for exposure to remove debris from the acetabulum and place the suture anchors. It is often useful to supplement this technique with additional reconstructive procedures. One additional technique is transposition of the greater trochanter. The greater trochanter has previously been reflected with associated gluteal musculature. Rather than replacing the trochanter at its anatomic position, create a new "bed" and stabilize the trochanter caudally and distally. This position exerts an internal and abduction force on the hip joint which stabilizes the femoral head within the acetabular cup.

A technique gaining popularity is the toggle technique using the TightRope system. The 2 hole button is passed through a drill hole in the femoral neck and toggled through a drill hole in the fovea to lock against the medial wall of the acetabulum. The arms of FiberTape are tensed to remove slack and the tied over the 4 hole button at the lateral surface of the greater trochanter.

Each of the described primary techniques carry a similar prognosis for long-term, pain-free hip function. Literature review and personal experience suggest approximately 85% of hips stabilized with a primary reconstructive procedure will be successful. Failures can be attributed to poor decision making, poor hip joint conformation, or lack of patient compliance. When a primary reconstruction fails, one must carefully assess hip joint conformation and decide whether or not preserving the joint is desirable. If the prognosis for maintaining a long-term, functional, pain-free joint is not reasonable, then a total hip replacement or femoral head ostectomy is indicated.

If one believes that there is not a reasonable chance of maintaining long term reduction following a stabilization procedure, an alternate procedure such as a femoral head ostectomy or total hip replacement must be considered.

Legg-Perthes Disease

Legg-Perthes disease is a non-inflammatory aseptic necrosis of the femoral head occurring in young patients prior to closure of the capital femoral physis. The collapse of the femoral epiphysis is due to an interruption of blood flow. The reason for the loss of blood flow is not known for certain but several theories have been proposed. The vascular supply to the femoral head in a patient with an open proximal femoral physis is derived solely from the epiphysel vessels. Metaphyseal vessels do not cross the physis to contribute to femoral head vascularity. Epihyseal vessels course extraosseously along surface of the femoral neck, cross the growth plate and then penetrate the bone to supply nourishment to the femoral epiphysis. Synovitis or sustained abnormal limb position may cause sufficient increased intra-articular pressure to collapse the fragile veins and inhibit blood flow. Also, an autosomal recessive gene has been proposed as a genetic cause for the development of aseptic necrosis of the femoral head. Once cell death has occurred, the reparative processes begin. The bone substance is weakened mechanically during the revascularization period and normal physiologic weight bearing forces can cause collapse and fragmentation of the femoral epiphysis. When this happens, incongruency of the femoral epiphysis and acetabulum result in degenerative joint disease. Fragmentation (fractures) of the femoral epiphysis and osteoarthrosis cause pain that leads to clinical lameness. Legg Perthes is diagnosed in dogs under 10 kg. Peak incidence of onset is six to ten months with males and females equally affected. Occurs bilaterally in 12 to 17% of the patients. Lameness usually presents as a slow onset weight bearing lameness that continues to worsen over a six to eight week period. Lameness may progress to non-weight bearing. Some clients report acute onset of clinical lameness. In these patients, sudden collapse of the epiphysis may have caused acute exacerbation of already present but imperceptible clinical lameness.

Other clinical signs can include irritability, reduced appetite and chewing at the hip area.

Manipulation of the hip joint at physical examination consistently elicits pain. With advanced disease, limited range of motion, muscle atrophy, and crepitus may be present. Radiographs show deformity of the femoral head, shortening of the femoral neck, and foci of decreased bone density within the femoral epiphysis. Diagnosis is often made when collapse and fragmentation have resulted in joint incongruity and degenerative joint disease. Conservative treatment with anti-inflammatory medication will benefit the patient but definitive treatment depends on surgical intervention. Excision of the femoral head and neck is the treatment of choice.