Kristin A. Coleman Gulf Coast Veterinary Specialists, Houston, TX, USA Femoral head and neck ostectomy (FHO) is a procedure with many different names and acronyms, including, but not limited to, femoral head and neck excision (FHNE), femoral head and neck osteotomy, and excision arthroplasty. FHO is performed to address the diseased, injured, or luxated coxofemoral joint.1–7 FHO was first developed in 1928 for human septic tuberculosis of the coxofemoral joint as the Girdlestone excision arthroplasty, and it has since been adopted in veterinary medicine as a “salvage procedure” treatment option for severe hip joint osteoarthritis secondary to hip dysplasia or other causes (Figure 46.1), fractures of the femoral head or neck, Legg‐Calve‐Perthes disease or other forms of avascular necrosis of the femoral head or neck, neoplasia, and acute or chronic hip luxation. Other indications include capital physeal fractures, acetabular fractures, and metaphyseal osteopathy of the femoral neck.7–14 The basic goal of the procedure is to remove the femoral head and neck to alleviate the pain from bone‐on‐bone contact between the femur and pelvis by allowing a “pseudo‐joint” to form, which is composed of dense fibrous tissue over the cut edge of femur, with the remaining hip musculature to provide support. FHO may be performed via one of two approaches: the traditional craniolateral approach and the more recently described ventral approach. Ventral FHO (vFHO) was originally reported in 1968 for addressing femoral neck fractures, but it is now used as a treatment for many other orthopedic diseases and conditions in small animals.15 While there are no long‐term studies evaluating objective outcome measures for animals undergoing ventral FHO, the perceived benefits include better visualization of the lesser trochanter compared to the craniolateral approach and the ability to perform the procedure bilaterally without having to re‐position the patient. The main benefit of the ventral approach over the more traditional craniolateral approach includes preservation of the cranial‐dorsal musculature and soft tissue support structures that need to take over the function of the hip post‐FHO, including the dorsal joint capsule and deep gluteal muscle tendon. Additionally, the only muscle transection that is needed in the ventral approach is the pectineus muscle. As pectineal myotomy has been described previously as a treatment option for hip dysplasia,9 the ventral approach offers a potential inherent advantage if the pectineus is not re‐apposed at the conclusion of surgery. Figure 46.1 Craniocaudal radiograph of the pelvis of a large breed dog with significant degenerative joint disease, characterized by marked osteophytosis, of the left coxofemoral joint. A non‐cemented total hip replacement has previously been performed on the right hip in this patient, and a tibial plateau leveling osteotomy (TPLO) plate is present on the medial aspect of the right tibia. Source: © Kristin Coleman. Sparing the dorsal support structures with the ventral approach could potentially minimize the craniodorsal malposition of the femur and “limb‐shortening” postoperatively that is reported following the traditional craniolateral approach.8,16 Subjectively, return to comfortable function in the limb is faster with the ventral approach versus the craniolateral approach. The cases when craniolateral approach is beneficial compared to the ventral approach are in patients with craniodorsal hip luxation or patients that have excessive inguinal fat that may hinder clear identification of surgical landmarks. Potential disadvantages of the ventral approach include proximity of the surgical dissection to the medial circumflex femoral artery and vein, that it is a subjectively more tedious procedure than that of the craniolateral approach (per the lack of visualization of the medial aspect of the greater trochanter), the challenge of removing additional bone after initial ostectomy, and the need to retract the iliopsoas muscle to begin the osteotomy.16 Overall, choice of approach is dependent upon the surgeon’s preference and comfort level, the patient, and the disease process being treated. A thorough conversation with the client is an important step prior to surgery to educate them about their pet’s disease process and the treatment options available. They should be counseled on other potential options for their pet depending on the animal’s age and presenting complaint. Such options include continued medical management, primary fracture repair (if an acute fracture is present), or other hip dysplasia surgical interventions such as juvenile pubic symphysiodesis (JPS), double or triple pelvic osteotomy, or total hip replacement (THR).17 As previously mentioned, while the goal of surgery is to make the patient more comfortable, a residual lameness may remain, and the kinematics of the limb are permanently altered. Owners should also be reminded that the success of surgery relies heavily upon their willingness to pursue physical therapy postoperatively, either with a professional rehabilitation therapist or with at‐home stretching and exercising. Even before surgery, the surgeon should palpate the various bony prominences in the proximal hindlimb area to ensure accuracy in surgical approach and execution. The triad of prominences of the craniolateral approach is the iliac crest, the ischiatic tuberosity, and the greater trochanter, with the latter representing the landmark around which the FHO incision is based. There are a few important structures to avoid during this surgical approach, particularly the sciatic nerve. This nerve runs just caudodorsal to the coxofemoral joint and is the main reason for externally rotating the femur while retracting prior to femoral neck transection. During the ventral approach, there is less risk of encountering the sciatic nerve. During the vFHO, care should be taken to identify and protect the femoral artery, femoral vein, and saphenous nerve, all of which lie on the cranial aspect of the pectineus muscle. After the pectineus muscle is transected and reflected distally, the medial circumflex femoral artery and vein are visualized tracking caudally and medially to the acetabulum with small branches that may be possibly disturbed during retraction. The majority of the muscles that are encountered are separated from their neighboring muscles and not transected. The only muscle to be potentially partially transected in the craniolateral approach is the deep gluteal muscle tendon, which is re‐apposed at the end of the procedure, and the only muscle to be transected in the ventral approach is the pectineus muscle, which is not re‐apposed. When the deep gluteal tendon is transected, this is typically performed in an “L”‐shaped incision, ensuring that enough tendon of insertion is preserved for closure at the end of the procedure. In the author’s experience, this transection is not always necessary as part of FHO. It is advisable to frequently palpate the coxofemoral joint to not lose sight of the target located deep within the surgical site. This is easily done by grasping the hindlimb at the distal femur and manipulating the femur through a range of motion, including adduction and abduction, to identify the joint or even just the luxated femoral head if this is the disease process being treated. Having the proper instrumentation is essential to any surgical procedure, and this is especially true of orthopedic surgeries. A general surgery pack should, at minimum, include a Bard blade handle, Brown‐Adson forceps, Metzenbaum scissors, curved Mayo scissors, a variety of hemostats, needle‐holders, and suture‐cutting scissors. An FHO surgery pack also includes a Gelpi perineal retractors (minimum of 2), Senn and/or Army‐Navy retractor, (optional) Hat spoon or round ligament cutter, Freer periosteal elevator (or other elevator), Hohmann retractors (minimum of 2), sagittal saw or an osteotome and mallet, and a bone rasp. The ability to lavage the surgical site, particularly during the osteotomy to cool the saw blade, and suction are recommended for this procedure. The additional instrument needed for the ventral approach is the right angle forceps (Figure 46.2). The patient is positioned in lateral recumbency with the affected side facing up.18 The affected hindlimb is clipped and prepped circumferentially from the stifle and proximally to the inguinal region medially and to the dorsal midline laterally. This allows the entire limb to be in the sterile field and manipulated throughout the procedure, which is important for confirming the completeness of the cut at the end of surgery. Self‐adhesive, such as white tape, may be used to cover the non‐shaved portion of the limb, and an exam glove is convenient to place around the paw. A “dirty prep” is performed using dilute chlorhexidine scrub and non‐sterile saline until the gauze lacks visible dirt or surface debris prior to taking the patient into the operating theater. Once the patient is positioned at the end of the surgery table, a standard hanging limb preparation is performed with a sterile glove using dilute chlorhexidine and sterile saline for a minimum of three rounds. At this point, quarter‐draping may commence, being sure to place the sticky drape or sterile Huck towel at least 1 cm in the sterile field from the hair to reduce the risk of hair contamination during the procedure. A water‐impermeable segment of drape or sterilized aluminum foil is used to grasp the distal aspect of the hindlimb. A non‐sterile assistant may “cut down” the limb from its hanging position (commonly, an IV pole), and after covering the paw with the water‐impermeable material, a sterile self‐adhesive bandaging material (e.g., 3M™ Vetrap™) is used to secure the drape or foil to the limb until no bandage material is visualized. A patient drape (with a small fenestration through which the sterilely prepped hindlimb is passed) is then used to cover both the patient and the caudally‐located instrument table (Figure 46.3a). One of the keys to this procedure is remaining aware of the location of the palpably identifiable greater trochanter. While performing this procedure in the early stages, it may help to mark the skin with a sterile marker on the proposed incision prior to cutting. Figure 46.2 Standard instrument table for FHO. Counterclockwise from top left: gauze, sharp/sharp suture‐cutting scissors, two small/pediatric Gelpi retractors, #15 Bard blade with handle, #10 Bard blade with handle, Freer periosteal elevator, three thumb forceps (Brown‐Adson, two types of rat‐tooth), two Senn retractors (one sharp, one blunt), Adson periosteal elevator, Hohmann retractor, curved Metzenbaum scissors, point‐to‐point bone reduction forceps, Mayo‐Hegar needle holders, two Army‐Navy retractors, sharps container, bowl with sterile saline, bulb syringe, several curved hemostats, and tray of instruments that are not commonly used (other than the two Hohmann retractors) in this procedure. If power equipment is not available, it is important to include a sharp osteotomes of various sizes and a mallet for performing FHO. Not pictured: monopolar electrosurgery pen and sagittal saw, which are on the patient table that is draped separately in some cases. Source: © Kristin Coleman. An incision through the skin and subcutaneous layers may either be straight or curvilinear (with the curved portion oriented cranially at the dorsal aspect). The incision is started dorsally just craniodorsal to the palpable greater trochanter and extends distally to approximately 1/3–1/2 of the femoral length parallel to and along the cranial aspect (Figure 46.3b). The incision should essentially be centered on and cranial to the greater trochanter (Figure 46.3c), which allows for the incision to be directed over the coxofemoral joint in most animals. This will also permit visualization of the caudally‐located biceps femoris, and an incision should be made through the superficial leaf of the fascia lata on the cranial edge of the biceps femoris to separate it from the cranially‐located tensor fascia latae (Figure 46.4). The division between these muscles is not always obvious; the change in fiber directions of one muscle compared to the other aids in identifying the partition. Once these two muscles are separated and the superficial and deep leaves of the fascia lata have been incised, a Gelpi perineal retractor is placed to aid in identifying the dorsally‐located gluteal muscles (Figure 46.5). Care should be taken caudally to not place the Gelpi retractor too deeply, as the sciatic nerve courses distally along the caudolateral aspect of the femur deep to the biceps femoris. The shiny fascia of the vastus lateralis muscle will be seen at this point, and the incision is continued proximally between the tensor fascia latae muscle (cranial) and superficial gluteal muscle (caudal). Note: Cats have a muscle that is derived from the biceps femoris that is part of the “hamstring” muscle group called the caudofemoralis. This muscle is located just caudal to the superficial gluteal muscle. The caudofemoralis muscle is absent in the dog and should not be confused with the gluteal muscles in the cat.18 Using a Senn retractor and an assistant, retract the middle gluteal muscle dorsally to reveal the characteristic deep gluteal muscle tendon with its insertion onto the greater trochanter (Figure 46.6). In larger patients, an Army‐Navy retractor may provide better visualization of this landmark. The deep gluteal tendon may be partially transected (~50% from the ventral aspect in the transverse direction) to aid in the exposure of the coxofemoral joint, but the author does not always find this necessary for adequate exposure of the femoral head and neck. If a tenotomy is performed, a stay suture should be placed onto the tendon for later re‐apposition to the remaining tendon fibers onto the greater trochanter. Directly beneath the deep gluteal tendon is the coxofemoral joint capsule, which may or may not be intact depending on the underlying reason for performing the FHO (e.g., chronic craniodorsal hip luxation may not have an appreciable joint capsule remaining on the dorsolateral aspect). If it is intact, an incision should be made through the capsule along the dorsal acetabular rim with a blade (#10, 11, or 15), then the round ligament (i.e., ligament of the head of the femur) should be transected (if intact) with a Hat spoon, round ligament cutter, or curved Mayo scissors. This step is most readily achieved with external rotation and adduction of the femur. Figure 46.3 Canine patient undergoing right FHO via craniolateral approach: initial incision. Cranial is to the right of each image. (a) Patient is positioned in left lateral recumbency. (b) A straight or curvilinear incision is made through the skin and subcutaneous tissue just cranial to the palpable greater trochanter to ensure that the surgical site is positioned over the coxofemoral joint. (c) Image B with femur overlay to demonstrate the proper placement of the incision to approach the hip. Source: © Kristin Coleman.
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Femoral Head and Neck Ostectomy (FHO)
Introduction
Indications/Pre‐operative Considerations
Anatomy
Instruments for FHO
Surgical Procedure
Craniolateral Approach
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