Newer Ventral Approach for Femoral Head and Neck Ostectomy (FHO)
Femoral head and neck ostectomy (FHO) is a good choice in cases that are refractory to medical therapy, as a less expensive alternative to total hip replacement surgery. The overall function (range of motion and strength) will not be as good in bigger, heavier dogs; however, they are usually far more comfortable through range of motion than prior to surgery.
Case Selection and Surgical Timing
Previously FHO was thought to be a last moment salvage procedure. It is much preferable to have the patient still well ambulatory and in relatively good body condition at the time of surgery versus being so overweight and muscle atrophied that the rehabilitation process is much harder.
Although the ideal timing for each patient is individual, this author typically recommends FHO when the patient is becoming refractory to good medical management. For example, the patient should be in healthy body condition with a regular moderate exercise regime. The dog should also be on joint supplements and may have gone from needing NSAID administration once every 3–7 days during more strenuous activity, to needing daily to twice daily NSAIDs as well as other analgesics such as gabapentin, tramadol or amantadine.
If the patient is very obese with significant muscle atrophy, enrolment into a professional physical therapy program (“pre-hab”) is strongly recommended prior to surgery to optimize the patient’s recovery.
Where possible, FHO should also be avoided in skeletally immature patients, particularly where other concurrent pelvic fractures may exist. These patients may be more prone to healing of the femoral bone cut to the pelvis or muscle contractures that carry a poor long-term prognosis for return to function.
FHO Ventral Approach
The main benefit of this approach over the more traditional craniolateral approach includes preservation of the cranial-dorsal musculature and soft tissue support structures that need to take over function of the hip post-FHO.
Additionally, the only muscle transection that is needed is the pectineus muscle. Pectineal myotomy has been described previously as a treatment option for hip dysplasia, so is also an inherent advantage of this approach. Subjectively, return to comfortable function in the limb is faster with this approach versus the craniolateral approach. This is the preferred FHO approach for the author in the majority of cases apart from those that have craniodorsal hip luxation or patients that have excessive inguinal fat that may hinder clear identification of surgical landmarks.
This approach is performed as outlined in Piermattei and Johnson’s Atlas of Surgical Approaches to the Bones and Joints of the Dog and Cat.
The femoral arterial pulse and adjacent pectineus muscle (which lies just caudal) are palpated, and a skin incision is made centered over the origin of the pectineus muscle. Careful blunt dissection with right-angled forceps is then carried out to isolate the origin of the pectineus m. During this process, care is taken to identify and protect the femoral artery, vein and saphenous nerve, which lie on the cranial aspect of this muscle. Once isolated, sharp transection of the pectineus muscle close to its musculotendinous origin on the prepubic tendon and iliopubic eminence is carried out.
With the pectineus muscle reflected distally, the medial circumflex femoral artery and vein that run caudally and medially to the acetabular portion of the pelvis can usually be seen. It may be necessary to free these vessels from the surrounding fascia and to retract them proximally. Small branches from these vessels may be disrupted during retraction and can be cauterized if electrocautery is available.
A separation between the iliopsoas and the adductor longus muscle is developed by blunt dissection. Retraction of the iliopsoas m. cranially and the adductor m. caudally exposes the rim of the acetabulum. Gelpi self-retaining retractors are useful for this step, although care should be taken to avoid trauma to the femoral neurovascular bundle with the sharp instrument tips.
The joint capsule can then be sharply incised to reveal the femoral head. The author prefers not to luxate the hip out of the acetabulum at this point, but leaves it in situ to help with stabilization during the osteotomy. Time and care should be taken to ensure sufficient joint capsule has been removed from the femoral neck to allow accurate removal of both the femoral head and neck. Best exposure of the neck of the femur can be developed by placing Hohmann retractors cranial and caudal to the femoral neck.
The author recommends having a bone model of a pelvis and femur in the operating theater to help guide correct orientation of the FHO cut. As the pelvic limb is typically abducted in a frog-legged position, orientation of the cut is typically ∼30–45 degrees off vertical, pointed towards the pelvis. Iliopsoas m. insertion on the lesser trochanter can readily be palpated; however, the greater trochanter will not be visualized due to the limited exposure of this approach and its dorsal-lateral location. If the orientation of the FHO cut is too perpendicular to the femur, it may risk inadvertent damage to the greater trochanter.
When performing the osteotomy, this author likes to mark the start of the osteotomy just proximal to the lesser trochanter (which is easier to palpate via this approach) with an osteotome. The angle of the osteotomy cut is approximately 25–45 degrees from parallel with the femur. When performing the osteotomy, it is essential to have an assistant scrubbed into the surgery to help hold the retractors and limb to allow for accurate orientation of the cut.
Note: it is very important not to be too perpendicular to the bone with the FHO osteotomy as inadvertent fracture of the greater trochanter may occur.
The osteotomy site should be carefully palpated post osteotomy to confirm configuration of the FHO osteotomy (lifting the leg can help palpation of the dorsal aspect of the cut).
Before the patient is recovered from anesthesia, post-operative hip-extended VD pelvic radiographs should be taken to confirm the configuration of the cut.
In the author’s experience, the main complications are related to insufficient rehabilitation (e.g., the patient was cage rested without sufficient range of motion and ended up with severe muscle contracture limiting extension of the hip). Leaving too much of the femoral neck can also be a technical pitfall of limb and saw positioning intra-op, which hopefully can be corrected when found on palpation or on the post-operative radiograph when the patient is still under general anesthesia.
Following surgery, the rehabilitation plan is focused on providing adequate analgesia to the patient to ensure that daily physical therapy can be carried out. The main focus of physical therapy is to encourage normal range of motion in the hip joint (particularly hip extension), to facilitate early normal weight bearing in the operated limb, and to slowly rebuild muscle strength in the upper limb musculature.