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 over-weight 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 via a Cranial Lateral Approach to the Hip Joint
This is the most common approach used by most surgeons when performing an FHO. A solid knowledge of the regional anatomy is essential to avoid inadvertent neurovascular damage, and to avoid un-necessary muscle transection or trauma. During this approach, most dissection is focused in fascia planes between versus through muscles.
A partial tenotomy of the deep gluteal muscle may be required for exposure of the femoral head and neck. In some dogs, especially in traumatic cranial dorsal hip luxation cases, this tenotomy may not be required, which is preferable to optimize gluteal mm function in the recovery period.
Once the hip joint has been exposed, tips for luxation of the femoral head out of the acetabulum include external rotation and adduction of the femur and use of a Hatt spoon (authors preference) or round ligament cutter to transect any remaining round ligament and provide leverage.
Clearance of sufficient joint capsule and soft tissue from the neck of the femur is recommended prior to making the osteotomy. The ideal FHO removes the entire femoral head and neck such that the osteotomy extends to the proximal aspect of the lesser trochanter. Palpation of these landmarks and marking the planned osteotomy with electrocautery or etching the bone with an osteotome are recommended. During the osteotomy with an oscillating saw or osteotome, the femur should be held externally rotated with the stifle pointing at the ceiling, and the femur parallel with the surgical table. The angle of cut will then be vertically orientated along the planned mark.
Once the femoral head and neck have been removed, careful palpation of the cut should be carried out to ensure that sufficient neck has been removed (i.e., the cut surface of the bone should extend just proximal to the lesser trochanter). If there is too much neck left behind, a second osteotomy can be performed, or a bone rasp can be used for smaller bone segments. Once the surgeon is satisfied with the femoral side, they should also put a finger into the acetabulum and bring the hip through normal range of motion to confirm that no bony impingement can be appreciated.
Closure begins with re-apposition of the joint capsule. Repair of the deep gluteal tenotomy is essential and can be facilitated by abduction of the femur to take tension off the closure. The fascia is then closed in one or two layers, prior to routine subcutaneous and skin closures.
FHO via a Ventral Approach to the Hip Joint
This is the author’s preferred approach for FHO where possible. 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 approach is performed as outlined in Piermattei and Johnson’s Atlas of Surgical Approaches to the Bones and Joints of the Dog and Cat. 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 electrocautery or an osteotome. The angle of the osteotomy cut is approximately 25 degrees from parallel with the femur. It is very important not to be too perpendicular to the bone with this osteotomy as inadvertent removal of the greater trochanter may occur. Similar to the craniolateral approach, 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).
With either approach, before the patient is recovered from anesthesia, a 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., 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.