Rationale, Patient Selection, and Timing

Surgically induced premature closure of the pubic symphysis has been shown to cause mediolateral shortening of the cranial pubic rami.80,127 Shortened pubic bones, fixed to the ventromedial aspect of the acetabulum, cause rotation of the acetabula ventrally, or ventroversion, during growth of the pelvis, and thus create increased coverage of the femoral head by the acetabulum. The procedure results in acetabular ventroversion and decreases hip distraction indices, pelvic inlet circumference, and pelvic width in treated dogs compared with control dogs.¹²⁷ The effect is similar to the rotation gained by a triple pelvic osteotomy without the greater expense, pain, and recovery associated with triple pelvic osteotomy.

The procedure is effective if proper consideration is given to the age of the dog, the degree of laxity, and other selection criteria. The incidence of osteoarthritis was dramatically decreased at 2 years of age in dysplastic dogs on which juvenile pubic symphysiodesis had been performed at 15 or 20 weeks of age.⁹⁰ A prospective clinical study compared long-term outcomes of dysplastic dogs undergoing juvenile pubic symphysiodesis with outcomes from triple pelvic osteotomy.⁷⁴ No significant differences were noted in lameness scores, extension of the hip joint, distraction index, peak vertical force, acetabular angle, radiographic osteoarthritis score, or owner-assigned clinical function scores between treatments, although the dorsal acetabular rim angle was significantly greater in dogs that underwent juvenile pubic symphysiodesis. This procedure does not eliminate joint laxity or progression of osteoarthritis in dysplastic dogs.⁷⁴ In a prospective study of 217 puppies 14 to 22 weeks of age treated with juvenile pubic symphysiodesis or no surgery, juvenile pubic symphysiodesis increased the odds of limiting the progression of hip dysplasia in puppies with mild to moderate laxity, although it was less effective if the puppies were severely affected.¹³³ Pubic symphysiodesis was ineffective in dogs older than 22 weeks of age.

The procedure is indicated primarily for puppies 12 to 20 weeks of age with palpable hip joint laxity. Distraction index radiography is a reliable method to determine hip joint laxity in dogs 4 months of age and older.2,125 Juvenile pubic symphysiodesis is more effective if done in younger puppies, particularly in puppies younger than 18 weeks of age.^8,90 A 10 to 15 degree per hip improvement is expected if performed at 16 weeks of age, but minimal improvement is seen when the procedure is performed at 20 to 22 weeks. Screening of puppies at risk at 16 weeks of age is recommended. Identification of puppies that will benefit from juvenile pubic symphysiodesis is challenging. Puppies with mild to moderate palpable laxity and radiographic evidence of a predisposition (laxity, joint incongruency) are the best candidates for juvenile pubic symphysiodesis.¹³⁴ Puppies with severe laxity and severe joint incongruency often demonstrate continued progression of disease despite the surgical procedure.¹³⁴ No studies have been performed to identify and validate definite selection criteria for juvenile pubic symphysiodesis. It is known that increasing laxity, as measured by the distraction index, is associated with increased risk of developing radiographic osteoarthritis of the hip joint, and that this relationship is breed specific. However, in general, dogs with a distraction index of less than 0.3 do not develop radiographic osteoarthritis, and risk increases as the distraction index increases. Disease-susceptibility curves indicate a sigmoidal relationship between distraction index and the probability of development of osteoarthritis, with the steepest part of the curve often occurring when the distraction index is between 0.5 and 0.8.¹¹⁰ Despite the recognized association between laxity and the development of hip dysplasia, the relationship between the distraction index and the benefits of juvenile pubic symphysiodesis remains investigational.

Previous juvenile pubic symphysiodesis surgery is not easily detectable after maturity, and juvenile pubic symphysiodesis should not be performed on sexually intact dogs. If dogs undergoing juvenile pubic symphysiodesis are not neutered, and animals with falsely improved hip phenotypes are used as breeding animals, they will perpetuate a genotype associated with hip dysplasia.

Surgical Approach and Procedure

The dog is anesthetized, and the caudal abdomen and inguinal area are prepared for aseptic surgery. Juvenile pubic symphysiodesis is commonly combined with elective castration or ovariohysterectomy, so the exact margins for aseptic preparation depend on the combination of intended procedures. The dog is placed in dorsal recumbency, and a standard approach to the pubic symphysis is performed.⁹⁷ In male dogs, the skin incision is made parallel to the penis and extends from just in front of the pubis caudally to the cranial edge of the scrotum. The subcutaneous fascia is incised, and collateral branches of the pudendal artery and vein are ligated; then the penis is retracted laterally to allow incision of the deep fascia and subperiosteal elevation of the origins of the adductor and gracilis muscles. In female dogs, the skin incision is made directly at the midline, and the subcutaneous fascia and adductor and gracilis muscles are separated in the same line. Cauterization of the pubic symphysis is performed with a standard cautery unit set at 40 W, with a unipolar electrode applied for 10 to 30 seconds at each cauterization point;⁹¹ this is repeated every 2 to 3 mm along the pubic symphysis (Figure 60-5). Only the cranial one third to one half of the symphysis should be ablated. Internal pelvic structures may be protected from excessive heat during cauterization by transrectal palpation by a gloved assistant, or by placement of a thin ribbon malleable retractor introduced into the pelvic canal from the cranial aspect of the pubis. Alternatively, the surgeon can make a small incision into the abdomen just cranial to the pubis and can monitor temperature by manual palpation from the cranial aspect of the pubis. Closure is performed in layers with reapposition of the adductor and gracilis muscles across the pubic symphysis used as the first layer, followed by closure of the subcutaneous fascia and then the skin.

Aftercare

No postoperative morbidity was reported in any experimental or prospective clinical study. There is no need to restrict activity after surgery beyond prudent precautions to protect the incision. Recheck radiographs should be performed as necessary to assess the degree of development of osteoarthritis and to diagnose lameness if clinical signs develop.

Rationale and Patient Selection

Pelvic osteotomy, or triple pelvic osteotomy as it is commonly performed, is a prophylactic surgical intervention intended to decrease abnormal hip joint laxity, normalize articular stresses, and improve hip joint congruity (Figure 60-6) via joint remodeling. Rotation of the acetabulum provides greater acetabular coverage of the femoral head to ensure continuous hip joint reduction through a normal range of motion (Figure 60-7).^113,114,124 Biomechanical studies suggest that triple pelvic osteotomy decreases the magnitude of the hip force and increases the contact area of the force application.^24,25 Pelvic osteotomy was first described in the veterinary literature by Hohn and Janes in 1969.⁴⁹ Many variations on the technique have been described over the past 50 years; however, the basic procedure described by Slocum is currently the most popular.¹²³

Immature dogs clinically affected by hip dysplasia with palpable or radiographic joint laxity, but with no radiographic signs of secondary osteoarthritis, are candidates for triple pelvic osteotomy. Generally, dogs will be candidates up to approximately 10 months of age, when many dogs develop radiographic secondary osteoarthritis, but in rare cases, dogs do not develop secondary arthritis despite lax hip joints at maturity and thus remain candidates for the procedure. Some minimal coverage of the femoral head is a necessary criterion for surgery because dogs that have no acetabular capture of the femoral head at all continue to subluxate after triple pelvic osteotomy and are not candidates for correction (Figure 60-8). Triple pelvic osteotomy may be performed unilaterally or bilaterally, although the author recommends unilateral surgeries staged 4 to 6 weeks apart.

Although controversial, the procedure is not recommended in dogs without clinical signs, as it is difficult to predict the exact degree of subluxation that will cause any dog to develop clinical hip dysplasia, or to what degree and at what age a dog will be affected. More reliable indices than direct palpation techniques should be used to predict clinical hip dysplasia if the procedure is to be performed in a dog without current clinical signs. The PennHIP distraction index provides a reliable assessment of hip joint laxity, and disease-susceptibility curves have been developed to provide information on the probability of developing radiographic evidence of hip osteoarthritis associated with a given distraction index. These curves provide the veterinarian and the owner with information regarding the probability that an individual will develop radiographic evidence of osteoarthritis based on laxity.¹¹⁰ However, the development of clinical osteoarthritis includes other factors, such as patient activity, breed, gender, weight, and age. Therefore, a variety of factors are included when one is considering whether triple pelvic osteotomy should be performed on dogs without clinical signs. Definitive recommendations for surgical intervention remain elusive according to the current literature.

Hip joint laxity is best assessed clinically via an Ortolani test on a sedated or anesthetized dog (Figure 60-9).²⁰ The animal is placed in dorsal recumbency with the stifle flexed and the femora held vertically. Pressure down the femoral shaft produces dorsal coxofemoral subluxation. While downward pressure is maintained, the femur to be examined is slowly abducted. In patients with subluxation, a click, known as the Ortolani sign, is produced during reduction of the femoral head into the acetabulum. Alternatively, the Ortolani test can be performed with the animal in lateral recumbency.²⁰ One hand grasps the stifle and applies a proximally directed force to the femur, while the other hand stabilizes the pelvis. Abduction of the femur produces similar reduction of the femoral head. The angle of reduction roughly corresponds to the rotation of the acetabulum needed. Dogs with an angle of reduction smaller than 30 degrees are good candidates for triple pelvic osteotomy. Some surgeons recommend the use of 20 degree triple pelvic osteotomy plates exclusively, because an experimental study using a special hinged plate showed that stable reduction of dysplastic specimens consistently occurred for acetabular ventroversion angles of 20 degrees.²⁵ Survey radiographs should be taken in Orthopedic Foundation for Animals (OFA) or PennHIP positions to confirm laxity and assess the degree of degenerative change.

Evidence

Triple pelvic osteotomy is an accepted, proven prophylactic treatment for hip dysplasia in immature dogs without secondary osteoarthritis. Clinical studies show consistent subjective improvement in dogs after triple pelvic osteotomy,81,82,113,114,124 with 92% to 93% satisfactory limb function noted postoperatively. Kinetic gait analysis is held by most surgeons, however, as the best objective measure for lameness outcomes.¹⁰¹ Kinetic gait analysis also has been used to confirm a high rate of positive outcomes after triple pelvic osteotomy surgery.^56,82,128 Significant increases in peak vertical force of dysplastic limbs occur as early as 8 weeks after triple pelvic osteotomy, and values for peak vertical force reach normal by 28 weeks postoperatively. Although triple pelvic osteotomy provides a high rate of successful functional recovery, secondary osteoarthritis may progress after triple pelvic osteotomy, despite improvement in joint stability.^56,60,81,128 Even when triple pelvic osteotomy does not consistently stop the progression of osteoarthritis, the resulting improvement in joint stability is usually sufficient to yield a functional outcome.¹⁰³

Surgical Approach and Procedure

For unilateral procedures, the limb is clipped from the hock to the dorsal midline on the lateral surface, and from the hock to the ventral midline on the medial surface. The surgical preparation area extends from the midlumbar area cranially to the perineal midline caudally. The dog is placed in lateral recumbency. The upper leg is abducted, and a 5 cm incision is made over the origin of the pectineus muscle transversely to the ventral midline. Subcutaneous tissues are reflected in line with the incision, and the medial circumflex femoral artery and vein are retracted distally. The hip joint is palpated, and the origin of the pectineus muscle is elevated from the iliopectineal eminence of the pubis. Just medial and cranial to the iliopectineal eminence, the pubis is palpated, stripped of periosteum, and isolated. A 1 cm segment of the pubis just medial to the acetabulum is removed, protected with a moist sponge, and saved for later use as a bone graft. Care is taken to protect the obturator nerve lying just caudal to this pubic segment. If the pubis has been carefully stripped of periosteum, there should be no resulting caudal abdominal hernia, but if abdominal fat or tissues are bulging from the prepubic region, the rectus abdominis muscle is sutured to the cranial edge of the external obturator muscle. The subcutaneous tissue and skin are closed in standard fashion by surgeon preference.

The limb is returned to its normal resting position, and a horizontal incision is made over the ischium (a vertical incision at the midbody of the ischium may be substituted at the surgeon’s discretion). Reflection of subcutaneous tissues in the same line exposes the ischiatic table. The insertion of the internal obturator muscle is incised along the caudal border of the ischial tuberosity, and the muscle is elevated dorsally to expose the dorsal surface of the ischium. Elevation of the semimembranosus and semitendinosus muscles ventrally exposes the ventral surface of the ischium. The ischium is transected at its midpoint by a reciprocating saw, a Gigli saw, or an osteotome. Using an osteotome risks propagating a fissure into the acetabulum, but alternatively, leaving 0.5 cm of bone intact at the cranial ischium with the use of an osteotome allows the surgeon to bend that portion of the ischium without complete separation along the osteotomy line. At the surgeon’s discretion, a hemicerclage wire may be placed through holes drilled on both sides of the osteotomy line for later stabilization of the ischial osteotomy. The incision is left open temporarily in case manipulation of the ischium is necessary to facilitate acetabular rotation.

A standard lateral approach to the ilium is performed.⁹⁶ The origin of the deep gluteal muscle is elevated from the ilium. An ilial osteotomy is performed with an oscillating bone saw extending from just caudal to the caudal dorsal iliac crest perpendicular to the long axis of the ilium and perpendicular to the plane of the ilial surface (Figure 60-10). This perpendicular cut allows an exact rotation around the long axis. Alternatively, some surgeons make the osteotomy from just caudal to the caudodorsal iliac crest and directed caudoventrally toward the ventral margin of the ilium at a 30 degree angle to the long axis of the ilium. The caudal ilial segment is grasped with a bone-holding forceps such as a Kern bone-holding forceps, is rotated laterally, and is secured at the surgeon’s discretion for a side-specific pelvic osteotomy plate. As previously noted, 20 degree plates are sufficient for most patients.¹³² First, the plate is secured to the caudal ilial segment with cortical or cancellous screws, then cancellous screws are used in the cranial ilial segment, with the ventral screw placed in compression mode. Cranial screws that extend into the sacrum have traditionally been considered to be associated with a decreased possibility of screw loosening,^121,137 but a recent report suggests that screw loosening occurs least when cancellous screws did not extend into the sacrum.²⁹ Screw loosening was significantly less prevalent with self-tapping screws than with pre-tapped screws.⁷⁷ Joint stability is assessed by testing the hip joint in a range of motion, including an Ortolani test. If instability persists, a plate with greater rotation can be substituted and a capsulorrhaphy performed, or a Lembert imbrication suture can be placed into the capsule to tighten the joint capsule. The pubic segment saved earlier is morselized and placed in the dorsal aspect of the osteotomy behind the rotated caudal ilium. The ischial hemicerclage wire, if placed, is now tightened to stabilize the ischial osteotomy. Both incisions are closed in standard fashion by surgeon preference.

Technique Variations

Some surgeons prefer to perform simultaneous bilateral triple pelvic osteotomys.¹³ For these procedures, the animal is placed in ventral recumbency, and both sides of the pubis are approached through a ventral midline incision; the pubic segments are removed bilaterally through the central incision. The animal then is placed in lateral recumbency and is surgically prepped, and a triple pelvic osteotomy is completed through caudal ischial and lateral ilial approaches, as previously described. Then the dog is flipped into the opposite lateral and surgically prepped, and the procedure is repeated.

A technique variation for the triple pelvic osteotomy procedure has been described in which the stabilization provided by the pelvic osteotomy plate is supplemented with a dynamic compression plate placed on the ventral aspect of the ilial body.⁴⁰ The purported advantages of this procedure include increased strength of fixation, less incidence of screw loosening, and less incidence of fixation failure. Disadvantages of the procedure include greater exposure and elevation of muscle from the ventral ilium, increased surgical time, and increased cost of the additional implants.

In many commercial pelvic osteotomy plates, a wire hole is present in the caudal half of the plate that was initially intended to allow hemicerclage wire placement around the plate and the ilium to facilitate plate application. A retrospective study has shown that use of the wire has no effect on postoperative implant stability.¹²¹

Aftercare

Radiographs are taken immediately postoperatively to assess proper positioning of the implants, and at 6 to 8 weeks postoperatively to assess healing. Continued hip joint subluxation is often seen on immediate postoperative radiographs, but subsequent radiographs taken several days postoperatively usually show that the hip joint “tightens” without additional intervention, and that good joint congruity has developed. After surgery, the animal is exercise restricted to a cage with minimal leash-walks allowed daily until healing is confirmed on follow-up radiography. Postoperative analgesic therapy consisting of opiates for 3 to 5 days and a nonsteroidal antiinflammatory is continued for 7 to 10 days. Additional physical therapy regimens are not necessary for good function outcomes but may improve the speed of return to normal function and mobility.

Complications of Triple Pelvic Osteotomy

Complications of triple pelvic osteotomy are primarily under the surgeon’s control. Poor surgical technique may result in damage to the sciatic or obturator nerve. Loosening of the cranial screws has been reported in up to 62% of dogs.⁶⁰ Early weight bearing and weak juvenile bone are hypothesized as possible reasons for screw loosening.^50,51 Screw loosening can be limited by the use of cancellous screws in the cranial segment, the use of longer screws that have purchase in the sacrum, and by strict exercise confinement after surgery.⁶ Ventral plate stabilization of the ilium and the pelvic osteotomy plate has been described and is highly effective in combating implant failure.⁴⁰ Early detection of screw loosening has been advocated to allow prophylactic intervention and avoid complications.¹² Obstipation and dysuria are reported complications secondary to narrowing of the pelvic canal.¹⁰⁶ Obstipation and dysuria are avoided by removing the most lateral portion of the pubis and by using pre-angled side-specific commercial pelvic osteotomy plates rather than twisted conventional plates.^45,69 Overrotation of the acetabulum has been reported to result in femoral neck impingement by the acetabular rim and decreased ability to abduct the hip.^{12,106,114,123} Selection of the minimal angle necessary to provide improved joint congruity is important to minimize complications of overrotation.^24,25

Rationale, Patient Selection, and Timing

Ostectomy of the femoral head and neck is intended to eliminate bone-on-bone contact of the diseased acetabulum and the femoral head and to permit the formation of a pseudoarthrosis composed of dense fibrous connective tissue lined by a synovial membrane. After excision, the acetabulum fills in with bone and the proximal femur remodels with bone resorption at the excision surface and bone production in the proximal femur. Enthesophytes form at the margins of the joint capsule.

Dogs are candidates for femoral head and neck ostectomy if clinical signs of pain and lameness cannot be alleviated by analgesic therapy, weight loss, or other nonsurgical means, and if they are not candidates for, or economic or environmental conditions dictate against, other methods of surgical therapy such as triple pelvic osteotomy or total hip replacement. The functional outcome of femoral head and neck ostectomy may be affected by surgical technique, duration of clinical signs, patient age, postoperative care and physical therapy, body weight, and disease severity.32,44,75,92 Body weight is the most commonly investigated factor in outcome. Dogs weighing less than 17 kg have better results than larger dogs^32,42,75,92; however, the surgery should be considered for larger dogs if total hip arthroplasty is not a surgical option, because femoral head and neck ostectomy still may result in improved quality of life if correctly performed. Patient age is not a consideration in otherwise healthy dogs; however, younger dogs generally have a better outcome than older dogs.

Femoral head and neck ostectomy should be performed when clinical signs are not acceptably alleviated by analgesic or other medical therapies, and when total hip replacement is not an option because of patient size, patient age, economic climate, or other considerations. Results of femoral head and neck ostectomy will be improved if consistent limb use by the animal has been maintained and extensive muscle atrophy is not present before surgery. These conditions do not preclude use of the technique, but once surgical intervention is warranted, it should occur as soon as possible, so that improvement in patient comfort occurs early and proper physical rehabilitation can be initiated as soon as possible to recover lost muscle tone and bulk.

Evidence

Published reports of clinical results after femoral head and neck ostectomy have primarily consisted of the results of veterinarian observations or client questionnaires, but most show improvement in clinical signs for the majority of dogs. Objective gait analysis data have become available only recently for current research dogs.9,30,32,44 Functional changes after femoral head and neck ostectomy include decreased abduction and extension of the hip, limb shortening and dorsal displacement of the femur, decreased stifle and hock angulation, and muscle atrophy. Recovery from the procedure to maximal improvement in function may take 6 to 8 months, and the function of younger dogs improves faster than that of older dogs.^9,92 Simultaneous bilateral femoral head and neck ostectomy has been reported and results in high levels of client satisfaction.¹⁰⁴

The cause of the poorer outcome in larger dogs has not been determined. Some studies suggest that bone-on-bone contact from inadequate excision or postoperative formation of enthesophytes or ectopic bone is the primary cause of poor outcome68,129; others suggest that the bone contact is too common to explain differences in clinical outcome.^31,33 Complete excision of the femoral neck, including removal of the lesser trochanter, may improve results.⁶⁷

Numerous attempts have been made to interpose tissue between the acetabulum and the femoral neck to improve clinical outcome after femoral head and neck ostectomy, but results have been equivocal or negative.* Muscle transpositions using the biceps femoris,^11,66,68 the deep gluteal muscles,⁹ and a vascularized rectus femoris muscle sling have been described. Ischiatic nerve damage has been reported in three dogs after biceps femoris or deep gluteal muscle flaps were used in combination with femoral head and neck ostectomy.^55,100 Kinetic gait analysis has failed to demonstrate improvement in weight bearing when interpositions have been used.^63,75 Muscle interpositions are no longer recommended clinically on a routine basis. If revision osteotomy is contemplated because of unacceptable bone-on-bone contact or extensive limb atrophy, muscle interposition may be used and outcome may be improved by the use of antibiotic prophylaxis, creation of a muscle flap base 1.5 times the width of the ostectomy surface, use of the caudal pass of the biceps femoris muscle flap, suturing of the muscle flap under minimal tension, suturing of the flap to the middle gluteal and vastus lateralis muscles, and careful identification and protection of the ischiatic nerve.⁶⁴