CHAPTER 27
FRACTURES OF THE PELVIS
CHARLES D NEWTON
- Anatomy
ANATOMY
Pelvic fractures account for 20% to 25% of the fractures seen in veterinary practice. Most involve at least two fractures and many involve all three bones of the pelvis. Because of its anatomical position, out of axial weight bearing, and its heavy muscular covering, half of all pelvic fractures can be handled adequately without surgery.
The pelvis is composed of several large, flat bones that form by their attachment to the sacrum, a rectangular, boxlike structure that gives shape to the caudal axial skeleton and serves as the point of attachment of the pelvic limbs to the axial skeleton. Each hemipelvis is composed of an ilium, acetabulum, ischium, and pubis (Figs. 27-1 and27-2).
The ilium is formed by a flat, concave wing cranially and a more narrow body or shaft caudally. In the immature animal, the crest of the ilium possesses an epiphysis that is evident radiographically and may separate as a result of trauma.
The acetabulum forms the pelvic component of the hip joint. It is a deep socket covered with articular hyaline cartilage. The deep-seated acetabular fossa serves as a point of attachment for the round ligament, which attaches the femoral head and acetabulum.
In the adult animal, the acetabulum is formed by components of the ilium, ischium, and pubis. The immature animal has a fourth bone, the acetabular bone, which also contributes to the acetabulum.
The ischium is an irregularly shaped bone that forms a portion of the acetabulum and contributes to the caudal floor of the pelvis. The ischium attaches to the ischium of the opposite hemipelvis via the symphysis ischii. The large ischial tuberosity possesses an epiphysis in the immature animal and may separate as a result of trauma.
The pubis is an irregularly shaped flat bone that forms a portion of the cranial and medial acetabulum and the cranial edge of the floor of the pelvis. The pubis is attached to the pubis of the opposite hemipelvis via the symphysis pubis. The conjoined symphysis pubis and symphysis ischii form the ventral prominent ridge of the pelvic floor termed the symphysis pelvis. It should be emphasized that the axis of the pelvis is not cranial- caudal. In fact, the pelvis has approximately a 45¡ angle of inclination. This is important when attempting to realign sacroiliac fractures and dislocations.
SURGICAL APPROACHES
Surgical exposure of the pelvis can be difficult in the hands of an inexperienced surgeon. The heavy musculature covering the bones, as well as the close proximity of the sciatic nerve and internal iliac vessels, add to the difficulty. A thorough knowledge of all regional anatomy is necessary before approaching the pelvis surgically. Enumeration of all surgical approaches to the pelvis it beyond the scope of this text. For a complete review, see Atlas of Surgical Approaches to the Bones of the Dog and Cat(23) A brief discussion of surgical approaches is offered here.
APPROACH TO THE ILIUM
The ilium may be approached either dorsally(9,23) or laterally.(18) The dorsal approach has the disadvantage of probable transection of the cranial gluteal artery and nerve during elevation and retraction of the middle gluteal muscle ventrally. The lateral approach utilizes an incision between the fascia lata muscle, and the middle gluteal muscle. The middle gluteal muscle can be elevated from its cranial-most origin on the ilial wing.
APPROACH TO THE ACETABULUM
The acetabulum is difficult to expose owing to the gluteal tendons that cross over it to insert on the femoral greater trochanter. Various approaches have been developed that allow exposure of the cranial, dorsal, or caudal portions. The cranial acetabulum can be approached as mentioned above by dorsal elevation of the gluteal muscles. Usually, for best exposure the dissection will be between the middle and deep gluteal heads.
Dorsal exposure is accomplished best by gluteal muscle tenotomy or by trochanteric osteotomy. Both techniques allow for complete gluteal retraction and visualization of the acetabulum. When possible, osteotomy is a better technique than tenotomy, since bony healing will occur more completely than tendon healing.
Exposure of the caudal acetabulum requires retraction of the biceps femoris muscle. The sciatic nerve is usually in view during this exposure and should be protected or retracted carefully
APPROACH TO THE ISCHIUM
The ischium is rarely approached surgically, since ischial fractures are seldom treated by open fixation. In those instances in which exposure is needed, the above-mentioned method of biceps retraction with gemellus and internal obturator tenotomy works well. More retraction will be necessary, and sciatic nerve protection is essential.
APPROACH TO THE PUBIS
With the dog or cat in dorsal recumbency, an incision is made directly over the pelvic symphysis. Elevation of the origin of the adductor muscle and gracilis muscles provides exposure of the pubic symphysis. More retraction will allow for visualization of the cranial pubic edge or the obturator foramen. (19,23)
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FIG. 27-1 (A) Canine pelvis, caudal-dorsal view. (B) Left os coxae, lateral aspect B. (Evans HE, Christenson GC Miller's Anatomy of the Dog, 2nd ed. Philadelphia, WB Saunders, 1979) |
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FIG. 27-2 Cranial-caudal (A) and medial-lateral (B) radiographic views of a normal feline pelvis. |
HISTORICAL CONSIDERATIONS
For many years fractures of the pelvis have been treated successfully using confinement for immobilization.(3) Prior to the introduction of antibiotics, this was the only treatment. When antibiotics made internal fixation a safe option, various methods of fixation were tried. Probably the first form recorded was the Kirschner-Ehmer device.(11,20) By palpation or by use of a fluoroscope, multiple pins were placed into fracture fragments and fragments were stabilized by attaching all the half-pins. Although some degree of reduction was possible by manipulation of the pins, usually it was incomplete, yet fixation was solid. The benefit of this technique seemed to be earlier mobilization of the animal and, therefore, fewer soft tissue complications and improved hip motion. Ehmer(13) described casting techniques for pelvic fractures.
With the advent of intramedullary fixation, the pelvis was approached surgically and fixed in absolute reduction. Most pinning techniques of today were introduced in the 1940s and remain unchanged or have been modified only slightly.
One device of historical note is the Lee clamp. Designed in the 1950s, it was used to immobilize ilial shaft fractures. While the device seems to have worked well, it is not in wide use today.
SIGNS AT PRESENTATION
Most animals display dysfunction of the pelvic limb or limbs associated with a pelvic fracture. The dysfunction may be complete and painful or incomplete and capable of allowing the animal to stand on the affected side. The severity of the associated trauma and soft tissue injury usually plays a major role in determining if the animal is capable of supporting weight.
Physical examination may not reveal crepitus in minimally displaced fractures. Complete fractures with displacement usually are palpable and result in deformity and crepitus. Rectal examination can often contribute information about the degree of medial displacement of fragments.(7)
ASSOCIATED INJURIES TO SOFT TISSUE
Depending on the degree of trauma that caused the pelvic fracture, soft tissue injuries may be minimal or severe. Approximately 8% of animals will have injuries or ruptures to the bladder or intrapelvic urethra. Therefore, any animal not seen to urinate or without radiographic or palpable evidence of a bladder must be evaluated further (Fig. 27-3).(33)
Herniation of the abdominal wall can occur in association with pelvic fracture. Bladder(32) or omentum may herniate through the tear. Injuries to associated structures of the nervous system are common. Ilial shaft or ischial shaft fractures can bruise, lacerate, or transect the sciatic nerve. Similarly, femoral nerve injuries can occur. Sacroiliac separation commonly results in temporary dysfunction of the sacral roots and pelvic plexus. This may produce fecal and urinary retention or incontinence. While the injury is usually mild and temporary, permanent loss is possible.
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FIG. 27-3 Lateral radiograph of a canine fractured pelvis demonstrates positive contrast cystogram. Note the contrast material in the abdominal cavity, indicative of bladder rupture. |
Vascular injury to the internal iliac artery or vein is likely in severely comminuted or "flattened" pelvic fractures. Iliac artery tears can result in severe bleeding with associated blood loss, anemia, or death. The blood loss may be into the thigh musculature, into hematomas beneath the gluteal muscles, or into the retroperitoneal space.
Skin injury and slough can occur over the back when the pelvic fracture was caused by a tire running over the pelvis. The associated skin loss may extend distally as far as the knees on the lateral thigh surface. If the animal was run over with its limbs in an abducted position, the skin of the groin and inner thigh may also slough.
Soft tissue injury associated with pelvic fracture is very common. One should assume that both have happened when evaluating the fracture and observe carefully for signs of the soft tissue injury. Any sudden, precipitous fall in packed cell volume probably indicates a severe vascular injury and should be investigated immediately.
RADIOGRAPHIC FINDINGS
Radiology plays a valuable role in determining the proper treatment in pelvic fractures. Many pelvic fractures are sufficiently well aligned or involve less vital portions of the pelvis that they do not require open reduction and internal fixation. The following radiographic findings are characteristic of pelvic fractures that are most amenable to open fixation:
Acetabular fracture
Fragments that result in hip instability, such as fracture of the ilium, ischium, and pubis resulting in a "free-floating" acetabulum
Severe reduction in size of pelvic canal
Grossly displaced fragments
Careful reading of the radiographs is required to ascertain the full extent of the fractures. Often, more than the standard ventral-dorsal and lateral views are required, especially when attempting to evaluate the weight-bearing portion of the acetabulum, in which oblique views may be helpful. Often, the hemipelvis will begin to rotate following fracture, thus rendering acetabular assessment difficult.
CLOSED REDUCTION AND IMMOBILIZATION
Closed reduction and immobilization are adequate and proper treatments in approximately 50% of pelvic fractures.(l2) The following radiographic criteria are used for closed treatment:
Incomplete fracture
Perfect or adequate alignment
Pelvic canal not compromised
Adequate stability for the hip
Sacroiliac separation that is in alignment or at most 50% overridden
Closed immobilization takes into account the above- mentioned criteria and assumes that immobilization provided by the surrounding muscle masses and cage rest will be adequate to proceed to uneventful union. Fragment reduction can be altered only mildly, however, it is possible to realign a dorsally placed ilial wing by forcing it ventrally. Occasionally, rectal palpation will allow some realignment of ischial fragments.(23) By forcing the pelvic limb into adduction over a large cotton fulcrum placed in the groin, some ilial shaft fractures can be better aligned.
Closed immobilization usually is accomplished by confinement in a cage or small area. Occasionally, hobbling the pelvic limbs to prevent adduction will help. Confinement for a period of 2 to 4 weeks is usually sufficient, although most animals will begin to stand and walk at 7 to 14 days. Owners must be warned against allowing their animals premature return to normal activity, since complete union may not occur until 6 to 8 weeks post fracture.(3,6,23)
OPEN REDUCTION AND INTERNAL FIXATION
Using the radiographic criteria mentioned above coupled with careful physical examination and assessment of function, approximately 50% of animals presenting with pelvic fractures require some form of internal reduction and fixation. The intent of surgery is to provide for a more anatomical result, better function, more comfort during the period of healing, and, hopefully, a more rapid union. In the breeding bitch, open reduction resulting in an anatomically perfect pelvic canal is more likely to allow for normal delivery of pups. Despite perfect reduction, occasionally proliferative callus may prevent normal delivery and necessitate caesarean section.
Open reduction of pelvic fractures should be accomplished as soon as possible following the animal's positive assessment as a surgical candidate. Reduction accomplished 24 to 48 hours following the fracture is much simpler than surgery after 3 to 4 days. By the fourth to seventh day, postfracture reduction is much more difficult and complete reduction may be impossible.
When an animal's general condition does not allow surgery before 7 to 14 days post fracture, the surgery is best not performed. Usually after 7 to 14 days of immobilization, the fragments cannot be moved and union is proceeding rapidly. While radiographically the pelvis will look unreduced and the end result may lack full normal function, the result will be adequate. Methods of fixation in open repair of the pelvis include intramedullary pins, pins and wires, orthopaedic wire, bone screws, bone plates, and Kirschner wires. Plate and screw fixation is very stable and more suitable for ilial fractures and acetabular fractures. Pin, pin and wire, orthopaedic wire, and Kirschner wire techniques are applicable in any part of the pelvis.
SACROILIAC SEPARATION OR FRACTURE
Occasionally, in an animal hit from behind, the sacroiliac separation will be bilateral with an intact pubis. This results in an anatomically normal pelvis that has been detached from the axial skeleton.
Sacroiliac fracture may occur unilaterally or bilaterally, resulting in instability of the hemipelvis and hip. In pups or kittens, sacroiliac fracture occurs through the cartilaginous junction of the ilium and sacrum, whereas in the adult it is a true fracture.
As stated above, when more than 50% override is present or hemipelvic and hip instability is present, open fixation is required.
Following surgical exposure of the fracture site using either a dorsal or ventral approach to the ilium, the fracture is either visualized or palpated to determine the fracture shape. Usually the C-shaped indentation from the sacrum is palpable on the medial ilial shaft and can be matched up to the sacrum. As has been suggested by Brinker,4 two vertical Kirschner wires (one in the sacrum and one in the ilium over the fracture site) will aid in alignment. When the two wires are superimposed, the fracture is aligned. The ilial shaft and sacrum meet at approximately a 45¡ angle; therefore, this relationship must be achieved in fracture reduction and fixation.
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FIG. 27-4 (A) Ventral-dorsal radiograph of a dog pelvis demonstrates bilateral sacroiliac separation, a right caudal acetabular fracture, and left hip luxation and subtrochanteric femoral fracture. (B) Radiograph demonstrates the result of reduction and fixation of the right sacroiliac separation using two interfragmentary screws. |
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FIG. 27-5 (A) Ventral-dorsal radiograph of a dog pelvis demonstrates unilateral sacroiliac separation and a contralateral ilial shaft fracture. (B) The postoperative radiograph demonstrates reduction and fixation of the sacroiliac separation with one interfragmentary screw and one Kirschner wire and reduction and fixation of the ilial shaft fracture using a pin and wire. |
Actual reduction is accomplished best by placing a lewen clamp in the greater trochanter or ischiatic tuberosity and pulling caudally. Once reduction and alignment are anatomical, the fracture can be held in reduction with a Kirschner wire. Definitive internal fixation can be accomplished using one or preferably two cancellous bone screws (Fig. 27-4). Two crossed Steinmann pins or one pin and one screw also provide excellent fixation (Fig. 27-5). Care should be taken regardless of type of fixation to avoid placing the device into the spinal canal of the sacrum.
When sacroiliac fracture accompanies ilial shaft fracture, the sacrum is treated following ilial shaft fixation. If ilial shaft fixation included a bone plate, the sacroiliac fixation can be accomplished using one of the screws that goes through the plate.
Postoperative management should include immediate weight-bearing but reduced levels of activity. Complications seen post fixation may include temporary urinary or fecal retention due to damage to the pelvic plexus;(2) fixation failure, more commonly seen when using pins or a single screw; sciatic entrapment between ilium and sacrum in fixation; and inadequate exposure and reduction resulting in ilial stabilization to L6 or L7.
ILIAL WING FRACTURE
Fracture of the ilial wing often does not require internal fixation. The wing, because it is cranial to the sacrum, often fractures without allowing hemipelvic or hip instability to occur. The justification for surgery is exaggerated malpositioning of the ilial wing or extreme pain and discomfort.
Surgical exposure of the fracture is accomplished best by elevating the middle gluteal muscle and retracting it dorsally. This should allow adequate visualization for reduction and fixation. Reduction is often possible using only digital pressure, but a Lewen clamp or Backus towel clamp may be helpful.
Internal fixation is accomplished using one or more Kirschner wires, Steinmann pins, or simple orthopaedic wire sutures. Two devices are far superior to one. In large dogs, interfragmentary compression with lag screws or small finger plates may be used. Since the largest volume of bone is in the dorsal ilial wing, that area should hold the implants. Postoperative management should include immediate return to normal activity. The likelihood of complications in ilial wing fractures is negligible.
ILIAL SHAFT FRACTURES
llial shaft fracture is probably the most common pelvic fracture. It is usually accompanied by ischial and pubic fracture within the same hemipelvis. The three fractures result in hip instability. Usually reduction and rigid fixation of only the ilial shaft fracture will result in reduction and fixation of the other two fracture sites.
Most ilial shaft fractures are transverse or oblique. The obliquity runs from cranial and ventral to caudaldorsal. Fracture usually results in the posterior fragment displacing medially into the pelvic canal and cranially. This displacement may result in injury to the internal iliac vessels, sciatic nerve, or rectum.
Surgical exposure is accomplished best using gluteal elevation and dorsal retraction.(18) Fracture reduction requires levering or lifting of the ilial shaft laterally while retracting caudally. A bone forceps to hold the femoral greater trochanter greatly facilitates the latter. In reducing oblique shaft fractures, it also helps to have ventral as well as caudal retraction on the trochanter. This allows the oblique fragment to rotate back into a more normal position. It is imperative that the reduction be adequate; otherwise, the ischial end of the fragment may remain depressed into the pelvic canal.
Temporary fixation is accomplished best using bone forceps across any obliquity or a Kern clamp at the site of a transverse fracture. Finger pressure may work but rarely is adequate to complete fixation.
Rigid internal fixation is accomplished best using intramedullary pins or plate and screw fixation.(5) Intramedullary pin fixation requires that the pins pass down the axis of the ilium.(1,8,14,15,21,31) Adequately rigid pins cannot be bent to pass retrograde; therefore, the pins should be introduced through the cranial medial surface of the ilial wing. This allows the pins to pass straight down the ilial axis. Two pins are superior to one because they provide rotational stability. Long oblique fractures may require the addition of an orthopaedic wire to reduce override (Fig. 27-5).
Plate fixation is well suited for ilial shaft fractures(12), since the plates are rigid and easy to apply (Fig. 27-6). It is imperative that the plate be adequately contoured to allow for both ilial and ischial alignment.(17) Plates should be of sufficient cross-sectional mass to support the reduction. Finger plates, adequate for cats and small dogs, are inadequate for German shepherds or Great Danes: the metal must be sized appropriately.(5,10)
Pin and wire fixation is sometimes the only fixation feasible in very small animals. If the ilial cortices are very thin or the medullary cavity nonexistent, small orthopaedic wire sutures or Kirschner wires and orthopaedic wire sutures may be the only possible fixation. Alignment can be accomplished in these cases, but rarely rigid fixation.
Postoperative care should include normal weight bearing but less total activity. This is accomplished best by keeping the dog on a leash for 2 to 4 weeks postoperatively.
Possible complications include vascular, nerve, or rectal injury at the ilial fracture site; sciatic entrapment at the ischial fracture site; fixation failure, most commonly seen in Kirschner wire fixations; pin migration;(25) infection; and narrowing of the pelvic canal.(28) Nonunion occurs rarely in ilial shaft fractures.
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FIG. 27-6 (A) Ventral-dorsal radiograph of a dog pelvis demonstrating unilateral ilial shaft and pubic fractures. (B) Radiograph demonstrates the result of reduction and fixation using a six-hole bone plate. Note that the plate has been bent to conform to normal pelvic anatomy. |
FRACTURES OF THE ISCHIUM
Ischial fracture rarely occurs as an independent lesion; usually it is found in concert with an ilial shaft fracture. In most instances, its presence is insignificant unless the fragments impinge on the sciatic nerve or unless a portion of the acetabulum is attached.
Following fracture, most ischial fractures displace into the pelvic canal. Occasionally, the fragment, or more specifically the ischial tuberosity, may displace distally, however, an intact sacrotuberous ligament will generally prevent this.
Most ischial fractures do not require internal fixation themselves; however, often while definitively treating an ipsilateral ilial shaft fracture, alignment and fixation of the ischial fracture will occur coincidentally. If sciatic entrapment is a concern during ilial reduction, the ischial site should be exposed to visualize the nerve.
There are several indications for internal fixation of ischial fractures. These indications are severe fragment displacement; acetabular fragment associated with the ischium; expected sciatic entrapment in fibrous response to an unstable fracture site.
In the above instances, surgery is necessary. Surgical exposure is gained by a caudal approach to the hip. This requires biceps femoris retraction and internal obturator and gemellus tenotomy. Internal fixation following reduction may take the form of intramedullary pins or wires or small plates. When fixation is necessary, a single pin placed in the ischial shaft is usually sufficient to obtain excellent fixation and union.
Ischial tuberosity epiphyseal fracture may occur in the immature animal. This fracture can result from trauma or avulsion. Unless displacement is great, internal fixation is unnecessary. In the rare instance in which internal fixation is necessary, small crossed Kirschner wires or interfragmentary screws are adequate fixation.
FRACTURE OF THE PUBIS
Pubic fractures rarely occur unless accompanied by fracture of the ilium or ischium. Alignment and fixation is not required, since the fragments either are brought into alignment by the appropriate fixation of the ilium or they have displaced ventrally out of the pelvic canal.
If reduction and fixation are deemed necessary, pubic fractures are surgically approached by a ventral midline skin incision and careful dissection through the adductor muscles on midline. Fixation by simple interrupted loops of orthopaedic wire is adequate.
ACETABULAR FRACTURE
Fractures of the acetabulum are discussed more easily if categorized as cranial, dorsal, caudal, or central. Acetabular fractures are difficult to manage, since all represent intra-articular fractures, and a reduction that is less than anatomical generally results in degenerative arthritis and/ or a degree of dysfunction of the hip. Two-part fractures are far easier to reduce and stabilize than three-part fractures. Severely comminuted fractures are often beyond repair and require a salvage procedure.
Closed immobilization of acetabular fractures is rarely indicated. Occasionally, undisplaced fractures or fractures of the caudal, non-weight-bearing portion of the acetabulum may be handled by closed means and progress to satisfactory results. The majority of the acetabular fractures, however, require open reduction and internal fixation to optimize the likelihood of good return to function of the hip.
CRANIAL ACETABULAR FRACTURE
Fracture in the cranial one-third of the acetabulum usually results in the caudal fragment displacing into the pelvic canal. This is due to the femoral head remaining with the caudal two-thirds, and in weight-bearing, the fragment depresses. Generally, the fracture line is oblique, running cranial and dorsal.
Surgical exposure may be adequately achieved by trochanteric osteotomy and gluteal retraction or occasionally by simple gluteal retraction. Reduction requires elevation of the caudal fragment and is accomplished by lifting the proximal femur laterally with a bone forceps. Once reduction has been accomplished, temporary fixation can be maintained using a bone forceps.
Internal fixation can be accomplished with interfragmentary screw fixation; small, appropriately contoured plates; or pin and wire techniques. Adequate fixation should be sufficiently stable to allow for full weight bearing immediately following surgery.
DORSAL ACETABULAR FRACTURE
Most dorsal acetabular fractures are transverse or three- part comminuted fractures. To be classified as dorsal, they fall into the cranial one-thrid of the acetabulum. Fragments displace, depending on which fragment is attached to the femoral head. When the round ligament attaches to the cranial fragment, the caudal fragment tends to displace mildly into the pelvic canal and the acetabular portion rotates dorsally. When the round ligament attaches to the caudal fragment, it tends to drive that fragment medially and dorsally into the pelvic canal. Surgical exposure requires complete removal of the gluteal insertion either by trochanteric osteotomy or gluteal tenotomy. Fragment reduction is often difficult, especially if the fracture reduction is performed more than 4 days following the fracture. Reduction requires lifting the caudal fragment laterally and often rotating it back into position. Often bone forceps are necessary to maintain reduction while fixation is attached. Comminuted fractures are reduced in standard fashion; that is, the fracture is built back to two parts, and the final two- part fracture is reduced. When reducing and manipulating dorsal acetabular fragments, one must be aware of the position of the sciatic nerve to avoid trauma to it. Fixation of dorsal acetabular fractures can be managed using small plates and screws,(30) pins or screws and a dorsal tension band,(16) or other pin and wire devices. Pins, wires, and methylmethacrylate(24) may be used to rebuild badly comminuted fractures. As with other acetabular fractures, full use of the joint should be encouraged after surgery (Fig. 27-7).
CAUDAL ACETABULAR FRACTURES
Fractures of the caudal acetabulum often do not require fixation. Assuming that the dorsal acetabulum (the weight- bearing surface) is intact, most animals do well with caudal fragments left in their displaced positions. The sharp edge of the fracture fragment may damage the femoral head, but severe damage does not occur. If the joint stability is altered, that is, the joint becomes easy to luxate caudally, reduction and fixation must be undertaken.
Surgical exposure of the fracture can be very difficult. A caudal approach to the hip by internal obturator and gemellus tenotomy is necessary, but further dissection is often needed(27)
Fragment reduction is difficult and at times impossible if the fragment is displaced medially and ventrally. One can elevate the fragment by using a bone forceps directly on the ischium to lift the articular surface. Internal fixation may be performed using small plates and screws or using pins. Careful retraction of the sciatic nerve is imperative during fixation.
Comminuted fractures often cannot be reduced or fixed adequately. In such instances, femoral head and neck osteotomy is appropriate in an attempt to rehabilitate the animal. If the remaining fragments are very mobile and likely to cause pain during hip rehabilitation, intemal fixation may still be necessary.
CENTRAL ACETABULAR FRACTURES
Trauma to the lateral side of the hip can force the femoral head through the center of the acetabulum into the pelvic canal. The center and a portion of the articular acetabulum are fractured and displaced into the pelvic canal as well. The remaining periphery of the acetabular articular surface remains intact. Reduction of this fracture is possible by elevating the proximal femur laterally; however, since the femoral head fits the fracture perfectly, it tends to displace again. No form of internal fixation adequately stabilizes this fracture. A salvage procedure is more appropriate to restore function.
POSTOPERATIVE CARE
Animals being treated with closed reduction and immobilization should be strictly confined. This means confinement in a cage or kennel to force restriction of activity. Two to three weeks of such lack of activity will usually be sufficient to allow the animal adequate fixation to begin walking. Continued care should include restricted activity on a leash or restriction to a small room until radiographic evidence of union.
Following internal fixation, animals should be encouraged to stand and walk as soon as possible. Restricted activity is necessary, but immediate, partial weight bearing will ensure no significant loss in range of hip motion.
Animals having had bilateral internal fixation deserve special attention. Great care must be exercised to return the animal, thus avoiding a "down" incision dehiscence. Animals will need a sling or towel under the abdomen for support to begin weight bearing. Motion of the limbs and hips should be encouraged. Use of an Ehmer sling following acetabular fracture may result in muscle tie-down and fibrosis around the hip. The resulting flexion deformity of the hip could lead to severe limb dysfunction. For this reason, Ehmer slings should be avoided, or, if used, removed early in the course of the convalescence.
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FIG. 27-7 Ventral dorsal (A) and lateral (B) radiographs of a dog pelvis demonstrate an acetabular fracture. (C, D) Radiographs demonstrate the result of reduction and fixation using a five-hole bone plate. The surgical exposure necessitates greater trochanteric osteotomy, and the tension band wire was used for fixation. |
PROGNOSIS
The prognosis for all flat bone fractures of the pelvis is excellent. Nonunion is rare, and return to good function following surgery is usual if alignment is good.
Acetabular fractures can have a very good prognosis if reduction and fixation are anatomical. Results with less than adequate reduction or fixation can vary from good to poor. Severe degenerative arthritis and limb dysfunction are included in the latter category.
COMPLICATIONS
Most complications accompanying pelvic fractures relate to soft tissues in the vicinity. Problems with associated nervous, vascular, bowel, or urethral structures are more common than primary bone problems. Most of these problems occur as a result of the fracture, not as a result of poor fixation; therefore, they must be properly evaluated in the preoperative patient.
A common complication of acetabular fracture is mild to moderate degenerative joint disease. It must be anticipated. Medical management of this problem is usually gratifying.
Pelvic fractures that eventually unite in severely abnormal positions may seriously compromise the pelvic inlet or outlet, resulting in difficulty in defecating or undergoing normal parturition. This problem is more commonly associated with feline pelvic fractures. If surgical correction is required, symphysectomy is necessary, using an insert to enlarge the diameter of the pelvic canal. Good results have been reported using this technique (22,29)
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