Ventral abdominal approach for screw fixation of sacroiliac luxation in clinically affected cats

Luc R. Borer Department of Small Animal Surgery, Vetsuisse Faculty-Zurich, University of Zurich, Winterthurerstrasse 260, 8057 Zurich, Switzerland.

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Katja Voss Department of Small Animal Surgery, Vetsuisse Faculty-Zurich, University of Zurich, Winterthurerstrasse 260, 8057 Zurich, Switzerland.

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Pierre M. Montavon Department of Small Animal Surgery, Vetsuisse Faculty-Zurich, University of Zurich, Winterthurerstrasse 260, 8057 Zurich, Switzerland.

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Abstract

Objective—To investigate sacroiliac luxation repair with positional screw insertion from the ventral surface of the sacral wing via a ventral abdominal approach in cats.

Animals—18 European shorthair cats.

Procedures—All cats underwent clinical examination including orthopedic and neurologic examination and assessment of lameness and pain before and immediately after surgery and 6 and 16 weeks after surgery. All sacroiliac luxations were stabilized with a single positional 2.4-mm cortical titanium self-tapping screw. The pelvic floor was also repaired in selected cats. Screw entry points and angles determined in a prior study of cadavers were used. Radiographs were taken before surgery and during follow-up evaluations to assess postoperative sacroiliac luxation reduction, implant placement, and repair stability.

Results—All implants were placed correctly. Iatrogenic sciatic nerve injuries occurred in 2 cats. Median time to ambulation was 1.5 days for cats with sacroiliac luxation as the sole injury. Radiographic outcome of sacroiliac luxation repair was excellent in 15 of 17 repairs, good in 1 of 17 repairs, and poor in 1 of 17 repairs. Clinical outcome was excellent in 11 of 15 cats and good in 4 of 15 cats.

Conclusions and Clinical Relevance—Insertion of a positional screw across the sacroiliac joint via a ventral abdominal approached can be an alternative to conventional techniques of sacroiliac luxation repair in cats. This novel technique allowed repair of bilateral sacroiliac luxation, repair of pelvic floor fractures, and treatment of soft tissue injuries of the abdominal cavity or abdominal organs with a single approach.

Abstract

Objective—To investigate sacroiliac luxation repair with positional screw insertion from the ventral surface of the sacral wing via a ventral abdominal approach in cats.

Animals—18 European shorthair cats.

Procedures—All cats underwent clinical examination including orthopedic and neurologic examination and assessment of lameness and pain before and immediately after surgery and 6 and 16 weeks after surgery. All sacroiliac luxations were stabilized with a single positional 2.4-mm cortical titanium self-tapping screw. The pelvic floor was also repaired in selected cats. Screw entry points and angles determined in a prior study of cadavers were used. Radiographs were taken before surgery and during follow-up evaluations to assess postoperative sacroiliac luxation reduction, implant placement, and repair stability.

Results—All implants were placed correctly. Iatrogenic sciatic nerve injuries occurred in 2 cats. Median time to ambulation was 1.5 days for cats with sacroiliac luxation as the sole injury. Radiographic outcome of sacroiliac luxation repair was excellent in 15 of 17 repairs, good in 1 of 17 repairs, and poor in 1 of 17 repairs. Clinical outcome was excellent in 11 of 15 cats and good in 4 of 15 cats.

Conclusions and Clinical Relevance—Insertion of a positional screw across the sacroiliac joint via a ventral abdominal approached can be an alternative to conventional techniques of sacroiliac luxation repair in cats. This novel technique allowed repair of bilateral sacroiliac luxation, repair of pelvic floor fractures, and treatment of soft tissue injuries of the abdominal cavity or abdominal organs with a single approach.

Pelvic fractures occur commonly in cats and in many instances are the results of traffic accidents; 22% to 32% of fractures caused by trauma involve the pelvis.1,2 Sixty percent of cats with pelvic fractures have unilateral or bilateral sacroiliac luxation, and 90% have pelvic floor fractures.1 The combination of unilateral or bilateral sacroiliac luxation and pelvic floor fractures is seen in 22% of cats with pelvic trauma.1,3 Up to 74% of cats with pelvic fractures have concurrent soft tissue or orthopedic injuries, particularly in the caudal portion of the abdomen and extrapelvic region; these include coxofemoral luxation, femoral fractures, sciatic nerve paresis, and abdominal wall ruptures.1 Other possible concurrent injuries include rupture of the ureters, urinary bladder, and urethra.

Sacroiliac luxation in cats may be treated conservatively or surgically. Conservative treatment is used for minimally displaced or unilateral sacroiliac luxation with no concurrent pelvic fractures and consists of analgesics, cage rest, and monitoring of urination and defecation. Pelvic outlet narrowing with subsequent obstipation was reported as a complication in cats treated conservatively.4 Surgical repair consists of stabilization of sacroiliac luxation or pelvic fractures for rapid pain relief and early return to ambulation. Indications for surgical stabilization of sacroiliac luxation and pelvic fractures have been described1,5–9 and include pain and inability to ambulate, neurologic deficits attributable to luxation, severe instability or displacement (> 50%) of 1 or both hemipelvises, pelvic outlet obstruction, and concurrent orthopedic injuries.

The classic sacroiliac luxation stabilization technique used in cats is the lag screw insertion from the lateral aspect of the ilium across the sacroiliac joint into the sacral body of S1.5,7,10–13 Techniques for precise lateral lag screw placement by use of a dorsolateral approach have been described.9 Even with identification of accurate anatomic landmarks, the area for safe screw placement is < 0.5 cm2,9 which increases the risk of implant misplacement and penetration and damage of the vertebral canal, L7-S1 disk space, sacral nerve canals, or pelvic canal. Alternative techniques with trans-sacral screw insertion for bilateral sacroiliac joint fracture-luxation in dogs and cats or a tension band wire technique in cats have been described but are also associated with the risk of implant misplacement.12,13

A ventral abdominal approach to the sacroiliac joints and a novel technique of screw placement from the ventral surface of the sacral wing for unilateral or bilateral sacroiliac luxation repairs have been described previously.14 The technique allows the stabilization of both sacroiliac joints and the assessment and treatment of the caudal portion of the abdominal wall, the organs in the caudal portion of the abdomen including the nerves, and the pelvic floor in a single surgery. The purposes of the study reported here were to clinically investigate sacroiliac luxation repair with positional screw insertion from the ventral surface of the sacral wing via a ventral abdominal approach in cats, to evaluate intraoperative or postoperative complications, and to assess the radiographic and clinical outcomes.

Materials and Methods

The study was conducted under a protocol approved by the Department of Small Animal Surgery, Vetsuisse Faculty-Zurich, University of Zurich, Switzerland.

Animals—Eighteen European shorthair cats that ranged in age from 6 months to 12 years (mean, 4.1 years) and weighed 3.2 to 6.1 kg (mean, 4.25 kg) were included in this prospective clinical study. Eight cats were neutered males and 10 were spayed females. Written consent from the owners was obtained before inclusion of cats in the study. Cats that had unilateral or bilateral sacroiliac luxation or type I sacral fractures represented by an oblique fracture line originating from the cranial part of the sacral wing and terminating on the articular surface of the sacral wing15 and that had sufficient intact sacral wing bone for screw placement met the inclusion criteria.

Presurgical assessment—After clinical stabilization, preoperative orthopedic and neurologic examinations with predefined study protocols were performed in all cats by a surgeon and a neurologist. Ambulation; ability to stand; lameness score; pain score; neurologic deficits of the hind limbs, bladder, anus, and tail; and other injuries were recorded. Lameness was scored from 0 to 5 and pain from 0 to 3 (Appendix).

Lateral and ventrodorsal radiographic views were obtained of all cats before surgery. The type and location of sacroiliac luxation, degree of craniocaudal luxation, other pelvic fractures, and other visible injuries identified on radiographic evaluation were recorded. The degree of craniocaudal luxation, expressed as a percentage, was measured on ventrodorsal radiographic views and calculated as the distance between the caudal edge of the ilial part and the caudal edge of the sacral part of the articular surface divided by the length of the sacral articular surface multiplied by 100.12

Surgery—After induction of general anesthesia, the hair on the ventral surface of the abdomen from the umbilicus to the tail, on both lateral aspects of the pelvis, and on both hind limbs from the hip joint to the tarsal joint was clipped. The skin was prepared for aseptic surgery, and the patients were placed in dorsal recumbency with the hind limbs left unbound.

A caudal median celiotomy was performed from the umbilicus to the pubis. The incision was extended to the caudal edge of the pelvic floor in cats with pelvic floor fractures, including simple fractures of the pelvic symphysis, unilateral or bilateral pubic body or ramus, and unilateral or bilateral ischial ramus fractures. The approach to the sacroiliac joint was as described in a previous cadaver study.14 Once the sacral and ilial surfaces of the luxated sacroiliac joint were observed and freed of soft tissue, Kocher forceps were placed lateral to the psoas major muscle on the tuber coxae of the ilial wing under digital control. Reduction of the sacroiliac luxation was achieved by traction of the ilium with the Kocher forceps and by manipulation of the free-hanging ipsilateral limb or by pushing the caudal aspect of the sacrum with curved Halstead hemostatic forceps. Ventral and caudal edges of the sacroiliac joint surface on the ilium were observed and aligned with the sacral wing edges for a complete reduction of sacroiliac luxation.

Once the sacroiliac luxation was reduced, small pinpointed forceps were placed between the sacral wing edge and the lateral surface of the ilium (method used in 2 cats) or a 1-mm Kirschner wire was placed through the sacral wing into the ilium (method used in all other cats) for temporary fixation of the sacroiliac luxation. The wire was placed with a drill sleeve and in an oscillating drill mode to avoid soft tissue damage. Care was exercised to ensure that the wire was placed caudal to the intended screw entry point and perpendicular to the ilium. It was important to push the dorsal part of the ilium medially by use of Kocher forceps or by manipulating the leg to achieve good contact dorsally between the sacral wing and the ilium during placement of the Kirschner wire, drilling of the screw hole, and placement of the screw.

The entry point for drilling and screw placement was on the ventral surface of the sacrum at the deepest point of the sacral wing and at the level of the promontorium of S1.14 Drilling from the ventral surface of the sacral wing across the sacroiliac joint into the ilial wing was performed with a 1.8-mm drill bit and drill sleeve at an angle of at least 45° to the vertical axis in a transverse plane (A angle) and at a 90° angle (B angle) to the longitudinal axis in a dorsal plane. The α angle was checked before drilling by use of a template consisting of a 1-mm Kirschner wire bent at a 45° angle and sterilized before surgery. Prior to drilling, the position of the cat was assessed to ensure that both sacral wings were at the same level relative to the table and thus in a horizontal position. An oscillating drill mode was used to reduce the risk of soft tissue damage. The depth of the drill hole was then measured, and a 2.4-mm cortical titanium self-tapping screw of adequate length was inserted in a positional fashion. After screw tightening, the temporary Kirschner wire was removed. The abdomen was then rinsed with warm lactated Ringer's solution and closed in 3 layers as follows: 2-0 polydioxanone was used to close the linea alba in a simple continuous pattern, the subcutis was sutured with 4-0 polydioxanone in a simple interrupted pattern, and staples were used to close the skin.

Postoperative assessment—Lateral, ventrodorsal, and craniocaudal (intrapelvic) radiographs were taken to assess screw position and sacroiliac luxation reduction. For the craniocaudal radiographs, the anesthetized cats were placed in a sternal and sitting position, with both hind limbs pulled cranially and the upper half of the body placed in a holding cushion. The beam was directed on the pelvis from a craniodorsal position, parallel to the vertebral canal of the sacrum.

The percentage of sacroiliac luxation reduction was defined on ventrodorsal radiographic views as the length of ilium in contact with the sacral articular surface divided by the length of sacral articular surface and multiplied by 100.12,16 The α angle of screws and the screw entry point in the sacral wing were measured on the craniocaudal radiographic views, and the β angle was measured on the ventrodorsal radiographic views, as described previously.14 Orthopedic and neurologic examinations were performed 48 hours after surgery. The time from surgery to ambulation was recorded. Cats were released from the hospital when they were ambulatory and capable of urination. The owners were asked to return their cats for orthopedic, neurologic, and radiographic examinations 6 weeks and 16 weeks after surgery.

Outcome—The overall outcome of cats was divided into radiographic outcome of the sacroiliac luxation repair, which was based on radiographic assessment of the implants and sacroiliac luxation reduction, and clinical outcome, which was based on orthopedic and neurologic function of cats. The radiographic outcome was graded as excellent (implant intact and sacroiliac luxation reduction maintained), good (signs of implant loosening and sacroiliac luxation reduction maintained), fair (implant bent or signs of loosening and minimal sacroiliac luxation displacement), or poor (implant broken or signs of loosening and sacroiliac luxation displaced). The clinical outcome was graded as excellent (no orthopedic or neurologic deficits), good (minor orthopedic or neurologic deficits), fair (moderate orthopedic or neurologic deficits), or poor (severe orthopedic or neurologic deficits; Appendix).

Results

Presurgical assessment—Clinical data of cats at the time of hospital admission were summarized (Table 1). Before surgery, 16 of 18 cats were unable to walk, and 13 of 18 cats were unable to stand. Seven of 18 cats had bilateral sacroiliac luxation (n = 6; Figure 1) or bilateral sacroiliac luxation with a type I sacral fracture15 (1). Eleven of 18 cats had unilateral sacroiliac luxation. The degree of dislocation of the sacroiliac luxation ranged from 20% to 100% with a mean ± SD of 52 ± 20%. Of 18 cats, 17 had additional pelvic fractures that consisted mainly of pelvic floor fractures. Ilial fractures (n = 4), tuber ischiadicum avulsions (3), or comminuted acetabular fractures (1) were also detected. Seven of 18 cats had concurrent abdominal injuries, such as abdominal wall rupture, avulsion of the rectus abdominis muscle, and diaphragmatic rupture. Ten of 18 cats had neurologic abnormalities because of trauma to the sciatic, pudendal, or coccygeal nerves. Twelve of 18 cats also had other fractures or injuries, which required surgical repair before or after the sacroiliac luxation repair.

Figure 1—
Figure 1—

Ventrodorsal (A) and lateral (B) radiographic views of the pelvis of a cat with bilateral sacroiliac luxation and craniodorsal luxation of the right femur. R = Marker to indicate right. L = Marker to indicate left.

Citation: American Journal of Veterinary Research 69, 4; 10.2460/ajvr.69.4.549

Table 1—Summary of clinical data of 18 cats undergoing surgical sacroiliac luxation correction via a ventral abdominal approach.

ConditionCats (n = 18*)
Before surgery 
   Unilateral sacroiliac luxation11
   Bilateral sacroiliac luxation7
   Sacroiliac luxation dislocation (> 50%)14
   Pelvic fractures17
   Pelvic floor fractures14
   Ilial fractures4
   Abdominal injuries7
   Neurologic abnormalities10
   Pelvic outlet narrowing14
   Other fractures or injuries12
Surgical results 
   Correct placement of screws21
   Postoperative sacroiliac luxation reduction (> 90%)17
   Other repairs via ventral abdominal approach11
   Surgical complications6

*n = 21 reductions.

Surgery—The interval between the patient arrival date and surgery varied between 0, operated immediately, and 3 days with a median value of 2 days (Table 1). Obturator nerves and the ventral nerve roots of L6 and L7 were swollen or edematous or had an abnormal color in 4 cats at the level of the sacroiliac joint. The obturator nerve was torn in 1 cat, and the ventral nerve roots of L6 and L7 were trapped and crushed in the sacroiliac luxation in another cat.

Twenty-one sacroiliac luxations were repaired with a screw in 18 cats. Screws were placed bilaterally in 3 cats with bilateral sacroiliac luxation and unilaterally in 4 other cats with bilateral sacroiliac luxation (Figure 2). Screws were placed unilaterally in 11 cats with unilateral sacroiliac luxation. The screw length ranged from 14 to 20 mm. Additional surgeries by use of the same ventral abdominal approach were performed in 11 cats for abdominal wall rupture or avulsion repair (n = 5), pelvic floor fracture repair (8; Figure 3), diaphragmatic rupture repair (2), type II sacral wing fracture15 repair (1), and contralateral sacroiliac luxation stabilization with a 1-mm Kirschner wire (1).

Figure 2—
Figure 2—

Ventrodorsal (A), lateral (B), and craniocaudal (C) radiographic views of the pelvis of the cat of Figure 1 with bilateral sacroiliac luxation after unilateral repair of the left sacroiliac joint. The β angle of the screw is 96° (panel A). The α angle of the screw is 46° (panel C). Other radiopaque metallic objects are skin staples. See Figure 1 for remainder of key.

Citation: American Journal of Veterinary Research 69, 4; 10.2460/ajvr.69.4.549

Figure 3—
Figure 3—

Ventrodorsal radiographic view of the pelvis of a cat with a bilateral sacroiliac luxation and pelvic floor fracture. The left sacroiliac joint was repaired with a screw and the pelvic floor fracture with a 2.0 locking plate. The pelvic ring was reestablished, and contralateral screw insertion was not considered necessary. See Figure 1 for remainder of key.

Citation: American Journal of Veterinary Research 69, 4; 10.2460/ajvr.69.4.549

Surgical complications occurred in 6 cats and included unstable temporary reduction of the sacroiliac luxation with the pinpointed forceps (n = 2); penetration of the hip joint by 1 screw of the pelvic floor repair (1); inadequate reduction of an ilial fracture, which hindered complete reduction of the sacroiliac luxation (1); iatrogenic injury of the L7 nerve root during screw placement (1); and hemorrhage from the external iliac vein (1). Other surgeries for repair of fractures or injuries not treatable through the ventral abdominal approach were performed in 12 patients and included 3 hip luxation reductions, 3 contralateral ilial fracture stabilizations, 2 open luxated tarsal joint stabilizations, 2 transverse S1-S2 sacrum fracture stabilizations, 1 femoral head excision arthroplasty, 1 tibial fracture stabilization, and cleaning of a skin and muscle wound.

Postoperative assessment—The α and β angles for screw placement were measured on postoperative radiographs. The α angle ranged from 36° to 54° with a median ± SD of 42 ± 7°. The β angle ranged from 73° to 114° with a median of 96 ± 11°. Maximal and minimal angles, to ensure being in the safe drill corridor, ranged from a 36° to 89° α angle and from a 73° to 138° β angle, as reported in a previous study.14 The screw entry point in the ventral surface of the sacral wing ranged from 25% to 56% with a median value of 47 ± 6% of the distance between the sacral wing edge and the sacrum median line. Percentage of craniocaudal sacroiliac luxation reduction ranged from 35% to 110%. The reduction was > 90% in 17 of 21 (81%) reductions, and a precise anatomic reduction was achieved in 11 of 21 (52%) reductions.

All cats were able to walk 1 to 16 days after surgery, with a median time of 3 days. For cats without orthopedic or severe neurologic injuries to their hind limbs (n = 6), the time needed to walk after surgery varied from 1 to 4 days, with a median time of 1.5 days.

Three cats were euthanatized 3, 30, and 5 days after surgery for reasons not directly related to the sacroiliac luxation repair. One of these cats had progressive necrotizing infection of the paw originating from its open tarsal joint luxation. The owner declined amputation of the cat's leg. The second cat had bladder paralysis attributable to a transverse sacral fracture, which did not improve within 30 days of surgical repair. The third cat had severe sciatic nerve deficits with loss of deep pain sensation because of impingement of the left ventral roots of L6 and L7 in the sacroiliac luxation before surgery. The owner requested euthanasia of the cat because of a lack of neurologic improvement after surgery.

The period between surgery and the first postoperative evaluation ranged from 6 to 11 weeks, with a median time of 7 weeks. The period between surgery and the second postoperative evaluation ranged from 16 to 44 weeks, with a median time of 18.5 weeks.

Of the 18 cats, 10 had neurologic abnormalities before surgery. Of these 10 cats, all had sciatic nerve deficits, 4 had pudendal nerve deficits, and 2 had coccygeal nerve deficits. Deficits varied from mild loss of proprioception to complete paraparesis or monoplegia, as well as anal tone reduction or bladder paralysis. Forty-eight hours after surgery, 9 of 18 cats had neurologic abnormalities. Of these 9 cats, 8 had sciatic nerve deficits, 3 had pudendal nerve deficits, and 2 had coccygeal nerve deficits. Iatrogenic neurologic abnormalities developed in 2 of these cats in which sciatic nerve deficits developed after surgery. At the time of the first postoperative evaluation, 4 of 15 cats had neurologic deficits. Of these 4 cats, 3 had sciatic nerve deficits and 1 had coccygeal nerve deficits. At the second postoperative evaluation, no neurologic abnormalities were detected. Lameness and pain scores were high before surgery in all patients and had decreased appreciably in most cats at the first and second postoperative evaluations.

At the first reevaluation, the reduction was maintained in 15 of 17 of sacroiliac luxation repairs. The remaining 2 sacroiliac luxation repairs had signs of instability. In 1 cat, the screw was slightly bent and a 10% cranial displacement of the ilium had occurred as evidenced on radiographic evaluation. In another cat, the screw was torn out of the sacral wing, but was still in the ilium, and a 35% cranioventral displacement of the ilium had occurred. In both cats, radiographs obtained at the second postoperative evaluation revealed no further displacement or implant failure.

The radiographic outcome of 17 sacroiliac luxation repairs was excellent in 15 repairs, good in 1 repair, and poor in 1 repair. The clinical outcome was excellent in 11 of 15 cats and good in 4 of 15 cats.

Discussion

The ventral abdominal approach and cortical screw placement from the ventral surface of the sacral wing for sacroiliac luxation repair used in this study has been described in detail in a cadaver study14 in cats and dogs. It was considered to be a possible alternative to other existing surgical techniques that were proven to be successful for sacroiliac luxation repair in cats.7,10–13

Lateral lag screw insertion is the classic surgical procedure for sacroiliac luxation repair used by most surgeons. The lateral approach may be divided into a dorsolateral approach or a ventrolateral approach; whereas the first is allowing a quick and simple access to the sacroiliac joint, the second allows implant placement under digital control or direct view of the sacral sacroiliac joint surface, decreasing the risk of implant disruption.10 As described in dogs,16 considerable risk exists for incorrect placement of the implant with resultant damage to the vertebral canal, L7-S1 intervertebral space, sacral nerve canals, or pelvic canal in cats because the area for safe screw placement is < 0.5 cm2 and the drill angles are difficult to estimate.9,11 The precision of lateral lag screw insertion was greatly improved by an in-depth description of the anatomic landmarks of the sacroiliac joint in cats.9

Screw placement from the ventral surface of the sacral wing via the ventral abdominal approach may minimize the risk of penetrating the vertebral canal, L7-S1 intervertebral space, sacral nerve canals, or pelvic canal.14 This novel technique allows repair of bilateral sacroiliac luxation, repair of pelvic floor fractures, and treatment of soft tissue injuries of the abdominal wall or abdominal organs by use of a single ventral abdominal approach. More than half of the cats in the study reported here had pelvic fractures, abdominal injuries, or both that were repaired via the same ventral abdominal approach.

Concurrent abdominal injuries, such as abdominal wall ruptures or diaphragmatic tears that were present in several of our patients, were easily identified and treated via the ventral abdominal approach. At the same time, other abdominal organs, especially those of the urinary tract, which is often injured in traumatized cats,1 could be assessed visually and treated surgically.

The repair of simple pelvic floor fractures, like symphysis pelvis dislocations, or simple unilateral or bilateral fractures of the pubic ramus, ischial ramus, or both with plates or cerclage wire may reestablish or add to the stability of the pelvic ring after the sacroiliac luxation repair, as described in human surgical literature.17 Moreover, it allows an adequate rotational realignment of both hemipelvises, which is not guaranteed with the sole repair of the sacroiliac luxation with a single screw, and may avoid entrapment of soft tissue between the bone fragments.18 These additional repairs required a caudal extension of the approach. Further studies are needed to evaluate a potential beneficial effect of pelvic floor repair in small animals.

The ventral abdominal approach was performed without complications and provided an excellent view of all important structures. Abdominal or pelvic injuries, retroperitoneal hematomas, and bone displacement did not impair the identification of the tendons of the psoas muscles; promontorium of S1; or regional nerves, major vessels, or ventral sides of the sacral wings.

Anatomic reduction of sacroiliac luxation by use of the classic lateral lag screw technique is limited by the correct recognition of specific landmarks on the sacral joint surface and on the lateral aspect of the ilium for precise screw-hole drilling.7,10,11,13 An advantage of the ventral abdominal approach is that it allows a direct view of the sacroiliac joint with clear identification of the luxated joint surface of the ilium and the contours of the sacral wing. This allows for an optimal reduction of sacroiliac luxation without risk of impinging an undetected nerve. Satisfactory reduction of the sacroiliac luxation was achieved intraoperatively in 17 of 21 reductions of this report by manipulation of the Kocher forceps on the ilium and the free-hanging limb. Only 11 of 21 sacroiliac luxations were anatomically reduced completely, which is in agreement with the opinion of other authors7,19 that accurate alignment is not essential for good clinical results. Reduction of 15 of 17 of our sacroiliac luxation repairs was maintained until the second postoperative evaluation.

Holding the temporary reduction with small pinpointed forceps, as done in the first 2 cats, was not stable enough to allow safe drilling, and the bone contact between the sacral wing and the ilium was lost dorsally when the drill bit pushed onto the ilium. Therefore, in the remaining cats, a 1-mm Kirschner wire placed across the reduced sacroiliac joint replaced the pinpointed forceps. This improved the stabilization of the joint for screw-hole drilling and screw placement considerably. Nevertheless, it was important to push the dorsal part of the ilium medially during placement of the temporary fixation to achieve good contact between both parts of the sacroiliac joint.

Retraction of the surrounding soft tissue, nerves, and vessels was essential to avoid damage to these structures and to ensure a good view of the surgical site. Poor retraction led to serious intraoperative complications in 2 cats; in 1 cat, the ventral nerve root of L7 was in contact with the screw threads during implant placement, resulting in sciatic deficits that were not apparent before surgery, and in the other cat, the external iliac vein was damaged, leading to hemorrhage. Ligation of the vein stopped the bleeding.

The median value of the screw entry point of 43% of the distance between the sacral wing edge and the median line was less than the value of 58% of the optimal entry point described in cadavers.14 The tendency of the drill to slide laterally because of the steep 45° drill angle could explain this discrepancy. This difference represented a real shift laterally of only 1 to 2 mm in cats and would be unlikely to influence the holding power of the implant. All screws were placed with α and β angles within the safety range described in a previous study.14 Because all screws were inserted in the safe drill corridor, crossed the sacroiliac joint, and penetrated both cortices of the ilium, we considered the implants to have been placed appropriately with a success rate of 100%.

The visibility of the obturator nerves and the ventral nerve roots of L6 and L7 at the level of the sacroiliac luxation was another advantage of the ventral abdominal approach. It provided the surgeon with an opportunity to confirm intrapelvic nerve damage and to give a more accurate neurologic prognosis. In a previous study6 of dogs and cats, 91% of the animals had neurologic abnormalities associated with pelvic fractures or sacroiliac luxation, but only 6% of the animals had confirmed damage to the intrapelvic portion of the sciatic nerve. Nerve damage, ranging from focal edema to complete severance, was seen in 5 cats of this report and more often affected the ventral nerve roots of L6 and L7. All of these cats had severe neurologic deficits, which corresponded to the involved nerves and their degree of damage prior to surgery.

The neurologic status of all patients that were not euthanatized returned to normal after a varying amount of time, after stabilization of the sacroiliac luxation and other pelvic fractures. The main improvement was detected between the first and second postoperative evaluations, 7 to 18 weeks after surgery. Iatrogenic nerve injuries developed in 2 cats and were attributed to inflammation of the nerves because of manipulation during surgery in 1 cat and to iatrogenic injury of the L7 nerve root during screw placement, as explained before, in the other cat. In the first cat, the neurologic status of the cat returned to normal before the first postoperative evaluation, and in the second cat, neurologic status returned to normal at the second postoperative evaluation.

A return to ambulation required a median time of 3 days, which was shorter than what would be anticipated with conservative treatment and is comparable to the results of other studies.12,13 This time was even shorter for cats without concomitant injuries to their hind limbs, as evidenced by the median time of 1.5 days for these cats.

The lameness and pain scores were useful tools to assess and compare the preoperative and postoperative clinical status of our patients. The rapid reduction in lameness and pain by the first postoperative evaluation, compared with the preoperative values and the normal values (score 0) of most cats at the second reevaluation, was evidence of the excellent clinical outcome by use of this new technique. The fact that 5 cats had lameness or pain scores > 0 at the second reevaluation was not related to the surgical method but to other injuries as follows: left femoral head excision (n = 1), right hip luxation (1), refracture of the right proximal tibia (1), persistent left side neurologic deficits (1), left tarsal joint luxation (1), and left-sided hip luxation and implant failure (1).

Radiographic follow-up revealed that the reduction of 15 of 17 sacroiliac luxation repairs was maintained without signs of implant loosening at the first and second postoperative evaluations, which supported an excellent radiographic outcome of the implants. Two postoperative complications were detected. In 1 cat, the screw bent slightly, which allowed a 10% movement of the sacroiliac luxation detected at the first reevaluation. This was probably because the cat shifted its weight onto the side with the implant because of pain on the left side caused by a femoral head excision and a comminuted acetabular fracture. The reduction of the sacroiliac luxation repair was maintained at the second postoperative evaluation, and therefore the radiographic outcome was scored as good. In the other cat, the sacral wing probably fractured and the implant pulled out. In that cat, the reasons for implant failure were unknown because, on postoperative radiographs, the screw placement was considered adequate. The radiographic outcome of this cat was graded poor, even though the reduction of the sacroiliac luxation had not changed on the second reevaluation.

The clinical outcome reflected the overall clinical improvement of the patients and was derived from the lameness and pain scores and neurologic abnormalities at the second reevaluation. It must be remembered that the assessment of the clinical outcome was based not only on the effects of the sacroiliac luxation repair but also on those of the treatment of all other fractures and injuries. Nevertheless, the fact that 11 of 15 cats were scored as excellent, 4 of 15 as good, and none as fair or poor supports the claim that the combination of a ventral abdominal approach and single screw placement from the ventral surface of the sacral wing is a safe technique for sacroiliac luxation repair. Prospective clinical studies are necessary to validate this new technique in dogs before it can be recommended for clinical use in this species.

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    Hulse D, Shires P, Waldron D, et al. Sacroiliac luxations. Compend Contin Educ Pract Vet 1985;7:493499.

  • 8.

    Brinker WO, Piermattei DL, Flo GL. Sacroiliac fracture-luxation. In: Small animal orthopedics and fracture repair. 3rd ed. Philadelphia: WB Saunders Co, 1997;398403.

    • Search Google Scholar
    • Export Citation
  • 9.

    Burger M, Forterre F, Brunnberg L. Surgical anatomy of the feline sacroiliac joint for lag screw fixation of sacroiliac fracture-luxation. Vet Comp Orthop Traumatol 2004;17:146151.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 10.

    Montavon PM, Boudrieau RJ, Hohn RB. Ventrolateral approach for repair of sacroiliac fracture-dislocation in the dog and cat. J Am Vet Med Assoc 1985;186:11981201.

    • Search Google Scholar
    • Export Citation
  • 11.

    Burger M, Forterre F, Brunnberg L. Sacroiliac luxation in the cat. Part 2: cases and results. Kleintierpraxis 2005;5:287297.

  • 12.

    Raffan PJ, Joly CL, Timm PG, et al. A tension band technique for stabilization of sacroiliac separations in cats. J Small Anim Pract 2002;43:255260.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 13.

    Kaderly RE. Stabilization of bilateral sacroiliac fracture-luxations in small animals with a single transsacral screw. Vet Surg 1991;20:9196.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 14.

    Borer LR, Voss K, Montavon PM. Ventral abdominal approach for screw fixation of sacroiliac luxation in cadavers of cats and dogs. Am J Vet Res 2008;69:542548.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 15.

    Anderson A, Coughlan AR. Sacral fractures in dogs and cats: a classification scheme and review of 51 cases. J Small Anim Pract 1997;38:404409.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 16.

    DeCamp CE, Braden TD. Sacroiliac fractures-separation in the dog: a study of 92 cases. Vet Surg 1985;14:127130.

  • 17.

    Tile M. Pelvic ring fractures: should they be fixed? J Bone Joint Surg Br 1988;70-B:112.

  • 18.

    Messmer M, Rytz U, Spreng D. Urethral entrapment following pelvic fracture fixation in a dog. J Small Anim Pract 2001;42:341344.

  • 19.

    Tomlinson JL, Cook JL, Payne JT, et al. Closed reduction and lag screw fixation of sacroiliac luxations and fractures. Vet Surg 1999;28:188193.

Appendix

Criteria for scoring signs of pain during manipulation of pelvis or hind limbs, extent of weight bearing on hind limbs, and orthopedic and neurologic deficits in cats with sacroiliac luxation.

table2
  • Figure 1—

    Ventrodorsal (A) and lateral (B) radiographic views of the pelvis of a cat with bilateral sacroiliac luxation and craniodorsal luxation of the right femur. R = Marker to indicate right. L = Marker to indicate left.

  • Figure 2—

    Ventrodorsal (A), lateral (B), and craniocaudal (C) radiographic views of the pelvis of the cat of Figure 1 with bilateral sacroiliac luxation after unilateral repair of the left sacroiliac joint. The β angle of the screw is 96° (panel A). The α angle of the screw is 46° (panel C). Other radiopaque metallic objects are skin staples. See Figure 1 for remainder of key.

  • Figure 3—

    Ventrodorsal radiographic view of the pelvis of a cat with a bilateral sacroiliac luxation and pelvic floor fracture. The left sacroiliac joint was repaired with a screw and the pelvic floor fracture with a 2.0 locking plate. The pelvic ring was reestablished, and contralateral screw insertion was not considered necessary. See Figure 1 for remainder of key.

  • 1.

    Bookbinder PF, Flanders JA. Characteristics of pelvic fracture in the cat. Vet Comp Orthop Traumatol 1992;5:122127.

  • 2.

    Hill FWG. A survey of bone fractures in the cat. J Small Anim Pract 1977;18:457463.

  • 3.

    Messmer M, Montavon PM. Pelvic fractures in the dog and cat: a classification system and review of 556 cases. Vet Comp Orthop Traumatol 2004;4:167183.

    • Search Google Scholar
    • Export Citation
  • 4.

    Schrader SC. Pelvic osteotomy as a treatment for obstipation in cats with acquired stenosis of the pelvic canal: six cases (1978–1989). J Am Vet Med Assoc 1992;200:208213.

    • Search Google Scholar
    • Export Citation
  • 5.

    Tomlinson JL. Fractures of the pelvis. In: Slatter D, ed. Textbook of small animal surgery. 3rd ed. Philadelphia: WB Saunders Co, 2003;19892001.

    • Search Google Scholar
    • Export Citation
  • 6.

    Jacobson A, Schrader C. Peripheral nerve injury associated with fracture or fracture-dislocation of the pelvis in dogs and cats: 34 cases (1978–1982). J Am Vet Med Assoc 1987;190:569572.

    • Search Google Scholar
    • Export Citation
  • 7.

    Hulse D, Shires P, Waldron D, et al. Sacroiliac luxations. Compend Contin Educ Pract Vet 1985;7:493499.

  • 8.

    Brinker WO, Piermattei DL, Flo GL. Sacroiliac fracture-luxation. In: Small animal orthopedics and fracture repair. 3rd ed. Philadelphia: WB Saunders Co, 1997;398403.

    • Search Google Scholar
    • Export Citation
  • 9.

    Burger M, Forterre F, Brunnberg L. Surgical anatomy of the feline sacroiliac joint for lag screw fixation of sacroiliac fracture-luxation. Vet Comp Orthop Traumatol 2004;17:146151.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 10.

    Montavon PM, Boudrieau RJ, Hohn RB. Ventrolateral approach for repair of sacroiliac fracture-dislocation in the dog and cat. J Am Vet Med Assoc 1985;186:11981201.

    • Search Google Scholar
    • Export Citation
  • 11.

    Burger M, Forterre F, Brunnberg L. Sacroiliac luxation in the cat. Part 2: cases and results. Kleintierpraxis 2005;5:287297.

  • 12.

    Raffan PJ, Joly CL, Timm PG, et al. A tension band technique for stabilization of sacroiliac separations in cats. J Small Anim Pract 2002;43:255260.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 13.

    Kaderly RE. Stabilization of bilateral sacroiliac fracture-luxations in small animals with a single transsacral screw. Vet Surg 1991;20:9196.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 14.

    Borer LR, Voss K, Montavon PM. Ventral abdominal approach for screw fixation of sacroiliac luxation in cadavers of cats and dogs. Am J Vet Res 2008;69:542548.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 15.

    Anderson A, Coughlan AR. Sacral fractures in dogs and cats: a classification scheme and review of 51 cases. J Small Anim Pract 1997;38:404409.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 16.

    DeCamp CE, Braden TD. Sacroiliac fractures-separation in the dog: a study of 92 cases. Vet Surg 1985;14:127130.

  • 17.

    Tile M. Pelvic ring fractures: should they be fixed? J Bone Joint Surg Br 1988;70-B:112.

  • 18.

    Messmer M, Rytz U, Spreng D. Urethral entrapment following pelvic fracture fixation in a dog. J Small Anim Pract 2001;42:341344.

  • 19.

    Tomlinson JL, Cook JL, Payne JT, et al. Closed reduction and lag screw fixation of sacroiliac luxations and fractures. Vet Surg 1999;28:188193.

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