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Application of an Intramedullary Pin or Interlocking Nail to the Tibia
202
PA RT T W O
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SURGICAL PROCEDURES FOR FRACTURES
TIBIAL FRACTURES
Application of an Intramedullary Pin or Interlocking Nail to the Tibia
CHAPTER 77
INDICATIONS Candidates include animals with single or comminuted tibial diaphyseal fractures.
OBJECTIVES • To achieve anatomic reduction of single fracture lines or restoration of normal bone alignment for nonreducible comminuted fractures The intramedullary (IM) pin is used in animals with high fractureassessment scores.1 The IM pin neutralizes bending forces at the fracture, and is combined with cerclage wire for long oblique fractures and with external fixation for transverse or short oblique fractures to neutralize rotational and axial compressive forces. The interlocking nail (ILN) neutralizes bending, rotational, and axial compressive forces at the fracture; it can be used for animals with medium and low fractureassessment scores.1
tracting the bone segments and approximating the fracture surfaces. Use pointed reduction forceps to manipulate the bone segments into reduction. Maintain the reduction manually for transverse fractures and with pointed reduction forceps for oblique fractures. Reduce comminuted nonreducible fractures by distracting the distal bone end with the IM pin or ILN and aligning the major segments of the bone. Stabilization: Apply an IM pin and type Ia external fixator to the cranial medial surface of the tibia to stabilize a transverse fracture (see Plate 77B). The IM pin should be smaller (50–60% of the medullary canal) to accommodate the fixation pins within the medullary canal. Place fixation pins in the metaphysis of each segment and about 1 cm on either side of the fracture line. Apply an IM pin and cerclage wire to a long oblique fracture (Plate 77C). Apply an ILN and four screws to the tibia for treatment of comminuted nonreducible fractures (Plate 77D).4
CAUTIONS ANATOMIC CONSIDERATIONS The tibia has a pronounced S-shaped curve in most dogs. The proximal and distal tibial articular surfaces cover the ends of the long bone, leaving little nonarticular surface to introduce an IM pin or ILN. The cranial branch of the medial saphenous artery and vein and the saphenous nerve cross the medial aspect of the tibia. The medial and lateral malleoli extend distally to the distal tibial articular surface.
It is important to avoid the joint surfaces with the IM pin or ILN. The range of motion of the hock should be palpated to detect pin interference in the joint. Rotational alignment should be monitored during the realignment of comminuted fractures.
POSTOPERATIVE EVALUATION Radiographs should be evaluated for fracture reduction or bone alignment and implant placement.
EQUIPMENT • Surgical pack, Senn retractors, Gelpi retractors, Hohmann retractors, periosteal elevator, pointed reduction forceps, Kern bone-holding forceps, Jacob pin chuck, IM pins, cerclage wire, wire tightener, wire cutter, external fixator clamps and connecting bars (or ILN equipment, including high-speed drill), bone curette for harvesting cancellous graft
PREPARATION AND POSITIONING Prepare the rear limb circumferentially from mid-femur to the phalanges. Position the animal in dorsal recumbency. Drape the limb out from a hanging position. Roll the animal slightly to access the medial aspect of the limb. The ipsi-lateral proximal humerus serves as a cancellous bone graft donor site.
PROCEDURE Approach: Insert the IM pin or the ILN from a point on the proximal medial tibial plateau midway between the tibial tuberosity and the medial tibial condyle (Plate 77A).2 Perform a limited medial approach through the skin and subcutaneous tissue to the fracture site for reducible fractures (see Plate 77A).3 Use an “open but do not disturb the fragments” technique to expose the proximal and distal bone segments with minimal disturbance of the fracture hematoma and bone fragments for nonreducible fractures. Incise the skin, and create soft tissue tunnels to the bone for fixator pin placement (Plate 77B). Reduction: Place an IM pin (sized to equal 60% to 70% of the medullary canal at the isthmus) in the proximal segment.2 Retract the pin within the medullary canal of the proximal segment. Reduce transverse and short oblique fractures by tenting the bone ends and levering the bone back into position. Reduce long oblique fractures by dis-
POSTOPERATIVE CARE The animal should be confined, with activity limited to leash walking. External fixator management includes daily pin care and pin packing as needed. Radiographs should be repeated at 6-week intervals. Fixator pins should be removed after radiographic signs of bone bridging are observed. Radiographs should continue at 6-week intervals until the fracture has healed. The IM pin should be removed when the fracture has healed.
EXPECTED OUTCOME Bone healing is usually seen in 12 to 18 weeks, depending on fracture and signalment of the animal.
References 1. Johnson AL, Hulse DA: Fundamentals of orthopedic surgery and fracture management, decision making in fracture management. In Fossum TW (ed): Small Animal Surgery, 2nd ed. St. Louis, Mosby, 2002. 2. Johnson AL, Hulse DA: Management of specific fractures: Tibial and fibular diaphyseal fractures. In Fossum TW (ed): Small Animal Surgery, 2nd ed. St. Louis, Mosby, 2002. 3. Piermattei DL, Johnson KA: An Atlas of Surgical Approaches to the Bones and Joints of the Dog and Cat, 4th ed. Philadelphia, WB Saunders, 2004. 4. Dueland RT, Johnson KA, Roe SC, et al: Interlocking nail treatment of diaphyseal long bone fractures in dogs. J Am Vet Med Assoc 214:59, 1999.
CHAPTER 77
A P P L I C AT I O N O F A N I M P I N O R I N T E R L O C K I N G N A I L T O T H E T I B I A
P L AT E 7 7
M
L
A Shaft of the tibia
Cranial branch of medial saphenous artery and vein
B
Saphenous nerve
C
D
203
PA RT T W O
•
SURGICAL PROCEDURES FOR FRACTURES
TIBIAL FRACTURES
Application of an Intramedullary Pin or Interlocking Nail to the Tibia
CHAPTER 77
INDICATIONS Candidates include animals with single or comminuted tibial diaphyseal fractures.
OBJECTIVES • To achieve anatomic reduction of single fracture lines or restoration of normal bone alignment for nonreducible comminuted fractures The intramedullary (IM) pin is used in animals with high fractureassessment scores.1 The IM pin neutralizes bending forces at the fracture, and is combined with cerclage wire for long oblique fractures and with external fixation for transverse or short oblique fractures to neutralize rotational and axial compressive forces. The interlocking nail (ILN) neutralizes bending, rotational, and axial compressive forces at the fracture; it can be used for animals with medium and low fractureassessment scores.1
tracting the bone segments and approximating the fracture surfaces. Use pointed reduction forceps to manipulate the bone segments into reduction. Maintain the reduction manually for transverse fractures and with pointed reduction forceps for oblique fractures. Reduce comminuted nonreducible fractures by distracting the distal bone end with the IM pin or ILN and aligning the major segments of the bone. Stabilization: Apply an IM pin and type Ia external fixator to the cranial medial surface of the tibia to stabilize a transverse fracture (see Plate 77B). The IM pin should be smaller (50–60% of the medullary canal) to accommodate the fixation pins within the medullary canal. Place fixation pins in the metaphysis of each segment and about 1 cm on either side of the fracture line. Apply an IM pin and cerclage wire to a long oblique fracture (Plate 77C). Apply an ILN and four screws to the tibia for treatment of comminuted nonreducible fractures (Plate 77D).4
CAUTIONS ANATOMIC CONSIDERATIONS The tibia has a pronounced S-shaped curve in most dogs. The proximal and distal tibial articular surfaces cover the ends of the long bone, leaving little nonarticular surface to introduce an IM pin or ILN. The cranial branch of the medial saphenous artery and vein and the saphenous nerve cross the medial aspect of the tibia. The medial and lateral malleoli extend distally to the distal tibial articular surface.
It is important to avoid the joint surfaces with the IM pin or ILN. The range of motion of the hock should be palpated to detect pin interference in the joint. Rotational alignment should be monitored during the realignment of comminuted fractures.
POSTOPERATIVE EVALUATION Radiographs should be evaluated for fracture reduction or bone alignment and implant placement.
EQUIPMENT • Surgical pack, Senn retractors, Gelpi retractors, Hohmann retractors, periosteal elevator, pointed reduction forceps, Kern bone-holding forceps, Jacob pin chuck, IM pins, cerclage wire, wire tightener, wire cutter, external fixator clamps and connecting bars (or ILN equipment, including high-speed drill), bone curette for harvesting cancellous graft
PREPARATION AND POSITIONING Prepare the rear limb circumferentially from mid-femur to the phalanges. Position the animal in dorsal recumbency. Drape the limb out from a hanging position. Roll the animal slightly to access the medial aspect of the limb. The ipsi-lateral proximal humerus serves as a cancellous bone graft donor site.
PROCEDURE Approach: Insert the IM pin or the ILN from a point on the proximal medial tibial plateau midway between the tibial tuberosity and the medial tibial condyle (Plate 77A).2 Perform a limited medial approach through the skin and subcutaneous tissue to the fracture site for reducible fractures (see Plate 77A).3 Use an “open but do not disturb the fragments” technique to expose the proximal and distal bone segments with minimal disturbance of the fracture hematoma and bone fragments for nonreducible fractures. Incise the skin, and create soft tissue tunnels to the bone for fixator pin placement (Plate 77B). Reduction: Place an IM pin (sized to equal 60% to 70% of the medullary canal at the isthmus) in the proximal segment.2 Retract the pin within the medullary canal of the proximal segment. Reduce transverse and short oblique fractures by tenting the bone ends and levering the bone back into position. Reduce long oblique fractures by dis-
POSTOPERATIVE CARE The animal should be confined, with activity limited to leash walking. External fixator management includes daily pin care and pin packing as needed. Radiographs should be repeated at 6-week intervals. Fixator pins should be removed after radiographic signs of bone bridging are observed. Radiographs should continue at 6-week intervals until the fracture has healed. The IM pin should be removed when the fracture has healed.
EXPECTED OUTCOME Bone healing is usually seen in 12 to 18 weeks, depending on fracture and signalment of the animal.
References 1. Johnson AL, Hulse DA: Fundamentals of orthopedic surgery and fracture management, decision making in fracture management. In Fossum TW (ed): Small Animal Surgery, 2nd ed. St. Louis, Mosby, 2002. 2. Johnson AL, Hulse DA: Management of specific fractures: Tibial and fibular diaphyseal fractures. In Fossum TW (ed): Small Animal Surgery, 2nd ed. St. Louis, Mosby, 2002. 3. Piermattei DL, Johnson KA: An Atlas of Surgical Approaches to the Bones and Joints of the Dog and Cat, 4th ed. Philadelphia, WB Saunders, 2004. 4. Dueland RT, Johnson KA, Roe SC, et al: Interlocking nail treatment of diaphyseal long bone fractures in dogs. J Am Vet Med Assoc 214:59, 1999.
CHAPTER 77
A P P L I C AT I O N O F A N I M P I N O R I N T E R L O C K I N G N A I L T O T H E T I B I A
P L AT E 7 7
M
L
A Shaft of the tibia
Cranial branch of medial saphenous artery and vein
B
Saphenous nerve
C
D
203