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The floating hip injury: patterns of injury
Injury, Int. J. Care Injured 33 (2002) 717–722
The floating hip injury: patterns of injury M. Liebergall∗ , R. Mosheiff, O. Safran, A. Peyser, D. Segal Department of Orthopaedic Surgery, The Hadassah-Hebrew University Medical School, Hadassah University Hospital, P.O. Box 12000, Jerusalem 91120, Israel Accepted 6 November 2001
Abstract Objective: To evaluate the relationship between mechanism of injury, type of femoral fracture and type of acetabular fracture in floating hip injury. Design: Historical retrospective. Patients: Twenty consecutive patients who sustained a floating hip injury, i.e. simultaneous ipsilateral fracture of the acetabulum and the femur. Intervention: Statistical analysis of the correlation between the mechanism of injury and fracture type. Results: Two main patterns of floating hip injury were observed. The first is the posterior type, which occurs due to a longitudinal force along the femur that causes first, a posterior type fracture of the acetabulum and thereafter, a midshaft femoral fracture. The second pattern is the central type, caused by a lateral blow to the greater trochanter, which then causes a central fracture-dislocation of the acetabulum and a proximal fracture of the femur. Conclusions: This observation explains the biomechanical nature of this injury and has treatment related implications. © 2002 Elsevier Science Ltd. All rights reserved.
1. Introduction Floating joint injury is a simultaneous skeletal disruption above and below a joint. It can be either extra-articular or intra-articular. Based on this definition, two types of floating hip joints were described: type A in which a pelvic fracture is associated with an ipsilateral femoral fracture, and type B in which the acetabular fracture is associated with an ipsilateral femoral fracture [1]. Most pelvic surgeons would define only type B as a “true” floating hip injury. This combination of injury, though not common [2,3], is important from its biomechanical implications and from the treatment point of view. By analysing the ipsilateral long bone (i.e. femur) fracture, it enables us to understand the mechanism and sequence of events that take place in causing an acetabular fracture. This combined injury also poses several treatment dilemmas. The femoral fracture should be surgically stabilised urgently [4], while, a later (3–5 days) reduction and fixation is recommended for the acetabular fracture [5]. It may result in two separate operating sessions and it can lead to surgical difficulties, such as in the case when ∗ Corresponding author. Tel.: +972-2-6776342; fax: +972-2-6434434. E-mail address: [email protected] (M. Liebergall).
a posterior approach to the acetabulum has to be carried out several days after insertion of an antegrade intramedullary nail (IMN) to the femur through the same anatomical site. Few studies have been published describing the mechanisms and patterns involved in this injury, most of them are case reports [2,3,6–8]. We present 20 consecutive ipsilateral femoral and acetabular fractures, which required surgical intervention, with relation to the mechanism of the injury, the different types of acetabular and femoral fractures that were found and the possible correlation between these factors. 2. Material and methods Between the years 1987–1999, 160 patients sustaining an acetabular fracture were operated on, at the Hadassah university hospital in Jerusalem. We have retrospectively studied, a sub-group of patients presented with the combination of acetabular fracture and ipsilateral femoral fracture. This group of 20 patients, with the “floating hip injury” represent 12.5% of all acetabular fractures that were operated on. There were 16 males (75%) and 4 females (25%). The mean age was 33.7 (range 20–60) years. Twelve (60%) of them sustained associated injuries.
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2.1. Injury mechanism The mechanism of injury to the limb was analysed and found to be a blow to the knee—dashboard injury in 10 patients (front seat passenger or driver) and a side blow to the trochanteric region in 10 patients (3 pedestrians, 2 motorcyclist, 1 rear seat passenger and 4 falls from height). 2.2. Fracture patterns
and six intertrochanteric fractures (31A). Twelve patients had a diaphyseal fracture (one patient had a combination of diaphyseal and sub capital fractures). None of the fractures were located in the distal third of the femur (A.O.33). The detailed classification of these fractures is presented in Table 1.
3. Surgical procedure
The acetabular and femoral fractures were classified according to the A.O. classification [9]. The femoral fractures were also defined either as diaphyseal or proximal. The acetabular fractures were defined as posterior or central. The fractures were classified as “posterior” whenever there was an involvement of the posterior wall or column: it included isolated posterior wall or posterior column fractures and transverse fractures with posterior wall involvement. The fractures were defined as “central” when there was a double column fracture or a transverse fracture without posterior involvement (Table 1). 2.2.1. Acetabular fracture There were four patients with type A fracture, six patients with type B and ten patients had type C fracture. None of the type A were of the A3 variety, i.e. anterior wall or column. All the B type fractures were of the B1.3a variety, i.e. a transverse fracture with posterior wall and no anterior wall involvement. Three patients sustained a posterior fracture dislocation. 2.2.2. Femoral fractures There were nine patients with fractures of the proximal femur (A.O.31) including three sub capital fracture (31B)
3.1. Timing Thirteen patients had both femoral and acetabular fractures operated on in one session. Of these, seven patients were operated on, few hours after injury while six were operated on, several days later. In seven patients, the femoral fracture was operated on an emergency basis and the acetabular fracture a few days thereafter. Of this last group, four patients were transferred from other hospitals after surgical fixation of the femur had been performed. 3.2. Femoral fractures Two sub-capital fractures (31B) were fixed using cannulated screws (one needed arthroplasty), intertrochanteric and high subtrochanteric fractures (31A), with a dynamic hip screw and side plate (six patients), while diaphyseal fractures were fixed using an IMN with or without distal interlocking (12 patients). One patient had a combination of intra-medullary nail and cannulated screws fixation for the femoral neck, due to a segmental fracture.
Table 1 Fracture patterns and mechanism of injury Patient
A.O. femoral classification
A.O. acetabular classification
Femoral fracture
Acetabular fracture
Mechanism
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
32-A3 32-A3 32-B3 32-A3 32-A3 32-A3 32-A2 32-A3 32-B2 32-A3 32-B2 32-B1 31-B2 31-B2 31-A3 31-A3 31-A3 31-A3 31-B3 31-A3
62-B1 62-B1 62-B1 62-A2 62-A2 62-A1 62-B1 62-B1 62-C2 62-A1 62-C1 62-C2 62-C1 62-C3 62-C1 62-C3 62-C1 62-B1 62-C2 62-C1
Diaphyseal Diaphyseal Diaphyseal Diaphyseal Diaphyseal Diaphyseal Diaphyseal Diaphyseal Diaphyseal Diaphyseal Diaphyseal Diaphyseal Proximal Proximal Proximal Proximal Proximal Proximal Proximal Proximal
Posterior Posterior Posterior Posterior Posterior Posterior Posterior Posterior Posterior Posterior Central Central Central Central Central Central Central Posterior Central Central
Dashboard Dashboard Dashboard Dashboard Dashboard Dashboard Dashboard Dashboard Lateral Dashboard Dashboard Lateral Lateral Lateral Lateral Lateral Lateral Lateral Lateral Lateral
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3.3. Acetabular fractures Dislocated hips in two patients were reduced immediately using close manner, under general anaesthesia. Fixation of the acetabular fractures was carried out using a posterior approach in eight patients, ilio-inguinal in six patients, ilio-femoral in two patients and combined anterior and posterior approach in four patients. 3.4. Prophylactic therapy All patients routinely received Indomethacin 25 mg, three times per day for 6 weeks as prophylaxis against heterotopic ossification. Since 1992, low-molecular weight Heparin was routinely used as prophylactic anti-coagulant treatment (14 of the patients received this treatment). 3.5. Follow-up Of the original 20 patients, 1 died 2 weeks after the trauma due to massive pulmonary emboli (this patient did not receive anti-coagulant prophylaxis). One patient was lost to follow-up, the remaining 18, all of whom were observed for at least 1 year (mean follow-up 74 months, range 12–160 months) were followed-up routinely in our clinic. All patients had radiographs and were examined on their last visit, before the publication of this study. Clinical evaluation of the involved hip joint was accomplished using the Harris Hip Scoring system. 3.6. Statistics Statistical analysis was performed using SPSS for Windows (Version 6.1). The one sided Fisher exact test was applied to each pair of factors.
4. Results 4.1. Mechanism of injury We have examined the relationship or possible correlation between three factors: mechanism of injury, type of femoral fracture and type of acetabular fracture. Each factor was dichotomized for that matter. Mechanism of injury: dashboard injury versus lateral impaction injury, femoral fracture: diaphyseal versus proximal fracture and acetabular fracture: posterior (A.O. types A1, A2, B1) versus central fractures. 4.1.1. Mechanism of fracture versus femoral fracture type A very strong correlation was found between dashboard injury and midshaft femoral fracture and between lateral impaction and proximal fracture of the femur (P = 0.0007).
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4.1.2. Mechanism of fracture versus acetabular fracture type A strong positive correlation was found between dashboard injury and “posterior” type of acetabular fractures, and between lateral impaction and “central” type of acetabular fracture (P = 0.003). 4.1.3. Femoral fracture type versus acetabular fracture type A strong correlation was found between midshaft femoral fractures and “posterior” type of acetabular fractures and between proximal fractures of the femur and “central” type of acetabular fractures (P = 0.003). 4.2. Clinical outcome Ten of the 18 patients who were available for follow-up had “posterior” type of acetabular fracture. All fractures healed within 3–6 months post-operatively, and there was no need for another surgical procedure for bone healing. However, two patients underwent removal of metals. The average Harris Hip Score for this group was 83.8, (range 63–100). Eight patients with “central” type of acetabular fracture were available for follow-up. Three of them underwent total hip replacement. One patient of these three, aged 73 with accompanied displaced subcapital fracture (A.O. 31B-3) underwent immediate acetabular fracture fixation and primary hip replacement. The other two patients needed hip arthroplasty due to post-traumatic arthrosis, 5 and 7 years after the initial internal fixation. The Harris Hip Score of the remaining five patients was 89 (range 82–100). There was no statistical difference between the Harris Hip Score of the above mentioned groups.
5. Discussion We have shown through analysis of patients with floating hip injury that there are two main patterns of injury. These patterns are determined by three different factors: mechanism of trauma, the type of femoral and acetabular fractures. In view of the relative extremity of the obtained P-values, these three factors are jointly positively associated in each pattern. A floating hip injury is a rare combination of fractures, that render the hip joint unstable both proximally and distally. Biomechanically, it is a challenge to understand the mechanism of this combination of injuries since, there is a skeletal failure at two close sites occurring at almost the same time. Due to its complex three-dimensional structure, the multiple forces involved and the various fracture patterns that exist, it is difficult to analyse acetabular fractures. On the other hand, it is simpler to understand a long bone fracture. Therefore, analysing these combinations of injuries has given us the opportunity to understand, the different forces and temporal sequence of events causing such an injury through the
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simpler structure and the better understanding of long bone fractures. Letournel [10] defined 10 different types of acetabular fractures, and emphasised that the position of the femoral head within the hip joint at the time of trauma will usually indicate the fracture type. Tile [5] defined two acetabular fracture mechanisms according to the direction of force applied to the acetabulm: a “dashboard” type injury and a “side blow” injury to the greater trochanter. This classical biomechanical interpretation of acetabular fractures was never proved by laboratory studies. Our findings regarding the different patterns of floating hip reinforce Tile’s observations. The first pattern we define is the posterior type injury (Fig. 1), which includes a posterior type acetabular fracture and an ipsilateral diaphyseal femoral fracture and is found among front seat passengers. This pattern begins by a direct
blow to the knee (“dashboard injury”), then the force is transferred through the femur to the posterior elements of the acetabulum (due to the flexion position of the hip joint), causing a posterior wall or transverse with posterior wall fracture of the acetabulum. It seems likely that, the acetabular fracture must precede the femoral fracture for this combination to exist. The continued force applied to the femur, then produces a bending force upon the diaphyseal part of the femur, which breaks in a transverse or short oblique fashion. This pattern combines also a possible knee injury, which can present as a patellar fracture, knee instability (tear of P.C.L.) or a simple knee effusion with a transverse/oblique midshaft femoral fracture and a posterior type acetabular fracture [11]. The second pattern is the central type injury (Fig. 2), which includes a central type acetabular fracture and an ipsilateral proximal femoral fracture. The old term “central fracture dislocation” which indicates migration of the
Fig. 1. Posterior type injury. (A) pre-operative X-ray demonstrates posterior hip dislocation associated with transverse and posterior wall acetabular fracture. The diaphyseal transverse femoral fracture is not shown; (B) immediate post reduction X-ray. The skin staples emphasize a postero-lateral approach which was used for fixation of both the acetabulum and the femoral fractures.
Fig. 2. Central type injury. (A) central type fracture dislocation of the acetabulum (C1: a double column fracture) associated with femoral neck fracture; (B) post reduction X-ray, the skin staples indicate an ilio-inguinal approach to the acetabulum. (The femoral fracture was fixed through another minimal lateral incision.)
M. Liebergall et al. / Injury, Int. J. Care Injured 33 (2002) 717–722
femoral head into the pelvis, refers to either double column fracture as well as some displaced anterior and transverse fractures without posterior involvement. This is found mostly among patients that fall from height and among pedestrians who are struck by a car. This pattern involves a lateral blow to the trochanteric region of the femur. The force is then transferred to the hip joint causing a centrally directed force in the acetabulum and thus, a central type of acetabular fracture. The proximal femoral fracture is caused either, by the remaining force that produce a bending force on the cervical part of the femur or simultaneously with the acetabular fracture by a force applied to the intertrochanteric/subtrochanteric region. No direct knee injuries were found in this pattern of injury, which agrees with the sequence suggested. Reviewing the reported literature of “floating hip” injuries [2,3,6–8] shows that most of them can be fitted to one of the two patterns described here. Another interesting observation is the absence of supracondylar fractures in these 20 patients. The accepted mechanism of injury for supracondylar fractures of the femur is of an axial blow to the femur, which is the same as for a dashboard injury [12]. A possible explanation is that, the distal femur absorbs most of the energy because of its proximity to the point of impact and the residual force that is applied to the acetabulum is insufficient to induce a fracture. Based on the Harris Hip Score, it is our impression that the clinical outcome of patients with floating hip is no different from those with isolated acetabular fracture [13]. This correlates with Matta’s observations on the outcome of acetabular fractures. In his study, the clinical results for the patients who had associated injuries were similar to those for the patients who did not [14]. However, the understanding of the different patterns of this unique injury may lead to some clinical and surgical applications. Acetabular fractures are often operated on, 3–5 days after injury [5], while femoral fractures are often operated on, less than 24 h after injury. In the case of posterior type “floating hip injury”, it is possible to address the acetabular and femoral fractures through a Kocher Langenback approach and fix both fractures at the same session starting with the femoral fracture (Fig. 1) [1]. This operation should be done using a lateral position, and not on a traction table. First an IMN is inserted through the piriformis fossa that is easily found in the Kocher Langenback approach, after tagging and cutting the piriformis tendon. Then, if the patient is hemodynamically stable, the surgeon, who is familiar with this approach, extends it, to fix the acetabulum. When it is not feasible to operate on both fractures in one session, because of either the fracture, the patient or the surgical team, it is possible to use a retrograde inserted IMN for the femoral fracture and thus, leave the posterior acetabular approach region untouched [15–17]. In such staged procedure, the femoral fracture is operated on first and traction is applied for the acetabular fracture.
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The central type of floating hip (Fig. 2) is usually addressed by two different surgical approaches and it is possible to operate at different times. Most “central” acetabular fractures, without posterior wall involvement are fixed through the anterior ilio-inguinal approach, while the femoral fracture is fixed through another lateral incision, without violating the hip abductors. It is also possible to address both fractures in this combination by using the extensile ilio-femoral approach. Evaluation of the clinical outcome might also indicate the two different types of floating hip with high incidence of joint replacement in the “central” type. In conclusion, two different types of floating hip injuries are reported with theoretical as well as practical implications. The results emphasize the importance and validity of fracture classification. Due to the new fracture classification, it was possible to define several fracture types, and to correlate them to the mechanism of injury.
References [1] Liebergall M, Lowe J, Whitelaw GP, Wetzler MJ, Segal D. The floating hip ipsilateral pelvic and femoral fractures. J Bone Jt Surg (Br) 1992;74 (B):93–100. [2] Meinhard BP, Misoul C, Joy D, Ghillani R. Central acetabular fracture with ipsilateral femoral-neck fracture and intrapelvic dislocation of the femoral head without major pelvic-column disruption. J Bone Jt Surg (Am) 1987;69 (A):612–5. [3] Mestdagh H, Butruille Y, Vigier P. Central fracture-dislocation of the hip with ipsilateral femoral neck fracture: case report. J Trauma 1991;13:1445–7. [4] Bucholz RW, Brumback RJ. Fractures of the Shaft of the Femur. In: Rockwood CA, Green DP, Bucholz RW, editors. Fractures in adults. 4th ed. Philadelphia: Lippincott, 1996 [chapter 27]. [5] Tile M. Fractures of the pelvis and acetabulum. 2nd ed. Williams, Baltimore 1995 [chapter 19]. [6] Browne RS, Mullan GB. Intertrochanteric fracture of the femur with ipsilateral central fracture of the acetabulum. Injury 1980;11(3): 251–3. [7] Harper MC. Traumatic dislocation of the hip with ipsilateral femoral shaft fracture: a method of treatment. Injury 1982;13:391–4. [8] Malkawi H. Traumatic anterior dislocation of the hip with fracture of the shaft of the ipsilateral femur in children: case report and review of the literature. J Pediatr Orthop 1982;2(3):307–11. [9] Muller ME, Nazarian S, Koch P, Schatzker J. The comprehensive classification of fractures of long bones. Berlin: Springer, 1996. [10] Letournel E. Mechanism of Acetabular Fracture, In: Letournel E., editor. Fractures of the acetabulum, 2nd ed. New York: Springer, 1993:23–8. [11] Mosheiff R, Safran O, Friedman A, Liebergall M. Midshaft femoral fracture, concomitant ipsilateral hip joint injury, and disruption of the knee extensor mechanism: a unique tirad of dashboard injury. Am J Orthop 1998;27(6):465–73. [12] Wiss DA, Tracy Watson J, Johnson EE. Fractures of the knee. In: Fractures in adults. 4th ed. Philadelphia: Lippincott, 1996 [Chapter 28]. [13] Liebergall M, Mosheiff R, Lowe J, Goldvirt M, Mattan Y, Segal D. Acetabular fractures—clinical outcome of surgical treatment. Clin Orthop Relat Res 1999;366:205–16.
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[14] Matta JM. Fracture of the acetabulum: accuracy of reduction and clinical results in patients managed operatively within 3 weeks after the injury. J Bone Jt Surg 1966;78 (A):1632–45. [15] Herscovici Jr D, Whiteman KW. Retrograde nailing of the femur using an intercondylar approach. Clin Orthop Relat Res 1996;332: 98–104.
[16] Sanders R, Koval KJ, DiPasquale T, Helfet DL, Frankle M. Retrograde reamed femoral nailing. J Orthop Trauma 1993;7(4): 293–302. [17] Patterson BM, Routt Jr ML, Benirschke SK, Hansen Jr ST. Retrograde nailing of femoral shaft fractures. J Trauma 1995;38(1): 38–43.
The floating hip injury: patterns of injury M. Liebergall∗ , R. Mosheiff, O. Safran, A. Peyser, D. Segal Department of Orthopaedic Surgery, The Hadassah-Hebrew University Medical School, Hadassah University Hospital, P.O. Box 12000, Jerusalem 91120, Israel Accepted 6 November 2001
Abstract Objective: To evaluate the relationship between mechanism of injury, type of femoral fracture and type of acetabular fracture in floating hip injury. Design: Historical retrospective. Patients: Twenty consecutive patients who sustained a floating hip injury, i.e. simultaneous ipsilateral fracture of the acetabulum and the femur. Intervention: Statistical analysis of the correlation between the mechanism of injury and fracture type. Results: Two main patterns of floating hip injury were observed. The first is the posterior type, which occurs due to a longitudinal force along the femur that causes first, a posterior type fracture of the acetabulum and thereafter, a midshaft femoral fracture. The second pattern is the central type, caused by a lateral blow to the greater trochanter, which then causes a central fracture-dislocation of the acetabulum and a proximal fracture of the femur. Conclusions: This observation explains the biomechanical nature of this injury and has treatment related implications. © 2002 Elsevier Science Ltd. All rights reserved.
1. Introduction Floating joint injury is a simultaneous skeletal disruption above and below a joint. It can be either extra-articular or intra-articular. Based on this definition, two types of floating hip joints were described: type A in which a pelvic fracture is associated with an ipsilateral femoral fracture, and type B in which the acetabular fracture is associated with an ipsilateral femoral fracture [1]. Most pelvic surgeons would define only type B as a “true” floating hip injury. This combination of injury, though not common [2,3], is important from its biomechanical implications and from the treatment point of view. By analysing the ipsilateral long bone (i.e. femur) fracture, it enables us to understand the mechanism and sequence of events that take place in causing an acetabular fracture. This combined injury also poses several treatment dilemmas. The femoral fracture should be surgically stabilised urgently [4], while, a later (3–5 days) reduction and fixation is recommended for the acetabular fracture [5]. It may result in two separate operating sessions and it can lead to surgical difficulties, such as in the case when ∗ Corresponding author. Tel.: +972-2-6776342; fax: +972-2-6434434. E-mail address: [email protected] (M. Liebergall).
a posterior approach to the acetabulum has to be carried out several days after insertion of an antegrade intramedullary nail (IMN) to the femur through the same anatomical site. Few studies have been published describing the mechanisms and patterns involved in this injury, most of them are case reports [2,3,6–8]. We present 20 consecutive ipsilateral femoral and acetabular fractures, which required surgical intervention, with relation to the mechanism of the injury, the different types of acetabular and femoral fractures that were found and the possible correlation between these factors. 2. Material and methods Between the years 1987–1999, 160 patients sustaining an acetabular fracture were operated on, at the Hadassah university hospital in Jerusalem. We have retrospectively studied, a sub-group of patients presented with the combination of acetabular fracture and ipsilateral femoral fracture. This group of 20 patients, with the “floating hip injury” represent 12.5% of all acetabular fractures that were operated on. There were 16 males (75%) and 4 females (25%). The mean age was 33.7 (range 20–60) years. Twelve (60%) of them sustained associated injuries.
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M. Liebergall et al. / Injury, Int. J. Care Injured 33 (2002) 717–722
2.1. Injury mechanism The mechanism of injury to the limb was analysed and found to be a blow to the knee—dashboard injury in 10 patients (front seat passenger or driver) and a side blow to the trochanteric region in 10 patients (3 pedestrians, 2 motorcyclist, 1 rear seat passenger and 4 falls from height). 2.2. Fracture patterns
and six intertrochanteric fractures (31A). Twelve patients had a diaphyseal fracture (one patient had a combination of diaphyseal and sub capital fractures). None of the fractures were located in the distal third of the femur (A.O.33). The detailed classification of these fractures is presented in Table 1.
3. Surgical procedure
The acetabular and femoral fractures were classified according to the A.O. classification [9]. The femoral fractures were also defined either as diaphyseal or proximal. The acetabular fractures were defined as posterior or central. The fractures were classified as “posterior” whenever there was an involvement of the posterior wall or column: it included isolated posterior wall or posterior column fractures and transverse fractures with posterior wall involvement. The fractures were defined as “central” when there was a double column fracture or a transverse fracture without posterior involvement (Table 1). 2.2.1. Acetabular fracture There were four patients with type A fracture, six patients with type B and ten patients had type C fracture. None of the type A were of the A3 variety, i.e. anterior wall or column. All the B type fractures were of the B1.3a variety, i.e. a transverse fracture with posterior wall and no anterior wall involvement. Three patients sustained a posterior fracture dislocation. 2.2.2. Femoral fractures There were nine patients with fractures of the proximal femur (A.O.31) including three sub capital fracture (31B)
3.1. Timing Thirteen patients had both femoral and acetabular fractures operated on in one session. Of these, seven patients were operated on, few hours after injury while six were operated on, several days later. In seven patients, the femoral fracture was operated on an emergency basis and the acetabular fracture a few days thereafter. Of this last group, four patients were transferred from other hospitals after surgical fixation of the femur had been performed. 3.2. Femoral fractures Two sub-capital fractures (31B) were fixed using cannulated screws (one needed arthroplasty), intertrochanteric and high subtrochanteric fractures (31A), with a dynamic hip screw and side plate (six patients), while diaphyseal fractures were fixed using an IMN with or without distal interlocking (12 patients). One patient had a combination of intra-medullary nail and cannulated screws fixation for the femoral neck, due to a segmental fracture.
Table 1 Fracture patterns and mechanism of injury Patient
A.O. femoral classification
A.O. acetabular classification
Femoral fracture
Acetabular fracture
Mechanism
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
32-A3 32-A3 32-B3 32-A3 32-A3 32-A3 32-A2 32-A3 32-B2 32-A3 32-B2 32-B1 31-B2 31-B2 31-A3 31-A3 31-A3 31-A3 31-B3 31-A3
62-B1 62-B1 62-B1 62-A2 62-A2 62-A1 62-B1 62-B1 62-C2 62-A1 62-C1 62-C2 62-C1 62-C3 62-C1 62-C3 62-C1 62-B1 62-C2 62-C1
Diaphyseal Diaphyseal Diaphyseal Diaphyseal Diaphyseal Diaphyseal Diaphyseal Diaphyseal Diaphyseal Diaphyseal Diaphyseal Diaphyseal Proximal Proximal Proximal Proximal Proximal Proximal Proximal Proximal
Posterior Posterior Posterior Posterior Posterior Posterior Posterior Posterior Posterior Posterior Central Central Central Central Central Central Central Posterior Central Central
Dashboard Dashboard Dashboard Dashboard Dashboard Dashboard Dashboard Dashboard Lateral Dashboard Dashboard Lateral Lateral Lateral Lateral Lateral Lateral Lateral Lateral Lateral
M. Liebergall et al. / Injury, Int. J. Care Injured 33 (2002) 717–722
3.3. Acetabular fractures Dislocated hips in two patients were reduced immediately using close manner, under general anaesthesia. Fixation of the acetabular fractures was carried out using a posterior approach in eight patients, ilio-inguinal in six patients, ilio-femoral in two patients and combined anterior and posterior approach in four patients. 3.4. Prophylactic therapy All patients routinely received Indomethacin 25 mg, three times per day for 6 weeks as prophylaxis against heterotopic ossification. Since 1992, low-molecular weight Heparin was routinely used as prophylactic anti-coagulant treatment (14 of the patients received this treatment). 3.5. Follow-up Of the original 20 patients, 1 died 2 weeks after the trauma due to massive pulmonary emboli (this patient did not receive anti-coagulant prophylaxis). One patient was lost to follow-up, the remaining 18, all of whom were observed for at least 1 year (mean follow-up 74 months, range 12–160 months) were followed-up routinely in our clinic. All patients had radiographs and were examined on their last visit, before the publication of this study. Clinical evaluation of the involved hip joint was accomplished using the Harris Hip Scoring system. 3.6. Statistics Statistical analysis was performed using SPSS for Windows (Version 6.1). The one sided Fisher exact test was applied to each pair of factors.
4. Results 4.1. Mechanism of injury We have examined the relationship or possible correlation between three factors: mechanism of injury, type of femoral fracture and type of acetabular fracture. Each factor was dichotomized for that matter. Mechanism of injury: dashboard injury versus lateral impaction injury, femoral fracture: diaphyseal versus proximal fracture and acetabular fracture: posterior (A.O. types A1, A2, B1) versus central fractures. 4.1.1. Mechanism of fracture versus femoral fracture type A very strong correlation was found between dashboard injury and midshaft femoral fracture and between lateral impaction and proximal fracture of the femur (P = 0.0007).
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4.1.2. Mechanism of fracture versus acetabular fracture type A strong positive correlation was found between dashboard injury and “posterior” type of acetabular fractures, and between lateral impaction and “central” type of acetabular fracture (P = 0.003). 4.1.3. Femoral fracture type versus acetabular fracture type A strong correlation was found between midshaft femoral fractures and “posterior” type of acetabular fractures and between proximal fractures of the femur and “central” type of acetabular fractures (P = 0.003). 4.2. Clinical outcome Ten of the 18 patients who were available for follow-up had “posterior” type of acetabular fracture. All fractures healed within 3–6 months post-operatively, and there was no need for another surgical procedure for bone healing. However, two patients underwent removal of metals. The average Harris Hip Score for this group was 83.8, (range 63–100). Eight patients with “central” type of acetabular fracture were available for follow-up. Three of them underwent total hip replacement. One patient of these three, aged 73 with accompanied displaced subcapital fracture (A.O. 31B-3) underwent immediate acetabular fracture fixation and primary hip replacement. The other two patients needed hip arthroplasty due to post-traumatic arthrosis, 5 and 7 years after the initial internal fixation. The Harris Hip Score of the remaining five patients was 89 (range 82–100). There was no statistical difference between the Harris Hip Score of the above mentioned groups.
5. Discussion We have shown through analysis of patients with floating hip injury that there are two main patterns of injury. These patterns are determined by three different factors: mechanism of trauma, the type of femoral and acetabular fractures. In view of the relative extremity of the obtained P-values, these three factors are jointly positively associated in each pattern. A floating hip injury is a rare combination of fractures, that render the hip joint unstable both proximally and distally. Biomechanically, it is a challenge to understand the mechanism of this combination of injuries since, there is a skeletal failure at two close sites occurring at almost the same time. Due to its complex three-dimensional structure, the multiple forces involved and the various fracture patterns that exist, it is difficult to analyse acetabular fractures. On the other hand, it is simpler to understand a long bone fracture. Therefore, analysing these combinations of injuries has given us the opportunity to understand, the different forces and temporal sequence of events causing such an injury through the
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simpler structure and the better understanding of long bone fractures. Letournel [10] defined 10 different types of acetabular fractures, and emphasised that the position of the femoral head within the hip joint at the time of trauma will usually indicate the fracture type. Tile [5] defined two acetabular fracture mechanisms according to the direction of force applied to the acetabulm: a “dashboard” type injury and a “side blow” injury to the greater trochanter. This classical biomechanical interpretation of acetabular fractures was never proved by laboratory studies. Our findings regarding the different patterns of floating hip reinforce Tile’s observations. The first pattern we define is the posterior type injury (Fig. 1), which includes a posterior type acetabular fracture and an ipsilateral diaphyseal femoral fracture and is found among front seat passengers. This pattern begins by a direct
blow to the knee (“dashboard injury”), then the force is transferred through the femur to the posterior elements of the acetabulum (due to the flexion position of the hip joint), causing a posterior wall or transverse with posterior wall fracture of the acetabulum. It seems likely that, the acetabular fracture must precede the femoral fracture for this combination to exist. The continued force applied to the femur, then produces a bending force upon the diaphyseal part of the femur, which breaks in a transverse or short oblique fashion. This pattern combines also a possible knee injury, which can present as a patellar fracture, knee instability (tear of P.C.L.) or a simple knee effusion with a transverse/oblique midshaft femoral fracture and a posterior type acetabular fracture [11]. The second pattern is the central type injury (Fig. 2), which includes a central type acetabular fracture and an ipsilateral proximal femoral fracture. The old term “central fracture dislocation” which indicates migration of the
Fig. 1. Posterior type injury. (A) pre-operative X-ray demonstrates posterior hip dislocation associated with transverse and posterior wall acetabular fracture. The diaphyseal transverse femoral fracture is not shown; (B) immediate post reduction X-ray. The skin staples emphasize a postero-lateral approach which was used for fixation of both the acetabulum and the femoral fractures.
Fig. 2. Central type injury. (A) central type fracture dislocation of the acetabulum (C1: a double column fracture) associated with femoral neck fracture; (B) post reduction X-ray, the skin staples indicate an ilio-inguinal approach to the acetabulum. (The femoral fracture was fixed through another minimal lateral incision.)
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femoral head into the pelvis, refers to either double column fracture as well as some displaced anterior and transverse fractures without posterior involvement. This is found mostly among patients that fall from height and among pedestrians who are struck by a car. This pattern involves a lateral blow to the trochanteric region of the femur. The force is then transferred to the hip joint causing a centrally directed force in the acetabulum and thus, a central type of acetabular fracture. The proximal femoral fracture is caused either, by the remaining force that produce a bending force on the cervical part of the femur or simultaneously with the acetabular fracture by a force applied to the intertrochanteric/subtrochanteric region. No direct knee injuries were found in this pattern of injury, which agrees with the sequence suggested. Reviewing the reported literature of “floating hip” injuries [2,3,6–8] shows that most of them can be fitted to one of the two patterns described here. Another interesting observation is the absence of supracondylar fractures in these 20 patients. The accepted mechanism of injury for supracondylar fractures of the femur is of an axial blow to the femur, which is the same as for a dashboard injury [12]. A possible explanation is that, the distal femur absorbs most of the energy because of its proximity to the point of impact and the residual force that is applied to the acetabulum is insufficient to induce a fracture. Based on the Harris Hip Score, it is our impression that the clinical outcome of patients with floating hip is no different from those with isolated acetabular fracture [13]. This correlates with Matta’s observations on the outcome of acetabular fractures. In his study, the clinical results for the patients who had associated injuries were similar to those for the patients who did not [14]. However, the understanding of the different patterns of this unique injury may lead to some clinical and surgical applications. Acetabular fractures are often operated on, 3–5 days after injury [5], while femoral fractures are often operated on, less than 24 h after injury. In the case of posterior type “floating hip injury”, it is possible to address the acetabular and femoral fractures through a Kocher Langenback approach and fix both fractures at the same session starting with the femoral fracture (Fig. 1) [1]. This operation should be done using a lateral position, and not on a traction table. First an IMN is inserted through the piriformis fossa that is easily found in the Kocher Langenback approach, after tagging and cutting the piriformis tendon. Then, if the patient is hemodynamically stable, the surgeon, who is familiar with this approach, extends it, to fix the acetabulum. When it is not feasible to operate on both fractures in one session, because of either the fracture, the patient or the surgical team, it is possible to use a retrograde inserted IMN for the femoral fracture and thus, leave the posterior acetabular approach region untouched [15–17]. In such staged procedure, the femoral fracture is operated on first and traction is applied for the acetabular fracture.
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The central type of floating hip (Fig. 2) is usually addressed by two different surgical approaches and it is possible to operate at different times. Most “central” acetabular fractures, without posterior wall involvement are fixed through the anterior ilio-inguinal approach, while the femoral fracture is fixed through another lateral incision, without violating the hip abductors. It is also possible to address both fractures in this combination by using the extensile ilio-femoral approach. Evaluation of the clinical outcome might also indicate the two different types of floating hip with high incidence of joint replacement in the “central” type. In conclusion, two different types of floating hip injuries are reported with theoretical as well as practical implications. The results emphasize the importance and validity of fracture classification. Due to the new fracture classification, it was possible to define several fracture types, and to correlate them to the mechanism of injury.
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