A posterior wall fracture is a partially articular fracture, characterized by a fracture of the posterior acetabular joint surface, without involvement of the entire posterior column.
According to the Letournel classification, these fractures are considered simple fractures with one predominant fracture line, but their prognosis is rather worse due to a high rate of accompanying articular pathologies compared to other fractures types.
Posterior wall fractures are often characterized by an additional posterior or posterior-cranial dislocation of the hip joint. The bone injury consists of one or more variable-sized fragments and can be associated with marginal impaction zones. Letournel divided this fracture type into pure posterior, posterosuperior, and posteroinferior fractures.3
Pure posterior fractures only involve the posterior wall of the acetabulum without extending to the acetabular roof and/or the posteroinferior horn of the lunate facet.3 The frequency of this subgroup in Letournel’s series was 15.9%, or 67% of all posterior wall fractures. In 26% of his cases, an additional marginal impaction was detected.
In posterosuperior fractures, the posterosuperior articular joint (acetabular roof) is involved, whereas no involvement of the lower joint part is present. Additionally, pure superior fractures are part of this subgroup. Here, transitions to the fractures of the anterior column are possible. This fracture type was observed in 2.75%, or 11.6% of all posterior wall fractures.3 A marginal impaction was detected in 34.6%.
In posteroinferior fractures the posterior horn, the subcotyloid fossa, and/or variable portions of the proximal ischial bone are involved without extension of the fracture line to the obturator foramen. The posterior cortex can be fractured up to the proximal greater sciatic notch. The frequency of this injury type was seen in only 0.5%, or 2.2% of all posterior wall fractures.3 Marginal impactions were not reported in Letournel’s series.
8.2 Radiological Criteria
Pelvic anteroposterior (AP) view. An isolated disruption of the posterior wall line can be detected. All other lines are normally intact (▶ Fig. 8.1). The teardrop figure can be involved in some cases, especially in extended fractures involving the quadrilateral surface. The acetabular roof may be involved in posterosuperior fractures.
Iliac oblique view. The classical lines seen on the alar oblique view show no disruptions (▶ Fig. 8.2). The fragment(s) can be visualized as dense bone structures in projection to the iliac bone.
Obturator oblique view. The size and the number of fragments are best seen on this view. The characteristic lines of the anterior column and the obturator foramen remain intact (▶ Fig. 8.3).
Computed tomography (CT). CT is necessary to analyze the exact size of the posterior wall fragment(s) and to visualize intraarticular fragments and marginal impaction zones of the femoral head and the acetabular surface, the localization of articular surface involvement, and extent of posterior hip dislocation and the rotation of the fragments (▶ Fig. 8.4). A three-dimensional (3D)-CT is only necessary to give a better anatomical understanding of fracture morphology. In rare cases, a plastic deformity of persistent intact parts of the posterior wall and column can be seen after a posterior hip dislocation. During injury, the dislocated femoral head presses against these intact posterior parts which results in a concave malalignment after reduction in comparison to the opposite side. Thus, an outside-in directed impaction can be seen, with a corresponding density of the cancellous bone within the remaining intact posterior wall/column.4
Transition forms to other fracture types. Large posterior wall fragments involving the quadrilateral surface and/or the proximal ischium can appear as transitions to posterior column fractures. Additionally, other incomplete, transverse fracture lines form transitions to transverse/posterior wall fractures. ▶ Fig. 8.5, ▶ Fig. 8.6, and ▶ Fig. 8.7 show typical examples of fractures of the posterior wall.
Fig. 8.1 Fracture of the posterior wall. The thin arrows mark the defect caused by the absence of the posterior wall fragment; the thicker arrows mark the fragments of the posterior wall.
Fig. 8.2 Fracture of the posterior wall. Typical posterior wall fracture on the ala oblique view; the marked line of the posterior column is uninjured; the arrows mark the dense shadow of the bony fragments.
Fig. 8.3 The obturator oblique view shows the intact lines of the anterior column and the obturator foramen; posterior wall fragments are marked with arrows.
Fig. 8.4 CT shows the displaced fracture fragments with the corresponding defect in posterosuperior column extending to the acetabular roof; schematically, the typical fracture course on axial CT views is shown. The 3D-CT clearly shows the true extent and localization of the fracture fragments.
Fig. 8.5 Typical fracture of the posterior wall with a singular fragment (OTA 62-A1.1).
Fig. 8.6 Multifragmentary posterior wall fracture without marginal impaction (OTA 62-A1.2).
Fig. 8.7 Posterior wall fracture with marginal impaction (OTA 62-A1.3) and additional femoral head fracture.
8.3.1 Injury Mechanism
The most common mechanism resulting in a posterior wall involvement is the dashboard injury, usually in traffic accident–related frontal collisions, with an axial pressure force along the femoral axis, directing the femoral head posteriorly against the posterior acetabular rim.5 This mechanism has been identified both clinically using accident research databases and experimentally.
Rupp et al found a frequent occurrence of acetabular fractures after this injury mechanism in contrast to previous investigations.6 In addition, the dashboard mechanism was evaluated experimentally. An average force of 5700 N was found in 74% of the tested cadavers to fracture the acetabulum. In 12 of 14 cases with an acetabular fracture (86%), an isolated posterior wall fracture or a combination with a transverse or T-type fracture was observed.6 In three cases, a femoral neck fracture was observed.
Dakin et al analyzed the dashboard mechanism and found a posterior wall fracture in 27 of 28 cases. All fractures of the posterior wall were caused by an axial force acting directly from frontal or frontolateral.7
McCoy et al analyzed 40 patients with known accident mechanism.8 A frontal collision caused a posterior hip dislocation with or without a concomitant posterior wall fracture in 70%.
The dashboard mechanism is an essential mechanism to produce a posterior wall fracture.
8.3.2 Fracture Mechanism
Posterior wall fractures are a result of a shearing fracture at the posterior column after a predominantly posterior directed dislocation. The resulting fragments can be of different sizes.
The typical injury mechanism is caused by a posterior directed force, often due to a dashboard injury mechanism. Attention has therefore to be paid to accompanying injuries of the knee structures and the thigh. Depending on the direction of the resulting force, fragments can be located directly posterior (below the acetabular roof), posterosuperior, and posteroinferior, respectively.
Fracture location is caused by the position of the hip joint at the time of impact. Depending on the extent of flexion, abduction, or adduction together with the individual antetorsion of the femur, the corresponding forces act posterolateral, central, or craniocaudal, respectively. The position of the hip joint at the time of the trauma is crucial for the type of posterior wall fracture.
Flexion of the hip joint < 90 degrees often results in posterosuperior fracture dislocations with a large posterior-cranial fragment. Flexion of 90 degrees leads to typical dorsal rim/wall fractures and flexion > 90 degrees can result in posteroinferior injuries of the posterior wall (▶ Fig. 8.8).
Fig. 8.8 Typical injury vectors dependent on flexion position of the hip joint creating different posterior wall fracture types according to Letournel.
In neutral position in the frontal plane or adduction, typical posterior injuries are expected, whereas an additional abduction of the hip joint results in a more central orientated force transmission, which can lead to an additional injury of the quadrilateral plate or to fractures with a transverse component.
The posterior wall fragment remains attached to either the capsule or a capsular disruption occurs. If the hip capsule is preserved, the femoral head is directed by the continuing forces against the remaining intact posterior column and acetabular cartilage, which can lead to typical marginal impaction zones in the posterior column (▶ Fig. 8.9).
Fig. 8.9 Mechanism, dependent on type of capsular lesion, resulting in posterior wall fractures and accompanying acetabular marginal impaction according to Letournel.
Furthermore, corresponding pressure and movement of the femoral head along the intact bone can result in shear injuries at the femoral head cartilage, femoral head impactions, or, in rare situations, to femoral head fractures (Pipkin fractures).
Böhler found that, in such mechanisms, elastic compression of the femoral head can occur, which may be one cause of posttraumatic femoral head necrosis after posterior wall fractures.11 This injury mechanism can also result in smaller additional fragments in the area of the fracture zone, clinically revealed as comminution areas or even intraarticular fragments.
The fragment of the posterior wall is usually attached to some part of the hip capsule, whereas a complete capsular or soft tissue release is uncommon.
In particular, additional acetabular cartilage injuries, especially marginal impaction zones or injuries of the femoral head, are common and may have prognostic value.
8.4 Concomitant Injuries
Only few data are available regarding concomitant injuries after posterior wall fractures.
Various data show that approximately 30% of all posterior wall fractures are isolated acetabular injuries without injuries to other body regions.12,13,14 Similar data were gathered from the Pelvic Database, Hannover Medical School in 2005. A total of 22.2% of cases presented with additional head injuries, 24.3% with chest injuries, and 6.6% with abdominal injuries. Additional injuries of the ipsilateral lower extremity according to a postulated dashboard mechanism consisted of 8.5% femur fractures, 8.8% knee ligament instabilities, 5.8% patella fractures, and 4% tibial plateau fractures.
Fig. 8.10 Example of a posterior femoral head dislocation, seen on an axial CT image.
Fig. 8.11 Close relationship of the sciatic nerve to the posterior wall fracture fragments.
8.5 Hip Joint Stability
Several groups analyzed hip joint stability after posterior wall fractures. In a clinical analysis by Larson, axial femoral pressure in 30 to 40 degrees flexion was performed and femoral head re-dislocation was considered as an unstable situation.16
Keith et al was one of the first to investigate the effect of the posterior wall fragment size on hip joint stability in nine cadavers.17 A repetitive osteotomy of the posterior pelvic rim was performed until an unstable hip joint was created. The extent of the resected posterior wall was determined by the remaining acetabular depth. The quotient of the affected versus the intact side was measured on axial CT (▶ Fig. 8.12). An axial stress test was then performed in 90 degrees flexion and 20 degrees adduction. Stable hip joints showed a posterior wall acetabular depth of 10–40%, whereas unstable hip joints had a 20–55% posterior wall involvement. Thus, a transition zone exists between 20% and 40%.
Fig. 8.12 Measurement of the size of posterior wall involvement based on axial CT slides according to Keith.41
Calkins et al performed a detailed CT analysis of posterior wall fractures (according to the Epstein classification) in 31 patients.18 A stress test was carried out in 90 degrees flexion, 0 degrees rotation, and 0 degrees adduction. Beside analysis of a resulting subluxation/dislocation of the joint, the Acetabular Fracture Index (AFI), the quotient of the maximum joint surface angle in comparable CT sections of the injured and the contralateral joint, was analyzed (▶ Fig. 8.13).
Fig. 8.13 Determination of the Acetabular Fracture Index (AFI) according to Calkins.13 (a) Determination of the AFI on axial CT. (b) Schematic AFI determination.
A total of 21 patients had a stable hip joint and 10 patients an unstable hip joint. A subluxation of the femoral head of more than 0.5 mm was found in 70% with unstable joints, in contrast to 0% in those with stable hip joints. No differences were found regarding fracture steps or gaps. In unstable fractures, a 65% involvement of the posterior wall was detected, whereas in stable fractures an average bony defect of 37% was measured. Correspondingly, a transition zone was defined between a 34% and 55% posterior wall defect.
In a further study, after osteotomy of the posterior wall, the fragment size, the relationship between capsular integrity, and the hip joint stability were analyzed.19 Even the hip capsule was intact, all hip joints with a 25% defect of the posterior wall were stable, and 75% of the hips with a 33% bone defect were stable. All joints with a > 50% defect were unstable. In contrast, in posterior capsular disruption, at least 86% of the hip joints with a defect of 33% were unstable. All hip joints with a defect smaller than 25% were stable and all hip joints with a minimum defect of 50% were unstable. In summary, a transition zone exists between a 25% and 50% posterior bony defect.
Various studies recommended CT analysis for radiological assessment of hip joint stability in the presence of fractures of the posterior wall.
The concept of Grimshaw et al includes the dynamic image-intensifier–assisted analysis of joint stability in general anesthesia.22 It is performed in supine position on a radiolucent table in full extension and neutral rotation of the hip joint. By careful flexion up to 90 degrees and slight axial pressure along the femoral shaft axis, the congruence of the hip joint is analyzed on the pelvic AP and the obturator oblique view. If the joint remains congruent, examination is additionally performed in 20 degrees adduction and 20 degrees internal rotation. Every subluxation (hip joint incongruence) is considered unstable.
A comparable investigation was performed according to the examination proposed by Keith et al and Calkins et al with analysis of a quotient of the greatest posterior defect at the posterior wall and the mediolateral length of the intact posterior wall, calculated on the same CT level (▶ Fig. 8.14). Compared to the gold standard (dynamic fluoroscopic examination), this modified Keith method resulted in 100% specificity, 100% sensitivity, and 100% positive predictive value.24 Intra- and interobserver reliability was independent of experience and the overall reliability was 0.80. Compared to the gold standard, sensitivity was 90% with a specificity of only 61%.25
Fig. 8.14 Measurement method for assessing the extent posterior wall involvement of axial CT slides according to Moed.69
In contrast, potentially unstable posterior wall fractures with a 20–50% fragment size had an intraobserver reliability relative to the gold standard of 0.65. The interobserver reliability was only 0.12 and therefore in the range of chance probability. Thus, in doubtful cases, surgery is recommended.26
A further analysis compared standard fluoroscopy-based dynamic stress examination with intraoperative Iso-C-3D dynamic stress evaluation in 45 degrees flexion and axial loading. In one of five cases, intraoperative 3D analysis revealed instability compared to the two-dimensional (2D) standard fluoroscopy technique and was therefore recommended as a superior technique.27
Recent data questioned the value of the fragment size in determining hip stability. Compared to dynamic stress fluoroscopic examination under general anesthesia, the most proximal exit point of the fracture in relation to the acetabular roof was found to be a better indicator of hip instability than the wall size as wall sizes less than 20% were shown to be unstable in 23% of the cases.28 The distance from the acetabular roof to the most proximal fracture line was 5 mm in unstable fractures versus 9.5 mm in stable fractures.
In contrast, a present clinical analysis in 17 patients with nonoperative treatment after dynamic stress fluoroscopic examination confirmed the value of analysis of the posterior wall fragment size with anatomical joint congruity and excellent radiographic and good to excellent clinical outcomes 30 months after injury.29
8.6 Biomechanics of Posterior Wall Fractures
Olson et al analyzed the influence of different posterior wall defects on contact forces of the femoral head at the remaining acetabulum in cadavers.30 In a standardized single-leg stance fracture model, Fuji pressure films were used to measure the resulting forces. A three-stage defect of the posterior wall was created by osteotomy on the posterior wall area 90 to 40 degrees to the horizontal plane—clinically, the most common area involved.
In the intact acetabulum, the contact region between the femoral head and the acetabular joint surface was 48% superior, 28% anterior, and 24% posterior. A one-third defect of the posterior wall resulted in a superior contact increase of up to 64%, whereas an anterior and posterior reduction of 21% and 15% were observed, respectively. With increasing defect size, a further superior contact increase was observed, whereas the extent of decrease in the anterior and posterior area was further reduced. The total contact area was reduced from 9.21 cm2 in the intact acetabulum to 6.87 cm2 in cases with a complete defect of the posterior wall.
Even small posterior wall defects lead to a minimum 1.3-fold increase of the superior contact forces, resulting in a theoretically increased risk of developing secondary arthrosis.
Taking these results into account, good results with conservative treatment of smaller posterior wall lesions can be expected.
In a further analysis, the effect of the anatomical joint reconstruction with a lag screw and additional plate osteosynthesis of a posterior wall fracture was correlated to the size of the contact area between the femoral head and the acetabulum in a single-leg stance simulation.31
Although the contact surface in the intact acetabulum was comparable both anterior, posterior, and superior, presence of a posterior wall fracture led to a rise in the superior contact area and the local compressive forces together with a corresponding decrease in the anterior and posterior contact area.
After anatomical reconstruction of the fracture, the superior contact area was reduced and the anterior and posterior contact surfaces increased, without achieving physiological values.31Therefore, it is assumed that the presence of a fracture affects the physiological mechanics of the acetabulum and even anatomical reconstruction cannot restore normal joint physiology.31,32,33 The physiological incongruence34,35 of the hip joint is therefore permanently disrupted.
This physiological incongruence leads to a uniform stress on the horn and flanks of the lunate facet and avoids circumscribed force maxima. The transverse acetabular ligament acts as a tension band34,36 (see ▶ 2).
Posterior wall fractures destroy the physiological incongruence of the hip joint.
8.7 Treatment Indications
8.7.1 Conservative Treatment
Conservative treatment is only indicated in small capsular avulsion injuries (Epstein type I injury37,38) or when the joint is stable during instability testing. Testing is performed with axial pressure in 90 degrees flexion and slight adduction.39
As already described, the size of the bony fragment can be determined by CT evaluation and an articular surface involvement < 30% normally excludes relevant joint instability. It has to be considered that even these small defects lead to a peak pressure increase in the superior joint area with a potential risk of degenerative joint changes.30
Indications for conservative treatment according to the CT analysis of Olson et al40 are:
No presence of fracture lines in the upper 10 mm of the joint (acetabular roof)
Presence of an exact joint congruence without traction treatment in all three conventional standard X-ray planes
At least 50% intact joint area in the most involved fracture area
After identifying a stable joint tested by dynamic fluoroscopy under general anesthesia,22 18 patients were treated conservatively. The fragment of the posterior wall showed an average size of 28%.24 In 22.2% a CT-morphologically stable fragment was present and in 77.8% an intermediate unstable fragment (20–50% size) was seen. After at least 2 years the average Merle d’Aubigné score was 17 points. All patients showed a good and excellent clinical result and no patients developed posttraumatic radiological changes. The clinical outcome was best when no fracture dislocation was present.
Conservative treatment included a physiotherapeutic treatment with muscle strength support, gait training, and coordination exercises. A partial weight bearing was allowed with one-fifth body weight for 6–12 weeks with subsequent increase. Full weight bearing was possible normally after 10–12 weeks.
8.7.2 Operative Treatment
In cases with concomitant diseases or local contraindications for an operative procedure, traction treatment is recommended. The presence of intraarticular fragments and acetabular marginal impactions are classical indications for surgery.
The great majority of posterior wall fractures are therefore treated surgically. Indications for surgical treatment include:
Unstable hip joint
Incongruence of the hip joint
Presence of a reduction handicap
Increasing sciatic nerve lesions
Femoral head fractures
Presence of an acetabular impaction area
Since approximately 72% of the fractures are associated with hip joint dislocation, emergency closed reduction is strictly recommended. Reduction is performed under general anesthesia and medical relaxation to avoid further damage to the cartilage structures of the femoral head and acetabulum. Various reduction methods are described the literature. The most common are the reduction maneuvers according to Allis, Bigelow, Böhler, Stimson, or Skoff.41,42
The Allis maneuver is performed by an axial pull in the supine position in 90 degrees hip and knee flexion with counterpressure on the pelvis under slight rotational movements.
The Bigelow maneuver is comparable to the Allis technique with the leg additionally held in a maximum adduction position.
The Böhler variant is similar to the Allis method; the surgeon uses a sling around their neck and the ipsilateral knee joint.
Stimson uses the prone position: the patient is fixed on the table with the hip joint positioned in 90 degrees flexion; gravity alone is able to reduce the hip joint in the majority of cases, sometimes a slight pressure directed to the floor can be helpful.
A modification of the Skoff technique was used in the lateral decubitus position of the patient; reduction is performed with two persons; first, a sling is positioned around the hip followed by counterforce transmission while pulling the leg distally in more than 90 degrees flexion, adduction, and external rotation.
Some of these techniques are schematically shown in ▶ Fig. 8.15.
Fig. 8.15 Schematic representation of different methods of closed reduction maneuvers for posterior dislocation of the femoral head. (a) Method according to Allis. (b) Method according to Bigelow. (c) Method according to Böhler.
Reduction should be performed as early as possible. The influence of the reduction time in relation to injury time on the development of a femoral head necrosis is still unclear. Only in pure hip dislocation, the 6-hour rule seems to be of value43 and in Pipkin fracture dislocations of the femoral head.44 In acetabular fracture dislocations, the influence of the reduction on prognosis time is still unclear.
8.8 Techniques of Osteosynthesis
8.8.1 Biomechanics of Osteosynthesis
Various works analyzed the effect of different osteosynthesis techniques on stability of reconstruction.
Goulet et al experimentally analyzed multifragmentary fractures of the posterior wall.34 A posterior wall osteotomy was performed and the resulting fragment was additionally transversally (type A) or concentrically (type B) cracked. In type A fractures, stabilization was performed only with one screw per fragment or in combination with an additional posterior reconstruction plate acting as a neutralization plate. The additional plate led to a significantly higher stiffness at the fragments, whereas no effect was seen on total stiffness.
The concentric type B fractures were stabilized with either an isolated reconstruction plate or an additional spring plate.45,46 Alternatively to the classic surgical technique with a one-third tubular plate or industrial produced plates, a modified distal radius plate can additionally be used as a spring plate.47 No significant differences were found between these techniques, but a tendency to a higher stiffness using an additional spring plate was observed.
A further experimental biomechanical analysis in pure posterior wall fractures compared fixation with two isolated lag screws and with two lag screws and a conventional reconstruction versus a locking plate found no statistically significant differences between these stabilization methods.48
Biomechanical comparison of fixation in posterosuperior and posteroinferior posterior wall fractures with two lag screws and a locking reconstruction plate and additionally fixing the posterosuperior fracture with a tridimensional memory fixation system showed higher instabilities of posterosuperior fractures.49
In a finite element analysis, fixation of a posterior wall fracture was simulated with two miniplates and one reconstruction plate, an isolated reconstruction plate, isolated two-screw fixation, and isolated miniplate fixation. The combination of screw and plate osteosynthesis resulted in maximal stability50
Based on these results, the following may be recommended:
Large, isolated fragments can theoretically be fixed alone with single screw osteosynthesis.
In multifragmentary fractures, an additional plate osteosynthesis leads to a significant increase of the overall stiffness.
Small avulsed fragments should be fixed with an additional spring plate.
There is no advantage using locking plates.
Zoys et al investigated the influence of the implant material on the stiffness of the osteosynthesis.51 In 10 cadaver pelvises, reproducible fractures of the posterior wall were osteotomized and fixed with lag screw fixation and plate osteosynthesis. Stainless steel implants showed a higher stiffness compared to titanium implants.
In the treatment of posterior wall fractures, steel implants are recommended.
However, anatomical reconstruction this fracture type does not result in an acetabular load distribution that is comparable to the preoperative, physiological situation. Pressure peaks remain in the superior acetabulum, whereas these parameters are reduced in the anterior and posterior acetabular parts.31
Operative stabilization of posterior wall fractures is typically performed using the Kocher-Langenbeck approach. Only in rare cases of posterosuperior fractures, which can extend to the anterior column, is a modification of the procedure necessary. As an alternative, surgical hip dislocation according to Ganz can be used in these situations to access the superior acetabular area.52,53
8.8.3 Reduction Techniques
Various instruments are available for reduction. The following reduction instruments are most frequently used (▶ Fig. 8.16):
Large pointed reduction forceps (Weller clamp)
Small pelvic reduction forceps for use with cortex screws (Farabeuf clamp)
Small pelvic reduction forceps for use with cortex screws (Jungbluth clamp)
Ball spike pusher
Universal chuck with T-handle for 5-mm Schanz screws
Fig. 8.16 Various commonly used reduction aids, from the left to right: ball spike pusher, T-handle, Schanz screw, Farabeuf forceps, Jungbluth-forceps.
A stepwise reduction maneuver is recommended for posterior wall fractures:
Distraction of the femoral head
Identification of (intra-)articular pathology
Reduction of marginal impactions
Reduction of the main fragment(s)
Distraction of the Femoral Head
To get an overview of the extent of the fracture zone, the hip joint is distracted or carefully subluxated together with positioning of the main fragment(s) of the posterior wall as posteriorly as possible. This normally allows for adequate inspection the joint.
Additionally, if not already avulsed due to the injury itself, the ligament of the head of the femur is dissected. In addition, a Schanz screw is inserted into the femoral neck allowing distraction of the femoral head (▶ Fig. 8.17, ▶ Fig. 8.18). Thus, existing intraarticular fragments or reduction inhibitors can be removed.
Fig. 8.17 Joint distraction using a Schanz screw with a T-handle inserted into the femoral neck.
Fig. 8.18 Intraoperative view of joint distraction, identifying the intraarticular pathology with multiple fragments and the intact ligament of the femoral head.
Identification of the (Intra-)Articular Pathology
It is crucial to identify marginal impactions. In rare cases, these fragments can be rotated up to 180 degrees and impacted into the cancellous bone of the posterior column and therefore can be difficult to find. Overlooked impactions fragments can result in articular stepoffs and gaps, which increase the risk of developing a secondary degenerative arthrosis.56,57
Reduction of Marginal Impactions
In the next step, reduction of identified marginal impactions is performed. Release of the cancellous bone must be carefully performed without damaging these fragments using a raspatory or chisel. These fragments are then reduced against the reduced femoral head, the latter acting as a template. The created cancellous defect should be filled up (▶ Fig. 8.19). Autogenous cancellous bone from the greater trochanter58 or alternatively from the anterior/middle iliac crest can be used. It may be helpful to perform a temporary fixation of these reduced impacted fragments with K-wires parallel to the joint surface (e.g., 1.4-mm diameter). Alternatively, screws or resorbable pins can be used.
Fig. 8.19 Reduction of marginal impaction: the upper pictures show the posterior border of the posterior column (dashed lines). The three marginally impacted fragments (HW1–3), which are displaced posteriorly, are clearly visible.
After reduction with a raspatory the fragments were reduced against the reduced femoral head, the latter acting as a template. If a cancellous bone defect remains, usually cancellous bone from the trochanteric region is used to fill up the defect. TI, ischial tuberosity; Si, ischial spine; Fim, greater sciatic notch; Hk, femoral head.
In elderly patients with poor bone quality, reduction can be supported by special bone cements to fill up the resulting defects.59 Free articular fragments should also be reduced anatomically.
Reduction of the Main Posterior Wall Fragment(s)
The main fragment is now addressed. The fracture side is dissected carefully with periosteal stripping of maximum 2–4 mm to allow accurate reduction control at the fracture line. If the size of this fragment is sufficiently large, a lag screw osteosynthesis is planned. The drill orientation should be parallel to the joint surface or directed away from the joint surface (▶ Fig. 8.20). To avoid intraarticular screw position, a primary in–out drilling can be performed. After reduction drilling is then completed and the screw can safely be inserted.
Fig. 8.20 Possible screw, wire, or pin orientations for fixation of posterior wall fragments.
A labral avulsion injury in acetabular fractures is a common phenomenon especially in fractures with a transverse component,60 posterior wall fractures,61 and additional posterior hip dislocation together with Pipkin fractures.62
It is still under discussion if refixation of a torn or avulsed labrum is necessary. Leunig et al recommended to leave an avulsed portion of a labrum untreated if it was intraoperatively stable and undamaged, whereas refixation was performed if it was unstable, intact, and attached to bony fragments.60 Pure resection was recommended in unstable and damaged labral tears.60
In acetabular fractures with a posterior wall fractures, labral injuries seem to be a constant intracapsular injury. It was recommended to preserve the labrum as much as possible61 as mechanical pain and functional impairments can be suspected if left untreated63 and superior results can be suspected after labral repair.64,65
8.8.4 Technique of Osteosynthesis
Subsequent to the reduction, a step-by-step fixation protocol is recommended:
Lag screw osteosynthesis of main fragments
Spring plate fixation of rim avulsions
Neutralization plate osteosynthesis
Temporary Fixation/Lag Screw Osteosynthesis
For temporary fixation of the main fragment(s), K-wires or reduction clamps are used. Occasionally, a ball spike pusher can be used to hold the reduction (▶ Fig. 8.21).
Fig. 8.21 Reduction of the main posterior wall fragment with a ball spike pusher.