Epidemiology

Epidemiological data on acetabular fractures are useful for preoperative planning, patient information, to determine the risk of adverse results regarding complications, and to determine fracture- and injury-related outcomes.

The heterogeneity of published data makes comparison of different studies difficult. Giannoudis et al in 2005 published a meta-analysis based on 3670 acetabular fractures.¹ Even these data were significantly heterogenic. Thus, any conclusion should be performed with care. Included data consists of several studies dealing with only posterior wall fractures,²^,³^,⁴^,⁵^,⁶ which results in an overrepresentation of this fracture type compared with other fracture types.

Additionally, including results of operative treatment using certain operative approaches can lead to bias as associated fracture types became more relevant.⁷^,⁸^,⁹^,¹⁰^,¹¹

More consecutive epidemiological data, available till 2005, were further analyzed.¹²^,¹³^,¹⁴^,¹⁵^,¹⁶^,¹⁷^,¹⁸^,¹⁹^,²⁰^,²¹^,²²^,²³^,²⁴^,²⁵^,²⁶^,²⁷^,²⁸^,²⁹^,³⁰^,³¹^,³²^,³³^,³⁴^,³⁵^,³⁶^,³⁷^,³⁸^,³⁹^,⁴⁰ Different parameters were analyzed, but not every study reported the same parameters.

5.2 Demographics

Data on gender could be analyzed from 3471 acetabular fractures in 3434 patients (23 publications).¹²^,¹³^,¹⁴^,¹⁵^,¹⁶^,¹⁷^,¹⁸^,¹⁹^,²⁰^,²¹^,²³^,²⁴^,²⁵^,²⁶^,²⁷^,²⁸^,²⁹^,³⁰^,³¹^,³²^,³³^,³⁴^,³⁵^,³⁶^,³⁹ A total of 3561 patients were male, and 1396 were female (male-to-female ratio: 2.5:1, or 71.8% vs. 29.2%, respectively).

Data concerning patient age at injury were published in 25 papers.¹²^,¹³^,¹⁴^,¹⁵^,¹⁶^,¹⁷^,¹⁸^,¹⁹^,²⁰^,²¹^,²³^,²⁵^,²⁶^,²⁷^,²⁸^,²⁹^,³⁰^,³¹^,³²^,³³^,³⁴^,³⁵^,³⁶^,³⁷^,³⁹ The mean age of 5004 patients was 33.6 years (range, 7–106 years).

Seven articles analyzed the side of the acetabular fracture.³^,¹²^,¹⁴^,²⁰^,²¹^,²³^,²⁶ In 338 cases, the left acetabulum was fractured, and in 279 cases the right acetabulum was fractured (54.8% vs. 45.2%; left-to-right ratio: 1.2:1).

Detailed descriptions of the trauma mechanism were published in 12 investigations.¹²^,¹⁴^,¹⁵^,¹⁶^,²¹^,²⁵^,²⁶^,²⁹^,³⁰^,³¹^,³⁶^,³⁹ A traffic accident was responsible for the fracture in 79.2% cases, a simple fall in 8.5%, and a fall from a height in 7.3%. In 5% of cases, other trauma mechanisms were reported.

Of 1394 traffic accidents, 74.4% sustained a car accident, 12.8% a motorcycle accident, 12% were injured as pedestrians, and 0.8% sustained bicycle accidents. A recent analysis reported that 82.1% of acetabular fractures were the result of a traffic accident.¹³

Injury severity was analyzed by Deo et al and Briffa et al.¹³^,¹⁷ The mean Injury Severity Score (ISS)⁴¹ was 18 and 17.2 points, respectively.

Data concerning the concomitant injuries were presented in 12 publications.¹²^,¹⁴^,¹⁵^,¹⁷^,¹⁸^,²¹^,²³^,²⁵^,²⁶^,²⁷^,³²^,³⁹ Overall, 51.2% of the patients had multiple injuries, with a range between 22.3% and 85%. A total of 23.5% had an additional traumatic brain injury (TBI),¹⁵^,¹⁸^,²¹^,²⁵^,²⁶^,²⁷^,²⁹^,³⁶ 11.6% a blunt chest trauma,¹⁵^,²¹^,²⁶^,²⁷^,²⁹^,³⁰ 8% a blunt abdominal trauma,¹⁵^,²¹^,²⁶^,²⁷^,²⁹^,³⁰^,³⁶ and 13.6% a simultaneous pelvic ring injury.¹²^,¹⁶^,¹⁷^,¹⁸^,¹⁹^,²¹^,²⁵^,²⁹^,³⁰^,³⁶

Data from German Multicenter Studies indicate that 50.6% had an isolated acetabular fracture, whereas 32.4% had at least one additional injury and 17% had multiple injuries.³³

Data focusing on mortality have to be carefully analyzed, because in many studies long-term results were the main inclusion criteria. A mean mortality rate after acetabular fractures of 1.1% can be expected.¹²^,¹⁵^,¹⁶^,¹⁷^,¹⁸^,¹⁹^,²⁰^,²²^,²³^,²⁴^,²⁵^,²⁶^,²⁷^,²⁸^,²⁹^,³¹^,³⁵^,³⁶^,³⁷ Nevertheless the “real” mortality rate has to be estimated higher. Investigations that analyze complete collectives of acetabular fractures detected a mortality rate between 2.9% and 4.8%.³³^,⁴²

Clinical Relevance

The typical patient with an acetabular fracture is a male patient between 20 and 45 years old. Since a high amount of the fractures is caused by traffic (car) accidents, the left acetabular is fractured more often than the right one. In 50% of cases, the acetabular fracture is accompanied by another injury, and in 25% an accompanying TBI can be expected. The mortality rate of acetabular fractures is approximately 3%.

5.3 Fracture Classification

Many studies used the Letournel classification to describe and analyze the different fracture types.²⁴ It has to be considered that, in the majority of studies, patients with operative stabilization of their acetabular fracture were analyzed, whereas patients with conservative treatment were insufficiently investigated. Thus, more complex acetabular fractures (associated fracture types) are supposed to be overrepresented in these clinical investigations and in epidemiological meta-analyses.

In the following, data concerning operative stabilized acetabular fractures are described first.

Detailed analyses regarding specific fracture types were available from 21 studies.¹²^,¹³^,¹⁴^,¹⁵^,¹⁶^,¹⁷^,¹⁸^,²⁰^,²²^,²³^,²⁴^,²⁵^,²⁷^,²⁸^,³⁰^,³¹^,³⁵^,³⁶^,³⁸^,³⁹^,⁴⁰

The distribution of the different acetabular fracture types in 4047 cases is shown in ▶ Fig. 5.1.

Fracture types that are typically treated by operative stabilization are posterior wall fractures, both-column fractures, and the associated transverse/posterior wall fractures. Together, they represent 58.9% of all surgically treated acetabular fractures. The frequency of simple fracture types was 39.1%, whereas the frequency of associated fracture types was 60.9%, respectively (▶ Fig. 5.2).

Analyzing only consecutive data of operatively and nonoperatively treated acetabular fractures represent a more realistic fracture type distribution. Data on this more specific distribution was available in 2258 acetabular fractures (▶ Fig. 5.1). The most common fracture types were the posterior wall fracture, the both-column fracture, and the associated transverse/posterior wall fracture, these three fracture types were responsible for 54.2% of all fractures. The frequency of simple fracture types was now 47.7%, whereas the frequency of associated fracture types was 52.3%, respectively (▶ Fig. 5.2).

Fig. 5.1 Distribution of acetabular fracture types according to Letournel (operative stabilized fractures only).

Fig. 5.2 Distribution of simple and combined acetabular fracture types according to Letournel classification (operative stabilized fractures only).

Clinical Relevance

The most common fracture types are isolated posterior wall fractures, both-column fractures, and the associated transverse/posterior wall fractures.

5.4 Quality of Reduction

To analyze the operative result, the quality of reduction in 4001 acetabular fractures was reported.¹²^,¹³^,¹⁶^,¹⁸^,²⁰^,²⁴^,²⁵^,²⁸^,³³^,³⁵^,³⁸ Using the criteria of Matta⁴³ an “anatomical reduction” (fracture gap/step 0–1 mm) could be achieved in 71%. Analyzing those studies that differentiate more detailed results, near anatomical reductions (fracture gap/step 2–3 mm) and imperfect reductions (fracture gap/step > 3 mm) were available in 1807 fractures: 73% anatomical reductions, 19.1% near anatomical reductions, and 7.6% imperfect reduction could be suspected.¹³^,³³^,³⁵^,³⁸

Certain studies correlated the rate of anatomical reduction in relation to the fracture type (▶ Fig. 5.3).¹²^,¹³^,²⁴^,²⁸^,³⁸ The worst reduction results were stated after T-type fractures and both-column fractures, whereas isolated posterior wall fractures showed the highest rates of anatomical reductions.

Fig. 5.3 Distribution of anatomical reduction of acetabular fractures according to Letournel classification.

Clinical Relevance

An anatomical reduction can be expected in approximately three-fourths of all acetabular fractures.

5.5 Nerve Injuries

5.5.1 Primary Nerve Injuries

Giannoudis et al reported a total of 16.4% trauma-associated primary nerve lesions.¹ The incidence increases to 40.3% in cases with an additional posterior hip dislocation.¹

Epidemiological data from the German Multicenter Studies Pelvis reported only 4% primary nerve lesions in 2073 acetabular fractures (1395 with open reduction internal fixation [ORIF]), with 7% at the time of discharge from the hospital. In 1.9% of cases, an iatrogenic nerve lesion was reported.⁴⁴ It has to be considered that ORIF was performed in only 67.8%.³³^,⁴⁴ Thus, it is likely that the data from primarily operated patients analyzed by Giannoudis et al¹ showed higher primary nerve lesion rates due to different fracture types, increased fracture displacement, and fracture instability.

According to the Letournel classification, the highest rates of primary nerve lesions were observed in isolated posterior wall fractures and posterior column fractures, whereas the lowest rates were seen in anterior column fractures.

Sciatic Nerve Lesions

Analyzing data from different publications for 2818 patients with acetabular fractures, 14.4% with a sciatic nerve lesion were identified.¹⁵^,¹⁶^,¹⁷^,¹⁹^,²⁰^,²¹^,²⁴^,²⁵^,²⁶^,²⁸^,²⁹^,³¹^,³²^,³⁶ Some authors distinguished between the peroneal and the tibial part of the sciatic nerve.¹⁵^,¹⁶^,¹⁹^,²⁹^,³²^,³⁶ In these studies, a total of 11% sciatic nerve lesions were reported. In 4.9%, the peroneal part was injured, and in 6.1%, the tibial part was injured. Russel et al observed a frequency of 14.5% sciatic nerve lesions.⁴⁵ Fassler et al described 15 patients with sciatic nerve lesions, corresponding to 25.9%.⁴⁶ A consecutive analysis by Laird et al reported a frequency of 6.8% for primary sciatic nerve lesions.⁴²

Femoral Nerve Lesion

Only limited data are available for primary femoral nerve lesions. Hardy described a case of a primary femoral nerve injury caused by severe displacement of an associated anterior column plus posterior hemitransverse acetabular fracture.⁴⁷ Intraoperatively, a discontinuity of 90% of the femoral nerve was detected. A recovery could not be seen up to 1 year postoperatively.

Gruson and Moed described primary femoral nerve injuries in 0.3%.⁴⁸ Both patients in this study showed a partial recovery with persisting sensitive impairments. The lesions were caused by a posterior wall fracture and an associated anterior column plus posterior hemitransverse fracture.

In a study by Matta of operatively treated patients, a primary femoral nerve lesion was detected in 1%.³⁸

Obturator Nerve Lesion

Primary lesions of the obturator nerve are a rare. Rommens described five cases, corresponding to 2.2%.³⁶ Ballmer et al observed one case (1.3%) but without any trend of recovery.¹² Tannast et al reported no obturator nerve lesion in patients treated operatively.³⁸

Clinical Relevance

Trauma-associated primary nerve lesions are seen with a frequency of 7–10% of all acetabular fracture types. In most cases, the sciatic nerve is involved.⁴⁹

5.5.2 Iatrogenic Nerve Lesions

Giannoudis et al analyzed a frequency of 8% iatrogenic nerve lesions after acetabular fracture treatment.¹ In 60% of cases, the sciatic nerve was involved.

Rommens et al reported a frequency of 7.1% of secondary nerve lesions after operatively treated acetabular fractures.³⁶ An obturator nerve lesion occurred in three cases, a femoral nerve lesion in one case, and a partial or complete lesion of the sciatic nerve was observed in all other cases (4.9%).

Mears et al reported a 6% incidence of iatrogenic sciatic nerve lesions.²⁸ Furthermore, two lesions of the obturator nerve and three of the superior gluteal nerve could be detected.

Letournel reported two lesions of the femoral nerve in association with an ilioinguinal approach (1.1%).²⁴

Gruson et al reported a rate of 0.3% of femoral nerve lesions.⁴⁸ These two cases were associated with operative treatment of a both-column fracture (extended iliofemoral approach) and a posterior wall fracture (Kocher-Langenbeck approach). The duration of operative treatment, a direct compression caused by prone position, and an iatrogenic intraoperative tension of the nerve were discussed.

Lesions of the lateral cutaneous femoral nerve (LCFN) were reported, especially after treating fractures using the ilioinguinal approach. Mayo et al described 67 (41.1%) lesions, with seven patients sustaining subjectively disturbing lesions.²⁷ Rommens et al reported a frequency of 25% lateral thigh sensory deficits after ilioinguinal approach.³⁶

Haidukewych et al investigated the effect of perioperative nerve monitoring on the rate of iatrogenic lesions of the sciatic nerve.⁵⁰ The overall rate of iatrogenic nerve lesions was 5.6%. In the monitored group, a higher amount of nerve lesions was observed, which could be correlated to the surgical approach.

Briffa et al described a rate of 1.8% for both iatrogenic sciatic nerve lesions and lesions of the obturator nerve, whereas iatrogenic lesions of the LCFN were observed in 14.3%.¹³

Clinical Relevance

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