Propensity for hip dislocation in gait loading versus sit-to-stand maneuvers: implications for redefining the dome of the acetabulum needed for stability of the hip during activities of daily living

Assessment of Force Applied During Examination Under Anesthesia Used to Determine Stability in Posterior Wall Acetabular Fractures

OBJECTIVES

Determination of hip instability associated with posterior wall acetabular fractures may be difficult. Thus, dynamic stress examination under anesthesia (EUA) was developed as a tool for guiding treatment. EUA uses positioning of the hip and application of force across the hip to detect instability. While aspects of the EUA technique seems consistently described in the literature and practiced by surgeons, some components are ill-defined. The goal of this study was to assess standardization of applied force during EUA among experienced acetabular surgeons.

METHODS

Fellowship-trained orthopaedic trauma surgeons with experience in acetabular fracture treatment performed EUA for posterior wall instability on an intact, fresh human cadaver. All surgeons used a similar method, and each expert performed EUA multiple times separated by a brief hiatus. The maximum force applied along the femur's vector in Newtons (N) was measured using a hand-held digital dynamometer.

RESULTS

The EUAs of 19 surgeons were evaluated. Five surgeons had been practicing for <5 years, six for 6 to 10 years, five for 11 to 20 years, and three for >20 years. The mean force applied during EUA was 173N, with a notable variability between surgeons (range, 77-368N). Notable variability was also observed between sequential measures of individual surgeons with six surgeons (31.6%) having a >50N range on repeat trials.

CONCLUSION

This is the first study to report force applied during an EUA to assess for posterior wall acetabular fracture stability. Notable variability was observed among surgeons performing the examination and in repeated examinations by the same surgeon, suggesting that results of EUA may be surgeon-dependent. Further study is needed to determine what optimal applied force should be used to assess hip stability after a posterior wall acetabular fracture.

LEVEL OF EVIDENCE

Level V. An assessment of a diagnostic tool.

Quadrilateral plate fractures of the acetabulum: Classification, approach, implant therapy and related research progress

The quadrilateral plate (QP) is an essential structure of the inner wall of the acetabulum, an important weight-bearing joint of the human body, which is often involved in acetabular fractures. The operative exposure, reduction and fixation of QP fractures have always been the difficulties in orthopedics due to the special morphological structure and anatomical features of the QP. Fortunately, there have been many effective methods and instruments developed for QP exposure, reduction and fixation by virtue of the combined efforts of numerous orthopedists. At the same time, each method presents with its own advantages and disadvantages, resulting in different prognoses. It is necessary to have a thorough understanding of the anatomy, radiology and fixation techniques of the QP in terms of patient prognosis optimization. In this paper, the anatomical features, definition and classification of QP, operative approach selection, implant internal fixation methods and efficacy were reviewed.

The Quadrilateral Plate in Acetabular Fracture Surgery: What Is It and When Should It Be Addressed?

The quadrilateral plate (QP) is the relatively flat surface of bone in the true pelvis lying directly medial to the acetabulum. This surface is frequently involved in acetabular fractures. Elderly individuals, in particular, commonly sustain anterior column fractures with incomplete or complete posterior hemitransverse fracture lines with associated QP comminution. If QP fracture lines propagate through the superior weight-bearing surface of the acetabulum, the femoral head may displace medially, leading to poor outcomes if not addressed. Fortunately, the collective work of many orthopaedic surgeons has resulted in numerous effective methods for approaching, reducing, and stabilizing the QP and the diverse family of fractures which affect it. A thorough understanding of the QP, its anatomy, radiology, and techniques for fixation, is required to optimize patient outcomes.

Biomechanical comparison of fixation techniques for transverse acetabular fractures - Single-leg stance vs. sit-to-stand loading

OBJECTIVES

To biomechanically compare five different fixation techniques for transverse acetabular fractures using both the single-leg stance (SLS) and the sit-to-stand (STS) loading protocols and to directly compare fracture gap motion (FGM) and relative interfragmentary rotation (RIFR).

METHODS

Transtectal transverse acetabular fractures were created on fourth-generation composite hemipelves in a reproducible manner. Five different fixation techniques were biomechanically assessed using both an SLS and STS loading protocol: anterior plate (AP) only, posterior plate (PP) only, anterior plate plus posterior column screw (AP+PCS), posterior plate plus anterior column screw (PP+ACS) and anterior plus posterior plate (AP+PP). After preconditioning, the specimens were loaded from 50 to 750 N with a ramp of 100 N/s. FGM and RIFR under loads of 750 N were measured using an optical 3D measurement system.

RESULTS

In the three groups of fixation techniques addressing both columns, STS loading resulted in higher mean FGM and in RIFR than SLS loading. No construct failure was observed. In the single plate groups (AP only and PP only), STS loading resulted in failure of all specimens before reaching loads of 750 N, while no failure occurred after SLS loading. No significant differences in FGM and RIFR were found between the double plate (AP+PP) and the single plate plus column screw (AP+PCS and PP+ACS) techniques.

CONCLUSION

SLS loading appeared to overestimate the strength of acetabular fracture fixation constructs and STS loading may be more appropriate to provide clinically relevant biomechanical data. Internal fixation of a single column might not provide adequate stability for transverse fractures, while strength of single plate plus column screw fixation and double plate fixation was comparable.

Is It Possible and Safe to Perform Acetabular-preserving Resections for Malignant Neoplasms of the Periacetabular Region?

BACKGROUND

Primary malignant tumors located near the acetabulum are usually managed by resection of the tumor with wide margins that include the acetabulum. These resections are deemed P2 resections by the Enneking and Dunham classification. There are various methods to perform the subsequent hip reconstruction. Unfortunately, there is no consensus as to the best management. In general, patients undergoing resection at this level will have substantial levels of pain and disability as measured by the Musculoskeletal Tumor Society (MSTS) scoring system. We believe there is a subset of patients whose tumors in this location can be resected while preserving all or most of the weightbearing acetabulum using navigation and careful surgical planning.

QUESTIONS/PURPOSES

(1) What complications were associated with this resection; (2) what oncological outcomes (histological margins and local recurrence) were achieved; and (3) what is the function achieved by these patients?

METHODS

This was a retrospective study of patients with periacetabular primary malignancy. From 2008 to 2014, we treated 12 patients who had periacetabular primary malignant tumors and in five, we performed resection with the weightbearing portion spared. During this period, our general indications to perform a resection that spared the acetabulum were the tumor with its resection margin not involving the weightbearing portion of the acetabulum. However, we did not perform this procedure in patients who had more cranial lesion involving the weightbearing portion or whose hip stability might be in question after the tumor excision. Three patients were women and the other two were men. Four were chondrosarcomas, whereas the other one was synovial sarcoma. Ages ranged from 46 to 60 years (average, 53 years). Minimum followup was 14 months (median, 37 months; range, 14-88 months); no patients were lost to followup before a 1-year minimum was achieved, and all patients have been seen within the last 9 months.

RESULTS

There were no intraoperative or early postoperative complications. None of the five patients had a positive margin by histological assessment. No local recurrences were detected. The median functional score by MSTS was 28 out of 30 (range, 27-30).

CONCLUSIONS

The roof of the acetabulum is the weightbearing portion of the acetabulum. It also maintains the stability of the hip. With precise preoperative planning of the resection and accurate execution of the procedure, the hip-sparing approach through partial acetabular resection can be performed in selected patients with malignant periacetabular neoplasms. Navigation makes it possible to minimize the amount of bone resection. In this preliminary report of a small number of patients, we had adequate short-term local tumor control. We believe the function is good, but we do not have a comparison group of patients to document improved function.

LEVEL OF EVIDENCE

Level IV, therapeutic study.