The treatment of acetabular fractures remains challenging, with injury patterns often widely variable and complex. Posterior wall fractures remain the most frequent variant, with concomitant fracture patterns commonly found.1–5,9 Posterior wall fractures are often viewed as “simple fractures,” yet consistently have been shown to be a major factor in failed fixation, loss of reduction, and poor long-term results both in early, delayed, and revision surgery.3,6–8 Mast et al described the use of “spring plates” as adjunctive fixation for comminuted posterior wall fractures in 1989.9 Biomechanical studies have shown a significantly greater load to failure of the fixation of concentrically comminuted posterior wall fractures with the use of spring plates and overlying compression plates in comparison with reconstruction plate alone.10 Technical modifications to increase the contact area for the spring plate through use of a T-plate have also been found to be successful.11
Adequate fixation of small comminuted or marginal posterior wall fragments can be difficult with conventional lag screw and buttress plate techniques. Often times, these independent posterior wall fragments are small and not amenable to lag screw fixation. They may be located near the rim of the acetabulum making them even more difficult to hold with a 3.5-mm plate alone. Attempted lag screw fixation of rim fragments can increase the potential risk from intra-articular screw penetration. No study to date has reported the use of one-third tubular plates, modified intraoperatively, as spring plates for additional fixation of comminuted posterior wall acetabulum fractures in a large consecutive series. The purpose of this study was to examine the rate of hardware failure for comminuted posterior wall fractures treated with spring plates when used in combination with standard 3.5-mm overlay buttress compression plating.
A 3 hole one-third tubular plate (DePuy-Synthes, Raynham, MA) was modified by cutting a small central portion of the terminal hole of the plate (Fig. 1). This leaves 2 adjacent end prongs. Both these prongs are bent at an angle of 60–90 degrees toward the undersurface of the plate in a pincer type bend. Any posterior column fracture patterns must be stabilized before reduction of the wall fragments is possible. The hooks must press on the bone fragments and not into the labrum. A 2-mm Kirschner wire (K-wire) is used to hold the comminuted wall fragments in a reduced position. Enough bone should be present between the entrance site of the K-wire and the rim of the joint surface. The K-wire is positioned behind the bony rim of the acetabular wall fragment directed away from the intra-articular marginal rim surface to avoid penetration of the joint space. The K-wire is seated into the intact or stabilized posterior column bone. The modified prong end hole of the plate can slide down the 2-mm Kirschner wire allowing the plate to sit at the point of the K-wire–bone junction. Spring plates are placed generally at 90 degrees to the articular fragments creating a buttress effect (Fig. 1). The medial hole of the spring plate is compressed to the retroacetabular bone with a 3.5-mm cortical screw. This compression of the malleable straight spring plate allows the plate to naturally contour to the retroacetabular surface, increasing the compression of the joint fragments (Fig. 1B). Spring plates are not precontoured to anatomically fit the residual intact bone. Contouring the custom plates would decrease the final spring plate compression as it reduces the loading of the plate by the contouring of the plate, resulting from the spring plate compression screw. A pelvic reconstruction compression plate, usually 8 holes in length, is placed over the spring plates to increase the stability of the spring plate effect and prevent postoperative loss of fixation. The spring hook plates should extend medially beyond the posterior wall 3.5-mm buttress plate.
After institutional review board approval, initial screening using CPT codes for open reduction internal fixation of posterior wall acetabular fractures between January 2000 and June 2017 identified 113 consecutive patients from a single surgeon. All Health Insurance Portability and Accountability Act policies were followed for each review. A retrospective review was performed. Inclusion criteria included surgical treatment of an acetabulum fracture with posterior wall component, use of a one-third tubular plate as a spring plate, and minimum age of 16 (skeletal maturity) at initial treatment. Exclusion criteria included surgical treatment of an acetabulum fracture without use of a spring plate.
Inpatient and outpatient records and operative reports were reviewed for patient demographics, initial diagnosis, and age at initial surgery, implant specifics, and complications by 1 author not involved in the patient's care. Information on spring plates included implant manufacturer, number, and type of plates used. Complications included hardware failure, mode of hardware failure, wound complications, and obvious pseudarthrosis. Treatments for all complications were included. Serial radiographs were obtained and reviewed for articular reduction. Final radiographs were graded according to the evaluation described by Matta et al.6 Non–weight-bearing ambulation was strictly maintained in patients and reinforced at clinic visits. No partial weight-bearing on comminuted posterior wall fragments was advised in any patient until at least 10 weeks from postoperative fixation. Two-tailed Student t tests were used to evaluate differences in continuous variables.
Fifty-two patients who underwent surgical management of acetabular fractures with customized spring plates used as adjunctive fixation between 2000 and 2017 met inclusion criteria. Mean age at initial surgery was 41 years (range, 16–89 years). The mechanisms of injury included motor vehicle accident (27), motorcycle crash (10), struck by vehicle (5), ground level fall (5), fall from elevated height (4), and work-related injury (1). Thirty-eight patients initially presented with hip dislocations and were reduced before definitive fixation. Of the 52 patients, 18 had additional articular marginal impaction that required elevation and bone graft placement. Independent lag screws in addition to spring plates were used in 25 patients.
Mean follow-up was 14.2 months (range, 6–140 months). An example of postoperative and final follow-up results is shown in Fig. 2. There were no hardware complications, no evidence of loosening or migration of the spring plates, no intra-articular screw penetration, and no recurrent subluxation or recurrent hip dislocation. Five patients required additional surgery, including 1 for heterotopic ossification (HO) resection and 4 for total hip arthroplasty (THA) due to advanced arthritis. Other complications included 3 patients (5.8%) with peroneal nerve palsies after surgery. All 3 patients with nerve palsies were showing signs of recovery at follow-up examination. Radiographic grades at final follow-up based on Matta et al6 included 42 excellent, 6 good, 1 fair, and 3 poor.
Although posterior wall fractures remain the most common variant of acetabular fractures, comminuted posterior wall fractures are uncommon.3,6,13 Posterior wall fractures can have devastating complications with failed early management, redislocation after stabilization, and with delayed treatment or revision fixation for malreduction.3,6–8,12–15 Fixation strategies for treating marginal posterior wall fragments have included lag screw fixation alone;16 however, screws alone although recommended historically by Letournel,3 are generally not preferred as definitive fixation of posterior wall fragments without buttressing these lag screws with reconstruction plates.17 Independent lag screws placed near the marginal rim of the posterior wall fragments have the potential risk of intra-articular penetration or further wall fragmentation. Monocortical screws placed through the locking reconstruction plates have been found to be successful, although a large series using this technique has not been performed.18
Mast et al first proposed the concept of spring plates for adjunctive fixation of comminuted posterior wall fragments in 1989.6 Richter et al19 further explored spring plate fixation demonstrating acceptable stability to comminuted posterior wall fragments. In the study by Ziran et al,11 a technical modification to the traditional spring plate was evaluated using a T-plate as spring plates. In their series of 33 patients with comminuted posterior wall fragments, only 1 patient (3%) had fixation failure. In the biomechanical study by Goulet and Bray5 (which is correct), it was found that the addition of spring plates significantly increased the load to failure when compared with reconstruction plate alone. In the current series, we found similar results. There were no hardware failures in all 52 patients treated with spring plates in addition to 3.5-mm locking pelvic or reconstruction plates.
In this series, 7.6% of patients (4/52) required subsequent THA secondary to posttraumatic osteoarthritis. This is consistent with what has been reported in previous studies.6,12,13,15 In the study by Tannast et al,13 the average survivorship of 816 acetabular fractures treated with open reduction internal fixation was 79%, with a hip arthroplasty conversion rate of long-term results of 13%. Risk factors for conversion to THA included age older than 40 years, non–anatomical fracture reduction, anterior hip dislocation, postoperative incongruence of the acetabular roof, involvement of the posterior wall, acetabular impaction, a femoral head cartilage lesion, recurrent femoral head dislocation or subluxation, initial displacement of the articular surface of greater than 20 mm, and utilization of the extended iliofemoral approach.6,13 Of the 4 patients in this series who required subsequent THA, 3 of 4 patients had age older than 40 years, all had posterior wall fracture/dislocations, and 50% (2 of 4 patients) had marginal impaction that required elevation and bone grafting. Patients younger than 40 years had significant concomitant injuries, including diffuse axonal injury and subsequent development of spasticity on the affected side.
Nerve injuries in the form of peroneal nerve palsies were found in 5.8% (3 patients) of patients in this series. In the literature, nerve injuries have been reported after surgical treatment of acetabular fractures from 3% to 23%.20–26 In the study by Lehmann et al,25 they found the greatest risk factors for nerve injuries included posterior wall acetabular fractures and the use of the Kocher–Langenbeck approach. The Kocher–Langenbeck approach was used in 41/52 patients (79%). Eleven of 52 patients (21%) required a Gibson approach combined with a surgical dislocation and reduction through a transtrochanteric exposure.
Eleven of 52 patients (21%) developed some form of HO, with 1.9% of patients (1/52) requiring HO resection as a subsequent procedure for limited range of motion. HO after surgical treatment of acetabular fractures has ranged from 7% to 100% in the literature, with the exact pathogenesis remaining unknown.25–28 In the study by Firazooabadi et al,29 prolonged mechanical ventilation was the only risk factor that predicted severe HO. In their series, 38 patients (12%) developed severe HO, and 5 of these patients (13%) required HO resection.
Limitations of this study include its retrospective design, limited patient numbers, and limited follow-up. However, there were no fixation failures in all 52 consecutive patients using the spring plate technique. It is possible that a greater pool of patients with a greater follow-up could reveal hardware failures that were unrecognized in this series of patients. The Mast concept of a combination of customized spring plates under screw compression combined with a 3.5-mm pelvic compression reconstruction plate overlay offers significant augmented stability in managing comminuted posterior wall fractures without hardware failure in the study cohort.10,11 Many of the confounding factors present in this study could be eliminated by conducting a prospective, randomized study. Our study, however, is the largest consecutive series evaluating the use of customized one-third tubular spring plates as adjunctive fixation in management of comminuted posterior wall acetabular fractures. It is hoped that our results will encourage further studies with greater patient numbers.
In summary, one-third tubular plates used as spring plates combined with a 3.5-mm overlay compression plate are an acceptable means of fixation of marginal and/or comminuted posterior wall fragments not amenable to lag screw fixation. Spring plates allow for definitive fixation of these comminuted fragments and stability to allow mobilization of patients without a significant risk of implant failure or intra-articular hardware penetration.
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