Anatomical reduction is the most fundamental determinant of good clinical outcomes in PWFs. However, some patients with PWFs still have poor post-operative functions even after anatomical reduction of the fracture. In our study, we comprehensively analyzed the relevance of possible patient factors and fracture pattern factors to both clinical and radiographic outcomes after anatomical reduction of isolated acetabular PWFs. We found that age, fracture comminution, and dome comminution were significantly related to clinical and radiographic outcomes. Age, a significant risk factor, showed a negative correlation with functional scores (HHS and MMAS) and radiographic changes. Furthermore, patients with fracture comminutions involving the weight-bearing zone of the acetabulum presented significantly lower HHS and MMAS and poorer radiographic outcomes (advanced OA, ON, and THA) than those without dome involvement.
Some prognostic factors for outcomes in patients after surgical treatment of PWFs have been reported in the literature; however, most studies discuss outcomes in all types of acetabular fractures [4, 10, 11]. A few studies exclusively evaluating PWFs have indicated that fractures occurring at an older age with intra-articular comminution or with marginal impaction mainly contributed to adverse effects and emphasized the importance of anatomical reduction [3, 6]. The quality of reduction affects the prognosis of acetabular fractures; however, some fractures are too comminuted to achieve anatomical reduction, resulting in a poor prognosis. Moreover, some patients may experience fracture displacement after undergoing an initial anatomical reduction. Unsatisfactory clinical outcomes of PWFs that were perfectly reduced initially are not uncommon. Factors associated with adverse effects in PWFs that were initially anatomically reduced remain unclear. In this study, we evaluated only PWFs with radiographic anatomical reduction to eliminate the factors of surgical impropriety and aimed to explore the prognostic factors that could affect postoperative clinical and radiographic outcomes. We demonstrated that dome comminution was the most significant factor associated with poor functional scores, advanced OA, and the need for THA.
Extensive fracture comminution makes it difficult to achieve anatomical reduction and is more likely to lead to poor clinical results . We excluded PWFs without radiographic anatomical reduction and focused on the significance of the area where the fracture was comminuted. The acetabular dome supports a tremendous weight-bearing load; hence, a fracture involving the weight-bearing dome is considered a risk factor for poor clinical outcomes. Ovre et al. retrospectively reviewed 450 acetabular fractures to analyze the relationship between clinical outcome and roof arc angle (angle between a vertical line drawn from the center of the acetabulum towards the acetabular dome and a second line drawn from the center of the acetabulum to the fracture) converted to a roof arc score . Their results indicated the significance of fracture lines in the acetabular dome to clinical outcomes. Our results showed a significant association between dome comminution and advanced OA. The acetabular dome is subjected to a lot of force during movement; therefore, a single buttress plate fixation may not be sufficient to stabilize the comminuted bone and prevent its displacement. The residual steps and diastasis causing joint incongruence on the weight-bearing dome seemed to be correlated with poor clinical outcomes and an increase in the risk of OA, femoral head ON, and rate of conversion to THA. THA for the treatment of failed acetabular fractures is a challenging procedure that usually results in inferior functional outcomes and higher complication rates than primary THA. Recently, experts have shown interest in performing THA for early rehabilitation in patients with femoral head impaction, pre-existing OA or ON, or osteoporotic bone with comminution in the acetabular dome . However, the risk of heterotopic ossification (HO) in THA patients may hamper rapid rehabilitation . Moreover, the incidence of HO was reported to be higher in patients undergoing acute THA for acetabular fractures and contributed to adverse effects on functional outcomes .
Age has been demonstrated to be a negative prognostic factor for acetabular fractures. The poor bone quality and higher rate of fragment comminution and marginal impaction in patients with advanced age preclude a secure fixation and lead to early implant failure and a higher rate of conversion to THA [17, 18]. Hence, some authors have suggested immediate THA for geriatric comminuted acetabular fractures for early mobilization . Extensive research has been conducted on all types of acetabular fractures in elderly patients; however, studies focusing on PWFs in older patients are scarce. Ferguson et al. reviewed 31 PWFs from 235 geriatric acetabular fractures and found that 64% of fractures were comminuted and 52% were combined with marginal impaction; however, they did not report their associations with clinical outcomes . The results from another review article including 15 studies on acetabular fractures in patients aged over 55 years indicated an average conversion rate to THA of 23.1% (0–45.5%) at a mean follow-up of 47.3 months . As reported in previous studies, we noted mark higher rate of comminution (66.7%, 6/9) in patients older than 60 years; and age was correlated negatively with both clinical and radiographic outcomes even after anatomical reduction.
Marginal impaction injuries represent chondral depressions in PWFs in which an osteochondral fragment is rotated and impacted into the underlying subchondral bone . Studies have reported that patients with PWFs and marginal impaction showed poor clinical outcomes because of the failure to identify the improperly reduced impacted fragments [7, 10]. With the advance in surgical techniques and awareness of fracture patterns from preoperative CT scans, clinical outcomes of PWFs with marginal impaction have improved [9, 21]. Preoperative CT scan provides more precise information about the status of margin impaction in an acetabular fracture and helps surgeons to ensure accurate fracture reduction, thereby preventing possible complications. A two-level reconstruction of marginal impaction, including reduction of the osteochondral fragment in an anatomical position using the femoral head as a template and impacting the void cavity with an autologous bone graft or freeze-dried allograft, can improve postoperative clinical outcomes . In this study, routine preoperative CT scans were performed to inspect the defect of marginal impaction precisely and a two-level reconstruction technique was used to ensure accurate reduction in patients with PWFs. Although there was no significant difference in functional outcomes or THA rate, PWFs with marginal impaction still exhibited a higher risk of radiographic OA.
In this study, we evaluated PWFs with radiographic anatomical reduction to eliminate factors of surgical impropriety. We demonstrated that dome comminution was the most significant factor associated with poor outcomes. As a result of the tremendous load on the acetabular dome and inaccurate evaluation of bone union from radiography, these patients may require longer periods of activity restriction and non-weight-bearing exercises. We also inferred that an additional spring plate over the dome region may be beneficial for securing comminuted fragments. Studies on the use of an additional spring plate over the dome area are ongoing.
Our study has certain limitations. First, the study was retrospective and included only a limited number of patients, particularly elderly patients; therefore, statistical conclusions of the relational comparisons should be interpreted cautiously. Second, postoperative reduction was evaluated with X-ray images, which may result in under-diagnosis of inadequate reduction. Although postoperative CT scans provide precise evaluation of fracture reduction, it was reported limited benefits to patients after fixation of acetabular fractures . There is still no consensus on the use of routine pelvic CT after surgery. Third, the follow-up period was relatively short and did not reveal the potential long-term complications associated with OA progression. Fourth, we evaluated only the impact of fracture-related factors on prognosis, and we did not consider differences in the soft tissue of individuals. Soft tissue composition before injury and degree of soft tissue injury may also have a significant impact on functional outcomes. A close relationship has been reported between hip OA and changes in collagen content in the fascia lata. The increase in collagen type I along with a decrease in collagen type III and hyaluronan levels results in facial stiffening, which may increase the risk of OA .