The pararectus approach in acetabular fracture fixation: evidence of reproducibility and learnability

Abstract

Purpose

The Pararectus approach is an anterior intrapelvic exposure introduced by Keel et al. for the management of anterior acetabular fractures. While its safety and effectiveness have been demonstrated, evidence regarding the learnability of this technically demanding method remains under discussion. This study compares the first fifty consecutive eligible cases treated by the approach’s inventor (group A) with the first fifty independent cases performed by a surgeon without prior acetabular subspecialization (group B).

Methods

Consecutive patients representing the first 50 Pararectus cases for displaced acetabular fractures in group A (2009–2013) and group B (2017–2021) were included. Baseline demographics were comparable except for age (64 vs. 73 years, p = 0.001) and trauma mechanism (high-energy trauma more frequent in group A, 46% vs. 12%; p < 0.001). Group A was treated using manually contoured reconstruction and buttress plates, whereas group B was managed with a standardized traction-table setup and a precontoured suprapectineal plate system (p < 0.001). Operative time, intraoperative blood loss, intra- and postoperative complications, CT-based reduction quality, reoperations ≤ 30 days, and conversion to total hip arthroplasty (THA) ≤ 24 months were analyzed.

Results

The analyzed outcomes demonstrated comparable operative parameters between both groups: (i) Operative time averaged 172 min (range 50–339) in group A and 165 min (90–266) in group B (p = 0.19), (ii) intraoperative blood loss was 1000 ml (250–6000) in group A and 900 ml (200–4500) in group B (p = 0.09), (iii) intraoperative complications occurred in 5/50 (10%) in group A compared with 3/50 (6%) in group B (p = 0.71), (iv) CT-based reduction quality was anatomical in 36/50 (72%) in group A and 31/50 (62%) in group B, imperfect in 14/50 (28%) vs. 16/50 (32%), and poor in 0/50 (0%) vs. 3/50 (6%) (overall p = 0.17), (v) postoperative complications occurred in 7/50 (14%) in group A and 5/50 (10%) in group B (p = 0.75), (vi) of these, reoperations ≤ 30 days were required in 7/50 (14%) in group A and 1/50 (2%) in group B (p = 0.066), (vii) conversion to THA ≤ 24 months was required in 5/50 (10%) in group A and 2/50 (6%) in group B (p = 0.70), with a mean time to THA of 13.8 months vs. 5.8 months (p = 0.22).

Conclusion

Operative parameters, reduction quality, postoperative complications, and conversion to THA ≤ 24 months were comparable between the two surgeons. These findings indicate that, within a standardized workflow and instrumentation, the Pararectus approach can be applied safely and reproducibly even during the early phase of independent practice.

Introduction

Over the past two decades, demographic shifts have markedly changed the spectrum of acetabular fractures. The incidence in patients older than 60 years has more than doubled, with a predominance of low-energy anterior column patterns featuring superomedial dome impaction, displacement of the quadrilateral plate, and medialisation of the femoral head [1, 2]. These injuries differ from those sustained by high-energy trauma and are frequently characterized by osteopenic bone, articular impaction, and comminution - factors that complicate reduction and fixation [3].

Anatomical restoration of the acetabular articular surface remains the cornerstone of successful joint-preserving treatment in displaced fractures [4, 5]. Historically, the ilioinguinal approach, first described by Letournel and Judet in 1964, became the gold standard for fractures involving the anterior column and wall [6, 7]. However, while providing excellent exposure, it is technically demanding, invasive, and associated with prolonged operative times, considerable blood loss, and approach-related morbidity such as heterotopic ossification and wound complications [8, 9]. These drawbacks are particularly relevant in older patients with reduced bone quality, comorbidities, and limited physiological reserves [1].

To overcome the limitations of traditional anterior approaches and to improve medial visualization, access to the quadrilateral plate, and management of superomedial dome impaction, less invasive anterior intrapelvic exposures were developed [10]. The modified Stoppa approach provides intrapelvic access to the anterior and posterior columns and allows direct buttressing of the quadrilateral plate, although its ability to address superomedial dome impaction and to control the medial aspect of the anterior column remains limited [11–15].

In this context, the Pararectus approach was introduced as an anterior intrapelvic, extraperitoneal exposure that combines key advantages of the ilioinguinal and modified Stoppa approaches [16, 17]. Anatomical and early clinical studies confirmed its feasibility, safety, and wide visualization of the pelvic brim, true pelvis, and quadrilateral plate [17, 18]. Subsequent retrospective analyses demonstrated favorable reduction and low approach-related morbidity in the initial clinical series [15, 18]. Clinical reports from centers outside the developer’s institution have shown comparable reduction quality, complication rates, and reproducibility [19–23]. Systematic reviews and meta-analyses have further shown that the Pararectus approach achieves comparable or superior reduction quality, lower intraoperative blood loss, and similar complication profiles relative to other anterior intrapelvic and ilioinguinal exposures [24]. A recent network meta-analysis found that intrapelvic approaches, including the Pararectus approach, performed more favorably than the ilioinguinal approach across key clinical outcomes, reinforcing the Pararectus approach as a reliable and established anterior option for acetabular fracture fixation [25].

This study aims to provide evidence on the reproducibility and learnability of the Pararectus approach. Thus, we hypothesized that the outcome in the first 50 patients operated by the approach’s inventor (MJBK, group A) and the first 50 patients operated independently by a surgeon not previously specialized in acetabular surgery (JDB, group B) would be comparable. Accordingly, operative parameters, radiological quality of reduction, and short-term outcomes (complications, reoperations, conversion to total hip arthroplasty) were compared between the two cohorts.

Patients and methods

Study design, patient selection and demographics

This retrospective comparative cohort study was approved by the local institutional ethics committee (Kantonale Ethikkommission Bern, Switzerland, Project ID 2023 − 01747) and conducted in accordance with the Declaration of Helsinki. The analysis included the first 50 consecutive patients treated via the Pararectus approach by the senior acetabular surgeon (MJBK, group A) between August 2009 and July 2013, and the first 50 consecutive patients treated independently by the early-career acetabular surgeon (JDB, group B) between August 2017 and December 2021. These two time periods corresponded to the establishment phase and the subsequent independent application phase of the Pararectus approach at our institution.

Patients presenting with displaced acetabular fractures suitable for management through the Pararectus approach were included and classified according to the system of Judet and Letournel [6]. Thirty-nine patients were excluded based on predefined criteria: Fracture configurations requiring an additional posterior approach (group A: n = 10, group B: n = 3), previous ipsilateral hip surgery (group A: n = 9, group B: n = 4), advanced, preexisting osteoarthritis necessitating primary acute total hip arthroplasty (group A: n = 4, group B: n = 1), pathological fractures secondary due to malignancy (group A: n = 2), or incomplete documentation (group A: n = 6). Accordingly, the effective caseload during the study periods comprised 81 eligible cases for group A and 58 for group B, of which 50 consecutive cases per group fulfilled all inclusion criteria and were analyzed (Table 1).

Table 1.

Patients’ demographics, mechanisms of injury, fracture characteristics, and surgical details in 100 patients treated with the Pararectus approach (50 cases operated by the senior acetabular surgeon (group A) and 50 cases by the early-career acetabular surgeon (group B). Data are presented as mean ± standard deviation (SD), or as median (range), and as number (percentage) for categorical variables

Parameter	Group A (n = 50)	Group B (n = 50)	p-value
Age (years)	64 (16–93)	73 (19–93)	0.001
Female gender, n (%)	9 (18)	7 (14)	0.786
Body mass index (kg/m2)	25	23	0.053
ASA score (median)	2	3	0.384
Previous abdominal surgery, n (%)	8 (16)	11 (22)	0.61
with mesh implantation	5 (10)	7 (14)
Mechanism of injury			< 0.001
Low-energy trauma, n (%)	27 (54)	44 (88)
High-energy trauma, n (%)	23 (46)	6 (12)
Fracture classification (Letournel)			0.51
Anterior column	4 (8)	6 (12)
Transverse	2 (4)	2 (4)
T-shaped	2 (4)	0 (0)
ACPHT	31 (62)	27 (54)
Both column	11 (22)	15 (30)
Fracture morphology
Dome impaction with disimpaction, n (%) (intraoperatively identified)	22 (44)	11 (22)	0.03
Medialisation of femoral head preoperatively (mm), CT	6.7 (0–32)	10.5 (-3-26)	0.019
Cranialisation of femoral head preoperatively (mm), CT	6.0 (3–28)	7.0 (17–28)	0.41
Surgical approach			1.00
Pararectus only	40 (80)	41 (82)
Pararectus + other (Smith-Petersen, Ilioinguinal 1st window)	10 (20)	9 (18)
Use of a suprapectineal plate, n (%)	0 (0)	50 (100)	< 0.001
Length of hospital stay (days)	10	9	0.28
Last follow-up (years)	5 (0.1-9.0)	2.2 (0.1–7.8)	< 0.001

The mean age was 64 years (range 16–93) in group A and 73 years (range 19–93) in group B (p = 0.001). There were no significant differences between groups regarding gender distribution, body mass index, ASA classification, previous abdominal surgery, or fracture configuration. However, high-energy trauma was more frequent in group A (group A: 46% vs. group B: 12%, p < 0.001), whereas low-energy trauma predominated in group B (group A: 54% vs. group B: 88%, p < 0.001). Fracture morphology according to the classification of Judet and Letournel was comparable between groups (p = 0.51). The majority of cases in both cohorts were anterior column with posterior hemitransverse (ACPHT) fractures (group A: 62%, group B: 54%), followed by both-column fractures (22% vs. 30%). Less frequent patterns included anterior column fractures (group A: 8% vs. group B: 12%), transverse fractures (group A: 4% vs. group B: 4%), and T-shaped fractures (group A: 4% vs. group B: 0%).

All procedures were performed according to a standardized Pararectus workflow as previously described in detail by Keel et al. [16, 17]. Patients were positioned supine on a radiolucent operating table or radiolucent extension table (Hana^® table, Mizuho OSI, Union City, CA, USA). When a traction table was used, mild hip flexion was applied dynamically to reduce iliopsoas and vascular tension, with positioning adjusted intraoperatively. Fluoroscopic imaging was performed with the image intensifier positioned on the fractured side and the operating surgeon standing on the contralateral side. Using this setup, standard ala and obturator views required for acetabular fracture fixation could be obtained reliably. Inlet and outlet views may be limited by the table column; however, this did not affect acetabular fracture surgery in the present series. In rare cases of very high anterior column fractures requiring extensive cranial imaging, positioning on a conventional radiolucent operating table was considered as an alternative. A table-mounted ring retractor system (SynFrame^®, DePuy Synthes, USA) was used in selected early cases but was not part of the later standardized setup. Accordingly, the Pararectus approach was performed in institution with established experience in intrapelvic trauma surgery and access to multidisciplinary support, including general, vascular, and urological surgical expertise on demand, advanced anesthesiological management, blood bank services, and interventional radiology when required.

In the early series (group A), conventional 3.5-mm reconstruction and infrapectineal buttress plates were used, while in the later series (group B) a precontoured suprapectineal plate system (Stryker^®, USA) was routinely employed (p < 0.001), allowing standardized fixation. Reduction was achieved under direct intrapelvic visualization and verified fluoroscopically. The mean length of hospital stay was 10 days for group A and 9 days for group B (p = 0.28).

Clinical evaluation

Clinical and perioperative outcomes were retrospectively evaluated for both groups using prospectively collected and documented operative and follow-up data. Parameters assessed included operative time and intraoperative blood loss, extracted from anaesthetic and operative reports, as well as the incidence of intra- and postoperative complications, as documented in the institutional hospital information system. Intraoperative complications comprised vascular or visceral injuries and events related to osteosynthesis material or instrumentation, while postoperative surveillance included wound-related and surgical site infection complications, neurological deficits, hernia-related events, and vascular or implant-related complications.

Routine clinical and radiological follow-up examinations were performed on the first postoperative day and subsequently at six weeks, and at three, six, twelve, and twenty-four months postoperatively, with extended follow-up up to five years when available. Standard radiographs were obtained at all follow-up visits, while computed tomography (CT) was performed postoperatively to assess the quality of reduction. Clinical outcomes included reoperations and conversion to total hip arthroplasty (THA) within twenty-four months after the index procedure. The latter was defined as failure of osteosynthesis according to previously published definitions in acetabular fracture outcome studies [4, 5].

Radiographic evaluation

All patients first underwent standardized radiographic imaging consisting of an anteroposterior pelvic view and 45-degree oblique iliac and obturator views. Preoperative CT was performed for detailed assessment of fracture morphology, and postoperative CT was used to evaluate the quality of reduction. Fracture configuration was classified according to the system of Judet and Letournel [6]. Postoperative reduction was evaluated on axial, coronal, and sagittal reformations. The maximal articular step-off within the subchondral roof arc was measured, and reduction quality was graded according to the criteria of Matta as anatomical when residual displacement was ≤1 mm, imperfect when between 1.1 and 3 mm, and poor when >3 mm [4, 26].

To further assess the accuracy of reduction, mediolateral and craniocaudal displacement of the femoral head were quantified using three-dimensional reformations as described in previous CT-based analyses [27]. Mediolateral displacement (medialisation) was measured as the perpendicular distance from the centre of the femoral head to a sagittal reference plane extending through the symphysis anteriorly and the sacrum posteriorly, while craniocaudal displacement (cranialisation) was determined as the perpendicular distance from the centre of the femoral head to an axial reference plane defined through the L5/S1 disc space. To ensure accuracy, the same measurements were performed on the contralateral, uninjured side, and the inter-side difference was used to define residual displacement. Measurements were performed independently by musculoskeletal fellowship trained radiologists.

Statistical analysis

Follow-up duration was recorded in months and expressed as median with range. Continuous variables were expressed as mean±standard deviation (SD) or median (range), depending on the distribution, while categorical variables were reported as absolute numbers and percentages. The assumption of normality for continuous data was tested using the Shapiro–Wilk test. Comparisons between the group A and B were performed using independent-samples t-tests or Mann–Whitney U-tests for continuous variables and Fisher’s exact or Chi-square tests for categorical variables. All analyses were two-sided, and a p-value < 0.05 was considered statistically significant. Statistical calculations were performed using IBM SPSS Statistics (Version 29.0, IBM Corp., Armonk, NY, USA).

Results

The median operative time was 172 min (range 50–339), and the median intraoperative blood loss was 1000 milliliters (250–6000) for patients treated by the senior acetabular surgeon (group A). In the cohort operated by the early-career acetabular surgeon (group B), the median operative time was 165 min (range 90–266), and the median intraoperative blood loss was 900 milliliters (200–4500). There was no statistically significant difference between groups in operative time (p = 0.19) or blood loss (p = 0.09) (Table 2).

Table 2.

Operative data, intra- and postoperative complications, and clinical outcomes in 100 patients treated with the Pararectus approach (50 cases operated by the senior acetabular surgeon (group A) and 50 cases by the early-career acetabular surgeon (group B)). Data are presented as mean ± standard deviation (SD), or as median (range), and as number (percentage) for categorical variables

Parameter	Group A (n = 50)	Group B (n = 50)	p-value
Operative time (min)	172 (50–339)	165 (90–266)	0.19
Intraoperative blood loss (ml)	1000 (250–6000)	900 (200–4500)	0.09
Quality of reduction, n (%)			0.17
Anatomical	36 (72)	31 (62)	0.31
Imperfect	14 (28)	16 (32)	0.68
Poor	0 (0)	3 (6)	0.24
Intraoperative complications, n (%)	5 (10)	3 (6)	0.71
Peritoneal perforation	2 (4)	2 (4)
Vascular injury	3 (6)	1 (2)
All postoperative complications, n (%)	7 (14)	5 (10)	0.75
Transient neurological paralysis	0	2 (4)
Intraarticular screw without revision	0	1 (2)
Secondary screw displacement	0	1 (2)
Reoperations ≤ 30 days, n (%)	7 (14)	1 (2)	0.06
Vascular bleeding	1 (2)	0
Ogilvie’s syndrome with cecal perforation	1 (2)	0
Persistent displacement, dome impaction, intraarticular screw, overlong screw	5 (10)	1 (2)
Conversion to THA ≤ 24 months, n (%)	5 (10)	2 (6)	0.70
Time to THA (months after index surgery)	13.8	5.8	0.22

Marked differences in the operative setup and instrumentation were observed between both series. In group A, none of the patients were treated on an extension table, and precontoured suprapectineal plates were not available at that time. Instead, low-profile small-fragment and standard reconstruction plates were used along the pelvic brim after being manually bent and contoured. A subtrochanteric pin was applied for femoral head retraction in 40 patients, and additional iliac-crest pinning was required in three cases. Dome impaction was identified intraoperatively in 23 patients; in 22 cases, the impaction was disimpacted and the defect was grafted (Fig. 1), while in one patient disimpaction was not performed because the remaining small, centrally located depression in the acetabular fossa was intraoperatively inaccessible and judged to be clinically insignificant based on CT and direct visualization. Vascular structures encountered intraoperatively included ligation or clipping of two iliolumbar vessels and seven corona mortis anastomoses.

Fig. 1.

(A) Preoperative anteroposterior pelvic radiograph showing a displaced anterior column posterior hemitransverse (ACPHT) fracture with superomedial dome impaction in an 82-year-old patient; (B) Postoperative radiograph following disimpaction, allograft filling, and buttressing with horizontal screws and reconstruction plates; (C) Coronal CT section demonstrating preoperative dome impaction (“brick sign”) [28]; (D) Postoperative CT confirming anatomic reduction and stable medial-to-lateral screw fixation

In contrast, in group B, all patients were treated on an extension table (Hana^® table, Mizuho OSI, Union City, CA, USA), and a precontoured suprapectineal plate system (PRO Pelvis Pelvic and Acetabulum Plating System, Stryker^®, Kalamazoo, MI, USA) was routinely used in all 50 cases. Only one patient required additional iliac-crest pinning. Dome impaction was intraoperatively identified in 12 patients, of whom 11 underwent disimpaction and allograft filling (Fig. 2). In one case, disimpaction was omitted because the dorsal impaction and small posterior wall fragment could not be adequately reduced under fluoroscopy while the hip remained stable, and further reduction was therefore not pursued. Vascular structures encountered intraoperatively included eight iliolumbar vessels and 25 corona mortis anastomoses, all of which were clipped or ligated as required.

Fig. 2.

(A) Preoperative anteroposterior pelvic radiograph showing a displaced ACPHT fracture with dome impaction in an 88-year-old patient; (B) Postoperative radiograph after disimpaction, allograft filling, and buttressing with horizontal screws and suprapectineal plate; (C) Coronal CT section showing preoperative impaction of the superomedial dome (“brick sign”) [28]; (D) Postoperative CT confirming anatomic reduction and stable reconstruction through the Pararectus approach

Anatomical reduction on postoperative CT was achieved in 36 patients (72%) in group A and 31 patients (62%) in group B (p = 0.31), while imperfect reductions were observed in 14 (28%) and 16 (32%), respectively (p = 0.68). Poor reductions (> 3 mm residual displacement) occurred in none of the group A cases and in three patients (6%) in group B (p = 0.24). Although the senior surgeon achieved a slightly higher proportion of anatomical reductions, the difference between groups did not reach statistical significance (p = 0.17).

Intraoperative complications in group A occurred in 5 of 50 cases (10%) (Table 2). Two small peritoneal perforations were identified and managed intraoperatively, and three vascular lesions (vena iliaca communis, vasa epigastrica, arteria obturatoria) were treated by ligation or suture repair without further sequelae. An inguinal hernia was encountered incidentally in one patient (2%) and was revised during the index procedure. Eight of 50 patients (16%), with a median age of 80 years (range 61–93), had a history of previous abdominal surgery, including five with prior mesh repair; dissection in these areas was unproblematic. No patient developed a postoperative hernia during follow-up. Within 30 days of the index procedure, seven reoperations (14%) were required. One revision on postoperative day two was performed for recurrent arterial bleeding from the superior gluteal artery. Another revision was required for paralytic ileus with caecal perforation due to Ogilvie’s syndrome. One patient underwent exchange of an overlong screw protruding toward the greater sciatic notch. Two patients required revision for persistent posterior-superior dome impaction with a residual step, and one patient for persistent displacement of the posterior column and posterior rim associated with intraarticular screws. The final revision addressed a dorsal gap with loss of containment at the transverse component.

Intraoperative complications in group B occurred in 3 of 50 cases (6%) (Table 2). Two small peritoneal perforations were identified and managed intraoperatively. One vascular injury of the vena iliaca externa was treated intraoperatively by suture repair without sequelae. Eleven of 50 patients (22%), with a median age of 78 years (range 67–91), had a history of previous abdominal surgery, including seven with prior mesh repair; dissection in these areas was unproblematic. No patient developed a postoperative hernia during follow-up. Within 30 days of the index procedure, one patient required reoperation for an overlong posterior column screw. Additional postoperative events included detection of an intra-articular screw position without revision, transient traction-related neurological deficits, and obturator nerve hyperalgesia associated with a small hematoma, all of which resolved with conservative management. At six-week follow-up, one asymptomatic secondary screw displacement was observed without need for revision.

In group A, five patients died within two years without undergoing THA and four were lost to follow-up, leaving 41 patients with at least 24 months of evaluable data. In group B, 12 patients died within two years without THA and seven were lost to follow-up, resulting in 31 evaluable patients. The median overall follow-up duration for the entire cohort was 5.0 years (range < 0.1-9.0) in group A and 2.2 years (range < 0.1–7.8) in group B (p < 0.001). Within 24 months of the index procedure, conversion to total hip arthroplasty occurred in 5 of 41 patients (12%) with available follow-up in group A and 2 of 31 patients (6%) in group B (p = 0.70); the mean time to THA was 13.8 months in group A and 5.8 months in group B (p = 0.22).

Discussion

The Pararectus approach has become a widely accepted minimally invasive technique for anterior acetabular fracture fixation, particularly in older patients, as it enables disimpaction of superomedial dome fragments under full visual control [16, 29, 30]. However, evidence on its reproducibility and learnability in less experienced hands outside the developer’s environment has remained limited. The present study directly compares the outcomes of the first 50 cases performed by the approach’s inventor with the first 50 cases of a surgeon without prior acetabular specialization.

Operative times, intraoperative blood loss, reduction quality, and rates of reoperation or conversion to total hip arthroplasty were comparable between the two cohorts, despite notable differences in the surgeons’ experience levels, with the senior surgeon having many years of independent practice and extensive pelvic and acetabular exposure, while the early-career surgeon performed his first independent cases during early subspecialty training. Intraoperative complications were infrequent in both cohorts and were managed safely without sequelae. Group A showed a higher number of reoperations within 30 days, almost exclusively related to residual displacement or implant issues rather than approach-specific morbidity. In contrast, group B exhibited fewer reoperations but a slightly higher number of minor postoperative events, including transient neurological symptoms and isolated implant-related findings that resolved or required no revision.

Beyond the quantitative results, several qualitative factors further explain the minor differences observed between both cohorts. MJBK, as the developer of the Pararectus approach, initially introduced and refined the technique during its implementation phase. His extensive background in pelvic and acetabular fracture surgery, including experience with the modified Stoppa and other anterior intrapelvic approaches, was instrumental in establishing the Pararectus access route and defining its anatomical windows. However, as with any new surgical technique, continuous intraoperative modifications were required, which dynamically influenced outcomes such as operating time and intraoperative blood loss. Notably, routine ligation of the corona mortis became standardized early, whereas systematic ligation of the iliolumbar vessels was adopted only after 2011. This is consistent with the vascular anatomy encountered during intrapelvic exposures, where corona mortis anastomoses and iliolumbar vessels are frequently present and require systematic identification and control. Recent data from a large cohort analysis [31] further underscore the high prevalence and variability of these vessels in anterior acetabular fracture patterns, supporting the relevance of standardized vascular exposure during the Pararectus approach. Beyond the first 50 cases, additional refinements such as the transition to traction-table positioning and the introduction of precontoured suprapectineal plates, which reduced operative time by eliminating the need for manual plate contouring, progressively improved the efficiency of the approach. In parallel, a standardized sequence of reduction - beginning with anterior column alignment and suprapectineal plate placement, followed by restoration of the quadrilateral surface and final posterior column realignment using a collinear reduction clamp - was established, offering a reproducible workflow even early in the learning curve. Together, these developments reflect the real-world evolution of the Pararectus approach from its developmental phase to a more mature and standardized application and may have influenced operative parameters independently of surgeon experience, thereby masking aspects of the true learning curve.

Independent use of the Pararectus approach by the surgeon in group B began in August 2017, from the outset with this standardized traction-table setup. In addition, the surgeon in group B had participated in the early developmental phase of the approach and had assisted in multiple group A procedures, which facilitated the adoption of the standardized technique. Consequently, he entered his clinical learning curve with a comprehensive anatomical understanding, hands-on experience from dissections and live cases, and immediate access to the fully standardized setup, including the use of the traction-table, routine iliolumbar vessel ligation, and the dedicated Stryker suprapectineal plate system. Although he was less experienced as an acetabular surgeon overall, these technical and logistical optimizations compensated for the expected learning curve effects, allowing his first 50 independent cases to achieve outcomes comparable to those of the senior surgeon. Both surgeons accumulated additional experience with the Pararectus approach outside the study cohort, as the technique was increasingly adopted for other indications such as pelvic ring injuries and revision procedures. Both surgeons had additional exposure to the Pararectus approach before the start of their 50 independent study cases; therefore, the cases included in this analysis reflect only the first consecutive independently performed acetabular procedures meeting the study criteria. This broader experience likely contributed to the procedural consistency observed across both series and supports the concept that once the approach and its technical principles are standardized, reproducible outcomes can be achieved even by surgeons in the earlier stages of their acetabular specialization.

The conversion rate to THA within 24 months remained low (12% in group A vs. 6% in group B), well below the 17–45% reported after isolated ORIF in the current literature [32] and even lower than the 13% conversion rate observed in the original Pararectus series by Keel et al. [18] and the 0–17% range reported for the modified Stoppa approach in the comparative literature [11, 13, 18, 33]. However, these comparisons must be interpreted with caution, as follow-up durations and patient characteristics differ between studies, and the present analysis was not designed to assess predictors of joint survival.

This study has several limitations. Its retrospective design carries inherent risks of selection bias, incomplete data capture, and uncontrolled confounding. The two cohorts were treated in different time periods, during which surgical instrumentation and perioperative workflows evolved substantially. The availability of precontoured suprapectineal plate systems and routine traction-table positioning in the later cohort may have improved procedural efficiency and reduced technical variability, potentially influencing outcomes independently of surgeon experience and masking aspects of the true learning curve. Although consecutive and well matched for most baseline parameters, the cohorts differed in patient demographics and trauma mechanisms, with a higher proportion of high-energy injuries in the younger patients of group A and predominantly low-energy trauma in the older patients of group B. Differences in injury mechanism and bone quality may have influenced fracture complexity, reduction difficulty, and fixation stability and thus represent additional potential confounding factors. As these were consecutive real-world case series, patient demographics and injury characteristics were not subject to experimental control and reflect routine clinical practice rather than predefined biomechanical conditions. Follow-up duration differed between the two cohorts, with a longer median follow-up in group A than in group B. While this may theoretically increase the likelihood of detecting late complications, the primary outcome of this study was early failure defined as conversion to total hip arthroplasty within 24 months after surgery. Previous long-term survivorship studies have demonstrated that most conversions to THA after acetabular fracture fixation occur within the first two years [5]. Accordingly, THA rates were assessed within a predefined and identical observation period for both cohorts, independent of total follow-up length. Functional outcome data were not consistently available due to the retrospective study design; therefore, the analysis was confined to early conversion to total hip arthroplasty as an objective and clinically relevant endpoint, particularly in an older patient population in whom avoidance of secondary procedures is critical. Another limitation is the prior exposure of the early-career surgeon to the Pararectus approach through cadaveric training and participation in earlier cases, which may overestimate learnability for surgeons without such preparation. However, this reflects a structured training pathway typical of contemporary surgical education rather than an untrained learning scenario. Finally, the relatively small sample size and low number of events limited statistical power for subgroup analyses and precluded reliable multivariate adjustment for potential confounders such as age, injury mechanism, or fracture complexity.

Beyond the methodological limitations, from a clinical perspective, the safe application of intrapelvic approaches also depends on an appropriate institutional setting. While immediate on-site vascular surgery is not considered mandatory, access to general, vascular, and urological surgical expertise on demand is clearly advantageous. Furthermore, access to interventional radiology should be available, as selective angioembolisation may be required in selected cases either preoperatively or as a rescue strategy for bleeding control [34].

The study also has notable strengths. It represents the first systematic comparison of two independent surgeons with identical case numbers and standardized imaging criteria, focusing on the learnability of the Pararectus approach. The inclusion of 100 consecutively operated cases, objective CT-based reduction measurements, and detailed complication reporting provides insight into the natural evolution of the technique from its experimental development phase to its standardized clinical application.

The findings of this study have practical implications. They indicate that the Pararectus approach can be safely adopted, provided that standardized instrumentation and training are available. Its ability to directly visualize and reconstruct the quadrilateral plate and superomedial dome makes it particularly suitable for the typical osteoporotic fracture morphologies now seen in the older population.

In conclusion, the Pararectus approach for acetabular fracture fixation proved to be safe, reproducible, and learnable when applied within a standardized surgical environment. Comparable operative parameters, reduction quality, and clinical outcomes were observed between the senior and the early-career surgeon, despite differences in overall experience. While acknowledging that surgical experience remains important in acetabular fracture management, these findings suggest that, within a modern standardized technical environment, acceptable and reproducible outcomes can be achieved during early independent practice.

Author contributions

R.S.: Writing – original draft, Investigation, Methodology, Formal analysis. S.I.: Writing – original draft, Writing – review & editing, Investigation, Methodology, Formal analysis. C.L.: Methodology, Investigation, Formal analysis. R.E.: Writing – review & editing, Validation, Supervision, Methodology, Investigation, Formal analysis, Conceptualization. H. B.: Validation, Supervision, Methodology, Investigation, Formal analysis. M.K.: Writing – review & editing, Conceptualization, Methodology, Investigation. J.B.: Writing – review & editing, Supervision, Project administration, Methodology, Conceptualization.

Funding

No funding was received for this study.

Data availability

No datasets were generated or analysed during the current study.

Declarations

Ethical approval

This retrospective comparative cohort study was approved by the local institutional ethics committee (Kantonale Ethikkommission Bern, Switzerland, Project ID 2023 − 01747) and conducted in accordance with the Declaration of Helsinki.

Competing interests

The authors declare no competing interests.