Abstract
Background and Aim
A tibial plateau fracture is an intra-articular fracture that affects the function and stability of the knee joint and requires careful evaluation and pre-operative planning. We determined the posterior tibial slope changes after tibial plateau fracture stabilization, aiming to help improve surgical success in maintaining the lower limb’s natural axis.
Methods
This retrospective case series involved all Golestan and Imam Khomeini hospital patients (Ahvaz, Iran) with Schatzker type IV–VI tibial plateau fractures from April 1, 2017, to March 30, 2020, who underwent surgical fixation. Data on the age, gender, body mass index (BMI), surgical approach, posterior tibial slope angle in the injured and healthy knees, pain, and knee joint instability were collected. We analyzed the data using SPSS version 22 and considered a significance level of P < 0.05.
Results
Among the 31 study participants, 24 (77.4%) were males. The mean age of the patients was 39.81 ± 14.41 years (21–78), with a mean BMI of 25.4 ± 2.7 (20.3–31.2) kg/m2 and hospitalization duration of 5.8 ± 9.3 days (3–29). Most patients had type VI fractures (48.3%). The posterior tibial slope angle shared no relation with age, gender, BMI, or surgical approach (P > 0.05). After tibial plateau fracture fixation, the posterior tibial slope angle significantly increased in the injured knee compared with the healthy knee (P < 0.05). Six months after the operation, the angle of the injured knee decreased but remained higher than that of the healthy knee (P > 0.05).
Conclusion
The tibial slope’s posterior column collapses more than its anterior column over time, reducing the posterior tibial slope angle. Therefore, the correct reduction of the tibial plateau’s posterior slope is more important.
Keywords: Tibial plateau fracture, Posterior tibial slope, Fixation, Knee joint
Introduction
A tibial plateau fracture is an intra-articular fracture representing 1.9–4% of all fractures [1]. Most cases are seen in people aged 30–60 [2]. However, with the improvement in life expectancy, the incidence of tibial plateau fractures in elderly patients is increasing [3]. Complex bicondylar fractures involve the separation of the articular part from the metaphysis or diaphysis with a change in the articular surface slope of the tibial bone (Schatzker type VI); such cases account for approximately one-fifth (20%) of tibial plateau fractures, representing the most challenging fracture pattern [4]. While the optimal surgery method for such fractures remains uncertain, maintaining the angles and axis of the lower limb is crucial in all reconstructive surgeries of the lower limb around the knee [5].
The tibial plateau slope angle is a major parameter in the biomechanics of the knee joint that affects its anterior–posterior stability, varus/valgus laxity, anterior cruciate ligament (ACL) stretching, flexion gap, and posterior femoral rollback [6, 7]. Also, the tibial slope is a significant factor in weight-bearing and implant design [8, 9]. Radiographic studies estimate the mean posterior tibial slope (PTS) at 13.6 ± 3.4° (range 3.8–23.9°). Alterations in the PTS may affect scissor forces on the tibia, anterior displacement of the tibia, and forces on the ACL. Therefore, an altered or reversed PTS may lead to poor clinical outcomes in tibial plateau fractures despite joint reduction and fracture union.
Despite the importance of restoring the correct tibial slope during injury management, there is limited work on optimal alignment in the sagittal plane during the repair of proximal tibial plateau fractures. The present study aimed to determine the PTS angle after fixation of the tibial plateau fracture in patients hospitalized in Ahvaz teaching hospitals, aiming to help improve surgical success in maintaining the lower limb's natural axis.
Methods
Study Design
This retrospective case series involved all Golestan and Imam Khomeini hospital patients (Ahvaz, Iran) with Schatzker type IV–VI tibial plateau fractures from April 1, 2017, to March 30, 2020, who underwent surgical fixation. The Ahvaz Jundishapur University of Medical Sciences Ethics Committee approved the study proposal, and all participants provided informed consent for inclusion. The inclusion criteria encompassed all patients with Schatzker type IV–VI tibial plateau fractures fixed surgically via the anterolateral (single) or anterolateral-medial (double) approach.
A computed tomography (CT) scan of the injured knee was obtained before fracture fixation to classify the fracture. Radiography of the injured knee was obtained in the lateral and anteroposterior views before and immediately after surgery, while both knees were imaged six months later. A radiologist evaluated the PTS of the medial compartment using the PACS system. The PTS was defined as the angle between the vertical line of the tibia's anatomical axis and the tibial plateau's tangent in the lateral X-ray [6]. Measurement of the PTS in a healthy knee is shown in Fig. 1.
Fig. 1.
Measurement of the posterior tibial slope (PTS) in a healthy knee
All patients' demographic characteristics (age, gender), body mass index (BMI), surgical approach, PTS in the injured knee immediately and six months after surgery, and PTS in the healthy knee were recorded in a data collection form.
Participants
A total of 285 patients were diagnosed with a tibial plateau fracture from April 1, 2017, to March 30, 2020, including 173 (60.8%) at Golestan Hospital and 112 (39.2%) at Imam Khomeini Hospital. Among them, 14.3% (41) patients had Schatzker type IV–VI tibial plateau fractures, including 15% (26/173) of patients at Golestan Hospital and 13% (15/112) of patients at Imam Khomeini Hospital. Of these patients, 31 completed the six-month follow-up and were analyzed in this study.
The patients were advised non-weight-bearing movements for the first six weeks after surgery and partial weight-bearing for the next six weeks.
Data analysis
Data were analyzed using SPSS version 22. We summarized continuous variables using the mean, standard deviation, and range. Using the Independent samples t test and analysis of variance (ANOVA), we compared the variables and assessed differences in ratios. The Pearson and Spearman statistical tests were used to check correlations. Significance was considered at P < 0.05.
Results
Among the 31 study participants, 24 were males (77.4%), and 7 (22.6%) were females. The mean age was 39.81 ± 14.41 years (21–78), with a BMI of 25.4 ± 2.7 (20.3–31.2) kg/m2 and hospitalization duration of 5.8 ± 9.3 days (3–29; median: 8). Most patients had type VI fractures (48.3%) (Table 1).
Table 1.
Characteristics of the study participants
| Variable | Mean ± SD | Frequency (%) |
|---|---|---|
| Age (years) | 39.81 ± 14.41 | – |
| Gender | ||
| Male | – | 24 (77.4) |
| Female | – | 7 (22.6) |
| Body mass index (kg/m2) | 25.4 ± 2.7 | – |
| Duration of hospitalization (days) | 9.3 ± 5.8 | – |
| Schatzker classification | ||
| IV | – | 7 (22.6) |
| V | – | 9 (29.1) |
| VI | – | 15 (48.3) |
Twenty-three patients (74.2%) underwent anterolateral-medial surgery, seven (22.6%) anteromedial, and one (3.2%) underwent anterolateral-medial and posterior surgery. During the follow-up visit, ten patients (32.3%) complained of knee pain in the injured knee. Two patients had an instability in the injured knee (6.5%).
The mean PTS in the injured knee immediately after surgery was 7.4 ± 1.7° with a range of 3.3–13.5°. Six months later, the PTS was 6.18 ± 1.6° with a range of 3.5–11.2°, while the mean PTS in the healthy knee was 6.1 ± 1.4° with a range of 3.2–10.5°.
The difference between immediate postoperative and follow-up (6 months) PTS angles had no relationship with age (P = 0.311), gender (P = 0.204), BMI (P = 0.316), fracture type (P = 0.077), knee instability (P = 0.179), knee pain, or surgical approach (P = 0.479) (Table 2).
Table 2.
The difference between immediate postoperative and follow-up (6 months) posterior tibial slope (PTS) angles in relation to other study variables
| Variable | PTS immediately after surgery, ° (Mean ± SD) | PTS 6 months after surgery, ° (Mean ± SD) | P value |
|---|---|---|---|
| Gender | |||
| Male | 7.58 ± 1.86 | 6.55 ± 1.6 | 0.204* |
| Female | 6.38 ± 2.02 | 5.27 ± 1.9 | |
| Knee (patella) instability | |||
| Yes | 6.6 ± 5.6 | 4.75 ± 0.07 | 0.179* |
| No | 7.58 ± 2 | 6.26 ± 1.76 | |
| Tibial plateau fracture type | |||
| IV | 7.34 ± 1.74 | 5.97 ± 1.49 | 0.077** |
| V | 8 ± 1.98 | 6.75 ± 1.63 | |
| VI | 7.31 ± 211 | 6.11 ± 2.03 | |
| Knee pain | |||
| Yes | 7.02 ± 1.86 | 5.64 ± 1.6 | 0.624* |
| No | 7.51 ± 1.95 | 6.56 ± 1.8 | |
| Surgical approach | |||
| Anterolateral-medial | 7.34 ± 1.74 | 5.97 ± 1.49 | 0.479** |
| Antero-medial | 7.59 ± 2.08 | 6.37 ± 1.92 | |
| Anterolateral-medial and posterior | 7.51 ± 1.95 | 6.2 ± 1.78 | |
Significance level: P < 0.05
*Independent samples t test
**Analysis of variance (ANOVA)
The mean PTS angles of the injured and healthy knees were significantly different. The mean PTS of the injured side immediately after fixation was greater than that of the healthy side (P < 0.001). Six months later, the PTS of the injured side decreased yet remained significantly greater than that of the healthy side (P < 0.001) (Table 3).
Table 3.
Statistical analysis of posterior tibial slope (PTS) angles in comparison with the healthy knee
| Healthy knee PTS, ° | Injured knee PTS, ° | P value | |
|---|---|---|---|
| Immediately after surgery | 6.1 ± 1.4 | 7.4 ± 1.7 | < 0.001 |
| Six months after surgery | 6.18 ± 1.6 | < 0.001 |
Significance level: P < 0.05
Discussion
Proximal tibial fractures affect the knee joint’s stability and function, with the ultimate therapeutic aim being to restore normal functioning. Restoring normal anatomy and ligament stability is paramount in achieving a pain-free joint with a fixed mechanical axis [10]. One issue overlooked in tibial plateau fractures is the posterior tibial slope (PTS) disruption. Alterations in the PTS may affect the rotational forces on the tibia, the anterior translation of the tibia, and the force on the ACL [10].
In this study, we determined the PTS after tibial plateau fracture fixation and compared it against the healthy knee in 31 patients admitted to Imam Khomeini and Golestan hospitals in Ahvaz, Iran. The mean PTS in the injured knee was 7.4 ± 1.7° immediately after surgery and 6.18 ± 1.6° six months after surgery. On the other hand, the mean PTS in the healthy knee was 6.1 ± 1.4°. We found that the PTS in the injured knee immediately after fixation was significantly higher compared with the normal knee. Six months after reduction and fixation, the severity of the slope decreased but remained significantly greater than that of the normal knee. It should be noted that the PTS in the injured knee remained within the normal range. Karimi et al. reported that the minimum normal medial compartment PTS in Iran is 2.4°, with a maximum of 13.9° [5].
Streubel et al. examined 74 similar patients and found that the PTS changes up to 20° compared with the normal limit in the healthy knee [11]. In contrast, another study on 83 patients demonstrated that most (72.4%) of those with complex fractures had normal PTS values [12]. Erdil et al. found that the mean PTS was 6.91 ± 5.11° after surgery, similar to that of the non-involved side (6.42 ± 4.21°) (P = 0.794). This finding contrasts with our results, perhaps due to the larger sample size in the Erdil et al. study [10].
The PTS angle in the sagittal plane tends to increase after tibial plateau fracture fixation. The theories that can be put forward to explain this issue include the lack of proper fracture reduction, the inaccuracy of knee radiographs and consequent measurement errors, and the anatomical difference between the right and left knees. Over time, the PTS decreases secondary to the collapse of the posterior segment of the tibial plateau slope compared with its anterior segment. During weight-bearing activities, the quadriceps contract the knee's anterior segment, while the hamstrings contract the posterior segment. Due to the greater strength of the quadriceps over the hamstrings, the posterior segment of the knee will collapse more, leading to a reduction in the PTS.
The measurement of the PTS using lateral radiographs has limited accuracy, particularly since the difference between the knee joint’s medial and lateral compartments cannot be precisely evaluated [13, 14], indicating a limitation of the present study. Most of our patients were males. The mean age was 39.81 ± 14.41 years, with a mean BMI of 25.4 ± 2.7 kg/m2. Our finding regarding gender is similar to the study of Streubel et al. on bicondylar tibial plateau fractures, though their patients had a somewhat higher mean age of 49 years [11]. Generally, fractures of the tibial plateau are caused by falling from heights or sports-related injuries and are more common in men with a mean age of 43. However, Qi-fang He et al. found that tibial plateau fractures were more common in older women [15].
In our study, the difference between immediate postoperative and follow-up (6 months) PTS angles had no relationship with fracture type, knee instability, knee pain, or surgical approach. There was also no difference in pain and instability of the injured knee compared with the healthy knee. However, Erdil et al. [10] reported that knee instability and laxity in the anterior–posterior plane were significantly greater in the injured knee after surgery than in the healthy knee. However, they reported no significant difference in the PTS angle between the injured and healthy knees. While Rade-Markers et al. reported anteroposterior instability in roughly 14% of patients with complex tibial plateau fractures, this finding was observed in only 6.5% of our patients [16]. It seems that if there is a difference of less than 15% in the PTS on the injured side relative to the healthy side, it will not increase the pain and instability of the knee joint. Although the PTS did not correlate with instability in our study, minimizing instability with anatomical correction of the PTS is essential for restoring knee function.
Conclusion
When treating a tibial plateau fracture, the main objective is to restore normal anatomy and ligament stability, thereby achieving a pain-free joint with normal function. This case series recorded an increase in the PTS in the injured knee after fracture fixation compared with the normal knee, which can affect the stability of the knee joint and is associated with ligament injuries. It is recommended to avoid inappropriate reduction to prevent such an increase in PTS after a tibial plateau fracture. Also, examining the PTS of the healthy knee joint with intraoperative 3D CT scan imaging can help achieve the correct PTS angle.
Research Limitations
The retrospective design and short follow-up period were the main limitations of this study. As such, we could not alter the surgical approach or use intraoperative CT imaging to achieve more accurate PTS angles. The effects of accompanying injuries to ligaments and menisci could also not be examined. Other limitations included the small sample size, meaning the results should be interpreted cautiously. While we recorded improved outcomes after six months, longer follow-ups period and larger sample sizes containing patients of different genders and ethnicities are necessary. In addition, we recommend CT imaging to separately assess the PTS angle in the knee joint’s medial and lateral compartments, as this is not possible with plain radiography.
Research Proposals
The study findings can assist in planning knee reconstruction surgery using the PTS. As anatomical indices vary across populations, such studies should be conducted in various regions. We also recommend a more extended period of follow-up as better results may be obtained following the further collapse of the tibial plateau’s posterior slope. Finally, preoperative assessment of the normal knee joint’s PTS would help achieve a similar angle in the injured knee, possibly averting postoperative complications related to discrepancies between the two knees.
Acknowledgements
This manuscript was revised regarding language, grammar, and writing quality by a native English-speaking language editor, Dr. Seyed Ali Hosseini (Native Editor Co., Iran).
Data availability
Datasets and their analysis of the present study are available from the corresponding author on reasonable request.
Declarations
Conflict of interest
The authors declare that they have no conflict of interest.
Ethical standard statement
This article does not contain any studies with human or animal subjects performed by the any of the authors.
Informed consent
For this type of study informed consent is not required.
Footnotes
Publisher's Note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
References
- 1.Hong G, Huang X, Lv T, Li X, et al. An analysis on the effect of the three-incision combined approach for complex fracture of tibial plateau involving the posterolateral tibial plateau. Journal of Orthopaedic Surgery and Research. 2020;15(1):43. doi: 10.1186/s13018-020-1572-4. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 2.Albuquerque RP, Hara R, Prado J, Schiavo L, Giordano V, do Amaral NP. Epidemiological study on tibial plateau fractures at a level I trauma center. Acta Ortopedica Brasileira. 2013;21(2):109–115. doi: 10.1590/S1413-78522013000200008. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 3.Court-Brown CM, McQueen MM. Global forum: Fractures in the elderly. Journal of Bone and Joint Surgery. American Volume. 2016;98(9):e36. doi: 10.2106/JBJS.15.00793. [DOI] [PubMed] [Google Scholar]
- 4.Garner MR, Warner SJ, Lorich DG. Surgical approaches to posterolateral tibial plateau fractures. The Journal of Knee Surgery. 2016;29(1):12–20. doi: 10.1055/s-0035-1564731. [DOI] [PubMed] [Google Scholar]
- 5.Karimi E, Norouzian M, Birjandinejad A, Zandi R, Makhmalbaf H. Measurement of posterior tibial slope using magnetic resonance imaging. Archive of Bone and Joint Surgery. 2017;5(6):435–439. [PMC free article] [PubMed] [Google Scholar]
- 6.Genin P, Weill G, Julliard R. The tibial slope. Proposal for a measurement method. Journal of Radiology. 1993;74(1):27–33. [PubMed] [Google Scholar]
- 7.Brandon ML, Haynes PT, Bonamo JR, Flynn MI, Barrett GR, Sherman MF. The association between posterior-inferior tibial slope and anterior cruciate ligament insufficiency. Arthroscopy. 2006;22(8):894–899. doi: 10.1016/j.arthro.2006.04.098. [DOI] [PubMed] [Google Scholar]
- 8.Zhang Y, Wang J, Xiao J, et al. Measurement and comparison of tibial posterior slope angle in different methods based on three-dimensional reconstruction. The Knee. 2014;21(3):694–698. doi: 10.1016/j.knee.2014.01.008. [DOI] [PubMed] [Google Scholar]
- 9.Bae DK, Yoon KH, Song SJ, Noh JH, Kim MH. The change of the posterior tibial slope after cruciate retaining total knee arthroplasty. Journal of the Korean Orthopaedic Association. 2008;43(2):207–212. doi: 10.4055/jkoa.2008.43.2.207. [DOI] [Google Scholar]
- 10.Erdil M, Yildiz F, Kuyucu E, Sayar Ş, Polat G, et al. The effect of sagittal plane deformities after tibial plateau fractures to functions and instability of knee joint. Acta Chirurgiae Orthopaedicae et Traumatologiae Cechoslovaca. 2016;83(1):43–46. doi: 10.55095/achot2016/007. [DOI] [PubMed] [Google Scholar]
- 11.Streubel PN, Glasgow D, Wong A, Barei DP, Ricci WM, Gardner MJ. Sagittal plane deformity in bicondylar tibial plateau fractures. Journal of Orthopaedic Trauma. 2011;25(9):560–565. doi: 10.1097/BOT.0b013e318200971d. [DOI] [PubMed] [Google Scholar]
- 12.Barei DP, Nork SE, Mills WJ, Coles CP, et al. Functional outcomes of severe bicondylar tibial plateau fractures treated with dual incisions and medial and lateral plates. Journal of Bone and Joint Surgery-American Volume. 2006;88(8):1713–1721. doi: 10.2106/00004623-200608000-00004. [DOI] [PubMed] [Google Scholar]
- 13.Gwinner C, Weiler A, Plachel F. Normalwerte—Wie bestimme ich den tibialen Slope richtig? Arthroskopie. 2021;34:10–13. doi: 10.1007/s00142-020-00416-9. [DOI] [Google Scholar]
- 14.Hoch A, Jud L, Roth T, Vlachopoulos L, et al. A real 3D measurement technique for the tibial slope: Differentiation between different articular surfaces and comparison to radiographic slope measurement. BMC Musculoskeletal Disorders. 2020;26:635. doi: 10.1186/s12891-020-03657-9. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 15.He Q-F, Sun H, Shu L-Y, et al. Tibial plateau fractures in elderly people: An institutional retrospective study. Journal of Orthopaedic Surgery and Research. 2018;13(1):276. doi: 10.1186/s13018-018-0986-8. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 16.Rademakers MV, Kerkhoffs GMMJ, Sierevelt IN, Raaymakers ELFB, Marti RK. Operative treatment of 109 tibial plateau fractures: Five- to 27-year follow-up results. Journal of Orthopaedic Trauma. 2007;21(1):5–10. doi: 10.1097/BOT.0b013e31802c5b51. [DOI] [PubMed] [Google Scholar]
Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Data Availability Statement
Datasets and their analysis of the present study are available from the corresponding author on reasonable request.