Surgical technique: aperture fixation in PCL reconstruction: applying biomechanics to surgery

An in-vitro three-dimensional surgical simulation technique to predict tibial tunnel length in transtibial posterior cruciate ligament reconstruction

BACKGROUND

During the transtibial posterior cruciate ligament (PCL) reconstruction, drilling depth excessively longer than the tibial tunnel length (TTL) is an important reason to cause popliteal neurovascular bundle injury when preparing the tibial tunnel. This study aims to develop an in-vitro three-dimensional surgical simulation technique to determine the TTL in anteromedial (AM) and anterolateral (AL) approaches.

METHODS

A total of 63 knees' 3-dimensional (3D) computed tomography models were included in this study. The SuperImage system was used to reconstruct the 3D knee model and locate the tibial PCL site. The established 3D knee model and the coordinates of the tibial PCL site were imported into Rhinoceros 3D modeling software to simulate AM and AL tibial tunnel approaches with different tibial tunnel angles (TTA). The TTL and the tibial tunnel height (TTH) were measured in this study.

RESULTS

In AM and AL tibial tunnel approaches, the TTL showed a strong correlation with the TTA (for AM: r = 0.758, p < 0.001; for AL: r = 0.727, p < 0.001). The best fit equation to calculate the TTL based on the TTA was Y = 1.04X + 14.96 for males in AM approach, Y = 0.93X + 17.76 for males in AL approach, Y = 0.92X + 14.4 for females in AM approach, and Y = 0.94X + 10.5 for females in AL approach.

CONCLUSION

Marking the TTL on the guide pin or reamer could help to avoid the drill bit over-penetrated into the popliteal space to damage the neurovascular structure.

Outcomes of physeal-sparing posterior cruciate ligament reconstruction for adolescents with an open physis

PURPOSE

The posterior cruciate ligament (PCL) rupture rarely occurs, especially in skeletally immature adolescents, and poses a dilemma in appropriately managing the open physis with its vast growth potential. However, although many epiphyseal-protecting techniques for anterior cruciate ligament (ACL) reconstruction have been reported, a similar problem in PCL reconstruction has received scant attention and needs more relevant research. So, this study aims to evaluate the short-term clinical and imaging results of the arthroscopic physeal-sparing reconstruction program.

METHOD

All the 13 patients we reviewed in this study have accepted the arthroscopic physeal-sparing PCL reconstruction from January 2019 to December 2022 in our Department of Orthopedics. Primary demographic data collected include gender (8 males and 5 females), age (11-15 years, average 13.3 years), follow-up period (15-35 months, average 25.2 months), injury mechanism (nine non-contact injuries and four contact injuries), and days following injury (1-10 days, average 5.3 days). The assessment of clinical outcomes included pre- and postoperative physical examination, knee functional scores, and imaging data.

RESULT

All patients in this study were followed up with an average 25.2-month (range 15-35 months) follow-up period. All the cases preoperatively had a positive posterior drawer test and turned negative at the final follow-up. The average ROM improved from 103.6° ± 11.4° to 132.6° ± 3.6° at the last follow-up (p < 0.05). The VAS score decreased from 5.8 ± 1.6 to 0.9 ± 0.5 (p < 0.05); the average KT-1000 healthy-side to affected-side difference decreased from 11.3 ± 1.6 to1.8 ± 0.5 mm. The comparison of all the knee functional scores (IKDC, Tegner scores, and Lysholm) at preoperative and last follow-up showed a significant difference (p < 0.05). None of the cases had operation-related complications, and all recovered to sports well.

CONCLUSION

The arthroscopic physeal-sparing posterior cruciate ligament reconstruction is a dependable and recommended treatment for posterior cruciate ligament rupture in adolescents with open physis, showing a striking improvement in knee function without growth arrest and angular deformity of the affected limb in the short-term follow-up.

The optimal tibial tunnel placement to maximize the graft bending angle in the transtibial posterior cruciate ligament reconstruction: a quantitative assessment in three-dimensional computed tomography model

Background

The graft bending angle created by the graft and the tibial tunnel has inevitably occurred during the transtibial posterior cruciate ligament (PCL) reconstruction. However, few studies quantitively analyzed this angle. This study aimed to (I) explore the optimal tibial tunnel placement to maximize the graft bending angle in the PCL reconstruction; (II) reveal the effect of the tibial tunnel placement on the graft bending angle.

Methods

This was an in-vitro surgical simulation study based on the three-dimensional (3D) computed tomography (CT). A total of 55 patients who took CT scanning for knee injuries were selected (April 2020 to January 2022) from the local hospital database for review. The 3D knee models were established on the Mimics software based on the knees' CT data. Using the Rhinoceros software to simulate the transtibial PCL reconstruction on the 3D CT knee model. The anteromedial and anterolateral tibial tunnel approaches were simulated with different tibial tunnel angle. The graft bending angle and tibial tunnel length (TTL) with different tibial tunnel angles were quantitively analyzed.

Results

The graft bending angle in anterolateral approach with a 50° tibial tunnel angle was significantly greater than it in anteromedial approach with a 60° tibial tunnel angle (P<0.001). There was no difference of the graft bending angle between the anterolateral approach with a 40° tibial tunnel angle and the anteromedial approach with a 60° tibial tunnel angle (P>0.05). The graft bending angle showed a strong correlation with the tibial tunnel angle (for anteromedial approach: r=0.759, P<0.001; for anterolateral approach: r=0.702, P<0.001). The best-fit equation to calculate the graft bending angle based on the tibial tunnel angle was Y = 0.89*X + 59.05 in anteromedial tibial tunnel approach (r2=0.576), and was Y = 0.78*X + 80.21 anterolateral tibial tunnel approach (r2=0.493).

Conclusions

The graft bending angle and TTL will significantly increase as the tibial tunnel angle becomes greater. Maximizing the tibial tunnel angle (50° tibial tunnel angle) in the anterolateral approach could provide the greatest graft bending angle in the PCL reconstruction. No matter how the tibial tunnel angle is changed in the anteromedial approach, using anterolateral approach might reduce the killer turn effect more effectively than using anteromedial approach.

Biomechanical comparison of proximal, distal, and anatomic tibial tunnel for transtibial posterior cruciate ligament reconstruction

No consensus has been reached on the optimal position of PCL tibial tunnel. The purpose of this study was to compare the biomechanical properties of proximal, distal and anatomic tibial tunnel in transtibial posterior cruciate ligament reconstruction. An in-vitro model of transtibial posterior cruciate ligament reconstruction was simulated using porcine tibias and bovine extensor tendons. Two models of biomechanical testing, load-to-failure loading, and cyclic loading, were performed in this study. The load-to-failure loading found that distal tibial tunnel resulted in greater ultimate load and yield load than the anatomic and proximal tunnel group (p < 0.05), whereas there were no significant differences in mean tensile stiffness among three groups (p > 0.05). The cyclic loading found no differences in the graft displacement at 250, 500, and 1000 cycles among three groups (p > 0.05). It was found that distal tibial tunnel showed superior ultimate load and yield load in load-to-failure loading testing compared with proximal and anatomic tibial tunnels, whereas no significant difference was found in terms of the mean displacement of the survived grafts in cyclic loading testing among three groups.

What Is the Maximum Tibial Tunnel Angle for Transtibial PCL Reconstruction? A Comparison Based on Virtual Radiographs, CT Images, and 3D Knee Models

BACKGROUND

To minimize the killer turn caused by the sharp margin of the tibial tunnel exit in transtibial PCL reconstruction, surgeons tend to maximize the angle of the tibial tunnel in relation to the tibial plateau. However, to date, no consensus has been reached regarding the maximum angle for the PCL tibial tunnel.

QUESTIONS/PURPOSES

In this study we sought (1) to determine the maximum tibial tunnel angle for the anteromedial and anterolateral approaches in transtibial PCL reconstruction; (2) to compare the differences in the maximum angle based on three measurement methods: virtual radiographs, CT images, and three-dimensional (3D) knee models; and (3) to conduct a correlation analysis to determine whether patient anthropomorphic factors (age, sex, height, and BMI) are associated with the maximum tibial tunnel angle.

METHODS

Between January 2018 and December 2020, 625 patients who underwent CT scanning for knee injuries were retrospectively reviewed in our institution. Inclusion criteria were patients 18 to 60 years of age with a Kellgren-Lawrence grade of knee osteoarthritis less than 1 and CT images that clearly showed the PCL tibial attachment. Exclusion criteria were patients with a history of tibial plateau fracture, PCL injuries, tumor, and deformity around the knee. Finally, 104 patients (43 males and 61 females, median age: 38 [range 24 to 56] years, height: 165 ± 9 cm, median BMI: 23 kg/cm2 [range 17 to 31]) were included for analysis. CT data were used to create virtual 3D knee models, and virtual true lateral knee radiographs were obtained by rotating the 3D knee models. Virtual 3D knee models were used as an in vitro standard method to assess the true maximum tibial tunnel angle of anteromedial and anterolateral approaches in transtibial PCL reconstruction. The tibial tunnel's entry was placed 1.5 cm anteromedial and anterolateral to the tibial tubercle for the two approaches. To obtain the maximum angle, a 10-mm- diameter tibial tunnel was simulated by making the tibial tunnel near the posterior tibial cortex. The maximum tibial tunnel angle, tibial tunnel lengths, and perpendicular distances of the tunnel's entry point to the tibial plateau were measured on virtual radiographs, CT images, and virtual 3D knee models. One-way ANOVA was used to compare the differences in the maximum angle among groups, and correlation analysis was performed to identify the relationship of the maximum angle and anthropomorphic factors (age, sex, height, and BMI).

RESULTS

The maximum angle of the PCL tibial tunnel relative to the tibial plateau was greater in the anteromedial group than the anterolateral group (58° ± 8° versus 50° ± 8°, mean difference 8° [95% CI 6° to 10°]; p < 0.001). The maximum angle of the PCL tibial tunnel was greater in the virtual radiograph group than the CT image (68° ± 6° versus 49° ± 5°, mean difference 19° [95% CI 17° to 21°]; p < 0.001), the anteromedial approach (68° ± 6° versus 58° ± 8°, mean difference 10° [95% CI 8° to 12°]; p < 0.001), and the anterolateral approach (68° ± 6° versus 50° ± 8°, mean difference 18° [95% CI 16° to 20°]; p < 0.001), but no difference was found between the CT image and the anterolateral groups (49° ± 5° versus 50° ± 8°, mean difference -1° [95% CI -4° to 1°]; p = 0.79). We found no patient anthropomorphic characteristics (age, sex, height, and BMI) that were associated with the maximum angle.

CONCLUSION

Surgeons should note that the mean maximum angle of the tibial tunnel relative to the tibial plateau was greater in the anteromedial than anterolateral approach in PCL reconstruction, and the maximum angle might be overestimated on virtual radiographs and underestimated on CT images.

CLINICAL RELEVANCE

To perform PCL reconstruction more safely, the findings of this study suggest that the PCL drill system should be set differently for the anteromedial and anterolateral approaches, and the maximum angle measured by intraoperative fluoroscopy should be reduced 10° for the anteromedial approach and 18° for the anterolateral approach. Future clinical or cadaveric studies are needed to validate our findings.

Biomechanical evaluation of a novel transtibial posterior cruciate ligament reconstruction using high-strength sutures in a porcine bone model

Background:

Multiple techniques are commonly used for posterior cruciate ligament (PCL) reconstruction. However, the optimum method regarding the fixation of PCL reconstruction after PCL tears remains debatable. The purpose of this study was to compare the biomechanical properties among three different tibial fixation procedures for transtibial single-bundle PCL reconstruction.

Methods:

Thirty-six porcine tibias and porcine extensor tendons were randomized into three fixation study groups: the interference screw fixation (IS) group, the transtibial tubercle fixation (TTF) group, and TTF + IS group (n = 12 in each group). The structural properties of the three fixation groups were tested under cyclic loading and load-to-failure. The slippage after the cyclic loading test and the stiffness and ultimate failure load after load-to-failure testing were recorded.

Results:

After 1000 cycles of cyclic testing, no significant difference was observed in graft slippage among the three groups. For load-to-failure testing, the TTF + IS group showed a higher ultimate failure load than the TTF group and the IS group (876.34 ± 58.78 N vs. 660.92 ± 77.74 N [P < 0.001] vs. 556.49 ± 65.33 N [P < 0.001]). The stiffness in the TTF group was significantly lower than that in the IS group and the TTF + IS group (92.77 ± 20.16 N/mm in the TTF group vs. 120.27 ± 15.66 N/m in the IS group [P = 0.001] and 131.79 ± 17.95 N/mm in the TTF + IS group [P < 0.001]). No significant difference in the mean stiffness was found between the IS group and the TTF + IS group (P = 0.127).

Conclusions:

In this biomechanical study, supplementary fixation with transtibial tubercle sutures increased the ultimate failure load during load-to-failure testing for PCL reconstruction.

[The killer turn in the posterior cruciate ligament reconstruction: mechanism and improvement]

OBJECTIVE

To summarize the research progress of killer turn in posterior cruciate ligament (PCL) reconstruction.

METHODS

The literature related to the killer turn in PCL reconstruction in recent years was searched and summarized.

RESULTS

The recent studies show that the killer turn is considered to be the most critical cause of graft relaxation after PCL reconstruction. In clinic, this effect can be reduced by changing the fixation mode of bone tunnel, changing the orientation of bone tunnel, squeezing screw fixation, retaining the remnant, and grinding the bone at the exit of bone tunnel. But there is still a lack of long-term follow-up.

CONCLUSION

There are still a lot of controversies on the improved strategies of the killer turn. More detailed basic researches focusing on biomechanics to further explore the mechanism of the reconstructed graft abrasion are needed.

Proximal, Distal, and Combined Fixation Within the Tibial Tunnel in Transtibial Posterior Cruciate Ligament Reconstruction: A Time-Zero Biomechanical Study In Vitro

PURPOSE

To compare the time-zero biomechanical properties of 3 graft fixation techniques (proximal, distal, and combined fixation) within the tibial tunnel in transtibial posterior cruciate ligament (PCL) reconstruction.

METHODS

Porcine tibias and bovine extensor tendons were used to simulate a transtibial PCL reconstruction in vitro. Load-to-failure testing was carried out in 3 groups: distal fixation alone (group I, n = 10), proximal fixation alone (group II, n = 10), and combined fixation (group III, n = 10). The load-elongation curve, tensile stiffness (in newtons per millimeter), ultimate load (in newtons), yield load (in newtons), energy absorbed to failure (in joules), and failure mode were recorded.

RESULTS

All graft-tibia complexes failed because the grafts slipped past the interference screws. The tensile stiffness, yield load, and energy absorption in group I were significantly lower than those in group II and group III (tensile stiffness, 19.25 ± 9.68 N/mm in group I vs 34.92 ± 16.48 N/mm in group II [P = .016] and 32.31 ± 13.79 N/mm in group III [P = .041]; yield load, 265.36 ± 144.52 N in group I vs 398.23 ± 57.04 N in group II [P = .006] and 424.94 ± 74.00 N in group III [P = .001]; and energy absorption, 5.16 ± 2.35 J in group I vs 19.95 ± 3.48 J in group II [P < .001] and 21.09 ± 4.29 J in group III [P < .001]). No statistically significant differences in biomechanical properties were found between group II and group III (P > .05).

CONCLUSIONS

Compared with distal fixation in transtibial PCL reconstruction, proximal fixation and combined fixation showed superior time-zero biomechanical properties.

CLINICAL RELEVANCE

Proximal fixation and combined fixation produced superior biomechanical properties to distal fixation in transtibial PCL reconstruction.

Evaluation of the permissible maximum angle of the tibial tunnel in transtibial anatomic posterior cruciate ligament reconstruction by computed tomography

INTRODUCTION

Excessive angle of the tibial tunnel may cause breakage of the posterior cortex in transtibial anatomic posterior cruciate ligament (PCL) reconstruction. However, a few studies have determined the permissible maximum angle of the tibial tunnel. The purpose of this study was to determine the permissible maximum angle of the tibial tunnel relative to the tibial plateau in transtibial anatomic PCL reconstruction and characterize the anatomic parameters of the tibial PCL attachment position.

MATERIALS AND METHODS

Computed tomography (CT) scans of a consecutive series of 408 adult knees with normal PCL attachment were measured. The parameters measured were the permissible maximum angle (PMA) of the 10 mm-diameter tibial tunnel relative to the tibial plateau, the distance from the anterior orifice of the tibial tunnel to the tibial tuberosity (OTD), the anterior-posterior diameter (APD) of the tibial plateau, the distance from the center of PCL attachment site to the posterior edge of the tibial plateau (PPED), and the angle between the tibial plateau and the posterior tibial slope where the PCL insertion site was (PSA). Subgroup analysis was performed to determine the correlations between parameters, and sex, age, and height. The measurement reliability was evaluated by intraclass correlation coefficients (ICCs).

RESULTS

The average value of PMA was 48.2 ± 5.4°, and it was not affected by sex, age, and height (P > 0.05). The values of OTD, APD, PPED, PSA, and height were significantly higher in males than females (OTD, P < 0.01; APD, P < 0.01; PPED, P < 0.01; PSA, P = 0.019; height, P < 0.01). With regard to age, we stratified the cases into three groups: the young (18-30 years old), the middle-aged (31-45 years old), and the elderly (46-60 years old). The mean value of OTD, APD, and height were significantly lower in the elderly than that in the middle-aged (P < 0.01, P < 0.01, P < 0.01, respectively). With regard to height, we stratified the cases into three groups: ~ 1.65 m (1), 1.66 ~ 1.75 m (2), and 1.76 m ~ (3). The mean value of OTD, APD, and PPED significantly increased with height, P < 0.05. The mean value of PSA was significant higher in II group than that in I group (P = 0.034).

CONCLUSIONS

There should be a limit to the angle of the tibial tunnel in transtibial anatomic PCL reconstruction to prevent the fracture of posterior tunnel wall. The permissible maximum angle (PMA) of the 10 mm-diameter tibial tunnel relative to the tibial plateau was 48.2°. Besides, the determination of the value of OTD, APD, PPED, and PSA could provide a clinical reference to insertion site, depth, and angle of the tibial drill guide in PCL reconstruction.

REHABILITATION FOLLOWING ISOLATED POSTERIOR CRUCIATE LIGAMENT RECONSTRUCTION: A LITERATURE REVIEW OF PUBLISHED PROTOCOLS

BACKGROUND

Surgical outcomes following isolated posterior cruciate ligament reconstruction (PCLR) have been noted to be less satisfactory than the anterior cruciate ligament. Limited understanding of optimal rehabilitation has been implicated as a contributing factor.

HYPOTHESIS/PURPOSE

The purpose of this review was to gather the literature related to isolated PCLR rehabilitation, extract and summarize current rehabilitation guidelines, identify timeframes and functional measurements associated with common rehabilitation topics and provide recommendations for future research.

STUDY DESIGN

Literature review.

METHODS

A literature review was performed for scientific publications that include a detailed rehabilitation program following isolated PCLR, published between January 2005 and March 2018. Data related to weight-bearing, knee range of motion (ROM), brace usage, specific exercise recommendations and suggestions for return to running and sport activities were extracted and categorized.

RESULTS

A total of 44 articles met inclusion criteria. Post-operative weight-bearing was discussed in 35 articles with recommendations ranging from no restriction to 12 weeks of limitations. Forty-two articles recommended the use of immediate post-operative bracing, the majority of which positioned the knee in full extension, with duration of use ranging from one to 12 weeks post-operatively. Although 30 articles offered detailed descriptions of ROM activity, there was significant variability in timing of initiation, angular excursion and progression of range of motion. Suggested timeframes for returning to sports activity ranged from four to 12 months, with only four articles providing specific objective strength or functional performance criteria necessary for progression.

CONCLUSIONS

There is substantial variation in nearly all aspects of published descriptors of rehabilitation following isolated PCLR. Most protocols are based upon biomechanical principles and clinical expertise, relying solely on timeframe from surgery to support rehabilitation decision making. Evidence to compare patient outcomes with specific loading, ROM progression and exercise strategies is currently lacking. Only a small number of protocols incorporate the use of specific objective performance goals to facilitate return to sport decision making.

No Clinically Important Difference in Knee Scores or Instability Between Transtibial and Inlay Techniques for PCL Reconstruction: A Systematic Review

BACKGROUND

It is unclear whether the biomechanical superiority of the inlay technique over the transtibial technique, arising from avoidance of the killer turn at the graft-tunnel margin of the proximal tibia during posterior cruciate ligament (PCL) reconstruction, leads to better knee scores or greater knee stability.

QUESTIONS/PURPOSES

This systematic review was designed to compare Tegner and Lysholm scores, and posterior residual laxity of the knee, between single-bundle PCL reconstruction using transtibial and inlay techniques.

METHODS

We searched MEDLINE^®, Embase^®, and the Cochrane Library for studies comparing Tegner and/or Lysholm scores and posterior residual laxity, in patients who underwent PCL single-bundle reconstruction with the transtibial and tibial inlay techniques. There were no restrictions on language or year of publication. Studies were included if they compared clinical outcomes in patients who underwent PCL single-bundle reconstruction with the transtibial and tibial inlay techniques; they simultaneously reported direct comparisons of transtibial and tibial inlay PCL single-bundle reconstruction; and their primary outcomes included comparisons of postoperative scores on knee outcome scales and posterior residual laxity. A total of seven studies (including 149 patients having surgery using a transtibial approach, and 148 with the tibial inlay approach) met the prespecified inclusion criteria and were analyzed in detail.

RESULTS

Our systematic review suggested that there are no clinically important differences between the transtibial and the tibial inlay single-bundle PCL reconstruction in terms of Tegner or Lysholm scores. Of the five studies that assessed Lysholm scores, one favored the transtibial approach and four concluded no difference on this endpoint; however, the observed differences in all studies where differences were observed were quite small (< 7 of 100 points on the Lysholm scale), and likely not clinically important. Of the four studies that compared postoperative Tegner scores, three identified no differences between the approaches, while one favored the tibial inlay approach by a small margin (0.5 of 11 points) suggesting that there likely is no clinically important difference between the approaches in Tegner scores, either. Finally, we identified no difference between the approaches in terms of residual laxity, either among the seven studies that presented data using Telos radiographs, or the five that reported on patients with residual laxity greater than Grade 2 on a four-grade scale of posterior drawer testing (28/107 for transtibial and 26/97 for tibial inlay).

CONCLUSION

We found no clinically important differences between the transtibial and tibial inlay approach for PCL reconstruction. Based on the best evidence now available, it appears that surgeons may select between these approaches based on clinical experience and the specific elements of each patient's presentation, since there do not appear to be important or obvious differences between the approaches with respect to knee scores or joint stability. Future randomized trials are needed to answer this question more definitively.

LEVEL OF EVIDENCE

Level III, therapeutic study.

Pearls and pitfalls of single-bundle transtibial posterior cruciate ligament reconstruction

Posterior cruciate ligament (PCL) injuries are rare, but they often require reconstruction, especially in the setting of combined ligamentous knee injury. Single-bundle transtibial PCL reconstruction is 1 technique for restoring this important ligament. However, this procedure is technically demanding, and complications can occur if poor techniques are used. This article analyzes the potential pitfalls of this procedure and presents the pearls that may ease the technical demands and reduce the risk of avoidable complications.