Abstract
Objectives
Partial ACL tears are increasingly recognized in young active patients. They can evolve into complete tears. Controversy exists regarding the need to spare intact ACL bundle as it has its advantages considering biomechanical strength, blood supply and proprioception. The current study determined the challenges in partial ACL tear management and assessed the functional outcomes.
Methods
Twenty consecutive patients with partial ACL tears were studied. Inclusion criteria were: age 16–45yrs and patients operated for partial ACL tear. Exclusion criteria were: combined ACL-PCL injuries, associated collateral injuries, complete ACL tear, chondral defect or bony malalignment and patients with radiographic signs of arthritis. ‘Partial’ tear was defined as continuous fibers from native tibial ACL footprint to native femoral ACL footprint in arthroscopy. Clinical and radiological assessment was done to evaluate anteromedial(AM) or posterolateral(PL) bundle tears. We used the term “ACL-augmentation” without disturbing the intact bundle or preserving the intact fibers as much as possible. Functional scoring was done using Lysholm score. Standard post-operative protocols were followed. Statistical analysis was done using SPSS software.
Results
Mean age of patients was 31.2 years. Physically active age group (<30yrs) included 62.5% patients. Males were 87.5%. Pain and instability were the presenting complaints in 75% and 70% respectively. Average duration of presentation since injury was 4.2 months. Sports activities were the most common mode of injury (45%) followed by road traffic accidents (37.5%). Anterior drawer test was positive in 40%, pivot shift in 35% and Lachman test was positive in 65%. On arthroscopy, 65% had AM bundle tears and 35% had PL bundle tears. The intact bundle was found lax in 13% cases. Associated meniscal tear was present in 28% patients. Stiff knee was the most common post-operative complaint. Preoperative Lysholm knee score of 74.5 improved to 87.7 at 12months (p < 0.001). Around 97.5% of the patients reported outcomes as good and fair.
Conclusion
The treatment strategy needs to be individualized. The ACL augmentation needs more systematic and accurate placement of portals while sparing the intact ACL fibers. For AM bundle, tibial tunnel entry point is about 1–2 cm medial to tibial tuberosity. For PL bundle, it is about 3–4 cm medial to tibial tuberosity to protect the AM bundle. Long term studies with greater number of subjects are required.
Keywords: Partial ACL tear, Augmentation, Cruciate ligament
1. Introduction
Anterior cruciate ligament (ACL) is a ligament of the knee which provides stability and prevents anterior translation. It resists >80% of the total resisting forces on anterior drawer test and also has proprioceptive function.1 It consists of two bundles-anteromedial(AM) and posterolateral(PL) bundle. The anatomic relationship between these bundles is 3-dimensional and the appearance is dependent upon the knee flexion angle.2
It is often injured in athletic activities involving contact like football, hockey, gymnastics and motor vehicle accidents which produce enough “sudden” stress to disrupt knee ligaments. Partial ACL (pACL) disruption can occur without a fall or direct contact when sudden, severe loading or tension is placed on the ligaments, such as when a running athlete plants a foot to suddenly decelerate or change directions.3 In traditional Indian sports like kabbadi, kho-kho and wrestling(kushti) pivoting is more common. One can also sustain pACL injuries in day to day activities like stepping down from a bus or fall from stairs.4
With increased sporting and outdoor activities/functional demands, increased awareness and wide availability of arthroscopic treatment modalities; the recognition and incidence of pACL tears has increased. Also, the spectrum of injury varies significantly. With conservative management, the rate of return to pre-injury activity level is very dismal at 50%. This is significant considering the young population affected.5 Hence, clinical assessment and management of partial-bundle injury is becoming important. The term “ACL-augmentation” has come into vogue without disturbing the intact bundle.6 Very few studies available are from Indian population regarding the incidence and outcomes following such injury.
Our institution is a tertiary health care center and a residential university with strong enrollment of students and wide ranging sports activities are available. Frequent presentation of young subjects with knee injuries prompted us to study the partial ACL tears at our institution. The present study aims to evaluate the clinical and radiological differences in AM and PL bundle ACL tears and to study the challenges in pACL tear management and assess the functional outcomes following pACL tear augmentation/reconstruction.
2. Materials and methods
The study was conducted in the department of orthopedics at a tertiary level referral center over a period of 24 months from July 2016 to June 2018. Required permission from institutional ethics committee was obtained and written and informed consent was taken. This was a retrospective analysis of prospectively collected data.
All the patients presenting with ACL injury and operated by arthroscopic multistranded hamstring tendon graft were evaluated. Inclusion criteria were: Age group 16–45yrs and patients operated for pACL tear. Exclusion criteria were: Combined ACL and PCL injuries, associated collateral ligament injuries, complete ACL tear, chondral defect or bony malalignment and patients with pre-operative radiographic signs of arthritis.
A total of twenty patients operated for pACL tears over the last 2-year period from June-2016 were included. Operative records were accessed and data compiled. Patients were called for follow-up and final clinical status recorded. Statistical analysis was done using SPSS software, IBM Corporation.
Patients in study age group who presented with unilateral knee complaints and history of trauma to the knee in the department of orthopedics were evaluated. In a relaxed patient in supine position, the uninjured knee was examined first to establish reference values after which the affected knee was examined. Following tests were done-anterior drawer, Lachman and pivot shift test for ACL injury. Associated structures were assessed by valgus/varus stress test (for collateral ligaments), McMurray's test (for menisci), posterior drawer test (for PCL) and reverse pivot shift test (for posterolateral complex).
Lachman test was graded as follows: A = firm endpoint, B = no endpoint; Grade I: 3–5 mm translation, Grade II A/B: 5–10 mm and Grade III A/B: > 10 mm translation. Anterior drawer test was graded as follows: Grade I- 5 mm; Grade II- 5–10 mm; Grade III- >10 mm translation.7,8
Pivot shift was graded based on lateral plateau displacement as follows: Normal-up to 5 mm, Grade I- 10–12 mm, Grade II- up to 18 mm, Grade III- > 20–22 mm. Based on medial plateau displacement, pivot shift grading was considered to be Grade I- 5 mm, Grade II- 10 mm and Grade III-15mm.9
“Partial” tear was defined as continuous fibers from native tibial ACL footprint to native femoral ACL footprint in arthroscopy with significant portion of a least 1 bundle healthy and potentially functional as judged by palpation with a probe and arthroscopic anterior drawer testing.10
Routine x-rays of the affected knee were done to look for bony avulsions. MRI was done for further evaluation. It has higher accuracy than clinical examination in detecting ACL tear when multiple ligaments are torn. Sagittal images are most useful for evaluation of ACL fiber orientation of the femoral and tibial attachments. Coronal images evaluate collateral ligaments and signal characteristics of ACL within the intercondylar notch.11 The ACL appears oriented like a “hand in pocket” from superolateral to anterior-inferomedial direction. Axial views assess ACL and PCL in the notch, bone contusion, para-articular fluid collections and the joint capsule. However, MR imaging for diagnosing partial ACL tears has been controversial with variable sensitivity (40–75%) and specificity (62–89%) in many studies.12,13
Risk assessment was done to identify appropriate cases for intervention. High demand patients with active life style were planned for surgical reconstruction. The treatment strategy considered symptoms, clinical examination findings, percentage of fibers remaining, associated injuries, length of time since the injury and daily physical work demands.14
2.1. Surgical tactic
“Augmentation” seeks to preserve the native ACL fibers. Under anaesthesia the patient was clinically examined. Tourniquet, side and heel support were applied. Diagnostic arthroscopy was performed using standard anterolateral (AL) and anteromedial (AM) portals. Partial ACL tear was confirmed and torn bundle was noted. Associated chondral lesions and meniscal tears if any were managed simultaneously. The posterolateral bundle was more easily identified when the knee is placed in figure-of-4 position.15
2.2. Graft harvest and preparation
Hamstring tendon graft-semitendinosus/gracilis were harvested and prepared in a standard fashion on graft board. Residual muscle was cleared and tendon ends were placed together with Krackow stitch using Ethibond no. 5. The graft was made multistranded and length and diameter were measured. A pressure of about 15 pounds was applied for 10–15 min for pre-stressing the graft.16
2.3. Reconstruction of AM and PL bundles
The remnants of the AM bundle were debrided with preservation of the PL bundle. The tibial guide with 55ᵒ angle and entry point approximately 1.5–2 cm medial to tibial tuberosity was used.17 For PL bundle, tibial tunnel is placed more medially about 3.5–4 cm from tibial tuberosity to avoid AM bundle. Intra-articularly it is placed in the posterior part of the tibial insertion, 5 mm medially to the lateral intercondylar eminence for PL bundle. For AM bundle, we marked the posterior border of anterior horn of lateral meniscus, around 10–15 mm from the posterior cruciate ligament between the two tibial eminences-medial and lateral.18
Femoral remnants guided the femoral tunnel placement by inside-out method for both the bundle tears. Low-velocity drilling was done to avoid further damage to ACL remnants. Also, iatrogenic injury to medial femoral condyle was avoided while femoral tunnel preparation via low anteromedial portal. A spinal needle was used to accurately mark the trajectory. Femoral tunnel was drilled leaving a 3 mm posterior wall and about 3 mm from the femoral articular surface with knee flexed to 120ᵒ. The shortest endobutton loop is 15 mm. To achieve at least 20–25 mm of graft in the femoral socket, the total channel length must be at least 35–40 mm [15 + (20 or 25)]. The impingement of ACL over PCL was prevented by leaving a bony posterior wall between the tibial tunnel and PCL and directing the tibial tunnel just lateral to the PCL.19
2.4. Graft fixation
After tensioning the graft for 20 cycles, an interference bioscrew 1 mm greater than the tunnel was used for tibial fixation with knee in 15ᵒ flexion and appropriate size endobutton was used on femoral side.20 Final arthroscopic check and joint lavage was done. Closure was done in layers with the graft remaining outside the tibial tunnel sutured to the periosteum. Sartorius fascia was closed, followed by closure of subcutaneous tissue and skin. Athroscopic portals were sutured with Nylon 2.0. Various parameters related to graft-length, diameter, stands; bone tunnels-length, diameter; fixation techniques-endobutton size, bioscrew size; surgery-duration, complications if any were noted.
2.5. Post-operative rehabilitation
The physiotherapy was started from the day of surgery with isometric quadriceps after weaning of anaesthesia effect. The regime was individualized and usually continued for at least 6mo post surgery. After ACL reconstruction, we observed following guidelines: On the day of surgery/next day: walking with crutches; at 3wks: discontinue crutches (when comfortable); at 6wks: discontinue brace; at 3mo: jogging/running in-line; at 6mo: Sport-specific agility training and at 9–12 mo: return to full activity. Full weight-bearing was permitted within the pain bearing capacity of the patients from the day after surgery with crutches. In most cases, crutches were required only for 3–4weeks after surgery. Crutches were discarded when patient was confident of walking without them with good control of the leg.21 Functional outcomes were assessed by Lysholm Knee scoring system and Knee Society Scoring system.22,23
Statistical analysis was performed using SPSS for windows. Data was expressed as either mean and standard deviation or numbers and percentages. The parameters were analyzed using unpaired t-test for comparison between two groups and paired t-test for comparison between pre-operative and post-operative outcomes. P-value <0.05 was considered statistically significant.
3. Results
This study was conducted in the Department of Orthopaedics of a tertiary referral center in eastern India. Twenty patients with pACL tears were included. Demographic parameters are shown in Table 1. Involvement of males is predominant due to involvement in outdoor activities. Sports activities like football, kabaddi and athletics were the most common mode of injury (45%) followed closely by road traffic accidents (37.5%). Physical fitness preparation for defence entrance also caused significant number of knee injuries. Clinical and arthroscopic findings are presented in Table 2.
Table 1.
Demographic parameters.
| Parameters | |
|---|---|
| Mean age | 31.2 ± 8.45 (range 19–45yrs) |
| Active group (<30yrs) | 62.5% |
| Males: females | 87.5%: 12.5% |
| Side of injury | Lt: 57.5%; Rt: 42.5% |
| Presenting complaints | Pain: 75%; Instability: 70%; Swelling: 20% |
| Duration since injury (avg) | 4.2 mo (range 2–6 mo) |
| Most common injury mode | Sports activities (45%); RTA (37.5%) |
Table 2.
Clinical and arthroscopic findings.
| Clinical examination findings | ||
|---|---|---|
| Positive | Negative | |
| Anterior drawer test | 40% | 60% |
| Lachman test | 65% | 35% |
| Pivot shift test | 35% | 65% |
| Arthroscopy findings | ||
| Bundle tears | AM tears: 65% | PL tears: 35% |
| Intact bundle | Lax: 13% | Functional: 87% |
| Meniscal tears | MM: 16% | LM: 12% |
Marking of portals with the help of cannula and an isolated PL bundle tear is shown in Fig. 1. Fig. 2 shows a reconstructed AM bundle and post-operative radiograph.
Fig. 1.
a) Portal marketing with 18Fr IV cannula. b) Posterolateral bundle tear seen in diagnostic arthroscopy (right knee).
Fig. 2.
a) Antermedial bundle shown after reconstruction (left knee). b) postoperactive X-ray showing fixation with endobutton and bioscrew.
In 80% cases, femoral tunnel length ranged from 40 to 45 mm. Femoral canal diameter was 8–9 mm in 85% cases. Tibial tunnel length ranged from 40 to 45 mm in 83% cases. Tibial tunnel diameter was 8–9 mm in 85% cases. Graft diameter was 8 mm in 65% and 9 mm in 35% cases. Endobutton length was 20–25 mm in 70% cases. Complications were seen in 4 cases. Stiff knee was the most common post-operative complaint.
The mean preoperative Lysholm knee score was 74.5 points which improved to 87.7 at 12months (p < 0.001). Around 97.5% of the patients reported outcome as good and fair.
4. Discussion
Partial ACL injury is a common occurrence these days due to increased participation in sports and road traffic accidents. The frequency ranges from 10 to 40% in various studies.24 However, incidence of symptomatic AM or PL bundle tear is reported to be between 5 and 10%.25 The clinical diagnosis can be challenging because findings may range from minimal clinical deficit to complete ACL laxity. The significance is that pACL tears can progress to complete ACL deficiency in 50% cases.26 This may be due to interruption of blood supply leading to necrosis of the intact fibers. The amount of initial ligament damage is significant predictive factor for evolution into complete tear.27
We considered arthroscopic definition of partial ACL tear, as presence of continuous fibers from native tibial ACL footprint to native femoral ACL footprint. The surgical treatment usually involved a standard ACL reconstruction where the residual portion of the ACL is sacrificed. The most important aspect of the study was to preserve the intact ACL remnant and doing an augmentation procedure which we propose to be beneficial to the recovery of an ACL-deficient patient.
Intact ACL stump is purported to have important role in the healing of ‘ACL graft’.28 First preservation of the intact remnant ensures mechanical strength in the early postoperative period while the graft strength during this period relies primarily on the fixation device. The intact bundle provides protection to the augmentation and hence, may allow faster rehabilitation and earlier return to sports. ACL remnants get scarred to the roof of the notch, lateral wall of the notch, or to the medial aspect of the lateral femoral condyle and may serve as biomechanical restraint against anterior translation.29
Second, keeping the intact bundle preserves its blood supply and helps in the healing process. Vascularized synovial envelope and penetrating vessels may develop around the ACL.30 Third, some proprioceptive innervation is maintained with advantages for the subjective outcome and safer return to sports/high demand activity by improving joint position sense.31 Georgoulis et al. investigated the presence neural mechanoreceptors in the remnants of the ruptured ACL as a possible source of reinnervation of ACL autologous graft and Adachi et al. measured the correlation between the number of mechanoreceptors and the accuracy of joint position sense with positive correlation to proprioception.32,33
Lastly, the intact bundle may optimize the accuracy of the procedure by increased arthroscopic orientation and bone tunnel placement at the insertion site. The bundle may serve as a guide for orientation and pint of reference for the proper placement of the graft (Siebold and Fu et al.).34
When ACL reconstruction is performed with sparing the intact bundle, tibial exit point of the tunnel was always found in the anatomical footprint of the bundle to be reconstructed (Buda et al.).35 In a study by Siebold and Fu, preliminary results showed good clinical results for AM and PL bundle augmentation at an average of 1yr postoperatively.36
This study was conducted to evaluate clinical outcome of partial ACL augmentation and also analyze the complications of surgery. The patients selected for our study were thoroughly examined clinically and provisional diagnosis was made. All these patients were subjected to arthroscopy and diagnosis was confirmed. This study was conducted on 40 knee joints in 40 patients.
The age of patients ranged from 16 to 45years. The majority of patients were below 30yrs (62.5%). Females participating in sports activity are more prone for ACL tears because of anatomic, environmental, hormonal and biomechanical factors. There were 35 males and 5 females in our study. This male predominance may be due to the fact that they are more involved in outdoor and sports activity in our scenario. Sports activity (45%) and RTA (37.5%) were the two most common modes of injury. Among the sport activity, cricket and football were most common. Others sustained injury during daily activities like slip on ground and fall from height.
Out of 40 patients, 23 patients (57.5%) had left knee involvement and 17 (42.5%) had right knee involved. The duration of symptom ranged from 1 to 30 months. Maximum patients in our study had sign and symptoms indicating towards ACL deficiency since 2–6 months (80.6%). The average duration of symptoms was 5 months.
In the current study, the most common primary pre-operative diagnosis was partial ACL tear. Most commonly associated injury was medial meniscus tear. A total of 11 patients (27.5%) had associated meniscal tear along with ACL injury. Six cases (15%) had medial meniscus tear and 5 cases (12.5%) had lateral meniscus tear. All the patients of meniscal injury were treated by partial meniscectomy.
Pain in knee joint was the most common (75%) presenting complaint. The second most common complaint was instability in knee joint (70%). Swelling in knee joint, locking sensation, stiffness of knee joint and limping were other presenting complaints. On clinical examination, Lachman test was positive in 32 patients (80%), anterior drawer test was found positive in 16 patients (40%) and pivot shift was positive in 26 patients (65%).
In the study of Li et al., the main presenting symptom was knee instability followed by knee pain and swelling. Pivot shift test was positive in 15 cases (60%) and Lachman test and anterior drawer test was positive in all 25 cases (100%).37
In present study, the pre-operative Lysholm score ranged from 61 to 90. Most of the patients (45%) fell in range of 71–80. The mean pre-operative mean score was 77.53 which improved to 87.7 at 12 months (p < 0.01). Stiff knee was the most common post-operative complication seen in 2 patients (5%). Post-operative anterior knee pain was seen in 1 patient. Considering study limitations, the study period was short with small number of patients. Longer follow-up studies with more number of subjects are required in future to know long term outcomes of this procedure.
5. Conclusion
There are many factors supporting the preservation of intact ACL stump instead of debriding it like increased mechanical stability, revascularization and proprioceptive innervations; better orientation of the graft, faster remodeling and better rehabilitation of the patient.
Augmentation or isolated reconstruction of the torn bundle is a demanding surgery. The ACL augmentation is performed in a fashion similar to traditional single bundle technique while protecting the intact ACL fibers. The arthroscopic portals should be accurately placed, bone tunnel preparation and drilling or milling should be effectively controlled to avoid damaging the intact ACL bundle and the space available in intercondylar notch should be judiciously managed.
The study has its limitations also in the absence of control group. Since this is an initial study, we did not randomize the patients. The on-table arthroscopy findings were shown to the patient and he was part of decision making. None of the patients consented for sacrificing the intact bundle and performing a full ACL reconstruction in our set-up.
The improvements in functional scores can be due to reconstruction itself. However, the graft size here was usually less than standard ACL reconstruction. It is proposed to further carry this work with case-control/randomized studies. Relook arthroscopy can also be considered in long term follow up in such cases.
Conflicts of interest
There are no conflicts of interest associated with this work.
Source of funding
Nil.
Footnotes
Supplementary data to this article can be found online at https://doi.org/10.1016/j.jcot.2019.08.018.
Appendix A. Supplementary data
The following is the Supplementary data to this article:
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