The best option for treating anterior cruciate ligament (ACL) ruptures is surgical reconstruction, but clinicians continue to debate which reconstruction technique to use. We have found in many cases of ACL rupture that a relatively abundant stump remains at the femoral or tibial stop of the ligament. Standard ACL reconstruction techniques recommend removing the residual ligamentous tissue to provide proper femoro-tibial tunnel positioning, and removing the stump also prevents excessive tissue in the intercondylar fossa, thereby preventing postoperative limitation of knee mobility due to impingement.
However, ACL stump fibers have the ability to produce collagen, which contains a large number of proprioceptive receptors, and the majority of these proprioceptive receptors are located in the subsynovial layer near the ACL tibial stop. These receptors contribute to the recovery of proprioception in the knee joint. Therefore, in this study, we retrospectively analyzed 253 cases of complete ACL rupture undergoing surgical reconstruction, and compared the data of patients in the group with the standard reconstruction technique and the group with the stump-preserving technique to further evaluate the efficacy of the stump-preserving technique.
Materials and Methods
I. General information
The data of 293 patients who underwent ACL reconstruction using arthroscopic technique from May 2004 to May 2010 were retrospectively analyzed, among which 253 cases had complete ACL rupture, 187 males and 66 females, with an average age of 28 years (16-52 years) and no other ligament rupture. The mean interval between injury and undergoing surgery was 4.2 months (7d to 8 months). All patients recalled symptoms of rapid swelling and inability to move after knee trauma, and preoperative MRI examinations were suggestive of ACL rupture. Patients were unable to return to pre-injury motion due to symptoms of knee instability, and the remaining symptoms included knee pain, swelling, and worsening of symptoms when running or walking up and down stairs.
Between May 2004 and December 2007, the authors performed arthroscopic ACL reconstruction using standard reconstruction techniques in 85 patients with complete ACL rupture, 68 males and 17 females, with an average age of 30 years (18-44 years).
Between January 2007 and May 2010, the authors performed arthroscopic ACL reconstruction using the stump-preserving technique in 168 patients with complete ACL rupture, 122 males and 46 females, with a mean age of 28 years (16 to 52 years).
There was no statistical difference in the mean age and sex composition ratio between the stump-preserving group and the standard group (P>0.05).
II. Surgical techniques
1. Surgical technique of the standard group
A conventional parapatellar arthroscopic approach was used, with lateral access to the arthroscope and medial access to the surgical instruments, to comprehensively explore the intra-articular structures and carefully examine the ACL injury. The tendon was pre-tensioned for 5 min with a weight of 9 Kg, and the ends of the tendon were braided with No. 2 ETHIBOND non-absorbable thread to form a double strand, then the graft was folded in the middle, No. 5 ETHIBOND non-absorbable thread was placed as a traction line, and the fold was then braided with 2-0 Vicryl thread. The folded area was then braided and sutured with 2-0 Vicryl suture to form a four-strand N-cord tendon graft.
The ACL femoral and tibial stop stumps were completely removed during the operation, the over-the-top point was revealed, and the femoral tunnel was established by drilling a guide needle from the anteromedial approach at the medial wall of the femoral epicondyle in the intercondylar fossa, 10:00 at the right knee and 2:00 at the left knee, with the knee flexed at 90°, and the corresponding drill bit was selected according to the diameter of the grafted tendon. Using the intersection of the medial tibial intercondylar crest and the posterior edge of the anterior angle of the lateral meniscus as the locating point, the lateral tibial ACL locator is placed, a guide needle is driven in, and the corresponding tibial drill is selected according to the diameter of the grafted tendon to establish the tibial tunnel.
The tendon was retracted into the femoral tunnel through the articular cavity from the external tibial tunnel opening, and the tendon was retracted for 20 times for knee flexion and extension activities, and the femoral side was fixed with absorbable interface screws in an inside-out direction, and the knee was flexed by 20°, and the tibial side retraction line was tightened, while the tibial plateau was pushed posteriorly, and the grafted tendon in the tibial tunnel was fixed with absorbable interface screws in an outside-in direction.
2. Surgical technique of the residual preservation group
The autologous N cord tendon graft is made in the same way as the previous method.
The stump of ACL in the intercondylar fossa and tibia was preserved without cleaning the residual traces of the ACL stop. In the middle of the attachment point of the ACL stump in the intercondylar fossa, the knee was flexed at 100°, and a guide needle was inserted from the anteromedial approach, and the corresponding drill was selected according to the diameter of the grafted tendon to establish the femoral tunnel. In the middle of the attachment point of the residual ligament at the tibial end, i.e., 4-5 mm posterior to the anterior edge of the footprint of the medial tibial intercondylar crest, the tibial lateral ACL locator is placed, a guide needle is driven, and the corresponding tibial drill is selected according to the diameter of the grafted tendon to establish the tibial tunnel.
The tendon is retracted from the external tibial tunnel through the joint cavity into the femoral tunnel so that the residual ligament is wrapped around the surface of the reconstructed ligament like a sleeve. The tendon was pulled for 20 knee flexion and extension activities, the femoral side was fixed with absorbable interface screws in an inside-out direction, the knee was flexed at 20°, the tibial side traction line was tightened, and the tibial plateau was pushed posteriorly at the same time, and the grafted tendon in the tibial tunnel was fixed with absorbable interface screws in an outside-in direction.
III. Postoperative management
The postoperative period was protected by adjustable-angle knee brace, and the mobility of the brace was 0 to 50° within 2 weeks, 0 to 70° between 2 and 3 weeks, 0 to 90° between 3 and 4 weeks, 0 to 120° between 4 and 6 weeks, and the brace was worn for ≥8 weeks; functional exercise of the quadriceps muscle was started immediately after the operation; two months with double crutches and partial weight-bearing of the affected limb; running and jumping were prohibited for six months after the operation, and after six months, it was possible to Straight jogging, one year after surgery can resume normal sports.
4. Evaluation method
All patients were evaluated preoperatively and postoperatively, and the evaluation methods included subjective assessment, objective assessment and proprioceptive function assessment. The objective assessment was the Lachman test; the subjective assessment was the Lysholm score; and the proprioceptive function was assessed using the threshold to detection of passive motion (TTDPM) [2]. The authors used the CPM for TTDPM trials, and the CPM was corrected before each trial using a protractor and stopwatch
. During the test, the patient’s vision and hearing were isolated and the affected limb was placed on the CPM with a starting angle of 30°, the CPM was held at 0.5°/s to straighten the knee joint and the timing was started immediately, and the timing was stopped as soon as the patient felt the change in knee angle, each angle was repeated three times, and the TTDPM value was calculated as the average time and multiplied by 0.5°/s.
V. Statistical processing
The data were statistically tested using SPSS 16.0 software, and the difference was considered statistically significant at P<0.05.
Results
At the 12th postoperative month, 211 patients were followed up, including 147 cases in the disability preservation group and 64 cases in the standard group. Both groups returned to daily work and life, and regained their pre-injury level of motion. The quadriceps atrophy was obvious in the early postoperative period, but gradually returned to normal after 6 months to 1 year of postoperative training, and joint stability was significantly improved.
Lachman test: 55 patients were negative, 7 weakly positive and 2 positive after surgery in the standard group of 64 patients; 132 negative, 10 weakly positive and 5 positive in the disability preservation group of 147 patients. Using the rank sum test for comparison between the two groups, P= 0.2199, the difference between the two groups was not statistically significant.
The preoperative and postoperative scores of the affected knee were scored by the Lysholm scale in both groups, and the preoperative score was 56.91 ± 8.88 and the postoperative score was 90.84 ± 7.62 in the standard group; the preoperative score was 57.43 ± 5.47 and the postoperative score was 92.09 ± 4.65 in the disability preservation group, and the two scores were compared using the independent samples t-test, and the preoperative scores were compared between the two groups, p= 0.214,p=0.462 in the postoperative period.
The TTDPM was 2.09°±0.16° in the standard group and 1.68°±0.22° in the disability-protected group. The results of the independent sample t-test were compared between the two groups.
The ACL is an intra-articular but extra-synovial dense connective tissue that is enveloped by the synovial membrane. The proximal end of the ACL is attached to the fossa of the lateral femoral condyle near the posterior medial edge and travels obliquely in an anteromedial direction, ending distally in the anterior intercondylar fossa of the tibial plateau.The function of the ACL is to limit the combined motion of anterior displacement and internal rotation of the tibia [3].ACL fracture will have a significant impact on the stability of the knee joint, and without treatment, secondary injuries to the knee joint will continue to worsen and the function of the affected knee will be severely affected. If left untreated, secondary knee injuries will continue to worsen and the function of the affected knee will be severely affected, making it impossible to perform daily life and sports.
Currently, arthroscopic reconstructive surgery is used for complete ACL ruptures, which has the advantage of being less invasive and more effective. Traditional ACL reconstruction surgery recommends removal of residual ligamentous tissue, which facilitates clear arthroscopic visualization and localization of the femoral and tibial tunnels, but successful surgery does not necessarily lead to better results. This phenomenon has prompted scholars to further delve into ACL and to consider the inadequacies of traditional ACL reconstruction surgery.
Junkin et al. found that the ACL is not only a mechanical structure, but also a proprioceptive organ, rich in nerves and blood vessels, which helps maintain knee balance while maintaining the mechanical stability of the knee joint, and Lee et al. found that the ACL not only provides the body with proprioceptive information, but also stimulates the body’s protective and stabilizing muscle reflexes. The vast majority of ACL breaks occur in the proximal 1/2 of the segment.
It has been reported that most of the proprioceptive receptors of the ACL are located in the subsynovial layer near the tibial stop. Therefore, the tissue of the stump, especially at the tibial stop, should be preserved as much as possible during ACL reconstruction, thus making these residual tissues an important source of reinnervation of the grafted tendon.
We retrospectively analyzed 211 patients with complete ACL rupture who underwent arthroscopic reconstruction of the ACL using an autogenous N cord tendon between May 2004 and May 2010. between May 2004 and December 2007, all patients were reconstructed using the standard reconstruction technique, and between January 2007 and May 2010, all patients were reconstructed using the stump preservation technique.
At one year postoperative follow-up, there was no significant difference in the stability of the affected knee between the two groups, but the preserved-stump group outperformed the standard reconstruction group when measuring proprioception of the affected knee using passive activity perception thresholds (P=0.001). We analyzed that retained stump reconstruction of ACL has the following advantages.
1. Promoting proprioceptive recovery
The residual tibial or femoral stump fibers can preserve most of the proprioceptive function of the ACL and provide better position sensation of the knee after surgery, thus facilitating rapid rehabilitation of the affected knee. Excitation of these mechanoreceptors is associated with proprioception of the knee joint, and mechanoreceptor excitation can induce neuromuscular reflexes that contribute to increased knee stability.
Georgoulis et al [1] found that mechanoreceptors exist in the residual bundle branches of ACL, and these receptors may be an important source of reinnervation in ACL grafts. Zhang Lyr et al. also found that the preservation of residual bundle branches and stump fibers in ACL reconstruction is beneficial to the recovery of knee proprioception after surgery. Therefore, preserving some of the bundle branches in ACL reconstruction is beneficial for the mechanoreceptors to grow into the graft tendon, and the recovery of knee proprioception is better after surgery.
2. Facilitate the positioning of the bone tunnel
The preserved stump provides the possibility of precise positioning of the bone tunnel between the tibia and the femur, and the residual fibers can be used as an important reference for positioning the femoral and tibial tunnels.
3. Prevention of tunnel enlargement
Webster et al. found that tunnel enlargement is caused by biological factors (joint fluid). joint fluid can enter the bone tunnel after ACL reconstruction and have a soaking effect on the tunnel and the graft. Numerous studies have shown that the levels of IL-6 and NO in the joint fluid are significantly increased after ACL reconstruction, and these inflammatory factors stimulate the activity of osteoclasts and mediate the onset of bone resorption, resulting in the enlargement of the bone tunnel.
Rodeo et al. found a significant increase in osteoclasts in the proximal tunnel after ACL reconstruction through animal experiments, and Junkin et al [8] used stump-preserving ACL reconstruction, and intraoperatively observed a significant reduction or disappearance of joint fluid backflow from the tunnel after stump preservation, thereby reducing the synovial fluid immersion effect as well as inflammatory factor-mediated osteolysis.
Despite these advantages of stump-preserving ACL reconstruction, it is important to consider the potential disadvantages compared with standard ACL reconstruction. Although there are currently no significant complications associated with this technique, the risk of limited joint motion due to excessive intercondylar fossa tissue requires further study
The risk of limited motion due to excess intercondylar fossa needs to be further investigated. There have been several clinical reports of cyclops lesion after ACL reconstruction, and most authors now believe that this lesion may occur due to repeated impingement of the residual ruptured ligament fibers with the intercondylar fossa and the deposition of cartilage and bone debris around the tibial tunnel opening, resulting in a fibrous nodular mass that leads to limited knee extension.
In our surgical case, the femoral and tibial tunnels were established and the residual cartilage and bone debris were thoroughly removed by using a planer to enter the tunnels; the knee was routinely placed in the extended position after fixation of the graft tendon to observe the presence of intercondylar fossa impingement arthroscopically, and if impingement occurred, intercondylar fossa enlargement was performed immediately, thus effectively preventing these complications.
In conclusion, we believe that the use of arthroscopic stump-preserving reconstructive surgery technique in patients with complete ACL rupture, with intraoperative preservation of the tibial and femoral stumps as much as possible, is conducive to precise tunnel localization and prevention of bone tunnel enlargement, and more importantly, accelerates reinnervation of the grafted tendon and better promotes early recovery of knee proprioception.