ACL injuries are often accompanied by damage to the meniscus and articular cartilage, [1] for which reconstruction is considered the best option to restore knee function, but there is still controversy over the surgical approach to reconstruction [2]. With the anatomical reconstruction of grafts and improvement of fixation methods, the mechanical stability of the knee joint has been greatly improved, but the subjective perception of patients is still unsatisfactory. the ACL is not only a mechanical structure but also a proprioceptive organ, rich in nerves and blood vessels, which assists in maintaining the knee joint balance while maintaining the mechanical stability of the knee joint [3]. In recent years, more and more scholars have started to perform intrathecal reconstruction of the ACL with preserved stump to increase joint stability and to promote vascularization of the graft and restoration of joint proprioception.
Therefore, this study hypothesized that preserving the original ACL stump and reconstructing the ACL with the graft penetrating through it could help establish a knee joint with a high degree of stability, contribute to tendon bone healing and proprioceptive reconstruction, and promote early recovery of postoperative knee function. 31 patients with ACL injury admitted from July 2009 to June 2011 were reconstructed by preserving the ligament stump and applying an autologous N cord tendon intrathecal The clinical efficacy of ACL intrasynovial reconstruction was compared with that of 37 patients who underwent autologous N cord tendon reconstruction without preserving the ligament stump during the same period, and the clinical efficacy of ACL intrasynovial reconstruction was compared with that of reconstruction without preserving the stump through postoperative follow-up analysis. The results are reported as follows.
1. Materials and methods
1.1 Clinical data
Sixty-eight ACL patients with reconstruction continuity from July 2009 to June 2011 complained of weakness, soreness and discomfort of the affected limb on admission, and limited acute turning and stopping. Preoperatively, the anterior drawer test, Lachman test, and axial shift test signs were all positive under anesthesia, and the KT2000 measurements were all >3 mm lateral-lateral difference, and the MRI examinations of the knee joint were all suggestive of anterior cruciate ligament injury.
Preserved stump intrathecal reconstruction inclusion criteria: all ACL injuries were first confirmed arthroscopically, and it was confirmed that more than 1/3 of the ACL tibial stump length was preserved. Exclusion criteria: combination of posterior cruciate ligament injury or grade III collateral ligament injury; combination of OutBridge grade IV articular cartilage injury; ACL tibial stump with inconspicuous or preserved length < 1/3. Thirty-one of these patients were enrolled in the preserved stump intrathecal reconstruction group.
Inclusion criteria for the stump cleaning group (control group): arthroscopic confirmation and preservation of <1/3 or >1/3 of the length of the ACL tibial stump; exclusion criteria: combined posterior cruciate ligament injury or grade III collateral ligament injury; combined OutBridge grade IV articular cartilage injury; 37 patients were enrolled in the stump cleaning group. All patients gave informed consent.
1.1.1 Intrasphincteric reconstruction group.
There were 18 male cases and 13 female cases; age ranged from 15 to 46 years, with an average of 28.4 years. Among them, 11 cases were left-sided and 20 cases were right-sided. There were 9 cases of combined meniscal injury and 8 cases of Outbridge degree I cartilage injury. The time from injury to surgery ranged from 2 to 22 weeks, with an average of 8.5 weeks. All patients in this group had a clear history of trauma, including 9 cases of car accident impact injury, 15 cases of sports injury, 6 cases of life sprain, and 1 case of heavy object smash.
1.1.2 Control group.
There were 21 male cases and 16 female cases; age ranged from 15 to 55 years old, with an average of 32.1 years old. Among them, 13 cases were left-sided and 24 cases were right-sided. There were 15 cases of combined meniscal injury and 16 cases of Outbridge degree I cartilage injury. The time from injury to surgery ranged from 2 to 50 weeks, with an average of 23.1 weeks. All patients in this group had a clear history of trauma, including 14 cases of car accident impact injuries, 12 cases of sports injuries, 5 cases of life sprains, and 6 cases of heavy object injuries.
In both groups, there were no statistically significant differences (P>0.05) in the general data of preoperative Lysholm score, International Knee Documentation Committee knee assessment scale (IKDC) score, gender, age, combined injuries, Lysholm score, IKDC score, and disease duration, which were comparable. The differences were statistically significant (P<0.05) when comparing the time from injury to surgery, but the patients with longer time from injury to surgery met the inclusion criteria.
1.3 Surgical method
Knee stability examination was first performed under anesthesia, including anterior drawer test, Lachman test, axial shift test, and KT2000 measurement. The knee was routinely examined using three accesses: anterolateral (LP), intermediate (CP) and anteroinferior assisted access (AMP) (Figure 1), and joint cavity cleaning was performed and the injured meniscus was sutured or trimmed. The morphology of the ACL stump was observed to assess whether it met the inclusion criteria. The same ACL reconstruction technique, i.e., single bundle isometric anatomical reconstruction, was used in both groups. In the intrathecal reconstruction group, a longitudinal incision of approximately 3 cm in length was made 3 cm medial to the midpoint of the tibial tuberosity on the affected or healthy side to expose the goose foot, and the semitendinosus and thin femoral tendons were excised with a tendon stripper for backup. With the knee flexed greater than 120°, an anterolateral approach was made for surveillance, the intercondylar fossa was cleaned and the lateral posterior wall of the intercondylar fossa was exposed, and a hollow drill was inserted through the anteroinferior auxiliary approach to locate the center point of the femoral stump of the ACL, i.e., below the resident’s crest and over the center of the lateral bifurcation crest of the intercondylar fossa, to create a suitable femoral tunnel.
3. Discussion
3.1 Advantages of preserving the stump for ACL reconstruction
In this study, we found no difference in anterior-posterior stability of the knee joint after surgery by applying an intrathecal reconstruction of the ACL with and without preservation of the stump by the autologous N cord tendon. However, there were differences in postoperative knee function scores, especially in early postoperative knee function scores. This suggests that reconstruction of the ACL by preserving the stump can establish a knee with a high degree of stability, contribute to the reconstruction of proprioception, and promote the recovery of postoperative knee function at an early stage. If the tibial stump of the ACL is preserved, it may have the advantage of accelerating graft vascularization, promoting proprioceptive recovery, and preventing tunnel enlargement.
3.1.1 Accelerated graft tendon vascularization
Even when the ACL is reconstructed anatomically, the recovery of function is unsatisfactory. The slower the rate of graft tendon ligamentization, the longer the postoperative recovery period. In recent years, some scholars have begun to study the process and mechanism of neurovascular regeneration and pathological bone tunnel enlargement of the graft in order to seek early restoration of normal function of the ACL [4]. Preservation of the tibial stump for ACL reconstruction accelerates the regeneration and ligamentization of the graft, and improves the biological habitat for tibial tunnel graft healing [5].The grafts used in ACL reconstruction have no blood supply and undergo ischemic necrosis, revascularization, proliferation, and remodeling in vivo. The faster the graft recanalization process, the less the adverse effects of necrosis.
The blood supply to the ACL is mainly from the surrounding synovial membrane and the small arteries of the infrapatellar fat pad [6], and after ACL reconstruction, the blood supply is provided by the infrapatellar fat pad, the tibial stump fibers, and the small synovial arteries between the anterior and posterior cruciate ligaments. Therefore, preservation of the tibial stump fibers, infrapatellar fat pad and surrounding synovial membrane is important for the vascularization of the graft.Annear et al. comparatively studied the rate and intensity of graft revascularization after preservation versus non-preservation ACL reconstruction and showed that preservation reconstruction promotes early graft vascularization [7].
3.1.2 Promotion of proprioceptive recovery
As a functional sensory organ, the ACL not only serves as a protective and stabilizing muscle response but also provides proprioceptive information. Restoring the proprioceptive function of the ACL is as important as restoring the stability of the ACL [5]. Sha Lin et al [8] showed that the mechanoreceptors in the lateral tibial stump could survive for a long time after ACL injury, and there was no significant degeneration and atrophy within 12 months after injury, so preserving the lateral tibial stump during ACL reconstruction may help patients recover their proprioception after surgery.Lee et al [9-10] compared the clinical efficacy of ACL reconstruction with preserving the ACL stump using autologous N cord tendon, and found that Patients with >20% preserved ACL stumps had significantly better knee function and proprioception than those with <20% preserved stumps, and immunohistochemical examination of the injured ACL ligament stumps revealed the presence of mechanoreceptors.
Ochi et al [11] detected reflex waves in the central nervous system by stimulating the injured ACL stump, indicating the residual receptors in the stump. Therefore, preserving the stump when reconstructing the ACL preserves these receptors and promotes the recovery of ACL proprioceptive function. In the preserved stump intrasphincteric reconstruction group, the length of the preserved ligament stumps were all more than 1/3, which was longer than the preserved ligament stumps reported in the literature. The reconstructed ligament could be wrapped by the ligament stump containing proprioceptors, which was conducive to the vascularization of the reconstructed ligament and the generation of proprioceptive fibers, and promoted the early recovery of postoperative knee function. In the early postoperative follow-up, it was also found that all knee function scores were higher in the preserved stump reconstruction group than in the control group.
3.1.3 Prevention of tunnel enlargement
Bone tunnel enlargement is one of the important causes of ACL reconstruction failure. Biological factors that cause bone tunnel enlargement include immune rejection of allogeneic tissue (allogeneic tendon), toxic substances (ethylene oxide, metals), osteoclast necrosis caused by thermal effects during drilling of the bone tunnel and cytokine-mediated nonspecific inflammatory reactions [12]. The arthroscopic surgeon is able to control many biological and mechanical factors. However, the presence of certain concentration levels of growth factors in the injured joint cavity is an inherent biological factor that cannot be easily controlled.
A few weeks after ACL injury or reconstruction, the levels of NO, various inflammatory factors such as IL-1, IL-6, and TNF-a concentrations in the synovial fluid of the joint cavity are increased [13].Barber et al. found that IL-1β, IL-6, and TNF-a activate osteoclasts and mediate bone resorption thus leading to bone tunnel enlargement [14].Zysk et al [15] found that in the postoperative joint night This “synovial fluid immersion effect” was also confirmed by Zysk et al [15], who found increased levels of IL-6 in the postoperative joint night, and that healing of the proximal end of the tunneled graft was incomplete and very slow.
Lee et al [3] first reported that after ACL reconstruction with preserved tibial stumps, the graft and stump were in close proximity to each other, avoiding synovial fluid leakage and reducing the “synovial fluid immersion effect” and the enlargement of the bone tunnel due to inflammatory factor-mediated osteolysis. Sun Lei et al [16] showed that preserving the stump for ACL reconstruction can significantly reduce or delay the leakage of joint fluid into the bone tunnel. In the group using intrasphincteric reconstruction with preserved stump, the tibial stump and the graft were in close proximity, which reduced leakage of joint fluid into the bone tunnel and prevented the enlargement of the bone tunnel. In the postoperative follow-up of the preserved stump reconstruction group, no bone tunnel enlargement was observed, and the tendon bone healed well.