Impact of Surgical Timing on Functional Outcomes after Anterior Cruciate Ligament Reconstruction.

Objectives: Although acute anterior cruciate ligament reconstruction (ACLR) is often avoided because of postoperative joint stiffness, delayed ACLR can lead to a longer recovery time and can have a negative impact on physical function due to detraining. This study aimed to determine the effects of acute ACLR on postoperative outcomes, including muscle strength, performance, and return to sports. Methods: A total of 110 patients who underwent anatomical ACLR using hamstring autografts were included in this study and were divided into three groups: acute (ACLR performed within 2 weeks after ACL injury), 2-6 weeks (ACLR performed between 2 and 6 weeks after injury), and 6-12 weeks (ACLR performed between 6 and 12 weeks after injury). Several parameters were evaluated, including range of motion, knee joint stability, isokinetic knee strength, performance, and return to sports. Results: No significant differences were found in the range of motion or knee joint stability between the groups. The acute group exhibited significantly greater quadriceps strength at 3 months postoperatively than the other groups (p < 0.05). The single-leg hop test showed that 66.7%, 38.7%, and 33.3% of the patients in the acute, 2-6 weeks, and 6-12 weeks groups, respectively, recovered to an LSI of 90% or greater (p = 0.09, Cramer's V = 0.27). All patients in the acute group were able to return to sports (p = 0.14; Cramer's V = 0.28). Conclusions: Acute ACLR is advantageous for the early recovery of strength and performance without adverse events. Acute ACLR may shorten the time spent away from sports activities.

Use of Unidirectional Porous ß-Tricalcium Phosphate in the Tibial Tunnel for Anterior Cruciate Ligament Reconstruction: A Case Series.

Bone defects in the tibial tunnel for anterior cruciate ligament (ACL) reconstruction can cause adverse events. The unidirectional porous tricalcium ß-phosphate (UDPTCP) has the potential to be used as a filling substitute for bone defects. In this case series, we present the first nine cases in which UDPTCP was used as a bone substitute in the tibial tunnel during ACL reconstruction. The patients comprised six males and three females, with an average age of 32 years (range: 16-50 years). A cylindrical UDPTCP measuring 10 x 20 mm was molded to fit the tibial tunnel and then implanted. At the one-year postoperative follow-up, none of the patients demonstrated any complications, and bone remodeling was observed on radiographs. Therefore, UDPTCP may provide a safe and reliable filling substitute for the tibial tunnel in ACL reconstruction.

Anatomical Single-Bundle Anterior Cruciate Ligament Reconstruction Using a Calcium Phosphate-Hybridized Tendon Graft with More than an Average of 5 Years of Follow-Up: A Follow-Up Study of a Randomized Controlled Trial.

Calcium phosphate (CaP)-hybridized tendon grafting using an alternate soaking process improves tendon-to-bone healing in anterior cruciate ligament (ACL) reconstructions. This study aimed to compare bone tunnel enlargement, knee osteoarthritis, and clinical results between CaP-hybridized tendon grafting and conventional grafting in anatomical single-bundle ACL reconstruction. This study was a follow-up of a randomized controlled trial. Between July 2011 and December 2015, 90 patients underwent unilateral anatomical single-bundle ACL reconstructions and were randomly assigned to the CaP-hybridized tendon grafting (CaP group, n = 45; age, 27.1 [14-54] years; sex, 21 males and 24 females) or conventional grafting (control group, n = 45; age, 22.9 [13-58] years; sex, 26 males and 19 females). The randomization was performed according to the days of the week when the patients first visited the outpatient. The CaP-hybridized tendon grafting was created intraoperatively. The tendon grafts were soaked in a calcium solution for 30 s. After that, the tendon grafts were soaked in a NaHPO4 solution for 30 s. This soaking cycle between the calcium solution and the NaHPO4 solution was repeated 10 times. The bone tunnel enlargement, osteoarthritis grade, clinical score, and sports level were evaluated in patients who could be followed up for >3 years (CaP group, n = 20, average follow-up period 6.0 [5.1-6.9] years; control group, n = 15, average follow-up period 5.6 [4.3-6.9] years). Clinical scores, sports levels, and osteoarthritis grades were analyzed using a generalized linear mixed model (GLMM) based on repeated measurement data from preoperative and final observations, with time, group, sex, age, and BMI as fixed effects and the effect of individual differences as variable effects. In addition, bone-tunnel enlargements were analyzed using generalized linear models (GLM) with group, sex, age, and BMI as the main effects. Compared with the control group, the CaP group exhibited significantly reduced bone-tunnel enlargement on the femoral side (anteroposterior diameter; CaP group, 7.9% [-1.1-16.8] vs. control group, 29.2% [17.9-40.5], p = 0.004, MCID 16.05, proximal-distal diameter; CaP group, 7.9% [-1.9-17.8] vs. control group, 22.8% [10.9-34.7], p = 0.062, MCID 15.00). The osteoarthritis grades progressed in both groups (p < 0.001). The clinical scores and sports levels were not significantly different between the groups. This study suggests that the calcium phosphate-hybridized tendon graft reduces femoral bone-tunnel enlargement after anatomical single-bundle anterior cruciate ligament reconstruction in an average >5-year follow-up period. A longer follow-up period is necessary to reveal the clinical effects of the calcium phosphate-hybridized tendon grafts in anterior cruciate ligament reconstruction.

Utility of axial magnetic resonance images for detecting meniscal ramp lesions associated with anterior cruciate ligament injuries.

Background: Ramp lesions (RLs), associated with anterior cruciate ligament (ACL) injuries, should be repaired to ensure postoperative knee stability. However, it is difficult to identify all RLs before surgery using conventional sagittal magnetic resonance (MR) images and arthroscopy from the anterior, medial, and lateral portals that are usually used during ACL reconstruction. We report the effectiveness of axial images for detecting RL. Methods: From January 2018, a total of 316 knees underwent primary ACL reconstruction with preoperative magnetic resonance imaging (MRI) examination at our hospital. Among these, 149 knees, which required meniscal suturing at the same time, were retrospectively investigated. This study evaluated 22 knees with confirmed RLs around the posterior horn of the medial meniscus. The effectiveness of the preoperative sagittal and axial MR images for detecting RL was assessed. With the MR image, a three-dimensional double-echo steady-state image with a flip angle of 25° was reconstructed into the sagittal and axial planes, respectively. Reconstructed images with 3-mm slices for sagittal slices and 1-mm slices for axial sections were used. The diagnosis was made based on the presence of RL (RL was present, RL may be present, and RL was not present) by four knee surgeons with more than 10 years of experience. Results: Approximately 53% of knee cases were diagnosed with RLs using sagittal images. Meanwhile, a diagnosis was achieved using axial images in 89% of cases. Conclusion: Axial MRI may be superior in detecting RLs.

Failure risks in anatomic single-bundle anterior cruciate ligament reconstruction via the outside-in tunnel technique using a hamstring autograft.

PURPOSE: To retrospectively evaluate the failure risk factors in anatomic single-bundle anterior cruciate ligament (ACL) reconstruction via outside-in tunnel technique using a hamstring autograft, and investigate the relationship between each risk factor. METHODS: The patients who underwent the ACL reconstruction with a minimum 1-year follow-up were included. We divided the patients into two groups - those who experienced graft failure (the failure group) and those who did not experience graft failure (the no failure group) - and compared their age, height, weight, sports activity level, graft size, and muscle strength. We defined graft failure as patients who underwent revision ACL reconstruction or had a second injurious ACL episode and those with a graft grade of C or D based on the International Knee Documentation Committee score. RESULTS: The study included 232 patients (101 male, 131 female; mean age at operation was 26.1 ±â€¯11.9 years). The failure rate was 11.6% (failure group: 27 patients; no failure group: 205 patients). The patients in the failure group were younger and had higher sports activity level than those in the no failure group. (p < 0.001 and p < 0.001, respectively). Patient body weight in the failure group was lower than that in the no failure group (p = 0.047). Regarding the graft size of the tibial side, the failure group had smaller graft sizes than the no failure group (p = 0.030). With respect to muscle strength, quadriceps strength 6 months after surgery in the failure group was stronger than that in the no failure group (p = 0.001). In addition, the hamstring/quadriceps strength (H/Q) ratios 3 and 6 months after surgery were lower in the failure group than that in the no failure group (p = 0.041 and p = 0.001, respectively). There was an association between the age and the body weight, between the body weight and the graft size of the tibial side, and between lower age and high sports activity. Moreover, the high quadriceps strength at 6 months and the low H/Q ratio at 3 months were related to the low H/Q ratio at 6 months. CONCLUSION: Young age, high activity sports level, low body weight, small graft diameter of the tibial side, high quadriceps strength at 6 months, and low H/Q ratio at 3 and 6 months can be failure risk factors in anatomic single-bundle ACL reconstruction via the outside-in tunnel technique using a hamstring autograft.

Safety and feasibility of using calcium phosphate hybridization method for quadriceps tendon-bone graft in anterior cruciate ligament reconstruction.

BACKGROUND: To improve tendon-to-bone healing in anterior cruciate ligament (ACL) reconstruction, a novel technique via the calcium phosphate (CaP) hybridization method for tendon graft using an alternate soaking process was developed. The use of the CaP hybridization method for quadriceps tendon-bone (QTB) graft in ACL reconstruction has not been reported in previous studies. Thus, this clinical trial aimed to clarify the safety and feasibility of using CaP hybridization method for quadriceps tendon-bone (QTB) graft in ACL reconstruction. METHODS: Eight patients (average age, 41.6 ±â€¯10.6 years; 2 men and 6 women) with unilateral ACL injury were included in this study. They underwent ACL reconstruction using QTB graft that hybridized CaP. The follow-up period was from 2 months to 4 years (average, 2.4 ±â€¯1.5 years). Cases of adverse events, including tumor formation, infection, fracture, contracture, severe pain, and re-rupture, were recorded. Moreover, clinical results (KT-1000 arthrometry, pivot-shift test, International Knee Documentation Committee grade, Lysholm scale, and sports activity level), and images of graft and bone tunnel (magnetic resonance imaging, arthroscopic appearance, and computed tomography) were also evaluated. RESULTS: No adverse events were observed in the follow-up periods. Postoperative clinical results showed improvement compared with the preoperative findings. The sports activity level after the surgery became equivalent to that before injury. There was no progression of bone tunnel enlargement. CONCLUSIONS: Using the CaP hybridization method for QTB graft in ACL reconstruction was safe and feasible in the clinical trial. Moreover, this method may improve clinical outcomes. In the future, it is necessary to verify the effect of the CaP hybridization method for QTB graft in ACL reconstruction.

Biological fixation between calcium phosphate-hybridized tendon graft and tibial bone tunnel in anatomic single-bundle ACL reconstruction - A case report.

The purpose of this study was to histologically observe a specimen of a calcium phosphate (CaP)-hybridized tendon graft-bone interface at the posterior side of tibial bone tunnel obtained during the revision anterior cruciate ligament (ACL) reconstruction. We present the case of a 15-year-old female who was returning to sports 7 months and 12 days after primary anatomic single-bundle ACL reconstruction with no instability. Re-rupture was diagnosed 9 months and 12 days after the surgery. At the joint aperture site, a firm biological fixation via direct bonding area, cartilaginous tissue, and dense collagen fiber were observed without the presence of a nonbonding gap area.

Morphological changes in the femoral and tibial bone tunnels after anatomic single-bundle anterior cruciate ligament reconstruction using a calcium phosphate-hybridized tendon graft in 2years of follow-up.

INTRODUCTION: A calcium phosphate (CaP)-hybridized tendon graft improves tendon-to-bone healing. The purpose of the study was to evaluate the progression of morphological changes in the femoral and tibial bone tunnels after anatomic single-bundle anterior cruciate ligament (ACL) reconstruction using the CaP-hybridized tendon graft versus an untreated tendon graft during 2 years of follow-up. HYPOTHESIS: We hypothesized that the CaP-hybridized tendon graft would prevent the progression of bone tunnel enlargement compared with the untreated tendon graft. PATIENTS AND METHODS: The CaP group comprised 19 patients, while the conventional group comprised 18. Computed tomography was performed at postoperative 1 week, 1 year, and 2 years. The bone tunnel enlargement and tunnel translation at the aperture of the femoral and tibial tunnels were analyzed. RESULTS: In the CaP group, the femoral bone tunnel did not expand during 2 years of follow-up. In the conventional group, the femoral bone tunnel diameters at postoperative 1 year and 2 years were enlarged compared with postoperative 1 week, and the proximal and distal walls of the femoral bone tunnel shifted proximally and distally, respectively. The femoral bone tunnel in the CaP group was smaller than that in the conventional group at 1 year postoperatively. Although the tibial bone tunnels expanded for up to 1 year postoperatively in both groups, the expanded bone tunnel reduced during 2 years of follow-up only in the CaP group. DISCUSSION: In anatomic single-bundle ACL reconstruction, the femoral bone tunnel in the CaP group did not expand or progress with time compared with the conventional group, while the tibial bone tunnel in the CaP group expanded for up to 1 year postoperatively and then reduced for up to 2 years postoperatively. The CaP-hybridized tendon can prevent the progression of bone tunnel enlargement. LEVEL OF EVIDENCE: Level II, Low-powered prospective randomized trial.

Anatomic single-bundle anterior cruciate ligament reconstruction using a calcium phosphate-hybridized tendon graft: a randomized controlled trial with 2 years of follow-up.

BACKGROUND: To improve tendon-to-bone healing in anterior cruciate ligament (ACL) reconstruction, a novel technique via calcium phosphate (CaP)-hybridized tendon graft using an alternate soaking process was developed. The purpose of this study was to evaluate the clinical results of anatomic single-bundle ACL reconstruction using the CaP-hybridized tendon graft with up to 2 years follow-up, and compare the outcome with conventional ACL reconstruction and preoperative data. METHODS: Ninety patients who required anatomic single-bundle ACL reconstruction were randomized to undergo either the CaP-hybridized tendon graft method (CaP group, n = 45) or the conventional method (conventional group, n = 45). At 1 and 2 years postoperatively, all patients were evaluated using KT-1000 arthrometry, pivot-shift test, International Knee Documentation Committee (IKDC) grade, Lysholm scale, and Tegner scale; at the same timepoints, bone tunnel enlargement was evaluated using computed tomography, and the tendon graft intensity was evaluated on magnetic resonance imaging. Tendon graft appearance was evaluated arthroscopically once after a period of up to 2 years postoperatively. Cases of re-rupture and adverse events were recorded in both groups. RESULTS: In both groups, the KT-1000 arthrometry, pivot-shift test, IKDC grade, and Lysholm scale results at 1 and 2 years postoperatively were superior to preoperative data; these results did not significantly differ between groups at either timepoint. The rate of increase of the cross-sectional area of the femoral bone tunnel in the CaP group was smaller than that in the conventional group at 1 year postoperatively. The other results did not significantly differ between the two groups at any timepoint. There were two cases of re-rupture in the CaP group, and six cases of re-rupture in the conventional group. There were no adverse events during follow-up in either group. CONCLUSIONS: Anatomic single-bundle ACL reconstruction using a CaP-hybridized tendon graft was safe, and resulted in improved clinical outcomes at 2 years postoperatively compared with preoperative data; the outcomes were comparable with the conventional method. A longer follow-up is needed to clarify the clinical effects of the CaP-hybridized tendon graft in anatomic single-bundle ACL reconstruction. TRIAL REGISTRATION: UMIN, UMIN000019788 Registered 14 November 2015-Retrospectively registered.

Radiolucent lines are decreased at 3 years following total knee arthroplasty using trabecular metal tibial components.

Objective To analyse location and frequency, and change over time, of radiolucent lines (RLLs) around trabecular metal tibial components in total knee arthroplasty (TKA). Methods Osteoarthritic knees in patients who had undergone TKA were retrospectively evaluated via analysis of RLLs on anteroposterior and lateral X-rays obtained at 2 and 6 months, and 1, 2 and 3 years following TKA. Results In 125 osteoarthritic knees from 90 patients (mean age, 75.0 ± 6.2; 21 male/69 female), frequency of RLLs around trabecular metal tibial components was generally highest at 2 and 6 months, and 1 year following TKA, then gradually decreased over the 3-year follow-up. Frequency of RLLs around trabecular metal tibial components was greater at the tip of the two pegs, particularly the medial peg, and around the pegs, versus other zones. No postoperative revisions were performed for loosening. Conclusions Over 3 years following TKA, RLLs were most frequently observed up to 1 year, then gradually decreased. RLLs were significantly more frequent in the medial peg zone and zones close to the medial peg than in other zones.

Investigation of perioperative safety and clinical results of one-stage bilateral total knee arthroplasty in selected low-risk patients.

BACKGROUND: An increased perioperative complication rate has been a concern with one-stage bilateral total knee arthroplasty (TKA). The purpose of this study was to retrospectively investigate the perioperative safety and clinical results of one-stage bilateral TKA in selected low-risk patients. METHODS: Sixty-seven patients who received one-stage bilateral TKAs for osteoarthritis who were American Society of Anesthesiology (ASA) class 1 or 2 were included in this study. Perioperative complications, blood loss, transfusion rate, blood laboratory results, and clinical results were evaluated up to 1 year after surgery. RESULTS: No major complications (deep infection, pulmonary embolism, cerebrovascular accident, myocardial infarction, death, or removal or revision of the implants) were observed. The average total blood loss was 1139.5 ml. The transfusion rate was 95.5%. Postoperative hemoglobin level and C-reactive protein level gradually improved up to postoperative day 21 (P < 0.01). Bilateral knee extension knee angles and clinical scores improved postoperatively as compared with preoperative values (P < 0.01). CONCLUSIONS: Although total blood loss and transfusion rate can be high, this preliminary case series suggested that the one-stage bilateral TKA in ASA class 1 or 2 patients can have high perioperative safety levels, and good clinical results can be obtained up to 1 year after surgery. If low-risk patients are selected for bilateral TKA, a one-stage procedure can be beneficial for patients, with a minimal increase in the risk of complications.

Calcium phosphate-hybridized tendon grafts reduce femoral bone tunnel enlargement in anatomic single-bundle ACL reconstruction.

PURPOSE: This study aimed to clarify the effect of calcium phosphate (CaP)-hybridized tendon grafting versus unhybridized tendon grafting on the morphological changes to the bone tunnels at the aperture 1 year after anatomic single-bundle anterior cruciate ligament (ACL) reconstruction. METHODS: Seventy-three patients were randomized to undergo the CaP (n = 37) or the conventional method (n = 36). All patients underwent computed tomography (CT) evaluation 1 week and 1 year post-operatively. The femoral and tibial tunnels at the aperture were evaluated on reconstructed 3D CT images. Changes in the cross-sectional area (CSA) and diameters of the femur and the tibia, and the translation rate of the tunnel walls and the morphological changes of both tunnels were assessed. RESULTS: There was a significant reduction in the increase in the CSA and the anterior-posterior and proximal-distal tunnel diameters on the femoral side in the CaP group as compared with the conventional group. On the femoral side, the translation rate of the posterior wall was significantly larger in the CaP group than in the conventional group, whereas the translation rate of the distal wall was significantly smaller in the CaP group than in the conventional group. CONCLUSIONS: As compared with the conventional method, the CaP-hybridized tendon graft reduced bone tunnel enlargement on the femoral side 1 year after anatomic single-bundle ACL reconstruction due to an anterior shift of the posterior wall and reduced distal shift in the femoral bone tunnel. Clinically, the CaP-hybridized tendon grafts can prevent femoral bone tunnel enlargement in anatomic single-bundle ACL reconstruction. LEVEL OF EVIDENCE: I.

Effect of calcium phosphate-hybridized tendon graft in anterior cruciate ligament reconstruction: a randomized controlled trial.

BACKGROUND: The authors developed a novel technique to improve tendon-bone healing by hybridizing calcium phosphate (CaP) with a tendon graft using an alternating soaking process. HYPOTHESIS: Anterior cruciate ligament (ACL) reconstruction using the CaP-hybridized tendon graft would have a better clinical outcome and reduce the percentage of bone tunnel enlargement compared with a conventional method because of the enhanced anchoring between the tendon graft and the bone. STUDY DESIGN: Randomized controlled trial; Level of evidence, 1. METHODS: Patients (N = 64) with unilateral ACL rupture underwent arthroscopically assisted single-bundle ACL reconstruction using a 4-strand semitendinosus tendon or 4-strand semitendinosus and gracilis tendons with EndoButton femoral fixation and screw washer tibial fixation. These patients were equally randomized to undergo the CaP (n = 32) or conventional (n = 32) method using a transtibial tunnel approach according to the closed envelope method. In the CaP group, the tendon graft was hybridized with the CaP at both ends of the graft. One surgeon performed all reconstructions without knowing which graft was prepared. Patients' backgrounds regarding age at surgery, gender, period before surgery, and associated meniscal injuries were similar in the 2 groups. All patients followed the same postoperative protocol. At 1 and 2 years after surgery, they were evaluated with the manual knee laxity test, KT-1000 arthrometry, International Knee Documentation Committee (IKDC) examination form, Tegner scale, and Lysholm scale. Also, 1 year postoperatively, bone tunnel enlargement was analyzed using computed tomography, intensity of the tendon graft by magnetic resonance imaging (MRI), and tendon graft appearance by arthroscopic examination. All the examinations were performed blindly. RESULTS: All patients underwent a minimum 2-year follow-up. KT-1000 arthrometry data indicated statistically significant decreased average anterior tibial translation in the CaP group compared with the conventional method group: 1.0 ± 2.0 mm versus 1.9 ± 1.6 mm (P < .05), respectively, at 1 year; 1.6 ± 2.1 mm versus 2.6 ± 2.4 mm (P < .05), respectively, at 2 years. The Lysholm score was higher in the CaP group than in the conventional method group at 2 years (96.9 ± 4.3 vs 91.7 ± 13.3, P < .05). The CaP-hybridized tendon graft reduced the percentage of bone tunnel enlargement of the anteroposterior diameter at the main joint aperture site 1 year postoperatively (femoral side: 15.5% ± 13.4% vs 22.1% ± 16.4%, P < .05; tibial side: 19.3% ± 17.1% vs 26.1% ± 13.7%, P < .05). The results of the pivot-shift test, IKDC grade, and Tegner score; the intensity of the tendon graft (MRI); and arthroscopic appearance were not significantly different at both follow-up periods in the 2 groups. CONCLUSION: The CaP-hybridized tendon graft improved anterior knee stability and Lysholm scores at the 2-year follow-up and improved anterior knee stability and reduced the percentage of bone tunnel enlargement in both tunnels at the 1-year follow-up compared with the conventional method for single-bundle ACL reconstruction. However, longer follow-up is needed to investigate the appearance of any increased instability.

Peripheral targets influence sensory-motor connectivity in the neonatal spinal cord: sciatic nerve axotomy in Bax-deficient mice.

In neonatal animals, peripheral nerve axotomy induces cell death in the corresponding dorsal root ganglion neurons and motoneurons, indicating that trophic interactions between these neurons and their targets control neuronal survival at this age. However, axotomy-induced cell death masks the role of peripheral tissues in regulating the central connections between these neurons in neonates. Since we have shown in Bax-deficient mice (Bax-/-) that transection of the sciatic nerve at postnatal day (P) 0 rarely induced apoptosis in motoneurons, we examined whether peripheral nerve axotomy eliminates synaptic connections between group Ia afferents and motoneurons in Bax-/-. After the axotomy, we observed in P7 Bax-/- that many axons survived in the fourth lumber (L4) dorsal root and that primary afferent projections to L4 motor pools also remained. Sciatic nerve stimulation evoked synaptic responses in L4 ventral roots in these mice although the amplitudes were considerably smaller and the onset latencies longer compared with the controls. Our results suggest that the monosynaptic connection between group Ia afferents and motoneurons is morphologically and functionally preserved following axotomy. Peripheral tissues may modulate synaptic connectivity but do not contribute to the maintenance of primary afferent projections in the stretch reflex pathway at an immature stage.

The effects of sciatic nerve axotomy on spinal motoneurons in neonatal Bax-deficient mice.

During development, the survival of spinal motoneurons depends on the integrity of the connection to their peripheral targets. Peripheral nerve axotomy induces apoptosis in neonatal neurons supplying axons to the nerve. Bax is known to promote apoptosis among developing neurons. To examine the effect of axotomy on spinal motoneurons in Bax-deficient (Bax-/-) and wild-type neonatal mice (Bax+/+), the sciatic nerve was axotomized on postnatal day (P) 0, and motoneurons in the fourth lumbar (L4) segment were visualized at P7 by acetylcholinesterase (AChE) histochemical staining. Presumably due to the reduction in naturally occurring cell death resulting from the deficiency of Bax, there were about 50% more AChE-positive cells in Bax-/- than in Bax+/+. Motoneurons in the dorsolateral motor pool of L4 project through the sciatic nerve. In Bax+/+, axotomy of the sciatic nerve induced significant cell loss in the pool. Most motoneurons survived such axotomy in Bax-/-, although they appeared atrophic and their AChE expression was decreased. Motoneurons may receive vital support retrogradely from their targets, and loss of such support may lead to hypofunction of spinal motoneurons, as indicated by the reduced production of AChE by axotomized motoneurons and their small size in Bax-/-.