Posterior tibial slope measurements based on the full-length tibial anatomic axis are significantly increased compared to those based on the half-length tibial anatomic axis.

PURPOSE: This study aimed to compare the difference in posterior tibial slope (PTS) measurements based on the full-length and half-length tibial anatomic axes of the same group of patients. It was hypothesized that the obtained PTS values would be affected by the length of tibia chosen during the measurements. METHODS: Full-length true lateral tibia radiographs were obtained for each patient who underwent anterior cruciate ligament reconstruction (ACLR) in our department. PTS measurements were obtained by measuring the angle between the full-length or half-length tibial anatomic axis and an average of the lateral and medial tibial plateau. The anatomic axis was defined as the center of the tibial diaphysis. The PTS measurements from the full-length and half-length true lateral tibia radiographs were obtained and compared. Additionally, the absolute difference and the relationship between the two PTS measurements were calculated and analyzed. RESULTS: A total of 200 ACL-injured patients were included in this study. The average PTS values using the anatomic axis were 15.9 ± 3.7° and 14.1 ± 3.7° on full-length and half-length true lateral tibial radiographs. There was a significant difference between the measurements with the full-length and half-length tibial radiographs (P < 0.01). Additionally, 49.5% (n = 99) of patients had ≥ 2.0° differences between the full-length and half-length anatomic axis PTS measurement techniques; meanwhile, a strong and significant linear relationship (r = 0.95; P < 0.001) was identified between the two PTS measurements. CONCLUSION: There were significant differences and linear relationships between PTS measurements that measured the anatomic axis from full-length and half-length true lateral tibia radiographs. Therefore, the obtained PTS values were strongly associated with the length of tibia chosen during the measurements. Surgeons should pay more attention to the measurement techniques and the tibial length when considering the role of PTS in ACL injury and ACLR failure. Knowledge of the association is very important for calculating potential closing wedge proximal tibial osteotomies to correct excessive PTS in the setting of ACLR failures. LEVEL OF EVIDENCE: IV.

Excessive lateral patellar translation on axial computed tomography indicates positive patellar J sign.

PURPOSE: The purpose of the study was to quantify the patellar J sign using traditional computed tomography (CT) scans. METHODS: Fifty-three patients (fifty-three knees) who suffered from recurrent patellar instability were included and analyzed. The patellar J sign was evaluated pre-operatively during active knee flexion and extension. It was defined as positive when there was obvious lateral patellar translation, and negative when there was not. The CT scans were performed in all patients with full knee extension; and the parameters including bisect offset index (BOI), patellar-trochlear-groove (PTG) distance, and patellar lateral tilt angle (PLTA) were measured on the axial slices. All the three parameters were compared between the J sign-positive group (study group) and the J sign-negative group (control group). In addition, the optimal thresholds of the three CT scan parameters for predicting the positive patellar J sign were determined with receiver operating characteristic (ROC) curves, and the diagnostic values were assessed by the area under the curve (AUC). RESULT: Among the fifty-three patients (fifty-three knees), thirty-seven (70%) showed obvious lateral patellar translation, which were defined as positive J sign (study group), and the remaining sixteen (30%) who showed no lateral translation were defined as negative J sign (control group). The mean values of the three CT parameters in the study group were all significantly larger compared to the control group, including BOI (121 ± 28% vs 88 ± 12%, P = 0.038), PTG distance (5.2 ± 6.6 mm vs - 4.4 ± 5.2 mm, P < 0.05), and PLTA (34.9 ± 10.5° vs 25.7 ± 3.4°, P = 0.001). Furthermore, the evaluation of ROC analysis showed that the AUC of BOI was the largest (AUC = 0.906) among the three parameters, and the optimal threshold of BOI to predict the positive patellar J sign was 97.5% (Sensitivity = 83.3%, Specificity = 87.5%). CONCLUSIONS: In this study, the prevalence of positive patellar J sign was 70%. The BOI measured from the axial CT scans of the knee joint can be used as an appropriate predictor to differentiate the positive J sign from the negative J sign, highlighting that the excessive lateral patellar translation on axial CT scan indicates positive patellar J sign. LEVEL OF EVIDENCE: IV.

Patients with high-grade pivot-shift phenomenon are associated with higher prevalence of anterolateral ligament injury after acute anterior cruciate ligament injuries.

PURPOSE: To compare the prevalence of concomitant anterolateral ligament (ALL) injury between patients with high-grade (grades II and III) pivot-shift and those with low-grade (grades 0 and I) pivot-shift phenomenon after acute anterior cruciate ligament (ACL) injuries. METHODS: Sixty-eight patients with an acute ACL injury who showed high-grade (grades II and III) pivot-shift phenomenon were enrolled as the study group. They were matched in a 1:1 fashion to another 68 ACL-injured control participants who showed low-grade (grades 0 and I) pivot-shift phenomenon during the same study period. Patients were matched by age, sex, and time from injury to surgery. A standardized pivot-shift test was performed under anesthesia for all the patients. Two blinded musculoskeletal radiologists reviewed the magnetic resonance imaging (MRI) scans for the presence of concomitant ALL injury. The grade of an ALL injury was divided into grade 0 (normal), grade I (sprain), grade II (partial tear), and grade III (complete tear). The prevalence and the grade of concomitant ALL injury were further compared between the study group and the control group. RESULTS: Overall, the prevalence of concomitant ALL injury in the study group (94.1%, 64/68) was significantly higher than that in the control group [60.3%, (41/68), P < 0.05]. Specifically, there were 49 patients (49/64, 76.6%) who showed grade II/III (partial/complete tear) MRI evidence of concomitant ALL injury, which was also significantly higher than that in the control group (12/41, 29.3%). CONCLUSIONS: Patients with high-grade pivot-shift phenomenon showed higher prevalence of concomitant ALL injury compared to those with low-grade pivot-shift phenomenon after acute ACL injuries. Careful assessment and proper treatment of this concomitant injury should be considered especially in knees with high-grade pivot-shift phenomenon. LEVEL OF EVIDENCE: III.

Complete posterolateral meniscal root tear is associated with high-grade pivot-shift phenomenon in noncontact anterior cruciate ligament injuries.

PURPOSE: The purpose of this study was to investigate whether the complete posterolateral meniscal root tear (PLMRT) would be associated with high-grade pivot-shift phenomenon in noncontact anterior cruciate ligament (ACL) injuries. METHODS: From 2013 to 2015, a total of 1095 consecutive patients were diagnosed as having noncontact ACL injuries and underwent primary ACL reconstructions. Among them, 140 patients were arthroscopically verified to have concomitant PLMRTs. Application of the exclusion criteria finally left 74 patients who were finally allocated into high-grade pivot-shift (grades II and III) group (n = 51) and low-grade pivot-shift (grades 0 and I) group (n = 23) according to the results of pre-operative pivot-shift tests performed under anesthesia. Predictors of high-grade pivot-shift phenomenon, including degree of PLMRTs, integrity of posterior MFLs, status of lateral meniscal extrusion, age, sex, body mass index (BMI), and KT-1000 arthrometer side-to-side difference (SSD), were assessed by multivariable logistic regression analysis. RESULTS: The proportion of patients with complete PLMRT in high-grade pivot-shift group was significantly larger than that in low-grade pivot-shift group. In addition, complete PLMRT was significantly [odds ratio (OR) 4.044; 95% CI 1.125-14.534; P = 0.032] associated with high-grade pivot-shift phenomenon in noncontact ACL injury, especially for those with a time from injury to surgery of ≥12 weeks (OR 16.593; 95% CI 1.073-56.695; P = 0.014). However, no significant association was identified between neither the integrity of posterior MFLs nor the status of lateral meniscal extrusion and the high-grade pivot-shift phenomenon. CONCLUSION: Complete PLMRT is identified to be an independent risk factor of high-grade pivot-shift phenomenon in noncontact ACL injuries, particularly for those with a time from injury to surgery of ≥12 weeks. LEVEL OF EVIDENCE: IV.

Biomechanical and Biological Findings Between Acute Anterior Cruciate Ligament Reconstruction With and Without an Augmented Remnant Repair: A Comparative in Vivo Animal Study.

PURPOSE: To investigate whether remnant-preserving anterior cruciate ligament reconstruction (ACLR) for acute complete anterior cruciate ligament (ACL) tears can improve the biomechanical strength, revascularization status, and proprioceptive recovery potential of the grafted tendons compared with conventional ACLR. METHODS: An acute complete ACL femoral detachment model was created in 60 rabbits. The animals were randomly allocated into the remnant-repairing ACLR group (group 1, n = 30) or the conventional ACLR group (group 2, n = 30). The ACL remnants were either acutely repaired with a femoral tensioning technique in group 1 or completely debrided in group 2. For group 1, remnant structural integrity was evaluated macroscopically and divided into grade A (bridging femur and tibia) and grade B (not bridging femur and tibia). Then, the remnant-to-graft healing capacity was assessed histologically. For intergroup comparisons, the biomechanical strength of the grafted tendons was evaluated by tensile tests and the revascularization status (vascular endothelial growth factor) and proprioceptive recovery potential (neurofilament) of the grafted tendons were evaluated by immunofluorescent staining. All assessments were performed postoperatively at week 24. RESULTS: In group 1, 60% of remnants (18 of 30) showed grade A and 40% (12 of 30) showed grade B structural integrity. An obvious remnant-to-graft interval could be detected through the whole length of the graft. Tensile tests showed that the ultimate failure loads of the grafted tendons were similar between the groups (P = .365). In addition, there were no significant differences in the number of vascular endothelial growth factor-positive vessels and neurofilament-positive mechanoreceptors at either the femoral (P = .887 and P = .578, respectively), midsubstance (P = .063 and P = .546, respectively), or tibial (P = .193 and P = .978, respectively) level within the grafted tendons between the groups. CONCLUSIONS: The acute remnant-repairing ACLR in our rabbit femoral ACL detachment model showed no biomechanical and biological advantages compared with conventional ACLR. The acutely repaired ACL remnants presented a high proportion of poor structural integrity and low remnant-to-graft healing capacity. CLINICAL RELEVANCE: During our clinical practice, conventional ACLR may still not be replaced by remnant-repairing ACLR for the treatment of acute complete ACL tears.

Clinical Outcomes of Combined Lateral Extra-articular Tenodesis and Intra-articular Anterior Cruciate Ligament Reconstruction in Addressing High-Grade Pivot-Shift Phenomenon.

PURPOSE: To evaluate the clinical outcomes of combined lateral extra-articular tenodesis (LET) and intra-articular anterior cruciate ligament (ACL) reconstruction (ACLR) in addressing the high-grade pivot-shift phenomenon. METHODS: The PubMed/Medline database was searched for articles reporting clinical outcomes of combined LET and intra-articular ACLR in treating ACL injuries with high-grade pivot shift. High-grade pivot shift was defined as the presence of moderate to severe rotational instability shown by a grade II or III manual pivot shift preoperatively (grade 0, normal; grade I, glide; grade II, clunk; and grade III, locking, according to International Knee Documentation Committee [IKDC] form). The postoperative manual pivot-shift grading during the clinical follow-up visit was the primary outcome variable. Moreover, the prevalence of residual pivot shift (grade I, II, or III), distribution of objective IKDC scores, and anterior knee stability were also compared between patients with and without an additional LET procedure. RESULTS: Seven studies were included. Overall, 326 patients (326 knees) with high-grade pivot shift underwent combined LET and intra-articular ACLR with a mean follow-up period of 46.2 months (range, 24 to 76 months). There were 274 patients (84.1%) with grade 0, 42 (12.9%) with grade I, and 10 (3.0%) with grade II pivot shift at the final follow-up. Among the 5 comparative studies, the prevalence of residual pivot shift was significantly lower (P < .05) in patients with LET plus ACLR (13.3%, 30 of 226) than those with isolated ACLR (27.2%, 67 of 246). However, the distribution of objective IKDC scores and anterior knee stability showed no significant differences between groups. CONCLUSIONS: The combination of LET and intra-articular ACLR was effective in eliminating the high-grade pivot-shift phenomenon. For ACL injuries with high-grade pivot shift, LET plus ACLR provided a significant reduction in the prevalence of residual pivot shift but no differences in objective IKDC scores and anterior knee stability compared with isolated ACLR at short-term follow-up. LEVEL OF EVIDENCE: Level IV, systematic review of Level I, III, and IV studies.

Prevalence of Lateral Meniscal Extrusion for Posterior Lateral Meniscal Root Lesion With and Without Concomitant Midbody Radial Tear in Anterior Cruciate Ligament Injury.

PURPOSE: To investigate the prevalence of lateral meniscal extrusion for patients with posterior lateral meniscal root lesions (PLMRLs) and for those with concomitant midbody radial tears (MRTs) in anterior cruciate ligament (ACL) injuries. METHODS: A database of consecutive patients undergoing primary ACL reconstruction between 2011 and 2013 was retrospectively reviewed to identify patients with isolated ACL injuries and those with associated PLMRLs. Patients with (1) unavailable preoperative magnetic resonance imaging scans, (2) other concomitant ligamentous injuries, (3) severe degeneration or malalignment, (4) infection or tumor, or (5) history of surgery on the injured side were excluded. For patients with associated PLMRLs (study group), degree of concomitant MRTs and status of meniscofemoral ligaments (MFLs) were verified arthroscopically. Prevalence of lateral meniscal extrusion was compared between (1) patients in the study group and those with isolated ACL injuries and between (2) those with and without concomitant MRTs in the study group. RESULTS: Of the 1,021 consecutive patients, 412 met the inclusion and exclusion criteria. Of those, 52 (5.1%) had an associated PLMRL (study group) and another 52 were randomly chosen from the 360 isolated ACL injuries as the control group. In the study group, 33 (63.5%) were arthroscopically verified to have concomitant MRTs. Prevalence of lateral meniscal extrusion was significantly higher (P < .0001) in the study group (30.8%; 95% confidence interval [CI], 18.3 to 43.3) than in the control group (1.9%; 95% CI, -1.8 to 5.6), whereas there was no significant difference (P = .758) between patients with (33.3%; 95% CI, 17.3 to 49.3) and without (26.3%; 95% CI, 6.5 to 46.1) concomitant MRTs in the study group. However, the 7 patients who showed either complete concomitant MRTs or absence of MFLs were all diagnosed to have lateral meniscal extrusion. CONCLUSIONS: The PLMRLs, identified in 5.1% of ACL injuries, appeared to result in lateral meniscal extrusion. Although the presence of a concomitant MRT did not further increase the prevalence of lateral meniscal extrusion in the setting of a PLMRL, surgical repair might still be necessary if a complete concomitant MRT or an absence of MFL was identified to restore normal meniscal functions. LEVEL OF EVIDENCE: Level III, prognostic case-control study.

Bone Contusions After Acute Noncontact Anterior Cruciate Ligament Injury Are Associated With Knee Joint Laxity, Concomitant Meniscal Lesions, and Anterolateral Ligament Abnormality.

PURPOSE: To examine the associated findings with bone contusions in patients after acute noncontact anterior cruciate ligament (ACL) injuries. METHODS: From January 1, 2011, to December 31, 2013, patients who underwent ACL reconstructions performed by the senior author (H.F.) were retrospectively analyzed. Presence and severity of bone contusion were determined from preoperative magnetic resonance images (MRIs) for each anatomic site including the lateral femoral condyle (LFC), lateral tibial plateau (LTP), medial femoral condyle (MFC), and medial tibial plateau (MTP). Multivariable logistic regression was used to calculate adjusted odds ratios (ORs) and 95% confidence intervals (CIs) for the associated findings (demographic data, preoperative physical examinations, concomitant meniscal lesions, intra-articular cartilage damages, and anterolateral ligament [ALL] abnormality) with bone contusions. Outcomes included the presence of bone contusions at each anatomic site (LFC, LTP, MFC, and MTP) and severity of lateral bone contusions (moderate/severe vs none/minimal). RESULTS: Among the 697 consecutive cases, 193 were finally selected. Prevalence of bone contusions seen on MRI was as follows: 60.6% LFC, 73.1% LTP, 6.2% MFC, and 21.2% MTP. Presence of bone contusions at LFC and LTP were significantly associated with high-grade (grade II and III) pivot-shift (ORLFC, 7.39; 95% CI, 1.99, 27.44; ORLTP, 2.52; 95% CI, 1.02, 6.24), concomitant lateral meniscal lesions (ORLFC, 3.23; 95% CI, 1.93, 11.31; ORLTP, 10.17; 95% CI, 1.86, 55.47), and ALL abnormality (ORLFC, 3.79; 95% CI, 1.46, 9.84; ORLTP, 4.47; 95% CI, 1.28, 15.58). However, none of the above associated findings was correlated with the presence of bone contusions at MFC and MTP. Furthermore, moderate/severe lateral bone contusions were still found to be significantly associated with high-grade (grade II and III) pivot-shift (ORLFC, 14.89; 95% CI, 2.71, 82.11; ORLTP, 6.76; 95% CI, 1.27, 36.06), concomitant lateral meniscal lesions (ORLFC, 17.34; 95% CI, 3.91, 76.87; ORLTP, 22.01; 95% CI, 5.08, 95.42), and ALL abnormality (ORLFC, 4.02; 95% CI, 1.33, 12.09; ORLTP, 2.57; 95% CI, 1.09, 6.04). CONCLUSIONS: For acute noncontact ACL injury, both the presence and the severity of lateral bone contusions are associated with high-grade (grade II and III) pivot-shift, concomitant lateral meniscal lesions, and ALL abnormality. LEVEL OF EVIDENCE: Level III, retrospective comparative study.

Iatrogenic medial patellar instability following lateral retinacular release of the knee joint.

PURPOSE: Iatrogenic medial patellar instability (IMPI) is a disabling but easily missed condition that is most often seen as a late complication of lateral retinacular release (LRR) procedures. The purposes of this study were (1) to summarize the available diagnostic methods and (2) to explore the contributing factors of IMPI following LRR procedures. METHODS: The MEDLINE, PubMed, EMBASE and Cochrane Library databases were searched for studies including diagnosed IMPI cases following LRR procedures. All patients were first divided into IMPI group and non-IMPI group based on the diagnostic methods of IMPI collected from studies. Univariate analysis was performed by comparing the two groups with regard to individual patient data (age at initial LRR, gender) and surgical details (type, releasing scope, combined surgeries and indication) of LRR procedures. Multivariate logistic regression was carried out to identify independent contributing factors for IMPI and to calculate odds ratios (ORs). RESULTS: Eight studies with 274 patients (300 knees) were finally included. Of those, 161 patients (171 knees, 57.0 %) had IMPI and 113 patients (129 knees, 43.0 %) had no IMPI. Univariate analysis revealed a statistically significant difference between both groups for releasing scope (P 1 < 0.001) and indication of LRR procedures (P 2 < 0.001), with releasing lateral retinaculum (LR) + vastus lateralis (VL) tendon and absence of tight LR during the initial LRR procedures being more common in patients with IMPI. The independent contributing factors for IMPI identified in the multivariate logistic regression analysis were releasing LR + VL (OR1 = 16.49) and absence of tight LR (OR2 = 14.37). CONCLUSIONS: The IMPI was more common in patient with an over-released LRR and patient who was absent of tight LR during the initial LRR procedures. Aggressive surgical corrections and inappropriate indications of initial LRR were two contributing factors for the late complications of IMPI. This study suggests that the IMPI may occur as a major complication of LRR, especially when the VL tendon is extensively released or when there is no confirmative clinical evidence of a tight LR preoperatively. LEVEL OF EVIDENCE: IV.

Is PLC repair of a peel-off femoral lesion an effective option in a multiligament setting?

PURPOSE: Treatment of posterolateral corner (PLC) injury in the multiligament-injured knee is still controversial. The aim of this study was to investigate the clinical outcome of acute or sub-acute surgical repair of Type 1 and 2 PLC peel-off lesions in a multiligament setting. METHODS: Mini-open direct repair of the PLC was performed in 13 patients. Combined PCL, ACL and MCL injuries were simultaneously managed. Telos valgus and varus stress radiographs at 30° of flexion with 150 N load were used to investigate medial and lateral joint opening. Posterior stress radiograph with 150 N load was used to investigate the function of the PCL. External rotational laxity was assessed with a dial test at 30° of knee flexion, and photographs were taken to measure angles. Anterior displacement was examined using the manual maximum test performed with a KT-1000 arthrometer. RESULTS: A statistically significant reduction between pre- and postoperative laxity values was achieved for every test. Particularly, lateral joint opening side-to-side difference reduced from 10.3 ± 4.0 to 1.0 ± 3.2 mm and external rotation reduced from 15 ± 8° to 0° ± 6° more than that of the contralateral uninjured knee. The medial joint opening side-to-side difference reduced from 11.5 ± 5.6 to 2.6 ± 2.7 mm in the 7 patients surgically managed for MCL lesion. The anterior tibial displacement side-to-side difference reduced from 14.0 ± 5.0 to 3.0 ± 5.0 mm in the 9 patients surgically managed for ACL lesion. The posterior tibial translation side-to-side difference reduced from 11.1 ± 5.1 to 4.4 ± 3.9 mm in the 11 patients treated for PCL lesion. CONCLUSION: The main finding of the current study is that acute repair of Type 1 and 2 PLC peel-off injury proved to be an effective procedure to restore PLC function in a multiligament-injured knee. These data enabled the current literature with an effective treatment option to face such a complex and various scenarios such as multiligament-injured knee. LEVEL OF EVIDENCE: IV.

Anatomical popliteofibular ligament reconstruction of the knee joints: an all-arthroscopic technique.

Injuries to the posterolateral corner of the knee present with variable injury patterns that have produced a number of reconstructive procedures in the literature. The present paper describes an all-arthroscopic technique that anatomically reconstructs the popliteofibular ligament (PFL) using either a semitendinosus autograft or an anterior tibialis allograft. During the surgery, the fibular insertion site as well as the distal portion of PFL is feasible to be identified under arthroscopy without any additional skin incision. Level of evidence V.

Quantitative evaluation of residual bony impingement lesions after arthroscopic treatment for isolated pincer-type femoroacetabular impingement using three-dimensional CT.

PURPOSE: The objective of this study is to determine the clinical characteristics of residual bony impingement lesions after arthroscopic treatment for pincer-type femoroacetabular impingement (FAI); and to determine the effects of residual bony impingement lesions on the clinical outcomes after 2 years of follow-up. METHODS: From December 2010 to January 2012, 42 patients underwent arthroscopic surgery for symptomatic pincer-type FAI. Clinical outcomes were evaluated using the modified Harris Hip Score (mHHS) and satisfaction scores. To quantitatively evaluate the acetabular bony impingement lesions, the acetabular bony impingement angles were measured on three-dimensional CT scans. The incidence and residual rates of residual bony impingement were calculated. According to residual rates, the patients were divided into three groups: group 1, residual rate <10 %; group 2, residual rate 10-20 %; and group 3, residual rate >20 %. RESULTS: Thirty patients met the inclusion criteria and were enrolled in this study. The mean age was 34.5 years. The mean follow-up was 26.3 months. Nineteen cases had residual bony impingement lesions after surgery. The incidence was 63.3 % (19/30). Sixteen cases (84.2 %) had residual bony impingement lesions posterior to the actual acetabular resection zones. The preoperative and postoperative bony impingement angles were 77.47° ± 21.31° and 12.94° ± 18.04°, respectively. The residual rate was 14.48 %. The overall mHHS significantly improved (P < 0.001) from 55.18 ± 7.96 preoperatively to 94.71 ± 4.39 postoperatively. The overall satisfaction rate was 76.66 %. The postoperative mHHSs of groups 1-3 were 95.86 ± 1.71, 95.23 ± 1.99, and 85.52 ± 6.41, respectively. Group 3 exhibited significantly lower postoperative mHHS compared to the other two groups (P = 0.001). The satisfaction rates in groups 1-3 were 92.86, 80, and 33.33 %, respectively. The satisfaction rate in group 3 was significantly worse than those of the other two groups (P = 0.017). There was a significant inverse linear relationship between the residual rate of bony impingement lesions and the postoperative mHHS (R (2) = 0.516, P < 0.05). CONCLUSION: The incidence of residual impingement lesions after arthroscopic pincer-type FAI correction was 63.3 %. The residual rate was 14.48 %. The residual impingement lesions were primarily in the posterior portion of the acetabulum. The clinical outcomes were associated with the residual rate of bony impingement lesions. The patients with residual rates >20 % exhibited significantly lower clinical scores and satisfaction rates.

Acute anterior cruciate ligament reconstruction with an augmented remnant repair: a comparative macroscopic and biomechanical study in an animal model.

PURPOSE: Our purpose was (1) to compare the structural integrity and healing capacity of the acutely repaired anterior cruciate ligament (ACL) remnants and (2) to determine whether the short-term postoperative biomechanical results of the acute remnant-repairing anterior cruciate ligament reconstruction (ACLR) were superior to the conventional ACLR. METHODS: An acute complete ACL femoral detachment model was created in 50 rabbits. The rabbits were immediately randomly allocated into the remnant-repairing ACLR group (group 1, n = 25) and the conventional ACLR group (group 2, n = 25). Each animal in both groups was subjected to unilateral ACLR with semitendinosus tendon autografts. During ACLR, the ACL remnants were acutely repaired with the femoral-tensioning technique in group 1, whereas the ACL remnants were debrided in group 2. The outcomes of the remnant were macroscopically evaluated in group 1. The remnant's structural integrity and remnant-to-graft healing capacity were divided into 3 categories (grade A, good; grade B, fair; or grade C, poor) according to 2 distinct criteria. Biomechanical tests including the anterior tibial translation test at 30° and 90° of knee flexion and tensile tests were compared between groups. All the macroscopic evaluations and biomechanical tests were performed postoperatively at week 12. RESULTS: The macroscopic evaluations of the ACL remnants in group 1 (n = 25) showed that the remnants' structural integrity was grade A (well-maintained continuity with an adequate amount of tissue and tension on probing) in 10 specimens (40%), grade B (fairly maintained continuity with thin and slack fibers detected) in 5 (20%), and grade C (resorption with no remnant left in situ) in 10 (40%). The remnant-to-graft healing capacities among the specimens with surviving remnants (grades A and B for structural integrity, n = 15) were all classified as grade C (an obvious remnant-to-graft interval through the entire length of the graft). For the biomechanical tests, there were no significant differences between the groups (25 in each group) with respect to the anterior tibial translation test at 30° (P = .15) and 90° (P = .91) of knee flexion and stiffness (P = .66), ultimate failure load (P = .11), and elongation at failure (P = .92). CONCLUSIONS: In our rabbit model of ACL femoral detachment, the acutely repaired ACL remnants showed a high resorption rate, low healing capacity, and poor biomechanical properties. The acute remnant-repairing ACLR had no evident superiority over the conventional ACLR in rabbits. CLINICAL RELEVANCE: The findings did not support the contention that the remnant-repairing ACLR, even performed in the acute setting, could produce better postoperative knee joint stability outcomes than the conventional ACLR.

Trochleoplasty versus nontrochleoplasty procedures in treating patellar instability caused by severe trochlear dysplasia.

PURPOSE: The purpose of this study was to compare the clinical outcomes and postoperative complication rates between patients who underwent trochleoplasty or nontrochleoplasty procedures in treating patellar instability caused by severe trochlear dysplasia (STD). METHODS: The PubMed database was searched using specific inclusion and exclusion criteria for clinical studies reporting indexed orthopaedic treatments of patellar instability caused by STD (Dejour type B to D). Participants within studies were classified into one of the 2 treatment groups: (1) the trochleoplasty group (group T) and (2) the nontrochleoplasty group (group N). Clinical outcomes and postoperative complications were analyzed. RESULTS: Seventeen studies were finally included. There were in total 459 knees that underwent the indexed orthopaedic treatments of patellar instability caused by STD (Dejour type B to D). Eleven studies, including 329 knees, formed the trochleoplasty group (group T), and the remaining 6 studies, including 130 knees, composed the nontrochleoplasty group (group N). All the clinical outcomes within groups had improved significantly (P < .05) at the final follow-up. No studies directly compared the clinical outcomes between the 2 groups. The postoperative complication analysis showed superior results for the trochleoplasty group in (1) patellar redislocation rate and (2) percentage of patellofemoral osteoarthritis (Iwano grade 2 or greater) progression findings but an inferior outcome with respect to the range of motion (ROM) deficit compared with the nontrochleoplasty group. CONCLUSIONS: This systematic review showed significant postoperative improvements both in patients undergoing the trochleoplasty procedures and in patients undergoing the nontrochleoplasty procedures for the treatment of patellar instability caused by STD in all the included studies. However, there is limited evidence regarding the comparative advantages toward the optimal treatment. The postoperative complication rate has been considered to be the best measurement of operative success. To prevent the patella from redislocating and patellofemoral osteoarthritis from progressing, trochleoplasty procedures should be considered. Meanwhile, one should be cautious about the postoperative ROM deficit before choosing trochleoplasty procedures. LEVEL OF EVIDENCE: Level IV, systematic review of Level III and IV studies.

The "lateral gutter drive-through" sign revisited: a cadaveric study exploring its real mechanism based on the individual posterolateral structure of knee joints.

BACKGROUND: Although the validity of the "lateral gutter drive-through" (LGDT) test has been proved to offer high sensitivity and specificity in diagnosing the posterolateral rotational instability of knee joints, the real mechanism on how the injury pattern of individual posterolateral knee structure triggers the positive LGDT sign still remains unknown. HYPOTHESIS: A certain amount of popliteus tendon (POP-T) laxity resulted from specific injury patterns of individual posterolateral knee structure or some degree of medial structural injury will lead to positive LGDT sign. STUDY DESIGN: Controlled laboratory study. METHODS: Seven non-paired intact cadaveric knees were divided into four groups and tested under unique sequential sectioning sequences including: (1) distal POP-T and popliteofibular ligament (PFL) (n = 2); (2) PFL and distal POP-T (n = 3); (3) lateral collateral ligament (LCL), distal POP-T and PFL (n = 1); (4) superficial medial collateral ligament (sMCL), deep MCL, posterior oblique ligament (POL), anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL) (n = 1). The LGDT tests and the measurements of external tibial rotational angle (ETRA) were first performed on all the intact knees and then at each time point when an additional structure was sectioned. Results of each LGDT test and the absolute value of increased ETRA compared with the intact knee were recorded. Each knee was tested at 30° of flexion. A navigation system was used to measure motion changes of the tibia with respect to the femur. RESULTS: Initially, the LGDT tests all showed negative on each of the intact knee. Isolated sectioning of the distal POP-T, PFL or the LCL produced increased but insignificant ETRA with the LGDT tests still negative. However, simultaneous sectioning of the distal POP-T and PFL produced significantly increased ETRA with the LGDT tests changed to positive. In addition, for the knee with medial structural injuries, the LGDT test could also be positive only when the posteromedial structures (sMCL, deep MCL, POL) and the cruciate ligaments (ACL and PCL) were all sectioned. CONCLUSION: In this cadaveric sequential sectioning study, the LGDT test showed positive merely at the following two situations: (1) the distal POP-T and PFL were both sectioned; (2) the posteromedial structures (sMCL, deep MCL and POL) and the cruciate ligaments (ACL and PCL) were all sectioned. CLINICAL RELEVANCE: Accuracy of the LGDT test in diagnosing acute or chronic posterolateral corner (PLC) injuries will improve with the information in this study. It was the combined POP-T and PFL injuries that finally led to a positive LGDT sign. However, one should be cautious to use the LGDT test in diagnosing the PLC injuries when posteromedial structures and cruciate ligaments were all involved.

The anterior cruciate ligament remnant: to leave it or not?

PURPOSE: The role of the anterior cruciate ligament remnant in anterior cruciate ligament reconstruction (ACLR) is debated. The purposes of this systematic review were (1) to summarize the clinical outcomes of patients undergoing remnant-preserving ACLR and (2) to investigate whether those outcomes were superior to standard ACLR. METHODS: The PubMed database was searched using specific inclusion and exclusion criteria for clinical studies reporting both preoperative conditions and postoperative outcomes of remnant-preserving ACLR. All reported postoperative complications were analyzed. In addition, a modified Coleman Methodology Score (CMS) system was used to assess the methodologic quality of the included studies. RESULTS: Thirteen studies were included with a mean CMS value of 71.7 (range, 57 to 92). In total, 546 patients underwent remnant-preserving ACLR by 3 different procedures: standard ACLR plus tibial remnant tensioning (n = 166), selective-bundle augmentation (n = 337), and standard ACLR plus tibial remnant sparing (n = 43). All clinical outcomes improved significantly (P < .05) at the final follow-up (mean, 27.9 months). Seven studies directly compared postoperative clinical outcomes between remnant-preserving ACLR and standard ACLR. In 6 of the 7 studies, similar postoperative clinical outcomes were reported between groups. One study reported superior clinical outcomes after remnant-preserving ACLR. There was no significant difference between groups regarding the overall rate of postoperative complications. CONCLUSIONS: The mean CMS showed moderate methodologic quality for the included studies. This systematic review showed significant postoperative improvements in patients undergoing remnant-preserving ACLR in all of the studies. However, further comparisons between remnant-preserving ACLR and standard ACLR showed inconsistent results in the 7 comparative studies, with 6 reporting equivalent postoperative clinical outcomes between groups. There was no significant difference in the rate of total complications between groups. The currently available evidence is not sufficiently strong to support the superiority of remnant-preserving ACLR. LEVEL OF EVIDENCE: Level IV, systematic review of Level I-IV studies.

Clinical and Second-look Arthroscopic Results for Derotational Distal Femoral Osteotomy With Medial Patellofemoral Ligament Reconstruction for Recurrent Patellar Dislocation With Increased Femoral Anteversion: A Series of 102 Cases With a Minimum Clinical Follow-up of 2 Years.

BACKGROUND: Derotational distal femoral osteotomy (DDFO) has been used to treat patients with recurrent patellar dislocation (RPD) with increased femoral anteversion. However, no study has reported second-look arthroscopic findings in the patellofemoral joint after DDFO. PURPOSE: To report clinical and second-look arthroscopic outcomes for DDFO with combined medial patellofemoral ligament reconstruction (MPFL-R) in treating RPD with increased femoral anteversion. STUDY DESIGN: Case series; Level of evidence, 4. METHODS: From 2015 to 2019, 131 consecutive patients (144 knees) with RPD were treated with combined MPFL-R and DDFO. Patients with a femoral anteversion angle >30° and a minimum 2-year clinical follow-up period were included in the study. Three-dimensional computed tomography was performed to evaluate rotational deformities of the lower leg. Radiographic parameters presenting bony abnormalities associated with RPD were measured. Second-look arthroscopic evaluations were available for 86 knees to assess patellar tracking and chondral lesion changes. Moreover, clinical and radiologic outcomes were assessed pre- and postoperatively at a minimum 2 years. RESULTS: A total of 102 knees in 92 patients were included in the present study with a mean clinical follow-up of 4.1 years (range, 2.0-5.6 years). Mean ± SD femoral anteversion changed significantly from 34.7°± 7.5° preoperatively to 11.3°± 0.2° postoperatively (P < .001), and mean tibial tubercle-trochlear groove distance decreased significantly from 19.6 ± 3.5 mm preoperatively to 17.4 ± 3.2 mm postoperatively (P < .001). In the majority of knees, at the time of second-look arthroscopic assessment, chondral lesion status remained unchanged at the lateral patellar facet (96%) and trochlear groove (95%); in contrast, chondral damage at the medial patellar facet was aggravated in 9 cases (10%). All functional scores (Tegner, Lysholm, visual analog scale, and Kujala scores) improved significantly at final follow-up. None of the patients experienced redislocation or subluxation after surgery. CONCLUSION: Chondral lesions in the patellofemoral joint remained unchanged in the majority of cases in second-look arthroscopy after combined MPFL-R and DDFO. Moreover, high-grade trochlear dysplasia and arthroscopic residual patellar maltracking might be associated with cartilaginous deterioration at the medial patellar facet after surgery.

Predictors of Graft Failure After Primary Medial Patellofemoral Ligament Reconstruction.

Background: The tibiofemoral rotation angle has been found to be higher in patients with recurrent patellar dislocations (RPDs) than in healthy people; however, little is known about the clinical significance of this finding. Purpose: To determine whether an increased tibiofemoral rotation angle is associated with graft failure after primary medial patellofemoral ligament reconstruction (MPFL-R) and to investigate the role of the tibiofemoral rotation angle in predicting MPFL-R failure in patients with RPDs. Study Design: Case-control study; Level of evidence, 3. Methods: We retrospectively analyzed the records of 632 consecutive patients with clinically diagnosed RPDs from 2011 to 2018. Postoperative stress radiography of the patellofemoral joint was performed to identify whether the graft failed. After a review, 33 patients who showed MPFL-R failure were allocated to the failure group. They were matched 1:2 to 66 participants who underwent successful MPFL-R (control group). The cutoff value and area under the curve (AUC) of the tibiofemoral rotation angle for predicting graft failure after primary MPFL-R were determined, and the risk factors for MPFL-R failure were assessed by multivariate logistic regression analysis. Results: The tibiofemoral rotation angle was significantly higher in the failure group than in the control group (16.4° ± 5.6° vs 6.4° ± 4.5°, respectively; P < .001). The cutoff value of the tibiofemoral rotation angle for predicting graft failure was 12.3° (sensitivity, 81.8%; specificity, 89.4%; AUC, 0.920). Overall, 3 risk factors for MPFL-R failure were determined: excessive tibiofemoral rotation (≥12.3°) (odds ratio [OR], 13.159 [95% CI, 2.469-70.139]; P = .003), a preoperative high-grade J-sign (OR, 7.674 [95% CI, 1.232-47.809]; P = .029), and a femoral tunnel malposition (OR, 6.976 [95% CI, 1.077-45.187]; P = .042). Conclusion: In this study, excessive tibiofemoral rotation, a preoperative high-grade J-sign, and a femoral tunnel malposition were identified as risk factors for graft failure after primary MPFL-R in patients with RPDs. More importantly, excessive tibiofemoral rotation ( ≥ 12.3°) may predict the failure of primary MPFL-R, which can help surgeons easily identify high-risk patients of MPFL-R failure before surgery.

Increased Posterior Tibial Slope Is Associated With Greater Risk of Graft Roof Impingement After Anatomic Anterior Cruciate Ligament Reconstruction.

BACKGROUND: Increased posterior tibial slope (PTS) has been reported to be associated with irreducible anterior tibial subluxation in extension after anatomic anterior cruciate ligament (ACL) reconstruction (ACLR), which raises concerns about the greater risk of graft roof impingement (GRI) although the tibial tunnel is positioned anatomically. HYPOTHESIS: Increased PTS would be associated with greater risk of GRI after anatomic ACLR. STUDY DESIGN: Case-control study; Level of evidence, 3. METHODS: Between January 2016 and December 2017, a total of 418 consecutive patients were diagnosed as having noncontact ACL injuries and underwent primary anatomic ACLR. Among them, 26 patients had ≥1 of the following features during the second-look arthroscopy: fractured/guillotined bundles at the tibial insertion or cyclops lesion. These patients were confirmed to have GRI and were allocated to the study group. They were also matched 1:2 to 52 control participants without GRI. PTS was measured on true lateral whole-leg radiographs. Intra-articular ACL graft signal intensity was evaluated on postoperative magnetic resonance imaging scans (mean, 32.8 months; range, 26-38 months) and divided into 3 grades (I, good; II, moderate; III, poor) based on degree of GRI. Moreover, anterior subluxation of the lateral compartment (ASLC) and medial compartment (ASMC) in extension relative to the femoral condyles were measured on postoperative magnetic resonance imaging scans and compared between the groups. In addition, predictors of GRI were evaluated using multivariate logistic regression analysis and included body mass index, PTS, pivot-shift test, KT-1000 side-to-side difference, and concomitant meniscal tears. RESULTS: PTS in the study group was significantly higher than that in control group (mean ± SD, 13.8°± 1.5° vs 9.5°± 1.8°; P < .05). In the study group (n = 26), patients with grade III (poor) graft signal intensity (n = 9) showed significantly higher PTS than those with grade II (moderate; n = 17) (16.4°± 1.7° vs 12.4°± 1.3°; P < .05). Moreover, the mean postoperative ASLC and ASMC in extension were significantly larger in the study group than the control group (ASLC, 4.1 ± 1.3 vs 0.8 ± 0.4 mm; ASMC, 4.3 ± 1.5 vs 0.9 ± 0.3 mm; P < .05). Furthermore, the abnormal degree of PTS (≥12°) was determined to be an independent risk factor associated with GRI after anatomic ACLR (odds ratio, 9.0 [95% CI, 3.7-30.2]; P < .001), whereas body mass index, grade of pivot-shift test, KT-1000 side-to-side difference, and concomitant meniscal tears were not. CONCLUSION: Increased PTS (≥12°) was associated with greater risk of GRI after anatomic ACLR. This may provide additional information for counseling patients with greater risk of GRI.

Development of heterotopic ossification after multiple-ligament reconstruction of the knee joint: Incidence and explanatory factor analysis.

BACKGROUND: The development of heterotopic ossification (HO) might nullify any benefit of multiple-ligament reconstruction of the knee joint. The purpose of this study was to investigate the incidence and the specific explanatory factors for the development of HO after multiple-ligament reconstruction of the knee joint. METHODS: From January 2011 to June 2016, 72 consecutive patients with knee dislocations received multiple-ligament reconstructions, of which 57 (79%) were available for a minimum follow up of 12 months and were included in this study. Anteroposterior (AP) and lateral radiographs were reviewed for all patients. This knee dislocation cohort was separated into two groups based on the presence or absence of HO for comparisons. In addition, the HO group was divided into three subgroups based on a modified quadrant grading system introduced by the senior author for further evaluation. Multivariate logistic regression analysis was then performed to identify specific explanatory factors predicting development of HO in patients after multiple-ligament reconstructions of the knee joint. RESULTS: Among the 72 consecutive patients, 57 (79%) were available for the clinical evaluations with an average period of 28.4 months (range, 12-51 months). Twenty-one patients (37%) showed radiological evidence of HO. The HO group (n = 21) showed significantly inferior results of knee flexion angle compared with the non-HO group (n = 36) (HO group vs. non-HO group: 124 ± 13° vs. 132 ± 5°; P<0.01). According to the quadrant grading system, there were seven patients with grade I, nine with grade II, and five with grade III HO. Subgroup analysis further revealed that higher HO grade would lead to lower knee flexion angle. In addition, multivariate regression analysis showed that concomitant posterior cruciate ligament reconstruction was the only independent explanatory factor predicting the development of HO after multiple-ligament reconstruction of the knee joint (P=0.018; odds ratio, 8.75; 95% confidence interval, 1.69-39.7). CONCLUSION: In this cohort of knee dislocations, the incidence of HO development following multiple-ligament reconstruction was 37%, with grade III HO showing the most inferior range of motion outcome. Moreover, concomitant posterior cruciate ligament reconstruction was the only independent predictor for the development of HO.