Although remnant-preserved ACL reconstruction (ACLR) restores knee joint stability and dampens the problem of acute ACL rupture-induced knee pain, an increasing number of patients still develop post-traumatic osteoarthritis (PTOA) after 10 to 15 years of ACLR. We previously found that remnant-preserved ACLR with concomitant medial and lateral meniscus repair may not prevent cartilage degeneration and weaken muscle strength, while the clinical features of PTOA are not clear. We hypothesized that remnant-preserved ACLR with concomitant medial and lateral meniscus tears is related to early cartilage damage, worse function recovery, patient-reported outcomes (PROs) and delayed duration to return to sports. The aim is to evaluate the remnant-preserved ACLR with complicated meniscal injuries in predicting which patients are at higher risk of osteoarthritic changes, worse function and limited activities after ACLR for 12 months.

Human ethical issue was approved by a committee from Xi'an Jiaotong University. 26 young and active patients (24 male, 2 female) with ACL injuries (Sherman type I and II) with concomitant medial and lateral meniscus within 2 months were included from January 2014 to March 2022. The average age of the ACLR+ meniscus repair was 26.77±1.52 (8 right, 5 left) and isolated ACLR control was 31.92±2.61 years old (7 left, 6 right). Remnant-preserved ACLR with a 5- to 6-strand hamstring tendon graft was operated on by the same sports medicine specialists. MRI CUBE-T₂ scanning with 48 channels was conducted by a professional radiologist. The volume of the ACL graft was created through 3 dimensional MRI model (Mimics 19, Ann Arbor). Anterior Cruciate Ligament OsteoArthritis Score (ACLOAS) was applied to score visible cartilage damage. IKDC 2000 score and VAS were assessed by two blinded researchers. Results were presented as mean± SEM of each group.

The cross-sectional area and 3D volume of the ACL graft were greater in the remnant-preserved ACLR+meniscus group compared with isolated ACLR (p=0.01). It showed that ACLR+ meniscus group had early signs of joint damage and delayed meniscus healing regarding ACLOAS compared to control group (p=0.045). MRI CUBE-T₂ prediction of radiographic cartilage degeneration was not obvious in both groups post remnant-preserved ACLR over 12 months (p>0.05). However, higher VAS scores, lower IKDC scores, and long-last joint swelling were reported in the ACLR+ meniscus repair group at the end of 12 months follow-up. Although remnant-preserved ACLR+ meniscus was able to maintain the restore the knee function, it showed delayed timing (>12 months) to return to play at the pre-injury stage, while no difference between the timing of returning to the normal daily routine of their ACLR knee compared to control (p=0.30). The cost of ACLR+ meniscus (average 10,520.76$) was higher than the control group (6,452.92$, p=0.018).

Remnants-preserved ACLR with concomitant injured medial and lateral meniscus repair shows a higher risk of cartilage damage, greater cost, worse functional performance, and longer time for young male patients to return to sports after 12-month follow-up compared to isolated ACLR. Further evidence and long-term follow-up are needed to better understand the association between these results and the risk of development of PTOA in this patient cohort.

Aims

This study aimed to investigate the role and mechanism of meniscal cell lysate (MCL) in fibroblast-like synoviocytes (FLSs) and osteoarthritis (OA).

Unstable slipped capital femoral epiphysis (SCFE) has an increased incidence of avascular necrosis (AVN). The purpose of this study was to determine if early identification and intervention for AVN may help preserve the femoral head.

We retrospectively reviewed 48 patients (50 hips) with unstable SCFE managed between 2000 and 2014. Based on two different protocols during the same time period, 17 patients (17 hips) had a scheduled MRI between 1 and 6 months from initial surgery, with closed bone graft epiphysiodesis (CBGE) or free vascularised fibular graft (FVFG) if AVN was diagnosed. Thirty-one patients (33 hips) were evaluated by plain radiographs. Outcomes analysed were Steinberg classification and subsequent surgical intervention. We defined Steinberg class IVC as failure in treatment because all of the patients referred for osteotomy, arthoplasty, or arthrodesis in our study were grade IVC or higher.

Overall, 13 hips (26%) with unstable SCFE developed AVN. MRI revealed AVN in 7 of 17 hips (41%) at a mean of 2.5 months postoperatively (range, 1.0 to 5.2 months). Six hips diagnosed by MRI received surgical intervention (4 CBGE, 1 FVFG, and 1 repinning due to screw cutout) at a mean of 4.1 months (range, 1.3 to 7.2 months) postoperatively. None of the 4 patients treated with CBGE within two months postoperatively progressed to stage IVC AVN. The two patients treated after four months postoperatively both progressed to stage VC AVN. Radiographically diagnosed AVN occurred in 6 of 33 hips (18%) at a mean of 6.8 months postoperatively (range, 2.1 to 21.1 months). One patient diagnosed with stage IVB AVN at 2.4 months had screw cutout and received CBGE at 2.5 months from initial pinning. The remaining 5 were not offered surgical intervention. Five of the 6 radiographically diagnosed AVN, including the one treated with CBGE, progressed to stage IVC AVN or greater.

None of the 4 patients with unstable SCFE treated with CBGE within 2 months post pinning developed grade IVC AVN, while all patients treated with other procedures after 2 months developed IVC or greater AVN. Early detection and treatment of AVN after SCFE may alter the clinical and radiographic progression.

Bone morphogenetic proteins (BMPs) are able to induce osteogenic differentiation in many cells, including muscle cells. However, the actual contribution of muscle cells to bone formation and repair is unclear. Our objective was to examine the capacity of myogenic cells to contribute to BMP-induced ectopic bone formation and fracture repair.

Osteogenic gene expression was measured by quantitative PCR in osteoprogenitors, myoblasts, and fibroblasts following BMP-2 treatment. The MyoD-Cre x ROSA26R and MyoD-Cre x Z/AP mouse strains were used to track the fate of MyoD+ cells in vivo. In these double-transgenic mice, MyoD+ progenitors undergo a permanent recombination event to induce reporter gene expression. Ectopic bone was produced by the intramuscular implantation of BMP-7. Closed tibial fractures and open tibial fractures with periosteal stripping were also performed. Cellular contribution was tracked at one, two and three week time points by histological staining.

Osteoprogenitors and myoblasts exhibited comparable expression of early and late bone markers; in contrast bone marker expression was considerably less in fibroblasts. The sensitivity of cells to BMP-2 correlated with the expression of BMP receptor-1a (Bmpr1a). Pilot experiments using the MyoD-Cre x Rosa26R mice identified a contribution by MyoD expressing cells in BMP-induced ectopic bone formation. However, false positive LacZ staining in osteoclasts led us to seek alternative systems such as the MyoD-cre x Z/AP mice that have negligible background staining. Initially, a minor contribution from MyoD expressing cells was noted in the ectopic bones in the MyoD-cre x Z/AP mice, but without false positive osteoclast staining. Soft tissue trauma usually precedes the formation of ectopic bone. Hence, to mimic the clinical condition more precisely, physical injury to the muscle was performed. Traumatising the muscle two days prior to BMP-7 implantation: (1) induced MyoD expression in quiescent satellite cells; (2) increased ectopic bone formation; and (3) greatly enhanced the number of MyoD positive cells in the ectopic bone. In open tibial fractures the majority of the initial callus was MyoD+ indicating a significant contribution by myogenic cells. In contrast, closed fractures with the periosteum intact had a negligible myogenic contribution.

Myoblasts but not fibroblasts were highly responsive to BMP stimulation and this was associated with BMP receptor expression. Our transgenic mouse models demonstrate for the first time that muscle progenitors can significantly contribute to ectopic bone formation and fracture repair. This may have translational applications for clinical orthopaedic therapies.