Alteration of cartilage surface collagen fibers differs locally after immobilization of knee joints in rats

Lateral Patellar Instability

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Patellar instability represents a common problem with an evolving understanding and multifactorial pathoetiology. Treatment plans should be based on the identification of contributing anatomical factors and tailored to each individual patient.

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Risks for recurrent instability are dependent on several patient-specific factors including patella alta, increased tibial tubercle-to-trochlear groove (TT-TG) distance, trochlear dysplasia, younger skeletal age, and ligamentous laxity.

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Cartilage or osteochondral lesions and/or fractures are commonly observed in first-time patellar dislocation, and magnetic resonance imaging (MRI) should be strongly considered. Advanced imaging modalities, such as computed tomography (CT) or MRI, should also be obtained preoperatively to identify predisposing factors and guide surgical treatment.

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Medial patellofemoral ligament (MPFL) reconstruction with anatomical femoral tunnel positioning is associated with lower recurrence rates compared with MPFL repair and has become a common and successful reconstructive surgical option in cases of instability.

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Lateral retinacular tightness can be addressed with lateral retinacular release or lengthening, but these procedures should not be performed in isolation.

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Tibial tubercle osteotomy is a powerful reconstructive tool in the setting of underlying skeletal risk factors for instability and can be of particular benefit in the presence of increased TT-TG distance (>20 mm), and/or in the setting of patella alta.

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The indications for trochleoplasty are still developing along with the clinical evidence, but trochleoplasty may be indicated in some cases of severe trochlear dysplasia. Several surgical techniques have indications in specific clinical scenarios and populations, and indications, risks, and benefits to each are progressing with our understanding.

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Combined femoral derotational osteotomy and MPFL reconstruction can be considered for patients with a femoral anteversion angle of >30° to improve patient outcomes and reduce recurrence rates.

Mechanical Unloading of Engineered Human Meniscus Models Under Simulated Microgravity: A Transcriptomic Study

Osteoarthritis (OA) primarily affects mechanical load-bearing joints, with the knee being the most common. The prevalence, burden and severity of knee osteoarthritis (KOA) are disproportionately higher in females, but hormonal differences alone do not explain the disproportionate incidence of KOA in females. Mechanical unloading by spaceflight microgravity has been implicated in OA development in cartilaginous tissues. However, the mechanisms and sex-dependent differences in OA-like development are not well explored. In this study, engineered meniscus constructs were generated from healthy human meniscus fibrochondrocytes (MFC) seeded onto type I collagen scaffolds and cultured under normal gravity and simulated microgravity conditions. We report the whole-genome sequences of constructs from 4 female and 4 male donors, along with the evaluation of their phenotypic characteristics. The collected data could be used as valuable resources to further explore the mechanism of KOA development in response to mechanical unloading, and to investigate the molecular basis of the observed sex differences in KOA.

Collagen: quantification, biomechanics, and role of minor subtypes in cartilage

Collagen is a ubiquitous biomaterial in vertebrate animals. Although each of its 28 subtypes contributes to the functions of many different tissues in the body, most studies on collagen or collagenous tissues have focussed on only one or two subtypes. With recent developments in analytical chemistry, especially mass spectrometry, significant advances have been made toward quantifying the different collagen subtypes in various tissues; however, high-throughput and low-cost methods for collagen subtype quantification do not yet exist. In this Review, we introduce the roles of collagen subtypes and crosslinks, and describe modern assays that enable a deep understanding of tissue physiology and disease states. Using cartilage as a model tissue, we describe the roles of major and minor collagen subtypes in detail; discuss known and unknown structure-function relationships; and show how tissue engineers may harness the functional characteristics of collagen to engineer robust neotissues.

Full-Scale Osteochondral Regeneration by Sole Graft of Tissue-Engineered Hyaline Cartilage without Co-Engraftment of Subchondral Bone Substitute

In this study, full-scale osteochondral defects are hypothesized, which penetrate the articular cartilage layer and invade into subchondral bones, and can be fixed by sole graft of tissue-engineered hyaline cartilage without co-engraftment of any subchondral bone substitute. It is hypothesized that given a finely regenerated articular cartilage shielding on top, the restoration of subchondral bones can be fulfilled via spontaneous self-remodeling in situ. Hence, the key challenge of osteochondral regeneration lies in restoration of the non-self-regenerative articular cartilage. Here, traumatic osteochondral lesions to be repaired in rabbit knee models are endeavored using novel tissue-engineered hyaline-like cartilage grafts that are produced by 3D cultured porcine chondrocytes in vitro. Comparative trials are conducted in animal models that are implanted with living hyaline cartilage grafts (LhCG) and decellularized LhCG (dLhCG). Sound osteochondral regeneration is gradually revealed from both LhCG and dLhCG-implanted samples 50-100 d after implantation. Quality regeneration in both zones of articular cartilage and subchondral bones are validated by the restored osteochondral composition, structure, phenotype, and mechanical property, which validate the hypothesis of this study.

Plaster, splint, brace, tape or functional mobilization after first-time patellar dislocation: what's the evidence?

With an incidence of 5.8 per 100,000 per year, patellar dislocations are commonly seen in the emergency department. Surprisingly, there are only a few studies available that focus on the results of the different non-surgical treatment options after first-time patellar dislocation. The aim of this review is to provide an overview of the most recent and relevant studies on the rationales and results of the non-surgical treatment for first-time patellar dislocation.

Patellar instability mainly affects young and active patients, with a peak incidence of 29 per 100 000 per year in adolescents. The medial patellofemoral ligament, a main passive restraint for lateral translation of the patella, is torn in lateral patellofemoral dislocations. Treatment of first-time patellar dislocation can be either conservative or surgical.

There are two options in conservative management of first-time patellar dislocation: immobilization using a cylinder cast or removable splint, or, second, functional mobilization after applying a brace or patellar tape.

The current available literature of conservative treatment after a first-time patellar dislocation is little and of low quality of evidence. Conclusions should be drawn with care, new research focussing on non-surgical treatment is therefore strongly needed.

Cite this article: EFORT Open Rev 2019;4:110-114. DOI: 10.1302/2058-5241.4.180016

The Role of Periarticular Soft Tissues in Persistent Motion Loss in a Rat Model of Posttraumatic Elbow Contracture

BACKGROUND

Elbow injuries disrupt the surrounding periarticular soft tissues, which include the muscles, tendons, capsule, ligaments, and cartilage. Damage to these tissues as a result of elbow trauma causes clinically significant contracture in 50% of patients. However, it is unclear which of these tissues is primarily responsible for the decreased range of motion. We hypothesized that all tissues would substantially contribute to elbow contracture after immobilization, but only the capsule, ligaments, and cartilage would contribute after free mobilization, with the capsule as the primary contributor at all time points.

METHODS

Utilizing a rat model of posttraumatic elbow contracture, a unilateral soft-tissue injury was surgically induced to replicate the damage that commonly occurs during elbow joint dislocation. After surgery, the injured limb was immobilized for 42 days. Animals were evaluated after either 42 days of immobilization (42 IM) or 42 days of immobilization with an additional 21 or 42 days of free mobilization (42/21 or 42/42 IM-FM). For each group of animals, elbow mechanical testing in flexion-extension was completed post-mortem with (1) all soft tissues intact, (2) muscles/tendons removed, and (3) muscle/tendons and anterior capsule removed. Total extension was assessed to determine the relative contributions of muscles/tendons, capsule, and the remaining intact tissues (i.e., ligaments and cartilage).

RESULTS

After immobilization, the muscles/tendons and anterior capsule contributed 10% and 90% to elbow contracture, respectively. After each free mobilization period, the muscles/tendons did not significantly contribute to contracture. The capsule and ligaments/cartilage were responsible for 47% and 52% of the motion lost at 42/21 IM-FM, respectively, and 26% and 74% at 42/42 IM-FM, respectively.

CONCLUSIONS

Overall, data demonstrated a time-dependent response of periarticular tissue contribution to elbow contracture, with the capsule, ligaments, and cartilage as the primary long-term contributors.

CLINICAL RELEVANCE

The capsule, ligaments, and cartilage were primarily responsible for persistent motion loss and should be considered during development of tissue-targeted treatment strategies to inhibit elbow contracture following injury.

Temporal Patterns of Motion in Flexion-extension and Pronation-supination in a Rat Model of Posttraumatic Elbow Contracture

BACKGROUND

The elbow is highly susceptible to contracture, which affects up to 50% of patients who experience elbow trauma. Previously, we developed a rat model to study elbow contracture that exhibited features similar to the human condition, including persistently decreased ROM and increased capsule thickness/adhesions. However, elbow ROM was not quantitatively evaluated over time throughout contracture development and subsequent mobilization of the joint.

QUESTIONS/PURPOSES

The purposes of this study were (1) to quantify the time-dependent mechanics of contracture, including comparison of contracture after immobilization and free mobilization; and (2) to determine what changes occur in capsule and joint surface morphology that may support the altered joint mechanics.

METHODS

A total of 96 male Long-Evans rats were randomized into control and injury (unilateral soft tissue injury/immobilization) groups. Flexion-extension and pronation-supination joint mechanics (n = 8/group) were evaluated after 3, 7, 21, or 42 days of immobilization (IM) or after 42 days of IM with either 21 or 42 days of free mobilization (63 or 84 FM, respectively). After measuring joint mechanics, a subset of these limbs (n = 3/group) was prepared for histologic analysis and blinded sections were scored to evaluate capsule and joint surface morphology. Joint mechanics and capsule histology at 42 IM and 84 FM were reported previously but are included to demonstrate the full timeline of elbow contracture.

RESULTS

In flexion-extension, injured limb ROM was decreased compared with control (103° ± 11°) by 21 IM (70° ± 13°) (p = 0.001). Despite an increase in injured limb ROM from 42 IM (55° ± 14°) to 63 FM (83° ± 10°) (p < 0.001), injured limb ROM was still decreased compared with control (103° ± 11°) (p = 0.002). Interestingly, ROM recovery plateaued because there was no difference between injured limbs at 63 (83° ± 10°) and 84 FM (73° ± 19°) (p > 0.999). In pronation-supination, increased injured limb ROM occurred until 7 IM (202° ± 32°) compared with control (155° ± 22°) (p = 0.001), representative of joint instability. However, injured limb ROM decreased from 21 (182° ± 25°) to 42 IM (123° ± 47°) (p = 0.001), but was not different compared with control (155° ± 22°) (p = 0.108). Histologic evaluation showed morphologic changes in the anterior capsule (increased adhesions, myofibroblasts, thickness) and nonopposing joint surfaces (surface irregularities with tissue overgrowth, reduced matrix), but these changes did not increase with time.

CONCLUSIONS

Overall, flexion-extension and pronation-supination exhibited distinct time-dependent patterns during contracture development and joint mobilization. Histologic evaluation showed tissue changes, but did not fully explain the patterns in contracture mechanics. Future work will use this rat model to evaluate the periarticular soft tissues of the elbow to isolate tissue-specific contributions to contracture to ultimately develop strategies for tissue-targeted treatments.

CLINICAL RELEVANCE

A rat model of posttraumatic elbow contracture quantitatively described contracture development/progression and reiterates the need for rehabilitation strategies that consider both flexion-extension and pronation-supination elbow motion.

[Research progress of rehabilitation after autologous chondrocyte implantation on knee]

Objective

To summarize the research progress of rehabilitation after autologous chondrocyte implantation (ACI).

Methods

The literature related to basic science and clinical practice about rehabilitation after ACI in recent years was searched, selected, and analyzed.

Results

Based on the included literature, the progress of the graft maturation consists of proliferation phase (0-6 weeks), transition phase (6-12 weeks), remodeling phase (12-26 weeks), and maturation phase (26 weeks-2 years). To achieve early protection, stimulate the maturation, and promote the graft-bone integrity, rehabilitation protocol ought to be based on the biomechanical properties at different phases. Weight-bearing program, range of motion (ROM), and options or facilities of exercise are importance when considering a rehabilitation program.

Conclusion

It has been proved that the patients need a program with an increasingly progressive weight-bearing and ROM in principles of rehabilitation after ACI. Specific facilities can be taken at a certain phase. Evidences extracted in the present work are rather low and the high-quality and controlled trials still need to improve the rehabilitation protocol.

Extension of knee immobilization delays recovery of histological damages in the anterior cruciate ligament insertion and articular cartilage in rabbits

[Purpose] To investigate the influence of knee immobilization period on recovery of histological damages in the anterior cruciate ligament (ACL) insertion and articular cartilage in rabbits. This knowledge is important for determining the appropriate rehabilitation approach for patients with ligament injuries, fracture, disuse atrophy, and degenerative joint disease. [Materials and Methods] Forty-eight male Japanese white rabbits were divided equally into the remobilization and control groups. The remobilization group had the right knee surgically immobilized, and was divided equally into four subgroups according to the duration of immobilization (1, 2, 4 and 8 weeks). After the immobilization was removed, the rabbits moved freely for 8 weeks. The control group underwent sham operation and followed the same time course as the remobilization group. The chondrocyte apoptosis rate and chondrocyte proliferation rate in the ACL insertion and articular cartilage were analyzed after remobilization. [Results] In the ACL insertion, the remobilization group had a higher chondrocyte apoptosis rate than the control group after 8 weeks of immobilization, and a lower chondrocyte proliferation rate than the control group after 4 and 8 weeks of immobilization. In the articular cartilage, the remobilization group had a lower chondrocyte proliferation rate than the control group after 8 weeks of immobilization. After 8 weeks of remobilization, the ACL insertion and articular cartilage are not completely recovered after 4 and 8 weeks of immobilization, respectively. [Conclusion] Our results suggest that 8 weeks of remobilization will result in recovery of the ACL insertion after 2 weeks of knee immobilization, and recovery of the articular cartilage after 4 weeks of knee immobilization. If 8 weeks of immobilization occurs, a remobilization duration of more than 8 weeks may be necessary.

Synovial C-Shaped Tibial Footprint of the Anterior Cruciate Ligament

Background:

Although numerous anatomic studies about the anterior cruciate ligament (ACL) structure and attachments have been performed, these studies have not reached consensus on the ACL footprint.

Purpose:

To investigate the existing controversy regarding the morphology of the tibial ACL insertion (footprint) and confirm histologically that the tibial ACL footprint is not completely filled with ligament tissue.

Study Design:

Descriptive laboratory study.

Methods:

The tibial ACL footprint was dissected from 20 different fresh-frozen cadaveric knees (all males; mean age, 68.8 ± 5.4 years [range, 55-80 years]; mean weight, 78 ± 6.6 kg [range, 45-93 kg]). Two knees, 1 with severe osteoarthritis and 1 with previous knee surgery, were excluded. The tibial ACL insertion was observed, and this area was longitudinally divided into 4 parallel slices (0%-25%, 25-50%, 50%-75%, and 75%-100%), embedded in paraffin wax, and stained with hematoxylin-eosin, alcian blue, and picrosirius-polarization. The specimens were measured using a microscope to determine the distances from the anterior to the posterior border of the ACL ligament tibial insertion and the distance from the posterior border to the end of the ligament fibers of the ACL ligament tibial insertions.

Results:

The 18 evaluated knee specimens confirmed the finding of a C-shaped tibial insertion of the ACL. The measurements showed that the ligament (vertical parallel collagen fibers) occupied only 30.8% of the complete insertion. The remaining area was filled with synovial tissue, demonstrating histologically the “C” shape.

Conclusion:

This study confirms macroscopically the C-shaped tibial insertion of the ACL and shows histologically that synovial tissue is an indirect insertion filling the major part of the footprint.

Clinical Relevance:

This anatomic study suggests a different shape of the ACL tibial footprint, which may be useful for new perspectives regarding ACL reconstruction surgery research.

Remobilization causes site-specific cyst formation in immobilization-induced knee cartilage degeneration in an immobilized rat model

An understanding of the articular cartilage degenerative process is necessary for the prevention and treatment of joint disease. The present study aimed to examine how long‐term immobilization‐induced cartilage degeneration is aggravated by remobilization. Sixty 8‐week‐old male Wistar rats were used in this study. The unilateral knee joint was immobilized using an external fixator for 8 weeks. The rats were killed at 0 and 3 days, and at 1, 2, 4 and 8 weeks after removing the fixator. After the rats were killed, the maximum knee extension angles were measured. Histological sections at the medial mid‐condylar region (non‐contact, transitional and contact regions of the femur and tibia) were prepared and scored. The cartilage thickness and number of chondrocytes were measured, and CD44 and Col2‐3/4c expression levels were assessed immunohistochemically. The histological assessment revealed progressive aggravation of cartilage degeneration in the transitional region, with a decreased number of chondrocytes and CD44‐positive chondrocytes as well as poor scoring over time, particularly in the tibia. Cyst formation was confirmed in the transitional region of the tibia at 8 weeks post‐remobilization. The cartilage thickness in the transitional region was thicker than that in the contact region, particularly in the tibia. Col2‐3/4c expression was observed in the non‐contact and transitional regions, and the knee extension angle was recovered. In conclusion, immobilization‐induced cartilage degeneration was aggravated by remobilization over time in the transitional region, followed by observations of a decreased number of chondrocytes and morphological disparity between different cartilage regions.