Changes in the hyaline articular cartilage after air exposure

Patella resurfacing during total knee arthroplasty is cost-effective and has lower re-operation rates compared to non-resurfacing

BACKGROUND

The decision to resurface the patella as part of total knee arthroplasty may be influenced by the surgeon's preference, education, training, tradition and geographic location. Advocates for non-resurfacing or selectively resurfacing may claim no difference in patient reported outcomes, and that resurfacing is associated with increased risks such as extensor mechanism injury or malalignment, problems with the design of the patella component and technical issues intraoperatively.

AIMS

To critically examine factors that should be considered in addition to patient reported outcomes in the decision process of resurfacing or non-resurfacing of the patella in total knee arthroplasty.

METHOD

A comprehensive literature search was conducted to identify factors that may influence decision making in addition to knee specific patient reported outcome measures such as surgical risks, patient quality of life, procedure cost, re-operation rate, implant design, surgeons learning curve and the fate of remaining cartilage in native patellae.

RESULTS

Patient-reported outcomes are equivocal for resurfacing and non-resurfacing. Critical analysis of the available literature suggests that the complications of resurfacing the patella are historic, which is now lower with improved implant design and surgical technique. Routine resurfacing was cost-effective in the long term (potential saving £104 per case) and has lower rates of revision (absolute risk reduction 4%). Finally, surgical judgment in selective resurfacing was prone to errors.

CONCLUSION

Patella resurfacing and non-resurfacing had similar patient-reported outcomes. However, patella resurfacing was cost-effective and was associated with a lower rate of re-operation compared to non-resurfacing.

Drying of open animal joints in vivo subsequently causes cartilage degeneration

Objectives

During open orthopaedic surgery, joints may be exposed to air, potentially leading to cartilage drying and chondrocyte death, however, the long-term effects of joint drying in vivo are poorly understood. We used an animal model to investigate the subsequent effects of joint drying on cartilage and chondrocytes.

Methods

The patellar groove of anaesthetised rats was exposed (sham-operated), or exposed and then subjected to laminar airflow (0.25m/s; 60 minutes) before wounds were sutured and animals recovered. Animals were monitored for up to eight weeks and then sacrificed. Cartilage and chondrocyte properties were studied by histology and confocal microscopy, respectively.

Results

Joint drying caused extensive chondrocyte death within the superficial regions of cartilage. Histology of dried cartilage demonstrated a loss of surface integrity at four weeks, fibrillations at eight weeks, and an increased modified Mankin score (p < 0.001). Cartilage thickness increased (p < 0.001), whereas chondrocyte density decreased at four weeks (p < 0.001), but then increased towards sham-operated levels (p < 0.01) at eight weeks. By week eight, chondrocyte pairing/clustering and cell volume increased (p < 0.05; p < 0.001, respectively).

Conclusions

These in vivo results demonstrated for the first time that as a result of laminar airflow, cartilage degeneration occurred which has characteristics similar to those seen in early osteoarthritis. Maintenance of adequate cartilage hydration during open orthopaedic surgery is therefore of paramount importance.

Cite this article: Dr A. Hall. Drying of open animal joints in vivo subsequently causes cartilage degeneration. Bone Joint Res 2016;5:137–144. DOI: 10.1302/2046-3758.54.2000594.

Efficacy of common surgical compounds in preventing articular chondrocyte death from desiccation

PURPOSE

Purpose of this study was to identify potential substances that prevent desiccation of chondrocytes.

METHODS

Macroscopically normal bovine cartilage explants (n = 80) were exposed to room air, or covered with surgical lubricant, Lactated ringer (LR) or Seprafilm (Genzyme Biosurgery, Cambridge, MA) for 0, 30, 60 or 120 min. The viability of superficial chondrocytes was measured after 48 h of incubation in tissue culture media at 37 °C by Live/Dead staining. Chondrotoxicity was measured as the extent of cell death below the articular surface. Statistical analysis was performed with a two-way analysis of variance on the data set and a subsequent Tukey's post hoc test.

RESULTS

Chondrocyte death correlated positively with the length of exposure, regardless of the treatment (p < 0.0001). The extent of superficial chondrocyte death was minimally lower in the LR (89.1 ± 2.6 %, 80.8 ± 1.2 %) and surgical lube (84.3 ± 1.8 %, 75.9 ± 2.7 %) groups than the control (82 ± 5.7 %, 65.6 ± 13.3 %) and Seprafilm group (77.6 ± 3.9 %, 63.3 ± 6.9 %) (p < 0.001) at the first two time points, with no significant difference between the latter groups. After 60 and 120 min, surgical lube resulted in less chondrocyte death than all other groups (70.4 ± 6.8 % and 60.9 ± 5.9 %, all p < 0.0001).

CONCLUSION

The data suggest that depending on the expected length of exposure of the articular cartilage surface, different compounds appear to be protective. For exposures exceeding 60 min, surgical lubricant demonstrated the highest protective potential. Results from this study indicate that protecting exposed articular surfaces with surgical lubricant for orthopaedic procedures lasting more than 1 h lead to decreased chondrocyte death and suggest improved cartilage functional outcomes postoperatively.

Airflow accelerates bovine and human articular cartilage drying and chondrocyte death

OBJECTIVE

Exposure of articular cartilage to static air results in changes to the extracellular matrix (ECM) and stimulates chondrocyte death, which may cause joint degeneration. However during open orthopaedic surgery, cartilage is often exposed to laminar airflow, which may exacerbate these damaging effects. We compared drying in static and moving air in terms of cartilage appearance, hydration and chondrocyte viability, and tested the ability of saline-saturated gauze to limit the detrimental effects of air exposure.

DESIGN

Articular cartilage from bovine metatarsophalangeal joints (N = 50) and human femoral heads (N = 6) was exposed for 90 min to (1) static air (2) airflow (up to 0.34 m/s), or (3) airflow (0.18 m/s), covered with gauze. Following air exposure, cartilage was also rehydrated (0.9% saline; 120 min) to determine the reversibility of drying effects. The influence of airflow was assessed by studying macroscopic appearance, and quantifying superficial zone (SZ) chondrocyte viability and cartilage hydration.

RESULTS

Airflow caused advanced changes to cartilage appearance, accelerated chondrocyte death, and increased dehydration compared to static air. These effects were prevented if cartilage was covered by saline-saturated gauze. Cartilage rehydration reversed macroscopic changes associated with drying but the chondrocyte death was not altered. Chondrocytes at the cut edge of cartilage were more sensitive to drying compared to cells distant from the edge.

CONCLUSIONS

Airflow significantly increased articular cartilage dehydration and chondrocyte death compared to static air. As laminar airflow is routinely utilised in operating theatres, it is essential that articular cartilage is kept wet via irrigation or by covering with saline-saturated gauze to prevent chondrocyte death.

Development of partial-thickness articular cartilage injury in a rabbit model

In humans, partial-thickness cartilage lesions frequently result in premature osteoarthritis. While rabbits often are used as a model for partial-thickness cartilage lesions, the natural course of cartilage surrounding such a lesion is largely unknown. We developed a rabbit model of a chronic partial-thickness cartilage defect and asked whether these defects led to (1) deterioration of surrounding cartilage macroscopically and microscopically (increased Mankin score) and (2) disturbances in proteoglycan metabolism. In 55 rabbits, we created a 4-mm-diameter partial-thickness cartilage defect on one medial femoral condyle. The surrounding cartilage was characterized during the course of 26 weeks. Contralateral knees were sham-operated. In experimental knees, we found cartilage softening and fibrillation at 13 and 26 weeks. High Mankin scores observed at 1 week were partially restored at 13 weeks but worsened later and were most pronounced at 26 weeks. Mankin scores in the experimental groups were worse at 1 and 26 weeks when compared with the sham groups. Mankin scores at 26 weeks improved compared with 1 week in the sham groups. Disturbances in proteoglycan metabolism were less evident. In this rabbit model, a partial-thickness cartilage lesion resulted in early markers of degenerative changes resembling the human situation.