Post-traumatic osteoarthritis--a medico-legal minefield

Quantification of bone marrow water and lipid composition in anterior cruciate ligament-injured and osteoarthritic knees using three-dimensional magnetic resonance spectroscopic imaging

PURPOSE

To quantitatively evaluate longitudinal changes in water and lipid in knee bone marrow with and without bone marrow edema-like lesions (BMELs) in subjects with acutely ruptured anterior cruciate ligaments (ACLs) or osteoarthritis (OA) using three-dimensional magnetic resonance spectroscopic imaging (3D MRSI).

MATERIAL AND METHODS

Ten ACL and 10 OA subjects who presented with BMEL and seven BMEL-free controls were scanned at 3T. All ACL and OA subjects had one-year follow-up scans. 3D MRSI was acquired in BMEL and adjacent bone marrow, and water content (WC) and unsaturated lipid index (UI) were calculated in each region of interest.

RESULTS

At baseline, ACL BMEL WC was significantly higher than ACL non-BMEL, OA BMEL, and control WC; ACL non-BMEL WC, ACL BMEL UI, and OA BMEL WC were significantly higher than control. ACL BMEL WC decreased significantly one year post-reconstruction; UI decreased non-significantly (p=0.09). No significant changes in OA BMEL or ACL and OA non-BMEL WC and UI were observed.

CONCLUSION

3D MRSI is a powerful method of quantitatively assessing the biochemical composition of bone marrow in OA and ACL-injured knees, which may serve as imaging markers to improve comprehension of primary and secondary OA pathology.

Comparison of T1rho relaxation times between ACL-reconstructed knees and contralateral uninjured knees

PURPOSE

The goal of this study is to compare the cartilage of anterior cruciate ligament (ACL)-reconstructed and uninjured contralateral knees using T 1ρ MRI 12-16 months after ACL reconstructions.

METHODS

Eighteen patients with ACL-reconstructed knees (10 women, 8 men, mean age = 38.3 ± 7.8 years) were studied using 3T MRI. Injured and contralateral knee MR studies were acquired 12-16 months post-operatively. Cartilage sub-compartment T 1ρ values of each injured knee were compared with the contralateral knee's values. Subgroup analysis of sub-compartment T 1ρ values in both knees was performed between patients with and without meniscal tears at the time of ACL reconstruction using a paired Student's t test.

RESULTS

In ACL-injured knees, the T 1ρ values of the medial tibia (MT) and medial femoral condyle (MFC) were significantly elevated at 12-16 months follow-up compared to contralateral knees. Patients with a medial meniscal tear had higher MFC and MT T 1ρ values compared to respective regions in contralateral knees. Patients with lateral meniscal tears had higher lateral femoral condyle and LT T 1ρ values compared to respective regions in contralateral knees. There were no differences between the injured and contralateral knees of patients without meniscal tears.

CONCLUSIONS

T 1ρ MRI can detect significant changes in the medial compartments' cartilage matrix of ACL-reconstructed knees at 1 year post-operatively compared to contralateral knees. The presence of a meniscal tear at the time of ACL reconstruction is a risk factor for cartilage matrix degeneration in the femorotibial compartments on the same side as the meniscal tear.

A retrospective cohort study of displaced segmental radial head fractures: is 2 mm of articular displacement an indication for surgery?

HYPOTHESIS

Many investigators agree that 2 mm of articular displacement is a reasonable indication for open reduction and internal fixation of Mason type II fractures of the radial head. However, there is no evidence to support that this degree of articular displacement is predictive of poor outcomes in conservatively treated fractures. We hypothesized there would be no difference between conservatively treated radial head fractures with greater 2 mm of displacement and those with less than 2 mm of displacement in terms of patient-reported or clinical outcomes.

MATERIALS AND METHODS

We reviewed databases of all radial head fractures in our region. The primary outcomes were the Patient-Rated Elbow Evaluation and Disabilities of the Arm, Shoulder and Hand questionnaires. Secondary outcomes included radiologic radiocapitellar arthritis and range of motion (ROM) at follow-up. Postinjury treatment protocols, as well as patient factors, were examined for their effects on outcome.

RESULTS

The results showed no significant difference in any outcome for conservatively treated radial head fractures with 2 mm (P = .8) or even 3 mm (P = .6) of articular displacement over a mean follow-up of 4.4 years. Early ROM and physiotherapy showed no significant differences in any outcome measure. Dominant hand injury showed no significant difference in patient-reported outcomes; however, ROM was significantly decreased on examination.

CONCLUSIONS

This retrospective review suggests that fracture displacement of 2 to 3 mm is not necessarily an indication for surgical fixation in isolated fractures of the radial head. In addition, it appears that postinjury ROM/physiotherapy does not play a large role in improving patient outcome.

Evaluation of bone bruises and associated cartilage in anterior cruciate ligament-injured and -reconstructed knees using quantitative t(1ρ) magnetic resonance imaging: 1-year cohort study

PURPOSE

To quantitate bone marrow edema-like lesions (BMELs) and the radiologic properties of cartilage in knees with acute anterior cruciate ligament (ACL) injuries using T(1ρ) magnetic resonance imaging over a 1-year period.

METHODS

Nine patients with ACL injuries were studied. Magnetic resonance imaging scans were acquired within 8 weeks of the injury, after which ACL reconstruction surgery was performed. Images were then acquired 0.5, 6, and 12 months after reconstructions. The volume and signal intensity of BMELs were quantified at baseline and follow-up examinations. T(1ρ) values were quantified in cartilage overlying the BMEL (OC) and compared with surrounding cartilage at all time points.

RESULTS

BMELs were most commonly found in the lateral tibia and lateral femoral condyle. Nearly 50% of BMELs resolved over a 1-year period. The T(1ρ) values of the OC in the lateral tibia, medial tibia, and medial femoral condyle were elevated compared with respective regions in surrounding cartilage at all time points; the difference was significant only in the lateral tibia (P < .05). The opposite results were found in the lateral femoral condyle. For the medial tibia and medial femoral condyle, none of the time periods was significantly different. The percent increase in T(1ρ) values of OC in the lateral tibia was significantly correlated with BMEL volume (r = 0.74, P < .05). At 1 year, the OC in the lateral tibia, medial tibia, and medial femoral condyle showed increased T(1ρ) values despite improvement of BMEL.

CONCLUSIONS

In patients after ACL tear and reconstruction, (1) the cartilage overlying BMEL in the lateral tibia experiences persistent T(1ρ) signal changes immediately after acute injuries and at 1-year follow-up despite BMEL improvement, (2) the superficial layers of the overlying cartilage show greater matrix damage than the deep layers, and (3) the volume of the BMEL may predict the severity of the overlying matrix's damage in the lateral tibia. T(1ρ) is capable of quantitatively and noninvasively monitoring this damage and detecting early cartilage changes in the lateral tibia over time.

LEVEL OF EVIDENCE

Level IV, therapeutic case series.

The limitation of acute necrosis in retro-patellar cartilage after a severe blunt impact to the in vivo rabbit patello-femoral joint

We have previously shown that surface lesions and acute necrosis of chondrocytes are produced by severe levels of blunt mechanical load, generating contact pressures greater than 25 MPa, on chondral and osteochondral explants. We have also found surface lesions and chronic degradation of retro-patellar cartilage within 3 years following a 6J impact intensity with an associated average pressure of 25 MPa in the rabbit patello-femoral joint. We now hypothesized that cellular necrosis is produced acutely in the retro-patellar cartilage in this model as a result of a 6J impact and that an early injection of the non-ionic surfactant, poloxamer 188 (P188), would significantly reduce the percentage of necrotic cells in the traumatized cartilage. Eighteen rabbits were equally divided into a 'time zero' group and two other groups carried out for 4 days. One '4 day' group was administered a 1.5 ml injection of P188 into the impacted joint immediately after trauma, while the other was injected with a placebo solution. Impact trauma produced surface lesions on retro-patellar cartilage in all groups. Approximately 15% of retro-patellar chondrocytes suffered acute necrosis in the 'time zero' and '4-day no poloxamer' groups. In contrast, significantly fewer cells (7%) suffered necrosis in the poloxamer group, most markedly in the superficial cartilage layer. The use of P188 surfactant early after severe trauma to articular cartilage may allow sufficient time for damaged cells to heal, which may in turn mitigate the potential for post-traumatic osteoarthritis. Additional studies are needed to improve the efficacy of this surfactant and to determine the long-term health of joint cartilage after P188 intervention.

Doxycycline effects on mechanical and morphometrical properties of early- and late-stage osteoarthritic bone following anterior cruciate ligament injury

As posttraumatic osteoarthritis (OA) progresses, the mechanical and morphometrical properties of the subchondral bone change and may be linked to damage of the articular cartilage. Potentially to slow that progression, doxycycline was administered orally twice daily (4 mg·kg−1·day−1) in skeletally mature canines after anterior cruciate ligament transection (ACLX). To test if doxycycline significantly altered the structure and function of OA bone, we tested cancellous bone mechanical properties, measured bone mineral content, and analyzed bone structure by microcomputed tomography. Our investigation focused on subchondral trabecular bone changes in the medial femoral condyle at 36 and 72 wk after ACLX. Significant mechanical changes discovered at 36 wk post-ACLX were less obvious at 72 wk in both treated and ACLX groups. Doxycycline treatment conserved bone strain energy density at 72 wk. Doxycycline had little effect on the degradation of superficial osseous tissue at 36 wk post-ACLX; by 72 wk, doxycycline in an ACLX model limited subchondral bone loss within the first 3 mm of periarticular bone with established OA. Significant bone loss occurred in the deeper trabecular bone for all groups. Substantial architectural adaptation within deeper trabecular bone accompanied changes in mechanics in early and established OA.

The extent and distribution of cell death and matrix damage in impacted chondral explants varies with the presence of underlying bone

Excessive mechanical loading can lead to matrix damage and chondrocyte death in articular cartilage. Previous studies on chondral and osteochondral explants have not clearly distinguished to what extent the degree and the distribution of cell death are dependent on the presence of an underlying layer of bone. The current study hypothesized that the presence of underlying bone would decrease the amount of matrix damage and cell death. Chondral and osteochondral explants were loaded to 30 MPa at a high rate of loading (approximately 600 MPa/s) or at a low rate of loading (30 MPa/s). After 24 hours in culture, matrix damage was assessed by the total length and average depth of surface fissures. The explants were also sectioned and stained for cell viability in the various layers of the cartilage. More matrix damage was documented in chondral than osteochondral explants for each rate of loading experiment. The total amount of cell death was also less in osteochondral explants than chondral explants. The presence of underlying bone significantly reduced the extent of cell death in all zones in low rate of loading tests. The percentage of cell death was also reduced in the intermediate zone and deep zones of the explant by the presence of the underlying bone for a high rate of loading. This study indicated that the presence of underlying bone significantly limited the degree of matrix damage and cell death, and also affected the distribution of dead cells through the explant thickness. These data may have relevance to the applicability of experimental data from chondral explants to the in situ condition.

Chronic changes in rabbit retro-patellar cartilage and subchondral bone after blunt impact loading of the patellofemoral joint

Animal models of acute joint injury are useful for study of changes in joint tissues that may eventually lead to degradative disease. Our laboratory has developed a joint trauma model using a single blunt impact to the patellofemoral joint of rabbits and documented softening of retro-patellar cartilage and thickening of its underlying bone out to 12 months post-trauma. In the present study, we examined changes in these joint tissues out to 36 months post-impact. Forty-nine Flemish giant rabbits were impacted on the right patellofemoral joint and sacrificed at one of six times: 0, 4.5, 7.5, 12, 24, and 36 months post-impact. A 30% reduction in the compressive modulus of traumatized retro-patellar cartilage occurred at 4.5 months versus the contralateral, non-impacted limb and remained at this reduced level out to 36 months. The fluid permeability of traumatized cartilage also increased over time from baseline and versus the non-impacted limb. Tissue thickness increased slightly at 4.5 months and then decreased over time to a 45% difference from baseline at 36 months post-trauma. While impacted cartilage revealed a significantly greater length of surface fissuring than contralateral, non-impacted cartilage, no time-dependent changes were evident in this study. Moreover, the number and depth of these impact surface lesions did not change as a function of time. Finally, the histological analyses indicated that the thickness of underlying subchondral bone increased over time from baseline and versus that in the non-impacted limb. This long-term study suggested an association between a decrease in the characteristic time constant of traumatized cartilage and thickening of the underlying subchondral bone. Any potential cause and effect relationship, however, must be investigated in future studies.

An analytical model to study blunt impact response of the rabbit P-F joint

While mechanisms of post-traumatic osteoarthrosis are largely unknown, excessive stresses and strains generated in articular cartilage and the underlying bone may play a role. In this manuscript a technique is described for studying the impact response of a diarthrodial joint. A mathematical model of the rabbit PF joint indicated that contact pressures predicted by a quasi-static plane strain linear elastic model compared well with experimental data when Poisson's ratio and Young's modulus of the cartilage were 0.49 and 2 MPa, respectively. This value for the elastic modulus compared well with that obtained from elastic analysis of short-time indentation experiments on cartilage from a previous study. The model analysis also suggested that surface fissuring of patellar cartilage occurs near areas where shear stresses and tensile strains are high. Impact location on the patella significantly influenced the distributions of shear stress along the bone-cartilage interface and tensile strains in the cartilage. These results may help explain some of the mechanisms of initial tissue damage reported elsewhere. Limited experimental data are presented here but the value of such mathematical models for estimation of material properties and for analysis of damage creation is clearly demonstrated.

Association of overweight, trauma and workload with coxarthrosis. A health survey of 7,217 persons

In a population sample health survey, body mass, previous trauma and physical stress were studied for associations with coxarthrosis. A sample of 8,000 persons representative of the Finnish population aged 30 or over was invited for examination, and 90 percent participated. On the basis of a standardized clinical examination, a physician diagnosed coxarthrosis in 6 percent of the women and 4 percent of the men. The prevalence rose with age. In persons with a past traumatic lower-limb injury, the odds ratio of unilateral coxarthrosis was 2.1 and of bilateral coxarthrosis 1.5, as adjusted for sex, age and other determinants using logistic regression. The sum index reflecting self-reported features of physical stress in present or previous occupations was directly proportional to the prevalence of coxarthrosis. Body mass index (kg/m2) was closely associated with bilateral coxarthrosis; the adjusted odds ratio (95 percent confidence intervals) for indices > 35, compared to those < 25, was 2.8 (1.4-5.7). In terms of the population attributable fraction, prior trauma, physical stress and body mass were estimated to explain 59 percent of the prevalence of coxarthrosis. The potential for primary prevention may be great, but longitudinal population studies are necessary to elucidate causal significance of the risk factors.